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THE

AMERICAN NATURALIST

Vou. XLIII January, 1909 No. 505

JUVENILE KELPS AND THE RECAPITULATION

THEORY. I.

PROFESSOR ROBERT F. GRIGGS

HIO STATE UNIVERSITY

I. Tue DEVELOPMENT oF CERTAIN KELPS

A. Renfrewia

For the preparation of a former article (Griggs, ’06)

on Renfrewia the writer had no very young plants, but

during the summer of 1907 he was enabled to collect a

full series at the Minnesota Seaside Station, Port Ren-

frew, B. C. This material is of interest for the study of

the development of this, the most primitive of the kelps

in comparison with the more complex forms.

The smallest specimen found, which measures a trifle

less than 4 mm. (Fig. 1), is not certainly determinable.

But one 13 mm. long (Fig. 2) had already developed a

peculiar swelling of the basal region which characterizes

the young plants. The primitive dise of most kelps and

of Renfrewia up to this age is rather flat and sharply

separable from the stipe, which ascends cleanly without

tapering from the top of the disc. In Renfrewia, how-

ever, the basal region of the stipe (the region which in

other kelps develops hapteric outgrowths) increases in

size. As the plant grows this swollen region becomes

more prominent till in plants 8 em. long (Fig. 11) the

1 Since publishing the original account of Renfrewia parvula in 1906 I

have found that it is apparently conspecific with Setchell’s (’01) Laminaria

ephemera earlier described from the California coast. | i Set-

chell’s name replaces mine and the plant becomes Renfrewia Eer

(Setchell).. Cf. Setchell, ’08 b.

6 THE AMERICAN NATURALIST [Vow. XLIII

Fic. 1. Renfrewia, 4 mm., shading shows the a of single and many-

levered areas in the lenin holdfast without basal con

Renfrewia, 13 mm., lamina many- am: ‘throughout basal cone

Lasmi G18, Y lamina about four-layered, spots already

shown ‘fa the cortex, holdfast. ei developed, plant apparently anchored by

filaments.

i Fic. 4. Lessoniopsis, 2.3 mm., spots in the lamina larger and more evident

distally, but still small near the transition erap ps aaa that growth is

wa localized, primitive Aine developing at bas

edophyllum, 2.3 mm., showing the chuck iiad primitive disc.

6. <gumecaenas 10 mm., lobes of primitive disc grown into the primi-

tive hates

holdfast is an almost straight-sided cone 5 mm. in diam-

eter and of about equal height. Though apparently in-

significant this character makes it easy to pick out Ren-

frewia from other kelps while yet very small. So far as

the writer is aware it is not present in any other kelp.

After the plant has reached about a decimeter in length

the basal cone ceases to increase and later is lost in the

growth of the stipe (Fig. 12). At the same time the dise

begins to enlarge and spread out on the substratum, giv-

ing a firmer hold for the increasing lamina above. This

enlargement is clearly in the region of the primitive dise `

and not in the conical basal swelling above, which remains

part of the stipe. These two tendencies of growth work-

ing together usually cause the sharp distinction between

the holdfast and stipe to reappear, and in plants more

than 15 em. long the conical base is seldom prominent

(Fig. 13). In adults the disc becomes very flat and thin

by its continued extension (Fig. 14).

Fics. 7-11. Renfrewia, series of young plants showing the development of

the per cone. Four fifths natural size.

IGS. 12-13. Renfrewia, older plants showing the gradual disappearance of

the pase cone heed nerease in size. Four fifths natural size.

Fic. 14. Renfrewia, base of an adult plant, fruiting area extending over

almost the entire an na, its margin indicated by shadows here and there, hold-

fast showing primitive hapteres. Four fifths natural size.

8 THE AMERICAN NATURALIST [Vow. XLIII

Some speculations as to the nature and significance of

this cone may be of interest. Of all the kelps Renfrewia

and Cymathere are the only ones in which the mature

holdfasts are restricted to the primitive disc region. In

the development of the latter genus, as traced by the

writer (’07), there is no indication of such an organ as

can be seen by an inspection of the figures then published.

Phyllaria and Saccorhiza differ in their holdfast char-

acters from all the other genera. Instead of putting out

hapteres directly from their stipes they develop bulbous

‘‘rhizogens’’ which form ring-like collars around the

stipe. From these the hapteres are formed by unequal

growth along their margins. Though the rhizogen in both

genera is separated from the primitive holdfast by a dis-

tinct interval on the stipe, it is essentially similar to the

basal cone of Renfrewia which we may consider as an

incipient rhizogen. This would indicate some leaning of

Renfrewia toward the Phylariate; but its paraphyses

are of the typical clavate form not at all similar to the

linear ones of that group. Whether this basal cone is a

nascent organ representing the beginning of the holdfast

or is a vestige of a Saccorhiza-like rhizogen is a puz-

zling problem. At some stage in their history the rhizo-

gens of Saccorhiza and Phyllaria probably passed

through this condition and remained for a longer or

shorter period without further development. On the

other hand, the obscuring of the cone in Renfrewia when

adult might suggest a vestigial organ. Perhaps the best

hypothesis is that Renfrewia was cut out from the main

advancing phylum of the kelps, isolated and fixed, at the

stage where the tendency to form a secondary holdfast

was just beginning to manifest itself.

The tissues of the many-layered lamina of Renfrewia

are apparently acquired after the fashion of other kelps,

but in Renfrewia the many-layered lamina begins its de-

velopment in smaller plants than in the Phylariate in-

cluding Cymathere. Even in the smallest specimen

(Fig. 1) there is only a small portion of the one-layered

blade remaining around the edge of the lamina. In the

No. 505] KELPS AND RECAPITULATION THEORY 9

13 mm. specimen (Fig. 2), the whole lamina is many lay-

ered without any signs of the one-layered portion persist-

ing around its edges. Apparently the embryonic lamina

is almost wholly transformed into the adult blade. Like

the adult, these young plants are light colored and delicate

in texture. They are narrowly elliptical in shape, cune-

ate at the base and rounding to the apex when not badly

abraded.

Except for the basal cone of the stipe young plants

15 mm. long in all characters are like the adult. The

adult is larger but the proportions remain the same.

Even in the histology there is probably very little differ-

erence, for, as described below, Renfrewia develops very

imperfectly the complex tissue system which character-

izes the higher kelps. What differentiation of tissues

appears is probably present long before adult size is

reached. Were it not for their reproductive maturity it

would be difficult to demonstrate that the adults were ma-

ture and not merely larger juvenile forms (Figs. 16, 17);

and they have been mistaken by competent observers for

juvenile forms of some other kelp.

B. Lessoniopsis

Lessoniopsis is a monotypic genus ranging along the

Pacific coast from California to Vancouver Island. It

was founded by Reinke (’03) to receive Lessonia littoralis

Farlow and Setchell (see Setchell, 03) which differs from

Lessonia in the marked dimorphism of the laminæ, as de-

scribed below.

The juvenile forms of Lessoniopsis are extremely

abundant during July and August at the Minnesota Sea-

side Station. They grow in clumps of many individuals

of all ages. As often as not these clumps start upon the

stipes of other kelps, so that one can obtain many hundred

specimens simply by cutting off a few old Laminaria

stipes. Though the mature plants are often single, it 1s

not at all unusual to find several large plants fused to-

gether, as was noticed by Reinke. The reason for this

habit of growth of the sporelings is a matter of some in-

10 THE AMERICAN NATURALIST [Vou XLII

terest. There is no difference, as far as the writer is

aware, between the fruiting habits of this and other kelps.

In quiet water the fragments of any fruiting lamina torn

off by the waves might lie undisturbed on the bottom and

the spores might germinate close to the point of libera-

tion. But this kelp is a cumaphyte growing exclusively

in the strong surf, and it is in surf-scoured situations

that the young plants are found best developed. This

would lead one to look for some method of basal branch-

ing or possibly budding of new lamine from the holdfast,

as is known in a few kelps which have ‘‘rhizomes.’’ But

though hapteres and stipes are occasionally so completely

grown together as to appear branches of one plant, no

evidence of such branching in the young plant has been

observed and the writer must conclude that the clusters

are due to starting of many spores at one point.

The young plants forming these clumps are thickly

splashed with checks of dark brown on the lighter color

of the body of the lamina. This is most conspicuous in

plants about 10 em. long and is clearly brought out in the

photographs (Figs. 15, 21). As they grow older the spot-

ting tends to disappear, but traces of it can usually be

found in specimens of any age. No other kelp of the

region is similarly marked except Pterygophora, in which

the spots when present are much less distinct. As this

appearance arises very early it is of the utmost service

in identifying the plants while yet too young to have de-

veloped any characters of the adult.

The smallest specimen found (Fig. 3) measured about

1.1 mm. in length. It was attached to the hapteres of

another plant of the same species twenty or thirty times

as long. When loosened from its hold it came away with

a mass of filamentous material which completely en-

veloped its base. In this tangle there was a considerable

portion of foreign matter; but the appearance of the finer

strands was that of a protonema-like felt organically con-

nected with the young kelp which seemed to spring from

it like the gametophore of a moss. On teasing this away

it was seen that the primitive dise had not yet developed.

Fic. 15. Lessoniopsis, 30 mm., lamina showing the characteristic spots,

midrib just beginning to appear, holdfast formed by conspicuous primitive

Fics. 16-17. Renfrewia, adult, raas penen to Lessoniopsis when

young, fruiting area covers almost the entire lamina in Fig. 16, but in Fig. 17

occupies only a small area at the out and Hert clearly discernible, spots in

Fig. 16, due to epiphytic alge. About one half natural size.

12 THE AMERICAN NATURALIST [VoL. XLIII

The base of the stipe was but slightly larger than the

portion above and gave off a large number of filamentous

processes, some of which seem to have pressed against

the substratum, while others apparently connected with

the filaments around the base. Notwithstanding its small

size this specimen had a well-developed stipe about a

dozen layers of cells in thickness. The internal cells are

considerably elongated, though not, as far as can be seen

by focusing, differentiated into a pithweb. The lamina

was already several cells in thickness even at the edge.

Since it was but little frayed, it hardly seems possible

that there could have been any remnant of the one-lay-

ered lamina which had not been transformed into the

many-layered adult blade. In this respect Lessoniopsis

would stand at the opposite extreme from Cymathere, in

which a large portion of the embryonic lamina is not

changed, but continues to grow and persists until the

plant is more than 20 cm. long.

The next larger specimen (Fig. 4) measures 2.3 mm.,

but its true length must have been about 5 mm., for it is

- sharply truncated a little above the base of the lamina.

The holdfast of this specimen was enlarged to form a

fairly well developed primitive disc, the base of which

was, as in the first specimen, more or less imbedded in a

mass of filaments apparently belonging to the kelp. The

lamina was much thicker and the spots were seen to be

in two layers, one on each side, just beneath the epi-

dermis. In the smaller specimen (Fig. 3), where one

spot overlapped another, the two layers could also be

made out, but the difference in focus was so slight as to

make it appear that they lay in contact, indicating that

the lamina was four cells in thickness. In the larger

specimen they were separated by a considerable interval |

which indicated a decided development of the pithweb

and cortex. Toward the extremity of the lamina the pig-

mented spots were very dark and most of them were con-

siderably elongated. They still consisted, however, for

the most part, of single cells. Farther back in the tran-

sitional region, they were lighter in color, round and more

No. 505] KELPS AND RECAPITULATION THEORY 13

like those of the first specimen (see Fig. 3). This shows

that the region of growth had been definitely localized as

a meristem at the base of the lamina (as in the mature

plant), while further out in the lamina growth was taking

place mainly by the enlargement of cells already formed.

From this point on the development of the species was

illustrated by many specimens of all ages. The first

marked change was the enlargement of the primitive disc.

In a specimen 30 mm. long (Fig. 15) the disc had reached

a diameter of 4 mm. At this stage it bears a striking

resemblance to that of the adult Renfrewia, being very

flat and closely appressed to the substratum. As in that

genus, the growth which causes the enlargement becomes

localized in certain regions, giving the disc a crenate mar-

gin. In places the localization had become sufficiently

pronounced to give rise to definite primary hapteres ex-

actly as described by MacMillan (’99) for young plants

of Nereocystis and by the writer in the adults of Ren-

frewia and Cymathere. These primary hapteres are of

course all restricted to the primitive disc. Soon after

this stage the secondary hapteres begin to arise around

the base of the stipe and become very abundant, quickly

obliterating the primitive holdfast. The age at which

branching and differentiation of the midrib appear varies

greatly. Sometimes the plant may reach a length of 80

mm., with only the beginnings of the midrib and of the

splitting to form the first branch (Fig. 21); while in one

plant of 160 mm. the perforation of the midrib for the

branch had only just been accomplished (Fig. 22). On

the other hand a specimen (Fig. 19) measuring only 18

mm. showed the position of the perforation plainly

marked out. The first appearance of the midrib is indi-

cated by two straight lines extending from the transition

region up into the lamina (Fig. 20). The lamina between

them grows thicker and takes on the characters of the

midrib, which gradually extends toward the tip. But

usually for a long time the two edges are more pro-

nounced than any other portion of the rib.

As is well known, the whole subfamily, the Lessoniatex,

Fics. 18-23. Lessoniopsis. Four fifths natural size.

18. Young plant at about the same stage as Fig. ane to which is at-

at shown in Fig.

Fic. 19. *lant gr in heavy surf, holdfast very large; plant dwarfed,

eS for first branch already appearing in the transition region

20. Plant from Se water grown to an unusually large hea with no

inateation of branching, midrib just formin

2 Similar to the last Prd for the beginning of the perforation.

22. Perforation comple

Wie, 23. imary rat “domplete, perforations formed for second

braad i, inner side of new laminæ beginning to form from the divided midrib.

3778

No. 505] KELPS AND RECAPITULATION THEORY 15

to which Lessoniopsis belongs, is characterized by the re-

peated splitting of the original unbranched lamina till the

plant comes to have a cluster of many leaves. The

method of this branching is peculiar to the kelps. Im-

stead of forking at the tip or sending out a new shoot as a

lateral proliferation, the branching begins in the trans-

ition region between the stipe and the lamina and ex-

tends upward until it reaches the tip of the lamina, thus

splitting it, while the stipe is divided, to a greater or less

extent in the different genera, by the downward extension

of the same process. This method of branching is the

necessary consequence of the position of the meristem,

which is situated at the junction of lamina and stipe, so

that all new growth is intercalated between the older por-

tions of both. It is obvious, therefore, that any new

structure, such as a branch, must originate in this region

of growth.

In Lessoniopsis the first indication of branching ap- -

pears in a slight depression in the midrib on each

side of the lamina at the transition region. These de-

pressions or pits enlarge and deepen until they meet and

form a perforation almost exactly at the base of the

lamina. It will be readily seen that if the split extended

uniformly upward through the midrib, it would result in

two unsymmetrical faleate lamine each with a rib along

its inner side. This, however, is not usually the case, for

new tissue forms between the divisions of the midrib and

soon duplicates on the inner side the outer edge of the

lamina (Fig. 24, a). Thus each of the new lamin is ap-

proximately symmetrical with respect to its midrib. In

the stipe the branching is carried far enough to involve

the whole of the meristem, so that future lengthening is

almost completely confined to the stipes of the branches.

Before the new laminæ have completely separated there

usually begins to appear at the base of each, the second

split, which is carried to its completion in the same man-

ner as the first. Thus branching continues again and

again so long as the plant lives. Since all the splitting is

dichotomous, the result should be a flat fan-shaped plant,

16 THE AMERICAN NATURALIST [Vor. XLIII

Figs. 24-26. Older Lessoniopsis. About one-sixth natural size

Fic. 24. Plant several times branched; at a the process of the TEE

of the inner side of the divided lamina from the midrib is clearly indicat

Fic. 25. i

wn.

Fic. 26. Plant still anderainett but with the characters of the adult; one

branch is lifted out by a background to show the sporophylls (s) and their

relation to the ordinary a which show the beginnings of division at their

bases as in the younger form

and sometimes this form is attained even in very old

plants, especially those growing in the quieter places, but

usually the stipes twist more or less and spread out in all

directions, giving the plant a tree-like aspect.

There is no change in this habit of growth until the

plant has attained a considerable age. But long before it

reaches its full size there appears another kind of lamina

among the narrow ones with midribs. These lack the

midribs and are much wider, with conspicuously rounded

or subcordate bases. The ribbed lamine are always

sterile, but these wider ones become sporophylls. Con-

sequently after their sporangia are discharged they

slough off and disappear, leaving for a time scars on the

stipe. The origin of these sporophylls is evidently dif-

ferent from that of the ordinary laminez. Since very few

new sporophylis are developed during the summer, at

No. 505] KELPS AND RECAPITULATION THEORY 17

least at Port Renfrew, it seems probable that their pro-

duction is a seasonal phenomenon taking place only for a

limited period before the fruiting season. However they

are formed, they do not reach their full size at first. The

youngest are always shorter and narrower than the older

and entirely lack the characteristic base. Some of the

smallest remind one of the young sporophylls of Pterygo-

phora and have the appearance of being outgrowths from

the meristem as in that species, but the writer does not

feel sure that they are normal. Further information on

the origin of the sporophylls will be very welcome because

of its importance in determining the relationships of this

plant to the other genera of kelps.

At length, by branching and production of sporophylls

a plant is formed with several hundred lamina, in extreme

cases reaching lengths of a meter, while the whole plant is

often two meters long. The stipe at the base becomes

10-20 em. in thickness and is marked with many annual

rings of growth. The holdfast clings so tenaciously to

the rocks that it will support a man’s weight. On a flat

bottom the plants stand upright, but they hang down when

growing on an overhanging cliff, as in the photograph

(Fig. 27). As in all water plants, their only way of main-

taining themselves in the strong currents in which they

live is by bending before them. Accordingly, rigidity is

developed only in very large basal portions of the stipe,

while the terminal branches have not sufficient stiffness to

support the plant when out of the water. Lessoniopsis

thrives only in places where the surf is very heavy and

is there found along with Postelsia, the sea palm, the

most typical of all the cumaphytes, but it does not with-

stand drying so well as that plant and consequently grows —

at a considerably lower level.

C. Egregia

To one acquainted with the kelps only through the more

widely distributed genera such as Laminaria and Alaria,

Egregia must always be the most interesting of the fam-

ily. Algologists agree in assigning to this plant the high-

18 THE AMERICAN NATURALIST (Vor. XLIII

Lessoniopsis (hanging) and Postelsia (upright) growing on an

Fig. 2

overhanging shelf exposed to D T surf, Lessoniopsis is about two meters

long and Postelsia, one half me

est place among the kelps as being the most specialized

of them all. It is a genus of the western coast, repre-

sented by two species, one northern, the other southern.

Both are extremely variable and in their many forms and

intergradations present to the taxonomist a problem of

more than usual diffculty. Some features of the mor-

phology of the northern species, Egregia menziesii, have

been presented in a paper by Ramaley (’03), illustrated

with some excellent figures of adult and middle-aged

plants, while Reinke (’03) has also given figures and a

brief description of somewhat younger plants. The de-

velopment of this species which grows abundantly at the

Minnesota Seaside Station, will be worth considering in

detail in connection with the other kelps discussed above

because of its greater complexity.

Egregia, like Nereocystis, has an extremely long stipe;

indeed, in proportion to its lemina its stipe is much longer,

but its character is totally different from that of Nereo-

cystis. In the latter plant the stipe stretches from the

holdfast, frequently attached to a depth of twenty or

No. 505] KELPS AND RECAPITULATION THEORY 19

thirty feet, like an anchor rope, to the surface, where it

holds the large float and laminæ against the impact of the

heavy surf. This stipe is often less than one centimeter

in thickness for half its length, but of such surprising

strength that the native fishermen tie their boats to these

ready-made anchors and ride out a storm, as noted by

MacMillan (’99). The stipe of Egregia, however, while

slender and flexible, is not bare, but covered with very

numerous short proliferations along its whole length giv-

ing it the appearance of a feather boa. Some of these

are photosynthetic areas, some sporophylls, some floats

filled with air. The presence of such organs as air

vesicles so near the holdfast shows clearly the plant’s

adaptation to a shallow-water habitat. It grows attached

to rocks which are never deeply submerged and are un-

covered even by a moderately low tide, where its branches,

buoyed up by their innumerable pneumatocysts, float with

their whole lengths on the surface of the water. To the

boatmen along that shore a thick bed of Nereocystis is a

sure sign of deep water, but a bunch of Egregia as surely

marks a rock to be avoided.

The youngest plants of Egregia are extremely difficult

to separate from those of Hedophyllum. The juvenile

forms of both these kelps are dark brown, distinguished

from most others of their size by shorter stipes, together

with a rather strong development of hapteres. The

youngest plant of Egregia found (Fig. 28) was 25 mm.

long, with a lamina about 20 mm. long and 10 mm. wide.

The holdfast had already developed a circle of secondary

hapteres, although the primitive holdfast could be made

out beneath the secondary. The stipe was but 3 mm.

long, cylindrical, and featureless except for a very slight

thickening about a millimeter below the base of the blade.

This appeared to be the beginning of the proliferations

which characterize the later stages of the plant.

The thickening of the stipe soon becomes more pro-

nounced and develops into a pair of horns about a milli-

meter long just below the base of the lamina and lying

in the same plane (Fig. 29). These are the only dis-

Fics. 28- a. Five sixtns natural s

Taron plant, "e pe enee aee from Hedophyllum at this

age, cf. Fig. 37, which is less ero

Fig. 29 lant showing the oat pair of proliferations on the stipe

Fic. 30. Plant with the transition region roughened by many capillary

proliferations, tuberculate ridges appearing in the base of the lar a.

Fie. 31. Base of a rages older ant s i i i

branch (b) made evident by

he appearance of proliferations its stipe, oa

rage (p) just appearing, base ipe remaining smo

G Frat Rogie get One half natural size

Fr Whole of tk lant wh in Fig. 31, proliferations on the lamina

absent at ‘he tt, but well developed below.

Fig. 33. uch younger plant than Fig. 32, capillary proliferations prom

in the teak da region, laminar proliferations just beginnin acorn

on margin of both pert ig lamina, tip of lamina smooth, other portions cov-

pee Ta pror tive ridg

34. Older plant

which the lamina has reached its maximum devel-

the stipe has begun to grow, several well-developed pneumatocysts

branches are evident among the outgrowths from the stipe.

sia and

and young

No. 505] KELPS AND RECAPITULATION THEORY 21

tinguishing features of the plant until it reaches a length

of about 40 mm. In plants of about this length a few

round tubercles begin to appear at the base of the lamina,

which has hitherto been smooth as in Hedophyllum. A

specimen 75 mm. long (Fig. 30) showed numerous tuber-

cles in the transition region, giving it a roughened appear-

ance; and there were three instead of two horns below

the zone of the tubercles. The basal portion of the stipe

was still smooth as in the youngest specimen. In this

plant the stipe had elongated scarcely at all and the

growth had been restricted to the lamina, which extended

through 70 of the 75 mm. of the plant’s length. Tubercles

similar to those of the transition region had also appeared

and these were shown by transmitted light to be connected

with streaks of denser tissue running lengthwise through

the lamina.

After this stage, as in Lessoniopsis there is some varia-

tion in the age at which the various structures appear.

A specimen 18 em. long (Fig. 33) will serve as.an illus-

tration of the next step. Here the streaks beneath the

tubercles of the lamina had become prominent ridges,

‘much larger than the small tubercles at their summits.

The ridges stood out so strongly as to cause depressions

on the opposite side of the lamina beneath them. This

gave the lamina a wrinked appearance and added greatly

to its strength. The margin was entire or slightly undu-

late, but at the base were a few short serrations which

looked much like the tubercles of the stipe. The rough-

ened region of the stipe was about 1 cm. in length and no

longer terete like the lower smooth portion, but somewhat

flattened. In place of the horns of the younger specimens

were several outgrowths, the largest of which bore a

small orbicular lamina. The holdfast had become nearly

2 em. in diameter by the great elongation of a few hap-

teres.

In view of the proportions assumed by the siult plant

the relation between the lamina and stipe in the juvenile

forms is most interesting. In the smallest specimen the

lamina is only about three times as long as the stipe.

22 THE AMERICAN NATURALIST [Vow XLII

But further growth is for a time almost restricted to the

lamina until the ratio is increased to ten or fifteen to one.

After this stage the stipe begins to grow and soon sur-

passes the lamina, which seldom exceeds half a meter in

length, while the stipe sometimes becomes fifteen or

twenty times as long.

A specimen 12 em. in length (Fig. 32) though only two

thirds as long as the one just described, was considerably

more advanced. The uppermost quarter of the lamina

was entire, as in the last plant, and below the tip were a

few serrations like those at the extreme base of the

former. Toward the growing point these outgrowths were

larger and had become spatulate proliferations about a

centimeter long, fringing the basal two thirds of the blade.

The stipe had reached a length of 3 cm. Its numerous

tubercles were much elongated and frequently dichoto-

mously branched, once or even twice giving the peculiar

roughened appearance characteristic of the adult. The

proliferations along the lateral edges of the stipe were

much more numerous than in the former specimen; some

of them were simple laminar appendages; others were in-

flated into small globular pneumatocysts (Fig. 31, p); on

others the stalks were roughened by small tubercles like

those of the main stipe. Some of these last, if detached,

might easily pass for young plants cut off just above the

holdfast.

Though marked changes are yet to occur before the

plant becomes mature, they may be understood by a com-

parison of the adult with this young plant (Fig. 32). The

most conspicuous change is of course the great elonga-

tion. While this is especially noticeable in the stipe, the

lamina likewise grows until it reaches a length of about

50 cm., but its width increases scarcely at all, seldom ex-

ceeding 4 em. The proliferations from this narrow

lamina become so numerous that they completely mask

the distinction between it and the stipe, and it is only by

close inspection that the lamina may be recognized. The

growth of the stipe carries the lamina far away from the

holdfast, where it is exposed to the severest action of the

No. 505] KELPS AND RECAPITULATION THEORY 23

waves, which lash the plant until the lamina together with

the meristem is torn off and there remain simply the stipe

and holdfast.

The stipe remains smooth for a few centimeters above

the large branching holdfast, this being evidently a per-

sistence of the smooth basal region of the young plant.

Some of the lower tubercles, however, disappear, so that

the smooth area now extends farther from the base than

originally. This portion is terete, but at a length of about

a decimeter the stipe becomes flat and strap-like about

four times as wide as thick.

In the younger specimens the proliferations from the

stipe and lamina are all small and not very numerous. In

the adult they enlarge very greatly and increase in num-

bers so as to become by far the most conspicuous feature

of the plant. The increase, both in number and size, is

most marked toward the growing point, those at the base

generally remaining small and scattered. Farther out

along the stipe they are found of all lengths up to about

12 em. and of various forms, as figured by Ramaley.

They stand as thickly as possible along the stipe; in some

places by actual count upwards of a hundred were found

in a single centimeter of its length. Of these only a few

were large and more than half less than a centimeter long.

Crowded as they are along the edges of the stipe, they

never arise from its faces, which are bare except for the

tubercles described above. The air vesicles are formed at

frequent intervals, providing sufficient buoyancy to keep

the plant floating just beneath the surface with the tips of

the proliferations emerging. When mature, they are

about 30 mm. long, with an average capacity of about one

cubic centimeter. Others of the outgrowths remain per-

manently small and become sporophylls. The outgrowths

on the lamina also increase in size and number, but become

neither so large nor so numerous as on the stipe. As

noticed by Ramaley, no bladders nor sporophylls develop

on the lamina.

Egregia becomes much branched before it is mature.

Although Ramaley suggests that the branching may have

dwarfed

ov.

i ia, base of small plant with the characters of the adult except

small number of branches, though only a few of those present could be

while the others were piled up in a mass to the left of the holdfast,

branch with a frilled margin. One fourth natural size

No. 505] KELPS AND RECAPITULATION THEORY 25

ah appearance similar to Lessonia, it is brought about by

a fundamentally different process, as has already been

noted by Setchell (’93) and by Reinke (’03), who figure

several stages in the development of a branch. Some of

the earlier proliferations, as stated above, soon develop

roughenings on their stalks like those of the main stipe

and take on the appearance of younger specimens of the

species (Fig. 31, b). This is the first external indication

of an important difference in the constitution of these out-

growths from the ordinary proliferations. For in them

has become differentiated a meristem independent of that

of the primary branch. They develop exactly as did the

main axis and soon become indistinguishable from it ex-

cept in the manner of attachment to the holdfast, possess-

ing all the structures which have been described for a

primary branch including other branches which in turn

go through the same process. After several such

branches have been formed there is a modification of the

process. The laminæ are dwarfed, while their margins

become conspicuously puckered and ruffled (Fig. 35, a).

Sometimes the ruffles are so pronounced as to completely

enfold the meristem. In such a branch proliferations

from the lamina appear very late, but the ruffle gives it a

similar aspect. The dwarfed condition of the laminæ per-

sists until the stipes become several centimeters in length,

when the usual relations of stipe and lamina become

manifest. Though roughening may appear on other

parts of the plant, the development of meristematic pro-

liferations is confined to the basal portion; branches do

not develop at a distance much exceeding 20 em. from the

holdfast. Around the base of any old plant there is al-

ways a large number of short branches in all stages of de-

velopment, but there are not often more than a dozen

long branches at any one time. The general appearance

of the numerous dwarf branches suggests that they may

not have a rapid development like the first branches, but

rather grow very slowly or lie dormant for a time like the

dormant buds of trees.

This method of branching is peculiar to Egregia and, as

26 THE AMERICAN NATURALIST [VoL. XLIII

Fie. Egregia grow in thick bed of kelp in which are prominent

Alaria oe a midrib) a g alii (in peat especially at right).

far as the writer knows, nothing like it occurs in other

kelps save in Thallasiophyllum. It is a matter of great

interest from several points of view. Morphologically it

gives the best reason for considering Egregia the highest

of the Alariatx, although that position would probably be

accorded it without question because of the differentiation

of the ordinary proliferations alone. The other members

of this subfamily produce outgrowths which function as

sporophylls, and in some of them, e. g., Eisenia, these be-

come the main photosynthetic areas of the plant. The

development of meristems in such outgrowths, leading to

the formation of branches, is the next step towards greater

complexity and the logical summit of the Alaria series.

But its greatest interest is from the ecological point of

view. The extreme length of the stipe pushes the grow-

ing point far out, where it is lashed severely by the waves

and frequently destroyed. Were the plant dependent on

this for its continued healthy existence, as in Laminaria, it

might easily be killed or at least handicapped for a con-

siderable part of the time by the loss of the blade until a

new one could be regenerated, as in many species of

Laminaria. But, should the older branches be injured,

these basal branches may develop at any time. By their

No. 505] KELPS AND RECAPITULATION THEORY 2T

presence the plant is practically possessed of a new basal

meristem supplementing and to a certain extent supplant-

ing the primary meristem. Once established in a favor-

able situation, a plant may therefore maintain itself in-

definitely, casting off old branches and developing new

ones continuously.

D. Hedophyllum

Because of the close similarity of the young stages of

Egregia and Hedophyllum sessile it will be of interest to

add a short description of the latter. It has already been

the subect of considerable study by Setchell, who has pub-

lished (’05) a discussion of its development well illus-

trated by figures. His paper, however, was written from

another point of view than the present, namely, the rela-

tionships of Hedophyllum sessile to the other species of

Hedophyllum and to Agarum and Thalassiophyllum.

Since from this standpoint the very young forms of Hedo-

phyllum are not important, Setchell was not particular to

obtain plants less than about 5 em. in length. But for a

comparison with Egregia the younger forms are of the

most interest. This species? is extremely abundant at

the Minnesota Seaside Station, outnumbering in individ-

uals any other kelp present on that coast. It grows at the

highest level occupied by the kelps, and in various situa-

tions as regards wave action.

Very young plants of Hedophyllum are difficult to dis-

tinguish with any certainty from Egregia and from the

various species of Laminaria growing in the same locality.

Hedophyllum is, however, much more abundant in adults

and juvenile forms, and as the specimens selected were

taken from beds composed mostly of Hedophyllum, the

probabilities are greatly in favor of a correct determina-

tion. The youngest plant (Fig. 5) measured approxi-

2 Though Puget Sound is given as the southern limit of the other Amer-

ican species, Hedophyllum subsessile, I have been unable to satisfy myself

of its occurrence at Port Renfrew. Two distinct series of juvenile forms

are, however, represented there, one with a narrow blade like those which

Setchell figures, and, as here described, another with a very broad, cordate

blade even when very young. What the relations of these may be to the

adult plant I have not yet fully determined.

37.

4S. 37-42. Hedophyllum, series of

Rp leases of the stipe

young plants mp heey e

origin of new ha

by the br ‘oadening of the tr ransition re

ıpteres higher and higher up the stipe. Four fifths payor size.

No. 505] KELPS AND RECAPITULATION THEORY 29

mately 2.3 mm. in length and the margin of the primitive

dise was nearly smooth. The edge of the lamina was only

one cell in thickness, but there were evidently several lay-

ers in the middle region and toward the base. In a spec-

imen 6.5 mm. long the holdfast had become distinctly

crenate around the edges and the one-layered lamina

had disappeared. The crenations had become much more

pronounced and had assumed the characters of primary

hapteres in a specimen 10 mm. long (Fig. 6).

By the time the plant reaches the length of an inch its

determination is not difficult. A specimen 28 mm. long

(Fig. 37) will serve for comparison with the youngest

Egregia described. The lamina is narrower and longer

than in that plant; the holdfast has not as yet developed

secondary hapteres and the stipe is shorter. Though the

stipe always remains short, it usually becomes longer

than is shown in this plant (about 5mm.). The narrow-

ness of the lamina is characteristic, but is not sufficiently

marked at stages earlier than this to render diagnosis

easy.

Soon after this stage secondary he begin to ap-

pear above the primitive holdfast. Though they arise in

circles as in the other kelps, they usually develop quite

unevenly in the young plant, some members of the circle

. becoming long, while others are yet mere knots on the

stipe. When a length of about 8 cm. is reached the stipe

begins to thicken and flatten. The transition region,

which has been sharply marked off, becomes less and less

distinct and the plant comes to consist of a lamina with a

cuneate base anchored by the holdfast (Fig. 42). This

condition sometimes persists until the plant has reached

a considerable size. More usually, however, the broaden-

ing continues and quickly brings about the adult condition.

When mature (Fig. 43), Hedophyllum sessile becomes a

broad, cordate, sessile plant anchored by a mass of hap-

teres at its base. Its lamina is torn to ribbons like a digi-

tate Laminaria, so that it may resemble one of the

kelps with true branching. The hapteres arise in circles

one above the other higher and higher up on the stipe

30 THE AMERICAN NATURALIST [Vouw. XLIII

Fic. aeg igege eit medium-sized plant showing the cordate lamina torn

by the A fully mature specimen would be a rosette so aon that its

rastai aon KU could not be made out, One fifth natural siz

until they obliterate it and even come to grow out from

the lamina itself. Thus there arises a thickened basal

portion of the lamina which forms a conical holdfast, as

in the other kelps, while new circles of hapteres may be

seen on its upper edge, growing out from the undifferen-

tiated lamina. By this process the holdfast region ex-

tends beyond the bases of the segments of the lamina so as

to give the old plant the appearance, not of one, but of

several independent lamine springing from a common

holdfast. Considering the similarity of the young plants

to Egregia, the divergence of the adults is very striking.

(To be concluded)

THE LARVA AND SPAT OF THE CANADIAN

OYSTER

J. STAFFORD, M.A., Pu.D.

MONTREAL

I. Tue Larva

In the summer of 1904, at Malpeque, Prince Edward

Island, on behalf of the Canadian Marine Biological Sta-

tion, I undertook to gather what information I could upon

the life of the oyster from the time it becomes a distinct

bivalve veliger to the time when it is recognizable by

every oyster fisherman as a spat oyster.

Brooks, of Johns Hopkins University, Baltimore, to

whom belongs the immortal. glory of having discovered

that American oysters are unisexual and that artificial

fertilization of the eggs and rearing of the larve are

possible, had worked out the spawning, fertilization,

segmentation, gastrulation and organization up to the

earliest microscopic free-swimming bivalve veliger, and

there was no lack of literature on oyster culture begin-

ning with macroscopic oyster spat of, let us say, the size

of one’s thumb-nail. But the intermediate stages,

mostly microscopic, seemed to be scarcely, if at all, known,

and there were many questions as to the time and place

where they might be found as well as to their anatomy

and comparison with other genera which required in-

vestigation.

The possibility of raising young oysters from eggs and

keeping them alive without admixture with other indi-

viduals or other species until one had seen the whole

series of continuous transformations into the adult

seemed next to impossible. I chose rather to learn to

recognize the larval oyster in plankton collections, a

method which had apparently received no attention. I

No. 505] THE CANADIAN OYSTER 33

EXPLANATION OF PLATE

a, anus; ad, anterior adductor muscle; bc, branchial chamber; bgl, byssus

land; c, chitin; e, eye spot; ne foot; g, gills; h, heel of foot; i, intestine;

l, liver; Ip, lower lip; m, ma ;-mo, mouth; oe, csophagus; og, supra-ceso-

phageal ganglion ; ot, otocyst ; z pirr adductor muscle; pg, pedal ganglion ;

s, larval shell ging Ha T "r (dissoconch, nepionic) ; sbc, supra-

ach

branchial cha ore st, sto $B ¥

Fros L 2 8,4, 8: erioa P fos adian oyster from bivalve veliger to

young spat, From the right side, drawn under the same conditions

throughout, Leitz microscope, oc. 3, obj. 2 (revolver). Zeiss

scare ae ual Drawing desk flush with stage and slanting

rhe at proper angle pi prevent distortio

sured under Leitz oc. 5 and obj. 4 A. a Leitz oc. microm.

val a Leitz stage microm

Frc. 1. m larva, aiias straight hinge ‘stage. .089 mm. high, .103 mm.

s 2. ere larva, early umbo stage. .138x.144 m

“ 3. Oyster larva, full grown. .31x.34 mm. Fig. v from the left side.

T 4. Oyster spat, with a pecking of the larval shell (prodissoconch) plainly

retained. .51x

wee 5. Oyster spat. Tee fon ge mm. The larval shell is .869 x.384

“ 6. Same as Fig. 1 drawn under oc. 3, obj. 4, for comparison with a Pies:

TA se

Fics. 7, 8, 9. Same as Fig. 3 drawn under oc. 3, obj. 4.

Fie. . Oyster nn ton the left, with several organs sketched go

S Same from the right, with dorsal hinge-line tilted towards the observer.

a è Pee from the left, with ventral gaping margin tilted esas the

er,

Fies. 10, 11, 12. ‘hehehe -hand drawings of full-grown living oyster larve, not so

highly magnified as Figs. 7, 8,

Fie. 10. atin larva, full-grown, from the left, velum protruded and partly

Tar Sanka ae Pae. attached to the slide by its fully expanded velum,

. Same Reik itis dabi surface, velum partly protruded.

ha p? 14, a “et 2” 13, 19, 20, 21. Sections of fall. -grown larve, drawn

Fie. 13. Pine memes sagittal (nearly), from the right. The foot being

Ere otkee Gk zm not split medially.

Porna seg f another

on he pret goths from above. a

eeper).

“17. Same (lower).

“ 18. Section frontal, transverse (anterior), from behind.

19. Same (medi

20. Same (near middle) of another series.

“21. Same (posterior) of same series as 18 and 19.

34 THE AMERICAN NATURALIST [Vou. XLII

had never seen an oyster larva or a young spat, but I

had followed the main stages in the life history of the

mussel,

Beginning my plankton-collecting at the end of the

first week in July, it soon became apparent that there

were many species of bivalve larve present in the water,

and in order to refer these with some precision to the

proper adults it would be necessary to carry on at the

same time a faunistic study of the Mollusea of Richmond

Bay. The commonest of these relative to my purpose

were found to be species of Mytilus, Mya, Venus, Clidio-

phora, Ostrea, Anomia, Mactra, Modiola, Pecten, Saxi-

cava, Macoma, Ensis, Yoldia, etc., and to find larvæ corre-

sponding to all of them was beyond my ability. Never-

theless, several larval forms gradually became familiar

and I referred them provisionally to certain adults. On

the twenty-fifth of July what I took for oyster larvæ

(Plate, Fig. 3) first decidedly claimed my attention and

as time went on I became more and more convinced of

the correctness of my surmises. But belief is not proof,

so I set to work experiments with a view to entrap oyster

larvæ on glass plates at a time when presumably the

larvæ become too heavy to swim with ease, settle towards

the bottom, creep about and select some clean, solid sur-

face upon which they fix themselves, and transform into

the youngest oyster spat. This was successfully accom-

plished on the sixteenth of August when I obtained a

minute oyster spat (Fig. 5) still preserving most evident

characteristics of the larva, but with the addition of a

rim of spat-shell, and later I found many’ minute spat-

oysters on various natural objects such as shells and

stones.

The plankton was collected in conical nets, made of fine-

meshed silk bolting cloth, attached at the broad end by

a rim of linen to an iron ring one foot in diameter, to

which were tied, at equal distances, three pieces of cod-

line, the other ends being brought together and secured

to a towing line. The small end of the net was also

No. 505] THE CANADIAN OYSTER 35

furnished with a linen rim in which was tied the neck

of a wide-mouthed bottle. To the towing line, in front

of the net, was fastened a sinker and the whole was

dragged through the sea-water, behind the little steamer

Ostrea, under reduced speed, for about a mile, when the

net was hauled up, the contained water carefully drained

through one side, after which it was dipped several

times right side up into the sea and raised so as to wash

all the plankton material down into the bottle. The

bottle could then be removed and corked, the net washed

by throwing it overboard again open, and other bottles

used for different places or different depths on the same

excursion.

In such a manner may be procured a wealth of plank-

ton material, but slight modifications in mode of operation

may be employed, depending upon the nature and object

of one’s research. The older bivalve larve are compact,

heavy, well protected, so that they will stand compar-

atively rough usage. By the time one reaches the labo-

ratory the great mass of the copepods may be dead and

sunk ,towards the bottom of the bottle, but underneath

this mass one can see the darker, granular, more sand-like

bivalves. These may be withdrawn by a glass tube and

emptied into a watch glass, the more superficial, lighter

things being again removed by a pipette. In this way

bivalve larve may be obtained, sometimes by thousands,

and almost entirely free from admixture with other ani-

mals, while among them, if collected at the proper time

and place, will occur oyster larve.

At Malpeque the full-grown, free-swimming, pelagic,

or more or less abyssal, or creeping larva of the oyster

(Figs. 3, 7, 8, 9) possesses a characteristic brownish-red

color—suggestive of the soil of its native island shores—a

shade which enables it to be immediately distinguishable

from every other bivalve larva with which it is associated.

The shell (prodissoconch) is asymmetrical, inequivalve

and inequipartite, the left valve being larger, more con-

vex and with a large umbo, the right one smaller, flatter

36 THE AMERICAN NATURALIST [Vou. XLIII

and with a moderate umbo, while the umbos have a

postero-dorsal position, projecting backwards and up-

wards and making the shell broader, deeper, squarer be-

hind and tapering but rounded in front. The largest

measure about .358 by .365 mm. in height and length, but,

owing to the different convexities of the valves, the

greater breadth above and behind, and the different de-

grees to which it may be tilted in this way or that, the

Same larva may vary much in apparent size and shape

according as to how it is presented to the observer.

The following are measurements of half a dozen larve

at different ages selected from a large number of records:

-131 x 138 mm., .138 x .144 mm., .207 x .241 mm., .241x .

276 mm., .296 x .345 mm., .345x.372 mm. The larval

shell of the young spat (Fig. 5) measures .369 x .384 mm.

and may be taken to represent the maximum size.

When mounted on a slide the larve are accustomed to

remain quiescent, and from their deep coloration are diffi-

cult to examine, but sometimes a more transparent one

permits certain organs to be traced. When freshly col-

lected and examined in a watch-glass of pure, cool water

from their native habitat, many of them exhibit the

greatest activity, swimming hither and thither or circling

round and round by means of the velum (Figs. 9, 10, 1,

12), a swimming organ which they protrude between the

antero-ventral margins of the shell-valves and expand in

a manner resembling the opening of an umbrella. The

margin of this is densely covered with large cilia, the

violent flapping of which propels the animal forwards

with the heavy body and shell suspended beneath the

velum. Jarring the watch-glass will cause the animal

to immediately withdraw its velum (Figs. 7, 8), at the

same time snapping the valves of its shell together and

dropping towards the bottom. Such observations illus-

trate the ordinary mode of locomotion and the response

to violent movements in the sea, for during heavy gales

a plankton net will take few or no larve near the surface.

An organ of immense interest to zoologists and of vast

No. 505] THE CANADIAN OYSTER 37

importance to the animal is the foot (Figs. 7, 8, 9), a

structure which I claim the privilege of having first rec-

ognized. The adult oyster is normally a quiescent, ses-

sile animal, having its left valve solidly cemented to a

rock or another shell. Under these conditions a creeping

foot, such as is possessed by a clam, a mussel, or a quohog,

would be of no service to the oyster, which in fact has

none. Influenced, no doubt, by this difference in the

adults, zoologists have been accustomed to think of the

oyster larva as being vastly different from other bivalve

larve, and repeatedly state that it has no foot, a miscon-

ception which justifies the view with which I started out,

viz., that plankton stages of oyster larve have been

neglected, embryologists jumping from early veliger or

phylembryo to late prodissoconch or early nepionic

periods. The foot, at the period we are studying, is well

developed, and is a most capable organ, by means of

which the animal can creep rapidly about and forcibly

flop its heavy shell from one side to the other. When

extended it is a long, slim, ciliated, muscular outgrowth

from the middle of the ventral surface of the body of the

larva, behind the velum. Its lower or posterior surface

sometimes appears flattened or even grooved lengthwise

(Figs. 18, 19, 21), and at a short distance from the base

of attachment there is a heel-like projection (Figs. 8, 9,

13, 14, 21) which doubtless contains the opening of the

byssus gland. When quiescent the foot is shortened, re-

tracted and closely tucked away behind the velum and

between the gills, but it can stretch so far as to perform

feeling movements over all parts of the body within the

shell and even bend up along the outside of the shell.

I have no doubt that at the end of the free-swimming

period, when the velum fails as an organ of locomotion

and the larva has to remain at the bottom, the foot then

proves to be of greatest service in freeing the little animal

from overwhelming sediment, creeping on to a solid sub-

stratum, clearing a suitable place for fixation, and. p

haps furnishing a transitory byssus.

38 THE AMERICAN NATURALIST [Vou. XLII

Lying against the inner sides of the shell-valves are

right and left folds of the mantle (Figs. 7, 18, etc.), the

free edges of which secrete the shell material and may,

like velum and foot, at times protrude beyond the margin.

Along each side underneath the mantle, past the base

of attachment of the foot to the body, lie the gills (Figs.

7, 8, 9, 19, 20, 21), extending backwards and downwards

to near the posterior edge of the shell; in the oldest free-

swimming larva there are about eight filaments in each

series, diminishing in size from before backwards, the

last ones being mere knobs; their lower ends are free,

but their upper ends spring from one continuous fold

that, behind the foot, joins its mate of the opposite side,

near the margins of the mantle. They correspond to the

right and left inner gills of the adult oyster.

The alimentary canal (Fig. 7) is much longer than the

body and in consequence has become folded, the greater

part lying to the left (Figs. 17, 19, 20) of the median

sagittal plane, but mouth, cesophagus and anus are

median. The mouth (Figs. 7, 13) is a funnel-shaped

opening lying immediately below and behind the velum,

to which its walls are attached and with which it is pro-

truded and withdrawn, so that it can only be functional

while the velum is to some extent expanded, when the ac-

tivity of its cilia may also contribute to the process of

feeding. The esophagus (Figs. 7, 13, 14, 19) lies be-

tween velum and foot in the median sagittal plane as

well as in or very near the median transverse plane of

the body. Here it passes dorsalwards, between the first

gill-filamets, and opens into the stomach with its large

brown lateral liver-sacs. The intestine passes back-

wards towards the right and then forwards towards the

left, when it again turns backwards and upwards in the

left umbo and finally downwards in the median plane over

the posterior adductor muscle.

In front and above the velum is an anterior adductor-

muscle (Figs. 7, 13, 18, ete.), running transversely be-

tween the valves, while below the posterior parts of the

No. 505] THE CANADIAN OYSTER 39

umbo is a larger, transverse posterior adductor muscle

(Figs. 7, 18, 21, ete.). Retractor fibers converge from

the velum to points in the umbos and there are intrinsic

muscle fibers in the velum, the foot and the mantle.

About the center of the animal, as viewed from one

side, and anterior to the gills are two conspicuous, black

pigment spots (eye specks, Figs. 3, 8, 9, 19) that, in

transverse sections of the larve, are found to be situated

right and left on the lateral walls of the body, just in

front of where their ectoderm becomes continuous on to

the outer surface of the first gill filament.

Immediately behind and below the pigment spots, but

on a deeper level, are right and left otocysts (Figs. 8, 9,

16, 19), each containing about a dozen otoconia. Sections

show them to be placed laterally in the proximal part of

the foot, close to where its ectoderm passes over on to the

inner surfaces of the first gill-filaments. Between the

otocysts, and of course behind the csophagus, are the

two connected pedal-ganglia (Fig. 19), and at the center

of the base of the velum, in front of where the esophagus

joins the stomach, is the supra-esophageal ganglionic

mass (Figs. 13, 14), protected in front by what appears

to be a yellowish-brown, flexible, chitinous layer which

gives origin to the muscle-fibers of the velum.

Transverse, sagittal, and horizontal sections (Figs.

13-21) of oyster larve, prepared in the usual way by

decalcifying the shells, staining in alum-cochineal, em-

bedding in paraffin, sectioning with a Yung microtome,

and mounting on a slide in Canada balsam, have contrib-

uted much towards an accurate understanding of the

relative positions of the organs.

Development naturally begins with small, simple eggs

and proceeds to larger and more complex larve. By the

time I had become oriented with regard to the latter and

proved to myself that they can actually metamorphose

into oyster spat it was of course too late for that season

to obtain and follow the growth of the youngest larve.

Examination of preserved plankton collections, however,

40 THE AMERICAN NATURALIST [Vou. XLII

although far from being as satisfactory as fresh, living

material, shows oyster larve (Figs. 1, 6) but little older

than the stages at which the observations of Brooks

closed, viz., six days old from the date of fertilization.

Brooks did not give measurements, so that it is impossible

to be exact on this point—I can only judge from the shape

and organization. Plankton collected July 11, 1904, be-

tween Curtain Island and Ram Island contains an

abundance of minute, transparent bivalve larve (phylem-

bryos) in what may be known as the straight-hinge stage

to distinguish them from the older larve with high umbos

(the umbo stage) that obscure and modify the hinge line.

A hasty and superficial observation of these combined

with the fact of their occurrence in proximity to oyster

beds might easily lead to the conclusion that they are all

oyster larve. But they are not. Many of them are

clams, a few are mussels, and one in a great number is

an oyster. A full statement of how I have determined

this would require too great a digression and will be

dealt with in another paper, but it results from a com-

parative study of bivalve larve in the different localities

of the Biological Station combined with researches into

the distribution of adult forms. Adults of the above-

mentioned genera are easily distinguished; the full-grown

larve less easily, for, since they bear little resemblance

to the corresponding adults, other marks of distinction

have to be selected; but the young larve are still more

difficult, for, according to the biogenetic law, the younger

they are the more nearly they resemble some stage of the

common original ancestor and of course approach one

another in likeness. Under such conditions the prac-

ticable, distinguishable characters may again be different

and require a more critical scrutiny. Since I first turned

my attention to bivalve larve I have found it necessary

to change my point of view and mode of procedure. One

can not safely trust to the eye in judging proportions,

but must resort to a definite and unvarying method of

measuring by means of ocular and stage micrometers.

No. 505] THE CANADIAN OYSTER 41

For each of the commonest species a table of lengths was

prepared, jumping only one of the smallest units of my

ocular micrometer at a time, and the heights were filled

in as individuals of these lengths occurred. Thus larve

of the mussel, the clam and the oyster, at the period we

are considering, measure as follows:

Length of

Length. Height. hinge-line.

Mussel o.oo ons Cit ie ee 15 10 11

CIA og OAA bare E 15 13 10

Oyster ... -oseiro sinoi i 15 13 7

—a table which will immediately make apparent the —

truth of many of my statements. The eye can easily per-

ceive a difference in the proportions of the mussel and

the clam, but it requires a certain refinement of judg-

ment to do the same for a clam and an oyster. Such an

oyster larva actually measures .103 x .089 mm. in length

and height, and has a short, slightly concave hinge-line

of scarcely half the length of the shell.

I have said that in collections of straight-hinge larve

but one in a great many is an oyster. A similar state-

ment might be made for any period in the larval existence

of the oyster. Upon one occasion when the umbo-stage

was most abundant I estimated that there was only one

oyster among twenty-five bivalve larve. Another time

I found that when the plankton net was towed at the sur-

face against a wind it caught about a quarter as many

oysters as in going back over the same distance with the

net sunk a few feet below the surface of the water.

I am of opinion that the study of plankton collections

for bivalve larve will be found a most useful help in de-

termining the breeding season—that is to say the height

of the breeding season. From the foregoing pages it

may be concluded that oyster larve are present in the

water from the eleventh of July to the first September,

and that oyster spat are present from the sixteenth of

August. This would seem to indicate that the second

half of August is taken up with the last stages of growth

of late larve and that the period of growth of the masses

42 THE AMERICAN NATURALIST [Vow. XLIII

falls between July eleventh and August sixteenth. Ta-

king it that the youngest larve I have described are little

older than those of similar shape and structure described

by Brooks, and allowing a possible retardation on account

of the climate, we should conclude that the eggs were de-

posited pretty close to the first of July. That spawning

does not take place much before this I judge from the

fact that in 1905, while I was at Malpeque preparing the

station for removal, I took plankton at intervals between

June seventh and twenty-sixth and this shows no oysters

and but few mussels and clams.

In the microscopic examination of the genital organs

for the purpose of determining the time of sexual ma-

turity, unless one examines a very great number taken

from many different localities, he may light upon an

abnormal number of individuals that are immature or

that have already spawned and so form a wrong concep-

tion as to the period of maximum spawning. Combina-

tion of both methods should give the best possible results.

I have purposely attempted to disregard the statements

of others in order to be entirely unbiased as to my results,

and from the facts of my own observations I am disposed

to think that the period of maximum spawning falls in

July, but that a few may spawn earlier and a greater

number may straggle in later. `

It is a matter of regret to me that it did not fall to my

lot to begin the study of oyster larva: during the first

summer at Malpeque, for then I could have used the

second summer to verify, fill in details, and follow out

suggestions. I have looked forward ever since for an

opportunity to do so, and this is my chief excuse for the

delay in publishing these results.

Chief points of importance resulting from the fore-

going work are:

1. Larval oysters are present suspended in the water

of Richmond Bay, Prince Edward Island, in July and

August.

No. 505] THE CANADIAN OYSTER 43

2. They may be taken in a plankton net at the surface

and at various depths.

3. All stages from the freshly fertilized egg to the

full-grown larva must be there.

4. The free-swimming period is, perhaps, considerable,

close on a month.

5. They feed and grow, while in the free-swimming

state, through a straight-hinge to an umbo-stage.

6. Normal fixation takes place when the larval shell

is about .38 m. in length, and then the spat period begins.

7. A metamorphosis occurs through loss of larval or-

gans as velum, foot, eye-spot, otocysts, ete., and a develop-

ment of new organs as spat-shell, additional gills, palps,

etc., is begun. |

8. The larval shell is asymmetrical, as is also to some

extent the contained body.

9. A foot, homologous with that of mollusks in general,

is present in the older larve.

10. The otocysts contain otoconia.

11. Pedal ganglia are present.

12. A byssus-gland is present.

13. Gills are present.

14. Eye-spots are present.

15. A rigid system of measurements has been used,

and a comparison of actual sizes at different periods of

growth introduced.

16. Numerous niceties of structure, shape, color, ac-

tivity, time, place, ete., are noted.

17. The spawning period has been limited.

18. Attention is directed to the importance of these

theses and observations as bearing upon problems and

methods of oyster culture.

LITERATURE

European works referring to the development of the oyster larva are

those of:

1. 1854. Lacaze-Duthiers. Mém. sur le dévelop. des Acéphales Lamellibr.

Comptes Rendus heb. des Séances de l'Acad. des Sciences,

Paris, XXXIX, pp. 102-106. Nouvelles observ. sur le

dévelop. des huîtres. Same vol., pp. 1197-1200.

2. 1882 (’83). Horst. A Contrib. to our Knowl. of the Develop. of the

44 THE AMERICAN NATURALIST [Vou. XLIII

Oyster (Ostrea edulis L.). Bull. U. S. Fish Com., II, pp.

9-167, 12 figs.

3. 1884 (’86). Horst. The Develop. of the Oyster daoerte edulis L.).

Rep. U. S. Fish Com., pp. 891-910, Pls. I and IT.

4. 1883. Huxley. Oysters and the Oyster Sethi. pem Illus. Mag.,

Oct. and Nov., pp. 47-55, 112-121.

American work must be conid to have originated with Brooks, whose

discoveries inspired investigators at home and abroad and pointed the way

to possibilities and methods of culture that were ably carried forward by

Ryder, Winslow, Rice and others. Of the = papers, reprints, summaries,

etc., published by Brooks I mention but o

5. 1880. Brooks. Development o of i Tegai Oyster. Rep. of the

. of Fish. of Maryland, pp. 1-18, 10 pls.

6. 1882 (’83). Brar, On the Mode of Fixation of the Fry of the

Oyster. Bull. U. S. Fish Com., II, pp. 383-387, 9 figs.

7. 1882-83 (’84). Ryder. A Sketch of the Life-history of the Oyster.

Ann. Rep. of the U. S. Geol. Surv., pp. 317-333,

$ 2.

8. 1882 (’84). Ryder. The Metamorphosis and Post-larval Stages of

Development of the Oyster. Rep. U. S. Fish Com., X,

pp. 779-791

9. 1884. pw A Contrib. to the Life-history of the Oyster. Fisheries

Fishery Industries of the U. S., Sec. I, pp. 711-758

10. 1882 a ` Wiot Rep. of Exper. in the Artif. Prop. of Oysters.

Rep. U. s. Fish Com., X, pp. 741-762.

11. 1889. Jackson. The Develop. of the Oyster with Remarks on Allied

ae Proc. Bos. Soc. Nat. Hist., XXIII, pp. 531-556,

12. 1890. a Phylogeny of the Pelecypoda. Mem. Bos. Soc. Nat.

Hist., IV, pp. 277-400.

Canada has pie “little towards a PERSA pa of oyster development.

Three rather unpretentious articles are know

13. 1896 (796). Prince. Peculiarities in a i gine of Oysters. Special

13.

14. 1904. ee The Canadian Oyster. The Canađian e of

Science, Montreal, IX, July, pp. 145-156, Figs. 1

15. 1905. Stafford. On the Larva and Spat of the he ‘Oyster:

THE AMERICAN NATURALIST, Boston, pp. 41-44. (Prelim-

inary to this paper.)

` BRIEF NOTES AND CRITICISMS

Brooks (No. 5, p. 25, of the preceding list) says: ‘‘ All my attempts

to get later stages than these failed, ete.’’ He refers to his Figs. 44 and

understand the claim that they might develop to this

stage in twenty-four hours.

Horst (2, 165; 3, 904) was unable to get stages older than his Fig. 12,

a straight-hinge shell of .16 mm., which according to Ryder (7, 791) would

be equivalent to an American laren of half this length, i. e., little younger

than my Fig. 1. He adds: ‘‘I have also been diskpoakebed in my attempts

No. 505] THE CANADIAN OYSTER 45

o procure oysters in these E of development by means of catching

Wes floating about in the sea

yder’s papers (6, 383; 7, 328-9; 9, 727) are not easy to correlate on

iscre

I conclude that Ryder had seen two stages is catchy of the game age

as two I have figured. His Fig. 1, magnified 183 times measures 14.5 mm.,

which would give the larva an actual length of .08 mm. His Fig. 3, mag-

nified 96 times, measures 29 mm. and similarly gives the young spat an

actual length of .3 mm. But his were both fixed, and in fact it was this

property which in Ryder’s methods afforded the chance of their ise

observed. He appears to have believed that the larger one (C. io

marked the proper stage of fixation but that under ‘‘favorable circum-

stances’? larve of the size of the smaller might become fixed and then

grow to the size, shape and structure of the larger, at which time they

first become spat. Considering that he obtained the small ones but once,

that they were attached in no regular position, and that the one figured was

was abnormal, due to unfavorable artificial conditions and that the normal

process is for the larva to remain free until it reaches the size of the

prodissoconch in the umbo of the young spat shell. Ryder’s view of the

duration of the free-swimming period as limited to twenty-four hours comes

nearer to a possibility if we remember that he doubtless had in mind this

ease of abnormally early fixation. A similar statement might be made with

regard to the sentence ‘‘The difference in magnitude between the oldest

artificially incubated fry seen by me and that of the youngest fixed embryos

which I coliected is very small.’’ These also agree very well with the larve

raised by Brooks and by Horst. He never saw larve between these two

stages in size. This represents a period during which the larve had to

grow to nearly four times their former diameter and undergo a very great

increase of organization. If the smaller stage can be raised as in Brooks ’s

making a month for the complete larval development. This time according

to Brooks, Ryder and others pages be reduced by very warm weather. It is

just possible that too high a temperature of small isolated quantities of

water may be one of the adverse conditions which have prevented larve æ from

being raised beyond this stage. In nature they not only have a broader

source of food supply but they ean also sink into cooler water.

Winslow (10, 757) thought that the oyster larva is predisposed b fix

itself very soon after — and when the shell is developed to a

slight extent the larve in quiet in one place at the bottom. I can.

believe that they do not a grai own efforts travel very far from the

of their origin for their locomotion is largely a cireling or to-and-fro move-

ment, but while suspended in the water they may be by tida

currents,

Jackson (12, 300) wrote: í Between the stage Fig. 25 and our next

stage, PI. XXIV, Figs. 1, 2, there is a blank in the knowledge of the

46 THE AMERICAN NATURALIST (VoL. XLIII

development of the oyster. It has not been described in the European

species, and all attempts to obtain it in our own species have failed. In

artificial confinement the oyster dies at this stage.’’ His Fig. 25 is Huxley’s

eut of a straight-hinge larva. Figs. 1, 2 of Pl. XXIV are Jackson’s own

youngest stage of the spat, obtained August 4, 1888, on glass put in a

drain-pipe trap on a sand-bar in Buzzard’s Bay. It was firmly attached

magnified 120 diameters the actual length of the recently free larva, now

a fixed nage was nearly .31 mm

e (13, 13) makes the statement: ‘‘I we dee: many small embryo-

acne it miles from any known oyster areas,’’? but as no measure-

ents or drawings accompany the paper one can not judge of their size

or age.

McBride (14, 151, 153) says: ‘‘ Judging from the size of free-swimming

larve caught by the tow-net .... During the latter part of the month

(August) the waters were swarming with larve which, from their exact

greement in shape and appearance with the larve of the European oyster,

were doubtless the later stages of the free-swimming young of the Malpeque

oyster. . . . The later larve which were captured by the tow-net are

A ned possessing a operon pee to the shell. ., : Fig. 4. Late

Larva e Oyster captured by the Surface-net.’’ The so-called late

larve are in mete ight of my deo: in reality somewhat early larve.

oes not correspond with what I found at the same place the succeed-

ing year. Upon examining Fig. 4 I find that it is not an oyster larva.

The measurements are 83, 70, 51 mm. which if divided through by 5.53

will give 15, 12.6, 9.2 mm. as the length, height and hinge-line. Referring

this to the = of comparison of a mussel, a clam and an oyster at this

period, on r page, it becomes evident that it could have been no

other thar! ps pisn of the clam

The shell of the larva was held to be perfectly symmetrical by Ryder

(6, 384; 7, 329; 8, 787; 9, 727), but Jackson (11, 541; 12, 312) observed

in his youngest spat that the lower left valve was ieee a deeper than

the upper right one.

A foot has been mentioned by. Duthiers, Horst, Brooks and

Jackson. Lacaze-Duthiers (1, 105) said: ‘‘En avant de 1’anus un appendice

pen saillant simule un rudiment de pon > Horst (2, 162) stated that

**A foot-like prominence is developed, whereby the animal assumes some

likeness to a young gastropod.’’ Brooks (5, 53) wrote: ‘‘Near the center

of the ventral surface—the top of Fig. 32—there is a well-marked and

constant a of the body wall, which occupies the region which,

in most molluscan embryos, gives rise to the foot, and which may a.

be regarded as a page ae of that organ.’’? In the same paragra

referring to the same figure he mentions ‘‘the primitive digestive cavi

and on page 68 ‘‘the primitive digestive tract opens by a wide appa $

No. 505] THE CANADIAN OYSTER 47

No one would claim that the part referred to in these extracts is the same

organ as I have described in very much later larve. Referring to Horst’s

1882 Fig. 6 or 1884 Fig. 10 we observe that it is only an asa prom-

inence, since it is bounded below by the invagination of the pute and

above by that of the shell- — et further Pe disappears later on as in

1882 Fig. 10 or 1884 Fig. 14. on (12, 302) affirmed: its nearest

approach to a foot known in the urs oe is that shown in Fig. 24,

p. 299 (after Horst), and I discovered no traces of a foot in my youngest

specimens.’’ The best that can be said about all references to a foot at

these early stages is that, by comparison with other species, they indicate

the place where, at a later date, through growth and specialization, a foot

as well as oo other bt are formed between the mouth and the anus.

“*Otoe . here recorded so far as I am aware, for the first time,’’

was written ge MeBride i 14, DN: but a pasa statement occurs in Lacaze-

thiers of 1 p- , ‘‘Enfin j’ai vu apparaitre les-otolithes . . .

quelques uaa aie fe mouvements . . . dont personne n’avait même

constati ]’existence.’’ MecBride’s ‘‘ Fig. 3. Larva of Oyster, six days old’’

shows two otocysts, and in the near, se one is a single otolith. There is

something wrong about this. The oyster has about a dozen otoconia in each

otocyst, a tact which Lacaze-Duthiers was perhaps aware of when he wrote

the words ‘‘ quelques globules. 7? Tf McBride’s Fig. 3 moe Coe

his observations then it is not an oyster but a clam which I kno

a single otolith in each otocyst. Clams are very abundant sities the Sash

immediately below where the station stood at Malpeque and it is a reason-

able inference that this larva was taken up in the water used. On the same

page occur the words ‘‘shell-gland . . . mistaken by Brooks for the gut.’’

‘rhis was first pointed out by Horst in 1882.

Regarding the presence of a byssus Ryder (6, 383; 7, 329; 9, 758) was

doubtful. Horst (3, 907) believed that he had noticed a small byssus.

J ackson irs 303) concludes that the oyster does not have a byssus at

any peri

The a of gills as well as the mention of symmetry in the following

extract is only one of the indications that Ryder’s (8, 787) conception of

an oyster larva was constantly associated with the straight-hinge "e

rical larva and the young bene is the absence of gills in the senior

and ie presence in the latter . . . two gill pouches . . . outer gill pouches. ’’

Jackson (12, 303) studied the gills of the youngest spat stage and knew

them to be the right and left innermost gills of the adult. He also men-

tions palps but says little about them. Jackson’s study of the gills was so

thorough and in general his observations were so exhaustive, considering

the limited material, that it is worth while being cautious before suspecting

him of an oversight, but I can not help thinking that what he took for

palps was nothing but the foot. His figures (12, Figs. 1, 2) show it imme-

diately behind the already shrunken velum and overlapped by the anterior

gill-filaments. The two transverse lines may have been due to its being

erumpled up, = oe split towards the end of the ventral surface may

have g

MONTREAL, Oct. 8, 1908.

SHORTER ARTICLES AND CORRESPONDENCE

SOME NOTES ON THE TRADITIONS OF THE NATIVES

OF NORTHEASTERN SIBERIA ABOUT THE

MAMMOTH

THE traditions of the Yukaghir very often mention the mam-

moth. They have a special name for him, xolhut. The spirit

of the mammoth (xélhut-Aibi—which means the mammoth’s

shadow), like the spirits of many other animals now living, ap-

pears in the rôle of a guardian spirit of certain shamans. A

shaman assisted by the spirit or soul of a mammoth (áibi means

shadow, spirit, and also soul) is regarded as the most powerful.

According to this notion one might say that there was a time

when the mammoth was a contemporary with man.

One Yukaghir tale relates to an episode in which the souls of

two shamans (father and son) were riding on the back of a

mammoth’s shadow.

Another tradition tells of the disappearance of the mammoth.

The creation of the mammoth was a blunder of the Superior

Being. In creating such an enormous animal the Creator did

not take into consideration the size of the earth and its resources.

Our earth could not stand the weight of the mammoth and its

vegetation was not sufficient to feed the mammoth race. The

mammoth fed on tree trunks which he ground with his teeth,

and in a short time the whole North of Siberia was deprived of

trees. Hence is the origin of the northern tundra. In the be-

ginning the earth had the form of an even plain, but by his

weight the monster animal in moving about caused the formation

of valleys and ravines in which rivers originated. In swampy

or sandy places the mammoth sank into the ground and disap-

peared under the earth, where he froze during the winter. Often

in the hole over him the water gathered into a lake. In this

way the mammoth gradually disappeared from the earth’s sur-

face. This is why now whole cadavers of the animal are to be

found in the frozen soil.

Among the Russianized Yukaghir of Nishnekolymsk I noted

a tradition on the disappearance of the mammoth of a biblical

No. 505] SHORTER ARTICLES AND CORRESPONDENCE 49

coloring. ` In the time of the flood Noah had to take besides the

other animals a pair of mammoths. But when one of them put

his fore legs on the raft he almost turned it over. Noah became

terrified and quickly pushed his raft away from the monster.

Thus all the mammoths perished.

Among the Chuckchee the mammoth is believed to be the |

reindeer of evil spirits. He lives underground and moves about

through narrow passages. When a man sees a mammoth tusk

protruding from the ground he must dig it up; otherwise the

tusk will sink back into the ground. Once, it is said, some Chuk-

chee found two mammoth’s tusks protruding from the earth.

They performed incantations and the mammoth came into sight.

They lived on the mammoth for a whole winter.

A similar belief I found among the Tungus. On my way

from the Okhotsk Sea to the Kolyma District over the Stanovoi

Mountains I once spent a night on the banks of the lake

‘‘Kémemnan’’ or the ‘‘Mammoth’s Lake.’’ Concerning the

origin of this name I was told that some time ago a family of

wandering Tungus encamped beside the lake. When they arose

in the morning they saw two pair of mammoth tusks appearing

from under the ice. The Tungus fled on their reindeer horror-

stricken, from the lake, but they all died except one small boy in

their next encampment.

' It is interesting to note that in the languages of the above-men-

tioned tribes the mammoth ivory is called ‘‘mammoth horn’’

(e. g., the Yukaghir call it ‘‘xd6lhut-6nmun,’’ i. e., horn or antler

of the mammoth), and not tusk or tooth, as if the people of

to-day have no proper conception of the appearance of the mam-

moth. On the other hand, the natives know that the Siberian

mammoth had a thick hairy tail and the oes grew from the

mouth.

The export of mammoth-ivory from Siberia is still considerable.

From the northern part of the Yakutsk Province alone (in

greater part from the New Siberia Islands) the Moscow market

receives 1800 pud (i. e., 64,800 English pounds) every year.

The weight of a pair of tusks is from 200 to 500 pounds, with an

average of 360 pounds. Hence the yearly exportation of ivory

of the Yakutsk Province is equal to the tusks of 152 mammoths.

When we take into consideration the period of 200 years since

the exportation began we find that tusks of 25,400 mammoths

were sent out of the Yakutsk Province. It must be added that

MA BOT. CARDEM

50 THE AMERICAN NATURALIST [Vow. XLII

in former years the export was considerably greater than it is

now.

WALDEMAR JOCHELSON.*

AGE OF TROTTING HORSE SIRES

THEORIES of heredity deduced from statistics always require

critical examination. Statistics of heredity, like those of other

subjects, offer striking possibilities to searchers for support of

preconceived theories. I have recently completed some work

with the trotting horse records, the result of which may be of

interest inasmuch as it does not corroborate the results of other

work in the same field.

Mr. C. L. Redfield has recently published a dynamic theory

of development based largely on the statistics of the age of

sires of average and of preeminent trotting horses. He as-

sumes that by exercise a horse acquires ‘‘dynamic development,’’

which facilitates speed and is transmitted. Dynamic develop-

ment will naturally be greater in old than in young horses; in

horses that are campaigned than in those not prepared for

racing. Other things being equal, an old stallions’ colts would

inherit greater dynamic development and be faster than other

colts sired by the same horse while younger. He found that the

average trotting-bred horses, represented by the first one thou-

sand animals listed in the Index Digest, were sired by stallions

at an average age of 9.43 years. Representing the superior

trotting horses by the 2.10 list, he based his calculations on the

males appearing in four generations of each pedigree. The

average time between generations in the male line in this in-

stance was found to be 14 years; the sires were therefore prac-

tically 13 years old at the time of service. The difference be-

tween 9.43 and 13 years as the ages of sires of average and 2.10

horses is a very striking one and forms the basis of argument

for the transmission of the dynamic development attributable

to advanced age.

The matter of inheritance of dynamic development produced

by racing, I propose to discuss at another time.

* Leader of the Riabouschinsky Expedition to Kamchatka, the Aleutian,

Komandorski and Kurile Islands. Organized by the Imperial Russian Geo-

graphical Society. From 1900 connected with the Jesup North Pacific

expeditions of the American Museum of Natural History. This contribu-

mte be of very great interest both to ethnologists and zoologists.—

No. 505] SHORTER ARTICLES AND CORRESPONDENCE 51

The following is from Mr. C. L. Redfield’s recapitulation of

his theory published in the Horse World, issue of February 27,

1906:

I said that I took one thousand registered stallions, alphabetically,

from the Index Digest of the Register, and calculated the ages of their

sires at the time when these registered stallions were foaled. From

these I determined that the average time between generations in the

male line was 10.43 years, which would give the average age of sires

as 9.43 years at the time of service. I then said that, making all

reasonable allowances for errors, the average time between generations

in the male line might be set down as between 10 and 11 years, and

that this period might be used as a standard in testing the age part

of the theory. So far no one claims to have tested the accuracy of

my calculation; no one claims that the figures I gave were wrong; and

no one has said that these figures can not properly be used as a stand-

ard; yet if I am to be controverted, one of the first things to be done

is to dispute the accuracy of my standard.

I then took the entire list of 2.10 trotters as an appropriate class

of animals to be used in testing the inheritance of dynamic develop-

ment, and I calculated the ages of their male progenitors for four

generations. The number of animals involved was over five thousand

and I gave the average time between generations in the male line for

the production of 2.10 trotters as being approximately 14.00 years.

his is an average of nearly 40 per cent. over the standard average

determined from the Register, and my explanation of this remarkable

difference was that it indicated the inheritance of acquired dynamic

development. So far no one has disputed the accuracy of my com-

putation and no one has attempted to give any other anaon of

such an unusual divergence from the natural order of thi

Am I right or am I wrong? If I am wrong will some one please

come forward with a better explanation.

It is to be noted that in the case of the average horses repre-

sented by the first thousand in the Index Digest, the ages of

their immediate sires only were computed, and found to average

9.43 years; whereas in the case of the horses in the 2.10 list

all the sires appearing in the first four generations were brought

in. Assuming 14 years to be correct for the average time be-

tween generations, this carries us back 56 years.

t horse that was uniformly successful as a sire of

speed was Hambletonian 10 foaled in 1849. In the sixties this

horse’s reputation as a sire of speed was established and he

did heavy stud service until the time of his death in 1873.

52 THE AMERICAN NATURALIST [Vow XLIII

This was the real beginning of the trotting breed of horses.

During the later years of the life of Hambletonian 10 and sub-

sequent to his death his sons were patronized by owners of

well-bred and speedy mares. The more successful of these

sons naturally received heavy stud patronage as long as they

remained serviceable. When the grandsons of Hambletonian

10, with two generations of speed-producing sires back of them

and out of selected female ancestry, came into service, it was

found that in many instances they sired faster colts than did

their sires or grand sire. Only in more recent years were

representatives of popular families used for stud purposes in

earlier life.

In view of these facts, I deem it unfair to base a conclusion

upon a comparison of two results, one of which (13 years as

the average age at time of service of sires in four generations

back of horses in the 2.10 list) comes largely from an investiga-

tion of the formative period of the. breed, while the other (9.43

years as the average age at time of. service of immediate sires

of average horses) mainly refers to more recent conditions. -

If the figures 9.43 and 13.00 had been derived by similar

means their value would be unquestionable. A really fair com-

parison would demand the same procedure in one case as in

the other. ` Either all sires in the four generations of the thou-

sand horses should be used or else bez the immediate sires” o

those in the 2.10 list.

; Assuming 9.43 to be correct for the average age of the s sires

when they produced the first one thousand horses in the Index

Digest, I have attempted to secure a similar figure for the

immediate sires of the horses in the 2.10 trotting list as pub-

lished in ‘‘Yearbook,”” Volume 22. The list published in that

volume contains 279 horses. In thirty cases the records failed

to show the horse’s age. In seven cases the age of the sire is

not given. This leaves 242 of the 279 in the list for which the

ages are shown.

Below are given two extremes and the average for 242 horses

regarding which there exists no uncertainty :

No. 505] SHORTER ARTICLES AND CORRESPONDENCE 58

of Sire

Horse Foaled Sire . Sire foaled at time of

Wentworth 2.0414 1903 Superior 1879 23.

Dolly Dillon 2.064% . 1895 Sidney Dillon 1892 2.

Average for 242 horses

Of the 242 horses, 1 was sired by 2 year old stallion

11 were sired by 3 year old stallions

17 were sired by 4 year old stallions

30 were sired by 5 year old stallions

19 were sired by 6 year old stallions

21 were sired by 7 year old stallions

21 were sired by 8 year old stallions

25 were sired by. 9 year old stallions

14 were sired by 10 year old stallions

17 were sired by 11 year old stallions

ye stall

pa]

2 were sired by 23 year old stallions

Taking 9.43 years as the average age of sires of average horses

and substituting 14 by 9.41 years as the average age of sires

of 2.10 trotting horses, it is evident that the records do not

reveal any superiority of the old sire over the younger one.

; . R. MARSHALL.

OHIO STATE UNIVERSITY.

THE OCCURRENCE OF BATRACHOCEPS ATTENUATUS

AND AUTODAX LUGUBRIS IN SOUTHERN

CALIFORNIA

RECENTLY the salamander Autodax lugubris has been found

near Los Angeles, Cal.* So far as I know, until this animal

was reported no salamanders were known to live in southern

California out from the mountains, although in the mountains

and eafions of the foothills here and there as far as San Diego,

another characteristic Pacific-coast salamander, Diemyctylus

‘1 Miller, L. H., Am. Nart., Vol. XL, pp. 741-742.

54 THE AMERICAN NATURALIST [Vou. XLII

torosus, has long been known. I have found it commonly in

a number of cañons of the San Gabriel range and heard of it in

other parts of southern California; in some places it seems to be

quite abundant.

Two years ago last spring, just after the winter rains were

over, a salamander was brought into the laboratory. It had

been found in a garden near an orange orchard in Claremont,

Cal., about four miles from permanent flowing water of the

mountains and several hundred feet above subterranean water;

the only water that could come to it was from rains and from

irrigation. It was a full-grown specimen of Batrachoceps

attenuatus. Some weeks later in the early part of June another

full-grown specimen was brought in from another locality near

Claremont. This time it was from a large, dry, uncultivated

area and was found under a stone. A few hundred feet from

the place where it was found there was a deep well. I after-

ward learned that ten or more years earlier a pond of consider-

able extent had covered this place.

During the winter of 1906-7 two small salamanders were sent

to me from San Diego. They were half-grown B. attenuatus.

The identification of these four specimens extends the known

range of this species some hundreds of miles.

In May of this year a number of other salamanders were ob-

tained from well up in the mountains north of Claremont, a

number of specimens of B. attenuatus and two full-grown speci-

mens of Autodax lugubris. The specimens of Autodax were

found in a narrow crevice in a high rocky wall. This sort of a

location is quite different from the other places where Autodax

has been found.

Judging from the character of the land and water of Lower

California it seems quite probable that one or all of the species

mentioned in this note may oceur farther south than San Diego.

ILLIAM A. HILTON.

PoMONA COLLEGE, CLAREMONT, CAL.

NOTES AND LITERATURE

EXPERIMENTAL EVOLUTION

The Effect of the Environment upon Animals.—The second vol-

ume of Bachmetjew’s great work, ‘‘Experimentelle Entomo-

logische Studien’’ (1), will be welcomed by all who are inter-

ested in the effect of external factors upon organisms. It wil

doubtless surprise many that, although dealing almost ex-

clusively with insects, the author reviews more than 1,200

papers. Even so, seasonal dimorphism, protective coloration

mimicry and parthenogenesis are only touched upon inci-

dentally as it is intended to take them up in a later volume.

Furthermore, practically none of the literature since 1905 is

included. The first 600 pages of the book are taken up with

short abstracts arranged in chronological order within appro-

priate groupings. These abstracts are then rearranged—often

being repeated verbatim—in the ‘‘theoretical part’’ according

to their bearing upon special problems. Although the author

states his opinions concerning the significance of the data thus

brought together, the reader is largely left to draw his own

deductions, as it seems to have been the aim of the author to

make a handbook to the literature of experimental entomology

rather than a dissertation in support of his own views. There

can be little room for doubt in view of this immense amount of

evidence that environmental factors are responsible for many—

perhaps most—of the variations and aberrations among insects.

However, there is, as yet, little proof that they produce heritable

modifications such as we believe real species to be made of. In

this regard Tower’s work with Leptinotarsa is a remarkable ex-

ception. Practically all the results so far obtained, while inter-

esting and important, belong to physiology rather than to

evolution.

Federly is continuing his work concerning the effect of ex-

ternal conditions upon the seales of Lepidoptera. A recent paper

(2) reviews the literature of albinism and gives certain original

observations. True albinism seems to be rare. However, cases

of ‘‘pseudo-albinism,’’ due to a reduction in the size of the scales

but not in the intensity of the pigment nor in the number of

56 - THE AMERICAN NATURALIST [VoL. XLIII

pigment-bearing scales, are fairly common. This condition

probably arises through an inhibiting action of the environment

upon the ‘‘scale mother cells.’’

An interesting case of an environmental effect which is not

easily reversed is given by Marchal (3). Lecanium corni, a

scale insect, becomes L. robiniarwm when reared upon Robinia

pseudo-acacia instead of its normal food plants, but the reverse

experiment does not succeed.

Salamanders are a close second to insects as favorite material

for the experimental study of the effects of the environment.

Powers has contributed a valuable paper (4) on the causes of

variation in Amblystoma tigrinum and promises proof that cer-

tain of these are inherited or at least perpetuated by reason of

inheritance. Differences in the amount and character of the

food produce remarkable modifications in the structure of the

animal. If, as is hinted, variations in the appetite are inherited,

we should have an interesting case of indirect transmission of

characters. Among the conclusions the author says:

“ Specific characters, in species which vary as A. tigrinum varies,

are, after all, strongly determined by environing conditions. There is

nothing new in this. But the study of this species seems to me to lend

it new weight and confirmation. If the broad head and large teeth of

the cannibal are acquired characters—and they conform to the defini-

tion of such—what are the narrow head and smaller teeth of the cus-

tomary daphnid-feeder? Are these specific and congenital characters?

They are more frequent, more “ typical ” in the species, but I am forced

to conclude that they are so chiefly because daphnids are numerous and

constitute a convenient and stimulating food. And the same may be

said of nearly all specifie characters; so readily are they modified by

a changed environment that we must conclude they are, in reality,

equally determined even by an unchanged environment. Congenital

tendencies in such species are not definitely specific, but only in-

definitely specifie. In this species, indeed, they are not always even

definitely generic.”

Mr. Powers naturally points out that many of our catalogued

species’’ are merely ontogenetic and believes that ‘‘the zoologist

must soon admit that the final test of many species must lie in

the rearing, and that, too, under controlled conditions.” We

may, perhaps, go further and say that this is the test of all

species, but that it is not worth while to apply the test in all cases.

It is probably true that many of our so-called species are not

orthodox species but are the results of reversible physiological

No. 505] NOTES AND LITERATURE 57

changes in the soma. However, they are the species as we have

them and it seems a hopeless task to go through the animal

kingdom and sort the named forms into ‘‘ontogenetic’’ species

and ‘‘orthodox’’ species. We shall probably be forced to recog-

nize that the names we give are merely convenient shorthand

descriptions of certain organisms, some of which are extremely

stable as to form and coloration, others not so much so. Our

problem is, then, to find out as much as we can about the causes

which bring about the differences which we note.

A new journal, Zeitschrift fiir Induktive Abstammungs- und

Vererbungslehre, has just been started. With Baur, Correns

and other authorities as editors, much is to be expected of it.

Frank E. Lutz.

LITERATURE

1. 1907. Bachmetjew, P. Experimentelle Entomologische Studien vom

physikalisch-chemischen Standpunkt aus. Zweiter Band.

Einfluss der äussern Faktoren auf Insekten. xevi + 944 pp.

with 25 plates. Sophia.

2. 1908. Federley, Harry. Uber den Albinismus bei den Lepidopteren.

Acta Societatis pro Fauna et Flora Fennica, XXXI, No. 4.

3. 1908. Marchal, P. Comptes rendus Soe. de Biologie, July. LXV,

No. 24.

4. 1907. Powers, J. H. Morphological Variation and its Causes in

Amblystoma tigrinum. Studies from the Zoological Labora-

tory, the University of Nebraska, No. T1. TT pages with 9 -

plates.

EXPERIMENTAL ZOOLOGY

The Influence of the Size of the Egg and Temperature on the

Growth of the Frog.'—What determines the difference in size of

two animals? It is the difference due to greater or less number

of cells, or, perhaps, to a difference in the size of their cells?

Does the animal grow by adding more new cells, or by increasing

the old cells? These are some of the problems which confront

the student of the phenomenon of growth in the animal and

plant kingdom alike.

The paper, the subject of this review, contains an account of

experiments which attempt to throw light upon these problems.

‘Einfluss der Eigrésse und der Temperatur auf das Wachsthum und die

Grösse des Frosches und dessen Zellen. “Von Robert Chambers, Arch. fiir

Mikroskopische Anatomie und Entwicklungsgeschichte, Vol. 72, Part 3, pp-

607-661, 1908,

58 THE AMERICAN NATURALIST [Vor. XLIII

Chambers experimented with eggs of Rana temporaria and R.

esculenta, and his object was to determine how the initial size

of the eggs and temperature affect the size of developing embryos.

He found that the eggs of both species show considerable varia-

tions in size, that are in no way connected with the prevailing

temperature of the locality from which those eggs are collected.

The average size of eggs varies not only with the species or

locality, but also with each individual frog. Furthermore, eggs

laid by one frog also present variations in size, which, in one

case, were 1.8 mm., 1.2 mm., 1.15 mm., and 1.05 mm. in diameter.

The eggs measuring 1.15-1.20 mm. were most abundant.

Contrary to what one might expect, there is no relation be-

tween the size of frogs and the size of eggs which they lay, and

small frogs with large eggs as well as large frogs with small eggs

are frequently found. i :

In the first place Chambers undertook to determine the rela-

tion of the size of an egg to the rate of its development and sub-

sequent growth of the embryo. He divided eggs of a single frog

into lots according to their sizes, and found, on rearing those,

that small eggs have a tendency to develop slightly faster than

large eggs. This tendency is marked only in the early stages,

for as the tadpoles commence to feed those developing from large

eggs grow faster and pass through metamorphosis sooner.? On

rearing eggs of two lots, one containing eggs of large and uni-

form size, the other containing eggs of various sizes, it was found

that the size of tadpoles varied considerably in favor of the

former. Besides, the tadpoles of the first lot have all meta-

morphosed in course of two weeks, while two months have elapsed

before the tadpoles of the second lot had all metamorphosed.

There is one point in connection with this experiment on which

unfortunately Chambers gives no information, and yet it may

alter the conclusion drawn from the experiment. He mentions

that there were 70 eggs in the first lot and 100 eggs in the

second lot. If the eggs of both lots were distributed in an equal

number of dishes there must have been fewer eggs of the large

size than of the mixed sizes to each dish. The difference in the

rate of development and in the size of tadpoles might have been

therefore caused by the more or less crowded condition of the

eggs, and not by the large or small initial size of the eggs. In

fact, Chambers resorts to this factor of the number of eggs de-

* See page 7.

No. 505] NOTES AND LITERATURE 59

veloping in a dish to account for the fact that in experiment

with eggs of 1.81 mm. and 1.20 mm. in diameter, the eggs of both

sizes developed equally fast. The less crowded condition, he

thought, compensated in that case for the small size of the eggs.

The question as to whether or not the initial size of the egg is

a determining factor in the rate of development seems to me,

therefore, still an open question.

Next, Chambers investigated the influence of the size of the

eggs upon development at different temperatures. Eggs of R.

temporaria of the same size were reared separately under tem-

peratures ranging from 10° to 25° ©. He found in this case

of R. temporaria, which spawns early in the spring, that both

large and small eggs develop at low temperatures, but only the

large eggs are capable of resisting higher temperatures. On the

contrary, in case of R. esculenta, which spawns in May and June,

all eggs develop well at high temperature (19°-27° C.) and only

the large eggs develop at low temperature (10°-12° C.).

Chambers therefore concludes that large eggs are more efficient

in withstanding extremes of temperature.

He found, furthermore, that when eggs of the same individual

are reared, under equal conditions of temperature, eggs larger

or slightly smaller than those of normal size (the size of the

majority of eggs is considered the normal size) develop to ad-

vanced stages, but the extremely small eggs invariably die out

while yet in the early stages of development. In a lot of eggs,

where the normal size was 1.5 mm. only 8 out of 23 eggs meas-

uring 1.15 mm. in diameter and none of those measuring 1.05

mm. reached an advanced stage. Chambers is strongly inclined

to think that there is a set limit to the size of the egg of a given

species, beyond which it can no longer vary without losing its

power of development. But the failure of abnormally

eggs to develop can also be interpreted differently, since the

exceptionally small size may be due to the circumstance that the

eggs have not yet attained full maturity.

Chambers states that large tadpoles develop always from large

eggs, and that the ratio between the volumes of different eggs

is maintained more or less constant during the early stages of

development, i. e., the tadpoles are in the same relation to each

other, as regards volume, as the eggs from which they have

develo

Regarding the cellular elements of the young developed from

60 THE AMERICAN NATURALIST [Vor. XLIII

large or small eggs, Chambers found from his study of sections

of various organs and tissues (lens, ear-vesicle, rectum, epl-

dermis, cartilage, muscle-fibers and blood-corpuscules), that the

size of the cells of a tadpole or young frog is in direct relation

to the size of the examined individual. This in general ogre

with the results from my own work, which I hope to publish in

the near future, on the cells of large and small salamanders.

Since, as was shown above, the size of the embryo depends

upon the size of the egg from which it develops, Chambers draws

the further-conclusion that the size of cells of an animal is deter-

mined by the initial size of the egg from which it has developed.

In another experiment, where eggs of R. temporaria were

reared at two temperatures of 10° and 25° C., the tadpoles of the

first set (10° C.) metamorphosed two months later than those

of the second set (25° C.), but the young frogs developed in the

medium with a low temperature (10°) were fully one and one

half times as large as those developed at a higher temperature.

Whether this large size was due to the low temperature or to the

fact that the tadpoles had been growing two months longer be-

fore metamorphosing, this point is not made clear. However, on

examining cells from the epidermis and rectum Chambers found

that the differences in total size of frogs, developed at a high

or a low temperature, extend also to their cells, so that large

specimens have correspondingly larger cells than small specimens.

But the initial size of the eggs and the temperature of the

medium are not the only factors determining the size of the tad-

poles and young frogs, because large and small individuals may

develop even from eggs of uniform size and under similar con-

ditions of temperature. What has been found in regard to the

variations in size of the eggs may of course be also true in case

of the sperms, which might thus be a factor determining the size

of the young. At any rate, Chambers made an interesting

observation that tadpoles developed from eggs of the same size

begin to vary only after the supply of yolk has been exhausted

and they have commenced to take in food. It is not improbable,

therefore, that the variations in size result either from an insuffi-

cient amount of food available for some tadpoles, as is the ease,

for instance, in growing starfishes,? or else the tadpoles may

consume unequal amounts of food under different conditions

of health.

* Mead, A. D. On the Correlation between Growth and Food-supply in

Starfish. Amer. NAT., Vol. 34, No. 397, pp. 17-23, 1900.

No. 505] NOTES AND LITERATURE ; 61

It is a matter of some interest that Chambers maintains that

the cells of large and small individuals developed from eggs of

uniform diameter are not of different but of the same size.

Thus he leads us to believe, and in fact he states it explicitly

at the close of his paper, that the principal factor determining

the size of cells of an animal is the initial size of the egg from

which it developed.

. Without giving mention to some objections to this general con-

decide which might be made on the basis of Chambers’ own

experiments, I wish to point out that the figures of cells given

in the text do not carry conviction, and, so far as I was able to

make out, they do not bear out Chambers’ contention. In the

drawings of cells of blood-corpuscles, epidermis and rectum,

which Chambers thinks to be of equal size, I find on careful ex-

amination that the cells are different. Of course, actual meas-

urements of the cells could make this matter clear, but, un-

fortunately, there are no measurements given in the paper.

' The introduction to the paper contains a résumé of a few

works in one way or another related to the problem. This résumé

of facts so widely seattered throughout the literature will doubt-

less be found useful.

The third part of the paper is devoted chiefly to extensive

theoretical considerations and does not therefore come within

the scope of the present review

In conclusion I should like to’ call attention to some defects

of a technical character, which obscure the meaning of the

text and frequently confuse the reader. In the explana-

tion to Fig. 1 it is said, for instance, that I marks a culture

developed from eggs of similar size, and. II marks those de-

veloped from eggs of different and not ascertained sizes. But

in the text referring to this Fig. 1 it is said that ‘‘Kulture II

wurde mit Eiern angefangen, welche von gleicher, ausgesuchten

Grösse waren.’’ Which of these data, whether those found in

the text or in the explanation to the figure, are the correct ones

the reader is at loss to know, while the understanding of this

point is important. On p. 635 we find reference to Fig. “A”

and Aa in text Fig. 2. As a matter of fact this reference was

found to apply to Fig. a and a* in the Text-fig. 5. In Table

V in the third column the date of spawning is given as June 5,

and the date of the first examination of the developing aubryos

is June 3.

62 THE AMERICAN NATURALIST (Vor. XLII .

There is, however, a more vital contradiction in the text. On

p. 620 in a discussion of the facts presented in Table I we read:

‘*Die kleineren Eier zeigten eine geringe Neigung sich schneller

zu entwickeln.” On p. 647 referring again to the Table I we

read: “In den Furchungs- und Gastrula-Stadien zeigen die

kleinen Eier die Tendenz, sich wenigerschnell zu entwickeln, als

die grösseren Eier.’ And further on, p. 647, and referring

again to the Table I, we read: ‘‘ Da wir nun aber gesehen haben,

dass die grossen und kleinen Eier sich gleichgut und gleichrash

entwickeln (s. Tabelle 1) ete.”

Thus it appears that the small eggs develop somewhat faster,

and slower than the large eggs, and just as well as the large

eggs!

SERGIUS MoRGULIS.

PARASITOLOGY

Cestodes of Birds.—Fuhrmann has recently published (Zool.

Jahrb., Suppl. 10, Heft 1) a most valuable monograph on the

Cestodes of Birds. He had at his disposal all the material from

the great European museums and from the private collections

of prominent European helminthologists, so that the work is

vastly more valuable than a mere literary revision with studies

on limited personal collections. In 1782 Goze described 14

species of Tenia from birds; in 1819 Rudolphi listed 54 certain

and 30 uncertain species, and in 1850 Diesing recorded 81 cer-

tain and 28 questionable species. Von Linstow’s Compendium

der Helminthologie and Nachtrag in 1889 gave references to 230

bird cestodes from 340 host species. In this investigation Fuhr-

mann had material from 200 more species of birds at his disposal

and recorded in all some 500 cestode parasites from them. When

one considers that 12,000 species of birds are known and Cestodes

have been collected from 540 only, it is clear that many more

new forms are to be expected; these are to come most prom-

inently from extra-European lands. North America which

Fuhrmann notes as relatively unexplored, will contribute its

share and I may add that investigations in this field are already

in finished manuscript as studies from my own laboratory.

Some of the general conclusions which Fuhrmann has reached

as a result of his 12 years of work in this field are of wide inter-

est. The distribution of cestodes among the various group of

birds shows that a given species occurs only in a given group

No. 505] NOTES AND LITERATURE Rete

of birds and hence is typical of it. Birds with similar food habits

shelter often radically different cestode parasites both in species

and in genera. On the other hand, related birds of different

food habits often show similar genera among their cestode guests

even though the species differ. A zoogeographice survey of the

cestodes in the various groups of birds shows a sharp contrast

between the species found in different regions and furnishes

strong evidence of the value of parasites as aids in zoogeographic

investigations. In this respect the cestodes are unquestionably

of the greatest value in the light of Fuhrmann’s studies.

It would be impossible to abstract the systematic portion of

Fuhrmann’s paper. Many of the doubtful and insufficiently

deseribed species of other authors are here positively evaluated

after comparison of the original material. Each genus is char-

acterized on the basis of the author’s investigations and the type

species designated. The other species are also listed with refer-

ences to the appropriate literature and to all known hosts. The

faunistic section contains a complete list of the hosts with their

cestode parasites and a record of the geographic distribution.

A good alphabetic index of families, genera, species and

synonyms, together with a full bibliography, closes the paper.

Though not stated specifically, the monograph appears to be con-

fined to the Cyclophyllidea and all will await with great interest

the publication by this author of further studies dealing with

other groups of avian cestodes.

A paper by Plehn (Zool. Anz., 33: 427) on a blood-inhabiting

cestode designated Sanguinicola, is of especial interest both from

the morphological and from the biological standpoint. The

animal occurs in the blood system of Cyprinid fishes, being most

frequently found in the bulbus arteriosus, and was originally

described in 1905 as an aberrant rhabdocel. In structure it

agrees well with the few monozoic cestodes classed together as

Cestodaria and often separated from other cestodes. The species

does not reach full development in this host, or at least in the

blood vessels, since no specimens with fully developed female

organs have yet been found. The author conjectures that it is

withdrawn by some blood-sucking parasite and undergoes fur-

ther development in that host. In view of the size of the worm

and its evident inability to reach even the superficial arterioles,

such a life cycle seems at least unlikely. The confessedly im-

perfect account of the structure of this worm makes any dis-

64 THE AMERICAN NATURALIST [Vor. XLIII

cussion of its precise genetic relationships unwise and the

proposed phylogeny of parasitic flatworms based upon it has

therefore only a purely suggestive value.

The Harben lectures for 1908, which were delivered by Pro-

fessor George H. F. Nuttall, of Cambridge, England, have been

printed (Jour. Roy. Inst. Pub. Health, July-September, 1908).

The topics covered are the ticks and the diseases which they

transmit to man and domestic animals; the diseases are among

the most important of those caused by animal parasites especially

and are due to spirochetes, piroplasma and filaria. Nuttall’s

account, which is the most complete résumé available in this field,

is notably lucid and scholarly in presentation.

Henry B. WARD.

ei ba A Sahin

SN al ae Ry anh Som Se as ge es A ei ae ee ee as ane bos ard te Ue aie ey eee

The Jou rnal of Geology

; a

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THE

AMERICAN NATURALIST

AEN: <, - Febeuay, We

CHARLES DARWIN AND THE MUTATION

THEORY*

CHARLES F. COX

Proressor Huco De Vrigs, in his American lectures

on ‘‘Species and Varieties, their Origin by Mutation,’’

claims that his work is ‘‘in full accord with the prin-

ciples laid down by Darwin,” and boldly asserts that

Darwin recognized both ‘mutation’? and individual

Variation, or ‘‘fluctuation,’’? as steps towards what Pro-

fessor Cope aptly called ‘the origin of the fittest.” I

think many persons unfamiliar with Darwin’s writings

must have been much surprised on reading Professor De

Vries’s statement, for it has been a common belief in the

scientific world for many years that the establishment

of the mutation theory would be fatal to Darwinism, or

would at least take from it its most original and essential

features. The perpetuation of this impression has been

due, very largely, to Mr. Wallace and certain of his fol-

lowers who have steadfastly refused to admit the possi-

bility of the evolution of species and varieties by any

form of saltation and have insisted more uncempromis-

ingly than did Mr. Darwin himself upon the exclusive

efficiency of selection exercised upon small, recurring in-

dividual fluctuations. In fact, many of Mr. Wallace’s

views have out-Darwined Darwin and yet Darwin, some-

. what unreasonably, has been held responsible for them.

* Presidential address at the annual meeting of the New York Academy

of Sciences, December 21, 1908.

"Preface by the author, p. ix.

* Second edition, p. 7.

66 THE AMERICAN NATURALIST [Vow. XLII

Accordingly Darwin has been charged with a radicalism

which he never professed and champions of a supposed

Darwinism have felt called upon to do battle against

theories which he never distinctly repudiated or which

he might even have accepted if he had known of them.

Thus, Professor Poulton, in his recently published i

‘Essays on Evolution,’’ attacks with great severity, un-

der the name of ‘‘ Batesonians,’’ believers in the validity

of mutation as a factor in the process of evolution,

although, as he admits, ‘‘mutation was of course well

known to Darwin.’ Now, I think we are justified in

saying that if mutation was ‘‘known’’ to Darwin, it must

have been, and still is, a veritable fact; and, if evolution

is a universal law of nature it can not, in that case, ex-

clude mutation. We, therefore, who believe in general

evolution are compelled to decide for ourselves whether

mutation has taken place and is now occurring; and we

who are really Darwinians—that is to say, we who believe

that Darwin set forth correctly the essential steps in the

evolutionary process—are interested in knowing whether

he actually recognized the fact of ‘‘discontinuous varia-

tion’’ or mutation, and, if so, how he fitted it into or

reconciled it with his system. :

The essential factors in organic evolution, from the

Darwinian point of view, are: (1) Variation, (2) inherit-

ance, (3) over-reproduction, (4) competition, (5) adapta-

tion, (6) selection and survival. The general explanation

of these factors is as follows:

1. All organisms vary continually and in every part

of their structures—that is to say, no two individuals are

exactly alike in any particular.

2. Nevertheless, characters anatomical, physiological

and psychological are in general transmitted to descend-

ants; in other words, progeny essentially resemble their

parents.

3. More animals and plants are brought into the world

than can possibly find means of subsistence.

*** Essays on Evolution,’’? 1908, p. xviii.

No. 506] DARWIN AND MUTATION THEORY 67

4. There results competition for what subsistence there

is, or, as it is otherwise called, a struggle for life.

5. Since out of all the variations that occur in the

constitutions or characters of organisms some must

happen to be in directions to give their possessors an

advantage, or advantages, in procuring the means of

existence, as compared with other individuals of the same

class, some of the new-born animals and plants are best

adapted to their surroundings or ‘‘conditions of life.’’

6. These best-adapted forms (‘‘the fittest’) will win

in the struggle for life and are figuratively said to be

selected; the unfit will in the end be exterminated. The

result is the origination (evolution) of new classes of

organisms out of the old ones and their substitution for

the earlier classes or groups.

Not one of these factors was originally discovered by

Darwin, but he first discerned their interrelations and

bound them together by a consistent and convincing phi-

losophy. He, for example, was not the earliest observer

of progressive change in the organizations and external

characters of animals and plants, but no one before him

had had the insight to perceive that this changeability

was the manifestation of a force great enough to burst

the artificial limits placed about the groups called species

and varieties and to enable them to transform themselves

into other groups better adapted to the changing environ-

ment. Before Darwin’s time every one, of course, had

ocular demonstration of the fact that there were differ-

ences between individuals and that descendants were not

in every respect like their ancestors. There was uni-

versal belief, however, that these variations never ex-

ceeded certain narrow boundaries built round species

like inviolable walls. Curiously enough, Darwin, who

first broke down these boundaries, took the same indi-

vidual variations as the principal foundations of his

selection theory. He assumed—for he admitted that it

could not be proved for any particular case—that these

small differences, which ordinarily fluctuate about a cer-

68 THE AMERICAN NATURALIST [Vou. XLIII

tain average for each species or variety, are at times

accumulated to such a degree as to carry all the members

of the group forward to a new center of oscillation so as

to constitute in effect a new group. It was not at first

his idea that a single individual, or a small number of

individuals, might occasionally develop evolutionary

force enough to over-leap suddenly the imaginary bound-

ary and become the nucleus of a new colony beyond;

that is the substance of the mutation theory; and, while

I think it ean be shown that Darwin more or less clearly

recognized the possibility of the occasional origin of-

permanent races by this method of saltation, there can

be no doubt that he entertained a strong bias in favor of

the evolution of species generally by slow and minute

steps.

As far as cultivated plants and domesticated animals

were concerned Darwin was willing to grant the widest

range of variation and the most abrupt changes, but as

to animals and plants in a state of nature he was more

sparing of his admissions that great and sudden depart-

ures from specific types might occur. This tenure of

the two points of view was due to his belief that the

domesticated animals and plants were more variable than

feral forms because of the direct influence of man upon

their surroundings and habits of life. Inasmuch as his

theory of the origin of species through natural selection

is founded on analogy between the deliberate operations

of breeders in choosing the most desirable individuals

of their flocks and gardens, and the inevitable sifting out

of feral forms through their competition with one another

in the struggle for existence, it is difficult to see why Mr.

Darwin hesitated about carrying the comparison to its

logical conclusion in the admission that what we now

call mutations, but what he referred to as ‘‘spontaneous

variations,’’ ‘‘sports,’’ ‘‘monstrosities,’’ ete., stand upon

substantially the same basis in nature as in cultivation.

According to the present-day views of scientific students

of animal and plant breeding, I understand, there is no

No. 506] DARWIN AND MUTATION THEORY 69

good evidence that cultivated plants and animals are more

subject to wide and abrupt variations than are those

living under natural conditions. On this point Professor

De Vries remarks that ‘‘it is not proved, nor even prob-

able, that cultivated plants are intrinsically more variable

than their wild prototypes.’ As to distinct mutations,

we must remember that plants and animals preserved

and nurtured by man are constantly under the eyes of

many thousands of pecuniarily interested observers,

while those in a state of nature are closely studied by but

a handful of scientific investigators. We must also

remember that it is only within a few years that a small

fraction of these men of science have been led to look for

cases of mutation, while all gardeners, farmers and

breeders have had the inducement of financial profit to

watch for marked variations among their stock and to

preserve such variations if desirable. The naturalists

specially interested in evolutionary questions are exceed-

ingly few in number, but their field of research is im-

mensely extended and varied. The number of those who

have raised animals and plants for gain, however, has

always been large, though the number of forms which they

have been called upon to consider have been relatively

few. The two fields have consequently had exceedingly

different degrees of scrutiny. But since De Vries and

others opened up the subject an astonishing number of

clearly proven cases of mutation have been discovered

in very various classes of organisms, just as numerous

paleontological evidences of evolution have been brought

to light as a consequence of Darwin’s turning men’s

minds in that direction.

As I have already intimated, Mr. Darwin undoubtedly

dealt with numerous cases of mutation among domesti-

cated animals and plants, and they gave him little or no

intellectual disquietude. In his work on ‘‘ Animals and

Plants Under Domestication” he gives a long catalogue

of ‘‘spontaneous variations” or ‘‘sports,’”” many of which

* ‘í Species and Varieties, their Origin by Mutation,’’ 2d ed., 1906, p- 66.

70 THE AMERICAN NATURALIST [Vou. XLIII

he freely acknowledges were the starting points of new

and constant races; and there is good reason to believe

that some of them peated before the animals and plants

which underwent the sudden changes had been actually

brought under domestication or cultivation; in fact, that

the mutations themselves suggested to men the directions

in which their breeding operations should be conducted.

For example, take the case of the tumbler pigeon: Mr.

Darwin remarks concerning this that ‘‘no one would ever

have thought of teaching or probably could have taught,

the tumbler pigeon to tumble,” but it seems to me

obvious that no one would ever have thought of accumu-

lating slight variations in the direction of tumbling. It

is much more reasonable to suppose that the birds which

were artificially selected as the progenitors of the present

race of tumbler pigeons actually tumbled—that is to say,

they were mutants. As to the origin of domestic races

through modifications so abrupt as to have been thought

by Darwin entirely independent of selection, he gave it

as his judgment, as late as 1875, that

It is certain that the Ancon and Mauchamp breeds of sheep, and almost

certain that the Niata cattle, turnspit and pug-dogs, jumper and

frizzled fowls, short-faced tumbler pigeons, hook-billed ducks, &e.

suddenly appeared in nearly the same state as we now see them. So it

has been with many cultivated plants.°

Now, considering, as I said a moment ago, that Mr.

Darwin’s theory of the origin of species by means of

natural selection has for its main foundation-stones facts

derived from observation of the effects of man’s selection

among domesticated animals and plants,—without which,

indeed, he admitted that he had no actual proof of the

operation of natural selection,—it is difficult to realize

the state of mind which led Mr. Darwin to add to the

sentence just quoted the following caution:

The frequency of these cases is likely to lead to the false belief that

natural species have often originated in the same abrupt manner. But

*** Origin of Species,’’ 6th ed., 1882, p. 210.

° Ans. and Pints. Under Dom., 2d ed., 1875, Vol. II, pp. 409-10.

No. 506] DARWIN AND MUTATION THEORY 71

we have no evidence of the appearance, or at least of the continued

procreation under nature, of abrupt modifications of structure; and

various general reasons could be assigned against such belief.

I am not aware that Mr. Darwin ever presented definite

and convincing reasons for the sharp demarkation here

attempted and, indeed, I can not see how the state of

knowledge in his time could have justified it, for, as I

have already stated, mutations had not been much looked

for among feral plants and animals. In fact, by abso-

lutely excluding from his theory the idea that mutation

could occur under nature, Mr. Darwin, by the force of

his great authority and influence, would have prevented

‘a careful weighing of the pros and cons, if the human

mind had at that time been prepared to weigh them. It

is practically only since the Darwinian hypotheses have

themselves been subjected to prolonged scrutiny, and

since De Vries and a few others entered upon detailed

experimental examination of this particular subject,

within the last twenty years, that the matter can be said

to have received anything like scientific treatment.

But, after all, Darwin was not wholly prejudiced

against a belief in the occurrence of mutations in nature,

for he several times expressed the opinion that the estab-

lishment of such a fact would in some ways be an ad-

vantage to the evolution theory. For instance, in a

letter of August, 1860, to W. H. Harvey, he says:

About sudden jumps: I have no objection to them—they would aid

me in some cases. All I can say is that I went into the subject and

found no evidence to make me believe in jumps; and a good deal point-

ing in the other direction.”

This of course refers to discontinuous variations in

organisms under natural conditions, for he had certainly

found evidence to make him believe in similar variations

among domesticated animals and plants. I think Mr.

Darwin never specified the directions in which a belief

in mutation would be a help to him, but, from casual

remarks made in various places, I faney he had in mind

t €t More Letters, ”? Vol. L p- 166. See also, Life and Letters, ’’ 1886.

Vol. II, p. 333. ;

72 THE AMERICAN NATURALIST [Vov. XLII

the way in which it would ease him over that difficult

subject, the imperfection of the geological record, and

would reconcile him with the physicists and cosmogonists

who were not disposed to allow him the lapse of past time

he required for the evolution of species by the accumu-

lation of successive minute or ‘‘insensible’’ individual

variations. But I will not discuss these points now.

What I wish to dwell upon at the moment is that Darwin

recognized and accepted the fact of mutation among ani-

mals and plants under domestication, although it is worth

while to repeat the statement that some of his cases

probably happened in a state of nature, since they oc-

curred at the very beginning of, and were the points of

origination for, man’s selective operations. As Mr.

Darwin himself says: ‘‘Man can hardly select, or only

with much difficulty, any deviation of structure excepting

such as is externally visible,’’*> which means, as I take it,

that nature usually presents some quite manifest varia-

tion before artificial selection begins, and this must have

been the case at the time when man’s first choices were

made, particularly when half-civilized and unobserving

men began the cultivation of our now domesticated ani-

mals and plants. It is necessary to remember, however,

in .this connection, that the mutation theory, as inter-

preted by De Vries, requires for its starting point only

a variation which marks a distinct separation of a form

from its parent group without connecting gradations, and

not necessarily any great or extraordinary change of

characters; for, as he says: ‘‘Species are derived from

other species by means of sudden small changes which,

in some instances, may be scarcely perceptible to the

inexperienced eye.’’? None the less it remains true that

man is apt to select only striking variations and hence

Mr. Darwin, in treating of ‘‘sports,’’ or what we should

now call mutants, among cultivated plants and animals,

usually speaks of them as wide departures from type,

or, rather, he deals only with such as are large deviations.

*** Origin of Species,’” 6th ed., p. 28.

***Plant Breeding,’’ 1907, p. 9.

No. 506] DARWIN AND MUTATION THEORY 73

Even when treating of organisms in a state of nature,

however, he admits that ‘‘there will be a constant tend-

ency in natural selection to preserve the most divergent

offspring of any one species.’ Returning to the sub-

ject of artificial selection, Mr. Darwin says:

No man would ever try to make a fan-tail till he saw a pigeon with

a tail developed in some slight degree in an unusual manner, or a pouter

till he saw a pigeon with a crop of somewhat unusual size; and the

more abnormal or unusual any character was when it first appeared the

more likely it would be to catch his attention.”

In another place he says:

It is probable that some breeds, such as the semi-monstrous Niata

cattle, and some peculiarities, such as being hornless, &e. have ap-

peared suddenly owing to what we may call, in our ignorance, spon-

taneous variation; . . . During the process of methodical selection it

has occasionally happened that deviations of structure more strongly

pronounced than mere individual differences, yet by no means deserving

to be called monstrosities have been taken advantage of.”

Now, in his work on Animals and Plants under Do-

mestication Darwin has given a long list of these widely

varying forms from each of which has descended a new

race conforming to his own test of a species, namely its

possession of ‘‘the power of remaining for a good long

period constant . . . combined with an appreciable

amount of difference.’* One of the most striking of

these cases is that of the ‘‘japanned’’ or ‘‘black- shoul-

dered” peacocks which have occasionally appeared ‘‘sud-

denly in flocks of the common kind,’’ which ‘‘ propaan

their kind quite truly,” which, according to good a

thority, ‘‘form a distinct and natural species,” and which

tend ‘‘at all times and in many places to reappear. hes

Mr. Darwin rejects the idea that these birds are the re-

sult of hybridization and reversion and declares in favor

” <í Origin of Species,’’ 6th ed., 1882, p. 413. :

“ Fbi, p. 25.

es Animate and Plants under Domestication,’’ 2d ed., 1875, Vol. I,

p- 96. See also, Vol. II, pp. 189-90.

"<í More Letters of Charles Darwin,’’ 1903, Vol. I, p.

“<í Animals and Plants under Domestication,” 2d ee 1875,

pp. 305-7.

Vol. I,

74 THE AMERICAN NATURALIST [Vow XLII

of their being ‘‘a variation induced by some unknown

cause,’’ and says that ‘‘on this view the case is the most

remarkable one ever recorded of the abrupt appearance

of a new form which so closely resembles a true species

that it has deceived one of the most experienced of living

ornithologists.’’ In all points this case agrees with the

modern idea of a mutation, even in the respect that it

comes from a family of birds not usually considered very

variable.

Concerning fowls Mr. Darwin remarks that

Fanciers, whilst admitting and even overrating the effects of crossing

the various breeds, do not sufficiently regard the probability of the

occasional birth, during the course of centuries, of birds with abnormal

and hereditary peculiarities. Whenever, in the course of past centuries,

a bird appeared with some slight abnormal structure, such as with a

lark-like crest on its head, it would probably often have been preserved

from that love of novelty which leads some persons in England to keep

rumpless fowls and others in India to keep frizzled fowls. And after

a time any such abnormal appearance would be carefully preserved from

being esteemed a sign of the purity and excellence of the breed; for on

. this principle the Romans eighteen centuries ago valued the fifth toe

and the white ear-lobe in their fowls.”

But Mr. Darwin’s cases of what we must regard as

saltations are not confined to the animal kingdom. We

might easily cull from his list numerous more or less

pertinent examples under the peach, plum, cherry, grape,

gooseberry, currant, pear, apple, banana, camellia,

crategus, azalea, hibiscus, althæa, pelargonium, chrysan-

themum, dianthus, rose and perhaps other plants. Con-

cerning useful and ornamental trees he says: ‘‘ All the re-

corded varieties, as far.as I can find out, have been sud-

denly produced by one single act of variation,’ and as

to roses, he remarks on their marked tendency to ‘‘sport’”’

and to produce varieties ‘‘not only by grafting and bud-

ding, but often by seed,” and quotes Mr. Rivers as saying

that ‘‘whenever a new rose appears with any peculiar

character, however produced, if it yielded seed’’ he ‘‘ex-

ibe

Animals and Plants Under Domestication,’’ 2d ed., Vol. I, pp. 242-4.

* Tbid., p. 384

No. 506] DARWIN AND MUTATION THEORY ris)

pects it to become the parent of a new family.” In this

connection Mr. Darwin called attention to the now well-

known fact that the mutative tendency is an inheritable

one by citing the case of the common double moss-rose,

imported into England from Italy about the year 1735,

which ‘‘probably arose from the Provence rose (R. centi-

folia) by bud-variation,’’ the White Provence rose itself

having apparently originated in the same way.” He

also called attention to the significant fact that many

abrupt variations were not to be attributed either to re-

version or to the splitting-up of hybrids. Thus he de-

clares:

No one will maintain that the sudden appearance of a moss-rose on a

Provence rose is a return to a former state, for mossiness of the calyx

has been observed in no natural species; the same argument is ap-

plicable to variegated and laciniated leaves; nor ean the appearance of

nectarines on peach-trees be accounted for on the principle of reversion.

Further on in the same work he says:

Many cases of bud-variation . . . ean not be attributed to reversion,

but to so-called spontaneous variability, as is so common with cultivated -

plants raised from seed. As a single variety of the chrysanthemum

has produced by buds six other varieties, and as one variety of the

gooseberry has borne at the same time four distinct kinds of fruit, it

is scarcely possible to believe that all these variations are due to

reversion. We can hardly believe . . . that all the many peaches which

have yielded nectarine-buds are of E parentage. Lastly, in such

cases as that of the moss-rose, with its peculiar calyx, and of the rose

which bears opposite leaves, in that of the Imantophyllum, &c., there

is no known natural species or variety from which the characters in

question could have been derived by a cross. We must |. all

such cases to the appearance of absolutely new characters in the bu

The varieties which have thus arisen ean not be distinguished by any

external character from seedlings. . . . It deserves notice that all the

plants which have yielded bud- Savini have likewise varied greatly

by seed.”

Now, Darwin was here treating of saltations among

cultivated plants, but it is instructive to read in this con-

*** Animals and sien Under Domestication,’’ 2d ed., Vol. I, pp. 405-6.

* Ibid., Vol. II, p.

<< Animals oak Pia Taje Donsstioaiiih 2d ed., Vol. I, Pp.

439-40,

16 THE AMERICAN NATURALIST — [Vou. XLII

nection the following passage in which he prepares the

ground for a belief in the possibility of similar abrupt and

wide variations under natural conditions. He remarks:

Domesticated animals and plants can hardly have been exposed to

greater changes in their conditions of life than have many natural

species during the incessant geological, geographical, and climatal

changes to which the world has been subject; but domesticated pro-

ductions will often have been exposed to more sudden changes and to

less continuously uniform conditions. As man has domesticated so

many animals and plants belonging to widely different classes, and as

he certainly did not choose with prophetic instinct those species which

would vary most, we may infer that all natural species, if exposed to

analogous conditions, would, on an average, vary to the same degree.”

But now let us take a specific example of spontaneous

variability which deeply impressed Mr. Darwin. It is

a ease which was brought to his attention in 1860 by Pro-

fessor W. H. Harvey concerning Begonia frigida, as to

which Mr. Darwin says:

This plant properly produces male and female flowers on the same

fascicle; and in the female flowers the perianth is superior; but a

plant at Kew produced, besides the ordinary flowers, others which gradu-

ated towards a perfect hermaphrodite structure; and in these flowers

the perianth was inferior. To show the importance of this modification

under a classificatory point of view, I may quote what Professor Harvey

says, namely, that had it “ occurred in a state of nature, and had a

botanist collected a plant with such flowers, he would not only have

placed it in a distinct genus from Begonia, but would probably have

considered it as the type of a new natural order.” . . . The interest of

the case is largely added to by Mr. C. W. Crocker’s observation that

seedlings from the normal flowers produced plants which bore, in about

the same proportion as the parent-plant, hermaphrodite flowers having

inferior perianths.”

This was written in the first edition of ‘‘Animals and

Plants under Domestication’? (1868) and was allowed

to stand in the second and last edition (1875). In both

editions, however, Mr. Darwin made the statement in an

entirely different part of the work, that ‘‘the wonderfully

anomalous flowers of Begonia frigida, formerly de-

scribed, though they appear fit for fructification, are

Berpe Vol. II, pp. 401-2. See also ibid., Vol. II, p. 278.

‘‘*Animals and Plants Under Domestication,” 2d ed., Vol. I, p. 389.

No. 506] DARWIN AND MUTATION THEORY 77

sterile.’’22 The last point, however, does not invalidate

the claim to this new type of Begonia as a mutant, since

the facts which determine its position in this regard are,

first, the sudden appearance of the form bearing three

kinds of flowers and, second, the production by seed of

descendants also bearing three kinds of flowers.

It is very evident that this case troubled Mr. Darwin,

for he referred to it a number of times and did not relish

Professor Harvey’s assertion that ‘‘such a ease is hostile

to the theory of natural selection, according to which

changes are not supposed to take place per saltum,” and

Harvey’s further declaration that ‘‘a few such cases

would overthrow it (natural selection) altogether.” Sir

Joseph Hooker attempted to explain the matter so as to

weaken Professor Harvey’s argument against the doc-

trine of natural selection, but Darwin himself wrote

Hooker, saying:

As the “ Origin ” now stands Harvey is a good hit against my talk-

ing so much of the insensibly fine gradations; and certainly it has

astonished me that I should be pelted with the fact that I had not

allowed abrupt and great enough variations under nature. It would

take a good deal more evidence to make me admit that forms have

often changed by saltum.

About the same time, namely early in 1860, Darwin

wrote to Lyell on this subject, saying:

It seems to me rather strange; he (Harvey) assumes the permanence

of monsters, whereas monsters are generally sterile and not often in-

heritable. But grant this case, it comes that I have been too cautious

in not admitting great and sudden variations.”

There is an added point of interest about this discus-

sion in the fact that it is the earliest record in print of

the consideration of saltation or mutation by Mr. Darwin.

You have doubtless noticed Mr. Darwin’s protest

against the belief in the occurrence of important changes

“per saltum.’’? He uses this expression with disap-

proval a number of times and yet his condemnation of

= Ibid., 1st ed., Vol. II, p. 166. Also ibid., 2d ed., Vol. TI, p. 10.

3 í Life and Letters,’’ 1886, Vol. II, p- 214. aar :

* Ibid., p. 275. Also, ‘‘ More Letters,” 1903, Vol. T, p. 141. -

78 THE AMERICAN NATURALIST [Vou XLII

the idea involved is not entirely unqualified, as is shown

by the following significant statement:

On the theory of natural selection we ean clearly understand the full

meaning of the old canon in natural history, “ Natura non facit saltum.”

This canon, if we look to the present inhabitants alone of the world,

is not strictly correct; but if we include all those of past times, whether

known or unknown, it must on this theory be strictly true.

This I understand to be in effect a protest against de-

ducing proof of separate creations from the imperfection

of the geological record, coupled with an admission that

saltation or mutation does, at least occasionally, occur

among existing living forms. I trust you perceive the

importance of the concession that natura non facit saltum

is not strictly correct as applied to the present inhabitants

of the world.

Having noticed Mr. Darwin’s repeated use of the words

per saltum, I now wish to revert to his frequent use of

the words monster and monstrosity and to call your at-

tention to the fact that they are not always employed

with exactly the same meanings. Sometimes by ‘‘mon-

strosity’’ he evidently intends to indicate a mere de-

formity of the nature of an accidental injury, or aborted

or perverted development, but more generally he refers

to a deviation from type wide enough, or discontinuous

enough, to exclude it from the category of variations

to which he supposed the operation of natural selection

must be confined. Among domesticated animals and

plants, however, the word monster as used by him often

meant no more than the word “sport.” In most cases

when he used this term or one of its derivatives he took

care to explain that monstrosities could not be qualita-

tively separated from other kinds of variations. Thus,

in writing to R. Meldola, in 1873, he says:

It is very difficult or impossible to define wh

variation. Such graduate into monstrosities

variations. I do not myself believe that these

advantage of under nature.”

* “Origin of Species,’’ 6th ed., p. 166. See als

"<í More Letters,’? 1903, Vol. I, p. 350.

at is meant by a large

or generally injurious

are often or ever taken

o ibid., pp. 156, 234, 414.

No. 506] DARWIN AND MUTATION THEORY 79

In the ‘‘Origin of Species’’ he wrote:

At long intervals of time, out of millions of individuals reared in

the same country and fed on nearly the same food, deviations of

structure so strongly pronounced as to deserve to be called monstrosi-

ties arise; but monstrosities cannot be separated by any distinct line

from slighter variations.”

He frequently repeats this statement and it is quite

clear that he intends to convey the idea that all varia-

tions are merely quantitative; at any rate he failed

to adopt a nomenclature that would enable his readers

to judge as to the degrees of difference he meant to

indicate by such adjectives as ‘‘insensible,’’ ‘‘minute,’’

“‘shight,’’ ‘“‘large,’’ ‘‘wide,’’ ‘‘sudden’’ and ‘‘abrupt,’’

as applied to variations. I am convinced, however, that

he had in mind an idea that there were two different

kinds of variations, namely, first, what he oftenest called

‘“individual variations,’’ by which he referred to the

ordinary differences between the single organisms of the

same group, or what mutationists now call ‘‘fluctuations, ’’

and, second, those radical and generally extensive devia-

tions from type which constitute an actual break with

the species, variety or race, and which are substantially

what we of these later times have named ‘“mutations. ””

There are places in Darwin’s works where the two kinds

of variation just mentioned are spoken of as ‘‘indefinite”’

and ‘‘definite’’ and as results, respectively, of the indirect

and the direct action of the conditions of life, and once

only, I think, he uses the term “fluctuating variability”

as synonymous with indefinite variability.” Now I do

not assume to say that the recognition of these distinc-

tions by Mr. Darwin proves that he clearly foresaw the

present-day mutation theory with its foundation in the

principle of unit characters, but I think it is true that

he had at least a glimpse of the coming modifications

*<<Origin of Species,’’ 6th ed., p. 6, also p. 33. See also Dreri

and Plants Under Domestication,’’ 2d ed., Vol. I, pp- 312, 322. Also

‘‘More Letters,’? 1903, Vol. I, 8.

p. 31

5<‘ Animals and Plants Under Domostiantion, 2d ed., Vol. I, PP-

280, 281, 345.

80 THE AMERICAN NATURALIST [Vou XLIII

to be required in his own theory to meet the then

dawning truth. De Vries declares that his own field re-

searches and testing of native plants are based ‘‘on the

hypothesis of unit-characters as deduced from Darwin’s

Pangenesis,’’ which conception, De Vries points out, ‘‘led

to the expectation of two different kinds of variability,

one slow and one sudden.’’”®

But the main point I wish to dwell upon at present is

that Darwin recognized, at least dimly, a kind of varia-

bility the results of which were essentially different from

the ‘‘individual’’ or ‘‘indefinite’’ variations, which mis-

takenly seemed to him alone capable of being acted upon

by selection. He was sorely puzzled by what he saw

and realized in this direction, for he had spent more than

twenty years of intense thought in elaborating his theory

that new species were evolved from older ones by the

gradual building up of new characters from extremely

small differences, and he feared that the admission of

saltation in any form meant the undermining of the foun-

dations he had labored so hard to construct. He had once

said:

When we remember such cases as the formation of the more complex

galls, and certain monstrosities, which cannot be acedunted for by

reversion, cohesion, &¢., and sudden strongly-marked deviations of

strueture, such as the appearance of a moss-rose on a common rose,

we must admit that the organization of the individual is capable through

its own laws of growth, under certain conditions, of undergoing great

modifications, independently of the gradual accumulation of slight in-

herited modifications.”

In the last edition of the ‘‘Origin of Species,’’ however,

which was published in the year of the author’s death,

although he introduces this apology: ‘‘In the earlier edi-

tions of this work I underrated, as it now seems prob-

ae the frequency and importance of modifications

Pe oe ec T he still later inter-.

a arieties, their Origin by Mutation,’’ 2d ed., 1906, p.

x gin of Species,’’ 5th ed., 1869, p. 151.

Origin of Species,’’ 6th ed., 1882, p- 171.

No. 506] DARWIN AND MUTATION THEORY 81

polates the following rather sweeping recantation :

There are, however, some who still think that species have suddenly

given birth, through quite unexplained means, to new and totally dif-

ferent forms; but, as I have attempted to show, weighty evidence can be

opposed to the admission of great and abrupt modifications. Under a

scientific point of view, and as leading to further investigation, but

little advantage is gained by believing that new forms are suddenly de-

veloped in an inexplicable manner from old and widely different forms,

over the old belief in the creation of species from the dust of the

earth.

In this sixth, and last, edition of the ‘‘Origin of

Species’? Mr. Darwin devotes to the task of answering

criticisms made by St. George Mivart far more space

than he had ever allowed to any other one critic and the

passage just read is evidently one of those inspired by

Mr. Mivart’s attacks. The sore point with Mr. Darwin

at that time was the doctrine of natural selection and, as

I have already remarked, he had adopted the erroneous

belief that this important principle must be greatly

weakened if not entirely sacrificed if any form of salta-

tion was to be admitted in nature. He had, therefore,

wavered between his loyalty to his cherished hypothesis

and his fearless devotion to truth. By this time, how-

ever, he had so long contemplated the possibility of the

origin of new species and varieties through single long

steps and had had so many convincing examples brought

to his attention, that his hesitancy and doubt concerning

the validity and sufficiency of the arguments urged m

favor of this mode of evolution were ready to give way,

and I regard the passage, which I am about to quote, as a

virtual surrender on this point. The fact that, in this

emphatic form, it was written at the close of his life, as

his last word on this subject, and that he must have felt

that it contained a concession very damaging to the

theory to the establishment of which that life had been

devoted, gives it, in my mind, a deeply pathetic signifi-

cance. Mr. Darwin says:

2‘ Origin of Species,’’ 6th ed., 1882, p- 424.

82 THE AMERICAN NATURALIST [Vou. XLIII

It appears that I formerly underrated the frequency and value of

[variations which seem to us in our ignorance to arise spontaneously |

as leading to permanent modifications of structure independently

of natural selection. But as my conclusions have lately been much

misrepresented, and it has been stated that I attribute the modifica-

tion of species exclusively to natural selection, I may be permitted

to remark that in the first edition of this work, and subsequently, I

placed in a most conspicuous position—namely, at the close of the In-

troduction—the following words: “I am convinced that natural selec-

tion has been the main but not the exclusive means of modification.”

This has been of no avail. Great is the power of steady misrepresenta-

tion; but the history of science shows that this power does not long

endure.

The sting of this vehement declaration is in the under-

lying implication that the limitation placed upon the

applicability of natural selection was deemed necessary

because of Mr. Darwin’s inability to free his mind from

the belief that it could not act upon large and sudden

variations as well as upon small and unimportant ones.

This point of view seems illogical when we consider his

repeated declaration that no qualitative distinction could

be established between the two kinds of variation, but it

may be partially accounted for by the fact that a slight

confusion at times existed in his mind concerning the

general modus operandi of natural selection, through

which he attributed to it a causal power as well as a mere

sifting effect. Both Lyell and Wallace took him to task

for this double use of the term and, therefore, in the third

edition of ‘‘the Origin’? he attempted to clear up this

point by means of this statement:

Several writers have misapprehended or objected to the term natural

selection. Some have even imagined that natural selection even induces

variability, whereas it implies only the preservation of such variations

as arise and are beneficial to the being under its conditions of life.“

: Nevertheless, almost side by side with this explana-

tion we find in the last edition of ‘‘the Origin,” the fol-

lowing sentences which were allowed to come down from

the first edition: ‘‘Natural Selection will modify the

=<‘ Origin of Species,’’ 6th ed., p. 421. See also, ‘‘Life and Letters,”

zo bier II, p. 243, and ‘‘ More Letters,’? 1907, Vol. I, p. 389.

Origin of Species,’’ 34 ed., 1861, p. 84.

No. 506] DARWIN AND MUTATION THEORY 83

structure of the young in relation to the parent, and of

the parent in relation to the young.” ‘‘Natural Selec-

tion . . . will destroy any individual departing from

the proper type.” If Darwin had adopted the simile

of a sieve, so effectively used by De Vries, he would have

drawn nearer to the recognition of the fact of ‘‘selection

between species,’’ even if he had not been prepared to

assent to De Vries’s counter proposition that there is no

‘‘selection within the species.’’ He might also have

escaped some of his apprehensions concerning the fate

of adaptation, which he thought to be endangered by a

belief in saltation; for the fact is that adaptedness is only

another name for fitness, and this is a quality inherent

in the organism and precedent to selection—that is to say,

natural selection merely sifts out for preservation the

adapted or fit, allowing the unadapted or unfit to perish.

Now, it is impossible to see why forms both adapted and

unadapted to their environment may not arise through

mutation and thus be offered to the operation of selection.

In fact, Mr. Darwin has supplied us with a good illustra-

tion of such a case in a rather naive passage which has

run through every edition of ‘‘the Origin,’’ to the fol-

lowing effect: | ; .

One of the most remarkable features in our domesticated races is

that we see in them adaptation, not indeed to the animal’s or plant’s

own good, but to man’s use or fancy. Some variations useful to him

have probably arisen suddenly, or by one step; many botanists, for

instance, believe that the fuller’s teasel, with its hooks, which ean not be

rivaled by any mechanical contrivance, is only a variety of the wild

Dipsacus; and this amount of change may have suddenly arisen in a

seedling.”

Surely, if Mr. Darwin could have looked at this case

with a perfectly free mind, he must have perceived that

the teasel’s adaptation to man’s needs would not have

fallen if man had failed to exercise his power of selection ;

and that the adaptation was not weakened by the fact

that it arose by a mutation. But that he was uncon-

= Ibid., 6th ed., 1882, p. 67.

* Ibid., 6th ed., 1882, p. 81.

"<í Origin of Species,’’ 6th ed., p. 22.

. SS eine .

84 THE AMERICAN NATURALIST (Vou. XLII

sciously biased in this matter is shown by an extract from

a letter written to Asa Gray, in 1860, in which he says:

I reflected much on the chance of favorable monstrosities (i. e., great

and sudden variation) arising. I have, of course, no objection to this,

indeed it would be a great aid, but I did not allude to the subject [i. e.,

in “the Origin ”] for, after much labor, I could find nothing which

satisfied me of the probability of such occurrences. There seems to me

in almost every case too much, too complex, and too beautiful adapta-

tion, in every structure, to believe in its sudden production.”

The idea involved in this passage is that adaptation is

produced—rather than preserved—by natural selection

and that, as natural selection must, according to Mr.

Darwin’s curious prepossession, act only upon slow and

small changes of character, adaptation itself must neces-

sarily be in every case a matter of gradual growth. This

sort of argument appears to justify the fear shared by

both Lyell and Hooker that Darwin was at times disposed

to stake his whole case on the maintenance of an unneces-

sary assumption. Hooker wrote him as early as 1859 or

1860 that he was making a hobby of natural selection and

overriding it, since he undertook to make it account for

too much.? Darwin mildly protested that he did not see

how he could do more than he had done to disclaim any

intention of accounting for everything by natural selec-

tion.*° In this discussion, however, it is apparent that

while Darwin was overloading the theory of natural selec-

tion with a responsibility for the origin of the adapted

or fit, he was at the same time undul

y limiting it to only

one class of the fit, namely those which had arisen by slow

degrees.

If he had taken the position that natural selec-

tion could and would operate upon any kind or any de-

gree of variability, he need not to have imagined that

his main doctrine was in Jeopardy.

But though Mr. Darwin could be stirred by attack to

a vigorous defense, and sometimes even to an over-

defense, of natural selection, he contended, at other times,

with equal vigor, that his main interest was with varia-

* << Life and Letters,’’ 1887, Vol. II, p. 333.

*** More Letters, ’’ 1903, Vol. I, p. 135

* Ibid., Vol. T, pp. 172, 213.

No. 506] DARWIN AND MUTATION THEORY 85

tion, however produced, which was the necessary basis

of the whole evolutionary process. He admitted, how-

ever, that the cause of variation was to him inexplicable

and, like all beginnings, it remains to this day a deep

mystery. Darwin said of it:

Our ignorance of the laws of variation is profound. Not in one case

out of a hundred can we pretend to assign any reason why this or that

part has varied.”

In another place he remarks:

When we reflect on the millions of buds which many trees have pro-

duced before some one bud has varied, we are lost in wonder as to

what the precise cause of each variation can be.”

He never definitely undertook to solve this mystery,

though he reflected and reasoned on it much. The near-

est he came to formulating a law concerning it was the

expression of his conviction that variability was more

a matter of organic constitution than a result of external

agencies. Thus he declares:

If we look to such cases as that of a peach tree which, after having

been cultivated by tens of thousands during many years In many coun-

tries, and after having annually produced millions of buds, all of which

have apparently been exposed to precisely the same conditions, yet at

last suddenly produces a single bud with its whole character greatly

transformed, we are driven to the conclusion that the transformation

stands in no direct relation to the conditions of life.

From examples like this Mr. Darwin deduced a *‘gen-

eral rule that conspicuous variations occur rarely, and in

one individual alone out of millions, though all may have

been exposed, as far as we can judge, to nearly the same

conditions’“4 and while this is, in a general way, M

accordance with the admission of De Vries that although

mutations are ‘‘not so very rare in nature,’ the num-

bers ‘‘under observation are as yet very rare,’”*° ">? shall

see a little later that Mr. Darwin’s deduction 1s not

*#<¢ Animals and Plants Under pease) OB a A ne

` : ibi d., E . ei a

Ibid., 2d ed., Vol. I, p- 441. See also, 4 , valp 276.

tion,” 2d ed., p. 597..

s cc Species and Varieties, their Origin by Muta

* Thid., p. 3.

86 THE AMERICAN NATURALIST [Vot. XLII

strictly accurate since it excludes the idea of a whole

genus or species or variety mutating at once.

While on this subject, I may mention that Mr. Darwin

anticipated the doctrine of the mutationists to the effect

that ‘‘when the organization has once begun to vary, it

generally continues varying for many generations.’

But as to variability having periods of activity Mr. Dar-

win’s opinion seems to have been unsettled. In a letter

to Weismann, in 1872, he remarks on the strangeness

‘about the periods or endurance of variability,’ but

in a letter to Moritz Wagner, in 1876, he says:

Several considerations make me doubt whether species are much more

variable at one period than at another except through the agency of

changed conditions.. I wish, however, that I could believe in this

doctrine, as it removes many difficulties.”

Practically this is the dilemma of the mutationists of

the present day: they are not in a position to prove that `

plants and animals have periods of mutation, but they

assume that it must be so, because the belief ‘‘removes

many difficulties. ’’

ne of Darwin’s perplexities, however, has been ex-

plained away, as I have already pointed out, by the dis-

covery that mutation is not confined to a single case out

of millions of individual forms, nor even to a single gen-

eration out of a long genetic line, but that, as in the case

of the Œnotheras (evening primroses), a whole genus

is likely to be in a mutating condition at the same time,

producing from each of several species numberless indi-

vidual mutants, which are themselves often in a mutating

condition, the parent stock meanwhile remaining per-

fectly constant. Such has been the ease with Œnothera

(Onagra) lamarckiana, which, while throwing off, since

it has been under scientific observation, in large numbers

not less than a dozen elementary species and retrograde

varieties, has bred true to its original type through at —

least one hundred and sixteen years, although there is

“** Origin of Species,’’ 6th êd., p. 5. ;

“** Life and Letters,’’? 1886 Vol. IIT

: k 155,

* Ibid., p. 158. Lets

No. 506] DARWIN AND MUTATION THEORY 87

considerable proof that it is itself a mutant from

(Enothera grandiflora, and none whatever for the asser-

tion, often made, that it is a hybrid. As at least nine

of its mutants have also bred true through many genera-

tions in pedigree cultures and doubtless had been con-

stant forms for a long time in a state of nature, there

appears to be no ground for Darwin’s fear that, granting

the occurrence of mutation, the mutants would be liable

to speedy extermination through inability to propagate.

Of course this would not be the case with even a single

self-fertilizing plant and it would not be true with ani-

mal mutants if, like plant mutants, they were produced

in numbers by the mutating stock. As to swamping by

intercrossing, it has been shown that, under Mendel’s

law, in the extreme case of the production of a solitary

mutant obliged to cross. with the parent form, if it pos-

sesses characteristics having a certain relation to the

parent, it can establish a race like itself and even sup-

plant the parent form, if it is only as well fitted for the

battle of life as is the progenitor.”

If Darwin had known these facts he would not have

written, or he would have greatly amended, the following

passage:

He who believes that some ancient hae was transformed suddenly

through an internal force or tendency into, for instance, one furnished

with wings, will be almost compelled to assume, in opposition to all

analogy, that many individuals varied simultaneously. It can not be

denied that such abrupt and great changes of structure are widely dif-

ferent from those which most species apparently have undergone. He

will further be compelled to believe that many structures beautifully

adapted to all the other parts of the same creature and to the surround-

ing conditions, have been suddenly produced; and of such complex and

-= wonderful co-adaptations, he will not be able to assign a shadow of an

explanation. He will be forced to admit that these great and sudden

transformations have left no trace of their action on the embryo. To

admit all this is, as it seems to me, to enter into the realms of miracle,

and to leave those of science.”

Of course Mr. Darwin was not entirely oblivious to the

fact that every important advance in knowledge must

” See Lock’s ‘‘ Variation, Heredity and Evolution, ”” 1906, p. 205.

“ct Origin of Specie Ae ee Paai cae

88 THE AMERICAN NATURALIST [Vou. XLIII

have the appearance, at first, of a move into a region of

mystery and uncertainty. The lapse of time and the

growth of familiarity with it are necessary to the reclama-

tion of a terra incognita.

Before leaving this branch of my subject, I desire to

call your attention to the very interesting fact that Mr.

Darwin himself once conducted a long series of experi-

ments which, it can hardly be doubted, resulted in the

production of mutants and that he just missed the dis-

covery of principles which are now the basis of scientific

pedigree cultures and are occupying the attention of in-

vestigators of the problems of variation and heredity.

In a letter to J. H. Gilbert, dated February 16, 1876, Mr.

Darwin writes:

Now, for the last ten years I have been experimenting in crossing and

self-fertilizing plants; and one indirect result has surprised me much,

namely, that by taking pains to cultivate plants in pots under glass

uring several successive generations, under nearly similar conditions,

and by self-fertilizing them in each generation, the colour of the flowers

often changes, and, what is very remarkable, they became in some of the

most variable species, such as Mimulus, Carnation, &e., quite constant,

like those of a wild species. This fact and several others have led me

to the suspicion that the cause of variation must be in different sub-

stances absorbed from the soil by these plants when their powers of ab-

sorption are not interfered with by other plants with which they grow

mingled in a state of nature.”

The point I particularly wish you to notice in this case

is that Mr. Darwin was employing practically the

methods now used by Professor De Vries, Professor Mac-

Dougal and others who are engaged in species testing,

by growing naturally variable or mutating plants under

conditions of rigid control, so as to exclude crossing or,

as De Vries calls it, vicinism. In this view of the matter,

it would be interesting to know what percentage of Mr.

Darwin’s plants exhibited the new and constant char-

acters and through how many generations his mutants

were found to breed true, for then we could compare his

results with those of investigators of our day. But his

attention was centered upon the endeavor to find a cause

@<<Tife and Letters,’’ 1886, Vol. IT, p. 343.

No. 506] DARWIN AND MUTATION THEORY 89

for the abrupt variations and not on the formulation of

laws of their action. Apparently he considered isolation

to be the principal secondary cause or favoring condition,

upon which view the obvious comment is that it requires

no great stretch of imagination to conceive of similar

isolation as occurring in nature and thus favoring muta-

tion among uncultivated forms.

Having now hastily reviewed the oscillations in Dar-

Win’s opinions concerning the kinds, the causes and the

laws of variation with relation to the origin of species, it is

not my purpose to enter upon a discussion of the present-

day mutation theory, which has grown out of a closer

study, and a more scientific treatment, of the problems of

_ variation and heredity than were attempted, or were

perhaps possible in Darwin’s time. It is desirable, how-

ever, to compare Darwin’s views with generalizations

from the mutation theory, which we can do, well enough

for our present purpose, by merely recalling the seven

laws which De Vries claims to be the logical outcome of

his twenty years of cultural experiments upon plants.

They are, with slight modifications as to wording and

order, as follows:

1. New elementary species appear suddenly without

intermediate steps. :

2. New forms spring laterally from the main stem.

3. New elementary species attain their full constancy

at once. f

4. Some of the new strains are elementary species,

while others are to be considered as retrograde varieties.

5. The same new species are produced in a large num-

ber of individuals.

6. Mutations take place in nearly all directions and are

due to unknown causes. :

7. Species and varieties have originated by mutation,

but are, at present, not known to have originated in any

other way. oe

Now, looking back over what Darwin wrote concerning

variation, I can not believe that he would seriously sah

90 THE AMERICAN NATURALIST [Vou. XLIII

disputed any of De Vries’s propositions except the last.

All would have had to stand or fall with that. He

recognized the fact that new species had sometimes ap-

peared suddenly without intermediate steps and that the

new forms had sprung laterally from the main stem. I

think he also substantially admitted that such new species

attained their full constancy at once. As to the fourth

affirmation of De Vries, with reference to elementary

species and retrograde varieties, Darwin had no knowl-

edge, for the distinction is original with De Vries. Dar-

win believed, as a general proposition, that ‘‘ species are

only strongly marked and permanent varieties, and that

each species first existed as a variety,” but, of course,

in admitted cases of mutation this can not be true; and

if Darwin had been obliged to concede De Vries’s seventh

proposition, the fourth might well have been allowed to

go with it. The same is doubtless the case concerning

De Vries’s fifth law, which sets forth in effect that similar

mutants are thrown off by many individuals of the same

species at about the same time. As we have already

seen, Mr. Darwin was convinced that if, for example, he

were to admit the origin by mutation of a species of flying

animal, for the reasons urged by Mr. Mivart, he would

be compelled to assume ‘‘that many individuals varied

simultaneously.” I, therefore, do not see that he would

have been interested, from a theoretical point of view, in

disputing either of the two last-named declarations of De

Vries except in connection with his seventh and last law,

to which I shall presently refer. The sixth law of De

Vries, which affirms that mutations take place in nearly

all directions, is practically the equivalent of Darwin’s

first law that all organisms vary continually and in every

part of their structure, provided it is agreed that muta-

tions are only quantitatively different from Darwin’s

‘‘individual variations,’’ which was Darwin’s own view. `

In so far as Darwin admitted the occurrence of mutation

at all, he must have agreed that it could proceed in any

= íí Origin of Species,” 6th ed., 1882, p. 412.

No. 506] DARWIN AND MUTATION THEORY 91

direction. But now we come to the conclusion of De

Vries which we know Darwin would not have accepted,

at least in its entirety. As we have seen, he was com-

pelled to concede that what we now call mutation had

occasionally taken place and become the starting point

of new races, but he was none the less unshaken in the

conviction that this process was exceptional and extraor-

dinary, and that, as a rule, a new species originated

by the gradual building up of minute and even insig-

nificant deviations from the average characters of an old

species, which deviations we now call fluctuations. We

know with what tenacity he held this view to the end of

his life. For the doctrine of ‘‘insensible gradations,”’

which touched mainly a minor premise in his general

argument for evolution, Mr. Darwin was, unhappily,

almost willing to relinquish the essence of the whole

matter, which was his claim to the discovery of a vera

causa in the evolutionary process. Notwithstanding

the prior claim of Patrick Matthew, and the partial antici-

pation of Alfred R. Wallace and others, the establishment

of the theory of natural selection was Mr. Darwin’s most

original and greatest achievement. Time has proved that

he could have afforded to stand upon the general validity

and applicability of this theory though every step in his

argument in its favor had needed review and modifica-

tion; for each passing year but adds to the impregnable

mass of proofs by which it is affirmed and supported.

Properly regarded, the mutation theory does not antag-

onize nor weaken the doctrine of natural selection—on

the contrary, it merely offers itself as a helpful substitute

for, or adjunct to, one of Darwin’s subordinate steps in

the approach to a consistent philosophy of the origin of

Species, leaving the last great cause of evolution as

efficient as ever. It is, therefore, one of the tragedies of

science that in this matter Darwin should have bees

ready to surrender his main position rather than to pe

ceive and to join forces with those who were —> >»

his aid, but whom he failed to recognize as friends. oS oes.

JUVENILE KELPS AND THE RECAPITULATION

THEORY. II

PROFESSOR ROBERT F. GREGGS

OHIO State UNIVERSITY

II. Tue Recapirutation THrory IN RELATION TO THE

KELPS

Any observations on juvenile kelps must call to mind

the recapitulation theory. This theory, though applied

both to animals and to plants, was built up exclusively on

zoological evidence and has been amplified and discussed

chiefly by zoologists. The reason is evident because of

the definite proportions and structure of the animal body,

the development of which must of necessity follow a very

definite course, while among plants the body is of such

loose and indefinite proportions that its development can

seldom be rigidly described. But while the botanists

have had very little to say about the recapitulation theory,

they have always approved it and considered that it ap-

plied to plants just as truly, though not as conspicuously,

as to animals.

It is somewhat surprising then to a botanist to find that

this theory is being very vigorously attacked by some

of the zoologists. One of the more recent papers is by

: Montgomery, who gives a review of the literature with a

general discussion of the theory in his ‘ ‘Analysis of Racial

Descent,’’ 1906. In summing up he says (p. 193) :

Therefore we can only conclude that the embryogeny does not furnish

any recapitulation of the phylogeny, not even a recapitulation marred

at occasional points by secondary change. . . . An analysis of the

stages during the life of one individual ean in no way present a knowl-

edge of its ancestry; and the method of comparing non-correspondent

stages of two species is entirely wrong in principle.

And again at the close of the chapter, p. 203:

The recapitulation hypothesis is ‘scientifically untenable and where

there has been transmutation of species, the embryogeny neither in

No. 506] KELPS AND RECAPITULATION THEORY 93

whole nor in part exactly parallels the racial history. The relation

between them is always that of an inexact parallelism. Considerations

based on any such idea of recapitulation are erroneous, and therefore

of no help in determining racial descent.

In these sentences Montgomery is voicing not alone his

individual opinion, but that of a very considerable school

of embryologists.

The general tenor of these statements is scarcely open

to question nor is the author’s conclusion as to the worth-

lessness of the recapitulation theory. However, there is

one word used in both the paragraphs quoted, though not

in the portion of the first cited, that is unfortunate in that

it is open to misunderstanding. It is the word exact.

Exact has a certain mathematical flavor, which makes its

application to living organisms difficult. Neither Mont-

gomery nor any one else believes that there are anywhere

two individuals, who are exactly alike in any respect

whatever. We may fairly assume, that Montgomery

means to say that there is no recapitulation of the racial

history of the embryo sufficiently exact to aid in deter-

mining racial descent; and we shall so interpret his state-

ments in the remainder of this paper.

A few years ago when the recapitulation theory was al-

most universally accepted one might have assumed that

the noteworthy features of the development of the kelps

were to be explained on that basis. But now in the face

of such attacks on the theory no such assumption may be

made. We shall therefore consider the development of

the kelps in relation to the theory and to the criticism

upon it in an effort to ascertain the real bearing of the

foregoing observations.

It must be admitted that the juvenile forms of all the

kelps are closely similar in a general way; but it does not

necessarily follow that they are so because of any recapit-

ulation of phylogeny. Such parallelism might be brought

about by entirely different causes. This possibility has

been perhaps most strongly urged by His, the eminent

embryologist, who in a different way makes quite as :

94 THE AMERICAN NATURALIST (Voi. XLII

strong an attack on the theory as does Montgomery. In

his ‘‘Unsere Koérperform ’’ as translated and quoted by

Morgan (’03, p. 71) who does not, however, assent, His

says:

In the entire series of forms which a developing organism runs

through, each form is the necessary antecedent step of the following.

If the embryo is to reach the complicated end forms, it must pass,

step by step, through the simpler ones. Each step of the series -is

the physiological consequence of the preceding stage and the necessary

antecedent for the following. Jumps, or short cuts, of the develop-

mental process, are unknown in the physiological process of develop-

ment. If embryonic forms.are the inevitable precedents of the mature

. forms, because the more complicated forms must pass through the

simpler ones, we can understand the fact that paleontological forms

are embryonal, because they have remained at the lower stage of

development, and the present embryos must pass also through lower

stages in order to reach the higher. But it is by no means necessary

for the later, higher forms to pass through embryonal forms because

their ancestors have once existed in this condition. To take a special

case, suppose in the course of generations a species has increased its

length of life gradually from one, two, three years to eighty years.

The last animal would have had ancestors that lived for one year, two

years, three years, ete., up to eighty years. But who would claim that

because the final eighty years species must pass necessarily through

one, two three years, ete., that it does so because its ancestors lived one

year, two years, three years, ete.? The descent theory is correct in

so far as it maintains that older, simpler forms have been the fore-

fathers of later, complicated forms. In this case the resemblance of

the older, simpler forms to the embryos of later fotms is explained

without assuming any law of inheritance whatever. The same re-

semblance between the older and simpler adult forms would remain

intelligible were there no relation at all between them.

There are two ways of looking at this view of His’s that

every form is the necessary antecedent of the succeeding.

These depend upon the length of stages considered.

we take stages separated by very small intervals of

growth, His’s contention must be true else there would be

no continuity of development. But this is nothing more —

than a statement of the fact that all growth must be grad- _

ual and is no law of development. If instead of small in-

tervals we take the whole development, the statement

No. 506] KELPS AND RECAPITULATION THEORY 95

would become: ‘‘The developmental stages of an organ-

ism are only the physiologically necessary steps for the

formation of its adult body from its earliest stage, which

is in most cases the egg.” This is definite and it can be

readily tested by the facts, while the other is so vague as

to be scarcely susceptible of any such test. There is no

middle ground between these two alternative interpreta-

tions of the statement. For if an organism is found to

which it will not apply if somewhat but not greatly sep-

arated stages be considered, all that is necessary is to

take shorter and shorter stages until finally any ontogeny

must conform to it. |

= Let us apply then, His’s view, thus interpreted, to the

kelps. We have so far confined the account to the ex-

ternal morphology and have said little about their histol-

ogy. This will be of interest here. The general plan of

structure is the same in both stipe and lamina and similar

in all kelps. Within the epidermis is the cortex composed

of polygonal or rounded cells which may be thickened and

hardened to form strengthening tissue. Within this is a

pithweb made up of irregularly interlacing filaments

which sometimes show very remarkable differentiation.

Oliver (’87) first worked out in detail, showing that in

Macrocystis and Nereocystis, especially, sieve tubes are

developed which form a regular zone of vertical vessels

around the less differentiated center of the pith. The

sieve plates of these become obliterated by the formation

of callus as in the spermatophytes. There is good reason

to believe that they are efficient in the transfer of mate-

rials from one part of the plant to another and their pos-

session may have made it possible for these plants to at-

tain the great lengths they sometimes reach. The simpler

internal pith consists of interlacing branching hyphae

which run in all directions. Many of these meet and at

their junctions develop sieve plates connecting them with

one another, at the same time becoming swollen at the ends

like the flare of a trumpet. Such trumpet hyphe are er:

mon in most members of the Laminariaceae. In Ren:

96 THE AMERICAN NATURALIST [Vou. XLII

frewia, however, the pith consists of only moderately

elongated cells which interlace somewhat as in other

kelps, but very much less conspiciously. The majority

of them are not longitudinal, but transverse in their gen-

eral course, so that a cross section shows more of them

cut lengthwise than a longitudinal (see figures, Griggs,

06). Scarcely any of them are sufficiently elongated to

merit the name of hyphæ. Very few give indications of

developing into trumpet hyphæ. It is evident that Ren-

frewia presents a transition from a pithweb of simple

polygonal cells to the complex differentiation of the high-

er kelps such as Nereocystis. Such plants must of neces-

sity pass through the condition of Renfrewia in order

to attain mature structure. We have here then a per-

fect illustration of the truth of His’s idea—save in one

respect. His contends that the developmental stages are

only the necessary morphological precursers of the adult.

But in this case they may be phylogenetic recapitulations

also. There is nothing in the evidence so far to prevent

a decision either way.

Let us consider some other features of the develop-

ment. All of the young forms pass through a period

when the stipe is short as compared with the lamina. In

all which have been described above except Hedophyl-

lum, this condition persists until a certain very definite

period, after which the stipe elongates rapidly (see figures

of Egregia). This condition is so similar to the adult

stage of Renfrewia that one is tempted to consider it a

recapitulation of such a stage. But instead it may be

only a necessary physiological adaptation which the

young plant undergoes early in its development in

order to provide a large photosynthetic area to furnish

the food necessary for rapid growth. A priori this would

seem a reasonable interpretation of the facts and it may >

be that we should consider them without other signifi-

cance. It is, however, difficult to believe that the simple

Renfrewioid form is the necessary precurser of adult

forms so diverse as Postelsia and Egregia, Eisenia and —

No. 506] KELPS AND RECAPITULATION THEORY 97

Nereocystis, Thallasiophyllum and Macrocystis. One

might imagine other forms upon which each of these

might have been built up more directly than on this

one. This is particularly true in the case of Egregia and

Hedophyllum, where, while the young are indistinguish-

able, the course of development is diametrically opposed.

Egregia dwarfs the lamina and becomes nearly all stipe;

Hedophyllum obliterates the stipe and becomes a sessile

lamina. If ontogeny represents merely stages physio-

logically necessary to the attainment of the adult form,

why should Hedophyllum produce a stipe at all?

Similar conditions are presented by very many other

cases, especially among animals where some organ is de-

veloped in the embryo which later disappears without

being of service either to the embryo or to the adult.

Such cases have in the past been the main evidence

brought forward for the recapitulation theory, as it has

been supposed they were explicable only on the basis of

a recapitulation of the phylogeny. Familiar examples

are cited by Morgan (see below), and many more might

be added.

Not all who attack the recapitulation theory go so far

as to discard it altogether. Many recognize in it a truth

and seek to modify it to fit certain facts. The form

which has the largest number of adherents is perhaps

that proposed by Morgan (’03), who believes that ‘ani-

mals in their ontogeny repeat not the adult, but the em-

bryonic stages of their ancestors; that the presence of a

certain structure in the embryo means that the ances-

tors of the species to which the organism belongs had

similar embryonic stages. This he calls the ‘Repetition

Theory.’? Much of the evidence which the zoologists

bring forward in favor of such a modification as against

any broader application is so conclusive, one must ac-

knowledge that such is a correct statement of the facts

in the particular cases cited, whatever the general law

of development may be. Morgan calls attention to the

fact that the gill-clefts and the notochord, structures on

98 - THE AMERICAN NATURALIST (Vou. XLII

the recurrence of which the recapitulation theory was

largely built, appear just as early in the embryo of the

fish and of Amphioxus, respectively, as in that of a mam-

mal. He cites the case of the baleen whale which forms

teeth in the embryo like any other mammal, but these

beginnings, instead of continuing their development, are

absorbed and do not even pierce the gums. The same

is true of the dental ridges of birds, where teeth begin

to form but soon disappear.

The evidence presented by the kelps clearly tends

to establish this repetition theory of Morgan. The juve-

nile forms of the plants have so many points in com-

mon that there can be scant doubt but that their ances-

tors had similar juvenile forms. It must be added here

also that those plants whose development we have traced

above are not special cases, but are only illustrations

of the facts common to all kelps. The writer has in

his possession full series of several genera which have

never been described at length. These and all others

which have been worked out follow the same course of

development. Among those upon which fairly complete

published data are available, may be mentioned: Agarum,

Barber, ’89; Alaria, Schrader, ’03, and others; Cyma-

there, Griggs, ’07; Eisenia, Setchell, ’96b, 05a; Lessonia,

Reinke, 03; Nereocystis, MacMillan, ’99; Pterygophora,

MacMillan, ’02; Saccorhiza, Barber, ’89; Thallasiophyl-

lum, Setchell, ’05a.

If we may consider the repetition theory established

how much will it help us with our phylogenetic problem?

Why should widely diverse forms have ancestors with

similar embryos? How were these similar stages acquired

and why do they persist? They must be meaningless s0

far as phylogeny is concerned, except as they are consid-

ered as stages which once led to the development in the

adult of the structures which they represent. But why

should embryonic characters persist and not adult ones?

Is there any line of demarkation between embryo and

adult beyond which the action of heredity changes?

No. 506] KELPS AND RECAPITULATION THEORY 99

Leaving these questions for the present, we may ex-

amine the facts in the development of our kelps, to as-

certain whether these juvenile forms repeat only other

juvenile forms or whether they go farther and approxi-

mate the adults of their ancestors. Nothing could be

more instructive on this point than the figure of the

young plant of Lessoniopsis printed beside the adults

of Renfrewia (Figs. 15-17). In all external characters

save the characteristic spots of Lessoniopsis and the re-

productive maturity of Renfrewia they are in essentials

identical. The structure of the holdfast is particularly

interesting. Both are simple dises strengthened by pri-

mary hapteres originating through the uneven growth of

the dise itself. The young of other kelps might have

been used for this comparison, e. g., Hedophyllum (cf.

Fig. 6), but Lessoniopsis retains these primitive char-

acters at a larger size than the others and therefore

lends itself more easily to photography while its deter-

mination is at the same time certain because of the spotted

lamina. In Pterygophora the correspondence is in all

respects just as complete, see MacMillan’s figures

(702). There persists for a considerable period the sim-

ple lamina with the short stipe on the primitive disc

and its primary hapteres for holdfast. After the sec-

ondary hapteres have appeared and until the midrib has

been formed the young plants are very difficult to dis-

tinguish from those of Laminaria saccharina which grows

in the same locality. These again are in all respects, ex-

cept size and reproductive maturity, like the adult plants

of their species.

It seems obvious that we can not well consider these

facts without comparing these non-correspondent stages

of Lessoniopsis and Renfrewia, and of Pterygophora and

Renfrewia and Laminaria. The simple facts of the case

are that Lessoniopsis and the others when still very -

pass through a condition which must be considered wee 2

in the generic limits of Renfrewia. Conversely, mo

adults of Renfrewia do not differ in any important phare

100 THE AMERICAN NATURALIST [Vou XLIM

acters save size and reductive maturity from the young

of the other kelps which have been studied. But Ren-

frewia, juvenile or adult, is not one of the ancestors of

these higher kelps. It is only a simpler form which we

take to have been left behind in the evolution of the

kelps. Our actual knowledge of their ancestors is al-

most nothing. But if we were to reconstruct a general-

ized common ancestor for the kelps, by projecting back-

ward, from the different tribes, lines indicating their ap-

parent course of evolution, until they converged and met,

we should have to conceive a plant very similar in all

respects to Renfrewia.

What then is to be said concerning structures which

do not recapitulate adult but only embryonic conditions?

In the toothless animals, the whale and the bird, the de-

velopment of teeth in the jaw is entirely unnecessary, as

has been pointed out in considering His’s idea. It may

even be said to hinder the attainment of the adult con-

dition. The same is true of the mammalian gill-slits and

of most of the structures which have in the past attracted

attention in connection with the recapitulation theory.

As the ancestral period, when such structures were fully

developed in the adult, becomes more and more remote,

the tendency to inherit them becomes less and less, be-

cause of the cumulative impulses given to the heritage

by the nearer ancestors. Consequently, they are succes-

sively less and less developed. Any gradual loss of in-

herited structures can, in the nature of the case, take

place only from the mature condition backward towards

the beginning of the life cycle; otherwise we should have

adult structures with no ontogenetic history. Therefore

we can understand why it is that in many cases only the

embryonic stages of ancestral organs persist in the on-

togeny.®

*The eutting off of end stages in the development of organs has given

rise to the idea that the adult stages are ‘é pushed back into the embryo.’’

Such a misconception easily arose from the loose language in which the

facts have often been expressed. Conklin (705) has rightly pointed out

its ineorrectness.

No. 506] KELPS AND RECAPITULATION THEORY 101

Thus the embryogeny will be gradually shortened by

the omission of more and more of the superfluous ances-

tral stages; and it will tend finally to retain only such

stages as are necessary to the attainment of the adult

form. It will be noted that this is the view of His, which

thus becomes a statement of an inevitable tendency in

development, which is very different from a complete law

of embryogeny. Though life cycles may approach very

closely such a limiting condition, it is doubtful if they

would ever completely realize it.

Besides changes in ontogenies brought about by the

cutting off of end stages no longer used there is another

source of change. This is secondary adaptation. It is

on this point that Montgomery largely makes his case,

insisting that organisms are as subject to change in one

period of their life cycles as another. In this matter also

we must agree that secondary changes are sometimes

very evident and conspicuous— probably more so among

animals than plants. The fetal membranes are very fa-

miliar examples of such secondary adaptations. But

though they are much modified the fact must not be

lost sight of that they are in part at least adaptations

of previously existing organs with different functions

and not new structures. Not only may an embryo adapt

itself to its conditions; it may simulate other forms; or

interpolate stages; or become otherwise modified as the

Species undergoes transmutation. Yet the important

point to consider is not that a few have done this, but that

the great majority have not falsified their heritage be-

yond all recognition, that they still persist ın spite of

changed conditions and secondary adaptation in preserv-

ing so many indications of their ancestry.

Montgomery considers this matter of secondary change

so weighty, not because of a great amount of observation

brought forth, but for logical reasons. He holds ah

The egg of a mammal is as dissimilar from that of a fish as their

adult stages, no matter whether their differences are perceptible or not.

This was the idea of the great old master Von Baer: The egg 1s as

‘much a bird as is the hen.

102 THE AMERICAN NATURALIST [Vow. XLIII

Although perfectly. true in a physiological sense, this is

incorrect in this connection. Potentially the egg of one

animal is as different from that of another as their adult

forms, but morphologically they correspond. Morphology

is not concerned with the ‘‘ growth energies’’ of organisms,

but only with their form and structure. A similar mis-

take was made by His in the quotation cited above, where

he takes for an illustration of his views an animal which

had lengthened its life over that of its ancestors. The

logical deduction from such an example under the re-

capitulation theory would be that the last form should

die at the end of each period, one, two, three years, etc.,

in order to recapitulate its ancestry, rather than that

it lives one, two, three years to do so. The absurdity

of this lies in the fact that length of days is not a morpho-

logical character. The recapitulation theory has nothing

to do with physiology; it is purely a matter of mor-

phology.

The degree of approximation between the young of

a higher form and the adult of a present-day lower

form of the same line depends upon the degree of spe-

cialization and divergence of the lower species from the

main path of descent. It is usually recognized that

most of the lowest and morphologically simplest organ-

isms are highly specialized for some particular mode

of life more or less different from the ancestral. This

specialization nearly always carries with it some struc-

tural adaptations, but these may not obscure the ances-

tral characters. Thus Marchantia has evolved a cham-

bered thallus highly differentiated, to adapt it at once

to an aquatic substratum and aerial life, but it still

retains a sporophyte perhaps very similar in some fea-

tures to that of the ancestors of the higher plants at

the liverwort stage. On the other hand, organisms are

occasionally found which give every indication of being

primitive. These are truly forms with arrested evolu-

tion. Renfrewia is an example; Anthoceros is another,

less free from specialization but contrasting strongly

No. 506] KELPS AND RECAPITULATION THEORY 103

with Marchantia. Such primitive types are few and

far between for obvious reasons: if an entire group

advances rapidly it moves up bodily into a higher

plane and leaves behind only such forms as stray into

some byway of specialization, which specialization would

be a bar to future progress except in the line upon which

the form had entered. All unspecialized forms left be-

hind in the advance of the race are likely to be displaced

early in the struggle for existence because of their lack

of particular adaptations. It is accordingly only in such

environments as present no specialized demands upon

their inhabitants that we may expect to find these prim-

itive forms and it will be observed that to a large extent

such is the case.

Wherever a form is found with simple unspecialized

structure it becomes at once a problem to decide whether

it is in reality primitive or a degenerate type. If there

is no paleontological history to aid in the solution a con-

clusive answer to this question is often impossible. How-

ever, unless there is definite evidence of degeneration 1n

vestigial structures or the like, as there is in many cases,

for example the mistletoes; it is generally safe to assume

that the present condition of the organism represents

its highest attainment in the process of evolution. De-

generate forms usually manifest a high degree of fixity

in their organizations and great variability is seldom

found in such forms: It might be suggested that the

apparently primitive structure of Renfrewia may be due

to degeneration from a condition more highly differen-

tiated. It possesses, however, no vestigial or unused

organs, with the exception of the basal cone of the stipe.

very portion of the plant is functional. There are nn

peculiarities about its structure which mark it as differ-

ent from the other kelps. On the contrary, its reproduc-

tion and its histology are similar to them. Its habitat,

quiet water just below the tide mark, is exactly that which

would be expected of the ancestors of the kelps v

they acquired adaptations enabling them te endure the

104 THE AMERICAN NATURALIST [Vou. XLIII

heavy surf and the drying incident to living above the

tide mark. At the same time it has such a high degree

of variability in its whole structure that it is difficult to

pick out characters sufficiently fixed to be of use in de-

scribing it. There seems to be no good reason to doubt

its primitive position.

Taking all the evidence into consideration,. it seems

to the writer that we are bound to conclude that though

organisms are subject to adaptation at any stage of their

life cycles and may gradually cut out superfluous stages,

yet, except as some such tendency has operated to change

the heritage, the development of the individual does re-

capitulate the history of the race. The degree of corre-

spondence of any individual cycle with its ancestral his-

tory is various in different cases but may be very close.

Recapitulation must take place if there is any force which

tends to make offspring like parent, if heredity is of any

importance in moulding the forms of organisms. On

the other hand, if there be any variability or transmuta-

tion of individuals in stages other than the adult end

stages of their life cycles, the recapitulation can not be

perfect, but must be marred at every stage where second-

ary change has taken place. The extent to which any

individual will recapitulate its phylogeny must therefore

depend on the balance maintained between these two

forces in the given case. The value of a study of on-

togeny for the taxonomist or phylogenist will depend al-

together on the facts of the special case. In each case

the evidence must be weighed before a conclusion can

be reached. Ontogeny may be of greater or less worth

in the attempt to build a rational system of nature. But

variable as its utility may be in different cases, the re-

capitulation theory states a fundamental law of a tend-

dency of the embryogeny and must be considered as one

of the several interacting tendencies which together con-

trol the development of animals and plants.

COLUMBUS, O., August, 1908.

No. 506] KELPS AND RECAPITULATION THEORY 105

LITERATURE

No attempt is here made to list the voluminous literature devoted to

discussions of the recapitulation theory. he more important papers have

been thoroughly listed and summarized in many of the standard general

works, e. g., Montgomer

Barber, C. A. On the aie and Development of the Bulb in Laminaria

bosa. Ann. Bot., 3, 41. 1899

Conklin, E. G. The Organization and Cell Lineage of the Ascidian Egg.

Jour. Acad. Nat. Sci. Philadelphia, vol. 13. 1905.

Frye, T. C. Nereocystis lutkeneana. Bot. Gaz., 42, 143-146, fig. 1. 1906.

Gepp, A. and E. S. Lessonia grasditolik Jour. Bot., 43, 1905.

a iirter. Zur Kenntnis der Tange. Bot. Zeit., vol. 43. 1885.

Griggs, R. F. Renfrewia parvula, New Kelp from Vancouver Island. Pos-

telsia, 1906, 247-274, pls. 16-19. 1906.

————. Cymathere, a Kelp from the Western Coast. O. Nat., 7, 89-96,

Pi Ife. 1: 1907:

Hooker, J. D. Flora ~~ 2, t: 171, 167. 188%.

Humphrey, J. E. the Anatomy and Devolpment of Agarum turneri.

Proc. Am. Acad., "88, 201. 1886

Kjellman, F. R. Laminariacee in Pflanzenfamilien, 1°, 242-260. 1893.

MacMillan, ©. Observations on Nereocystis. Bull. Torr. Club, 26, 273-296,

. 361-362. 1899.

Observations on Lessonia. Bot. Gas, 30, 318-394, pis: 19-20.

1900

. The Kelps of Juan de Fuca. Postelsia, 1901, 193-220, pls. 22-

26. 1901.

Observations on Pterygophora. Minn. Bot. Stud., 2, 723-741,

pls. 57—62. :

Montgomery, T. H. The Analysis of Racial Descent in Animals. New York.

1906.

Morgan, T. H. Evolution and Adaptation. New York. 1903.

Oliver, F. W. On the Obliteration of the sieve ‘abe in the Laminaria.

Ann. Bot., 1, 95. 1887.

Postels and Ruprecht. Tllustrationes algarum.

1840.

Ramaley, Francis. Observations on Egregia Menziezii. Minn. Bot. Stud.,

3, 1-9, pl. 1-4. 1903. eo fan

Reinke, J. Studien zur — Entwiekelungsgeschichte der

inariaceen. Kiel.

Saunders, D. A. Alge E the Harriman Alaska Expedition. Proc. Wash.

Acad. Sci., 3, 391-486, pls. 18-62. 1901.

Schrader, Herman F. Observations on Alaria nana.

157-166, pl. 23-26. 1903.

Setchell, W. A. Concerning the Life History g ET

Proc. Am. Acad., 26, 177-217, pls. 1 and 2.

. Classification and Geographical Distribution of the Laminaria-

ceæ. Trans. Conn. Acad., 9, 333-375. ete

eee

~ 1896a.

4, 9, ti 1-1 pl 8

Minn. Bot. Stud., 3,

dermatodea.

=`. Eisenia arborea. Erythrea,

—«1896b. oa

106 THE AMERICAN NATURALIST ([Vov. XLIII

———. The Elk Kelp. Erythrea, 4, 179-184, pl. 7. 1896c

896c.

————. Laminaria sessilis in California. Erythrea, 5, 98. 1897.

29. 1901.

—— Post Embryonal Stages of Laminariacee. Univ. Cal. Pub. Bot.,

2, 115-138, pls. 13-14. 1905a.

——, B

egeneration among Kelps. Ibid., pp. 139-168, pls. 15-17.

1905b.

Nereocystis and bier Bot. Gaz., 45, 125. 1908a.

- Critical Notes on the Laminariacee Nuov Notarisia 19: 90-101.

Rev. Jour. Roy. Mic. Soc., 1908, 474. 1908b.

Setchell, W. A., and Gardiner, N. L. Algæ of Northwestern North America.

Univ. Cal. Pab. Bot., 1, 165-418, pls. 17-27. 1903.

Sykes, Miss M. G. Antiy and Histology of Macrocystis and Laminaria

rina. Ann. Bot., 22, 291-325, pls. 19-21. 1908.

Recherches sur ja Zono des Algues et les Antheridies des

Cryptogames. Ann. Sci. Nat., ser. 3, 14, 240, t. 30.

DeToni, J. B. Sylloge ORE 3, 316-374. 1895. ;

Wille, N. Beitr. Physiolog. Anatase Laminariaceanum. Univ. Fests. til.

K. M. skar, TI, Anleidung Regjieringsjubilaeet. 1897.

Williams, J. L. Germination of the Zoospore in Laminari

62, 613. 1900.

Yendo, K. On Eisenia and Ecklonia.

iaceæ. Nature,

Bot. Mag. Tokyo, 16, 203. 1902.

- two new Marine Alge from Japan. Ibid., 17, 99-104, pls. 2

and 3. 1903a.

Hedophyllum spirale sp. nov. Ibid., 17, 165-173, pl. 6. 1903b.

NOTES AND LITERATURE

PLANT PHYLOGENY

The Origin of the Archegoniates.—There is in the theoretical

discussion of plant evolution perhaps no gap which is more

difficult to bridge than that between the thallophytes and the

archegoniates, or more precisely that between the higher alge

and the liverworts, mosses and ferns. The most recent discussion

of this problem is by Schenck, one of the authors of the ‘‘Lehr-

buch der Botanik,’ who is convinced that the archegoniates

arose from the Phæophyceæ or brown alge.

A number of earlier writers have endeavored to relate the

archegoniates to the Chlorophycee or green alge. This has

generally been attempted through Coleochete or Chara. Coleo-

chete has been a favorite type for the reason that its fruit, de-

rived from the germination of the egg, is a globular multicellular

structure somewhat resembling the sporophytes of the simpler

liverworts in the order Ricciales. Allen, however, has reported

that the phenomenon of chromosome reduction takes place dur-

ing the germination of the egg and not at the end of this period

of fructification, which clearly indicates that the latter de-

velopment is not the homologue of a sporophyte. A comparison

of the sexual organs of Coleochxte with those of the arch-

egoniates presents further difficulties, for the antheridia and

oogonia of Coleochete are unicellular structures very different

from the multicellular sexual organs of the archegoniates. The

general morphology of Chara is somewhat moss-like, but in this

form also the life history fails to present any evidence of an

alternation of generations comparable to that of the archegoni-

ates. Furthermore, the essentially unicellular structure of the

oogonium (the protective investment of which is clearly a sec-

ondary feature) bears no fundamental resemblance to an arche-

gonium, and its remarkable antheridium is unique among the

sexual organs of plants.

The Rhodophyceæ or red algæ have a highly developed sporo-

phytic phase, but their diverse morphology as well as that of the

“Schenck, H. Ueber die Phylogenie der — und der Char-

190

aceen, Baaler” s Botan. Jahrbuchern., XLII,

107

108 THE AMERICAN NATURALIST [Vow XLII

gametophyte is so very different from anything present in the

lower achegoniates that relationships between the two groups

seem hardly possible. The work of Yamanouchi on Polysi-

phonia clearly indicates that the tetraspore mother cell when

present is the seat of reduction mitoses terminating the sporo-

phytic phase of the typical life history of the higher red alge.

The sexual organs of the red algæ are also far removed in struc-

ture from the sexual organs of the achegoniates.

Davis in 1903 first pointed out the resemblance of the achegon-

ium and antheridium of the bryophytes to the plurilocular

sporangium or gametangium of the brown alge, and advanced

the view that the former arose from such a type of sexual organ

as the latter through the differentiation of a sterile protective

envelope around the gametes (in response to terrestrial life

habits), and such sexual evolution as would give the highly de-

veloped condition of heterogamy present in the archegoniates.

Davis, however, was unwilling to concede the probability of an

origin of the archegoniates from the brown alge because of the

great morphological differences between the two groups, but

suggested that there may have been forms of green alge with

pluriloctlar sporangia, now extinct, from which the bryophytes

have been derived.

Schenck accepts the view of Davis that the sexual organs of

the archegoniates are homologous with plurilocular gametangia

and derived from them, but argues for a direct origin of the

archegoniates from the brown alge. He gives an excellent

series of figures, selected from various authors, which illustrates

the principal forms of plurilocular sporangia and gametangia

of the brown alge, and presents a similar series of figures of

antheridia and archegonia of bryophytes and pteridophytes

showing various points of resemblance in their structure and de-

velopment. The resemblances are easily followed between the

gametangia of the lower brown alge (Pheosporee) and the

sexual organs of mosses and most liverworts. However, there

are difficulties when the antheridia and oogonia of Dictyota, the

endogenous antheridia and sunken archegonia of Anthoceros,

and the sunken sexual organs of certain eusporangiate pterid-

ophytes, Lycopodium, Selaginella, Isoetes, ete., are compared

with plurilocular gametangia of brown alge in an attempt to

derive in a direct manner the former from the latter. The re-

viewer agrees with Schenck that plurilocular sporangia and

gametangia of the brown alge are in the same class of repro-

No. 506] NOTES AND LITERATURE 109

ductive organs with archegonia and antheridia, but would not

be willing to go so far as to hold that the latter have been

derived directly from the former.

There follows then in Schenck’s paper an attempt to homolo-

gize the spore mother cell of the archegoniates with the tetra-

sporangium of the Dictyotaces, based on the fact that the mitoses

in both cells are reduction divisions terminating the sporophytic

phases of life histories with an alternation of generations. The

endogenous formation of spore mother cells in the archegoniates

is regarded as an ecological adaptation associated with terrestrial

life habits. The analogy is perfectly clear, but it may well be

questioned whether it suggests so close a relationship as to

justify an homology, especially since reduction phenomena are

now known for a number of unrelated groups of alge and fungi.

The tetraspore mother cell of the red alge is probably in most

forms also the seat of chromosome reduction terminating a sporo-

phytic phase. The mitoses in the zygote of Spirogyra have

recently been shown by Karsten to be reduction divisions, as has

been suspected, and it is altogether probable that similar reduc-

tion mitoses will be found to occur with the germination of the

eggs of Œdogonium and a number of other alge, and for certain

phycomycetes as well. All of these cells in being the seat of reduc-

tion mitoses are analogous to the spore mother cells of arche-

goniates, but that would not warrant their being considered as

homologous with the latter structures. There is, on the contrary,

good reason to believe that in plants reduction phenomena became

established as features in the life histories of a number of groups

quite independently of one another, as the evidence indicates was

also true of the processes of sexual evolution and the differen-

tiation of sporophyte generations. Chromosome reduction as a

Physiological process seems to be a corollary of sexual nuclear

fusions, but the cells concerned in the former are less likely to

be homologous with one another than the cells concerned in the

latter, since they are a part of a new phase which tends to become

elaborated as the intercalated sporophytie generation. Tt is clear

that a number of types of gametes throughout the plant kingdom

are not homologous, and equally clear that several different forms

of cells associated with chromosome reduction are not homologous.

inally, Schenck compares the gametophytes and sporophytes

of the archegoniates with the thalli of the brown algæ, but 5

~ B doubtful whether he really strengthens his case. The resem-

_ blance of the gametophytes of thallose liverworts to band-shaped

110 THE AMERICAN NATURALIST (VoL. XLIII

forms of the brown alge is but superficial and does not extend

to fundamental anatomical features. Indeed, both the brown

alge and the bryophytes present so remarkable a variety of

vegetative structure that it is very difficult to pick out types

which may be held to be representative of the two groups.

Schenck refers frequently to the conditions in the Dictyotales,

but this assemblage is very far from being representative of the

' brown algz as a whole and stands rather as a group of very

uncertain relationships. The simpler gametophytes of the

pteridophytes may more readily be compared to the thalli of

some of the lower brown alge, but they are very different

from the higher forms where the sexual conditions are those of

heterogamy, and, moreover, this simplicity in some types of

pteridophytes is rather evidence of that general principle of

plant evolution according to which the gametophytes become

reduced in structure as the sporophytes attain higher levels of

complexity. It is of course much more difficult to make com-

parisons between the sporophytes of the achegoniates and the

thalli of the brown alge. ;

This portion of Schenck’s paper appears to the reviewer to

give very little support to his speculation and herein lies its

principal weakness, for if the vegetative morphology of the

brown alge is not suggestive of relationships to the archegoniates

the resemblance between their sexual organs can scarcely alone

carry much force, especially since the latter may with great

probability be supposed to refer to older and more primitive

conditions. The reviewer is still inclined to his opinion that

there have probably existed groups of the green alge now extinct,

the sexual organs of which were plurilocular gametangia, from

which the archegoniates may have arisen. We have at present

suggestions of such types in Schizomeris, Stigeoclonium tenue

irregulare and conditions occasionally found in Draparnaldia

and Chaetophora. That such groups of extinct green alge may

have originally had close relationships to the brown alge is

quite possible.

In the last section of this paper Schenck discusses the origin

of the Charales. Of especial interest is the suggestion that the

puzzling antheridium of this group may be interpreted as a —

sorus of antheridial filaments developing endogenously and may

be compared to the sori of plurilocular sporangia which are pro-

duced externally on the surface of certain brown alge. Accord- —

Ing to this view the globular male organ of the Charales is really

a Collections of the United States National Museum.

No. 506] NOTES AND LITERATURE 111

a complex of eight clusters of true antheridia in the form of

filaments, and the entire structure constitutes a sorus-like struc-

ture in which the antheridial filaments arise endogenously. This

conception has strong support in the abnormal conditions de- ;

seribed by Ernst for Chara syncarpa where antheridial filaments

were found developing externally from cells below the oogonium

giving an hermaphrodite association of sexual organs. Schenck

considers the Charales to be much more closely related to the

brown alge than to the green, basing his views on the above

considerations together with certain resemblances between their

vegetative structure (characterized by nodal and internodal

regions) and that of certain brown alge, Spermatochnus, Des-

marestia, ete.

BrapLEY M. Davis.

HOLOTHURIANS

Clark’s The Apodous Holothurians.'—Revisions of genera and

larger groups require more painstaking care and research than

most other forms of biological study, certain current opinion

to the contrary, notwithstanding. Dr. Clark’s memoir is a good

example of a revision applied to a difficult group of animals. It

is a well-executed and well-matured piece of work, and one

which fulfills all reasonable expectations. It is easily the most

important treatise that has ever been published upon the families

Molpadiide and Synaptide.

The monograph is based upon a critical examination of about

2,200 specimens in the collection of the National Museum, and

is divided into four parts. The classification of the two families

is first discussed and a table of accepted genera, with type

Species, is given. Part II is an annotated list of the species in

the collection of the National Museum, including descriptions

of new genera and species. Part II contains an account of

the Synaptide, their morphology, embryology, physiology, ecol-

ogy and taxology, with keys to genera and species, and a short

notice of each species, special attention being given to the

geographical distribution. In Part IV, the Molpadiidwe are

treated in a similar manner. Of the thirteen plates, three are

__ The Apodous Holothurians, A Monograph of the Synaptide and

Molpadiide, Ineluding a Report on the Representatives of these Families in

By Hubert Lyman

_ Clark. Smithsonian Contributions to Knowledge, Part of Vol. XXXV, 231

PP. XIMI plates, 1907 (issued early in 1908). — oo -

112 THE AMERICAN NATURALIST [Vou XLII

in color. The figures are intended to illustrate not only the

new forms described, but also previously known species that

have not been figured and some others, figures of which will

be of service to the student. In a number of instances the

nomenclature has been changed, and has been placed on as

firm a basis as possible by the use of the generally accepted

principles of the International Code. It will be seen that the

monograph has a wider scope than a systematic revision, in-

eluding as it does accounts of the anatomy, embryology and

physiology.

The interesting account of the history of the classification of

the two families is followed by an important consideration of

the characters used in classification, and a discussion »of the

subfamilies and leading genera. Twenty-nine genera, of which

8 are new, are accepted, distributed as follows: Synaptine, 11

genera (2 new) comprising 60 species; Chiridotine, 7 genera

(3 new) with 22 species; Myriotrochine, 3 genera, 6 species;

Molpadiide, 8 genera (3 new and 1 new name) with 46 species.

Dr. Clark has discovered that Ankyroderma is practically a

juvenile condition of Trochostoma. As generally defined the

former is distinguished from the latter by the presence of

rosettes of racquet-shaped rods from the center of which there

extends outward a conspicuous anchor. It was found, from a

study of more than 350 specimens of these two genera, that the

presence of anchors and rosettes of racquet-shaped rods can

not be regarded as even a constant specific character. For ex-

ample, small specimens of Trochostoma intermedium Ludwig

with very thin skin are clearly Ankyroderma. Large specimens

have a rather thick body wall and very numerous deep red or

brown bodies in the skin, but no rosettes. The rosettes dis-

integrate into heaps of rounded colored bodies which differ

from calcareous plates or particles in being chiefly phosphoric

acid and iron. They are therefore quite unlike the ordinary

calcerous deposits of holothurians, and are named ‘‘phosphatic

deposits. ’’

Eliseo y laap of these facts our knowledge is as yet too

y clear conelusions. Chemical analysis’ of the

* The composition of these bodies is given as FePO, + 4H,O = 66.2

SOE BE sat Cac. 84 Tiene in al probably Mg preen

much variation; probabl prege aR per of CaCO, is suhjeat =e

into ooien bodi = ae Page careous particles are first transformed

3 most important substance present, and

No. 506] NOTES AND LITERATURE 113

deposits shows that the colored bodies are radically different from the

ordinary deposits in the skin. Both are possibly connected with the

process of excretion; but why one should replace the other it is cer-

tainly hard to say. That the change is closely connected with the

age of the individual seems to me almost certain, though it must be

remembered that size in echinoderms is not a sure criterion of age. It

is interesting to note that most of the species of Ankyroderma described

have been less than 60 mm., while many of the Trochostomas range

over 75” (p. 19).

The name Trochostoma antedates Ankyroderma, but both are

synonyms of Cuvier’s Molpadia (1817) which ineludes also

Haplodactyla Grube (not Semper), as well as the long-dis-

carded Embolus Selenka, and Liosoma Stimpson (not Brandt).

In this enlarged genus Molpadia, twenty-seven species are

recognized.

Some of the more important changes in the limits or names

of genera, as well as certain new genera, will be noted. Synapta

is monotypic and restricted to S. maculata Chamisso and Eysen-

hardt (S. beselii authors) ; Oestergren’s Chondroclea is called

by the older name Synaptula; Leptosynapta Verrill is rein-

stated for the inhærens group; Synapta kefersteinii is made the

type of a new genus Polyplectana; the recently described

Opheodesoma is accepted for the Euapta glabra group; the old

species Chiridota rufescens is made the type of a new genus

Polycheira; Tæniogyrus Semper, for Chiridota australiana

Stimpson, is accepted as distinct from the later Trochodota Lud-

wig; Chiridota japanica v. Marenzeller is made the type of

Seolidota, new; Achirodota is founded upon Anapta inermis

Fisher, and Toxodora Verrill is reinstated. The most important

change in the Molpadiide has already been noted. Haplodactyla

Semper 1868 (not Grube, 1840) is renamed Aphelodactyla, with

five species. Ceraplectana and Himasthlephora are two new

genera, the former near Molpadia, the latter related to Gephyro-

thuria Koehler and Vaney.

It has occurred to the present reviewer that, had space per-

mitted, a very useful feature would have been the insertion of

a complete diagnosis under each species not described in P art

II. It is not possible to include in keys all the positive char-

acters of a species, nor is it always possible for the average

as the color deepens, it decreases rapidly in amount. Apparently the

calcium as well as the CO, is excreted as these changes take pa a

143). The presence of phosphatic deposits is limited to the upe

114 THE AMERICAN NATURALIST [Vou. XLIII

student to have access to original descriptions. No one is able

to tell when an apparently useless character (from the system-

atist’s standpoint) and therefore one invariably omitted from

keys, may not assume prime importance in the light of unnamed

material. The practical difficulty that one has in depending

upon literature and concise revisions is this. By testimony of

keys (and figures too) one may have a species very close to a

named species, yet there may be present in the questionable

form additional characters of which no mention is made in keys.

If one has not access to the original or some later authentic

description he is ‘‘up a stump.’’ The writer has so often

found himself in this undesirable position that he speaks with

some feeling on the subject.

However, the lack of descriptions is partly compensated for by

the excellent notes under ‘‘Remarks,’’ and in some cases by the

republication of figures. Students of the group have every

reason to be grateful to Dr. Clark for a very timely and useful

memoir, and one which has in several instances reduced to

order what was seemingly hopeless chaos.

W. K. FISHER.

LEPIDOPTERA

The Blue Butterflies of the Genus Celastrina.—In the second

volume of Mr. J. W. Tutt’s ‘British Butterflies,” recently pub-

lished, is a most exhaustive account of the small blue butterflies

represented in Europe by Celastrina (vel Cyaniris, vel Lycæna)

argiolus, and in America by the common and widely distributed

C. pseudargiolus. The latter insect has long attracted much

attention, owing to its remarkable polymorphism, which has

been elucidated very fully by Edwards and Scudder. Mr. Tutt

has gone over the whole subject afresh, and with the assistance

of Dr. T. A. Chapman and Mr. G. T. Bethune-Baker, has been

able to reach a number of very interesting conclusions. It

appears that Celastrina is essentially an old world type; found,

or represented by close allies, in every one of the great zoological

regions of the Eastern Hemisphere, though feebly represented

in Australia and Africa. In America, it is represented by C.

pseudargiolus and its subspecies, one of which extends as far

south as Panama. An examination of the structural characters,

especially the genitalia, shows that pseudargiolus is not in any

way definitely separable from the palearetie argiolus, of which

it must be considered a geographical race. It appears probable | 3

No. 506] NOTES AND LITERATURE 115

that C. argiolus reached America in late Miocene times, and

being able to live on a great variety of plants, spread widely,

producing various local races. So long as it was restricted to

temperate regions, it did not come to differ radically from the old

world type; but the form gozora Boisduval, of the mountains

of Mexico and Central America, is very striking in appearance.

Even this last, however, has the genitalia and other structures

of genuine argiolus. This case is especially instructive, because

it indicates that an insect may spread very widely, invading

regions with exceedingly diverse climates, and yet not change

materially in the characters of the genitalie armature. When

we remember how frequently allied species of insects, inhabiting

the same or similar regions, are separable by genitalic characters,

it seems that these are little or not at all connected with obvious

environmental factors. To say that genitalie modifications are

due to ‘‘mutation’’ does not really explain them; it remains to

be shown, if that is possible, what it is that breaks down an

established genitalie type, giving rise to new forms which rank

as species. In the case of Celastrina, it is not to be assumed

that its structural features are so immobile that they are in-

capable of modification. As a matter of fact, the numerous old

world species are distinguished by the possession of very dis-

tinct genitalia, each very constant within specifie limits. In

Asia there are very distinct races, having precisely the structure

of C. argiolus, and at the same time species exceedingly like

argiolus superficially, but quite different in their genitalie ap-

pendages. From the standpoint of the natural selectionist, it

may be remarked that there was nothing to be gained by

genitalie differentiation in America, so long as only one species

of Celastrina inhabited the country; and further, that the range

of the insect, with all its local modifications, was practically

continuous. It may be that in Asia (especially among the

islands) distinet species arose, adapted to special food-plants

and other conditions, and that whenever these spread so that

their ranges overlapped, crossing—by throwing the organism

out of gear with its environment—was injurious, and so tend-

encies to genitalic modification were preserved. If these arose by

simultaneous mutation,’ not by random seattering variation, they —

might in such a ease lead to a pure differentiated race. SUS

gestions of this sort are of course to be taken with an adequate

Supply of salt, but they have their use as stimulating enquiry.

‘Or, perhaps, were already present as Mendelian recessives? — ee x

116 THE AMERICAN NATURALIST [Vou XLIII

Some years ago, in an address before the Entomological Society

of London, Professor Poulton raised the question whether the

ability to mate successfully was not after all something main-

tained by rigid natural selection; and if I remember his argu-

ment correctly (I do not possess a copy of his paper), he

believed that differences in the sexual organs might be expected

to arise whenever selection ceased to operate. Since that time

Tower has produced striking evidence of the small amount of

divergence which suffices to throw an organism (in his instances

beetles) out of the race. In this connection it may also be

remarked that the singular fertility between different races of

men, dogs, cattle, ete..—many of these differing exceedingly in

many characters of color and form—may be attributed to the

effects of natural selection. The purest breeds of dogs, and no

doubt the best established races of men, are after all great

mongrels; and in the course of time no doubt interracial in-

fertility would be absolutely discriminated against. However

active the imagination may be in picturing causes and effects,

it can but pause before such cases of genitalie modification as

are described by Dr. J. B. Smith in his revision of the moths of

the genus Homoptera and its immediate allies, just published

by the U. S. National Museum. In some of these moths the

sexual organs are extremely asymmetrical. ‘‘In the males the

asymmetry is between the harpes of the two sides, which in

extreme cases are totally dissimilar, with processes on one side

for which there is no counterpart on the other, and which are

and this structure is directly correlated to thes loros found

in the female.” These peculiarities are all figured most care-

fully.

T.: D. A. CocKERELL.

VERTEBRATE PALEONTOLOGY

The Lysorophide.— In 1875 D

Illinois, a local collector of fo

Bend,” on Salt Fork, on the Tat

r. J. C. Winslow, of Danville,

No. 506] NOTES AND LITERATURE 117

Chicago, where it now is. In 1877 Cope published a description

of several forms from among the remains collected at ‘‘Horse-

shoe Bend’’ among which was the form Lysorophus tricarinatus,

based on three vertebræ, which Cope took to be of reptilian

nature. Fyrom the fact that the bones were very similar to some

found in the Texas Permian, Cope concluded that the Illinois

deposit was likewise Permian; and such it is usually regarded.

From the discovery of a similar deposit in Pennsylvania by

Raymond? it seems more probable that the deposit in Illinois is

Pennsylvanian, as is the deposit in Pennsylvania.

In the summer of 1907 Dr. S. W. Williston sent the writer to

the Illinois locality for the purpose of settling the stratigraphy,

if possible, and to secure more material to illustrate the forms

which are so meagerly known. The deposit was found to be

already exhausted and after a month’s work scarcely a handful

of bones was secured. The stratigraphy was almost impossible

of determination, though Dr. Stuart Weller, who visited the

locality, was of the opinion that the circumstantial evidence was

very strong in favor of its being upper Pennsylvanian. Since

the discovery of similar deposits in Pennsylvania of undoubted

Pennsylvanian age it seems no longer necessary to doubt the

Carboniferous age of these Illinois deposits. In 1902 in **Con-

tributions from Walker Museum, Vol. I, p. 45,’’ Case announced

the discovery of typical vertebre of the Lysorophus tricari-

natus type from the Permian of Texas. Last June Case? de-

scribed the skull of the Lysorophus tricarinatus and came to the

conclusion that the form was an amphibian. Later in the

summer and almost simultaneously papers by Broili* and

Willistont appeared on the same subject. Broili emphatically

denied the amphibian nature of Lysorophus and Williston

proved conclusively that the form is not only an amphibian, but

is even allied to the modern Urodela. Broili reaches the

astonishing conclusion that Lysorophus ‘‘erscheint daher nach

den in der Systematik geltenden Grundsätzen fiir richtiger, -

zu den Lacertiliern zu stellen. ”?

Williston shows very conclusively that the form is an un-

doubted amphibian and gives the following characters to support

his views: skull pointed with no evidence of orbits, paired

' Science, N. S., Vol. XXVI, No. 676.

* Bull. Amer. ‘ee Nat. Hist., Vol. XXIV, p. 531.

*Broili, Anat. Anz., Bd. XXXIII, No. 11/12. ti

‘ Williston, Biol. Bull., Vol. XV, No. 5. a

118 THE AMERICAN NATURALIST [Vou. XLII

eplotics present, supraoccipital unpaired, condyle unossified,

branchial apparatus well developed, vertebral column slender,

limbs apparently absent, ribs long, somewhat curved and flat,

neurocentral. Williston concludes:

“The only aberrant character to distinguish Lysorophus from the

Urodela is the long and rather broad ribs, unknown among these

modern animals or their possible ancestors, the Branchiosauria. It is,

however, very evident that the earliest ancestors of both these groups

must have long ribs, and their persistence in Lysorophus would be

nothing remarkable.”

But why need we conclude that the early ancestors of the

Amphibia must have had long ribs? There is no geological

evidence of such, and the oldest known branchiosaurian, Micrer-

peton caudatum Moodie from the middle Pennsylvanian cer-

tainly possesses very short ribs. The animals associated in the

Carboniferous with the Branchiosauria, as a rule, possess long

ribs, but do we need to infer that the Branchiosauria and the

Microsauria had the same ancestry ?

In all the long stretch of geological time there has never

existed a branchiosaurian nor a true urodele which had long

ribs, and so far, aside from the frogs found in the Tertiary, —

these are the only true amphibians known in the fossil state.

It is exceedingly incongruous to class the Miecrosauria and

Branchiosauria in the same order Stegocephala. Their organ-

ization is totally different. To be sure, the long ribs in Lyso-

rophus might have developed secondarily as Williston suggests,

but why do we need to assume even this when among the mod-

ern Gymnophiona we find long ribs and every other character

which is present in the Lysorophus? It is also possible that

the Gymnophiona are true Caudata, in which case there would

be no distinction and it may be that Lysorophus will be of

great assistance in bridging over this gap between the Caudata

and the Gymnophiona.

Certain it is that-the form is a most interesting discovery and

one of the most important in the phylogeny of the extinet — ae

Amphibia in many years. I quote herewith from a letter to |

Dr. Williston from Dr. Broom which the former was so kind

as to send me during the course of our correspondence on the

subject :

“The skull (of Lysorophus) is to my mind undoubtedly Urodele and

singularly like that of Amphiuma which I believe to be the noiro

living ally. I am convinced that it is not a Gymnophionid . . -

No. 506] NOTES AND LITERATURE 119

Here are then three various points of view offered for study—

one, of Broili, that the form is a lacertian ; two, that of Williston

and Broom, that the form is a member of the true Caudata ; three,

the suggestion offered here that the form may be one of the

Gymnophiona. In further support of the view of the gym-

nophionid character of the form is the snake-like character

assumed by Lysorophus. Case has noted that the vertebral

column is usually coiled where there is any considerable portion

of it preserved and Dr. Williston remarked to the writer of

the same fact which he had observed in the field while in Texas

the past summer. The palate structure of the Lysorophus is

against the idea of the form being a member of the Gymnophiona,

at least so far as we know the palate; further knowledge of this

structure will undoubtedly solve the problem.

Further study of the form will also reveal other facts as to its

anatomy and we are hoping to hear much from the recent collec-

tions of Drs. Williston and Case from the Texas Permian.

Stegocephala—In an endeavor to reach some definite conclu-

sions in regard to the correct classification of the extinct

Amphibia, investigators all over the world are issuing contribu-

tions on various phases of the subject. One of the more recent

advances is a study of the vertebre of the Carboniferous forms

by Hugo Schwarz,! of Griefswald, Germany. He has studied

the exact characters of the vertebra of forms from the coal mines

of Linton, Ohio, of which there are specimens preserved in

Berlin and in Griefswald, and also specimens from Nirschan

bei Pilsen. The work was done under the advice of Dr. Otto

Jaekel and the paper shows a strong bias of Jaekel’s views.

The methods of study adopted by Schwarz are the same as

those proposed by Jaekel five years ago. The specimen is re-

moved from the soft coal, in which it is imbedded, by chemicals

and by mechanical means and an impression is made of the

mold by wax, plaster or guttapercha. While most of Jaekel’s

results show that the methods have some advantages, yet it is

to be doubted if they are the best in all cases. The interpretation

of the material is a puzzle at the best, and when the elements

are disturbed it is often very difficult to form any idea of their —

re Jaekel experienced this especially in his discovery of

the ‘‘perisquamosal’’ in Diceratosaurus, a structure which does-

not exist in other species of this genus and was probably due

' Beiträge zur Paleon. und Geol., Oesterreich-ungarns, ` BA. XXI

120 THE AMERICAN NATURALIST ([Vou. XLIII

to breakage in the form which Jaekel studied. Schwarz has,

on the other hand, obtained excellent results, and his descriptions

of the vertebre of the various forms will be of great service to

the student even though his conclusions are not accepted.

new family ‘‘Ophiderpetontide’’ is proposed to include

the genera Ophiderpeton and Thyrsidium, the former of which

was included in Lydekker’s Dolichosomatide. The family

characters are solely those exhibited by the ribs and vertebre.

Under the heading of Ophiderpeton the author rediscusses the

question of the ‘‘Kammplatten’’ and dismisses the subject with

the remark ‘‘dass sie nichts mit den Stegocephalen zu tun

haben.’’ Herein he has committed an error, for Fritsch has

distinetly figured? a nearly complete specimen of Ophiderpeton

persuadens Fr. with the ‘‘Kammplatten’’ in place near the

cloacal region of the animal. The whole question of the

‘‘Kammplatten’’ has recently? been reviewed by the present

writer. There is a great deal of uncertainty as to wHat the

true nature of the ‘‘Kammplatten’’ really is. That they do

occur in selachians as stated by Fritsch* does not at all imply

that they may not also occur in Ophiderpeton, and they cer-

tainly do occur here if Fritsch has correctly interpreted his

specimen.

Schwarz adopts the two suborders Aistopoda and Microsauria

for the ‘‘Holospondylen Stegocephalen,’’ but does not seem to

understand the differences which exist between these two sub-

orders, and especially is this true when he includes the Ptyoniide

in the Microsauria, since Ptyonius and its allies are typical

members of the group Aistopoda. There is really but little

difference between the groups Aistopoda and the Microsauria

structurally, and, as Schwarz suggests, they undoubtedly arose

rom the same stem much as did the lizards and snakes, but a

they are just as distinctly members of different groups as are

the Lacertilia and Ophidia. No form is more typically an

aistopod than the Ptyonius. The subordinal characters are

found in the vertebræ, in the lack of limbs, the elongation of the a

body and especially in the attenuation of the skull with its con- —

comitant structural differences.

The final conclusion attained by the author is edt with :

Jaekel, he would divide the Stegocephala into two groups, the

* Fritsch, 1901, ‘‘Fauna der Gaskohle,’? :

Suppl 1. IV, p. 89

3 Biol. Bulletin, Vol. XIV, No. 4, 1908, ea alee <

S der Boh. Gesell., 1905.

No. 506] NOTES AND LITERATURE 121

temnospondylous groups and the holospondylous group. In

the first group he would place all the forms which possess

rhachitomous, embolomerous and stereospondylous vertebræ, and

in the second group the forms which are usually known as

Aistopoda and Microsauria. He evidently excludes the Branchio-

sauria from the Stegocephala proper, in which the present writer

heartily agrees.

The contribution is a distinct advance in the knowledge of the

forms described and it is to be hoped that we may have more

information on the European forms which have been only too

little studied and described.

The Cotylosauria—The anatomy of this peculiar group of

reptiles has been further elucidated by the recent studies of

Williston! and Broili.2 Williston restudied the form first de-

scribed by Cope under the name of Parioticus incisivus. The

University of Chicago possesses a nearly complete skeleton of

this form and from his studies of this specimen Williston reached

the conclusion that the form belongs ‘rather in the genus

Labidosaurus and is a typical cotylosaurian. He has given

detailed figures of the anatomy of the various portions of the

skeleton and a restoration of the form in so far as it is known.

Broili has also given a restoration of a species of Labidosaurus,

L. hamatus. He has mounted the entire skeleton free. Thi

was impossible in the case of the specimen studied by Williston.

Broili’s restoration is a welcome addition to the knowledge of

the Cotylosauria, although I am sure the animal, were he alive,

would prefer not to have such an awkward sway in his vertebral

column. One of the peculiar things about the Cotylosauria

is the absence of lateral line canals which might be expected

to be present from the close resemblance in their organization

to the Stereospondyli, in which these canals are well developed.

Dr. Williston searched carefully for the canals, but without

success. The presence or absence of the canals may, at some

future time, be one of the chief distinguishing characters be-

tween the forms which we call reptilian and those we call

amphibian.

As a postscript to his article on Iyoiopha Williston has o

figured and described the ventral ribs of Labidosoures: incisivus. < oe

* Journ. Geol., Vol. XVI, No. 2, 1908. : oo

* Zeit. Deut. oh geol. Gesell., Ba. 60, H. 1, 1908.

* Biol. Bull., Vol. XV, No. 5, 1908.

122 THE AMERICAN NATURALIST [Vou XLII

From the presence of these small abdominal ribs Williston con-

eludes that: ‘‘This character adds another evidence of the rela-

tionship between the Procolophonia and Labidosaurus, and de-

stroys its value as a group distinction.’’ Broili, on the other

hand, sees closer relationship between the Cotylosauria and the

Stegocephala.

The Oldest Known Reptile.: —Dr. S. W. Williston has recently

redescribed the type specimen of the oldest known reptile.

This form, which Williston proposes to call Isodectes copei sp.

nov., was doubtfully referred by Cope to the genus Tuditanus,

but subsequently he referred it to the Texas genus Isodectes.

It certainly does not belong in Tuditanus, and while there is no

positive evidence that the form belongs in the genus Isodectes

it seems well to leave it there until the characters of Isodectes

are better known. The specimen is No. 4457 of the U. 5.

National Museum. It is preserved in a block of soft coal from

the Linton mines of Ohio which have furnished nearly all of

the remains of Carboniferous quadrupeds yet known in North

America. The Linton mines were undoubtedly located well

down in the Pennsylvanian and there has not yet been described

a reptile from a lower horizon. The affinities of the form are

doubtful though its close relationship to the Microsauria is well

established. The intercentral attachment of the ribs and the

apparent loss of the hypocentra in Isodectes copei, may require

a revision of the theory of the formation of the reptilian verte-

bre. The absence of abdominal ribs in this form is significant

in the light of the recent discussions of the relationships of the

early reptiles.

The Age of the Gaskohle—Students of vertebrates the world

over have become accustomed to accepting Fritsch’s interpreta-

tion of the age of the Gaskohle of Bohemia as Permian. It is

with some surprise, though not a little gratification, to note that

through the recent studies of European geologists and paleon-

tologists the deposits in Bohemia are now being regarded as

Upper Carboniferous. The facts and arguments are well set

forth by Broilit in a recent discussion on Selerocephalus. Be-

sides thus adding to the stratification of the forms of Amphibia

the new fact is thus brought out that the large form Sclero-

* Journ. Geol., Vol. XVI, No. 5.

* Jahrbuch d. K. K. Geol. Reichsan., Bd. LVIII, H. I.

No. 506] NOTES AND LITERATURE 123

cephalus, which is possibly temnospondylous, occurs first in the

Upper Carboniferous. A close parallel of this is found in the

discovery of Eryops by Case? in the Upper Pennsylvanian of

Pennsylvania. The progress of discovery is thus forcing further

and further back into geological time the origin of the Amphibia.

We now know nearly all of the types of the so-called Stego-

cephala from the Carboniferous and some of them occur well

down in the system.

The results given by Broili are based in large part on the

geological and paleobotanical studies of Weithofer and Feist-

mantel. The report is a lengthy one and occupies some twenty

pages, including lists of the vertebrates and the plants which

occur in the ‘‘Gaskohle schichten.”’

Bison occidentalis.—In the last issue of the Kansas University

Science Bulletin Dr. C. E. McClung" has described and figured

a mounted skeleton of Bison occidentalis. This specimen was

first noted by Williston in 1902.2 It was laterè described by

Stewart as belonging to the species B. antiquus which is now

assigned to B. occidentalis. The skeleton has only recently

been mounted by Mr. H. T. Martin and is noteworthy as being

the only mounted skeleton of a Pleistocene bison. The speci-

men is further noteworthy because of an arrow point found

under the right scapula as if it had been imbedded in the flesh

before death. From his study of the mounted skeleton Dr.

eClung reaches the conclusion that the extinct species was of

a more cursorial type than is the modern Bison bison.

Nectosaurus.—Three years ago Dr. J. C. Merriam’ gave to the

world a memoir on a peculiar group of marine reptiles which

he had discovered in the Triassic rocks of California and to

which he gave the appropriate name of Thalattosauria. He

has recently? added to the knowledge of the Thalattosauria by

additional notes on the anatomy of Nectosaurus. From his

recent studies Merriam concludes that Nectosaurus is a shore

dwelling form and the evidence seems strong enough to warrant

* Annals Carnegie Museum, Vol. IV, No. III-IV, 1908.

sions. Univ. Sci. Bull., Vol. IV, No. 10.

‘mpi Geol., Vol. XXX, International Congress of Americanists, 1902.

Kansas Univ. Quarterly: 1897.

' Memoirs Calif. Acad. Science, Vol. V, No.

University of California Publications, pede Vol. 5, No. 13. e i

124 THE AMERICAN NATURALIST [Vou XLII

the conclusion that Nectosaurus is not a young form of Thalat-

tosaurus as the author suspected when he wrote his memoir on

the Thalattosauria.

Callibrachion.— F". von Huene has restudied! the original speci-

men of Callibrachion gaudryi Boule and Glan. from the figure

published in Mem. Soc. d’Hist. Nat. d’Autun, 1893, Taf. 3, and

has republished this figure as a page plate. He was led to this

study by the fact that the three incongruous characters of

coronoid process of the mandible, opisthocclous cervicals and

the presence of only about 20 presacral vertebra being assigned

to the form and on these characters it had been assigned to the

Protorosauria by earlier authors and later to the Pelycosauria

and here it is placed by Case in his ‘‘Revision of the Pely-

cosauria.’’. Huene comes to the conclusion that the form is a

close relative of Paleohatteria

“ Hieraus folgt, dass Callibrachion nicht zu den Pelyeosaurien

gehoren kann, sondern sich Paleohatteria sehr nahe anschliesst und

wohl als einer ihrer direkten Nachkommen aufzufassen ist.”

He is then of the opinion that the earlier authors were right

in assigning Callibrachion to the Protorosauria. There are 23 .

presacral vertebree whch are amphicelous as in the Paleohatteria. i

The coronoid process is wanting in Callibrachion. :

Roy L. Moonie.

PARASITOLOGY

The Sleeping Sickness Bureau, recently established in London,

has begun the publication of a bulletin. The first number

(October, 1908) is devoted to a review of the ‘‘ Chemotherapy

of Trypanosomiasis.” The treatment of trypanosomiasis in

man, the biological accommodation of trypanosomes to chemo-

therapeutic agents and the treatment of experimental animals

are considered in succession. A bibliography of some 200 titles

concludes the number. Future issues of the bulletin will in-

clude all the current literature of trypanosomiasis.

The following items excerpted from the summary of this mass

of experimental material are of primary biologie interest. The

use of any trypanocide by itself can not be justified. Combined

therapy has the advantage that each drug can be used in smaller

doses. The alternation of trypanocidal agents avoids the habit-

uation of the parasites to a single remedy which has been thor-

*Centralblatt für Mineral. Geol. Paleontologie, 1908, No. 17.

No. 506] NOTES AND LITERATURE 125

oughly demonstrated through laboratory experiments. A second

paper deals with the medical results of segregation camps and

of chemical therapy in Uganda.

In the Huxley lecture, delivered at Charing Cross Hospital,

October 1, 1908, Sir Patrick Manson, speaking on ‘‘Recent

Advances in Science and their Bearing on Medicine and Sur-

gery,’’ discussed some points of great interest to biologists. At

the start he noted the propriety of this theme for a Huxley

lecture since the successful study of tropical diseases both de-

pends on the use of those methods so consistently and powerfully

employed by that great master of natural science, and also deals

primarily with animal organisms, protozoa and helminthes, as

disease producers and their special vectors, commonly arthropods,

while bacteriology is relegated to a secondary place. In the

study or teaching of tropical medicine this fact must be recog-

nized by the addition to each staff of a protozoologist, a helmin-

thologist, and an arthropodologist with suitable library and

laboratory facilities. After presenting a synoptic table which

outlines the principal tropical diseases with their causal and

intermediary agents, the lecturer proceeds to discuss the ap-

propriateness and value of biological theories in scientific ad-

vance with special reference to this field. Certain blood-

inhabiting protozoa require a second host as a medium for a

sexual cycle, as for instance the malarial plasmodium makes

use of the mosquito. Is this to be regarded as a general law

applicable to all such protozoa? The answer to this question

is of fundamental importance in practical medicine as well as

of intense interest to the biologist. The case of the sleeping

sickness trypanosome will serve as an example for testing the

problem.

The chief argument in favor of such a law is to be found in

analogy, and though it must be used with caution the evidence

in this case is distinctly favorable. All animals appear to re-

quire periodie sexual changes, and in other protozoa a sexual

cycle necessarily interrupts the periods of asexual reproduction

if the existence of the species is to be prolonged beyond nar-

row limits. In many cases where the existence of such a sexual

cycle had long been denied it has been demonstrated by more

intensive study. So highly developed a form as the trypanosome

can hardly be an exception to this rule. By analogy such a

stage would be. found outside the human body and probably

in the appropriate carrier of the disease, the tsetse fly.

126 , THE AMERICAN NATURALIST [Vow XLII

On the other hand, four arguments have been brought forward

against the acceptance of such a law: (1) No such sexual phase

has yet been demonstrated in any trypanosome. The history

of science gives scant weight to such negative evidence, especially

when one considers the minuteness of the organism and the re-

fractory character of the object studied, the tsetse fly. (2)

The sexual phase of the trypanosome may be passed in the

vertebrate blood and thus the tsetse fly be a mere mechanical

carrier. There is, however, no evidence favorable to this view,

either in observation or by analogy. (3) The successful inocu-

lation of the trypanosomes through a long series of vertebrate

hosts has been held to indicate that a sexual cycle is unnecessary.

Yet similar laboratory transfer has been practised with the

malarial plasmodium, for instance, though such a sexual cycle

in the mosquito is demonstrated beyond all question. (4) An

insect intermediary is apparently unnecessary in one trypano-

some, that which causes dourine or mal du coit in horses, and

therefore is not a biological necessity in any other species of

trypanosome. This Sir Patrick Manson regards as the most

formidable argument yet advanced against the law under dis-

cussion, but does not consider it as final. He devotes much

space to the consideration of details in the case and the pre-

sentation of an alternative hypothesis which is too involved to —

reproduce in abstract. While the discussion presents many

points of interest, yet the entire absence of experimental evidence

in its support leaves this view as at present a bare working

hypothesis. It may be added further that even the total re-

jection of this hypothesis does not necessitate the adaption of

the view it combats. Much further investigation is needed

before one can say with any confidence how the evidently ex-

ceptional case of the dourine trypanosome is to be explained.

He concludes: i

P I hold, therefore, that the existence of a sexual phase in the

sleeping-sickness trypanosome, T. gambiense, and other trypanosomes,

is more than probable, and that it has not been disproved; that the

argument founded on the natural direct communicability of dourine in

the ; apparent absence of an insect intermediary for its germ, T.

equiperdum, is not valid; and that the evidence hitherto adduced is

distinetly in favor of a law to the effect that blood-haunting protozoa

having arthropod vectors require, and make use of, these vectors for =

necessary sexual development.

1s passed in the arthropod, and not in the vertebrate, I cannot explain,

Why the sexual stage of these parasites ae

No. 506] NOTES AND LITERATURE ou ST

any more than I ean explain the contrary arrangement which obtains

in the blood-haunting nematodes, the sexual stage in their case being

passed in the vertebrate host, the asexual in the insect.

“T have no doubt, while listening to these remarks, it has occurred

to some of you, as it has often occurred to me, that the principles I

have endeavored to express have a wider application than that which

I have directly indicated, that our disease germs and our ectozoa—

insignificant though the latter appear to be—are correlated more fre-

quently than is generally suspected; that, in fact, there is a necessary

relationship between them.” Henry B. Warp.

EXPLORATION

Camp-fires on Desert and Lava.'—Lovers of outdoor life in the

far distant west will be delighted on opening W. T. Hornaday’s

recent work, ‘‘Camp-fires on Desert and Lava,’’ to observe, on

the back of the half title page, a figure of the omnipresent

Eleodes in very characteristic attitude. This little black crea-

ture by his position seems to be pointing us heavenward, but far

from it. He is ever ready to present us with a drop of sticky

brown fluid which has a horrible odor and whose stain will with-

stand the strongest soaps. The beetle forms a fitting intro-

duction to the delightful account which follows.

The author needs no introduction to the reading public nor

to the zoologist. To the one he is already well known by his

previous volumes and to the other by his connection with the

National Museum and with the New York Zoological Park as

well as by his scientific writings, not the least important of which

is his ‘‘Extermination of the American Bison,’’ published in

1889. Mr. Hornaday is an enthusiastic collector and observer.

All those who follow him into the Pinacate region, described in

the present work, will never regret it.

On our present maps the region visited by Mr. Hornaday and

his friends is variously located; suffice it to say that it is in the

northwestern part of Mexico and not many miles from the Gulf

of California. The region was attractive for several reasons,

among which was the one that it had never been explored by

any scientist or if it had there was no record of it. Other

reasons which attracted the party to the region were the possible

presence of big game and for Dr. MacDougal, who originated

the plan, there were untold new plants, of a type very inter-

esting to him, to be discovered. Dr. D. T. MacDougal made

* William T. Hornaday, Camp-fires on Desert and Lava. Illustrated. ?

_ Charles Seribner’s Sons, New York, 1908. nO alae S

126 THE AMERICAN NATURALIST (Vou. XLII

up the expedition under the auspices of the Carnegie Institution

to extend his researches on the desert flora, and on the journey

down to Mexico the author tells us of their visit to the famous

‘Desert Botanical Garden’’ near Tueson, Arizona, of which

Dr. MacDougal was one of the originators, and from which

point the expedition outfitted.

To those who have explored in the semi-arid regions of the

western states the account given by Mr. Hornaday of their

cross-country trip, recalls many familiar scenes. The cold morn-

ings, the blistering hot days and the delightfully cool evenings

are all features of a trip into the desert regions of the west.

All the scenes along the trail are brought before the reader by

pictures from pen and camera. The colored photographs are

especially striking. Botanists will find an interesting account

of the desert flora of southern Arizona and northern Mexico and

the zoologist will find a description of the few animals which

can manage to exist in this forlorn region. There is ever an

attraction in the desert; even the barrenness of things and the

apparent absence of all life make what little life there is all the

more interesting.

On the arrival of the party near the Pinacate region a long

camp was made and short exploring trips were conducted from

the main camp. This was made necessary from the fact that

the character of the country forbade further progress with the

wagons. At this place also occurred the only ‘‘row’’ of the

trip. Old campers know how painful it is to have a ‘‘row’’ on

in camp. It is painful for those immediately concerned and —

for those who have to witness it. Their stay at Pinacate was of

some length and full of success. They secured much big game —

and saw many interesting plants and photographed many new

plants and craters which abounded there. The most abundant —

large mammal was the mountain Sheep, Ovis canadensis. The —

author gives, in chapter XXIV, a discussion of the geographical :

like himself again.” 1s un

exploring trip into the unknown regions of the southwest.

Special Reference to the

The American Naturalist

A Monthly sane established in 1867, Devoted to the Advancement of the Biological Sciences

Factors

of Organic Evolution and Heredity

ENTS OF THE AUGUST NUM

The tops Bird Life of Minois: A pine

Study. Professor S. A. FORBES.

The woe Cycle of Paramecium when subjected to a

ag Environment, Dr. LoRANDE Loss Woop-

CONTENTS OF SEPTEMBER NUMBER

Some results of the Fl eraga "op cage of 1908,

rofessor T. D. A. COCKER

E pt ala ogy 0 of Myosurus Aint Dr. Leroy D.

Another r Aspect of the Species Question, Dr, J. A.

Pisco ar oratories and one Foran ata ager lg The ‘Origin of the Bates Eyes of Vertebraies

ae N oe and El r Doi "He lity—Spuri Allel

i a otes an itiru: poet iiy—Spurious elo-

Biometry as ett Enwanps AN, ien morphism, Results of Some Recent Investiga-

Shorter Articles and Correspon a : The Genus Ptilo- tions, W. J. SPILLMAN. Human Anatomy

erinus, rda Mie, CL panay A New Rhinoceros Pryor on Sexual and Family Variation in Centers

from the Buea: Miocene of Nebraska, HAROL of Ossification, C. R, B. Plant Cytolog 0-

rogis: pecan ag ag eo oe = blame aa

Hots “nr L —Sor R AD 3 1 o ans—

oo a a Cet fect i tad n aby yee anf thurioidea, Professor CHARLES L. E En-

BRADLEY M, Davis. Ornithology- Riddle on the teropnaiaim-Beosnt gS on the ee

Gene: of F m ‘a ta, Pr p ii

Jeuess of Fault-bars and in Paaa T d. Fa aay Paleontology—Cese on Pelycosauria Sete

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THE

AMERICAN NATURALIST

Vou. XLIII March, 1909 No. 507

INVITATION PAPERS AT THE BALTIMORE

MEETING OF THE BOTANICAL SO-

CIETY OF AMERICA

Ar the recent Baltimore meeting of the Botanical Soci-

ety of America, three series of special papers were read

by members who were specially requested by the council of

the society to prepare them for the occasion.

The first set of papers dealt with certain phases of

recent advance in our knowledge of vascular anatomy

in plants. These papers, read on December 29, were by

J. M. Coulter and E. C. Jeffrey.

The papers of the second series were read at a sym-

posium on ‘‘Present Problems in Plant Ecology,” on

Wednesday, December 30. The participants were H. C.

Cowles, B. E. Livingston, C. H. Shaw, V. M. Spalding and

E. N. Transeau.

The papers of the third series were read at the Dar-

win Memorial Session, held on Thursday, December, 31.

These addresses gave estimates of Darwin’s work in

three fields of botanical investigation. The participants

were Wm. Trelease, F. E. Clements and H. M. Richards.

In accordance with the instructions of the society, all

of the above mentioned papers are here published in full.

Dunoan S. JOHNSON,

Secretary.

OFFICE OF THE SECRETARY,

BALTIMORE, MD., February 1, 1909.

DARWIN MEMORIAL SESSION

In response to a letter announcing the plans for the

arwin Memorial Session, and suggesting that some

129

130 THE AMERICAN NATURALIST [Vou. XLII

word of greeting on that occasion would be very appro-

priate, and pleasing to his botanical colleagues in Amer-

ica, Professor Francis Darwin sent the following letter

to the president of the Botanical Society of America. It

arrived, unfortunately, for a reason stated in the letter,

too late for the meeting, but it obviously belongs with

the other contributions thereto.

13, Mapinetey Roan, CAMBRIDGE. Dec. 23, 708.

Dear Sir;

Owing to absence from home I am only now able to answer your

very kind letter. I am afraid my answer can not reach you in time,

which I much regret. I should have liked to express thro’h you as

president my sympathy with this assembling of American botanists

to honour my father’s memory. It is a source of sincere satisfaction

to me to know that such a meeting is to be held. I am reminded o

my father’s words to Asa Gray:

“Hooker has forwarded to me your letter to him; and I can not

express how deeply it has gratified me. To receive the approval of a

man whom one has long sincerely respected, and whose judgment and

knowledge are most oe admitted, is the highest reward an

author can possibly wish for

Your meeting is a postirimsus “ reward,” and though I have no

right to speak for English botanists I know that they will appreciate

it as it deserves.

Yours sincerely,

s DARWIN.

DARWIN AS A NATURALIST: DARWIN’S WORK

ON CROSS POLLINATION IN PLANTS

PROFESSOR WILLIAM TRELEASE

WASHINGTON UNIVERSITY

CHARLES Darwin is rated as a great man, and there are

really not many to-day who would dispute his. title to

this verdict; but he did not come easily to it.

In botany, he never did a thesis on morphology or eytol-

ogy, or photosynthesis; he was puzzled rather than de-

ranged by nomenclature; the reason that he provided for

the compilation of an index to the names and authorities

of all known flowering plants and their countries, in a

way, is a confession that he was not a taxonomist; and

a really fair all-round doctor’s examination, with botany

as a major, would have been likely to give him more

than the proverbial trouble. He does not seem to have

considered himself a botanist, and perhaps has never

been admitted to the fraternity formally—though he has

opened our eyes to some of the most interesting aspects

of plant physiology, baring their secrets in a masterly

way with the rough-and-ready direct methods and appa-

ratus of an adept. .

His earlier publications were on geology and zoology.

My impression is that botanists—aside from the very few

who know—looked on him in his lifetime rather as a

zoologist. And yet even to-day amusement may be de-

rived from reading what has been made public of the

debate before the French Academy, when his name was

under discussion for membership in the zoological section

of that great body and one of the immortals was ready

to place a hundred zoologists before him because of their

contributions of demonstrable facts to the science.

The greatness of the man itself long stood in the way

of its recognition. He had not classed himself with suffi-

131

132 THE AMERICAN NATURALIST [Vou. XLIII

cient minuteness in the subdivision of science. Looking

back on his career, it is not difficult to see that the geo-

logical problems opened up to him by the voyage of the

‘‘Beagle’’ would have afforded an interesting field for

detailed life work in geology which would have placed

him quickly among the foremost geologists of his day

if he had devoted himself to them and continued to pub-

lish on that subject and for those specialists. Even the

French savants saw in his barnacle studies the work of

far more than a tyro; but he did not choose to devote

himself to the morphology and classification of animals.

So little had he been thought of generally as knowing

anything of botany, that the Gardeners’ Chronicle re-

viewer of his orchid book expressed himself as doubly

constrained to care in critically analyzing it. He was

somewhat like a versatile witness questioned individually

by the members of a polyglot jury, each using and under-

standing his own language and getting nothing more than

a minute fragment of the whole testimony: he can hardly.

be said to have had a hearing before his peers—of whom

it would have been hard, even, to draw a full panel at

any time in the world’s history.

Darwin was really a philosopher. His son speaks of

him as seeming to be so charged with a theorizing power

that no fact, however small, could avoid releasing a

stream of theory which itself magnified the fact in im-

portance; but just enough to his theories not to condemn

them unheard, so that he was willing to test what would

seem to most people not at all worth testing. This is at

once the key note to his life work and his greatness in

influencing human thought. Though his philosophy has

received unusual, and perhaps undue, attention, through

clashing with some of what had become incorporated in

the theology of his day, his service in molding our way

of seeing nature may be coordinated with that of the

great men who have reduced the movements of the

planets to a physical basis and the transmutations of

matter to terms of chemistry.

No. 507] BOTANICAL SOCIETY OF AMERICA 133

Curiously, the human mind of the twentieth century

does not seem to be superior as a reasoning machine to

that of the time of the Greeks, and it is not surprising

that the general conclusions of Darwin’s philosophy had

been reached in one form or another all the way along

the past three thousand years. That his name goes into

history as their father, results from the way in which he

arrived at and substantiated them rather than from their

novelty: his greatness in great thought is the natural

achievement of a large mind reaching its ends by way of

the painstaking study of little things.

So full a discussion of Darwin from many points of

view is provided in the symposium of our fellow society,

the American Association for the Advancement of Sci-

ence, and in the allotment of subjects for our own Darwin-

session, that I should use time to little advantage if I

were to go into illustration of this, outside the special field

assigned me on the program—to the discussion of which

I have been asked to preface this general introduction.

I wish that I might quote Darwin’s first utterance on

the subject that has been assigned specially to me for

this meeting, but I do not know where to find it. In his

autobiography, he states that in 1838 or 1839 he had

begun to attend to the cross fertilization of flowers by

means of insects, from having come to the conciusion in

his speculations on the origin of species, that crossing

Played an important part in keeping specific forms con-

stant. Even then he had noticed the floral dimorphism

of Linum. In the preface to his book on the fertilization

of orchids he explains that its publication resulted from

the criticized exclusion (because of lack of space) of

detailed facts substantiating an opinion expressed in his

work on the origin of species, that it is apparently a uni-

versal law of nature that no hermaphrodite fertilizes

itself for a perpetuity of generations—a law which he

has stated in a variety of other phrases, and the sugges-

tion of which he owed to Knight. The introductory

134 THE AMERICAN NATURALIST (Vou. XLII

chapter of his book on the effects of cross and self-fertil-

ization in the vegetable kingdom indicates that this con-

clusion, based on his personal observations on plants,

was guided to a certain extent by the experience of

breeders of animals (which is detailed at length in his

book on the variation of animals and plants under

domestication).

It was, therefore, not a novice who entered the botanical

field when, in October, 1857, Darwin contributed a one-

column note to the Gardiners’ Chronicle on bees and fertil-

ization of kidney beans, which he was attracted to through

‘*believing that the brush on the pistil, its backward and

forward curling movement, its protrusion on the left

side, and the constant alighting of the bees on the same

side, were not accidental coincidences, but were connected

with, perhaps necessary to, the fertilisation of the flower.’’

His subsequent papers and books, vivifying floral ecology,

were therefore as inevitable from one who was moved

by a new teleology in natural science as was the superb

publication of a half century earlier by Sprengel, who,

seeing the petal-hairs of a Geranium, sought after their

meaning in the firm conviction that the wise Author of

nature had not created even a hair in vain.

Darwin’s publications in this field are not numerous;

omitting abstracts and reprints of papers published in

full, and later editions and translations, they number only

twenty-two. They are remarkably direct in purpose,

simple in treatment, clear in reasoning, and free from a

controversial or dictatorial spirit. His own observations

and experiments were rarely accepted at their face value,

but were checked up with rather unusual care; and, as

we now know from his published letters, his conclusions

were commonly subjected to the criticism of a very select

private audience before going to the world at large.

The comprehensiveness of the studies underlying these

publications may be indicated by the statement that

*See bibliography at end.

No. 507] BOTANICAL SOCIETY OF AMERICA 135

nearly 350 genera of plants, represented by about 600

species (several of them in a number of contrasted forms

and varieties), are made the subject of comment. No

insignificant proportion of this large number were under

observation or experimental cultivation through a con-

siderable number of years—the series on which the

‘Cross and Self-Fertilization’’ volume was based having

been grown in numbers and with painstaking care through

more than a decade; and the plants measured and the

seeds counted were very many. No observer was so

insignificant that his observations escaped analysis if

they came to the knowledge of the great naturalist, though

Darwin was sorely tried by the positive statement of

some non-existent facts; and some of the prettiest work-

ings of his mind are shown in the elimination of untenable

conclusions which had been drawn by predecessors whose

observations were recorded in sufficient detail to permit

another to winnow them afresh. Enthusiasm in fitting

his own observations into his theories occasionally led

to error when facts were scanty or incompletely made

out, but in such cases these were usually employed with

a word of caution and errors were eliminated with a

charming candor when discovered subsequently ; and few

writers have more gracefully accepted rectifications by

others—even when bluntly phrased or embodied in

aggressive criticism, as was sometimes the case.

First, last and always, his studies were directed to the

species question, but in his pollination studies, as in

every other field that he entered, he bent himself to col-

lateral details with the zeal of a specialist. He was never

oblivious to the treacherous frailty of small numbers and

few series; but his innate soundness of judgment was

checked and confirmed, here and there, through the re-

handling of his data by one to whom the analysis of

figures was a specialty. The dainty instruments of pre-

cision in the use of which physiologists train their under-

graduate students, were neither used nor desired by him;

136 THE AMERICAN NATURALIST [Vou XLII

but his experiments were devised with very unusual ex-

pertness and, like his figures, made to reveal their own

defects and reenforce one another as indicating directions

of high probability even where they were seen to stop

far short of proof.

The problems which Darwin here set before himself

for solution were primarily the explanation of natural

phenomena—most of which others had observed in a gen-

eral way—which in his belief could not be meaningless.

Though doubtless not his first essay, his first publication

on the subject, in 1857, primarily stated observed facts

in Phaseolus and attacked them in this spirit, but in-

cidentally he analyzed the reasons why and how bees

visit flowers and what their intelligence is, and faced the

broad question why varieties of beans do not freely mix

if their flowers are really so formed as to secure frequent

intercrossing. The behavior of introduced plants sepa-

rated from their natural pollinators, further came into

the next paper, with a distinct enunciation of Knight’s

law. Why Vincas do not seed; what their pollinators

are; the details and meaning of what Dr. Gray has called

heterogony, understanding which gave him unparalleled

satisfaction; why flowers of two or even three nominal

genera should sometimes appear on one plant of Cata-

setum; the substantiation of Knight’s law by detailed

arguments of adaptation selected from a single family

of plants; the reason why Lythrum salicaria is repre-

sented by three sets of individuals as distinct from each

other in floral characters as if they belonged to different

species, and incidentally why Lagerstremia should pos-

sess a (less clearly analyzed) stamen-variability ; why the

wild oxlip should be held for a hybrid between other

closely related primroses and why these are specifically

distinct; an extensive experimental testing of the utility

underlying Knight’s law; and a comparative analysis

of heterogony, Sex-separation, and cleistogamy: these

were the questions set for answer in subsequent publi-

eations.

No. 507] BOTANICAL SOCIETY OF AMERICA 137

The methods by which the problems were attacked

were neither many nor complicated. Patience and fore-

thought and perseverance are their chief characteristics.

Observation, not exclusive of any discernible fact; ex-

perimentation, with control of the incidental results of

manipulation; testing the parent condition of seeds sup-

posed to be pure; consideration of alternative explana-

tions of phenomena, and especially of those opposed to

the conclusions adopted; counting, weighing, measuring

—almost beyond belief; ingenious substitutions for in-

sects in laboratory and garden observations on struc-

tures concerned in pollination; watching insects at work

on flowers and supplementing such observation by nota-

tion of the record of their visits afforded by the flowers

themselves; confirming the identity of doubtful pollinia

on a moth by restoring their original color through

moistening them; field observations at all hours and

under all climatic conditions; ascertaining pollen-tube

development in prepotency questions; painstaking polli-

nations to cover numerous permutations: such were the

methods.

The results of Darwin’s work in this field are not easily

epitomized. Itis not going too far to say that he secured

universal recognition of Sprengel’s unheeded demonstra-

tion that the structure of many flowers serves to ensure

their pollination by unconscious insect aid; he broadened

this by enough detail to warrant the conclusion that in

general it serves to ensure cross-pollination by such aid,

in this way substantiating Knight’s law ‘‘nature intended

that a sexual intercourse should take place between neigh-

boring plants of the same species’’; he gave experimental

demonstration of the benefits of crossing, not in itself,

but through the interbreeding of individuals which for

several generations have been subjected to slightly dif-

ferent conditions, or as he puts it, to ‘‘what we call in our

ignorance spontaneous variation’’; and he showed at

once the utility of assured partial self-fertilization as

Sais hi Ba 2a

138 THE AMERICAN NATURALIST [Vov. XLII

effected by cleistogamic degradation, the benefits of as-

sured crossing resulting from the combined structural

and physiological differentiation characteristic of heter-

ogony, and the probability that complete sex-separation

‘‘did not commence and was not completed for the sake

of the advantages to be gained from cross-fertilization’’

—but has rather to do with the general problem of divi-

sion of labor.

His manner of presenting conclusions is at once inter-

esting, convincing and charming. Egotism abounds in

his writings; but the ‘‘I’’ and the ‘‘niy’’ are not those

of the man thinking in first-person pronouns, but of

one unwilling to speak in a cathedratic manner and

careful to state even obvious conclusions as merely the

results to which he as an individual had been unavoidably

led. He wrestled with thought synonymy even more

earnestly than men now do with that of species; and, for

instance, by his use of the word ‘‘ fertilization, ’’ not infre-

quently compels the reader to take his perfectly unesca-

pable meaning broadly and not too literally; and his in-

ability to find better words to express the significance of

floral structures than ‘‘adaptation’’ and ‘‘contrivance,’’

reveals the deep basic idea of teleologic causation that

the human mind has embodied in the machinery for utter-

ing human thought. His phraseology is often aphoristic.

For instance: ‘‘No one will understand the final cause of

the structure of many flowers without attending to this

point” [resultant crossing] ; ‘‘ Who would have been bold

enough to surmise that the propagation of a species

should have depended on so complex, so apparently arti-

ficial, and yet so admirable an arrangement?’’ [as that

in Catasetum]; ‘‘A fortunate accident for the plants’’

[if the detention of moths in securing Orchis nectar, long

enough for the pollinia to harden on to them. were acci-

dental]; ‘‘Nature abhors perpetual self-fertilization”’;

; ‘Belief that flowers of any plant are habitually fertilized

in the bud, or are perpetually self-fertilized, is a most

No. 507] BOTANICAL SOCIETY OF AMERICA 139

effective bar to really understanding their structure’;

sexual differences may ‘‘characterize and keep separate

the coexisting individuals of the same species in the same

manner as they characterize and have kept separate those

groups of individuals, produced from common parents

during the lapse of ages or in different regions, which

we rank and denominate as distinct species’’; ‘‘Illegiti-

mate unions [in heterogonous plants] are hybrids formed

within the limits of one and the same species.’’

Through it all, too, runs a thread of similar sentences

revealing the soul of the man, groping only after the

truth, to whom ‘‘the whole subject is as yet hidden in

darkness.’’ In this spirit he lived, worked and wrote.

Quite apart from success in accomplishing the direct

purpose for which he worked, he succeeded to an excep-

tional degree in stimulating the research instinct in

others, and directing it into attractive and prolific fields,

seeing realized almost immediately his prediction that

what had been held for trivialities might, when under-

stood, ‘‘exalt the whole vegetable kingdom in most per-

sons’ estimation.’’

Things did not always go in his work as. they were

expected to—his first belief that if every bee in Britain

were destroyed there would be no more pods on the kid-

ney beans in that country, gave place to the certainty

that a small percentage of fruit may set without such aid,

and this particular species afterwards gave him less than

the customary evidence of the benefits of crossing; but

in general his expectation was sustained, or gave place

to a better result for his general needs, and incidentally

provided a wealth of detail consonant with his evolu-

tionary theories and not yet known to be explicable on

other grounds. Aside from this participation in his

broader achievements, his work on floral ecology and

fertilization, as has been said, has furnished one of the

greatest stimuli of modern times to purposeful coordi-

nated observation of minutiæ, not one of which is mean-

ingless—in a field open to all who can see, whether or

140 THE AMERICAN NATURALIST [Vou XLII

not enjoying the privileges of great libraries and labo-

ratories.

That he hovered very close to the edge of discoveries

that were reserved for others, is clear to every one

familiar with his publications. The effect of foreign

pollen in modifying the seed (aside from the embryo)

and fruit, was early known to him; but neither his studies

nor those of others in his day were equal to the demon-

stration of double fertilization—even as to-day we go no

further than the endosperm in accounting for these phe-

nomena. ven his second botanical paper (1858) de-

tailed at length a gardener’s observations and his own

experiments on a mongrel lot of beans which Darwin

had the acuteness to test by growing some of the parent

seed as well, and thus to demonstrate that this itself

must have been crossed and not pure. Mendel’s law—

hardly deducible from these facts, but again suggested

in his study of the heredity of style- and stamen-length

in illegitimate unions of heterogonous species (which he

contrasts with hybridization)—escaped him, and the

obscurity of its publication seems to have prevented him

from enjoying its benefits at all in his analysis of the

complex problems of heredity. He was on the verge

of knowing the important part that light sometimes plays

in the phenomena of germination, but at most barely

knew it. To him had not come the fundamental dis-

tinction between fluctuating and mutating variations; and

the demonstration that cumulation of the latter and not

accretion of the former underlies organic evolution was

left for others—to whom the basal mystery of causation

is likely long to remain as obscure as it confessedly was

to Darwin. Convinced, beyond the possibility of doubt,

of the benefits of sexual differentiation with attendant

union of elements derived from different individuals,

he paused before the question why this differentiation

is beneficial up to a certain point and injurious if carried

still farther; confessing in candor that he did not know

what is the nature or degree of the differentiation, and

No. 507] BOTANICAL SOCIETY OF AMERICA 141

adding with characteristic humility that at the end he

still stood in awe before the mystery of life.

Large as is his service to botany, even in the partial

field assigned me on this program, it is but an incident

in his life-long struggle with this great mystery on the

border-line between the discoverable and the eternally

unknowable.

DARWIN’S PUBLICATIONS ON POLLINATION AND FERTILIZATION

1. Bees and fertilisation of kidney beans. Gard. Chron. 1857:

2. On the agency of bees in the fertilisation of papilionaceous own, and

on the crossing of kidney beans. Gard. Chron. 1858: 828-9.—Ann.

& Mag. of Nat. Hist. iii. 2: 459-465.

3. The origin of species by means of natural selection: or the preservation

of favored races in the struggle for life. London, 1859, ete.

Ind

ex.

4, Fertilisation si British orchids by insect agency. Gard. Chron, 18€0:

incas. . Chr i: 552.

6. Fertilisation of orchids. Gard. ras . 1861: 831.

7. Vineas. Gard. Chron. 1861:

8. On the two forms, or di jipii condition, in the species of Primula,

~ on their aypan sexual relations. Journ. Linn. Soc., Bot.

7-96.—Abst. in Gard. Chron. 1861: 1048-9.

9. On a three Raat sexual peeh of Catasetum tridentatum, an

orchid in the possession of the Linnean Society. Journ. Linn. Soc.,

Bot. 6: 151-7.—Abst. in pas Se? on. 1862: 334-5.—Transl. in

Ann. des Sci. Nat., Bot. iv. 19: 255.

10. On the various apa by ae onl and foreign orchids are

tertilised s paes and on the good effects of intererossing. Lon-

, 1862,

11. On the TUME x two forms, and on their reciprocal sexual relation,

in several species of the genus Linum. Journ. Linn. Soc., Bot. 7:

69-83.—Read Feb. 5, 1863

12. On the en gry of the three forms of Lythrum salicaria. Journ.

. Soc., Bot. 169-196.—Read June 16, 1864.

13. On the hia and oo -like nature of the offspring from the weed

timate unions of dimorphie and trimorphie Bae. Journ. Linn.

oc., Bot. 10: 393-437.—Read Feb. 20, 1868.

14, On ~ specific difference between Primula veris, Brit. Fi. (var. officinalis

Linn.), P. vulgaris, Brit. Fl. (var. acaulis Linn.), and P.

genus Verbascum. Journ. Linn. Soe., Bot. 10: 437-454.—Read

Mar. 19, 1

15. The variation of adk and plants under Aoraastioa ti: London.

1868, ete. Index.

142 THE AMERICAN NATURALIST [Vow XLIII

16.

17.

18.

19.

20.

21.

22.

Notes on the fertilization of orchids. Ann. & Mag. of Nat. Hist. iv. 4:

Fertilisation ‘of ae CNT Gard. Seats Sept.. 1871: 1166.

Fertilisation of the ariacee. Nature 9: 460.

The part of cross- per self- eapi in the vegetable kingdom.

76, ete

The reat forms of flowers on plants of the same species. London,

, ote.

Fertilisation of plants. Gard. Chron. n. s. 7: 246.

Fritz Müller on flowers and insects. Nature 17: 78.

DARWIN’S INFLUENCE UPON PLANT

GEOGRAPHY AND ECOLOGY

PROFESSOR FREDERIC E. CLEMENTS

UNIVERSITY OF MINNESOTA

Darwin dealt with plant geography only incidentally

in connection with origin by descent. He was concerned

chiefly with the bearing of migration upon community

of origin, and consequently with the question of single

and multiple origin of species. In his discussion of mi-

gration is found some consideration of barriers, endemism

and isolation, but only in so far as these contribute to his

main theme. On what might be called the ecological side

proper, i. e., the response of the individual, Darwin made

his greatest contributions. Leaving apart his studies of

pollination, movement and insectivorous plants, the ecol-

ogist must consider his fundamental work in variation

and adaptation, together with his conclusions upon the

questions inseparably connected with them, namely, com-

petition, selection, inheritance of acquired characters and

mutation.

In estimating Darwin’s influence in all these matters,

I have endeavored to keep in mind three view points:

(1) his exact opinion upon each question, (2) his actual

contribution to it, and (3) his share in our present knowl-

edge of the subject, as well, perhaps, as his influence in

shaping our present opinions where they do not rest on

experimental knowledge. Several inherent difficulties

have manifested themselves during this attempt. Chief

among these is the impossibility of ascertaining what

might be called the majority opinion of botanists, a diffi-

culty aggravated by the fact that no two botanists would

draw the same line between what is proved and what 1s

merely held. In addition, Darwin’s own views seem to

have remained plastic to a degree not always evident in his

most widely read books. This has brought the curious re-

sult that his earlier views have often had much the greater

143

144 THE AMERICAN NATURALIST [Vou XLII

influence in moulding opinion, while his later views

are more in accord with scientific knowledge. Further-

more, it must be borne in mind that Darwin was the great

apostle of origin by descent. It was his unique mission

to bring the scientific world to accept this doctrine, a task

of such magnitude that methods of origin, for the time

at least, were relatively unimportant. In attempting to

determine Darwin’s actual contribution, one is confronted

by the task of deciding how much credit is to be given to

the discoverer of a new idea or principle, and how much

to him who applies it and establishes it. It is fairly well

known that Darwin was not the first to formulate the prin-

ciple of evolution. Even in regard to natural selection,

often accepted as distinctly Darwinian, Darwin himself

has shown that he was anticipated by three other writers.

Yet the fact remains that Darwin has contributed more

to the foundations of biology than all of his forerunners.

A careful rereading of the ‘‘Origin of Species” and the

‘Variation of Animals and Plants under Domestication”

has been found necessary to make Darwin’s views emerge

clearly from the mists of tradition and of recollection. It

has seemed desirable also that he should himself speak

in his own words, without the handicap of paraphrase

and of the personal equation. Together with the mani-

fest difficulty of making accurate and definite statements

of the consensus of botanical opinion on mooted ques-

tions, this necessarily results in a more or less frag-

mentary and detached account of such a vast field.! Its

value lies wholly in recalling to us Darwin’s actual views

without interpretation or emendation, so that each may

determine for himself what part Darwin’s work plays in

his own views, and in botanical] opinion as he sees it.

DISTRIBUTION

Darwin formulated three laws of distribution: (1)

Neither the similarity nor the dissimilarity of the in-

Eig epes given after the various excerpts are to the sixth edition

fan ) of the Origin of Species,’’ and to the second edition (1875) of the

ariation of Animals and Plants under Domestication. ’’

No. 507] BOTANICAL SOCIETY OF AMERICA 145

habitants of the various regions can be wholly accounted

for by climatal or other physical conditions,’’ (2) ‘‘bar-

riers of any kind or obstacles to free migration, are re-

lated in a close and important manner to the differences

between the productions of various regions,” (3) ‘‘the

affinity of the productions of the same continent, or of the

same area, though the species themselves are distinct at

different points and stations.’’? These scarcely need

comment, for they arise clearly from the law of origin by

descent. They are such an intrinsic part of the founda-

tion of plant geography as to require an effort to recog-

nize the fact that it was once necessary to formulate them.

SINGLE AND MULTIPLE ORIGIN

From the very nature of his task, Darwin was forced

_ to assume that species were first produced at one spot.

To-day the fact that the same species may arise at two

or more distinct places merely strengthens the law of

descent, but in Darwin’s time this would have greatly

increased the difficulty of supporting his doctrine by the

evidence drawn from the distribution of plants. Dar-

win’s views upon this question were far from uncertain,

as the following excerpt indicates.

It is obvious that the individuals of the same species, though now

inhabitating distant and isolated regions, must have proceeded from

one spot, where their parents were first produced. We are thus brought

to the question which has been largely discussed by naturalists, namely,

whether species have been created at one or more points of the earth’s

surface. Undoubtedly there are many cases of extreme difficulty in

understanding how the same species could possibly have migrated from

some one point to the several distant and isolated points where now

found. Nevertheless, the simplicity of the view that each species was

first produced within a single region captivates the mind. He who-

rejects it, rejects the vera causa of ordinary generation with subsequent

migration, and calls in the agency of a miracle.

This view seems to be little more than an inheritance

from the special creationists. It doubtless reflects the

prevailing opinion of Darwin’s time, and probably is m

*«<Origin,?? 2: 129, oe |

*** Origin,’’ 2: 186.

146 THE AMERICAN NATURALIST [Vou. XLIII

accord with the consensus of opinion at present. What

the current opinion is can only be a matter of conjecture,

but notwithstanding the proofs of multiple origin af-

forded by adaptation and mutation, it would seem that the

majority of botanists and nearly all zoologists still adhere

to the doctrine of single origin.

MIGRATION

Darwin’s treatment of migration is limited to evidence

of the possibility of distant and occasional migration as

the explanation of the many puzzles of distribution. It

is evident that his position in regard to single origin

caused him to turn to migration as the necessary solution

of all the problems of distribution. His attitude upon

both questions is shown by the following statement:

Whenever it is fully admitted, as it will some day be, that each

species has proceeded from a single birthplace, and when in the course

of time we know something definite about the means of distribution,

we shall be enabled to speculate with security on the former extension

of the land.*

His experiments upon the carriage of seeds and fruits

by ocean currents and by birds, though necessarily crude

and simple, are classic. They still serve to indicate one

of the really fundamental points of attack in the detailed

quantitative study of migration.

VARIATION

A brief summary of Darwin’s views upon variation is

an impossibility. Under the headings ‘‘Causes of Varia-

tion,” ‘‘Habitat as Cause,’ “Use and Disuse,” I have

assembled his own statements to make clear his position.

These seem to differ in some essentials from the views

often ascribed to Darwin, or at least held by many who

regard themselves as his followers. They appear to be

more in accord with the views of the ecologist who looks

to the habitat for the final explanation of all changes,

than with the opinions held by biologists in general. They

show Darwin to have been much more in sympathy with

* tt Origin,”? 2: 140,

No. 507] BOTANICAL SOCIETY OF AMERICA 147

Lamarck and Saint-Hilaire than he was himself aware.

He thus becomes the connecting link between these two

great but less appreciated seers, and the investigators

of to-morrow whose success will rest on the experimental

study of the habitat as the primary cause.

Causes of Variation.

I have hitherto sometimes spoken as if the variations so common and

multiform with organic beings under domestication, and in a lesser

degree under nature—were due to chance. This, of course, is a

wholly incorrect expression, but it serves to acknowledge plainly our

ignorance of the cause of each particular variation.

No doubt each variation must have its efficient cause, but it is as

hopeless to discover the cause of each as it is to say why a chill or a

poison affects one man differently from another. Even with the modi-

fications resulting from the definite action of the conditions of life, when

all or nearly all the individuals which have been similarly exposed, are

SY ‘ae we can rarely see the precise relation between cause

and e

We mus . .. conclude that organie beings, when subjected during

several generations to any change whatever in their conditions, tend to

vary: the kind of variation which ensues depending in most cases

in a far higher degree on the nature or constitution of the being,

than on the nature of the changed conditions.

Those authors that adopt the latter view—that variability must be

looked at as an ultimate fact, would probably deny that each separate

variation has its own exciting cause. Although we can seldom trace

the precise relation between cause and effect, yet the sorme

presently to be given, lead to the conclusion that each modification

must have its own distinct cause, and is not result of what we

blindly eall accident.®

Habitat as Cause.

With respect to what I have called the indirect action of changed

conditions, namely, through the reproductive system being affected, we

may infer that variability is thus induced, partly from the fact of this

System being extremely sensitive to any change in the conditions.

Many facts clearly show how eminently susceptible the re tive sys-

tem is to very slight changes in the surrounding conditions.’ :

Changed conditions of life are of the highest importance in causing

variability, both by acting directly upon the organization, and indi-

rectly by affecting the reproductive system. It is not probable t that

variability is an inherent and necessary contingent under all cireum-

stances,”

P: ‘‘ Origin,’ ? 1: 164. ++¢Varintion,”” 2 273. a oe

"*'Variation,”? 2: 299, *¢¢Variation,’? 2: 282. °‘Origin,”” 1: 10.

148 THE AMERICAN NATURALIST [Vou XLII

These several conditions alone render it probable that variability

of every kind is directly or indirectly caused by changed conditions

of life. Or, to put the case under another point of view, if it were

possible to expose all the individuals of a species during many genera-

tions to absolutely uniform conditions of life, there would be no

variability.”

We have good reason to believe, as shown in the first chapter, that

changes in the conditions of life give a tendency to increased variability,

and in the foregoing cases the conditions have changed, and this would —

manifestly be favorable to natural selection, by affording a better

chance of the occurrence of profitable variations.

Use and Disuse.

It is notorious, and we shall immediately adduce proofs, that in-

creased use or action strengthens muscles, pau; sense-organs, ete.,

and that disuse, on the other hand, weakens them

There can be no doubt that with our anciently doinestionted animals,

certain bones have increased or decreased in size and weight owing to-

increased or decreased use. With animals living a free life and

occasionally exposed to severe competition, the reduction would tend

to be greater, as it would be an advantage to them to have the develop-

ment of every superfluous part saved.“

CoMPETITION

_In spite of the importance Darwin assigned to com-

petition, for to him it usually comprises the whole process

of natural selection, he gave little thought to its analysis

and almost none to its investigation. His ideas of com-

petition were drawn largely from Lyell and Herbert, and

he was content to take it as a universal and fundamental

process among living things, without detailed inquiry

into its working or its precise relation to the origin of

new forms. Darwin’s actual contribution rests chiefly

upon his formulation of the following law of competition,

which recent quantitative experiments indicate to be

fundamental :

As species of the same genus usually have, though by no means invar-

ably, much similarity in habits and constitution, and always in structure,

the struggle will generally be more severe between them if they come

into competition with each other, than between the species of distinet

nera.

wee Origin, 7? 1: 49, HET Variation, 17 9: 934.

8 «¢ Origin,?? 1: 100. 138 ¢<¢ Variation,’’ 2: 276.

“** Variation,’’ 2: 280.

No. 507] BOTANICAL SOCIETY OF AMERICA 149.

Competition has, however, been almost completely

neglected until the ecologist has begun the investigation

of it in the last few years, and there are few subjects in

which botanical opinion is so completely unformed.

INHERITANCE OF ACQUIRED CHARACTERS

Darwin’s opinions upon this subject appear to have

been modified little with time, contrary to the case with

other views. Here again he was in almost complete

accord with Lamarck and Saint-Hilaire, but he seems to

have had little effect upon current opinion, especially

among zoologists. The experimental ecologist would

doubtless follow Darwin in regarding the inheritance of

acquired characters as proved beyond question. Indica-

tions are not lacking that more and more botanists are

coming to the same point of view. Darwin’s attitude

may be summed up in the following:

The increased use and disuse of various organs produces an inherited

effect.

With plants, the period of vegetation is easily changed, and is in-

herited, as in the case of summer and winter wheat, barley and

vetches.”

Changed habits produce an inherited effect, as in the period of the

flowering of plants when transplanted from one climate to another.”

Habit is hereditary with plants, as in the period of flowering, in the

oe of sleep, in the amount of rain requisite for seeds to germinate,

ete.

Perhaps the correct way of viewing the whole subject would be to

look at the inheritance of every character whatever as the rule, and

non-inheritance the anomaly.”

MUTATION

Darwin’s attitude towards the sudden appearance of

striking variations, of sports, and monstrosities towards

what is now called mutation, is one held by the majority

of American botanists to-day. To the latter, DeVries

has supplied the scientific proof of origin by sudden and

striking variation, but only a small number, the followers

of DeVries, regard mutation as the fundamental or uni-

T. Origin,’? 1: 93. 18 << Variation,” 2: 273.

™<¢Variation,’? 2: 285. 18¢¢Qrigin,’? 1: 12.

®<¢Origin,’? 1: 173, » <‘ Origin,” 1: 15.

. 150 THE AMERICAN NATURALIST [Vou XLII

versal process. Zoologists, it would seem, incline to

look with greater favor upon mutation as the regular

method of origin.

At long intervals of time, out of millions of individuals reared in the

same country and fed on nearly the same food deviations of structure,

so strongly pronounced as to deserve to be called monstrosities, arise;

but monstrosities cannot be separated by any distinct line from slighter

variations. All such changes of structure, whether extremely slight or

strongly marked, which appear amongst many individuals, living to-

gether, may be considered as the indefinite effects of the conditions of

life on each individual organism.”

Some naturalists have maintained that all variations are connected

with the act of sexual reproduction, but this is certainly an error: for

I have given in another work a long list of “sporting plants,” plants

which have suddenly Aes a single bud with a new and sometimes

widely different character.”

Some sdarsntics useful to man have probably arisen suddenly, or

by one s

No one seppiebe that our choicest productions have been produced

by a single variation from one stock.”

It may be doubted whether sudden and considerable deviations of

structure such as are occasionally seen in our domestic productions, *

more especially with plants, are ever permanently propagated in a state

of nature.”

I saw also that the preservation in a state of nature of any occasional

deviation of structure, such as a monstrosity, would be a rare event,

and that if first preserved, it would generally be lost by subsequent

intercrossing with ordinary individuals.”

ADAPTATION

Darwin recognized the three fundamental methods of

origin in nature, namely, variation, mutation and adapta-

tion. It seems probable that to mutation he assigned its

approximate value. In the ‘‘Origin of Species,” varia-

tion with selection was given the preeminent place, and

adaptation a minor one. Later, adaptation assumed

greater importance to his mind, and there is some evi-

dence that he may have assigned to it a value greater than

that of variation. He had come to see more clearly that

natural selection operated upon things already produced,

*«<Origin,?? 1: 9. 2¢<Origin,?? 1: 11.

"<< Origin,” 1: 34. * << Origin,”? 1: 37.

* << Origin,” 1: 52. *<<Qrigin,?? 1: 111.

No. 507] BOTANICAL SOCIETY OF AMERICA 10i

and to catch a glimpse of the fact that indefinite action,

i. e., variation, and definite action of the habitat, i. e.,

adaptation, were at bottom the same thing.

His changing view point is recorded in his letters, and

hence his later views are not generally known. As a

result, scientific opinion has been more or less stereotyped

in the well-known statements of the ‘‘Origin of Species”

and has maintained in greater or less degree a position

which Darwin himself had forsaken. Darwin’s later

opinions upon adaptation, as upon the causes of variation,

and upon the inheritance of acquired characters, did not

differ essentially from those of Lamarck. More im-

portant than this, for Lamarck was a prophet, not an in-

vestigator, they are in accord with the first results of the

application of exact ecological methods to the question

of the origin of new forms in natural habitats. |

- As far as I am able to judge, after long attending to the subject, the

conditions of life appear to act in two ways—directly on the whole

organization or on certain parts alone, and indirectly by affecting the

reproductive system.”

ooking at many small points of differences between species,

which, as far as our ignorance permits us to judge, seem quite unim-

portant, we must not forget that climate, food, ete., have no doubt

produced some direct effect.”

In all cases, there are two factors, the nature of the organism, which

is much the most important of the two, and the nature of the conditions.

The direct action of changed conditions leads to definite or indefinite

results. In the latter case, the organization seems to become plastic

and we have much fluctuating variability. In the former case, the

nature of the organism is such that it yields readily when subjected

to certain conditions, and all or nearly all the individuals become

modified in the same way. It is very difficult to decide how far

changed conditions, such as climate, food, ete., have acted in a definite

manner. There is reason to believe that in the course of time the effects

have been greater than can be proved by clear evidence.”

The greatest mistake I made was, I now think, I did not attach suffi-

cient weight to the direct influence of food, climate, ete., quite inde-

pendently of natural selection. When I wrote my book, | ae

some years later, I could not find good proof of the direct action (i. e-

in producing definite variations) of the environment upon the species.

Such proofs are now plentiful.”

Origin,” 1: 8. sí Origin,” 1: 104. tas

® «Origin, ? 1: 165. 2 íí Life mi z rs,” 3: 159, 1876.

DARWIN’S WORK ON MOVEMENT IN PLANTS

PROFESSOR HERBERT MAULE RICHARDS

CoLUMBIA UNIVERSITY

Ir is remarkable, when one considers the central inter-

est of Darwin’s life, that he should have found time and

strength to devote so considerable a portion of his energy

to purely botanical work. It is natural and fitting at

this time that the major interest of the world should be

directed to his larger achievements, but it should not be

lost sight of that his botanical work alone represents no

small labor accomplished. We may indeed not always

agree at present with his conclusions and may differ

even as to actual observations, but the fact remains that

he developed a number of highly important topics re-

lating to plant behavior.

His lines of investigation among plants were indeed

somewhat special, for he made no pretence of covering

completely the field of even that side of botany which in-

terested him, but simply investigated certain more or

less important phases of plant life that came under his

notice. It may be expressed, perhaps, by saying that his

botanical studies were his avocation, and were employed

by him in a measure as a recreation from the exactions

exercised by his larger tasks. That does not mean,

however, that there was anything dilettantish in the spirit

of his attack on botanical problems or that his work along

these lines was not as thorough as his circumstances per-

mitted. Thoroughness indeed was an important element

in all that Darwin undertook and the patient application

to even small details is the secret of much of the value of

these botanical studies.

From his published letters it would seem that his work

with plants was to him of the nature of a pastime,

serious indeed but none the less a pastime, in which he

often found himself so interested that all other lines of

152

No. 507] BOTANICAL SOCIETY OF AMERICA 153

intellectual activity were for the time forgotten. Possibly

what first inclined him to study plants was the delight

of observation and experiment to which he so keenly

reacted, for, placed as he was in the country and in none

too good health, these faculties found their easiest and

most natural outlet in his garden. Even when he was

least well, so long as he was able to exert any effort at

all, his plants claimed his interest and one of his friends

speaks of how in the daily walk about the garden path

there was always some experiment or some particular

plant which was to be watched and noted.

He did not himself make any claim to being a trained

botanist and, without in any way reflecting upon the value

of,the work which he did, it must be admitted that he was

not. He freely asked help of his botanical friends and

freely it was given.

Most of his botanical contributions were published in

book form and it is to be noted that they had a relatively

wide circulation for books of a special character, a fact

which speaks well for the manner of treatment and gen-

eral interest of the subjects about which he wrote. Of

these works there are three which especially concern the

subject of this address and these are as follows: ‘‘In-

sectivorous Plants’’ published in 1875, ‘‘The Movements

and Habits of Climbing Plants” which appeared first in

1865 in the Journal of the Linnean Society and was after-

wards printed in book form, and ‘‘The Power of Move-

ments in Plants’? which bears the date of 1880. It is

not the intention to take these up seriatim or discuss each

detail, but rather to point out what seem some of the more

important and crucial aspects of the various subjects

treated therein. :

Perhaps the most important single fact that Darwin

elucidated was that of the universality of the oscillations

of the growing points of plant members. This he termed

cireumnutation, a word now generally adopted; and by it

he meant the swinging motion of plant extremities as

they progress through space, due to inequalities of

154 THE AMERICAN NATURALIST [Vou XLII

growth. He was not indeed the first to observe individ-

ual instances of either periodic or ephemeral movements

of a more or less pronounced degree, but to him belongs

the credit of first insisting upon the fact that all growing

organs describe a more or less spiral orbit. He de |

veloped this idea with such enthusiasm that he carried |

his line of thought to extremes and concluded that all

plant movements were but modifications and adaptations

of circumnutatory motions. Only in the cases of the

motions of Mimosa leaves and Drosera. tentacles did he

express his doubt as to the applicability of the principle

of circumnutation to all plant movements. He included

all forms of tropisms, contact responses, other than those

named, under this one head. In the final chapter of ‘‘The

Power of Movement in Plants’’ he says:

It has been shown that the following classes of movement all arise

from modified cireumnutation, which is omnipresent whilst growth

lasts, and after growth has ceased, whenever pulvini are present.

These classes of movement consist of those due to epinasty and hypo-

nasty,—those proper to climbing plants, commonly called revolving

nutation, the nyctitropie or sleep movements of leaves and cotyledons,

and the two immense classes of movement excited by light and gravi-

tation.

In the next paragraph he excepts the contact move-

ments of Mimosa and Drosera, already referred to,

saying:

Although so many movements have arisen through modified circum-

nutation, there are others which appear to have a quite independent

origin; but they do not form large or important classes.

When we consider the nature of the man and reflect

that the whole trend of his mind was towards the concept

of unity in the organic world it does not seem extraordi-

nary that he should have taken such an attitude; an

attitude too that was helped on by the extreme simplicity

of his methods of experimentation. The very fact that he

approached the question with a mind entirely free from

bias had its advantages, but it also brought a greater

chance of being too easily swayed by his own point of

view. It must be remembered also that the distinction be-

No. 507] BOTANICAL SOCIETY OF AMERICA 155

tween autonomous and induced or paratonic movements

was not so sharply drawn then as it is now. At present

we place the tropistic movements due to whatsoever exter-

nal cause, under the general class of aitonomic movements,

in contradistinction to cireumnutation, epinasty, hypo-

nasty and so forth, which we are pleased to term auto-

nomic or due to internal causes. In the latter class, it must

be confessed, the relegation of movements to autonomous

causes is often a mere confession of ignorance, as is well

instanced by the older opinion first advanced by Darwin

that the twining of stem climbers is wholly autonomic. It

is only in the sense that the movements of fixed plant

organs are in the vast majority of cases ultimately due to

unequal growth changes that we can say that circumnuta-

tion is the fundamental process concerned. In other

words, it is only if we were to define cireumnutation as the

power of plant parts to show either unequal turgescence

or unequal growth that we could accept the universality

of Darwin’s statement.

As far as his observations on circumnutation proper

are concerned, or, as he would have termed it, unmodified

circumnutation, his conclusions are of the highest value,

and form even to the present day really a large part of

our literature on the subject. By the simplest means

he plotted the orbits, so to say, of a very considerable

number of growing tips. Entirely aside from any

especial interpretation to be placed upon them, his de-

scriptions of the behavior of seeds during germination

and of the growth of seedlings, give a clear and accurate

account of the general organography of the adolescent

plant.

In another very important direction were the researches

of Darwin rewarded by far-reaching results; namely, in .

the matter of the transmission of stimulus in plants. Un-

til the publication of his experiments it had been largely

overlooked that there might be a separation in space

between the percipient and motor zone in tropic re-

sponses. It is true, no doubt, that some of his methods

156 THE AMERICAN NATURALIST [Vou. XLIII

and even some of his conclusions were faulty, but never-

theless the credit belongs to him for establishing a point

of departure from which further developments of first

importance have come. The demonstration of so funda-

mental a fact has had no inconsiderable influence in the

understanding and interpretation of sense perception

among plants.

Although many observers at first contended against the

possibility of such a propagation of stimulus and denied

the accuracy of Darwin’s results, yet the general correct-

ness of his statements has been established even though

‘differences in interpretation may have crept in. One

reason, no doubt, why it was difficult to admit and support

Darwin’s conception and to corroborate his results, is

that the region capable of perceiving a stimulus is so

localized and the conduction to the responsive area is

over so short a distance. One may gather from his writ-

ings that he did not regard the response to stimuli in the

nature of a release of a regulatory mechanism, as it is

now so commonly understood: his point of view indeed

as to the nature of such tropic responses as being merely

a modified form of cireumnutation was against such an

interpretation. His attitude was of course that of the

teleologist, for he was ever keen to uncover purpose in

the reaction of organisms. In his concluding remarks

and summaries, while he suggested the interpretation of

such responses along the line of consciousness he ex-

hibited a considerable reserve and went no farther than

indicating the appropriateness of a comparison of the

Similarity to the responses in lower animals. He did

not enter largely into the somewhat fruitless field of the

philosophical discussion of the question. His reserve

possibly but reflects the greater caution of a past genera-

tion in interpreting protoplasmic response universally in

terms of what we know about the problem in higher ani-

mal forms, but be that as it may, one is inclined to the

opinion that it was Darwin’s own reluctance to commit

himself too unreservedly which restrained him, for in

No. 507] BOTANICAL SOCIETY OF AMERICA 157

other matters he has amply shown that he was not afraid

to combat what to him were mere conventionalities.

A large portion of his book on climbing plants is

devoted to a consideration of the tendril bearers and

takes up a wide range of forms. The exceeding sensitive-

ness of these organs to contact Darwin was one of the

first to appreciate, but he went somewhat astray in sup-

posing that mere pressure was enough to induce the

characteristic coiling response. It was not thoroughly

understood until later that weight alone is not sufficient,

but that the stimulus must involve some more intricate

contact shock. He did not understand that the exciting

body must have a certain degree of what one may eall

roughness and consequently he did not understand the

inaction of tendrils to raindrops. !

His conclusions did not wholly agree with the now

accepted explanations of the nature of the response of

tendrils but it inclined to the view that the rapid reply of

incurving tendrils was primarily caused by turgor

changes ultimately rendered permanent by growth. More

recently it has again been claimed that the curvature is

wholly a growth phenomenon, but in so much as turgor

changes are often apparently so greatly concerned with

the first stages of cell enlargement incident upon growth,

may not the initial curvature be after all a matter of

unequal turgor pressure on the two sides of the tendril?

Here as in other places Darwin considered the response

of contact stimulus a form of modified nutation.

Although Drosera and similar plants were not con-

sidered by Darwin in this connection, in so much as some

phases of his study had to do with their response to con-

tact irritation, it is suitable to introduce the matter now.

His investigation of the behavior of Drosera was espe-

cially detailed and represented at the time a great ad-

vance in the knowledge of the habits of this insectivorous

form. There is not, as a matter of fact, any more elabo-

rate or complete study at present, although his results :

were published some thirty years ago. Many important —

158 THE AMERICAN NATURALIST [Vow XLII

observations were made by him, especially that the gland

at the tip of a tentacle is exclusively the sensitive region

and that a stimulus can be propagated down the cen-

tral tentacles and along to and up the adjacent ones.

Although he made most careful and repeated examination

of the protoplasmic behavior as the stimulus progressed,

and noted some curious changes which take place in the

protoplasm of the responding tentacles, yet he was un-

able to advance any explanation of the physics of the

process. Indeed, none has been offered since and much

that Darwin said is still the last word on the subject.

Extending his work from the effect of mechanical

stimuli to chemical ones, Darwin showed that many sub-

stances of very various kinds could effect a very vigorous

response. He was, indeed, the first to make an en-

deavor at a close study of the insectivorous or rather

carnivorous plants. Not only were his observations on

the inflection of the tentacles of Drosera and the trapping

of insects by this and other forms largely new; but also,

and what was more important, perhaps, his investigations

into the digestive action of their secretions were really

the first in the field. His experiments along this line

were especially exhaustive; and, with the exception of

some details later writers have done little by way of

correction or amendment. He did not it is true, isolate

any specific enzymes but nevertheless we came to the con-

clusion that a pepsin-like enzyme was excreted by these

plants, which enables them to digest external proteid

material. He also noted the rennet-like action of the ex-

eretion in Drosera and arrived at the just conclusion that

the curdling of milk due to the latter could not come from

the acidity of the excretion alone, though at that time little

or nothing was known concerning vegetable rennets. It

is not to be wondered, when one considers the lesser

acquaintance which was then possessed of ferments in

general and plant enzymes in particular, that Darwin did

not further discuss or attempt to investigate the enzymes

which he had discovered and to determine whether they

No. 507] BOTANICAL SOCIETY OF AMERICA 159

were peptic or tryptic or whether the curdling power was

due to a specific enzyme, apart from the others.

The complexity of ferment action and the possible co-

existence of several distinct enzymes in one secretion was

not fully appreciated at that time, and working as Darwin

of necessity did, he was not in close enough touch with

these matters as they then stood to branch out on his own

account into very new fields. What he did do was to

make a careful and pretty exhaustive empirical study

of the action of the excretion of the glands on a great

range of substances. If his list of the latter included

a number which were immaterial by way of affording new

light on the question and a few which, owing to their

mode of preparation, gave inconclusive or erroneous re-

sults, it matters very little. He proved successfully the

main thesis which he maintained, namely, the ability of

these insectivorous plants to avail themselves of proteids

as food. When one considers how much even to-day in

the study of enzymes depends on almost pure empiricism

and what valuable results have in the past been obtained

by such methods, one does not cavil at Darwin’s mode of

attack, although at times it may impress one as a bit

happy-go-lucky. |

= As a detailed study of the habits of an organism his

extended observations on Drosera stand out as a master-

piece of this kind of work and the collective result of

this work may justly be regarded as one of his best pieces

of botanical investigation.. It is evident from his letters

that he took the keenest interest in this plant, which

apparently stimulated his imagination and his desire

towards investigation as much as any one thing which

came under his notice. It was a subject peculiarly well

fitted for his type of investigation, for in it he did not

require elaborate mechanical aid to arrive at important

results and the previous literature on the subject was

scanty and for the most part of minor importance. He

had an almost clear field and made the most of his oppor-

tunity by producing a work which must for all time re-

160 THE AMERICAN NATURALIST [Vou XLII

main the basis of our knowledge of these interesting

forms. He pushed it as far as his means at hand per-

mitted, and while in many points he could not arrive at

definite conclusions, it is a fact that most of his un-

answered questions are unanswered still. While his

knowledge of plant physiology may not have been broad

enough for him to correlate this special form of nutrition,

with the general problems of plant metabolism it is to

be remembered that after all it was not from such a stand-

point that he took up the problem.

There is one characteristic which is particularly ad-

mirable in all of Darwin’s botanical work and that was

his endeavor in so far as he could to examine an abun-

dance of different forms which would illustrate any topic

under investigation. This is the more to be remarked

since he was not really very fortunately placed in the

matter of obtaining material. For keeping his plants

after he had obtained them he had to depend entirely

upon such facilities as his own garden and greenhouse

afforded. Being unable himself to collect material to

any extent, he had to depend upon the generosity of his

friends and correspondents, who, it may be said, responded

with alacrity. None but one of very active mind and great

perseverance would have accomplished what he did in

an experimental way under the difficulties which beset

him, and his work affords a good example of how a rela-

tively large amount can be accomplished by even a little

time given continuously. Entirely aside from any abso-

lute value which these books may have, they were an

important contribution at that stage in the development

of plant physiology, to the literature on the subjects on

which they touched. No man with a less well developed

faculty for detail and continued effort could have kept

the thread of the work so well, despite the many inter-

ruptions to which it was subjected. Their value, it may

be said, is more to botanical science than a merely senti-

mental one—it is rather in many respects one of real

achievement.

No. 507] BOTANICAL SOCIETY OF AMERICA 161

It has been stated that one of the greatest services

rendered by Darwin to the study of natural history was

the revival of teleology. The presence of this mode of

thought in his work shows no better anywhere than in

his work on the movements of plants, where it apparently

afforded to him one of his liveliest interests. In the light

of the present disfavor into which teleological interpreta-

tions have fallen these statements, which are indeed in

accord with the mental attitude of Darwin, require some

comment. It is not that-one need raise one’s voice in

favor of teleology as such, to apologize for his purposeful

explanations of the form and function of organs; but it

should in justice be said that it is where teleological evi-

dence and teleological reasoning are accepted as a finality

or where they lead to prejudgment that the most mischief

is done. Darwin’s whole make-up and trend of thought

was such as to make him turn to immediate causal ex-

planations for natural phenomena and he unquestionably

was a teleologist, but in the main his interpretations were

tempered by common sense, intellectual reserve and

balanced judgment. It has been rightly said, too, that

his teleology had a far wider and more coherent plan than

that of his predecessors and it may be added it was less

positive than that of some of his contemporaries and

some of those that followed him.

It is wholly natural that with a mind like his, which

ranks him with the greatest correlaters and unifiers of

loose facts that the world has known he should also

have attempted to unify the explanations of the phe-

nomena examined in his botanical researches and his posi-

tion as to the fundamental nature of cireumnutation was

no doubt a result of his temperamental attitude towards

large questions. But while we need not necessarily fol-

low him in all of his generalizations the fact remains that

he did no inconsiderable service to botanical science if in

no other way than, at least, in showing what may be

learned from the close and careful examination of the

Plant as a living organism.

162 THE AMERICAN NATURALIST [Vot. XLIII

In a final summing up of Darwin’s studies that have

come under discussion here, perhaps a fair statement may

be made by saying that he investigated, as accurately as

both his knowledge and his facilities for experimentation

allowed, a large range of plant forms which illustrated

the especial subjects in which he was interested; that

he discovered or drew attention to many important facts,

either previously unknown or neglected regarding the

habits of the plant forms which he had under observation ;

that if his interpretations were at times faulty, his ob-

servations were in the main accurate; and that he revivi-

fied subjects which had often times become only of more

or less academic interest. Darwin himself—none better

—recognized that many of his experiments must be un-

satisfactory and his explanations merely tentative; and he

was ready enough to accept correction which appeared

to him justified. The very fact that he brought to his

botanical researches a mind fresh and unprejudiced lends

a peculiar value to his work. Unhampered by tradition

and with an open mind, he interpreted the facts as he saw

them, and we must remember that some of our criticisms

may be in part due merely to the greater complexity of

our own interpretations, than to any absolute superiority

of them. Despite the advances which have been made,

it should not be forgotten that Darwin’s influence was in

the direction of sound investigation; and we should not

pass over ungratefully this phase of plant physiology

from which has come much that is of the first importance

to-day. As a stimulus to later investigators Darwin’s

work, whether in botany alone or in other fields, has had

a profound influence on the plant physiologist though

he may not always recognize it. It would be our shame

if we could not have improved over the concepts of the

Science as current in Darwin’s time, and our misfortune

if we think that these betterments are not capable of as

relatively great advance in the future.

AN EXAMINATION OF DARWIN’S “ORIGIN OF

SPECIES” IN THE LIGHT OF RECENT

OBSERVATIONS AND EXPERIMENTS

PROFESSOR EDWIN LINTON

WASHINGTON AND JEFFERSON COLLEGE

Axsout three years ago, some members of a local club,

to which the writer belongs, having heard that Darwinism

was on its death-bed, a report on the origin of species was

ordered. The present paper is made up from notes pre-

pared for that occasion.

In a letter to Hooker, March 9, 1885, Professor Huxley

says:

I have been reading . . . the book [Origin of Species] for the nth

time. ... It is one of the hardest books to understand thoroughly

that I know of, and I suppose that is the reason even people like

Romanes get so hopelessly wrong. (“Life and Letters,” II, 204.)

If Huxley, who helped to fight Darwin’s battles when

“The Origin of Species’? was young, who talked and

argued with its author, can make such a statement con-

cerning the book, it is little wonder that people come to

different conclusions after reading it now.

My examination of Darwin’s great work in the light

of present-day beliefs has resulted in the finding of

numerous passages which support the following theses:

1. Darwin’s main thesis is the doctrine of descent as

against the theory of the immutability of species.

2. A secondary thesis accounts for the origin of species

by the theory of descent with modification through varia-

tion and natural selection.

3. Two kinds of variations are recognized: (a) Fluctu-

ating variations as now understood, but including also

variations of such a degree as would make steps in de-

velopment as great as those which separate existing

varieties. (b) Sudden changes, or sports.

It is to be observed that this ainaani. of varieties

163

164 THE AMERICAN NATURALIST [Vot. XLIII

is not quite in agreement with the present-day distinction

between fluctuating variations and mutations. Indeed,

there are many who think that the distinction between

the ampler fluctuations, on the one hand, and the lesser

mutations, on the other, is not entirely established.

Darwin nowhere claims that natural selection is of the

nature of a creative force.

I shall now cite a few passages in support of the above

findings. References are made to the sixth edition. All

italics are mine.

I. The main thesis is the origin of species by descent

as opposed to the theory of the immutability of species

or the independent creation of species.

While Darwin believed that varieties are incipient

species he also believed that this identity had not yet

been demonstrated. In speaking of the resemblance of

varieties to species he says:

Independently of the question of fertility and sterility, in all other

respects there seems to be a general and close similarity in the offspring

`of crossed species and of crossed varieties. If we look at species as

having been specially created, and at varieties as having been produced

by secondary laws this similarity would be an astonishing fact. But

it harmonizes perfectly with the view that there is no essential differ-

ence between species and varieties (pp. 261-2).

Again:

It has been asserted over and over again by writers who believe

in the immutability of species that geology yields no linking forms

(p. 208).

And on page 290:

Let us now see whether the several facts and laws relating to the

geological succession of organic beings accord best with the common

view of the immutability of species, or with that of their slow and

gradual modification through variation and natural selection.

Also:

This grand fact of the grouping of all organic beings under what is

called the natural system is utterly inexplicable on the theory of erea-

tion (p. 413).

A few pages farther on he Says:

If species be only well-marked and permanent varieties, we can at

No. 507] DARWIN’S “ORIGIN OF SPECIES” 165

once see why their crossed offspring should follow the same complex

laws in their degrees and kinds of resemblance to their parents, .. .

as do the crossed offspring of acknowledged varieties. This similarity

would be a strange fact if species had been independently created and

varieties had been produced through secondary laws (p. 417).

On the following pages, 418-419, he summarizes facts

such as the close resemblance between existing and ex-

tinct forms on the several continents, the inhabitants of

oceanic islands, on islands near continents, and closes

with this sentence:

Such eases as the presence of peculiar species of bats on oceanic

islands and the absence of all other terrestrial mammals, are facts

utterly inexplicable on the theory of independent acts of creation.

I make but one more quotation in this connection.

Near the end of the book, in a sentence which the careless

reader might understand to refer to something like the

modern mutation theory, he says:

Under a scientifie point of view, and as leading to further investiga-

tion, but little advantage is gained by believing that new forms are

suddenly developed in an inexplicable manner from old and widely

different forms, over the old belief in the creation of species from the

dust of the earth (p. 424).

Such quotations could be multiplied many times, for

over and over again throughout the book he speaks of

his theory as standing for the mutability of species as

against the independent creation of species. Indeed, so

convincing to the world was Darwin’s argument in sup-

port of his main thesis that the word Darwinism to the

popular mind stands for the theory of descent, as it is

perfectly right that it should do.

iI. A secondary thesis is an attempt to account for the

origin of species by the theory of descent with modifica-

tion through variation and natural selection.

I shall now attempt to show by quotations:

1. Darwin’s view of the part played by fluctuating

Variations.

2. The rôle of sudden variations.

3. The part taken by natural selection.

1. The following quotations would prove a narrow and

166 THE AMERICAN NATURALIST (Von XLII

restricted meaning for the theory of descent with modi-

fication through variation if it were clear that Darwin

always meant fluctuating variation when he used the word

variation.

On page 156 he says:

Why should not nature take a sudden leap from structure to struc-

ture? On the theory of natural selection we can clearly understand

why she should not; for natural selection selects only by taking

advantage of slight successive variations; sue can never take a great

and sudden leap, but must advance by short and sure, though slow

steps.

In attempting to explain the puzzling phenomenon of

the so-called neuter, really undeveloped female animals,

he says:

As natural selection acts only by the accumulation of slight modi-

fication of structure or instinct, each profitable to the individual under

its conditions of life, it may reasonably be asked, how a long and

gradual succession of modified architectural instinets, all tending

towards the present perfect plan of construction, could have profited the

progenitors of the hive-bee

The answer to this query, by the way, begins with a

sentence which has a very modern sound:

This difficulty, though appearing insuperable, is lessened, or, as I

believe, disappears, when it is remembered that selection may be applied

to the family, as well as to the individual, and may thus gain the desired

end (pp. 229-230). :

The following utterance should be read with Darwin’s

main thesis in mind:

If numerous species belonging to the same genera or families have

really started into life at once the fact would be fatal to the theory of

evolution through natural selection (p. 280).

Inferences have been drawn from the foregoing sen-

tence as though Darwin had written: If numerous species,

etc., have really started into life by variations greater

than fluctuating variations, as that term will be under-

stood at the beginning of the twentieth century, the fact

would be fatal to the theory of evolution through natural

selection.

Although, in his concluding chapter he makes use of

such expression as:

No. 507] DARWIN’S “ORIGIN OF SPECIES” 167

. . . Complex organs . . . have been perfected . . . by the accumula-

tion of innumerable slight variations.

He also says:

It is, no doubt, extremely difficult to nce by what gradations

many structures have been perfected . p. 404).

Again, on pp. 413-414:

As natural selection acts solely by accumulating slight successive,

favorable variations, it can produce no great or sudden modifications;

it can act only by short and slow steps.

I think that it is evident from Darwin’s discussion

of varieties of oaks that he would not have regarded

such work as that of DeVries on the evening primrose

as making a revision of the foregoing sentence necessary.

Even if DeVries’s mutants are what he thinks them to

be, that is, elementary species, still evolution of species

by that means must be by ‘‘short, slow steps.”

Even if it should be shown that species originate only

by mutation, the following sentence might be permitted

to stand:

~ New species have come on the stage slowly and at successive inter-

vals, and the amount of change after equal intervals of time, is widely

different in different groups (p. 417).

2. By the following quotations I shall attempt to show

the rôle which that kind of variation, now called muta-

tion, plays in the evolution of species according to Dar-

win’s view.

When it is noted that DeVries makes use of facts

recorded by Darwin in support of his views, it will be

seen that there is some reason for suspecting that some

of the facts which in Darwin’s day were thought to be

of the grade of fluctuating variations were really of the

kind now believed by many to be something quite dif-

ferent.

On page 22 is this statement:

Some varieties useful to him (man) have probably arisen suddenly,

or by a step.

Examples are cited, e. g., the fuller’s teasel, the turn-

spit dog, ete. DeCandolle’ s memoir on the oaks of the

168 THE AMERICAN NATURALIST [Vou. XLIII

world is alluded to. This gives the rank of species to the

forms which differ by characters never varying on the

same tree and never found connected by intermediate

states. Out of 300 species at least two thirds are pro-

visional species. Thus Quercus robur has twenty-eight

varieties, all of which, excepting six, are clustered

round three subspecies.

Commenting on this condition of things, that is, where

there is no clear line of demarcation between species and

subspecies, and between subspecies and varieties, or be-

tween lesser varieties and individual differences, he thus

concludes :

Hence I look at individual differences, though of small interest to

the systematist, as of the highest importance to us, as being the first

steps towards such slight varieties as are barely thought worth record-

ing in works on natural history, and I look on varieties which are in

any degree more distinct and permanent, as steps towards more strongly-

marked and permanent varieties; and at the latter as leading to sub-

species, and then to species (pp. 41-2).

A well marked variety may therefore be called an incipient species;

but whether this belief is justifiable must be judged by the weight of the

various facts and considerations to be given throughout this work

(p. 42).

Darwin noticed that wide-ranging, much-diffused and

common species vary most; also that species of the larger

genera in each country vary more frequently than the

species of the smaller genera; further, that many of the

species included within the larger genera resemble vari-

eties in being very closely, but unequally related to each

other, and in having restricted range (pp. 42-45).

The following sentence is interesting in this connection:

Every one who believes in slow and gradual evolution, will of course

admit, that specific characters may have been as abrupt and as great as

any single variation which we meet with under nature or even under

domestication.

The above-quoted sentence follows a notice of Mivart’s

belief that new species manifest themselves with sudden-

ness and by modifications beginning at once, of which

Darwin says:

No. 507] DARWIN’S “ORIGIN OF SPECIES” 169

This view, which implies great breaks or discontinuity in the series,

appears to me to be improbable in the highest degree (p. 201).

Such statements appear to be contradictory, until it is

remembered that the kind of new species meant by Mivart

would involve such violently sudden changes as the three-

toed Hipparion giving rise immediately to the one-toed

horse; or the wing of a bird suddenly appearing in

place of the fore-limb of some dinosaur.

Indeed, it seems to be to be demonstrable that the

statement of Darwin’s views respecting variation requires

but little change to bring them into harmony, or, at least,

make them include, the origin of varieties by mutation.

By abrupt variations which dre yet not greater than

a single variety may show, he means such cases as the

six-fingered Kelleia family, or the ancon ram. It is of

this kind he is speaking when he says:

Excluding such cases of abrupt variations, the few which remain

would at best constitute, if found in a state of nature, doubtful species,

closely related to their parental types.

On the other hand, it is clear that he included under

ordinary variations some, at least, which may now be

called mutations. Thus:

Although very many species have almost certainly been produced by

steps not greater than those separating fine varieties; yet it may be

maintained that some have been developed in a different and abrupt

manner. Such admission, however, ought not to be made without

strong evidence being assigned (p. 20:

This is probably as good a place as any to call attention

to the fact that in the title of the book the theory is not

stated to be the origin of species by the natural selection

of favored individuals, but by the natural selection of

favored races. Morgan’s term the survival of LANA

does not appear to me to be any improvement on this.

To my mind a still better statement is that which stands

at the head of a syllabus of lectures by Professor James

D. Dana, “On the Theory of the Origin of Species

through Natural Causes.’’ ee

Resuming the citations, the following explicit state-

ment is illuminating: io. ae

170 THE AMERICAN NATURALIST [Vow XLII

By the theory of natural selection all living species have been con-

nected with the parent species of each genus, by differences not greater

than we see between the natural and domestic varieties of the same

species at the present day; and those parent species now generally

extinct, have in their turn been similarly connected with more ancient

forms; and so on backwards always converging to the common ancestor

of each great class (p. 266).

Here is a sentence which anticipates some recent specu-

lations respecting a so-called plastic period in the life of

a species:

It is a more important consideration, leading to the same result,

as lately insisted on by Dr. Falconer, namely, that the period during

which each species underwent modification, though long as measured

by years, was probably short in comparison with that during which it

remained without undergoing change (p. 279).

To the same purport is the following:

This gradual increase in number of the species of a group is strictly

conformable with the theory, for the species of the same genus and

the genera of the same family, can increase only slowly and progress-

ively . . . one species first giving rise to two or three varieties, these

being slowly converted into species, which in turn produce by equally

slow steps other varieties and species. . . (p. 293).

Concerning the origin of varieties he has this to say:

The complex and little known laws governing the production of

varieties are the same, so far as we can judge, with the laws which

have governed the production of distinct species (p. 415).

In the following passage provision appears to be made

for the origin of varieties by mutation:

I have now recapitulated the facts and considerations which have

thoroughly convinced me that species have been modified, during 4

long course of descent. This has been effected chiefly through natural

selection of numerous successive, slight favorable variations; aided

in an important manner by the inherited effects of the use and disuse

of parts, and in an important manner, that is in relation to adaptive

structure, whether past or present, by the direct action of external

conditions, and by variations which seem to us in our ignorance to arise

spontaneously. It appears that I formerly underrated the frequency

and value of these latter forms of variation, as leading to permanent

modifications of structure independently of natural selection, . - -

He adds, in answer to certain recent criticisms that he

placed at the end of the introduction to his first edition,

the following words:

No. 507] DARWIN’S “ORIGIN OF SPECIES” 171

I am convinced that natural selection has been the main but not the

exclusive means of modification (p. 421).

3. The following explicit statement makes it very clear

that Darwin did not regard natural selection in the light

of an originating cause:

Some have imagined that natural selection induces variability, whereas

it implies only the preservation of such variations as arise and are bene-

ficial to the being under its conditions of life (p. 63).

It would appear that Huxley, in 1860, thought that

natural selection was being urged as an originating cause.

He says:

It is not absolutely proven that a group of animals having all the

characters exhibited by a species in Nature has ever been originated by

natural selection, whether artificial or natural.

He also thought that Darwin embarrassed himself by

the use of the aphorism, natura non facit saltum; that

nature does make a jump now and then, and that a

recognition of the fact is of no small importance in dis-

posing of many minor objections to the doctrine of trans-

mutation. In 1861, in a letter to Hooker, he says:

The great desideratum for the species question at present seems to me

to be the determination of the law of variation. . . . Why does not

somebody go to work experimentally, and get at the law of variation

for some one species of plant?

In 1885 he was reading the ‘‘Origin of Species”’ and

finding it one of the hardest books to understand that he

knew. In 1888 he says in a letter to Hooker:

: Darwin has left the causes of variation and the question whether it

18 limited or directed by external conditions perfectly open.

Writing to Bateson, February 20, 1894 (?), he says:

l see you are inclined to advocate the possibility of considerable

“saltus” on the part of Dame Nature in her variations. I always

took the same view, much to Mr. Darwin’s disgust, and we used often

to debate it.

In the light afforded by these comments of ele , and

after a careful rereading of the ‘Origin of Species,” I

am inclined to the belief that in the brilliant work of

Hugo DeVries we may have a key to a real understanding

of the difficulties in question.

112 THE AMERICAN NATURALIST [VoL. XLIII

Huxley, with his tendency to reach conclusions quickly,

which, he confesses, sometimes led him into mistakes,

saw intuitively, let us say, that the beginning of varietal

differences might be by a sudden leap. While Darwin,

who reached conclusions only after careful examination

of all possible contributing data, although realizing that

the origin of species from variations, by natural selection

had not been proved, thought that they furnished the

most favorable material for natural selection to work

upon. At the same time, I think that I have shown by

means of numerous quotations from the ‘‘Origin of

Species’’ that the very slight changes which DeVries has

shown to mark the beginning of some varieties, while

recognized by Darwin, were thought of by him as of the

same order as ordinary (now called fluctuating) varia-

tions. This view is justified, I think, by his frequent

use of the word step. Possibly this explains why Huxley

found the book such a hard one to understand thoroughly.

It also throws some light on the unsatisfactory condition

in which Darwin is supposed to have left the question

of the origin of varieties. To my mind, instead of this

being a blemish on Darwin’s work, as it seems to be held

by some recent writers, it is, when the state of biological

knowledge in his day is taken into account, in harmony

with his known caution and sagacity. To blame him for

not making a sharp distinction between fluctuating

varieties and mutations would be like finding fault with

Copernicus for not knowing what Kepler and Newton

discovered, or criticizing Newton harshly because his

theory of light left much for subsequent workers before

the electro-magnetic theory was possible.

THE DISTINCTION BETWEEN DEVELOPMENT

AND HEREDITY IN INBREEDING

DR. EDWARD M. EAST

THE CONNECTICUT AGRICULTURAL EXPERIMENT STATION

THERE is among animal breeders a tendency to frequent

out-crossing as a preventive of a feared deterioration

of the breed through inbreeding. This fear is of long

standing, probably having arisen contemporary with, or

as a result of, the repugnance to incest possessed by so

many human tribes. This general state of mind on the

ethical question has brought about an unwarranted belief

that there is a physiological law opposed to inbreeding

per se. Inbreeding undoubtedly results in many cases

of: deterioration, but the success of the few daring spirits

that have inbred superior stock shows that the cases of

deterioration were merely made possible by the course

pursued, and were not its direct and constant result.

In the vegetable kingdom a slightly different state of

affairs obtains. Some species thrive under inbreeding

while others appear to deteriorate. Maize is reduced

in vigor in one generation, so that the difference between

selfed and crossed plants is noticeable in seedlings two

weeks old. Other natural species have evolved intricate

mechanisms whereby they are perpetually self-fertilized,

and some have even given up sexual reproduction for

parthenogenesis (Taraxacum), and yet have survived in

competition by their hardiness and prolificacy. Darwin

even found that in species that generally appeared to

be injured by inbreeding (Ipomea purpurea and Mimulus

luteus), individuals were occasionally produced that were

not affected. ;

The classical researches which included the above ob-

servations are familiar to all. Direct comparison of

crossed and selfed plants, and investigations into the —

mechanical means by which plants are cross-fertilized,

173

174 THE AMERICAN NATURALIST [Vou XLII

all pointed to the truth of the dictum ‘‘ Nature abhors

perpetual self-fertilization,’’ which, by the way, simply

corroborated the results that Knight had obtained a half

century before. That there are important exceptions

to this rule was recognized, however, and Hays,’ arguing

from the case of wheat, suggested that it be changed to

read: ‘‘Nature abhors a radical change which would re-

quire species to cross in much closer or in much more

radical relationship than is their long established habit.”’

Each of these sayings is probably correct as far as it goes.

Nature does seem to have provided more for cross-fertil-

ization than self-fertilization. Yet the very fact that

all species do not cross-fertilize naturally, shows that

although cross-fertilization may be a desirable thing—

a thing to be provided for by nature—it does not follow

that inbreeding and decrease in vigor hold the relation

of cause and effect because they are often linked together.

As a matter of fact, the data that we possess regarding

the supposed degeneration through inbreeding do admit

an entirely different explanation, an explanation more

compatible with contemporary knowledge. The hy-

pothesis, first suggested by Shull,? is that the danger

from self-fertilization in naturally cross-bred species may

be due simply to the isolation of biotypes. It is an

established fact, although the cause is unknown, that

crosses between nearly related types (in both animals and

plants) are usually more vigorous than either of the par-

ent types alone. Since inbreeding tends to isolate types

homozygous in their characters, these homozygous types,

coming from species naturally crossbred, are thus de-

prived of the stimulus which came through free intercross-

_ing and appear to deteriorate.

A little later the present writer? pointed out that a

1 Hays, W. M. ‘‘Plant Breeding.’? Bull. U. S. D. A. Div. Veg. Phy. &

2Shull, G. H. ‘‘The Composition of a Field of Maize.’’ Ann. Rpt.

Amer. Breeders’ Assn. 4: 1908. :

* East, E. M. ‘‘Inbreeding in Corn,’’ Ann. Rpt. Conn. Agr. Exp. Sta-

tion, 1907-8.

No. 507] DEVELOPMENT AND HEREDITY 175

reconsideration of the work of Darwin and others shows

that it accords with this theory. As a single example

from Darwin we may consider the experiments with

Ipomea purpurea, which were his longest, being carried

on as they were for ten generations. If an actual degen-

eration were taking place it might be expected that the

difference in height between the crossed and the selfed

plants should have gone on increasing in the later genera-

tions. Such was not the case, however, and Darwin him-

self remarked upon it. Nevertheless, the results ob-

tained were what should have been expected by the hy-

pothesis just given, for after a few generations even the

erossed plants in such a small lot would have become

more or less inbred, and would lave approached the in-

bred stock in size. In further support of this view it is

noticeable that the crossed flowers varied in color in the

earlier generations, but became more uniform toward the

end of the experiment, while the selfed plants were uni-

form in color throughout the whole time. This, then,

explains why his out-crosses with other stock showed

greater vigor than did cross-fertilization within a type,

the latter strain having become more nearly identified

with the selfed plants through continued close breeding.

Such results as the above from Darwin, my own ex-

periments with maize and tobacco, together with the

ready agreement of the facts in other breeding work with

which I am familiar, indicate that this problem of de-

generation combines two questions; the one a question of

heredity, the other a question of development. Daven-

port* has recently called attention to what I consider the

former question, suggesting that deterioration through

inbreeding may be due to the isolation of homozygous

Tecessives, or the combination of recessive di-hybrids.

This is undoubtedly true when the allelomorphic pair

under consideration is the presence and absence of some-

thing essential to the normal development of the organ-

_ Davenport, C. B, ‘‘ Degeneration, Albinism and Inbreeding.’’ Science,

: N. 8., 28: 454, 455, 1908. one

176 THE AMERICAN NATURALIST [Vou XLIII

ism. But the principle will probably be found to apply

also where there is presence of an abnormal dominant

character. We do not know many such characters at

present, but susceptibility to rust in wheat and congenital

cataract in man may be cited as approaching our meaning.

The instances where the presence or absence of evil

qualities is brought to notice through their isolation

by inbreeding are few in number, however, and can not

account for the large number of cases where there is a

loss of vigor by this means.

Let us consider just what this deterioration, so-called,

is. Does it represent an actual degeneration in heredi-

tary characters? In general it does not. Darwin’s ex-

periments consisted mainly in comparing heights of

plants. His measure of vigor, then, is a measure of

rapidity and amount of cell division. In no cases does

he speak of losses of characters, and seldom of disease.

Even where disease appeared, it usually appeared alike

in inbred and cross-bred plants. In my own experiments,

I have observed some twenty-five families of maize in-

bred for two generations, and a lesser number through

the fourth generation, and have not found a single sign

of degeneration. In all characters of stalk, leaves, roots,

male inflorescence, female inflorescence, and mature seed,

the plants were normal. It is merely in the matter of

size of plant and ear, and thereby yield, that the plant

compares unfavorably with cross-bred plants. _

Further, there is no continuous decline in yield as

should be expected in actual degeneration. There is

somewhat greater difference between fourth generation

inbred and cross-bred plants than there is between those

of the second generation. This last fact may be ex-

plained by considering the frequency with which heter-

ozygotes in certain characters are selected even in the

most careful work. Not all character pairs can be kept

under observation, and from the mere fact of its being

inbred we can not presume that the isolation of a homo-

zygous strain is complete. The past summer one of our

No. 507] DEVELOPMENT AND HEREDITY 177

fourth-year inbred families was found to be heterozygous

in the character pair presence and absence of color in

the silk. But there is absolutely no indication that there

is loss of vigor after the isolation of a homozygous in-

dividual.

It seems, then, that this type of degeneration (the

common type) is limited to a partial loss of power of

development, a reduction in rapidity and amount of cell

division. The phenomenon is readily apparent in open

fertilized plants like maize, for there the vigorous grow-

ing hybrids are continually being formed in nature.

When the components of these hybrid strains are isolated

by inbreeding, reduction in vigor is immediately seen.

In plants like tobacco, which are naturally inbred, no

degeneration is suspected, for the natural plants are

taken as the standard. There is an increase in vigor,

however, when inbred tobacco strains are crossed, and if

the F, generation is then taken as a standard, there is a

loss of vigor through inbreeding comparable to that

which takes place in maize.

Upon what theoretical basis can these facts rest? In

the first place, whether or not we accept the theory that

the nucleus is the bearer of all hereditary characters,

nevertheless we must believe that amphimixis has two

functions, the one a recombination of hereditary char-

acters, and the other a stimulation to development. — Tf

we postulate that there is an increase in this stimulation

when two strains differing in gametic structure are com-

bined, we satisfy all observed conditions. This will ex-

plain why decrease in vigor and not degeneration of char-

acters is usually the sole effect of inbreeding, and will

also show why this decrease must reach a limit with the

complete isolation of an individual homozygous in all

characters, and never will result in a complete degenera-

tion, or ‘‘running out,’’ of the strain. One other effect

sometimes noticed in inbreeding is also thoroughly in

accord with the hypothesis. This is decrease in fertility.

Since fertility must necessarily start with the union of

178 THE AMERICAN NATURALIST (Vor. XLIII

the gametes and their subsequent division, a decrease

in this stimulation in species which have for ages de-

pended upon cross-fertilization may result in decreased

fertility.

We can scarcely form a definite idea of the mechanism

through which such a stimulation may take place. There

may. be chemical compounds found in different strains

that react when brought together. If this were the case

we should expect to find separate families with like

‘‘eompounds’’ which when crossed would not be more

vigorous than when inbred. It would be difficult to. estab-

lish such a thing experimentally. On the other hand,

the actual fact of difference" i in gametic constitution may

set up a biological ‘‘action’’ analogous to ionization. If

this were true, and individuals of the F, generation

heterozygous in all differentiating characters were

selected in succeeding generations, there should be no

reduction in vigor, while individuals of the F, genera-

tion, homozygous in their characters, should compare in

vigor to the P, generation. This hypothesis we are test-

ing, but results will necessarily be slow. -

The F, generation of thirty maize crosses were grown

in 1908 on well fertilized land in Connecticut. They

were planted three feet six inches each way, about four

stalks to the hill. Seeds from the same parent ears®

which were used to make the crosses were also grown

for comparison. Only fifty hills of each of the crosses

and of each parent could be grown on account of limited

space, but the soil conditions were such that a very fair

® The objection will be raised that beyond a certain amount of difference

between gametes, there will be sterility. It is generally true that there is

sterility with wide differences in botanical or zoological characters, but

there are res bat and we must not fall into the same old rut of putting

the two down as cause and effect because there is at present no other

explanation. It is definitely settled that in certain cases the bar to fertility

is merely the mechanical inability of the spermatazoon to penetrate the

ov It seems reasonable that the stimulation effect may be illustrated by

borrowing Galton’s polyhedron

*The parent ears were, therefore, one year older, but their germination

was good, and their growth equal to inbred seed of the same ages as t

hybrid seed.

No. 507] - DEVELOPMENT AND HEREDITY 179

indication of the comparative vigor of each strain was

obtained. Unfortunately crows and chipmunks played

havoc with the ‘‘stand’’ in a number of cases, and ac-

curate figures can not be given except in the following

four cases where the stand was perfect.

A white dent no. 8 yielded 121 bushels per acre (at 70

pounds per bushel); a yellow dent no. 7, which had been

inbred artificially for three years, yielded 62 bushels per

acre; the cross between the two varieties, no. 79 X no.

8 3, yielded 142 bushels per acre.

Longfellow, no. 34, an eight-rowed, yellow flint yield-

ing 72 bushels per acre, was crossed with the same no. 8

white dent, yielding 121 bushels per acre; the resulting

cross yielded 124 bushels per acre.

Sturges’s hybrid, a twelve-rowed, yellow flint with a

tall, non-branching stalk partaking of the characters of

dent varieties, was also crossed with no. 8 white dent.

The flint parent yielded 48 bushels per acre, while the

cross yielded 130 bushels per acre.

Two families of a yellow dent variety, which had each

been inbred artificially for three years, were the parents

of the fourth cross. No. 12, yielding 65 bushels per acre,

was crossed with no. 7, yielding 62 bushels per acre.

The F, generation yielded 202 bushels per acre. This

last result is somewhat distorted, as five stalks per hill.

of the cross were allowed to grow while of the parents

only four seeds per hill were planted. About 90 per

cent. of the seeds produced mature stalks. Notwith-

standing the closeness of planting to which this cross

was subjected, however, casual observation was sufficient

to show that it soared far beyond each parent in vigor

of plant and size of ear.

In the remainder of the field every possible combina-

tion of dent, flint and sweet maize was grown, and in

every case an increase in vigor over the parents was

Shown by the crosses. It is to be regretted that com-

parable yields could not be obtained in every instance,

mt, as a matter of fact, the differences were so — :

180 THE AMERICAN NATURALIST [Vou. XLIII

to the eye that it is almost unnecessary. The figures

presented do not show the average increase to be ex-

pected by a cross. The manuring was heavy, the culti-

vation intensive, and the yields were beyond the ordi-

nary. But they do show that in practically every case

a combination of two high-bred varieties of seed corn is

more vigorous than either parent.

The importance of this fact in commercial corn growing

is considerable, and is likely to increase in the future,

for the following reason. The corn breeding methods in

use vary as to detail, but their purpose is the same,

namely, to produce high-yielding strains. The older

idea was that continued selection of plus fluctuations

would invariably yield results. At present, there are

more adherents to the view that man can do more than

isolate from the mixture of types we call a commercial

variety the most perfect type that nature has produced

in this variety. It is all line breeding, and as it is

carried on on small plots, the tendency toward the pro-

duction of an inbred strain increases with the length of

time the work is prosecuted. Thus, unless new mutations

intervene, chance of improvement is limited to the latent

possibilities of the first breeding plot.

Shull” has already suggested that either definite recom-

bination of previously isolated biotypes, or relaxation

of selection after partial isolation and rejection of the

less efficient biotypes, will be found to be the logical

procedure in corn breeding.

The writer has become a convert to the first method

* Since this manuscript was sent to the printer the writer received from

Dr. Shull, as a timely coincidence, a copy of a paper that he had read at

the menial meeting of the American Breeders’ Association, in January,

1909. In it he deals with a similar method of corn-breeding, namely, the

actual isolation of homozygous strains by artificial inbreeding, and t eir

recombination later. His method is more correct theoretically, but less

practical than that of the writer. From this paper I inferred that his

views must accord with the theory presented in this paper. Replies to my

inquiries show that our ideas are strictly in harmony, although Dr. Sh

had not treated the theoretical phase of the subject, having considered it

as beyond the scope of his paper.

No. 507] DEVELOPMENT AND HEREDITY 181

in a modified form, and suggests the following scheme.

There must always be corn specialists to continue line

breeding, and this method is not for the corn breeder, but

the corn grower. The latter should purchase from the

line breeder two strains of seed each year, and grow the

F, generation of the cross between them.

The method requires a small isolated hybridization plot

in addition to the commercial field. In this plot the two

strains are planted in alternate rows. The male in-

florescence is removed from one strain at flowering time

and all of the seed for the commercial field selected from

this crossed strain. Some hybrid combinations will be

found to be more vigorous than others, but I am con-

vinced that practically any cross within the subspecies

will be profitable. Crosses between the subspecies, while

more vigorous than the mean between the parents, have

certain disadvantages, such as variation in the time of

ripening, which make them less desirable for practical

use.

BREEDING EXPERIMENTS WITH RATS

PROFESSOR T. H. MORGAN

CoLUMBIA UNIVERSITY

The following experiments chiefly between the black

and the roof rat were undertaken as one of a series to

determine how far the Mendelian law of discontinuous

inheritance applies to wild varieties and species. Most

of the cases of Mendelian inheritance have been deter-.

mined from domesticated forms in which the varieties

seem to differ from each other in the loss of one or more

characters. Until we know more about the results when

wild varieties are crossed with their wild species or

with other varieties, we can not safely apply Mendel’s

law to the process of evolution.

There are two species of house rats found in this coun-

try in addition to the common gray or Norway rat. One

of these is the black rat, Mus rattus, that still exists in

isolated communities in the north. It also infests, 1

believe, certain ports in the southern states and Central

America.

The other, the roof rat or Alexandrian rat, is said to

have been introduced from Mediterranean ports by ships.

Tt is generally described as a variety of the black rat.’

The roof rat is gray, it has the ticked or barred gray hair

common to most wild rodents. It may, therefore, be

looked upon as the original form from which the black rat

has been derived. If this is the case we might expect to

find that the gray color is the dominant one and the black

the recessive, especially since in the domesticated species

of the Norway rat, black is recessive to gray.

To my surprise I found that in the first generation the

1The black rats used in these experiments were obtained at Amherst,

Mass., through the kindness of Mr. Clarence Birdseye. I am indebted to

the Carnegie Station at the Tortugas and to Dr. Stockard and to Professor

Edwin Linton for obtaining and transporting the roof rats used in these

experiments.

182

No. 507] BREEDING EXPERIMENTS WITH RATS 183

hybrids are black whichever way the cross is made.

Black is dominant to gray. In all I have thirty-two

such individuals.? These black hybrids inbred have pro-

duced one litter of four black? and one gray. The num-

bers are too small to furnish conclusive data, but as far

as they go they indicate that the two colors follow Men-

del’s law.

The roof rats are white below as is also the Norway

rat, but there is a peculiar difference. In the roof rat the

white hair is white to its very base, i. e., it is not ticked..

In the Norway rat the ventral hair has a dark base as in

most other rodents.

All attempts to cross the black rat or the roof rat with

the Norway rat, or with its.domesticated varieties have

failed, although by putting young rats together I have

had them live in harmony for a year or more. It would

appear that the two species M. decumanus and M. vattus

are infertile.

‘On the contrary as stated above M. vattus and M. alex-

andrinus are perfectly fertile inter se.

In respect to the ticking of the ventral hair it is inter-

esting to note that spotted gray mice of the domesticated

breeds have the hair of the white spots uncolored all the

way to the base, as in the albino. I have found a wild

species of brown mouse that has a white belly and the

hair is ticked, i. e., it has a dark base. When such a

mouse is crossed with a spotted mouse the first genera-

tion is gray with a white belly—the hair being ticked.

Such mice inbred produce amongst other combinations

some spotted mice. In these mice wherever a white

spot extends down the sides and across the belly the

region of the spot on the belly has hairs white to the

base. In other words, the white spot dominates the white

belly in the same way that it dominates the gray hair of

the sides and back.

? There is some variation in the color of the black hybrids of the first

generation. One that was reddish black at first later became black.

“In the second generation the four black individuals, still yo Read? ee

Some differences in Pa shades ot black.

184 THE AMERICAN NATURALIST [Vou. XLIII

If the white belly of the roof rat turns out to be a

character separable from the uniform gray coat, as I

have found to be the case with white-bellied gray mice,

we may expect to find in the second generation of hybrids

some gray rats with a gray belly.

The chief point of theoretical interest in these results

concerns the origin of the black color in the black rat.

If it is produced by the loss of the ticking factor, as

Castle suggests for other black rodents, it is inexplicable

why the black should dominate when crossed with the

ticked gray coat of the roof-rat. If, on the other hand,

the rat has arisen by the black color spreading over and

obscuring the ticking beneath, then we could understand

how it dominates in the first generation; also why the

result is different from that when the black variety of

the Norway rat is crossed with a gray rat. It remains

for further work to settle this point.

The common gray or Norway rat has, as stated, a white

belly—the white hairs having a black base. When such

a rat is bred to an albino having black (possibly gray

also) as a latent character, the first generation contains

only gray rats as Crampe and Doncaster have shown;

but the color of the belly varies—a point that has hitherto

escaped notice In some individuals the ventral hair is

a slate-color, in others it is nearly white. In both the

base of the hair is blackish. There appears to be an

almost, perhaps a complete, gradation between white and

slate-colored belly. The extremes may be accounted for

as follows: The albino may carry black-bearing and gray-

bearing germ cells. When the former unite with a gray-

bearing germ cell of the gray Norway rat, the addition

of black may cause the black base of the ventral hair

to extend farther out towards the tip, making the belly

slate-color. When a gray-bearing germ cell (of the

albino) meets the gray-bearing germ cell of the albino,

little or no change may take place in the ventral region.

Another interpretation is also possible. The albino

may carry a uniform coat, i. e., one that gives gray (or

No. 507] BREEDING EXPERIMENTS WITH RATS 185

slate) below instead of white. The presence of this

condition may dominate in some of the first hybrids.

In addition to the points noted above it should be

recorded that in nearly all of the individuals, resulting

from a cross between a wild gray Norway rat and an

albino, there occurs a pure white spot or streak on the

belly, as other observers have recorded. The hair of

these spots is white to its base. This result is obviously

due to the incomplete dominance of the uniform coat.

The albino in my experiments, carried, latent, not only

black, but a spotted ‘‘condition,’’ as the second generation

demonstrated. The presence of this condition in the

hybrids of the first generation is shown to the extent of

the white ventral spot. This region of the body is, as

it were, a ‘‘weak’’ area in which the recessive character

displays itself, although elsewhere, as a rule, the spotting

is suppressed. The result shows that at certain points

in the pelage a recessive character may crop out in a

dominant-recessive individual.

In the second generation gray, black, spotted gray,

spotted black and albinos appear, as others have already

shown. In the uniform gray individuals a series of types

occur varying from rats with white bellies, like that of

the wild gray rat, to those with a uniform slate-colored

belly. The gray color itself is subject to some variation

—the result depending perhaps on the condition of the

black present.

SHORTER ARTICLES AND DISCUSSION

THE CHUB AND THE TEXAS HORN FLY

In the upper reaches of the waters of the Niobrara River,

locally known as Running Water, the common chub, Semotilus

atromaculatus, is very abundant. One may with a hook and

line secure many dozens of them in a very short time. In

Running Water they scarcely ever attain a greater length than

eight inches. During the past summer while out on a collecting

trip into the Miocene beds of northwestern Nebraska, some in-

teresting observations were made on certain feeding habits of

the chub which may prove of interest to those naturalists who

are especially interested in animal behavior and intelligence.

The horn fly, Hæmatobia serrata, according to Kellogg, is

a European insect which gets its popular name from the habit

of clustering on the bases of the horns of cattle. It was first

introduced into this country about 1886 or 1887 and its spread

has been so exceedingly rapid that in a very few years it has

become an annoying pest to western cattle. Mr. James H. Cook,

a prominent ranchman of Sioux County, Nebraska, told me that

No. 507] SHORTER ARTICLES AND DISCUSSION 187

he had never seen the horn flies so abundant as they were the

past summer. They literally swarmed around the cattle and

since the majority of the stock was dehorned the insects would

settle all over the backs and sides of the animals although they

were in some cases observed to cluster around the horn bases.

At Harris’s ford, where the collecting parties crossed Running

Water, several hundred cattle watered all summer. The lower

part of the ford is quite shallow, scarcely attaining a depth of

more than a foot; somewhat to the right the water deepened so

that the cattle in drinking would be submerged nearly to the

middle line of their bodies. At noon the cattle would begin to

come to water and would continue coming for some hours on hot

days; on cooler days they would delay their coming somewhat;

and on rainy days they frequently did not come at all. The

following observations were made on hot, bright days as our

party was returning to camp from the morning work. Mr.

Albert Thomson called my attention to the actions of the fishes

and we together made the following observations repeatedly. |

The cattle would almost always enter the stream at the shallow

part of the ford and gradually wade up stream, drinking as they

went, until they came to the deep place near the fence where

the water reached well up on their bellies. The chubs seemed

to be unusually numerous at the ford, and we often wondered at

the great numbers of the little fishes which we could see in

schools in the clear water. Their presence was soon explained.

As soon as the cattle entered the stream at the shallow place in

the ford the chubs would come out from their cool and shady

retreats under the grasses along the sides of the bank and hasten

to meet the cattle at the shallows. Often we saw as many as a

dozen or more chubs following a single cow. As soon as the

water came near the bellies of the animals the chubs would leap

out of the water and catch the horn flies from the sides of the

cattle. Often we saw them leap as much as half their length out

of the water to secure a fly which was high up on the animal’s

Side. These observations were made on several consecutive days,

and on the last day but one I was so fortunate as to secure a

Photograph of a chub in the act of catching a fly from the side

of a cow and the photograph is published herewith. | |

e That the fishes actually learned that the dark spots on the —

= Sides of the cattle made good food, there can be no doubt. Just —

one how they first learned it we may not know. The chubs had fur-

188 THE AMERICAN NATURALIST (Vor. XLIII

ther learned that the coming of the cattle meant food for them,

hence they would meet the cattle in the shallows and follow them

to deeper water. The act of these fishes leaping to secure flies

from the sides of cattle is so unysual that it is deemed worthy of

notice and it is hoped that the incident may be of service to

those interested in animal behavior.

Roy L. Moonie.

UNIVERSITY OF KANSAS.

NOTICE OF A NEW CAMEL FROM THE LOWER

MIOCENE OF NEBRASKA

In the autumn of 1906, the writer found a nearly complete

skeleton of a camel, in the Lower Harrison Beds, near Agate,

Sioux County, Nebraska. The skeleton is finely preserved and

articulated. It had apparently been washed into a heap while

the muscles still held the bones together, for it is literally tied

in knots. On this account it has only been partly removed from

the matrix, and so a complete description is deferred.

The type (No. HC125, private collection of the writer) is an

adult animal, and consists of a complete skull and jaws, a

practically complete vertebral series, fore limbs and feet, pelvis,

sacrum, and the greater portion of the hind limbs and feet.

The latter were damaged by erosion. It is referred to the genus

Oxydactylus, and the specific name of Campestris is proposed.

It is apparently closely related to O. longipes, but is a much

smaller and somewhat less specialized type. This seems the

more natural when we remember that O. longipes was found

in a somewhat later horizon. The skull in general contour is

very similar to O. longipes, but exhibits some distinct features.

The upper incisors are proportionally slightly larger than those

of O. longipes, the third incisor being a little larger than the

canine. The diastema separating these two teeth is relatively

shorter than in the latter, and the facial portion of O. campes-

tris is relatively shorter. The premaxillae are separated at

the proximal extremity by an unusually large U-shaped open-

ing, 8 mm. wide and 10 mm. long. P? and P? are slightly more

robust in the present species. The limbs are long and slender,

though much shorter than those of O. longipes. The meta-

carpals are entirely separate. On the sides of the proximal end

* Annals of the Carnegie Museum, Vol. II, No. 3, pp. 434-475, 1904.

No. 507] SHORTER ARTICLES AND DISCUSSION 189

of the metacarpals are small, flat, rugose bones, remnants of

metacarpals II and V. When the specimen is entirely cleaned

of the matrix, a more complete description will be given.

MEASUREMENTS

O. campestris. O. longipes.

Sarmis longth of skuil o. iinei 290 mm.

engt

h of diastema I” to canine........ mm. 13 mm.

foes of diastema canine to P’........ 12 mm. 14 mm.

Length of diastema P* to P?............ 15 mm. 18 mm.

Lengtn of continuous molar-premolar series 88 mm. 102 mm.

Length of metacarpals.............6.. 275 mm. 345 mm.

Length of proximal phalanx............ 51 mm. 66 mm.

Length of median phalanx............. 20 mm. 31 mm.

Breadth of metacarpals III and V...... 15 mm. 23 mm.

HAROLD JAMES COOK.

September 15, 1908.

NOTES AND LITERATURE |

The Chondriosomes as Bearers of the Hereditary Qualities.—

Meves, in a paper entitled, ‘‘Die Chondriosomen als Trager

erblicher Anlagen” presents a new and interesting view in

regard to the bearer of the hereditary qualities. Since Hert-

wig, ’75, reached the conclusion that fertilization consists in

the union of male and female pronuclei, the nuclear theory of

heredity has been criticized by many able investigators, and the

new interpretation which Meves gives at this time indicates that

many are still dissatisfied with the all-sufficiency of the theory,

and are eagerly seeking and grasping, as it were, the first visible

sign of any other substance which may serve to carry the heredi-

tary qualities.

Meves finds in the chick embryo, between the second half of the

first and the first half of the fourth day of incubation, by means

of special fixing and staining reagents, a large number of inde-

pendent threads, fibers, rods or granules. The shape of these

structures varies in different cells and at different times in the

same cell, although they are all one and the same substance. He

concludes that these structures are identical with the ‘‘ Cytomik-

rosomen’’ of la Valette St. George, the ‘‘Mitochondrien’’ of Benda

and the ‘‘Chondriokonten’’ of Meves, and proposes to unite them

under the term ‘‘Chondriosomen.’’ He also believes that the

granules of Altmann, except those produced by regents, are iden-

‘tical with the chondriosomes. They have been described by

Benda, Meves and others in various tissue cells, plant cells and

in sex cells. Benda, 03, suggested that possibly the mitochon-

dria might play a rôle in heredity, and with this suggestion

Meves agrees. ;

Nigeli’s idioplasm hypothesis and many other similar theories

have been advanced to account for heredity, but these have been

eriticized on the ground that they lack a material substratum,

and that they are purely speculative. Meves believes that the

‘‘fantastie structure,” as it was called by Sachs, has now be-

come a reality in the chondriosomes. While Nägeli supposed

the idioplasm to produce different differentiated products by

_1 Archiv fiir Mikroscopische Anatomie und Entwicklungsgeschichte, Bad.

72, 1908.

190

No. 507] NOTES AND LITERATURE 191

special activities on the surrounding cytoplasm, Meves believes

that the differentiated parts arise by a direct metamorphosis of

the chondriosomes.

Meves realizes that the nuclear substance answers fully the

demands of a hereditary substance, namely, that in fertilization

the two parts must be equivalent, that there must be a reduction,

and that there must be an equal division in cleavage. However,

he says that it has not been proved that the nuclear substance

and hereditary substance are identical, or that the nuclear sub-

stance is the only hereditary substance. He then asks the ques-

tion, how far do the chondriosomes satisfy conditions demanded

of a hereditary substance. It is evident that the quantity of

chondriosomes present in the egg cell is much greater than that

brought in by the sperm. This fact, he says, presents no great

difficulty, if we suppose that the specifie qualities of the chon-

driosomes becomes expressed through the configuration of trans-

verse sections. According to Nägeli, an over-supply of idio-

plasm may be thrown out from the idioplasmic system at the time

of fertilization and become changed into yolk. In favor of this

view Van der Stricht and his students have shown that a part

of the mitochondria of the egg cell are changed into yolk granules.

There is also the possibility that the male chondriosomes, after

entrance into the egg, multiply and divide. There is not an

equal division of the chondriosomes in cell division, as there is

of the choromatin, but they do approximate to equality of divi-

sion and any difference may be made good by increased growth.

As there is a reduction of the chromatin before fertilization,

_ Meves suggests that there may be a reduction of the chondrio-

somes. However, he has not seen even the slightest indication

of a reduction, and until some evidence is forthcoming, such

a suggestion must remain as a mere speculation. Duesberg,

07, has shown that there is a mass reduction of the chondrio-

somes in the two spermatocyte divisions, but in the egg this is

not true, as the chondriosomes remain scattered throughout the

cell, and the resulting cells are very unequal in size.

Meves suggests another way to prevent the increase in the

reditary mass, and this is as Nägeli has shown. Nägeli supposes

the male and female idioplasm to unite as a mixed product. A

cross section through the union of the embryonic strands shows

that the idioplasm strands, in relation to the number of micelle

Tows, remains unchanged. A paternal and maternal EOS

192 THE AMERICAN NATURALIST [Vou. XLIH

thread in fertilization, then, must unite end to end to form one of

double length. While Meves ascribes a large part in the trans-

portation of hereditary qualities to the chondriosomes, he does

not claim that they alone, to the exclusion of the nucleus, carry

these qualities. He thinks that both nucleus and cytoplasm

work together, the qualities of the nucleus being carried by the

chromosomes, those of the cytoplasm by the chondriosomes.

F. PAYNE.

Cultural Bed-Mutations in the Potato.—E. Heckel’ has reared

the white-flowered Solanum maglia from tubers received from

Sutton and from Vilmoyin. The young plants resembled per-

fectly typical S. maglia. They were transplanted from the

greenhouse to a fertile garden where common potatoes had been

grown the year previously. The tubers obtained differed

greatly from those planted and those characteristic of this

species. They weighed from ten to twenty times as much. One

in particular weighed 135 grams; the flesh instead of being

watery and slightly bitter as it typically is, was compact and

full of starch—the tuber was edible. This tuber being planted

gave, the next year, five tubers from 87 to 62 grams in weight.

The other tubers (of smaller size) yielded tubers of from 50

to 5 grams—the smallest having the size of the typical tubers

of S. maglia. The author refers to the large potato obtained

by him from S. maglia as a mutation, but suspects that its size

may have been influenced by the previous growth in the same

soil of the common tubers.

t Ann. des Faculté des Sci. Marseille, XVI, 1907.

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THE

AMERICAN NATURALIST

Vout. XLI April, 1909 No. 508

HEREDITY OF HAIR COLOR IN MAN

GERTRUDE C. DAVENPORT anp CHARLES B. DAVENPORT

STATION FOR EXPERIMENTAL EVOLUTION, CARNEGIE INSTITUTION

OF WASHINGTON

INTRODUCTION

Types of Hair Color.—The heredity of hair color in

mammals is a subject of great complexity, not to be

lightly entered upon. It is a subject in which much

knowledge has been gained in recent years through

the work of Bateson and his associates, Castle and

his pupils, Cuenot and others. Nevertheless certain

important points remain uncertain. First, and funda-

mental for our purpose, is the question of the number

of factors involved in any hair color. All are agreed

that there is a special red pigment (a lipochrome) that

stains the hair diffusely. In clear red hair one sees, in

sections, a yellowish red tinge that is not bound up with

any structures. With a high power one sees elongated,

spindle-shaped bodies, which are apparently the remains

of nuclei and are devoid of granules. In all other hair

(except that of albinos) one sees granules grouped in the

spindle-shaped bodies. In black hair (Chinaman, Fig.

A) these granules are large and numerous in each group

(average, 12) and appear of a dark brown color. In very

dark brown hair (negro, Fig. B) the granules are perhaps

a little larger but much less numerous in each group

(average, 6); and the color is a much less intense brown.

In hair of a cold, mouse brown (Fig. C) (about No. 25 in

193

194 THE AMERICAN NATURALIST [Vou. XLIII

E. Fischers’s hair scale!) the granules are small, very:

few in each group (average 4) and slightly colored. The

dark red hair of the orangutan is due chiefly to granules

whose color is well reproduced by sepia on a clear back-

ground; but in the head hair of the golden babboon, which

is striped golden and black, much diffuse golden pigment

is found and (in the black zones) dark sepia granules of

P e è S

Ip fb 8 2e :

ae ee 2 3 ., ; r 2 $

E RG H s å í

-s © i z ri Ld ; : a

bg" Ste i * r P :

oe ete 6 fstt.c te, f Sag

ee ee Sone

8 ° 8 o é pe

: 2o 3 3 b P : ?

: ig ioe i : eee

; s, i 3

° : ° H : i

Fie, A. X 1150. Fie. B. X 1150. FIG. C. X IUN

CHINAMAN. LEON M. (NEGRO). MOUSE-BROWN. “ʻA.

medium size and frequency. In twoscore preparations

of the hair of man and primates we have not found in

any instance,jet-black granules such as are characteristic

of black mice. In our preparations, many of which are

thin sections kindly cut for us by Miss Lutz, the granules

vary in size, number and intensity, but there is no discon-

tinuity between the lighter and darker sepia pigments ;

and, as stated, we have not found a coal black hair either

in Chinese, Japanese, Indian, Negro or Italian, and not

even in the black spider monkey. ‘There is an interesting

parallel case in poultry where even in the Black Minoreas

and the Black Cochin the pigment is a dense sepia brown.

We conclude, therefore, that such discontinuous color

types as are described in domesticated animals such as

1 Made by Franz Rosset, Freiburg i/Br. See E. Fischer, Korrespondens.

Blatt, Deutsch. Gesell. f. Anthropologie, Ethnologie %. Urgeschichte,

XXXVIII, 141-147. September—December, 1907.

No. 508] HEREDITY OF HAIR COLOR IN MAN 195

fancy mice and guinea pigs under the names of yellow,

chocolate and black are not fundamentally distinct, but

have probably been made so in the process of perfecting

the standard groups. Indeed, a casual acquaintance with

the variety of human hair color as one meets with it in

the streets of any large city shows that there are all inter-

grades between yellow, light brown, dark brown and black

hair and even the reds pass (through dark red and red

brown) into the warm browns. It may consequently be

concluded, at least provisionally, that there are two main

types of pigment in human hair; a reddish yellow, which

finds its intensest development in bright red, and a sepia

brown whose intensity varies from a light yellow to dark

brown and black. Finally, the two pigments may be

combined? and in such cases the brown pigment may quite

obscure the red.

The conclusion here reached concerning the factors in-

volved in human hair color are not, we fear, in accord

with the recent investigations on other mammals. They

rather speak against the theory of well-developed unit

characters in human hair pigment. Brown and black

colors there are and an intensifier or a diluter; on the

other hand, these are not well defined units but occur in

all conceivable degrees. The facts of intensity in human

hair color indicate that the absence of selection made on

the basis of intensity has resulted in the blending of color

unit characters or has not afforded the selective means

by which they have elsewhere been formed. :

General Scheme of the Tables.—The data concerning a

single family are placed in one line. At the extreme left

are given certain reference letters by which the family

is designated. Then follow the number of children in the

designated family that have hair of the class named at

the top of each column. The following six columns give

the color of the hair of the mother (M), father (F),

‘mother’s mother (MM), mother’s father (MF), father s

mother (FM) and father’s father (FF) so far as

2 Tt is clearly seen in the hair of the mother of the Lyn family (Table os

X, b). ae ee

196 THE AMERICAN NATURALIST [Vou. XLIII

The principal abbreviations of the names of hair colors

are as follows: br, brown; chest, chestnut; dk, dark; fl or

flax, flaxen; gold, golden; It, light; med, medium; 2,

black; v, very; yell, yellow. Names of colors in paren-

theses ( ) indicate juvenile condition.

Classification of the Tables.—Three series of tables

may be considered. A, including cases where black or

A. Herepiry IN ÅBSENCE oF BLACK on Brown PIGMENT

IN PARENTAGE

TABLE I. DISTRIBUTION OF HAIR COLOR IN OFFSPRING WHEN NEITHER

PARENT SHOWS BROWN PIGMENT

Reference ANCESTRY.

Letters. Tow. vat "aola. Red. M. F. MM. MF. FM. FF.

Rit 4 flax flax flax flax flax flax

Hak H 2 et ee e T S eee

Dex i 4 blond blond blond blond blond blond

Ste-E 2 gold = flax þr be It. br. Niaz)

Reg-A 6 gold gold gold gold gold gold

Edw i g dk. red lt. red — an — —

Swe . 2 1 _ | It. red Woe It. br. dk. br. dk. br. dk. br.

brown pigment is absent from both parents; B, including

cases when brown is present in both parents nuk red is

not visible in either; and C, including cases where both

brown and red are visible in the parentage.

B. Herepiry or Buack AnD Brown PIGMENT IN

PARENTAGE

TABLE II. DISTRIBUTION oF HAIR COLOR IN OFFSPRING OF PARENTS ONE

OF WHOM HAS THE LEAST INTENSITY OF BROWN (F'LAXEN,

GOLDEN) AND THE OTHER A SLIGHTLY GREATER

INTENSITY OF BROWN (LT. BR.)

OFFSPRING. ANCESTRY.

Reference 2 ee : ; K 5

Hog p [a] è = fx; i

Letters. 23 3 r E sj fi = = a a

Pi a re

Boy-A 2 flax lt. br. It. br. blond It. bi It. br.

Hal-A 1 4 1 t fox N ti flax

Deg Lt lt. veil: lt. br. br dk. br. It. on lt. br.

The foregoing 7 families, comprising 36 children, illus-

trate a simple case. When both parents lack the brown

pigment the children will all lack it. When the diffuse

No. 508] HEREDITY OF HAIR COLOR IN MAN 197

pigment has a weak intensity in the parents it will have

the same character in the children; but where it has a

strong intensity, as red, in the parents it may have the

strong intensity in some (Swe) or all (Edw) of the

children.

As compared with Table I, Table II shows a greater

variation in the offspring—the classes light brown and

yellow brown make their appearance and comprise just

50 per cent. of the offspring, a result that accords with

the hypothesis that light brown is heterozygous and flaxen

or light yellow is recessive, for, DR X RR is expected

to yield 50 per cent. of the DR (light brown) type. We

note here as in Table I that the hair is in no case darker

in the children than in the darker parent; but it may be

less dark.

TABLE III. DISTRIBUTION OF HAIR COLOR IN THE OFFSPRING WHEN BotH

PARENTS HAVE LIGHT Brown HAIR

OFFSPRING. ANCESTRY.

Ref : = $ : : : f :

Letters. | 4 SAAE 7 é syge

S e E P=]

a Mm g a a

Byr 5 1 27 |ltbr itbre _dk-br._ _ N. It. br, br.

Klo t 1 It. br. (fl. ) It. br. (f. ) It. br.(A.) N. It.” br.

Pla-B 6 tb uie I. be. It br. X. j

Ste-G 2 lt. br. lt. br. r. . br. . —

rie 2 keo kie ie Makipi

Sob 24 iuni ae |

Assuming two cases of ‘‘auburn brown” in Byr family

to be essentially golden brown (this hair has not been

seen by us) it appears that when both parents have light

brown hair either all of the children are of the same type

(Pla-B, Ste-G, Tuc. families) or else of the light brown

and lighter (yellow brown to flaxen—Byr?, Klo. family).

In the first case the parents act like homozygous domt

inants toward the lighter types; in the second case like

heterozygous dominants. a

In this case we obtain a total of 42 offspring, 16, or 38 o

per cent., dark brown and brown, and 26, or 62 per cent., —

light brown or lighter. Taking dark brown bai oe. ey oe

198 THE AMERICAN NATURALIST [Vou. XLIII

TABLE IV. DISTRIBUTION OF HAIR COLOR IN THE OFFSPRING WHEN ONE

ARENT HAS DARK BROWN HAIR AND THE OTHER LIGHT BROWN

(a) The Darker Parent Produces ‘‘ Light’? Germ Cells as well as ‘‘ Dark.’’

OFFSPRING, ANCESTRY.

Reference | |; , Ë TE H : ;

e r ee Re Ae . : iS :

Letters. a 2 = 3 4 R z = Pe = = Z fa

b 2

Bri 4 1 dk.br. It.br. lt.br. dk.br. dk. br. flax

Dou- 1 29 1I de be uir: kbr dk br) dk br, 1 pi

Dou-B 3 .br. dk.br. dk.br. lt.yell.br. dk.red

Fir 1 3 lt. br. br.

Loc-B 2 dk.br. lt.br. yell.-br. dk.br lt.br. yell.-br.

Loe 4 dk.br. lt.br N.

Mat-B 2 It.br. dk.br. b: dk. br It.br. dk.br.

Mor-A 2 dk.br. It.br. It.br. dk.br. dk.br. N

Ran-B So p dk. br. It.br. kbe -br E Ie

Sho 1 2 dk.br. lt.br. It.br. It.red dk.br. br.

Totals 13 12% 5101

26 16

zygous and dominant to light, expectation is 50 per cent.

of the offspring as dark as or somewhat less dark than

the darker parent and 50 per cent. light. The observed

frequencies are of the expected order.

(b) The Darker Parent is not Known to be Heterozygous in Hair Pigment.

OFFSPRING, ANCESTRY.

ren ae A =

Toor, a 3 Ay & I a o A £

2 4 2 A N o N ao o eeu

Bin 1 32 dk. br. It. br. dk.br. dk.

Fis 3 1 dk. br. lt. br. dk.br. dk.br. It. br. lt. br.

Fri 2 1 dk. br. It. br. br. N. blon

Gil-B 1 2 1 dk. br. lt. br. dk.br. dk.br. It.br. It. br.

ue 2 2.4 It. br. dk.br. dk. br È N

Hal-E 19 3 dk. br. It. br. br. It.

uf 1 2 It. br. dr. br. It. br. dk. br. dk. br. dk. br

Lat-A 2 9 1 iv.dk.br. It br. N N

Pot 2 2 dk. br. It. br. dk. br. dr. br. dk. br. dk. br.

Rog-B 3 1 dk. br. It. br. dk. br. dk. br. N. lt br

Sin 9 lt.br. dk.br. lt.br. — ‘‘dark’’ dk. br

Sne 2 It. br. dk.br. It. br. dk. br. dk. br.

Wil-D 1 19% 9 lt. br. dk.br. lt.br. lt.br. dk. br.

Totals t S% 8H

28 22

In this case we obtain in a total of 50 offspring, 22, or

44 per cent., dark brown and brown and 28, or 56 per cent.,

No. 508] HEREDITY OF HAIR COLOR IN MAN 199

light brown or lighter. Were the dark brown parents

truly homozygous in hair color, and did the hair color of

the offspring not grow darker with age, Mendelian ex-

pectation would be 100 per cent. dark brown. Actually,

the result falls far short of that, just as the necessary

conditions are far from being met. It is highly probable

that in some of these families (notably Gil-B, Gue and

Huf, and probably also Lat-A and Wil-D) the darker

parent actually forms germ cells that lack black pigment.

Of the four lightest haired children the ages of three

that are known are 8, 10 and 15 years—ages at which the

adult color is not fully shown. Under these circum-

stances one can not predict with certainty the outcome

of matings.of this class. One can only say that the

proportions of light brown children and those with lighter

hair should be less in proportion to the darker haired

children in class B than in class A. The actual propor-

tions in the two classes are in the direction of this ex-

pectation.

TABLE V. DISTRIBUTION oF HAm COLOR IN THE OFFSPRING WHEN ONE

PARENT HAS BLACK HAIR AND THE OTHER Licht Brown HAm

(No DIVISION, ON ACCOUNT oF FEWNESS OF FAMILIES

OFFSPRING. ANCESTRY.

Referenc Ceo i

Lotiors. (YU SA ym : „i E 4 z

fi ao 4 z = = s E ty

fa Q © 5 lanl 3 = : ae

Car-B 13 i) & ke ee li br It br.

y 3 N kbe Gk br D ; ;

rák 1 N. ltbr. dk.br N. dk. br. dk. br.

-ig s j No kw bwe N. kekk

one 1 2 2 lke K toe oe

ad 2 N. lt br. dk. br. “light” It.br. N.

a $ It. b am K. we ngeng TRR ERT

Str-B 91 l = ra lt. ey N. N à lth B br. —

Tre ~o f N kiwe S Ie >~ —

Totals 281156 561

=~~

21 12

Assuming what is probably true for all the families,

that the black-haired parent produces an equal number of

~ germ cells with a tendency toward lighter hair and toward

= black, we should expect an approach toward an equality —

200 THE AMERICAN NATURALIST [Vor. XLII

of light and dark haired offspring. Actually, the lighter

colors are in excess—a result again doubtless due to the

TABLE VI. DISTRIBUTION oF HAIR COLOR IN THE OFFSPRING WHEN ONE

PARENT HAS BLACK HAIR AND THE OTHER BROWN HAIR

OFFSPRING. | ANCESTRY.

Reference ey H

Hos u ee R . 3 j :

Letters E 3 Py a yA = fa = = 5 m

Blo-A 3 2 N. br. — — —

Jas Pow N, <br. br. N. flax N.

Clu-A 3 br. N. — — — —

Clu-B Bed 1 ij bri N. as — —— —

Col-C 1 I zol bres. T N. dk. br lt. br.

Dru-B 3 N. þr. — — — —

Hen LA pr.o N: br. N. yell.-br.

Hof I2 bi N hwe ky N. N.

Koo 1 1 br oN. i ; r. br.

Lea l 2 br N. br. br. br. br.

Mil-A tI N he br. N. N. br.

Ros 2 3 N. br br br. br. N.

a 4 bro N. br br br N.

Ste-D pr N: — — —

Sto-B t l Tbe- N dk. br N.

Ver 1 } N. br. br It. br. dk. br N.

Totals ar 0 6 0 |

GAA Seis

22 33 |

relative immaturity of the children as compared with their

parents.

Assuming, as in the discussion of Table V, that the

blacks are heterozygous (except in the Ste-D family) we

should expect an equality of dark and light haired off-

spring modified by preponderance of the lighter type

owing to the immaturity of the average of the offspring.

Actually, with brown hair and lighter there are 41 chil-

dren as opposed to 7 (Ste-D omitted) kith either black or

dark brown hair. When we compare the proportion of the

children having hair brown or darker in this Table (60

per cent.), with that in Table V (36 per cent.) we realize

‘how much more frequent the darker classes have become

with the increased darkness in the hair of the second

parent.

On account of the impossibility of drawing the line be-

tween the dark and the light shades of hair and on account

No.508] HEREDITY OF HAIR COLOR IN MAN 201

of the light color of immature offspring we are able only

to compare this section with that which follows.

TABLE VII. DISTRIBUTION oF HAIR COLOR IN THE OFFSPRING WHEN BOTH

PARENTS HAVE DARK BROWN OR BLACK HAIR

(a) When Both Parents Probably Form Light Germ Cells and Dark wm

Equal Numbers

OFFSPRING. ANCESTRY.

Reference Eae E =

Letters. |Z £ = m & m wel si E = fa a =

a Q öy a A si a fu fy

Ee ae i een a

Cam-A 1 43 2 N: N tmd” N l

an 2 PONG ‘ dk.br N br. lt.br

Cla-A 1 3 | dk.br. dk.br. lt.br. dk.br It.br. bbt

ur 1 1 | dk.br. dk.br. It.br.. br. It.br. dk.br.

ue I1 1 dk.br. dk.br. blond dk.br. dk.br. blond

Gla-B ‘3 7 2il N. N. yell.-br. N. N Dr,

Gor-A g8 -2d Jae K N. br. Eo p

ad 21 |dk.br. N. N. It-br. br.

Har- A 1 3 3- 2 dk.bè N. br. br, br. br.

Hem-A 1l l be N. N. br. N. yell.-br.

Mck 1 IN- N br. w N br

Rol i di N: dk.br. br- N It.br. dk.br.

Sim 1 1 N. N. N. It.br. It.br. It-br.

Totals $3838 205 19101

29 35 Ce PD a a ae

Assuming that the qualities of light hair color and dark

hair color (or absence and presence of intensifier) segre-

gate in parents of mixed origin expectation is that Series

A would yield 75 per cent. dark haired offspring, but on

account of the impossibility of drawing the line between

the dark and light shades of hair and on account of the

light color of immature offspring we are able only to com-

pare this series with series b in which expectation 1s 100

per cent. offspring of the darker color. Actually, in

series b there are 59 individuals light to 137 (or about

70 per cent.) dark while in series a only 55 per cent. are

dark. A part of these light haired individuals probably oe

result from recessive light hair color of parents and a =

part from immaturity. |

202

THE AMERICAN NATURALIST

[ Vou. XLIII

(b) When Both Parents are not Known to Form Light Germ Cells

OFFSPRING,

Reference

Letters.

Chest.

bt BO

pas

Mr ewww k BD

We we ee fe

bm OO

w ed

DO pei ped pad WR

e OW WORD m AMDI IN N O Wm m woa | Dk. Br.

WO ij ë Nj pi

bb peh pd jad pod

WO O N H t

| 5

Wol a o

1824144 30723113

19 years old. *6 years old.

3 “‘blond,”? 1-9 years old.

ANCESTRY.

Eoo gok g g

dk.br. dk.br. dk.br. dk.br. dk.br. N.

dk.br. dk. br. i N. dk.br. N.

dk.br. N bwe N. N. N.

dk.br. dk.br. N. lt. br. — dk. br.

N. N. dkr N. N. dk.br.

dk.br. N. N. N: N. dk. br.

No cM dki N. dk.br lt. br.

N. N. N. N. N. —

N. dk.br. hr. N. lt. br lt. br.

dk.br.dk.br. br. dk.br. br. dk. br.

dk.br. N. N. N. N. N.

N. N. br. N. N. N

dk.br. dk.br. N. N. N. yell.-

dk.br. N. br. dk.br. dk.br. br.

N. N. N. N. N. N.

dk.br. dk.br. N. N. ee N.

N. dk. be. N. N. dk. br

dk.br dk.br. dk.br. dk.br. ae sy dk.br.

dk.br.dk.br. br. N. N. br.

N. N. N. N. N. N.

dk.br. N. N. N. dk.br. dk.br.

dk.br; N, 2 dk br. N, — N.

N N. N. N. N. N.

dk.br. dk.br. br. br. dk.br. dk.br.

N. dk.br. gold N. N. k.br.

dk. br. dk. br. dk.br. dk.br. br. lt. br.

N. N. N. N. br. yell.-br

dk.br. N. dk.br. N. N.

N. N. — — N. —

dk. br. dk. a dk.br. N. N. flax

dk. br. br. N. ON, N.

i ak. br. br. N. N. N.

dk.br. N. N. yell.-br. N. N:

dk.br. dk.br. dk.br. dk.br. 16. br. N.

N. N. : x N. N.

dk.br. dk. br. dk.br. dk.br. dk.br. dk.br

No N, N. N. N. N.

N. dk.br. be N. br. dk. br.

dk.br. dk.br. N. N. N. N.

dk.br. N. dk.br. N N. N.

N. N. N. N. N. N.

N. N. N. dk.br. N.

dk.br. N. dibr N. dk.br. N.

dk.br. dk.br. dk.br. yell.-br. dk.br. dk.br.

dk.br. dk. br. A N. dk.br. dk br

N. N. N. dk.br. m

N. N. N. N. N.

* Also 3 flaxen, 5 to 10 years old. *Also

No. 508] HEREDITY OF HAIR COLOR IN MAN 203

C. Herepiry oF Rep anD Brown PIGMENT

We have seen that the red series is quite independent

of the yellow-brown series. Clear red-haired individuals

lack black pigment themselves and can not transmit it to

their offspring. This is, at least, a priori probable; but

despite careful search we have found no case of two

parents with clear red hair. One case of clear red and

dark red is given in Table I., Edw family, in which all

three children have red hair. We have one of dark red

X dark red parentage with the following remarkable

record (as yet unchecked).

| OFFSPRING. | ANCESTRY.

Reference | g 2 z : A

ers. | 5 = 4 E | = i = f Z fu

| = os = fu

| ee ee | =

iiaiai i ISOMER PR SEESE sp TEA EE E ET E

| |

Dey-B | 1 3 1 4 (dei dikin = N br. N

We interpret this case to mean that the red is absent

in some children (owing to heterozygotism of the par-

ents) and dilute in others and here masked by black

pigment.

TABLE VIII. DISTRIBUTION or HAIR COLOR IN THE OFFSPRING WHEN ONE

PARENT HAS Hair oF A CLEAR RED COLOR; THE OTHER OF A BROWN

= OFFSPRING. ANCESTRY.

S “a oa a

sc ue £ oe eS : : “ £ 5 2

SI jeg. sSyas a F fa Ss fa i

at ji ga g ó + S

Bon iwm kM N e br.

Sov i2 il red br. No No o o r.

i 4 1 Noo r D 2 o

Hur 3 tri ki kw ak be ke dk. br.

May [1] 1 1 ited “ty ered fat yell be Ob

Web 111 2 Ste N Bm E A

Totals| 1 211 1 1 3 2 6

In this table the yellow-brown series of colors predomi-

nates among the offspring over the reds. ge a

pret to mean that, as the red parents are usually hetero a

zygous in the intensity of red that they bear, we have

approximately one half of the offspring without any Z

only a slight) tendency toward red. Even when red-

204 THE AMERICAN NATURALIST (VoL. XLII

dominates over its absence it is frequently completely

hidden by black or even dark brown. In consequence

of the cooperation of these two causes we are not sur-

prised to find considerably more than half of the offspring

(70 per cent.) showing no red.

TABLE IX. DISTRIBUTION OF HAIR COLOR IN THE OFFSPRING WHEN THE

PARENTS HAVE DARK HAIR CONTAINING HypostatTic RED

(a) Both Parents Have Hypostatic Red

g Z OFFSPRING. ANCESTRY.

ts Re ee g 3

ee (Seared o n 3 g ; . = a = f

A RRS A AR ake

— acer oe a

Ear l 1 | dk.br. dk.br. dk. ns It. red np = red

Hog-B 1 1 1 dk.br. dk.br. chest. N. —

Kel 2 : —

Smi-D mE a o dk.br. N, N. chen: eat chest.

Totals 221 2 0 4 3

(b) Only One Parent is Known to Have Hypostatic Red.

—

5 N. N br. chest. br. N.

y 1 1 dkbe N: they N. red

Gla-A 3 o 2 N. dkbr N. che. dk.b bi N.

ot 3 i i N. r N. N. ed

Pat-A Loki as 38 N. N. dk.br. N, AE

Wan-A 1t N. dkbr. dk. h. dk.red br. dk.br.

Wel-A 2 2-5 1I N. dkbr. N. dk.red — dkbr.

Whe-D 1 1 N. N. dk.red N. ltr. :

Woo-B 2 N. dk.br. dk.br. gold chest. gold

Totals Sib? 56I9 18 li

Tables VIII to X give data for answering the very

difficult question of inheritance of red when associated

with melanic pigment. The chief difficulty is due to the

masking of the diffuse by the more intense granular

pigment. The following resultS seem, despite this diffi-

culty, established.

1. Two light-haired parents whose hair is without red

will have no red-haired children (Table I).

2. When one parent only forms ‘‘red hair’’ gametes,

while the other forms exclusively gametes containing the

darker phases of melanic pigmentation, the offspring will

show no red hair; a fortiori, if neither parent forms ‘‘red

hair” gametes, no red hair will appear in the offspring.

(Table IX, b; compare also Tables IV, V, VI and VIL.)

No. 508] HEREDITY OF HAIR COLOR IN MAN 205

TABLE X. DISTRIBUTION OF HAIR COLOR IN FAMILIES CONTAINING RED-

IRED CHILDREN; AND THE HAIR COLOR OF THE ANCESTORS

oF THESE FAMILIES

OFFSPRING. | ANCESTRY.

Reference H a eo a oN]

Letters. 4 aGsag eA 2 3 2 | > -= k 3 te

fa “3 5 s A a r 5 s i | = a = fai fu

(a) Both Parents Have Red Visible in Hair

Edw | 21 | dk.red It.red — se ala a

(b) Only One Parent Has Red Visible in Hair

Bur-B 3 1 auburn dk.br. auburn auburn dk.br. dk. br.

Ww 4 br. br.-red N. br. H D

in 1 1 dk.br. dk.red dk.br. dk.br. lt.br. dk.br.

Hol-D 1 1 wa ak be ake o N o D

Lyn 2 lisred-be w W e y

Mur l l 1 dkred Itbr. dk.red N. dkbr.dk.br.

Mye } i 2 r. dk.red red woo N br.

Pad 1 4| lt.br. dk.red N. ee E

Rav 1 1 dk.red dk.br. dk.red —

Wri 3 dk.br. sandy dk.br. br. sandy be:

Web t 1i 2 2 mM o N Ww N N.

Totals 23 5 5120166

18 22

Bol 11 i 4 dbe N. Itbr. dk.br. — —

Zar 1 1 Jikbr. dk.br. v.dk.br. br.-red dk.br. red

Eis 2 1 br. Itbe. dkbr. hi lii br.

Fan io $ we N 9 a n 8

Fra-D N. N. DE

eg 2 2 1? It.br. lt.br. br I br. in

ce 42 1 lithe bw b tb. - —

Gri 1:3 a211 11.8 k ooe?

Had-A 2 E N e A

a 1 2 N. No o — —

cg-B 13 3 N. br.

Pra ťi o 1 |yelh-br. dk br. gold N. N. dk.br.

Ram oe its a eo Rae

Ric i il x K N N. N. 4

Sco 21 1 1i aa E E EA

Tay t í il ete kee w . dk.

Wal-C 21 3 2 ye N. dk.br. dk.br.

Wri-a 3 11 2 akw N. dkbr. N

Totals | 145 1313962 20 11

uU~

51 33.

3. When, on the other hand, both etn though ed

dark « a tes, about hree sixteen

, produce ‘‘red hair” gamete: “(Table IX, a:

of the offspring will have clear ze hair.

the ratio is 3 in 12.)

206 _ THE AMERICAN NATURALIST [Vou. XLII

4. Conversely red-haired children result from the

union of two ‘‘red hair’? gametes. If there is no black

pigment to be considered all children, in such cases, will »

have red hair. If one parent has visible red and the other

none (though probably heterozygous) then about half of

the children show the lipochrome pigment and the other

half the melanic pigment (Table X, b). If neither parent

of red-haired children shows red in its (dark) hair then

expectation is that only three sixteenths of the offspring

will have red hair. Table X, c, shows only those families

in which red actually occurs. Now in some families with

the potentiality of red in one quarter of the offspring,

but having only four or fewer children, a red-haired child

may fail to occur and such a family would be excluded

from the table. Such an exclusion would tend to reduce

the proportion of non-red offspring in the total. Conse-

quently instead of 86 per cent. of the offspring in Table

X, c, being non-red, actually only 61 per cent. are such.

In the families given there are numerous cases where

the red haired are to the non-red haired offspring as 3

is to 13 or as nearly so as the size of the family permits.

This is true of the Bal, Elt, Fro, Gri, Ram, Sco and Tay

families. The other families show not unreasonable

divergencies from the typical 3 to 13.

5. All results are in accord with the statement that red

and black constitute two independent series; that red is

dominant over no red, as the deeper shades of melanic

pigment are dominant over the lighter; and that the dense

granular melanie pigment tends to hide the diffuse pig-

ment. Thus in Table VIII the gametes of the red-haired

parent may be given as n.R; those of the brown-haired

parent as N.r; where N, n. are abundance and sparsity

of melanic pigment, respectively, and R, r presence and

absence of lipochrome (red) pigment, respectively. Then

the zygotes will be of the various forms: nR (red soma),

NR (brown or black, red hypostatic), Nr (plain brown

or black), n.r. (flaxen to light brown). The matings of

Table IX, a, are of the order (NR, Nr, nR, nr) X (NR,

No. 508] HEREDITY OF HAIR COLOR IN MAN 207

Nr, nR, nn). Expectation in 12 offspring is 6.7 dark

brown or chestnut, 2.3 clear red, 2.3 pure brown or black

and .7 very light brown. ‘This expectation is approxi-

mately realized in the totals. The matings of Table

IX, b, are of the order (NR, Nr, nR, nr) X (Nr). There

is actually a total of 51 individuals and expectation in

this case is 25.5 offspring with deep melanic or chestnut

hair and 25.5 offspring with pure melanic pigmentation

of some grade. No pure red should appear and none

does occur. The matings of Table X, b, are of the order

(NR, nR) X (nR). They should give an equality of off-

spring of the two types: NnRR (melanic pigmentation

with hypostatic red) and nnRR (red with little or no

black). The matings of Table X, c, are of the order

(NR, nR, Nr, nr) X (NR, nR, Nr, nr). This should yield

in a total of 73 offspring 43.9 having dark melanic pig-

ment combined with (hypostatic) red; 14.6 with pure

brown of some grade; 14.6 with pure red and 4.9 with-

sparse melanic pigmentation (yellow brown). The im-

portant proportional excess of the reds is explained in

the last paragraph.

D. Is Innenrrance or Harr Conor at ALL BLENDING AND

CAN IT BE SAID TO CONFORM TO GALTON’S Law? |

We have seen that, despite the difficulties offered by

change of hair color with age and by the masking of

heritance in hair color can be brought into accord with

the ordinary formula for alternative inheritance. But

it may fairly be asked, since brown pigment is not a well-

defined unit character, whether hair color may not equally

conform to the blending type of inheritance. If there

were blending (‘‘as in human skin color’’?) then the off-

spring of a dark and light should all be intermediate.

Table V is important in this inquiry. If blending oc-

curred the offspring of black and light brown should all

be brown (or light brown because of immaturity) but

dark browns and a black oceur; so in Table VI the 9

blacks oppose the hypothesis; also in Tables VIII and

208 THE AMERICAN NATURALIST [Vou. XLIII

IX, a, the occurrence of red is not in accord with the

hypothesis. Certainly there is no blending in an ‘‘all N’’

ancestry of red and yellow as in the Ram, Ric-C and Wol

families of Table VII, b. The results clearly do not

accord with the law of blending inheritance.

It remains to consider if inheritance of hair color fol-

lows Galton’s law which states that the two parents deter-

mine 50 per cent. of the ancestry, the four grandparents

together 25 per cent. and earlier ancestry altogether form

the remaining 25 per cent.

Taking the 12 families of Tables X, c, whose grand-

parents are all given, we have in the parentage a total of

0 red in 24 parents; and of 5 red in 48 grandparents, or

about 10 per cent. Assuming the same proportion of

red in the unknown earlier ancestry, we have the total

expected proportion of red in the offspring given by

the sum

0-24 xX 50= 2

5-48 X 25=

-104 X 25 = A 6

5.2 per cent.

Actually, there are about 40 per cent. of the red type,

and, making every allowance, at least 18 per cent. are to

be expected. Five per cent. certainly fits the facts very

badly. We conclude, therefore, that Galton’s law does

not fit the facts as well as Mendel’s law and that heredity

of hair color is alternative.

E. THE NON-TRANSGRESSIBILITY OF THE UPPER LIMIT

While the application of the law of alternative inherit-

ance to human hair color lacks something in ideal clear-

ness and precision, one general rule stands out promi-

nently. It is that in the midst of the varying degrees of

intensity of the melanic pigmentation the intensity of the

melanic pigmentation of the offspring never exceeds that

of the more intense parent.

The general intensity relations of ER hair pigment

in parents and offspring are brought out in Table XI.

An inspection of this table shows that, in general, in

No. 508] HEREDITY OF HAIR COLOR IN MAN 209

TABLE XI.

| HAIR COLOR OF OFFSPRING.

Grade | : % é |

of Darker ; 5 ; = A

heer E 3 5 Z 5 # y z Sealine

a > 3 © s a

Flax 4

ell. 11 2

Yell. br 1 4

zold S 6

Lt. brown 4 1 2 5 14 3

rown Fino ed 4 4 4 23 24 5

Dark brown | 4 2 A 5 66 25 58 6

Black pack 4 5 8 60 37 49 40 4

the melanic series, the grade of intensity of hair pig-

mentation in the offspring does not exceed that of the

darker parent. The only exceptions appear in the

‘‘brown’’ and ‘‘dark brown’’ parentage, where a small

percentage of children are represented as of the next

darker grade. Many more such cases were in our orig-

inal records, but wherever the question was asked of the

recorder whether the hair of the child, A, exceeded in

darkness that of the darker parent, B, the reply was

almost without exception negative. Samples of hair were

asked for and these never proved darker in the children

than in the parents. A common source of error lies in

not disconnecting the effect of a slight grayness in the

parent. In one sample of hair from a mother that was

reported lighter than the daughter the gray hairs were

carefully picked out, when it appeared that the natural

color of the hairs of the mother and child were as like

as possible. Consequently one is justified in laying no

stress on the 11 children out of 600 (less than 2 per cent.)

in which the hair color was returned as darker than that

of the parents—particularly as despite efforts these re-

turns could not be confirmed. It follows, then, that par-

ents may be assured that their children will eventually

have hair as dark as the darker parent or of a lighter

tint, but not darker. Consequently, parents with flaxen

or yellow hair will have children all alike and like them-

selves in this respect. But parents with black hair may

have children withe flaxen hair or with light brown hair

S Gr

. 5

210 THE AMERICAN NATURALIST [Vou. XLIII

or (because of the masking qualities of black pigment)

with red hair.

What is the relation of this principle to the law of

alternative inheritance? The latter is only a special

ease of it. When characters A and B are crossed the

more intense character appears in the offspring—the less

intense character is recessive—the ‘‘heterozygous”’ chil-

dren do not exceed the more intense parent. If, now, two

such heterozygous persons be mated, one fourth of their

offspring show the recessive condition, which by hypoth-

esis is of a lower grade than that possessed by the par-

ents; the remainder of the offspring may attain the grade

of their parents; but they will not exceed that grade.

This principle of the non-transgressibility of the upper

alternative inheritance only, but also for blending in-

heritance—indeed, it seems to be of universal appli-

eability.

An exception to this rule is exhibited by some heter-

ozygous forms. The cross of a high-combed fowl and

a low-combed is a fowl with one intermediate grade —

of comb. Two heterozygous combs in the parentage

throw, inter alia, high combs. Not all cases of heter-

ozygous forms constitute exceptions to this law of the

non-transgressibility of the upper limit, and human hair

color seems, even in the heterozygous condition, to follow

the law. The workings of the principle are veiled in

some cases of eryptomeric characters, i. e., built up of

hidden factors.

Certain important consequences flow from this prin-

ciple. These one of us has pointed out in a brief com-

munication to Science. If the progeny stands on the

average in respect to a character at a lower grade than

the parents then, if inbreeding is practised, the two

parents of the next generation will probably have this

character at a lower level than their parents and will pro-

duce children having the character less well developed

than they have it themselves. If inbreeding be practised

for several generations it is clear that in some, ay least.

8 Vol. XXVIII. pp. 454-455, October 2, 1908.

No. 508] HEREDITY OF HAIR COLOR IN MAN J11

of the children, the character in question would probably

become quite degenerate. Since the note in Science was

published we have read a paper by Feer, to which our

attention was called by the title ‘‘Der Einfluss der Blut-

verwandschaft der Eltern auf die Kinder.”* This paper

comes very near to our point of view. After showing

that retinitis pigmentosa and congenital deaf-dumbness

are the diseases most closely associated with inbreeding

the author concludes that they are not so much inheritable

diseases in the usual sense as inheritable diseases of

degeneration, and depend on degeneration of the em-

bryonic ectoderm. It seems clear from such data as Feer

adduces that our general thesis will hold true for many

human characters—that inbreeding does not cause them

to degenerate, but having a tendency to degenerate, in-

breeding will prevent any recovery and, in addition, will

hasten the downward tendency from generation to gen-

eration. The only way to avoid progressive degeneration

is to bring in (usually necessarily from outside) blood

with the tendency to produce the characteristic in a well-

developed condition.

Combining now the results of the three studies on eye

color and hair color and form made by us,° it appears that

two parents with clear blue eyes and yellow or flaxen

straight hair can have children only of the same type, no

matter what the grandparental characteristics were; that

dark eyed and haired, curly-haired parents may have

children like themselves but also of the less developed

condition. In the latter case what the proportions of

each type will be is, for a fairly large family, predictable _

by a study of the immediate ancestry.

CARNEGIE INSTITUTION OF WASHINGTON,

DEPARTMENT OF EXPERIMENTAL EVOLUTION,

COLD Spring HARBOR, N. Y.,

December 1, 1908.

* Separate, Berlin, 1907 ; also ‘‘ Jahrbuch fiir Kinderheilkunde, ’’ pees

oat C. and C. B. Davenport, ‘Heredity of Eye-Color in Man,’ Science, ©

N. S., XXVI, pp. 589-592, November 1, 1907; ‘‘ Heredity a aE

-in Man,’’ AmrRICAN NaruraLsT, XLII, pp. Ber 29, mP 1908.

A MECHANISM FOR ORGANIC CORRELATION?

G. H. PARKER

PROFESSOR OF ZOOLOGY, HARVARD UNIVERSITY

Tar year 1909 is notable for its many historical asso-

ciations. It is not only the fiftieth anniversary of the

publication of ‘‘The Origin of Species,’’ but it is also the

centenary of the birth of Charles Darwin and of the

publication of Lamarck’s ‘‘ Philosophie Zoologique.’’ To

the American its associations with Lincoln are precious

memories. But it is not to these historical matters that

I wish to refer. Science ever looks forward, not back-

ward, and it is on certain modern aspects of the move-

ments centering about the problem of evolution and espe-

cially on those connected with the name of Darwin that

I wish to speak.

Although biologists have been familiar with Darwin’s

theory of natural selection for almost fifty years, it must

be confessed that they are only at the threshold of the

problem of evolution. That species have arisen by trans-

mutation is now universally admitted, but how transmuta-

tion has been accomplished remains at present one of the

unsolved riddles. The Lamarckian factors, though pos-

sible, must be set down as still unproved. Natural selec-

tion, so far as observation and experiment go, seems to

play a real part in transmutation, but the extent of its

application is still a matter of much uncertainty. Even

the recently advanced mutation theory, on which hopes

at one time ran high, is coming to assume at best a supple-

mentary rôle. In fact it is evident that the most serious

efforts of the past have failed of full accomplishment and

it seems likely that the process of transformation is not

exclusively dependent upon any single principle, but is

of great complexity involving in all probability a consid-

1 Read before the Boston Society of Natural History, February 12, 1909.

212

No. 508] MECHANISM FOR ORGANIC CORRELATION 213

erable number of factors. Of these factors we are only

beginning to get glimpses. I believe they will come into

clearer view only as we progress in the solution of general |

biological problems. It is my intention to bring before

you very briefly one of these lines of progress and to

point out its possible bearing on the problem of evolution.

You are all doubtless familiar with the claim that

Darwinism or natural selection is at best only a partial

or insufficient factor in evolution. Its actual workings

seem to be concerned with the elimination of only the

most poorly adapted members of any stock; it is a process

that is not closely enough adjusted to call forth those

slight but constant differences which every systematist

recognizes as the distinguishing marks of a species. To

quote from a recent criticism:

Every student of systematice zoology or botany has a keen realization

. of the fact that a majority of the distinguishing characters which

he recognizes in the various species . . . that come under his eye are

of a sort that reveal to him no trace of particular utility.

For this reason it is believed that these characters could

not have been produced through natural selection. I

hope to show you, however, that we can make the admis-

sion implied in this quotation, to the effect that specific

characters are not necessarily useful, and still be able

to explain their occurrence and fixity through Darwinism.

A general outline of this proposition has already been

given by Plate in his consideration of correlation. Ac-

cording to this author the development of a specific char-

acter of no special use may take place through correla-

tion, that is, through that unknown law of growth by

which an indifferent organ may be so bound up with ne

related to a useful organ that it, the indifferent organ, 18

perfected along with the useful organ as this latter 18

developed or specialized through selection. In this way

it is conceivable that a specifie character, even though

useless, may arise at least indirectly through natural

selection. It is to be noted that Plate’s conception of —

the mechanism of correlation is not detailed; in fact, he =

214 THE AMERICAN NATURALIST [Vou. XLIII

describes this principle as an unknown law of growth.

It is to this aspect of the subject that I wish to direct

your attention.

Only a superficial acquaintance with organisms is

needed to make one familiar with many examples of cor-

relation. A hairy integument is always associated with

mammary glands; albinism in fur and skin is accom-

panied with a red color in the eye; and many other ex-

amples of correlated characters might be given. The

question that we have to consider is the nature of the

association in correlated characters and much light can

be thrown upon this, I believe, by a study of the ductless

glands.

The ductless glands such as the thyroid, the suprarenal

bodies and the hypophysis of the brain were originally

supposed to be functionless, but recent work has shown

them not only to be functional but absolutely essential

to the continuance of life. The removal of the supra-

renal bodies from a mammal is invariably followed by

death within a few hours and the loss of the hypophysis

or the thyroid is also fatal though only after a somewhat

longer interval. It is thus quite evident that these or-

gans are of vital importance and that the continuance

of life is dependent upon their presence. But they are

not only necessary for life; they profoundly influence the

form and structure of the organism in which they occur.

This is best seen in the case of the thyroid. In extreme

disease of this gland or after its removal in the higher

mammals, the skin thickens and thus produces a mis-

shapen aspect in the features and the extremities, there

is a tendency to the loss of hair, and the nervous organs

are so affected that the animal sinks into a condition of

semi-idiocy (cretinism). Thus there are not only funda-

mental internal changes, but the external features such as

a naturalist might use in describing a species are pro-

foundly modified. Certain external features, then, in

the normal animal are correlated with the state of the

thyroid and, as disease and experiment show, they fluctu-

No. 508] MECHANISM FOR ORGANIC CORRELATION 215

ate with the changes in the state of this gland. Our nor-

mal skin and features are thus dependent upon the in-

tegrity of this internal organ.

The mechanism of correlation between two such organs

as the thyroid and the skin has already been somewhat

worked out. It is natural to suspect that this correla-

tion is nervous, for both thyroid and skin are supplied

with an abundance of nerves coming from a common

central organ. But the fact that the symptoms already

described as the result of the removal of the thyroid can

be checked and even made to disappear by grafting into

the animal that has lost its thyroid, a part of a living

gland from another animal, shows conclusively that the

nervous system is not concerned. : The further observa-

tion that animals devoid of thyroids may be kept in

normal condition by injecting thyroid juice into them

or even by feeding them with fresh thyroid glands from

other animals, has suggested the idea that this gland

produces a substance which makes its way into the blood

and is thus carried to those parts of the body where it

is needed. It is through this substance that the skin is

influenced in that in the absence of this material the skin

suffers serious change. The mechanism of correlation

between the thyroid gland and the skin, then, consists in

a substance produced by the gland and carried in the

fluids of the body to various organs, including the skin,

whose growth and appearance is thereby modified.

Similar observations have led to a like conclusion con-

cerning the action of the suprarenal bodies and the

hypophysis. These organs, like the thyroid, produce

substances that make their way into the fluids of the

body and influence its structure and action in so profound

a way that they are absolutely essential to its continued

existence. In the case of the suprarenal bodies the active

substance has been isolated and is known as adrenalin.

Since these internal secretions have the power of calling

forth or exciting very marked changes in the body, they

have been given the general name of hormones. It would,

216 THE AMERICAN NATURALIST [Vot. XLIII

however, probably be a mistake to regard the production

of these hormones as limited to a few organs such as the

thyroids, suprarenal bodies, ete. The most recent work

in this field points to the conclusion that all active organs

of the body, nerve centers, muscles, glands, ete., produce

hormones which in the blood probably exert extensive in-

fluences on the parts with which they come in contact, and

examples of this kind are being rapidly discovered. It

was formerly supposed that the secretion of the pan-

creatie juice, which is poured into the small intestine

when the partly digested food from the stomach reaches

that organ, was dependent upon a nervous signal given to

the pancreas from the intestine, but it is now well estab-

lished, through the brilliant work of Bayliss and Starling,

that the action of the acid food on the walls of the in-

testine produces a hormone, called secretin, which when

carried in the blood to the pancreas will cause that organ

to secrete. The evidence of this lies in the fact that when

a small amount of secretin is injected directly into the

blood stream of a mammal, the: pancreas, whose nerve

supply may have been cut off, will begin to secrete with-

out the presence of food in the intestine. Still more

remarkable is the correlation between the mammary

glands and the embryo in mammals. It is well known

that as the time for the birth of a mammal approaches,

the mammary glands of the parent grow in‘size and struc-

tural changes appear preparatory to the secretion of milk.

This correlation between the growth of the embryo and

the growth of the mammary glands can not depend upon

nervous coordination, for the nerves of the embryo have

no connection with those of the maternal body. The

_ correlation depends upon a substance, a hormone, pro-

duced in the body of the embryo and transmitted to the

blood of the mother, whereupon it so influences the mam-

mary glands as to start their growth. The evidence for

this lies in the fact that if the extracted juice of a rabbit

embryo is injected periodically into the circulation of

a virgin female rabbit, her mammary glands can be in-

No. 508] MECHANISM FOR ORGANIC CORRELATION 217

duced to take on the growth characteristic of the early

stages of pregnancy though she is absolutely without

young.

Another important set of bodily correlations are those

that exist between the reproductive glands and the sec-

ondary sexual organs such as the comb, hackles and spurs

of the common male fowl. It is well known that if the

genital glands of a young male fowl are removed before

it has attained maturity, it will fail to perfect its sec-

ondary sexual organs and the usual external evidences

of maleness may be absent. But if, as Shattock and

Seligmann have shown, a small piece of a male gland is

grafted into a young castrated male the comb, hackles,

and spurs may develop as in a normal bird. It is, there-

fore, highly probable that the reproductive glands, like

the ductless glands, produce hormones by which the de-

velopment of the secondary sexual organs is determined.

Not only are hormones produced in the adult body,

but they are very probably formed during development.

Such at least seems to be the condition in the correlated

growth of the vertebrate eye and its lens. As is well

known, the eyeball in the vertebrate is formed around

an outgrowth from the brain; the lens is developed from

the skin in such a position as to fit the forming ball. This

interesting correlation in position between the external

lens and the deep-seated eyeball has been made clear by

Lewis who has shown that when the forming eyeball of

a given species of frog is covered by grafting over it skin

from the abdominal region of even another species of

frog, this foreign abdominal skin will begin to form a

lens in an appropriate position for the underlying eye-

ball. Apparently the eyeball gives out a substance, a

hormone, that so influences the adjacent skin that, irre-

spective of its source within certain limits, it forms a

lens. Thus embryonic correlations may also depend

upon hormones. ae

These numerous examples show that many organs of

the body produce hormones that profoundly affect the

218 THE AMERICAN NATURALIST [Vow. XLIII

form and structure of many other organs, external as

well as internal. And further that these hormones are

in some cases absolutely essential to the continuance of

life. In short we must consider the interior of every

organism as exhibiting an environment to which every

organ probably contributes and by which every organ

is more or less influenced. The hormones of this en-

vironment are the mechanisms of correlation and by

means of them one organ influences another. It is no

longer necessary to describe organic correlation as an

unknown law of growth. It is the dependence of one

organ on another through the hormones that the in-

fluencing organ produces.

Granting this condition, it follows that natural selec-

tion may well be conceived to modify an internal hormone-

producing organ, if this organ is of vital significance, and

incidentally thus to establish a new internal environment

that would so influence the form and external configura-

tion of a given organism that it would be called a new

species and yet none of the new external features by

which this organism would be described might show the

least usefulness.

RECENT ADVANCES IN THE STUDY OF

VASCULAR ANATOMY?

I. VASCULAR ANATOMY AND THE REPRODUCTIVE

STRUCTURES

PROFESSOR JOHN M. COULTER

UNIVERSITY OF CHICAGO

Ir is perhaps unfortunate that the names applied to

the great divisions of botanical investigation shift in

their meaning from time to time, but it is inevitable.

The content of a subject shifts with the men who put

content into it. The morphology of to-day is not the

morphology of half a century ago, either in its content

or motive; or rather there are several conceptions of

morphology existing side by side, some as an inheritance,

and others as acquired characters. The older conception

of morphology, presented, for example, in the model text-

books of Asa Gray, is one thing; and that introduced by

the work of Hofmeister, which very slowly made its way

into this country, is a very different thing.

This more recent morphology adds to the old knowl-

edge of structures the relation of these structures in a

scheme of phylogeny. Its importance lies not so much

in the fact that it solves the perennial problem of

phylogeny, as in the fact that it calls for the selection

and comparison of structures throughout the plant king-

dom. It takes the enormous débris of material that has

accumulated and sifts it, passing over the trivial, em-

phasizing the important, and building up the body of

knowledge into a structure that has some form. As

knowledge advances, the trivial of yesterday may become

the important to-day, and vice versa; but the building of

a structure, upon any plan, is work of a higher order

1 Papers prepared by request of the Council and read at the Baltimore

meeting of the Botanical Society of America.

220 THE AMERICAN NATURALIST ` [VoL. XLIII

than the mere collection of building material, and espe-

cially stimulates further work to strengthen it or to

demolish it.

In the decade we are considering there has come into

the morphological camp a powerful ally. For conven-

ience, we speak of it as vascular anatomy; but it is the

application of the spirit of the new morphology, the evolu-

tionary morphology, to the vascular system of plants.

Before this reinforcement, the modern morphology was

dealing almost exclusively with the reproductive struc-

tures: sporangia and sex-organs, with their associated

structures. It had pressed these structures to the limit

of technique, developing morphological cytology. With

the vascular system brought into the morphological per-.

spective, the first step was taken towards the inclusion

of vegetative as well as reproductive structures. It now

remains for some one to begin the organization of the

remaining vegetative regions upon the same basis; and

then morphology will have its facts fairly before it.

The history of the subject called ‘‘anatomy”’’ serves

well to illustrate the spirit of modern morphology. It

applied to such a mass of facts as are brought together,

for example, in DeBary’s ‘‘Comparative Anatomy of

Phanerogams and Ferns,’’ a task which the author re-

garded as the extreme of drudgery. The older morphol-

ogy included more or less of this material, for in those

days one fact was just about as important as another, and

some of these anatomical facts were conspicuous enough

for even elementary students to recognize. As is well

known, the newer morphology eliminated this whole enor-

mous body of material. The reason is evident and suff-

cient. It was so completely unorganized that it could

not be used in any phylogenetic structure; and the repro-

ductive structures could be so used. All but the blindest

morphologists recognized that this vast accumulation of

so-called anatomical material would have to be reckoned

with some day. It has now developed that the vascular

system has been the first thing organized out of the

No. 508] STUDY OF VASCULAR ANATOMY 221

anatomical rubbish pile, and it has been promptly and

warmly welcomed by modern morphology.

The organization of vascular anatomy upon an evolu-

tionary basis came at a most auspicious time, for the

phylogenetic lines, guarded only by the anatomy of re-

productive structures, had begun to show signs of waver-

ing. Wider researches had begun to dissipate rigid

categories into mists. Such veterans of definition as

archesporium, sporangium, sporophyll, ete., had been put

to flight. Especially did experimental morphology play

havoc. It made hereditary structures lose their rigidity,

and raised the question whether the hen that sits on the

eggs is not more important than the one that lays them.

It certainly intensified the conviction that any structure

might arise any number of times. This made schemes

of phylogeny essentially paper schemes. They were

good illustrations of what the phylogenetic succession

might have been, but they could carry no assurance of

what the phylogenetic succession actually had been.

This whole situation has been steadied, at least

morphologically, by the recent development of vascular

anatomy, including as it does the enormously important

ancient history of the vascular groups, which was largely

denied to the reproductive morphologist. The difference

between matching forms and investigating structure is

nowhere more clearly illustrated than in the recent de-

velopment of our knowledge of fossil plants. Morphol-

ogy, therefore, really has another ally that came in com-

pany with vascular anatomy, and that is actual history,

which must always be reckoned with.

As a result of this triple alliance, what has been the

progress of morphology during the last decade? Our

subject necessarily limits us to the vascular plants; but

it might be said, in passing, that most important progress

has been made in bryophytes and thallophytes as well.

Students of gametophytes and sexual organs, of spore-

producing members, of the vascular system, of : fossil

plants, have been investigating with wonderful energy,

y Hd THE AMERICAN NATURALIST [Vou. XLIII

and all with phylogenetic relations in view. This has

meant. comparison at every step; and as a conse-

quence, there is available to-day a wealth of important

information such as we have never possessed before.

The process of sifting has gone along with the work of

accumulation, so that our facts are sorted, and in shape

to use. We may not use all this material, but whatever

has been collected with a phylogenetic purpose must be

reckoned with. One interesting result from this wealth

of material has been the loosening up of all our concep-

tions of structures. No definitions have stood; and our

statements to elementary classes are all with important

mental reservations. This substitution of a general

situation for a rigid definition is also a substitution of

knowledge for terminology, and introduces into our

phylogenetic schemes a conception of variation that

makes them workable.

So many definite lines of attack have resulted in still

more numerous schemes of phylogeny. Each investi-

gator naturally regards his own field of work as phylo-

genetically the important one, otherwise he would not

be working in it. A detailed examination, however, of

all the schemes based upon extensive investigation re-

veals the fact that the differences have to do in the main

with subordinate features. Certain large conclusions

may be regarded as fairly well established, so far as our

present information goes. Some of them I may venture

to mention, for they represent fairly well the progress

of a decade. Of course the progress of largest im-

portance is the fact that so much trained investigation

is being directed along so many convergent lines that

meet in the problem of phylogeny. Never was morphol-

ogy so well equipped as it is now. The large results to

be mentioned are those concerning which there is sub-

stantial agreement; which means results that must have

stood the test of morphology, anatomy and history.

Discredit has been thrown upon the cell-by-cell studies

of such structures as the embryo, gametophytes, sex or-

No. 508] STUDY OF VASCULAR ANATOMY 223

gans, and sporangia; and upon the layer-by-layer studies

of growing points. This means that an immense amount

of detailed work has been swept into the limbo for facts

at present useless. Early developmental studies of a

few forms seemed to establish definite sequences in cell-

divisions and definite functions for so-called generative

layers. This kind of research was its own corrective, for

as investigations multiplied, definite sequences and func-

tions disappeared in a maze of variation. The definite

thing proved to be not the details of development, but the

general organization developed. For example, the im-

portant facts in reference to the development of the

embryo are no longer thought to be the sequence of the

first dozen cell-divisions, but the organization of tissue

systems and organs. The leptosporangiate sporangium

may develop in a great many different ways, but the

general result is a sporangium of some definite type.

Particularly futile has proved to be the detailed study of

the development of independent gametophytes, for they

react remarkably to environment, and can be made to do

almost anything. At growing points it was once supposed

that each cell was predestined to contribute to one of the

generative layers, and dermatogen, periblem, and plerome

were traced through a mass of indifferent meristematic

tissue. After organization, they can be recognized ; but

there is nothing definite in the details of their origin.

It is generally conceded that no great group of plants

has been derived from any other existing group. For

example, the origin of pteridophytes from bryophytes 1s

hardly a debatable question. The study of reproductive

structures alone made such a connection seem quite rea-

sonable to the scientific imagination. We had even

selected the responsible bryophyte forms, and showed

how Anthoceros gave rise to the most primitive leafy

sporophyte. Now that much other testimony has accu-

mulated, such a connection is too dificult even for a vigor-

ous scientific imagination. Even the staunchest supporter

of this connection, and the one who has worked it out in-

224 THE AMERICAN NATURALIST [Von. XLIII -

greatest detail, has acknowledged its improbability.

Bryophytes are no longer thought of as having given

rise to pteridophytes, but as illustrating here and there

the path along which the ancestral pteridophytes may

have traveled. Just how we should classify these an-

cestral pteridophytes makes no difference until we meet

them.

The origin of gymnosperms is another conspicuous

illustration of fhe same point of view. Paleobotany has

achieved no greater triumph than the discovery of an

extinct group of fern-like seed-plants, commonly called

pteridosperms, but better called Cycadofilicales. Our

knowledge of the group is remarkably complete, so that

their connections present no greater difficulties than do

those of living groups. Since most of these old seed-

plants had been described as paleozoic ferns, it was

assumed at first that this was a demonstration that

gymnosperms have been derived from ferns. Sober

second thought reminded us that ferns as we know them

are essentially modern; that the reputed ancient ferns

have turned out to be seed-plants; and that the actual

ancient ferns, therefore, are unknown. Conceding even

that some of the old fern-like plants are ferns, or Primo-

filices as they have been called, which is very reasonable,

the record of the fern-like seed-plants is just as old. The

ferns as we know them, therefore, probably did not give

rise to gymnosperms, but they may well illustrate stages

in the evolution of gymnosperms.

The case is still clearer in connection with the origin

of angiosperms. When the Gnetales were first studied,

the logic of the morphology of that day suggested that

they had given rise to angiosperms, and so the connection

with gymnosperms seemed to be established. Nothing

could be more clear than that flower, embryo-sac, and even

vascular tissue were well on their way to the angiosperm

condition. But then Gnetales have no discoverable his-

tory, and angiosperms have, not to speak of other diffi-

culties. As a consequence, those who are most insistent

No. 508] STUDY OF VASCULAR ANATOMY 225

upon establishing a phylogenetic connection between

Gnetales and angiosperms claim only that they are lines

of parallel development from a common hypothetical

ancestry. It is the use of history as a check that has

changed our point of view as to phylogeny more than any

single factor; and it is the recent vascular anatomy that

has given us a trustworthy history.

The transformation in our conception of the inter-re-

lationships of pteridophytes deserves mention. Ever

since alternation of generations was recognized, the ordi-

nary fern, with its seductive prothallium, has been gen-

erally thought of as the living pteridophyte nearest the

bryophyte level. It is now recognized that the Filicales,

as a whole, are more clearly connected with seed-plants

than is any other group of pteridophytes, and that we

must look elsewhere for the most primitive living type of

vascular plants. Whether we find them in some of our

club-mosses or in Ophioglossum may be an open question

for some, which vascular anatomy and history are in a

fair way to decide. In any event, vascular anatomy and

history have strikingly confirmed, in a general way, the

conclusions of the morphology of reproductive parts.

The change of view as to gymnosperms has perhaps

been the most striking change of the last decade, and this

has “seen brought about by remarkably aggressive work

in‘s | lines of approach, beginning with the discovery of

swi nming sperms in the cycads and Ginkgo. Of course,

the most sensational discoveries since have been the ex-

istence of Cycadofilicales and the remarkable strobilus of

th» Bennettitales. These discoveries have been supple-

mented by morphological work in almost every genus,

anatomical work in all the important groups, and an un-

precedented uncovering of the gymnosperm history. Now

we recognize the group as starting with fern-like plants,

bearing microsporangia and megasporangia as the ferns

do sporangia. From this start a strobilus was worked

out, whether primitively monosporangiate or amphispo-

rangiate or both is not clear. One line (cyeadophyte)

226 THE AMERICAN NATURALIST [Vou. XLIII

retained more primitive characters in its sexual reproduc-

tion and vascular system; another line (Cordaitales),

while retaining the more primitive sexual reproduction,

developed a more advanced type of vascular system,

which has continued in Ginkgoales in one direction, and

in Coniferales in the other, associated in the latter with

a more advanced type of sexual reproduction.

This gymnosperm situation may illustrate a fact that is

becoming more and more apparent. On the basis of the

older reproductive morphology the cycads are more

ancient than the conifers; on the basis of history the

reverse is true. The cycads are relatively modern, but

have persistently retained certain ancient features; yet

the logic of the older morphology would have insisted that

conifers are derived from cycads. It is a fact, therefore,

that primitive features are not necessarily a mark of age,

even among closely related groups. The testimony of

all features must be considered, and this checked up by

history, before any rational conclusion can be drawn.

The most baffling tangle of relationships among gymno-

sperms at present is that presented by the tribes of Conif-

erales. The perplexity of the situation is due to the fact

that as yet morphology, vascular anatomy and history

are at variance. Of course, history must determine the

actual sequence, and then our contradictory morphology

and anatomy can be straightened out. For example,

morphologically in Taxinee are advanced; in wood

structure they are also said to be advanced; but they are

also reputed to retain the old mesarch structure, which

would indicate that they are primitive. When we know

what they are historically, we can determine whether this

anatomical feature is primitive because the group is

primitive, or because this character of the bundle has

lagged behind. Of course, these ‘‘mesarch’’? bundles may

not be mesarch in the old sense, and the centripetal wood

may be explained away; if so, the group will be advanced

in all its characters and will not need the testimony of

history.

No. 508] STUDY OF VASCULAR ANATOMY 227

This fact of ‘‘lagging behind’’ is coming more and

more into evidence. I do not mean by this that the

lagging structures always advance sooner or later, for

they may simply persist as veterans. A conspicuous

illustration of it is found in the evolution of the micro-

sporangiate and megasporangiate structures of seed-

plants. In the most primitive group of seed-plants

known, the Cycadofilicales, the microsporangia are still

at the fern level, produced in the same relations and of the

same general structure as are the sporangia of ferns;

while the megasporangiate structure has become a highly

organized ovule, which in some way has replaced the

sorus. The relations to the sporophyll are the same, but

the structure has become very much changed. There is

an enormous hiatus in our knowledge in reference to the

heterosporous ancestors of these primitive seed-plants,

but during all that development of heterospory to the

seed-condition, the microsporangia remained practically

stationary. Even among the Mesozoic Bennettitales, the

microsporangia are still fern-like synangia, although a

highly organized strobilus has been developed; and among

modern cycads the same persistent lagging of the micro-

sporangia is evident. All this means that no single char-

acter, however primitive, can establish the phylogenetic

level of a group. All the testimony must be in, and

especially the history, before one can feel any reasonable

assurance as to conclusions.

The new conception of the monocotyledons is so clearly

a triumph of vascular anatomy that the other phase of

morphology is hardly entitled to a share in it. And yet,

now that it is evident that the monocotyledons are a

specialized offshoot from the primitive dicotyledonous

stock, many things in the older morphology become

clearer. There are those intergrades, as they may be

called, between the monocotyledonous and dicotyledonous

condition, which have given so much trouble to the pigeon-

hole botanist, who insists that a given seed-plant must be

a monocotyledon or a dicotyledon. We recognize now

228 THE AMERICAN NATURALIST [Vou. XLIII

that these intergrades are what might be expected, and

they occur in the general region which, according to the

vascular anatomist, gave rise to the monocotyledonous

offshoot. It has always interested me to see how con-

vinced we become by our own definitions. We have legis-

lated that the last resort for distinguishing monocotyle-

dons and dicotyledons is the cotyledon character; all other

characters have been found to be liable to exception. I

submit it to you whether any single character selected in

this way as final arbiter could not function equally well

as a character of last resort. This business of ‘last-resort

characters is nothing less than harking back to an arti-

ficial system. It is hardly conceivable in these days that

such a character can really exist. It is the totality of

characters that- must place an organism, a most difficult

. test to apply, but none the less essential. A conspicuous

illustration of this situation is that of Selaginella. It is

assumed that the last-resort character of a seed-plant is

the seed; and yet no definition of a seed can be constructed

that will exclude all species of Selaginella and include all

seed-plants. Then why is not Selaginella a seed-plant?

Simply because its other characters forbid such an asso-

ciation. There is no conceivable reason, therefore, why a

dicotyledon may not be monocotyledonous and still remain

a dicotyledon, or vice versa. The vascular anatomist tells

us that one of the surest marks of a monocotyledon is the

amphivasal bundle; and at the same time he points out

amphivasal bundles among dicotyledons.

I am pressing this point perhaps unduly, but there is a

growing tendency that should be checked. This is to

transfer groups on a single character, or to propose

phylogenetic connections without weighing or waiting for

all the characters involved. It is easy to construct a satis-

factory scheme based upon one character; it has thus far

proved impossible to construct a satisfactory scheme

based upon all the characters we happen to know.

The spirit that animates modern morphology is no-

where more evident than in its effect upon teaching.

No. 508] STUDY OF VASCULAR ANATOMY 229

When this type of work was introduced into the labora-

tories of this country, almost any available material was

used. This material was studied in great detail, impor-

tant and trivial things being kept at a dead level. The

purpose was to train in observation rather than to develop

any picture of the plant kingdom. This detailed study

meant the handling of a few types. The pedagogical

slogan of those days was a few types thoroughly studied.

The few types selected were naturally those most avail-

able, and by some irony of fate these most available things

turned out to be the most unrepresentative types possible.

You are familiar with the old list: Spirogyra, standing

for green alge; Marchantia, for liverworts; a leptospo-

rangiate fern, for pteridophytes, and so on. Now all this

has been changed. The purpose is to give some concep-

tion of the evolution of the plant kingdom, not in detail

or in any rigid way, but in general perspective. The

threads on which the facts are strung are such as these:

the transition from a one-celled to a many-celled body,

the evolution of reproductive methods, the origin and

differentiation of sex, the acquisition of the land habit,

the origin and development of the alternation of genera-

tions, the origin of the leafy sporophyte, the evolution of

the vascular system, the evolution of the seed, the origin

and evolution of the flower. How can ‘‘a few types thor-

oughly studied’’ illustrate such things or give any such

perspective?

This means much illustrative material, carefully

selected, and each form used to illustrate some definite

and important fact. It is not many types hastily studied,

but many types studied carefully for the few points that

are really important. The difference between the older

view and the recent one, both in teaching and in research,

is the difference between an indiscriminate mass of un-

related Details obtained from a few representative forms,

and a selected mass of related details obtained from a

large number of representative forms. oes es

These somewhat miscellaneous statements may serve ©

230 THE AMERICAN NATURALIST [Vou. XLIII

to illustrate the point of view that has been developed,

which after all is the significant thing in our progress.

It would be tedious and unprofitable to enumerate the long

list of important new facts that have been discovered.

Besides, these new facts are most of them so technical

that any brief reference to them would be intelligible

only to those who do not need the information. In clos-

ing, I may venture to suggest a future development which

seems extremely desirable. The general problems upon

which we are now engaged must involve the examination

of an enormous amount of material before we can feel any

confidence in our conclusions. It ought to be possible to

associate investigators or laboratories in a general attack

upon any problem conceded to be important enough to

justify such a united effort. Whenever this has been

done in a laboratory possessing several investigators, the

result has been striking. We must begin to combine our

detached efforts, the guerilla method of attack, and sup-

port individual effort by association. The scheme is only

a thought, and the details may make it impossible, but

I believe that we have reached a point where something

of this kind is demanded for definite and substantial

progress.

Il. Tue Progress or PLANT Anatomy DURING THE Past

DECADE

PROFESSOR EDWARD C. JEFFREY

HARVARD UNIVERSITY

Tue fascinating problem of the alternation of genera-

tions in the higher plants is responsible for the fact that

the attention of morphologists, since Hofmeister, has been

turned largely to the spore-producing organs and the

gametophytes. This tendency can be counted as entirely

fortunate, for the closer affinity of the gametophyte with

the presumably ancestral forms and the progressive re-

No. 508] STUDY OF VASCULAR ANATOMY 231

duced and simplified structure, which it presents in the

vascular series, has made it particularly suitable for the

initial stages of modern morphological development.

With the discovery of zoidogamous fertilization in Cycas,

Ginkgo and the lower fossil gymnosperms, the revelation

of the remarkable mode of fertilization in the Araucari-

nex, simulated at least in the Podocarpinee, the uncover-

ing of the phenomenon of breech fertilization in the lower

Amentifere and the elucidation of other striking phe-

nomena connected with the male gametophyte, we have

come to realize that it is the male sexual generation and

the sporogenous apparatus, producing it, which carry the

highest phylogenetic interest. The origin of the seed

from the megasporangium, although beyond question on

general morphological grounds, still largely lacks illumi-

nating facts to lighten the darkness of its past.

The more complicated sporophytic generation of the

higher plants, except as to its special sporogenous struc-

tures, has much more recently been attacked by evolution-

ary morphologists. Its very complexity, however, and

the possibility of following its structures into the remot-

est past, make it of the greater importance from the

standpoint of the theory of descent. The evidence derived

from its study serves, moreover, to control, amplify and

enrich the conclusions reached from the standpoint of the

morphology of the gametophyte alone. We have, accord-

ingly, begun to realize that the anatomical examination of

the sporogenic organs of vascular plants is quite as 1m-

portant as the cytological study of the process of sporog-

eny itself, and that the fern-like mode of fertilization

obtaining in the lower gymnosperms, living and extinct,

has its not less important or significant equivalent in the

presence of cryptogamic or centripetal primary wood. | In

fact, with the realization of the importance of the sporo-

phytic generation in the higher plants, we are now for the

first time in a position to begin our phylogenetic book-

keeping by double entry, with greatly added security as

to the final accuracy of the balance we may strike.

232 THE AMERICAN NATURALIST [Von XENI

Perhaps nowhere is the advantage of morphological

bookkeeping by double entry more clearly illustrated than

in the case of the conifers. Forming with the other living

gymnospermous species a restricted but illustrious ‘‘four

hundred,’’ they have quite held their own in botanical

interest, in spite of the overwhelming numbers and im-

portance of the modern mob of angiosperms. The older

and entirely superficial morphology, led to the conclusion

that simple forms and structures are more primitive. On

this basis the conclusion was reached that those simple

and coneless conifers, the Taxineæ or yews, are the oldest

and that the pines or Abietineæ, with their very compli-

cated cone-structures, are most modern. It has, moreover,

been inferred that the coniferous tribes represent a series

of progression beginning with the yews and ending with

the pines. The microscopic study of the gametophytes

began the disintegration of this system. The discovery

of zoidogamous fertilization in Ginkgo, which in Engler

and Prantl’s Natürliche Pflanzenfamilien, you will find

included with the yews, made it at once apparent that this

remarkable genus, sole survivor of an abundant stock,

once flourishing through the entire northern hemisphere,

could not be included under the Taxinee, or link the latter

with the still more ancient Cordaitales, confined to the

Paleozoic. Thus deprived of the reputation of an illus-

trious ancestry, the yews have since been disrespectfully

kicked up the phylogenetic stairs by the younger genera-

tion of gametic morphologists. A corresponding but re-

versed process has in the meantime taken place at the

other end of the coniferous series. It has been shown by

the gametophytic morphologists, that the sexual genera-

tions of the pine tribe are more complicated, and for that

reason more primitive in the reduced members of the

alternation, than any other conifers, characteristically

found in the northern hemisphere. From the sporo-

phytic side it has been shown that the cone-structure of

Pinus affords an anatomical explanation of the strobilar

organization of the other tribes of conifers on the basis

No. 508] STUDY OF VASCULAR ANATOMY 238

of commonly accepted principles of reduction and adhe-

sion. Further, it has recently been discovered that the

leaves of the ancestral pines (Prepinus) had the same

cryptogamic type of centripetal wood-bundles, which are

found in the Cordaitales, universally regarded as the

Paleozoic stock to which the conifers as a whole are most

nearly allied. There is further evidence of the antiquity

of the Abietineous or pine tribe based on important ex-

perimental data and on the origin of coniferous pitting,

which need not be entered upon here. If, in accordance

with the facts very briefly indicated above, we cast up our

phylogenetic balance by double entry for Pinus, we find

it on both sides overwhelmingly in favor of the superior

antiquity of the Abietinee, or pines, as compared with the

Taxinex, or yews. It would take much too long to cast

even hastily the balances for the remaining tribes of

conifers and in the case of those at present mainly or

wholly confined to the southern hemisphere the data are

as yet not complete. Even though the books are not yet

ready to be opened for the final judgment, the results of

recent morphology on both the gametic and sporophytic

sides make it clear that the conifers, contrary to the con-

clusions of the old superficial morphology, are a series

of reduction and not one of progression and that their

most complicated forms are consequently the oldest and

those of simplest guise the most modern.

One of the most striking confirmations of the truth of

the theory of organic evolution is found in the recapitula-

tionary phenomena of animals. The colt, for example,

in the course of its individual development passes

through the phases of progressive loss of digits, presented

geologically by the equine stock from the Mesozoic to the

present. The young mammal in its earlier stages of

ontogeny possesses the gill arches and the segmented

musculature of the fish. In the principle of recapitula-

tion presented so clearly in the development of animals,

our zoological brethren may fairly claim that on their side

of the house the truth of evolution is declared by the

234 THE AMERICAN NATURALIST [Vot. XLII

mouths of babes and sucklings. Although our seedlings,

unlike the sucklings, are dumb, they are by no means

speechless. One of the most striking triumphs of modern

plant anatomy is to have discovered many examples of

recapitulationary confirmation of the principle of evolu-

tion. To take a modern and striking instance, let us con-

sider our common and flourishing northern genus, the oak.

You are all familiar with the very broad rays which con-

stitute so ornamental a feature of the structure of oak

wood. You are likewise doubtless aware that the weight

of paleobotanical evidence speaks for the derivation of

the oaks from ancestors resembling the chestnuts since

the older oaks approach the chestnuts both in their foliage

and in their reproductive organs. The wood of the chest-

nut differs, however, strikingly from that of oaks by the

entire absence of large rays. It has been recently dis-

covered that certain oaks of the gold-gravels (Miocene

Tertiary) of California have their large rays composed

of aggregations of smaller rays. In the seedlings of cer-

tain of our existing American oaks this condition, inter-

estingly enough, is a passing phase, which by the loss

of the separating fibers in the congeries of small rays

produces the characteristic large rays of the adult. This

condition of development in the living oaks is all the

more significant because in certain breech-fertilized or

chalazogamic amentiferous trees of the present epoch,

such as the alder, the hazel and the hornbeam, such aggre-

gated so called false rays are a permanent feature of

structure in the adult. From the anatomical side, in the

ease of the lower Amentifere, we have accordingly at

the same time an interesting example of the general

biological law of recapitulation and a confirmation of the

view expressed by Treub and Nawaschin, on evidence

from the gametophytic and reproductive side, that the

breech-fertilized Amentifere are relatively primitive

angiosperms.

Perhaps the most valuable service which anatomy is

rendering to phylogeny and evolution is in connection

No. 508] STUDY OF VASCULAR ANATOMY 235

with the elucidation of the affinities of extinct plants.

Certain cryptogamic trees of the Paleozoic, the Lepido-

dendrids, Sigillarians and Calamites, were, for example,

long regarded by competent botanists as seed plants on

account of their arboreal habit. The anatomists stoutly

maintained, however, that from the structure of their

primary wood they must be eryptogams. The subse-

quent discovery of their reproductive structures entirely

confirmed the anatomical view. More recently from the

study of the anatomy of certain fern-like plants with

secondary growth, from the Paleozoic, English and Ger-

man anatomists reached the conclusion that they were

gymnosperms and allied at once to the ferns and to the

cycads. Within the past decade, the brilliant discoveries

of Oliver, Scott, Kidston, Grand’Eury and David White

in regard to the nature of the reproductive organs of

these plants, prophetically dubbed by Potonie, the Cyca-

dofilices, have confirmed the truth of the anatomical view

as to their affinities in every particular. Let us take a

still more modern instance. There are present in the

later Mesozoic strata huge quantities of impressions of

the cones and leafy twigs of conifers. These have been

referred on features of superficial resemblance to a num-

ber of genera of living conifers as well as to others not

represented in the existing flora. Since they are very

numerous, let us take one typical example, which is at the

same time significant. Many species of Sequoia have

been described from the upper Jurassic and the Cre-

taceous beds, on the evidence of the impress upon the

stony or argillaceous matrix of their cones and leafy

branches. Dr. Arthur Hollick and the present speaker

have been fortunate enough to secure by new methods of

236 THE AMERICAN NATURALIST [Vov. XLIII

or Araucarinese, and have not even the slightest affinity

with the living genus, which externally they so strikingly

simulate. The reference of the fossil genus just de-

scribed to its true affinities as well as similar results in

the case of a large number of other Mesozoic conifers,

likewise erroneously placed in the system, leads to im-

portant general conclusions in regard to the evolutionary

history of coniferous gymnosperms, which are too lengthy

and too technical even to be mentioned here.

But it is not only in connection with extinct plants that

anatomy has shown itself the useful servant of phylogeny.

The enforced use of anatomical criteria in the case of

fossil forms, where such evidence is absolutely indispen-

sable, has resulted in a new and broader point of view in

general botanical morphology. Within the decade we

have begun to realize fully the great constancy of fibro-

vascular structures. This may perhaps be best exempli-

fied by a special case. Superficially there is no organ of

the plant more prone to vary extremely, within near

lines of affinity, than the leaf. If, however, we look

within, it presents anatomical features of great con-

stancy. In the case of the leaf, perhaps the most hope-

lessly variable feature is its size. Anatomically, how-

ever, there are just two sizes of leaves, large leaves

(megaphylls) and small leaves (microphylls), which are

absolutely characterized by their anatomical relations.

The foliar strands of the megaphyll, or large leaf, pass

off from the woody cylinder of the stem, leaving corre-

sponding gaps in its wall. Those of the microphyll, or

small leaf, equally constantly leave no such gaps in their

exit from the woody cylinder. It is even possible to

divide the whole vascular series into two clean-cut phyla

on the basis of the anatomical features of leaf size, viz.,

the Pteropsida with, anatomically speaking, large leaves,

including the ferns, gymnosperms and angiosperms and

the Lycopsida, structurally speaking, small leaved forms

including among living plants only the club-mosses and

horsetails.

No. 508] STUDY OF VASCULAR ANATOMY 237

I have tried to show above, with all necessary brevity,

that the services of anatomy to phylogeny and the doc-

trine of descent during the past decade have been neither

few nor unimportant. Perhaps the most important gen-

eral result of recent work in the modern morphological

field, not restricting it, of course, to anatomy, may best

be expressed in the words of the eloquent and philosoph-

ical apostle to the gentiles, viz., that the things seen are

temporal, while the things unseen are eternal. You may

think that I have too much emphasized the importance

of internal morphology. One example will serve to show

that I have not. You are all familiar with that great

German work on the morphology (or, as its author prefers

to call it, the organography) of the higher plants, which

not very long ago appeared in a traduction de luxe from

the Oxford University Press. If you scan it from cover

to cover, I do not believe you will find a single figure of

the fibro-vascular structures. Not even the proverbial

halfpenny’s worth of bread is present to qualify the

oceans of sack. It is not surprising that we should hear

from such a source a strong note of morphological pessi-

mism. On a recent occasion in our own country, the dis-

tinguished author of the work in question compared the

task of his science to that of Sysiphus, of classic fable,

condemned to roll up the mountainside a stone which

continually rebounds. We may confidently expect that

the morphology of the future, distrusting the superficial

anfracutosities of the steep, will bring the profitless

rolling stone to rest in the very heart of the mountain

itself.

SHORTER ARTICLES AND CORRESPONDENCE

A NOTE ON THE DEGREE OF ACCURACY OF BIO-

METRIC CONSTANTS

The statement is frequently made, either in comment or

criticism upon biometrie work, that such work is often caused

to take on an unwarranted appearance of precision and exactness

by the keeping of a larger number of decimal places in the tabled

constants than the character of the original data justifies. The

contention is made that under no circumstances whatsoever can

any statistical constant be more accurate than the data on

which it is based. It is held that if one makes a series of meas-

urements accurate to a tenth of a millimeter, it is a logical

absurdity to table the mean or standard deviation deduced from

these measurements to hundredths of a millimeter. Not only

is this contention made from time to time by biologists, but

occasionally even by a mathematician, a fact which of course

tends strongly to confirm the biologist in his opinion. Thus

Engberg? specifically says (p. 11) referring to mortality statis-

tics: ‘‘The constants can not be more accurate than the data on

which they are based.’”

The reply which the statistician makes to the criticism

that constants can not be more accurate than the data on

which they are based is generally that the accuracy of a sta-

tistical constant depends not alone on the accuracy of the-

original measurements but also upon the number of such meas-

urements. Further it is pointed out that, because of this fact,

it is possible to deduce from measurements known to be individ-

ually inaccurate constants of a high degree of accuracy, provided

that the errors in the measurements are unbiased (that is as

often in excess as in defect of the true value) and that there

are enough of the data. Finally the statistician contends that

the only proper measure of the accuracy of a statistical constant

*Engberg, C. C. The Degree of Accuracy of Statistical Data. Univ.

of Nebraska Studies, Vol. III, No. 2, pp. 1-14, 1903.

*In passing it may be said that any one who is sufficiently interested in

the phenomenon of a professional mathematician taking this curious position

will find an entirely adequate and satisfactory discussion of the matter in

Nature. Vol. 69, p. 93, where Engberg’s paper is reviewed.

238

No. 508] SHORTER ARTICLES AND CORRESPONDENCE 289

(always assuming that the original data are not collected in a

deliberately dishonest or biased manner) is its ‘‘probable

error.’’ Unfortunately this statement of the case appears not

to carry conviction to the non-statistical worker. It has seemed `

to the writer that if the assertion made by the statistician

regarding the point under discussion is true, it ought to be pos-

sible to demonstrate it in such a manner as to carry conviction

to anybody.

With this object in view the experiment to be described was

tried. Some time ago the writer measured for another purpose

the lengths of 450 hens’ eggs. The measurements were made

with a large steel micrometer caliper manufactured by Browne-

Sharpe & Co., reading directly to hundredths of a millimeter.

The utmost care was exercised in the making of the measure-

ments; they were all made under the same conditions as to light,

temperature, ete. ; the caliper was held in a specially constructed

stand to get rid of the error arising from expansion and con-

traction if it is held in the hand; the micrometer screwhead was

fitted with a ratchet which mechanically insures that the same

pressure shall be exerted on the object in every case; all meas-

urements were made by the same observer who has had consider-

able experience in close micrometer measuring. The maximum

length was the thing measured. There is every reason to believe

that these measurements to hundredths of a millimeter are as

accurate as it is possible to make them with the instrument used.

This being the case all will agree that any statistical constant

deduced from them can be held to be accurate to hundredths of

a millimeter at least. Now let it be supposed that these eggs

had been measured only to the nearest millimeter instead of to

the nearest hundredth of a millimeter. By how much would the

statistical constants deduced from the ‘‘millimeter’’ data differ

from those deduced from the ‘‘hundredth millimeter data?”

To answer this question it is necessary to calculate some statis-

tical constant for the two sets of data. The mean was chosen

as the simplest possible constant. The actual measurements

to hundredths of a millimeter were used as one set of data. The

‘‘millimeter’? data were obtained by discarding the decimals

of the original measurements. In this discarding a record iag

raised 1 mm. whenever the decimal portion of the original

* The biometrician will, of course, recognize that the problem here so

volved is the same as that of the influence of the fineness of grouping on

the value of constants. oe

240 THE AMERICAN NATURALIST [Vou. XLII

figure was .51 or greater. When the decimal part of the record

was .49 or less the integral part stood unchanged. In the 450

measurements there were six cases in which the decimal portion

of the record was exactly .50. In one half of these cases the

record was raised 1 mm. and in the other half was left un-

changed, when the decimals were discarded. This is obviousiy

the only fair way of dealing with such cases since, for example,

51.50 is exactly as near to 51 as it is to 52.

The originai measurements and the ‘‘millimeter’’ data after

discarding the decimals were then each added and re-added with

a calculating machine. The resulting sums were:

When the measurements were kept When the measurements were

to the nearest hundredth of a mm. kept to the nearest whole mm.

25,341.95 25,346

Dividing each of these figures by the total number of cases,

450, we get for the means the following:

Mean from “hundredth mm. data” Mean from “millimeter data”

56.315

The difference between these two figures is .009. That is, there

is no difference between the two averages until the third decimal

place is reached. To two places of figures both means are 56.32.

But this can only mean that the mean or average obtained when

the records are made only to the nearest millimeter is more

accurate, by two places of decimals, than the data on which it

is based.

In interpreting this statement of fact it must not be held to

signify that biometric measurements’ should not be made with

the greatest attainable degree of accuracy. Because statistical

constants, when the number of cases dealt with is large, are

more accurate than the data on which they are based gives no

excuse for rough measuring. The reason for this, of course,

lies in the principle, which actual experience shows to be cor-

rect, that the finer and more accurate the measuring the less

chance of the data being unconsciously biased. Statistical con-

stants can only be more accurate than the original data when

the data are strictly unbiased. The ‘‘applied psychology’’ of

practical measuring teaches that unconscious bias goes out of the

records just in proportion as the measurements are made finer.

RAYMOND PEARL.

MAINE EXPERIMENT STATION.

No. 508] SHORTER ARTICLES AND CORRESPONDENCE 241

PURE STRAINS AS: ARTIFACTS OF BREEDING

Students of the minute anatomy of plant or animal tissues

are on their guard against artifacts. Chemical reagents often

contract or coagulate the protoplasm or cause the precipitation

of granules or crystals. The artificial results of the methods of

preparation have to be distinguished from the normal structures

of the protoplasm. Precautions are equally necessary in the

study of evolution and heredity, to avoid mistaking artificial

products of breeding for typical conditions.

Close-bred, uniform groups of plants and animals form the

basis of the idea of ‘‘pure strains,’’ ‘‘elementary species’’ or

‘‘biotypes.’’ If the descendants of the same parents appear

sufficiently alike the strains are said to be ‘“pure.’’? General

inferences regarding heredity and evolution are being based

on the assumption that this uniform ‘‘purity’’ represents a

natural condition. Yet there can be no doubt that the methods

used in maintaining and testing the purity of strains are calcu-

lated to produce an artificial uniformity of characters, commonly

accepted as the proof of purity.

If the habits of a plant will permit, the readiest method of

securing uniform progeny is by vegetative propagation. Never-

theless, the idea of pure strains is not usually connected with

vegetative varieties, for it is recognized that uniformity lasts

only while vegetative propagation is continued. As soon as

seeds and seedlings are grown the natural individual diversity

reappears. The vegetative propagation only conceals the in-

herent diversity by devices that avoid the production of seedlings.

The uniformity of groups of seedling plants 1s of the same

artificial nature as the uniformity of vegetative varieties. Par-

ticular methods of reproduction are necessary to secure uniform

seedlings—methods which may not be essentially different from

those represented by cuttings or offshoots. Plants grown from

buds or cuttings have only one parent, and the same is true of

seedlings produced by self-fertilization. It is only when con-

jugation is restricted to cells of the same individual or of closely

related individuals that uniform seedlings are obtained. : The

external formalities of conjugation are preserved, but without

the essential diversity of descent which gives conjugation a

hysiologiecal significance.

r The aeiy of varieties of wheat and other strictly self-

fertilized plants depends as closely upon self-fertilization as

242 THE AMERICAN NATURALIST [Vov. XLIII

the uniformity of vegetative strains upon vegetative propagation.

As soon as individual wheat plants are crossed, even inside the

same variety, a wide range of diversity reappears. Self-fertiliza-

tion, like vegetative propagation, brings uniformity by suppres-

sing the inherent tendencies to diversity. Pure strains continue

to seem pure as long as only one set of characters is brought into

expression, but the latent diversities do not cease to be trans-

mitted, and at once reappear when hybrids are made, or selection

is relaxed, or the plants are transferred to new conditions.

It is true that uniformity like that of the pure strains of

domesticated varieties is sometimes found in nature, but even

this does not prove that uniformity represents a truly normal

condition of reproduction. Having learned that artificially

restricted descent produces uniformity in domesticated varieties,

it is easy to understand that natural conditions of close breeding

ean also produce uniformity. 3

he methods of reproduction that yield uniform offspring

often appear very effective from the environmental standpoint,

feriority. All indications point to the probability that long-

continued vegetative propagation, self-fertilization or close

breeding bring the same deterioration, sterility and ultimate

extinction to wild types as to domieationtad varieties. It does

not appear that the vigor and fertility of organisms can be

permanently maintained by the methods of reproduction re-

quired for pure strains. Free interbreeding among diverse

individuals to form a continuous network of descent is the

natural relation of the members of species.

The physiological inferiority of pure strains forbids our ac-

ceptance of theories of evolution and heredity based upon the

idea of uniformity. Neither uniformity itself nor the attendant

phenomena of mutation and Mendelism represent primary bio-

logical facts, typical of organic existence and evolutionary

progress. The restriction of descent to closely similar and

closely related individuals is a change from a natural state to

a relatively artificial, atypical condition. Darwin saw in the

facts of Mendelian inheritance a definite evidence of the abnor-

mality of mutations, but the significance of this relation is not

fully appreciated until we perceive that the uniformity of pure

strains already marks a first step toward degeneration.

WASHINGTON, D. C.,

February 10, 1909.

O. F. Coor.

NOTES AND LITERATURE

HEREDITY

The Nature of ‘‘ Unit’’ Characters.—QOne of the clearest pre-

sentations of Mendelian principles that has appeared recently

is that of Dr. E. Baur in Beihefte zur Medizinischen Klinik,

Vol. 4, 1908, pp. 266 et seq. He has given special at-

tention to inheritance in crosses between the various varieties

of Antirrhinum majus. He states that he knows 250 dis-

tinguishable varieties of this species, but he has never found

amongst them characters that do not obey Mendel’s law. He has

demonstrated fifteen pairs of characters for the species, which

is more than the number of chromosomes present, from which

fact he concludes that the chromosome as a whole can not be

considered as the basis of Mendelian unit characters. Others

have cited as a basis for the same belief that more character

pairs are known in Pisum than there are chromosomes present

in the cells. This conclusion is not a necessary one, as is seen in

the following. Speaking in a general way, the chromosomes are

present in pairs of homologues. For each pair in the eells of a

given individual there is a homologous pair in the cells of other

individuals of the species. For convenience we may designate

one of these pairs as A chromosomes, a second as B chromosomes,

etc., the same pairs as a rule being found in different individuals

of the same species.

If we consider the species as a whole, the number of pairs of A

chromosomes is equal to the whole number of cells in all the

individuals of the species. It is conceivable that, since certain

of these A chromosomes may trace back thousands of generations

before their ancestral lines unite, it is possible that there may be

an indefinite number of subgroups of A chromosomes in the

species, and that each subgroup may represent a heritable dif-

ference from other groups. But each of these subgroups would

represent a Mendelian character. Hence, there might possibly

be an indefinite number of Mendelian character pairs in a species

having only a single pair of chromosomes. ae

But these characters could not all exist in one individual.

Only two of the subgroups could be present together. Hence,

in such a species, only two independent (not correlated) domi-

243

244 THE AMERICAN NATURALIST [Vou. XLIII

nant characters could be present, and these two would present a

case of what Bateson calls spurious allelomorphism, for they

would separate from each other in the reduction division.

It is clear, therefore, that the presence in a species of more

Mendelian character pairs (presence and absence constituting a

pair) than there are chromosomes does not prove that Mendelian

characters do not appertain to the chromosome as a whole. If,

however, in a species having one pair of chromosomes we could

get into a single individual more independent character pairs

than two, or if we can get even two dominant characters that are

independent of each other, and not allelomorphic to each other,

then we should have proven that Mendelian characters do not

appertain to whole chromosomes. In general, if, in a species

having 2n chromosomes, we can bring together in a single indi-

vidual more than n independent dominant characters, no two

of which are allelomorphic to each other, then it would be proved

that Mendelian phenomena are not simply phenomena of the

chromosomes. In a recent communication to the writer, Dr. °

Baur recognizes the justice of the above point of view and hopes

to be able to test the matter in the near future. Dr. Shull will

make a similar test at the Cold Spring Harbor Station. This,

it would seem, is a simple and direct method of testing the

validity of the theory advanced by many investigators, that the

chromosome itself is the basis of the so-called unit character.

Even if this theory should be substantiated, it does not follow

that the chromosome represents a unit character in the sense in

which the term unit character is understood by most Mendelists.

Shull has very justly pointed out! that ‘‘there is no evidence of

the existence of a pair of internal units (allelomorphs).’’ : The

term ‘‘unit’’ has been applied to Mendelian characters on the

assumption, which I regard as untenable, that there is in the

germ plasm a definite organ set aside for each hereditary char-

acter. An elaborate theory of inheritance and evolution (De

Vries) has been erected on this assumption. Mendelian phe-

nomena can be explained in a wholly different manner, and one

which is more consistent with the idea of the chemical basis of

life processes, as the following illustration shows.

Let us designate the chromosome pairs in our common domesti-

cated cattle as A, B,C, ... L. Let us assume that the chromo-

somes in each of these pairs are capable of several types. of

metabolic activity, and that each of them, by its action on the

nutritive materials furnished it, gives rise in the cell to as many

*See Science, February 12, 1909.

No. 508] NOTES AND LITERATURE 245

metabolic products as it has metabolic activities. Doubtless some

of these products will be similar for a number of chromosomes.

We may thus represent the chromosomes and their functions:

(AA) — functions a, b, ¢, d,

(BB) — wi bea

(CC) — ie abo o qd

(EE) — n a, b, f

Ete Ete

Now, of the numerous B chromosomes in the species, some may

perform the function e in a manner differing from the others.

This function may fail entirely in some of them. Let us assume

that the production of horny substance requires that the functions

a, b, e and f shall be normal. If in a given group of individuals

the function e fails, which function may represent the produc-

tion of a given chemical substance in the cell, then horns fail to

develop. Individuals without horns would thus be represented

as follows:

(AA) —a, b, ¢, d.

(BB)— b,c, d.

(CC) —a, b, d.

(EE) —a, b, Í.

Ete. Ete.

Omitting from consideration those chromosomes which are not

concerned in the hereditary difference in question and remem-

bering that the poll character is dominant, the heterozygote

between the horned and polled forms would be

B—b, ce, d, e; B—b, ce d. (heterozygote polled).

Generation F, would consist of

1. B—b, c, d, e; B—b, e, d, e (horned).

2. B—b, c, d, e; B—b,.c,d (heterozygote polled).

3. B— b, ¢, d; B—b, c,d (homozygote polled).

or three polled to one horned. Thus we derive the well-known

Mendelian ratio entirely independently of any idea of unit char-

acter in the germ plasm. Rather we assume that horns are due

to the presence in the cell of certain substances each produced

by the chromosomes, as a result of their chemical constitution ;

and the poll character is due to the failure of a single chromo-

some to perform a particular function. When a hereditary

difference between two varieties is thus due to a difference in a

single set of homologous chromosomes, such difference will þe-

246 THE AMERICAN NATURALIST [Vou. XLIII

have as a simple Mendelian character. If it be due to differences

in two sets, it will behave as a compound character of two factors,

and so on.

All known Mendelian phenomena may thus be explained as

due to differences in the chemical constitution of the chromo-

somes in different groups. It is thus seen that Mendelian

phenomena lend no support to the theory that each hereditary

character is represented in the germ plasm by a separate entity.

The question as to the nature of the chromosome differences

which are thus seen to be able to account for the phenomena

first interpreted by Mendel will be considered at another time.

The differences between the metabolic activities of homologous

chromosomes here assumed may be due to differences in the

relative amounts of given substances in the chromosomes con-

cerned, or they may be due to differences existing in different

regions of the chromosomes. In the present state of our knowl-

edge of the chromosomes we are not ready for any theory on

this point. Should Shull or Baur succeed in getting into a single

individual more independent (neither correlated nor allelo-

morphic) dominant characters than there are chromosome pairs,

then we shall at least know that the chromosome as an individual

structure is not responsible for Mendelian characters. This is

the one question which must be settled before Mendelian theory

ean make further progress.

Much recent work has been done which bears on the relation

between chromosomes and hereditary characters.

First of these should be mentioned the important contribution

made by Professor E. B. Wilson, published in Science, January

8, 1909. This paper is so accessible that it is unnecessary here

to review it in full. Suffice it to say that Professor Wilson and

his students have demonstrated an important relation between

sex and certain chromosomes and chromosome groups. In gen-

eral, the cells of the species studied contain an ‘‘X-element’’

which in some species consists of one chromosome, in others of

two, in others three, and in one species of four chromosomes, but

which acts as a unit in the reduction division; i. e., all the chro-

mosomes of the ‘‘element’’ pass to the same pole. In all the spe-

cies studied, the cells of the female contain two of these X-ele-

ments, while those of the male contain but one. The males of

some of the species contain no homolog (synaptic mate) for this

element, but others contain an element which Wilson ealls the

Y-element, with which the X-element pairs in the reduction divi-

sion. In every case the Y-element, when present, consists of a

No. 508] NOTES AND LITERATURE 247

single chromosome. In every case, therefore, the female is homo-

zygote for the X-element, while the male is heterozygote either

for X and Y, or for X and absence of X. Wilson shows that the

above relations hold in a wide range of organisms, and suggests

that it may be a very general relation. There are reasons how-

ever, for suspecting that the relation is not the same for all

organisms. In a previous paper? I pointed out a number of cases

which indicate that the female may be heterozygote and the male

homozygote for sex, though some of the phenomena cited may be

explained on a different basis. Miss Durham and Miss Marryatt*®

have recently worked out one of the cases referred to in my

former article, which is a case in point. In certain strains of

canaries, black-eyed females mated with red-eyed males give only

black-eyed males and red-eyed females. This may be explained,

as the authors point out, by assuming a correlation between eye

color and sex. Letting X represent the chromosome element

characteristic of the female and Y that of the male, assuming

that Y is responsible for black pigment in the eye and that in

some individuals Y has lost the pigment-producing power, the

facts are rendered intelligible by the following assumptions re-

garding the gametic constitution of the types:

Black-eyed female — X Y-B, in which Y and B belong to the

same chromosome element.

Red-eyed male = Y-b Y-b, where the function B is absent.

Here the females produce two kinds of eggs, namely, X and

Y-B, while the males produce one kind of sperm (Y-b). This

gives progeny of two types, namely, X Y-b (red-eyed females)

and Y-B Y-b, black-eyed males. All the phenomena cited by

Miss Durham and Miss Marryatt are explicable by assumptions

similar to the above, though the occasional occurrence of black-

eyed hens in the mating of black-eyed hens with pink-eyed cocks

renders it necessary to assume that in some hens the X-element

ean also give rise to black pigment, or at least stimulate its

production in some other element.* The facts cited in my pre-

vious paper regarding the inheritance of the bar character in the

plumage of poultry further indicate that the female = not the

male may be heterozygote for sex, as do also Doneaster’s results

2 AMERICAN NATURALIST, September, 1908.

3? Rep. IV, Evol. Com., Roy. : ,

+ The BRERA constitution here assumed is not w of the ore

They assume that B and Y are separate, but that B is ‘‘repelled’’ by X,

thus giving the same results as above. |

248 THE AMERICAN NATURALIST [Vou. XLIII

with the moth Abraxas. It is hoped Professor Wilson may be

able to make cytological studies on some of these cases.

The fact that such characters as eye color in canaries, barring

in poultry, and melanie types in Abraxas may be coupled with

sex points strongly to the chromosomic nature of these char-

acters. The work of Professor R. R. Gates, and that of Miss

Annie E. Lutz on the chromosomes of (Enothera points strongly

to the assumption that chromosomes are the elements with which

we have to deal in the study of hereditary characters. Their re-

sults indicate that mutations of the De Vriesian type are due to

accidents in mitosis. Miss Lutz remarks :°

The numbers of chromosomes are closely associated with external

characters in the first and last, and probably also in the second group.

Professor Gates has also expressed the opinion that abnormal

chromosome behavior may account for the mutation phenomena

observed by De Vries. It seems probable, therefore, that muta-

tions of this character do not represent what we may call normal

evolutionary changes, but that the latter must be sought in

changes in the chemical constitution of the chromosomes.

W. J. SPILLMAN.

ENVIRONMENT

The Effect of Environment upon Animals.—‘Katy-did, Katy-

didn’t?’ seems to continue to be a fair summary of the situation

with respect to the heredity of acquired characters and the part

played by environment in evolution. Wallace wrote in . the

Fortnightly Review (January, 1908) restating his belief in

natural selection and recommending a careful study of Reid’s

‘‘The Principles of Heredity’? and Ball’s “Are the Effects of

Use and Disuse Inherited?’’ Rev. Henslow followed his advice

and has published a short, suggestive and very readable book?

on ‘‘The Heredity of Acquired Characters in Plants,” in which

he states with even more assurance than before the conclusion

of his “‘Origin of Plant Structures,’’ that ‘‘the Origin of Species

is due to the joint action alone of the two great factors of evolu-

tion—Variability and Environment—without the aid of natural

selection.’’ This additional assurance seems to be the result of

the growth of the ecological school of botanists and his belief that

ecologists are ‘‘all at one’’ in accepting the fact that evolution

in plants is the result of the effects of the environment which can

become heredity.

* Science, February 12, 1909.

*London, John Murray, 1908, 107 pp.

No. 508] NOTES AND LITERATURE 249

In 1876 Darwin had become a true ecologist. In this year he wrote

to Professor Moritz Wagner as follows: “ The greatest mistake I made

was, I now think, I did not attach sufficient weight to the direct

influence of food, climate, ete., quite independently of natural selection.

When I wrote my book and for some years later, I could not find a good

proof of the direct action [i. e., in producing definite variations] of

the environment on the species. Such proofs are now plentiful [Hens-

low says ‘ universal ’].”

Plant ecologists . . . are accepting “ Adaptation” by response as a

proved fact. . . . A complete change of front has taken place within

the last twenty years, but as Darwin himself was the first [?] to pro-

pound this view, I called it “ The True Darwinism.”

Zoologists have been rather behind the botanists in ecological

work, but the zoological school of ecology is growing and it does

seem true that the more organisms are studied with regard to

their relations to their environment, ‘‘at home,’’ the stronger

becomes the belief in the importance of environment in evolution.

Whether this is ‘‘True Darwinism’’ or something else is im-

material, only so it be true.

The most serious difficulty has been to get a good way of

accounting for the inheritance of characters produced by the

environment. Cunningham? seems now convinced that this

difficulty is removed by ‘‘hormones,’’ or internal secretions,

retracting his former idea that the nexus between secondary

sexual characters and the gonads is nervous. Starling’s proof

that the growth of mammary glands in an unimpregnated rabbit’

is caused by injection of extracts of foetuses from pregnant rab-

bits is given as an illustration of the working of hormones. Ap-

plied to the development in phylogeny of horns, for example, it

is supposed to work about as follows:

Since the development of the somatic sex-characters is due to the

stimulation of the cells by a hormone derived from the gonad, it is

conceivable that the gametes may be affected by the internal secretion

of the somatie cells whose development constitutes the sex-character.

It is quite possible that the hormone in the case of the gonad, per-

haps in all cases, is merely the waste product of metabolism occurring

in the cell-multiplication. Whether this is so or not, the somatie sexual

strueture, such as the antler, would naturally exerete into the blood

special substances, and these being in the blood the gametes would be

2¢¢The Heredity of Secondary Sexual Characters in Relation to

ion ‘ . x = ¥ 2 ` P SEN

Hormones, a Theory.of the Heredity of Somatogenie Characters.’’ Archiv

Entwicklungsmechanik, XXVI, 3, 1908. : -o

250 THE AMERICAN NATURALIST [Vou. XLIII

parts of the soma give out to the blood specifie chemical substances

which have a marked effect on development, and in presence of which

the gametes develop. If we suppose that certain parts, e. g., the

frontal periosteum in the ancestors of deer, are stimulated to hyper-

trophy by external stimulation, this entails an increase in the hormone

produced by this part of the body, and this hormone will affect the

protoplasm of the gametes which obtain their nourishment from the

lood. Mendelians and the majority of modern authorities on heredity

and evolution assume that certain material parts of the gametes corre-

spond and determine particular parts and characters of the soma, and

therefore the hormones derived from these parts of the soma may well

have an influence on the corresponding determinants in the gametes.

. I must of course assume different hormones for different bones

of the body, so that increased hormone from the frontal bone causes

modification of the determinant corresponding to that bone, not of

bone in general. Thus we have a material chain of influence from a

particular part of the soma to the gamete, and from the latter to the

corresponding part in the next generation. Whether this suggestion

be true or not, it at least destroys the contention that we can not form

a conception of the means by which a change in the soma ean effect

a corresponding part in the descendant. The hypothesis I have sug-

gested would explain ordinary adaptations more easily than secondary

sexual characters. It might be applied, for instance, to the hoofs, toes

and legs of Ungulata. I hope soon to test my hypothesis by physio-

logical experiment. If there is an influence from the parts of the

soma to the determinants of gametes, then an ov of one kind of

animal grafted into another, ought to show an alteration in the char-

acter of the individuals developed from that ovary.

The author has apparently not seen an account of Guthrie’s

work of grafting ovaries. However, it is far from certain, or

believable, that specific hormones are given off when the head

is rubbed, which affect specific determinants in the germ which

eause that specific part of the head to hypertrophy in the next

generation in the special sex corresponding to the germ whose

containing soma had its head rubbed. Doubtless there are those

who would consider this to be complicated pangenesis worse com-

plicated. There seems to be a further point consistently ignored

by adherents to such a theory. They point out that only those

animals have horns which fight by butting and believe that this

proves that horns are developed by butting. They imply that

if horses fought by butting they would develop horns; but it

seems rather likely, on the other hand, that if horses had horns

they would fight by butting. Cunningham, himself, quotes

Rörig to the effect that stags with no antlers guard the females,

No. 508] NOTES AND LITERATURE 251

not by butting, but by fighting with their fore feet. Likewise

Henslow claims that similar structures in widely different plants

in similar environments prove that these structures were di-

rectly produced by the environment. On the other hand, it can

not be denied that some of these cases may be due to the similar

selective aetion of similar environments.

Even Weismann was prepared to admit the inheritance of ac-

quired characters in Protozoa, but Jennings* has thrown experi-

mental doubt upon that also. In a second paper® he shows that

the environment is, indeed, a large factor in determining the size

of Paramecium, but, as yet, he has found no proof that these

effects are inherited. Even selection seems powerless to affect

the size within a ‘‘pure line.” However, pure lines differing

in size can easily be isolated by selection, thus confirming by a

zoological example the results reached by several botanists,

notably Johannsen. The variation curve of size is considered to

be formed by a mixture of pure lines whose dimensions are modi-

fied by the environment and growth factors.

FrANK E. Lutz.

EXPERIMENTAL ZOOLOGY

Hybridology and Gynandromorphism.—Raepke * has made a de-

tailed examination of some of the hybrids (bastards) between

certain species and varieties of Smerinthus (ocellata, populi and

its variety Austanti). The material was obtained from the

famous hybridologist Standfuss.

The anatomical results may be summed up as follows:

The internal genitalia of the normal male moths show much

variation but in the hybrids the variations are more extreme;

and often amount to ‘‘anomalies,’? and monstrosities, in the

internal organs. Sperm elements are present and reach different

stages of maturity, most of them degenerate later, producing

a few imperfect spermatozoa. The female hybrids show also

greatly modified sexual anomalies, both the germinal region

as well as the ducts may be abnormal or even absent. Hand in

+í‘ Heredity, Variation and Evolution in Protozoa. I. The Fate of

New Structural Characters in Paramecium, with Special Reference to the

Question of the Inheritance of Acquired Characters in Protozoa.’’ Journ.

Exp. Zool., 5, pp. 577-632, 1908.

5 c‘ Heredity, Variation and Evolution in Protozoa. II. Heredity and

Variation of Size and Form in Paramecium, with Studies of Growth,

Environmental Action and Selection.’’ Proc. American Phil. Soc., XLVII,

190, 1908.

1 Raepke, W. Jena. Zeitsch. f. Naturwissens., XLIV, 1908.

252 THE AMERICAN NATURALIST [Vou. XLIII

hand with these modifications there appear male secondary

sexual characters in the female as more or less rudimentary

male genital appendages at the end of the body. It would seem

to follow that the female is heterozygous, a fact of some general

interest. The discovery raises once more the question of the

cause of gynandromorphism in insects, for obviously these

hybrid moths show adumbrations at least of such a condition.

In this connection it is of interest to give Raepke’s summary o

Standfuss’s results regarding the sex of hybrid moths and the

occurrence amongst them of gynandromorphism.

He classifies the results under five headings:

First, those hybrids that are so abnormal (atypic or sexless)

that their sex can not be determined.

Second, those hybrids in which only one sex develops,

generally the male; females also rarely appear, but these so im-

perfect that reproduction is impossible. The males also are

sterile.

Third, those hybrids in which both sexes appear in normal

proportions; the females sterile, the males crossed back to the

parent species fertile in various degrees. The offspring of such

a union are, however, very abnormal and monstrous both in their

primary and in their secondary sexual organs. In certain series

gynandromorphs appear in surprisingly large numbers.

Fourth, those hybrids in which the females although appearing

normal lay either no eggs or abnormal eggs. The males are

like those in the last category or like those in the next.

Fifth, those hybrids in which the females produce fertile eggs.

These eggs produce only embryos or if the caterpillar stage is

reached at all the young are weak. Whenever it has been pos-

sible to rear moths by crossing back these females to the parent

species (or from the male hybrids of the same cross) only males

develop but in such scanty numbers that they have not been

tested further.

Whether in the last instance only males are produced because

they are hardier than the females or because of some more

fundamental relation is not evident from the results.

n the other hand the italicized statement in the third cate-

gory calls for further examination. What is the cause of the

production of so many gynandromorphs?

Two hypotheses have been suggested in recent years along

cytological lines that offer at least a formal solution of the

problem. Boveri suggested that the entering sperm fuses not

with the female pronucleus, but with one of the nuclei derived

No. 508] NOTES AND LITERATURE 253

from the first division of that pronucleus. Morgan suggested

that the result could equally well be ‘‘ explained ’’ un the assump-

tion of polyspermy—one sperm nucleus fusing with the egg

nucleus and the other (or others) producing cells independently

of the segmentation nucleus. The gynandromorphs described

by Toyama seemed to be a test case. An analysis of his results

gave evidence in favor of my suggestion. In connection with

the occurrence of two kinds of spermatozoa in moths—‘‘ male

and female producing’’—the question arises whether on my

view the male parts of the gynandromorph are due to a male

or to a female producing sperm. In my paper I suggested that

since the female sperm is the homologue (from the chromosomal

point of view) of the egg nucleus minus its two polar bodies

that such a ‘‘ female-producing ’’ sperm might produce the male

parts. This suggestion fits in completely with the view of sex-

determination recently adopted by Wilson. It sounds para-

doxical at first that a ‘‘ female-producing ’’ sperm could produce

a male soma, yet if we look to the chromosomes alone as sex

preducers such a view is tenable. Moreover if in the bee there

is produced only female-producing sperm—as the evidence

strongly indicates—then on my view the male parts must come

from a female-producing sperm., On Boveri’s view the nucleus

that makes the male parts is the same (after one division) as the

ege-pronucleus which is also male producing and the homologue

of the ‘‘female-producing’’ sperm

T. H. MORGAN.

ECHINODERMATA

Red Sea Crinoids..—Mr. Herbert C. Chadwick has just pub-

lished the first account of the crinoid fauna of the Red Sea, his

paper being based upon a collection made by Mr. Cyril Cross-

land, under the direction of Professor W. A. Herdman, of the

University of Liverpool. From time to time notices have ap-

peared relating to various Red Sea comatulids, but they have

been widely scattered, and some of them more or less forgotten,

so that before the appearance of this paper an idea of the Red

Sea crinoids could only be obtained by a most laborious search

through a large number of more or less rare and inaccessible

volumes.

Mr. Chadwick found six species in the material submitted to

1 Reports on the Marine Biology of the Sudanese Red Sea.—VII. ‘‘The

Crinoidea.’’? By Herbert C. Chadwick, A. L. S., Curator of the Port Erin

Biological Station. Journ. Linn. Soe. (Zool.), vol. 31, pp. 44-47.

254 THE AMERICAN NATURALIST [Vor. XLIII

him, representing only two families, the Himerometridæ and the

Antedonidæ, in the former the genera Oligometra, Stephano-

metra, Dichrometra and Heterometra, and in the latter Irido-

metra. All of these genera range throughout the East Indian

region, and are characteristic littoral types of that area.

The first crinoids known from the Red Sea were Tropiometra

carinata and Heterometra savignii, both of which were well fig-

ured by Savigny in his ‘‘Deseription de l’Egypt’’ in 1817, the

former identified by Audouin as ‘‘Comatula sp.,’’ the latter as

‘Comatula multiradiata.’’ There is no further reference to the

first of these figures; but de Blainville in 1836 copied the second

in the atlas to his ‘‘Manuel d’Actinologie’’; in doing this he

made a curious mistake, for the plate is lettered ‘‘Comatula

adeone’’ though in the text the description of Comatula adeone

is taken from Lamarck, and the species is stated to have ten

arms. In the following year the ‘‘Penny Eneyclopedia’’ copied

de Blainville’s account of Comatula adeone, multiradiate figure

and all, and the same slip was made by the ‘‘ Natural History’’

of Knight published in 1867.

Riippel, in the course of his travels, found in the Red Sea

an interesting multiradiate comatulid upon which he bestowed the

MS. name of Comatula cucomelas, but he does not appear to

have mentioned it anywhere in his works. In 1833 Leuckart

came across his specimens in the Senckenburg Museum, and

published the name, together with the locality, though without

any diagnosis.

In 1841 Professor Johannes Müller described his Alecto savi-

gnii, based upon specimens which had been brought from the

Red Sea by Hempricht and Ehrenberg, and he also identified the

Comatula multiradiata of Audouin, figured by Savigny, as this

species. In 1869 von Martens recorded Miiller’s Alecto palmata,

which had been originally described from India, from the Red

Sea, though he apparently did not know that this was the same

form as that recorded as Comatula leucomelas by Leuckart in

1833.

Nothing more was recorded regarding Red Sea comatulids for

some time; Moseley analyzed the coloring matter from an uniden-

tified species from Suez (possibly Oligometra serripinna), and

Ludwig in 1880 listed two of the species known from that locality,

but omitted the third. Carpenter, in the ‘“‘Challenger’’ report

was unable to add anything, though he increased the known

range of Heterometra savignii by recording it from Museat and

No. 508] NOTES AND LITERATURE 955

Kurrachee. In 1890 Dr. Hartlaub described Dichrometra klun-

zingeri from Koseir, and identified the Comatula leucomelas of

Riippel with the Alecto palmata of Professor Müller.

Mr. Chadwick did not find Tropiometra carinata nor Dichro-

metra klunzingeri in the collection examined by him, but he

did find the other two species known from the Red Sea, Hetero-

metra savignii and Dichrometra palmata; the remaining four

species recorded include one family and three genera new to the

region; they are, Oligometra serripinna, Iridometra parvicirra,

Stephanometra marginata and Dichrometra protectus.

Oligometra serripinna is recorded from Suez Bay, where it was

dredged at a depth of 10 fathoms; the specimens differ from the

type in the greater number of cirrus joints, and, in view of the

general constancy of the cirrus characters in this genus, may

eventually turn out to be a recognizable form, as may also those

recorded under the same name from Ceylon; correlated, as

usual, with the more numerous cirrus joints, the lower pinnules

have also more numerous joints.

Iridometra parvicirra, discovered by the *‘ Challenger’’ among

the Philippine Islands, is recorded from ten fathoms in Suez Bay.

The single specimen has a large number of cirrus joints for the

genus, which, together with the furrowed first primibrach, would

suggest that it was rather closer to the I. nana group of species

than to I. parvicirra; the former occur from Mauritius to Japan,

while the latter were previously known from the Philippines and

Japan.

We share the author’s doubt in regard to his identification of

Stephanometra marginata, which he records from Suez Bay, in

ten fathoms.

Dichrometra protectus (under the later name imparipinna)

is given from Suez Bay, and Suakim. The number of arms in `

the specimens is unusually small, and it would have been well

worth while to have recorded their size. In addition to the

localities cited by Mr. Chadwick, the species is known from Cebu,

Philippines, Fiji and Singapore.

Dichrometra palmata was found on the coral reef at Misharif

Island, Khor Dongola, and from between tide marks at Suez.

Heterometra savignii (emended, following Carpenter, to

savignyi) is recorded from four fathoms in Suez Bay, from nine

fathoms at Ul Shubuk, from ten to twelve fathoms at Khor

Shinab, and at the anchorage at Salaka; the distribution of

the species is given as ‘‘Red Sea, Ceylon,’’ but I am unable to

recall any record from the latter place; Carpenter gives it from

256 THE AMERICAN NATURALIST [Vou. XLIII

as far east as Kurrachee, and says that it ‘‘is not known to

extend further eastwards,’’ and I know of no subsequent addi-

tions to its range; Mr. Chadwick did not give it from Ceylon

in his list of the crinoids of that island published in 1904.

In the introductory paragraph Mr. Chadwick mentions the

interesting fact that none of the Comasteride are known from

the Red Sea. They probably occur there, however, and will

eventually be discovered when more extended work is under-

taken. The absence of any species of Zygometride is note-

worthy, arid also that of Himerometra, one species of which,

H. persica, was first described from the Persian Gulf and sub-

sequently found in the Philippines. He also takes occasion to

point out a weakness in Dr. F. A. Bather’s argument for the

treatment of a syzygial pair of brachials as two single brachials

united by syzygy, instead of a single brachial ‘‘with a syzygy,’’

the treatment adopted by Carpenter and Hartlaub. Mr. Chad-

wick’s contention is that if the two brachials united by syzygy

were originally, as urged by Dr. Bather, united by the ordinary

oblique muscular articulation of the distal portion of the arm,

which oblique muscular articulation had been transformed into

a syzygy at the same time dropping its pinnule, the pinnule upon

the resultant epizygal would be upon the same side as that upon

the joint preceding the hypozygal, instead of on the opposite side,

as is always the ease. Mr. Chadwick is inclined to believe that

this is evidence in favor of the views of Hartlaub and Carpenter,

and against the ideas of Dr. Bather. I maintain that the

syzygial pair is the morphological equivalent, not of one joint, as-

urged by Carpenter (in part) and Hartlaub, nor of two joints

as supposed by Dr. Bather and apparently considered by Pro-

fessor Perrier, but of three joints, the central one of which has

dwindled and disappeared, so that the oblique muscular articula-

tions on its proximal and distal ends have become superposed,

their ligaments, being dominant over their muscles, fusing and

forming the radiating figure which is the original of the later

more perfected syzygy, while the muscles, and with them the

pinnule sockets (borne by the muscular fossæ) have disappeared.

Thus the syzygy originally, instead of having a single pinnule,

as supposed by Dr. Bather, had two, which neutralized each other,

so that the syzygy in its perfected form has no effect on the

pinnulation. AUSTIN HOBART CLARE.

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December 7, 1908.

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THE

AMERICAN NATURALIST

Vor. XLIII May, 1909 No. 509

THE CATEGORIES OF VARIATION

PROFESSOR S. J. HOLMES

UNIVERSITY OF WISCONSIN

Ir is a well-established fact that what are commonly

called variations include modifications of quite different

import in relation to the process of evolution. Whether

or not the variations that are induced in the soma, either

by its own activities or through the influences of the en-

vironment, have any effect in shaping the course of evolu-

tion as they were held to do by Lamarck and his followers,

it is evident that they do not count in this process in the

same way as variations that arise in the germ. But

among the germinal variations themselves there are

classes of unequal significance. Variations differ mark-

edly in regard to their stability or permanence. Many

variations after their first appearance persist with little

modification for an apparently indefinite time. Of these

what are commonly called mutations afford conspicuous

examples; these are abrupt variations which breed true

or nearly so from the start, having their own fluctuating

variability, to be sure, but around a mean which does not

approach that of the parental type in successive genera-

tions. Other variations behave quite differently. They

may be selected generation after generation, modifying

the stock up to a certain point, after which, if the variety

is left to itself, there is revision towards the original par-

ent. It is held by many that these two classes of varia-

tions are fundamentally distinct, and that only the first,

257

258 THE AMERICAN NATURALIST [ Vou. XLIII

so-called discontinuous variations, play an important role

in the origination of new species.

A considerable proportion of what is described as

fluctuating variability is, in many cases, simply somatic

variation, having no relation to the germ plasm. It is

evident, however, that all fluctuating variability can not

be such, otherwise species could not be modified by ordi-

nary methods of continued selection. Our mathematical

curves represent two kinds of variability lumped together

and which it is in most cases practically impossible to

separate. The character of height, for instance, in

human beings is to a certain extent an inherited one, but

it is determined to a marked degree by influences opera-

ting after birth. The usual curves of variation represent

both and may even include also variations in the nature

of mutations which fail of discrimination from the rest

of the aggregate.

De Vries distinguished three kinds of germinal varia-

tions, elementary species, retrograde varieties and fluctu-

ations. These three kinds he conceives to be sharply

distinguished and produced in different ways. All con-

genital variability is regarded by him as resting upon

qualitative or quantitative changes in the pangens or the

organic units of which he conceives living matter to be

built up. The pangens form the basis of the unit char-

acters, or independently variable elements of the organ-

ism, there being a special kind of pangen for each such

character. Variations in the number of pangens cause

variations of the fluctuating type which obey Quetelet’s

law of chance frequency distribution. De Vries main-

tains and attempts to prove by the citation of several

examples that through the selection of such variations

modification may be carried to a certain point, but soon

a limit is reached beyond which selection is incompetent

to effect further improvement. Moreover, continued

selection must be practised in order to maintain the con-

dition which has been reached, else the stock will in the

course of a few generations revert more or less completely

to the ancestral mean.

No. 509] THE CATEGORIES OF VARIATION 259

Retrograde varieties, according to De Vries, are

sharply distinguished from fluctuations. They are, as a

rule, constant from the start, and differ from the type

in only one or at most a very few respects.

They originate for the greater part in a negative way by the ap-

parent loss of some quality and rarely in a positive manner by acquir-

ing a character seen in allied species.” “By far the greatest part

of the ordinary garden-varieties differ from their species by a single

sharp character only. In derivative cases, three or even more such

characters may be combined in one variety, for instance, a dwarfed

variety of the larkspur may at the same time bear white flowers or even

double white flowers, but the individuality of the single characters is

not in the least obscured by such combinations.

These varieties, says De Vries, ‘‘do not possess any-

thing really new.’ The loss of a character is merely

apparent. ‘‘On a closer inquiry we are led to the as-

sumption of a latent or dormant state. The presumably

lost characters have not absolutely, or at least not per-

manently disappeared. They show their presence by

some slight indication of the quality they represent, or

by occasional reversions. They are not wanting, but

only latent.’’ In other words, the only difference be-

tween retrograde varieties and the types is the latency

or patency of certain characters. The same kinds of

pangens are present 1 in the germ plasm of both.

Elementary species, on the other hand,

are distinguished from their nearest allies in almost all organs. There

is no prominent distinctive feature between the single forms of Draba

verna, Helianthemum or of Taraxacum; all characters are almost

equally concerned. The elementary species of Draba are characterized,

as we have seen, by the forms and the hairiness of the leaves, the

number and height of the flower stalks, the breadth and incision of the

petals, the forms of the fruits, and so on. Every one of the two

‘hundred forms included in diis collective species has its own type,

which it is impossible to express by a single term. Their names are

chosen arbitrarily. Quite the contrary is the case with most of the

varieties, for which one word ordinarily suffices to express the whole

dilliri.

The most important distinction which De Vries draws

between retrograde varieties and elementary species 1s

a physiological one. They

260 THE AMERICAN NATURALIST [ Vou. XLIII

behave in quite different manner, when subjected to crossing experi-

ments, and the hope is justified that some day crosses may become

the means of deciding, in any given instance, what is to be called

species, and what variety on physiological grounds.

When varieties are crossed with the parent type the

character that is active in one or the other of the forms

will usually be patent in the first generation of offspring.

In the second generation there is, according to De Vries,

a segregation of characters which takes place in con-

formity to Mendel’s law. Ordinary sugar corn, for ex-

ample, differs from the usual type in having a part of

the starch replaced by sugar in the kernels, which conse-

quently become wrinkled when dry. When these two

forms are crossed the active character of starchy kernels

is present in all the members of the first generation. In

the second generation there is a segregation of these

characters, one fourth of the offspring being wrinkled

kernels, and three fourths smooth ones. Approximately

one third of the latter produce only smooth kernels in

subsequent generations, while the other two thirds split

up again in the expected Mendelian ratio.

In the crossing of varieties it is possible, according to

De Vries, for all the corresponding characters of the two

forms to become paired. As the distinguishing feature

of the variety is the latency or patency of one or more

characters, these characters ‘‘will unite as well as though

they were both active or both dormant. For essentially

they are the same, only differing in their degree of ac-

tivity. From this we can infer that, in the crossing of

varieties, no unpaired remainder is left, all units com-

bining in pairs exactly as in ordinary fertilization.” As

the varieties differ only in the dominance or latency of

certain characters, offspring obtained through crossing

them differ only in the same way. For such unions De

Vries gives the name ‘‘bisexual crosses,’’? inasmuch as

there is ‘‘complete bisexuality, all unit characters com-

bining in pairs.’’

_ In the crossing of the elementary species of Œnothera

De Vries found that in the first generation there was a

No. 509] THE CATEGORIES OF VARIATION 261

splitting up of the progeny in various ratios, but that the

second and subsequent generations bred true to type,

thus presenting a condition just the reverse of Mendelian

inheritance. For instance when the mutant rubrinervis

was crossed with the parent type Lamarckiana the first

generation of hybrids were either rubrinervis or La-

marckianas, the proportion varying greatly in different

lots. The two kinds of hybrids did not split up in the

second generation but bred true to type. Similar results

were obtained by crossing several other elementary

species of Lamarckiana but this kind of behavior does

not seem to be generally characteristic of the elementary

species of other forms.

In the crossing of elementary species there is, accord-

ing to De Vries, one unit character which is not mated,

since |

the differentiating mark is present in one of the parents and not in

the other. While all other units are paired in the hybrid it is not.

It meets with no mate and must therefore remain unpaired. The

hybrid of two such elementary species is in some way incomplete and

unnatural. In the ordinary course of things all individuals derive

their qualities from both parents; for each single mark they possess

at least two units. Practically but not absolutely equal, these two

opponents always work together and give to the offspring a likeness

to both parents. No unpaired qualities occur in normal offspring;

these constitute the essential features of the hybrids of species and

are at the same time the cause of their wide deviations from ordinary

rules.

These differences between variations were predicted

by De Vries on the basis of his pangen theory, and in his

essay on ‘‘Intracellular Pangenesis’’ published in 1889

he expresses the opinion that fluctuating variability which

rests upon numerical variation of the pangens plays but

a minor part in the modification of species. The ‘‘art-

bildende” or species forming variability, is dependent

upon the appearance of an entirely new kind of pangen.

When categories of variation are anticipated a priori on

the basis of a theory of the constitution of living matter

there is naturally produced a temptation or bias towards

262 THE AMERICAN NATURALIST [ Vou. XLIII

reading the classification into nature and to the over-

looking of transitional stages, and we shall therefore en-

quire if the distinction which is made between elementary

species and varieties is a valid one.

In the first place, there does not seem to be any very

good reason why on the pangen theory elementary species

should differ in numerous characters from the parent

form. A pangen is the basis of a single unit character.

Elementary species are produced through the origination

of a new kind of pangen. If the becoming latent or

dominant of a pangen affects only one unit character of

an organism, it is not evident, when a new kind of pangen

is produced, why the whole organization of the plant

should be so profoundly influenced. Why should not the

awakening of a dormant pangen produce as great a

change as the production of a new pangen of a somewhat

different quality. Says De Vries:

There ean be little doubt but that all the attributes of every n

species are derived from one principal change. But why this onl

affect the foliage in one manner, the flowers in another and the fruits

in a third direction, remains obscure. To gain ever so little insight

into the nature of these changes, we may best compare the differences

of our evening primroses with those between the two hundred ele-

mentary species of Draba and other similar instances. In doing so

we find the same main feature: the minute differences in’ nearly all

points.

De Vries nowhere gives us a much clearer explanation

as to why elementary species and varieties should differ

in this way and we must probably be content with re-

ferring the matter to different degrees of ‘‘correlation.’’

It is evident that there are allied groups separated by

small differences throughout the entire organization, and

there are other groups which differ apparently in single

characters only, such as the presence or absence of hair,

spines or certain colors. Hornless cattle and six-toed

eats do not seem to present any general or constitutional

differences from the other members of their species, but

this is a subject upon which we should exercise great

caution, as very slight differences in the rest of the organ-

No. 509] THE CATEGORIES OF VARIATION 263

ization may be correlated with pronounced differences

in a single part.

Among the forms arising by mutation from @nothera

lamarckiana De Vries distinguishes three varieties,

levifolia, brevistylis and nanella. These forms are called

varieties instead of elementary species because they dif-

fer from the type in a few characters only and because

of their different behavior when crossed. But even ac-

cording to De Vries’ own description the points of differ-

ence are not limited to a single character. Levifolia, for

instance, is

chiefly distinguished from Lamarck’s evening primrose by its smooth

leaves, as its name indicates. The leaves of the original form show

numerous sinuosities in the blades, not at the edge, but anywhere be-

tween the veins. The blade shows numbers of convexities on either

surface, the whole under surface being undulated in this manner. It

lacks the brightness of the ordinary evening-primrose or Cnothera

biennis. These undulations are lacking or at least very rare on the

leaves of the new levifolia. Ordinarily they are wholly wanting, but

at times single leaves with slight manifestations of this character may

make their appearance. They warn us that the capacity for such

sinuosities is not wholly lost, but only lies dormant in the new variety.

The leaves of levifolia are also ‘‘a little narrower and

more slender than those of the Lamarckiana.’’ But

levifolia also shows differences in the flower. ‘<The

yellow color is paler and the petals are smoother. Later

in the fall, on the weaker side branches these differences

increase. The levifolia petals become smaller and are

devoid of the emargination at the apex, becoming ovate

instead of obcordate.’’

Brevistylis is characterized by its short style. The

stigma is different in shape from that of the parent form;

there are differences in the ovaries, and there are only

a few seeds produced. These differences may possibly

depend upon a single varying character, although

the leaves of the O. brevistylis are more rounded at the tip, but the

difference is only pronounced at times slightly in the adult rosettes, but

this character the plants may be discerned among the others, some

weeks before the flowers begin to show themselves.

264 THE AMERICAN NATURALIST [ Vou. XLIII

Nanella is a dwarf plant, but it is not distinguished by

its smaller size alone.

From its first leaves to the rosette period, and through this to the

lengthening stem, the dwarfs are easily distinguished from any other

of its congeners. The most remarkable feature is the shape of the

leaves. They are broader and shorter, and especially at the base they

are broadened in such a way as to become apparently sessile. The

stalk is very brittle, and any rough treatment may cause the leaves to

break off. . F e stems are often quite unbranched, or branched

only at the habe of the spike. Strong secondary stems are a striking

attribute of the Lamarckiana parent, but they are lacking, or almost

so in the dwarfs.

So far as morphological evidence is concerned, the dif-

ference between the above forms and elementary species

are not so sharp as to inspire one with much confidence

in the essential distinctiveness of the two classes. Al

of these so-called varieties differ in various parts of their

organization. It may be said that these differences are

dependent through correlation upon the variation of a

single character, but if any one maintains that smooth

leaves and paler flowers, or small size, brittle stem and

short leaf stalks are related in this way, the burden of

proof is on his shoulders. If a half dozen characters in

different parts of the plant vary it would indeed be diffi-

cult, amid a considerable amount of fluctuating varia-

bility, to separate on morphological grounds a retrograde

variety from a true elementary species, especially since

experts are sometimes troubled in distinguishing some

of the elementary species from one another. Indeed, De

Vries admits that it is often very difficult to decide

whether a given form belongs to one or the other of these

two groups, but he states that in such cases we have a

means of testing the matter experimentally by the forma-

tion of crosses. Let us see, therefore, ‘how the test of

crossing works out.

In the case of the varieties of Œnothera lamarckiana

there is in the second generation a splitting according to

the Mendelian ratio when the variety is crossed with the

parent form, but with varieties of other forms this does

No. 509] THE CATEGORIES OF VARIATION 265

not seem to be an invariable occurrence. Davenport has

shown that albinism in poultry is in some cases a non-

Mendelian character, and the same is probably true, ac-

cording to Castle, for the lop-eared condition in rabbits.

In the inheritance of long and short hair in guinea pigs

there is also a marked departure from Mendelian ratios.

In silkworms Kellogg has shown that while most features

are Mendelian, cocoon color in some cases follows Men-

delian ratios, but in others it proved to be ‘*inconstant

as to dominance and recessiveness and numerical propor-

tions, and may even break down and blend.” Deaf-

mutism also refuses to come under Mendelian categories

according to the statistics compiled by Bell. The fore-

going are cases of apparent retrograde variations which

form an exception to Mendel’s law, but it must be ad-

mitted that the majority of such variations which have

been investigated show a fair approximation to Men-

delian ratios.

In the crosses between the elementary species of

(nothera lamarckiana there is commonly a splitting

up in the first generation with absence of splitting in the

second and subsequent ones. Hybrids of O. Lamarckiana

and O. biennis, however, have nearly the aspect of the

latter species and remain true in the second and subse-

quent generations without reversion or splitting. Crosses

between O. muricata and O. hirtella produced hybrids

showing the characters of both parents. These were

progagated through four generations and remained ‘‘true

to this type, showing only slight fluctuations and never

reverting or segregating the mixed characters.”’ In-

stances of constant hybrids between different species are

very common and it is unnecessary to specify them here.

Such constancy according to De Vries is “‘one of the best

proofs of unisexual unions’’ or unions between distinct

elementary species in which there is always one unpaired

. pangen. pa TE

The attempt to make a general rule for the hybridizing

of elementary species leads to many difficulties. In

266 THE AMERICAN NATURALIST [ Von. XLIII

poultry, as Davenport has pointed out, such characters

as pea and rose comb, extra toes and the presence of

muffs and beards on the head, are acquisitions which

developed since the domestication of the original an-

cestral species. They certainly can not be regarded

as the outeropping of latent characters which are rep-

resented in allied forms, but are in the line of progres-

sive variation and therefore according to theory de-

pendent upon the production of new kinds of pangens.

any definite rule of inheritance and none of them follow

Mendel’s law, the extra toes do not seem to come under

any definite rule of inheritance, and none of them follow

the rule for the hybridization of elementary species.

Consider the forms of the common potato beetle studied

by Tower. These arise suddenly, breed true to type and

differ from the parent form in many characters, some of

which are apparently in the line of progressive evolution.

They seem to be as truly elementary species as the

mutants of Œnothera lamarckiana. Yet when crossed

with the parental type they produce hybrids which in

most cases give a mixed progeny segregating according

to Mendel’s law.. If we can not call these forms ele-

mentary species there is no way of distinguishing such

except through breeding experiments, and the distinction

De Vries draws between elementary species and varieties

amounts to nothing more than the fact that crosses be-

tween certain groups follow Mendel’s law, while crosses

between others do not. There is no correlation between

any structural criterion of species and the criterion

afforded by breeding experiments.

Now when we attempt to make a classification on the

basis of breeding experiments alone we fare little better.

With blended inheritance in the first and all subsequent -

generations, partially blended inheritance, total resem-

blance of hybrid to one or another parent with or without

subsequent splitting, incomplete segregation of char-

acters, splitting of offspring of hybrids in various incon-

stant and non-Mendelian ratios, and many other irregular

No. 509] THE CATEGORIES OF VARIATION 267

manifestations of heredity, the difficulty of maintaining

a sharp distinction between varieties and elementary

species on the basis of behavior in inheritance is apparent.

Are we to classify a six-toed cat as a variety or an ele-

mentary species? The variation is apparently limited

to a single character and it has therefore one of the marks

of a variety, but the variation is doubtless a progressive

one and not due to an awakening of a latent character, and

hence possesses one of the features of an elementary

species. When crossed some of the offspring of the

first generation may inherit the variation and some not,

and the same is true for the following generation; but

there is apparently no splitting according to the law of

Mendel. So far as our knowledge goes the situation is

the same in respect to polydactylism in man.

The second volume of the Mutationstheorie, which

seems to have been little read by most expositors of De

Vries, affords several examples of irregular behavior of

the hybrids between elementary species which are very

difficult to classify. Crosses between @nothera nanella

and O. rubrinervis, for instance, the one a retrograde

variety of Lamarckiana and the other a distinet elemen-

tary species, gave very variable results, with splittings

in the first and succeeding generations in very inconstant

ratios, and the occasional production of blends which

bred fairly true. We have here a curious combination

of the characteristics of unisexual and bisexual crosses.

It would not be difficult to bring forward many other

cases which refuse to fall within the scheme of classifica-

tion propounded by De Vries. There are many kinds

of variations which are inherited in many kinds of ways.

The pangen theory of the celebrated botanist has proved

a deceptive guide and has led its author to do scant justice

to many classes of facts which do not fall in line with it.

Hypotheses about paired and unpaired pangens have de-

termined De Vries’s classification of the different kinds

of variations and profoundly influenced his interpretation

of his extensive and valuable researches. The octrine

268 THE AMERICAN NATURALIST [ Vou. XLIII

of intracellular pangenesis has never received the logical

development that characterizes Weismann’s theory of

the germ plasm and is considerably inferior to the latter

as a scholastic production. The explanation it affords

of the alleged distinction between varieties and elemen-

tary species is, as we have seen, practically no explanation

at all. The theory may be consistent with the facts of

Mendelian inheritance and the supposed independent

variability of parts, but why it should lead one to antici-

pate that elementary species differing from the parent

throughout their organization originate by a single sud-

den leap is not so clear. Rather it would lead one to

expect that organisms would be modified, a part here and

a part there, corresponding to the independently variable

elements determined by particular pangens, of which there

are numerous kinds, until the whole was slowly trans-

formed. De Vries, however, is careful to explain that a

single pangen may be responsible for certain characters

found in various parts of the organism, such as the color

of leaves, flower and fruit, and that pangens are supposed

to influence each other’s manifestation so that a variation

in a single pangen may have a far-reaching effect. In

a chapter on the association of characters in his recent

book on Plant Breeding a great deal of emphasis is laid

upon the value of a study of the correlation of the dif-

ferent parts of the plant. He says:

We come to the conception of a general interdependency of all

parts, organs and qualities of an organism. They are governed more

or less by the same laws which cause them to undergo corresponding

changes when subjected to the same influences.

Tt seems to me that the author is here upon treacherous

ground. Through the assumption of manifold correla-

tions De Vries attempts to account for a. change in a

single pangen which has to do primarily with one inde-

pendently variable part of the organism producing a

modification of the organism as a whole, but in so doing

he is taking the foundation away from the argument upon

which the justification of the pangen assumption rests.

No. 509] THE CATEGORIES OF VARIATION 269

To the extent that the organism is a whole of interde-

pendent parts, to just that extent it gives evidence of not

being a piece of mosaic work and hence removes the neces-

sity for a hypothesis of discrete germinal units. De

Vries even goes so far as to say that ‘‘in order to be

correlated the characters must begin by being independ-

ent entities which through some later means may come

into relation with others.’ At one time it is argued that

the existence of pangens is proved by the fact that the

parts of the organism are independently variable; and

now it is said that we must assume that pangens must

exist to account for the parts being correlated; that is,

for the fact that they are not independently variable!

The most salient feature of the mutation theory is that

the process of evolution is conceived to take place by

sudden steps of considerable magnitude. This has been

heralded with éclat as enabling us to get rid of certain

difficulties inherent in the Darwinian theory, such as the

assumed absence of intermediate forms between existing

and fossil species and even the contention that the geo-

logical history does not afford time enough for the process

of evolution as it was formerly conceived to take place.

But it is not correct to say that a mutation is neces-

sarily a large variation. Mutations may be very small

steps, falling far within the limits of ordinary fluctuating

variability, as is especially emphasized by De Vries in

his later writings. :

In groups (such as brambles, roses, buttereups, willows and maoy

others) where large numbers of species are closely allied, the differ-

ences between any two of them become smaller, and the number of -

distinct forms increasing, the distinction in the end may become re-

duced to a single differential mark for each two neighboring types.

Such differences must be assumed to be produced each by a single

mutation.

In the light of experiments made at Svalof, De Vries

now concludes that ‘‘ordinary varieties of cereals are

built up of hundreds of elementary forms which with few

exceptions have hitherto escaped observation. The high

variability which is commonly attributed to our ordinary

270 THE AMERICAN NATURALIST [Vou. XLIII

varieties of cereals consists only in the differences among

the constituents of the mixtures.’’ Much of the improve-

ment of grains that was formerly obtained by continued

selection De Vries ascribes to the unconscious selection

of elementary species and the gradual improvement of an

originally mixed stock. Rimpau’s rye, a stable race

obtained by gradual selection, is thus accounted for, but

the burden of proof is here on the part of the mutationists.

It is apparently not so easy to test the rôle of mutations

versus fluctuations in the improvement of species, because

if one should secure a stable race by the usual process

of selection, the mutationist might urge that, after all,

amid the confusion of seemingly fluctuating variability,

there were some mutations which escaped notice, and,

through the unconscious selection of these and their off-

spring, the stock was gradually purified and converted

into an improved stable form. ,

Where ordinary varieties include ‘‘hundreds of ele-

mentary forms,’’ separated by characters which in many

cases are so small that they ‘‘may be scarcely perceptible

to the inexperienced eye,’’ how is one to tell whether he

is dealing with mutations or ordinary fluctuations? The

latter may be much greater in extent, and,.as we have seen,

there is no structural criterion by which a mutation may

be recognized. Crossing experiments give us no certain

test and we have therefore to fall back upon the criterion

of stability and class as mutations those variations which

breed true from their first appearance. Here the oppor-

tunities for begging the question are excellent. If by

the ordinary process of selection a stable race is pro-

duced we can of course ascribe it to the unconscious choice

of one or more undetected mutations. To be sure, stable

races can be produced only on the basis of stable varia-

tions, and if this is all that the mutation theory neces-

sarily implies its divergence from Darwin’s teaching is

not very wide.

If now it should turn out that stability is a matter of

degree the last distinguishing feature of the mutation

No. 509] THE CATEGORIES OF VARIATION 271

theory would be destroyed. This is a question upon

which we are sadly in need of light. Some of De Vries’s

own mutations are, however, quite inconstant and show

a strong tendency to revert to the parent species.

(Enothera scintillans, when self-pollinated, produced from

8 per cent. to 52.9 per cent. of Lamarckianas and 34 per

cent. to 69 per cent. of its own kind and a variable number

of other mutants. O. elliptica and O. linearis repeat their

kind in still smaller ratios. The reversion of these

mutants like their origin is sudden, but it shows an un-

stable condition of their germ plasm and it may be ques-

tioned if this reversion is essentially different from the

slower reversion which often follows the cessation of the

selection of ordinary fluctuations.

That the differences between mutations and fluctua-

tions are not so fundamental as the pangen theory implies

is indicated by several facts, some of the most suggestive

of which have been furnished by De Vries’s own experi-

ments. For a number of years De Vries carried on a

series of experiments on the corn-marigold Chrysan-

themum segetum, with the purpose of creating a double-

flowered variety. De Vries chose a garden variety of

this form, grandiflorum, and raised several generations,

selecting the seed each time from heads which contained

13 rays florets. After four years of propagation, when

he was satisfied of the purity of the isolated strain, De

Vries began to discard all plants with less than 21 rays

in the terminal head. The selection was continued for

a number of generations when a plant appeared which

seemed to form a promising one for the production of a

double variety.

It was not remarkable for its terminal head, which exhibited the

average number of rays of the 21-rayed race. Nor was it distinguished

by the average figure for all the heads. It was only selected because

it was the one plant which had some secondary heads with one ray m

than all the others. This indication was very slight, and could not

have been detected save by the counting of the rays of thousands of

heads. But the rarity of the anomaly was exactly the indication

wanted, and the same deviation would have had no significance what-

272 -= THE AMERICAN NATURALIST [Vou. XLIII

ever had it oceurred in a group fluctuating symmetrically around the

average figure. On the other hand, the observed anomaly was only

an indication, and no guarantee of future developments.

From this slight indication De Vries selected for three

years more and found that the

average number of rays increased rapidly and with it the maximum

of the whole strain. The average came up from 21 to 34. . . . The

largest numbers determined in the succeeding generations increased by

leaps from 21 to 34 in the first year, and thence to 48 and 66.in the two

succeeding summers.

Up to this time, while there was a great increase in the

number of ray florets, there was no trace of doubling, but

in a few of the best heads ‘‘the new character suddenly

made its appearance.” If sudden, the step was certainly

a very modest one. A single plant was found in which

careful inspection revealed ‘‘three young heads with some

few rays in the midst of the disk.’ ‘‘Had the germ of

the mutation,” asks De Vries, ‘‘lain hidden through all

this time? Had it been present, though dormant, in the

original sample seed? Or had an entirely new creation

taken place during my continuous endeavors? Perhaps

as their more or less immediate result?’’ It is ae

that ‘‘The new variety came into existence at once’’

but when? While certain that a mutation must have

appeared, De Vries is uncertain when and where it ap-

peared. ‘‘The leap,’’ he says, ‘* may have been made by

the ancestor of the year 1895, or by the plant of 1899

which showed the first central rays, or the sport may have

been gradually built up during these four years”? (italics

mine

During the next two years improvement by selection

was kept up.

‘The average number of rays which had already risen from 13 to

34 now at once came up to 47 and 55. . . . The maximum numbers

came as high as 100 in 1900 and even 200 in 1901. . . . Real atavists

or real reversionists are seen no more after the first purification of

the race.

A variety which is pronounced ‘‘permanent and con-

stant’ was produced whose lower limit of the number

No. 509] THE CATEGORIES OF VARIATION 273

of rays was raised to about 34, ‘‘a figure never reached

by the grandiflora parent.’’

The unbiased reader who has carefully followed the

account of the production of this double flower can

scarcely escape the feeling that the interpretation of the

facts according to the mutation theory is at times some-

what strained. The starting point of the whole process is

the selection of fluctuations. Now and then the selection

of a somewhat more pronounced variation was made; but

the so-called mutations had very small and weak begin-

nings, and De Vries is uncertain just where they occurred

and even suggests that they may have been built up grad-

ually! The selection of fluctuations seems to have had

the effect of inducing variations of greater stability, if

not greater extent, in the same direction. It is not unrea-

sonable to suppose that the appearance of florets with

ligulate corolla on the disk is due to the same factors

which cause the increase in the number of ray florets, and

the variation may be in reality not so discontinuous as

it seems. In fact we are ignorant of the stability or the

real discontinuity of many of the steps in advance towards

the production of the double flower. Tf a mutation can

make its appearance as an extra ray floret in one case,

and by the occurrence of two or three ligulate corollas

on the disk of a few flowers of the plant in another, and

if both these characters can be increased by selection until

they reach a stable condition that is far more highly

developed than their original one, the facts do not lend

much support to a theory of the saltatory origin of

species. Rather they would indicate that species have

been formed along lines determined by selective processes

much in the same way as Darwin conceived them to be.

By a similar method of selection Burbank has produced

a scarlet variety of the California poppy, Eschscholtzta

californica. He noticed one flower with a fine searlet line

on one petal. From the seed of this plant other poppies

with scarlet lines were produced, but only to a slight

extent. After selection was practised for some years

274 THE AMERICAN NATURALIST [ Vou. XLIII

a race of pure scarlet poppies was finally obtained with

no indication of their yellow ancestor. This case is cited

by De Vries as one of mutation, but certainly it required

more than one mutation to bring about the result.

Discontinuity may often be more apparent than real,

the discontinuous variations in the soma being the out-

come of continuous variability instead of abrupt changes

in the germ. Let us consider from this point of view

the occurrence of digital anomalies such as polydactylism,

cleft hand, ete., which are frequently cited as illustrations

of discontinuous variability. These anomalies are often

strongly inherited, but in most cases which have been

fully studied, the inheritance, while partly alternative,

is not Mendelian. In the race of polydactylous guinea

pigs which Castle has produced and bred for a number,

of generations the anomaly appeared in different indi-

viduals in various stages of completeness. The parent

of the group, a male, bore an imperfectly developed toe

_ on his left hind foot. The extra toe contained a claw and

probably the phalanges, but it was loosely attached and

hung limply down on one side. This male produced 27

young, of which 15 were polydactylous. Of the latter some

had an extra digit on both hind feet, others had it on but

one, and in a few individuals the digit was more fully

developed than in the father. In subsequent generations

the anomaly appeared in very different degrees of de-

velopment, some animals having a fully developed digit,

others having a loosely hanging toe with or without a nail,

while in extreme cases there was only a fleshy bag of skin

without bones or claw which often shriveled up and dis-

appeared a few days after birth. The variation, when

appearing on one side alone more frequently was limited

to the left side (1. 630, r. 589), and when unequal on the

two sides the left one was usually the better developed.

Normal and polydactylous individuals did not segregate

in Mendelian ratios. In some instances the normal condi-

1 See also the experiments of MacCurdy and Castle in relation of con-

tinuous and discontinuous variation in rats. Publications of the Carnegie

Institution, No. 70, 1907.

No. 509] THE CATEGORIES OF VARIATION 275

tion gave evidence of being recessive, but this was not

borne out by many other cases in which crosses be-

tween normal individuals produced polydactylous young.

Crosses of normal individuals both of which were of

polydactylous ancestry yielded a much higher per cent.

of polydactylous young than did crosses in which one

individual came from a normal breed, thus showing a

certain tendency in the blood towards polydactylism even

when it did not manifest itself by any outward mark.

Different males of the same amount of polydactylous

ancestry often showed great variation in the potency

with which they were able to transmit the anomalous

character.

The evidence goes to show that we are dealing here

with a tendency which, whatever may be its basis, varies

continuously and not abruptly, although producing varia-

tions which, taken alone, would naturally be classed as

mutations. The extra toe is a new character, but the

polydactylous breed behaves neither like an elementary

species nor like a retrograde variety. The character flue-

tuates to the vanishing point and even beyond (as shown

by crossing experiments with individuals of different an-

cestry) and shows varying degrees of fidelity of trans-

mission in different strains. Do we not havea condition

intermediate between the abrupt discontinuous variations

which breed true with great fidelity and ordinary fluctua-

- tions? It might be said that we have to do with a muta-

tion which fluctuates to an unusual degree, although it

originally depended upon a sudden change in the germ

plasm; but the assertion would have no evidence to rest

upon. It might be said, on the other hand, that the varia-

tion is dependent on the undue activity of some of the

factors of normal development, an expression, for im-

stance of increased growth tendency in the part at a cer-

tain period, and that this tendency is kept from definite

expression until it reaches a certain strength, when it

manifests itself as a sudden variation. This conclusion

is warranted, I believe, not only by the great variability

276 THE AMERICAN NATURALIST [ Vou. XLII

of the anomaly, but by the fact already cited that normal

individuals of abnormal ancestry are more apt to produce

abnormal offspring than are normal individuals of an-

other strain.

The studies of. Lewis and Embleton and of Pearson on

the inheritance of split hand and split foot in man yield

results in many respects similar to the preceding. Al-

though the normal condition seems to be recessive, segre-

gation does not occur in Mendelian ratios. Often both

hands and both feet were abnormal, but frequently not

in the same way, and in many cases there were marked

differences in the variations on the two sides of the body.

As Pearson remarks, it is difficult to specify in such cases

what the unit character may be. With this, that or the

other bone present in some individuals and absent in

others and represented in very varying degrees of de-

velopment, the inheritance gives little evidence of definite

units of any kind. What is inherited appears to be a

condition which manifests itself in varying ways and de-

grees and which can not be accounted for by any theory

of the sharp segregation of characters.

Why certain germinal variations are strongly inherited

and others not is a problem of much interest, but the solu-

tion of it may lie, not in the supposed behavior of distinct

morphological entities representing certain parts, but in

the physiological relations of the basis of the variation

to the organized structure of the germ plasm. The sex

cells are organisms as well as the bodies that arise from

them; they have the same capacity for self regulation;

and it is not at all probable that all kinds of variations

that may arise in response to the various influences to

which they are subjected should be retained to the same

degree. Weismann has made the suggestive comparison

between the variations of an organism and the oscillations

of a polyhedron on one of the faces upon which it rests.

If the oscillations are small the body tends to come to

rest in the same situation as before; if they are larger it

may topple over upon a new face about which it may oscil-

No. 509] THE CATEGORIES OF VARIATION 27T

late as around a new center of equilibrium. Weismann

postulates a self-regulating power in the germ plasm

which keeps numerous minor fluctuating variations from

producing any essential modification of the stock. iH,

however, a certain variation forms a new center of stabil-

ity it may be permanent. The various mutants of Œ no-

thera lamarckiana, most if not all of which contain the

potency of giving rise to any of the others and which pre-

sent very different degrees of stability, may be due to

more or less stable forms which the germ plasm may as-

sume rather than the creation of new kinds of germinal

units. The stability of a variation may be due, however,

not so much to its extent as the analogy with the polyhe-

dron might lead us to expect as to its kind. Variations

which are physiologically congruent with the organized

structure of the germ plasm form stable races; those

which are not tend to become reduced sooner or later to

the norm through the regulatory activity of this sub-

stance.

The germ plasm may be conceived to exercise, in regard

to its variations, a kind of selective activity which may

manifest itself as a proneness of the organism to vary

along certain lines. It is well known that there are partic-

ular types of variation which crop out independently and

more or less frequently and may be faithfully perpetu-

ated. Polydactylism, split-hand and split-foot, albinism

and melanism, the appearance of races of hairless animals

and glabrous plants, the development of nectarines from

peaches and peaches from nectarines, the origin of peloric

flowers, ete., have occurred many times in independent

2 Tt is of course possible that the m tations of Œnothera Lamarckiana

result from the impurity of the stock. The species has been for a tii

time cultivated as an ornamental flower, and we have nothing but conjecture

regarding its origin. Should it turn out to be derived from a mixture of

two or more forms the mutation theory would be deprived of some of its

best evidence, but there would still remain a considerable number of muta-

tions from pure ancestry. In @Œnothera gigas the interesting e

been discovered that there is double the normal number of chromosomes.

Whether this is the cause or the effect or merely one instance of the dif-

ferences between this mutant and the type is unknown. ae

278 THE AMERICAN NATURALIST [ Vou. XLIII

strains. These phenomena may be compared to various

anomalies which take their origin in the soma. The em-

bryo in its development is liable to certain accidents

resulting in the production of teratological phenomena

such as hare-lip, double formations, anencephaly and

many others. ‘These anomalies fall into certain classes

and in many cases can be attributed to particular defects

of development. The germ plasm also may be regarded

as liable to certain classes of accidental modifications

which produce heritable variations of more or less clearly

defined types. No one would think of attributing anom-

alies of somatic origin to the development of a new kind

of organic unit. If the same mutation appears time after

time, would it not be more reasonable to suppose that it

arose after the fashion of somatic anomalies than that it

depended upon the creation each time of the same kind

of a new pangen? The fact that mutations can be in-

duced through the influence of the environment certainly

favors such a view. ‘Tower found that in Leptinotarsa

certain variations or mutations arose repeatedly in inde-

pendent strains and that by subjecting the beetles to un-

usual conditions during the period of active development

of their germ cells the proportion of these sudden varia-

tions could be very greatly increased. The variations

thus produced belonged to a few well-marked types, and

while it would be hazardous to set bounds to the possible

number of mutants the species may produce, it is probable

that the number is subjected to a certain limitation im-

posed by the peculiar organization of the germinal sub-

stance.

The selection of variations by the germ plasm may be

illustrated by some observations of Jennings upon inherit-

ance in Protozoa. In a few specimens of Paramecium

it was noticed that the body was furnished with a spine-

like excrescence. During fission the spine was trans-

mitted to but one of the individuals, the acquired peculi-

arity not arising on the other. In one case the spine was

transmitted through twenty-one generations, when the

No. 509] THE CATEGORIES OF VARIATION 279

strain disappeared. In other cases the spine was

gradually diminished during successive divisions and

ultimately disappeared. Other anomalies such as crook-

edness, blunt ends, bent tip of body and various abnor-

malities, provoked by artificial mutilation, while persisting

for a variable number of generations, were eventually

regulated out, leaving a normal strain.

In like manner we may imagine that through environ-

mental changes the germ plasm becomes affected by

modifications which in the course of a few generations

become regulated out, thereby causing a reversion to the

primitive stock. Reversion may thus be conceived as but

a manifestation of form regulation. Variations to be

permanent must be accepted by the organized structure of

the germ cells, so that they may be included instead of

excluded by the processes of functional equilibration

to which these cells like other parts of the organism are

continually subjected. The congruity of the variation is

the important thing; whether the variation be large or

small, sudden or slow, is of much less consequence.

After all, it may be asked, granting that variations may

be interpreted in the manner here set forth, do not the

phenomena of Mendelian inheritance, showing as they do

that characters may be separated and combined in many

different ways prove that these characters must be borne

by some sort of units in the germ plasm? This is a con-

clusion which is adopted by a large number of Men-

delians, but, plausible as it seems, it is, I believe, a totally

erroneous view. In the first place it is open to question

if the assumed purity of the gametes is a fact even in

typical cases of Mendelian inheritance, but, granting that

there is an absolute separation of ancestral tendencies,

it by no means follows that there is any sorting of indi-

vidual unit characters apart from the complex of tend-

encies which make for the production of the organism

as a whole. Hereditary anlagen may perhaps be shuffled

and sorted as wholes, but if the germ plasm were com-

posed of discrete parts representing the unit characters

280 THE AMERICAN NATURALIST [ Vou. XLIII

of the individuals, the result would probably be utter con-

fusion instead of orderly development. We might as-

sume that albinism is dependent upon the peculiar prop-

erties of a single chromosome, that length of hair is de-

pendent upon the constitution of a second chromosome,

that a short tail is associated with a third, and so on.

These characters may not be represented by any kind

of structural element; they may have their basis in the

general chemical constitution of the chromosome and be

produced during development in a purely epigenetic

fashion. Chromosomes probably have their individual

peculiarities of chemical constitution as might be expected

from the fact that the chromatin content of an individual

represents contributions from many different ancestors.

Each chromosome or even a small constituent of the chro-

mosome may have a relation to the inheritance of the

whole body, but the peculiarities of one chromatic element

may dominate in one part, those of another chromatic ele-

ment in another. When albinism is eliminated it does not

mean that this character alone is separated, but the anlage

of an albino organism. Even if it is shown that the num-

ber of separate characters which Mendelize is greater than

the number of chromosomes of the variety, Mendelian

phenomena can be explained on the basis of sorting out

ancestral tendencies as wholes instead of unit characters.

The facts of Mendelian inheritance at present known do

not necessarily give any support to the theory of discrete

bearers of unit characters, or the theory of the inde-

pendent variability of parts as conceived by De Vries and

Weismann. This is a point which, I believe, needs to be

emphasized on account of the uncritical acceptance of

these views by so many writers on heredity and variation.

The presence or absence of certain characters may be

independent of the presence or absence of certain others,

but this fact may very readily be accounted for without

having recourse to a particulate theory of inheritance.

The mixing up and separation of characters in inherit-

ance, far from proving the independent variability of

No. 509] THE CATEGORIES OF VARIATION ` 281

parts, is just what renders the proof of this theory ex-

ceedingly difficult. The alleged independent variability

of parts is Weismann’s strongest proof of his doctrine

of determinants. If a pit in the ear or a white tuft of

hair on the head can be transmitted for several genera-

tions without involving any other change in the organism,

we are forced to assume, according to Weismann, that

there is a small part of the germ plasm varying independ-

ently of the rest which forms the basis or determinant

of this character. But the contention particularly diffi-

cult of proof is that the characters really do appear in

independence of the other parts of the organism. <A

variation may conceivably depend upon a general change

in the constitution of the substance of heredity, although

manifesting itself most conspicuously in a single part.

A pit in the ear may be the most obvious sign of the very

slight constitutional differences between two individuals.

It is common to find two closely allied species or varieties

differing markedly in one or two features and much less

conspicuously in numerous other parts of their structure.

Peculiarities of horns are sometimes associated with less

noticeable characteristics of the hair, thus pointing to a

common origin of these features in some general modifica-

tion of the ectoderm which in turn may result from some

change affecting the germ plasm as a whole. Albinism

which is so often cited as a unit character is a peculiarity

of far reaching correlations, being often associated with

impaired sight or hearing, diminished fertility, and even

lessened power of resistance to disease.

To establish the independent variability of parts re-

quires a much closer study of possible correlations than

has yet been made. ‘The task is rendered particularly

difficult by the varied combination and segregation of

ancestral tendencies, which we have just considered. If

we can account for the independence of certain characters

on the ground of combining and sorting ancestral tend-

encies as wholes, one has to disprove the possibility of

_ applying this explanation of the appearance of a partic-

282 f THE AMERICAN NATURALIST [ Vou. XLIII

ular variation before the latter can be regarded as giving

evidence of a corresponding determinant. The burden

of proof is on the shoulders of the upholders of the doc-

trine of determinants and it is a far heavier one than the

champions of this doctrine commonly appreciate. Let us

suppose that among the various sets of hereditary tend-

encies that find expression in the organization of an indi-

vidual one should include the production of a particular

variation in a single small part. The constitutional differ-

ences which may go along with this peculiarity and of

which it may be regarded as one expression may be modi-

fied or kept from becoming manifest by other and rival

sets of hereditary tendencies thereby rendering it almost

impossible to detect the correlations that really exist, and

giving the character the delusive appearance of independ-

ence. The question of the independent variability of

parts is a crucial one for the particulate theories of in-

heritance, but it is one so beset with practical difficulties

that a final answer may not soon be forthcoming.

In the preceding discussion the attempt has been made

to show that the various categories of variations recog-

nized by De Vries and others are not sharply separable

either on morphological grounds or by their behavior

when subjected to crossing experiments. The attempt

was made also to show that neither the facts of variability

nor those of Mendelian inheritance give any support to

the doctrine of pangens, determinants, or other assumed

bearers of unit characters, and that unit characters, as

elements than can enter or depart from the complex of

tendencies that make up an organism probably have no

existence. It is evident that variations differ in their

stability, but the explanation of this fact may lie in the

physiological relations of the variation rather than in

some hypothetical representative unit. Whether the

variations of the discontinuous type have been influential,

in any marked degree, in shaping the course of evolution

is a question upon which we need much more evidence.

Mutations, as we have seen, may be very small affairs.

No. 509] THE CATEGORIES OF VARIATION 283

About the only criterion by which they may be recognized

is their stability, and even that gives some evidence of

being a matter of degree. No limit has been discovered

to the minuteness of the stable modifications that may

occur, and it may happen that further study will reveal

the comparatively frequent appearance of very slight

variations of this kind. In fact, considerable progress

has even now been made in this direction by the study of

grains; and the number of more or less stable modifica-

tions that are likely to be discovered threatens to over-

whelm systematists with the labor of naming and describ-

ing them. In many organisms not propagated by self-

fertilization the detection of these small steps is no easy

task and the attempt to describe them all would undoubt-

edly prove a futile effort. Among human beings, for

instance, what are we to designate as elementary species?

We meet with all grades of differences from well-marked

family traits to those which separate the Caucasian from

the negro. Are we to regard the Hapsburg lip which

was transmitted with fidelity for many generations as

the mark of an elementary species? It was apparently

a new character and therefore presumably dependent

upon a new pangen or determinant. The Celts, Teutons,

Slavs, etc., differ by more or less constant characters

which are constitutional and not confined to single parts,

and the same may be said of the various subdivisions of

these groups. The Aryan stock to which these groups

belong is separated by still greater differences from the

other subdivisions of the Caucasian race, and the latter

in turn differs still more widely from the negroes and

Mongolians. One has considerable difficulty in disposing

of these groups either as varieties or elementary species.

They can not from De Vries standpoint be considered

the results of fluctuating variability on account of their

constancy even under very varied external conditions.

If the small divisions have arisen by slow changes, as

everything indicates, there is no logical halting place

short of admitting that the greater ones may have done

284 THE AMERICAN NATURALIST [ Vou. XLIII

the same. In fact a survey of the racial differences of

man in their varying degrees and kinds and their correla-

tion with geographical distribution shows us pretty

clearly that these differences have been slowly acquired

by the summation of very small variations. These groups

are not related as the so-called retrograde or digressive

varieties are, but they are based on differences in general

constitution affecting the shape of the skull, the character-

istic complexion, the general temperament, and many

other traits too numerous to specify. They may have

arisen by minute, discrete, stable variations, but to call

each step in advance an elementary species seems absurd,

and to talk of the immutability of species still more so.

We gain little by characterizing as elementary species

the small steps of which there may be a dozen or more

separating a German from a Frenchman.

Students of geographical distribution as a rule set

little store by the theory of mutation. The relation of

variation and species-forming to distribution as illus-

trated by the work of Gulick and Hyatt on the Achatin-

nelide, the Sarasins on the snail fauna of Celebes, of

Plate on the mollusca of the Bahamas, and of many stu-

dents of the mammals, birds and fishes of North America

indicate that the steps concerned in species-forming have

been very modest ones. If sudden mutations of consid-

erable magnitude have been a not uncommon source of

varieties of domesticated animals and cultivated plants

it does not follow that the selection of comparatively

small variations has not been the predominant method

of species-forming in a state of nature.

After fifty years from the publication of Darwin’s

‘‘Origin of Species” we are still debating, and more

lively than ever, the central problem of that epoch-making

book; but it is not improbable the views of its sagacious

author will prove more nearly correct than those of most

of his modern critics. Much remains to be done before

the problem is finally solved, and there are few fields

No. 509] THE CATEGORIES OF VARIATION 285

before the nee that are more fruitful and

alluring.®

8? Mendelism and Unit aee —Since this article on the Cat

gories of Variation was sent in for publication several articles Ai

A whose contents ayr have nie referred to had they been pub-

lished somewhat earlier. One of these is a short paper by W. pillman in

‘‘ The Nature of Unit Characters,’’ in the April number of this journal, in

which an interpretation of so-called unit characters is given which is, in

many respects, similar to my own. Reference to Mr. Spillman’s views would

naturally be expected in an article appearing later than his in the same

journal, so that it may be well to state that the proof of my paper was

returned to the publishers in the first part of February, and that no

modification of the paper has since been made. I am glad to find myself in

agreement with Mr. Spillman at least to the extent that the facts of

Mendelian inheritance do not compel us to adopt a particulate theory of

heredity. That Mendelian inheritance can be explained by the sorting

process which is supposed to take place in the reducing divisions of the germ

cells I feel by no means assured, there are grave difficulties in the way of

such an interpretation. But if this explanation prove to be the correct one

it would be far from justifying the PEETA accepted doctrine of unit

characters with all its evolutionary implicati

Reference might also be made to some Schalk articles by De Vries, espe-

cially one on the crosses of Oenothera nanella (Ueber die Swillingsbas-

tarde von a nothera nanella. Ber. Bot. Ges. 26, p. 667, 08), inasmuch as

present writer that no.sharp line can be drawn from the results o

experiments between elementary species and so-called retrograde varieties.

THE GENERAL ENTOMOLOGICAL ECOLOGY OF

THE INDIAN CORN PLANT

PROFESSOR S. A. FORBES

ILLINOIS STATE ENTOMOLOGIST

Ecorocy being the science of the interactions between

an organism, or a group of organisms, and its environ-

mept, and between organisms in general and their en-

vironment in general, this complex of relations may, of

course, be divided in various ways. The division here

used implies a centripetal grouping of the facts of rela-

tionship around single kinds of organisms, and the group

of facts to be discussed is that of which the corn plant is

the center and the insects of its environment are the

active factors.

A prolonged study, extending over many years, of the

entomology of the corn plant, the economic results of

which have been published in my seventh and twelfth

reports as State Entomologist of Illinois (the Eighteenth

and Twenty-third of the office series) has left in my pos-

session a considerable body of information capable of

treatment from the standpoint of pure ecology, and the

beginnings of such a treatment are here assembled þe-

cause of the rising interest in ecological investigation and

the promise which it gives of interesting and important

results, and because of a wish to illustrate, in some meas-

ure, the general scientific value of such materials, of

which, it scarcely need be said, the economic entomol-

ogists of this country have accumulated a large amount.

INSECT INFESTATION OF THE CorN PLANT

We know of some two hundred and twenty-five species

of insects in the United States which are evidently at-

tracted to the corn plant because of some benefit or

advantage which they are able to derive from it. The

286

No. 509] ECOLOGY OF INDIAN CORN PLANT 287

principal groups of this series are ninety species of

Coleoptera, fifty-six species of larve of Lepidoptera,

forty-five species of Hemiptera and twenty-five species

of Orthoptera. The other insect orders are represented

by seven or eight species of Diptera and one or two of

Hymenoptera. Every part of the plant is liable to in-

festation by these insects, but the leaves and the roots

yield the principal supplies of insect food, either in the

form of sap and protoplasm sucked from their substance

by Hemiptera, or in that of tissues and cells devoured

by the subterranean larve of Coleoptera, and by cater-

pillars, grasshoppers and beetles, feeding above ground.

Lack or SPECIAL ADAPTATIONS

Notwithstanding the great number of these insects, and

the variety and importance of the injuries which they

frequently inflict upon the corn plant, there is little in its

structure or its life history to suggest any special adapta-

tion of the plant to its insect visitants—no lure to insects

capable of service to it, or special apparatus of defense

against those able to injure it. The fertilization of its

seed is fully provided for without reference to the agency

of insects. It has no armature of spines or bristly hairs

to embarrass their movements over its surface or to

defend against their attack its softer and more succulent

foliage. It secretes no viscid fluids to entangle them,

and forms no chemical poisons or distasteful compounds

in its tissues to destroy or to repel them. The cuticle of

its leaf is neither hardened nor thickened by special de-

posits; its anthers are neither protected nor concealed ;

and its delicate styles are as fully exposed as if they were

the least essential of its organs. Minute sucking insects

are able at all times to pierce its roots and its leaves with

their flexible beaks, and with the single exception of its

fruit there is no part of it which is not freely accessible

at any time to any hungry’enemy. Only the kernel,

S = which is supposed to have been lightly covered in the

= wild corn plant by a single chaffy scale or glume, “as

288 THE AMERICAN NATURALIST [ Von. XLIII

become, in the long course of development, securely in-

closed beneath a thick coat of husks, impenetrable by

nearly all insects; and we may perhaps reasonably infer

that, among the possible injuries against which this con-

spicuous protective structure defends the soft young

kernel, those of insects are to be taken into account.

There are, of course, many insect species, even among

those which habitually frequent the plant, which are un-

able to appropriate certain parts of its substance to

their use, but this is because of the absence of adaptation

on their part and not because of any special defensive

adaptation on the side of the plant. Thus we may say

that, with the exception of the ear, the whole plant les

open and free to insect depredation, and that it is able

to maintain itself in the midst of its entomological de-

pendents only by virtue of its unusual power of vigorous,

rapid and superabundant growth. Like every other

plant which is normally subject to a regular drain upon

its substance from insect injury, it must grow a surplus

necessary for no other purpose than to appease its

enemies; and this, in a favorable season, the corn plant

does with an energetic profusion unexampled among our

cultivated plants. Insects, indeed, grow rapidly as a

rule, and most of them soon reach their full size. Many

species multiply with great rapidity, but even these the

corn plant will outgrow, if given a fair chance, provided

they are limited to corn itself for food.

Turning to the other side of the relationship, we may

say that the corn insects exhibit no structural adaptations

to their life on the corn plant—no structures, that is to

say, which fit them any better to live and feed on corn

than on any one of many other kinds of vegetation.

This was, of course, to be expected of the great list of

insects which find in corn only one element of a various

food, and that not necessarily the most important; but it

seems equally true of those which, like the corn root-

worm or the corn root-aphis, live on it by strong prefer-

ence, if not by absolute necessity.

No. 509] ECOLOGY OF INDIAN CORN PLANT 289

Aphis maidiradicis, the so-called corn root-aphis, is not

especially different in adaptive characters from the other

root-lice generally, and it lives, indeed, in early spring,

on plants extremely unlike corn. Finding its first food

on smartweed (Polygonum), and on the field grasses

(Setaria, Panicum, ete.), it is scarcely more than a piece

of good fortune for it and for its attendant ants if the

ground in which it hatches is sometimes planted to corn,

in which it finds a more sustained and generous food-

supply than in the comparatively small, dry and slow-

growing plants to which it would otherwise be restricted.

The larva of Diabrotica longicornis, usually known as

the corn root-worm, is, of course, well constructed to

burrow young corn roots, but it differs from related

Diabrotica larve in no way that I know of to suggest a

special adaptation to this operation, except in the mere

matter of size. If it were larger it would probably eat

the roots entire, as does the closely related and very

similar larva of D. 12-punctata. Indeed, there is some

reason to believe that D. longicornis may breed in large

swamp grasses, since the beetle has been found abundant

in New Brunswick in situations where it is difficult to

suppose that it originated in fields of corn, and where

such grasses are extremely common. Even the special

corn insects seem, in short, structurally adapted to much

more general conditions than those supplied by the corn

plant alone, and if they are restricted largely or wholly

to this plant for food, this seems due to other conditions

than those supplied by special structural adaptations.

In short, in the entomological ecology of the corn plant

we see nothing whatever of that nice fitting of one thing

to another, specialization answering to specialization,

either on the insect side or on that of the plant, which

we sometimes find illustrated in the relations of plants

and insects. The system of relations existing in the corn

field seems simple, general and primitive, on the whole,

like that which doubtless originally obtained between

plants in general and insects in general in the early stages

of their association. 7

290 THE AMERICAN NATURALIST [ Vou. XLIII

Such adaptations to corn as we get glimpses of are

almost without exception adaptations to considerable

groups of food plants, in which corn is included—some

of these groups select and definite, like: the families of

the grasses and the sedges, to which the chinch-bug is

strictly limited, and others large and vague, like the

almost unlimited food resources of the larve of Lach-

nosterna and Cyclocephala under ground. These are

evidently adaptations established without any reference

to corn as a food plant, most of them very likely long

before it became an inhabitant of our region, and applying

to corn simply because of its resemblance, as food for

insects, to certain groups of plants already. native here.

Entomo.LoaicaL Ecotocy oF CORN AND THE STRAWBERRY

Corn being, in fact, an exotic or intrusive plant which

seems to have brought none—or at most but one'—of its

native insects with it into its new environment, it will

be profitable to compare the entomological ecology of this

introduced but long-established and widely cultivated

plant with that of some native species which is also gen-

erally and, in some districts, extensively grown.

We may take, for this purpose, the strawberry plant,

whose insect visitants and injuries I studied carefully

several years ago. About fifty insects species are now

listed as injurious to the strawberry, and about twenty

of these also infest corn. Two fifths of the known

strawberry insects are thus so little specialized to that

food that they feed on other plants as widely removed

from the strawberry as is Indian corn. On the other

hand, six species, all native, are found, so far as known,

only, or almost wholly, on the strawberry, at least in that

stage in which they are most injurious to that plant.

These are the strawberry slug (Emphytus maculatus) ;

the strawberry leaf-roller (Phoxopteris comptana) —occa-

sionally abundant on blackberry and raspberry, to which

it spreads from infested strawberry plants adjacent; two

1 Diabrotica longicornis Say.

No. 509] ECOLOGY OF INDIAN CORN PLANT 291

of the strawberry root-worms—the larve of T’ypophorus

aterrimus and of Scelodonta nebulosus; the strawberry

crown-borer (T'yloderma fragarie) ; and the strawberry

aphis (Aphis forbesi).

Not even one of this considerable list exhibits, so far

as I can see, any special structural adaptation to life on

the strawberry plant. The two root-worms mentioned,

for example, are no better fitted to feed on strawberry

roots than is a third strawberry root-worm—the larva of

Colaspis brunnea, which lives on the roots of corn and

timothy also. Emphytus maculatus might feed, for all

the structural peculiarities which one can see, on the

leaves of roses as well as does the common slug or false-

worm of those shrubs—and so of the others of the list.

Even the strawberry crown-borer, which lives in all

stages solely on that plant, might, so far as structure and

life history are concerned, feed and develop in any other

thick-rooted perennial. The difference seems to be one

of habit.or preference solely, and not of structural

adaptation.

-. Our impressions of the extent, nicety and frequency

with which insects and plants are mutually adapted are

indeed commonly much exaggerated, owing to the fact

that our attention is especially drawn to notable cases of

curious, precise or particularly advantageous adjustments

between organisms, while no general study is made of

the entire system of relations obtaining between all the

members of an associate group, varying widely, as these

do, in respect to the intimacy, importance and exclusive-

ness of the association. For this same reason, in part,

we ordinarily have no accurate idea of the relative fre-

quency and primacy of structural, or static, adaptations

—particularly obvious, especially interesting, and poem-

ingly ingenious, as they often are—and of those more =

obscure adaptations of preference, behavior, habit and

the like, which, taken together, we may call dynamic.

292 THE AMERICAN NATURALIST [ Vou. XLIII

CLASSIFICATION OF ADAPTATIONS TO Foop

A plant-insect group—a group, that is, composed of

a plant and its insect visitants—is not, in fact, usually

marked, either as a whole or in any of its several parts,

by the presence of adaptive structures special to that

group. The structural adaptations of insects are, as a

rule, much too broadly shaped to fit them closely to any

one plant, and where such a fitting is found, it is clearly

due to some other than the structural factor. Such facts

bring us to a consideration of the whole subject of the

variations and classification of the adaptations of insects

to their food resources.

These adaptations may be classed as structural, physio-

logical, psychological, synethic,? local, biographical and

numerical. All structural adaptations are, of course,

physiological, in a sense, but I use the word physiological,

as a matter of convenience, for functional adaptations

not based on obvious structural peculiarities, as where

an insect equally capable of feeding on the sap of two

plants, and readily availing itself of either, nevertheless

thrives: and multiplies better on one than on the other,

the adaptation being evidently digestive or assimilative

rather than obviously structural. The San José scale,

for example, feeds readily on a great variety of trees and

shrubs, on some of which it thrives poorly and spreads

but little, while on others it multiplies enormously and

spreads with great rapidity. The word psychological

may be applied to cases of apparent choice or evident

inclination, as between the various available food plants

of the environment. Those fixed peculiarities of habit

or behavior which adapt an insect to one food plant or

class of food plants rather than to another we may call

synethic adaptations, in the absence of any existing word

applicable in this sense; local adaptations are those in

which the usual haunts and places of resort.of an insect

species, however determined, bring it into common con-

tact with an available food plant, the frequency of this

* Adaptations of habit.

No. 509] ECOLOGY OF INDIAN CORN PLANT 293

contact being quite independent of the degree of the fit-

ness of such plant for its food; biographical adaptations

are those based on a correspondence between the life

history of the insect and its organic food supply, such

that the latter shall always be accessible in sufficient

quantity to meet the varying needs of the dependent in-

sect at the various stages of its growth; and numerical

adaptations are the consequence of such an adjustment

of the rate of insect multiplication to the plants or ani-

mals of its food that only the unessential surplus of this

food shall be appropriated, leaving its essential maximum

product undiminished.

These several classes of adaptations limit each other

variously, the most desirable food of an insect being that

which is found within the area common to all of them.

That is, the most important food plants of a vegetarian

species will be those which are well within its structural

capacities of discovery, access and appropriation; within

its physiological powers of easy digestion and profitable

assimilation; and within its habitual range and location;

and which are consistent with its usual preferences and

habits of action, and are well adapted to furnish con-

tinuously amounts of food answering to its varying neces-

sities during the different stages of its life.

ADVAN TAGES OF BIOGRAPHICAL ADAPTATION

It is obviously to the advantage of any insect species

that it shall have its largest possible food supply coin-

cident with its own largest demand for food—that is, at

the climax of its period of growth. In a species restricted

to one annual food plant the most favorable relation will

usually be that in which the life history of the plant and

that of the insect coincide, the egg-laying period of the

one corresponding to the seeding period of the other, the

hatching of the insect being virtually simultaneous with

the germinating period of the plant, and the period of

most rapid growth being coincident in both. This kind

of adaptation is well illustrated by the life histories o-

294 THE AMERICAN NATURALIST [ Vou. XLII

Diabrotica longicornis and the corn plant. This beetle

lays its eggs in fall when the ear is maturing, and the

larve hatch in spring when the corn plant is young and

growing slowly, and they feed on the roots during the

entire growing season of the plant. It is evident that

such a well-adjusted insect will have an advantage, other

things being equal, over a poorly adjusted competitor for

food from the same plant, since it will be able, as a rule,

to leave a more vigorous and abundant progeny; and

similarly, any part of a species which, by aberration of

life history, may come to be poorly adjusted to its food

plant, will suffer as a consequence in comparison with

the normal members of the species, with the result that

these biographical characters of the insect will tend to

become permanent and characteristic in the same sense

in whieh its structural characters are.

It should be noticed, also, that such an adjustment is

an advantage to the host plant as well as to the dependent

insect, since it distributes the depredations of the latter in

a way to make them relatively slight when but little in-

jury can be borne, and concentrates them, on the other

hand, where the largest injury can be supported with the

least serious consequences. Such a well-adjusted insect

will get the maximum amount of food with the minimum

injury to the plant, and such a plant-insect pair will have

a competitive advantage over a poorly adjusted pair in

which a greater injury is done to the plant than is neces-

sary to the maintenance of the insect.

The same reasoning applies, and the same rule holds

good, for species with a more heterogeneous food, except

that in respect to them we must substitute for the single

plant the entire group of plants to which the insect resorts

for food. At this point, however, the facts become too

complicated for successful analysis, especially in view of

the difference of abundance from year to year of the

plants of a considerable list, and the effects, on the food

supply, of variable competitions among the various species

resorting to it. It may be said, in general terms, how-

No. 509] ECOLOGY OF INDIAN CORN PLANT 295

ever, that when the life history of a food plant, or the

common history of a group of such plants, exhibits suffi-

ciently constant characters to serve as an adaptive matrix,

an adaptation to it of the life history of those insects

strictly or mainly dependent on it for food is more or less

likely to follow.

MUTUAL BIOGRAPHICAL ADJUSTMENTS OF COMPETITORS

An example of the competitive relations into which corn

insects of widely different character, origin, habit and

life history may be brought by their dependence on the

same food plant may be found in Diabrotica longicornis

and Aphis maidiradicis. Both pass the winter as eggs in

the earth of the corn field, the aphis hatching sooner than

the root-worm, and developing two or more of its short-

lived generations before the Diabrotica larva is out of the

egg, gaining thus the advantage of an earlier attack in

greater numbers. It is also able to take much more

rapid possession of a field of corn because of its command

of the services of ants in finding its way to the roots of

the plants which the tiny and feeble Diabrotica larva

must search out for itself.

Later the root-aphis gives origin to young, many of

which acquire wings and may thus disperse as their local

attack upon the plant becomes unduly heavy, while the

root-worm must take its chances for the year in the field

where the eggs were left the previous fall. The aphis

feeds at first on the sap of young weeds common 1n spring

in all cultivated fields, and may thus save itself even

though the ground is planted to wheat or oats, an event

which causes the death by starvation of every root-worm

hatching from the egg. :

In respect to rate of multiplication, the root-aphis has,

of course, a truly enormous advantage as compared with

the corn root-worm, and yet, notwithstanding all these

facts favorable to the aphis, its injuries to corn m Illinois

are seemingly no greater than those done by the core

root.worm, This is due partly to the fact that, through

296 THE AMERICAN NATURALIST [ Vou. XLIII

the winged members of the early generations, the per-

centage of which increases as conditions become locally

less favorable, the aphis largely leaves the field in which

it originally started, and early breaks the force of its

attack by a general distribution of it. The depredations

of the root-worm, on the other hand, increase with the

growth of the insect until about September first, and in-

crease also, at a rapid rate, from year to year in a field

kept continuously in corn. It follows, as a consequence,

‘that the principal damage by Aphis maidiradicis is done

to the corn while it is young, and that by Diabrotica to

the well-grown plant.

This serial order of injuries to the corn plant, due to

the relation of the life histories and rates of multiplica-

tion of these two competing insects, is an advantage to

both of them, and, indeed, to all three, corn included, since

the plant would be more seriously injured or more cer-

tainly destroyed if both its insect enemies attacked it

together than it is where their attacks are made succes-

sively. Competitors for food from a living plant find

it to their advantage, and to that of the plant they feed

upon, to avoid a simultaneous competition; and such a

plant-insect group would, of course, prevail, other things

being equal, over a competing group not so adjusted.

Natural selection tends, no doubt, to establish these mu-

tually advantageous relations between a plant and its

constant insect visitants. With respect to these two corn

insects, however, it must be admitted that no proof is

apparent that such adaptation of life histories and habits

as we here see is due to anything more than an accidental

collocation of species whose significant peculiarities were

already established when they came together.

A similar but more striking example of a serial succes-

sion of injuries to the same plant is to be found among

the strawberry insects, as I showed several years ago.*

Three coleopterous larve belonging to the same family

°*¢On the Life Histories and Immature Stages of Three Eumolpini,’’

Psyche, Vol. 4, Nos. 117-118, January-February, 1884; and No. 121, May,

1884.

No. 509] ECOLOGY OF INDIAN CORN PLANT ', 207

(Chrysomelid) but to different genera (Colaspis, Graph-

ops and Typophorus), and to species native in the

United States, are all so closely adapted to underground

life and to the root-feeding habit that they are distin-

guishable from one another only by rather slight and in-

conspicuous characters. They are often associated in

large numbers in the same fields, living wholly on the roots

of strawberry plants, which they affect in an identical

manner, so that from the appearance of the injury itself

one could not possibly tell which of the three species was

present in the field. One of these root-worms, the

Colaspis larva, feeds also on the roots of other plants,

especially on those of timothy and corn, but the two other

larve have been found only among strawberry roots.

They seem thus to be strict competitors for food from

the same part of the same plant, and as their locomotive

capacity is poor, they are unable to avoid one another’s

company by migration under ground.

The strawberry plant, however, grows continuously

throughout the season, and each of these three insects,

having a short larval period, feeds on strawberry roots

for only a part of this growing season. It is an inter-

esting and striking fact that the life histories of the three

competing insects are so related that the larve do not

infest the plant at the same time, but follow one another

in close succession, beginning early in May and ending

late in the fall. The first of the species, the Colaspis

larva, feeds from about May, to the end of June, the

Typophorus larva follows in July and August, and the

Graphops larva begins in August and continues until fall.

Consistently with this difference, the species concerned

hibernate in different stages of development—Colaspis ap-

parently as an egg, Typophorus undoubtedly as an adult,

and Graphops as a larva in its subterranean cell, from

which adults emerge the following June to lay their eggs

in July. With such a distribution of their attack, each

of these three species is able to maintain itself on the

strawberry in numbers as large as would be possible for

298 THE AMERICAN NATURALIST [ Vou. XLIII

all three taken together if they made their assault on the

plant simultaneously. The advantage to both plant and

insects of this adjustment of life histories—if one may

call it suech—is obvious at once.

That some actual adjustment of larval periods has

here been made is rendered somewhat more probable by

the fact that a closely related species of Graphops which

infests the wild primrose (Œnothera biennis) in southern

Illinois, has a life history different from that of the

species which breeds in the strawberry—hibernating as

an adult, like Typophorus, and not as a larva, like the

strawberry species of its own genus.

MALADJUSTMENT OF COMPETITIONS

The corn plant is in greater danger from insect ravage

during the first month of its life than at any later time.

This is because it offers then a comparatively scanty

supply of food, so that a small number of insects may

work great destruction; because the single small plant

is much more easily killed than a larger one; and because

a larger number of active rival insects infest corn when

it is young than at any other time, some of them begin-

ning with the recently planted or just sprouting seed.

The young roots, the underground part of the stalk, the

stalk above ground, and the leaves, both before and after

they unfold, are all liable to infestation by several species

at the same time. The seed is injured by the wireworms,

the seed-maggot, the Sciara larva and the larva of

Systena blanda; the roots, by the wireworms, the root-

aphis, the corn root-worms, and the white-grubs; the stalk

under ground, by the wireworms, the root-aphis, the

southern corn root-worm, and the bill-bugs; the stalk

above ground, by the bill-bugs, the cutworms, the web-

worms, the stalk-borers, and the army-worm—sometimes

by the chinch-bug also; and the leaves, by the bill-bugs,

the web-worms, the cutworms, the army-worm and the

first generation of the ear-worm.

This concentration of injury upon the corn when it is

No. 509] ECOLOGY OF INDIAN CORN PLANT 299

young is a case of maladaptation, since the plant has

least to offer when it is most heavily drawn upon. -It

will be noticed, however, that this early spring attack is

mainly delivered by insects which come into corn from

some other vegetation, chiefly from grass, and whose oc-

currence in the corn field is searcely more than accidental.

The motive to an adjustment of habits and life histories to

the capacities of the plant is therefore virtually wanting,

and seems at any rate impossible, owing to the variability

and inconstaney of the several factors involved.

CONCLUSION

From the foregoing it will be seen that the corn plant

is not only an exotic in its origin, but that, aside from its

relation to man, it still remains an unnaturalized for-

eigner, not sufficiently adapted to our conditions to sur-

vive without the constant supervision of a guardian and

the services of a nurse. The corn field contains an arti-

ficial ‘‘association’’ persistently maintained by human

agency in the midst of a hostile environment, to which it

would promptly succumb if left to itself, and as such it

would seem to offer to the ecologist all the advantages of a

vast and long-continued experiment, by a study of whose

results he may learn something of the manner in which

ecological relations may be affected when a plant takes

advantage of a single favoring condition to push its way

into a territory foreign to its former habits.

This corn plant, at least, which has certainly lived in

our territory under the care of man for several centuries,

and perhaps for some millenniums, has even yet no

specialized friends active in its service, and no struc-

turally adapted enemies enlisted against it, such special-

izations of injurious relationship as one detects being

clearly due to other than structural differentiations.

During all this long period, it has been widely and

steadily forced into a strange ecological system which has

nevertheless scarcely yielded to it at any point. It has

produced, it is true, by its enormous multiplication and

300 THE AMERICAN NATURALIST [ Vou. XLII

extension, a profound effect on the numbers and distribu-

tion of some insect species, reducing the area of multipli-

cation for several, which, like the cutworms and the

army-worm, formerly bred in the turf of our native

prairies, but can not breed in fields of corn; and immensely

_ extending the range and increasing the number of others

which have found in this plant a better and far more

abundant food supply than that originally available to

them. Insect species which, like Diabrotica longicornis

and Aphis maidiradicis, were almost unknown fifty years

ago within our territory, have now, through their increase

in cornfields, arisen to the rank of dominant species.

But the few discernible insect adaptations to the offer-

ings of the corn plant are physiological, psychological,

synethic and biographical, and apparently not structural

at all. Slight and seemingly incipient as they are, we

have no sufficient reason to conclude that they are recent

results of the association of the corn plant with the in-

sect; both parties of the association may have been sub-

stantially what they now are when they first found each

other, and such mutual fitness as they exhibit may be

merely like that of angular stones shaken together in a

box until like surfaces seem to cohere, simply because

in this position the fragments can not readily be shaken

apart.

We may also derive, from this discussion, support for

the idea that adaptations of insects to their environment

are largely, and often primarily, psychological—that they

are often, in the first instance, specializations of prefer-

ence or choice, or, as we may perhaps more safely say,

of tropic reaction. Species which would otherwise com-

pete with each other, with disadvantageous consequences

to each, escape these disadvantages by acquiring, one or

both, different habits of reaction, under the influence of

which they separate, one going for its principal food to

the corn plant, for example, and the other continuing

on the strawberry, although structurally each remains

equally fit to feed on either. Physiological, or even struc-

No. 509] ECOLOGY OF INDIAN CORN PLANT 301

tural, adaptation may follow the psychological, but as

secondary to it. This is only saying in other words that

the central nervous system, on which special functioning

peculiarities of habit depend, is subject, like any other,

to adaptive variations, and that these variations may

either follow and reinforce those of some other organ

or organs tending to the same end, or that they may arise

independently of any other; and this is merely extending

to insects a generalization very obvious with respect to

man—finding warrant for the extension, as we do, in the

facts disclosed by an examination of the general economy

of insect life.

NOTES AND LITERATURE

BIOMETRICS

Some Recent Studies on Growth.—The problems presented by

the phenomena of growth change are not only peculiarly adapted

to quantitative treatment, but perhaps more obviously and

clearly demand the application of quantitative methods for their

solution than does any other single large class of biological

problems. In the study of variation and heredity it is an open

question as to what relative importance is to be assigned to quan-

titative as compared with qualitative differences between organ-

isms. But however much interest or significance qualitative

changes occurring in connection with the growth process may

have, it yet remains an indisputable fact that the fundamental

and essential feature of the process is a quantitative change.

While this has, of course, always been recognized by students of

the subject, there still is to be seen evidence of the influence of

the modern biometrie standpoint in recent studies in this field.

This is chiefly apparent in the increasing attention paid to pre-

cision and refinement in the mathematical methods used in the

analysis of the distinctively quantitative phases of the problems

of growth.

The most recent contribution in the series of memoirs by

Professor H. H. Donaldson! and his students dealing with vari-

ous phases of the problem of growth in the white rat is in some

respects to be regarded as the most fundamental which has yet

appeared. This paper gives in detail the basic data regarding

the growth of the body as a whole and of the central nervous

‘system in the white rat which have been collected in the course

of a very extensive and thorough investigation. These data are

given in a ‘‘general table’’ occupying thirteen pages and com-

prise records for 458 male and 215 female normal white rats.

For each of these animals (with the few omissions of single

measurements in scattered individuals unavoidable in so large

a piece of work) there are recorded the following data: Series

1 Donaldson, H. H. A Comparison of the Albino Rat with Man in

Respect to the Growth of the Brain and of the Spinal Cord. Journ. of

Comp. Neurol. and Psychol., o XVIII, pp. 345-392, Plates II and IIl,

1908.

302

No. 509] NOTES AND LITERATURE 303

number, sex, age in days, body weight, brain weight, and spinal

cord weight, each in grams. That the utmost care was taken to

ensure the accuracy of these weight records really does not need

saying in an American biological journal. The body weights

are recorded to a tenth of a gram, and the brain and cord

weights to a ten-thousandth of a gram. These unique data, in-

volving thirteen years in the collecting, constitute a scientific

achievement of much significance, not alone because of the in-

trinsic importance of the records for the study of growth prob-

lems, but also because they are a monumental example of biolog-

ical data collected with physico-chemical exactness. The paper

will stand as a classic in the literature on growth.

The first portion of the paper deals with the growth of the

rat’s brain. The brain-weight data are plotted to a base line of

body weight instead of to a base line of age and when so arranged

are graduated with a curve of the general type.

y=A-+C log («+ 8)

where y denotes brain weight, x body weight and A, C and £ are

constants.

The actual theoretical curve for the brain weight of the white

rat is as follows:

y = .569 log (x—8.7) + .554.

This curve gives a very excellent graduation of the observa-

tional data. In fact, a closer agreement between theory and

observation could not reasonably be expected. It is of some

interest to note that this curve which describes the growth of

the rat’s brain in weight is of the same general type which

has been found by Pearson and by the present writer to deseribe

growth changes in various organisms.’ It is all the time becom-

ing more evident that this type of curve is a very useful one

for growth work. Experience is showing that it undoubtedly

has a wide range of applicability in describing the quantitative

changes occurring in growth and various sorts of regulatory

phenomena. While this fact is empirically obvious, no ulterior

biological significance is to be attached to it. The biological

significance of this fact appears to the present writer to be of

the same kind as would attach to the discovery that some par-

ticular stain was useful for differentiating a wide range of cell

* Of., for example, the data regarding growth in the plant Ceratophyllum

presented in Carnegie Institution Publication No. 58. _ :

304 THE AMERICAN NATURALIST [ Vou. XLIII

structures, not before known to have anything in common.

Such a result might mean that these structures all had a common

cause or mode of origin, but to draw such a conclusion in the

absence of confirmatory evidence of another kind than that

afforded by the stain would be an exceedingly hazardous pro-

ceeding.

Donaldson points out that while the logarithmic curve

describes very well the growth of the brain for the whole period

from birth to maturity, the simpler relation proposed by Dubois,

according to which the brain weight increases as some simple

proportion (here the seventh root) of the body weight, fails to

do this, since it holds only for the later growth period of the

rat’s brain. It fails entirely to graduate the data during the

period of rapid growth.

The second portion of the paper deals with the growth of the

spinal cord. This again is found to follow a logarithmic curve

of the same general type as that which graduates the brain

growth data though, of course, with different values of the

several constants. Succeeding portions of the paper deal with

the growth of the entire central nervous system and with the

comparison of the growth of the brain in the rat and in man.

Limitations of space forbid a detailed discussion here of the

numerous significant results set forth in the paper. Certain

points of particular interest from the biometrie standpoint may,

however, be touched upon briefly. First with regard to the

correlation data, Donaldson finds that the weight of the brain

in the white rat is very closely correlated with body weight, the

coefficient of correlation between these two variables being

.76 + .01. This appears to indicate a very much closer relation-

hip in this organism than in man, though of course it must

always be remembered that the body weight data for man which

have been available for the study of this correlation are autopsy

records and therefore not too trustworthy. The correlation

found between brain weight and age is also very much higher

than the corresponding correlation in the case of man, the coeffi-

cient here being .52 + .03. The spinal cord weight is found to

be even more closely correlated with body weight than is brain

weight ; the coefficient being .86 + .01. Here there are no human

data available for comparison. The data presented also indi-

cate a very high degree of correlation between the weight of

the brain and the weight of the spinal cord. The coefficient of

No. 509] NOTES AND LITERATURE 205

correlation here is .88 + .01. All of these correlation coefficients

are positive.

The high values of these correlation coefficients for the rat

as compared with man suggest an interesting question: Are

we to conclude on the basis of these results (and similar ones

obtained by Kellicott from his study of the toad) that there is

a general tendency for the various parts of the body to be more

closely correlated in lower organisms than in man? In the

writer’s opinion such a conclusion is at present very doubtful

for two reasons. In the first place the human data on which

correlation studies have been made are meager and, from their

method of collection, not altogether trustworthy. In the second

place the coefficients of correlation published by Donaldson (the

same considerations hold with reference to Kellicott’s toad

data, though not to so great a degree relatively) probably have

spuriously high values. This arises from the fact that they

are deduced from material which is very heterogeneous in

respect to age. The biometrie constants for all characters which

change with age by growth will have their values affected in

such material. It is a well-known fact, of which the mathe-

matical proof was first given by Pearson, that heterogeneity of

material operates to increase apparent correlation. ‘To such

an extent may this occur that several sets of data, each of which

taken alone shows no correlation whatever between two charac-

ters, may when combined exhibit a high degree of correlation

between these characters. Such correlation obviously has little,

if any, biological significance. In the work here under dis-

cussion no account is taken of the possible effect in increasing

apparent correlation of the age (= growth) heterogeneity of

the material. It seems desirable if brain-weight (or other)

correlations are to have full significance for comparative pur-

poses, that they be based either on adult material in which all

growth changes have reached a minimum, or at least on material

which is homogeneous in respect to some definitely marked

period of the life cycle. :

A further point of less practical significance which is ap-

parently overlooked by Donaldson in his discussion of correla-

tion results is that in at least all of his cases in which the regres-

sion lines are plotted in the paper the correlation is markedly

skew. In such cases, of course, the correlation coefficient can

not be taken as the true measure of the actual correlation.

Instead, resort must be had to the correlation ratio (4). —

306 THE AMERICAN NATURALIST [ Von. XLIIL

The facts regarding the sex relations in the weight of the

central nervous system and its growth in the rat are very

interesting. Just as in man the brain of the male rat is abso-

lutely somewhat heavier than is that of the female rat of the

same body weight. The difference, however, is very small. It

is believed by Donaldson that this small difference which re-

mains in favor of the male in respect to brain weight is prob-

ably open to further reduction as other variables are taken into

account. In general the quantitative relations of the growth

of the central nervous system are found to be similar in man

and the white rat.

A paper with very much the same general standpoint as the

one just discussed has recently been published by Kellicott.’

The immediate problem with ne this paper has to do is

stated in the following words (p. 319):

We are led to inquire whether the normal growth of an animal may

not be actually a complex of growth cycles of component parts. It

is quite possible to examine this question from the morphological as

well as from the physiological side and the present paper represents

an attempt to discover whether the brain and viscera of the dogfish

grow similarly or in divefse ways as somewhat independent units of

growth.

The investigation is based on data obtained from a series of

315 dogfish (176 females, 139 males) ineluding specimens from

birth up to those of large size and presumably considerable age

(maximum weight observed 8,434 grams). On these fish the

weights of the following organs were determined: brain, heart,

rectal gland, pancreas, spleen, liver and gonad. In addition the

total body weight was determined in each case. The weighings

were made in all cases except body weight to hundredths of a

gram.

Since it was impossible to determine the exact age of the

specimens, the whole of the material is dealt with from the

standpoint of total body weight as a base. The author justifies

this procedure on two grounds, one necessity, and the other that

such factors as ‘‘food and temperature are known to be of more

importance than age in determining the size of fish.’’

The specimens studied do not represent a random sample of a

fish population, but were especially selected to get a represen-

* Kellicott, W. E. The Growth of the Brain and the Viscera in the

Smooth Dogfish (Mustelus canis Mitchell). American Journal of Anatomy,

Vol. VIII, pp. 319-353, plates 1-7, 1908.

No. 509] NOTES AND LITERATURE 307

tative size series. The data so obtained were plotted, each indi-

vidual being entered separately. Smooth curves were then de-

rived from these and the bulk of the paper is occupied with a

discussion of the facts brought out by these smoothed curves.

The only statement as to how the observational data were

smoothed is the following (pp. 322-323) :

The curves were derived from these records by calculating a series

of average weights of each organ in successive groups of individuals

and a line formed by connecting these averages was then smoothed to

a curve so as to reduce to a minimum the plus and minus deviations of

the averages. The groups from which the averages were derived varied

in extent from 100 to 1,000 grams in different regions of the entire

group, according to the rate at which the character of the curve was

changing.

From this the inference would appear to be that the smooth-

ing was done by a free-hand graphical process. If this infer-

ence is correct the logical justification of the procedure in the

present case is difficult to see. If the curves have enough in-

trinsic significance to warrant smoothing at all (as these for

the dogfish certainly do) it is hard to understand why the smooth-

ing should not be done by an accurate method. Of course cases

will arise in practical work where the points to be brought out

by data are not of sufficient importance to Warrant the labor

involved in graduating them accurately. But in the present

case the whole discussion centers about the forms and relation-

ships of the smoothed curves.

The point involved here is not a trivial or insignificant one.

Any one who has had experience in fitting parabolas and similar

curves to observational data knows what unexpected effects on

the general contour of a curve a few outlying points may have,

when the rigidly ‘‘ fair ’’ method of least squares is used in the

smoothing. The difficulty may be put in this way: in curves

of the sort dealt with by Kellicott the observations are very

scattering over a considerable part of the total range of the

curve. In many instances only two or three observations will

be averaged to get a point on the smooth curve. But surely it

can not be maintained that the average given by two individuals

will uniformly be the same as would appear if 25 individuals

were to be used. The two individuals may happen to be the

mediocre ones which will give nearly the true average; but on

the other hand they are not unlikely (as the right-hand ends of :

308 THE AMERICAN NATURALIST [Vor XLII

all of Kellicott’s curves except that for brain weight clearly

show) to be widely divergent from mediocrity. But the ‘‘free-

hand’’ method of smoothing assumes, actually if not intention-

ally, that the average based on two individuals is just as ‘‘right”’

(i. e., expressive of the true relationship which it is the purpose

of the investigation to discover) as is that based on 25. This

obvious error any adequate method of curve fitting will avoid.

- The bearing of these remarks further appears clearly in the

case of some of the relative curves, wherein the percentage which

the particular organ weight is of the total body weight is plotted.

As was to be expected from what is known of growth in man

the general trend of these percentage curves is downward.

While this is the general trend, several of the curves (e. g., the

heart curve, plate 2) show at the very beginning a slight rise to

a maximum and then the downward curve. It is plain from the

discussion that Kellicott considers the rise at the beginning of

these percentage curves to be a real and significant phenomenon

of growth. It is very doubtful, however, whether the data war-

rant such a conclusion. Before accepting it one would like to

see the measurements of a much larger number of very young

(i. e., just hatched) individuals added to the curves, and then

have a curve fitted by some adequate method to the observations.

The general result of this interesting and careful piece of

work is to show that the regression line of organ weight on body

weight in dogfish of different sizes is not of the some form for all

organs. Some organs (e. g., rectal gland, pancreas) show a

nearly linear increase in weight as the body increases in size;

others (e. g., the brain) show the logarithmic like curve which

one associates with growth curves. The author gives an inter-

esting discussion of the significance of the fact that the muscular

and skeletal tissues tend to ‘‘outgrow’’ their visceral accompani-

ments in forms of indeterminate growth like the dogfish. He

regards the condition of determinate growth seen in higher verte-

brates as ‘‘an adaptation on the part of the organism, such that

muscles and supporting tissues cease their growth at such a

point that brain and viscera remain ‘competent to maintain a

physiological balance.”

In passing it may be noted that Kellicott’s work, while itself

strictly morphological, suggests on every page problems for

experimental work on the physiology of the growth process. In

No. 509] NOTES AND LITERATURE 309

this connection a recent paper by Burnett‘ is of interest. This

paper, though not specifically concerned with growth problems

as such, brings out in a very clear way the marked differential

effect which may be produced on a single organ system (the

skeleton) by differences in the food of the growing animal.

Different foods, with all other conditions constant, led to an

average difference in the breaking strength for five bones of the

body of 356 pounds per 100 pounds body weight. The relative

magnitude of this difference is indicated by the fact that the

maximum observed average breaking strength was 681 pounds

per 100 pounds of body weight. This difference is brought about

not by an increase in the size of the bone as a whole, but by a

thickening of its walls. Burnett’s detailed results are well worth

careful study from the standpoint of experimental morphology.

A new and suggestive view in regard to the ultimate physiol-

ogy of the growth process has been put forth recently in two

papers by Robertson.’ In brief this view is stated by the author

in the following words (first paper, p. 612):

1. In any particular cycle of growth of an organism or of a partic-

ular tissue or organ of an organism the maximum increase in volume

or in weight in a unit of time oceurs when the total growth due to the

cycle is half completed.

2. Any particular cycle of growth obeys the formula log «/(A — z)

= K(t—t,) where x is the amount (in weight or volume) of growth

which has been attained at time ż, A is the total amount of growth

attained during the cycle, K is a constant and t, is the time at which

growth is half completed.

3. The above relations are such as would be expected to hold good

were growth the expression of an autocatalytic chemical reaction.

As I have pointed out in the introduction, cell-division has been shown

by Loeb to be the expression of an autocatalytie synthesis of nuclear

material. The fact that the above relations hold good shows that, in

all probability, sg gee or the synthesis of cytoplasm, is also an

autocatalytie reac

These conclusions, if well founded, are certainly of very

fundamental importance. It therefore seems desirable to ex-

t Burnett, E. A. The Efost of Food on tbe Proskag Sirens of

` Bones. ok 107, Nebr. Expt. Stat., pp. 11-39, 1908.

* Robertson, T. B. On the Normal Rate of Growth of an Individual and

its Biochemical Significance. Arch. f.. Entwicklungsmech., Bd. 25, pp. 581-

614, 1908. Further Remarks on to Normal Rate of Growth of an Indi-

vidual and its Biochemical Significance. Ph = we ae 108-118, 1908.

310 THE AMERICAN NATURALIST [ Vou. XLII

amine with some care the nature of the reasoning and the evi-

dence on which the conclusions rest. The first point in this

regard to be noted is the fundamental assumption made by the

theory that the growth process is in its quantitative relations

determinate either as a whole, or in its cyclical units. In the

fundamental formula quoted A is the total amount of growth

attained in the cycle. This means that unless there is assumed

to be an indefinitely large number of cycles of growth, there

comes a time for every organism to which the theory is to be

applied, after which no more growth occurs. Regarding this

fundamental assumption of Robertson’s theory Kellicott, whose

own researches particularly well fit him to speak with authority

on the point, has the following to say (loc. cit., p. 342) :

Observations of many of the lower vertebrates in nature (Fulton,

01, ’06) and in captivity, such as the giant salamander and some

reptiles, show that these grow indeterminately; Agassiz’s, ’57, observa-

tions upon Chrysemys are typical. As a recent example of the failure

to make this distinction we might mention the work of Robertson, ’08,

who has devised certain formule for the description of growth and has

brought out the very suggestive fact that the growth curve of an

organism or organ or tissue is similar to that given by an autoeatalytie

reaction. These formule hold good upon the assumption that the

organism or organ has a definite period of growth at the end of which

increase in size ceases. This is true for the higher vertebrates, but for

all the indeterminately growing forms we ean not determine any such

“final weight” of the body or organ upon which to base a formula.

We could not assume the maximum discovered size as the “ final weight ”

beeause this is subject to such extreme variation; in the dogfish, in-

cluding both sexes, we might find the “ final weight ” anywhere from

2,000 to 8,000 grams and even higher.

That this point has some force in limiting the field of applica-

tion of Robertson’s view can not be denied. It would still ap-

pear to be possible to apply the theory to lower vertebrates and

invertebrates, however, on the assumption that growth in those

cases consists of an indefinite number of cycles, to each one of

which separately the ‘‘law’’ applies. It remains to be investi-

gated as to whether the growth in such forms is, as a matter of

fact, definitely cyclical in character.

The general line of reasoning adopted by Robertson in de-

veloping his theory of growth is as follows: The starting point

is the idea advanced by Loeb ‘‘that the process of synthesis of

nuclein, which is the most salient phenomenon immediately suc-

No. 509] NOTES AND LITERATURE 311

ceeding fertilization, partakes of the characteristics of an auto-

catalyzed chemical reaction, since the velocity of the synthesis

inereases, during the initial stages of cell-division, in proportion

as nuclear material has already been synthesized.” He then

- raises the question as to whether the formation of fresh cytoplasm

during the growth of an organism may not also be an autocata-

lytic reaction. It is pointed out that:

The increase in weight or volume of an organism may not improbably

be regarded as equivalent to an increase of cytoplasm, and if both of

the processes concerned in growth, namely nuclear and cytoplasmic

synthesis, are autocatalytic in character the inerease in weight or

volume of an individual with increase of time should display the

chemical change and the time in an autocatalytie reaction.

This work of Peter is cited to show that the temperature-

coefficient of cell division and of growth is that of a chemical

reaction. Robertson’s own papers are solely concerned with the

presentation of evidence to show that growth curves of organisms

are of the same type as the curve of an autocatalytie reaction.

Various observations on the growth of certain animals, plants

and man are cited from the literature. To each group of these

data the theoretical curve of an autocatalytie reaction is fitted.

Theoretical and observational curves are then compared, and it

is maintained that the graduations obtained are good ones. The

agreement between observation and theory which is held to be

shown by these comparisons is the only new evidence presented

by Robertson in support of the conclusions quoted above.

The data presented in the papers may first be considered with

reference to the soundness of the contention on which the whole

reasoning ultimately rests: namely, that the theoretical curve for

an autocatalytic reaction actually does give a good fit for ob-

spondence between theory and observation is very far from

being sufficiently close to warrant the conclusion that such is

the case. To bring this point out in a concrete fashion let us

312 THE AMERICAN NATURALIST [ Vou. XLIII

examine some of the tables given. Table I of the first paper

(pp. 581-591) deals with Donaldson’s® data on the growth of the

male white rat in respect to body weight. In this table are given

the observed body weights for rats of different ages and the

calculated body weights according to the autocatalytiec growth

curve. In addition there is given a column showing the differ-

ences in grams between the observed and the calculated body

weights. Now it is a first principle of scientific curve fitting

(and on this point science and common sense are as usual in

agreement) that a curve which gives a good graduation of

observational data will fairly and equably distribute the errors.

That is to say, a theoretical curve if it is to be regarded as

fitting the data should strike through the observations in such

way that there will be on the average as many and as great

differences where theory is in excess of observation as there are

where it is in defect of observation. If a great majority of the

differences between theory and observation are in one direction

there is clearly a bias and the theoretical curve can not fairly

be said to be an adequate representation of the observations.

Now, let us examine the actual facts for Robertson ’s Table I. In

this table are included 63 separate observations or ordinates. In

one case out of the 63 the theoretical and the observed ordinate

exactly agree. Of the remaining 62 cases where theory and

observation can be compared the calculated ordinate is greater

than the observed in only 14. The observed ordinate is greater

than the calculated in 48 cases out of the 62. Furthermore, the

total deviation between observation and theory when theory is

greater than observation is 19.6, whereas when observation is

greater than theory the total deviation is 706.0! This certainly

does not look like a fair distribution of the errors when in 77

per cent. of the ordinates the theoretical curve lies always on

the same side of the observational line.

Let us turn to Table II. This table is exactly like Table I

except that it deals with Donaldson’s data for the growth of

female white rats in body weight, whereas Table I deals with

the males. In this table there are in all 50 ordinates. Of these

one again shows an exact agreement between observation and

theory. In 43 or 88 per cent. of the remaining 49 ordinates the

calculated value is less than the observed. Only in 6 eases is

the caleulated value greater than the observed! Practically the

° Boas Memorial Volume, New York, 1906.

No. 509] NOTES AND LITERATURE 3138

whole of the theoretical curve in this case lies on the same side

of the observed line. The sum total of the plus deviations

equals only 1.15, whereas the sum total of the minus deviations

equals 199.05!

Let us take still another example, this time from near the end

of the first paper. In Table IX (p. 610) are presented Donald-

son’s’ data regarding the growth of the brain in the frog and

the fitted curve. In this table are 21 ordinates available for the

comparison of theoretical curve and observational data. The

deviation between theory and observation is plus in 18 out of the

21 cases and minus in 3 cases only. Two ordinates (making with

the 21 the total of 23 tabled) show exact agreement between

theory and observation. In spite of this extraordinarily uneven

and biased distribution of the errors this statement follows

Table IX:

It is evident that the agreement between theory and observation is

excellent, such divergences as exist being evidently irregular and acci-

dental in their nature.

Surely a system of errors in which 86 per cent. are in excess

and only 14 per cent. are in defect and in which the mean per-

centage deviation per ordinate for the plus deviation is 8 per

cent. can not fairly be said to be ‘‘irregular and accidental’’ in

its nature.

Other examples showing the same thing might be cited from

the papers. The tables which have been chosen as illustrations

of the point under discussion have been taken in preference to

‘others for two reasons; one that they were long tables, involving

a fairly large number of ordinates, the other that the observa-

tional data in these tables were obtained by most careful and

painstaking measuring and are absolutely trustworthy. On such

data, if anywhere, a theoretical eurve may fairly be expected

to give good results.

To summarize this part of the discussion it may be said

that the discrepancies between observation and theory are so

Robertson’s ingenious, suggestive and potentially

hypothesis. It is possible that better values for the constants

of the theoretical curves might be found and in this way better

1 Jour. Comp. Neurol., Vol. VIII, 1898.

314 THE AMERICAN NATURALIST [Vou. XLII

agreement between theory and observation be obtained. Until

this is tried it would appear to be impossible to form any just

and significant estimation, on the basis of the only kind of evi-

dence which Robertson presents, namely, the comparison of

curves, as to the value of his theory as a general theory of

growth. On many general grounds the theory is particularly

suggestive. Can not evidence of another and more convincing

kind than that adduced in the present papers be brought for-

ward in its support?

The kind of evidence under discussion, when used for a pur-

pose like the present one, can at best have but inferential sig-

nificance; it can never be of demonstrative worth. It is based

on a process of reasoning which assumes a fundamental or

necessary relationship to exist between two sets of phenomena

because the same curve describes the quantitative relations of

both sets. A little consideration indicates that this method of

reasoning certainly can not be of general application, even though

we assume it to be correct in particular cases. The difficulty

arises from the fact that the mathematical functions commonly

used with adequate results in physical, chemical, biological and

mathematical investigations are comparatively few in number.

The literature of science shows nothing clearer than that the

same type of curve frequently serves to describe with complete

accuracy the quantitative relations of widely different natural

phenomena. As a consequence any proposition to conclude that

two sets of phenomena are causally or in any other way funda-

mentally related solely because they are described by the same

type of curve is of very doubtful validity. A few examples will

make clear the point here under discussion. ú

In a recent paper Armsby: shows that the rate of gain of

protein per thousand pounds live weight in growing animals

follows extremely closely the following curve: g = 135/ (a + 20),

where g is gain in protein per day per 1,000 lbs. live weight

and a is age in days. This curve, as his Fig. 1 clearly shows,

fits the observational data at hand remarkably well. This equa-

tion is the equation of a rectangular hyperbola. But it is a

well-known fact that the relation between degree of dissociation

and degree of dilution in dilute solutions is given by a hyper-

bola. Now in so far there would appear to be exactly the same

* Armsby, H. P. Feeding for Meat Production. Bureau of Animal

Industry, Bulletin 108, pp. 1-89, 1908.

No. 509] NOTES AND LITERATURE 315

kind of logical basis for the conclusion that since the same curve

describes the rate of protein gain in growing animals as de-

scribes dissociation phenomena, therefore rate of protein gain is

a dissociation phenomenon, as would exist for the conclusion that

growth is an autocatalytie reaction provided there were good

agreement between observed and theoretical curves in the latter

case. A point of difference in the two cases is that Robertson

presents several curves in support of his conclusion, whereas

Armsby gives but a single hyperbola. But even this difference

is in some degree offset by the fact that Armsby’s curve involves

growth data from four different animals collected by a number

of observers. But the most ardent advocate of the plan of

deducing fundamental relationships from similarity of curve

type would not maintain that the rate of protein gain in growing

animals is in any causal or fundamental way directly related

to the phenomenon of dissociation in dilute solutions.

Let us take still another case. One of the fundamental gas

laws is that the ‘‘pressure of any given mass of gas varies

directly as the absolute temperature if the volume of the gas

remains constant.’’ The mathematical expression of this rela-

tion is the equation of a straight line. Now Galton, Pearson and

their co-workers have shown, with a wealth of data drawn from

man and other organisms, that the regression of offspring on

parent in parental inheritance is a linear function. If the mean

conditions of a characteristic of the offspring of each group of

parents be plotted these plotted points will fall on a straight

line, within the errors of random sampling. This result rests

on a great mass of exact measurements. But of course no one

would attempt seriously to maintain that parental inheritance

and regression are phenomena of gas pressure.

The point which the writer would make is this: If there is

good evidence on other than quantitative grounds that two sets

of phenomena are qualitatively alike it is is pertinent and sig-

nificant to present as additional and confirmatory evidence data

tending to show that these sets of phenomena are similar in

their quantitative relations. But similarity of quantitative rela-

tions between phenomena can not safely be taken as proof (or,

in the absence of qualitative data sufficient alone practically

to establish the point, even as particularly weighty evidence)

of qualitative identity, because of the observed general lack of

uniqueness in the quantitative relations of natural phenomena.

316 THE AMERICAN NATURALIST [Von. XLIII

In a word the final proof of qualitative identity of phenomena

must always in last analysis be qualitative in its nature; quanti-

tative evidence in such cases can at best have but an inferential

confirmatory bearing on the qualitative point at issue.’

RAYMOND PEARL.

EXPERIMENTAL ZOOLOGY

Are the Drone Eggs of the Honey-Bee Fertilized? Cuénot’ has

put to the test once more Dzierzon’s famous theory in regard to

the nature of the drones of the hive bee. Dzierzon, as is well

known, furnished strong evidence in favor of the view that the

egg that produces a drone is not fertilized. An obvious test of

this view is found in crossing a virgin queen of one race by a

male of another race. All of her worker offspring should be

hybrids but her drone offspring should be purely maternal in

character. It is said that the failure of one such experiment

to give the expected results caused Dzerzon to abandon tempo-

rarily his theory. Other workers too have from time to time

found that the drones in such cases sometimes show hybrid

characters and this argument has been repeatedly urged against

Dzierzon’s theory despite the large amount of evidence of a

different kind to the contrary.

Cuénot crossed a virgin female of the black or Italian bee of

pure race with a ‘‘ yellow bee ”’ also of pure race. All the workers

produced showed the yellow bands of the yellow parent; some

300 drones were black like the mother, two only showed a large

yellow band at the top of the abdomen (recalling the more

numerous yellow bands of the yellow bee), and about a dozen —

other males also showed some yellow bands on the abdomen.

‘* Do those yellow bands indicate hybridization? °’ Such bands

were never found in the males of neighboring hives. The ex-

periment is inconclusive, Cuénot says, but it shows the necessity

of examining not only the purity of the pure races but also the

extent of their variation. The possibility that these few hybrid

males may have arisen from eggs laid by the hybrid workers is

not considered by Cuénot but until this possibility is also ex-

cluded the results can not be maintained to show the hybrid

nature of the drones except in the latter sense. If the males

° Cf. the discussion regarding the simple logarithmic growth curve on

p. 304, supra

*Cuénot, L. Comp. Rend. Soc. Biol., LX VT, 1909.

No. 509] NOTES AND LITERATURE 317

have arisen as here suggested from the eggs laid by the hybrid

workers the fewness of such individuals in comparison with the

large number of pure males is explained. On the other hand

the apparently well established view that drones come from un-

fertilized eggs does not exclude the possibility that fertilized

eggs might also under certain exceptional conditions produce

males.

T. H. MORGAN.

THE UPHOLDING OF DARWIN

Poulton and Plate on Evolution.—The boundary lines of political

geography are supposed to have no influence in determining scien-

tific beliefs. In science one is cosmopolite. But hedged in by a

nation’s boundaries is a people of one blood, men of a common

genealogy, and hence of some identity of hereditary endowment.

It may not be so easy, therefore, for an Englishman to be French

in scientific tenets as he may imagine. The coincidence that the

majority of conspicuous English biologists, such men as Wallace,

Galton, Lankester, Archdall Reid, Edward Poulton and others,

hold so strongly to the natural selection dogma, and, except for

the German founder of the school, are the most outspoken up-

holders of neo-Darwinism, may be indeed more than a coincidence.

It may be unconscious scientific patriotism. And so in France,

there is no question of the strong leaning of present-day French

biology toward Lamarckism. How much more pitiful, in the

light of this fact, let us add, seem the neglect and contempt of

the great French evolutionist in his lifetime by his Gallic

colleagues! But he has now his reward. Scientific patriotism

is bringing his name and his teaching to be the glory of French

biology. —

I would not press my theory too hard. As Weismann is the

founder of neo-Darwinism the Germans ought to be neo-Dar-

winists, but they mostly are not; and as Haeckel is a monist,

they ought mostly to be anti-dualists, but again they mostly

are not. Also, as America is more Anglo-Saxon than Latin,

we ought to be more Darwinian than Lamarckian, but we are

not. So my theory, like many another of even greater plausi-

bility, but ill stands hard wear. Even in England there are men

who see other factors in evolution than natural selection, and

to tell the truth these men in the minority are after all the truer

upholders of scientific patriotism, for like them Darwin also saw

318 THE AMERICAN NATURALIST [ Vou. XLIII

other agents than selection that made for modification and

descent. And so my theory, perhaps, wears quite through and

should go to the rag-bag.

The latest conspicuous exposition of the English neo-Darwin-

ian point of view is that embodied in Professor Poulton’s ** Es-

says on Evolution’’ (1908, Oxford). Not that the essays them-

selves are ‘‘latest,’’ for their various dates cover the decade

between 1896 and 1906, but they are put out now, with revisions

and some additions, as the expression of the diatinotiahed au-

thor’s present point of view. This is clearly and strongly that

of a neo-Darwinian, a thoroughgoing selectionist.

The most important and interesting parts of the book are

certainly those in which the author exposes the facts and theories

of insect mimicry and uses them for argument. These facts

and theories are not only the field in which Professor Poulton

is especially at home—a field, indeed, which he practically owns

—but are also the field in which lie some of the most potent

testimony for the deification of selection. Weismann and other

neo-Darwinians have never overlooked the stumbling block to

Lamarckians and orthogenesists that protective resemblance,

warning colors and mimicry constitute, but Professor Poulton

with his immense resources of personal knowledge in this field

makes to the same end, far more effective use of the facts. The

least pleasing and, for that matter, least profitable part of the

book to its readers is the polemic introduction, far too bitter and

parou, discussing Matata, Mendelism and natural selec-

tion.’’ It mars the book.

The essays cover a wide range of subjects: ‘‘The age of the

earth”; “‘the definition of species’’; ‘‘ Huxley and selection, ”’

in which is maintained the surprising thesis that the great

champion of Darwin ‘‘was at no time a convinced believer in

the theory he protected”’; ‘‘a remarkable anticipation of modern

views on evolution,’’ in which Weismann’s arguments against

the inheritance of acquired characters are shown to have been

in rather full measure advanced s James Cowles Prichard, the

“ines e e aa

the facts and theories of e extensively a mo

these in the last th A =i mimi. : Tha otpori

most fascinating ad de ae ee maet e pe :

we can have the snes ana E e w

promised more soe treatment

No. 509] NOTES AND LITERATURE 319

in a future book as the latest authoritative exposition of the

subject. The book is completed by an amazing analytical index

of eighty-three pages, one sixth of the whole book. No reviewer

will ever be able to taunt Professor Poulton with that too

familiar, ‘‘we regret to note the insufficiency of the index.”

Finally an entomologist may be pardoned for ‘‘ pointing with

pride,’’ in connection with this book to the splendid work for

evolution and general biology that the insects have achieved,

in the tireless and skillful hands of Professor Poulton. They

have painted a wonderful picture in colors of the possibilities

of adaptation and the marvelous capacity of selection—or some

other factor. For the moment selection has all the best of the

presumption, but this may depend in considerable measure on

its great good fortune in the strength of its champion. There is

certainly no gainsaying this strength. Professor Poluton, en-

trenched in his special field of insect bionomics, is perhaps the

most serious antagonist that the neo-Lamarckians have to face.

Of somewhat different point of view, and wholly different

type, is the other book of Darwinian upholding, which I have

at the moment under my eyes. In 1899 Ludwig Plate of the

Berlin Landwirthschaftliche Hochschule delivered an address

at the meeting of the Deutsche Zoologische Gesellschaft in Ham-

burg, which was printed in the proceedings of the society under

the title ‘‘Uber die Bedeutung des Darwin’schen Selections-

prinzips.’’ This address both as spoken and printed attracted

much attention and the demand for it induced Professor Plate

to expand and reprint it in book form in 1903. The admirable

comprehensiveness of the discussion in the new form still fur-

ther inereased the interest and demand, as a result of which we

have now a revised and still more expanded third edition of

nearly 500 pages (twice the size of the second edition) under

the title: ‘‘Selectionsprinzip und Probleme der Artbildung,’’

with the subtitle ‘‘Ein Handbuch des Darwinismus’’ (1908,

Engelmann, Leipzig). The author in the meantime has been

made a professor of zoology in the University of Berlin as well

as in the Landwirthschaftliche Hochschule.

Plate is an able friend and defender of selection, but his point

of view is not that of Poulton. The Englishman holds rigidly

to the neo-Darwinian anti-Lamarckism; the German takes the

real standpoint of Darwin, he calls on the inheritance of ac-

quired characters to aid selection in its evolutionary task. He

320 THE AMERICAN NATURALIST [ Von. XLIII

fights Weismanism in almost all of its aspects: panmixia, ger-

minal selection, Allmacht of selection. He resists also any

serious encroaching of the mutation theory in the province of

species-forming and adaptation. His detailed account and rea-

soned criticism of De Vries’s famous theory are admirable. :

Isolation, especially those forms of it which may be classified

under the general head of ‘‘Biologie isolation,’’ is treated in

extenso. In this connection Plate opposes those statements of

Wagner and D. S. Jordan, which claim that new species do not

arise, or do so only very rarely, in the same geographic range.

He refers to the hundred Gammarus species in Lake Baikal, the

numerous Cladoceran species of Bythotrephes in the Caspian

Sea, and the eighty or more chromid kinds in Lake Tanganyika,

as examples of nearly related forms that have long inhabited

the same limited region and yet among which evolution has

steadily gone forward. He discusses the old question of the

inheritance of acquired characters in a new way, and those

pages in which he explains and justifies his admission of the

logical necessity of such an inheritance to explain certain types

of adaptation constitute one of the most important parts of the

book. His treatment of the Darwinian theory of sexual selec-

tion and candid admission of its weaknesses is another ad-

mirable instance of the broad-mindedness of this Darwinian

champion. Finally his account of the objections to selection and

their refutation or recognition as partly valid is simply com-

plete, as is his consideration of the species-forming theories

auxiliary to selection.

But this fugue of praise grows monotonous, and yet it is hard

to introduce any new measure. Perhaps the sparse scattering

of pictures may be criticized as being far too meager if illustra-

tion was really needed, and easy reading of the text is a little

interfered with by the introduction of date and page references

into the lines; but these are trifles. The book is excellent ar-

ranged both for logical sequence of presentation and for easy

reference to any particular phase or topic of the wide subject

treated. Professor Plate’s acquaintanceship with the active

work now going on along the various lines of evolution study

and with the literature of the whole subject is manifestly nearly

exhaustive. It is especially pleasant to note his generous recog-

nition of American work.

YUK

Paris, March, 1909.

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THE

AMERICAN NATURALIST

Vout. XLII June, 1909 No. 510

HEREDITY AND VARIATION IN THE SIMPLEST

ORGANISMS?

PROFESSOR H. 8. JENNINGS

JOHNS HOPKINS UNIVERSITY

UNICELLULAR animals present all the problems of hered-

ity and variation in miniature. The struggle for ex-

istence in a fauna of untold thousands showing as much

variety of form and function as any higher group, works

itself out, with ultimate survival of the fittest, in a few

days under our eyes, in a finger bowl. For studying

heredity and variation we get a generation a day, and

we may keep unlimited numbers of pedigreed stock in a

watch glass that can be placed under the microscope.

Work in this field, so far as it has yet been carried, gives

in simple form results which are typical of the trend of

investigation over the entire subject; it gives a sort of

diagram of the main facts of heredity and variation.

For this reason it appears worth while to present here

the main results in their bearing on general questions.

Technical accounts of the investigations have been pub-

lished elsewhere,? but these are rather forbidding, owing

*A paper read before the Scientific Association of Johns Hopkins

University.

2 Jennings, H. S., ‘‘Heredity, Variation and Evolution in Protozoa.’’

I, ‘‘The Fate of New Structural Characters in Paramecium, with Special

Reference to the Question of the Inheritance of Acquired Characters in

Protozoa,’’ Journ. Exper. Zool., 5, 1908, 577-632. II, ‘‘ Heredity of Size

and Form in Paramecium, with Studies of Growth, Environmental Action

and Seleetion,’’ Proc. Amer. Philosophical Soc., 47, 1909,

321

322 THE AMERICAN NATURALIST [Vou. XLIII

to the mass of statistical data involved. For the evidence

of the statements here made the reader is referred to

these.

Unicellular organisms are essentially free germ cells

—germ cells that are subjected to the immediate action

of the environment, both direct and selective. For long

periods they propagate without that intercrossing which

so tremendously complicates the study of heredity in

higher animals. Here if anywhere we should see readily

the effects of environment and of selection in modifying

a race.

Let us look first at the direct action of the environ-

ment: the ‘‘inheritance of acquired characters.’’ It has

commonly been thought that under the conditions found

in these organisms ‘‘acquired characters’’ are readily in-

herited. This is because the progeny arise by division

of the parents; they are therefore the same as the parent.

It would seem a matter of course therefore that they

should have the same characteristics as the parent, how-

ever these characteristics arose.

But when we examine just what occurs in the produc-

tion of the new individuals, we find—as usually happens

when we look closely at biological processes—that the

thing is not so simple after all. We find that in repro-

duction the characteristic features of the parent disap-

pear? and are produced anew in the offspring. Thus in

Paramecium (Fig. 1) the characteristic form of the ends,

the oral groove, the shape of the body—these disappear

during fission, and reappear in the growth of the young.

In Stylonychia (Fig. 2) all the appendages are absorbed

at division; they appear anew in the young, in their

characteristic structure, number and distribution, by a

process comparable to the development of organs in a

higher animal.

3 Certain exceptions to this, of no theoretical importance, are mentioned

in the original papers. Certain characters sometimes pass directly to one

of the offspring, but their — is of course always by new

production.

No. 510] HEREDITY AND VARIATION 323:

Reproduction in these creatures may then be compared

to the dissolving of a crystal in its mother fluid; on re-

crystallization the new crystal appears with the same

form and angles as the parent. But it is really a new

on SSS

T ame

OD A aie

ee Se

Fig. 1. Changes in form shown by Paramecium during reproduction. a,

form of adult; b to e, successive stages of fission: f. g, immature young; h,

young after reaching adult form.

Fic. 2. Stylonychia, after Wallengren. a, adult, showing the appendages;

d, stage preparatory to fission. At # and y have appeared the beginnings of the

new sets of appendages of the two progeny to result from fission, after the

disappearance of the old appendages.

324 THE AMERICAN NATURALIST [Vou. XLIII

crystal, with new-formed angles. The analogy of repro-

duction with recrystallization is striking in many ways,

as we shall see farther. -

Thus inheritance is, here as elsewhere, not transmis-

sion but new production. The question of heredity then

is: What characters will thus be produced anew? Will

the progeny reproduce any character that the parent

happens to have?

When we study the matter in such an organism as

Paramecium (Fig. 1), we find that all the characters

common to the race—the ‘‘ normal’’ characters—are

regularly reproduced. But how about characters that are

not typical; characters that have been produced in the

individual parent by the environment; ‘‘abnormal’’ char-

acters, and the like? It is easy to produce such new

characters by environmental action, and it is easy to

find in certain cultures individuals that present unusual

features. Specimens with altered form, with new ap-

pendages, with differently arranged parts, are not very

rare. Many of those found in natural cultures corre-

spond in appearance to what we might expect of a mu-

tation.

Will such untypical characters reappear in the progeny,

so that we shall get a race with the new characteristic?

Examination of a large number of cases in Paramecium

shows that these untypical characters are never repro-

duced in the young. Sometimes such a thing as an

appendage may pass bodily to one of the progeny, just

as a parasite clinging to the outer surface might do; but

there is no multiplication of such a character; no tend-

ency to produce a race bearing it. The young reappear

in the form typical for the race, without regard to the

individual peculiarities of the parent.

What is produced in the new generation therefore de-

pends on the fundamental constitution of the race, not on

the accidental form of the parent. Again the analogy

For many examples of this, with figures, see the first of the papers

‘already referred to.

No. 510] HEREDITY AND VARIATION 325

with crystallization forces itself on us. The character-

istic form of crystals is easily changed; by filing off the

angles we might convert a large number of pyramidal

crystals into the quite new form of cubes. But if we

dissolve these and allow them to recrystallize, we obtain,

not cubes, like the parents, but the original crystalline

form characteristic for that particular chemical com-

pound.

If we should modify the chemical constitution of the

substance, it would then crystallize in new shapes. If

we could modify the fundamental constitution of the

organism we should probably find it likewise appearing

in new forms. Whether this occurs at times in uni-

cellular organisms we shall ask later. But it is im-

portant to grasp the fact that it does not occur often nor

easily; that the ordinary activities of life do not ob-

servably bring it about; that the mere presence of a new

character in the parent has no evident tendency to pro-

duce such a result. Many of the untypical forms found

in Paramecium were such as one might imagine due to

an alteration in the fundamental constitution of the race

(a mutation?), but the new characteristic was not repro-

duced in the progeny.

But besides the untypical or ‘‘abnormal’’ characters of

certain individuals, there are the common differences

among individuals that are fully ‘‘normal.’’ In the Pro-

tozoa, as in all organisms, differences in size and propor-

tion among differing individuals are common; variation

is the rule here as everywhere. We must then examine

these differences, under the question already set forth:

What characters are produced anew in reproduction?

Will the progeny produce anew these diversities of the

parents, in such a way that from large parents arise large

progeny, from small parents small progeny, from inter-

mediate parents intermediate progeny? |

In Paramecium we find individuals differing greatly in

size. From a ‘‘wild’’ lot of Paramecia we isolate such

differing individuals and propagate from them, all under

326 THE AMERICAN NATURALIST (VoL. XLIII

the same conditions. We find that many of these differ-

ences are inherited; from large individuals we get large

races; from small individuals small ones. We find, then,

that Paramecium consists of many races, differing from

each other in mean size slightly but constantly. Eight of

these different races were isolated and propagated for

hundreds of generations; some were carried through sev-

eral complete ‘‘life cycles.’? Each such race consisted

of specimens all derived from a single parent individual.

Unquestionably many other races exist, that could be

isolated by proper means.

206 200 194 176 142 125 100

Fic. 3. Diagram showing the relative mean lengths of the eight different

races of Paramecium*that were isolated. The magnification is about 340 diam-

eters. The actual mean length of each race is given in microns below the cor-

responding outline.

Fig. 3 is a diagram showing the relative mean lengths

of the eight races isolated, as determined by measuring

at intervals lots of 100 or more individuals of each race.

The mean length for any race is constant under given

conditions. The differences between adjacent races are

very slight ; thus, between the races c and i of the diagram

the difference in mean length was but five to seven

microns or .00028 inch. For measuring such constant

differences between races even the ‘fourth decimal place

of the biometrician,’’ so heavily contemned of late, would

Seem to be required. This gives us something of a

measure of the minuteness of the steps by which evolu-

No. 510] HEREDITY AND VARIATION 327

tion may occur, if we hold that one of these races has

arisen from another.

We find then that by selection we can isolate many

races of different mean size, and that the relative mean

size is inherited in each race.

But another fact of equal importance comes forth.

Within each race (derived from a single parent) the size

of the different component individuals varies extremely.

The.largest specimens of a given race are more than twice

as long as the smallest specimens, and every intermediate

dimension occurs. We may therefore represent the com-

position of a single race by the diagram of Fig. 4. These

Fic. 4. Diagram of a single race, showing the variations in the size of the

individuals, The race represented is D of Fig. 3, and the magnification is the

same as in Fig. 3 (340 diameters). The individuals vary from 80 to 256 microns

in length.

differences in size are due to growth, to amount of nutri-

tion, and to other environmental conditions; a detailed

analysis of the action of these factors is given in the

second of the two papers above referred to.

Now we come to the most important point. Are the

varying sizes within the single race inherited? Will

large specimens produce large progeny, small ones small

progeny, so that from a single race we can get several,

of differing sizes? And can we by repeated selections of

328 THE AMERICAN NATURALIST [Vou. XLIII

the largest individuals for breeding steadily increase the

mean size of a race?

Breeding from the extreme specimens—the largest and

smallest—of a single race, we get several hundred indi-

viduals from each. Both produce progeny of the same

mean size. Each produces a whole series of varying in-

dividuals, just like the original racial series (Fig. 4);

the series produced by the largest individual is exactly

like that produced by the smallest, or by any other. The

differences between the individuals within such a series

are due to growth and environment. Such differences

are not inherited: the race breeds true, without regard

to the peculiarities of the individual parent. A great

number of such breeding experiments were carried out,

in which selection was continued for many generations,

but the results were invariably the same. Selection

within the pure race is of no effect on the size.

Furthermore, marked differences in the parents due to

different environments become quickly equalized in the

progeny when the environments are made the same.

Thus environmental effects are not inherited. Neither

selection nor environmental action changes the size of the

pure race.

Thus in our study of the ‘‘normal’’ variations we come

to the same result as in our previous study of abnor-

malities, new characters, apparent mutations, and the

like. What is produced in inheritance depends, not on

the evident external features of the parent cell, but on

the fundamental constitution of the race. Each race has

its own peculiar constitution, and under different condi-

tions this same constitution gives rise to various sizes and

forms, producing thus the variations within a race, illus-

trated in Fig. 4. But all these different individuals of

a race are potentially the same; at the same age and under

the same conditions throughout, all would be alike.

Now consider again the species as a whole: in this

No. 510] HEREDITY AND VARIATION 329

case Paramecium (aurelia or caudatum or both)’ We

have found it made up in the way indicated in Fig. 5. It

consists of a series of many races, differing in mean size;

while each race is made up of a series of individuals,

210

(yqagusee i nayanoes

Nhe pm 990000

sia 4.400600

POUONO OUA,

> MANO Higagadssss

: DO

OLLA

l pooto

. 5. Diagram of the species of Paramecium, as made ed a e y

different races of Fig. 3. Each horizontal row represents a

individual showing the mean size in each race is indicated pa a Vs ep Sp

above it. The mean of the entire lot is shown at æ@-v. The numbers show the

measurements in microns. The magnification is about 43 diameters.

that are of varying size, though potentially alike. Refer-

ence to this diagram will help to understand certain

fundamental facts of variation, heredity and the effects

of selection in these organisms.

5 For a discussion of the species question in Paramecium see the second

of the original papers, pp. 498-500.

330 THE AMERICAN NATURALIST [Vou. XLII

As the diagram shows, individuals of the same size are

found in many different races. An individual of the size

shown at a might belong to any one of the eight races.

Thus from individuals of the same size we may get many

different results in breeding. Similarly, individuals of

very different size (as the extremes of any horizontal

series) may produce progeny of identically the same char-

acter. We can not tell by its external characters to what

race a specimen belongs; breeding is the only test. In

higher organisms, as is well known, we often find a sim-

ilar state of affairs.

How will selection act on such a complex species?’ As

we have seen, selection within a single race is without

effect. But if we make selections among the individuals

of a mixed collection of races, such as Fig. 5 shows, we

reach most instructive results. By making our selections

in the proper way, we for a time make steady progress

toward a certain goal. We will suppose that we do not

know of the existence of these races; this is the case with

most experiments in selection. From the species as a

whole, as shown in Fig. 5, we will select for increased

size. Let us follow the old plan of selecting many indi-

viduals showing the desired character; we will preserve

all specimens above the mean size of the entire collection.

That is, we divide the collection at x — x rejecting all

those to the right. By so doing it is evident that we

exclude all specimens of the two smallest races c and i,

while preserving the majority of the specimens of the ~

larger races. Allowing these to propagate, we of course

get a mixture of the remaining larger races; hence the

mean size of the whole collection will be greater than at

first. Selecting again those above the mean size of this

lot, we drop out another small race, and the mean of the

collection as a whole again rises a little. We are making

good progress in the improvement of our species. By

taking successive steps of this character, dropping out

the smaller races, first partly, then completely, one after

another, we can for a long time continue to improve by

No. 510] HEREDITY AND VARIATION 331

selection. But finally we reach a stage in which all but

the largest race have been excluded. Thereafter we can

make no farther progress. In vain we choose for breed-

ing the largest specimens of the lot; all belong to the same

race, so that all. produce the same progeny. Selection

has come to the end of its action.

It is well known that this is a course of events com-

monly observed in selective breeding. Improvement oc-

curs for a time, then stops. We might have produced

the final result at once, in our infusoria, by merely isolat-

ing at the first selection the largest individual of the

entire lot; its progeny would have produced at once a

pure race of the largest size attainable. Selection here

consists simply in isolating already existing races; it

produces nothing new.

Thus the facts in Paramecium furnish an excellent

illustration, in the simplest possible form, of the prin-

ciples of breeding for improvement so convincingly set

forth in de Vries’s recent work on plant breeding, and in

his other writings.

It is well known that in inheritance extremely marked

parental characters appear less marked in the progeny;

the progeny of extreme parents are on the whole nearer

the mean than were the parents. This fact is spoken of

as regression. The reason for this is clear in such a

collection as Fig. 5. Suppose we breed from the very

largest specimens of the entire collection. These are the

largest individuals of the largest race. They produce,

as we have seen, like any other specimens of that race,

progeny of merely the mean size for that race. The

progeny will then of course be on the average smaller

than their parents, but they will be above the mean size

of the species as a whole, since they belong to the largest

race. Thus ‘‘regression is not complete’’; the progeny

diverge from the parents toward the general mean of the

species, but do not reach it. If however we consider a

single pure race alone (Fig. 4), and breed from the ex-

332 THE AMERICAN NATURALIST [Vou. XLII

tremes, then ‘‘regression is complete,’’ since the progeny

are of the mean size for the race as a whole.

Work with ‘‘pure lines’’—where no intercrossing of

races or individuals occurs—is possible with but few or-

ganisms, and little of it has been done. In the few in-

vestigations carried on in this way, the same conditions

have been found that we have set forth above for Para-

mecium. They were first shown by Johannsen® to hold

for beans and barley, and later by Elise Hanel for Hydra.’

The fact that there exist diverse races, tending to breed

true, has of course been shown for many species, but in

most cases it is difficult to maintain pure lines, and thus

to absolutely demonstrate the relations above set forth,

as has been done for beans, barley, Hydra and Para-

mecium. In the Protozoa it has of course been possible

to carry the work through an immensely greater number

of generations than in many celled organisms. The ex-

tremely important work of Barber® has shown the same

condition of affairs to exist in yeast and bacteria, though

with certain additional factors to be mentioned later.

When we deal with organisms that continually inter-

cross, the conditions of course become immensely com-

plex. Each individual represents, as it were, many

diverse lines, whose appearance and disappearance in the

hide-and-seek way characteristic of Mendelian inheri-

tance makes interpretation extremely difficult. There is

not wanting evidence that the same principles are at work

even here; that the results of the study of ‘‘pure lines”?

give the clue by the aid of which the more complex re-

sults of selection in biparental inheritance may be un-

raveled. If this is the case, then selection would act even

here also by isolating diversities that already exist, not

by producing diversities. There are of course some not

J Meens ei ‘‘ Erblichkeit in Populationen und in reinen Linien,’’

68 pp., Jena,

* Hanel, Sya ‘ating bei ungeschlechtlicher Fortpflanzung von

Hydra grisea,’’ Jenaische Zeitschr., 43, 1907, pp. 321-372.

* Barber, M. A., ‘‘On Heredity in Certain Micro- cece ’ The Kansas

University ERER Bulletin, 4, 1907, 1-48, pl. 1-4

No. 510] HEREDITY AND VARIATION 333

yet thoroughly analyzed facts that are difficult to inter-

pret on this basis, so that its general adequacy remains

to be determined.

The work with Protozoa emphasizes further certain

important points regarding variations. The interest of

studies in variation lies mainly in the assumption that the

variations are heritable, supplying material for selection

and evolution; this assumption is openly or tacitly made

in most work on the subject. Yet when we actually de-

termine how far this is true, we find (as we have seen)

that in a pure race of infusoria all the differences be-

tween individuals are environmental and without signifi-

cance in inheritance. If we study these variations by

biometric methods and laboriously work out numerical

coefficients of variation (as the author has done on a large

scale in his original paper) we acquire data which are

perhaps not without some sort of interest, but which have

no bearing on inheritance or selection or evolution. The

‘‘standard deviation’’ and ‘‘coefficient of variation’’ ex-

press in a pure race mere temporary conditions, of no con-

sequence in heredity. If we could make all conditions

of growth and environment the same throughout our pure

race, all the evidence indicates that the standard deviation

and coefficient of variation would be zero, and this is the

positive value of their assistance in determining what

shall be the characteristics of the progeny.

Even when we deal with mixtures of diverse races the

coefficient of variation is, as a rule, mainly determined by

differences due to growth and environment. ‘‘Wild’’

cultures of Paramecium, consisting of many races, may

not give higher coefficients of variation than those ob-

tained from pure races. The coefficient of variation is

then by no means an index to the permanent heritable dif-

ferentiations in a collection; its value may be high when

there are no such differentiations, or low when such dif-

ferentiations exist. The important question for all such

work is: What diversities are heritable, what are not?

This is an experimental question, and the réle of statis-

334 THE AMERICAN NATURALIST [Vor. XLIII

ties in answering it is a most subordinate one. When an

author deals in standard deviations and coefficients of

variation, the first question the reader should ask is: Has

the author determined what part of the diversities thus

measured have any bearing on heredity? They may have

absolutely none.

Thus the mere fact that observable variations exist

between individuals can not properly be appealed to as

furnishing material for selection and evolution, as has

been so generally done. Most such variations have in the

organisms studied absolutely no bearing on the evolu-

tionary process, and there seems little doubt but that this

is true for organisms in general.

Tilustrations of the practical bearing of these points

may be found without departing from the particular or-

ganism with which we are dealing. It has been shown

that the two products of the division of a single individual

Paramecium often differ in size at a given time, so that

‘‘variation’’ occurs in non-sexual as well as in sexual

reproduction.® But these ‘‘variations’’ are mere tempo-

rary fluctuations, without effect in heredity, so that their

relation to evolution is nil. Again, Pearl showed that

conjugants are less variable than non-conjugants. This

is true even within the limits of a single race, as I can con-

firm from extensive studies. But all the variations in

such a ease, both in the conjugants and non-conjugants,

are purely temporary matters, without effect on poster-

ity; so far as evolution or heredity or selection goes they

can be left quite out of account."

Comparative studies have often been made of the varia-

bility of higher animals under different methods of re-

production, under different conditions, etc.; the varia-

? Simpson, J. Y., ‘‘The Relation of Binary Fission to Variation,’’

Biometrika, 1, 1902, 400-404. Pearson, K., ‘‘ Note on Dr. Simpson’s Memoir

on Paramecium oe: et Sica, 1, 1902, 404-407.

* Pearl, R., ‘‘A Biometrical Study of Conjugation in Paramecium,”’

Biometrika, 5, ’1907, 213-297.

Thi course is no criticism of Pearl’s paper, which is one of the

foundational ones for this line of work. When different races are present,

the less variability of the conjugants is of the greatest significance.

No. 510] HEREDITY AND VARIATION . 836

bility of parthenogenetic generations has been compared

with that of sexual generations, and the like. These have

no meaning for evolutionary questions unless we know

whether any of the diversities are heritable. In general,

it would appear that most observed variations are not

heritable.

Perhaps more important even than the distinction be-

tween temporary modifications and really heritable dif-

ferences is another point regarding ‘‘variations.’’ Even

leaving aside the temporary modifications, much discus-

sion of variation assumes that the word implies an

actual change from one condition to another. This is

obviously a very different matter from mere observance

of two different conditions in different individuals. If

our object is to discover how far we have actually ob-

served evolution taking place, the distinction between

variation as an active change and variation as an exist-

ing condition (of permanent differentiation between two

races) is absolutely fundamental. Evidently, observa-

tion of the mere fact that permanent differentiations exist

between races is a totally different matter from observa-

tion of the changes by which evolution occurs; it is com-

patible with almost any theory of the origin of diversities;

for example, with that of special creation. As a matter

of fact, do we find the existing races changing or perma-

nent? What light does our study of variations throw on

this?

In Paramecium, in the extensive study of many races

for hundreds of generations by exact statistical and ex-

perimental methods, not one single instance was observed

of variation in the sense of an actual change in a race. In

the detailed paper, coefficients of variation are given al-

most by the hundred, and permanent diversities of race

are registered minutely and in numbers. But these mean

nothing so far as real change in any race is concerned.

So far as the evidence goes, every race was essentially

the same throughout the work, and may have been the

same for unnumbered -a before.

336 THE AMERICAN NATURALIST [Vou. XLIII

For clear thinking it is of the greatest importance to

distinguish variation as a process from variation as an

existing static condition of diversity. If this distinction

is not made, we may delude ourselves into thinking we

have seen evolution occurring, when all we have seen is

the complexity that induces us to invent the theory of

evolution. The difference is just the difference between

seeing a problem, and seeing its solution; between asking

a question and answering it.

But is there indeed no evidence that actual racial

changes occur in unicellular forms? On this point we have

the extremely important work of Barber.11 Barber was

the first to undertake in bacteria and yeasts the study of

‘pure lines’’—of races derived entirely from a single

individual. In general his results were the same as those

set forth above for Paramecium. Many races of yeasts

and bacteria exist, and these races are constant (with the

exceptions to be noted). Environmental effects were not

inherited, and long continued selection was of no effect in

changing such a race. Barber studied also unusual indi-

viduals; he found, just as I have set forth above for Para-

meicum, that their peculiarities were, as a rule, not in-

herited. But he did find a few cases of peculiar individ-

uals within a pure race, that transmitted their peculiari-

ties to their descendants. Here we have then actual

changes in a race; variations in the dynamic sense. In

this way there were produced races of yeasts having cells

of a different form; races of bacteria composed of longer

rods than the parents. But such cases were extremely

rare. Variations that perpetuate themselves were found

only in one individual among thousands. Barber’s work

goes as strongly as my own against the significance of the

common variations among individuals—such variations

as are measured by the coefficient of variation—for hered-

ity or evolution.

To recapitulate, we find that the unicellular organisms

are made up of numerous races, differing minutely but

n Loe. cit.

No. 510] HEREDITY AND VARIATION 337

constantly. The individuals of any race vary much

among themselves, but these differences are matters of

growth and environment, and are not inherited. What

is produced in reproduction depends on the fundamental

constitution of the race, not on the peculiarities of the

individual parent. The fundamental constitution of the

race is resistant to all sorts of influences; it changes only

in excessively rare instances, and for unknown causes;

in a study of thousands of individuals of Paramecium,

through hundreds of generations, hardly a single case

of such change was observed.!? Most differences be-

tween individuals are purely temporary and without sig-

nificance in inheritance; the others are permanent diver-

sities between constant races. Systematic and continued

selection is without effect in a pure race, and in a mixture

of races its effect consists in isolating the existing races,

not in producing anything new.

To give in brief an account of the general results of

extensive work, it is necessary to make definite state-

ments, and to omit conditions, exceptions and qualifica-

tions. This the reader is asked to remember; the details

may be found in the original papers. The results are

based on study and measurements of more than 10,000

individuals of Paramecium, kept under experimental con-

ditions for many generations. But science is essentially

incomplete and its results at any time are not final. The

author expects to make strenuous attempts to overthrow

the generality of some of the results set forth.

12 A single doubtful case is described in the first of the author’s two

papers: certain individuals of a race acquired a hereditary tendency to

remain united after fission, while others did not show this tendency, or

showed it less strongly.

THE COLOR SENSE OF THE HONEY-BEE: IS

CONSPICUOUSNESS AN ADVANTAGE TO

FLOWERS?

JOHN H. LOVELL

In 1895, Professor Felix Plateau, of the University of

Ghent, began the publication of a long series of papers,

in which he asserted that Hermann Miiller, in formula-

ting his theory of the evolution and use of floral colors,

had been misled by a too vivid imagination; and that an-

thophilous insects are attracted chiefly by odor. Ina list

of his papers prepared by himself and now before me

Plateau states that his latest contribution, entitled Les

insects et la couleur des fleurs,! contains a ‘‘summary of

the whole.’’ The conclusions of many years of patient

research are given at the close of this paper as follows:

“ In the relations between the insect fertilizers and entomophilous

flowers, the more or less bright coloration of the floral organs has not

the preponderating rôle which Sprengel, H. Müller and their numerous

adherents have attributed to them. All the flowers in nature might

be as green as the leaves without their fertilization being compromised.

The sense of smell so well developed among most insects far from being

a secondary factor is probably the principal sense which discovers to

them the flowers containing pollen and nectar.”

_ By fertilization Plateau doubtless means pollination,

for fertilization is an entirely distinct phenomenon, often

not occurring until many months after the pollen has been

placed upon the stigma. Plateau’s conclusions have not

met with general acceptance; and in some instances, as

he himself naively remarks, have been criticized in a

‘‘ merciless manner.’’

Florecology is, however, greatly indebted to him not

only for many very interesting observations and experi-

Plateau, F. Les insects et la couleur des fleurs. L’Année Psy-

PRR 13, 67-79, 1907.

338

No. 510] COLOR SENSE OF THE HONEY-BEE 339

ments, but also for insisting that the whole subject of the

relations of insects to the colors of flowers should be re- .

examined and tested experimentally. With the exception

of the criticisms of Bonnier, in 1879, Miiller’s doctrine

had remained unquestioned, for no other theory of the

significance of brilliant floral leaves is so satisfactory as

that they serve as signals or flags to attract the attention

of anthophilous visitors. It is well to recall that the

great authority, which has been attached to the name of

Müller, rests on innumerable observations and collections, —

which were continued up to the morning of his sudden

death from a pulmonary complaint while studying the

flowers of the Tyrol. He is still justly regarded as the

foremost of floreecologists. Says his biographer Ludwig:

“ He is not dead, he lives and will live so long as a flower enraptures

the eye of an investigator. His bright spirit will live on and, we hope,

like that of his teacher and friend Darwin long be a light on the way

to truth in the heart of nature.”

Plateau’s first paper dealt chiefly with the concealment

of the flowers of the dahlia with green leaves; and his

second, which appeared in the following year, with the

removal of petals. In the last-named communication he

describes how he removed the larger part of the corolla

of Digitalis purpurea, Lobelia erinus, Enothera biennis,

Ipomea purpurea, Delphinium ajacis, and Antirrhinum

majus; and with the exception of A. majus found that the

inconspicuous stumps were visited by insects almost as

frequently as the unmutilated flowers. He, therefore,

concluded that neither the color nor the form was im-

portant, and that insects were attracted by the fragrance

alone. I shall again refer to these experiments after

relating my own, which gave very decisive results dia-

metrically opposed to those of Plateau.

? Ludwig, F. Das Leben und Wirken Professor Dr. Hermann Miiller’s.

Botanisches Centralblatt, 17, 404, 1884.

3 Plateau, F. Comment les fleurs attirent les insects, II. Bul. Acad.

roy., Bruxelles, 32, 504-34, 1896. I have not been able to obtain this paper,

the reprints bitig exhausted. The experiments are described, tly

with sufficient detail, in Knuth’s Handbook of Flower Pollination, and it

is upon this account that I have depended.

340 THE AMERICAN NATURALIST [Vor. XLII

To determine the influence of the petals of the common

pear, Pyrus communis, upon the visits of the honey-bee,

Apis mellifera L., a medium-sized tree in full bloom was

selected for observation. The day was clear, warm and

calm, the bees were numerous and no other insects were

present.

A cluster of seven blossoms near the end of a branch

was watched for fifteen minutes and received eight visits

of the honeybee. The petals were now all removed and

it was observed for a second quarter of an hour. Though

a number of bees flew near by, it received not a single

visit. During a third fifteen minutes there were two

visits, due in part to association, for the bees came from

other blossoms on the same tree, which had proved the

first source of attraction.

Two other clusters of flowers, growing side by side but

nearer the bole of the tree, consisting each of eight

flowers, were observed for fifteen minutes and sixteen

separate visits of the honeybee were noted The petals

of one of these clusters were now removed. During

fifteen minutes the adjacent cluster, which still retained

its petals, received eleven visits, while not one was made

to the cluster without petals. In one instance a bee

hovered over it but did not alight.

These results were much more conclusive than I had

expected; for, in the second experience, it might have been

supposed that the odor exhaled by the evaporating nectar

of the denuded blossoms would have attracted the bees,

which were only an inch or two distant; but their move-

ments were evidently determined almost entirely by the

presence of the petals.

On a warm pleasant morning in August at 11:30 o’clock,

(am., I selected for experiment two groups of flowers

belonging to Borago officinalis, or the common borage.

They were distant apart about six inches; one contained

five flowers; the other, which was at a little higher eleva-

tion, contained four flowers. They were both watched

for ten minutes. The first received fifteen visits from

No. 510] COLOR SENSE OF THE HONEY-BEE 341

the honey-bee, the second thirteen visits. The location of

my apiary not far away furnished a large and continuous

supply of visitors. The rotate corollas, together with the

cone of black anthers, the stamens being attached to the

base of the petals, were now removed from the five flowers

of the first group. There remained the green calyx, the

pistil, and the green dise surrounding it which secretes

the nectar. The two groups were now observed for a

second ten minutes, the first received no visits, the second

seven visits from the domestic bee as previously. Once

a bee hovered around the denuded flowers of the first

group but failed to alight. The much smaller number of

visits made to group number two during the second in-

terval may in part have been due to the less conspicuous-

ness of the whole patch of flowers. There were scattered

upon the ground many partially withered corollas and

twice a bee was seen to fly down toward them. With a

lens of twenty diameters I examined three of the de-

foliated blossoms and in two of them found eight or nine

small drops of nectar, so that had a bee alighted upon

them it would have been richly rewarded for its discern-

ment. The flowers possessed no perceptible odor. Three

points in the second part of this experiment should be

carefully noted; first, that the flowers from which the

corollas had been removed, though they contained an

abundance of nectar, received no visits; second, that the

flowers left complete received a much less number of

visits than during the first interval; third, that the bees

were attracted by the wilting corollas lying upon the

ground.

On August 14, I made the following experiment upon a

staminate flower of the garden squash, Cucurbita maxima.

The weather was clear and warm. During an observation

of ten minutes it received twelve visits, eight of which

were made by honey-bees and four by workers of Bombus

terricola Kirby. The perianth was then removed close

to the cup-shaped reservoir, but the denuded flower with

its prominent club of stamens and yellowish dise was still

342 THE AMERICAN NATURALIST [Vou. XLII

a conspicuous object though much less so than before.

It was watched for a second ten minutes and received

only one visit, from a bumblebee (Bombus. terricola).

During the first interval no visit was counted that the bee

did not enter the corolla and go down to the honey re-

ceptacle. Within a few inches of this ‘‘stump’’ and a

little lower down there was another squash flower, the

corolla of which had wilted and was nearly closed. Dur-

ing the second ten minutes this flower received five visits,*

two from B. terricola and three from honey-bees, though

they were unable with a single exception to find an en-

trance. ‘There can be little doubt that had the corolla

been present on the first flower these bees would have

entered it.

On the fifteenth, the weather being favorable, the ex-

periments on the owes of Cucurbita maxima were con-

tinued. Two flowers, both staminate, growing side by

side, their corollas touching, were selected. Number one

appeared rather older than number two, which had evi-

dently expanded very recently. Both were observed for

ten minutes. Number one received six visits, four from

Bombus terricola, two from the honey-bee; while number

two received thirteen visits, all from bumblebees (B. terri-

cola). The fresher condition of this flower probably

accounted for the larger number of visits. Both the calyx

lobes and the corolla were now cut away from number two,

the most attractive flower, leaving only the dise and the

monadelphous club of stamens. This was by no means

an inconspicuous object, as the yellowish dise is 15 mm.

in diameter, and the yellow anthers are over 2 em. long.

The two flowers were watched for ten minutes. No visits

were made to number two; but number one received

twelve visits, six from honey-bees and six from B. terri-

cola. Itis evident that the corolla was a great advantage,

and that number one suffered in competition with number

two, the number of visits to number one greatly increasing

when number two was rendered comparatively incon-

*The bees alighted upon the corolla and tried to enter it.

No. 510] COLOR SENSE OF THE HONEY-BEE 343

spicuous. Shortly after this experiment was completed

a honey-bee was seen to visit the decorollated flower of

number two; and inserting its tongue through one of the

narrow slits in the top of the cup-like receptacle it re-

mained sucking for two minutes, finding evidently an

ample quantity of nectar. It then visited flower number

one, but its further flight was not followed. A moment

or two later a honey-bee was again seen on the nectar

receptacle of number two, which was doubtless the same.

individual, for its subsequent flight was followed and it

returned twice afterwards, finding the nectar here more

abundant than in the complete flowers. Later a fifth visit

was observed, probably by the same bee. There were

many more bumblebees present than honey-bees, and the

greater capability of the honey-bee in finding the nectar

and in making the most of its discovery is noteworthy.

During this whole time number one, from which the

corolla had not been removed, continued to be frequently

visited by bees. The corolla of the squash possesses an

agreeable fragrance, but the defoliated flower also exhales

a strong though coarser and more weed-like odor. The

visits were recorded on the instant they were made.

In these experiments the visitors were not a miscel-

laneous group of insects belonging to several orders and

differing widely in their habits of visiting flowers and,

according to Miiller, in their color sense; but the flowers

of Pyrus communis and Borago officinalis were visited by

Apis mellifera alone, and of Cucurbita maxima by Apis

mellifera and Bombus terricola, allied species, which are

placed by some authors in the same family. The visits

were purposive and not ambiguous, as is not infrequently

the case with the visits of many diptera and even of the

less specialized bees. To the complete flowers the number

of visits were numerous and decisive. On the contrary,

they ceased almost entirely to the decorollated flowers,

though they contained an ample supply of nectar; while

at the same time in the control observations made for the

yurpose of comparison they continued numerous. The

344 THE AMERICAN NATURALIST [Vou XLIII

few exceptions may be explained by the odor of the

evaporating nectar, and by the tendency of bees to return

habitually to a place where they have once obtained food.

That the white, blue and yellow corollas were beneficial

to the flowers of their respective species does not admit

of question. To attribute this advantage to any other

cause than conspicuousness would appear to be a per-

version of the facts.

Let us again refer to Plateau’s experiment with Digitalis

purpurea. The larger part of the tubular corolla was

cut away leaving a cup-shaped stump 1 cm. long, which

was visited by two bees, Bombus terrester L. and An-

thidium manicatum L., nearly as frequently as when the

flower was complete. Knuth suggests that the nectar

now being exposed to the sunshine and wind must evapo-

rate more rapidly, give out a stronger odor, and should

attract more insects than when it was concealed at the

bottom of the long corolla-tube. As this was not the case,

he holds that the uselessness of the bright corolla was not

proved. I should explain the continuation of the visits

of the two species of bees as follows. A cup-shaped

flower 1 cm. long is by no means very inconspicuous per se.

The bees had already visited these flowers and learned

that they contained nectar; and they would come again

to the same place in accordance with their well-known

custom of returning habitually to a locality where they

have once procured food. They would find smaller, more

open flowers with perhaps a stronger odor; but that in-

sects with the keen discernment of bees should be greatly

deceived by this change is highly improbable. The re-

sults observed by Plateau in the excision of the corolla

of Digitalis purpurea are precisely those which would

have been expected. The force of this objection occurred

later to Plateau himself in the case of flowers masqued

with green leaves, as when he enveloped with the leaves

of rhubarb the inflorescence of Heracleum, for he says:

“Or, jai effectué en 1895 et 1896, aux débuts de ma longue serie de

recherches sur les rapports entre les Insects et les fleurs, des expériences

No. 510] COLOR SENSE OF THE HONEY-BEE 345

que lon n’a certainement pas oubliés et dan lesquelles je constatais de

multiples visites d’Insects à des fleurs dont toutes les parties colorées

étaient cachées ‘par du feuillage. L’objection que les résultats de ces

expériences ancienne étaient précisément et exclusivement dus au

souvenir de l’emplacement se.présente immédiatement à l'esprit.”

“ Je reconnais bien volontiers que cette objection frappe juste pour

certaines des expériences en question.”

But in my experiments with the heads of simple dahlias

masqued with grape-leaves, Plateau continues, the mem-

ory of a place visited habitually does not wholly explain

the behavior of the insect visitors. In some instances

he covered up only the dise florets, leaving the ray florets

exposed; in others he covered the entire upper face of the

capitulum, both ray and disc florets, but not the under

side, with green leaves, and both bees and butterflies

(species of Bombus, Megachile, Pieris and Vanessa) con-

tinued to fly toward the inflorescences and often found

the pollen and nectar by creeping under the covering of

leaves. Plateau concludes that the rays do not act as

signals, and that the form and bright colors of the capitula

of dahlias are not an important influence in attracting

insects.

These conclusions are disputed by Forel, who in the

following interesting experiment shows that bees in their

visits to covered dahlia heads are guided by both memory

and sight. In a dahlia bed containing forty-three floral-

heads of different colors he covered up twenty-five with

grape-leaves bent around them and fastened with pins.

Of four others he covered only the discs, while of one he

covered the rays, leaving the dise visible. The bees were

so numerous that at times there were two or three to a

flower. The bees ceased at once to visit the completely

covered heads; they continued, however, to fly to the

heads with only the discs covered, though they immedi-

ately abandoned them, except in a few instances where

* Plateau, F. Note sur l’emploi de recipients en verre. Bul. Acad. roy.,

Bruzelles, No. 12, pp. 741-75, 1906. Vid. pp. 771-2.

Forel, August. Ants and Some Other Insects, translated by William

Morton Wheeler. The Open Court Publishing Co., Chicago.

346 . THE AMERICAN NATURALIST (Vor. XLIII

they succeeded in finding the central florets beneath the

leaves; but to the dahlia with the dise exposed and the

rays covered they continued to fly as usual. But the bees

remembered the earlier condition of the dahlia bed and

seemed to be seeking the dahlia heads which had so sud-

denly disappeared. Soon a poorly concealed specimen

was detected and visited, then another, and at the end

of about three hours the entrances at the side and below

were discovered and the hidden flowers were again being

visited. Forel says:

“Plateau, therefore, conducted his experiments in a faulty manner

and obtained erroneous results. The bees still saw the Dahlias which

he at first incompletely concealed. Then, by the time he had covered

them up completely, but only from above, they had already detected

the fraud and saw the Dahlias also from the side. Plateau had failed

to take into consideration the bees’ memory and attention.”

To Forel’s criticisms published, in 1901, in Rivista di

Biologia Generale, Plateau has replied in part: That not

only bees but numerous diurnal lepidoptera visited the

masqued dahlias, and that while it was freely admitted

that insects could see the under side of the covered

capitula and the radiating form and red or rose color

of the floral ligules, yet they were without attractive

value, as it was only very rarely that an insect ap-

proached the inflorescence of this side.” To these state-

ments I will again refer later. His further explanations

as well as his assertions that his opinions have in some

particulars been misunderstood by Forel are immaterial

to the present discussion. But in admitting that the

visits of hymenoptera can be partially explained by

memory Plateau practically abandons his position so far

as his experiments with dahlias are concerned.

Forel, as has already been mentioned, points out that

Plateau has attached too little importance to the bee’s

memory and attention. These are, indeed, qualities more

likely to be appreciated by the practical apiarist than the

‘Plateau, F. Note sur l’emploi de recipients en verre, Bul. Acad. TOY.,

Bruxelles, No. 12, pp. 772-75.

No. 510] COLOR SENSE OF THE HONEY-BEE 347

entomologist. A single example will suffice to show the

strength of the bee’s memory for location. During Sep-

tember and the early part of October, while carrying on

various observations, I accustomed honey-bees to visit the

window of my library for honey and sugar syrup, and now

nearly a month and a half later, though they have not

been fed since, they still continue to return whenever

warmer weather permits. I have little doubt that when

the winter is past and they resume flight in April, as in

the experience of Huber, they will come again. I shall

certainly expect them.

The great perseverance and power of observation ex-

hibited by bees, when searching for nectar in a locality

where they have previously procured it, is likewise well

illustrated by Forel’s experiment. For more than three

hours they continued to look for the missing dahlia

flowers, until finally they detected a way to reach them

under the leaves. This acuteness of sense is also well

shown in the following experiment, which I performed

on October 6 after most of the natural flowers had

perished.’

I accustomed a number of bees to visit a red glass slide,

3 inches long by 1 inch wide, on the center of which was

a small quantity of honey The slide was placed in the

sunlight on the top of a white box about two feet high.

A second white box was then placed fifteen feet from the

first and to this the red slide was removed. A bee found

the honey at the end of six minutes and a few seconds

later another came. In ten minutes there were four bees.

During this interval the bees were continually flying

around the first white box. I now removed the second

white box but left the first undisturbed. An hour later

*It is instructive to compare this experiment with one described by

Lubbock, where the attention of the bees was preoccupied. ‘‘I placed a

saucer of honey,’’ he says, ‘‘close to some forget-me-nots, on which bees

were numerous and busy; yet from 10 a.m. till 6 only one went to the

taking

and being difficult to divert.’’ (‘‘Ants and Some Other In-

ie taati by William Morton Wheeler, p. 21.)

348 THE AMERICAN NATURALIST [Vou. XLIII

I replaced the second white box, but for the red slide I

substituted a plain glass one. A bee found it almost

immediately, probably one of the earlier visitors. The

slide was now carried to a third position and placed upon

an unpainted support fifteen feet from each of the white

boxes, the three stations forming the angles of an equi-

lateral triangle. Here it was soon found by two bees.

The plain glass slide was then placed on the grass in the

center of the triangle, where it was quickly discovered

by two bees and a third came a little later. The slide was

now placed on the grass fifteen feet outside of the equi-

lateral triangle. It was so inconspicuous that a child,

who under my direction approached within a foot of it,

failed to see it until a bee alighted in the grass. It re-

quired twenty minutes for the bees to find it, and perhaps

they would not have done so then had it not been near the

route they were pursuing in going back and forth to the

hive. It is very evident from this experiment that a

force of bees searching for nectar or honey are not easily

deceived, but perceive very keenly. The slide was in

the sunlight and the attractive influences were the re-

_ flected light, the yellow color of the honey (it was golden-

rod honey, which is amber-colored), and its odor.

In view of the above observations it can excite no sur-

prise that the bees passed readily under the green leaves

which Plateau had pinned on top of the Dahlia capitula.

The factors by which they were guided were memory and

the senses of sight and smell. When the bees returned

they found the covered dahlias still in their original posi-

tion, and though they were not bright colored from above

they possessed conspicuousness of size and form; and

when the bees in flying about saw the form and color of

the rays from beneath and perceived the characteristic

odor they recognized promptly the presence of dahlia

flowers. Plateau’s contention that the form and color

of the under side of the capitulum, which was plainly

visible, exerted no influence because the insects very

rarely approached the head from that side, is without

force, for the bees never having found the nectar on the

No. 510] COLOR SENSE OF THE HONEY-BEE 349

under side, directed their flight toward the aperture or

passageway under the leaves, remembering that the nectar

was obtained from the disc Aowera. It is not justifiable,

says Kienitz-Gerloff, to infer that the color of uncovered

flowers plays no part in attracting insects, because when

they are covered the odor continues attractive.®

Plateau repeatedly mentions that the covered dahlia

heads were visited by species of Vanessa and Pieris as

well as by bees; but while it is admitted that the mental

attributes of bees exceed those of lepidoptera, yet the

conclusion that the latter were influenced by odor aione

is unwarranted. When a butterfly thrust its proboscis

beneath the leaves it showed perception of the form of the

inflorescence and memory of the location of the nectar. In

the following experience the butterflies exhibited keener

powers of observation than some of the less specialized

hymenoptera. The flowers of Iris versicolor are polli-

nated by bees; and the nectar, which is secreted at the

base of the sepals, is protected by the arched petaloid

styles, so that it can not be obtained by butterflies in the

legitimate way. I have seen Pamphila mystic Seudd.

standing on the ovary below the perianth and sucking the

nectar through the crevice between the sepal and the

style; while the larger banded red butterfly, Limenitis

disippus Godt. obtains the nectar in the same way from

above. On the other hand, an hymenopter, which escaped

capture, carefully examined the center of two flowers but

failed to locate the nectar. There is good reason, then,

to infer that the butterflies in Plateau’s experiments were

influenced by the position and form of the dahlia heads

and the color of the rays below as well as by the odor.

The criticism of Kienitz-Gerloff is also as Montane

here as in the case of bees. -

The experiments of Plateau with covered dahlia heads,

therefore, were not well adapted for the purpose intended,

and afford an insufficient basis for drawing the conclusion —

that bright coloration is not advantageous to flowers.

*Knuth, P. Handbook of Flower Pollination, 1: 205.

VARIATION IN THE NUMBER OF SEEDS PER

POD IN THE BROOM, CYTISUS SCOPARIUS

DR. J. ARTHUR HARRIS

CARNEGIE INSTITUTION OF WASHINGTON

Waite at Wood’s Holl in August, 1907, I collected

about 100 pods each from a series of 23 bushes of the

broom Cytisus scoparius. On a vacant lot not far from

the Marine Biological Laboratory the plants were grow-

ing vigorously, completely covering the space with

bushes, many of which were higher than a man’s head,

and with stalks about an inch in diameter at the base.

The material was gathered for an investigation of the re-

lationship between the number of ovules formed and the

number of seeds developing per pod. But when the

counting was taken up the determination of the number

of aborted ovules proved so difficult that I feared the

results would be untrustworthy and gave up the project.

While working over the data I noticed that Pearson! has

recorded a series of countings of broom from an English

locality, and it has seemed worth while to compare the two

lots of material.

Many biologists have held the opinion that changed

conditions of life, such as may be supposed to prevail

when a species is transferred from one habitat to another,

imply an increase in variability. The theories concern-

ing the reason for this phenomenon need not be discussed

here. I think the general idea will be familiar to all. I

think about the only attempts to determine quantitatively

whether there is any increase in the variability of a

species when introduced into a new habitat are two studies

by Bumpus. He first considered the variability of the

egg of the introduced sparrow? and concluded that it is

decidedly more variable in the United States than in its

* Pearson, K., and others, Phil. Trans. Roy. Soc. Lond., A, 197, 335, 1901.

*Bumpus, H. C., ‘‘The Variations and Mutations of the “Introduced

Sparrow,’’ Biol. Lect. Mar. Biol. Lab. Wood’s Holl, 1896-97, 1-15.

350

VARIATION IN NUMBER OF SEEDS 351

native country. In judging Bumpus’s data on the directly

measurable characters by the standard deviation instead

of the range of variation Pearson? concluded that the

American egg is not more variable than the English but

rather less so when a more representative English series

is taken. It is quite impossible to determine from the

color and shape appreciations whether Pearson’s English ©

or Bumpus’s American series is the more variable, but it

seems to me upon rereading Bumpus’s paper that he

makes a very good case for a greater variability in color

and shape of the eggs of his American as compared with

his English series. However, Pearson’s suggestion of a

possible change in the color of the egg must be remem-

bered. Vernon‘ considers the American eggs more vari-

able in shape and color. ;

Bumpus’s second attempt to secure data upon this

question was with the introduced Littorina.” He found

from an examination of three English and ten American

series, each of about one thousand individuals, that the

American shells are much more variable than those from

the British Isles. Duncker who has reworked the data to

express the variability in terms of the standard deviation

and theoretical instead of empirical range agrees with

his conclusions.

The results reviewed above indicate that more data on

this question are much needed. Although his conclusions

were based upon somewhat unsatisfactory statistical

methods Professor Bumpus deserves very large credit for

his thoroughly pioneer attempts to solve some of the

problems of evolution in the only way in which they can

be solved—by the collection of pertinent quantitative

data. The problem of variation is such a complex one:

* Pearson, K., ‘‘ Variation in the Egg of the Sparrow,’’ Biometrika, 1,

247-249, 1901.

* Vernon, H. M., ‘‘ Variation in Animals and Plants,’’ New York, 1903.

*Bumpus, H. C., ‘‘The Variations and Mutations of the Introduced

Littorina,’? Zool. Bull., 1, 247-259, 1898. >

*Duncker, G., ‘‘Bemerkung zu dem Aufsatz von H. C. Bumpus: The

Variations and Mutations of the Introduced Littorina,’’ Biol. Centralbl.,

18, 569-573, 1898.

352 THE AMERICAN NATURALIST [Vou. XLIII

and sources of error are so numerous that great stress is

not to be laid upon the results of the examination of a

single series of material, but all conclusions must be

tested repeatedly and on widely dissimilar organisms.

The present lot of broom deserves consideration in this

connection.

Cytisus is a native of Europe which has been reported

from several localities in the United States. Mr. Vinal

N. Edwards writes me that he started the colony from

which my collection was taken in 1887 when he set out

forty small plants which he dug up on Naushorn Island.

In 1898 it was all cut down level with the ground when it

came up thicker than ever. He thinks it was first planted

on Naushorn Island some fifty years ago.

It seems hardly worth while to look farther for the

ultimate origin of the colony since we have only a single

series of European data for comparison. Several years

ago Pearson collected ten pods each from a series of 120

plants at Danby Dale. To render his series readily com-

parable with my own I have multiplied his frequencies by

Taste I

VARIATION IN NUMBER OF SEEDS OF BROOM

eee | I eee

0 a 3 — 2

1 15 4 il

2 28 24 4

3 54 43 H

4 88 59

5 101 129 —28

6 144 142 2

7 183 170 13

8 235 183 52

9 254 213 41

10 250 244 6

4 192 242 —50

13 186 216 —30

13 183 190 — 7

E 125 149 —24

} 89 101 12

61 63 2

f 32 47 —15

18 9 14 5

19 T 3 4

20 2 1 1

Totals 2,239 2,239

VARIATION IN NUMBER OF SEEDS 353

the ratio 2,239/1,200 and placed them beside mine in

Table I. The character of the pods is also shown graph-

ically in the diagram where the solid lines represent the

English and the dotted lines the American pods.

e 1ra 2.0 2:0 4 608 wR Roem ea a

I think these polygons agree remarkably well. The

empirical range is essentially identical. In both cases

the highest class is 20. Pearson found no pods with an

entire absence of seeds in the 1,200 which he examined,

though he suggests that such may exist; I found 2 in the

2,239 of my lot. At first the differences between the fre-

quency of pods in the individual classes, as shown in the

fourth column of the table, and graphically in the dia-

gram, seem rather large. But we must remember that

two series of countings from the same individual would

show many chance differences in their frequencies, and |

354 THE AMERICAN NATURALIST [Vow. XLIII

that neither of the series with which we are dealing is

large enough to give very trustworthy results for the

frequency of individual grades. We might avoid to some

extent the difficulties introduced by the errors of random

sampling by graduating the observed frequencies by some

satisfactory fitting formula, but it does not seem profit-

able to take up the labor of curve fitting on the available

data. We may, however, calculate the means and varia-

bilities with their probable errors. The constants and

their differences appear in Table II.

The means show that the Wood’s Holl plants have

about three tenths of a seed more per pod than the Danby

Dale series. This is to be expected from the diagram

where the polygon for the American series is seen to lie

a little further to the right than the English. But the dif-

ference is only about four times its probable error and so

only doubtfully significant even for the samples in hand.

I think no one can examine these results and not be con-

vinced that so far as is shown by the physical constants

Taste IT

COMPARISON OF STATISTICAL CONSTANTS OF BROOM

Average ~ aid hiroa Standard Deviation Coefficient of

ble Err and Probab'e Error. Variation.

Danby Dale 9 .6425+.0691 3.5466+.0488 36.780

W ’s Holl 9.9982+.0502 3.5236-+.0355 35.242

Difference .3557+ .0854 —.0230 —1.538

the two collections, one gathered in England and the other

in America and counted and reduced by independent ob-

servers, are practically identical when we have regard to

the probable errors of random sampling. And this not-

withstanding the fact that the age of the plants, the num-

ber of plants involved, the ancestry of the individuals,

and the climatic and soil conditions under which they

grew are not taken into consideration or allowed for in

any degree! If the constants were based on some char-

acter which the qualitative biologist would guess to be

little influenced by the environment one might not be sur-

prised at their close agreement; but we are dealing with

No. 510] VARIATION IN NUMBER OF SEEDS 355

a character dependent not merely upon the internal and

external factors determining the form of all plant organs,

but upon the environmental factors influencing the

chances for fertilization as well. Furthermore, it may be

noted that we are dealing not with a little variable char-

acter, but with one having a coefficient of variation of

about thirty five per cent. This is about two or more

times the value of the coefficient of variation of the ordi-

nary vegetative characters of plants, but not an extra-

ordinarily high value for seed numbers, as determined

from large series of unpublished data.

Summarizing the results of this note, I think we may

say that so far as is shown by this one series of material

Cytisus is no more variable in the habitat to which it has

been very recently introduced than it is in one of its na-

tive habitats. As a matter of fact it is slightly, though

not significantly, less variable at Wood’s Holl than at

Danby Dale. Possibly the sensible identity of the varia-

bility of the two samples may be due to the small number

of individuals which furnished my series of data. These

in their turn were probably derived from very few ances-

tors. I attach no great importance to the results. They

simply show that so far as the present material is con-

cerned there is no evidence in favor of the theory that

the introduction of a species into a new habitat increases

its variability. Possibly some other character than num-

ber of seeds per pod would have shown an increased

variablity. I use this character merely because I had

the data on hand as a by-product of some other work and

felt that it would be better to let it contribute its bit of

evidence on this problem than to throw it away. Pos-

sibly as a fellow biologist remarked when I showed him

the closeness of agreement of the constants from the two

series the result is ‘‘ purely accidental.’’ There are many

possibilities of error in work of this kind. But until we

have a large number of series of quantitative data it will

be quite impossible to say whether or not there is any-

thing of value in the theory of an increased TEORI of

‘introduced species.’’

PRESENT PROBLEMS IN PLANT ECOLOGY!

Tue TrenpD oF EcotocicaL PHILOSOPHY

PROFESSOR HENRY C. COWLES

UNIVERSITY OF CHICAGO

Tmar Schimper was a prophet as well as an ecologist

of the first magnitude is well attested by this sentence

from the preface to his plant geography:

The ecology of plant distribution will succeed in opening out new

paths on condition only that it leans closely on experimental physiol-

ogy; thus only will it be possible to sever the study of adaptations

from the dilettantism which revels in them, and to free it from

anthropomorphic trifling, which has threatened to bring it into com-

plete discredit.

The close interdependence of physiology and ecology

is being more and more recognized; this is made manifest

by a survey of the titles presented to the botanical meet-

ings year by year. Suggestive among this year’s titles

are: Bog toxins and their effect upon soils; experi-

mentally induced root-regeneration in Parthenium; the

relation of evaporation to the treelessness of prairies; are

alpine plants exposed to increased evaporation? Titles

such as these would have been quite impossible a few

years ago through the failure of ecologists to recognize

the fundamental necessity of building their work upon

physiological foundations. Quite as fundamental but

less fully recognized, especially by many physiologists,

is the dependence of physiology upon ecology. The in-

creasing sanity of physiological problems is due in large

measure to the wholesome influence of ecology. In the

old days when physiology was a mere laboratory science,

and therefore artificial, no experimental test could be too

*A series of papers presented before the Botanical Society of America

at the Baltimore meeting, by invitation of the Council.

ia 356

No. 510] PROBLEMS IN PLANT ECOLOGY 357

bizarre to be applied to plants. A thing never to be lost

sight of is that evolution has taken place out of doors,

and that the contortions of a puny plant in our illy lighted

and gas-ridden laboratories do not solve our most im-

portant problems. In recent years no physiological work

of greater import has appeared than that from the Desert

Laboratory, where the direct stimulus to research has

been contributed by the desert itself and its ecological

problems.

The developments of the past decade, therefore, make

it essential that physiology and ecology break down the

barrier erected for them in Madison in 1893, where it was

declared that physiology is experimental and ecology ob-

servational. The ecologist must experiment in order to

resolve a natural complex of factors into its individual

elements, while the physiologist must be a student of

field conditions, if he wishes to deal sanely with the

great problems connected with the evolution of form

and behavior. Recognizing, then, the interdependence if

not the complete identity of experimental ecology and

field physiology, it becomes necessary to consider the

underlying philosophy that serves as a motive for all

research along these lines. The importance of one’s .

philosophy upon his research can scarcely be overesti-

mated, for it determines the problems to be attacked,

the methods to be employed, and, on account of the per-

sonal equation, is likely to give some color to the results

secured. But it is not necessary that the working theory

be true; indeed it is often better that it be most untrue,

since it may thus lead to the testing of more theories than

might otherwise be employed. The fundamental test of

a working theory is that it be that one which will stimu-

late the maximum of discriminative research. There can

be given no better illustration of an unproductive theory

than the theory of vitalism. This supposes that there is

a fundamental difference between the living and the non-

living, hence one would not expect a vitalist to lead in

the attempt to create living matter by experiment.

358 THE AMERICAN NATURALIST [Vou. XLII

Vitalism, whether true or not, conduces to lethargy, be-

cause it assumes a barrier instead of attempting to find

if the supposed barrier can be broken down. Thus the

mechanistic theory of life is best as a working hypothesis

because it leads to decisive experimentation and to the

attempt to create living matter, and in this way leads

to the solution of many great problems and may some day

cause the settlement of that greatest of all problems, the

origin of life. On the other hand, vitalism, by assuming

to answer the question in a way that transcends the possi-

bility of experimental test, is a hopeless theory and leads

to repose and scientific slumber rather than to activity.

While theories of vitalism in whatever form have ever

blighted scientific endeavor, they have been especially

harmful in ecology. No biologists are brought into closer

touch with life than are the ecologists; their whole atmos-

phere is pregnant with dynamics and the aspect which

they have of plants is that of extreme plasticity. The

ecologist comes into daily contact with profound changes

in plant form and behavior, and he sees ever before him

the panorama of succession. What wonder is it that many

ecologists have been carried off their feet by vitalism

and have dabbled in anthropomorphic similes? And

what wonder that, because of this attitude, some of our

best biologists have seen naught in ecology but superficial

vaporings or scientific nonsense? But the view-point of

ecology has been shifting, indeed has largely shifted, and

there are reasons for believing that the ecologists are now

closer to the problems of to-morrow than many of the

other biologists. The rescue of ecology from dilettant-

ism and anthropomorphic trifling, which Schimper so

keenly wished for a decade ago, has been essentially real-

ized. It may be of value to outline the steps that have

led to the present happy state.

From the beginning one of the greatest of ecological

problems has been that of the origin and significance of

adaptations. In other days the solution was sought in

special creation, one of the most unscientific of all

No. 510] PROBLEMS IN PLANT ECOLOGY 359

theories, because altogether subversive of experiment.

The entire question was prejudged at the outset. The

theory of special creation, however, has not been espe-

cially harmful, because it has generally seemed so un-

likely as to have received but little support among scien-

tific men. Perhaps the most baneful of all ecological

theories has been the Lamarckian theory of direct adapta-

tion. In its day, that is before 1859, it marked a distinct

advance, because it was the first significant attempt to

displace special creation by something better. The

great merit of Lamarckism was the recognition of plas-

ticity, the substitution of a dynamic for a static nature.

Had it been generally accepted, it might easily be said

to have marked the greatest single step in the advance

of scientific thought, but the world was not then ready

for dynamic conceptions. The leaven of Laplacian as-

tronomy had scarce begun to work, and the Lyellian

geology was as yet unborn.

The evil wrought by Lamarckism is due to its accept-

ance by modern biologists. It is essentially a vitalistic

theory, presupposing that plants and animals have some

inherent mysterious power to contravene the ordinary

laws of matter. They are supposed to be able to sur-

vive hard conditions because able to adapt themselves

advantageously. Of course it is clear that those plants

which do respond favorably to changing conditions will

be most likely to survive, but adaptationists have appar-

ently overlooked the fact that thousands of species must —

have died because unprovided with an adequate capacity

for advantageous response. Their conception of nature

is distorted by centering their attention upon those suc-

cessful plants that appear to have survived because of

their adaptations. The depressing effect of the adapta-

tion hypothesis is most obvious in that it has encouraged

sterile imaginings as to the advantages of this, that or the

other plant structure and has thus discouraged attempts

to discover the real facts involved in the origin of such —

structures.

360 THE AMERICAN NATURALIST [Vou. XLIII

Evidence against the reality of adaptation in a sub-

jective sense has been accumulating. At first sight the

increase of cutin in plants exposed to increasingly xero-

phytic conditions, or the increased development of air

chambers in plants exposed to increasingly hydrophytic

conditions look like adaptations, and such changes cer-

tainly seem advantageous. However, there are facts that

point in another direction. There is no more important

source of strength in plants than that afforded by bast

and similar mechanical tissues. Yet recent experi-

menters have failed to get any significant response in

the way of great bast development by exposing growing

organs to considerable tension. Bast primordia, how-

ever, are very plastic and respond readily to changes in

moisture. Thus we have in bundles of bast fibers tissues

that do not adapt themselves to a demand for tensile

strength, although such a response would be highly ad-

vantageous; on the other hand, they respond to increased

transpiration, although it has not been claimed that bast

fibers are of especial value in checking transpiration.

Again, increased conduction, whether due to high tran-

spiration or other causes, often results in an increased

development of the vascular tract. The advantage of

such a modification is at least dubious in xerophytes, but

the case is much more striking in such plants as Arte-

misia, when parasitized by Orobanche. The Artemisia

root is stimulated to excessive development by the attack

of the parasite, and examination shows that the vascular

tract in particular is greatly increased. If this change

in the Artemisia root is an adaptation, it is an adaptation

for the Orobanche and not for itself, and what adapta-

tionist could expect a plant to be so altruistic as all this?

Similar phenomena are seen in fungus and insect galls,

and in the cynipid galls in particular, food accumulates

in large amount in definite layers around the larval cham-

ber. Can the oak be supposed to be so thoughtful for the

insect as to provide it food? Or, if one chooses the other -

horn of the dilemma, can the insect be supposed to have

No. 510] PROBLEMS IN PLANT ECOLOGY 361

learned the habits of the oak, and found just how to tap

it? How much more sane it is to regard these and all

other plant reactions as brought about through the in-

fluence of specific stimuli, treating any advantage that

may come (or any disadvantage) as quite incidental to

the main problem!

At the present day Lamarckism and adaptation are

searcely as detrimental to ecological thinking as is the

misapplication of Natural Selection. The publication

of the ‘‘Origin of Species’? in 1859 influenced biological

thought more profoundly than any other work of all his-

tory. It compelled the world to accept the doctrine of

organic evolution, and it showed most clearly why certain

species die and others live. But it shed only a little light

on the great questions involved in the evolution of new

species. In view of this it seems most unfortunate that

the book was entitled ‘‘The Origin of Species’’; the

alternative title commonly printed just beneath in smaller

type presents the real thesis of the book: ‘‘ The Preserva-

tion of Favored Races in the Struggle for Life.’’ Per-

haps in part because of the title, but more because of

Darwin’s over-zealous supporters, natural selection has

been made a fetish and has been supposed to account for

new forms and structures, as well as for their preserva-

tion. In other words, it has been erroneously regarded

by many as a theory of evolution instead of a means of

accounting for the perpetuation or destruction of species

previously formed. The theory of natural selection has

worked great harm in the ecological study of plant struc-

tures. Thorny plants have been supposed to be selected

by reason of animal incursion, and such complex things

as floral structures have been supposed to be the result

of parallel selection on the part of flowers and insects.

There is no adequate evidence, experimental or otherwise,

for views of this character. Such experimental work as

has been done appears to show that the success or failure

of a plant rarely depends upon this or that little advan-

tage, upon which natural selection may be supposed to

362 THE AMERICAN NATURALIST [Vou. XLIII

work, but rather that its perpetuation depends for the

most part upon other things than its so-called adaptations.

Few more perfect adaptations for their function can be

thought of than the digestive glands of insectivorous

plants, and yet there is no evidence in support of the idea

that such plants have been able to survive by reason of

these glands. The evolution of such a complex flower

as that of the orchid along lines that are parallel with the

evolution of the mouth parts of a special insect requires

a nicety of operation that seems staggering, and all the

more because the flower, at least, seems to have evolved

so far along the lines of zygomorphy as to be a source of

disadvantage rather than of advantage, an impossible

idea to the natural selectionist. The facts of regenera-

tion show, as pointed out so ably by Morgan, that plants

and animals are often in a position to make an instant

new reaction to conditions unlike those to which they have

ever been accustomed, and that these reactions may or

may not be advantageous; in any case, natural selection

can have no possible connection with their origin. The

trend of the time, especially among botanists, is unmis-

takably toward the abandonment of natural selection as

a theory of evolution, but ecological work is finding a

dominant place for it as one of the controlling factors in

succession. The student of vegetation dynamics, more,

perhaps, than any other, finds displayed before him an

incessant struggle for existence; in the changing condi-

tions, the fitness of an old species to remain or of a new

species to displace, it is commonly a matter of profound

importance in the vegetative change produced.

This is not the place to enter upon a discussion of those

evolutionary theories that to-day hold the foremost place.

We are awaiting with keen anticipation the noteworthy

symposium on evolution that is to make this meeting

historic. Suffice it to say that the downfall of the theory

of adaptation does not mean the downfall of epigenesis

or of extrinsic theories in general. The likelihood of a

profound influence of the external world upon the trend

No. 510] PROBLEMS IN PLANT ECOLOGY 363

of evolution was never more evident in the past than it

is to-day. The work of Klebs has opened up almost limit-

less possibilities along such lines. The intrinsic theories

of evolution, such as orthogenesis and heterogenesis (or

mutation) are also vigorously maintained. All such

theories, both extrinsic and intrinsic, appear to be in

harmony with the present results of ecological research,

and the future alone may say whether some or all of these

and more are true.

To the working ecologist the necessary consequences

of the abandonment of the idea of adaptation and of nat-

ural selection as a causative factor are most vital. First

and foremost there comes the possibility of disad-

vantageous trends in evolution. To some extent such

tendencies will be checked by the destructive operation

of natural selection, so that only such new species as are

most fit are likely to survive and have progeny. But in

view of the ideas that have generally prevailed in past

years, it can not be emphasized too strongly that plants

may retain useless structures and even structures that

are moderately harmful, and yet live on if they also

possess other structures or habits that are sufficiently ad-

vantageous. This conception at once relieves ecologists

of one of the most arduous of their former duties, the

establishment of an advantageous function for every or-

gan, and of a benefit in every function. The chapters on

the uses of palisade cells, crystals, poisons, latex and the

myriad kinds of hairs are likely to be shorter and less

dogmatic in future ecological treatises. Even such or-

gans as stomata are apparently being divested of their

erstwhile most important asas the regulation of

transpiration.

It has been so long the fashion to regard the various

kinds of floral structures as most useful thatit may be

thought ecological heresy to question their utility. The

intimate correlation between the evolution of the insect

and the flower was such a pretty story that it seems rude

to question it, but do we have any adequate evidence of

364 THE AMERICAN NATURALIST [Vou. XLIII

advantage in the myriad diversity seen in flowers, much

less any advantage great enough to have been of sig-

nificance in directing to any notable degree the trend of

evolution? It is usually assumed that dichogamy, hetero-

styly, prepotency of foreign pollen, and zygomorphy are

advantageous characters because they promote cross

pollination or pollination by special insects, but the facts

on which such conclusions are based are very slender.

There are many plants which are regularly close-polli-

nated and they seem to succeed as well as others. The

Composite are often regarded as the highest of the seed

plants, and they are of especial interest because they are

a group that is ecologically successful as well as morpho-

logically advanced, features that often fail to coincide

elsewhere. But the Composite show comparatively little

zygomorphy or insect selection; as a group they are

notably geitonogamous or even autogamous, and yet none

of the supposed disadvantages of close pollination are

evident. Indeed the massing of flowers in heads and the

consequent facilitation of pollination between near-by

flowers may be one of the reasons for their great success.

But there are reasons for believing that any or all kinds

of pollination are vastly inferior to vegetative reproduc-

tion in determining the success of a group. The notable

success of the grasses and sedges is doubtless due to their

rhizomes far more than to their flowers, and in the duck-

weeds and many aquatics the flower has become almost

a negligible quantity. Such considerations make it at

least doubtful whether many conspicuous floral structures

possess the great advantages in the life of plants that

have been commonly ascribed to them.

The conception that plant structures may often have

originated quite independently of any important use or

function, or even independently of any environmental

influence is useful at many points. It explains how there

can exist the phenomenon of ‘‘ over-adaptation,’’ which

appears to be exhibited in the orchid flower and in the

testa of many xerophytic seeds. It makes possible a new

No. 510] PROBLEMS IN PLANT ECOLOGY 365

and seemingly saner ecological classification of plant

structures.

The work of Witte seems to show that plant forms may

be either obligate or facultative, that is that they may be

inherent or may be subject to environmental control. In

a xerophytic flora, such as that studied by Witte in

Sweden, there are many plants of dwarf habit. Experi-

ment shows that these dwarfs behave very differently in

mesophytie conditions. Some develop into tall and

luxuriant plants, while others remain as truly dwarf as

in xerophytic soil. The dwarfness of the former is facul-

tative, of the latter obligate. The former is clearly a

response or reactive xerophyte, owing its form to its sur-

roundings; the latter appears to be an inherent or con-

genital xerophyte, the cause of whose development is as

yet unknown. It is probable that further experiment

along these lines will show that many other plant forms

apparently identical are most unlike in nature and origin.

Time will permit but one further illustration. In meso-

phytie forests one sometimes finds plants that appear to

be xerophytes. A notable example of this is seen in

many species of Begonia and Peperomia that grow in the

depths of the rain forest. Both in external aspect and

in all the details of leaf structure such plants appear

xerophytie; it seems almost certain that these plants are

congenital xerophytes, species whose xerophytism is

stamped upon them to such an extent that age-long ex-

posure to the moisture of the rain forest has not de-

stroyed it. Whether congenital forms in the final anal-

ysis differ in any radical degree from reactive forms can

not now be told; it may be that all plants are or have been

plastic, but it is clear that the recognition of the double

possibility in the interpretation of plant structures is at

present advantageous.

A minor but necessary matter is that of terminology.

One of the unfortunate features about language is that

expressions lag behind ideas. Long ago we knew that

the heart is not the seat of the emotions, but our language

366 THE AMERICAN NATURALIST [Vou. XLIII

still retains the old phrases. We continue to speak of the

rising and setting of the sun. In like manner we still

employ such terms as adaptation, adjustment, accom-

modation and regulation, although these are vitalistic

words which imply that plants and animals can transcend

their environment and can contravene the ordinary laws

of matter (though it is to be pointed out that the word

adaptation is harmless when used objectively). The old-

time ecologist was very anthropomorphic and delighted

in words derived from ¢Aé» (I love). Ecological litera-

ture is still burdened with such words as xerophile,

geophilous and entomophily; particularly objectionable

is the word myrmecophily, since it is found that plants

merely endure the visits of the ants. Such terms as

storage and reserve food appear to imply forethought on

the part of the plant and should be abandoned. Words

like normal and type are far too freely used, for it can

not be emphasized too much that one structure or habit

is about as normal or typical as any other. The word

function, which is per se harmless, has almost come to be

a synonym of purpose and may, perhaps, give way largely

to rôle. It is not an inconsequential matter that we clothe

our ideas with words that are correct and adequate. It

is worth the effort, even if we are obliged to substitute

a cumbersome though scientific phrase for a euphonious

but anthropomorphic word. But of course our language

is less important than our thoughts. Our scheme of

philosophy is fundamental, for it determines the motive,

the scope and the direction of our research. The most

blighting of philosophies is that which predicates a maxi-

mum of dogma, the most stimulating is that which de-

mands a maximum of experimental test.

DISCUSSION ON PROFESSOR CoWLES’S PAPER.

Proressor SHaw: If we should, as Professor Cowles says, discard the

word ‘‘storage’’ and, in short, if I understand him correctly, all the words

which carry teleological ideas, I should like to inquire what we shall say.

What resources of the language shall we use to talk to a class about a

starchy tuber and avoid implying purposeful adaptation?

No. 510] PROBLEMS IN PLANT ECOLOGY 367

PROFESSOR COWLES: It is a difficult question that Professor Shaw asks,

I have been working at that om hae years, and I have not all of the

answer yet, but I have part o We now use the word ‘‘response,’’

which I am convineed is gage ate of no teleological idea. To speak of

a response in the living and non-living will answer nearly all purposes, and

is entirely free from teleological ideas. The word ‘‘storage’’ is more

difficult to handle; personally I use the word accumulation. Take the

word ‘‘gall,’’ for instance—oak gall; one would hardly teach his class that

an oak gall stores, but to speak of food accumulation of an oak gall is not

incorrect.

PROFESSOR CLEMENTS: It seems to me that Professor Cowles puts em-

phasis on por wrong part of the dilem If we change our ideas in the

proper direction, it is not at all faa what we call them. ‘‘Response’’

implies more is vitalism than adaptation, yet I would adopt the idea and

let the word stand.

R. LIvINGSTON: We sometimes try to cut short our PE too

much, as there is a tendency in all things to adopt shorter expressi in-

stead of long ones, and finally a phrase comes to be a single word, p if

the process goes on long enough, a short one. In the present stage of

ecology, there is perhaps too much tendency to cut our phrases down to

single words before the majority of people who are using the words have yet

Pokey what the phrase means, and I am quite agreed with Professor

Cowles t we can sometimes find other pa as in the case of accumu-

lation hes of storage, which will express the point; but, I think that

in many cases, in order to keep our ideas clear, so that elamentary students

understand them, we must express the thing in sare rs language, so

as to say exactly what we mean. With reference to adaptation, there are

one or two points which ecologists have had to study, and of which Professor

pecial :

operation of natural selection in the succession of certain plants. In the

survival of the fittest species, for instance—what makes these species the

fittest? It is their adaptation to their environment. We may be able to

disprove certain specifie cases of adaptation that have been passing current

and taken for granted for years, but can we get rid of the general ides

at all?

PROFESSOR CowLEs: These are = which I had to leave out of iil

paper, on account of my limited time. Personally I distinguish betwee

adaptation in the subjective and in ‘tae objective sense. It is quite corre

purpose, in a short time our ideas change so that our term has to be made

more elastic. Now it seems to me that one of the difficulties always being

met with is having to adapt our language to our changing ideas. Would

368 THE AMERICAN NATURALIST [Vot. XLII

it not be better to have a less hard and fast terminology, to have a few

terms that are Aili applicable, and then use in a definite way a

description, so that a person, in reading the description, will of necessity

get from that seri the idea which the author wishes to convey, and

instead of building up a vast terminology, we shall have a few simple terms

of general paisa se apply these sittin with anng so that with

the growth of our ideas, beginners or even person

accustomed to the use of the words, will have a priii to wines pe new

ideas to the old terminology?

Proressor BoLLEY: If, as Professor Cowles says, plants respond to

stimulation, will he grant that these er a may be hereditary, and if

they are ai Pe is it not adaptation?

PROFESSOR COWLES: I would rather not go into this question of heredity.

I don’t think we know enough about it to ask or answer that. on’t

believe it has been proved that there could be such response as is suggested,

nor have we disproved it.

PRESENT PROBLEMS OF PHYSIOLOGICAL

PLANT ECOLOGY

DR. BURTON E. LIVINGSTON

Desert BOTANICAL LABORATORY

By physiological ecology is here meant merely the

study of the factors which determine the occurrence and

behavior of plants growing under uncontrolled conditions.

Field physiology would be almost a synonym for the

term here used. Pure physiology proceeds, as far as is

possible, by controlling conditions. By varying known

conditions and measuring the plant responses definite

relations are established between stimulus and response.

But ecology must perforce proceed without the known

conditions, without the synthetically built-up environ-

ment of pure physiological research. Here it is neces-

sary to measure and analyze natural conditions and to

relate these to the behavior of the plants. The problem

of measuring the plant phenomena, the determination

of the number, size, form, structure, etc., of the plants

involved, is essentially the same for both lines of study,

but that of measuring environmental conditions is, of

course, much more difficult where the latter are uncon-

trolled.

There is a principle of scientific research, that in an

investigation which involves the measurement of a num-

ber of causal factors and the relation of these factors to

resulting conditions, the various measurements should be

of as nearly equal accuracy as possible. Where a num-

ber of complex factors are to be dealt with, as in ecology,

progress must come, on the one hand, from a refinement

of methods of measurement and, on the other, from better

interpretations of the data resulting from these measure-

ments. -According to the principle just stated, we should

ever seek to improve those of our methods which are the

369

370 THE AMERICAN NATURALIST [Vou. XLII

least accurate, not those which are the most easily suscep-

tible of improvement. It is, indeed, often a waste of

energy to seek the highest possible accuracy in all of a

series of measurements where one or more are at best of

low accuracy. The accuracy of the resulting summation

must be subject roughly to the error of the least accurate

of the members.

It is not my purpose to submit any recommendations

as to improvement in the general philosophy of ecology,

although we must all realize that one of our greatest

hindrances at present lies in the careless thinking which

fills our literature with wrong or at least misleading

imaginings, such as are suggested by the Jonah-like

words, adaptation, use, purpose, ete. It is to certain

lines along which improved methods of measurement

seem desirable that I wish to call your attention at the

present time. Our methods for dealing with the plant re-

sponses, with the effects of environment, already possess

a general accuracy far surpassing that exhibited by the

methods employed in measuring the environmental con-

ditions which act as causes. I am unable to avoid men-

tioning, however, one phase of plant measurement which

has so far received an almost insignificant minimum of

attention, both from physiologists and ecologists. I refer

to the subterranean portions of the plant. The relations

existing between the environmental factors and the de-

velopment and behavior of underground stems have

been studied for some forms by Vochting, Klebs and

others. Roots have usually been studied in water or in

air and only in the last few years has their behavior in

the natural medium, the soil, been seriously taken up.

A number of agriculturists have attacked the problem

here suggested, but of course with reference to cultivated

plants. Freidenfeld has made, as far as I am aware, the

first attempt at a really broad study of the ecology of

roots. The work of Dr. Cannon on the root systems of

desert plants shows how extremely important subter-

ranean competition may sometimes be. It would seem

No. 510] PROBLEMS IN PLANT ECOLOGY 371

that the underground portions of ordinary plants are well

worthy of more attention than has heretofore been ac-

corded them.

We turn now to the environmental factors. When it

is sought to determine the causes influencing the behavior

of plants growing under natural conditions, two very

different methods may be resorted to, the observational

and the experimental. By the experimental method we

try to determine, on the one hand, the kind and amount

of vegetation and, on the other, the magnitude of the vari-

ous physical conditions which make up the environment.

From these two series of observations are selected paired

concomitant factors or groups of factors, and when

the same concomitants appear in a number of such pairs

the conclusion is drawn that the relation between the

paired factors is a causal one. By the experimental

method we seek to control the conditions to a greater or

less degree, either synthetizing an artificial environment

(experimental physiology), or growing the same plant

forms under various natural environmental complexes.

This sort of work may be termed experimental ecology.

In so far as the environment is artificially synthetized, it

is comparatively easy of measurement, but where natural

conditions are allowed to obtain, the experimental and

the observational methods both require the measurement

of uncontrolled factors, and thus present great difficulties.

The complexity of natural conditions makes it neces-

Sary often to break them up into component parts and to

measure the parts separately. For convenience in hand-

ling, these factors have been classified into climatic and

edaphic, but I fail to see that such a classification has any

relation to the activities of the plant. I shall, therefore,

speak here merely of environmental factors, classifying

them, for ease in discussion, into those which are active

above the soil surface and those which are active below

it. Each group must, of course, be further analyzed

according to the purposes of the investigation. But it

must be remembered that the data from separate com-

372 THE AMERICAN NATURALIST [Vou. XLIII

ponent factors usually need to be again summed in order

to express the environment as a whole. For the great

general problems of plant geography it seems inadvisable

to attempt too extended an analysis, rather is it better to

seek methods of measurement which will furnish in-

tegrated evaluations of groups of environmental condi-

tions. With our present lack of knowledge, the pressing

of the analysis too far often results in such a complex of

data that an interpretation is impossible. A fairly satis-

factory integration of the main air factors seems to be fur-

nished by the atmometer; as to the soil factors, we have

made hardly a beginning in this direction. In the fol-

lowing paragraphs I shall first consider the measurement

of the air factors, denoting by this term all factors which

are active above the soil surface, whether or not the air

is actually involved.

Atmospheric Factors.— Atmospheric pressure can be

easily measured by means of the barometer, curves are

automatically constructed by the barograph. Consider-

ing the perfection of this instrument, it is rather unfor-

tunate for ecology that the plant is so little influenced by

the natural variations in atmospheric pressure.

Temperature is very important in plant activities, and

we have practically perfect instruments for its measure-

ment and for the construction of its curve. Unfortu-

nately we have as yet no well-tested method by which

temperature can be interpreted in regard to its effect.

A beginning which promises much has been made by Dr.

MacDougal with his integration of the thermograph

record and Professor Lloyd has told me of a new method

devised by him for interpreting maxima and minima.

Here lies one of the best fields for the scientific ecologist

with a mathematical turn of mind.

_ Wind velocity can be measured and recorded by means

_ of the ordinary forms of anemometer, but the instruments

are not well suited to field work, largely on account of

their expense. Perhaps improvement may be forthcom-

ing along this line.

No. 510] VARIATION IN NUMBER OF SEEDS — 373

The conditions of humidity, which appear to be so im-

portant to plant life, can best be measured directly by

means of the dew-point apparatus, but the instrument

is not as satisfactory in the operation as could be desired.

The whirled psychrometer and the wet and dry bulb

thermometer are more easily operated and are quite

satisfactory as regards results, especially where the

humidities dealt with are not too low. Attention may be

called here, however, to the inadequacy of the wet and

dry bulb thermometer without a strong current of air.

The current should be so strong that any increase in its

velocity would produce no further lowering of the tem-

perature of the wet bulb. The hair hygrometer is unre-

liable unless often standardized by some other instru-

ment. Especially is this so in regions where the humidity

is usually low or where its fluctuations are very great.

Much improvement is surely possible in connection with

this factor.

The evaporating power of the air, an integration of

the effects of temperature, wind velocity, relative humid-

ity, and, to some extent, of light intensity, is at least not

as difficult of measurement as formerly. The porous cup

atmometer can be made to give data for a curve as well

` as a final integration for a long period. It seems that

we may expect much from this or some similar instru-

ment.

Precipitation data are easy to obtain with amply suffi-

cient accuracy, but the factors of superficial and subter-

ranean run-off as well as that of evaporation from the’

soil surface (all of which are almost hopelessly difficult

to measure) make these data very hard to interpret, ex-

cept for particular localities. Their final interpretation

will probably go hand in hand with that of evaporation

and soil moisture.

For the measurement of light intensity—a factor which

has been shown conclusively to be of prime importance

in many ecological problems—we have at present no re-

liable and practical instrument. The delicate bolometer

374 THE AMERICAN NATURALIST [Vou. XLII

would doubtless give the data needed, but it is not well

suited to field work and is at best too expensive. The

so-called photometers (such as those used in photog-

raphy) are unsatisfactory in the extreme, both theoret-

ically and practically. They are, of course, not photom-

eters at all, but actinometers, and for our purpose it is

to be remembered that the shorter light waves are at

least not the most important in plant activity. Here again

is a field that should prove wonderfully fertile to him who

has the courage and patience to cultivate it.

The determination of the composition of the atmos-

phere is important in certain lines of investigation and in

the solution of general ecological problems in certain

regions. For this purpose the methods already at hand

are perhaps satisfactory enough, though we are unable

to obtain automatic records of fluctuations in these con-

ditions.

Soil Factors.—If the factors active above the soil sur-

face present great difficulties, those active in the soil

present greater ones. What knowledge has been gained

by the agriculturists is seldom at the disposal of the

ecologist, perhaps partly from the nature of the agricul-

tural literature, and partly from a too common feeling

that agriculture and ecology are far apart. (It appears

to me that ecology is the legitimate and necessary meet-

ing-place for scientific botany and scientific and practical

agriculture.) But the agriculturists have not made any

very great progress in this field. Their measurements

of soil conditions are too often merely determinations

of the various amounts of inorganic salts which can be

extracted from the soil by one or another cleverly chosen

solvent. In some cases determinations are made of the

total amount of organic matter in the soil, but it appears

that these chemical results lack much in ease of inter-

pretation, so much that they are of little value to the

ecologist.

Soils have been classified by various workers according

to the size of the component particles, but I have not

No. 510] PROBLEMS IN PLANT ECOLOGY 375

found any adequate method of interpretation by which

the data of the physical analysis may be made to aid in

the explanation of vegetational conditions. There is no

doubt that these data contain much valuable information,

if we but knew how to interpret them.

A beginning has been made in the important and funda-

mental inquiry into the attraction of the soil for water

and the ability of the soil to conduct water to plant roots,

but our ignorance in this regard is even more dense than

that concerning the normal physiology of the roots them-

selves.

The geological origin of soils (a subject which makes

up a large portion of the text-books on soils) is of no

possible importance in either agriculture or ecology.

Mitscherlich—the author of the most scientific book on

soils which I have come upon—says in his preface,

For our cultivated plants the geological origin of the soil in which

they grow is in no way important; the growth of the plants must

always depend upon the present physical and chemical constitution of

the soil.

Of course this is just as true of uncultivated forms.

But attention needs to be called here to the principle

already mentioned, namely, that in the pioneer work in

such a field as this it is often not well to analyze the great

general factors to too great an extent. Great general

vegetational features may be compared with great general

soil features, and wonderfully enlightening results have

come from such comparisons, as, for example, those ob-

tained by Dr. Cowles and his associates in this field.

The possible importance of small amounts of organic

chemical substances in the soil has been strongly empha-

sized by the work of the Bureau of Soils and by that of

Dr. Dachnowski and others, and evidence in this regard

is rapidly accumulating from all parts of the world.

There is now little reason to doubt that bog soils and

others which are poorly drained owe the character of

their vegetation in great part to the presence in the soil

of toxic bodies. There is evidence that many well-

376 THE AMERICAN NATURALIST [Vou. XLIII

drained soils contain similar substances. The ecologist

can not afford to neglect this important line of advance.

The water conditions of the soil have not received the

attention which their importance justifies. For deter-

mining the amount of soil moisture our methods are con-

fessedly crude and unsatisfactory, yet they have not

been employed as extensively as their accuracy seems to

justify. Graphs of the fluctuations in the water content

have yet to be constructed, although their construction is

comparatively simple and their value for our purpose

must be very great. Such curves should replace the

bare and almost useless data of precipitation and run-off.

Improved methods of measuring soil moisture will of

course be of great value, if such can be devised.

As to the rate at which the soil can supply water to

the plant—quite a different question from that dealing

with the amount of soil moisture—we know almost noth-

ing. This rate of possible supply, or the resistance

offered by the soil to water absorption by roots, is, I

think, perhaps at present the most important problem

in all ecology, and it has hardly been touched upon.

But the problems here suggested seem to be as difficult

as they are important.

We know almost nothing in a quantitative way about

the relations between the oxygen of the soil and plant

development. If this field should be developed we should

undoubtedly be placed in condition to explain many dark

and complicated points. The capillary power of the

soil apparently determines, other things being equal, both

the rate of water supply and that of oxygen supply, and

perhaps the best that can be done here, in the absence

of more perfect methods, is to study plant behavior with

reference to capillary power and water content. But

ecologists have hardly even attempted to relate the easily

determined capillary power (which is constant in any

given soil) to the vegetation, and it is difficult to foresee

what important results might be forthcoming from such

a simple study.

No. 510] PROBLEMS IN PLANT ECOLOGY old

The temperature of the soil can be measured and

recorded with about as great ease as can that of the air.

But we meet here the same difficulties in regard to in-

terpretation.

Finally, for a goodly number of ecological investiga-

tions, the bacterial flora of the soil must be investigated.

The agriculturists have made good progress here and we

may do well to follow them. The possibilities are very

great.

In conclusion I should like to call attention to what

appears to me to be the one great general need of ecolog-

ical work, namely, the need of quantitative studies. It is

only through such studies that the science of the relation

of the plant to its environment can make real progress.

DISCUSSION oF Dr. LIvVINGSTON’S PAPER.

Dr. Burns: I am heartily in accord with all Dr. Livingston has said,

and I have a lot of records of light readings, that I think I have had for

the past six or seven years, that I don’t know what to do with. An ecolog-

ical work, for instance, will dilate on rain force, and then leave that alone,

and presently suggest something entirely different. It seems to me that

e could work on something in the line of the determination of the maxi-

mum and minimum of light, and along this line I have been trying to work

out the amount of shade that these plants can endure before they will die

out and be succeeded by some other plant, but I have not got on very far.

Dr. Ponp: It would be very valuable if we had some work bearing upon

an analysis of a given factor in a given case, and it may be interesting to

a that.a recent article really attempts E I refer to the article of Ball’s“

‘‘ Temperature and Growth.’’ Of course, Soari is an external

ee Its effect on growth may be either unseen or apparent in som

outward manifestation. This article shows, by a aisha analysis, that the

innit pon of that fungus and finally stopped its growt

SOR BARNES: May I take this opportunity to say that I hope very

much some of the reforms will be adopted, not only by ecologists, but

fraternity cH

quotation that our ideas never keep pace with the growth of our language,

and our language never with our ideas, has more truth in it than we

imagine. Our ideas have not always kept pace with the growth of our

language (laughter). It is greatly to be hoped that the language will not

be strained any farther. We need no extensive growth of that, and while

far be it from a mere editor to suggest to any ecologist that a page of

tabular matter not only costs three times as much to set up, but seems

378 THE AMERICAN NATURALIST [Vot. XLIII

actually useless and trifling, yet I hope that these suggested reforms will

become actuali

LIVINGSTON: In that very connection it oceurs to me that perhaps

up, that is analysis of conditions. What found out about physical

conditions—then comes the question, how do these conditions come into

existence? That is, perhaps, a part of the study of ecology. ery often

e have to take he analysis back in order to explain how conditions arise;

fa instance, this plant grows less because of light, heat and moisture condi-

tions. Now I might enquire how these conditions are brought about? By

a tree growing alongside or the absence of vegetation—so we see how

ecology site ever to other fields!

R. FITHS: I recall, in connection with the gentleman ’s statement

regarding aa and heat, a surprising experience I learned of ta

to a commercial gentleman in Arizona—a commercial man but a scientific

one at the same time, a gentleman connected with the solar motor industry,

of which you have heard a great deal, and I was surprised at the results

of his measurement of light and heat, the measurement of heat particularly.

He measured heat, of course, in direct relation to his machine—the reflecting

surface of his machine—by a thermometer placed in a black box, with its

face to the sun, the box simply being an open one, with the open side to the

sun. Much to my surprise he informed me positively than an hour’s sun-

light on the Atlantie Coast was more efficient than an nie ’s sunlight on the

desert of Arizona. Now, that may be an obvious fact to botanists, but

it was not to me at the time. I subsequently thought of the matter, and

thought possibly I could see reasons for it, but it had never occurred to

rainfall the atmosphere is clearer. The transmission of heat is more

certain and undoubtedly his statement was true. He has demonstrated it

with his e. I presume it is due to the presence of a large amount

of foreign material in the atmosphere.

NOTES AND LITERATURE

NOTES ON EVOLUTION

THE retirement of Ernst Haeckel from his chair in the Uni-

versity of Jena is a punctuation mark—fortunately not a period

—in the long and noble story of ‘‘ Haeckelismus in der Zoologie.’’

I am aware that the coining of this phrase by Karl Semper and

the subsequent use of it by some zoologists and many theologists

were not of the nature of compliment to the veteran fighting

evolutionist of the Thiiringian hills. The phrase was meant

to connote reproach, but I prefer to see in it an unavoidable

recognition of the great influence and importance of Haeckel’s

work in the history of biology and evolution. We may decry

speculation in zoology and phylogeny in evolution, but without

scientific imagination we do not go far forward in any science,

and the principles of evolution studied without reference to

their practise would leave bionomics far more ‘‘philosophical’’

and much less ‘‘biological’’ than we would have it. Even if

Haeckel’s speculations and vigorous championship of them had

done no more than serve as a stimulus to others to work in order

to fight them, they would have had their inestimable importance

in evolutionary history. As a matter of fact many of the

Haeckelian speculations of the early days are now the accepted

and incorporated evolution commonplaces of the present day.

Haeckel gives up lecturing to the Jena students and peering

over their shoulders at their dissections to devote himself espe-

cially to the building up and care of his new Phyletic Museum.

He is now seventy-five years old, and for forty-five years has

taught, investigated and written at Jena. Now he gives up part

of this work to undertake something else in its stead. A glorious

record! And one not uncommon in German scholastic life.

Leuckart was lecturing vigorously every day in the week except

Sunday up to within two weeks of his death at seventy-six, and

the number of active and anything but superannuated pro-

fessors in German universities beyond the pees fund retir-

ing age is suprisingly large.

The new Phyletic Museum at Jena has T established solely

379

380 THE AMERICAN NATURALIST [Vot. XLIII

through Haeckel’s personal activity and largely through his

personal financial aid. He has given to it 30,000 M. of money

and his private library and collections. The building, for

which original gifts amounting to 100,000 M. were obtained is

now finished and the gathering together and arrangement of

collections are going on. It is hoped to have sufficient material

on hand and arranged by next spring (1910) to justify the

public opening. The building was formally taken over by the

University of Jena last July (1908) on the occasion of the cele-

bration of the 350th anniversary of the university’s founding.

The gathering of the collections and their maintenance must

depend entirely in private gifts, and Haeckel makes an earnest

appeal to all friends of the development theory for financial aid.

Money may be sent to the Rentamt der Universitit Jena, Jener-

gasse 8, Jena. Donors of sums of 10,000 M., or over, will have

their names engraved on a tablet of ‘‘Hwige Mitglieder des

Phyletischen Senates’’ placed in the entrance hall of the mu-

seum. Professor Haeckel writes in a recent letter that the total

expense of establishing the museum will be about 200,000 M.,

of which 130,000 M. have so far been raised.

In Germany there goes on a steady discussion of the Vital-

ismus versus Mechanismus subject. There is a constant run-

ning disputational conflict between the mechanicalists and the

neo-vitalists. The latter find their champion in Hans Driesch,

while among the former Otto zur Strassen is one of the most

active: If Driesch were not so keen in his criticisms and so adroit

in his argumentation victory would have been long ago with his

antagonists, for he supports an impossible position. But he

uses the method of offense and not of defense; he attacks the

weak places in mechanicalism and constantly shifts the burden

of proof to the shoulders of the mechaniealists. It is the

method made famous, and for long successful, by Weismann,

in his war on neo-Lamarckism. But Weismann had in the end,

when his position was attacked, to make great concessions, and

so it will be with Driesch. Neo-vitalism is really not new,

despite its new terminology, but is simply paleo-vitalism very

adroitly rehabilitated; and vitalism under any form is irrecon-

cilable with the spirit of scientific progress.

A very interesting example of the advance of mechanicalism

at the expense of vitalism on one hand and finalism on the other,

No. 510] NOTES AND LITERATURE 381

is that of the attitude and work of Dr Pierre Janet, the brilliant

Salpetriere student of nervous functions. In a recent book,

‘‘Les Nevroses,’’ and more especially in a course of lectures now

being given in the Collége de France on the expression and in-

fluences of the emotions and sentiments, Janet discards almost

entirely the finalistic explanations so well established by Dar-

win’s epoch-making book. In their place he substitutes mech-

anistic explanations, and his reasoning has great cogency.

The finalistic type of explanation of vital phenomena is very

plausible and seizing. We snarl when we are angry because

we want to scare our neighbor by showing him we are about to

bite; or rather, as we no longer bite, we do it because our an-

cestors did when they wanted to warn their neighbors to keep

to their own tree; and we smile because it is useful to show an

opposite state of odink.

But Janet—and others—find that smiling is the mechanically

produced contortion of muscular stimulus due to strong emo-

tional shock or mental agitation, and this mental agitation is

not at all necessarily one of joy or friendliness or risibility.

We smile often when we want to weep, when we are surprised,

when we are embarrassed, when we are terrified. The facial

muscles are roughly divisible into two unequal sets; one, above,

of more and stronger muscles; the other, below, of fewer and

weaker ones. When the stimulus comes the muscular pull of

the upper set is stronger and our mouth corners go up and the

contortion we call a smile is produced. But various emotions

may produce the stimulus. If the contortion, that is the smile,

is useful, well and good; but it is not a result of usefulness.

A brick is red because it contains by very virtue of being a

brick certain chemical components in physical state, of which

an attribute is redness. We ask for no further explanation

of the brick’s color. But let a butterfly’s wing be red, and

though the waste uric granules in its cuticular scales be of chem-

ical and physical nature to compel them to absorb other colors

and reflect red just as brick stuff does, we demand more explain-

ing. We must have utility in this red; we must have a finalistic

explanation, and if this explanation be not readily afforded by

Darwinian selection or Lamarckian adaptation we have still

left the ever-ready and always sufficient explanation of vitalism.

The butterfly’s wing is usefully red because the butterfly is alive.

382 THE AMERICAN NATURALIST [Vov. XLII

We must admire the durability of the good old inheritance

of acquired characters problem, even if its repeated resuscita-

tion is sometimes a little less than interesting to us. However,

our lessening of interest in it in no way reflects any lessening

of its importance. It is still the crux of the whole species-

forming problem. Neither mutations-theory nor Mendelism

make its solution any less imperatively needed.

A recent important contribution, not of discussion alone but

of new facts, to the inheritance of acquired characters problem

is that of Jennings, who finds that, contrary to the admission

on theoretical basis of even some of the most thoroughgoing

anti-Lamarckians, acquired characters are not inherited in

the Protozoa; at least in those Protozoa which were the sub-

jects of Jennings’s brilliant observation and experimentation.

This may be a serious blow to the neo-Lamarckian side of

the case—or it may not. It is if the old statement of the

problem is to be always adhered to, but for some time now

this statement has been recognized to be faulty and outworn.

The neo-Lamarckian, taking the aggressive, prefers to put

it this way: How are we to explain the fact that heritable

differences distinguishing species or constant varieties (ele-

mentary species?) are often identical with those differences, un-

inherited, which can be produced ontogenetically among indi-

viduals of a single species of the group by submitting them to

varying environmental or nutritional conditions? The fact ex-

ists and the presumption that it raises is that these identical

species (heritable) differences have had the same. ultimate

causes which under our very eyes produce the non-heritable

differences of the ontogenic varieties.

What is needed is the mechanism of cumulation or conversion of

the non-heritable differences into identical heritable ones. This

mechanism must, of course, concern itself with reproduction,

with the germ-cells; and put as Jennings strongly puts it, it

seems at first sight as if it must be an impossibly complex

mechanism. But after all it.is the change that has to be com-

plex. The mechanism needed is one capable of producing

changes of seeming great complexity. But comparatively sim-

ple mechanical transformers that produce very complex physio-

logical changes are not unknown in biology, and there may,

after all, be one awaiting discovery by Jennings, or some other

No. 510] NOTES AND LITERATURE 383

equally ingenious and persistent student of this good old en-

during problem of acquired characters.

YuUS

Paris, March, 1909.

DE VRIES’S SPECIES AND VARIETIES

Species and Varieties—About two years ago De Vries’s

‘‘ Species and Varieties: their Origin by Mutation” was trans-

lated into German. A translation’ of the same work has now

appeared in French and no doubt it will ere long find a place

in the literature of a number of other tongues.

As the first book which presented in a popular form the dis-

tinction between fluctuations and mutations, the world-wide cir-

culation of this book means much for the advancement of modern

biological conceptions. This is particularly true because a

just delimitation of these two kinds of variations has been made,

and can be made, only through the application of experimental

methods. The result of the enlarged circulation of this work

must be to stimulate the use of these methods among the biol-

ogists of every country in which it is made accessible.

The French edition was translated by Dr. L. Blaringhem, who

is already well known because of his numerous studies on varia-

tions apparently induced by traumatism. He was a student of

the well-known French biologist, the late Professor A. Giard,

and to the memory of the latter, the French edition is dedicated.

Professor Giard was to have written a preface to this edition,

but illness which later resulted in his death rendered this im-

possible. A very brief prefatory note by the translator and

one by the author are the only additions to the text of the

English edition.

Already some subjects considered in this book could ad-

vangeously receive a somewhat different treatment, but it is

perhaps better to allow the book to stand as it was originally

written, so to take its position as a classic, retaining a historical

value when its current biological value shall have been eclipsed

by other works presenting the results of subsequent experimenta-

tion. This is evidently the attitude assumed by the author and

y et variétés: leur naissance par Mutation,’’

Paris

Vries, H.

Traduit de Tii par L. Blaringhem, pp. viii + 548, 1909.

Felix Alcan.

384 THE AMERICAN NATURALIST [Vou. XLII

translator, in presenting this edition without amendment of

any kind.

GEORGE H. SHULL.

EMBRYOLOGY

On the Totipotence of the First Two Blastomeres of the Frog’s

Egg.—It was found by Roux that if one of the first two blasto-

meres of the frog’s egg is injured with a hot needle, the unin-

- jured blastomere will develop into a half embryo. Morgan

found, however, that if the egg were kept in an inverted position

after the injury of one blastomere, the other would develop into

a whole embryo. He attributes this difference to the rearrange-

ment of the ‘‘mosaic’’ structure of the egg by flowing of sub-

stance, of different specific gravity (Born). However, he sug-

gested to me that the half embryo obtained by Roux might be

due to the presence of the injured blastomere. In Triton, when

` the first two blastomeres are separated, each gives rise to a whole

embryo (in case the first cleavage plane would have become the

median plane). I have been trying various methods for re-

moving one of the first two blastomeres of the frog’s egg, and

succeeded in getting a small per cent. of the remaining blasto-

meres (of Chorophilus triseriatus) to develop. The puncture of

the egg membrane caused it to shrink down on the remaining

blastomere and left an opening for bacteria. Although there

was a great mortality in the operated eggs, quite a number of

them gastrulated (as wholes), and several of them reached the

tadpole stage. The pressure of the egg membrane seemed, to

hinder their further development and none of them ha.ched, ,

although one lived until I fixed it for sectioning, after the con-

trol eggs had hatched. In no case was a half gastrula found,

and as this is the earliest stage at which the bilateral symmetry

is very pronounced, all of the embryos were wholes as far as

could be observed. Probably all operated eggs in which the

median plane would not have coincided with the first cleavage

plane died before gastrulation.

J. F. McCLENDON.

UNIVERSITY OF MISSOURI, April 8, 1909.

SE Ee Rg nee NEES Oe OL ORS AM oe DEM ES FI TENOR Bee | eS ST Oe AES ET EROT

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THE

AMERICAN NATURALIST

Vout. XLIII July, 1909 No. 511

SELECTION INDEX NUMBERS AND THEIR USE

IN BREEDING?

DR. RAYMOND PEARL ann FRANK M. SURFACE

AGRICULTURAL EXPERIMENT STATION, UNIVERSITY oF MAINE

I. Tue NATURE or THE SELECTION Process

WHATEVER one’s views regarding the relative impor-

tance of different theories as to the method of inheritance

for practical breeding, it must be recognized that the

vast majority of all the actual breeding operations which

are being carried on by plant and animal breeders at the

present time are conducted by some method of selection.

The belief is firmly held by most practical breeders that

the bulk of the improvement which has been made in

domestic plants and animals has been as the result of

selection. While it is also coming to be recognized that

hybridization may play an extremely important part in

breeding operations either by causing increased variation

or by bringing about a recombination of characters, ac-

cording to Mendelian principles, yet selection must always

be used as a supplement to hybridizing in practical breed-

ing. The higher degrees of perfection demanded in judg-

ing ring and show room are only attained by the most

careful and close selection. The manner in which suc-

cessful selection operates, that is whether by isolation of

pure or homozygote strains from a mixed population or

by the gradual cumulative effect of adding together slight

' Papers from the Biological Laboratory of the Maine Agricultural

Experiment Station, Orono, Maine. No. 11.

385

386 THE AMERICAN NATURALIST [Vou. XLIII

fluctuating variations, need not here concern us. In

either case the breeder is continually meeting the same

practical problem of selecting breeding stock with refer-

ence to several characters.

It is an obvious fact that a breeder practically never

wishes to improve only one single characteristic of the

plant or animal which he is breeding. What is usually

desired is to improve several characteristics at the same

time. Thus, with dairy cattle, while the main object in.

breeding is to increase the amount and quality of the milk

other things such as constitutional vigor, breeding capac-

ity and the like can not be lost sight of in making the

selections of breeding stock. Or in maize breeding, to

take an illustration from the plant side, while one may be

desirous of increasing the protein content of maize, in

breeding for it he must always keep in mind the confor-

mation of the ear, size of ear, yield and a whole series

of other characteristics.

While it is generally true that one wishes in practical

breeding to improve more than one feature at the same

time, it is an extremely difficult thing to make concur-

rently close selection of two or more characteristics of an

organism. This difficulty is essentially a psychological

one. It is the difficulty of trying to do more than one

thing with the mind at the same time. The way in which

this operates in breeding by the method of selection may

be illustrated by an example. Suppose one is attempting

to improve a strain of maize with respect to (a) earliness

and to (b) conformation of the ear at the same time.

When beginning his field selection of plants he makes a

resolution that he will keep to a certain standard with

reference to both of these characteristics and will accept

nothing below those standards. Presently he comes to a

plant which is by far the earliest in the field. It by a

great deal surpasses all others in respect to this char-

acter, yet unfortunately the ear of this plant falls below

his chosen standard for conformation of ear. What is to

be done? Logically the plant ought to be rejected. But

No. 511] SELECTION INDEX NUMBERS 387

if the breeder is deeply interested in improving the corn

with respect to earliness what actually will happen will

be this: he will decide to take this plant on account of its

earliness and in spite of the defects of the ear. In selec-

tion work every degree of compromise of this kind is

made and the larger .the number of characters one at-

tempts to deal with at the same time the more compro-

mises are made. Where shall the line be drawn beyond

which further compromise shall not be permissible?

Il. THe THEORY or SELECTION INDEX NUMBERS

It would seem to be highly desirable to devise, if pos-

sible, some method for the use of the breeder who is

practising selection which would get over in a greater or

less degree the difficulty which has been outlined in the

preceding section. What is needed is some method

whereby a selection of several characters may be made at

the same time in an absolutely impersonal and impartial

manner without throwing out absolutely those individ-

uals which are especially good with respect to a single

one of the group of characters undergoing selection and

mediocre or poor with respect to the other characters of

the group. It has occurred to us that a way of reaching

this desired end is found in the use of what we have

called ‘‘selection index numbers,’’ borrowing the termi-

nology and something of the idea from the literature of

political economy.

An ‘‘index number’’ in the sense here used means a

single mathematical function which combines in itself the

values of several independent or correlated variables.

In such a function each of the variables may be weighted

in any desired manner to meet the needs of the particular

problem. Having decided the relative degree to which

each variable shall be weighted, the index number as

finally calculated gives an absolutely impartial and im-

personal summing up of the total combined value or effect

of the variables entering into it.

The theory of a breeding index number may be illus-

388 THE AMERICAN NATURALIST (Vor. XLIII

trated by a concrete example. Let the matter of improv-

ing maize by selective breeding be taken. Suppose that

a breeder starts with a promising variety of yellow dent

corn. This variety, while promising, has never been im-

proved by breeding at all. The ears are only fair in

respect to size and shape. The principal aim of the

breeder of this corn, let us suppose, is to increase the

‘‘earliness’’ (i. e., shorten the time of maturing), but at

the same time he wishes to improve the other character-

istics of the corn—size and shape of ear, relative pro-

portion of corn on cob, and yield per acre. In making

field selections of plants to furnish seed for testing out

by the ‘‘ear-row”’ or other method, the breeder will en-

deavor to select with reference to as many as possible of

the points enumerated above in addition to ‘‘earliness.”’

Further it will be desired after the ears have been har-

vested and dried to take careful account in selecting the

seed of at least the following points: Shape of ear, length

of ear, circumference of ear, condition of tip and butt of

the ear, kernel shape, germination and proportion of

shelled corn to cob. Now if a plant happens to be especi-

ally early, even though it be relatively poor in respect to

these ear characters, it is likely to be selected to furnish

seed, in spite of these defects. But it is possible to devise

a formula for a selection index number which shall give

whatever weight may be previously agreed upon to each

of these several variable characters of the corn which

have been enumerated. Having settled upon a particular

formula, the selection of seed then becomes essentially a

purely mechanical matter so far as the characters in-

cluded in the formula are concerned. The value of the

index will be determined by the relative contributions

from each of the included variables. If the breeder cal-

culates such a selection index number, and takes no ears

with an index below that standard, it will then be pos-

sible for him to select with reference to a series of char-

acters in an unbiased and impartial manner.

No. 511] SELECTION INDEX NUMBERS 389

Analytically considered a selection index is an expres-

sion of the general form

I, = ¢(2, y, P, G aW) (1)

where J, denotes the selection index and a, y, p, q, ete.,

are the variables upon which it desired to carry out

selection. The practical question which has to be solved

in forming a selection index in any given case as to what

shall be the form of the function ¢. The formula for an

index should fulfill the following requirements:

1. It should be simple and easily calculated.

2. The value of the index should increase as the desira-

bility of the individual as a breeder increases.

3. The index should be relatively more sensitive to

small changes in important characters than to those in

unimportant characters; that is, the variables should be

differentially weighted.

4. The value of the index should decrease as undesir-

able characters become relatively marked.

It has seemed to the writers that to a first approxima-

tion the following general form of expression will be

found to be well suited for a selection index:

Gn by + cat: bw (2)

t @Got+bqecert--- tnt

In this expression xv, y, 2, --:, w are variables which be-

come more desirable (i. e., from the breeder’s standpoint)

as their values increase; whereas p, q, f, ++, t are vari-

ables which become more desirable as their values de-

crease.2 The quantities a, b, c, --:, n, and a’, b’, C ---, w

are constants to be given arbitrary values in the pro-

portions that the different variables are to be weighted.

It will be seen that a selection index number as de-

scribed above is in a sense an adjunct or supplement to

a score card. The index affords a means of condensing

the entire information which the score card gives into

one unit which can be then dealt with individually.

? Cf. actual indices for poultry and corn, pp. 392 and 397 infra.

390 THE AMERICAN NATURALIST (Von. XLIII

Selection indices of the character above described may

be separated into two general categories. These cate-

gories may for the sake of convenience be designated as

(a) fundamental and (b) special. A selection index is

to be regarded as fundamental when it includes in its

formula those characters of an organism which every

breeder will wish to maintain at a high grade or improve,

whatever may be the special purpose for which he is

breeding. Thus, for example, in maize breeding whether

the breeder is working for high protein or high oil con-

tent or earliness, he will always desire to have well-shaped

ears with good tips and of good size, a high yield of

shelled corn to the acre and good vitality (i. e., germi-

native capacity) in his seed.

These and other characteristics which we need not take

space here to enumerate are in a sense fundamental or

universal characteristics which every breeder wishes to

improve or, at least, to keep at a high standard. Similar

considerations obtain in breeding dairy cattle or poultry

for performance. Besides the performance in respect

to milk production or egg production every breeder of

these animals desires that what may be called the ‘‘breed-

ing capacity’’ of his stock shall be constantly improved

or, at least, not impaired. By ‘‘breeding capacity”? is

meant ability to produce numerous and vigorous healthy

offspring, to put the matter in the broadest way. An

index number which has to do with these universally de-

sired characters may be called the fundamental selection

index for each type of organism.

On the other hand, by a special selection index is to be

understood one which includes those characteristics which

a breeder is specially and particularly working to im-

prove. In the case of the corn breeder working for high

protein, the protein content of the ear will constitute one

of his special selection indices either by itself or in com-

bination with some other characters. In dairy cow breed-

ing the butter fat content of the milk will be a special

selection index. :

No. 511] SELECTION INDEX NUMBERS 391

What may be called the final selection index may be

formed by combining mathematically the fundamental

and special indices in a single index number.

III. A SELECTION INDEX ror POULTRY

The writers are engaged in the experimental breeding

of poultry and of maize with reference to utility char-

acters. One of the special aims of the poultry breeding

work is to learn how to fix superior egg production in a

strain by breeding. In the corn breeding the chief special

aim is to improve a strain of sweet corn in respect to

earliness, so that it may mature seed under Maine cli-

matic conditions. In connection with this work the idea

of selection index numbers has been developed. It is

proposed to discuss here the particular selection indices

which we are using for poultry and for sweet corn simply

as an illustration of the theory of: such index numbers

and of their application in actual practical breeding

operations. It is not our intention to maintain in the

least that the indices kere given are the best which could

be devised or even that they are not subject to change in

our own hands with further experience. They are still

in the experimental stage. Our only reason for calling

attention to the particular forms of indices which we are

using at this time is that we believe that the general idea

of selection indices as set forth in this paper may prove

to be a useful one to the breeder working in other fields.

The fundamental idea of a selection index number is a

most elastic one. Any one may adopt and modify these

indices and weight the different variables, in any way

to suit his individual needs. But there is no doubt that a

general plan of this kind becomes more intelligible if

concrete illustrations of its operation are given. The

specific selection indices now to be discussed are pre-

sented solely as illustrations of the general theory.

In the case of poultry breeding a fundamentally de-

sirable thing, whatever may be the special object of the

392 THE AMERICAN NATURALIST (Vou. XLII

breeder, is reproductive or breeding capacity in the birds.

A ‘*200-egg’’ hen is of very little value as a breeder if she

is not able to produce when mated with a good male bird

a fair precentage of chickens which will live.

It is very generally stated by practical poultrymen

that the point on which it is most often decided whether

a given commercial venture in the poultry business shall

succeed or fail is the expense involved in the hatching

and rearing of the chickens. The female that will pro-

duce eggs which will yield a high proportion of chickens

from the eggs set, and whose chickens live through to

marketable age is an extremely desirable bird from a

practical standpoint.

The fundamental selection index which we have chosen

for poultry relates primarily to the breeding capacity of

the female. The value of this index for a particular bird

can only be determined after her breeding capacity has

been tested. This poultry selection index comes into

application in deciding which of the pullets that have

been tested as breeders in their pullet year shall be kept

over to be used as breeders in their second year of life.

The formula which has been provisionally adopted in

our work as a fundamental poultry selection index is as

follows:

_ d(a+ bd)

yf asi

The following scheme shows the meaning of the letters

in the formula:

I, = general or fundamental poultry selection index for

an individual bird.

a = percentage of this bird’s eggs which hatched.

b= percentage of eggs actually laid by this bird to the

total number it was possible for her to lay between

February 1 and June 1 (i. e., the breeding season)

of the year for which the index is calculated.

c = percentage of this bird’s eggs which were infertile.

d= percentage of chicks hatched from this bird’s eggs

No. 511] SELECTION INDEX NUMBERS 393

which died within three weeks from the date of

hatching.

A brief discussion will make clear the reasons why

these particular variables are chosen for the index and

are arranged in the formula in the manner that they are.

A bird’s value as a breeder increases as the percentage

of her fertile eggs which hatch increases. Therefore a

should go into the numerator of the index fraction.

Similarly a bird’s value increases as a breeder in pro-

portion to her egg production in the breeding season. A

bird which produces few eggs during the breeding season

(whatever she may have done before) ipso facto can not

produce many chickens. Instead of using the actual egg

production in the index the relative or percentage produc-

tion is used, for reasons which have been discussed in a

previous publication by the present writers.’

Now in distinction to the factors so far discussed it is

clear that a hen’s value as a breeder decreases as the

number of infertile eggs which she produces in a given

time increases. To put this factor into the breeding

index is, of course, equivalent to asserting that the hen

plays at least an equal part with the cock in determining

fertility. This is undoubtedly the case, though it is not

the place here to present detailed evidence on the point.

Since relatively poor fertility of the eggs is an unde-

sirable characteristic c is put in the denominator of the

index fraction. The case is the same in regard to d.

If the chicks produced by a particular bird are weak and

die early when given the same treatment as that under

which other chicks thrive, it is an indication that that

particular bird is not desirable as a breeder. .

In order to give a concrete idea of the values which

this poultry selection index may take in actual cases Table

I has been prepared. This table gives the value of I,

for a number of pullets which were tested as breeders

in the spring of 1908, as well as the values of the com-

ponent factors in each case. The cases given in the table

* Cf, Me. Agrie. Expt. Station, Bulletin No. 165, pp. 46-48.

394 THE AMERICAN NATURALIST [ Von. XLIII

are not a random sample of the breeding flock but were

definitely selected to illustrate the behavior of the index.

TABLE I

SHOWING REPRESENTATIVE VALUES OF THE SELECTION INDEX IN POULTRY

AND ITS COMPONENT PARTS

DATA FOR BARRED PLYMOUTH RocK PULLETS *

Soe Seige alel ee

a Bw) 3 ice | | Š Eo | BS |

a| 53| gsi m6393 a] 53) Be! 5| 88.13

S| 8| s| 53| g4 S || S | «3| a| Sal gal 7.

a <55 Aes O wg [A g wg E te} <4 Aes | O ws As ee | EY

zZ Bin Sa ga) as-is || A Dal £4) CA) PETE

S| S| gei | Se" 2 | g | ce gel S | Sh 8

2 pis] Sa Eo oons 2 Ge) g LE Sa | B „a | 3

a) g £ Cia | ai a far e (u |

10 | 21 | 1833) 36 |33.33| 2.8 || 29| 28 |28.33| 27 | 0 | 100

160 9 |15.83| 42 |. 0 | 29|| 23| 39 |35.83| 28 | 8.33| 10.0

402 | 14 |33.33| 30 |50.00| 2.9 || 428| 46 | 40.08! 20 |22.22 | 10.0

352 | 12 |41.67| 14 |60.00| 3.6 || 122| 49 |34.17| 15 |23.53 | 10.5

31.67 | 32 |69.23| 4.0 5| 41 | 37.50! 36 | O | 106

438 | 35 |35.00| 45 | 37.50; 42|| 712| 42 50.00) 20 | 20.00, 11.2

441 | 38 |20.00| 33 | 33.33| 4.3|| 408| 48 | 45.66) 16 | 22.73) 118

21 35.00| 14 | 44.44) 5.0|| 38| 61 | 37.50; 9 | 28.00) 13.0

393 | 12 | 47.50) 9 | 50.00) 5.0 || 731| 27 | 35.83) 23 | O | 13.1

705 | 38 | 26.67| 34 | 25.00/ 5.4|| 395| 29 | 37.50) 24 | 0 3.3

717 | 24 |21.67| 19 | 20.00| 5.7)| 43) 56 |54.17| 6 | 35.29) 133

39 | 23 |29.17| 26 | 16.67| 6.0|| 409| 37 | 46.67! 4 | 25.00; 13.9

32 |37.50| 16 | 33.33| 6.9|| 771| 43 | 60.00} 13 | 22.22) 142

746 | 59 | 28, 15 | 47.06| 6.9|| 19| 68 | 24.17| 24 | 6.66; 145

87 | 36 |39.17| 17 | 35.71| 7.0|| 152| 26 | 39.17) 11 | 9.09) 15.5

61 | 32. 15 | 50.00! 7.1 || 366! 52 | 25.83, 13 7.14 A

442 | 41 | 68.33| 38 | 28.57| 8.2|| 768| 74 45.00) 20 | 9.38) 19.6

400 | 44 | 47.50! 16 | 38.10} 8.2|| 434| 72 (58.33) 17 | 14.28/ 20.2

18 | 40. 8.3) 25.00 | 8.5 || 750| 5 | 52.50 16 10.00 20.3

757 | 23 | 51.67; 10 |3077 8.9 770| 71 |50.83| 9.8| 12.82) 25.8

29.1 6 | 27.27| 9.1|| 752| 48 |59.17| 6 | 12.50) 275

112| 17 | 46.67| 18 | 25.00/ 9.3|| 397; 38 |40.00| 6 | 5.89) 303

753 | 61 | 47. 46 |10.53| 9.4|| 168| 88 |35.83| 4.7| 13.89) 31.6

407 | 41 | 41.67| 18 |2353| 9.7|| 749| 57 |46.50| 4 | 6.45| 45.2

From this table the following points are to be noted:

1. The selection index ranges in value between 2.8 and

45.2 in the cases chosen for illustration. These figures

do not represent the extreme values which may be ob-

tained for this index. They suffice, however, to bring

out the point of practical importance that the index

fluctuates through a wide numerical range as the value

of the birds as breeders changes.

*It should be said that all the records given in this table were made

under uniform conditions as to housing, feed, age of birds, ete. The hateh-

ing was all done in incubators.

No. 511] SELECTION INDEX NUMBERS 395

2. A study of the detailed figures of the table makes it

apparent that the index is a perfectly impartial and ac-

curate measure of a bird’s breeding performance. Thus

to take an example, bird no. 402 has a low selection index

(2.9), while bird no. 168 has an index more than ten times

larger (31.6). Do these figures represent fairly the dif-

ference between these two birds in respect to breeding

performance? Let us examine the detailed figures. But

14 per cent. of the fertile eggs from bird no. 402 hatched

as against 88 per cent. of the fertile eggs of no. 168. In

regard to number of eggs laid during the breeding sea-

son the two birds are about equal, with what advantage

there is in favor of no. 168. But on turning to the ques-

tion of fertility of eggs we see that 30 per cent. of the

eggs of no. 402 were infertile as against only 4.7 per cent.

in the case of no. 168. The same condition obtains in

regard to the vitality of the chicks. Fifty per cent. of the

chicks from no, 402 died before attaining the age of three

weeks, whereas but 13.89 per cent. of no. 168’s chicks died

within this time. There is no doubt of the great superior-

ity of 168 over 402 in breeding performance. The index

gives an exact measure of its degree or amount.

3. The detailed figures bring out clearly the further

_ point that the value taken by the index is not unduly in-

fluenced by any one factor. Low values for one variable

may be offset by high ones in another. In general, the

variables which form the numerator of the index fraction

are seen to increase as the index increases. The reverse

holds in general for the variables in the denominator of

the index. The facts regarding the two variables, a

(percentage of fertile eggs hatched) and c (percentage of

infertile eggs) are shown graphically in Fig. 1.

The diagram shows that the percentage of fertile eggs

hatched in general increases as the selection index in-

creases in value, but with much greater fluctuations from

bird to bird. On the other hand the percentage of in-

fertile eggs in general decreases as the value of the index

increases, but again with much greater fluctuations. The

Se & 2. 8: a

Variables a and c

Fie. 1 iagram showing the relation to the value _ the ena index =

the r given in Table I; O-———O selection index ; . Ti

two of the variables entering into it. The abscissæ pigas the biras 5 arranged »

fertile eggs hatched; @-- -@ percentage of infertile eggs.

No. 511] SELECTION INDEX NUMBERS 397

smoothing effect of combining the four variables into one

index number appears most clearly from the diagram.

4. In Table I, one half of the birds have a selection

index equal to or greater than 10. This is about the

value which it would seem desirable to take as a divi-

sion point in selecting breeders. A bird with an index

below 10 can not be regarded as a good breeder.

Summarizing, we believe the poultry selection index

deseribed, or some modification of it to suit particular

needs, to be a useful aid in practical breeding operations

with poultry. It measures in an exact and impartial

manner the performance of a bird as a breeder in any

given season. On the basis of the knowledge so gained

the breeder can select birds which are to be retained for

further breeding. It substitutes an exact and impartial

measure, in the place of a rough, general impression of

the relative effect of several variables.

IV. A SELECTION [NDEX ror Sweet Corn

The idea of selection index numbers is being applied in

connection with investigations in breeding sweet corn

(Zea Mays saccharata). In this work the selection

index is based on the characters of the ear. A brief dis-

cussion of this index is introduced here for two reasons,

viz., (a) to illustrate the adaptability of the selection in- |

dex idea to widely different classes of breeding problems,

and (b) to show how such index numbers supplement the

score card in breeding operations. In planning this corn

selection index the underlying idea was that set forth by

way of example earlier in the paper (p. 386, supra).

The actual index number used for sweet corn has the

following formula:

1 4+3B+20

T D+EH F?

The meaning of the letters in the equation are shown in

the following scheme.

A = Length of ear multiplied by the circumference of the

ear (L X Cir.). This gives a measure of the ab-

solute size of the ear.

398 THE AMERICAN NATURALIST [ Vor. XLIII

100 times the weight of grains shelled from butt and

B tip of ear.

Total weight of shelled corn from whole ear

B is the percentage which the grain on butt and tip is of

total grain on the ear. This gives a measure of the ex-

tent to which ends of the ear are covered with grain.

100 times the circumference of the cob at the middle

Circumference of ear at middle.

This measures in effect the average percentage depth

of kernel (by difference).

100 times the weight of the cob.

Total weight of shelled corn from the whole ear.

pia

E = (circumference of ear at butt)—(circumference of

ear at tip). A measure of the shape of the ear.

F = 100—the observed percentage germination of grain

from this ear.

All measurements and determinations are made on the

thoroughly dried ear and are recorded in centimeters and

grams.

As an illustration of the way in which this index is cal-

culated a single example may be worked out in detail

Fic. 2. Photograph of sweet corn ear No. 596 for which the selection index

number is calculated in the text, i

Let us determine the value of I, for the ear of sweet comm

_ shown in Fig. 2, and recorded in our notes as ear No. 596. —

For this ear the following measurements were re- _

corded: 2

No. 511] SELECTION INDEX NUMBERS / 899

TiS OER Fiala cin esl ob bo a Cn ee CaaS sip Sees 14.8 cm.

Circumference oo. A A E ses meee ence aes 12.9 +

Weight AOT a T E a 118.0 gr.

Weight of shelled corn .......serssersrerrrerees 97.0 ‘*

Weight of corn shelled from butt and tip ....---- 22.8 ‘*

Weight of cob ......eeecereeeeeceenrccereerers B10 5"

Cob circumference ....... essere ester ter ereeeee 7.9 em,

Butt circumference .......+- eee eee eee reece ereee 9.3 Mie

Tip circumference .......+--+++eeeeereesrereees 6.5 ‘f

ROWE os Pecan ill ice Ge ec RWS A eee ha ib ee Re gS we 16

Number of kernels in average TOW .....+.++++e0+ 33

Germination (100 kernels tested) ....-+--++++++5 100 per cent.

Using these data to calculate the selection index it ap-

pears that:

A = 14.8 x 12.9=190.9

100 x 22.8

NEVIN BAT L

B we

3B — 70.5

100X793

29C — 122.4

100 x 21.0

p= 97.0 21.6

E = 9.3 — 6.5 = 2.8

F = 100 — 100 = 0

F? = 0

Whence we have:

__ 190.0 + 70.5 + 1224. 333.8

L= 15.7

Me + eee | AET

The value of the index in this case is much above the

average for the particular variety of sweet corn of which

this ear is a representative. This is, of course, as it

should be, since the ear is a particularly fine one for

sweet corn. Its aristocratic lineage is apparent from the

photograph. Some ears of this variety give a value for

the index of as low as 1.0 or even lower. It is obvious

that the index number for an ear of one variety is not

directly comparable with that for an ear from another

400 THE AMERICAN NATURALIST [Von XLII

variety. Corn index numbers, as formulated above, are

only directly comparable within a single variety. They

may of course just as well be used in judging a dent corn,

for example, as for the sweet corn here discussed. The

average ear of dent corn will obviously give a different

value for the index from that given by the average ear of

sweet corn.

Any one familiar with the score cards used in judging

corn in the various agricultural shows and fairs in this

country will recognize that the corn selection index form-

ula here given combines in one expression quantitative

determinations of a majority of the characters which ap-

pear on the score card. The index in a way takes the

place of the judge. It impartially ‘‘cuts for each defect”?

according to a previously agreed upon system of weights.

By the combined use of the index number, scales and

measuring tape, unconscious or conscious partiality and

bias is inevitably and absolutely taken out of the judging.

The selection index idea seems capable, when properly de-

veloped to meet the needs of particular cases, of supply-

ing in some measure that thing which has been so long

desired in all kinds of stock judging, whether of plants

or animals, viz., an absolute base or datum plane.

V. SuMMARY

The purpose of this paper is to call the attention of

those interested in breeding operations to the usefulness

of what we have called ‘‘selection index numbers’’ in

such work. The idea of such index numbers is to com-

bine in a single numerical expression the values of a

series of variable characters with regard to all of which

the breeder wishes to practise selection at the same time.

The analytical expression of this idea is discussed and

its adaptability and usefulness are illustrated by ex-

amples drawn from poultry and maize breeding. It is

shown that selection index numbers form a valuable

adjunct to the score card in stock judging.

A CONTRIBUTION TO THE THEORY OF

ORTHOGENESIS !

DR. ALEXANDER G. RUTHVEN

University OF MICHIGAN Museum

SEVERAL reasons have been given why biological dis-

cussion has, for a number of years, ceased to center about

the fact of evolution and is now chiefly concerned with the

factors, for such is evidently the case: the principal aim of

modern biological researches is apparently to throw light

upon the question of method. It is now a part of com-

mon knowledge that Darwin considered the natural selec-

tion of fluctuating variations to be the principal factor

in evolution, and some of his successors have gone so

far as to see in it a sufficient one; but, while few biologists

will probably be disposed to deny that natural selection

is an efficient factor in evolution, there seems to be now

on hand a sufficient body of data to show that it is far

from being the only one. Among other methods? that

have been emphasized, mutation and orthogenesis may be

mentioned, each of which has its adherents, and it is the

last named of these that seems to be the principal one

concerned in the evolution of a group of snakes that I

have recently monographed—the genus Thamnophis (the

garter-snakes ).®

I will briefly summarize the conditions that prevail

in this group:

1. The genus Thamnophis consists of four groups of

1 Read at the Darwinian Celebration of the Michigan Academy of Science,

April 1, 1909.

*I mention only these three (selection, mutation and orthogenesis), as

they appear to me to be the only ones that can be considered to have been

dominant methods in the evolution of the forms in the genus that consti-

tutes the basis of this discussion.

“Ruthven, Alexander G., ‘‘ Variations and Genetic Relationships of the

Garter-snakes,’’ Bull. 61, U. S. Nat. Museum

401

402 THE AMERICAN NATURALIST [ Vou. XLII

closely related forms, each group ranging both northward

and southward from the Mexican plateau (which is their

center of dispersal) into North and Middle America.

2. Each group consists of a series of forms, the ranges

of which adjoin and correspond to different geographical

regions.

3. The forms of the same group may intergrade or not,

but in either case they come in contact where the geo-

graphic conditions with which they are associated meet,

and the areas of transition in characters correspond to

the areas of intermediate environmental conditions.

When the forms intergrade the transition in characters

takes place gradually in the intermediate region, and

where there is apparently no intergrading at present the

two forms become most like each other in this region,

there being no abrupt changes in characters between two

directly related forms.

4. Each group tends to become progressively more

dwarfed away from the Mexican plateau, each form

. usually being more dwarfed than its neighbor toward

the center of origin, and less so than the representative

whose range adjoins it on the side away from the center.

= 5. The relative size is correlated with the number of

labials and rows of body scales, and these two characters

—size and scutellation—constitute the only apparent

specific differences, except in the few cases where they

are accompanied by differences in color or relative tail-

length. 3 ™

6. The amount of dwarfing is not associated with par-

ticular geographic regions, but the scutellation and rela-

tive size of any form is that of its immediate ancestor

plus the dwarfing which it has itself undergone. Thus |

a dwarf form of one group frequently occurs in the same

region with a much less dwarfed representative of an-

other group, the difference in relative size being due to

differences in the number of forms between the one in-

question and the center of origin. |

7. The variations in the characters of each form fluctu-

No. 511] THE THEORY OF ORTHOGENESIS 403

ate about a mean, and the transition in characters between

the different forms is brought about by a gradual varia-

tion of the average type.

Students of evolution problems will recognize in this

summary (a) the old story of the association of different

forms with different environmental conditions, (b) the

so-called definite or determinate evolution, and (c) that

the phylogenetic variations are gradual.

It has long been noted that, among animals of the same

group, the different forms are generally associated with

different environmental conditions. In some cases it

seems that these forms may occupy different habitats in

the same environment, but in by far the greater number

of instances, at least among terrestrial animals, directly

related forms inhabit different, but neighboring, geo-

` graphic areas. That there is some connection between the

differentiation of such a group and the diversities of the

region it occupies has usually been assumed; at least it

is a fact that must be considered in any explanation of

evolution. It is explained by natural selection on the

assumption that the different conditions in the two re-

gions demand different adaptations on the part of the

organism, but this explanation will apparently not hold

in the case of the garter-snakes, for there is certainly no

advantage in dwarfing per se. It might be assumed (and

it would be pure assumption) that this trait is correlated

with unperceived adaptative characters, but this would

seemingly be trying harder to save the theory of natural

selection than to explain the facts. I have pointed out

that there is no relation between the amount of dwarfing

and particular habitats, but that forms (belonging to

different groups) of quite diverse scutellation may oc-

cupy the same region. Apparently the conditions in

each region do not call for a particular size (as would,

it seems to me, be approximately the case if the struggle

for existence in each habitat required that the forms be-

come dwarfed), but only act to modify to some extent

the invading form, the relative size of the latter being

404 THE AMERICAN NATURALIST [Vou XLIII

determined as much by the modifications which the group

has previously undergone as by those to which the par-

ticular form has been subjected.

I believe that these objections to the operation of selec-

tion in the evolution of these forms also argue against

De Vries’s mutation theory as an explanation, for, while

it is easily conceived that mutations may have arisen

within the limits of fluctuating variation in each case,

we must also assume that the new form pushed into the

new environment, or at least now occupies it to the ex-

clusion of immediately related forms, because better fitted

for it, which does not seem to be the case. What seems

to have actually taken place is that as each group pushed

out from the center of origin it became modified each

time it encountered a new region of environmental condi-

tions, not by the selection of forms better adapted to the

new conditions, but by the modification of the entire sec-

tion that invaded the new region. This may be tested

more thoroughly by an examination of the method of

evolution.

Perhaps the most striking characteristic of this genus

is the manner in which evolution has taken place along

definite lines. Although the forms frequently have other

distinctive characters, they nearly all have this in common

that they are more dwarfed than the form from which

they have been derived, and there is no case in the genus

where a form is larger than its neighbor toward the center

_of origin. The history of each group has thus been one

of progressive dwarfing as it departed from the center

of dispersal.

It is too often overlooked by students of evolution that

natural selection can cause directed evolution (orthoselec-

tion) ; for in order that it may do so it is only necessary

that there be an accruing advantage in the increased

development of a character. The characters must thus

be utilitarian, however, which is apparently not true in-

this case. Moreover, it would certainly be taxing the

theory to make it account for the continued development

No. 511] THE THEORY OF ORTHOGENESIS 405

in the same direction in the four groups, when one con-

siders the great variety of conditions with which they

are associated. To explain this definite development on

the basis of orthoselection it would be necessary to adopt

the point of view that each form in each group found it of

advantage in the struggle for existence in its particular

environment to become more dwarfed than its immediate

ancestor, which is to my mind unthinkable when one con-

siders that we have in this genus four groups that push

out in all directions from the center of origin, into desert,

grassland and forest regions, in the tropical and tem-

perate zones, and yet in every case the modifications asso-

ciated with each region are practically of the same nature

and non-adaptive. We meet the same difficulties if we

attempt to apply the mutation theory to explain this

definite evolution, for, while de Vries’s mutants arise

suddenly and are definite steps in new directions, he

states in regard to the accumulation of characters :*

It is not by mere chance that the variations move in the required

direction. They do go, according to Darwin’s view, in all directions,

or at least in many. If these include the useful ones, and if this is

repeated a number of times, cumulation is possible; if not, there is

simply no progression, and its type remains stable through the ages.

It seems from this that in order to explain the evolution

of a group by a series of modifications more or less similar

in kind the mutation theory of de Vries is forced to fall

back upon natural selection. If I have rightly inter-

preted the conditions, I believe that natural selection, with

or without the assistance of the mutation theory, fails

as an explanation of the definite evolution of this genus,

and that we have here an example of true orthogenesis,

i. e., progressive modifications in each group without the

aid of natural selection. i

The nature of the variations is very interesting itt

several ways, and throws further light on the problem,

for, although one must be cautious of forming conclu-

Vries, H., ‘‘Species and Varieties, Their Origin by Mutation,’’ —

p. 572.

406 THE AMERICAN NATURALIST (Vou. XLIII

sions on this subject without the controlling evidence of

experimentation, certain general relations seem to be

apparent.

I have stated that the variations in each form fluctuate

about a mean, but that this mean varies, approaching in

the intermediate region that which characterizes the next

form on its line of descent. That the different forms

also originated in this way is shown in the numerous

instances where they actually intergrade. This is essen-

tially the idea of mutation (in the sense of Waagen and

Scott) or ‘‘phylogenetic variation’’, which is not to be

distinguished from individual variation by any character

of quality or quantity, but by the fact that it pursues a

determinate direction by the gradual shifting of the nor-

mal type. Conn? states that:

It should be noticed that these considerations in regard to variations

along definite lines have less significance in connection with such char-

acters as can be supposed to advance by general averages. Some organs

have been advancing in definite directions for long generations, but if

the advance consists of an increase or decrease in size of the organs there

is not needed any law of determinate variation to explain the matter.

If it be an advantage to have an organ increase in size, and if variations

in this organ occur around an average type, then without any necessity

of supposing a special law directing variations, we can understand how

natural selection will continue to increase the size of the organ in

question

All this is very true, for it is only orthoselection work-

ing on the average type, but as selection seems to be de-

barred in this case, the characters being non-utilitarian,

we apparently have in the garter-snakes a case of evolu-

tion along fixed lines as the result of definite variation.

Even if we could admit the selection of fluctuating varia-

tions as the dominant factor in the evolution of these

forms, we should encounter the additional difficulty that

it (seléstion)3 is apparently unable to create a new species,

the form slipping back to the original condition when

the selection ceases. The nature of the variations also

seems to me to debar de Vries’s theory of mutations as 4

*Conn, H. W., ‘‘The Method of Evolution,’’ p. 146.

No. 511] THE THEORY OF ORTHOGENESIS 407

possible explanation, for, according to de Vries, the

specific changes are sudden and fixed, the new race ap-

pearing fully formed, which is certainly not the case in

these snakes, unless we consider the new race as having

been formed by small successive mutations of the same

kind, which would, if I understand him rightly, be con-

trary to de Vries’s idea of mutations, for he says that

they ‘‘take place so far as experience goes without definite

direction.” We have apparently in these snakes an

example of definite but gradual variation, in that there is

in each group a gradual development of forms along a

fixed path, without the aid of natural selection.

A theory that accounts for the definite evolution of

this genus without the aid of selection is that there has

been in each group a gradual modification of the forms

under the influence of the environment. The deter-

minate variation of the average type, the close association

of the forms with different geographic regions and the

consequent correspondence of areas of transition in char-

acters with intermediate geographical conditions, would

seem to render this conclusion unavoidable, if, as seems

evident, selection is not operative here. It should be

noted, however, that, while the evolution of the genus

has been distinctly orthogenetic and associated with the

environment, it does not appear that the latter has, as

has often been supposed by adherents of this theory, a

specifie effect. This would be difficult to determine if

we were dealing with one group, for example one that

pushed northward from the Mexican plateau, for here

there would be an increasing difference in climatic condi-

tions, associated with accumulated modifications, between

the range occupied by the form at the center and that of

the most outlying species. But when all four groups

are considered it is seen that the same modifications

appear whether the group is pushing into the tropic or

temperate regions, or into deserts, semi-arid plains, or

humid forests, and it is difficult to, conceive of ‘environ-

mental conditions common to all of the regions occupied

408 THE AMERICAN NATURALIST [ Vou. XLII

by these snakes that would exert such a specific effect

upon them. It seems rather that throughout the genus

the germ cells have such a restricted number of potential

responses that the different groups have tended to vary

in the same direction (homoplasy) under the influence

of the environments which have been encountered; that

is to say; the similarity of the response is conditioned by

the constitution of the animal, the environment only

acting as a stimulus upon the germ cells.

This theory would seem to satisfactorily explain why

some directly related forms intergrade while others do

not, for if infertility is in proportion to physiological

diversity, as Darwin held, it is quite evident that as the

new form produced as a group pushes into a new region

becomes more or less modified, it will also probably be-

come physiologically different from the parent stock and

be more or less unable to cross back. This is essentially

Eimer’s Genepistasis, or Entwicklungstillstand, the

standing still of certain forms at definite stages in de-

velopment while others continue. But it should be noted

in this case that the forms that progress each time are

always associated with new geographic regions, and do

not occur, as Eimer holds that they can, in the same re-

gion with the parent stock.

In conclusion I would like to point out that the purpose

of this paper is to describe the method of evolution in the

genus Thamnophis rather than to discuss the cause of the

variations. It is evident that the suggested relation be-

tween the action of the environment and the nature of the

response of the organism can only be tested by experimen-

tation. I may add further that the interpretation offered

of the conditions in this genus depends upon whether or

not the relationships of the forms and the lines of de-

velopment are as outlined. In pursuing work of this

kind it soon becomes apparent that the relationships of

any form can only be determined with certainty when

the conditions that prevail throughout the genus have

been examined carefully, and, conversely, that erroneous

No. 511] THE THEORY OF ORTHOGENESIS 409

ideas of relationships are very liable to result from in-

complete knowledge of the course of evolution in the

group, so that it is very hazardous to select a few forms

of a genus and endeavor to discover the laws governing

their development. An illustration can be drawn from

this genus: butleri, which lies entirely within the range

of sirtalis, may, so far as its characters go, easily be con-

ceived to have been derived from the latter, and, if so,

a different theory of the factors involved in its evolution

must be sought to explain its origin. That it has more

probably been developed from radix by dwarfing only

becomes relatively certain when the lines of evolution `

in the genus have been worked out. This should discour-

age attempts to adduce as evidence for or against any

theory the relationships of particular forms before the

genus has been studied as a whole, and the general lines

of development determined.

THE ‘‘PRESENCE AND ABSENCE”

HYPOTHESIS'

DR. GEORGE HARRISON SHULL

STATION FOR EXPERIMENTAL EVOLUTION, CARNEGIE INSTITUTION OF

WASHINGTON

In Mendel’s? discussion of the behavior of character-

istics in the offspring of splitting hybrids, the phenomena

of segregation are described in terms of pairs of antago-

nistic characters. He assumed that these are represented

by pairs of internal units, one member of each such pair

coming from one parent, the other from the other parent.

This idea of pairs of characters in Mendelian hybrids has

been generally entertained until somewhat recently, and

is still perhaps not uncommonly held. De Vries* made

use of this conception in stating what he thought to be a

fundamental distinction between species and varieties,

assuming that the differentiating features of varieties a

are represented by units which are homologous with corre- 4

sponding units of the species from which such varieties

sprang, and which are paired with those units on crossing, |

while different species lack such homology and pairing 4

of determiners. —

About six years ago in a paper on Mirabilis crosses,

Correns* stated the members of several Mendelian ‘‘ pairs

of characters,” as the presence and absence of single

characters. Cuénot® in a paper doubtless written simul-

* Read before the Botanical Society of America, at Baltimore, December

31, 1908.

* Mendel, J. G. ‘‘Versuche über Pflanzen-Hybriden.’’ Verhandlung des

N PaL LE E E Brünn IV

e Vries, H

AE A pe O a A A S ETTA

: oe and Varieties: Their Origin by Mutation,’’

pp. roe 1904. See p. 251 et

*Correns, C. “Weitere pa zur Kenntnis der dominierenden

Merkmale und der Mosaikbildung der Bastarde.’’ Ber. d. deutsch. Bot.

Ges. 21: 195-201, Ap. 23, 1903.

*Cuénot, L. ‘‘L’hérédité de la pigmentation chez les souris’’ (2me

note). Arch. de Zool. éxpér. et gén., 1 (4th S.): 33-41, 1903.

410

No.511] “PRESENCE AND ABSENCE” HYPOTHESIS . 411

taneously with Correns’s paper, but published several

months later, used the same expression,® and most recent

writers on Mendelian inheritance have adopted the

method of presenting the characters in the terms of

presence and absence.’

But while this change of usage has gradually taken

place, little attention has been given to the real signifi-

cance of the newer method of statement, except by Hurst,’

who gives a good general discussion of the presence and

absence hypothesis in a paper read before the Third In-

ternational Conference of Genetics two years ago.

Hurst showed that of 44 Mendelian characteristics of

various plants and animals studied by him, 41, or more

than 93 per cent., can be appropriately described in terms

of presence and absence. As one reviews these various

characteristics, he can not avoid the feeling that in a

number of cases the presence and absence could be read

quite as well backward as forward, and it will doubtless

be impossible in many cases to decide which is the positive

character and which its absence. Thus in the contrast

between a yellow and a green pea, the yellow is described

*Cuénot has not followed up the idea however in the a of a

ea peat but continues to treat the supposedly antagonistic charac-

as if the alike positive and represented by antagonistic internal

a nr he conceives to be the chromosomes. The idea that the chromo-

somes are the determiners of the Mendelian unit-characters has been also

advocated by Spillman, but the latter appears to accept the correctness of-

e presence and absence h

* Davenport considers ‘‘ presence and absence’’ a relatively rare phenome-

non. He says: ‘‘I think it is clear that dominance in heredity appears iam

a stronger determiner meets a weaker determiner in the germ. The extre

case is that in which the strong determiner meets a determiner so aak

; >?

ance.’’ Proc. Amer. Phil. Soc., 47: "i 1908. See p. 63.) In papers

which have come to hand since my pa was read at Baltimore, Bateson

and his co-workers, and Castle have, on a other hand, declared. unequivo-

ale for the presence and absence ee , as having general validity.

See Bateson, Saunders and Punnett, ‘‘ Experimental Studies in the Physi-

ology of Heredity.’’ Reports to te Evolution — of the Royal

Society, IV, pp. 40, 1908, see p. 2, and Castle, W. E., ‘‘A Mendelian View

redity,’’ Science , 29: 395-400

; , March 5, pe

urst, C. C. ti Mendelian Ohataietdre in Plants and ‘Animals.?? Report

of the Third International Conference on Genetics, pp. 114-128, 1906.

412. THE AMERICAN NATURALIST [ Vor. XLIII

as present in the yellow pea and absent in the green pea.

What is to hinder us from describing the green as present

in the green pea and absent in the yellow one? Similarly

in the contrast between tall and dwarf, one could perhaps

say ‘‘presence and absence of dwarfness on a tall basis”

as appropriately as ‘‘presence and absence of tallness

on a dwarf basis,’’ and there seems no sufficient reason

why the palm type of leaf in Primula should not just as

well be considered a shortened fern type, as the fern an

elongated palm type, or that the thrum is a shortened |

pin-eye quite as well as that the pin-eye is an elongated 4

thrum. But notwithstanding such difficulties as these, 4

there can be no question that most of the phenomena of

Mendelian inheritance are more simply stated in terms

of presence and absence than in any other way.

It has appeared to several writers as a difficulty for this 3

hypothesis that in a number of cases what appears to be a

the absence of a character is dominant over its presence.

There are a number of noteworthy cases of this kind.

Thus, in cattle the hornless condition is dominant over

horns; in most breeds of poultry white plumage domi- a

nates over colors and white legs over yellow legs; in |

snails unbanded shells dominate over banded, and less

banded over more banded; in wheat, smooth heads domi-

nate over bearded; in flowers having a yellow plastid |

color, white is dominant over yellow; in canary birds the

presence of a mottled pattern is dominated by its ab-

sence, though in most cases color patterns are dominant

over their absence. Thus in the mottled varieties of —

beans, for instance, the mottling factor is dominant over

its absence, and in rabbits, the English-marked, Dutch-

marked, tan-marked, tortoise-yellow, and agouti patterns

are in each case dominant over their absence.

At several places Hurst states (loc. cit.) that the as-

sumption that a certain character is the presence-char-

acter would ‘‘imply the dominance of that character,”

though in eight instances among the 44 he cites, he

definitely places the absence dominant over presence. In

No.511] “PRESENCE AND ABSENCE” HYPOTHESIS 413

speaking of thrum and pin-eye Primulas (p. 122) he says:

If we regard it as presence and absence of pin on a thrum basis this

would imply dominance of pin over thrum in the zygote.

Again regarding the dominance of short hair « over

Angora in rabbits (p. 125) he says:

If on the other hand we regard it as presence and absehee of Angora

on a short basis, this would imply dominance of Angora over short in

the zygote.

Both Bateson and Davenport appear to have tacitly

agreed that the dominance of absence over presence is

a difficulty for the ‘‘presence and absence’’ hypothesis,

for both have taken oceasion to explain that what ap-

pears to be the absence of a character may really be the

presence of a positive inhibiting factor. Indeed, Daven-

port® has taken the position that the positiveness of a

character determines its dominance, and, therefore, all

cases in which the absence of an external character domi-

nates its presence must be explained by the existence of

a positive factor in whose presence the given external

character can not be produced. Thus, he says:

A progressive variation, one which means a further stage in ontogeny

son WH ominant; a variation that is due to abbreviation of the

Be sai ae process, which depends on something having dropped out,

will be recessive

While I Se the probability that there are posi-

tive inhibiting factors, as well as factors which produce

specific structural and color characters, I think it can be

shown that such an assumption is not necessary for the

explanation of the dominance of the absence of a char-

acter over its presence. I will assume for the sake of the

discussion that the presence and absence hypothesis is

correct, and that the absence is real, having no internal

unit to represent it. This assumption seems to me, as

it did to Hurst, to be simpler and more practical than the

alternative idea that the internal units are paired in the

heterozygote, having a representative for absence as well

as one for presence. I believe there is no fact on record’?

* Davenport, C. B. Report of the Third International Conference te

Genetics, p. 139, 1906.

» Except perhaps so-called ‘‘spurious allelomorphism.’’

414 THE AMERICAN NATURALIST [Vou. XLIIL

which can not be as well explained on the basis of a

single unit, as a pair of units.

On this basis the fundamental difference between the

three classes of individuals produced by self-fertiliza-

tion of a heterozygote may be simply stated thus: There

are two classes of homozygotes, usually designated

DD and RR, and the heterozygote, usually referred to

as DR. The difference between the two kinds of homozy-

gotes with respect to any unit-character is, that one—

pauniiy the DD—has one pair of allclomonpiia or

*‘genes’’!! in addition to those possessed by the other

kind of homozygote—usually the RR. As the two kinds

of homozygotes are often not appropriately called dom-

inant and recessive, I will call the one which has the

added pair of genes (i. e., the one which has 2n-+-2 genes)

the ‘‘positive’’ homozygote, and the one which lacks

them (i. e., the one with only 2n genes) the ‘‘negative’’

homozygote. If we designate collectively the common

features of two parents which differ from each other in

a single unit-character by the letters BB, and the differ-

entiating genes by the letter A repeated as often as the

gene is repeated in each nucleus of the soma or sporo-

phyte, the positive homozygote will have the composition

AABB, the negative homozygote will be simply BB, and

the heterozygote will be ABB; and whatever differences

are observable in these three classes of individuals must

be due obviously to the presence of none, one, or two

‘t A” genes in each nucleus and to the reactions of these

with the underlying factors which have been here collect-

ively represented by ‘‘ BB.’

In order to see the bearing of these assumptions upon

questions of dominance we must consider briefly the na-

ture of the unit-characters. Regarding the nature of the

genes themselves—the primary character-producing

“= This*word is proposed by Dr. Johannsen as a substitute for words such

as pangenes, ids, allelomorphs, ete., which have been used to denote an

internal something or condition upon whose presence an elementary morpho-

logical or physiological characteristic depends. The word ‘‘gene’’ has the

advantage that it does not assume by its form or derivation any hypothesis

as to the ultimate character, origin or Dopavior of the determining factor-

No.511] “PRESENCE AND ABSENCE” HYPOTHESIS 415

units—I have nothing to suggest, for to that question I

am, like Professor Bateson,'? inclined ‘‘to hold my fancy

on a tight rein;’’ but there can be no doubt that the visible

Mendelian characters are always secondary, and but

little doubt that they are all dependent at some stage of

analysis upon chemical relations.

This is too obvious to need discussion in the case of

color-characters, and in those structural characters

which involve only some by-product of the metabolism of

the cells as, for instance, the starchy or sugary char-

acter of the endosperm in maize. It requires perhaps a

more daring flight at present to assert that such struc-

tural characters as hairiness, branching, lobation and

serration of leaves, production of horns, extra toes, dif-

ferent forms of comb, etc., which involve the number,

direction and succession of cell-divisions, depend like-

wise upon the intimate chemical nature of the proto-

plasts; but even if it could be shown that physical prop-

erties of the protoplasm are to a certain degree

determining conditions of cell-division, the resulting

structures could hardly conceivably be permanent hered-

itary features, unless these physical properties are de-

pendent at last upon the chemical composition of the

protoplasm.

Having arrived at the conclusion that all the Mendel-

ian characters are dependent upon chemical relations,

we may return to the question of dominance, and the re-

lation between the two kinds of homozygotes and the

heterozygote, and see to what extent the known facts

may be interpreted in terms of chemical experience.

A fundamental principle in this connection is the law

that the extent of a reaction between two chemicals is

determined by the amount of that reagent which is pres-

ent in less relative quantity, and not by the one which is

present in excess. When the positive homozygote,

AABB, and the heterozygote, ABB, are alike, i. e., when

there is complete dominance of presence over absence, it

12 Bateson, W. The Methods and Scope of Geneties, 49 pp., Cam-

bridge, The University Press, 1908. See p. 12.

416 THE AMERICAN NATURALIST (Vou. XLIII

may mean that already the presence of the one unit A of

the heterozygote is sufficient to result in the maximum

reaction, in which case the doubled factor AA of the posi-

tive homozygote can do no more. When, on the other

hand, one unit A is not sufficient to produce a maximum

reaction with the other factors present, the AA of the

homozygote produces the corresponding character in

greater intensity, and the heterozygote will be intermedi-

ate between the two homozygous parents. Both of these

conditions are frequently realized.

The case I have wished to deal with specifically is that

in which the heterozygote—the ABB individual—does

not differ in external aspect from the negative homozy-

gote, BB, so that the ratio becomes 1:3 instead of 3:1,

this is the situation in which the absence of a character

is dominant over its presence. In such a case the char-

acter determined by A is latent in the heterozygote. To

show that this situation is possible it need only be pointed

out that in a number of familiar instances a precipitate

is formed or some other visible reaction takes place only

in the presence of a certain excess of one of the reagents.

It is perfectly clear that in any such case, one may add

nearly enough of the reagent which is required to be in

excess, and no apparent reaction will take place, but if

the quantity of this reagent be doubled the characteristic

reaction will occur. Now this is just what I conceive

may take place in certain crosses. In the heterozygote

where the chemical unit A (of whatever nature) occurs

but once in each nucleus, no reaction becomes apparent,

but in the pure-bred forms bearing the unit A in double

quantity, i. e., AA, the specific character (or reaction)

produced by this unit appears. The heterozygotes will

then be indistinguishable from the negative homozygote,

and in the offspring of two heterozygotes bred together

there will be among every four individuals on the average

three which have the character absent and one which has

it present, or in other words ‘‘absence will be dominant

over presence,’’

No.511] “PRESENCE AND ABSENCE” HYPOTHESIS 417

Very neat laboratory experiments can be arranged to

illustrate this behavior, with any reaction in which a cer-

tain excess of one of the reagents is required, and while

these reactions will probably be in most cases of much

ereater simplicity than those presented by the interaction

of the hereditary units, and they can, therefore, be con-

sidered only as presenting analogies, I am convinced

that such analogies are not unfair ones.

It is especially easy to arrange an experiment showing

such a result in the case of certain organic substances

known as indicators, as litmus and phenolphthalein, for

here one needs to assume only that the single, unpaired

unit in the heterozygote produces such a quantity of acid

or alkali as will not quite change the character of the

cell-sap of the negative homozygote with respect to acid-

ity or alkalinity. Thus if I make an alkaline solution of

litmus and add to it as the product of one assumed unit,

A, such a quantity of any acid as leaves the solution still

slightly alkaline, I may allow this to represent the hetero-

zygote. Then the homozygote possessing the acid-pro-

ducing unit A will have it in double quantity or intensity.

When I add this second portion of acid to the solution it

is instantly changed from alkaline to acid, as is indicated

by a change from blue to red color. The negative homo-

zygote lacking the acid-producing unit and the two hetero-

zygotes are alike blue, while the individual which is pure

with respect to this unit whose specific external manifes-

tation is the production of a red color, alone possesses

that character, and this results in a realization of the

ratio, 3 absences to 1 presence, or the dominance of ab-

sence over presence. This example has the advantage of

being conceivably duplicated in the case of many vege-

table color-characters, for the very widely distributed

anthocyan which gives the red and blue colors is an indi-

cator similar to litmus, and could have been used in this

experiment instead of litmus.

Whether the situation here outlined is actually attained

in the case of red and blue flowers in nature can not per-

418 THE AMERICAN NATURALIST [ Vou. XLII

haps be demonstrated. If is the general experience that

blueness is dominant over its absence, but this is just the

result I have pictured here as a case in which absence of

redness or of acidity is dominant over its presence. I

know of no way of determining whether red flowers are

blue flowers with an added factor for acidity, or whether

blue flowers are red with an added factor for alkalinity,

and, indeed, it is conceivable that both of these situations

may be presented in different species. However, my

purpose. is attained if I have shown that there is no

greater theoretical difficulty involved in the dominance of

absence over presence than in the dominance of presence

over absence, and that the assumption that any given

character is due to the presence of an added internal unit

does not ‘‘imply the dominance’’ of that character.

The non-appearance of an externally visible character

in the heterozygote, although the corresponding internal

unit is present, as must always be the case when real ab-

sence is dominant over presence, plainly presents a kind

of latency somewhat different from the four types recog-

nized by me’? in a recent article in the American Nat-

uraList. For the sake of uniformity with the termin-

ology there adopted I may call this new kind of invisibil-

ity “‘latency due to heterozygosis.’’ Like all the other

types of latency except that due to fluctuation, the latency

resulting from heterozygosis produces no deviation from

definite characteristic ratios.

I recall at present only one case in which we can cer-

tainly identify latency due to heterozygosis, for the

reason that, just as we have seen above in regard to blue

and red flowers, it may be quite impossible in any partic-

ular instance to decide which is the positive character and

which its absence. In a particularly interesting cross

between a yellow and a reddish snail, Lang‘ has found

“Shull, G. H. ‘‘A New Mendelian Ratio and Several Types of

Lateney,?? Awxptcan Narona , 42: 433-451, July, 1908.

“Lang, A. Ueber die Bastarde von Helix borhan s Müller und Helix

nemoralis L. Eine Untersuchung zur paren enya Vererbungslehre. ©

Jena: G. Fischer. 1908.

No.511] “PRESENCE AND ABSENCE” HYPOTHESIS 419

that the heterozygotes are yellow when young and red

when they grow older. In this case the appearance of

yellow in the young stage leaves no doubt that this is the

fundamental color upon which the red is superposed.

The pure bred red snail—the positive homozygote—is

red from its earliest stages. This latency of the red char-

acter in the young heterozygotes produces a dominance

of the absence of red over its presence in the early stages

of development, and if the snails are classified at this

time, the F, is found to consist of 3 yellows to 1 red.

Later in life the heterozygotes become red and the census

shows 3 reds to 1 yellow.

The rather frequent occurrence of heterozygotes lack-

ing the usually dominant character may be quite appro-

priately said to present cases of latency due to the com-

bination of fluctuation and heterozygosis.

i SUMMARY

The ‘‘presence and absence’’ hypothesis assumes that

what appears to be a pair of characters in Mendelian in-

heritance is really the presence and absence of a single

character. This hypothesis has now won the support of

most of the leading experimental students of heredity.

The fact that the absence of certain characters dominates

over their presence has appeared to some to be a difficulty.

This paper shows that no such difficulty is involved and

simple chemical experiments are cited which, if dupli-

cated among plants and animals, as they no doubt are,

would give the dominance of absence over presence, with-

out recourse to ‘‘inhibiting factors.’’

When absence dominates over presence the positive

character is latent in the heterozygote. Such cases may

be said to show latency due to heterozygosis. This condi-

tion is exemplified by some of Lang’s snail crosses. The

same phenomenon is involved in many cases of failure

of dominance in heterozygotes.

STATION FoR EXPERIMENTAL oe

COLD SPRING HARBOR, L.

December, 1908.

PRESENT PROBLEMS IN PLANT ECOLOGY !

ILI. VEGETATION AND ALTITUDE

PROFESSOR CHARLES H. SHAW

THe MEDICO-CHIRURGICAL COLLEGE, PHILADELPHIA

In the study of the relation of plants to environment,

there are few problems of greater interest than those

presented by the vegetation of mountains. The general

facts are somewhat familiar, and reference to them is

here necessarily brief. Whatever the vegetation of the

surrounding country, mountains are usually forested;

the forest is often composed of several zones in whic

different kinds of trees successively predominate; higher

up the forests finally cease and give place to grassland

of perennial herbs and low shrubs—these are some of the

more general facts of mountain vegetation. There is

bound up with them not only strangeness and beauty,

but also a series of most interesting problems in the

ecology of plants.

If I understand rightly the reason for this symposium,

my duty is to state, as well as in brief compass I may,

the present state of our knowledge in regard to these

phenomena. In general, they rest back upon physical

environment. In so saying, however, it must be kept in

mind that biotic factors early modify the primitive phys-

ical ones; the reason for the occurrence or absence of a

species may be the conditions created by other species.

The important factors which vary with altitude seem to

be heat, light, precipitation, evaporation, and a factor

made up of several of those named, namely, length of sea-

son. Let us consider these severally, and try how far

*A series of papers presented before the Botanical Society of America,

at the Baltimore meeting, by invitation of the council.

420

No.511] PRESENT PROBLEMS IN PLANT ECOLOGY 421

we may at present determine the part played by each in

connection with the plant life of mountains.

1. Heat.—From the days of Humboldt to the present,

the vast importance of temperature in this connection

has been recognized. In spite of this, our knowledge is

rather scanty and vague. It has been usual to attribute

great importance to the severe cold of mountain tops.

This view, however, is entirely open to challenge.

Mountains which rise up from warm plains certainly can

not be invaded by plants which are killed by frost, but

is there warrant in any physiological knowledge we

now possess for supposing that extreme low temperatures

are of any especial significance for plants which endure

freezing? There is reason for believing that some woody

plants are cracked by severe cold, but I believe the gen-

eral question must be answered in the negative. That

treeless mountain tops are not so because of great cold

is shown by two facts: First, in cases-that have been

investigated, timber lines do not bear any direct relation

to isothermal lines; and furthermore, forests do exist in-

the coldest districts on the globe. Herbaceous plants,

too, taken even in the active condition, are known to sur-

vive extremely low temperatures, undisturbed.

We may note in passing the obvious fact that, for most

low growing mountain plants, deeply buried as they are

under snow, extreme winter temperatures do not come

in for consideration at all.

That the lower temperatures of air and soil during the

growing season are factors of great importance is not

to be doubted. More specific information is not easy to

obtain. Direct observation avails nothing, for we can

hardly point to a single feature of anatomy or histology

which is called forth by or conditioned upon heat or

cold. In order to make further progress, recourse is

naturally had to instrumental study. In the use of this

method, many pitfalls await the worker. It is relatively

easy to secure data of temperature, but vastly difficult

to interpret them. It seems to me that, seeing a good

422 THE AMERICAN NATURALIST [Vou. XLIII

many ecologists are making use of temperature data, this

point will bear some emphasis. Feeling that ecology is

new, and exact instrumental work is the kind that counts,

it is very easy, when one has secured a fine series of

readings, or better still, a complete thermographic trac-

ing for a growing season, to entertain the impression that

he has accomplished something of note; whereas the fact

in the matter simply is that if he has done his work well,

it is of a quality with the routine work of a weather

bureau. To relate the physical data to the manifold

activities of a living plant is another matter, and calls

for all the power of critical thought and all the knowledge

of physiology which any man can command.

For our purpose, it seems possible to do little more

than to point out some difficulties to be surmounted. To

begin with, any method which assigns increasing values

to higher temperatures must go astray as soon as the 2

plant’s optimum is passed, and for most of the plants we

are dealing with, we do not know where that is. If, also,

as there is some reason to believe, the growth-tempera-

ture curve has more than one maximum, a still further a

difficulty would be brought in. <

Furthermore the ecologic optimum is made up of many

harmonic optima, and may vary in different life phases

of the same plant. In experiments in forcing fruit trees,

it has been found that the optimum for blooming is mark-

edly lower than for other periods for the plant’s activity.

Finally the temperatures recorded are for the soil or air,

whereas the ones wanted are those that prevail within

the plant. Leaves and shoots are warmed by sunshine

and cooled by the evaporation of water. In this way tem-

peratures may be brought about which differ materially

from those recorded by a thermometer alongside. In the

case of an Alpine plant, sheltered in some sunny angle

of rock, how widely the temperature within its leaves —

may differ from that shown by a thermometer near by, —

properly set up for air temperatures in shade!

On the positive side, there seems less to be said. It

No.511] PRESENT PROBLEMS IN PLANT ECOLOGY 423

ean not be doubted that the plant life of mountains is in

no small degree modified and controlled by temperature,

but who can put his finger on definite facts and say ‘‘this

temperate forest is on this mountain in the tropics because

of temperature,’’ or ‘‘this Alpine plant is a dwarf be-

cause of cold.’’ Strongly as we may suspect such points,

we must be cautious about including them within the

realm of our positive knowledge.

The peculiarities of Alpine plants have been thought

to be due, in part, to great daily variation in temperature;

that owing to the greater clearness and rarity of the

atmosphere, the plant is more exposed to heating by

intense sunshine by day, and cooling by more rapid radia-

tion at night. Since growth takes place particularly at

night, it seems evident that marked night cooling would

lead to reduced size. That this is actually true has been

proven by placing growing plants each night in the ice

chest. At present more light is chiefly needed as to what

temperatures are really experienced by Alpine plants over

night. Air temperatures, at any rate, are more equable

at high altitudes. In connection with the work in the

Selkirks during the past summer, two complete thermo-

graphic records were taken, one meter from the surface,

same hillside and exposure, at altitudes of 800 m. and

1,700 m., respectively. The daily maxima recorded at

the upper station were notably less than at the lower;

the nightly minima only slightly so. (Freezing point

was not recorded for many weeks.) Such data accord

well with the general results of meteorologists. They

refer of course only to air temperatures.

Briefly summarizing, we may say that our knowledge

of the relation of heat to mountain vegetation is not great.

The importance of extreme low temperatures has been

much overestimated. The significance of moderate tem-

peratures is not yet capable of exact interpretation. The

hypothesis of night cooling as a cause of alpine dwarfing

needs further physical facts as a basis.

2. Precipitation.—That mountains are tlangi of

424 THE AMERICAN NATURALIST [Vou. XLII

greater precipitation and that the vegetation of moun-

tains is largely dependent upon atmospheric water are

ideas familiar to every one. Schimper has further

suggested that light showers at high altitudes favor the

development of grassland rather than forest. This idea, —

to be tenable, requires the further assumption that the

soil in the grassland zone is deficient in water supply.

This may be true for lower latitudes, but it scarcely seems

admissible for northern mountains where the late melting

snows leave the soil supplied with all the water it can

hold.

In quite a different way, too, precipitation in the form

of snow becomes a decisive factor for vegetation. Ina

paper read before this society, a year ago, I showed that

the timber line of the Selkirks was due to the heavy

snow beds at those altitudes. By a coincidence, Cowles

showed elsewhere, at the same time, that in a number of 3

places in North America snow beds and timber line were

causally related. :

3. Closely connected with the question of heat and pre-

cipitation is another factor of prime importance in some

mountains, namely, Length of Season.

In respect to this factor at least two points of view are

necessary. For trees and plants growing on wind-swept

spots, length of season is a question of temperature.

For the vast majority of low-growing plants, on the other

hand, length of season is also a question of emergence

from snow beds to air and sunshine.

Taking up, first, the question of forests, it has been

said that the total heat available at high altitudes is not

sufficient for the maturing of new wood, and more partic-

ularly, that the season is too short for the ripening of

good seed. Both of these ideas must stand or fall simply

upon evidence, and so far as I am aware, none of a re-

liable character has been brought forward. It may be

remarked that seedling trees usually seem abundant

enough at timber line. It would be of interest to gather

seeds of balsams, etc., growing at timber line and learn

No.511] PRESENT PROBLEMS IN PLANT ECOLOGY 425

if they germinated properly. When one considers the

fact that elevated forests are usually coniferous, Myake’s

studies on photosynthesis by evergreen trees during

winter become of interest. One may well inquire if

trees of this kind obtain in this way a distinct advantage

over others at high altitudes.

Turning to the low growing plants, we find their prob-

lems of a somewhat different nature. In the Alps, the

Caucasus, the northern Rockies and the Selkirks to men-

tion only a few examples, large tracts of lofty grassland

lie buried under snow until the close of the vernal period.

If one visits the higher forests of the Selkirks in June,

he must journey in the snow. Arriving at the alpine

fields, he finds them at the summer solstice, still hidden

under an almost unbroken covering of white. In the

month that follows, they will be gradually exposed. Dur-

ing the ten or fifteen weeks that remain, they must ac-

complish nearly the whole sum of their annual activities.

The ability to do this must be a decisive factor in their

struggle for existence. Carex nigricans ordinarily occurs

mingled with other plants; but in moist hollows, where

the snow has lingered until the middle of July, it often

forms patches to the entire exclusion of competitors.

Where the snow does not melt till the first of August, it

is absent and the visible vegetation consists of poly-

trichum only. Where snow persists till late in August,

the soil thus exposed is destitute of visible vegetation.

Walking in the verdant alpine fields at the end of Au-

gust, one finds each unmelted patch of snow bordered by

plant societies in the order mentioned. Do we not read

in this that of phanerogamous plants present the sedge

is best able to compress its life processes into a brief

period; that the moss is able to live with even shorter

time allowance, but that even the moss is unable to main-

tain itself under conditions of such brevity of season as

are represented by twenty or thirty days at the close of

summer? It is hardly to be doubted that many other

less easily traced questions of association and occurrence —

are decided by length of season.

426 THE AMERICAN NATURALIST (Vor. XLI

4. Light.—Since a certain proportion of light is ab-

sorbed during passage through the atmosphere and par-

ticularly by the layers next the earth’s surface, it seems

plain that light becomes more intense with increasing

altitude. If so, its relation to vegetation is a matter of

much interest.

Notwithstanding that the question has received con-

siderable attention, our knowledge of it is still in a rather

unsatisfactory condition as will appear from the follow-

ing: :

Bonnier, Schimper, Schroeter and indeed most of those

who have written upon the subject, express the belief

that the more intense light is a factor of importance in

connection with Alpine vegetation. They give reasons

indicating that a greater intensity exists, and noting the

reduced leaves and shoots and prominent flowers of

alpine plants, state that the former is the cause—in part

at least—of the latter. The conclusion, however, has

not been put to the test of discriminating experiment.

Any further discussion of the subject brings in a gen-

eral consideration of light as an ecological factor. I

trust a brief digression may be permissible.

Since light is a form of solar energy, efforts have nat-

urally been made to compute its intensity from astro-

nomical data. Attempts have been made in several

quarters to calculate light intensity for any day and

hour of sunshine for the year at a given latitude. They

do not, however, seem to have been happy in escaping fun-

damental error. For, in making calculations from the

sun’s altitude, there is not one varying factor, but several —

which must be reckoned with: (1) The amount of

radiant energy falling upon a horizontal surface varies

with the sine of the sun’s altitude. This law is per-

ceived by every one. It has sometimes been neglected,

in the thought apparently, that since leaves stand at all

angles, it is unnecessary to reckon what a horizontal sur-

face may receive. Yet the direct light available for the

total vegetation of a hectare or any other area is func-

No.511] PRESENT PROBLEMS IN PLANT ECOLOGY 427

- tioned upon the angle made with the sun’s rays. The

law of the sine may, therefore, not be neglected. (2)

Within the atmosphere we have the phenomenon of dif-

fuse light from the sky. At the earth’s surface it be-

comes a factor of no small importance, very likely sur-

passing for vegetation in general that of the direct rays

of the sun. It is, of course, derived from direct light,

but for it the law of the sine is far from valid. In gen-

eral, it is subject to less variation. It’is probably

affected by many factors not easily observed, presence

of dust, vapor, ete., and its numerical computation bor-

ders on the impossible. A table showing light intensity

for any given day or hour, might possibly, if all fac-

tors were taken into account, show the value of direct

light, but it is open to question, if this is what the

botanist chiefly wants to know. (3) The length of the

path of a ray of light through the earth’s atmosphere,

and, therefore, the fraction of it which is absorbed, in-

creases with decreasing elevation of the sun. Quite

apart from diminution due to decreasing angle of inci-

dence, the light wanes as the sun approaches the horizon.

This fact is sometimes clearly seen; sometimes appar-

ently overlooked. (4) Absorption in the lower, denser,

dust, water-vapor and carbon dioxide bearing layers of

the atmosphere is relatively far greater than in the upper

and rarer ones. This last holds good, especially for the

shorter rays. This third consideration comes to the

foreground in a study of altitude and vegetation.

Here then are several varying factors; some of them

difficult to caleulate, and none of which may be neglected.

Moreover, as will be shown below, there is reason for

doubting whether any theoretical calculations are valid,

even for clear days.

Wiesner has carried on extensive studies upon light

and plants, extending over several decades. He offers

-data to prove that light, for a given time and place, with

cloudless sky, can by no means be caleulated from astro-

nomical data. His readings taken in different parts of —

428 THE AMERICAN NATURALIST [Vou. XLII

the world show astonishing irregularities. In Buiten-

zorg, the light diminished rapidly between eleven and

twelve o’clock under apparently clear sky. Similar data

were recorded for Cairo, Egypt. The maximum inten-

sity obtained anywhere in the world was not in the trop-

ics, but in Yellowstone Park. Though some of his re-

sults seem rather incredible, it must be owned that his

methods appear ample and critical—far beyond any-

thing else undertaken by a botanist. He has emphasized

the distinction between direct and diffuse light. He

finds the proportion of the former to increase greatly

with altitude, and sees in this a factor of much impor-

tance for vegetation. His results in regards to altitude

and light are not so full as could be wished, but he at-

tributes the maximum observed in the Yellowstone to

altitude, and, in general, assigns a high importance to

light as a factor in alpine climate.

On the other hand, Clements states that in Colorado

the variation of light with altitude amounts to a very

small percentage and concludes that such differences as

exist are too small to receive serious consideration in a

study of mountain vegetation. The chief thing, there-

fore, that appears certain is that the whole question is

in an unsatisfactory condition. In such a situation, one

or two points must be kept clearly in view.

First, data as to light intensity must be obtained by

methods which will pass muster with physicists. A cer-

tain body of such data are available. Time is lacking

to take up the question here, but the work of Cayley,

Violle, Langley and others might be cited to show that a

considerable increase in light intensity with altitude does

exist.

In the second place, it must be borne in mind that the

relation of the plant to light is a complex one. In some

of the work above quoted there seems to be the whole-

sale error of assuming that the importance of light for

the plant is to be judged by observation upon its rela-

tion to the process of photosynthesis. It seems super- |

No.511] PRESENT PROBLEMS IN PLANT ECOLOGY 429

fluous to emphasize that light is not only a source of

energy, but a factor which now stimulates, now inhibits

various activities of the plant in a profound degree.

It is the highly refrangible rays which suffer greatest

absorption by the atmosphere. The light at the surface

would, therefore, differ in quality from that at higher

altitudes. In studying the question, it appeared to me

desirable to learn whether any responses by plants could

be found to alterations in quality—alterations, neverthe-

less, in which all kinds of rays should still be present.

I therefore endeavored to set up experiments which

should merely add a proportion of certain rays to an

already sufficient daylight illumination. The results,

while far from being as full and conclusive as could be

wished, seem to indicate pretty clearly that plants do

respond to such a variation in quality. Internodes were

observably shorter and leaves more hairy under the bluer

light.

Perhaps the whole question can be summed up in say-

ing that the relation of vegetation to variations in light

due to altitude are poorly understood; that more data

from trained physicists would be welcome, but that the

experiments still remain to be made which would enable

us to interpret such data with confidence.

5. Evaporation.—Since pressure becomes less, wind

velocity increases, and insolation becomes greater with

increasing altitude, it has seemed necessary to conclude

that the evaporation rate increases. Toward the sum-

mits of many mountains, e. g., the White Mountains and

Adirondacks, the decisive relation of wind to forest

vegetation can hardly be doubted. In these cases there

is good ground for assigning evaporation as the cause

of timber line with all that it involves. The death of

buds and twigs is probably chiefly due to drying in cold

weather.

Most of the leading writers agree without question

that evaporation is more rapid at higher altitudes.

Schimper lays much emphasis upon it; Schroeter writes

vividly of the drying of skin experienced by alpinists

430 THE AMERICAN NATURALIST [Vou. XLIII

and mentions the dry cured meat prepared by peasants

in some places in the Alps, which, it is stated, is due to

the greater drying power of the air. The reasoning is

all but conclusive. There can be no doubt though, that

the verdict of the soundest reasoning ought to be con-

firmed in the court of experimental evidence.

In 1907, Livingstone measured evaporation in the Santo

Catalina mountains and found a decrease with altitude.

This, perhaps, was not surprising, seeing that the series

began in the desert below and extended to the cool moun-

tain regions above.

During the past summer, I set up two series of instru-

ments in the Selkirks at altitudes ranging from 800

m. to 2,900 m. Mountain flanks having a fairly uniform

exposure were chosen, only short horizontal distances

were involved, two stations were chosen at each altitude

so that one might check the other. The season was favor-

able, being unusually warm and dry; one series was in

perfect operation for twelve weeks. The results on the

whole seem to exclude the idea that in the Selkirks

evaporation increases with altitude. The maximum in

each case was at the next lowest station, altitude of 1,100

meters. Above that there was a gradual and irregular

diminution. It may be that the lower temperatures of

higher altitudes more than offset the factors which make

for increased evaporation. Indeed, it appears certain

from the above data that for the Selkirks, such is the case. —

The data in question, however, present only weekly

totals. The possibility that excessive evaporation may

take place during certain portions of the day, still remains

to be studied. It must be ever kept in view, too, that it

is not the absolute amount of transpiration which is s0

much of importance to the plant, as the balance between

water supply and water loss. If the lower soil tempera-

tures of higher altitudes make the obtaining of water

more difficult, then the same or even a diminished evapora-

tion rate might demand increased power of resistance 0D

the part of the plant.

No.511] PRESENT PROBLEMS IN PLANT ECOLOGY 481

In trying to unravel the problems of mountain vegeta-

tion, it must never be forgotten that the plants of the

present are descended from preexisting ones; facts of

heredity are everywhere; phenomena that are found to-

day not seldom hark back to conditions of the past.

In concluding, allow me to offer a plea for a service,

which I have been thinking for several years would be

one of the most helpful which could be rendered to this

adolescent science of ecology, namely, that some one

whose knowledge of physics and physiology fits him for

such a task should overhaul and scrutinize our ideas and

methods. Not counting minor and ephemeral papers,

there can be no question that ecology, at the present time,

contains not a little of discernible error. Rumors have

been heard that zoologists are beginning to study ecol-

ogy and looking to botanical methods for hints for de-

veloping their own. Within the family, it may be said

that if wide-awake guests are coming, it is time to set

the house in order. Moreover, ecology is finding a large

place in elementary text-books, and in this way errors

are being propagated. The interest alike of science and

education in this field could in no way be better served

than by a relentless pruning.

DISCUSSION OF PROFESSOR SHAW’S PAPER.

DR. LIVINGSTON: A remark was made by Professor Shaw in the be-

ginning of his paper, which suggests that we sometimes lose sight of physi-

eal facts. A certain plant is not killed or shut out by the fact that other

-plants are near it, but by the fact that light conditions or moisture con-

ditions or evaporation conditions or temperature conditions are different

from those in which they might live. It seems to me that to speak of

biotie and physical conditions leads to confusion; the thing the plant feels

must be a physical thing.

PROFESSOR SHAW: In my remark I meant to clear up certain cases

where one might lose sight of the fact that plants had largely modified

physical conditions. -I presume the very ease which gave rise to that

sentence was this: there are some reasons for supposing that in the

is at something like 4,000 feet in altitude. A forest has developed there,

and the condition of low evaporation rate has come about on account of

that forest.

SHORTER ARTICLES AND CORRESPONDENCE

PLEISTOCENE SWAMP DEPOSITS IN VIRGINIA

Buried swamp deposits of Pleistocene age are far more abun-

dant in the Atlantic coastal plain than was suspected a few years

ago. A large number of such deposits are exposed by the com-

paratively recent cutting of the waves along the western shores

of the Chesapeake Bay and the estuaries of our southern rivers.

These deposits vary greatly in botanical interest from point to

point. In some no recognizable remains have been found, in

others these are limited to the stumps of the cypress, while still

others contain the remains of a considerable flora. It seems evl-

dent that quite a number of modern species are more restricted _

in their northward range than they were during certain inter-

glacial periods or even post-glacial time, while others are extend-

ing their range at the present time. Among the former the

red bud or Judas-tree (Cercis canadensis Linné) and the osage

orange (Tokylon pomiferum Raf.) might be mentioned, both oc-

curring in the interglacial beds of the Don Valley near Toronto

in Canada. Another species abundant as far northward as New ©

Jersey in inter- or post-glacial time was the bald cypress

(Taxodium distichum Rich.), and the loblolly pine (Pinus taeda

Linné) also appears to have withdrawn southward since the late _

Pleistocene. The water elm (Planera aquatica Gmel.), on the —

other hand, appears to have retreated southward in the late

Pleistocene and to be readvancing at the present time.

Numerous Pleistocene swamp deposits are described in the

recently published account of the Maryland Pleistocene’ and

their contained fossil plants have been admirably exploited by

Dr. Hollick, who enumerates over 40 species from beds of

age in Maryland.? Similar deposits are to be found at many =

points in the Old Dominion, although very little attention has

been thus far devoted to their description.

In 1906 the writer described? Fagus americana (nuts) Vitis

sp. (seeds), Hicoria glabra (fruit), Taxodium distichum (seeds

* Maryland Geol. Surv., Pliocene and Pleist., 1906.

? Ibid., Systematic Paai, pp. 217-237, pl. 67-75.

° Berry, Torreya, Vol. 6, pp. 88-90, 1906.

432

No.511] SHORTER ARTICLES AND CORRESPONDENCE 433

and cone-seales) and Nyssa biflora (seeds) from the Talbot or

latest Pleistocene formation at Tappahannock, Va

During the last two years peat deposits of late Pleistocene age

have been discovered at numerous points along the Potomac,

Rappahannock and James rivers. These usually contain char-

acteristic stumps of the cypress, often of large size, and the asso-

ciated peat furnishes recognizable plant remains, generally seeds,

of Nyssa, Vitis, Fagus and Taxodium, the latter usually the most

abundant. Associated with the plant remains are fragments of

the elytra of beetles, occasional insect galls and molluscan re-

mains. Evidently most of these Pleistocene peats indicate the

presence of cypress swamps, but this is not always the case, since

in some instances we find representatives of upland vegetation,

while in other cases the fossils show that the vegetation was open

and marsh-like with a scattering of trees of oak, birch and pine.

Where quiet water conditions followed the subsiding forest-bed,

deposits of clay are to be found and these often contain frag-

ments of leaves along with casts of the shells of Unio if the

locality is toward the head of the ancient estuary, or shells of

Rangia cuneata if the waters were more saline. The latter is

very abundant in Pleistocene deposits of this sort from Maryland

southward and it is also a member of the modern fauna, confined,

however, in the latter case to the Gulf of Mexico.

Fig. 1 shows the bed of massive hard peat a short distance

above Tappahannock, Va., from which the above mentioned spe-

cies were collected. It is exposed for a thickness of four or five

feet and shows many cypress stumps in place with the ‘‘knees’’

protruding through the recent narrow sand-beach. Overlying

the peat is a layer of drab plastic clay from one to four feet thick

and carrying fragments of leaves. Above this there is from ten

to fifteen feet of coarse sand. The Rappahannock has cut into

the bluff along its south bank, exposing this old cypress swamp

for a distance of over one half a mile.

Where the forest-bed was succeeded by waters which were

agitated by wave action or swift currents the overlying deposits

are sands or gravels laid down on the more or less planed surface

of the old swamp. Fig. 2 shows such a condition of affairs in

an exposure just above the junction of Parrotts Creek with the

Rappahannock River. The line of apparent unconformity is

sharply defined running across the center of the picture. Below

are seen the cypress trunks and roots embedded in an impure

peat which was planed off by wave or current action as the

434 THE AMERICAN NATURALIST — [Vou. XLII

Fic. 1. Talbot Cypress

Swamp near Tappahannock, Virginia.

Fic. 2. Talbot swamp deposit just above junction of Parrotts Creek and the

Rappahannock River.

No.511] SHORTER ARTICLES AND CORRESPONDENCE 435

swamp subsided. Upon this surface lie the coarse sands shown

in the upper half of the photograph.

The additions to the Pleistocene flora of Virginia are enumer-

ated below. Those from below Port Royal were collected by

Dr. L. W. Stephenson, of the U. S. Geological Survey, who has

also kindly furnished the two photographs here reproduced.

FAGALES

BETULA NIGRA Linné.

Knowlton, Amer. Geol., vol. 18, p. 371, 1896.

rad Journ. Geol., vol. 15, p. 34 T.

—, AMER. Nat., vol. 41, p. 692, pl. 2, figs. 2—4, 1907.

This riverside and flood-plane species appears to be abundant

in the swamp deposits of our southern coastal plain, due doubt-

less to its abundance along the rivers which contributed their

flotage to these deposits. The present occurrence is based upon

leaves from the right bank of the Rappahannock River one and

one half miles below Port Royal.

QUERCUS sp.

A number of fragments of leaves, evidently those of some oak

but too fragmentary for even tentative specific determination, are

contained in the collection from the right bank of the Rappahan-

nock River one and one half miles below Port Royal, and unde-

terminable acorns occur in the Talbot deposits near the Nomini

Cliffs on the south P of the Potomac.

FAGUS AMERICANA Swe

Hollick, e Geol. Surv., Pli. and Pleist., p. 226, 1906.

Berry, Torreya, vol. 6, p. 88, 1906.

F ourn. Geol., vol. 15, p. 341, 1907.

; ER. Nar., vol. 41, p. 692, pl. 2, fig. 7

Fagus ferruginea pora Laa Am. Journ, Sci., vol. 27, A pe 1859.

eol. Tenn., p. 427, pl. 7 (K), fig. 11, 1869.

Fagus Veieiginies Ait., Knowlton, Amer. Geol., vol. 18, p. 371, 1896.

Mercer, Journ, Phila. Acad. (11), vol. 11, pp. 277, 281, fig. 8

(15), 1899.

The characteristic leaves and burrs of this species occur in the

Talbot deposits near the Nomini Cliffs. No nuts were found

associated with the other remains, but an extended search was

not made. This species was one of the commonest trees of the

Pleistocene if we may judge from its abundant remains at a

large number of localities in Pennsylvania, Maryland,- Virginia,

West Virginia, Tennessee, North Carolina and Alabama.

CELTIS OCCIDENTALIS Linné.

Bony endocarps, or stones, sometimes enclosed in the lignitized

436 THE AMERICAN NATURALIST [ Vou. XLII

exocarp, and not distinguishable from those of the modern tree,

occur in the peat deposits near Tappahannock. In the modern

flora this wide-spread species ranges from the Atlantic to the

Pacific and from southern Canada to eastern Texas and Florida.

It has not heretofore been recorded in the fossil state. The

genus dates back to the middle Eocene in this country, but it is

not abundantly represented at any horizons. Leaves described

as Celtis pseudo-crassifolia by Hollick* occur in the older Pleis-

tocene (Sunderland) of Maryland. Abroad the genus is com-

monly represented in the late Tertiary, at least two species being

recorded from the Pliocene, but none so far as the writer is

aware from the Pleistocene.

SPINDALES

ILEX CASSINE Linné.

This species which in the modern flora is a denizen of low

woods and river banks near the coast from Virginia to Florida

and west to Louisiana has not heretofore been found fossil.

Eight specimens of leaves are in the collection from the right

bank of the Rappahannock River one and one half miles below

Port Royal. They are identical with the less elongated leaves

of the modern plant and would seem to indicate, if their habitat

has remained unchanged, that the Talbot coast line was much

farther to the west of where it is to-day, a fact fully borne out

by the areal distribution of the deposits of the Talbot Sea. They

also show that in Talbot time this species ranged somewhat

farther north than it does at the present time, since southern

Virginia marks its present northern limit according to Sudworth.

ERICALES

DENDRIUM PLEISTOCENICUM Berry.

rry, Journ. Geol., vol. 15, p. 346, 1907.

Leaves of this species deseribed originally from the Pleistocene

of central North Carolina are present from one and one half

miles below Port Royal on the Rappahannock River. They are

considerably smaller than the North Carolina leaves, but are

identical with them in outline and venation and they are also

very similar to the leaves of the existing Dendrium buxifolium

bite = og pape pointed out, they probably repre-

Dendrium hu oe ate Pe =n opia npo

i gerı and the pine-barren species Dendrium busi-

folium were derived. DWARD W. BERRY.

JOHNS HOPKINS UNIVERSITY, BALTIMORE, MD. ;

* Hollick, loc. cit., p. 230, pl. 71, fig. 9.

NOTES AND LITERATURE

HEREDITY

A Case of Non-Mendelian Heredity.—That hereditary characters

which behave in accordance. with Mendel’s law of segregation

depend in some way upon the chromosomes can hardly be ques-

tioned. Biologists, however, have been loath to believe that all

hereditary characters are thus related to chromosomes. It is es-

pecially gratifying, therefore, to find completely worked out a

type of inheritance which differs radically from the Mendelian

type and which appears to be entirely cytoplasmic in character.

The law of transmission in this case is of unusual interest. The

case is reported by Dr. Erwin Baur, of Berlin.*

In this paper Dr. Baur describes several types of variega-

tion. The first consists of variegation due to pathological con-

ditions (auto-infection or auto-intoxication) and is not hered-

itary. By overcoming the auto-intoxication such plants are con-

verted into ordinary green plants. On the other hand, ordinary

plants can be infected with this condition by graft-symbiosis

with an infected plant. This condition is not transmitted by

seed. It is called by the author ‘‘infectious chlorosis,” and

is accompanied by a partial loss of green pigment in the chloro-

phyll grains. Several previous papers on this type of chlorosis

by the author are referred to.

The second type of variegation consists of fully constant

races whose chromatophores carry a diminished amount of green

coloring matter, but the normal amount of yellow coloring matter.

These races have distinctly yellowish-green leaves. In crosses

with green races the yellowish green behaves as a Mendelian

recessive.

The readers of this journal will remember that a similar char-

acter in tomatoes was reported recently by Professors Price and

Drinkard, of the Virginia Experiment Station, and the character

in this case behaved also as a Mendelian recessive.

‘Erwin Baur. The Nature and Hereditary Relations of the Albo-Mar-

ginate Horticultural Variety of Pelargonium zonale. Zeitsch. f. Abst.- u.

Vererb., Ba. I, 1909, H. 4.

437

438 THE AMERICAN NATURALIST (Vou. XLII

In another class of yellowish-green races, which are in a sense

constant, the yellow-green plants are all heterozygote and Men-

delize into one fourth clear yellow incapable of development,

one fourth pure green, constant in later generations, and two

fourths yellow-green, which splits again as above. This case was

treated of by Dr. Baur in a former paper.?

Many other types of variegation exist. One of them is re-

ported in the review of Professor Correns’s paper below. The

present paper of Dr. Baur’s deals with another type of variega-

tion, namely: white margined leaves, such as those found in

varieties of Acer negundo, Cornus alba, Pelargonium zonale and

numerous other species. The investigation was confined largely

to the last-mentioned species. Little was previously known of

the inheritance of this character. Several authorities had stated

that such plants (with white margined leaves) produce only

seedlings that are pure white and incapable of development.

Dr. Baur’s studies show that the white margined plants of

P. zonale are covered with two or three layers of cells containing

colorless chromatophores which can not assimilate CO, but which

can manufacture starch from sugar. The whole plant is covered

by this white tissue. Near the leaf margin the two white layers

form the whole of the tissue and thus give the peculiar marking

on these leaves.

The line of demarcation between the white cells and ordinary

cells is definite. One gets the impression that all the descendants

of a white cell are white and all those of a green cell are green.

This can not be definitely determined by microscopic study, but

the experimental results reported below practically prove that

such is the case.

Four white margined plants obtained from different sources

all, when self-fertilized, produced only white seedlings, which

soon died because they were incapable of assimilating CO,. Some

of these plants occasionally produced green branches which arose

by the green tissue breaking through the superficial covering of

white. Seed from these green branches produced normal green

plants which propagated true to seed. On the other hand, white

branches, when close fertilized, produced only white seedlings.

(An occasional branch was pure white without the underlying

green tissue.).

* Ber. d. Den. Bot. Gesell., 25, 1907,

1, 1908, p. 124.

p. 442, and Zeitsch. f. Abst.- u. Very ae

No. 511] NOTES AND LITERATURE 439

Crosses made between flowers on pure white branches and

other flowers on ordinary green plants gave thirty-nine green

seedlings and seven green-white marbled plants. These crosses

were made both ways, but only one seed, resulting in a green .

plant, was raised from the cross of green (<') on white (9).

Several crosses made both ways between white margined plants

and ordinary green plants gave 199 pure green, 41 green-white

marbled, and 4 pure white seedlings. Crosses between white

margined and pure white branches gave all pure white seedlings.

Evidently, white branches and white margined branches produce

only white gametes, while green branches or green plants produce

only green gametes.

Of the green-white marbled seedlings—that is, green and

white spotted, some formed only white leaves and died when the

spotted cotyledons ceased to function.

A second class formed only green leaves and became ordinary

green plants when the spotted cotyledons dropped off. Their

seedlings, about 50 in number, were all ordinary green plants.

A third class grew stems that were white on some sides and

green on others. On such stems leaves attached to white surface

were wholly white, and those attached to green surface were

wholly green. Leaves attached on the line of union between

green and white were correspondingly green and white.

Branches which grew from the axils of the leaves behaved in

exactly the same way as the leaves in regard to the green and

white color.

These facts render it clear that the marbled seedling consists

of two kinds of tissue—green and white. The descendants of

white cells are white and those of green cells are green. A green

and white seedling or branch may become either green or white

by the growing point becoming overeapped by the one or the

other kind of tissue. Of 23 marbled plants observed 20 became

green and two white in this manner.

But the development of a marbled branch or plant may proceed

in a different manner and one which clears up the difficulty con-

cerning the nature and hereditary relations of the white marbled

plants. In a marbled stem the line of contact between the two

kinds of tissue may extend radially inward, or the white

tissue may extend in a thin layer some distance over the green.

A leaf rising centrally on a line of contact extending radially

inward will be half white and half green; but a bud originating

440 THE AMERICAN NATURALIST (Vou. XLIII

from a part of the stem where the green tissue is covered by a

thin layer of white is itself constituted of green tissue covered

by white and produces ordinary white margined leaves. New

albomarginate plants may thus be obtained from these marbled

seedlings by taking branches which thus arise from parts of the

stem where the white tissue forms a thin layer over the green.

The white margined plants are thus to be regarded as ‘‘ periclinal

chimeras,’’ while the marbled plants are ‘‘sectorial chimeras.”’

White or green branches may arise from the white margined

plants as the result of irregularity in cell division at the growing

point.

The inheritance of the albomarginate character is now clear.

In a white margined plant pollen and ovules are produced from

white tissue only and hence carry only the white character. The

seedlings are therefore white.

Sectorial chimeras were found in which the green tissue was

superficial and the white central, thus giving leaves that were

green on the margin and a paler color in the center, on account

of the white tissue in the center of the leaf. One of the plants

grown from a green branch occurring on an albomarginate plant

was of this nature. Its seed produced only ordinary green

plants.

The origin of the mosaic seedlings from a cross between white

margined and green is not yet fully clear. Careful study of

such of these seedlings as were recorded pure white revealed

indications of green tissue in the hypocotyls. Likewise, ney

regarded as pure green revealed indications of white tissue.

of the seedlings from the green-white cross are probably mosaics,

the differences being due to the fact that in some of them the

white tissue, in others the green, is confined to a few cells, the

remainder of the plant developing from the other tissue.

It is important to note that in some of these mosaics, or maT-

bled plants, white ‘‘islands’’ may appear in several parts of the

plant. These islands are evidently not derived one from the

other. It can, therefore, be asserted that the differentiation of

these white cells occurs more than once during the development

of a plant and that the white cells must result from the division -

of cells that are green in appearance. (It is important to re- —

member that green is dominant in the cross.) Just when these

white cells arise can not be stated so positively. They may cer-

tainly arise after the formation of the cotyledons has begun.

No. 511] NOTES AND LITERATURE 441

The author offers the following tentative explanation of the

origin of this white tissue in the crossbred green-white plants.

The fertilized ovum contains both green and white chromato-

phores. In cell divisions of the embryo the chromatophores are

distributed to the daughter cells more or less according to chance.

If a cell receives only white chromatophores this cell will have

only white descendants. If a cell receives only green chromato-

phores its descendants will be pure green cells. A cell receiving

both kinds may later produce either pure white or pure green at

any cell division. Should a cell which is later to develop into

cotyledons and growing point receive only one kind of chro-

matophores, then the resulting seedling will appear to be only

pure white or pure green, as the case may be. Since pure white

cells may have only pure white descendants and pure green only

pure green, while mixed cells may have three kinds of descend-

ants, it naturally follows that after many cell divisions the per-

centage of mixed cells in the plant practically vanishes.

The above hypothesis makes only one assumption that is not

demonstrated ; that is, that the fertilized egg cell has two kinds

of chromatophores, namely: white and green. According to cur-

rent teaching the chromatophores are derived entirely from the

egg cell; but, according to the author, this may well be considered

not an established fact. If current teaching on this point is cor-

rect, then we have here a very remarkable case. It would then

be necessary, according to Dr. Baur, to assume that in the cross,

female white on male green, a part of the white chromatophores

of the egg may become green under the influence of the male

nucleus, and that in the reciprocal cross a part of the white chro-

matophores would have to become green under the influence of

the male nucleus. Such a condition is thinkable, but no such

ease is known. Should it be proven, however, that the male

sexual cell carries chromatophores, then the inheritance of the

albomarginate character is fully explained.

These results of Dr. Baur’s call for a detailed study of the

chromatophores from one sexual cell stage to the next. The

writer would suggest another possible explanation of the phe-

nomena discussed above. The male nucleus may bring with it

into the cell something which is not a part of the nucleus itself

but is cytoplasmic in its nature. This may develop and give rise

to a part of the cytoplasm of the fertilized egg. Then something

in the chemical constitution of this cytoplasm causes the chro-

pices pse

aini ee ae re

442 THE AMERICAN NATURALIST (Vou. XLIII

matophores which develop in it to lose their power of assimilating a

CO,. Subsequent cell division would occasionally throw off cells 4

of pure white, which would give rise to the white tissue. This is 4

only suggested as a mere possibility. That the condition can a

hardly be caused by the male nucleus itself would seem to be |

indicated by the fact that descendants of this nucleus must be a

present in those cells which are pure green. If the white char-

acter were carried by the chromosomes, then it would appear that

all the green cells would necessarily be affected. There seems to

be no question that the white character is cytoplasmic in its 7

nature, and this would account for the fact that it does not fol-

low Mendel’s law of segregation in the reduction division. The

segregation, in fact, occurs in somatic divisions.

Professor Correns reports another interesting study of variega-

tion in a recent article,’ of which the following is a summary.

Plants deficient in chlorophyll have hitherto been called

“aureas.” The author now restricts this term to plants which

are deficient in chlorophyll but which have the normal amount

of yellow-color materials, zanthophyll sige carotin. Those defi-

cient in all three are termed ‘‘chlorinas.’’ Those of the latter

type obtained in commerce were found j be dwarf as compared

with normal sorts. The leaves and flowers are also relatively

smaller. This smaller size is shown to be partly a consequence

of deficiency in chlorophyll and the consequent insufficient

nourishment of the plant. On the other hand, it is partly due

to a specifie Mendelian character of dwarfness, and the Men- _

delian dwarf habit is strictly correlated with small leaves and

small flowers.

The chlorina races are fully constant. Variegated races have

spots of green on leaves otherwise of chlorina type. In some

cases these spots vary in number and size from leaf to leaf; in

others they are hereditarily fixed. Some of the variegated races,

on account of the smallness of the green spots, are difficult to

distinguish from the chlorina types. On some of the variegated

plants, especially those having much green, typical green

branches occur, and this phenomenon is characteristic of the

plants on which it occurs. That is, the same plant year after .

year produces these green branches. Every possible gradation —

* Investigations on Inheritance of Yellowish Green and Variegated Races

of Mirabilis Jalapa, Urtica pilulifera and Lunaria annua. Zeitsch. f- Abst-

u. Vererb., 1, 1909, H. 4

No. 511] NOTES AND LITERATURE 443

exists between a small green fleck on a leaf and a typical green

branch.

The variegated types do not reproduce strictly true to seed.

They sometimes throw green plants. These green plants do not

simply represent extremes of variation because they are too

numerous and offer a secondary maximum in the curve of dis-

tribution. On the other hand, variegated plants have thus far

not produced any of the pure chlorina type. Some of the pure

green reversions produced progeny all of which are green, A

larger number gave some variegated and some green, the green

nearly always predominating in the progeny. The thus obtained

variegated plants gave some normal green progeny, and the nor-

mal greens thus obtained gave only oceasionally all normal greens.

A green branch on a variegated plant, when self fertilized, gave

three variegated and four green plants. It was not possible to

explain variegation in these species as a cross between the chlo-

rina and the normal green types. In the cross between chlorina

and typica (normal greens) the latter is dominant, but not abso-

lutely so. The chlorophyll content of the hybrids is about 90

per cent. of that in the normal greens. In some cases in the

second generation of this cross, the hybrids split into chlorinas

and greens in perfect Mendelian fashion. In others variegated

plants occur in the second generation; the reason for this is

given below. —

Dwarf and normal stature behave as a pair of Mendelian char-

acters independent of leaf color, the dwarf habit being recessive.

Generally speaking, chlorina plants not dwarf were not quite so

tall as the normal greens because of their inability to manufac-

ture starch at normal rate. The tall chlorinas and the dwarf

greens produced from this cross were new types, the latter being

especially attractive.

In the cross variegata on typica the latter is dominant and

segregation occurred in Mendelian fashion. On account of the

variability of the variegated type (this type produced some

greens) the per cent. of greens in F, was somewhat in excess of

75 per cent. Here again the semi-dwarf and normal stature

acted as a pair. In the cross between chlorina and variegata the

latter proved to be dominant. Normal splitting occurred in the

second generation. As in other cases, a few greens arose from

the variegated plants. The medium stature of the variegated

plants behaved as a pair with the dwarf stature of the chlorina —

plants.

444 THE AMERICAN NATURALIST (Von, XLIII

In each of three experiments the cross variegata on typica

gave chlorinas, variegated plants and normal greens in the

ratio 1:3:12. The plants used in these crosses were known to

be constant. In one experiment a cross between typica and

chlorina gave in F, 63 green, 4 variegated and 3 chlorinas. Here

also the chlorina form was known to be constant. This unusual

behavior is explained by Professor Correns in the following

manner:

The occurrence of normal greens amongst the progeny of

variegata is due to the revival of a latent factor for green (G).

The color factors present in the various types are assumed to be

G = presence; g — absence (or latency) of green factor.

V = presence; v — absence (or latency) of variegata factor.

C = presence ; ce — absence (or latency) of chlorina factor.

V is epistatie to C.

G is epistatic to V and C.

Variegated races have the formula gVC (or gVe).

Chlorina races have the formula gvC.

Normal green races have the formula GVC (or GvC, or GVe,

or Gye).

The cross between green and variegata thus becomes:

GVC + eVC, in which F, = 3 green to 1 variegated; or

GvC + gvC, in which F, — 12 green, 3 V and 1 C.

The cross green on chlorina becomes: _

GvC + gvC, in which F, —3 green to 1 chlorina; or

GVC + gvC, in which F, = 12 green, 3 V and 1 C.

The cross variegated on chlorina becomes :.

gVC + gv, in which F, =3 V+1C.

The cross between the very distinct species Mirabilis Jalapa

variegata and M. longifolia typica give hybrids that are quite

alike in F,, but highly variable in F,. Yet all the characters

involved appear to ‘‘Mendelize.’’ For instance: green and

variegated leaves, normal and dwarf stature, erect and trailing

habit form Mendelian characters.

In contradistinction to the white margined P. zonale studied

by Baur, a white margined form of Lunaria annua studied by

Professor Correns reproduced true to seed, and when ¢

with a green leafed form the margin behaved as a recessive ;

Mendelian character.

A recent article by Whitney i in the Journal of Experimental

Zoology* is of interest in connection with the type of heredity

No. 511] NOTES AND LITERATURE 445

found by Baur in P. zonale, as it bears upon the relation of plas-

tids in the cytoplasm to heredity. Eggs of Hydatina senta were

subjected to centrifugal force, which separated the contents into

three layers, described as a pink zone, a middle clear zone and

a gray zone. The first cleavage plane was variously arranged

with reference to these zones in different eggs, yet the eggs devel-

oped into normal adults which produced normal young. This

would seem to indicate that the plastids in the pink and the gray

zones have little to do with differentiation in development. This

does not prove, however, that other plastids might not have such

influence.

Professor Teen L. Kellogg, of Leland Stanford University,

has recently published an important paper on inheritance in silk

worms.® In common with Coutagne and Toyama he found many

Mendelian characters in these insects. This was especially the

ease for characters of the larve. For instance, the mouricaud

pattern (a dark form) in the larve was dominant to white. The

same was true of the tiger banded, or zebra, type of coloring.

A white type with a well marked darker pattern, which in the

laboratory is known as ‘‘the patterned type’’ behaved usually as

a unit character recessive to zebra and dominant to white. Its

behavior was entirely Mendelian in crosses with white, but there

was some irregularity in crosses with zebra. The irregularities

mentioned by Professor Kellogg are fully explained by assuming

that the pattern character and the zebra character are inde-

pendent Mendelian characters, and that when both are present

in the same individual they can both be discerned.

The author was puzzled a good deal by the behavior of white

and attributes the fact that it was sometimes dominant and some-

times recessive to individual or strain idiosynerasies. <A large

number of matings are given with their results in the first and

second generation to illustrate the idiosyncrasies relating to

inheritance of white. Evidently, Professor Kellogg was dealing

with animals in which there are two distinct types of white, one

dominant and the other recessive. A similar case has been well

made out for poultry, and I have found indications of two such

white characters in swine, though the recessive white in swine is

not fully made out. All of the irregularities in the inheritance

*D. D. Whitney. Effect of a Centrifugal Force upon Development and

Sex. Journ. of Exp. Zool., VI, No. 1, January, 1909.

ë Leland Stanford University Publications, University Series No. 1.

446 THE AMERICAN NATURALIST (Vou. XLII

of white found by Professor Kellogg fall immediately into line

with Mendelian principles by the assumption of these two types

of white, which are sometimes found in the same individual.

Some of the most interesting work reported by Kellogg relates

to cocoon coloring. He found one type of salmon colored cocoon

which when crossed with either the dominant or the recessive

white behaved as a Mendelian unit and broke up into every shade

from very pale salmon to golden yellow. This is an interesting

case of a variable Mendelian character. Generally speaking, the

various cocoon colors were Mendelian units, the only irregularity

being the marked variation of some of the colors after hybridiza-

tion. Wing pattern in the adults and the color and adhesive-

ness of the eggs showed no Mendelian differences. Apparently

the variations which occur in these characters are due to the

fluctuations of a single Mendelian character, and hence no pairs

are formed.

The effect of insufficient nutrition on the dominance of char-

acters was studied, the results being entirely negative. Kellogg

attributes the Mendelian nature of the larval color characters to

their origin by mutation, while the fluctuating variability of

cocoon characters are supposed to be due to their origin by selec-

tion of fluctuating characters. As pointed out by the writer else-

where, the manner of origin of a character, whether by gradual

modification or by sudden change, has no relation to its Men-

delian behavior, so that the fact that certain characters behave

as Mendelian characters is in no way an indication that they arè

mutations. zii

Certain characters which fluctuated widely, and in which no

indication of Mendelian inheritance was found, were amount and

quality of silk in the cocoon, wing pattern, wing venation, Cer- —

tain larval markings, degree of adhesiveness in eggs and the

number of broods produced in a season. These characters pre-

sent very interesting objects of study, and it is gratifying to

learn that Professor Kellogg is giving them further attention.

Coutagne is quoted to the effect that selection for ten years had

no effect on the richness of silk. This is important in its rela-

tion to the effect of selection on fluctuating characters. .

One of the races on which these studies were made lays eggs

which are non-adhesive. When crossed with races laying a

hesive eggs, the non-adhesiveness disappears and does not rea

pear even in the second generation ordinarily. This suggests

No. 511] NOTES AND LITERATURE 447

that non-adhesiveness is due to the latency of a character which

is revived under the stimulus of hybridization. It is stated that

wing pattern does not seem to be capable of any considerable

modification by even a most careful and persistent selection.

This is in line with all recent work on selection in fluctuating

characters when the effect of hybridization has been eliminated.

Variations of wing venation are of special interest. They sel-

dom took the form of additions to the system of veins, and when

they did the modifications were only slight. Generally, these

variations consisted of the loss of veins in part or in whole. In

many cases veins became reduced to tracheæ without chitinous

covering. In a few cases tracheæ appeared in what may be sup-

posed to be the position of ancient veins, thus representing par-

tial restorations of lost characters. Many sports occurred in

wing pattern. Generally speaking, these were not hereditary.

Melanism occurring as a sport showed a slight tendency to be

inherited, and further studies of this matter are in progress.

Occasional moths with power of flight and less frequently appear-

ing individuals with rudimentary wings showed no tendency to

transmit these characters.

Some of the most interesting features of Professor Kellogg’s

work are the marked fluctuations of characters whose stages can

not be fixed by selection. Yet the fact that certain of the races

were constant with respect to a particular stage of such a char-

acter, as, for instance, the Italian salmon with reference to cocoon

color, which on hybridization breaks up and becomes highly

fluctuating, is of great interest. The question whether fluctua-

tions can be fixed by selections is as yet debatable. The Italian

salmon seems to be such a fixed stage. On the other hand, some

of Professor Kellogg’s results indicate that the Italian salmon

may be a compound character, a fact which might account for

its variability. Perhaps long continued selection might, after a

while, fix such characters, especially when the fluctuations cover

such a wide range. The writer hardly agrees with the assump-

tion that such characters are non-Mendelian. It would seem

rather that their stages are simply not stable from generation to

generation. If they could be fixed by selection or otherwise one _

might then expect the fixed stages to behave toward each other

as Mendelian pairs. ;

Dr. East reports some interesting studies on inheritance in

448 THE AMERICAN NATURALIST [ Vou. XLI

sweet corn.’ He points out that Correns has shown that the —

peculiarity of sweet corn is due simply to inability to complete 4

the formation of normal maize starch.- The presence and absence

of this starch forming ability behaves as an ordinary Mendelian

pair. The absence of the ability to form starch is the one char- ‘

acter peculiar to the sweet corn group. It is shown that the —

sweet corn may be either of the dent or the flint type in potential

hereditary characters, and suggests that the early history of —

sweet corn indicates that it arose amongst the flints and spread _

to the dents by hybridization. Dent corns tend to have from

12 to 28 rows; flints usually have 8 and may have 12 rows as the

mode. Dents are little given to tillering, while tillering is char-

acteristic of flints. Flint varieties are also characterized by large

bracts at the end of the husks, dents by small bracts or none.

Sweet corn, on the other hand, runs the whole gamut of the above

characters. For instance, Stowell’s Evergreen is a dent, having

16 to 24 rows. Golden Bantam and Black Mexican are flints.

When the starch forming character is introduced into sweet

varieties from either dent or flint sources the dent or flint char-

acter of the sweet parent becomes evident. The author thinks —

that the dent or flint character appearing in sweet corn is deter-

mined largely, but possibly not entirely, by the character pos-

sessed by the female parent.

W. J. SPILLMAN

E. M. East. A Note Concerning Inheritance of Sweet Corn. Sci

N. B, XXIX, No. 742.

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CONTENTS OF THE JANUARY NUMBER

m Kelps and the ranna n Theory. P

r ROBERT F, G

— Spat of the Canadian Oyster, Dr. J,

Shorter settee and ae ndence: Some Notes on

the Traditions the Natives cel a

Siberia anrai the Mammoth Wa LDE ao moe

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of pais e attenuatus emipaea

poe eg Mari in Southern California, WILLIAM

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o a e D tae e Eggan emperature on

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silology—Cestodes of Birds, Professor HENRY B

ABD,

CONTENTS OF THE FEBRUARY NUMBER s

Barei Darwin and the Mutation Theory. CHARLES Fos

Jarai -Kalpa and the _ Son Theory. IL

ROBERT F, G:

rature : sear Piihi Origin of

the Archegoniates, Dr. BRADLEY M. Davis. Holo

thurians—C ’s The Apodous Holo

aise Som i Heed

th ark’s thurians, W. K.

FISHER. Lepidoptera—The Blue Butterflies of the

Genus Cel ina, Professor T, D. A, COCKERELL. Ver-

tebrate Paleontology-The Lysorophidæ; Stegocephala; —

The pe anges — Oldest Known Reptile; The

a Brot, oe i Oceid

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tology B. Wa = g Teun ration- Cani p-ámes a

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CONTENTS OF MARCH NUMBER

ogy. Professor EE Cs orgie

Darwin's Work on Movement in Plan

5 “Darwin's Influence u upon Plant Plant Gioni and Ecol-

Professo

a Development and Heredit

(be Eowanp M. East. xis

with Rais. Professor T. H.

Shorter At else Check

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5l the Lower Lower Miocene of f Nebraska, HAROLD J

A Mechanism for Organic Correlation.

Recent Ads Aaval the Study of Vascular Anatomy.

n ances in ar

ar Anatomy and the Reproductive Struchire®.

The Chub andtho Texas

CONTENTS CF THE APRIL NUMBER ae

Heredity of Hair Color in Man. GERTR C. DAVE

PORT and CHARLES C, DAVENPORT.

pear Jonn M. COULTER.

of n to ay

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oat courae o e Hiom

Ra Ymo z re Strains as

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Notes and Literature:

racters, Dr.

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: ynan TO 0

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AMERICAN NATURALIST

Vou. X EII August, 1909 No. 512

THE NEW FLORA OF KRAKATAU

PROFESSOR DOUGLAS HOUGHTON CAMPBELL

STANFORD UNIVERSITY

In August, 1883, there occurred in the Straits of Sunda,

between Java and Sumatra, the most violent volcanic

eruption of which there is any record. This catastrophe

involved the island of Krakatau (Krakatoa, as it is

usually written in English), as well as the two small

neighboring islands, Verlaten and Lang Island. As a

result of this eruption about two thirds of the larger

island, which was nine kilometers long and five in width,

disappeared, while the other islands were noticeably in-

creased in size, and the whole floor of the ocean in the

vicinity was completely changed. It was estimated that

the total amount of matter ejected during the successive

eruptions from May to August amounted to eighteen

cubic kilometers, and this immense mass of stones, ashes

and volcanic dust was scattered over an enormous area,

the ashes being carried many hundred miles, and life of

all kinds upon the islands was completely annihilated.

Many will recall the brilliant crimson sunset skies that

were observed all over the world some months later.

These were caused by the presence of fine volcanic dust

from Krakatau which, suspended in the upper atmos-

phere, was carried entirely around the world. The

detonations from the explosions were said to have been

heard nearly three thousand miles away; and at Buiten-

449

450 THE AMERICAN NATURALIST [Vou. XLII

zorg and Batavia, in Java, about 150 kilometers away,

the explosions were likened to the discharge of cannon

near at hand, and were so violent as to shake the houses

to such an extent that objects were thrown down.

The effect of the great mass of hot ashes and pumice

that completely covered the islands, was to entirely de-

stroy every vestige of the luxuriant vegetation which

before the eruption clothed the island of Krakatau with

a dense forest extending from the shore to the summit

of the highest peak, Rakata, 832 meters in height.

The island of Krakatau, therefore, after the eruption,

was very efficiently sterilized, and offered a most un-

usual opportunity for studying the establishment of

the vegetation upon a large area absolutely barren and

comparatively isolated. The nearest land is an island

some nineteen kilometers distant on which the vegeta-

tion was also largely destroyed, while the large islands

of Java and Sumatra are respectively 35 and 45 kilo-

meters distant.

Fortunately there was a man who fully appreciated

the importance of this unique opportunity, and deter-

mined to trace the reestablishment of the new flora upon

the desolated island. The botanical world owes a great

debt to Professor Treub, the distinguished botanist who

has done so much to advance the study of botany in the

tropics, both by his own important investigations and by

the building up of the unrivaled facilities for research

offered by the magnificent gardens and experiment sta-

tions in Java.

Treub’s visit was made in 1886, three years after the

eruption, and subsequently the island was again visited

by him in 1897, and a third expedition was made in 1905.

In the spring of 1906, while engaged in botanical study

at the mountain station Tjibodas, in Java, I received

word that a visit to Krakatau was being arranged for,

and was invited to join it. The results of this trip have

been presented in admirable fashion by Professor A.

No. 5121 THE NEW FLORA OF KRAKATAU 451

Ernst,! of the University of Zürich, to whose efforts and

energy the successful results of this trip were largely

due. Considering the very brief time at our disposal,

the amount of material secured by Professor Ernst and

the completeness with which it was worked out were

really remarkable.

On the morning of April 24 our little party set sail

from Tandjong Priok, the harbor of Batavia, for our

brief cruise among the islands of the Straits of Sunda,

for Krakatau. The little coasting steamer ‘‘Snip’’

(Snipe), which had been placed at our disposal for the

trip, proved most comfortable, and her captain did every-

thing possible to make our trip a pleasant one. The

party included, besides Professor Ernst, Mr. ©. A.

Backer, of the Buitenzorg Gardens, whose intimate

acquaintance with the Malaysian flora was very much

appreciated, and Dr. A. A. Pulle, of the University of

Utrecht, who, like myself, was working at Buitenzorg.

The weather proved all that could be asked, and the

voyage over the calm, dazzling blue sea among the pic-

turesque islands was one long to be remenibered. As

we sailed out of the harbor we could see in the distance

the great voleanoes Salak and Gedeh, which dominate

Buitenzorg, and which had become quite like old friends.

On the slopes of Gedeh lies the mountain station Tjibodas,

where I had spent several happy weeks, and to which I

was going back on my return from Krakatau. Oppor-

tunity was given us to stop at several points en route,

one being Vlakke Hoek, the southernmost point of the

westerly peninsula of Sumatra. All of the places where

we stopped showed a most interesting strand flora, in-

cluding many striking plants, some of which we en-

countered again on the shores of Krakatau. The shallow

lagoons within the coral reefs of these islands were full

of interesting things, corals, sea anemones, gorgeously

1The New Flora of the Voleanie Island of Krakatau.’’ By A. Ernst,

Ph.D., professor of botany in the University of Zürich. Translated by A.

C. Seward, F.R.S., professor of botany in the University of Cambridge.

Cambridge, at the University Press, 1908.

452 THE AMERICAN NATURALIST — [Vou. XLIII

colored fish and many interesting alge. Professor Ernst

collected a large number of striking siphoneous alge

which abound among the coral reefs. (For a list of the

plants collected at these intermediate stations, see Pro-

fessor Ernst’s Memoir, pages 9 to 18.)

Vlakke Hoek was devastated by the great waves result-

ing from the eruption of Krakatau, the waves reaching a

depth of fifteen meters and sweeping away practically

everything except the great iron light house tower, which

alone remains of buildings existing before the eruption.

From Vlakke Hoek we crossed the Straits of Sunda to

the southwest coast of Java (Java’s first point), and en

route had our first view of the peak of Krakatau rising

above the clouds to the east. The bold shores of the

Javanese coast presented a great contrast to the flat,

monotonous shore at Vlakke Hoek in Sumatra. The

difference in the topography of the land is reflected in

the plants, which were strikingly different from those of

Vlakke Hoek (see Ernst, pages 24 to 26). Early in the

morning of April 26, we approached the Krakatau group

of islands.

The view of the island of Krakatau from the north

is most impressive. During the great eruption the vol-

zanic peak Rakata was cleft down the middle, so that

from peak to base its northern side presents a perpen-

dicular cliff half a mile high, falling sheer into the sea,

which at the foot of the cliff is now more than three

hundred meters deep. The exposed face of the cliff

forms a perfect median section of the cone, and the ar-

rangement of the rocks of which it is built up offers a

most extraordinary picture. Professor Ernst took some

admirable photographs, which are reproduced in Plate

IIT of his Memoir.

At six o’clock we dropped anchor and soon after were

taken ashore in one of the ship’s boats. The landing was

made on the east side of the island where the outer part

of the beach forms a broad zone of mingled pumice, coral

and all sorts of débris; fragments of driftwood, seaweed

No. 512] THE NEW FLORA OF KRAKATAU 453

and a conglomeration of seeds and fruits washed up by

the tide. Many of the fruits washed upon the shore

were those of characteristic strand plants like cocoanuts,

serew pines, Nipa palms and others. Most of these show

various devices for facilitating their transport by water,

and some of them had germinated and were trying to get

a foothold in the loose mass of pumice and coral sand.

Above this outer drift zone there is a characteristic

sandy belt where various typical strand plants have es-

tablished themselves. The long prostrate stems of

Ipomea pes-capre, that most ubiquitous of tropical

strand plants, sprawled over the sand, and with these

were masses of the curious grass, Spinifex, and a yellow

flowered leguminous plant Vigna lutea, a euphorbia with

thick, waxy leaves, and various other species common

to the outer littoral zone of the Indo-malaysian region.

While fruits of the Nipa palm were found, the plant has

not yet got a foothold in Krakatau, and there is as yet

no mangrove formation established.

Back of the beach a thrifty belt of forest is conspicuous

and could be plainly seen long before we reached the

island. Some of the trees in this forest are at least

fifty feet high, the tallest being specimens of the curious

Casuarina equisetifolia Forst., a genus mainly confined

to the Australasian region, but with a few species widely

distributed throughout the Malayan Archipelago. Asso-

ciated with these were found specimens of screw pines

(Pandanus sp.), and the striking Terminalia Catappa L.,

whose whorled branches and great shining leaves make

it one of the most notable of tropical trees. Perhaps

the most beautiful of all the trees of this strand forest is

Barringtonia speciosa Forst., a tree with large, glossy,

dark green leaves and great white flowers with a crown

of stamens looking like an enormous myrtle flower. The

curious four-sided angular fruits of this tree are very

common along the beach. Of the few climbing plants the

most conspicuous was Vitis trifolia L.

After spending some time exploring the beach arid

454 THE AMERICAN NATURALIST [Vou. XLIII

strand forest, we pushed inland toward the south, not

without much exertion and perspiration. The unclouded

rays of an equatorial sun beat down pitilessly upon us,

and when, after struggling over blocks of pumice and

through thickets of tall grasses and bushes, we finally

reached a small grove of cocoanut palms, full of fruit,

we threw ourselves down on the ground under their grate-

ful shade and took a well-earned rest. No time was lost

in sending one of the natives up into a tree for green

nuts, which were thrown down and quickly opened, and

never did anything taste better than the cool, sparkling

cocoanut water after our exhausting march through the

fierce heat of the jungle.

From the ship we had seen that the ravines on the

flank of the Rakata were filled with a dense growth of

trees, forming the beginning of a new forest, but it was

quite impossible to guess what the trees were. * We tried |

to cross the open tract lying between the belt of forest

on the shore and the cone in the center of the island, but

we had to give up the attempt after penetrating some

distance inland, following the dry bed of a stream for

part of the way. The land was terribly rough and cov-

ered in many places with a dense jungle of grasses ten or

fifteen feet high, through which he had to hew a path with

the wicked-looking cutlasses which every Malay carries

when traveling. The way lay over steep ridges, which

grew worse and worse as we approached the cone, and

finally we realized that with the short time at our dis-

posal, and the limited means of cutting our way through

the jungle and scrub, we should have to give up the

. attempt, which we did very reluctantly, and retraced our

steps to the shore, where we embarked for the ship.

The monotony of the journey over the grass steppes in

the interior of the island was broken by encounters with

countless ants which built their nests everywhere, in the

crevices of the rocks, among the roots of the grasses and

shrubs, and even hanging from the branches of the

shrubs and trees; and as we scrambled up the steep slopes

No. 512] THE NEW FLORA OF KRAKATAU 455

of the frequent small ravines, down would come showers

of ants, swarming all over us but not doing any serious

damage. Few showy flowers were seen, the most stri-

king being several terrestrial orchids, one of which

Arundina speciosa Bl. was quite common and decidedly

handsome.

After boarding the ship, we sat sail for the north side

of the island, where a landing was made at the base of

the rock wall formed by the fractured face of the riven

cone of Rakata. As we approached the face of the cliff,

we were startled to see what looked like puffs of smoke

rising from various fissures in the cliff. Remembering

the history of the mountain, and also having just received

the news of the eruption of Vesuvius and the terrible

earthquake at home, the thought occurred that perhaps

Krakatau was getting ready for another outburst, which

to say the least, was not reassuring. But we finally

discovered that the ‘‘smoke’’ was merely clouds of dust

caused by the falling of débris from the face of the cliff.

Our landing was made in a broad bay where there is

a narrow beach, but the development of the strand flora

is much less advanced than on the south side of the island.

Ferns were noticeably abundant, as they were on the

other parts of the island when it was first visited after

the eruption. Nephrolepis exaltata Schott was espe-

cially frequent, and in the crevices in the rocks we found

numerous prothallia and young plants of a species of

Gymnogramme and of several other ferns. Some of

the ferns and other plants which were growing upon the

ground here are usually epiphytes. Of these Polypodium

quercifolium L. was the most conspicuous.

After exploring the interior and strip of land at the

base of the cone, we returned to the ship. Before the

sun went down we set sail for Java and soon the peak

of Krakatau was left behind us. The next morning

found us safely back in Tandjong Priok.

456 THE AMERICAN NATURALIST [Vou. XLIII

Tue ReEESTABLISHMENT OF THE FLORA oN KRAKATAU

When the island was first visited by a geological ex-

` pedition two months after the eruption, the whole surface

was buried under a layer of ashes and pumice averaging

thirty meters in depth, and in some places as much as

sixty meters. Thus, of course, every trace of life must

have been quite annihilated and the sterilization was com-

plete. An analysis of the ashes showed that, except for

phosphorus and nitrogen, all of the elements necessary

for plant life were present. (See Ernst, p. 50.) Ernst

suggests that the other elements necessary for the estab-

lishment of a new flora were conveyed from the main-

land in the form of dust, and that as a result of the in-

tense electrical activity which accompanies the almost

daily rains of the equatorial region, the atmospheric

nitrogen is oxidized into the nitric and nitrous acids

which furnish the necessary nitrogen. This with the

salts and traces of organic matter in the ashes would

have been sufficient in a very short time to allow the es-

tablishment of the first micro-organisms upon the island.

The first botanical expedition, as already stated, was

made under the direction of Professor Treub in 1886,

_ three years after the eruption. During this interval a

considerable number of plants had already established

themselves upon the island. The most important fact

brought out by this trip was the great importance of the

blue-green alge in the early establishment of the new

vegetation. Thin blackish, slimy films, formed by a

number of species of Oscillatoria and other blue-green

forms, were found in great quantity coating the surface

of the ashes, and the gelatinous matrix of these low plants

offered a substratum which was favorable for the germi-

nation of the spores of ferns and even for the seeds of

afew phanerogams. It was found that the colonization

of the island was quite as marked in the interior and

upon the high cone as it was along the shore, but the

plants of the interior of the island were for the most part

No. 512] THE NEW FLORA OF KRAKATAU 457

quite different. A remarkable fact was the great pre-

ponderance of ferns in the new flora. In the period of

three years no less than eleven species had established

themselves and formed the predominant feature of the

new vegetation. In our visit to the north side of the

island, where the reestablishment of the vegetation, as

we have seen, was less advanced than on the south side,

this preponderance of ferns was very marked, whereas

in the other parts of the island they have been to a very

great part supplanted by the phenogamous immigrants

and several species seem to have disappeared. In the

drift zone of the beach Treub found nine species of

seedling plants, and in the central part of the island

eight, two of which were the same as those upon the shore.

Of the remaining six, four were composites and two

grasses, all forms which would be distributed readily

by the wind. These phanerogams, however, were far

less numerous as individuals than were the ferns.

A series of visits to the islands was projected by Treub,

but unfortunately the plan could not be carried out, and it

was not until 1897 that a second expedition visited Kra-

katau. This second expedition was also under Treub’s

direction. In the interval of more than ten years that

had elapsed since the first visit the number of plants had

greatly increased and most of the island was covered

with vegetation which began to show the characteristic

formations which are now so conspicuous. The ‘*Pes-

capre” formation, i. e., the beach zone characterized by

the predominance of Ipomea pes-capre, was well estab-

lished, but the belt of strand forest now so marked upon

the southern side of the island was entirely wanting in

Krakatau, but the beginning of such a forest was found

upon the neighboring Verlaten Island. Almost no trees

were met with, and even shrubby plants were not numer-

ous. The grassy ‘‘steppe’’ lying between the beach and

the base of the cone was conspicuous and probably not

very different from its present condition. The total

number of vascular plants collected on this second ex-

458 THE AMERICAN NATURALIST [Vou. XLIII

pedition amounted to sixty-two, of which twelve were

pteridophytes and fifty phanerogams. The ferns still

predominated in number of individuals.

A third party visited the island in 1905, but the results

of this expedition have not yet been published.

A very full account of the present flora is given by

Ernst (pp. 37 to 48). In the three expeditions the results

of which have been published a total of 137 species is re-

corded. While a very large majority of these are phaner-

ogams, representatives of all the principal groups of

plants have been collected. In the earlier expeditions

the preponderance of ferns, as we have seen, was very

noticeable, but at present this is not the case and they

have largely given place to the more aggressive phanero-

gams. We collected only six species of ferns and one of

Lycopodium, the wide spread L. cernuum, while on the

first and second expeditions eleven species were noted,

and although it is true that we failed to reach the center

of the island, where in all probability other species would

have been encountered, it may be noted that we collected

seventy-three species of phanerogams against forty-eight

| Species recorded at the time of the second expedition.

Of the lower plants only two species of mosses have

been collected and a single species of antheroceros (this

was found only on the second expedition). We found

the two species of mosses growing fairly abundantly, but

no liverworts. Whether the latter grow in the central

part of the island remains to be seen, but it is highly

probable that some of the very numerous species of Java

and Sumatra will be found there. The scarcity of bry0-

phytes is remarkable, as it is generally assumed that their

_ Spores are readily disseminated; and the contrast with

the ferns which so quickly colonized the island is most

striking. Three species of fleshy fungi have been col-

lected and a considerable number of species of diatoms

and blue-green alge were among the earliest settlers of

the island. :

Professor Ernst made some interesting studies on the

No. 512] THE NEW FLORA OF KRAKATAU 459

bacteria, collecting from several places samples of soil

which were placed in sterilized tubes. These were ex-

amined by Dr. E. De Kruyff, bacteriologist of the Agri-

cultural Department at Buitenzorg, and the soil was

found to contain the usual proportion of bacterial’ forms,

both ordinary soil bacteria and putrefactive types. An

interesting discovery was the presence of a new aerobic

nitrogen-fixing bacterium, which was named Bacterium

krakataui. B. radicicola is present in abundance in the

root tubercles of the numerous leguminous plants which

now abound on the island. It is evident that the differ-

ent kinds of bacteria must have very early established a

foothold upon the sterilized island surface and were no

doubt among the factors which rendered the establish-

ment of the higher types of vegetation possible.

A most interesting find was a single thrifty female

specimen of Cycas circinalis. This tree had a trunk

nearly two meters in height, and the size of the plant

suggested that it was a survivor of the original flora; but

Ernst states that this is impossible, as the portion of the

island where it is growing belongs to the new shore

formed since the eruption. :

AGENTS IN DISTRIBUTION

Ernst has treated very fully the question of the agents

by which most of the members of the new flora were in-

troduced (pages 53 to 68). There seems no doubt that

the earliest immigrants—bacteria, blue-green alge, ferns

and mosses, were wind borne, and the same is probably

true of the first phanerogams found upon the island, com-

posites and grasses, but other agents have been active in

transporting seeds and fruits to the shore of the devas-

tated island, and of these the ocean currents have prob-

ably been most important. There is no question that the

fruits and seeds of the strand plants are probably all

water borne, and Ernst called attention to the important

part played by driftwood in introducing new plants

whose seeds might have been lodged in the erevices in the

460 THE AMERICAN NATURALIST [ Vou. XLII

bark, or he even suggests the possibility of young plants

being transported on uprooted trees. The shore of the

island is covered with masses of logs and fragments of

trees which might very well have brought with them not

only vegetable immigrants, but animals as well. An in-

teresting case was that of the two species of fleshy fungi,

Polystictus, which were found growing upon logs lying

on the shore, and whose mycelium almost certainly had

been growing in the logs before they were drifted out to

sea.

Birds have undoubtedly also played their part in the

introduction of seeds, especially those of fleshy fruits

such as the species of Vitis, common near the shore, and

several species of figs found somewhat further inland.

The rapid development of the vegetation in the nine

years between the visit to the island in 1897 and our visit

in 1906, and especially the great increase in the forest

vegetation, makes it evident that before very long the

forest which originally covered the island will be again

in possession. Already the belt of forest along the shore

is working inland, and it is to be expected that the patches

of forest in the ravines flanking the cone in the interior of

the island are spreading shoreward, so that in the course

of time the intermediate belt of grassy land will probably

be completely obliterated and the forest will once more

be in undisputed possession of the entire island.

A MALE CRAYFISH WITH SOME FEMALE

RGANS

PROFESSOR E. A. ANDREWS

THe Jouns HOPKINS UNIVERSITY

THE crayfish to be described here was peculiar in being

a male with some few of the external characters of a

female. If by the term gynandromorph we understand

_ an individual that shows both male and female organs in

different parts of the body, though the normal individ-

uals have but one set of sexual characters, we may call

this crayfish a gynandromorph.

Compared with other known cases of mingled sex in

the crayfishes this one is peculiar in being chiefly all male,

while most of the other cases on record are predominantly

female.

Before describing this crayfish it will be useful to recall

- that the sexual organs of crayfishes consist of the gonads,

ovary and testis, their ducts, certain modified limbs to

ensure the transfer of the sperm to the female from the

male; and in the crayfishes of the genus Cambarus, a

sperm receptacle upon the female in which to store up

the sperm till the time the eggs are laid.

The ovary of the female is a median mass that becomes

filled by the large eggs and from it an oviduct passes

down on each side of the body to open out upon the base

of the antepenultimate leg, right and left, as a rounded

hole that is closed by an operculum, except at the time

of egg laying.

The testis of the male is a similar but smaller body

from which a convoluted duct leads down each side to

open out on the base of the ultimate leg at the tip of a

perceptible papilla which is turgid with the pressure

of the blood.

The limbs of the female are reduced, or nbori upon the

461

462 THE AMERICAN NATURALIST [VoL. XLIII

first somite of the abdomen, while those on the second are

like the following ones. But the limbs on the first somite

of the abdomen of the male are quite remarkable conduits

that conduct the sperm; and the limbs of the. second

somite are peculiarly adapted to fit against the first as a

necessary part of this sperm-transferring apparatus.

The limbs of the thorax may also be modified so that

some of them bear hooks for holding the female.

In the case of Cambarus the female sperm-receptacle

is a unique median pocket in the shell, which is of as much

physiological necessity for the race as are the ovary, the

testis and the male appendages that transfer the sperm.

The gynandromorphie crayfish to be described was a

small sized and probably immature male of the species

Cambarus affinis, taken in a lake at East Hampton, Conn.,

by Mr. Kenneth N. Atkins.!

The external appearance of this specimen was that of

a male 55 mm. long with small chele only 30 mm. long,

having the hand 15 mm. long and 5 mm. deep. The

antenne were 45 mm. long. The papillæ of the fifth or

ultimate legs seemed normal. The second abdominal limbs

were as usual in a male but the first were of the puerile

or so-called second form of male limb very like that

found in a young normal male five months old and 38

mm. long. The tips were blunt and there was a free

joint above the basal joint. The attaching hooks of the

third, or antepenultimate, legs were short and blunt, but

normal for the young male. There were the usual long

male hairs on the spine between the ultimate legs, and

t The finding of this species in this locality is of pipin as bearing

pon the geographical distribution of crayfishes. New England being

singular in the fewness of its crayfishes, which are largely phos to the

drainage into the St. Lawrence, the Retr to be settled is whether the

crayfishes are absent because they never got there or because some character-

istics 3 climate, soil or pga peie are inimical to them. It

seems that these erayfishes were first observed in this lake some nine years

ago, being, it is thought, a there by fishermen. Since these crayfish

are fairly abundant there now this is evidence that crayfish can live in

s region, and favorable to the idea that the relative absence of cray-

a throughout these states is due to their not having migrated in there.

No. 512] MALE CRAYFISH WITH FEMALE ORGANS 463

no sign of any female organ, the sperm receptacle, an-

terior to it.

To these male external features there were added the

two female openings on the antepenultimate legs. On

the right the basal segment of the leg bore a well-formed

normal female orifice, that is, a soft, round, depressable

area, or operculum. This opened along the median edge

as a curved mouth bounded by a narrow stiff rim of hard

shell. On the left the opercular area was perhaps some-

what less perfect, its median side being more a straight

line which opened as a mouth, and the curved bounds

were more vague. The hard rim was thicker, apparently

by the amount that the straight mouth should have been

curved to make the normal contour.

On dissection the internal organs were found to be

entirely those of a male, for the above female openings

had no connection with the interior and there were no

oviducts nor ovaries. On the right the operculum, when

pushed in, showed a short conical pocket that received

a needle point but. appeared to end blindly as a mere thin

chitinous continuation of the shell inwards. This pocket

was flat. The mouth was a little more than 1 mm. long

and the pocket slightly shorter than the mouth, on the

right side. On the left the mouth slit led into a pocket

of less extent.

The essential internal organs of this animal were the

testis and the two efferent ducts. The testis was a

median mass some 3 mm. long under the heart, with two

anterior lobes about 2 mm. long rising upwards in front

of the heart. Besides this well-developed part the testis

was continued back over the intestine as a short minute

membranous thread and forward between the stomach

and the hepato-pancreas as a clear tubular membrane,

or sterile part of the testis about 2 mm long, from the

right and from the left lobe.

Where the right and left lobes joined the median lobe

the different duct sprang out each side and, passing back

alongside of the median lobe some 3 mm., went away at

464 THE AMERICAN NATURALIST [Vou. XLIII

right angles over the surface of the dorsal muscle-mass

that comes into the thorax from the abdomen on the

side of the thorax, without any coils or turns, some 4

mm. Each duct then descended in a slightly sinuous

course to the projecting base to which the antepenultimate

leg is attached, where it became thicker and, making a

short semicircular curve, entered the basal joint of the

leg and passed straight out to the tip of the papilla.

The duct contained sperm.

Comparing these findings with the anatomy of normal

young males and females of the same species, we see that

in a male of 65 mm. killed in October the first pair of

limbs on the abdomen have much more perfected tips

and lack the joint near the base; while internally the

sperm ducts that lie alongside of the median part of the

testis are so coiled as to be there about 20 mm. long

instead of 4mm. The duct was also larger and contained

more sperm. Allowing- for the differences in size and

in time of year, the two specimens are essentially alike

and we may regard the abnormal one as perfect in all its

male organs, though they had not reached their final form.

Doubtless this male would have been able to transfer its

sperm to a female in the proper season, that is, in the fall.

Serial sections of the testis show no indications of

any hermaphrodite nature, no ovogenesis in any part.

On the other hand, the different duct and the collecting

tubules contain some nearly mature sperms. Some 0

the acini show spermatogonia with equatorial plates.

The two sham oviduct-openings of this specimen when

compared with the real openings of a female of October,

some 60 mm. long, show the closest agreement externally.

But there is the fundamental difference internally that

the normal mouth, instead of leading into a blind, minute

pocket, continues directly as a wide and comparatively

- straight tube some 10 mm. upwards to the ovary.

In brief, then, this gynandromorph was a young male

that would have functioned as such at the next breeding

season, yet it presented two female characters, openings

No. 512] MALE CRAYFISH WITH FEMALE ORGANS 465

as if to lead to ovaries, but with no internal connections

and no discoverable use. These sham openings stand

in the proper place for the oviduct openings of a female.

A review of the literature fails to show any abnormal

crayfish with just these combinations of male and female

characters; in fact, as before stated, most of the known

eases are females with some male features. Recorded

abnormalities of crayfishes include the cases of repetition

of parts in one sex and the cases of mixtures of traits of

two sexes. The former have been brought together by

Bateson in ‘‘ Materials for the Study of Variation,’’ Mac-

millan, 1894, the latter by Hay in ‘‘Instances of Her-

maphroditism in Crayfishes,’’ Smithsonian Miscellaneous

Collections, 1905.

In his monograph on the crayfishes of Pennsylvana Ort-

mann has recently described five additional cases in Cam-

barus, in which the external sex organs are more or less

mixed and in part defective.

Bateson found that in 586 females of Astacus fluviatilis

there were 23 abnormal cases. In these, besides the usual

openings upon the bases of antepenultimate legs, there

were one or two similar openings upon the penultimate,

the ultimate or even upon all; making a maximum of

three pairs of openings. Moreover, the oviducts gen-

erally branched so that more than one pair of oviduct

openings might be functional, but in other cases the

extra openings might end blindly and be of no use. Of

714 males onty one was abnormal and that presented

not a duplication, but a suppression of organs, having

no trace of a generative opening upon the right side, while

the sperm duct of that side hung blindly in the body

cavity.

A real case of duplication of sexual characters in a male

crayfish was recorded, in a rather inaccessible publication,

the Indiana University Bulletin, by W. J. Moenkhaus,

in 1903. He found in Cambarus viridis a male that had

in addition to the usual first and second male limbs of the

abdomen the third pair modified to exactly resemble the

466 THE AMERICAN NATURALIST [Vou. XLIII

second, in plan, and to differ from them but slightly in

the detail with which this was carried out.

These cases of duplication of external organs must not

be confounded with the gynandromorph here described

since that has both male openings and female openings

and not a mere duplication of the openings of one sex.

There is so much difference between the male papille of

_the fifth legs and the operculate openings of the ante-

penultimate legs of the female that we must regard them

as two morphologically and physiologically distinct or-

gans and their occurrence upon the same animal is not

the same thing as the duplication of one set upon one

animal. This is true even if there were reason to sup-

pose that both kinds of openings may have had some

common origin in the past. :

The cases of hermaphrodite crayfishes previously on

record were considered by Hay along with most inter-

esting new cases. It appears from his paper that there

are in crayfishes no known cases of such complete, typical,

gynandromorphs as that of the lobster described in 1703

as having both external and internal organs of the male

on the left side of the body and of the female on the right.

All crayfish gynandromorphs, but one, are really either

males or else females as regards the gonads, and have

added but some of the external organs of the opposite

sex. One isa female with a little testis as well as external

organs of the male. -

The numerous cases of crayfishes from the southern

hemisphere with the external openings of both males and

females described by different authors are especially

interesting as resembling the gynandromorph of this pres-

ent paper, since it was found by Lénnberg,? that when-

ever the internal anatomy was made out, the animal had

either a testis or an ovary, and if there was a testis the

normal ducts led to the normal male openings, while the

redundant female openings had no internal connections,

though the testis did send out an extra duct towards the

* Zool. Anz., 1898.

No. 512] MALE CRAYFISH WITH FEMALE ORGANS 467

pseudo-female opening; while if there was an ovary the

oviducts went to the normal openings and the extra male

openings were of no use, though here again the ovary

sent out a duct towards the useless male openings.

-~ The extra openings, however, Lönnberg found to be

shams, or closed openings, yet they look like the openings

of the opposite sex.

This state of things, the perfect male or female with

sham openings and pseudo-ducts of the opposite sex,

seems to be the usual, if not the only, condition found in

many species of the genus Parastacus, to judge from all

the specimens that have been studied. The relationship

between Parastacus and Cambarus is, however, believed

to be so very remote that one can not suppose the present

ease of abnormality in a species of Cambarus has any

genetic connection with what seems to be the rule in

many, but not all, species of Parastacus.

The other recorded gynandromorphs are one specimen

of Astacus and fourteen of Cambarus, and all except one

are females that have some male characters added.

The superfluous male characters are sometimes but the

modification of the first abdominal limbs to resemble those

of the female, in others both these and the following limbs

are just like the male limbs. In one the male attach-

ment hooks, and the male openings and even the hirsute

spine posterior to the somite of the sperm receptacle,

that is, all the external characters of the male, are

present along with normal ovary and oviduct.

This last was the most hermaphroditic of all known

erayfishes. It was the female Cambarus affinis, 106 mm.

long, described by Hay. This seemed externally a male

and attempted conjugation with a female, having a good

set of male external organs. But internally it had a

large ovary with nearly mature eggs and two perfect ovi-

ducts. The specimen was thus deficient in lacking the

sperm receptacle that a female of this kind of crayfish

should have in order to get the eggs fertilized. In addi-

tion to the ovary there was a small testis, on the right,

468 THE AMERICAN NATURALIST [Vou. XLIII

with a duct leading to a single male opening on the ulti-

mate leg. Though no sperm was present it seemed as if

sperm might have been made. It appears that this

individual could have been of little or no use to the race.

With this exception all sexually abnormal crayfishes, as

far as known, are either males or females with either some

duplication of organs that belong to that one sex or else

the addition of external organs of the opposite sex. But

in Parastacus there is also some duplication of internal

ducts, which needs additional investigation to show how

far it is duplication and how far it may be the addition

of ducts of the other sex. As far as Lénnberg’s observa-

tions go the extra ducts were like the normal of that sex

and not like those of the other sex.

_ The fact that the male may have merely the external

openings of the female sex without any internal female

organs shows that the gonad is not necessary as a stim-

ulus for the making of the external organ, that the ex-

ternal organ is not correlated with the gonad by any

internal secretion or other means, necessarily. At the

same time Parastacus shows that when there are extra

openings, or rather sham openings, the gonad sends extra

ducts towards those openings so that there seems a corre-

lation between the gonad and the external organ that

belongs to the opposite sex. However, Lénnberg found

in some of the testes of Parastacus objects that he thought

might be eggs; so that the purity of the gonads is some-

what doubtful.

There is a possibility that these males may have had

enough development of a hermaphrodite gonad to supply

a stimulus to the surface that would make the external

female organs begin to develop in the right place for a

female having ovaries, though the gonad was essentially

male.

The gonads of crayfishes are late in becoming visible

in the ontogeny of the individual and the external organs

do not show till the eggs have hatched and passed into

the third larval stage, after two moults. Whether these

No.512] MALE CRAYFISH WITH FEMALE ORGANS 469

external organs would develop at all without the internal

gonad can only be determined by future experiment, but

the abnormal cases above cited show that the external

organ may be formed without the gonad of that sex to

which the external organ ought to belong and make it

probable that the external organs and the gonads are so

independent that we need not suppose one leads to the

formation of the other.

The sex of the crayfish is not merely the possession

of egg or sperm, but of something made evident in a

variety of places over the body, as sex organs that are

accompanied by the necessary reflexes and instincts to

use them.

That the sex is rather intimately dependent upon func-

tion seems to be indicated by the occurrence of the two

forms of male, known as the first and second, which alter-

nate in such a way that at the breeding season the ex-

ternal organs of the male are perfect, while at another

time of year the same male has relapsed into a juvenile

state in which the sperm transfer organs are as they

were in youth and probably of little or no functional

value. These morphological changes are made possible

by the shedding of the shell and the growth of what is

practically a new organ.

We have then some reason for supposing that back of

the visible sex organs there is some state or condition

of the organism that can at least modify the structure

of the sex organs.

Nothing is known as to the origin of these gynandro-

morph crayfishes. But regarding the eggs as at first

able to make either male or female, or make more than

one individual under certain circumstances, the gynan-

dromorph may be looked at as a partial realization of

the entire set of possible organs. The causes may lie

in physiological states present at various stages of ontog-

eny. Where a whole species is gynandromorphic the

egg may be predestined in the ovary to produce a mix-

ture of organs. When only an occasional individual has

470 THE AMERICAN NATURALIST [Vou. XLII]

a few external organs added to the normal set the causes

may lie in conditions not found till late, after fertilization.

Just as the determination of sex may be due to dif-

ferent conditions in various animals and plants, so the

repression or the expression of one or another sex organ

may be due to diverse causes acting at various periods

of ontogeny, and not to any single factor. Moreover, we

do not know how far the gynandromorph may be the

result of aberrations independent of the causes of deter-

mination of the gonads.

However amongst the insects, where gynandromorphs

are well known, there are reasons for restricting our

surmises as to the time of origin of the mixed expression

of sex organs. Here the mixing seems to be associated

with the period of fertilization. In the honey bee the

sex is determined, apparently, in fertilization and the

phenomenal cases of gynandromorphs, such as those

studied by V. Siebold in 1863, in the Eugster hive, have

often been explained as due to abnormal fertilizations.

This interpretation has been most acutely elaborated by

T. H. Morgan on the basis of the facts of experiments

upon echinoderms and the results of Toyama upon

hybrid moths. He is finally led to the view? that the

egg nucleus by itself would produce male, the sperm

nucleus by itself also male, but the two combined produce

female. The gynandromorph would be the result of

polyspermy. It would be a sort of combination of indi-

viduals, the one female, arising from the part of the egg

containing the fused egg and sperm nucleus; the other,

male, arising from the part of the egg in which extra

sperms developed without contact with the egg nucleus.

The female parts of the gynandromorph would have two

parents and should be mixed in a hybrid, the male parts

would have but one parent and should be pure in a hybrid.

The hypothesis of polyspermic origin of gynandro-

morphs might be applied to the crayfish with the common

assumption of two sorts of sperm, male producing and

*This journal, November, 1907.

No. 512] MALE CRAYFISH WITH FEMALE ORGANS 471

female producing.* We assume that every egg is fertil-

ized and will be male or female according to the sperm

that unites with its nucleus. But a gynandromorph

might arise by adding to the male or the female some

organs of the opposite sex due to the independent de-

velopment of the opposite kind of sperm in parts of the

egg. All sorts of gynandromorphs might be imagined

upon this basis. Moreover, we might assume the abnor-

mal cases of duplication of sex organs in one individual,

such as studied by Bateson, to be due to the independent

development of sperms that happened to be of the same

kind as the one that fused with the egg nucleus. In

theory we might even refer the doubleness of organs not

concerned with sex to some sort of super-fertilization.

Whether such hypotheses have any value may be de-

termined by future experiments in the cross breeding

of crayfish. Such experiments may enable us to decide

whether gynandromorphs arise before, during or after

fertilization and may throw light upon their causation.

The crayfishes in this part of the world, are especially

well adapted to these experiments, for if crosses can be

obtained at all, we may expect to distinguish between

pure and mixed sex organs, since both the male and the

female have external organs that are at the same time

essential sex organs and characteristic specific characters.

_ Meanwhile the totality of facts known seems to mean

that the gynandromorph crayfishes are caused by un-

known disturbances, which may happen at various periods

of ontogeny, though probably more often in the ovarian

egg; that these disturbances may have no connection with

the gonads; and that if in some cases the disturbances are

possibly associated with polyspermy, in general they seem

more fundamental and deep seated amidst the causes of

symmetrical form within the egg.

BALTIMORE,

January 11, 1909.

‘In some crayfish there are visibly different forms, some are wound

clockwise and some counter clock, some have more and others less rays.

PRESENT PROBLEMS IN PLANT ECOLOGY!

IV. Prostems or LocaL DISTRIBUTION IN Arp REGIONS

PROFESSOR VOLNEY M. SPALDING

Desert BOTANICAL LABORATORY

Tue physical conditions prevailing in arid regions are

such as render it unsafe to admit without further investi-

gation generalizations regarding their plant life which

have been drawn from studies conducted elsewhere. This

is sufficient justification of an attempt to analyze certain

problems which confront the student of desert ecology in

his efforts to apply knowledge or principles drawn from

previous experience. These problems have the advantage

of a certain clearness of definition, which corresponds in

a way with the sharp features of the desert and its char-

acteristic vegetation. Their solution may involve great

difficulties, and some of them, with our present methods,

may be incapable of solution, but they are, at all events,

capable of clear statement.

In the attempt to present such a statement, which may

or may not prove successful, I shall for the present limit

the discussion to the desert country of the southwestern

United States, for the sufficient reason that my own

studies have been conducted in that region; and I shall

omit all consideration of the higher elevations of the

mountains, which, though in the desert, are not of it; so

that whatever is said at this time will be understood to

apply to the floor of the desert, that is the great plateaus

and valleys which from Texas to California lie between

the mountain peaks and ranges, together with the long

slopes and low hills which border them on every hand

and form the natural approach to the mountains. |

* A series of papers presented before the Botanical Society of America,

at the Baltimore meeting, by invitation of the council.

No.512] PRESENT PROBLEMS IN PLANT ECOLOGY 473

Proceeding in a manner that will be indirectly a record

of personal experience, one of the first questions pre-

sented to a student of desert botany is this: What are

the conditions that determine the successful occupation

of a desert habitat by certain plants, but prevent its

occupation by others?

It will be necessary at the outset to understand what

is meant by a desert habitat, since on this point the pop-

ular conception—and possibly that of some botanists—

is not clear. There is as much difference between habi-

tats in the desert as in any other region, possibly more,

and their definiteness of location and relative sharpness

of demarcation form one of the most striking and char-

acteristic features of arid regions. The rivers of the

valley trough, such as the Santa Cruz, the Gila and Salt

Rivers in Arizona, though inconstant, are none the less

the main drainage channels between the adjacent water

sheds. Along their banks water-loving willows, cotton-

woods and arrow-weed find a congenial home. The

adjacent flood plain, with its water table within reach

of their roots, is the natural habitat of the mesquite and

some other semi-mesophytic species. Within its limits

the areas known as salt spots are inhabited by various

halophytes, especially by species of Atriplex and Suaeda.

Just beyond the fiood plain is the long slope, a most char-

acteristic feature of desert topography, which rises slowly

to the foot of the mountains, often miles away, its soil

and drainage conditions presenting a sharp contrast to

those of the flood plain, and its vegetation being corre-

spondingly different. The low outlying hills, in their

turn, present quite as marked peculiarities of soil, and

furthermore introduce differences of aspect which are

correlated with marked differences of vegetation. In

‘short, the habitats of such a desert region as that of

southern Arizona, as far as edaphic relations are con-

cerned, present conditions which vary all the way from

distinctly hydrophytic to extreme xerophytic, and all

these may be in close proximity.

474 THE AMERICAN NATURALIST [Vou. XLII

For all these habitats the fact is to be emphasized that

the general climatic conditions are the same, and it is

important to note that not a few of the plants which grow

where a sufficient or even abundant water supply is as-

sured are nevertheless marked, as a rule, as plants of

an arid region by their coriaceous, hairy or otherwise

xerophilous leaf structure. The point to be specially

noted here is that while plants of the arid, or semi-arid

southwest grow in a great variety of habitats, some of

which are by no means dry, all are subject to the severe

conditions of a desert climate, especially intense insola-

tion, low percentage of atmospheric moisture, and drying

winds. The problem, therefore, of the occupation of any

one of these habitats is successfully met only by those

plants that are already adapted, or are capable of indi-

vidual adjustment to the dry air and hot sun in which

they must live; all others inevitably fail.

This will be made clear by reference to the introduc-

tion, or attempted introduction, of various cultivated

plants, a subject which presents a most instructive his-

tory. The yards of Arizona cities constitute an experi-

ment station in which year by year, at private instead

of public expense, the availability of one species after

another for desert planting is being determined. From

the great number of plants successfully cultivated there

seems, at first sight, to be sufficient justification for the

reiterated assertion that anything will grow here if you

only give it water enough, but closer attention to the

actual facts of the case makes it evident that this state-

ment is true only in part, and that there are many plants

that will grow only indifferently or not at all under the

atmospheric conditions which prevail here, especially in

the summer time. To give a few examples, geraniums,

the universal easily raised plants of moister regions, are -

very uncertain, some varieties accommodating themselves

fairly well to the desert air, while others fail altogether.

Cannas and gladioli, which grow side by side in the east,

part company here, the former making a good growth in

No. 512] PRESENT PROBLEMS IN PLANT ECOLOGY 475

Arizona gardens, the latter failing altogether. Those who

have handled roses for a period of years have learned

what varieties may be expected to do well in the dry air

of the desert, and what ones may be counted out, and so

on through a long list of plants which, by knowledge

gained in the costly school of experience, are coming to

be depended on, or are being rejected one after another,

as they are found to be unsuited to the environment into

which they have been brought. Thus, in a purely em-

pirical way, it has been found that many plants success-

fully cultivated in regions of greater atmospheric hu-

midity make an entirely normal growth in the desert, if

their roots are well supplied with water, but that others,

however well cared for in this respect, either fail com-

pletely, or come short of making a healthy growth, and

that this is especially true in the summer months when

desert conditions are most pronounced.

With the accumulation of such facts the more evident

does it become that a very complicated problem is here

presented. Why is it that one plant, properly watered,

does well in the desert, while another, though treated in

the same way, makes a poor growth or fails altogether?

At first thought it would seem as though there must be a

difference in the capacity of the root systems of the two

plants for absorption, and that this may be a sufficient

explanation of their different behavior; but it is evident

on consideration, that with precisely the same capacity

for root absorption, a plant in which transpiration is suc-

cessfully regulated may thrive in an atmosphere in which

one subject to excessive transpiration will perish. The

most elaborate experiments and the most exact deter-

minations of rate of absorption—assuming that such de-

terminations are possible—would be very likely to throw

no light on the problem. Comparisons of the transpira-

tion rate of the plants in question appear more promising,

but the same difficulty arises in an attempt to pursue the

investigation along this line, for there is no reason to

suppose that two plants of widely different rates of trans-

476 THE AMERICAN NATURALIST [Vow. XLII

piration can not successfully occupy the same habitat

if their capacity for root absorption differs in the same

ratio. But supposing that with infinite patience and with

a reasonable approach to accuracy both sets of physio-

logical data have been determined, we are still, quite pos-

sibly, entirely in the dark as to the real cause of the

different behavior of the plants under investigation. It

may be in their case that the whole matter of absorption,

conduction, and transpiration is beside the mark, and

that certain plants can not succeed in the desert because

the intense insolation exerts directly a prejudicial in-

fluence to which they have not become inured. The intri-

cate nature of the subject is apparent, and it is also evi-

dent that there is little encouragement for any one to

take it up who has not had extended training and thorough

equipment for physiological research. Yet with all its

difficulties the problem is an attractive one, and the

abundance of material to be had in any desert city, to-

gether with the great mass of data that has accumulated

in the hands of horticulturists and at the experiment

stations, offers the best of opportunities for extended and

fruitful work.

If, as we have seen, the different deportment in the

desert of plants growing, or having the opportunity to

grow, side by side in well watered ground, is an exceed-

ingly complicated matter, by how much are the difficul-

ties increased when we pass from a habitat of uniform

and highly favorable conditions, to the various and often

extremely trying conditions which prevail in different

neighboring habitats, such as the dry slopes underlaid

by caliche, the salt spots and others. If the case of a

plant growing in well watered soil may become desperate

because of the scorching winds or the intense insolation

to which its top is exposed, what hope is there for one

that assays to grow where both dry air and dry soil pre-

sent the supreme test of endurance? As a matter of fact

only relatively few species meet the test successfully,

yet there are some that do, and they present some of the

No.512] PRESENT PROBLEMS IN PLANT ECOLOGY 477

most instructive data yet derived from the study of

desert plants.

But little reflection is needed to arrive at the conclu-

sion that the classical question regarding the relative

importance of physical constitution and chemical compo-

sition of the substratum to plant growth—though like the

poor it promises to be always with us—does not, and can

not reach the heart of the problem. For every plant

which successfully holds its place in a true desert habitat

there is a delicate balancing of the regulation of trans-

piration, the power of absorption, the capacity of the

conducting system, the presence or absence of storage

tissues, and, we may well believe, the possession of proto-

plasmic properties which contribute to its powers of en-

durance. This being the case, it would seem that in

future, investigations of the habitat relations, of desert

species especially, must be directed mainly to the plant

itself. The advantage of a thorough knowledge of soils

is too obvious to call for comment, but it must be re-

membered that we are as yet only at the threshold of a

greater and more promising work, namely, the investiga-

tion of the physiological requirements and capabilities

of plants that can grow in a true desert habitat as com-

pared with those that can not. In such comparative

study lies, as it seems, the hope of real progress. It is

impracticable for any investigator, at the present time,

to mark out a straight path for others to pursue, and it

would very properly be regarded as an impertinence

were he to attempt this; yet there are certain obvious

suggestions that may be offered.

In the first place, important results have already fol-

lowed the simplest experiments and observations when

these have been conducted with exactness and with a

definite end in view. To refer to a specific case,—Pro-

fessor Thornber, of the University of Arizona, under-

took a few years ago to compare the habits of certain

desert plants. as regards germination. It was found that

while the seeds of some species germinated at a given

478 THE AMERICAN NATURALIST (VoL, XLIII

temperature, others could not be made to do so until they

had been subjected to temperatures approaching the

freezing point. These latter were seeds of winter an-

nuals, and by this method a fundamental physiological

difference between them and the summer annuals was

established. Doubtless an indefinite amount of instruc-

tive and necessary work remains to be done in this direc-

tion, but the key to the situation was found in carrying

out the simple experiments described. Again, partly as

a relief from severer work, Dr. Cannon undertook, in the

midst of his investigations at the Desert Laboratory, to

map the distribution in the soil of the roots of some of

the plants growing in the vicinity. Hardly was the work

well in hand, and the root topography of less than half

a dozen species mapped, when it was found that the clue

to certain facts of distribution, blindly observed up to

that time, had been discovered. I have spoken of this

in more detail in another connection.

Obviously it is indispensable that determination of

physiological data and of those belonging to the physical

environment should proceed step by step together; and

nowhere is this more strikingly true than in the investi-

gation of soil relations. To refer to one more case of

recent experience,—within the past year Dr. Livingston

has determined the percentage of soil moisture present

in soils obtained from each of the topographic areas of

the Desert Laboratory domain and the adjacent flood

plain of the Santa Cruz River. His studies were con-

ducted independently, though naturally not in ignorance

of ecological studies which were being carried out at the

same time on the same ground. It now appears that a

well-nigh perfect correspondence exists between the two

sets of facts obtained by independent workers, so perfect,

in truth, that a causal relation offers the only satisfac-

tory explanation. The accumulation of physical data,

however, has proceeded so far and so satisfactorily that

the successful conduct of this line of investigation may

be regarded as assured, but for the plant the relations

No. 512] PRESENT PROBLEMS IN PLANT ECOLOGY 479

are more complicated, and their investigation corre-

spondingly more difficult. It seems likely that in the

study of ecological relations from the side of the plant

we shall employ more and more the methods and con-

ceptions of physics and mathematics, but the fact is too

patent to call for argument that neither now nor here-

after can these methods and conceptions be employed

exclusively. In fact there has never been greater need

than at the present time for exact observation coupled

with correct judgment, and these can never be replaced

or superseded so long as this department of botanical

investigation continues to be cultivated. This will re-

ceive additional emphasis in the following division of the

present paper.

The relations of desert plants to each other present a

chapter, the importance of which has been unduly min-

imized until the general impression, even among botan-

ists, seems to be that desert plants are to be studied only

in relation to their physical environment; they are

thought to grow so far apart, in ‘‘open’’ associations,

that they are quite uninfluenced by each other’s pres-

ence, Like other erroneous or incomplete conceptions,

this may be true in part, especially where the most ex-

treme desert conditions prevail, as for example in parts

of the Colorado or Mojave Deserts, but in the great semi-

arid region of the southwest, taken as a whole, it is most

misleading. The Desert Laboratory of the Carnegie

Institution was located where it stands on account of

the great natural advantages which the region and local-

ity offer for the study of desert plants in place, yet I

venture the assertion that over at least nine tenths of the

area of the laboratory domain the establishment of a

plant in the place which it occupies is conditioned quite

as certainly by the influence of other plants as by that

of the physical environment. It hardly needs more than

simple observation to convince one that severe competi-

tion is the rule, though naturally its severity is height-

ened and the result hastened by the prevailing adverse

physical conditions.

480 THE AMERICAN NATURALIST (Vou. XEHE

Beginning with some of the most obvious cases, the

winter annuals of southern Arizona present an instance

of as unmistakable competition of individuals with indi-

viduals and species with species as can be found in the

eastern forest region of the United States. As the

warmth of spring follows the winter rains the ground is

thickly carpeted with Amsinckia, Pectocarya, Bowlesia,

and various other herbaceous plants, which stand thick

together and present to the eye the familiar crowding

which is seen in a field of grain too thickly sown. Cer-

tain individuals dwindle and finally die, robbed of water,

food and light by their stronger competitors. It might

be interesting to repeat the experiment in the laboratory

and to tabulate the results statistically, but it could

hardly add to the conclusiveness of the demonstration.

The same is true of the manifest competition of species

with species, as seen for example in the occupation of

relatively extended areas by some of the perennial

grasses which, but for their presence, would certainly be

covered, as the adjacent areas are, by a thick growth of

other plants. Here the actual advance of the grasses

from year to year may be observed, and such observa-

tions for the sake of more definite statement are now in

progress on the Desert Laboratory domain. Convincing

evidence of competition is thrust upon one’s attention in

passing from the desert to areas beyond its borders, and

if the transition is abrupt, as for example on the western

edge of the Salton Basin, where the desert abuts almost

upon a mountain wall, the case is all the more striking.

In this instance a straight course of less than five miles

brings one from the actual desert, with its characteristic

sparse growth of salt bushes, creosote bush, galleta grass,

and the like, to the chaparral of the mountainside. Along

the way the desert species fall out one by one, and are re-

placed by elements of the chaparral. As far as can be

judged by their habits elsewhere and from their known

range in altitude, there is absolutely no reason for this,

except their inability to compete with plants of the cha-

No. 512] PRESENT PROBLEMS IN PLANT ECOLOGY 481

parral, which, however incapable of normal develop-

ment in the desert, hold their own ground, where the con-

ditions are less strenuous, so tenaciously and completely

that the desert species make no headway against them.

This, of course, is an interpretation merely, but with

such an accumulation of evidence we are now in a posi-

tion to proceed with the problem along definite lines with

the expectation of definite results. Sowing together

seeds of desert and other plants, the transference of in-

dividuals to denuded areas beyond their natural limits,

and multiplied comparative observations of the deport-

ment of different species on the ‘‘edge of the desert’’ are

simple and obvious methods of procedure at the outset.

Some of this work has already been done, enough to con-

vince those engaged in it that in general the problem

of the successful occupation of a desert habitat involves

the recognition of actual competition on the part of its

would-be occupants, a competition severe enough in some

quarters to set up a barrier beyond which, in the midst of

otherwise entirely favorable environmental conditions,

they can not pass. .

In their relations to each other, desert plants fre-

quently exhibit not merely competition but accommoda-

tion. This has been clearly shown by recent studies of the

root systems of certain cacti and other plants by Dr. W.

A. Cannon. To take a striking example—superficial ob-

servation of the association of the sahuaro (Cereus gi-

ganteus) with one of the palo verdes (Parkinsonia

microphylla) and some other shrubby perennials gives

no satisfactory clue to the reason of this relation, and

the common explanation that they are plants of similar

biological requirements, and therefore grow together, is

altogether inadequate and in part misleading. The

careful study, however, that has been given to the root

systems of these’ plants brings out the important fact

that they grow close together by virtue of simple accom-

modation, which enables them to utilize to the utmost the

seanty rainfall. The roots of the sahuaro are spread

482 THE AMERICAN NATURALIST [VoL. XLIII

just beneath the surface of the ground, where they take

up and promptly pass on to the storage cells of the trunk

the water brought to them by every light rain. The roots

of the palo verde, on the other hand, extend much more

deeply into the ground, and are in a position to utilize

the water which soaks down to lower levels after heavier

rains. Thus the sahuaro profits by all rains, light and

heavy alike, while its constant companion, the palo verde,

is free from all competition on its part for the water

which penetrates to lower levels. Much the same thing

is seen on the flood plain of the Santa Cruz and other

rivers, where the mesquite, with its deep roots reaching

to the water table, is associated with Bigelowia and other

plants, the roots of which extend to relatively shallow

depths. In short, it appears that just as in a tropical

forest the vegetation occupies successive ‘‘stories,’’ so

here the root systems of various plants habitually reach

to different depths, and thus enable at least some species

that would otherwise compete with each other to live in

close and advantageous association.

From what has been said, it is evident that in the suc-

cessful occupation of a desert habitat the mutual rela-

tions of the associated species play a highly important

part. It is not quite easy at this stage of progress to

point out the exact steps by which these complicated re-

lations are to be determined and estimated; meantime

the homely and effectual method of patiently gathering

the data that are obtainable by careful observation is

open, and as far as it has been pursued has yielded val-

uable results.

The broad general problem of the local distribution of

desert plants is necessarily approached along the several

lines that have been indicated. As we have seen, atmos-

pheric conditions, whether of intense insolation or eX-

treme dryness, that obtain in arid regions are limiting

factors which many plants successfully meet, but to

which many others succumb. There has been great need

of more practical methods of determining and estimating

No. 512] PRESENT PROBLEMS IN PLANT ECOLOGY 483

the inflaence of atmospheric factors, and it is a matter of

congratulation that the methods devised by one of the

participants in this discussion, already widely in use in

different parts of the United States, promise to meet

this need to a degree that could not.be hoped for at an

earlier period. But it is never to be forgotten that under

the same atmospheric conditions, and with equal chances

in other respects, the deportment of two plants side by

side, their capacity for adjustment let us say, is so differ-

ent that the essential problem lies first of all in the

physiological capabilities of the plant itself.

More strikingly true, if possible, is this seen to be the

case when the relation of desert plants to the soil is con-

sidered. It is well that so much soil work has been done,

that we have soil maps, that determinations of water ca-

pacity and other physical as well as chemical character-

istics have been ascertained in so many habitats, and that

we have a growing literature embodying observations of

the relations of plants to underlying rocks, in short that

the substratum has been the object of so long and so

thorough study; there is no danger that we shall have

too much of this, but there may be danger that we may

sometimes forget to place the emphasis where it belongs,

namely, on the fact that every species and every variety .

of plant is a law to itself in its relations to rock or soil.

It is true enough that the different percentages of alkali

salts at different distances from the center of a salt spot

stand apparently in causal relation to the growth of dif-

ferent plants in corresponding concentric zones, but it is

equally true that this zonal arrangement is also the vis-

ible expression of the capacity of these different plants

to cope with the conditions there existing, and of this

capacity, if it is to be expressed, as some day it must, in

physical measurements, how inadequate is our knowl-

edge. How greatly we need to really know the physio-

logical constants, not of one but of many desert plants.

Tt is in the same line of thought, and with the same

purpose, that I have referred to the inadequate concep-

484 THE AMERICAN NATURALIST [Vot. XLIII

tion according to which the relations of desert plants to

each other have been so persistently overlooked or at

least underestimated. It may now be set down as an

established fact that over a large part of the arid or semi-

arid territory of the southwest, competition on the one

hand and accommodation on the other have much to do

with the association of plant species and the density of

the plant cover. Far more, it would seem, than has

usually been thought, the character of various associa-

tions in this region is determined not simply by the

physical but also by the living environment. More than

ever too, it is plain that the path of progress lies in the

direction of applying to the plant itself, in its natural

surroundings, the experimental methods of the physical

laboratory. Notable and fruitful beginnings have been

made in this direction, but one who has attempted quan-

titative work with the sahuaro or ocotillo in the open

need not be told that it involves difficulties not presented

by seedlings of Vicia faba grown in pots, and that prog-

ress will necessarily be slow. ;

Thus far adjustment and adaptation have not directly

entered into the discussion, although a moment’s thought

shows that all the paths along which we have come con-

verge right here. If one variety of geranium flourishes

in the desert air, while another by its side dwindles and

dies, we can only say at present that the latter is not

‘‘adapted,’’ or is apparently incapable of ‘‘adjustment”’

to the atmospheric conditions in which it has been placed.

We find that plants growing in the wash near the Desert

Laboratory do not, as a rule, succeed in gaining a foot-

hold on the long slope leading to the hill near by; they

are not adapted to the soil conditions there existing; but

the creosote bush, which makes its home on these slopes,

grows—thanks to its capacity of adjustment—even more

luxuriantly in the wash than on its own domain. Simi-

larly, certain plants of the salt spots grow better beyond

than within their limits; they have become adapted to —

large percentages of alkali salts, but their capacity of

No. 512] PRESENT PROBLEMS IN PLANT ECOLOGY 485

adjustment is such that they grow just as well or better

along an irrigating ditch carrying fresh water. Various

other plants in the immediate neighborhood have not, be-

come adapted to the conditions prevailing in the salt

spots, nor do they appear capable of adjustment to them,

and accordingly are not found growing in such places.

We need not multiply citations of these familiar cases.

Adaptation and adjustment have long been words to con-

jure with, out of the desert as well as in it, but we have

made so little real scientific progress in the definition and

determination of the things for which they stand, that

some of our foremost students of ecology seem ready to

abandon the effort, while others apologize when they use

the terms, as if they were myths and had better be left

alone. But nothing is gained, and much may be lost, by

this method of procedure. We are face to face with a

great body of phenomena of the most striking character,

in connection with which these words are fittingly em-

ployed. We can not ignore the existence of the facts,

and as scientific men we can not let them alone, while

they insistently rise at every turn in our pathway and

demand investigation. True it is that they bring in

their train whatever is fundamental in biological inquiry

—heredity, the direct influence of the environment, and

differences in the properties of protoplasm in different

plants. It is not customary, however, in laboratories

worthy of the name, to shun investigations that approach

to the deep mysteries of life. There is every reason why

students of ecological problems should seek, not shun,

this difficult but hopeful line of study. I say hopeful ad-

visedly, for within the past three years there have come

under my observation various definite cases of adjust-

ment in plants, some of which have been accurately meas-

ured, correlated with external factors, and expressed

by curves. Though essentially more difficult, there is no

reason, as far as now appears, why the different degrees

of adaptation of two species or varieties to a given ex-

ternal factor may not be similarly determined and

486 THE AMERICAN NATURALIST [ Vou. XLIII

graphically represented, as the expression of a definite

difference of physiological activity, as shaped by hered-

ity, in relation to that particular factor. Very little, as

far as I am aware, has yet been accomplished in this

direction, but it is a way that is wide open, and one that

should attract those real investigators who, knowing

difficulties, do not shrink from them.

We have considered in a way far from exhaustive

some of the problems which specially interest the student

of desert ecology, but which in their broader relations

are not confined within geographical limits. In the ef-

forts now being directed towards their solution the

trend, as it appears to the writer, is not so much away

from any previous form of thought or method as towards

the wise and persistent use of every means that promises

results. Progress is certainly being made in the direc-

tion of greater exactness; we are learning something of

the possibilities of well-directed cooperation; and in

these and other ways in which ‘‘science returns to the

obvious’’—to use the apt words of Francis Darwin—is

an encouraging promise for the future.

PRESENT PROBLEMS IN PLANT ECOLOGY

V. Tue RELATION oF THE Ciimatic Factors TO

VEGETATION

PROFESSOR EDGAR N. TRANSEAU

Eastern ILLINOIS STATE NORMAL SCHOOL

1. The Recent Advance in Point of View.— Perhaps

the most interesting and important advance that has been

made during the last decade in the study of the relation

of plants to environment is in regard to the point of view.

It is difficult to say just when the movement began, but

it is assuredly true that it has only recently gained recog-

nition. To a certain extent the movement has involved

the substitution of the ecological for the floristice method

in geographic problems involving climate. It has re-

sulted in a general dissatisfaction with the older descrip-

tive methods and has tended toward a better appreciation

of the value of exactness both in the delineation of vegeta-

tion and the quantitative analysis of environmental com-

plexes. The movement has further brought to our atten-

tion the necessity for investigating vegetation processes

by experimental methods comparable to those by which

plant processes have long been studied. As I see it,

however, these are secondary phenomena attending the

substitution of dynamic and genetic views of vegetation

for the century-old static conception of plant distribution.

Fourteen years ago it was possible for one of the most

prominent students of the North American biota to say :*

It appears, therefore, that in its broader aspects the study of the

geographie distribution of life in North America is completed. The

primary regions and their principal sub-divisions have been mapped,

the problems involved in the control of distribution have been solved,

and the laws themselves have been formulated.

1 Yearbook, U. S. Dept. Agrie., 1894, p. 214.

487

488 THE AMERICAN NATURALIST [Vou. XLII

Such a claim could have been made only for a static

system, since a genetic conception of the problem neces-

sarily involves the indefinite postponement of the ap-

proach toward a final solution.

The appearance of the classics of Warming and

Schimper served to impress all with the inherent com-

plexity of the problem. We are no longer deeply con-

cerned with the discussion as to whether temperature

or moisture is the more important geographic factor.

Neither do we hope to erect a stable system of geographic

divisions upon either of these bases. When we recall

that for North America alone not less than sixty different

proposals of geographic zones and regions have been pub-

lished during the last century, the futility of the point

of view which disregards all but one or two climatic fac-

tors and emphasizes boundary lines, must be apparent.

But we shall be still more impressed with the inadequacy

of these proposals if we attempt to relate the actual dis-

tribution of plants or plant formations to these ‘‘ regions.”’

Recently there has been a rapid increase of local ecolog-

ical studies in which the successional processes of vegeta-

tion have been emphasized. These studies have appre-

hended to a greater or less extent the dynamics of the

habitat and the plant formation. The separation of the

local vegetation into stages has assumed the dominance

in each, of a distinct complex of environmental factors.

The occurrence of distinct boundaries has neither been

assumed nor insisted upon.

Local studies, however, can not lead to general concep-

tions of vegetation unless compared and united into larger

units. This brings us to the fact that the larger units

generally recognized are transcontinental zones and re-

gions. But zones and regions are static entities. They

are developed upon assumptions wholly different from

those upon which the local studies have been founded.

Usually in zonal classification temperature is recognized :

as all-important and rainfall an unfortunate disturber a -

symmetry. Not a few are based upon phenological as-

No. 512] PRESENT PROBLEMS IN PLANT ECOLOGY 489

sumptions long since proved untenable or still awaiting

experimental evidence. In other words, the succession

of local plant formations which has consciously depended

upon changes in the concomitant action of many soil,

climatic and historical factors, is made to fit into a larger

unit whose fundamental basis is a single or at most two

climatic factors. It is to be noted further that the prob-

lem most debated in connection with zonal arrangements

is the boundary; that the term ‘‘zone’’ implies uniformity

of structure and homogeneity of composition. But the

most striking fact about the geographic distribution of

individual species is their dominance in some region and

their decline in importance and frequency as we depart

thence in any direction. Plant formations in their dis-

tribution show the same phenomenon. Further, it ap-

pears that the optimum areas of scores and hundreds of

species nearly coincide. In brief, actual plant distribu-

tion, through its lack of uniformity and homogeneity, its

tendency to concentric dispersal, and the coincidence of

the optimum areas of many species, seems to demand

larger units in harmony with the processes, structure,

composition and origin of their components. Whether

we choose to call them ‘‘centers of dispersal’’ is of small

moment, as compared with the recognition of the fact that

zones and their sub-divisions are not natural organiza-

tions of plants or plant formations. Of course, this

criticism does not refer to the use of the very convenient

expressions of certain spatial and temperature concepts,

viz., torrid, temperate and polar zones.

The unsatisfactory character of zones as a basis for

classification is felt also by students of climatology.

Especially is this true of the classification of the climatic

types prevailing on continents. The schemes of Hult

(1892-3), Koppen (1900), Supan (1903) and Herbertson

(1905) are especially interesting in this connection.”

Further, the provinces pointed out by Supan for North

2 Ward, R. DeC. ‘‘Classifieation of Climates,’’ Bull. Amer. Geog. Boc.,

38: 401-412, 465-477, 1906.

490 THE AMERICAN NATURALIST [Vot. XLIII

America show a remarkable coincidence with the natural

vegetation centers. If future work both on climate and

plant distribution should bring these fundamentally dif-

ferent view-points into essential agreement we should

have the possibility of a completely dynamic and genetic

system of vegetation and climatic units.

2. Sources of Error in Applying Climatic Data.—One

of the sources of confusion in the use of the climatological

data supplied by the Weather Bureau, in connection with

vegetation studies, lies in the placement of the instrument

shelter. The data derived recently by means of recording

instruments placed in various topographic situations,

show such great comparative variations, that the applica-

bility of meteorological records made under the condi-

tions represented by some of the weather stations may

be called into question. Fortunately descriptions of the

climatological stations of the United States are now

available? and selection of stations which truly represent

the conditions of at least one local habitat may be made.

A second source of error in the comparison with vegeta-

tion of climatic data as represented on charts is the fact

that the means do not always represent actual local con-

ditions, but may have been corrected for altitude above

sea level. Such corrections, however, have not been made,

except in the case of the barometric pressure maps, in the

recent climatological bulletin of the Weather Bureau.

3. Recording Instruments for the Measurement of the

Climatic Factors.—The increasing number of those who

are attempting to secure by means of recording instru-

ments, habitat data regarding temperature, relative hu-

midity, ete., is the most hopeful sign of progress in the

solution of the climatic problems of plant distribution.

We now have fairly satisfactory recording instruments —

for temperature, humidity, rainfall and sunshine. The

porous cup atmometer recently added to this list places

* Henry, A. J. ‘‘Climatology of the United States,’ Bull. Q, U. Se

Dept. Agrie., Weather Bureau, 1906.

No. 512] PRESENT PROBLEMS IN PLANT ECOLOGY 491

at our disposal a recording instrument whose importance

can not be overestimated. Because of its directly appli-

cable data, its slight cost and ease of manipulation, it may

well take precedence in comparative habitat investi-

gations.

The greatest desideratum in the way of habitat study

now seems to be an instrument for the measurement of

light values. It seems probable that the effects of the

varying light intensities and qualities in the habitat are

generally underestimated at the present time. The com-

parative studies already made with actinometers and

photometers are suggestive, but the value of the data as

indicative of relative light conditions from the standpoint

of vegetation is open to serious question. Thus far

photographic papers have been most generally used.

Aside from the high percentage of error attending the

matching with standards of the colors developed, these

papers are almost wholly affected by the most refrangible

rays of the visible spectrum. Plant functions in general

find their optima among the least refrangible rays. Ow-

ing to selective absorption, a decrease in the intensities of

one portion of the spectrum does not necessarily imply

a similar decrease throughout. The objection urged

against photographic paper also holds for the use of other

substances which develop precipitates or gas pressure

under the influence of light. Unless papers can be de-

vised which have an increased range of sensitiveness and

which can be used in.connection with color screens, the

continuance of actinometric measurements in habitats

seems almost a gratuitous pursuit.

Naturally the spectro-photometer has been suggested

for overcoming this difficulty. By means of photographie

methods, in which a diffraction grating is used for the

dispersion-piece and photographic plates of known sensi-

tivity to the various light rays, more accurate results

might be obtained. The difficulties of manipulation, how-

492 THE AMERICAN NATURALIST [Vou. XLIII

ever, seem to preclude the use of this method at the

present time.*

The method suggested by Zederbaur of using a spectro-

photometer in connection with colored prisms and a

standard lamp has been hailed by some as a solution of

this problem.®> It also involves several important sources

of error, but these may not prove to be insuperable.

This method has the great advantage over the actinom-

eter in that it takes into account light quality. With

certain modifications, some of which are suggested by

Zederbaur, this instrument may prove to be a step toward

a better means of light measurement.

4. Some Climatic Problems of V egetation.—But even if

the time is approaching when it may be possible to obtain

both qualitative and quantitative estimates of the climatic

factors related to vegetation processes, we should regard

this merely as a preliminary to more important investi-

gations.

We have as yet almost no observational or experimental

data from a modern point of view, on geographic varia-

tion as related to climate.. The reports concerning the

results of the cultivation of certain varieties of agricul-

tural and horticultural plants suggest a large field for the

application of experimental methods.

A fundamental consideration in experimentation along

this line is the use of pedigreed plants. It seems possible

that many of the discordant results obtained by physiol-

ogists may be traced to physiological races within the

species. The use of seeds from the same plant, branch,

or fruit is not sufficient caution unless the pollination has

been guarded. Where the growth of such large numbers

of plants as would be essential to an experiment in geo-

graphic variation is necessary, the results could have

little value unless the plants used had been analyzed by

*Wallace, R. J. ‘‘Studies in Sensitometry,’? Astrophysical Journal,

25: 116, 1907. |

*Zederbaur, C. ‘‘The Light Requirements of Forest Trees and i

Methods of Measuring Light.’? English translation. Forestry Quarterly,

6: 254, 1908.

No. 512] PRESENT PROBLEMS IN PLANT ECOLOGY 493

scientific plant-breeding methods and been shown to con-

sist of an elementary species or variety. Too much in-

sistence can not be placed on this point. The use of

homogeneous material is an indispensable prerequisite.

If the experiments are to contribute to the better under-

standing of the greater vegetation units the experiment

stations will need to be critically located.

Probably the most promising field for experimentation

at the present time is the investigation of the processes

of vegetation. There are so many vague notions and

dogmatic statements regarding the processes of competi-

tion, migration, adjustment, ete., in relation to the cli-

matic factors, that the rewards for pioneer work will be

ample. Here again the methods and materials must be

carefully considered. In certain of these problems pedi-

greed (or better perhaps standardized) plants will give

far more definite conclusions than those whose composi-

tion is unknown. In others, the more nearly we approach

actual habitat conditions and investigate actual habitat

processes, the more useful will be the results.

Experiments thus guarded may lead not only to a better

understanding of vegetation, but they will also contribute

to the science of evolution. If the methods used will bear

inspection both from the standpoint of the process of

heredity and from the processes of vegetation, natural

selection and adaptation may be resolved into processes

of more definite meaning.

The recognition of the importance of the results of

ecological investigations in the practice of agriculture,

horticulture and forestry has added much to their in-

trinsic interest. Some of the problems are perhaps be-

yond the reach of the individual worker. Fortunately

there are several institutions in the United States within

whose scope these problems lie. That they have already

begun the publication of contributions to this field is the

best evidence that both the larger and the smaller prob-

lems of the climatic relations of vegetation will be more

adequately studied in the near future. :

NOTES AND LITERATURE

- RECENT EXPERIMENTS ON THE INHERITANCE OF

COAT COLORS IN MICE

The domesticated varieties of rodents, rabbits, guinea-pigs,

rats and mice, have furnished exceptionally favorable material

for analyzing the facts of Mendelian inheritance. The simple

formule that at first sufficed to explain the results have become

more complex as the work has progressed until, at present, the

situation has become not a little intricate owing to the different

interpretations that the facts have received. This complication

is, however, paralleled by progress in the study of plants, fowls,

pigeons, sheep, swine, beetles, moths, snails, ete. Despite the

elaboration that Mendel’s originally simple law has undergone, ~

it is significant how little there is in later discoveries that is

believed to be incompatible in principle with this law, which may

seem to vindicate itself in every direction where new facts come

to light. This is nowhere better illustrated than in the latest

facts and newest theories relating to inheritance of color in mice.

The earlier work of Allen, Darbishire, Davenport and Cuénot

has given the relative order of dominance of the colors. These

stand yellow (Y), gray (G), black (B), chocolate (Ch) and

white (W). Each color is dominant to all that follow it in the

order given and recessive to all that precede. Cuénot’s results

with white mice—albinos—showed that albinos stand in a class

by themselves. White mice may carry latent! the factor for

producing any color, although so long as white mice are mated,

they produce only white. Cuénot’s suggestion has been widely

adopted, namely, that two factors are essential to produce any

color ; one of these is common to all colors and is called the color

producer (C), the other is specific for each special color (Y, G,

B or Ch). When C is absent, no color can arise, although the

other factor, the determinant, may be present; hence white mice

are characterized by the absence of the color producer (C)

*The term ‘‘ latent ’’ has come to have another significance in recent

work. In general it now means the presence of one factor only when two

are necessary for the development of a charact: ;

494

No. 512] NOTES AND LITERATURE 495

although they carry one or more of the color determiners. In

fact no white mice are known in which all determiners are

absent, and from the nature of the case none could arise. An

example may make this clearer. It is assumed that white mice

first arose by the loss of the factor ©. Suppose this occurred in

a gray mouse, CG. It would then contain only the factor G and

no C. For convenience the absence of C is represented by the

letter A. It might appear that nothing—no symbol—would

better represent this condition, but in practise it is convenient to-

indicate the absence of C; or in other words, to represent the

paired character (nasini here) of C. A, therefore, is the

allelomorph of C, i. e., C and A form a pair of contrasted charac-

ters. An example will again make this evident. A gray mouse-

CG crossed with an albino mouse AG, produces a colored mouse

with the formula, CGAG. In the germ cells of this mouse the

A and g which give, as possible com-

binations, CG and AG. If we suppose two such mice, male and

“female, are paired, the possible unions of their germ cells may

be represented thus:

contrasted characters are

AG CG

AGAG AGCG

A GCG CG

1AGAG; 2AGCG; 10GCG

The first term is a pure albino (extracted recessive) ; the second,

a gray mouse carrying white recessive (a dominant recessive or

heterozygote) ; the third term, a pure gray (extracted domi-

nant). If the A’s were omitted in the formule the outcome

would be the same, but its presence is useful in arranging the

contrasted characters in the germ cells; for, C always has A or

C as its allelomorph, never G (or any other determiner). Hence

the advantage of the symbol A. Failure to arrange the pairs

of allelomorphs properly will give results incompatible with the

theory.

In another graphic way the utility of representing an absent

factor by some symbol can readily be shown. Suppose the

characters are carried by certain material bodies in the egg—

a purely preformation conception that dominates (or is latent

in) all recent Mendelian speculation. If the color determiner is:

496 THE AMERICAN NATURALIST (Vou. XLII

carried by one body and the color producer’ by a different one,

the pairs of allelomorphs will be œ Gi every gray mouse carries

these two pairs which separate at some time in the germ cells so

that each germ cell (egg or sperm) carries one of each, C, G.

Now an albino must arise by failure of a germ cell to contain C,

the germ cell is simply 0 (zero) G, but since the same body that

carried C may still be present (only one of its characters, namely

C, being absent) the presence of that body is represented by A.

et us now work out the case a step further. If this germ

cell, AG, combines in fertilization with another germ cell, CG,

of another individual, the resulting individual will be CGAG.

The allelomorph pairs will be $. z If such a mouse again

pairs with a gray one, only gray mice will result. In time,

however, enough mice of the formule CGAG will arise so that

two such may meet; then and only then will an albino mouse

appear amongst the gray offspring. Thus the conditions that

produce the albino must arise two or more generations before

the actual albino mouse is discovered.

This example shows, on the theory, how sports of this kind

(recessive) that appear in nature are due to conditions that

arise in the germ cells of an individual several generations

earlier. The only possibility, on the theory, that such recessive

sports could appear at once would be when several individuals

changed in the same direction at the same time. Then the possi-

bility of two germ cells of the same kind meeting would be

realized. Recognizing the rarity of the appearance of sports,

one may hesitate to assume that two such forms appear at the —

same time and pair with each other.

This view is based on the assumption that sports arise by the

dropping out of one character in a germ cell. If the absent

characters arise in some other way, after the germ cells have met

for example, the situation is different, but the assumptions here

made are in conformity with present-day development of Men-

delian inheritance.

Our case was selected, however, not to illustrate how recessive

sports arise and later appear, but to show how absent factors

may be represented by bodies that in hybridizing become the

partners of bodies containing that factor. Hence the sorpi

advantage of representing such absent factors by a d

No. 512] NOTES AND LITERATURE 497

symbol standing for imaginary bodies; for such bodies, on this

assumption, may earry other characters that remain, even though

one be lost, and these other characters would still be subject to

Mendelian rules and be associated with the absence of a character.

In the earlier work on mice and other forms the different

colors, Y, G, B, Ch, W, are represented as allelomorphie pairs.

Thus Y pairs with G, or G with B, or Y with Ch, ete. It follows,

that if these color determiners are carried by definite bodies,

these must always be the same kind of body or homologous

bodies; otherwise they would not stand in this relation to each

other. Thus a gray mouse paired with a chocolate would give a

gray mouse, GCh whose germ cells would give the pair gh’ Two

such mice paired would give:

G Ch

G G G Ch

GCh ChCh

1GG, 2G Ch, 1Ch Ch

Similarly for every other combination. As a matter of fact

gray by chocolate gives not only gray and chocolate but some

black mice in the second generation. The formule fail to

explain this result. Bateson, who was one of the first to point

this out, was led therefore to a new formulation of the facts, and

Cuénot to still another. Their views will be given later.

Another difficulty in connection with the inheritance of yel-

low was soon discovered by Cuénot. Yellow mice bred to yellow

give not only yellow, but other colors as well. This would occur,

of course, if the yellows were heterozygous. Thus YG by YCh

would give yellows (YY, YG, YCh) and grays (CG). Some of

the yellows should be YY, and two such paired should give =a

yellows. Cuénot was unable to produce such pure yellows.

therefore adopted a special explanation (selective kiiin)

for this case. His view will come up again later.

A third complication arose in the case of dilute colors. In

certain experiments, that need not be given here in detail,

Cuénot found that the only assumption that would account for

the facts was that two other factors—a strengthening or enfore-

ing character (foncé) F, and a weakening or diluting factor

498 THE AMERICAN NATURALIST [Vou. XLIII

(dilué) D. The presence of F changes chocolate to black, the

presence of D (in the absence of F) changes black to chocolate,

and chocolate to dilute chocolate (or silver fawn).

n certain races of colored mice, the eyes are pink (absence of

pigment) as in albinos. The presence of the factor that pro-

duces this condition has an effect on the coat color, according

to Cuénot, hence he introduces a further set of factors that affect

the color. By means of these several factors the inheritance in

complex cases was explained.

It has been pointed out that in all gray rodents the color gray

is due to a banded or barred condition of each hair. Each hair,

in fact, contains bands of yellow, black and chocolate, arranged

in definite sequence and in definite regions of limited extent.

Hence gray is not a color in the sense that yellow or black or

chocolate are colors, but is made up of all three. It is their ar-

rangement that is the chief agent in producing gray animals.

For this reason Castle has introduced a further factor, a barring

or ticking factor instead of a gray factor. Hence gray is no

longer allelomorphic to the other colors, but these colors are

characterized by the absence of the barring factor and by the

presence of one (or more) of the other colors.

Finally the hairs of black mice are known to contain chocolate

pigment, so that black is not strictly allelomorphic to chocolate,

although crossed with chocolate the Mendelian ratio for black

and chocolate appears.

These and other discoveries show that the first representation

of the pairs of characters will no longer suffice to account for

the conditions that exist, although they give the Mendelian

expectation for the cases first studied. We may next proceed

to examine in more detail the hypotheses advanced to meet the

more complex situation.

Bateson and his co-workers have discovered certain cases of

inheritance which have led them to assume that in crosses the

allelomorph of a given character is the absence of that char-

acter. For mice the following symbols are used:

se... nooo Gray or agouti

CR: aa a‘ Blac

Coa ei ee Cinnamon agouti

Co n Chocolate

No. 512] NOTES AND LITERATURE 499

So long as gray is bred to gray each character has its like for

its allelomorph ; C E È But each germ cell will contain

only one C, one G, one B. Similarly for any other color bred to

its like.

If gray (CGB) is bred to chocolate (Cgb) the resulting mouse

has the composition CGBCgb. The allelomorphs are Si of p

These hybrids bred together give the results shown in the next

table. The possible germ cells of each will be CGB, CGb, CgB,

Cgb, which by combination give the results here shown: 12

grays, 3 blacks, 1 chocolate.

CGB CGB B CGB

CGB CGb CgB Cgb

gray gray gray gray

CGb CGb CGb b

CGB CGb CgB Cgb

gray gray gray gray

CgB CgB CgB B

iB CGb Cg g

gray gray black black

Cgb Cgb Cgb Cgb

B b CgB Cgb

gray gray black chocolate

Thus the black mice that appear in this cross in the second

generation are due to the absence of G and to the presence of

the factor B. The single chocolate amongst the 16 mice is due

to the absence of both G and B in the presence of C. Hence,

Miss Durham recognizes chocolate (Ch) and color factor (C)

as the same. Cuénot accounts for the results as follows. The

gray mouse has the strengthening factor F along with C and G.

The chocolate mouse has the diluting factor D along with C and

Ch. The combination gives FCGDCh. The pairs are p» 5 j A

Omitting C, present in all combinations, we find the possible

combinations are FG, FCh, DG, DCh. Two such mice crossed

give the kinds of offspring shown in table on page 500.

The results are 9 gray, 3 dilute gray, 3 black, 1 chocolate, and

these are the actual numbers realized. The dilute grays are

grays without black and are known as cinnamon agoutis. When-

ever F occurs with Ch the combination gives black, whenever D

occurs alone with Ch (once) the result is chocolate.

500 THE AMERICAN NATURALIST [Vou. XLII

FG FG FG co ee

FG FCh | DCh

gray gray gray | gray

FCh FCh FCh | FCh

FG FCh

gray black gray black

DG DG DG | DG

FG FCh DG DCh

gray gray gray | gray

DCh h DCh DCh

FG | DG ). Dek

gray black | gray chocolate

Both hypotheses account for the numerical outcome. Some

other criterion must decide between them. The criterion is

found in the recent work of Miss Florence M. Durham who has

pointed out that chocolate can not be dilute black, since a dilute

form of black is known, which is quite different from chocolate.”

Let us examine her results.

Black and chocolate are found either in a dense condition

when the mouse is called black or chocolate, or in a dilute state,

i. e., with the pigment granules scattered. Dilute black is blue

and dilute chocolate is silver fawn in the ‘‘ fancy.” Black

dominates blue and chocolate dominates silver fawn on the older

terminology. But it is known that black mice often contain

chocolate whose presence is obscured by the darker color, black.

This relation Bateson calls epistatic. In the same sense black is

epistatie to blue; and chocolate is epistatie to silver fawn.

Black crossed with blue gives black only. Such heterozygous

blacks inbred give 3 blacks to 1 blue. Similarly chocolate

crossed with silver fawn gives chocolate. These inbred give 3

chocolate to 1 silver fawn.

The most interesting result reported by Durham, is seen when

black, i. e., blue, is crossed with chocolate. The result is black,

because the chocolate supplies the strengthening factor and makes

the dilute black dense black which is epistatie to chocolate.* In

*There may be two quite distinct meanings however attached to

t‘ dilute.’? Cuénot means the black pigment is changed to chocolate pig-

ment. Durham means that the black pigment granules are sparse 1 in the

dilute form. See next footnote.

? This experiment n that Durham’s interpretation of the dilute

color is correct; Cuénot’s is incompatible with the experiment, unless the

SPA for Durkan’ s p colors is different from the diluting factor of

Cuéno

No. 512] NOTES AND LITERATURE 501

the second generation such black mice give approximately

9 black, 3 blue, 3 chocolate, 1 silver fawn,

which is the Mendelian expectation.

When blues are mated to silver fawns the offspring are all

blue. These inbred give three blues to 1 silver fawn.

Miss Durham’s hypothesis gives a consistent account of the

relation of the dense and dilute colors to each other.

The dilute colors are modified to some extent, as Cuénot first

showed, by the condition of the eye color. Most mice with

colored coats have black eyes. The black eye is due to black

pigment in most cases, but in chocolates and in some yellows

the dark eye is due to chocolate pigment, as Castle and Durham

have independently found. A silver fawn with pink eyes may

be of a different color from a silver fawn with dark eyes. How

this modification results is not yet known. In fact, this relation

of dilute colors to eye color offers a promising field for further

inquiry.

An examination of the hair of dilute mice shows great differ-

ences in the amount of pigment in each hair and the color of

the animal is modified by the average number of hairs of a given

kind. <A considerable range of shades is evident. Whether

this is only a fluctuating character, or whether pure races of

different shades can be made that give Mendelian proportions,

if crossed, remains to be worked out. It is not entirely certain,

I think, that the pigment granules themselves are not only scat-

tered to varying degrees but may be even lighter or darker.

Whether this is due only to size or to another factor is not yet

own.

These dilute colors should combine with ticking to produce

different shades of gray in addition to cinnamon agouti. Some

of the grays that I have met with appear to fall under this

head.t Whether the diluting factor for black and chocolate

will act as a diluter for yellow is not known. Here we meet

with a question of great importance in further study of the

colors in mice.

In addition to albinos with pink eyes, white animals with black

eyes are known to occur in many groups of animals. Such a

race of fancy mice exists. Miss Durham reports that these

white mice crossed with colored mice with uniform coats produce

‘ Thus cinnamon agouti crossed to silver fawn may produce in the second

generation a pinkish agouti with light chocolate in place of dense chocolate..

502 THE AMERICAN NATURALIST [Vou. XLIII

in the first generation some spotted mice. This result I have

also repeatedly obtained. It remains to be discovered what

relation exists between the white of such mice and the white of

common spotted mice, for in these the spotting disappears in

the first generation. It appears that the white mice with black

eyes are derived from spotted mice in which the spotting has

been carried so far that pigment remains in the eyes alone. If

these mice are only extremes of the spotted conditions the results

seem to indicate that a recessive character has been changed

to a partially dominant one. Perhaps one might say that

physiologically it has become stronger. On the other hand, these

black-eyed white mice may have arisen not from extremes of

ordinary spotted mice but from a different relation between

black and white. It is interesting, however, to note that in rats

the recessive spotted coat also partially dominates in the first

generation.

Cuénot has shown that ordinary spotted mice behave towards

mice with uniform coats as a simple recessive, appearing in the

second generation as 1 to 3. But I have found in practise that

it is almost impossible to give an exact classification of the mice

in the F, generation. In some individuals there may be only

a small white tip to the tail, or only a few hairs may be white.

Whether to classify such mice as dominant or recessive is largely

arbitrary. White hairs not infrequently appear in mice that

seem to be uniform in color. I find them quite abundant in

wild black rats (Mus rattus). In man they appear in old age,

and in horses when the skin is injured, ete. These considera-

tions raise the question whether the problem may not after all

be physiological, the result being due to the activity of the cells

rather than to the absence of factors in the sense in which that

term is ordinarily used in Mendelian hypotheses. If so, the

entire result may be one of physiological activity rather than

one of presence and absence of factors in a morphological sense.

The inheritance of the yellow color in mice has been a stand-

ing puzzle. Cuénot attempted to explain the facts on the as-

sumption that a yellow bearing sperm can not fertilize an egg

bearing this color, but ean fertilize any other sort of egg. In

other words selective fertilization takes place. Hence every

yellow individual contains latent another color; it is yellow be-

cause yellow ‘* dominates ’’ (?) the other colors. But if selective _

fertilization can take place in regard to.the individual characters

No. 512] NOTES AND LITERATURE 503

carried by the germ we introduce a conception entirely foreign

to the whole Mendelian scheme. There is no evidence of selec-

tive fertilization in this sense known elsewhere and it seems a

very questionable advantage to introduce the factor into the

Mendelian process. The evidence that Cuénot brought forward

in a second paper to show that selective fertilization takes place

is open to criticism. He points out that since half the eggs

can not be fertilized by half the sperm, there should be fewer

young born when yellow is crossed with yellow than when yellow

is crossed with any other color. His data show in fact a lower

birth rate for yellow by yellow than when yellow is fertilized

by other colors. Two objections to this argument may be ad-

vanced. First we must suppose that there are sufficient sperm

present to fertilize the few eggs set free at each menstruation.

Even if a yellow egg is not fertilized by a yellow sperm it should

be fertilized by one of the other sperms. Second the fertility

of the yellow mice is in my experience lower than that of other

colors.

In order to avoid the hypothesis of selective fertilization and

accepting Cuénot’s statement that pure (homozygous) yellow

mice do not exist, I suggested tentatively that the yellow-pro-

ducing factor is not allelomorphie to the other colors, but that

the germ cells of yellow mice are represented by the symbols

Y(B), B(Y), to take a single example; in other words that

yellow and the other color, black in this case, alternately domi-

nate and recede. In this way the numerical results follow. I

went so far as to suggest, as a theoretical possibility, that a

similar mechanism might explain the alternate nature of the

germ cells in all Mendelian cases and pointed out how this

view could be tested. I have made one such test with entirely

negative results, so that I think this interpretation must be

abandoned.

An experiment that I made with yellow mice showed, how-

ever, that the yellow bearing germ cells of yellow mice do carry

other color factors than yellow, and this result, which is not

in harmony with Cuénot’s assumption for the behavior of yellow

color in the gametes, offers the possibility of a different explana-

tion. I crossed a yellow mouse with a spotted black mouse of

known ancestry—it carried black only. Some of the offspring

were yellow. Two of these inbred gave yellows, blacks, choco-

lates and albinos. Obviously the yellow bearing germ cells

504 THE AMERICAN NATURALIST [Vou. XLII

of the grandparent carried the chocolate determiner since this

was known to be absent in the black grandparent. Hence the

yellow germ cells transmit the determiners for other colors.

Cuénot has objected to this conclusion on the ground that the

chocolate grandchild was due to a diluting factor carried by the

yellow grandparent. This objection would be valid if choco-

late is the dilute form of black, but Miss Durham has shown that

the dilute form of black is not chocolate and that chocolate itself

has also a dilute form. This relation I have also seen in my

experiments. Furthermore had there been a diluting factor in

my original yellow, of which there is no evidence, I should have

obtained blues and silver fawns in some of see PESE that

were inbred for some time but this is not the ¢

It is probable therefore that the yellow aai is spew the allelo-

morph of the other colors but may be transmitted along with

them. Its allelomorph would be in Bateson’s sense the absence

of yellow. Even this assumption fails however to show why pure

yellows do not appear, and we must look still further for an

explanation of the behavior of yellow in inheritance.

Castle has made some important suggestions that bear on this

question. The gray coat of rabbits is due, according to his

analysis to at least five distinct unit characters represented in

the formula

A—C—B—E

C is the color producer; A is the factor for ticking; B stands

for black; U for uniform (i. e., not spotted) distribution of

color; I is the intensifier or Scale Steg and E a factor that ~

governs the extension of black over the body. For a black

rabbit the same formula holds with A left out. For a’ yellow

rabbit E is replaced by R, a factor that stands for the absence

of black. A sooty yellow rabbit is like the last with A absent.

It will be noticed that there is no factor in these formule for

yellow, because yellow is assumed to be present in all these

rabbits, but since it has never been lost its claim to be looked

upon as a unit character is not established. Castle believes that

yellow is always present if C is present. Yellow rabbits there

fore differ from gray, as stated above in the absence of E (not

No. 512] NOTES AND LITERATURE 505

of B, black) by which is meant that black is prevented from

developing except in the eyes and the skin of the extremities.

How far further analysis will justify these conclusions is uncer-

tain, but the interest of the hypothesis lies in the character

of the attempted analysis, for the composition of races of dif-

ferent colors is no longer explained as the result of a single

color determiner but as the outcome of a considerable number

of such determiners. The more recent speculations in Mendelian

inheritance show a strong tendency to follow this direction. It

might be said that color depends on the absence of certain deter-

miners rather than on the presence of a special one.

It does not appear that Castle’s scheme for rabbits will apply

to mice unless amended, for the relation of yellow to the other

colors appears to be different, and there is no evidence to show

that it is present in black or in chocolate."

The most recent attempt to account for the heredity of yellow

in mice is that of Hagerdoorn.. He points out that there are

several kinds of yellow mice, a conclusion familiar to every one

that has bred the animals for certain individuals give only cer-

tain other colors than yellow in the offspring. I have examples:

of this in my own experiments. Moreover, one can determine

what those other colors may be by crossing yellows with other

colors and breeding together the yellow offspring. Hagerdoorn

also assumes that, in some yellows at least, an inhibiting factor

must be present. This point may seem not improbable® from

the fact that two yellows may produce in addition to yellows,

grays and blacks or chocolates. Since the parents carried the

factors for these colors and since they did not appear their

absence may be attributed to suppression. So far little excep-

tion can be taken to the view since it is in harmony with certain

facts. But it is further assumed that the barring factor that

determines the distribution of the pigments on the individual

hairs is ‘‘ composed of two factors, one of which is the modifying

factor present in the ‘dominant’ strain of yellow rodents. Its

action, we see, is a partial inhibiting of the two darker pigments

whenever these are present with it in one zygote.’ I therefore

propose the name of ‘inhibiting factor’ for it.” The other

5 The grounds for this statement are given later in the case of mice.

* Unless yellow is formed by combination.

™ As shown by the absence of black or chocolate in the yellow band of

the hair.—T. H. M.

506 THE AMERICAN NATURALIST [Vou. XLIII

component of the barring factor is called the ‘‘marking factor.”

If the marking factor is present and not the barring, the mouse

would be black. A black mouse therefore contains a yellow

band but this can not be seen because the black and chocolate

pigments obscure it. If this is correct one would expect to

extract from a black mouse the yellow pigment by a solvent for

yellow. I shall give below the evidence that negatives this

Hagerdoorn also thinks that yellow may be due in some

eases to the absence of all pigments but yellow. In such a case

either the marking or the inhibiting factor may also be present

without its presence being noticeable. The following six classes

of yellow mice are recognized:

(a) Present black, chocolate and yellow plus inhibiting factor.

(b) Present chocolate and yellow plus inhibiting factor.

(d) Present yellow plus inhibiting factor.

(e) Present yellow plus marking factor.

(f) Present yellow.

Hagerdoorn states that he has ‘‘proof’’ of the existence of

five of these six groups. Group (ce) alone has not yet been

recognized. Moreover he obtained homozygous individuals of

each of these groups. Homozygous individuals of the same group

bred to each other produce pure yellow strains, that is, strains

that never produce any other color than yellow. The reason

that Cuénot and others never obtained pure yellow is due to the

fact that they crossed yellows of different strains and under

such circumstances mice of other colors will appear. In passing,

however, it should be noted that in Hagerdoorn’s classification

of yellows if individuals of strains (a), (b), (d) and (f) were

crossed only yellows should appear in the first and in all subse-

quent generations. Thus the chance of getting pure yellows

is as four to two, and it does not seem probable with so much

in favor of hitting upon these combinations that such strains

would not have been obtained by Cuénot or Durham, who have

studied the problem extensively.

Hagerdoorn’s evidence in favor of his classification of yellow

is obtained by crossing yellows, not with each other, but with

mice of other colors or with albinos of known (?) composition.

The pairings are too complicated to discuss here in detail and in

the absence of numerical data, to show how often the results

No. 512] NOTES AND LITERATURE 507

cited occurred it would not be profitable to attempt to go further

into the,matter. One example alone of extreme importance may

be cited. One yellow male mated to chocolate gave only choco-

late young; the same male mated to black gave only black young.

If the number of young is large enough to establish the case con-

clusively it is a distinct advance in our study of yellow mice.

Hagerdoorn assumes that this yellow male contains yellow alone

and that neither the barring nor the inhibiting factor is present.

Hence the cross with black gives only black because the black

obscures the yellow in the hair. Similarly for chocolate. If

this is the correct interpretation as much yellow could be ex-

tracted from these hybrids as from a yellow mouse but this test

was not made. The only other possible conclusion would be

that not enough young were obtained to show that yellows were

not produced by this pairing. We must await the publication

of the numerical data. It should be added that the yellow male

was tested by crossing with an albino strain possessing the bar-

ring factor and only yellow young appeared. This shows the

absence of black or chocolate in the yellow, for were they present

some gray mice should have appeared according to the hypoth-

esis. Whatever discoveries the future has in store for us these

experiments are of great interest, especially in so far as they

point out a better method for studying yellows than any so far

reported. The assumption that yellow pigment is present in

black and chocolate can be readily tested. I have made such

a test and find that black hairs put into caustic potash give no

evidence of yellow to the extent that yellow exists in yellow hair

as shown by the same solvent.’ The fact that caustic potash

also extracts chocolate to some extent complicates the result.

The hypothesis seems also to call for the presence of yellow

pigment throughout the gray hair and not only in the yellow

band. It is more difficult to test this view and observation

would be of no avail since the yellow might be obseured by the

presence of black or chocolate. It is a point of no small im-

portance to remember that if an inhibiting factor combined with

a marking factor gives the barred or ticked hair of gray mice

these factors act at only a particular period in the formation

of the hair by suppressing the development of black and choco-

late, for the tip and the base of such a hair are dark. If mark-

* Whether some blacks exist without yellow is a further question not

touched by this test. | . |

508 THE AMERICAN NATURALIST [Vou. XLII

ing here and elsewhere in animals is due to factors of the sort

postulated they are controlled (?) by a periodic function of the

hair bud. We meet here with the same problem the embryol-

ogist encounters in proportionate development or interrelation

of the parts. Whether this is a dynamic function (epigenetic)

or ean be referred to a system of factors in the germ is a difficult

problem and for the future to decide.

Before leaving this question of yellow mice a few well known

facts may be stated. Yellows exist from a deep orange to a

pale lemon yellow. All intermediate gradations may be found.

Whether these are in reality a graduated series or a series of

overlapping conditions we do not yet know. The presence of

other pigments combined with yellow is also familiar to every

student of these mice. If yellow is due to an inhibiting factor

that factor must at times very imperfectly do its work of in-

hibiting. I have a race of sports of the house mouse with white

bellies, gray backs and yellow sides. The hairs on the sides

may be pure yellow, which should be due to the action of the

inhibiting factor in this particular region only, since on the rest

of the upper surface the hairs are ticked. Even in gray mice

single hairs may be yellow.

In some yellow mice the belly is pure white. This must be

due to a further factor that in this region inhibits the yellow, the

yellow itself being the result of another inhibiting factor. In

other words an inhibitor of yellow must also be postulated. It

might be assumed of course that the white belly is due to the

absence of yellow in the region, but since the mouse can produce

yellow its absence in the belly must also be accounted for by

some special assumption. Again we meet with the localization

factor—a problem that Mendelian studies have scarcely yet ap-

proached except by the purest symbolic representations.

The fact that many rodents change the color of their hair

according to age indicates that the physiological condition of

the animal is an important factor in determining its color.

the mechanism of Mendelian inheritance involves only the

shuffling of morphological determinants, as implied in many

current conceptions of the mechanism of inheritance, the changes

that take place in the same individual are difficult to under-

stand unless it be admitted that temporal and local conditions

affect the development of the determiners. Such an admission

is practically equivalent to referring the development of a color,

No. 512] NOTES AND LITERATURE 509

for example, to the extent to which physiological (chemical)

processes are carried out in an individual or part of an indi-

vidual. Inheritance from this point of view would be a physio-

logical process depending on an inherited degree of activity of

the protoplasm (subject to local modifications) rather than the

result of sorting out of morphological unities.

Since the preceding review and criticism was written an im-

portant paper by Oscar Riddle has appeared in which he takes

the same position that I have done elsewhere? in regard to the

process of Mendelian inheritance. He bases his criticisms on

some facts concerning the changes that certain melanin colors

undergo as the result of the stage of oxidation to which they are

carried. If what happens outside the body furnishes any hint

in regard to what takes place in the formation of color in animals

and plants these facts rehearsed by Riddle are of great im-

portance in relation to the inheritance of color-production. He

writes

Here is then a possible picture of the basis of Mendelian segrega-

tion and proportion, but without recourse to hypothetical “ particles ”

or to immutable and immortal factors. An apparently very specifie

end-result of an oxidation would be traceable in the germ only in the

strength or pitch of a general vital process, and not at all in mnemons

or representative particles packed with unthinkable precision, order

and potentiality into (presumably) the chromosomes. . . The nature

of present Mendelian interpretation and description inextricably com-

mits to the “doctrine of particles” in the germ and elsewhere. It

demands a “ morphological basis” in the germ for the minutest phase

(factor) of a definitive character. It is essentially a morphological

conception with but a trace of functional feature. Although heredity

is quite surely a functional process of major complexity, it may be

reealled that the primary and fundamental Mendelian conception of

this process utilizes not a single finding of the science of biochemistry,

. With an eye seeing only particles, and a speech only symbolizing

them, there is no such thing as the study of process possible. . . It

color inheritance at least—has strayed very wide of the facts; it has

put factors in the germ cells that it is now quite certainly our privilege

? See Chapter XXVII in my ‘‘ Experimental Zoology,’’ 1907, where the

before Pe American Breeders Association, Vol. V,

510 THE AMERICAN NATURALIST [Vou. XLIII

to remove; it has declared discontinuity where there is now proved

continuity; it has postulated preformation where there is now evident

epigenesis.

T. H. MORGAN.

LITERATURE CITED

Allen, G. M. Heredity of Coat Color in Mice. Proc. Am. Acad. Art and

Sci., XI, 190

panty W. E. Fifty Years of Darwinism. New York, 1909.

Castle, W. E. and Allen, G. M. The Heredity of Albinism. Proc. Am.

dad Arts and Sci., XXXVIII, 1903.

Cuénot, L. L’ Hérédité de la Pigmentation ches les Souris. Arch. de Zool.

Exp. et Gen., 1902, 1903, 1905, 1907.

D. Note on esu

Mice with European Albino Races. Biometrika, 2.

Davenport, C. B. Color Inheritance in ya Science, XIX, 1904.

Durham, F. M. A preliminary Account of the Inheritance of Coat Colors

n Mice. Reports to the rdias Committee, j ;

Hagedoorn, A. L. Inheritance of Yellow Color in Rodents. Univ. of Cali-

fornia Publications in Physiology, March, 1909

Morgan, T. H. The Assu pap Cii y of the Germ Cells in Mendelian Re-

sults. APENE XXII,

Some a in n Heredity in Mice. Science, XXVII, 1908.

———. What are ‘‘ Factors ’’ in Mendelian Explanations? American

Breeders i ay v ps 9.

Riddle, O. Our wledge of Melanin Color Formation and its Bearing on

the Mendelian Daeron of Heredity. Biol. Bull., XVI, 1909.

SOME EXPERIMENTS IN BREEDING SLUGS

Certain large naked mollusca or slugs, common in Europe, are

noted for their numerous and striking color-variations, some 0:

which seem to be correlated with climatic conditions. Little

has been known concerning the inheritance of these color-forms,

but Mr. Walter E. Collinge has recently made some experiments

in breeding two of the species, Arion ater (or empiricorum) and

A. subfuscus. The results of this work are given in the Journal

of Conchology, the short paper containing them being Mr. Col-

linge’s address as president of the Conchological Society, de-

livered October 17, 1908. As the publication is available to

few in this country, and the facts cited are very interesting, it

seems worth while to abstract part of them.

Arion ater is a very large and handsome slug, of which the

following color-varieties were used or appeared in the experi-

ments:

(1) ater, pure black. I was not quite clear about the meaning

No. 512] NOTES AND LITERATURE 511

of the expression ‘‘typical,’’ as used by Mr. Collinge, but in reply

to my question, he writes that in every case it was ‘‘the pure

black form, not nigrescens or plumbea.”

(2) castanea, a brown variety. .

(3) rufa, a red variety. The reddest forms occur on the

continent of Europe. The above three have the body uni-

colorous, though the foot fringe may vary.

4) albolateralis, with the back black and the sides white, the

two colors sharply separated. A very handsome variety, of

restricted range, especially common in Wales. Mr. Collinge

writes me that the specimens he used were found in the vicinity

of Birmingham.

(5) scharffi, like albolateralis, but the sides yellow instead of

white.

In the first experiment, castanea was paired with ater, and the

former laid 39 eggs, of which 24 were hatched and raised to

maturity. These proved to be: 12 ater (with slight variations

in foot fringe), 10 rufa, 2 castanea. From this lot, rufa was

paired with castanea, and gave 14 in the next generation, of

which four were ater, eight rufa and two castanea.

From the pairing of two of the eight rufa, fifteen slugs were

raised, eight being rufa, two ater, and five subvarieties of

castanea. (Mr. Collinge does not explicitly state eight rufa,

but in a letter he confirms this interpretation of his account.)

From the pairing of two rufa of the last generation sixteen adults

were raised, twelve being ater, two subvarieties of rufa, and two

subvarieties of castanea. Thus the experiment was carried to

F,, with results which are thoroughly Mendelian so far as the

segregation of characters goes, but difficult to explain in regard

to the appearance and proportions of the different kinds. It

will be noted that rufa was twice chosen for breeding, to the

exclusion of the other varieties, and the second time gave many

more black slugs than the first. None of the bicolored forms

appeared.

In a second experiment two albolateralis were aael hatte

a progeny of 22 slugs, 20 being ater and 2 scharff.

extraordinary that I asked Mr. Collinge particularly men ”

and he confirms the result as stated. One would expect albo-

lateralis to be homozygous, but the experiment shows that it is

either heterozygous (in which case the proportions are hard to

explain) or the results are incapable of explanation by any

512 THE AMERICAN NATURALIST [Vou. XLIII

ordinary hypothesis. I can not help suspecting that the parent

slug had really paired earlier with a specimen of ater, the

progeny in consequence not actually having the origin stated.

In that case, supposing ater to be dominant, the results would

not be so anomalous. It is not so easy to explain the results

of the first experiment by the hypothesis of previous pairing,

as in that, except for the original pair, the slugs were under

observation from their birth.

Seeking a possible explanation of the albolateralis case, I con-

sulted Dr. C. B. Davenport, who practically concurs with my

view, writing: ‘‘The result of Collinge’s mating is inexplicable

to me except upon one or the other of two hypothesis; either

that the parents were heterozygous or else, as you suggest, the

supposed parents were not the actual ones, and one had previ-

ously paired with a black slug. Of course if albolateralis is a

heterozygote, then striping is dominant as is usually the case

and uniformity recessive. Uniform black would then be active

in one quarter of the offspring, but the great proportion of pure

black speaks against this hypothesis’’ (litt., March 22, 1909).

T. D. A. COCKERELL.

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thuri *s The Apodous Holothurians, W. K.

; era—The Blue Butterflies of the

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tebrate Paleontology-The Lysorophidæ; Stegocephala ;

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pareng Work on orein <a

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An Examination of Darwin ’s “Origin o a eet in the

Light of Recent Observations and riments.

Piotemor EDWIN Lin '

The Distinction bapian saori and Heredityin —

Inbreeding. i

Breeding pel actos with Rats, Professor T. H.

MORGAN.

Shorter Articles and Discussion : The Chub and th o Texas

Horn Fly, Dr. Roy L. Moone: A New Camel from

sa wer Miocene of Ne JA

Notas and Literate Heredity—The Chondriosomes as __

ee of the. Hereditary y fae Dat F. PAYNE

ral Bed Mutations in the P

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Zoology—Cuénot on the Honey Bee, Professor T p

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THE

AMERICAN NATURALIST

VoL. XLIII September, 1909 No. 513

ON AN EARLY TERTIARY LAND-CONNECTION

BETWEEN NORTH AND SOUTH AMERICA

R. F. SCHARFF, Pu.D., B.Sc.

NATIONAL MUSEUM OF IRELAND, DUBLIN

Tmar the two great continents—North and South

America—have only become joined to one another by

land in later Tertiary times, is a widely accepted assump-

tion. Yet the various authorities who have made this

problem a subject of special investigation have not all

come to precisely the same conclusions as to the geological

age during which this union of the two continents was

brought about.

A study of the marine fishes on both sides of the isth-

mus of Central America, for example, convinced Dr.

Günther! that up to a recent geological period the latter

was only represented by a chain of islands similar to that

of the Antilles. But the number of species of fishes on

the Atlantic and Pacific coasts of Central America that

were supposed to be identical has been considerably re-

duced during more recent surveys. They no longer

amount to more than 4.3 per cent. of the total number of

fishes known to occur in both areas. Professor Jordan?

on that account maintains that the isthmus has not been

depressed during the lifetime of most of the existing

species. The submergence, he argues, must have super-

vened at a more remote time. In the belief that the

1 Günther, A. C. L. G., ‘‘Study of Fishes,’’ p. 280.

2 Jordan, D. S., ‘‘Study of Fishes,’’ Vol. I, pp. 274-280.

513

514 THE AMERICAN NATURALIST [Vou. XLII

Miocene may be taken as the date of origin of the modern

genera of marine fishes, he contends that an open com-

munication between the two oceans may have existed

during that geological period. It is important to note

that the sea currents seem at that time to have set west-

ward, thus favoring the transfer of Atlantic rather than

Pacific types across the isthmian area.

Mr. Regan? is inclined to put the date still a little

further back in urging that the marine connection between

the two oceans ceased to exist at the beginning of the

Mioeene.

An investigation of the Crustacea and their distribu-

tion led Dr. Ortmann‘ to the conclusion that at the dawn

of the Tertiary era an oceanic connection was in actual

existence between the Atlantic and the Pacifie in the a

isthmian region. This communication, he thinks, per- os

sisted until the Miocene. In the commencement of that

period the isthmus was elevated, thus joining North and

South America.

The Mexican amphibians and reptiles have been uti-

lized by Dr. Gadow® in the solution of the same interest-

ing problem with the result that he assumes the establish-

ment of land-continuity between North and South America

in either late Oligocene or early Miocene times.

The whole character of neotropical zoology, remarks

Dr. Wallace,’ whether as regards its deficiencies or its _

specialties, points to a long continuance of isolation of —

South America from the rest of the world, with a very

few distant periods of union with the northern continent. —

Geologists have discussed this subject mostly from a

paleontological evidence. Professor Gregory’ clearly se

demonstrated that the idea of an interoceanic connection

as late as the Pleistocene period, as suggested by Dr. r

Spencer, could no longer be entertained. In arr k a

Regan, C. T., ‘Fishes of Central America,’’ p.

* Ortmann, A. E, ‘‘ Geographical Distribution of Doan p. 359.

* Gadow, H., ‘Mexican Amphibians and Reptiles,’’ p. 236.

Wallace, A. R., ‘‘ Distribution of Animals,’’ Vol. IL, p. 80.

1 Gregory, J. W., , ‘‘Palæontology of the West Indies,’’ p. 305.

"a Spencer, J. W., ‘‘ Reconstruction of an Antillean Continent,”? 1 p-

No.513] EARLY TERTIARY LAND-CONNECTION 515

at a final decision as to the approximate date of orgin

of the Central American land bridge, he was mainly

influenced by Professor Scott’s reference to the occurrence

of Caryoderma a supposed glyptodont edentate in the

Miocene Loup-Fork deposits. He urged, therefore, that

the waterway across Central America was in all likelihood

finally closed in the lower Miocene or possibly even in the

upper Oligocene. As Caryoderma, however, is now be-

lieved to be a reptile and not an edentate, this argument

no longer holds good.

Less definite are the results obtained by Dr. Hill’ after

a careful study of the rocks near the Isthmus of Panama.

The only geological periods, he thinks, since the Mesozoic

era, during which the Pacific and Atlantic Oceans could

have been in communication with one another, would be

the Eocene or Oligocene. It is important to note that Dr.

Hill’s conclusions were based entirely on his observa-

tions at the Isthmus of Panama. The geology of the

remainder of Central America is as yet too imperfectly

known to form the basis for similar speculations.

The most important pronouncement perhaps which has

yet been made on the subject under discussion is that by

Professor Osborn.’ His intimate knowledge of the fossil

terrestrial mammals of North America enabled him to

affirm that North and South America were joined to one

another more than once, as Wallace had suggested. The

first union occurred in Mid-Cretaceous and perhaps early

Tertiary times. Hereafter the continents separated once

more until the Pliocene period.

Dr. Smith Woodward,” Mr. Lydekker and also Pro-

fessor Depéret™ hold similar views with regard to the

more recent junction of the two continents.

The evidence on which Professor Osborn based his be-

lief in the first and much earlier land connection between

North and South America was unknown when Mr. Lydek-

‘Hill, R. T., ‘‘ Geological History of. the Isthmus of Panama,’’ p. 269.

1 Woodward, A. S., ‘‘ Palwontology,’’ p. 429.

™ Depéret, C., ‘‘Transformations of the Animal oes ’ p. 282.

516 THE AMERICAN NATURALIST [ Vou. XLII

ker!? wrote his work on the Geographical History of Mam-

mals. He was under the impression, therefore, that the

mammalian fauna of the South American region had been

totally isolated from that of North America up to about

the end of the Miocene. I shall shortly return to Pro-

fessor Osborn’s views as soon as I have completed my

brief historical review of the first problem.

Professor Lapparent!* concurs with Mr. Lydekker’s

opinion that the interchange of waters between the At-

lantic and Pacific oceans across Central America could

only have ceased to exist at quite the end of the Miocene

period.

Finally, in his treatise on the development of conti-

nents, Dr. Arldt'* maintains that the Central American

land bridge must have originated at the commencement

of the Pliocene period, and with this view I fully agree.

Part of Central America no doubt had already risen

above the ocean at a much earlier period, but in its present

outlines and extent it must be regarded as a geologically

recent development.

All those in fact who have seriously considered the

problem, either from the standpoint of a marine or a ter-

restrial zoologist or from that of a paleontologist concur

in the opinion that North and South America were sepa-

rated from one another by a marine channel or by wide

seas during part of the Teritary era. This, however, is

the oyly point in which there is a general agreement.

While some contend that the junction between the two

continents had only been effected in comparatively recent

geological times, others hold that within the life history

of the great class of mammals, either in the early Tertiary _ a i:

or late in the Secondary era, a land bridge between North

and South America had once before existed, by means of

which an interchange of the faunas could have been

brought about. It is this supposed earlier land connec

* Lydekker, R., ‘‘ Geographical History of Mammals,’’ p. 119." —

* Lapparent, A. de, ‘‘ Traité de Géologie,’’ p. 1318.

“ Arldt, Th., ‘‘ Entwicklung der Kontinente,’’ p. 597.

No.513] EARLY TERTIARY LAND-CONNECTION 517

tion and its probable nature and extent that I wish to

discuss.

Dr. Wallace already vaguely indicated that there may

have been several very distant periods of union in the

past of the Southern with the Northern continent. This

supposition received a startling confirmation by the dis-

covery first by Dr. Wortmann and then by Professor

Osborn? of true armadillo remains in the middle Eocene

beds of Wyoming. If he does not actually speak of a

direct land connection between the two continents in early

Tertiary times, Professor Osborn’ suggests as much in

his remark that this discovery ‘‘adds another fact to the

growing evidence that North and South America were

related in the Mid-Cretaceous and perhaps early Tertiary

and then separated again until the Pliocene.’? He does

not specify in any way in what manner this relationship

had been brought about. His views would be of particu-

lar interest, considering that Dr. von Ihering’s extensive

zoological and botanical researches have led him to believe

that the South American continent itself must be of com-

paratively recent geological origin.

The latter declares that South America had arisen as a

continent only since the Oligocene period. It then con-

sisted of two parts united by a narrow strip of land in the

west, which later on developed into the great mountain

chain of the Andes. These two parts, which he calls

“« Archiplata’’ and ‘‘ Archiguiana,’’ were previously sepa-

rated from one another. The first embraced Chile, Ar-

gentina, Uruguay and southern Brazil, the other the high-

land of Venezuela and Guiana. Each of these possessed,

according to Dr. von Ihering,” its own characteristic

fauna and flora and these were totally distinct from one

another.

A somewhat similar theory as to the origin of South

America, largely based on the geographical distribution

of fresh-water decapods, has been advanced by Dr. Ort-

15 Osborn, H. F., ‘An Armadillo from the Middle Eocene,’’ pp. 163-165.

1 Osborn, H. F., ‘‘ Mammalian Paleontology,’’ p. 99.

* Thering, H. von, ‘‘Archhelenis and Archinotis,’’ p. 79.

pantie es a

2 E ie eee Mala

518 THE AMERICAN NATURALIST [Vou. XLIII

mann.'* In place of the present Southern continent he

thinks that toward the end of Mesozoic times, there

existed the old Brazilian land (Archiplata), an Antillean

continent (including the West Indies and Venezuela) and

also the Chilean coast range. These three land masses

were separated from one another by wide oceans. Just

before the close of the Secondary era the Antillean conti-

nent, and with it Venezuela and even the Galapagos

Islands, became united with western North America, the

latter being then -still detached from eastern North

America. When Venezuela in early Tertiary times at

last became fused with the other larger South American

land masses, the interoceanie connection across Central

America had severed it from North America.

Under such geographical conditions the Wyoming

edentates alluded to by Professor Osborn could only have

been derived from Venezuela, it being the sole portion of =

the present Southern continent that had any relationship.

with North America in those remote times. No fact, how- A

ever, has been brought to light, either in the recent or a

fossil history of the edentates to lead us to imagine that 2

they had originated in the northern part of South

America. i

That South America owes its origin to the union of —

several independent land masses is so clearly indicated by —

the existing fauna of the continent, that a similar evidence _

should also be revealed by a study of its rocks and fossils.

The geology of South America is unfortunately as yet

little known. Yet even such a cautious observer as Pro-

fessor Suess’? ventured to suggest, on stratigraphical —

grounds, that an arm of the sea may have penetrated right >

across the continent in Cretaceous times. The are rehaic

raised above the sea, since the younger formations mee

to be superimposed with great regularity further an

further to the west of this ancient formatii l

* Ortmann, A. E., ‘‘ Geographical Distribution of Deeapods,’’ pp. 225

366. 6

* Suess, E., ‘‘ Antlitz der Erde,’’ Vol. II, p. 683.

No.513] EARLY TERTIARY LAND-CONNECTION 519

Katzer™® contends that during part of the Mesozoic era

the Pacific ocean extended eastward to the shores of this

land, whose rivers then drained westward into the ocean,

as they even continued to do until Miocene times.

While it is therefore by no means evident from the

geologist’s point of view how and when the various land

masses became joined to form the present South America,

the geographical distribution of the living fauna, together

with a study of the paleontology, has furnished most

valuable hints as to the probable geological history of the

continent.

Dr. Gill claims that the fishes are among the best indi-

cators of former geographical conditions. Turning to the

most recent studies on the South American fish fauna,

those of Professor Eigenmann,” we find that he also is

impressed by the dissimilar elements of which it is com-

posed. He explains this varied character of the fauna by

the supposition that two independent land masses, origi-

nally separated in the region of the Amazon valley, be-

came welded together in early Tertiary times.

In his attempted restoration of the geographical con-

ditions of South America during the Eocene period, Pro-

fessor de Lapparent** depicts an’ aspect contrasting with

that of other observers, and yet he recognizes a division

of South America into two parts, for he represents the

continent as being dissevered by a marine channel be-

tween the Rio Negro in Argentina and Southern Peru.

Of all the maps illustrating ancient distribution of land

and water, that of Dr. Arldt** is the most striking in origi-

nality. He connects northern South America in late

Cretaceous times by land with western Mexico, but not

by way of Central America. He assumes that the latter

was submerged at that time and that an independent land

bridge extended from southwestern North America —

through the Galapagos Islands to Colombia. This north-

» Katzer, F., ‘Geologie des Amazonengebietes,’’ p. 254.

z Eigenmann, C. H., ‘‘ Fishes of South and ee Ameren,” p. 528.

z Arldt, Th., ‘‘ Entwicklung der Kontinente’’ fae 19).

520 THE AMERICAN NATURALIST (Vou. XUME

ern complex of land was isolated from the southern part

of South America by a wide sea channel stretching right

across the continent.

His conception of an extensive land having once flour-

ished to the west of Central America, while the latter was

largely submerged, is not altogether new. In alluding to

the east-westward trend of the Antillean Cordillera and

its abrupt termination on the Pacific coast of Guatemala,

Professor Suess?t makes a suggestion as to its former

westward prolongation. Precisely at the point, he say

where the arcuate continuation of this chain might be

expected to meet the principal chains of South America,

lie the volcanic Galapagos Islands.

. Various indications in the structure of the Isthmus of

Panama moreover left the impression on Dr. Hill’s*

mind that large areas now covered by the Pacifie, to th

west of the isthmus, were once replaced by an extensive

land surface. |

Nothing more, however, can be deduced from geologi i

testimony as to the presence of any land corme No

methods will have to be employed in order to discos

manner by which the Focene armadillos reached

America. -

If we examine the whole eastern Pacific coast |

Jurassic times to the present day. One of these

part of western Mexico and Lower California, the ot

strip of the southern coast line of Chile. Itis the |

coast cordillera which Dr. Burckhardt? believed t

remaining remnant of a mighty Pacific continent,

porphyritic conglomerates of Cretaceous age are

* Suess, E., “‘Antlitz der Erde,’? Vol. II, p. 263.

* Hill, R. T., ‘‘ Geology of the Isthmus of Panama,’’ r

= Burckhardt, C., ‘‘ Traces géologiques d’un continent,”

No.513] EARLY TERTIARY LAND-CONNECTION 521

against its eastern flank, whereas still further east the

latter grade into fine-grained rocks, thus indicating that

the land from which they were derived lay westward, out

in the ocean. —

While we need not here dwell upon the theory of a

former Pacific continent?” so ably supported by Professor

Haug on purely geological grounds and by Professor

Hutton on zoogeographical data, I should like to draw

attention to some features in the geographical distribution

of animals and plants which prove that southwestern

North America and southwestern South America are inti-

mately related to one another in their fauna and flora.

This relationship can not be explained as the product of a

similarity in soil and climatic conditions. Tt is not a case

of mere convergence. It can be shown that it already

existed in the distant past, and I venture to think that this

relationship implies the presence of a former direct land

connection between these two ancient areas, when the

continent of South America was still in the making.

It was Dr. Wallace?’ who first directed attention to the

remarkable fact that many genera of insects from the

north temperate regions reappeared in temperate South

America, being generally absent in the intermediate sta-

tions. He explained this phenomenon by the supposition

that the northern forms had traveled southward during

successive glacial epochs when the mountain range of the

Isthmus of Panama might have become adapted for their

advance in that direction. Their southward passage was

believed to have been facilitated by storms and hurricanes

which carried the insects across unsuitable territories.

This interpretation of a striking feature of geo-

graphical distribution seems to have been considered

satisfactory at the time. At any rate no one has raised

any protest so far as I am aware. Yet I am not at all

disposed to admit its correctness.

* More detailed information on the theories relating to an ancient Pacific

continent will be published in my work on the geological history of the

American fauna. i

* Wallace, A. R., ‘‘ Distribution of Animals,”” Vol. II, pp. 45-47.

522 THE AMERICAN NATURALIST [ Vou. XLII

Let us take, for example, the case of Carabus, a genus

of running beetles so familiar to North American ento-

mologists. They are by no means easily transported to

great distances by gales and hurricanes as Dr. Wallace

avers, for the simple reason that these beetles can not fly.

Their wing cases are permanently soldered together, and

being generally found under clods of earth or beneath |

stones, the action of winds can have no appreciable influ- a

ence on their dispersion. They are typical inhabitants of =

the northern hemisphere, being abundant in Europe,

northern Asia and North America. A single species

occurs in western Mexico. No Carabus has ever been

taken in Central America or in the northern or middle

states of South America. Yet in Chile and spreading

into Argentina, no less than eleven species have been

observed. For a distance of about fifty degrees of lati-

tude the running beetles of the genus Carabus are quite

absent and then reappear further south in numbers.

Those entomologists, like Mr. Born,?° who have made a

special study of the Carabide, consider them eminently

fitted for the purpose of demonstrating former changes of

land and water. )

Of the northern genera of butterflies Colias, Lycena

and Argynnis, which occur in Chile, the presumption, at

any rate is admissible that they might have been trans-

ported to these far distant southern latitudes by acci-

dental or occasional means of dispersal, such as those sug- —

gested by Dr. Wallace. Yet the case of the ant Lasius, 4

northern genus, which reappears in Chile, is more difficult

of explanation on such an hypothesis. , .

We can not say of any of these invertebrates that they

are confined to western Mexico in North America, thou, n

this appears to be the most southerly point on the north-

ern continent where they occur. On the other hand the

primitive earthworm Kerria is only known from Lower

California and from the southern part of South America

in Chile and Argentina. From the latter country it seems

to have spread into Paraguay and southern Brazil. —

” Born, Paul, ‘‘Zoogeographisch-Carabologisehe Studien’? —

No.513] EARLY TERTIARY LAND-CONNECTION 523

Of particular importance is the ancient genus of land

molluscs Bulimulus. It is quite peculiar to America. Its

nearest relation appears to be the Melanesian Placostylus.

Bulimulus, which is almost characteristic of the west

coast of America, is now divided into three great groups,

one of which has its headquarters in Chile and Peru, the

second is met with on the Galapagos Islands, Central

America and the West Indies, the third is confined to

Lower California and Mexico. These three groups are

very similar in appearance, but Dr. Pilsbry% maintains

that this resemblance, which is particularly noticeable

between the Mexican and Chilean forms, is not so much

a proof of close relationship as the result of similar en-

vironment. At any rate we notice here three distinct and

discontinuous centers of radiation, two of which are situ-

ated on very ancient land surfaces, while the third mostly

occupies islands whose origin certainly dates back to

early Tertiary times.

Probably a still more ancient invertebrate is the curious

Peripatus, an archaic arthropod with an extremely dis-

continuous distribution. Three distinct groups inhabit

America. One of these is confined to southern Chile,

another seems to have spread northward along the Andes

from a Chilean center as far as Ecuador. At a distance

of twenty degrees of latitude north of this northern out-

post it reappears in western Mexico, while in Central

America lives a third and perfectly distinet group which

has spread thence to the West Indies and eastern South

America.

In its three distinet centers of distribution all along the

west coast of America it bears a certain resemblance to

the range of Bulimulus just alluded to. The range is

certainly suggestive of a very ancient and more direct

communication than obtains at present between western

Mexico and Chile. :

The flora of the new world retains far more pronounced

traces of that curious relationship between the southwest-

ern areas of its two continents. The plants of both Chile

» Pilsbry, H. A., ‘Manual of Conchology,’’ Vol. X, p. 127.

524 THE AMERICAN NATURALIST [Von XLII

and southwestern North America, moreover, are better

known than are the animals. Whatever may be the

cause, not only is there a resemblance between families

and genera in the two areas; the general similarity of —

the landscape and especially the occurrence in both of a

profusion of cactuses strikes the casual observer at once.

Many specimens of northern plants recur in identical

forms in those distant regions of South America.

Professor Asa Gray?! and Sir Joseph Hooker long ago |

directed attention to this very remarkable phenomenon.

More recently, Professor Engler’? and Professor Bray _

have emphasized this affinity and speculated on the prob-

lems connected with it. The flora of the Rocky Moun-

tains including the Sierra Nevada Mountains above the

transition zone, and the mountains far to the south of

them, though separated from one another by a stretch

Anemone, Geranium, Spiræa, Geum, Rubus, Saxifraga,

Vaccinium, Gentiana, Hieracium and others. The

greater number of forms occurring in the southern con-

Yet certain species, even of the R

alpine region, reappear in the extra-tropical An

towards the southern extremity of South America, beir

mountains as well as the tropical Andes. Among

Professor Bray mentions particularly Gentiana pro

trata, Trisetum subspicatum, Primula farinosa and

variety magellanica, Draba incana, Alopecurus alp

Saxifraga cespitosa, Polemonium microcanthum 7

Collomia gracilis. oo

The lower Sonoran elements of plant life are like

represented in the extreme south. Oxytheca dend i

Chorizanthe commissuralis and Lastarriwa chilensis

example, do not occur in the vast regions that

sta ans A., and J. Hooker, ‘‘ Vegetation d. Rocky Mountain :

” Engler, A., ‘‘ Entwicklungsgeschichte d. Florengebietes,” ” u

No. 513] EARLY TERTIARY LAND-CONNECTION 525

the two areas. A few of these plants may possibly have

been casually introduced from the one to the other. But

Professor Bray** expresses the opinion that in most cases

we have to deal with forms which were connected by a

remote ancestry, and which flourished at a time and under

conditions which permitted a more general distribution.

What these conditions were like he does not venture

to inform us, but it must be evident that this flora is much

older than the Pleistocene, during which time it has been

supposed that the climatic conditions may have favored

a southerly advance of northern forms. Specific

changes, among certain plants as well as among some

Animals, seem to proceed with extreme slowness. We

have the example of the still living redwood tree (Sequoia

sempervirens) which has persisted unchanged since

Mesozoic times, for the fossil Sequoia Langsdorfi is now

considered identical with the modern form.

It appears to me possible, therefore, that the well-

known and extremely discontinuous range of some of the

alpine plants may be interpreted by the assumption that,

like Sequoia, they are of vast antiquity and that they have

spread along a continuous mountain chain which once

extended in a direct line from southwestern North

America to western Chile, before the Andes had risen

from the floor of the ocean.

We know that a similar relationship between North

America and southern South America prevailed already

in Mid-Cretaceous times. No less than seventy-five per

cent. of the plant remains recently discovered in a Mid-

Cretaceous plant-bearing layer in Argentina are char-

acteristic types of the Dakota-group flora.

Commenting on this discovery, Mr. Berry** dwells on

the remarkable agreement of this southern flora with that

developed in Mid-Cretaceous times in western North

America. He urges that it certainly points to a com-

munity of origin. In these ancient South American de-

posits all the familiar northern genera Liriodendron, _

= Bray, W. L., ‘‘Relations of the North American Flora,’’ pp- 709-716.

* Berry, E. W., ‘‘Mid-Cretaceous Geography,” p. 510.

526 THE AMERICAN NATURALIST (Von. XLII

Liquidambar, Cinnamomum and Sassafras are met with.

Even Platanus, Populus, Quercus and others are repre-

sented. No wonder that Mr. Berryt came to the con-

clusion that a geographical connection must have existed

between North and South America during Mid-Cretace-

ous times. He thought that the plants referred to had

spread southward from the north, while Professor Os-

born favors the view that his Eocene Armadillo had ad-

vanced from the south. 3

Before concluding this short review on the avidan

pointing to an early Tertiary direct land bridge between

the southwestern portions of North and South America,

a few observations on the paleontology of Patagonia and

Chile may somewhat elucidate this interesting problem.

Edentates occur in the oldest Tertiary deposits of

Patagonia or even pre-Tertiary, if Dr. Florentino

Ameghino” is correct in assigning a Mesozoic age to the

latter. The position which this savant has taken up and

so courageously defended has been almost universally —

assailed. Professor Ameghino still holds that the now

famous fossiliferous strata of Santa Cruz, which have

yielded such a surprisingly rich harvest of mammalian

remains are of Eocene age, while the likewise terrestrial

Notostylops beds belong to the Cretaceous series.

The great majority of geologists, on the other hand,

_ are of opinion that the Santa Cruzian deposits — ee

the Miocene and the Notostylops beds to the

period.

These beds are separated by marine strata which ha

been carefully investigated by the members of the Pri <

ton Expedition to Patagonia. The invertebrates ¢

lected were described by Dr. Ortmann, who consid

them as certainly of Miocene age. He thus concurs

the opinion arrived at independently by the many emmen

paleontologists, that both the terrestrial deposits a!

alluded to, the Notostylops and Santa Cruzian beds

of Tertiary age.

Che, Flo., ‘‘ Formations sédimentaires di e Patagonie.”

ann, A. E., ‘í Princeton Expedition,’’ p. 288.

No.513] EARLY TERTIARY LAND-CONNECTION 527

To all appearances the question was finally settled when

Dr. von Ihering’ again challenged the results obtained

by Dr. Ortmann, pointing out certain discrepancies in his

determinations. Dr. von Ihering now maintains that

only 4.9 per cent. of the species from the Santa Cruz

marine beds are still living and, as the formation more-

over corresponds to those of Oamaru in New Zealand

and of eastern Australia, now generally included in the

Eocene, he feels no hesitation in placing the Patagonian

marine beds in the latter series. He, therefore, entirely

supports Dr. Fl. Ameghino’s latest views as to the

Eocene age of these strata.

If Dr. von Ihering’s conclusions are substantiated, and

his arguments appear to me convincing, the more recent

terrestrial Santa Cruzian deposit must be either of

Oligocene, or as Dr. Ameghino believes, of Upper Eocene

age.

Let us for a moment consider the geographical condi-

tions in early Tertiary times of that region of South

America in which these beds are found. The similarity

in character of the Patagonian marine fauna on the east

coast with the Tertiary of northern Chile on the west

coast of the continent implies the existence of a connec-

tion between the two oceans. This supposition is further

strengthened by the fact that eight per cent. of the eastern

or Patagonian species of marine mollusca are found in

the western Tertiary beds of Navidad in Chile.

Since a number of northern types of molluses make

their appearance in the upper divisions of the Patagonian

beds, Dr. von Ihering suggests that the supposed old land

connection between Brazil and Africa had at that time

been ruptured, thus opening a way for an invasion of the

northern fauna. I have not previously alluded to this

land bridge, Ihering’s southern Atlantis or Archhelenis,

because I am not dealing with this problem at present. :

Tt is not necessary, however, to conclude from the pres-

ence of northern molluses in the upper Patagonian marine

beds that this supposed land bridge had broken down —

= Ihering, H. von, ‘‘ Mollusques fossiles de 1’Argentine,’’ p. 95.

528 THE AMERICAN NATURALIST [Vou. XUM

completely in upper Eocene times. They could just as

well have come from the Pacific, which seems to have

freely communicated with the Atlantic across Patagonia.

Not only are these northern invaders present in the

Chilean deposits on the Pacific coast, there are many

genera in the latter according to Dr. von Ihering,’ such

as Conus, Purpura, Oliva, Cassis, Cyprea and Littorina

which never penetrated as far east as Patagonia at all.

They thus denote the manner of dispersal of all the

northern forms from north to south, and it appears as if

they had gradually crept southward along some ancient

coast line. But since there is no reason to suppose that

the present Pacific coast of South America had come into

existence already in early Tertiary times, we may assume

that the ancient coast line lay farther west.

Down to Miocene times the influence of the Caribbean

and even the European marine fauna continued to be

felt on the Pacific side of South America. Dr. Ortmann?’

tells us that the north Peruvian Miocene fauna shows

close affinities with the faunas alluded to. Several ob-

servers remarked on the circumstance that when Cen-

tral America was submerged in early Tertiary times,

the Caribbean and Atlantic species generally seemed to

be drawn towards the Pacific by a strong current. We

have noticed that the effects of this current in carrying

northern Atlantic forms are traceable in the Tertiary

deposits all along the Pacific coast of South America as

far south as northern Chile and even on the Atlantic side

of the continent in Patagonia, which then freely com-

municated by a marine channel with the Pacific.

On the other hand, the Tertiary molluses of Chile a

California are very distinct from one another. This a

parently implies that a barrier was interposed betw:

the northern coasts of California or rather between `

main portion of the Pacific coast line of North America

and that of South America. Hence it tends to supp?

my argument, that western Mexico and part of lo

*Thering, H. von, ‘‘Mollusques fossiles de 1’Argentine,”’ iz 514.

” Ortmann, A. E., ‘‘Tertiary Invertebrates of Santa Cruz,’ 7D. 320.

No.513] EARLY TERTIARY LAND-CONNECTION 529 ,

California had a direct land connection with Chile. Dr.

von Thering*® suggests that the Antillean are which is

continued to Guatemala and there abruptly terminates

on the Pacific coast may have been continued westward

in early Tertiary times in a great peninsula comprising

the Galapagos and Sandwich Islands. He applied the

term ‘‘Pacila’’ to it.

My reason for preferring to connect western Mexico

and Chile in the manner I conceived, rather than adopt

Dr. von Thering’s proposal, is that the spreading of Carib-

bean and Atlantic shallow water forms of molluscs indi-

cates a continuous shore line running north and south.

The Pacific coast of South America as it appears to-

day had not yet emerged in early Tertiary times. The

Andes were only just beginning to make their appear-

ance. They must have risen as a series of islands

parallel to the ancient coast that lay out in the west.

I picture to myself southern Chile as forming the ex-

treme apex of a long penisula extending southward from

western Mexico. Sometime during the Eocene period it

became disconnected from Patagonia. The long penin-

sula was subsequently more and more reduced in size

until only high mountains, such as the volcanic cones of

the Galapagos Islands, remained above water. The

peculiar lizards belonging to the genera Amblyrhynchus

and Conolophus inhabiting these islands have their near-

est relation in Phymaturus, which is confined to Chile,

and not as we might expect to the much less distant Peru,

Ecuador or Colombia. As long as any parts of the

peninsula remained above water and attached to Mexico,

it may have added its mammalian fauna to that of North

America.

In such a manner it may possibly have come to pass

that the northern genus of porcupine Erethizon is, ac-

cording to Professor Scott, more like the fossil Steiromys

from the Santa Cruz beds than the latter is to any of the

South American porcupines. Steiromys, as Professor

1 Ihering, H. von, ‘‘ Archhelenis und Archinotis,’” p. 318.

530 THE AMERICAN NATURALIST (Vou. XMM

Scott“ informs us, is only a little more primitive than

Erethizon, the change from the one to the other involving

but a slight modification.

Erethizon is unknown in North America from pre-

Pleistocene deposits, but there is no reason to assume

that it had not originated long before the Pleistocene

period. South American types of mammals may have

existed in western North America from early Tertiary

times onward without having left their remains in the _

more ancient deposits. =

The theory of the former existence of a great lobe of

land connecting western North America with southern

South America during the beginning of the Tertiary era,

while Central America and northern South America were _

still largely submerged is sustained by many facts in the

geographical distribution of plants and animals. It

seems to me to explain the undoubted affinities prevailing

in the two areas in a better manner than by any other |

hypothesis. Against it may be urged that it is an un-

warranted supposition to assume that existing species of ;

plants can have preserved their specific characters since

the Eocene period. Still we must not forget that one

plant at least, Sequoia sempervirens, has lived witho

any appreciable change down to the present time from $

the testimony elicited from a botanical source,

remain zoological factors of importance as buttresses €

the hypothetical bridge I have constructed.

May, 1909.

BIBLIOGRAPHY

Ameghino, Florentino. Les formations sédimentaires du Cretacé supériev

ta ge de Patagonie. Anal, Mus. Nacional de Buenos Ai

s sér.), Vol. 8, 1906.

Arldt, Th. Die Panira der Kontinente und ihrer Lebewelt, Leipzig,

1907

Berry, E. W. A Note on Mid-Cretaceous Geography.

Vol. XXIII, 1906.

Born, P. Zoogeographiseh -Carabologische Studien. Entomol. Wochenb

Vol. XXV, 1908.

“ Scott, W. H., t Mainai of Santa Cruz,’’ p. 417.

Science (N. 8)

No.513] EARLY TERTIARY LAND-CONNECTION 531

med W. L. The Relations of the North sr Flora to that of South

merica. Science (N. 8.), Vol. XII,

parker C. Traces slologigant ets ancien Continent pacifique. Revista

useo de la Plata, Vol. 10,

mgt a The Transformations = fh Animal World. (Intern. Scient.

es.) London, 1909.

Figen, C. H. The Fresh-water Fishes of South and Middle America.

Popular Science Monthly, 1906

Engler, A. Versuch einer Entwicklungsgeschichte des Extratropischen

Florengebietes. Leipzig, 1879-1882.

Gadow, H. The Distribution of preg Amphibians and Reptiles. Proc.

Zool. Society, London, Vol.

Gregory, J. W. Contribution to ple a and Physical Geology of

the West Indies. Quart. Journal Geol. Soc eagles 51, 1895

Gray, A., and J. Hooker. Die Vegetation des y Mountain Gebietes und

ein Vergleich derselben mit der anderer wasnt Engler’s Botanische

Jahrbiicher, Vol. 2, 1882.

TES AWC, DL G: An Introduction to the Study of Fishes. Edinburgh,

Hill, ti è The Galgil History of the Isthmus of Panama. Bull. Mus.

Comp. Zoology, Harvard, Vol. 28, 1898.

Ihering, H. von. Archhelenis und Archinotis. Leipzig, 1907

___——. Les mollusques fossiles du Tertiaire et du Cretaeé supérieur de

l’Argentine. Anal. Mus. Nac. Buenos Aires, Vol. 14,

Jordan, D. 8. A Guide to the Study of Fishes, Vol. I, tT 1905.

Katzer, F. Grundzüge der Geologie des unteren Amazonengebietes. Leip-

ig, 1

Lapparent, í. de. Traité de Géologie, 4° éd. Paris,

Lydekker, R. A Geographical History of Mammals. sanction 1896.

Ortmann, A. E. The Geographical Distribution of Fresh-water Decapods and

its Bearing upon Ancient Geography. Proc. Amer. Philos, Soc., Vol.

41, 1902.

————._ Tertiary Invertebrates. Report Princeton Univ. Exped. to Pata-

gonia, Vol. IV.

Osborn, H. F. An Armadillo from the Middle Eocene (Bridger) of North

America

904.

; Te en Years’ Progress in the Mammalian Paleontology of North

America. Comptes Rendus lle: Congrés intern, de Zoologie, Berne,

1904.

Pilsbry, H. A. Manual of Conchology, Vol. X, 1895-96.

Regan, C. T. Biologia Centrali-Americana. Pisces. 1906-08.

Das

Suess

Scott, W. H. Mammalia of the Santa Cruz Beds. Report Princeton Exped.

to Patagonia, Vol. V, 1903-05.

Spencer, J. W. Reconstruction of the Antillean Continent. Bull. Geol.

Soc. America, Vol. 6, 1895.

Wallace, A. R. The Geographical Distribution of Animals. Tondon. 1876.

Woodward, A. 8. Ouilinos of Vertebrate te Palæontology. Cambridge, 1898.

NOTES ON THE RELATIONS OF THE MOLLUS-

CAN FAUNA OF THE PERUVIAN ZOOLOG-

ICAL PROVINCE

DR. WILLIAM HEALEY DALL

SMITHSONIAN INSTITUTION

Havre recently summarized the faunal relations exist-

ing between the mollusca of the deep sea, off the western

coast of South America, and those of other regions,’ it

has happened that in reporting on a collection of mollusca

submitted for examination by the government of Peru, it

fell to me to compile a census of the mollusca inhabiting

the shallow waters and coasts of the region known as

the Peruvian zoological province. Such an enumeration

had not been made for something like half a century. The

much fuller knowledge of these animals now possessed

by scientific students makes the number of species belong- _

ing to this region much greater than was formerly sup-

posed, and modifies in consequence the conclusions {ors

merly arrived at.

The littoral fauna has practically nothing in common —

with that of the abysses. The relations of the two groups —

of animals to each other, to adjacent faunas, and to the -

Tertiary fauna, have recently assumed a special interest,

from the discussions by von Ihering and others as to the

routes of Tertiary migrations. -

It was thought therefore that a summary of the results

deduced from a study of this faunal list would have &

certain general interest not only for malacologists but for

the students of historical geology. a

The littoral marine mollusean faunas of the west coast :

of the two Americas, excluding the Arctie and Antarcue

faunas properly so-called, were recognized more h

* Bull. Mus. Comp. Zool., XLIII, No. 6, pp. 207-211, 1908.

532

No. 513] MOLLUSCAN FAUNA 583

half a century ago in their main outlines by Woodward.’

They comprise, beginning at the north:

1. The Oregonian Province, extending from the limit of

floating ice in Bering Sea south to Point Conception, Cal.

2. The Californian Province, ranging from Point Con-

ception south to Lower California.

3. The Panamic Province, from Lower California in-

cluding the Gulf of California, south to the Bay of Guaya-

quil, Ecuador.

4. The Peruvian Province, extending from Guayaquil

south to the vicinity of the island of Chiloë in southern

Chile.

5. The Magellanic Province, from Chiloë to the Fuegian

Archipelago, and for a short but undetermined distance

north on the Argentine coast, on the Atlantic side.

These provinces will eventually be recognized as con-

taining minor divisions, with which, on this occasion, we

are not concerned.

The distribution recognized in the term province ap-

pears to be directly dependent on the temperature of the

surface stratum of the sea, which, in its turn, is distributed

by ocean currents. In the case of the Peruvian Province

a branch of.the eastward-flowing South Pacific current

diverges from the main stream and impinges upon the

coast of South America in the vicinity of Chiloë Island.

Thence it follows the coast northward, until by the north-

westerly trend of the Peruvian shores it is diverted, in the

vicinity of Point Aguja and Cape Blanco, to the west-

ward, where it continues in the direction of the Galapagos

group of islands. This current, known as the Peruvian

or Humboldt current, throughout its entire extent main-

tains a temperature (varying with the season) of from

65° to 70° Fahrenheit. The temperature of the surface

off Aguja Point, Peru, in November, was 65° F. The

temperature of the water in the Magellanic Province in

mid-summer varies from 50° F. in the straits themselves,

to 55 °F. on the Chilean coast in the vicinity of Valdivia.

2<: Man. of the Mollusea,’’ pp. 373-377, 1856.

534 THE AMERICAN NATURALIST [Vow XEM

The surface temperatures of the Peruvian current, as

related to those of the Magellanic water, are therefore

warmer; and, as compared with the Panamic waters,

markedly colder. Precisely such a relation to the coast

of North America is held by the southerly branch of the

North Pacific current, which reaches the coast near Sitka

with a summer temperature of 65° to 68°. This has

diminished in the latitude of San Francisco Bay to 54 °F.,

but the current continues until in the vicinity of Point

Conception, California, it is diverted off shore in a man-

ner entirely analogous to the fate of the Peruvian current

at Point Aguja.

The water of the Panamic Province is less disturbed

by currents, receives the full heat of the tropical sun, and,

as shown by Professor Alexander Agassiz, emerges from

the Gulf of Panama, follows the coast toward Cape San

Lorenzo, and is there diverted off shore toward the Gala-

pagos Islands. Trees from the mainland with leaves —

still adhering to them are occasionally cast upon the

shores of the Galapagos, as observed by Professor Agas-

siz; showing clearly that the current is not only present

ak has no inconsiderable motion. The temperature ot

this water near the coast of Ecuador and only a few miles-

from the limit of the Peruvian current, in November,

varied from 70° to 83° F., and in March and April from

78° to 85° F. Among the Galapagos Islands the range in

April was 81° to 83°

It will be noticed herótom that the currents fully

account for the peculiarities of the Galapagos mollusk

fauna, which exhibits large contributions from the Pan-

amic and Peruvian faunas with only a very unimportan’

tincture of the Indo Pacific in its make-up.

ber at right angles to the Peruvian current off Point

Aguja, by the U. S. S. Albatross, began with a tempera-

ture of 65° F. close in shore, rose quickly to 69° and | Me

to 70° in the middle of the current, and declined +

69° F. on its western edge. :

No. 513] MOLLUSCAN FAUNA 535

The first exploration of the molluscan fauna of the

Peruvian Province which was systematically carried on,

was that of Hugh Cuming. He was resident for some

years at Valparaiso, later dredged and collected vigor-

ously at various points of the Bay of Guayaquil. Tradi-

tion has handed down the account that a severe earth-

quake (referred to by Darwin in the Voyage of the

Beagle) laid bare a long stretch of coast where the shore

mollusks, elevated above their natural situs, were accessi-

ble to the collector by the thousand. Mr. Cuming collected

largely, and on his return to England these collections

gave an opportunity to the systematic naturalists to de-

scribe many new Peruvian and Chilian shells. This lasted

for a good many years. Broderip, Sowerby, Swainson,

Gaskoin, Powys, Deshayes and Reeve worked on these

collections during the first half of the nineteenth century.

According to Woodward? Mr. Cuming’s collection em-

braced 222 species from the coast of Peru, south of Paita,

and 172 species from the coast then politically included

in Chile. Of these probably half were common to the

northern and southern portions of the province. A little

later the explorations of Humboldt and Bonpland added

a few species; the majority of their collection, it would

seem, was not worked up.

M. Aleide D’Orbigny’s South American investigations

seem to have been, so far as this province is concerned,

largely restricted to the Chilean portion of it. He col-

lected 160 species, one half of which were common to

Chile and Peru, while only one species was common to-

Callao and Paita. The inference naturally drawn from

this last fact by Woodward and others was that the north-

ern border of the province lay between those two ports.

But this conclusion was due to imperfect knowledge, and

is completely refuted by later information. At present

more than 200 species are known to be common to Paita

and Callao.

D’Orbigny’s report with its atlas of fine illustrations

* Manual, p. 376. :

536 THE AMERICAN NATURALIST [Vou. XLII

is a classic source for information, relating, however, to

South America as a whole rather than to the Peruvian

Province.

Collections made by Gay and others, worked up in

his monographie Historia de Chile, by Hupé, form the

third large and well-illustrated contribution to the mala- — a

cology of the province, chiefly restricted of course to the

southern or Chilean portion.

The last important contributor to a knowledge of this

fauna in these earlier days was the German naturalist

Philippi, who added numerous species and useful illus-

trations in the Zeitschrift fiir Malakozodlogie, his ‘‘ Ab- |

bildungen,’’ and his ‘‘ Atacama Reise.’’

Of course many minor contributors to the work, suchas

Lesson, Jonas, etc., might be mentioned, but I propose in

this hasty sketch to touch only on the most important.

The list of Tschudi’s collection, ostensibly from Pern, as

described by Troschel unfortunately contains numerous

exotic Indo Pacific and Panamic species, so that its au-

thority is seriously impaired. More recently the re-

searches of Ludwig Plate, the Princess of Bavaria and

others, have added essentially to our knowledge.

In considering the distribution of species along the coast

of the province it should not be forgotten that the collec-

tions have not been made with equal thoroughness on

different parts of the coast. The ports of Guayaquil,

Paita, Callao and Valparaiso have naturally been much 2

more thoroughly explored than any of the rest, and the -

careful collecting which would obtain the smaller species —

is not recorded to have been done at all, anywhere. :

Dredging also is practicable with difficulty, except in

the sheltered harbors which occur so rarely on this coast, —

or by the aid of a large steamer which could be had only

under Government auspices on account of the great ex-

pense involved. 2

The small lots of material derived from the mud which |

came up on the anchor of the Albatross at one or two

points, show that proper exploration will certainly reveal :

No. 513] MOLLUSCAN FAUNA 537

the presence of many small species new or extralimital

which are at present unknown. In determining what

species should be included in the list I have depended

somewhat upon the known characteristics, as regards dis-

tribution, of the groups to which the species belong. For

instance, if I found a species reported from Guayaquil

and belonging to a widely distributed group such as the

Pholadidex, though not actually reported from a Peruvian

loeality, I have not hesitated to include it, knowing that in

all probability it will be found on more thorough search

in Peruvian territory. There can be little doubt that a

large number of the more mobile of the Panamic species

reaching the Bay of Guayaquil will be found to have ex-

tended their range more or less within the northern bor-

der of the Peruvian Province; just as a certain number

of the characteristic Magellanic species have traveled

beyond their strict limits and mingle with the southern

members of the Peruvian fauna. Species properly be-

longing to the Panamie Province and not reported as far

south as Guayaquil or the Galapagos Islands, have been

omitted from the list.

It will be observed that the list contains only a few

minute shells. Doubtless these exist, and will be found

when carefully sought for, but, as previously indicated,

the majority of collectors seem to have confined their

attention to the more conspicuous species.

I have included a certain number of pelagic forms,

cephalopods, pteropods and nudibranchs, which are not

strictly littoral, but are found occasionally thrown on the

beaches or are captured within a short distance of the

shore.

In any first census of this kind, some species will be

included which later investigation will exclude. I have

rejected a number of Tschudi’s species as obviously ex-

otic, but a small number remain which are doubtful, and

which are indicated as needing confirmation. I have also

omitted a few names which seemed to be almost certainly

due to misidentification or to a confusion —— such

Bae... THE AMERICAN NATURALIST (Vou. XU

localities as Arica and Africa. ‘‘ Lumping ”’ closely re-

lated species, such as some of the Siphonarias, has led

certain authors to include purely Atlantic forms with

their Pacific analogues under one name. So far as time,

and the access to specimens, permitted I have tried to

disentangle such cases and use only the name definitely

belonging to the Pacific form. In making her dredgings

the U. S. Fish Commission steamer Albatross seems to

have avoided shallow water; and in the case of Dentalium,

which has a wide range in depth, I have included a few

species actually dredged beyond the 100 fathom line, but

which will in all probability be found within it when

sought for. No other deep-water species, however, has

been admitted. An account of them will be found in my ~

Albatross Report of 1908. In scanning the list those

unfamiliar with the repetition of names so prevalent in

Spanish geographical nomenclature will need to remem-

ber that there is a Tumbes in Chile as well as in Peru,

and be on the look out for analogous cases. Species of

Auriculide which are exclusively littoral, although pul-

monate, have been included, also the salt-water Cyrenas,

my aim being to include all species which are to be found

along the shores of the province on the beaches and in the

adjacent waters of the sea. Whatever deductions from

the list may be necessary hereafter, I am convinced that

they will be more than made up for by future additions

from the ranks of the minuter species. ie

It is probable, though not by any means certain, that

when we eliminate the overflow from the Panamie and

Magellanic Provinces, the remaining fauna on this long-

stretch of coast may be susceptible of division into sub-

faunas, but it is too early to speculate about this possible j

feature of the distribution. e

I have indicated in the preceding remark, the nature

of the reservations which must be made in discussing the

statistics of our present census of the Peruvian Fawna,

and subject to those reservations we may now proceed t

consider the figures. xe

No. 513] MOLLUSCAN FAUNA 539

The total number of species appears to be 869, of which

64 are pelagic and may be omitted from consideration in

the matter of distribution, leaving 805. Taking the pres-

ent political limits of the two countries as a starting

point, we find seventy-one species reported from Peru

exclusively, and one hundred and three restricted to Chile.

But, as political and biologic boundaries rarely have any-

thing in common, these data are not especially significant.

We have 174 species restricted to Peru or Chile and 141

common to Peru and Chile, making 315 species proper to

the Province itself. In addition to these we have 253

species common to the Panamie Province and to Peru,

and 239 species of the Panamie Province which are known

to reach the northern border of the Peruvian Province at

or near Cape Blanco, many of which will doubtless be

found to have a more extended southerly range. In addi-

tion to these there are 25 species whose range extends

from Upper California south to Peru or even to Val-

paraiso.

At the southern extreme of the Peruvian Province it

receives 41 recruits from the Magellanic Province, few of

which range north of Valparaiso. Of the whole 805

species enumerated which are not pelagic, only 24 are

known from the West Indies or Atlantic Ocean, most of

which are Pholads, borers, or limpets; forms peculiarly

liable to transportation long distances on ships or floating

timber. The only species which can be regarded as also

Indo-Pacific, are even fewer in number and to be included

in the same category.

Eliminating all the pelagic species and all the Panamic

species not shown to be now actually domiciled within the

limits of the Peruvian Province, we have a population for

and province of 566 species of littoral marine mollusks.

In Bulletin 84, of the U. S. Geological Survey, pages

25-28, 1892, I have shown that the average population

for a warm temperate area (when the temperature ranges

from 60° to 70° F.) is about 500 species of shell-bearing

mollusks. Adding the species of nudibranchs, naked

540 THE AMERICAN NATURALIST (Vor. XLI

tectibranchs and littoral cephalopods enumerated in our

list, it would seem that the average is pretty well main-

tained in the case of the Peruvian Province.

Dismissing the minuter species from consideration as

insufficiently known, the more striking characteristics of —

the Peruvian fauna may be summed up as follows:

1. There is an unusual proportion of the species which

are black or blackish or of a lurid tint. This feature of

the fauna has attracted attention from all who have

studied it, and has been discussed by von Martens. It is

particularly marked among the zoophagous groups.

2. The fauna is notable for its Fissurellide and Ac-

mide, its trochids of the genus Tegula, its numerous and

peculiar chitons, its numerous cancellarias, the develop-

ment of Calyptræidæ, of species of Arcide and of Thais, —

Chione, Semele, Petricola, Mulinia, all represented by

numerous species.

3. The deficiencies in the fauna are as marked as the

redundancies. There are notably few pectens or Lucinas, —

and the Tellinide are poorly represented. Acteon, the

smaller tectibranchs, Conus, the Turritide especially, the —

Marginellide, Fusinus and its allies, Epitonium (Scala)

and the Pyramidellide are all very poorly represented. 5

Calliostoma and Margarita, Haliotis and Pleurotomaria Es

aré absent or barely represented. -

The notion that the mournful colors of so many of the

species might be correlated with the huge beds of kelp

characteristic of these shores, seems to be negatived

the fact that in California similar kelp-beds afford a shel-

ter to some of the most brightly colored Trochide, ete.,

and that, as I am informed by Mr. Coker, red and green

Seaweeds are abundant on the rocks below low-water

mark, on a large part of the coast of Peru, and presum-

ably also of Chile. This and a number of other problems

await the investigators of the future.

Lastly, a survey of the characteristic groups of which

the fauna is largely made up leads to the conclusion thai

the fauna is chiefly of southern origin. In spite of the

No. 513] MOLLUSCAN FAUNA | 541

fact that many species are common to the Panamic fauna

and a relatively small number to the Magellanic fauna,

the more conspicuous types, like the blackish species of

Tegula, have a Magellanic rather than a tropical charac-

ter. This particular group has extended its range to

Alaska on the north, and Japan on the northwest, but its

metropolis is in southern Chile. The type represented by

the various species of Thais and Acanthina has traveled

the same road, and so has the Protothaca group of

Veneride.

If we may accept as the original metropolis of a special

type of mollusk that region where it is developed in the

greatest number and variety of species and perhaps also

with the most extreme limits of size and ornamentation,

we shall have for example Buccinum and Chrysodomus

focused in the boreal Pacific region; certain types of

Thais and Acanthina in the region of southern Chile.

Cook has called attention to the relation between Thais

lapillus and the Oregonian T. lamellosa, and other spe-

cies in the tropics of the Panamic and Antillean region;

but viewed from an eastern Pacific standpoint the rela-

tively few Atlantic forms may easily have originated in

the Pacific where their existing representatives show a

much more luxuriant development. There is only one

Thais of the nucella type in the north Atlantic, but the

north Pacific has five or six. It is very remarkable that

in the Peruvian Province we have not a single distinctively

old-world type of Mollusk. Those which seem to be such

are really cosmopolitan types more familiar to us from

old-world localities, perhaps, but not necessarily of old-

world origin.

REMARKABLE DEVELOPMENT OF STAR i

FISHES ON THE NORTHWEST AMERICAN

COAST; HYBRIDISM; MULTIPLICITY OF

RAYS; TERATOLOGY; PROBLEMS IN EVO-

LUTION; GEOGRAPHICAL DISTRIBUTION

PROFESSOR A. E. VERRILL

YALE UNIVERSITY

No other part of the world, of similar extent, so far as

known, has so many species of shallow water and littoral :

starfishes as the coasts of Alaska and British Columbia,

including Puget Sound. Many of the species range from

an Francisco to the Aleutian Islands, but the most

favored region is from Puget Sound to southern Alaska. ;

The forms known to me, including those from arctic

Alaska, are about eighty species, besides fifteen named

varieties. No doubt special physical conditions there

have favored the remarkable development of this group,

as well as certain other groups, on that coast.

The entire region has a very broken coast line, innu-

merable islands, bays, fiords and straits, giving a :

extent of sheltered coast line, bathed in pure sea-water

and swept by strong tidal currents, all of which are y

forms, like the starfishes, most of which feed pee

on mollusks.

These favorable conditions are notably shown by

great abundance of individuals as well as species, 2

also by the great size that many of the species attain. At

least eight of the species of Asterias and al pecon

there over two feet in diameter.?

t Among other groups havi ing a similar remarkable development on

coast are the Polyplacophora (Chitons), limpets,

annelids (Sabellidæ), ete.

* Among these very large species are Asterias columbiana Ver., 4 oie

schelii (St.) var. rudis V., A. forcipulata Ver., Pisaster ochraceus

542 :

No. 513] STAR-FISHES 543

Perhaps the relative uniformity of the temperature

during the entire year is one of the most important

factors in determining, or permitting, the great abundance

of life on this coast, just as it is in the deep sea. Although

the water is cold, it is not subject to great extremes of

heat and cold, like those of the eastern coast of North

America. The rapid tidal currents have a powerful effect

in preventing extremes of temperature, by constantly

mixing the deeper water with the shallow.

But the nature of the starfish fauna and that of other

groups, like the chitons, forces us to conclude that similar

favorable conditions have existed on that coast con-

tinuously for several geological periods, and that no great

extermination of marine life occurred there, even during

the glacial period.

A number of the genera and higher groups are peculiar

to that coast; others have there a remarkable development

in number and variety of species, showing that their evo-

lution must have gone along continuously for vast periods

of time. In many cases primitive and highly specialized

species of a family are associated. Therefore, that coast

offers unusually favorable conditions for studying the

evolution of the genera and species, having there their

chief development. We should naturally expect to find

still surviving there, representatives of some of the com-

paratively early or primitive species, associated with

those of more modern origin, of the same groups. Such

appears to be the actual condition in many instances.

However, the complete elucidation of these questions

will require a large amount of careful investigation and

very extensive collections.®

P. giganteus (St.), P. Lutkeni (St.), P. papulosus Ver., Pycnopodia hel

anthoides St. Also Asterias acanthostoma sp. nov., allied to Troschelii,

but with long proximal adambulacral spines; dorsal spines small, acute,

reticulated; proximally in transverse combs; rays very long.

3 The collections that I have personally studied are large, but not always

as complete as desirable. They are from the Canada Geological Survey,

the Provincial Museum of British Columbia, Washington ta pete

Yale University Museum, U. S. National Museum, Harrima

pedition and others.

544 THE AMERICAN NATURALIST (No. XLII

HysripIsM

One difficulty in these studies arises from the fact that

certain of the species, usually very distinct, seem to hy-

bridize in localities where their ranges overlap and the _

breeding seasons are coincident. Owing to the small vari-

ations in temperature the breeding season of most species

is probably unusually prolonged, and this affords better

opportunities for hybridization. Among such apparent

hybrids, I will mention particularly those between As-

terias epichlora, a small, usually six-rayed, diplacanthid

species, and Pisaster ochraceus (fig. 7), a large, coarse, a

five-rayed, monacanthid species. The latter ranges from

San Diego, Cal., to middle Alaska, and is one of the most

abundant littoral species. The former ranges from Puget

Sound to the Aleutian Islands. At Sitka and adjacent

regions, on rocky shores, it is one of the very abundant

littoral species. Although normally six-rayed, five-rayed

Specimens are common. It is one of those species that

have the habit of carrying the eggs and young attached in —

clusters around the mouth. ae

From Sitka, Wrangel, etc., I have had a considerable

number of specimens that appear to be true hybrids be-

tween these two very diverse species. They generally —

have the small size and form of epichlora, but some have

the reticulated and nodular arrangement of the dorsal

spines of ochraceus. And what is still more striking,

several of them, looking like true epichlora, have more or

less of the huge, sessile, dentate, dermal pedicellarie (fig.

7) characteristic of ochraceus and the other species |

Pisaster. a

I have named six marked varieties of epichlora, which

do not seem to depend on hybridization; or at least a

could not satisfy myself of it. But those that I consider

hybrids do not conform toany of the determinatevarieties.

However, it is easy to understand that if hybrids occur,

as I believe they do, between A. epichlora and A. hexachs,

which are much more closely allied and also occur C

monly together, it would not be easy to determine th

f 3

‘a

ef.

No. 513] STAR-FISHES 545

fact. The same would be true in the case of hybrids be-

tween either of the latter and A. Troschelii, another com-

monly associated species at Sitka, ete. For although the

latter is a large, five-rayed species, with long rays, when

young it often closely resembles some varieties of epi-

chlora. Therefore it is not very unlikely that some of the

so-called varieties of the latter may also be hybrids.

More extensive collections with minute comparisons can

alone determine such questions.

The number of species of starfishes on that coast of the

family Asteriidæ (usually referred to the genus Asterias),

known to me is forty, with twelve named varieties. With

so many species, many of them with overlapping ranges,

numerous hybrids are likely to occur. The same remarks

would, most likely, apply to certain groups of mollusks,

annelids, ete., in which large numbers of species occur

together.

Mouripuicrry or Rays

So far as known to me, no other region can be compared

with the northwest coast, in respect to multiplicity of

rays. It is particularly noticeable in the Asteriide, a

family that is generally five-rayed in all other parts of the

world, though there are many exceptions.*

On the northeast coast of America there are only two

exceptions: Asterias polaris, with six rays (Labrador and

northward), and Stephanasterias albula, with six to nine

rays, and autotomous; (from New England northward).

Of the forty northwest American species of Asterias and

Pisaster, twelve, or thirty per cent., have normally six

rays.

Besides these, the remarkable related genus, Pycnopo-

dia, is peculiar to that coast. Its single species, P. heli-

*It is also noteworthy that the genus Heliaster with several species,

having from twenty-four to fifty or more rays, is peculiar to the Pacific

coast of America (Lower California to Peru). The record of one species

from Hawaiian waters is probably an error.

5 Among these are Pisaster giganteus (St. ), A. polythela Ver., A. hez--

actis (St.), A. equalis (St.), A. epichlora (Br.), A. polaris var. acervata

(St.), A. macropora Ver., L Katherinæ Gray, A. dubia Ver. = A.

Katherina Per., non Gray.

546 THE AMERICAN NATURALIST [Vow. XLIII

a b

Fic. 1.—Arbacia equituberculata; a, normal form; b, quadriradial specimen.

anthoides, which ranges from California to middle Alaska

(Yakutat, ete.), has, when adult, twenty to twenty-four

rays. It begins life as a five-rayed or six-rayed star, but

acquires new rays, by budding in new rays, a pair at a

time, symmetrically and side by side in succession.’ This

process is not known to occur in any other starfish, except

in Labidiaster, which is an Antarctic genus of the family

Brisingide. Several peculiar Antarctic starfishes seem

to be allied to north Pacific forms.

But even those species of Asterias, etc., that are ordina-

rily five-rayed, occur not very rarely with six rays, and

the six-rayed species may occur with five rays (see note, |

teratology). In other families the same peculiarity 18

‘See Professor W. E. Ritter and G. R. Crocker (Proc. Washington

Acad. Sci., Vol. II, pp. 247-274, 1900), who give a good account of es

process. I have observed many examples like theirs, but have also studied

some in which there were five primary rays, and a few in which some new

rays were produced, also, at irregular places, but this is unusual.

‘TI have recently collected many specimens of the very common

New England species, A. Forbesii, near New Haven, Conn., which mr

rays and six rays, and some that have seven, eight and even nine rays,

examining many thousands. About 1 in 2,000 has six rays; 1 m per

3,000 is four-rayed; 1 in about 10,000 is seven- or eight-rayed, at a ae

and place. Some of those with more than six rays may be due to comp

repairs of injuries received in early life, with development of aee at

(See H. I. King, ‘‘Regeneration in Asterias vulgaris’? Arch. Entwis

most of the four-rayed and six-rayed instances.

five rayed

No. 513] STAR-FISHES 547

noticeable. Thus the peculiar genus Pteraster, which

carries its young in a dorsal marsupial pouch, is found all

around the world, rather sparingly, and with one excep-

tion® all the known species have until now, been five-

rayed. The very young, taken from the pouch, agree in

number of rays with the mother. On the northwest coast

six shallow-water species are known, besides an addi-

tional allied genus.® One of these (P. octaster Ver.) has

eight rays; another six rays.

Of Solaster, five shallow-water species are known. Of

these, one (S. constellatus Ver.) seems to have, normally,

but eight rays, an unusual number in the genus. The

others have from nine to thirteen rays, the number vary-

ing in each species.

TERATOLOGY

Besides the species that normally have an increased

number of rays, or vary indefinitely, there are others

which have, more or less rarely, a smaller or larger num-

ber, as monstrosities. I propose to mention here a few

such cases. Various other monstrous variations occur

somewhat frequently, such as forked rays, supernumerary

rays arising from the dorsal surface, ete. But these will

mostly be discussed elsewhere.

The common large Asterina miniata, which ranges from

south of San Francisco, Cal., to middle Alaska, becomes

175 mm. in diameter. It is normally five-rayed, but I

have studied more than a dozen six-rayed specimens (fig.

2), which are regular and normal in all other respects;

some are of full size; most of the large six-rayed ones

were collected at Ocean Grove, Ore., by Professor W. R.

Coe. In the same lot was one four-rayed specimen, 135

mm. in diameter. It is a little irregular, the greater part

of one ray having been reproduced, but not to full size.

s Pteraster (Heraster), obscurus (Per.) == Temnaster heractis Ver.,

has normally six rays (rarely seven). It is from Newfoundland Banks and

Aretie ocean. Two other shallow water species occur on the New England

coast, both five-rayed.

* This genus Pterasterides Ver. nov. is proposed for P. aporus Ludwig.

It is peculiar in having no dorsal gong nae, hs oregcheromaigas

ee T l membrane.

548 THE AMERICAN NATURALIST [Vov. XLIII

Dermasterias imbricata is a common five-rayed or pen-

tagonal species, but we have one regular, six-rayed, young

specimen from Sitka. The majority of our specimens

have numerous large bivalve and trivalve pedicellarie in

rows, below, and smaller ones dorsally, though most

writers describe it as destitute of pedicellariz. A regular

six-rayed Henricia leviuscula from Alaska occurred, and

also a six-rayed H. sanguinolenta var. pectinata from

Bering Sea.

Solaster Stimpsoni Ver. — Crossaster vancouverensis

De Loriol, 1897. One specimen of this species from

British Columbia has one of the rays forked below, near

the mouth, thus producing ten regular rays as seen from

Fig, 3.

Fig, 2.

Fic. 2.—Asterina miniata; 6-rayed example, reduced.

Fig. 3.—Ctenodiscus cristatus; a, normal, underside; b, 4-rayed.

above; the forking affects the ambulacral groove and jaw,

the corresponding jaw being nearly abortive. The num-

ber of rays varies from nine to eleven.

Pisaster ochraceus (Br.). One medium-sized specimen

from Monterey and a large one from British Columbia

have six regular rays.

Asterias (Leptasterias) hexactis (St.). Several five-

rayed specimens from Sitka agree with the typical six-

No. 513] STAR-FISHES 549

rayed ones in size and structural details. One from Van-

couver Island has seven regular rays.

Asterias epichlora (Brandt). Although this species

was originally described as five-rayed, its normal, or most

common condition is six-rayed (var. alaskensis Ver., var.

nov.), with a more or less evident median dorsal row of

small capitate spines, and numerous smaller capitate

spines forming a reticulated pattern over the back.’® One

specimen from Victoria has seven rays, due to the forking

of one ray about at the middle; another is regularly eight-

rayed. The five-rayed form is, perhaps, rather too fre-

quent to be classified under Teratology, but in the several

collections of epichlora examined by me, at least 90 per

cent. of the specimens were six-rayed. The young, carried

by six-rayed adults, were all six-rayed.

Ctenodiscus crispatus. Of this abundant species I have

from New England a considerable number of regular four-

rayed specimens. The few west coast specimens are five-

rayed (fig. 3, a, b).

SIGNIFICANCE OF RADIAL VARIATION; A PROBLEM IN

EvoLUTION

When we consider the geological antiquity and remark-

able persistence of the five-rayed condition™ in echino-

derms, generally, it seems remarkable that so many

genera and species of existing starfishes should have ac-

quired the peculiarity of having higher numbers.

All the classes of echinoderms, except perhaps holo-

thurians, had attained highly organized and specialized

conditions even in the Ordivician period. With the ex-

ception of certain cystidians and a few true crinoids, the _

* Whiteaves, De Loriol (1897) and others have incorrectly identified A.

Troschelii as this species. The five-rayed form is apparently the same as

A. sadnichensis De Loriol, described and figured in 1897, Mem. Soc. Phys.

Geneva, Vol. XXXII, No. IX, p. 23, pl. ii (xvii), figs. 3-5

“ The case is analogous to that of gastropods, which in primordial times

acquired the habit of forming right- -handed spiral shells, which has pre-

modern

families and genera that are normally left-handed, and some species that ; r .

are as often left-handed as right-handed (Achatinella sp.). No good

reason is known why the left-handed condition is not as good ss the other. = : ‘

550 THE AMERICAN NATURALIST [Vou. XLIII

numerous known Silurian species of crinoids, starfishes,

ophiurans and echinoids were regularly five-rayed.

From the Devonian, several genera of starfishes with

multiple rays are known. They have the aspect of Cross-

aster, Labidiaster and Cronaster. But their real affini-

ties are doubtful. Those found in the Mesozoic and Ter-

tiary times, with rare exceptions, are five-rayed.

At the present time all echinoids and holothurians are

normally five-rayed. Instances of monstrous specimens

with four rays or six rays are very rare in these large and

universally distributed groups.'?

The modern ecrinoids only rarely depart from the

five-rayed condition, even as monstrosities. The ophiu-

rans show more variation in this respect. The common

genus Ophiactis, varies, when young, from six-rayed to

eight-rayed in nearly all of its species. But such species

are usually autotomous, and when adult become regularly

either five-rayed or six-rayed.

Ophiocoma pumila, at Bermuda, is about as often regu-

larly six-rayed as five-rayed. Ophioglypha hexactis of

Kerguelen Island is regularly six-rayed.

I have observed a large, regular, four-rayed example of

Ophiomusium Lymani from deep water off the New Eng-

land coast, but it was selected from thousands of five-

rayed ones. Other radial variations in ophiurans are

known to me, but they are not common, although the

species are very numerous and many are often taken in

vast numbers. :

Among living starfishes radial variations are far more

“In the Museum of Yale University there is a full grown, regularly

four-rayed example of the sea-urchin, Arbacia ewquituberculata (Fig. 1, b),

from the Azores. So far as known to me this is the only known instance

in that common species.

Bell (Jour. Linn. Soc. London, Vol. XV, p. 126, pl. v, 1880) described

a quadriradiate specimen of a sea-urchin, Amblypneustes formosa, but it

was not ag regularly developed.

Stewart, op. cit., p. 130, described a specimen of A. griseus with six

oo but that, also, was somewhat irregularly developed.

Philippi (Arch. fiir Naturg., 1837, III, p. 241, pl. v) deseribed a

quadriradiate Echinus melo, which was also a little irregular. A few other —

cases are known among echinoids. Ž

No. 513] STAR-FISHES 551

common than in either of the other classes, as already in-

dicated. But why this is so is a perplexing problem in

evolution.

No doubt there are some advantages in the five-rayed

condition, or else it would not have remained so constant

through all the geologic ages. But it is equally certain

that it is more advantageous for certain starfishes, in

their special environments, to have six or more rays,

otherwise they would not have retained this condition.

We must conclude that all these variations originated, at

first, as ‘‘ sports,’’ which have persisted by heredity and

natural selection, because they were advantageous. It is

easy to conjecture that, in the case of two starfishes, simi-

lar in size and structure, living together on a rocky shore

and exposed to violent surf, the one with six rays would

be able to cling more securely to the rocks than the one

with five rays. Therefore, because of the increased num-

ber of ambulacral sucker-feet it might well be the form

preserved by natural selection, unless for some other im-

portant but unknown reason, the five-rayed condition has

certain other more important advantages.

It is certainly true that most of the species with mul-

tiple rays live among rocks in situations exposed to the

surf.12 This is true of the various shallow water and

littoral species of Solaster and Crossaster, which usually

have nine to thirteen rays (rarely eight or less). Itis also

true of the several species of Heliaster with very numer-

ous rays, and many other such species, as well as the

numerous five-rayed and six-rayed species of Asterias

and Pisaster. ;

But the power of effectually clinging to rocks may be

perfected in other ways, involving an increased number of

sucker-feet. This is often attained by lengthening the

rays, as in many species of Asterias; by crowding the

suckers into more than four rows, as in Pyenopodia and

some large species of Pisaster; and by increasing the size

and strength of the suckers. os

1 The family Brisingide, however, is confined to deep water. All the

species are multirayed, with long rays.

552 THE AMERICAN NATURALIST (Vou. XLIIT

These same adaptations would also be useful in ena-

bling the creatures to securely hold their prey, especially

while, at the same time, holding fast to the rocks.

I am inclined to believe that the increase of rays has

been due more to the advantages gained in holding the

food securely than for holding to the rocks, though both

go together. The starfishes are the most predacious of

the echinoderms. Although they feed largely on gastro-

pods and bivalve mollusks, they also feed on each other,

and on large holothurians, echini, and other relatively

large creatures.

However, we must admit that, so far as now known, the

five-rayed and six-rayed individuals of a species appear

to be equally well nourished and grow to equal size.

Also that the normally six-rayed species of Asterias are

no larger, nor more robust, than the allied five-rayed

species, in the same environment. Even the four-rayed

individuals, including the four-rayed sea-urchin (Arba-

cia), mentioned above, appear to be well fed’ and of

average size.

Some, at least, of the many-rayed Brisingide use their

slender rays for clinging to the deep-sea Gorgonians. 1

have observed that the Odinia americana Ver. thus clings

to the branches of Paragorgia arborea with its twenty

long rays. In such cases numerous rays would be ad-

vantageous.

It must be borne in mind that the variation in the

number of rays is necessarily attended by extensive

changes in the number, size and form of all the skeletal

plates; also in the number of ambulacral feet and water

tubes, nerve ganglions, nerve cords, stomach lobes, he-

patic glands and all other internal organs. A six-rayed

specimen has twelve reproductive glands, instead of the

ten in its five-rayed competitor. If the number of ovules

be proportionately large, it would produce twenty per

cent. more young. So, likewise, it would have an addi-

tional stomach-lobe and two more hepatic glands. This

would, perhaps, be of considerable advantage in the diges-

tion of food and cause more rapid growth. We know that —

No. 513] STAR-FISHES 553

there is great variation in the size of different individuals

of young starfishes of equal age, of the same species, de-

pendent on temperature and relative abundance of food.

But I know of no experiments or observations to connect

this with the number of congenital rays.

DISTRIBUTION

A number of Arctic species occur in Bering Sea and

as far south as the Aleutian Islands, or somewhat farther.

Most of these are circumpolar, as Crossaster papposus,

Solaster endeca, Henricia sanguinolenta, Ctenodiscus

crispatus, daiira polaris, Asterias hyperborea (=A

arctica Murd.), A. græenlandica— A. cribraria St. and

others.

Some Arctic species are peculiar to the north Pacific

side, so far as known, as Pterasterides aporus (Ludwig),

Tosia arctica Ver., Asterias polythela Ver., Allasterias

rathbuni Verrill, Pteraster octaster Ver.'* and others.

But exclusive of the Arctic forms, the entire starfish

fauna of the coast, from the Aleutian Islands to San

Francisco, is peculiar to that coast, so far as I can de-

termine, and is rather sharply limited, both northward

and southward by temperatures only. Some species’

are closely related to North Atlantic ones, and evidently

represent divergent groups derived from a common stock,

at no very remote period. However, the cases of greatest

interest are those of generic types peculiar to the fauna,

some of which have no near allies elsewhere. Among

such genera I may mention here a few examples: Pycono-

podia, with no near allies; Acantharchaster Ver., a very

isolated genus; Dermasterias, with a single species; Gly-

phaster Ver. (type Leptychaster anomalus Fisher), with

* These last four species are described in the Amer. Jour. Science, July,

1909, with others from the same coast.

“Among these are Hippasteria spinosa Ver., closely related to H.

phrygiana; Leptychaster millespina Vers closely related to L. arctica. It

differs in having smaller dorsal pa with fewer spinules, more trans- —

versely elongated supero-marginal plates; much finer and more numerous

adambulacral apie four or five in the furrow series. Mediaster equalis

St., related to M. bairdii V.; Luidia foliata Gr., allied to L. aes oe

Aretie forms o

Borie of these were evidently p P from

554 THE AMERICAN NATURALIST [Vou. XLII

3. 5.—Henricia tumida Ver. sp. nov.

Fic. 6.—H. spatulifera sp. ; ad, adambulacral spines; m, marginals;

ab, abactinal pseudopaxille# ; much enlarge

Fic. 7.—Large unguiculate and denticulate dorsal pedicellarie of Pisaster

ochraceus; b, c, separated valves.

one species (G. anomalus) : and especially Pisaster, which

has there eight, large, massive species (mentioned above,

p. 542). I am unable to refer with certainty any of the

species described as Asterias, from other regions, to this

group, as restricted, unless it be the six-rayed species, A.

Perriert Smith, from Kerguelen I. This agrees with

it closely. It is monacanthid and has large dentate pedi-

cellariæ.

Cosmasterias sulcifera (Per.) Sla., from southern

South America, is also pretty nearly allied to Pisaster,

but is diplacanthid and has few dorsal major pedicellariæ,

which are not particularly large. This is the type of

Cosmasterias Sla. and it seems better to keep the latter

name for this and allied diplacanthid species. Tt is evi-

dent, however, that these Antarctic forms are the nearest

relatives of Pisaster.

Bunodaster, gen. nov., resembles Astropecten, but has

Trans. Phil. Soc., Vol. 168, p- 273, pl. xvi, figs. 2-2b, 1879.

No. 513] STAR-FISHES 555

convex abactinal pseudopaxille; triangular actinal area

of about three V-shaped rows of tesselated plates; cur-

tailed inferomarginals; numerous adambulacral spines.

Type B. Ritteri, nov. (Fig. 4), has inferomarginals with

a distal group of small spines, elsewhere finely spinulose;

furrow spines about five to a plate and eight to twelve on

actinal side; no spines on superomarginals. California

(Prof. W. G. Ritter).

The peculiar northern species, Allasterias rathbuni, is

represented on the Asiatic coast by A. versicolor (Sla. sp.

of Japan), which has alternately one and two ambulacral

spines, and by A. amurensis (Lutk.), Japan to Siberia.

Many of the other species of Asteriide are only remotely

allied to those known in other faune. This family and

the genus Asterias are world-wide in distribution, but no

other region has such a variety of forms.

The family Pterasteride is also uncommonly well de-

veloped. Seven species have been found in shallow water,

besides others in deep water. They all belong to the re-

stricted genus Pteraster, except the remarkable form, P.

aporus Ludwig, for which I have proposed the new genus

Pterasterides (see p. 547, note). It has no dorsal oseu-

lum, and the spines around the nephridial or central pore

do not reach the marsupial membrane. The Retaster,

described by Clark from Puget Sound, I refer to Pteras-

ter (P. gracilis). The P. reticulatus Ives, which ranges

from Puget Sound to middle Alaska, is a very large spe-

cies and is the most common one. P. hebes Ver. and P.

octaster Ver. are very unlike any species from other

regions.

The genus Henricia (formerly Cribrella) is also repre-

sented by numerous species and varieties. H. tumida —

Ver., from North Alaska, Cape Fox and C. Disburne,

Fig. 1, is remarkable for its large swollen disk and short,

stout rays. H. spatulifera Ver. southeast Alaska, Fig. 2,

is remarkable for its broad paddle-shaped or spatuliform

adambulacral spines which are much crowded proximally

(see figures). £

SHORTER ARTICLES AND CORRESPONDENCE

IS THERE A SELECTIVE ELIMINATION OF OVARIES

IN THE FRUITING OF THE LEGUMINOS2®?

DurInG the past few years I have had occasion to have counted

the number of ovules formed per pod in series of many thou-

sands of pods of various species of Leguminose. While engaged

at this work a side problem of considerable interest presented

itself. Since time to follow this up has not been fortheoming

for a couple of years, I will publish my data and suggestions for

the benefit of any unoccupied botanist.

It is evident that the distribution of ovules, as seen in series of

mature pods, does not necessarily represent that of the ovules in

the newly formed ovaries. It is possible that the distribution of

ovules per ovary in the flower buds may have been modified as

the fruits matured by a selective elimination of certain classes of

pods. This selective elimination might modify mean or varia-

bility or both. One such case is very probably to be found in

ovaries with but a single ovule in species normally producing

several. If the single ovule be fertilized it may develop into a

seed or not, according to various circumstances; but if it fail to

develop, the pod will, in most cases at least, fall from the plant.

Whether the same factor is at work in the case of ovule classes of

a higher order can only be determined by special investigation,

but it seems quite possible that such an influence might affect

very materially the constants of mature as compared with newly

formed ovaries.

In the spring of 1907 I attempted to get some light on this

question by the collection of material at different times from

individual red bud trees, Cercis Canadensis, growing in the

North American Tract of the Missouri Botanical Garden.

The flowers of Cercis are produced in an umbel-like cluster

from the old wood. These clusters are composed of from two to

seventeen flowers. Many of the inflorescences produce only one

to four fruits. The per cent. of flowers which mature fruits

varies widely from year to year and from tree to tree, but it is

evident that there is a very heavy elimination of ovaries. The

question to be answered is: Have the eliminated ovaries a dif-

556

No. 513] SHORTER ARTICLES AND CORRESPONDENCE 55T

ferent mean or variability, or both, for the number of ovules

which they produce than those which develop into mature fruits?

Cercis seems to be a form well adapted to an investigation of

this question. The ovaries can be quickly dissected out of the

flowers which have been dropped into aleohol for preservation.

Absolute alcohol renders the walls sufficiently clear that by the

aid of the light from a properly adjusted mirror of the dissecting

microscope the ovules may be counted very easily. Clove oil

may be used as a clearing agent, but it soon renders the ovules

as well as the walls transparent, and great watchfulness is re-

quired in the countings.

On March 28 a series of one hundred inflorescences was taken

from each of three trees and dropped into alcohol for future

study. This was at a time when most of the flowers were open,

but when none had fallen from the trees. The whole inflores-

cence was taken because (a) it was desirable to avoid any possi-

bility of an unconscious selection of flowers in gathering, and

(b) because it seemed desirable to determine whether the posi-

tion of an ovary on the inflorescence might exert any influence

upon the number of ovules produced.

On April 3 a second lot of material was collected, but in an

entirely different manner. Many of the blossoms were ready to

fall. The trees were shaken, not too violently, so as to secure the

flowers which were ready to drop, but not to dislodge those with

ovaries which might continue to develop. In preserving this

material all the flowers belonging to inflorescences which had

fallen were discarded, since it seemed possible that some of them

might have been brushed off by twigs rubbing together. All the

flowers were open, and, if their very frayed condition may be

taken as a criterion, most of them had been visited by insects.

The ovaries were dissected out of the flowers at once and dropped

into absolute alcohol. Unfortunately the second collection from

Tree II was lost.

On April 6 a third collection was made in the same manner as

the second.

My intention had been to collect the matured pods of these

trees in the fall for comparison with the ovaries. taken in earlier

stages of development, but, unfortunately, the severe frosts

which followed the early opening of spring in St. Louis, in 1907,

killed most of the Cercis fruits and preehidog the carrying oat =

of this part of the work.

558 THE AMERICAN NATURALIST [Vou. XLIII

In taking up the counting of the ovules per pod it was found

that the aleohol had rendered the material so brittle that it was

out of the question to keep the flowers in serial order from the

base of the inflorescence, and consequently all attempt at a de-

termination of this point was abandoned for the first collection.

As a matter of fact the flowers are so closely grouped in the

inflorescence of the red bud that the determination of their se-

quence would not be easy even in freshly gathered clusters. A

priori, one would suppose that in an inflorescence so shortened as

this, position on the axis would have little influence upon the

character of the ovaries. But of course this point should be

investigated, for if there is a sensible correlation between posi-

tion on the inflorescence axis and number of ovules, and between

the position of an ovary on the inflorescence and its chances of

growing into a mature fruit, this might introduce a serious

difficulty into the comparison of eliminated and matured ovaries,

in consequence of those of certain types being eliminated merely

because of their position on the inflorescence.

TABLE I

FREQUENCY OF NUMBERS OF OVULES PER OVARY IN VARIOUS

COLLECTIONS OF CERCIS

Tree. Pelt ieiet @.) 6-16 | od sls | wht ee

Lel. 3| t| 49/279 |476 |76| 4/11, 899

I.—Lot 2 | | | 2] LI 2] 8] 118] 219 | 39) 3 391

Lot 3 | | ti 28/113 |17911323] 2| 358

II.—Iot 1 | 1 |1 | 5/32/1177 | 327 | 431 |100| 4 10. 1088

Lot 3 | | 2| 58|126|112| 21; 2 1 32

1II.—Lot 1 10} 23/198 | 341 | 179| 11 14 776

I1I.—Lot 2 | 4] 8| 85/177| 68| 5 1 = 348

ILI.—Lot 3 + 2110} Shi 4701-77). 64 i 1, 348

The numbers of ovules per ovary for the several series of ma-

terial are seriated in Table I. In a very small percentage of the

cases it was impossible for one reason or another to determine

the number of ovules. These cases are placed in the ? column; —

in calculations they have not been considered, N being reduced by

their number. I have no reason to think that these ovaries are

in any way different from the others, and so they might have — :

been discarded without comment, but in material of this kind it

is best to account for every individual. Perhaps the single entry

in the 0 column is due to one of the ovaries being too young.

No. 513] SHORTER ARTICLES AND CORRESPONDENCE 559

The constants from Table I are given in Table IT.

Regarding first the means, we note that there is no constant

difference between those of the different collections. This is true

without considering the probable errors, which at once take away

any opportunity for theorizing on these points. Inspection shows

the same conclusion to be necessary concerning both absolute and

relative variabilities.

TABLE II

CONSTANTS FOR OVULES PER OVARY IN VARIOUS COLLECTIONS OF CERCIS

| Standard Devi-

Collections. Ovaries. Han mar Fae ation ona and Y A r

| Probable Error.

Tree LAoti 888 7.6531+.0172 .7631+.0122 9.9718

Tree I. Lot 2 387 7.7312+-.0276 | .8070-++.0195 10,4386

Tree J. Lot 3 356 7.6235+.0285 .7995+.0202 10.4875

Tree II. Lot 1 1077 5.3556+.0207 | 1.0091--.0146 18.8429

Tree II. Lot 3 321 5.3052--.0331 .8826+.0234 16.6375

Tree ITI. Lot 1 762 4,9041-+.0216 .8844--.0152 18.0339

Tree ITT. Lot 2 | 342 4,8830-+.0299 .8224+-.0212 16.8426

Tree III. Lot 3 | 347 4.9567 +.0306 .8459+.0236 | 17.0677

So far as this series of data goes, therefore, we have no reason

to think there is any selection in the elimination of the ovaries

which do not develop into mature fruits. Most unfortunately

the mature fruits are not available for comparison. This ren-

ders it necessary to draw the comparisons not between the con-

stants for all the ovaries formed and the fruits maturing, but

between the constants for the original population of ovaries and

those for the fallen flowers. While not so satisfactory as the

former method, the latter is quite justified in the present case,

since the second collection represented the first of the ovaries to

be eliminated from the tree and the third was taken from the

main bulk of those which were to fall. During the last two

years I have not succeeded in getting suitable data for the num-

ber of the ovules in trustworthy samples of ovaries formed and

ovaries maturing in either this or other species of Leguminose.

In our present dearth of quantitative data concerning selective

elimination, this seems a good line to follow far enough to get

conclusive positive or negative results. Perhaps some other

tanist can collect adequate masses of data.

J. ARTHUR Harris.

CARNEGIE INSTITUTION OF WASHINGTON,

COLD SPRING HARBOR, L. I.

NOTES AND LITERATURE

ICHTHYOLOGY

Ichthyological Notes.—The State Laboratory of Natural His-

tory of Illinois has published an elaborate work entitled ‘‘The

Fishes of Illinois,’? by Dr. Stephen A. Forbes and Robert Earl

Richardson. In this work is given a full account of the topog-

raphy of the state of Illinois, with excellent descriptions of all

the species of fishes found in the state. Many of these are illus-

trated by colored plates, and the work is done with admirable

conseientiousness and accuracy. An especial feature of the

work is the very full account of the food of the different species

of fishes.

In the Proceedings of the United States National Museum

(Vol. XXXV, 1908), Professor J. O. Snyder describes eighteen

new species of fishes from southern Japan and from the Riu

Kiu Islands. Professor Snyder was the first ichthyologist to

visit this most interesting group of islands.

In the same Proceedings, Professor Theodore Gill shows that

the name Chcerodon is the oldest name for the genus commonly

called Choerops.

In the same Proceedings, Professor Snyder describes two rare

fishes, from California, Rimicola eigenmanni, with which E.

muscarum is identical, and Plagiogrammus hopkinsi.

In the Proceedings of the Academy of Natural Sciences of

Philadelphia (1908), Henry W. Fowler gives an excellent

synopsis of the Cyprinide of Pennsylvania, with notes on the

material examined by Professor Cope. One new species, No-

tropis keimi, is described from the Allegheny River.

In ‘Annales de la Société Géologique du Nord” (T. XXXVI,

1907), Maurice Lariche presents observations on the fossil fishes —

of Patagonia, showing that the species of shark recently described

as Cretaceous belong to the lower Miocene. a

In the same Proceedings (T. XX XV, 1906), Lariche gives

review of the fossil fishes of the north of France. In his nomen-

elature he pays little attention to the law of priority.

In the same Proceedings, Lariche records various fossils from

Brittany and other parts of France. “

560

No. 513] NOTES AND LITERATURE 561

In the Bulletin of the Geological Society of Belgium (1908),

Lariche records the presence of a species of Amia in the Hamp-

stead Beds of the Isle of Wight.

In ‘‘Comptes rendus de 1’ Association Française pour |’ Avance-

ment des Sciences,’’ Congress of Lyons (1906), Lariche de-

scribes and figures numerous species from Tertiary rocks near

Montpellier.

The same author describes, in the ‘‘Annales de l’Université

de Lyon” (1908), the vertebrates of the Nummulitique de

l’Aude.

In the Bulletin of the Museum of Natural History, of Paris

(1908), Dr. Jacques Pellegrin describes numerous characins

from South America.

In “La Revue Coloniale’’ of Paris (1908), Dr. Pellegrin dis-

cusses the fresh water fishes of French Guiana, with their ver-

nacular names.

In the Bulletin of the Southern California Academy of Sci-

ences (1909), Mr. J. Z. Gilbert publishes an account of certain

California flounders, with a figure of an unnamed fossil flounder

from Miocene rocks at Lompoc, California. This species belongs

to the large-mouthed group, with very strong teeth, but the body

cavity is considerably larger than in the related species of the

present time. The species will soon be described in detail by

Mr. Gilbert. 3

In the Proceedings of the Academy of Natural Sciences of

Philadelphia (1908), Professor Snyder describes the large

ribbon-fish from Monterey Bay, California, under the name of

Trachypterus seleniris.

In the Proceedings of the New York State Teachers Associa-

tion for 1907, Dr. Wilder discusses the usefulness of the dog-

fish for educational purposes.

In the Proceedings of the American Philosophical Society for

1908, Dr. Wilder diseusses the brain of the extraordinary

Japanese Chimera, Rhinochimera pacifica. Dr. Wilder looks

forward to the time when ‘‘no child shall reach the age of ten

without exposing for himself, drawing, deseribing and dissecting

the brain of some shark.’’

In the Popular Science Monthly (October, 1908), Professor

W. S. Tower describes ‘‘The Passing of the Sturgeon” in

America, the five species being practically exterminated all at —

once by murderous fishing methods. The most aggravated case

562 THE AMERICAN NATURALIST [ Vou. XLII

of this kind is the destruction of the species inhabiting the

Lake of the Woods by Michigan fishermen who took them by

thousands from their spawning beds in Rainy River, preserving

the eggs for caviar and throwing the bodies aw ay.

In the Biological Bulletin, XIV (1908), B. G. Smith records

the spawning habits of the minnow Chrosomus, this work being

part of a series of investigations undertaken by the advanced

students of Professor Jacob Reighard, of the University of

Michigan.

In the Bulletin of the Bureau of Fisheries (Vol. XXVIII,

1907), Professor Snyder records the ‘‘Fishes of the Coastal

Streams of California,” Hybopsis crameri, Rhinichthys ever-

manni and Ptychocheilus * umpquæ are described as new species

from the Umpqua region in Oregon, and Catostomus humbold-

tianus from Humboldt County, California. Professor Snyder

shows that Leuciscus caurinus is a species of Leuciscus, and not

identical with Mylocheilus lateralis. Professor Snyder gives an

interesting map of the coastwise streams, showing the distribu-

tion of the different faunal groups.

In the same Bulletin, Professor Snyder discusses the ‘‘Fish

Fauna of the Lakes of Southeastern Oregon’’ with reference to

the distribution of the different forms. Catostomus warnerensis

and Rutilus oregonensis from Warner Lake, and Rutilus colum-

bianus from the Columbia River, are described as new species.

A map of the isolated Warner Lake region, the remains of Lake

Idaho, is given.

In the same Bulletin, the paper on the habits and dis-

tribution of fishes in the Sacramento Basin, by the late

Cloudsley Rutter, is published. The manuscript, prepared be-

fore the death of the lamented author, who was one of the

most careful observers of fishes connected with the Bureau of

Fisheries, has been revised by Dr. Evermann. In this paper,

Catostomus microps, Cottus asperrima(us) and Cottus macrops,

new species from Modoe County, California, are described.

In the same Bulletin (1908), Jordan and Richardson describe

the fishes collected in the Philippines by Richard Crittenden

McGregor. Eleven new species are described and figured, and

two hundred and ninety-five species are mentioned with critical

notes.

In the Hamburger Magalhensische Sammelreise (1907), Pro-

No. 513] NOTES AND LITERATURE 563

fessor Einar Lönnberg describes the species taken in the Straits

of Magellan.

In the Publications of the Department of Education of

logue of the fishes of Ontario, with plates of many of the more

important species. This is prepared primarily for the use of

the teachers of Ontario, and is part of a volume containing all

the vertebrate animals. It will prove extremely useful for the

purposes for which it was prepared.

In a report of the Biological Survey of State of Michigan

(1907), Thomas L. Hankinson gives a biological survey of

Walnut Lake, with numerous plates, photographs and other

illustrations, showing the nature of the fauna and flora.

In the Michigan Academy of Science, Mr. Hankinson gives

a list of fishes of Hillsdale County, Michigan.

In the Annuaire du Musée Zoologique de l’Académie Im-

périale des Science de St. Pétersbourg (T. XIII, 1908), L. Berg

gives a list of the fishes of the River Kolyma, with descriptions,

mostly in Russian, of the various species found there.

In the same Annuaire is given a list of the fishes of the

River Obi.

In the Journal of the College of Sciences of the Imperial Uni-

versity of Tokyo (1908), Shigeho Tanaka describes six new

species and two new genera of fishes from Japan, with notes on

other rare forms.

In the Annotations Zoologica Japonenses (1908), Tanaka

gives a description of eight additional new species from Japan.

In the same Journal (1908), Tanaka describes ‘“Tide-Pool

Fishes of Misaki, Japan,’’ with two additional new species.

In the same Journal, Tanaka records the fishes of Lake Biwa,

with one new species.

In the Zoological Magazine (1908), Tanaka again records, in

Japanese, the fishes of Lake Biwa, the largest of the Japanese —

lakes. :

In the Transactions of the Natural History Society of Sappor 0;

Professor K. Otaki deseribes the Stickle-backs of Japan, in

Japanese and in English, one new species being described. oe

In the same Transactions, Professor Otaki ia the com-

mon sturgeon of northern Japan, Acipenser m

In the Sitzwngsberichten of the Vienna “Academy (08, De oe

564 THE AMERICAN NATURALIST [ Vou. XLIII

Viktor Pietschmann describes the sharks of Japan, with de-

scriptions of some new species.

In the same Sitzungsberichten, Dr. Pietschmann describes also

two new Japanese species of shark, and he has also a paper com-

paring the European species of Mustelus with each other.

In the Smithsonian Miscellaneous Collections (1908), Pro-

fessor Gill gives in detail the story of the devilfish, Manta, with

numerous illustrative plates.

In the Proceedings of the Zoological Society of London (1908),

Dr. Regan gives a valuable revision of the sharks of the family

Orectolobide. To this family he refers Rhinodon, Gingly-

mostoma and other forms usually placed in separate families.

In the Annals and Magazine of Natural History (1908), Mr.

Regan describes a collection of fresh-water fishes from Costa

Rica, with several new species. Joturus stipes, from Central

America, is made the type of a new genus, Xenorhynchichthys.

A new genus, Tomocichla, near Herichthys, is also deseribed.

In the same Annals, Mr. Regan discusses the systematic posi-

tion of Stylophorus, which he places near the Allotriognathi. He

discusses the work of Professor Starks on the same species, who,

in the Bulletin of the Museum of Comparative Zoology, for 1908,

makes Stylophorus the type of a new suborder, Atelaxia. The

work of both of these anatomists shows that Stylophorus is re-

lated to Trachypterus and also to Velifer.

In the same Annals, Mr. Regan revises the species and sub-

species of Coregonus found in Great Britain.

In the same Annals, Mr. Regan revises the char of Great

Britain, adding a number of new species. Four old species and

five new ones are recognized in place of the single Salvelinus

alpinus, recognized by Day as found in British waters.

In the same Annals, Mr. Regan describes the species of char,

six in. number, found in the rivers of Ireland. He recognizes

the fact that these species are of relatively recent date, and

perhaps only partially separated from one another.

In the same Annals, Mr. Regan discusses a classification Of :

the scombroid fishes, or mackerel-like fishes. He recognizes the

extremely close relation of the Carangidæ with the pereh-like

forms, or Serranide. ;

In the same Annals, Mr. Regan revises the genus Elops,

showing that instead of a single species, Elops saurus, there are —

seven well-marked species. This conclusion the writer has been

No. 513] NOTES AND LITERATURE 565

able to verify in part, having specimens of Elops hawaiensis

from Formosa as well as from Hawaii. Regan describes Elops

affinis, from Mazatlan and Jalisco, the species being based on

a specimen sent as Elops saurus by the present writer.

In the same Annals (1909), Mr. Regan takes up the impossible

problem of defining the orders and sub-orders and equivalent

groups of the teleostean or bony fishes. The paper is most

suggestive and valuable, but no one adjustment of the intricate

interrelationships of these fishes is likely to be more permanent

than any other. It is encouraging, however, to notice the

practical agreement between Mr. Regan’s classifications and

those adopted by American naturalists in matters in which the

facts have become clearly apprehended.

In the same Annals, Mr. Regan gives an account of the fishes

of the group Salanginæ, mostly of eastern Asia.

In the same Annals, Mr. Regan gives an account of new fishes

from Lake Candidius, in Formosa.

In the Annals of the South African Museum (1908), J. D. F.

Gilchrist and W. W. Thompson give descriptions of fishes from

the coast of Natal, with descriptions of numerous species.

In the same Annals, Gilchrist and Thompson give an account

of the blennies of South Africa, the species referred to Clinus

being especially numerous.

In the Annals of the Queensland Museum, J. D. Ogilby de-

scribes numerous new or little-known fishes from the Queensland

Museum in Brisbane. Among other things, he claims that the

name Dampieria should supersede Labracinus, recently resur-

rected to take the place of Cichlops, which is preoccupied.

In the Publications of the Department of Fisheries for New

‘South Wales, David G. Stead gives an interesting account of

the beaked salmon, Gonorhynchus.

In the same Publications Mr. Stead gives descriptions of three

new species of fishes from New South Wales.

In the Proceedings of the Royal Society of Queensland (1907),

Mr. J. D. Ogilby deseribes seven new species of fishes from the

coast of Queensland. He divides the genus Tylosurus into three,

separating from it Stenocaulus, with body short and deep, the

type being krefftii, and Euryeaulus, with the caudal elande

strongly keeled, the type platyura.

In the same Proceedings, Mr. Ogilby P namerous new oe : 2

Species and genera of fishes from Queensland.

566 THE AMERICAN NATURALIST [ Vou. XLI

In the ‘‘Scientific Investigations of the Fishes of Ireland”

(No. V, 1908), Holt and Byrne record certain fishes of the Irish

Atlantie Slope.

In the Bulletin of the Department of Agriculture in the Dutch

East Indies (1908), Van Kampen describes the larva of

Megalops, which passes through changes similar to those already

recorded for Albula.

In the Norwegian journal Naturen for 1908, Stejneger dis-

cusses in Norwegian the species of char found in Norway,

Salvelinus salvelinus and Salvelinus alpinus.

In the Journal of Comparative Neurology and Psychology

(Vol. XVIII, No. 6, 1908), Professor J. B. Johnston describes in

detail the nervous system of the lamprey.

In the same Journal, Professor Johnston further discusses the

physiology of the nerves of the lampr

In the Anatomical Record (Vol. IL. Na. 6, 1908), Professor

Johnston discusses the question of the presence of the glosso-

pharyngeal nerve in the hagfish.

In the same Journal, Professor Stockard gives a note on the

same subject.

In the Zoologischen Jahrbuchern of Jiessen (1908), E. P.

Allis, Jr., discusses the bloodvessels in various bony fishes.

In the same Journal, Dr. E. Philippi discusses the name and

development of certain viviparous fishes of the genus Glari-

dichthys.

In the American Breeders Association (Vol. IV), the Com-

mittee on Breeding Fish, J. W. Titeomb, Chairman, discuss the

possibility of improvement of fish stock by selective breeding.

In the Memoirs of the Royal Society of Copenhagen (1908),

Dr. H. F. E. Jungersen gives an elaborate account of the genera

of fishes related to Centriscus. This is a most valuable contribu-

tion to our knowledge of the fishes of this type, and ought to

help settle the questions as to their relationship to other related

forms.

In the Transactions of the Royal Society of Edinburgh (Vol.

45, 1907), W. E. Agar gives a valuable account of the paired

fins in Lepidosiren and Protopterus, with special reference to

the nerve structures,

In the Annual Report of the Department of Marine and

Fisheries for Canada, are given valuable studies of the effect of

dynamite explosions and sawdust on fish life. The evil effects _

No. 513] NOTES AND LITERATURE 567

of dynamite are here clearly emphasized by Professor A. P,

Knight. Professor Knight does not, however, find the effect

of sawdust as injurious as has been hitherto supposed. A strong

solution of sawdust poisons fish and fish fry, through the agency

of compounds dissolved out of the wood cells. Fishes will desert

a river polluted with freshly made sawdust, going down stream

or into tributaries to escape from the disagreeable influence of

the sawdust extracts. Waste matters which would be deadly

in one river will pass away and prove of little harm in another,

where the conditions are different.

~ In the Journal of Morphology (1908), Reighard and Mast

describe the development of the hypophysis of Amia.

In the Journal of Experimental Zoology (1909), Professor

C. R. Stockard describes the development of the young of

Fundulus heteroclitus in magnesian solutions instead of salt

water. The result is the development of cyclopean fish, with

a single coalesced eye on the top of the head. It is thought that

magnesia possesses an anesthetic effect, and is inhibitory in its

influence on muscular activity. It, therefore, retards the out-

pushing of the eyes in the embryo, leaving the eyes without

energy for perfect development, and at times without energy

sufficient for their normal separation.

In the Outing Magazine (September, 1908), Bonnycastle Dale

describes the mystery of the salmon, and its desperate struggle

to breed in the waters of the Columbia, with some excellent

photographs.

Under the head of ‘‘The Fishes of Japan,’’ Otaki, Fujita and

Higurashi continue their fifth volume of discussion of the Japa-

nese fisheries and fishing methods. The fourth volume contains

_ colored plates of a number of Japanese food fishes. The text 1s

entirely in Japanese.

DAVID STARR JORDAN.

PARASITOLOGY

The question as to the relation of the tse-tse fly which is abso-

lutely demonstrated to be the transmitting agent of sleeping

sickness and the parasite of the disease is one that has been dis-

cussed pro and con with great vigor. Minchin and others con-

tend most powerfully that the fly is a mere mechanical vector o —

while Manson and his supporters, chiefly, it must be confessed, o

568 THE AMERICAN NATURALIST [Vou. XLII

from a theoretical standpoint, have maintained that the fly stood.

in the same relation to the disease as the mosquito held to

malaria. As already indicated, the definite evidence thus far

secured has seemed to favor the view that the fly is a mere me-

chanical agent. Some recent experiments in East Africa are of

tremendous importance in this discussion. Kleinet under date of

December 28, 1908, reports from Kirugu, German East Africa,

an experiment which apparently demonstrates that flies may

infect after a long interval. Heretofore it has been claimed

that flies would not infect later than forty-eight hours after

biting infected hosts. A longer interval is good evidence of

the existence of a developmental cycle in the fly. Kleine’s

experiment may be summarized as follows:

Nagana, an animal disease due to Trypanosoma Brucei, does

not occur in the Kirugu region. Animals which had been

naturally infected by the bite of the tse-tse fly, Glossina

morsitans, were brought from a locality seven days’ march dis-

tant and were kept in isolation. Other flies, Glossina palpalis,

caught on the Mori River, were fed for three days on the in-

fected animals and from the fourth to the seventeenth day

inclusive for each day on a fresh healthy animal. From the

eighteenth to the twenty-fourth day the flies fed on a single

sheep; from the twenty-fifth to the twenty-ninth day on a single

ox. Frequent blood examinations were made of the experi-

mental animals and on the twelfth day after the flies were put

on the ox which was first used on the twenty-fifth day of the

experiment, numerous trypanosomes were found in the blood of

this host. Then the sheep first employed as host on the eight-

eenth day was examined and found also to be infected. All

the other experimental animals remained uninfected. Goats,

calves and sheep were used to feed the flies from the fortieth

to the fiftieth day and all were infected. The author concludes:

‘From this it is seen that flies which for many days after the

ingestion of blood containing trypanosomes were not infective,

afterwards became so and infected a sheep and then an ox.’

The Royal Society has received a telegram dated April 3 from

Colonel Sir David Bruce which announces the confirmation of

Kleine’s observations, and a letter received April 30, dated

Mpumu, Chagwe, Uganda, April 3, confirms the cablegram

***Positive Infektionsversuche mit Trypanosoma Brucei dureh Glossina

palpalis.’” Deutsche medizinische Wochenschrift, 18 Marz, 1909; 469-470. —

No. 513] NOTES AND LITERATURE 569

notice and says that the Commission had ‘‘repeated Dr. Kleine’s

experiments with Trypanosoma gambiense and Glossina palpalis,

also with a trypanosome of the dimorphon type and the same

tse-tse flies and found the flies infective after 16, 19 and 22

days.’’

It is apparently impossible to escape the conclusion that the

parasite of human sleeping sickness, Trypanosoma gambiense,

also undergoes a cycle of development in its transmitting agent,

Glossina palpalis, and that the fly bears the same relation to

the parasite which the mosquito does to the malarial organism.

It is unnecessary to indicate in detail the tremendous importance

of this discovery.

Old fables die hard and among them must be placed the oft-

repeated story cited in many modern texts of good standing

that in some parts of Italy and France the population makes

use of certain fish tapeworms (Ligula) which are found in the

body cavity of various eyprinids, as a delicacy under the name

of macaroni piatti or ver blane. In 1894 Monticelli demon-

strated the incorrectness of the story, but it continues to be

cited as a biological marvel even by recent writers of repute.

Recently Parona has again exploded the myth in an interesting

brochure entitled ‘‘Les Liguliphages ou soi-distant mangeurs des

ligules.’’' Nowhere in Italy is such a habit found; the error

is as persistent as false and deserves general contradiction until

it is finally eliminated from our text-books. Rudolphi reported

that at times the Ligule are eaten with the tench which they

infest, being taken for the fat of the fish. From such a simple

beginning the fable grew until it was said that certain fish

culturists raised tench to obtain the ligule which they harbored.

The final stamp of reality was imparted to the fable when a

French savant wrote that these biological noodles are eaten at

Lyons as in Italy!! Like the tales of early naturalists, which

Linné copied so faithfully, that tapeworms occur in brooks and

springs, so let the marvellous story of the liguliphages be con-

signed to the care of writers on unnatural history and forever

more be eliminated from serious consideration.

Sambon and Seligman? have recorded studies on the hemo-

gregarine of reptiles, describing many new species and affirmin e

* Bull. pop. pisiculture, n. s., 4.

* Jour. Trop. Med., Dosint; 1908.

570 THE AMERICAN NATURALIST [Vou. XLII

that their life history manifests two cycles; the schizogonie or

vegetative cycle, in the blood of vertebrates and characterized

by asexual multiplication with the sporogonic, characterized by

sexual reproduction. They enumerate merozoites, schizonts,

sporonts, ete. Patton? recounting his work on the same objects

states that careful feeding operations with larval nymphal and

adult ticks under most favorable conditions at the King Insti-

tute, Madras, and several years’ study of similar parasites in

amphibia and their transmitting leeches, for comparative pur-

poses, have entirely failed to elucidate the extra-corporeal life

histories of the intracellular parasites of either reptiles or

mammals, He regards the transmission of these parasites as

mechanical and questions the interpretation of the different

forms described by the other authors from the peripheral blood

of snakes. He inclines to consider all their forms as belonging

to a single species of hemogregarine and in closing calls atten-

tion to Prowazek’s error in regarding cysts found in a pentastome

from a python as developmental stages of Hæmogregarina

pythonis when in reality they represent part of a cycle of a

parasite peculiar to the pentastome and have nothing to do with

the hæmogregarine of the snake. Patton might have cited

numerous similar cases of confusion between normal parasites

of a supposed transmitting agent and the missing developmental

stages of the parasite under investigation.

In the same journal‘ Patton gives a brief though valuable

résumé of the genus Herpetomonas which emphasizes certain

points of great importance in this connection. These flagellates

are parasitic in the alimentary tract of insects, though those

which occur in blood-sucking insects are in no wise related to

blood parasites. Their developmental cycle consists of a pre-

blepharoplast, multiplies by simple longifission or multiple seg-

mentation, and occurs in the insect’s mid gut. In the flagellate

stage the organism forms a single flagellum and is found in

both mid gut and hind gut, while the postflagellate stage is char-

acterized by massing of the herpetomonads in the midgut and

the formation of cysts which pass out in the feces. Many are :

undistinguishable in their preflagellate stages and a partial study —

* Parasitology, December, 1908. ne

* Parasitology, December, 1908.

No. 513] NOTES AND LITERATURE 571

may lead to confusion of true herpetomonads with Crithidia or

young trypanosomes, such as has actually occurred in more than

one instance.

He closes thus:

As the life-cyeles and general structure of the three human parasites

are similar to those of well-known Herpetomonads, I see no reason for

placing them in a distinct genus. The differences in their develop-

ment, such as the formation of the flagellum, methods of division and

the fact that their preflagellate stages are passed in man only justify

their being regarded as specifically distinct from such species as H.

musce-domestice, H. sarcophage, H. culicis, H. lygæi and many others.

In the opinion of others, just the points noted justify inclu-

ding the three human parasites in a separate genus, Leishmania.

H. B. Warp.

PLANT CYTOLOGY

The Permanence of Chromosomes in Plant Cells——The problem

of the individuality of the chromosome is receiving the attention

of a number of plant cytologists. Briefly stated the problem

concerns the permanence of the chromosome as an organ of the

cell, enquiring whether the chromosomes are present as struc-

tural entities in the resting nucleus and whether they have come

down from a line of ancestral structures reproducing by fission

in the mitoses throughout the life histories.

In 1904 Rosenberg presented claims that the chromosomes

may be recognized in the resting nuclei of certain plants and

cited Capsella bursa-pastoris as a favorable type for their demon-

stration. Overton in 1905 traced the chromosomes of certain

dicotyledons to aggregates of chromatin in the resting nuclei

which he designated as prochromosomes, believing them to be

autonymous structures representing the chromosomes in this

stage of nuclear activity. Other investigators have reached

similar conclusions. Nevertheless a number of plants is known

in which the forms of the chromosomes during the interkineses —

are so changed by progressive alveolization or vacuolization as

well as by the reticular union of chromatic masses through

anastomoses that the outlines of the structures can not be fol-

lowed in the irregularities of the chromatic and linin network.

Whether the chromosomes in such nuclei really lose their

identity as autonymous structures is not of course established _ = .

simply by the negative evidence that they have not been traced -o

572 THE AMERICAN NATURALIST [ Vou. XLII

by the technical methods at our command. ‘These difficulties,

however, have been clearly set forth by Mottier and other au-

thors, some of whom are unwilling to accept the hypothesis of

the permanence of the chromosome.

Four papers have recently appeared which give further evi-

dence of the presence of prochromosomes in the resting nucleus

and also present some important conclusions on the history of

the chromatin during synapsis. In the latter feature these

authors (Overton, Lundegardh and Rosenberg) support the view

that during synapsis the sporophytic chromosomes by the

parallel association of two spirems become grouped in pairs to

form the reduced number of bivalent chromosomes character-

istic of the heterotypic mitosis.

Overton! presents the results of studies on the pollen mother-

cells of Thalictrum purpurascens, Calycanthus floridus and

Richardia africana. He finds that the sporophytie (somatic)

nuclei previous to the heterotypie mitosis have their chromatin

in the form of definite bodies arranged in pairs with linin inter-

vals between. The bodies are prochromosomes and were traced

through synapsis to the chromosomes of the heterotypic mitosis.

Overton interprets the grouping of the prochromosomes in pairs

to mean that there are two spirems of paternal and maternal

origin in the sporophytie nuclei which he believes remain dis-

tinct throughout the sporophytie phase of the life history. The

parallel threads become more distinct just before synapsis and

become very closely associated during the synaptie contraction,

but remain distinet from one another.

The association of the sporophytic chromosomes in pairs 18

most intimate during postsynaptic stages when these elements

become more or less closely united in various ways to form the

bivalent chromosomes (in the reduced number) characteristic

of the heterotypie mitosis. This is the period in the life history

when the sporophytiec chromosomes are most likely to influence

one another by conjugation or by the mutual interchange of

substance.

The first or heterotypie mitosis in the pollen mother-cells dis-

tributes the sporophytie chromosomes associated in pairs. At

this time each sporophytic chromosome undergoes a longitudinal

"Oy B., ‘f On the Organization of the Nuclei in the Pollen

Mother-cells of Certain Plants, with Especial Reference to the Permanente

of the Chromosomes,’’ Ann. of Bot., XXIII, p. 19, 1909. ,

No. 513] NOTES AND LITERATURE 573

fission in preparation for the second or homotypie division so

that chromosome tetrads are present during the metaphase of

the heterotypic mitosis. The split chromosomes remain distinct

during the interkinesis between the two mitoses and the halves

are distributed by the homotypie division to the nuclei of the

pollen grains.

The nuclei of the pollen grains show prochromosomes arranged

in a single series and it seems probable that they retain this ar-

rangement throughout the gametophytie phase of the life his-

tory. It also seems probable that the fertilization of the egg nu-

cleus effects the close association of two such series of chromo-

somes, thus accounting for the pairs of prochromosomes arranged

on parallel threads, and that this association is maintained

throughout the history of the sporophyte until the distribution of

the sporophytie chromosomes by the heterotypic mitosis. Never-

theless it is but fair to point out that these inferences are not as

yet supported by direct evidence, that is to say, the history of

the chromosomes has not been followed throughout the life his-

tory of any of these seed plant.

Lundegardh? introduces his paper with a good summary of

the two views concerning the origin of the bivalent chromosomes

of the heterotypie mitosis, (1) the theory of the parallel asso-

ciation of two spirems (Junktionstheorie), and (2) the theory

of the folding of a single spirem (Faltungstheorie). His in-

vestigations are based on several types of the Composite (Calen-

dula officinalis, Achillea millifolium, Anthemis tinctoria and

Matricaria chamomilla), and on Trollius ewropeus of the

Ranunculacee. Unfortunately these forms are not treated

serially but with reference to the critical phases of the processes

of the reduction divisions so that it is very difficult for the reader

to follow the text and figures consecutively for any of the types.

The difficulty is further increased by the crowding and ill ar-

rangement of the figures. In deference to the reader too much

care can not be given to these matters.

Lundegardh finds for the types of the Composite that the

prochromosomes (Gamosomen) are generally arranged in pairs

(Gamomiten) in the resting nucleus of the pollen mother-cell.

In Trollius, on the other hand, the chromatin is in the form of

numerous granules distributed on a delicate linin network and

_ *Lundegardh, H., ‘“‘ Ueber Reduktionsteilung in den Pollenmutterzellen |

einiger dicotylen Pflanzen.’’? Svensk. Bot. Tidsk. IIL, p. 78, 1909. :

574 THE AMERICAN NATURALIST [Vou. XEM

prochromosomes could not be recognized. As the nuclei of these

Composite approach synapsis the pairs of prochromosomes be-

come connected with one another by delicate threads along which

the chromatic substance is distributed so that two parallel sys-

tems of threads are constructed which finally become so closely

associated as to form a single spirem. The chromatin granules

of Trollius gather and fuse into larger masses which are at first

more numerous than the chromosome count but show a tendency

to pair. These are distributed over a delicate linin network

upon which the chromatin becomes distributed. Finally the

chromatic masses fuse thus forming a single spirem.

The later history of the reduction processes is similar in all

of the types. The spirem splits (strepsinema stage) and seg-

ments into the reduced number of bivalent chromosomes which

become distributed in the nuclear cavity (diakinesis) as pairs of

chromosomes. The halves of the split segments of the spirem

may then be regarded as the sporophytic chromosomes to be

distributed in two sets by the heterotypic mitosis. A contrac-

tion during the strepsinema stage (second contraction) is not

regarded as of special significance, but merely as an accom-

paniment of this period in the development of the bivalent chro-

mosomes. The phenomenon of synapsis is regarded as especially

significant since it is the period when the sporophytie chromo-

somes are in their most intimate relation to one another.

Rosenberg in two recent papers gives additional evidence in

support of his belief (1904) in the permanence of the chromo-

somes, and develops further his views on the significance of

synaptic phenomena. The first paper? deals especially with

Hieracium venosum and H. auricula. A brief introduction out-

lines clearly the problems concerned with the prochromosome or

gamosome theory and their relation to the views on the interpre-

tations of the events of synapsis and the reduction divisions.

The chromatin is present in the resting nuclei of the archespor-

ium as irregular deeply-staining masses almost always situated

at one side of the nucleus. These are interpreted to be prochro-

mosomes or gamosomes, their number corresponding generally

to the number of chromosomes which for the sporophyte is four-

teen and eighteen in these two species of Hieracium. As the —

nuclei of the pollen mother-cells approach synapsis the prochre-

*Rosenberg, O., ‘‘ Zur Kentniss der priisynaptischen Entwicklungs-

phasen der Reduktionsteilung,?’ Svensk Bot. Tidsk., I, p. 398, 1907.

No. 513] NOTES AND LITERATURE 575

mosomes are found associated in pairs distributed over a net-

work. The further history of the reduction mitoses is not de-

scribed, so that the investigation is incomplete in a number of

important features.

The second paper of Rosenberg* deals with Crepis virens, one

of the Composit, a form remarkable for the small number of

chromosomes, which are six for the sporophyte and three for

the gametophyte generation. A further important peculiarity

is a difference in the size of the chromosomes which makes it

possible to follow the individual elements through succeeding

mitoses with some degree of certainty. This is, so far as the

reviewer is aware, the first account for plants of such a differ-

‘entiation of chromosomes as has been described for animals by

a number of zoologists.

The nuclei of the sporophyte (somatie) show six small pro-

chromosomes in the resting stage from which are organized dur-

ing the prophases of the vegetative mitoses two short rod-shaped

chromosomes, two very long bent elements, and two chromosomes

about midway in length between these extremes. The resting

nuclei of the pollen mother-cells have six prochromosomes more

or less clearly grouped in pairs. Synapsis presents a series of

parallel threads intimately united at intervals. From this con-

dition a thick coiled spirem is organized which clearly shows its

double nature in the frequent longitudinal separation of portions

as though it were split. The free ends of the chromosomes com-

posing the spirem may at times be distinguished. A gradual

contraction of the spirem leads through stages comparable to

those described as a second contraction by various authors to

the period when the six chromosomes, grouped in three pairs,

may be clearly recognized (diakinesis).

The chromosome group on the approach of the heterotypic

mitosis consists then of a pair of small, almost spherical, chromo-

somes, a pair of long rods, and a pair of short rods. These

correspond to the three different sizes of chromosomes present

in the vegetative sporophytic mitoses, but are more condensed or

shortened. Thus the heterotypic mitosis is a true reduction

division distributing the six chromosomes in two sets each of

which consists of a spherical chromosome, a long rod, and a

chromosome intermediate in shape between these two. These

“Rosenberg, O., ‘‘ Zur Kenntniss von den Teese 7 der ee es

4, 1909. Be

positen,’’ Svensk Bot. Tidsk., III, p. 64.

576 THE AMERICAN NATURALIST (Vou. XLI

chromosomes divide during the anaphase of the heterotypic |

mitosis in preparation for the second or homotypic mitosis so

that they appear at the poles of the heterotypic spindle in the :

form of three split chromosomes or pairs. 4

The members of these three pairs are distributed by this division —

so that the nucleus of each pollen grain receives three chromo-

somes, a short, a long, and a middle-sized element, and these may

be recognized in the resting nucleus by three prochromosomes.

A brief examination of the mitoses in the embryo-sae sup-

ported the conclusions above outlined.

Brapiey M. Davis. —

The Study of Stellar Evolution

An Account of Some Modern Methods of Astrophysical Research

By GEORGE ELLERY HALE

The introduction of photographic methods, the improvement of telescopes, and

the rapidly increasing appreciation of the value to peony of physical instruments

and processes, have revolutionized the observatory. From a simple observing

eat it has been transformed into a great ener! laboratory, where images of

the a and stars are studied with aagi powerful instruments, and celestial pheno-

mena are experimentally imitated with the aid of electric furnaces and other sources

of rept heat. The result has ‘poets a great gain in our knowledge of the origin,

development, and decay of stars. This books explains in a popular way how the

life histories of the sun and stars are investigated. One hundred and four half-tone

plates, made from the best astronomical negatives, place before the reader the most

recent results of celestial photography in most of its ph

250 pages, 104 plates, 8vo, cloth; net $4.00, postpaid $4.27

Address Dept. 38

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Published in Europe by William Wesley and Son, 28 Essex Street, Strand, London, Price, 16s. 6d.

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Seed pag Figen psychology, the vi he to thom studies,

pa himii Essa ;

‘he New Realism ~:

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onsciousness a Sas ,

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ESSAYS PHILOSOPHICAL AND „PSYCHOLOGICAL

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prodan OF MARCH NUMBER

t the Baltimore Meeting of the porat

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Darwin’s proram upon Plant Geography and Ecol-

ogy, Professor FREDERIC E. CLEMENTS.

a s Work on Steere in Plants. Professor

Mau

An eia of Darwin’s “Origin of eine

a“ of Recent brow iaae and

Professor EDWIN LIN

The Distinction between Development and Heredity in

Inbreeding. Dr. EDWARD M, East,

mi Experiments with ts. Professor T. H.

Bhoster Aiticles and Discussion : The Chub and th » Texas

Horn Fly, Dr. Roy L. MONE, A New Camel from

the Lower Miocene of Nebraska, HAROLD JAMES

in the

nts,

Notes and Literature : Heredity—The energy apr as

Bearers of the Hereditary — F. PAYNE,

Cultural Bed Mutations in the Potato.

CONTENTS OF THE APRIL NUMBER

Heredity of Hair — in Man. komans. C. DavEN-

PORT and Sig 3 Es C, DAVENP:

A Mechanism fo rent S Corrie, Professor G, H,

Recent A ‘Advances i in the Study

Breedin ng.

Notes and Literature: Hered

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Chara Ay , DR. W. ERL yt

R. nah (K Eepertndniii

bridolo and ‘Gynandremo hi Profesct ne

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AUSTIN Salant CLARK.

CONTENTS OF THE MAY NUMBER

The Categories of Variation. Professor S. J. HOLMES.

The General Entomological Ecology of the Indian Corn

Plant. S. A. FORBES,

Notes and Literature: Biometrics—Some Recent Studies

on Growth, Dr. RAYMOND PEARL. Experimental

Zoology—Cuénot on the Honey Bee, Professor T. H.

MoRGaN. The Upholding of Darwin—Poulton and

on ion K.

CONTENTS OF THE JUNE NUMBER

Heredity and Variation in = PHT: onii

NNING:

Professor H. S. JENNI

The Color Sense ofthe Toe is

ness an oe eee Flowers? Tosi H.L

Tri in the Num pe in the

oo pons

Present Problems Teologi Plant Ecol:

Ecology. Dr.

Taas and Lay sweet

SHULL. Marge ology — i

the agh Two na msaeRe of the j

Dr. J. F. McCCLENDO ;

5 CONTENTS oF THE JULY Paar nore

3 SA kanap Numbers and their

z a o Dr. GEORGE

: Present ‘Problems in Plant Fe iaae and

Me Articles or Capres Hf Saaw " Pleistocene

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THE

AMERICAN NATURALIST

Voi. XLII October, 1909 No, 514

THE NON-MUSCULAR ARTICULATIONS OF

CRINOIDS

AUSTIN HOBART CLARK

Ir has been long known that the non-muscular articula-

tions in the crinoid arm, synarthries or bifascial articula-

tions, and syzygies, have an entirely different effect

upon the arm structure than do articulations possessing

muscle bundles, straight or oblique muscular articulations.

The muscular articulations are composed of three ele-

ments (Figs. 1 and 7); (1) the dorsal ligament, bounded

ventrally by a strong transverse ridge running across the

middle of the joint face, (2) the interarticular ligaments,

just ventral to the transverse ridge, occupying triangular

areas one on each side of the central canal, and (3) the

muscle bundles, occupying two large distally rounded

areas, separated by a narrow median ridge or furrow; in

straight muscular articulations (Fig. 1) the transverse

ridge separating the dorsal ligament fossa from the inter-

articular ligament fosse runs at right angles to the dorso-

ventral axis of the joint face, and the two interarticular

ligament fosse and two muscular fosse are of equal size,

while in oblique muscular articulations (Fig. 7) the trans-

verse ridge is strongly diagonal in position, and the two

interarticular ligaments and two muscular fosse are, on

one side crowded, on the other drawn out, and therefore

unequal.

The non-muscular articulations (Figs. 5 and 11) are -o

577

578 THE AMERICAN NATURALIST [ Vou. XLII

= =

ig cular

Fig. 1. Articular Face of a sina esis) are m, mus

fosse ; il, interarticular ligament f ; dl, al ligam tween

Fig. 2. rsal External View iy a ‘Str ra at a beest Bere be

two hoa

Angle

"IG. 3. Two straight Muscular Articulations revolved through an

of jn . incide.

Fic. 4. he same, superposed so that their central Canals Co

Fig. 5. A synarthr icles.

Fic. 6. External Dor sal View of a ge rthry between two ossic usculat

7 rticular Face of an Oblique Muscular Articulation; ™, >

fossa ; ps, pto socket; il, as attaslir ligament fossa; dl, dorsa!

ossa.

No. 514] ARTICULATIONS OF CRINOIDS 579

bound together with ligament fibers similar to those of

the dorsal ligament of muscular articulations; in syn-

arthries (Fig. 5) these fibers are segregated into two

large bundles lateral in position, separated by’a dorso-

ventral ridge across the joint face; in syzygies (Fig. 11)

the fibers are scattered over the whole joint surface,

which is broken up into alternating ridges and furrows

radiating outward from the central canal, which may, in

certain of the more specialized forms, such as the Pen-

tacrinitidæ, become obsolete except about the periphery

of the joint face.

Muscular articulations are often doubled, thus forming

an axillary from which two arms arise; this never hap-

pens in the case of non-muscular articulations ; moreover,

muscular articulations are primarily pinnulate, the pin-

nule arising from a pinnule socket in the proximal outer

part of one of the muscular fosse. The difference between

straight and oblique muscular articulations was orig-

inally a difference in pinnulation. In the most primitive

type of crinoid arm found among the recent forms, oc-

curring in the family Pentametrocrinide, we find the fol-

lowing sequence of articulations: (1) straight muscular,

uniting the radial to the first post-radial joint, (2) syn-

arthry, uniting the first two post-radial joints, (3) oblique

muscular, uniting the second and third post-radial joints;

all the succeeding articulations are oblique muscular,

except for the interpolation of occasional syzygies. The

first oblique muscular articulation bears the first pinnule ;

the addition of a pinnule socket on one side of the joint

face causes a certain amount of crowding, and a conse-

"Wie. 8. External Dorsal View of three oblique Muscular Articulations.

Fic. 9. Two Oblique Muscular Articulations revolved cdg an angle

Fig. 10. ii same, superposed so that their central Canals Coincide.

- A Syzygy

Fig. 12. External Dorsal View of a Syzy, between two Ossicl es

ourse across the arm is the mean ong a course of the preceding an

succeeding oblique muscular articulations. ‘

A Biserial Crinoid Arm.

A Monoserial Crinoid Arm, EY the triangular joints, the

indices. a an ae biserial arrangemen

580 THE AMERICAN NATURALIST [Vou. XLI

quent depression dorsally of that half of the transverse

ridge, which is compensated by a ventral depression of

the opposite half; this alteration in one half of the trans-

verse ridge is a necessary consequent of any alteration

in direction of the other half, for the transverse ridge is

the fulcrum upon which the bending of the arm occurs,

and the fulcrum must always be a straight line to admit

of any motion at all. Although primarily pinnulate, in

certain rare cases oblique muscular articulations are

sometimes found non-pinnulate, as in Atelecrinus,

Hypalometra, Cyllometra, and Perometra; but this is a

purely secondary condition, and one peculiarly prone to

reversion, showing it to be somewhat unstable. In all

cases, the position of the first oblique muscular articula-

tion is the second articulation beyond the last straight

muscular articulation of the arm. The oblique muscular

articulations always alternate in the position of their

diagonal transverse ridges, and the transverse ridges of

succeeding joints form angles of approximately 90° with

each other; therefore, a single brachial has proximally

an articular face with the transverse ridge from a left

ventro-lateral to a right dorso-lateral point, and distally

an articular face with the transverse ridge running from

a left dorso-lateral to a right ventro-lateral position.

The pinnule socket always occurs on the side on which

the end of the transverse ridge is dorso-lateral in post

tion; hence, pinnules occur on alternate sides of the arm

at succeeding articulations. In reality, of course, the

alternation of the pinnules is the fundamental cause of

the alternation in the direction of the transverse ridge,

but, from the absence of pinnules on oblique muscular

articulations in certain recent types, it is more convenient

to speak of it as if the reverse were the case.

Non-museular articulations are never doubled, are

never pinnulate, and moreover, never affect the pinnula-

tion in any way; the pinnule on the next succeeding MUS-

cular articulation is on the opposite side from that of the oe

preceding muscular articulation, just as if the non-mus-

No. 514] ARTICULATIONS OF CRINOIDS 581

cular articulation were not there, but the two joints con-

nected by it merely a single joint.

Of the non-muscular articulations, the synarthry occurs

in the proximal part of the arm, the last synarthry im-

mediately preceding the first oblique muscular, and im-

mediately succeeding the last straight muscular articula-

tion; all the non-muscular articulations succeeding the

first oblique muscular articulation are always syzygies.

In the simple arms of the Pentametrocrinide we find a

straight muscular articulation, a synarthry, and then a

series of oblique muscular articulations, interspersed

with occasional syzygies. In this family the first

brachial immediately follows the radial; but in all the

other comatulids and in the recent species of the Pen-

tacrinitide (except in the genus Metacrinus) the first

brachial is separated from the radial by one or more

interpolated division series, each composed of a redupli-

eation of the first two brachials interpolated between the

primitive first brachial and the radial. In these, how-

ever, the structure is the same; a series of synarthries

alternating with straight muscular articulations occurs up

to the first oblique muscular articulation, beyond which

are found only oblique muscular articulations and

syzygies. This is the primitive arrangement of the

comatulid and pentacrinite arm, no matter how many

times division may occur; but in certain specialized

types, as Endoxocrinus and the Zygometridx, one or more

of the synarthries may be secondarily replaced by

syzygies. )

From the above discussion it is evident that (1) non-

muscular articulations are morphologically radically dif-

ferent from muscular articulations; and (2) that there

is a distinct interrelation between the two types of mus-

cular articulations and the two types of non-muscular

articulations; that is, that proximal to the first oblique — ee

muscular articulation only straight muscular articula- ~

tions and synarthries are found, while distal to the first -

pial PEOR $ Ey

oblique muscular ır only obliq ue n vuscu $

582 THE AMERICAN NATURALIST [ Vou. XLII

articulations and syzygies; moreover, the synarthries

always alternate with the straight muscular articulations,

while the occurrence of the syzygies is more or less, and

often very, irregular.

Bearing these facts in mind, we are able to reach a

definite concept of the morphological significance of the

synarthries and syzygies, in terms of straight and oblique

muscular articulations. We have seen that the trans-

verse ridges of succeeding oblique muscular articulations

are always approximately at right angles to each other,

and we may from this infer a fundamentally alternate

position in all muscular articulations. The first articu-

lation, uniting the radial to the first post-radial joint is

straight muscular, with the transverse ridge at right

angles to the dorso-ventral axis of the joint faces; accord-

ing to what we found to be the case in oblique muscular

articulations, the next articulation should be straight

muscular, with the transverse ridge at right angles to

that of the first, or coinciding with the dorso-ventral axis;

but such an arrangement would leave the muscles and the

interarticular ligaments on one side of the arm, and the

dorsal ligament on the other, which would be manifestly

absurd; but we actually find a transverse ridge running

along the dorso-ventral axis of the joint face, with on

either side of it a dorsal ligament bundle, in every way

the same as the dorsal ligament bundle of the preceding

straight muscular articulation. The synarthry, then,

appears to consist fundamentally of the dorsal ligaments

of two straight muscular articulations, abutting upon a

common transverse ridge, which is at right angles to the

transverse ridge of the preceding straight muscular

articulation (Figs. 3 and 4). Not only does the nid

scopical comparison of the two individual muscle bundles

of the synarthry with the dorsal ligament bundle of the

straight muscular articulation bear out this interpreta- = i

tion of the origin of the synarthry, but the morphological a

effect of the synarthy upon the arm structure is at once

explained. Non-muscular articulations never bear r :

No. 514] ARTICULATIONS OF CRINOIDS 583

nules; pinnules are borne upon the muscular fosse of

muscular articulations; in the projection of one straight

muscular articulation upon another to form the synarthry,

the interarticular ligaments and the muscles are cut out,

and only the dorsal ligament remains; with the elimina-

tion of the muscular fosse, the pinnule sockets are lost;

hence, synarthries can never bear pinnules, as the pin-

nule-bearing element of the articular face is omitted from

their composition. Synarthries never affect the pinnula-

tion; if a pinnule be borne on the left side of a straight

muscular articulation preceding a synarthry, the pinnule

on the next succeeding straight muscular articulation will

invariably be upon the right side. A synarthry is pri-

marily composed of two coalesced succeeding muscular

articulations, one of which potentially bears a pinnule

upon the opposite side from that of the other; these two

primitive elements of the synarthry, being of exactly op-

posite tendencies in respect to their pinnules, counteract

each other upon being merged, and hence we find the syn-

arthry neutral in regard to pinnule arrangement; the

synarthry possessing primarily (morphologically) two

pinnules, the next following muscular articulation has its

pinnule thrown to the opposite side of the arm from that

on the muscular articulation preceding. Thus a syn-

arthry, in reality, instead of having no effect upon the

pinnule arrangement, has a double effect (though with

the same result), throwing the pinnule to one side of the

arm and back again within the compass of a single

articulation.

Muscular articulations are frequently doubled, thus

forming an axillary from which two similar arms arise;

synarthries are never doubled; they are already double

articulations, and a further doubling would be equivalent

to a quadrupling of muscular articulations.

The syzygy is different from the synarthry only be-

cause it is formed from two oblique instead of straight

muscular articulations (Figs. 9 and 10). A rotation a

a straight muscular articulation through 90° brings we

584 THE AMERICAN NATURALIST [Von XLII

transverse ridge into the dorso-ventral axis; hence, the

transverse ridges of the two: primitive straight muscular

articulations coincide, and remain unchanged in the re-

sultant synarthry; a rotation of two succeeding oblique

muscular articulations 90° will, as their transverse ridges

are already at right angles to each other, keep them in

the same relative position; projecting one of them upon

the other, the two transverse ridges form a right-angled

eross; since the muscles and interarticular ligaments, be-

ing recessive when compared with the dominant dorsal lig-

ament, disappear, we get an articulation consisting of a

mass of dorsal ligament fiber crossed by radiating ridges.

This crossing of the two fulera upon a single joint face

effectually prevents any movement at the articulation,

and thus we get the primitive syzygy. The multiplica-

tion of the radiating ridges is without doubt a secondary

development, though possibly four of them represent the

distal edges of the interarticular ligament fosse. The

interpretation of a syzygy as a combination of the liga-

ments of two oblique muscular articulations explains the

uniformly single condition of the syzygy, the absence of

pinnules, and the neutrality of the syzygy in regard to

pinnulation, this being brought about in the same way

as in the synarthry, the resultant of two straight mus-

cular articulations.

The interpretation of synarthries and syzygies just

proposed involves a doubling up and merging together

of the elements of two muscular articulations. This, it

might well be argued, would be an occurrence improbable

in the extreme in a linear series of joints and articula-

tions. The ambulacral system of echinoderms, however,

is composed primarily of a double series of joints, plates

or whatever the elements may be, the first element alone

being single. Thus in the urchins the oculars stand at

the head of the double row of plates composing the

ambulacra; and in the crinoids the radials stand at the

end of an ambulacral system composed, in many genera,

of two rows of plates, side by side, in biserial arrange —

No. 514] ARTICULATIONS OF CRINOIDS 585

ment. The similarity is even more striking; in the

urchins new plates are added only between the ocular and

the next succeeding plate, and it has been urged that the

addition of new plates only at the ends of the arms in

crinoids constitutes an important morphological differ-

ence between the ambulacral systems of the two groups.

I have recently shown, however, that in almost all the

recent crinoids (and similarly in many of the fossils)

plates are added between the radials and next following

joints (interpolated division series) just as in the urchins;

the process of interpolation is different, but the result is

morphologically identical in the two cases. J. S. Miller

in 1821 first called attention to the similarity of a crinoid

to an inverted Cidaris, but I believe the resemblance be-

tween the ambulacral systems of the two are closer and

more fundamental than was supposed either by Lovén

or by Carpenter. All the recent and most of the fossil

erinoids have uniserial arms, but the brachials are always,

at least in the proximal third of the arm, triangular or

obliquely wedge shaped, a condition which is most pro-

nounced in the young. Now, applying Jackson’s law of

‘‘localized stages,” we may assume in the crinoid arm

that the joints which are ontogenetically the oldest are

phylogenetically the oldest also; and we should thus be

led to look for ancestral characters toward the arm bases.

Here we find joints much more triangular than farther

out, the distal and proximal ends being very oblique;

hence we should infer an ancestry of forms with sharply

triangular brachials; but certain comatulids go even far-

ther in the proximal third of the arm, the brachials hav-

ing borders so oblique that the inner apices of the tri-

angles do not reach to the opposite border of the arm.

Judging from recent forms alone, then (to say nothing

of the fossils), we are irresistibly led to the conclusion

that the biserial condition is the fundamental condition

of the crinoid arm, just as the double row of ambulacral

plates is the fundamental condition in the urchins, and a

that the monoserial arrangement is purely secondary, ae

536 THE AMERICAN NATURALIST [Von XLII

an adaptation to special conditions of existence. The

change from a biserial to a monoserial arrangement in

the crinoids is merely a matter of an elongation of the

arm, and a slipping in of the joints in one series between

those of the other (Fig. 9). It has been suggested that

Encrinus, Platycrinus and the other biserial crinoid

genera are derived from monoserial ancestors because the

new joints as they are formed at the arm tip are always

monoserial in arrangement; but apart from the mechan-

ical difficulties in the way of biserial termination to a

free arm like that of the crinoids, we find that almost the

same is true in the urchins; plates are added one by one

abutting upon the median ambulacral line just behind the

oculars, which move out by lateral growth first to one side

then to the other, just as the monoserial plates at the tip

of a Platycrinus or Encrinus arm, on increasing in size,

more laterally first to one series, then to the other; the

supposedly, monoserial tip in biserial crinoid genera,

therefore, appears to be, in reality not monoserial at all,-

any more than the proximal (post ocular) portion of the

ambulacra in the urchins is monoserial.

The slipping in of the two series of joints in the

biserial crinoid arm in the transition from a biserial to a

monoserial condition undoubtedly first gave rise to syn-

arthries and syzygies, the former originating from the

coalescence of two straight muscular articulations, the

latter from the coalescence of two oblique muscular

articulations. I have been unable to study the joint faces

of crinoids of the biserial type, and therefore have not

traced the process, but, judging from the data at hand

there seems to be much in favor of such an origin for

spnarthries and for syzygies, and I hope to be able to

adduce additional evidence in support of it in the future.

A study of the ontogeny of Antedon does not help us, —

for in that type the synarthry and the syzygy are onto- .

genetically older than the beginnings of the deposition

of calcareous matter, and the synarthry between the first

two postradial joints is ontologically nearly or quite as

No. 514] ARTICULATIONS OF CRINOIDS 587

old as the phylogenetically much more primitive straight

muscular articulation between the radial and the first

postradial joint, and ontologically older than the straight

muscular articulation succeeding it. Neither can we

hope for any light when we know the embryology of the

Pentacrinitidx, for the early stages of the Pentacrinitide

are undoubtedly practically the same as those of the

comatulids, the orly tangible difference in the adults

being an enormous increase in the number of the short

discoidal joints occurring at the top of the Antedon stem,

and (of secondary importance) the retention of the stem.

I have only been able to examine a very few fossils in

regard to the interbrachial articulations; the results of

my study of Vintacrinus have already been published;

Pentacrinites (‘‘Extracrinus’’) is exactly like Isocrinus

(restricted, i. e., excluding Endoxocrinus) except for the

small detail of the heterotomous instead of dichotomous

condition of the extraneous division series, and Mar-

- supites is exactly like Antedon, even in the position of

the proximal syzygies; but I am convinced that a detailed

and careful study of the articulations and articular faces

of the joints in the fossil crinoids is one of the best lines

of procedure in the elucidation of their systematic

relations.

ON SOME DINICHTHYID ARMOR PLATES

FROM THE MARCELLUS SHALE

BURNETT SMITH

SYRACUSE UNIVERSITY

INTRODUCTION

Toven Devonian beds in many parts of the world fre-

quently furnish an abundance of piscine fossils, this is

not the case with their cotemporaneous deposits of the

state of New York. In this region every bit of evidence

which may add to our knowledge of the anatomy, geo-

graphical distribution and geological range of the

Devonian members of the class may at any time become

of interest, for amid profuse invertebrate faunas the fish

remains are usually rare, inconspicuous and fragmentary.

It is, therefore, believed that a recent find of the com- .

plete ventral armor! (together with some other bones)

of a small species of Dinichthys is worthy of some notice

in spite of the fact that the preservation leaves much to

be desired and also that any interpretations based on the

material are apt to prove untenable when more complete

and more perfectly preserved specimens are brought to

light.

DESCRIPTION OF THE FIGURES

The specimen in question came from the concretion

zone of the Marcellus Shale in the vicinity of Syracuse,

N. Y., and was collected by the writer in the summer of

1908. Its geological horizon is not determinable with

absolute certainty, but it lies not far (within fifteen feet

at most) above the top of the Agoniatites Limestone,

which in this section is itself confined to the lower fifteen

* The writer must express his indebtedness to Dr. Louis Hussakof and to

Dr. Charles R. Eastman, both of whom generously examined the photo-

graphs of this specimen and gave him invaluable assistance in the inter-

pretation of its osteology. `

588

No. 514] DINICHTHYID ARMOR PLATES 589

or twenty feet of the Marcellus Shale formation. The

geological position of the specimen together with its size

and the character of its external ornamentation points

strongly to its identity with Dinichthys halmodeus

(Clarke).? It is realized perfectly that this identification

may prove incorrect but for purposes of convenience the

specimen will throughout this paper be considered as

belonging to that species.

The fossil occurs as a probable nucleus for one of the

large concretions, though its position in the mass is ex-

central. It has been laid bare by the removal of a part

of the concretion and apparently has been subjected to

weathering for a considerable time. This has resulted

in the loss of nearly all of the external ornament, only

one or two small patches of bone exhibiting the super-

ficial tuberculation. How much of the skeleton has dis-

appeared with the missing portion of the concretion it

is impossible to say, for diligent search has failed to

reveal its presence in the immediate neighborhood.

The concretions at this horizon are crossed by at least

two sets of irregular planes of fracture which have been

infiltrated with barite, calcite and other minerals. We,

therefore, have (1) lines crossing the specimen which are

incident to the formation of the concretion itself, (2) lines

of fracture in the fossil which are independent of struc-

tural features and (3) the lines which mark the bound-

aries of the different bones. This fact is mentioned here

in order to call attention to the many lines in the accom-

panying photograph (Fig. 1) which must be distin-

guished from those which represent organic structures.

As stated before, the parts preserved are: (1) the

nearly complete ventral armor with its elements in nat-

ural association and (2) other scattered bones among

which a postero-dorsolateral and an antero-dorsolateral

stand out conspicuously (see Figs. 1 and 2).

The Ventral Shield.—In the median region the antero-

*Coccosteus (1) halmodeus Clarke. John M. Clarke. New and Rare —

Species of Fossils from the Horizons of the Livonia Salt Shaft. Report

State Geologist, N. Y., 1893, p. 161. o Ce

590 THE AMERICAN NATURALIST [Vou. XLIII

ventromedian is well preserved posteriorly, but its an-

terior portion has been broken away. ‘The impression

of this missing part is, however, well preserved on the

surface of the matrix and there is no difficulty in restor-

ing the outline of this plate on its forward margin.

Posteriorly it meets the postero-ventromedian, the limits

Fic. 1. Dinichthys halmodeus (?) (Clarke oe a retouched)

of eg ventral shield with associated bones. a long he elliptical

surface on which the specimen is exposed measures about ey cm.

of the two plates being indicated by a curved line whose

convex side is directed forward. The postero-ventro-

median is clearly outlined, though its surface has been

considerably crushed. The antero-ventrolaterals border

the two median plates on either side. It is impossible

No. 514] DINICHTHYID ARMOR PLATES 591

to make out the exact limits of their inner margins on

account of the weathering to which they have been sub-

jected. They lie in a plane higher (more ventral anatom-

ically) than the median plates and undoubtedly over-

lapped them slightly. On the posterior lateral borders

Fic. 2. D. halmodeus (?) (Clarke). Drawing made a of

the photograph shown in Fig. 1. AVM, antero-ventromedian; PVM, postero- .

ventromedian; AVL, antero-ventrolateral ; PYL, postero-ventrolateral ; PDL,

postero-dorsolateral ; ih ero-dorsolateral ; L suborbital?; 2, antero-super-

ognathal?; 3, possibly a pda of the dorsomedian.

of the postero-ventromedian lie the two postero-ventro-

laterals. The inner margins of these ons are also hard

to delimit. They were overlapped by the osteo -o

laterals, for they lie at a lower (ana

plane. The inner nargis of all four ¢

592 THE AMERICAN NATURALIST [Vou. XLIII

are believed to have been broken or to have weathered

away. If this is the case we have exposed the actual lat-

eral outlines of the two median plates. The shape of the

entire ventral shield is quite accurately indicated by the

outer margins of its constituent plates in spite of fractur-

ing and some displacement. The left antero-ventrolateral

still retains a small patch of the exterior surface showing

a tuberculation similar to that of a Dinicthyid cranium

from Manlius, N. Y., which has been referred by Eastman

to D. halmodeus. A few obscure tubercles are also

present on the left postero-ventrolateral. As exhibited

in this specimen the two median plates appear to be quite

flat. The antero-ventrolaterals are much crushed, but

apparently were slightly convex on their ventral surfaces.

The postero-ventrolaterals show convexity on their outer

or ventral surfaces.

Bones without the Ventral Shield.—The most con-

spicuous of these are the postero-dorsolateral and the

antero-dorsolateral. The former of these is flat, and

though it is much weathered, it appears to furnish us

with about the outline of the original plate. The latter

is decidedly convex and though much weathered it shows

the articular projection and the canal.

Above (forward of) the ventral shield is a confused

mass of bones, some of them exhibiting sharp tooth-like

denticles, while beyond this again is another poorly pre-

served antero-dorsolateral exhibiting both the canal and

the articular projection. No cranial plates can be made

out with certainty, though the bone marked 1 in Fig. 2

might be interpreted as a suborbital, while at 2 is a bone

suggesting an antero-supero-gnathal.

CoMPARISON WITH OTHER SPECIMENS

As far as the author knows, only two other specimens

of Dinichthys with the ventral armor plates in natura

association have been recorded. The first specimen was

"N. Y. State Museum Memoir, 10, p. 128, pl. 10.

No. 514] DINICHTHYID ARMOR PLATES 593

described by Von Koenent and referred with doubt to

D. minor. In this case the material was too poorly pre-

served to admit of the exact determination of the dif-

ferent bones. In the second specimen the preservation

is quite satisfactory and we are indebted to Dr. Eastman®

for its description. He has referred it tentatively to

$ 1, restoration of the ventral shield of Coccosteus decipiens Ag.

(modified from Smith Woodward). 2, restoration of the ventral shield of

Dinichthys halmodeus (?) (Clarke), no attempt being made to indicate overlap.

3, restoration of the ventral shield of D. newberryi (?) Clarke (after Eastman).

Bones lettered as in Fig. 2.

D. newberryi Clarke. This latter example shows all six

of the ventral plates but little removed from the original

position. In his restoration Dr. Eastman illustrates

the conditions of overlap and brings the bones into the

positions which it is believed they occupied in life.

Comparing now (Fig. 3) the restoration of D. new-

berryi (2) with that here regarded as D. halmodeus it

will be seen that in each case the antero-ventrolateral

overlaps the postero-ventrolateral and that all four

ventro-laterals overlap the two median plates. When,

however, the relations of the two medians are considered

we are unable to carry the comparison farther. In D.

‘A. von Koenen. Ueber einige Fischreste des norddeutschen und

böhmischen Devons. Abhandl. K. Gesell. Wissensch. Göttingen, Vol. XL,

pp- 1-37, Plates I-IV, 1895. ;

°C. R. Ea On the Relation of Certain Plates in

Bull. Mus. Comp. Zool. Harvard, Vol. XXXI, October, 1897, pp- 26 ant M, oe

Plate I, fig. 2 and Plate IV.

594 THE AMERICAN NATURALIST [Vou. XLII

newberryi (?) the antero-ventromedian overlaps the

postero-ventromedian. In the present specimen we can

not prove that some overlap did not occur, for the point

of junction is much eroded. We can, however, say that

no such overlap is indicated and that the two plates

appear to be separated by a thin curved suture which

is convex anteriorly and concave posteriorly.

When the postero-ventrolaterals are compared with

those of D. newberryi (?) the general outlines and pro-

portions exhibit great similarity, but this is not the case

with the antero-ventrolaterals. In these plates not only

is there an apparent difference in the posterior over-

lapping margins, but the anterior lateral projection is

turned posteriorly and not anteriorly as in D. newberryi

(?). This gives the entire front margin of the ventral

shield an evenly convex outline quite different from the

bow-shaped line shown by D. newberryi (?) and in Hussa-

kof’s® restoration of D. curtus. As a whole the ventral

shield exhibits general relations of length to breadth not

unlike that of D. newberryi (?) but is proportionately

much broader and stouter than the restored plastron of

D. curtus to which reference has been made.

COMPARISON WITH CoccosTEUS

All authorities on the Arthrodira have united in as-

signing to Dinichthys halmodeus a primitive position

among American Dinichthyids and the species is re-

garded as having diverged only slightly from the an-

cestral genus Coccosteus. These relationships have been

made out by studies`on the cranium, the infero-gnathals —

and on the dorsal body plates.

If then the specimen here considered is indeed specif- T

ically identical with D. halmodeus we have further con-

firmation of the practically intermediate position which - ae

the species holds between Coccosteus on the one hand 4

and the highly specialized species of Dinichthys on the

other. |

*L. Hussakof. On the Structure of Two Imperfectly Known Dine

thyids. Bull. Am. Mus. Nat. Hist., Vol. XXI, Art. XXV, p. 412.

No. 514] DINICHTHYID ARMOR PLATES 595

That the ventral armor of the present specimen be-

longed to a primitive type is shown: (1) by the fact that

the antero-ventromedian and postero-ventromedian are

not fused as in such specialized forms as D. terrelli’ and

(2) by the fact that the anterior lateral angles of the.

antero-ventrolaterals are directed posteriorly giving this

portion of the ventral shield an outline similar to that of

Coccosteus (see Fig. 3).

The fact that the antero- and postero-ventromedians are

united by suture and not merely touching or even sepa-

rate shows an advance from the condition of these ele-

ments in Coccosteus, but taking the sum of the char-

acters in the ventral shield we have, on the whole, a

closer approximation to this latter genus than to

Dinichthys.

DISTRIBUTION oF DINICHTHYS IN THE New York PROVINCE

In his recent memoirs Dr. Eastman lists eight species

of Dinichthys as occurring in the Devonian of the New

York-Pennsylvania Province. Of these six are confined

to the upper Devonian, that is, they are found only above

the top of the Hamilton shales. Of these, three at least

are common to both the New York-Pennsylvania and the

Ohio province, while three appear to be restricted to the

New York-Pennsylvania province. The Middle Devonian

yields but two definite species, D. lincolni Claypole and

D. halmodeus (Clarke). Both are, as far as known,

restricted to the Marcellus division of the Middle De-

vonian, D. lincolni is known by a single tooth found in

the upper part of the Marcellus Shale twenty-five feet

below the basal limestone of the Hamilton. D. halmodeus

is, according to the same authority, known by three speci-

mens: (1) the type cranium, (2) a dorsomedian plate asso-

ciated with the type cranium and possibly belonging to

_ the same individual and (3) a cranial fragment. The

"See Hussakof’s figures, Mem. Am. Mus. Nat. Hist, Vol. IX, pt. IE,

N. Y. State Mus. Mem., 10, 1907.

596 : THE AMERICAN NATURALIST [Vou. XLII

type material is reported by its original describer as

having come from the Livonia salt shaft, Livingston

County, N. Y., and its geological horizon is about forty

feet above the base of the Marcellus Shale. It lies just

below the Stafford Limestone bed of the Marcellus in a

black shale and its associates make a typically Marcellus

assemblage. Among them are such invertebrates as

Orthoceras subulatum, Styliolina fissurella, Chonetes

mucronatus, Leiopteria levis and Leiorhynchus limi-

taris? The cranial fragment figured by Dr. Eastman’?

is reported as having come from the Agoniatites Lime-

stone, Hendrick’s Ledge, west of Manlius, Onondaga

County, N. Y. :

The Agoniatites Limestone in Onondaga County lies

about thirteen feet above the base of the Marcellus forma-

tion, is about two and one half feet thick and is both

underlaid and overlaid by the black friable Marcellus

shales.1! The specimen which has been the subject of

this brief paper was found in a limy concretion from the

upper black shale above the Agoniatites Limestone and

probably within ten feet of it. At this point both the ~-

shales and the concretions are alike very poor in fossi's,

none having been found in the shale and a single Ichthyo-

dorulite being the only yield from an examination of

many other concretions.

From the evidence of stratigraphy it appears that the

limestone lentils of the Marcellus shales are the expres-

sions of changing geographical conditions and invading

faunas.‘ They are not everywhere at the same geolog-

ical horizons with relation to the base of the Marcellus,

and as they represent iavasions the limestone in one

locality may be cotemporaneous with shale in a different

Dp ates Report on the Livonia Salt Shaft. Rep. State Geol.

N. Y., 1893, p. 8

w New York ae Mus. Mem., 10, pl. 10. :

“John M. Clarke. Mavediiua tes ee of Central and Western New Ž

York and their Faunas. N. Y. State Mus. Bull., -

N. Y. State Mus. Bull., 82, p. 43. The Agoniatites Limestone does

not lie between the Wareeli and Cardiff shales as Dr. Eastman has n

advertently stated on p. 129, N. Y. State Mus. Mem., 10.

No. 514] DINICHTHYID ARMOR PLATES 597

locality. These limestones then give us the history of

areas in the old Marcellus sea which were covered from

time to time by invading faunas. It is natural therefore

that we should find a species of Dinichthys probably one

of the most mobile animals of the time associated: (1)

in one locality with the large cephalopods of the Agoni-

atites Limestone, (2) in another with the small brachio-

pods and pelecypods of the typical black shale and prob-

ably not far from an area occupied by the Stafford fauna

and (3) in the unfossiliferous black shale from which

the present specimen came.

In his paper cited above Dr. Clarke brings out evidence

to show that the Agoniatites Limestone and some of the

lower Marcellus black shale in central and eastern New

York is the time equivalent of some of the upper Onon-

daga of the western portion of the state. This lends a

peculiar interest to the Onondaga County specimens of

D. halmodeus which coming as they do from the lower

Marcellus lived in a muddy portion of the great New

York embayment at no great distance from an area to the

west in which Onondaga Limestone conditions prevailed.

It is therefore not unreasonable to expect that D. hal-

modeus or some very closely related form may in time

be found in the upper Onondaga deposits of this latter

region.

ARE SPECIES REALITIES OR CONCEPTS ONLY?

PROFESSOR J. H. POWERS

UNIVERSITY OF NEBRASKA

In the American Naturauist for April, 1908, there ap-

peared the reprint of some remarkable papers, consti-

tuting a symposium by the greater botanists of the

country on ‘‘Some Aspects of the Species Question.’’

The attitudes taken toward questions of the nature and

reality of species were, on the whole, tentative and ques-

tioning. But the opening paper presents, with the utmost

lucidity and startling positiveness, a definite conception

as to the nature of species: ‘‘Species have no actual ex-

istence in nature.’’ They are not realities. Individuals

alone are real. Species are concepts only, concepts

framed by the human mind, and arbitrarily framed

withal, for no better reason than its own convenience.

Species are compared to spoons, made to fit the human

mouth, or the mouth of Linnezus; and until it can be dem-

onstrated—so runs tke argument—that this organ has

departed appreciably from the typical oral aperture of

the great Swede, so long must we continue to fashion our

species-spoon-concepts to the exact dimensions of his

model.

Now these views, although not wholly new, were a sur-

prise to the writer, both in themselves, in the extremity

of their statement and still more in the high authority by

which they were supported. Do such things still happen

in the botanical world? he queried. Surely no zoologist

would for a moment, ete. But hold! ‘Another Aspect

of the Species Question,’’? by a zoologist this time, and

containing the duplicate assertion that many zoologists, :

‘‘long since reached a satisfactory solution of the species _

a y ST from the Zoological Laboratory of the University of N ebraska,

* By Dr. J. A. Allen, Naruratist for September, 1908.

598

No. 514] ` ARE SPECIES REALITIES? 599

question by recognition of the fact that species . . . have

no real existence, but are merely man-made concepts,

purely arbitrary and conventional.’

Is this the dictum of biological science to-day? This

by-product of early triumphant Darwinism, with the fear

of special creation still upon it, this handy postulate of

the sorters of dried birdskins and dried plants, eager to

affix tag and title to the whole fauna and flora of a conti-

nent—is this the last word of science? Or is it even the

limit toward which we are tending? To the writer the

reply is unhesitatingly in the negative.

But how refute this proposition of the unreality of

species? What reasons have been offered to support it?

Unfortunately none. Often suggested in the past, it has

been suggested only, and it is now put forward as a self-

evident proposition, heavily weighted with authority in

lieu of evidence.

Forced by my interest in the subject I have been obliged

myself to seek the evidence on both sides of the propo-

sition. I can find but two possible reasons, or rather

causes, why species are, or may be, thought unreal. These

I wish to state and analyze briefly. Be it fully stated

here, however, that I do not for a moment impute these

reasons to the minds of scientists whose view of species

I am calling into controversy. I find it very difficult to

imagine what considerations may have influenced them to

the adoption of an hypothesis which seems to me not only

fundamentally incorrect but highly injurious to scientific

thought and experimentation. I simply assert that, after

years of consideration, I can find no other causes for such

an assumption and I deem the setting forth of the error

in these a useful piece of work.

First of all, then, I think that the unreality of species

is frequently assumed, at least by young and careless

thinkers, because of what I will term lapses into un-

critical, child consciousness. This seems a hard saying,

and yet nothing is easier than to fall back into methods of

thought which we know to be erroneous, but which, just

at the times when we feel most certain of ourselves, creep

600 THE AMERICAN NATURALIST (Von. XLII

back upon us because they are the ingrained methods of

early uncritical experience.

Now the concept of species is roughly equivalent to the

concept of kind and this is acquired very early in life.

‘ What’s ’at?’’ asks the child, pointing perhaps to its

first sharply perceived bird, a robin, say, in the grass.

“That’s a bird, Johnny,—that’s a robin.’’

‘What’s bird? What’s robin?’’

‘‘Why a bird is a thing with feathers and wings and

that flies. And a robin is a kind of bird. There is a

whole lot of them alike, with red on their breasts like that

one, and that makes one kind; that makes them robins.’’

By such experience, such questions and such replies,

rapidly extended, the child soon learns the meaning of the

word ‘‘kind” as it is applied to living things, and later,

he transfers this meaning, only a little sharpened, to the

word ‘‘species.’’ .

But those of us who have formed and retained the habit

of reviewing our childhood thinking know that these

meanings, these concepts of kinds, never seemed wholly

real to us as children, and this simply because the objects

of them were not wholly perceived. This or that kind of

bird, as a group, a totality, a whole, was a great vague

somewhat, fading out on all sides where it transcended

our actual experience; it was luminous only in the center

where actual experience and memory kept is partially

real. The child ascribes reality to perception, and only

semireality to conception. But slowly, in adult life, do

we partially free ourselves of the sense of unreality in

the objects of our conceptual thought.

In science, however, we certainly should and do learn to

test, judge and finally affirm the realities back of our con-

cepts, as well as back of our percepts and simple memory

images. We know that unvisited foreign countries are no

less real than our own, despite their shadowy vagueness

ın conception. We ascribe exactly the same reality to —

the surface of the earth at the south pole that we do to —

that under our feet, despite that it has never been per-

ceived by man. More still, plurality, multiplicity, per-

No. 514] ARE SPECIES REALITIES? 601

plexing as they are to perception and imagination, do not

deter us from the ascription of full reality to aggregates.

A forest is not less real than a single tree; a swarm of

bees is as circumscribed a reality as a single insect. The

fauna or flora of an entire continent is surely conceived

as a definite objective reality as much as though it were

the smallest, the most homogeneous of units. The solar

system is a reality as truly as is a single planet; the

planet as truly as is the dewdrop; the dewdrop as truly,

nay, more truly than is the atom.

I say that in adult life, and especially after thorough

scientific training, we correct the naive error of ascribing

reality only to that which is obviously a unit or which has

been vividly perceived. But I deem that, beyond ques-

tion, we are frequently subject to lapses in our thought,

lapses into the child consciousness in which the unitary

object of perception seems to us the only true reality.

The truth is that if species are denied reality because

they are pluralities instead of units, individuals have

absolutely no right to a better status. Individuals are

pluralities. We may recall President Jordan’s humorous

refutation of Descartes’s celebrated maxim: I think

therefore I am. Descartes, said Jordan, had no right to

consider himself a unity; he had no right to the singular

pronoun. Descartes was an aggregate of cells; these are

the active units. He must at least have said: we think,

therefore, we are. ‘

Of course the cells, too, are not really units, but again,

are aggregates,—nay, they are aggregates of aggregates

of aggregates of aggregates at least; they are, moreover,

in all probability, quite as fluctuating aggregates as 1s a

whole species; so that, finally, if unity is to be the test of

reality, the atom itself, or the electron, withal, is abso-

lutely the only reality with which science has to deal.

But alas for even this bed rock of reality. It, too, is not

even good sand. For scientific theorists tell us, and un-

doubtedly with truth, that atoms and electrons are purely

imaginary creations, hypothetical x’s only, by means of a

which we steady our thought while deciphering the se

602 THE AMERICAN NATURALIST [Vou. XLIII

quences of phenomena. Thus the quest for reality along

the road of unity lands us in a complete reductio ad ab-

surdum, acceptable possibly to some metaphysicians, but

utterly repugnant to the clarified common sense of

science.

If this line of thought as to the status of the individual

and the species seems unprofitable or pressed too far for

the taste of many, let us return to a closely related but

more practical consideration which is now a live factor

in several working lines of biological science. I refer

to the fact that individuals are not units in another sense,

—the sense, viz: that they have complex life-histories,

and must be so thought of and so spoken of if they are to

be treated in a scientific as opposed to a popular sense.

An individual animal or plant is not a static but a dynamic

thing. It does not all exist at any one time, but exists

only as a series or succession of stages, bound together

by physical continuity and causation, each preceding stage

being an indispensable condition of the next. We can not,

thus, by any possibility, handle and ‘‘sort’’ individuals.

We can not even perceive them by a simple perceptive

process. All we handle, sort or recognize is specimens;

but these, dead or alive, are but fractions of individuals,

signs or suggestions of individuals—non-existent at the

moment—but which we then proceed to build up in

thought by a long process of that same conceptual nature

which we use in arriving at our knowledge of species.

If any one is disposed to gainsay this assertion then

let him reply to the question: which, or what, is an indi-

vidual insect? Is it the fertilized egg or some embryonic

stage, some younger or older larva?—is it the pupa or the

imago? Possibly some one may reply, ‘‘the imago; this

is at least the adult individual, and the only reality neces- _

sarily considered in dealing with species.” But this is

surely an unscientific position to hold at the present time,

even with regard to the insect; while, if we shift our at-

tention to certain other groups of animals, where growth ;

and to some extent morphological change persist through-

out life, even the momentary suggestion of a fixed, stable

No. 514] ARE SPECIES REALITIES? 603

“adult individual ’”’ leaves us. The common assumption

that there is a fixed, or at least a typical adult state is

often more assumption than fact, or if partially true, due

to the accident of constant average environmental con-

ditions. Thus the writer was astonished to find that an

adult salamander, tallying with every character of the

‘“typical individual’’ would yet, under favorable environ-

ment, betake itself to a new period of development and,

larva like, issue therefrom so changed in its supposedly

fixed characters of adulthood that nothing short of con-

tinuous observation could convince one of its individual

identity, or rather continuity with the former phases of

itself. To know individuals, then, means to know life-

histories. To know life-histories means to save and sift

our perceptual experience, and to solidify it, little by

little, into concepts quite as complex as are those in and

through which we know species themselves.

Yet it is admitted that individuals are real, despite this

fact that they are made up of phase on phase of shifting

though correlated characters, only a part of which we can

ever perceive. Why then not admit that species are real?

Are they not, likewise, groups of interrelated units (units

in the practical working sense of this word)? Are not

these units—the individuals—bound together by a com-

mon genesis as truly as are the cells of the individual’s

body? Are not these individuals further united by com-

mon interactions—sexual and otherwise—between each

other, and between themselves and a common environ-

ment? Variable criteria all, it is true, but yet assuredly

real criteria. |

But with these last expressions we have in reality

passed to another phase of the subject—from the means

by which we know species to the nature of species them-

selves, and some may well have thought that this transi-

tion should have been made immediately. Few, it may be

said, are child-like enough to deem species unreal because

they are plural and but partially perceived; few are 50-

herbarium-driėd, so museum-minded, in thought as to con-

fuse specimens with individuals and deem

604 THE AMERICAN NATURALIST [Von XLII

because they may easily be seen and handled. The true

reason why some deny reality to species lies, it may be

said, not in the nature of our knowledge, but in the nature

of the groups of objects which we conveniently pit

as species.

Species, it may be stated, are not sharply delimited

groups of individuals; species pass into each other and

into varieties by insensible gradations. Species are not

permanent but transient assemblages of individuals; spe-

cies change as environment changes. In short, an exag-

gerated Darwinistic conception of the nature and origin

of specific groups may be advanced as a reason for deny-

ing them full objective reality. We all know Darwin’s

conception of species, as accentuated varieties, which

were in turn due to accentuation and multiplication of

individual differences. Genera, too, he viewed as over-

grown species, in which variation and extinction, together

with other less obvious causal factors, had led to segre-

gation into minor groups, now, in their turn become

species. Species were expanded varieties; genera ex-

panded species.

But certainly this view did not imply, in Darwin’s own

mind, the non-existence, the unreality of species in nature;

though it did imply their derivation by ‘intermediate

stages, one from another. If we recall his work definitely

we shall remember that he found it necessary to introduce

a long and labored analysis to account for the very fact

of the sharp segregation between allied species—how it

was that characters diverged and genera became broken

_ Into compact and contrasting groups rather than remain-

ing a sheer chaos of connected and interlacing forms.

In short, if species are not realities, what aberration of

intellect led Darwin to work twenty years collecting facts

as to their origin? If species are ‘‘concepts only,” why

did he go to sheep-breeders for light on their nature and

genesis instead of to logicians and psychologists? It 18

these latter who tell us of the nature and origin of con-

cepts. Why did not Darwin entitle his work, ‘‘The Non-

existence of Species??? :

No. 514] ARE SPECIES REALITIES? 605

But we have progressed since Darwin, it may be said.

I hope we have a little. But have we or have we not pro-

gressed toward a conception of animate nature as a chaos

of such seething instability that distinctions are essen-

tially arbitrary and boundary lines between groups of

forms to be drawn only at the pleasure of the individual

with due reference to high authority and venerable tra-

dition? Until I read the luminous article of the leader of

the aforesaid symposium I had certainly thought not. I

had been led to believe that we were progressing, all in

all, in the opposite direction.

I lay claim to no particular knowledge of things bo-

tanical. I know there are certain genera of plants where

specific and varietal characters are much confused and

very possibly undifferentiated. Definite species may in

such cases be very possibly undeveloped or degenerate,

and therefore non-existent. I remember that in my her-

barium days I wondered that botanists would carry their

system through, whether or no, and describe species

where they themselves plainly doubted their reality. It

seemed to me this was following the final advice of the

Devil in Faust and building systems of words without

meaning. I little dreamed, however, that they would ever

go so far as to defend the whole Mephistophelean hypoth-

esis of an essentially arbitrary system of words without

objective validity.

Surely some botanists are feeling their way far from

this conclusion, when, as for example De Vries, after half

a life time of experimentation, formulates a theory of

species which is not only that of a real thing in nature, but

approaches in definiteness and demarcation to the con-

ception of a chemical compound. Species, for De Vries,

are almost chemical compounds. Are chemical com-

pounds—chemical species, so to speak—are they realities,

or are they too concepts only? |

When I began this paper I had in mind to employ the

majority of my space in the presentation and analysis of :

facts concerning a few species with which I have worked =

personally and which have been chosen with definite re-

606 THE AMERICAN NATURALIST [Vou XLII

gard to the matter of the light they might throw on the

nature and origin, and consequently upon the reality or

non-reality, of species. But the brief space remaining will

permit scarce a reference to them. Moreover, single in- —

stances in biological fields can never prove general laws;

they can, at most, illustrate them and prepare our minds

for wider proof.

Let us look for a moment, however, at the group of little

animals known as Hydra. Linneus, with his long spoon,

swallowed the whole genus at a gulp. He knew there

were differences, as his description shows, but he called

all by the one binomial, Hydra polypus. Soon, however,

zoologists became convinced that Linnæus had been eating

too fast. There were more species than one. But how

many? Even yet unanimity has not been reached. Does

this constitute an argument for the unreality or for the

conventionality of species? In truth it does not. The

genus Hydra has never been fully investigated. Inter-

minable discussions of the undecipherable problems of

priority have not been lacking; some good observations,

and, much more to the point, some good culture experi-

ments have been made. But year-long, controlled an

pedigreed cultures are required, cultures successfully car-

ried through sexual as well as asexual phases. Had these

been carried out, as I trust they have been by the writer,

the truth of the conclusion would have been amply demon-

strated, that we have within the genus Hydra (whether

or not we shall ever be able to name them) a number of —

highly autonomous aggregates of individuals, separated,

the one from the other, by a large number of minute but |

highly constant differences. These groups are such, as

are commonly and appropriately called species, despite

the fact that the ordinary student with the collecting

_ bottle may be unable to distinguish them. To deny them

reality or treat their systematic segregation as a matter

of convention only is as inappropriate, because as untrue

to the facts, as to deny the reality of any and all distinc-

tions in nature. —

Certain of these differential characters are of speci

No. 514] ARE SPECIES REALITIES? 607

interest in connection with the problem of the separate-

ness of species. Thus two of these groups that outwardly

resemble each other the most, and whose distinctness is

still doubted by some eminent zoologists, prove, under

examination with modern technique, to be possessed of

extraordinary histological differences. Hardly may we

find in the whole mammalian series corresponding types

of cells showing so fundamental differences in structure

as are shown by the cnidoblasts of the two species which

(since we must choose among the questioned specific

titles) are probably to be designated as Hydra fusca and

H. diecia. Species, therefore, which Linnæus could not

distinguish and which it may be hardly possible for the

ordinary student to distinguish with the care commonly

devoted to such subjects, may yet be separated by differ-

ences which seldom obtain between much more remotely

related types.

Did space permit, I might also illustrate from this

genus of organisms the proposition that the integrity, and

hence the reality, of species is not destroyed by the fact

that certain individuals of one may be transformed into

members of another. I will but refer to the fact that it is

possible, though extremely difficult, to transform H.

viridis into another, a white Hydra (H. fusca), differing

from it in practically every specifie character. I do not

refer to the mere bleaching of the green species. This,

up to a certain point, is easy, but carries with it no sig-

nificant morphological changes. The transformation

which I have effected (in both directions) does carry with

it such changes, and once produced they are extremely

permanent through an indefinite number of generations

and in spite of many environmental changes.

Of course we may, if we will, degrade these types from

specific to varietal rank, although they probably deserv a.

the specific distinction. But the point of emphasis is the

relative autonomy of the two groups. I have never been a

able to even find them in the same habitat. Interbreeding =

is precluded by their sharply separated periods (fall and

spring respectively) of sexual development. SP

608 THE AMERICAN NATURALIST [ Vou, XLIII

then, may be sharply demarcated despite of the possibility

of reciprocal derivation.

Lastly I had wished to defend the seeming paradox that

species may be not only real, but all but absolutely stable

despite of the widest variability. This is not a contradic-

tion in terms. The stability of a species depends upon

its refusal to vary in certain given directions, i. e., away

from its specific characters, or, secondly, upon the non-

transmissibility of such variations when once produced.

The variability of a species, however pronounced, may

mean only the production of non-specific characters or

the production of characters of whatsoever order which

are not repeated in the offspring.

Thus it proved to be with the species of salamander—

Amblystoma tigrinum—upon which I spent several years

of almost continuous experimentation. Variability and

instability of species, when I began my work, for me

were synonyms; when I concluded they had lost almost

all relation in meaning. The astounding variation of this

species was in the main but a somatic by-play in re-

sponse to environing forces. However, wholly against

first impressions, it turned out that this somatic variation,

despite its variety and extent, yet had its marked limi-

tations. How I did strive to make Amblystoma punc-

tatum out of A. tigrinum—such a little thing, too—just to

make a leopard salamander out of a tiger salamander. I

did not even try it until my third season’s experimenting.

It was really too insignificant a task. Had I not observe

nature working much greater changes?—and, by imi-

tating her methods in experiment, had I not gained the

key to her processes? Had I not passed the bounds of

specific and even generic characters? Indeed, certain wise

ones had nodded gravely, and suggested no less than fam-

ily rank for the best of my handiwork. Just to make A.

punctatum out of A. tigrinum! Besides I had the thing

three quarters done already, time and again, as a by-

product of my other work. At last I concluded, however,

to make a few bona fide A. punctatum just for the fun,

and to plague certain species people. And for season

No. 514] ARE SPECIES REALITIES? 609

after season I plagued myself at the rate of sixteen hours

per day to accomplish this and other kindred things all

relating to the stability or instability of this one species.

And how much I accomplished, and yet how absolutely

little. I made the characters all right, at least of the

adult; unless possibly the special distribution of a few

skin pores about the head eluded me. Last of all I even

segregated the palatine teeth into groups and dragged

them well back toward the throat in true punctatum style.

It was easy, given time and the knowledge how. Though

alas, while I was corralling this chief character, the whole

herd of lesser ones which I had previously rounded up

were absolutely certain to escape me.

In short, my seeming success was abject failure. Char-

acters, but never in perfect combination; and then, not a

trace of tendency toward transmission. I found no mor-

dant of conditions penetrating enough to bring germ cells

into the slightest harmony with my special somatic

policies.

Species unreal! It may be that they are in some

ghostly sense toward which my imagination has not wan-

dered. It may be that many alleged species are unreal

enough. But the majority of those with which I have

dealt, although chosen for the very reason of their seem-

ing or possible unreality, so to speak, have yet left upon

my mind the impression of almost indissoluble entities.

An exaggerated impression it may be. Had I been

collecting facts about geographical races, for example, I

might have verged toward other conclusions. But such

study, if it makes for a seeming fluidity of nature, is

confessedly but tentative and superficial, and its facts

about species are but a part of the facts. Does Mendelian-

ism, for instance, with its unit characters and its mathe-

matics of heredity, make for the unreality of species? Do

modern experimentalists claim to be dealing with species

as concepts only? : e

This leads to a last word. Is it of any importance how-

we think of species? May we, equally well, think of spe- o

cies as conveniently segregated groups of more or less

610 THE AMERICAN NATURALIST (Vor. XLII

similar objects, associated for convenience sake with a

single appellation; or as correlated, genetically unified

groups, as segregated portions of reality (convenient or

inconvenient for our intelligence) which nature somehow

sets apart, regardless of whether we know and name them

or not? To the writer it seems a matter of the first im-

portance. If organic nature is so fluid that our distine-

tions are conventional only, if specific names are but

handy helps by which we point out this or that sizeable

mass of organic territory, then must our whole attitude

be altered accordingly. It is no wonder that those who

hold this view are satisfied with nothing short of a general

knowledge of a whole fauna or flora. But if species are

downright realities (as science counts reality), subtle,

illusive realities, perhaps, still less than half understood,

yet existent, demanding ever more exact definition and

deeper explanation, then their knowledge becomes a new

and better thing, and the impetus they offer to investiga-

tion is wholly changed. Then must we recognize the right

to modify Linnean species whenever they disagree with

reality, however much we respect Linnean authority.

The whole spirit of modern biological research seems

to the writer to demand the conception of species as

realities,—not all alike, in their reality, of course. Lin-

næan species, elementary species, physiological species, .

ontogenetic, phylogenetic Sspecies,—these and more may

well prove to be essentially unique phases of nature’s

reality. But does not the thought of the investigator

that steadies itself by these conceptions of species as

realities fully justify itself by results?

And if there are other reasons for the assertion of the

unreality of species, over and above the return to that

child-like thought which sees reality only in the obvious

units of perception, over and above a carelessly exag-

gerated idea of variation as obliterating all but conven-

tional distinctions, what, we ask, are they?

SHORTER ARTICLES AND DISCUSSION

A LIGHT-WEIGHT, PORTABLE OUTFIT FOR THE

STUDY AND TRANSPORTATION OF ANTS

1. Nests:—For some time I have been observing ants in arti-

ficial nests. I have used Fielde (1900-1904) nests ten inches

long and six inches wide, a size which needs cleaning less often

than the sizes used by Miss Fielde, and gives the ants, especially

species of large stature, more freedom. Though these nests are

in most respects satisfactory they have proved, when of this size,

to be too heavy to be easily carried about on a journey. In

order, therefore, to diminish the weight, nests of the same gen-

eral plan as Fielde nests were made of aluminum instead of

glass. Necessarily, however, the construction was quite different

from the prototype. From a flat sheet of light-weight aluminum

(0.28 mm. thick) was cut a piece of the form shown in Fig. 1.

Aluminum of this thickness can easily be cut with an ordinary

pair of sheers. The lines c, d, g, h, and e, f, i, j, were ruled on

the aluminum with a lead pencil; at each of these lines the metal

was bent at right angles by a tinsmith. Thus k, l, m, n, became

the vertical sides of a shallow tray one half inch deep, while 0,

P, q, r became a practically continuous overhang projecting hori-

zontally inward one half inch as a marginal part of the tray.

The parts of o, p, q and r, which overlapped each other at the-

corners of the tray, were firmly fastened together by MeGills’

fasterners.! The tray, or nest was divided into two approxi-

mately equal chambers, A and B, by a partition five inches long.

This was made of a strip of aluminum an inch and a half wide,

bent, as shown in Fig. 1 (enclosed in chamber A). The base (t)

was attached to the floor of the tray by means of three MeGills’

fasteners, one at each end and one in the middle (s, Fig. 1), so

that u served as an upright between chambers A and B, while v

*A much better joint would be produced by a method of soldering

aluminum; but when the first trays were made I was not aware that such |

a method was known. More recently it was learned through Professor A.

G. Webster, of Clark University, yora Mass., that a technician in his

department had invented a method of soldering aluminum, and raa

Webster has kindly had soldered for me some of my E o

611

612 THE AMERICAN NATURALIST [Vou. XLII

formed an overhang over one of the chambers, and, together with

0, p, q and r, served to support the glass roof-panes, one cover-

ing chamber A, the other chamber B. v was made half an inch

longer at each end than t and u, the projecting ends resting on 0

and p to which they were fastened, thus giving the tray addi-

tional rigidity. As in the Fielde nests, the necessary ventilation

and tightness of roof were secured by using strips of Turkish

toweling, which were glued to the upper surfaces of 0, p, q, r

and v. All cracks in the corners and around the partition were

stopped with putty. In one chamber a wet sponge was kept, and

in the other food. Either chamber, or both, could be darkened

by pasteboard covers placed on top of the roof-panes.

5 0

X k }

m n

A s B f

q} te

aw r

S j

BE T A S l k

p at

Fig. 1.

2. Traveling Case.—In order still further to diminish the

weight of the outfit, and render it more convenient in traveling,

certain modifications were made in the Fielde (1904, p. 28)

traveling case. For part of the plan and all the construction I

am indebted to my mother. The case (Fig. 3) was made as fol-

lows: The floor, roof and ends were made of wood three eighths

inch thick, each composed of a pair of strips two inches wide,

placed parallel to each other and two inches apart. Four strips

of heavy tin, about six inches broad and as long as the width of

the floor (about six inches) were bent at right angles, like

‘“‘angle irons,” to form the corners of the case where the ends

met floor and roof. The strips were nailed securely to the tins,

leaving the desired space of two inches between the strips of

each pair. The case was twenty-one and a half inches long, six

No. 514] SHORTER ARTICLES AND DISCUSSION 613

and a half inches high and six inches from front to back, inside

measurements, and it was divided into two chambers of equal

size by a vertical partition. The back and front were made of

book-binder’s board, the back having a few large circular holes

to allow for ventilation, and the front serving as a door. The

entire case was covered with woolen cloth, which was carried

over and nailed to the front edges of the case at top and sides,

thus forming a cloth-covered jam for the door to shut against.

The cloth covering at the bottom of the door served as a hinge.

Fie. 2.

The door when closed was fastened by a brass ring which fitted

over a screw in the front edge of the top of the case. The trays

were supported on ledges made of strips of thick tin bent at

right angles and serewed to the end walls of the chambers at

suitable heights, as seen in Fig. 2, which shows one tray resting

on its ledges and covered with its pasteboard mats. The corners

of the tin ledges were rounded; to prevent the screw-heads from

wearing the edges of the trays as the latter were inserted and

withdrawn, the vertical part of the ledges and their screws were

covered with strips of thick paper, glued to the walls between

the ledges.

This case was designed to accommodate twelve nests, but since

two of my trays were not of the standard size adopted for the

rest, I provided for their accommodation by putting in a false

614 THE AMERICAN NATURALIST [Vou. XLIII

roof, cutting off the space for the two upper trays, and omitting

the partition from this space. When packed with nests of the

Fielde type the whole outfit weighed about twenty-six pounds;

but when packed with my aluminum nests, only about half as

much, the weight of the case alone being about six pounds.

A strong leather shawl-strap, with stout handle, was used in

carrying the case.

PAPERS CITED

Fielde, peg M., helpers Ant-nests,’’ Biol. Bull., Vol. II, No. 2, 1900,

1-85, 3

Fielde. Adele M., ‘* Portable Ant-nests,’’ Biol. Bull., Vol. VII, No. 4, 1904,

pp. 215-222, figs. 1-3.

Epiru N. BUCKINGHAM.

Boston, Mass.

ee OF CAINOLESTES WITH POLYPRO-

ONTA AND DIPROTODONTA

See has been described by Mr. Oldfield Thomas (1895)

who placed it in the family Epanorthide of the suborder Dipro-

todonta, which includes several fossil forms described by

Ameghino. Sinclair, however, in the ‘‘Report of the Princeton

Patagonian Expedition’’ (1901-6) gives the name Cznolestide

to these small Santa Cruz Diprotodonts, from the genus Cæno-

lestes, which, although a modern form, is more primitive than

any of these fossils in regard to the diprotodont character of

the teeth.

In view of the phyletic interest attaching to this form, as

_ perhaps the starting point for the evolution of diprotodont tooth

structure, it was considered advisable to make more completely

detailed drawings of the skull than had before been done, in

respect principally to sutures and foramina, and to compare

skull and other characters with types of Polyprotodonta and

Diprotodonta.

The skull from which the accompanying drawings were made

is the specimen which Sinclair figured in his report, loaned to

me through the courtesy of Dr. J. A. Allen, from the collection

of the American Museum of Natural History. I am indebted

also to Mr. W. K. Gregory, of the museum, for many helpful

suggestions during the course of the work.

Among the general marsupial characters of the skull of Cæno-

lestes may be mentioned the following: absence of pituitary

No. 514] SHORTER ARTICLES AND DISCUSSION 615

fossa and clinoid process, terminal nares, nasals broad poster-

iorly, malar forming wall of glenoid fossa, premaxillæ not touch-

ing frontals; on the ventral surface—palatal vacuities and

palatal ridge, small lamellar pterygoids, alisphenoid bulla, and

annular tympanic.

Fic..1. Palatal aspect of cranium of Cenolestes — x As.bl,

alisphenoid bulla; a.pl.cac, anterior palatine vacuity; Bo, ssoetptal Bs,

basisphenoid; c.f, condylar foramina; car.can, carotid pele car.f, ca

foramen; eust.f, Dordi opening ; cae exoccipital ; Fa ov, foram i grais:

f.l.p, foramen lacerum posterius ; Ma, malar; Ms, mastoid; Ma, m Haans Per,

periotic; p.gl.f, post-glenoid pegen Pl, palatine; p.l.f, postero-lateral tora-

men; pl.r, palatal ridge; p.pl.v . posterior ee vacuity; Ps, enoid ;

ie pterygoid; pt.p, pte oe pro cess of palatine; Pms, Pue, eae ae

subsquamosal foramen; st.m.f, stylomastoid Seana: tr.can,

Ty, tympanic. :

Marsupial characters in the foramina are seen in the follow-

ing: foramen lacerum anterius confluent with optic (sphen-

orbital foramen) ; presence of postero-lateral palatine foramina,

lachrymal duct on anterior margin of orbit, transverse canal,

carotid foramen perforating —— orai gan fora-

616 THE AMERICAN NATURALIST — [Vou. XLII

mina, subsquamosal foramen. In identifying foramina in the

squamosal I have followed the descriptions given by Cope.

Two characters more or less peculiar to Cenolestes are, as

mentioned by Thomas: pterygoid processes of palatine long,

slender and delicate; ant-orbital vacuity between nasals and

maxille, found elsewhere only in ruminants.

Polyprotodont Characters.

1. Dental formula like that of the Dasyurid genera Thy-

lacinus, Phascologale, namely :

i4el 3m4:

13¢Cz7pMm3gMs;

Side view of skull of Cwnolestes, x 3. a.o.v, Antorbital vacuity;

1G, 2;

ang, angle; As, alisphenoid; As.bl, alisphenoid bulla; c, le

psig foramen; Ty tympanic; V?, infra-orbital foramen. The

e part of the cranium with which the condyle of the mandible articulates.

A this family the incisors are numerous, small, subequal, canines

arger than incisors. This agrees with the condition in the

upper jaw of Cænolestes. l

a Close resemblance in external form to Phascologale—rat-

e or opossum-like in form (Thomas).

3. Resemblance to Dasyurus skull, (a) in general shape, (b)

No. 514] SHORTER ARTICLES AND DISCUSSION 617

pterygoid processes of palatine slender and delicate (in the

specimen figured the process is missing from the left side), (c)

alisphenoid bull similar in general form.

4. Marked resemblance to Antechinomys and Sminthopsis

skulls in size, shape and delicate character of the bones; absence

of strong crests or ridges.

5. Palate long and narrow, similar to characteristic Polypro-

todont form, with long and narrow palatal vacuities.

6. Lower jaw very similar to Dasyurus, Phascologale, and

especially to Antechinomys and Sminthopsis in inflection of

angle, and proportionate size of angle, condyle and coronoid.

7. Rudimentary pouch (Thomas, after Tomes), as in Phascolo-

gale and Marmosa.

8. Fore and hind limbs about equal.

9. Pes non-syndactyl as in Dasyures and opossums.

10. Foot plantigrade—resembles Phascologale in number and

position of pads, and short clawless hallux (Thomas).

Diprotodont Characters (Thomas, Sinclair).

1. Condition of teeth—(a) one large lower incisor, cutting, `

forward projecting, (b) other incisors and canine in lower jaw

vestigial as in Epanorthide, (c) anterior premolars small, show-

ing tendency toward condition seen in Phalangers, where they

are vestigial.

2. Pattern of teeth—molars like Phalanger molars rather than

the Polyprotodont type. In Petauroides and Trichosurus there

are four cusps on incipient ridges; in Cænolestes the ridges have

increased in extent to form a lophodont type.

CONCLUSION

Sinclair concluded that Cænolestes is very like the primitive

Phalangers, and the two families are probably related, not con-

vergent; that, while the fossil Cænolestidæ are too speci |

in tooth structure to be the direct ancestors of the Phalangers,

yet there is probably a common ancestry. Later, he gave weight

to the possibility of convergence to account for the resemblance

in tooth structure (p. 443). This latter view would seem to be

more in accord with the facts known about Cænolestes, for ex-

cepting tooth structure, there appears to be no other important

character which links it with the Diprotodonts and there are

several, as given above, which link it with the Pores

618 THE AMERICAN NATURALIST [Vou. XLII

While there is undeniably a series of forms connecting Czno-

lestes with the Diprotodonts in tooth structure, yet Cenolestes

itself is so generalized in this respect that we may perhaps in

the absence of other corroborating characters, question its in-

clusion within this group. Possibly it may be found to be an

offshoot from the Polyprotodonts, as it appears structurally to

be more generalized than any Diprotodont, and therefore it

might well occupy a separate suborder, as Thomas suggested—

the Paucituberculata of Ameghino.

PAULINE H. DEDERER.

COLUMBIA UNIVERSITY

May 26, 1909.

LITERATURE

Cope, E. D. Foramina Perforating the Squamosal in Mammals. Proc.

Am. Phil. Soc., 1880.

sborn, H. F. Evolution of Mammalian Molar Teeth. 1907.

Sinaladr, Report of the Princeton Patagonian Expedition, 1896-1899.

1901-1906.

Thomas, O. On Cenolestes, a still Existing Survivor of the Epanorthide

of Ameghino. Proc. Zool. Soc., 1905, p. 870.

NOTES AND LITERATURE

COMPARATIVE PSYCHOLOGY

Bohn’s ‘‘The Birth of Intelligence.’’!—The good critic, says

Anatole France, is he who recounts the adventures of his

soul among masterpieces. If the reviewer recounts his ad-

ventures with Dr. Bohn’s fascinating book, he can perhaps

give a better idea of it than in any other way. Dr. Bohn

has for years been engaged in a study of the behavior of

the animals of the seashore, as influenced by the conditions

under which they live. His published papers set forth that

the behavior of these animals—the worms, crabs, snails, sea

anemones and the like—is wonderfully dependent on the past

influences they have undergone; the changes of tides, of day

and night, and the like, leave their records on the animals, so

that after removal from these agents, the creatures still show

the habits formed under their influence. Thus the behavior of

these creatures is not fixed and final, but surprisingly modifiable.

Such complete and overwhelming confirmation of the results and

views that had been independently expressed by the present

reviewer and going even beyond what he had anticipated, could

not be received by him otherwise than with enthusiasm; he

recommended the work to his friends and wrote a laudatory

review ;? as Bohn in the present volume notes with satisfaction,

his work ‘‘surprised the Americans’’ (p. 71). But the reviewer’s

enthusiasm was met in some quarters by skepticism and criti-

cism; it was pointed out that Bohn’s results are largely given

en masse, as it were, and with a striking lack of that precision

of detail and of method which most of us have felt requisite for

establishing scientific results; Yerkes in 1906 said, in a review

of his papers, ‘‘They are not thoroughly satisfactory scien-

tifically for they continually suggest questions, doubts and new

problems.” The work was of precisely the kind, some urged,

in which inaccuracy, carelessness or prejudice would enable one

* Bohn, Georges, ‘‘ La Naissance de 1’Intelligence,’’ Paris, 1909.

* Psychological Bulletin, 5, 1908, pp. 180-183. _

* Journ. Comp. Neurol. and Psychol., 16, 1906, p. 238.

619

620 THE AMERICAN NATURALIST (Von. XLII

to reach results seeming to confirm whatever theory the author

wished to establish.

It was, therefore, with special interest that the reviewer

greeted the appearance of a general work by Bohn; on the one

hand, it would naturally deal with phenomena that the reviewer

is convinced are of special importance; on the other, it was

hoped that the care and accuracy of presentation would be such

as to remove all doubts as to the validity of Bohn’s scientific

results.

As to the first point, a general examination seemed to show

one’s best hopes gratified. The book might be called an ampli-

fication of the text—‘‘The reactions of a living creature at a

given moment depend not only on the present conditions, but on

all the conditions of the past life—not only the life of the

individual under consideration, but also that of its ancestors”’

(p. 259). This is the spirit in which I have desired to see

written a book on behavior.

The book is not put in the form of a connected account, but

is rather a series of discussions of general topics and problems,

illustrated by examples. Discussion of the work and views of

other investigators occupies a large space; here the author paints

in large, sweeping strokes, pronouncing as to good or ill with

absolute confidence. This method makes lively reading, but it

requires great and accurate knowledge of details and a most

fair and judicious spirit to use it and remain scientific ; without

these qualities it is cheap, easy and misleading. The author’s

qualifications in these respects we shall inquire into later.

Many of the author’s general principles and methods seem

excellent; he attempts to distinguish the varied different factors

in behavior; to establish definite meanings for terms long under

doubt or controversy (so for example the term tropism); to

search for objective factors everywhere; he recognizes fully the

complexity and modifiability of behavior. The reviewer finds

especially sympathetic the section on the uselessness of the idea

of instinct as an analytic concept; the emphasis on the fact that

all adaptation or ‘‘finality’’ is a problem, not a solution (p.

286); the idea of the ‘‘struggle against variation’? (Ch. 15),

* This sentence is used by Bohn as a summing up of ideas expressed by

Semon; it seems to me however to express the idea of this book, though here

Bohn possibly might not agree.

No. 514] NOTES AND LITERATURE 621

and indeed many other matters. Even where he would disagree,

the discussion is interesting and often valuable.

Little reading of the book is necessary to show, what has been

evident from recent papers, that the author is a hero worshipper,

and that at present the hero of his tale is (most deservedly in

a book on the objective study of behavior) Jaeques Loeb. Yerkes

is given a place as a worthy follower of the master, while the

present reviewer takes the rôle of the villain in the plot. It

will be worth while to translate Bohn’s characterization of three

American investigators, as giving an example of his style of

thought and expression. I quote from an article in the Revue

Scientifique of May 16, 1908, which gives some picturesque fea-

tures not taken into the book.

I have pronounced the name of Galileo; I can not resist the tempta-

tion to inscribe by the side of this name that of the biologist Jacques

LOEB.

Certainly since Galileo times have changed. No longer are revolu-

tionary savants persecuted, at least not openly. There are free coun-

tries such as America for men such as Jacques Loeb. Beyond the

ocky Mountains, on the shores of the most beautiful bay in the

world, at Berkeley, opposite San Francisco, are the laboratories whither

the Californians have called the great biologist; it is in a scene truly

fairy-like that Loeb works without ceasing and whence he sends forth

the ideas which pass through the world to give a significance to

biological researches.

However, in America they continued to gather facts. And a savant

of great worth, Yerkes, completed without noise the work of Loeb’

by searching out, with a spirit of method truly remarkable, how asso-

ciations are formed in animals; his two memoirs on the acquisition of

habits in the frog and the crayfish will remain classic and must serve

as models to all those who attack the same questions. Yerkes has

shown a quality that is rare among psychologists; that of not attempting

to choose a personal attitude and to attach his name to a system; he

has endeavored constantly to establish facts with all the rigor desirable

and to give to them wise interpretations.

Suddenly’ JENNINGS appeared on the scene; he presented a system;

ë This passage is found also on page 42 of ‘‘ La Naissance de 1’Intel-

ligence.’?

° The precise reference here seems to be to ‘‘the phenomena of association

studied by Loeb in the lowest animals,’’ words which he has employed a

little before.

"The fact is of course that I had"been publishing papers on this line

of work for a number of years before Yerkes began; and that I suggested

622 THE AMERICAN NATURALIST [Vow. XLIII

that of trial and error, with disciples already’ numerous, he under-

took a crusade against what he called the “ orthodox theory of trop-

isms ”; he east trouble into the spirits, and certain ones could believe

for an instant that the work of Loeb was about to crumble. It re-

mained entire. The hurricane which had made such ravages in America

made itself felt even in Europe, where it had little trouble to demolish

the frail constructions of M. Nuel.®

The part sketched for the third actor in the plot is certainly

an unworthy one, but there is after all something dramatic about

figuring one’s self, after Bohn, as a sort of demon that rides

upon the storm, carrying trouble to the poor creatures of earth;

so this, with the pleasure of seeing the ideas of the complexity

and modifiability of behavior in lower organisms for which I

have long worked, so completely triumphant in Bohn’s book,

must perforce be my consolation. It is the traditional fate of

innovators to suffer condemnation that their work may prevail.

But there remains the second point to consider; in the book

the author gives us a study not only of phenomena at the sea-

shore, which we can not test for ourselves, but of the work and

views of other investigators, which we can ourselves examine.

Here is a test for the accuracy, thoroughness and conscientious-

ness of his work, for his mental grasp and his freedom from

prejudice—a test for which we have above mentioned the need.

Does he stand this test in a way to set at rest the doubts that

have been expressed as to the trustworthiness of his scientific

results in difficult fields?

For this test I naturally examined his presentation of my own

work, since that is the matter with which I am best acquainted;

rthermore I was of course curious to see why he presents me

as one of the powers of darkness, while I have welcomed him as

a support and ally. And here to my extreme disappointment I

found things which I think may again ‘‘surprise the Amer-

icans’’ and every one else that has any ideals as to scientific

accuracy. It would certainly be difficult for any author to

the application of the idea of trial and error and criticized the theory of

tropisms only after seven years of constant work, during which time I had

published many papers on the subject. It is more dramatic to bring me

in ** tout à coup ’’ and the shackles of chronology or other mere facts are

not allowed by Dr. Bohn to interfere with effective presentation, as we shall

see later.

ae ae lavenir de la psychologie comparée,’’ Revue Scientifique

No. 514] NOTES AND LITERATURE 623

present a more thoroughly incorrect account of another’s work,

both as to material facts and as to general views and principles,

than Bohn has given of my own. A citation of some typical

examples will enable the reader to form an idea of the author’s

practise and ideals of accuracy.

Any one acquainted with my work on the reactions of lower

organisms will recall that I found and set forth, with what

seemed to many wearisome repetition, that the cause of reaction

is in a large proportion of cases a change in external conditions,

variation in concentration of chemicals, in degree of tempera-

ture, intensity of illumination, ete. Now, Bohn has likewise

observed this (as had many previous workers), and he makes

large use of it in explaining behavior; under the name of

«sensibilité différentielle’’ it forms one of his three main factors

in behavior. He is even inclined to lay claim to a certain

originality in this.’

_ Amid the ruins [of other men’s ideas] the reader, I hope,

will see already some new constructions arising. Certain chap-

ters, those consecrated to vital rhythms and to sensibility to

differences figure for the first time in a book on comparative

psychology (p. 3).

For this purpose it is convenient that he feels prepared to

assert that I had never recognized this as a cause of reaction!

The idea of sensibility to differences has escaped Jennings.” In gen-

eral, Jennings has not carried far enough the analysis of the move-

ments of the lower organisms; as he has not taken account of the phe-

nomena of sensibility to differences, he has been led to speak of “ trial

and error.’

Such statements appear again and again throughout the book,

and form the basis for repeated condemnations of my work. It

would be difficult to make statements more completely contrary

to the facts. As this is the source of most of Bohn’s mistakes

in regard to my work, it is well to consider the matter in some

detail.

No doubt is left as to what is meant by ‘“‘sensibilité différ-

entielle’’; it is discussed in full with numerous examples; it is the

? Though he recognizes that Loeb had made use of the same idea.

<< La notion de sensibilité différentielle a échappé à Jennings,’ p. 179.

“<< D’une façon générale, Jennings n’a pas poussé assez loin 1’analyse

des mouvements des organismes inférieurs; comme il n’a pas tenu compte

des phénoménes de sensibilité différentielle, il a été amené parler d’essais

et erreurs,’’ (p. 191)

624 THE AMERICAN NATURALIST [ Vou. XLII

same as Loeb’s ‘‘Unterschiedsempfindlichkeit’’ and signifies re-

actions to changes in the environmental conditions. ‘‘II] s’agit,

en effet, de réponses 4 des variations plus on moins brusques des

diverses forces du milieu extérieur’? (p. 167)

Consider in connection with the above statements from Bohn,

the following: In the table of contents of my book on the ‘‘Be-

havior of the Lower Organisms’? (1906), we find the caption

- Change of Conditions as a Cause of Reaction. Turning to the

indicated chapter (XVII), as any one would naturally do who

desired to form a conception of my results on this matter, we

find that the second numbered paragraph begins:

The most general cause of a reaction is a change in the conditions

affecting the organism. This has been illustrated in detail in the de-

seriptive portions of the present work (p. 293

Practically the entire chapter is taken up with an analysis

and discussion of variations in the environmental agents as

causes of reaction. In the descriptive portions of the work the

point is set forth most explicitly again and again. Taking the

account of Paramecium as a type, we find the following:

It is clear that the cause of reaction is the change from one solution

or temperature to another (p. 51). The animal, having been subjected

to certain conditions, becomes now subjected to others, and it is the

transition from one state to another that is the cause of reaction. This

is a fact of fundamental significance for understanding the behavior of

lower organisms” (p. 52). But as its movements carry the animal

from one region to another, the environmental conditions affecting it

are of course changed, and some of these changes in condition act as

stimuli, causing the animal to change its movements (p. 58). In the

reactions to mechanical stimuli, chemicals, osmotie pressure, heat and

cold, and powerful light, the avoiding reaction is caused by the transi-

tion from one external condition to another, by change in the intensity

of action of some agent (p. 78). Examination has shown us thai the

cause for this reaction is some change in the conditions (p. 108).

For other organisms the point is likewise developed in detail

and stated with equal explicitness. Thus, for Ameba: ‘‘T

cause of a reaction—that is, of a change in moyvement—is in

most cases some change in the environment’’ (p.. 19); for Bac-

teria: ‘‘The reaction is caused as a rule by a change in the

environment of the organism’’ (p. 37); for the reactions of

Stentor to light: “all together, then, our experiments have

1? The italics are in the original.

No. 514] NOTES AND LITERATURE 625

thus far shown that the cause of the avoiding reaction is the

change from darkness to light” (p. 131); for Euglena: ‘‘It is

clear that the reaction is due to the decrease in the intensity of

light’’ (p. 136); for reactions of infusoria in general to chem-

icals: ‘‘The reaction is in each case caused by a change from

one concentration to another’’ (p. 123); for their reactions to

light: ‘‘To sum up, we find that the reactions to light oceur in

the infusoria in essentially the same way as do the reactions to

most other stimuli. . . The cause of reaction is a change

in the intensity of light”? (p. 149). Pages could be filled with

quotations from my book to the same effect.

In my earlier papers the matter is dealt with in an equally

full and explicit way. My paper on ‘‘Reactions to Light in

Ciliates and Flagellates'® is mainly devoted to showing in detail

that the reactions are due to variations in the intensity of light.

A section headed ‘‘Nature of Agent causing the Reaction’’ be-

gins ‘‘The primary and essential cause of reaction is a change

of illumination” (p. 65). My paper on ‘‘The Behavior of Para-

mecium’’!* has a section headed Nature of Stimulation, in which

we find the following:

An examination of the facts shows that as a general rule the effective

stimuli consist of some change in the conditions (p. 464)

These quotations are not isolated; they are mere typical sen-

tences in an extended elaboration of the point set forth, and

they could be multiplied almost indefinitely.

How then Bohn could make the statement that I had not

taken account of this matter is inexplicable. But assuming that

I was unacquainted with the fact that forms in reality the

foundation of my presentation of the causes of reaction, the

author of course cannot possibly understand my account of

behavior; it is to him necessarily an edifice without foundations

and innst therefore crumble to earth. This is the source from

which all of his misconceptions and (unintentional) misrepre-

sentations of my work flow as naturally as water from a spring.

The chief errors thus arising are the following.

1. He ig neoenoaily utterly unable to understand my concept

of ‘‘trial and error.’

2. He is entirely prevented from grasping the nature of aid

criticisms of the tropism idea. :

* Carnegie Institution, Publ. 16, 1904, pp. 29-71. ;

e Pira, best Neurol. Psychol., 14, 1904, pp. 441-510. é

626 THE AMERICAN NATURALIST [Vou. XLII

3. He is led to suppose that my account, being wrong in prin-

ciple, must also be wrong in details, so that he attempts to cor-

rect details, by giving usually the same explanation that I had

already-given; or at times some other causal explanation that he

devises, without experiment, to account for the facts; this often

leads him into curious errors.

4. He is inevitably driven to suppose that I reject determinism

in behavior.

5. He is naturally led (though here without real basis as it

seems to me, save by additional error of the same sort) to attrib-

ute to me psychic, anthropomorphic and finalistice explanations

in place of causal ones.

Let us look briefly at certain of these points.

1. My concept ‘‘trial and error’’ the author is forced by his

mistake to suppose designed to take the place of an experimental

analysis based on a real knowledge of the causes of reaction. His

account of its origin is:

As he has not taken into account the phenomena of sensibility to

differences, he has been led to speak of trial and error (p. 191).

The fact is that the idea of trial and error was based precisely

on reactions due to ‘‘sensibility to differences’’; to changes in

the conditions, and I have again and again stated that fact.

For example:

Just what is the nature of the stimulation which produces this reac-

tion by “trial and error” in Paramecium? An examination of the

faets shows that as a general rule the effective stimuli consist of some

change in the conditions.”

The purpose of the concept was to bring under a unified point

of view a complex of stimulations and reactions which had the

interesting and important result of bringing the organism into

conditions adapted to it, yet not including ‘‘anything differing

in essential principle from such methods of action as we

in the inorganic world.’* The concept is useful only in at-

tacking the problem of how adaptation is brought about without

the operation of ‘‘final causes.’? To speak of ‘‘trial and error”

of course does not get rid of the necessity of finding a deter-

mining cause for every phase of the reaction, any more than

to call a reaction ‘‘tropism’’ has this result. It has been pre

me ia PeR of Paramecium, ”? Journ. Comp. Neurol. and Ege ae

14, 1904, ae

mee ncn of the Lower Organisms,’’ 1906, p. 343.

No. 514] NOTES AND LITERATURE 627

cisely my endeavor to show just how each phase was determined

so as to show that ‘‘there is no evidence that a final aim is guid-

ing the organism.’”"* The application of the phrase ‘‘trial and

error’’ to lower organisms arose as follows: The organisms react

to changes in the conditions by movements of a peculiar char-

acter, which subject them to various environmental changes.

Some of these changes cause them to react further, still further

changing the conditions. Finally, as a rule, their continued

movements bring them into conditions which do not cause them

to react by further movements; since they do not react further

they remain in these conditions. There is, as I have repeatedly

attempted to show, evident experimental cause for every detail

of this behavior.

We do not need any purpose or idea in the mind of the organism,

or any “psychoid” or entelechy, to account for the change of be-

havior, for an adequate objective cause exists.

But we need a name for such behavior; we need as it were to

throw a net about it, gathering it together, so as to grasp its

essential points, to the exclusion of unessential details. I have

often characterized it as the selection of certain environmental

conditions as a result of varied movements. For a briefer

phrase, I found in common use for behavior in higher animals

that is objectively similar, the expression ‘‘trial and error,’’ so

I employed this, specifying’ with the greatest care that it was

only the similarity in objective features that I desired to bring

out.” Later developments have shown that the designation was

an unfortunate one, since readers not accustomed to distingush-

ing the phenomena on which a concept is based from other

things that may be intermingled with it in particular cases are

inclined to read into it in every case all that may occur in con-

nection with it in any case; this seems to be Bohn’s method of

procedure. Other authors have found no difficulty in grasping

the point involved; so Driesch in his recent volumes on the

“Science and Piiloaspliy of the Organism’’; and Pillsbury in

his paper on ‘“‘Trial and Error as a Factor in Evolution,”

* Tbid., p. 343.

8 Ibid., p. 342.

2 See the note at the end of my paper on ‘‘ Trial and Error,’’ ‘* Contr. —

to pee Study of the Behavior of the Lower Organisms,’’ 1904, p. 252;

Behavior of Parameci ium,’’ Journ. Comp. Neurol. and Pano 14, =

a p. 461.

"Pon. Sei. MONEN, ais pp. 277-282.

628 THE AMERICAN NATURALIST [Vou. XLIII

where the ‘concept is applied, in precisely the significance I gave

it, to inanimate things. Objection to the phrase as liable to lead

to misunderstanding among the uncritical I am glad to recognize

as justified, so that I no longer employ it, but Bohn merely

ranges himself among the uncritical.**

Bohn’s inattention to my statements as to the cause of reaction

of course leads him to suppose that whenever I speak of trial

and error I mean that there is no experimental cause for the

reactions; hence if he can show that there is experimental cause,

this does away with the concept of trial and error! He there-

fore takes up a number of cases of reaction described by me

(pp. 172-175, 187-195, ete.), shows, as I had done before, that

they are due to changes in environmental conditions, and con-

cludes that my exposition is wrong; that the application of the

idea of trial and error is a mistake. His idea of trial and error

is that it involves chance, in the sense of being undetermined.

By the analysis that I have made above, I have been led to reject

many of the pretended trials and to show that the chance was most

often only an illusion (p. 279)

In whose mind was the illusion? My own statement has been:

Everyone of these movements is, of course, as absolutely determined

as the most orthodox tropism.”

Again, Bohn says: ‘‘ Indeed, many of the sinuosities of the path

followed by the lower animal can Bnd an explanation in the

combination of the tropisms and the phenomena of sensibility

to differences” (p. 279), and in all seriousness he copies some

of my figures and instructs me that the reactions shown are due

to changes in the environmental conditions, just as I had shown

before him. Some of the facts here are almost incredible; they

throw a strange light on the author’s accuracy and intelligent

grasp. Thus, in the case of one of the figures copied from me

(on p. 188), from which he draws on p. 191 the conclusion that

I have ‘‘not taken into account the sensibility to differences,”

2 It is a remarkable fact that in an earlier review of my book (Bul.

Inst. Gen. Psychologique, 1906 (?), p. 282), Bohn understood correctly

understands. It would be most interesting to know the internal history of

the change by which Bohn has been brought from a position of intelligent

comprehension to one of blind misconstruction of my work. It is mani-

festly not due to further study of my work, since, as we have seen, he now

shows extraordinary lack of acquaintance with the main points I made.

= Journal of Experimental Zoology, 3, 1906, p. 452

No. 514] NOTES AND LITERATURE 629

in the very description of the figure, that I gave, both in my

Contributions (p. 55) and my book (p. 139), I stated repeatedly

and in detail that the cause of the reaction was the change in

intensity of the light. I even pointed out on the figure just

where this cause came into operation. I added this in the ex-

planation of the figure (though given also in full in the text),

in order that no one, however careless, could miss it; but Bohn

has succeeded in doing so. In an account of the reactions of a

ciliate infusorian that purports to correct my own, at the mo-

ment when the animal reverses its course the author says: “‘It

is at this moment that I introduce the notion of sensibility to

differences’’ (p. 193). This introduction having been made

years before? and the acquaintance having been intimate ever

since, the ceremony is hardly worthy of the solemnity with which

the author invests it.

Bohn’s inability to catch the idea of ‘‘trial and error” as I

presented it is further due to two other points: (1) To speak

merely of sensibility to differences seems to me quite insufficient

for characterizing the reaction; the most important point is

what the organism does. Different organisms do very different

things and the same organism in different conditions reacts

differently, under the same stimulus. What the organism does

is the matter to which my attention has been primarily directed.

Now, in those reactions that I called ‘‘trial and error’’ the

organisms perform complex movements of such a character that

they subject it to many different conditions. This was the basis

for the use of the word trial, it meant this and nothing more.

(2) Bohn is content to speak of ‘‘sensibility to differences,’’ with-

out analyzing the matter further. I carried the analysis much

further, bringing out, not only the fact that the organisms react —

to some environmental changes and not to others, but that there

is some system in this; that there is a relation between the

changes to which the given organism reacts, and its own internal

physiological processes; I tried to show that it reacts as a rule

to changes that interfere with its physiological processes, 1D

**¢ The change in the solution at this point produces the charaeteristi¢

reflex ’’; Jennings, 1900, Amer. Journ. Physiol., 3, p. 399. ‘ Many sor a

changes in the environment produce a certain characteristic reflex ’’ ie

Jennings, 1900, Woods Hole Biological Lectures for 1899, p. 104. “ The

direct cause of the reaction is a change in the nature of the — r

medium ’’: Jennings, 1901, Amer. Journ. Physiol., 6, p- 35. See aie p

tations given on a previous page. eS a

sorts of

630 THE AMERICAN NATURALIST [Vou. XLIII

such a way that it leaves the region where these changes oceur.

It was here that I pointed out especially that for each step ‘‘an

adequate objective cause exists.’’ These relations, which Bohn

neglects, are fundamental both for an understanding of the con-

cept under discussion, and for any real understanding of be-

havior.

2. The same causes that prevent Bohn from understanding

what I meant by ‘‘trial and error’’ equally prevent him from

understanding my criticism of the tropism theory. He says:

Jennings, from lack of having made the distinction between tropism —

_ and sensibility to differences, has been led to criticize, in an unjust

manner, the tropisms of Loeb (p. 173). The notion of sensibility to

differences has escaped Jennings; this investigator made the mistake

of confounding it with that of tropisms, ete., ete. (p. 179).

Now, my reason for criticizing the application of the theory

of tropisms was precisely because I did make the distinction

Bohn speaks of. I dealt with a question of fact. The reac-

tions of the organisms I studied had been commonly designated

tropism (or taxis) and I used the same term until I had shown

clearly what the nature of the reaction was. Then, being in-

terested in the facts of behavior, I made an analysis showing that

as a matter of fact the behavior did not consist of tropisms, that

‘the theory of tropisms is not of great service in helping us to

understand the behavior of these lower organisms.’”* I can

readily understand how it might be held that the theory is of

service for certain reactions, but it is hardly worth while to

attack my presentation on such mistaken ground as that I did

not distinguish tropisms from reactions to variations in the

environment. I have set forth in full my position on the

tropisms in a recent paper,” so I may pass over it here. There

is little in Bohn’s impassioned defense of the tropisms that I

could not assent to in principle; though I might object to the

application to particular cases, and especially to the views which

he attributes to me on the matter. i

Points with which I could warmly agree are the following:

He warns against ‘‘the deplorable results into which authors

have been led by adopting the view according to which there

would be tropisms everywhere’’ (p. 241). He says that ‘‘the

activity of lower animals is composed of complex elements;

*«< The Theory of Tropisms,’’? Pub. Carn. Inst., 16, 1904, p. 105.

"Foo Pee of the Behavior of the Lower Organisms

Science, May 1, 8.

Bag

No. 514] NOTES AND LITERATURE 631

tropisms, phenomena of sensibility to differences, associative

phenomena’? (p. 241) (he might have added others). ‘‘It is

very possible that the nervous system and the sense organs lend

their help and facilitate the processes of which the tropisms

are the consequence’’ (p. 124); the tropisms are variable (p.

132) ; they are mixed with all sorts of other activities (p. 132).

“Tt is often said that the tropisms are irresistible movements,

but this applies of course only to the case where the tropisms

are of an intensity sufficient to overwhelm the animal; to annihi-

late its other motor manifestations’’ (p. 132). A similar state-

ment could of course be made for any cause of movement what-

ever. Bohn’s definitions of the tropisms seem on the whole such

as to command assent, though I reserve certain criticisms in de-

tail, such as the strange bringing of the will into the definition

of an objective phenomenon (p. 117, ete.).

As to the views attributed to me, Bohn says ‘‘for him the

tropisms would be the result of an apprenticeship; of long series

of trials” (p. 137). In this and similar passages the author

follows his usual plan of making a positive statement without

citation of his basis for it. I am not aware of ever having ex-

pressed any such view as is here attributed to me. On the con-

trary, I have said that the method of trial and error “‘is in com-

` plete contrast’’ with the tropisms,?° while on the same page (and

elsewhere) I have said that behavior of the stereotyped char-

acter of the tropisms occurs also.

3. As remarked above, Bohn assumes that it is necessary to

correct my account in detail as well as in principle. His usual

method, as we have seen, is to give the same explanation that I

had already given. Either a feeling that nothing good could

come out of my work, or his natural habit of mind, has led him

in other eases into extreme carelessness of statement. One or

two examples must suffice. On page? 190 he says, in duming

my account of reactions to light:

There is a factor of which Jennings has not taken account, it is the

factor of time. A certain time is necessary for orienting itself.

Compare the following from Jennings:

Thus the orientation is gradual and for a certain stretch after the

light has begun to act the organism is not completely oriented. With a

fairly strong light however, the period of time required for SI

orientation is very slight.

=<: The Method of Trial and Error,’’ Publ. Carn. Inst., 16, 1904, p. 50.

632 THE AMERICAN NATURALIST { Vou. XLIIT

My entire analysis, properly understood, will be seen to largely

depend on the fact that a certain time is required, and to be

devoted to accounting for it. This analysis Bohn has evidently

never looked into with care, since, as we have seen, he is not

even aware that I attributed the reactions to variations in the

intensity of light. It is well to give the devil his due; if one

does it with care he may find he is not dealing with the devil

at all!

Among the most remarkable feats of the author along this

line is his attempt to recount and explain my description of the

behavior of two amæbæ, one of which pursued and captured the

other. The captor a after engulfing b, returns on its course,

carrying the prey b (at 6, 11, 14 of Fig. 21 in my book; at 4

and 7 of Bohn’s copy of the figure). Bohn says that the re-

turning of the captor a is a mere recoil (‘‘reeul’’), due to the

separating of b from a; in place of b a glass rod would do just

as well.

The Ameeba a quits with difficulty the contact with the solid body

which one moves; when one breaks the contact suddenly the mechanical

change which results from it for Amceba a determines the recoil of the

latter.

In the description of the figure the author points out just

where the ‘‘recoils’’ occur. Now the facts are, as I took pains ~

to describe in my account, that this reversal of movement which

Bohn calls the recoil (as at Bohn’s 4, 7) takes place not when

the prey escapes, but after the captor has enclosed it; having

captured its prey the captor returns on its course. Beha ’S ex-

planation is then quite inadmissible. In copying part of my

figure Bohn unfortunately omits precisely the portion that shows-

the larger amæba carrying the smaller after reversal of its course

(at 6 of my figure).

4 and 5. I have given a sufficient number of illustrations of

the author’s accuracy and grasp of my work to make it easy .

to conceive the value of his accusations of indeterminism, of

anthropomorphism; of such criticism as ‘‘Jennings has not

carried far enough the analysis of the movements of the lower

organisms.” (This from a writer who does not so much as

know that I attributed reactions to variations in the environ-

mental conditions !)

n ed Pr to Light in Ciliates and Trenen Publ. Carn. Inst.,

1904,

No. 514] NOTES AND LITERATURE 633

The attributions of indeterminism, anthropomorphism, ete

have their source in his mistaken statement that the idea of reac-

tions to variations in environmental conditions had escaped me;

in his book he places them on that basis. With the demonstra-

tion of his mistake on that point they fall to the ground. Let

us put the matter clearly once for all. Either Bohn can or he

can not cite passages from my work which justify his assertions

and implications that I deny determinism and that I give an-

thropomorphie and non-objective explanations in place of causal

ones. He has not as yet made, either in his book or his number-

less papers, any attempt to give such citations. If he can do so,

it would be worth while, that we may see on what basis he is

proceeding. If he can not, to continue to make such statements

is unscientific, for they are not verifiable.

Alas! then, we find that our author does not stand the test

that we hoped might set at rest the doubts as to the accuracy

and trustworthiness of his scientific results in difficult fields.

I have not attempted to test the remainder of his account, but

I fear that similar qualities might be found there. Has the

author shown, in his account of the work above analyzed, accu-

racy and care of the same kind that he employs in reporting what

happens in the infinitely more difficult field of nature? If not,

why not? And if he has—How much are his scientific results

worth ?

From the literary standpoint the book is one that makes

interesting reading, and many of the general ideas are worthy

of attention. But such confusion, inaccuracy and misstate-

ments of fact as we have pointed out above are almost or quite

sufficient to remove it from the field of science.

H. S. JENNINGS.

MAMMALOGY

Osgood’s Revision of the Mice of the Genus Peromyscus.—'The

genus Peromyseus is one of the most widely distributed and

most numerously represented genera of North American mam-

mals, its range including the whole continent from the Arctic

barren-grounds to Costa Rica and Panama. It is, further-

more, one of the most interesting from the viewpoints of mor-

phology and evolution, and also historically, in as much as it typi-

fies and illustrates the progress of North American mammalogy.

It includes, as at present restricted, only the small field mice >

634 THE AMERICAN NATURALIST [Vow. XLII

familiarly known as wood mice, deer mice, vesper mice (in allu-

sion to their semi-nocturnal habits), or white-footed mice (from

the fact that nearly all have white feet). They are at home in

all sorts of environments, from moist woodlands to the open,

semi-arid deserts, and vary in size from an animal smaller than

the common house mouse to species nearly the size of a two

thirds grown brown rat. The extremes of the group differ

widely, not only in general size but in the size of the ears, the

relative length of the tail, in coloration, and in dental and cranial

characters. They are all subject, each after his kind, to a wide

range of color variation, dependent upon age, season and abra-

sion of the pelage. They are also a plastic group, responding

quickly to changes in the environment, so that quite diverse and

geographically widely separated forms are often connected by

an unbroken chain of intergrades, which renders the satisfactory

allocation of closely allied forms extremely difficult, owing

largely to the complications that have arisen from the bestowal

of names upon what prove to have been intermediate forms.

The naming of species and subspecies has been, in most instances,

necessarily haphazard, since for a quarter of a century there has

been no attempt to coordinate the work of the numerous describ-

ers who have raised the number of named forms from about a

score in 1885 to fully 200 in 1908.

For several years Mr. Wilfred H. Osgood! has been at work

upon a monographiec revision of the genus, based upon a critical

study of over 27,000 specimens, including the available material

in all the principal collections, both private and publie, in this

country, supplemented by the examination of types and other

important material in the museums of Europe. ‘‘This material,”

says the author, “‘ineludes all the types, both of valid forms and

synonyms. In almost all cases in which no types exist, good

series of topotypes, or specimens from near the type localities,

have been available.’’ The greater part of the specimens ex-

amined were collected by the Biological Survey, under the direc-

tion of Dr. C. Hart Merriam, with the special purpose of bring-

mg together the material necessary for the proper monographie

revision of the group. The results of Mr. Osgood’s studies are

Fauna, No. 28. Published April 17, 1909. 8vo, pp. 1-285, pl. i-viii, colored

map, and 12 text figures (small distribution maps).

No. 514] NOTES AND LITERATURE 635

most welcome and will mark an era in the history of the genus,

and for a long time to come will be the standard reference work

for the group and the point of departure in future investigations.

The first member of the genus to receive a name was the com-

mon white-footed mouse of the northeastern United States, called

by Kerr in 1792 Mus agrarius americanus, renamed Mus sylvati-

cus noveboracensis by Fischer in 1829, both authors regarding it

as a variety only of a European species. By 1850 the number of

named forms had increased to 9, to which were added 8 during

the next decade, of which 13 were formally recognized by Baird

in 1857. During the next twenty-five years only two or three

new names were added to the list, but from 1885 on to date the

number rapidly increased; ‘‘no fewer than 167 names for new

or supposed new forms of Peromyscus,” says Osgood, ‘‘have

been proposed since 1885,’’ to which 14 were added by him in the

present paper, making a total of approximately 200 names to be

dealt with in the consideration of the group. In the present re-

vision 143 of these names are accepted as representing valid

forms, of which 53 are given the rank of species and 90 are

treated as subspecies. Of the 53 species, 23 are monotypic and

20 are polytypic, or include one or more subspecies, P. manicu-

latus including 35 forms, P. leucopus 12, and so on down to

monotypic species. According to the author’s own statement

(p. 24) : ‘The number of bona fide species scarcely exceeds forty,

and of these some half dozen eventually may be reduced in

rank.’’

In early days the white-footed mice, in common with all other

mice, were referred to the Linnean genus Mus. Later (1853-

1874) they were referred to Waterhouse’s untenable genus

Hesperomys, a name replaced by Coues in 1874 by Vesperimus

in a subgenerie sense for certain North American species form-

erly referred to Hesperomys, and later (1891) given full generic .

rank for the group of forms now placed under Peromyscus. It

was soon discovered, however, that Vesperimus was antedated

by Sitomys Fitzinger (1867), which name had hardly become

current before it was found, in 1894, to be antedated by Pero-

myscus Gloger (1841), which bids fair to remain the accepted

name for the genus. (This case is thus fully cited as an illus-

tration of the vicissitudes of generic nomenclature in the attempt

to secure permanency of names through the necessary pe

tion of the rule of priority.)

636 . THE AMERICAN NATURALIST [Vou. XLII

As already noted, while the group is a compact one, through

the close interrelation of all the forms referred to it, the ex-

tremes of differentiation are widely diverse, but there are no

trenchant lines of division, for, ‘‘if a single character becomes

pronounced, it is merely an extreme development which may be

traced back by stages to a widely different condition.’’ Mr. Os-

good, however, considers it desirable to recognize six divisions as

subgenera, in order to indicate clearly the relationships of the

diverse forms included in the genus. Two of them (Podomys

and Ochrotomys) are here for the first time characterized; two

others (Baiomys and Megadontomys) have been accorded by

some authors the rank of genera, mainly as a matter of conveni-

ence in dealing with so large a group.

It would require too much space to go into details respecting

Mr. Osgood’s methods of dealing with the specially difficult cases,

but the general outcome of his researches is of such general inter-

est and has such a wide bearing that it seems desirable to give a

few passages from his general introduction in his own words.

Thus, under the heading ‘‘ Variation’’ (p. 16), he says:

Among western forms, variations of such an extremely local and

sporadic nature often occur that one may almost believe them to have

been produced in one or at most a very few generations. Such varia-

tions, of course, are slight, and doubtless produced immediately upon

contact with certain conditions. Thus if the range of a given form

includes a few square miles of lava beds, specimens from that area show

an appreciably darker color than the normal form occupying the sur-

rounding region. > And whenever similar conditions are repeated else-

where, even on a small scale, the same result seems to follow. Again,

specimens from the bottom of a dark wooded canyon may be noticeably

darker than those from an open hillside only a few hundred yards away.

‘In the absence of absolute proof one can scarcely avoid the suspicion

that if the progeny of paler individuals were transferred at an early

age to the habitat of darker ones, they would, quite regardless of in-

herent tendencies, develop a darker color, or, similarly, a lighter color

if the process were reversed.

Local and geographic variations are great, so great indeed that,

excepting a few species of very limited range, all the species have devel-

oped geographie peculiarities by means of which they have been sub-

divided into more or less numerous (geographic) races or subspecies.

One species, P. maniculatus, which in its various forms ranges from sea

to sea and from the Arctie Circle to the Isthmus of Tehuantepec,

remains constant only where conditions are practically identical; hence

It 1s represented by a definable subspecies in almost every faunal area

which it enters. The readiness with which local variation is induced

No. 514] NOTES AND LITERATURE 637

and established appears also from the large number [22] of distinguish-

able insular forms. Much of the local variation, however, can not be

considered subspecific. Certain forms, although preserving the same

general characters throughout a definite range, nevertheless show slight

and sometimes unique variations in nearly every local series from within

the range. In these cases, where no two series of specimens from

respective localities are exactly alike, and where no two ean be asso-

ciated except upon the basis of characters common to all, it is necessary

to disregard slight variations and treat the entire association under

one name.

Under ‘‘Intergradation’”’ (p. 17) he eontinues:

Until recent years continuous and perfect intergradation was demon-

strable only in relatively few cases. And even now, although proven

beyond doubt in group after group, in many eases it is merely taken

for granted. That intergradation exists even more widely than is gen-

erally supposed appears from the study of groups in which material

is abundant. Of Peromyscus we have more complete series than of

any other genus of American mammals; that is, not only are there more

specimens, but many more localities are represented and the gaps in

known distribution are usually few. Barriers impassable to many

other mammals have little effect on these mice, for they range continu-

ously, although not always without undergoing change, from sea level

to great altitudes, and from the very humid to the very arid regions.

Moreover, since usually they are so abundant and easily obtained, rep-

resentatives are available from nearly every locality in North America

ever visited by a mammal collector? Within the range of one species

(maniculatus) it is probable that a line, or several lines, could be drawn

from Labrador to Alaska and thence to southern Mexico throughout

which not a single square mile is not inhabited by some form of this

species. They are wanting in the extreme north, but there is scarcely

a corner south of the Arctie Circle in which they do not oceur. With

such wide and continuous distribution perfect intergradation must take

place between related forms of different faunal areas, and with such

complete peters this intergradation must be plainly evident in

nearly all case

Clamsification’ becomes, then, as has been said,’ like dividing the spec-

trum and depends largely upon the standards set, for, theoretically at

least, the possibilities of subdivision are unlimited. It is not strange,

therefore, that hundreds and even thousands of specimens are inter-

grades almost equally resembling two or more adjacent forms. Many

* American collectors of wide experience, in comparing notes, regard as

worthy of remark the few occasions on which they have found themselves

in localities where they ‘‘couldn’t catch Peromyscus,’’ and in such places,

as a rule, they were also unable to catch anything else. :

* Ridgway, ‘‘ Birds North and Middle America,’’ ’ Pt. L P- i 1901.

638 {HE AMERICAN NATURALIST .- (Vor. XLII

of these intergrades for convenience may be referred with some degree

of assurance to the form they most closely resemble, but many specimens

fall so near the imaginary line between two or more subspecies that it

is practically impossible to classify them other than as intergrades. A

particularly troublesome class is one which approximates the color of

-one form and the cranial characters of another, thus reducing the ques-

tion to one of relative importance of characters.

In view of the foregoing it is evident that taxonomic difficul-

ties can easily arise, not only in this but in many other large

groups of conspecific forms, through the unconscious, and hence

unavoidable, bestowal of names upon intermediate and unrepre-

sentative variants—upon connecting links between types that

reach their full development at some more or less distant point

from the locality which happened to be represented by the early

describer’s limited material. While his act may have been justi-

fiable at the time from the circumstances of the case—absolute

ignorance, due to lack of material then nonexistent in collections,

of the range and variants of the group as a whole—it has re-

sulted in difficulties of synonymy and procedure that must. for-

ever involve the subject, and introduce the element of personal

equation into their settlement. As said by Osgood,

The reviser is often confronted with three names representing steps

in development, . . . one of the designated forms being intermediate

between the other two. If, as often oceurs, the recognition of only

two forms seems necessary, and the intermediate has been named before

either of the extremes, its name, having priority, must stand, and it

beomes necessary to decide which of the names representing the

extremes shall be considered a synonym. ... A reviser in dealing with

such names is compelled first to determine the number of recognizable

forms without regard to names.

The type specimens are then referred, according to their re-

semblance, to the recognizable forms, and the names of the forms

determined by the rule of priority.

Another difficulty is the temperamental, the viewpoints of dif-

ferent authors as to what degree of differentiation entitles forms

to recognition. In the main Mr. Osgood has taken what appeals

to the present writer as a judicial course, and has threaded his

way with good judgment through the maze of difficulties insep-

arable from his subject. At all events he has methodized and

correlated our present knowledge of the group, and clearly pre-

sented the relationships of the scores of minor forms that com-

pose it. For the present at least it may be accepted and honored

No. 514] NOTES AND LITERATURE 639

as the last word, but of course not as the final adjustment, which

must come slowly, as new material is gathered from the lesser

known areas of the range of the genus, especially from the region

south of the United States.

His paper is accompanied by a key to the species, and also by

keys to the subspecies where such are required. A colored map

shows the distribution of the species and subspecies of the Pero-

myscus maniculatus group, with indication of the intergrading

areas between the recognized forms. The twelve text figures con-

sist of small maps showing the range of all of the other species

and subspecies. There are also tables giving the average and

extreme external and cranial measurements of series of speci-

mens of each form. Seven of the eight plates illustrate the

skulls of some fifty or more species and subspecies (from photo-

graphs), while plate eight gives enlarged figures of the teeth and

soles of the several subgenera.

It is to be regretted that the bibliographical references are

restricted to the citation of synonyms, and thus fail to give clues

to the work of previous authors, so essential to subsequent inves-

tigators in following up the history of a species or group, and

hence of high importance in monographie treatises like the pres-

ent. Aside from the convenience such references afford, they are

important as a means of coordinating definitely, from the mono-

grapher’s standpoint, the work of previous authors. Further-

more, in the lists of ‘‘specimens examined,’’ only the localities

and number of specimens from each are mentioned, the name of

the collector and the collection where the specimens are located

being omitted, thus giving no clue to the particular specimens to

which the monographer refers. This, however, is obviously due

to a faulty system of treatment rather than to the preference of

the author, since the same method characterizes the long list of

important monographs issued under the auspices of the Biolog-

ical Survey. The addition of these essential items of informa-

tion would considerably increase the amount of text, and for this

reason have perhaps been omitted, since it is known that, for a

long time at least, the restriction placed by the officials “‘higher

up’’ in the Department of Agriculture on the technical publica-

tions of the Biological Survey were practically prohibitive of

monographiec papers exceeding a certain number of pages. —

J. A. ALLEN,

AMERICAN a OF NATURAL HISTORY,

New Yor

640 THE AMERICAN NATURALIST [Vou. XLII

LEO ERRERA

In Memoriam Léo Errera.—One can not ask for more loyal

friends than those who have undertaken to keep alive the

memory of the Belgian botanist Léo Errera, who died August

1, 1905, in his forty-seventh year. Botanists throughout the

world have been favored with publications relating to the life

of the lamented author and investigator, and volumes of his |

collected papers. The little volume, ‘‘ Notice sur Léo Errera,” a

by Leon Fredericq and Jean Massart tells pleasantly the story 3

of his life and labors and recreations, and closes with a chrono-

logically arranged bibliography of his writings, including nearly

three hundred entries. His first paper appeared in 1874 when

but sixteen years old, and this was followed a year later by two

papers (one botanical), and from this time they appeared an-

nually in increasing numbers, almost to the day of his death.

In fact, ten papers were published posthumously by friends and

colleagues who arranged or completed them for publication.

A list of the ‘‘distinctions’’ bestowed upon him, ineludes his

membership in various scientific societies, as well as the diplomas,

medals, ete., which were awarded him.

Of the series of volumes planned to include a collection of

his works under the general title of ‘Recueil d’CSuvres de Léo

Errera’’ three are already published. The present arrangement

includes six volumes. Volumes I. and II. are devoted wholly

to Botany. The first contains papers on the Vegetation of the

Environs of Nice, a review of Schuebler’s ‘‘Pflanzenwelt Nor-

wegens,’’ the structure and modes of reproduction of flowers,

heterostyly of primroses, a critique on systematic botany, sug-

gestions as to certain neglected researches on bacteria and com-

pass plants. The second volume contains papers on the respira

tion of plants. Latin names of plants, the scientific basis of

which these volumes must have for the botanist. Volume II.

which is not yet published, will contain papers on general physiol-

ogy; Volume IV., not yet published, will include philosophical

papers, largely botanical; Volume V. is to be pedagogical and-

biographical. Volume VI, containing miscellaneous poetical and

prose papers, has already appeared. It gives one another view

of this versatile man.

CHARLES E. BESSEY.

Methods in ach semi i

By CHARLES J. CHAMBERLA

Second edition, revised and much enlarged; 272 pages, with 88 into 8vo, cloth; net $2.25,

postpaid $2.39

HE first complete manual to be published on the subject of botanical micro-

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“Will no doubt find a place in every well-regu- “It is an excellent book for the prides

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private students.’’— Plant World.

A eased ef Guide i in Pog ig

AUL G. HEIN

158 pages, interleaved, ri 37 illustrations, Kag ro pi $1.50, postpaid $1.61

CLEAR and concise presentation of bacteriological technique, designed pie

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reference book for the biological teacher =F | investigator, as well as for iraani

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By MICHAEL F. GUYER |

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HE title of this book will explain its scope. It is intended as oratory |

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The American Naturalist

A Monthly Journal, established in one Devoted to the Advancement of Deft eg eg Sciences

erence to acters

with Special Ref.

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CONTENTS OF THE APRIL NUMBE

Heredity of Hair Colorin Man, GER S C. Dee

PORT and CHARLES C, DAVENPOR

A yr eng for Organic pOurraaion. Professor G. H.

RKER.

Recent Advances in the Study of Vascular A

Vascular Anatomy and the Repr sarare Na Structures.

Professor Jo. ed M. COULTER.

The Progress of Plant Anatomy Durin

pey a mra ees f the Bi etri Constants, D

oi rap ig iom: rie m: R.

RAYMOND ey Pure Strains as Artifacts of

bonny tr Y Cook.

Notes and L maya Heradity—The ? aig tebe = Unit’

Charac eps J. SPILLMAN. Znvir

Dus aan E EL d ism, Professor T. Hy-

MORGAN. py E i mnia aden Hed ide Crinoids, Dr.

AUSTIN HOBART CLARK.

CONTENTS OF THE MAY NUMBER

The Categories of Variation. Professor S, J. Hommes,

The General Entomological Ecology of the Indiam Corn

Plant. S. A. FORBES.

Notesand Literature: Biometrics—Some Recent Studies —

on Growth. DR. RAYMOND PEARL. Experimental

Zoology—Cuénot on the Honey Bee, Professor T. H.

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CONTENTS OF THE JUNE NUMBER

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Variation in the Number of Seeds per Pod in the

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Broom, Doctor J. ARTHUR

. in Ecology

The Trend of Ecological Philosophy. Professo:

The a < of ogical aa

: ; Physiol t

Ecology. DR. BUR Doan N.

Notes Literature: Notes on Evolution, V, L. K.

DeVries’s Species — DR. GEORGE n

the First Two f the ž

Dr. 5. F. McC x Sie

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The Piere ede gy Absence ” ‘Hypotheals Dr, Groxer F

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Present Problems in Plant Ecol = Nesta iat

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Shorter Articles and pia araa nee d i 2

nau Deposits in Virginia. Dr. ee

Neu and Literature : Pog ay, EE er Case ve See

delian Heredity. : x

tive Elimination of Ovaries im in rg be

+ De. HARRIS. a

VOL. XLIII, NO. 515

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MERICAN

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THE

AMERICAN NATURALIST

Voi. XLII November, 1909 No. 515

THE AMERICAN TOAD (BUFO LENTIGINOSUS

AMERICANUS, LeCONTE)

A Srupy in Dynamic BioLocy

NEWTON MILLER

CLARK UNIVERSITY

InTRODUCTION

For some years it has been my desire to inaugurate a

series of university theses aimed distinctively at study-

ing important American species as forces in nature.

This kind of work has seemed to me logically the next

step in the advance of American natural history. In

fact, it is hard to imagine any other line of real advance

possible. Species are not discovered, determined, named

and classified for the mere sake of making it possible for

people to learn their names. :

No matter how common the species, when we ask the —

questions: What does it do in the economy of nature?

What position does it occupy in the vital organization

of American natural history? What are its relations —

to human interests? In short, what expression have -

we of the species as a force in nature? When we ask a

these questions of the commonest animals, we find our-

selves almost as near the verge of human knowledge as

with an undiscovered species. No less a man than .

win himself led off in the field of dynamic biolog :

his study of “Earthworms and Vegetable Mould.” A

642 THE AMERICAN NATURALIST [Vou. XLII

large number of living forms await study from a similar

point of view.

If we determine accurately the work of an individual

and multiply this by the number of individuals, we have

an expression of the species as a force in nature. Hence

it is true, in general, that the commoner or more numer-

ous a species is, the more important its biological work.

We accordingly begin this series of dynamic studies with

one of the commonest of American animals. |

Of the ten species of Bufonide now recognized in the

United States B. l. americanus has the widest range,

which includes almost the entire continent of North

America east of the Rocky Mountains. It is, therefore,

probably the most valuable type of the group.

The insect problem, further, is one of the most im-

portant in the entire field of American natural history.

It finds partial expression in the annual tax of $795,100,-

000 which insects impose upon our agricultural resources.

This is a rigidly conservative estimate made by the

department of agriculture and does not include costs of

abating annoyance or losses of household goods or those

occasioned by spread of human disease. A large pro-

portion of this loss might be most economically prevented

by a reasonable knowledge and utilization of insectivo-

rous animals. With all our books, bulletins and talk about

it, we have scarcely made a practical beginning in this

direction as a people. :

In seeking animal allies to aid in the solution of the

insect problem we should choose those which will do the

work required most effectively and at the same time

present the fewest objectionable features. A good many

birds are efficient destroyers of insects, but become in-

jurious if their numbers are unduly increased. Many

insects are parasitic and predaceous, but, in general,

their breeding or regulation is beyond human control.

Clearly an animal to be depended upon to hold insects

in check should be one which man can breed in any de-

sired numbers and, on account of the enormous repro-

ductive possibilities of insects, a form which he can in-

No. 515] THE AMERICAN TOAD 643

crease rapidly. We may do much by way of increase

of insectivorous birds, and even bats may prove valuable

allies. We may be grateful for the help of predaceous

and parastic insects, and good work has been done in

importing parasites of foreign insect pests, but clearly

we need all the assistance we can find; and all the above

agencies are scarcely controllable enough to be depended

upon.

For an insectivorous animal which conforms to every

requirement of the situation, ease of control and rapid

increase, non-injurious, in any numbers, an active feeder

in abundance and a patient faster in scarcity, the toad

stands probably first on the list among American insec-

tivorous animals. Experiments are now being carried

on also with the bob white or American quail with every

prospect that this form may prove of equal, if not supe-

rior, efficiency, and it will carry added values, in food,

sport and weed-seed destruction; but this species is

rapidly being exterminated from a large portion of its

former range, and it will require a long time for methods

of propagation and protection to be worked out and be-

come generally known.

A good deal of unnecessary balancing of accounts has

been done of late in attempting to calculate the economic

value of species from analysis of the foods. In some

cases this has yielded results of some value, but, in gen-

eral, they have been misleading. Even a small percent-

age of the gross food of a hawk or shrike, for example,

if it consists of a valuable species, might render the

predaceous species injurious. In the case of beneficial

insects, excepting the honey bee which is under human

control, if a species will destroy all the injurious insects,

it detracts little or nothing from its efficiency, if it take

the beneficial insects as well. This principle applies —

particularly to the toad, which takes everything in the

form of an insect, worm or slug that comes in its way. _

Instead of filling its stomach four times in twenty-four

hours, as Kirkland estimated, Mr. Miller finds that the

toad takes but a single meal a day. This is no diseredit

644 THE AMERICAN NATURALIST [Vou. XLII

to the efficiency of the species. It means, simply, that we

should require four times as many to do the work, and,

with the number of eggs produced, this offers no difficulty.

Given a pond or even a small pool insured against dry-

ing up during the late spring and early summer, and

from which natural enemies are eliminated, toads will

breed in any desired numbers up to the limits of in-

sect food supply. It would probably, however, be diffi-

cult or even impossible to find a single farm in the

United States or Canada, although suffering severely

from depredations of insects pests—not even the agri-

cultural experiment station farms—which makes any

provision whatever for the breeding of toads. In fact,

reports so far gathered reveal the fact that farms in

the agricultural states of Indiana, Ohio and Illinois are

almost entirely destitute of the species. It is probably

safe to infer that the toad has been exterminated already

from a considerable portion of the cultivated land in the

agricultural states. Is this an inevitable result of drain-

ing land, and modern methods of tillage? If this be true,

can any changes or adjustments be made which will per-

mit the increase of the species? Will the value of the

toad’s work warrant anything of the kind? Would it

pay to establish special breeding places like our present

fish hatcheries, or possibly in connection with them?

In order to answer these and many other questions we

must have the data of the life and work of the species.

To gather these in a manner, if possible, complete enough

to serve as a guide and basis for practical action is the

purpose of Mr. Miller’s work.

THe American Toan (Bufo lentiginosus Americanus

LeConte)

The ancestors of the Bufonide first appear as fossils

in the Oeningen beds below the Miocene Tertiary strata.

The group now has a wide range, being found in all

parts of the temperate and torrid world with the excep-

tion of Australia and the oceanic islands. The greatest

number of species is found in the torrid regions. The

No. 515] THE AMERICAN TOAD 645

Bufondiz are represented by nine genera and more than

a hundred species. Bufo takes its origin in the Sonoran

subregion, i. e., the southwestern part of the United

States. It is the only genus found in the United States

and is represented by ten species, most of which belong

to the southern states. The species lentiginosus and its

varieties are found throughout the eastern part of the

United States and Canada. Two varieties, americanus

and fowleri, share this region (Massachusetts).

Jordan and Cope class the American toad along with

Fowler’s as a variety of Bufo lentiginosus.

My object in this work is to give as completely as

possible the entire life and work of one species as nor-

mally lived in its own environment. Observations were

made continuously throughout the year on the species,

Bufo lentiginosus americanus, the results of which are

given under the heads, Spawning Habits and Seasons;

Development, Habits, and Food; Hibernation; and

Enemies.

collecting the data for this paper, also for valuable

criticisms of the manuscript. He also kindly consented

to write the introduction. I wish also to thank Mr. F. E.

Chidester for assisting me with the feeding-tests and

in obtaining data on the daily life of the toad.

SPAWNING HABITS AND SEASONS

Observations were made for the springs of 1907 and

1908, but if not otherwise stated the data for this chapter

refer to the spring of 1907. Mention is made of 1908

when this season varies from that of 1907. ~

Toads were first seen in 1907 on the twenty-eighth of o

March and on the thirteenth of April in 1908. An adut

male was found in the water on the night of March 29,

1907, but was so numb that he could not give the usual oe

chirp when picked up. From March 29 to April a -

there was a decided drop in the temperature and toads

* More recently Miss Dickerson has given these toads specific : * seen

i. e., Bufo americanus and Bufo fowleri. tte eee

646 THE AMERICAN NATURALIST [Vou. XLII

were not seen again until the night of the twenty-second

of April, on which date seven males were found trilling

in pond no. 1.2. Hight days later when the migration to

the ponds reached its maximum, mated pairs were

abundant on the streets and elsewhere on their way to

the water. ‘Trilling began in 1908 on the twenty-third

of April and spawning on the twenty-fifth, ending May 13.

The seven toads mentioned were the first heard trilling

this season. They were sluggish and when taken up

between the thumb and finger could not chirp, although

they made the attempt.

The accompanying curves show the number of toads

as well as the number of males and females that were

found in pond no. 1 on the night of April 24 and suc-

ceeding nights (Fig.1). Spawn was found here the twenty-

mòi \

hot

if ay as te 27 23 29 so si Hy i 2 3

Fic. 1. Curves showing the number of toads in pond, No. 1, during the spawning

season. No. 1, Females. No. 2, Males. No. 3, Total.

sixth. The males were most active on this and the night

of the twenty-ninth. On these dates they were trilling

vigorously and actively swimming about. If they saw

an object moving they swam to it with all possible speed.

When it was a male, which was usually the case, he was

seized, but loosed as soon as he chirped. They even came

2 This pond is located at the foot of a small steep hill in a pine grove in

Park Avenue Place within a hundred yards of a large permanent pond. It

is V-shaped, not more than fifteen feet wide by fifty feet long, and during

the spawning season was about eighteen inches deep. For the most part it

is filled with leaves, some water plants and debris from a near-by dumping

ground. Rains are its only source of supply and it goes dry in summer.

No. 515] THE AMERICAN TOAD 647

to me as I waded out or made a disturbance in the water.

All the females on the night of the twenty-seventh and

succeeding nights were removed from the pond to the

laboratory.

To sum up my observations on this pond we find: first,

that the males are the first to reach the water; second,

that there were two waves of spawning activity; third,

that not less than ninety-two females visited this pond;

fourth, that on an average 88.8 per cent. of the toads in

the water at any given time during the spawning season

were males.

Of eighty-two taken at random from the streets after

the breeding season 60.8 per cent. were females. Kelli-

cott gives the proportion of males to females of those

collected along Lake Erie, Ohio, as 175:266; King for

toads near Bryn Mawr, Pa., 713:823; i. e., 39.7 per cent.

46.5 per cent., respectively, were males.

The females leave the water as soon as they spawn

(from six to eighteen hours after reaching the pond).

It is probable that the males return to the ponds night

after night, which accounts for their apparent excess in

numbers during the spawning season.

Observations were made on five ponds, and it was

found that the periods of maximum spawning were not

simultaneous in all. In no. 1 and no. 2,° the spawning

‘period reached its maximum on the nights of April 29

and 30; in no. 3,4 May 1 and 2; in no. 4,5 May 14 and 15;

in no. 5,° May 18 and 19. 3 :

* Pond no. 2 is at the junction of Park Avenue and Maywood Street. it

is a permanent pond of about thirty yards in diameter with a depth of three —

feet. Around its west, north and east edges is a dense growth of. bushes,

some growing far out into the water. The south side has its growth of flags

and water grasses. To the south and west is an open field, while buildings

are near to the east and north. ; ; ke ee

‘No. 3 is an overflow of Beaver Brook in an open place just below May

Street. This pond is permanent, but the water falls soon after the spring

rains to such an extent that most of the spawn is lost

648 THE AMERICAN NATURALIST [Vou. XLIII

Why should there be this difference of twenty days be-

tween the spawning periods of toads in no. 1 and those in

no. 2? It can partially be explained by a cold wave which

set in on the fourth of May and stopped laying until the

ninth. Even so, the toads in no. 1 had finished spawning

before the cold wave came. Neglecting the five days

of cold weather, there still remains a difference of fifteen

days. These ponds are not more than a mile and a half

apart. The elevation is practically the same, also the

surroundings. Therefore the environments of the two

ponds do not seem sufficiently different to account for

so much difference in the spawning periods.

My observations indicate that toads proceed to the

ponds immediately after emerging from winter quarters.

If this be true, then there is a second laying, or some

toads do not come from hibernation until late in June.

Observations on one toad in my experiments on hiberna-

tion suggest that the latter is true. This female came

out for the first time May 28, and if she had gone to the

water at once, she would have been thirty-three days

later than the first that spawned. I might add that I

have seen no large toads among these late layers. All

the females are about forty grams or less in size.

The bulk of the spawn for the spring of 1908 was laid

in all the ponds between May 2 and 6. A minor period |

of spawning occurred on the eleventh to thirteenth.

The first few warm days of spring bring out the toads

and soon the males are heard in the ponds. In a few

more days the females follow and spawning begins at

once. I have seen no toad eggs in running water, al-

though there is a small stream within less than two hun-

dred feet of ponds where many toads spawned. How-

ever, Dr. Hodge informs me that toads spawn in Rock

River, Wis., and Ottawa River, Canada, and Mr. Morse

states that toads generally spawn in small streams in

Ohio. Toads in this region prefer small ponds in which

about two hundred yards long by twenty wide. Its depth is probably three

feet. Trees surround it and a three-hundred-foot hill rises at its west side.

Buildings skirt all sides of the park except the west.

No. 515] THE AMERICAN TOAD 649

to spawn. Pond no. 1 is within a hundred yards of a

large permanent pond, and when there were a hundred

or more toads in the former, very few were to be found

about the latter.

In natural ponds toads congregate more or less during

the spawning season and in a given pond 90 per cent. or

more of the eggs are laid within a radius of fifteen feet.

In three of the four natural ponds observed the eggs

were deposited in an area less than fifteen feet in diam-

eter. Other places similar to those where the spawn was

laid existed in these ponds, but were used only by a very

few toads if at all. Usually only a portion of the grassy

place chosen was used (Fig. 2). The artificial pond in

Fic. 2. Pond No. 1. Circle shows the spawning place.

University Park gives almost the same results. Here

the edges are kept clean and the toads had to deposit

their spawn on the bottom. Nevertheless, all the eggs

laid here before May 4 were deposited in an eight by

ten foot strip of the north shore.. Later, May 9-15, eggs

were laid all along the north and northeast sides, with

a few scattered spawn along the south. The two or three

650 THE AMERICAN NATURALIST [Vou. XLIII

pairs that may occasionally be found in ponds during

the latter part of May and June may deposit their eggs —

any place about the ponds. I found a little colony of

some twenty pairs June 4-8 laying in a space not more

than six feet in diameter in an overflow of Beaver Brook.

My observations for the spring of 1908 on the same ponds

confirm the above statements. The spawn in the various

ponds was deposited in almost exactly the same places

as the previous year.

Since in general only limited areas are used for spawn-

ing it would indicate that there is some choice among

toads for spawning grounds. This is done by the males,

but without the purpose of having the spawn deposited in

such and such a place. They reach the water two or three

days before the females and begin their trilling. They

seek out each other and repeatedly attempt copulation

with one another. In this way all the males in the pond

are soon brought together. Even a day or two before

the females arrive they are assembled, usually, on some

grassy spot out in deep water, to which they return after

a fruitless attempt to mate with other males. The fe-

males, following the trill of the males, come at last to this

circle where they mate and lay. Thus these resting

places of the males eventually become the spawning

grounds. The observations of Mr. Courtis, later repeated

by myself, support the view that the females come to the

males.

The spawning place is usually a grassy plot well out in

the pond where the dead grass or weeds come to within

two or three inches of the surface. In artificial ponds

where such places do not exist a shallow place along the

edge is used. In the former case the female, as a rule,

does not go down to lay, while in the latter practically

all spawning is done under water.

Should it turn cold while the toads are spawning they

leave the water until the temperature again rises. Mean-

while, they may be found concealed in the grass or leaves,

or sunning themselves at the edge of the pond, often the

No. 515] THE AMERICAN TOAD 651

male still clinging to the female with which he had

mated before leaving the water.

As with all amphibians the eggs are fertilized outside

of the body. In mating the male clasps the female just

back of her fore legs and then places his hind feet upon

her thighs. This is the position maintained throughout

except at intervals during oviposition. The intervals

are about fifteen minutes apart. At such times the

female straightens her body, raises her head, and stretches

her hind legs backwards. The male hooks his feet be-

tween the female’s hind legs, thus forming a basket be-

tween the feet and legs of the male and the legs and

body of the female. (Fig. 3.) In this basket are now

Fic. 3. Shows the formation of the basket in which the eggs are fertilized.

deposited probably two or three hundred eggs, while

simultaneously the male ejects his sperm. Boulenger 15

no doubt mistaken in the purpose of this process when

he writes that the male (B. vulgaris) aids the female m

652 THE AMERICAN NATURALIST [Vou. XLII

oviposition by pulling the eggs strings with his toes.

That the male ejects his sperm at this time was demon-

strated by microscopical examination of a slide applied

to the anus of the male just before and during oviposi-

tion. In the former case, very few if any spermatozoa

were found, while, in the latter, they were found in

abundance.

As soon as the eggs and sperm are ejected the toads

remain quiet, holding the mass in the improvised basket

perfectly quiet from one to three minutes. This is ample

time for the spermatozoa to get well attached to the eggs,

since fertilization takes place within four minutes from

the time the eggs leave the oviduct. The female now

moves along, stretching out the strings of eggs just laid.

Most of the eggs are deposited in water not more than

ten inches deep. Those found in weedy and grassy places

are, usually, not over four inches under water. In Uni-

versity and Elm Park ponds where the toads were much

disturbed, a large number of eggs was deposited some

distance from the edge at a depth of eighteen inches or

more. This deep laying seemed of no particular dis-

advantage, since a toad can remain underwater as long

as fifteen minutes, which is ample time to fertilize the

eggs and stretch out the egg strand.

The eggs are encased in a continuous, cylindrical, gel-

atinous strand of three to four millimeters in diameter.

The gelatinous coat is added in the oviduct, and as soon

as ejected absorbs water and swells. In this way there is

a mass of .0225 gram of jelly-like substance about each

egg, which serves as a means of protection. Eggs re-

moved from the ovary weigh on an average .0024 gram

and measure 1.1 to 1.2 mm. in diameter. When laid

they are variously spaced in the strands even of the same

Spawn (Fig. 4). Sometimes they are crowded together

so that as many as three may be in the same cross-section,

or again regularly spaced at intervals of about 1 mm.

The strings may be laid by either twos or fours. I have

not observed in smaller toads (under 7 cm.) more than

two strands being deposited at the same time, but in the

No. 515] THE AMERICAN TOAD 653

larger females four are not uncommon. ‘The time re-

quired for oviposition varies between six and eighteen

hours.

The number of eggs in spawns may be said to vary

with the sizes of the toads. Thus females 6 em. long lay

Fic. 4. Spacing of the eggs as seen in a single spawn.

about 4,000 eggs while a toad 9 em. long may lay 15,000.

The smallest spawn observed consisted of 3,929 eggs and

the largest 15,835. These were laid in the laboratory.

On making some computations on the largest spawn,

we find that the eggs weigh 38 grams and with the

gelatinous covering, 394 grams. ‘This latter weight is

about five times the weight of the toad. Again, allowing

a space of 1.5 mm. for each egg, we get 41 meters, or 134

feet as the length of the strings.

Only the males trill or make any sounds. While trill-

ing the mouth and nostrils are closed and a pouch under

the throat is inflated. Trilling in the full strong note

was observed only in connection with mating. Miss

Dickinson describes the call as follows:

The sustained note is not only high pitched and tremulous, it seems

to have a dual character as though a low note was droned at the same

654 THE AMERICAN NATURALIST [Vou. XLII

time that the high one is whistled. Imitate the call by whistling the

upper and at the same time humming the lower of the following notes:

Concerning the call of the toad after the breading season

she writes:

I have heard this feeble note of the toad in August only some half

dozen times (the toads were under observation in “moss garden” in

the house).

One of the toads in experiment no. IT. gave this call

April 5, 6 and 22. I heard at least ten toads giving this

feeble note on the afternoon of the twenty-first of Sep-

tember, 1907, and at night of the same date just before

a thunder storm. In 1908 this trill was heard as late

as September 26. This note is not at all similar to that

of the breeding season. It is about the same pitch but

much weaker, more guttural, and not so long. The trill

is not so distinct as in the spring call. :

Tt has already been stated that on an average 88.8 per

cent. of all the toads in a pond at any given time are males.

Thus, for every female there are seven males. Often a

male clasps a female before she reaches the water and she

must carry him to the pond. At the pond a lively scene

follows until the female with her mate reaches the spawn-

ing place. I have often observed two or three males

clasping the same female and a few instances of four.

In such cases the female is helpless and is usually held

underwater. Darwin states on the authority of Dr. Giin-

ther that a female is sometimes drowned during the strug-

gle among the males. In these contests the male always

gets hold of the female, for he will not hold another male.

The one that first clasps the female in the mating posi-

tion can not be dislodged, no matter how much stronger

his rivals may be. The female, if she is in the water,

helps her partner evade the other males by diving or sink-

ing. This she does repeatedly and to good advantage

during oviposition.

Males can not distinguish at sight males from females.

For this reason they are continually clasping one another.

They have a call of three or four notes which they utter

im rapid succession when taken up between the finger and

No. 515] THE AMERICAN TOAD 655

thumb, or clasped by another male. This seems to be a

warning signal, for a male will release another as soon

as he chirps. In ponds males fight over a dead male as

though it were a female. They will clasp anything mov-

ing or which touches their breast that they can hold.

It was mentioned above that spawn was deposited at

a depth of eighteen inches or more in certain ponds. This

depth appeared to be unusual, still the eggs developed

normally. The following experiment was made with 500

eggs to test the effect of depth on hatching. One hundred

eggs were placed in each of five tumblers over the tops

of which were stretched pieces of cheese cloth. These

tumblers were then attached six inches apart to a stick

which was fastened upright in pond no. 2.

The experiment was started the twenty-first of May.

The eggs in the lowest vessel developed much faster than

those in the top, apparently as much as a day ahead. This

can probably be explained by the fact that a cold wave

came the day the experiment was started and continued

for four or five days. Thus the surface was cooled more

than the deeper water, but the final result of the hatching

of the eggs at different depths was the same. A similar

experiment made in pond no. 4 gave uniform develop-

ment for eggs at depths between six and twenty-four

inches. From these data it is seen that depth to as much

as twenty-four inches does not affect materially the hatch-

ing of the eggs.

Counts made on eggs in various places show that 68

per cent. to 90 per cent. are fertile. On an average, devel-

opment begins in 85 per cent. of the eggs.

DEVELOPMENT, Hasits AND Foop

The toads leave the water as soon as they spawn. De-

velopment proceeds rapidly in the eggs from which tad-

poles emerge within two to six days, depending upon the

temperature. At this time the larva is about 3 mm. long

without mouth or appendages. On the under side of its

head behind the buccal area are two small erescent-like

depressions known as ‘sucking disks.’’ These ae.

656 THE AMERICAN NATURALIST [Vouw. XLII

glands, however, and it is by their sticky secretion and not

by suction that the tadpole attaches itself to objects.

For a day or two after hatching the tadpoles cling most

of the time to the gelatinous strings or near-by plants.

The tail is noticeably compressed on the second day and

Fic. 5. Toad tadpoles feeding on a pout in a natural pond.

the larva makes excursions from time to time, eventually

reaching the shallow water. The mouth is formed in

three to seven days, and the larve begin feeding. Hence-

forth the tadpole is a voracious feeder, living largely upon

the slime at the bottom of the pond and that collected upon

sticks and plants. Meats, fresh or putrid, are eagerly de-

voured and vegetable matter is also eaten. In this way

the tadpoles play the part of scavengers (Fig. 5).

The first gills are external and are soon replaced “by

internal ones.

The first indication of transformation is the growth of

the legs. They appear as small knobs or buds about the

twentieth day of the tadpole’s life. Both pairs grow rap-

idly and within ten days may be fully formed. The front

legs, concealed in the gill chamber, appear suddenly a

short time before the tadpole leaves the water. One is

thrust out at the breathing pore and the other breaks di-

rectly through the operculum. The tadpole is now almost

ready to abandon its aquatic life and within a day it may

No. 515] THE AMERICAN TOAD 657

do so. A few days previous to this time, the tail has be-

gun to shrink and by the second day out of the water may

be completely absorbed. Meanwhile great changes take

place in the region of the head. The eyes become en-

larged and elevated; the larval beak or jaws are lost; the

mouth broadens and a tongue forms; the gill slits close

and the lungs mature. The long coiled alimentary canal

shortens and differentiates into stomach and intestine.

The color changes from a jet black to a brownish tinge

with faint spots. The skin is yet perfectly smooth. All

of this growth, development and metamorphosis from the

egg to the completion of the toad may take place in thirty-

two days, or two hundred, as in the case of some kept in

the laboratory in a poorly fed condition.

The following table is given to show the rate of growth

and development.

TABLE I

Total Length, | Body Length, | Hind Leg, | Weight,

o mm. mm, mm, Grams.

pril 29, eggs laid. 0024

May 4 larvæ still in the gelatin. 3.5

5 6 i gece 1 SOF ce 4

“cc ? ce a9 (a4 ae (3 € s

i g out of the gelatin 7.0

‘ 6c ce

ec 13 ce ce ce “ec cc z .0157

z 15 a a aa S a té 10.5 .0132

‘ 19 “s C6868 (73 11.0 .0199

t DE u ef Nera 6c ) .0295

ec ga tr Che tt tt 7 .0385

ie 25 AS (45 bi (3 ‘0 0566

te 27 t4 COO Re ee 4 5 1.0 0901

ee 29 «Ot 4b A t4 ie 2.0 1310

June 2 « Ae 00 Ot t 4 2.5 .15

‘ i ta K 66 8 95 3.0 .1460

ts t4 T 6c 34 10.0 3.5 1570

t g “ Ho oen tc 4.4 10.0 4.0 .1680

A 9“ Hu a a 25.8 10.0 5.7 .1700

‘< 10 largest specimen. 28.0 10.5 7.0 p

_ 12 one transformed. 25.3 10.0 8.7 pps

s Ag u t 10-25.0 10.0 11.0 „AVA

_** 18 all metamorphosed. 10.0 10.0 11.5 0796

The weight given for the eggs is that previously de-

termined for those removed from the ovary. To weigh

the tadpoles, they were placed upon a glass slide covered _ :

with filter paper which was moistened sufficiently to keep -

658 THE AMERICAN NATURALIST [Vou. XLIII

the tadpoles alive. The larva, slide, etc., were weighed,

and then, removing the tadpoles by means of a dissecting

needle, the slide, etc., were again quickly weighed. This

method gave me the weight desired without killing the

tadpoles. There was of course some evaporation and loss

of water in removing the larve. But, since it was aprox-

imately the same for each weight, the data are not affected

to any great extent.

This table is the average weight and measurements of

eighteen tadpoles which were kept in a vessel by them-

Fig. 6. Transformation. a, day before leaving the water; b, just leaving the

ter; c, day after leaving the water.

selves with water plants. Their food was mostly dog-

biscuit with a little meat. _

Toads just metamorphosed were seen for the first time

on the morning of the twenty-third of June. During the

next ten days most of the toads of the early spawn aban-

doned the ponds. The number leaving the water at this

time is probably 90 per cent. of all that emerge during the

summer. At this time eggs and tadpoles. in all stages

and toads just metamorphosed could be found in the same

pond. Tadpoles were in the ponds as late as August 15.

Larve from eggs laid April 29th were kept in the labora-

tory until October 20.

: Newly emerged toads are so susceptible to transpira-

tion that they must remain in damp places for a few days.

Many remain near the ponds in the grass, under stones,

etc., during the day, thereby escaping the fate of those

wandering away too soon. At nights or on cloudy days

during the time that tadpoles are transforming, the vicin-

ity of ponds may be alive with young toads migrating

from the water. ;

The great numbers that leave the water or places of

No. 515] THE AMERICAN TOAD 659

hiding during a rain, have led to the belief that toads are

rained down.

After abandoning their aquatic life, these little toads

simply eat, grow and endeavor to escape their enemies.

_By the first of October, their weight at the time of meta-

morphosis has been increased more than sixty times.

In other words, they double in weight almost every sixteen

days.

Reports indicate that toads are very unequally dis-

tributed both as to the country in general and to local

areas. Killicut found them abundant along Lake Erie in

Ohio. Here in Massachusetts they are very numerous.

Through the northern half of Indiana toads can almost

be said to be scarce, while in the southern half they are

found in considerable numbers. Few were:observed in

the vicinity of Waterloo, Iowa. Reports from Wisconsin

and Minnesota indicate that this species is well repre-

sented in these states, while in Maine and Ohio they are

said to be abundant.

Toads are more numerous in and about towns than

elsewhere. Very rarely is a toad seen in a large field

which is under cultivation. Only fifty toads were seen

during a whole season on one thousand acres of farming

land in central Indiana. This scarcity may be accounted

for by two factors, i. e., first, that pasturing and tillage

kill the toads or, second, that the extensive drainage has

exterminated the toad by depriving it of breeding places.

Sufficient data are not at hand, as yet, upon these two

points of general and local distribution to draw conclu-

sions.

During the summer the toad leads a solitary life and no

more utters the ringing trill of the breeding season. On

very rare occasions, which may be as late as September

21, he may strike up a weak, shorter and more guttural

note, which is much inferior to the vigor and fullness of

the mating call. This note is so rare that the toad may

be considered silent throughout the summer.

Rarely, except at night or on cloudy days, is the toad ie

seen hopping about. Late in the fall, however, he may —

660 THE AMERICAN NATURALIST [Vou. XLIII

be found sunning himself in the grass. At this time

he is sluggish and apparently only waiting for cold

weather to put him to sleep. Toads come out of their

hidings on rainy days, and, especially, on nights follow-

ing rainy days. I counted fifty-two toads in a vacant lot

between 7:00-8:00 r.m., July 22, after a hard rain in the

afternoon. Counts repeated here for the next nine days

at the same time in the evening varied between 0 and 16,

and most of the times there were less than six toads to be

seen. On the twenty-second many of this year’s toads

were seen, but on the following nine days, scarcely one

could be found. In general, throughout the summer the

toad passes the day in concealment in damp sheltered

places, while the night, the toad’s day, is spent in for-

aging.

Some of the toads in the above observation of July 22

were shedding their skins, and many appeared to have

just done so. This process is frequent and often takes

place immediately after the toad comes from its place of

concealment.

The one in experiment IV shed her skin every seventh

to eleventh day, or on an average once every 8.2 days

from October 23 to April 8. Those in Experiment III

did not shed so often nor as regularly ; some going as long

as four weeks without shedding, unless they did so in

their burrows. I have seen some indications that shed-

ding is done while the toad remains buried, and the proc-

ess may be frequent and regular although the toad re-

mains concealed. `

The process is accomplished by pushing the skin for-

ward to the neck by the hind feet and then pulling it off

over the head by the fore feet. That on the hind legs

and feet is rubbed off against the sides of the body, while

that on the fore legs and feet is pulled off by the jaws.

The skin is removed from the feet and legs in a manner

very similar to that of seizing a glove by the top and turn-

ing 1t wrong side out as it is pulled off. As the skin is

raked over the head it is seized by the jaws and swallowed.

Previous to the removal of the skin, the new skin secretes

No. 515] THE AMERICAN TOAD 661

a viscid substance that loosens the old from the new and

leaves the body moist for a short time after the old skin

has been shed. The whole process is accomplished in

about two minutes.

The following is a record of the work done by an adult

male (weighing 36 g.) in twenty-seven hours. The dis-

tance traveled in this time was 85 feet, and the number

of insects taken, 23. Twenty hours and five minutes were

spent in burrows and, for the rest of the time, the toad was

active only one hour and forty-seven minutes. It is prob-

able that the period of activity from 7:20-8:40 a.m. would

have been lessened had not another toad entered the bur-

row of the one under observation and forced him out.

More than half of the total distance traveled in the twenty-

seven hours was covered in quest of a second burrow.

The following is the time spent in the burrows.

July 25, 1:50 p.m—7 :55 P.M.

July 25, 11:50 p.w—2:30 a.m.

July 26, 4:05 a.m.—7 :20 a.m.

July 26, 8:40 a.m.—4:00 p.m.

The food taken consists entirely of animal matter. Min-

eral or vegetable material is often found in the toad’s

stomach, but it is there by accident. I have found as

much as 0.07 gram of coal and sand in the stomach of a

5.5-gram toad; it had just swallowed its skin and along

with it the coal and sand which stuck to it. I have also

seen pieces of grass, winged seeds and other bits of plants

snapped up and swallowed with insects.

The amount a toad will eat in twenty-four hours seems

somewhat astonishing if we were to judge from various

reports. Miss Ellen M. Foskett records one feeding of a

large toad as ninety to one hundred rose beetles. She also

adds that ‘‘ the toad showed no signs of wishing to con-

clude his meal.’? Kirkland found ‘‘ the remains of sev-

enty-seven myriapods in a single stomach, fifty-five

army worms in another, sixty-five gypsy moth caterpil-

lars in a fourth. In these cases, however, but one kind

of food was present and the toads were above the usual

size.’ He states further, on the authority of Mr. J. E.

662 THE AMERICAN NATURALIST [Vovu. XLIII

Wilcox, that a toad ate twenty-four fourth moult gypsy

moth larve in ten minutes; again, on authority of F. H.

Mosher, that a toad ate thirty to thirty-five full-grown

celery worms in three hours at intervals of about twenty

minutes. Eighty-six house flies are recorded by Dr. C. F.

Hodge as being snapped up in less than ten minutes.

Dr. J. R. Slonaker fed an eighty-gram toad all the beef-

steak and flies it would eat for two days. On the first

day, December 7, it ate 2.8 grams of beefsteak and three

flies; on the second, 3 grams of beefsteak and twelve flies.

From further feeding he concluded that his toad would

eat on an average forty flies per day.

A. H. Kirkland, H. Garman and F. A. Hartman have

given us much valuable information on the food of the

toad from careful analyses of stomach contents. Kirk-

land examined one hundred and forty-nine stomachs col-

lected from April to September, of which he gives the fol-

ing as a fair specimen. The toad was killed at 9:00 p.m.

May 11, 1896, and found to contain: ‘‘9 ants (C. Pennsyl-

vanicus), 6 cutworms, 5 myriapods (Julius sp.), 6 sow-

bugs (Parcello sp.?), 1 weevel (Hylobius pales) and 1

carabid beetle (Pterastichus sp.?)’’; total 28. Kirkland’s

report shows that 84 per cent. of the toad’s food consists

of 28 per cent. lepidopterous insects and their larve, 27

per cent. beetles, 19 per cent. ants, 10 per cent. myriapods.

The insects alone were represented by eighty species.

The five records which follow are those of Garman.

No. 20, a toad 14g inch long, obtained on the Experiment Farm,

August, 1896. 2 Drasterius elegans, 1 Diabrotica 12-punctata, X Sytena

temata, 1 millipede (Polydesmus), 1 bug, fragments of ants, 6 chinch

bugs and fragments of others.

No.1, a toad of medium size, captured beneath an electrie burner,

Lexington, Ky., Oct. 1, 1894, had eaten 27 ants, 19 sowbugs, 3 spiders,

1 caterpillar, and 10 plant-lice; total 60.

No. 2, a toad 1 inch long, captured in a celery patch, Lexington, Ky.,

Sept. 2, 1891, had eaten 14 ants and 1 caterpillar; total 15.

No. 3, captured in a strawberry patch, Lexington, Aug. 5, 1890, had

eaten 2 large ground beetles, 1 tiger beetle, 1 corn root-worm beetle,

1 lady beetle, 8 small ground beetles and 9 ants; total 22.

No. 4, taken Lexington, July 26, 1890, had eaten 2 Colorado potato

No. 515] THE AMERICAN TOAD 663

beetles, 1 click beetle, 4 bugs (Cydnide), 1 tiger beetle, 1 moth, 7 ground

beetles, 6 ants, 1 millipede and 1 sowbug; total 24.

- The above data on six stomachs are given in order to

show what a toad feeds upon while in its natural habitat.

So far as known a toad will eat any arthropod, molluse or

worm that it can easily swallow, without regard to spines,

stings, noxious odor or taste. The question then is, in

determining the economic importance of the toad’s feed-

ing habits, not to know how much it can or will eat, but

to know, how much it actually does eat. Owing to the

slow digestive rate of the toad, stomach examinations give

us a close approximation to the desired information.

It is stated by Kirkland that a toad will fill its stomach

four times per day. This seemed to me to necessitate

rather rapid digestion for a cold-blooded animal, and I

made the following experiment to test it.

August 8, a female weighing 35 grams was killed thir-

teen hours after having fed on three Colorado potato

beetles and two grasshoppers. Examination of the stom-

ach showed the beetles still entire. The grasshoppers

had disintegrated, but none of the food had passed from

the stomach.

August 26, 2:00 r.m., two toads, nos. 1 and 2, weigh-

ing seven and twenty-five grams, respectively, were fed

chiefly on grasshoppers. Eighteen hours later, no. 1 was

killed and at the end of twenty-two hours, no. 2. All of

the food was still in the stomach of no. 1 but well digested.

Stomach no. 2 contained a portion of the food, but most

had passed into the intestine.

August 30, 11:30 r.m., a toad weighing twenty grams

was fed on two beetles, two grasshoppers and one fly.

When examined eight hours later the stomach showed :

the grasshoppers well digested, but not disintegrated

and the fly and both beetles still entire.

These tests demonstrate that a toad can not fill its stom-

ach more than once in twenty-four hours. A toad will

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666 THE AMERICAN NATURALIST [Vou. XLIII

The results given in the following table are of feeding

tests made in order to see how much and how often a toad

will eat. The tests were made with sweepings and, as

grasshoppers formed the greater part, the experiment was

carried on largely with them. This, I think, does not af-

fect the experiment to any great extent, since toads show

very little preference, if any, for certain species of insects.

If toads are placed in cages with sweepings, various spe-

cies are taken at random, provided only that they be mov-

ing and of a size easily swallowed.

Ten toads, half males and half females, were chosen

for each test. Each toad was confined separately in a

glass cage (4 X 5X 7 inches) in which was about two

inches of moist earth. Throughout test no. I, insects

were kept constantly before the toads. The insects were

weighed and counted, then put into the cages with the

toads. In test no. II the toads were allowed to feed, one

at a time, in a wire cage containing insects. The cage

with the insects was weighed before the toad was put in

and then weighed again after the toad was removed.

Allowance had to be made for loss by evaporation in de-

termining the amount eaten. A more satisfactory cage

was constructed entirely of glass for test no. III. It

measured 8 X 10 X 10 inches and had on its bottom a half

inch of dry sand for the absorption of moisture. Evapo-

ration from this cage was less than a gram in ten hours.

Insects were placed in it and the process of weighing

followed as in test no. II.

In nos. I and III the toads were not disturbed unless

they were out of the earth. But in no. IT they were dug

up every day, if necessary, in order that they be offered

food at least once.

The folowing are the results of the three feeding tests.

The data show that for test no. II the toads feed oftener

than in the other two experiments, but that the amount

eaten, in proportion to the weight of the toads, is 3 and

2 per cent. less than in tests nos. I and ILI, respectively.

The time represented in these experiments is equal to

that of one toad for 260 days, 96 of which were passed

No. 515] THE AMERICAN TOAD 667

without feeding. In other words, a toad refuses food on

36.9 per cent. of the days. Therefore instead of a toad

filling its stomach four times in twenty-four hours, accord-

ing to Kirkland, it may eat (probably fill its stomach)

once in a day and a half. The average amount eaten per

toad per day in these 260 days is 1.12 g. The average

weight of the toads is 36.6 grams, which is about the

weight of the largest males or of a medium-sized female.

These feeding tests show that the amount eaten at one

feeding compares very closely with the stomach contents

as recorded by Garmann, Hartman, and Kirkland. Fur-

thermore they demonstrate: (1) That the stomach of a

toad is not a rubber bag with an unlimited capacity as

commonly’ supposed; (2) that the toad when feeding, if

food is abundant, soon fills its stomach; (3) that toads

do not feed every day. This was suspected, since toads

are seen in greater numbers on rainy nights.

Usually as soon as the toads fed they buried them-

selves and remained so from one to ten days. Sometimes

their eyes and nostrils were left exposed. Even so, in-

sects placed in their cages usually failed to tempt them

to leave their burrows.

If we take the mean, 36.6 grams, as an average sized

toad, we find that it eats on an average, 26 insects or 1.12

grams per day. Counting May, June, July and August

as a toad’s feeding months, it will eat in this time some

3,200 insects, or 134.4 grams.

To estimate the value of a toad’s work in dollars and

cents is rather difficult, since the toad eats beneficial as

well as harmful insects. Garman from his data does not

hesitate to class the toad with useful animals, yet he would

not have us overlook the number of beneficial insects

eaten. According to Kirkland eleven per cent. of its food

consists of insects directly or indirectly valuable to man

and eighty per cent. is either directly injurious or ob-

noxious. He computes on the data previously given

of a stomach content that a toad is worth $19.88 per year

for the cutworms alone which it destroys. He assumes

that a toad fills its stomach four times a day with 6 cut- : Be

668 THE AMERICAN NATURALIST [Vou. XLII

worms and other insects for three months and that the

cutworms do damage to the amount of one cent each.

Granting that cutworms are injurious to the amount

of one cent each and that they work four months in-

stead of three, still Kirkland’s estimate is about four

times too large, for a toad can not fill its stomach more

than once in twenty-four hours. Furthermore, my experi-

ments show that it eats, on an average, only once in one

and a half days. These factors give the toad a value

of about $5 per year on the basis of Kirkland’s estimate.

Such figures may be approximately correct for green-

houses, gardens or truck farms, but on the whole I am

inclined to think they are too large for farming districts.

(To be concluded)

NOTES ON THE BEHAVIOR OF THE DOMESTIC

FOWL’

PHILIP B. HADLEY

RHODE ISLAND AGRICULTURAL EXPERIMENT STATION

Durine the month of February, 1909, the writer’s at-

tention was called to an interesting feature of the be-

havior of a buff rock cockerel kept in the poultry depart-

ment of the Rhode Island State College at Kingston,

Rhode Island. Having briefly described the facts of the

case to Dr. Robert M. Yerkes of the Department of Psy-

chology of Harvard University, and having been informed

by him that the behavior in question was somewhat note-

worthy, the writer has collected data, secured photo-

graphs, and desires to present the following description,

believing it may be of interest to students of animal be-

havior. The point of behavior under consideration con-

sists in the acquired habit of an adult barred rock cock-

erel of ‘‘working’’ an automatic feeder, containing bran

and grain, located in one of the colony houses of the

poultry department, and by this action of securing a

larger amount of the grain constituent than the feeder,

working by itself, would naturally be able to supply.

The automatic feeder in question is of a type manu-

factured by John Anderson, of Slocums, Rhode Island,

and involves mainly a box (Fig. 1, B) containing feed,

and a tray (T) suspended beneath it. The dimensions of

the box are roughly sixteen by eleven by eight inches.

The food material escapes from the box through a nar-

row opening at the back and bottom of the feeder, and is

caught in the tray, which is thirteen inches long by seven

and one half inches broad, and is suspended eleven inches

form the floor. The supply of food material falling on the

tray is regulated by a balance system. The tray 18 50

* Papers from the Division of Biology, No. 5. Published August, 1909. ae

669

670 THE AMERICAN NATURALIST [Vov. XLIII

Fig: ‘I:

suspended from the point F that, when it is lightened

(consequent to feeding), it rises and simultaneously ad-

mits a new supply of food material from the box. As

soon as a sufficient amount to increase the weight of the

tray has fallen, the latter drops again and automatically

shuts off the supply. This process of filling and empty-

No. 515] BEHAVIOR OF THE DOMESTIC FOWL 671

ing continues as long as there is material left in the box

and there are fowls to eat from the tray.

The material contained in the automatic feeder is usu-

ally a mixture of bran, wheat, and whole corn. While both

the hens and the cockerel eat a fair amount of the bran

constituent, they like the grain, especially the whole corn,

much better. This predilection is exhibited especially by

the cockerel, which attempts to obtain a minimum amount

of the bran and a maximum amount of the corn, Usu-

ally there are from four to eight hens, together with the

cockerel, attempting to feed from the tray at the same

time. As a consequence, the grain, which is mixed with

the bran, is in the tray but a short time before it is

eaten, and nothing but the bran remains. When this

condition has come about the cockerel proceeds to ‘‘work’’

the feeder. This is accomplished in the following

manner.

As shown in Fig. 1, the cockerel while eating almost

invariably stands at the left-hand corner of the feeder.

At this point he usually feeds from the corner of the tray,

while the hens feed from both sides or from the ends, some

of them standing between the feed-tray and the wall,

where there is a free space of ten and one half inches. As

soon as the corn has all been eaten the cockerel steps

back sufficiently to clear the corner of the tray, takes a

few steps forward around the corner, raises its head high

and gives a vigorous push or peck to the beam desig-

nated (a) in Fig. 1. The force of this blow usually serves

to throw out the board slat which holds the food back in

the box; and, as a result, fresh material falls upon the

tray, the increased weight of which immediately closes

this outlet from the box. As soon as more corn has fallen

on the tray the cockerel hastily returns to his former

position at the corner of the tray and devours as many

of the kernels as possible before the hens have again

cleared the receptacle of grain; whereupon the cockerel

again leaves the tray and pecks the beam. The final re-

sult of this continuous performance is that the tray be-

672 THE AMERICAN NATURALIST [Vou. XLII

comes so heavily stocked with the bran constituent that it

will not longer work automatically, sometimes becoming

so heavy that even the most vigorous pecks of the cock-

erel no longer serve to raise it and admit more food.

The movements of the cockerel in working the feeder

are, as a whole, characterized by directness and accuracy.

Occasionally, however, there is a slight hesitation in

striking the beam. In such a case the bird leaves the

tray and turns toward the beam, but returns to the tray

before having struck, as if influenced by the thought that

grain had already entered the tray or that the other birds

would secure it first. This hesitation is usually followed,

however, by the complete successful performance. The

accuracy of the strike is noteworthy, and a deep groove

has been worn on the edge of the beam at the point where

the beak strikes.

The cockerel mentioned above is a fine specimen of the

buff rock variety. It was hatched at the Rhode Island

College Poultry Plant in February, 1908, and now meas-

ures twenty-three inches in height. The bird has been

confined in the colony house (with appended yard) for

about four months, and the type of behavior described

had been observed about two months before it came to

the notice of the writer. It thus seems probable that the

bird had been in the house with the feeder accessible for

about two months before the trick was learned. At the

time of writing (April 5, 1909) the cockerel still has access

to the automatic feeder and works it regularly every day.

Since making the observations recorded in the pre-

ceding paragraphs the writer has secured other data

which show that the ability to work the automatic feeders

is not restricted to the previously mentioned buff rock

cockerel alone, but is also possessed by several of the

hens located in the same colony house, and by another

white Orpington cockerel in an adjoining poultry house.

While the behavior of the white Orpington cockerel is

in most respects similar to that of the buff rock, the action

of the buff rock hens is somewhat different. When the |

No. 515] BEHAVIOR OF THE DOMESTIC FOWL 673

hens feed from the tray, a few of them, as has been re-

marked, stand back of the automatic feeder, i. e., between

it and the wall, a space of about ten and one-half inches.

In this position the feed tray is slightly more than breast

high (thirteen and one-half inches) at the top of the rim,

while slightly above the head of the birds (nineteen inches

from the floor and six inches from tray) runs a guide-

board, eleven by two and one-half inches. This board,

which really serves as a guide to the food falling from the

box into the feed-tray, is so hung that if it be struck from

behind outward the effect is the same as that of striking

the beam (a) at the point designated; that is, the grain is

let into the feed-tray. Striking the guide-board from

before does not accomplish this result. Now it appears

that several of the hens have learned the trick of oper-

ating the supply by striking from behind, with their

bills, the guide-board designated above. To accomplish

this the bird merely needs to raise its head from the tray

and to stretch its neck slightly in order to reach the board

which is sharply pecked. It appears, however, that the

hens do not attempt this manceuvre so often as the cock-

erel performs the other. This is perhaps for two reasons:

first, the hens do not care so much for the grain; and sec-

ondly, the cockerel is apparently always quite ready to

save the hens the trouble of working the feeder for them-

selves.

How long was required for the hens to learn the trick

of operating the feeder is not known; nor are any data at

hand regarding the proficiency shown at successive stages

in the process of learning. When the performance was

first observed by the writer the technique was already

perfected. It would be interesting to learn how, in the

experience of the cockerel, the connection was first made

between the movement of the beam and the presence of

fresh corn on the tray. The matter would be easier of

explanation were the action in question one which, on the

first performance, could easily have been accomplished by s

chance, as, for instance, the case of the dog or cat acci-

674 THE AMERICAN NATURALIST (Von XLII

dentally striking the latch when leaping or pawing at the

door for admittance. In the present instance there is

performed an action which requires the cockerel to leave

temporarily the primary object of his attention, and to

perform a manceuvre which it seems could hardly have

been hit upon accidentally, while the bird was engaged

in the process of feeding.

Since writing the above paragraphs the writer has

made other observations which add new interest to the

subject in hand. In order to prevent the buff rock cock-

erel from working the feeder a piece of sheet tin was

nailed to the beam which had been struck. This was

placed over the beam in such a way as to protect the

latter on the top, where the cockerel had usually struck it,

as well as on the sides. This sheet of tin extended down-

ward to within about one-eighth of an inch of the bottom

of the beam, and hung about one-fourth of an inch outside

of the same. Thus the whole of the beam, except one-

eighth of an inch of the lower margin, was protected from

the beak of the cockerel, and it was expected that this

precaution would effectually prevent all further ‘‘work-

ing’’ of the feeder. This result, however, was not forth-

coming, for within two days after the sheet of tin had

been placed on the feeder the cockerel was found to have

modified his behavior to suit the new unfavorable con-

ditions. Now, instead of attempting to strike the beam

from above, as previously, he reached with his beak un-

derneath the projecting sheet of tin, and, grasping the

lower margin of the beam, bore it downward with a kind

of pulling motion from beneath. This movement, it is

apparent, is somewhat different from the one first de-

scribed. It is, moreover, the only means by which the _

feeder could possibly be worked by manipulating any

accessible part of beam. It is barely possible to consider

the second manæuvre as a direct modification of the first,

although a different part of the beam is struck, and with

a different movement on the part of the bird. It is diffi- | : co

No. 515] BEHAVIOR OF THE DOMESTIC FOWL 675

cult to see how this second reaction could have been de-

veloped as a result of an accidental success, especially

when it is borne in mind that the manceuvre was first ini-

tiated and fully perfected within two days of the time

when manceuvre number one was discontinued. Whether

manœuvre number two is a modification of number one,

whether it arose from imitation (which is doubtful, since

no person or other fowl is known to have performed the

action before it was perfected by the cockerel), or whether

it is the result of a chance success following random move-

ments, the writer is not prepared to state. Notwithstand-

ing the fact that manceuvre number two is so different

from number one, it is perhaps more reasonable to as-

sume tentatively the correctness of the first hypothesis.

But this does not explain the origin of manœuvre number

one, although it surely demonstrates a very effective modi-

fiability in the behavior of the cockerel. In the present

instance it is also noteworthy, perhaps, that when the first

manceuvre was prevented by the presence of the sheet of

tin, the cockerel did not profit by an imitation of the hens,

which continued to work the feeder from behind as in the

first case mentioned above.

Believing that there are certain theoretical considera-

tions arising from the foregoing observations which would

be of interest to comparative psychologists, the writer

has requested Doctor Yerkes to add hereto comments that

seem pertinent to the question in hand. The writer would

also take this occasion to express his thanks to Mr. Roy H.

Waite, Assistant in Biology, for preparing the photo-

graph which accompanies this paper; also to Mr. Holden,

of the College poultry plant, for some of the data here

presented.

COMMENT UPON DR. HADLEY’S OBSERVATIONS

Neither casual observation nor systematic experimentation with the

domestic fowl has furnished many instances of the type of behavior

described by Dr. Hadley. Consequently his observations have considerable

interest and value for students of animal behavior.

It is scarcely necessary to say that the most serious defect in this account

676 THE AMERICAN NATURALIST [Vow. XLIII

of the behavior of a cockerel is the lack of the pa of the formation of

the habit. This defect is the author’s misfortune, as well as the reader’s,

but it is not his fault, inasmuch as the habit was engan perfect when

he first observed it. To attempt to interpret the behavior in psychic terms

or to point out its significance would be futile in the absence of definite

knowledge of the conditions which originally gave rise to it. This is but

on2 of the innumerable instances in which we need more facts instead of

speculation.

adley has suggested that the connection between pecking the beam

process, had to do with the acquisition of the food-getting act. I wish the

facts were adequate to prove or disprove this possibility. They are not, in

my opinion, and it is therefore out of place to discuss them from that point

of view.

The reader can but wonder whether the hens which operate the feeder

acquired their method of obtaining grain under the influence of imitation.

The conditions apparently furnish an excellent opportunity for the experi-

mental study of imitation in fowls.

Surely the wisest and safest, if not the most riage yh comment which

the student of animal behavior can make concerning Dr. ey’s observa-

tions is ‘‘let additional facts appear before interpretation is permitted.’’

T M. YERKES.

VITALITY OF PINE SEEDS AND THE DELAYED

OPENING OF CONES

PROFESSOR W. C. COKER D

UNIVERSITY OF NORTH CAROLINA

On a visit to California in July, 1908, my curiosity

was aroused by the remarkable retention of the still

unopened cones in Pinus attenuata (P. tuberculata) the

knob-cone pine, and to a somewhat less conspicuous degree

in the Monterey pine (Pinus radiata). Trees of Pinus

attenuata may frequently be seen several feet in diam-

eter and thirty or forty years old, still retaining unopened

all the cones they have produced during their lives, the

lowest cones circling the tree within hand’s reach from

the ground. As all cones are borne on new growth it

is obvious that as the branches increase in thickness the

peduncles of the cones must be broken loose from their

connection with the wood, so as to allow the cones to be

pushed out by the annual growth, or the cones will be

covered as the tree develops and finally imbedded in

the wood. As the cones of P. attenuata are narrow at

the base and thus more easily caught by the annual

layers, the latter alternative sometimes occurs and the

cones are covered by the growth of the tree.

The cones that remain on the surface of the trunk and

branches have no organic connection with the tree, and

their peduncles, which are almost an inch long, may be

twisted out like a cork from a bottle. It is a well-known

fact that in this case the cones never shed their seeds

until the tree or branch that bears them dies.

This remarkable peculiarity is exhibited to almost as

great a degree by Pinus radiata (Monterey pine). Of

this tree J. G. Lemmon says :! ; |

1 Sierra Club Bulletin, Vol. 2, p. 74, 1897.

677

678 THE AMERICAN NATURALIST [Vou. XLII

Trees four and five inches in diameter may be seen on Point Pinos,

still retaining every cone they have produced, circling the trunk and

limbs from base to apex. Of course the lumber is perforated with

holes, the channels formed by the cone-stems on their many years’

journey from heart to bark.

Other species of western American pines whose cones

are serotinous to a greater or less degree are P. muricata,

P. contorta, P. contorta var. Murrayana (the lodge pole

pine) and P. “chihuahuana. Of P. muricata Lemmon

says :? ‘‘The cones have been known to remain unopened

for twenty or thirty years, then to release good seeds,’’

but he says in another place of the cones of the same

tree: ‘‘They usually open at the time the leaves at the

same point fall away from the stems.” The Gardener’s

Chronicle for April 24, 1909, gives a good illustration

of this pine showing old unopened cones, and in the -

same number, Mr. W. J. Bean says: ‘‘Some of the trees

at Kew bear cones which must have developed more

than a quarter of a century ago.’’

Of the eastern American pines the only ones to retain

their cones unopened after maturity are the jack pine

(P. Banksiana) of the north, the Table Mountain pine

(P. pungens) of the Alleghanies, the pond pine (P.

serotina) of the southern states, and P. clausa of the

gulf coast and eastern Florida. In the case of the last

species the cones may become imbedded in the wood as

in P. attenuata.*

That this remarkable habit of cone retention is of use in

the struggle for existence, at least under the peculiar

conditions that exist in our western country, is be-

lieved by a number of observers. The explanation that

is usually offered is well expressed by John Muir in

‘Our National Parks” page 104. Speaking of Pinus

attenuata (under the name of P. tuberculata) he says:

*** Handbook of West American Cone-bearers,’’ 3d ed.

* Erythea, Vol. 2, p. 160, 1894.

*In Garden and Forest, Vol. 10, p. 232, Professor C. S. Sargent remarks

that cones of P. muricata often become imbedded in the bark, but in a letter

to me he says that this ‘‘ appears to be erroneous.’’

No. 515] VITALITY OF PINE SEEDS 679

This admirable little tree grows on brushy, sun-beaten slopes, which

from their position and the inflammable character of the vegetation are

most frequently fire-swept. These grounds it is able to hold against

all comers, however big and strong, by saving its seeds until death,

when all it has produced are scattered over the bare cleared ground,

and a new generation quickly springs out of the ashes.

This statement of Mr. Muir’s implies that all or a

large part of the seeds produced during the life of the

tree are capable of germination when shed, and this

seems to be the opinion of others (see Lemmon, as quoted

above, under P. muricata).®

Now it is a well-known fact that pine seeds as a rule

are very perishable (seeds of P. palustris will not germi-

nate, according to my experience, the second spring after

their maturity) and it is important to test by actual ex-

periment to what extent seeds retain their vitality under

such conditions. In looking over the literature I can

d but one experiment that has been made to enlighten

us on this point.

In 1874 Dr. Engleman collected a branch of Pinus

contorta from Colorado (the plant being probably var.

Murrayana, or lodge pole pine) and after keeping it four

of the Harvard Arboretum, to test the seeds. Professor

Sargent planted the seeds in 1879, and his results, as re-

ported in Bot. Gazette, Vol. 5, p. 54, 1880, were as follows:

* The reference to Pinus radiata by Vernon Bailey on page 34 of C. Hart

Merriam’s ‘‘Results of a Biological Survey of Mount Shasta, California’?

(North American Fauna, 16, 1899) would indicate that its seeds have a

ass time on Mount Shast ys:

‘‘ The trees were loaded with cones, in whorls of three to seven around

the branches, and down the trunks to 10 or 12 feet from the ground. Some

of the cones must have been 20 or 30 years old, and perhaps much older.

I cut off a lot of the old lower cones to see if the seeds were good, and put

them on a boulder and eracked them with a few hard blows of the ax. All

of them were full of worm dust, with only now and then an undiscovered

seed or a fat white worm. Cones of medium age (5 or 6 years back from

the end of the branch) were invariably oecupied by worms and worm dust,

and usually contained few good seeds. Cones only 1 or 2 years old were

rarely wormy. A great many of the old cones had been dug into by wood-

peckers, either for seeds or, more likely, for the fat white grubs that live on-

the seeds.’’

680 THE AMERICAN NATURALIST [Vow. XLIII

Seeds of 1865 and 1868 did not germinate.

1869 ..... 24

1870 .... 25 seeds planted, 4 germinated.

1871 .... 6 seeds planted, 2 germinated.

1872 .... 19 seeds planted, 5 germinated.

1873 .... 9 seeds planted, none germinated (cones probably not mature).

This experiment shows that at least some of the seeds

of P. contorta (var. Murrayana?) are capable of germi-

nation after retention in the cones for nine or ten years.

My interest having been aroused in this subject while

in California, I was led to observe more closely the cones

of our native P. serotina on my return to South Carolina

and it was soon found that the cones of this species often

remain attached and unopen for a much longer time than

ever reported. In his ‘‘North American Silva,’’ Vol.

3, p. 117, Michaux says:

The cones arrive at maturity the second year, but do not release their

seeds before the third or fourth.

Sargent follows this statement in his ‘‘Silva’’ and

Britton says (in ‘‘North American Trees’’) that the cones

‘“‘remain closed for several years before dropping the

seed.’? In the neighborhood of Hartville, South Caro-

lina, it was not at all uncommon to find cones that had

remained unopened for ten or even more years, and the

opportunity was taken to collect cones of different ages

for a test of the viability of the seeds. The cones were

taken to the New York Botanical Garden and there the

test was made in June of this year. Seeds that were

obviously blasted or dead (as shown by floating in water)

were discarded, and are recorded as ‘‘rejected’’; only

apparently sound seeds were planted. The seeds were

first germinated between filter paper in Sphagnum moss

for about five days until the radicals appeared. A count

was then made and the result recorded in the columns

of June 29 in the table below.* All the seeds, whether

germinated or not, were then planted in soil in pots, and

*Cone No. 1 was not included in this count because its seeds were by

mistake planted in soil before the count was taken.

No. 515] VITALITY OF PINE SEEDS 681

the seedlings that appeared were counted on July 127

and July 22, with results as shown in the table below.

Germinated.

Years Old. Rejected. Planted. June 29. July 12. July 22.

3 31 32 ? 27 28

4 10 14 6 9 9

4 6 15 13 9 9

6 7 57 30 40 39

6 0 62 52 51 52

6 yd 60 58 53 48

7 3 88 42 50 44

8 7 49 10 34 33

8 5 27 2 15 18

8 3 42 0 31 33

9 5 34 3 2 0

9 2 31 10 16 7

14 32 61 33 24 21

14 2 67 7 11 11

Increased numbers in the later readings are due to de-

layed germinations: decreased numbers to failure to

emerge or to damping off after emergence.

It should be noted that the conditions that exist in

these serotinous cones are almost ideal for the preserva-

tion of the vitality of the seeds. While some exchange

of gases is allowed, the spores of fungi and bacteria are

effectually excluded; and most important of all, a suffi-

cient humidity is maintained to prevent a fatal de-

hiscence. That this humidity is due to contact with the

moist wood of the live tree is shown by the mechanical

opening of the cone through drying when it is removed

from the wood, or when the tree dies. This opening,

however, is not always either prompt or complete.

* This counting was, in my absence, kindly made by Mr. Fred. J. Seaver.

THE AFFINITIES OF THE ECHINOIDEA

AUSTIN HOBART CLARK

Tar recent discovery that the crinoids in their ontog-

eny increase the number of their ambulacral post-radial

ossicles by the interpolation of numerous ossicles (in

pairs) between the first two primitive brachials and the

radial, forming what are known as ‘‘interpolated division

series,’’ as well as by the addition of brachials in a linear

series at the growing tip of the arm, where only hereto-

fore addition to the number of the brachials was sup-

posed to occur,! has shown that in the manner of increase

of the number of ambulacral segments there is a close

similarity between the crinoids and the echinoids, both

groups adding new plates between those already formed

and the radials (oculars), whereas in the ophiuroids and

the asteroids new plates are added only at the tip of the

arms, not, however, at the extreme tip, as in the crinoid

arm, but just proximal to a permanent plate; and the

question naturally arises, can the commonly accepted

view regarding the interrelations of the various classes

of the Echinodermata be maintained in the light of the

present state of our knowledge?

So long ago as 1821 J. S. Miller remarked on the simi-

larity of an inverted Cidaris to a crinoid, and this simi-

larity was also noticed by Lovén. That this similarity is

not superficial but in reality fundamental has become in-

creasingly evident to me during the course of my studies —

on the echinoderms, and I have now no hesitation in sta-

ting that the crinoids and the echinoids have much more

in common, and are much more closely related to each

other, than either group is to the asteroids or the ophiu-

roids.

_ Considering only the external skeleton, we find that,

in the crinoids and echinoids (1) the ambulacrals in-

* Proc. U. 8. Nat. Mus., Vol. 35, No. 1636, pp. 113-131.

682

No. 515] AFFINITIES OF THE ECHINOIDEA 683

crease by the addition of plates proximally between

the youngest plate and the radial (ocular) ; no permanent

terminal plate is present; (2) the ambulacral plates al-

ways alternate in position; (3) the so-called infrabasals

are inconstant (crinoids) or entirely wanting (echinoids

and many ecrinoids); (4) imbrication of ambulacrals is

more or less constant; (5) the ambulacrals are on the

surface, so that the nerves, water vascular system,

schizoceel, ete., are on the inner side, protected by them;

(6) there are no definite or constant accessory plates in

the ambulacral system; (7) the oral skeleton, when pres-

ent, can not be directly derived from the ambulacral

system; (8) the interambulacral plates are in more or

less regular columns; but they always start from a single

plate; (9) the interambulacral plates extend laterally out-

ward from the ambulacrals, forming a closed capsule ;

(10) the plates of the ambulacral system encroach regu-

larly, when at all, upon the peristome, which remains

round; (11) the spines are long and usually slender, and

are attached to round and prominent spine bosses (pres-

ent among crinoids in one genus only) ; (12) the ambula-

erals are directly continuous with, and in the same plane

as, the radials (oculars) : on the other hand, in the ophiu-

roids and asteroids (1) the ambulacrals inerease by the

addition of plates distally between the youngest plates

and the permanent terminal; (2) the ambulacrals are

always opposite each other (a possible exception in cer-

tain paleoasteroids); (3) the infrabasals are ontogenet-

ically constant; (4) there is no imbrication of the ambula-

erals; (5) the ambulacral ossicles lie deep, so that the

radial structures are outside of them; (6) definite and

constant adambulacral ossicles or lateral shields are

present; (7) there is a peculiar oral skeleton of modified

ambulacral plates; (8) the interambulacral plates are m

regular rows, starting as some multiple of two; (9) the

interambulacral plates enclose more or less the ambu-

lacral plates; (10) the plates of the ambulacral system

encroach irregularly upon the peristome, making it more

or less sharply stellate; (11) the ambulacral paa a :

684 THE AMERICAN NATURALIST [Vou. XLII

never bear spines; (12) the ambulacrals are not con-

tinuous with, nor in the same plane as, the so-called

radials or terminals.

This would be sufficient in itself to convince any one

that the crinoids and echinoids formed one well circum-

scribed group, while the asteroids and the ophiuroids

formed another similar group, entirely distinct; but the

‘‘soft parts’’ furnish abundant additional evidence lead-

ing to the same conclusion.

In the urchins and the crinoids the anus is always well

developed and functional, while in the asteroids and

ophiuroids it is absent, or, if present, does not serve as

an exit for refuse matter; the crinoids and urchins have a

large and definite peristome which is circular in shape

and more or less filled with dermal plates; in the aster-

oids and ophiuroids the peristome is very much reduced,

stellate and without dermal plates; in the crinoids the

ambulacral plates are united by ligaments externally and

by two parallel rows of muscle bundles internally; in the

echinothurids, which alone among the echinoids have a

flexible test, the plates are united by more or less liga-

mentous connective tissue, and within the test there are

five pairs of muscle sheets, inserted along the two outer

edges of the ambulacral series; the asteroids and ophiu-

roids have two pairs of muscles, a dorsal and a ventral

instead of one pair and a dorsal ( external) ligament. In

the crinoids and echinoids the intestinal canal is narrow,

tubular, without marked sac-like expansions, and always

lies in coils of which there may be as many as four; in

the asteroids and ophiuroids the digestive system runs

direct from the mouth to the anus (when present) with-

out convolutions, but has sac-like widenings, and may

have branched radial outgrowths. In the crinoids and

the echinoids the gonads are connected with the axial

organ in the young, but not in the adult; in the asteroids

and ophiuroids they are connected with the axial organ

throughout life. In the echinoids and crinoids the

pseudo-hemal system is closed on all sides; in the as-

teroids and ophiuroids it connects by means of numerous

No. 515] AFFINITIES OF THE ECHINOIDEA 685

small apertures with the body-cavity, and, at one point in

the pseudo-hæmal ring, with the axial sinus. A blood vas-

cular system is doubtfully present in the ophiuroids and

asteroids, but well developed in the echinoids and

crinoids. In the echinoids the axial sinus surrounding

the stone canal, originally a part of the cceelom, is in open

communication with the ampulla into which the madre-

porite opens. This is comparable to the condition in the

erinoids where the madreporie pores open into the body

cavity more or less opposite the openings of the stone

canals, but:is quite different from the condition found in

the asteroids and ophiuroids.

Having now shown that the crinoids and the echinoids

are closely related, it remains to be seen how an homology

may be drawn between the skeletal elements of the twe.

This is not nearly so difficult a performance as might ap-

pear at first sight. The primibrachs of a crinoid repre-

sent the first four ambulacral plates of an urchin, which

have slipped in between each other so as to lie in a single

row; in this single row of four plates the second has dis-

appeared, as shown by the synarthry,? while the third and

fourth have united to form an axillary. All the plates in

the crinoidal post-radial series up to the third brachial of

the free arm represent the ambulacral series of the

urchin; the long and tapering crinoid arms from the third

brachial onward are homologous to the auricles and

apophyses of the urchin, which have become turned out-

ward instead of inward, have become interiorly united,

and have increased enormously in length. The crinoid

stem is the central (sur-anal) plate of the urchin; origin-

ally free, the crinoids first became sessile through simple

attachment by the central dorsal plate; this gradually in-

creased in thickness, becoming a thick stalk, like that of

Holopus; later, owing to the increasing length, fractures

were developed transversely, and finally the long jointed

crinoid stem resulted.

It has been urged, from their radiate structure, that

the echinoderms were primarily fixed; but I can not see

* AMERICAN NATURALIST, Vol. 43 (October, 1909), pp- 577-587.

686 THE AMERICAN NATURALIST [Vou. XLIII

why the octopus could not be assumed to have been de-

scended from stalked ancestors along the same lines. It

seems to me that the echinoderms are rather like the

bivalve molluses or the crustacea which contain both free

and fixed types, the former in the great majority. The

crinoids are the only recent fixed echinoderms; but in the

fossil crinoids, as Lang pointed one in Marsupites and I

independently showed in Uintacrinus, there are forms

which exhibit no evidence of ever having been attached;

in fact the evidence is quite the other way. In these

forms the centrale may be, instead of the centro-dorsal,

really the dorso-central, in which case we should get an

interesting homology with the echinoids.

The association of the holothurians with the echinoids,

and hence with the crinoid-echinoid stem, seems to me to

be abundantly justified. The following classification of

the echinoderm groups is proposed as showing the inter-

relations of these groups better than any of the synopses

previously published.

Phylum ECHINODERMATA

I. Subphylum ECHINODERMATA HETERORADIATA.

A tozoa.

1. Crinoidea.

2. Cystidea.

3. Blastoidea.

B. Ovozoa.

1. Echinoidea.

C. Vermiformes.

1. Holothuroidea (Bohadschoidea).

II. Subphylum ECHINODERMATA ASTRORADIATA.

. Ophiobrachiata.

1. Ophiuroidea.

B. Stellarides.

1. Asteroidea.

In this table the sequence of groups must not be taken

to represent a phylogenetic line; in no class of animals is

a phylogenetic sequence more difficult of conception than

in the echinoderms. While the heteroradiate echino-

derms are, judged by ordinary standards, more perfect

than the astroradiate, judged from the echinoderm point

of view solely, they can not be considered so well de-

veloped as the latter.

THE EARLY BREEDING HABITS OF AMBLYS-

TOMA PUNCTATUM

ALBERT H. WRIGHT anp ARTHUR A. ALLEN

CORNELL UNIVERSITY

Casuan observations made at Ithaca, during the past

‘eight or nine years, upon the habits of Amblystoma

` punctatum have emphasized the need of an intensive

study of the early breeding habits of this species, and

consequently during the spring of 1908 considerable at-

tention was given to this phase of its life history.

The best collecting ground for this species was found

to be along the eastern border of the marsh at the head

of Cayuga Lake where it is skirted by a state road and

by the tracks of a trolley line. Here it is necessary for

the salamanders from the hill, on their way to suitable

breeding grounds, to cross the tracks and in so doing’

many are killed by the passing cars. Heretofore, it was

believed that the majority came from the ravines which

cut through the hill in this locality. To test this, a trap

was placed at the mouth of one of the culverts under the

road. The trap yielded only eight specimens during the

ten days in which the species was migrating. It would,

therefore, seem that the salamanders came mainly from

the hill itself. For the study of spermatophores and

eggs ponds on the hilltop near the university proved most

fruitful. Six ponds were visited daily. In these, count-

less spermatophores and several hundred bunches of eggs

were deposited. A chart of each pond was prepared

and upon this, for future reference, the position of sev-

eral areas of spermatophores and each bunch of eggs

were indicated with the date of deposition. ,

The first appearance from hibernation for this species

from 1903 to 1908 follows: :

| 687

688 THE AMERICAN NATURALIST [Vou. XLIII

1906, March 28.

1907, March 24

1903, March 13.

1904, April 1 :

1908, March 23.

1905, April 1.

In 1908 the first appearance occurred the evening of

March 23, when the maximum and minimum air tempera-

ture, were 47° and 42° F. The water temperatures of the

two ponds under observation on the following morning

were 42° and 48° F., respectively. On the above dates

of first appearance from 1903 to 1908, the U. S. Weather

Bureau Station at Ithaca obtained the following maxi-

mum and minimum air temperatures:

Max: Temp. Min. on Year. Max. Temp. Min. bape

1903 52° e 1906 1a 32° F.

1904 55 36 1907 61 43

1905 64 37 1908 47 42

From this it is obvious that a temperature approxima-

ting 50° F. or more almost invariably caused the species

to emerge.

To verify this conclusion, a careful record of the mi-

gration across the railway in 1908 was kept and a sum-

mary follows in tabular form:

aes primey i

Da f y Number Captured Number Killed

oes SENETA Stakiai]: urine Cen Tote,

March 24 | 49° | 220 1 1

March 25. | 37 | 19 |

March 26. | 65 | 37 | ~ | 15 15

March 27. | 63 | 36 | 9 | 13 22

March 28. | 72 | 41 | 31 24 55

acs 29. 41 30 |

arch 30. | 48 | 33 “ s i ies.””!

March 31. ie s } cold, cloudy weather with snow flurries.

PE : 48 27 | 17 | | 17

pil 4. | 50 | 18 3 (in th | |

April 6. | 62 | 40 ey | 1 | i

_ Total, | | 60 | 54 | mo

In this table as in the preceding 50° F. appears the

normal effective temperature of migration. The crest

‘Climatological Report for March, 1908. New York Section of. the

Climatological gèr of the Fep Bureau in Cooperation with Cornell

University. By W. M. Wilson, p.

No. 515] BREEDING HABITS OF AMBLYSTOMA 689

of the migration in 1908 came when the maximum air

temperature ascended to 60° or 70° F. In two other

years the same conditions obtained as shown in the ac-

companying data:

Date of Crest. Max. Temp. Min. Temp.

1901, April 21. 72° 42°

1901, April 22. 86 62

1907, March 27. 70 45

1908, March 28. 72 42

The males begin the migration, as the following table

will-indicate :

Date (1908). Number Killed. Number Captured Alive.

March 26, 15 males,

March 27, 5 males, 4 females. 6 males, 3 females.

March 28, 10 males, 14 females. 12 males, 19 females.

April 1, 7 males, 10 females.

Thus we see the males began the migration. The next

evening, the females appeared in small numbers and the

third evening they predominated and continued thus for

the remainder of the migration.

In 1908, the migration each evening across the railway

began between 7:30 and 8:00 o’clock. By means of an

acetylene lamp, the salamanders were observed crawling

along close to the rail, often following it for some dis-

tance. At times they were seen attempting to cross the

track by raising themselves erect on their tails. Even

with this aid, scarcely more than the head came above

the rail. In this position they often remained until

crushed by the passing cars. Generally, however, they

followed along the rail until they came to the joints,

where the projecting bolts enabled them to work their way

over.

The evening upon which spermatophores were first de-

posited, two salamanders were seen ‘‘nosing’’ each other,

and one of the two depositing spermatophores. Neither

was captured, and so to determine if this were a part of

the regular. courtship of the species, several salamanders

collected along the track were taken to the laboratory —

690 THE AMERICAN NATURALIST [Vow. XLII

and placed in jars as follows: Jar No. 1, seven males;

No. 2, several each of males and females; No. 3, a male

and a female. These specimens had not reached the

water, and were carried to the laboratory in a dry bag.

The temperature of the water in the jars was 65° F., or

fifteen to twenty degrees warmer than that in the ponds.

The seven males of jar no. 1 showed no excitement and

deposited no spermatophores until a day or two later.

Then, the total of spermatophores for the whole seven

was much less than that deposited by the single male of

jar no. 3.

In jar no. 2 the males and females became excited the

moment they were placed together and many spermato-

phores were deposited at once. This experiment was

repeated the following evening with a different set of

salamanders and the males began to deposit spermato-

phores within fifteen minutes after being placed with the

females. No eggs were deposited earlier than two days

after the deposition of the first spermatophores.

In jar no. 3 the male, at first, showed no signs of ex-

citement, but upon coming in contact with the female,

he became very restless, and ‘‘nosed’’ her about in a

definite manner. It seemed to be the object of the male

to bring the top of his head in contact with the venter

of the female. The throat region of the female seemed

to be preferred, although he often began in the cloacal

region or even at the tip of the tail and rubbed the dorso-

lateral part of the head along her whole ventral side.

After each performance of this kind, the male swam away

and grasped one of the sticks with its hind legs, bringing

the cloaca close to the stem. The tail quivered for a

moment and, with an arching of the region just caudad

of the cloaca, the vent was lifted from the spermatophore.

Then, he immediately returned to the female and began —

again the ‘‘nosing’’ process. The time consumed in de-

positing a spermatophore varied from 3 to 16 seconds,

the periods for thirteen consecutive depositions being:

5, 3, 6, 10, 13, 12, 7, 11, 12, 16, 11, 10, 10 seconds, re-

No. 515] BREEDING HABITS OF AMBLYSTOMA 691

spectively. In this way twenty-two spermatophores

were deposited in 45 minutes.

Most of this time the female remained quiet. Three

times, however, she slowly moved over a spermatophore

until the vent rested upon it. Then the hind limbs

closed about it. In this position the female remained,

each time, for ten to fifteen seconds and apparently made

no effort to take any portion of the spermatophore into

the cloaca as does Diemyctylus. It seemed to us rather

that there was a simple passage of the spermatozoa from

the spermatophore into the cloaca of the female.

Evidently, then, the female must be present at the time

the spermatophores are deposited and in this we find the

explanation for the delay in deposition of spermatophores

after the species has first appeared from hibernation.

The males begin the migration but no spermatophores

are deposited until the arrival of the females. In the

spring of 1908 the migration began the evening of March

26, but spermatophores were not recorded until the

morning of March 28, after the arrival of the females.

With the arrival of the females and the ensuing court-

ship, spermatophores are deposited. These are usually

found in stagnant or slowly moving water, four to twelve

inches deep, though they are occasionally recorded in

water one and one half to two feet in depth. They

occur in groups numbering from 2 to 125, covering an area

of one half to three feet square. The usual number in

a group is between 30 and 50. The spermatophores and

the spermatozoa recently described by Smith? need no

discussion here,

After the first spermatophores are deposited, an in-

terval elapses before the first eggs are recorded. In

former years this interval has varied from a few hours

to seven days and we had been led to believe that the

females did not come to the ponds until their eggs were

ripe. This belief is no longer tenable. After the cloacal

* Smith, B. G., ‘‘ The Breeding Habits of Amblystoma punctatum Linn.,’?

AMERICAN NaTuraList, XLI, No. 486, June, 1907, pp. 381-385.

692 ‘THE AMERICAN NATURALIST [Vou. XLII

inclusion of the spermatozoa several hours or days may

elapse before the eggs ripen and ovulation occurs. ‘‘In

1903 one interval of 2 days was recorded; in 1904, one

of 4 days; in 1906, one of 6 days; in 1907, 4 days in one

pond, 5 in another, and 7 in a third.’’

‘*Hgg-laying generally begins about the first of April.

In two or three of the last eight years, eggs have been

noted before that date. In this period, the earliest record

is March 20, 1903. In 1901 they did not begin depositing

eggs until after the middle of April. The egg-laying

for the species may extend over a month or more. Rarely

do we find fresh eggs after May 1. In 1907 our latest

record for fresh eggs is April 30; our latest for fresh

spermatophores in the same pond, April 27.”

The number of eggs in a complement varies from 130

to 225. These may be deposited in one to ten bunches,

two or three per female being a fair average. There is not

necessarily uniformity in the size of the bunches, for one

female was known to deposit two bunches, one of 140

eggs, the other of 32.

At least thirty minutes are usually consumed in de-

positing a normal bunch of eggs. One female in de-

positing a bunch of 140 eggs remained beneath the sur-

face for over an hour. During this time she neither

strove to get into a position where she could keep her

nostrils out of the water, nor did she once arise to the

surface for air. As in other cases, the eggs came out

Slowly without apparent effort or straining, sometimes

but four in a minute. During deposition she was motion-

less, except for occasional slow movements of the tail.

Immediately after deposition, however, for two or three

minutes, she swayed back and forth vigorously to disen-

gage herself, for the fresh jelly stuck to the under side

of her tail and cloaca. Ten hours later another bunch

of 32 eggs finished the complement.

* Wright, A. H., ‘Notes on the Breeding Habits of Amblystoma pune-

tatum,’’ Biological Bulletin, Vol. XIV, No. 4, April, 1908, p. 286.

NOTES AND LITERATURE

MARINE BIOLOGY

Papers from the Tortugas Laboratory of the Carnegie Institution

of Washington, Vol. I, 191 pp., Vol. II, 325 pp. (Carnegie In-

stitution of Washington Publications No. 102 and 103, 1908. )

The first collection of memoirs published in the name of the

laboratory itself, from this practically tropical marine station,

is highly creditable to the students who made the researches, to

the director of the laboratory, Dr. A. G. Mayer, and to the great

Institution which, on the financial side, has made the studies

possible. Still more it is an impressive embodiment of the per-

ception and conception that the sea is a vast, inexhaustible mine

of the raw material out of which biological science is con-

structed; and that this material can be transformed into finished,

useful product only on the ground to which it is native. Such

writings drive home the truth with special force that would we

really know nature we must go where nature is; we must study

her in her home.

The two volumes contain nineteen papers written by fourteen

naturalists, and the range of topics is almost as wide as the field

of marine zoology. Yet nearly every one of these papers con-

tains something, some of them many things, that a biologist who

daily breathes the air of a large, expansive biological philosophy

will want to make memorandum of for future use.

The apparel of the matter presented approaches, though does

not reach, perfection. The most serious defect in the outer gar-

ments is the lack of aid to general consultation. Not only feos

there no alphabetical index, but the list of papers at the begin-

ning of each volume is without page references, so one must

hunt through the volume for any paper he may want to consult.

The principle of the greatest good to the greatest number is

against allowing scientific books, especially, to go out wanting

such useful incidentals as these. The numberings and letter-

ings of some of the illustrations are too small and indistinet to

be easily read by artificial light. oS

Defects in some of the inner garments are more unfortunate —

than any in the outer. It is not necessary as one of the authors —

seems to think, to ‘‘investigate into” a subject. To just investi-

: 693 See

694 THE AMERICAN NATURALIST [Vou. XLI

gate it is enough. ‘‘Further observations are needed .. .

especially with reference as to whether,’’ ete. Why the ‘‘as

to’’? This sentence is bungling. But worse than bungling is

the statement that ‘‘organie data function’’ in controlling, ete.

Such expressions as this can not be let off on the plea of hasty

composition, imperfect proof reading, established usage within a

special field, or something of the sort. They mean hazy think-

ing. Literary form isnot a vital thing especially to technical

science. Nevertheless, considerable attention to it pays in the

long run for effort in this way is promotive of clean, clear

thought.

It seems to the reviewer that the word ‘‘reaction’’ is being

overworked by some students of animal behavior. What more

is there in a medusa’s ‘‘fishing reaction” than in its plain

fishing? And what is the gain in speaking of a bird’s alighting

on a stake as a ‘‘reaction’’? There is a quality seemingly pos-

sessed in some degree by all minds, that tends to accept a new

name for an old familiar phenomenon as in some way more

explanatory of that phenomenon than the old name. Anything

that encourages this tendency is not good for objective science.

More, perhaps, in science than in any other domain of knowl- .

edge is there need of vigilance against bondage to words.

The subjects treated in the collection may be ranged under

these heads: Cytology, normal development, regeneration, faunal

zoology and animal behavior. Some of the papers fall exclu-

sively under one head while others contain matter belonging to

two or more. Such notice and comment as can be made here

will be ranged under these headings.

Cytology: H. E. Jordan (‘‘The Germinal Spot in Echinoderm

Eggs’’) concludes that the chromosomes in Echinaster crassispina

are derived from the nucleolus, and that they arise ineonstantly

in different species of echinoderms from any part of the germinal

vesicle that contains the chromatin material, such containers

being either the nucleolus or nuclear reticulum or both, and that

nothing in this research supports the theory of individuality of

the chromosomes. The same author (‘‘The Spermatogenesis in

Aplopus mayeri’’) finds an accessory chromosome in the phasmid

studied and believes the ‘‘history of this accessory chromosome

gives evidence that it at least possessed a strict morphological

and probably also a physiological individuality.” One would

like to know whether this statement implies that there might be

No. 515] NOTES AND LITERATURE 695

a morphological without a corresponding physiological individ-

uality. If such an individuality is implied it is a queer kind

of individuality, or would be for any other bodies than chromo-

somes. But chromosomes have had so many queer things

attributed to them that queerness with them has almost ceased

to be queer.

In a third paper (‘‘The Relation of the Nucleolus to the

Chromosomes in the primary Odcyte of Asterias forbsii’’) the

same author expresses the belief that ‘‘all the hereditary ele-

ments are persistently held by the chromosomes . . . and that

these merely receive nutritive material from the nucleolus.’’

It may be granted that the figures and descriptions presented

show material to be transferred from the nucleolus to the

chromosomes. What the evidence is that this material is all

nutritive and none of it hereditary would be extremely impor-

tant. Certainly no such evidence is presented in this paper.

The fourth paper that contains cytological matter is ‘‘The

Habits and Early Development of Linerges mercurius, by —

E. G. Conklin. The egg of this medusa presents concentric

layers, the outermost of which is protoplasm nearly free from

yolk. As in the eggs of various other ccelenterates, cell-division,

at least the first division, begins in this peripheral layer; but

contrary to what has been held for some other species, the

nuclei and chromosomes are here somewhat distant from the

point at which the first visible changes toward division occur.

There seems, consequently, no observational ground for guppa

ing that this outer layer does not actually start up the division.

This would appear to be a very significant point. Conklin gets

no evidence that cell-division is ever amitotie in this species as

it has been reported to be in one or two other coelenterates.

Normal Development: W. K. Brooks and B. McGlone show

(“The Origin of the Lung of Ampullaria’’) that in the pul-

monate studied, the lung seems to be quite a different structure

from that of other pulmonates and hence the conclusion 18

reached that ‘‘there is no reason to think that there is any re

cestral connection or relation between the lung of Ampullaria

and that of the pulminates.’”? In the paper by Conklin noted

under cytology, it is shown that gastrulation in the medusa

studied usually takes place by invagination, but sometimes by

the immigration of a mass of endoderm cells at the vegetal pole, -

and the author remarks on the close relationship between the a

696 THE AMERICAN NATURALIST ([Vow. XLII

two processes. The off-hand way in which this fact is now

treated, as compared with the almost frantic contention of

twenty years ago that the two are fundamentally different, at

least in phylogenetic significance, may well be reflected upon

when our minds are turned toward theoretical biology.

Regeneration: Under this head there are two valuable papers.

One (‘‘An Experimental Study of the Rate of Regeneration in

Cassiopea xamachana’’) is by Chas. R. Stockard, and the other

(‘Some Internal Factors concerned with the Regeneration of

the Chelæ of the Gulf-weed Crab’’) is by Chas. Zeleny. Stock-

ard finds no support in this research for the hypothesis that

activity of the regenerating part accelerates or influences in any

special way the regeneration. By cutting pieces of various

shapes and sizes from the bell of the medusa, he gets the interest-

ing result that on the animal itself the ‘‘regeneration rate is

fastest from the portion from which most tissue has been re-

moved’’; and on the pieces cut away regeneration is ‘‘ fastest

from the part from which the least tissue has been removed.”

The reviewer would raise the inquiry, Does not this conclusion

say essentially that the removed tissues of Cassiopea are replaced

in the way necessary to effect the quickest and surest restoration

of the original form of the animal regardless of the form and

place of the cut?

Zeleny’s researches were directed at two fundamental points:

‘The quantitative determination (1) of the effect of successive

removal of an organ upon its power to regenerate and (2) of the

character of the changes, if any, produced in the uninjured

parts of the animal by such removal.” The summarized results

are: (1) ‘When the correction for change in power of regenera-

tion with size or age is made it is found that successive removal

neither retards nor accelerates the regeneration of the right

chela.” The criticism may be ventured that this conclusion is

too unqualified for the number of tests made, there having been

but three removals of the same chela in the same individual.

As we commit ourselves more and more to quantitative methods

in biology, we shall see more and more clearly, so it appears,

the importance of the principle of ‘‘large numbers.” On the

second object of the research the result was: ‘‘The removal and

regeneration of the right chela produces no change in the growth

of the uninjured left chela.”

Faunal Zoology: The titles belonging primarily under this

head are: ‘‘The Pelagic Tunicata of the Gulf Stream,’’ by W.

No. 515] NOTES AND LITERATURE 697

K. Brooks; ‘‘Notes on the Medusz of the Western Atlantic,”

by H. F. Perkins; ‘‘Helminth Fauna of the Dry Tortugas,” by

Edmondson.

A sad interest attaches to the paper by Professor Brooks, it

having been published after its author’s death. Fitting indeed

it is that some of the last works from Brooks’s masterly hand

should be on the group of animals on which his most distin-

guished observational researches were made. A few unim-

portant inadvertencies occur in the paper due to the fact that

illness prevented the author from putting his manuscript in

final form for publication. Some of the figures of Plate I are

labeled S. florida, and some S. floridana. Floridana is the right

name. The title is somewhat misleading since no general treat-

ment of the tunicate fauna of the Gulf Stream is contained

in the paper. As a matter of fact ‘‘observations on certain

morphological points in the subgenus Cyclosalpa’’ would have

been a better title for the first and second parts of the paper.

Perhaps the most important general point discussed by Pro-

fessor Brooks is that of the similarity between the muscle bands

of Salpa and Doliolum. He had previously tried to dispel the

erroneous distinction, as he believed, between the two that is

suggested by the terms Hemimyaria as applied to Salpa, and

Cyclomyaria as applied to Doliolum.

In a third section of the paper written in collaboration with

Carl Kellner, a new appendicularian, Oekopleura tortugensis, is

described. Some ‘‘Notes on Embryology” add a little to our

meager knowledge of the development of this group of animals.

Perkins’s paper on Medusz is by no means a faunistice study

in the narrow sense, it containing quite as much that would

come under the head of animal behavior as under that of faunal

zoology. One of the new species, Cladonema mayeri, is treated

at length, not only the hydroid, and medusa forms being fully

described, but as well various activities and attitudes being dwelt

upon in a lively, appreciative manner. There may be a little

danger in speaking of a jelly-fish as ‘‘evineing the keenest inter-

est in the prospect of a meal,’’ but such expression has at least :

the merit of recognizing the coordinated though complex and

characterizing activities of the organism under a special stim-

ulus; and at the present time the tendency is to allow lower

organisms too little rather than too much of psy chic e ce oe 2

698 THE AMERICAN NATURALIST [Vou. XLIII

Efforts to secure embryos of Cassiopea xamachana were unavail-

ing, no males being found even though over one hundred indi-

viduals were examined!

Linton’s studies on parasitic worms lead him to the con-

clusion that generally these organisms are not as abundant

either in species or individuals, for an equal number of hosts

(fishes) in tropical as in northern waters.

An interesting case of identification is mentioned by Linton.

The spiral valve of some shark, with its contents, came to him

for study. From the entozoa present, taken with the other

intestinal contents, he concluded that the organ belonged to

Galeocerdo tigrinus. It was later found that the jaws of the

specimen had been saved. Examination of these proved the

original identification to have been right. Question: Where

were the “‘determinants’’ of the characters by which this identi-

fication was made? Were they in the germ-cells of the shark

or in those of the entozoa that inhabited the shark’s intestine?

Of course the case would present no difficulty to a consistent

determinantist because the determinant doctrine is founded (un-

wittingly) exactly on such an a priori basis that observed facts

can not touch it. As well expect to hurt a ghost with a charge

of buck shot, as the determinant theory with objective facts.

Several new species and genera of endoparasitic worms are

described in the paper. `

Animal Behavior: Under this head come the largest number

of titles and, on the whole, probably the most important observa-

tions contained in the volumes. This is as-it should be, coming,

as the studies do, from a laboratory located by design in a

peculiarly rich zoological region that is at the same time remote

from the great centers of scientific activity. The titles are:

‘The Annual Breeding-Swarm of the Atlantic Palolo,’’ by A.

G. Mayer; “‘Rhythmical Pulsation in Seyphomeduse,’’ by A. G.

Mayer; ‘‘Habits, Reactions and Associations in Ocypoda

arenaria,’’ by R. P. Cowles; ‘‘Habits, Reactions and Mating

Instincts of the Walking Stick, Aplopus mayeri,” by C. R.

Stockard; ‘‘A Contribution to the Life-History of the Booby

and Man-o’-War Bird,” by F. M. Chapman; ‘‘The Behavior of

Noddy and Sooty Terns,” by J. B. Watson; and ‘‘An Experi-.

mental Field-study of Warning Coloration in Coral-reef Fishes,”

by Jacob Reighard.

As already indicated, some of the papers noticed under other

No. 515] NOTES AND LITERATURE 699

heads contain interesting matter that belongs here. This is

especially true of Conklin’s paper on Linerges. It is practically

out of the question to give within the limits of a brief review an

adequate summary of the contents of this group of papers. The

Atlantic Palolo has been under observation by Dr. Mayer for

nine years, and various interesting details in the ‘“‘swarming’’

of this species have been made out. Besides the principal swarm

(near the last quarter of the moon, between June 29 and July

28) there may be a few smaller swarms before and after this.

Experiments indicate that moonlight falling on the rocks in

which the worms live is indispensable to the swarming.

Mayer’s studies on the pulsation of the medusa of Cassiopea

xamachana is a continuation of work of his previously reported

one. The idea that sea water is a balanced solution for this

species, and that the animal manufactures its own stimulant

to the rhythmical contractions by the ‘‘constant formation of

sodium oxalate in the terminal entodermal cells of the marginal

sense-organs,”’ is still further dwelt upon. Mayer concludes, in

agreement with some other observers working on other animals,

that in this species, ‘“‘conductivity of the subumbrella tissue is

independent of contractility. Dr. Cowles’s article on the

‘‘sand-erab’’ is especially distinguished at first sight by some

of the admirable illustrations it contains. It is shown that

this crab, in which one chela is decidedly larger than the

other, almost always digs its burrow with the side having the

smaller chela and enters the burrow after it is dug, with that

side in the lead. This, Dr. Cowles remarks, is probably ad- .

vantageous to the animal in that the larger chela is in the

more favorable position for defense. It would seem that this

case might have an interesting bearing on the question whether

structures take their characteristic forms to meet demands

imposed upon them or are used to the best advantage for

the organism after they are in existence. In which service are

the chela exercised more, in digging or defending and cap-

turing? Possibly the question might be answered observa-

tionally. The investigator concludes that the crabs do not dis-

tinguish colors visually and do not hear in the ordinary sense;

that they see outlines; that the so-called auditory organs are equl-

liberating organs; that the tactile sense is well developed ; and

that the animals have memory and profit by experience, and

form habits. |

The peculiar structure and habits of the walking-stick, ey oe

700 THE AMERICAN NATURALIST (VoL. XLIII

Aplopus, afford the animals protection in a high degree accord-

ing to Stockard’s investigations. Under certain circumstances

when the antenne are removed the ‘‘forelegs are readily pressed

into service as feelers.’ Males were found to copulate even

in a dark room with the amputated abdomina of the females.

Chapman gives some interesting information on the domestic

and civil polity of the booby and the man-o’-war bird. For

example, the male and female booby seem to change off in their

home duties, the one staying with the nest for a time while the

other fishes. Each pair of birds is closely limited to its own

small nest area during the breeding time, the rule being enforced

by prompt action on the part of members of the colony gen-

erally if a particular individual ventures outside his own

precincts. The booby seems to have the habit of laying two

eggs, only one of which yields a bird. Although not belonging

properly under the present heading, mention may be made of

Chapman’s observation on the order in which the feathers of

pterylæ appear and the rate at which they grow. This seems

to the reviewer an important subject and one deserving more

attention than it has received. ;

ithout minimizing the value of the papers so far noticed,

the two still unnoticed, namely those of Watson and Reighard,

are probably the most valuable of the whole collection, judged

by the number and character of the observations recorded. In

his introductory remarks Professor Watson refers to his work

as preliminary and speaks with some doubt about the possibility

` of its being continued. From the beginnings made on several

problems of the utmost interest, it is greatly to be hoped that

the Tortugas Laboratory will see to it as one of its first con-

cerns that these investigations are kept up. To get some clear

light on the one problem of how terns which seemingly have

never been over the ground before, can find their way from

Cape Hatteras to the Bird Key, something like a thousand miles,

would amply justify the expenditure of the institution’s entire

income for a number of years were so heavy an outlay neces-

sary. Fortunately the work would probably not be greatly ex-

pensive. Biologists will do well to recognize that exactly in

such phenomena as these occultism and superstition have their

strongest roots to-day, and that these roots are by no means frail

and sickly. Any victory that science can win in these frontier

Tegions counts for more toward the general enlightenment of

No. 515] NOTES AND LITERATURE 701

mankind than many won in already well cultivated conquered

territory. For the many facts brought out on the relation of

the sexes during the breeding period; on the care of progeny;

on the instincts and habits of the young; on the intelligence,

individual and comparative, of the two species studied; and

many other topics, the paper itself must be consulted.

Reighard’s investigation being in a field that has long been

a storm-center of theoretical biology, will probably attract more

readers than any other one in the volumes. In the reviewer’s

opinion it will, too, exercise a wide and beneficent influence

toward rectifying one of the most remarkable aberrations to

which scientific speculation has been subject in any domain of

science for many a decade. It was the reviewer’s privilege a

few years ago to spend some time observing the fishes about the

coral-reefs of the Hawaiian Islands. From this experience as

well as from various others more or less kindred, he is convinced

of the essential soundness of Reighard’s results. More than

that, he is convinced that any naturalist, the windows of whose

mind are not darkened with the heaviest screens of adverse

dogma, would be likewise convinced were he to examine the

evidence for himself.

We must be content with a single quotation from this paper:

Coral-reef fishes are not conspicuous because they are in the reefs;

they are in the reefs because they are conspicuous and can not therefore

leave the reefs, and because, being in the reefs and taking food as they

do, there is no reason for their being inconspicuous. The reefs condi-

tion their conspicuousness; they are in no sense its cause.

` We should certainly want more light than the author has

given on the meaning of the statement that reefs condition but

in no sense cause the conspicuousness of the fish. But passing

this as of minor importance it is to the first part of the state-

ment that we turn for the real meat of the case. If it be really

true, and we recognize the truth, that the ‘color of these fishes

has arisen we know not how, but that having become thus elab-

orate and conspicuous, the fishes find protection as well as fooc

among the corals, then are we at the threshold of the problem

of how the color has arisen, with our senses and wits open to re-

ceive evidence of whatever sort bearing on the problem. The

unfortunate thing about the natural selection theory has been

not so much the error it contains as the fact that it has been

made an absolutist theory; one of the sort, that is, that sivas Pi ee

702 THE AMERICAN NATURALIST [Vou. XLIII

door in the face of inductive science. It is time to be undeceived

in this matter.

Wm. E. RITTER.

La JOLLA, CALIF.,

Sept. 20, 1909.

EXPERIMENTAL ZOOLOGY

Inheritance of Color in Pigeons.—The breeding experiments of

pigeons, described by R. Staples-Brown in the Proceedings of

the Zoological Society of London for 1908, pages 67-104, are

of interest because he repeated certain experiments by which

Darwin obtained a reversionary type resembling Columba livia.

Darwin concluded that domesticated pigeons sprang therefore

from the wild rock pigeon. The varieties of pigeons used by

Staples-Brown were with one exception identical with those used

by Darwin and the experiments were planned on similar lines.

Darwin’s experiment, it will be recalled, was as follows: A:

black Barb was crossed with a white Fantail and a black Barb

with a red Spot (white bird with tail and tail coverts red having

a red spot on the forehead). Upon mating hybrids produced

by these two crosses Darwin obtained a pigeon identical with

Columba livia, excepting that ‘‘the head was tinted with a shade

of red, evidently derived from the Spot, and was a paler blue

than in the rock pigeon.” Staples-Brown substituted a black

and white Nun for Darwin’s red Spot which was not readily

obtainable.

A Nun is a white bird with certain well-defined markings of

black, blue, red or yellow. The individuals used in Staples-

Brown experiments were black and white, the black appearing

on the chin and throat, part of the outer flight feathers, a few

secondaries and tertiaries, the tail and upper and under tail

coverts. The Barb pigeon is self-colored, black, red, yellow, dun

or white, with a small beak and the skin around the eyes broad

and ecarunculated. Black Barbs only were used in these experi-

ments. The Fantails used were white. When the Barb X Fan-

tail hybrids were bred to the Barb X Nun hybrids no rever-

sionary types were produced. These experiments were discon-

tinued owing to lack of space. However, when Barb X Fantail

hybrids were mated together some of the offspring had blue

feathers. The blue color was chiefly on the tail as described by

*** Animals and Plants under Domestication,’’ 2d edition, Vol. I, p. 209.

No. 515] NOTES AND LITERATURE 703

Darwin. A black tail bar was present and the wing coverts

and back were of a smoky black color, obscuring the wing bars

which are common to the rock pigeon. The reversionary type

in some cases appeared in the F, generation. A similar result

was obtained by Darwin in the F, generation from a Nun and a

red Tumbler.

The author explains the fact of the reversionary blue not

appearing until the F, generation in the Barb X Fantail cross,

by assuming that the F, individuals contain some element which

prevents the appearance of blue. This, he holds, is the factor

for black self color, which.is epistatiec to blue. In the recom-

bination of factors in F,, those combinations containing blue

without the black factor produce individuals with blue feathers,

while those with the black factor exhibit black feathers but no

blue ones.

Reference is made to other cases of reversion (sweet Peas and

Stocks) in which its occurrence is due to the meeting of com-

plimentary factors. He adds, ‘‘In the case of the Barb X Fan-

tail cross the evidence is not yet sufficient to show whether the

factors needed to produce the atavistic condition are all present

in the Barb and their effect merely hidden by the presence

of the black factor, or whether a necessary factor is introduced

by the fantail; but the fact that no blues came in the F, made

from an F, (Barb X Fantail) X F, (Barb X Nun) distinctly

suggests that some factor of the blue did come from the Fantail.”

The general result of the Barb X Fantail experiments shows ą

dominance of black and blue to white. This dominance, how-

ever, is imperfect, as the majority show some white feathers. In

the F, generation from such crosses, the following types were

obtained :

Black.

Black with some white feathers.

ue.

Blue with some white feathers.

ed.

White with some colored feathers.

; ite.

The significance of the presence or absence of the white

feathers is obscure. It was first thought that the white feathers

indicated that the bird was producing white-bearng- gametes.

This is not true in all cases.

704 THE AMERICAN NATURALIST [Vou. XLIII

In matings of blues with white feathers, whites were produced, and

a definite proportion of homozygous blues was to be expected. With

one exception, however, all the blues produced from these matings

showed some white feathers.

Some of these were probably homozygous, but it could not be

tested without making use of a large number of such birds. The

order of dominance was found to be black, blue, red and white.

In minor characters, such as irides, color of beak and claws, the

author obtained the following results; white irides dominate

black, and there is some evidence of correlation between white

iris and black plumage. There was also marked correlation

observed between the pigment in the beak and to some extent in

the claws, and the plumage. In general, white-plumage birds

have white beaks and claws. In the case of eye-wattles, red is

dominant over flesh color. -

B. B. Horton.

The Study of

Stellar Evolution

An Account of Some Modern Methods of

Astrophysical Research

By GEORGE ELLERY HALE

The introduction of photographic methods, the improvement of telescopes, and the rapidly in-

creasing appreciation of the value to astronomy of physical instruments and processes, have revolu-

tionized the ohare From a simple observing station it has been transformed into a great

physical laboratory, where images of the sun and stars are studied with many powerful instruments,

and celestial phenomena are experimentally imitated with the aid of electric furnaces and other

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THE

AMERICAN NATURALIST

Vöi. XLIII December, 1909 No. 516

THE CUTICULA AND SUBCUTICULA OF TRE-

MATODES AND CESTODES

PROFESSOR HENRY S. PRATT

HAVERFORD COLLEGE

THE membrane which forms the outer covering of the

body of trematodes and cestodes and is usually called the

cuticula differs in certain important particulars from that

of other invertebrates, and its morphological significance

has long been a matter of dispute. The most noticeable

feature of this difference is the apparent lack of a hypo-

dermis in these worms, the cuticula being bounded on its

inner surface by the superficial muscle layers and the

parenchyma which fills the body-cavity.

In the last few years, however, a theory of the cuticula,

which in the early years of modern helminthology was.

the prevailing one, has been revived by Professor F.

Blochmann (1896), who has presented its claims to recog-

nition with so much force and ability that it has been

accepted by most helminthologists and zoologists as best

accounting for the facts. It has also found its way into

some of the best text-books and bids fair to become, in

the ordinary course of events, one of the dogmas of

science. a

According to this theory, the cuticula of trematodes and

cestodes is a true cuticula morphologically, which is

secreted by a hypodermis, as in other invertebrates. This

hypodermis, however, has undergone a metamorphosis,

for instead of forming a continuous layer of cells situated

705

cuticula ; 2, basal membrane

cells; 6, nerve;

706 THE AMERICAN NATURALIST [Vou. XLIII

immediately beneath the cuticula, it has dropped back of

some or all of the superficial muscle layers into the paren-

chyma, its constituent cells have become more or less.

separated from one another, and it forms the broken or

irregular tissue called the subcuticula.

Fig. 1, which is taken from Blochmann’s paper and ap-

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Fic. 1. Transverse section from Ligula, a cestode (after Blochmann). 1,

; 3, circular muscles; 4, parenchyma ; 5, subcuticular

7, dorsoventral muscles; 8, longitudinal muscles; 9, calcareous

body ; 10, excretory canal; 11, sense-cell; 12, myoblast; 13, flame-cell; 14, gland-

cell; 15, sense-organ.

pears also in Claus and Grobben’s ‘‘Lehrbuch,’’ Braun’s

‘* Menschliche Parasiten’’ and Lankester’s ‘‘Zoology,’’

represents a section of the body-wall of a cestode (Ligula)

and shows the relation of the cuticula to the subcuticular

No. 516] THE CUTICULA OF CESTODES 707

cells as conceived by Blochmann and adopted by the au-

thors of these text-books.

Fig. 2 from Hein (1904), who follows Blochmann

closely, shows the same relations in the digenetic trema-

todes. It will be seen in both these figures that the sub-

cuticular cells form a distinct although irregular layer

and are joined with the inner surface of the cuticula by

long projections. These Blochmann and Hein regard as

the ducts through which formative material is added to

Fic. 2. Longitudinal section from Fasciola hepatica, a digenetic trematode i

(after Hein). 1, cuticula ; 2, spine; 3, circular muscles ; 4, longitudinal muscles ;

5, oblique muscles; 6, subcuticular cells; 7, parenchyma.

the cuticula, of which these cells are thus the matrix. It

will further be noticed in these figures that the sub-

cuticular cells apparently do not form a part of the paren-

chyma in which they lie, and also that among them are

sense cells and gland cells which are usually conceded to

have an epithelial origin. :

Another theory of the cuticula which is not very differ-

ent from Blochmann’s is that of Brandes (1892), who

also considers the structure in question to be the product

of the subcuticular cells (Fig. 3). These, however, he

conceives to be single-celled glands which are joined with

708 THE AMERICAN NATURALIST [Vou. XLII

the cuticula by means of ducts passing between the super-

ficial muscle fibers. Brandes’s theory is based upon an

examination of a considerable number of monogenetic

and digenetic trematodes, in both of which groups he finds

practically identical structural conditions in the cuticular

and subeuticular layers. His

drawings, however, are very

diagrammatic. The subcuticu-

lar cells certainly do not exist

in any trematodes in the form

in which he shows them, and

those in his figures of mono-

genetic trematodes are not the

subeuticular cells at all, but the

single-celled glands which are

present at the forward end of

most of these worms.

+ ar mila Tennent (1906) and others

See aai anan have adopted Brandes’s view.

It will at once be noted that the

main difference between his theory and that of Blochmann

lies in their interpretation of the subcuticular cells, the

former holding them to constitute a hypodermis and to be

consequently an epithelium of ectodermic origin, the latter

considering them simple gland cells which are derivatives

of the parenchyma.

These important theories, although they may seem to

account for the facts in the animals investigated and to

place the whole matter upon a substantial logical basis,

have, however, met with considerable opposition, and, it

seems to me, are not well grounded. It is quite evident

that if they are true they must have universal applica-

tion. If the subcuticular cells are the matrix of the cuti-

cula, whether we consider them to be single-celled glands

or the constituent parts of a hypodermis, then they must

be present in all trematodes and cestodes, since this pecul-

iar cuticula characterizes all of these worms (with the

No. 516] THE CUTICULA OF CESTODES 709

exception of the Temnocephalide) from their early larval

stages to those of the adult.

But this is far from being the case. The subcuticular

cells are wanting in probably the whole group of mono-

genetic trematodes, also in most of the Aspidobothride

and in certain other digenetic trematodes. Goto (1894,

1899) has made a careful anatomical study of over forty

species of monogenetic trematodes belonging to some six-

teen genera, and has found no subcuticular cells in any

V A

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: Pes

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iv Ñ O S g vier ee . ee

Ss SET jae

Fig. 4. Transverse section from Dionchus agassizi, a monogenetic perme

(after Goto). 1, cuticula; 2, parenchyma; 3, muscles; 4, single-celled glands;

5, parenchyma nuclei.

of them (Fig. 4). He directed his attention specially to

the discovery of these cells in the worms studied by

Brandes, but says: ee

i ial attention to the point, I have utterly

oa. ce cells so beautifully drawn by

Brandes in his figures in the very same genera that he describes.

Cerfontaine (1899) has also made a study of some

twenty-eight species of monogenetic trematodes with the

Same result (Fig. 5).

It is true that peripheral single-celled glands are pres-

ent in probably all of these worms, the ducts of which can

be easily seen (Figs. 1 and 4) to pass not merely to but

through the cuticula to the outside surface of the raga ;

These gland cells are usually grouped at the forward end

710 THE AMERICAN NATURALIST [Vou. XLIII

of the body or in the neighborhood of the suckers, and are

variously interpreted as sticky or mucous glands or as

irritants to increase the flow of the juices which serve as

the food of the worm. They do not extend over the whole

body or any large part of it, and are not the subcuticular

E AM y Ss, =

Pry:

AZA soan mAr att Sonat

eee

Pires w gs 4

Fic. 5. Longitudinal section from at ee vulgaris, a monogenetic

trematode (after Cerfontaine). 1, cuticula; Sa nchyma ; 3, circular muscles ;

4, longitudinal muscles ; 5, ae rah nuc

cells, nor are they so considered by any authors who have

studied them. They also differ markedly in shape from

the subcuticular cells, being more or less pear-shaped and

regular in outline, each cell having a distinct and single

Longitudinal section from Stichocotyle nephropis, an aspidobothrid

jatar” ‘Nickerso on). 1, cuticula; 2, muscles ; 3, parenchyma; 4, intestine; 5,

pharynx; 6, mouth; 7, parenchyma nuclei

duet of large size. The subcuticular cells, on the other

hand, are often irregular in shape, often anastomosing

with one another and in many cases having the appear-

ance of parenchyma cells. They also show no ducts at all,

‘No. 516] THE CUTICULA OF CESTODES 711

but in many forms are connected with the cuticula by

branched or anastomosing processes (Figs. 1 and 2) which

are interpreted by many to be ducts.

The lack of subcuticular cells in Aspidobothride has

been shown by Monticelli (1892) and Nickerson (1902)

for Cotylogaster, Nickerson (1894) for Stichocotyle (Fig.

6), and Osborn (1904) for Cotylaspis. Single-celled

glands are, however, present in all these worms.

In the other digenetic trematodes and in cestodes, also,

although subeuticular cells have been shown to be present

in most of the forms whose finer structure is known, it is

certain that some do not possess them. In Distomum

(1885) found none of them, and in Hemiurus crenatus and

Gasterostomum gracilescens Lander (1904) and Tennent

(1906), respectively, found them only in very small num-

bers. In all digenetic trematodes and cestodes, also, it

can very often be shown that the cells in question bear

no adequate relation to the cuticula beneath which they

lie. Thus they are present sometimes in certain parts

of the body only, as has been shown in my study of

Apoblema (1898), in which the appendix of the youthful

distome, although covered with exactly the same cuticula

as in the rest of the body, is entirely without subeuticular

cells. The suckers, also, in cestodes and the tail of the

cercaria have none of these cells, although they possess

a cuticula.

In many digenetie trematodes, too, the subeuticular

cells, although present, are entirely too few in number

to produce the thick cuticula present, as shown in Hem-

urus crenatus (Fig. 7) by Lander, and in numerous other

cases. It must be remembered in this connection that the

cuticula of trematodes and cestodes is probably at all

times a growing tissue, which is constantly being renev ed

on its inner surface in proportion as it wears away on its

outer, so that if the subeuticular cells are its matrix they

should be equally present in all parts of the body and at ee

all times of the animal’s active life. Be

712 THE AMERICAN NATURALIST [Vou. XLIII

In many digenetic trematodes the cuticula is not of

equal thickness on all parts of the body and these varia-

tions in thickness are not correlated with corresponding

differences in the subcuticular cells beneath them. For

instance, the cuticula of the appendiculate distomes has

numerous transverse rings which give a longitudinal sec-

tion a serrated appearance. These rings are due solely to

Fic. 7. Transverse section from Hemiurus crenatus, an appendiculate dis-

tome (after Lander). 1, cuticula; 2, longitudinal muscles; 3, subcuticular cells 5

4, parenchyma.

variations in the thickness of the cuticula, the inner sur-

face of it being quite smooth, and we might expect the

subcuticular cells, if they secreted the cuticular, to be

larger or more numerous beneath the rings. This is, how-

ever, not the case, these cells showing no variations what-

ever beneath these cuticular rings.

The relations of the spines, hooks, scales and other

special cuticular structures to the subcuticular cells also

furnish an argument against the epithelial or glandular

nature of the latter. These spines and hooks are of very

common occurrence and are often very prominent objects

in trematodes and cestodes, their function usually being

to aid in anchoring the parasite to its host. They are

seen in their simplest form in the digenetic trematodes,

(Fig. 2) in which they usually appear as specialized parts

of the cuticula. In the monogenetic trematodes and the

cestodes, on the other hand, they are often of huge size

and of more or less complex structure and may extend be-

sea the cuticula among the muscles and the ‘parenchyma

cells.

That these organs are similar in essentiai structure and

No. 516] THE CUTICULA OF CESTODES 713

in origin to the cuticula has been very well shown by

Looss (1894), Young (1908) and other authors, who have

traced their development and growth.

If now the cuticula is the product of the underlying

subcuticular cells, we should expect to find some special

development of them beneath the hooks and spines, espe-

cially where these are very large, just as in the integu-

ment of insects a cuticular hair or scale is invariably

situated over the enlarged hypodermal cell which pro-

duces it. Nothing of the sort exists, however, in trema-

todes and cestodes. The subcuticular cells beneath the

hooks and spines do not differ in size, number or arrange-

ment from the adjacent cells, and in the monogenetic

trematodes, which are often provided with gigantic hooks,

no subeuticular cells at all are present. In the six-hooked

embryo of cestodes the hooks make their appearance in

the embryonic parenchyma, while there are as yet no

subeuticular cells present. The parenchyma is thus the

matrix of the hooks at this early stage of the animal’s

existence.

Another point of importance is the essential difference

in structure between the cu-

ticula of trematodes and ces-

todes and that of other worms

and of arthropods in which

the cuticula is the secretion

of an undoubted hypodermis.

In the former the character-

istic lamellate structure of a

cysticercus of Tenia serrata (after Young).

Section of wall of young

trematode (after Cerfontaine). 1, cuticula; 2, nuclei in the

chyma ; 4, muscles.

714 THE AMERICAN NATURALIST [Vow. XLII

typical arthropod or worm cuticula is never present (al-

though it may be made up of several layers), but, on the

other hand, a fundamentally fibrous structure can often

be demonstrated with perfect clearness, the fibers being

sometimes in very evident connection with the paren-

chyma beneath and a portion of it (Figs. 8 and 9).

In fact, the so-called ducts of the subcuticular cells are

nothing more nor less than the fibrous projections of

these cells which, together with similar projections of the

parenchyma cells themselves, sometimes extend to, and

occasionally, especially in young animals, into the cutic- _

ula. In certain cases these fibers may arrange them-

selves so as to form a series of vertical strands in the

cuticula, passing between its inner and outer surfaces,

and have been interpreted in the past to be pore-canals,

structures which are probably not present in any trema-

todes or cestodes. Whatever toughness of texture the

cuticula of these worms possesses is probably due to this

fundamentally fibrous or leathery structure. The cutic-

ula is further exceedingly elastic; it is often very soft

-or even semi-fluid and easily destroyed in caustic potash

and as the result of maceration; and it is never moulted

as a whole nor can it be usually separated from the tissues

beneath—all of which characteristics are foreign to the

cuticula of other worms and of arthropods. :

The differences between an undoubted hypodermis

and the subecuticular cells are also fundamental and very

striking, and are not satisfactorily explained by Bloch-

mann, who compares with them the hypodermal cells of

Hirudo and other animals which may be more or less

separated from one another by parenchyma and other

tissues. The origin of these cells forms the embryonic

parenchyma, as shown clearly by many authors, and the

frequent anastomosing of them with one another and with

the surrounding parenchyma, are characters which no

hypodermis possesses.

It is true that there is a strong superficial resemblance

between the subcuticular cells in cestodes—but seldom or

No. 516] THE CUTICULA OF CESTODES 715

never in trematodes—and epithelial cells, without which it

is not likely that any one would ever have thought of this

epithelial theory. These cells in cestodes are, as we have

seen, usually elongated and spindle-shaped and lie paral-

lel to one another, so that they look a good deal like iso-

lated epithelial cells. But it must also be noticed (Fig.

1) that all the other cellular elements of the peripheral

region—the parenchyma cells, the gland cells and the

sense cells—are also elongated and spindle-shaped and lie

parallel to one another and to the subeuticular cells. Ap-

10. Golgi section from a cestode (Ligula) showing the branched in-

Sertion of the dorsoventral muscles in the cuticula (after Zernecke). 1, cuticula ;

2, the muscles; 8, sense-organ; 4, nerves; 5, sense-cell.

parently some common cause, in the nature of a tension

in a dorsoventral direction, has acted upon the entire

peripheral region of the body of the worm, distorting

more or less all the structures in it. Leuckart (1886) has

suggested—and Leuckart’s suggestions are always fruit-

ful—that this spindle form is due to the action of the

powerful dorsoventral muscles which run across the

716 THE AMERICAN NATURALIST [Vou. XLIII

proglottid and are inserted in the cuticula of each surface

by numerous branching strands (Fig. 10). He even

thought that the spindle cells might be the tendons of

these muscles, which, however, is not the case, since Zer-

nicke (1895) and others have demonstrated the branched

insertions just mentioned. It is my opinion, however,

that it is the pull of these muscles and especially of their

branched insertions which interweave themselves among

all the peripheral tissues of the body (Fig. 10), which

has thus distorted all the cellular elements in this region

and caused them to assume their cl teristic shape

and appearance. And this opinion is confirmed by the

fact that in the scolex and between the proglottids, where

these muscles are weak or absent, the subcuticular cells

are not spindle-shaped, but have the form of ordinary

parenchyma cells (Leuckart).

The embryological and larval history of these worms

also furnishes arguments against the epithelial theory.

The cuticula comes into existence, both in trematodes and

cestodes, before the subeuticular cells have differentiated

and grows independently of them (Figs. 8 and 11). Its

early growth has been well described by Looss for trema-

todes in Diplodiseus (1892) and in a considerable number

of distomes (1894) and by Roewer (1906) in distomes,

and for cestodes by Young (1908) in Cysticercus pisi-

formis. These authors show also very conclusively that

when the subcuticular cells do finally make their appear-

ance it is as differentiations of the embryonic paren-

chyma cells and that at no time is anything like an epi-

thelium present in the position in which they are

found (Fig. 8).

The moulting of the outer epithelium (ectoderm) in

larval trematodes and cestodes has also an important

bearing upon this question, inasmuch as in consequence

of it the adult worm is entirely composed of tissues de-

rived primarily from the interior embryonic cell mass

(endoderm or mesenchyme). The subcuticular cells can

not consequently be of ectodermal origin and can not be

No. 516] THE CUTICULA OF CESTODES ANG

homologous to the hypodermis of other invertebrates. In

trematodes this moulting may occur in each of the larval

stages. It has been directly observed in the miracidium

many times, among others by both Thomas (1883) and

Leuckart (1886) who saw the miracidium of Fasciola

hepatica shed its ciliated ectoderm when it entered the

liver of Lymnea trunculata. In the redia and cercaria

stages it has also been directly observed by a number of

investigators. Looss has made the most complete record

of his observations. He (1892, 1893, 1894, also Braun,

1893, p. 818) has seen both the redia and cercaria shed

its outer epithelium in about a dozen species of distomes,

as just remarked, after which procedure the young worm

was covered with the definitive cuticula. This Looss con-

siders the product of secretions of the entire body of the

parenchyma.

Although the cerearia has thus been seen to shed its

peripheral epithelium, there have been recorded a num-

ber of cases where it is not shed all at one time, portions

remaining until the cercaria is fully grown or nearly so.

The appendiculate distome I described some time ago

(1898) was a good example of this procedure. The ap-

pendix of the young worm in this case retained its cer-

carian ectoderm although the male genital organs were

mature and spermatozoa were being produced. The re-

mainder of the body was without an epithelium, but was

covered by the characteristic cuticula, which was also

present beneath the epithelium on the appendix. This

epithelium was soon after moulted and then the outer

covering of the appendix was exactly similar to that of

the rest of the body.

In cestodes the early stages of development are very

similar to those of trematodes, the ectoderm having been

observed by Schauinsland (1885), Leuckart (1886) and

others to be moulted in exactly the same way. It is the

opinion of many students of cestodes, however, that the

stage in which an outer epithelium is present is passed

over in most of these animals. The young worms thus

718 THE AMERICAN NATURALIST [Vow. XLIII

never have an outer epithelium, but the characteristic

cuticula is their’earliest body-covering. l

Although there can be no doubt that the outer epi-

thelium of trematode and cestode embryos and larvæ is

often, perhaps usually, moulted, it must be mentioned

that cases have also been récorded in which no such

moulting has apparently taken place. Schauinsland

(1883) has shown that in the embryo of Distomum tereti-

colle, the ectoderm gradually loses its cell boundaries and

nuclei and becomes metamorphosed into a cuticula. A

similar process has been described by Leuckart (1886) in

the young redia of Fasciola hepatica,

by Zeller (1872) in the embryo of Poly-

stoma, and by other authors.

These facts and others which will be

mentioned have led many helminthol-

ogists to subscribe to a third theory of

the cuticula of tr todes and ces-

todes—that which sees in it a meta-

morphosed or cuticularized epithelium

(ectoderm). This is one of the oldest

Fic. 11. Section of Of the theories relating to the cuticula,

cercus of Tenia serrata DAVIN been first proposed by Wag-

ener in 1855, and in later years having

such able supporters as Monticelli,

Goto, Nickerson and Braun, although the last named has

apparently abandoned it in favor of Blochmann’s theory.

It is based mainly upon the facts that embryonic and

larval ectoderms have been observed in a degenerate

condition as just stated, and also that frequently nuclei

are found imbedded in the adult cuticula. These nuclei

are sometimes well formed (Fig. 12), but often have the

appearance of being in a more or less broken-down condi-

tion and to be degenerating. Open spaces and vesicles are

also often present in the cuticula.

Much has been observed which supports this theory.

Braun (1893, p. 590) found numerous oval nuclei in the

cuticula of Monostomum mutabile, Maclaren (1905) found

, Cu-

ticula; 2, parenchyma.

No. 516] THE CUTICULA OF CESTODES 719

them in Distomum sp. (Fig. 12), Monticelli (1892, 1894)

in a number of trematodes, Nickerson (1902) in Cotylo-

gaster, Cerfontaine (1899) in Squalonchocotyle vulgaris

(Fig. 9): many other authors also have seen and de-

scribed them. There can be no doubt that however one

may interpret the alleged cuticularization of the embry-

onic and larval ectoderms,—and Brandes, Looss, Braun

and others will not admit that it has been demonstrated,

Fic. 12. Section of the cuticula of a distome containing nuclei (after Mac-

laren). 1, cuticula ; 2, nucleus imbedded in cuticula. -

—nuclei or nuclei-like bodies occasionally appear in the

cuticula of both larval and adult trematodes and cestodes.

These have been variously interpreted by different au-

thors. Blochmann (1896), for instance, asserts that they

are the end organs of sense cells which are imbedded in

the cuticula, while Looss (1893) thinks they may be por-

tions of formed material in the act of passing from the

parenchyma into the cuticula.

It seems to me that the occurrence of nuclei in the

cuticula has been recorded by too many competent ob-

servers to be explained away in any such manner. They

undoubtedly do occasionally occur, being either nuclei

which are parts of a degenerating epithelium or perhaps

those which belong to the peripheral portion of the paren-

chyma and have become enclosed in the rapidly forming

and growing cuticula. This last probability is strength-

ened by the observation of Maclaren (1905) and others

that such nuclei occur most frequently in the cuticula of

young worms, and by those of Young (1908) and Cer-

fontaine (1899) who show, respectively, that the cuticula

720 THE AMERICAN NATURALIST [Vou. XLIII

of the very young larva is composed essentially of fibers

and nuclei closely bound together (Fig. 11) and that the

adult cuticula may be in direct connection with the sub-

jacent parenchyma and contain some of its nuclei (Fig.

9). It is conceivable, however, notwithstanding these

facts, that foreign objects such as particles of coagulated

blood, which often adheres to the outer surface of these

worms, could be forced into the soft cuticula from the

outside as a result of the pressure to which the worms are

often subjected in their natural environment, or perhaps

in the compressor or under the cover-glass of the investi-

gator, and thus appear like degenerating nuclei in it.

The vesicles, which often appear in the cuticle, are prob-

ably artefacts due to the influence of reagents on the soft

cuticula of a dying or a compressed animal. The cuticula

also macerates very rapidly, in fact it is often the first

part of the body to show death-changes, and may easily

become vesicular by the passage of fluids or gases into it

from the parenchyma or from the outside.

In my own opinion this theory of the metamorphosed

epithelium breaks down, at least as a universal theory,

for several reasons. In the first place, the outer epi-

thelium is undoubtedly moulted in very many larval

trematodes, as has been observed by many competent ®

observers, and a worm can not both shed its epithelium

and still enjoy the possession of it, even in a modified

form. The theory can not thus have general application.

In the second place, even if the ectoderm of the embryo or

larva is cuticularized in certain cases, as has been ob-

served, the cuticula of the adult worm is not yet accounted

for, as the worm increases in size many-fold, often many

thousand-fold, while growing from the larval to the adult

condition. In other words, the cuticula of the mature

worm may be quite a different structure from that of the

larva, and if it is true that the cuticula of the larva is a

metamorphosed epithelium, then that of the adult is

formed of a different material and in a different way. In-

asmuch as the cuticula is constantly growing on its inner

No. 516] THE CUTICULA OF CESTODES 721

surface and being flaked off on its outer, it is not a struc-

ture which is formed once for all but one which depends

on a more or less uniform secretion from the tissues |

beneath.

What then is the morphological significance of the cuti-

cula of trematodes and cestodes if it is neither a meta-

morphosed epithelium nor the product of an underlying

hypodermis or of single-celled glands. I believe that it is

the peripheral portion of the parenchyma which forms the

outer coating of the body after the disappearance of the

larval epithelium (ectoderm), and which has been solidi-

fied into a thick membrane by the secretion of cuticular

substance from the whole body of the parenchyma. That

the entire parenchyma can thus have a secretory function

is proved by the formation by it of the fluid with which

it is permeated and its vesicles are filled and also of that

which fills the cavity of a cysticercus.

This theory seems to have originated with Leuckart

(1886, p. 367). It has been explained and defended at

great length by Looss (1893, 1894, also Braun 1893, p.

818, note) and subscribed to by Pratt (1898), Cerfontaine

(1899) and Young (1908). It is in certain respects an

unusual theory, inasmuch as it implies the absence of an

integumental covering of ectodermic origin, which is

characteristic of the rest of the Metazoa. But the life

conditions of trematodes and cestodes are peculiar and

unusual. These worms are exclusively parasitic ani-

mals, being the only large groups of Metazoa, so far as I

recall, of which this is the case, and this parasitic habit

is undoubtedly correlated with the disappearance of the

larval ectoderm and the formation of the parenchymatous

cuticula, as well as other special features of the structure

of these worms.

The most primitive trematodes, the Temnocephalida,

are an exception to the rest of the group in possessing an

integument composed of a cuticula with an underlying

hypodermis, although having the typical trematode struc-

ture in other respects. These animals are found adhering

722 THE AMERICAN NATURALIST [VoL. XLIII

to the surface of turtles and fresh-water crustaceans and

are not true parasites, inasmuch as they feed upon small

animals in the water and not upon the vital juices of the

host. They probably form a connecting link between

turbellarians and trematodes, representing the first step

of the ancestors of the latter towards the acquisition of

parasitic habits. The next step was taken as the result

of the migration of the worms from the surface into the

mouth and cloaca and on to the gills, and then into the

internal organs, of the aquatic hosts. The worms thus

became true parasites. They learned to feed upon the

blood or the other juices of the host and were habitually

enclosed or immersed in its tissues and exposed to the

disintegrating action of its fluids. It is probable, as a re-

sult of these things, that the changes occurred which char-

acterize the body-covering of these worms. The integu-

ment which is common to most worms apparently would

not furnish a sufficient protection to animals thus situ-

ated, and it consequently came about in the course of

their evolution that the outer epithelium with its cuticula

was moulted or at least disappeared and the parenchyma

acquired the property of forming a thick cuticula-like

membrane on its outer surface to protect the animals

from the peculiar dangers of their environment. A pro-

tective function similar to this is, as Leuckart points out,

very frequently exercised by cuticula-like connective

tissue structures of various kinds throughout the animal

kingdom.

Von Graff (1903) has made the observation, it is

interesting to note, that in certain of the parasitic turbel-

arians (Synccelidium) a process similar to this has evi-

dently gone on, for the animals have lost their integu-

mental epithelium together with its cilia and are covered

with a cuticula similar to that of trematodes.

The first steps in the formation of the cuticula have

been minutely observed, as already stated, in the trema-

todes by Looss (1892, 1903) and Roewer (1906) and in

cestodes by Young (1908). According to Looss, it first

No. 516] THE CUTICULA OF CESTODES 723

appears as a fine line between the muscle-layers and the

outer epithelium (ectoderm) of the redia and cerecaria,

which gradually broadens and when the epithelium is

finally shed, becomes the outer covering of the body.

Looss has observed this proceeding in a dozen or more

different species of trematodes and believes it to be gen-

eral to the entire group.

According to Young, the cuticula of the young cysti-

cercus is a delicate layer which is composed of a ground-

work formed of fibrillar projections of the embryonic

parenchyma cells and a homogeneous translucent cement-

like substance produced by these cells (Figs. 8 and 11).

The subcuticular cells have not yet differentiated from

the embryonic parenchyma. The young cuticula soon be-

gin to scale off on the outer surface and is constantly -

being added to on the inner. In the course of time two

layers show themselves in the cuticula, the inner of which

alone contains the cement-like substance, the outer layer,

which in later stages may be very thin or be entirely lost,

forming the so-called hair-layer which sometimes char- `

acterizes the outer surface of cestodes and is exclusively

fibrillar.

The later history of the cuticula is a continuation of its

larval history. Although formed principally as a secre-

tion of the parenchyma, it is at all times a part of it and

will often show, even in the adult stage, a fundamentally

fibrillar structure. It is also, as has been stated, never

moulted and can not be easily separated from the struc-

tures beneath.

Very important in a study of the whole question, is the

relation of the gonoducts and the excretory vesicle to the

surrounding parenchyma, inasmuch as the walls of these

structures have essentially the same structure as the

outer body-wall, being lined by a cuticula at the back of,

which are the parenchyma and usually muscle fibers.

What then is the developmental history of these ducts?

It has recently-been shown by Balss (1908) in cestodes

_ and Roewer (1906) in trematodes that the history of the

724 THE AMERICAN NATURALIST [Von. XLIII

formation of the gonoducts as well as their structure, is

essentially similar to that of the body-wall. The walls of

each of these ducts (except those of the uterus in ces-

todes) are formed at first of a single-layered epithelium

which develops from a primitive chord of epithelial cells

by the appearance in it of a lumen. This epithelium,

however, quickly degenerates and disappears and at the

same time the surrounding parenchyma secretes a cutic-

ula which forms the permanent coating of the tubes. The

spines which are often present in the cirrus and vagina

are formed in the same way. 7

The terminal excretory vesicle has also primitively an

epithelial wall like that of the gonoducts, as has been

shown by Looss (1894) and in my study of Apoblema

(1898), which is replaced by a parenchymatous cuticula

as in the case of the gonoducts.

The cause of the change in the structure of the walls of

these ducts from an epithelium to a parenchymatous

cuticula is probably identical with that which has been

brought about a similar change in the structure of the

body-wall. Not only is the outer covering of the animal

apt to be affected injuriously by the juices of the host, but

the walls of the large ducts opening to the outside as well,

and both have consequently undergone an identical trans-

formation.

What then are the origin and function of the subeutic-

ular cells? That they belong genetically to the paren-

chyma has been proved with the utmost conclusiveness by

the embryological researches of Looss, Young, Balss and

others. The conclusion, based by Blochmann and Hein

upon anatomical evidence, that they form an epithelium

needs, but has not yet received, embryological support;

in fact, not a scintilla of embryological evidence has been

produced either by them or any one else in the thirteen

years which have elapsed since Blochmann’s paper was

published. And purely anatomical evidence in an obscure

matter like this should be received with the greatest cau-

tion, especially since the extreme parasitism of these

No. 516] THE CUTICULA OF CESTODES 725

worms has affected all their organs and tissues in so

marked a degree.

The function of these cells is a much more difficult

matter to determine, and two diametrically opposed

classes of views have been expressed concerning it. Ac-

cording to one of these, they form a specialized tissue

with either a secretory or an absorptive function. Ac-

cording to the other, they are an unspecialized embryonic

tissue, which has no direct physiological relation to the

other structures of the body.

If the almost unanimous decision of all the investiga-

tors who have studied trematodes and cestodes is to be

accepted, the subcuticular cells are glandular or secretory

in function and, as we have seen, the cuticula is the prod-

uct of their secretion. Some years ago (1898) I sug-

gested that they (as well as the single-celled glands)

may secrete, not the cuticula itself, but some substance

which tends to render the cuticula immune to the disin-

tegrating effects of the body-fluids of the host in which

they pass their lives. That the cuticula of endoparasitic

trematodes and of cestodes does possess some special

means of protecting itself and the other tissues of the

worms seems certain. Looss, for instance, has taken Dis-

tomum tereticolle from the stomach of the pike, where

the worm was pressed tightly against the stomach-wall by

large masses of actively digesting food. Something in this

case must have prevented the worm from being digested,

too. This special means of defense is not to be looked

for in the physical structure of the cuticula itself, which is

usually soft and easily injured, but in some chemical sub-

stance which neutralizes the action of the juices of the

host. It is possible that the subcuticular cells secrete

some such substance, especially as the ectoparasitic

trematodes, which are in most cases either not sur-

rounded by the tissues of the host or are only partially so,

do not, as we have seen, possess these cells.

What the reaction of these secretions would be must

depend upon the nature of the fluid in which the worm is

726 THE AMERICAN NATURALIST [Vou. XLIII

immersed. If it lives in the stomach of the host, for in-

stance, the reaction would probably be alkaline and the ac-

tion of the digestive juices would thus be neutralized. In

other locations the reaction would be different and might

be very complex.

A small minority of investigators, however, but im-

portant and influential though small, does not believe in

the glandular function of the subeuticular cells. Rind-

fleisch and Leuckart (1886, p. 366) first expressed the

opinion that, in cestodes at least, they are simply pecul-

iarly formed connective tissue cells which in certain places

may lose their spindle form and assume quite the form of

ordinary parenchyma cells. This is the case, for instance,

as already stated, in the scolex and between the pro-

glottids.

Looss (1893) also regards the subeuticular cells as

connective tissue structures, interpreting them as embry-

onic and unspecialized cells which are destined to develop

into parenchyma and muscle strands as the worm in-

creases in size, and he supports his views with such a

mass of detailed observations and such cogent reasoning

that it is likely they would be generally adopted if the

belief in the secretory nature of the subcuticular cells

were not so firmly fixed in the literature of the times.

Looss shows that the interior cells of the germ-balls of

the cercaria develop into the nervous system, the genital

organs, the intestinal ceca and the parenchyma—all after

the first appearance of the cuticula. But all of these cells

do not at once so develop. The young worm must grow

often many thousandfold before it reaches adult size,

and this increase in size is made possible through the

persistence in an undifferentiated condition of certain of

these interior embryonic cells, which during the life and

growth of the worm are constantly forming new paren-

chyma cells, as well as other structures. The formed

parenchyma cells do not divide. In the cerearian tail,

which is destined to have but a very short existence, all

of these cellular elements become parenchyma cells and

No. 516] THE CUTICULA OF CESTODES 727

muscle strands and no embryonic cells persist; hence no

subeuticular cells are present. f

Originally these indifferent cells lie around all of the

growing organs, especially the genital organs, as well as

near the periphery of the body. But in the course of the

growth of the worm all disappear except those near the

periphery, which become the subcuticular cells and may

remain throughout life, giving rise to new parenchyma

cells, and also to muscle strands and to flame-cells. In

old digenetic trematodes, however, they may also disap-

pear (Lander, Maclaren). Looss compares these cells

to the cambium of plants, which is also an indifferent

tissue which gives rise to certain specialized tissues

throughout the life of the plant.

The only authors who have fully subscribed to this

theory, so far as I know, are Nickerson (1894) and Staf-

ford (1896), who support it by observations drawn from

the study of Sichocotyle and Aspidogaster, respectively,

although Schuberg (1894), Lander (1904), Balss (1908).

Young (1908) and others have declared in favor of the

parenchymatous origin of the subcuticular cells.

That so few have done so is probably due, as I have al-

ready indicated, to the fact that the belief in the glandular

nature of the cells in question is so firmly fixed in the

minds of helminthologists as to have axiomatic force.

But it must never be forgotten, notwithstanding this cir-

cumstance, that this particular function has never been

proven for these cells. No one has yet seen them produce

a secretion and the supposed ducts that are seen in con-

nection with them in some, although by no means in all

species, and the possession of which is perhaps the prin-

cipal proof which has been brought of their glandular

nature, are not ducts at all. In contrast to them we might

indeed place the single-celled glands, whose ducts are al-

ways perfectly plain and whose secretion can be seen. It

must also be remembered that neither Leuckart nor

Looss, each of whom, it will be generally conceded, has

surpassed all contemporary investigators in his knowl-

728 THE AMERICAN NATURALIST [Vou. XLIII

edge of parasitic worms, has attributed a glandular func-

tion to these cells, but, as we have seen, has interpreted

them in quite a different way.

SuMMARY

1. The cuticula of trematodes and cestodes is not

homologous to that of other worms and of arthropods.

2. The euticula of trematodes and cestodes is the per-

ipheral portion of the parenchyma, being composed

mainly of secretions of it.

3. The subeuticula is not an epithelium or a hypo-

dermis, but belongs genetically to the parenchyma.

4. The subeuticular cells are not present in the mono-

genetic trematodes, in most of the Aspidobothride and in

many digenetic trematodes, or in any trematodes or ces-

todes during the earliest larval stages when the cuticula

first forms.

5. The function of these cells is not known, and although

most authors have ascribed a glandular or secretory func-

tion to them it seems likely that they form an indifferent,

embryonic tissue which develops into specialized tissues

as the worm increases in size.

LITERATURE

, H. H. Ueber die Entwicklung der Geschlectsgiinge bei Cestoden nebst

Bemerkungen zur Ectodermfrage. Zeitschr. f. wiss. Zool., Bd. 91, p.

266, 1

piika y Die Epithelfrage bei Cestoden und Trematoden. Hamburg,

1896.

Brandes, G.. Zum feineren Bau der Trematoden. Zeitschr. f. wiss. Zool.,

bes 53, $ 558, 1892.

Bra winbodea: Bronn’s Klassen u. Ordn., Bd. 4, p. 306, 1893.

atas, P Contribution à 1’Etudé des Octoootylidés. Arch, d. Biol.,

T. 16, p. 345, 1899.

Goto, z Studies on the a eg Trematodes of Japan. Jour. Coll.

ci. Imp. Univ. Jap., Vol. 8, pil 4.

Goto, S. Notes on some Exotice Species of jo. Trematodes. Jour.

Coll. Sci. Imp. Univ. Jap., Vol. 12, p. 263 ;

v. Graff, L. Die Turbellarien als Parasiten par Wirte. Festschrift für

1902. Graz, 1903. ;

Lander, C. H. The Anatomy of Hemiurus crenatus (Rud.) Lühe, an ap-

pendiculate Trematode. Bull. Mus. Comp. Zool., Vol. 45, p. 1, 1904.

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Leuckart, R. Die Parasiten des Menschen, ete. 2te Aufl. Leipzig, 1886.

s, A. Ueber Amphistomum subclavatum, Rud. und seine Entwicklung.

Festschrift f. R. Leuckart. Leipzig, p. 147, 1892.

Looss, me Zur iad 2 nach der Natur des Kine a. ete. Verh.

. Ges. Wiss. math.-phys. Cl., Bd. 45, p. 10, 1893.

i "e Die iioi unserer Fische und Frösche. Bibl. Zool., Heft. 16,

ei i

Maclaren, N. Ueber die Haut der Trematoden. Zool. Anz., Bd. 26, p. 516,

1903.

Monticelli, F. S. Cotylogaster michaelis, ete. Leuckart’s Festschrift, p.

8, :

Monticelli, F. S.* Studii sui Trematodi endoparassiti. Zool. Jahrb. Anat.,

3, Suppl., 1893.

Nickerson, W. S. On Stichocotyle nephropis, ete. Zool. Jahrb. Anat., Bd.

5, p. 447; 1894.

Nickerson, W. S. Cotylogaster occidentalis, ete. Zool. Jahrb. Anat., Bd.

15, p. 597, 1902.

Osborn, H. L. On the Habits and Structure of Cotylaspis insignis Leidy.

Zool. Jahrb. Anat., Bd. 21, p. 201, 1904.

Pratt, H. S. A Contribution to the Life-history re Anatomy of the Ap-

pendiculate Distomes. Zool. Jahrb. Anat., Bd. 11, p. 351, 1898.

Roewer, C. F. iträge zur Histogenese von pati He helicis. Jen.

Zeitschr. f. Norcal: Bd. 41, p. 1885, 1906.

Schauinsland, H. Beiträge zur Kenntniss der Embryonalen Entwicklung

der Distomeen. Jen. Zeitschr. f. Naturwiss., Bd. 16, p. 465, 1883.

EPEN e embryonale Entwicklung der Bothriceephalen. Jen.

ee yara Bd. 19, 1886.

ie eee i Zur Histologie der Trematoden. Arb. a. d. Zool.-zoot. Inst.

Wurz., Bd. 10, p. 167, 1894.

Stafford, J. T Structure of Aspidogaster conchicola. Zool. Jahr.

nat.,

Tennent, D. H. $ Study of the Life-history of Bucephalus, ete. Quart.

Jour. Micr. Sci., Vol. 49, p. 635, 1906.

Thomas, A. P. The Life History of the Liver-fluke. Quart. Jour. Mier. Sci.,

Vol. 23, p. 90, 1883.

Young, R. T. The Histogenesis of Cyticereus pisiformis. Zool. Jahrb.

Anat., Bd. 26, p. 183, 1908.

Zeller, E. Untersuchungen rates die Entwicklung und den Bau des Poly-

stoma integerrimum. Zeitschr. f. Wiss, Zool., Bd. 22, p. 1, 1872.

Zernecke, E. Untersuchungen i den feineren Bau der Cestoden. Jena, `

THE AMERICAN TOAD (BUFO LENTIGINOSUS

AMERICANUS, LeCONTE). II

A Strupy ın Dynamic Brotoay

NEWTON MILLER

CLARK UNIVERSITY

HIBERNATION

Lirrie is known about the toad during the winter. An

anonymous article in Cornhill states that toads go down

in the mud by ponds and become encysted in balls of clay.

Allen is of the same opinion. More recently Gage says

he thinks they go into the ground for hibernation and not

under boards, stones, etc., as supposed. Toads were

found under leaves in March, 1895, by Kirkland, who also

states that they ‘‘do not hibernate singly, as a rule and it

is not an uncommon thing to find in winter or spring a

dozen or more closely packed together under a rock,

board or in some other sheltered spot.’? Various indi-

viduals tell me that they have ploughed up toads in the

fields or dug them up in gardens or flower beds in the

spring. There is little doubt that in this latitude they

normally pass the winter in the ground.

Toads bury themselves for the winter or often for the

day in loose earth. To do this they always go down

backwards. With a forward lateral movement of the hind

feet the earth is pushed out and to either side and the

body forced into the hole by the front legs. The loose

earth falls over the head as the toad descends, thereby

filling the burrow. In this way little trace is left to tell

of the whereabouts of the toad.

It is probable that those found under leaves, ete., in

early spring had emerged from winter quarters during a

warm spell and had taken temporary refuge in such places.

: 730

No. 516] THE AMERICAN TOAD 131

Experiment No. I.

An experiment on hibernation was begun October 8

Holes: twenty-eight inches deep were dug in three dif-

ferent localities. Into each hole was placed the four

sides of a 14 x 36 x 36 inch cage made of }-inch-mesh wire

netting. Then the holes and cages were filled to the level

of the ground. Twenty toads were placed in each cage

and a wire covering sewed on, thus making an enclosure

without bottom, filled with soft earth and with a free

space of eight inches between the ground and the top.

Cage A was placed on an exposed north slope of a hill

beneath two pines. The slope at this point was prob-

ably 20°, therefore no water stood in or about the cage.

The ground here is at least two thirds sand and gravel.

Little protection was furnished by the pines, since their

lowest branches were twelve to fifteen feet above the

ground.

Cage B was located in a dry, well-sheltered place under

the drooping branches of some spruces on a hill-side fac-

ing the east. So well was it protected that the sun never

reached it and very little rain or snow. ‘The sagen at

this point is a sandy clay.

Cage C was sunk under a maple tree in a place not

more than four feet above the water in a near-by pond.

No protection was furnished by the maple. Ashes, sand

and loam in about equal parts composed the soil at this

place. |

The toads for this experiment were collected from the

fourth to eighth of October. Each was weighed and

marked by cutting off a toe. Those in A were put out

the eighth of October and those in B and C the following

day. One to several toads were found out of the earth

in one or all the cages until November 26 with the ex-

ception of the twenty-ninth of October. My notes show

a very slight tendency for those in cage A to hibernate

before those of B and C.

After the twenty-sixth of November nothing was seen

732 THE AMERICAN NATURALIST ([Vouw. XLIII

of the toads until the twenty-eighth of March, when A

was dug up, and eleven days later cage C. Fourteen

were found in A, of which only three were alive. The

depths at which they were found varied from one to

twenty-four and a half inches. All above sixteen inches

(the depth to which the ground was frozen) were dead.

In C thirteen were found, of which nine were alive.

There had been a trench dug near one end of the cage

in the fall and the earth in this end was frozen to a depth

of twelve inches. Two toads near the surface and two

in the frozen end, one at a depth of twelve inches, were

dead. Those alive were down below the frost line, which

in this place was between eight and nine inches.

The accompanying table shows the weight of each

live toad at the time it was put out and when dug up,

also the depth at which it was found.

CAGE C

No. of Each Toad, | Weight, October 9. | Weight, April a s Depth in Inches.

1 | 50.5 | 44.0 15

3 | 19.5 | 15.0 94

4 24.0 | 18.8 124

5 27.0 | 25.6 143

7 32.5 26.6 20

S | 27.0 | 23.9 10

10 | 24.5 | 21.2 163

12 5.5 4.6 11

o N | Be y 15.8 15

CAGE A

No.of Each Toad. | Weight, October9. | Weight, March 29. | Depth in Inches.

10 16.5 | 12.9 173

13 | 9.5 | 7.0 174

AE 20.5 bake ie ee

Average loss of weight 3.8 grams.

The total loss of weight was 15.3 per cent. of total weight.

B was not disturbed, and the first toad to appear was

no. 1 on the thirtieth of April, and the second and last

was no. 7 on the twenty-eighth of May.

No. 516] THE AMERICAN TOAD 733

Experiment II

Another experiment was made on two toads which

were placed in a 7x 7x7 inch wooden box that contained

some four inches of rather dry clay. A stone was laid

on top and the box sunk ten inches in the side of a bank

composed of clay and gravel. On the first of March,

when the box was dug up, the ground all about it was

frozen so hard that it had to be dug out with a pick. The

earth in the box had been moist enough to freeze into

clods, which were easily broken with the fingers. Both

toads were alive, but no. 2 died two days later without

showing any other signs of life than the beating of its

heart. No. 1 moved her legs feebly as soon as broken out

of the clay, had her eyes open in less than five minutes

and within ten minutes more she was crawling about on

the snow. Only the tips of some of her toes seemed to

be frozen, but these never became sore. No. 2, as far as

I could detect, was not frozen more than no. 1. No. 1

began feeding on the second day and during the re-

mainder of the winter showed no signs of hibernating.

Experiment No. III

For this experiment a 12 x 12 x 24 inch glass aquarium

was used in which was placed about three inches of moist

earth. Six toads properly labeled were put in the cage,

which was kept within eight inches of my radiator. As I

was in my room most of the day and slept there at night

I could watch them closely. I had a supply of meal

worms, and every time a toad appeared it was given all

it would eat. They came up usually about 8:30 P.M. and

buried themselves by 10:00 p.m. Frequently they shed

their skins and went down at once. No. 4 had the habit

of only half burying herself and, probably, one fourth

of the time was spent thus, but during this time she was

rarely found sleeping.

The weight and sex of each toad was as follows:

734 THE AMERICAN NATURALIST [Vow. XLIII

Os i es Be aes 8.8 grams

We Re Soaks oes cee URS EU RS eed vee» 27.8 grams

EES AAR”, earner Meru er emg mea ie or ere er war rear a 22.2 grams

Re es oe wh ees aes kee kt ca seve es 76.5 grams

Oe Oe a Ck ee eee py Pee wesley 6.5 grams

PO Or eis sre T EE A vee Sree Hee os 39.0 grams

These toads were under daily observation from Oc-

tober 23 to April 1, excepting five days from December

26 to 30. Fig. 7 is given as an average month’s record

Toao No.

p | BRNENIA 2A

: pe | ) I

í j | Pris oh

| | ESS

Po ee ] TESTER, 8

7 | | ETES

| + | Hit CBRL D

Nov. 25 "0 geet ‘ Me ts 15 20 25

Fic. 7. Record of six toads for one month.

of this experiment. The continuous lines represent the

time the toads spent under the earth; the breaks, the

number of times the toads came up out of the earth; the

figures in the breaks, the number of meal worms eaten

at such times.

Experiment No. IV

This experiment was also carried on in my room,

from the twenty-third of October until the eighth of April.

During this time a female, weighing forty-eight grams,

was kept in a small bell jar which contained, besides the

toad, only a small thin piece of sponge. The sponge was

kept moist and a piece of glass over the top of the jar

prevented too rapid evaporation.

When the toad was placed in the jar she was cold, numb

and to all appearances hibernating, but five hours after

being brought into a warm room she was wide awake,

and from then on to the end of the experiment was never

seen with her eyes closed nor showing the least signs of

hibernation. She fed throughout the winter, eating in

all, the small number of 173 meal worms or their equiva-

"At the end of the experiment nos. 2, 5, 6 had increased their weight,

respectively 7.4, 4 and 0.49 grams.

No. 516] THE AMERICAN TOAD 735

lent, but at no time did she go longer than nine days

without feeding. Eight worms were the most she ever

ate at one time, while one to three constituted her usual

meal. She refused food during the day and fed only

from 7 to 10 p.m.

Experiment No. V

This experiment is a duplicate of no. IV. with the

exception that two small toads (about 8 grams) were

used. The experiment began on the twenty-third of

October and continued until the death of the toads,

which, for the male, occurred December 15 and for the

female, February 10. The female fed throughout this

time with the exception of two periods, November 7-17

and December 18—-February 10. During these two in-

tervals she at times appeared to be hibernating or simply

sleeping. It was almost a month before the male began

feeding, but afterwards fed until he died. At no period

did he show any tendency to hibernate. The male es-

caped from the cage and was found dried up. The female

refused food from December 18 to February 10, became

emaciated and died as though starved.

Conclusions

From experiment no. I, it is seen that toads go down

into the ground to hibernate and that all of those not

below the frost line in unsheltered places, perish.

Experiment no. II shows that toads in protected places

can resist freezing temperature.

It is a question whether toads make any preparation

at all for the winter more than simply burying deeper

than they are accustomed to do in the summer. Experi-

ment no. I shows that some had not hibernated as late

as November 26. Toads are active until it becomes too

cold for them to capture insects; as a cold wave comes,

the toads for the first time begin to prepare for winter

by digging a little deeper. As the ground gets colder,

736 THE AMERICAN NATURALIST [Vou. XLIII

they go further down, keeping a little below the frost

line. I have found no evidence that toads select places

in the fall and then proceed to bury themselves at once

to a depth of eighteen to twenty-four inches.

Toads kept in a warm room do not have periods of

torpidity. Boulenger says that batrachians never go

into complete lethargy. The one in experiment no. IV

was never asleep and those in experiment no. III were

always wide awake and active when dug up. None of

them became sluggish. The female of experiment V

was, at times, during two periods seen with her eyes

closed, but at these times she was easily awakened by a

slight touch or a jar of the cage. At no time did she

appear to be more than napping. All of the toads kept

in my room fed throughout the winter, although eating

only a small quantity. The period of least activity was

from January 19 to February 19, when only one fed.

. Three of these toads fed eagerly during April, May and

~ June.

There is no evidence that toads seal up their eyes,

mouth and nostrils as a preparation for hibernation.

Winter to the toad is only a long day, a suspension of

work, a sleep. He is ready to begin his daily routine

as soon as warmed up even in midwinter.

ENEMIES OF THE ToapD

When we consider the number of eggs laid and find

that the number of toads does not increase, we are led

to ask the question, What are the forces that keep the

species in check? If we take the low figure of eight

thousand eggs for an average spawn, then all of these—

as well as all the eggs of the other spawns of a single

female—or the toads that develop from them, except two,

must meet a premature death in order that the species

may just hold its own. This seems to be what is taking

place with the toad.

What happens to this multiple of eight thousand eggs

is partially known. There is no period from the laying

No. 516] THE AMERICAN TOAD tet

of the egg until death by old age that the egg, larva or

toad is not subject to attack. I have found little evidence

of the eggs being eaten in the ponds. Crayfish confined

in the laboratory ate a few. Saprolegnnia destroy a small

per cent. of the eggs, not by attacking the fertile ones

directly, but by spreading from those that are decaying.

The gelatinous sheath which envelops the delicate eggs

is almost a perfect protection, but, as soon as the tadpoles

wriggle out of it, they are preyed upon by fish, newts,

crayfish, insects, and especially the predaceous aquatic

larve of insects.

I give the results of my feeding tests to show how de-

structive some of the enemies of the tadpoles are.

i 7 No. | ‘Rate

S |

pecies, | No. Time. Kill led. | per Day.

Dr EPa ny TE Libellula s sp.? | Máy 24-Jun une 24. | | 500) 4

Dragonfly nymph, Ju 1-June 37| 4

Water beetle, Rollie June 21-Jun 40|) 4

e3 0)

May 9-June 23. | 4,800 |

Giant w. beetle, Diea ja | 26.

June 13-June 33. | 425 | 42.

Water tiger, rae s larva

Giant w. bug, stome americanum.

ewts, Distiiolas we

Crayfish, Cambarus barton

Leopard frog larva, Rana

Pickerel, Esox sp.? (four inches long).

Se Re RS Ep

July 9-July 14. 66 Le g

June 22-June 24.; 80) 26.

The above tests, with the exception of nos. 2 and 9,

were made with tadpoles which were hatched from eggs

laid about April 28. Since the transformation of the

larve of this early laying began the twenty-second of

June, it is seen that a portion of these tests were made

with tadpoles almost ready to abandon the water. Those

for no. 9 hatched on the twenty-fifth of June. No. 2

was fed for the first five days on tadpoles of the early

spawn and the rest of the time on those hatched June

25. Only one tadpole a day was destroyed by this nymph

during the first five days.

In treating the above data it must be taken into con-

sideration that these tests were made in the laboratory

and that tadpoles constituted the whole of the food of

these animals during the tests. This is a very abnormal

condition compared with that found in nature.

738 THE AMERICAN NATURALIST [Vou. XLIII

Two toads just metamorphosed were found in the

stomach of a green frog about a week old. Mr. E. H.

Eaton tells me of finding a toad an inch long in the

stomach of a leopard frog. Adult toads could not be in-

duced to eat the young. They would take them up, but

immediately reject them.

The drying up of ponds during May and June kills

great numbers of the tadpoles. More than 90 per cent.

of the spawn is laid in the early spring when the ponds

are full. The tadpoles migrate to the shallower water,

where they find food and warmth. Here they crowd

into small pockets, and as the water lowers are left in

the isolated puddles to perish, unless timely rains refill

the pond. The ‘‘drying-up process” is disastrous not

only to the larve, but also to the toads. Great num-

bers just emerged are no doubt dried up before they

find damp sheltered retreats. Adults also soon perish

if deprived of moist places. I give the following to

show the rapidity with which transpiration and absorp-

tion of water may take place in toads. A toad weighing

4.4 grams when placed in water, weighed 5.5 grams fifty-

five minutes later. One hour later, after having been

kept at a temperature of 85° F. in a box made of blotting

paper, it weighed 4.8 grams. Another toad treated as

above weighed 3.8, 4.5 and 3.8 grams, respectively. A

third weighed 39.8 grams when placed in one fourth inch

of water and 49.9 grams three hours later. This is a

gain of 25 per cent of her first weight. This toad was

capable of reducing her weight 8.7 grams by ejecting

water. From these experiments it is seen how im-

3 moisture is to the toad and why toads seek damp

places.

Birds play no small rôle in the destruction of the toad.

Of the domestic varieties ducks, chickens and guinea

fowls are always mentioned and to these Kirkland adds

geese as feeding on toads, especially

just as

they acs emerging: the young jus

No. 516] THE AMERICAN TOAD 739

‘Crows, grackles and several species of ducks and

herons,’’ writes A. K. Fisher, of the Biological Survey,

‘Care known to feed on small frogs and tadpoles, and un-

doubtedly do not discriminate in favor of toads.” He

presents further evidence to prove that the screech owl

must be considered as a destroyer of toads. By stomach

examinations of a‘number of crows, W. B. Burrows finds

that the toad is a common article of food. Young par-

tridges were tested on this point. They eagerly picked up

the little toads, thereby killing them, but usually refused —

to eat them. Miss M. Morse reports the quail as feeding

on young toads. As for predatory birds, the toad is an

agreeable morsel of food. Mr. Fisher writes me that

he has observed the broad-winged hawk feeding on toads

while the latter were spawning. He also found ‘‘ five

stomachs of the red-tailed hawk, eight of the red-shoul-

dered hawk, and five of the broad-winged hawk which

contained the remains of toads.’’ From the observations

of Mr. F. H. Mosher, he states that ‘‘the marsh hawk is

one of the worst enemies of the toad, destroying large

numbers of them during the spawning season.’’ He

also states on the same authority that a toad was found

in the nest of a Cooper’s hawk.

Skunks and raccoons are the only mammals reported

as feeding upon toads. Mr. E. H. Short writes that in

his locality skunks destroy great numbers in the late fall,

and that he found in October, 1904, the remains of seven

toads which had been killed in one night (by a skunk?).

His evidence on this point does not seem conclusive.

Concerning raccoons, Dr. H. B. Davis occasionally feeds

toads to those he has in confinement.

Professor Surface records twenty-seven species and

varieties of serpents from Pennsylvania, of which ten

feed on toads, and two others are suspected. The feed-

ing habits of some of these have not yet been deter-

mined and it may be found that part of them use the

toad as food. Toads constitute 414, 20, 16 and 15 per

cent. of the food, respectively, of the spreading adder

740 THE AMERICAN NATURALIST [Vou. XLIII

(H. platirhinas), the striped water snake (R. leberis),

the common garter snake (T. sirtalis), and the spotted

water snake (N. sipedon). The common garter snake

and the spotted water snake are reported also as feeding

on tadpoles.

Some of the game fish feed upon frogs and, pre-

sumably, they take toads also. Perhaps many toads are

thus destroyed during the spawning season. We have

reason to think that fishes feeding on insects and small

fish devour tadpoles also. In pond no. 4 eggs were laid

by the thousands and a large per cent. of them hatched,

but not a single toad emerged. By the twenty-fourth of

May not more than 200 tadpoles of the first laying re-

mained and a few days later not one was to be found.

There are fishes and ecrayfishes in this pond and the

probabilities are that they destroyed the tadpoles.

Boys are very destructive to toads in the spawning

season. This spring no less than one hundred and ten

toads were killed about ponds nos. 1, 3 and 4. In 1897

Dr. Hodge records as one day’s count two hundred dead

about pond no. 4, and also that two boys had killed and

carried away 300 from the same pond the day before.

Judging from my experiments, many toads die during

the winter. As stated in the chapter on hibernation,

sixty toads varying in size from 2 to 55 grams were put

out in cages in the fall. Neglecting those under five

grams (which I have reason to think escaped before cold

weather) there were left fifty-one, of which only fourteen

came out alive in the spring. This is a loss of 72.5 per

cent., which surely must be above normal. However,

further experiments and observations lead me to think

that toads are killed if completely frozen. January 30,

I permitted a toad 6.5 em. long to bury itself in a cage

containing a mixture of moist clay and loam. The cage

was then subjected to a temperature of — 10° F. for

twenty-four hours. At the end of this time the toad

was frozen solid, and when thawed out showed no signs

of life.

No. 516] THE AMERICAN TOAD 741

Another experiment, begun December 28, temperature

54° F., was made on five toads ranging between 3 and

7.5 em. in length. These toads were put in a wire cage

filled with leaves and then buried in leaves, which had

drifted into an angle of a building. March 13, the cage

was examined and all the toads found dead. These toads

during this time had been subjected to several days of

0° F., weather.

On March 28 I examined a drift of leaves. Two dead

toads were discovered half buried in the ground beneath

leaves. There were about eight inches of leaves over

them.

Contrary to these observations are those Kirkland,

which might lead one to infer that toads can pass the

winter successfully under leaves in this region. But as

Mr. Kirkland’s observations were made in March, and

as toads in favorable springs emerge from their winter

quarters in this month, we are inclined to believe that

those he found under leaves had previously come out of

hibernation and had taken temporary refuge where he

found them.

The sewers of a town constitute a most destructive trap

for toads. Sewer cleaners tell me that they take out

‘piles of toads’’ especially in the fall and spring. Exam-

ination of the ‘‘man holes’’ in May shows that there are

on an average four toads in each one. At this rate, for

Worcester alone, there are no less than 24,000 toads thus

caught, which probably means their death also. It is mak-

ing a low estimate to say that 50,000 toads perish annually

in the sewers of Worcester. Itis very probable that more

adult toads in a city are killed by this means, alone, than

by all others combined.

I give the following table as a rough estimate of the part

that each known factor plays in holding the species in

check.

Percentage of destruction until time of metamorphosis

caused by:

742 THE AMERICAN NATURALIST [Vot. XLIII

Non-fertile ogn seers wus Bee cde evel Sense ae te ses 15 per cent.

Drying Up Of ponda. foc ccc cece certs see ieee ces 25 per cent.

RRM, BOWER; DER, CG ee ee hice eines renyah re 39 per cent.

PUREE a ee Ves cisea Cue deyeeN et eeu Roe est eee s 1 per cent.

T ee ee Ey or bee pa ae 6 aes eee ar ees 5 per cent.

ONE ia a Bae ces ree Nia ea oo E va eS 85 per cent.

The remaining 15 per cent. may meet the following fate:

DEINE WD os seepia iai peewee 20 per cent. = 3 per 100 eggs.

Domestic fowls and other birds ... 10 per cent. = 1.5 per 100 eggs.

TI bak E ee anes nba 6 per cent. = .9 per 100 eggs.

Bort io foo ee cs a ee as 2percent.—= .3 per 100 eggs.

Sewers, wells, ete. ..... es Mone Sy is 15 per cent. = 2.25 per 100 eggs.

Mechanical means ............... 10 per cent. = 1.5 per 100 eggs.

i eye wi E yee 25 per cent. = 3.75 per 100 eggs.

PROGRES evn toy we Reeders 3 per cent. = .45 per 100 eggs.

Miscellaneous (including old age) .. 9 per cent. = 1.25 per 100 eggs.

SUMMARY

B. l. americanus spawns from the latter part of April to

the first of July.

This species lays in small ponds and only a portion of

each is used as a spawning ground.

The males are the first to reach the water in the spring.

88.8 per cent. of all the toads in a pond at any given

time are males. Males are in proportion to females as

80.7 : 100.

Trilling in the full vigorous voice is heard only during

the mating season.

Females respond to the call of the males.

Males will not hold other males.

Spawn may be deposited at a depth of eighteen inches

ormore. This depth does not affect materially the hatch-

ing.

Fertilization takes place in an improvised basket formed

by the hind feet of the male and the body and hind legs of

the female.

85 per cent. of the eggs laid in natural ponds are fertile.

viposition requires six to eighteen hours.

The laying of two or four strands of eggs at a time can

not be considered of specific importance.

No. 516] THE AMERICAN TOAD 743

Toads lay 3,900 to 15,800 eggs at one laying.

The eggs hatch in two to six days, depending upon the

temperature.

Metamorphosis takes place in thirty-two to two hundred

days.

On an average the tadpoles double their weight seven

times in thirty-two days.

The tadpoles are omnivorous.

Toads feed entirely on animal matter. No food is

taken unless it shows signs of life.

Toads refuse no insects, worms or slugs which they can

swallow.

On an average toads feed only once in a day and a half.

The average amount eaten in a day by a toad is 1.12

rams.

About 80 per cent. of the toad’s food consists of harm-

ful insects.

Toads may be active from the latter part of March to

the middle of November.

Toads are chiefly nocturnal.

Toads go into the ground to pass the winter.

The greater per cent. of those that do not get below the

frost-line perish.

In the strictest sense of the term, toads do not hibernate

if kept in a warm place.

Toads feed throughout the winter if kept warm, al-

though eating comparatively little.

No preparation is made for the winter other than bury-

ing to a depth below the frost line.

Some toads do not hibernate until after the middle of

November.

The eggs are seldom eaten by other animals.

Great numbers of tadpoles are destroyed by insects and

insect larve.

Birds, fishes and reptiles feed upon tadpoles.

A large per cent. of the eggs and larve are killed by the

lowering of the water.

Toads are destroyed, chiefly, by all classes of verte-

744

THE AMERICAN NATURALIST [Von XLII

brates; by drouth and winter, and by the sewer systems

of towns.

1876.

1899.

LITERATURE

American Encyclopedia, Vol. XV, pp. 7

Allen, G. M. Notes on the Reptiles and Batrachians of Intervale,

New Hampshire. Proc. Bost. Soc. Nat. Hist., Vol. XXIX, pp.

63-75.

Allen, J. A. Catalogue of the ae ger Batrachians of Massa-

chusetts. Proc. Bost. Soc. Nat. His PA

Assheton, R. Notes on the Ciliation 4 beicaapa of Amphibian

Embryo. Vol. XXXVIII, p. 465.

Beddard, F. E. Animal Coloration. London, p. 159.

Bos, J. R. Amphibia, oe Zoology, pp.

eter td G. A. The s Batrachians of Parone, Vol. I, pp:

23-67; Vol. II, pp. eya

Boudlen get, G. A. Poisonous Seecretions of Batrachians. Nat. Sci.,

I, pp. 18

Brimle = C. B. Batenchians poe at Raleigh, North Carolina.

ER. NAT., Vol. XXX, p.

Briti, P. Crapud. Traité Pe Zool logie Agricole, pp. 240-242.

Buckland, W. On the Vitality of Toads Enclosed in Stone and

Wood. Amer. Jour. Sci., Vol. XXIII, pp. 272-277.

Conradi, A. F. Toads Killed by Squash Bugs. Science, Vol. XIV,

p- S

Cope, E. D. Batrachians of the Permian Period of North America.

AMER. NAT., Vol. XVIII, pp. 26-29.

Cope, E. The fi me Distribution of Batrachians and

Repül 3 in North America. AMER. Nat., XXX, pp. 886-902 and

1003-1026.

Cope, E. D. Batrachians of North America. Bull. U. S. Nat. Mus.,

No. XXXIV, pp. 277-281.

Courtis, D. A. Response of Toads to Sound Stimuli. AMER. NAT.,

Vol. XLI, pp. 677-682.

de Fischer, J. Rôle des Amphibians en Agricultur

Dickerson, M. Bufo lentiginosus americanus. The Frog Book,

pp. 63-88.

Ditmars, R. L. eE of the hipp of New York City.

Amer. Mus. Jour., Vol. IV, pp. 186—

Gage, S. H. The Life History of the a College of Agriculture,

Cornell University.

Gage, S. H. porsier Transformation and Growth of the Com-

mon Toad (B. l. americanus). Proc. Amer. Ass. Adv. Sci.,

XLVII, pp. 374-37

Garman, H. The Food of the Toad. Ky. Agri. Exper. Station Bull.,

No. 91, pp. 62-68.

Garman, H. Synopsis of the Reptiles and Amphibians of Illinois.

Bull. Ill. State Lab. Nat. Hist., III, pp. 335-339.

Hartman, F. A. Food Habits of ‘Pinus Lizards and Batrachians.

Tr. Kansas Acad. Sci., XX, pt. 2.

No. 516] THE AMERICAN TOAD 745

1903.

1882.

1898.

1875.

1907.

1901.

1907.

1904.

1882.

1904.

1871.

1888.

1901.

1905.

1900.

1906.

1863.

1882.

Hay, W. P. On Batrachians and Reptiles. Forest and Stream, LX,

pp. 425-6.

Hinckley, M. H. Mouth Structures of Tadpoles of Anurous Ba-

trachian. Proc. Bost. Soc. Nat. Hist., XXI, pp. 307-314

Hodge, C. F. The Common Toad. Nature Study Leaflet, Wort,

Mas

Huxley, a, H. Amphibia. Encyclopedia Britannica, 9th ed., I, pp.

750-771

Kellicott, W. E. Correlation and Variation in B. l. americanus.

Jour. Exper. Zool., IV, No. 4.

King, H. D. The Maturation and Fertilization of the Egg of B.

lentiginosus. Jour. Morph. I, pp. 293-330.

King, H. D. Food as a Pastir in the Determination of Sex in

Amphibians. Bio. Bull. of Marine Bio. Lab., XIII, No. 1, pp.

40-56.

Kirkland, A. H. The Habits, Food and Economie Value of the

American Toad. Mass. Agri. College Bull., No. 40.

Legrips, M. V. Vitality of Toads. aculedge. I, p. 202. (This is

probably Buckland’s experiment and misquoted, as the same

experiments are given with the same result. See ‘‘Cosmos.’’)

spiel M. Batrachians and Reptiles of Ohio. Bull. Ohio State

, Series 8, No. 18, pp. 96-123.

cas F. W. Some Statements concerning the Frogs and Toads

Pound at Cambridge, Mass. Proc. Bost. Soc. Nat. Hist., IX, pp.

229-230.

Ryder, J. A.. ‘Ventral Suckers’’ or Sucking ‘‘Disks’’ of Tad-

poles of different Genera of Frogs and Toads. Amer. NAT.,

, p. 263

Sharp, D. L. Wild Life near Home, p. 313.

Short, E. H. Editorials (on Skunks). aut XXII, pp. 132-135.

and 188-

Slonaker, J. R. Some Observations on the Daily Habits of the Toad

(B. lentiginosus). Ind. Acad. Sci., pp. 167-170.

Stone, W. Amphibians and Reptiles of New Jersey, Pennsylvania

and Delaware. AMER. NAT., oig pp. 159-170.

Verrill, A. E. Catalogue of Reptiles and Batrachians found in n the

Vicinity of Norway, Maine. Proc. Bost. Soc. Nat. Hist., IX, pp.

195-199

Yarrow, H. C. North American Reptiles and Batrachians. Bull.

24, U. S. Nat. Mus., pp. 166-167.

Tee eee

OBSERVATIONS ON COPULATION AMONG

CRAWFISHES WITH SPECIAL REFER-

ENCE TO SEX RECOGNITION

DR. A. S. PEARSE

UNIVERSITY OF MICHIGAN*

Duriye the past winter the writer kept about three

hundred crawfishes in aquaria for a couple of months and

had opportunity to observe their copulating reactions

from time to time. As the published statements in regard

to sex recognition in the genus Cambarus are somewhat

meager, the results of some of these observations may be

of interest. The species represented in the aquaria were,

Cambarus blandingi acutus Girard, C. diogenes Girard

and C. virilis Hagen. Most of the observations here re-

corded were made upon the last-named species, but noth-

ing was observed in the behavior of the others to make it

appear that there was any essential difference in the

mating reactions of these forms.

Andrews! was the first to give a caret account of

copulation in the genus Cambarus. He discovered that

while the male holds the female on her back beneath him

a spermatophore is transferred from his abdominal ap-

pendages to the cavity within the annulus ventralis of the

female, where it remains sealed up until the eggs are laid.

Andrews gives an excellent account of the details of the

process but refers only indirectly to sex recognition. He

remarks (p. 868):

When a male is put into a vessel with a female he seems ere long to

become aware of the presence of the female and does not act. as he does

when only males are present. The female generally retreats and may

* Contributions from the Zoological Laboratory of the University of

Michigan.

Andrews, E. A., ‘‘ Conjugation in an American Crayfish,’’? AMER.

Nar., Vol. 29, 1895, Wo. 345, pp. 867-873.

746

No. 516] COPULATION AMONG CRAWFISHES TAT

even resist the attacks of the male, but generally this is not done with

much vigor, and very soon after being seized by the male the female

passes into a state of passivity, resembling death.

Hay? in a recent paper makes statements which give a

somewhat different aspect to the matter. In speaking of

an hermaphrodite crawfish he says (p. 228)

It might be added that during the time the specimen was kept alive

it was seen in conjugation with a female of the same species and a

little later was itself seized and held for a short time in the usual

manner by a male. The latter, however, is a matter of little importance,

as I have several times observed the same thing in the case of two

males neither of which was hermaphrodite.

An adult male of the genus Cambarus is easily dis-

tinguished from a female of the same species by his larger

chelæ and narrower abdomen, and the sex of any indi-

vidual can of course be accurately determined by examin-

ing the first two pairs of abdominal appendages. Whether

such differences are as readily discriminated by the sen-

sory receptors of a crawfish as they are by the human

eye is perhaps open to question. According to the quota-

tion from Andrews it would appear that a male is able to

recognize a female as such, but the statements of Hay

might be interpreted in such a way as to lead to the

opposite conclusion.

A series of five experiments was carried out to test the

ability of male crawfish to discriminate members of the

opposite sex. In the different experiments from two to

seven males were separated from females which they had

been holding and put together in a flat circular dish

(which measured thirty centimeters in diameter and con-

tained clean water to a depth of about five centimeters).

After such treatment the crawfishes were active for a

time and moved restlessly about the dish. During this

period of activity one male often tried persistently to

copulate with another male, but such attempts were

always resisted, and, although individuals were turned

ay, W. P., ‘‘ Instances of Hermaphroditism in Crayfishes,’’ Smith-

onian Mise. Coll., Vol. 48, 1905, Pt. 2, No. 1593, pp. 222-228.

748 THE AMERICAN NATURALIST [Vou. XLIII

over in some cases, they always eventually succeeded in

freeing themselves. After these males had been allowed

to ‘* fight ’’ thus among themselves for from half an hour

to two hours (the time varied in different experiments)

they became comparatively quiet and finally came to rest

in a group at one side of the dish in such a way that their

bodies were in contact with each other. After they had

remained in this condition of rest for at least half an

hour a female which had just been released from copula-

tion with a different male was gently introduced into the

dish with them.

Tn all five of the experiments the female moved about

the dish and came in contact with one or more of the

males, and sometimes she even walked over them, but

nevertheless there were only two attempts at copulation

within half an hour after a female had been placed in the

dish. In one of these cases a male attempted to grasp

another male after the female had been introduced, but

he soon desisted from the attempt and all the individuals

in the dish then became quiet again. In the other instance

one of the (two) males attempted to turn over the female

as soon as she came in contact with him (not as soon as

she was introduced into the dish). These experiments

showed that males which had recently been in active copu-

lation were not necessarily induced to copulate again by

the immediate presence of an active female.

Five other experiments were performed which were

similar to those just described except for the fact that

the female was introduced into the dish with the males

before they had come to rest. In this second series copu-

lation took place within half an hour in every case. The

results make it appear that the readiness with which copu-

lation is undertaken by a pair of crawfishes depends upon

the physiological state of the male, for, as Andrews has

stated, the male usually takes the active part in the ma-

ting reactions, while the female remains passive.

Another series of observations showed that the readi-

ness with which copulation takes place depends largely

No. 516] COPULATION AMONG CRAWFISHES 749

upon the ‘‘ chance ’’ coming in contact of two individuals

which are in proper physiological state. On five differ-

ent occasions when the aquarium, which contained two

hundred crawfishes, was visited and no pairs were found

to be copulating or attempting to do so, all the individuals

were dragged into the center of the aquarium and heaped

together in a pile. They were then allowed to remain

undisturbed for half an hour. During this time there was

an active scramble and many individuals necessarily came

in contact with each other. In all the experiments from

three to five pairs were found to be in copulation at the

end of the half hour. These observations showed that

individuals had been present in the aquarium which were

in the proper physiological state for copulation, for as

soon as they came in contact with each other the usual

mating reaction took place.

There are many factors which might possibly exert an

influence on the copulatory reflexes of a crawfish and it

is easily conceivable that such stimuli as temperature,

light and chemical substances might be of importance in

this connection. In regard to temperature Bell? has ob-

served (p. 625) that, after a number of individuals had

been warmed,

The males showed marked sexual activity, rushing up to the females,

pushing them about, seizing them and trying to turn them over in spite

of their vigorous resistance. One of the males did succeed in turning

a female on her back twice, although she struggled violently to eseape—

a thing which a female never does in the ordinary sexual act.

He concluded that, ‘‘ the rise of temperature seemed to

stimulate the males to sexual activity but not the fe-

males.’’ During the present experiments it was observed

that there were fewer cases of copulation when the tem-

perature of the water in the general aquarium was below

11° C. than when the temperature was above that point.

Apparently temperature is of some importance as exert-

ing an inhibitory or excitatory action on the copulatory

impulse.

3 Bell, J. C., ‘* Reactions of the Crayfish,’?’ Harvard Psychol. Ser., Vol.

2, 1906, pp. 615-644.

750 THE AMERICAN NATURALIST [Vou. XLIII

Chidester! has recently shown that the general activity

of crawfishes is greater at night and it would therefore

seem probable that copulation would be more likely to

take place in the dark than in the light. In order to ascer-

tain if this supposition was correct, two oblong dishes

were placed side by side in front of a window and were

filled to a depth of five centimeters with water which was

of the same temperature in the two dishes (11° to 14° C.

in different experiments). One of the dishes was allowed

to remain exposed to strong light, but not to the direct

rays of the sun, and the other was completely enclosed in

a tight wooden box which was painted black on the inside

and covered by a movable lid. In each experiment two

pairs of crawfishes which had been copulating or attempt-

ing to do so were isolated and a separate male and female

placed together in each dish, after which their behavior

was noted at short intervals of time. In order to elimi-

nate the effects due to the individuality of any particular

crawfish, the individuals. of each quartette were changed

about as much as possible in successive trials. After the

first copulation, the male was changed from the dark dish

to the one in the light, and the male which had been in the

light took his place; after the next trial the pairs were

interchanged, and finally the two females were changed

about. By this method of procedure there was an oppor-

tunity to compare the rapidity of copulation in the light

and in the dark. The results of the experiments are

given in Table I.

TABLE I.

Showing the results of seven experiments to ascertain whether certain

crawfishes would copulate more quickly in dark or in light. (L indicates

that the pair in the light copulated first; D, the pair in dark copulated

first; E, both pairs copulated at the same time.)

_ Experiment, lci 2 | 38 biel Sea ae

Trial 1 [LID SPE rh pee

Trial 2 3 3 interchanged DL BoD det oe te

Trial 3 Pairs interchanged | LILIDIDIDI DID

Trial 4 QQ interchanged | L|E|L|D!|4L| DD

*Chidester, F. E., ‘* Notes on the Daily Life and Food of Cambarus

bartonius bartoni,’? Amer. NAT., Vol. 42, 1908, No. 503, pp. 710-71

No. 516] COPULATION AMONG CRAWFISHES 751

In twelve of the trials copulation took place first in the

light; in fourteen cases the pair in the dark copulated

first, and in the other two instances the two pairs occupied

the same period of time in becoming united. Twenty-

eight different individuals were given twenty-eight op-

portunities to copulate and approximately an equal num-

ber of ‘‘ first °?’ copulations took place in the light and

the dark. From these experiments it appears that condi-

tions of light stimulation are apparently of little conse-

quence, at least where individuals which are in a state of

excitement are concerned.

Attempts were made to arouse males to a state of activ-

ity by adding extracts to the surrounding medium. The

males were separated from their mates and allowed to

become quiet in a dish of clean water. Various portions

of females which had been recently copulating were then

added, and although pieces of ovary, pieces of abdomen

and extracts from these organs and from the whole body

were used in this way, nothing but negative results were

obtained. The males remained quiet and exhibited no

signs of excitement within half an hour after the portions

of the female’s body had been added. From these results

it does not seem probable that copulation is brought

about by the action of any secretion given off by the

female which might serve to excite the male.

The results of all the experiments described indicate

that sexual union is more or less a matter of chance. Ifa

male and a female which are in the proper physiological

condition come together they will copulate with equal

readiness in the light or dark. Neither sex can be said to

be wholly responsible for the act of sexual union and

although the male usually assumes the active part, it is

_ not an invariable rule. An instance was observed in

which one female fought almost continuously with another

for over two hours. When this pugnacious individual

was placed in a dish with several males she walked about

actively and grasped them with her chele, but as soon as

one of them grasped her and attempted to turn her over,

TOR THE AMERICAN NATURALIST [Vor. XLIII

she became quiet and was soon in copulation. If we ex-

amine Table I it will be seen that in experiments 1 and 6

the same male copulated first in four of the trials, but in

experiments 2, 4 and 5 the male which copulated first in

trial 1 was equalled or excelled by the rival male in the

three succeeding tests. No female copulated first in all

four trials.

In all the observations cited no evidence was seen which

would go to show any power of sex descrimination in the

erawfish. During the mating season the instinct of the

male is to grasp and turn over every crawfish which

comes in his way. The method is one of trial and the

result of such random movements depends largely upon

the reactions of the individual with which copulation is

attempted. If this individual is a female of the same

species the attempt may meet with success but if it is a

male or a female of another species the effort at sexual

union is usually of short duration. The lack of dis-

criminative ability on the part of the males is shown by

the fact that they often attempt to copulate with indi-

viduals of their own sex. This fact in itself is not of

course very conclusive as similar behavior is often ob-

served in many higher animals, such as dogs and cattle,

in which the males are doubtless able to recognize the

females as such. Furthermore, on two occasions males

were observed to be in copulation with females which had

been dead for twelve hours and in another instance a male

of one species (Cambarus virilis) was found in copulation

with a dead female of another species (C. blandingi acu-

tus). This last observation is of especial interest for, as

Andrews® says (p. 474) it is not known ‘‘ whether the

male stylets and the female annulus are closely adjusted

to each other in each species or not. Experiments should

at least decide whether the males of one species can fill

the annuli of other species or not.” The observation

just cited shows that two different species can at least

* Andrews, E. A., ‘ The Annulus Ventralis,’’ Proc. Boston Soe. Natur.

Hist., Vol. 32, 1906, No. 12, pp. 427-479, pl. 43-48,

No. 516] COPULATION AMONG CRAWFISHES 753

unite sexually as I was careful to observe that the stylets

of the male were actually inserted into the annulus of the

female. Whether a spermatophore can be transferred

under such circumstances is of course still a question.

The observations described in this paper would lead to

the conclusion that the crawfishes have little or no power

of sex discrimination. The male ‘‘ tries ’’ every crawfish

which he meets and the instinct of the female is to remain

passive under such treatment while another male will at-

tempt to escape. The sexes come together as the result

of random movements or in the course of the daily travel-

ling about in search of food. Holmes? reached similar .

conclusions as a result of his observations on amphipods.

Male amphipods, however, would not attempt to copulate

with a dead female and in this respect their powers of dis-

crimination apparently excel those of the crawfish.

° Holmes, S. J., ‘£ Sex Recognition among Amphipods,’’ Biol. Bull., Vol.

5, 1903, No. 5, pp. 288-292.

SHORTER ARTICLES AND CORRESPONDENCE

DEGENERATION ACCOMPANYING INBREEDING

Ir seems now generally conceded that inbreeding per se is not

injurious but that when a similar defect in the germ plasm comes

from both sides of the family the children do not rise in respect

to this character above the parental level. The effect of close

inbreeding in small isolated communities is, at any rate, always

interesting, and affords an excuse for the following note, based

on facts gleaned from a letter sent me by Rev. H. East, a mis-

sionary whose headquarters are at Haka, Chin Hills, Burmah.

Rau Vau village has been isolated for about seven generations.

It contains about sixty houses and possibly two hundred inhabit-

ants. Of these ten are idiots, many are dwarfs and some hydro-

cephalic. A number of cases of syndactylism and brachydactyly

occur. Mr. East was not able, offhand, to state how these pecul-

iarities are inherited, but it is to be hoped that he will be able

to report on this subject later. Certainly, heredity in such a

community deserves careful attention.

C. B. DAVENPORT.

A NOTE OF THE PRAIRIE-DOG OWL WHICH RE-

SEMBLES THE RATTLESNAKE’S RATTLE

In looking over an earlier number of the AMERICAN NAT-

uRALIST’ I find a note under this head by F. B. Loomis in which

he deseribes a note of the adult burrowing owl which so closely

resembled the rattle of a rattlesnake that not only the members

of his party, but their horses as well, were deceived.

. . + it alighted and began a third rattle; and this time all saw its

stretched neck, bulging eyes, open beak and vibrating tongue. The

whole appearance of the bird indicated assurance that it would thus

frighten off any enemy; and it certainly deceived the four plain-bred

horses, as well as the men, all of whom had for weeks been familiar

with rattlesnakes, and two of them for years.

This reminds me that about sixteen years ago I made some

observations on the same subject. It is particularly interesting

‘Am. Nart., Vol. XLI, pp. 725-726, 1907. :

No. 516] SHORTER ARTICLES AND CORRESPONDENCE 155

to me to note that the horses were invariably frightened by the

“rattle,” for in thinking of my own experience I have often

considered that perhaps my observations were somewhat preju- `

diced that rattlesnakes are so popularly supposed to occupy the

holes with the owls. The observations which Loomis records

here were for an adult bird, while mine were upon the young.

A burrow was dug out and a nest of eight young secured.

When taken from the burrow, and with great frequency, these

young birds—still in the downy condition—made this sound.

As I remember it, this occurred every time they were disturbed.

These birds were taken in Cheyenne or Rawlins County, Kansas,

‘while Loomis’s observations were made in Wyoming. Loomis

seems to regard the note as peculiar to the one individual he

observed, for he writes:

If it sueceeds in teaching this trick to its young, a protective habit

of great value will be formed.

Whether the prairie-dog owl generally has this note I am quite

unprepared to say, but my observations in northwestern Kansas

indicate that it is not an individual peculiarity. It is so easy to

attribute adaptive significance to characters that our attitude

toward such suggestions should always be very critical; whether

the note described is ever of any service to the bird would be a

difficult problem for a field ornithologist. It would be interest-

ing to know whether notes of this kind are peculiar to the prairie-

dog owl, or whether they are also heard in species which have no

possible association with the rattlesnake. Some one familiar with

birds in the field could probably answer this question.

J. ARTHUR HARRIS.

NOTES AND LITERATURE

THE CAUSATION OF SEX?

Tars book is the work of a general practitioner of medicine.

For twenty years he has collected clinical facts and materials

upon which he now claims to have built up a new theory of sex.

The theory has been put to the test in forecasting the sex of the

unborn child and proved adequate in 97 per cent. of cases. The

cause of sex being known in man, the determination of sex is

readily accomplished. A summary disposition of Schenk’s once-

famous superior-vigor-theory is made by simply citing the clin-

ical fact of the occasional simultaneous birth of both a boy

and a girl.

The theory dissociates absolutely the male parent from any

influence in sex causation—thus differing from several otherwise

closely similar hypotheses. It is simply that ‘‘sex depends upon

which ovary supplies the ovum fertilized.’’ The clinical mater-

ials employed in proof are: (1) Sexually differing families; (2)

extra-uterine pregnancy; (3) pregnancy in double uteri; (4)

multiple pregnaney; (5) migration of ovum (internal and ex-

ternal; (6) preponderance of male over female births. Further-

more, the author denies validity to all arguments, respecting sex

in man, from analogy with invertebrates or even lower verte-

brates, believing ‘‘women not analogous to any living thing.”

Respecting the anatomy and physiology of the female genera-

tive organs the following facts are noted and employed in the

construction of the theory: (1) Lower position in pelvis of right

ovary and internal opening of right oviduct; (2) larger caliber

of right oviduct; (3) larger size of right ovary; (4) occasional

presence of two ova in a Graafian follicle; (5) recorded cases

of double nuclei in the mammalian egg; (6) corpus luteum as

indicator of ovary from which the impregnated ovum came; (7)

dependence on common cause, consequently close coincidence, of

ovulation and menstruation (proof: scars of corpora lutea cor-

respond to the number of menstrual periods experienced). The

***The Causation of Sex,’’? by E. Rumley Dawson, London, H. K. Lewis,

1909, pp. 190, 21 illustrations,

756

No. 516] NOTES AND LITERATURE 157

foregoing statements are supported mainly by quotations from

various recognized authorities.

Chapters 3 and 5, dealing with the Formation of the Ova and

Fertilization respectively, are vulnerable at various points to

the criticisms of gratuitous assumption, specious reasoning and

flagrant disregard of recent biological advance, more particu-

larly respecting the questions of heredity and sex. Absolutely

no notice is taken of the work of Bateson, Davenport and Castle

on Mendelian inheritance, nor of the cytological and experi-

mental results concerning the determination of sex respectively

of Wilson and Correns. But however scant the appreciation of

the bearing of results from non-human materials on the general

problem, and however radical the ideas here expressed, the

theory as such remains essentially unaffected.

In chapter 3 it is urged that ‘‘Each ovum has its own definite

and unalterable sex, being either male or female according to

the ovary from which it is derived.’? Though microscopic evi-

dence of such difference is not yet forthcoming it is asserted to

obtain ‘‘just as between the eggs of two different women.’’

‘‘ Similarly the ovum of a negress is indistinguishable by our

present appliances from the ovum of a blonde, yet we know full

well that if fertilized one produces a black child while the other

gives rise to a white one’’ (p. 29). Assuming, as this line of

reasoning does, that there is identity (or at least close similar-

ity) between the process of sex-inheritance and color-inheri-

_ tance, both would seem to be due, in a large measure, to the

influence of the male. For the ovum of a negress fertilized by

the spermatozoon of a blonde male might give rise to a black

child, but it would more likely be a mulatto, perhaps almost in-

distinguishable from a sane erin sex may be influenced

or determined by the spermatozoo

Identity in the mechanism of saris whether it concern sex,

color or other unit characters, is widely accepted; but Dr. Saw:

son seems to posit such identity or the absence of it depending

upon the conclusion he desires to reach. Above he posits iden-

tity; but he reasons incorrectly in an attempt to reach a desired

conclusion,

In a later chapter (chapter 5), starting with the assumption

that the ‘provision in the human ovum of multiple avenues of

entrance (the radiating pores of the zona pellucida) looks as

though multiple spermatozoa are required to enter thereby in

order to fertilize the human ovum,’’ he argues that the “ differ-

758 THE AMERICAN NATURALIST [Vou. XLIII

ent number of paternal and maternal features and character-

istics inherited by the respective children must be due to a vary-

ing quantity of the paternal body or germ-plasm carried to each

ovum fertilized by the varying number of spermatozoa’’ (100

or more). He argues for the necessity in human fertilization of

multiple spermatozoa on the basis of (1) prolific supply at each

ejaculation (200,000,000—Lode) ; (2) very frequent renewal; (3)

long life in oviduct. According to this argument the color

of the child resulting from the development of the egg of a

blonde fertilized by the spermatozoon of a negro would be

blonde if only one sperm entered, black if many entered—the

direct contrary of his former position.

Again, the author holds that there is no question of heredity

or ‘‘the exhibiting of ancestral tendencies or peculiarities in a

varying degree’’ among the invertebrates! All that is necessary

here at fertilization is to provide stimulus to development; con-

sequently one spermatozoon will do. Even among cod or her-

ring one sperm is held to be sufficient for the same reason. The

number of spermatozoa demanded for the expression of any

particular degree of inheritance is believed to be indicated by the

number of micropyles in the egg. If always only one, or the

same number of spermatozoa, entered the human ovum there

could be no such thing as somatie variation. Evidently our

author knows little of the later studies on the nature of fertiliza-

tion and the function of the chromosomes in relation to sex and

general inheritance. It is stated that ‘‘many spermatozoa en-

tering the ovum lead to a father-like child whether boy or girl;

a few only entering leave the yolk still maternally superior or

prepotent so that the child whether boy or girl takes after the

mother’’ because it is too much to ask of a single chance sperma-

tozoon “‘besides fertilizing the ovum nucleus, also . . . to settle

the sex of the coming child and likewise impart to the oosperm

the form and face, talents and tendencies, coloration of hair,

skin and eyes, movements and mannerisms, and even diseases of

the father” (p. 42). And yet by the hypothesis that in the

chromosomes of a single Spermatozoon reside such potency can

be explained the various phenomena of Mendelian inheritance

—Moreover, characters can be added and subtracted in accord

with this theory. How could the phenomenon of color domi-

nance in mice and guinea-pigs be explained on Dawson’s as-

sumption? Of course he will always reply that there is no

No. 516] NOTES AND LITERATURE 759

analogy between heredity in guinea-pigs and the human female.

Evidently he has not yet accepted even the fact of evolution.

Absolute identity of the process of fertilization is asserted to

be disproved by the results of merogony. The connection is

obscure, but if the findings of Boveri and Delage in echinoderms

have any bearing on the matter it would be to show that a single

spermatozoon is prepotent over the greater extranuclear mass of

the ovum and determines an organism with male characteristics.

Similar examples of loose reasoning and unwarranted state-

ment appear in chapter 6. Here it is said that it is ‘‘reasonable

to suppose that the association of the left ovary with the produc-

tion of the female sex is due to the fact that the weaker sex

should result from the weaker side of the body.” How will Dr.

Dawson prove that the female is the weaker sex, or that the left

side of the brain is the weaker, or that left-handed persons are

weaker on that side? ‘‘To inquire why the ovary of the right

side should have been chosen for the production of boys rather

than the other side seems as fruitless and as useless as to inquire

why the liver should have been placed to the right and the spleen

to the left of the body.’ Surely this is giving a curious turn to

the method of reasoning by analogy. The position of the liver

and spleen, as also of the stomach and other viscera, is deter-

mined largely by the mechanical factor of pressure under which

they mutually adapt themselves to their narrow confines. Orig-

inally they also were symmetrically placed with respect to the

body axis as are the gonads and kidneys which remain so defin-

itively. With as much reason might one argue that the right

eye sees only the upper colors of the spectrum and the left the

lower, or that one kidney secretes the mineral and the other the

organic matter of the urine or that the right testicle gives rise

to blondes and the left to brunettes.

All this, however, has little bearing on the essential point of

the theory, which is based upon the following facts and cases:

(1) Woman has one-sexed children only by different men; (2)

father produces both-sexed children with different wives but

only one sex with each wife (in both of these instances the

woman is supposed to be unilaterally sterile) ; (3) man gets

both-sexed children with one of his wives but only one sex with

the other ‘“beeause she is unilaterally sterile.’’ If it depended

on the male, it is argued, he should get both-sexed children with

both wives. The theory is further supported by animals also:

(1) cow covered by fifteen bulls has seventeen calves, all female;

760 THE AMERICAN NATURALIST [Vor. XLIII

(2) mare covered by more than six different stallions had ten

foals, all male; (3) bitch covered by two different stud dogs gave

birth in two litters to six male dogs; (4) sow gave birth to a litter -

of ten boar pigs. In all these cases the female is supposed to

have been unilaterally sterile. One might urge against the

cogency of these facts as supporting the theory that the law of

probability and the hypothesis of Mendelian dominance could

explain them as well as the supposition of unilateral sterility.

In chapter 8 cases of pregnancy are reported to prove the

theory. The proof here consists in showing cases of male and

female pregnancy with the corpus luteum in the right and left

ovum respectively ; six cases of the former are given, and three

of the latter (one doubtful). Among the vast number of pos-

sible cases, these eight might very well be mere coincidences—

for when exceptions occur he invokes the aid of a migration of

the ovum.

Chapter 9 considers cases of extra-uterine pregnancy to prove .

the theory. Twelve cases are reported of tubal pregnancy and

a corpus-luteum-bearing ovary on the same side. Accordingly,

if pregnancy be in the right oviduct and the foetus a male, one is

justified in declaring the ovum came from the right ovary. Nine

such eases are described; and five in which a female foetus was

found in the left oviduct. Furthermore, two cases of twin-preg-

naney, one extra-uterine and the other intra-uterine are shown

to conform to the rule. Dr. Seligson of Moscow, is said to have

collected fourteen cases of males developing in the right tube

and females in the left. Two cases of right ovarian pregnancy

of male sex are given, and one reverse case.

Chapter 10 takes up cases of pregnancy after unilateral

ovariotonry. Five examples of male births after removal of the

left ovary are submitted, and four where females were born

after the right ovary was removed. A case is reported of right

ovariotomy combined with resection of the left ovary, followed

by the birth of a girl. Many exceptions are admitted, but they

are ascribed to incomplete removal of the ovary in question, or

the regeneration of ovarian tissue from the pedicle, or to the

presence of an accessory ovary. Thus these examples lose much

of their force.

Cases of pregnancy in abnormal uteri are discussed in chapter

11. Seven cases are recorded, four in which the right halves of

double uteri were pregnant with males, and three where the left

halves contained females. Exceptions, which are frequent, are

No. 516] NOTES AND LITERATURE 761

charged to a migration of the ovum from one side to the horn of

the opposite side. And ‘‘in those animals such as pigs, cats, rab-

bits and mice—whose offspring are truly multiple—the fcetuses

are mixed up in the two cornua; but..... the ovaries contain

between them a corresponding number of corpora lutea, both

individually as regards sex and collectively as regards num-

ber’’ :

An interesting presentation is given in chapter 15 of supposed

reasons why more boys are born than girls. Statistics recorded

for over 200 years show this to be a fact, the proportion being

106 males to 100 females. More boys are said to be born by rea-

son of the greater number of male eggs liberated, and by reason

of easier access of spermatozoa to male ova, both due to the

anatomical facts above enumerated. Nature thus attempts to

compensate for the greater male mortality at birth and during

the first five years.

Multiple conceptions are brought under the hypothesis. The

woman is held responsible for plural pregnancies; nevertheless

the author is forced to admit exceptional cases (p. 144).

In chapter 22 Dr. Dawson attempts to analyze the more obvi-

ous objections to his theory. ‘To the criticism that it is too me-

chanical he answers that all life is essentially mechanical, e. g.,

respiration, circulation, menstruation. With the fact that the

majority of birds have only one ovary, yet the hen lays eggs of

both sexes, he has considerable trouble. But he makes argument

impossible by simply stating that woman is not analogous to the

hen. He seeks support for this contention by citing the fact that

birds are asymmetrical in other respects, 7. e., absence of right

carotid artery and right jugular vein, adding that it is ‘‘no

more necessary to assume identity between birds and women in

the matter of the causation of sex, than in the matter of circu-

lation.’’ It must be pointed out that originally (before hatch-

ing) both the circulatory and reproductive systems of birds are

identical, at least as concerns bilateral arrangement, with those

of the human embryo. It seems more reasonable, on the basis

of comparative embryology and physiology, that the human

ovaries have an identical, interchangeable and compensatory

function just as the kidneys, the testes, the eyes and the ovaries,

as respects menstruation, are known to have.

The two concluding chapters deal with the problem of fore-

casting sex and the production of sex at will. Knowing that the

gestation period is 40 weeks and that 13 ovulations normally

762 THE AMERICAN NATURALIST [Vou. XLIII

occur per annum and that the ovaries normally function alter-

nately, one need know further merely the date of birth and sex

of the previous child to compute the sex of the coming child. It

is evident that the ovulation in the same months varies in suc-

cessive years (due to the fact that there are 13 ovulations).

From this point then we can work to the tenth month previous

to the expected birth. Hence ‘‘if children are born in the same

month an odd number of years apart they are of opposite sex; if

an even number of years intervenes they are of the same sex’’

(p. 183). Accordingly then the ‘‘ production of sex at will must

consist in avoiding any attempt at fertilization in the months

during which an ovum is produced of the sex not desired. Dr.

Dawson believes it possible that some day by means of some

modification of the Réntgen or other rays, we may actually see

an ovary ovulate. At present there appears no way of deter-

mining the sex of the first-born. |

The book as a whole furnishes entertaining and suggestive

reading. One leaves it unconvinced, but stimulated perhaps to

test the theory by careful observations of his own clinical mate-

rials. One feels, however, that the author is not justified in his

extreme position that even higher vertebrates can teach us noth-

ing with respect to the cause of sex and heredity in man. Surely

one trained in general biology, especially cytology and compara-

tive embryology can not accept the ‘‘theory’’ as anything more

than an unverified hypothesis. Of course the array of clinical

facts at first seems to give the theory a semblance of solidity;

but this is rapidly dispelled by the arbitrary disposition made of

numerous exceptions. By the same methods it would probably

be as easy to prove the reverse position, 7. e., that females come

from the right ovary and males from the left. The problem of

sex can never be solved by the method of collecting clinical ma-

terials alone—and Dr. Dawson’s book represents perhaps the

last effort at such a solution. Clinical materials will always be

valuable adjuncts, but the essence of sex resides probably as

much in the male gametes as in the female, and its final elucida-

tion seems indicated along the lines of a cytological (chromo-

somal?) interpretation of Mendelian phenomena.

H. E. JORDAN.

INDEX

NAMES OF CONTRIBUTORS ARE PRINTED IN SMALL CAPITALS

ALLEN, and

WRI

of PA E Hare m, 687

ALLEN, J. F Revision of

the Genus Paora,

Amblystoma PE, ALBERT Pt

WRIGHT and ARTHUR ALLEN

American Toad, Newson ee

ARTHUR,

Piva cg Plant,

sea = Decade, EDWARD C. JEF

; 230

ws, E. A, A Male hgh (aes

with some Female Organs

Ants, Dac for the Study of, Taare

UCKINGHAM,

Apodous Holothurians, bs L. Clark

s Wo. Fis

Archegoniates, aak. on the Or-

r of the, BRADLEY M. Davis,

Ania. —— Local e

on, VoLNEY M. SPALD 472

Armor Plates, Dinienthyd, ‘BURNETT

SMITH, 588

Arms sby, H. P., Feeding for Meat

Production, RAYMOND PEARL, 309

a of Breeding, Pure Strains

s, O. F. CooK, 241

Bactmetjew’s Experimentelle Ento-

mologische Studien, FRANK E.

UTZ, 55

Hatraslioccne attenuatus and Auto-

dax lugubris in grain Cali-

ILLIAM A. Hr 3

Mendelian Heredity, W. J. SPILL-

MAN, 437

Bee, Honey, Color Sense in the,

— Jonn H.

Tava of the Domestie Fowl,

ILIP B. HADLEY

Bem, Epwa ARD W., T

ap. Spani in Vi nia, 432

Panni Pu E, In Ten oriam

Errera

Biometric Constants, Accuracy of

the, RAYMOND ND PEARL, 238

Biometrics, 238, 302 |

Bohn’s The Birth of Intelligence,

H. S. Jenntnes, 619

763

Abert H.

IGHT, ai Br OAE Habits

| Breeding,

| B. “Mora

| a

Progress during |

meier with Rats,

18 oe Strains

i Asda Of, O. F.

and FRAN

pa on the A

oy L.

oa e kas:

aiee 122

W. K, and B. MoGlone,

Lung of pa e WILLIAM E.

Bufo lentiginosus americanus, Le-

Conte, Newron MILLER, 641, 73

The

Burnett, E. = Breaking

Strength of Bones, RAYMOND

PEARL, 309

Butterflies, Blue, of the Genus

Celastrina, T. D. A. COCKERELL,

114

— Polyprodonta and Pi-

prodonta, PAULINE H. DEDERER,

Camel from the Lower Miocene of

Nebraska, HAROLD JAMES COOK,

eee

CAM Dovueias Hovueuton, The

New a ti of Krakatau, 449

Canadian na arva and Spat

of, J. S RD,

CASTLE, W. ges Colors in Rab-

bits, 7. H rgan, 504

Categories of Variation, 8. J.

OLMES

Cestodes, of Birds, Henry

B. Warp

62; and Trematodes, The Cuticula

and Se tna of, HENRY S.

Cnadwick, H C., Red Sea rem

OBART

Chambers, Robert, Size of the Egg

and ‘Temperature and the Growth

of the Frog, SERGIUS MORGULIS,

Chapman, oi M., Life History of

the Booby, Witttam E, RITTER,

Chondriosomes as Bearers of the

inca ary Qualities, F. PAYNE

Chromosomes, The Permanence of,

764

in Plant Cells, BRADLEY M. Davis,

571

Chub and the Mla Horn Fly, Roy

L. Moonie, 186

prer AUSTIN HOBART, Chadwick

n Re d Sea beer 253: No on-

ewar Articulati s of, 5 Pi:

of the Tande “682

Holo-

‘Affinitie es

Toueis ” Plant Geography and

Ecology, 143

Climatic Factors and Vegetation,

E ANSEAU, 4

COCKE , T. D. A., Tutt on Blue

Butterflies of the Genus Celas-

trina, 114

OKER, W. C., Vitality of Pine

Seeds, 677

Collinge, Walter E., Pe s

— ng fica Y D A. Coc

Color ean 4 the Honey Bee, JOHN

338

H. Lovett,

Conklin, E. G., ces mercurius,

WILLIAM E, Rrrr , 699

Constants, Biometrie, Degree of Ac-

curacy of, RAYMOND PEARL, 238

Cook, HAROLD Ja peti Camel from

the Lower Miocene of Nebraska,

Cook, O. F.,

ists of Breedin

Copulation among Cr, oe with

ag al Reference ve br ecogni-

tio S ARS

Pontis Organic, j “Mechanism

for, G. H. PARKER, 212

Correns on arlesatine:

SPILLMAN, 442

COULTER, Jonx M., Vascular Anat-

my and t he Reproductive Struc-

W d

tures, 219

ow Les, HENRY C., Ecological Phi-

keon 356

Cowtes, R. P., The Sand- Crab, 699

Cox, Gaana Charles Darwin

and the Mutation Theory, 65

Crawfishes, Le Sot anton. with

Special Reference cogni-

tion, . PEARSE

a Fish, Male with some Female

Organ NDREWS, 461

Crna Nanay ‘Articula-

zaoa of, AUSTIN HOBART CLARK,

ae Pollination in Lane

wins Work on, WILLIA

LEASE, 131

Cuénot, L., Drone

Honey Bee,

Dar-

TRE-

Eggs of the

T. B. Moni 316;

Pure potep as Arti- `

ng, 241

THE AMERICAN NATURALIST

[Vou. XLIIT

Inheritance of Color in Mice, T.

H. MORGAN, 494

be de on “Hormones,” FRANK

, 249

Pe i ges Sub-Cuticula of Tre-

het and Cestodes, Henry S.

Pratr, 705

DALL, WittraM HEALEY, The Mol-

luscan Fauna of the Peruvian

Zoological Province, 532

Darwin, Charles, and the Mutation

CHARLES s 65: a8

a Naturalist; Darwin’s Work o

Cross Pollination in Plants,

WILLIAM TRELEASE, 131; Influ-

Pla

tion and r Boy Epwin Lin-

163

baai CHAR B. and GER

RUDE C., Heredity of Hair Color

in Man,

DAVENPORT, C. Ps aaah gy ac-

ermanence of Chromo osomes

in "Plant Cells, 571

Dawson, E. Rumley, on the Causa-

tion of Sex, H. JORDAN, 756

DEDERER, ee H. Cænolestes,

Polyprodonta and Diprodonta, 614

erat y accompanying Inbreed-

RT, 76

ing, C. B. DAVENPO

Development and d Heredity in In-

eeding, Epw East, 1

DeVries’s Rocce and Varieties,

Grorce H. SHULL, 383

Dinichthyd Armor Plates, BURNETT

SMITH,

Distribution, Local, on Arid

ADLEY,

A, Coat Colors

e B. a 494

East, Epwarp M., ore

ity in Inbreeding, 173

East, .. Inheritance in Sweet

Corn J. Spr N, 4

Echinodermata, 253

Echinoidea, Affinities of, AUSTIN

OBART RK, 682

mea Piat. Henry C.

356

No. 516]

Ecology, and Plant Geography, D

win’s Wo

rk on, WILLIAM Tar-

rn Plan ; ORB

286; Physiological Plant, BURTON

LIvINGston, 369; Plant, Present

Problems in, CHARLES H. SHAW,

420

Entomological Ecology ot the In-

ro an Corn Plant, 8. A. FORBES,

Peseta tt the pans a ia Ani-

mals, FRANK E. LUT

Errera, m in Memoriam, —

Bes

Evolution, ace on, VER E.

iad as Poulton ae. d Pinks

. KELLO 7

Benanti, Bevlution, 55; Zool-

ogy, 57, 251, 316, 494, 702

Federly on the Scales of Lepidop-

, 55

eas Frank E. Lutz

L. "Clark’s The

Apodous Holothurians, 111

Flor of Krakatau, DOUGLAS

i a CAMPBELL, 44

Forbes, S. A., Entomological Ecol-

ogy ‘of the Indian Corn Plant,

Fowl, Fane De Behavior of,

Pure B. Hap 669

oa 1 a the Triipotenst of the

First Two Blastomeres of, J. F.

MCCLENDON

Fuhrmann on ‘the Cestodes of Birds,

Henry B. Warp, 62

GRIGGS, ROBERT Juvenile e

and rake pea i i riai Theory, 5

Growth, Recent Studies on, RAY-

MOND PEARL, 302

Hapiey, Parie B., The sn

of the Neale Fow L

— and the Phyletie ies

oe Jena, Vernon L. KELLOGG

aged A L, Dores =

Yellow Color in Rodents, T.

More 505

Hair Color in ma Heredity of,

C. and

CHARLES AvENPORy, | 193

Harben Lectures, Henry B. WARD,

J. ARTHUR, Variation =x

che ones of | ‘per |

the Broom, 350; Selective Elim-

So of Ovaries iting

he I ose, 556; Note of

the Prairie doa O Owl, which re-

in the Frui

INDEX 165

sembles the Ratuesnake’s Rattle,

764

Fe on Cultural Bed Mutations

the Potato, 192

Heredity, 190, 243, 437; and Devel-

CHARLES B. DAVENPORT, 193; and

Variation in the Simplest Orgi

isms, H. S. JENNINGS, 321; Non-

i se of, J.

Mendelian, a Ca W

SPILLMAN,

HILTON WILE M À., Batrachoceps

attenuatus eat: Autodax lugubris

in Southern California, 53

Hotmes, S. J., ategories ot Varia-

tion, 257

Holothurians, 111

Hornaday’s Ca amp-fires ar Desert

and Lava, Roy L. Mooptr, 127

Horse Sires, Age of Trotting, F R

PAETE , 50

HORTO TB r Inheritance of Color

in Pigeon 8, 7

Hue - Mae? Callibrachion, Roy

L. Moo

Hybridology ai Gynandromorph-

T. H. Morean, 251

Ichthyology, Notes on, DAVID STARR

JoRDAN, 560

Ber P Open: a anu Hered-

ity in, Epwarp M. BY, 173;

Degeneration aa ahi C. E.

DAVENPORT, 764

Inheritance, of Coat Colors in Mice,

T- Morean, 494; of Color in

Pigeons, B. B. Horton, 702

Janet, Pierre, Les Nevroses, VER-

si LLOGG

381

JEFFREY, Epw ARD C., The Progress

of Plant pie ga during the Last

san 230.

JENNI H. S., Heredity

and

Variation in the Simplest jen

1; Bohn’s the Birth of

TOA HSA 619

Jennings, H. S., Acquired Charac-

ters in Protozoa, FRANK., E. LUTZ,

sse thay on L. Ke

JOCHELSON, WALD) Traditions

in anar Siberia about the

Mam

JORDAN, DAVID STARR, Notes on Ich-

} ba

Echinoderm Ta Wma. E. Rrr-

TER, 694

766

KeLLICOTT, W. E., Growth ot Prani ;

and Viscera in the Dogfish, RAY

puns PEARL, 306

jg Y, L. Poulton and Plate

tween OLE

Kenlows, V: L, “Inheritance in Silk-

tion Theory, Roperr F. Griaes,

. 92

Kleine on Nagana, H. B. WARD, 568

Krakatau, The New Flora of, Doue-

LAS HOUGHTON CAMPBELL, 449

an, AE Spat al g Canadian

STAFF

Land "Ceti ction, ve Earl

ARF 3

Leguminose, Selective Elimination

of Ovaries in p so iting of the,

J. R. HARRIS,

Lepidoptera, ne

yton, Epwiy, Darwin’s Origin of

Species in the Light of Recent

Observation and Experiment, 163

Linton, oh in amg Worms,

WILLI

TTER,

LINTON, sags a E

Plant Ecology, 3

a ELL, JOHN H., The Color Sense

. in the Honey Bee, 338

Taia nih; FE Origin of the Bi-

valent Chromosomes, BRADLEY

Lutz, rik pk E., The Effect of the

Environment upon Animals, 55,

MCCLENDON, J. Fr raps Egg, the

potn i of "the First Two, 384

ison oaiit,

McClung, C. E., Bi

Y L. Mooi ering 123

hamia 633

Mammoth, “Tra ditions about, in

Northe aste

ern Siberia, WALDEMAR

on, 48

Marechal on Environmental Effect,

Marine Bivlocy, 6

Marsnatt, F. R., "Am of Trotting

Horse Sires, 50

Mayer, A. G., Tortugas Laboratory

of the Carnegie Institution,

Witiiam E. RITTER, 693; Cassi-

opea, 699

Merriam, J. C., Nectosaurus, Roy

L. Moopre 123

Meves on Chondr riosomes as Beare

of the Sarola Qualities, F.

Payne, 190

Mice, The ee ” — Col-

ors in, T. H. More

THE AMERICAN NATURALIST

(Vou. XLII

er oP ahr The American

ad, 641

Won Bone of the bide

PARE ee i WIL

y DALL, 53

Moopte, Ror a “The T eorophide,

Hugo Stego-

Sena. 119; Williston em Broili

on the Cotylosauria, 1215 ‘The

mouent Known Reptile, 12z Tice

n the Age of the Gaskohle

MeCling on shite "oeeidetalis,

ifs; eC. g on

saurus 123; von uen on

Calibrachion, 12 124; Hornaday s

n Desert and Lava,

The Chub and the ‘Lexas

-. H., Breeding Experi-

ments with Rats, 182; “Hyb pridol-

ogy and Gynandromorphism, 25

Cuénot on tne Drone Eggs of t nt

Honey Bee, 316; aga: pate of

Coat Colors in Mice

gan SERGIUS, =e Cnam-

bers the Size of the Egg and

Temperature and Growth or the

Frog, 57

Movement i in Plants, Darwin’s Work

on, RBERT MAULE RICHARDS,

152

Mutation naan, me a Dar-

win, CHARLES F. 65

Note of the Prairie-dog Ow:, which >

the Rattlesnake s Rat-

. ARTH

nie and ilaaha i 55 107, 190,

256, 301, 379, 437, 494, 619, -694

Organic oe. S Mechanism

r, G. H. Pag

Onesie The ‘Theory of, ALEX-

HVE

OVERTON, ermanence

Chromosomes, BRADLEY M. Davis,

Ow, Prairie-dog, Note which

mbles the Rattlesnake’s Rattle,

i RTHUR HARRIS, 764

pg Sa Larva ana Spat

buna ba 567

A el A Mechanism for

rganie ee ae 212

Patton on a rpetomonas,

u E

WARD

No. 516] INDEX 767

Payne, F., The Chondriosomes as oe of the Carnegie Insti-

Bearers: of the Hereditary Quali- tution, 693

ties, | Pagea T. The ab “pean Rate

PEARL, ee ND, Accuracy oe aes of Growth, ig Bled PEARL, 309

Biometric Consta nts, 238;

and FRANK M. SURFACE, Selection

: SN

ARSE, A. S., Copulation among

iaag with Special reer

nce to Sex gerrnana

Perkina, = i use, Teu

E. Rir n

Peruvian loolooa] Province, Mol-

lus ater: of, ILLIA

Saee era of Color in,

WwW C.

HEALEY

Pigeons,

B. B. Horton, 702

Pine Seeds, Vitality of,

COKER

Pea, 107; Cytology,

71; Progress during

EDWARD C. JEF-

677

Phylogeny,

Anatomy,

ihe ‘Last Decade,

FREY, 230

Pleistowne Swamp pg sae a age

ia, Epwarp W. BER

Cross, can

k TRE-

in rr

Pellinacion,

hea WILLIAM

win’ si

LEASE, 1l

Potato, ae on Cultural Bed

Mutations in,

Poulton and Plate on Evolution, V.

L, Kraan. 317

Powers, J. H., Are Species Realities

or Concepts only? 593

Powers on e Variation in Am-

blystoma oe

PRATT, HENE , The ua and

Sub- 'Cuticula of Trematodes and

Cestodes

en ah ae ne

E Harrison SHULL

Pacchoices, Comparative, 619

Raepke, W., on Hybridology ans

Gynandr omorphism, T. H. Mor

GAN, 251

Rata, Breedi ing rl alee with,

H. Morean, 1

Reca tulation neal and saps

ps, Ropert F. Griees, 5, 92

Reighard, Jacob, Warning Sait

; ILLIAM E. RITTER, 701

Reparbuotiee Structures and Vas-

cular Anatomy, Joun M. Covr-

pg 219

RICHARDS, HERBERT Maure, Dar-

shoyi e Work on cement i

„i

Riddle, e 3 as np Color Forma-

H. MORGAN

Mey Wid b ge

| pr O., Permanence of y

ADLEY

| RUTHVEN, ALE

| Banas.

mosomes, BR M. Davis,

573

ER G., The The-

ory of EEEREN 401

Scuarrr, R. F., An Early Tertiary

Land Connection, between North

and South America, 513

Archegoniates, BRADLEY M. Davis,

Hugo, on Stegocephala,

Sex, Recog ognition, Copula

Crawfishes, with peen reference

, 746; the Causa-

oe ey fees son on,

Sleeping ag tvez Bureau, HENRY

B. WAR

ae Experiments a Breeding, T.

COCKEREL

URNETT, akiw Armor

SPALDING, VOLNEY s-

tribution on Arid Reg T

Species, Are they Realities or Con-

cepts only? J. H. , 59

SPILLMAN, ature of

W. N.

ee Characters, 243, Heredity,

Pape D, J., Larva and Spat of the

pes aa Oyste er, 31

Sta dgserell on the op arbi Amer-

ican x VERR 542

T ians e "HAS. | Regeneration,

696 ; Aplopus ia 99

Su phe ne FRANK M.. and RAYMOND

Bieta aan Numbers

boy ae Use in Breeding, 385

Swamp Deposits, Pleis pal in

Virginia, Epwarp W. Berry, 432

‘Tertiary Land Connection between

rth and South America, R. F.

HARFF, 513

Toàd, The "American, Newton MIL-

LER, 641, 730 Cp ae ce:

768

Tortugas Laboratory of the Car-

oe Institution, WILLIAM E.

TTER,

Traditions in E Siberia

ut mmoth, EMAR

TRELEASE, Sia Ai Darwin as a

i on

Na ; Dar Wor

Cross Pollination in Plants, 1

Trematodes d Ces , The Cu

ticula ain Sub-Cuticula of, HENRY

S. PRATT, 705

Trotting Hin Sires, Age of, F. R.

SHALL,

Tutt, J. W., "Blue Butterflies of sm

Genus Celastrina, T. D. A. Coc

Variation, Categories of, S. J.

HotMeEs, 257; and Heredity in

the Simplest s H.

JENNINGS, 321; in the Waker of

Seeds per Pod in the Broom, J.

THUR Harris, 35

Vascular Anatomy and the Repro-

THE AMERICAN NATURALIST

[ Vou. XLIII

ech Structures, JoHN M.

ER, 219

Viestation and Climatic Factors,

DGAR TRANSEAU, 487

VERRILL, A. E, Development of

Starfishes on the Northwest

Amer ast, 542

Vertebrate Paleontology, 116

Vitality of Pine Seeds, W. C. COKER,

677

Wa ARD, Henry B., The Cestodes of

ex, N, 44

Williston on the I, Lysorophide, 116;

on the Cotylosauria, 121; on the

ge now wn Reptile, "Roy L.

Moo

Wils B. n Chromosomes and

Heredi Sams pp asen We U:

SPILLMAN, 24v

WRIGHT, ALBER Hy ART

ALLEN, Br oiia Habits of ae

blystoma punctatum, 687

The American N aturada |

A Monthly Journal, established in 1867, Devoted to

erence actors

with Special Ref to the F;

the’ Advancement of the Biological Sciences

of Organic Evolution and Heredity

CONTENTS OF THE JUNE NUMBER

Heredity and Variation in the Simplest Organisms.

Professor H. 8. JENNINGS.

re crags Sense ofthe Honey Bee — Is eg ame p

n Advantageto Flowers? Jonn H,

hrer Te the Number of Seeds pet Pod in the

Broo! yrs Cytisus scoparius. nae DP

reseat eae IRA = Plant ra a, E

The Trend of Ecological Philosophy. Professor

Henry C. Cowie

The Present Problems of enon a Plant

> DR: psig LIVINGsT

rapar

DeVri S

SHULL. ape ger bag ithe Totipotence of

the First res of the Frog’s Egg.

-g FpMocuas

CONTENTS OF THE JULY NUMBER

Selection Index Numbers and their Use in Breeding.

Dr, RAYMOND PEARL and FRANEK M. SURFACE,

A as to the Their of Orthogenesis Dr,

R G. RUTHVE:

The ppan and Absence” n ypothesis. Dr. GEORGE

ARRISON SHULL,

eas Problems in Plant Ecology : i ago and

Altitude. Professor Craries H, S

ayni Articles and Correspondence = Pleistocene

oe Deposits in Virginia. Dr. Epwarp W.

REY.

Notes and Literature: Heredi

delian Heredity. Dr. W. J.

-À Case of Non-Mene

SPILLMAN,

CONTENTS OF THE AUGUST NUMBER

The New Flora of Doveras

HOUGHTON C.

A Male Crayfish with Some Female Organs. Professor

E. A. ANDREWS.

Present Problems in Plant Ecology :

The Relation of the Aar yet UE

Notes and Literature: Recent a the In-

heritance of Coat Colors in a Professor T. H.

Professor T. D. A, COCKERELL,

CONTENTS OF SEPTEMBER NUMBER

ween N

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Development of Starfishes on

ees Ps bag age oh Salil of Raya A

in Evolu Sy LRN 2

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The Non-muscular Articulations of Crinoids, AUSTIN |

HOBART CLARK.

"On Some Dinichthyid Armor Plates from the Marcellus

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Aze Spacicn Realities or Canstpts oniy. Professor J. H, a T

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Shorter Articles and a Sele ff

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of the Chick and the Pig

: By FRANK R. LILLIE

; 60 pages, 12mo, paper; net 25 cents, postpaid 27 cents

LL be found a valuable contribution toward the establishment of a standard

of t abaa work for students aniy and for others Saa con-

nide t