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AMERICAN NATURALIST

A MONTHLY JOURNAL

DEVOTED TO THE ADVANCEMENT OF THE BIOLOGICAL SCIENCES

WITH SPECIAL REFERENCE TO THE FACTORS OF EVOLUTION

VOLUME XLVI

wo Lot. Garden

1913

NEW YORK

THE SCIENCE PRESS

1912

THE

AMERICAN NATURALIST

Vou RIN January, 1912 No. 541

THE INHERITANCE OF COLOR IN SHORT

HORN CATTLE

H. H. LAUGHLIN

CARNEGIE STATION FOR EXPERIMENTAL EVOLUTION,

‘OLD SPRING HARBOR, N. J.

In order to adduce further evidence bearing upon the

problem of the inheritance of color in cattle the follow-

ing observations on the occurrence of dominant and reces-

sive whites in other animals are reported. Many species

of animals have some strains with solid white coats and

others with coats made up of both white and pigmented

areas. The white in such latter coats is always possessed

in a somewhat definitely arranged and progressive system

of areas characteristic of each species, spreading from

the first of these areas until the entire body is covered.

Thus in the guinea pig the whitening process begins with

the underline and large ‘‘centripetal’’ body blotches and

spreads until the hair, skin and body pigments are

entirely removed, the eye and the ‘‘centrifugal’’ coat pig-

ments persisting the longest. In the domestice cat the

process begins with the anterior underline and collar,

from which areas it spreads in large blotches. The

rabbit’s pigment areas behave similarly. With the parti-

colored dog of any or no breed, the whitening process

begins with a white line down the middle of the face, a

6 THE AMERICAN NATURALIST [ Vor. XLVI

white chest, a white collar and generally a white tail tip.

With cattle of all breeds and crosses possessing broken

color patterns the process begins with a white belt at the

rear flank, continues with another at the fore flank, a

white underline and a white forehead. With horses of the

English breeds it begins with a blaze face and white feet,

continuing with large body blotches. With the French

and the desert breeds it seems to begin witha ‘‘dappling’’

of the body hair—dark pigment persisting longest on the

legs—and continues through a lighter ‘‘dappling’’ to

white, the skin remaining black, while the sharper whiten-

ing process seems to follow the sequence observed in Eng-

lish breeds. In the case of the piebald negro the median

face line is quite noticeable. Thus, while there is for each

species a characteristic pattern, there is in reality a some-

what common pattern in all species of mammals possessing

particolored individuals. This common pattern is de-

seribed as follows: White line down the face, white under-

line, white anterior belt or collar, white rear flank belt

and white feet and switch. These white areas may, in

animals possessing but little white, be represented by

several smaller areas, but always near the median line

of the areas white in the larger pattern, which smaller

areas may fuse as the pattern becomes coarser. Thus

the white nose and forehead in some cattle may in

others make a continuous white line down the face.

The white spreads from the areas just defined with much

the same sequence as a fire would spread over a ‘‘hide-

shaped’’ meadow, starting at the centers homologous

to the first white areas of the coat. In all cases the

pigments seem to persist the longest in and about the

eyes and ears and at the buttock—the ‘‘centrifugal

areas’’ mentioned by Castle.

The coat of a white Shorthorn may consist of: (1)

Solid dominant white covering red (quite rare); (2)

some definite coat areas dominant white covering red,

others albinic white (very common); (3) some areas

albinic white, others dominant white not covering red

No. 541] INHERITANCE OF COLOR IN CATTLE 7

(quite common). In eye color the white Shorthorn is

either blue or brown; the roan and red Shorthorns are

always brown eyed. The characteristic pigment areas

may, in domestic animals, become subjected to rigid selec-

tion, resulting in modified forms—as the white belt of the

Dutch belted cattle and the white head, neck and under-

line of the Hereford. Approximations to the former and

to the reciprocal of the latter modifications (not of the

species pattern) are commonly observed among Short-

horns. In general, however, color patterns are quite

characteristic of the species and are quite persistent.

Greatly modified patterns are seldom seen and, moreover,

the reciprocal coloration is never seen.

Not only does the whitening process begin at definite

centers quite specific for each species, but it also seems

to be definitely progressive in tissues carrying pigment.

Thus, the whitening process begins in man with the skin,

extending to the hair, the iris, and finally the choroid.

Partial albinos often have blue eyes—the absence of the

iris pigment but the presence of the choroid. In the

guinea pig the hair and skin pigments generally seem to

disappear before those of the eye. Castle’® reports a

guinea pig with an area of red hair underlaid by a patch of

black skin, and observes that a white dog may have a

patch of pigmented skin somewhere under the hair coat.

Similar phenomena are found in all species having parti-

colored strains. It is a matter of common observation

that a white patch of skin or hair unsymmetrically cover-

ing but one eye of a dog or horse sometimes gives this

animal a ‘‘glass eye,” i. e., unsymmetrical eye color, the

blue eye being surrounded by white hair and skin while

the dark eye is surrounded by dark tissues; this, however,

is not always the case, for many times both eyes are dark.

In horses and cattle the hair is first whitened, then the

skin, the iris and the choroid follow in the order named.

A black horse or cow may have a spot of white hair on

some portion of the body; it may be entirely underlaid by

# í Heredity of Coat Characters in Guinea-pigs and Rabbits,’’ p. 46.

8 THE AMERICAN NATURALIST [ Von. XLVI

black skin—this is especially apt to be the case with small

spots, or under the center of such an area there may be a

pigmentless skin—generally characteristic of the larger

areas, while its margin is underlaid by black skin, but

never the reverse. In some instances, however, the pig-

mentless skin and hair areas exactly coincide. The hoof

of the white foot of a horse or cow is generally white,

that of the dark foot always black; however, quite often

a white patch or streak will extend to the hoof and then

come to an abrupt end, the hoof continuing in a vertical

line the same pigment possessed by the skin immediately

underneath the lighter hair patch giving rise to the hoof ;

thus the hoof is as dark or darker, but never lighter, than

the hair patch immediately above. In spotted horses it

is observed that a white coat spot crossing the mane will

sometimes whiten it, while in other instances it will not.

Mr. Chas. E. Burns, the pony breeder of Peoria, Ill.,

writes:

We naturally expect spotted Shetlands from spotted ancestors but

ean say that very frequently I have bred a spot to a spot and the off-

spring has been a solid color. On the other hand, I have very fre-

quently had spotted colts from solid-colored parents. The fact that

there is spotted blood in the ancestors of the solid colored ponies ac-

counts perhaps for the spots, and vice versa. There seems to be no

sure rule in governing the color of a Shetland. The mane and tail are

not always the same color as the adjacent color patches of the coat.

Very frequently I have seen a white mane come right out of a black

patch, although as a general rule the color of a mane is the same color

as the adjacent coat of the pony. This is general also as regards the

tail, but very frequently, as I say. a black tail comes out of a white

spot, or a white tail out of a black spot, and often the tail is both

blaek and white.

Mr. C. R. Clemmons, of Coffeyville, Kans., writes:

I have been breeding spotted Shetlands for twenty-five years. I find

that many mares of a solid color will bring spotted colts quite regu-

jarly when bred to a spotted stallion having considerable blood from

these colors but every now and then there will be a foal of perfectly

plain color as the result of this same mating. I am of the opinion,

however, that a spotted color breed could be obtained by breeding in

these colors and perhaps inbreeding.

No. 541] INHERITANCE OF COLOR IN CATTLE 9

The mane and tail of a spotted Shetland are not always of the same

color as the adjoining patches of the coat, there is sometimes a dis-

tinct color line between the mane and tail and the coat.”

Mr. W. A. Long, of Greeley, Ia., offers the following

evidence :

We have no recollection of seeing any roan Belgian stallions with

white manes and tails. Our experience with the roan stallions has

been that the colts are principally roan Je have in mind one roan

stallion that we imported that sired 68 elke one year and they were all

roans out of all colors of mares. We handle many chestnut horses

with white manes and tails, and they sire principally all chestnut

colts, but there will be some bays and other colors, as all colors are

represented in the Belgian breed. They do not all sire the white mane

and tail but many of the colts are so marked.

Mr. A. W. Hawley, of Pioneer, Ia., says:

I had a beautiful light mane and tail chestnut from a black Belgian

mare and a black Percheron stallion.

The roan stallion above referred to doubtless corre-

sponds exactly to either type No. 7 or No. 8 of Shorthorn

cattle, the dominant duplex white always persisting and

the hairs of the second network remain either red or

black, making the familiar ‘‘red-roan’’ or ‘‘blue-roan,’’

depending upon the gametiec composition of the dam,

epistacy and the laws of chance. Belgian horses resemble

Shorthorn cattle in that they are a breed of many colors,

including the interesting roan. Indeed, the roan, silvered,

barred, ‘‘agouti,’’ mottled, piebald, flea-bitten and other

variegated types of animals of all species so charac-

terized seem to behave in inheritance in a manner typified

by the roan Shorthorn.

While the mane and tail are generally of the same color

as the adjacent body coat, there is often. a pigment

differentiation—the coarser hair whitening first. This

phenomenon is also exemplified in the case of black or —

: spotted eats, which often have white ‘‘mustaches’’ grow-

ing from black or dark skins and coats, but never the —

reverse. Among wild animals the silver fox and the

10 THE AMERICAN NATURALIST [Von. XLVI

silver-tipped bear present instances of the whitening

process beginning with the hair tips. Recall, in this con-

nection, the lighter colors sometimes present on the hair

tips of the cattle crosses reported by Professor Went-

worth, and the ‘‘albinic’’ superficial tissues of the Silkie

fowl with its pigmented deeper tissues. Thus it seems

that with mammals and with some birds the whitening

process begins with the more superficial tissues and con-

tinues to the deeper ones; with mammals, coarse hair,

fine hair, skin, nail, sclerotic, iris, choroid, being the order

followed.

Permit a short digression into the plant kingdom. Of

the two or three hundred varieties of the dent corn, all

of the yellow and red varieties have red cobs and all of

the white varieties have white cobs, with the exception of

St. Charles County white, which has a red cob.

Jack-stock breeders in America are making an effort to

establish a ‘race of black animals with white points, and

the following evidence, while primarily bearing on this

problem, is typical of the behavior when not involving

the whitening process of pigments of domestic animals.

In the Breeders’ Gazette, May 10, 1911, a breeder states

this problem:

A jack is of good size, well made in every way but he is of maltese

color. He is exactly the color of his sire and his sire was a popular

jack in his locality and a first-class mule-getter. Is this color a real

objection? What is the prevailing color of mules sired by the mal-

tese-colored jacks?

To which L. M. Monsees, of Sedalia, Mo., the jack-stock

breeder and authority, responds:

I have seen some extra good mule jacks of the maltese color. A

maltese or blue jack, if from a good, large family of good blood, and

himself a good individual, will no doubt prove a good breeder. He

should be expected to get good solid colors—bays, blacks, browns,

blues and chestnuts.

Thus it seems probable that, when different parental

pigments, but not the whitening process, are involved, the

No.541] INHERITANCE OF COLOR IN CATTLE 11

pigments of the offspring are due to either a simple Men-

delian mixture of various dilutions of parental pigments

with their resultant hypostatic effect, or to minor reaction

between the determiners presented by the two parents

resulting in modified pigment bodies.

Barrington, Lee and Pearson’s study of color in the

eray-hound—Biometrika, 1904—presents evidence that

might well be given such an interpretation. Their elabo-

rate tables measure accurately the correlation of the

color of ancestry and offspring in this animal, but they

do not explain what takes place in the zygote upon its

creation by the union of two somewhat differently

organized and differently descended gametes ; nor do they

clarify the conception of gametic organization. It is,

however, primarily a study in the mathematics, not the

chemistry, mechanism nor biology of inheritance.

The black mane, tail and feet of the bay and of some

blue roan horses, and the white mane, tail and feet of the

chestnut Belgian seem to indicate that in horses the

whitening process may proceed somewhat out of synchro-

nism in its tissue and area sequences. The white mane

and tail seem to be causatively correlated with the chest-

nut coat of the Belgian, which white seems to be recessive

to the heavier pigments. Moreover, when the destroying

process attacks highly organized pigment bodies, is the

destruction always complete? May there not be resting

stages in this destruction and may not the series—blacks,

browns, bays, chestnuts, sorrels, duns and creams—be-

sides being different dilutions and hypostatic effects of

different pigments, represent these stages? Further-

more, may there not be a pigment sequence as well as

an area, tissue and ontogenetic sequence involved in the

whitening process? And are the chestnut, sorrel, dun

and cream pigments the ones most readily destroyed by

the antibody?

Note in this connection that in dogs and other mammals

having some individuals with black, tan and white areas, _

the black areas are quite often bordered by a zone of tan,

12 THE AMERICAN NATURALIST (Von. XLVI

and often small tan but rarely small white spots are

found within the larger black areas. These are the con-

ditions expected if the tan were an intermediate product

resulting from the attack of the destroying antibody

upon the determiner for the heavier pigmentation. The

sequence of color bands along the hairs of the wild and

agouti cavies, viz., heavily pigmented brown tip, yellow

band and leaden base, is also suggestive of the same

derivation of the yellow.

Besides an area progression and a tissue progression

involved in the whitening process in animals, there is

also an ontogenetic progression of the same process.

In man and in many pigmented animals a progressive

grayness, called ‘‘senile white,” comes with old age, in

some strains earlier than in others. White horses—

dominant white—are always born pigmented, but soon

change to white—juvenile white, it might well be called.

White Leghorn fowls are hatched white and, save for a

senile deposit of pigment, remain so.

The observed facts seem to demand intra-zygotie in-

hibition and reaction quite closely approximating the

following hypothetical processes: In a germ cell of

some heavily pigmented animal, say, of a black Angus

bull, let there be a specific chemical determiner (N) for

black pigment in the entire skin and hair coat and in the

sclerotic, choroid and iris. This determiner reacts like

and indeed may be a body closely related to the enzymes,

in that both may be weakened, exhausted, or totally in-

hibited without being impaired or destroyed by the pres-

ence of varying amounts of an antibody of some sort,

still greater amounts of which set up chemical reaction

resulting in partial or total destruction, depending upon

the relative quantity and intimacy of the two bodies in

much the same manner as trypsin is totally inhibited

but not destroyed by .05 per cent. of lactic acid, but is

totally destroyed by .1 per cent. of hydrochloric acid."

_ In the germ cell of a white mate of the aforementioned

1 Green, ‘The Soluble Ferments and Fermentation,’’ p. 198.

No. 541] INHERITANCE OF COLOR IN CATTLE 13

animal let there be an antibody (W) (analogous to the

acids in the above illustration) substituted for and

placed homologously to the determiner (N) for black

pigment, which antibody is capable of weakening, in-

hibiting and finally of totally destroying the deter-

miner according to the relative quantity and intimacy

of the two bodies. Let this antibody (W) exist in a

quantity large enough to totally inhibit the ontogenesis

of N, but not to effect its destruction. Now let fertiliza-

tion take place; the F, generation is white. A white so

behaving is said to be dominant. Because there was

only inhibition of N with no chemical reaction between

N and W, and segregation may take place in later gen-

erations according to the familiar formula, F, is said to

be simplex in reference to this unit character. If, how-

ever, the antibody in quantity sufficient for inhibition

makes its intrusion de novo into a gamete possessing a

determiner for N and this mutant germ cell meets

another of similar origin or descent, and the total

amount of the antibody is still sufficient to cause reac-

tion, a duplex dominant white offspring results, which,

mated with one of its own kind, will establish a race of

white animals, inhibiting somatically in heredity until

further disturbance by extraneous intrusion or by hy-

bridizing the determiner N. Animals of this sort upon

hybridizing—as Davenport has shown in his white Leg- |

horn crosses—may be made to yield the ancestral colora-

tion. If the antibody exists in quantity sufficiently great

to inhibit absolutely all of the determiner, with an excess

sufficient to cause chemical reaction destroying a por-

tion of N, then partial albinism results and the off-

spring, although entirely white, will possess some definite

areas of dominant white covering pigment, and others of

albinie white, breeding exactly like the white Short-

horns designated in this study as type No. 6. If, how-

ever, in the germ-cell of the white mate a still larger

quantity of W be present (exactly large enough to ef-

fect the total destruction of N) upon fertilization N and

14 THE AMERICAN NATURALIST [ Vou. XLVI

W react and are destroyed, the F, generation is white—

this time albinic white, mutants. W and N both being

destroyed, these animals are nulliplex and breed accord-

ing to the familiar formula.

As still another alternative, let W exist in still larger

quantities and the mating take place; not only is all of

N destroyed but there is an excess of W which gives

some areas of duplex dominant white not holding the

pigmented color as a recessive trait—in quite the same

manner as the Shorthorns designated in this study as

type No. 9 possess a coat solid white, some areas of

which are dominant white not covering the red and the

remainder of the areas are albinic white. A still greater

amount of W will apparently effect the total destruc-

tion of N, making the offspring in the entire coat duplex

dominant white, not holding N latent in the gametes and

not capable of ‘‘reversion.’’

Let the antibody exist in very small quantity, insuff-

ciently large to inhibit the ontogenesis of N, and let fer-

tilization take place. It is conceivable that the antibody

in such small quantity might have the same effect upon

N as alcohol has upon an enzyme, in which case N would

play its usual part in ontogenesis, but, being constantly

harassed by W, would finally be inhibited or destroyed.

The F, generation would then show senile grayness, as

in man; here again the most superficial tissues are first

attacked. If the antibody (W) is a trifle more concen-

trated the F generation will be born pigmented, but will

develop juvenile white, as with the white horse, which

as previously described is born with pigmented hair

and skin—the skin remaining black and the hair turning

white. Thus the process seems to be progressive, de-

pending upon different intrusions de novo—‘‘muta-

tions’’—and different inheritance lines for the pre-

sentation of various quantities of the antibody effecting

the destruction of N in a definitely progressive onto-

genetic, area and tissue sequence.

This is the hypothetical picture of intra-zygotic reaction

No.541] INHERITANCE OF COLOR IN CATTLE 15

demanded by the somatic behavior in inheritance of coat

pigments and patterns in Shorthorn cattle and in the

other instances above cited.

Now, let some further observations be reported and

then fitted to this conception for its support or rejection.

In the Breeders’ Gazette (April 12, 1911) in response

to an inquiry concerning the behavior in inheritance,

with special reference to the possibility of spotted off-

spring of a white stallion, described as follows:

He is white with pink skin and would be albino but for a very few

small specks in the skin and his dark eyes.

Dr. W. E. Castle answers:

The dark-eyed white condition is closely related to the piebald con-

dition. It may indeed be regarded as an extreme variation of the

piebald state in which the white spots cover the entire body except the

eye. Most black-eyed white animals produce a certain number of

piebald offspring, even when bred to animals exactly like themselves.

In reply to a request, W. P. Newell, of Washburn, Ill.,

the owner of the white stallion, supplies the following

data:

The albino offspring of my stallion do not have pink eyes, but have

“ glass” or “ watch ” eyes.

Their hoofs are white or flesh color; there are no spots in the skin

and not a colored hair on them. Not all of his white colts are albinos,

some of them have a few colored hairs in mane or ears; these I do

not refer to as albinos.

As a two-year-old this stallion was bred to six mares. Each one of

these six produced a white colt..

As a three-year-old he had thirty-nine mares; got thirty-three in foal.

About half of these were white, the others solid colors. These mares

were very ordinary and of all colors, every size, shape and age. Fol-

lowing are a few of the instances: Bay mare got white colt; bay got

black colt; two blacks got white colts; black got black colt; white and

buckskin spot got pure albino; dapple gray got white colt; flea-bitten

gray got white colt; three or more brown mares got white colts; two or

more brown mares got brown colts; brown mare got pure albino; one

sorrel got pure albino; one sorrel got brown colt. This will give you

an idea of how his colts are colored.

Nothing is given and not much can be deduced con-

16 THE AMERICAN NATURALIST [ Vou. XLVI

cerning the gametic make-up of these brood mares, but

this interesting stallion seems to be barely on the domi-

nant white side of the critical border between dominant

white and albinic white. Had the whitening factor been

a little more concentrated in the zygote giving rise to

him, doubtless the ontogenesis of his choroid would have

been inhibited or destroyed, the determiner for much

of his more superficial pigmentation would have been

destroyed and he would have been a true albino. Some

of his germ cells seem to contain the antibody W in

quantity and distribution adequate to inhibiting the

quantitatively definite determiner for pigmentation

found in some of the gametes of many pigmented mares ;

others of his gametes seem to lack this specific anti-

body, having in its place a determiner for dark pigmen-

tation, hence, he is apparently simplex with reference

to his dominant white determiners. If one of his

gametes possessing W unites with a mare’s gamete pos-

sessing pigmentation determiners greater than the

quantitatively definite determiner above referred to,

the inhibition will either not take place or it will take

place incompletely—in the latter case resulting in some

modification of the solid-color coat and skin condition.

If the mare’s gamete possessing less of the pigmenta-

tion determiners than the optimum quantity above re-

ferred to meets one of the stallion’s gametes possessing

W, the offspring will be white—dominant if the relative

concentration of the determiner and the antibody is such

as to cause only inhibition; recessive, i. e., ‘‘albinie” if

reaction occurs.

Let us consider the criteria of albinism. The general

conception among investigators and writers on the sub-

ject seems to be that all strains of albinos have origi-

nated through dropping from the germ-plasm deter-

miners for pigmentation previously possessed, rather

than to have descended from ancestral types never pos-

sessing such pigmentation. Generally an animal is

designated as ‘‘albino’’? when inhibition and reaction

No.541] INHERITANCE OF COLOR IN CATTLE 17

have covered the entire skin, hair, nail and eye pig-

ments. Castle'® in his ‘‘Heredity of Coat Characters

in Guinea-Pigs and Rabbits,” excepts ‘‘centrifugal’’

areas. There is, moreover, no reason to believe that the

pink eye of an animal may not result from the inhibition

of the pigment determiner as well as from its destruc-

tion. In the progressive development of whiteness from

senile white, juvenile white, dominant white covering

pigment, albinie white, to dominant white not covering

pigment, there seems to be, as we have seen, a species of

tissue resistance as well as of area progression to this

inhibition and reaction; the pigment of the deeper

tissues being more generally resistant, or at least slower

or later in succumbing to the attacks of the antibody.

These deeper tissues, when dark and covered by the

pigmentless tissues, give rise to a condition that is

proved by experimental breeding generally to be domi-

nant white. This is quite consistent with the present

conception, for if the skin below is still pigmented it is

quite probable that the hair pigments are only inhibited

and not destroyed, and by the time the inhibiting proc-

ess reaches the choroid, the destroying process is prob-

ably quite complete in the hair, and the animal is quite

‘properly designated as an ‘‘albino’’—recessive white.

It must be borne in mind, however, that albinism may be

either partial or complete; it may affect, the entire coat

color or it may affect only a limited area or a specific

tissue. In partial albinism the eye is often blue—the ab-

sence of superficial pigments but presence of the deeper.

Thus albinos become of great interest, and the study

of their behavior very complicated, on account of this

nascency of mutation. The intricate organization of the

_ gamete can be determined only by the study of its onto-

genetic sequence and end which, however, strongly sug-

gest that chemical bodies within the germ cell behave

exactly as such bodies within the test tubes of the lab-

oratory. The disturbance of a single determiner may

* << Heredity of Coat Characters in Guinea-pigs and Rabbits,’’ p. 9.

18 THE AMERICAN NATURALIST [Vou. XLVI

cause an accompanying correlation in something like the

following manner: Consider the determiner for some

definite somatic structure in a germ cell of one parent

to be destroyed by an antibody analogously placed in

the germ cell of the other parent; this chemical reaction

must leave a product, which product it is conceivable

may cause considerable havoe in so intricate a mechan-

ism. There is no reason to believe that this product

would of necessity confine itself to reactions with de-

terminers first attacked; it might indeed be conceived to

disturb or to destroy certain determiners for other

tissues and forms.

The Silkie fowl seems to have received a very

severe and peculiar upset in its determiners for

pigmentation—note its black eyes and black deeply

seated body pigments, together with its ‘‘albinic’’

plumage. Neither is there any probability, except

by chance, of parallelism or similarity between the

mechanical or chemical cause of such reaction and

the resulting determiners—a notion savoring some-

what of the earlier conceptions prevalent in some

quarters, of ante-natal influence—for Weismann?’ ex-

perimenting with Vanessa appears to have effected color

changes by means of temperature and Tower” to have

permanently upset that portion of the germ plasm of

Leptinotarsa determining pigmentation by means of

humidity and temperature. Thus, units may be made

and unmade, and thus a foreign body or force entering

a germ cell may conceivably cause a long series of reac-

tions, each product becoming a new reagent affecting

the determiners of many forms and tissues, if by chance

lethal damage is not done before equilibrium is reached.

Moore in his paper ‘‘A Biochemical Conception of

Dominance,” says:

When fertilization occurs, the germ cells bring into contact certain

substanees which are set free to react upon each other. Some of these

1 cí Germ Plasm,’’ p. 379.

%<í An Investigation in Chrysomelid Beetles of the Genus Leptinotarsa.’ ’

No. 541] INHERITANCE OF COLOR IN CATTLE 19

substances may react simply with cther substances and obey the Guld-

berg-Waage law of mass action, while others are of the nature of

enzymes (ferments) and accelerate reactions which are already going

forward at a very slow rate.

It has been many times demonstrated that a positive

determiner in a gamete of a simplex individual is not as

‘‘pure”’ as one from a duplex individual; furthermore,

a soma developed from a zygote made up of a gamete

containing a positive determiner, and another char-

acterized by its absence, is not as strong in the char-

acter in question as one produced by two duplex parents.

Thus, Davenport”? has shown that in mating dominant

white fowls with pigmented fowls there is often an ‘‘im-

perfection of dominance,’’ giving rise to some more or

less scattered pigmentation in F,; this he demonstrated

experimentally and, among other things, finds that

Two white Leghorns crossed by a black Minorea produced only white

hybrids, but the female hybrids at least had some black feathers. .. .

No barring resulted from crossing white Leghorn with . . . black

Minorca. . . . Of 26 hybrids between black Cochin and white P NE

8 were barred black and white.

And he concludes that—

alongside of dominance we must place an important modifying fac-

tor—the factor of the strength or potency of the representative of the

given character in the germ plasm. This is clearly a variable quantity.

If it is very potent we get a typically Mendelian result but if it is

weak, we will have imperfect dominance or failure to develop alto-

gether.

Thus the determiner for pigmentation in the black

Cochin seems to be more concentrated than the same

determiner in the black Minorca. Or is it possible that

the antibody, although present in quantities theoretically

in excess of the amount necessary for complete inhibition,

fails to effect such inhibition completely for the same

reason that the analogous phenomenon, due to some

aA Biochemical Conception of E University of California

Publications in Physiology, Vol. 4, No. 3, p. 11.

=‘<*The Imperfection of be reg American Breeders’ Magazine,

Vol. 1, No. 1, p. 42.

BO THE AMERICAN NATURALIST (Vou. XLVI

mechanical necessity, is commonly observed in chemical

experiments?

Obviously, the mass of the determiner for pigmenta-

tion is as potent a factor in determining the end result as

the mass of the destroying antibody. The kind or quality

of the pigment seems also to be a factor; the yellow or

sorrel pigments seem to be destroyed more readily than

the black or brown. It is also apparent that, due-to a

difference in the relative mass of the determiner and the

antibody in the zygote, one cross may affect total destruc-

tion of the pigment while another parallel or reciprocal

one may not. Thus, as above mentioned, Davenport’s

white Leghorn on black Minorea cross gave only white

or nearly white offspring, while his parallel cross, viz.,

white Leghorn on black Cochin, gave considerable black

pigment in the offspring. It has also been observed that

the barred Plymouth Rock male, which is much less

heavily pigmented than the female, when mated with a

white Leghorn female gives only white offspring, but

- the reciprocal cross, viz., the white Leghorn male on the

barred Plymouth Rock female gives barred, mottled,

gray, creamy and white offspring regardless of sex. In

this latter mating the two gametic elements, viz., the de-

terminer for pigmentation and the destroying antibody,

seem to be present in quite closely chemically balanced

masses and it would be interesting to know whether in

this cross the fluctuations across the color line are due to

accidental variations in the strength of the individual

gametic elements in question or to the Mendelian phe-

nomenon.

There is still another white possessed by birds and

mammals known as ‘‘structural white,’’ characterizing

some arctic animals such as the arctic fox, which is white

the year around, and the arctic hare and the ptarmigan,

which are pigmented at one season and white at the

other. It would be interesting to know whether the fur

and feathers of these animals in their unpigmented

phases possess oxidized pigments. There are, more-

No. 541] INHERITANCE OF COLOR IN CATTLE 21

over white pea fowls. The gorgeous hues of the common

pea fowl are due both to pigments and to defraction and

it would be interesting to know whether the white pea

fowl has lost its pigments or defraction surfaces, or both.

Animals of heavy pigmentation—as the blackbird,

the crow and the negro—are said to be more subject to

pre-senile and albinic white than others less heavily pig-

mented. Enzymes may be inhibited or destroyed by an

excess of their own products. May it be indeed that the

antibody (W) is itself a product of the determiner (N)?

To throw further light upon the whole problem, among

other things, a careful study should be made of the be-

havior in inheritance of the age of graying of the hair

and beard in man. If the conclusion of this paper pre-

sents a true picture, early graying of the hair and beard

will be found to be dominant over the later manifestation

of the same phenomenon. It is further anticipated that

a chemical analysis of senile white and juvenile white

tissues will show the same absence of somatic pigment as

Gortner2* has shown in his study of albinic and dominant

whites.

In this study of Shorthorn cattle nine theoretical game-

tic coat-color types are defined. As previously stated, the

striking fact is this: The roan of type No. 3 (which is

reciprocally colored as compared with the ordinary color

pattern of cattle) is never observed, and quite probably

the red of type 2 is also missing. The reason is appar-

ently as follows: The antibody inhibiting and destroying

the determiner R (for red pigment) first attacks through

mechanical and chemical necessities the determiner for

coat pigment in the somatic areas of Set 1 (roughly—

flank, heart girth, forehead) and progresses systemat-

ically through the areas of Set 2 (roughly—underline,

barrel, legs and quarters, head and neck) according to the

following scheme:

= íí Spiegler’s ‘White Me’anin’ as related to Dominant or Recessive

White,’? THE AMERICAN Naturatist, Vol. XLIV, p. 501. ;

22 THE AMERICAN NATURALIST [ Vou. XLVI

TABLE VIII

| Gameti e |. Ga ametic | Number of, Examples of Some

Class | Formula for| che ses ar ‘Inheritance Breeds of Cattle

ve | Ament of Antibody | Areas of Unitsin | Representative of

tage | resent | First At- | pe At lEntire Coat the Respective Rest-

ieee ack. | ack, | Pigmenta- | ing Stagee of od

| (Set 1) (Set 2 J tion Whiten ng Proces

—| —— ——— | --

1. (None or too little to w,P, w,P, | One. Angus and solid

| start inhibition. black breeds

| | enerally.

determiner for pig- | two spotted breeds

mentation of the areas groups. | generally.

of Set 1.

3. | Enough o Wi WLP, | WPi | One. White park

hibit the | rete bod | | cattle of Bri-

| tain.

4. nough more to start| w.p, | W,P, | Two or |Not fe neat

reaction and to de- two b i breed

stroy the determiner | | groups. | nor ever ob-

for pigmentation of

the areas of Set 1.

5. nough more to con-| Wp

served in mon-

One. Casita albi-

WP2

Two or|White Short-

horns of Type 9

W2P2 |

| tw

ody in place of deter- | | | groups. | of this paper.

e j

6. | Enough more to de- | WP:

it anti- |

7. |Enough more to de- W,p, W.p, | One. Remotely pos-

sible that some

y in place of deter- | | strains of British

miner for pigmenta- | | white park ss

tion of areas of Set 2. | are of this type.

W = presence of antibody. P = presence of determiner for pigmentation.

w = absence of antibody. p = absence of determiner for pigmentation.

In Shorthorn cattle, classes 4, 5 and 7 of this table are

not met with, neither are conditions parallel to class 4

ever observed in any other mammals. The further expla-

nation may be as follows: Reaction between W and R does

not begin until an excess of W is present (a condition not

hard to parallel in the chemical laboratory) but when

reaction does begin it is quite rapid, destroying all of R

and most likely leaving an excess of W at the point of

first attack. This would eliminate Class 4 (type 3 of

the series previously described) and Class 5 (pure

albinos) of this table. There may be ‘‘albino’’ cattle;

No.541] INHERITANCE OF COLOR IN CATTLE 23

Pearson** reported a rumor of a herd of such but he was

unable to locate it. Wilcox and Smith” describe a race of

white cattle—Polled Albino—made by crossing a white

Shorthorn cow with a polled bull of unknown breeding.

The Swedish cattle were thought to possess ‘‘ pink eyes’”’

and if so were probably albinic in their entire coat; the

Polled Albinos are doubtless ‘‘partial albinos.” White

Shorthorn cattle are generally blue-eyed, however, a con-

siderable percentage are brown eyed.

The following chart of the ancestry and offspring of

‘White Rose,” the first cow purchased by Mr. J. F

Hagaman, of Leonard, Mich., is prepared from data sup-

plied by him:

Far ass set

Koan

a Cot toet Banes re Spring wood

Rr,

Whitt

Roars.

Cuart No. 3 ý

He aiso writes:

I purchased another cow, Daisy Dean, red and white. All her an-

cestors were red, red and white, or roans. She was bred to Park Farm

Prince (roan) and produced twin bull calves both white. They were

exactly alike and were made into steers. A drover took them to Bos-

ton where they sold for $500. ... All the white calves had blue eyes,

flesh-colored noses and light skins.

Dr. D. M. Kipps, of Fort Royal, Va., writes:

I feel sure I never had a white Shorthorn with a black nose; I had

one or two that had slightly cloudy noses. I think every one had pink

“(On the Inheritance of Coat-Colour in Cattle,’’ Biometrika, 1905-06,

p. 436. É

21‘ Farmers’ Cyclopedia of Live Stock,’’ p. 369.

24 THE AMERICAN NATURALIST [ Vor, XLVI

skin underlaying the white coat and nearly every one had slightly

reddish hair on the inside and around the outer rim or auricle of the

ear.

Mr. J. H. Hawkins, of Xenia, O., writes:

Will say I have never seen a white Shorthorn with pink eyes. My

white Shorthorns have pure white coats, pink skins and brown eyes.

As to black noses, they are not a rare thing to see . . . now and then.

Shorthorn cattle were made from the Anglo-Saxon reds

—Class 1 of the above table No. VIII; the Flecking—

Class 6; the Romano-British—Class 3, and probably some

other primitive types. Evidently none of the breeds of

domestic cattle has yet reached stage 7, i. e., solid domi-

nant white not capable of reversion. The Shorthorns of

to-day present all the possible combinations of Classes 1,

2, 3 and 6.

In reference to the fact that the race of duplex yellow

mice has never been produced and in view of what Castle®

says,—viz., that the union between germ cells carrying

only yellow pigment is doubtless affected, still all such

germ cells from some cause are doomed to destruction,

may it not be that in so delicately adjusted a mechanism

two of these specific determiners present a lethal dose?

May this not be one of the causes of the limits of hybridi-

zation and of the sterility of hybrids? The germ cells are

doubtless distinguished by both a specifie architectural

and a specific chemical organization of the greatest nicety

of adjustment and balance. The closest approach in the

chemical world to their behavior is that of the enzymes,

which, though not entering into reactions, may bring them

about; while in the course of its own continuity the germ

plasm gives rise to cells of its own kind, supplying them

with bodies behaving in an enzyme-like manner sufficient

for their own continuity and for a long series of onto-

zenetic processes.

It is obvious that a disturbance of some consequence

would follow the advent of a foreign body or of unusual

æ ‘í Modified Mendelian Ratio amorg Yellow Mice,’’ Science, December

16, 1910, Vol. XXXIT, p. 868.

No. 541] INHERITANCE OF COLOR IN CATTLE 25

quantities of a normal body presented either by hybrid-

izing or by osmotic intrusion; perhaps it may clarify the

conception to make analogy to the degree and sequence

of reactions in test-tubes or other containers of more

complicated design holding the same chemical in varying

quantities, places and degrees of nascency, wrought by

the addition of varying quantities of the same reagent.

The inhibitions and reactions expected from such condi-

tions would begin at definite places, would continue in a

more or less definite suecession characteristic of each set

of conditions, would complete a reaction first in definite

parts and would proceed with varying degrees of speed,

might effect a reaction and deposit an excess of reagent in

some parts before even reaching other parts. Let there

be an equilibrium following reaction; then add more of

the reagent or of the chemical acted upon and it is easy

to picture subsequent reactions all of which are closely

analogous to the processes which the study of Shorthorn

cattle leads us to believe have taken place within their

gametes and zygotes. The behavior of their coat color

and that of many other animals demand such behavior

within the zygote. Thus such processes seem to account

for the coarse mosaic or the spotted, and the fine mosaic

or the roan color coat, the imperfection of dominance,

reversion, the origin of the mottling and barring of fowls,

the progressive dappling of horses, the peculiar behavior

of ‘‘albino’’ guinea pigs, the characteristic behavior of

coat pigment and patterns in Shorthorn cattle, and other

similar phenomena. The stag, but not the doe, caribou

possesses a beautiful white collar, and it may be that sex-

limited characters are wrought by a sort of ‘‘havoec’’ or

series of progressive reactions, preceding chemical equi-

librium caused by the introduction of the essential sex-

determiners. :

A human family is recorded? in which a pre-senile

gray spot oceurs in the beard of the left cheek of many

of its male members. In possible explanation, it is sug-

= Files Eugenies Record Office, Cold Spring Harbor, L. I.

26 THE AMERICAN NATURALIST [Vou. XLVI

gested that a small quantity of some antibody somehow

inhibited or destroyed a portion of the determiner for

pigmentation in the germ cell from which this family

sprung. This indeed points toward a possibility that unit

characters may arise from a partial destruction of larger

units; that a determiner for a unit character behaving

precisely in unit fashion may be a complex capable of

being shattered into a large number of independently be-

having ch ters. Small as the germ cell is and quanti-

tatively insignificant as the determiner for the skin and

hair pigment must be, the facts demand that this body

consist of many molecules arranged in definite structure,

each one destined for a somewhat definite ontogenetic

process leading to a definite somatic end. Thus the often

inherited specific color mark seems to indicate that a

color pattern once produced—no matter how intricate or

complex—will reproduce itself exactly until its deter-

miners are disturbed by unbalanced bodies or forces pre-

sented by fertilization or otherwise.

The Shorthorns are a race of white cattle caught in the

making and preserved in the nascent state by a rigid selec-

tion. It is thus conceivable that mutations may arise

constantly, and that they may be progressive in char-

acter. Complications resulting in somatic effect are

legion, but nothing occurs in the germ cell giving rise to

new ch ters, splitting up and combining others and

dropping out still others, that can not be analogously

pictured with the simple operations of the chemical

_ laboratory, and as Shull ’s?s illuminating ‘‘Simple Chem-

ical Device to Illustrate Mendelian Inheritance’’ seems

to indicate, the analogy is too constant and too far-reach-

ing to be cast aside as a mere pedagogical device. It may

indeed be a simple statement of facts of intra-gametic

and zygotic behavior and the analogy may no longer be

needed to picture the actual conditions.

*The Plant World, Vol. 12, pp. 145-153, July, 1909, and companion

paper, ‘‘The ‘Presence and Absence’ Hypothesis,’’ THE AMERICAN NAT-

URALIST, Vol. XLIII, No. 511, pp. 410-419, July, 1909.

No. 541] INHERITANCE OF COLOR IN CATTLE 2

The evidence of this study of Shorthorn cattle is to

support that theory of unit segregation incompatible with

a somatic blend in the ultimate unit, and that theory of

heredity permitting intra-zygotic inhibition and reaction

in response to specific set conditions.

The mutually corroborative evidence of the authentic

history of this breed of cattle, the behavior of their coat

pigments and patterns as recorded in the most extended

authentic records of pedigree breeding of domestic ani-

mals, analogy to the occurrence and behavior of pigments

in other animals, and the close fitting of the final work-

ing hypothesis, amply justify the following conclusions:

1. Shorthorn cattle as a race possess two kinds of white

hair. (A) White, dominant to all pigments (analogous

to the white of the Leghorn fowl) in a series of areas

varying somewhat: in size and shape but in a given indi-

vidual always definite and genetically independent—a

few at the front flank belt, a larger number or larger

areas about the rear flank belt, a few along the underline

and a fine network covering the remainder of the body.

A few animals from their Romano-British ancestry have

the entire coat of dominant white. An area of dominant

white may be duplex or it may be simplex. In the former

case its possessor will throw only gametes with deter-

miners for dominant white; in the latter alternately ga-

metes with determiners for dominant white and for red.

(B) White, recessive to all pigments (analogous to the

white of the Silkie fowl) in a series of definite areas gen-

erally smaller than those of the dominant white, forming

a fine network about the neck and head, the sides and

back, and the hind quarters and legs—quite precisely

excluding the areas of the dominant white network.

From their Dutch ancestry, this mosaic may in some

strains be quite coarse. It is doubtful if a strain albinic

white in its entire coat exists within the Shorthorn breed.

2. The color effect of an indiviđual Shorthorn is deter-

mined by the registering of fortuitously one of the alter-

nate color phases of each of the genetically independent

28 THE AMERICAN NATURALIST | Vou. XLVI

color areas gametically possessed by each of the two par-

ents, together with such intra-zygotic inhibitions and re-

actions between the determiner for pigmentation (R) and

the antibody (W) as may result from definite concentra-

tions and intimacy of these two bodies presented by the

two parents upon the formation of the zygote.

SUPPLEMENTARY OBSERVATIONS ON THE

DEVELOPMENT OF THE CANADIAN

OYSTER

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

BIOLOGICAL STATION, DEPARTURE Bay, B. C.

In the Amertcan Narurauist of January, 1905, Janu-

ary, 1909, June, 1910, I have given some account of obser-

vations (in 1904) on the development of the oyster at

Malpeque, Richmond Bay, Prince Edward Island, Canada.

Opportunity to verify, continue, and extend these ob-

servations was again afforded in 1909, when I studied

the oyster in the most important centers along the east

coast of New Brunswick.

In the present summer, 1911, being occupied at the

Pacific Biological Station of Canada, in Departure Bay,

near Nanaimo, Vancouver Island, I have the privilege of

observing some of the Prince Edward Island oysters

transplanted to this vicinity in 1905, as well as adding to

my acquaintance the little British Columbia oyster, so

different in size, appearance, habits and reproduction.

In the intermediate years, not being located in oyster

regions, I devoted a good deal of time to other bivalve-

larve, largely with a view to making my studies of the

oyster more secure, the main results of which have been

given in a paper ‘‘On the Recognition of Bivalve Larve

in Plankton Collections,’’? unreasonably delayed in publi-

cation at Ottawa.

Tn all this work I have kept sample preservations with

dates and ‘localities, which have often proved of great

service in judging of questions that subsequently arose.

My first work began where that of Brooks left off, and

showed for the first time that later stages of the oyster-

larva undoubtedly exist, and when, where and how they

30 THE AMERICAN NATURALIST [ Vou. XLVI

may be procured, as well as the length of the period of

their free-swimming life. The larve obtained by Brooks,

Rice, Ryder, Winslow, and others were obtained by cul-

ture from fertilized eggs, and were at most six days old,

and in the young straight-hinge stage. In Europe larve

of a similar age, size and structure had been taken from

the infra-branchial cavity of the parent oyster by Da-

vaine, Lacaze-Duthiers, Costé, De la Blanchére, Gwyn

Jeffries, Saunders, Salensky, Mobius, Horst and Huxley,

but the older, later or larger stages were quite unknown.

This left room for some speculation as to the exact time,

place and manner in which the succeeding stages should

be found, as well as occasioned the prevalent mistake that

the free larva settles down at this period to become a

fixed spat. Brooks wrote. ‘‘All my attempts to get later

stages than these failed . . . and I am therefore unable

to describe the manner in which the swimming embryo

becomes converted into the adult, but I hope that this

gap will be filled, either by future observations of my own

or by those of some other embryologist.’’ In a similar

way Jackson, at a later period, speaks of ‘‘a blank in the

knowledge of the development of the oyster.” This

‘‘gap” or ‘“‘blank’’ is now completely filled. My studies

prove that the larva continues to live as a larva in the

sea-water about oyster-beds for two or three weeks

longer, where it swims about, feeds, grows and changes

in structure, and that it first settles down to become a

sedentary spat, fixed to shells or other objects, at an

age of three to four weeks from fertilization—the length

of time depending to some extent on temperature, food,

individuality or such causes. This information has been

gained through the method of procuring oyster-larve

from the waters of oyster-areas by means of a plankton-

net, and connecting them in series with younger stages

obtained by fertilization and culture and with older

stages obtained by catching spat on glass, shells, ete., so

as to make out the complete life-history.

The discovery that the hitherto unknown stages of the

No. 541] THE CANADIAN OYSTER $1

oyster-larva can be conveniently obtained by a plankton-

net carries with it the possibility of a practical applica-

tion of inestimable value in the culture of oysters. From

the time of the early Roman Empire it has been known

that oyster-spat can sometimes be obtained on ropes,

anchors, piles of wharves, stones, shells or other natural

or artificial objects in the sea, and some sort of method

of culture has long been in use in many countries. At

times men have risen to exalted conceptions of the possi-

bility of finding a practicable, safe and sure method of

catching, retaining, and rearing the young spat. I quote

Winslow to the effect that ‘‘Thousands of dollars would

be annually saved by the Connecticut oystermen if they

could determine, with even approximate accuracy, the

date when the attachment of the young oyster would

occur. Hundreds of thousands would be saved if they

had any reliable method of determining the probabilities

of the season.” This is now possible.

It is well known that oyster or other shells dried and

whitened in the sun form the very best oyster-collectors

or cultch. To put these back into the water haphazard

has often resulted solely in the loss of all the labor of

preparation. In even a few days they may become cov-

ered with a slimy coating which reduces or largely

destroys their efficiency. The point is to be able to deter-

mine with accuracy, for each season and for every local-

ity, when oyster-larve are present in the water full-

grown and ready to settle as spat, so as not to run the

risk of losing adequate value for the laboriously pre-

pared cultch.. A man instructed and qualified in the

method of taking plankton and in identifying oyster-

larve can tell almost to a day when is the proper time to

put out cultch so as to obtain an abundant and copious

set of spat. It is not enough to know about the time, or

to know the time for certain previous years, or to know

the average time.

Three methods are open to the expert: (1) Examina-

tion of the genital organs of adult oysters to determine

32 THE AMERICAN NATURALIST [Vou. XLVI

when the eggs are ripe, (2) examination of the sea-water

to learn if oyster-larve are present and in what stage,

(3) examination of natural or improvised objects in the

water to discover if young spat are already formed. The

first is not immediately determinative because of the long

period of development separating spawning and spat-

ting. The last is not very practicable because of the diffi-

culty of finding and recognizing the youngest spat before

the period is gone by for putting out cultch. The second

is the only practicable and conclusive method and its

efficiency is proportionate to the number, care and ac-

curacy of the observations. Its success will increase with

experience.

This method makes use of the colossal number of larvæ

lavishly provided by nature to offset the exigencies and

accidents of life and insure a reasonable chance of keep-

ing up the stock. I believe that all the larve an army of

men could raise up and turn into the sea would not ma-

terially alter the number of successful individuals in the

set of spat. But on the other hand a few culturists could

enormously increase the chances for a successful catch

by spreading an abundance of suitably prepared cultch

at the proper time and place.

In the paper of 1909 I have described the method of

obtaining plankton, the appearances and measurements

of the oyster-larve to be recognized, the time of the year

to begin making observations. In the paper on ‘‘Bivalve

Larve’’ I distinguish in sizes, shapes, colors, the com-

monly occurring associates of the oyster-larve which

might be taken for the latter. In the present paper, after

long reflection, I suggest a practical application of the

knowledge acquired.

I should not omit to mention that the paper of 1910

connects the larva, through the youngest microscopic

spat, with the macroscopic spat of fishermen and finally `

with the adult. Similarly in 1909 I performed extensive

artificial-fertilization experiments, while at Shediac,

Caraquette and Malpeque, in order to connect the small-

No. 541] THE CANADIAN OYSTER i

est plankton stages of oyster-larve with culture-stages

and through these back to the egg. Larve by the million

were reared in beakers of sea-water at a temperature

little above 20° C. and with a specific gravity (salinity)

varying somewhat under 1020. I also carried Caraquette

oysters to Malpeque and raised up larve from eggs cross-

fertilized between two such obviously different varieties

as the small, narrow, curved, thick, hard and heavy Cara-

quette oyster and the fine, large, broad, straight, clean,

smooth specimens from the Curtain Island beds.

In 1896 and again in 1905 the Canadian Government

had Atlantic oysters transshiped to the Pacific and put

out at selected places. In the latter year some of the

places were chosen by Captain Kemp, expert in oyster

culture.

Being occupied this summer at our Pacific Biological

Station, I have taken advantage (although not requested

to do so) of my proximity to three of these places to

search for the transplanted Prince Edward Island

oysters, and to examine plankton taken in the vicinity.

At the first place, Hammond Bay, being a small bay and

close to hand, I could easily over-run all the beach at low

water, and soon discovered the dead shells that had been

deposited too far above low-water mark. At Nanoose

Bay, some twelve miles away, perhaps five miles long and

a mile and a half wide, with extensive flats at low tides,

this was not so easily done. Having spent three summers

with Captain Kemp, I thought now to test my judgment

of where he would select to deposit the oysters. As the

tide was unfavorable at my first visit I used the dredge,

and was afterwards surprised to learn that I had actually

calculated to within a few rods of the place. At the

second visit I went to look at other parts of the bay, but

on the third returned and, with a favorable tide, could

wade and pick up some of the oysters. This was at 3

P. M., July 17, and I took 16 fine living specimens of the

Malpeque oyster for examination—two or three of them

with pieces of Prince Edward Island red-sandstone still

34 THE AMERICAN NATURALIST (Vou. XLVI

attached to them. They varied from two and three

fourths to five inches in length, some of them showing

considerable growth. This proves that Atlantic oysters

can be transplanted to the Pacific and remain healthy

and grow. Upon reaching home I proceeded to examine

some of the oysters and it turned out that only one had

already spawned while the other fifteen were ripe and

generally somewhat distended with eggs or sperm.

This proves that the transplanted oysters can come to

maturity and ripen the reproductive elements.

At 7.10 P. M. of the same day I put together eggs and

“sperm in a tumbler of sea-water and at 7 A. M. next

morning there was an abundance of segmentation stages

and free-swimming larve. This proves that the oysters

can spawn and that the eggs can develop into young. I

make these statements because of a prevailing opinion

that the transplanted oysters have all died, and the few

people who think there are still some living are dogmatic

in their assertion that they do not breed.

Plankton taken at intervals at Hammond and Nanoose

Bays had not yielded any oyster larve, which became ex-

plainable upon finding the condition of the reproductive

organs. A further observation on this was afforded on

the 26th of July, when I examined a second lot (obtained

at a very low tide the day before) from Nanoose Bay.

The forty-seventh oyster examined was the first to yield

good ripe eggs—all previous ones were spawned with the

exception of four or five which were ripe males. The

interval between these two visits had been the hottest of

the summer and the oysters had nearly all spawned in

this period—slightly later than is usual on the Atlantic.

On the 27th I made a trip to Oyster Harbor (Ladysmith),

about fifteen miles from here, where I had better luck in

getting track of the few transplanted oysters. In a-

similar way I examined several individuals and took

plankton which for the first time contained larve of the

Atlantic oyster—recognizable by their shape and meas-

urements but not presenting such a deep pink or brown

No. 541] THE CANADIAN OYSTER 35

coloration as in their native home. For comparison

with my former papers I will give the measurements of

a single specimen with the characteristic postero-dorsal

high umbos, the large convex left valve, and the smaller

and flatter right valve, velum, foot, pigment spot and the

rest. Ocular V, objective 4, 42 long by 37 high

(—.289 x .255 mm.). This proves that larve grow up.

There is only one other bit of evidence possible and that

is to find spat. This I have not done as yet. It is too

early for this year’s spat and I have not seen any un-

doubted specimens of a former year’s spat. One can

judge that the comparatively few descendants of two

and a-half barrels deposited at Hammond Bay, five

barrels at Nanoose Bay, and one barrel at Oyster

Harbor, when dispersed over the broad areas at their

command, would not prove very conspicuous objects,

which is again complicated by the presence of millions of

British Columbian oysters of varying sizes, shapes, and

complexions.

I regard my findings as conclusive and would urge the

transplanting of Atlantic oysters (Ostrea virginica

Gmel.) to the Pacific in greater quantities. The At-

lantic clam (Mya arenaria L.) has propagated enor-

mously here notwithstanding the fact that it has more

competitors in its particular habit than in its original

home.

Ostrea lurida Carp.—Even before making any head-

way in the foregoing researches, I had begun to gather

information on the occurrence, size, shape, color, struc-

ture, breeding, etc., of the British Columbia oyster.

This species is not common in Departure Bay, or in

Hammond Bay, but a few specimens may be found under

stones exposed at about one hour from low water in

front of the C. P. R. cable house in the former, and just

inside the far point of the latter, and are usually so

broadly and solidly attached (with the left valve against

the under side of the stone and hence uppermost) that it

is scarcely possible to separate them without destroying

36 THE AMERICAN NATURALIST (Vou. XLVI

the attached surface. But on the extensive flats at the

upper ends of Nanoose Bay and of Oyster Harbor they

occur free on the surface by thousands and more or less

covered with barnacles.

Good specimens reach two inches in length by an inch

and a half in breadth, with a straight dorsal margin and

a semicircular ventral curvature. The right, upper or

smaller valve is nearly flat or but little convex and fits

into the margins of the larger, convex, lower or left valve,

the greater part of the lower and posterior margin being

scalloped, while the left valve has corresponding ridges

and points. The color is usually dark (those under

stones lighter) with the older parts weathered grayish

and the umbonal region of the left valve is often attached

to a small stone or another oyster or bears a scar. Imn-

ternally the shell is extensively pigmented, dark, with

smaller bands or blotches of lighter pearl, while the

muscle sear is rather lighter and banded. The mantle is

broadly margined with dark, which may also creep up

on to the abdomen.

The most interesting feature in connection with the

Pacific oyster of Canada is its divergence in some re-

spects from the mode of breeding of our Atlantic species.

In the British Columbia form there is no primary sepa-

ration of individuals into males and females—the sexes

are united in each individual. In other words each in-

dividual is bisexual, monecious or hermaphrodite. In

this respect it is identical with the English or common

European species (Ostrea edulis L.).

My first observations were made on July 12, on

specimens procured under stones near the Biological

Station. Nearly all appeared to be males, and, as they

were of small size, I took it that, as commonly occurs,

the males had ripened earliest. But one was of medium

size and contained eggs that at once attracted my atten-

tion on account of their large size, opacity and rare ex-

hibition of nucleus. Measured exactly as all my former

measurements, these gave: Oc. V, obj. 2—6.5; Oc. V,

No. 541] THE CANADIAN OYSTER 37

obj. 415; Oc. V, obj. 772. Another individual, ob-

tained since, with an abundance of eggs oozing from the

oviduct, pure and ripe, gave the almost unvarying meas-

urement of the egg as: Oc. V, obj. 775. This when

calculated is 75 X 1.45»—108.75» = slightly over .1

mm. = slightly over 450 inch — fully twice the diameter

of the egg of the Atlantic oyster, and perhaps identical in

size with the egg of the English oyster.

In making measurements it is important to use only

ripe eggs, as in this case, and to select those that are

spherical or nearly so and not flattened by the weigth of

the coverslip, as well as to extend the measurements to

many individuals in order to exclude all possibility of a

slip. The nucleus is between one half and two thirds .

the diameter of the egg.

Upon turning particularly to spermatozoa I found

them in every individual—even between the eggs of those

containing eggs in the gonad. The younger individuals

had no ova, but all sperms. Some of the older ones had

a few big, soft, opaque, irregular, elliptical, oval or

nearly spherical eggs, scattered among irregular masses

of less than half their size, which are balls of spermatids

on the way to development into spermetozoa. One of

these measured 46» 40», and each one is kept in a

dancing or rolling movement, somewhat like that of many

infusoria, by the flapping of the tails of the ripening

sperms on the surface. Between these masses are mil-

lions of mature, free, dancing spermatozoa, of which the

tails are rarely visible until one searches for them with

a high power. I have not yet made extensive measure-

ments of the sperm on account of the difficulty of measur-

ing such exceedingly small objects with certainty, but I

believe the sperm of the British Columbia oyster is

smaller than that of the Prince Edward Island oyster,

which may have some relation to the particular mode of

fertilization, such as being introduced by the respiratory

current. In some parts of the gonad ova may be plenti-

ful, while at other parts there are only sperm-balls.

38 THE AMERICAN NATURALIST Vou. XLVI

Later, in the warmer weather, the sperm may be pretty

well run off and the reproductive organ contain mostly

eggs. In this way the younger oysters, and the older

oysters at the beginning of the season, may be physio-

logically males, while older oysters at the height of the

breeding season may be physiologically females.

Oysters from Hammond Bay showed the same phe-

nomena.

Upon finding an abundance of larger oysters on the

surface at Nanoose Bay, I brought home a pail-full of

picked specimens to serve as a convenient stock for ob-

servation and experiment. On July 16 I found a speci-

men with perhaps half a teaspoonful of eggs in various

stages of segmentation, lying free in the lower valve—a

mass of white granules. The ripe eggs ooze into the

infra-branchial cavity and lie on and between the gills,

i. e., between the two folds of the mantle, where they are

retained apparently without any retaining, sticky matrix.

I suppose that it is here they first meet with ripe sperms

from other individuals, for I do not believe that at this

time the sperms of the same individual are physio-

logically capable. The whole oyster appears exhausted,

the gills rent, the flesh collapsed, soft and parts of it

almost rotten. On July 24 I opened one hundred of

the stock supply and found six with eggs, embryos or

conchiferous young, in the infra-branchial cavity. All

the others were in process of spermogenesis and

oogenesis.

An experiment that has often seemed possible to me is |

to do the same with the European oyster, by way of

artificial fertilization, as Brooks did with the American

oyster. Now that I had an oyster essentially the same as

the European I tried it, and with seeming success, but

of course it is difficult to be sure that sperm from another

had not already had access to the eggs. Unripe eggs

are no good; eggs already freed from the gonad may

have come in contact with sperm. This restricts one to

finding a specimen just before but just on the point of

No. 541] THE CANADIAN OYSTER 39

extruding its eggs. I also tried Atlantic oyster eggs

with Pacific oyster sperms, as well as Atlantic oyster

sperms with Pacific oyster eggs, but without success, as

one might suppose. I put eggs, embryos and larve of

both species together under the same coverslip for com-

parison—those of the small British Columbia oyster

looking like giants beside those of the large Prince Ed-

ward Island oyster. This is a curious phenomenon

which I have several times observed on other species,

e. g., the very large eggs of Astarte compared with the

small eggs of large species like Mactra.

For the study of segmentation, ete., the Atlantic species

is of advantage on account of smaller size and greater

transparency. The order of segmentation appears to be

the same in both—both subject to variations such that it

would require a great number of painstaking observa-

tions to decide exactly what is the normal mode in good

healthy eggs. I have, on both sides of this continent,

spent considerable time in trying to determine the order

of segmentation, the cell-lineage, the planes of cleavage,

the succession of nuclei, the effect of gravitation, the

constant and continuous orientation of successive stages,

the origin of the shell-gland and the mode of formation

of the shell, etc., but can not discuss such subjects here.

I may briefly state, however, that I believe Brooks failed

to observe the shell-gland, in his original work, and at

one particular stage mistook the relation of the shell-

valves to the blastopore which made it necessary to re-

verse his orientation of the embryo—hence his use of the

terms dorsal and ventral are misleading. The polar

bodies are dorsal at first—later, if they persist, they may

become displaced anteriorly. The blastopore is ventral,

the velum anterior, the shell-gland dorsal, the mouth

ventral. There is no foot, nor rudiment of it, in pre-

conchiferous stages.

I have found conchiferous young of the British Colum-

bia oyster retained within the parent’s shell until their

own minute shells were .138 mm. in length. I believe

40 THE AMERICAN NATURALIST [ Vor. XLVI

they remain longer, for, according to Möbius, the young

of the European oyster leaves the parent at a size of .15

to .18 mm. (Horst gives .16 mm.; Huxley 459 inch). I

have taken larve of O. lurida in plankton (identified by

comparison with those from a parent, and also by the

structure, shape and size) of a length of .165 mm. as well

as different larger sizes. They still had a straight-hinge

line of half the length of the shell—unlike the O. virginica

which at this size is already passing into the umbo-stage

and with a much shorter hinge-line. The larve of O.

lurida are not pink or brown but have five or six dark

blotches in the region of the liver and in the velum, in

contrast to the general light shade.of the rest of the

animal.

THE EFFECTS OF ALCOHOL NOT INHERITED

IN HYDATINA SENTA

DR. D. D. WHITNEY

WESLEYAN UNIVERSITY

Many experiments have been performed and much

published concerning the effects of alcohol upon living

organisms. Hodge, Calkins, Lieb, Woodruff, Estabrook,

Matheny, and others, have observed its influence on the

rate of growth and reproduction in certain unicelluar

organisms. Abbott, Hodge and others have carried on

some experiments with mammals by which they have

demonstrated that the resistance to certain bacterial in-

fections is lowered by the influence of alcohol. Hunt and

Woodruff found an increase of susceptibility to certain

poisons in the animals subjected to alcohol. Abel and

Welch have summarized in general the pharmacological

action and the pathological effects of aleohol upon man

and some of the other mammals.’

Stockard has produced abnormal fish embryos and

Féré has produced abnormal chick embryos by the use of

aleohol, while Hodge, Newman, Sullivan and others have

demonstrated the harmful influence of aleohol upon the

embryos of mammals and man during pregnancy.

The evidence taken altogether with a few exceptions

shows that when living organisms in any stage of their

life are subjected to alcohol in appreciable quantities eaer

are as a whole or in part unfavorably affected by it.

In nearly all of the previous work observations have

been made especially upon the organisms themselves

which have been directly subjected to the influence of

alcohol at some stage of their life. As the harmful effects

1I am greatly indebted to Dr. F. E. Chidester for placing at my dis-

posal his bibliography and notes of his forthcoming paper, ‘‘Cyelopia in

Mammals,

42 THE AMERICAN NATURALIST (Vou. XLVI

of alcohol on the organisms subjected to its influence have

been so conclusively demonstrated, it seems desirable to

determine whether the offspring of alcoholic individuals

in the subsequent generations are normal or show any

of the weaknessess of their alcoholic ancestors. In other

words the problem is to find out whether the descendants

of alcoholic parents are in any way inferior to the normal

individuals of the species and, if so, for how many genera-

tions the weakness continues.

That the parental use of aleohol in human beings affects

some of the offspring in the first filial generation is un-

doubted by many observers, yet Pearson and Elderton

have recently shown that the school children of alcoholic

parents are as normal as the children of sober parents

in physique and intelligence. However, the results set

forth in this paper do not purport to have any relation-

ship with the effects of alcohol upon man and his descend-

ants.

While working with the rotifer, Hydatina senta, obser-

vations have been made which show that while alcohol

decreases the rate of reproduction and increases the sus-

ceptibility to copper sulphate, still these harmful effects

of alcohol disappear in the second generation after the

alcohol has been removed from the culture water. The

grandchildren show none of the alcoholic weaknessess of

the grandparent, but are as normal as the individuals

whose grandparents never were subjected to alcohol.

Hydatina senta can be readily reared and controlled in

the laboratory in the manner described in a former paper.

Alcohol can be added directly to the liquid medium in

which the animals live. A large amount of the liquid is

drawn through the mouth, indirectly by means of the pul-

sating bladder, into the alimentary canal, and the dialyz-

able parts pass through its walls into the body cavity and

then finally out through the excretory ducts to the exterior

of the body. In this way the animal is bathed both on the

outside and on the inside of the body by the solution in

which it is living. Consequently all internal parts and all

No. 541] EFFECTS OF ALCOHOL IN HYDATINA 43

organs of the animal are subjected to whatever dialyzable

chemical substance there may be in the solution.

The young females grow to maturity very rapidly and

lay eggs which develop and hatch within a few hours.

This extremely short life-cycle, from egg to egg in forty-

eight hours, more or less, makes this animal a very favor-

able form with which to work. Many generations can be

reared in a short time and as much information gained in

a few weeks as it would require years to obtain from

some of the other forms.

Experiments were first carried out to determine what

influence a } per cent., 4 per cent. and 1 per cent. alcoholic

solution had upon the race when it was subjected to it

continuously for many successive generations. Precau-

tions were taken to have all conditions, excluding the alco-

holic conditions, in each generation exactly identical.

The experiments were conducted in the same room so

that the temperature was always uniform for each genera-

tion. The same amount of food culture from the same

jar was always mixed with the same amount of water or

with the same amounts of the various alcoholic solutions

thus making the proportion of food culture to the mixture

always alike. This mixture was then poured out into

watch glasses and one young female rotifer put into each

glass. At the end of forty-eight hours the young female

had matured, layed eggs some of which had hatched, and

young daughter-females would be found swimming in the

dish. One of these daughter-females was isolated to start

the next generation in the same manner as the mother was

originally isolated. This was continued for twenty-eight

consecutive generations. The twenty young females

which were isolated to form the first generation were the

grandchildren of the same grandmother, thus making the

control, and the other three strains or groups all start

originally from one female of one race. This was a very

vigorous race hatched from a winter egg which was taken

from a general mixed culture jar in the early spring.

Table I shows the detailed and summarized data of the

(Vou. XLVI

THE AMERICAN NATURALIST

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EFFECTS OF ALCOHOL IN HYDATINA.

No. 541]

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46 THE AMERICAN NATURALIST (Vou. XLVI

observations made upon the twenty-eight generations

while they were subjected to the influence of the alcohol.

One can not compare strictly the number of individuals in

the different generations because of the changed condi-

tions, especially of the temperature, and in some instances

the length of time between the generations. However,

the ratios between the strains or groups in all the genera-

tions may be compared and will show general uniformity.

The first few generations of the + per cent., and the 4 per

cent. alcoholic strains show a fluctuation in the rate of

reproduction above and below that of the control; but this

rate of reproduction in the 4 per cent. alcoholic strain

never rises to that of the control after the sixth genera-

tion. In the 4 per cent. alcoholic strain the rate of repro-

duction never rises to that of the control after the third

generation. In the 1 per cent. alcoholic strain the rate

of reproduction even in the first generation does not equal

that of the control. The summary shows in the average

number of offspring for each female that the alcoholic

strains differ in the rate of reproduction according to the

amount of alcohol used. The more alcohol used the lower

the rate of reproduction.

Another test to show the influence of the 1 per cent.

alcohol in this same series was made by removing some of

the individuals from the alcoholic solution and placing

them in a 1/14,000 G. M. copper sulphate solution? and —

comparing the resisting power, or the ability to live, of

this strain with that of the control when both were sub-

jected to the copper sulphate solution. Table II shows

the detailed data and Table III shows the summary. In

the control 96.8 per cent. of the individuals lived forty-

eight hours and produced young, while only 15 per cent.

of the individuals taken from the 1 per cent. aleoholic

strain in the XIII-XV generations lived forty-eight hours

and produced young. This shows that the susceptibility

to copper sulphate is greatly increased by the alcohol.

* Various solutions of copper sulphate were tried and the one employed

was selected because it appeared to be of the maximum strength which the

control could withstand.

No. 541]

TABLE II

EFFECTS OF ALCOHOL IN HYDATINA

SHOWING THE LOWER RESISTING POWER TO COPPER SULPHATE OF FEMALES

EARED THIRTEEN . TO

FIFTEEN GENERATIONS IN A 1 PER CENT

. ALCO-

HOLIC SOLUTION, AND ALSO SHOWING THAT THE RESISTING POWER

HAS BEEN REESTABLISHED IN THE SECOND GENERATION AFTER

REMOVED

THE ALCOHOL HAS BEEN

(See Table III for Summary)

g os yahoo G. M. Copper Sulphate Solution

E PE

= = pe

2 Ree 24 Hours 36 Hours 48 Hours

| E

1 | Control 5| Alive Alive + young | Alive + young

Second water generation 5| Alive Alive + young | Alive + young

1 v alcohol 5| Aliv All dead

2 | Control 5| Alive Alive + young | Alive + young

Second Faroes generation 5| Alive Alive + young | Alive + young

Sine 5| 2 dead ll dea

3 10| Alive Alive + young | Alive + young

Second water generation | 10 ive Alive + young Alive + young

4 ontr 5| Alive Alive + young | Alive + young

a water generation 5| Alive e + yo Alive + young

5 | Control 10| Alive Alive + young ve + young

tear Habeo generation | 10) Alive e + young | Alive + young

6 5| Alive ive live + young

Second by gl generation 5| Alive 2 dead 3 alive + young

1%a 5| Alive 4 dead 1 dea

7 | Contr so 5| Aliv Alive Alive + young

Second water generation 5| Alive Alive Ae F zomg

1 % alcohol 5| Alive 4 dead

8 | Control 5| Alive Alive + young | Alive g ges me

ng Araind generation 5| Alive Alive + ss Alive + y

A Jaj | 5| 3 dead

9 5| Alive | Alive ry young | Alive + young

ial water generation 5| Alive | Alive + young | Alive + young

1 % alcohol 5| Alive Alive but in | 1 dead ers

poorer condi- nearly

ion. Fe Fewer young

aÁ

10 | Control 10/ Alive Alive + young | Alive + young

Second water generation | 10| Alive ive + young | Alive + young

1 % alcohol 10| 5dead | 5 dead, fewer 6 dead +fewer

5 young young

11 | Control 10; Alive Alive + young | Alive + young

Second water generation | 10| Alive Alive + young Alive + young

12 | Control 10| Alive Alive + young Alive + young —

Second water generation | 10| Aliv Alive + young | Alive + young

1 % alcohol 10) Alive 6 +young

13 | Control 10) Alive | Alive + young | Alive + young ©

Second water generation | 10| Alive Alive + young | Alive + young

1 % alcohol 10! 3 dead 5 dead Ty

14 | Control 20. 4 dead 4 dead 4 dead + young

Second water generation | 20) 3 dead 3 dead - 3 dead + young

1 % alcohol 20 19 dead All dead

15 ntro! 10| Alive Alive Alive + young

Second water generation | 10| 6 dead 6 dead 6 dead, young

1 % aleohol 10) All dead

48 THE AMERICAN NATURALIST (Vou. XLVI

On July 1, these four strains of rotifers were carried to

Woods Hole, Mass. Owing to the high temperature diffi-

culty was experienced in growing proper food cultures

and consequently by July 4 many of the animals had died

and those that had survived were in a very bad condition

and had very few offspring. It is interesting to note that

more of the animals in the alcoholic strains died at this

time in the twenty-eighth generation than in the control

strain. The experiments were discontinued on account of

these unfavorable conditions.

TABLE III

SHOWING SUMMARY OF TABLE IT

Copper Sulphate Solution

No. of | r Cen

Young No, p Disa in No. Died in| No. Died in St End of Living ar

Females | Hours | 36 Hours | 48 hours Dr pwa

Isolated | | : ts Toate

Control ....... H |. 4 4 96.8

Second water |

generation ... 125 | 9 11 He 91.2

1% aleohol.... 1900 -1 52 78

The data in these three tables seem to show that alcohol

from 4 per cent. to 1 per cent. has a decided influence in

lowering the rate of reproduction ‘and also in lowering

the power of resisting copper sulphate in the individuals

of the 1 per cent. alcoholic strains. Presumably the

resisting power to copper sulphate of the 4 per cent. and

the 4 per cent. aleoholic strains was similarly lowered,

but this was not determined.

This decrease of the reproduction rate and the in-

creased susceptibility to copper sulphate can be consid-

ered as an indication that the ‘‘general vitality’’ of the

race had been lowered in that the individuals were much

inferior to the control individuals in their ability to cope

with adverse conditions and to leave offspring with which

to continue the race.

Since it is shown that alcohol decreases the ‘‘general

vitality’’ of these animals the condition of their offspring

now remains to be considered. Table IV gives the de-

No. 541] EFFECTS OF ALCOHOL IN HYDATINA 49

tailed and summarized data of experiments showing the

comparative reproduction rates of the offspring from the

three alcoholic strains between generations XI and gen-

eration XXIII, special emphasis being laid upon the off-

spring from the parents in the 1 per cent. alcoholic strain,

and the reproduction rate of the control or normal strain.

Young females were isolated from the three alcoholic

strains placed in media containing no aleohol and reared

two generations parallel to the alcoholic strains. In this

way they were under exactly the same conditions as the

control strain. The isolations of young females from the

ł per cent. and the $ per cent. aleoholic strains were dis-

continued after a few experiments and the time devoted

to experiments with the 1 per cent. strain. As this strain

in Table I showed the lowest reproduction rate and was

decidedly susceptible to the influence of copper sulphate,

it was assumed to have suffered the most of any of the

three strains subjected to aleohol and therefore was con-

sidered to be the most favorable to show the effects of

alcohol upon the offspring. For the sake of clearness all

the data are so arranged in Table IV as to show the three

rates of reproduction in the same generation, of the con-

trol, alcoholic strains, and the aleoholie strain with the

alcohol removed. In the first water generation the young

females were isolated from the preceding alcoholic gen-

eration soon after hatching and reared in media contain-

ing no alcohol. Thus the formation of the egg from which

each young female hatched and all the embryonic develop-

ment occurred in the alcoholic solution. After being

transferred to culture water lacking alcohol they grew to

maturity and reproduced. This generation is called

Water Generation I. Some of the young daughter-fe-

males from Water Generation I were isolated to form

Water Generation II.

In comparing the rates of reproduction in the Water

Generation I with the rate of reproduction in the same

generation of the alcoholic strains it is seen that in all

eases the rate of reproduction is higher in the Water

THE AMERICAN NATURALIST [ Von. XLVI

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EFFECTS OF ALCOHOL IN HYDATINA 51

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52 THE AMERICAN NATURALIST (Vou. XLVI

Generation I than it is in any of the corresponding

aleoholic strains. However, it never reaches that of the

control. In the Water Generation II the rate of repro-

duction is much higher than it is in Water Generation I

and equals the reproductive rate of the control. This

demonstrates that one of the ill effects of alcohol is par-

tially eliminated in the first generation and is entirely

eliminated in the second generation after the alcohol has

been removed.

Very probably the rate of reproduction of Water Gen-

eration I, which is lower than that of the control, is due

to the fact that the females in their embryonic develop-

ment were subjected to the influence of alcohol from which

they never fully recovered after they were transferred

to water solutions containing no alcohol. They were thus

perhaps influenced while in the growth and maturation

stages of the egg inside the body of the mother or, after

the egg was laid in the alcoholic solution, in the embry-

onic stages which occurred inside the egg membrane be-

fore hatching. Soon after hatching the females were put

into the solutions free from alcohol.

This transmission of a low reproduction rate to Water

Generation I is in reality not a hereditary transmission

of a characteristic, but is probably the result of the direct

influence of the aleohol upon the mother during her em-

`- bryonic development. —

Tables II and III show the effect of copper sulphate

upon Water Generation II. Of the individuals tested

91.2 per cent. lived forty-eight hours and produced young

in the copper solution. This is only about 5 per cent. less

than the number of individuals of the control living and

producing young for the same length of time in the cop-

per solution. It can be concluded from these observa-

tions that the resisting power to copper sulphate has

been restored practically to normal and that these indi-

viduals are no more susceptible to its influence than the

individuals of the control.

Billings states to the Committee of Fifty in his report,

No.541] EFFECTS OF ALCOHOL IN HYDATINA 53

which is based on over five thousand reports of cases of

insanity, that : ‘‘ Inherited tendency to insanity, due to the

use of liquor by parents, is reported in one hundred and

twenty-two cases ... while six cases were ascribed to

the intemperance of the grandparents. These statistics

must be received with caution as showing possibilities

rather than as definite evidence. To prove that the

insanity of one generation is due to alcoholic excess of a

previous generation, and is not merely a coincidence,

requires that other causes of degeneration shall be care-

fully studied, and duly allowed for.’’

It is, however, evident from the six cases reported that

some, at least, of the medical examiners believe in the

transmission of alcoholic weaknessess from grandparents

to grandchildren.

Bunge, from an investigation extending over two thou-

sand families, found that chronic alcoholic poisoning in

the father was the chief cause of the daughter’s inability

to suckle and that this inability was not usually recovered

from in subsequent generations. These results have been

severely criticized by Bluhm and their validity ques-

tioned.

Mariet and Cambemale gave considerable quantities of

alcohol to a female dog during the last week of her preg-

nancy. She gave birth to a litter of seven puppies, of

which four were dead, two apparently healthy but men-

tally backward, and one, No. 7, both physically and men-

tally backward. No.7 was a female and grew to maturity

free from the influence of alcohol and mated with an

apparently healthy dog. All of the puppies of her first

litter were abnormal to such a degree that they were con-

sidered worthless. One had club feet and a clefted

palate, another had a eonspicuous ductus Botalli, and

another developed muscular atrophy in its hind legs.

If these observations and interpretations are correct

they may demonstrate either the same fact that is shown

in Water Generation I of Table IV, namely, that when a

mother is subjected to the influence of alcohol during her

54 THE AMERICAN NATURALIST (Vou. XLVI

own embryonic development she shows some sign of

weakness at her period of reproduction, or, that the

grandchildren are affected by the influence of alcohol

upon their grandparents. However, only one experi-

ment alone like the above is not sufficient to prove any-

thing, and furthermore, Hodge in speaking of dogs says:

‘We do not attach much importance to the greater per-

centage of deformity, since this is of somewhat common

occurrence in kennels.”’

If the transmission of an alcoholic weakness to subse-

quent generations is possible in any living organism, it

ought to be actually demonstrated in some manner, but

if it is a delusion, the sooner it is dispelled the better.

These experiments with Hydatina senta are an attempt

to determine, in one race of animals only, whether cer-

tain aleoholic weaknesses are truly hereditary and the

evidence found is negative.

It by no means follows that these results would be

found to be true in man. Alcohol primarily affects the

nervous system and may have a very different action on

the highly organized nervous system of man than it does

on the lowly organized Hydatina, whose nervous system

is extremely simple. Furthermore, the germ substance in

man is probably very different from the germ substance

in the rotifer and alcohol might have a very different

effect upon it.

SuMMARY

1. Four strains of parthenogenetic rotifers originally

descended from the same female were observed throughout

twenty-eight successive generations. One strain was kept

as a control and the other three strains were kept in a

+ per cent., a 4 per cent. and a 1 per cent. solution of

alcohol. The rate of reproduction was lower in the alco-

holic strains than in the control and it was proportion-

ally lowered according to the amount of aleohol used.

2. The individuals of the 1 per cent. alcoholic strain in

the XI-XV generations showed a decidedly increased

susceptibility to copper sulphate.

No. 541] EFFECTS OF ALCOHOL IN HYDATINA 55

3. When the alcohol was removed in generations XI-

XXII, the rate of reproduction increased noticeably in

the first generation and in the second generation the

reproduction rate equaled that of the control.

4. Individuals of the second generation after the alco-

hol had been removed were no more susceptible to copper

sulphate than individuals which had never been sub-

hres to alcohol.

. The general conclusion is that alcohol in 4 per cent.,

4 per cent., and 1 per cent. solutions is danaa to this

race of rotifers when it is subjected to it continuously for

many generations. The weaknesses developed by the

parental use of alcohol are partially eliminated in the

first generation after the alcohol has been removed, and

practically completely eliminated at the end of the second

generation after the alcohol has been removed. In other

words, the grandchildren possess none of the defects

caused by alcohol in the grandparents.

6. These results in general show that alcohol in the

percentages used affects only the somatic tissues of the

animal, and if they are subjected to its influences indefi-

nitely, generation after generation, the race would prob-

ably become extinct because of its ‘‘lowered resistance

power’’ to unfavorable conditions. However, if the alco-

hol is removed it is possible for the race to recover and to

regain its normal condition in two generations, thus

showing that the germ substance is not permanently

affected by the aleohol.

BIBLIOGRAPHY

Abbott, A. C. 1896. The Influence of Acute Alcoholism upon the Vital

EED of Rabbits to Infection. Jeur. Exp. d., Vol.

Abel, J. J. 1903. A Critical Review of the Pharmacon Aetion of

Ethyl Alcohol, with a Statement of the Relative Toxicity of the Con-

stituents of Alcoholic arenge Physiological Aspects of the Liquor

Problem, Vol. 2. Houghton, Mifflin and Co., Boston and New York.

Ballantyne, J. W. 1902. pen e Pathology and Hygiene. William

Green and Sons, Edinburgh.

Billings, J. S. 1903. Relations of Drink Habits to Insanity. Physiological

Aspects of the Liquor Problem, Vol. 1. Houghton, Mifflin & Co., Boston

and New York.

56 THE AMERICAN NATURALIST (Vou. XLVI

Bluhm, Agnes. 1908. Die Stillungsnott. Zeitschrift fiir Sojiale Medizin.

1909. Sexual Probleme.

Bunge. 1907. Die Zunehmende Unfähigkeit der Frauen ihre Kinder zu

Calkins, G. N., sa Lieb, C. C. 1902. Studies on the Life-history of Pro-

tozoa—II. e Effects of Stimuli on the Life-cycle of Paramecium

caudatum. pos fiir Protistenkunde, Vol. I.

Estabrook, A. H. 1910. Effects of Chemicals on Growth in Paramecium.

Jour. Exp. Zool., Vol. 8.

Féré, Ch. 1899. Cinquantenaire de la Société de Biologie. Vol. Jubilaire.

Hodge, C. F. 1903. The Influence of Alcohol on Growth and Development.

Physiological Aspects of the Liquor Problem, Vol. 1. Houghton,

Mifflin & Co., Boston and New York.

Hunt, R. 1907. Studies on Experimental Alcoholism. Bull. No. 33, Hyg.

lá b., U. S. Pub. Health and Mar.-Hosp. Serv., Washington

Mairet, Ac et Combemale. 1888. Influence PRLR de Vileohol « sur la

descen iihi, C. R. de Se. de L’ Acad. des Se. Paris. Vol. 106, pp. 667-

Matheny, W. A. 1910. Effects of Alcohol on the Life-cycle of Paramecium.

Jour. Exp. Zool., Vol. 8.

Newman, G. 1906. Infant Mortality, pp. 72-77.

Piati. K., and Elderton, E. . A First Study of the Influence of

Parental Alcoholism on the Saiga and Ability of the Offspring.

London, Dulau and Co., 37 Soho Square, W.

1910. A Second Study of the tease of Parental Alcoholism on the

Physique and Ability of the Offspring. London, Dulau and Co., 37

Soho Square, W.

Pearson, K. 1911. Questions on the Sy and of the Fray. No. III. Lon-

don, Dulau ay Co., 37 Soho Squar

Stockard, C. R. 1910. The Influence a Aleohol and other Anesthetics on

Embryonie Development. Am. Jour. of Anat., Vol. 10.

Sullivan, W. C. . A Note on the Influence of Maternal Inebriety on

the spr " Jour. cf Mental 8c., Vol. 45, pp. 489-503.

1906. Aleoholis

Welch, W. H. n06e: The Pathological Effects of Alcohol. pego

Aspects of the Liquor Problem, Vol. 2. Boston and New

Houghton, Mifflin & Co.

Whitney, D. D. 1910.

e Indice = oa Conditions upon the Life

ol.

1911. The Poisonous Effee ects,of acini Beverages not Proportional to

their Puree Contents. Science, Vol. 3

Woodruff, L. 1908. Effects of Alcohol on ie Life-eyele of Infusoria.

Biol. Bull., ‘Vol. 15.

ARY, 1912

FEBRU.

XLVI, NO. 542

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AMERICAN NATURALIST

Vou. XLVI February, 1912 No. 542

SOME ASPECTS OF CYTOLOGY IN RELATION

TO THE STUDY OF GENETICS!

PROFESSOR EDMUND B. WILSON

CoLUMBIA UNIVERSITY

THe consideration of genetic problems from the stand-

point of cytological research sometimes encounters a

certain opposition or prejudice which seems to me to be

due to a misunderstanding of the position that is actu-

ally held by many cytologists. It probably grows pri-

marily out of a conviction that the heredity of particular

traits is not to be explained by referring them to the

operation of particular cell-elements or ‘‘determiners,”’

but results from an activity of the whole cell-system, or

of the whole organism, regarded as a unit. With this

view, as will appear, I am essentially in agreement. In

the second place, the opposition is a kind of reaction or

protest against the theory of pangens or biophores and

the too elaborate logical constructions that have been

built upon it, especially by Weismann. I also consider

this theory untenable, or at least unnecessary. I will

therefore attempt to outline a point of view from which

I think genetic problems may reasonably be regarded

from the standpoint of the cytologist.

The most essential result of modern genetic inquiry I

take to be the proof of the independence of the so-called

1A paper read before the American Society of Naturalists at the

Princeton meeting, December 28, 1911.

58 THE AMERICAN NATURALIST [ Vou. XLVI

‘<unit-characters’’—that is to say, that they may be inde-

pendently combined, disassociated and re-combined in

many different ways. The independence of these char-

acters often seems to be complete; more rarely it is

limited by definite phenomena of ‘‘coupling’’ or ‘‘repul-

sion.’’ The interesting facts recently brought to light by

Bateson and Punnett in case of certain unit-characters

in plants, and by Morgan in case of sex-limited char-

acters in flies, demonstrate that coupling or repulsion,

as exhibited in the F, generation, are a consequence of

an original association or separation in the grandparental

gametes. In the cases referred to, characters that enter

the F, zygote in the same gamete tend to ‘‘couple’’ (re-

main in association) in the gametes produced by this gen-

eration; while if these same characters enter the F,

zygote in different gametes they tend to ‘‘repel’’ each

other (remain separate) in the ensuing gamete-forma-

tion. This is almost a proof that the factors for coupled

characters are borne by a common vehicle or substratum

in the germ-cell, while in repulsion they are borne by

separate ones. Not alone such facts, but the whole

history of unit-characters points unmistakably to the

conclusion that they are in some way connected with

material substances or bodies; and that it is the com-

binations, disassociations and recombinations of the latter

that explain the corresponding behavior of the former.

For example, in sex-limited heredity the peculiar linkage

of certain unit-characters with sex becomes readily intel-

ligible, as several writers have recently pointed out, if

factors necessary for the production of these characters

are associated in the same material body with a factor

that plays a certain necessary rôle in the production of

sex. In this particular case, as it happens, we are actu-

ally able to see a material body (the ‘‘X-chromosome’’)

which undergoes precisely such a mode of distribution

with respect to sex and sex-limited characters as is de-

manded by the hypothesis. The question must here be

squarely faced, in a very real and concrete form, whether

No. 542] SOME ASPECTS OF CYTOLOGY 59

unit-characters are in fact dependent upon separate ma-

terial bodies or substances, and whether the chromo-

somes can be regarded as such bodies or the carriers of

such substances.

Without entering upon the evidence in detail I shall

take it for granted that both these questions may be an-

swered in the affirmative. Accepting this (if only for

the sake of argument) how can such a conclusion be

reconciled with the ‘‘action of the whole,’’ and how form-

ulated so as to escape the pangen-theory? The latter

theory has fallen into discredit for two reasons. One is

because of the quasi-metaphysical assumption that the

‘‘physical bases” or ‘‘determiners’’ of unit-characters

are organized, self-propagating germs. Let us lay this

assumption altogether aside as incapable of verification,

and think of the ‘‘determiners’’ in a more vague way

only as specific chemical entities of some kind. The

second and more serious objection lies against the notion

that the ‘‘determiners”’ are to be regarded as ‘‘bearers’”’

of the corresponding characters. This is a fundamental

error, as may be made clear, I think, by a specific illus-

tration. It has been proved that many ‘‘unit-characters”’

‘are not units, but require for their production the co-

operation of several factors, as is shown with especial

clearness in the heredity of color. In such cases, as is

now generally recognized, we should not speak of ‘‘unit-

characters” but of unit-factors. Different ‘‘unit-char-

acters’? come into view as particular unit-factors are

added to or subtracted from a given combination in the

zygote. The factor for gray color in mice, to take a

familiar example, operates by inducing a reaction of the

germ that can only take place in the presence of several

antecedent color-factors lower in the scale ; and the latter,

in turn, are only operative in the presence of still another

factor that is necessary to the production of any color.

The first and most obvious suggestion given by such

facts is that what is added to or subtracted from a given

combination or state of equilibrium in the zygote is some

60 THE AMERICAN NATURALIST (Vou. XLVI

kind of chemical entity which induces a specific reaction

of the germ sooner or later in its development. But

beyond this it is perfectly evident that however far back-

wards we may* follow such a series of unit-factors, at

every stage they play their specific rôle only in so far as

they form part of a still more general apparatus of

ontogenetic reaction that is constituted by the organism

as a whole. The whole of this apparatus, the entire

germinal complex, is directly or indirectly involved in

the production of every character. We find it convenient,

indeed necessary, to treat particular factors of reaction

(i. e., the ‘‘determiners’’) as if they were concrete and

separate things. Such, in fact, they may be, as already

indicated; but when we speak of them as ‘‘bearers’’ of

the corresponding characters, we are using a figure of

speech that may be highly misleading. The reactions

(characters) which they call forth are not ‘‘borne by”’

them. They appear as responses of the germinal organi-

zation operating as a unit-system; and it is to this sys-

tem as a whole that every character belongs, or by which

it is ‘‘borne’’—if indeed we may permit ourselves to

employ the latter expression at all.

The point of view thus indicated may, I think, be made

entirely clear by a chemical illustration. A number of

writers, among them Adami, Guyer and Kossel, have

of late called attention to the parallel that may be drawn

between the physical basis of heredity and the complex

molecular groups of the proteins and other organic com-

pounds. It is a most suggestive one, though it is not to

be taken too literally—indeed I shall employ it only as a

kind of allegory or illustrative fiction. No one can fail

to be struck with the really remarkable analogy, in

method and in results, between the precedure of modern

genetic experiment and that of modern organic chem-

istry. Just as the qualities of a particular protein may

be definitely altered by the addition, subtraction or the

substitution one for another of particular side-chains or

molecular ‘‘Bausteine,’’ so the addition, subtraction or

No. 542] SOME ASPECTS OF CYTOLOGY 61

substitution of particular ‘‘determiners’’ or ‘‘factors’’

in the zygote calls forth specific responses that lead to

the production of corresponding characters. The reason-

ing that applies to the first of these cases seems equally

applicable to the second. No one, I suppose, would hold

in the first case that the particular molecular groups or

‘*Bausteine’’ concerned in the change are ‘‘bearers of’’

(i. e., are alone responsible for) the resulting new quali-

ties. The qualities of any protein, as Kossel has recently

urged, belong to the molecule as a whole, and are not to

be regarded as the sum of the qualities of its constituent

‘*Bausteine.’? Why should we regard in a different light

the ‘‘determiners’’ (chemical substances?) concerned in

the second case? They are, clearly, not to be regarded

as ‘‘bearers’’ or ‘‘physical bases’’ of the characters

which depend upon their presence or absence. They are,

I repeat, only differential factors of ontogenetic reac-

tions that belong to the germ considered as a whole or

unit-system.

In all this I am but expressing what I believe to be the

point of view of many recent writers on genetic prob-

lems; but what I desire to emphasize is that the prob-

lems of cytology should be regarded from the same point

of view. It is our task to see whether an apparatus

of ontogenetic response can be discovered in the cell that

fits with such a conception of the general process of de-

termination. Is there cytological evidence of the exist-

ence in the germ-cell of such specific factors of reaction

as I have referred to—in the nucleus, in the protoplasm,

or in both? I think that observation and experiment

alike have produced such evidence. Such experiments as

those of Boveri on multipolar mitosis, and of Herbst and

of Baltzer on the relations of the chromosomes in recip-

rocal crosses in sea-urchins have almost conclusively

shown that the chromatin does in fact play a causative

role in determination. Observation has gradually estab-

lished the existence of a complex process of segregation

and distribution of the nuclear materials in karyokinesis.

62 THE AMERICAN NATURALIST [ Vou. XLVI

maturation and fertilization, that shows a most striking

parallel to that of the factors of determination. That a

somewhat similar apparatus of distribution may exist

also in the protoplasm of the cell is indicated both by

recent observations on the chondriosomes, or plasto-

somes, and by earlier results on experimental embry-

ology. If in the brief discussion that follows I confine

myself to certain phenomena of the nucleus it is because

the history of the chromatin is more fully and accurately

known.

The progress of cytological inquiry tends steadily, I

think, to sustain the view first clearly formulated by Wil-

helm Roux that the nucleus contains many different sub-

stances which undergo orderly groupings and distribu-

tions in the karyokinetic phenomena. These processes

are in some measure made visible to us in the formation

of spireme-threads, in their history in cell-division, and

in the still imperfectly understood but perfectly definite

events of synapsis and reduction. In his well-known

paper on the significance of the karyokinetic figure, pub-

lished in 1883, Roux maintained that the nucleus is the

seat of many different ‘‘qualities.’? He committed him-

self to no definite view as to what these ‘‘qualities”’

really are; but the implication is not far to seek that they ~

have a chemico-physical basis and may be different chem-

ical substances. On this general assumption he based his

well-known interpretation of karyokinesis, of which the

essential postulate was that the ‘‘qualities’’ (substances?)

become arranged in linear series in the spireme-thread,

and by longitudinal splitting of the thread may thus be

equally divided (or otherwise definitely distributed) to

the daughter-nuclei. I believe that many of the later

advances of cytology lend additional support to this con-

ception.

1. In the first place, the evidence gives strong ground

for the conclusion that the chromosomes, to which the

spireme-thread gives rise, are not homogeneous, but com-

pound bodies. I do not here refer to the well-known fact

No. 542] SOME ASPECTS OF CYTOLOGY 63

that the spireme-threads often consist of linear series of

granules. I have in mind the fact that the number and

size-relations of the chromosomes often differ materially

as between different species, even nearly related ones, and

that in at least one case (that of the X-chromosome) it is

an established fact that a particular chromosome which

in some species is a single body may be represented in

other species by two or more components that sometimes

show constant and characteristic differences of size. The

natural interpretation of this fact is that the chromo-

somes are compound bodies, consisting of different con-

stituents which undergo different modes of segregation

in different species. We may here find a rational expla-

nation, both of sex-limited heredity, as I have elsewhere

indicated, and of other kinds of coupling.

2. Recent studies on karyokinesis and maturation em-

phasize anew the importance of the mitotic transforma-

tion of the chromatin-substance, and add weight to

Roux’s original interpretation of this phenomenon.

Nothing in recent cytological research is more interest-

ing than the discovery by Bonnevie, Pinney, Davis, and

others that new chromosomes may arise within the old

ones in the form of tightly coiled or convoluted threads,

which uncoil or unravel to form separate spireme-threads.

In karyokinetic division these threads may be formed

already inside the telophase-chromosomes of the preced-

ing division, as was discovered by Bonnevie. In other

cases, an example of which is given by certain Orthoptera

first reported upon by Miss Pinney, they are first visible

in the early prophases, when they are seen uncoiling

from massive bodies formed from the old chromosomes

and equal in number to them. The same remarkable

process occurs in the early auxocytes, as the chromosomes

are preparing for conjugation in synapsis, as has been

shown particularly by Davis, whose observations, like

those of Pinney, I have recently been able to confirm

and extend. In many insects the presynaptic spireme-

threads do not arise, as has often been described in other

64 THE AMERICAN NATURALIST [Vou. XLVI

forms, directly from a chromatin-network. They arise

from massive bodies, each of which resolves itself into a

closely convoluted thread which then uncoils before con-

jugation takes place. Why should chromosomes that are

already formed as massive bodies delay their division

or conjugation until so remarkable a redistribution of

their substance has taken place? It is not a necessary

condition of conjugation, as is proved by the case of both

the sex-chromosomes and the m-chromosomes, which do

in fact conjugate in the massive condition. All the facts

become intelligible in the light of Roux’s hypothesis that

the formation of the spireme-threads effects a linear

alignment of different constituents in preparation either

for division or for a definite type of association in pairs

in synapsis.

One of the most interesting applications of this view to

genetic phenomena is that suggested by Janssens in his

theory of the ‘‘chiasmatype,’’ which has recently been

applied by Morgan to the explanation of coupling and

repulsion. In the twisting together of the spireme

threads, either in synapsis or at a succeeding stage, and

the subsequent secondary splitting of the thread in one

plane is provided a very simple mechanical basis, both

for the free interchange of factors between the homol-

ogous chromosomes and for the phenomena of coupling

or repulsion, which are otherwise so difficult to compre-

hend. I do not maintain that this particular interpreta-

tion, or the more general one of Roux, is demonstrably

true, or that no other explanation can be found. I only

hold that they are legitimate conceptions which may be

tested by observation and experiment, and which must be

fully reckoned with as intelligible interpretations of the

facts before we can set these facts aside as utterly mys-

terious or as a meaningless by-play.

3. I would lastly recall the experimental proof by

Boveri that the chromosomes differ among themselves in

their physiological relation to development, and the cor-

responding cytological fact that they differ among them-

No. 542] SOME ASPECTS OF CYTOLOGY 65

selves also in respect to size, behavior, or both. In one

case only has it thus far been possible to demonstrate a

constant relation between particular chromosomes and

particular characters, namely in the case of sex and sex-

limited characters. It is true that in this case we are not

able to assert that the sex-chromosomes are the primary

determining cause of sex—indeed, there seems to be good

evidence to the contrary. Unless, however, we are pre-

pared to defend the proposition that the sex-chromosomes

are absolutely functionless we shall not, I think, escape

the conclusion that they form one of the factors in sex-

heredity.

I will not enter upon the analytical subtleties of the

problem whether the chromosomes, or the substances

that they contain, are permanent and self-propagating

elements or are merely temporary products of an unseen

underlying activity—whether they are causes, effects or

mere accompaniments of the specific reactions with which

they are somehow connected. These are fundamental

questions; and some of them can not yet be answered.

But we should not hesitate to adopt what seems likely to

be for the time the most reasonable and fruitful working

view. ‘‘Hypotheses,’’ said Pasteur, ‘‘come into our labo-

ratories by armfuls; they fill our registers with projected

experiments, they stimulate us to research—and that is

all.” In my view studies in this field are at the present

time most likely to be advanced by adopting the compara-

tively simple hypothesis that the nuclear substances are

actual factors of reaction by virtue of their specific chem-

ical properties; and I think that it has already helped us

to gain a clearer view of some of the most puzzling prob-

lems of genetics. But even if we adopt the opposite view

that the formation, segregation and distribution of these

substances are only signs or indices of what lies behind

them, we still have in this direction one of the most prom-

ising paths of approach to a study of the activities of the

germ-cells in heredity. .

It will perhaps be said that such conceptions of the |

66 THE AMERICAN NATURALIST [ Von. XLVI

nuclear organization as have here been indicated are both

vague and artificial. Vague and crude they undoubtedly

are; and so they will remain until we have far more

thoroughly explored a field of inquiry in which we must

for the present make a shift with crude ideas unless we

are content to work with no ideas at all. They may be

artificial too; but it appears to me that in this respect

they differ only in degree from the graphic formulas of

structural chemistry. The chemist does not hesitate to

picture definite topographical or spatial relations in the

complex organic molecule—symmetrical and asymmetrical

forms, cyclic or ring-formations, linear series, side-

chains and other such graphic constructions. It is by

their use that the whole science of organic chemistry has

been built up, and that such men as Emil Fischer and

Kossel have made nearly all of their advances in our

knowledge of those most complex of known organic com-

pounds the proteins. And these constructions are re-

garded by eniinent investigators as something more than

mere figurative expressions or symbols. They are taken

more literally as representations or models—rude, no

doubt, but as far as they go real—of the actual arrange-

ments in space of the various molecular groups or pro-

tein ‘‘Bausteine.’’ If therefore observation and experi-

ment lead the eytologist to postulate definite topograph-

ical relations among the nuclear substances, and if such

a conception help him to explain the results of genetic

studies, he finds himself in good company, even though

his present clumsy notions regarding the nuclear organi-

zation can as yet make no approach to the exact and ele-

gant constructions of the chemist.

The essential conclusion that is indicated by cytolog-

ical study of the nuclear substance is that it is an aggre-

gate of many different chemical components, which do

not constitute a mere mechanical mixture, but a complex

organic system, and which undergo perfectly ordered.

processes of segregation and distribution in the cycle of

cell-life. That these substances play some definite rôle

No. 542] SOME ASPECTS OF CYTOLOGY 67

in determination is not a mere assumption, but a conclu-

sion based upon direct cytological experiment, and one

that finds support in the results of modern chemical

research. Professor Kossel has recently said that every

peculiarity of the species and every occurrence affecting

the individual may be indicated by special combinations

of protein ‘‘Bausteine.’’ The point of view that has here

been indicated is entirely in accordance with such a con-

ception. The results of cytological inquiry fit with the

view that there are many such combinations in both

nucleus and protoplasm; and the interest of cytological

study lies in the fact that we can in some degree follow

out their modes of segregation and distribution with the

microscope. We are still utterly ignorant as to how these

processes are determined; and the more one studies them

the more one’s wonder grows. I would certainly be one

of the last to disparage the brilliant results that have

been attained through the prolonged and patient labors

of cytological observation and experiment. They stand,

I believe, among the most interesting and valuable

achievements of modern biology. But these studies have

as yet made no approach to their limit, and a vast unex-

plored field still lies before us. We may as well recognize

the fact that our present rude notions of cell-organiza-

tion have not yet progressed very far beyond the paleo-

lithic stage of culture; but they are of use in so far as

they help to open new points of view or to discover new

facts, whether in cytologic or in genetic inquiry. It seems

to me that in both regards they have already proved

worth while.

THE CORRELATION BETWEEN CHROMOSOMES

AND PARTICULAR CHARACTERS IN HY-

BRID ECHINOID LARV Æ’

PROFESSOR DAVID H. TENNENT

Bryn Mawr COLLEGE

Tue student of genetics who bases his researches on

‘the development of echinoderms has become quite accus-

tomed to the criticisms of his friends to the effect that his

work can have little point until he can show. them indi-

viduals of a second or a third generation, and he receives

these criticisms at their full value.

Our ignorance on this subject has been clearly defined.

First, little is known of the inheritance in the adult

hybrids of the characters of the parent species, and sec-

ond, it is not known that these hybrids become sexually

mature.

The ready acceptance of these ideas has blinded us, in

a measure, to the fact that for the solution of some of the

problems of heredity, the echinoderms offer material of

unusual advantage. The plants, insects and vertebrates

are peculiarly adapted for the elucidation of the later

aspects of heredity; the echinoderms are available for

information concerning the processes which occur during

and immediately after fertilization.

In the course of this paper I shall show that we are

now in a position to predict certain characters in the

adult hybrids from a knowledge of the germ cells of the

ancestors and, granted the sexual maturity of the hybrid

adults, to predict the character of their germ cells.

The evidence that I shall bring forward is based on a

study of chromosomes. The advantages afforded by

echinoderms for such a study, lie in the fact that not only

may we study the chromosomes during the divisions of

1 Read before the American Society of Naturalists, Princeton, 1911.

No. 542] CHROMOSOMES IN ECHINOID LARV 2 69

the normally fertilized egg, but we may study the chromo-

somes of the egg itself, i. e., the maternal chromosomes,

in artificially parthenogenetic eggs; we may study the

chromosomes of the spermatozoan, i. e., the paternal

chromosomes, in fertilized enucleated egg fragments;

and we may study the chromosomes in cross-fertilized

eggs, identifying here those which have come from one

parent or the other.

The first subject of which I shall speak is the correla-

tion of certain chromosomes with sex.

The conclusions reached by Baltzer, from a study of

Echinus and Strongylocentrotus, are known to most of

those present. They find their readiest expression in the

statement that ‘‘in Echinoids the female is digametic

while the male is homogametic.’’ I have expressed else-

where the idea that this generalization is too broad and

that the statement should be limited to the cases for

which the condition was described; but I must do more

than this. I can admit that apparent condition for but

one of Baltzer’s cases, that of Echinus, for his own illus-

trations for Strongylocentrotus indicate that this form

is in agreement with another interpretation, and not with |

the one given.

In the forms which I have studied, the male is digametie,

the female homogametie, as in the insects.

The first case that I shall submit is that of Tripneustes

esculentus (Hipponoé), in which the evidence is espe-

cially clear, although not submitted to the ultimate anal-

ysis that has been given to the second case.

_ In Hipponoé, I have been able to show, by the study of

cross-fertilized eggs, made in connection with straight

fertilized Toxopneustes and Hipponoé eggs by two of my

students, Miss Heffner and Miss Pinney, that a chromo-

some of peculiar form, namely hook-shaped, is trans-

mitted by half of the Hipponoé spermatozoa, and that the

eggs which receive it must become males.

The evidence here is clear. Such an element never

occurs in straight-fertilized Toxopneustes eggs. It is

70 THE AMERICAN NATURALIST [ Vou. XLVI

found in one-half of the straight fertilized Hipponoé

eggs; it is found in half of the Toxopneustes eggs which

have been fertilized by Hipponoé sperm, and it never

occurs in Hipponoé eggs fertilized by Toxopneustes

sperm,

There is then absolutely no appeal from the fact that

in Hipponoé the spermatozoa are of two classes, one

with, the other without, this idiochromosome.

The second case that I shall submit is that of Lytechi-

nus, better known to us as Toxopneustes. Here I am

able to give evidence gained by a study of straight fertil-

ized eggs, artificially parthenogenetic eggs, fertilized

enucleated egg fragments, and four crosses, the recip-

rocal Hipponoé X Toxopneustes and Arbacia X Toxop-

neustes crosses.

The study of straight fertilized Toxopneustes eggs

showed two classes of zygotes, one with two V-shaped

chromosomes, the other with three. This seemed in

agreement with conditions in Echinus, although obviously

there was no chance of tracing the source of the hetero-

chromosome in such material.

Those who have devoted any attention, to the chromo-

somes in Echinoids know the difficulties involved in such

-~ a study. The chromosomes are all small; most of them

have the form of short, straight or slightly bent rods,

while but three or four, at most, may be distinguished by

peculiarity of form. Difficulties attend the study of even

these chromosomes. The V’s in Toxopneustes, for ex-

ample, best seen in the anaphases of division, may have

both arms brought into contact and so resemble a single,

somewhat thickened rod.

Since this is true, it should be easier to determine size

differences when only the haploid number is present than

when the full number of chromosomes is in the division

figure.

So far as I am aware, none of the cytological work on

artificial parthenogenesis in Echinoids has been done

with the idea of an individuality of form of chromosomes

No. 542] | CHROMOSOMES IN ECHINOID LARV Æ 71

in mind. The chief aim has been the determination of the

presence of the haploid number of chromosomes and of

the fact that auto-regulation does not occur. This is true

for results published as late as 1910.

In my study of this material I have found that all of

the eggs are alike, possessing among the others two V-

shaped chromosomes.

In the fertilized enucleated egg fragments, two classes

are evident. Half of the spindles show two V-shaped

chromosomes in each anaphase plate while half show but

one. I have no conclusive evidence for showing whether

we are dealing with an X chromosome or with X and Y

chromosomes. Counts are decisive for either view, and

therefore valueless. I believe that this is a matter which

ean be decided only by a study of the soe cene, ogeieus

of these forms.

For some reason there is a belief in the tradition that

in Echinoids the somatic number of chromosomes is

thirty-six and in one case eighteen. Counts of perfect

polar views of anaphase plates in Toxopneustes give the

numbers thirty-seven and thirty-eight, but even from

these I do not feel warranted in applying a sex formula.

It will be noted that the number of V’s does not agree

with our expectation from the straight-fertilized eggs.

I can only say that my description is of the facts as I

find them in my preparations. From this it would seem

that the number of V-shaped chromosomes in straight-

fertilized Toxopneustes eggs should be three and four.

These facts are further substantiated by conditions in

the Hipponoé X Toxopneustes crosses. |

The second point of which I wish to speak is that of

correlation of chromosomes and larval characters. The

only larval structure which has a form sufficiently definite

to be used for comparison is the skeleton. The most ad-

vantageous forms for this purpose are those in which

the pluteus of one parent has skeletal arm rods of a

simple straight form and the other rods of the latticed

type. |

13 THE AMERICAN NATURALIST [Vor. XLVI

It is well known that an apparent confusion exists

among observations on hybrid Echinoid larvæ, as to

whether plutei of a maternal type, a paternal type or of

mixed form are derived from certain crosses. Different

results have been obtained by different investigators and

by the same investigators working in different regions,

or in the same region in different seasons.

From my own results I am convinced that there is no

reason for believing that any of these observations are

incorrect and that this dissimilarity of results may be

traced to the influence of the constitution of the sea water

at different times and places, to temperature, ete.

If we look into the matter carefully we find that there

is a correlation between the fate of the maternal and

paternal chromatin and the character of the plutei.

It is a remarkable fact that in the general literature of

genetics, authors who have noted the fact of elimination

of chromosomes, as shown by the researches of Baltzer

and Herbst, have not also noted their retention in some

cases, and the influences of this retained chromatin on the

character of the larve.

It may be seen, by the examination of Baltzer’s tabu-

lation, given in his 1910 paper, that in the cases cited an

elimination of presumably the introduced paternal chro-

mosomes is followed by a pluteus of the maternal type,

and that the retention of all the chromosomes may be

followed in some cases by a pluteus of a mixed or inter-

mediate type, in other cases by a pluteus of the maternal

type. To these cases I must add the case of the retention

of chromosomes followed by a pluteus of the paternal

type, this being afforded by the Hipponoé ¢ X Toxop-

neustes 2 cross. :

In this instance we have a clear example of Hipponoé

dominance with respect to larval skeletal character, and

this dominance is correlated with the retention of Hip-

ponoé chromosomes.

I have not asserted that every Toxopneustes egg which

is fertilized by Hipponoé sperm gives rise to a pluteus

No. 542] CHROMOSOMES IN ECHINOID LARVZ 73

with a Hipponoé skeleton. The largest percentage of

the eggs does respond in this manner; a smaller per-

centage dies in the blastula and gastrula stage, and a

still smaller percentage shows little or no trace of pater-

nal influence.

_If we take the eggs of such a fertilization and examine

them during the segmentation stages, we shall see that in

these eggs the greatest number show normal division

figures, and by normal I mean those of the almost dia-

grammatic sort which may be seen in straight-fertilized

Toxopneustes eggs, figures which give no indication of

any chromosome elimination, while the smaller number

show aberrant figures with varying degrees of elimi-

nation.

The normal division figures correspond in number to

the plutei with the paternal type of skeleton and the

aberrant figures to the plutei of intermediate and mater-

nal character.

Clearly, then, in the hybrids of Echioid crosses we

may have dominance of one species or the other with

respect to the skeleton, and this dominance may be trans-

mitted by the egg or by the spermatozoan. Of the con-

siderable number of crosses that I have made, only one,

the Hipponoé & X Toxopneustes oo eross gives this

evidence.

Some facts of interest are demonstrated by the Arba-

cia X Toxopneustes crosses. These crosses are made

with difficulty and I had never succeeded in getting them

until the past summer. The chromosomes in Arbacia

are much smaller than those in Toxopneustes and I had

hoped that material from this cross would be of use when

compared with my experimental Toxopneustes material.

Here, however, I found that there is an elimination of

chromosomes from the first, an elimination which may

involve the rejection of not only the foreign chromo-

somes, but some of those of the egg as well, the result

being that, in some instances, the full haploid number of _

neither is retained, and few — pass meet the |

blastula pa —

74 THE AMERICAN NATURALIST [ Vou. XLVI

A further insight into the effect of the retention of

foreign chromatin is given by partially arrhenokaryotic

and partially thelykaryotic plutei. In such larve, with

their asymmetrical bodies and skeletons, we may dis-

tinguish regional differences by nuclei of different sizes,

and by a study of segmenting eggs we may find how these

nuclei have arisen. In some instances we know that the

fertilization processes have been so modified that subse-

quent divisions of the egg contain only paternal nuclear

material and are paternal in character. In other regions

part or all of the foreign chromatin is present and has

modified development.

The conditions noted in the plutei find correlation in

the following conditions in the egg.

1. Retention of all chromosomes and dominance of one

species over another with respect to skeletal characters.

2. Elimination of part of the chromatin and dominance

of one species over another with respect to skeletal char-

acters.

3. Elimination of part of the chromatin and interme-

diate skeletal cl ters

4. Elimination of part of both paternal and maternal

chromatin and inhibition of development.

The first three, at least, may all occur in a given lot of

eggs, and, since this is true, depend in part on chance,

just as we may have imperfect mitotic figures in straight-

fertilized eges.

The second and third cases may indicate an incom-

patibility between the chromosomes and the cytoplasm

of the egg; the fourth case, not this alone, but an incom-

patibility between the chromosomes themselves.

Finally as to our ability to predict the character of the

adult from the characters of the larve.

It is clear that in Hipponoé and Toxopneustes we may

predict sex, since we have seen that maleness and a

heterochromosome of paternal origin are correlated. It

is thus evident that if chemically fertilized Hipponoé and

Toxopneustes eggs develop to sexual maturity these in-

No. 542] CHROMOSOMES IN ECHINOID LARVÆ 75

dividuals will be females, the reverse of our belief con-

cerning the naturally parthenogenetic egg of the bee. In

cases similar to those described by Baltzer for Echinus,

half the adults will be males and half females.

A prediction as to other characters is difficult to make,

for the fact that one species is dominant over another

with reference to larval skeletal characters give no idea

as to other characters.

Nevertheless, in the cases of partial arrhenokaryosis

which I have mentioned we should expect a region of the .

larval body containing only paternal nuclear material to

place its stamp on that part of the adult body arising

from it. A natural hybrid showing pure regional resem-

blances to one species or another is theoretically possible

and would find its explanation in partial arrhenokaryosis.

For the inheritance of most characters we must fall

back on our knowledge of natural echinoderm hybrids,

which is increasing steadily.

We should expect that where parts of both contribu-

tions of chromatin have been retained and an inter-

mediate pluteus has resulted the adult will be of the

mixed type. One of the supposed Echinoid hybrids de-

scribed by Mortensen fulfils this expectation.

The proof of these predictions lies in the rearing of

hybrid larve to the adult condition. This we know to be

possible. It requires only laboratory advantages of an

unusual type, care, time and an accurate knowledge of

the natural history of echinoids.

DARWIN’S THEORY OF EVOLUTION BY THE

SELECTION OF MINOR SALTATIONS

HENRY FAIRFIELD OSBORN

COLUMBIA UNIVERSITY

THERE is an opinion which is becoming more widely

prevalent daily that Charles Darwin’s theory of selection

rests upon ‘‘fluctuations’’ which may not be heritable.

Nothing could be further from the facts.1

It is true that Darwin finally came to believe in the

inheritance of somatic modifications (in the modern sense

of bodily changes) caused by the direct action of environ-

ment as well as by habit (ontogeny), but in his original

(1859) and final (1872) opinion evolution was chiefly due

to the selection of heritable ‘‘individual differences.”’

Darwin’s true meaning as to ‘‘individual differences”?

is not to be found in his language, but in the cases he

cited; he has been widely misunderstood? as believing in

continuous evolution whereas he chiefly believed in dis-

continuous evolution.

Darwin’s final opinion? may we cited with a transposi-

*De Vries is partly responsible for this general misunderstanding of

Darwin. In ‘‘Die Mutationstheorie,’’ Leipzig, 1901, pp. 21-27, we find a

very full discussion of the opinions of Darwin in which the interpretation

is reached that Darwin was not clear in distinguishing ‘‘variation’’ and

‘mutation. ’’

* Cox, Chas. F., ‘‘ Charles Darwin and the Mutation Theory,’’ Ann. N. Y

Acad. Sci., Vol. XVII, No. II, Pt. III, February 10, 1909, pp. 431-451.

This is a most conscientious and peananive — of Dai rwin’s opinions in

which the following conclusion is reached: ‘ we have seen, he was com-

pelled to concede that what we now call Hest 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 extra-

ordinary, and that, as a rule, a new species originated by the gradual build-

ing up of minute and even insignificant deviations from the average char-

acters of an old species, which deviations we now call fluctuations.’’ [P.

ssi = our own. ]

2 ‘‘The Variation of Animals and Plants under Domestication,’’ Vol.

1, p. 397.

No. 542] DARWIN’S THEORY OF EVOLUTION 77

tion of sentences and italicizing of important words, as

follows:

-... we have abundant evidence of the constant occurrence under

nature of slight individual differences of the most diversified kinds; and

we are thus led to conclude that species have generally originated by,

the natural selection of extremely slight differences. This process may

be strictly compared with the slow and gradual improvement of the

racehorse, grayhound, and gamecock. As every detail of structure in

each species has to be closely adapted to its habits of life it will rarely

happen that one part alone will be modified; but as was formerly

shown, the co-adapted modifications need not be absolutely simultaneous.

Many variations, however, are from the first connected by the law of

correlation. Hence it follows that even closely allied species rarely or

never differ from one another by one character alone . . . from the

history of the racehorse, grayhound, gamecock, ete., and from their

general appearance we may feel nearly confident that they were formed

by a slow process of improvement; and we know that this has been the

case with the earrier-pigeons as well as with some other pigeons. . . . It

is certain that the ancon and mauchamp breeds of sheep, and almost

certain that the niata cattle, turnspit, and pug dogs, the jumper and

frizzled fowls, short-faced tumbler pigeons, hook-billed ducks, ete., sud-

denly appeared in nearly the same state as we now see them. So it has

been with many cultivated plants. The frequency of these cases is

likely to lead to false belief that natural species have often originated in

the same abrupt manner. But we have no evidence of the appearance,

or at least of the continued procreation, under nature, of abrupt modi-

fication of structure, and various general reasons will be assigned

against such a belief.

Thus Darwin, on the admirable ground that no evidence

had been adduced in nature of such transformation, re-

jected the hypothesis of major saltatory evolution as

causing the natural appearance of entirely new types of

animals or plants or of entirely new and profoundly

modified organs. There was no evidence in 1872 and

there is none to-day of the sudden appearance in nature

of such a breed as the ancon sheep. On the other hand,

Darwin’s meaning as to “‘slight individual differences of

the most diversified kinds,” as clearly conveyed in the

hundreds of observations he cited in ‘‘The Origin of

Species” (edition of 1872) and especially in his ‘‘ Varia-

tion of Animals and Plants Under Domestication,” is : oe

78 = THE AMERICAN NATURALIST [Vou. XLVI

that such individual differences were in the nature of

minor saltations of character, structural or functional,

and always hereditary. Since Darwin observes that

natural selection may be strictly compared with the slow

and gradual improvement of the racehorse, grayhound,

etc., if we collect all the observations which he assembled

as to the genesis of the racehorse and grayhound we may

gain a concrete understanding of his opinions as to the

genesis of species. It will appear that many of the new

characters which Darwin cites, and he used the term

‘‘new characters’’ interchangeably with ‘‘individual dif-

ferences,’’ are clearly identical with minor saltations or

with the ‘‘mutations of De Vries,’’ as generally under-

stood by zoologists to-day.

‘We may therefore conclude,” observes Darwin,*

‘‘that, whether or not the various existing breeds of the

horse have proceeded from one or more aboriginal stocks,

yet that a great amount of change has resulted from the

direct action of the conditions of life, and probably a still

greater amount from the long-continued selection by man

of slight individual differences.’’ Among the examples

he cites in amplification of this conclusion are the fol-

lowing:

(1) Eight incisors or two super-normal; (2) canines in

females; (3) a nineteenth or posterior rib; (4) a supple-

mentary hock-bone; (5) a reversional trapezium and

Mtc.V; (6) horn rudiments in the frontal bones one or

two inches in length; (7) tailless foals which, he observes,

might have produced a new breed; (8) curled hair corre-

lated with short manes and tails and mule-like hoofs.

All the above ‘‘individual differences’’ are cited by

Darwin as hereditary; all are ‘‘discontinuous’’ in Bate-

son’s sense or ‘‘mutations’’ in De Vries’s sense. In other

parts of Darwin’s works most of the numerous references

made to ‘‘individual variations’’ in horses are of the

same character, namely, saltatory and hereditary. Al-

though (5) cited above is a ‘‘reversion,’’ reversions and

*** Animals and Plants under Domestication,’’ Vol. I, p. 55.

No. 542] DARWIN’S THEORY OF EVOLUTION fh: ae

ontogenic modifications are, for the most part, clearly

distinguished as belonging to another category.

Similarly Lutz’ has kindly analyzed for the writer

twenty-one cases cited by Darwin among insects as possi-

ble material for selection and as indicating modifications

by environment. Eight of these cases are doubtful;

seven cases represent ‘‘gradations,’’ or ‘‘slow degrees,’’

probable or possible continuity; six cases represent dis-

continuity. It seems to Dr. Lutz that Darwin made the

most of the cases of discontinuous variation he knew

about, but that for the most part he had continuous

variation in mind.

It is therefore of interest, in view of the neglectful and

almost contemptuous attitude of certain writers toward

Darwin’s observations, to make a fresh summary of the

principles found scattered through the pages of his great

work on ‘‘Variation,’’ reexpressing some of these prin-

ciples in modern terms.

Darwin on ‘‘ New Cuaracters’’ AND ‘‘[NDIVIDUAL DIFFER-

ENCES’’® as EXPRESSED IN MoperX TERMS

(1) Newly appearing characters arise from unknown

causes, either stable in heredity, variable in heredity, or

not hereditary at all.” (2) ‘‘Individual variations’’ are

minor suddenly appearing characters, heritable. (3)

Characters of all kinds, whether new or old, tend to be

‘inherited. Those which have already withstood environ-

ment will, as a rule, continue to withstand it and be truly

transmitted. (4) A change of environment is principally

but not invariably the source of new variations. (5)

There are periods of variability or mutability in which

many new characters appear. (6) New characters are

observed to accumulate in successive generations in the

* Frank E. Lutz, letter to the writer, December 15, 1911, ‘‘ References to

insects in the ‘Origin of Species,’ —_ those bearing on the question

of continuity versus discontinuity.’

*See American edition, 1900, ‘‘Animals and Plants under Domestica-

tion,’’ dated by Darwin January, 1872.

? Vok L 9; 87:

80 THE AMERICAN NATURALIST [ Vou. XLVI

same direction. (7) There is a predisposition to similar

progressive variations in descendants of one stock

(termed ‘‘analogous or parallel variation’’) due to un-

known causes acting on similarly constituted organisms.’

(8) There is a marked prepotency in heredity in saltatory

types, e. g., ancon sheep, turnspit dogs. (9) There is ‘‘in

a certain sense’’ a mosaic inheritance (after Naudin)

observed in hybrids, or character segregation by self at-

traction and self affinity. Similarly there is an exclusive

inheritance, as observed in characters derived exclusively

from the father or mother and lying dormant or latent

for many generations. (10) There is a particulate inher-

itance, for example, of the special quality of vigor and

endurance observed in descendants of the racehorse

‘*Hiclipse’’; i. e., a dominance of single characteristics.

(11) A large number of individual variations cited are

antithetic characters rather than slight or infinitesimal

gradations of similar cl ters, €: g.,

Erect ears Drooping ears

Fertility Sterility

Immunity < Non-immunit :

Resistance to environment Non-resistance to environment

(12) Environment directly affects the antithetic charac-

ters of sterility and fecundity. (13) New characters may

appear and old ones disappear at any stage of develop-

ment.® (14) There is a similar age heredity or inher-

itance at corresponding periods of life. (15) There is a`

sex-limited heredity. (16) There is a correlated varia-

bility or coupling of new characters in heredity, e. g.,

black color of the skin and immunity from disease. (17)

Particulate inheritance as shown in non-blending colors,

e. 9., gray and white mice produce piebald young, or gray

or white young, but never a blend between gray and

white. (18) Old characters lying latent are ready to be

evolved under certain old environmental conditions.

Thus we observe the ontogenic revival of feral characters

*Vol. II, p. 329.

°’ Vol. TI, p. 392.

No. 542] DARWIN’S THEORY OF EVOLUTION Cae

in feral environment, and of domesticated characters in

return to domestication, e. g., barking in dogs. (19)

Ontogenic reactions to environment are observed in all

external and internal characters in animals and plants.

(20) Under selection Darwin anticipated the theory of

organic or coincident selection.!°

SuMMARY

Darwin did not so sharply distinguish in language as

Weismann and Mendel have taught us to between the

different kinds of variation and different factors of evo-

lution, yet in his observations and the cases he cites his

perception is absolutely clear between heredity, ontogeny,

environment and selection as interoperating factors. In

fact, he remarks! on the frequent difficulty of distin-

guishing between the inextricably mingled factors of

ontogeny (e. g., effects of use and disuse), and of corre-

lated or coadapted variability and of spontaneous varia-

tions. A comparison of all the various kinds of varia-

tion cited by Darwin in his two great volumes shows that

they fall into the following four classes:

I. ‘‘Individual variations,’’ ‘spontaneous variations,”’

new suddenly appearing heritable characters, practically

equivalent to the minor mutations of De Vries, believed

by Darwin to be the chief material of natural selection

and evolution.

II. Sports, or major saltations, such as the ‘‘mau-

champ,” ‘‘ancon’’ and ‘‘niata’’ breeds, believed by Dar-

win not to occur in a state of nature.

III. Fluctuations of proportion, congenital and hence

transmissible, equivalent to the quantitative variation of

Bateson, best illustrated by Darwin in his theory of the

evolution of the long neck of the giraffe:

So under nature with the nascent giraffe, the individuals which were

the highest browsers, and were able during dearths to reach even an

inch or two above the others, will often have been EER for they

* Vol. II, pp. 317, 318.

” Vol. II, p. 327.

82 THE AMERICAN NATURALIST (Vou. XLVI

will have roamed over the whole country in search of food. That the

individuals of the same species often differ slightly in the relative

lengths of all their parts may be seen in many works of natural history,

in which careful measurements are given. These slight proportional

differences, due to the laws of growth and variation, are not of the

slightest use or importance to most species. But it will have been other-

wise with the nascent giraffe, considering its probable habits of life;

for those individuals which had some one part or several parts of their

bodies rather more elongated than usual, would generally have survived.

These will have intererossed and left offspring, either inheriting the

same bodily peculiarities, or with a tendency to vary again in the same

manner; whilst the individuals, less favored in the same respects, will

have been the most liable to perish.

IV. Fluctuating variability, clearly distinguished by

Darwin from II and not especially connected by him with

the process of evolution.

December 30, 1911

THE COLOR SENSE OF THE HONEY-BEE: THE

POLLINATION OF GREEN FLOWERS!

JOHN H. LOVELL

WALDOBORO, ME.

CARL NAGELI, in a memoir often cited, after stating the common opin-

ion that insects are especially attracted by the bright coloration of floral

organs, says: “ We understand now why there are no green flowers;

they would be invisible in the midst of foliage,”

We seem to dream when we read these lines written seriously by a

naturalist. As the lists below demonstrate, not only are there a large

number of green or greenish flowers, invisible or scarcely visible in the

midst of foliage, but insects discover them without the least diffculty.

This false notion of the non-existence of green flowers, which can

only be excusable among those unacquainted with botany, has arisen

from many causes; the plants which bear flowers of this nature are only

cultivated when they are of medicinal use or are valuable for food, when

they are frequently regarded as vegetables rather than as flowers. In

foreign countries natural history collectors travelling for horticulturists

disdain everything which has not at least a decorative foliage. Further-

more, the authors who attach great importance to the coloration of the

floral envelopes for the attraction of insects have often neglected to

mention in their works that such and such a species, though fertilized

by winged arthropods, possesses green or greenish flowers. H. Miiller

has committed this fault many times, and Charles Darwin in his cele-

brated work on the fertilization of orchids passes over the color usually

in silence.

` A reaction was necessary; it was important to remind biologists that

there exists a long series of green flowers, greenish, or scareely visible,

which insects find as easily as the others, despite the absence of their

so-called attractive colors.’

Plateau then proceeds to enumerate 91 entomophilous

species, of which 41 had green or largely green flowers,

<The Color Sense of the Honey-bee: Is Conspicuousness an Advantage

to Flowers???’ Amer. NAT., 43, 338-349, June, 1909; ‘‘The Color Sense of

the Honey-bee: Can Bees Distinguish Colors??? Amer. NAT., 44, 673-692,

84 THE AMERICAN NATURALIST [ Vou. XLVI

38 greenish and 12 brownish or brown flowers, to the

larger part of which insect visits had been observed by

himself or other floroecologists. Of 72 of these forms he

examined the color himself and observed insect visits to

63 of them, or more than two thirds. Plateau believed

that the visits of insects to green flowers very strongly

supported his views, and in one of his last papers on the

pollination of Listera ovata, an orchid with green flowers,

he again returns to this subject. In a letter to the writer

he states that he had made innumerable observations on

the pollination of green flowers, which had extended over

twelve years. His conclusion as finally expressed is as

follows:

It is not the colors more or less bright of the corollas but other causes.

which guide to flowers their winged pollinators. Green or greenish

flowers notwithstanding their hue similar to that of foliage are as

effectively fertilized by insects as white, blue, red, or yellow flowers,.

consequently, all these floral colorations might disappear from nature

without the pollination and reproduction of plants being diminished.’

It is desirable to examine briefly the pollination of

green flowers and to consider whether this conclusion is

sustained or not.

A familiar example of a yellowish-green flower attract-

ive to insects is offered by the garden asparagus (As-

paragus officinalis). The flowers are mellifluous, pleas-

antly scented and frequented by honey-bees and less

often by smaller species of bees. Müller says that ‘‘in

spite of their inconspicuous color they are easily visible

at a distance”; but Plateau describes them as ‘‘peu

visible,’’ an illustration perhaps that an observer is apt

to be influenced by his point of view as well as by the

color of the flower. As the result of personal trial I find

that they can be distinctly seen at a distance of at least

fifty feet. Another yellowish-green flower is Tilia ulmi-

‘folia, or basswood, which, according to both Müller and

Plateau, is sought by honey-bees in immense numbers.

This is also true of the American basswood (Tilia ameri-

* Plateau, F., ‘‘La pollination d’une orchidée a fleurs vertes ‘ Listera

ovata R. Br.’ par les insectes,’’ Bull. Soc. roy. Belgique, 46, 339,,1909.

No. 542] COLOR SENSE OF THE HONEY-BEE 85

cana), which, according to Root, an eminent authority on

American apiculture, furnishes more honey than any

other plant known, with perhaps the single exception of

the white clover. Other greenish, or dull-colored flowers,

which the honey-bee was observed to visit were Ampel-

opsis quinquefolia, Teucrium Scorodonia, Comarum pa-

lustre, Atropa Belladonna, and several species of Scro-

phularia.

But of the 91 greenish or brownish hued species the

honey-bee was seen to visit only 27, that is, there are no

recorded visits of this bee to a little over seventy per cent.

of the listed flowers. To four species there are no rec-

ords of the visits of any insect. The remaining species

were chiefly visited by flies, sometimes minute species,

beetles, and the less specialized Hymenoptera; but He-

dera helix was attractive to wasps and Platanthera bi-

folia to Lepidoptera. How meager the number of visits

was should be noted: Celastrus Orixa was visited

only by the domestic fly and one other species of Diptera;

Alchemilla hybrida only by small Muscide; Alchemilla

alpina in the Alps by one beetle and two Muscide; Alche-

milla fissa in the same mountains by three Muscide; the

sessile green flowers of Herniaria glabra were visited

only by very small insects; the yellowish-green flowers

of Amarantus retroflexus by the domestic fly and one

beetle; Lepidium Smithii by small flies and many beetles

of the genus Altica; Angelica pyrenea by one beetle and

two flies; three species of Euphorbia were visited only

by flies; Salsoda Soda by Syritta pipiens and microscopic

Diptera; among brownish flowers Pelargonium triste was

visited by one fly; Vincetoxicum purpurascens only by

Musca domestica; the brown-violet flowers of Veratrum

nigrum and the reddish flowers of Neottia Nidus-avis

only by flies. According to this list, in a few instances

greenish flowers secreting nectar very freely are visited

by a large number of insects, but the majority of the-

species are evidently not well adapted to entomophily. —

*Root, A. I., ‘The ABC of Bee Culture,’’ p. 38, 1903. |

86 THE AMERICAN NATURALIST [ Vou. XLVI

This conclusion is sustained by an examination of the

green flowers of eastern North America. In the terri-

tory east of the 102d meridian and northward of North

Carolina and Tennessee there are 1,244 green or dull

colored flowers, of which 1,021 are anemophilous or hydro-

philous, while 223 are entomophilous or autogamous.

The wind-pollinated flowers are small and usually grèen-

ish, as in the 705 species of grasses and sedges, from

which the inference is commonly drawn that anemophily

and inconspicuousness are correlated. In the few excep-

tions (about 27 in the flora of the eastern states) where

anemophilous flowers have brighter hues, as in the golden

yellow aments of the yellow birch and the deep red pani-

cles of the field sorrel (Rumex Acetosella), the colors of

the small flowers are usually determined by the produc-

tion of yellow or red pigments in great abundance by the

vegetative organs—the entire plant of the field sorrel

being sometimes red-colored.

Of the 223 green flowers, which are entomophilous or

autogamous, many have no petals, as fifteen species of

the Polygonacee and eight species belonging to the

Caryophyllacee, also in several Rosaceæ, in Acer sac-

charinum and Didiplis diandra. Many are self-fertilized,

as Triglochin and Scheuchzeria, and the orchids Habe-

naria hyperborea and Epipactis viridiflora, and the small

green flowers of Lechea and Penthorum sedoides. Some

have the petals caducous and depend upon their scent to

attract insects, as the Vitaceæ. Many are visited chiefly

by flies and the smaller bees, as various Melanthacex, the

Smilacee, and the green flowers of the Asclepiadacee.

A few species secrete nectar freely and attract numerous.

visitors, as the rock maple, basswood and the dark green

pistillate flowers of Rhus typhina. Large green flowers,

which are fragrant, nocturnal and are pollinated by

moths, are found in exotic Solanaceæ and Orchidaceæ. It

1s obvious that bright coloration is less important to

moth flowers than a strong Scent, since red and blue

No. 542] COLOR SENSE OF THE HONBY-BEE 87

shades are invisible at night. But as a whole green

flowers are small or even minute and attract few insects.’

Since in Europe and America, where the insect fauna

is rich both in species and individuals and the flora dis-

plays a great variety of brilliant hues and delicate shades,

dull-colored flowers are not well adapted to entomophily,

it may be inferred that in a country where the flowers

are largely greenish there would be a scarcity of antho-

philous insects. According to A. R. Wallace and G. M.

Thomson this condition is partially realized in the Islands

of New Zealand. Wallace says:

In New Zealand where insects are strikingly deficient in variety the

flora is almost as strikingly deficient in gayly colored blossoms. Of

course there are some exceptions, but, as a whole, green, inconspicuous

and imperfect flowers prevail to an extent not equalled in any other part

of the globe, and affording a marvellous contrast to the general brillianey

of Australian flowers, combined with the abundance and variety of its

insect life. We must remember, too, that the few gay or conspicuous

flowering-plants possessed by New Zealand are almost all of Australian,

South American, or European genera. .. . After the preceding para-

graphs were written, it occurred to me that, if this reasoning were

correct, New Zealand plants ought to be also deficient in scented flowers,

because it is part of the same theory that the odors of flowers have, like

their colors, been developed to attract the insects required to aid in their

fertilization. I therefore at once applied to my friend Dr. Hooker, as

the highest authority on New Zealand botany; simply asking whether

there was any such observed deficiency. His reply was, New Zealand

plants are remarkably scentless.

After quoting the above passage, G. M. Thomson, who

resided in New Zealand and made a special study of its

fioroecology adds:

It is impossible to differ from this reasoning in toto, because the

statements and facts on which it is founded are to a great extent correct

though in the light of more recent oni they require considerable

modifieation.®

Bees and intone. according to Thomson, are com-

paratively rare; while Diptera, of which it is estimated

* Lovell, John H., ‘‘The Colors of Northern Gamopetalous Flowers,’’

AMER. Nar. i 365-384 and 443-479.

, G. M., ‘‘On the Fertilization of New Zealand Flowering

Plants Si ea Proc. N. Z. Inst., 13, 241-288, 1880; Wallace, A. + Phe

Geopraphinas Distribution of Abia, > 1, 457-464.

88 THE AMERICAN NATURALIST [Vou. XLVI

there may be a thousand species, are here the chief agents

in the pollination of flowers, whereas in America and a

large part of Europe they occupy the second place and in

the Alps the third place. Neither honey-bees nor bumble-

bees were found in New Zealand at the time of its dis-

covery.

The phylogenetic history of green flowers likewise

strongly supports the view that they are not well adapted

to pollination by insects. In the opinion of many emi-

nent botanists all greenish, inconspicuous flowers have

been derived by retrogression from larger entomophilous

ancestors. This theory has been very ably developed by

Professor C. E. Bessey in his taxonomy of the Angio-

sperms, for which he suggests the restoration of the more

appropriate name of Anthophyta. The buttercups

(Ranales), the water plantains (Alismales) and roses

(Rosales) are regarded as primitive and are placed at

the beginning of the Anthophyta. The typical flower was

entomophilous, of large size, and its organs were sepa-

rate and spirally arranged. Engler’s spiral series of

Monocotyledons, which is composed of orders mostly

devoid of a perianth, is derived from a liliaceous type;

while the Apetale are treated as reduced forms and dis-

tributed among the petalous Dicotyledons.”

A similar view is adopted by Arber and Parkin in their

discussion of the origin of Angiosperms. They reach the

conclusion ‘‘that the Apetalous orders without perianth,

such as the Piperales, Amentiferous families and Pan-

danales, can not be regarded as primitive Angiosperms,

_ but have been derived from ancestors with a well-de-

veloped perianth. Entomophily . . . has supplied the

‘motive force,’ which not only called the Angiosperms

into existence, but laid the foundation of their future

prosperity.’’> Even if Engler’s system of classification

"Bessey, Charles E., ‘‘The Phylogeny and Taxonomy of Angiosperms,’’

Bot. Gaz., 24, 145-178, 1897; “A Synopsis of Plant Phyla,’’ University

Studies, 7, 275-373, 1907; ‘‘The Phy

29, 91-100, 1909, ete.

-Arber B. A: Newell, and Parkin, John, ‘‘On the Origin of Angio-

sperms,’’ Journal of Linnean Society (Botany), 38, 29-80, 1907.

letie Idea in Taxonomy,’’ Science,

No. 542] COLOR SENSE OF THE HONEY-BEE 89

is accepted and the apetalous orders be regarded as primi-

tive it does not support the thesis that small, green

flowers are at no disadvantage in attracting insects be-

cause of their inconspicuousness. That reduction and

change from entomophily and conspicuousness to ane-

mophily and inconspicuousness has occurred repeatedly

in widely separated families is not questioned by any eco-

logist or taxonomist. This is illustrated by the genera

Artemisia, Ambrosia, etc., among the Composite; in

Ricinus of the Euphorbiacex ; probably also in the family

Juncacex, and in species of Thalictrum, Fraxinus, San-

guisorba and Poterium. The evidence supplied by the

phylogeny of green flowers is wholly in favor of the value

of color contrast for gaining the attention of insects.

Approaching the problem from another direction, the

Rev. George Henslow in his work on the self-fertiliza-

tion of plants finds that ‘‘inconspicuous flowers sees gi

most invariably self-fertilizing, or else inconspicuous.’

There are several reasons why inconspicuous flowers are not likely to

be intererossed by insects: (1) Their unattractiveness; (2) the absence

of hohey-secreting organs; (3) the want of scent; (4) they frequently

do not expand, or at most remain half open, especially in cold or inclem-

ent weather, while perfectly cleistogamic flowers are, of course, never

open; (5) their structure sometimes would seem absolutely to prevent

the ingress of insects (such appears to be the case with Polygonum

Convolvulus and-P. hydropiper, the flowers of which seem to be always

closed, and with many others.

He regards existing inconspicuous forms not as primi-

tive, but as derived from conspicuous progenitors, which

in turn owed their origin to the selective influence of

insects.° ;

It has been shown that Plateau’s conclusion is not sus-

tained either by the phylogeny and distribution or by the

ecology and manner of fertilization of inconspicuous

flowers, which have almost universally been compelled to

adopt anemophily or autogamy. In the few exceptional

cases there are present other allurements, as odor and

nosar, which sooner or later attract insects; but this

Henslow, George, ‘‘On the Self-fertilization of Plants,’’ Trans. -Pe

Soc. (Botany), Ser. 21, 317-398, 1880.

90 THE AMERICAN NATURALIST [ Von. XLVI

does not prove that ceteris paribus color contrast is not

an advantage. No assertion is made that bees have an

antipathy to green, only that flowers of this hue are not

as readily seen amidst the foliage. Very likely a green

flower opposed to red or yellow leaves would attract the

attention of insects as readily as the reverse contrast.

Following the example of Plateau, I have included the

species of Tilia among greenish flowers, but it is doubtful

whether the inflorescence of the American basswood

should be considered as inconspicuous. The flowers are

of medium size, sweet scented, produced in vast quanti-

ties, and are described by a disinterested observer as

‘‘vellow and rather pretty.’’ The nectar is so copious

that a single hive of bees has obtained 66 pounds in three

days, and its odor is so strongly aromatic that it can be

perceived throughout an entire apiary.° It may, how-

ever, serve as an example of an exceptional species. The

importance of scent as an attractive factor was, of course,

recognized by Miiller, but green flowers are usually odor-

less, as pointed out by both Hooker and Henslow."!

As additional evidence that insects will visit green.

flowers Plateau describes how he placed honey on seven-

teen anemophilous flowers, as grasses, sedges, rushes and

on species of Rumex and Chenopodium, and observed

visits of honey-bees, flies and a few other insects.12 He

also fashioned crude imitations of flowers from the liv-

ing leaves of the red currant (Ribes rubrum) and the

sycamore (Acer Pseudo-Plantanus), in which he put

* Root, A. I., ‘‘The A B C of Bee Culture,’’ p. 397, 1903. A single

colony of bees belonging to the late Dr. Gallup, of Orleans, Iowa, once

gathered 600 pounds of basswood honey in thirty days. Doolittle, G. M.,

‘‘ Honey from Basswood,’’ Gleanings in Bee Culture, 36, 23, 1908.

“A nectariferous flower may be both green and scentless and yet be

found by bees. According to Fritz Miiller the flowers of a species of

Trianosperma in South Brazil are visited very abundantly all day long by

Apis mellifica and species of Melipona, although they are scentless, greenish,

quite inconspicuous, and to a great extent hidden by the leaves. ‘‘

Fertilization of Flowers,’’ p. 270.

“Plateau, F., ‘‘Comment les fleurs attirent les insectes,’’? Bull. Acad.

roy. Belgique, ins partie, 3me série, 34, 602-612, 1897.

No. 542] COLOR SENSE OF THE HONEY-BEE 91

honey, and they attracted bees and flies.1* Attention is

also called to the secretion of nectar by extra-floral nec-

taries upon the petioles of Prunus, the stipules of Vicia

and the leaves of various trees. These sources of sweet

secretions are frequently visited by Hymenoptera and

other insects, as well as over-ripe or partially decayed

frut.

A more interesting example than any given by Plateau

of the secretion of nectar by extra-floral nectaries is

furnished by the American cotton plant. Besides the

nectar glands within the flowers there is a small gland on

the center rib on the under side of each leaf, which at —

times secretes nectar very freely. When the atmospheric

conditions are right, says Mr. J. D. Yancey. in a recent

number of Gleanings in Bee Culture, drops of nectar will

collect on these leaf glands so large that they may be

readily tasted; and a bee has to visit only a very few to

obtain a load.

At such times they neglect the blossoms entirely, and the honey

comes in with a considerable rush. I could not tell that this honey was

any different in either color or flavor from that gathered from the

blossoms.

No other plant in this country besides cotton is known

to me which has extra-floral nectaries, which are of value

as a source of honey; but in favorable years there occurs

on a scale of enormous magnitude an illustration that

honey-bees will readily learn to gather sweet liquids from

green leaves. In many parts of Europe and Ameriċa

Aphididæ, or plant-lice, and scale insects (Lecanium)'*

excrete a sweet substance called honey-dew in such large

quantities that not only the leaves of the trees, but even

the grass and the sidewalks, are coated with it as with a

varnish. Honey-dew is attractive to many insects, as

bees, ants, wasps and flies. In California it is sometimes

In Hawaii enormous quantities of honey-dew are produced by a leaf-

hopper. Phillips, E. F., ‘‘The Souree of Honey-dew,’’ Gleanings in Bee

Culture, 38, 177, 1910.

* Loe. cit., 5me partie, p. 868.

* Loc. cit., 4me partie, p. 604.

92 THE AMERICAN NATURALIST [ Vou. XLVI

so abundant that bees gather large stores of it, and Pro-

fessor Cook says that he has sold it by the barrel.'®

From Sevensville, Montana, a correspondent of Glean-

ings in Bee Culture wrote a few years ago that the honey-

dew had been in a continuous flow throughout the whole

season, and dripped on the sidewalk every night in large

quantities. Another bee-keeper at Dupont, Indiana,

states that, in 1884, his bees gathered about two tons of

honey-dew from the leaves of the oak, hickory, beech and

wild grape. But the year, 1909, was in the opinion of

well-informed apiarists the greatest year for honey-dew

ever known in America. Bee-keepers everywhere re-

ported a scarcity of white clover and basswood honey and

that the bees were storing honey-dew. Professor Surface

says:

I have never known a year in all my studies of entomology, and in a

correspondence of thousands of persons each month, during which

plant-lice, or aphids, have been so abundant as they have this year

(1909), and consequently the honey-dew was likewise unusually abun-

dant.”

Many tons of this sweet excretion were consumed by

the bees during the following winter.

I have dwelt at some length on the collection of honey-

dew in order to establish beyond any question, not only —

that domestic bees would, but that they do gather large

supplies of sweet substances from green leaves. If addi-

tional evidence could strengthen this statement it is fur-

nished by every apiary, where bees frequently may be

seen feeding on materials of every hue, or entering dark

supers, hive-bodies, or boxes, through narrow crevices or

small apertures no larger than a bee’s body in search of

honey. Honey-bees require a great amount of stores and

it would be greatly to their disadvantage, if their actions

were dominated by bright coloration to such an extent

that they were prevented from obtaining food supplies

1 Root, A. I., and Root, E. R., ‘‘The A BC and X Y Z of Bee Culture,’ ’?

p. 273, 1910.

* Surface, H. A., ‘‘Sources of Honey-dew,’’ Gleanings in Bee Culture,

37, 623, 1909. l

No. 542] COLOR SENSE OF THE HONEY-BEE 93

from every available source. It is, then, freely admitted

that bees will collect sweet liquids, after they have once

been found, from green or dull-colored surfaces; but

this is very far from proving that bright coloring is not

an advantage to flowers, and it is astonishing that such a

claim based on the above facts should ever have been

made. .

Knuth in reviewing the observations of Plateau on

greenish and brownish flowers very properly raises the

objection that ‘‘Plateau has not compared the frequency

of insect visits to inconspicuous and conspicuous flowers

of the same size, and it is only experiments of this kind

which can help to settle the point at issue.’”!* This omis-

sion is fatal to Plateau’s argument, and it is difficult to

understand why control experiments were not employed.

It is the object of the present paper to present the results

of a long series of experiments, in which honey-bees

under similar conditions were given the choice between a

conspicuous and an inconspicuous object.

s a preliminary inquiry it is of interest to determine

whether plants with diccious inflorescence afford any

assistance in deciding this question. As is generally

known, the staminate flowers of entomophilous and some-

times of anemophilous diclinic species are more con-

spicuous than the pistillate. This is well shown by the

genus Salix. Willow branches bearing staminate aments

are offered for sale in New England cities in early spring,

and are used for decorative purposes in the churches of

England on Palm Sunday. Careful observation and col-

lection of the visitors of Salix discolor (the glaucous or

pussy willow), the earliest species of Salix to bloom in

this locality, shows that the number of insects attracted

by the staminate aments is much greater than by the

pistillate. The difference is, indeed, so marked as to be

readily apparent to any one who will keep an individual

shrub of each form under observation for a few hours.

13 Knuth, Paul, ‘‘Handbuch der Bliitenbiologie,’’ 1, 394, 1898; ‘‘ Hand-

book of Flower Pollination,’’ translated by J. R. Ainsworth Davis, 1, 207, —

1906. a as

94 THE AMERICAN NATURALIST [Vor. XLVI

Another common dicecious plant is Rhus typhina L.

(Rhus hirta (L.) Sudw.).1° The staminate flowers are in

large white panicles. The thyrsoid, pistillate flower-

clusters are dark green; but as they are terminal and

borne well above the foliage they are visible at a long

distance, i. e., they have conspicuousness of position. Two

large groups of this shrub, or small tree, one of which

was pistillate and the other staminate, growing in an

open woodland only a short distance apart, were selected

for observation. During two collecting trips in July,

1909, I secured on the staminate blossoms 77 visitors, but

only 6 on the pistillate. Of the visitors to the staminate

flowers 63 were bees, 2 wasps, 2 flies, 8 beetles and 2

Hemiptera. Of the visitors to the pistillate flowers 4

were bees and 2 wasps. Even a brief inspection is suff-

cient to show that the staminate flowers are more attract-

ive to insects than the pistillate.

The staminate inflorescence of Salix discolor and Rhus

typhina is, then, undoubtedly more conspicuous and

attractive to insects than the pistillate; but is this larger

company of visitors due wholly to its brighter coloration?

Evidently not. Great numbers of honey-bees and many

species of Andrena frequent the staminate aments of

Salix to procure pollen for brood-rearing. At least five

species of Andrena are oligotropic visitors of this genus.

Examination of the polleniferous scopa of the bees taken

on the staminate flowers of Rhus typhina showed that

they all contained pollen except nine specimens of Proso-

pis (P. modesta Say and P. zizie Rob.), a primitive

genus, the species of which possess only feebly developed

brushes on the posterior legs, which are not used for

carrying pollen. Of the eight species of beetles taken on

the staminate flowers microscopic examination showed

an abundance of pollen on the mouth-parts of four. The

other four beetles were of small size, and it was not

definitely determined whether they or the other insects —

mentioned above were feeding on pollen or not. But this

2 The flowers of Rhus typhina are given as polygamous in most plant

manuals, but they are certainly diccious, as is also stated by Müller.

No. 542] COLOR SENSE OF THE HONEY-BEE 95

was of little consequence, since the proof is ample that in

the case of the staminate plants of Rhus typhina, as in

Salix, the pollen is an important factor in attracting

visitors.

It is commonly believed that insects are attracted first

to the staminate flowers of entomophilous diccious plants

by their greater conspicuousness, from which subse-

quently they carry pollen to the pistillate flowers. For in-

stance, Müller says of the dicecious flowers of Asparagus

officinalis: ‘‘This instance confirms Sprengel’s oft-re-

peated rule that the male flowers of diclinic plants are

more conspicuous than the female, whence insects are

likely to visit the two kinds of flowers in their proper

sequence.’’2? But it is clear that many insects never fly

to the pistillate flowers, since if they did the number of

visitors to the two kinds of flowers would be equal. This

is especially true of female bees, which, having obtained

their load of pollen, often return directly to the hive or

nest. Of the four bees taken on the pistillate flowers of

Rhus typhina only two had pollen on the scopa of the

hind legs. After collecting the pollinators of this species

for several seasons I think it probable that some of the

species of bees taken on the staminate flowers are never,

or very rarely, found on the pistillate blossoms.” Spren-

gel’s rule must, therefore, be accepted with considerable

reservation.

The observations on diccious flowers not proving well

adapted for the purpose intended, owing to the presence

of pollen as an attractive factor, the following experi-

ment was tried. The flowers of Gerardia purpurea have

a rose-colored, campanulate corolla and a short bell-

shaped calyx. The species is common in this locality and

is sparingly visited by bumblebees. When a large bou- —

quet of the flowers was placed in front of a hive of black

bees, it received very little attention. Apparently they

contained no nectar. I now placed in the throat of a

” Müller, H., ‘‘The Fertilization of Flowers,’’ p. 549. |

2 This is also true of dichogamous flowers. Robertson, C., ‘‘ Flowers

and Insects,’’ Bot. Gaz., 27, 41, 1899.

96 THE AMERICAN NATURALIST [Vou. XLVI

large number of flowers a small drop of honey. From a

number of other stems I removed all the corollas and all

conspicuous buds, and between the green calyx teeth I

also put a drop of honey. So abundant was the honey on

the green calyces that it could be seen at a distance of

four feet. I could detect no scent in the complete flowers;

certainly they seem to possess none comparable with that

of honey. The two clusters of plants, the one decorallated

and the other with its flowers complete, were placed on

opposite sides of a glass of water, which was set near the

entrance of a hive of black bees. The bees immediately

showed a decided preference for the flowers retaining their

corollas, as many as five visiting them at one time; while

there were no bees on the denuded flowers though they

were on the side of the glass nearer the hive. Later the

bees discovered, as was to be expected, the honey on the

green calyces and removed it. It is evident that to place

honey on small green flowers, as in the experiments of

Plateau with grasses and sedges, and when it is finally

found by insects to conclude that conspicuousness is not

an advantage is unjustifiable. The bees gave a decided

preference to the brighter-colored flowers, and the fact

that they subsequently discovered and removed the honey

from the green calyces furnishes no evidence whatever

against the benefit of color contrast.

But a method of experimenting was wanted, which

would permit of varying the conditions under which the

conspicuous and inconspicuous objects were exposed, and

of counting the number of visits to each. This was ob-

tained in the following manner: A small number of

honey-bees were trained to visit for honey an unpainted,

dull-gray board raised upon a support two feet high. A

short time before the honey, which was placed directly on

the board, was wholly removed, a conspicuous and an

inconspicuous object were placed at equal distances from

the board and at a known distance from each other. As

soon as the bees had consumed the honey they began

describing a series of ever widening circles in search of

a new supply until one or both of the above-mentioned

No. 542] COLOR SENSE OF THE HONEY-BEE 97

objects were discovered. The number of visits made to

each in a given time was then counted, and served as a

basis for estimating numerically the value of conspicu-

ousness.

On October 1, 1909, a small number of bees were accus-

tomed to visit the dull-gray board, on which there was a

small quantity of honey. For convenience this board will

be called the feeder. While the bees were busily at work,

I put a blue slide (prepared by placing the floral leaves

of the bee larkspur (Delphinium elatum) between two

glass object slides, 3 X 1 in.), on the center of which there

were a few drops of honey, on the grass of the lawn about

three feet from the base of the feeder; and on a dandelion

leaf three feet from the base of the feeder and five feet

from the blue slide honey was also placed. As soon as

the supply of honey on the feeder was exhausted the bees

began circling in the air. In a few minutes one bee had

found the blue slide, in ten minutes two bees, and in

twenty-five minutes five bees; but none had found the

honey on the dandelion leaf. I now placed beside the

dandelion leaf an apple leaf with a comparatively large

quantity of honey on it, and at the end of forty minutes

one bee found it and a little later a second bee. I doubt

if they would have found it then had they not for some

time previously been flying low searching for honey in

the grass, having from their previous experience with

the blue slide learned to look for it there. In this experi-

ment the advantage was clearly on the side of the con-

spicuous object. It would appear that if two flowers

were blooming at some distance apart, the one bright

colored and the other green, the former would be the more

likely to be pollinated.

On October 3, at 12:33 r.m., I repeated this experiment.

The blue slide, a dandelion leaf, both on the grass, and

the base of the feeder formed the angles of an equilateral

triangle, each side of which was three feet. Honey was

placed on all three as before. Two minutes after the last

drop of honey on the feeder had disappeared three Italian

98 THE AMERICAN NATURALIST (Vou. XLVI

bees found the blue slide. At 12:40 there were eight bees

on the blue slide, but not one had found the honey on the

dandelion leaf. Five minutes later there was one bee on

the leaf.

If bees are guided by odor exclusively in their search

for nectar, and contrast in color with green foliage is no

advantage to flowers, then it would seem as though they

should find a quantity of free honey as readily as when it

is associated with bright coloration. About thirty Italian

bees were accustomed to visit the gray-colored board, or

feeder, which, as previously stated, rested upon a support

two feet high. Six feet from this support and six feet

apart, the three forming an equilateral triangle, were

placed two poles each 43 feet high. On top of one of the

poles was placed a quantity of honey so large that it ran

down on the side, and was visible at a distance of twenty

feet. To the top of the other pole was attached a cluster

of yellow ‘‘immortelles’’ (Helichrysum bracteatum)

gathered many years ago, and which appeared to be

absolutely devoid of scent. Each of the flowers was about

14 inches in diameter and the cluster was 3 inches long

by three inches wide. At 11:10 a.m., the bees were per-

mitted to consume all the honey on the feeding board. In

three minutes there were three bees and one fly on the

flowers, but no insects had found the free honey. In five

minutes there were four bees and one fly on the flowers,

and one bee on the free honey. At 11:20 the latter bee

left for the hive and five minutes later returned; a second

bee also alighted on the side of the pole and began suck-

ing the honey which had run down from above; two flies,

apparently house flies, also came. At the same time there

were six Italian bees on the flowers. At 11:30 a. m., there

were six Italian bees and one fly on the flowers, but only

one bee on the free honey. The flowers not only attracted

the bees earlier than the free honey, but three times as

many of them.

I now transposed the poles. But to the top of the pole

on which there had previously been the supply of free

pee AE

No. 542] COLOR SENSE OF THE HONEY-BEE 99

honey I fastened a single yellow ‘‘immortelle’’ one inch

across. The individual flower enjoyed the advantage of

position since it stood where the cluster had been before.

Honey was placed on all the flowers. At 11:50 a.m.,

there were nine Italian bees and a Syrphid fly on the

cluster of flowers and three Italian bees and one fly on the

single flower. The larger and more conspicuous object

notwithstanding its changed position received the greater

number of visitors.??

The following experiments were made in 1910, and only

black bees were employed. As in the experiments of the

preceding year, the bees were trained to visit the same

dull gray board placed upon a support two feet high. On

September 14, 1910, at 12:40 r.m., the bees were carrying

away syrup of sugar from the feeder. Nine feet from its

base I put out on the grass of the lawn a dried yellow

flower of Helichrysum bracteatum 14 inches in diameter,

containing a small quantity of honey. On the opposite

side of the feeder at a distance of nine feet from its base

I laid a Red Astrachan apple leaf, 2 inches long by 14

wide, on the center of which there was an ample supply

of honey. There were at least twenty-five bees on the

board and later the number increased. At 12:55 they had

wholly consumed the sugar syrup. At 1:07 a bee came to

the flower, but left almost immediately. At 1:10 a second

bee came to the flower, but soon left, and a few moments

later a third visit was made in the same way. No bees

had found the leaf. As the honey was excellent I could

account for the brief stop made by the bees only on the

ground that they were looking for sugar syrup. In the

next experiment this was offered to them.

At 1:20 r.m., I again put sugar syrup on the feeder,

and removed the flower and leaf from the grass. Another

‘‘immortelle’’ 14 ins. in diameter and another Red As-

trachan apple leaf, 2 inches long by 14 inches wide, were

laid on the grass on directly opposite sides of the feeder,

Cf. Miiller’s remarks on Geranium, Epilobium, Polygonum and the

Alsiner.

100 THE AMERICAN NATURALIST [ Vou. XLVI

but six feet instead of nine feet away from its base. The

leaf was on the same side as before, as was also the

flower. Sugar syrup, which is odorless, was placed on

each. At 1:30 the bees finished the syrup on the feeder.

One bee flew almost immediately to the flower, but made

a brief stay. At 1:34 a second bee came and sucked, and

three minutes later a third bee came. No bees had found

the leaf.

Sugar syrup was again put on the feeder, and the

flower and leaf were moved three feet nearer its base,

each now being distant three feet. At 1:47 the syrup on

the feeder was all consumed, but even previously one bee

had come to the flower. At 1:47 a bee flew over the leaf,

but did not alight. At 1:50 three bees came to the flower,

and a moment later a fourth, and afterwards two more.

At 2 r.m., there were three bees on the flower, a fourth

came a little later and then a fifth. No bees had visited

the leaf.

Syrup of sugar was again placed on the feeder. At 2:5

P.M., I put out the yellow flower and apple leaf used in

the irst experiment. On these, it will be remembered,

honey had been placed. They were laid on the grass on

opposite sides of the feeder, each three feet distant from

its base. At 2:10 the sugar syrup on the feeder was all

removed. A bee soon came to the flower, but did not

stop, a second bee came and sucked, a third bee came, but

did not stop, several bees came but did not stop; but at

2:13 there were three bees sucking honey on the flower.

A bee flew slowly over the leaf I thought it would cer-

tainly be attracted by the scent of the honey, but this was

not the case. The experiment was continued a little

longer and one or two more visits were made to the

flower, but none to the leaf.

The results obtained in the four preceding experiments

are deserving of careful attention. While the yellow

flower containing honey and the one containing scentless

sugar syrup were visited many times by bees, the leaves

remained wholly unvisited, though the supply of syrup

No. 542] COLOR SENSE OF THE HONEY-BEE 101

or honey on them was plainly visible at a considerable

distance. According to the reiterated statement of

Plateau all flowers might be as green as their leaves

without their pollination being compromised, and color

and form are of little consequence in comparison with

odor. But the experiments showed that color contrast is

of great value, and in these particular experiments indis-

pensable. If the leaves provided with an ample supply

of honey or syrup could not obtain a single visit under

the conditions described, where a large number of bees

were brought into their immediate vicinity, how little

chance there would be for an isolated plant with small

green flowers growing in a secluded location attracting

visitors! But a bright-colored flower in the same locality

would be much more likely to gain the attention of pollin-

ating insects.

On September 20, 1910, at 2:15 r.m., numerous black

bees were coming to the feeder for honey. At a distance

of three feet away I laid on the grass a bright yellow

flower of golden glow (Rudbeckia laciniata) two inches in

diameter. On the opposite side of the feeder three feet

from its base, I laid the end of a spike of Amarantus

retroflexus about three inches long. The small, pale

green flowers are thickly crowded in panicled spikes. An

ample supply of honey was placed on both. In the course

of fifteen minutes there were 18 visits to the flower of

golden glow and only 8 to the Amarantus cluster. If a

bee flew to either object, but did not alight because of the

large number of bees already there, this was counted as a

Visit.

The bees were again accustomed to visit the feeder.

In the preceding experiment one of the objects had been

placed on the east side of the feeder and the other on the

west. Both the flower of the golden glow and the spike

of Amarantus were now laid side by side on the grass in

the sunshine three feet to the north of the feeder. There

was honey on both. In less than ten minutes there were

fifteen visits to the golden glow and only three to the

102 THE AMERICAN NATURALIST [Von XLVI

spike of. Amarantus. At one time there were five bees

on the golden glow and only two on the spike of

Amarantus.

At 2:45 p.m., I repeated the preceding experiment, but

I placed the flower of the golden glow and the spike of

Amarantus on the south side of the feeder three feet

from its base, but only three inches apart. Honey was

put on both at the beginning of the experiment. In ten

minutes there were 18 visits to the golden glow and 5 to

the green spike of Amarantus. At one time there were

four bees on the flower of golden glow, but only one on

the spike of Amarantus. It often happens when a bee

comes to a flower on which one or more bees are already

at work that they will all fly up in the air and then all or

in part settle down again. Such flights were not counted.

Frequently a bee flew directly to the golden glow as

though it had been seen from a distance.

It will be remembered that Plateau put honey on the

green inflorescence of several species of Chenopodium,

besides other anemophilous flowers, and when it was

found by insects reasserted his oft-repeated conclusion

that winged pollinators are guided to flowers almost ex-

clusively by odor and that color contrast is of little value.

Plateau employed no control experiments, but it appears

from the experiments just described that though the odor

of the honey drew insects to the green inflorescence,

nevertheless it was at a disadvantage because of the

absence of bright coloration.

In several of the experiments of 1909 a blue slide was

used, prepared by placing the leaves of the perianth of

the bee larkspur (Delphinium elatum) between two glass

object slides tied firmly together with black silk. It

might perhaps be objected that the scent of these floral

leaves would escape through the narrow crack between

the two glass slides. While I think this improbable, and

that in any event it would be so slight as to bear no com-

parison with that of the honey placed upon the upper

glass slip and, therefore, would exert no influence on the

No. 542] COLOR SENSE OF THE HONEY-BEE 103

behavior of the bees, still it seemed desirable to test the

matter. For this purpose the following experiment, clos-

ing the series of 1910, was performed on September 23.

A blue slide was prepared as described and the edges

were sealed with several applications of gold size, the

odor of which is no doubt unpleasant to bees. The blue

slide, a dandelion leaf, and the base of the feeder formed

the angles of an equilateral triangle, each side being

three feet in length. As the weather was becoming

colder the bees were not flying freely. An ample supply

of honey was put on the blue slide and the leaf, which

were laid on the grass of the lawn at 9 r.m. At 9:20 the

honey on the feeder was entirely consumed. Presently

a bee hovered over the blue slide, but did not alight.

Another bee hovered over the blue slide for a long time

and finally alighted. A second, third and fourth visit was

made by bees at intervals. At 9:40 I discontinued the

experiment. No attention had been paid to the honey on

the leaf, though in the sunlight it could be seen for a long

distance. The hesitation of the bees at first may have

been caused by the repellent odor of the gold size. Bee-

keepers never paint their hives inside, as the scent of

paint is believed to be disliked by bees. The blue slide

and the leaf were left in position and when twenty minutes

later I examined them again all of the honey had been

removed from the slide, but that on the leaf appeared to

be untouched. Evidently the only factors which had in-

fluenced the bees in the previous experiments were the

honey and the color.

Of the series of experiments performed in 1911 only

three will bedescribed. A few observations were thought

desirable in which one or two bees were employed instead

of a larger number, in order that the behavior of an indi-

vidual bee might be followed when given the choice be-

tween a conspicuous and an inconspicuous object. A few

bees were accustomed to visit a glass slide for honey. |

While they were absent at the hive, the slide was re-

moved and a large rhubarb leaf was laid in its place. ©

104 THE AMERICAN NATURALIST [ Vou. XLVI

About two inches from the base of the leaf there was put

a quantity of amber-colored honey sufficiently large to

form an oval mass, which could be seen in the shade at a

distance of twenty feet. Twelve inches from the honey

and a few inches from the apex of the rhubarb leaf there

was placed a bright red flower of the Zanzibar balsam

(Impatiens sultani), an inch in diameter, on which there

was a small amount of honey.

A bee returning from the hive went directly to the red

flower, where it took up its load and flew away.

A bee came to the red flower. Two more bees came and

were impounded. The first bee left for the hive.

A bee returned to the flower. A second bee came, both

flew up in the air, and one of them went to the mass of

honey but soon returned to the flower. The first bee left

for the hive. I attempted to impound the second, but it

escaped.

A bee came to the flower, and after five minutes re-

turned to the hive.

The bee returned to the flower. A second bee came, and

hovered in the air for some time, but finally settled by

the bee on the flower. Both bees left for the hive. Both

bees returned to the flower, and when they again left I

discontinued the experiment. The rhubarb leaf was re-

moved and the bees were given honey on a glass slide.

It seems impossible to explain the behavior of the bees in

this experiment on the supposition that they were guided

chiefly by odor. In view of the large quantity of honey

and its easy accessibility there would have been no occa-

sion for surprise had the bees given it much greater

attention.

After carefully removing the honey from the rhubarb

leaf I placed near its apical end four flowers of the Zanzi-

bar balsam, forming a bright red square. On one petal of

each flower there was a small drop of honey. Ten inches

away near the base of the rhubarb leaf I put a single

petal of a balsam flower on which there was a large drop

of honey. While both bees were away I removed the

No. 542] COLOR SENSE OF THE HONEY-BEE 105 .

glass slide and substituted the rhubarb leaf, reversing

its position, however, so that the small object was where

the larger had been before.

Both bees returned to the cluster of four balsam

flowers. One of them presently flew over to the single

petal, but soon returned to the cluster; later it again

went to the petal and again returned. Both bees left

for the hive. :

A bee returned to the cluster, did not alight, but flew

over to the petal and sucked. When the second bee re-

turned it disturbed the bee on the red petal, and both

went to the cluster. One of the bees left for the hive.

A bee came from the hive to the cluster. One of the

bees then flew over to the petal but did not alight, re-

turned to the cluster. Both bees left for the hive.

Both bees returned to the cluster. One of them left for

the hive and on its return went to the petal. The bee on

the cluster left for the hive.

While the cluster of four red flowers received the

greater number of visits, as would be expected, more

attention was given to the drop of honey associated with

a red petal than was received by the larger oval mass of

honey alone in the preceding experiment.

In a series of interesting experiments with cotton

flowers where the visitors were chiefly a species of Melis-

sodes (M. bimaculata), recently described by Allard, it

was observed that when a flower was partially screened

by leaves the attention it received decreased ; and when

the petals were masked on both sides with sections of

green leaves the flower was ignored entirely.” This re-

sult was confirmed by the following experiment. On a

cloudy, windy day while a number of black bees were

visiting the feeder for honey, I placed on the grass two

red flowers of the Zanzibar balsam; each was five feet

from the base of the feeder and their distance apart was

3 Allard, H. A., ‘Some Experimental Observations concerning the behav-

ior of Various Bees in their Visits to Cotton Blossoms,’’ AMER. NAT., 45, :

615 and 672, 1911. -

106 THE AMERICAN NATURALIST [Vou. XLVI

two feet. There was a small quantity of honey on both.

One of these blossoms I screened with dandelion leaves

on the side toward the feeder, but it was visible in every

other direction. Some time after the honey was all con-

sumed on the feeder two bees flew over the unconcealed

flower but did not alight. A wasp (Vespula victua

Sauss.)24 found it and at the end of half an hour it was

visited by a bee. The partially concealed flower received

no attention. During this experiment the bees seldom in-

spected objects on the lawn though they frequently flew

to where I was sitting, ten feet away.

The conclusion derived from a study of the phylogeny,

ecology, distribution and fertilization of green flowers

that they are at a disadvantage in attracting insects be

cause of their color was fully sustained by a long series

of experiments, in which honey-bees were given the choice

between a green and a bright colored object placed on a

green background, or between a conspicuous and an in-

conspicuous object. In the experiments described both

black and Italian bees were employed, the number of

which varied from one to fifty. The observations ex-

tended over portions of three seasons. Conspicuous and

inconspicuous objects were in some instances placed dia-

metrically opposite to each other at varying distances,

in other cases side by side or a few feet apart. In six

experiments there were no visits to the inconspicuous

object; while in the other experiments the number of

visits to the conspicuous object was much larger than to

the inconspicuous object, usually twice or three times as

large. The theory that bees in gathering nectar are in-

fluenced only by the olfactory sense and not by color or

form does not afford a satisfactory explanation of the

facts presented. If, however, bees are guided by the

sense of vision as well as by that of smell, then their rela-

tions both past and present to green flowers are not

difficult to understand. To reject a natural and wholly

“For the determination of this species I am indebted to Mr. S. A.

Rohwer.

No. 542] COLOR SENSE OF THE HONEY-BEE 107

satisfactory explanation of their behavior in favor of an

improbable hypothesis has the appearance of shunning

the truth in a vain search for novelty.

CoNCLUSIONS

Green flowers are not well adapted to entomophily, and

many species, possibly all, have been derived by retro-

gression and degeneration from larger more highly de-

veloped entomophilous forms. They are usually small,

or even minute, and are often incomplete, while ane-

mophily and autogamy prevail. Entomophilous green

flowers are as a whole sparingly visited by insects belong-

ing to the less specialized families, and as a rule retain

the power of self-fertilization.

The fact that insects have been observed feeding on

over-ripe or decaying fruit, or the glandular secretions

of the vegetative organs of plants, or the excretions of

Aphidide on foliage, or greenish or brownish flowers, or

dull-colored receptacles which have contained sugar or

sweet liquids, affords no evidence that conspicuousness

is not an advantage to entomophilous flowers. Any sur-

face, whether it is bright or dull-colored, on which there

is nectar or honey, will be freely visited by bees for

stores after these liquids have once been discovered ; but

they will not be discovered as quickly on a surface which

does not contrast in hue with its surroundings as on one

which does so contrast.

The experiments and observations of Plateau on green

or greenish flowers in the absence of control or compara-

tive observations are fallacious, as pointed out by Knuth,

and do not prove that ‘‘all flowers might be as green as

their leaves without their pollination being compro-

mised.’’

When honey-bees are given the choice between a con-

spicuous and an inconspicuous object under similar con-

ditions, they exhibit a preference for the former. This

preference is sufficiently marked to account for the de-

velopment of color contrast in flowers. oo

SHORTER ARTICLES AND DISCUSSION

IS THE CHANGE IN THE SEX-RATIO OF THE FROG,

THAT IS AFFECTED BY EXTERNAL AGENTS,

DUE TO PARTIAL FERTILIZATION?

In a review in this journal (XLV, 1911) of certain experi-

ments by Kuschakewitsch!? on frogs’ eggs in which by delaying

fertilization for 89 hours he obtained 100 per cent. of males,

I pointed out that unless more than half of the eggs were fèr-

tilized the interpretation of the 100 per cent. ratio might be mis-

leading. For should the delay act more injuriously on one kind

of egg than on the other, assuming two kinds to exist, the result

might mean only selective destruction by an external agent

rather than a change in sex of the eggs. I found no explicit

statement in the section of Kuschakewitsch’s paper dealing with

these results to show whether or not all of the eggs had been

fertilized, but in a recent rejoinder? to my review Kuschake-

witsch points out that he had stated that practically all of the

eggs (‘‘so gut wie alle Eier’’) were fertilized and developed.

This information is given in an appendix which I had overlooked.

His statement completely sets aside the possibility of the sug-

gestions that I made, but leaves the explanation of his results as

obscure as before.

The details of the principal experiment and of some of the

others are of interest. A pair of copulating frogs were caught

at 12:00, midday, May 31. The female began to lay at once.

At 6:00 p.m. the male was removed. On the 4th of June at

8:00 p.m. the eggs that had remained in the uterus of the female

were artificially fertilized. They are recorded as 89 hours old

at this time. Practically all segmented, and only 5 died at the

gastrulation stage. From this lot, 434 eggs hatched. Only 12

deaths occurred later. Three hundred of the tad-poles were

examined at the time of or after metamorphosis. Of these, 299

were males, and one was a bilateral hermaphrodite.

There can be little doubt, therefore, that, in some way, delay in

fertilization has caused practically all the eggs to produce males;

and the evidence is the clearer since the eggs fresh laid, fertil-

ized by the same male, produced 55 males and 53 females.

It may seem futile, therefore, to attempt to explain this result

in any other way than as the result of the action of the environ-

ment on the sex of the egg. But how has the environment

* Festschrift, R. Hertwig, Bd. II, 1910.

* Anatom. Anzeiger, 1911.

108

No. 542] SHORTER ARTICLES AND DISCUSSION 109

acted? The evidence that sex is regulated by an internal mech-

anism has become so strong in recent years that until the action

of the environment is made clear one may well hesitate to accept

the case as showing that sex is actually changed or produced by

an external agent. Curiously enough, every one seems to have

overlooked still another possibility that may solve the difficulty.

The delay in the fertilization may cause the polar spindle to stick

to the surface of the egg so that it fails later to take part in the

development, in which case the sperm nucleus alone would pro-

duce the nuclei of the embryo. Or, on the other hand, the delay

may cause the early stages in the formation of the female pro-

nucleus to progress so far that after fertilization the sperm nu-

cleus may be excluded in part or entirely from the development.

In either case the presence of a single nucleus would be expected

to give rise to a male. It is significant in this connection that

the changes described by King that affect the sex-ratio of the

frogs’ eggs produce a higher percentage of males.

There is another curious fact in relation to sex-determination

in the frog. Pfliiger described a high percentage of hermaph-

rodites amongst the tadpoles. Kuschakewitsch has given a de-

tailed account of the development of the hermaphroditic glands.

Most or all of these organs are later transformed into testis.

In general it may be said that eggs from a pair give either equal

numbers of males and females; or a mixture of males, females,

and hermaphrodites; or all hermaphrodites (potentially males).

It is possible that the pseudo-hermaphroditic condition may be

connected with the failure of one of the two pronuclei to take

part in the development.

If the explanation that I have suggested is correct we might

expect to find evidence in its support from the number of chro-

mosomes in the tadpoles that develop from these late fertilized

eggs. This would be expected if it is the male pronucleus that

gives rise to the nuclei of the embryo. But if it is the female

pronucleus that is responsible for the result, the number of chro- —

mosomes in the cells of the embryo might be haploid or diploid —

depending on whether the second polar body was, or was not —

given off. At any rate, this suggestion should be put to the

test of observation before we conclude that sex may be deter-

mined by external agents. If the view here suggested prove

true, sex is still determined by an internal factor in the same

sense that the sex of the bee’s egg is determined by the presence

of ane or of two promot o a

NOTES AND LITERATURE

HEREDITY

A SUBJECT of vital importance to the theory of heredity is the

behavior of the chromosomes during the life history of the cell,

and especially during the process of cell division. This subject

has received an enormous amount of attention from investigators

but there is far from unanimity amongst cytologists as to the

actual phenomena of cell division, not to mention the signifi-

cance of these phenomena. Realizing that the heterotypic di-

vision in gametogenesis is the critical point in the life history of

the organism, so far as the theory of heredity is concerned, at-

tention has been concentrated very largely on this division.

This is in some respects unfortunate. A good many investigators

who have studied this division have attempted to interpret the

phenomena observed without full knowledge of the behavior of

the chromatic elements in ordinary somatic divisions, and have

attributed to phenomena observed in the heterotypic division

very special meaning for inheritance, when these same phenom-

ena are regular occurrences in all divisions, and hence are to be

interpreted in their relation to growth rather than to reproduc-

tion. :

The writer is not a cytologist, and realizes fully that his

opinions on cytological questions will not be regarded seriously,

especially by those who have worked at problems of this char-

acter until they have gotten fixed in mind certain theories as to -

the meaning of the phenomena observed. Nevertheless, he has

given careful attention to published results of investigations of

this character, and has been driven by study of these results to a

particular interpretation of the principal phenomena reported.

It has seemed to me for some years that the double spireme so

often reported in the heterotypie division, and so often inter-

preted as a conjugation of homologous chromatin elements, al-

though this double spireme occurs in somatie divisions, appar-

ently quite as generally as in the heterotypic, is nothing

more than the expression of a division of chromosomes which

really occurs at least as early as the resting stage following the

previous nuclear division. It appears that this division may

begin at an even earlier period.

110

No. 542] NOTES AND LITERATURE iit

Fraser and Snell, in their paper on ‘‘The Vegetative Divisions

in Vicia faba,” present important evidence on this point. They

show very clearly that the division begins in the teleophase of the

previous division. This beginning of chromosome division in

teleophase had earlier been noticed by Gregoire, and by Stromp,

as pointed out by Fraser and Snell, but these earlier investiga-

tors had not perceived the meaning of this phenomenon. Fraser

and Snell were able to follow the life history of the chromosomes

through their complete history from one teleophase to the next

(in root tips and in other somatie parts, as well as in the game-

tophyte stages), and they show clearly that the double nature

of the spireme is due to splitting which begins as the daughter

chromosomes congregate at the poles in the teleophase of the

previous nuclear division.

That this double spireme is not due to the approximation of

two elements, one representing maternal and the other paternal

chromatin, is further shown by the fact that in the pollen cell,

where the chromosome number is haploid, and hence where there

can be no question of union of elements from the two parents,

exactly the same phenomena occur.

Another very interesting fact shown by these investigations

(of Fraser and Snell) is that some of the elements which be-

have as single chromosomes, so far as their distribution on the

spindle and to the poles is concerned, are made up of segments

united end to end, as if two or more small chromosomes were

united more or less closely into a larger one. The authors point

out the possible significance of this fact for Mendelian coupling,

and suggest that it may also be of significance in connection with

the fact that in some species more Mendelian factors have been

observed than there appear to be chromosomes.

East and Hayes have recently published the results of ex-

tended investigations on inheritance in maize.” After discuss-

ing the taxonomy of the group and pointing out the adaptability

of maize to genetic investigations (or the lack of such adapta-

bility), the authors give an excellent résumé of former investiga-

tions with this interesting group of plants.

A brief account of their results follows. Amongst endosperm

characters they found that starchiness (S) is dominant to its

*Ann. of Bot., 1911 845-856.

7B. M. ong pe Hayes: Bul. No. 167, Conn. Exp. Sta.—“ Inher-

itance in Maize.’’

112 THE AMERICAN NATURALIST (Vou. XLVI

absence, non-starchiness (s). When S came from the ¢ parent

zenia appeared in all cases. All F, seeds showing zenia proved

to be heterozygous. No extracted recessives of the F, generation

ever proved to be heterozygous. ‘‘From this one may conclude

that the second male nucleus that fertilizes the endosperm nu-

cleus always bears the same characters as the first male nucleus

- that fertilizes the embryo nucleus, or egg.’’ A few seeds, all

heterozygous, were part starchy and part not; 7. e., one side was

starchy. The authors consider that this confirms Correns’s view

that, in such cases, the second male nucleus did not fuse with the

endosperm nucleus but that each developed separately.

One semi-starchy ear occurred, grown from a non-starchy seed.

The authors suggest two possible causes for this phenomenon.

Hither there is an incomplete segregation, resulting in contamin-

ation of a gene by its allelomorph, this contamination, by selec-

tion, being capable of accumulative effects, or the semi-starchy

ear arose as the result of a progressive variation. They point

out that the infrequency of this phenomenon is an argument

against the theory of partial or incomplete segregation, and

incline to the idea that it is a case of progressive variation. The

data presented certainly favor this interpretation of the case.

YELLOW AND Non-YELLOW ENDOSPERM

Two independent factors for yellow were found, each capable

of producing yellow endosperm. The colors produced by these

two factors appear to be the same. The pigments occur in

rhombic plates, and are insoluble in water, but soluble in ether,

chloroform, ete. They appear to be related to the anthochlorins.

Some crosses between yellow and white gave the ratio 3:1, due

to the presence of only one of the factors for yellow. Others.

gave the dihybrid ratio, Yellow appeared as xenia in the hybrid

seeds (seeds which produced the F, plants).

Yellow was dominant, but imperfectly so under certain con-

ditions, so that, in certain crosses in which the grains had soft

starch at the tip the heterozygotes could be distinguished from

the homozygotes. In other crosses yellow was completely

dominant.

The same original ear of some of the parent stocks had some

seeds containing both factors for yellow, while other seeds on the

same ear had only one of these factors.

The two yellow factors together generally gave darker yellow

seed than one factor alone.

gates oa an

No. 542] NOTES AND LITERATURE 113

PURPLE AND NON-PURPLE ALEURONE CELLS

The experimental data relating to crosses between purple and

non-purple races indicate two factors, P and C, which, when to-

gether, produce purple color in the aleurone layer. In some of

the non-purples used one of these factors was missing, in others.

both. In certain combinations one of these factors alone pro-

duced faintly colored purple. In most of the crosses splashed

purple occurred, part, but not all, of the heterozygotes having

this peculiarity. It was not hereditary, but behaved in subse-

quent generations as pure purple.

In one family red aleurone occurred in F,. It appeared to be

due to the interaction of two factors R and C.

In one family of this cross (purple non-purple) the F, gen-

eration gave purples, reds, and non-purples in the ratio 12:1: 3.

The actual numbers were 1,843:188:545. The ratio 12:1:3 did

not occur in F,, but instead one fifth of the ears bearing F,

grains gave the ratio 9:3:4. Several possible hypotheses to

explain these anomalous results are discussed and discarded,

amongst them Bateson and Punnet’s hypothesis of the formation

of gametes in the ratio TAB : 1aB:1Ab: Tab. The data from F,

agree best with the assumption that the constitution of the two

parent types was pcR and PCR respectively, but the F, ratio

is not explained by this hypothesis. The authors leave the ques-

tion as to the real explanation an open one. The reds in this

family were different in color from the reds of the family pre-

viously mentioned. Not only that, but all the F, reds found in

this family proved to be homozygous, indicating that both par-

ents possessed the factor F.

Other families of this cross gave results that indicated the

presence in the non-purple parent of a factor which more or

less completely inhibited the development of purple. Some non-

conformable results were found, due probably to the presence of

other factors, one at least of which appeared to modify purple

by making it lighter.

In the above crosses xenia was found as follows: when non-

starchy races were fertilized by pollen from starchy races (no

xenia appeared in the reciprocal cross) ; when non-yellow endo-

sperm is crossed with yellow endosperm. In this case xenia al-

ways appeared when yellow was used as the male parent. It

also appeared in the reciprocal cross when the grains of the fe-

male parent had extensive development of soft starchy endo- —

sperm at the end of the grain, as in these cases the he

114 THE AMERICAN NATURALIST [ Vou. XLVI

yellow was lighter in color than the homozygous, and hence dis-

tinguishable from it. In crosses between yellow and non-yellow

endosperm, when the non-yellow endosperm was entirely soft

(not corneous), as in the so-called flour corns, xenia appeared in

all cases, for reasons just stated. When the endosperm of the

non-yellow parent was entirely corneous, as in the popcorns, xenia

usually occurred only when yellow was used as the male parent,

though in a few instances it was perceptible when the cross was

made the other way. Xenia also occurred when purple or red

aleurone was crossed with non-purple, or non-red, when the pur-

ple or red was used as the male. The only other case in which

xenia was observed was in crosses between white and red (or

purple) when the white (male) parent carried an inhibiting

factor for purple and red. Sometimes the reciprocal cross shows

xenia, since the inhibition of red or purple is not always com-

plete. The following law regarding xenia is formulated by the

authors: when two races differ in a single visible endosperm

character in which dominance is complete, xenia occurs only.

when the dominant character is the male; when they differ in a

single visible endosperm character in which dominance is in-

complete or in two characters both of which are necessary for the

development of the visible difference, xenia occurs when either

parent is used as the male.

Correns’s conclusion that where xenia occurs the seeds showing

it are always hybrid is confirmed. This shows that Mendelian

segregation must occur previous to the division of the pollen nu-

cleus. The authors found no case in which a seed showing no

xenia where it is to be expected proved to be a hybrid; i. e., the

hybrid in which xenia is to be expected always showed xenia

though like Webber and Correns they found seeds showing xenia

on only one side. This is interpreted as the result of the inde-

pendent development of the endosperm nucleus and the second

male nucleus.

In crosses between podded maize (maize having each grain

covered by husks) with common maize, the pod character proved

to be a dominant Mendelian factor, which segregated perfectly

Red sap colors appear in maize in the pericarp, the cob, the

husks, the silks, the glumes, and in the anthers.

Red pericarp (R) without red on the cob or in the silk, crossed

with white pericarp gave three reds to one white in F,, the segre-

pakn being perfect.

No. 542] NOTES AND LITERATURE 115

‘An ear of corn was found where only white corn had been

planted, one side of which produced grains with red pericarp,

the other white or striped with red. The red here seemed to be

due to the same factor as in the case just noticed (R). Red

grains from this ear gave red and white ears in equal numbers.

The white and striped grains gave white ears and ears with a few

striped red seeds in equal numbers. A selfed red ear in this

generation gave three reds to one’ white in the next. The orig-

inal red and white (or striped) ear is accounted for as a somatic

variation, part of the ear varying from white to red, the remain-

der from white to striped. In this family red cob is perfectly

correlated with red pericarp.

Two other red pericarp colors, apparently independent of the

above, were found. One is a dark red occurring in stripes which

radiate from the point of the attachment of the silk to the grain.

The other is a dirty red, more abundant at the base of the grain,

and nearly wanting at the tip. It occurs in Palmer’s Red

Nosed Yellow variety. It is completely coupled with red silks.

Two other red pericarp factors were found. They are very

similar, but not allelomorphiec to each other. They give a rose

red pericarp, but do not develop except in sunlight. They are

barely perceptible on ears covered by heavy husks.

Red cob color proved to be dominant to white and the cross

segregated in a 3:1 ratio. Red cob appears not to be correlated

with any of the red pericarp colors.’

Red silk color presented some difficulties, and the data are not

analyzed. In some instances a 3:1 F, ratio was obtained, in

others a third type with red hairs on a greenish-white silk oc-

curred, the F, numbers being 198 reds, 29 greenish-whites with

red hairs, and 94 greenish-whites. Red silks may occur with no

other red on the plant.

Red glumes were always accompanied by red in other parts of

the plant, though in one race the only other red was in the silks.

The question whetherall these reds are due to one or to dif-

ferent genes is discussed most interestingly (pp. 109-10), but

the discussion is too long to quote here.

It is gratifying to note that these authors are not afraid to

mention the chromosomes in connection with Mendelian factors.

For several years an inexplicable obsession seems to have pos-

sessed biologists in this matter. Apparently every one regards

? But see reference to Emerson’s results below. 3 ae

116 THE AMERICAN NATURALIST [ Vou. XLVI

it as highly probable that these cell organs are in some way

responsible for Mendelian phenomena, yet a large number of

biologists seem to be afraid to refer to them in this connection.

Crosses between flint and dent varieties indicated that the dif-

ference between these two classes relates to two factors in some

ease, especially when the dent parent has considerable corneous

endosperm, and to two or more factors, especially when the dent

parent has little corneous starch. This seems to be another case

where several similar factors exist, as found in earlier inves-

tigations by East, by Nilsson-Ehle, and by Shull.

Crosses between races having different modal numbers of rows

of grain on the cob indicate clearly that several similar factors

are here concerned. The evidence that segregation occurs is,

the authors believe, conclusive. The data could not be definitely -

analyzed because of the fluctuating variation of the various bio-

types, and the small differences between adjacent biotypes.

Height of stalk and length of ear behave similarly. Apparently

size of grain does the same.

Irregular rows of grain occur both as fluctuations not inherited

and as a hereditary characteristic. Should the percentage of

irregular rows be higher than about 4 per cent. the authors think

the irregularity is probably hereditary.

This paper closes with a discussion of the inheritance of var-

ious abnormalities found during the progress of the work.

The Journal of Genetics for August, 1911, contains some arti-

cles of unusual interest. R. N. Salaman presénts the results of

an investigation on the inheritance of the peculiar physiognomy

known as the Jewish face. He shows that this is a simple Men-

delian character. It is distinctly recessive to the ordinary Eu-

ropean (Gentile) physiognomy, though the hybrids sometimes

show traces of the Jewish face, especially late in life. On the

other hand, this peculiarity is dominant over the Pseudo-Gentile

face sometimes seen amongst the Jews; also to the Gentile phy-

siognomy of the Moors and certain ithe Mediterranean peoples.

We may explain this in terms of the presence-absence hypothesis

by saying that the distinctive type of face seen amongst the

Hebrews is due to the presence of a gene, while in the peoples of

northern Europe there is a gene which inhibits the Jew face char-

acter. The data presented, while not extensive, seem to be quite

conclusive that the character segregates as a so-called unit char-

acter. Salaman’s paper is an exceedingly clear presentation of

data, and is written in a style that is attractive and readable. |

No. 542] NOTES AND LITERATURE 117

Bateson and Punnett* give the results of their study of the

inheritance of the peculiar black pigmentation in the skin, perios-

tium, and other tissues of the silky fowl. While some excep-

tions occur, the results on the whole are in agreement with the

assumption of a pigment factor, P, and an inhibiting factor J,

the latter exhibiting the phenomenon of spurious allelomorphism

with the female sex factor. The authors suggest that the excep-

tions found may be due to failure of the repulsion supposed to

exist normally between the female sex factor and the inhibiting

factor,

While a large part of the work on which Mendel’s principles

of heredity depend has been done with pigments, very few in-

vestigations have been undertaken in order to determine the

connection between the phenomena of inheritance of these pig-

ments and the chemical reactions which underlie these phenom-

ena. This is quite natural, since few of those who have con-

ducted the investigations relating to Mendelian inheritance have

had the training, and hence the opportunity, to study the chem-

ical side of the question. Likewise, those relatively few individ-

uals who have become well versed in the highly complex and

difficult subject of physiological chemistry have seldom had any

direct interest in the phenomena of inheritance. The wisdom of

an endowment for an all-sided research of heredity such as the

Carnegie Institution of Washington has provided at Cold Spring

Harbor is manifest in the fact that Dr. Davenport has been able

to institute research on both sides of the question. The results

secured by Mr. Gortner in his study of the origin of melanin,

and its relation to the phenomena of Mendelian inheritance will

be eagerly read by students of Mendelism. In the May number

of the Journal of Biological Chemistry Mr. Gortner gives some

exceedingly interesting results of his work. He shows that the

body filling of the meal worm (Tenebrio moliter) contains two

oxidases, a laccase-like enzyme, and a powerful tyrosinase. Also

that there is a chromogen present in the larva which, when acted

upon by the tyrosinase, gives a series of colors ending in a black

melanin-like body. Larve killed by ether developed pigment

when left exposed to air, but when the air was excluded by car-

bonic acid or nitrogen no pigment developed. When the larvæ

were heated (in water) sufficiently to destroy the activity of the

tyrosinase but not that of the laccase, no pigment formed.

The oxidase was evidently present in relatively large amounts, oe

* Jour. of Gen., Aug., 1911, pp. 185-203.

118 THE AMERICAN NATURALIST [ Vou. XLVI

but the chromogen only in small quantities. The results indi-

cate that the chromogen is formed slowly and used as formed.

In the September number of the same journal® the same author

deals with the nature of dominant and recessive white. He

shows that, in so far as the presence or absence of pigment is

concerned, these two types of white, in certain mammals, are as

indistinguishable to the chemist as they are to the breeder. He

accepts the view that pigment is formed by the action of an

oxidase on a chromogen, and points out that dominant white

arises from the presence of a third body which prevents the reac-

tion between the oxidase and the chromogen. This might occur

in three ways: (1) the third substance, such as orcin, resorcin,

phloroglucin, or other substances of similar nature, may act on

the chromogen and thus prevent its oxidation; (2) it may itself

be oxidized by the tyrosinase, thus preventing action on the

chromogen; (3) it may act as a true anti-oxidase, and in some

manner inhibit the action of tyrosinase.

The author gives abundant data to show that alternatives 1

and 2 are excluded in the cases with which he worked. Hence

the action must be of the third type—an inhibitory action. He

shows that dominant whites contain no pigment lacking in re-

cessives. He also shows that ‘‘ aromatic compounds which carry

two hydroxyl groups in the meta position to each other are

capable of inhibiting the action of tyrosinase on tyrosin.” If,

then, such a substance should occur in the animal body a domi-

nant white would result. Recessive white is presumably due to

the absence of either the chromogen or the oxidase, while at the

same time no inhibiting factor is present. From this it would

appear that an albino might be dominant to color if it carried the

inhibiting factor, yet it would require considerable work to dis-

tinguish between such an albino and a true dominant white,

i. e., by its genetic behavior.

To explain the occurrence of recessive whites which are not

albinic, and which are dominant in some crosses, we have the

following considerations. Orcin inhibits the action of tyrosinase

on tyrosine, but is itself oxidized by a specific enzyme. If we

represent tyrosine by C, tyrosinase by T, orcin by O, and the

specifie enzyme which oxidizes orcin by P, then an individual

containing only C and T would be colored, CTO would be white,

R. A. Gortner: ‘Studies on Melanin: IIT. The Inhibitory Action of

Certain Phenolie Substances upon Tyrosinase.’’ Jour. of Biol. Chem., Vol.

X, No. 2, Sept., 1911.

No. 542] NOTES AND LITERATURE 119

the cross CTO X CT would be white (i. e., white would be dom-

inant), the cross CTO X CTP would be colored (white reces-

sive), while the cross CTO TP (both white) would be colored.

It appears, therefore, that Gortner has been able to construct a

theory that renders intelligible the behavior of all kinds of white

color in inheritance, and to give what seems to be a very plaus-

ible chemical explanation of all these cases. We, of course,

already understand why the cross of two whites of types Ct and

cT should give color and why both of the latter types of white are

recessive to color.

Readers of the Narurauist are familiar with my contention

that in order to show that the chromosomes, as a whole, are not

responsible for Mendelian characters, it must be shown that more

independent dominant characters can be put into a single indi-

vidual than there are pairs of chromosomes. The fact has been

repeatedly cited that more Mendelian characters have been found

in Pisum than there are pairs of chromosomes, and the claim is

made that this disproves the chromosome theory of Mendelism.

I have repeatedly shown that this is not the case. There might

be a thousand Mendelian characters demonstrated for Pisum,

but until it is shown that more than six of them are genetically

independent, the chromosome theory is not affected thereby. It

has heretofore been assumed that two factors, each of which

when crossed with its absence behaves as a so-called unit char-

acter, are genetically independent of each other. This assump-

tion appears to be involved in the ‘‘presence-absence’’ hypo-

thesis. This hypothesis, as usually applied, seems to imply the

presence or absence of a particular body in the cell, which body,

when present once, passes into only one gamete, and that there

are as many such genetically independent bodies as these are

Mendelian factors. When correlation of Mendelian factors

occurs, it is assumed to be due to the adhering together of twe

of these bodies; likewise when the so-called spurious allelomor-

phism occurs, it is because two of these bodies repel each other.

I wish here to repeat what I have often said before, that the

fact that two factors each behaves as an allelomorph to its ab-

sence does not prove them to be genetically distinct. The occa-

sion for this repetition is some pertinent evidence which has just

been presented by some exceedingly interesting work of Profes-

sor Ronse ’s.° He found that red cob (with white pericarp)

R. A. Emerson: ‘‘Genetie Correlation and Spurious Allelomorphism in

States 24th An, Soha ik er et Ma, p

120 THE AMERICAN NATURALIST [ Vou. XLVI

X absence of red gives the usual Mendelian phenomena of 3 red

cob: 1 white in F,. Likewise, the cross red pericarp (with white

cob) X absence of red gives 3 red pericarp: 1 white. Thus each

of these types (factors) behaves as an allelomorph to its absence.

Hence they should be due to genetically independent genes. But

such is not the case; they are allelomorphic to each other.

Some students would say that this is because they repel each

other. But this explanation does not satisfy in this case, for it

can hardly be doubted that red cob in the one case and red peri-

carp in the other are due to the same cause, acting differently

in the two cases. I am of opinion that many similar cases of

factors behaving as allelomorphs to their absence will be found

to be also allelomorphie to each other. Such cases have usually

not been looked for. Quite a number of them have been reported,

and I hope some time to be able to bring them all together for

reference. Emerson’ gives a case in beans, in which a variety

with green leaves and green pods was crossed with another hav-

ing green leaves and yellow pods. F, consisted of three of the

former to one of the latter. Here green was allelomorphic to

absence of green. Later he crossed two varieties, one with green

leaves and green pods, the other yellow leaves and pods. F, com

sisted of three of the former and one of the latter. Here green

was again allelomorphic to its absence. These two crosses ap-

parently show that yellow pods with green leaves and yellow

pods with yellow leaves are not genetically distinct. Yet if yel-

low had been dominant in both these cases, it would have been

the usual custom to consider that the two different yellows were

independent genetically, because each was allelomorphic to its

absence. It would be interesting to know how the two yellows

would behave if crossed. It would not be at all surprising to

find these two ‘‘absences’’ exhibiting the phenomenon of spur-

ious allelomorphism. The case would be still more interesting if

a variety could be found with yellow leaves and green pods.

W. J. SPILLMAN ©

(To be continued)

Th a |

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AMERICAN NATURALIST

Vou. XLVI March, 1912 o ge eae

PROBLEMS OF EVOLUTION AND PRESENT

METHODS OF ATTACKING THEM?

PROFESSOR EDWIN G. CONKLIN

PRINCETON UNIVERSITY

Tue problems of evolution have been much the same

from Darwin’s day to this, but the present methods of

attacking them are in many respects different from those

which prevailed a generation ago. One great problem

with which the earlier naturalists were concerned, viz.,

the fact of evolution, is by common consent, no longer a

problem; if it has not been demonstrated that the living

world arose through evolution, it has at least been ren-

dered so probable that demonstration could add little to

our certainty. And yet we should all like to see the

demonstration of evolution on a large scale, such as must

have been operative in the past history of living things,

but we have little reason to hope that such a demonstra-

tion will soon be made. .

The enduring problems of evolution concern the means

or factors of transmutation. Here also the old method of

attack, viz., observation and induction, led to no certainty

but only to probabilities of a lower order than those

which speak for the truth of evolution. For the past

twenty years the futility of the old theories and discus-

sions has been generally recognized, and the desire for

more exact knowledge has been keenly felt. Consequently

1 Introductory address in the annual discussion before the American

Society’ of Naturalists, Princeton, N. J., December 28, 1911.

121

122 s THE AMERICAN NATURALIST [Vor. XLVI

analytical and experimental work on the problem of the

factors of evolution was begun some twenty years ago

and has been continued with ever-increasing interest to

the present time.

In*the first enthusiasm over the experimental method

of attack it seemed to many students of this problem that

at last a path had been found which would lead straight

to the goal, that the causes of all evolution were about to

be revealed, and that the practical control of evolution,

with all that this implies, was almost within reach. About

that time a young physiologist said to the Director of

the Zoological Station at Naples, ‘‘Why do you spend so

much money publishing these beautiful monographs on

the Fauna and Flora of the Gulf of Naples?’’ Dr. Dohrn

replied, ‘‘ You are the first person who has ever asked me

such a question; many have asked how and where I got

the money, but no one has asked why. What do you

mean?” ‘‘Only this,’’ said the physiologist, ‘‘that

within twenty-five years we shall be making experiment-

ally an indefinite number of faunas and floras, and the

present one will then be only one of many.’’ In the

opinion of many investigators at that time, experimental

evolution was soon to give us a new world of living

things, and it was about to reveal conclusively the causes

of evolution. We have now had one or two decades of

this experimental evolution, and it may be worth while

to inquire, What has been the net result? If the answer

should seem to be somewhat discouraging I would beg to

remind you that is so chiefly because the problems have

been found to be much greater than was at first supposed.

The experimental method as applied to the evolution

problem has justified itself; it has set the problem in a

clear light and it has brought forth facts of the greatest

significance, but it has not enabled man to do in twenty-

five years what it took nature twenty-five million years

to do.

The most significant work on geneties since the time

of Darwin is that which is identified with the name of

No. 543] PROBLEMS OF~EVOLUTION ` 123

Mendel. According to the doctrine of Mendel and his

followers each organism is composed of a multitude of

unit characters, which do not blend nor lose their identity

when mixed with others as a result of sexual reproduc-

tion, but which may be expected to come out in the end,

practically as they went in at the beginning. This con-

clusion has modified in a striking manner the entire con-

ception of evolution and heredity. We no longer discuss

the origin of species, but rather the origin of characters;

we no longer rely upon chance to bring out certain hered-

itary characters, but are enabled at will to make many

analyses and syntheses of these characters. These dis-

coveries probably mark the greatest advance ever made

in the study of heredity; they have made it probable that

evolution proceeds by the evolution of individual charac-

ters; but have they shed any light on the method and

manner of this evolution? Permutations of Mendelian

characters we may have without number, of new combina-

tions of these there may be no end, but, so far as known,

no new characters are formed by such temporary com-

binations, there is no ‘‘creative synthesis,’’ no lasting

change. Evolution depends upon the appearance of new

characters; the discoveries of Mendel show us how to fol-

low old characters through many combinations and

through many generations, but they do not show us how

new characters arise. These discoveries have given us

an invaluable method of sorting and combining hered-

itary qualities, but Mendelian inheritance, as commonly

expounded, does not furnish the materials for evolution.

Many modifications of Mendelian inheritance have been

described, many alterations of dominance, or blending of

characters, the causes of which are not yet well under-

Stood. Perhaps in these ‘‘unexplored remainders’’ may

be found the causes of new characters. It is not yet cer-

tain that the unit characters, or rather their determiners

in the germ, are beyond the reach of environmental in-

fluence ; it is not certain that in their mixture with others

they never combine or influence each other in such man-

ner as to form new unit characters. Indeed, it is difficult

124 THE AMERICAN NATURALIST [ Vou. XLVI.

to understand how new characters could ever appear

except under one or the other of these conditions. We

particularly need at this time more knowledge of the

mechanism underlying the gross phenomena of Men-

delian inheritance, and then perhaps we may learn under

what conditions this mechanism may be altered.

As a result of the work of Mendel and his followers we

know much more about heredity than was known before,

we have learned how to separate and to combine hered-

itary characters, we have learned to look for evolution in

the appearance of new characters, but we have not learned

how to produce new characters.

Practically all who have ever thought or written on

evolution have found the principal causes of the trans-

mutation of old characters into new ones in the action of

extrinsic, or environmental, forces on the organism. As

the result of years of labor on this subject Darwin con-

cluded that ‘‘variability of every sort is due to changed

conditions of life.” It is well known that environmental

changes produce many kinds of modifications in organ-

isms, and in general these modifications are the more pro-

found the earlier they occur in ontogeny; it is known that

slight alterations of the germ cells may produce great

modifications of adult structure, and it seems reasonable

to suppose that environmental changes of the right sort

applied to the germ cells at the right stage would lead to

a permanent modification of the substance of heredity

and hence to the appearance of new characters of evolu-

tionary value. And yet one of the most striking results

of recent work is to show the small effect of environ-

mental changes of all sorts on racial characters. Marked

individual modifications may be produced which do not

become racial. Usually not one of thousands of varia-

tions which oceur have any evolutionary value. These

variations come with changing environment and with

changing environment they disappear. Just as in the

individual, so also in the race there seems to be a power

No. 543] PROBLEMS OF EVOLUTION 125

of regulation which causes a return to the type, when

once this has been departed from.

In several instances recent investigators have found,

or have thought they have found, experimental evidence of

the inheritance of characters acquired through environ-

mental changes. But these evidences are by no means

conclusive. In a few cases it is known that the effects

of changed environment last through two or three genera-

tions and then disappear. In such cases racial, or speci-

fic, regulation is slow; in most cases this regulation takes

place in the first generation after the environmental

change disappears. Perhaps in this lingering effect of

a changed environment we have the first indication of the

appearance and fixation of a new character. Here, un-

doubtedly, much work of value remains to be done.

Very rarely a sudden variation, or mutation, arises

which is perpetuated by heredity and which forms the

basis of a new race. In most cases which have been care-

fully studied such mutations consist in the dropping out

of some old character rather than in the addition of a new

one, but at least they represent modifications of the hered-

itary characters, and as such they furnish material for

evolution. Whence and how they appear we do not know,

for like the kingdom of heaven, they come without obser-

vation. Their infrequency, amidst the multitude of

somatic variations, indicates the wonderful stability of

racial types and teaches respect for Weismann’s doċtrine

of a germplasm, relatively stable, independent and con-

tinuous. :

This distinction between somatic and germinal varia-

tions, between those which concern only the individual

and those which are inherited and furnish material for

evolution, marks the greatest advance in the study of

evolution since the work of Darwin. And just as these

germinal variations are the only ones of importance An

the process of evolution, so the question of their origin 1s

the greatest evolutionary problem of the present day.

How are such germinal variations produced? Do they

occur as the result of extrinsic or of intrinsic causes? By

126 THE AMERICAN NATURALIST [ Vou. XLVI

instinct we are all Lamarckians and are inclined to fol-

low Darwin in ascribing variability of every sort, germi-

nal as well as somatic, to changed conditions of life. But

this is by no means a necessary conclusion. It is con-

ceivable that germinal variations result from combina-

tions of different germplasms, as Weismann supposed,

that the determiners of Mendelian characters do not

always preserve their individuality, but sometimes unite

in such way as to modify the unit characters; but as yet

we have no evidence that new characters are formed in

this way, and the study of Mendelian inheritance has

made this possibility less probable than it once was.

Again it is possible that germinal variations, and new

hereditary characters, may result from intrinsic changes

in the germplasm, comparable to the spontaneous changes

which occur in radium, for instance; such a view of

transmutation through intrinsic, spontaneous, changes

has points of resemblance to the doctrine of orthogenesis,

but of its truth or falsity we have no sufficient evidence.

If changes in the germplasm may be induced by ex-

trinsic conditions, then a real experimental evolution will

be possible; if they can not be so induced we can only look

on while the evolutionary processes proceed, selecting

here and there a product which nature gives us, but

unable to initiate or control these processes.

IMI

Darwin’s theory that selection is the most important

factor in preserving and building up evolutionary char-

acters remains to this day a theory. The brilliant re-

searches of our distinguished guest, Professor Johann-

sen, and of our President, Professor Jennings, have

shown that the selection of fluctuations, or somatic varia-

tions, have no permanent effect in modifying a race; but

selection or elimination of germinal variations may be

an important factor in evolution, though it has little or

nothing to do with the formation of new characters, and

serves merely as a sieve, as De Vries has expressed it, to

sort the characters which are supplied to it.

No. 543] PROBLEMS OF EVOLUTION 127

On the other hand, selection of favored races and elimi-

nation of the unfit is still the only natural explanation of

fitness, of adaptation, in organisms. As a species-form-

ing factor selection is probably of less importance than

Darwin supposed; as a possible explanation of the won-

derful adaptations which allliving things exhibit it seems

to be all important; but extensive experimental investi-

gations of the causes of adaptation are greatly needed.

The microscopic study of the germ cells during the past

twenty-five years—their growth, maturation, union in

fertilization, and their subsequent development—has fur-

nished material of the greatest importance for the com-

prehension of the mechanism of heredity and evolution,

and yet almost everything in this field remains to be done.

The parts played by the different constituents of the cell

in assimilation, regulation and heredity are still in doubt,

and in spite of many alluring hypotheses we know prac-

tically nothing about the way in which hereditary char-

acteristics arise from the germ. The study of the cellu-

lar basis of heredity has to a large extent been guided

and influenced by our knowledge of the gross phenomena

of heredity, and this must always be the case; but the

brilliant discoveries of the last few years as to the cellu-

lar basis of sex show the great assistance which the study

of cytology may render to the science of genetics. Many

interesting experiments have been made upon the germ

cells in the attempt to shift dominance, to modify inher-

itance, to create new characters; in a few instances it has

been shown that certain modifications of the embryo or

adult organism follow certain modifications of the germ,

but in no instance has it been shown that such modifica-

tions are inherited and are consequently of evolutionary

value.

Not merely the constitution of the germ and the ways

in which this may be modified, but also the precise man-

ner in which the structures of the germ become trans-

128 THE AMERICAN NATURALIST [ Vou. XLVI

muted into the structures of the adult are evolutionary

problems of the greatest importance. It is an amazing

fact that the great problems of ontogeny—viz. the under-

lying causes and mechanism of differentiation—are

to-day, after more than a century of scientific observa-

tion and experiment, almost as complete a mystery as

ever. If we are as yet unable to determine the precise

manner in which the structure of the germ evolves into

the structure of the adult in the common, ever-present

phenomena of reproduction, it is small wonder that we

have been unable to determine in detail the way in which

one race is transmuted into another.

In conclusion I think it must be admitted that the ex-

perimental study of genetics has been a little disappoint-

ing. We had supposed that organisms would be more

tractable, more willing to evolve, than we find them. The

older view that organisms were plastic and could be

moulded ‘‘while you wait’’ now reminds one of the view

of certain childless theorists, that children are plastic

clay in the hands of parents or teachers; both of these

views neglect the fact that the living organism, delicate

and responsive beyond compare, is still wonderfully

strong, stable and stubborn. So far as the factors of evo-

lution are concerned experimental study has thus far

been a weeding-out process, and at times it seems that

nothing will be left.

The problems of evolution are as much problems to-

day as they ever were, and though some of these prob-

lems may soon be solved, we may rest assured that there

will always be the evolution problem. The path which

we thought led straight to the goal has had to be retraced

with much labor; the hilltop from which we confidently

expected to see the spires of Eldorado has only served to

show us how great are the difficulties before us. But this

is the order of nature, the common experience of all

search for truth, and we would not have it otherwise.

‘‘For to travel hopefully is a better thing than to arrive,

and the true success is to labor.”

LIGHT THROWN BY THE EXPERIMENTAL

STUDY OF HEREDITY UPON THE FAC-

TORS AND METHODS OF EVOLUTION’

DR. C. B. DAVENPORT

COLD Spring HARBOR, N. Y.

THe most important contribution of modern studies in

heredity to the topic of evolution has been a new formu-

lation of the problem. Until a decade ago the problem

of organic evolution was regarded as synonymous with

that of the origin of species. We were, however, not

agreed as to the definition of species; on the contrary,

we realized that our notion of the term was exceedingly

hazy. And, doubtless, the reason why we made so little

progress in getting at the methods of evolution was be-

cause of this bad formulation.

To-day all this is changed. We think less of the origin

of species and more of characteristics; of their nature,

their origin and their distribution. The concrete ques-

tion of the origin of a given species has become broken

up into the questions of the origin of its differential

characters. Thus, the problem of the origin of man has

been broken up into the problems of loss of the tail, of

the hairy coat, of skin pigmentation, of melanic iris pig-

mentation, the acquisition of a more complicated brain

structure, the reduction of the lower part of the face,

the acquisition of the ability to learn to count and

talk, to wear clothes, to be honest, truthful, regardful of

the property rights of others, and to exercise self-control

in the sex sphere. So long as we formulated our problem

as the explanation of the ‘‘origin of the human species,”

as though the human species were an indivisible unit, so

of Natu-

Read (with slight alterations) before the American Society

ralists at Princeton, December 28, 1911.

129

130 THE AMERICAN NATURALIST [ Vou. XLVI

long we floundered helplessly in the quicksand of un-

clearness and complexity; now that we recognize our

study to be the history of any inheritable trait we move

on surer ground. And so, in general, progress is to be

made in the future by careful attention to the evolution

of characters.

The second change in the formulation of the problem

that is due to the modern study of heredity is that we no

longer consider even the character as the ultimate unit

of evolution, but regard it rather as a product of such a

unit. For the character is, in some way or another, de-

termined by the conditions in or the constitution of the

germ-plasm and these conditions and this constitution,

though very different from the adult characters, are

their germinal representatives; and these germinal rep-

resentatives are the real units to be studied. Thus we

do not to-day formulate our problem as the evolution of

man, or of a blue-eyed man, but ask how the determiner

for brown-eye became lost from the germ-plasm. So, in

general, the problem of evolution is formulated as that

of the history of the germinal determiners of characters.

Besides formulating more precisely the problem of

evolution, modern studies have discovered certain

methods of evolution which were not appreciated a

decade ago. First, we have come to realize that, though

not uniformly, yet to a surprising degree, characteristics

are independent of one another and, hence, that their

determiners in the germ-plasm are commonly not bound

together. The evidence for this is found in the breeding

experiments that have been performed on scores of

species of animals and plants, both feral and domesti-

cated. Breeders have taken advantage of this independ-

ence to create almost any desired combination of known

characters. Thus, in poultry the single pea or rose

comb may be combined with a black, white or game

plumage, with or without unfeathered shanks. The

shepherd’s purse that grows by the roadside may be

made with either of two forms of capsules combined with

No. 543] FACTORS AND METHODS OF EVOLUTION 131

four forms of leaf in the rosette stage; fruit-flies (Droso-

phila) may have any one of several colors of eye com-

bined with either short or long wings, and so on. The

characteristics that are associated in an individual are,

for the most part, not necessarily associated. The group

of characteristics that distinguishes individuals of one

‘‘ species”? from those of another is largely an accidental

one; and it is, therefore, not surprising that we so often

find individuals which in one, two or several characters

differ from the conventional description of their species,

and these have in the past caused great difficulty to the

species maker.

The fact that most characteristics are not necessarily

associated—that they may occur in various combinations

—certainly accounts for the multiplicity of ‘‘varieties’’

in domesticated species; and for much of the variation in

feral species. Moreover, it probably accounts for the

presence of many ‘‘species’’ in a genus. I may repeat

here what I wrote in 1909.

Dr. Ezra Brainerd has shown how many wild “species” of Viola

have arisen by hybridization, as may be proved by extracting from them

combinations of characters that are found in the species that are

undoubtedly ancestral to them. In such highly variable animals as

Helix nemoralis and Helix hortensis it is very probable that individuals

with dissimilar characters regularly mate in nature and transmit diverse

combinations of characters to their progeny. Indeed, if one examines a

table of species of a genus or of varieties of a species one is struck by

the paucity of distinctive characters. The way in which species, as

found in nature, are made up of different combinations of the same

characters is illustrated by the following example, taken almost at

random. Among the earwigs is the genus Opisthocosmia, of whieh the

five species known from Sumatra alone may be considered. They differ,

among other qualities, chiefly in the following characters (Bormans and

Kraus, 1900) :

Size: A, large; a, small

Wing-seale: B, brown; b, yellow.

Antennal joints: C, unlike in color; c, uniform.

Forceps at base: D, separated; d, not separated. —

Edge of forceps: E, toothed; e, not toothed. 3

Fourth and fifth abdominal segments: F, granular; f, not granular.

132 THE AMERICAN NATURALIST [ Vou. XLVI

The combinations of these characters that are found are as follows:

Opisthocosmia ornata: AbcDEF.

insignis: ABcDEf.

longipes: AbCDEf.

tenella: AbCdef.

minuscula: aBCDEf.

Other species occur, in other countries, showing a different combina-

tion of characters, and there are characters not contained in this list,

which is purposely reduced to a simple form; but the same principles

apply generally.

The bearing upon evolution of the fact that species are varying com-

binations of relatively few characters is most important. Combined

with the fact of hybridization it indicates that the main problem of

evolution is that of the origin of specific characteristics. A character,

once arisen in an individual, may become a part of any species with

which that individual can hybridize. Given the successive origin of the

characters A, B, C, D, E, F, in various individuals capable of inter-

generating with the mass of the species, it is clear that such characters

would in time become similarly combined on many individuals; and the

similar individuals, taken together, would constitute a new species. The

adjustment of the species would be perfected by the elimination of such

combinations as were disadvantageous.

Second, modern studies have taught us that we have

regarded the steps of progress in evolution in too crude

a way. One school adhered to the view that characters,

as we know them in the adult, arose gradually in phy-

logeny as in ontogeny, i. e., that the germ-plasm under-

goes a development as the child does. Another school

proclaimed for discontinuity in phylogeny; i. e., that the

conditions in or the constitution of the germ-plasm un-

dergoes from time to time more or less abrupt changes.

Such abrupt changes are not altogether unknown in

ontogeny ; for the sundering of a chromosome or the per-

foration of a membrane involves essentially abrupt or

discontinuous processes. The new era of experimental

breeding is leading us to a position that is in some

respects intermediate between the views of these two

schools. We have discovered a hitherto unsuspected

multiplicity of inheritable units, indicating a vaster com-

» plexity of the system of determiners in the germ-plasm

No. 543] FACTORS AND METHODS OF EVOLUTION 133

than we had dreamed. Sometimes a prominent charac-

ter is represented by a single determiner like (perhaps)

roseness of the comb of the fowl; but in most cases there

is a multiplicity of factors, as in human hair and skin

pigments, in the yellow of mice, in shank feathering of

fowls and in seed coat-color of oats. In consequence of

the fact of this multiplicity of factors and of the fact

that a variable number may be present in different cases

the adult character appears in numerous grades of de-

velopment.

Indeed, the gradation of characters is, in these cases,

such that one has to recognize that discontinuous varia-

tion passes over into continuous variation, in the sense

that 40, 41, 42 form a continuous series, if not in the

sense that x, x + dx, «+ 2dz, etc., do. If a desire for

uniformity leads us to conclude that all variations in the

germ-plasm are discontinuous at least we see in many of

these variations sufficient justification for the continuity

hypothesis of the old-fashioned selectionist. The new

light that has been thrown on the subject is the certainty

of discontinuity in most cases and apparent continuity

only in the limiting case. The reason why the old con-

tinuity hypothesis was for so long a time accepted was

that we had underestimated the fineness and the multi-

plicity of the units of inheritance.

Third, experimental work has thrown a new light on

the process of selection. It is clear that Darwin confused

under this term two ideas that we now sharply separate ;

namely, the selection of the most favorable individuals

and the selection of the most favorable blood, race, strain

or pure line (biotype, Johannsen). In so far as not the

soma but the germ-plasm is the proper basis of selection

it is clear that the favorable biotype is what we should

seek for to make most rapid advance. By this means

Pearl has increased the fecundity of his poultry; thus,

probably Castle has extended step by step the color

pattern of rats; this poultry fanciers have improved the

color pattern of Barred Plymouth Rocks; thus I have

gained a syndactyl race of fowl.

134 THE AMERICAN NATURALIST [ Vou. XLVI

The method of personal selection has been widely used

by the less philosophical breeders. I do not think it fair

to Darwin to designate it as the exclusively Darwinian

selection. Whether advance can be made by personal

selection seems to me still an open question. Granting

our inability to reason about genotypical constitution

from the phenotypical, still, other things being equal,

and in the long run and with great numbers of individuals

an extremely high variant is more apt to belong to a

genotype with a high mean than to one with a low or

intermediate mean. Thus a breeder who selects merely

the very best somas of a large number will be apt to

select any superior biotype that may occur in his mate-

rial. This is doubtless the reason why breeders who con-

sider only the somas of their breeding stock nevertheless

sometimes make progress; for they are occasionally for-

tunate enough to stumble upon a new biotype.

Fourth, the results of experiments have thrown light

on the long-discussed question of the discontinuity be-

tween species, of the swamping effects of intercrossing

new varieties with the parent species and the necessity

for isolation to permit new varieties to become established

as distinct species. We now realize that the danger of

swamping which formerly seemed so logically necessary

is, from our new point of view, not really to be seriously

considered. Characters are rarely, if ever, swamped.

Apparent swamping by intercrossing occurs when the |

new character depends on many determiners. But it is

not, even in this case, really swamped; for no true blend

occurs but, on the contrary, a segregation of the original

extreme conditions takes place. This is well illustrated

by the case of human skin color. When the germ cell

that carries white skin color unites with the germ cell

that carries black skin color the ‘‘white’’ character seems

swamped in the offspring; but the swamping is only

apparent. Two mulatto parents have children of various

tints and, occasionally, one with a cleat white skin, as well

as one with a black skin like the original negro ancestor.

No. 543] FACTORS AND METHODS OF EVOLUTION 186

Neither white nor black is truly swamped. The extreme

white or black conditions are rather rare, as is to be ex-

pected where a multiplicity of factors is involved. Thus,

if there were two (2) factors P’, P” involved in the negro

skin then in F, one in sixteen should be negro-black, one

in sixteen pure white, and half of the remainder should

be light mulatto and half dark mulatto. Although studies

on this subject are not sufficient to warrant exact quanti-

tative conclusions, it is certain that more than two and

probably more than three factors are involved in the

pigmentation of the negro. If a number of mulattoes

inhabited (as sole occupants) an oceanic island, and bred

there, in the course of generations both the white and the

black types of skin color would be found again—the two

extreme types are not swamped. Consequently from our

present point of view, isolation is much less essential

than was formerly thought to be the case. Practically

important as it may be to keep races pure and ensure the

absence of intergrades or hybrids, it is not essential to

the survival of new traits that have arisen in the midst

of the old stock.

Fifth, the experimental study of heredity has thrown

light upon the question of the origin of new determiners.

Every critical experiment that has been tried demon-

strates again that the somatic condition exercises little

or no influence upon the determiners in the germ-plasm.

The first crucial experiment on this subject of which I

know was that of Francis Galton, who infused into tt gil-

ver-gray” does the blood of either yellow, black and

white, or common agouti rabbits. In one case an angora

buck and yellow doe had their carotid arteries So con

nected that for over half an hour the blood of each

flowed into the body of the other; so that about one half

of the blood of each was alienized. Yet, when the rab-

bits that had been operated upon were used as parents,

the offspring indicated that their germ-cells had under-

gone no modification ìn consequence of the foreign blood.

Recently the question has been revived by Guthrie, who

136 THE AMERICAN NATURALIST [ Vou. XLVI

made the experiment of engrafting foreign ovaries into

foster mothers very unlike the original females whence

they were taken. He concluded that the offspring were

modified in such a way as to prove that the transplanted

germ-plasm had received something from the foster

mother. Unfortunately Guthrie erred here, as my repeti-

tion of his experiments showed. For unquestionably, the

hens that were operated upon regenerated their proper-

ovaries and produced no eggs from the engrafted ovaries.

Dr. Phillips, working with Castle, engrafted black-bear-

ing eggs from one female guinea pig into albino guinea

pigs and then mated the females that had been operated

upon with an albino male. All offspring were entirely

black, proving, first, that the engrafted ovaries were

functional and, second, that the determiners of the en-

grafted germ-plasm were not modified by the soma of the

albino mother. On the other hand, the experiments of

Standfuss, Tower and Kammerer on animals and Mac-

Dougal on plants apparently indicate that under the

influence of various conditions of moisture, temperature

and chemical action the germ-plasm may be changed.

These results, probable as they are, await confirmation.

If fully confirmed they will afford a picture of one way

in which new determiners may originate.

Finally, some light has been thrown by modern experi-

mental studies on the subject of adaptation—for Darwin

the corner stone of organic evolution. But here, it must

be confessed, the contribution has not been great. That

there is such a thing as selective elimination is plainer

than ever. That some characteristics are compatible

with the environment and some incompatible is incon-

testibly true. Two cases in poultry illustrate this. I

have a lot of rumpless fowl; the cocks are sexually active

and the hens lay numerous eggs; but every egg is sterile,

for the reason that the erection of the tail feathers in the

hen is essential to the clean exposure of the cloacal open-

ing for the transfer of the sperm. Hence, since in the

rumpless hens the cloacal opening is not accessible to the

No. 543] FACTORS AND METHODS OF EVOLUTION 137

sperm, such a sport must, in nature, be eliminated.

Under domestication it is continued by trimming away

the feathers that cover the vent. Similarly, winglessness

in male fowl renders copulation difficult because the

wings serve the cock as balancers while treading the hen.

These then are examples of characteristics that must be

eliminated in nature. In the case of certain striking

colors in poultry there is evidence that they are selected

against; their possession gives their owner a handicap.

On the other hand certain new characteristics of fowl

may be preserved because apparently they offer no handi-

cap. Thus in the rumpless fowl the oil gland is absent

and the birds seem to be none the worse on that account;

their plumage’is bright and quite as resistant to a wet-

ting as that of birds with an oil gland at the base of the

tail. The striking fact that our experimental work yields

is the great number of new characters that seem to bear «

no relation to fitness or unfitness, but are truly neutral.

Thus I can not find that polydactylism, shank-feathering

or its absence, and the lower grades of single, pea and

rose comb have any adaptive significance for poultry.

One can invent adaptive explanations for them or their

absence in birds, but there is no reason for thinking that

the explanations are significant. On the other hand,

there is accumulating considerable experimental support

for Darwin’s theory of sexual selection; but of this it is

early to speak. On the whole, I think it may be fairly

said that experimental work supports the principle of

selective elimination but finds many characters that are

wholly neutral. i

To sum up, modern experimental study of heredity has

given-a new formulation to the problem of evolution and

has given definite data on the method of evolution. It

formulates the problem of evolution as the problem of the

nature and origin of the germinal determiners of char-

acters. It has shown that, for the most part, the new

determiners arise one at a time and are independent ef

one another, may occur in any combination and may be

138 THE AMERICAN NATURALIST [Vou. XLVI

transferred from one strain or species to another. It

has been shown that the unit characters are much more

numerous and finer things than we had thought and,

therefore, that the steps of evolution are frequently very

small ones and are taking place in many directions. It

has shown the relative unimportance of the isolation fac-

tor, since true blends of characters rarely, if ever, occur.

It has demonstrated the lack of influence by soma upon

germ-plasm; but has rendered it probable that external

conditions may directly modify the determiners of the

germ-plasm. It brings support for the view of selective

elimination of undesirable traits but finds that many, if

not most, characters that arise are neutral in respect to

any adaptive significance. Finally, it looks forward with

a justifiable expectancy to the completer experimental

test of the factors of evolution and their eventual com-

plete elucidation.

LITERATURE CITED

MEE A. de, and EE H. 1900. Forficulidæ and Hemimeridæ. Das

eich, 11 Lief. Berlin.

dastia W. E., and Pe J. ©. 1911. On Germinal Transplantation in

Vertebrates. Carnegie Institution of Washington, Publication No. 144.

Davenport, ©. B. 1909. Inheritance of Characteristics in Domestic: Fowl.

Carnegie Institution of Washington, Publication No.

Davenport, C. 1911. The Transplantation of Cvaries in Chickens.

Jeurnal of iirohotoas, 22: 111-122.

BIOTYPES AND PHYLOGENY

Dr. HUBERT LYMAN CLARK

MUSEUM or Comparative ZOOLOGY, CAMBRIDGE, Mass.

[Tue substance of this paper was presented to the

American Society of Naturalists at the Princeton meet-

ing under the title ‘‘Pure Lines and Phylogeny.” Dr.

Johannsen entered an emphatic protest against the use

of ‘‘pure line’’ in the sense of a group of individuals

characterized by an identical combination of the same

determinants. Subsequent conversation with Dr. Jo-

hannsen, and the recent clear exposition by Shull (Sci-

ence, Jan. 5, 1912, pp. 27-29) satisfied me that what I had

considered ‘‘pure lines’’ (such as those distinguished by

Jennings in Paramecium) are the pure strains called

biotypes by Johannsen. I have modified my paper ac-

cordingly and have avoided using the term ‘‘pure line.’’

I have also abandoned the very convenient term ‘‘pheno-

type’’ because my use of it as a contrast to biotype is

not strictly in accord with Johannsen’s usage of it as a

contrast to ‘‘genotype.’’ At Princeton, I protested

against Johannsen’s use of the word genotype, because

the word is preémpted for a totally different usage.

_I suggested a substitute, but this failed to meet

with Dr. Johannsen’s approval. Since I have seen

Shull’s definition of ‘genotype’? (to which Dr. Johann-

sen himself referred me), I think the objection to the

word is greater than before because ‘‘type’’ implies a

single definite thing or model and Johannsen’s ‘*gen-

otype’’ is not that but is ‘‘the fundamental hereditary

. combination of genes of an organism.” In other

words it is not a concrete thing but the intangible char-

acter of that thing. It seems to me the termination

“‘plast?? (mAaords, moulded, formed, i. e., formed from

139

140 THE AMERICAN NATURALIST [Vor. XLVI

the genes) expresses the idea better than “type”? (TÚTOS,

a figure, impression, model) and ‘‘oenoplast’’ is quite

as euphonious as ‘‘genotype.’’ The adjective form is

equally satisfactory, while the use of this term will not

require the abandonment of ‘‘gene.’’ In the following

pages therefore I have used ‘‘genoplast’’ and ‘‘geno-

plastic’’ in place of genotype and genotypical and I do

not believe any misunderstanding will be possible. I

have no desire to insist on these words, however. The

whole matter is a very trivial one and I would very much

prefer that Dr. Johannsen should himself choose a substi-

tute for ‘‘genotype.’’ I can not, however, agree with him

that genetics and systematic SERE are so far apart

that no confusion can result from using identical terms

in totally different senses. I believe that so far as pos-

sible workers in any branch of biology ought to keep in

touch with as much of the whole field as may be possible,

and that we should all endeavor to avoid ambiguity and

unintelligibility in the use of such technical terms as are

necessary.—H. L. C.]

Systematic zoology and botany deal primarily with

species and varieties, and can not therefore be expected

to throw light upon the existence of genoplastic groups.

Indeed, only those systematists who deal with organisms

which reproduce asexually or parthenogenetically are

likely to have any personal contact with them or even to

meet with direct evidence for or against their occurrence.

Since, however, the existence of such pure strains (bio-

types) seems to have been definitely proved! the question

of their relationship to the phylogenetic problems with

which the systematist has to deal becomes one of some

interest.

‘The problems of phylogeny are those of complicated

polygenoplastic groups—so complicated indeed that the

most complex of chemical compounds is simple in com-

parison. The study of these problems makes for caution

* JENNINGS, H. 8., 1911, AMERICAN NATURALIST, Vol. 45, pp. 79-89.

No. 543] BIOTYPES AND PHYLOGENY ' 141

in affirming that any one theory or hypothesis contains

all the truth. Thus we are coming to realize that neither

the Darwinian nor the De Vriesian theory of the nature

of the material upon which selection works is altogether

complete in itself and that neither when properly under-

stood wholly debars the other. If we accept the current

Mendelian and genoplast theories of heredity, must we

not admit that all variation is fundamentally discontin-

uous and that what has been called continuity is not

really such? It may be convenient to use such terms as

‘‘continuity’’ and ‘‘discontinuity’’ but are they not sub-

jective ideas rather than objective realities of impor-

tance? So, too, is it necessary to claim that the geno-

plast theory of heredity contains all the truth and that

the transmission or ‘‘phenotype’’ theory is wholly false?

It is easy to see how in pure line breeding ‘‘ancestral in-

fluence’’ is, as Johannsen says, ‘‘a mystical expression

for a fiction” but in the complicated polygenoplastic

groups of the higher Metazoa it is hard to see why the

history of the formation of a gamete may not be of im-

portance. Is this not virtually admitted by Johannsen

when. he grants the existence of ‘‘perturbations by in-

fection or contamination’’? And if this be granted, why

is there any necessary antagonism between the genoplast

theory of heredity and the belief that ‘‘discrete particles

of the chromosomes’’ may be ‘‘bearers of special parts

of the whole inheritance ’’?

However this may be, none of us has any doubt that the

discovery of biotypes has been a real stimulus to experi-*

mental work, and there is no reason why it may not also

be a stimulus to the investigation of phylogenetic prob-

lems even though it does not assist greatly in their im-

mediate solution. Among the difficulties of the system-

atist perhaps none is better known than that which we

may call the problem of large genera—genera made up

of dozens, in some cases indeed of hundreds, of species,

many of which are poorly defined and more or less inter-

grading. Some of these genera, as Crategus, Unio and

142 THE AMERICAN NATURALIST [ Vou. XLVI

Salmo, have become notorious and are not infrequently

referred to as proof of the futility of systematic work.

Does the discovery of biotypes afford any help in explain-

ing the existence of such genera?

I think that it does, particularly when considered in

connection with the broadest interpretation of Mendel’s

law. If we compare one of these inclusive genera with

one which contains few and well-defined species, we see

that the essential difference lies in the latter having the

characters sharply defined, with little diversity and no

blending, while in the former the same or similar char-

acters show so much diversity and such a tendency to

blend that the resulting recombinations are most perplex-

ing. It has occurred to me that we have here a condi-

tion of affairs analogous to what we find in the develop-

ment of the individual. Certain individuals with unlike

parents show what seems to be a blending of the parental

characters, while in numerous other cases the characters

of the individual can be referred unhesitatingly to one or

the other parent. Thus, as the well-known investigations

of Castle have shown, if lop-eared rabbits are crossed

with rabbits having ordinary ears, the character of the

ears in the offspring can not be referred to one parent

rather than to the other, while if pigmented and albino

rabbits are crossed, the color-character of the offspring

in succeeding generations can be so referred without

difficulty. This difference has been interpreted by Dav-

enport and others as due to the potencies of the deter-

minants, the apparent blending being associated with

equipotency or an approach thereto, while the distinct

characters result from allelopotency. Now may it not

be that a similar inequality of potency occurs among

the biotypes which go to make up a species? And so

when reproduction takes place we find some species in

which well-defined characters are dominant and the re-

sulting individuals form easily recognized groups, while

in other species there is a lack of definiteness and a blend-

No. 543] BIOTYPES AND PHYLOGENY 143

ing of characters which make the resulting forms most

confusing.

Jennings has shown that there are inherent difficulties,

which have so far been prohibitive, in securing crosses

between biotypes of Paramecium under experimental

conditions, yet it is obvious that such crossing must

occur constantly in nature; otherwise the whole geno-

plast theory becomes reduced to an absurdity. Granting

then the natural crossing of biotypes, let us consider the

case of a species, which for simplicity’s sake we will

suppose is made up of three biotypes (1, 2 and 3), each

of which is distinguished by certain character-combina-

tions, designated a, b and c, respectively. If the union

of 1 and 2 is readily effected, while that of 1 and 3 or

that of 2 and 3 rarely occurs, it is evident that ab will

far more commonly characterize the species than ac or

be which will indeed seldom appear. The species will

therefore approach identity with one of its biotypes,

which may thus be considered the dominant strain. The

inequipotency of the biotypes and the resulting definite-

ness of character in the species are obvious. If, however,

the union of 1 and 3, and of 2 and 3 are as readily effected

as that of 1 and 2, ac and be will occur as frequently in

. the species as ab. In such a case the biotypes are equi-

potent and the resulting species may be correspondingly

ill-defined.

The hypothesis here suggested of the ‘‘inequipotency

of biotypes’’ may thus be the explanation of the existence

of the well-defined species so generally known, while the

occurrence of large heterogeneous assemblages of either

Species or varieties may be interpreted as due to an un-

usual equipotency. The experimental determination of

the existence of this hypothetical difference in the po-

tency of the biotypes within a species would well be worth

while, if it should ever prove to be possible. The study

of large heterogeneous groups may suggest some other

lines of investigation into the nature and even the origin

of biotypes. For example, such groups occur chiefly, if

144 THE AMERICAN NATURALIST [Vou. XLVI

not wholly, in the more specialized portion of any stock

and in some cases at least appear to be associated with

the fading-out or senescence of that particular branch.

This suggests the possibility that the potency of a biotype

ultimately alters, even though there is no visible or tan-

gible evidence of change.

A second problem which puzzles the systematist is the

variability in the value of a character for distinguishing

species, genera and even higher groups. Color is a fa-

miliar example of this. It is of real value among birds

and in numerous other cases, but is almost worthless

among many invertebrates. Does the knowledge of the

existence of biotypes help us to understand why this is?

At first thought one might say that here again the inequi-

potency of the biotypes was the explanation of the phe-

nomenon, but further consideration will show that this is

not the case, for of course the potency of a biotype will

involve all of its characteristic determinants and not

merely that or those associated with the character in

question. It is clear then that the value of any char-

acter for distinguishing species from each other—in

other words, its value for systematic work—depends on

the actual determinants in the genoplastic groups com-

posing those species. The variability in systematic value

shown by a given character is due then, not to the

potency, but to the composition of the biotypes involved.

Thus if all the biotypes contain identical color determi-

nants, then color will be an absolutely constant char-

acter in that species, but the greater the diversity in the

color determinants of the biotypes the more variable will

the color of the species be and the less useful the color

be as a distinguishing character. Conversely, we may

say that the value of color in systematic work will depend

on the degree of identity in color-determinants among

the biotypes composing the species concerned. If this is

so, the study of systematic characters and the measur-

ing of their diversity may suggest some characteristics of

biotypes as yet unsuspected. Thus biometrical work

No. 543] BIOTYPES AND PHYLOGENY 145

even in a polygenoplastic population receives an added

indorsement.

A third problem of the systematist (and for this occa-

sion the last) is found in the fact that diversity of mor-

phological characters in any given species is not hap-

hazard or indiscriminate, but is generally restricted to

such definite lines as to indicate more or less distinct

stages in the phylogenesis of that species. The belief that

diversity is significant and that its meaning may be dis-

covered has received extraordinary confirmation in Jack-

son’s just published, magnificent monograph on Echini?

in which the subject is very fully discussed. An illustra-

tion taken from his work will help to make clear the de-

sired point. In any regular sea-urchin, such as Arbacia

or Strongylocentrotus, a group of ten plates surrounds

the periproct, five of which are radial in position and are

called oculars while the other five are interradial and are

called genitals. Now in some echini all of these ten plates

are in contact with the periproct and thus form a simple

continuous ring but in most of the Recent species, the

oculars are much smaller than the genitals and some or

all of them are separated from the periproct by the meet-

ing of adjoining genitals. In other words, some of the

oculars may be excluded from the periproct and such are

said to be exsert, while those which separate adjoining

genitals and reach the periproct are called insert. Now

Jackson has demonstrated conclusively, contrary to the

widely held belief that the insertness of oculars is a mat-

ter of age and size, that for each species of sea-urchin

there is a characteristic arrangement of the genito-ocular

ring and that this arrangement is oftentimes a very con-

Stant character. Thus in 2,100 Arbacias from Woods

Hole, 87 per cent. have all the oculars exsert and in more

than 20,000 Strongylocentroti from Maine 95 per cent.

have the two posterior oculars insert. |

Having demonstrated the constancy of this character,

Jackson has gone on to an analysis of the variations from

* Jackson, R. T., 1912. Mem. Boston Soc. Nat. Hist., Vol. VII.

146 THE AMERICAN NATURALIST [ Vou. XLVI

the normal arrangement, occurring in large series of

adult specimens. And he has clearly shown that these

variations are nearly always significant. There are 32

possible arrangements of the plates of the genito-ocular

ring and there is no mechanical or structural reason why

any one of them should not occur. If variation were

perfectly haphazard every one would occur and there is

no obvious reason why they might not occur, with equal

frequency. Yet in fifty thousand specimens examined by

Jackson, representing 137 different species of Mesozoic.

and Recent Echini, ten of these possible arrangements

never occurred, and of the remaining 22 fourteen are so

rare that altogether they aggregated less than 14 per

cent. of the specimens. As a very large proportion of

these were individuals abnormal in some other particular,

it is fair to say that of 32 possible arrangements of the

genital and ocular plates only eight (or at most ten) occur

normally. Even more striking are the following facts:

When only a single ocular plate is insert, it is one of the

posterior pair; this is the case in 994 per cent. of the

specimens having one ocular insert.

When two oculars are insert, they are the posterior

pair in more than 99 per cent. of the cases and in every

case one of them belongs to that pair.

When three oculars are insert, they are the two poste-

rior and usually the left, but sometimes the right ante-

rior; this is demonstrated by almost 99 per cent. of the

cases.

When four oculars are insert, the one exsert is invar-

iably either the mid-anterior or right anterior.

These figures show how surprisingly definite variation

is in a character which, so far as we can see, might vary

with equal ease in any one of 32 ways. Yet it is only

when we examine a particular case that the significance

of this definiteness appears.

Jackson’s work is full of such cases, but as most of

us are familiar with Strongylocentrotus, we will consider

an illustration from that genus, which, in the old, broad

No. 543] BIOTYPES AND PHYLOGENY 147

sense, accepted by Jackson, includes more than twenty

species. Of these some have the ambulacra relatively

simple, the compound plates being made up of only four

or five elements each, while in the more specialized spe-

cies there may be as many as ten elements in each com-

pound plate. The various species can be arranged

roughly in a series beginning with the simplest and end-

ing with the most specialized? and Jackson shows that

the species with the simplest ambulacra (S. lividus)

has ‘‘no oculars insert’’ as the species character, with

‘‘right posterior ocular insert’? as a common variant,

while those with the most complex ambulacra (S. fran-

ciscanus and purpuratus) have two and often three

oculars insert. Now in our common Strongylocentro-

tus from Maine, while practically 95 per cent. have two

oculars insert, nearly 3 per cent. have only one insert, as

in the common variant of S. lividus, while about 2 per

cent. have three insert as in the usual variants of S. pur-

puratus. Jackson calls these arrested and progressive

variants, respectively, according to whether they resem-

ble a more simple or a more complex allied species.

Whether the terminology be accepted or not, the signifi-

cance of such facts can not be ignored. Are we any

better prepared, with our present knowledge of the ex-

istence of biotypes, to understand the reason for this

significance of variation?

If we compare a polygenoplastic group with a highly

complex chemical compound, an analogy is suggested

which warrants our answering this question affirma-

tively. In building up such a compound synthetically,

the specific properties of the constituents result in the

formation of certain definite compounds. These sub-

Stances are necessary for the further combinations

without which the ultimate compound could not be

formed. In other words, the formation of the desired

product is possible only because the chemical reactions

*There are some interesting exceptions, but as they do not affect the

subsequent argument, they need not be d here.

148 THE AMERICAN NATURALIST [ Vou. XLVI

will take place in an orderly sequence, in consequence

of the fixed specific properties of the elements involved.

Now any existing species of plant or animal is a

similar union of diverse elements and the possibilities of

its development would seem to be limited by the same

conditions which limit the formation of the chemical

compound, namely, the nature of the elements and

the orderly sequence of the reactions. (In either

case external conditions, the environment, would make

a profound difference, but for simplicity’s sake we may

omit reference to that influence.) As long as one be-

lieves that the elements composing a species are poten-

tially variable in all directions, it is evident that only the

pressure of external conditions can prevent an indefinite

and unmeaning variety in the product. Such a belief

results in making natural selection through the environ-

ment the supreme directive agent in evolutionary prog-

ress, and really puts more responsibility upon that im-

portant factor than it can reasonably be expected to

bear. But as soon as it is shown that the elements in-

volved are persistently unchanging to a remarkable de-

gree, it becomes clear that an orderly sequence in their

successive interactigns will follow just as in the forma-

tion of a chemical compound. Now biotypes are the

biological elements which enter into the formation of a

species, and the discovery of their existence and apparent

persistency makes the existence of an orderly sequence

in development quite comprehensible and indicates

clearly why diversity is so rarely haphazard. As in the

chemical synthesis, used as an illustration, the final re-

action follows necessary antecedent reactions, so in the

development of the species the last step necessarily de-

pends on the preceding, and the evolution of a group is

therefore bound to be strictly linear and in definite direc-

tions. Now just as in a chemical synthesis without add-

ing to or subtracting from its original constituent ele-

ments the process may be stopped, altered or accelerated,

either by addition or removal of some substance or by

No. 543] BIOTYPES AND PHYLOGENY 149

change in the external conditions, so the process of de-

velopment of a species or of any of its component indi-

viduals may be arrested, altered or accelerated by similar

means. Thus variants arise, individual or racial, some-

times slight, sometimes marked, but necessarily within the

limits laid down by the specific properties of the biotypes

involved. This may be well illustrated by one of Jack-

son’s discoveries about variation in the genito-ocular |

ring of the common tropical sea-urchin, T'ripneustes.

In specimens from Florida and the West Indies, 36 per

cent. have only the two posterior oculars insert, 38 per

cent. have three (the left anterior plus the posterior) and

18 per cent. have four (right and left anterior plus the

posterior). Evidently then individual variants both ar-

rested and progressive are common but within very re-

stricted limits. Further than this it appears that in

Bermuda a racial variant can be distinguished, for in

specimens from that locality 61 per cent. have only two

oculars insert, 35 per cent. have three and only 2 per cent.

have four. Now it matters not at all whether the Ber-

muda race is considered an arrested variant or the West

Indian form a progressive variant; the important fact

is the evidently marked but definitely limited racial diver-

sity. The study of such variants, however little light it

may throw on the immediate cause of their appearance,

is bound to help make clear the normal line of develop-

ment of the species to which they belong, and emphasizes

the definiteness and the significance of their diversity.

But if biotypes are really the fixed and unchanging ele-

ments which compose a species, the problem as to why

this diversity is so commonly definite and significant is

apparently simplified not a little by our knowledge of

their existence.

It is unnecessary to suggest any other phylogenetic

problems and the bearing of the study of genetics on

them, for if in these which I have suggested it has not

been shown that such study is helping us to understand

these problems better and is even indicating solutions,

150 THE AMERICAN NATURALIST [ Vou. XLVI

multiplication of such cases will not help the matter.

Personally, I believe that the experimental work now so

extensively carried on in the study of genetics is throw-

ing a flood of light on all biological questions and that

systematists not only may but must make use of the

demonstrated results of such study, in attacking their

own special problems, if they are really in earnest in the

_ purpose to solve them.

SHORTER ARTICLES AND DISCUSSION

A LITERARY NOTE ON MENDEL’S LAW

THE ever-increasing extension of the doctrine of Mendelism

brings it year by year to the attention of a widening circle

of general readers. Its application in the field of eugenics has

aroused a popular desire for a further knowledge of the now

famous principles of Mendel. Owing to the relative inacces-

sibility of Mendel’s original publication the exact terms in which

he formulated his conclusions have not been readily available.

To meet in some measure this lack of ready reference the fol-

lowing brief, synoptic statement of the fundamental principles

of Mendel is here presented in his own words, together with

certain collateral notes that may be of value to students of this

important law.

The general term ‘‘Mendel’s Law”? is usually applied to sev-

eral complex principles discovered by Gregor Mendel while

studying inheritance in certain plant hybrids. Various other

designations, however, appear in the literature, e. g., Mendel’s

“Law of Heredity,’ ‘‘Law of Inheritance,’ ‘‘Laws of Alter-

native Inheritance,” and ‘‘Law of Varietal Hybrids.’’* These

principles were enunciated by Mendel in a paper entitled, “‘ Ver-

suche über Pflanzenhybriden’’ (‘‘Researches on Plant Hy-

brids’’), which appeared in the Verhandlungen der naturfor-

schenden Vereines in Briinn, Vol. 4, 1865, Abhandlungen, pp.

3-47,5 but escaped the attention of biologists until the year

1900, when by De Vries, Correns” and von Tschermak,* they

*Castle, W. E., Proceedings American Academy - of Arts and Sciences,

Vol. 38, 1903, p. 535.

7 Biffin, R. n. Journal Agricultural Science, Vol. 1, 1905, p. 1.

x Weldon, W. F, R., Biometrika, Vol. 1, 1901, p. 228.

“De Vries, H., ‘‘ Species and Varieties,’’? Chicago, 1905, p. 716.

* Reprinted in Fora: Vol. 89, 1901, pp. 364-403.

*De Vries, H., ‘‘Das Spaltungsgesetz der Bastarde,’’ Berichte der

deutschen Sitaki Gesellschaft, Vol. 18, 1900, pp. 83-90.

"Correns, C., ‘‘@. Mendels Regel über das Verhalten der Nachkom-

menschaft der Kaaa, ? Berichte der deutschen botanischen Gesell-

schaft, Vol. 18, 1900, pp. 158-168.

151-

152 THE AMERICAN NATURALIST [ Vou. XLVI

were independently and almost simultaneously rediscovered.?

Mendel’s principles have been rephrased by later writers, and

they are now usually referred to as the Law of Dominance, the

Law of Segregation, and the Law of Recombination, respectively.

I. THe Law or DOMINANCE!

This so-called law is derived from the following principle of

Mendel (‘‘ Versuche,’’ etc., pp. 10-11

In der weiteren Besprechung werden jene Merkmale, welche ganz

oder fast unverändert in die Hybride-Verbindung übergehen, somit

selbst die Hybriden-Merkmale repriisentiren, als dominierende, und

jene, welche in der Verbindung latent werden, als recessive bezeichnet.

Translated this principle reads:

Those characters which pass entirely or almost entirely unchanged

into the hybrid combination and consequently in themselves represent

the characters of the hybrid, are designated as dominant, and those

which become latent in the combination are termed recessive.

Since dominance is rarely absolute this principle is not general

and should not be termed a law; indeed Mendel did not claim

it as a law. Recent statements of the ‘‘Law of Dominance’’

may be thus summarized:

When the two parents differ in respect of two contrasted characters,

only one, the dominant character, will appear in the hybrid. Domi-

nance, however, is seldom perfect, so that the dominant character in a

hybrid seldom reaches as full expression as in the dominant parent.

II. THE Law or SEGREGATION.

Mendel’s second principle (‘‘Versuche,’’ ete., p. 17) is thus

stated :

* Von Tschermak, E., ‘‘ Ueber künstliche Kreuzung bei Pisum sativum,’’

Zeitschrift fiir z landutetashutdions Versuchswesen in Oesterreich, Vol.

3, 1900, pp. 465-

*De Vries’s Bas was received for publication on March 14, 1900, and

that of Correns on April 24, 1900. Tschermak, in a postseript to his com-

T, says: ‘‘Die giciehucitios Entdeckung Mendels durch Correns,

de Vries (Berichte der deutschen piange Gesellschaft, 1900) und mich

sila mir besonders erfreulich,’

w<‘ Man hat dieses die pare aa! genannt,’’ Correns, C., ‘‘ Uber

Vererbungsgesetze,’’ Verhandlungen der Gesellschaft deutscher Naturforscher

und Arzte, 77 Versammlung, 1905, Part I, Leipzig 1906, p. 207

No. 543] SHORTER ARTICLES AND DISCUSSION 153

Da die Glieder der ersten Generation unmittelbar aus den Samen der

_ Hybriden hervorgehen, wird es nun ersichtlich, dass die Hybriden je

zweier differirender Merkmale Samen bilden, von denen die eine Hälfte

wieder die Hybridform entwickelt, während die andere Pflanzen gibt,

welche constant bleiben, und zu gleichen Theilen den dominirenden und

recessiven Character erhalten.

This may be translated as follows:

Since the members of the first generation” arise directly from the

seeds of the hybrids, it is now evident that hybrids, for each pair of

differentiating characters, form seeds, one half of which develops again

the hybrid form, while the other half produces plants which remain

constant and in equal proportions receive the dominant and recessive

characters.

Various terms have been applied to this law by different

authors, e. g., ‘‘Law of Disjunction,’’!* ‘‘Law of Purity of Germ

Cells,” “Law of Separation of Characters in Crosses,’’* and

“Law of Dichotomy.’ Generalized, the law may be stated in-

the following form:

In self-fertilized species an individual which is a hybrid with refer-

ence to a particular pair of characters tends to produce progeny one

fourth of which is of pure race like one of the parents of the hybrid,

another fourth of pure race like the other parent, while the remaining

half is hybrid, like the original hybrid itself,”™ that is, “ from the inbred

heterozygote come dominants and recessives in the proportion of 3:1,

and only one dominant in three is pure, the other two being hetero-

zygote.” ee

The above statement is purely objective ;** it states the results

* This is He F, generation of current literature.

“De Vries, H., Comptes rendus de l’académie des sciences, Paris, Vol.

130, 1900, ny 845-847,

* Castle, W. E., Proceedings American Academy of Arts and Sciences,

Vol. 38, 1903, p. 5 537.

“De Vries, H., Journal Royal Horticultural Society, Vol. 25, 1901,

p. 243.

“ Davenport, C. B., Biological Bulletin, Vol. 2, 1901, p. 307.

* Spillman, W. J., " $6 Application of Some of ‘te Principles of Heredity

to Plant Breeding,’ ? eya No. 165, Bureau of Plant Industry, U. 8.

Dept. Agriculture, 1909, p. -.

* Punnett, R. C., eee 1 Cambridge, 1907, p. 23.

"Por this paragraph. and the one immediately iy eee the writer is

indebted to Professor W. J. Spillman.

154 THE AMERICAN NATURALIST [ Vou. XLVI

of a cause, but gives no hint of that cause. It is not strange,

therefore, that the modern statement of this law should have

gravitated backward toward the fundamental cause underlying

the law. The more usual statement of it at the present time is

an inference from the facts observed, and may be stated as

follows:

When an individual is heterozygous for a given character it produces

two kinds of gametes with reference to that character, one like those

of one of its parents and the other like those of the other parent.

Mendel himself gives the corresponding statement of the law

of recombination ; that is, he states the inference about the kinds

of gametes a hybrid must produce, as inferred by the types of

the resulting progeny.

The principle of segregation, closely approximated long prior

to Mendel both by Goss? and by Sageret, was clearly enun-

ciated by Naudin,”* but these writers did not formulate their

*<<Tn the summer of 1820, I deprived some blossoms of the Prolific blue

of their stamens, and the next day applied the pollen of a dwarf Pea, and

of which impregnation I obtained three pods of seeds. In the following

spring, when these were opened, in order to sow the seed, I found, to my

surprise, that the colour of the Peas, instead of being a deep blue, like their

female parent was of a yellowish white, like the male. Towards the end

of the summer I was equally surprised to find that these white seeds had

produced some pods with all blue, some with all white, and many with both ~

blue and white Peas in the same pod.

‘*Last spring, I separated ‘al the blue Peas from the white, and sowed

each colour in separate rows; and I now find that the blue produce only

i while the white seeds yield some pods with all white, and some with

both blue and white Peas intermixed.’’—Goss, John, ‘‘On the Variation in

the Colour of Peas, occasioned by Cross Tuiprepnation. ?? In a letter to the

Secretary. Read October 15, 1822. Transactions of the Horticultural So-

-_ of London, Vol. 5, 1824, pp. 235.

T.r Ainsi done, en definitive il m’a paru qu’en général la ressemblance

de l’hybride à ses deux ascendans consistait, non dans une fusion intime des

divers caractèrs propres à chacun d’eux en particulier, mais bien plutôt dans

une guitars: soit égale, soit inégale, de ces mêmes caractères: je dis

égale u inégale, parce qu’elle est bien loin d’être la même dans tous les

individs hybrides provenant d’un même origine; et il y a entre eux, une

rès grande diversité. ’’_Sageret, A., ‘‘Considérations sur la praduction des

hybrides, des variantes et des variétés, en général, et sur celles de la fa

des Cucurbitacées en particulier.”? Annales des sciences naturelles, Vol. 8,

1826, p. 302.

aí Tous ces faits vont s’expliquer naturellement par la disjonction de

deux essences specifiques dans le pollen et les ovules de 1’hybride.’’

No. 543] SHORTER ARTICLES AND DISCUSSION 155

results in terms of numerical ratios as did Mendel. Knight?

and Gärtner”? as well as Wichura,?* Godron®® and Vilmorin?’

‘í Supposons, dans la Linaire hybride (L. vulgaris X L. purpurea) de

première génération, que la disjonction se soit faite A la fois dans l’anthere

et dans le contenu de l'ovaire; que des grains de pollen appartiennent totale-

ment à 1’espéce du père, d’autres totalement a 1’espéce de la mère; que dans

d’autres grains la disjonction soit nulle ou seulement commencée; admet-

tons encore que les ovules soient, au méme degré, disjoints dans le sens du

père et dans le sens de la mère; qu’arriverat-il lorsque les tubes polliniques

descendront dans l’ovaire et vont chercher les ovules pour les féconder?

Si le tube d’un grain de pollen, revenue à 1’espéce du père, recontre un

ovule disjoint dans le méme sens, il se produira une fécondation parfaite-

ment légitime, dont le resultat sera une plante entièrement retournée A

l’espéce paternelle.’’

Naudin, Ch., ‘‘ Nouvelles recherches sur ]’hybridité dans les végétaux,’”

Nouvelles archives du muséum d’histoire naturelle de Paris, Vol. 1, 1865,

pp. 150, 153

*<<Blossoms of a small white garden pea, in which the males had pre-

viously been destroyed, were impregnated with the farina of a large clay-

coloured kind with purple blossoms. The produce of the seeds thus ob-

were increased from seven to eight, to eight or nine, and not unfrequently,

in one variety to ten. The newly made gray kinds I found were easily made

white again by impregnating their blossoms with the farina of another white

kind. In this experiment some of the seeds in the same pod would produce

gray, = others white offspring, as occurs frequently in animals, which

bring many young ones at birth, when the breeds of the male and female

are of teat colours.’

ight, T: A, “A Treatise on the Culture of the Apple and Pear, and on

the Manufacture of Cider and Perry.’’ Ludlow, 1801, pp. 37-88, footnote..

26t Het allerduidelijkst evenwel is de invloed van leet vreemde stuifmeel

op de eitjes in dit opzigt bij de Leguminosen, wanneer b. v. de stempel van

Pisum sativum luteum met het stuifmeel van Pisum sativum viride bestoven

wordt, zoo ontstaan in deszelfs peulen zaadkorrels welke aan die der moeder

gelijk zijn, doch andere van eene groene en nog andere van eene gevlekte,

dat is, van eene groene en gele kleur. Deze zaadkorrels uit de eerste voort-

teling, zoowel de groene als de gele en de gevlkte, geven in de tweede voort-

teling pe, die hetzelfde verschil, als die uit de eerste voortteling,

opleveren,

Gärtner, C. F., ‘‘Beantwoording der Prysvraag over bastardeering,’’

N atuurkundige Verhandelingen van de le, Maatschappy der Weten-

pen te Haarlem, Vol. 24, 1838, p.

_ “ Wichura, Max, ‘‘ Die Baster dbežruchtung $ im Pflanzenreich, erläutert an

den Bastarden der Weiden,’’ Breslau,

156 THE AMERICAN NATURALIST [ Vou, XLVI

also seem to have come very near to the discovery of Mendel’s

principles.

III. THe Law or RECOMBINATION”*

This law is based pee the following Mendelian principle

(‘‘Versuche,’’ ete., p.

Die Nachkommen der Hybriden, in welchen mehrere wesentlich ver-

schiedene Merkmale vereinigt sind, stellen die Glieder einer Combina-

tionsreihe vor, in welchen die Entwicklungsreihen für je zwei differi-

rende Merkmale verbunden sind.

This principle may be thus translated :

The progeny of hybrids, in which several- essentially different char-

acters are combined represent the terms of a series of combinations, in

which the development series for each pair of differentiating characters

are united.

Spillman in his recent paper entitled ‘‘The Application of

Some of the Principles of Heredity to Plant Breeding,’’** thus

concisely states this law:

In the second generation of a hybrid there tends to occur every pos-

sible combination of the original parent characters.

This law was also discovered by Spillman independently 1m in

1901 and announced provisionally by him in a paper read before

the Association of American Agricultural College and Experi-

ment Stations in November of that year.?°

The clearest and most comprehensive account of Mendel’s work

extant is probably that of Bateson?’ in which may be found a

full discussion of the doctrine of Mendelism together with a

translation in English of Mendel’s original papers. The French

*Godron, D. A., ‘‘De l'espèce et des races dans les êtres organisés,”’

2d ed., Vol. 1, Paris, 1872, pp. 180-266.

*Vilmorin, E, “Note sur une expérience relative à 1’étude de 1’hérédité

dans les végétanx,? ’ Paris, 1879, pp. 1-11. Extrait des mémoires de la

société nationale d’agriculture de France—Année 1877.

"cí Gesetz der Selbständigkeit der Merkmale,’’ Correns, l. c., p. 208.

* Bulletin No. 165, Bureau of Plant Industry, U. S. Dept. Agriculture,

1909, p. 22.

* Bulletin No. 115, Office of Experiment Stations, U. S. Dept. Agri-

culture, "s

” Bat

» 88.

a, W, ‘*Mendel’s Principles of Heredity,’’ Cambridge, 1909.

No. 543] SHORTER ARTICLES AND DISCUSSION 157

translation by Chappellier,** and also the recent works by Baur,**

aecker,** and Goldschmidt,** will be found very useful to the

general student of Mendelism.

W. W. STOCKBERGER

U. S. DEPARTMENT OF AGRICULTURE

THE RANGE OF SIZE IN THE VERTEBRATES

A SMALL shrew, Microsorex winnemana, recently described

from Virginia by Preble, is said, if conclusions from but two

specimens may be drawn, to be the smallest species of shrew and

therefore the smallest mammal yet known from America. These

specimens measured 78 and 86 mm., respectively, in total length.

Microsorex hoyi (Baird) of the eastern and central states aver-

ages from 82 to 88 mm. and Sorex fontinalis Hollister and Sorex

personatus Geoffroy are but slightly larger. Blarina parva (Say)

a short-tailed shrew, averaging in total length about 75 to 80 mm.,

is in this respect smaller than M. winnemana, but much larger

in breadth, cranial and other characters. The smallest existing

mammal is probably a minute Crocidura of the subgenus

_ Pachyura from Madagascar.

The Insectivora, essentially an archaic and primitive group,

reached its highest development in point of numerous and di-

verse adaptations in the Middle Eocene, from which there has

been a gradual and steady decline. Sorex is known from the

Middle Oligocene, Talpa, the mole from the Upper Oligocene

and Erinaceus, the hedgehog from the Lower Miocene. These

are some of the oldest of existing genera of mammals. The

Malayan genus Gymnura, an Erinaceid, was said by Huxley’ to

possess the most generalized structure of all placental mammals.

The persistence of the group is without doubt due in a large part

to the small size and relative inconspicuousness of its members.

* Chappellier, A., ‘‘Recherches sur des hybrides végétaux (Traduction

francaise). Bulletin Scientifique de la France et de la Belgique, Vol. 41,

1907, pp. 371-420,

* Baur, E., ‘‘Einfiihrung in die experimentelle Vererbungslehre,’’ Berlin,

1911,

= Haecker, V., ‘‘ Allgemeine Vererbungslehre,’’ Braunschweig, 1911.

* Goldschmidt, R, ‘‘ Bintührung in die Vererbungswissenschaft,’’ Leip-

zig, 1911.

* Proc. Biol. Soc. Wash., Vol. 23, P. 101, 1910.

? Proc. Zool. Soc. London, p. 657, 1

158 THE AMERICAN NATURALIST [ Vou. XLVI

The separation of Madagascar from Africa has permitted the

continuance of the relatively large Centetide, the tenrecs, of

which Ericulus, Centetes and Hemicentetes have developed a

spiny coat and Limnogale has become aquatic. Similarly, the

rare and interesting Zalambdodont, Solenodon, has been able to

continue an existence by isolation in Cuba and Hayti. Even

thus isolated, Solenodon, judging from its extreme rarity, barely

maintains a foothold. The aberrant Tupaiide, or Oriental tree

shrews, are, as indicated by their name, arboreal and the African

Macroscelididæ, or elephant shrews seek refuge by leaping and

by skulking. The South African Chrysochloride, or golden

moles, and the familiar Talpide are subterranean. A subter-

ranean habitat implies a restricted stature. Erinaceus, the well-

known hedgehog, and the African Potamogale, the only rela-

tively large non-insular insectivores, are well protected, the

former by its spiny coat and the latter by its aquatic habits.

The Soricide containing the smallest members of the order are

largely nocturnal. During the long stretch of time since the

Eocene culmination of the group and the gradual evolution of

more modern mammalia, the Insectivora have become extinct

with the exception of those especially protected, insular, sub-

terranean or of insignificant size. Smallness here seems an

attendant trait of archaism. The earliest American mammals,

the Triassic Protodonts, Dromatherium and Microconodon and

among recent mammals certain Murine rodents closely simulate

this diminutive stature.

The massive Rorqual whale, Balenoptera sibbaldii Gray, of

the North Atlantic, sometimes reaching a length of eighty-five

feet, is the bulkiest vertebrate which has ever existed. The

Cetacea are likewise a primitive and probably degenerate group.

Other aquatic mammals, such as the Sirenia, Pinnipedia, etc.,

similarly reach immense proportions, due, very likely, to the lack

of a compensatory element in the environment. The tallness of

the giraffe, which is an adaptation to arboreal grazing, produced

by an elongation of the cervical vertebræ, coordinated of course

with limb structure, has independently arisen in at least one

other family. The giraffe-camels of the genera Oxydactylus and

Alticamelus, respectively, of the American Oligocene and Mio-

cene, parallel the existing giraffes.

The smallest known bird is Calypte helene (Gundlach) of

No. 543] SHORTER ARTICLES AND DISCUSSION 159

Cuba, measuring in total length but 57 mm.* Several other hum-

ming birds, notably Mellisuga minima (65 mm.) of Jamaica, are

but slightly larger. The Trochilide comprise about 600 known

forms, most of which are excessively small. Patagona gigas of

the higher Andes, the largest of the group measures about 215

mm. in length. The size of the members of this family is an

adaptation to the physical requirements of a highly active life,

which is essentially that of securing food while hovering before

blossoms. The Nectariniide or sun-birds of the Ethiopian and

Indian Regions parallel the Trochilide in size and brilliancy.

The Dicæidæ or ‘‘ Flower-peckers ’’ of India and Australia, and

the Troglodytide and Regulide, wrens and kinglets of this

country, likewise contain very small forms.

Spherodactylus sputator Gray (45 mm. plus), occurring in

the West Indies, is one of the very smallest of American rep-

tiles. S. notatus Baird (50 mm.) of Florida and the West Indies

and a number of other West Indian lizards are hardly larger.

The largest of existing lizards are members of the Varanide of

Africa, Asia and Australia, the Malayan Varanus salvator

(Gray) reaches a length of eight feet. Of the adaptive radia-

tions which the Lacertilians have undergone, that branch con-

taining the Amphisbenidx, minute, legless, burrowing forms of

tropical America and Africa, is of peculiar interest. This family

presents a most remarkable illustration of the principle of

heterology of Cope, of parallelism and convergence of other

authors. Through the dominance of essentially similar environ-

mental factors, certain species have come to resemble the earth-

worm with such fidelity, that the very chickens which follow

the plow are said to seem unable to differentiate and indiserim-

inately pick them up.’

These remarks may apply equally well to the Typhlopide

and Glauconiide, still widely distributed in tropical countries,

archaic and degenerate, sightless, burrowing snakes, relicts of a

once cosmopolitan assemblage, which contain the very smallest

known Ophidians. Helminthophis petersi Boulenger (110 mm.)

of Ecuador, Typhlops anchiete Bocage (119 mm.) of Angola,

Africa, Glauconia dissimilis (Bocage) (104 mm.) of the White

Nile and Glauconia bilineata (Schlegel) (110 mm.) of the West

* Ridgway, Rep. U. S. Nat. Mus., 1890, p. 295 (1892).

* Boulenger, ‘‘Cat. Lizards Brit. Mus.,’’ 2d ed., Vol. 1, p. 219, 1885.

* Eigenmann, Biol. Bull., Vol. 8, no. 2, p. 60, 1905.

160 THE AMERICAN NATURALIST [ Vou. XLVI

Indies, are some of the smallest species. The largest existing

reptile is the Ganges crocodile, Gavialis gangeticus (Gmelin) of

northern India, which is said to attain a length of thirty feet or

more. This, however, is insignificant in comparison with that

attained by the sauropodous dinosaurs of the Mesozoic. The

American genera Atlantosaurus, Brontosaurus, Camarasaurus

and Diplodocus were immense creatures. Atlantosaurus im-

manis Marsh of the Wyoming Upper Jurassic, supposedly terres-

trial from mechanical considerations, is one of the largest land

vertebrates which has ever existed, probably upwards of one

hundred feet in length. The uncompensated extravagance of

energy in the maintenance of such immensity, coupled with the

small and primitive brain, were without doubt to a great extent

factors in the extinction of these gigantic vertebrates. These

animals are without living descendants. _

The familiar ‘‘spring peeper,’’? Hyla pickeringii (Storer),

about 20-28 mm., of eastern North America is the smallest

American Hyla and thus one of our smallest batrachians. The

Hylidx, comprising about 150 species, have a practically cosmo-

politan distribution with the exception of Africa and the Malay

Archipelago. Essentially arboreal, in the dense, steaming

tropical forests of South America they attain the highest diver-

sity of generic and specific types. H. pickeringii does not ordi-

narily ascend into the trees until early in autumn. A number

of true frogs are as small or smaller, thus Arthroleptis sechel-

lensis Boettger of the Seychelles, interesting from its habit of

carrying its eight or nine tadpoles affixed by their ventral sur-

faces to its back, is but about 20 mm. in length of head and

body. The smallest salamander of the eastern United States is

the red-back, Plethodon cinereus erythronotus Green, an elon- ©

gate form of about 75 mm. The largest salamander and the

largest existing batrachian is Megalobatrachus japonicus (Tem-

minck), the giant salamander of Japan, which reaches a length

of over five feet. At no time have the Batrachia been the domi-

nant type of vertebrate life, either in size or variety of forms.

It is among the fishes that we find the smallest known verte-

brates. Thus, Mistichthys luzonensis H. M. Smith,® an extraor-

dinarily minute goby from Lake Buhi, Luzon, P. I., is accorded |

this distinction. The average length of this species is 12.9 mm.

The average for egg-bearing females which exceeds the average

* Science, N. S., Vol. 15, p. 30, Jan. 3, 1902.

No.543] SHORTER ARTICLES AND DISCUSSION . 161

for males by one millimeter is 13.5 mm., the maximum is 15 mm.,

and the minimum is under 12 mm. This species is said to be a

food fish of considerable importance as it is seined by the natives

in large quantities, dried in cakes or mixed with spices, and is

eagerly sought for. The great majority of the six hundred

known species of Gobiide are less than 75 mm. in length.

Philypnus dormitor (Lacépède) of Central America and the

West Indies, the largest of the family, reaches a length of

600 mm.

The Etheostomine or darters contain some of the smallest

spiny-rayed fishes. Microperca punctulata Putnam (25-38 mm.)

of the Central States is next to Elassoma evergladei Jordan

(20-33 mm.) a minute percoidean of our southeastern swamps,

the smallest American spiny-rayed fish and a number of other

darters are but slightly larger. Heterandria formosa Agassiz,

a diminutive viviparous Peeciliid, occurring in swamps and

ditches from South Carolina to Florida, was for a long while

considered the least of American vertebrates. This species has

an average length of 19 mm. for males and 25 mm. for females.

Acanthophacelus bifurcus of the ponds and creeks of British

Guiana, recently described by Eigenmann,’ is still smaller; the

average for both sexes is 21.5 mm. and the largest of 74 speci-

mens is 29 mm. long. A number of pregnant females are but

20 mm. in total length and one of these, preserved in alcohol, in

the Indiana University collections weighs but .076 gram. The

weight of living specimens is probably somewhat greater. The

exact measurements of this specimen (I. U. No. 11,765) are as

follows: total length 20 mm., length to base of caudal 16 mm.,

depth 5 mm. and breadth or thickness 3 mm. The smallest male

specimen here, one in full nuptial coloration, measures 19 mm.

over all. In all probability, the smallest new world vertebrate is

Heterandria minor Garman,’ from Villa Bella, Brazil. The

average total length of this species is 18 mm. for males and 20.5

mm. for females. Females of but 19 mm. ‘‘contain fully devel-

oped embryos.’? With this may be contrasted the bulk ot

Arapaima gigas (Cuvier) of neighboring streams of Brazil and

Guiana, said to reach a length of fifteen feet and to be the largest

Strictly fresh-water fish known,

" Annals Carnegie Museum, Vol. 6, p. 52, 1909.

` Memoirs Mus. Comp. Zool., Vol. 19, no. 1, p. 92, 1895.

162 THE AMERICAN NATURALIST [ Vou. XLVI

The Peeciliide or killifishes, found in most warm portions of

the globe, comprise about two hundred very small species, the

largest Fundulus, Anableps, ete., seldom exceed 300 mm. In

the inviting streams of Central America where the majority of

species occur, adaptive radiation, as in every large family of

fishes, has taken place, from the central type Fundulus, result-

ing in the depressed catfish-like Rivulus, the beaked garpike-like

Belonesox, the sunfish-like Goodea, the earp-like Cyprinodon, ete.

The origin of these small forms may probably be explained

by the selective migration and the successive adaptation of the

species occupying the deeper reaches of the streams. The

Peeciliide usually feed at the surface and thus may tend to

disseminate throughout the full extent of the shallower waters.

Acanthophacelus has evidently been derived from Pecilia, from

which it differs chiefly in the acquirement of two rows of retrorse

hooklets on the modified anal fin of the male, while Heterandria

is of a different type with conical, carnivorous dentition and

shortened alimentary tract. Further exploration may reveal

still smaller species of these interesting little fishes, which are

likely, however, to pass unobserved by all but the trained

naturalist.

ARTHUR W. HENN

INDIANA UNIVERSITY

BLOOMINGTON, INDIANA:

NOTES AND LITERATURE

HEREDITY

F. E. Lutz contributes a very interesting paper* in which he

presents evidence bearing on the effect of selection in a ‘‘pure”’

strain. Amongst wild flies of this species (Drosophila ampel-

ophila) about one third of one per cent. present abnormalities in

wing venation. By selection and inbreeding he was able to pro-

duce strains with practically 100 per cent. abnormality. In a

good many crosses the abnormal venation behaved as a Mendelian

recessive in which dominance of normal was not perfect. But

in other cases the phenomena observed departed widely from

the typical Mendelian behavior. The author suggests that the

abnormality is due to a factor which has high fluctuating vari-

ability, and that these fluctuations are to a certain extent in-

herited. It is shown that Galton’s law of ancestral inheritance

does not apply to individual families, even when these are large

(100 to 200 individuals).

If we knew the real cause of this abnormality we might pos-

sibly be able to reason about its peculiar behavior with some

hope of elucidating it. Any attempt at explanation must

necessarily be largely hypothetical. The writer would suggest

that most of Lutz’s data point to the presence of two factors for

abnormality, one much stronger than the other, and one or both

of them highly variable (fluctuating variability). Davenport

found such a case (two factors, one stronger than the other).

for the hood in certain fowls.? The writer has often thought

there ought to be cases of Mendelian factors which just barely

give rise to visible expression in the soma. Since all characters

exhibit fluctuating variability, such a factor should behave much

as the character which Lutz studied.

Lutz concludes that he has produced effects by selection in ‘‘ pure

lines.”? This is much to be doubted. The results he secured by

Selection fit very well the curves shown in my paper on ‘Some

of the Principles of Heredity Applied to Plant Breeding’ ”™” for

3‘ Experiments with Drosophila Ampelophila Concerning Evolution, ’’

F. E. Lutz, Carnegie Institution of Wash., 1911. `

* Proc. Wash. Acad. Sci., ‘Lecture on Heredity, ”” by C. B. Davenport.

* Bulletin Bureau of Plant Industry, No. 165.

| 163

164 THE AMERICAN NATURALIST [ Von. XLVI

selection in dihybrids. Lutz’s results seem to be further compli-

cated by the fact, to which he calls attention, that the great

variability of the character in question gave apparent normals

that were really abnormals genetically, and this very fact ren-

dered the establishment of really pure lines a matter of great

difficulty, if indeed not an impossibility. A line is not necessar-

ily pure (genetically) because it has descended through many

generations of the closest possible inbreeding from a single orig-

inal pair. It is only pure in a Mendelian sense when all its alle-

lomorphs are duplex and the members of each pair of them are

identical in character. An individual might be pure in this

sense even though both its parents were complexly bred mon-

grels. On the other hand, if Lutz’s original pair were not thus

pure, their descendants would only by chance constitute a pure

line. It is very doubtful if Lutz has really proved the effect of

selection in modifying a pure line, for it is not established that

he worked with a pure line, in the sense in which that term

is now used.

Professor E. B. Wilson has recently published an excellent

review of cytological investigations relating to sex inheritance."

There appears now to be no doubt of the relation of sex to cer-

tain chromosomes in dicecious organisms. This relation is also

interpretable from the Mendelian viewpoint, so that we may say

that sex inheritance belongs in the category of Mendelian phe-

nomena. In nearly all organisms thus far studied the female is

to be regarded as homozygous and the male heterozygous for

sex. Hence the male produces two kinds of spermatozoa, while

the females produce only one kind of egg. When an egg is fer- _

tilized by the one type of spermatozoa the zygote is a female; if

by the other, the zygote is a male. In general, the female dip-

loid nuclei contain two of the sex chromosomes or two groups

of them when the sex chromatin element is compound. The

nuclei of the male contain only one of these elements, with or

without a synaptic mate different from it in character. In sea

urchins it has been shown that it is the female that is heterozy-

gous. But in this case the female possesses one of the sex ele-

ments and the male none. In both cases the female is charac-

terized by an excess in the number of the sex elements as com-

pared with the male.

A large number of ordinary Mendelian characters have been

“**The Sex Chromosomes,’? Arch. f. Mikrosko. Anat., Bd. 77, 1911,

pp. 249-271,

No. 543] NOTES AND LITERATURE 165

shown to be sex limited in inheritance in such a manner that it

seems certain they are in some way connected either with the

sex-determining chromatic element or with the synaptic mate

of this element (in the heterozygous sex). This links these

characters with the chromosomes, and further strengthens the

chromosome theory of Mendelian inheritance.

The writer is fully aware of the danger, in dealing with sta-

tistical data, of drawing conclusions from insufficient data or

from data that have not been submitted to a full mathematical

analysis, such as the determination of means, norms, standard

deviations, and coefficients of correlation. Although I have no

very full or accurate data on the subject and have not actually

determined statistically the coefficients of correlation between

the characters about to be mentioned, I am of opinion, after

more or less superficial observation extending now over nearly

half a century, that there is a noticeable degree of correlation

between positiveness of statement, and inaccuracy of statement.

An illustration of this correlation will be found in a paper by Dr.

J. Arthur Harris, published in the November (1911) number of

this journal. It is now fairly well established that the norms

of a group of related genotypes can, in some cases at least, be

arranged in a frequency curve. In my review of de Vries’s

“The Mutation Theory’’? I cite this fact to show that the type

of variation represented by these genotypes comes under the head

of what de Vries there defines as ‘‘continuous variation,” as

opposed to the ‘‘discontinuous variation,’’ in which the norms of

the variants can not be thus arranged. In Dr. Harris’s paper he

represents me as having cited the fact that these genotype norms

form a frequency curve as a proof of the genotype hypothesis.

I have not been able to find the time to look up other similar

citations in this paper to see whether the same inaccuracy applies

to them. The type of correlation we are considering is further

illustrated in this paper in Dr. Harris’s definition of genotype,

from which he omits the word ‘‘homozygous.’’ The definition

is further inaccurate in including clonal varieties under the

definition of genotype. The author of the term genotype, in a

recent lecture in this city, defined it as ‘‘the descendants of a

single homozygous individual propagated by self-fertilization.’’

= AMER. NAT., Dee., 1910. ;

* Since the above was written it has been pointed out by several writers

that the word genotype should be replaced, im the above sense, by ‘‘ biotype”?

or ‘pure line.’’

166 THE AMERICAN NATURALIST [Vou. XLVI

THE DISTRIBUTION OF PLANTS IN NORTH

| A

AME

A COMPREHENSIVE account of the phytogeography of North

America has long been a desideratum, and it will be welcome

news to botanists that this need has at last been filled. The

work of Dr. Harshberger,' just issued, is an imposing volume,

which will be quite indispensable to all students of plant dis-

tribution, and evidently represents an enormous amount of

labor on the part of the author. A fair criticism that might be

made is that it perhaps is too comprehensive. The book in the

writer’s opinion could have been very considerably reduced in

volume without lessening its value, by drastic cutting of the

first three parts, which are really introductory, and yet take

up nearly half the book. The really essential facts concerning

the geology, geography and climatology of North America could

certainly have been presented in much less space. There is much

needless repetition, and the arrangement of the topics is at times

very confusing.

In addition to Dr. Harshberger’s own work there is a summary

of the book, sixty-three pages in extent, written in German by

the editor of the series, Professor O. Drude.

It is the fourth section of Dr. Harshberger’s book which will

undoubtedly be of most value to the average botanical student.

This deals with the North American phytogeographical regions,

formations and associations, and comprises an account of the

floras not only of the whole North American continent, but of

the West Indies as well. |

Nearly one hundred pages are devoted to the history of work

published on the floras of various parts of North America, the

bibliography alone comprising forty-six pages. This makes up

Part One of the work. The second part—Geographic, Climatic

and Floristic Survey—ocecupies seventy-seven pages. In this

section are given very much in detail an immense body of facts,

many of which could have been omitted without materially less-

ening the value of the summary. Nevertheless it contains very

much that the student will find exceedingly useful.

This section makes very clear the great range of conditions on

the North American continent, which explains the richness and

variety of its flora. Very full statistics are given in this chap-

*««Phytogeographie Survey of North America,’’ John W. Harshberger,

‘*Die Vegetation der Erde,’’ Vol. XIII.

No. 543] NOTES AND LITERATURE 167

ter, including many tables, temperature, rainfall, ete. From

the eternal ice and snow of Greenland to the equatorial condi-

tions on the Isthmus of Panama, practically the whole gamut

of climate depending upon latitude is covered. Moreover, the

great variety in topography in North America results in pre-

cipitations ranging from practically nothing in the extreme

deserts of the arid southwestern United States and Mexico, to a

rainfall of two hundred inches or more in some tropical regions

like parts of Jamaica.

The presence of lofty mountains permitting a rich Alpine flora

in the northwestern parts of the United States and Canada, is

also an interesting feature of the vegetation of North America.

In his division of the phytogeographical regions Harshberger

recognizes four main divisions: Northern, Central, Southern and

West Indian. The United States lies almost entirely within the

second of these, only the region of the Great Lakes and a small

area in the Gulf region encroaching respectively upon the

northern and southern zones. The natural phytogeographical

areas, however, are by no means determined by latitude alone,

this being especially the case in the central zone, where there

are several quite unrelated fioristic regions lying in practically

the same latitude. Such, for example, are the eastern forest area

and the western Cordilleran region.

The pronounced continental climate of the great plains, with

its yearly range of temperature from arctic cold to tropic heat,

may be contrasted with the uniform mild climate of the Pacific

Coast, where longitude plays quite as important a rôle in deter-

mining the distribution of plants as does latitude. For example,

Victoria in latitude 48 has a mean temperature for January of

41.9° F., while St. Louis, almost 10° further south, is 12 degrees

colder. This illustrates the differences in the conditions between

the Pacific Coast region and the pronounced continental climate

of the Middle West. i

The southern area, including Mexico and Central America, 1s

for the most part tropical in its climate, except for the temperate

uplands of Mexico. Within the United States, Florida and the

Southernmost tier of states adjacent to Mexico, really belong to

the southern area rather than to the central one.

In the third part of his volume Dr. Harshberger treats at

great length the geologic history of North America, and its bear-

ing upon the origin and distribution of the present flora. In

168 THE AMERICAN NATURALIST [Vou. XLVI

the course of this section he expounds his own views as to the

origin of the North American flora, and the factors which have

brought about its present distribution. While this section con-

tains much important and interesting material, it can not be

said that its arrangement is all that could be desired. After a

perusal of the 174 pages contained in it, there is left in one’s

mind a very confused impression of a conglomeration of geology,

phytogeography, and the origin of floras, together with other

more or less disconnected topics. A large part of this section

deals again with the phytogeographical areas already discussed

at length in the previous section, and repeated in the fourth

part of the book, but deals with them from the standpoint of

centers of distribution rather than merely from latitude. It is

to be regretted that the subject of the phytogeographical areas

has not been treated as a connected whole, and also materially

reduced, so as to bring out the salient points, instead of present-

ing a mass of details of very varying importance.

While, as might be expected, the plants treated are for the

most part the flowering plants, still the lower plants are not en-

tirely neglected, the Algæ especially coming in for a fuller

treatment than is usually accorded them in works on plant dis-

tribution.

As the flowering plants, especially Angiosperms, are the pre-

dominant plants of the existing land floras, the geological history

of the country before the Cretaceous is of relatively small impor-

tance as bearing upon the distribution of the existing vegetation,

since it is not until the Cretaceous, or at the earliest the Sub-Cre-

taceous is reached, that recognizable remains of Angiosperms

are met with. Professor Harshberger gives an excellent ac-

count, with maps, of the distribution of land and water areas

during the Cretaceous and their significance as affecting the

future distribution of North American plants.

During the lower Cretaceous a solid land mass occupied ap-

proximately the present area of North America, but was sepa-

rated from South America by a wide gap through what is now

Central America, allowing free communication between the At-

lantic and the Pacific. At that time also there was still a broad

land connection with Western Europe. Throughout the north-

ern area both of the old and new world, it is evident that a

_ very uniform vegetation flourished, with Conifers as the predom-

inant trees.

No. 543] NOTES AND LITERATURE 169

During the later Cretaceous extensive changes took place.

The great western mountain chains were thrown up and com-

munication with South America was established; but there was

a complete separation of the eastern and western land masses.

A broad body of water extended without interruption from the

Arctic Ocean to the Gulf of Mexico, and the whole of the great

plains region to the east of the Rocky Mountains was then sub-

merged. Professor Harshberger believes that this was the per-

iod which determined the separation of the Eastern and Western

coniferous floras, and the foundation of the great differences in

the general floral characters of Atlantic and Pacifie North

America. :

The Cretaceous is notable in the history of the vegetable king-

dom as the time when the highest types of plants first appeared,

or at any rate when they are first recognizable. There are no

certain evidences of Angiosperms previous to the Sub-Creta-

ceous. Apparently the Cretaceous was a period of great devel-

opment of new plant forms, perhaps conditioned by the great

changes in the physical character of the continent, these changes

undoubtedly causing great changes of climate as well. Harsh-

berger thinks that the Cretaceous was probably characterized by

periods of mutation—used in the sense of De Vries. Whatever

may have been the reason, during the Cretaceous most of the

modern angiospermous types, and many of the living genera

appeared. The great feature of the later Cretaceous and Ter-

tiary forests was the preponderance of dicotyledonous trees and

shrubs whose remains are found in great numbers. It is certain

that many existing herbaceous genera must also have been

present, but with rare exceptions these have not been preserved

as recognizable fossils, no doubt owing to their perishable tis-

sues which were not fitted to leave fossil remains except under

exceptionally favorable conditions.

he high northern extension of the Cretaceous and Tertiary

forests, especially in the Miocene, shown by the fossil deposits

as far north as Greenland and Spitzbergen, indicates a relatively

warm climate for these higher latitudes of the northern hemi-

Sphere. Moreover this northern forest belt seems to have been

much the same throughout the whole extent of the northern

hemisphere, very many species occurring both in the eastern

and western hemisphere. Many of the most characteristic of

the Miocene genera still exist in America, especially in the great

170 THE AMERICAN NATURALIST [ Vou. XLVI

deciduous forest region of the southern Appalachians. Among

the widespread Miocene genera which still exist in America

may be mentioned Magnolia, Liriodendron, Vitis, Sassafras,

Aralia, Nyssa. Indeed it is supposed that some of the Miocene

species still survive. Among these are the southern Cypress

(Taxodium distichum), Balsam Poplar (Populus balsamifera),

Sweet Gum (Liquidambar styraciflua), Black Walnut (Juglans

nigra) and many others.

With the redistribution of the forest flora due to the glacial

epoch, many of these types disappeared from western America

and Europe but have survived in eastern America and eastern

Asia. It is clear also that genera now confined to the Old World

also existed at that time in North America. A long list of the

Cretaceous and Tertiary genera of North America shows, for

example such extra-American genera as Banksia (Australia),

Casuarina (Australia and Malaysia), Encephalartos (South

Africa), Eucalyptus (Australia), Ginkgo (China), Hedera (Eu-

rope, Asia), Sterculia (tropics of the Old World and Austral-

asia).

During Tertiary times the eastern and western parts of tle

continent were again united, and there seems to have been a

fairly uniform northern flora throughout the Atlantic and Pa-

cific regions, although the separation of the Atlantic and Pacific

floras was already indicated, the difference in climate no doubt

being influenced by the changes in elevation caused by the up-

lifting of the great western mountain masses, inducing a drier

climate in the interior of the continent. It seems probable that

to the north of the great forest belt extending across the con-

tinent was an arctic flora, remnants of which are found in the

Alpine regions of the higher mountains where they presumably

took refuge after the migrations subsequent to the great glacial

epoch.

It is pretty generally agreed that the present distribution of

plants in America is mainly the result of the advance of the

great glacial sheet from the north. In the southward retreat

of the great forest belt there was a division which, it has been

suggested, was caused by the presence of the dry ‘plains of the

interior, which were unfitted for forest growth, and thus acted

as a wedge separating the western forest, predominantly of

coniferous trees, from the eastern forest mainly deciduous in

character. Whether or not this is the true explanation, the fact

No. 543] NOTES AND LITERATURE 171

remains that at present the western forest is composed in the

main of a great variety of coniferous trees adapted to dry sum-

mer conditions, while the eastern forest is distinguished by its

great richness in deciduous trees adapted to a humid summer

climate. Close to the retreating line of the forests, there pre-

sumably followed a belt of arctic vegetation clinging to the edge

of the advancing glaciers.

With the retreat of the glaciers the plants advanced north-

ward again, and the present distribution was finally established.

Owing to the much greater altitude of the western mountains, it

is especially upon these that we find a true Alpine flora, the more

or less changed remnants of the arctic vegetation forced south-

ward by the advancing ice sheet. It is true that a few arctic

plants, like the Greenland sandwort, occur upon the highest

peaks of the Appalachian system, but the number of these is com-

paratively insignificant when compared with the rich and beauti-

ful Alpine flora of the Canadian Rockies and the Cascades.

At the close of the glacial epoch the distribution of the plants

was practically as at present, the most marked features being the

eastern and western forest areas and the great open region of

the great plains.

Part four deals with the floral regions as they now exist in

North America. Probably most botanists will feel that the

weakest feature of this account of the flora of North America is

its lack of proportion. While the relatively uniform flora of the

Atlantic half of the continent receives over 150 pages, the Rocky

Mountain flora is dismissed with 23 pages, and the extraordi-

narily varied and interesting flora of the Pacific Coast with less

than fifty. This no doubt is to be explained by the author’s

very intimate acquaintance with the flora of the Atlantic states,

and his evidently very casual observations at first hand upon

that of the western third of the continent; but he has not shown

the best judgment in the selection of topics for discussion, deal-

ing at great length with relatively very unimportant regions.

Nearly as much space is given to a discussion of the pine-barren

flora of the Atlantic Coast states as to the whole of the Pacific

Coast from Alaska to Mexico. The multiplication of details

in the discussion of the floras of small and unimportant areas,

results in a general sense of confusion, and one is often at a loss

to see the bearing of many of the detailed descriptions of local

floras upon the larger problems. Itis a pity that the abundant

172 THE AMERICAN NATURALIST [VoL. XLVI

materials had not been better digested, and much might just as

well have been omitted. The contrast between the over-elabora-

tion of many topics dealing with the Eastern flora, and the very

casual treatment of the far more important and divergent condi-

tions of the Rocky Mountain and Pacific region, is both striking

and regrettable. However, with all these serious faults, the

patient reader will be able to get a fairly comprehensive view of

the extremely diverse features making up the flora of the North

American continent.

With the last retreat of the great ice sheet, there moved into

the territory thus uncovered plant migrants from various sources.

Keeping close to the retreating ice sheet are the various strictly

arctic or glacial types, and south of this northernmost flora is

the extensive development of bog and tundra formations, which

form so important a feature in the arctic and subarctic regions

of Alaska, Canada and Greenland.

This northern area in America shows three sections, ranging

from east to west. Greenland, separated from the mainland by

the deep water of Baffin’s Bay and Davis Strait, belongs really

with Europe, its scanty flora being composed almost exclusively

of European types like those of Scandinavia and Lapland. The

middle region extending from Labrador to the Mackenzie River:

is marked by a larger preponderance of purely American types.

Westward, including Alaska, the aretie flora is again charac-

terized by a preponderance of Old World species. Out of 364

species of Western Arctic America no less than 320 occur in

Northwestern Asia, many of them extending southward to the

Altai and Himalaya Mountains. Of the 379 species belonging to

the middle region 73 species are strictly American, the other 306

occur also in the arctice regions of the Old World.

The characteristic ‘‘ tundras ’’ are plains whose subsoil is per-

manently frozen, but whose surface soil is covered with a dense

growth of mosses or lichens, among which grow in places dwarf

Alders, Willows, Birches, and various ericaceous shrubs, e. g.,

Cassiope, Andromeda, Vaccinium, Ledum, ete., as well as many

herbaceous plants, some with showy flowers like the Iceland

poppy. It is evident that the arctic flora is remarkably uniform _

throughout the whole northern hemisphere.

In connection with a study of the land plants some interest-

ing features may be noted in regard to the arctice American

Alge. There is a remarkable difference between the Algæ of the

No. 543] NOTES AND LITERATURE 173

arctic regions of the Atlantic and the Pacific, many striking

genera including the giant Kelps being quite unrepresented on

the Atlantic side of the continent. Harshberger thinks that

this points to these two regions as being distinct centers of de-

velopment and distribution, and it may also show that some of

the extraordinary Kelps of the Pacific Coast may be relatively

recent developments.

South of the arctic zone is a sub-arctic forest zone, also of

very similar composition throughout its whole extent from Labra-

dor to Alaska. This forest is largely composed of Conifers, the.

predominant trees being White and Black Spruce, Balsam-Fir,

Tamarack and Scrub pine.

With the Conifers are associated Aspens, Balsam Poplars, Wil-

lows, Alders and Birches. Swamps and peat bogs abound and

in these as well as in the forest itself grow many attractive

shrubs and herbaceous plants. Ericaceous shrubs are especially

abundant, Rhododendron, Kalmia, Ledum, Vaccinium, etc., as

well as wild Roses, species of Rubus and Ribes, ete. In the

Sphagnum bogs, especially in the eastern portions, are found

Pitcher plants, Sundew, and several beautiful Orchids. A con-

siderable number of species, e. g., Pyrola rotundifolia, Linnea

borealis, Cornus Suecica, are identical with Old World species,

and most of the genera, although not the species of trees, are the

same.

To the southward of this uniform forest zone a greater diver-

gence in the floras is noted, and within the United States the

character. of the vegetation changes radically as one proceeds.

from the Atlantic seaboard westward.

The whole of the eastern third of the United States may be

said to comprise one great phytogeographical area, although of

course there are certain regions where the flora has a more or less

marked type of its own. Nowhere within this area are the

mountains of sufficient elevation to form barriers against the

ready migration of plants, and the whole region is one of abun-

dant rainfall. The whole area being continuous, the result is a

very uniform flora, when contrasted with the Pacific side of the

continent. Many species of trees, e. g., Elms, Oaks, Walnuts,

Hickories, ete., occur throughout the range and the same is true

of very many herbaceous plants. It is true that the number

of species is much greater in some parts than others, owing to

more favorable conditions of soil and temperature, but there are

174 THE AMERICAN NATURALIST [ Vou. XLVI

no such radical differences within the area as those, for instance,

between the Southern California desert and the Redwood belt

of the coast region of the same state. The most important fea-

ture of this Eastern area is the great development of the dicoty-

ledonous forest trees. Probably nowhere outside the tropics is

to be found a richer forest fiora, and the trees, both by their

size and variety, constitute a truly magnificent forest. This

forest reaches its finest development in the Southern Alleghenies

of western North Carolina and in parts of the Ohio and Missis-

. sippi Valleys. Unlike the northern forest belt and the forests

of most parts of Europe, this forest is composed of a great many

species intermingled. It is stated by Harshberger that probably

the richest forest vegetation in the north temperate zone is found

in the lower Wabash Valley in Illinois, where one hundred and

seven species of trees occur. In an area of less than a square

mile in extent seventy-five species of trees were counted.

While many of these trees belong to European genera, e. g.,

Poplar, Beech, Birch, Oak, Elm, Ash, etc., many genera are

absent from the European forests. Such, for example, are the

gums (Liquidambar and Nyssa), Magnolias, Tulip trees (Lirio-

dendron), Hickories, Locusts (Gleditschia and Robinia), the Cy-

press (Taxodium), ete. Some of these trees reach really gigan-

tic size, in regard to which Harshberger gives some striking fig-

ures. Thus a Red Oak is cited which was seven feet in diameter,

with a height to the first branch of ninety-four feet, and a total

height of one hundred and eighty-one feet. A White Oak and

Bur-Oak of nearly equal size.are mentioned, while a Cotton-

wood (Populus monilifera) was eight feet in diameter and one

hundred and ninety feet in height. Thus it will be seen that

some of the Eastern deciduous trees almost rival the Pacific

Coast Conifers in size. Other giants of the eastern forest are

the White Pine, the Sycamore and Tulip tree. With these are

associated many shrubs and climbing plants, as well as a charac-

teristic flora composed of herbaceous plants, usually flowering in

the early spring before the leaves appear upon the trees.

In the Mississippi Valley the forest is almost exclusively com-

posed of deciduous trees, but in the Appalachian forest there is

a mixture of coniferous trees, especially Pines and Hemlocks,

while in the north the proportion of these Conifers increases

and at the same time many of the deciduous trees disappear, and

the forest then consists of a comparatively small number of spe-

No. 543] NOTES AND LITERATURE 175

cies. In many parts of the northern states there is a prepon-

derance of Beech and Maple, with a comparatively small number

of other trees growing with them, but nowhere in the real forest

area do we find the pure forests of Beech or Oak which are

common in northern Europe.

In marked contrast with the preponderance of deciduous for-

ests over most of the eastern states, are the areas known as Pine-

barrens, characterized in certain districts by an almost pure for-

est of Pines, usually of a single species. Professor Harshberger

gives a very exhaustive account of the Pine-barren flora, which

he has evidently studied with great care.

At the north the prevalent Pine is Pinus rigida, with which

are found associated some scrub oaks, Nyssa, Liquidambar,

Sassafras and others, as well as a rich growth of showy ericace-

ous shrubs. The poor sandy soil is especially adapted to Erica-

cee, and Huckleberries, Azaleas, Kalmias, Rhododendrons, ete.,

are conspicuous features of the undergrowth. There are also

extensive cranberry bogs where many beautiful Orchids occur,

as well as Pitcher plants, Sundews and other interesting bog

plants. In the coastal bogs of North Carolina grows the unique

Venus’s fly trap (Dioncea) and the long trumpets of the South-

ern Pitcher plants.

Over extensive regions of the Gulf states reaching into Texas

are extensive forests of Pines, whose value as timber trees is only

too well appreciated. The most important of these southern

Pines is the long-leaf pine (P. palustris).

In the southern portion of the Atlantic states there is an infu-

sion of tropical types; the most striking of which are the Palms,

the common Palmetto reaching as far north as the coast regions

of North Carolina. Certain genera of unmistakable tropical

affinity reach even to the northern states. A conspicuous ex-

ample is the Paw-paw (Asimina), a representative of the charac-

teristic tropical family of Custard-apples. In the Gulf states

there are many examples of plants of tropical affinities, includ-

ing certain Orchids and members of the Pineapple family, of

which the most familiar example is the Spanish moss, Tillandsia.

The southern part of Florida is very different in its flora from

the northern portion, which is essentially the same as that of the

other Gulf states. The southern extremity of Florida together

with the Florida Keys really belongs to the West Indian floristic

region. This is the only part of the United States which has a

176 THE AMERICAN NATURALIST [ Vou. XLVI

real tropical flora. Along the coast there are extensive Man-

grove swamps and the strand flora includes many West Indian

types. Among the strand plants is the ubiquitous Ipomæa pes-

capre found on every tropic beach throughout the world. An-

other very widespread tropical plant occurring in the swamps

along the shore is the stately fern Acrostichum aureum. This

is also a common and conspicuous plant in the Nipa swamps of

the East Indies.

A feature of southern Florida is the presence in the grassy

lands of the everglades and in the dry sandy pine forests, of

areas covered with hardwood trees. These wooded areas are

known as ‘‘hammocks,’’ and the vegetation, both the trees and

lower growing plants, are mainly tropical types, for the most

part West Indian species. There are many epiphytic Orchids

and Bromeliads as well as tropical species of ferns, Palms, Figs,

Mahogany and other West Indian types. In this region is found

the only Cycad (Zamia floridana) occurring in the United

tates.

Proceeding westward, the rich forest vegetation of the Atlan-

tic Gulf states and the eastern Mississippi Valley begins to thin

out with the falling off in the rainfall toward the interior. In

western Michigan, Indiana and Illinois there are already en-

countered open prairies, and the forest is much less luxuriant.

Open groves of Oaks, Hickories and Walnuts, the so-called ‘‘oak ©

openings,’’ are characteristic formations of this region. Fur-

ther west these disappear, and the whole country forms a con-

tinuous open prairie. How far the formation of the prairie is

due to climatic causes, i. e., insufficient rain and cutting winds,

and how much is due to compact soil (loess) which often under-

lies them, and which seems unfavorable for tree growth, is not

quite clear; but throughout the prairie region trees are practi-

cally confined to the beds of the streams and the sheltered gullies

between the hills.

Still further westward the prairie insensibly merges into the

semi-arid plains, which end abruptly at the foot of the grent bar-

rier of the Rocky Mountains.

Compared with the eastern third of the continent the flora of

the great central plains is scanty. Grasses predominate, but

there are a good many showy flowers which adorn the prairie in

the spring and summer. Conspicuous among these are numer-

ous Compositæ, Rosin Weed, Rudbeckia, Sunflowers, Asters,

Golden-rods, and many others.

No. 543] NOTES AND LITERATURE An

The western third of the continent is much more varied in its

topography than the Atlantic side, and shows a correspondingly

greater richness and diversity in its flora, since the climatic dif-

ferences, due to the extremely varied topography, are much

greater than is the case in the eastern states.

Rising abruptly from the plains, the Rocky Mountains form

the beginning of the great complex of mountains and deserts

that stretches to the Pacific Coast. Unlike the worndown Appa-

lachian system, the western mountains are extremely rugged,

and their much greater elevation, rising above the level of per-

petual snow, permits of a true Alpine flora. The region bor-

dering on the great plains is arid and semi-arid, and has a pro-

nounced continental climate, with great extremes of heat and

cold and a scanty rainfall.

The lower elevations are mostly destitute of forests except

along the water courses and in sheltered cafions. Higher up the

precipitation increases, and at elevations of from five to ten

thousand feet a fairly heavy forest is found, in many places

composed mainly of coniferous trees. Of these the most im-

portant are the Rocky Mountain Yellow-Pine, the Douglas Fir,

the Lodge-pole Pine and Engelmann Spruce. At the lower ele-

vations where trees are found they are mostly of Eastern species,

some of which, like the White Elm and Cottonwood, are found

sparingly as far west as the base of the Rockies.

For the most part, however, the Rocky Mountain flora is allied

to that of the Pacifie Coast and the arid southwestern region

whose plants are mainly of Mexican origin. A marked feature

of the eastern Rocky Mountains is the formation of beautiful

glacial parks, which are especially well developed in Colorado.

The floors of these parks are covered with a rich carpet of grasses

and showy flowers, and the mountainsides support a fairly dense

growth of Pines and Spruces with a few deciduous trees like the

Aspens and Birches. To the west of the main range of the

Rockies lies the elevated arid plateau of the Great Basin, inclu-

ding most of Nevada, Utah, northern Arizona and New Mexico.

This region especially the southwestern portion is one of the

most interesting botanical areas of the continent. It is continu-

ous with the Mexican plateau which seems to have been the center

of development for the many interesting and peculiar xerophytic

types which are so remarkably developed in this region. — Amg

these the Cacti take first place, an almost exclusively American

fe Sp i

178 THE AMERICAN NATURALIST [Vou. XLVI

family. Other striking and characteristic forms are Yucca,

Agave, Mesquit (Prosopis), the Creosote-bush (Larrea), the

Ocotilla (Fouquiera) and several other characteristic American

genera. This peculiar xerophytic flora is especially well devel-

oped in southern Arizona, and visitors to Tucson have an excel-

lent opportunity of seeing it in great perfection. i

In the northern part of the Great Basin region the Cacti are

almost entirely absent and the desolate country is covered by

Sagebrush, Greasewood, and many scrubby Composite, produc-

ing a landscape that is monotonous in the extreme.

In the northwestern area, through Canada and the northern

tier of states, the true desert is practically absent, and the moun-

tains are covered with a heavy growth of timber mostly made up

of western Conifers. The other plants are largely subarctic and

northern types, but mingled with these are a good many western

genera, such as Pentstemon, Fritillaria, Gilia, and others.

On the western slope different conditions prevail and the ame-

liorating effects of the west winds from the Pacific make them-

selves felt. This is, however, not fully seen until the last of the

mountain ranges is reached, the great Cordillera, which stretches

practically without a break from Alaska to Patagonia. It. is

this great barrier, averaging in California some ten thousand feet

in height, that largely determines the character of the Pacific

Coast climate. Protected entirely from the sudden changes of

the great interior continental area, with prevailing westerly

winds from the vast Pacific whose temperature scarcely changes

from one year’s end to the other, the whole western coast enjoys

an extraordinarily equable and temperate climate.

On the Pacific Coast topography is a far more important fac-

tor than latitude in determining climate. Close to the coast the

climate is uniformly cool, and seldom either hot or cold. San

Francisco in latitude 37°, with an annual mean temperature of

56° F., shows a range of scarcely ten degrees between the hottest

and the coldest months. Sitka, 20° farther north, has a winter

temperature about the same as that of New York City. Natur-

ally the character of the climate has affected the vegetation pro-

foundly, and with the great differences in elevation and precipi-

tation found along the Pacific Coast, the variety of the vegeta-

tion is much greater than in Atlantic North America.

The coast of Alaska, as far north as about sixty degrees, has

a winter temperature about the same as that of the middle

No. 543] NOTES AND LITERATURE 179

Atlantic states, but with a very heavy precipitation, so that it

supports an extremely dense forest of large coniferous trees, of

which the Tideland or Sitka Spruce (Picea Sitchensis) and the

Hemlock (Tsuga Mertensiana) are the predominant trees. There

is an impenetrable jungle of undershrubs and herbaceous plants

of almost tropical luxuriance.

Further south the Sitka Spruce is largely replaced by the

Douglas Fir, the characteristic tree of the coast region about

Puget Sound and northern Oregon. This tree rivals the Cali-

fornia Redwoods in height though not in bulk. At the lower

levels of the coast in Washington and northern Oregon the

forest over large areas is composed almost exclusively of this

species, but back from the coast at the higher levels this is to

considerable extent replaced by Pines, Firs and Hemlocks. This

change in the forest is very clearly shown on the slopes of Mt.

Rainier.

The undergrowth of this northern forest is very much like

that in Alaska. Among the characteristic species are Rubus Nut-

kanus, Rubus speciosus, several species of Elder, the Vine-leaved

Maple (Acer circinnatum) and the Devil’s-club (Echinopanar

horridum). At the lower levels Alders and Poplars of large size

are common along the streams, and with these are found the Big-

leaved Maple (Acer macrophyllum). Where the forest has been

destroyed, especially in burnt-over areas, the ground is covered

in mid-summer with a sheet of pink flowers of the Fire-weed

(Epilobium angustifolium), Bracken ferns of gigantic size and

the striking Aroid, Lysichiton Kamtchatcense, give a tropical

aspect to the dense undergrowth. Most of the herbaceous plants

are northern types, Linnza, Oxalis, Smilacina, Clintonia, Cornus

canadensis, ete. i

At an elevation of about five thousand feet there begins an

Alpine flora which is especially well developed on the higher

snow-capped mountains of the Cascades and the Canadian

Rockies. On Mt. Rainier, where the line of perpetual snow

descends to but little over six thousand feet, the close turf, left

uncovered for a couple of months after mid-summer, is covered

with masses of brilliant flowers of great variety and beauty.

Among the most striking of these are two heathlike plants,

Bryanthus and Phyllodice, a very large and beautiful Erythro-

nium (E. montanum), a splendid crimson Castilleia, bright blue

Lupins, Veronica, white Valerian, several species of Pedicularis,

Anemone, Mimulus, Gentian, and many others. o

180 THE AMERICAN NATURALIST [ Vou. XLVI

Passing southward from Oregon into California, the outer

coast mountains from the Oregon line to Santa Cruz, some fifty

miles south of San Francisco, are dominated by the Redwood (Se-

quoia sempervirens), the tallest of all trees, which reaches its

greatest development in the northern coast counties of Mendocino

and Humboldt. These giant trees occur only in the narrow belt

within reach of the heavy summer fogs which prevail along the

coast. In most parts of the Redwood belt there is a greater or

less mixture of other trees, e. g., Madroño (Arbutus Menziesi),

the Tan bark Oak (Quercus densiflora) the Douglas Fir, wild

Nutmeg (Torreya californica), the wild Bay tree (Umbellularia)

and the big-leaved Maple.

South of San Francisco there is a rapid diminution in the rain-

fall and the Redwoods gradually disappear and are replaced

by more xerophytie types. Some of these, like the Monterey-Pine

and Cypress and the Torrey Pine of Southern California, are of

very restricted range, forming scattered forests along the coast,

and extending down to the very edge of the ocean.

Many of the plants of the Redwood belt are northern types

which thrive in the cool forests of the outer coast range. Repre-

senting familiar northern and southern genera may be men-

tioned species of violets, Trillium, Clintonia, Oxalis, Smilacina,

Asarum, Aquilegia, Delphinium.

Of characteristic shrubs of this region there may be cited spe-

cies of Ribes, Ceanothus, Gaultheria, Rhododendron, Azalea,

Vaccinium, Rubus and Arctostaphylos. In middle California

these northern plants follow the shady cafions almost to the

level of the valleys, where they mingle more or less with the

valley flora which is comprised mostly of strictly Western types.

In many places along the Coast there is an extensive devel-

opment of sand dunes, which support a very rich and interesting

flora. Characteristic plants of the sand dunes are species of

Abronia, Lupinus, Erigeron, Œnothera, Eschscholtzia, Fragaria,

Mesembryanthemum.

In middle California three ranges of mountains parallel with

the coast are found. The Outer Coast-range skirts the ocean,

and a break in this at San Francisco forms the Golden Gafe,

opening into the Bay of San Francisco, which receives the united

waters of the two rivers draining the great central valley. The :

_ latter is separated from several smaller valleys to the west, the: =

most important being the Santa Clara Valley, by the inner Coast

No. 543] NOTES AND LITERATURE 181

Range which farther south joins the outer Coast Range. The

rainfall in these valleys shut off from the ocean by the inter-

vening mountains is relatively small, and the floors of the

valleys are usually open plains with only a scattered growth of

spreading trees, mostly Oaks. In the great central valley much

of the land is too dry to support any tree growth and there are

extensive grassy plains recalling the prairies of the Middle West.

The open valleys and the foothills are the home of an extra-

ordinary variety of beautiful flowers, which in spring spread a

gorgeous carpet over the landscape. These flowers are largely

annuals which start into growth at the first autumn rains, and

flower in the early spring, ripening their seeds and dying with

the oncoming of the summer drought. There are also many

bulbous plants, some of great beauty like the exquisite Mariposa

lilies and Brodiwas. While some of these valley plants like the

California Buttereup and species of Clover are allied to Eastern

types, the great majority are western or belong to western and

southwestern genera. Representative genera are Lupinus, Or-

thoecarpus, Eschscholtzia, Nemophila, Gilia, Platystemon, Go-

detia, Clarkia, and an extraordinary variety of showy Com-

posite.

A characteristic feature of the hillsides and dry mountain

slopes is the ‘‘Chaparral,’’ a dense and often impenetrable

growth of shrubs of many kinds, scrub Oaks, Chinquapin,

Poison-oak (Rhus), Buckeye, Ceanothus, Ribes, Heteromeles,

Adenostoma. Most of these are evergreen, but some like the

Buckeye and Poison-oak, are deciduous. i

- To the east of the great valley lies the Sierra Nevada, rising to

an altitude of nearly fifteen thousand feet with a flora of great

variety and beauty. The lower slopes covered with chaparral

and with scattered Oaks and Digger Pines (P. Sabiniana) give

way at higher altitudes to perhaps the finest coniferous forests

in the world. At an altitude of about four to six thousand feet —

is the great forest belt where grow the scattered groves of the

Giant Sequoia, associated with hardly less imposing Sugar Pines,

Yellow Pines, Firs and Incense Cedar. As an undergrowth

there are found Dogwoods, Oaks, Aspens, and many beautiful

flowering shrubs like the Azaleas, Ceanothus, Philadelphus. The

low meadows near the water courses are full of showy flowers,

Lupins, Castilleia, Lilies, Veratrum, Monk’s-hood, Larkspur, and

many others. ; oes |

182 THE AMERICAN NATURALIST [ Vou. XLVI

In the chaparral may sometimes be seen the magnificent Wash-

ington-lily and the stately Humboldt-lily, while under the shade

of the great Conifers the vivid crimson Snow-plant (Sareodes)

may often be found.

Southern California is largely a desert region, the transverse

Tehachapi range of mountains shutting it off from the great

central valley to the north. The Mojave desert, south of the

Tehachapi, is an arid plateau whose scanty vegetation is of a

marked xerophytic type. Cacti are abundant and the most

striking plants are the tree Yuccas (Y. arborescens). Other

species of Yucca with magnificent panicles of white flowers also

occur, flowering in the late spring and early summer. Farther

south there are rich valleys opening toward the sea, and less

arid than the tableland to the north, and the Colorado desert to

the southeast. The latter region, which includes Death Valley,

is a desert of the most pronounced type, some of it lying below

sea level, and extremely hot and dry. Opening into the Colo-

rado desert, however, there are small cafions with permanent

streams coming down from the lofty mountains, and supporting

a more or less mesophytic growth of Cottonwoods, Sycamores

and Willows, and in some of the cañons there are imposing

groves of the stately Washington Palm (Washingtonia filifera).

This southern region is really part of the great Sonoran region

of Mexico and its vegetation is essentially the same.

The remarkable range in conditions often within very short

distances, e. g., the eastern and western slopes of the Coast

ranges, results in an extraordinary variation in the vegetation

within a relatively small distance, and perhaps no equal area in

the world, outside the tropics, can show a greater number of spe-

cies than California. Moreover, a very large number of these

species are endemic and there are also very many peculiar genera.

Some of the genera are characterized by a great number of spe-

cies. Thus the genus Ribes (see Harshberger, p. 273) is credited

with forty species against thirteen for the whole region covered

by Britton and Brown’s Manual. Other large genera are Calo-

chortus, Orthocarpus, Pentstemon, Lupinus, Trifolium, Gilia.

Professor L. R. Abrams has kindly furnished the writer with

some data showing the remarkable endemism of many California

genera. Of the forty known species of Ceanothus thirty occur

in California, and twenty-five of these are endemic. Sidalcea

with a total of nineteen species is represented in California by —

No. 543] NOTES AND LITERATURE 183

seventeen, of which thirteen are peculiar. California has some

sixty species of Lupinus, out of a total of about one hundred

described species, and of these forty-five are endemic. More

than half of the known species of Gilia occur in California and

more than half of these (thirty-four out of fifty-seven) are en-

demic. Many other cases could be cited but these will suffice to

show the extraordinary degree of endemism exhibited by the

flora of California.

The remarkable development of coniferous trees in California

is of course famous. Within the state are nearly twice as many

species of coniferous trees as in the whole region east of the

Rocky Mountains. Moreover, a considerable number of these

species are quite peculiar to the state, and often of very limited

range, as for example the Big Tree and the Monterey Pine and

Cypress.

While the flora of Oregon and Washington has much in com-

mon with the Rocky Mountain region, and even with the Atlantic

states, the northern elements are much less prominent in Cali-

fornia, although owing to the southward trend of the mountains,

many northern types reach far southward, especially in the cool,

moist forests of the outer Coast range, where such northern

genera as Trillium, Oxalis, etc., are abundant. There is a cer-

tain number of types which seem to be of Asiatic affinity, e. g.,

Fritillaria, Lysichiton, and Tan-bark Oak, but in the drier re-

gions the plants are for the most part allied to Mexican and

South American forms. Of the latter there are certain species

belonging to Chili and Argentina which also occur in California,

but are absent from the intermediate territory.

An interesting feature of the Pacific flora is the occurrence

of certain genera belonging to the Mediterranean region, e. 9.,

Arbutus, Cupressus, Lavatera, and there are also a few Old

World Ferns and Liverworts which are absent from Eastern

North America. Of the latter we may cite Woodwardia rad-

icans, Equisetum telmateia, Targionia hypophylla. The sur-

vival upon the Pacific Coast of these latter types, which are prob-

ably old ones, is presumably due to climatic reasons, and perhaps

this explanation may apply to the occurrence of the phenogamic

genera as well, a case comparable to the many correspondences

between the flora of eastern Asia and that of Atlantic North

America.

Only a small part of North America lies within the tropics,

184 THE AMERICAN NATURALIST [ Vou. XLVI

and much of this is so elevated that the flora is not really a

tropical one. The whole of the interior of Mexico is an elevated

tableland, with a flora closely resembling that of the southern

and southwestern United States.

The eastern coast of Mexico, together with Central America:

and Panama, possesses a tropical flora belonging with that of

South America. In this region Palms, Aroids, Cannaceæ, Bom-

bacæeæ, arborescent Leguminose, and other tropical types

abound, and there is a very rich development of epiphytic

Orchids and Bromeliads.

The extreme southern part of Florida, as we have seen, is the

only part of the United States which properly belongs to this

tropical area, although a good many Southern types extend

much farther north than this. Such Southern types are the

Palmettos, Tillandsia, and other Gulf-state species.

While the eastern coast of Mexico has a humid hot climate with

the typical tropical flora, the western coast is extremely arid

with a scanty xerophytie vegetation.

The West Indian region is treated by Dr. Harshberger as a

distinct province. There is developed here a rich and interesting

flora, allied, as might be expected, to that of the American main-

land, but comprising many peculiar species. The larger islands

are very mountainous and great differences in the vegetation

conditioned by topography may occur within very short dis-

tances. This is well illustrated in Jamaica, where the vegeta-

tion on the north and south sides of the island is very different,

although only forty miles apart. This difference is caused by

the presence of a range of mountains over seven thousand feet

high in the middle of the island. Jamaica is remarkable for the

great development of Ferns, being perhaps the richest area of

its size in the world. It is said that some five hundred species

occur in the island, which has an area of only about four thou-

sand square miles.

Dr. Harshberger’s handsome volume is illustrated with a pro-

fusion of excellent figures, many of them original photographs, — Ms

which add greatly to the value of the book, which must remain

for a long time to come the standard work on the distribution of

the plants of North America.

Dovetas HouGHTON CAMPBELL |

STANFORD UNIVERSITY,

December, 1911

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THE

AMERICAN NATURALIST

Vor. XLVI April, 1912 No. 544

THE CONTINUOUS ORIGIN OF CERTAIN UNIT

CHARACTERS AS OBSERVED BY A

PALEONTOLOGIST'

DR. HENRY FAIRFIELD OSBORN

RESEARCH PROFESSOR OF ZOOLOGY, COLUMBIA UNIVERSITY, CURATOR EMERITUS

OF VERTEBRATE PALEONTOLOGY IN THE AMERICAN MUSEUM OF

ATURAL HISTORY, VERTEBRATE PALEONTOLOGIST

UNITED STATES GEOLOGICAL SURVEY

One method of ascertaining the height of a mountain

is with a single instrument, the barometer; another

method is by triangulation with several instruments.

Thus we may differ from Johannsen in his remark that

morphology as a science of great collections in museums

is of no value in genetics. The brilliant progress in

heredity of the last nine years, beginning in 1903 with

the rediscovery of Mendel’s law, should not blind us to

the four broad inductions from paleontology,’ that trans-

formation is a matter of thousands or hundreds of thou-

sands of years, that to the living observer all living

things may be delusively stationary, that invisible tides

of genetic change may be setting in one direction or

another observable only over very long periods of time,

*One of. the Harvey Lectures of 1912, delivered before the Harvey

Society, January 20, 1912, Abstract presented in the Annual Symposium

of the Society of American Naturalists, Princeton, December 28, 1911.

* Osborn, Henry F., ‘ ‘Darwin and Paleontology.’’ One of the addresses

in ‘*Fifty Years of Darwinism.’’ 8vo. Henry Holt & Co., New York,

May 1, 1909. ee

185

186 THE AMERICAN NATURALIST [Vou. XLVI

that discontinuous mutations or saltations may be mere

ripples on the surface of these tides.

Whatever the truth as to this thought, by a strange

paradox it is certain that some stationary characters,

some apparently dead things in the eyes of the zool-

ogist and botanist, become movable and alive in the eyes

of the paleontologist. Thus a paleontologist comes be-

fore the Harvey Society of Physiologists and Physicians

with the conviction that his vision is of a different angle

from that of the experimentalist, and that by the tri-

angulation of experiment, of anatomy and of paleontol-

ogy the truth may at least be more nearly approached.

Is there more evidence of discontinuity and of law-

lessness, or of continuity and of law, in the origin of new

characters? Perhaps no more appropriate question

could be chosen as the subject of a lecture in memory of

William Harvey, the author of the doctrine of epi-

genesis, for the essence of this doctrine is that of

‘‘suecessive differentiation of a relatively homogeneous

rudiment into the parts and structures which are char-

acteristic of the adult.’”’ Paleontology is at one with

embryology in the belief that differentiation is in the

main gradual and continuous.

Yet to our question the answer prevailing among ex-

perimentalists and Mendelians at the present time is that

there is little evidence either for continuity or for law;

this despite the fact that a large part of the evidence for

discontinuity in the origin of characters is most un-

sound. In fact, our first purpose in this Harvey Lecture

is to show how surprisingly unsound this evidence 1s

when we consider that discontinuity has become prac-

tically a dogma among a very large number of zoologists

and botanists. It is true that the evidence for discon-

tinuity in the heredity of characters is as convincing as

that for discontinuity in the genesis of characters is de-

batable. Our second purpose in this Harvey Lecture 1S

to show that the evidence for continuity in the genesis

of certain characters in man and other mammals is very

No. 544] ORIGIN OF UNIT CHARACTERS 187

strong indeed, further, that some of these characters,

while apparently continuous in origin, certainly become

discontinuous in heredity; from which it follows that

discontinuity in heredity constitutes no proof of discon-

tinuity in origin.

The question is, how do these manifold characters of

which the body is made up arise, continuously or discon-

tinuously? A conservative opinion from what may be

gathered in the whole field of observation at the present

time is that while the greater part of evolution is continu-

ous, especially in the origins of certain parts and in the

development of certain proportions, there must also be

a discontinuity, especially in numerical or meristic struc-

tures, such as vertebre and teeth, and in chemical com-

ponents and reactions which are essentially antithetic

or discontinuous. In other words, there is both continu-

ity and ‘discontinuity, and one problem is to show what

is continuous and what is discontinuous.

The history of ‘‘characters’’ is our quest, and now

that attention is concentrated all along the line of obser-

vation in plants and animals, living and fossil, on the

genesis and behavior of single characters, we have laid

the train for substantial progress. A vast gain is that

which relegates the problem of species to a side issue, or

rather to an incidental result of the accumulation of a

greater or less number of units.

A “‘character’’ may be racial shape of head or length

of limb, it may be a cusplet on a grinding tooth, color of

hair, or a sportive white lock of hair, it may be the brown

or blue color of the eye, it may be the speed of a horse,

or the obstinacy of a mule, in short, any structure or

function, simple or extremely complex, which is stable

and distinct in heredity. A ‘‘new character’’ is some-

thing which is unknown before, it may be a new unit,

like the horns of cattle, it may be a new form or propor-

tion of such a unit. ‘‘I understand by the term unit char-

acter,” observes Morgan, ‘‘any particular structure or

function that may appear in heredity independent of

188 THE AMERICAN NATURALIST [ Vou. XLVI

other characters. Such unit characters may in them-

selves be extremely complex and include the possibility

of further splitting up.’’ The point where Mendelism

bears on the problem is, therefore, the continuous or dis-

continuous origin of the thousands of characters which

display this more or less complete discontinuity in hered-

ity.

I. EVIDENCES ror DISCONTINUITY

Darwin has been widely misunderstood of late as be-

lieving in continuity,? whereas he chiefly believed in dis-

continuity. In his original (1859) and final (1872)

opinion evolution is due chiefly to the selection of herit-

able ‘‘individual differences’’; these have been under-

stood by some as ‘‘fluctuations.’’ His true meaning as

to these individual differences is to be found in the cases

he cited, which may be collected from hundreds of ob-

servations in the ‘‘Origin of Species’’ and ‘‘ Variation

of Animals and Plants under Domestication,’’ to the

effect that such individual differences or new characters

were in the nature of minor saltations, structural or

functional, and always hereditary. If we note some of

the observations which he assembled in commenting on

the genesis of the race horse and the grayhound, breeds

which he used by way of illustration of the genesis of

new forms in nature, we find they include such suddenly

appearing new characters as horn rudiments, tailless-

ness, curliness of the hair, characters which are discon-

tinuous in Bateson’s sense, or mutations in that of De

Vries ;> intermingled with these new characters he cited

* Cf. Poulton, E. B., ‘‘ Darwin and the ‘Origin,’ ’’ 1909, pp. 49-50. —

observation and study of Nature led him to the conviction that large varia-

tions, although abundant, were rarely selected, but that evolution proceeded

gradually and by small steps,—that it was ‘continuous’ and not ‘discon-

tinuous.’ °? In answer to this opinion of the most eminent British exponent

of pure Darwinism it may be said that small steps are discontinuities.

(H. F. O. :

*Osborn, H. F., ‘‘Darwin’s Theory of Evolution by the Selection of

Minor Saltations,’’ AMER. NATURALIST, Vol. XLVI, No. 542, 1912, pp- 1e

* In 1909 L. Plate showed clearly that the ‘‘mutations’’ of De Vries are

practically identical with the ‘‘individual differences’’ of Darwin. See

‘*Darwinismus und Landwirthschaft,’’ Berlin, 1909.

No. 544] ORIGIN OF UNIT CHARACTERS 189

others which are obviously reversional. That he be-

lieved in the adding up of minor saltations there can be

no question; but on the admirable ground that no evi-

dence had been adduced in nature of evolution by major

saltations, he rejected St. Hilaire’s hypothesis of the

natural appearance of entirely new types of animals

and plants, or of new or profoundly modified organs;

there was no evidence in 1872 and there is none to-day

of the sudden appearance in nature of such a breed as

the short-legged Ancon sheep. Morgan remarks,’ ‘‘Dar-

win undoubtedly supposed that by the continuous selec-

tion of minor saltations a character could be slowly

shifted in the direction of Selection. This also appears

to be the opinion of the conservative mutationists of the

present day.’’

Aside from his chief emphasis in the selection of ‘‘in-

dividual differences’? Darwin also undoubtedly believed

in the selection of heritable fluctuations of proportion

as illustrated in his classic rebuttal of Lamarck in re-

spect to the long neck of the giraffe:

So under nature with the nascent giraffe, the individuals which were

the highest browsers, and were able during dearths to reach even an

inch or two above the others will often have been preserved; for they

will have roamed over the whole country in search of food.

slight proportional differences will favor survival and will be trans-

mitted to offspring.

If unusual length of neck in the giraffe, as in man, is

a saltatory and heritable character, there is no reason

why this classic case also may not strengthen the opinion

that Darwin was essentially a mutationist. Fluctuations

of proportion, the transmission of which is now in dis-

pute, however, formed a small part of Darwin’s scheme,

nor was fluctuating variability especially connected by

him with the process of evolution.

A very critical reexamination of Darwin’s works

leads us, therefore, to largely dissent from the influen-

tial opinion of De Vries’ that there was always a doubt

* Morgan, T. H., letter, January 11, a ’? Leipzig, 1901 24.

* De Vries, Hugo, ‘‘Die Mutationstheorie,’’ Leipzig, s

190 THE AMERICAN NATURALIST [Vou. XLVI

in Darwin’s mind as to whether ‘‘the selection of muta-

tions” or ‘‘the selection of extreme variants” played

the greater part in the origin of species. As above noted,

the actual cases which Darwin cited and his repeated

emphasis shows that minor saltations of the De Vries

type were chiefly in his mind.

It is obvious that Darwin could not draw such sharp

distinctions either in language or in definition as we may

to-day, profiting by forty years of experiment and of

analysis.

Let us therefore closely examine the kinds of saltation

or discontinuity in mammals which have been recorded

during the last fifty years by Darwin, Bateson and others

and see what they signify.

1. Major and Minor Saltations in Mammals as Supposed

Material for Selection’

The above exposition of Darwin has a very direct bear-

ing on the problem of continuity and discontinuity be-

cause the saltations which he believed to be among the

possible materials of natural selection and of evolution

were chiefly drawn from the very same sources of evi-

dence, namely, hybridization and artificial conditions of

environment, which are now drawn upon by the ad-

herents of discontinuity; the only difference is one of

degree, not of kind. The great saltatory characters of

Darwin cited below (Table I) in mammals are no more

profound than those cited by De Vries as composing the

supposed ‘‘elementary’’ species of (nothera. It is

therefore interesting to compare twenty distinct types or

forms of major and minor saltation in eleven different

types of mammals. Our authorities are Allen, Azara,

Bateson, Brinkerhoff, Castle, Darwin, Davenport,

Haecker, Percival, Poulton, Ridgeway, Root, Seton, Sut-

ton, Twining. The accompanying table presents at once

the very impressive result obtained by this comparison.

*The writer is greatly indebted to Dr. Charles B. Davenport, of the

Carnegie Institution Station for Experimental Evolution, and to Professor

T. H. Morgan, of Columbia University, for criticism and suggestion on

this section.

No. 544] ORIGIN OF UNIT CHARACTERS 191

TABLE I

COMPARATIVE TABLE OF SALTATIONS

1 8| 4/5) 6] 7/8) 9/10\11

a |e

o|2|& n 2a

g/£/3(8|3/8| 2/2 /2\3/2

alal Sajag £ =

1. Proopic brachycephaly, abbreviation of face.. x x

2. Sudden development of horns on hornless races} |X x

3. Absence of horns on horned races........... XIX

4. Supernumerary horns on horned races....... x

5. Absence of 1 horn on horned races.........- xX

B Jaw appendages. leo aa eee x x Kii

7. Taillessness, absence of caudals............- XIX x |X x

8. Earlessness, absence of the external ear...... |

9. Single ears, loss of one ear............+--:- | x

10. Short-leggedness, or limb abbreviation ...... XX

11. Consolidation of paired hoofs, syndactylism. . X x

12. Polydactylam -er os eee ee KIXKI XIXIX A x

13. Epidermal thickenings. ............0+---0% x | x

14...Mottled skin markings. ...°006.05 6423152 XIXI X i

15. Excessive hairiness, or length of hair........ XIXI XIX XXIX X

16. Hairlessness, entire absence of hair......... R x x

17. Excessively fine or silky hair...........---- x| |X| x | x

19. Reversed halts 3 re oh ia he eee x x

19. ito hair loGKSs | 4k ee ee ea | |

20. rirletl-RAIr 655s kainic Reed ee XIX TA x

3a. Duplication of horns (tramsverse)........--- ay. eis fe Nom Geel ate

The very uniformity of the result makes us suspicious

as to the significance of saltations, major or minor, in

evolution. In eleven different kinds of mammals, namely,

man, horses, cattle, sheep, deer, pigs, dogs, cats, rabbits,

guinea pigs, mice, we observe that. saltations exactly or

closely similar repeatedly occur. These saltations are of

the same kind, in fact, they partly include those which

were regarded by Darwin as possibly part of the evolu-

tion process through selection, namely, as stable in in-

heritance and as under certain circumstances favoring

the animals which possessed them.

We evidently have to do with abnormal disturbances

of the germinal factors or determiners. Some of these

saltations are very stable in heredity and certain of them

become widespread; some are prepotent and dominant,

others are recessive (e. g., angora, Or ‘long coat”? in

rabbits, Castle); some (e. g., bent tail in certain mice,

192 THE AMERICAN NATURALIST [Vou. XLVI

Plate) follow neither the Mendelian law nor the prin-

ciple of blended inheritance.

On the unit-character doctrine we know that one of

three things is happening in the germ plasm.

First, a ‘‘determiner’’ may drop out and we see a race

of mammals springing up without tails, or color, or hair.

In cattle the determiner for horns is dominant, therefore

something is added.

Second, a ‘‘determiner’’ may be suddenly lost or modi-

fied, and we see excessive hair, curly hair, silky hair,

dwarfed or short limbs, brachydactylism. ,

Third, and even more inexplicable, there occurs the

appearance of a new ‘‘determiner’’ or the removal of an

‘‘inhibitor’’ and we observe horns suddenly arising on

hornless races like horses and rabbits.

That fancy breeds can be established through the ab-

normal behavior and selection of these ‘‘determiners”’

there is no question. That nature works through the

sudden appearance of new and favorable ‘‘determiners’’

is as yet unproved; it is absolutely disproved in the case

of horns, for through paleontology we know that horns

arise in a continuous manner. The only mammal known

to us at present in which it would appear that a duplicate

horn may have sprung into existence through saltation

is T'etraceros, the four-horned antelope of India. Salta-

tion is possibly of significance in the case of the sudden

alteration of hair character because we know of a very

considerable number of curly-haired horses in Mexico

and South America, which are, however, eliminated by

breeders for the reason that correlated with curliness of

the hair are apt to arise certain other characters in the

hoofs and limbs which are unfavorable.

Under wild or natural conditions in mammals we have

as yet secured no direct evidence of such origins or estab-

lishment of saltations either major or minor. There is

reason to believe that peculiar or anomalous mammals if

they do arise are driven away from the herds.

It would appear that the obvious abnormality of the

No. 544] ORIGIN OF UNIT CHARACTERS 193

majority of these characters throws the remainder as

well as saltatory new characters in general under sus-

picion of abnormality.

Paleontology, however, furnishes the most direct evi-

dence of the abnormality of saltations in some of the

hard parts shown in Table I by presenting counter evi-

dence that such profound changes as abbreviation of the

face (proopie brachycephaly), development or loss of

horns, reduction or absence of caudal vertebra, abbrevia-

tion or elongation of the limbs, syndactylism or consoli-

dation of separate metapodials have all been established,

wherever we know their history, through continuity and

not through discontinuity.

2. Bateson’s Evidence (1894) of Discontinuity

Bateson in 1894° was the first to clearly advance the

discontinuity hypothesis as a mode of origin of species

in its modern form. At the time this work appeared it

suffered a searching review from Scott.1° Mutationists,"!

however, still refer to it as laying the foundations for the

discontinuity hypothesis. In order to test the ‘‘ Materials

for the Study of Variation” critically in the light of the

subsequent advance in paleontology, Dr. W. D. Matthew,

who is without bias in the question, was requested to

examine all the cases of discontinuity in mammals cited

by the author with reference to the question whether or

not these cases have any real significance in evolution.

He reports:

Of the 320 cases of discontinuity cited in mammals the greater part

are obviously teratological and have no direct significance in relation

to paleontologie evolution except for a very few instances such as the

supernumerary or fourth molar teeth of Otocyon. While not signifi-

cant [in evolution] these teratological cases are interesting because

they show the prevalence of homeosis, and indicate that many of the

? Bateson, Wm., ‘‘Materials for the Study of Variation Treated with

Especial ogari to Discontinuity in the Origin of Species,’’ Maemillan

& Co., London, 1894.

” Scott, W. B., ‘‘On Variations and Mutations,’’ Amer. Jour. Science

(3), Vol. XLVIII, 1894, pp. 355-374 E

“Darbishire, A. D., ‘‘ Breeding end the Mendelian Discovery, 8vo,

Cassell & Co., London, 1911.

194 THE AMERICAN NATURALIST [ Vou. XLVI

remaining eases which might [otherwise] be considered normal salta-

tions or reversions may actually be teratologic, but disguised by

homeeosis; all of the possibly significant cases (such as the supernu-

merary molars) are thereby placed under suspicion. Setting aside this

suspicion the minority of the “ significant ” cases in teeth and feet may

be said to afford evidence of the meristic variability of vestigial and

rudimentary structures. Bateson’s statement that such variability is

related not to non-functionalism but to terminal position in a series

appears to me directly in conflict with his [Bateson’s] own evidence,

as it certainly is with all my experience. This accords with commonly

observed data in paleontology, for no paleontologist would question

that vestigial teeth or bones are apt to [finally] disappear by “ discon-

tinuous” evolution. As to the appearance by saltatory evolution of

new and primarily functional parts in teeth or feet, I know of no ade-

quate paleontologic evidence in its favor. It is either demonstrably

false or decidedly improbable. In the cases of supernumerary teeth

(Otocyon myrmecobius, Cetacea, etc.) saltatory evolution may be re-

garded as reasonable in default of any paleontologic evidence to the

contrary. Meristic or numerical evolution in fully functional verte-

bre is intrinsically probable as the only method of evolutionary

change.

The fact that so many cases of supernumerary teeth are associated

with asymmetry throws doubt on the significance of all such cases;

asymmetrie variations and those occurring only in upper or only in

lower teeth have no analogy in paleontology; such cases as occur ab-

normally are recognized as of a different and non-significant class than

normal evolutionary changes.

A summary of Matthew’s report is as follows:

Bateson cites 323 cases of discontinuity in vertebre,

teeth and skull. Of these 286 are abnormal, or teratolog-

ical, or reversional, and have absolutely no significance

in evolution; ten cases of supernumerary (or fourth

molar) teeth are possibly significant because among the

mammals there are a few genera with fourth molars

which may possibly have arisen by saltation. There re-

main only thirty-seven cases which may be ranked as

‘probably significant,” and these are the meristic addi-

tions or reductions of vertebre in the spinal column,

significant because of the well-known variations in the

vertebral formule of different mammals, and secondly

because vertebre can be added or subtracted only dis-

continuously.

—

No. 544] ' ORIGIN OF UNIT CHARACTERS

SUMMARY OF BATESON’s 323 CASES

E E

2 oa $9

S & A

3 3 55

[r9] = =

Z £ S

E Svoo a a 17 27”

(asymmetry)

L Toh.. A 83 107 67

E OBE Gun ou, Gao yale py cea eee « 110

210 37 67

* Numerical variations of cervical, dorsal and lumbar vertebra.

Additional molars, ef. Octocyon, Myrmecobius, Cetacea. Six cases insuf-

ficiently described.

The fact that the vast majority of germinal anomalies

examined in the above review of Darwin and of Bateson

have no significance in evolution in a state of nature,

throws all germinal anomalies under suspicion as natural

processes, important as they may be in artificial breed-

ing and hybridizing. Yet some of these anomalies in

mammals are less profoundly discontinuous than those

which De Vries has cited in plants under the designation

of ‘‘mutations.’? The most important of these De Vries’

mutations may now be considered.

3. Evidence for De Vries’s Mutation Theory

In 1901 the biological world was aroused as it had not

been since 1859 by the publication of De Vries’s hypoth-

esis.2 Here was a new and apparently sure foundation

for discontinuity in the supposed sudden appearance of

elementary species or ‘‘mutants’’ arising with the acqui-

sition of entirely new characters, new forms of plants or

animals quite free from their ancestors and not linked to

them by intermediates. The influence and vitality of this

great work is shown in a citation from Darbishire (1911,

op. cit., p. 5):

The view that species have originated by mutation is based on Prof.

de Vries’ observations on the Evening Primrose (nothera Lamarck-

iana) (Fig. 1). Working with this form, he was able to witness, for

the first time, the actual process of the origin of new species. —

“De Vries, Hugo, ‘‘Die Mutationstheorie,’’ Leipzig, 1901, p. 24.

196 THE AMERICAN NATURALIST [ Vou. XLVI

- Critical analysis during the past two years by Davis

and by Gates'® of the very species Œnothera Lamarck-

iana on which De Vries chiefly based his monumental

work, tends to show that O. Lamarckiana is possibly a

hybrid of O. biennis and.O. grandiflora and not a natural

species. Thus the ‘‘elementary species’? which are

springing from it in various gardens may prove to be

comparable to the familiar results of hybridization in

mammals and birds.

Davis, on the basis of his prolonged experimental

researches, says:

Indeed, the theory of De Vries may fairly be said to rest chiefly

upon the behavior of this interesting plant, the account of which forms

so large a part of his work “ Die Mutationstheorie ” (2 vols., Leipzig,

(1901). ... In a brief perusal of the work one is struck by the opti-

mism of its author and the brilliancy and breadth of his exposition of

the views set forth. . . . The analysis of the data amassed by Darwin,

in which it is shown that Darwin’s “ single variations ” are the same as

De Vries’s mutations seems to the reviewer particularly effective. .. .

Probably the time will soon come when nearly all biologists will be

ready to admit that mutation or the sudden appearance of new forms

has been an important factor at least in species formation of plants

and animals. Admitting this it remains to be discovered what rela-

tion these sudden appearances bear to the general trends of evolution

which are apparent in so many phylogenies [italics our own] .

for granting the facts of mutation we have only accounted for a miero-

evolution, and it is still to be shown that the larger tendencies can be

sufficiently accounted for by the same means without the intervention

of other factors. . . .

The skepticism of both these botanists is striking.

Their opinions as to the existence of larger evolutionary

trends are exactly in accord with those of paleontologists.

4. Evidence for Discontinuity from Mendelian Heredity

and Experimental Selection

The newest bulwark of the discontinuity hypothesis

is that erected since 1903 by the revival of the great dis-

* Davis, Bradley Moore, ‘‘Genetical Studies on CEnothera. II. Some

Hybrids of Gnothera biennis and O. grandiflora that resemble O. Lamarck-

iana,’’? AMER. NATURALIST, Vol. XLV, April, 1911, pp. 193-233. Gates,

R. R., ‘‘ Mutation in (Enothera,’’ AMER. NaTuRALIST, Vol. XLV, No. 538,

October, 1911, pp. 577-606.

No. 544] ORIGIN OF UNIT CHARACTERS 197

covery of Mendel (1865) and by the negative results of

experiments on fluctuating or quantitative variation.

From the prevalence of discontinuity in heredity, the

separateness of ‘‘unit characters’’ as they appear in the

body and the equally sharp separableness of their com-

plex of ‘‘factors,’’ ‘determiners’? or ‘‘genes’’ in the

germ has arisen the theoretical assumption of the dis-

continuity of origin of all characters in the germ. We

shall now show that this assumption is a non-sequitur.

First, however, the truly marvelous and epoch-making

Mendelian discoveries require our especial examination

in their bearing on the problem of continuity and discon-

tinuity. We have reviewed" the contributions of Allen,

Bateson, Castle, Cannon, Cuénot, Darbishire, Davenport,

Durham, Farrabee, v. Guita, Haacke, Hagedoorn, Har-

mon, Hurst, Laughlin, Morgan, Pearson, Plate, Punnett,

and Rosenoff. This review covers unit characters only

as observed in mammals, to which none the less the prin-

ciples discovered by Mendel in the common garden pea

(Pisum sativum) apply with striking uniformity.

The prevailing field of the researches of these talented

investigators in mammals has been in color characters,

chemical in essence, in various species of rodents, chiefly

mice and guinea pigs, also in Ungulates, such as horses

and cattle, the latter studied less by experiment than from

stud books. Hair form in rodents and in man and skin

pigment have also been exactly investigated. The most

striking general result is the principle of antithesis of

characters which mutually exclude each other, as typified

by the antithesis of Mendel’s ‘‘tallness’’ and ‘‘short-

ness’’ in peas.

The second great feature is that when these antithetic

characters meet in the germ cells, one dominates over the

other; this dominance is a sort of perpetual prepotency.

‘‘Prepotency,’? observes Darbishire, ‘‘is an attribute of

individuals and capricious in its appearance... . What-

ever be the nature of this power . . . it is clear that it

“ With the aid of Miss Mary M. Sturgess, now attached to the Carnegie

Institution Station for Experimental Evolution at Cold Spring Harbor, L. I.

198 THE AMERICAN NATURALIST [Vou. XLVI

has nothing to do with dominance . . . dominance is an

invariable attribute of particular characteristics. ”’!5 Plate

(1910), on the contrary, observes, ‘‘ But a variety of facts

seem to indicate that a reversal of dominance may occur

under certain circumstances and a dominant character

may become recessive, and vice versa.’"® Such reversal

of dominance would appear to be the case in a compari-

son of the mule (cross between ass ¢ and horse 2) and

the hinny (cross between the horse ¢ and the ass 9).

When antithetic characters or functions meet in hered-

ity, there is either ‘‘prepotency,’’ or ‘‘dominance,’’ or

‘‘recession’’ (i. e., latency), or ‘‘inhibition,’’ a something

which indirectly prevents the appearance of characters,

or ‘‘imperfect dominance,’’ or ‘‘blending.’’ In brief,

there are degrees of separableness and antithesis.

Dominance, Conservative or Progressive.—It will be

seen at once that progressive evolution through discon-

tinuity would depend on the dominance of racially new

characters and types. The experimental evidence is con-

flicting, it does not show that new characters are neces-

sarily dominant.

There are many instances of dominance of wild species

(older type) over domesticated species (newer type);

thus De Vries suggested (1902) that the dominant char-

acters are those which are racially older. One case among

the mammals is that the wild gray color in mice domi-

nates over grades below it, black, brown, and white

(Plate, 1910).

Examples of dominance in single characters are that

more intense dominate over less intense colors (Plate,

1910, Davenport, 1907); in the eyes, brown over gray,

gray over blue; in the skin, brunettes over blondes (Dav-

enport, 1909), piebalds over pure albinos (Plate, 1910).

In the hair, wavy or spiral forms dominate over straight

(Davenport, 1908). This would have some bearing onthe

discontinuous fading out of color in desert races like the

quagga, which lost all the stripes of its relative the zebra.

* Darbishire, op. cit., p. 96.

1 Plate

No. 544] ORIGIN OF UNIT CHARACTERS 199

The idea that the positive or present character domi-

nates over the negative, latent or absent character has

become the prevailing one.

It seems highly probable, observes Davenport (1910), that the fu-

ture will show that many more advanced or progressive conditions are

really due to one or more unit-characters not present in the less ad-

vanced condition. In that case it will appear that there is a perfect

accord in the two statements that the progressive and the “ present ”

factor are dominant (pp. 89-90) . . . the specific characteristics are

mostly those that appear late in ontogeny (p. 86) .. . the potency

of a character may be defined as the capacity of its germinal deter-

miner to complete its entire ontogeny. If we think of every character

as being represented in the germ by a determiner, then we must recog-

nize the fact that this determiner may sometimes develop fully, some-

times imperfectly and sometimes not at all [italics our own]...

When such a failure occurs in such a normal strain a sport reaillte.

Potency is variable. Even in a pure strain a determiner does

not always develop fully and this is an important cause of individual

variability (Davenport, 1910, p. ;

Plate similarly favors the hypothesis of dominance of

newer or progressive characters. He observes (1910):

The [Mendelian] laws of inheritance favor progressive evolution in

two ways, for .. . higher, more complicated characters are generally

dominant to the tower, and . . . qualitative characters usually follow

the Mendelian principle in the ease of closely related forms (races,

varieties) while in the crossing of species they follow intermediate [or

blended] inheritance as a rule. In the latter case there is the possibility

that the crossing may have a swamping effect, but this can play no

large rôle on account of the infrequeney of hybrids between species

(Plate, 1910, p. 606).

The same author is of the opinion that phyletic evolu-

tion is discontinuous as regards the transformations of

the determinants [determiners], but in most cases is con-

tinuous in their visible outward workings. He thus main-

tains that while germinal transformations are discon-

tinuous there may be no real antithesis between con-

tinuous and discontinuous somatic variation.

Thus Mendelians appear to agree, first, that there are

grades of continuity and discontinuity, that there are —

antithetic characters which are sharply discontinuous,

others which are ihe continuous, blended or intermedi-

200 THE AMERICAN NATURALIST [ Vou. XLVI

ate. Second, it would appear that complete discontinuity

or entire dominance or recession are qualities in heredity

which may gradually evolve. Many characters show im-

perfect dominance (Castle, 1905) ; gametic purity is not

absolute (Castle, 1906) ; selection is of importance in the

improvement of races (Castle, 1907). . There are a num-

ber of truly blending characters, such as lop-earedness

in rabbits (Castle, 1909), cross blends of long and short

hairs (Castle, 1906), cross blends between short- and lop-

eared rabbits which are permanent (Castle, 1909), blends

in weight inheritance and in skeletal proportion (Castle,

More recent work has tended to show (Hatai, 1911)**

that blended inheritance may be considered to be a lim-

ited case of alternative inheritance where dominance is

imperfect. Thus Mendel’s law of alternative inheritance

may be considered as the standard in all the cases re-

ferred to it (Hatai, 1911, p. 106). Certain characters

which were considered formerly to blend are now re-

garded as showing a certain kind of segregation or unit

inheritance. Thus Davenport (1909) observes:

Skin pigment does not show thorough blending inheritance, but segre-

gation (sometimes imperfect), a more pigmented being imperfectly

dominant over a less... . The reason, the same author observes (1909,

for the blending of hair and skin color in man is the non-development

of distinct color unit-determiners owing to the fact that in man for a

long period there has been no selection for intensity of color, whereas

in the lower mammals definite color determiners have long been main-

tained by selection.

Thus the prevalent recent opinion among Mendelian

observers is that there is a real discontinuity between the

germinal or blastic characters and what the paleontol-

ogist or morphologist generally observes, is only an ap-

parent continuity between somatic characters.

polices Shinkishi, ‘‘The Mendelian Ratio and Blended Inheritance,’’

MER. NATURALIST, Vol. XLV, No. 530, February, ii pp. 99-

* Aaa of the skin seems to depend in man on a series of color

intensity units, possibly one or a few large units, more probably a number

of small units so close together as to be almost continuous (Davenport,

1910).

No. 544] ORIGIN OF UNIT CHARACTERS 201

Since, however, the behavior of somatic characters

forms our only means of knowing whether the deter-

miners are continuous or discontinuous, it is obvious

that this opinion requires further examination in the con-

ceptions of Johannsen.

5. Johannsen’s Pure Line Theory’?

The theoretic contrast between the real discontinuity

of the blastic determiners and the delusive continuity

of visible or somatic form is pushed to its extreme in

the ‘‘pure-line’’ conception which marks the latest de-

velopment in heredity, an advance upon Weismann’s

germ-plasm theory and Mendel’s unit-character law.

Through experiments on successive generations of self-

fertilizing plants (the garden bean), Johannsen has

reached a standpoint which may be briefly stated as

follows:

A “pure line” is composed of the descendants of one pure strain

‘or homozygotie organism exclusively propagated by self fertilization;

such pure lines demonstrate the stability of hereditary constitution in

successive generations where undisturbed by cross breeding or ming-

ling with other strains, showing that the only real changes in organ-

isms are those due to the sudden appearance of new determiners in the

germ.

To replace the word determiner the term gene is proposed. The

genotype represents the sum total of all the genes in the fertilized

germ cell, gamete or zygote: we do not know a genotype but we are

` able in experiment to demonstrate “ genotypical differences.” The

biotype is a group of similar genotypes or pure strain individuals.

Gene, genotype, and biotype are not seen; they are the smaller and

larger units of heredity.

. The phenotype is what we see; it is the developing organism.

Morphology supported by the huge collections of the museums has

‘operated with “phenotypes” in phylogenetic speculation. It is thus

a science of phenotypes and is not of value in genetics because pheno-

type description is inadequate as the starting point for genetic in-

quiries. The adaptation of phenotypes through the direct influence of

environment [Buffon’s factor] or of use and disuse [Lamarck’s fac-

tor] is not of genetic importance. Ontogenesis is a function of the

12 Johannsen, W., ‘‘The Genotype Conception of Heredity,’’ AMER.

Naruratist, Vol. XLV, No. 531, March, 1911, pp. 129-159.

202 THE AMERICAN NATURALIST [ Vou. XLVI

genotype, but the genotype is not a function of ontogenesis. The idea

of evolution by continuous transitions from one type to another has

imposed itself upon zoologists and botanists, who are examining chiefly

shifting phenotypes in very fine gradations. There is such a continu-

ity in phenotypes but not in the genotypes from which they spring.

All degrees of continuity between phenotypes may be found, but real

genetic transitions must be distinguished from the transitions which we

find in museums.

Genotypes, it is true, can only be examined by the qualities and re-

actions of the phenotypes.

Such examination shows that within pure lines—if no new muta-

tions or other disturbances have been at work—there are no geno-

typical differences in the characters under examination. The only real

discontinuity is that between different genotypes. The mutations ob-

served in nature have shown themselves as considerable discontinuous

saltations. There is no evidence for the view that mutations are prac-

tically identical with continuous evolution. In pure lines no influence

of special ancestry can be traced; all series of progeny keep the geno-

type unchanged through long generations. Discontinuity between

genotypes and constant differences between the genes show a beautiful

harmony between Mendelism and pure line work.

Selection will have no hereditary influence in changing genotypes.

Even the selection of fluctuations in pure lines is ineffective to produce

a new genotype

Heredity may thus be defined as the presence of identical genes in

ancestors and descendants, or heredity stands for those properties of

the germ cells that find expression in the developing and developed

phenotype.

Similarly Jennings observes:” What distinguishes the different

genotypes, then, is a different method of responding to the environ-

ment. And this is a type of what heredity is; an organism’s heredity -

is its method of responding to the environmental conditions [p. 84].

. It appeared clear, and still appears clear, that a very large share

of the apparent progressive action of Selection has really consisted

in the sorting over of preexisting types, so that it has by no means the

theoretical significance that had been given to it [p. 88]... . I had

hoped to accomplish this myself, but after strenuous, long-continued and

hopeful efforts, I have not yet succeeded in seeing Selection effective

in producing a new genotype. This failure to discover Selection re-

sulting in progress came to me as a painful surprise, for like Pearson

I find it impossible to construct for myself a “ philosophical scheme of

evolution,” without the results of Selection and I would like to see

what I believe must occur [pp. 88-89]. . . . It would seem that the

diverse genotypes must have arisen from one, in some way, and when

we find out how this happens, then such Selection between m

No. 544] ORIGIN OF UNIT CHARACTERS 203

will be all the Selection that we require for our evolutionary progress

[p. 89]

Thus Johannsen’s general conception of the origin of

progressive or retrogressive new characters is that SIS

is sufficient to state that the essential point in evolution

is the alteration, loss or gain of the genes or constit-

uents of the genotype . . . all evidences as to ‘muta-

tions’ point to the discontinuity of the changes in ques-

tion.’

6. Negative Results of Experiments on Quantitative

Variation

We agree with Johannsen that a delusive appearance

of continuity might arise through selection of degrees

of hereditary fluctuation in structure or function, for ex-

ample, of tallness or shortness of stature, of intensity or

faintness of color. Some Mendelians discard fluctua-

tions altogether as non-hereditary; thus Punnett (1911,

p. 138) observes: ‘‘At the present time we have no

valid reason for supposing that they [fluctuations] are

ever inherited.’’

The question, however, is not as to quantitative onto-

genic variations caused by favorable or unfavorable en-

‘vironment or by changes of habit, but as to heritable

fluctuations springing from the germ plasm. Experi-

ments have been directed to the point whether variations

in size, in proportion, etc., of unit characters as distin-

guished from the unit characters themselves are trans-

mitted.

Davenport has reached negative results; he observes

(1910) :

In the last few decades the view has been widespread that char-

acters can be built up from perhaps nothing at all by selecting in each

generation the merely quantitative variation that goes farthest in the

desired direction. The conclusion upon which De Vries laid the great-

est stress, that quantitative and qualitative characters differ funda-

mentally in their heritability, is supported by our experiments (p. 96).

I have made two tests of this view using the plumage color of poultry

» Punnett, R. C., ‘‘Mendelism,’’ Macmillan Co., 1911 (3d edition).

204 THE AMERICAN NATURALIST [ Vou. XLVI

(p. 94). ... After three years of selection of the reddest offspring no

appreciable increase of the red was observed except in one case, which

looks like a sport (p. 96). These fluctuating quantitative conditions

depend on variations in the point at which the ontogeny of the char-

acter is stopped; and the stopping point is in turn often if not usually

determined by external conditions which favor or restrict the ontogeny.

Thus the selection of redness of comb, of polydactylism, of syndactyl-

ism, have not proved the inheritance of quantitative variations. Ap-

parently, within limits, these quantitative variations have so exclusively

an ontogenie signification that they are not reproduced so long, at

least, as environmental conditions are not allowed to vary widely.

Similarly Love?! from experiments on the yielding

power of plants remarks:

Unless further studies produce different results we can say from the

facts at hand that there is no evidence to show that a basis exists for

cumulative selection.

Similar conclusions have been reached by Pearl

(1909)?? in the breeding of fowls for laying purposes.

All the above results are negative.

Even the positive or affirmative results obtained by

Cuénot and later by Castle, wherein quantitative char-

acters may be shifted in one direction or the other by

selection are now given a new interpretation by certain

Mendelians. For example, Cuénot showed by continued

selection of lighter colored mice that the coat became

paler; and Castle has shown that in rats the coat through

selection may be made darker. Castle remarks (1911) :**

_I prefer to think with Darwin that selection . . . ean heap up

quantitative variations until they reach a sum total otherwise unattain-

able, and that it thus becomes creative.

He cites cumulative results in the development of a

fourth toe in the hind foot of guinea-pigs and in the

modification of the dorsal striping of hooded rats.

2 Love, Harry H., ‘‘Are Fluctuations Inherited?’’ Contr. VI, Lab.

Experim.. Plant-Breeding, Cornell Univ., AMER. NATURALIST, You XLI IV,

No. 523, Tuy, 1910, pp. 412—423..

™” Pea ond, ‘‘Is there a ee Effect of Selection?’ é

foes ad ERARE 2, 1909, H, 4.

*% Castle, W. E., ‘‘The Nature of Unit aui The Harvey Lec-

tures, delivered andes the Auspices of the Harvey Society of New York,

8vo, J. B. Lippincott Co., pp. 90-101.

No. 544] ORIGIN OF UNIT CHARACTERS 205

Morgan’s remarks (1912) on these positive experi-

ments are as follows:

Castle has been very guarded in regard to the interpretation of: the

results of selection in this case. It is probable that extreme selection

is necessary to maintain the higher stage reached. It does not breed

true and slips back easily. If this is correct it suggests: first, that

nothing permanent has been effected in the germ-cells; and second,

that the result is due to the discovery of more extreme eases of fluctu-

ating variations than ordinarily occur.

The general import of these experiments and opin-

ions is that fluctuations in the determiners, or genes, can

not be utilized to establish a new quantitative mean. It

is obvious that what have been measured by biometri-

cians as hereditary ‘‘fluctuations’’ might be regarded

as ‘‘saltations’’ of all degrees, but such saltations do

not represent new determiners in the Mendelian or

Johannsen sense; they are mere fluctuations in existing

determiners. Pure Mendelians would allege that tall-

ness in man or other mammals can only be accumulated

through the saltatory origin of ‘‘tall’’ determiners which

are not connected continuously through intermediate

forms with the antithetic ‘‘short’’ determiners. As to

Stature Brownlee observes (1911, p. 255) :**

I think that I have shown that there is nothing necessarily antagon-

istie between the evidence advanced by the biometricians and the Men-

delian theory. . . . (1) If the inheritance of stature depends upon

a Mendelian mechanism, then the distribution of the population as

regards height will be that which is actually found, namely, a distri-

bution closely represented by the normal curve.

6. Summary as to Discontinuity and Mendelism

Genetics is the most positive, permanent and trium-

phant branch of modern biology. Its contributions to

heredity are epoch-making. But heredity is the conserv-

ative aspect of biology, and experimental genetics thus

far reveals the laws of conservation.

* Brownlee, J., ‘<The Inheritance of Complex Growth Forms, such as

Stature, on Mendel’s Theory,’’ Proc. Roy. Soc. Edinburgh, Vol. XXXI,

PE D. 1911, pp. 251-256.

206 THE AMERICAN NATURALIST [ Vou. XLVI

Genetics has not yet brought us one single step nearer

the solution of the problem of the progressive origin of

new characters in mammals.. The very independence,

multiplicity and discontinuity of the units leave us

farther afield. In place of what used to be regarded as

the instability of the organisms, as a whole, we now have

to conceive of the instability of thousands, nay hundreds

of thousands of units.

As shown in our analysis of the saltations cited by

Darwin and Bateson, Mendelism has revealed the fact

that the majority of saltations simply reflect failures in

the germinal mechanism. The inference is natural that

the remaining minority also represent anomalies, or law-

less conditions. Over a half century of anatomical re-

search among mammals has failed to demonstrate in a

state of nature the sudden origin of a single new pro-

gressive character which has become fixed in the race.

Nor have Mendelism and experimentalism released us

from the hard confines of examination of the germ

through the soma; behavior of unit characters in the

soma is the sole means of knowing the behavior of the

‘‘determiners’’ in the germ. If the unit characters in

the soma behave discontinuously we are forced to the

conclusion that their determiners behave discontinu-

ously; if, on the contrary, these unit characters behave

continuously, are we not forced to the conclusion that

there is a continuity in the behavior of the correspond-

ing determiners?

Let us therefore proceed to consider the value of some

of the evidence for continuous behavior in the origin of

certain new characters, again repeating our opinion that

certain other characters are antithetic, without interme-

diates, and consequently discontinuous both in heredity

and in origin.

(To be concluded*

THE BOTANICAL SOCIETY OF AMERICA

At the Washington meeting of the Botanical Society of

America, the following papers constituting a symposium

on Modern Aspects of Paleobotany were read by invita-

tion of the council, on December 28th.

I. “The Relations of Paleobotany to Geology.”

F. H. Know. Ton.

II. ‘‘The Relations of Paleobotany to Botany.”

1. ‘Phylogeny and Taxonomy.’’ Joun M. CoULTER.

2. ‘‘Morphology.’’ Epwarp (©, JEFFREY.

3. OOO. oe. ArtHur HOLLICK.

In accordance with the instructions of the Society these

papers are here printed in full.

‘Grorce T. Moore,

Secretary

MODERN ASPECTS OF PALEOBOTANY

I. Tue Revations oF PALEOBOTANY TO GEOLOGY `

DR. F. H. KNOWLTON

UNITED STATES GEOLOGICAL SURVEY

AurHovucH there is vague mention of fossil plants in

literature as early as the thirteenth century, and unscien-

tific adumbrations in the faintly growing twilight of the

succeeding centuries, the real science of paleobotany did

not have its beginning until well on in the nineteenth cen-

tury. With the publication, in 1828, of Brongniart’s

“Histoire des végétaux fossiles”? and the ‘‘Prodrome,’’

there was given to paleobotany ‘‘that powerful impetus

which found its immediate recognition and called into its

service a large corps of colaborers with Brongniart, rap-

idly multiplying its literature and increasing the amount

207 .

208 THE AMERICAN NATURALIST [ Vou. XLVI

of material for its further study.’’ Ward. In the suc-

ceeding decades, even to the close of the century, the

students of paleobotany were mainly occupied in accumu-

lating data as regards distribution, both areal and

vertical, and the opening decades of the present century

find the subject a recognized, respected, coequal part of

the general field of paleontology.

Paleobotany, together with all the other branches of

paleontology, admits of subdivision into two lines or fields

of study—the biological and the geological—depending

upon the prominence given to the one or the other of

these phases of the subject. The biological study is, of

course, concerned especially with the evolution of the

vegetable kingdom, that is, with the tracing of the lines

of descent through which the living flora has been devel-

oped. As this side of the question will be taken up by

other contributors to this discussion, it may be dismissed

from further consideration, as the geological aspect is

almost exclusively the phase of the subject to which the

present paper is devoted.

In the first place it will be necessary to call attention

to the fact that the successful use of fossils of any kind

as stratigraphic marks is—or at least may be—entirely

independent of their correct biological interpretation.

To most botanists, and indeed to some paleobotanists,

this statement will doubtless come as a surprise, since

they have come to imagine that the impressions of plants,

the form in which they are most made use of in this con-

nection, are so indefinite, indistinct and unreliable that

they can not be allocated biologically with even reason-

able certainty, and hence are of little or no value. Asa

matter of fact hardly anything could be further from the

truth, and it can be confidently stated that it makes not

the slightest difference to the stratigraphic geologist

whether the fossils upon which he most relies are named

at all, so long as the horizon whence they come is known

and they are clearly defined and capable of recognition

under any and all conditions. They might almost as well

No. 544] BOTANICAL SOCIETY OF AMERICA 209°

be referred to by number as by name, so long as they fill

the requirements above demanded, though of course every

stratigraphic paleontologist seeks to interpret to the very

best of his knowledge the fossils he studies. He may—

doubtless often does—make mistakes in his attempts to

understand them, but his errors are undoubtedly fewer

than he is not infrequently charged with! His faculty

of observation is rendered acute from the close study of

the restricted and often fragmentary material available,

and he has learned to see and make use of characters

which are often overlooked or wholly neglected by the

botanist. The latter, even when he has before him the

complete living plant, including root, stem and foliar and

reproductive organs, sometimes experiences difficulty in

correctly placing his subject, and, to judge from some

recent work, there are paleobotanists who study only the

internal structure of fossil plants and yet are beset with

extreme difficulty in interpreting their biological sig-

nificance.

It may then be taken as settled that the needs of the

stratigraphic geologist will be met if he is supplied with

a series of marks or tokens by which he may unfailingly

identify the various geological horizons with which he

deals, while to the historical geologist who makes use of

fossils in unraveling the succession of geological events,

the correct biological identification is of the greatest im-

portance, for upon this rests his interpretation of the

succession of faunas and floras that have inhabited the

globe. As the late Dr. C. A. White has said: ‘‘If fossils

were to be treated only as mere tokens of the respective

formations in which they are found, their biological clas-

sification would be a matter of little consequence, but

their broad signification in historical geology, as well as

in systematic biology, renders it necessary that they be

classified as nearly as possible in the manner that living

animals and plants are classified.”’ :

While it is in no way desired to overlook or underesti--

mate the biologie value of such fossil plants as have for-

210 THE AMERICAN NATURALIST [ Vou. XLVI

tunately retained their internal structure in condition for

successful study, it is probably safe to say that their

value to geology as compared with the impressions of

plants is as 1,000 to one, and had we only the former, there

never could have been developed the science of strati-

graphic paleobotany. For example, the collections of the

U. S. National Museum embrace over 100,000 specimens

of the impressions of Paleozoic plants, whereas of those

showing internal structure there is hardly a half dozen

unit trays full. In the Mesozoic and Cenozoic collections

belonging to the same institution there are thousands

upon thousands of specimens from hundreds of localities

and horizons, while of those retaining their internal

structure there are so few that they can almost be num-

bered in tens.

There is another and an excellent practical reason why

the impressions of plants are, and will always remain, of

more value to geology than those exhibiting internal

structure, no matter how well this structure may be pre-

served. As soon as a plant impression is exhumed it is

instantly ready for study and may be interrogated at

once as to the stratigraphic story it has to tell, whereas

the plant with the structure preserved usually shows

little or nothing on a superficial examination, and re-

quires laborious, expensive preparation before it can be

identified. For example—to make a personal applica-

tion—for the past five years I have annually studied and

reported on from 500 to 700 collections, each of which em-

braced from one to hundreds of individuals, and with

them have helped the geologists to fix perhaps fifty hori-

zons in a dozen states. If it had been necessary to cut

sections of these specimens before the geologist could

have had his answer, it is safe to say that very little

would have been accomplished.

All fossil plants must be interpreted by and through

the living flora. In the more recent geological horizons

the plants are naturally found to be most closely related

to those now living, but as we proceed backward r time

No. 544] BOTANICAL SOCIETY OF AMERICA 211

the resemblances grow less and less and finally we find our-

selves in the presence of floras a large percentage of which

are without known or clearly recognized living represen-

tatives. In describing these and making them available

for stratigraphic use it has been necessary to give them

generic and specific names, after the analogy of the living

floras, so that we may have convenient handles by which

to use them. Many of these are confessedly what may

be called genera of convenience, such, for example, being

many of the genera of the so-called ‘‘ferns’’ of the Paleo-

zoic. Some—but especially botanists—unfamiliar with

the geological use of fossil plants, have argued that it is

unsafe, or even actually unwise to venture to give names,

not only to those without living representatives, but even

to those obviously belonging to living groups. A reply

to this objection seems unnecessary in view of what has

been said. _

The practical application of fossil plants as an aid to

geology may be briefly mentioned. There have been de-

seribed from—let us say—North America, upwards of

5,000 species, of which number some 1,200 are confined to

the Paleozoic, perhaps 2,000 to the Mesozoic, and 1,500 to

the Cenozoic. During the sixty or seventy years that

this information has been accumulating it has developed

that certain species or other groups enjoy a considerable

time range, and therefore are of little value in answering

close questions of age, while others are of such limited

vertical distribution that their presence may indicate in-

stantly a definite horizon. Thus, if hej d in association

impressions that we have named Sequoia N ordenskiöldi,

Thuya interrupta, Populus cuneata, etc., it is known in-

stantly that we are dealing with the lower Eocene Fort

Union formation, since not one of these species, together

with several hundred others, has ever been found outside

thishorizon. Innumerable other concrete examples could

of course be given, though hardly necessary, yet it may

be instructive to note that within a single geographic

province—the Rocky Mountain region—the several plant-

212 THE AMERICAN NATURALIST [Vor. XLVI

bearing formations present are characterized as follows:

The Kootenai by 120 species, the Colorado by perhaps 50

species, the Dakota by 460 species, the Montana by 150

species, the Laramie by 140 species, the Arapahoe by 30

species, the Denver by more than 150 species, the Fort

Union by from 500 to 700 species, etc., ete. This shows

that, as Professor J. W. Judd once said: ‘‘ We still regard

fossils as the ‘Medals of Creation,’ and certain types of

life we take to be as truly characteristic of definite periods

as the coins which bear the image and superscription of _

a Roman emperor or of a Saxon king.’’

Just a word may be said on the economic application

of stratigraphic paleontology. It is perhaps safe to say

that never in the history of American geology has there

been so close an interrelation and dependence of geology

on paleontology as at present, and of this confidence

paleobotany may justly claim its full share. Thus, of the

even dozen of paleontologists in the employ of the U. S.

Geological Survey and covering all branches of the sub-

ject, four are paleobotanists.

Among the many subsidiary problems connected with

the application of paleobotany to geology, the use of

fossil plants as indices of past climate occupies a most

important place. As the majority of plants are attached

to the substratum and hence are unable to migrate like

most animals when the temperature of their habitat be-

comes unfavorable, they must either give way or adapt

themselves gradually to the changed conditions of their

environment. Tlé@efore, fossil plants have always been

accorded first place as indices of past climates. ‘‘They

are,” as Dr. Asa Gray has said, ‘‘the thermometers of

the ages, by which climatic extremes and climate in gen-

eral through long periods are best measured.”’

To those who have not given especial consideration to

the subject, the idea appears to obtain that climatic varia-

tions, such as now exist, are normal or essential and that

they were present without marked differences during all

geological ages.’ It is now established, however, that this

No. 544] BOTANICAL SOCIETY OF AMERICA 213

conclusion is entirely without geological or paleobotan-

ical warrant, and that the most pronounced climatic dif-

ferentiation the world has known extends only from the

Pliocene to the present. As a matter of fact we of to-day

are living in the glacial epoch in what possibly is only an

interglacial period, and we know that the time which has

elapsed since the close of the last ice-invasion has been of

less duration than was one, and possibly two, of the Pleis-

tocene inter-glacial periods. We also know that the cli-

mate was milder during these inter-glacial intervals than

has obtained since the final retreat of the ice, as shown by

the fact that in eastern North America certain species of

plants then reached a point some 150 miles further north

in the Don Valley than they have since been able to

attain. The development of strongly marked climatic |

zones, at least between the polar circles, is, then, ‘‘excep-

tional and abnormal, and we have no evidence that in any

other post-Silurian period, with the possible exception of

the Permo-Carboniferous period, has the climatic distri-

bution and segregation of life been so highly differen-

tiated and complicated as in post-Tertiary times.’”

The regular and normal conditions which have existed

for vastly the greater part of geologic time, have been

marked by relative uniformity, mildness and comparative

equability of climate. This is abundantly shown by the

almost world-wide distribution and remarkable uniform-

ity of the older floras: When, for instance, we find the

middle Jurassic flora extending in practical uniformity

from King Karl’s Land, 82° N., to Louis Philippe Land,

63° S., we have conditions which not only bespeak a prac-

tically continuous land-bridge, but exceptionally uniform

climatice conditions. To have made this possible there

could have been neither frigid polar regions nor a torrid

equatorial belt, such as now exist. Theabsence of growth-

rings in the stems of these plants, as well as the presence

of such warmth-loving forms as cycads and tree-ferns,

point to the absence of seasons and the presence of mild

and equable climatic conditions.

1See White and Knowlton, Science, N. S., Vol. 31, 1910, p. 760.

214 THE AMERICAN NATURALIST [ Von. XLVI

Another example of similar import is afforded by the

early Pennsylvanian flora, that is, the flora of the lower

part of the Upper Carboniferous. Wherever terriger-

ous beds of this age have been discovered, representa-

tives of this peculiar flora, which includes such common

genera as Lepidodendron, Sigillaria, Sphenophyllum,

etc., have been found, this distribution ranging from

South Africa to Brazil and Argentina, and thence over

the northern hemisphere.

Similarly, the Mississippian flora (Lower Carbonifer-

ous) has been found in Spitzbergen, Greenland and arctic

Alaska, and thence south over Europe and America, and

although somewhat older than the last, is distinctly re-

lated to that in Argentina.

On passing up in the geologic time scale we find that

during late Mesozoic and early Cenozoic time the present

dominant types of vegetation were firmly established.

With what probability of success may these floras be in-

terrogated as to the climatic conditions under which they

existed? We find from a study of the present flora that

certain types of vegetation, as well as certain plant asso-

ciations, have definite climatic requirements. Thus, Ar-

tocarpus, or the bread fruit trees, are now confined to

within 20° of the tropics, showing that they require the

moist heat of the torrid regions. If, now, we find that

Artocarpus once throve in Greenland 70° or more north,

during Cretaceous time, we feel justified in assuming that

its climatic requirements were not very different from

those of its living representatives. And when we find

that it was then in association, as it is to-day, with cycads,

tree-ferns, cinnamons, palms and other distinctly tropical

forms we are confirmed in the opinion that at that time

Greenland must have enjoyed a tropical or at least a

sub-tropical climate.

Another example is afforded by the Fort Union forma-

tion. In the rocks of this horizon, which now occur on

the wind-swept, almost treeless plains of the Dakotas,

Wyoming and Montana and thence northward to the val-

No. 544] BOTANICAL SOCIETY OF AMERICA 215

ley of the Mackenzie, are found remains of Sequoia, Tax-

odium, Thuya, Ulmus, Populus, Vitis, Platanus, Sapin-

dus, Viburnum, Corylus, Juglans, Hicoria, etc., ete. From

this array we feel justified in assuming a cool to mild

temperate climate for this early Eocene flora, and further,

from the presence of numerous, often thick beds of lig-

nite, that there was a much higher precipitation than at

present.

A layer of fan-palm leaves a foot in thickness in a for-

mation in northern Washington indicates climatic re-

quirements in which the minimum temperature did not

fall below 42° F. The presence of numerous West In-

dian types in the Miocene lake beds of Florissant, Colo-

rado, would alone point to almost tropical conditions, but

as these are associated with others of more northern

affinities, it seems safe to predicate at least a warm tem-

perate, or possibly sub-tropical climate.

II. Tue RELATIONS or PALEOBOTANY To Botany

1. Phylogeny and Taxonomy

PROFESSOR JOHN M. COULTER

UNIVERSITY OF CHICAGO

Ir is impossible to disentangle morphology and phy-

logeny, for the largest motive in modern morphology is

to construct phylogenies. An excessive amount of over-

lapping will be avoided in this paper by laying the em-

phasis upon the inferences to be drawn from morpho-

logical investigations as to probable lines of descent,

rather than upon the morphological results themselves.

It should be kept clearly in mind that the material of

paleobotany, as indicated by the program, is not always

used to contribute to the science of botany. The determi-

nations of plants inthe interest of geological horizons are

of immense service to geology, but of comparatively little

value to botany. This means that some paleobotanists

are geologists, and some are botanists, and it is the work

of the latter that concerns us at this time.

216 THE AMERICAN NATURALIST [ Vou. XLVI

The recent rapid development of our knowledge of the

structures of fossil plants is familiar to botanists, con-

stituting as it does one of the most remarkable chapters

in the history of our science. This has been due not only

to the elaboration of a technique for sectioning petrifac-

tions, but also to the inclusion of the vascular system

among the morphological material that is recognized to

be significant in conclusions concerning phylogeny. From

the standpoint of paleobotany, the vascular system is its

most valuable asset for vascular plants, for its chances

of preservation exceed those of any other structures ex-

cept the seed, and its significance in phylogeny is far

more apparent and extended than that of the seed. Asa

result of this paleobotanical connection, the phylogeny of

the vascular groups can be made now a resultant of com-

parative structures and actual history. Many an old

phylogeny, based upon the comparative structures of ex-

isting plants alone, has been contradicted by history,

which, in the nature of things, must furnish the final

check upon any proposed phylogeny.

The topic of this paper is really an invitation to indi-

cate some of the recent reactions of modern paleobotany

upon the phylogenies of vascular plants. The title in-

cludes taxonomy, but in so far as this deals with great

groups, defined or discovered, it is covered by the state-

ments concerning phylogeny. So far as it deals with the

recognition of individual forms, it is clear that paleo-

botany must learn to recognize the relationships of fossil

plants, or there will be no reliable taxonomy or phy-

logeny. So long as paleobotany depended upon the form

resemblances of detached organs, there could be no tax-

onomy in the real sense. It was merely a cataloguing of

plant material. But when it learned to uncover struc-

ture, it began to establish a real taxonomy. The contri-

butions of paleobotany to taxonomy, therefore, may be

summed up in the statement that it has begun to extend

our schemes of classification into the ancient floras; that

this has resulted in a far truer view of the great groups

No. 544] BOTANICAL SOCIETY OF AMERICA 217

than their expression in the present flora can possibly

give; and that this makes a rational phylogeny possible.

I will address myself in the main, therefore, to phy-

logeny, as involving all the taxonomy that is of large im-

portance. When paleobotany to-day assembles the great

series of paleozoic pteridophytes, the impression is very

different from that of a few years ago. It is true that we

have always heard of the giant forms of the Paleozoic

and their dwarf representatives of to-day. We con-

trasted Lepidodendron with Lycopodium, and Calamites

with Equisetum, and the total impression was the strik-

ing difference in size.

Now we have learned that these paleozoic Lycopodiales

and Equisetales were not merely comparatively large, but

that they were also comparatively complex. For exam-

ple, we have learned that their huge bodies developed

secondary wood and had attained heterospory. We be-

gin to understand that vascular plants, with the exception

of Angiosperms, were as completely differentiated, so

far as the great groups are concerned, at the beginning

of our records as now; and that the phylogeny in sight is

not that of one great group following another, but of all

the great groups spraying out into more and more modern

expressions.

Not long ago, our morphology taught that the homo-

sporous Lycopodium is the modern representative of the

arborescent, paleozoic club mosses, and that the hetero-

sporous Selaginella is a modern offshoot. Now we find

that the paleozoic forms, with their heterospory, their

ligules, and their other structures, link up with Selagi-

nella; and we are asking, where are the ancestors of Ly-

copodium? Not long ago Isoetes, once suspected of being

responsible for the monocotyledons, was fluttering be-

tween Filicales and Lycopodiales, and at last had settled

down as an anomalous member of the latter group; and

now modern paleobotany assures us that its whole struc-

ture suggests that it is a much reduced and compacted

Lepidodendron. Thus the anomalous Isoetes has a ten-

218 THE AMERICAN NATURALIST [ Vou. XLVI

tative connection, and the very normal Lycopodium has

none.

Once we talked of the evolution of the strobilus as

shown by Lycopodium, Selaginella, and Equisetum, and

fancied that we saw in these modern forms the highest

expression of the pteridophyte strobilus. Now we know

that these strobili of to-day are excessively simple as

compared with those of the Lycopodiales and Equisetales

of the Paleozoic. The evolution of the pteridophyte

strobilus that is in sight, therefore, is an evolution from

a complex strobilus to a simple one.

According to the old morphology of external form, the

club mosses were entirely capable of having given rise to

the conifers. With some knowledge of structure this

idea faded away, except in certain quarters, and the bril-

liant discovery of the so-called ‘‘ seed-ferns ’’ seemed to

dispose of it entirely. Now we find among the paleozoic

lycopods, notably some of the herbaceous ones, that a

seed-like structure has been attained, and we have ‘‘seed-

club mosses’’ as well as ‘‘seed-ferns.’’ This does not

mean that the club mosses gave rise to conifers or to any

other existing group of seed plants, for more important

structures forbid it; but it does mean that the paleozoic

groups had advanced very far; that the seed-condition

may have been attained by several groups of paleozoic

pteridophytes; and that it takes more than a seed to dis-

tinguish a ‘‘seed-plant.”’

These are a few illustrations of the upsetting facts that

modern paleobotany has been introducing into the old-

time phylogenies of Lycopodiales and Equisetales.

It is among the phylogenies of Filicales, however, that

modern paleobotany has wrought the greatest change, so

far as pteridophytes are concerned. The old picture in-

cluded a luxuriant fern vegetation during the Paleozoic,

which culminated in the Coal-measures, whose so-called

‘‘fronds’’ made up at least one half the vascular flora.

The occasional attached synangium or sorus was plainly

like those of the Marattiacee, and since the Marattias

No. 544] BOTANICAL SOCIETY OF AMERICA 219

are eusporangiate, these paleozoic ferns were eusporan-

giate. And so we settled back comfortably to the convic-

tion that the paleozoic ferns were Marattiacex, repre-

sented to-day by a small tropical family; that the euspo-

rangiate habit and synangia are historically older condi-

tions than the converse; and that the leptosporangiate

habit and sori of free sporangia are comparatively

modern.

The change of view that modern paleobotany has intro-

duced must be familiar to most of you. The abundant

fern vegetation of the Paleozoic has vanished, having

been replaced by a great group of fern-like gymno-

sperms; many of the marattiaceous synangia have proved

to be the microsporangiate structures of these same gym-

nosperms; there is no indication that the eusporangiate

habit is older than the the leptosporangiate; and it is en-

tirely clear that our earliest known ferns had free spo-

rangia and not synangia. In fact, after the first revul-

sion of feeling, following the discovery of the fern-like

gymnosperms, the question was seriously raised, is there

any evidence of paleozoic ferns? Of course no one

doubted their existence, but where is the evidence?

Paleobotany has now begun to answer this important

question. Evidence of the existence of a group of arbo-

rescent, Marattia-like ferns during the Upper Carbonifer-

ous is accumulating. Much of this evidence is negative,

for it consists simply of the fact that many species of cer-

tain of the large, so-called ‘‘frond genera” have not been

found to be fern-like gymnosperms. On the doctrine of

chance this may be worthy evidence. It simply means

that a vast display of fern-like leaves must contain some

ferns. The positive evidence, however, is supplied by

vascular anatomy, and is found in the stems called Psaro-

nius. The structure of these stems has been compared

recently with the very characteristic structure of the

stems of the living marattias, and the close relationship

is obvious. Moreover, the leaves of Psaronius belong to

one of the largest frond genera, and some of them bear

220 THE AMERICAN NATURALIST [ Vou. XLVI

Marattia-like synangia. So clear is the evidence that

Scott has called these arborescent Marattias, of the later_

Paleozoic, Palzeo-Marattiaceae, and they may well stand

for the precursors of the much humbler Marattias of

to-day. |

But these ancient Marattia-like forms were not the

oldest ferns, for paleobotany has revealed a much older

assemblage of undoubted ferns, so old, in fact, that the

assemblage is called Primofilices. They are represented

not only by numerous detached sporangia, many of which

have the annulus characteristic of modern leptosporan-

giates, but all the essential structures of one well-char-

acterized family, the Botryopteridex, are known. These

still somewhat vague Primofilices are extremely suggest-

ive and perplexing. The free sporangia and the annulus

of the Botryopteridee suggest leptosporangiate connec-

tions; but the sporangia are not borne as among the lep-

tosporangiates, nor is the annulus of the same character.

The sporangia are in clusters terminating the bare

branches of a rachis; and the annulus is a vertical, multi-

seriate band on one side or both sides of the sporangium.

In fact, the so-called ‘‘rudimentary’’ annulus of Osmunda

suggests a reduced multiseriate annulus of one of the

Botryopteridee. The vascular system, however, is very

characteristic and very primitive, and is so varied as to

suggest a synthetic type that might have given rise to all

the diversities found in modern ferns.

The possibilities of paleobotany are well shown in con-

nection with these Primofilices. One of its form-genera,

Stauropteris, known only as sporangia, has been discov-

ered by Scott with germinating spores. The germination

of a fern spore is so different from that of a microspore

of gymnosperms, or of any other heterosporous plant

with which we are acquainted, that it is clear that Staur-

opteris is a fern sporangium and not the microsporan-

gium of some gymnosperm. When germinating spores

are preserved, and also the swimming sperms of paleo-

zoic gymnosperms, as recently described, we may expect

No. 544] BOTANICAL SOCIETY OF AMERICA 221

that paleobotany will presently be able to uncover all of

the essential morphology of the great fossil groups.

This picture of paleozoic ferns is somewhat dim yet,

but were it not for the recent work in paleobotany we

should have no picture at all, or, what is worse, an

entirely false one.

The most conspicuous contribution of modern paleo-

botany, however, is its remarkably complete reconstruc-

tion of the phylogeny of gymnosperms. Our present

records of this group extend through a longer period and

are more continuous than for any other vascular group.

It was not only associated with the paleozoic pterido-

phytes of the Coal-measures, but it was contemporaneous

with pteridophytes throughout all their recorded history.

Seed-plants, therefore, are just as old as any vascular

plants, so far as our records go. It is clear that seed-

plants have descended from pteridophytes, but when our

records begin, they had already descended.

Our conception of gymnosperms before the paleobo-

tanical work of the last decade, will emphasize the change

that has taken place. We thought of them as cycads,

conifers, and gnetums; and the morphology of that time

undertook to develop a phylogenetic sequence with these

three groups. Cycads were clearly the most primitive

gymnosperms, and when Ginkgo was found to share with

them in the retention of swimming sperms, it was just as

clearly a ‘‘transition’’ form, on its way from cycads to

conifers. In the dim paleozoic background Cordaitales

lurked, but they were quite detached from living gymno-

sperms, a group that belonged to the gelogist rather than

to the botanist. I fancy that many a student of gymno-

sperms in those distant days never even heard of Cor-

daitales. The contrast between such a perspective of the

group as I have just indicated and the perspective we

possess to-day is due almost entirely to paleobotany.

In the first place, it resurrected the most primitive

group of gymnosperms, the Cycadofilicales, called by our

English brethren the Pteridosperms. It is a group that

222 THE AMERICAN NATURALIST [ Vou. XLVI

had always been with us, disguised as paleozoic ferns, and

the story of its recognition and rehabilitation is about the

most sensational one in the annals of paleobotany. This

meant that Cordaitales had a companion group, and that

there were two great gymnosperm assemblages during

the Paleozoic. Then the question arose as to the rela-

tionship of these two groups. There was no historical

sequence to answer the question, for the two groups were

observed side-by-side, and very distinct, as far back as

the records go. This threw the answer back upon com-

parative structures, and this testimony is clear. If the

two groups have been derived from ancient ferns, and

the structure of Cycadofilicales hardly admits of any

other conclusion, it is evident that the Cordaitales have

departed much further from that origin. Therefore, if

the two groups are related to one another genetically, and

the discovery at various paleozoic horizons of persisting

synthetic forms that combine features of both groups

seems to make this reasonably assured, the Cordaitales

were derived from Cyecadofilicales older than any we

know. :

The beginning of our perspective, therefore, is that

very ancient ferns, earlier than any of our records of

vascular plants, gave rise to a Cycadofilicales stock, which

persisted throughout the Paleozoic; and that this stock,

also earlier than any of our records, gave rise to the Cor-

daitales branch. The records begin with these two stocks

working along towards their modern expression, and all

Mesozoic and modern gy perms can be referred to

them. In other words, the gymnosperm genealogical tree

comes into sight as two strong branches of a dichotomized

trunk whose existence and character are hypothetical.

The Mesozoic branches from these two paleozoic stocks

furnish us with another triumph of paleobotany, and this

achievement is of peculiar interest to Americans.

The Cycadofilicales of the Paleozoic contributed to the

Mesozoic the gy perms once known as ‘‘fossil cy-

cads,’’ a group so dominant and so characteristic that the

No. 544] BOTANICAL SOCIETY OF AMERICA 223

Mesozoic was long called ‘‘the age of cycads,” so far as

its vegetation is concerned. These characteristic Meso-

zoic forms are known now as the Bennettitales, and their

resurrection from rich Mesozoic deposits of America is

due to the skill and patience of our American colleague,

Dr. Wieland. They retained many of the primitive fea-

tures of the Cycadofilicales, but departed from them

chiefly in the development of a strobilus. Not only so,

but the strobilus is peculiar among gymnosperms, all of

which have strobili except the fern-like Cycadofilicales.

The strobilus of Bennettitales is bisporangiate, and the

two sets of sporophylls are related to one another as they

are in the flowers of Angiosperms. With the investment

of sterile bracts, the strobilus as a whole bears a remark-

able structural resemblance to such a flower as that of

Magnolia. This resemblance has proved to be very se-

ductive, for it has led to the claim that Bennettitales rep-

resent the ancestral forms of angiosperms. It is not the

province of the present paper to discuss this claim. It

has in it as a basis just enough of structural resemblance

and of historical timeliness to make a plausible argu-

ment, but hardly enough to carry conviction to those who

must take other facts into consideration. In any event,

the Bennettitales are a notable group, and paleobotany

has revealed them to us.

Along with them, the true cycads, or Cycadales, began

to appear, apparently never a dominant group, and they

have persisted in the tropics to the present time. The

cycads as we know them, therefore, are the modern rep-

resentatives of an old phylum, which included Bennetti-

tales in the Mesozoic and Cycadofilicales in the Paleozoic,

a phylum aptly called the Cycadophytes. The cycads

present us with that paradox with which students of phy-

logeny are familiar, namely, they are structurally very

primitive, but historically modern. So far from being

the oldest of living gymnosperms, they are younger than

the conifers and the ginkgos.

The Cordaitales of the Paleozoic had already developed

224 THE AMERICAN NATURALIST [ Vou. XLVI

strobili, and had made notable changes in the vegetative

body, changes which characterize the second great gym-

nosperm phylum, fittingly called the Coniferophytes.

The connections of the paleozoic Cordaitales with the

Mesozoic ginkgos and conifers are very obvious, and

these two groups, associated with Bennettitales and some

Cycadales, made up the mesozoic gymnosperm flora.

The Ginkgoales are really a mesozoic type, for their rep-

resentation to-day by a single species is probably due to

preservation by culture. It is an interesting fact that

the ginkgos, directly connected with the paleozoie Cor-

daitales, have retained the primitive reproductive struc-

tures of that group and of the Cycadophytes, but ad-

vanced in vegetative structures as did the conifers. The

group is very old in its reproductive methods, and modern

in its vegetative body.

The great gymnosperm group of the Mi aoabis, as of

the present time, is the Coniferales, and their deployment

during the Mesozoic is a subject of fascinating interest.

The so-called tribes of conifers are found distinctly dif-

ferentiated during the Mesozoic, and the determination

of their relative ages is one of the triumphs of vascular

anatomy. My colleague in this symposium, Professor

Jeffrey, has lived in the storm center of this work, and

it would not be fitting for me to invade his own special

field. It may be said, however, that to discover that the

Abietineæ (the pine tribe) are the oldest conifers is up-

setting the older phylogeny fully as much as paleobotany

has done for other gymnosperm groups.

The conifers are distinguished among the other gym-

nosperms that have been discussed, in being modern both

in reproductive methods and vegetative structure.. In

contrast with cycads, therefore, they present the same

paradox conversely, that is, they are structurally younger

than cycads, but historically older.

This hasty outline of gymnosperm history, which pa-

leobotany has interpreted for us, proves convincingly

that no plant phylogeny is adequate until it has included

No. 544] BOTANICAL SOCIETY OF AMERICA 225

the historical record, which of course is the province of

paleobotany; and furthermore, that general conclusions

= based upon the study of the living flora alone are more

apt to be false than true.

The great problem of paleobotany to-day is the history

of angiosperms. Having perfected a weapon in the at-

tack upon gymnosperms, it remains for the paleobotanist

who is a vascular anatomist to uncover the origin of our

greatest group, with its comparatively brief history.

The origin is probably recorded in the Mesozoic, and we

wish to see the significant structures, and not guess at

external form, and much less guess at purely hypothetical

connections. To this great task paleobotany is turning.

We have had the guesses; and I am confident that pres-

ently we shall have the facts.

II. Tar RELATIONS or PALEOBOTANY TO Botany

2. Morphology

PROFESSOR EDWARD C. JEFFREY

HARVARD UNIVERSITY

Tue morphology of Goethe’s metamorphoses, a hun-

dred years ago, was entirely external morphology, illum-

inating at the time and for many decades later; but now

for over a quarter of a century extinct, except so far as

it lives on for descriptive purposes in manuals of sys-

tematic botany. It has been replaced by a conception

of morphology, based not on external form but on inter-

nal structure. The replacement has been slow in this

country, where, unfortunately, morphology is still very

largely a thing of external threads and patches. The

father of plant morphology in its modern form, was, as

you all know, Wilhelm Hofmeister, who, over fifty years

ago, began to put the subject on a truly evolutionary

basis. Like many other men of genius, he was before

his time and received little hab reer from his less

oo BO det

226 THE AMERICAN NATURALIST [Vou. XLVI

But it is Professor Coulter’s task to deal with morphol-

ogy, particularly in its paleobotanical aspects, in rela-

tion to systematic botany, as is specially fitting, since the

laboratories over which he presides at Chicago have up

to the present time been the greatest single influence in

putting American morphology on a modern and progres-

sive basis. His important relation to systematic devel-

opment in this country is also well known, representing

as it does an earlier but not less striking phase of his

botanical activity. My excuse for even referring to sys-

tematic matters in these preliminary remarks is the

close relation in which they necessarily stand or should

stand to morphology and paleobotany. Darwin in his

immortal ‘‘Origin of Species,’’ although but little given

to figurative language, has described morphology as the

soul of natural history. It is to be feared that there is

just ground for complaint, that the botanical natural

historian has in the past too often worn his soul upon his

sleeve or has even appeared to lack that necessary ad-

junct of higher existence. Internal morphology now

holds the field and all other lines of botanical activity

from systematic botany to plant physiology must take

account of its doings, if they are to make solid and en-

during progress. |

If a change has come in recent years in the point of

view of morphology, an equally important shifting of

position has taken place, during the past few decades in

the attitude of paleobotany. Until the late seventies of

the nineteenth century, paleobotany had to do practically

with the external form of plants alone, as they appear as

impressions in the rocks. It is true that Brongniart in

the earlier years of the last century realized the impor-

tance of internal structure in the case of fossil plants and,

as Dr. Scott has recently pointed out, his views on this

subject are so clear and fit actual conditions so well, that

they read as if they were written only yesterday. But

Brongniart had few followers even among his own coun-

trymen. To the Englishman, Williamson, belongs a large

No. 544] BOTANICAL SOCIETY OF AMERICA 227

- part of the credit of putting paleobotany on a really

satisfactory footing. He insisted on the absolute neces-

sity of taking into consideration internal structure as

well as external form, and went so far in some of his

writings as to state that imprints or impressions alone,

of extinct plants, had little scientific value. What may

be called the evolutionary bias of Englishmen, a fortu-

nate inheritance from the greatest of all biologists,

Charles Darwin, has led them far in the pursuit of paleo-

botany on anatomical lines. We need only call to mind

the demonstration on anatomical grounds that the

greater part of the trees of the Coal Period were, in spite

of their arboreal habit, in reality vascular cryptogams,

a demonstration absolutely confirmed later when it was

possible to study, in detail, their reproductive organs.

An even more striking illustration of the same kind is

supplied by some of the fern-like forms of the Paleozoic,

which have long appeared in the catalogue as vascular

cryptogams. Here too it was first shown on anatomical

grounds, and afterwards from the examination of the or-

ganization of the reproductive structures, that outward

appearances were entirely deceptive and that the organ-

isms in question were in reality seed plants of a prim-

itive type. These two illustrations, which might be in-

definitely multiplied, serve to indicate the very impor-

tant services which the study of internal organization

has rendered both to the natural system and to the doc-

trine of evolution. They further make it clear that the

aphorism of mundane existence, which admonishes us

not to trust to appearances, holds equally well in the

domain of plants. Paleobotany, like morphology, has

accordingly at the present time entered into the anatom-

ical phase of development.

So long as morphology concerned itself mainly with

the external form of the reproductive structures of exist-

ing plants and paleobotany had perforce to content itself

for the most part with the impressions upon the rocks

of the foliar organs of extinct ones, there was little to

228 THE AMERICAN NATURALIST [ Vou. XLVI

bring these two branches of botanical science together. -

The systematic botanist was accordingly quite safe in

ridiculing the insufficiency of the evidence upon which

the conclusions of the older paleobotany was founded.

With the advent of the anatomical phase of development

in both morphology and paleobotany, the two sciences

have become united on the basis of common interests and

are both enormously strengthened by the union. Morphol-

ogy, from being the exponent of a priori philosophical

ideas, applied to the question of the evolution of plants,

and derived for the most part from the inner conscious-

ness rather than from any truly scientific and inductive

study of facts, has become the logical fancy-free hand-

maiden of evolution. Paleobotanical science, on the other

hand, having realized, especially in the case of the older

plants, which are naturally of the greatest importance

from the evolutionary standpoint, that the external form,

even the external form of the reproductive structures,

is often very deceptive as to real affinities, has come to

regard as most important the much less variable internal

organization of extinct plants. Paleobotany is in the

position to supply us now, for the first time, with reliable

facts regarding the organization and true systematic

affinities of the ancient vegetation of the earth, and

morphology has reached a condition of maturity where

facts are infinitely more important than philosophical

fancies, however charmingly expressed.

It is unfortunately the case that morphology, until

comparatively recently, has been quite as unscientific in

its methods as the systematic botany with which in the

earlier years of its existence as a branch of botanical

science it was intimately allied. The recent important

change of attitude in plant morphology is practically en-

tirely due to extensions in our knowledge of the organiza-

tion of extinct plants. Sachs in the second part of his

classic ‘‘History of Botany,’’ which deals with plant

anatomy and similar matters, deplores this unsatisfac-

tory condition in the following words: ‘‘Owing to the ex-

No. 544] BOTANICAL SOCIETY OF AMERICA 229

traordinary diversity of opinion that exists among botan-

ists even on the most general questions in the science, it

is extremely difficult to ascertain what can be considered

a common possession,—an unfortunate condition of things

from which no science suffers perhaps so much as

Botany.’’ Until comparatively recently these words

were as true of plant morphology and plant physiology

as when they were written, nearly forty years ago. If

there is any mitigation of the situation it is because of

the application of chemical and physical laws to the un-

derstanding of the functioning of plant structures and

the facts of modern paleobotany to the elucidation of the

structures themselves. There can be no doubt whatever,

that, without the background supplied by our increasing

knowledge of fossil plants, the picture painted by the

morphologist and embryologist of the evolution of plants

is without depth and entirely without perspective. We

literally can not see our wood for the countless trees

which have crowded into the foreground representing its

most modern stage of development. It is certainly im-

possible to formulate even the rudiments of the evolu-

tionary perspective of plants in the absence of paleo-

botanical facts as the enduring and fundamental back-

ground.

It is accordingly impossible to deny that in the past

morphology has been largely fanciful, where it has de-

parted in any way from the bare description of the facts

of structure in modern plants, or has -attempted to

arrange them in accordance with any general or scien-

tific principles. True the situation has been relieved not

a little, as a result of the study of development and com-

parative anatomy, but the difficulty has always been

here to decide the direction in which a comparative or

developmental series should be read. The indispensable

sense of direction can alone be supplied by sighting down

` the fingerposts of the past, the records of fossil plants,

which show us the real path by which evolutionary ad-

vancement has been made in any given case. — -

230 THE AMERICAN NATURALIST — [Vou. XLVI

One of the commonest fallacies of the older morphol-

ogy was to regard simpler structures as more ancient

and complicated ones as more specialized and modern.

This error is very deeply implanted in the existing highly

artificial systematic arrangement of the higher plants.

For example in the case of the conifers, the Taxaceæ

are put lower than the Pinacex, on account of the simpler

organization of their reproductive and vegetative struc-

tures. The paleobotanical record, however, shows us

clearly that the Pinacex, particularly the abietineous

Pinacee, are among the most ancient repr tatives of

the coniferous stock, while the Taxacex, particularly the

genus Taxus, stand for the class in its most modern con-

dition of development. Let us take another illustration

from the Angiosperms. Systematic text-books invari- |

ably place the Monocotyledones below the Dicotyledones,

on the basis of their simpler organization. This view

of the matter does not accord, however, with the results

of anatomical and paleobotanical research, which clearly

show that the Monocotyledones are neither ancient in

their occurrence nor primitive in their organization, but

represent a condition of reduction from ancestors which

were essentially dicotyledonous in their more important

characteristics. These two illustrations, which might be

multiplied indefinitely from systematic works, show that

the older morphology was essentially fanciful and phil-

osophical in its methods and by no means worthy of the

name of an inductive science.

The new morphology, purely inductive in its pro-

cedure, is solidly founded on the testimony of the rocks

and considers no sequence valid, unless it is clearly

supported by the evidence derived from the study of

fossil forms. It shows itself moreover scientific in

its firm adhesion to valid general principles and

its disregard of uncoordinated facts. These general

principles too are few in number and are as easily

grasped in their simplest form as are the great general-

izations of the sister sciences, chemistry, physics and

No. 544] BOTANICAL SOCIETY OF AMERICA 931

astronomy. The three most important laws or general

principles of morphology are those which have to do with

recapitulation, reversion and retention. The first is

common to both plants and animals, while the other two

are infinitely better illustrated by botanical than zoolog-

ical facts. The validity of these laws has long been ad-

mitted in a somewhat hazy and unpractical fashion. It

has remained for morphology based on paleobotany to

bring them into prominence as the fundamental working

principles of the investigator of plant evolution. They |

are in fact the rudiments, the three R’s of biological sci-

ence, with which even the tyro should become well

acquainted.

We can not do better than take a particular illustra-

tion of these laws as applied to botanical facts. The

conifers show themselves particularly favorable for the

elucidation of general evolutionary principles, because

they not only constitute a large, varied and widely dis-

tributed element of our existing flora, but can be traced,

with trifling intérruptions, continuously far into the past.

Of the conifers there is one tribe at the present time

entirely confined to the southern hemisphere. I refer

to the Araucariinex, of which the New Zealand Kauri and

the Norfolk Island pine may appropriately stand as

examples. In the Mesozoic period, the middle ages of

our earth, they flourished throughout the entire world.

It is often considered that the Araucariinee represent

the most ancient group of conifers. This belief appears

to be based on a too common fallacy, that groups nearly

extinct in the existing flora necessarily represent ancient

forms. A further basis for the hypothesis of the extreme

antiquity of the Araucarian conifers is derived from

their habit and the general features of organization of

their wood, in both of which respects they present points

of resemblance, by no means complete, however, with

those Paleozoic gymnosperms to which the origin of the

general coniferous class is by common consent of morphol-

ogists and paleobotanists referred, namely, the Cordai-

232 THE AMERICAN NATURALIST [ Vou. XLVI

tales. If we follow the Araucariinee backward step by

step, as recent additions to our knowledge now permit us

to do, into the past, we find that although in the Tertiary

they retained very largely the characteristics which they

present to-day in the Cretaceous, particularly in the

Lower Cretaceous and in the Jurassic, they become less

and less like their existing representatives and more and

more like the Abietinex, the actually dominant conifers

of the northern hemisphere, both in general organiza-

tion and wood-structure. . To save time let us consider

only three points of anatomical organization, for com-

parison. The existing Araucariinee are remarkable

among conifers and gymnosperms generally, in possess-

ing leaf-traces which continue to'be formed in the wood

by the cambium, long after the leaves which they origi-

nally supplied have ceased to exist. The old trunk of a

Kauri or an Araucaria, for example, shows on the outside

of its wood marks representing the traces of leaves,

which may have disappeared hundreds of years pre-

viously. This feature has been seized upon by Professor

Seward as one of undoubted primitiveness. It is cer-

tainly bizarre, and if one accepts the unusual as the cri-

terion of antiquity, the Araucariinee certainly could

qualify for an ancient lineage on this character. This

view does not however accord with paleobotanical facts. .

In the Lower Cretaceous we find very many undoubted

Araucarian trunks, in which the leaf-traces were not

persistent as in the existing representatives of the tribe

and in the Jurassic and Triassic trunks of this type

become practically universal. This at once makes it

clear that the persistent leaf-trace, so characteristic of

the living Kauri and Araucaria, is not an ancestral fea-

ture of the Araucarian stock. Recently we have sent

out from Harvard a botanical expedition to Australasia.

At my suggestion Messrs. Eames and Sinnott, who were

its personnel, have brought back old seedlings of the two

existing Araucarian genera. On investigation of the

lower region of these in proximity to the cotyledons, it

No. 544] BOTANICAL SOCIETY OF AMERICA a

was found that here the leaf-traces were ephemeral in

their persistence, exactly as in the older Mesozoic repre-

sentatives of the Araucarian stock from the Lower Cre-

taceous, Jurassic and Triassic deposits. Here appears

a very striking example of the validity of the law of re-

capitulation as exemplified by the young individual, the

seedling stem for a short part of its vertical length re-

peating ancestral conditions which have long. disap-

peared in the adult. Let us consider two remaining

characters together, in order -to economize time. The

water pores of the tracheids in existing Araucarian con-

ifers occur in a crowded and alternating condition and

are deformed or flattened by mutual contact, a feature

of resemblance to the oldest known gymnosperms. This

feature is in marked contrast to the pit arrangements of

the other existing tribes of conifers, where the water

pores are loosely grouped and when numerous and mul-

tiseriate are opposite. Another unusual feature of the

wood of existing Araucariiner is the absence of wood

parenchyma, a feature likewise illustrated by the woods

of the Paleozoic gymnosperms. If we follow the Arau-

carian conifers below the horizon of the present, we ob-

serve in the older representatives a condition of pitting

of the tracheids, which the lower we go geologically,

becomes more and more like that found in the other tribes

of conifers, particularly the Abietinex, so much so that

Gothan, who has recently described the Jurassic woods

of Spitzbergen and other arctic islands, which in the

Mesozoic supported a luxuriant flora, has identified them

as of Abietineous affinities. It is further found in the

case of those Mesozoic fossil woods which most nearly

resemble the living genera Agathis and Araucaria, that

wood parenchyma was exceedingly abundant. Now let

us examine our Araucarian seedlings in regard to these

features. The wood of the cotyledonary region here ex-

emplifies both the characteristic pitting and presence of

wood parenchyma of the Mesozoic Araucarioxylon type.

Thus the Araucariinee, which we are able to follow very

234 THE AMERICAN NATURALIST [ Vou. XLVI

far back into the past, present a very striking illustra-

tion of the biological law of recapitulation. Other fea-

tures of the seedling might have been considered with the

same result.

But ancestral conditions are not in plants confined to

the young individual. We find them also illustrated in

connection with the principles of retention and reversion.

The law of retention is well exemplified by the root, cone

and first vegetative annual ring of the Araucariinee,

where the Mesozoic features of structure appear only

less completely than they do in the seedling. The law

of reversion is likewise illustrated readily in this tribe

of conifers in connection with injuries, for the wood

formed subsequently to wounds shows Mesozoic charac-

ters, which are not a feature of normal structure.

It appears clear from the illustration which I have

chosen, only one among many possible ones from the re-

sults of recent coordinated anatomical, developmental,

experimental and paleobotanical investigations, that we

have definite laws of plant evolution. It is further clear

that like Ulysses we must ‘‘follow knowledge like a sink-

ing star” into the night of the past, if we are to reach

durable general biological principles. The laws of re-

capitulation, retention and reversion, founded on cases

where it is possible to trace an unbroken sequence of

forms, are likewise applicable to the elucidation of con-

ditions in groups the past of which is as yet insufficiently

known. A very notable example of this kind is pre-

sented by the Angiosperms. Here more than anywhere

else among the higher plants philosophical views in re-

gard to evolution prevail. You are doubtless all famil-

iar with the generally accepted dictum, forming a feature

of all elementary botanical instruction, that the woody

stem of perennial Dicotyledones is derived from one of

herbaceous texture. This conclusion is based on the old

fallacy, that simpler conditions are necessarily antece-

dent to more complex ones and antedate them in time.

If we investigate the primitive type of stem organization

No. 544] BOTANICAL SOCIETY OF AMERICA 235

in the Dicotyledones, in accordance with the principles

of recapitulation, retention and reversion, we arrive at

very different conclusions indeed and of much greater

significance from the standpoint of evolution.

It will save time to take a concrete illustration. In

the cross section of a small branch of the oak we find

the woody part of the stem, composed of ten alternat-

ingly outstanding and depressed segments, separated

from one another by ten large so-called primary medul-

lary rays. In accordance with the herbaceous hypothesis

of the origin of the woody stem, the projecting segments

are supposed to correspond to five originally entirely

separate bundles. Further the intervening depressed

segments of the cylinder, set off from the others by the

ten large rays, are supposed to represent parts of the

wood which have been secondarily interpolated through

the activity of a so-called interfascicular cambium. If

we examine the facts in the light of the general principles

of plant evolution, a very different and much sounder

conclusion is reached. Let us take only the seedling

evidence, for the other accords absolutely with it. In

the cotyledonary region of the young stem we find for a

number of years a completely continuous woody cylinder,

without either large rays or depressed segments. At

this level in fact the rays are entirely narrow ones of the

gymnospermous type. Both the broad rays and the seg-

ments which they delimit appear only later. The so-

called large primary rays are in fact formed as a result

of the fusion of smaller rays into aggregates around the

incoming leaf-traces. The broad rays of the oak are-

consequently fusion products and not at all primitive

structures. They are clearly related as a storage device

for the strands which enter the stem from the leaves.

There are two broad rays to each leaf, corresponding to

its two strongly developed lateral traces, and since the

phyllotaxy of the oak is of the 2/5 type, there are nor-

mally and originally five pairs of large rays in the stem.

The depression of five of the segments delimited by the

236 THE AMERICAN NATURALIST [ Vou. XLVI

large leaf or foliar rays below the level of their fellows

presents another interesting problem in evolution, into

which there is not time to enter at present. It is enough

to say that the so-called primary or large rays of dico-

tyledonous stems are not primary or primitive struc-

tures at all, but are of secondary origin and formed from

what was originally wood, in order that the assimilates

_ from the leaves may more readily and conveniently be

stored for future use. We have thus an explanation of

the relation of the woody to the herbaceous stem, which

is at once in harmony with the general principles of plant

evolution and at the same time with physiological neces-

sities. The fallacy of considering the herbaceous as the

primitive type is further made clear. There is in fact

every reason to believe that the early Dicotyledones were

entirely woody perennials, just as the forbears of the

existing herbaceous Pteridophyta have been shown by

paleobotanical and anatomical investigations to have

been derived from arboreal ancestors of the Paleozoic.

The clear realization of the universal validity of the

primary laws of plant evolution depends almost entirely

on our increased knowledge of the organization of fossil

plants. There has come to morphology as a consequence

of the study of ancient forms a new birth, quite compar-

able to the remarkable intellectual awakening in Europe,

at the beginning of the modern period, resulting from

the rediscovery of the ancient classics of the Greeks and

Romans. This awakening, known as the renaissance, has

its exact counterpart in plant morphology and our en-

thusiasm over the discovery of new fossil remains which

throw a light on the origin of existing plants is not dif-

ferent from that experienced by the enlightened citizens

of the Italian cities at the end of the middle ages, over .

the unearthing of a new manuscript of Virgil or of

Horace. As a result of this impetus the morphologist

has already in the past decade revolutionized the system-

atic arrangement of the Gymnosperms and the work in

this special field has scarcely begun. In the case of the

No. 544] BOTANICAL SOCIETY OF AMERICA 237

Angiosperms, change is also in the air and I venture to

predict that within two or three decades at most we shall

have made substantial progress towards a scientific, that

is, a natural, classification, of what is at present a huge

and hopelessly confused labyrinth, penetrated at best in

a halting way by the tenuous and insecure thread of our

present highly artificial system.

The future presents many interesting possibilities for

the morphologist and the paleobotanist and let us hope

for the systematist as well. Obviously we are now on the

threshold of the discovery of a system of plants which

shall depict their evolutionary sequence. Would that we

might count on the sympathetic cooperation of all sys-

tematic botanists in this stupendous and intellectually

attractive task. Unfortunately in the thirties of the last

century systematic botany parted company with plant

morphology and has appeared since somewhat to resem-

ble the man with the muckrake in the vision of the im-

mortal tinker. Although there hangs above it the shin-

ing diadem of a natural system, with which to crown its

arduous labors of many years, the raking together of

straws, sticks and even antique dust seems to present an

invincible attraction. The assiduous strokes of the rake

may glean additional straws and sticks; but although

we may all agree that he is a benefactor of mankind who

makes two living blades of grass sprout where there was

one before, we shall scarcely consent with unanimity

that the making of more new species out of old ones, is

a highly commendable scientific occupation. A great

danger on the systematic side appears at the present

time to inhere in the doings of so-called world congresses.

Recently the paleobotanists of those countries which are

mainly active in the investigation of fossil plants have

agreed unanimously and publicly to repudiate the vote

of the recent congress at Brussels, imposing upon them

Latin diagnoses of extinct plants. The students of fossil

plants, although they have to do with organisms no

238 THE AMERICAN NATURALIST [ Vou. XLVI

longer living, regard their science as a live one and are

consequently strongly unwilling to shroud its doings in

the pall of a dead language, perhaps not the less because

the mandate to do so comes as the result of a Russian

ukase. The present world congresses of botanists seem

to present certain ominous resemblances to the world

councils of the church about the time of the Reformation

in Europe. The so-called ecumenical councils of Chris-

tianity were unfortunately characterized at that time by

reactionary tendencies, including among others a prefer-

ence for the Holy Writ in the Latin rendering of the

Vulgate. Unless there is some relaxation of the medie-

val attitude upon the part of the majority of systematic

botanists, there is reason to fear a reformation in botany,

as uncontrollable as that led by Martin Luther and John

Knox in religion. It is sometimes said in favor of Latin

diagnoses of plants, that the older literature of system-

atic botany is in the Latin tongue. The same is true of

the equally venerable sciences of chemistry and astron-

omy, yet for that reason the chemists and astronomers

of to-day do not think it necessary to perpetuate the writ-

ten language of the alchemists and astrologers. Botany

has likewise, let up hope, passed through what corre-

sponds to the alchemistical and astrological phase of

development and need not conceal its doings in the

dog Latin of a Paracelsus or an Albertus Magnus. Con-

ditions in this country are hopeful in this respect, for

although we are not wholly free from the pedantry that

maketh and loveth a Latin diagnosis, the large majority

of American systematists are entirely progressive in

their point of view. May they prevail and in the course

of time, with all modesty, impress their attitude on the

European cultivators of this important field of botanical

activity.

No. 544] BOTANICAL SOCIETY OF AMERICA 239

II. Tue RELATIONS oF PALEoBoTANY TO BOTANY

3. Ecology

DR. ARTHUR HOLLICK

New York BOTANICAL GARDEN

As I understand the object of a symposium it is not to

provide opportunity for the reading of exhaustive or

highly technical dissertations, or for the presentation of

new material, but rather to present recognized facts as

clearly as may be, with recent interpretations of their

meaning or significance, in order to enlist interest in and

to stimulate discussion of the subject under considera-

tion; and this seems to have been the view which was

taken by those who have preceded me. In such connec-

tion it is my privilege to present the claims of ecology to

recognition, in indicating the relations between botany

and paleobotany.

Plant ecology, as the term is commonly defined and

understood, is that branch of botany which deals with the

study of the interrelations of plants and their relations

to environment. As a distinct science it is practically a

product of the present generation. I do not know exactly

when the term was first employed in scientific literature,

but it certainly was not in general use in connection with

botany at the time of my earliest contributions to the

subject, and I did not then know that I was dealing with

ecology when discussing certain floras and their accom-

panying geologic and physiographic features of enyl-

ronment.

The ecologie relations between botany and paleobotany

are mostly concerned with the problems of phytogeog-

raphy. Paleobotany has supplied the explanations of

numerous puzzling facts in regard to the geographic

isolation of certain genera ; the occurrence of some genus

or species only in certain widely separated regions of the

earth; and the problems in connection with many endemic

floras. Indeed the phenomena of plant distribution 1n

210 THE AMERICAN NATURALIST [Vor. XLVI

general at the present time would be lacking in logical or

adequate explanation but for the facts which have been

brought to light by the study of fossil plants in regard to

distribution in the past. Many such instances might be

cited, but for the purposes of this symposium a few of

the most striking only need be recalled to serve as con-

crete examples of the general abstract propositions.

In the earlier part of the last century, when the science

of paleobotany was in its infancy, and much that we now

know about living plants had not been learned, numerous

remains of coniferous trees were found in Europe and

elsewhere in the Old World, in deposits of relatively

recent geologic age. For the most part these remains

were either identified as living genera or were given

generic names designed to indicate their nearest appar-

ent relationships with such (Pinites, Tawites, Arauca-

rites,etc.). Other similar remains, however, which could

not be satisfactorily compared with any living ones, were

given new generic names. Among these latter may be

mentioned certain small cones associated with leafy

twigs, which were assumed at the time to represent an

extinct coniferous genus. Large areas of the New World,

however, were yet unexplored and many hitherto un-

known living genera were awaiting discovery and de-

scription. One of these was Sequoia, a genus of two

species only, confined in their distribution to scattered

groves on the western coast of the United States. Ecol-

ogy was an unknown science when these groves were dis-

covered, but the relatively limited number of the indi-

vidual trees, and their geographic isolation, at once

attracted attention and aroused interest and discussion

in regard to their ancestry and the phenomenon of their

peculiar distribution. Paleobotany supplied the desired

information. When the generic characters of Sequoia

were made known they were seen to be identical with

those of the supposed extinct fossil coniferous genus of

the Old World. Further than this, however, similar re-

mains, comprising numerous different species, were sub-

No. 544] BOTANICAL SOCIETY OF AMERICA 241

sequently found extending through Siberia to the eastern

coast of Asia and through Europe, Iceland, Greenland

and the Arctic regions to Alaska, and thence southward

to the home of the two remaining living species on the

western coast of North America. The phytogeographic

problem of the genus Sequoia, as we know it to-day, was

thus resolved into the geologic problem of the causes

which produced the climatic changes resulting in the ex-

tinction of the genus over vast areas where it formerly

existed, and the total extinction of all except two of the

numerous species by which it was formerly represented.

Modern areal limitation of the genus was thus shown by

paleobotany to be a result of former areal elimination.

(Incidentally it may be remarked that this example

also involves a question of nomenclature which, however,

I trust our chairman may declare to be not germane to

the subject and hence ineligible for discussion. It is one

of the few instances in which a genus was known and

named as a fossil before it was discovered and named in

its living form.)

The genus Taxodium, comprising two, or possibly three

living species, is confined to the southern United States

and Mexico, so far as its present distribution is con-

cerned. Up to the close of the Tertiary period, however,

it flourished throughout what are now the temperate and

arctic zones of North America and Eurasia,—not only

the genus, but apparently the identical species yet living

and others now extinct. Paleobotany has adduced ample

proof of these facts, so that, as in the case of Sequoia, the

present distribution of Taxodium is explained as merely

the result of its elimination from other regions where it

formerly existed.

The monotypic genus Ginkgo, which by many is also

regarded as representing a monotypic family and order,

is confined, so far as its natural distribution is concerned,

to eastern China and Japan. No known facts could ade-

quately account for its taxonomic and geographic isola-

tion until paleobotany revealed the multiplicity of its ex-

242 THE AMERICAN NATURALIST [ Vou. XLVI

tinct specific and allied generic forms, and its former

wide distribution throughout the Eurasian and North

American continents.

Another monotypic living genus, Sassafras, limited in

its present distribution to eastern North America, repre-

sents an ancient type of angiosperm vegetation whose

fossil remains have been found not only throughout

North America, but also in many parts of the Old World.

These are merely a few of the many examples of

generic isolation—geographic and taxonomic—the expla-

nations of which have been supplied by the study of

paleobotany.

Other apparent peculiarities of distribution, such as are

represented in our living flora by Liriodendron and Ne-

lumbo, genera which are restricted to eastern Asia, east-

ern North America and the central American regions, are

exceedingly difficult to explain satisfactorily on any

theory of migration in recent times; and the theory of

origin de novo in each of the widely separated regions is

too thoroughly discredited to merit discussion. None of

the known facts of recent plant migration, or evolution,

or mutation, are adequate to explain the conditions as we

now find them. Paleobotany, however, has demonstrated

that such apparent peculiarities of generic distribution

are readily explained when the facts of former distribu-

tion are ascertained. Each of these genera was formerly

world-wide in its distribution and prolific in species; but

changes in environment caused their extinction in all ex-

cept the widely separated regions which they now inhabit,

reducing the species of Nelumbo to two, and of Lirioden-

dron to one. What have been regarded as problems of

distribution, explainable by improbable theories of mi-

gration or evolution, have thus been shown by the facts

of paleobotany to be merely some of the many examples

of isolation due to elimination in intermediate regions. `

‘The peculiar endemic flora of Australia did not origi-

nate de novo by reason of its isolation. Paleobotany has

shown that the living endemic flora of Australia in many

No. 544] BOTANICAL SOCIETY OF AMERICA 243

of its characteristic elements, such as the genus Huca-

lyptus, represents what the general vegetation of the en-

tire earth was like at the close of Mesozoic time, when

the continent of Australia was isolated from the rest of

the world. Elsewhere than in Australia climatic and

physiographic changes subsequently eliminated the Me-

sozoic types of vegetation and evolved new ones; but in

Australia the conditions remained almost stationary, and

that continent to-day, so far as its native flora and fauna

are concerned, is still in a late Mesozoic or early Neozoic

stage of development. It is an endemic flora not because

it has evolved new types by reason of its isolation, but

because it has remained stationary by virtue of this rea-

son, while the great bulk of the world’s vegetation has

changed.

And so the paleobotanist extends the right hand of fel-

lowship to the botanist and says, ‘‘when you are puzzled,

or in doubt, don’t despair, come to us,’’ for individually

or collectively we can, probably, suggest reasonable ex-

planations, not only as to why living plants have come to

be where they are, but also how they have come to be

what they are. |

SHORTER ARTICLES AND DISCUSSION

THE INFLUENCE OF CAVE CONDITIONS UPON

PIGMENT DEVELOPMENT IN LARVA OF

AMBLYSTOMA TIGRINUM

One of the possible methods of approach to the problem of

the origin of the modifications of cave animals is by experiments

in which outside forms are kept under conditions normally

encountered by animals living in caves. In following up this

method of approach, it seemed best to select forms as plastic as

possible (if perchance there are forms which are plastic with

reference to modifications by cave conditions). Typical cave

animals, 7. e., species highly adapted for cave life, perhaps

without exception belong to families and genera having many

members showing an inclination toward cave habitation either

by actually frequenting or living in caves or by inhabiting

similar dark and retired situations elsewhere; so that it might

seem that these groups possess a certain plasticity toward modi-

fications by cave conditions. Especially might this plasticity

be expected in the particular species which already show a tend-

ency to live under conditions resembling those of caves.

Young animals may be expected to be more responsive to

changed environment than adults, and since many of the uro-

deles live in caves and similar situations, and their eggs and

young can be obtained in numbers and reared with comparative

ease, amphibian larve were selected for some of the experiments.

Newly laid eggs of Amblystoma tigrinum were collected (in

some cases were laid in jars in the laboratory where some of the

adults were confined) from March 30 to April 4, 1911. The

eggs, in small lots, were placed in a number of 6-inch battery

jars, and the jars divided into two lots, Series A and Series B.

Series A was placed in the artificial cave while Series B was

kept on a laboratory table adjacent to and directly in front of

a west window. Otherwise the two series were, as far as pos-

sible, subjected to like conditions. Unfortunately it was not

possible to keep Series B at as low or as uniform a temperature

as Series A. Development was somewhat slower on the average

with Series A than with Series B, and both of these developed

slightly less rapidly than a third series, Series C, observed in the

pool where the eggs were laid and the larve allowed to develop

244

No.544] SHORTER ARTICLES AND DISCUSSION * 245

under natural conditions, but as I shall attempt to show later

neither temperature differences nor different rates of develop-

ment materially influenced the amount of pigment developed.

The animals were fed on alternate days with an abundance

of daphnids and cyclops, and later with small bits of tender

beef. The amount of pigment developed was judged by making

accurate determinations of the color of two definite regions of

the skin of each individual. For the body color, determinations

were made for a region to one side of the median line and about

midway between the pectoral and pelvic limbs. This is the

most heavily pigmented region of the larva. For the head

color the region immediately anterior to a line from one eye

to the other was used. This is usually the least pigmented por-

tion of the animal. The colors were obtained by means of the

Milton Bradley color tops and the records made in percentages

of black, white, orange and yellow, which when blended most

nearly matched the color of the skin of the animal. The orange

used in these tops most nearly resembles the No. 101 of

Klincksieck et Valette’s ‘‘Code des couleurs’’ and the yellow

is intermediate between Nos. 206 and 211. All the color records

under consideration for Series A and B were made within two

weeks and under uniform conditions so that the results ought

to be strictly comparable. The records for the somewhat more

rapidly developing Series © were made about three weeks

earlier. The results tabulated include color records for all the

surviving individuals of Series A and B and sixteen individuals

selected at random to constitute Series C.

The average body color of the Series A, numbering 22 indi-

viduals, reared in the cave, contained 49.7 per cent. of black,

16.9 per cent. white, 9.3 per cent. orange and 24.1 per cent.

of yellow; or 49.7 per cent. black and 50.3 per cent. non-black.

The extreme range in degree of pigmentation was from 32 black

and 68 non-black to, in the case of one individual decidedly

darker than its fellows, 70.5 black to 29.5 non-black. The

average head color was 38 per cent. black and 62 per cent. non-

black (26.7 white, 7.0 orange and 28.3 yellow) with 27 per

cent. and 51 per cent. as the extremes in amounts of black.

On the average, Series B (7 individuals), reared in labora-

tory light, had a body color of 86.1 per cent, black and 13.9 per

cent. non-black (4.7 white, 2.4 orange and 6.8 yellow), and a

head color of 76.1 per cent. black and 23.9 per cent. non-black

(8.4 white, 4.0 orange and 11.5 yellow). The range for the

body color was from 82 to 90.5 black and for the head color : : : : -

740° THE AMERICAN NATURALIST [ Vou. XLVI

from 62.5 to 90 black, ranges distinct from and not at all over-

lapping those for Series A reared in darkness.

Series C (16 individuals), living in the outdoor pool under

natural conditions, had an average body color of 86.6 black and

13.4 per cent. non-black (4.5 white, 3.1 orange and 5.8 yellow),

the extremes ranging from 77.5 to 93 per cent. black. The

head color averaged 78.3 black and 21.7 non-black (7.7 white,

4.2 orange and 9.8 yellow) with 61 per cent. and 90 per cent.

the extremes in amount of black. The data for all three series

are shown together in the adjoining table.

| Body | Head

4 xs

x| s| 8] 2 \|gs|/4|2| | & \32

5 a 8 D on Z a si ee O'i

et o a ee ee ee:

| ae

Series A (cave): |

et ea »: -| 70.5 29.5 51.0 | 49.0

PAPRIGRG a a 32.0 68.0 |27.0 |

AVOPAQOR Wr uae ra | 49.7|16.9| 9.3 124.1 50.3 38.0 26.7 | 7.0 28.3 62. 0

Series B (laboratory) | |

es:

Darkat. n 90.5 9.5 90.0 | 10.0

Piehtest 23 82.0 18.0 (62.5 37.5 5

AVARO, oe oo ae 86.1| 4.7 | 2.4 | 6.8 |13.9 | 76.1; 8.4| 4. A ‘11.5 5123. 23.9

Series C (pool):

Extremes:

Parkent. oA 93.0 7.0 90.0 10.0

ETES PERAE E E E Tho 5161.0 39.

Avera a | 86.6| 4.5 | 3.1 | 5.8 |13.4 |78.3 | 7.7 | 4.21 9.8 (21.7

It will be noted that the series reared in laboratory light

(Series B) and the one developing under natural conditions in

the outdoor pool (Series C) agree very closely in the amount of

pigment development, the average percentages of black in the

body color determinations being 86.1 and 86.6, and for the head

color 76.1 and 78.3 respectively, while the extremes for the two

series differ but slightly. However, the most significant fact

is that these series differ so sharply from Series A reared in the

dark and having an average body color of only 49.7 per cent.

black and an average head color of 38 black. On the average

those reared in darkness have about four times as much non-

black in the body color as those reared in light, while the darkest

individual of the cave series, really aberrant for that series

because it is so dark with 70.5 per cent. black in the body color

No. 544] SHORTER ARTICLES AND DISCUSSION (247

and 51 per cent. in the head color, has decidedly less pigment

than the lightest individual of either Series B or Series C, with

77.5 per cent. black in the body color and 61 black in the head

color.

The percentage differences in color between the series reared

in darkness and the two series reared in light do not adequately

represent the color differences as perceived by the eye. The

average person probably would not hesitate to call the lighter

individuals of Series A ‘‘white,’? and on the other hand would

probably class the various individuals of Series B and C as

‘dark gray’’ or ‘‘coal black.’”’

There appear to be no reasons for thinking that the marked

differences in pigment development were due to differences in

nutrition or differences in temperature. Series B so closely

resembled Series C in amount of pigment development that it

is evident the differences in temperature and food did not

greatly influence their pigmentation, yet Series B was reared in

a west room subject to great fluctuations in temperature because

of the extreme exposure to the summer sun during the afternoon,

and the temperature of this series on the average was probably

higher than in the outdoor pool in which Series C developed,

while the food was exclusively daphnids, copepods and bits of |

beef. On the other hand Series A was maintained at a quite

uniform temperature consistently lower than either of the other

series. Fischel (’96) and Flemming (’97) found that with

certain salamander larve (the former at least used larve of

Salamandra maculata) temperature differences influenced the

amount of pigment development, the individuals reared at from

4° to 7° C. being much darker than individuals reared at from

15° to 20° C., indicating that for Salamandra maculata the lower

temperature favors greater pigment development. Inasmuch

as my lightest series, Series A, was reared at the lowest tempera-

ture of any and yet was markedly lighter than the others, and

that Series B and C did not differ widely in amount of pigment

development although reared under somewhat different tem-

perature conditions renders it improbable that temperature in-

fluences produced the differences in pigmentation observed.

Series A and B were fed in every way alike and so far as

could be judged took about the same quantities of food. While

as a whole Series A developed less rapidly than Series B, part of

Series A developed more quickly than some of Series B yet each

individual possessed an amount of pigment similar to the others

of its series, Hence the evidence strongly points to ‘the con- . oe

248 THE AMERICAN NATURALIST [ Vou. XLVI

clusion that the differences in amount of pigmentation were not

due to differences in temperature, food or rate of development

but solely or in much the greater part to the absence or presence

of light.

The difference in pigmentation between Series A on the one

hand and Series B and C on the other is fully as great as the

difference in pigmentation between certain species that live

habitually in caves and others which do not. To this point the

case looks most significant. With the approach of transforma-

tion, however, the amount of pigment rapidly increases, par-

ticularly on the lighter regions of the larve, and this increase

is more pronounced with those reared in darkness than with the

others. Nevertheless there still remains a marked difference in

pigmentation between the transformed individuals of Series A

reared under cave conditions and Series B reared in the light.

Color records of a few recently transformed salamanders

were taken before the spots so characteristic of the adult were

definitely formed. An attempt was made to get careful records

of the general blended color effect independent of the mottling

which is quite pronounced at this stage, during which the pig-

ment is being segregated to form the definite color pattern of

the adult. The average body color of the transformed sala-

manders of Series A was 70.2 per cent. black and 29.8 per cent.

non-black, and the average head color 68.2 black and 31.8 non-

black. These averages for Series B are: Body color, 89.7 black

and 10.3 non-black; head color, 87.7 black and 12.3 non-black.

No transformed individuals of Series C were obtained. Unfor-

tunately records of transformed individuals of Series A and B

were made of only 2 and 5 individuals, so these are scarcely more

than sample records, but they are probably fairly representative

of their respective series, and they clearly indicate that after,

as well as previous to, transformation a distinet difference in

pigmentation persists between the salamanders reared and al-

lowed to transform in the cave and those developing and trans-

forming in the light. A. M. Banta

CoLD SPRING HARBOR, N. Y.

REFERENCES

Fischel, A. ’96. Ueber Beeinflussung und Entwickelung des Pigments.

Archiv f. mikr. Anat. u. Entw., Bd. 47, pp. 719-734.

Flemming, W. ’97. Ueber den Einfluss des Lichts auf die Pigmentierung

der Salamanderlarve. Archiv f. mikr. Anat. u. Entw., Bd. 48, pp. 369-

374, also pp. 690-692, ;

Klincksieck, P., et Valette, T. 08. Code des Couleurs. Paris. 46 pp.

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THE

AMERICAN NATURALIST

Vout. XLVI May, 1912 No. 545

THE CONTINUOUS ORIGIN OF CERTAIN UNIT

CHARACTERS AS OBSERVED BY A

PALEONTOLOGIST!

DR. HENRY FAIRFIELD OSBORN

RESEARCH PROFESSOR OF ZOOLOGY, COLUMBIA UNIVERSITY, CURATOR EMERITUS

OF VERTEBRATE PALEONTOLOGY IN THE AMERICAN MUSEUM OF

NATURAL HISTORY, VERTEBRATE PALEONTOLOGIST

UNITED STATES GEOLOGICAL SURVEY

Il. EVIDENCES ror CONTINUITY

Abandoning the historical background, we come to our

own subject, the origin and establishment in continuity

of characters which when established exhibit many of the

distinctive features of unit characters, namely, segrega-

tion, stability, pure heredity, and possibly, although this

has not yet been demonstrated, dominance and recession

im successive generations.

In fifteen previous papers of the writer beginning in

18893 the observation is repeatedly made that all abso-

lutely new characters which we have traced to their very

beginnings in fossil mammals arise gradually and con-

tinuously. One by one these characters, which are inde-

pendently changing in many parts of the organism, at

the same time accumulate until they build up a degree of

change which paleontologists designate as a ‘‘mutation’’

* Osborn, H. F., ‘‘The Paleontological Evidence for the Transmission

of Acquired Characters,’? AMER. NaTuRALIST, Vol. XXIII, No. 271, July,

2399, pp. 561-566.

249

250 THE AMERICAN NATURALIST [Vov. XLVI

in the sense of Waagen, who proposed this inter-specific

term in 1869. Finally they reach a sufficiently impor-

tant phase to designate the stage as a species.”°

These new characters were first (1891) termed ‘‘defi-

nite variations’’; subsequently (1907)? the term ‘‘recti-

gradations’? was applied to them. Rectigradation is

merely a designation for the earliest discernible stages

of certain absolutely new characters. It involves no

opinion nor hypothesis as to genesis; it is a simple mat-

ter of observation. Referring to the figure (p. 274) of

the upper grinding teeth of the horse, the majority of

the fourteen characters have been observed to arise as

rectigradations.

Quite different is the allometron. This is a new desig-

nation for the continuous change of proportion in an ex-

isting character which may be expressed in differences

of measurement. Since 1902 and especially during the

past year the behavior of allometrons has been very

carefully investigated by myself and by my colleague,

Dr. W. K. Gregory.

REcTIGRADATION—a qualitative change, the genesis

of a new character.

ALLOMETRON =a quantitative change, the genesis

of new proportions in an ex-

isting character.

The distinction between a rectigradation and an allo-

metron is readily grasped: when the shadowy rudiment

of a cusp or of a horn first appears it is a rectigradation ;

when it takes on a rounded, oval or flattened form this

2 This sentence may be contrasted with that of Punnett (op. cit., p. 15):

‘í Speaking generally, species do not grade gradually from one to the other,

but the differences between them are sharp and specific. Whence comes

this prevalence of discontinuity if the process by which they have arisen is

one of accumulation of minute and almost imperceptible differences? Why

are not intermediates of all sorts more abundantly produced in nature than

is actually known to be the case???

H. F., ‘‘Evolution of Mammalian Molar Teeth to and from

the Triangular Type,’’ 8vo, Macmillan Company, September, 1907.

No. 545] ORIGIN OF UNIT CHARACTERS 251

change is an allometron. In mammals rectigradations

are comparatively few; allometrons comprise the vast

number of changes in the hard parts. In the origin of

cusp and horn rudiments rectigradations are parallel

(see Fig. 3), in the changing proportions of a skull

allometrons are divergent (Figs. 1, 3).

Granting, without at present considering the evidence,”®

that these rectigradations and allometrons arise con-

tinuously through entirely unknown laws, that they are

blastic or germinal characters, the question’ arises, do

they become separable as unit or alternating characters

in heredity.

In general, paleontology furnishes quite as strong

proof as Mendelism or experimental zoology as to the

individuality, separableness, and integrity of single char-

acters in evolution. But, whether both rectigradations

and allometrons are separable in heredity can only be

demonstrated through experiments on cross breeding or

hybridizing. |

The special object of this Harvey lecture is to show

that certain at least of the rectigradations and allome-

trons observed in mammals are separable in heredity,

that they split up into larger and smaller groups or

units, some into partially blending units, others into ab-

solutely distinct or non-blending unit; finally that at

least in the first cross they exhibit dominance. .

The very important remaining question whether, like

the quality of ‘‘tallness’’ or ‘‘shortness’’ in Mendel’s

classic experiments on the pea, these allometrons con-

tinue to split into dominants and recessives in later

crosses, has not been investigated but is probably ca-

pable of investigation in mammals which do not become

sterile in the first hybrid generation. _

Five examples of the continuous evolution of recti-

gradations and allometrons may be cited, namely: —

3 This evidence is for the first time fully presented in the writer’s mono-

graph on the ‘‘Titanotheres,’’ in preparation for the U. 8. Geological

ey. P

252 THE AMERICAN NATURALIST [Vor. XLVI

1. Skull and horns of titanotheres (Figs. 1, 3, 4).

2. The horns of cattle (Fig. 2).

3. The cranium of man (Fig. 1).

4. The skull of horses (Figs. 4, 5, 6, 7).

5. Teeth (Fig. 8).

One of the most salient examples of the genesis of

unit characters through continuity is that of the evolu-

tion of horns, i. e., of the osseous prominences on the

skull. Horns are now known definitely to be ‘‘unit char-

acters,’’ first through their sudden and complete disap-

pearance in the niata and polled breeds of cattle; second,

because they conform to the laws of sex-limited inherit-

ance. The question is, do horns originate continuously

or discontinuously ?

ance

Brach.

Mes, ol.

Fig. 1. CONTINUOUS ORIGIN OF ALLOMETRIC ‘“ UNIT CHARACTERS ” IN THE

CRANIUM (A) AND SKULL (B) oF MAN AND TITANOTHERES.

A, Man Brachycephaly Mesaticephaly Dolichocephaly

B, Titanotheres Brachycephaly Mesaticephaly Dolichocephaly

(Paleosyops) (Manteoceras) (Dolichorhinus)

1. Horns of Titanotheres

The titanotheres are an extinct family of quadrupeds

distantly related to the horses, tapirs and rhinoceroses,

No. 545] ORIGIN OF UNIT CHARACTERS 253

to the evolution of which the author has devoted twelve

years of investigation, assisted by Dr. W. K. Gregory.

As set forth in an earlier contribution?’ the genesis of

horns as rectigradations has been observed in four or

five distinct phyla of titanotheres. These phyla descend

independently from a single ancestor of remote geologic

age. Both in respect to new cusps on the teeth and new

horn rudiments on the skull there is observed what in

our ignorance may be called an ancestral predisposition

to the genesis of similar rectigradations. This predis-

position betrays the existence of law in the origin of cer-

tain new characters; it recalls a sagacious remark of

Darwin:

. . . The principle formerly alluded to under the term of analogical

variation has probably in these cases often come into play; that is, the

members of the same class, although only distantly allied, have in-

herited so much in common in their constitution, that they are apt to

vary under similar exciting causes in a similar manner; and this would

obviously aid in the acquirement through natural selection of parts or

organs, strikingly like each other, independently of their direct in-

heritance from a common progenitor.” :

Briefly, the origin of the titanothere horns is as fol-

lows: (a) from excessively rudimentary beginnings, 1. e.,

rectigradations, which can hardly be detected on the sur-

face of the skull; (b) there is some predetermined law

or similarity of potential which governs their first exist-

ence, because (c) the rudiments arise independently on

the same part of the skull in different phyla at different

periods of geologic time; (d) the horn rudiments evolve

continuously, and they gradually change in form (4. €.,

allometrons) ; (e) they finally become the dominant char-

acters of the skull, showing marked variations of form

in the two sexes; (f) they first arise in late or adult

stages of growth, but are pushed forward gradually into

™<<The Four Inseparable Factors of Evolution. Theory of their Dis-

tinct and Combined Action in the Transformation of the Titanotheres, an

Extinct Family of Hoofed Animals in the Order Perissodactyla,” Science,

N. S., Vol. XXVII, No. 682, January 24, 1908, pp. 148-150. —

”<<Origin of Species,’’ Vol. II, p. 221.

Fic. 2, CONTINUITY E ONTOGENESIS OF THR HORN AND Horn SHEATH IN CATTLE IN Seven STAGES, 1-7. After preparations by Mr, 8S.

EL Chubb in the aaa A i American Museum of Natural History

1. Adult, 9 years, completed osseous horn and horny sheath. 2. Yearling, 18 months, sea Wwe shifting of osseous horn to occiput. 38. Calf, 2 months,

continuous shifting of osseous horn to occiput. 4. Calf, 2 weeks, Roope shifting of osseous horn to occiput. 5. Fatal stage, 9th month, bony swell-

ing, and epidermal swelling pointed, 6. Fetal stage ?6-7th month, epidermal swelling, paren with pointed hair tuft. 7. Foetal stage, ?5th month,

epidermal swelling, covered with 40 scattered hairs

No. 545] ORIGIN OF UNIT CHARACTERS 255

earlier and earlier ontogenic stages until they appear to

arise prenatally.

In the titanotheres (Fig. 3) the bony swelling is seen

at the junction of the nasals and frontals (black sha-

ding), in dolichocephalic skulls it appears chiefly on the

nasals, in brachycephalic skulls chiefly on the frontals.

Its original low, rounded shape is like that seen in the

ontogeny of the horns in eattle.

2. Horns of Cattle

The phylogenesis of the horns in titanotheres (Fig.

3) is exactly similar to the ontogenesis of the horns in

Bovidae (Fig. 2), in which the dermal rudiments first ap-

pear soon after the complete formation of the bones of

the skull in the unborn young, and the osseous rudiments

appear as rounded protuberances in the 8th month.

In the ontogenesis of horns in cattle three distinct ele-

ments are involved: (a) a psychic predisposition to use

the horn, (b) a dermal thickening over the bony horn

swelling which in ontogeny precedes the swelling, (¢) ap-

pearance of the bony swelling itself.

The ontogenesis is observed to be accompanied by a

marked allometric change in the skull which shifts the

horn backward from the side of the cranium to the side

of the occiput by the obliteration of the parietal bones.

3. Cranium of Man.

A third instance of continuous development is that of

the form of the cranium in man (Fig. 1), an allometric

evolution, or change of proportion, which is of especial

Significance because, according to the unanimous testi-

mony of anthropologists,*! head form is the result of

very gradual change either in the elongate (dolicho-

cephalic) or broadened (brachycephalic) direction.

* Ripley, Wm. Z., ‘‘The Races of Europe, a Sociological seas ae

D. Appleton & Co., 1899, 624 pp:

256 THE AMERICAN NATURALIST [Vor: XLVI

The matter is directly pertinent to the present discus-

sion because ‘‘long heads’’ and ‘‘broad heads’’ are con-

tinuously crossing and we know what the direct and ulti-

mate effects of such crosses are. The evidence has im-

portant bearing also on the influence of selection, environ-

ment, and inheritance or the effects of use and disuse.

Determination of the proportions of the cranium or

the cephalic index is one of the standard tests or race;

it is an expression of the greatest breadth of the head

above the ears and the percentage of its greatest length

from the forehead (glabella) to back, the latter measure-

ment being taken as 100. Three types adopted by anthro-

pologists are:

Extreme Range

Brachycophali¢, 80.1 and Shove .sise-sessoeridiser ire 100-80

Mosocephabe, T9180 (oo oes Seas cases es tse eee 80-75

Detiehocepialis, Td aud below 6. a. 5s i ek wees 75-62

Among the present races of Europe the widest limits

of variation between brachycephaly and dolichocephaly

are in the averages between 73 and 87; individual ex-

tremes of 62 and 100 have, however, been observed.

These extremes in European head form do not coincide

either with geographic or political boundaries, but are

attributed to the entrance into Europe of brachycephalic

and dolichocephalice types which evolved in Asia. Simi-

larly among the aborigines in America the indices range

from a low dolichocephaly as among the Delaware, Pima

Indians, etc., to a decided brachycephaly as among the

Athabascan tribes in Panama, Peru, and other localities.

A significant fact in Europe is that dolichocephaly and

brachycephaly are extremely stable characteristics in

heredity. The significant fact in America is that through

a very long period of time the various races of Indians,

who are believed to have had originally a similar origin,

have acquired under conditions of geographic isolation

considerable diversity in the proportions of the head.

Similarly A. Keith?? from the present distribution of the

2 Keith, A., Journ. Royal Anthropological Institute, 1911. See Nature,

Vol. 88, No. 2195, November 23, 1911, p. 119.

No. 545] ORIGIN OF UNIT CHARACTERS 257

Negro tribes in equatorial Africa has reached the follow-

ing conclusions:

There has been free intermigration; in the course of their evolution,

the tendency of one tribe has been towards the accentuation of one set

of characters, of another towards another set. Thus the Dinka ac-

quire high stature and narrow heads; the typical Nigerians low stature

and narrow heads; the Basoko wide, short heads and low stature; the

Buruns wide heads and high stature. Interbreeding may have played

its part; but if it had played a great part we should have found

greater physical uniformity than there is. The influence of Arab blood

on these tribes has probably been exaggerated.

It appears that environment has not any direct in-

fluence on head form, but that geographical isolation

affords the several varieties of man as well as other

mammals a chance to develop their peculiar head charac-

ters. Elliot Smith states (letter, August 12, 1911):

In my opinion the conditions of dolichocephaly and brachycephaly

must have developed very slowly through exceedingly long periods of

time and in widely separated areas amidst widely different environ-

ments. Brachycephaly is especially distinctive of the Central Asian

high plateau populations, dolichocephaly of the littoral and plain-

dwelling peoples; but these “unit characters” are now so fixe that

environment is powerless to modify them in a thousand years or so.

...1 do not believe for a moment in Boas [that is, in Boas’s observa-

tions (1911) on the rapid influence of environment in modifying head

form].

Elliot Smith takes very strong ground as to the lack of

evidence that environment directly produces any modi-

fication of head form; he implies that such modification,

if natural, would only show itself after thousands of

years of residence; environment no doubt has indirect in-

fluence. Hrdlička, on the other hand, has obtained defi-

nite results in the influence of environment on the vault

and face form of the Eskimo;** it remains to be shown

how far these changes are ontogenic. The recent con-

clusions of Boas (1911)* that dolichocephaly and brachy-

2 Hrdlička, Ales, ‘‘Contribution to the Anthopology of Central and

Smith Sound Eskimo,’’ Anthr. Paper Am. M. N. H., V, Pt. TI, 1910, p. 214.

“ Boas, Franz, ‘The Mind of Primitive Man,’’ 8vo, Macmillan Com-

pany, New York, 1911, 924 pp.

258 THE AMERICAN NATURALIST [Vou XLVI

o>.

P H M

Fig. 3. ue AND ALLOMETRONS IN TITANOTHERES, Continuity

in pa Se oe a seous horns in titanotheres. P =ł2d lower gapen

H= of na and — (shaded) showing osseous horn; S = S;

M= ae i a i bon

nope lay a oo (dolichocephalic) titanothere.

, a

Il. Paleosyops, a broad-headed (brachycephalic) titanothere. |

I. Eotitanops, an ancestral (mesaticephalic) titanothere.

II-V belong A four eperen phyla which Reon in their allometric

evolution of head (8) d foot si een on (M) but give rise to independe:

pans ae e pong the o

us horn

usps on Pt premolar teeth (P) and of

rudiments (H) on the seat

No. 545] ORIGIN OF UNIT CHARACTERS 259

cephaly are congenitally altered by environment in the

first generation are modified by his statement that this

action in bringing diverse head forms together would not

go so far as to establish a uniform general type.

No anthropologist has offered any satisfactory expla-

nation as to the adaptive significance of dolichocephaly

or brachycephaly. It is well known that these differences

of head form are not associated with intellectual ability

or mental aptitude. Boas writes (April 8, 1911):

So far the matter is very perplexing to me. I feel, however, very

strongly with you that changes in type are very liable to be progres-

sive in definite directions. . . . To my mind it seems no more diffieult

to assume that this predetermined direction should continue from

generation to generation than to make the much more difficult assump-

tion that notwithstanding. all internal changes the egg-cell of one

generation should be absolutely identical with that of the preceding

generation.

Apart from the disputed question of the direct influence

of environment and of human selection there is absolute

unanimity of evidence and of opinion on the one point

essential to the present discussion, namely, as to the con-

tinuity of allometric variation which establishes different

extremes of head form under conditions of geographic

isolation. ;

Granted that these extremes evolve continuously, do

they become discontinuous in heredity? |

One of the general results of crossing long-headed and

narrow-faced types with broad-headed and broad-faced

types is what is known as disharmonic heredity, namely,

that condition in which the face and cranium do not hold

together, but broad faces may couple with long skulls, or

vice versa (Boas, 1903).*° Boas concludes that there can

be no question that the mixture of a long-headed and of

a short-headed race may lead to disharmonism, one race

contributing head form, the other facial expression.

As to stability or segregation in heredity the latest

3 Boas, Franz, ‘‘ Heredity in Head Form,’’ Amer. Anthropologist, Vol.

5, No. 3, July-September, 1903, pp. 530-538.

260 THE AMERICAN NATURALIST [Vou XLVI

opinions of Boas, Elliot Smith and Hrdlicka have been

sought. Boas is one of the most positive as to the hered-

itary stability of head form. He observes (1911, pp.

7-9):

Among European peoples head proportions are considered among

the most stable and permanent of all characteristics. In intermarriage

of “ dolichocephalice ” and “ brachyeephalic ” individuals the children

do not form a blend between their parents but inherit either the

dolichocephalie or brachyeephalie head form. Head form thus con-

` stitutes a case of almost typical alternating heredity (p. 55). No evi-

dence has been obtained, however, to show that either brachyeephaly

or dolichoecephaly is dominant. Children exhibit one head form or the

other, and the cephalie index or ratio of breadth to length undergoes

only slight alteration during growth, or ontogeny.

Elliot Smith (letter of August 12, 1911) is ‘‘firmly

convinced that the form of cranium, orbits, nose, jaws,

limb bones, etc., in the ‘Armenoid’ and ‘Proto-Egyptian’

series are very stable or even fixed ‘unit characters’

which do not really blend, but that certain elements of

mosaic assemblage of characters pe be grafted on to

others belonging to the other race.’

Opinions as to Blending.—It will be noted that Boas

(1895) admits a certain blending of head form in crosses.

Hrdlička (letter, November 1, 1911) speaks even more

guardedly as to the hereditary stability of head form.

He says:

As to the head form constituting a “ unit character ” which does not

blend in intermixture, I am not able to give a conelusive opinion, but

my experience and other considerations lead me to be very skeptical

that such is the case to any great extent. The subject is a very com-

plex one and requires considerable direct investigation in different lo-

calities and with different peoples before the exact truth can be known.

. As to the statement that long or broad head form is a stable or

unit character not blending in intermixture, I think that only the first

part of the proposition may be held as fairly settled. But even then I

should change the word “stable” to “ persistent,’ and qualify the

phrase by adding “under no greatly differing and lasting environ-

mental conditions.”

That prolonged interbreeding or intermixture tends

to break down the stability of hereditary head form is

No. 545] ORIGIN OF UNIT CHARACTERS 261

indicated by Boas, Elliot Smith, and Ripley, as well as

by Hrdlicka, as quoted above. Thus Ripley (1899), p.

55) observes: —

The plotting of cephalic indices on a map of Europe shows that

there is a uniform gradation of head form from several specifie centers

of distribution outward.

In Italy over 300,000 individuals taken from every

little hamlet have been measured. In the extreme south

we find the dolichocephalic head form of the typical —

Mediterranean race; the type changes gradually as we

go north until in Piedmont we find an extreme of brachy-

Brontother.™

a Eohippus

Fig. 4. CONTINUOUS ORIGIN or ALLOMETRIC “ UNIT CHARACTERS ” IN THE

SKULL OF VARIOUS UNGULATES.

D Dolichocephaly, Opisthopic : Pr

(Titanotheres) (Equines).

In the ancestral Eotitanops and Eohippus the facio-cranial index is very

similar. In the descendants of these Is, as i ed by the dotted lines,

the facio-cranial indices are widely divergent; in the Titanotheres (Bronto- —

therium) the cranium is elongated; in the horses (Equus) the face is elongated.

262 THE AMERICAN NATURALIST [Vou. XLVI

‘cephaly of the Alpine type, recalling the broad-headed

Asiatic type of skull. Thus (Ripley, p. 56) ‘‘pure phys-

ical types come in contact and this means ultimately the

extinction of extremes.” Applying these principles to

the present case, it implies the ultimate blending of the

long and the narrow heads and the substitution of one

of medium breadth.

Elliot Smith also (letter, August 12, 1911) implies a

gradual modification or blending of head form through

prolonged intermixture. He observes:

Egypt does not give a clear answer to your queries because her ex-

ceedingly dolichocephalie brown race [related to the Mediterranean

race of southern Europe] underwent a double admixture (cirea

3,000 3.c.) with moderately brachyeephalie “ Armenoids” from Asia

and dolichocephalie Negroes from Africa. The Mediterranean Egyp-

tians are on the whole a little broader-headed than they were 6,000

years ago, and this may be due in part to a slow development toward

mesaticephaly; but it is mainly the result of an admixture with alien

bracephalies and mesaticephalics. There is an unquestionable tendency

toward the elimination of the extremes of narrowheadedness and

broadheadedness.

Hrdlička (letter, December 5, 1911) observes:

As to the effect of the mixture of brachycephalic and dolichocephalic

individuals or peoples, I am led to believe that there is in the results

of such mixtures a large percentage of more or less intimate “blend ”

of the two forms, for such a condition is indicated by the curves of

distribution of the cephalic index among such national conglomerates

as the French, Germans, different tribes of the American Indians, ete.

These curves, if sufficiently large numbers of individuals have been ex-

amined, all approach more or less the ideal camel-back curve. If no

“blend” existed, we should be bound to get the double or dromedary-

back eurve. Of course the effects of mixture and the effects of environ-

ment are with our present means often impossible of separation, they

often obseure each other. Yet the indications are that there is gener-

ally a considerable amount of more or less mixture of the many ele-

mentary constituents of the hereditary characters [known collectively

as] dolichocephaly and brachycephaly.. With this there coexists doubt-

less some tendency toward a differentiation into the two opposite forms

of the head.

Thus in human head form we have proofs of continuous

No. 545] ORIGIN OF UNIT CHARACTERS 263

allometric change strictly comparable to that which oc-

curs in the crania of lower mammals, especially as ob-

served in the horses and titanotheres; the extremes are

produced in so-called pure human races under geographic

isolation; when these pure races are brought together

there arises disharmonism or alternating heredity or

both. Neither the dolichocephalic nor brachycephalic

type is as yet known to be dominant; opinion is divided

as to whether in the first cross the heredity is pure or

whether there may be a tendency to produce an inter-

mediate form; opinion is nearly unanimous that pro-

longed interbreeding produces blends.’

4. Skull of Titanotheres.

The continuity of allometric evolution in the skull of

the titanotheres (Fig. 4) has been the subject of pro-

longed investigation by the writer, assisted by Dr. W.E

Gregory, involving thousands of measurements, many of

which belong in strictly successive phyletic series.

Allometry (i. e., the measurement of allometrons) here

applies to the skull as a whole. We secure the cephalic

index by dividing the breadth across the cheek arches by

the total basilar length of the skull. There are also other

indices, such as the facio-cranial, in which we measure

continuous trends of allometric change; brachycephaly

and dolichocephaly arise independently in four different

phyla or lines of descent. The adaptive significance is

sometimes apparent, sometimes obscure. As shown in

Fig. 1 the titanotheres, like man, exhibit facial abbrevia-

tion and cranial elongation (postopic dolichocephaly) in

contrast with the facial elongation (proopice dolicho-

cephaly) of the horses. These phenomena are similar

to those of cytocephaly, or the bending down of the face

upon the base of the cranium as observed in the reindeer

T. H. Morgan observes that a blend may occur in the first generation,

F,, even where perfect segregation occurs in F.. The results of crossing

the equine skull as described below indicate a tendency to blend in the

first cross.

264 THE AMERICAN NATURALIST [Vowu. XLVI

(Rangifer) and the hartebeest (Bubalis). Cytocephaly

is an ontogenetic and phylogenetic new character, aris-

ing or developing continuously.

As in the case of the human skull; the causes of these

profound changes in head form are entirely unknown;

the mechanically adaptive significance is sometimes ap-

parent, sometimes obscure. The evidence is strengthened

by the examination of the titanotheres that human selec-

tion has little or no influence on human cranial form.

The great point to emphasize is that this allometric evo-

lution in the skull and all parts of the skeleton is the pre-

vailing phenomenon of change in the skeleton of mammals.

It is constantly in progress and is universally, so far as

we can observe, a continuous process. As displayed in the

four phyla of titanotheres (Fig. 3), the elongation or

broadening of the foot bones proceed independently and

are divergent, while in the same mammals the rectigra-

dations exhibited in the rise of similar cusplets on the

teeth and similar horn rudiments on the face are parallel;

in the former ease no ancestral predisposition seems to

be operating, in the latter case ancestral predisposition

certainly seems to operate; this is why the internal laws

controlling the origin of new allometrons and of new

rectigradations and allometrons are regarded as essen-

tially dissimilar.

Paleontological analysis of these rectigradations and

allometrons even unaided by experimental heredity re-

veals the essential feature of the ‘‘unit character’’ prin-

ciple, namely, that what we are observing is. an incredibly

large number of unit elements each of which enjoys a

certain independence of evolution at the same time that

each unit is adaptively correlated with all the others. For

example, in the upper and lower grinding teeth of horses

alone there are 504 cusp units, each of which has an inde-

pendent origin and development; at the same time each

cusp is more or less distinctly correlated in form with

the all-pervading dolichocephaly or brachycephaly of the

skull; in fact, from certain single cusps of the teeth we

No. 545] ORIGIN OF UNIT CHARACTERS 265

can often determine whether the animal is brachycephalic

or dolichocephalic

N:P,

Monophyletic

-= _

opera

MULE

arta wes trne NAg

Polyphyletic RSE

IMPERFECT BLENDING OF

CROSS-BREEDING AND

HE FacraAL BONES IN ASS (MALE),

5. ALLOMETRIC “ UNIT

CHARACTERS ” OF TH Horse (FEMALE) AND

MULE.

Bones of the side of the face, Ass.

Bones of the side of the face, Mule.

Bones of the-side of the face, Horse.

The horse is oo polyphyletic,

arrow points to C, a distinct bum

ass, “ihe

the ass is probably sonm e

k point at ‘wich feast De of

F.P

oO. The

rse and mule, not observed in the

the nasals is i L =la

266 THE AMERICAN NATURALIST [Vou. XLVI

The question arises as a result of the somewhat con-

flicting evidence as to the crossing of brachycephals and

dolichocephals in man, what happens when we cross two

phyla of lower mammals which have been diverging along

separate allometric lines and in the meantime have ac-

quired a greater or less number of new characters which

when sufficiently developed attain specific rank.

The answer is given very distinctly in the cross between

the dolichocephalic horse (E. caballus).and the meso-

cephalic ass (E. asinus). Here we learn again that pro-

found differences have been established through con-

tinuity and that we are enabled to split up these differ-

ences into distinct or partially blending units through

cross breeding.

5. Blended or Alternating Heredity in Horses.**

So high an authority as J. Cossar Ewart (1903) has

sustained the prevailing view that in the mule there is

generally an imperfect blending of the characters of the

immediate parents; the same author, however, notes that

mules occasionally serve as examples of unit or exclusive

inheritance. He cites two cases: (1) a mule out of a

well-bred, flea-bitten New Forest pony closely resembles

her sire, the ass; (2) a ‘‘calico’’ mule, on the other hand,

is surprisingly like his dam, an Indian ‘‘painted’’ pony.

This painted mule demonstrates that the ass is not always

more prepotent than the horse. From this author’s very

extensive breeding experiments the following conclusions

are reached: the less fixed or racially valuable characters

* The writer is indebted to Mr. S. H. Chubb, Mrs. Johanna Kroeber

Mosenthal and to ee W. F Gregory for many of the observations and all

of the measurem ich this comparison is based. The materials

studied are three pe of fe ass (¢ E. asinus), ten of the horse (9 E.

caballus), and four of the mule, all adult with teeth in approximately the

same stage of we

3 The most resent (1912) opinion of Ewart is much more gues as to-

the operation of Mendel’s law in pure breeding strains of

horses. See

‘t Eugenics and the Breeding of Light Horses,’’ The Field, kia 10.

1912, pp. 288, 289.

No. 545] ORIGIN OF UNIT CHARACTERS 267

of zebras either blend with or are dominated by the cor-

responding characters in their horse and ass mates,

Thus, as influencing dominance or prepotency, the value

which a character has attained in the past struggle for

existence seems to count for something. In zebras and

in horses certain physical and mental traits are more

highly heritable than others. Among the characteristics

which are often handed down unblended in zebra-horse

hybrids and to a less extent in zebra-ass hybrids are the

size of the ears, the form of the hoofs, the massiveness of

the jaws; while among psychic characters are transmitted

the extreme caution, the wonderful alertness and

quickness.

The new results brought forward in this Harvey lecture

from the comparison of the skull and teeth of the horse,

ass and mule on the whole strengthen the theory of unit in-

heritance both in rectigradations and inallometrons. The

measure of unit character inheritance as contrasted with

blended inheritance is very precisely brought out in the

detailed study of the twenty-two characters which are

examined below. Before discussing these characters in

detail it is interesting to point out that the ancestors of

the horse and the ass have probably been separated for

at least 500,000 years. In the meantime the horse has

become extremely dolichocephalic, the ass has remained

comparatively mesocephalic; the horse has a relatively

long, the ass a relatively short face; the horse has highly

complex, the ass has somewhat simpler grinding teeth;

the horse exhibits advanced adaptation to grazing habits

and has become habituated to a forest and plains life in

comparatively fertile countries, while the wild ass is by

preference a browsing animal, finding its food in exces-

sively arid countries where there is a marked dearth of

water and water courses. The physical and psychical

divergences in these two animals have developed over an

enormously long period of time. Every single tooth and

bone of the horse and ass show differences both in recti-

gradation and in allometric evolution.

268 THE AMERICAN NATURALIST [Vor. XLVI

One feature which tends to make the results of the

cross less clear and distinctive than they are is that

while the ass is monophyletic (being descended with

ASS

MULE

HORSE |

Fic, 6. CROSS-BREEDING AND IMPERFECT BLENDING OF SUB-ALLOMETRIC “ UNIT

CHARACTERS ” OF THE NASAL BONES IN ASS (MALE) AND HORSE (FEMALE).

view of nasals and naso-frontal suture, Ass.

Top view of nasals and naso-frontal suture, Mule.

Top view of nasals and naso-frontal suture, Horse.

8 = point of section shown in Figs. 3 and 5

No. 545] ORIGIN OF UNIT CHARACTERS 269

modification from the wild E. asinus of northern Africa),

the domestic horse is not a pure strain and is certainly

polyphyletic, having in its blood that of several races,

such as the Arab and the Forest or Norse horse, animals

which have specific distinctness although they still inter-

breed.®® To this mixed strain or polyphyletic heredity of

the horse, are probably attributable many of the allometric

variations in the bones of the skull and in the enamel

pattern of the teeth of the mule in some of which we

observe a nearer approach to the ass type than in others.

If we could cross the ass with a pure horse race like the

Steppe or Prjevalsky horse we should probably obtain

more precise results. Another disturbing feature in the

comparisons and indices given below is that we do not

know the exact structure of the skull of either of the

parents from which the mule skulls examined were

derived.

Despite these sources of fluctuation and of error, the

general results obtained are fairly positive and definite.

The first point of interest in the segregation of unit

characters in the mule is that connected with the three

germinal layers, namely, the epiblast, mesoblast and hypo-

blast. All the characters of epiblastic origin appear to be

derived from the sire, namely, the epidermal derivatives,

the distribution of the hair, especially in the mane and

tail, the hoofs, ete., are those of the ass, although the color

pattern, as in the ‘‘calico’’? mules described by Ewart,

may be derived from the mare. The nervous system and

psychie tendencies, all of epiblastic origin are also

derived from the ass, including minor psychic character-

isties, such as aversion to water. Still more striking,

perhaps, is the fact that the enamel pattern of the grind-

ing teeth, again of epiblastic origin, is mainly that of the

ass, although, as shown below, there are some inter-

mediate and some distinctive horse-like characters in the

* There are many absolute charactérs which separate the Arab from the _

Norse horse, among them the invariable presence of one less vertebra in the ee ae

lumbar region of the back. ee

270 THE AMERICAN NATURALIST [Vow XLVI

teeth of the mule; this may be partly connected with the

mesoblastic derivation of the dentine of the teeth.

Monophyletic

MULE

Polyphyletic

CROSS-BREEDING AND raglan SEPARATION OF ALLOMETRIC “ SUB-

Fig. 7.

— Cnanscrres ” OF THE NASAL BONES IN ASS (MALE), HorSE (FEMALE)

Mid-section of nasal bones, Ass.

Mid-section of nasal bones, Mule.

Mid-section of nasal bones; Horse.

Y1, Y? = variations in the depth of pa — in the mule. V1, V? = varia-

tions ta the depth of the nasals in the ho

Mesoblastic derivatives, on the other hand, are divided

between the sire and dam, the skeleton and limbs of the

mule being mainly proportioned as in the ass, while the

skull of the mule, as we shall see, is almost purely that

of the horse.

Blended and Pure Inheritance in the Bones of the Face

Blending—A comparison of the bones of the side of

No. 545] ORIGIN OF UNIT CHARACTERS Zil

the facial or preorbital region shows intermediate or

partly blended form and proportions both of the nasals,

premazxillaries, frontals, and lachrymals, in which, how-

ever, the mule approaches E. caballus rather than E.

asinus. Attention may be called to some of the details

of the comparison: (1) Suture between the nasals and

premaxillaries: in E. asinus short and elevated, in the

mule intermediate but more like the horse; in the horse

elongated and depressed (see Fig. 5). (2) Naso-frontal

suture on the top of the skull: in the ass straight or trans-

verse; in the mule incurved, more like the horse than the

ass; in the horse arched or incurved (see Fig. 6). (3)

Depth and convexity of the nasals: in the ass shallow and

flattened; in the mule deeper, more like the horse; in the

horse highly arched. (4) Bump or convexity on posterior

third nasals: in the ass very slight; in the mule moderate,

more like the horse than the ass; in the horse strong (see

Fi. y).

The same tendency in the mule to exhibit a slight de-

parture from the horse toward the ass type is shown in

the outlines of the bones of the face (Figs. 3, 4, 5). Com-

paring step by step the premaxillaries, maxillaries,

nasals, and lachrymals, while the proportions and the

sutural outlines are mainly those of the horse, there is a

more or less distinct blending, or intermediate character

in the direction of the ass; see especially the naso-pre-

maxillary suture, the degree to which the nasals extend

downward on the sides of the face to join the maxillaries,

and the degree to which the nasals extend on the sides of

the face to join the maxillaries. In this naso-maxillary

junction certain horses approach the ass type. The char-

acteristic bump on top of the nasals of the horse is trans-

mitted to the mule, and the highly characteristic trans-

verse suture between the frontals and the nasals, as seen

from the top (Fig. 4), is rather that of the horse than of

the mule.

Non-blending.—More definite results are shown in the

heredity of the indices or ratios between the various por-

1. Cephalic Index:

272 THE AMERICAN NATURALIST [Vowu. XLVI

tions of the skull and of the teeth; these indices are ex-

tremely constant allometric specific characters, they are

independent of size. For example, the indices of a

diminutive pony and of a giant percheron would be the

same. Similarly the indices of a diminutive donkey and

of a very large ass would be the same.

The index is the best and most exact form of express-

ing mathematically the profound differences between the

skull of the horse and that of the ass. Indices have the

value of specific characters; they are of especial signifi-

cance in the present discussion in comparison with those

in the face, cranium and palate of man and of the titano-

theres above considered.

Chief among the allometric differences are the follow-

ing: (1) Inits proportions the ass has a relatively shorter

space between its grinding and its cutting teeth, the

bit-opening; this is correlated with the fact (2) that the

ass has a relatively broader and shorter skull than the

horse; also with (3) the fact that the ass has a relatively

longer cranium (postorbital space) and shorter face

(preorbital space) than the horse; (5) the ass also has

relatively broader grinding teeth correlated with the

broader skull; (6) correlated also with its less elongate

skull the ass has a relatively rounder orbit than the

horse, 7. e., the vertical and horizontal diameters are more

nearly equal. (7) A very distinctive feature is the angle

which the occiput makes with the skull; this is one of the

marked specific features of the ass.

NoN-BLENDING OR PURE INHERITANCE INDICES IN THE SKULL

Width of skull X 100 Ass 46,9-49.9

Basilar len gth

Diast

2. Diastema Index: echoed i at ee

Basilar length of skull

Length i

3. Cranio-facial Index: mgri of crantem X 190

Length of face

Mule 40.8—43.6

Horse 40.4—44.1

Ass 15.6-17.6

Mule 18.6-21.9

Horse 18.2—23.0

Ass 56.3—61.0

Mule 48.9-51.8

Horse 45.3—49.9

No. 545] ORIGIN OF UNIT CHARACTERS 273

Vertical diameter of orbit X 100 Ass 96.0-104.2

> Mule 78.7— 99.1

Horse 84.2— 93.5

Orbital Index :

: Ass 15.2-16.0

Transverse diameter of M? X 100

Molar Index: iia ee ~ sage Mule 14.2-14.9

otal length of entire molar series Horse 13.9-15.7

Angle between vertex of skull and line Ass 52.5-60.0

connecting most posterior points of Mule 61.0-66.5

Occiput-vertex occipital crest with condyles, Horse 64.0-76.5

angle Index: i. e., nearly all horse skulls will stand

when set up on end, some mule skulls

(one out of four), no ass skulls

Distance from palate to posterior end of Ass 93.8-111.7

Vomer Index: vomer X 100 Mule 95.5-110.3

Distance from vomer to foramen magnum Horse 72.8- 86.5

The above indices prove that the mule has not a primi-

tive skull like that of the ass on a larger scale, but has

essentially the skull of the horse, namely :

1. A long, narrow skull, as a whole.

2. A long diastema, or space for the bit.

3. A short cranium and a long face.

4. A long, oval orbit.

5. A relatively elongate and narrow set of grinding

teeth.

6. A vertically placed occiput.

The one character in which the mule resembles the ass

is the elongation of the vomer behind the bony palate. It

should, however, be distinctly stated that while the indices

given above are those which probably prevail in mules,

there are overlaps in the (4) orbital index and (6) occi-

put-vertex angle. Thus in one mule the orbital index

agrees with that of one of the asses.

Enamel Pattern of Grinding Teeth.—In the marvel-

ously complex pattern of the grinding teeth the ‘‘unit

character” transmission is quite sharply defined in the

majority of characters, while intermediate or slightly

blended in the minority. In general in the grinding teeth

of the ass the main enamel folds are less complicated

274 THE AMERICAN NATURALIST [Vou. XLVI

than in the horse and there are fewer secondary or sub-

sidiary folds; the ass especially lacks the ‘‘pli caballin’’

(fold 5) which is usually a very pronounced specific

character of the horse. The mule shows a very slight

indication of this fold and thus resembles the ass. The

folds: (1,3,4) ASS

folds: (1,2,3,4) MULE

folds: (1,2,3; 4,556) HORSE

ROSS- PRORDING AND SEPARATION OF espadana aes DISTINCT

N THE ENAMEL FOLDINGS AND PATTERN OF THE GRINDING

A o

OF Section through the crown a the third

eau ainia (p* or 4th premolar) ass (male), horse (female) and mule.

No. 545] ORIGIN OF UNIT CHARACTERS 275

subsidiary folds in the grinders of the mule are simpler

than those in either the horse or the ass. The grinder

of the mule would be pronounced by any systematist not

knowing its mixed parentage to belong to the ass rather

than to the horse, especially in the absence of the ‘‘pli

eaballin’’ (fold 5), in the form of the hypostyle (hs, fold

6), in the smaller size of the protocone (pr), the large

size of which is very distinctive of the horse. A very

detailed study and comparison of the grinding teeth in

the horse, ass and mule made by an independent ob-

server, Dr. W. K. Gregory, gives the following result:

Secondary folds: protocone, pr.

paracone, pa

metacone, me

hypocone hy.

protoconule pl.

metaconule ml.

Secondary elements : parastyle, ps.

ostyle, ms

hypostyle, hs

Primary elements:

fold (ie es Horeca. <2 Male . 3.55% Ass

Told 2 Ue ees Se cea Mule.

fold: 3 i428; Horse =: Males. Ass

Tod é eo oe Horie 3005), jo hd eres ASS

Tod Oo es Hor

UNIT CHARACTERS IN GRINDING TOOTH OF THE MULE

Distinctly ass-like: 5 character

say ‘ tal peculiar to ass.

Less distinctly ass-like: 6 characters

Common to horse and ass: 5 characters 5 common to horse and ass.

Distinctly horse-like: 2 characters a samdir to horse.

Less distinctly horse-like: 4 characters } r

It would be especially desirable to compare the same

enamel characters in the hinny, which is a cross be-

tween the male horse and the female ass, in which it is

well known that the E. caballus and E. asinus char-

acters are differently distributed.

Summary.—Out of the 28 characters examined in the

skull and teeth of the mule, 18 are distinctly derived

either from one parent or the other with very slight, if

any, tendency to blend, 10 characters show a distinct

tendency to blend.

276 THE AMERICAN NATURALIST [Vou. XLVI

This evidence, in the opinion of T. H. Morgan, is in

entire accord with the modern views of hybridizing;

parallels for each instance can be given; without the

evidence of the F, generation no conclusions adverse

to Mendelism are possible. Even the differences in re-

ciprocal crosses, i. e., horse ĝ, ass 9, can be understood

if sex-limited inheritance prevails in some characters.

To confirm the results suggested by this F, genera-

tion of the horse and ass, it would be necessary to inter-

breed races of mammals to F, or F, to ascertain whether

these characters of the skull and teeth really mendelize.

It is doubtful whether such specific types of mammals can

be found, and whether sufficient stability of character

exists in artificially produced races.

Sufficient evidence has been adduced, however, to show

that a very large number of characters which are to the

best of our knowledge of continuous origin, present all

the appearance of ‘‘unit characters?’ in the first genera-

tion of hybrids.

II. Conciuston

Is it not demonstrated by this comparison of results

obtained in such widely different families as the Bovide,

Hominide, Titanotheriide and Equide that discontinu-

ity in heredity affords no evidence whatever of pages

tinuity of origin?

As to origin, it is demonstrated in paleontology that

certain new characters arise by excessively fine grada-

tions which appear to be continuous. If discontinuities

or steps exist they are so minute in these characters as to

be indistinguishable from those fluctuations around a

mean which seem to accompany vey stage in the evolu-

tion and ontogeny of unit ch

IV. THEORETICAL CONSIDERATIONS

After having attempted to confine our discourse to

facts it is a pleasure to relax into the more genial at-

mosphere of opinion and hypothesis.

No. 545] ORIGIN OF UNIT CHARACTERS Zit

The principle of pre-determination, which results in |

the appearance of rectigradations, involves us in radical

opposition to the opinions of the Bateson-DeVries-

Johannsen school. There is an unknown law operating

in the genesis of many new characters and entirely dis-

tinct from any form of indirect law which would spring

out of the selection of the lawful from the lawless. This

great wedge between the ‘‘law’’ and the ‘‘chance’’ con-

ception, which since the time of Aristotle has divided

biologists into two schools of opinion, is driven home by

modern paleontology.

Paleontology, in the origin of certain new characters

at least, compels us to support the truly marvelous phil-

osophie opinion of Aristotle, namely:

Nature produces those things which, being continu-

ously moved by a certain principle contained in them-

selves arrive at a certain end.

While recent biology has tended to sharply distin-

guish bodily from germinal processes and to place chief

emphasis upon evolution appearing to originate in the

germ cells, we must not forget that for a hundred million

years or more,,or from the beginning of life, the germ

plasm has had both its immediate somatic and its more

remote environmental influences. Because the grosser

form of Lamarckian interpretation of transmission of

acquired characters has apparently been disproved, we |

must not exclude the possibility of the discovery of finer,

more subtle relations between the germ plasm and the

soma, as well as the external environment. There are

several phenomena, which have been observed only in

paleontology, that afford evidence for the existence of

such a nexus; because it appears that certain germinal

predispositions to the formation of new characters, con-

nected, as Darwin conjectured, in some way with com-

munity of descent, are only evoked under certain so-

matic and environmental conditions, without which they

appear to lie in a latent, potential or unexpressed form.

All that we may be able to observe are the modes of

278 THE AMERICAN NATURALIST [Vou. XLVI

operation in the genesis of new characters and in the

adaptive trends of allometric evolution without gaining

any intimate knowledge of what the causes are. This

thought may be made clear through the following anal-

ogy. Naturalists observed and measured the rise and

fall of the tides long before Newton discovered the law

of gravitation; we biologists are simply observing and

measuring the rise and fall of the greater currents of

life. It is possible that a second Darwin may discover

a law underlying these phenomena bearing the same re-

lation to biology that the law of gravity has to physics,

or it is possible that such law may remain forever un-

discovered. Another analogy may make our meaning

still clearer. Ontogenesis is inconceivable, for example,

the transformation of an infinitesimal speck of fertilized

matter into a gigantic whale or dinosaur; we may watch

every step in the process of embryogeny and ontogeny

without becoming any wiser; in a similar sense phylo-

genesis may be inconceivable or beyond the power of

human discovery. Not that we accept Driesch’s idea of

an entelechy or Bergson’s metaphysical projection of

the organic world as an individual, because we must be-

lieve that the entire secret of evolution and adaptation

-is wrapped up in the interactions of the four relations

that we know of, namely, the germinal, the bodily, the

environmental, with selection operating incessantly as

the arbiter of fitness in the results produced. In the

meantime*” we paleontologists have made what appears

to be a substantial advance in finding ever more con-

vineing evidence of the operation of law rather than of

chance in the origin and development of new characters,

something which Darwin had clearly in mind.*!

* Osborn, Hick. “Ths peta Mechanism and the Search for the

Unknown Factors of Evolution,’’ Biol. Lect. Marine Biol. Lab., 1894,

AMER. N ON Vol. XXXIX, No. 341, May, 1895, pp. 418—439.

“1 Darw. has.: ‘‘I have spoken of vyarlations sometimes as if they

were due i dha This is a wholly incorrect expression; it merely serves

to acknowledge plainly our ignorance of the cause of each particular

variation. ’’

THE BIOLOGY OF THE CRAYFISH

F. E. CHIDESTER

RUTGERS COLLEGE

INTRODUCTION

Tue first reference to the crayfish in scientific litera-

ture is in Aristotle’s ‘‘History of Animals,’’? where he

speaks of the ‘‘small Astaci which breed in the rivers.’’

Aristotle and the older naturalists used the term Astaci

to include both the crayfish and the lobster.

Faxon divides the crayfish into two great groups (24):

One, restricted to the northern hemisphere, is found

in Europe, Asia and North America. The other is found

in the southern hemisphere, in Australia, Tasmania, New

Zealand, Fiji Islands, Madagascar and South America.

The islands now inhabited by crayfish, such as Eng-

land, Japan and Cuba, were probably once connected

with the mainland.

In speaking of the distribution of the crayfishes, Faxon

Says:

The northern family of crayfishes contains two genera, Astacus and

Cambarus. These groups occupy distinct geographical areas. The

genus Astacus is found in the old world in Europe and western Asia

as far as the Aral and Caspian Seas, and in America in the region west

of the Rocky Mountains, draining into the Great Salt Lake and the

Pacifie Ocean. It is thus seen to occupy the western sides of the two

northern continents. Cambarus is found in North America east of the

Rocky Mountains, in the region which is bounded on the north by Lake

Winnipeg and New Brunswick, and on the south by Guatemala and

Cuba. Crayfish thus are discontinuous genera, that is, genera which

now occupy widely separated areas, such as Astacus in Europe and

Pacifie North America, but which once ranged over the intervening

ranges as well.

It is comparatively easy to distinguish the common

Cambarus from the Astacus of Europe and western

America. Members of the genus Astacus have eighteen

279

280 THE AMERICAN NATURALIST [Von. XLVI

gills, while those of the genus Cambarus have but seven-

teen. The female of the genus Cambarus has a false

pouch, the annulus ventralis, which serves as a sperm re-

ceptable, while in Astacus the sperm is deposited on the

posterior part of the thorax in spermatophores.

Dr. A. E. Ortmann has made most careful studies of

the distribution of the crayfish. References to his papers

will be found in my bibliography. Dr. Ortmann writes

me that there are in the United States and Central Amer-

ica, 74 species of Cambarus and 5 of Potambius (Asta-

cus). Inthe United States excluding Mexico, Guatemala

and Cuba, there are 64 species of Cambarus and 5 of

Potambius.

The European word ‘‘crayfish’’ is used by teachers of

zoology, probably because of Huxley’s classic, ‘‘The

Crayfish. ”’

Ortmann found (38) that not only was ‘‘crawfish”’

used by Say, 1817, earlier than ‘‘crayfish’’ by Huxley,

1880, but that in this country ‘‘crawfish’”’ is the popular

name.

‘‘Crayfish,’’ ‘‘crawfish,’’ or, as it is sometimes incor-

rectly called, ‘‘erab,’’ come from the same root, Old Ger-

man, ‘‘ Krebis,’’ from which are derived, on the one hand,

the modern German ‘‘ Krebs ”’ and the English ‘‘ crab ’’;

on the other hand the French ‘‘ ecrevisse,’’ the English

and the American ‘‘ crayfish.’’

The crayfish on which my own observations have been

centered belong to the species Cambarus bartonius bar-

toni, the only species which has migrated into New Eng-

land.

My work was carried on in the field and in the labora-

tory continuously for nine months. In the field I have

watched the activities of the crayfish in the small ponds

with which Worcester, Mass., is so well supplied. At

night I used a powerful acetylene gas lamp. In the lab-

oratory I made use of two large aquaria, one of them an

ordinary running water aquarium with a pile of sand at

No. 545] THE BIOLOGY OF THE CRAYFISH 281

one end, and the other a still water aquarium arranged

to furnish a more nearly natural habitat.

In this paper I have not touched upon the anatomy or

the work on regeneration, but have confined myself to

what is generally known as ecology or biology. In the

attempt to make the paper fairly complete I have referred

in the text to the numbers in the bibliography.

It is a pleasure to acknowledge my indebtedness to Dr.

C. F. Hodge, Dr. Newton Miller and Dr. J. P. Porter, of

Clark University, Dr. A. E. Ortmann, of the Carnegie

Museum of Pittsburgh, and Dr. E. A. Andrews, of Johns

Hopkins University.

SENSES

Touch.—Touch is probably the sense of greatest value

to the crayfish. It is sensitive to touch over the whole

surface of the body (16), especially on the chelae and

chelipeds, mouth parts, the ventral surface of the abdomen

and the edge of the telson.

Vision.—The crayfish, in common with the insects, has

a compound eye. It is believed by many that the com-

pound eye is a visual apparatus which is almost worthless

for detecting the forms of objects, especially if these

objects are stationary; but that it may furnish a very defi-

nite response to stimuli of moving objects.

Bell’s experiments with the crayfish (16) showed that

there was no response to stationary objects. The case was

entirely different with large, moving objects. The

response was not due to any change in the intensity of

light such as that caused by a shadow falling on the ani-

mals, for they would react to a movement made on the

opposite side of them from the window. Reaction to

smaller moving objects was not so marked.

Crayfish are sensitive to strong light and hide during

the day under stones, among roots of plants near the bank,

and in burrows in the bank. It is a noteworthy fact that,

in France, the people catch crayfish by building huge fires

on the bank at night to attract them.

282 THE AMERICAN NATURALIST [Vou XLVI

My own experiments indicate that in nature the cray-

fish will retreat from a strong light, but will approach a

dim one. In the spring I found that it was extremely diffi-

cult to frighten a crayfish from its food by means of my

acetylene light. In collecting at night it is very easy to

attract crayfish from some distance by setting a light on

the bank so that it dimly illuminates some little space of

water.

Smell and Taste.—Very little experimental work to.

determine the senses of smell and taste in any of the crus-

tacea was done until Bell, in 1906, tested the reactions of

the crayfish (15) to chemical stimuli, applying meat juice

by means of a fine pointed pipette to various parts of the

body. He found that the antenne, antennules, mouth

_ parts and chelipeds were especially sensitive.

Recently (1910) Holmes and Homuth published the

results of an extended series of experiments on crayfish

in which the outer or inner rami of the antennules were

removed; the antennules were removed entirely; the

antenne were removed; the chelipeds removed; and in

some specimens the brains were destroyed. (33).

They found that the outer rami of the antennules bear-

ing the olfactory sete were especially sensitive to

olfactory stimuli, that the inner rami of the antennules,

the antennz, the mouth parts and the tips of the chelipeds

were all sensitive to some extent to olfactory stimuli.

It is probable that in the crayfish we have a very highly

developed topochemical sense, or contact-odor sense.

Forel uses this term (25) in speaking of the fact that in

ants, odors are apparently detected by the contact of the

antenne.

Bell found that the crayfish was sensitive to food when

not in contact with it. I experimented with freshly cut

meat and with meat which had been exposed to the air for

some time so that the cut surfaces had dried, and found

that the crayfish would go toward and seize the fresh meat

first. Evidently the diffusion of the meat juices was

readily detected.

No. 545] THE BIOLOGY OF THE CRAYFISH 283

Hearing.—It has been pretty clearly demonstrated by

Bell that the crayfish has no sound reactions. He tried

experiments (16) such as rapping on a board floating in

the water, snapping a metal snapper in and out of the

water, and setting tuning forks in vibration in the water,

but got no response.

It is possible that the crayfish is sensitive to the sound

made by the movement of the mouth parts of another

crayfish. This has not been proved.

Equilibrium.—Bunting found that young crayfish with

the statocysts removed would swim upside down as

readily as right side up (18). It is also pretty certain

that the older crayfish have a sense of equilibrium,

although the response to rotation in their case is not

definite, but purely individual.

MATING, SPAWNING AND DEVELOPMENT.

The process of mating in Astacus differs from the

process in Cambarus. In the case of Astacus, the males

approach the females in October, November and January.

The male seizes the female with his pincers, throws her on her back

and deposits the spermatic matter, firstly on the external plates of the

caudal fin, secondly on the thoracic sterna around the external open-

ings of the oviducts. During this operation the appendages of the

first two abdominal somites are carried backwards, the extremities of

the posterior pair are enclosed in the groove of the anterior pair; and

the end of the vas deferens becoming everted and prominent, the semi-

nal matter is poured out and runs slowly along the groove of the an-

terior appendage to its destination, where it hardens and assumes a

vermicular aspect (20

After an interval of from ten to forty-five days, oviposition takes

place. The female rests on her back and bends the abdomen forward,

forming a chamber into which the oviduets open. The eggs are passed

into the chamber by one operation, usually during the night, and are

plunged into a viscid, gray mucus with which it is filled. The sperma-

tozoa pass out of the spermatophores and mix with this fluid, fertiliz-

ing the ova, but just how, and what becomes of them, are unknown (20).

The female of Cambarus differs from the female of

Astacus in having a false pouch, the annulus ventralis.

Andrews found that this pouch does not appear in Cam-

284 THE AMERICAN NATURALIST [Vou. XLVI

barus affinis until the individual has reached a third stage

after leaving the egg.

The method of sperm transfer in C. affinis, and that

of C. b. b. as well, is as follows:

The male everts the bent, nozzle-like papille at the mouth of the

vasa deferentia and through them discharges sperm into an actual

tube that passes down each of the first two abdominal appendages or

stylets. Both first and second pairs of stylets are locked together by a

peg and groove contrivance. The sperm thus passes through a closed

tube from the vasa deferentia into the annulus ventralis without com-

ing into contact with the water. Copulation lasts from two to ten

hours and may be repeated by either animal with some other (3, 4).

In a previous paper, I pointed out (21) that the males

do not distinguish the females and that males ‘‘ repeat-

edly grasp other males, and sometimes, in spite of their

frantic struggles turn them over and attempt to copulate

with them.’’ The crayfish is at such a state of nervous

tension during the period of sexual activity, that the

female will curl her abdomen at the slightest touch and the

male will at first grasp any rounded object presented to

him and attempt to overturn it. A stimulus so slight as

the slow lowering of the water when I siphoned it from

the closed tank, was sufficient to cause violent activity

among the males, with the result that all the females were

soon held by males.

Pearse, in a study of crayfish made in the laboratory

with no attempt to reproduce natural conditions (40), has

made many interesting observations and experiments,

verifying my statements (21) and adding the discovery

that a male will copulate with a dead female. He dis-

covered that the male of one species had succeeded in ad-

justing his stylets to the annulus of a dead female of

another species.

Andrews has just published a paper (13) in which he

mentions seeing males attempt to copulate with dead and

bound or paralyzed males and to actually go through all

the activities of mating with dead females except the in-

jection of the spermatophores and plugging of the annu-

lus. He agrees with my previous statement that the males

No. 545] THE BIOLOGY OF THE CRAYFISH 285

do not recognize the females, and suggests that the differ-

ence from the standpoint of the crayfish between the sexes

is a difference of behavior, which difference is perceived

by muscle and touch sense.

The passivity of the female when seized is marked in the

crayfish, but as I shall show in another paper, in the

marine crabs the female is not passive but aids in the

movements preliminary to conjugation.

It is possible, though I have not at present enough

observations to support the theory, that in the crayfish

and the lobster, deposition of sperm is most effective when

the female has just moulted and the annulus ventralis or

the ventral surface, as the case may be, is clean. In crabs

where fertilization is internal, it is necessary that the shell

be soft; softness is of course of no use where the fertiliza-

tion is external, in fact it might be injurious; but the

cleanness of a new coat may facilitate the deposition of

the spermatophores, and the retention of the plug.

Anatomically there should be no difficulty in crossing

the different species of Cambarus. It would be interesting

to see if spermatophores deposited by a male Astacus on

the shell of a female Cambarus would fertilize the eggs.

It is quite probable, however, that the female would not

leave the spermatophores on her thorax and abdomen

until the time of egg extrusion.

Andrews (13) transplanted sperm receptacles of several

females to females of another species and the mutilated

females lived to lay eggs but the eggs did not develop.

Males would not fill the transplanted receptacles.

Andrews found that conjugation between species may take

place to some extent, but did not succeed in any case in

securing sperm transfer and actual crossing of species.

There seems to be no well-marked mating season in the

cold-water species, including the species on which my

observations were made. In the ponds, mating crayfish

were not found later than November 1, but in the labora-

tory copulation occurred at intervals during the fall,

286 THE AMERICAN NATURALIST [Vowu. XLVI

winter and spring. It is probable that in its native haunts

the crayfish behaves differently.

In the spring the males die off in great numbers. This

is a phenomenon which is noted in many arthropods, and

seems to be a wise provision of nature to prevent the now

useless males from using up the food required for the

spawning females and the young crayfish. Some of the

males, however, live to a good old age. I have found

several that were over 90 mm. long.

In the case of C. bartonius bartoni there are two more

or less well-marked spawning seasons, fall and spring.

The fall laying, as indicated by females brought into

the laboratory, is during the latter part of September and

all through October and November. The spring laying

extends from about March 15 to about May 15.

Andrews observed the process of laying in Cambarus

affinis. For four or five days previous to laying, the

female cleans her abdomen diligently and is exceedingly

sensitive to disturbances during that time. The actual

laying is done in deep water at night. It takes from ten

to thirty minutes to extrude the two hundred to four

hundred eggs. Each egg is attached by a tiny filament to

the abdominal hairs (9).

The time of fertilization is supposed to be when the

eggs are laid, as they pass over the annulus ventralis.

Andrews found that on the removal of the annulus before

the eggs were extruded, the eggs were unfertilized and did

not develop.

When first extruded the eggs are almost black, but as

development goes on they become reddish in color and at

the end of about four weeks, when the young crayfish are

hatched, they are nearly transparent. The time of devel-

opment, from the extrusion of the eggs till the crayfish are

detached from the parent, is about E weeks in the

species which I studied.

Even after the young are detached Front the swimmerets

of the mother, for several days they do not venture far

from her, and taking warning at any apparent danger,

No. 545] THE BIOLOGY OF THE CRAYFISH 287

scuttle under her abdomen. It is probable that here the

visual sensitivity to moving objects is more highly

developed than in the adult in comparison with other

senses.

The young crayfish moults very frequently during the

first year.

I found that two or three days before moulting the adult

crayfish come up into the shallows exposing their cara-

paces and drying them out thoroughly. The first time that

I saw this prolonged drying-out process I did not think it

significant, for I have seen crayfish in ponds where the

water was pure and fresh, elevating their carapaces for a

few minutes at a time. It is a habit which is not neces-

sarily caused by impure water, for the same thing was

noted by me in the laboratory with animals in the run-

ning-water tank.

When I noted by the number (in oil paint) on its back

that the same individual was continually remaining only

partly submerged, I made a note and watched develop-

ments. Later, in three other crayfish I noted this pre-

liminary drying out, and predicted the approximate time

of the moults. This was convenient knowledge, for a

crayfish in difficulty with his half removed os coat falls

easy prey to his brethren.

It is possible that the aeration of the attached young by

the mother is for the purpose of enabling the young cray-

fish to moult more readily. Observations like these have

not been reported for other crayfish or for marine crusta-

ceans, but it seems possible that in the crayfish we have

such a drying out of the old exo-skeleton as we find taking

Place i in insects, like the dragon fly, which live for a time

in the water.

Andrews made a thorough study of the young of both

Astacus and Cambarus and found that in Cambarus the

young four months old averaged about 41 mm. in length.

During the winter of the first year there is no increase in

size, but the second summer of life marks an increase of

thirty per cent. in length (12).

288 THE AMERICAN NATURALIST [Vou. XLVI

I have found females but one year old with eggs, and the

development went on in the laboratory just as in the more

mature females. The largest female that I captured was

102 mm. in length. The largest male was 90.5 mm. long.

Foon.

Crayfish are omnivorous. I have previously shown

that C. bartonius bartoni prefers fresh animal food to

stale animal food or either fresh or stale vegetable

food (21).

Some crayfish eat a great deal of vegetable matter,

one species, the chimney builder, Cambarus diogenes,

seeming to prefer it. The vegetable matter eaten con-

sists of dead leaves, potato, onion, young corn and

buckwheat,

The animal food consumed by the crayfish consists of

worms, insects, insect larve, a few fish, frog, toad and

salamander eggs, and occasionally a dead fish or frog.

I have seen crayfish devour a hapless relative who was

endeavoring to rid himself of his old shell. Sometimes

females eat eggs from their own abdomens and even

devour their own freed offspring.

Enemies.—The crayfish suffers from internal and

external enemies. Among the plants which live symbiot-

ically with the crayfish are diatoms, bacteria and sapro-

legnia. Internally, Distoma cerrigerum and Branchiob-

della have been noted. But these are not all the enemies

of the crayfish. Besides man, who uses thousands of

dollars worth of crayfish for food and as a garnish, many

small animals find them palatable.

Many fish, including the black bass, Micropterus,

which fishermen find very partial to crayfish, eat them.

Professor Surface reported (38) that the salamanders

Cryptobranchus allegheniensis and Necturus maculosus,

are among the chief enemies of the crayfish.

Ortmann mentions seeing the water snakes, Natris

sipedon and N. lebens, when captured, disgorge crayfish

No. 545] THE BIOLOGY OF THE CRAYFISH 289

and has also found garter snakes, Eutenia sirtalis, in

the holes of Cambarus monongalensis.

In the laboratory and in the field I have found that the

common box turtle catches many crayfish.

Many birds, including the eagle, king-fisher, wild ibis

and turkey, have been observed with crayfish in their

claws; or the remains have been seen at the nests.

CRAYFISH as [INJURIOUS CREATURES.

The river species do not especially injure human in-

terests except in occasionally capturing a few toads, fish

and frogs, but the burrowing species are cited by Ort-

mann (38) as being very injurious, especially in the low-

lands of Pennsylvania, Maryland and West Virginia.

They make mud piles which clog harvesting machines,

and are considered by the farmers in Maryland as such

pests that it is common to throw unslacked lime over the

fields in order to kill the unwelcome tenants.

West Virginia farmers claim that the crayfish de-

stroy crops of buckwheat, corn and beans by eating the

young sprouts.

Great damage is done by the burrowing species Cam-

barus diogenes, in burrowing into dams on ponds and

reservoirs, one notable instance being the levees of the

Mississippi (38).

To destroy crayfish it is customary to throw Uae,

slacked lime over the fields, or to pour carbon bisulphide

into the holes, or to drain the infested area.

None of these measures is efficacious, the first two

methods being impracticable on account of the difficulty

in reaching the bottom of the burrow and the second,

simply lowering the water level, only delays matters a

little.

VALUE OF THE CRAYFISH.

è?

At the present time, with the lobster fishery in a state

of decline, it seems as if the crayfish could be profitably

substituted for its larger cousin.

290 THE AMERICAN NATURALIST [Vou XLVI

In a carefully written paper (11) Andrews sets forth

the possibilities of crayfish propagation. |

He states that, from the small region on the Potomac

between Washington and Fort Washington, it was esti-

mated that there were half a million crayfish sent

annually to New York.

New York, New Orleans, Chicago, Milwaukee and

San Francisco, and many other large cities consume

large quantities as food.

In 1902, the U. S. Fish Commission reports state the

crayfish catch of Monroe Co., Florida, was 55,664 pounds,

worth $3,382.

In Oregon, 116,400 pounds, worth $7,760, were caught

in one year.

With crayfish maturing in one season and growing to a

length of from four to five inches in three years; and con-

sidering the large number of eggs (100-600) laid by one

female, there should be but little difficulty in supplying

a large demand for these animals.

When we consider that the large Astacus readily

adapts itself to the slight difference in environment in

the east, we see that the crayfish is a very practicable

substitute for the lobster.

There should be no difficulty in disposing of the

smaller Cambarus, either as fresh food or canned, as we

get the abdomens of shrimps.

In the school and college laboratories, the anatomy of

the crayfish has been studied ever since Huxley wrote

‘‘The Crayfish.’’ The habits and activities of the young

and adult crayfish are of great interest and profit for

study. The animal is suited for many kinds of experi-

ments, and the large ganglia and nerve cells are readily

removed and are excellent for neurological work. The

psychologists should find a profitable subject for study

in the relations of mother and offspring for the few days

just after the young are detached from the mother’s

swimmerets.

Daily Life—From a lengthy series of observations,

No. 545] THE BIOLOGY OF THE CRAYFISH 291

including the continuous study of several specimens for

twenty-four hours, I have concluded (21) that the cray-

fish shows his greatest activity at nightfall and at day-

break. In nature the crayfish is less active during the

day than he is in captivity, since, as a rule, he has more

hiding places in his natural habitat.

Pearse has stated (40) that the number of matings

occurring in two boxes, one being painted black and

closed entirely, and the other being exposed to light, did

not vary to any extent. It is obvious from the work of

Andrews and myself that the fact that crayfish in a state

of sexual tension, stimulated by transference to different

receptacles, copulate as well in the light as in the dark,

does not bear on the question of normal activity. The

difference between night and day must not be assumed

to be entirely that of light, in experiments on higher

invertebrates. _

It is possible that the tendency of the crayfish to re-

main in hiding during the day is to some extent lessened

when sexual feeling is strong, but this seems rather im-

probable under natural conditions.

In my specimens hibernation was well marked. I was

careful to change the water daily in my still-water

aquarium, thus keeping it fairly cool. Several of my

crayfish hibernated as long as six weeks at a time, in

closed burrows in the bank of this miniature pond.

BIBLIOGRAPHY

1. Abbott, ©. C. 73. Notes on the Habits of Certain Crayfish. AM.

Nart., Vol. 7, pp. 30-34.

2. Abbott, C. ©. ’85. How the Burrowing Crayfish works. Inland

Monthly. Columbus, Ohio, Vol. 1, pp. 31-32.

3. Andrews, E. A. ’95. Conjugation in an American Crayfish. Am. NAT.,

Vol. 29, pp. 867-873. L

4. Andrews, E. A. ’04. Breeding Habits of Crayfish. AM. Nat., Vo

38, pp. 165—206.

04. Crayfish Spermatozoa. Anat. Anz., Vol. 25, pp-

©]

705. nee Sperm Receptacle of Cambarus. J. H. U.

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292 THE AMERICAN NATURALIST [Vou XLVI

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577 ;

PRESENT PROBLEMS IN SOIL PHYSICS AS RE-

LATED TO PLANT ACTIVITIES?

PROFESSOR BURTON E. LIVINGSTON

THE JOHNS HOPKINS UNIVERSITY

Tr is from the point of view of the physiologist and not

from that of the analytical physicist that I propose here

to consider some of the most obvious and insistent of the

non-chemical problems of the soil. We shall thus be

interested not in the physics of the soil, but in the rela-

tion of some of its physical properties to certain plant

activities. This is a somewhat unusual point of view, for

most soil investigators have studied the soil largely to

the exclusion of the plant, bringing refined chemistry

and physics to the statement of one member of the equa-

tion and stating the other member largely from the

standpoint of the unscientific man. This generalization

applies to studies upon both the physics and the chem-

istry of the soil, but, owing to the majesty of the great

chemist Liebig? and to the multitude of his followers,

soil physics has nowhere received the attention which it

deserves, and the relation of the physical condition of

the substratum to plant activities remains perhaps the

most fundamental and at the same time most neglected

of all the various environmental relations.

Since we are certain that the water relation is of ex-

ceedingly great importance in the control of plant proc-

esses, and since so many other physical soil conditions

depend largely upon soil moisture, I shall consider here

primarily only the water relation of terrestrial plants

Par in the Symposium on Problems of the Soil, before Section G,

. A. A. S., at the Washington meeting.

Speke te in regard to the present contention, the title of Leibig’s monu-

mental work, ‘‘Die Chemie und ihrer Anwendung auf Agrikultur und Phys-

iologie,’’ 1846.

294

cae soe eon fs

No. 545] PRESENT PROBLEMS IN SOIL PHYSICS 295

below the soil surface. But, as will shortly appear in

some detail, to appreciate the problems before us it will

be necessary, not only to deal with the internal condi-

tions of the root system together with the external ones

of the soil, but also to bear constantly in mind certain

relations which obtain above the soil. I shall begin with

a brief treatment of the water relations of the plant,

with special reference to the physical conditions of its-

subterranean environment.

In order that the water content requisite for the

various physiological processes may be maintained, the

condition must obviously be fulfilled, that the ratio of the

rate of water income to that of water removal must never

fall below unity. Now, the removal of free water from

the physiological system of the plant occurs in three

general ways: (1) the fixation of water by growth, etc.,

(2) the excretion of liquid water at the periphery and (3)

the loss of water vapor by transpiration. The first two

of these are usually negligible, and the prime aerial con-

dition of plant activity—as far as the water relation is

concerned—is the rate of loss of water vapor. This loss

is to a variable extent controlled by conditions within

and without the plant, but we do not need to give these

attention now. The main point for us to bear in mind is

that, for the activities of the majority of terrestrial

plants, it is requisite that the entrance of water through

the roots must equal its rate of exit through the leaves

and other aerial parts.

Of course water will not, in general, enter through the

roots faster than it is removed from the plant body or

fixed therein by growth and metabolism, and the critical

consideration in respect to the soil water relation is not

the actual rate at which water is entering (this depend-

ing upon the internal conditions of the plant as well as

upon the soil), but the maximum possible rate at which it

May enter if the prerequisite internal conditions arise.

In this respect, then, that soil is best suited to continued

physiological activity, which possesses the highest power

296 THE AMERICAN NATURALIST [VoL. XLVI

of supplying moisture to the absorbing regions of the

plant.

It would seem, a priori, that a flooded soil should offer

the least possible resistance to water movement, but such

a soil appears indirectly to reduce water entrance in

many forms by influencing (probably directly or indi-

rectly in a chemical way) the internal conditions of the

plant, and it is only with a soil in a considerably drier

condition than the flooded one, that we find the optimum

subterranean environment for ordinary plant processes.

As the soil becomes drier, its direct resistance to water

intake by the roots increases, slowly at first, then rapidly,

and at a certain stage (for any given complex of aerial

conditions, and hence for any given transpiration rate)

the combined resultant of the movement of soil moisture

to the root surfaces and that of these surfaces through

the soil (by growth) falls to a magnitude so low that the

processes of transpiration and of growth, etc., remove

water from the tissues more rapidly than it enters below.

This condition of the substratum is approximately what

is usually termed the wilting point, and the remaining

water in the soil is said to be unavailable for plants.

In researches which have yet to be published, my asse-

ciates and I have shown that this wilting point is not the

constant which it has been supposed to be, for either soil

or plant. It is possible to cause the lower limit of ‘‘avaul-

able’’ water in the soil to assume almost any magnitude,

within a broad range, for any given plant, merely by

altering the rate of transpiration,—through proper

changes in the evaporating power of the air and the

intensity of the impinging solar radiation. The wilting

point thus ceases to have any meaning at all, unless the

corresponding rate of transpiration is known, or unless,

indeed, the aerial environment is known to be the same

throughout any series of cultures the data from which

are to be compared.

The primary problem, then, which must be quantita-

tively solved if we are to place the soil water relation in

No. 545] PRESENT PROBLEMS IN SOIL PHYSICS 297

a way that may lead to a scientific foundation, is con-

cerned with the maximum rates at which various soils

may furnish moisture to the root systems of whatever

plant forms with which we may be dealing. To such an

end, our knowledge of the physiology and ecology of

roots must be enormously increased, but with this phase

of the matter we need not here concern ourselves. It is

obvious, however, that the really crucial question with

regard to any soil, the properties of which we wish to

study with reference to plant behavior, is this: at what

rate, and for how long a time, can it deliver water to unit

area of a water-absorbing surface? This is a purely

physical question and one for which it ought not to be

very difficult to find adequate methods of attack. Indeed,

the method of studying evaporation from soil surfaces

already offers approximate results in this direction.

This maximum rate of delivery per unit of cross sec-

tion must be related in some manner to the soil charac-

ters which are now often measured; the power of water

delivery will vary with the percentage of water content

for any particular soil, and its graph will most likely ex-

hibit a critical point under about the same conditions as

those which accompany the critical points for evapora-

tion from the soil, the apparent specific gravity of the

latter, its penetrability (as recently brought out by Cam-

eron and Gallagher), its critical moisture content and

its moisture equivalent (as brought out by the centrif-

ugal method of Briggs and McLane). That the critical

point in maximum rate of delivery of moisture will be

found to correspond to the ordinarily observed optimum

water content for many plants is also to be expected, but

the physiologist will not make the mistake of supposing

that this optimum water content will not vary largely

with the nature and condition of the plant and also with

its rate of transpiration. That this critical point, with soils

of varying water content, will be found to be related to

the size, nature and arrangement of the soil particles is

likewise fairly certain, and it may confidently be ex-

298 THE AMERICAN NATURALIST [Vor. XLVI

pected that this point will exhibit some definite relation

to the heat of wetting (as this property has been devel-

oped by Mitscherlich), and perhaps also to the commonly

determined water capacity or water-retaining power of

the soil. The last named is a property which, as I have

previously pointed out, seems especially worthy of inves-

tigation by ecologists who are seeking some easily de-

termined soil characteristic for use in studies on plant

distribution.

In this connection it is well to call attention to the

apparent futility of the method of mechanical analysis,

which is resorted to so extensively—and so expensively

—in attempts physically to describe the solid portion of

the soil. I think I do not exaggerate when I say that the

physical analysis has shown itself to be practically worth-

less for any physiological purpose. It assuredly does

furnish a means of describing a given soil sample with

considerable accuracy, and if two samples could ever be

found to exhibit exactly the same proportions of the

different sized particles, it might plausibly be supposed

that, ceteris paribus, these should possess the same rela-

tions toward water and toward plant roots, but the con-

verse of this statement is not at all true. This method

furnishes a mass of data from which no one has yet been

able to derive any single comprehensive summation that

will express anything definitely as to the possibilities of

the given soil as a substratum for plants. Undoubtedly

the size of the component soil particles plays a large part

in determining how the water conductivity varies with

different conditions of soil moisture, etc., but we need to

seek some feature which may be much more readily meas-

ured for the soil as a whole than merely the proportions

of various-sized particles.

Should we be able to find out the relations which obtain

between the maximum rate of water delivery and the

other soil characters that I have mentioned, it might at

length become possible physically to assay a given soil

by the determination of one or more of the latter, sub-

No. 545] PRESENT PROBLEMS IN SOIL PHYSICS 299

sequently passing to the real point of interest by means

of an interpretation, but such a possibility is at present

so far removed from actuality that it seems highly desir-

able to begin with attempts to measure the soil property

which directly influences plants. In any event, it can not

be too strongly emphasized that such soil studies as I

am suggesting must always be carried on simultaneously

with studies on the behavior of plants, and also with ade-

quate determinations of the water-extracting power of

the aerial environment. It seems quite likely that we

shall be able empirically to determine some highly im-

portant principles bearing upon the water relations which

exist between plants and soils, without having yet suc-

ceeded in analyzing the mode of manifestation of these

into its elementary physical propositions—just as it has

recently been possible to work out exceedingly valuable

principles with reference to the relation of plants to

evaporation, without any one’s having yet succeeded in

determining the quantitative dependence of this climatic

factor upon its components, water and air temperature,

air humidity and air movement.

When a little headway has been gained in the dynamic

study of the soil in relation to plant processes, we shall

probably begin to be able to interpret and correct, and

place upon a proper quantitative basis, some of the eco-

logical classifications of plants and the physical classi-

fications of soils, which already occupy so much of our

literature.

Another aspect of this whole question of the water

relations of the subterranean parts of the terrestrial

plant may be worthy of attention. The majority of the

physical soil studies which have so far been made depend

upon the removal of the soil sample from its natural

position, with consequent and usually profound altera-

tions in the arrangement of its component grains, upon

which arrangement assuredly depend some of the most

fundamental of the soil qualities which we need to know

about. Various methods have been devised aiming to

300 THE AMERICAN NATURALIST [Vou XLVI

avoid this difficulty, but all are exceedingly cumbersome

in the operation and are at best of somewhat doubtful

efficiency. Here is suggested a line of work which has

already been attempted by a number of enthusiastic

students, many of whom have afterward given up in

despair without even publishing their experience. The

director of one of the great European experiment sta-

tions told me of a somewhat elaborate apparatus which

he once constructed for determining soil moisture in situ.

He concluded with the remark, ‘‘the principle was cor-

rect enough, but the method proved useless.’’ Jam sure

that he is not alone in his experience. But the problem

of soil instrumentation will not be dropped; I am confi-

dent that the future will develop methods in soil physics

which will not necessitate any alteration in the soil at

the time a determination is made. Studies upon the soil

properties in the light of their rôle in plant environment

and accompanying studies on the physics of plant activi-

ties will do much toward furthering our science in this

direction. The actual accomplishment of this end may

not be very far off; we may take heart from such facts

as this, that a single decade has sufficed to bring aerial

navigation from the limbo of scoffed-at impossibility (in

the minds of all but a very few scientists) into the cate-

gory of accomplished fact. And the importance of ade-

quate methods for the study of problems of the soil is far

greater, and probably will ever remain far greater, than

that of any problem of transportation.

To summarize my suggestions:

1. The soil water relation is of fundamental impor-

tance if we are some time to know about and be able to

predict and control plant processes.

2. The moisture of the soil, as well as its other fea-

tures, is most profitably to be studied as plant environ-

ment, the relations which obtain between plant activity

and soil phenomena comprising a fundamental and

primary requirement for the scientific advance of our

knowledge.

No. 545] PRESENT PROBLEMS IN SOIL PHYSICS 301

3. The physical nature of the subterranean environ-

ment of terrestrial plants is effective in controlling plant

activities, mainly with regard to the possible rate of de-

livery of water by the soil to unit area of absorbing roots.

4, It is highly desirable to study this power of water

delivery with reference not only to the growth of plants

but also to other soil characteristics, some of which are

already commonly measured.

5. The whole problem of the physics of the subter-

ranean surroundings of rooted plants awaits the develop-

ment of an instrumentation which will not necessitate the

preliminary destruction of some of the most important

soil properties before the soil can really be studied.

SHORTER ARTICLES AND DISCUSSION

FURTHER NOTES REGARDING SELECTION INDEX

NUMB

RS!

THE purpose of the present communication is to correct and

extend a former paper from this laboratory? dealing with the

use of index numbers in mass selection operations. In the cor-

respondence which the writer has had with various workers re-

garding that paper it would appear that a point which it was

intended should be emphasized has been rather overlooked.

This is that the examples of index numbers therein given for

sweet corn and for poultry were intended merely to illustrate

the principles involved. They were not put forward as the best

formule which could be devised, even for the organisms dis-

cussed. It was pointed out that the particular formula to be

used should be devised by each worker to fit his particular needs.

Apparently a number of workers have adopted without change

the formule given in our first paper. I wish again to empha-

size that unless these happen to meet exactly the particular needs

of the breeder, it is highly desirable that he develop formule of

his own, involving the same general principle, but adapted to

his special conditions.

I. CORRECTION OF AN ERROR IN THE FORMULA OF A SELECTION

INDEX NUMBER FOR CORN

In our first paper there is an error in one of the equations for

the selection index for sweet corn (loc. cit., pp. 397-399).

This error has given trouble to some workers desiring to use

this index number in breeding work with corn, and may cause

confusion in the future. Doubtless some of those who have used

the index in their work have, like the writer, made for them-

‘selves the somewhat obvious correction. Nevertheless, to insure

that there may be no further confusion it seems desirable to pub-

lish a formal correction.

*Papers from the Biological Laboratory of the Maine Experiment

Station, No. 35.

? Pearl, R., and Surface, F. M., ‘‘Selection Index Numbers and Their

Use in Breeding.’’ AMERICAN NATURALIST, Vol. XLIII, pp. 385-400, 1909.

302

No. 545] SHORTER ARTICLES AND DISCUSSION 303

The corn index number has the following formula

fa A-+3B 4.20

~ D+ ue

The definition of the variable C given on p. 393, by an un-

fortunate slip of the pen, which escaped detection in the proof,

as such things will, gives precisely the inverse effect from what

it should. The equation should read as follows:

100 times the circumference of the cob at middle

Circumference of ear at middle

C= 100 —

The example on p. 399, which was worked out after the text

. Was written, followed the erroneous text with scrupulous exacti-

tude in theory, but with a slip in the arithmetic. The correct

value of J, for the ear used as an example is

190.0 + 70.5 477.6 338.1

he sake S

Experience in the use of this index suggests that in the equa-

tion for C given above it may be advantageous to substitute

‘‘diameter”’ for ‘‘cireumference’’ in each case. The diameters

can be much more easily and accurately measured and they

probably give a better appreciation of the relative kernel depth

than do the circumferences.

II. A SELECTION INDEX NuMBER FOR BEANS

The writer has under way at the present time some breeding

experiments with a very interesting variety of beans, known

locally as the ‘‘Old-fashioned Yellow Eye.” It is a variety ap-

parently scarcely known now outside of northern New England.

Owing to certain defects it has been replaced in most of the bean-

growing sections of the country where formerly grown by the

Improved Yellow Eye, a perfectly distinct and in many respects

inferior type. From the standpoint of experimental genetics

the old-fashioned yellow eye bean promises to furnish material

of great interest and value in the unraveling of such problems

as pattern inheritance, the effect of selection in pure lines, ete.

Aside from the technically biological considerations, however,

304 THE AMERICAN NATURALIST [Vou. XLVI

this bean possesses much economic significance in Maine. It is

esteemed above all other sorts for baking purposes, and if a

strain could be developed which would possess (a) high yielding

qualities, (b) reasonable disease resistance and (c) earliness

and uniformity of maturing it would be of great value to the

bean growers of the state. In connection with the purely bio-

logical studies an attempt is being made to see whether a pure

line possessing these desirable qualities may not be found.

In this specific breeding problem we obviously have the con-

ditions which demand the aid of selection index numbers. Sev-

eral characters (not one only) must be concurrently selected.

An estimate must be formed in each case of the net worth of an

individual plant (or of a biotype), taking into account at least

all of the three factors named. In order to do this impartially

and accurately a selection index number has been devised.

In deriving this bean selection index a general equation of a

slightly different type than that discussed in our former paper

has been employed. In that paper (loc. cit., p. 389) the general

formula suggested is

fa” + by ce es Ee

: reer Ge ee et lb:

In the case of beans (and very likely this may prove true for

other plants and animals as well) it has seemed desirable to form

an index number on the plan of the following type of equation:

axy + bwz + --- + nuv

apronda TAI

In this equation, as before, a, b, c,...n, and a’, b,

n’ are constants, given arbitrary values in accordance ae the

scheme of weighing adopted, and z, y, z, w, u, v, are variables

which measure characters increasing in desirability (from the

breeders’ standpoint) as their absolute magnitudes increase,

while p, q, r, s and t are variables measuring characters which

decrease in desirability as their absolute magnitudes increase.

The variables specifically taken account of in the bean selection

work are:

Y = Absolute yield. The weight in grams of dried shelled

beans per plant.

No. 545] SHORTER ARTICLES AND DISCUSSION 305

V = Relative yield. The percentage which Y is of the weight in

grams of the whole plant. This factor measures the

degree to which the plant transforms its food materials

into seeds rather than into foliage parts.

P = Number of pods per plant.

B = Mean number of beans per pod.

D = Disease-maturity index. The percentage which the number

of perfectly matured beans free of disease (anthrac-

nose) is of the total number of beans originally set in

the pods. This measures the degree to which the per-

formance of the plant in seed production approaches

its promise in that regard. It does not separate disease

resistance from earliness and completeness of maturity,

but from a purely practical standpoint this is not essen-

tial. By making separate counts of diseased and imma-

ture beans it would be possible to take account of each

of these factors by itself. It must be understood further

that the separation of diseased beans is not absolutely

complete. Only those are counted as diseased which

show to the unaided eye evidence of anthracnose infec-

tion. It has not been found feasible as yet to get a

simple and satisfactory measure of the degree of attack

of other bean diseases. Hence, for the present, only

anthracnose is being taken account of specifically in

the selection index number.

` These variables are combined in the following bean selection

index number:

The values taken by this index number for a particular strain

of Old-fashioned Yellow Eyes are shown in Table I.

From the table it is clear that the index may take a rather

wide range of values, depending upon the character of the plant.

Further, the value of the index is obviously not unduly influ-

enced by any particular variable. The high index values seem

clearly to indicate the plants wick e te best, taking all

things into account. This, of course, is the goal sought.

It is of interest to note the values taken by the index in the

ease of a bean of quite different type, namely, a White | field oe

306 THE AMERICAN NATURALIST [Vou. XLVI

TABLE I

VALUES OF THE SELECTION INDEX NUMBER FOR A SERIES OF PLANTS OF

MORSE’S OLD-FASHIONED YELLOW EYE BEAN, TOGETHER WITH THE

VARIABLES ON WHICH THE INDEX DEPENDS

No. | Ta Yield Index EERDE prr Weight of Pods | a

873 OO. Shen: ma 55 eas 5 60.

85 79 2 36.36 3.90 AT 0 33.33

86 1.24 | 10 41.67 3.43 .50 7 62.50

61 ist | 15 00 3.77 .39 13 | 41.45

98 1.37 41.67 3.20 58 75.00

95 £5) 1:21 56.40 2.73 33 15 57.77

59 1.56 | 13 54.17 3.78 55 58.82

76 173 |12 46.15 3.42 43 12 54

62 00 | 16.1 49.53 4.33 50 9 64.10

84 2.08 50.97 3.58 43 12 67.44

71 2.58 | 24.5 64 3.47 56 15 55.98

2.92 8 59.99 2.87 49 15 69.77

89 3.26 | 20.5 52.58 3.71 50 14 70.37

55 3.43 59.38 3.69 42 16 69.49

69 3.73 1 59.99 3.73 57 11 75.61

92 3.73 | 12 59.99 3.57 57

90 3.83 | 19.5 59.10 3.33 53 12 77.50

56 3.97 | 30.9 59.42 4.33 47 18 58.97

63 447 |23 51.10 4.53 41 17 70.13

75 5.35 | 39 59.99 4.07 47 27

81 5.51 | 27 64.27 3.18 51 17 75.93

7.32 | 27 59.99 3.42 46 19 80.38

70 7.37 | 26 61.16 3.59 46 i See

60 7.56 | 19 55.07 3.38 36 16 87.04

78 8.47 | 29 61.70 3.19 46 21 80.97

8.79 | 30 63.17 4.14 56 14 84.48

67 9.42 | 23 52.88 3.68 34 19 86.59

83 9.50 | 26 59.10 3.14 43 22 84

g2 | 10.09 | 3 61.24 3.67 46 18 98.48

97 | 10.38 | 50.5 44.11 5.42 29 41 57.21

79 15.30 | 3 62.50 3.48 43 31 88.93

73 | 17.04 | 38 60.31 3.89 42 26 86.1

pea bean. Table II gives the index and component aaa:

for a series of plants of such a variety.

The range of values here is large. The extremely high values

are probably much larger than will ever be obtained for a bean

of the yellow eye type, though it is rather risky to make such

a prophecy. Two factors help in reaching such high index

values in the case of this variety. One is the tendency to prolifi-

cacy, there being relatively many pods per plant and beans per

pod. The other is the rather high disease resistance of the

3 Plant injured by cut worms.

* Plant injured by cut worms, but subsequently grew. x

No. 545] SHORTER ARTICLES AND DISCUSSION 307

plants. They mature, apparently free from disease, a large

proportion of their seeds

TABLE II

VALUES OF THE SELECTION INDEX NUMBERS FOR A SERIES OF PLANTS OF

SNow FLAKE FIELD BEANS

; Mean

Plant lecti Absol Yield otal N: i

No. Sever Yield ader Pen por Weight pe a yp a gd

1864 7 31.82 4.13 21 8 87.88

1924 4.42 23 46.95 5.30 16 33 54.42

187 6.5 44.82 5.86 17 7

191 12.25 38 56.72 6.06 24 34 73.30

183 12.86 9 56 4.10 22 10 95.12

190 25.44 55 48.24 5.10 30 42 79.91

188 30.72 6 7.80 5,35 32 40 82.71

84 71.98 50.5 57.14 5.64 19 52 91.81

185 101.12 40 57.14 5.35 22 34 96.71

Of course, the index numbers may, strictly speaking, be com-

pared only among plants of the same variety. The absolute de-

sirability of a variety for a particular purpose depends upon

many other factors not taken account of in the index number.

These numbers can not be used directly and solely as measures

of the relative worth of varieties.

It is hoped that this bean selection index number or some mod-

ification of it may be found useful by other workers. It will, at

any rate, serve to illustrate further the adaptability of the gen-

eral idea of such numbers to a wide range of practical selection

work. In the present instance a selection index number is

applied to the measurement of the relative worth of different

distinct biotypes, rather than in the mass selection of fluctuat-

ing variations, in which latter type of work such numbers were

shown in our former communication to be useful.

RAYMOND PEARL

UNIVERSITY OF MAINE

NOTES AND LITERATURE

PROTOZOA:

THAT so expensive and highly specialized a text-book as this

of Doflein’s should run through a whole edition in less than a

year is a tribute to the excellence of the work and an index to

the scientific activity in this field of biological research. An

indication of the rapid progress now in the making in protozo-

ology may be derived from the fact that every chapter in this

elaborate work has been rewritten or substantially emended

and the number of pages and illustrations increased by fifteen

per cent. in this third edition, the second having been issued

less than two years ago. The main changes include the insertion

of a chapter on the origin of the Protozoa, the conception of

species within the group, and the phenomena of variation and

heredity as revealed by methods of culture and experiment,

especially by the study of pure lines and the results of selec-

tion. Doflein calls attention to the appearance of direct adapta-

tions in parasitic organisms in response to definite environ-

mental factors in the form of chemical substances such as

atoxyl and various compounds of arsenic and of antimony,

unknown in the normal environment of the protozoan organism.

These adaptations result in so-called resistant races and may be

heritable. The possibility of control, the large numbers avail-

able and the rapidity of multiplication of these pathogenic

organisms unite to open an inviting field, thus far too much

neglected by the investigator in experimental evolution.

Considerable additions are made to the discussion of repro-

duction, especially to the maturation of the gametes, in which

homologies to maturation in the Metazoa are becoming increas-

ingly definite. The detailed discussion of the various groups

of protozoa is noticeably extended in the case of the Spiro-

chætes, the Hemosporidia and the Sarcosporidia.

***Lehrbuch der Protozoenkunde. Eine Darstellung der Naturgeschichte

der Protozoen mit besonderer Beriicksichtigung der parasitischen und patho-

en Formen.’’ Dritte stark vermehrte Auflage. Von Dr. F. Doflein.

xii + 1043 pp., mit 951 Abbildungen im Text. Jena, Gustav Fischer, 1911.

M. 26, gb. M. 28.50.

308

No. 545] NOTES AND LITERATURE 309

Doflein is inclined to accept the evidence that Schaudinn’s

account of Entameba histolytica is based in part upon phe-

nomena attendant upon processes of degeneration and suggests

that Viereck’s E. tetragena is probably the most widespread

form causing ameebic dysentery, and that the two are possibly

identical, but that the organism according to the rigid laws of

priority should be called Entamaba dysenteriae (Councilman

and Lafleur).

The doubtful group Chlamydozoa established by Prowazek

for that group of immunizing organisms with a filterable virus,

the supposed etiological factors in such diseases as vaccinia,

variola, trachoma, molluscum contagiosum and epithelioma con-

tagiosum, is still denied admittance by the author to the Pro-

tozoa on the ground that the minute structures described by

Prowazek are not themselves with certainty proved to be living

organisms. Doflein admits, however, that the evidence is con-

Stantly increasing that we have to do in the case of these dis-

eases with parasitic organisms, but thinks they may be more

closely related to the bacteria than to the protozoa.

It is a matter of regret that the non-parasitic groups, such, for

example, as the pelagic Foraminifera and Radiolaria, and non-

parasitic flagellates can not receive in a work of this sort com-

mensurate treatment with pathogenic forms of confessedly great

biological, as well as medical and hygienic interest. The author

expresses the hope that medical research may in the near future

so clear up contested points that less space will be required for

the discussion of pathogenic forms. The present output is,

however, not very promising for a reduction in extent in this

field. The fact is that a six-volume edition of the Protozoa in

Bronn’s ‘‘Thiereich’’ is needed to give anything like an ade-

quate review of the results now achieved in the fields of Pro-

tozoology.

CHARLES ATWOOD KOFOID

UNIVERSITY OF CALIFORNIA

HEREDITY

H. M. Leake’ gives additional results of his studies of inheri-

tance in cotton. The flower color factors found were yellow,

Pale yellow and red, the latter being due to red sap color which

showed not only in the flowers but in stems and leaves as well.

“<< Studies in Indian Cotton,’’ Jour. of Gen., Aug., 1911.

310 THE AMERICAN NATURALIST [Vou. XLVI

Yellow was completely dominant to its absence and to pale yel-

low. Red was incompletely dominant. The very interesting

fact developed that although yellow behaved as an allelomorph to

its absence in crosses with white, it was also allelomorphic to pale

yellow in crosses with the latter. This indicates that pale yellow

is simply a modified form of yellow, a fact in entire accord with

my teleone theory of Mendelian inheritance, and opposed to the

de Vriesian idea of the immutability of the so-called unit charac-

ters. An interesting case of correlation was found. White (ab-

sence of yellow) is hardier than yellow.

In shape of leaf Leake uses as an empirical means of describ-

ing leaf shape a formula which is essentially the ratio between

the length and breadth of the central lobe. The pure races (and

the author took the pains to work with pure races) may be di-

vided into two groups with reference to this ‘‘leaf factor,”

namely those in which it is less than 2, and those in which it is

greater than 3. No cases were found in pure races in which the

value of this factor was between 2 and 3. F, between these

groups gave intermediate leaf factors. F, apparently behaved

as if the cross involved a single gene, but fluctuating variation

obscured the results considerably. Crosses between F, and

either parent form gave only the intermediate and the one par-

ent form, the same difficulty appearing from fluctuation in the

character. This strongly confirms the conclusion that a single

gene is responsible for the difference between these two groups.

Earliness of flowering late flowering proved to be a very in-

teresting study. The author had previously discovered that

types with sympodial secondary branches flower early, while

those having monopodial secondaries are late flowering. This re-

lation had also been noticed by others, the early or late flowering

being a result of the manner of branching. Length of vegetative

period (time between planting and first flower) proved to be

highly fluctuating, varying widely as between different seasons.

F, between the monopodial and the sympodial types was inter-

mediate between the parents, but nearer the sympodial (early)

parent. F, gave a continuous series extending from the early

parent nearly to the late parent, the frequency curve for the

earliness in the F, population being monomodal. While the

author does not pursue the subject further, it may easily be

shown that this is exactly what Mendelian theory calls for on

the assumption that several factors, each alike in effect, their

No. 545] NOTES AND LITERATURE 211

effects being additive, are responsible for the parental differences,

especially when the character in question fluctuates widely as

compared with the differences between the several genotypes

occurring in F,. Thus, suppose three factors, A, B and C, each

alike in effect, and each producing the same average increase in

length of vegetative period. The F, generation of the cross abc

X ABC will consist of the genotypes aabbcc, aabbCC, aaBBcc,

AAbbcc, aaBBCC, AAbbCC, AABBcc and AABBCC and their

crosses. The genotype aabbcc would be similar to the early

parent. Genotypes AAbbcc, aaBBcc and aabbCC would con-

stitute a group one stage later in flowering. AABBcc, AAbbCC

and aaBBCC constitute a third stage, while AABBCC would be

equivalent to the late parent. Thus the four stages resulting

from these three factors tend to be present in the ratio 1:3: 3:1,

which ratio is merely one way of stating the properties of an

ordinary frequency curve. LEarliness being nearly completely

dominant, the norm of this curve would be shifted toward the

early parent, as Leake found was the case. Even if this progeny

were selfed to the tenth generation, by which time heterozygosis

would have largely disappeared, the mixture of the four geno-

types would still give a monomodal curve. The only exception

to this would be cases in which fluctuating variation is not trans-

gressive between the genotypes. It is possible that more than

three genes were involved in Leake’s crosses.

Crosses between pure lines having no leaf glands and those

having leaf glands gave intermediate F,. F, gave evidence of

segregation, but the intermediate and apparently highly fiuctu-

ating character of the heterozygotes rendered positive conclu-

sions difficult or impracticable.

Complete correlation occurred between flower color and length

of petals. White petals were little if any longer than the brac-

teoles, while yellow petals were about twice as long. Interme-

diates did not occur, and no exceptions were found in over 100,-

000 plants.

Red sap color was independent of the size of the petal but

when present it lengthened the vegetative period. This paper is

exceedingly clear and lucid in treatment, and we may expect

much valuable work from the author in future.

Dr. Shull has resumed his interesting studies of Bursa. He

*Dr. G. H. Shull, ‘‘ Defective Inheritance-Ratios in Bursa Hybrids,’’

Verh. d. Naturforsch. Ver. in Brünn., Bd. XLIX.

312 . THE AMERICAN NATURALIST [Vou XLVI

had previously shown that four genotypes of Bursa bursa-pas-

toris are the four Mendelian types corresponding to two inde-

pendent factors (AABB, AAbb, aaBB, aabb). In his paper

above cited he deals with a cross between one of these types

(aabb) with a genotype of Bursa Heegeri corresponding to the

type AABB. The factors A and B in this cross behave in the

usual Mendelian fashion, departures from expected ratios being

explained by variation in dominance in one of the families. But

the factor or factors governing differences in the seed pod of

these two species present departures from expected ratios that

are not fully understood. There is evidence that at least two

genes are concerned in this difference. If only one gene were

concerned the ratio between the two types of seed capsule in F,

should be 3:1; if there are two genes, the ratio should be 15:1,

three genes, 63:1.. The ratios observed in F, were 4.67:1 (in-

stead of 3:1), 15.6:1, 24:1 and 63.5:1. The latter ratio, ob-

tained in a rather large family (129 individuals), suggests three

genes. The first and fourth of the above ratios are rather wide

departures from expected ratios, and their meaning is not yet

clear. The matter is still under investigation. There seems to

be little doubt that Dr. Shull has added another case to the in-

teresting class of Mendelian characters that may be represented

by more than one independent gene, such as those found by Nill-

son-Ehle, in oats and wheat and by East in corn.

A very interesting paper by Gortner,7® giving further results

of his studies on melanin formation, appeared in the December

(1911) number of this journal. He was able to show the color

pattern in the Colorado potato beetle is due to the fact that the

chromogen z secreted only in certain spots, while the oxidizing

enzyme, which is of the tyrosinase type, is present generally in

the elytron.

W. J. SPILLMAN

* Dr. R. A. Gortner, ‘‘Studies on Melanin,’’

AMER. i V,

No. 540, pp. 743 et seq. ee

VOL. XLVI, NO. 546 “ JUNE, 1912

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THE

AMERICAN NATURALIST

VoL. XLVI June, 1912 No. 546

A FIRST STUDY OF THE INFLUENCE OF THE

STARVATION OF THE ASCENDANTS UPON

THE CHARACTERISTICS OF THE

DESCENDANTS—I

Dr. J. ARTHUR HARRIS

CARNEGIE INSTITUTION OF WASHINGTON

I. [INTRODUCTORY REMARKS

One need not search widely in biological or agricultural

literature to encounter discussions of the influence of the

conditions to which the ancestors are exposed upon the

characteristies of the offspring which they produce. To

review here the mass of more or less pertinent literature

would lead us too far afield from our present main pur-

pose, which is simply to present the data and state the

apparent conclusions from an experimental and statis-

tical study of the influence of starvation and feeding upon

the characteristics of garden beans. It is sufficient for

the moment to point out that some biologists have attrib-

uted a very important rôle to the environment of the

mother in determining the characteristics of the off-

spring. It is perhaps superfluous to say that others of

equal authority have expressed diametrically opposite

opinions.

The problem is, therefore, a real and an important one.

Unfortunately the serious investigator who publishes in

this field is sure to be between two large and several

313

314 THE AMERICAN NATURALIST [ Vou. XLVI

smaller fires. If after cultures of a few generations he

finds that the offspring of starved parents do not differ

from those which have been well fed, he will be railed at

for having wasted his time in demonstrating what was

obvious in advance. At the same time he will be criti-

cized by others for not having carried out his experiments

‘for a sufficient number of generations to allow the accu-

mulation of small effects of the environment’’ on the

ascendants before deciding against the possibility of some

influence upon the descendants of ancestral environ-

mental conditions. If he finds that there are measurable

differences between series of individuals whose ancestry

has been subjected to opposed conditions, the results are

sure to be dismissed in many quarters as of little impor-

tance because of purely physiological and not hereditary

significance.

The very fact of the inevitability of criticism—what-

ever the results obtained—seems to render it even more

highly desirable to appeal to the facts afforded by a large

and detailed experimental investigation. Naturally such

an experiment can never be so large and so refined as to

be beyond all criticism.

The problem is not merely of wide interest from the

purely biological viewpoint, but it is of first rate impor-

tance from the practical side as well. The biggest pump-

kin, the heaviest bull, and the finest ear of corn are the

resultant of germ plasm and environment—of nature and

nurture, to use Galton’s apt words. But in paying fabu-

lous prices for the seed of prize winners little thought is

given to the question of the proportionate importance of

breeding and feeding in producing this excellence. From

the practical standpoint it seems desirable to know —

whether parents—animals or plants—of as nearly as

possible the same hereditary endowment differ at all in

their capacity for producing high-grade offspring because

of the superior care and feeding which admits them to

the show bench. If it be found that the well-fed mother

produces finer, or poorer, offspring than the starved one,

the practical significance of the result is obvious and the

No. 546] INFLUENCE OF STARVATION 315

further biological problems of the nature and permanence

of this influence will be open for investigation.

Finally it may be said in passing that the work on these

beans was so carried out that data for many other prob-

lems besides those discussed here were secured. That of

the pure line, that of the relationship between the size of

the seed planted and the characteristics of the plant

produced, that of the relationship between the size of

the plant and the fertility of its pod and the size of the

seeds which it produces, that of the relationship between.

the ovule characters of the pod and its fertility, may be

mentioned. These will shortly be made ready for publi-

cation; hence if the reader encounters these series of

beans in several different places he must not assume du-

plicate publication. The mass of data in hand is so great

that it is either necessary to scatter the material in this.

way or to withhold it all for several months or years until

it can be presented in one volume. The former scheme

for several reasons seems the most expedient.

Il. STATEMENT OF PROBLEMS AND DESCRIPTION or MATE-

RIALS AND METHODS

A. Limitation of the Problem

The purpose of this paper is to present the results of a

series of experiments to determine whether plants whose

ancestors have been starved differ from those whose an-

cestors have been well fed.

It might seem to the reader that the first step in such a

problem would be to define starvation and feeding, to list

the factors underlying these conditions, and to ascertain

the weight of each of these factors in determining the

characteristics of a series of plants subjected to them.

This seemed to me in undertaking these particular ex-

periments precisely the course which one should not fol-

low. Physiologists, especially those concerned with plant

nutrition in the agricultural stations, have devoted a

quarter of a century or more to these very problems.

316 THE AMERICAN NATURALIST (Vou. XLVI

But concerning the influence of the feeding or starving of

the parent upon the characteristics of the offspring, we

have little direct experimental knowledge.

It seemed expedient therefore to neglect for the mo-

ment the problem of the various edaphic and metereolog-

ical factors which determine the characteristics of the

individual and to ascertain whether the subjecting of

parent plants (or parents and earlier ascendants) to dif-

fering environmental conditions has any influence upon

the characteristics of the offspring. It was therefore

only necessary to find fields in which the soil barely sus-

tained a given variety and others which produced a luxu-

riant growth. The first would represent for the species

in question starvation fields.

The judgment of the relative richness of the plots by

their actual productiveness is justified by our ignorance

of the nature of soil fertility.

The reader who is inclined to criticize this method of

approaching the problem as very coarse may be reminded

of the following points:

(a) The complexity of the problem of soil fertility is

such as to preclude a trustworthy evaluation of the par-

ticular factors determining the productiveness of any

parcel of ground. For this reason I have purposely

omitted all but the barest descriptions concerning the ex-

perimental plots employed.

(b) Artificial soils or water culture media of known

chemical composition were carefully considered and ruled

ont. In the first place, the technical difficulties seemed

almost unsurmountable. Again, it seemed desirable to

earry on the experiments under conditions as nearly as

possible identical with those to be met with in practical

agriculture. Chemically prepared nutrient solutions are

useful in the physiological laboratory, but they do not

occur in practical farming, while soils which are ‘‘sterile”’

*Soil experts now agree that chemical analyses of soils furnish no sure

criterion of their productiveness.

No. 546] INFLUENCE OF STARVATION 317

and those which are ‘‘productive’’—for what reason we

do not know—do.?

The solution of our problem is to be sought by means

of a series of comparisons which fall into two classes.

The first is designed to test the influence of the environ-

ment upon the characteristics of the individual; the sec-

ond is intended to show what influence, if any, the treat-

ment of the ancestors has had upon the offspring.

The first series of comparisons is essential in that it

brings out clearly the extent to which the ancestors were

modified by the environment to which they were sub-

jected. It affords no evidence whatever as to the factors

to which these effects are due. The second set of com-

parisons is the important one. Our problem, the reader

must distinctly understand, is not to determine why some

individuals are depauperate and others luxuriant, but

whether the rendering of individuals depauperate

through the environment to which they are subjected has

any influence upon the measurable characteristics of their

offspring.

B. Material

The materials upon which this study was based were

furnished by five series of garden beans, Phaseolus vul-

garis. Two of these were the common white Navy. The

third was a strain of Burpee’s Stringless first grown

from commercial seed at the Missouri Botanical Garden

in 1905. The other two were from the seed of the White

Flageolet and Ne Plus Ultra which Dr. Shull had used in

his hybridization experiments.*

2Our great ignorance of the problem of soil fertility is attested by the

words of Professor Hall in a chairman’s address before the Sheffield meet-

ing of the British Association (Science, N. S., Vol. 32, p. 364, 1911). He

said:

‘‘The fertility of the soil is perhaps a vague title, but by it I intend

to signify the greater or less power which a piece of land °

in, the causes which make one

small ones, differences which are so real that a farmer will pay three or

even four pounds an acre rent for some land, where he will regard the other

as dear at ten shillings an acre.’’

* Shull, G. H., Science, N, S., Vol. 25, pp. 792-794, 828-832, 1907; AMER.

Nat., Vol. 42, pp. 433-451, 1908.

318 THE AMERICAN NATURALIST [ Vou. XLVI

The two Navy series first came to my attention on the

farms of George A. Harris and Elmer Dille at Mount

Hermon, near Plantsville, Athens Co., Ohio, in the fall of

1907. From the Harris farm 160 plants were taken,

giving rise to 160 ‘‘pure lines.’ These are the Navy H,

or NH series. From the Dille field 550 plants were taken

STARVED

WELL FED

COMPARISON FIELD

1910

Diagram I. Cultural history of the Navy D series. The history of the Navy

the same, and can be expressed by substituting H for D as the first

habitat letter in the formule.

and yielded 550 ‘‘pure lines,’’ designated as the Navy D

series. These two fields furnished, as explained in detail

in a subsequent section, the starvation and feeding tracts

of the experiment.

Dr. Shull’s seeds saved for individual plants of a crop

of 1907 yielded 80 lines of Ne Plus Ultra and 100 of White

Flageolet.

The history of these strains during the course of the

No. 546] INFLUENCE OF STARVATION 319

experiment is shown by the diagrams. The seriations of

number of pods per plant appear in the Data Tables 4,

B and C.

TABLE A

PODS PER PLANT

Series 1| 2 3 | 4 s|6 171819 | 10| 11 | 12/18 | 14| 15 | 16 | Total

D 55 (229/165, 63| 24| 8| 4| 1 | i a SA a E p 550

DD 46 |107|141| 89| 57, 36/16 |11| 3| 4| 2|—|—| 1/—|—| 513

DDD |10 61| 93 107| 67 55/31 | 24 5 | 4|—| 1} 1|—|—;—|_ 459

HD '235|333 282/192 Wy 8)-7 1 Pt a ee

HDD |49 |172)234'208 204 var ede 34/22| 9| 9f 3| 3! 2| 1) 1,204

USD = |53 |111| 95| 30) 8} 3| —|—|— |—|—|— ||} |-| 312

USDD |25| 64| 42| 34| 33| 19/12) 3| 1) 2} 1/—|—|— | 1| 287

39 100/118 76| 43 26/12 13 —| 1;—|—|—|— -|—| 428

FSDD |13| 52| 98| 91! 64 43\/15| 4 RRE | 1: —+|—| - 387

For convenience of reference I designate the 1907, 1908

and 1909 cultures the ancestral series and the 1910 crops.

the comparison series. The fitness of these terms will be

apparent.

C. Experimental Methods and Collection of Data

Experimental methods may conveniently be explained

under three heads: Selection and Care of Seed, Cultural

Conditions, and Collection of Data. `

1. Selection and Care of Seed

The necessary requirements are two. First, it is essen-

tial that the material subjected to the various environ-

mental factors shall be identical in its hereditary tenden-

cies. Second, it is essential that in the routine of grow-

ing, harvesting and planting no purely physiological (as

contrasted with hereditary, germinal or genetic) sources

of differentiation shall be introduced.

Consider the first requirement.

We have learned from both biometric and Mendelian

researches that it is impossible to know from the simple

inspection of an apparently uniform group of individuals

whether or not they are really identical as to germinal

constitution. It is therefore idle to plant seeds of some

individuals under starvation and seeds of other individ-

320 THE AMERICAN NATURALIST [Von. XLVI

TABLE B

~ NUMBER or PODS PER PLANT

Series H | HH | HHH | DH \ DHH|\ USS | USH| USHH | FSS | FSH | FSHH

1 — ti 4 4&4 | = | [= — 4 | — —

2 — 8 10 10 GN hes 1 3 5 1 6

3 1 10 20 16 9 2 2 6 12 4 5

4 4 TI 36 21 | 12 2 5 Lt 21 4 H

5 3 25 52 20 | 10 3 5 15 24 9 9

6 + 34 62 20 | 26 6 6 24 6 20

7 6 41 78 29 | 39 | 16 | 15 27 25 | 14 26

8 T 55 91 26 | 42 | 17 | 20 38 38 | 12 34

9 10 58 82 36 | 43 | 3 17 28 43 | 22 32

10 12 | 97 43 | 52 | 48 | 40 | 23 | 67 31

11 76 91 | 35 | 51 | 4 17 15 24 33

12 12 78 96 39 | 37 | 54 | 22 12 43 | 22. 42

13 12 94 115 | 34 | 47 | 48 | 28 ri 65 | 22

14 9 74 34 | 40 | 49 | 25 3 47 | 24 34

15 7 2 60 28 | 35 | 52 | 23 3 50 | 25 25

16 T 83 72 35 | 19 | 37 | Z6 3 42 | 23 16

u 9 69 52 35 | 22 | 49 | 18 X 27 | 19 10

18 8 66 39 30: 12 3] B 4 46 | 27 13

19 5 56 29 24°) 17 | 32 | 20 — 31 | 19

20 1 25 | 21 | 11 3i | — | 36 | 17 10

21 i 51 25 16 5118 | 12 — 42 | 19 7

22 3 41 12 9 T 1.22 6 — 99 i 12 2

23 5 | 46 8 | 13 4 | 20 3 2 14 | 23 3

24 3 37 fi il 3 | 12 5 — 12 8 2

25 2 | 28 6 5 6 | 16 4| — ; 11} ll 1

26 2 27 6 8 4 | 10 2 — 16 | 12 1

27 2 19 1 9 2 T 3 — 9 | 12 2

28 4 12 2 Ti e A 5 4 | 13 =

29 1 14 1 10 am 2 1 — yi 7 seeing

30 2 23 2 5|—-{|— 1 8 2 a

31 1 20 = 2 D ire — 5 6 =

32 — 12 3 nA ag 1} — a 2 2 —

33 — 10 — 5i 3 | — -— 2 + ==

34 1 10 2 3 | — TA — 4 3 1

35 — 11 — es BE cae — 2 4 m

36 1 4 = 220 aa ee — 1 1 oe

37 1 7 — 4| — 2 | = — 4 3 Zer

38 no 6 — 3|ļ— | — — |— 1 —

39 = 5 — LC = 1 1 — Le =

40 i 5 -| — U care 1 — — 1 =

41 — 3 — — | — | — |— — — 2 oa

42 = 2 1| — | — = Ile ee

43 — 3 = |t 2 1 —

44 1 — fo pe a 1 -—

45 = 2 == 1 |— — — Iie

46 1 5 — EN Ra Ge nei — | — —

47 — 1 ae ee ee ee See lire =

48 — — Tie 2) — Lop = SEE

49 — 1 ne fee pe Gas MEE f pois

50 — ous een ee ee eg ae os La ean pie

51 — 1 Ga Gees A ome oe Wee aoe

52 — 2 a Kan EA ha E See —

54 — 2 L aad a aa Ea a T pie

55 = 1 a E E AT Baie ei set

56 — t oo ech ae f coe eh ek oe aes ae

67 1 se ER a, Cee a Pe gs. ==

Totalplants| 160 |1,484 |1271 |670 | 565 | 680 |361 | 224 |868 |475 | 429

No. 546] INFLUENCE OF STARVATION 321

uals of apparently the same uniform variety under feed-

ing conditions. The only certain method of securing the

TABLE C

NUMBER OF PODS PER PLANT

| |

Series Hea kE | ee beste | |

ME stale mi

HHC 8! 816 26 35 30 25/31/30 46 25/23 23 21 28 14|18| 5| 9| 8|12/12|11| 4| 4 23

HHHC 8 13 20'34 41/48 38 35 43 37 2636|25 24/19 17/10/14/15| 810| 8| 5| 3| 4 2| 3

HDC 6/10 2526|29 30/26 28 25 14/12|11/16 23 16] 9/10/11) 5| 5| 7| 5| 4| 4 31. 3\—

HDDC (11115/233536 3532/43 28/34/19|29/32/17,17|1019|13,15) 6| 5| 4| 4| 4) 1| 3| 2

DDC 616 12 12/20 22/26 14 6 8j16|15/15| 8| 7| 4| 5| 6| 1| 2) 1| 1—| 1) 1|—

DDDC 6/10/14 23/30, 27/21 22 21 161 si : me 7| 2| 1| 2| 4| 2| 1—

C 921/193 41,94132185i20.30, p3 18 1513 16 1 1113| 7| 5| 1| 7| 2| 2| 1}—

DHHC 7 17|30 38 45 4052 40 27 271911 1719 a n 9110| 6| 1| 4i 4| 4| 2| 4

SC 3| 5/15 22/2 25 31 a2 609 60 a7 28 28 31 30 29 15/10] 6| 6| 5| 3| 2| 1| 2) 1 1 2

USSC 1—| 5 $10 212931233143 24 2 19| 6| 8| 8| 6| 3| 3| 11/—| 3| 1

SHC 1) 1) zii 19 28/31/38 18 39 22/22/25 1 8| si 71 7| 3| 4| 1| 2) 1-H

USHHC |2|7 7 13 31 3131|36 3541 soe pel 12) 6/11] 9| 5| 7| 2| 1—| 1-1

SDC 510) 921 42/43 43 44 19 2 13115111| 8! 5! 2, —! 1— Em

USDDC |4| 117 10114222728 36136137 28/23/15|13/11| 9| 7| 1| 2| 1⁄1—| 1 —|—|—i—

SC 1| 6| 9 14/17/29 0 29 26 30 45 3831 21 31 29 27/13 1715181912 14/10| 7 6

FSSC 2| 6| 810/132 | 21308 35 26 25 25 = 3/17|10|10| 8| 4| 3| 2| 4

FSHC |—| 2| 9 18/20 33 302834 21 35/31|19/24/17|14 14| 91114) 7| 7| 8 6 5| 3 —

FSHHC |—| 7/15 20 36 3531 pae 7 41/39/30 21,19 aclauing 17/11) 8|10/12)10 7

FSDC ola es 6 9 14 24 17 21 23 20 26 2818) 9 16| 6| 7| 8| 9111] 4| 4| 1| 3| 3| 2

FSDDC |1| 2| 8110 14|23|25 3132/3024140 ae aolaaiasiis\isiolasiiel 9|13|15|10| 9 5

i LA e ehoketa at Total

Series itd ee |35] 42|43|44|46|47 49|51|52|55/79| piants

| i | | ENE cere ERTA Meron Scam

HHC agli 24 Li yg fe AT

auae | 1a hili HHA H HH HH 5

DC -4a 111132 Hi likre 376

HDD |——}2 i1 2 4-2 eee 498

DC 11 —— ———— —| 255

DDDC 3\—|—| 2 | 3 i—i i—mar 331

HC —|3 |1 |1 |2 | ——|—i 1 |2 |---|! —|—| 452

DHHC əl—| 1 |3 |1 1 i i k 598

USC al N EA LEI 580

USSC | ah saint: BSD

SHC | —|————— =l S21

USHHC |—|1 | 1 —i—|——— 399

SDC ik Fle TS ie Hon SS IE a ES = $50

USDDC | Fs es E Vat SI en A =| 938

FSC 2al3 6l3l6l1l1l2l1 2—1 H+ 586

FSSC iilh in at ee 50

FSHC 3/3 — 2 |2 |1 |2 |——————— iced’ a

FSHHC holle sls lalalala =s —|12-—--+ +I eS

FSDC 2\— 3 —|—|—-}1 | 1 |---| 1 = 307

FSDDC 2i3i3i6l2i-ti3eiie eee 538

desired result is to divide the seeds of individual plants.

If this be done and if all the lines* be represented —

‘Line or pure line is used merely in the genealogical sense.

San THE AMERICAN NATURALIST [Vou. XLVI

throughout the experiment by approximately the same

number of individuals, we shall not only be sure that like

hereditary tendencies went into all branches of the ex-

periment at the beginning, but can feel confident that no

material source of error is introduced by a change in the

mean hereditary tendencies in either branch of the ex-

periment through the selective elimination (by reason of

relative unfitness for the chosen habitats) of certain (dif-

ferentiated) lines.

These are ideal conditions, quite unattainable among

the innumerable difficulties of practical experimentation.

Omitting all particulars, I believe we may with reason-

able security consider the seeds which went into the orig-

inal starvation and into the original feeding series ran-

dom samples from the same individual plants. These

lines were maintained with moderate success throughout

the experiment.

The following details concerning the methods of ma-

nipulating the material may not be irrelevant.

Every seed was, so far as could be determined by in-

spection, perfectly formed and developed.” No seeds in

which the coats were sensibly wrinkled were included,

since this might indicate either a premature drying of the

seed in the pod, or a subsequent wetting.’

In harvesting, the plants were left in the field as long

as possible to allow the pods to ripen. They were then

gathered, and wrapped intact in newspaper to permit any

possible translocation of remaining plastic materials

from the stems or the pod walls to the seeds."

* Every seed was examined at least once. Unfortunately this can not

preclude the possibility of a seed containing a weevil which had not emerged

up to the time of planting. A large proportion of the seeds planted in these

experiments was also weighed individually for use in pure line and other

D, US, FS and BG individuals—

“I have carried out no experiments to determine what the real causes

are of this wrinkling.

* This precaution applies to only two of the original series, to NH and

ND, but not to FS, US and BG.

No. 546] INFLUENCE OF STARVATION 323

2. Cultural Conditions

Having prefaced that the purpose of this study is not

to determine what chemical and physical factors produce

in the individual the effects which we designate as star-

vation, we are free to choose for the ancestral series any

plots which present reasonably extreme conditions of

starvation and feeding.

The two fields in southeastern Ohio seemed perfectly

adapted to the purposes of the experiment. Their crops

of the common Navy beans presented the most diverse

appearance. The H field—that grown by Mr. Geo. A.

Harris bore a moderately heavy crop. The D field—

grown by Mr. Elmer Dille—seemed to have almost if not

quite as good a stand, but the plants were exceedingly

small.

The differences were apparently not due to variety,

for both were, in so far as could be seen, identical. They

were obviously not referable to cultivation, for both had

been equally well tended. The differences seemed en-

tirely attributable to the exceedingly poor soil of the D

field.

Minute description of these two fields is quite unneces-

sary. They were about a mile apart, and hence under

the same general conditions of climate. Neither was

level. Field H was much longer than wide and sloped

from the ends towards the middle, where the ground was

apt to be a little too damp. Plot D was situated on an

exposed ridge where practically all the surface soil had

washed away.

The plants originally growing upon these fields formed

the starting point for the starvation-feeding comparison.

This was in the fall of 1907. In 1908 transfers were

made, in order that we might be sure that genotypically,

as the pure linist would have it, the plants cultivated on

both fields were the same. Other varieties were also

added in 1908. These points are made quite clear by the

diagrams.

The comparison furnishing the test of the influence of

324 THE AMERICAN NATURALIST [Vou. XLVI

the D and H conditions upon the offspring should not

be made on either of these fields.®

Three fields? under control of the Station for Experi-

mental Evolution at Cold Spring Harbor were chosen

for the comparison. All the Navy series were tested

USH

T FED

USS

WELL FED

ao FED

COPPA FIELD

Diagram 2. Cultural history of the Ne Plus Ultra ee series. The White

Flageolet (F) series was subjected to an identical treatmen

on one field and all the Ne Plus Ultra and White Flageo-

let on another. The third field was devoted to the

*A number of breeders hold that among plants there is a gradual adap-

tation to the substratum; when plants are transferred from one locus

to another there is a ‘‘new place effect.’? Tf, now, the series grown OP

the starvation field for two years should from some such process of adap-

tation be better able to thrive under these conditions than a series newly

transferred there from a rich soil, or vice versa, the comparison would be an

6 oan unfair one.

The facts bearing T this point derivable from our material will

probably be discussed lat

Three were selected Pae accidents of season and culture do occur

and it is as unwise to plant all one’s experimental seed on a single field

as to carry all one’s pedigreed eggs in one basket.

No. 546] INFLUENCE OF STARVATION 325

fourth variety, BG, which must be reserved for a later

paper. .

The following method was adopted for counteracting

the possible hetereogeneity!® of the fields upon which

the plants were grown.

The different strains must be subjected to as nearly

as possible a random sample of the conditions afforded

by any plot. This end is secured by labeling each seed

individually and then scattering those of a particular

series quite at random over the field. If, then, certain

spots are somewhat more fertile or slightly moister

than others, all lines will have equal chances of being

represented there. If this were not done an undetected

differentiation in the substratum might induce quite de-

ceptive differences in the crops.

In these experiments I did not, unfortunately, work to

quite this degree of refinement. For technical reasons,

it was desirable to have each of the varieties planted in

separate rows. Each seed was placed in an individually

labeled envelope and the envelopes of a series thor-

oughly shuffled. The series were then planted in rows,

which were scattered as nearly as possible at random

across the field. By this means an almost but probably

not quite random distribution was secured.

3. Collection of Data

The recording of the data from the mature plants was

an onerous but relatively simple process.

As noted above, the plants were wrapped individually

at harvest time when as nearly dry as they could be

* Conditions were sp worse than those under which much of the experi-

mental evolution work has been done. At the same time I must frankly

confess that to the biometrician the comparison fields left much to be

available. In stating that conditions are in defect of those desired by the

biometrician, we may perhaps remember that they have the advantage K

presenting no experimental artificiality, but of being precisely the so

which would be met in ordinary agriċultural practise.

Entirely too little attention has been paid to these matters by experi-

mentalists. Compare,‘for instance, some suggestions in AMER. NAT., Vol.

wan. THE AMERICAN NATURALIST [Vou. XLVI

allowed to become in the field, and after thoroughly dry-

ing stored until they could be studied. They were then

placed in a saturated atmosphere for a few hours until

the pods could be handled without snapping open, and

records made of the number of pods per plant and num-

ber of ovules and seeds per pod. The seeds were then

stored until thoroughly dried at laboratory temperature

and humidity, when they were looked over for weighing.

Particulars concerning the various characters will be

given in the special sections. }

D. Methods of Analysis of Data

1. Pertinent Comparisons

The possibility of an influence of ascendant starvation

upon descendant characters is to be tested by a series of

comparisons. The number which might be made, and

with profit, is so great that space requirements impose a

stringent limitation.

A first restriction is effected by basing the compar-

isons upon the simplest of the statistical constants.

A second limitation is effected by the exclusion of all

comparisons showing the relative influence of environ-

mental conditions on different varieties. Possibly this

question will be considered in another place. Such inter-

racial and inter-varietal comparisons are in this paper

quite incidental to those which are strictly intra-racial

and intra-varietal.

Finally the comparisons within the varieties must be

limited"! to those which seem absolutely essential to our

purposes. The constants for the 40 series are given so

that the reader may make any comparison he deems

desirable.

In the dichotomous system adopted for these experi-

ments, one branch of the stem material was subjected to

“In all we have three distinct varieties represented by 40 series of

material—18 of Navy and 11 each of White Flageolet and Ne Plus Ultra.

If all the 4n(m—1) comparisons within each variety were made for the

three constants, A, e, and CV, 789 differences and their probable errors

would have to be calculated for each character observed.

No. 546] INFLUENCE OF STARVATION 327

starvation and the other to feeding. Both ancestral and

comparison series allow of two kinds of comparisons,

intra-ramal and inter-ramal.

In the first case the comparisons will be made within the

same branch of the dichotomous system, i. e., the off-

spring of the starved parents and starved grandparents

will be compared with plants whose parents only were

starved, both parents and grandparents being in the

direct line of descent.??

In these tests the individuals grown on the comparison

field bear to each other the relationship of ‘‘aunts’’ and

“nieces.” Such comparisons are possible where the seed

retains its vitality for a number of years. They are

open to criticism unless it be known that the age of the

seed has no influence upon the characteristics of the

plants developing from them.*®

In the second class, the inter-ramal, are those compar-

isons between points on different branches of the dichoto-

mous scheme. Here two subclasses may be recognized.

In the one the comparisons are between strictly homolo-

gous points on the starved branch and on the well-fed

branch. The effect of one generation’s starvation will

be compared with the effect of one generation’s feeding.

In this case comparisons will be made between ‘‘first’’

and ‘‘first’? cousins. Or Mendelianwise, all individuals

compared will be F,, F, or Fx. Such comparisons will-

be called direct inter-ramal comparisons.

In the second subclass, the comparisons will be made

between different points on the two branches; all com-

” 32Tn the same manner any one who desires may compare plants whose

parents and grandparents were well fed with those whose parents only were

well fed. This is not done here for the simple reason that I do not know

that the well fed series were grown at an extreme of feeding at all com-

parable with the extreme of starvation which was possible in these experi-

ments. If they were not, one would expect to find a smaller influence, if

any, upon the offspring.

18 It may have occurred to the reader that a valuable comparison for our

purpose could be made within the starvation series by determining, e. g.,

whether USDD whose parents USD had been starved, had a lower value for

any character than USD whose parents US were not grown under starva-

tion conditions. Such tests are, however, useless because both edaphic and

meteorological conditions may differ from year to year. —

328 THE AMERICAN NATURALIST [Vou. XLVI

parisons will be between ancestral individuals or their

offspring belonging to different generations. Such will

be called cross inter-ramal comparisons.

The most crucial test is that afforded by the direct

inter-ramal comparisons. Both the intra-ramal and the

cross inter-ramal comparisons have the disadvantage

that the (possible) seed age factor is not excluded.

Again, atmospheric (meteorological) factors play a much

larger part where different seasons instead of a single .

season are involved.

Turning to our own available data, we note the fol-

lowing points concerning the comparisons:

Only such comparisons as can be made on the basis of

both ancestral and comparison series are discussed, al-

though data for some others, e. g., NH, ND, US, FS, USC,

FSC are given.

In all cases the differences are taken

Starvation

less

feeding

so that when starvation tends to reduce a character the

difference bears the negative sign.

If we continue our attention strictly to those within

the strain, we have the following inter-ramal compar-

isons:

Direct Cross

HD-HH HD-HHH

HDD-HHH . HDD-HH

DD-DH DD-DHH

DDD-DHH DDD-DH

USD-USS USD-USHH

USD-USH USDD-USS

USDD-USHH USDD-USH

FSD-FSS FSDD-FSS

FSD-FSH FSDD-FSH

FSDD-FSHH FSDD-FSH

If we go beyond the limits of the populations formed

by splitting the seeds of the same individual into two

No. 546] INFLUENCE OF STARVATION 329

lots, and consider the Navy D and Navy H comparable,

we get:

Direct ross

DD-HH DD-HHH

DDD-HHH DDD-HH

HD-DH HD-DHH

HDD-DHH HDD-DH

2. Statistical Formule Employed

Methods ample for all the needs of this study are fur-

nished by the simplest of the Pearsonian statistical for-

mule. The comparisons in the main are restricted to

those based on the mean, standard deviation and coeffi-

cient of variation.

These do not fully describe a population, but they fur-

nish more information concerning it than do any other

three simple constants, and are sufficient for our pur-

poses. The methods of calculation are now familiar

or readily accessible to all biologists. The original data

are available for any other comparison, e. g., that based

on skewness.

The chief possibility of untrustworthiness in the sta-

tistical constants seems to me to lie in a possible biolog-

ical source of error introduced by growing the compar-

ison series in rows instead of mixing all the individually

labeled seeds together and scattering them quite at ran-

dom over the entire field.'* If because of the irregular-

ity of the fields, some of the rows were subjected to

slightly better and some to slightly poorer conditions

than the average, and if the rows of an individual series

were not distributed over the field in a perfectly random

manner, a slight source of differentiation quite undetect-

ible by the statistician’s simple probable error would be

introduced. I suspect this to be the case, and conse-

quently our probable errors are perhaps too low as cri-

teria of the existence of differentiation due to the treat-

ment of the ancestry. i

Fortunately we are not limited to a single comparison,

“ As an extra precaution half rows were frequently used.

330 THE AMERICAN: NATURALIST [ Vou. XLVI

but- have- several . pairs. Any one of these might be

wrong in its indication of the influence of ancestral en-

vironment because of uncontrollable factors making for

heterogeneity on the comparison tract, but as long as

these factors differ from series to series in a purely ran-

dom manner, we shall expect to get trustworthy values

by averaging the results for the several comparisons.

This averaging may be done in one or both of two ways.

Most easily one'may simply note the number of alterna-

tive cases, above zero and below zero, and calculate the

probable error of either class by the formula

67449 VN X OX 5

since, unless. there be an influence of the treatment of

the ancestors, the probabilities of differences lying above

and below zero are equal. In the second case, the true

mean and standard deviation of the series of differences

may be obtained and the probable error of the mean

difference calculated by the familiar formula

E = 67449 —

Hue OV

It only remains to say that, except when specified,

Sheppard’s modification was not applied in the calcula-

tion of the moments.

HE PRESENTATION oF DATA AND COMPARISON OF

CONSTANTS

i Number of Pods per Plant in Navy, White Flageolet

and Ne Plus Ultra Beans

The purpose of this section is to present the data for

number of pods per plant in three varieties, represented

by 40 series and over 21,000 individuals, and to draw the

comparisons which may profitably be based upon them.

The other characters for these varieties and all of the

data for still another variety are reserved for later treat-

ment. This character, which is the most easily deter-

No. 546] INFLUENCE OF STARVATION 331

mined of any, is also subject to considerable possibility

of error. It is impossible to know from an inspection of

the matured plants that some of the pods have not been

lost by accident. Another difficulty is introduced by the

fact that some varieties of beans have a tendency to make

a ‘“‘ second growth’’ when they are allowed to stand in

the field after they are completely ripe. Unless frosts

are very late these second growth pods rarely mature.

If the plants be allowed to stand in the hope that they

will ripen these second growth pods, the normal crop of |

re i

90 g ee a8 Ga

ft -----0--—-0m | NDD f

ae ck

80 j 7 Lad i a L

ji : ——e——o =| NH jt

To oi Ai

HAA

ode

i /

ite

( 6 WA U Mo S H WD 35 w 6S

Diagram 3. Number of pods per plant in NDD, ND D, NHH series.

All series are reduced to a pércentage basis and the relative frequencies | summed

from the ing. The influenc ce a starvation in the reduction ‘ot the number

of pods is very conspicuous.

‘ara at eee a ee ee) ee ee

er may either lose their seeds, if the weather be E

or decay if the weather be wet. All that can be done is

to watch the plants carefully, to harvest as soon as prac-

tically-all the pods that are ripe, and to pull off any sec-

ond growth sprouts. This apparently introdùces a con-

siderable personal equation into the work, but even if true

it is unavoidable. I do not believe that a palpable source

of error was introduced since (a) a large proportion of

the plants do not show the second growth at all; (b) when

332 THE AMERICAN NATURALIST [ Vou. XLVI

they do, a person with a little practise will make very

few mistakes; (c) even if errors are made, the treatment

is the same for all series.

All the pods counted had at least one matured seed.

This specification is necessary since, especially in the

autumn, some plants produce quite a number of half de-

veloped and completely sterile pods. If these were in-

eluded there would be no point where a line could be

WHITE FLAGEOLET F NE PLUS ULTRA

FSD AND FSH USD AND USH

STARVED, 1908 STARVED, 1908

| : FED, 1908 FED, 1908

L L n p aa

0 410 20. Jo 40 50 0 10 20 ag 40

ams 4 and 5. Percentage frequency of number of pods per plant under

sta and feeding conditions for White’ Flageolet and Ne Plus Ultra series,

drawn between the number of flowers and the number

of pods produced by an individual.

The record forms do not interest the general reader.

The original data are given in Tables 4A—-C. The phys-

ical constants appear in Tables I-III. :

The extreme sensitiveness of the number of pods per

plant to environmental conditions is seen at once from an

No. 546]

INFLUENCE OF STARVATION

333

inspection of the tables of raw data, and better still from

the three graphs, diagrams 3-5, for the number of pods

per plant in the 1908 series.1®

We may now summarize as briefly as possible, and

largely by diagrams, the results which may be gathered

TABLE I

Series Mean and Probable Standard Deviation (Coefficient of Variation

Error and Probable Error and Probable Error

NH 15.2375 = .4042 7.5800 + .2858 49.746 = 2.294

NHH 16.9919 + .1518 8.6696 = .1073 51.022 = 0.781

NHHH 11.9308 = .0977 5.1652 + .069 43.293 + 0.679

HD 3.9682 -0348 1.9433 + .0246 48.972 = 0.755.

NHDD 5822 .046: 2.3756 + .0327 51.844 + 0.884

D 2.6782 + .0335 1.1662 + .0237 43.545 + 1.040:

DD 3.5926 = .0563 1.8917 + .0398 52.657 1.384.

NDDD 74 1.9329 = .043 43.855 1.149

DH 14.6179 = .2148 8.2422 = .1519 56.385 = 1.330

NDHH 11.8265 = .1408 4.9595 = .0995 41.935 = 0.978

NHHC 11.9597 = .2212 7.3010 = .1564 1.047 + 1.

NHHHC 10.6498 = .1788 6.2390 = .1264 58.583 = 1.541

DC 10.9362 = ‘2747 7.8970 = .1943 72.210 = 2.539

NHDDC 10.2851 + .1 6.1042 = .1305 350 =

NDDC 9.3098 = .2259 5.3470 = .1597 57.434 = 2.210

NDDDC 9.9819 + .2360 6.3673 = .166 63.789 = 2.252

DHC 9.9801 + .2079 6.5532 = .1470 662 d

NDHHC 9.9851 + .1827 6.2839 = .1292 62.933 = 1.732

TABLE II

Series Mean and Probable Standard Deviation (Coefficient of Variation

Error and Probable Error. and Probable Error

USS 15.7382 = .1562 6.0379 = .1104 38.365 = 0.798

USH 14.0416 + .1972 5.5542 + 94 39.555 = 1.138

USHH 8.4375 = .1462 3.2439 = .1034 38.446 = 1.250

SD 2.5929 04 1.2265 =. 1 47.300 = 1.536

USDD 3.6203 .0919 2.0986 =. 57.970 + 2.322

USC 10.1434 = .1285 4.3846 =. 43.226 + 1.050

USSC 11.7068 + .1594 4.6188 = .1127 39.454 + 1.102

USHC 9.9844 + .1541 4.0936 = .1090 41.000 1.262

USHHC 10.1 .1564 4.6299 = .1106 45.794 1.

USDC 8.4474 = .1331 3.8477 = .0942 45.549 + 1.326

USDDC 10.1231 + .1426 3.8579 + .1008 38.110 + 1.132

3 The 1908 instead of the 1907 series was chosen for these graphical

comparisons, since the number of available series is cnr HR as com-

pared with two—and since the num

giving much epe results.

eader may care to make.

quite comparable, they have been reduced to a percentage In the

first where data for four series are laid side by poal the per-

mn t

ber of individuals is

The data are available for any ep A com-

nder. the results for all series

To re

uch greater,

basis.

centages have been summed from the beginning for each pod class. In the

ney of each cae of

second

tage freque

pods per plant is represented by the height of a line.

and third

the percen

334 THE AMERICAN NATURALIST [ Vou. XLVI

TABLE III

Serica Mean and Probable Standard Deviation | Coefficient of Variation

Error and Probable Error and Probable Error

FSS 15.0265 + .1697 7.4134 = .1200 49.335 = 0.974

SH 17.2947 + .2456 7.93 = .1736 45.889 = 1.197

FSHH 11.8415 + .1562 4.7959 = .1104 40.501 = 1.075

SD 3.4252 + .0552 1.6929 + .0390 49.424 + 1.390

FSDD 4.0362 + .0593 1.7294 = .0419 42.848 + 1.215

C 14.2218 = .2056 Ta = 1454 51.895 = 1.268

FSSC 12.9562 + .1856 6.1678 = .1313 47.605 + 1.222

FSHC 12.2431 += .2068 6.3729 = .14 52.053 = 1.483

FSHHC 14.1505 + .2115 7.9996 += .1495 56.532 = 1.353

DC 9055 = .2616 6.7949 + .1850 52.652 = 1.787

FSDDC 14.4981 += .2090 7.1885 = .1478 49.583 = 1.245

from the tables of constants. As already emphasized

the comparisons between the ancestral series are of in-

terest for our present purposes only in so far as they

furnish proof that the parents of the comparison series

were conspicuously differentiated in type and variability

because of the environmental conditions to which they

were subjected. The reader must always keep in the

foreground the fact that our problem is not to determine

in detail what the causes of this differentiation are, but

merely to show that a conspicuous differentiation exists

and to ascertain whether it has any weight in determining

the characteristics of the offspring.

he differences between the starved and well-fed an-

cestral series are so well marked that constants are best

represented by graphs for all the series. In diagrams 6

and 7, which embody data for all possible comparisons

for A and v, roughly made, the key number of the va-

riety is given along the left-hand margin. The value of

the constant for the ancestral series is indicated by the

position of a solid dot when the series is a starved one,

and by the position of a circle when it is a well-fed one.

The value of the constant for the offspring of each of

these ancestral series grown upon the comparison field

is shown by the position of a solid square under a sep-

arate scale. Thus the key to the comparison series is

given by adding C to the formula for the ancestral series.

The graphs for the mean number of pods per plant and

for the standard deviation of number of pods per plant

No. 546] INFLUENCE OF STARVATION 335

brings out with great force and clearness the following

facts:

(a) The difference between the ancestral series sub-

jected to the S and H conditions and those subjected to

the D environment is very great. In all cases means and

SCALE OF MAGNITUDE FOR

ANCESTRAL SERIES

13 04 15 86 17

SCALE OF MAGNITUDE FOR

COMPARISON SERIES

9 0

| arn een ER. reo ae ee 412 68 as

BER RO. etek: |

STRAIN AND SERIES OF PLANTS

----4

---"

Diagram 6. Mea

Subjected to various

n number of pods

conditions of

sta

per plant in ancestral, or as

cendatit, seri

. the oi

to environmental conditions. The comparison series, however, show much smaller

> ny

differences, and no clear indications of -an influence of the ancestral conditions.

standard deviations are conspicuously higher when the

plants are well fed than when they are starved. _

(b) There are considerable differences ‘between a

strain grown on the same field in different years.

336 THE AMERICAN NATURALIST [Vou. XLVI

Season is evidently a large factor in determining number

of pods per plant. This is most striking in the means

but it is also detectible in the standard deviations. For

the means we note that in each of the four strains the

average was conspicuously lower in 1909 than in 1908 on

the H field and slightly higher in 1909 than in 1908 on the

SCALE OF MAGNITUDE F SCALE OF MAGNITUDE FOR

ANCESTRAL is COMPARISON SERIES

o e428 E k o 2s hee ee

NAVY 4

NHH =

NHHH E |

NHD tr a

NAVY

w s

a NDD a

z L

z NDDD -4-- a

= P E arcane Oe le ade sa E]

“ULTRA

faal

m uS

=] USS O m

a =

< USH Pe

< USHH a

x i

Ps UsD z

FLAG.

FS |

FSS x a

FSH t= a

FSHH a

FSD 4 =e

Diagram 7. Standard deviation of number of pods per plant in ancestral

and comparison series. Compare the explanation of diagram 6.

D field. The standard deviations show precisely the

same results for the H field, but the differences between

1908 and 1909 for the D crops are relatively small.

considerable, but it is impossible to be certain of any in-

fluence of the treatment of the ancestors.

No. 546] ` INFLUENCE OF STARVATION 337

(a) and (b) are facts to be expected from the common

experience of all those who have occupied themselves ex-

tensively with the growing of plants; they are sum-

marized here merely because it is idle to discuss (c)

unless the results for (a) are clean cut.'®

Turn now from diagrams to physical constants. Con-

sider first the intra-ramal comparisons, those cases in

which individuals whose ancestors have been starved for

a longer period are contrasted with individuals in the

same line of descent whose ancestors have been starved

fora shorter period of time. The necessary constants

appear in Table IV.

TABLE IV

i R Ancestors Starved _ Ancestors Starved 1r

Description of Material irs Goneri on hree pa ack

Ancestors starved for one generation:

USDC series:

Standard deviation............. + 0.0102 + 0.1378

aise of papain epee acres — 7.439 = 1.743

FSD FSDDC series:

i E AE Mune eel e bo Wine es alee + 1.5926 + 0.3348

rrp Vee Covina. 2. cis Corah 0.3936 + 0.2369

ə _ Coefficient of variation.......... — 3.069 + 1.178

NHDDC series:

PE EA Bho rb 6 views 0.6511 0.3309

Standard deviation............. — 1.7928 = 0.2341

Coefficient of variation.......... —12.960 = 3.031

Ancestors starved for two generations o

: se

CANE ARE E ee + 0.6721 = 0.3266

andard deviation............. + 0.9203 + 0.2311

Coefficient of variation.......... + 6.355 = 3.155

Two of these means seem to be significant in compar-

ison with their probable errors, and both of these indicate

that starvation of the ancestry for two as compared with

one generation, increases the number of pods on the off-

spring plant. But, it must be remembered that the seed

is necessarily a year older for a single generation of

starvation only. Furthermore, the series are too few

and the differences are entirely too small—only 1.6 pods

—to lay particular stress upon it.

The second set of comparisons, the inter-ramal, those

* Those noted under (b) may be treated more fully later.

338 THE AMERICAN NATURALIST [Vou. XLVI

between individuals whose ancestors had been subjected

to distinctly unlike treatment is made in Tables V-VIII.

Consider first the means. Altogether there are 28

inter-ramal comparisons, direct and cross. The number

of pods is smaller in the plants whose ancestors had been

starved in 16 out of 28 cases. If there were no relation-

ship between the conditions to which the ancestors were

subjected and the number of pods which their offspring

produced, one would expect 14 to be negative, providing

the errors of random sampling had not to be allowed for.

But the probable error is

6145V 28 «5x 5179.

Clearly a difference of 2+ 1.79 has no significance.

If now we restrict the comparison to differences signifi-

cant with regard to their probable errors, and consider

Diff./Eairr. > 3 to be significant, we note that only 11 out

of the 28 differences may be regarded as statistically

trustworthy. Of these, 9 have the negative and only 2

the positive sign. Certainly this looks as though there

were a very slight effect of the starvation of the ances-

tors, but nevertheless an effect quite detectible by the

statistical methods.

This point may be tested further by takin ‘the aver-

ages, regarding sign, of the pertinent differences for the

series of the three varieties. To make sure that slight

racial differences between ND and NH do not obscure the

results we recognize two classes of comparisons, within

the strain and between strains. The results are:

Navy, Within Strains, A == — .515

etween Strains, A = —. .515

General Average, A =— .515

Ne Plus Ultra, A= — 1.315

White Flageolet, A= + .585

In all cases except the White Flageolet aie! the

number of pods is s slightly lower when ihe ancestors have

‘been starved. |

* Note also that the two cases of significantly positive differences occur

in the White Flageolet variety.

No. 546]

INFLUENCE OF STARVATION

TABLE V

Description of Material

| Ancestors Starved for

One Generation

NHDC

339

Ansira Stirred foi

Two Generations

NHDDC

Ancestors well fed for one generation:

NDHC series:

Ancestors well rg for two generations: |

NH s = serie

Cat Eels. EE A E

MOS n aa eres ERS

Standard Pa aE a s A See

ent of variation

ine well fed for three generations:

NHHHC series

Standard oii :

Coefficient of variation..........

Lak 0.9561 + 0.3445

| + 1.3438 + 0.2437

| + 6.548 + 3.238

| — 1.0235. =-0.3527

| + 0.5960 = 0.2494

| +11.163 = 3.071

| + 0.9511. + 0.3298

+ 1.6131 + 0.2332

| 49.277 = 3.073

.2864 = 0.3277

| + 1.6580 + 0.2319

+ 13.627 = 2.970 `:

+ 0.3050 + 0.2780

+ 0.4490 + 0.1965

— 6.312 + 2.604

— 1.6746 + 0.2881

— 1.1968 = 0.203°

— 1.697 + 2.393 -

+ 0:3000 + 0.2596

— 0.1797 + 0.1836

— 3.583 = 2.396

— 0.3647 = 0.2569

— 0.1348 = 0.1817

+ 0.767 + 2.262

TABLE VI

Description of Material

| Ancestors Starved for

| Two pene Ws ations

Ancestors Starved for

Three pen rege

NDD

Ancestors well fed for one generation:

NDHC series:

MGatis i046 hia eee vis

oefficient of variation

Ancestors well fed for two generations:

NHHC series:

Standard deviation.............) =

NDHHC series

Oo He oe E TET E a Se ee a oc ie

‘Coefficient as Variation....54% ini.

Ancestors well fed for Tee generations:

C series

en soe sae ATE moe N

CoeMeient of Saini Pepe PRI

— 0.6703 = 0.3071

— 1.2062 = 0.2170

— 8.228 = 2.98

S z pose + -on

2236

> 3. ory + ae 805

— 0.6753 + 0 .2905

0.2054

— 0.9369 +

— 5.499 = 2.807

‘— 1.3400 + 0.2881

— 0.8920 + 0.2037

+ 0.0018 + 0.3145

— 0.1859 + 0.2225

— 1.873 + 3.019

— 1.9778 = 0.3234

— 0.9337 =

+ 2.742 + 2,838

— 0.0032 =

+ 0.0834 = O10

-+ 0. ps .841

— 0. .2961

+ 0.1283 + 0.2093

+ 5.206 = 2.729

= 1149 + 2.694

Consider now only the ten direct inter-ramal ‘ind the

ten cross inter-ramal, forming the twenty possible intra-

varietal comparisons.

comparisons which are availabl

seven have the negative and three the positive sign. |

Of the ten direct intra-ramal

e from the four series,

two cases only is Diff. /Baice > 3, and in one case i

340 THE AMERICAN NATURALIST [Vou. XLVI

TABLE VII

Ancestors Starved for | Ancestors Starved tor

Description of Material One Generation Two Generations

USDC USDDC

Ancestors bal fed for one generation:

— rie

E E oo E re ee — 3.2594 = 0.2076 | — 1.5837 = 0.2138

Standard GOVIRLION pe. E a — 0.7711 = 0.1470 | — 0.7609 = 0.1513

pba of VOR, oo E. + 6.095 = 1.724 | — 1.344 = 1.579

wahe

Ste ae ey cn E eee — 1.5370 + 0.2037 | + 0.1387 = 0.2100

Standard dorato a cae eo, — 0.2459 = 0.1442 | — 0.2357 = 0.1483

Coefficient of injec Bogie acs + 4.549 = 1.830 | — 2.890 = 1.695

Ancestors well ee rations:

USHHC se

Maer a yp a i eee es — 1.6629 + 0.2054 | + 0.0128 = 0.2117

Standard deviation............. — 0.7822 + 0.1453 | — 0.7720 + 0.1497

Coefficient of veins E T E — 0.245 = 1.859 | — 7.684 = 1.726

TABLE VIII

Description of Material

Ancestors Starved for

ne Generation

FSDC

Ancestors Starved for

wo Generations

FSDDC

Ancestors well fed for one generation:

ries:

ee ee eee reer eset ete eee tees

ee ee R ee AS

FSHC

wane oe déviation. o r.a

Coefficient of ane PEE es

Ancestors rane fed for two generations:

FSHHC series

I sires Bare ier ae mew i

All these are negative.

— 0.0507 + 0.3208

+ 0.6271 + 0.2269

+ 5.047 = 2.165

+ 0.6624 + 0.3335

+ 0.4220 + 0.2358

+ 0.599 = 2.322

— 1.2450 + 0.3365

— 1.2047 + 0.2379

— 3.880 + 2.241

+ 1.5419 + 0.2795

+ 1.0207 + 0.1977

+1.978 + 1.744

+ 2.2550 + 0.2939

+ 0.8156 = 0.2078

— 2.470 + 1.936

+ 0.3476 + 0.2973

— 0.8111 + 0.2102

Bae 83

There are no statistically signifi-

cant positive differences, the actual values being .013

+ .212, .348 + .297, and .662+ .334. The two larger of

these occur in the White Flageolet series.

the ten direct comparisons is — .589 pods.

The mean for

Of the ten cross inter-ramal comparisons, five are neg-

ative and five are positive; six are significant with regard _

to their probable error, four with the negative and two

with the positive sign. In both cases of positive differ-

ences (i. e., where the seeds from starved ancestors pro-

duced more pods than those from fed ancestors) the seed

from the fed plants was a year older than that from the

starved plants. The average*for the cross comparisons

is —.262 pods.

No. 546] INFLUENCE OF STARVATION 341

Consider the standard deviations.

As already noted, and as is clearly to be seen from the

graph, the standard deviations for the starved and fed

ancestral series show differences agreeing in general with

those seen in the means. This is to be expected, since

A and e are generally closely correlated. For this rea-

son it is idle to discuss the influence of starvation or

feeding upon variability on the basis of the standard

deviation alone.

Turning to the comparison series, we note that of the

28 differences, taken altogether, 17 are negative and 11

positive. The deviation from expectation is therefore

3+ 1.79, and can not be asserted to be significant.

Again taking Diff./Hair. > 3 as indicating differences

significant with regard to the errors of sampling, we note

that 17 cases out of 28 are statistically significant. Of

these 17 cases, 12 are negative and 5 are positive. Con-

sider averages as before:

Navy, Within Strains, A = — .165

Between Strains, A = — .053

General Average, A = — .109

Ne Plus Ultra, A= — 595

White Flageolet, A= + .145

Again limiting comparisons to the strictly intra-

varietal, and segregating into direct and cross inter-

ramal comparisons, we find that of the ten direct com-

parisons possible in the four lots, six are negative and

four positive in the sign of the difference. Only four are

statistically significant, i. e., Diff./Eart:. > 3, and all are

negative. The average is —.221. Of the ten cross inter-

ramal comparisons, seven are negative and three are

positive in sign; with regard to their probable error, eight

are significant; of these five are negative and three are

positive. The mean for the series is —- - 181.

Note the following points elative varia-

bilities as expressed by the coefficients. of variation.

Taken altogether, fifteen differences are negative and

thirteen are positive in sign. Accepting a difference of

342: THE AMERICAN NATURALIST [ Vou. XLVI

three times its probable error as statistically significant,

we note that altogether only six out of the twenty-eight

differences may be regarded as trustworthy. Of these

four are positive and two are negative in sign. Taking

means as for the two preceding constants, we find:

Navy, Within Strains, 4 = -+ .912

Between Strains, A = -+ .912

General Average, A = + .912

Ne Plus Ultra, A = —.,253

White Flageolet, A= — 946

With mean differences as slight as these, one certainly

can not argue that the starvation of the parents has had

any pronounced influence upon the relative variability of

the offspring.

j PROVISIONAL SUMMARY

1. The foregoing pages are devoted to a statement of

problems, description of methods and the presentation of

a first part of the data secured in a biometric investiga-

tion of the influence of the starvation of the ascendants

upon the characteristics of the descendants in garden

beans. Since several months will necessarily elapse be-

fore all of the materials can be worked up, it has seemed

undesirable to withhold the constants already calculated

and checked, viz., those for number of pods per plant in

three varieties represented by forty series comprising

altogether about 21,000 individuals. The publication is

therefore partial but in no sense preliminary. Several

questions that might be discussed on the basis of the data

presented are passed over until more series of material

can be lined up. The conclusions drawn—even for num-

ber of pods per plant—are provisional merely. =

2. The purpose of this research was not to ascertain

the physico-chemical factors to which starvation is due,

but to determine whether such artificial depauperization

of the ancestors has any influence upon the characters of

the offspring. Such ordinary ‘‘fertile’’ and ‘‘sterile’’ or

‘‘good’’ and ‘‘poor’’ agricultural land was therefore

No. 546] INFLUENCE OF STARVATION 343

taken for the ancestral series as would produce moder-

ately extreme conditions of depauperization and luxu-

riance in the crops.

3. The influence of from one to three generations star-

vation of the ascendants upon the characteristics of the

adult descendants is not conspicuous, in fact hardly to be

detected by the eye in the field. Statistical constants

seem, however, to show a slight yet unmistakable influ-

ence of the treatment of the ancestors in the form of a

slight decrease in the number of pods per plant.

4. The published data are as yet insufficient to justify

any discussion of the question of the cumulative influence

of the starvation conditions, or of the mechanism through

which the characters of the offspring plants are modified.

Evidence on these and various other pertinent questions

are being gathered as rapidly as possible.

MENDELIAN PROPORTIONS AND THE IN-

CREASE OF RECESSIVES

PROFESSOR FRANCIS RAMALEY

UNIVERSITY OF COLORADO

REcENTLY in working over some data! on the inherit-

ance of lefthandedness, certain questions came up,

which seem of considerable interest, as: Does the pro-

portion of lefthanded people remain the same from cen-

tury to century or does it diminish or increase? In any

case, how does the result come about? Although well

aware of the present-day aversion to arm-chair biology,

it yet seems that these problems can hardly be attacked

from the experimental side, and that a theoretical dis-

cussion may be of some value.

It may be stated at the outset that I consider left-

handedness to be a true Mendelian recessive,? and also

that there is no selective mating with reference to the

character. There seems also no reason to suspect that

lefthanded people exhibit less fertility? than normal in-

dividuals. If these suppositions are correct, the con-

dition offers a happy opportunity for study, since most

human characters thus far examined are such as might

be likely to be affected by selection.

Concerning the first question asked above, no positive

answer can be given, for there are no statistics. It is

probable that the affection is a very old one, and not of

recent origin. If it tends to increase it might be expected

that a very considerable part of the population would

now show the condition, while if it is decreasing, we

*As yet unpublished.

* Evidence for this view is shown by Professor H. E. Jordan in the

Breeders’ Magazine, Vol. II, pp. 19-29 and 113-124. My own observations

confirm this belief.

* My own records even suggest the opposite condition, but this is prob-

ably merely chance due to the small numbers studied.

344

No. 546] MENDELIAN PROPORTIONS 345

should, after all the long period of its existence, find

only a few persons with the condition.

_ On the ‘‘presence and absence’’ theory lefthandedness

is due to the loss or ‘‘dropping out’’ of the factor or de-

terminer for righthandedness. If such loss could occur

in the past, why not from time to time now? If so, why

would not the proportion of lefthanded people continu-

ally increase?

In a population where the dominant, the heterozygote

and the recessive have a certain proportion, slight

changes in the relative numbers seem to have no perma-

nent effect. There is a tendency to stability and unless

a certain point is passed because of the appearance of an

unusual number of recessives, there will be a return to

the usual ratio. The mathematical features of the case

have been discussed by Dr. W. J. Spillman,‘ and by Mr.

G. H. Hardy. The earliest clear statement of the case

which I have seen is by Dr. George H. Shull*® in his dis-

cussion of elementary species in Bursa bursa-pastoris.

The fact of the stability of certain ratios and instabil-

ity of others can be readily comprehended froni the fol-

lowing tables (I, II, III). We may let RR represent a

pure righthanded individual, Rr, a heterozygous right-

handed individual, and rr, a lefthanded individual. As

a first example it may be supposed that a large popula-

tion exists in which the various types occur in the fol-

lowing proportions, viz. :

1 pure righthanded:2 heterozygous righthanded:

1 lefthanded, or,

RR:2Rr: rr.

Random matings would occur in such fashion that mem-

bers of each group would mate with those of their own

group or with members of other groups. The various

possibilities are represented in Table I. The filial gen-

* Science, x S, Vol. XXVIII, pp. 252-254, 1908.

* Ibid., pp. 50.

« olenos, x a. Vol. XXV, pp. 590, 591, 1907.

346 THE AMERICAN NATURALIST [ Vou. XLVI

eration derived in Table I is composed of the three types

in the same ratio as in the parental generation.‘

TABLE I

MATINGS AND OFFSPRING IN A LARGE POPULATION HAVING THE COMPOSITION

1 RIGHTHANDED: 2 HeETEROZYGOUS RIGHTHANDED: 1 LEFTHANDED

E .

- Offspring .

Matings eee ed

RR Rr rr

HR SR eee ee 1

Pile Ct eo ei Ce ks ae eet cers 1 1

More See N ree 1

IRT X RR. osa es ee 1 1

OUr A Rr oa bas ook E 1 2 1

Bier KR PR ee ee 1 1

0 RR oe ae ek ee eee 1

i ARF ee ee 1 1

a OE es E ek ay 1

prem E ee a ean 4 8 4

a ye a a 1 2 1

As a second example, the ratio 2:2:2 may be taken.

This will give the results shown in Table II. The ratio

2:2:2 is not constant, but stability is reached in Fj,

which is found to show the same ratio as our previous

ease, Viz, 152+ 1,

TABLE II

MATINGS AND OFFSPRING IN A LARGE POPULATION HAVING THE PROPORTION

2 RIGHTHANDED: 2 HETEROZYGOUS RIGHTHANDED: 2 LEFTHANDED

(2BR : 2Rr : 2rr)

ffs

SO Offspring pee ee

RR Rr Tr

IRR x IRR yc, baa 4

SRR x2r 2 2

3RR x ar 4

R IRR a a 2 2

Gy x SB is a ae 1 2 1

Be Me. ea 2 2

Oy MSR. oe 4

Ber SCOR a a 2 2

MP ee a 4

Toa a ee cere OG Ie ae tad 9 18 9

OP ee 1 2 1

TI am indebted to my colleague, Professor Saul Epsteen, of the Depart-

ment of Mathematics, for checking my method of analysis.

No. 546] MENDELIAN PROPORTIONS 347

In Table III a few possible matings are shown with

the percentage of recessives and the constant ratios

which appear in the next generation. It is apparent

from examination of the figures that if a disturbance

takes place there is often a partial return in the next

generation to the original condition. Sometimes this

return is complete, as would occur if, beginning with the

ratio of 1:2:1, some disturbance should make it 1:1:1.

In the next generation there would be a return to the

1:2:1 condition. There were 25 per cent. of recessives

at the beginning. This became changed to 33.3 per cent.

by mutation but returned in the next generation to 25

per cent.

TABLE III

EXAMPLES OF RATIOS. OF DOMINANTS, HETEROZYGOTES AND RECESSIVES,

TOGETHER WITH THE CONSTANT RATIOS DERIVED IN THE

FILIAL GENERATION. THE CONSTANT RATIOS ALL HAVE THE FORM

+ BP

A? + 2AB

Original Ratio Per Cent. Recessives | Constant Ratio in F, | Per Cent. Recessives

Ba 5 We i 33.3 25.0

Eh 2 50.0 o: Fa a 39.0

Gn Se 66.6 6: 9 56.2

L235 25.0 Constant Constant

£3331 20.0 25.0

L<t6:<2 33.3 25:70:49 34.0

1:4:4 44.4 Constant Constant

IRR Gey 40.0 1 x

4:4:1 11,2 (Constant Constant

4:6:1 9.0 766 :16 13.2

But there is not always a diminution of this kind. If

the original ratio be 4:4:1, which is constant, and this

be changed by mutation to 4:6:1, the original 11.1 per

cent. of recessives is at first reduced to 9 per cent., only

to rise in succeeding generations to 13.2 per cent. It is

very easy to overestimate the importance of the tend-

ency to return to a stable ratio, since such stable ratios

are practically without limit, and instead of returning

to the same ratios, it is easily possible to reach stability

in a new ratio somewhat different from the original.

This may be shown by an example (Table IV).

348 THE AMERICAN NATURALIST [ Vou. XLVI

TABLE IV

FIGURES SHOWING THE FORMATION OF A NEW STABLE RATIO IN A POPULA-

TION HAVING AT FIRST THE COMPOSITION 4:4:1 WHEN A SMALL

NUMBER OF HETEROZYGOTES BECOME RECESSIVES THROUGH ordan

Ratio in the original population: 400 : 400 : 100 — 11.1 per cent. recessive.

Ratio after mutation: 400 : 396 : 104 — 11.5 per cent. recessive.

Ratio of the next generation:

89,401 : 90,298 : 22,801 — 11.2 per cent. recessive.

The change i Im any case is not so simple as mathemat-

ical study would at first suggest, for many of the indi-

viduals mate with members of earlier or later genera-

tions. When a considerable number of recessive mutants

appear in a given generation this excess is, in part, re-

duced by matings with members of the normal genera-

tions before and after them. Hence a return to the nor-

mal or usual condition is made easy. These considera-

tions naturally suggest a reason for the comparative

stability of species within a genus or of elementary

species within a Linnean species.

From what has been said it will be seen that unless a

recessive character is arising by mutation at some ap-

preciable rate there will be little or no increase in the

proportion of individuals exhibiting this character. On

the other hand, whenever a considerable number of mu-

tants do appear the normal condition: of equilibrium is

disturbed and a new stable ratio becomes established in

which the recessives are in larger proportion.

There are probably many recessive characters which

are not the objects of natural selection by the environ-

ment nor of sexual selection in mating. Lefthandedness

may well be such a character. It certainly seems that

the proportion of individuals with such characters will

increase slowly through long periods of time. Let it

supposed, for example, that the proportion of dominants,

heterozygotes and recessives in the general population

is 9:6:1. Now it is probably far easier in mutation for

a given factor to drop out than to be added. If, however,

the dropping out and addition could take place with

No. 546] MENDELIAN PROPORTIONS 349

equal facility, there would still be much in favor of the

recessive. In the supposed ratio 9:6:1 it is possible for

any one of the dominants or heterozygotes to lose a de-

terminer. In other words, on the average fifteen out of

sixteen individuals have an opportunity to vary toward

lefthandedness; that is, 93.9 per cent. On the other

hand, only the heterozygotes and the recessive can vary

toward righthandedness; seven out of sixteen, therefore,

have this possibility, or 43.7 per cent. of the population.

If, therefore, the addition of the factor were as easily

accomplished as the loss of the factor—which is probably

never true—loss of a factor would be more than twice as

likely to occur as gain. With the ratio 1:2:1 opportuni-

ties are of course equal for upward and downward muta-

tion. In a population with more than 25 per cent. of

recessives, the number of heterozygotes plus recessives

is greater than the number of heterozygotes plus domi-

nants, as, for example, with the ratio 1:4:4, in which the

recessives make up 44.4 per cent. of the population.

It would seem from the above that there is a constant

tendency for the proportion of individuals showing non-

important recessive characters to increase, unless indeed

mutative changes occur so slowly that the population is

constantly held back to a stable ratio. We are led natur-

ally to the thought that for species in general the indi-

viduals showing recessive mutations may be expected to

increase at the expense of the original type, unless the

characters lost are of some real importance to existence

or to mating. Just this sort of thing has probably taken

place with the shepherd’s purse, Bursa bursa-pastoris.

It can hardly be doubted that the numerous species de-

scribed by Almquist! are derived from a single original

species. If the total number of Bursas in the world re-

mains the same from century to century and these ele-

mentary species appear in some number from time to

* Noted by Dr. George Harrison Shull, ‘‘ Advance Print from the Pro-

ceedings of the Seventh International Zoological Congress, Boston Meeting,

350 THE AMERICAN NATURALIST [Vou XLVI

time, they must be crowding upon the original form.

Other examples in great number will occur to any one.

Thus there can be little doubt that primitive man was

dark-skinned and dark-eyed. The various modern races

were produced—so far as skin-color and eye-color are

concerned—by dropping out the factors (determiners)

for these characters. In our own Caucasian race, it

seems not unreasonable to suppose that we are tending

toward a condition of blondness, for there seems to be no

natural or sexual selection against this character.®

I am not unmindful of the fact that an apparently un-

important character such as righthandedness may be

bound up with other characters of great consequence.

In such case lefthandedness might mean, for example, a

distinct inferiority in metabolic activity..°. Unless the

recessiveness is associated with weakened nutrition or

other enfeebled condition, it would seem most natural

for elementary species, when once originated, to increase

in number of individuals by continued mutation.

Dr. Shull points out in his paper previously cited on

“Elementary Species and Hybrids of Bursa’’ that reces-

sive mutants may have an advantage over dominant mu-

tants if fluctuating conditions tend to eliminate now one

form, now the other. The killing off of dominant mutants

may be easily accomplished, but this is not the case with

recessives.'' This is perhaps only another way of sta-

ting the well-known fact that it is hard in plant or animal

° The claim that light-skinned and light-eyed people are not adapted to

* Cf. the observations by Professor Thomas Hunt Morgan upon .mutants

of the fruit Pe Drosophila, in the Journal of Experimental Zoology, Vol.

XI, p. 408,

“To a own words: ‘‘The recessive mutant may be preserved

inde: gautis under the protection of the dominant characteristics of its more

successful parent. Such prolongation of the life of a recessive may serve

to tide it over times of special stress or may continue its existence until the

various distributing agents have carried it beyond the limits of the habitat

in which it is a failure into others in which it may become a success.’’

This same idea has been suggested by my colleague, Professor T. D. A.

Cockerell, in a conversation regarding the general question of increase of

recessives.

No. 546] MENDELIAN PROPORTIONS 351

breeding to get rid of recessive characters which are not

wanted.

SuMMARY

In the foregoing digegussion an attempt has been made

to exhibit clearly the facts of stable ratios involving

Mendelian dominants, heterozygotes and _ recessives.

While suggested by a study of lefthandedness, what has

been said will apply to any recessive character which is

not selected against in mating and which does not affect

the success of the organism in other ways. I have tried

to accord full value to the mathematical features of the

case, and have pointed out the various checks which tend

to hold the population in a given ratio. Yet I have been

unable to escape the conclusion that recessive mutants,

unless inherently weak in some respect, must tend to

increase in numbers at the expense of original dominant

types. These conclusions are reached from a considera-

tion of the following points: (1) The greater ease with

which characters may be lost than gained. (2) The great

number of combined dominants and heterozygotes which

through mutation may reach a simpler condition as com-

pared with the small number of recessives and hetero-

zygotes which may be imagined as affording opportunity

for mutation to dominance.!2 (3) The more likely sur-

vival of recessives in an environment of changing con-

ditions in which now the dominant and now the recessive

is hard pressed to maintain its existence.

12 Unless the ratio of the three types is 1:2: 1, when the opportunities

are the same in each direction.

THE INCONSTANCY OF UNIT-CHARACTERS!

PROFESSOR W. E. GASTLE

HARVARD UNIVERSITY

THERE can be no reasonable doubt that Mendel’s law

is of fundamental importance in genetics. It explains so

many of the anomalous facts and seeming contradictions

encountered in practical breeding. The basic fact under-

lying this law is the existence of unit-characters, inde-

pendently inherited. Their independence makes it pos-

sible to combine them in any desired way through the

agency of cross-breeding.

In the first flush of enthusiasm over the rediscovery of

Mendel’s law it was thought by some that recombination

of unit-characters through crossing was to solve all the

problems of breeding relating to the production of new

and improved varieties. But experienced animal breed-

ers have, as a rule, been very conservative in their ex-

pectations, a conservatism justified by the knowledge of

how painfully slow and tedious is the process of improv-

ing a breed in any essential regard. For though it is

easy enough in two generations to get new color varieties

by crossing breeds of different color, the new creations

will, in respects other than color, not be the same as

either of the breeds crossed; they may be inferior to both

in every respect but color, and it will be a difficult, if not

impossible, task to restore the desirable qualities lost.

The reason is that our improved breeds differ from each

other in so many minor characteristics that it is quite

impossible to give attention to all of them simultaneously.

For as the number of variable characters resulting from

a cross increases, a particular combination of characters

will become more rare in occurrence and harder to fix.

Soon after it was discovered that unit-characters exist,

* An address delivered at the University of Illinois, April 19, 1912.

352

No. 546] INCONSTANCY OF UNIT-CHARACTERS 353

the question was raised whether they are or are not con-

stant.

In our descriptions we call these characters A, B, O,

etc., and the recombinations are AB, BC, AC, ete. In

our formule A is always A, and B is always B, but it is

an open question whether in our living animals the char-

acteristics or qualities designated by these symbols are

from generation to generation as constant and change-

less as the symbols. Bateson and Johannsen and Jen-

nings have assumed that they are, that a horn is always

a horn, and a toe a toe. When it is pointed out that

horns are not all alike, that they differ in size, shape and

color, the reply is made that these differences are due to

other things, that is, that these are independent qualities

not inherent in the horn itself. Now there is force in this

argument because we know that a particular color can be

dissociated from the horn, why not also size and shape?

Nevertheless if we dissociate from the horn all color,

size and shape we shall have no horn left. The real unit-

characters, therefore, which we can think of in a con-

crete way and deal with in actual breeding operations are

differences in degree of horn-development, in length,

thickness, curvature or coloration. Who shall say

whether these differences are few or many? We can con-

ceive of an infinite number of gradations in size, shape

and color between known extremes and it is difficult to

believe that any one of these is impossible of realization.

Nevertheless an important body of present-day natural-

ists, those who with De Vries believe in mutation, would

have us think that these minor gradations are not herit-

able. Their reasoning is as follows. Suppose we cross

horned with hornless cattle. All the immediate offspring

are hornless, and the grandchildren 3 hornless to 1

horned. The horned grandchildren breed true. No

intermediates occur. Clearly one unit-character differ-

ence exists between horns and no horns. Therefore no

stable intermediate class can exist unless this unit-char-

acter changes. This they consider to be impossible. If

we call attention to a short-horned race as evidence

354 THE AMERICAN NATURALIST [Vou. XLVI

that the horn character may vary, they assure us that

this condition is due to a different unit and is not deriv-

able from the other, and they challenge us to produce it

from the other. If we begin measuring the horns of our

cattle and picking out those a little shorter than the

average, we find that offspring are obtained with horns

of practically average length. Perhaps we repeat the

selection half-a-dozen times and begin to get a barely

appreciable result. They interrupt, ‘‘See here,” they

say, ‘‘you’re not getting anywhere; give up and acknowl-

edge yourself beaten. If you stop your selecting for a

single generation, the little you have accomplished will

disappear. See meantime what we mutationists have ac-

complished; we have dehorned half-a-dozen breeds by

simple crossing. This is more than you could do in a

thousand years.” Such comment on our work is ex-

tremely disquieting, for our progress is slow, and we can

only reply, ‘‘Your method is the quicker one to get rid

of a character altogether, but you admit yourself power-

less to create a condition which you do not possess fully

realized at the outset. We do not admit ourselves so

helpless; we hope to get something which we do not now

have, and we are willing to wait a while for it. We be-

lieve that we can create what does not now exist. This

you confess yourself powerless to do.”

The foregoing states fairly, I think, the present views

regarding selection as a tool of the breeder held on one

hand by the mutationists and pure-line advocates, and

on the other hand by a minority of Mendelians who like

myself consider selection an important creative agency

in breeding.

The fundamental point of difference between these two

views lies in their different conception of unit-characters.

To the mutationist unit-characters are as changeless as

atoms and as uniform as the capacity of a quart meas-

ure. Theoretically an atom is an atom under all circum-

stances, and a quart holds the same anywhere and every-

where. But the worldly-wise know that the actual quart

is not the same in all places; it is apt to be smaller at the ©

No. 546] INCONSTANCY OF UNIT-CHARACTERS 355

corner grocery than in the U. S. Bureau of Standards,

and the dishonest tradesman will select effectively for

diminished size among the various quart measures

offered on the market, unless his selection is carefully

restrained by legislation. Similarly actual unit char-

acters are modifiable under selection; only one blindly

devoted to a contrary theory will be able long to shut his

eyes to this fact. For several years I have been engaged

in attempts to modify unit-characters of various sorts

by selection and in every case I have met with success.

I shall speak first of the case least open to objection

from the genotype point of view which requires:

1. That no cross breeding shall attend or shortly pre-

cede the selection experiment, lest modifying units may

unconsciously have been introduced, an

2. That only a single unit-character shall be involved

in the experiment.

These requirements are met by a variety of hooded rat

which shows a particular black and white coat-pattern.

This pattern has been found to behave as a simple Men-

delian unit-character alternative to the self condition of

all black or of wild gray rats, by the independent investi-

gations of Doncaster and MacCurdy and myself. The

pigmentation however in the most carefully selected race

fluctuates in extent precisely as it does in Holstein or in

Dutch Belted cattle. Selection has now been made by

Dr. John C. Phillips and myself through 12 successive

generations without a single out-cross. In one series se-

lection has been made for an increase in the extent of the

pigmented areas; in the other series the attempt has been

made to decrease the pigmented areas. The result is that

the average pigmentation in one series has steadily in-

creased, in the other it has steadily decreased. The de-

tails of the experiment can not be here presented, but it

may be pointed out (1) that with each selection the

amount of regression has grown less, i. e., the effects of

selection have become more permanent; (2) that advance

in the upper limit of variation has been attended by a

like recession of the lower limit; the total range of varia-

356 THE AMERICAN NATURALIST [Vou. XLVI

tion has therefore not been materially affected, but a

progressive change has been made in the mode about

which variation takes place.

3. The plus and minus series have from time to time

been crossed with the same wild race. Each behaves as

a simple recessive unit giving a 3:1 ratio among the

grandchildren. But the extracted plus and the extracted

minus individuals are different; the former are the more

extensively pigmented.-

4. The series of animals studied is large enough to

have significance. It includes more than 10,000 individ-

uals.

The conclusion seems to me unavoidable that in this -

case selection has modified steadily and permanently a

character unmistakably behaving as a simple Mendelian

unit.

In my experience every unit-character is subject to

quantitative variation, that is, its expression in the body

varies, and it is clear that these variations have a ger-

minal basis because they are inherited. By selection

plus or minus through a series of generations we can in-

tensify or diminish the expression of a character, that is,

we can modify the character.

In an earlier lecture I showed that long hair and rough

coat in guinea-pigs each differ from the normal condi-

tion by a single unit-character. In 1906 I showed that

both these characters are subject to quantitative varia-

tion, and that such variations are heritable. The same

is true of polydactylism in guinea-pigs, a condition in

which a fourth toe is present on the hind-foot. A poly-

dactylous race of guinea-pigs was unknown until I cre-

- ated one by selection from among the descendants of a

single abnormal individual which had a rudimentary

fourth-toe on one hind-foot. For several generations in

succession those individuals were selected for parents

which had the best-developed extra-toe, and thus was

obtained a good 4-toed race.

Another character built up slowly from small begin-

nings is the silvered variety of guinea-pig. It originated

No. 546] MENDELIAN PROPORTIONS 357

from a tricolor race in which was observed an individual

having white hairs interspersed with red on the lower

side of the body. Selection has been made to increase

the amount of the silvering and to get it on a black back-

ground. This involved increase of the black areas in the

coat as also of the silvered areas. In this task, difficult

because it involved simultaneous modification of two un-

related characters, steady progress has been made. The

best animals are now silvered all over except at the ex-

tremities.

Even albinism, the first-discovered of all Mendelian

characters in animals and by every one acknowledged to

be a single and simple unit-character, even this is vari-

able. In rabbits, for example, some albinos are snow-

white without a trace of pigment in the fur or skin, while

others (the so-called Himalayan type) are heavily pig-

mented at the extremities (nose, ears, feet and tail).

And yet we can not discover that these two kinds of al-

binism differ by any second unit-character which might

account for the difference. Their albinism is different.

Between the extreme types of the snow-white and the

Himalayan albino, various intermediates exist, but all

are clearly albinos, producing only albinos when bred

inter se. They represent quantitative variation within

the albino type.

Similar quantitative variation within colored classes

of animals is well known. Thus in mice an extreme

quantitative reduction of the pigmentation has produced

an animal with pink eyes and faintly colored coat. Such

an animal, however, is not an albino, though less heavily

pigmented than many Himalayan rabbits, for if the pink-

eyed mouse is crossed with an albino, fully pigmented

young result.

In guinea-pigs I several years ago set myself the task

of reducing as much as possible the pigmentation of a

black race, in hopes thus of obtaining blues. I first

crossed the blacks with a light yellow (cream-colored

race). In the heterozygotes the black was somewhat re-

duced in amount. The lightest of these were selected

358 THE AMERICAN NATURALIST [ Vou. XLVI

and again crossed with yellow. By this means the black

was after several generations much reduced. The hairs

were distinctly yellowish at base and the part above sooty

black in appearance. Recently a pink-eyed animal has

appeared in this race with hair light sooty-black in spots.

This evidently is an extreme variation in the direction

which selection has taken throughout the experiment and

probably similar in nature to the pink-eyed variation in

mice. There can be no question of recombination of

independent Mendelian factors in this experiment, be-

cause (aside from albinism) only a single Mendelian fac-

tor is involved. The heterozygotes, as regards black,

have consistently behaved as simple heterozygotes, and

the experience of all observers agrees with my own that

black in guinea-pigs is a simple Mendelian unit. If so it

is clearly a unit modifiable under selection.

In yellow animals, as in blacks, individuals of varying

intensity occur, the darkest known as reds, the lightest

as creams. A complete series of intermediates can be

obtained if so desired. If we select any two widely sep-

arated stages in this series fairly stable in their breeding

capacity and cross these, they Mendelize, 7. e. they behave

as if there were a single unit-character difference be-

tween them. Now this fact is instructive, for it throws

light on the nature of unit-characters in such cases.

They are not things in themselves distinct and separate

from the organism concerned; each is a quantitative

variation plus or minus in some one character possessed

by the organism. Each quantitative condition of a char-

acter tends to persist from cell-generation to cell-genera-

tion. When two quantitatively unlike conditions of a

character are brought together in a fertilized egg, they

- tend to keep their distinctness in subsequent cell-gen-

erations and to segregate into different gametes at re-

production, i. e., they Mendelize. Only by a figure of

speech are we justified in recognizing a unit difference

between them. That difference might equally well be

half as great as it is, or a quarter as great, or a thou-

sandth part as great. _A mono-hybrid ratio would result

No. 546] INCONSTANCY OF UNIT-CHARACTERS 359

equally in each case, upon crossing the two quantitatively

different stages. It is the substantial integrity of a

quantitative variation from cell-generation to cell-gen-

eration that constitutes the basis of Mendelism. All else

is imaginary.

We can distinguish and trace the history of these

quantitative variations from generation to generation

only when the differences between them are of some size.

This has led many to think that only variations of some

size are inherited (the mutation theory) and others to

deny that such variations can be increased in size by se-

lection (the genotype theory). Others still observing un-

mistakable evidence that small variations are heritable

no less than large ones conceive that the large variations

which can be increased or decreased by selection are com-

posed of a certain number of smaller ones cumulative in

their effects (the multiple factor hypothesis). A fatal

objection to this idea is the fact that these quantitative

variations behave as simple units, not as multiple ones,

and so give mono-hybrid ratios, not polyhybrid ones.

The only logical escape from this dilemma for one de-

voted beyond recall to a pure-line hypothesis will be to

assume further that the assumed multiple units are all

coupled, 7. e., all united in a single material body so that

in cell-division they behave as one unit, for practical

purposes are one unit. This position will be logically

unassailable, for we shall never know whether the body

which in practise behaves as one is in the last analysis

composite. Chemists tell us (or used to) that water is

composed ultimately of atoms of hydrogen and atoms of

oxygen not further dissociable, uniform in size and

weight and hard and indestructible as rocks; neverthe-

less for practical purposes we drink our cup of water and

do not chew it. I for one will be content with the ad-

mission that variation is as continuous as water and will

not press the argument against discontinuity into realms

of the ultimate.

The majority of the characters dealt with by the ani-

mal breeder are less simple in behavior than color char-

360 THE AMERICAN NATURALIST [Vou. XLVI

acters. They are also from the economic standpoint

more important. Their careful study is therefore desir-

able. Several years ago I undertook the study of size

inheritance in rabbits. I found that when rabbits of un-

equal size are mated, the young are of intermediate size,

i. e., neither large nor small size dominates in the cross.

Further, segregation does not apparently occur among

the grandchildren, for these vary about the same inter-

mediate mode as the children, though somewhat more ex-

tensively. My conclusion was that the inheritance in

such cases is non-Mendelian, since neither dominance nor

segregation occurs. I called it blending. The experi-

ment with rabbits has been repeated on a much larger

scale by my pupil, Mr. E. C. MacDowell. He finds, how-

ever, that the variability of the grandchildren is consid-

erably greater than that of the children, though it

seldom extends far enough to include the extreme condi-

tions found in the grandparents. This result is’ con-

firmed by observations upon ducks made by Dr. Phillips.

It is evident therefore that size is not a simple unit-char-

acter, for there is no dominance and no evidence of seg-

regation other than the increased variability of the sec-

ond hybrid generation. But cases of this kind have

recently been interpreted as involving multiple unit char-

acters and so as possible Mendelian. This interpretation

has been suggested by interesting observations made by

Nilsson-Ehle on color-inheritance in oats and wheat.

In crossing colored with uncolored varieties he ob-

tained inheritance ratios of 15:1 or 63:1, instead of the

usual 3:1 of colored to uncolored progeny in the second

generation from the cross. The ratios obtained in these

exceptional cases were such as should occur when two or

three independent unit-characters are involved in a cross.

But Nilsson-Ehle could discover only a single kind of color-

production. The conclusion which one naturally draws

from these facts is that the color factor in these cases

was localized in two or three distinct bodies independent

of each other in their splittings and migrations during

cell division. Now Nilsson-Ehle argues with much plaus-

No. 546] INCONSTANCY OF UNIT-CHARACTERS 361

ibility that if in a case such as this dominance were

wanting, i. e., if the cross always produced intermediates,

the bulk of the second-generation offspring would also be

intermediate, with only an occasional complete segrega-

tion. He suggests that size differences may involve units

of this sort, without dominance though fully segregating.

This attractive hypothesis would account for the known

facts of size inheritance fairly well, involving only the

existence of multiple units which may be perfectly stable

and changeless in character. Nevertheless this hypothe-

sis has not been established beyond question. It is quite

possible that we are stretching Mendelism too far in

making it cover such cases. Dominance is clearly absent

and the only fact suggesting segregation is the increased

variability of the second as compared with the first hy-

brid generation. This fact however may be accounted

for on other grounds than the existence of multiple units

of unvarying power.

If size differences are due to quantitative variations

in special materials within the cell, it is not necessary to

suppose that these materials are localized in chunks of

uniform and unvarying size, or that they occur in any

particular number of chunks, yet the genotype hypothe-

Sis involves one or both of these assumptions. Both are

unnecessary. Variability would result whether the

growth-inducing substances were localized or not, pro-

vided only they were not homogeneous in distribution

throughout the cell. Crossing would increase variability

beyond the first generation of offspring because it would

increase the heterogeneity of the zygote in special sub-

stances (though not its total content of such substances)

and this heterogeneity of structure would lead to greater

quantitative variation in such materials among the

gametes arising from the heterozygote. Thus greater

variability would appear in the second hybrid genera-

tion.

As a matter of fact we know that protoplasm is not

homogeneous, and that there are substances widely distri-

362 THE AMERICAN NATURALIST [Vou. XLVI

buted in the cell, not localized in chromosomes, which

may well have an influence on size.

But whatever our conclusion may be concerning the

theoretical explanation of size inheritance, the practical

manipulation of it must clearly be different from that of

color inheritance. All possible combinations of color

factors existing in two distinct races we can secure

within two generations by crossing. New conditions of

color we can often obtain by the slower process of selec-

tion, thus modifying existing color factors. Modification

is, I believe, often accelerated by crossing, quite apart

from the effect it has in bringing about recombination,

because it has a tendency to increase quantitative varia-

tion.

Size is an unstable character, ever varying. Slow

changes in size can be effected by selection without any

crossing whatever. Change in size is made more rapid

by crossing, because variability is increased thereby.

If further increase in size is desired regardless of other

qualities two large races should be crossed and the larg-

est second-generation offspring should be selected. Pro-

gressive diminution in size should be sought in a similar

way, crossing the smallest breeds.

If a medium-sized race is desired, it may be obtained

by crossing a large with a small race and inbreeding the

offspring. Physiological limitations undoubtedly would

prevent unlimited size variations either plus or minus,

yet when we consider what extreme differences exist

among dogs, as for example between ‘‘toy terriers” and —

‘‘oreat Danes,’’ we can scarcely doubt that the limits of

possible size variation have not been approached in most

of our domesticated animals.

SHORTER ARTICLES AND DISCUSSION

INHERITANCE OF COLOR IN THE ALEURONE CELLS

OF MAIZE

In those plants of which there is a considerable knowledge of

the heredity of flower sap color, namely, Antirrhinum, Lathyrus,

Matthiola and Primula, it has been found that an hypostatie

color factor is often necessary for the production of an epistatic

color. For example, a basic factor generally designated as C

being present, a flower becomes red by the addition of a factor

FR, and becomes magenta or purple by the addition of still

another factor P. The zygotic formula of a pure red flower is

RRCC and of a pure purple flower is PPRRCC; ‘but a flower

with the zygotic formula PPCC is colorless.

On the other hand, certain seed coat and other colors of wheat,

of beans and of other plants do not need the presence of the hypo-

static factor for the formation of the epistatic color. For ex-

ample, Nillson-Ehle crossed a black glumed oat BBGG with a

white glumed oat bbgg. In the F, he obtained 12 black: 3 gray:

1 white. The actual ratio was 9BG: 3Bg:3bG@:1bg, but as the

black was produced whether the gray factor was present or not,

the visible ratio was as given above.

The natural conclusion is that in the first category the epis-

tatic factor is more specific in its action than it is in the second

category. If one accepts the interpretation that color is formed

by the action of an enzyme on a colorless chromogen, he must

conclude that the epistatic enzyme of the first kind can only

produce its action, if, by the presence of the hypostatic enzyme,

the chromogen has already been carried through a necessary

preliminary reaction. -An epistatic enzyme of the second kind,

however, is sufficient unto itself and is absolutely independent

of the action of the hypostatic enzyme. One may even assume

that the chemical bases upon which the two enzymes of the

second category act are independent of one another.

Perhaps a concrete illustration will show the difference of

action in these two cases better than description. In the black

glumed oat BBGG, one can imagine the black color or the gray

color wiped out mechanically. Thé other color remains. In the

863

364 THE AMERICAN NATURALIST [Vou XLVI

purple flower PPRRCC, if the red factor is wiped out no color

is left.

In an earlier paper East and Hayes' found four independent

gametic factors in maize, each of which affects the production

of color in the aleurone cells of maize. These four factors are a

basic color factor C, a reddening factor R, a purpling factor P,

and an inhibiting factor J which prevents the development either

of the red or of the purple color. Of the various points of

interest in the interpetation of the inheritance of these factors,

two have been investigated further. The first is the cause of

modified colors. This will be discussed at length in another

paper. The second is the action of the reddening factor R and

the purpling factor P. It was then thought that the presence

of the factor P together with C was all that was necessary for

the production of the purple color. It can now be shown that

the purple color develops only when the three factors P, R and

C are present. The production of color in the aleurone cells

of maize is therefore analogous to that in the flowers of the

genera described above, which was designated as category one.

This interpretation of the facts makes little difference in the

general behavior of these colors in inheritance and is only in-

teresting in so far as it unifies the interpretation of the aleurone

colors in maize with the sap colors of certain flowers.

The following scheme will show the differences in behavior in

the two schemes.

1. A purple crossed with a non-purple gives 3 purple : 1 non-

purple in F,. Here there is no difference in the two schemes.

The proper interpretation gives this result from crosses

PPRRCC X PPERce or

PPRRCC X PPrr€C.

2. A purple crossed with a non-purple gives 9 purple : 7 non-

purple in F,. The old interpretation was that this occurs when

the F, has the formula PpCc. The present interpretation is

that it occurs when the formula of the F, is PPRrCc.

3. A purple crossed with a non-purple gives the formula

PpRrCc in F,. If the R factor is unnecessary for the pro-

duction of purple, the ratio in F, will be (a) 36 purple : 9 red :

19 white. If R is necessary for the production of purple the

ratio in F, will be (b) 27 purple : 9 red : 28 white. A sample

1<<Tnheritance in Maize,’’ Conn. Agr. Exp. Sta. Bull., 167: 1-141, 1911 -

No. 546] SHORTER ARTICLES AND DISCUSSION 365

family of F, segregates gave the following ratio which may be

compared with the closest possible expectancy under each theory.

AGtHAL ORUIE sosro. eek es 191 purple : 56 red : 180 white.

EROF (A)... 240 purple : 60 red : 127 white.

Theory (D) rr ee 180 purple : 60 red : 187 white.

This suggests theory B, but is not conclusive. Conclusive

evidence comes from the F, generation. On theory A, every

36 purple F, seeds should give on the average the following

results in F,:

4 ears all purple. f

10 ears segregating 3 purple : 1 white.

4 ears segregating 9 purple : 7 white.

2 ears segregating 3 purple : 1 red.

4 ears segregating i purple : 3 red : 1 white.

4 ears segregating 9 purple : 3 red : 4 white.

8 ears segregating 36 purple : 9 red : 19 white.

On theory B, every 27 purple F, seeds should give on the

average these results in F,:

1 ear all purple.

4 ears segregating 3 purple : 1 white.

2 ears segregating 3 purple : 1 red.

4 ears se ing 9 purple : 7 white.

8 ears segregating purple : 3 red : 4 white.

8 ears segregating 27 purple : 9 red : 28 white.

is7]

The crucial test is the appearance of families showing the ratio

12 purple : 3 red : 1 white. No such family has ever appeared.

On the other hand they did divide nicely into families with ratios:

of 9:3:4 and 27:9:28. Of the first type the total progeny

of nine families was 935 purple: 318 red: 436 white. The closest

theoretical ratio on the basis of 9:3:4 would be 950 purple : 317

red : 422 white. Of the second type the total progeny of four

families was 423 purple : 127 red : 396 white. The closest pos-

sible ratio on the basis of 27: 9:28 would be 400 purple : 133 red

: 414 white.

All other tests made corroborated the interpretation that the

P factor can produce purple only when R and C are present.

E. M. East

TORY OF GENETICS,

Bussey INSTITUTION OF HARVARD UNIVERSITY

366 THE AMERICAN NATURALIST [Vou. XLVI

NUCLEAR GROWTH DURING EARLY DEVELOPMENT

In reading Conklin’s recent paper on the relative growth of

nucleus and cytoplasm in developing eggs,! I was at first some-

what puzzled by certain of the relations brought out. The mat-

ter is one that bears directly upon so many important problems,

and Conklin’s paper is one of such fundamental importance,

that possibly a statement of the difficulty and its apparent solu-

tion may be worth while. Work done with the thoroughness

that characterizes all that Conklin puts forth partakes to a cer-

tain degree of the inexhaustibleness of nature, in that it is pos-

sible to discover in it relations not explicitly set forth by the

author.

Conklin’s most notable result is that the relative proportions

of nuclear and cytoplasmic materials do not appreciably change

during early development, as they have been supposed to do.

The bearing of this upon the theory that cleavage is a process of

rejuvenescence, owing to the enormous increase of nuclear ma-

terial relative to the cytoplasm, is evident. The point which I

wish to discuss has no bearing upon this fundamental result, but

relates to the rate of nuclear growth.

On this point Conklin sums up his results for Crepidula as

follows:

“The rate and amount of nuclear growth during cleavage is much

less than is generally believed. Whether the nuclear volume is taken

when the nuclei are at their maximum, mean or minimum size, the

nuclear growth is far from 100 per cent. or a doubling, in each division.

In Crepidula the nuclear growth is not more than 5 per cent. to 9 per

cent. for each division from the 2-cell to the 32-cell stage, and less than

1 per cent. for each division after the 32-cell stage” (p. 40).

Similar figures are given for the other animals studied.

Now, if I have gotten clear on the matter, what Conklin here

means is that when any cell divides, the increase of nuclear ma-

terial thus produced is on the average but 5 to 9 per cent. of the

amount that was present in an early stage of the egg, and spe-

cifically in the two-cell stage. This is a different method of ex-

pressing the rate of growth from that often employed. The

question perhaps most often answered when the rate of nuclear

growth at cell division is given is the following: How much is

1 Conklin pes ‘‘Cell Size and Nuclear Size,’’? Journal of Experimental

Zoology, 12, 1-9

No. 546] SHORTER ARTICLES AND DISCUSSION 367

the nuclear material of a given cell increased when that cell

divides? Or, what is essentially the same, when several cells

are present, as usually in a developing egg: In what proportion

is the total nuclear material increased when all of the cells

divide once? It appears to me that these questions are the

ones that have been in mind when it has been held that the nu-

clear material increases nearly 100 per cent. at each cleavage,

so that the relation of the ratio used by Conklin to the ratio

implied by them is of interest.

The ratio implied in the questions just set forth—the ratio

of increase in the nuclear material of a given cell after that cell

has divided—is of course obtained by dividing the nuclear vol-

ume of the two resulting cells by this volume in the mother cell ;

or by dividing the total nuclear volume of the egg after all its

cells have divided once by the total volume before the cells

divided. (Inclusion of several cells, each of which divides once,

of course does not of itself alter the ratio.) Performing these

operations for the mean nuclear volùmes in Crepidula, as given

in Conklin’s Table 9, one finds the ratios in question to be for

the second cleavage 1.40, for the third 1.25, for the fourth 1.19,

for the fifth 1.89. That is, in passing from the 2-cell to the 4-cell —

stage, the nuclear volume of each mother cell increases 40 per

cent.; in passing from the 4-cell to the 8-cell stage, the increase

is 25 per cent.; from the 8- to the 16-cell stage it is 19 per cent. ;

from the 16- to the 32-cell stage it is 89 per cent. These ratios

are not 100 per cent. at each division, but they approach it more

nearly than the ratio Conklin employs. If we average the in-

crease for these four cleavages, we find the mean to be 43 per

cent. That is, at each cleavage, the nuclear volume of the cell

increases on the average by 43 per cent.

It may be noted that even with an absolutely constant ratio

between the nuclear volume in a given cell before cleavage and

that in its products after cleavage, the ratio employed by Conk-

lin would, as a rule, if I have correctly interpreted it, decrease

rapidly as we pass to later cleavage stages. The relation be-

tween the two ratios would be that shown by the following

formula, in which «== Conklin’s ratio; r= the (constant) ratio

of the nuclear volume after division of a given cell to the nuclear

volume before that war n= the number of the cleavage

(1, 2, 3, ete.) :

368 THE AMERICAN NATURALIST [Vou. XLVI

For example, if r—1.5 (so that the nuclear volume of any

cell increases 50 per cent. when that cell divides), then for the

result of four cleavages (producing 16 cells) the formula gives

z= soc Be = se a 16.96 per cent.

If Conklin employed the 1-cell stage as his standard of com-

parison, the above formula would be

t= 4° (2)

It will be found that for any increase less than 100 per cent.

of what was present before division (that is, r— 2), Conklin’s

ratio (from formula 1 or 2) decreases in the later stages of

cleavage, even though the law of increase, so far as each cell by

itself is concerned, remains absolutely the same. Thus, if at

the division of every cell its nuclear volume increases 50 per

cent., Conklin’s ratio (formula 1) will give 25 per cent. for the

result of the second cleavage, 20.83 for the third, 16.96 for the

fourth, 13.54 for the fifth, 10.64 for the sixth, 8.25 per cent. for

the seventh, ete. This appears to-be the reason why Conklin

finds the rate of nuclear increase, as shown by his ratio, to bè

less in later stages; it is not due to any change in the relations

so far as what happens in each cell is concerned.

H. S. JENNINGS

IS THERE ASSOCIATION BETWEEN THE YELLOW

AND AGOUTI FACTORS IN MICE?

IN the generally accepted formulæ for the colors of mice, as

worked out by Cuénot, Bateson, Durham and others, there is

assumed to be a factor, Y, for self yellow color, which is epi-

static to T, the ticking or agouti factor (also known as G). The

various types have the following constitution :

YoUowW 5 pa Sak e ae es eee Sac Yt yt, or Yt yT?

Agouti (including cinnamon) ................. yT yT, or yT yt.

Black and chocolate (including dilute forms) .. yt yt.*

*On the formule adopted here this factor Y is probably to be considered

an inhibitor.

been shown by Cuénot and others (see especially Castle and ~

Little, Science, N. S., 32, 868, 1910) that mice homozygous for Y do not

exist, the reason probably being that the YY zygotes, though formed in the

expected proportions, do not develop.

* Blacks differ from chocolates in having a black factor, B. Agoutis

also carry this factor, while cinnamons lack it. Yellows may or may not

bear it, but the two types are distinguishable by their eye color.

No. 546] SHORTER ARTICLES AND DISCUSSION 369

If yellow mice of the sort one usually obtains be bred together

they produce yellows, blacks and chocolates—almost never any

agoutis. But if such yellows be bred to agoutis and their yellow

offspring be mated together the result is only yellows and

agoutis. It has been pointed out by Morgan‘ that this last result

is inconsistent on the current formule, since blacks or chocolates

should also be expected. For example, if we assume, as I think

we must, that ordinary yellow mice usually have the constitution

Yt yt, then the cross under discussion would be as follows:

Yellow—Yt yt

Agouti—yT yT

Yt yT—yellow

Y —agouti

F, yellow—gametes—YT Yt yT yt

YI ILT IY a gs

x24 38 y7 | yt

Yt re Yt Yt

yr | Yt | yP | yt

ye £2 ch R

YF i Yi yT | yt

yt | yt | yt | yt

YT | Ye | yT | yt

Total, omitting all YY’s: 8 yellows, 3 agoutis, 1 black or chocolate.

It seems to me that the easiest way of explaining why this

mating actually does not produce blacks and chocolates is by the

assumption of linkage or association (‘‘gametic coupling’’)

between the agouti and yellow factors. The fanciers, from whom

most yellows come, ordinarily keep few agouti mice. It is there-

fore probable that most yellows carry no T, and for this reason

Y and T really show ‘‘spurious allelomorphism’’ or repulsion

instead of ‘‘gametic coupling.” There seems to be no evidence

that Y and T ever occur in the same gamete. The evidence

which has led to this conclusion is as follows:

Miss Durham has found that if ordinary yellows be mated

‘Ann. N. Y. Acad. Sci., 21, 87, 1911. It was at Professor Morgan’s

Sas ae that I took up this problem.

šI shall use the term association to cover both coupling and repulsion.

“Journ. Genet., 1, 159, 1911.

370 THE AMERICAN NATURALIST [Vou. XLVI

together they produce two yellows to one black or chocolate,

no T being present. Her total figures are 451 yellows to 241

blacks and chocolates, to which should be added Little’s’ record

of 31 yellows to 24 blacks and chocolates. If ordinary yellows

be mated to chocolates or blacks the result is an equal number

of yellows and of blacks or chocolates. Miss Durham’s figures

are 282 yellows and 319 blacks and chocolates. Both these

crosses are cases of monohybridism, T never being present, and

Y alone being involved.

If ordinary yellows be bred to pure agoutis, the result should

be equal numbers of yellows and agoutis, as shown above. The

actual results obtained are as follows:

Yellow Agouti Authority

53 39 Durham.

16 14 Morgan.

69 53

If the P, agouti used in this cross were heterozygous in T, then

the expectation would be two yellows, one agouti, and one black

(or chocolate). Apparently Morgan is the only one who has

reported such a cross. He obtained 4 yellows, 5 agoutis, and.

1 black.

' The results of the four crosses above are explicable without

the assumption of association between T and Y, since in no case

was an animal bred from which was heterozygous in both, and

only in such cases does association ever become apparent. But

such heterozygous mice should be obtained in the cross between

agouti and yellow. If these be mated together the ordinary

expectation, as shown by the diagram above, would be 8 yel-

lows, 3 agoutis, and 1 black or chocolate. The actual offspring

recorded from yellow by yellow giving agouti are:

Yellow Agouti Black and Chocolate Authority

108 62 Durham.

15 9 0 Morgan.

123 71 0

This is approximately two yellows to one agouti. It is the result

which would be expected if one of the parent yellows were pure

for T (TY Ty). But, with the possible exception of 20 of Miss

Durham’s,’ all the above 194 mice were from yellows out of yel-

* Science, N. S., 33, 896, 1911.

*It would appear from the context that these 20 also belong to the

category under discussion, but a definite statement to that effect is not given.

No. 546] SHORTER ARTICLES AND DISCUSSION 371

low by agouti. No other crosses of yellow by yellow gave agouti,

so that it seems in the highest degree probable that the original

(P,) yellows were pure for t. That being the case the F,

yellows must all have had the formula tY Ty. But since they

produced only 24 yellows to 14 agoutis it follows that association

occurs between T and Y, thus:

Yellow—t¥ Ty

Yellow—tY Ty

Ty tY

tY Ty

(tY tY)

Ty Ty—1 agouti.

—2 yellows.

These 7-bearing yellows have also been bred to chocolates and

blacks. If there were no association this mating should produce

two yellows, one agouti, and one chocolate or black. But Miss

Durham has obtained only 30 yellows and 37 agoutis—practi-

eally equal numbers, with no blacks or chocolates. On the asso-

ciation hypothesis this cross should produce the following result:

Yellow—tY Ty

Chocolate or black—ty ty

tY ty—1 yellow.

Ty ty—1 agouti.

Apparently the ticking factor and the factor which produces

yellow mice are associated very closely. There appears to be no

evidence that ‘‘crossing over’’ ever occurs. It can not be sup-

posed that Y is the same as ¢, with whiich it always occurs, since

in that case all mice not agouti, or even heterozygous for T,

would be yellow, and black and chocolate would not exist. It

should be noted that if one adopts Castle’s mouse formule (see

Castle and Little,” ete.), it is still necessary to suppose that

association occurs but now between the restriction factor, R,

and the agouti factor, A.

A. H. STURTEVANT

COLUMBIA UNIVERSITY,

February, 1912

? Science, N. S., 30, 313, 1909.

372 THE AMERICAN NATURALIST [Vou. XLVI

THE MALTHUSIAN PRINCIPLE AND NATURAL

SELECTION

In the last edition of his essay on population, page 2, Malthus

laid down the following biological proposition from which he de-

rived his well-known sociological conclusion :

The cause to which I allude is the constant tendency in all animated

life to increase beyond the nourishment prepared for it.

It is incontrovertibly true that there is no bound to the prolific plants

and animals, but what is made by their crowding and interfering with

each others’ means of subsistence. (Italics mine.)

In plants and irrational animals, the view of the subject is simple.

They are all impelled by a powerful instinct to the increase of their

species; and this instinct is interrupted by no doubts about providing

for their offspring. Wherever, therefore, there is liberty, the power

of increase is exerted; and the superabundant effects are repressed

afterwards by want of room and nourishment.

The great influence of this book upon Darwin is well known

and so it is not surprising to find him writing in the ‘‘ Origin of

Species,’’ page 60,

A struggle for existence inevitably follows from the high rate at

which all organic beings tend to increase.

And again on page 72,

Each organic being is striving to increase in geometrical ratio; each,

at some period of its life, during some season of the year, during each

generation or at intervals, has to struggle for life and to suffer great

destruction.

It is quite natural, therefore, to find that in the current texts

and in the class room, that natural selection is taught as starting

from the contrast of a limited subsistence and a very large birth-

rate (and I confess that I have been guilty). So strong an im-

pression is thus made, that to most people, and unfortunately

many sociologists, natural selection has come to mean that factor

of evolution which is caused by an excessive birth rate.

The fact is frequently lost sight of that natural selection effects

its results by differential success in mating (sexual selection),

and differential fecundity (fecundal selection), as well as by a

differential age at death (lethal selection). Even when we con-

fine our attention to lethal selection, we shall see that a very

large share of its action is in no way dependent upon the ade-

quacy of the food supply. Such selection may well be called non-

No. 546] SHORTER ARTICLES AND DISCUSSION 373

sustentative selection to distinguish it from that which is so de-

pendent.

Sustentative selection is generally thought to be nearly always

in operation. In every group of animals in which I have made

any special field observations, namely, bryozoa, birds and

beetles, the falsity of this belief has been impressed upon me.

With fresh-water bryozoa the food supply can scarcely ever be

taxed. The limiting conditions seem to be largely inconstancy

of the bodies of water, the danger of being eaten, and the limited

extent of suitable substrata.

With birds, when one really sees an emaciated individual, the

result of some accident which has made it difficult for it to ob-

tain food, one is struck by the very great contrast with other

birds. In my experience, in skinning birds in the state of Wash-

ington, summer and winter, I never opened one not well equipped

with abdominal fat. On the other hand, the great loss of the

young birds by adverse weather and the large variety of pre-

daceous enemies is common knowledge.

With lady beetles there is a more direct relation of the num-

bers to food supply, but even here it is a question of finding food,

rather than any real lack of it. The food supply of the adult

beetles, embracing aphids, pollen and spores, is superabundant.

The principal causes of death seem to me to be due to inability

of the females to distribute the eggs proportionately to the dis-

tribution of aphids, and, secondly, the unreliableness of aphid

stocks, owing to their rapid annihilation when one of the numer-

ous aphid diseases or parasites becomes rampant. One may

often hunt over many colonies of aphids without finding any

coccinellid larve, and then at last find one of the same species

with several large egg masses. So many larve will hatch in this

case that they will consume all the aphids before they themselves

have all become mature. As a result, they will wander, only a

few surviving who may have the efficient instincts and good for-

tune necessary to discover another stock of aphids.

Of the half dozen or so species of the large coccinellids most

common in the United States, it is common to find here one

species abundant, and there another, though some others are also

found. Attempts to account for these contrasts in numbers on

grounds of temperature, humidity, altitude and the like, have

proved unsuccessful. I think it is because the instincts of egg-

laying and of migration of the larve of one species or another is

better adapted to the species of spar ye TENE pane

374 THE AMERICAN NATURALIST [ Vou. XLVI

in that vicinity. Evidence to this effect is seen in the fact that

certain shrubs that are aphis-infected for a short time only in the

early spring sustain only Adalia bipunctata. The wild parsnip,

which becomes infected with other aphids later, sustains Adalia

bipunctata in numbers smaller than three of its competitors. If

we take the herbivorous coccinellids, we will find similarly in

some places an abundance of food that they have not touched,

while some other patches of suitable plants may be stripped.

In conclusion, then, we see that in the bryozoa and birds,

sustentative selection does not play the dominant rôle imputed to

it. In the lady beetles, where the supply of food is seen to limit

their numbers, it is not because there is not food enough, but

because the individuals are not properly distributed with refer-

ence to that food. The sustentative selection in this case must be

differentiated as indirect. The evolutionary significance lies in

the fact that where the sustentative selection is indirect, the

species may become more abundant through variations which ad-

just the individuals better to the food supply.

I believe there is a fundamental reason for this subordination

of sustentative selection. The reproductive rate is not merely

an arbitrarily large number, which necessarily causes a severe

struggle, but is just such a number as is best adapted, in general,

to the needs of the species. The extreme members of that school

which emphasizes the importance of the variations at the expense

of selection can scarcely object to this, for fecundity is always

variable and these differences are known to be inheritable in

many cases.

Now the number of progeny which is best adapted to the needs

of the species is that number which is large enough to sustain

the losses from all non-sustentative causes of death, but not large

enough to invoke death by starvation. Such a species is obvi-

ously less liable to extermination than one in which the hostile |

influence of underfeeding always handicaps. If grasshoppers

conformed to the Malthusian conceptions of many evolutionists,

there should be no alfalfa, for that favorite food would all be

eaten up before it could be harvested. The world teems with

herbivorous animals of one kind or another, and yet also teems

with plants, most of which are eaten by many species of animals.

I can see no other explanation than that the species are not ordi-

narily subject to sustentative selection, and that when it is, it is.

generally the indirect selection rather than the direct. oe

Indirect sustentative selection is less injurious to a species, be-

No. 546] SHORTER ARTICLES AND DISCUSSION 375

cause those individuals which do become well placed thrive. The

burden of starvation passes by a number of the individuals to

fall upon the others. In this way, the evil effects of a general

underfeeding, which is the necessary result of direct sustentative

selection, is avoided. In cases, then, where indirect sustentative

selection is operative, the reproductive rate is that which will

produce enough individuals to find many of the favored places

and withstand the non-sustentative causes of death. Where

direct sustentative selection might be theoretically expected, as

in the case of the large birds of prey, in regions where they are not

persecuted, the rigors of a mers struggle are avoided by low

reproductive rates.

While the reproductive rate must be looked upon as a char-

acteristic which has its adaptations like other characteristics, it

has one peculiarity—its increase is always opposed by lethal se-

lection. The’ chances of life are reduced by reproducing inas-

much as more danger is entailed by the extra activities of court-

ship, and later, of the care of the young, since they reduce the

normal wariness of individual life. The species, therefore, al-

ways keeps the reproductive rate at the lowest point which will

suffice for the reproductive needs of the species. For this reason

alone we should expect the non-sustentative selection to be the

predominant kind.

Gulick and Pearson have shown that there is a normal conflict

between natural selection and fecundal selection. Fecundal se-

lection is said by them to be constantly tending to increase the

reproductive ratio, while lethal selection asserts its power to re-

duce it, because the reproductive demands on the parents reduce

their chances of life by interference with their natural ability of

self-protection. This is quite true, but the analysis is incomplete,

for an increased number of progeny not only decreases the life

chances of the parents, but also of the young, by reducing their

endowment and care.

A further reason for believing in the predominance of non-

sustentative selection is the fact that the species that have

evolved furthest are well known to be of low fecundity.

imself, even where there is no artificial restraint, has one of the

smallest reproductive rates known. If sustentative selection had

been predominant, we should expect higher fecundities in these

highly evolved species than in the lower ones.

The fundamental formula of Malthusianism, that the number

of individuals i in a species tends to increase in geometrical ratio,

376 THE AMERICAN NATURALIST [Vou. XLVI

is misleading, and a great mass of biological and sociological

writing has been led into error by it. Of course, there can be no

objection to the position that since the number of progeny ex-

ceeds the number of parents, there must be many premature

deaths, or the species will increase in numbers. But this is a

truism. The real essence of Malthusianism lies in the conclusion

that a sustentative struggle must arise, and there lies the error.

The Malthusian conception of the rate of reproduction is that the

rate is such that the food supply must be overtaxed and a struggle

for existence will take place. The conception here urged is that

each species has such a reproduction rate as will suffice to with-

stand the premature deaths and sterility of some individuals, and

yet not so large as to press normally upon the limits of the food

supply.

I believe the common over-estimation of the rôle of sustenta-

tive selection, and the neglect of the non-sustentative, is largely

historical in origin, and that it is maintained by improper teach-

ing. : :

In teaching natural selection, the fault is generally made of

starting with the Malthusian contrast between the limitation of

the food supply and the rate of reproduction. The current con-

ception will not be righted until we learn to teach natural selec-

tion more correctly. While the rate of reproduction is the

proper place from which to start, this should be treated, not as a

fixed quantity to which nature must accommodate itself, but as

that number which just exceeds the great number of premature

deaths and suffices to replace the parents. Then the premature

death of the 999 must be explained. After an examination of

these causes the student can not but grasp the master rôle of the

non-sustentative form.

Finally, then, we see from these considerations, that the com-

mon assumption that every species is as common as it can be,

because it is living up to the limits of subsistence is erroneous.

A relaxation of any of the causes of death in most cases will in-

crease the numbers.

[This article was written while the author was on the staff of the Station

for Experimental Evolution at Cold Spring Harbor, N. Y., of the Carnegie

Institution of Washington. ]

RoswELL H. JOHNSON.

BARTLESVILLE, OKLA. .

THE

AMERICAN NATURALIST

VoL. XLVI July, 1912 No. 547

GENETICAL STUDIES ON CENOTHERA. III

FurtHeR Hysrips or (nothera biennis ann O. grandi-

flora THAT RESEMBLE O. Lamarckiana‘

DR. BRADLEY MOORE DAVIS

UNIVERSITY OF PENNSYLVANIA

Tue following paper will describe my cultures of

(Enothera, grown during the season of 1911, which bear

upon the working hypothesis announced in a previous

contribution (Davis, ’11) to the effect that Gnothera

Lamarckiana arose as a hybrid between types of O.

biennis and O. grandiflora. The cultures of 1911 gave

results much more striking than those of 1910 and 1909

and marked progress has been made towards the synthe-

sis of a hybrid between these two species which will be

so similar to Lamarckiana as to be practically indistin-

guishable by the usual taxonomic tests.

The problem before me seems to be chiefly that of find-

ing and selecting among the various strains or races of

biennis and grandiflora the most favorable types with

which to work. As the study has progressed I have been

surprised at the wealth and variety of forms which

taxonomically are included in the species O. biennis, but

which can be readily differentiated in ‘‘pure line” cul-

*An abstract of this paper was presented before the American Society

of Naturalists on December 28, 1911.

377

378 THE AMERICAN NATURALIST [Vou. XLVI

tures as biotypes and which so far have held their char-

acters through two and three generations. (Mxnothera

biennis is much more rich in biotypes than O. grandiflora

probably because it is more hardy and adaptive in its life

habits, growing over an immense geographical range and

under a great variety of climatic and soil conditions. It

is clear that any one who cared to give an extended

period to the study of O. biennis could differentiate

scores of elementary species in the assemblage of forms

included under this name.

Further acquaintance with O. Lamarckiana has led me

to believe that under this name must be included a num-

ber of races. Excluding the more striking of the‘‘mutants’’

of De Vries, there still remain strains that differ from

one another in such characters as the size of buds and

flowers, relative height of the stigma, forms of the cap-

sules, tint of the foliage, ete., and these strains, when

selected and carried on in ‘‘pure lines’’ hold their pecul-

iarities and are true biotypes, although the differences

between them may be so small as to have little or no taxo-

nomic value. We have then under O. Lamarckiana a

diverse assemblage and no one will ever be able to prove

that any one type is identical with the original since the

account of the original and the herbarium material

available do not give the information necessary for a full

description.

The types called Lamarckiana, as now cultivated, have

come down to us perhaps entirely from cultures of

Messrs. Carter and Company of London at about 1860,

but they have come down through diverse channels with

abundant opportunities for hybridization and that differ-

entiation that results from selection, conscious or other-

wise, on the part of gardeners. In the experimental

gardens we are working chiefly with the strains that have

passed through the hands of Professor De Vries, who,

however, began his work (about 1886) many years after

the plant had been in cultivation. This material of the

experimental gardens has then been subjected to a large

No. 547] GENETICAL STUDIES ON ŒNOTHERA 379

amount of selection and every worker who is following

genetical methods is continuing to differentiate, more or

less perfectly, strains or biotypes. I have in my own cul-

tures separated in ‘‘pure lines’ several strains which

differ in the size of the flower, the height of the stigma

relative to the tips of the anthers, and the depth of color-

ation in the foliage, and these strains have held true in

my limited cultures.

These points must be borne in mind in judging the

results of my studies, for it is one thing to attempt the

synthesis of a hybrid taxonomically similar to Lamarcki-

ana, and it would be quite another to attempt to match

exactly a particular biotype of this plant. The prob-

abilities of obtaining a hybrid the exact counterpart of

a specific biotype are small; for the reason that very many

characters or groups of characters give to these strains

their peculiarities. The probabilities of obtaining a

hybrid the characters of which will be matched largely or

wholly by forms of Lamarckiana are, however, in the

writer’s opinion, excellent and such a type is meant when

we speak of a hybrid taxonomically similar to Lamarck-

iana or indistinguishable from it.

e announcement of Gates (’10) that certain marginal

notes in a copy of Bauhin’s ‘‘ Pinax,’’ 1623, give an accu-

rate description of Lamarckiana and establish its pres-

ence in Europe at this early date has proved to be a false

alarm. These notes consist of matter, copied on the

margin of a page, from the longer description of Lysi-

machia lutea corniculata found in the appendix (pp. 520,

521) of the ‘‘Pinax.’’ The readiness with which Gates

and Hill (’11) have accepted as reliable the statement of

Bauhin that the flowers of this form are 3 inches long

above the ovary, in the face of the statement a few lines

below that the capsules become 2-3 inches long (a mani-

fest absurdity), is inexplicable to the writer. It shows a

naive confidence in the descriptions of the early botanists

which is searcely to be expected in the consideration of so

difficult a problem as the origin of O. Lamarckiana.

380 THE AMERICAN NATURALIST [Vow. XLVI

Gates (’lla, p. 101) also believes that the description of

Lysimachia Americana by Hernandez (‘‘Nova Plant.

Anim. et Miner. Mex.,’’ p. 882, 1651) is that of Lamarck-

iana ‘‘in the strict sense.’’ This account is quite as

vague in character as others of the period and the figure

is very crude. Gates emphasizes the statement concern-

ing the leaves ‘‘sinibus levibus excavata’’ and regards

this as descriptive of the characteristic crinkling of the

leaves of Lamarckiana. He gives no consideration to the

petals clearly drawn as mucronate or to the stigma

figured on about the level of the anthers, and is not im-

pressed with the description and figures of the leaves as

like the willow. The writer must express his astonish-

ment that an identification of this plant with Lamarckiana

should be claimed chiefly on a single character loosely

described, ignoring important points that radically dis-

agree, and giving no weight to the evident inaccuracy of

the description and figure. Gates has changed his posi-

tion respecting the account of Bauhin which in this later

paper (Gates, ’1la) is referred to biennis in agreement

with the general opinion of botanists, but I have found

no further reference by him to the description of Her-

nandez. ;

There have been then no new developments to modify

my view that O. Lamarckiana was unknown previous to

the description of Lamarck’s plant at Paris in 1797,

about eighteen years after the introduction of O. grandi-

flora at Kew in 1778. There is less reason to lay stress

upon the appearance of this plant in the gardens at Paris

since the evidence seems clear that the Lamarckiana of

to-day has genetic relation to the cultures of Carter and

Company of London about 1860. I shall have more to

say on this point in connection with the valuable sheet in

the Gray Herbarium and the interesting history of its

probable relation to these same cultures of Carter and

Company. This seems to the writer perhaps the most im-

portant herbarium sheet known bearing on the problem of

the origin of nothera Lamarckiana. It will be con-

sidered in the latter part of this paper.

No. 547] GENETICAL STUDIES ON ŒNOTHERA 381

I have recently had the opportunity of examining two

herbarium sheets of American wild plants, referred to

in my earlier paper (Davis, ’11, p. 227), which were

thought by De Vries (’05, p. 386) to be O. Lamarckiana.

The first of these, at the New York Botanical Garden, is

a specimen collected by A. W. Chapman in Florida (1860

or earlier). Duplicates of this material are said to be at

the Biltmore Herbarium and at the Missouri Botanical

Garden (MacDougal, ’05, p.6). The second sheet, at the

Philadelphia Academy of Natural Sciences with an appar-

ent duplicate at the New York Botanical Garden, is of a

specimen collected by C. W. Short near Lexington, Ky.

This specimen was later considered by Miss Vail to be

O. grandiflora and a possible escape from cultivation.

There is nothing on these sheets from Florida and Ken-

tucky that is not represented in a fair range of herbarium

material of grandiflora such as may now be found in my

own collections and at the New York Botanical Garden.

In no point do the sheets closely approach Lamarckiana

except that they have large flowers. In justice to Pro-

fessor De Vries it should be stated that he expressed his

opinion before the rediscovery of the habitat of Enothera

grandiflora by Tracy in August, 1904, and consequently

before there was available the extensive material of this

species now assembled. Could he have made the com-

parisons at present possible he would not, I am sure,

have given the opinion quoted above.

There has then so far been found in the American

herbaria and records, and these have been very thor-

oughly examined by various workers, no evidence that

(nothera Lamarckiana is at present or ever has been a

component of the American flora as a wild native species.

There are in the south and west certain large-flowered

species of @nothera of considerable interest because of

their possible affinities with grandiflora, and these should

be studied by those in a position to do so. A number of

these are represented in American herbaria; others in

the British Museum are referred to by Gates (’1la, p.

382 THE AMERICAN NATURALIST [Vou. XLVI

591). That an identification with Lamarckiana can ever

be made from the average herbarium sheet seems to the

writer almost impossible, for the specimens of Œnothera

formerly collected rarely give a fourth of the informa-

tion necessary to make a critical comparison with

Lamarckiana. With the clear evidence that the present-

day Lamarckiana holds a genetic relation to the cultures

of Carter and Company, about 1860, the problem of its

origin has become much more tangible than formerly.

and this matter will be taken up in our discussion of these

cultures in relation to the sheet in the Gray Herbarium

at Harvard University.

American botanists are not likely to believe that

Lamarckiana, if present in America in 1860, has become

so quickly extinct, knowing as they do the vitality of our

rich @nothera flora. For example, O. grandiflora has

actually persisted in the same locality since its first dis-

covery by William Bartram in 1776. Let those interested

in the problem of the status of Lamarckiana use their

best endeavors to discover this plant in the field, but let

them give us their results not only by herbarium material

covering the entire life history, but above all through seed

that can be sent to the workers in the experimental

gardens.

The material of this paper will be arranged under the

following headings: (1) Methods, (2) Large- and Small-

flowered Biotypes of @nothera Lamarckiana, (3) Further

Races of Œnothera biennis L., (4) Further Races of

nothera grandiflora Ait., (5) Hybrids in the F, Gener-

ation from the Cultures of 1911, (6) Hybrids in the F,

Generation from the F, Hybrid Plants 10.30La, and

10.30 Lb, (7) The Probable Composition of the Cultures

of Carter and Company from Evidence Furnished by the

Sheet in the Gray Herbarium, (8) Further Considera-

tions on the Possible Origin of nothera Lamarckiana

as a Hybrid of O. biennis and O. grandiflora.

As in previous seasons, I am greatly indebted to the

Bussey Institution and to the Botanic Garden of Harvard

No. 547] GENETICAL STUDIES ON ŒNOTHERA 383

University for the facilities that have made possible

these studies.

1. MzTHODS

The methods of culture were the same as those of the

previous season (Davis, 711, p. 196). I have, however,

adopted the system of collecting and sowing seed capsule

by capsule as being the safest way of regulating the

size of the cultures and obtaining a fair average of

results both qualitative and quantitative. Furthermore

the seeds which go into a seed pan are counted so there

is obtained some data on the percentage of germinations.

The count can not be made strictly accurate, for there are

in @nothera varying proportions of obviously abortive

seeds which so grade into seed of questionable fertility

that good and bad could not be separated unless dis-

sected. Nevertheless, these counts are important, espe-

cially in cases where it is fundamental that all fertile

seed be germinated, as in the comparison of reciprocal

crosses.

2. LARGE- AND SMALL-FLOWERED BIOTYPES OF

(Enothera Lamarckiana

The experience of the writer during the past six years

has forced upon his attention the fact that there is a wide

range in the bud and flower measurements of Gnothera

Lamarckiana in cultures that are practically indistin-

guishable as to their vegetative characters.

De Vries in his ‘‘analytical table of flowers, fruits and -

seeds’’ (‘‘The Mutation Theory,’’ Vol. I, p. 452, 1909)

gives the measurements of the petals of Lamarckiana, on

the average, as 3-4 em. long. I am growing strains or

biotypes of Lamarckiana derived from seeds of De Vries

in which the petals measure from 4-4.5 em. in length and

similar strains have been sent tome from England, where

essentially the same form is cultivated under the name

biennis var. grandiflora. These very beautiful plants

constitute a sort of élite race and apparently represent

384 THE AMERICAN NATURALIST [Vou. XLVI

the best that the gardener’s art (probably in large part

selection more or less in ‘‘pure lines’’) has been able to

accomplish.

There have, however, twice come to me seed of La-

marckiana through different sources (all originally from

De Vries) that has given numbers of plants with much

smaller flowers, but otherwise presenting essentially the

same characters as the large-flowered types. From

such plants I have had no difficulty in establishing strains

(B, D, Y, and Z) in which the petals measure about

2.5 em. (for figure, see Davis, 711, p. 216). The strains

have been perfectly true through two generations,

although the cultures have been small. The stigmas

in these plants are about on the level of the tips of

the anthers, sometimes a little above, in one strain

(B) somewhat below. In this respect the flowers resem-

ble those of biennis in sharp contrast to some of the large-

flowered Lamarckiana in which the stigma is 6-7 mm.

above the tips of the anthers, even higher than is typical

of grandiflora. The point should be emphasized that

when these small-flowered plants are grown side by side

with the large-flowered forms there is no hint of impor- —

tant differences between the plants until the time of

flowering, when the large and small buds first clearly

define the two types.

Some authors will refuse to admit that the small-

flowered plants are Lamarckiana. They will insist that

the true Lamarckiana is always large-flowered and that

these variants are ‘‘mutants’’ or perhaps aberrant types. _

Yet the fact remains that the large- and small-flowered

types are indistinguishable in taxonomic practise except

for the bud and flower characters, and the writer can

but believe that the large-flowered forms have been

steadily selected by those who have for so many years

carried Lamarckiana along to its present state.

Whether the small-flowered forms illustrate reversion

towards a biennis type of flower is a matter worthy of

critical attention. The behavior of my hybrids between

No. 547] GENETICAL STUDIES ON ŒNOTHERA 385

biennis and grandiflora so far tested in the F, genera-

tion (briefly described later in the paper) showed clearly

that there is a segregation of flower size. Some types of

flowers appeared in the F, that were even larger than the

grandiflora parent species and as large as the largest

Lamarckiana; others were smaller than the flowers of the

F, hybrid parent, although none were so small as the

biennis parent species. Between the large and the small-

flowered F, hybrids was an apparently perfect range of

intermediates.

Gates (’11b) has criticized the comparison of the

flowers of my hybrid plants 10.30La and 10.30Lb to those

of Lamarckiana (Davis, ’11) on the ground that their

measurements were too small (petals 2.2 em. long), being

unwilling to recognize the existence of small-flowered

types of Lamarckiana. He apparently, however, fails to

appreciate that the problem is only in part what may

appear in the F, generation. It is the behavior of the

hybrids in the second and later generations that will

demonstrate the possibilities of the double organization

of the F, hybrid, and the results of my cultures of the F,

generation indicate that forms with flowers fully as large

as those of the largest-flowered Lamarckiana may be

readily obtained in abundance. It may prove more diffi-

cult to establish in the hybrids certain points of stem

coloration and leaf form, but my later studies indicate

that these results will depend chiefly upon proper

discrimination in the choice of parents for the cross,

especially among the large variety of biotypes included

in biennis. 3

3. Furruer Races or @nothera biennis L.

I have discarded for experimental purposes the races

biennis A and biennis B which were used in the first

crosses with O. grandiflora (Davis, 11). These have

been supplanted by biotypes much more favorable for

the purposes of the investigation. Among the American

wild forms of biennis the best so far obtained is biennis D

386 THE AMERICAN NATURALIST [Vow XLVI

of my cultures—a fairly large-flowered type (petals

about 2 em. long) with relatively broad leaves and a

green stem the papillate glands? of which are colored red

by anthocyan.

This form, biennis D, is widespread. It is common in

the suburbs of Boston, and I have seen it at Woods Hole,

Plymouth, and in the neighborhood of Philadelphia.

There is considerable variation in the breadth of the

leaves. Similar plants may also be found with clear

green stems indicating that the red coloration of the

glands may not always be a firmly established character

in the strains that show it.

The plant which was the starting point of the strain

biennis D grew wild in the grounds of the Bussey Insti-

tution in company with a number of similar types. From

self-pollinated seed a culture of 51 plants was brought to

maturity in the summer of 1911, all the plants being alike,

even to the red coloration of the glands on the stems.

7 Apparently there has been but little study of the surface tissues of

he tions.

ever, former statements of the absence of external glands 7 the group

younger portions of the plants more or less of a somewhat sticky moisture,

and the problem is from what cells do these secretions come. The hairs

on these plants are of two types, both unicellular, (1) short hairs attached

directly to the surface, (2) much longer and stouter hairs each arising

from the top of a papilla. The papilla in section is seen to consist of a

ages of the epidermis into which extends a number of hypodermal

cells. These hypodermal cells in younger portions of the plant are filled

eek a dense viscous-like subst ance, as are also some of the epidermal cells.

old portions of the plants these cells, like those of the hypodermal tissue

in general, are found to be quiteempty. Thus the appearance of the contents

of the cells composing the papilla indicates that it is secretory in function

and I have consequently termed it a gland. The structure is important in

experimental studies since its coloration in some forms follows that of the

stem on which it lies (green or reddish) while in other pay the papilla

may be colored red upon green stems and ovaries. We trust that the evi-

dence presented above will justify the term gland ati if correct,

preferable to the designations papille, pustules, tubercles, red tubercle- ie ke

bases, red prickles, papillose based, red tuberculate, ete., that have been

applied by my correspondents to this structure, or to ‘the hair.

No. 547] GENETICAL STUDIES ON GENOTHERA 387

The original plant was crossed in 1910 with the strains

grandiflora B and D (for descriptions see Davis, ’11,

pp. 205-207) and the interesting F, hybrids described in

this paper were from this cross.

The chief characteristics of the strain biennis D, when

under good cultivation, are as follows:

1. Rosettes-——Mature rosette (Fig. 1) about 4 dm.

Fic. 1. Mature rosette of @nothera biennis, D (11.13a).

broad. Leaves broadly elliptical, 2-2.5 dm. long, some-

what crinkled, margin sinuate, irregularly toothed and

cut below, green with occasional red spots.

9, Mature Plants.—The mature plants ( Fig. 2), 1-1.5

m. high, have long irregularly spreading side branches

from the rosette and main stem; collar? at the base of the

branches inconspicuous. Stems green above, punctate

collar is suggested for the swollen ring at the base of the

larger branches, which in some species of Œnothera (e. g., grandiflora) is

very conspicuous.

388 THE AMERICAN NATURALIST [Vou. XLVI

Fig. 2. Mature plant of @nothera biennis, D (11.13a).

with red papillate glands at the base of long hairs. Basal

leaves on the main stem elliptical (Fig. 3), about 17 cm.

long, without ‚marked crinkles, irregularly toothed ;

leaves above lanceolate.

3. Inflorescence.—Bracts lanceolate, 4—4 length of buds

(Fig. 3), frequently deciduous, leaving the fruiting

branches destitute of leaves.

4. Buds.—About 5 em. long, the cone 4-angled. Sepals

green, pubescent with numerous long. hairs arising from

papillate glands among which are short hairs; sepal tips

not markedly attenuate.

5. Flowers.—Fairly large (Fig. 3). Petals about 2

No. 547] GENETICAL STUDIES ON ŒNOTHERA 389

em. long. Stigma lobes slightly below tips of anthers,

3 mm. long, pollinated in the bud. Papillate glands on

ovaries red.

6. Capsules —Gradually narrowing from the base,

2-2.5 em. long.

7. Seeds.—Light brown.

Fic. 3. Flowering side branch of @nothera biennis, D (11.13a), with a leaf

from the lower portion of the main stem.

A comparison of biennis D with the strains biennis A

and B (Davis, ’11, pp. 198-200) will show that it has

certain important characters, present in Lamarckiana,

which were not exhibited by those types of biennis first-

390 THE AMERICAN NATURALIST [Vou. XLVI

employed in my crosses. The most important of these

characters are (1) the stem coloration, green punctate

with red papillate glands, (2) a broader rosette leaf

somewhat crinkled, and (3) broader and larger foliage

leaves. The flowers, half again larger than those of

biennis A and B, are of a size more favorable to give

large-flowered hybrids approaching Lamarckiana when

grandiflora is employed as the other parent of the cross.

Although the differentiation of biennis D as a biotype

has marked a great advance in the possibilities of my

experimentation, there are undoubtedly other races of

biennis which will prove better for my purposes. Thanks

to correspondents, I have received seed of biennis from

England and the continent that is likely to give types of

great interest, and more favorable strains among the

American forms are likely to come to hand. There are

some beautiful large-flowered English and Dutch forms

of biennis which in their broad and crinkled leaves and in

their habit are very similar to Lamarckiana, but I have

not as yet found among them the stem coloration desired.

However, it is to be expected that broad and crinkled-

leaved types of biennis will be discovered with red-colored

glands upon the stems and ovaries and such forms when

crossed with grandiflora are likely to give the hybrids

most like Lamarckiana. It will take some time to differ-

entiate such strains, but they are certain to exist since

these characters are presented in part by various types of

biennis. Indeed they seem likely to prove not uncommon

judging from the collections that have come to me during

the past year from botanists who have kindly interested

themselves in the problem.

In my previous paper (Davis, ’11, p. 201) mention was

made of a southern Œnothera (strain S) which appeared

in cultures from the wild seed collected by Tracy as

(nothera grandiflora. Further studies have shown that

the plant is annual, its rosette being small and transitory

as in grandiflora. The form has been described and

named nothera Tracyi by H. H. Bartlett (711). I have

No. 547] GENETICAL STUDIES ON ŒNOTHERA 391

crossed this species with grandiflora, but the hybrids were

very far from Lamarckiana chiefly since the hybrids had

narrow leaves and lacked the persistent rosettes asso-

ciated with the usual biennial habit of the latter plant.

The results show clearly that any form crossed with

grandiflora to produce Lamarckiana-like hybrids must be

one with large persistent rosettes such as are presented

by the northern types of biennis.

4. Furrner Races or Gnothera grandiflora Arr.

A type of Gnothera grandiflora appeared in my cul-

tures of 1910 (Davis, ’11, p. 204), first noted because of

its rosette of green, much crinkled leaves. This strain,

grandiflora I, was further cultivated in 1911 but has

proved less favorable for my purposes than the strains

A, B, and D, chiefly for the reason that its leaves have a

pronounced petiole and the stems bear towards their tips

dense clusters of flowering side shoots. The strain

grandiflora I is a well-defined type very different from

the much more common forms of grandiflora and as

such is of interest.

To add to the data on the composition of Œnothera

grandiflora as it grows wild (Davis, ’11, pp. 202-205) a

culture of 169 plants from wild seed, collected by Tracy

at Dixie Landing, Alabama, in 1907, was brought to

maturity during the season of 1911. In this culture 42

plants proved to be @nothera Tracyi referred to above,

9 plants were unmistakably of the strain grandiflora I,

and the remaining 118 plants were close to the strains

grandiflora A, B, and D, which it will be remembered are

so similar as to be essentially of one type.

It seems clear from my cultures of wild seeds, a total

during the past four years of about 300 plants, that the

prevailing form of grandiflora is that represented by the

strains A, B, and D, previously described (Davis, ’11,

pp. 205-207). There is a range of variation, chiefly in the

breadth of the leaves, and these strains (A, B, and D) are

392 THE AMERICAN NATURALIST [Vou. XLVI

the broader-leaved, more luxuriant forms such as the

gardener would be likely to select for cultivation.

5. HYBRIDS IN THE F, GENERATION FROM THE

CULTURES oF 1911

The most important cultures of 1911 in the F, genera-

tion were those of the following combinations of parent

species.

1. grandiflora B X biennis D (11.35).

2. grandiflora D X biennis D (11.32).

3. grandiflora I X biennis D (11.37).

4. grandiflora D X Tracyi (11.33).

Of these the most interesting, with respect to the

resemblance of some of its plants to Lamarckiana, was

the first culture in the list—grandiflora BXbiennis D

(11.35). The greater part of this account will conse-

quently be devoted to this culture, but the others will be

Fig. 4. E rosette of an F, hybrid grandiflora B x biennis D (11. 35),

compared with that of Lamarckiana Z (11.7).

briefly described, chiefly with reference to the coloration

of the papillate glands in which all four cultures agree in

exhibiting a behavior that was not tò be expected.

l. grandiflora B X biennis D (11.35).—This culture

No. 547] GENETICAL STUDIES ON ŒNOTHERA 393

was derived from the contents of two capsules containing

about 300 seeds. From these 247 seedlings appeared in

the pans within six weeks ; 198 young rosettes were potted

and finally 180 large rosettes were set out. Thus, in re-

ducing the culture, 67 smaller rosettes which gave less

promise of developing into vigorous plants were dis-

carded.

The similarity of the young rosettes of the hybrid to

those of Lamarckiana is shown in Fig. 4. The mature

Fic. 5. Mature rosette of the F, hybrid 11.35a, preven B x biennis D;

representative of the mass of the ¢

rosettes (Fig. 5) presented characters that were clearly

blends in various degrees between the parent types,

blends very hard to define because of a range of varia-

tion in the leaves. The leaves were conspicuously

crinkled as in Lamarckiana, differing from the latter

types of my cultures chiefly in being more deeply toothed

and cut at their bases and in being colored a slightly

darker shade of green with more’numerous reddish spots

394 THE AMERICAN NATURALIST [Vou. XLVI

of anthocyan. The rosettes resembled those of Lamarck-

iana very closely in their morphology, much more closely

than those of my earlier hybrids (see Davis, ’11, Figs. 9

and 12), as would be expected from a cross involving the

broader-leaved biotype biennis D.

Continued experience with the rosettes of Gnothera

has shown that there is a greater range of variation

among the F, hybrids of the species crosses than might

be expected by those whose studies have been upon

hybrids of closely related races. It has always been pos-

sible to arrange the mature rosettes of a large culture in

a series with a small group at each end that differ and

incline towards the two parents. It is my method to set

out the rosettes in this order and generally the rosettes

at the ends will develop into mature plants exhibiting a

similar degree of divergence from the mass of the cul-

ture. But this is by no means a fixed rule and rosettes

giving promise of a certain line of development may

grow into mature plants of an unexpected type. I have

emphasized the divergence between the rosettes at the

extremes of an F, generation, but it must not be supposed

that these plants constitute classes. On the contrary, in

large cultures they apparently range insensibly into the

mass.

A comparison of the parents of this cross, grandiflora

B (see Davis, ’11, pp. 205-207) and biennis D described

above, will show that they differ chiefly in the relative

form, size and proportions of their organs, and their

characteristics would be expected to be present in the F,

hybrids in blended relations, as is the fact. The only

character observed that might be sharply contrasted as

present or absent in these parents is the coloration of the

papillate glands which in biennis D are red on green

stems and ovaries, and in grandiflora D are uncolored,

i. e. lack the red. The hybrids of the F, generation

naturally might be expected to exhibit either the presence

or absence of the red coloration in these glands as one oF

the other condition might be dominant.

No. 547] GENETICAL STUDIES ON ŒNOTHERA 395

To my surprise, with the appearance of the main stem

from the rosettes two classes of plants became at once

defined in the culture of these F, hybrids: Class I, repre-

sented by 12 plants with red glands on the ovaries and

the green portions of the stems, and Class II, repre-

sented by 168 plants in which the papillate glands simi-

larly situated lacked the red coloration. There were

apparently no intermediates, with respect to this char-

acter of gland coloration, between these two well-defined

types which usually differed in other respects, as noted

elow.

The mature plants of the two classes could generally

be sharply contrasted with one another in the following

respects.

Crass I (12 PLANTS) Crass II (168 PLANTS)

Papillate glands colored red on the Red coloration absent from the

ovaries and green portions of the papillate glands on the ovaries

Mature SPR (Fig. 6) symmetrical Mature plants (Fig. 8) somewhat

ollar at base of the long straggling in habit, collar at ba:

hai inconspicuous. of s branchés more ĉon-

spicu

Lower leaves (Fig. 7) narrowly el- Lower Tivi (Fig. 9) broadly el-

TEEM, lanceolate on upper por- a ovate on upper portion o:

tions lant.

Bud cones 4-angled. me cones round in section,

Stigma lobes 6-7 mm. long. Stigma lobes 3-4 mm. long.

Capsules about 3.3 em. long. Capsules about 2.3 em. long.

racts persistent, developing on Bracts deciduous, the fruiting

fruiting branches into lanceolate branches becoming nearly or

leaves, wholly destitute of leaves.

We have said above that the two classes of plants

could usually be sharply contrasted with respect to the

characters listed. There were found no exceptions as

regards the coloration of the glands, but with respect to

the other characters some variation was exhibited, espe-

cially among the large number of plants in Class II. For

example, the plant of the culture most resembling

(Enothera Lamarckiana (11.35La, to be described later)

was representative of Class II in all respects except that

396 THE AMERICAN NATURALIST [Vow XLVI

it had 4-angled buds. Class II was more diversified than

Class I, but this was probably because of its being repre-

_ sented in the culture by fourteen times as many plants.

It is of interest to compare the hybrids of these two

classes with their parents. The plants of Class I resemble

the biennis parent in the red glands on ovaries and green

stems, inconspicuous collars, narrower leaves, and 4-

angled buds; they resemble the grandiflora parent in

having longer stigma lobes, longer capsules and persist-

ent bracts. The plants of Class II resemble the grandi-

flora parent in the absence of the red coloration in the

glands on the ovaries and green portions of the stems,

and in having more conspicuous collars, broader leaves,

and round buds; they resemble the biennis parent in

having shorter stigma lobes, shorter capsules, and decid-

uous bracts. It will be noted that the contrasted char-

acters are mixed for both classes of plants, some of them

being biennis-like and some of them grandiflora-like.

Thus neither class could be claimed as patroclinous or

matroclinous except it were established that gland colora-

tion, size of collar, form of leaves and form of buds are

more important specific characters than length of stigma

lobes, length of capsule and the persistent or deciduous

nature of the bracts, or vice versa. Of these diverse

characters who would be willing to express the opinion

that one set or the other is not of consequence in a de-

scription of the forms? Yet it would be necessary to

disregard one or the other set of characters if either class

of hybrids were defined as patroclinous or matroclinous.

We have stated before that the plants of the culture

were set in the ground with the few more biennis-like

rosettes at one end of the bed, and the few more grandi-

flora-like at the other end, and that these extreme forms

graded insensibly into the mass of the culture. It is

important tọ note that not one of the 12 plants of Class I

was at either end of the series, but they were scattered

irregularly through the culture, in some cases 2 or 3 close

together, but usually wide apart. I know as yet no way in

No. 547] GENETICAL STUDIES ON G@NOTHERA 397

which the representatives of Class I can be distinguished

in the rosette condition; they certainly do not constitute

either of the small groups of rosettes that are more

like one or the other of the two parents.

The differentiation of these two classes of hybrids in

an F, generation appears to be similar to the phenomenon

of ‘‘twin hybrids’’ reported by De Vries (’07) although

the contrasted characters are somewhat different. The

behavior is most interesting, especially in its relation to

the results expected in F, generations according to gen-

Fic. 6. Mature plant gea i sah hybrid 11. “sang — B x biennis D;

tative of Class

eral experience and Mendelian laws. We should have

expected the red coloration of the papillate glands of the

biennis parent to be either dominant or recessive to the

uncolored glands of the grandiflora parent; as a matter

aoe THE AMERICAN NATURALIST [Vou. XLVI

of ‘fact, both conditions appeared with apparently no

UN RE E It would, however, be unsafe to regard

this behavior as an exception to Mendelian laws since

there is the possibility that the strain biennis D is hetero-

zygous with respect to the red coloration of its papillate

glands. To be sure, a culture of 51 plants from self-polli-

nated seed of the wild plant (biennis D) were uniform

even to the red coloration of the glands on the green

stems and ovaries, but, nevertheless, there are similar

wild biennis types that lack this coloration, and there has

Fic. T. plas tiles side branch of the F, hybrid 11.35m, grandiflora B x biennis D;

esentative of Class I. At the left is a leaf from the

lower portion of the main stem

No. 547] GENETICAL STUDIES ON CENOTHERA 399

not yet been time to determine whether or not the strain

biennis D is homozygous in all of its characters. The

matter has no especial bearing on the immediate purposes

of my studies, but will become vital to further investiga-

Fig 8. Mature plant me a F, hybrid 11. =f Agger B x biennis D;

presentative of Clas

tions on the behavior of the characters of gland colora-

tion in the Œnotheras.

My plans for the further study of these hybrids in

second generations involve cultures in pure lines from

representative plants of both Class I (11.35m, Figs. 6

and 7) and Class II (11.35a, Figs. 8 and 9), and cultures

400 THE AMERICAN NATURALIST [Vou. XLVI

of reciprocal crosses between these same representatives

(11.35mXa and 11.35axm). The results of the reci-

procal crosses will be awaited with especial interest in

view of De Vries’s (711) recent paper on double reciprocal

crosses. Furthermore, a large second generation will be

grown from self-pollinated seeds of a plant (11.35Za) in

Class II selected as being in more respects similar to

Fig. 9. s side branch of the F; hybrid 11.35a, grandiflora B x biennis D;

representative ~ Class II. At the left is a leaf from the

lower portion of the main stem

Lamarckiana than any hybrid of my crosses so far grown.

Let us consider the hybrids just described with respect

to their resemblance to Lamarckiana. As regards the

No. 547] GENETICAL STUDIES ON @NOTHERA 401

size of the flowers both classes of hybrids presented

essentially the same types (petals 2.5-2.7 em. long),

closely intermediate between those of the parents, but

the flowers of Class I were similar to those of Lamarck-

iana in the length of the stigma lobes, in their 4-angled

buds and in having red glands on their ovaries. In the

form and size of the capsules and in the deciduous habit

of the bracts Class II had the advantage of a closer

resemblance to Lamarckiana. In the broader and some-

what crinkled leaves the advantage was very much in

favor of the plants in Class II, but in the coloration of

the glands on the stem the plants of Class I were

Lamarckiana-like. The situation seems mixed and we

must await the outcome of the cultures as planned above

in the hope of some interesting conclusions. The writer

in selecting a representative of Class II (11.35Za) as

more like Lamarckiana than any other plant has laid the

greater emphasis upon the characters of foliage and

buds (in this plant stout and 4-angled), believing that

these characters of Lamarckiana are more important and

more difficult to obtain in hybrids than many of the

others.

A description of this plant (11.35Za), the F, hybrid, so

far obtained, most closely resembling O. Lamarckiana,

will now follow, arranged to bring out its important char-

acteristics in comparison with those of the parent species

and with Lamarckiana.

Hysrip 11.35La

1. Rosette——The rosette of this plant was unfortu-

nately mutilated by cut worms which destroyed the cen-

tral bud so that the shoots that grew to bear flowers were

all from side buds. The rosette, however, was similar

to that shown in Fig. 5 (11.35a), that is to say, it was

representative of the mass of the culture. My attention

` was first attracted to this plant by the greater length and

breadth of the leaves upon the young side shoots and their

conspicuous crinkling, well illustrated i in Fig. 10. As tiie

402 THE AMERICAN NATURALIST [Vou. XLVI

side shoots elongated (Fig. 11) the foliage retained the

promise of the earlier condition (Fig. 10), the shoots

bearing leaves distinctly larger and more crinkled than

the other plants of Class II, but of the same form.

Fic. 10. Rosette of the F, hybrid 11. St grandifiora B x biennis D.

R oe destroyed by cut worms; side shoots developing

h large, cones P a leaves

2. Mature Plant.—Five strong side shoots, 1.1-1.3 m.

high, (Fig. 12) developed from the mutilated rosette.

Their stems. were green above, reddish below, the

papillate glands following the coloration of the stem,

i. e., they were green (uncolored) on the ovaries and

younger portions of the stem as in Class I, and not red

as in my cultures of Lamarckiana. The basal leaves,

about 23 em. long, were broadly elliptical and strongly

crinkled, the margins scarcely toothed except at the base;

No. 547] GENETICAL STUDIES ON CENOTHERA 403

the leaves above were ovate or broadly elliptical; all

leaves had short petioles. The leaves on the plant

throughout the history recorded by Figs. 10, 11 and 12

were so similar in form, size, and texture to those of my

cultures of Lamarckiana that I do not believe the plant

could have been easily separated by its foliage if grown

among them. The absence of red colored glands on the

green stem and ovaries appeared to the writer to be the

only character of importance distinguishing it from

Fic. 11. Young plant of the F, hybrid 11.35La, grandiflora B x biennis D,

showing Lamarckiana-like foliage of large, crinkled leaves.

Lamarckiana during its development up to the time of

flowering.

3. Inflorescence. —The inflorescence (Fig. 13) pre-

sented. shorter internodes than is characteristic of

Lamarckiana as I have observed it, and was in conse-

quence more flattened at the top, in this respect resem-

bling the inflorescence of gigas. The bracts were similar

404 _ {HE AMERICAN NATURALIST [Vou. XLVI

in form to those of Lamarckiana, but were not quite so

closely sessile.

4. Buds.—The buds, about 7 em. long, were strongly

4-angled (in this respect departing from the rule in Class

Fic. 12. Mature e “ Agra F, hybrid 11.35La, gřandiflora B x biennis D,

h Lamarckiana-like foliage.

II). Their pubescence was like that of Lamarckiana,

long hairs arising from papillate glands among muc

shorter hairs which were, however, less numerous than

in Lamarckiana. The sepals were green, their tips of

medium length, not markedly attenuate as in grandiflora;

No. 547] GENETICAL STUDIES ON CENOTHERA 405

the cone of the bud was stout. The strong resemblance

of the buds in form to those of Lamarckiana was an im-

portant point in the choice of this plant as favorable for

further cultivation. They were, however, from 2-3 em.

shorter than those of the large-flowered Lamarckiana,

Fig. 13. Flowering side branch of the F, hybrid 11.35La, grandiflora B x

biennis D. At the left is a leaf from the lower third of a side stem.

but as large as the small-flowered type. There should be

little difficulty in obtaining larger sizes in the P.

generation.

5. Flowers.—The flowers were medium-sized, petals

about 2.5 cm. long. The stigma lobes, 3—4 mm. long, were

slightly below the tips of the anthers. Ovaries were

406 THE AMERICAN NATURALIST [Vou. XLVI

green (without red-colored glands). The flowers were

indistinguishable from those of the small-flowered types

of Lamarckiana except for the absence on the ovaries of

red-colored glands. They differed from the large-flow-

ered types (petals 4-4.5 em. long) not only in size, but

also in the shorter stigma lobes which were not above the

tips of the anthers. My experience has shown that the

flowers in a second generation of these @nothera hybrids

will present a wide range in their measurements, many

flowers surpassing in size those of the grandiflora parent

and equalling the largest forms of Lamarckiana. Conse-

quently there is good reason to be hopeful of obtaining

large-flowered types in the F, generation.

6. Capsules—The capsules, about 2 cm. long, were

stout and similar to those of Lamarckiana. The bracts

exhibited the deciduous tendencies of Class II, a

Lamarckiana-like habit.

7. Seeds.—The seeds were of a shade of color inter-

mediate between the light and dark brown of the parents.

Speculation as to the probabilities of the behavior of

these F, hybrids (11.35La, 11.35a, and 11.35m), and the

reciprocal crosses (11.35 a X m, and 11.35 m x a) in the

second generation, is not called for, since we hope in afew

months to have data on the questions involved. Some of

these problems concern the general behavior of species

crosses and are to the writer as interesting and im-

portant as the attempt to synthesize a Lamarckiana-like

hybrid between biennis and grandiflora. It may, how-

ever, be pointed out that there are no important char-

acters of Lamarckiana which are not represented in some

one of these hybrids or in their parents, except those of

the somewhat larger size of certain organs. Since my

cultures have shown that hybrids of @nothera in the F,

generation frequently present marked advances over

their parents in the measurements of petals, leaves, etc.,

these differences of size in an F, hybrid are likely to

prove more apparent than real.

2, grandiflora DX biennis D (11.32)—As would be

No. 547] GENETICAL STUDIES ON ŒNOTHERA 407

expected, this cross was very similar to that just described

(11.35, grandiflora B X biennis D). The 195 plants

brought to maturity fell into two classes distinguished by

precisely the same groups of characters as in the previ-

ous cross. Class I with red papillate glands, etc., was

represented by 11 plants; Class II by 184 plants. Cer-

tain small differences of foliage, apparent only on close

inspection, together with the fact that no plant seemed

as favorable for my purposes as 11.35La, determined the

selection of the other culture (11.35) as the one upon

which to base further studies.

3. grandiflora I X biennis D (11.37). The rosettes of

this cross (Fig. 14) were more like those of Lamarckiana

Fic. 14. Mature rosette of an F, hybrid, grandiflora I x biennis D (11.37).

A type of rosette very similar to that of Lamarckiana.

than in any of my hybrids so far obtained, but the mature

plants were disappointing. The strain grandiflora I has

a strongly petioled leaf, and the stems bear dense clusters

of flowering side shoots. These characters appeared in

408 THE AMERICAN NATURALIST [VoL. XLVI

pronounced form in the F, hybrids rendering them less

favorable for my studies than the crosses with the strains

grandiflora B or D. The culture was interesting since

it presented two classes of F, hybrids as in cultures 11.35

and 11.32, separated by identical groups of characters.

Out of 144 plants brought to maturity 4 plants were of

Class I and 140 plants were of Class II.

A culture of the reciprocal cross of these types, biennis

D X grandiflora I (11.39), was started late in the season

after the appearance of the paper of De Vries (11) on

double reciprocal crosses, but the culture was unable to

reach maturity. By September 15, out of a total of 171

rosettes, 31 had sent up side shoots of sufficient length

(2-4 dm.) to determine the coloration of the papillate

glands; 21 of these plants had red glands on a green

stem, and in 10 plants the glands were uncolored.

4. grandiflora D X Tracyi (11.33)—The F, hybrids

of this cross were remarkable plants 2.5-3 m. high,

developing from transitory rosettes and with a luxuriant

foliage of narrow leaves. As noted before, the plants

were very far from Lamarckiana. It is a cross that is

likely to occur in nature where the two species grow

together as at Dixie Landing, Alabama, and this possi-

bility must be reckoned with in analyses of the two

species. @Œnothera Tracyi has the red coloration of

the papillate glands characteristic of biennis D. The

40 plants of the culture fell sharply into two classes dis-

tinguished by characters similar to those of the crosses

between biennis D and grandiflora. There were 3 plants

of Class I, with red glands, etc., and 37 of Class II.

The cultures of the F, hybrids as recorded above have

given data that can not be satisfactorily discussed until

similar crosses have been made with parents that are

beyond question homozygous. My strains grandiflora B

and D have now been carried in pure line for three gen- —

erations and have proved uniform, but the parent plants

biennis D and Tracyi were from wild seed. It does not

seem probable that the latter types are heterozygous, for

No. 547] GENETICAL STUDIES ON ŒNOTHERA 409

the reason that both have the habit of close pollination,

but, nevertheless, the forms are not above suspicion. As

the data stand the most interesting features shown by

the F, hybrids are: (1) The absence of dominance on

the part of any character of the parents, including the

coloration of the papillate glands, (2) the sharp differ-

entiation of two classes of hybrids (twin hybrids?)

clearly distinguished by groups of characters, and (3)

the absence of marked patroclinous or matroclinous con-

ditions in either of these two classes. The differentia-

tion of two classes of hybrids has been a new phenomenon

in my experience with F, hybrids of Œnothera which

have previously proved remarkably uniform except for

the extremes represented by a few plants somewhat ap-

proaching the respective parents.

6. HYBRIDS IN THE F, GENERATION FROM THE F, HYBRID

Pruants 10.30La andn 10.30Lb.

In my paper of a year ago (Davis, ’11, pp. 211-217)

two plants were described and figured which among the

hybrids up to that time most closely resembled nothera

Lamarckiana. They were the F, hybrid plants designated

10.30Za and 10.30Lb, the result of the cress grandiflora

B X biennis A. Cultures from self-pollinated seed of

these two plants were grown in the season of 1911, giving

considerable data on the behavior of such a cross in the

second generation. :

These F, hybrids were not grown with the expectation

that any of the plants would be taxonomically the same

as Lamarckiana, since it had been apparent for some

months that the strain biennis A is not so favorable a

biotype as many others to cross with grandiflora in the

hope of obtaining Lamarckiana-like hybrids. The

hybrids were grown to satisfy my keen desire to observe

the behavior of such a cross and in the hope that its study

would prove helpful in the planning of future work.

The mass of the F, hybrids held in their characters

410 THE AMERICAN NATURALIST [Vou. XLVI

within a certain wide range of variation, but a large

number of very striking types appeared, which, if they

come reasonably true in a third generation, must be

regarded as new forms of specific rank. These variants

constituted in some cases classes entirely distinct from

all of the other plants and in other cases were extreme

types of segregates connected by intermediate forms more

or less closely with the mass of the hybrids. Although the |

two F, parent plants of these cultures, (10.30Za and

10.30Lb) were sisters, their progeny was far from similar.

Each F, hybrid plant gave rise to its own peculiar set

of variants and the character of the plants constitut-

ing the mass of the cultures likewise differed greatly.

The present description of the cultures will be very brief,

but a more full and illustrated account may follow if

studies of the more interesting of the variants in a third

generation make the publication of such an account seem

desirable,

1. THe F, Generation (11.41) FROM THE HYBRID PLANT

10.30La

This culture was grown from the contents of 26 cap-

sules containing in all about 3,300 seeds. From these

1,505 seedlings appeared in the pans within 5-7 weeks,

and 1,451 grew into well-developed rosettes. It was

possible to select from the rosettes a group of 141

which were smaller than the average and had strongly

etiolated leaves; these rosettes developed a peculiar

group of dwarfed plants apparently constituting a clearly

defined class in the culture. The mass of the rosettes

presented a remarkable range, from many that resembled

very closely the rosettes of grandiflora, distinguished by

having broader leaves cut at the base (see Davis, ’11,

Fig. 6), to much smaller rosettes with narrow leaves

somewhat biennis-like in form. Between these extremes

was an assemblage of intermediates so various in char-

acter that I was unable to make any satisfactory classi-

fication further than the selection of the 141 etiolated

No. 547] GENETICAL STUDIES ON ŒNOTHERA 411

types. It may be said, however, that the green rosettes

inclined more towards the female parent of the cross,

grandiflora B, than towards the male, biennis A. The

plants set in the ground numbered 1,310 green rosettes

and 141 etiolated.

The green rosettes were set out with the more grandi-

flora-like at one end and the more biennis-like at the

other. In general the plants at the more grandiflora-

like end were at maturity considerably larger 1.5-2 m.

high, than those towards the more biennis-like end where

a small group of plants (about 20) remained small, 6

dm.—1.2 m. high. Among the larger plants were many

(about 50) with flowers as large as or larger than those

of the grandiflora parent, but these could not be sepa-

rated as a class since the variation on individual plants

was considerable and they intergraded with great per-

fection into the mass of the culture. The smaller plants

at the more biennis-like end were variable, but all had

flowers 2-4 times larger than those of the biennis parent.

The larger flowers had petals measuring 44.5 em. long

(those of grandiflora B are about 3.3 em. long); these

flowers were therefore as large as the largest-flowered

types of Lamarckiana. The large flowers also, as a-rule,

presented the grandiflora relation of the stigma to the

anthers, i. e., the stigma lobes were well above the tips of

the anthers. Thus in flower size the culture showed a

clear segregation, but inclined markedly towards the

larger size of the grandiflora parent, in many cases sur-

passing this flower in its measurements.

The foliage of the culture presented a range of varia-

tion that defied my attempts at classification. That of

some of the larger-flowered plants closely resembled

grandiflora, and a few of the smaller plants had a foliage

approaching that of biennis, but the leaves throughout

the culture as a whole were larger than those of the

parents of the cross and generally distinctly crinkled.

The mass of the culture was fairly close to the F,

hybrid plant, 10.30La, from which it came, but there was

412 THE AMERICAN NATURALIST [Vot XLVI

much variation from this plant in the measurements

and proportions of the organs with the greater tendency

towards the grandiflora parent type. There was, how-

ever, no constancy apparent and plants with flowers

similar to grandiflora might present a foliage of a dif-

ferent type, most frequently in the form of larger and

strongly crinkled leaves. A few plants were so close to

grandiflora that taxonomically they would probably be

included in the range of this species, although they could

not be considered identical with the strain grandiflora B;

there were no segregates so close to biennis A.

A count was made with the assistance of Mr. H. H.

Bartlett of the plants with green stems (biennis-like) and

of those with red stems (grandiflora-like). This was ex-

tremely difficult for the reason that the mass of the cul-

ture presented intermediate or mottled conditions similar

to the F, hybrid plant 10.30La. ‘However, of the 1,310

plants, 195 were classified as red-stemmed and 192 as

green-stemmed; the red were markedly nearer the more

grandiflora-like end of the culture and the green nearer

the biennis end. The expected number according to

simplest Mendelian ratio should have been about 327

plants of each color. Considering that anthocyan is so

variable in its appearance, and consequently most un-

satisfactory for a study of color inheritance, these results

are by no means against Mendelian expectations. No

two persons independently would make the same count in

such a culture, for the results all depend upon what con-

ditions of the plant are defined as intermediate’ or

mottled. |

The culture presented a number of remarkable types

which no taxonomist would think of identifying with

either biennis, grandiflora, or the F, hybrid plant 10.30La.

These will not at. present be described in their many

characteristics, but will be briefly listed.

11.41¢, a type with conspicuously crinkled leaves, repre-

sented by about 170 plants, apparently intergrading with

other forms of the culture.

No. 547] GENETICAL STUDIES ON C2NOTHERA 413

11.41bk, represented by 13 plants, narrow leaves,

flowers very light yellow, anthers sterile.

11.41s, a single plant similar to 11.41bk except for

broader leaves.

11.417, representing the class separated as 141 etio-

lated rosettes. The plants of this class as they developed

gradually outgrew the etiolated conditions of the younger

stages, but remained dwarf. They varied greatly among

themselves in flower size and foliage, and a dozen differ-

ent types could have been selected.

The above list does not include the numerous types of

segregates which clearly differed specifically from the F,

hybrid plant 10.30La. These forms, being of hybrid

origin, are of course marked segregates presenting in

varying combinations and degrees characteristics of the

parents of the cross, bignnis and grandiflora.

2. Tue F, Generation (11.42) FROM THE HYBRID PLANT

10.30 Lb

From the contents of 5 capsules, containing about

1,200 seeds, a culture of 992 seedlings appeared in the

pans within 6-8 weeks and grew into well-developed

rosettes. From these a group of 147 rosettes were

readily selected for their uniformly small size and

narrow leaves. They gave rise to a definite class of

dwarfs which remained absolutely distinct from the rest

of the culture; the plants were not etiolated or in other

respects similar to the class of dwarfs separated in the

culture (11.41) from the sister hybrid, 10.30La. The

rosettes constituting the mass of the culture presented a

wide range of form similar to that shown in 11.41, with

the extremes approaching the rosettes of the biennis and

grandiflora parents. Between the extremes was the

similar large assemblage of intermediates of varying

degrees which made a classification of the rosettes im-

possible. There was apparently no clearly marked

tendency of the rosettes in the culture as a whole to

resemble either of the parents.

414 THE AMERICAN NATURALIST [Vou. XLVI

The plants set in the ground numbered 833 large

rosettes and 90 of the dwarf. This culture at maturity

proved much more varied than the former (11.41). The

plants at the more grandiflora-like end of the culture were

in general considerably larger (1.7-2 m. high) than those

at the biennis end (1-1.5 m. high), but there were many

exceptions to the rule. The foliage proved exceedingly

diverse. Occasional: plants (about 20) presented a

foliage similar to grandiflora although never matching

the parent strain in all respects; a smaller number of

plants (about 5) presented a foliage resembling that of

biennis. The foliage, excluding the exceptional types,

ranged from lanceolate leaves to broadly elliptical or

ovate leaves with well defined crinkles.

Many plants bore flowers as large as and larger than

those of the grandiflora parent and with a similar rela-

tion of the stigma lobes to the tips of the anthers. The

larger flowers equaled in size those of the largest-flowered

types of Lamarckiana. Other plants bore flowers ap-

proaching in size those of the biennis parent, but never

so small. There was no fixed relation of the larger

flowers to the plants more grandiflora-like in foliage or

of the smaller flowers to those more biennis-like, although

larger and smaller flowers were in some instances found

on plants approaching the respective parents.

The mass of the culture was fairly close to the F,

hybrid plant 11.30L6, varying from it in habit, and in the

form and measurements of the leaves and flower parts.

There was not so strongly marked a tendency on the part

of the plants towards the grandiflora parent as was

exhibited by the former culture. The flowers, as indi-

cated above, showed the same progressive advance in

size, many of them being larger than those of grandiflora

and none so small as those of the biennis parent.

A count of the plants made with Mr. Bartlett led to a

classification of 104 red-stemmed and 90 green-stemmed

in the group of 833 plants. The remainder of the culture

presented intermediate or mottled coloration similar to

No. 547] GENETICAL STUDIES ON C2NOTHERA 415

the F, hybrid plant (10.3020) from which they came.

The red-stemmed plants were most numerous towards the

more grandiflora-like end of the culture and the green-

stemmed towards the more biennis-like end.

A larger number of remarkable new types appeared in

this culture than in the former (11.41), types specifically

different from either biennis or grandiflora, or the F,

hybrid plant 10.30Zb. The list is as follows:

11.42e, a type represented by 4 plants with small and

narrow leaves, and medium-sized flowers.

11.427, leaves small, irregularly toothed, flowers

medium-sized, capsules large (about 3.3 em. long) ; repre-

sented by several plants and intergrading with the mass

of the culture.

11.429, medium-sized plant with large flowers and Jarge

crinkled leaves; a type rather common and intergrading

with the mass of the culture.

11.42), a single plant with almost linear leaves, flowers

very small (petals 6 mm. long), anthers sterile. In its

foliage this plant seems. very close to De Vries’s

‘‘mutant’’ Œnothera elliptica.

11.421, medium-sized flowers; remarkable for its broad,

entire, and very much crinkled leaves.

11.42r, the class separated as 147 small rosettes with

narrow leaves of which 90 were saved and grown to

maturity. The mature plants, 3-4 dm. high, rarely

branched, bore medium-sized flowers, and constituted a

clearly defined class of dwarfs.

There are not included in the above list the numerous

segregates with characters in various combinations ap- .

proaching one or the other of the parents of the cross.

Some of these types clearly differed specifically from the

F, hybrid plant 10.30Lb.

A consideration of these two cultures (11.41 and 11.42)

of hybrids in the second generation will bring out certain

important conclusions that may be summarized.

1. In the immensely greater diversity exhibited by the

F, generation over that of the F, is clearly shown a

416 THE AMERICAN NATURALIST [Vou. XLVI

differentiation of the germ-plasm expressed by the ap-

pearance in the F, plants of definite tendencies in dif-

ferent directions towards the parents of the cross. This

sems to the writer the essential principle of Mendel-

ism and does not necessarily involve the acceptance of

the doctrine of unit characters and their segregation in

either modified or unmodified form.

2. Certain characters of the parent species have ap-

peared in the F, segregates in apparently pure condition,

but the very large range of intermediate conditions indi-

cates that factors governing the form and measurements

of organs (if present at all) must in some cases be con-

cerned with characters so numerous and so small that

they can not be separated from the possible range of

fluctuating variations. If this is true such characters

seem beyond the possibility of isolation and analysis and

the unit character hypothesis for these cases has little

more than a theoretical interest.

3. Both cultures certainly showed a marked progres-

sive advance in the range of flower size, the largest

flowers having petals somewhat more than 1 em. longer

than those of the grandiflora parent. There was a

similar advance in the size of the leaves and the extent of

their crinkling. These progressive advances would

seem to demand on the unit character hypothesis either the

modifications of the old or the creation of new factors.

4. The absence of classes among the F, hybrids (except

for the dwarfs) further works against the unit character

hypothesis as of practical value in the analysis of a

hybrid generation of this character. It should be remem-

bered, however, that there were in this cross no sharply

contrasted distinctions of color, anthocyan coloration

proving most unsatisfactory for the purposes of a gene-

tical study.

5. Both cultures presented a class of dwarfs, very

different from one another and from the F, hybrid plants

10.30Za and 10.30Lb. This phenomenon of nanism has

No. 547] GENETICAL STUDIES ON CNOTHERA 417

appeared also in all previous F, generations that I have

grown and presents a most interesting subject for study.

6. The extreme variants of the cultures would rank as

new species different from either parent of the cross and

from the F, hybrid plants. Their germinal constitution

(provided it is stable) on the hypothesis of unit char-

acters apparently must involve the modification of old

factors or the creation of whole sets of new factors in

large numbers, a degree of complication unfavorable to

the hypothesis.

7. The progeny of the F, hybrid plant 10.30La was

very different from that of 10.30Lb although these two

plants were sisters. What would have been the compli-

cations if F, generations had been grown from a hundred

or a thousand sister plants!

7. THe PROBABLE CoMPOSITION OF THE CULTURES OF

CARTER AND COMPANY FROM EVIDENCE FURNISHED

BY THE SHEET IN THE Gray HERBARIUM

Brief reference was made in a former paper (Davis,

"11, p. 228) to a very interesting sheet in the Gray Herba-

rium of Harvard University, which shows a plant with

characters in part those of @nothera Lamarckiana, but,

in the writer’s opinion more largely those of grandiflora.

This sheet bears notes in the handwriting of Dr. Asa

Gray to the following effect—in ink, ‘Œ. Lamarckiana,”’

‘Hort. Cantab. 1862,’’ and ‘‘from seed of Thompson,

Ipswich’’; in pencil and probably of a different date

‘‘said by English horticulturists to come from Texas.”’

It was the habit of Dr. Gray at that time to use herbarium

labels marked Hort. Cantab. and this fact, together with

the absence of other writing on the sheet indicates that

the plant was grown in the botanical garden at Cam-

bridge, Massachusetts.

The date, 1862, suggested a possible genetic relation-

ship of this plant in the Gray Herbarium to the cultures

of Messrs. Carter and Company of London about 1860 of

plants which were grown for the market under the name

418 THE AMERICAN NATURALIST [Vou. XLVI

(Enothera Lamarckiana and which seem to have been the

starting point of the Lamarckiana now under cultivation.

The only descriptions which we have of these cultures

are the very unsatisfactory accounts in The Floral Maga-

zine, Vol. II, Plate 78, 1862, and in ‘‘ L’Illustration Horti-

cole,’’ Vol. IX, Plate 318, 1862, both accompanied by the

same figure of an impossible Hnothera.

An inquiry was at once started to determine the mean-

ing of the note ‘‘from seed of Thompson, Ipswich,’’ and,

thanks to the courtesies of correspondents, the matter

now seems clear. There seems to have been no botanist

or horticulturist of the name of Thompson in Ipswich,

Massachusetts, at that period from whom Dr. Gray could

have obtained this seed. The reference is almost certain

to have been to William Thompson of Ipswich, England,

who died several years ago. William Thompson ‘‘was a

seedsman in a small way of business, but a most enthu-

siastic cultivator with correspondents in all temperate

countries and the introducer of numerous herbaceous

plants more particularly annuals and biennials.’’ He

corresponded with Kew as early as 1860.

It is ina high degree probable that William Thompson,

with his interest in novelties, obtained from Carter and

Company their new @nothera and that the seed sent to

Dr. Gray was either directly from this source or from

plants cultivated by Thompson. It will be remembered

that Carter and Company stated that they received their

seed from Texas, which accords with Dr. Gray’s note

‘‘said by English horticulturists to come from Texas.”

If this interpretation of the history of the sheet in the

Gray Herbarium is correct the plant was very close

indeed to the cultures of Carter and Company, possibly

not more than one or two generations removed, since

these plants were probably cultivated as biennials. This

sheet then gives evidence on the composition of the cul-

tures of Carter and Company immensely more valuable

than the obviously-inaccurate plate of The Floral Maga-

No. 547] GENETICAL STUDIES ON CGENOTHERA 419

zine and the description that tells little of value for the

- problem under consideration.

The following is a description of this sheet in the Gray

Herbarium:

1. Stems and Foliage——The stem bears long hairs

arising from papille (glands) which are colored red as

in Lamarckiana and are about as numerous as in that

species. A detached leaf (Fig. 15, a), about 18.5 em. long

with sinuate margins, slightly lobed below, and with some

evidence of former crinkles, suggests by its shape (al-

though too small) the basal leaves of Lamarckiana. The

upper foliage is similar to a broad-leaved type of grandi-

flora, the leaves being short-petioled and not so nearly

sessile as in Lamarckiana.

2. Inflorescence.—The inflorescence has longer inter-

nodes than in Lamarckiana and consequently is not so

compact; in this respect it resembles grandiflora. The

bracts are broad at the base, slightly toothed, and per-

sistent, becoming lanceolate leaves on the fruiting

branches as in grandiflora.

3. Buds.—The buds (Fig. 15, b) are about 9.5 cm. long,

not stout and 4-angled as in Lamarckiana, but with a cone

circular in section as in grandiflora. Sepals apparently

green, their tips attenuate as in grandiflora and project-

ing 1 cm. beyond the folded petals; pubescent, with long

hairs arising from papilla among much shorter sessile

hairs as in Lamarckiana.

4. Flowers.—The flowers are somewhat larger than

those of any grandiflora known to me. Petals about 4.5

em. long, as long as those of the largest forms of La-

marckiana., Stigma lobes about 8 mm. long, close to 9

mm. above the tips of the anthers, in these respects agree-

ing with both Lamarckiana and grandiflora. :

5. Capsules.—The capsules, about 3 em. long, are of

medium thickness and similar to those of grandiflora;

they are not so stout as the capsules of Lamarckiana.

The persistent leafy bracts and long internodes give the

420 THE AMERICAN NATURALIST [Vou. XLVI

fruiting branches a marked resemblance to the conditions

characteristic of grandiflora.

This plant then presents grandiflora characters in the

upper foliage of the plant, in the longer internodes of the

”

`G. 15. Sheet in the Gray Herbarium of Harvard University. An M@nothera

grown by Dr. Asa G at Cambridge, Massachusetts, in 1862 and probably

derived directly or nie ‘tly from the cultures of Carter and Company of

Pone which were pragas under the name Lamarckiana. The specimen on

this herbarium sheet has important characters of grönulora. indicating a rela-

iocielite to this species

inflorescence and the persistent bracts, in the form of the

buds (4-angled) with attenuate sepal tips, and in the

longer capsules of medium thickness. The plant resem-

bles Lamarckiana in the red coloration of the papille on

No. 547] GENETICAL STUDIES ON ŒNOTHERA 421

the stem at the base of the long hairs, and in the form

and size of a large detached leaf (probably basal). The

form of the flowers is essentially similar to either grandi-

flora or the large-flowered types of Lamarckiana; their

size is very close to that of the latter plant, which it also

resembles in the pubescence of the sepals. In this mix-

ture of characters the most important are, in the writer’s

opinion, distinctly grandiflora-like and indicate a. close

relationship to some strain of grandiflora.

The short description in The Floral Magazine, Vol. II,

1862, quotes the following from Carter and Company.

‘We received, about four years ago, some seed from

Texas unnamed. When we had flowered it, we sent some

blooms to Dr. Lindley, who pronounced it to be Œnothera

Lamarckiana, a species, we believe, introduced into Eng-

land by Mr. Drummond. Its height is between three and

four feet; it blooms the first year, is a very hardy

biennial, and: is superior to any other @/nothera in the

size and number of its blossoms, which measure four

inches in diameter.’’ Of the characteristics noted in this

quotation, all of which fit Lamarckiana, the most impor-

tant is the statement that the plant is ‘‘a very hardy

biennial,’’ although this is somewhat weakened by the

remark that ‘‘ it blooms the first year.” :

Now grandiflora is clearly annual and the @notheras

of the south and southwestern United States are, as far as

the writer is aware, generally annual or perennial. A well-

defined biennial habit, characterized by the development

of largeand short persistent rosettes, is an adaptation to

the short seasons of northerly climates. The question arises

whether the plants raised by Carter and Company are

represented or could have been represented in the Texan

flora. We know that Texas and the southwest generally

have some large-flowered @notheras and it may be that

the climatic conditions of certain mountainous regions

would favor the development of a biennial habit. How-

ever, botanical exploration has not yet brought forward

any plant of the Lamarckiana type. In the absence of

422 THE AMERICAN NATURALIST [Vor. XLVI

corroborative evidence we can hardly at. present accept

as beyond doubt the statement that the seeds of Carter

and Company were from Texan plants.

It is a confused situation with a number of possible

explanations which are not worth a discussion until we

have more evidence at hand. This evidence may come

through other herbaria sheets comparable to the one in

the Gray Herbarium, although examinations by my corre-

spondents of the collections at the British Museum, at

Kew, and at Cambridge University indicate that there is

nothing at these centers. Evidence may also come from

field studies in America, which should be pushed by

western and southern botanists in a position to observe

(Enothera throughout the season. The writer sowed

about 200 seeds (60 years old) from one capsule on the

sheet in the Gray Herbarium, but there have been no

germinations after being four months in the seed pan; the

experiment, a forlorn hope, needs no apology, considering

the importance of the problem—the composition of the

cultures of Carter and Company.

The most important point for the writer’s hypothesis

of the hybrid origin of @nothera Lamarckiana as a cross

between biennis and grandiflora is the strong evidence

that the cultures of Carter and Company contained forms

with characters in part grandiflora-like and in part

biennis-like, for it must be remembered that Lamarckiana

in its hardy biennial habit and in other characters resem-

bles the latter species. It is possible that the plants were

hybrids at that period (1860) for if the sheet in the Gray

Herbarium is representative of the composition of these

cultures, the plants were very different from the present

day Lamarckiana. Even if the plants of Carter and

Company came from Texas as a form related to grandi-

flora there would of course have been abundant oppor-

tunities for hybridization with biennis before De Vries,

a quarter of a century later, began his studies.

No. 547] GENETICAL STUDIES ON (ENOTHERA 423

8. FURTHER CONSIDERATIONS ON THE POSSIBLE ORIGIN OF

(Hnothera Lamarckiana as a HYBRID oF

O. biennis and O. grandiflora

Among the most interesting of the results from the

cultures of the past summer (1911) have been those con-

cerned with the behavior of the hybrids of biennis and

grandiflora in the second generation. In the progeny of

the F, hybrid plants 10.30La and 10.30Lb there was clear

evidence of an advance in the size of the flowers which

carried them in many plants beyond the size of the

grandiflora parent and as far as the larger-flowered

forms of Lamarckiana. The petals of these F, hybrid

plants measured about 2.2 cm. ; those of the largest of the

F, flowers measured 4.5 em.; grandiflora B has petals

about 3.3 em. long and those of the largest-flowered forms

of Lamarckiana measure about 4.5 em. There was a

similar advance in the size of the leaf and the extent of

its crinkling, although the leaves did not reach the condi-

tions characteristic of Lamarckiana. This is clearly pro-

gressive evolution and doubtless can be maintained

through selection, though there may be in later genera-

tions constant retrogressive variation. :

This demonstration of a progressive advance in flower

measurements in the F, generation disarms those critics

(as Gates, 711) who in prematurely discussing my F,

hybrid plants 10.30La and 10.30Lb apparently failed to

appreciate the basic principle that the characteristics of

an F, hybrid are shown by what it will do in the F, gen-

eration and not by what it may seem to be. No experi-

menter in touch with present-day genetics would hope to

get a perfect Lamarckiana type in the F, generation from

a cross between biennis and grandiflora, for the reason

that the characters of these species could neither blend

nor appear as dominant or recessive in such a manner as

to give this type. But with a proper selection of parent

biotypes there is good reason to be hopeful that from the

F, generation of such a cross forms will appear with

424 THE AMERICAN NATURALIST [Vor. XLVI

characters so shifted and modified as to match very

closely those of Lamarckiana. ,

My hypothesis does not of course demand that La-

marckiana arose with all of its characters fully present.

as the result of a simple cross. There have been abund-

ant opportunities for repeated crosses of a most varied

character during the long period in which this plant has

been under cultivation. That the plant hybridizes readily

in nature is evidenced by the complex assemblage of

varied types found in such localities as the sandhills of

Lancashire, England, where Lamarckiana-like forms are

growing wild in great numbers together with types of

biennis. The fundamental feature of the hypothesis is

the belief that Lamarckiana exhibits the behavior to be

expected of a complex hybrid and that its characteristics

are those likely to come from a mixture of germ-plasms

from types of biennis and grandiflora.

I shall not, in order to perfect a synthesis of Lamarck-

iana-like hybrids, depart from my plan of experimenting

with wild races of biennis and grandiflora, for the most

important feature of the line of experimentation under

way is the study of the behavior of species hybrids. Such

a study offers the opportunity of treating experimentally

one of the most vital problems of genetics,—the possibili-

ties and methods of the progressive evolution of specific

characters through hybridization.

The studies have not yet proceeded sufficiently far to

justify a detailed comparison between the various forms

of F, hybrids and the ‘‘mutants’’ of De Vries. It is clear,

however, that the F, generation will give numbers of

types that differ from F, hybrid plants in the same

manner as the ‘‘mutants’’ differ from Lamarckiana.

Some of the variants have characters so different from

the F, parent hybrid plants that they would stand in

taxonomic practise as new species, others have differ-

ences of such a nature that they might be called progres-

sive, or retrogressive varieties. The chances are im-

mensely against obtaining a Lamarckiana-like hybrid

No. 547] GENETICAL STUDIES ON ŒNOTHERA 425

which will produce the same series of variants as the

‘‘mutants’’ obtained by De Vries, for the reason that no

' two F, hybrid plants in so complex a cross as that

between biennis and grandiflora are likely to give exactly

the same set of variants. This principle is strongly indi-

cated in the diverse F, progeny of the two sister plants

10.30La and 10.300.

It is, naturally, important for my hy pothesis that

a like hybrids continue to give in successive

generations similar variants after the manner of La-

marckiana, but, as noted above, it is not necessary that

they be taxonomically the same forms (i. e., gigas, rubri-

nervis, nanella, ete.), or that they be produced in the same

proportions. Upon these points we shall sooner or later

have definite data.

The results from the work of the past summer (1911),

described in this paper, have strengthened the writer’s

hypothesis in the following respects:

1. A definite advance has been made in obtaining more

favorable F, hybrids by employing a biotype of biennis

(biennis D) with characters closer to those of Lamarck-

tana than the characters of biennis A and B previously

used. l

2. The F, generations from the hybrid plants 10.30La

and 10.30Lb have shown that large numbers of variants

may arise from a cross between biennis and grandiflora,

some of apparently new specific rank, others exhibiting

variations of either a progressive or retrogressive

nature, and very many presenting in various degrees of

complexity a segregation of the characters of the parents.

3. The progressive advance in flower and leaf size over

that of the parents of the cross indicates that selection of

the sort common among gardeners (i. e., the choice of the

largest and most vigorous plants) might readily estab-

lish a race surpassing in these and other respects both

parent plants. It is exactly this sort of selection which, —

in the writer’s opinion, has established the ea

forms of Lamarckiana. |

426 THE AMERICAN NATURALIST [Von. XLVI

It is to be regretted that the terms mutant and muta-

tion are being used so variously by different workers in

the fields of genetics. ‘‘Mutations’’ have been described

which are obviously from heterozygous parentage, in

some cases small differences, as of color or measurement,

in other cases very large differences. In contrast to

these have been described ‘‘mutations’’ from possible

homozygous parentage. Germinal variation due to the

mixing of different germ-plasms, and consequently from

heterozygous material, is a common phenomenon and

easily defined. Germinal variation in homozygous ma-

terial presents an equally clear concept.: The two types

of variation should be sharply distinguished for one of

‘the most important fields of genetical research is the

study of possible germinal variations in homozygous

stock and the conditions under which they may occur.

In our understanding of germinal variations (muta-

tions) as distinguished from somatic variations (fluctua-

tions) a great advance has been made towards a clear ap-

preciation of the problems involved. The problems cen-

ter in the study of germinal variations which are of two

types since they may be due to the mingling of germ

plasms (amphimixis), or to environmental influences.

Amphimixis is of course responsible for heterozygous

conditions now better understood as a result of Mende-

lian studies. Relatively little is known, however, of the

conceivable effects of environment as a source of germi-

nal variation. It may be doubted whether the specific

terms ‘‘mutation’’ and its alternative ‘‘fluctuation,’’ as

commonly used, are well chosen since the concepts are so

clearly expressed by the designations germinal and

somatic variations.

It is clear that De Vries regarded the ‘‘mutants’’ of

Lamarckiana as variants from a type representative of a

wild species and as nearly homozygous as most well-

defined species. That the Lamarckiana with which De

Vries worked was strongly heterozygous, in fact a hybrid

of biennis and grandiflora, is the hypothesis for which I

am trying to present as much evidence as possible. By

No. 547], GENETICAL STUDIES ON GENOTHERA 427

this hypothesis, if finally accepted, most of the

‘‘mutants’’ of De Vries are likely to fall into the class of

variants due to the mixing of different germ-plasms. If

the word mutation, in the sense of De Vries, is to have

a meaning more precise than that of variant it must be

kept for the type of variation from homozygous stock.

That germinal variations may occur in homozygous

material seems to the writer more than probable, and it

is possible that many small variations are of this type.

The trend of experimental investigation, however, dis-

tinctly indicates that large variations (ranking as salta-

tions) are rare if present at all in homozygous material,

and consequently can not be important factors in organic

evolution. The variations considered by Darwin are

chiefly either the small variations in relatively homozy-

gous forms, or the large and small variations from heter-

ozygous stock.

UNIVERSITY OF PENNSYLVANIA,

February, 1911

LITERATURE CITED

Bartlett, sA H., ’11. @Œnothera Tracyi sp. nov. Rhodora, Vol. XIII, p.

209, 1911.

Davis, B. M., 711. Some Hybrids of Œnothera biennis and O. grandiflora

that reacinbte O. Lamarckiana, AMER. NAT., Vol. XLV, p. 193, 1911.

De Vries, Hugo, ’05. Ueber die Dauer der Mutationspériods os Gnothera

Tiitii. Ber. deut. bot. Gesell., Vol. XXIII, p

De Vries, Hugo, ’07. On Twin Hybrids. Bot. Gaz., Vol. p a p. 401,

1907.

De Vries, Hugo, ’09-’10. The Mutation Theory. Chicago, 1909-10.

De Vries, Hugo, 711. ene nfo AT Bastarde von @Œnothera

biennis L. und O. muricata L. Biol. Centbl., Vol. XXXI, p. 97, 1911.

Gates, R. R., ’10. Tho Earliest Description of Ginothera Lamarckiana.

Beicnce, Vol. XXXI, p. 425,

Gates, R. R., ’lla. Early aaee a Records of the CEnotheras.

Proc. Towa Acad. Sci. for 1910, p. 85, published in 1911.

Gates, R. R., ’11b. Mutation in Œnothera. AmER. Nat., Vol, XLV, p.

+» VOL č

il, A. + Shull, = H, a Small, J. K., 05. Mutants

and Hybrids of the Œnotheras. Carnegie Inst., Pub. 24, 1905.

MacDougal, D. T., Vail, A. M., and Shull, G. H., ’07. Mutations, Varia-

tions and Riclationships of üis Œnotheras. Carnegie Inst., Pub. 81,

1907.

EVIDENCE OF ALTERNATIVE INHERITANCE

IN THE F, GENERATION FROM CROSSES

OF BOS INDICUS ON BOS TAURUS

DR. ROBERT K. NABOURS

KANSAS STATE AGRICULTURAL COLLEGE

. THe common domestic cattle of India appear to be a

distinct species (Bos indicus). They are mainly charac-

terized by a large hump on the fore shoulders, short

horns, large drooping ears, extensive dewlap and sheath

(Fig. 1). There are several varieties, or breeds, but they

are so commonly hybridized that it is exceedingly difficult

to ascertain which are the pure strains and which hybrids.

In this respect they are probably analogous to. Bos

taurus. In size they vary greatly, ranging from very

diminutive breeds to those the largest individuals of

which weigh upwards of 2,000 pounds. The males are

considerably: heavier than the cows. The colors also vary

considerably, the most common being creamy buff, brown,

ashy gray, red, black and white, and blends of these.

They appear to be highly resistant to the cattle dis-

eases of tropical and subtropical countries, and they are

immune to the attacks of cattle ticks, that is, ticks do not

remain attached to them and suck their blood (Figs. 1

and 9), and they are said to be less liable to suffer from

the effects of the bites of insects than any of the breeds of

Bos taurus.

They are very gentle and docile. In India the males

are used as beasts of draught, and are yoked to the plow,

being the main animal used for tilling the ground. They

are very agile, being able to travel thirty or more miles

a day, carrying a heavy burden, or drawing a cart with a

considerable load on it. Recently they have been intro-

duced into Jamaica in considerable numbers, where they

428

No. 547] ALTERNATIVE INHERITANCE IN BOS 429

ty =

Fig, 1. suas bull (Bos indicus) When in good condition,

is bull weighs 2,000 pounds.

are used on the banana plantations. It is generally re-

ported that the strong draught oxen of Spain have been

derived from crosses between Indian cattle and the native

Spanish cattle, but the evidence is at best only anecdotal

and nothing whatsoever seems to have been recorded of

430 THE AMERICAN NATURALIST [VoL. XLVI

the inheritance behavior of the progeny of any of the

crosses.

The hump of some of the largest specimens may weigh

as much as fifty pounds, and it is esteemed by English

residents of India as a delicacy for the table. From the

Persian province of Gilan, on the Caspian, the humps,

smoked, of a small breed are shipped to parts of Russia

where they are in much demand as a delicacy. The meat,

products of these cattle, on the whole, are said to be

unexcelled. Some of the breeds give milk that is ex-

cessively rich in quality, but it does not appear that any

of them produce it in large quantities.

It appears that Brahma (Bos indicus) cattle were first

brought to the United States in 1853 by Mr. Davis, of

South Carolina. These cattle were subsequently taken

westward and their progeny distributed throughout the

southwest and parts of Mexico. In southern Texas and

parts of Mexico there are many native cattle that are

said to carry the blood of these cattle and other Indian

stock which were secured from menageries and circuses.

The common brindle cattle of these regions are said to be

descendants of the Indian on native cattle. Wherever

these part Indian cattle are found there is a general im-

pression among stockmen that they are thriftier and

larger than the native stock and more resistant to the

ravages of diseases, ticks, and insect pests.

In 1906 Mr. A. P. Borden, of Pierce, Texas, imported

about thirty head of Brahma cattle, mostly young bulls,

and since then he has been crossing them quite exten-

sively on native Texas cattle and on grade Durhams and

on grade Herefords. For an account of the experiences

in importing these cattle and the beginning of the experi-

ment, the reader is referred to Mr. Borden’s interesting

paper, ‘‘Indian Cattle in the United States,’’ The Ameri-

can Breeder’s Magazine, Vol. 1, No. 2.

In September, 1911, Mr. Borden kindly permitted me

to visit his herds for the purpose of studying them and

making photographs. The following preliminary ac- —

No. 547] ALTERNATIVE INHERITANCE IN BOS 431

count of three of the herds is given, because they tend to

show definite inheritance results. The study of the herds

and the work of making the photographs were greatly

hampered by the absence of the head herdsman, the rain,

ə, ı hybrids T Bos indicus on Hereford. The heifer on the right

weis sax ,000 pounds at twelve months of age. The bull on the left weighed

1,450 ip ipi at twenty-six eb of age. Photo furnished by Mr. A. P. Borden.

and the very short time at my disposal. I plan to make

a further study of them at an early date.

Whenever the Brahma cattle have been crossed on

grade or pure Herefords, the color characters of the

latter are on the whole dominant in the F, progeny (Figs.

i Hybrids from Bos indicus on Hereford and Durham. rae bull in the

center is from peters mother and weighed about 1,400 pounds 22 months

of age. All are tick-fre

432 THE AMERICAN NATURALIST [Vou. XLVI

3 and 4). The F, progeny from crosses on grade Dur-

ham show the Durham color and other characters to be

dominant. The progeny from crosses on native Texas

cattle of unknown constitution are very variable. In

some cases the F, progeny from the latter resemble the

Brahma greatly. However, this apparent dominance of

the Brahma in many cases, when crossed on native cattle,

is probably altogether due to the fact that a considerable

proportion of the native cattle already have Brahma

characters in them—their immunity to ticks and other de-

sirable qualities having favored their perpetuation since

the early introduction of the Davis and other Brahma

stock.

Herp No. 1

This herd consists of twenty-five or thirty F, cows

(Fig. 5, adults) from a white Brahma sire on grade Dur-

‘1G, 5. Fy mothers from Bos — on grade Durham and a few te Here-

for oa The white calf, on the right, is from F, half-brother of the co The

pure Durham calf, on left, and seed in center are from Durham sire.

hams and a few grade Herefords. Twenty-four of these

F, cows were mated to their Brahma-Durham F, half-

brother, and eighteen F, calves were produced. Of

these, six are white and resemble the grandfather white

Brahma. One of the calves is shown in Fig. 5, on the

right. The remaining twelve F, calves from these

crosses of hybrid X hybrid resemble the Durham mostly,

No. 547] ALTERNATIVE INHERITANCE IN BOS 433

though there is evidence of the Hereford characters in a

few. A few of these F, cows were mated to a registered

Durham bull. Only two of the F, calves from these crosses

were observed. They are shown in Fig. 5, on the left and

in the middle. The one on the left is a pure Durham in

all respects. The one in the center is a typical Brahma.

Durham hybrid. A downpour of rain and the scattering

of the herd prevented further observations.

Herp No. 2

The F, cows of this herd are the product of a Brahma

male on grade Hereford and grade Durham in about

Fic. 6. The cows are from Bos indicus on impure ea and the calves

from these F, cows bred back to Bos indic

equal proportion. These F, cows show the color char-

acters of the Hereford and Durham quite distinctly,

Fic. 7. The yearlings are from Bos indicus x high-grade Hereford Fi

hybrids bred back to Bos indicus.

though there is slight evidence of the hump of the

Daku sire, and the dewlap is somewhat enlarged (Fig.

434 THE AMERICAN NATURALIST [Vou. XLVI

6, adult). (The brothers of these cows were not ob-

served.) The F, calves of this herd are from a Brahma

sire on these F, cows. My notes fail to show whether or

not the sire of the F, calves is the same as that of their

F, mothers. The sire of the F, calves appears to be in-

termediate in color between the white and brown Brahma.

The calves are of two distinct types, about one-half of

them having the Brahma characters and the other half

bearing the characters of their hybrid mothers (Fig.

6, calves). In the figure (Fig. 6) a good type of the

hybrid resembling the mother is the sucking calf at the

right, while several apparently pure Brahmas are shown

in the foreground.

Herp No. 3

The F, cows of this herd are the progeny from a

Brahma sire on high grade Hereford cows. The F,

calves and yearlings are from another Brahma sire on the

Brahma-Hereford hybrid. On counting these thirty-two

calves and yearlings, it was found that seventeen of them

resemble mostly the sire and grandsire Brahma while

fifteen come nearer to the type of the Aybnd mothers |

(Fig. 7, calves and yearlings).

CONCLUSIONS CONCERNING THE INHERITANCE BEHAVIOR

It appears that the color patterns of Herefords and

Durhams are dominant in the F, generation. However,

the hump, large sheath and dewlap of the Brahma show

slightly in the Brahma X Hereford or Durham F,

progeny. It is clear that in the F, generation, pure

Brahma and pure Durham are segregated. Indications

are that when the parent strains are pure the segregation

follows the simple law of alternative (Mendelian) in-

heritance. However, the conditions of the experiment,

the lack of full knowledge of the constitution of the

parents and the inadequate observations prevent any

positive conclusions as yet concerning the ratios.

No. 547] ALTERNATIVE INHERITANCE IN BOS 435

Immunity To THE Texas CATTLE Ticks

I am able fully to confirm Mr. Borden’s statements

(loc. cit.) that the pure Brahma cattle and the hybrids

are perfectly immune to the Texas cattle tick. Fig. 8

shows the ordinary conditions of the native Durham or

Hereford cattle, while Figs. 9, 1 and 3 show the condi-

Fic. 8, A _ tick-infested Hereford Fic. o A sie indicus cow free

fre ticks.

Each of TE cows has suckled a calf during sa summer and both

e been together in the same pas

tions of the pure Brahma and ee all running

together on the same range. I was not able to ascertain

definitely the inheritance behavior of this character (im-

munity to ticks) in the F, progeny. However, it is ex-

pected that data on this point will be available in the

spring or summer of 1912.

SIZE AND PROLIFICNESS

The statement by Mr. Borden (loc. cit.) that the

hybrids running on the range average about 50 per cent.

436 THE AMERICAN NATURALIST [Vou. XLVI

larger than the ordinary native range cattle is fully con-

firmed by my observations. The hybrids shown in Fig.

4 (center), which had had no other advantage than the

range conditions, weighed 1,400 pounds at two years old.

The hybrid heifer, shown in Fig. 3 (at the right), which

had run on the range, weighed 1,000 pounds at twelve

months old. The bull, Fig. 3 (on the left), weighed 1,450

pounds at 26 months of age. These weights appeared to

me to be more than 50 per cent. greater than the average

of the native cattle at the same age kept under similar

circumstances.

A pure Brahma bull will put seventy-five to eighty

cows with calf each season, while the native or even high-

grade Hereford or Durham will impregnate only twenty-

five or thirty cows.

I desire to express my gratitude to Mr. Borden for

courtesies shown me while studying and photographing

the herds and for reading and correcting the manuscript,

and to Professor T. J. Headlee for the arrangements

which made the trip possible; I am further indebted

to Professor Headlee for suggestions while writing the

paper and arranging the illustrations.

SHORTER ARTICLES AND DISCUSSION

ON THE INHERITANCE OF TRICOLOR COAT IN

GUINEA-PIGS, AND ITS RELATION TO GAL-

TON’S LAW OF ANCESTRAL HEREDITY*

In 1889 the late Francis Galton formulated a ‘‘law of ancestral

heredity’? which he believed would prove to be of general

applicability in as much as he had already applied it with

gratifying results to two widely different categories of cases, viz.,

the height of man and the color of dogs. The law as stated by

Galton is:

The two parents contribute between them, on the average one-half,

or (0.5) of the total heritage of the offspring; the four grandparents,

one-quarter, or (0.5)?; the eight great-grandparents, one-eighth, or

(0.5)*, and so on.

The validity of Galton’s law has since been seriously called in

question, though neither of his two cases has yet received a

wholly satisfactory explanation, but sufficient progress has been

made in the study of heredity to show the unsoundness of the

basic principle on which Galton’s generalization rested. In

reality there is no such thing as ‘‘ancestral’’ inheritance; for we

inherit from our parents only, not from our more remote an-

cestors. It is true that a knowledge of the more remote ancestry

may help us to understand better what we have inherited from

our parents, but it is clear that such knowledge of the ancestors

will not enable us to predict the character of their descendants in

the precise manner outlined by Galton. In a specific case, the

inheritance of albinism in mice, I made in 1903 a test of the

comparative value of Galton’s law and Mendel’s law in predict-

ing the character of offspring, with the result that Mendel’s law

gave predictions closely according with observation, whereas

predictions based on Galton’s law proved wholly unreliable.

As regards height, however, and other size characters, Gal-

ton’s law is quite as good a basis for predicting the result of

particular matings as is Mendel’s. Indeed it is not clear that

either of them is applicable to such cases as human stature.

‘From the Laboratory of Genetics of the Bussey Institution, Harvard

University.

437

438 THE AMERICAN NATURALIST [Vor. XLVI

The other case studied by Galton, the inheritance of the tri-

color condition in Bassett hounds, no one up to the present time

has attempted to explain on any ground other than that taken

y Galton in his law of ancestral heredity, although it is now

generally conceded that his law does not apply to color in-

heritance in general. :

The tricolor condition seen in dogs is found in very few other

animals, one of which however is the guinea-pig, the tricolor

variety of which I have had an opportunity to study for some

years. The observations made on tricolor guinea-pigs throw

light on the facts observed by Galton regarding tricolor dogs.

They show wherein Galton’s interpretation fails and what ad-

vantages a Mendelian interpretation has as applied to this case.

The tricolor condition of guinea-pigs is one of long standing.

Cuvier reports it as depicted by Aldrovandus, who made the

first scientific description of the guinea-pig, soon after 1550.

This color variety had probably been in existence for a long

time before the discovery of America. The natives of Peru still

rear it for food in the recesses of their adobe cabins, as their

ancestors have doubtless done for untold centuries. Neverthe-

less it does not breed true, and can not be made to do so.

The tricolor animal is white marked with irregular but distinct

blotches of black and yellow. Tricolors produce besides tri-

colors young which are black-and-white or yellow-and-white, but

never in my experience those which are wholly free from white.

In other words they breed true to spotting with white, but not to

spotting with black and yellow. The black-and-white as well as

the yellow-and-white offspring of tricolor parents may produce

tricolor young. Indeed any one of these three conditions is able

to produce both the others. See Table. Nothwithstanding the

TABLE SHOWING THE KINDS oF YouNG PRODUCED By A RACE OF GUINEA-

PIGS CONTAINING TRICOLOR INDIVIDUALS

B-W, black-and-white; Y-W, yellow-and-white; T, tricolor

Parents 1S

T B-W Y-W Per Cent. T

T... 8 1 5 57

TXS B-W 9 3 5 53

TS Y-W 13 2 9

B-WX B-W. 1 3 2 17

B-WX Y- 6 | 1 1 75

Y-WX Y-W i i 9 45

oe a $ | P 31 52

No. 547] SHORTER ARTICLES AND DISCUSSION 439

fact that neither the black-and-whites nor the yellow-and-whites

produced by tricolors breed true, there are races of black-and-

white and of yellow-and-white guinea-pigs which do breed true.

It remains to explain why the others do not. A black-and-white

animal which breeds true may be considered to possess some

chemical substance necessary for the production of color (which

we call a color-factor) distributed irregularly throughout its

coat. Wherever this substance is wanting no color is formed

and a white area results. The specific factor for black (prob-

ably an enzyme) is however everywhere present in the coat so

that wherever color forms the color is black. Such races as

this breed true.

The yellow-and-white animal which breeds true may likewise

be considered to have an irregularly distributed color-factor, but

to lack entirely in its coat the black factor. Hence the color,

wherever formed, is yellow.

Yellow races also exist which do not bear spots of white, but |

which have spots of black. In such animals the color-factor is

evidently uniform in distribution, whereas the black factor is

irregularly distributed.

Now the tricolor race is a yellow one spotted both with white

and with black, i. ¢., it results from irregularity in distribution

through the coat of two different chemical substances, the color

factor and the black factor. These two factors are known to be

independent of each other in heredity. See Castle (1909). It

is therefore not to be supposed that they will commonly coincide

in distribution. If the black factor extends over all the colored

areas, the animal will be black-and-white. If the black factor

falls only on areas which lack the color factor, it will produce no

visible effect, and the animal will be yellow-and-white. If,

finally, the black factor falls on some of the colored areas but not

on all of them, those in which it falls will be black, the others

yellow, and the uncolored areas of course white. Hence a tri-

color will result. But the gametic composition of these tricolors

Will not be different from that of the black-and-whites or red-

and-whites produced by the same race, since all alike will be

characterized by irregularity in distribution of the same two

factors. A tricolor race on this hypothesis should be unfixable,

as has up to the present time been found to be true.

The same line of explanation will answer equally well for the

case of the Bassett hounds studied by Galton. These Galton

440 THE AMERICAN NATURALIST [Vou. XLVI

classifies as either ‘‘tricolor’’ or ‘‘non-tricolor’’ (‘‘lemon-and-

white’’). A third variety, ‘‘black-and-tan,’’? is mentioned by

Galton, but disregarded in his statistical treatment. He does not

state whether it may or may not possess white spots, but I

strongly suspect that the ‘‘black-and-tans’’ produced by spotted

Bassett hounds would also be spotted, in which case they would

correspond with the category black-and-white of guinea-pig

races containing tricolors. For the ‘‘tan’’ feature of black-and-

tan dogs is in reality due to a pattern factor as distinct from

black as is the agouti pattern of guinea-pigs. Hence so far as

spotting is concerned Galton’s disregarded ‘‘black-and-tans’’

were probably black-and-whites which happened to possess the

‘‘tan’’ pattern (light spot over eye, light belly and legs below).

If so, the behavior of the dogs accords in every point with that

of the guinea-pigs as regards color inheritance. For Galton

observed that neither tricolors nor non-tricolors breed true, but

each sort may produce the other, though it produces more of its

own kind. The same is true for guinea- pigs; see Table. It is

desirable that any one having the opportunity should look into

the breeding capacity of Bassett hounds which are black-and-

white or ‘‘black-and-tan.’’ If they can produce ‘‘tricolor’’ and

“‘lemon-and-white young,” the parallel between the breeding

capacity of tricolor guinea-pigs and tricolor dogs will be com-

pletely established. W. E. CASTLE

BUSSEY INSTITUTION,

HARVARD UNIVERSITY

BIBLIOGRAPHY

Castle, W. E.

1903. The Laws of Heredity of Galton and Mendel, and Some Laws

Governing Race Improvement a Selection. Pree. Amer. Acad.

of Arts and Sci., Vol. 39, pp. 223-242.

1905. Heredity of Coat harioti i in Guinea-pigs and Rabbits. Carnegie

nstitution of Washington, Publication No. 23.

Castle, W. E., in collaboration with H. E. Walter r, R. C. Mullenix and S. Cobb.

1909. Studies of Inheritance in Pe Carnegie Institution of Wash-

ington, Publication No.

Cumberland, C

1901. The Guinis -pig or Domestic Cavy. 100 pp. illustr. London, L.

Upcott Gill

Galton, F

1889. Natural Inheritance. Macmillan Co., London and New York.

1897. The Average Contribution of Each Several Ancestor to the Total

Heritage of the Offspring. Proc. Roy. Scc. London, Vol. 61,

pp. 401-413,

VOL. XLVI, NO. 548 | AUGUST, 1912

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THE

AMERICAN NATURALIST

Vout. XLVI August, 1912 No. 548

A CASE OF POLYMORPHISM IN ASPLANCHNA

SIMULATING A MUTATION

PROFESSOR J. H. POWERS, Px.D.

UNIVERSITY OF NEBRASKA

Durtne the fall of 1909 the writer accidentally dis

covered a case of heterogenesis in the genus Asplanchna

which bore all the earmarks of a bona fide mutation. The

two forms concerned were quite sufficiently different to

be classed as distinct species, and even as strongly

marked species. The transition was sudden and com-

plete, without apparent intergradation. The transition

was also in one direction only, and it could not be con-

sidered as in any sense due to an immediate cross, be-

cause the reproduction of the Asplanchna, aside from

resting eggs, is wholly parthenogenetic.

Subsequent study of the same species, during the fol-

lowing spring, as it appeared in several different loca-

tions, supplemented by extensive experiments, showed

that the phenomena in question were not those of typical

mutation, but are rather to be classed as striking in-

stances of polymorphism. As, however, their interest

depends in large measure, for the writer at least, upon

the ease with which they may be mistaken for mutation, I

i will first describe the facts as they appeared in the

original collection of material.

This collection was made about October 1, in the

remnant of a vile pool on the alkali flat west of the city

441

442 THE AMERICAN NATURALIST [ Vou. XLVI

of Lincoln, Nebraska. This portion of the flat has for

years been used as a dump, having been filled in several

feet in depth mainly with compost. Two years previ-

ously a heavy summer flood had excavated a cavity, the

size of a village lot, to the original alkali bottom, and in

this cavity the pool remnant, to the depth of about one

foot, remained. The water was dark brown with alkali

and the essence of compost, but it suited Asplanchna

exactly, for while almost no other plankton was present

the Asplanchnas were so abundant as to almost touch one

another; the sweep of a yard with a 20-inch dip-net

brought up a double handful of the strained animals.

My original study was confined to material from this

single collection because, a day or two later, a heavy rain

flooded the pool, killing the Asplanchna to the last

individual,

The collection in question contained two distinct types

of Asplanchna. The dominant form, outnumbering the

other several hundred to one, was of a large humped

type, closely akin to Asplanchna amphora. I shall, how-

ever, postpone a detailed discussion of the species, as it

is intricate, and unfortunately involves some controversy,

while the interest in the phenomena which I wish to

describe is not specially dependent upon it. Reference

to Fig. 1 will show fairly well its general appearance, and

I need but add at present that it was of very large size,

frequently measuring 1,500» in length.

Sparsely distributed among the mass of these animals

was a mammoth rotifer of related yet very different type.

It was saccate, or, more truly, campanulate, in form. Its

robust body, without humps, somewhat exceeded in length

that of its more slender companion, while its enormous

ciliated wreath or corona was extended beyond all limits

that the writer ever expected to see in a rotifer. Its

transverse diameter frequently equaled the entire length -

of the animal, This massive giant swam about with a

typical though rather slow Asplanchna movement, vibrat-

ing or flapping first one portion and then another of the

No. 548] A CASE OF POLYMORPHISM 443

ciliated corona in a very conspicuous fashion. When it

met one of the other rotifers in a head-on collision it was

much less inclined to contract or turn a quick somersault

than was the companion type. As to the specific,

varietal, or other classification of this large campanulate

Asplanchna I could find nothing. I concluded that it

must be an as yet undescribed species. Its distinctness

was further borne out by the results of detailed study.

The characters hitherto most extensively used for

specific definition in the genus Asplanchna are size, body

form, type and development of nephridium, and the form

of the trophi. As to the nephridia of the two forms in

question, they -proved, indeed, sufficiently different.

Although built upon the same general type, their size and

the number of flame cells bespoke wide separation.

Rousselet, who is the first authority upon the classifica-

tion of rotifers, in his last article! discussing the species

of Asplanchna expresses his belief that the number of

flame cells is constant in each species, although he admits

that it is very difficult to make strictly accurate counts of

these delicate organs. He assigns to Asplanchna

amphora about 40 flame cells, and this is a much higher

number than has hitherto been found in any other species.

My preparations permitted much better counts than may

be made on the living animal, but still I am not certain

of exactness. I found, however, that even the humped

rotifers frequently bore about 50 flame cells on a side,

and in many instances I found 55. In the campanulate

type the number was astonishingly greater. Not only

was the nephridial tube bearing the tags longer, stretch-

ing from the knotted portion near the bladder in a wide

diagonal curved line to the lateral edge of the corona, but

it was very thickly studded throughout the greater por-

tion of its length with the flame-bearing tags. The

number was certainly variable in larger and smaller

Specimens, but it was frequently about 100, and in a

_ "On the Specific Characters of Asplanchna intermedia,’’ Hudson, Jour.

Queck. Mic. Club, Second Series, Vol. VIII, pp. 7-12.

444 THE AMERICAN NATURALIST [ Vou. XLVI

number of instances, by thoroughly conservative counts,

I reached the surprising number of 115. The nephridial

development in this giant rotifer is therefore in propor-

tion to its large size and massive tissues. The trophi

also proved sufficiently different and of a size hitherto

quite unknown in the genus. A glance at Figs. 3 and 4,

showing the trophi of the two types drawn to the same

scale, will show at once their great difference. A detailed

discussion of their minor features will show them to be

still further apart.

In general, then, to judge by the structure of the

females, the two types seemed very distinct, and several

weeks of painstaking study, including the examination of

several thousand individuals, left me with very little

doubt that I was dealing with what we ordinarily class as

distinct species.

It was while examining some of my first mounted slides

of the large Asplanchna that I came suddenly on the evi-

dence of apparent mutation. As is well known, the

young of Asplanchna are highly developed before birth,

and in the material which I was studying this chanced

to be true to an unusual degree. My mounted slides, too,

were perfectly transparent, giving views not only of all

the organs of the adult, but of every organ and almost

every histological detail in the structure of the unborn

young. Examining these young, I noticed at first noth-

ing peculiar; the young within the humped rotifers bore

humps even more marked than those of the adult, it being

one of the recognized characters of A. amphora that these

body extensions reach a maximum development in the

young at about the time of birth. The first young noted

in the campanulate type were also, in all respects, essen-

tially like the parents.

I was, therefore, astonished to suddenly hit upon 4

large campanulate rotifer containing an unborn rotifer,

not of its own, but of the other, the humped type, Fig. 2.

The word mutation was the first thing that framed itself

in the midst of my inarticulate consciousness. But of

No. 548] A CASE OF POLYMORPHISM 445

course I neither accepted at once the suggestion nor the

apparent facts before me. Mutation, although among

things proven, is among the things proven to be rare, and

is therefore to be accepted in any given case only after

fullest verification. Moreover, facts themselves are fre-

quently deceiving. Perhaps the young humped As-

planchna did not belong within the body of its seeming

parent. Perhaps it was some accidental inclusion forced

through some invisible aperture in the side of the larger

organism. In short, was it really in the uterus? Per-

haps it had been swallowed by the adult campanulate and

had managed afterward to tear its way through the

digestive tract, which latter organ had then healed and

allowed the prey to continue development in the body

cavity. |

While I was asking myself these questions and others,

I was also assiduously seeking for more examples, for if

the phenomena were regular more examples would cer-

tainly be found.

A number were indeed discovered, and every possible

explanation was eliminated except that they were, as they

appeared to be, young humped rotifers which were pro-

duced by normal parthenogenetic development within the

giant campanulate type. I was able to discern, for some

of them, that they were within the uterus, and in every

way in normal position. The only slight sign of ab-

normality was that they usually seemed to be a little

small for the parental organism producing them; they

filled less of the body cavity than did corresponding

young that were developed true to type. But upon

second thought this was but one more sign of the com-

pleteness of the heterogenesis. These humped young

were developing of exactly the size that they would have

developed within the body of a humped parent; within

the body of a campanulate they naturally left room, so to

Speak, to spare. The internal organs, too, of these

heterogenetic young bore out, in detail, the conclusion

Suggested by the external appearance. The lighter

446 THE AMERICAN NATURALIST [Vou. XLVI

musculature, the narrower ovary- or shell-gland, were

obviously characteristic of the smaller humped type.

Most definite of all, however, was the evidence of the

trophi. These are universally recognized as yielding

characters of specific rank. They are wholly developed

before birth, and they were very different in the two

types in question. I used, therefore, the utmost pains to

ascertain the nature of the trophi in these heterotypic

young. The result was without question; the trophi in

every case indicated a complete and sudden transition

from the campanulate to the smaller humped type. This

was true both in regard to size and in details of structure.

I concluded, then, after the study of every organ which

I could make out with clearness in the material at my

disposal, that these atypic young in the large campanu-

late Asplanchna represented, not an ordinary variation,

but the sudden production of one type by another and

quite distinct one.

But a number of questions suggested themselves at

this point. In what number were these mutants, if such

they really were, being produced? Was the production

of one type by the other occurring in both directions, or

only in the one in which I had chanced to find it? And,

again, could transition specimens or any signs of grada-

tion between the two types be found among the adults,

or individuals of any age, in the material at hand?

As to the first question, I examined carefully 270

mounted adults of the giant campanulate type. Nearly

all were in reproduction, but only 90 of them contained

young sufficiently advanced in development and suffi-

ciently well placed to allow a certain judgment as to their

type. Of the 90 unborn young nearly one fourth (22)

were indisputably of the humped type, while 68 were just

as certainly of the parental or campanulate type. Noth-

ing should be made here of the ratio of one fourth and

three fourths. The phenomena in question are not the

result of a cross, and, moreover, the determination hinges

upon several factors; for one thing, upon my caution,

No. 548] A CASE OF POLYMORPHISM 447

when dealing with the earlier embryos, in rejecting any

case which was not quite certain. In other words, had I

been working with live material and rearing the animals

to a proper stage, a considerably larger proportion than

one fourth would probably have turned out heterotypic.

To answer the second question—i. e., whether this

atypical reproduction were occurring in both directions

or in one direction only—I first made a preliminary

examination of several thousand individuals of the

humped form, a high percentage of which contained well-

developed embryos. I found no indication of any de-

parture from normal reproduction. I then examined

critically one thousand individuals, recording results in

each case. Of this one thousand individuals, 419 con-

tained young sufficiently developed and well placed to

admit of safe determination. All were plainly of the

parental type; nor did I find a single case in all this

material that even suggested strong variation toward the

larger humpless rotifer.

Transitional specimens, however, could, if present, be

more certainly found among adults, or at least among in-

dividuals after birth. This was my third query. Did

such exist? Throughout my entire examination I sought

for them, but with little success. At certain stages in

development each species approaches a little nearer to

the other species. Thus the young of the larger, cam-

panulate type are not only smaller, but have slightly

bulging sides, suggesting the possibility of humps.

Their corona, too, although very heavy and broad, is less

disproportionately so than in the fully grown adult. But

in no case was it difficult to determine the relationship of

such specimens; other characters placed them at once,

especially the enormous and differently formed trophi,

which are fully developed before birth. Very old adults

of the smaller humped type might possibly, at first glance,

be taken for variants toward the larger form, in that

their humps become smaller and less sharply marked off

from the general body wall. In no other character, how-

448 THE AMERICAN NATURALIST [Vou. XLVI

ever, do they approach the campanulate type. Putting

aside such stages, which, with a little practise, fall

naturally into place, the amount of further variation did

not prove to be great. The humps, both lateral and

ventral, on the smaller. type, did show a considerable

amount of variation in relative size. And in numerous

cases it was of interest to note that such variations were

plainly hereditary; i. e., an extra large female with, say,

relatively small humps, would contain a large young in-

dividual that was obviously of the same type.

But these minor variations were to be expected; as

well as their tendency toward transmission, but they had

no evident connection with the type of change of which I

was in search.

Of true transitional types I discovered but two possible

instances. These two individuals were quite alike, but

differed notably from any others of the thousands

studied. Each was, all in all, indisputably a humped

rotifer, but decidedly beyond the ordinary maximum size

and with disproportionately small humps. The corona

of each was much broader and its cells much heavier than

in any other humped individuals observed; the body

walls and musculature also were much heavier, taking the

deep stain shown otherwise only by the campanulate.

All of these characters approached more or less the

campanulate type. Most striking, however, were the so-

called ovaries. In each case they were of the heavy type

shown by the larger rotifer. The nephridia did not

admit of careful observation. The most crucial organ of

all, however, the trophi, agreed wholly with the humped

type in form, and, though large, did not exceed the

maximum size found in the ordinary type. Studying

these two individuals with care, I came at last to the con-

clusion that, although in a sense they might be called

transitional, they were after all only variants of the

humped type—variants pointing toward, but not actually

leading to, the production of the campanulate type.

All in all, then,.my search for signs of genetic rela-

No. 548] A CASE OF POLYMORPHISM 449

tionship between the two types seemed to leave the evi-

dence for mutation sharp and clear: the transition from

the giant humpless Asplanchna to the smaller humped

type was sudden and complete; it involved many char-

acters; it was being effected in many individuals simul-

taneously; it was a transition in one direction only; in-

termediate types and fluctuating varieties seemed, in all

the material studied, no more in evidence than was to be

expected in any two species of one genus. At the close

of this part of my study it seemed that I had found an

ideal case of mutation, agreeing in every particular with

the definitions of the concept put forward by its origi-

nator, DeVries.

However, just as I was finishing the study of the pre-

served material at hand, and deeming that I had reached

the above conclusions with full certainty, I was suddenly.

halted by coming into possession of more living material,

and material so surprising that my well-worked-out re-

sults again assumed the character of problems, and I

resolved, if possible, to subject the whole to the test of

experimental method and further observation.

It was about the middle of March, 1910, that the

Asplanchna began hatching in a large covered aquarium

jar in which I had placed some of the resting eggs the fall

before. Between the last of March and the 10th of

April the species also began to appear gradually in two

ponds, in which, fortunately, the available food organisms

for many weeks were wholly different. Observations

were thus begun upon the species under diverse condi-

tions, even from the start. And, as they were continued

with but few and short interruptions through the spring,

summer, and well into the succeeding fall,? the variety of

conditions under which the development of the species

was followed included very wide extremes. Thus, during

a cold period in early April the species multiplied in

Shallow ponds upon which ice was forming nearly every

*Since the above was written nearly all of the eo recorded have

again been observed during a second season.

450 THE AMERICAN NATURALIST [Vou. XLVI

night, while heavy prevailing north winds kept the water

in continual turmoil. On the other hand, in July and

August, I was able to study the species in both permanent

and temporary ponds during periods of the hottest

summer weather.

Side by side with these observations, and correlated

with them as far as possible, a large number of culture

experiments were carried out.

The general method was as follows: The ponds were

visited several times a week, and such observations as

possible made on the spot. Then large quantities of the

animals, together with their food organisms, were

brought to a basement laboratory and placed in large

aquarium jars. These mass collections were sometimes

obtained by merely dipping up the water and the organ-

isms it contained in their natural degree of dispersion; at

other times the organisms were much concentrated by the

addition of large numbers taken with suitable nets. Flew

results were more interesting than the observation of the

resulting phenomena in parallel aquaria in which the

animals had been placed, now in small numbers, and

again in various degrees of concentration bus to almost

actual contact.

The material in these mass cultures was critically ex-

amined and followed from day to day. Then, when-

ever interesting phenomena seemed to be occurring,

either in the ponds or the mass cultures, or in both, iso-

lation experiments were begun with single individuals,

or with a definite number carefully selected and exam-

ined one by one.

To my satisfaction, the animals proved remarkably

adapted to experimental treatment. They withstand a

great variety of environmental influences, providing only

that two conditions are rigidly met. In the first place,

a copious food supply must be furnished; and second,

the fluid medium (it may be saturated with such ingredi-

ents that one hardly speaks of it as.water) in which the

animals have developed must be left practically un-

" No. 548] A CASE OF POLYMORPHISM 451

changed. This latter condition limits the range of pos-

sible experiment, but I could not once succeed in getting

Asplanchna to live and reproduce in any other than its

native fluid ;? even dilution of one fourth with water from

some other source seemed in every case to preclude a suc- `

cessful culture. In nature, too, every rain which diluted

to an appreciable extent the vile ponds in which this

Asplanchna flourishes results in the death of the entire

stock, which is only replaced by the hatching of new in-

dividuals from resting eggs.

As to food, many organisms were tried, and a number

proved available. Best of all, for the smaller forms of

the Asplanchna, Paramecium proves an ideal food.

Other rotifers come next, of which I used especially Hy-

datina and Brachionus; while, surprising as it would

appear, the crustacean, Moina paradoxa, although a

large-sized member of its group, provides, under certain

circumstances, an available food supply for this over-

grown and voracious rotifer. The adult Moinas are not

eaten, but young and even half-grown individuals may

be regularly eaten by the mammoth campanulate form I

have described. The humped rotifers ingest the crusta-

cea with difficulty, but succeed in doing so at times to a

considerable extent. j

Omitting further reference to methods, and refraining

from any attempt to describe the course of experiments,

I will briefly give their results, prefacing only that I make

no general statement which is not based on the outcome of

at least ten separate experiments or as ample observa-

tions in nature, or on both.

The first of these results which I will state, although

nearly the last that I demonstrated, is the error of my

original conclusion in regard to the relationship betwen

the two types already described. The campanulate and

humped types do reproduce each other reciprocally, al-

though with very different frequency in the two direc-

* This does not apply to cultures started from sepen eggs. These may be

hatched and the young developed in varied m

452 THE AMERICAN NATURALIST ~~ [Vou. XLVI

tions. Moreover, transition forms (in every feature ex-

cept the trophi) do oceur between them under given

though unusual conditions. The phenomena thus fall

more naturally under the rubric of dimorphism than

under that of mutation; although, as will be apparent

later, the phenomena with this rotifer bring the two con-

cepts into closer relation than they have perhaps ever

been brought before.

The second general result of work with the living ani-

mals was the surprising discovery that the species is not

only markedly dimorphic, but trimorphic, possessing a

third form—a smaller saccate type which differs from

both the humped and the campanulate types quite as

much as these differ from each other, and which, curi-

ously enough, differs far more, in external appearance

at least, from these other forms of its own species, than

it does from an allied but distinct species, Asplanchna

brightwellt,

I shall return to this latter point of specific distinctness

again. But by way of description I will here state that

this sacecate type, as I shall call it, although showing a

considerable range of fluctuating variability, is a rather

primitive but typical Asplanchna. In size it averages

much smaller than either of the other types dealt with,

reproductive individuals ranging from about 500. to

1,200 in length. In outward form it resembles closely,

now A. brightwelli, now A. priodonta. The corona, when

the animal is seen from the end, is always circular, as 1s

typical for the genus, never showing the strong dorso-

ventral flattening which is the invariable condition in

the humped and campanulate types. Correlated with

this cireular corona is the general cylindrical shape of the

animal. When placed on a slide in a shallow drop of

water these saccates characteristically rest on their sides

instead of their dorsal or ventral surfaces as do both of

the larger types. The trophi are of the same type as are

those of the humped Asplanchna, except that they are a

little smaller and proportionally a little more robust.

No. 548] A CASE OF POLYMORPHISM 453

The internal organs are of the same general character,

although more compact and filling more of the body space

than in the two larger forms, two of them, however, be-

ing notably different in development.

First, the nephridia. I have not studied these in

stained preparations as I have in the other types, but,

using living material, I make out a decidedly variable

number of flame cells; they range from as low as twenty

to nearly forty. It is at least plain that the number

averages much less than in the humped form, and but a

fraction of that in the: campanulate. The difference

would seem to be plainly correlated with the general dif-

ferences in the size of the organisms.

Singularly in contrast to the smaller sis pitidte is the

development of the contractile vesicle or bladder. This

is a small organ in both the humped and campanulate

types, but in the much’ more diminutive saccates it be-

comes very much larger, filling, when expanded, a large

part of the body cavity. I have examined considerable

numbers from diverse sources and reared under different

conditions, to make sure that this contrast was not acci-

dental. I find no exceptions to it. Like the number of

flame cells, this matter of size of the contractile organ,

relative to that of the body, has been hitherto considered

a specific difference.

A final peculiarity of the saceate type, although a var-

iable one, is its tendency toward an excessively rapid

rate of parthenogenetic reproduction; it is usually

crowded with embryos. Four, five and six are frequent ;

sometimes I have counted nine; while in many individuals

they are so closely packed that counting is out of the

question. These numerous young are also frequently

born at a disproportionately small size, even compared

with the diminutive parent, thus still farther increasing

the extremes of size which the species presents. It seems

probable that this smaller and less developed type is

itself, to some extent, a product of this rapid rate of

multiplication. I have found it multiplying at a slower

454 THE AMERICAN NATURALIST [Vou. XLVI

rate—i. e., producing but one or two embryos; but such

instances were always due to degeneration or growth un-

der unfavorable conditions. I may add by way of con-

trast that the humped form most typically produces but

one young at atime. Thus, in the material of my orig-

inal study, among one thousand individuals I found but

sixteen showing the more or less simultaneous develop-

ment of two embryos, and none showed more than two.

The campanulates regularly develop several embryos at

once, four and five being common numbers; but in their

capacious bodies there is no overcrowding, and certainly

no curtailment of nutrition.

As to the occurrence, the definite relationship, and

the causes of the production of the three types of the

species, I have ascertained most of the facts, though

not all.

The saccate form is, I think, unquestionably the only

form that emerges from the resting egg. In all cases—

seven in number—in which I have examined temporary

ponds within a few days after formation and found this

rotifer just appearing, or in which I have caught the spe-

cies evidently close to its first appearance, I have found

either nothing but the saccate type, or numerous saccates,

together with transitional and humped types. In the

majority of these cases the saccates have been rapidly

displaced by the humped type, which, in nature at least,

very rarely reverts to the production of the smaller form.

As soon as the species is in full swing, so to speak, count-

less numbers may be examined for weeks without a sac-

cate occurring. All of these phenomena have been par-

alleled in my aquaria, and I have also repeatedly observed

the birth of the humped type from the saccate parent.

This is usually in instances where the high numbers of de-

veloping embryos in the saccate parent have given place

to few or to but one. Usually, too, the parent is a rather

large saccate and the humped young a rather small ex-

ample of its type. But occasional instances have been

noted where the humped young, a moment after birth or

No. 548] A CASE OF POLYMORPHISM 455

as soon as it had assumed complete expansion, appeared

fully a third larger than its saccate parent. The act of

giving birth to such heterogenetic issue is a decidedly

prolonged and painful process for a rotifer, very differ-

ent from the ordinary, sudden expulsion, well known in

Asplanchna. .

Turning to the consideration of the actual cause of the

transition from the saccate to the larger humped form,

I have not discovered it definitely. The cessation of

the rapid rate of reproduction, already spoken of, seems

a partial proximate cause, though it itself I can not ex-

plain. It seems in part a mere matter of the number

of generations following hatching from the resting egg.

But a copious food supply and generally favorable con-

ditions probably favor the change. In early spring the

saccate form maintained itself for several weeks in a

pond where, in July, after drying up and being refilled

by rain, the saccate form began to produce the humped

form sparingly within four days, and was very soon sup-

planted by it. In another pond of purer water and seem-

ingly less well adapted to the species, the saccate form

appeared scantily in early May, and struggled on spar-

ingly for three weeks, feeding mainly upon the flocculent

masses of blue-green alga, but somewhat upon Brach-

ionus; it then disappeared entirely, having produced no

form but its own so far as I could discover. Yet in isola-

tion cultures from this same stock, when fed on Para-

mecium, I raised, after several generations, a number of

rather small humped Asplanchna.

While I have seen little evidence, thus far, that either

of the larger types give rise to the saccate form in nature,

yet in two small cultures I have produced a population of

from one hundred to several hundred small saccates by

the degeneration of the humped stock. In one case the

colony was a very old one and the degeneration possibly

due to this fact; in the other it was plainly the result of

diluting the culture medium with tap water. The small

saccates, even when they had dwindled to a half dozen,

456 THE AMERICAN NATURALIST [Vou XLVI

before total lapse, still bore developing embryos in their

diminutive bodies.

The typical case of relationship, however, is, plainly,

for a few generations of rapidly developing saccates to

be succeeded, after a few transitional forms, by a con-

tinuous and ever-increasing population of the humped

type.

As to the occurrence of the humped type, this is, prac-

tically, as just stated. Although never hatching from the

resting egg, it soon supplants the smaller and earlier

form and then continues to multiply, in favorable local-

ities, until put an end to by drought, rain, or the exhaus-

tion of the food supply. I do not believe that it can mul-

tiply indefinitely, however, for in even my largest aquar-

ium jars, the species invariably seems to die out after

several crescendos and decrescendos of development.

The largest cultures have lasted about five months. That

their death is not due to the accumulation of metabolic

products in the unchanged water seems probable, because

in one case a new generation hatched from resting eggs

soon after the death of the first, and showed no signs of

weakness, although growing in the same long-used

medium. |

The occurrence of the giant campanulate form is a to-

tally different matter from that of the other two types.

It never occurs alone. It never occurs in newly hatched

cultures or young stocks. It rarely occurs in great

numbers, and never does it do so, so far as I have ascer-

tained, in nature when feeding upon what may be called a

normal food. On the other hand, in old stocks that have

* This holds good under all ordinary conditions. Since the above was

written, the experiment has been made of hatching out hundreds or thousands

of resting eggs in a very small space—e. g., a three-oz. bottle, i in almost

pure tap water. The results of this experiment are very striking. aced

thus from the start almost without nutrition, a few of the more vigorous

animals begin cannibalism at once, with the result of a an early appearance

of both the humped and the campanulate types. In just what generation

they thus appear is not known, but very probably in sa second and thir

respectively, The development and saltation oceur with but few individuals,

the majority starving to death or serving for food only.

No. 548] A CASE OF POLYMORPHISM 457

become numerous, I find this giant type invariably pres-

ent. The original collection which I studied was about

typical in this respect. I have not ascertained the exact

proportion which the campanulates bear to the humped

form in any given case, for experiment shows that it is

capable of variation within wide limits; but I think that

in nature they would rarely equal one to one hundred.®

What was the relation of these two types? Weeks of

all but continuous work were necessary to decipher it.

The fact that the two types were so frequently associated

indicated probable connection, but did not demonstrate

it; the fact that the campanulate always appeared only

long after the development of the humped form was again

suspicious, but proved nothing. Isolation cultures of the

campanulates soon showed, as my mounted material had

done, that they regularly produced not only their own

type, but a considerable proportion of the humped type as

well. But the reverse process is at least so rare that I

have been as unable to find it among my living material, as

I was among that which I had mounted. Scores of isola-

tion cultures, begun with few or single individuals, fed

on diverse types of food, and nearly all very successful,

remained negative in result, with the exception of one

of my very first attempts. I was trying out the rotifer,

Hydatina, as a possible food for the humped Asplanchna,

and placed half a dozen of the ordinary type in a watch-

glass with many of the smaller rotifers. Soon, among

the young produced, there appeared one that rapidly

developed into the giant type; but subsequent trials, car-

ried on as long as this special food supply lasted, were

negative in results.

Over against these failures, however, a large number

of my mass cultures yielded at once all but conclusive

evidence that the larger type was somehow derived from

the smaller. These cultures were started as follows:

*During the recent summer one pond in which the species developed

copiously from spring to August showed at the latter period a much higher

number—about one campanulate to 20 humped.

458 THE AMERICAN NATURALIST [Vou. XLVI

From the surface of a pond several feet in depth, and at

a point several feet from the shore, a large quantity of

the humped type were collected with a small net. This

material and the entire pond, so far as my investigations

had gone at this time, had shown none of the larger form,

and the care with which the material was taken from the

surface rendered it improbable that a resting egg of the

larger form should contaminate it, the resting eggs of all

these rotifers being heavy and sinking at once.° This

material was placed in clean transparent jars of several

liters, although beside each larger culture was usually

placed a smaller one in a tall thin vessel which permitted

careful scrutiny of the entire contents with a low-power

lens. It was almost impossible to crowd the animals to

the point of injury, though perhaps every other visible

organism would die. Now in all of these crowded mass-

cultures, whether large or small, whether fed, half-fed,

or starved, the campanulate form made its appearance

within at most a week. Sometimes a single individual,

either young or fully developed, would first be discov-

ered; more frequently a number would be present before

noticed. But in every instance the sudden appearance of

the large form was followed by its very rapid multiplica-

tion, coincident with a still more rapid diminution in

numbers of the humped form. The latter were eaten up

by the former, even adults of the humped type falling

victims to the prodigious ingesting power of the campan-

ulates. This all but complete displacement, in the

course, say, of three weeks, of one form by the other,

was a striking and almost astonishing spectacle. I have

not observed it in nature, however crowded the species

becomes in its natural situation. But in my culture —

dishes it was the regular occurrence in case the individ-

uals became sufficiently numerous.

*It has later been ascertained that, F certain circumstances, some of

the resting ova may again rise and fl at; in a windy pool, however, they

would very soon be blown to the esate and age Yet the foree of the

experiments cited is reduced.

No. 548] A CASE OF POLYMORPHISM 459

The suggestion of cannibalism as the cause was thus

all but conclusive; but I was able to press the proof one

step farther. My isolation cultures, started with one or

a few individuals, invariably failing, I decided to try

cultures started with a larger number of individuals,

each one of which was first subjected to examination un-

der the microscope. 240 individuals were thus isolated

and placed in a single stender dish, care being taken to

reject any that deviated never so little from the normal

humped type, especially as to extra size. In the rapidly

multiplying culture thus started there appeared within

a week several typical campanulates, and the whole sub-

sequent course of the culture duplicated the develop-

ments which had taken place in the mass cultures already

described. This is as near as I have come to actually

observing the production, by the humped Asplanchna,

of its larger humpless congener. I have not witnessed

the birth of the one from the other or seen it in uteri.

The demonstration of fact is, however, sufficiently com-

plete, and the farther conclusion is sufficiently plain, viz.,

that the transition in this direction between the two types

is a relatively rare one. Not every humped Asplanchna

possesses the power, whether this depends upon size,

ingestive reaction or digestive capacity, to produce the

larger form. Indeed, this power would seem to reside in

but very few individuals.

As soon as I had reached even the tentative conclu-

sion that cannibalism must be the cause of this marked

heterogenesis, I set about to determine, if possible, why

this should be the case. Was there some magic in the

cannibalistic diet as such? Was it merely a case of rich

nutrition? Or was the result perhaps due to the mere

size of the ingested food organisms?

Excessive feeding with most of the usual food organ-

isms of the species was plainly without result. So long

as the Asplanchnas were relatively few or greatly out-

numbered by their food organisms they glutted them-

selves to repletion without unusual consequences in re-

460 THE AMERICAN NATURALIST [ Vou. XLVI

production. Thus in the case of one pond, an algal-

feeding Brachionus developed until it exceeded in num-

bers anything that I had ever before observed under sim-

ilar conditions. The surface water was so filled with

them that one observer pronounced it as thick as good

tomato soup. In this medium the humped Asplanchna

gorged itself during days of rapid multiplication. Every

stomach was packed with the smaller rotifers; yet no

change in type resulted. Finally the Asplanchnas liter-

ally ate up the Brachionus, but themselves disappeared

a short time after this was accomplished without having

produced any of the giants. Yet condensed material

taken from this same source and placed in large culture

dishes did produce the cannibals some time after the

Brachionus had been devoured. It follows from this in-

stance, as well as from a number of others equally con-

clusive, that mere feeding on the flesh of rotifers, so to

speak, is not sufficient to cause the change.

The same proved true of over-feeding on Paramecium

and several other protozoa that were greedily eaten.

I was the more surprised, therefore, to discover one

other food organism, and one only, so far as my observa-

tions extend, which is fully competent to bring about the

same result. It is the Daphnid-like crustacean, Moina

paradoxa. It seems almost incredible that a rotifer

should feed upon this robust entimostracan, even the

young of which are born of a size which would seem be-

yond the utmost stretch of a rotiferean stomach. More-

over, this Asplanchna does not by any means invariably

attack Moina. It may disappear, seemingly from starva-

tion, in a pond where Moina is present and rapidly mul-

tiplying. This has also happened repeatedly in my cul-

tures, and I have placed numbers of the young Moinas in

watch-glasses together with the Asplanchna without hav-

ing them eaten. Yet in other very similar cases the

young Moinas are ingested by the Asplanchnas—by the

humped form, and rarely by the larger saceates. The

very youngest Moinas may even at times be ingested by

No. 548 | A CASE OF POLYMORPHISM 461

the smaller saccates. It seems probable that the vigor

of the Asplanchna stock, and, I think, the period in the

reproductive cycle (number of generations since the rest-

ing egg), have much to do with the refusal or attack of

this oversized food organism. Be this as it may, how-

ever, the habit of eating the young Moinas, once started,

seems to rapidly become fixed in not only the individual,

but its progeny and the whole subsequent stock; although,

weeks later, perhaps, this feeding reaction may again be

lost, and the last rotifers starve to death in the presence

of abundance of young Moinas. Such starving stocks

may be again revived, when almost perished, by the sup-

ply of a smaller food organism.

Now the feeding upon this crustacean has, to all ap-

pearance, the same effect in bringing about the produc-

tion of the large campanulate type as has cannibalism. I

have not proven it with the same precision, but I have

observed the transformation of mass cultures from the

smaller to the larger type under circumstances that sug-

gested the all but certain conclusion that Moina-feeding

was the initial cause. I have also reared large numbers

of the campanulates, for weeks at a time, by using the

young Moinas as food. Under these circumstances the

humped rotifers all but disappear from the cultures. A

few always remain, because they are continually being

produced, in minor numbers, by the campanulate type.

But as very few of the humped young are able to acquire

the habit of Moina-feeding, they starve to death without

reproduction or fall victims to their mammoth progen-

itors.

In one instance, and one instance only, I have followed

the transformation of the Asplanchna to its largest type,

through Moina-feeding, in nature. The case interested

me much, being very different from any other instance

that I have followed, and showing to an astonishing de-

gree the protean possibilities of the species. As usual,

the first appearance of the species was in this instance

by scattered individuals of the saccate form. Their food

462 THE AMERICAN NATURALIST [ Vou. XLVI

consisted chiefly of Brachionus and Hydatina. These

organisms were not numerous, however, and were ex-

hausted just as the countless hordes of the young Moinas

appeared. Under these circumstances a wholesale tran-

sition to Moina-feeding occurred, even while the As-

planchna was in its earlier phases of development. The

smaller humped forms had just begun to appear when

the Moina-feeding began, both by these humped individ-

uals and by not a few of the larger saccates. The species

became for a few days indescribably chaotic. So far as

body form was concerned, transition stages could be

found between every possible type and variation. This

is the only instance in which I have found the saccate

form giving rise to the campanulate without the humped

intermediate, but it certainly did so to a considerable ~

extent in this case. The outcome of Moina-feeding in

this pond was the establishment, after about nine days,

of a new equilibrium for the species. The giant campan-

ulates had become in this instance, and this instance only,

among my observations in nature, the preponderant type,

reproducing their own form in the main, but also a few

slender, long-humped individuals. Of these latter a very

few managed to ingest the Moinas and to reproduce, while

the majority showed empty, shrunken stomachs and no

developing embryos. All traces of saccate and transi-

tional forms had disappeared.

I will note, in passing, that the campanulate form which

is produced by the Moina-feeding is not quite identical

with that procured by cannibalism. The size reached is

even a little larger, and the animals have the appearance

of being even more powerful in general musculature;

but the flaring corona never becomes quite so extreme;

the animals never assume quite the bell-like form which

the most majestic cannibals present.

(To be concluded)

HARDINESS IN SUCCESSIVE ALFALFA

GENERATIONS

L. R. WALDRON

DICKINSON, NortH DAKOTA

In 1908 Mr. Charles J. Brand, of the Department of

Agriculture, inaugurated an experiment in alfalfa to de-

termine, among other things, the relations that different

strains of alfalfa have to the cold of severe winters. The

writer aided in this investigation..

For this purpose 68 regional strains of alfalfa were

assembled from the various alfalfa regions of the world,

many of them being foreign in immediate origin. The

alfalfas were planted in hill and drill rows, and during

the season of 1908 the rows were thinned so that accurate

countings could be made. There were in the neighbor-

hood of 80 plants to each strain. The winter of 1908-09

was particularly severe to alfalfa, and as a consequence

most of the strains were sadly deleted. :

Twelve of the 68 strains were entirely killed, no living

plants remaining. Twenty-eight of the strains killed out

over 90 per cent., and over 60 per cent. of the strains

killed out over-80 per cent. There were but 3 of the 68

strains that killed out less than 10 per cent. The killing

of the American alfalfas was severe as indicated by the

fact that the 9 strains from Utah killed over 90 per cent.,

while the 3 Montana strains killed over 65 per cent.

The hardier strains were those of more recent foreign

origin. Two strains of the Grimm alfalfa had an aver-

age killing of less than 5 per cent., thus being the hardiest

im the nursery, N eglecting the 12 strains that killed out

entirely, the average killing of the nursery amounted to

17.51 per cent., using each strain as a unit.

' Charles J. Brand and L, R. Waldron, ‘‘Cold Resistance of Alfalfa and

Some Factors Influencing It,’’ Bulletin. 185, Bureau of Plant Industry,

- S. Department of Agriculture.

463

464 THE AMERICAN NATURALIST [Vou. XLVI

During the summer of 1909 the seed produced by the

living plants was saved from each strain separately. In

the spring of 1910 a sowing was made of the original seed

that had sown the first nursery, which had been desig-

nated as nursery A. This sowing was known as

series 201. In addition another sowing was made in

1910, known as series 202, from the seed collected

from nursery 4 in 1909. This sowing was from seed se-

cured from plants that had survived the severe winter of

1908-09. In addition a number of rows were sown with

seed from nursery A plants, selfed during the summer of

1909.

This second experiment, carried on by the writer, con-

sisted of a number of duplicate rows seeded (a) with seed

from original geographical sources, and (b) rows seeded

with daughter seed obtained from the plants surviving

the winter of 1908-09. These two seedings comprised

112 150-foot rows, each row containing up to 150 plants.

During the summer of 1910 the rows were thinned and

accurate countings were made. In the spring of 1911,

after growth was well started, a determination was made

of the number of dead plants, and in addition the living

plants were gauged as to their vigor, on a basis of 1 to 10,

the best plants receiving the highest markings.

The data obtained indicated the apparent increase of

hardiness among the different strains. A possible

source of error was the effect of vicinism in nursery 4

in producing hardiness in the progeny plants constitut-

ing series 202. Limited space prevents presenting the

evidence which would lead one to think that this error

was slight in effect and probably nearly negligible.

Only a brief summary of the results can be presented

in this article, a detailed account of which must be left

to a future publication. In the first place, let us regard

the comparative results of the winters of 1908-09 and

1910-11 upon the strains in nursery A, and upon those

of series 201. These two sowings were from the same

lot of seed, and had they been representative samples one 2 —

No. 548] HARDINESS IN ALFALFA 465

would have expected that they would have fared rela-

tively the same in the two winters. Deviations that

might appear could be charged to the differences of the

two winters, as we may suppose that alfalfa becomes ac-

climated in different ways to different types of cold.

The relation of the killing of the plants in nursery A

and in series 201 is presented in the correlation table of

Means of Duplicate Strains, 1910—11

11 16 21 26 31 36 41 46 51 56 61 66 71

15 20 25 30 35 40 45 50 55 60 65 70 75

Means of Original Strains, 1908—09.

(S)

—

a 1 Lt

OOrRONWD RN ENR RE RR ORF CONF

O45 0° 8h SAS 2 Ss 2 a Be

Fig. 1. Correlation of the means of various strains of alfalfa. Original

nursery A seeding subject, duplicate of thes strains in 201 series relative.

Coefficient of correlation, + 0.62 +0.06. Standard deviation ‘of Y, 24.85 + 1.57.

Standard deviation of X, 19.62 + 1.24.

Fig. 1. The means of nursery A are the average per

cents. of killing for the different strains, and the means

of the duplicate seeding, series 201, are the correspond-

ing per cents. for that nursery. In the table, the nursery

A means appear as subject, and the means of series 201

appear as relative. The table shows good correlation

amounting to + 0.62 + 0.06, thus indicating that the two

series of alfalfa were affected relatively the same by the

two winters. This fact is perhaps more strikingly shown

when the two series of means are platted on coordinate

466 THE AMERICAN NATURALIST [Vou. XLVI

paper. The ups and downs of one series correspond

very closely with the ups and downs of the other series.

The mean killing of series 201 was 27.43 + 1.75 per cent.

as against 77.51 + 2.21 per cent. in nursery A, indicating

that the second winter was the milder one.

The relation between the killing experienced by series

201 and series 202, during the 1910-11 winter, is ex-

pressed by the correlation table of Fig. 2. In this case

the 201 series is subject and the 202 series is relative.

The mean of the 202 series amounts to 6.43 + 0.66. The

correlation in the table amounts to + 0.46 += 0.07. As

Means of 202 Series

ELCIO (230-96

0 31

5 10 15 20 25 30 365

O° S16 ¢ 7 9

6 1018 1 4

1558.6 9

$16 20| 2 1- i 4

B21 25| 2 13 5

226 30| 2 3

Sal 35|3 J 4

> S 36 40 1 1-1 3

646 50|1 1 1 114

è 51 55 1: í 1 3

= 56 60 1 1 2

61 Gi i 1 3

66 70 0

71 75 1 1

24 7 1 1 56

Fig. 2. Correlation of the means of various strains of alfalfa. Duplicate

seeding of nursery A (series 201) subject, progeny of the hardy plants of nur-

sery A (series 202) relative. Coefficient of correlation, + 0.46 = 0:07. Standard

deviation of Y, 19.62+1.24. Standard deviation of X, 7.35 = 0.46.

indicated by the means of the two series, 27.43 and 6.43,

there was a remarkable apparent increase in hardiness.

This is partially expressed in the correlation table, but

in the table the most pronounced changes do not work

for a strong correlation.

For instance, one Utah strain killed out 59.6 per cent.

in the 201 series, while its offspring killed but 6.2 per

cent. in the 202 series. This indicates a weak correlation

but a great increase in hardiness. There were but 3

instances of the 202 series killing more severely than the

No. 548] HARDINESS IN ALFALFA 467

901 series. Two of these instances were Turkestan al-

falfas. The third one was due to the fact that the 202

row was an outer row, thus not afforded protection by

an adjacent row.

In our theoretical discussion of the data we can

scarcely more than present the problem. Within the

limits of the pure Medicago sativa, as pure as it exists

to-day, the fact is patent that there is a wide range of

diversity in hardiness among the different strains of

alfalfa, dependent in greatest measure upon their geo-

graphical origin. Strains of Medicago sativa that have

been grown for long periods in cold climates, e. g., Mon-

golian alfalfas, are found to be hardy during the severe

winters of this country. Upon the other hand the strains

of this species which have been grown for long periods in

hot countries, e. g., Arabia and Peru, were found to be

exceedingly tender in cold districts. Thus at Dickinson,

North Dakota, it has never been possible to bring alive

through the winter a single plant of the Arabian alfalfas,

and only under exceptionally favorable conditions has it

been possible to winter any of the Peruvian alfalfa

plants.

The diversity is so great between the Arabian and the

Mongolian alfalfas that we must consider that hardiness

has actually been added to the alfalfas which have become *

hardy, or that hardiness has been lost to alfalfas that

have become tender.2 It is not unlikely that changes

have been brought about in both directions. The simple

problem is, has this change come about through the

“law of ancestral inheritance,” or must the change be

accounted for by distinct mutations occurring within any

particular strain of alfalfa? Or is it possible that

changes have come about through conformity to both

methods?

*The fact is not lost sight of that an increase of hardiness may possibly

be brought about by a recombination of certain (at present unknown)

morphological characters physically responsible in different ways for the

‘Presumably complex character of hardiness. See Nilsson-Ehle, ‘*Kreuzungs-

untersuchungen,’? Lunds Univ. Ars., Bd. 5, Nr. 2, p. 114. Also a forth-

coming article by the writer in the American Breeders’ Magazine.

468 THE AMERICAN NATURALIST [ Vou. XLVI

The belief that any strain of alfalfa is made up of

many substrains with various steps of hardiness has

been arrived at largely by a priori methods. We find

that there are distinct morphological types of alfalfa

within a strain which breed true, and that with other

plants there are physiological types within any strain or

variety likewise breeding true. It is reasonable to sup-

pose that the same is true in regard to hardiness in al-

falfa.

One of the Utah strains of the 201 series killed 42.8 per

cent. from a total of 76 plants, and at the same time this

strain of the 202 series sown from seed secured from

three mother plants killed but 3.5 per cent. from a total

of 131 plants. We have established at once a compara-

tively hardy alfalfa from one quite tender. With this

Utah alfalfa, as with several others, it is difficult to avoid

the conclusions that the strain is made up of many bio-

types, relative to hardiness, which show their indepen-

dent character even when no precaution is taken against

interbreeding

We have also experimental evidence upon this point.

Alfalfas that were selfed in 1909 were from both hardy

and tender strains of alfalfa. A selfed Mexican plant

had progeny that showed absolute hardiness during the

winter of 1910-11, while the mother strain killed 24.5

per cent. Others of the selfed alfalfas acted in the same

manner, producing offspring behaving radically differ-

ent from the behavior of the parent strain. In some

cases progenitors of non-hardy strains were selected from

hardy strains.

It seems likely then that any regional strain of alfalfa

as far as hardiness is concerned, is made up of biotypes

with different cold resistant qualities. An alfalfa of

this nature when moved to a colder region loses the rep-

resentatives of the tender biotypes leaving the hardy

ones for propagation. But this explanation accounts in

no measure for the absolute changes of hardiness which

some alfalfas must have undergone to have allowed the

No. 548] HARDINESS IN ALFALFA 469

species to accommodate itself to extreme climatic con-

ditions.

While it is evident that there are alfalfas in existence

to-day which do not contain elements of hardiness suffi-

cient to allow them to live through the severer winters

of the United States, this statement apparently does not

hold for the alfalfas that are grown in the New World,

with the exception perhaps of the alfalfa known as the

Peruvian.’

Inasmuch as the South American alfalfas grown in

hot regions contain elements capable of surviving very

severe winters, it is apparently not necessary to assume

recent mutative periods in the species. Inasmuch as

the alfalfa plant grown in the New World contains ele-

ments of hardiness allowing it to persist through periods

of severe cold, it is reasonable to assume that this ele-

ment of extreme hardiness may be dissociated from the

elements of lesser hardiness, even in the tenderest

strains, in such a manner that it can be carried from

generation to generation. This practical result has not

yet been attained, not because such a result is theoret-

ically impossible, but because no systematic attempt has

been made. It is evidently a saner thing to commence

practical breeding with those forms nearest to the one

desired.

* Charles J. Brand, ‘‘ Peruvian Alfalfa,’’ Bulletin 118, Bureau of Plant

Industry, U. S. Department of Agriculture. The Peruvian alfalfa is con-

sidered varietally distinct. This and the Arabian alfalfa have not as yet

been found to possess elements capable of amelioration to the»severe con-

ditions of the north. Whether these two forms are retrograde mutants

derived from the old alfalfa stock is pasillo to determine at this time.

One would be inclined to believe that such is the case.

The historically and long-continued growth of. alfalfa in hot régions

almost precludes the hypothesis of the loss of cold-resisting biotypes, which

would obtain were the alfalfa strain transferred to a hotter region.

SOME FEATURES OF ORNAMENTATION IN

FRESH-WATER FISHES

HENRY W. FOWLER

THE ACADEMY OF NATURAL SCIENCES OF PHILADELPHIA.

Tue fishes known as the minnows (Cyprinide) and

suckers (Catostomide) are familiar types to almost

everybody. Certain of them during the spawning-season

exhibit peculiar dermal excrescences or tubercles, these

often rendering their appearance quite striking if con-

trasted with that of other seasons. These tubercles have

long been known in many forms, though they do not seem

to have been elaborately studied in connection with the

relationships of the various groups in which they appear.

Considerable difficulty may be encountered by those wish-

ing to make studies of them, not only as they are seasonal

and the fishes often difficult to secure at the required

time, but also as they crumble and rub or drop off in al-

coholic preparations, sometimes not even leaving the

usual scars. It is hardly possible to arrange the dis-

tribution of the tubercles into distinctive groups of sig-

nificance. Perhaps when enlarged and few in number on

the head they contrast strongly with other cases, such as

when very numerous and universally distributed. It

may also be added that in a great many of the fishes be-

longing to the families under consideration no tubercles

appear at any season, and this is often generic as well

as specific.

As now understood the minnows embrace the largest

family in ichthyology, having about 210 genera and 1,500

species in North America, Europe, Asia and Africa.

They are mostly fishes of great similarity, small in size,

weak, and among the most difficult in which to distinguish

species. In this respect our local forms are very fre-

quently no exception. Passing over the different genera

470

No. 548 |

ORNAMENTATION IN FISHES

EXPLANATION OF PLATE

The figures are merely outlines, showin

All are drawn with the accompaning

a Campostoma anomalum

g Chrosomus erythrogaster.

- Pim es promelas

. Not:

io otropis whipplii ponpe E RE,

ma Notropis cornutus.

Notropis chalybæus.

Oycleptus pin, beg

. Moxostoma macro

g the ac aon of the tubercles.

line representing

agra ce

Rhinichthys atronasus.

ybopsis kentuckiensis

472 THE AMERICAN NATURALIST [Vou. XLVI

and species from the Middle States region it has been

“my opportunity to study in the present connection, the

following conditions are found.

The stone roller (Campostoma anomalum) occurs in

the Mississippi Valley. In spring or early summer the

adult males sometimes have the entire upper surface of

the head and body covered with small tubercles, though

on the fins I have only found them extending on the rudi-

mentary dorsal rays.. Though mostly attended with higk

coloration, red being more or less conspicuous at most of

the bases of the fins, this is not always the case. Others

were found full of spawn, without tubercles, but in high

color.

The red-bellied dace (Chrosomus erythrogaster) is one

of the most brilliant of all our common freshwater fishes,

occurring mostly west of the Alleghanies. The adult

spawning male has the entire head and body almost

everywhere covered with minute tubercles in the greatest

profusion. No females with tubercles have been secured.

The fat-heads (Pimephales promelas and P. notatus)

are remarkable for their black heads, in the case of

spring males, besides having only a few large conspicuous

tubercles on the muzzle. The former species occurs only

west of the Alleghanies while the latter is found in all the

river-basins of Pennsylvania. The tuberculate males

seem to be the exception, or of short duration in that

condition, as among hundreds of examples of the latter

but few were found.

The fall fish (Semotilus bullaris) and creek chub (5S.

atromaculatus) are two well-known fishes. The former

occurs only east of the Alleghanies, and the fully adult

male is with brilliant rosy sides and mostly rosy fins.

Though reaching a length of nearly two feet, examples

three inches long have been taken with fully developed

eggs. The only tuberculated examples were all over a

foot in length, and had only their muzzles densely

covered with small tubercles. No nests were ever found

made by the small fish of three or four inches in length.

No. 548] ORNAMENTATION IN FISHES 473

The nests discovered were attended only by large fish.

The creek chub occurs in most all our mountain brooks,

and reaches a maximum length of ten inches, though

males five inches long have tubercles. These tubercles

are féw, but quite conspicuous, and occur usually as a

pair over each eye and one in front of the latter. Large

examples have the scales on the hind part of the back

thickened, or but slightly tubereulated. No tuberculated

females of either species were secured.

The true dace (Leuciscus elongatus and L. vandoi-

sulus) are represented by the former in streams west of

the Alleghanies and by the latter in streams east of the

Alleghanies. In both species the spring males have

crimson sides and the top of the head minutely, but incon-

spicuously, tuberculate. In the eastern species occasion.

ally a female will be found with tubercles on its head

above, and also similar brilliant coloration to that of the

male.

A few species of shiners (Notropis) present cases of

tuberculated males. The silver fin (N. whipplii analo-

stanus) of our eastern streams has the body and basal

Portions of the fin-rays largely covered with small

tubercles in the adult male. The adult female is occa-

sionally tuberculate. . The red fin (N. cornutus), found

in almost all of our streams, has the adult male very

gaudy in spring, its tubercles appearing very conspicu-

ously on the muzzle, front and predorsal region. Occa-

sionally a tuberculatefemaleisfound. Intheiron-colored:

shiner (N. chalybeus), often brilliant in the spring, the

males sometimes have the muzzle, front and predorsal

with many rather large tubercles. No females with

tubercles were found.

The male of the long-nosed dace (Rhinichthys cata-

racte) when fully adult has its snout, top of head, entire

back and rudimentary dorsal rays minutely tuberculate

in the spring, The adult male of the black-nosed dace

(R. atronasus), one of our most abundant fishes, has the

front and predorsal region minutely tuberculate in spring

474 THE AMERICAN NATURALIST [Vov. XLVI

and early summer. No tuberculate females of either

species have been found.

The crested chub (Hybopsis kentuckiensis) is remark-

able for the adipose-like frontal crest of the adult male in

the spring, somewhat suggestive of the hooded seal.

This species reaches ten inches in length, and examples

half that size were taken with tuberculate muzzles, though

without the crest.

The suckers are represented by 14 genera and about

77 species, mostly in North America, though several occur

in eastern Asia. The following notes will show the con-

ditions in those I have examined.

The carp-suckers (Carpiodes) occur in our waters

mostly west of the Alleghanies. In several species (C.

difformis, C. velifer and C. cutisanserinus) all have

tuberculated muzzles or snouts in the spring males. In

fact the last of these was so named by Cope for the

fanciful resemblance of this very character to ‘‘goose-

flesh.’’

The black horse (Cycleptus elongatus) has the body

finely tuberculated over its entire upper surface in the

spring. The upper surfaces of the paired fins are also

tuberculated. Only large or old examples were

examined.

Our common fine-scaled sucker (Catostomus commer-

sonnii) is the only one of its genus east of the Alleghanies

I have found tuberculate. It occurs all over our Middle

Atlantic States. The tubercles appear within a very

great range of age. Examples three inches long were

found with well developed milt and roe, like those nearly

two feet in length. The smallest examples with

tubercles, which were only on the lower caudal peduncle

surface, lower caudal lobe and anal fin, were four inches

long. Others, nearly of the maximum size attained by

the species, were found with exactly the same arrange-

ment of the tubercles. Examples with the entire upper

surface of the body and head, besides the dorsal and

paired fins tuberculated, were always over a foot in

No. 548] ORNAMENTATION IN FISHES 475

length, though seldom more. Further, I have every rea-

son to believe these small fish were also spawning with

the large ones, as I captured specimens of similar dis-

parity in the same waters in the spawning-season. That

many males spawn without ornamentation also appears

likely. No tuberculated females were found.

The chub sucker (EHrimyzon sucetta oblongus) has

quite pronounced sexual differences, the spring males

showing usually three large tubercles on each side of the

snout, the anal rays tuberculated, and usually the last

rays more or less incised. These characters only appear

in males over five inches, and until the maximum size

(eleven inches) is obtained.

The red horse (Moxostoma), with its numerous species,

often exhibits the anal fin tuberculated (M. macrolepi-

dotum). I have not obtained recent material, however,

for these studies.

In conclusion the following may be stated.

First. The disposition of the tubercles in the orna-

mentation of breeding males is not always complete in

the known design sometimes attained by certain in-

dividuals.

Second. The development of the tubercles may obtain

in comparatively small or young individuals provided

they are sexually mature. Tubercles occur, so far as I

have observed, in the very young, especially in those

species which undergo considerable transformation in

certain apparent generalized characters, such as the

development of the lateral line, change in coloration from

ii or spotted color-pattern to a more uniform tint,

ete,

Third. The tubercles are subject to individual char-

acteristics in being retained or lost for a greater or

shorter period after the spawning season.

Fourth. The adult male alone in most species exhibits

the tubercles, and though occasionally also present in the

female of some species the latter seldom assumes equal

evelopment in other respects, such as bright pigment,

476 "THE AMERICAN NATURALIST [Vou. XLVI

Fifth. Sexually mature fishes spawn without the

tubercles appearing, and in some cases frequently.

Sixth. The effect of different waters, like those of the

sluggish warm lowland cedar-swamps where dark and

blackish, as contrasted with clear cold rapid upland

streams, does not seem to materially change the degree

of development.

Seventh. Many species have the inner pectoral rays

furnished with tubercles, and these no doubt are of

assistance to the males in clasping the females during the

spawning operations.!

t For the spawning in detail of some species see Reighard, in Science,

XVII, April 3, 1903, p. 531, and Bull. Bur. Fisheries, XXVIII, 1908, pp.

1111-1136, Pls. 94-120.

THE FORMATION OF CONDENSED CORRELA-

TION TABLES WHEN THE NUMBER OF

COMBINATIONS IS LARGE

DR. J. ARTHUR HARRIS

CARNEGIE INSTITUTION OF WASHINGTON

AFTER the principles of any method of research are

laid down by those who have the genius or the good for-

tune to make fundamentally new contributions, there

always remains much to be done in the refinement, simpli-

fication, or adaptation of methods to render them most

practically applicable in the routine of investigation.

This is especially. true in the modern higher statistics,

where, at the very best, the labor is excessive.

One of the most onerous of the statistical processes is

the determination of correlation in cases in which each

individual measurement must be weighted by comparison

with a series of others. In an earlier number of this

journal! a method was described for the rapid formation

of the heavy intra-class and inter-class? correlation and

contingency surfaces by the use of a machine permitting

simultaneous multiplication and summation. Methods

of dealing with such correlations without the formation

of tables will be published later. But abstract formule

in the hands of inexperienced calculators are apt to lead

to erroneous constants, which in the absence of the orig-

inal data can never be corrected. Again, the validity of

the correlation coefficient as a measure of interdepend-

ence depends largely upon linearity of regression. Hence,

tables should be given whenever possible. The purpose

of this note is to show how, in the case of relationships

***On the Formation of Correlation and Contingency Tables when the

aa of Combinations is Large,’ AMER. Nat., Vol. 45, pp. 566-571,

* These terms will be clear from their context in this note; they will be

more precisely defined later.

477

478 THE AMERICAN NATURALIST [ Vou. XLVI

involving a very large number of combinations, the chief

advantages of the correlation (but not the contingency)

surface may be even more easily realized than in the

method already described.

By condensed correlation tables are to be understood

those giving the (weighted) frequencies for a first char-

acter x and the first (and where necessary also the sec-

ond) rough moment about 0 as origin of the associated

array of the y character.? From such a tablet r may be

quickly obtained® and the means of arrays calculated for

linearity of regression tests.

In principle, the formation of these reduced tables is

very simple. Let x, y, 2, ---, be measures on the indi-

viduals of the same or associated classes. Let there be

n, P, q, ***, of these individuals. Then if n, p, q, =, I(x),

=(y’), =(2), ee z(a"), 3(y”*), 3(2°), ae (where 3 indi-

cates a summation within the class and the dashes indi-

cate that the measures are to be regarded as deviations

from 0) be again summed for each of the component

measures, seriated by grades, the four columns—grade

of ‘‘first individual,” weighted frequency, and the two

rough moments about 0 for associated individuals—thus

secured for each character either constitute the desired -

table or one from which it may be easily derived.

The arithmetical routine will be determined largely by

the nature of the records. Roughly, two cases are possi-

ble: n, p, q, ---, are small, m is small or large; n, p, q,°*")

are large, m is small, m being the number of classes or

groups of classes.

Suppose n, p, q, ---, small, say 4-20. The best method

*In direct intra-elass correlations z and y are measures of the same kind;

in ¢ross intra-class correlations de are different; in inter-class relation-

ships they may be the same or differ

*For example, Table X of Bonne, Vol. 8, p. 61, gx or Table II

nec ales Table I of the Amer. Nart., Vol. 44, p. 695, 1

The Arithmetie of the Product Moment we pater fot the Coeff-

desk a Correlation,’?” AMER. NAT., Vol. 44, pp. 699, 0.

€ Cases where both the numbers within n clea ae the number of classes

are large are very rare because of the great labor required in making the

observations.

No.548] CONDENSED CORRELATION TABLES 479

is to write the values of the first character under consid-

eration—designated for convenience as the subject—

down the side of a separate sheet for each class. Oppo-

site each entry is then written n, 3(a’) and 3(2”*), p, 3(y’)

and 3(4”), q, 3(2’) and 3(z2’") and so on, according to the

relationships desired. Thus, the measure used as the

_ subject and the number and summed first and second

powers of deviation of the individuals of the relative

array may be for the same or different characters or

classes, depending on whether direct or cross, intra-class

or inter-class correlation is to be computed. In any case,

the number and moments are only once determined for

each class—their repeated entry on the sheet is merely

rapid clerical work.

This done, the sheets are clipped into strips by subject

entries, the strips seriated according to the subject, and

the class numbers and moments summed for éach grade

on the machine.

For inter-class correlations, the resulting table is cor-

rect, embracing as it does, say, S(pq) entries. For intra-

class relationships, say for x, the entries are too high by

S(n), S(x) and S(x?) since it comprises S(n*) entries

when only Sn(n—1) are desired. Hence, the actual fre-

quency for each subject grade must be subtracted from

the weighted frequency, and the products of the actual

frequency by the grade and by the square of the grade

must be deducted from the first and second summed

moment column, respectively.

When the number of individuals per class, n, p, q, 18

large (e. g., 25 or over) another procedure is desirable.

The classes of the subject character are seriated (in

transverse rows) in a table of vertical columns captioned ©

by the grades. Opposite each row is entered n, =(«’) and

3(a"), p, 3(y') and 3(y”), q, 3(2) and 3(2”), +, for all

characters to be correlated. The associated (weighted)

values for each subject grade are quickly gathered by

multiplying up and summing simultaneously the fre-

480 THE AMERICAN NATURALIST [Vou. XLVI

quencies in each column of the subject seriations by the

opposed entries in the relative (number and summation)

columns. Again, the result is the desired table or one

from which it may be derived.

Illustrations will make the methods most clear. Table

I shows the frequencies for the different grades of radial

asymmetry’ of quinquilocular fruits gathered from 34

individuals of Hibiscus Syriacus in the Missouri Botan-

ical Garden in the fall of 1907. Table II gives the seria-

tions for the locular composition’ of the same fruits.

The last two columns of Table I and the next to the last

two of Table II give the first two summations for each

individual.®

radial asymmetry is at standard deviation of the number of ovules

per a. about the mean number ee ovules per fruit. See Biometrika,

Vol. 7, pp. 476-479, 1910, an “fall dise

At the head of this table the soctislaata z asymmetry are for condensa-

tion en to only two places. In all the calculations, however, they have

used to six places. Their values and their true squares as ‘ased in the

eee e are:

Asymmetry a a?

00 .00

400000 .16

489897 .24

632455 .40

748331 56

800000 64

427 .80

979795 .96

1.019803 1.04

1.095445 1.20

1.166190 1.36

000 1.44

1.264911 1.60

1.356466 1.84

1.600000 2.56

* Expressed here simply as the number of locules per i an ‘‘odd”

number of ovules. Cf. Biometrika, Vol. 7, pp. 483-487, ae

°” The last two columns of Table II give the peal Pe of Table I for.

convenience in determining the cross intra-class tables. When the cross —

intra-class tables are to be formed with asymmetry as the subject the

=(c’) and Z(e”) column may be added to Table I. Here it is omitted for

convenience in publication.

481

CONDENSED CORRELATION TABLES

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TABLE

SERIATIONS AND SUMMATIONS FOR LOCULAR COMPOSITION BY INDIVIDUALS

m Locular Composition—Number of

È “ Odd” Locules per Fruit N Le) | 2°) S(a') 3(a’)

0 I 2 3 4 5

Pree | oe tos ee OE 99 | 168 | 466 44.540951 | 28.24

2 196 (25 £184 GS 99 | 131 | 351 91.411571 | 17.28

3 | 46| 361i ii 99 77 F Mi 24.561697 | 12.16

4 | 67 | 30 D e ak 87 42 60 15.792043 7.38

oO 10 | 241-83 124-2 1 224 | 654 50.586565 | 31.76

6-1 98-18) 48 | 24 11-13 | 106: {220° | 612 51.819299 | 32.00

T Vth St o 1i 2) 200. 1.7102. | 250 25.580710 | 12.80

e 130191 Sh 22 37 124 9 225 | 691 45.621836 | 26.32

O i a (811 47) 29 1 3.402 | 191 | 533 50.105424 | 31.04

O era e elor 7 = 4 10s 131. | Bt 40.556715 | 24.64

Horer ar 7r a 101 | 104 40 46.631638 | 27.92

12 EINI 2s) oot 0 99 | 199 | 521 51.558133 | 31.44

13° Sn r24] 971 0l 3.9 97 118 84 34.471473 | 20.40

14 | 59| 33 ta ee 97 44 58 15.792043 6.64

15 9) l9 r242: 8| å 98 | 211 | 599 50.254513 | 33.44

ie HAS Sab Te fed od | 99 96 02 27.941002 | 14.64

1 St eo on ie Fa | 100 168 | 427 34.791567 | 19.28

18 50 b-26 ta eB oe 99 TI 15148 24.159111 3.04

Io 266 Ist oR TI le 99 55 | 113 17.750439 9.36

W 72 | 21 |B 1 bee te oo 38 66 12.719177 6.24

I Ae 87 to &} 45 4-100 4106 |= 250 30.618961 | 17.76

22 Al | 38} 907 16 | 4i 3 | 100 | 132 | 368 29.498695 | 16.00

B34 Sa 355) 641 12 Sr e 100. | DO 988 33.917659 | 19.04

m 1 32 1 10-) 28 | a7 6 | 8 99 | 150 | 410 39.675350 A4

D EAT 136) 28 bd | 5b - 101} 160 + 8798 44.876305 | 25.28

26 | 26 231 14'|°10 | 3 98 | 165 | 475 37.794451 | 22.16

2 be | 31 1. 10 | Be ik = 00 57 89 20.164872 9.76

28. |38 1 30| i i 100 97 42 287 29.402270 | 14.80

29 & | 27 |31 20| 16 96 | 189 | 491 52.288755 | 32.56

30 | 44 | 975-4 O12 98 96 | 216 31.425564 | 18.72

st U1 IA | SF) 44 19] 5 | 100 | 231 | 717 49.34444 30.16

oe | 28 | 33 | 24 Ie 4] 3 | T10 | 138 | 32 41.749890 | 26.24

ss 80 1-26) 17 1-441 5T 157 | 475 42.901029 | 29.04

34 tI 251 2 t2119: 1 1 10 | 227 | 6590 52.456526 | 31.84

TABLE III

LOCULAR COMPOSITION

0 1 2 3 4 5

i ios — ae a S 49

.400000 - — 30 ee = 187 —

.489897 2i ai 420 | 306 — -=

D .632455 neo ion we l i a

3 748331 —— — 179 Gi —

z] .800000 45| 101 e an 12 4

E .894427 — se es es 1| —

2 .979795 14 12 = 5 2

Be 1.019803 ae ak 6 1i —— a

= 1.09544. —— — T 1 — —

E 1.166190 a 8 ioe a

m 1.2 = eto oal

1.264911 o 1 a a e rae

1.356466 — how 1 1 ae pai

1 + nes ies pee ae a

Totals, 1,098 | 886 | 688 | 461 | 205 55

483

CONDENSED CORRELATION TABLES

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484

THE AMERICAN NATURALIST

class tables.?°

The columns under ‘‘

(Vot XLVI

From I and II, the machine quickly compiles four work-

ing tables—a direct intra-class for asymmetry, a and

another for locular composition, c, and two cross intra-

gross values’’

TABLE VI

ASYMMETRY AND LOCULAR COMPOSITION

Gross Values Values to be Deducted | Working Table

.00 | 108,324 | 117,335 288,699 | 1,087 245 | 1,225 | 107,237 | 117,090 | 287,474

Al 91,608 | 127,391 332,887 1 141/8 | 3,122 90,691 | 125,913 329,1

.48 72,52 117,550 318,254 726 | 1,758 | 4,434 1,8 ,792 13,820

.63 18,427 | 30,358 81,952 1 7 1,291 18,243 | 29,879 ,661

.74 20,879 36,577 100,993 209 | 448 9 20,67 36,129 100,007

.80 16,162 26,180 70,5 162 169 393 16,000 26,011 70,167

.8 nri 54 18,09 38|: 4 53 3:10 ,508 18,040

.97 3,2 5,014 13,422 833 42 142 8,252 4,972 13,280

1.01 1,707 3,040 8,460 ITA 45 123 1,690 2,995 337

1.09 19 379 1,06 2 | 5 13 195 37 1,052

1.16 910 ,600 A 9 19 41 901 1,581 4,365

1.20 503 | 1,024 2,954 H s 5 98| 1,019 2,949

1.26 102 191 523 $ | 1 1 101 190 522

1.35 196 422 1,198 2 | 5 13 194 417 1,185

1.60 | 103 131 5 1 | 0 0 102 131 311

338, 719 | 473,741 | 1,243,777 | 3,393

4, 740 | 12, 442| 335,326 | 469,001 ti, 231,335

fal 990,949 | FUTVA o

TABLE VII

LOCULAR COMPOSITION AND LOCULAR COMPOSITION

‘Los. | Gross Values Values to be Deducted Working Table

Comp.

| n | Total c’ Total «°? n | Total c’ Total e? n Total c’ Total r:

| | ewer

0 109,418 | 117,758 288,576 | 1,098 | 0,000 | 0,000 | 108,320 117,758 288,576

1 448 | 118,815 305,713 886 886| 87,562 | 117, 929 304,827

2 TOTA 111,775 302,47 688 | 1,376 | 2,752| 68,079 110,399 ,

a 46,075 78,15 213,853 461 | 1,383 | 4,149) 45,614 76,768 209,704

4 20,521 37,538 105,540 205 0 | 3,280} 20,316 36,718 102,260

5 | 5490| 9704|) 27620) 55| 275| 1375| 5435| 9,429| 26,245

338,719 | 473,741 | 1,243,777 | 3,393 | 4,740 (12,442 | 335,326 | 469,001 | 1,231,385.

Tables IV-VII give the results.

p=q, a total S(p?) =S(q?) =S(pq) entries, whereas in

S{p(p—1)1 =

S{q(q—1)], and in the cross intra-class Sipit

the direct

intra-class

relationships

ee are desired.

r the relationship between radial asymmetry and locular compe

These contain, S

sition, ay other for the correlation between locular composition and

asymmetry.

he same end result, and Beas one need

be found unless the linearity of both regressions is to be t :

Of course, both give

since

No.548] CONDENSED CORRELATION TABLES 485

From these gross values must be deducted, therefore,

the actual frequency for each grade of the subject and the

product of the frequency by the first and second power

of the grade in the case of direct intra-class correlation,

or the frequency of the grade and the sum of the first and

second powers of the values of the relative character in

the same fruit in the cross intra-class correlation. Data

for these are given in the table showing the correlation

-for asymmetry and locular composition of the same fruit,

Table III. The second set of three columns in Tables

IV-VII gives the quantities so calculated from Table ILI

to be deducted. The final three columns are in each case

the working tables.

The first and second moments for the (weighted) popu-

lation A and o are given by the totals of the two final

columns. Or those for the subject character may be cal-

culated (and a check for the accuracy of the totals

secured) from the grade of the subject and the weighted

frequency column."

From our working tables, indicating by S a summation

from our final tables, we determine by the methods of

Amer. Nar., Vol. 45, pp. 693-699, 1910, these values:

| For Asymmetry

S(a’) =121,938.5928, Aa= .363642,

S(a’?) = 71,692.2400, ==.285093.

For Locular Composition

S(c’) = 469,001, Ac==1.398642,

S(e”) == 1,231,335, Oc = 1.309906.

For Asymmetry and Locular Composition

Table IV, S(a,/a.’)—= 48,818.9505, r= .1637,

Table VI, S(a,/c.’) =192,072.3309,'* r= .1716,

Table V, S(c,’a9’) =192,072.3308,” r= .1716,

* Of course in pfactise, the second population moment may be calculated

by S[(n—1)2(2")], S[(p—1) 29], S{(q—1)2(2")],.-., thus

obviating the labor of forming the third columns, which are included here

for completeness of illustration merely.

"The difference of .0001 is due to the necessity of lopping off the last

two places of the six decimals in the asymmetry coefficient in the one case

while they can be retained in the other. Of course, it is of no practical

Significance.

486 THE AMERICAN NATURALIST [ Von. XLVI

Table VII, S(c,’co’) =763,048.0000, r—.1861.

While primarily illustrations of method, these results,

if they are substantiated by further work, seem to me of

considerable biological interest. They show not only that

individuals of H. Syriacus differ in the radial asymmetry

and in the locular composition of their fruits, but that

when an individual bears fruits above the average

asymmetry, it also produces fruits above the average in

number of ‘‘odd’’ locules. Apparently, this cross corre-

lation is as high as either of the direct correlations.

Two biological interpretations are possible. (a) The

production of radially symmetrical ovaries and those

with a high number of odd locules depends upon the same

morphogenetic tendencies of the primordia,!* which give

rise to the fruit. (b) There is in Hibiscus an intra-indi-

vidual selective elimination similar to that demonstrated

in Staphylea, the intensity of which differs from indi-

vidual to individual in such a way as to bring about

(statistical) correlation for characters originally uncor-

related.

The discussion of these points falls outside the scope

of the present note where the data serve merely as a

random illustration of a very rapid method of carrying

out the routine of a widely applicable statistical pronti

COLD SPRING HARBOR,

April 25, 1912

3 In the individual fruit radial asymmetry and locular composition are

necessarily associated (cf. Biometrika, Vol. 7, pp. 491-493, 1910). In

Staphylea, correlations of r==.22 to r==.33 have been noted. Table III

be gives r= .527 for asymmetry and locular composition of the same

coer in all these relationships Re is not linear, and the corre-

lations abe be interpreted with cautio

“ Biometrika, Vol. 7, pp. 452-504, 1910; Science, N. S., Vol. 32, pp. 519-

528, 1910; gje Na f. Ind. Abst. u. Vererbung, Vol. 5, Pn. 273-288, 1911;

Pop. Sci. Mo. Vol. 78, pp. 534-537,

SHORTER ARTICLES AND DISCUSSION

PRODUCTION OF PURE HOMOZYGOTIC ORGANISMS

FROM HETEROZYGOTES BY SELF-FERTILIZATION

Has any one worked out formule for determining the rate at

which organisms become homozygotie through continued self-

fertilization? The problem is of interest in various connections,

but principally perhaps with relation to the ‘‘pure line’’ work.

Johannsen worked, for example, with self-fertilizing beans that

are held to be homozygotie in all respects. I have often heard

the questions raised: How probable is it that such plants really

are homozygotic? Is it indeed possible that they have reached

a purely homozygotice condition?

I have not come across a working out of this matter, and

finding it necessary to deal with the problem in connection with

studies of inheritance in Paramecium, it will perhaps be useful

if I put on record the results.

The principles which underlie the matter are the following:

(1) In self-fertilized organisms, all characteristics that become

once homozygotic, remain homozygotic forever after, since there

is no method in self-fertilization of introducing a gamete that

is diverse in this respect; (2) characteristics heterozygotically

represented become homozygotie in a certain proportion of the

offspring. - The problem becomes essentially this: in what pro-

portion do the heterozygotie characters become homozygotic, and

how great a proportion of all the organisms will therefore have

become thus homozygotic after a given number of self-fertiliza-

tions ?

Suppose that we begin with an organism in which all separable

characters are heterozygotically represented.

1. Consider first a single pair of such alternative characters,

which we may call { = The gametes produced will be A, a,

*At the moment of receiving the proof of this note I receive also the

masterly paper of East and Hayes (‘‘Heterozygosis in Evolution, and in

Plant Breeding,’’ Bulletin 243, Bureau of Plant Industry, June 5, 1912),

in which this matter is dealt with and a general formula given. ‘‘The

487

488 THE AMERICAN NATURALIST [VoL. XLVI

A, and a, and when these combine in all possible ways, they give

zygotes AA + Aa 4- aA + aa; that is, two homozygotes and two

heterozygotes. Thus, the self-fertilization of such an organism

gives 14 the progeny homozygotic (with respect to this charac-

teristic); 14 heterozygotic. If we let x= =the proportion of

homozygotes, y the proportion of heterozygotes (with respect to

one character), then after the first self-fertilization

x= Y¥, of all.

y =l% of all.

Now, after the next self-fertilization, of course the homozy-

gotes x remain pure, so that half of all the progeny are still ho-

mozygotes on this account. The heterozygotes y of course again

break up, in the way already set forth, one half into x, the other

half remaining y. Since y included half of all, this will give 4

of 4% (= of all) as x, % of % (= of all) as y.

So the total proportion for the homozygotes x becomes after

the second fertilization

s= y% + (%)’?=%,

while

| y= (14)? =, :

This process is repeated after each fertilization, so that if

there are n fertilizations in succession, the total number of homo-

zygotes x, becomes

a= + (%)?+ (%)*.. . up to (%4)*.

i ; 2 1 i

This expression reduces to % = ye? where n is the number

of fertilizations. l g

_For the heterozygotes, y, on the other hand the formula is

simply

y= (14).

These then are the formule in case we deal with but one pair

of characters. They express (1) the proportion of all the organ-

isms that will be homozygotic (or heterozygotic as the case may —

be), after a given number n of fertilizations; (2) also they of

course express the relative probability for a given case, as to

whether it shall be homozygotie or heterozygotic.

2. When we are to deal with two or more pairs of characters,

the problem may be attacked in two ways. One is by the gen-

eral principles of probabilities; the other is by analyzing the

case of two or more characters in the way exemplified above.

The two methods give the same results. . oa

The first method is far the simpler. It is merely an appli-

cation of the principle that when we know the probability for i

No.548] SHORTER ARTICLES AND DISCUSSION 489

each of two or more things separately, the probability that all

of them shall happen is the product of the separate probabil-

ities for each. Now, we know that the probability æ for the

homozygotic condition with respect to one character is

2” —1

oe o&

For two characters it is then

2” — 1 2"—1 iv

p) x (= > or ( Qn y

ae 2"—1)\°

For three characters it is of course uae and in general,

for any number m of characters, the probability æ for pure ho-

mozygotes (or the proportional number of pure homozygotes) is

(EFE)

By similar reasoning, the proportion of all the organisms that

will be heterozygotie with respect to all the m characters is

y = (1%).

With two or more characters, there will be of course a consid-

erable number of the organisms that are homozygotie with re-

spect to some characters, heterozygotic with respect to others.

If we call the proportion of these z, then

e=1—(x+y).

And if we let v be the total proportion that contains any

heterozygotic characters (so that v=y + 2), then

J 2n pen 1 m gas u (2" — 1)"

v=1- (4) =— p.

E- z

These formulæ may readily be deduced algebraically, or veri-

fied, by a detailed analysis of a case of two or more characters.

It may be worth while to indicate the method followed, by taking

up the simpler case of two pairs of characters. Call these { x

nd s - The gametes formed are AB, Ab, aB, and ab. When

these combine in all possible ways (as indicated in the diagrams

given in Bateson’s Mendelism), these give the following results:

14BAB +. 14AbAb + 1aBaB + labab + 24Bab +

2AbaB + 24BAb + 24 BaB + 2Abab + 2aBab = 16.

It will be observed that of the entire 16, the first four are pure

homozygotes, the second four are pure heterozygotes (heterozy-

490 THE AMERICAN NATURALIST [Vou. XLVI

gotic with respect to both characters) ; while the last 8 are mixed

(homozygotic with respect to one character, heterozygotie with

respect to the other). Letting z= pure homozygotes, y = pure

heterozygotes, z==mixed,:we find thus that

= 4, y=, e-= ¥f, of all.

Now, by an analysis of the sort already given, it will be found

that at the next self-fertilization, remains x; y breaks up, 14 of

these ‘becoming z, 14 becoming z, and 14 remaining y; z breaks:

up, 14 of these becoming x, 14 remaining z.

Now, when we recall that before the second fertilization æ was

1; Y, 14, and z, 14 of all, we see from the above that after the

second fertilization

2 — 1y

2=4 + (%X%) + UXW =A= (=H),

y=(%4 X uU) =Yo= (%2)”,

z= (V2 X Y2) + (12 X U) == (%)* + (4).

These are the same formule for x and y that were obtained

by the other method (since here n and m are each 2). This

method however gives in addition a direct formula for z.

It is easy to verify the formulæ for three pairs of characters,

though of course the conditions become here somewhat more

complex.

We may now summarize our formulæ, and show the results

they give in certain examples.

Let =the proportional number of organisms that are pure

homozygotes (with respect to all the characters con-

sidered),

y =the proportion that are heterozygotiec with respect to

all the characters considered,

z=—the proportion that are mixed,

v= the proportion that have any heterozygotic characters.

Then, if nthe number of successive self fertilizations and

m = the number of pairs of characters,

we ( ae y, (1)

y= (14), (2)

z=1— (z +y), (3)

Y= a ie (4)

Examples—(1) Suppose that there have been eight self-fer-

tilizations, and that we are dealing with 10 pairs of characters.

What proportion x of the organisms will be homozygotie with

No. 548] SHORTER ARTICLES AND DISCUSSION 491

respect to all the 10 characters? What proportion will be

homozygotic with respect to any given one character? To any

two or three?

Taking first the case for the entire 10 characters, by formula

(1)

8 10

“= (- z) = (a 3 = log. 9.9830020 = .961617.

Thus, out of 100 individuals, somewhat above 96 would be

pure homozygotes; or by formula (4), but one in 26 would be

heterozygotic in any respect (v= .038383).

With respect to any one character formula (1) gives

pa 1 Bao

C= (=)= aT a .9960937 5,

so that all but 4 in 1,000 would be homozygotes with respect to

that character.

In the same way we find that with respect to any two char-

acters the proportion of homozygotes would be .9922; with re-

spect to three, .9883; with respect to four, .9845, ete.

(2) Suppose that there are 20 pairs of characters, and that

‘there have been 20 self-fertilizations, Then

oP TN / 1048 SIO

t= (=>) = (x oas576) = log. 9.9999957 = .999998.

That is, of a million individuals, all but two would be pure

homozygotes.

It thus appears that if the number of separably heritable

characters is not very great (say not above 100), while the or-

ganism has been self-fertilized for many generations, it is to be

expected that practically all of the organisms will be homozygotic

with popet to all their characters, they will be ‘‘pure homo-

zygotes

H. S. JENNINGS

YELLOW AND AGOUTI FACTORS IN MICE NOT

‘‘ ASSOCIATED”

In a recent number of the AmerIcaN Naruraist Mr. Sturte-

vant! suggests that these two color factors may bear to each other

the relation which Bateson has called ‘‘repulsion’’ or ‘‘spurious

allelomorphism’’ and which Morgan now includes with ‘‘coup-

ling’’ in a more general category, ‘‘association.’? The supposed

* Sturtevant, A. H., ‘‘Is there Association Between the nye and —

Factors in Mice??? Am. Nar, Vol. XLVI, No. 546, p. 368, 1

492 “OTHE AMERICAN NATURALIST [ Von. XLVI

relation is such that the characters involved fail to pass into the

same gamete even though they may be present together in the

parent zygote. That yellow and agouti in mice are not in gen-

eral so related is shown conclusively by experiments which will

be more fully described elsewhere, but which may be briefly

summarized in the following table:

Parents Offspring

Mating

Both Yellow Yellow Agouti Black or Brown

185 894 X895 1 1 5

10 502.24 X502.5A 10 2 1

397 3,908 X875 4 2 2

273 2,049 X875 5 1 1

159 786 X784 5 3 ul

446 Unmarked 4,054 8 6 2

500 Unmarked 4,152 2 3 1

545 — x4,1 4 2 1

467 chins 9 i Pa 1

519 Cuniacked sn oo 6 2 1

543 2 1 3

397 3,908 y pia 4 2 2

240 1,828 X 1,829 10 1 6

113 562X 563 6 3 2

173 1,074X 563 2 1 2

Total 78 31 31

In these experiments yellow animals bred inter se have produced

non-yellow young half of which are agouti and half of which

are non-agouti. It seems therefore to be wholly a matter of

chance whether a yellow animal heterozygous in agouti trans-

mits that character with yellow or apart from it. Sturtevant’s

contrary conclusion is due in part .to his reliance on the insuffi-

cient numbers observed by Morgan and in part to his overo a

certain of the results reported by Miss Durham. For, in a

tion to the category of matings of yellow mice cited by Sturte-

vant, she reports matings of sable (yellow) mice inter se which

produced 17 sable (yellow), 8 yellow, 5 agouti, 4 black, and 2

brown young, a result in harmony with that which I have de-

scribed.

In the matings reported by Miss Durham in which yellow

parents produced only yellow young and agouti young, it seems ~

probable that one or both of the yellow parents was homozygous

in agouti. The same was probably true in the similar experi-

ments of Morgan. This would explain why all the noae

young were agouti marked.

As further evidence that yellow and agouti are wholly

independent characters may be cited experiments of my ow?

in which yellow animals evidently heterozygous in agouti were | is

No. 548] SHORTER ARTICLES AND DISCUSSION 493

mated with brown animals which invariably lack agouti.

There were produced 15 young, of which 7 were yellow, 5 agouti

and 3 black or brown. Evidently the yellow parent transmitted

non-yellow (black or brown) in 5 cases associated with agouti,

and in 3 cases not so associated. On Sturtevant’s hypothesis all

non-yellow young should have been agouti.

C. C. LITTLE

LABORATORY OF GENETICS,

BUSSEY INSTITUTION, HARVARD UNIVERSITY,

June 17, 1912

PHYSICAL ANALOGIES OF BIOLOGICAL PROCESSES

Two schools or methods of thinking of heredity and other

general problems are recognized among biologists. Some hold

that all biological phenomena are to be explained in terms of

physical and chemical properties of unorganized matter. Others

are inclined to believe that the activities of living matter repre-

sent agencies or relations not shown in the inorganic world. The

first view has been called materialism, the second vitalism.

These distinctions are not as important as sometimes supposed,

because of our inadequate knowledge of the properties of matter,

whether organic or inorganic. The materialistice view may be

said to have a practical advantage in encouraging the investiga-

tion of the physical and chemical phenomena of the organic

world, but vitalism may claim at least an equal advantage in

permitting the recognition of facts that lie on the other side of

the biological field, where the analogies of physics and chemistry

find little or no application. Thus the specific constitution or

speciety of living matter, the fact that organisms maintain their

existence and make evolutionary progress only in groups of

individuals united into specific networks of descent, involves the

recognition of a condition or property quite foreign to the usual

conceptions of the physicist or the chemist. Yet this universal

condition of speciety must be considered as a general basis or

background for any strictly biological study of the organic

world. We may count, weigh, measure or analyze the bodies

and activities of organisms from as many other standpoints as

we please, but it is idle to draw general biological conclusions |

from any merely mathematical or physical data. The true

biological significance of statistical and physical facts has to be

determined by biological analysis. es,

494 THE AMERICAN NATURALIST [ Vou. XLVI

desirable and legitimate. Even an incomplete and inadequate

analogy may be very useful for descriptive purposes. But when

the elaboration of an analogy interferes with perception of the

fact it is supposed to elucidate the limitations of the method

become apparent. This danger may be illustrated by a recent

attempt to define biological evolution in physical terms.

In the minds of most of us the term ‘‘evolution’”’ is associated

probably more closely with the biological than with the physical

sciences. Yet the concept is essentially physical in character,

and is definable in exact terms probably only in the language

of physics. For in its last analysis we may define evolution as

the history of a material system undergoing irreversible trans-

formation. To the physicist, therefore, the study of evolution

is essentially the study of irreversible changes, and the law of

evolution is the law of increasing entropy, or, more generally, of

the increasing probability of the successive states of any rea

material system. j

Whether such definitions have any practical advantage as aids

to further investigation may be questioned. Exact terms are

of little use in biology unless they are also concrete, that is,

unless they convey an idea of something that can be seen, Or at

least imagined. Physicists are much more tolerant of mathe-

matical and metaphysical abstractions. The habit of using ab-

stract conceptions often leads to the announcement of wonderful

discoveries that resolve themselves, ón closer inspection, into

purely metaphysical manipulations of terms. Thus it is con-

sidered one of the notable services of a ‘‘supreme biologist” that

he should have identified chemical reactions with organic

tropisms, tropisms with instincts, instincts with morals, and then

predicted a chemical analysis of morality.? :

Such inferences only show that the vocabulary has been thrown

into solution, not that any concrete insight has been gained.

Physical terms can be set into formule as mystical as a wizard’s

incantations. Sleight of hand is discredited, but verbal miracles

are still performed with ‘‘scientifie principles.’ When 80-

ealled physical science runs to seed in antinomies it becomes

plain that we are back again in the vicious circles of meta-

physical deduction.

To describe biological evolution as a process of irreversible

transformation seems especially inappropriate because it is of

1 Lokta, Alfred J., ‘‘ Evolution in Discontinuous Systems,’’ Journ. Wash.

Acad, Sciences, Vol. II, No. 1, 1912, pp. 2-4.

21t The Chemistry of Morals,’’ Current Literature, 52: 180, February,

1912.

No. 548] SHORTER ARTICLES AND DISCUSSION 495

the very nature of biological changes to be reversible, or recur-

rent in each generation. Only by limiting the idea of evolution

to changes in the underlying mechanism of transmission could

the specification of irreversibility be made to apply.

Nor is there justification for considering biological evolution

under the caption of discontinuous systems. Variations, in the

sense of changes of expression of characters, are often discon-

tinuous, but this does not mean that evolution is discontinuous.

Some biologists have supposed that new characters constitute

new species, but in reality we have to think of the old species

as developing the new characters instead of the characters

originating the species. As long as species are considered only

in a statistical or biometrical sense, the existence of different

species will appear to rest on evidence of mathematical discon-

tinuity. But for any truly biological purposes such discon-

tinuity must be considered as a result of evolution, rather than

as a condition or cause of evolution. All characters, in the

evolutionary sense of the word, are first presented as differences

among the members of species. Such differences are always

variable, or alternative in expression, which is another way of

saying that they are reversible; that is, they appear and dis-

appear, or are expressed in various degrees, in the different in-

dividuals belonging to the same specific group.

The phenomena of mutation represent discontinuity among

members of the same species, rather than differences between

Species. Natural species seldom have the same kinds of differ-

ences as mutative variations. The theory that species originate

by mutative changes of characters is well calculated to deceive

physicists and biometricians who are not familiar with the facts

of diversity in natural species. Ortmann diagnosed the diffi-

culty with the mutation theory by saying that DeVries does not

know what a species is. Familiarity with species is seldom con-

sidered as a necessary qualification for the study of evolution

and heredity. Indeed, most of our physiological and mathe-

matical biologists have dismissed species as something too 1m-

definite for their purposes. They prefer to begin with i

definition that can be stated in exact terms and turned into

figures or formule. The casual choice of words like irreversible

or discontinuous becomes fraught with a vast importance, seldom

mitigated by any appreciation of the fact that most of one

anguage of biology is merely descriptive and comparative, and

hence to be understood only in relative senses.

If we cut through a tree top it will appear that the branches ee

are discontinuous, but if we follow individual branches oa, le

496 THE AMERICAN NATURALIST [Vou. XLVI

effect of discontinuity is lost. For some purposes the process

of growth might be described as continuous or gradual, and

for other purposes as discontinuous, for there are daily inter-

ruptions or variations in the rate of growth. Darwin compared

the evolution of species to the growth of branches on a tree.

Theories that would supplant Darwin’s conception of continuity

in the evolution of species are not based on equal familiarity

with the facts. Constructive evolutionary progress comes by

gradual changes in the characters of species, not by saltatory

transformations of one species into another. That albinism and

other defects appear as mutations and show Mendelian in-

heritance does not destroy or even conflict with the evidences of

continuity in the evolution of species.

The many different applications that can be made of such

terms as continuity or discontinuity show how little is gained by

the choice of any particular statement of biological facts as a

basis for deduction or mathematical elaboration. That new

facts can be learned by syllogizing is no longer believed. Is

more to be gained by turning syllogisms into mathematical

formule? Even when physical analogies can be more definitely

drawn the biological relations of the facts seldom permit any

complete application of mathematical methods of thought.

Taking evolutionary deviations into account, the recurrent life

cycles of organisms could be considered as spirals and this might

appear to bring them within the range of mathematical treat-

ment. Yet no regularity of form could be ascribed to such

spirals, for evolutionary intercalations of new characters are not

merely additions at the ends of definite series, but are likely to

intervene in any part of the life cycle. Moreover, such inter-

calations are made without throwing the remainder of the cycle

out of adjustment.

From the historical standpoint evolution may be presented as

a series of transformations, but from the standpoint of heredity

the results must be treated as permanent and coexistent, not

merely as successive reactions. Each member or part of the

eycle must be supposed to carry the determinants or potentiali-

ties, the powers of reproducing every other part. And we

know further that these potentialities continue to be carried in

latent or recapitulated form, even after they have ceased to

come into normal expression. In other words, the piological

system retains latent possibilities of reversion, the maps, as it

were, of courses of development long since abandoned. Even —

though the characters be considered as irreversible in the sense

of having permanent transmission they are subject vever 3

No.548] SHORTER ARTICLES AND DISCUSSION 497

to endless vicissitudes of internal and external relations that

influence the expression of characters.

Thus the life-cycle spiral is not a single line, but is resolved

into a vast multiplicity of lines, tracing back to all the different

ancestors. The expression relations of the characters can be

analyzed, in a measure, by breeding experiments and by compar-

ing behavior under different conditions, but the nature of the

system is such that its most permanent and stable adjustments

are those that are farthest removed from the influences of the

environment. Hence the futility of mathematical treatments

that attempt to combine environmental vicissitudes with the

entirely inconsistent facts of biological evolution. Instead of

evolution representing a law of increasing probability of suc-

cessive states, the contrary would be more nearly true. The

more specialized the organization the less the probability of

passing to another state. Thousands of species are extinguished

to one that develops a higher type of organization. Instead of

evolution representing a summarized result of environmental

influences, it is rather to be considered as a history of ways of

avoiding such influences. There are no facts to show that evolu-

tionary progress is caused by environmental agencies or by in-

ternal mechanisms. The causes of evolution lie in the structure

of the species.

The crowning complexity of the biological system is that the

life-cycle spirals do not remain separate and distinct from each

other, but are thoroughly interwoven to form a continuous net-

work of descent for each species or group of interbreeding indi-

viduals. It may be that a mathematical formula could be made

for a spiral wire mattress or a Turkish rug, but this would afford

only a faint analogy for the complications that attend the evolu-

tion of a species. To describe a species as a network of descent

may be only a figure of speech, lacking altogether in mathe-

matical exactness, but it is a way of pointing out a concrete

biological fact. When the facts are essentially complex any

statement that conceals or disregards the complexity is to that

extent specious and misleading. :

Many of the results of evolution can be described in simple

terms of quantity or sequence, but to consider such statements as

definitions, or to suppose that they confer any special license for

mathematical elaboration, is to disregard the true nature of the

facts and problems of biology. For purposes of physics or

chemistry individual plants or animals may be considered as-

machines, but for purposes of evolution the whole species repre-

sents the machine in which the patterns of new characters are

498 THE AMERICAN NATURALIST ~ [Vou XLVI

woven. If mathematical elaboration is to serve any useful

purpose in showing how evolutionary progress is made the nature

of the machine, the specific organization or speciety of the

organic world, must be recognized.

O. F. Cook

WASHINGTON, D. C.,

March 15, 1912

ON FAIRNESS AND ACCURACY IN SCIENTIFIC

REVIEWING

TO THE EDITOR OF THE AMERICAN NATURALIST: Aal one who

takes a turn at the critical hoe with the object of ridding the

biological field of some of the noxious products of fertile imagina-

tions untrammeled by quantitative facts must expect just the

sort of attack which appears in your recent issue (AMER. NAT.,

March, 1912, p. 165).

1. Dr. Spillman has not felt the purpose, methods or results

of my paper worth statement. Instead he illustrates by it the

‘“‘noticeable degree of correlation between positiveness of state-

ment and inaccuracy of statement.’? And for the reason: ‘‘in

Dr. Harris’s paper he represents me as having cited the fact

[sic] that these genotype norms [sic] form a frequency curve

[sic] as proof of the genotype hypothesis [sic].’’

One excuses the minor inaccuracies and would be glad to pass

over the whole assertion with the simple comment that it seems

ToJo but to protect himself against further accusations of

‘‘inaccuracy of statement’’ he must add, it is not true.’

What I did do was to cite Dr. Spillman among three others in

substantiation of the opening sentence, ‘‘Several times recently

we have been told that the means of a character in a series of

pure lines form a ‘Quetelet’s curve.’ °? I based this on his state-

ment concerning pure lines, ‘‘They not only do not differ in

their characters as the @nothera mutants do, but their norms

present a regular series coming under ‘Quetelet’s Law’ ’’ (AMER.

Nar., Vol. 44, p. 760). Surely no injustice has been done so far.

Later in the paper I did make a statement (which still holds

true) remotely similar to the one quoted above, and said specific-

ally ‘‘A case in point is a paper by Roemer.’’ There was no

reference whatever to Dr. Spillman—expressed, suggested, in-

sinuated, intimated, implied, . . . or intended.

2. Although it is clearly without any justification, the fore-

going criticism would, it seems to me, have gained in strength by —

specificity and moderation of statement. But Dr. Spillman con- —

No. 548] SHORTER ARTICLES AND DISCUSSION 499

tinues: ‘‘I have not been able to find time to look up other similar

citations to see whether the same inaccuracy applies to them.”’

There are four ‘‘similar citations’’: one to a paper Dr. Spillman

has already read, or at least reviewed for the AMERICAN NAT-

uRALIST (Vol. 44, p. 761), one to a few lines in the German Zeit-

schrift for genetics, one to thirteen lines in the AMERICAN NAT-

URALIST (Vol. 45, p. 423) reviewing the fourth, which has again

been considered in these pages (AMER. Nart., Vol. 45, pp. 686-

700)

3. Dr. Spillman reiterates: ‘‘It is now fairly well established

that the norms of a group of related genotypes can, in some cases

at least, be arranged in a frequency curve.’’ Thus, he tells us,

genotypic differences fall under de Vries’s category of fluctu-

ating variation, while in discontinuous variation ‘‘the norms can

not be thus arranged.”’

Personally, I have not the slightest prejudice against these

conclusions, but I can not accept them without proof. Dr. Spill-

man cites none. So far as I have been able to ascertain there is

not a single series of trustworthy quantitative data in support

of these pregnant generalizations.

4. I acknowledge my fault in omitting homozygous. This was

a serious blunder on my part! By including it, one can always

reason in a circle and to prove his preconceptions assume that

the original ancestors of a line were or were not homozygous,

according to the outcome of his experiments. This is the loop-

hole through which the supple genotypist can always crawl when

the evidence on the other side gets a little too strong. Again, in

the genotypic ritual, ‘‘I wish to publicly repent.’’

5. But is not the reviewer a little over-zealous when he con-

tinues, “the definition is further inaccurate in including clonal

varieties under the definition of genotype’’? In doing this I

merely followed the example of the best specialists. My paper

ein correct in terminology, as I believe it still is in facts, when

"4 Toni to press. Several months after the paper Dr. Spillman

n criticizing appeared, changes in terminology were forced by

the dictator of the whilom orthodox”? genotypic ‘‘school’’!

J. ARTHUR

NOTES AND LITERATURE

DISTRIBUTION AND ORIGIN OF LIFE IN AMERICA!

-The aim and scope of Scharff’s very welcome book is well

stated in his own closing words (p. 435): ‘‘I have endeavored

in this work to show how the gradual evolution of our continents

and the former changes of land and water can be demonstrated

by a study of the geographical distribution of living animals

and plants. Whenever possible I have taken advantage of our

paleontological and geological knowledge in furtherance of this

object, and I venture to think that I have succeeded in unravel-

ing some intricate problems of the paleogeography of America.

Indirectly I have thus been able to indicate the manner in

which North and South America became populated and the ex-

tent to which these continents took part in supplying animals and

plants to other regions of the world.’’ Scharff has certainly

done all this and much more besides. Never before has a book

upon zoogeography appeared culling and collating the thoughts

and observations of such a host of investigators. The fact that

his evidence comes not only from practically every group of the

animal kingdom, but very often from plants as well, make the

deductions far more convincing, radical as they often are, than

they would ever be otherwise. Extensive as is the bibliography,

there are still a few unfortunate omissions, and some typograph-

ical errors mar an otherwise excellent piece off press-work. In

the second edition, which can not but appear, the use of bee

would wisely be omitted. The words ‘‘Professor,’’ ‘‘Dr.’ and

‘‘Mr.’’ are used in a rather promiscuous manner. They are not

always judiciously bestowed.

The fifteen chapters take up the study of the fauna of the

hemisphere, beginning af the north with Greenland and proceed-

ing southward.

In Chapter I the relation of the hoii of Greenland to both

Europe and America is convincingly dealt with and Scharft’s

first excellent map shows the Pliocene bridge which extended

from Great Britain through the Orkneys and Iceland to Green-

land and on across to Arctic America. In this chapter the ee

*«*Distribution and Origin of Life in America.’’ By R. F.

New York, The Macmillan Co., 1912. Pp. viii + 497, 21 maps.

500

No. 548] NOTES AND LITERATURE 501

tion ‘“Did animals survive the ice age?” is first mooted and

Scharff prepares us for what is perhaps the most welcome and

far-reaching opinion which he, we think successfully, endeavors

to prove. His belief is that we have been accustomed to en-

tirely misjudge the extent and importance of the glacial epoch

and to exaggerate excessively the part which it has played in

influencing the distribution of our present flora and fauna, In

this the, reviewer heartily agrees and recalls that in Percival

Lowell’s ‘‘ Evolution of Worlds’’ the question is attacked from an

entirely different standpoint and a similar conclusion reached.

Scharff concludes that ‘‘The prevalent geological opinions as to

the nature of the Ice Age thus dominate all biological thought

in reference to problems of distribution.’? If we emancipate

ourselves from these preconceived notions in our speculations

on the origin (for example) of the existing fresh-water mussel

fauna, we must arrive at different conclusions.

In Chapter II, then, we have discussed the general features

of the fauna of northeastern North America with special refer-

ence to this theory of a comparatively insignificant Ice Age.

The third chapter deals with the animals of the Canadian

northwest. Ptarmigans, lemmings and gophers, the bison,

wapiti deer, our tree porcupine, ete., are discussed and their

origin pointed out. There is, however, no reason for conelud-

ing, as Scharff does, that the American magpie is more similar

to the European form than the Asiatic. All these palæarctic

races of magpies are so closely related and the differences be-

tween them are so slight as not to permit of any such conclu-

sions as Scharff draws from them. The other chapters on North

America deal with the fauna of the Rocky Mountains, the ani-

mals of the eastern states, the fauna of the Continental basin

and of the southeastern states and Bermuda. In this chapter

We meet again with an opinion which, while it can not but gain

ground as time goes on, now seems radical in the extreme. Ber-

muda has always been considered a most typical ‘‘oceanic is-

land,’’ yet here we have the view advanced, and well defended,

that Bermuda is the remnant of an ancient belt of land which

joined it to a southern land mass extending across the Atlantic

Ocean. This would account for the presence of both European

and American elements in the indigenous fauna, ik which,

as Scharff shows, is composed wholly of types bearing ‘‘the im-

Press of vast antiquity.’’

Tn the following chapter (No. IX) we have more detailed oa

502 THE AMERICAN NATURALIST [Vou. XLVI

cussion of this bridge between the old and new worlds. In spite

of the fact that there are still a considerable number of natur-

alists who adhere to the old dicta regarding the permanence of

land forms and ocean basins, there can be but little doubt that

the open-minded student will be convinced by what Scharff has

to say regarding the absolute necessity of postulating extensive

changes in the forms of the continents to account for the present

distribution of animals and plants. :

Next follows a discussion of Central America and the West

Indies (Chapters X and XI). The fauna of both these regions

is carefully analyzed and the very many seeming anomalies of

discontinuous distribution are explained, often for the first time,

by postulating a series of geographical changes far too elaborate

to attempt to summarize in a short review. Suffice it only to

say that the treatment of the Lesser Antilles is disappointing

and the important part which they have played in joining

Antillea (sometimes also spelled Antillia), if perhaps only for

a very short time, with that region which is now northeastern

South America, is overlooked or receives but scant consideration.

The existence of Onycophoran types on many of the Lesser An-

tilles should have suggested further investigation.

The twelfth chapter deals wholly with the origin and relation-

ship of the fauna of the Galapagos Islands. These islands are

also considered to be the remnant of a former considerable ex-

tent of land which for a time was connected with a land mass

extending from north to south along what is now the west coast

of both Americas, but at some distance out in the Pacific Ocean.

This connection of North with South America is certainly nec-

essary to explain a host of otherwise inexplicable distributions.

Parts of the present territory of Central America are known to

have been submerged up to comparatively recent geologic times.

Baur’s pioneer theories regarding the Galapagos Islands here

receive the appreciation which they have always so richly de-

served. They are corroborated by evidence recently accumu-

lated, all of which is used by Scharff to fine advantage. After

some discussion favoring Scharff’s theory, which presumes that.

there has been an extensive land mass occupying a considerable

part of what is now the Pacific Ocean west of the present land

areas, the author passes to a discussion of the South American

fauna, which fills the rest of the book. (Chapters XI-XV;

pp. 336-435.) In this the views of von Ihering and Ameghino

carry special weight, and to this they are certainly fully entitled.

No. 548] -= NOTES AND LITERATURE 503

Every one has previously been inclined to belittle the splendid

energy and self-sacrificing zeal which have stood back of Ame-

ghino’s sensational accounts of his discoveries. To any one who

has known Ameghino and who has heard him give his own

reasons for his conclusions and describe his own treasures, this

kindly appreciation by Scharff will seem well merited. This

does not, of course, mean that we must accept all of Ameghino’s

theories, especially those regarding the origin of man.

review, in the true sense, of Scharff’s book is impossible!

Each page is replete with valuable data, well digested, and is

pregnant with suggestion. All of the critics of Scharff’s previ-

ous works will agree that they are certainly suggestive in the

extreme, even if their postulates may not be accepted. . It seems

caviling indeed to conclude this notice with a list of little faults,

yet they are very evident, some of them, and may be corrected

easily in subsequent editions. Thus on page 20 we should have

Carabus nemoralis, instead of memoralis, a species which is not

confined to Nova Scotia, but which for years has been the com-

monest large Carabid about Boston and Cambridge. On page

141, dealing with the pine-barren flora and its northward pro-

longation, we find no mention of the most important contributions

which have ever appeared regarding the relationship of the flora

of Newfoundland with the coast regions further south, those of

Merritt L. Fernald, while, besides, no mention is made of the

writings of Witmer Stone or Harshberger, both well known in

connection with their work on the pine barrens. Again on page

151 we are surprised to learn that raccoons breed well in con-

finement and also to find no mention of the species of Procyon

described by Miller from the French West Indian Island of

Guadeloupe. The knowledge of this fact would have been of

great interest in connection with the occurrence of Procyon may-

nardi on New Providence, which Scharff admits is an enigma,

and the other remarks on the dispersal of raccoons. On page 173

we read north Carolina, elsewhere correctly North Carolina.

On page 180 we find Crocodilus americanus spoken of as the only

West Indian species in the genus, the important Crocodilus

rhombifer being passed by. On page 204 no mention is made

of Boulenger’s discovery of Bombina maxima from Yunnan, a

fact which is most important, fulfilling the prediction made by

Stejneger that a discoglossoid toad would be found in this area,

the center of dispersal of the group. On page 266 we find Por-

torico, one word; on the map it is given correctly as Puerto

504 THE AMERICAN NATURALIST [Vou. XLVI

Rico. On page 281 Saurecia and Panolopus are mentioned; the

former is hardly entitled to generic rank, a fact important in this

connection, while the genus Panolopus Cope has been shown by

Garman to have been based upon a specimen artificially muti-

lated. On page 282, in speaking of Capromys no mention is

made of C. ingrahami, a peculiar species long known from one

of the Plana Cays in the southern Bahamas. On page 289

Todite should read Todide, while on page 291 it would have been

worth while mentioning the fact that de la Torre, of Havana,

has published the account of finding fossil ammonites of Jurassi¢

age in the Sierra de Vinales, western Cuba. Such trifling errors

and omissions do little to mar the book! Its general excellence

carries it.far beyond petty criticisms. While the views which

Scharff expresses will doubtless meet with opposition from many

naturalists of the ‘‘old school,’’ nevertheless they represent those

which have been gaining ground fast and which will in time be

held by all zoogeographers. As James Bryce’s ‘‘ American Com-

monwealth’’ came from England, so indeed does Scharff’s Amer-

ican Animals coming from Ireland stand as by far the most im-

portant contribution to a knowledge of the subject it discusses.

Indeed, it is likely to remain so for many a long day.

T. BARBOUR

The American Naturalist

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THE

AMERICAN NATURALIST

Vout. XLVI September, 1912 No. 549

ASYMMETRIC COLOR RESEMBLANCE IN THE

GUINEA PIG!

PROFESSOR JOSEPH H. KASTLE AND G. D. BUCKNER

As is well known, the guinea pig shows the greatest

diversity of color, and a great diversity in distribution of

: color over the body of the animal. In the course of our

experience with these animals in physiological and toxi-

ecological work we have seen pigs that were entirely black,

others that were entirely brown, others of a pure albino

variety, and more commonly than any of these pure color

strains, those showing apparently every possible varia-

tion in the arrangement and distribution of these funda-

mental colors over the body. To what extent the color of

the guinea pig and its variations as the result of the cross

breeding of several strains of different colors have been

the subject of exact scientific observation, we are unable

to say, and the subject is so far removed from those ordi-

narily engaging our attention that it would take us too

long to familiarize ourselves with this knowledge, partic-

ularly should it prove in any way extensive. Inthe course

of some of our recent investigations, however, we have

observed what seems to us to be a rather remarkable case

of asymmetric color resemblance and distribution of

color on the part of the daughter for the mother in the

guinea pig, which is perhaps worthy of note to those more

deeply interested in matters of this kind.

One of our female guinea pigs which has been under

observation and experimentation for some time, No. 68,

was aborted by means of calcium lactate? on March 29,

1 From the Laboratory of the Kentucky Agricultural Experiment Station.

? Kastle and Healy, ‘‘Caleium Salts and the Onset of Labor,’’ Jour. of

Infectious Diseases, Vol. X, 1912, 378-382.

505

506 THE AMERICAN NATURALIST [ Vou. XLVI

1912. No bad effects resulted from the abortion and the

pig soon regained her normal condition and was returned

to the piggery on April 9, 1912. Shortly after this she

again became pregnant and during the greater part of

her pregnancy she was kept in a small cage with another

female pig as one of a set of pigs employed in the study

of the calcium metabolism of the guinea pig.® At the con-

clusion of these observations she was again returned to

the piggery on June 13, 1912, and on June 24, 1912, she

was again brought back to the laboratory. During the

day she gave normal birth to three pigs, weighing respect-

ively 40, 40.5 and 43.5 grams. One of these young pigs

was dead when examined a few hours after birth, the

other two were alive. Of the latter, one was paralyzed

in its hind quarters and died, probably of inanition, a

few days after birth. The remaining pig, a female, was

normal in every respect and is alive and well to-day

(August 5, 1912), and now weighs 157 grams. It was

observed by Dr. Buckner that the color markings on the

young pig are like those on the mother, except that these

markings are on exactly opposite positions on the body.

In other words, these two pigs, mother and daughter,

show an asymmetric color resemblance. That such is the

case is evident from the photographs, Figs, 1, 2, 3 and 4,

although these fail to show this as well as the originals

for the reason that the actual colors are wanting. Fur-

thermore, this remarkable resemblance is a little obscured

and marred by the fact that the young pig has consider-

ably longer hair than the mother, probably as the result

of an Angora strain. Unfortunately, too, nothing is

known regarding the parentage of this pig on the male

side. The following is an exact description of the two

pigs, which in order to render comparisons more easy,

is printed in double columns and given for opposite por-

tions of the body, in order to bring out the asymmetric

character of the resemblance. :

MOTHER Pig Youne Pig (FEMALE)

The mother pig is 9 inches long The young pig is 6 inches long, and

from tip of tail to tip of nose and 24 inches wide ecross widest part

*Kastle, Healy and Shedd, ‘‘Caleium in its Relation to Anaphylaxis’’

(in press),

No. 549]

: 8% inches in width across widest

part of body, Weight 570 grams.

(August 5, 1912.)

Right cheek and area surrounding

right eye, light tan.

Mouth, nose and middle of forehead

white, the white area on forehead

hak has

narrowing somewhat ju ehin

the middle ears then

broadenin ut over shoulders

back.

Right ear an intimate mixture of

` black and tan, giving the impres-

sion at first glance of black.

The greater part of the right side is

almost pure light tan, darkening

shoulder to a point where the front

leg joins the body

The right front leg is light tan with

the exception of the upper part of

the foot which is white.

The inside of right ankle and foot

is nearly hairless and shows a

well-defined black spot in the skin.

Left fore foot, left fore leg and left

middle and rear portion of back.

Under part of mouth and under jaw,

a down over left fore leg

ite. Th

right side = the chest which is

very light ta

Left ear is nearly hairless and white,

ASYMMETRIC COLOR RESEMBLANCE

507

of body. Weight

(August 5, 1912.)

157 grams.

Left cheek and area surrounding

left eye, light ta

Mouth, nose and middle of forehead

hi he

over shoulders, eia aaraa

somewhat over upper part of back.

Left ear is covered especially to-

with S

amount of white hair PT

in front and under

- The greater part of the left side of

this pig from a point about the

like a white collar on the left side

of the pig near the raei and

which is broader and m

developed than in the si

The left front leg is light tan ex-

tending ay to foot, the top of

which is

The inside of the left ankle and foot

is nearly hairless and shows a well-

defined black spot in the skin.

Right fore foot, right fore i and

right side, ‘incinding right hind

leg entirely white, with the a

tion of a small area of light tan,

over the middle and rear portion

of back

Under part of mouth and under jaw,

side of the chest which is light

tan

Right ear is

nearly hairless and

508 THE AMERICAN NATURALIST [ Vou. XLVI

with a small area of tan extend- white, with a small area of tan

ing over the front of ear. extending over the front of ear.

Rump entirely white. Rump entirely white.

Eyes black. Eyes black.

Left cheek and area surrounding left Right cheek and area surrounding

eye is tan, extending to left ear. right eye is tan, extending back to

ear.

It will be observed — a careful examination of the

photographs, Figs. 1, 2, 3 and 4, that these pigs show

certain minor differences in color distribution over the

body. These are due in part at least to the fact that the

Fie. L

hair of the young pig is considerably longer than that of

the mother—the latter being a smooth haired pig, whereas

the former shows an Angora strain. Thus it will be seen

from Fig. 1, that the small patch of white hair over the

left eye of the young pig is larger than the corresponding

patch of white over the right eye of the mother, other-

wise the asymmetrie resemblances shown in the front

view of the two pigs is essentially perfect, barring the

somewhat longer hair of the young pig. In Fig. 2, the

white band extending around the left fore shoulder of the

young pig is decidedly wider and more evenly distributed

than the white marking over the right shoulder of the

mother. This is doubtless due in part to the fact that the

hair of the young pig is longer and consequently overlaps

No. 549] ASYMMETRIC COLOR RESEMBLANCE 509

the tan-colored hair immediately back of the white area.

It will also be observed that in the young pig there is a

narrow strip of white hair surrounding the lower margin

of the left ear, whereas in the mother such a marking is

not shown in the corresponding area of the right ear.

Fig. 2.

Here again this difference in the photograph, Fig. 2, is

accentuated by reason of the longer hair of the young

animal.

In Fig. 3 we certainly have a beautiful illustration of

the asymmetric distribution of color in these two guinea

pigs, the only points of difference being a very small area

of white hair immediately under the left ear of the

mother that is not apparent under the right ear of the

young pig; and also a carrying forward of the tan area

nearer to the mouth on the right cheek of the young pig

than on the left cheek of the mother.

‘ig. 4 also serves to show the asymmetric color resem-

blance in these pigs, somewhat imperfectly, however, on

account of the partial disarrangement of a portion of the

long tan-colored hair of the small pig. Hence we note, in

Fig. 4, a slight extension of the white area into the darker

area on the back of the small pig. As a matter of fact,

however, a careful examination of the animals showed a

perfect asymmetric resemblance so far as distribution of

color is concerned, when looked at from the back. This

could doubtless be brought out by other photographs, but

510 THE AMERICAN NATURALIST [ Vou. XLVI

it is difficult to obtain good photographs of guinea pigs

in all positions on account of their nervousness.

Despite these minor differences in color distribution

over the bodies of the young pig and its mother, there

can be no question that we have here a remarkable case of

asymmetric color resemblance between this female guinea

pig and one of her offspring. It would seem further that

this asymmetric resemblance and distribution of color

in the young pig as compared with the mother is a char-

Unfortunately, as

has already been pointed out, nothing is known as to the

No. 549] ASYMMETRIC COLOR RESEMBLANCE 511

parentage of the young pig on the male side, and no

record was kept of the color of the other two pigs of this

litter, for the reason that this peculiar resemblance be-

tween this pig and the mother had not been observed at

the time that the other two pigs of the same litter died.

Our recollection is, however, that the pig of this litter

that was born dead was pure tan, whereas the one whose

hind quarters were paralyzed and that died a few days

after birth was white with tan and black markings. So

far as we can recall, however, these markings were al-

together different in arrangement and distribution from

those of the mother.

To the chemist the matter of asymmetry as affecting

the physical and chemical properties of certain chemical

compounds, especially those containing carbon, and as

applied to the constitution of such compounds, has since

the memorable researches of Pasteur on the tartaric

acids and the later work of Le Bel and Van’t Hoff, been a

particularly fruitful field for observation and research.

It is also a matter of interest to observe in this connection

that the character of the asymmetry shown by certain

compounds of carbon greatly influences their assimi-

lability by the lower plants. To what extent asymmetric

conditions hold in the ovum and germ-cell we have no

means of determining at present, and as already indi-

cated in the foregoing, it is a subject which takes us too

far afield from matters ordinarily engaging our attention.

We have reason to believe, however, that asymmetric

color resemblance in animals such as has been described

in the foregoing, is rare and from the point of view of

the chemist, extremely interesting and suggestive, and

affords a subject which, in our opinion, would probably

repay a more extended study on the part of those inter-

ested in animal breeding and the study of inherited char-

acteristics.

In conclusion, we desire to express our thanks to Mr.

T. R. Bryant, of the Station Staff, for his kindness in

making the photographs used in the illustration of this

article.

ON DIFFERENTIAL MORTALITY WITH RESPECT

TO SEED WEIGHT OCCURRING IN FIELD

CULTURES OF PHASEOLUS VULGARIS

DR. J. ARTHUR HARRIS

- CARNEGIE INSTITUTION OF WASHINGTON

INTRODUCTORY REMARKS

In the rather voluminous literature of seed testing,

comparatively little attention has been given to the pos-

sible relationship between the characteristics of the seed

(or of the plant from which it was gathered) and its

viability. This is of course attributable to the fact that

such work has been done chiefly for immediately prac-

tical ends, the object being in most cases to determine,

by germination tests of a small sample, the suitability of

a given bulk of seed for commercial planting.

To the student of natural selection, however, the car-

dinal problem of viability is to determine whether the

capacity for development of a seed is a function of its

patent or potential (i. e., of its own measurable or of its

inherent but as yet undeveloped) characteristics. A

satisfactory solution of this very complicated problem

would, I believe, be of rather wide interest. At the out-

set, however, one must fix clearly in mind that if a selec-.

tive mortality be demonstrated, it has no necessary bear-

ing upon the question of the origin of species. Natural

selection may maintain a type already differentiated as

well as mould new forms but in order to do either the

variations upon which it acts must be heritable. But in

any case the results would be of interest to the physiol-

ogist concerned with the problems of the relationship

between form and function. Finally, exact information

on the relationship between structural characteristics

and viability—if they exist—may be of some practical

importance in agriculture and plant breeding.

512

No. 549] ON DIFFERENTIAL MORTALITY 513

The purpose of this paper is to present the first results

of a series of studies on the relationship between the

structural characteristics of the parent plant or of the

seed itself and its viability. The data here recorded

relate only to seed weight and are drawn from an exten-

sive series of field plantings of carefully selected and

individually weighed seeds of the common bean,

Phaseolus vulgaris. They are properly described as a

by-product, for the experiments were not carried out

especially nor in the most satisfactory manner to test the

existence of a selective mortality.

The conditions in field cultures of individually labelled

seeds are such that many factors besides the weight of

the seed are concerned in determining whether or not a

seed shall develop into a mature plant. Some are lost by

dashing rains separating seeds and labels, after which all

questionable cases have to be thrown away. Some are

destroyed by rodents and some by the unavoidable acci-

dents of cultivation. In natural selection terminology,

the non-selective death rate—the death rate which is no

function of the characteristics of the individual—is very

high. This tends to obseure the selective death rate, if

such exists.

For just these reasons, I have never taken account of

the characteristics of the seeds which failed to develop

into mature plants, although the desirability of testing

for the existence of a selective mortality for seed weight

has been in mind almost from the beginning of the breed-

ing experiments with garden beans in 1907. The records

of those which developed to maturity were available for

studies of heredity, influence of size of seed planted on

characteristics of the plants produced, and so on. Data

for the entire parental population from which the seeds

planted were drawn were at hand for the study of the

influences of season and environment. Under these cir-

cumstances, the only need for a record of the seeds which

failed to develop to maturity would be for testing the

hypothesis of the existence of a selective death rate. As

514 THE AMERICAN NATURALIST [ Vou. XLVI

suggested above, it seemed a priori improbable that a

selective mortality could be detected in the large non-

selective death rate of field cultures. But from an exam-

ination of the data which have accumulated during the

last several years, it appears that the a priori scepticism

which led to omitting records of the characteristics of the

seeds failing to develop was unjustified. There appears

to be, in fact, a selective mortality detectible by proper

methods, even in field cultures.

The evidence upon which this statement is based is of

the following kind. We know (a) the weight of all the

seeds weighed in any year and (b) the weights of the

sub-sample of seeds which developed into mature fertile

plants in any subsequent year. Now the sample or

samples which were planted were purely random draw-

ings from the grand population forming the entire mass

of seeds weighed for any culture. The physical con-

stants for the distribution of weights of these sub-samples

planted are, therefore, identical with those of the grand

population, plus or minus the errors of random sampling.

Ideally, to determine whether there be a differential mor-

tality, we should compare the physical constants (means,

standard deviations, and coefficients of variation) of the

seeds which produced mature plants either with the con-

stants of those of the same sub-samples which failed to

do so or with the constants for the entire sub-sample

planted. Practically, our end can be attained with rea-

sonable exactness by comparing the constants of seeds

which develop to maturity with those of the general popu-

lation from which the plantings were drawn. The only

objections to this procedure are two: (a) the results will

be vitiated if the series of seeds planted are in any Way

selected, i. e., not a purely random drawing from the

general population, (b) the probable errors of random

sampling in the drawing of the sample for planting are

added to the probable errors of sampling due to the non-

selective (purely random) death rate.

The first objection does not hold in the series discussed

No. 549] ON DIFFERENTIAL MORTALITY 515

here, for I am confident that the plantings were true

random samples of the general population of seeds

weighed. With regard to the second, we note merely that

its influence will make the detection of a selective mor-

tality more difficult. If we find indications that the

chances for development of a seed are conditioned by its

weight we must therefore consider that the influence of

weight is probably even stronger than is indicated by our

evidence. Indeed, there might be a selective death rate

scarcely detectible by the methods necessarily used in

this study, but if these methods do indicate a selective

elimination, we may have considerable confidence in its

reality.

Studies of viability are generally limited to the capa-

city for forming a growing seedling, but there is no rea-

son why tests should not be made more stringent by

extending them to the capacity of the embryo for devel-

oping into a fertile plant. This has been done in these

experiments.

PRESENTATION OF DATA

The seriations of weights of seeds for the general

populations are given in Table I; those for the sub-series

of seeds which actually developed into fertile plants in

Table II. The seriations for the grand populations are

designated by the key letters of the crops of plants which

produced them, those for the viable sub-samples by the

key letters of the crops into which they developed.'' The

weights are recorded in units of .025 gram range; class 1

being 0-025 gram, class 2, .025-.050 gram, ete. The

constants are also expressed in terms of these units, but

any one desiring to do so may easily transmute them into

fractions of grams.

The biometric constants for the grand populations are

given in Table III. Those for the sub-samples which

actually produced fertile plants appear in Table IV.

* These key letters are the same as those used in other papers published or

in preparation. Hence, further information can be obtained by tho:

who desire.

THE AMERICAN NATURALIST — [Vou. XLVI

516

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518

TABLE III

BIOMETRIC CONSTANTS FOR GENERAL POPULATION OF SEEDS WEIGHED

THE AMERICAN NATURALIST

[Vou. XLVI

Mean wo het pene

Standard Deviation

Coefficient of Variation

; ES

eerie and Probable Error esa and Probable Error

MES ec oe | 9.474 =.013 1.490+.009 | 15.727 +.101

Iaa Ea Ss E 9.774 =.011 1.421+.008 | 14.537+.082

13 A eG E 8.529 = 012 1.458+.009 | 17.099+.103

Bee aoe 7.496 +.0 1.310.013 | 17.470 +.182

jhe 5 ee A eae 8.487 +.019 | 1.377 +.014 16.218 +.163

NOR e 8.852+.015 | 1.555 +.011 | 14.089 +.121

We cl ere nee | 2.605+.025 | 18.218+.184

ten... 04 +.04 2.413 =.034 | 16.987+.244

ee 10.690 =.041 | 1.921+.029 | 972 +.279

et 8.229+.018 | 1.434+.013 | 17.427+.156

DAE 8.516+.016 | 1.092 +.011 12.826 +.135

PD- Se 56+.016 | 1.034 +.011 14.858 +.161

Sea gg hae Ren een 22.272+.081 | 3.796+.057 17.044 +

OG. Go ae | 17.601 +.024 | 3.264 = .017 18.542 +

GCR eoo | 18.919+.034 | 2.674 =.024 14.131 +. 177

GGD. os 14.972.036 | 2.498 + .026 16.681 +.193

ee ae coe 15.667 + .04 | 3.137 + .028 20.023 +.186

TABLE IV

BIOMETRIC CONSTANTS FOR SEEDS WHICH PRODUCED FERTILE PLANTS

Series Mean and Probable Standard Deviation Coefficient of Variation

Error and Probable Error and Probable Error

NED oo 9.458 = .027 1.507 = .019 15.932 +.207

NEG be 9.445 + .026 1.508 + .019 15.962 + .203

NHS ooo 9.275 + .025 1.332 + .018 14.356 + .196

NAD 2 5 459 = .0 1.409 = .019 16.657 + .235

NDA ges 7.624 + .033 1.283 + .024 16.833 +.319

NDD n 7.733 =.039 1.318 + .028 17.049 +.

NÐDD -n 756 = 1.304 + .029 14.892 +.339

NOBH o 8.929 = .035 1.244 + .025 13.930 +.285

ti]. > POO Sete 14.143 = .070 2.713 + .050 19.180 + .364

AS E Soe Rea TET 14.330 = .094 650 =. 18.495 +.480

Wee ete 14.394 =.101 632 +. 18.283 +.510

pt) SSR Se doer rs 14.496 = .076 2.583 = .054 17.819 +.381

USHR oes 13.942 = .087 1.927 + .061 13.820 +.449

Usp 6 ee 10.852 = .078 TTT =. 16.371 +.521

iao Ee A 8.204 = .033 1.434 = .023 17.478 +

PH o o. 8.326 + .045 1.438 = .032 17.276 + .389

PSD a oe 8.224 + 047 1.430 = .033 17.383 +.413

PO oe ee 8.312 + .039 1.397 + .028 809 =.

Pane 2 8.483 + .035 1.075 = .025 668 =.

DE -o 7.194 = .036 1.045 =.025 14.520 +.359

GO es 22.324 = .091 3.727 = .065 16.695 = .297

GOR oe 17.659 + .094 3.359 + .066 19.020 +.389

GOM on. 17.305 = .093 3.079 = .066 17.792 +.392

GGD.. = og 17.545 =.095 3.188 = .067 18.168 =.395

COne R E 17.448 = .096 3.023 = .068 17.327 + 402

GONE... o 18.038 = .083 2.445 = .059 13.555 +.331

DIE oe 15.515 =.088 2.410 + .062 15.536 + .410

Beate ee as 15.524 + .059 +, 19.121 +.280_

hase 4)

No. 549] ON DIFFERENTIAL MORTALITY 519

in all cases. Only the deviations of the sub-samples from

the general population, i. e., the differences obtained by

Sheppard’s correction was appked to the second moment

subtracting constants for the general population from

those for the sub-samples producing fertile plants, as

given in Table V, require our attention.

Consider first the differences in mean seed weight.

They are equally divided between positive and nega-

tive, the average weight of the seeds which produced fer-

tile plants being in 14 cases higher and in 14 cases lower

than that of the general population of seeds from which

the plantings were made. The average value of the posi-

TABLE V

aena OF ee FOR SEEDS PRODUCING gms PLANTS WITH

OSE FOR THE GENERAL POPULATIONS WEIGH

s Mean and Probable | s andard Deviation | Coefficient of Variation

Series Compared Error | a and Probable Error | and Probable Error

NBD-NH....... —.016 =.030 | +.017+.021 | + .205+.230

NHH-NG......: —.030 = .030 +.018 +.021 ob 2a

: NHHH-NHH#.... — .500 = .028 — .089 + .020 | 181 =.212

NHDD-NHD.... — .070 +.030 — .049 + .021 — 442 +.257

NDH-ND....... +.128 + .038 .026 + .027 — +

3 8 A +.237 = .043 +.009 = .031 — 421+.412

NDDD-NDD + .269 + .045 — .073 + .032 — 1.326 +.376

NDHH-NDH +.078 =.038 —.312 +.027 — .159+.310

(SOUR TA —.154=+.025 +.108 + .056 962 + .408

UBH-US8.: o. +.033 =.101 +.046 +.071 277 + .514

Ms Pie eco +.098 = .107 +.027 +.076 + 542

cy A +.200 = .084 —.021 +.0.

USHI USH eine .262 + .099 — 486 + .070 3.167 + .511

USDD-USD..... +.163 =.088 —.145 + .062 — 1.601 =.591

FSS Pn.. EG — .025 +.037 .000 + .026 + .051 +.331

PSH-fS oe _ + .048 +.004 + .034 151 +.419

FSD-FS. 5 ee; 004 + .050 —.004 = .035 — .044 + 442

PSC FE o +.084 = .043 —.037 = .030 — .618 +.374

FSHH-FSH...... — .033 = .039 —.018 = .027 158 + .325

FSD Doon +.238 + .039 +.011 =.028 Bn

CO +.052 +.122 -. .086 ~

GH-GG........ +.057 = .097 +.095 = .068 + .478 +.402

GGH:-GG....... — .297 = .096 —.185 + .068 ~

GD-GG........ —.057 = .098 —.076 + .069 374

GGD:-GG....... 154 = .099 — .240 + .070 —1.215 + .414

GGHH-GGH.. 2+.089 228 + — 576 +.375

GGDD-GGD + .542 +.095 —.087 + .067 — 1.145 + .453

ce eas +0 —.168 + 36

tive differences is +.163 units; of the negative differences

—.188 units; of the entire series of 28 comparisons

520 THE AMERICAN NATURALIST [ Vou. XLVI

—.012 units. Considering the differences individually

in comparison with their probable errors? we note that if

we regard a difference at least 2.50 times its probable

error as statistically significant, 10 of the differences may

-===

se mm m OO

-----0

-------0

kh-------0

——

Peed

DIAGRAM I

Differences in Means.

be looked upon as trustworthy. Of these 5 are positive

and 5 are negative. If we require Diff./E arr. — 4.00, we

find only 7 trustworthy cases, 4 positive and 3 negative m

sign.

Diagram I shows graphically the amount and the sign

*It is somewhat difficult to decide just what ratio of the difference to its

probable error should be used to indicate trustworthiness. As already

emphasized, we have in reality two instead of one random sampling to take

into consideration in the comparisons which we are drawing. The ratios

Dif'./Eaifs. are available to the reader who may assign to them any signifi-

acting he sees fit. The general trend of the series furnishes much stronge?

evidence for a selective mortality than does the apparent statistical trust-

worthiness of any individual comparison.

No. 549] ON DIFFERENTIAL MORTALITY 521

of the differences between the general and the viable

samples. Here the different comparisons are shown from

left to right in the order in which they are given from

top to bottom in Table V. The distances of the solid dots

below the zero bar indicate the amount of the negative

deviations, the circles above the positive deviations.

From all of these considerations, we conclude that

seeds which produce fertile plants are on the average

neither lighter nor heavier than random samples of the

population.

While the results for the means furnish no evidence

for a selective mortality, the standard deviations are very

suggestive of its existence. In 19 cases, the S.D. of the

seeds which produce fertile plants is lower than that of

the series from which they were drawn, while in 9 cases

it is larger. The deviation from the equality to be ex-

pected if the differences were due purely to an infinite

number of random sampling is therefore

5 +. 67449 v.5 X.5 X 28=—5+1.79,

which is perhaps statistically significant. The chances

against the result being due to the errors of sampling are

roughly the same as those against 19 heads and 9 tails, or

vice versa, in coin tossing.

Not only the inequality of the divisions of the signs

into positive and negative, but the magnitude of the

deviations themselves evidence for a selective mortality

which reduces variability without sensibly affecting the

average. The 9 positive deviations average -++.037; the

19 negative — .122; the whole 28, —.071. The far greater

magnitude of the negative deviations is made clear by the

generally greater lengths of the bars below the zero line

in diagram 2. Considering the individual differences in

their relation to their probable errors, we note that in 7

cases the difference is over 2.5 times its probable error.

All of these are negative in sign. -

The coefficient of variation, that is, 100¢/m, should show

most clearly whether both larger and smaller seeds fail

522 THE AMERICAN NATURALIST [ Vou. XLVI

to develop, thus bringing about a reduction in variability

which is independent of any change in the mean. The

results given in the final column of the comparison table

V, evidence even more strongly than the standard devia-

tions in favor of such a selective elimination. They are

-—-- == www ee

ey yap

Differences in Standard Deviations.

lower for the seeds which develop into mature plants in

21 out of the 28 cases. Thisisa deviation from equality of

T + 67449 V.5X.5X28—7 + 1.79.

The averages are:

For positive deviations, + .325

For negative deviations, —.712

For all deviations, — .453

Diagram 3 makes the reason for these differences clear

to the eye. With regard to their probable errors, the sx

No. 549] ON DIFFERENTIAL MORTALITY 523

cases which are perhaps statistically significant, are all

negative in sign.

SUMMARY AND Discussion

Taken altogether the data seem to me to indicate a real

differential mortality in seeds of Phaseolus vulgaris in

o TI eet a Be I

z |

Differences in Coefficients of Variation.

field cultures. This selective death rate is of such a

nature that the mean of the viable seeds remains prac-

tically the same as that of the original populations while

their variability is reduced. In short, both large and

small seeds are less capable of developing into fertile

524 THE AMERICAN NATURALIST [ Vou. XLVI

plants than are those which do not deviate so widely

above or below the type.

While the evidences in support of these conclusions are

fairly strong, it must not be forgotten that we are dealing

with a problem of great delicacy upon materials grown

under conditions such that the accidental (purely non-

selective) death rate must be quite high, and with records

not especially collected for our present purpose. Posi-

tiveness of assertion must therefore be reserved until

more critical evidence collected ad hoc is available. The

reader will note, however, that the conclusions here

recorded are based on many thousands of observations.

Although experiments are already under way, the gather-

ing of the data necessary for a more thorough investiga-

tion of the problem will be a long task, and it seems only

right that the results obtained incidentally should be

placed on record for the benefit of those who may have

opportunities for like observations.

To me personally, the results were surprising. First,

I had doubted whether a selective mortality could be

detected by the methods used. Second, I had supposed

that if a differential viability were found, it would be

limited to a weeding out of the lighter seeds. This latter

presupposition was based on the fact that a positive cor-

relation had already been demonstrated? between the

weight of the seed planted and the number of pods pro- -

duced, and a priori it seemed reasonable to suppose that

viability and capacity for forming plants with large num-

bers of pods would bear the same relationship to the

weight of the seed. Both questions deserve much more

detailed and refined study.

Two questions concerning these results will be fore-

most in the mind of the biologist: (a) What is the signifi-

cance of the selective elimination for evolution? (b)

What are the underlying causes of the differential mor-

tality? ae

* Harris, J. Arthur, ‘‘On the Relationship between the Weight of the

Seed Planted and the Characteristics of the Plant Produced,’’ Biometrika,

Vol. 9, No, 1, 1912.

No. 549] ON DIFFERENTIAL MORTALITY 525

The answer to (a) depends, as has been pointed out

above, upon the inheritance or non-inheritance of the

variations in seed weight. This question can not be dis-

cussed as yet, but from the data in hand, it seems to me

likely that this selective elimination has little or no evo-

lutionary significance. Certainly it is, as far as our evi-

dence goes, not a cause of progressive change but only a

factor tending to preserve an established type. It would

then be an illustration of the ‘‘periodic selection’’ of

Pearson.

The answer to (b) must be sought in the physiological,

and of course ultimately, in the chemical and physical

properties of the seeds of different weights. Experi-

ments directed to its solution are under way.

COLD SPRING HARBOR, L. I.,

July 15, 1902

A CASE OF POLYMORPLISM IN ASPLANCHNA,

SIMULATING MUTATION. II

PROFESSOR J. H. POWERS,

UNIVERSITY OF NEBRASKA

I may next state some further observations which I

was able to verify again and again in regard to the trans-

ition of one form of the species to another. As I have

said, forms intermediate between the saccate and the

humped, between the humped and the campanulate, and

even between the saccate and the campanulate, occur.

This statement applies to external body form, and to

some-extent to the nephridia and other internal organs,

with the exception, however, so far as I have yet observed,

of the size of the contractile bladder. This latter seems

to have its large size only in the small saceate type, and

I have observed no indications of gradual transitions to

the form possessed by the larger rotifers. More sig-

nificant, however, is the case of the trophi. I have ex-

amined these in a great many individuals that in body

form were more or less intermediate between the dif-

ferent types; but in nearly every instance the variations

of this organ seem to be abrupt and discontinuous; the

trophi are either of one type or the other. The only

instances found that in any sense transgress this state-

ment were the trophi of a few saccates produced as the

result of the slow degeneration of the larger form, in the

culture which I have before mentioned. These animals

showed trophi that had plainly lost a number of the more

delicate characters which I had otherwise found universal

through such a wide range of material, and, simultane-

ously with this, they had become in a degree transitional

between the two types; the angle of the inner tooth and

a slight crossing of the tips plainly related them to the `

cannibalistic type, while in size and general form they

526

No. 549] A CASE OF POLYMORPHISM 527

belonged to the other. I will record here also two in-

stances in which I have found the cannibalistic trophi

in the humped rotifer. The two specimens were almost

the last humped individuals found in a culture on the

verge of extinction, through cannibalism; they were prob-

ably the progeny of campanulates. Both were large

specimens of the humped type, one showing a rather heavy

corona and rather small humps, and being, therefore, in

some sense, of a transitional character. It bore campan-

ulate trophi 2574 long—rather undersized—in which,

however, the large lamellate teeth of this type were even

unusually developed. The other bore typical campanu-

late trophi 270% long, These animals contained large

unborn humped rotifers of normal type, with normal

trophi of 154» and 170», respectively. In these two in-

stances, therefore, the transition from the campanulate

to the smaller type occurred one generation sooner in

general body form than it did with the trophi, thus em-

phasizing the partial separateness and non-correlation

between the variations in these differently formed struc-

tures.

Next as to duration of transition periods and the num-

ber of transitional individuals. If conditions are favor-

able the periods are very brief and the number of transi-

tional types so few that they are readily overlooked un-

less careful search is made at just the right time. The

entire population of a teeming Asplanchna pond readily

changes from the saccate to the humped type in one week.

As before said, the saccates give birth directly to forms

with well-developed humps, and these humped young may

be at birth as large or even larger than the parent type.

One more generation of growth and reproduction may

then give large-sized, fully typical humped individuals.

Along with these abrupt transitions there usually occur,

however, a lesser number that are a little more gradual.

Individuals occur like saccates in all respects save that

they possess the inconspicuous dorsal hump; others are

small with the lateral and ventral (posterior) humps

528 THE AMERICAN NATURALIST [ Vou. XLVI

scarcely showing at birth, but developing to a moderate `

extent rapidly afterward.

With less favorable conditions the transition is pro-

longed and the number of intermediate individuals is

greatly increased. I have observed no instance, how-

ever, in which the species remained for longer than two

weeks in a chaotic condition. Either the transition is

soon effected or the numbers rapidly decrease and the

species disappears

Nearly similar statements may be made with regard to

the transition from the humped to the campanulate type.

As already stated, its advent usually occurs by the ap-

pearance of a very few individuals with the utmost

abruptness. Aside from the fact that the ontogeny is

here somewhat more extended—they, the young, being

considerably smaller than the adults, with much less ex-

panded corona—there is apparently little, if any, sense of

transition. I think it probable that the humped indi-

viduals which actually give rise to the very first campan-

ulates are individuals of somewhat extra size and vigor.

Such individuals have been found at different times as

well as in the case of the two mentioned in my first inves-

tigation, but their actual production of the young canni-

bals has not been observed. In any case their deviation

from the ordinary humped type is not great and the usual

transition has all the abruptness that the most pro-

nounced mutationist could anticipate. Moreover, as long

as the species is thriving and reproduction copious, the

two forms remain separated from each other as sharply

as do the most distinct species. This is the most fre-

quent condition by far in which one finds them.

When, however, conditions become less favorable,

which fact usually means that the food supply of the

- humped form is failing, a change intervenes. The

humped individuals usually remain quite as they were,

without reduction in size or loss of other characteristics,

save a much slower rate of reproduction. But this re-

duces numbers, and especially the number of young.

No. 549] A CASE OF POLYMORPHISM 529

The cannibals can and do ingest their full-sized con-

geners, but they are by no means successful in every at-

tack. One may observe them, with empty stomachs,

making scores of furious but futile attempts at capturing

their adult neighbors. It is largely the young hump-

bearers which, though nearly full grown, fall ready vic-

tims to the all-embracing coronex of the cannibals. Thus

it follows that any reduction of the food supply of the

lesser type immediately impoverishes the larger one as

well. The consequences of this are curiously dissimilar

in different cases, although always one of two results in-

tervenes. The cannibals may become even more canni-

balistic, destroying the entire humped population of all

ages, and their own young as well, until the culture is

finally obliterated by the death, from old age, of a few

veterans which are without further food supply. This

has happened again and again in my large culture

dishes.” In a few cases it has happened that a culture,

when at the point of extinction, would again revive by the

multiplication of the humped form. This is due to the

fact that the last starving cannibals, reproducing, as

they always do, both their own type and the humped type

as well, fail to eat up perhaps a single member of their

humped progeny, which then survives to start a new cycle

under less strenuous surroundings. I have carefully fol-

lowed this decline and survival as thus stated.

In about half of the cases, however, a very different

effect is registered upon the campanulate form by the

lessening food supply and the falling numbers of the

other type. It undergoes a considerable degeneration,

which may perhaps reduce it to the form from which it

arose, although I have not been able to fully demonstrate

this. But forms more or less intermediate are produced

by the starving cannibals. The trophi remain typical,

but the enormous coronas, as well as the breadth of the

entire animal, are much reduced. In the single instance

already mentioned in which degeneration gradually re-

duced the humped type to a small size, and finally to the

"I have recently observed one very similar instance in nature.

530 THE AMERICAN NATURALIST [ Vou. XLVI

most diminutive saccate form, I was surprised to find

that the campanulates present in the culture degenerated,

pari passu, with the other type. They became much

smaller, lost their flaring coronas, and nearly every sign

of their outward specialization. Yet, generation after

generation, they maintained their cannibalistic habits,

their heavy musculature, and above all the campanulate

type of trophi, the only change in these latter organs

being a reduction in size.

In the main, then, transitional periods are brief ; transi-

tional forms few. Unfavorable conditions prolong some-

what the existence of both. But the species always is

soon eliminated or sets up a new equilibrium under the

new conditions.

A few words further may be added at this point upon

the matter of fluctuating variation shown by the different

forms of this species. Without recording such varia-

tions mathematically, I have endeavored to ascertain as

fully as possible the answers to three questions: First,

how great is the amount of such variation? Second, is

fluctuating variation especially correlated with one or

other of the types of heterogenesis above described?

And third, what causes are operative in producing it?

As to the amount of fluctuating variation, certain facts

have already been mentioned that come under this head-

ing. I will but add here the general statement that each

of the three types is, in itself, highly variable—quite suffi-

ciently so to be regarded as a decidedly variable species

were it really an independent form. |

As to the second point, the question of the correlation

between fluctuating variation and the mutation-like

transitions, this has also been partially discussed. under

the heading of transitional types. But it is necessary to

add the unqualified statement that no evidence has been

discovered for such correlation. Variation is one thing;

heterogenesis another. The two phenomena contrast,

rather than are related. Thus the transition from the

saccate to the humped rotifer is often made when the

No. 549] A CASE OF POLYMORPHISM - 531

saccate type is in its most typical condition, at least so

far as form is concerned. Of all the minor fluctuating

forms found among the saccates the one that most

suggests the humped type is that which I have character-

ized above as urn-shaped. The bulging sides of such a

form might readily be thought to be the forerunners of-

at least the lateral humps; but during the entire study I

have been unable to observe the humped form originating

from this urn-like variety.

Furthermore, the saltations from type to type do not

necessarily occur, and I think do not usually occur, when

the amount of fluctuating variability is greatest. This is

especially true of the formation of the campanulates from

the hump-bearers. This transition occurs when the

latter are at a culmination of development and vigor, and

in this condition the species is, until saltation occurs,

relatively uniform.

Under the third question, as to causes of fluctuating

variability, I will record at present but two points, one

general and one special.

The greatest amount of general fluctuation seems

always to occur under relatively unfavorable conditions.

Favorable conditions, on the other hand, tend to produce

full development with relative uniformity among the

individuals of any given type.

One special instance of variation interested me so

much that I followed it whenever found, in the effort to

get at its exact cause. This is the variation in the length

of the three conspicuous humps which characterize the

commoner form. The amount of this variation is,

although I have not measured it, very great. The humps

may be but angular projections upon the body’s outline,

or they may elongate until they might be appropriately

described as finger-shaped. The type represented in the

illustration, Fig. 1, may be taken as typical. This type is

repeated in countless numbers, with but moderate varia-

tion, so long as conditions are normal, which means

chiefly, so long as the food supply is uniform and ade-

532 THE AMERICAN NATURALIST [ Vou. XLVI

Fie. 2.

papieeonne amphora, OF THE HuMPED FORM (FORM B), Teor

PIC YOUNG VELOPING Pasonssoonsericaziy WITHIN THE Bopy OF THE

PARENT. Magnification ee 8 diame sit

Fic. 2. Asplanchna amphora, campanulate form (form C), showing hetero-

typic young developing ‘parthenogenetic within the body of the parent. This

figure is dra from ecim n because it exhibited well the hetero

typic teprotüstiok in| ther ei idee k Ta not represent the true form of the

nd contracted the cor na, obliterating thus pa bell-like form ring

the anterior portion highly convex instead of concave as in life. The convex

end of Fig. 1 is, on the contra ary, quite ia pos oT Bigs being much

more paged killed in perfect form. Ma gnification about 8 d eters.

-$ ed, ophi of humped and campanulate SSS respectively.

The ydh in size is Teeter shown by these figures. Had average speci-

mens been chosen, Fig. 4 would have been twice the length of Fig. 3. Im

figures the “a y jaws” are omitted, they being so weakly

to be quite destroyed in process of extraction. I

e :

pieces, the outriggers, are omitted for the same reason.

210 diameters.

No. 549] A CASE OF POLYMORPHISM 533

quate. The individuals with smaller humps are always

transitional or degenerative in origin.

But what could be the cause of the hypertrophy of

the humps to fully double their usual prominence, and

this in individuals that always gave evidence of starva-

tion? Such individuals occurred in certain cultures in

considerable numbers, and constituted a very extreme

type; the animals were always much more transparent

‘than any others, the body wall being thin and the internal

organs usually pale, shrunken, and undeveloped, the

stomach empty, and embryos lacking. The general body

form was extremely slender, with corona but two thirds

average width, while the ventral, or rather posterior,

hump was not only long, but developed a secondary pro-

longation, as it were, from the end of the original one.

Such animals swim, all but habitually, with the lateral

humps retracted, and in this condition are so slender as

hardly to suggest the genus Asplanchna, the form being

apparently more nearly that of Hydatina. But with the

thrusting out of the lateral humps a singular transforma-

tion occurs; these structures are so long that their ex-

panse equals or exceeds the animal’s length, and so

slender that the animal’s forward motion bends them

backward. In my notes I designated these extreme

animals as the ‘‘cross-bow type.’’

As already mentioned, they occurred in considerable

numbers in several of my mass cultures. I also obtained

them several times under controlled conditions in isola-

tion experiments, but I found no clew to the cause of

their production until I discovered that they were fre-

quently produced by the gaint campanulates, and espe-

cially by the campanulates that were Moina-feeders. It

seemed very striking that this variant, which carried the

development of the humped form to its utmost extreme,

should be thus produced by the robust companulates in

which there are no humps, and in which, indeed, all the

characteristics are at the farthest possible remove from

the type in question. Yet these cross-bow hump-bearers

534 THE AMERICAN NATURALIST [ Vou, XLVI

formed a regular part of the progeny of the massive

crustacean-feeders. All but invisible, they swam rest-

lessly about seeking for available food, which was not

present, until many of them fell victims to the greedy

members of the parental stock.

This combination of overfed parent and foodless

progeny offered the suggestion of the cause I was seek-

ing, which was then readily confirmed by experiment.

Maximum nutritive conditions before birth and the entire

absence of available food for at least 24 hours after birth

produces the slender transparent type with the hyper-

trophied humps. Under these conditions the body wall,

and its projections, which are highly developed even at

birth, continue to develop for a considerable time after-

wards, undoubtedly withdrawing nutrition from the in-

ternal organs—stomach, digestive glands, ovary, ete.—

these thereby undergoing a partial atrophy.

A certain interest attaches to this explanation, because

it not only furnishes the rationale of an extreme type of

fluctuating variation in this rotifer, but because the facts

closely parallel the incidents in the development of the

male of the same species. The males at birth lack, of

course, the chief internal organs of the female, and

can not draw upon them as sources of nutrition, but they

do draw upon the rudimentary digestive tract until,

before death, it has frequently quite disappeared. More-

over, the males undergo a progressive development of

the body wall and to some extent of the humps during

the two to four days of their active life. The male thus

becomes more differentiated in the active portion of its

organization, absorbing meanwhile what little inactive

tissue there is to absorb. The same thing happens to the

young foodless female, save that there is more tissue to

absorb, and the process is not carried so far.

Sufficient investigation would doubtless unravel each

of the other minor fluctuations which the three forms of

the species undergo, and most of them will all but cer-

tainly resolve themselves into factors of nutrition. Few

No. 549] A CASE OF POLYMORPHISM 535

species of animals are capable of so numerous and varied

nutritive transitions and respond to them in so funda-

mental and varied manners as does this Asplanchna.

Before closing this paper it becomes a disagreeable

necessity to attempt some more definite systematic place-

ment of the forms of Asplanchna here discussed. The

task is a difficult one for several reasons. In the first

place, it is obvious that the facts here recorded tend to

disturb our very conception of what constitutes a species

in this genus. If we accept the interpretation of poly-

morphism as, on the whole, a little more applicable to the

facts of heterogenesis here cited than would be the in-

terpretation of mutation, the question is obviously raised

whether several of the other Asplanchna types hitherto

described as distinct species may not likewise be closely

related genetic forms, connected, as are those here de-

scribed, either with each other or possibly with these

very types. Thus a relationship is readily thinkable

between A. ebbesbornii and A. intermedia or A. sieboldi,

or possibly of one or the other with A. brightwelli;

although the disparity of the males in this last type

renders relationship less probable.

Moreover, in the literature of the subject the claim has

been made at least once that such a relationship exists

between European forms, as the following quotations

from Wesenberg-Lund’ in which he cites Daday to this

effect, will show:

Uber die Fortpflanzungsverhiltnisse der Asplanchnen kann ich Fol-

gendes mittheilen—v. Daday (“Ein Fall von Heterogenesis bei den

Riiderthieren.” Mathem. und Naturw. Berichte aus Ungarn, 7. Bd.,

1888-1889, p. 140) hat fiir Asplanchna sieboldi einige ganz merkwürdige

und bisher exceptionelle Fortpflanzungsverhiiltnisse geschildert. Seiner

Meinung nach findet man hier zwei verschieden geformte Weibchen,

theils solche, die den gewöhnlichen schlauchförmigen Asplanchna-Typus

haben, theils solche, die den eigenthümlich geformten Männchen dieser

Art gleichen; diese sind durch 4 conische Erhöhungen characterisiert,

und sind diese Erhöhungen derartig vertheilt, “dass je eine auf die

Mittellinie des Bauches und der Rückseite, eine auf die rechte und eine

* Wesenberg-Lund, C., ‘‘Ueber danische Rotiferen und über die Fort-

pflanzungsverhiiltnisse er Rotiferen,’’ Zool. Anz., 1898, Bd. 21, pp. 200-211.

536 THE AMERICAN NATURALIST [ Vou. XLVI

auf die linke Seite fällt, wodurch, von vorn betrachtet, die Form eines

gleichschenkeligen Kreuzes sichtbar wird” (Daday, p. 153). Jedes

dieser zwei verschieden gebauten Weibchen vermag sowohl Weibchen

ihrer eigenen Gestalt parthenogenetisch hervorzubringen, als auch Weib-

chen der anderen Art; ferner auch Männchen und, nach der mit diesen

erfolgten Begattung Dauereier (pp. 206-207).

Daday’s work on the rotifers has in general been fre-

quently criticized and all but discredited, and this ob-

servation on his part of a reciprocal relationship between

A. sieboldi and a saccate Asplanchna fares no better at

the hand of Wesenberg-Lund. He replies that he has

himself reared A. sieboldi in an aquarium for a month,

that he has studied them thoroughly and has found no

such reproductive phenomena. He continues, that Daday

has simply been mistaken in his observations, having

failed to distinguish the humped A. sieboldi from the

saccate rotifer, because the humps of the former species

are often retracted, giving it for the moment a saccate

form.

This criticism of Daday’s reported observations may

of course be correct, but it seems as naive as it is severe.

It is of course true that the humped rotifers retract the

lateral humps; but the position of these protuberances

always remains marked by folds of the body wall, while

the ventral hump is not retracted at all. Daday must

indeed have been a poor observer to be thus deceived, the

more so, in that the moment these animals are placed

under the pressure of a cover glass or even in a very

shallow drop of water on a slide, the pressure of the cover

glass or their own weight forces them to expand the

humps and instantly reveal their type of structure. In

the light of my own study it seems far more probable that

Daday was correct in his reported observations than that

Wesenberg-Lund is correct in his criticism of them.

The fact that Wesenberg-Lund reared the humped

Asplanchna for a month without the occurrence of hetero-

genesis is of no especial significance. The writer has

reared the humped form discussed in the present paper

for longer periods than this with the same result.

No. 549] A CASE OF POLYMORPHISM 537

Heterogenesis is confined to special periods or caused by

special conditions as above set forth.

However, not only is the question of species confused

by the presence of heterogenesis in the genus, but another

difficulty which I had not anticipated manifests itself;

viz., the discovery that the descriptive work which has

already been done upon the genus has not, even the best

of it, been sufficiently accurate to be trustworthy. I

make this statement with the utmost reluctance, and only

after I have spent weeks of effort to bring my observa-

tions upon single points into accord with the statements

of Rousselet, who is not only the highest authority on the

group in question, but who has, as already stated, made

the last and most detailed pronouncement upon the

species of the genus. I have failed, however, in my

efforts. Nor are the discrepancies such as may, with

probability, be explained by the assumption of differ-

ences in the material which we have examined. ‘Thus, to

take an example from Rousselet’s description of the jaws.

He says:

At the tip there is really but a single point . .. ; on crushing the

jaws a “ah a ridge seen in side view is oe over and simulates

a second t

SRRA in his supplement, has also spoken a similar

effect, viz.:

When the ramus is subjected to pressure from above the deep plate

is bent by the glass (to which it stands at right angles), and its free

lower corner is twisted, so as to look sometimes like a second tooth, just

below the extreme apex, sometimes like a small plate.

Now in spite of these statements I seemed to see the

thin lamellate plate-like second tooth near the apex of

every jaw in case the conditions for its vision were at

all adequate, and in the giant campanulate this structure,

so delicate in the ordinary type, becomes greatly de-

veloped, forming a large cutting tooth, which, when the

jaws are closed, meets with its fellow of the opposite side,

in the middle line. That this thin triangular tooth in the

ordinary form was a false appearance produced by the

538 THE AMERICAN NATURALIST [ Vou. XLVI

bending over of the corner of a ridge by the pressure of a

cover glass seemed improbable, and I immediately put it

to test in various ways. For one, I extracted a large

number of the trophi by means of potassic hydrate in

deep watch-glasses. Here there was obviously no pres-

sure, yet the structures in question were quite visible,

even before the trophi had been transferred to a slide, or

touched by any instrument. Moreover, these thin

lamellate teeth are never quite symmetrical on the two

rami, and this delicate discrepancy is always on the same

side of the animal, as I ascertained later in stained and

mounted preparations. I carried my study of the trophi

farther by mounting many which I had extracted in deep

hollow-ground slides, including with them a small bubble

of air. By giving the slide a quick tilt the air bubble

could be made to strike and overturn the trophi in dif-

ferent ways. By then replacing the slide quickly under

the microscope, views could be had of the trophi before

they had settled to the ordinary horizontal position. A

half hour of such attempts readily furnished views of

every part of the trophi, seen from almost every possible

angle. Portions so thin as to be invisible in one view

become visible in another; optical sections at all points

make possible the arrival at the correct form. I regret

that in my drawing I have been able to show so little of

the delicate complexity of these structures; but Rous-

selet’s view of their structure—that ‘‘the chitinous ma

terial is bent at right angles throughout the length of

the rami, forming an inverted L in cross section’ ’—is

certainly very far from correct. The structure varies at

different points; ridges thicken and fade out in complex

and sinuous fashion, quite as we should find them in the

complex chitinous jaw of an insect, or, for that matter,

in the jaw-bone of a mammal.

The tips of the jaws are interesting, and I find no

description of the jaws of any species of Asplanchna, by

any author, which coincides with my observations.

Nevertheless, this may be due to the inadequate study of

No. 549] A CASE OF POLYMORPHISM 539

these difficult structures by systematists who can devote

but little time to a given point. I find the two rami are

never alike at the very tips. I am not speaking now of

the delicate lamellate teeth already mentioned which are

a little distance removed from the tips, but of the very

extremities. Of these latter, one is bifid, or ends in two

delicate tips; even these again are never quite sym-

metrical, but the one which is toward the animal or

posterior is a little smaller and shorter. Furthermore,

the split in the tip of this jaw is not a simple cleft such

as one might produce by splitting the end of a stick with

a knife, but is a triangular groove, the base or open side

of which is toward the inside or concave aspect of the

ramus, the apex toward the outside. As aforesaid, this

cleft divides the tip of the ramus, but it is also continued

on the inner aspect of it considerably farther than it

extends on the outer, becoming thus shallower and

shallower as it extends farther from the divided tip.

The opposite ramus is not bifid, but tapers to a point, and

the tapering is of such a nature that the jaw near the

tip is more or less triangular in cross section, so as to fit,

not only into the cleft between the tips of its fellow

ramus, but farther into the triangular groove on its inner

side as well. Thus these delicate chitinous jaws, when

closed, lock together in double manner.

The study of hundreds of examples of the trophi of

the humped rotifer as it occurred in the material first

_ examined left upon the mind of the writer a very distinct

impression of the minute delicacy of detail and very great

uniformity which prevails in these structures. Varia-

bility seemed almost wholly confined to the matter of

size,

Turning briefly to the trophi of the ecampanulate type,

I will say that they differ regularly from those just

described, not only in the features shown in the figure,

such as general size, breadth of rami, more acute angle

of the lower inner tooth, ete., but in other marked features

besides. The inner tooth, smaller in proportion as well

540 THE AMERICAN NATURALIST [ Vou. XLVI

as set at a different angle from the corresponding struc-

ture in the humped type, is here fused with the ramus

instead of being merely bent over inward from its outer

margin. But the tips differ most; the secondary lamel-

late teeth, as before mentioned, become very large,

though variable, structures. -They always meet in the

middle line when the jaws are closed; they have wavy or

corrugated surfaces, and thin down to a sharp cutting

edge. The tips of the rami are modified most of all.

They are slender and greatly extended in length, meeting

and passing at an acute angle. Neither tip is bifid, and

the asymmetry between the two rami is much less

marked. The jaws do not interlock, when closed, in the

sense in which they do in the humped type; instead, the

tips invariably cross, like the mandibles of a crossbill, the

farther closing being prevented by the meeting in the

middle of the lamellate teeth. Occasionally I have

noticed a campanulate whose jaws had sheared past in

the wrong way; the lamellate teeth then did not meet

to prevent farther closing, and the animal had apparently

lost control of the organs, as the two halves remained

crossed well down to near their bases. ;

Returning to Rousselet’s description of the trophi of

A. amphora, which must, of course, be compared only

to the trophi of the humped type, I will say that despite

the discrepancies in detail which I deem due to inaccuracy

of observation, it remains true, nevertheless, that his gen-

eral figure of the trophi of this species coincides essen- ,

tially with the general appearance of the trophi as I find

them in the humped and saccate types, and this con- `

stitutes a fair reason for assigning, provisionally, the

material which I have studied to the species Asplanchna

amphora.

However, I can not leave this matter of the trophi with-

out instancing a surprising observation which I have

made the past summer on the trophi of the related

species, Asplanchna brightwelli—an observation which :

again complicates, in an entirely new way, the question r

of species in the genus Asplanchna. a

No. 549] A CASE OF POLYMORPHISM 541

As soon as I had discovered the fact that the humped

Asplanchna which I was studying was represented by a

saccate type which in many characters approached closely

to Asplanchna brightwelli, I began an extended search

for this latter species, in order to study closely the ques-

tion of relationship or non-relationship. At different

times, throughout a period of one year, I succeeded in

finding A. brightwelli in five different ponds in my own

vicinity. The species tenants ponds of a different char-

acter from those in which the larger Asplanchna

flourishes, and is associated with a somewhat different

micro-fauna. In but one instance have I found the two

species developing together, and in this case the larger

Asplanchna did not pass beyond the saccate condition, in

which it was also present but sparingly. The resem-

blance of its occasional representatives to the more

numerous and likewise saccate individuals of A. bright-

welli was so great as to almost prevent its detection.

Only my constant work with the larger species could have

sharpened my attention to the point of noticing any

especial lack of homogeneity in the material. Yet the

saccates of the larger species were regularly a little

longer and about one fourth broader than the adult A.

brightwelli. They differed also in a number of minor

constant characters. But none of these have hitherto

found place in any specifie descriptions, with the excep-

tion of the difference in the trophi. The trophi of the

larger saceates agreed with the description and figure

which I have given in everything save that they were a

little undersized. The trophi of A. brightwelli agreed in

their general outline with the figure given for this species

by Rousselet; they possessed the more delicate, perfectly

oval contour, and invariably lacked the large inner tooth,

just as Rousselet asserts that he has always found them

to do. Into the question of the form of their tips and

the presence or absence of the all but invisible lamellate

teeth I do not go. Such study as I have given them led

me to think that they were constructed in these respects

542 THE AMERICAN NATURALIST [Vow.XLVl

essentially, but not exactly, as were those of the type

which I had already studied. I was much pleased to thus

substantiate, at least in a general way, on this American

material, Rousselet’s judgment on the distinction between

the trophi of these two species. I will add that a score

of culture experiments started with single individuals

of the two types fully confirmed their distinctness. De-

spite their very close resemblance, I reared from one set

of the delicate saccates the humped amphora type with

which I was so familiar; while parallel cultures, with

identical conditions as to food and temperature, pro

duced no modification in the A. brightwelli other than a

slight increase in size.

I therefore reached the conclusion that, delicate as are

the differences which separate the saccate form of 4.

amphora from the invariably saceate A. brightwelli, they

were none the less sharply demarcated. Ignoring other

features, it seemed perfectly safe to trust the one char-

acter of the absence or presence of the larger inner tooth

on the trophi.

Imagine my surprise, then, when, upon visiting an

entirely different locality—Custer County, South Dakota

—I discovered an Asplanchna in countless numbers

which completely upset this distinction and introduced

me to a seemingly new type of variation within the genus.

It was in the charming little mountain lake (or rather

reservoir, for the original site contained a mere pool

which has now been increased to a depth of 80 feet by an

artificial dam) called Sylvan Lake, that I came upon the

rotifer in question. The lake was indeed swarming with

rotifers of different species, which constituted the

majority of its plankton. Monarch of them all, and

profiting greatly by its superior size and ingesting power,

was a superb Asplanchna. Aside from a slight excess

in size every outward character indicated A. brightwelli.

Moreover, I had found the species in the very nick of

time, for both males and resting eggs were copiously

present. Among very large numbers of these which I

No. 549] A CASE OF POLYMORPHISM 543

immediately examined not one differed outwardly from

the brightwelli type. But examination of the trophi

yielded the astonishing result that in every instance they

bore a strong inner tooth in the exact position in which

this is found in A. amphora. I examined large numbers

of them and found that in all the features which I could

study with the facilities I had in the field, there was no

obvious variation whatever.. It should be mentioned that

in outline these trophi presented the close approach to a

perfect oval which is characteristic of the brightwelli

type. The strong inner tooth alone gave them decidedly

the aspect of the jaws of Asplanchna amphora.

This discovery is plainly again confusing, as to specific

distinctions between the types. Fortunately, however,

it serves at least to clear up certain contradictions in the

literature of the subject. Rousselet, in the article above

mentioned, dealt especially with this point. He figures

the jaws of A. brightwelli, to use his own expression, as

he has ‘‘invariably found them’’—i. e., with an oval out-

line and without the inner teeth. He concludes that the

earlier writers on the genus—Dalrymple, Brightwell,

Hudson—had certainly confused two different species of

Asplanchna, describing the trophi of A. amphora as be-

longing to A. brightwelli.

My examination of the Sylvan Lake material shows

that no such error need be ascribed to them. A. bright-

welli simply exists in two distinct races (genotypes?) ;

Rousselet has invariably found but one of these, just as I

myself have done in my own vicinity; while Brightwell

very probably found and described the other, which I

have found so abundant in the South Dakota lake.

The finding of A. brightwelli with two distinct types

of trophi may seem but a trivial matter, but taken in its

full connection it is not without interest. A. brightwelli

seems, in general, an all but constant species. Yet, judg-

ing by morphological test, it should be closely related to

A. amphora, a species which experiment shows to be

phenomenally variable.

544 THE AMERICAN NATURALIST [ Vou. XLVI

What, then, is the relationship—the physiological and

genetic relationship—between these two types? Jen-

nings in his recent work on the ‘‘Characteristics of the

Diverse Races of Paramecium’’ has prophesied that the

more exact study of the life history of rotifers will

demonstrate that much of their apparent variability is

really due to the presence, within specific limits, of

numerous fixed: races.

Now the study, as here outlined, of the variation of A.

amphora, brings to light a condition-which in no wise

substantiates this prophecy. No fixed races are present;

but strongly demarcated yet temporary types, on the one

hand, and fluctuating variations, on the other, which are

all or nearly all the result of nutritive stimuli. Is it

possible that, in spite of this, the closely related A.

brightwelli will present the fixed races which Jennings

suggests?

I have aleady indicated that a series of about twenty

culture experiments with the type of A. brightwelli first

found by me yielded no significant modification. At the

present writing I am again following this species in

copious natural development and again conducting a

few mass cultures without finding anything but farther

proofs of constancy.

I am also succeeding in rearing very large numbers

of A. brightwelli of the type whose trophi present the

inner tooth. . The resting eggs, which were brought from

Sylvan Lake the preceding August, were kept over winter

in a small amount of the lake water and hatched out in

March by adding tap water and raising the temperature

by placing the dish in the sunlight. The culture medium

has slowly been quite changed to the somewhat alkaline

and saline water of the writer’s locality. The cultures

have also been heavily fed upon organisms to which they

are certainly unaccustomed in nature. Some cannibal-

ism has been induced. But the trophi remain obstinately

true to their own type, and the general morphological

changes have been confined to a considerable increase in

No. 549] A CASE OF POLYMORPHISM 545

size of a few individuals, with perhaps.a somewhat dis-

proportionate expansion in breadth of corona. Yet the

results of a preliminary six weeks’ culture of this type of

_ A. brightwelli are essentially similar to those which fol-

lowed my attempts to modify the first type: they are

negative.

Much more extended and varied experiments must be

made before reaching final conclusions upon the con-

staney of these two races of A. brightwelli. Yet they

certainly promise to bear out in the main Jennings’s pre-

diction of relatively fixed races within the species.

Yet the foregoing does not entirely complete the pic-

ture of variation as I have found it in A. brightwelli.

While the rearing of thousands of individuals and the

examination of a very large amount of material in nature

give the appearance of two stable genetic types, yet in the

rarest instances mutation-like changes of the most

marked character probably do occur, just as they do in

A. amphora.

While at Sylvan Lake it occurred to me that the very

favorable conditions under which A. brightwelli was there

developing, including the preying upon a number of dif-

ferent organisms, were as well adapted as possible to

bring about mutational changes such as I had found to

occur in A. amphora. Day after day I examined large

amounts of material with wholly negative results. But

a favorable morning at the very close of my stay at the

lake enabled me to collect several liters of plankton as

thick as cream in consistency, with perhaps four fifths of

its bulk living Asplanchna. Pouring this in the thinnest

possible layers, into broad dishes, and placing these above

a black surface, I proceeded, by means of a powerful

reading lens, to search for any individual Asplanchna

showing marked deviation from type. Minor deviation

could not, of course, be thus detected. To my great sur-

prise, my search was finally rewarded by the finding of

three individual rotifers, and three only, of quite aston-

ishing proportions. They were certainly Asplanchna;

546 THE AMERICAN NATURALIST [ Von. XLVI

that they were derived from the brightwelli I of course

have no proof, but in the light of my study of A. amphora

it seems probable. They were campanulate forms, dif-

fering from the slender saccate A. brightwelli even more |

than the campanulate A. amphora differs from the

smaller types of its species. Seen in dorsal view, when

freely swimming in a drop of water without cover glass,

they presented almost the form of an equilateral triangle

with one rounded corner; this was the posterior end; the

entire opposite side being taken up by the loose flapping

corona. I regret that, in my haste, I was unable to study

these forms precisely, and much less to prove their re-

lationship. But I hope that the isolated observation may

perhaps induce others to seek among crowded stocks of

Asplanchna of different species for rare and much mod-

ified forms. If, as I believe will be the case, they are

found to occur occasionally in A. brightwelli and perhaps

other species, it will throw an added light upon the changes

which so readily take place in A. amphora. The rarity

of their occurrence will render clearer the relationship of

the phenomena to the recognized instances of mutation.

Before closing the discussion of facts relative to the

specific determination, statements must be made with re-

gard to the males and to the resting eggs. Similar males

are produced by all three of the forms which the am-

phora-like Asplanchna assumes. The humped and cam-

panulate types produce them copiously; the saccate type

but rarely and at periods when it is about to pass over

into the humped form. These males are always of the

well-known type bearing two lateral humps. They quite

agree with Rousselet’s determination, except that he evi-

dently assumes the size to be uniform, whereas I find it to

be extremely variable, the limits being as three to one.

The largest males, often present in abundance, reach fully

the size of the humped females; i. e., a length of 1500».

The cause for the wide divergence in size is the varying

degree of development at birth. This affects them as it

affects the young females, except that the young males, —

No. 549] A CASE OF POLYMORPHISM 547

being unable to feed and thus continue their development,

are obliged to remain at approximately the same diver-

gent sizes at which they are born.

In regard to the resting eggs, they are, of course, as are

the males, produced by all three types, and but rarely by

the smaller saccate form. The number produced by one

individual varies greatly with the degree of nutrition.

But one to three are matured if the females are poorly

fed after fertilization; whereas as many as six are fre-

quently present at one time in the body when nutrition is

high, and very rarely as many as nine may be seen. The

large campanulates usually show a high number, but it

does not exceed the maximum produced by the humped

form. The color of the egg, which Rousselet uses as a

specific character, is variable in this species. In in-

dividuals fed on Paramecia the eggs are quite white;

in individuals reared on Brachionus they are light yellow

to orange; while in Moina-feeders they are dirty white

to brown. Again, the volume of yolk, i. e., the filling or

not filling of the egg cavity, which Rousselet also regards

as important, I find to be highly variable in the eggs

of both this species and of A. brightwelli. It is par-

tially a matter of the age of the egg; but eggs are fre-

quently deposited in the most different conditions with

regard to this character. There remains the size of the

egg and the appearance of the egg coats, both of which are

highly characteristic and relatively uniform. The size

of the egg is much less, relative to the size of the animal,

than is the case in A. brightwelli; but the actual size is

larger and exceeds the dimensions given by Rousselet

for A. amphora, viz., from about 200» to 225», as con-

trasted with his figure, 170». This is surprising, in that,

in the case of A. brightwelli, my measurements of the

resting egg—170» to 190»—is less than the figure—205p

—given by Rousselet.

The egg envelopes, which I have studied in an almost

indefinite amount of material, grown under very diverse

conditions, are the most uniform and at the same time the

548 THE AMERICAN NATURALIST [ Vou. XLVI

most peculiar feature which I have found in the species.

They plainly do not agree with Rousselet’s characteriza-

tion of the egg of A. amphora: ‘‘The outer shell en-

velope consists of numerous much smaller globular trans-

parent cells’’ (smaller than the cells in egg coat of A.

brightwelli) ‘‘through which a finely dotted inner mem-

brane can be seen.’’ I find that at a certain intermediate

stage of development a dotted inner membrane can be

seen, the dots being the ends of either tubes or

rods making up a thick inner coat; the rapidly devel-

oping outer shell, however, soon obscures these dots and

the coat assumes at first a wrinkled, then a heavily cor-

rugated, surface. The corrugations are so disposed that

many of them converge at two opposite poles of the egg.

I deem it quite impossible that this characteristic and

beautiful structure should have been overlooked by any

one studying this species in detail and with the full char-

acters which it possesses in the writer’s vicinity. It

therefore seems very probable that the type of A. am-

phora studied by Rousselet was not identical with that

studied by the writer, and it may accordingly prove

necessary to eventually separate the form I have

studied from the original type of the species, ascribing

it varietal rank, based on at least this one character of

the egg coats. The systematic predicament in which

this would place these beautiful rotifers would indeed be

pathetic or intolerable or humorous, according to our

attitude toward things systematic. We should have two

varieties, separated from each other by a single fixed

character only, and one of these varieties would comprise

within itself, besides a host of minor variations, three dis-

tinct types, each of which differs from its fellow, not only

more than do the varieties differ from each other, but

more than the whole species, at its nearest point of ap-

proach, differs from its closest congeners. |

There is not the least known reason why actual facts

of genetic relationship should not be as complicated as

this, and if they are so we must deal with them systemat- —

No. 549] A CASE OF POLYMORPHISM 549

ically in some fashion. It is evident, however, that the

species in question and other allied forms should be more

intensively studied by workers in other localities before

we venture upon the final solution of so intricate a ques-

tion. For the present all that needs be said is that the

material studied by the writer and designated by the

phrases, the saccate, the humped, and the campanulate

forms, belongs to the species Asplanchna amphora, as at

present constituted; and it seems no less certain that this

material is sharply segregated from A. brightwelli, de-

spite the exceeding closeness of this latter species to the

above mentioned saccate form of A. amphora.

A brief résumé of the chief characters of Asplanchna

amphora, as here studied, will be of use to rapid workers.

It is as follows:

Species trimorphie, each of the three forms showing fluctuating vari-

ation and occasionally intergradations.

Form A, saceate type, produced from resting egg and multiplying by

rapid parthenogenesis, through several generations; corona about equal-

ing diameter of body or less, nearly cireular in outline, agreeing with

the cylindrical body, which rests on side when water is withdrawn;

body without humps or with small dorsal hump only; flame cells vary-

ing in number from approximately 20 to 40; contractile vesicle large;

trophi as in next form, oe smaller—about 95 p to 135 p long.

Length of entire sar 500 p to 1,200 p

Form B, humped type, PREBE E known as Asplanchna

amphora, PEARS from form A by rapid saltation and reproducing

chiefly its own type; body conical, strongly flattened dorso-ventrally,

with one posterior, one dorsal, and two lateral humps of varying size

and habit of carriage; corona oval, agreeing with the flattened body,

which causes animal to rest on dorsal or ventral surface when water is

withdrawn; flame cells 40 to nearly 60; contractile vesicle small; trophi

strong, typically from 150 p to 170 p in length, though varying from

130 » to 200 p, enclosing when closed an area which is not oval but

widest in its distal third, with prominent tooth projecting inward

seemingly from the inner though really folded over from the outer

margin of each ramus, delicate lamellate teeth near the tips and the two

rami interlocking when closed by means of one bifid and one pointed

tip; accessory jaws, as also in forms A and C, very pid developed.

Length of entire animal approximately 1,000 » to 1,800

Form C, campanulate type, originating usually from gums Basa

result of cannibalism, and reproducing both its own form and form B;

550 THE AMERICAN NATURALIST [ Vou. XLVI

body very broadly saceate to broadly campanulate in form, with very

heavy walls and musculature, strongly flattened dorso-ventrally, never

with humps; corona oval and very broad, its breadth frequently equal-

ing the length of the animal; anterior end of animal, within corona,

concave instead of convex; flame cells approximately 80, to 115 p;

contractile vesicle small. Animal resting when water is withdrawn on

dorsal or ventral surface ; trophi very large, typically from 300 p to 340 p

in length, enclosing a narrowly oval area; inner teeth relatively less

prominent than in preceding types, set at an acute angle with the ramus

and more firmly fused with it than in the preceding types; lamellate

teeth near tips of rami much developed and meeting, with cutting edges,

in middle line; tips of rami not interlocking but shearing past each other

when closed. Length of entire animal approximately 1,800 u to 2,500 p.

In conclusion, it may be pointed out that the type of

variation shown by the rotifer here discussed seems

somewhat peculiar, in that it lies seemingly on the line

between germinal variation and variation which is com-

monly supposed to be somatic. To use recent phraseol-

ogy, it is difficult to say whether the types which this spe-

cies of Asplanchna produces should be called genotypes

or phenotypes.!° They are like genotypes in that when

once produced they manifest a marked tendency toward

stability, each type reproducing itself through a number

or even a multitude of generations after the special con-

ditions which favored their origin have ceased to be

present. They are to some extent like phenotypes in that

this stability is less than that of true species, yielding,

though rarely, to degenerating or other modifying con-

ditions.

* As the proof of this article passes through my hands, one of the above

terms—‘ phenotype’ ’—is already a matter of ancient history; while

to the study of other rotifers and protozoa—are already known to the

writer which harmonize even less than the facts of the present paper vin

the rigid conceptions which some set forth with show of finality.

No. 549] A CASE OF POLYMORPHISM 551

It is worth noting—though this is in part but restating

the last thought in different language—that the varia-

tions here described differ from the majority of those re-

cently recorded for minor invertebrates ;'' for example,

the modifications in Daphnia, Bosmina, and Asplanchna,

so carefully observed by Wesenberg-Lund. These latter

variations are in the main variations in external form

only, and seemed to be pure reactions to external con-

ditions, taking place, for example, when the surrounding

medium has reached a certain temperature, and again

lapsing very soon after the temperature has dropped.

Such variations fall naturally under the rubrics of sea-

sonal polymorphism, temporal variation, or eyclomorpho-

sis. The variations which we have studied in Asplanchna

refuse to be thus classified.

It is true that the stability of these variants is mark-

edly different, being greatest for the humped type and

least for the minor saccate form, but a stability that

tends strongly to resist external influences is none the

less obvious for each. And this seems to the writer to

render it highly probable that each of these variations is

of germinal origin. If this is the case it is the more

striking that this germinal variation 1s itself a variable

and elastic quantity, originally initiated by nutritive

causes,

In one sense only may it be said that these mutational

variations do occur in a rhythmic or cyclical fashion, in

that, namely, each form may produce a fertilized or rest-

ing egg that tends to return to the common starting point.

The variations are therefore obviously not transmitted

through the resting egg as they are through partheno-

genetic ova. It is, however, by no means certain that

there is complete community of kind in all the young

hatched from resting eggs. Such observations as have

already been made seem to show that the progeny of the

resting eggs of this species are by no means uniform,

1 Some of the variations recorded in the recent work of Woltereck ap-

proach more closely to those here recorded for Asplanchna,

552 THE AMERICAN NATURALIST [ Vou. XLVI

physiologically or morphologically. Some stocks seem

larger than others from the start, and apparently gave

rise more readily to the second and third types. It will

require much careful experiment to ascertain the cause of .

these diversities, and whether a tendency toward the

transmission of variations actually lies in the resting egg.

If such proves to be the case, light will be immediately

thrown upon the farther problem, namely, whether the

saltations here described are intimately related to a true

species-making process. All in all, it seems that they

probably are thus related, especially as the forms pro-

duced parallel so closely other types of the genus which

are now universally regarded as definite and circum-

scribed species. |

But are these other types of the genus definite and cir- ‘

cumscribed species, or are they (some of them at least) 7

but semi-independent types, occasionally brought into

existence by unusual nutritive conditions and then main-

taining for a time only their partial or complete auton-

omy? Unfortunately these remaining forms of the

genus are not accessible in the writer’s vicinity. But a

they would seem well worthy of careful study, both ob- |

servational and experimental, where they may be found,

and it seems to the writer that such study, sufficiently

prolonged, will bring to light a species-making process

in rotifers which is somewhat different from any as, yet :

demonstrated in the animal kingdom. 3 i

It is just possible that these saltational phenomena may

be purely local, or at least greatly exaggerated in the

genus Asplanchna. The food reactions of this genus are

undoubtedly extreme, and the development of their par-

thenogenetic ova in close proximity to this spasmodic

and very variable nutritive supply may possibly make

this genus exceptional. But no fundamental organic phe- _

nomenon is wholly isolated and unlike the phenomena of

other species. If nutrition can modify the germ cells in

the genus Asplanchna and thus bring into existence new

types, nutrition surely must be a factor on a wider scale.

SHORTER ARTICLES AND DISCUSSION

AN UNUSUAL SYMBIOTIC RELATION BETWEEN A

WATER BUG AND A CRAYFISH

WRITERS on animal ecology and popular entomology have

made us familiar with a remarkable habit of various species of

water bugs belonging to the genera Zaitha and Serphus. In

these forms it has been established that the female seizes a male

and by superior strength and apparently against his will, cov-

ers his back with her eggs. These adhere together and to his

tegmina to form a dense mass as thick as his own body. Con-

verted thus into ‘‘an animated baby carriage” as Howard puts

it, the male carries the whole brood about with him until they

hatch, providing them with protection and, possibly, improved

aeration. It is worthy of note that the habit has been observed

in widely separated parts of the world, viz., both coasts of

America, Europe, and Japan.

The writer has observed a somewhat analogous adaptation in

another group of aquatic Hemiptera, the Corixide—a habit that

appears to be so extraordinary that he has refrained from de-

scribing it until it should have been found to be other than a

local instance. Quite by accident he discovered that a similar

observation had been made previously by S. A. Forbes" so that

it seems rather improbable that the circumstances should be

accidental.

During the summer of 1910 it was observed that numbers

of the crayfish taken from a pond near Columbia, Mo., were

covered with the eggs of some insect. When hatched out in

aquaria these were found to be a species of waterboatman.? The

crayfish were those of a common species of the neighborhood,

Cambarus immunis Hagen and both young and old were in-

vested with the eggs. In well covered specimens the telson, the

legs, the sides of the abdomen, and nearly the whole of the

cephalothorax, including the eye stalks, and basal parts of the

1 Forbes, Bull. IU. Mus. of Nat. Hist., I, pp. 4-5, 1876; ibid., AMER. NAT.,

XII, p. 820, 1878.

2 The species has been described elsewhere (Canad. Entom., XXXI, pp.

113-121, 1912) as Ramphocoriza balanodis n. gen. et sp. and a full account

of its metamorphoses given.

553

554 THE AMERICAN NATURALIST [ Vou. XLVI

antenne, were clothed with a felt-like cloak of tiny eggs each a

little less than a millimeter long and imbedded in a small cup

which is affixed to the carapace. The cup has been described

for other species of Corixide which attach their eggs to stems

of water plants and is not to be considered as a special adapta-

tion in the present instance. It was found, however, that the

carapace was slightly impressed for the reception of each egg

cup, as if the affixing of the egg had either softened the chitin

somewhat, or had taken place before the hardening subsequent

to ecdysis had been completed.

In a ‘List of Illinois Crustacea,” under Cambarus immunis,

Forbes (l. c.) states that:

About one fourth or one half the specimens taken from stagnant

ponds in midsummer [in Central Illinois] are more or less completely

covered above by the eggs of a species of Corixa, probably C. alternata

Say, since this is much the commoner of the two species found in

such situations, the other being as yet undescribed. :

As the present writer has taken Ramphocoriza in Illinois it is

highly probable that it was the ‘‘yet undeseribed’’ species men-

tioned by Forbes. The same species of water bug is also found

in Texas, so that it is more than likely that the distribution of

the insect is coincident with that of the crayfish Cambarus im-

munis. Forbes states also that a ‘“‘careful search of the weeds

and other submerged objects in the ponds discovered no other

place of deposit of these eggs.’’ The writer also can testify to

the same point. The waterbug in question is abundant where

found, but its distribution is not general and it is not improb-

able that it is conditioned by the presence of the crustacean

species with which it has undertaken this unusual partnership.

All the Corixide are strong flyers and ‘‘swarm’’ at maturity,

so that with the general similarity of habitat which exists

throughout the Mississippi Valley there is no other reason why

Ramphocorica should not be equally as well distributed as some

other species of Corixids (e. g., Arctocorisa interrupta Say)

found there. nae

The insect when mature, measures but 5-54 mm. in length

and a very large number of females must simultaneously par-

ticipate in the egg laying so to cover an individual crayfish.

o count was attempted of the eggs on any one crayfish but the

number must often run well up into the hundreds. ;

The investiture of eggs commingled with debris certainly —

No. 549] SHORTER ARTICLES AND DISCUSSION 555

556 THE AMERICAN NATURALIST [ Vou. XLVI

renders the crayfish less conspicuous and it probably profits by

the arrangement in much the same was as do various shore-

crabs which are decorated with sponges, alge or ccelenterates.

Whether the water bug improves its chances against racial ex-

termination by the adoption of such a pugnacious protector it

may be too much to assume, but at any rate whatever the util-

itarian value of the habit it must be of the same nature as that

which obtains in the widely distributed genus, Zaitha. An ob-

servation of the manner of egg laying on the crayfish would be

of much interest.

JAMES F. ABBOTT

WASHINGTON UNIVERSITY

DOUBLE EGGS!

UNDER some such caption as the above there have appeared

from time to time in zoological literature various accounts of

anomalous eggs, chiefly of the common hen. These have nat-

urally elicited more or less popular interest, and various expla-

nations have been proposed concerning them. While it is no

part of the present purpose to review the history of these phe-

nomena it may not be amiss to merely call attention to a few of

the more striking titles under which they have been described.

For example, Barnes (63, ’85) has described cases under the title

“Ovum in Ovo”; and Schumacher (96), “Ein Ei im Ei”;

Parker (06), ‘Double Hens’ Eggs”; and quite recently Pat-

terson (711), “A Double Hen’s Egg,” are typical of numerous

titles appearing in the literature. The chief purpose of the

notes which follow is to call attention to an earlier paper by the

writer (’99) and to describe subsequent facts which have come

to his knowledge. The only reason for specially referring to

the earlier paper (’99) is that it seems to have been wholly

overlooked by later observers of these phenomena, and this is the

more strange in that both Parker (706) and Patterson (711), to

whom the journal (Zool. Bull. ) was quite familiar and access-

ible, make no mention of it.

In Fig. 1, which is reproduced from the article just cited, are

Shown the essential features of the first case which came to my

direct knowledge some time prior to the date of the paper in

question. As will be noted this presents a very clear illustra-

* Contributions from the Zoological Laboratory, Syracuse University.

No. 549] SHORTER ARTICLES AND DISCUSSION 557

tion of that class of egg anomalies known as ‘‘ovum in ovo,”

and its simplest interpretation appears to be that originally

given to it by Schumacher (’96), namely, that it is the result of

a return of the egg up the course of the oviduct by an anti-

Fig. L

peristalsis of that organ, and then later a descent during which

the egg would receive a second deposition of albumen, shell

membrane and finally a second shell, giving it just the consti-

tution shown in the figure, and described in my paper (p. 228).

In Fig. 2 is shown a case which differs in essential respects

from the preceding. The egg came to my knowledge through

the kindness of my colleague, Dr. C. G. Rogers, in whose father’s.

poultry yard it was produced. This egg, as will be observed, was

double in a rather unusual way. Here we have as shown from

the outside an egg of rather larger size than usual, but other-

wise apparently perfectly normal. When broken to be used in

the kitchen the anomalous internal condition was revealed. The

sketch will make clear in just what this anomaly consisted,

558 THE AMERICAN NATURALIST [ Vou. XLVI

namely, the inclusion of a miniature egg within the larger and

in about the position and relation shown in the figure.

A double egg of similar character has been recently described

by Patterson (Am. Nar., Jan., ’11), though differing in that the

anomaly comprised two fairly large eggs, as shown in his sketch

(Fig. 4), while in my own specimen the inner egg was quite

minute though otherwise normal. Some further discussion of

these cases will appear in a later section of the paper.

Fic. 3. Abnormal hen’s egg x io.

In Fig. 3 is shown a third anomaly differing from either of

the preceeding in a very marked way. The photograph of the

specimen, about one half natural size, gives a better impression

of the specimen than any verbal account could do. The most

striking feature is that of shape, which is rather gourd-like, and

was sent to me by the father of Dr. Rogers with the rather

facetious suggestion that the contiguity of the poultry lot to the

garden, over whose fence hung a squash vine, might afford a

clue to an explanation! The egg was laid aside for a time

awaiting photography, and when later I opened it for a critical

study it was found to have lost so largely by evaporation that

an exact account of all its details could not be made. This may

be stated, however, that in the larger end of the egg was an ap-

parently normal yolk and normal albumen. The smaller end

seemed to have had only albumen, though it was yellowish, as if

there might have been yolk matter distributed through it.

this one can not be certain, and I must leave the matter as doubt-

ful. However, I am disposed to submit the general statement

given above, namely, that the egg was comprised of about nor-

No. 549] SHORTER ARTICLES AND DISCUSSION 559

mal parts in the larger end, and the smaller probably having

only albumen, its yellowish tint having resulted perhaps from

the evaporating process which had taken place.

In the matter of explanation or interpretation of these facts I

have little to add to what has been presented in the earlier paper

or by other observers. Of the literature at my command the

paper of Parker (op. cit.) seems to me to present upon the

whole the best discussion. And I may add in this connection

that Parker’s paper is further valuable in its rather full bibliog-

raphy of the subject. As already mentioned in connection with

the account of Fig. 1, the true interpretation seems almost cer-

tainly that there cited. One has but to apprehend the essential

physiological operations involved in the process of the so-called

antiperistalsis to perceive just how there would result the strue-

tures present in the egg. If it should be queried why such depo-

sition might not have taken place on the ascent of the egg by

antiperistalsis as well as during the later descent, it may suffice

to admit that perhaps it did occur. However, in case the re-

turn of the egg up the oviduct took place soon after its original

descent the glandular structures would be in a state of exhaus-

tion and hence capable of only slight discharge; but in either

case, save only the action of the shell gland whose only effect

would be to add to the thickness of the original shell, the effect

would prove the same, namely, a second layer of albumen, a

second shell membrane and finally a second shell just as was the

case. Parker’s contention as to the fact of antiperistalsis seems

to me conclusive. The facts of normal eggs in the body cavity

of hens, cases of which I have known, seem impossible of ex-

planation by any other view.

The case involved in Fig. 2 is rather more complex, though not

so difficult of correlation with known processes as might seem.

First, let us direct attention to the minute inner egg. Such

miniature eggs are fairly familiar to any one who has much to

do with poultry culture or care. They are oftenest found with

the first ovulation of young hens, and the writer has known of

them from boyhood as pullets’ eggs. They probably represent

an early or premature ovulation at the beginning of sexual ac-

tivity. The discharge of such minute yolk would involve only

comparatively slight stimulus of the uterine glands and hence

a meager discharge of albumen, ete., hence the minute size. Ex-

cept in matter of size such eggs are usually normal and call for

560 THE AMERICAN NATURALIST [ Vou. XLVI

small account in themselves. Now in the second place, let us

consider what might happen at any time with the discharge of

such premature eggs from the ovary. If followed soon by the

discharge of a mature egg from the ovary and its normal descent

it might well overtake the smaller specimen at some portion of

the oviduct and easily include it within the larger mass of al-

bumen. This, it seems to me, is probably just what happens in

the majority of such eases, possibly in all. I do not overlook the

still more anomalous case cited by Herrick (’99), in which the

smaller included egg is in the yolk instead of the surrounding

albumen. Of this Herrick offers no definite explanation ; indeed,

there may be some doubt as to exact facts in this case, the inclu-

sion having been found in a cooked egg and details being un-

certain.

Concerning the specimen of Fig. 3 there is little to be said.

Its bizarre shape is remarkable, but here again the element of

doubt as to the definite composition of the contents of the

smaller end—handle of the squash—render unprofitable any at-

tempt to discuss or speculate as to its real significance. Whether

there may have been some rupture of the original yolk and the

segregation of a portion in one end with the extruded part in

the other may be a possible explanation; or whether some mal-

formation of the oviduct may have been a disposing cause must

remain open questions. Various egg shapes are familiar to

those handling large numbers of eggs. I have myself seen many

such, though none resembling the one here under consideration.

That conditions of confinement, close inbreeding, or other fea-

tures of habit or environment may have an influence in such

matters are altogether possible. Association with unusual

shapes, colors, ete., at certain times may affect domestic animals

variously; e. g., witness the very interesting story of Jacob’s

spotted cattle (!), still the contiguity of garden and poultry

yard referred to above can hardly be considered as a vera causa

in this instance! Cuas. W. HARGITT

SYRACUSE UNIVERSITY

LITERATURE CITED

Hargitt, Chas. W. Some Interesting Egg Monstrosities. Zool. Bull., Vol.

TI, 1899.

Herrick, F. H. 1899a. A Case of Egg within Egg. Science, Vol. IX, P-

364; ibid., b. Ovum in Ovo. Am. Nat., Vol. 33, p. 409.

Parker, G. E Double Hens’ Eggs. Am ie: Vol. 40, p. 13, 1906.

Patterson, J. T. 1911. Aw. Nart., Vol. 45, p. 54.

NOTES AND LITERATURE

AMERICAN PERMIAN VERTEBRATES!

Tus work might have been entitled Some American Permian

Vertebrates. It is not a general treatise on the vertebrates

found in the Permian of America, but one on a few amphibians

and a number of reptiles to which the author has recently been

giving his attention. The book is, however, not less valuable

because of its limitations.

For a number of years Dr. Williston has been making col-

lections from the Permian deposits of Texas. He has been

studying these collections, as well as the materials secured by

Cope and now in the American Museum of Natural History in

New York, and the collections, now in Yale University, brought

together by Marsh. Dr. Williston has found some remarkably

well preserved remains and these have been most skillfully pre-

pared by his assistant, Mr. Paul Miller; and in this book we

have some of the results of their labor.

Thanks to Williston, Broili, and Case, our knowledge of the

interesting animals of the Permian has been greatly increased.

We seem to be justified in believing that during the Permian the

principal orders of reptiles took their origin, or at most had not

yet diverged far from the parent stem. It is therefore of the

highest importance that every scrap of materials be studied that

is likely to throw light on these reptiles and their relationships.

As it seems necessary for.a reviewer to discover some errors

and deficiencies, some fly in the ointment, let this duty be first

accomplished.

The text is well printed and the text-figures well made and

effective. Most of the plates are excellent, especially these made

after drawings. Those reproduced from photographs, as Plates

XXVI-XXVIII, are useful mainly in showing that the author

had a sufficient basis for his line drawings. These Permian

fossils are very refractory subjects for photography, being vari-

ously mottled and stained. There are, however, methods for

1:1 American Permian Vertebrates,’’ by Samuel W. Williston, professor

of paleontology in the University of Chicago. The University of Chicago

Press, Chicago, Ill. Pp. 145; 38 plates and 32 text-figures. Price $2.50 net,

2.68 postpaid.

$2.68

561

562 THE AMERICAN NATURALIST [ Vou. XLVI

hiding such stains and giving the objects a uniform color, so

that light and shade produced by the varying surfaces need not

be interfered with; and it might be well to test these methods on

such fossils.

he reader, at least this one, can not always determine the

exact size of the animals described; for example, that of

Seymouria baylorensis. On page 140 we are told that the figures

of the plates are of the natural size, unless otherwise stated,

wherefore we might conclude that the figure on Plate X XVI is of

the size of nature. However, on pages 51 and 52 the figures of

the same skull are explained as being one half the natural size,

and they are somewhat more than two thirds the size of the skull

of Plate XXVI. As the author seems not to state the size of

the animal we are left in doubt.

The present writer would suggest that the important Plate y

ought to have had its figures lettered so as to indicate what names

the author intended to apply to the various elements. By

digging in the text with sufficient assiduity the unfamiliar stu-

dent may, after struggling perhaps with such expressions as

‘‘the real, so-called coracoid”? (p. 57) and ‘‘the so-called true

coracoid” (pp. 97, 100), determine to what parts the various

terms are to be applied.

Inasmuch as Dr. Williston argues that the exact content of the

terms Theromorpha and Pelycosauria and the exact relation-

ships of the groups can not yet be determined, it would appear

better to have retained Pelycosauria for the order which he calls

Theromorpha, especially since Case has employed Pelycosauria

in his monograph on the group. It is still more difficult to

follow Dr. Williston in displacing the well-founded family name —

Clepsydropide in favor of Sphenacodontide ; when, according tO

is own researches, the genus Sphenacodon, with great prob-

ability, does not belong in the same family as Clepsydrops.

Having uttered these mild complaints, it is a pleasure to

recognize the value of the services rendered to science by Dr.

Williston in his descriptions of Limnoscelis paludis, Seymour@

baylorensis, Varanosaurus brevirostris and Casea broilii. These

descriptions are based on materials so complete and so abundant

that practically the whole osteology of each is known. The re-

mains form a marked contrast with those on which Cope was —

compelled to found most of his work on the Permian reptiles —

and amphibians.

No. 549] NOTES AND LITERATURE 563

The genera Limnoscelis and Seymouria belong to the Coty-

losauria; Varanosaurus and Casea to the Theromorpha. The

types of Limnoscelis paludis are in Yale University, and were

collected many years ago in New Mexico for Marsh. One speci-

men is a skeleton lacking only the skull, the front feet and a part

of one hind foot; the other lacks only parts of the hinder feet.

And all these parts are in their natural positions! What more

can the paleontologist desire? Doubtless he will regret that the

animal had not fallen into some pool of asphalt that had the

property of preserving the flesh and internal organs. The prin-

es skeleton described by Williston had a length of about 7

fee

a genus Seymouria was originally iaa by Broili on

two skulls obtained in Texas. Williston secured in 1910 a speci-

men of another species of the genus and this specimen had

missing only a part of the tail; and he expects yet to secure even

this. The bones are all in the closest natural articulation and

are neither distorted nor compressed. This reptile was about

2 feet long.

Varanosaurus was described by Broili on a skull and part of a

skeleton. Williston has secured of another species 25 skeletons,

of which 6 or 8 have been recovered in greater or less perfection

from the matrix. He figures a mounted skeleton and states that

it measures just 44 inches in length. The head is long, narrow

and pointed in front.

Casea broilii was a reptile about 3 feet in length. Its head is

small, short, broad and deep. Williston presents a figure of a

restoration composed of three individuals; but he thinks that in

his collection there remain other skeletons. Among the pecu-

liarities of the reptile are a large parietal foramen and a large

infratemporal vacuity.

r. Williston presents at length the structural features that

belong to the two orders Cotylosauria and Theromorpha. These

are very instructive; but when we compare the two sets of

characters we find that nearly all of them are either common to

the two orders or of no great value. The Cotylosauria, how-

ever, possess no temporal vacuities, while the Theromorpha have

one on each side. The former are said to have the lachrymal

prolonged to the anterior nares; the latter not so. However,

the figure, 25, of Varanosaurus represents this bone as reaching

the nost

564 THE AMERICAN NATURALIST [ Vou. XLVI

Williston evidently regards the presence of a temporal vacuity

as sufficient to justify the separation of Varanosaurus and Casea

from the Cotylosauria; and he may be right. His position could

not be questioned if it could-be shown that the presence or the

absence of this feature indicated the divergence of two phyla;

that the one group gave origin to descendants that retained the

temporal roof intact, while the other started a line that developed

one or two vacuities on each side. However, that proposition

can hardly be proved as yet.

In Varanosaurus the temporal roof is mostly lacking and there

is no lower temporal arch, differing in the latter respect greatly

from Casea. Dr. Williston is led to discuss the value of the

vacuities and arches in the classification of the reptiles. He

recognizes three chief types, perhaps three chief phyla: (1) the

Cotylosauria, with unbroken temporal roof; (2) the type in

which there are two vacuities and two arches; (3) the single-

arched type, in which there is a single vacuity bounded below

by the jugal and quadratojugal. He thinks that there may be

a fourth type, that in which a vacuity is bounded below by the

postorbital and the squamosal. He is, however, unable to see the

distinction between the two types with a single vacuity, and is

inclined to believe that all single-arched reptiles have arisen from

asingle type. The present writer is unable to understand clearly

the position taken. . l

Inasmuch as the temporal roof is primitively, as in the Coty-

losauria, complete and composed of two series of bones, it is ae

vacuities which developed in them that are the important matters

to consider. It seems to the writer that a single vacuity may

have originated in five different ways:

1l. By the development of the upper vacuity alone.

2. By the development of the lower one alone.

3. By the appearance and extension of a vacuity in the

postorbito-squamosal arch.

4. By the gradual reduction of the postorbito-squamosal bar,

allowing the upper and the lower vacuities to unite.

5. By the reduction of the lower arch, leaving only the upper

vacuity.

The matter may be further complicated by changes in ee

temporal roof such as are found in some of the turtles: (1) Its

lower border may be eaten away, resulting finally in a condition

such as appears to exist in Varanosaurus ; (2) the hinder border |

No. 549] NOTES AND LITERATURE 565

and upper part of the roof may by degrees disappear until there

is left only a narrow lower arch; and even this may waste away.

Among the turtles the modifications in the temporal roof, numer-

ous and extreme as they are, are not regarded as of great im-

portance. It may be different, however, among the other

reptiles. If so, then, as it appears to the writer, there might be

five phyla of reptiles possessing in the temporal roof a single

vacuity.

It is to be hoped that Dr. Williston’s researches will lead

to a solution of the difficult problem involved in the higher

classification of the reptiles.

O: P: Hay

U. S. NATIONAL MUSEUM

FEDERLEY’S BREEDING EXPERIMENTS WITH THE

MOTH PYGÆRA

INTERESTING results have recently been obtained by Federley*

by breeding moths of the Notodontid genus Pygæra. Three

common European species furnished the material—P. curtula,

P. pigra and P. anachoreta.

The hybrids were not all equally easy to obtain. Numerous

matings involving P. anastomosis were made, but no offspring

were obtained. Anachoreta males show little inclination to

pair with curtula females, but when such pairing occurs nearly

all the eggs start developing, yet only a few reach the adult

stage. On the other hand, the reciprocal mating (curtula male

to anachoreta female) is easily accomplished, but produces only

about 30 per cent. fertilized eggs. Of these most of the males

and some of the females reach the adult stage. Thus it appears

that ‘‘Paarungsaffinität”’ (tendency to mate), ‘‘sexuelle Affini-

tät” (tendency toward fertilization) and ‘‘physiologische Affin-

ität (tendency to produce fertile offspring) are independent.

One great difficulty met with was that the adult F, hybrids

were very sterile. Only a single F, moth was raised, and only

a few from the various back crosses (F, by P,).

One of the characteristics of the species anachoreta is the

presence of a white spot on the first abdominal segment of

the caterpillar. In one of Federley’s races of pure anachoreta

there appeared, in the same brood, two caterpillars lacking the

*Arch. Rass.- u. Gesellsch.-Biol., 8, 281, 1911. Reviewed also by M.

Daiber, Zts. ind. Abstamm.- u. Vererb.-Lehre., 6, 90, 1911.

566 THE AMERICAN NATURALIST [ Vou. XLVI

spot. The mutation proved to be an ordinary Mendelian reées-

sive. This spot is absent normally in curtula, and in crosses

between anachoreta and curtula it does not appear in F,, or at

least is never of the full size. Its behavior in this hybrid is

somewhat complicated, and more data will probably be re-

quired in order to explain it. But Federley’s assumption of

imperfect dominance of the same gene which behaves as a com-

plete dominant in the anachoreta mutant seems hardly. justifi-

able. The fact that the character behaves in the mutant as

though due to a single factor does not mean that it must. al-

ways so behave. It may depend upon the simultaneous pres-

ence or absence of several genes. If in the ‘‘spotless’’ mutant

one of the required genes has dropped out, then the addition of

that one to the complex will give the spot, and a case of Men-

delian monohybridism will result. But curtula may be ‘‘spot-

less’’ because it lacks some other part of the required combina-

tion, in which case the behavior might be quite different from

that in the case of the mutant.

When curtula and pigra were crossed, some of the F, imagos

emerged after a pupal stage of about two weeks, while the. rest

hibernated as pupe. The moths resulting from the two lots

were quite different, the first (summer generation) being more

similar to curtula, the second (spring generation) more like

pigra. That this difference is not due to the effects of temper-

ature is indicated by an F, moth reared from eggs laid by an

individual of the summer generation. This moth hibernated

in the pupal stage, yet resembled the summer generation. Fur-

thermore, low temperature experiments on these curtula-pigra

hybrids and upon curtula-anachoreta hybrids gave entirely neg-

ative results. Several facts bearing on this problem are given.

Seasonal dimorphism is never a well-marked phenomenon in-

Pygera, and does not seem to occur at all in the three species —

dealt with by Federley. From pigra he was unable to rear a

summer generation. In the case of curtula, the Finnish races —

father. From the reciprocal cross only males were reared. These

also resembled anachoreta. However, Standfuss reared both —

No. 549] NOTES AND LITERATURE ` 567.

sexes but does not mention any dimorphism. Federley seems un-

decided as to whether this is a case of ‘‘spurious allelomor-

phism’’ (i. e., sex-linkage) or a reversal of dominance due to

a difference in sex (similar to the case of horns in sheep). But

if, as he is inclined to suppose, Standfuss really got no dimor-

phism in his reciprocal cross, then this can not be a case of re-

versal of dominance, since if it were, reciprocal crosses would

give the same results. It seems more probable that there is

here a case of true sex-linked inheritance, the female being

heterozygous for sex, as in Abraxas. Just what character is

caused by the sex-linked gene is difficult to discover from Fed-

erley’s account, but since this gene must be carried by anacho-

reta, let it be represented by A. The following formule, “which

I would suggest, in which MM denotes a male, Mm a female,*

will then explain Federley’s results:

curtula g — aM aM

anachoreta g AM am

aM Pr per similar to anachoreta.

M am — Ẹ similar to curtula.

anachoreta ĝ— AM AM

curtula r aM am

AM oM — —d similar to anachoreta.

AM am — Q similar to anachoreta.

The following back crosses were made:

curtula 9 — aM am

AM aM —o similar to anachoreta.

aM aM — ¢ similar to curtula.

AM am — Q similar to anachoreta.

aM am — 9 similar to curtula.

This last mating produced only three males, which were very

like the F, males. The next cross, and the expectation on the

hypothesis of sex-linkage, is:

anachoreta 9— AM am

AM AM) _ dé similar to anachoreta.

aM AM

AM am — Q similar to anachoreta.

aM am — Q similar to curtula.

I have given my reasons for adopting this sex formula for birds and

estan in another paper (Jour. Exp. Zool., 12, 499, 1912).

568 THE AMERICAN NATURALIST [Vou XU

All the males from this cross were again similar to anachoreta,

and there was apparently a fair number of them raised. All

the females belonged to the anachoreta type, but they are said _

to have been few in number.

Thus, although the classes are not all filled, because of the

small numbers obtained, the results of the back crosses are in

agreement with the hypothesis that we have here a case of sex-

linkage of the Abraras type.

One interesting point is that in the cross of curtula male by

anachoreta female, from which ‘‘hundreds’’ of females were

raised, there occurred a single female resembling the males.

This furnishes another case of partial sex-linkage, in addition

to the one reported by Bateson and Punnett? and the others

which I have analyzed in another paper.*

In practically all of Federley’s cases the offspring of back

crosses strongly resembled the hybrid parents, but he explains

this as probably due largely to the great mortality of the

caterpillars. In only a few cases were more than three or four.

offspring reared from such crosses. In two such back crosses :

there appeared caterpillars which had entirely new colors, pre-

sumably due to recombination, but unfortunately none of these —

survived until the imaginal stage.

A. H. STURTEVANT —

* Jour, Genet., 1, 293, 1911.

* Jour. Exp. Zool, 12, 499, 1912.

VOL. XLVI, NO. 550 OCTOBER, 1912

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AMERICAN NATURALIST

VoL. XLVI October, 1912 No. 550

GAMETIC COUPLING AS A CAUSE OF

CORRELATIONS

G. N. COLLINS

Bureau or Puant Inpustry, U. S. DEPARTMENT OF AGRICULTURE

\ Waen two distinct characters consistently occur to-

gether in the offspring of a hybrid, the phenomenon is

termed in Mendelian parlance ‘‘gametic coupling.’’ If

the characters sometimes occur independently, but appear

together more frequently than they should by chance, the

term ‘‘partial gametic coupling’’ is applied. If the char-

acters occur together less frequently than is to be ex-

pected, the condition is termed ‘‘repulsion,”’ while if they

never occur together in the same individual it is called

‘‘spurious allelomorphism.”’ .

In mathematical language, characters that show par-

tial gametie coupling are said to be ‘‘positively corre-

lated,’ those that show repulsion, ‘‘ negatively corre-

lated.” If they always occur together in the same indi-

vidual, the correlation is said to be ‘‘perfect’’ or ‘‘com-

plete,’’ while if they never occur together the negative

correlation is perfect.

When characters that show a positive correlation or

partial gametic coupling are derived from the same

parent, they are termed ‘‘coherent’’ by Cook (1909, p.

16). Many of the examples of partial gametic coupling

formerly reported in Mendelian literature were probably

of this nature, but with the attention foeused on the idea

that all cl ters were independent units, the possibility

of such coherence was not considered, and it is sometimes

569

570 THE AMERICAN NATURALIST [ Vou. XLVI

not to be determined from the data presented whether

the correlated characters were derived from the same or

different parents. This phenomenon of coherence, which

appears to most field naturalists and practical breeders

as a well-known fact, strikes the followers of Mendel as a

novel idea, to judge from the following (Bateson & Pun-

nett, 1911, p. 6):

The fact, however, that the mode in which factors are combined in

the original parents ean influence the distribution of the factors

among gametes of F, introduces a new conception into genetic phys-

iology.

The difficulty of ‘‘breaking up” combinations of char-

acters has so long been a stumbling block to breeders that

to them the conception can hardly be considered new.

The suggestion that the number of individuals in which

two characters are combined bears a definite relation to

the number in which they occur singly is without doubt a

direct outgrowth of Mendelian investigations and meth-

ods of thought. Perhaps this latest application of

mechanical conceptions to biology may stimulate research

as did Mendel’s original discovery. On the other hand, —

there are many who think that the application of Mende-

lian formule has already been pursued to an absurd

point by the factoring and subfactoring of characters and

the assumption of intensifying and inhibiting determ1-

nants. Those not already abreast of Mendelian literature ~

are not likely to be impressed with the further refinement

that aims to devise formule for expressing gametie

relations between two of these already complicated Men-

delian systems. a

In considering the relation between two Mendelian

characters four possible combinations are involv

hus, if A and B be taken to represent the appearance 0!

the two characters, and a and b their non-appearance,

these four combinations would be expressed as follows:

AB, Ab, aB, and ab. The theory of gametic coupling

assumes that an attraction or other unknown relation

exists between the determinants of the two characters,

No. 550] GAMETIC COUPLING 571

which results in their occurring together in gametes more

frequently than they occur separately.

`` There appears to have been a preconceived idea that

the ratio between the number of gametes in which the

determinants for two characters occurred together and

the number in which they were separated would be either

as 3:1, or 7:1, or 15:1, ratios that are common in Mende-

lian inheritance of single characters. The reason for this

expectation is not apparent.

The persistence with which it is sought to utilize the

numbers 4, 8, 16, etc., representing powers of 2, in the

interpretation of correlations reminds one of the argu-

ments used at the dawn of science to bring all natural

phenomena into some relation with the numbers 4 and a

Galileo’s suggestion that there were more than seven

planets was answered by Lizzi:

There are seven windows in the head, two nostrils, two eyes, two

ears, and a mouth, so in the heavens are there two favorable stars, two

unpropitious, two luminaries, and Mereury alone undecided and in-

different. From which and many other similar phenomena of nature,

such as the seven metals, ete., which it were tedious to enumerate,

we gather that the number of planets is necessarily seven. (Snyder,

1907, p. 203.)

The levity of the comparison disappears when one

seeks a reason for assuming that the number of gametes

in which *the characters occur together will be to the

number of gametes in which they occur apart as 7:1 or

15:1 or 31:1, etc., and not some intermediate proportion.

~ In the following pages an attempt is made to review

briefly the experiments: which have been advanced as

proof that the various degrees of correlation fall into

this definite series.

The first attempt to refer the correlation of characters

to definite differences in the gametes was made by Bate-

son, Saunders, and Punnett (1906, p. 9) in explaining

observed correlations between purple flower color and

long pollen grains in hybrid sweet peas.

. A close approach to the Observed F, numbers would be given

572 THE AMERICAN NATURALIST [ Vou. XLVI

by a system in which each 16 gametes were composed, thus: TAB +

laB + 14b + Tab, where A is long pollen and a round pollen.

Purple Red | White

Observed ...... tee 18 | 7 381 | 1,199 | 394

Calculated ..... 1,448.5 | 122.7 | 122.7 | 401.5 | 1,220.5 | 407.4

The numbers under ‘‘White’’ may be disregarded in

this connection since the distribution of long and round

pollen grains in this group shows a close approach to the

normal 3:1 ratio.

Some of the numbers in the ‘‘observed’’ series are

above and some below the corresponding numbers of the

‘“ caleulated’’ series. That the calculated series approx-

imates the observed series is obvious, but there is no way

of determining the degree of this approximation. No

method has been proposed for making definite compari-

sons between such series of numbers. Without some

standard of comparison it is difficult to see that anything

is gained by resorting to gametic formule to represent

the degrees of association between characters.

A customary and direct method of comparing the de-

grees of relationsbip that exists between any two charac-

oie is to compute the coefficient of correlation or Yule’s

‘‘coefficient of association.’’

In the following discussion Yule’s ‘‘coefficient of asso-

ciation”? (1900) is used. By this method the complete —

independence of two character pairs is represented by 0,

complete association by 1. Intermediate degrees of re-

lationship are expressed by the intermediate decimals. —

If the four classes of individuals are represented g a; b,

c and d, the coefficient of association is

(a xX d)—(bXc)

(axd t Oxo)

Since this coefficient can be computed directly from the

observed numbers the predication of gametic formule af

a means of expressing degrees of association of charac: :

ters becomes unnecessary.

No. 550] . GAMETIC COUPLING 573

With relationships expressed as coefficients of asso-

ciation, probable errors can be calculated. Thus it be-

comes possible to determine whether the approximations

between observed ratios and those calculated from the

different gametic formule are closer than would result

from chance.'

The difficulty of securing a 7:1 distribution by dichot-

omous cell division was appreciated by Bateson and his

collaborators in the example first cited. The possibility

that the coupling was in an 8:1 ratio was also suggested

and kept in mind for a time until a grouping that approx-

imated that resulting from a gametic coupling of a 15:1

ratio was obtained. Regarding the choice between the

7:1 and 8:1 ratios to explain the numbers observed in

the first experiment, the authors remarked (Bateson,

Saunders and Punnett, 1908, p. 3):

. we are still unable to decide finally between them.

But this indecision was apparently overcome in a subse-

quent paragraph on the same page. After citing two

examples that were referred to a 15:1 ratio, the theory

that the couplings follow a definite series was launched

in the following statement:

The undoubted existence of these two grades of gametie coupling in

the Sweet Pea suggests that each may find its place in a scheme of

increasing intensity of gametie coupling, such as is shown in the

accompanying table, where the two allelomorphie pairs are represented

by Aa and Bb:

1 Heron has pointed out (1911, p. 109) that the results secured by Yule’s

formula for the ‘coefficient of association’? do not approximate the true

coefficient of correlation, except where the two divisions are near the mean

of the entire population. This condition is not met, of course, by characters

that oceur in one fourth and three fourths of all the individuals. But since

the present discussion is confined to examples that approximate the form

3n? — (2n — 1) :2n —1:2n— 1:n?— (2n— 1), where 2n = the number in

the gametie series, they afford a regular sequence and, though the actual

values are somewhat arbitrary, they should not be misleading as a means of

comparing the degrees of relationship represented by the different gametic

formule. Thus if the classes observed in an experiment show the same

coefficient of association as the classes calculated from some particular

gametic ratio, the two series will also give the same coefficient of correla-

tion, though the actual values may differ.

574 THE AMERICAN NATURALIST [ Vou. XLVI

pameni oo Zygotes yrs mag | peee

AB ab Aand B ADA. B oT A nor

1: 7. cy i 4 9 3 3 hy z> |

ariel: = B 41 : 7 To s 9 =

Tii- T16 177 eb ip : 49 == S

ei si: D-3 737 See S 3 Si 22 024

m—1:1:1:n—l=2n 3n?—(2n—1) : ma. 2n—1 : n?—(2n—1)=—4n?

The first term in the series is a simple case of dihybridism in nied

no coupling exists. The second term we have not yet encountered.

But we have an ample series of experimental data which satisfy the

third term; and the experimental evidence for the existence of the

fourth term rests upon two independent cases.

To facilitate the use of the coefficient of association as

a means of determining what gametic ratio most closely

approximates observed ratios, Table I has been pre-

pared. This table shows a series of gametic ratios in

which the less frequent combinations are taken as 1, and

the resulting zygotic series, with the number of indi-

viduals that would occur in each of the four classes, fol- —

lowed by the coefficient of association, calculated from

the numbers in the zygotic series. The ratios in heavy

type are those representing the powers of two to which

correlations have been referred under the theory of —

gametic coupling.

TABLE I

RATIOS OF GAMETIC COUPLING

Coefficient of

: nes Series Zygotic Berkes Association

123.449 0:3 :8:4 0

oiii oe Eo 558

auS i154 +3 41:7:7: “ 766

“a a 66:9:9:1 858

O45 145 97 oe 905

Gt st G 134 : 13 : 13 : 36 .932

7 1 i:? 177 : 15 : 15 : 49 -949

S-1 11.8 226 : 17:17: 64 961

9- 1:1:9 281 : 19 : 19 : 81 969

12s 10 342 : 21 : 21 : 100 975

coe re ee 409 : 23 : 23 : 121 979

B:1i:1i- p 482 : 25 : 25 : 144 982

13:1:1: 13 561 : 27 : 27 : 169 .985

M:i: 1: i 646 : 29 : 29 : 196 .987

w:1:1i: B Tal * S1 : 931 : 95 .

16 :1:1: 16 834 : 33 : 33 : 256 990

pS eee ry : 68 : 68 : 961 :

S:1:1:6 12,161 : 127 : 127 : 3,969 -9993

197: i:i- : 255 : 255 : 16,129 9998

No.550] GAMETIC COUPLING 575

Returning to the consideration of the original example

of gametic coupling in the sweet peas, the coefficient of

association, .958 + .004, is seen to be intermediate be-

tween that resulting from a 7:1 and an 8:1 ratio.

Notwithstanding the fact that the figures correspond

somewhat more closely with an 8:1 than they do with a

7:1 ratio, an evident preference for numbers that are

powers of 2 is shown when the possibility of an 8:1 ratio

is discussed. Instead of saying that 18 gametes are con-

cerned, the number is spoken of as 16+ 2, and the fact

that a ratio of 15:2 would give almost exactly the ob-

served association is not even considered.

The next example of gametic coupling to be reported

was in the same series of crosses (Bateson, Saunders

and Punnett, 1908, p. 11), where the progeny of four

individuals showed the following grouping: 296:19:27:

85. This is referred by the authors to the theoretical 7:

1 ratio, though it shows almost the same association as

an 8:1 ratio, that is, .960. The probable error, .008,

would indicate, however, that with this number of indi-

viduals such a deviation might easily be due to chance.

The numbers are, therefore, too small to afford evidence

affecting the choice between a 7:1 and an 8:1 formula.

From the progeny of one of these four individuals

consisting of 111 plants and showing an association of

.914, 10 individuals showing both dominant characters

were selected and propagated. The progeny of the 10

plants taken together gave the following grouping: 493:

25:25:138. This grouping is considered only in con-

nection with the 7:1 and 15:1 distribution, though the

association .982+ .004 would indicate that a gametic

series of 12:1 would most closely fit the numbers. The

deviation from the 7:1 ratio is 9 times the probable

error, and from the 15:1 ratio, about twice the probable

error.

With respect to the characters considered separately,

the classes secured from each of the 10 individuals

showed a remarkable conformity to the expected 3:1

576 THE AMERICAN NATURALIST [ Vou. XLVI

ratio. In the degree of association between the char-

acters, however, no such uniformity was exhibited.

Leaving out of consideration two families represented

by only a few individuals, the coefficient of association

varies from .910 to .990. In terms of gametic coupling

this shows a range from 6:1 to 16:1, and since the series

as a whole accords with a 12:1 ratio it is not apparent

why only 7:1 and 15:1 ratios are considered. :

Individuals were again selected from two of the fam-

ilies which showed the highest correlation, and grown the

following season. The progeny from the first family

behaved irregularly and the presence of some disturb-

ing process was suspected, though the deviations with

respect to the individual character pairs were less than

the probable error.

The second family gave individuals with the follow-

ing grouping (Bateson, Saunders and Punnett, p. 12):

983:26:24:170 (association .987 + .0026). Of this it

is said:

It is obvious that the numbers in this group of families accord very

closely with the figures expected on a 15 : 1 : 1 : 15 basis, and the

view that this is the system actually followed receives confirmation

from the distribution of the pollen and color characters in F, families

from the Bush X Cupid crosses where the following figures were ob-

tained: 131:6:5:42. (Association .989 = .005.)

Here again when it is said that the figures ‘‘ accord

very closely,’’ it can only be meant that they accord

closely with one of the formule in the hypothetical series

as compared with other members of the series. The

numbers are, of course, inadequate to afford evidence as

to whether the observed figures accord more closely to

those resulting from a 15:1 combination than they do,

for example, to a 16:1 or a 14:1, yet the results are

taken to support the original assumption that the group-

Ings are in powers of two.

The examples of gametic coupling thus far reported —

are summarized by Bateson and Punnett as follows

(1911, p. 5):

No. 550] GAMETIC COUPLING 577

. No ease yet known.

Sweet Pea. Blue factor and long pollen.

Primula sinensis. Magenta color and short style.

Sweet Pea. Fertile anthers and dark axils.

No ease yet known.

. Pisum. Development of tendrils and round seed.

. Sweet Pea. Blue factor and erect standard.

Oo Ge

m Go + Or sy =) GO

Tea Sep E

As we have seen, the first example is closer to an 8:1

ratio. The second example is apparently based on an

experiment comprising 47 individuals (Gregory, 1911,

p. 12). The classes were 33:3:1:10, and the author

states,

.. the partial coupling observed is almost entirely certainly of the

for T 1:1

The reason for this assurance is not apparent since the

grouping is really nearer to that resulting from a 15:1

ratio. The probable error, .015, is so large, however,

that it would be impossible to determine the grade of

coupling closer than to say that it probably falls some-

where between 8:1 and 31:1.

The third example referred to the 15:1 ratio appears

to be based on 885 individuals showing an association of

.993 + .0017, indicating a coupling of about 20:1, the

deviation from the 15:1 association being 2.9 times the

probable error.

With respect to the examples where the association is

closer, none of the reported experiments have been con-

ducted on a sufficient scale to determine whether the

gametic ratios that are multiples of two are approxi-

mated more closely than other ratios. One of the most

exact approximations thus far reported is that of Vil-

morin and Bateson (1911, p. 10) where the numbers 319:

4:3:123 (association .9994+.0003) were obtained.

This is certainly a close approximation to the figures

that would result from a gametic coupling of 63: 1:1: 63,

which for this number of individuals would be 333.27:

3.48:3.48:108.77. Yet the observed numbers can be still

more closely approximated by assuming that the coup-

578 THE AMERICAN NATURALIST [ Vou. XLVI

ling was in the proportion of 75:1, which would give the

figures 334.57 : 2.98 : 2.98 : 109.47. The observed numbers

are somewhat closer to the 63:1 than to the 127:1, the

proportion next above in the proposed series. But why

avoid the intermediates?

It should be kept in mind that the series was built up-

in the first place, not because the observed numbers

agreed with some member of this series more closely

than was to be expected by the laws of chance, but ap-

parently for a priori reasons, because the numbers in

this series were in accord with the Mendelian ratios for

the appearance of single characters which represent = |

powers of 2. oe

When the correlation is as high as in the above ex- —

ample it would require, not hundreds of individuals, but J

tens of thousands to prove that the observed numbers a9

were in accord with those resulting from any particular

gametic ratio. In the experiment referred to the 61:1

ratio, there are two classes represented by 4 and 2 in-

dividuals, respectively. A change of two or three in-

dividuals in each of these classes would cause the array

to correspond as closely with a 31:1 or 127:1 ratio as

it now does with the 63:1.

In the very nature of things any observed association

must fall nearer to some one of the calculated ratios

than to any other, yet in the discussion of these experi-

ments this seems not to have been appreciated. The

data would have supported in the same way any other

choice of preferred ratios. |

COHERENT CHARACTERS In Hysrips or CurnesE MAIZE

Beginning in 1908, experiments have been conducted

with a variety of maize secured from China. The endo-

sperm of this Chinese variety is of a peculiar waxy tex-

ture, a character thus far not reported in any other

variety.

There are two strains of the Chinese variety, Onè

white, the other with colored aleurone. In a series of

No. 550] GAMETIC COUPLING 579

hybrids between Chinese and American varieties made

by Mr. J. H. Kempton and the author, the waxy char-

acter was found to be definitely recessive in the first gen-

eration. In the second generation the character reap-

pears apparently unchanged in slightly less than 25 per

cent. of the individual seeds.

Crosses between white Chinese and colored American,

and colored Chinese and white American showed a pro-

nounced coherence between the texture of the endosperm

and the color of the aleurone layer.

Results of the first season’s work in this field were

reported at the International Conference of Genetics in

Paris, 1911. At that time no attempt was made to de-

termine the gametic ratios necessary to account for the

observed correlations.

In these crosses the characters segregate with defi-

nitely alternative expression, but the classes seldom

show simple Mendelian ratios. In only one cross were

two of the four classes even approximately equal.

In the results of the next season’s work there were

five additional ears sufficiently near the 3:1 ratio in both

characters to be considered from the standpoint of gam-

etic coupling. The data derived from these five ears,

and from the one of the previous season, are shown in

Table IT.

TABLE IT

7 re armena manaa panan Shs SAART ig ve v e

No. gai Ros Waxy Horny kasd Association Tenn k iiia

152 | 183| 112| 20 | 22 | .761 =.049 w t ow

301 | 579| 372| 62 | 63 | 82 | .773«.020 .007 0.24

302 | 536 343 | 52 | 53 | 88| .833+.024 067 2.79

627, 409| 57 | 62 | 99 | .839+.021 073 3.48

325 | 650, 434| 55 | 61 |100 | .856+.019 .090 4.74

380 | 161| 104| 17 | 18 22 | .764+.058 .002 0.03

“Total 2736) 1774 | 263 | 279 |420| 8215011 | 055 | 500

The ratios obtained in these six cases might be hailed

as a prediction fulfilled, since in every case the numbers

approximated those that would result from a 3:1:1:3

ratio, which has remained a gap in the theoretical series.

580 THE AMERICAN NATURALIST [Vou.XLVE

In three of the six ears the deviation from the cor-

relation resulting from a 3:1 ratio is less than the prob-

able error. The deviation for the total is less than

three times the probable error, and might readily be

only a chance deviation. In two of the ears, however

(Nos. 303 and 325), the deviations are rather large to be

ascribed to chance.

In view of the fact that previously reported experi-

ments fail to show an equally close approximation to

other members of the proposed series, there is no ade-

quate reason for assuming that the present approxima-

formule represented by the powers of 2. That no such

regularity exists in the interrelation of different char-

acter pairs is more definitely demonstrated by the ex-

periments described below. These results indicate that

the association of characters may be determined after

the conjugation of the gametes. .

COHERENCE oF CHARACTERS NOT ALWAYS THE RESULT OF

Gametic DIFFERENCES a

If correlations are in all cases due to gametic differ-

ences, there should be no correlations exhibited in a

cross with a Mendelian formula Aabb XaabB. In our-

experiments with corn this would be represented by a

cross between colored-waxy and white-horny, where the

first is heterozygous in aleurone color and the second |

heterozygous in endosperm texture. The colored aleu-

of the gametes should bear the white character, and

those of the male parent the waxy character. The =

No. 550] GAMETIC COUPLING 581

nificance of crosses of this nature was not realized at

the time pollinations were being made, and but 5 ears of

this kind were secured. In two of these ears there is a

significant correlation. The classes exhibited in the five

ears are shown in Table III.

TABLE III

Ear No. Gant Pha White | White Colored Colored | Coefficient of

No. Seed | White Waxy Waxy | Horny Waxy Horny Association

472 | 505 | 30.1 | 464 | 91 | 61 143 210 | .873+.057

471 | 368 | 48. | 480 | 109 | 68 70 121 | 47 *.056

314 | 283 | 44.5 | 52.7| 65 | 61 84 73 | —.038+.081

272 | 395 | 61.2 | 47.1 | 122 | 120 64 89 | .171+.068

256 | 141 | 468 | 489 | 27 | 39 42 33 | —.295 =.105

The two ears in which the correlation appears sig-

nificant (Nos. 471 and 472) have a common ancestry,

different from that of the other ears. The history of

these ears is as follows: In 1908 a plant of a white Mex-

ican variety was pollinated by a Hopi variety with col-

ored aleurone, producing a pure white ear, Mh19. In

1909 a plant from Mh19 was pollinated by white Chinese,

the variety possessing the waxy endosperm. The result-

ing ear Dh14 had white and colored seed inthe proportion

of 2 white to 1 colored, with no trace of the waxy endo-

sperm. In 1910 a plant from a colored seed of Dh14 was

self-pollinated, producing an ear Dh142L2 with the fol-

lowing classes: white-waxy 99, white-horny 89, colored

waxy 51, colored horny 348. This represents an associa-

tion between colored and horny of .767, almost exactly

that expected on a coupling ratio of 3:1, but it will be

582 THE AMERICAN NATURALIST [Vou XLVI

noticed that the two middle classes are not equal. In

1911 two plants grown from white horny seeds of

Dh142L2 were pollinated by a plant from a colored waxy

seed of the same ear, producing the two ears, Nos. 471

and 472. The pedigree of these two ears is graphically

shown in Diagram 1.

The plants which bore ear 472 bore also a second ear

which was self-pollinated. Contrary to expectation,

this ear showed slight traces of aleurone color. That

there was a tendency to produce aleurone color in this

extracted recessive is also indicated by the low percen-

tage of the total white seeds in ear 472, which is 30 in-

stead of 50.

With ear 471 there is every indication that one of the

parents was homozygous with respect to the recessive

color character and the other with respect to the texture

of the endosperm. A self-pollinated second ear from

the plant that produced ear 471 had 24 horny seeds and

5 waxy, all of them white. A self-pollinated ear was

also secured from the plant which was the male parent

of both 471 and 472. This ear had 31 white seeds and

128 colored, all of them waxy. The total percentage of

white seeds in ear No. 471 was 48, a close approximation

to the expected 50. ,

The nature of this experiment seems to preclude the

application of the theory of gametie coupling which —

would explain correlations by assuming attractions Or —

repulsions between the character determinants in the

gametes. While attractions which might cause some

combinations to be represented by larger numbers of

gametes would disturb the Mendelian ratios, they could

not produce the effect of correlation or coherence of

characters. o

Thus the female parent might produce more gametes

bearing white and waxy than it did colored and waxy, m

there might be a greater fatality among the colored

waxy gametes. Any such disparity in the classes of

the gametes would result in more than 50 per cent. of

No. 550] GAMETIC COUPLING 583.

the zygotes showing the recessive characters, but even

so, there would be no correlation.

On the presence and absence hypothesis, a positive

correlation between two dominant characters like aleu-

rone color and horny texture must be considered a dif-

ferent phenomenon from a positive correlation between

color and waxy texture (Bateson, 1909, pp. 151, 158).

The first case has to be looked upon as an example of at-

traction, the second of repulsion. This appears an un-

necessary complication, as Emerson (1911, p. 79) has

pointed out. The significant fact would seem to be that

both cases may be considered as examples of coherence.

Appreciation of the fact that many of the cases of

gametic coupling are examples of coherence makes any

assumed regularity in the degree of correlation still

more absurd. But in spite of cases of coherence that

result in reversal of correlation, the idea that the char-

acters are represented by material particles that remain

unchanged by association in the zygote continues to be

held. To preserve the conception of pure unit charac-

ters, theories of positional relations of unit characters-

are now being proposed. Simple Mendelian ratios can

also be explained by positional relations of character de-

terminants as well as by theories of alternative trans-

mission (Swingle, 1898; Cook, 1907, p. 353), and this view

has the advantage that it can accommodate facts which

indicate a complete transmission of characters.

A theory to explain how positional relations of de-

terminants in the chromosomes may be responsible for

the phenomenon of coherence has been proposed by

Morgan (1911). The suggestion is that coupled or pos-

itively correlated characters may lie close together in

the chromosome and that in the conjugate generation

pairs of chromosomes are twisted around each other.

If, as claimed, the chromosome pairs split in a single

plane, characters which lie close together in the original

chromosomes would seldom be separated, while char-

acters remote from each other in the chromosome would

stand an even chance of being separated.

584 THE AMERICAN NATURALIST [ Vor. XLVI

If the position of the various determinants in the

chromosomes is definite, only slight variations in the de-

gree of association among hybrids between the same

parental strains would be expected, but there would be

no reason to expect that the different degrees of correla-

tion should fall into a definite series.

SELECTIVE PoLLINATION

From the standpoint of complete segregation or alter-

native inheritance of characters there remains the pos-

sibility of correlations being the result of selective pol-

lination. It is conceivable that the ovules which bear

one of the segregating characters are more readily fer-

tilized by pollen bearing another character with which

it was associated in the parent. As applied to our own

experiments, ovules which are potentially waxy might

be more readily fertilized by pollen which is potentially

white.

If correlations are the result of selective pollination,

no correlation should be shown as the result of crossing

an individual that is heterozygous with respect to both

of the character pairs with an individual showing both

of the recessive characters, for in such a cross the gam-

etes of one parent would be all of one kind. In our own

experiments, crosses between plants from hybrid seed

showing horny endosperm and colored aleurone (both

dominant characters) with plants from white waxy seeds

(both recessive characters) should throw light on this

point.

If the correlations result from numerical inequalities -

in the classes of the gametes, the seed classes resulting

Same as the gametic classes produced by the heteroZy—

gous parent. Thus, if the seed classes in a self-pollin-

ated ear correspond to those expected from a 3:1 ratio, :

the same plant when crossed with a plant showing both ;

recessive characters should show classes in the ratio, —

3 white-waxy, 1 white-horny, 1 colored-waxy, and 3 col

No. 550] GAMETIC COUPLING 585

ored-horny. On the other hand, if the correlations re-

sult from selective pollination, no correlation should ap-

pear in such a cross since the pollen is all of one kind.

Ears that represent crosses of this kind are described in

Table IV. It will be seen that in all of the seven ears

there is a significant correlation.

TABLE IV

Colored | Colored White Whit Coefficient of

Ear No. No. Beeds H nt Waxy Horny Waxy Association

144 600 125 40 232 203 464 + .054

250 245 19 74 104 48 —.788 + .04

251 377 52 29 138 158 B45 + .077

390 458 115 35 94 214 764+.

391 231 65 10 49 107 868 = .032

392 316 84 16 68 148 840 = .051

401 518 3 29 263 223 —.839 +.061

It is interesting to note that in two ears, Nos. 250 and

401, while the correlation is relatively high, it is reversed;

i. e., the positive correlation is between colored aleurone

and waxy endosperm instead of between colored aleurone

and horny endosperm as was the case in the original F,

ears. Whether the correlation is positive or negative

does not affect. its use as evidence in eliminating the pos-

sibility of selective pollination, so long as the correlation

is significant. From the standpoint of the presence and

absence hypothesis, the coupling or attraction has given

place to a repulsion.

The results shown in Tables III and IV indicate that

the association of different characters may be deter-

mined at different stages in the ontogeny of the indi-

vidual, much as the appearance or non-appearance of a

simple character may occur at different times in the life

history. Thus in ears 471 and 472, Table III, the corre-

lated characters must have become associated after the

formation of the gametes, while the absence of positive

correlation in ears 314 and 317 of the same table shows

that in these ears where associations in the gametes were

excluded no correlations were subsequently produced.

The results in Table IV further show that excluding the

586 THE AMERICAN NATURALIST [Vou. XLVI

possibility of selective pollination did not prevent the

appearance of significant correlations. It appears no

more reasonable to assume that the number of individuals

is always determined at the time the gametes are formed,

than it would be to argue that the number of nodes des-

tined to bear a juvenile type of foliage are definitely de-

termined at this time.

The theory of gametic coupling advanced by Bateson

and Punnett leads them (1911, p. 6) to entertain the idea

that, while segregation is definite and complete, the ap-

parently significant cytological processes of maturation

may have nothing to do with the phenomenon. These

authors would have the association of characters deter-

mined before the maturation divisions.

Now that we know of a series involving as many as 256 terms

(127 +1+1-+127) it is most difficult to conceive that such a se

tem can be produced in the maturation-divisions of the ovarian tissue

of such a plant as a sweet pea. We may well be tempted to look

much earlier in the developmental processes for the establishment of

these differentiations, and it is not impossible that they may be estab-

lished as early as the embryonic constitution of the sub-epidermal

layer itself.

The suggestion that segregation occurs early 1m be

ontogeny of the individual was apparently occasioned by

the belief in the definiteness of the mathematical rela-

tions between different character pairs. As We have

seen, there is little evidence for this belief. The correla-

tion shown in ear 471, Table III, affords a definite indica-

tion that such associations of characters may be form

after the production of the gametes.

Even though the definite and material segregation of

characters be maintained, all grades of correlation could

still be determined during the two nuclear divisions that 7

follow synapsis. The process might be looked at aS

follows:

When two character pairs are involved in a hybrid, the ss

tetrads resulting from the different mother cells WOU

No. 550] GAMETIC COUPLING 587

all be of three types with respect to the two characters

involved: (I) AB, AB, ab, ab; (IL) AB, Ab, ab, aB; (III)

Ab, Ab, aB, aB. Each of these fulfills the condition

deemed necessary from a Mendelian standpoint, that two

daughter cells of each tetrad receive the dominant and

two the recessive determinants. Where A and B are

correlated, it may be assumed that tetrads represented

by (III) are not formed. If the two remaining kinds

were produced in equal numbers, a gametic ratio of

3:1:1:3 would result. By the formation of two mother

cells of type I for every one of type II, a ratio of 5:1:1:5

would result. The formation of these two types of mother

cells in different proportion would provide for all de-

grees of correlation.

Additional examples of gametic coupling, some of

which, at least, are in the nature of coherences, are re-

ported by Gregory (1911, B, p. 128). Asin our experiments

with hybrids of Chinese maize, examples of gametic

coupling were encountered of a lower order than 3:1:1:3,

the lowest ratio in the theoretical series. Even this dis-

covery did not result in his questioning the validity of

the hypothesis. A further refinement was devised to

accommodate the results. Advantage was taken of the

possibility that the gametic coupling may exist in only

one sex:

For the time being it may be pointed out that a very close approx-

imation to the observed numbers is given by the assumption that a

coupling of the form 7 : 1 : 1 :7 is present in gametes of one sex only,

gametes of the opposite sex being produced in equal numbers of all

four kinds.

In such a case, a gametic coupling of the 7:1 in one sex,

with all classes equally represented in the other sex,

would result in an association of .542, slightly lower than

that resulting from the ordinary 3:1 ratio. By a similar

fractioning of the 3:1 ratio, the series can be provided

with a still lower member, with an association of .390.

In all recently reported experiments the reality of the

588 THE AMERICAN NATURALIST [ Vou. XLVI

proposed series of ratios seems to be taken for granted

and results are viewed only from this standpoint.

It is hoped that the previous discussion may operate to

check this practise of referring examples of coherence

to preconceived gametic ratios without considering the

possibility that an apparent agreement may be only a

chance approximation.

So long as the preconceived series is taken for granted

and intermediates are not considered, the results of all

experiments will seem to give additional evidence in sup-

port of the series.

We have seen that the results of previously reported

experiments do not correspond to the ratio in the ex-

pected series more closely than they do to others that are

intermediate, and furthermore that in some cases, at

least, the associations are not due to relations of the

determinants inside the gametes at all, but occur after

the stage of karyapsis, or nuclear fusion, has been

reached (Cook and Swingle, 1905).

SUMMARY

The theory of gametic coupling assumes that correla-

tions between two Mendelian character pairs are caused

by attractions or, repulsions between character-units K

determinants, previous to the formation of the germ cells. _

These attractions or repulsions are supposed to increase

the number of gametes bearing certain combinations of

determinants. o

The further assumption that the various degrees of :

association observed between different character-palts

will fall into a regular series represented by powers of 2,

as in simple Mendelian hybrids, appears to have been

accepted without adequate analysis of the data on which

it was based. a

An examination of the early examples shows that it

was only by neglecting the possibility of intermediate

ratios, and thus begging the question, that the observed

No. 550] GAMETIC COUPLING 589

numbers could be said to agree with those of the proposed

series.

‘The lack of any standard or method for making quanti-

tive comparisons between observed and expected series

has made it impossible to determine the degree of the

supposed approximations. Yule’s coefficient of associa-

tion is proposed as a criterion of comparison, and to

make possible the determination of probable erors.

In several cases correlations have been found to be

reversible, depending on the way the characters were

combined in the parents. This fact has further compli-

cated the theory of gametic coupling, making it necessary

to assume that characters which at one time attract each

other, at others exhibit repulsion.

In hybrids between Chinese and American varieties

of maize coherence has been found between the texture of

the endosperm and the color of the aleurone layer. Ina

few cases, the degree of the correlation approached very

closely to that expected from a gametic coupling ina 3:1

ratio (Table II).

Correlations were found in crosses of the Mendelian

form Aabb X aabB (Table III). Such correlations are

held to indicate that in some cases at least, the correla-

tion between the characters must be determined after the

formation of the gametes.

On the other hand, correlations resulting from crosses

of the form AaBb X aabb eliminate the possibility of

selective pollination as a general cause of correlations

(Table IV).

The general conclusion is reached that associations

between characters, like the appearance of single charac-

ters, may rise at different stages in the ontogeny of the

individual.

WASHINGTON, D. C.,

March, 1912

590 THE AMERICAN NATURALIST [ Von. XLVI

LITERATURE CITED

Bateson, W.

Mendel’s Principles of Heredity. Cambridge.

Bateson, W., and Punnett, R.

1911. On the Inter- AE EA of Genetic Factors. Proc. Roy. Soc., B,

Vol. 84, ar C pp. 3-8.

Bateson, W., Saunder and Punnett, R. C.

1 Sasser N peas in a cea ere of Heredity. Report

III, Evolution Committee of Roy. Soc., pp. 1-53.

1908. Experimental Studies in the Eilear of ere Report

IV, Evolution Committee of Roy. Soc. 1—60.

Cook, O. F.

1907. Aspects of Kinetic Evolution. Proc. Wash. Acad. Sci., Vol.

é 7-403.

1909. Suppressed and Intensified Characters in Cotton Hybrids. U. 8.

Dept. of Agriculture, Bureau of Plant Industry, Bulletin 147.

Cook, O. F., and Swingle, W. T.

1905. Evolution of Cellular Structures. U. S. Department of Agri-

ulture, Bureau of Plant Industry, Bulletin 81.

Emerson, R. A.

1911. Genetic Correlation and Spurious Allelomorphism in Mai

wenty-fourth Annual Report of the Nebraska avin

Experiment Station, pp. 58-90

Gregory, R. P.

1911. A. Experiments with Primula — Jour. Genetics, Vol.

y No. 2, pp. 73-132, Mar

B. On Ganette Coupling and ee in Primula Sinensis.

Proc. Roy. Soc., B, Vol. 84, No. 568, pp. 12-15.

Heron, D.

1911. The Danger of Certain Formule Suggested as Substitutes for

the Correlation Coefficient. Biometrika, Vol. 8, pp. 109-12

Morgan, T. H.

1911. Random Segregation versus rie in Mendelian Inheritance.

Science, N. S., Vol. XXXIV, p. 384

Snyder, C.

7. The World Machine.

Swingle, W. T.

1898. Some Theories of Heredity and of the Origin of Spá cies Con-

sidered in Relation to -e Phenomena of Hybridization. Bot.

Gazette, Vol. 25, pp. 113.

Vilmorin, P. de, and Bateson

1911. A Cis of Gametic Coupling in Pisum. Proc. Roy. Soc. B,

ol, 84, No. 568, pp. 9-11

Yule, G. U.

1900. On the Association of Attributes in Statistics. Phil. Trans.

Roy. Soc., A, Vol. 194, pp. 257-319

MICE: THEIR BREEDING AND REARING FOR

SCIENTIFIC PURPOSES!

DR. J. FRANK DANIEL

UNIVERSITY OF CALIFORNIA

I. INTRODUCTION

NotTWITHSTANDING many shortcomings mice have con-

tributed much to the advancement of science and the serv-

ice of mankind. To realize this we have but to recall

that it was by crossing the white with the gray mouse

that Mendel’s Law of Inheritance was first found to

apply to the animal kingdom (1); that from a study on

mice some of the earliest concepts of immunity were ob-

tained (2); and that from experiments now in progress

on them an insight is being gained into the nature of

cancer (3). These and similar experiments indicate

something of the scope to which these animals have been

put.

The ease with which white mice can be handled poe

them, in many ways, preferable for experi n to

vihor and larger rodents. But, owing to a dasni

notion that they are difficult to rear under laboratory

conditions, their usefulness has been greatly curtailed.

The method usually employed in the breeding of mice

has been what we may term extensive. By this I mean

that many animals are kept from which to obtain off-

spring. I have set myself the task of breeding mice in-

tensively, that is, of keeping relatively few, but of keep-

ing these under dantition: which will insure their pro-

ductivity. It is the purpose of this paper to describe the

way in which this was done.

Il. Tue Iytenstve Breeprne or MICE

A. Detrimental Factors

l. Marked Fluctuations in Temperature.—Probably

no single factor is more likely to be overlooked than that

Mice, to produce to the best advantage, require an

- equable temperature. While they can withstand extremes

“From the Zoological Laboratory, University of California. |

591

592 THE AMERICAN NATURALIST [ Vou. XLVI

of heat or cold, such extremes are not conducive to their

productivity. At 35° C. I have found breeding to be

greatly impeded, and at a temperature as low as 2° C.

the young born are subject to a number of mortal ills

which practically prevent their reaching maturity. But

a constant temperature of either of the above extremes

is not so detrimental as is great fluctuation in tempera-

ture. A mouse taken from favorable conditions and sub-

jected to daily fluctuations of from 30° C. to 2° C. soon

becomes a different animal physiologically. The fur

which was sleek and glossy roughens, the exposed veins

in the ears and tail darken, and the animal is readily re-

duced to a condition which, if prolonged, not infrequently

terminates in death. If after having reached this con-

dition, however, the animal be promptly restored to

equable conditions of temperature, its fur becomes sleek,

signs of anemia disappear and the mouse regains its

normal health and vigor often with surprising rapidity.

2. Parasitism.—lf mice, even under the most favor-

able conditions of temperature, become badly parasitized

breeding ceases and unless they are ridded of the para-

sites the adult mice as well the young fall victims to this

pest. To test the effects of parasitism, I have taken

mice from fresh stock, kept under excellent conditions,

and have placed them in infested nests, with the result

that in a few days the mice became sluggish, and many

sooner or later died.

When the two factors—parasitism and wide fluctua-

tions in temperature—are combined, the animals, espe-

cially the young, die in great numbers.

B. Factors Essential to Intensive Breeding

1. Construction and Equipment of Cases.—In general,

where a number of mice are to be kept together, the wire

and wood cases described by Yerkes (4) has been much

used. But for intensive breeding I have found it better

to keep few mice in a case, and to keep these under better

conditions of sanitation than is possible in the above ease.

I know of no better plan to insure sanitation than to

construct cases which will offer little surface upon which

No. 550] BREEDING MICE 593

dirt may collect, and which at the same time will make

evident that which has accumulated. Such a case should

be made with a perforated bottom and should be pro-

(A j E E. g CA g

; ()

O Q

| O

p O

FRONT VIEW or CASE. W.R., water receptacle; M.R., milk recep-

dicts: ri PEE to nest; F, opening to food.

Na a a a

6-3 Wes View co Caan. FF, food funnel; M.R., milk receptacle; N. B.,

nest box: Gb, galvanized iron back (near its bend) ; F, entrance to food cup BO.

vided with sides of glass. Briefly described,’ the case

that I have constructed consists of a framework of light

. Wood, a back of galvanized iron and sides, front and par-

*For detail see description accompanying drawings 5h ses nae

594 THE AMERICAN NATURALIST [ Vou. XLVI

tition of 10 X 12 glass. The top is made of screen wire;

the bottom of + inch wire mesh (hardware cloth).

WR MR

ee) OE) CO. Ooa

Screen Wire

Lii W \

Fic. 3. ToP oF CASE, WITH A PART REMOVED TO SHOW How THE GLASS

PARTITIONS AND ENDS (X) ARE FIXED INTO THE FRAME. WR., water recep-

tacles; T, a bent piece of tin covering the upper end of the glass to increase

the height of the partition and at the same time to cover the sharp edge of

the s.

AA E a SERS

<? ?,

ee a

EuGl

SSK x

SRE SS

IAF i Sc SS een:

Oe x S

BSS SS

BOERS

res

are

Fic. 4. Borrom Virw or THB Case. The wire mesh is partly drawn in tò

Show its relation to the end (End. gl.) and front glass (Fr, gl.), and to the

galvanized iron back (Gb). Fr., frame.

From a sanitary point of view too much emphasis can

hardly be placed upon the construction of the bottom.

By using 4 inch wire mesh through which waste material

will readily fall, I have succeeded in providing a case

which in a large measure is self cleaning. The cases thus

constructed are placed on a long trough-like table, cov-

No. 550] BREEDING MICE 595

ered with galvanized iron, which drains into a sink, By

flushing off the top at intervals, the waste is easily dis-

posed of.

While the use of glass in case building may imply an

increase in the cost of construction, yet in the above plan

it is believed that this cost has been reduced to a mini-

mum, and that a case has been provided which in addi-

tion to its quality for observation assures unusual con-

ditions of sanitation.

A point of great importance in the construction of

such a case is that the galvanized iron back and the side

and front glasses rest on the mesh-bottom so that waste

material in falling through does not strike the frame-

work of the case. It will be seen from a view of the bot-

tom (Fig. 4) that the back of the case is bent inward

an inch from its base so as to come well out on the mesh

bottom, and that the sides and front are placed well over

the line of the framework of the bottom.

2. Nest Boxes and Nesting Materials.—I have followed

with satisfactory results the largely used plan of hav-

ing a winter and a summer nest box. The winter nest

box is made by cutting a chalk box to three-fourths size.

This is filled two-thirds full of nesting material. The

summer nest is a small sized box similarly furnished.

Various materials have been tested for nesting, to

many of which objections can be made. Cotton although

warm, retains odor and at the same time offers a more

serious objection in that the young often become en-

tangled in it, and are thus permanently injured or even

killed. Excelsior I have found to make a good nest if

lined with some sort of soft material, as, for example,

crude floss. One of the most satisfactory materials

which I have tried for nesting is the shredded paper

used in the packing of china. If this can not be procured

at the china store it may be prepared by cutting up any

kind of soft paper. ;

3. Food Receptacles and Food.—1 have tried various

kinds of food receptacles, most of which have given little

or no satisfaction. The difficulty of keeping the food

reasonably clean in open food cans is so great that some

596 THE AMERICAN NATURALIST [ Vou. XLVI

sort of device for its protection is essential. The plan

that I have found most successful has been te place bird

cups in the nest box so that the mouse can procure the

food through an opening in the front of the box. The

cups are further provided with an apperture in the top

through which, without opening the case, food may be

added. This method of feeding, by preventing the mouse

from running over the food, holds in abeyance the spread

of disease.

The most satisfactory food that I have used for mice is

wheat, added to which is a small amount of stale bread.

These, together with milk—which is given by a modifica-

tion of the method below described for water—constitute

the daily and constant diet. Occasionally sunflower seed

and a few leaves of lettuce may well be given for a change.

4. Water Receptacles—tThe inverted bottle which is

now in general use for supplying water has done much to

eradicate ills resulting from a bad water supply. By this

device a large quantity of water can be provided which is

a great advantage in general cultures. In many kinds of

experiments, however, it is desirable to keep water in

greater purity than is possible even by this method. To

do this I have found a device which is strikingly simple

and at the same time singularly effective in that it keeps

the water in contact only with glass. My plan consists in

closing the end of a specimen-tube (or test-tube) in a

frame so that the opening is just large enough to retain

the water drop when the tube is filled and inverted in the

case.” These inverted tubes are inserted through holes

made in the top of the case and are prevented from fall-

ing through by means of small rubber bands placed

around the closed ends of the tubes. The tube may then

be removed and refilled without opening the case, the

refilling being done from a siphon bottle.

The addition of these devices for food and water to a

mesh-bottom case I have found to aid much in the inten-

*The tube for milk, instead o

in the test-tube, has the en

this being the ease with w

per can be cleaned.

f having one end closed permanently as

d closed with a rubber stopper, the advantage of

hich such an open tube upon removal of the stop-

No. 550] BREEDING MICE 597

sive breeding of mice. But to rear mice successfully

further requires a practical knowledge of their breeding

habits.

III. Breeprne Hasrrs or Mice

Copulation in mice is a well-defined act which usually

follows only upon the persistent efforts of the male. It is

marked by a period of union which lasts for several

seconds (ten to twenty-five) and is followed by an interval

of more or less complete rest. :

Practical questions for the breeder are: 1. When will

copulation oeccur—that is, when is the period of heat? 2

What is the duration of this period? 3. How often does

the period of heat recur? To the last of these questions

my experience can offer no answer; and to the second my

observations add little. In one case, however, after a

double copulation had been observed in the evening copu-

lation again took place on the following morning. The

fact that the beginning of heat is shown in some as early

as five hours after parturition and is delayed in others as

long as thirty-six hours thereafter makes it difficult to

determine with exactness the duration of this period.

As to the first question—When may copulation be

secured?—two periods can be determined with consider-

able accuracy. One of these closely succeeds parturition,

the other follows upon a period of rest.

In the first case, if the female has given birth to young,

copulation will usually take place, if she is put with the

male, within from five to twenty-four hours.* In my own

experience I have found that the greater number of births

take place in the early morning, and that copulation will,

in such a case, occur from seven to eight o’clock in the

evening. The female is not invariably in heat at this

time, however, as has been shown by a considerable

number of cases which I have observed.

The second period in which copulation may be expected

is after a mother has gone through an interval of rest,

* This is seen to correspond roughly to the time of ovulation in mice, as

shown by Long (5), the period given being from 144 to 28} hours after

parturition.

598 THE AMERICAN NATURALIST [ Vou. XLVI

either after having suckled her young or after having lost

them. She will then ordinarily copulate within a few

days after having been put with the male. The following

representative table of ten eee cases emphasizes

this point.

TABLE I

Example | Put with Male | Young Born Interval Elapsing, Days.

1 April 2 April 25 23

2 April 5 April 26 21

3 April 12 May 22

a April 19 May 11 22

5 April 29 May 21 22

6 May 14 June 6 23

7 May 18 June 11 24

8 May 26 June 24 29

9 May 27 | June 18 22

10 June 11 | July 3 22

Out of the above ten cases in which the females had not

suckled young for some time, and then were put with

males, nine cases of copulation evidently resulted early,

since the young were born within an interval only a little

greater than the normal period of gestation following a

rest (that is, 20 days) (6).

The eighth case, although unusual, has been further

accentuated by more recent data which show that the

female may remain with the male for long periods with-

out becoming pregnant. This is not conclusive evidence,

however, that an unsuccessful copulation may not have

taken place within that time. In fact, I have found that

in a surprising number of cases copulation does not result

in fertility. As an example of this may be cited 25 con-

secutive cases which I observed, 10, or 36 per cent., of

which resulted in infertilty.

In interpreting this sterility I was at first inclined to

believe that it was due entirely to the females, but since

then I have found males in many cases unproductive-

Some of these were useless for breeding because they —

were practically unresponsive, rarely if ever copulating 5

others, although among the most active males, proved un-

fertile. The following example may be given to show

such a case.

No. 550] BREEDING MICE 599

TABLE Ila

RECORD OF ¢ No. 6

No. of Q Palos ts | s | epa] Eo 14 | 10

12/14 12/23 12/27 12/30 1/6 | 4/3 | 4/19

Fert. Infer. Fert. |Infer. Infer. Infer. Infer.

12/3 | 12/7 | 12/8

A E A |Fert. |Infer.|Fert.

In the above table is given the record of one of the most

active males that I have yet had. The record, however,

shows that, although mated with vigorous females, only

40 per cent. of the copulations resulted in offspring. The

table further shows that after a rest from January to

April infertility is still shown. At this later period the

male had become inactive, so that it was difficult to secure

a copulation.

A relatively high index of fertility is shown in the

record of a male designated as No. 5.

TABLE IIb

RECORD OF ¢ No. 5

No. of Q sjaje eas Pee 8.

Date of copulation. |

| | | | |

| 12/3 | 12/7 | 12/28) 1/3 | 1/17 | 1/21 | 3/8 | 3/13 | 3/13 | 4/6

Number 5 when mated with females equally as active as

those with which No. 6 was mated gave 80 per cent. of

fertility. Within this series were also two other copula-

tions by the same mouse, but since these were with female

No. 4, which always proved fertile, they were eliminated

and only those counted which were entirely comparable

with those of No. 6.

It may be said that both males and females are found

which have a low index of fertility. Intensive breeding

requires that these be eliminated and that those be

Selected the copulations of which result in a high per-

centage of fertility.

When fertility does result from a copulation, the en-

suing period is of singular interest to the investigator.

This I have discussed in a former paper® in which I have

* Seriously ill after the birth of her young.

* Loe. cit.

600 THE AMERICAN NATURALIST [ Vou. XLVI

shown that the period of gestation depends upon the state

of the female. If the pregnant female is not suckling

young, parturition with but rare exceptions takes place on

the twentieth day after copulation. If she is suckling on

the other hand, the period varies with the number of

young suckled. Thus, for example, if the mother be

suckling five during gestation she may be expected to go

about twenty-five days; if ten thirty days. :

Parturition, which terminates the period of gestation is

normally of brief duration, even in case a large litter is

born. But this is not invariable, for I have observed

eases in which labor was prolonged, and some in which

unaided birth was impossible.

We are inclined to believe that in mankind the difficulty

of giving birth, which not infrequently results in the death

of the mother, is due to the artificialities of civilized life.

But here we find the same stern fact emphasized in a type

remotely removed from any such influence.

IV. REARING or THE YOUNG

The most hazardous time in the life of a mouse is the

first few days of its existence. Born helpless and naked

it is dependent upon the mother not alone for nourish-

ment but for warmth as well. Some mothers at this time

are most solicitous for their young, building elaborate

nests for them and giving such care to the young as to

tide them over this early period. Others there are that

not only withhold the requisite care, but which at this

time prove the most serious menace. Some of these

bundle their young away in the nesting to die; while

others in bad conditions openly destroy them. This sin-

gular and, so far as I am aware, unexplained phenomenon

of destroying the offspring, is carried to a high pitch in

the case of mice. Under unfavorable conditions of tem-

perature, nesting and the like, I have seen three or four

litters destroyed in succession. Miller (7) in a study of

the brown rat shows that this destructiveness in the rat

1s carried to even a greater extent than in the case of the

mouse,

No. 550] BREEDING MICE 601

If the young escape the perils of the first few days they

usually grow rapidly and, at the end of a few months,

reach maturity. There is a disease, however, which at the

` end of the second week may attack the young, leaving

them emaciated or, when more severe, killing them in

great numbers.

Between birth and maturity four well-defined stages

occur. To know these is often of practical service to the

breeder for the determination of age, sex and the like.

The first stage is that in which the newly-born young

have a peculiarly red and transparent skin through which

is seen the stomach white with milk. Following this at

the end of the sixth or seventh day a second stage is evi-

dent in which the body is covered with flaky scales of

dandruff—the forerunners of a coat of silky fur. A third

important stage, which I have designated as the early

Stage for distinguishing sex’ is usually shown on the

ninth or tenth day, at which time the mamme in the young

females appear. These can be observed for an interval

up to the thirteenth or fourteenth day, at which time the

fur usually obscures them.

Determination of sex after the body is covered with fur,

for example at the time of weaning, is often difficult. Be-

cause of this I have found it advantageous at the end of

the third period to mark the young females by clipping a

tuft of fur at the root of the tail, so that later, when they

are to be mated, no difficulty is found in distinguishing

with certainty males from females.

The fourth period, on the fourteenth day, is character-

ized by the advent of sight. This like all other periods

Shows slight variation. While in a few cases I have found

the eyes to open as early as the thirteenth day, in others,

equally normal in other respects, I have found them to be

delayed until the fifteenth and even the sixteenth day.

The regularity with which this period occurs, however,

1S a sufficiently exact criterion to make it an index of age.

From the fourteenth day to the twenty-first, the date

“This does not mean that sex can not be determined earlier than this

Period. As a matter of fact, sex can be determined at birth, this, however,

18 difficult and less certain than to determine it at the third period.

602 THE AMERICAN NATURALIST [ Vou. XLVI

at which the young should be weaned, no definite change,

except increase in size, is shown.

With the period of sexual maturity we may count the

cycle of development complete. This does not imply, how-

ever, that growth ceases at this time. The time at which

mice reach sexual maturity varies greatly. While I have

had some mice to pair at six weeks, this is rather unusual.

It has been my experience that under ordinary cireum-

stances both the males and females reach sexual maturity

in the second or third month. From this time on for the

next few months the mice are in the prime of the repro-

ductive period, beyond which, at the end of ten to twelve

months of age, activity diminishes and, for purposes of

breeding, the mouse is of little further service.

V. PRACTICAL SUMMARY

The ease with which white mice can be handled makes:

them in many cases preferable for experimentation to

other and larger rodents, but their usefulness has been

greatly curtailed because of a wide-spread notion that:

they are difficult to rear under the conditions of the

laboratory.

The purpose of this paper is to give an intensive

method by which I have been able to rear then in abun-

dance. By ‘‘intensive’’ I mean that relatively few mice

are kept from which to breed, and that these are kept

under conditions which insure productivity.

Especially detrimental to intensive breeding are

parasitism and marked fluctuations in temperature. Hot.

air heat, the temperature ranging from 20° to 25° C., has

proved most satisfactory. Heat from an oil stove whem

continued for a considerable length of time proved un-

satisfactory.

Mice which are badly parasitized are useless for breed-

ing purposes. Various kinds of sprays and powders are

used to rid them of the parasites. Some of these, how-

ever, I have used with disastrous results. Parasitism

may be best prevented by using a case that is readily

cleaned. My cases are washed weekly with hot water to

No. 550] BREEDING MICE 603

which is added ‘‘gold-dust’’ and a small amount of petro-

leum; the nest-boxes, into which the mice are put at the

time of cleaning, are partly closed and then removed from

the case.

Essential to intensive breeding is an adequately

equipped case. A most essential requisite is a wire mesh

bottom through which waste material readily falls. If

such a case be placed on a table with a trough-top lined

with galvanized iron, waste matter can easily be drained

into a sink. For nests the case is provided with three-

fourth sized chalk boxes filled two-thirds full of shredded

paper. Food (wheat) is procured by the mice through

an opening in the front of the nest box from bird cups

placed inside of the box. These are filled from the out-

side without opening the case. Water may be kept in

excellent condition in test-tubes which are closed suffi-

ciently to retain the water drop when the tube is inverted

in the case; these are filled from a siphon bottle.

A knowledge of breeding habits is of great importance

in intensive breeeding. Copulation in mice is a well-

defined act, which lasts from ten to twenty-five seconds

and is followed by a more or less complete rest. It nor-

mally takes place on the day that a litter is born. In

females that have gone through a period of rest it will

usually occur a few days after the female has been put

with the male. Copulation may or may not result in fer-

tility. By a selection of males and females with a high

index of fertility the number of offspring may be greatly

Increased.

The period which a non-suckling mother carries her

young is a few hours short of twenty days. A mother

suckling young, on the other hand, carries her litter

twenty plus the number that she is suckling. Thus a

mother suckling five will go practically (20 +5) twenty-

five days, while one suckling ten may be expected to run

(20+10) thirty days. |

In rearing the young it is well to remember that the

Sreatest mortality results within the first two or three

days of life. At this time the young must be kept warm.

Under bad conditions the mother may destroy them.

7”

604. THE AMERICAN NATURALIST [Vou. XLVI

From birth to maturity mice pass through several well-

defined stages which to the breeder are of importance for

the determination of age, sex and the like. These are 1

an early stage in which the skin is peculiarly red so that

through it may be seen the stomach white with milk; 2

a second stage at six to seven days in which the body is

covered with flakes of dandruff; 3 a stage at nine or ten

days in which the mamme appear in the females. This I

have designated as the stage for the early determination

of sex; 4 on the fourteenth day a stage at which the

eyes open. :

At twenty-one days the young should be weaned. From

this time on slight change 1 is shown except increase in size

until sexual maturity is reached. This usually occurs in

the second or third month. From this time up to the end

of ten months or a year of age the mouse is in the height

of the breeding period; beyond this time, for purposes of

breeding, the mouse is usually of little further service.

BIBLIOGRAPHY

1. Cuénot, L. 1902. La loi de Mendel et L’hérédité de la pigmentation

chez les souris. Arch. de Zool. Exp. et Gén., 3°-série, Tome X (Notes

et Revue, p. xxviii).

2. Ehrlich, P. 1891. Experimentelle Untersuchungen über Immunität.

Deutsche med. Wochenschrift, p. 976. i

3. Bashford, E. F. 1909. Cancer in Man and Animals. Lancet, clxxxvii,

p. 691

4. Yerkes, oberi M. 1907. The dancing mouse; a study in animal be-

havior. The Macmillan Company. .

5. Long, J. A. and Mark, E. L. 1911. The pein of the Egg of the

Mouse. Pub. on Inst. (Washington, D. C.), No. 1

6. Daniel, J. Frank. 0. Observations on ee Pelt of Gestation in

White Mice. ey ‘be Zool., 5.

7. Miller, Newton. 1911. Repeodiuctiaal: in the Brown Rat. Am. Nat.

XLV, p. 623,

THE DISTRIBUTION OF HYLA ARENICOLOR

COPE, WITH NOTES ON ITS HABITS

AND VARIATION

C. H. RICHARDSON, JR.

STANFORD UNIVERSITY `

_ Srupents of zoogeographical distribution are fre-

quently hindered by the scarcity and inexactness of the

published data in the particular group which they are

studying. Especially is this true of students of western

North American amphibians, for they must rely largely

upon the publications of the early exploring expeditions

in which localities were often stated in a most general

way and at times with doubtful accuracy.

Our present knowledge of the distribution of the tree

toad, Hyla arenicolor Cope, is very incomplete. Many

of the references to its occurrence are extremely indefi-

nite and unreliable and in no case has enough material

been gathered to give the limits of its range in any one

region. It was first discovered and named Hyla affinis

_ by Baird! in 1854, the description being based upon one

specimen from the state of Sonora, Mexico. Later Cope*

found this name to be preoccupied and replaced it with

arenicolor. At the present writing this tree toad is known

to inhabit parts of southern California, Utah, Arizona,

New Mexico, Texas, and Mexico. , Southern California is

included in its range on the strength of two specimens

collected in 1875 by H. W. Henshaw,’ and no additional

records of its occurrence within the state have been made

by the herpetologists who have explored this region.

Within the last few years, however, the University of

California Museum of Vertebrate Zoology has acquired

a number of specimens of Hyla arenicolor from various

*Proe, Acad. Nat. Sci. Phila., p. 61.

*Jowrnal Acad. Nat, Sci. Phila., 1866, p. 84.

* Yarrow, Bull. U. 3. Nat. Mus., No. 24, 1882, pp. 24, 175.

605

606 ` THE AMERICAN NATURALIST [Vor XLVI

localities in southern California. Through the kindness

of the director, Professor J. Grinnell, the writer has been

extended the privilege of examining these specimens and

the results are incorporated in the present article.

Specimens from the following localities have been

studied, all of which are in the Museum of Vertebrate

Zoology unless otherwise stated.

TABLE A

No. of

Speci- Locality Altitude Date ‘Collector

mens

8 |Mountain Spring, San Diego Co., Cal. About 1909

4,500 ft.| Mar. 25 |F. Stephens

1 |La Puerta, San Diego Co., Cal. About

4,500 ft.| June 5 |F. Stephens

1 |Warner’s Pass, San iy Co., Cal. 4,000 ft.| June 22 |F. Stephens

1 |Julian, San Diego Co., Cal 3,750 ft.| July 29 |F. Stephens

1906

3 |Pine Mt., near Escondido, Cal. 2,750 ft.| Sept. 4 |J. Dixon

1908

1 |Carrizo Creek, Santa Rosa Mts., Cal. 3,000 ft.| June 22 |J. Grinnell

2 |Dos Palmos Springs, Santa Rosa Mts.,

3,500 ft.| May 26 J. Grinnell

9 |Deep Canyon, Santa Rosa Mts., Cal 3,000 ft.| June 21 J. Grinnell

1 (Lower Palm Canyon, San Jacas Mts.,

Cal. 800 ft.| June 15 |J. Grinnell

2 |Oak Springs, upper Palm Canyon, San

Jacinto Mts., Cal. 4,750 ft.| June 11 |J. Grinnell

4 |Base of San Jacinto Mts. near Cabazon, May 5 |W. P. Taylor

Riverside Co. a Cal 1,700 ft. and 7 and C. H.

Richardson

4 |Sierra Madre, Los Angeles Co., Cal. 1,500 ft.| May, 1904/J. Grinnell

1903

20 Arroyo Seco Canyon near Pasadena, Cal.| 1,500 to Aug. 3

i 2,000 ft. and 23 |J. Grinnell

1 |Tejunga Valley, Los Angeles Co., Cal. About 1910

1,500 ft.| Apr.1 |J. Grinnell

1 renee: University coll.) Upper Santa C. H: Rich-

Anita Canyon, Los Angeles Co., Cal. | 3,500 ft.| Aug. 7 ardson, Jr.

In California, Hyla arenicolor is now known to range

northward along the coast mountains from near the Mex-

ican boundary to the Tejunga Valley, Los Angeles

County. In San Diego County it occurs on both the coast

and desert slopes of the mountains; in Riverside County,

on the desert slope, and in Los Angeles County, so far

as known, only on the coast slope. No records of its

eke Nt

E ae

=: 4

TEs

No. 550] HYLA ARENICOLOR COPE < BOT

occurrence in San Bernardino County are at hand,

but a careful search will undoubtedly reveal its presence

there. Throughout this region, its habitat appears to be

confined to streams and mountain springs between 1,000

and 5,000 feet elevation. Here the writer has found it

associated with such trees as Alnus rhombifolia, Platanus

racemosa, and Acer macrophyllum and in this state at

least it may be regarded as an inhabitant of canyons

within the upper sonoran zone. It is apparently more

strictly aquatic than the smaller Hyla regilla Baird and

Girard, whose range in southern California is, in part,

coextensive with it. The former species has never been

found far away from the vicinity of water, while the

latter has often been seen under vegetation a considerable

distance from it.

The following meager notes indicate that the breeding

season of Hyla arenicolor extends from late spring until

fall: Two females from Sierra Madre, Los Angeles

County, May, 1904, one from Warner’s Pass, San Diego

County, June 22, 1909, and one from Pine Mountain, near

Escondido, San Diego County, Sept. 4, 1906, contain large

eggs. There is also a young specimen from La Puerta,

San Diego County, collected on June 5, 1909, in which the

tail has not been entirely absorbed.

Miss Dickerson‘ has described the rapid color changes

that take place in this species. The writer noted that a

light-colored individual which was captured on a granite

rock changed to a dark gray mottled with lighter mark-

ings when placed for a short time in a covered tin pail.

The widely scattered record stations given below, some

of which are too inexact to be of great value, suggest that

Hyla arenicolor lives in suitable places over practically

the entire southwestern part of the United States and a

considerable portion of the Mexican tableland as well.

Little has been written concerning its habitat preferences

within this region. Stejneger® has found it in the Grand

* The Frog Book, Doubleday, Page and Company, 1906, p. 122.

"N. A. Fauna, No. 3, 1890, p. 117.

608 THE AMERICAN NATURALIST [Vou. XLVI

Canyon of the Colorado, Arizona, at an elevation of

1,000 feet above the river and in the bottom of the

cai von. Ruthven’s* specimens from Sabino Canyon,

Santa Catalina Mountains, Arizona, were ‘‘found among

bushes on the floor of the canyon’’ in the ‘‘ willow-poplar

association.’’

TABLE B

No. of

Speci- Leoality Date Authority

mens

MPEG POON, PACKING jer ccs’ S wives oe eos Cope; Baird

Guana juato, Mexico eae are esas Gee PESIN 4 E

RIWROUIRIOTG, E S vo or es ee, S Duges

grt Sg City of Masta: and Chihuahua,

AE E T Win Bad ec ely Lara ir OH an P a Oe eee

Valley eal a OF TOMA MeRIOO: 2 Fle. Secs. Cop

1 |Del Rio, hin idee a es Obie pee a ea A Witmer aay

a O P E AA e T Se eee oe ee ee he Boulen

1 Santa Fe, sow MOR CG eee ees June, 1873 pt

a (ort Winmeate, New: Mexico... J. - 32.0. oo os oo ee, ope

BPO ein cis ea Owls ies A e 1872 arrow

IT Me aO a eaa ae aa a aa a e Miss Dickerson

Lepper Colorado Hive 2 fico S a o Cope

White River Can S Soe A E AN PEE ae ope

6 [Grand Snara of paa dolorido. Arizona | Sept. 3, 1889| Stejneger

Fort Whipe Arons osana ee Cope

2 abino iosal Santa Catalina Mts.,

E E E E TEE E EAT May 23,1903) Ruthven

2 Southern CRABS oe ae 1875 Yarrow

Specimens of Hyla arenicolor from southern Cali-

fornia agree quite closely with the published descrip-

tions. Cope’ states that the diameter of the tympanum

is equal to two thirds that of the eye fissure, but in ten

specimens measured (see following table) this ratio is

shown to be 47.7 per cent., or not quite one half. Boulen-

ger’s Hyla copiis described from two specimens obtained

at El Paso, Texas, and now considered synonymous with

Hyla arenicolor, has the diameter of the tympanum one

half that of the eye fissure, a fact which suggests that this

character is subject to considerable variation throughout

the range of the species. The ratio between the length

of the body and that of the hind limb is also subject to

* Bull. Am. Mus. Nat. Hist., 1907, p. 509.

"Bull. U. 8. Nat. Mus. , 1889 , No. 34, pp. 369-370.

* Annals and Magasiné Nat. Hist., 1887, p. 53.

609

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pronounced variation in southern California specimens.

The heel of the limb when extended forward usually

reaches to the anterior border of the orbit,® but in young

individuals it often extends to the tip of the snout.

he =

THE DISTRIBUTION OF Hyla arenicolor COPE IN CALIFORNIA ACCORDING TO THE

LOCALITY RECORDS.

j Ei || | | l

The table also shows that there is a well-marked dif-

ference in the size of the sexes, the female being larger,

especially in the length of the body and hind limbs.

BIBLIOGRAPHY

Baird, 8. F.,

1854. DER of New Genera and Species of North American

Proc. Acad. Nat. Sci. Phila., p. 61.

1859. United States and Mexican Boundary Survey: Batrachia, p. 29,

4-7.

pl.

-Boulenger, G. A.

Catalogue Bratrach. Salient., p. 373.

1887. Descriptions of New Reptiles and Batrachians in the British

useum. Annals and Magazine Nat. Hist., p. 53.

1888. Description of New Brazilian Batrachians, Hyla copii. Annals

and Magazine Nat. Hist., p. 189.

* Cope, loc. cit.

No. 550] HYLA ARENICOLOR COPE 611

Cope, E. D,

1866. Journal Acad. Nat. Sci. Phila., p. 84.

1866. On the Reptilia and Batrachia of the apera a of the

Nearctic Region. Proc. Acad. Nat. Sci. Phila., p.

1875. Check-list of North American Patraihii and a gee Uz.

. Nat. Mus., No. 1, pp. 31, 90.

1880. On the dadana Position of Texas. Bull. U. S. Nat. Mus.,

No. 17, p. 47.

1885. The Riverside Natural History, Houghton, Mifflin and Company,

III, p. 338.

1887. Batrachia and ea anes of Central America and Mexico. Bull.

. S. Nat. Mus, No. 32,

1888. AMERICAN CEH p. '80.

1889. The Batrachia of S America. Bull. U. S. Nat. Mus., No.

34, p. 369, figs. 1-7.

1896. The Geographical Dber of Batrachia and Reptilia in

North America. AMERICAN NATURALIST, 30, pp. 1014, 1021,

1022.

‘Coues, E.

1875. U. S. Geological Survey West of the 100th Meridian, Zoology

5, p. 630.

Dickerson, Miss M.

106. The Pog Book. ‘Doubleday, Page and Company, p. 122.

` Plates XLVII and XLVIII.

Ruthven, A. G.

1907. A Collection of Reptiles and Amphibians from Southern New

Mexico and Arizona. Bull. Am. Mus. Nat. Hist., p.

Stejneger, L;

1890. Annotated List of Reptiles and Sni, Collected by C.

Hart Merriam and Vernon Bailey on San Francisco

Plateau and Desert of the Little sae Arizona, with

Descriptions of New Species. N. A. Fauna, No. 3, p. 117.

Stone, W.

1903. A Collection of Reptiles and nga ond from Arkansas,

Indian Territory, and Western Texas. Proc. Acad. Nat. Sci.

Phila., p. 539.

Yarrow, HC

1875. U. S. Geological Survey West of the 100th Meridian, Zoology

> P-

1882. Check- list of North American Reptiles and Batrachians. Bull.

. S. Nat. Mus., No. 24, pp. 24, 175.

THE UNEXPECTED OCCURRENCE OF ALEU-

RONE COLORS IN F, OF A CROSS BE-

TWEEN NON-COLORED VARIETIES

F MAIZE

PROFESSOR R. A. EMERSON

UNIVERSITY OF NEBRASKA

Brrore the Mendelian methods of analysis became

available, considerable wonder would doubtless have been

excited by the ‘‘mysterious’’ appearance in F, of one

colored grain—purple or red—to every five or six white

ones in case of a maize cross, both parents and F, of

which had only white grains. An occurrence of this

sort has recently been noted in one of my maize cultures

and the F, numbers are explained here as a trihybrid or

tetrahybrid ratio. The crosses in question were made

primarily for a study of size inheritance and fairly large

numbers have been grown. The varieties concerned are

two dwarfs of distinctly different types, Tom Thumb pop

and California Rice pop, and a tall type Missouri dent.

The facts with reference to aleurone color are these: Tom

Thumb pop, a ‘‘white’’ corn (i. e., having non-colored

aleurone), was crossed with Missouri dent, also a white

corn. Three generations of hybrid plants—four gener-

ations for aleurone and other endosperm characters—

have been grown without the appearance of any but

white grains. The same white-seeded Missouri dent was

also crossed with the white-seeded California pop. The

three hybrid generations grown to date have shown no

aleurone color. Furthermore, when the same white Tom

Thumb pop was crossed with the same white California

pop, only white grains appeared in F,. But both of the

two ears containing F, seeds—the only ones that have

been produced as yet—had a sprinkling of both purple

and red grains, too many to be explained as due to care-

612

No. 550] ALEURONE COLORS 613

less guarding against foreign pollen and too few to be ac-

counted for by any simple monohybrid or dihybrid for-

mula. The actual numbers of grains of the various sorts

were as follows:

a anes 43 purple, 10 red, 308 white.

ee SS rer 32 purple, 11 red, 222 white.

BNE soe esas 75 purple, 21 red, 530 white.

The fact is familiar that in crosses of purple with

white varieties of corn, there often appear in addition to

the monohybrid ratio of three purple grains to one white

one, purple, red and white grains in the dihybrid ratios

of 9:3:4 (Hast and Hayes! and Emerson?). It is also

well known that in similar crosses purple and white

grains may appear in F, in the reversed monohybrid

ratio of 1:3 or the dihybrid ratio of 9:7 (Hast and

Hayes’). East? has recently shown that for the produc-

tion of purple aleurone there must be present three Men-

delian factors, C, R, and P, and has demonstrated for

purple, red, and white grains the trihybrid ratio of 27:9:

28. C is a general color factor, that must be present

ordinarily in order that any color may develop, R a fac-

tor that has to do with the production of red aleurone

when C is present, and P a factor for purple that is ef-

fective only in the presence of both C and R. Thus

CRP gives purple and CRp red, while all the other

possible combinations give white. All this is on the as-

sumption that a fourth factor J, an inhibitor of color de-

velopment, is absent. Purple color of the aleurone may,

therefore, be said to depend upon the presence of three

factors and the absence of one, CRPi, red color upon

the presence of two factors and the absence of the two

others, CRpi, and whites upon the absence of either one

of the two factors C or R or upon the presence of a third

factor, I, cRP, CrP, or CRPI, ete.

*E. M. East and H. K. Hayes, Conn. Agr. Expt. Sta., Bul. 167 . 57-

100, 1911. yes, . Agr. Expt, l , » PP

— A. Emerson, Amer. Breeders’ Assoc., vol. 6, pp. 233-237, 1911.

E. M. East, AMER. Nar., vol, 46, pp. 363-365, 1912.

614 THE AMERICAN NATURALIST [Vou. XLVI

If the numbers obtained in F, of the cross of Tom

Thumb pop with California pop are to be regarded as

constituting a tetrahybrid ratio, all four aleurone factors.

must be heterozygous in F, the formula being CcRrPpli.

The F, generation would then be constituted as follows:

ye ae ee ee ae eS 27 purple

earra a n a E i oe a cs 9 red

27 CRpl Pe ee gen ee Bee at ae 220 white

scorpi |

If either C or R is homozygous in F,, the resulting F,

ratio should approximate 9 purple: 3 red: 52 white.

The actual numbers fell between these two theoretical.

ratios, as is seen from the following comparison:

Purple Red White Total

Tetrahybrid ratio ........ 22 538 626

Observed numbers ........ 75 21 530 626

Inod Patio 2. 88 29 509 626

From the ratio alone it is plainly impossible to say

whether the cross in question is a tetrahybrid or a tri-

hybrid. Of course behavior of the reds and purples in F,

will settle the matter. If, for instance, either C or R is.

homozygous, one third of the F, red grains should breed

true and two thirds produce reds and whites in the ratio

of 3:1, while if both are heterozygous, only one ninth of

No. 550] ALEURONE COLORS 615-

them should breed true, four ninths produce a 3:1 ratio,.

and four ninths produce a 9:7 ratio. Similarly, if either

one of these two factors is homozygous, of the F, purples.

one ninth should breed true, two ninths give purple and

red 3:1, two ninths purple and white 3:1, and four ninths.

purple, red, and white 9:3:4. But if both factors are

heterozygous, out of the twenty-seven F, purples only one-

should breed true; two yield purple and red 3:1; four,

purple and white 3:1; four, purple and white 9:7; eight,

purple, red and white 9:3:4; and eight, purple, red and’

white 27:9: 28.

The results of intercrossing Tom Thumb pop, Missouri

dent and California pop, so far as they are known at

present, might be obtained if the three varieties had

either of the following sets of formule, or any of the-

modifications of them suggested below:

Tom Thumb pop ICRP ICrP

Missouri dent IcohP or twrf

California pop icrp icRp

Among the allowable modifications of the above for--

mulæ are these: The formulæ for Tom Thumb pop and

California pop may be interchanged. Substitutions of

C for R and R for C may be made if carried throughout

the set. P may be present in any one or two varieties

and absent from any one or two. Where J is present im

Missouri dent and also in one of the other varieties, R

may be present in all three varieties, absent in any one

variety, or absent in Missouri dent and either one of the-

other varieties.

A NEW SUBSPECIES OF ZEA MAYS L.

DR. WALTER B. GERNERT

UNIVERSITY OF ILLINOIS

Waite harvesting a plot of yellow dent corn, a strain of the

Leaming variety grown on the Illinois Agricultural Experiment

Station fields in 1909, one of the workmen found a peculiarly

shaped ear which was laid aside in the drying-room as a cu-

riosity. The corn in which this ear was found came from a

strain that had been subjected for several generations to an

ear-row selection for high protein content by a mechanical in-

spection of the endosperm.:

This new type of ear which reproduces faithfully in its prog-

eny is cone-shaped in outline and gives the appearance ex-

ternally of being composed of a mass of kernels borne on num-

erous irregular branches (see ‘‘a’’ in the figure). A longitu-

dinal section (at ‘‘b’’) displayed kernels throughout the ear.

The ‘‘branched’’ form is a prolification of the fleshy type of

4 to 30 or more-rowed cob common to all varieties that to the

writer’s knowledge have béen described to date. For this new

type the writer proposes the name Zea ramosa, from the Latin

“‘ramosus—having many branches.’’ This name is proposed

in conformity with the bi-nomial classification of Sturtevant?

which is now generally recognized. We will not here discuss

the precedence nor the desirability of Sturtevant’s nomencla-

ture for the subspecies of corn which were all grouped at first

by Linneus under the general head Zea mays.

The new type Z. ramosa (branched) is as much deserving of

a specific name as are any of the six groups recognized by Stur-

tevant, namely: tunicata (pod), everta (pop), indurata (flint),

indentata (dent), amylacea (soft), saccharata (sweet). The

first of these six groups has a more or less monstrous develop-

ment of glumes into pods which inclose each kernel on the ear

with leafy bracts known as the husks. The classification of the

other five groups is based on differences in characters situated

in the endosperm of the kernel.

* Representative samples of the ears thus obtained for planting in the

next year were also analyzed chemically to determine the efficiency of the

method of mechanical selection. `

* Sturtevant, E. L., Bul. Torr. Bot. Club, 21: 319-343, 1894; Off. Exp.

Sta, U. S. D. A., Bul. 57: 7-108, 1899,

616

No. 550] ZEA MAYS 617

The ear of Z. ramosa, which is always of a definite form, is

borne at the usual place near the middle of the culm and is not

to be confused with sparsely branched ears sometimes found on

the culm nor with ears frequently found in the tassels on ordi-

). a, external

. 619). c, tassel ( . 620).

linois Agricultural Experi-

: iD TASSEL IN CoRN (Zea ramosa

view of parent ear. b, longitudinal section of same (p

Photographs by Flora Sims and by courtesy of the Il

ment Station.

THE NeW TYPE or EAR AN

nary corn plants. Such abnormalities which are fluctuating

in their inheritance have thick pasal branches of fleshy cob—

which may be as long or longer than the primary cob itselfi—

and may bear from two to a dozen or more rows of kernels on

each branch. Furthermore, no male florets have as yet been

found in any of the ears of Z. ramosa and they are always

covered with normal husks.

618 THE AMERICAN NATURALIST [ Vou. XLVI

A feature of especial interest in the new type is the fact that

the tassels of such plants are also invariably much branched and

cone-shaped. (A reduced photograph of the tassel is shown at

**e.’’) No instance has yet appeared in which this correlation

did not exist.

No. 550] ZEA MAYS 619

During the last three years the writer has had under obser-

vation a large number of varieties and their hybrids. He has

been able to isolate more than a dozen tassel types which are

strikingly different in shape and which are distinct from each

other in inheritance. Some

of the characters of these

types are plainly correlated

with certain characters of

the ear. Advantage can un-

doubtedly be taken of this

fact in analyzing the be-

havior of such fluctuating

phenomena as size, shape,

and number of parts.

This correlation between

tassel and ear permits the

selection of individuals in

the field before the silks

pollenated at will. In an

investigation not yet pub-

lished, the writer has found

that the tassels in a large

number of varieties. are

usually out and fully ex-

panded one or more days

before ` any pollen is shed

from the anthers, while the

tassels produce pollen at an

average of from one to three T

days before the silks appear on the same plants. ,

During the first season (1910) in which the branched ear was

-tested to see if it would reproduce the character only two out

of fifty kernels planted produced individuals bearing the

branched ears. It was at this time that the correlation between

the tassel and ear type was discovered. The fact that only two

Plants of- the Z. ramosa type were obtained this first year indi-

cated that either the character was reproduced only occasionally

or that it was a recessive character and that the parent was

Pollenated largely by neighboring plants bearing normal ears

which must be dominant to the branched form. It was pre-

620 THE AMERICAN NATURALIST [ Vou. XLVI

dicted? that the latter explanation was the true one, and the

results from another generation (grown in 1911 from hand

pollenated ears) have substantiated the prediction. Our data

for this year show that the branched form of ear and its ac-

companying tassel type are recessive to the fasciated, cylindri-

eal form of ear from which they originated.

Perhaps no one is ready to draw the limits upon that inde-

finable term ‘‘species,’’ but Mendelian studies have thrown a

bright light upon this mooted question. It is now very evident

that sterility in hybrids is not a safe guide for determining

what shall be a species. Darwin reported a number of cases to

show the fallacy of this theory which was at one time advanced

by Kölreuter, Gartner and others. Mendelian studies have

disclosed a number of cases of sterility (I have found several

in corn) which are not due to hybridization nor to species’ dif-

ferences.

Systematic classification should be founded upon either the

genotype or upon the Mendelian basis. The genotype basis

would be feasible for self-bred and apogamous, including par-

thenogenetic, types of reproduction; while the Mendelian basis

would undoubtedly be the most satisfactory for types of plants

and animals that are continually mix-fecundated. We are

learning that there are an almost inestimable number of char-

acters in corn and that they may be quickly distributed to all

the representatives of the six species-groups by hybridization.

As an example: the kernel colors; red, yellow, blue and their

absence (white) are found in all of the groups. If we were to

give each distinct character, wherever we find it, a specific clas-

sification we should have many more species than we now recog-

nize. This is especially true with regard to economic plants.

Such classification is desirable, however, and will soon be

needed from a Mendelian standpoint if from no other. As an

instance: we have evidence that there are more than twenty

reds or phases of red color in corn alone, and a system for their

classification is desirable. As was mentioned above, we have

isolated a dozen distinct tassel types, each possessing a number

of characters that may be easily redistributed by hybridization.

The inheritance of detail in both plants and animals is various:

l ***The Analysis of Characters in Corn and Their Behavior on Transmis-

sion,” a paper submitted May 13, 1911, to the graduate school of the

University of Illinois as a detects thais.

No. 550] ZEA MAYS 621

when true dwarfs and true giants are hybridized, size segre-

gates distinctly in their progeny; but when fluctuating shorts

and talls are hybridized, size exhibits a so-called ‘‘ blending’

behavior that is generally complex. Thus it is evident that for

recording such characters and their method of segregation we

already need for the sake of conformity, brevity and ease in

reference a definite, simple, systematic classification of charac-

ters irrespective of species, varieties or individuals. Bateson,

by grouping characters of similarity under one head; Tscher-

mak and others, by distinguishing ‘‘types’’ of segregation, have

already taken a step toward this end.

The newly discovered type of corn is so radically different

from all others yet reported, and since we are at present recog-

nizing six species-groups of Zea, it seems very appropriate to

add Z. ramosa as a seventh. And yet the writer will not be dis-

appointed if the proposed addition is not recognized.

That Z. tunicata and Z. ramosa both originated as mutations

we have no doubt; but as to the causes which led to the pro-

duction of these two peculiar types, we have no definite knowl-

edge. It has been proposed that new forms, aside from those

developed by hybridization, are due to accidents in mytotie di-

vision; and yet those same writers are perhaps not ready to

admit that even the greater proportion of the myriads of diverse

forms of plant and animal life that exist on the earth to-day are

accidents! This, of course, has nothing to do with the fact of

chance meeting of gametes in reproduction.

The writer has evidence (not yet published) upon various

Strains of pod varieties and their hybrids with other podless

varieties to show that the pod character, in that form, never was

the normal or original pod or glume in Z ea; and it is also evi-

dent that the new branched ear, as it is, is not a reversion to

a former one. As may be seen at “‘b’’ in the illustration, the

pithy core of the cob is not affected by the branching in the

outer zone. The branches are somewhat fleshy and contorted

as well as being very numerous. As stated above, no male

florets have yet been found in the ears of the branched corn.

Such evidence points to the conclusion that this is not a case

of at least total reversion.

As is generally the case in such instances, it is only a matter

of conjecture as to the causes that led to the production of this

individual which, in so far as is known, was different from all

622 THE AMERICAN NATURALIST [Vou. XLVI

others in the history of the strain. Mr. W. T. Craig, who has

been connected with the corn-breeding work at the University

of Illinois for a number of years, states that to his knowledge

no ear similar to this has ever been harvested on any of the

breeding plots at this station.

The selection in the particular strain in which the branched

ear was found has since been discontinued and thus we do not

know whether the type would ever have occurred again in the

same strain. Hybrid progeny from this parent strain are, how-

ever, yet being grown at this station; but no other individuals

like the one here described have been found.

Several more generations of the branched corn should be

grown before we can make any reliable statements as to its

economic value. It is hoped that the new type may be devel-

oped by hybridization and subsequent selection among the seg-

regates (which work is in progress now). As yet it does not

bear as much grain as the unbranched ear in the strain in which

it was found. The parent ear of Z. ramosa measured approx-

imately 5.5” in length and 9” in circumference. Very little dif-

ference was found in the size of the other parts of the plants

except that of the tassel, which is also slightly smaller on the

new type.

The branched ear is apparently an ideal form to feed whole

to livestock. The cob is of such nature that it may be readily

masticated with the kernels and without the necessity of grind-

ing or chopping before it is fed. It may also prove to be an

ideal type for ensilage. Whether it will yield well enough to

justify its production for any of these, or other purposes, re-

mains to be investigated. 3

NOTES AND LITERATURE

PATTEN ON THE ORIGIN OF VERTEBRATES, AND

THE GENERAL QUESTION OF THE VALUE

OF SPECULATIONS ON THE PHYLOG-—

ENY OF ORGANIC BEINGS?!

From the standpoint of range of topics covered, amount of

work performed, and time devoted to its execution, this work by

Patten may without exaggeration be spoken of as monumental.

Many of the facts set forth are original observations by the au-

thor and his students, and of those not original a large propor-

tion have seemingly been personally studied by him. Further-

more, nearly all the large number of figures are either original

or bear the stamp, by way of modification of borrowed figures,

of Patten’s well-known skill as an illustrator.

A list is appended comprising 26 titles of papers and ad-

dresses by the author or the author in collaboration with his

students; but unfortunately references to the works of other

investigators drawn upon are rather few, often somewhat in-

definite, and not well set out in the text. In a book so abound-

ing as is this one in argumentation, many of the main conten-

tions of which are open to debate, sources due to authority ought

to be given exactly and without stint.

Frequent as is the occasion in scientific books to estimate

worth from the two viewpoints of facts presented and theories

defended, rarely is the importance of keeping the two distinct

So great as in this case. Many of the chapters, notably V to

XII and XVI to XX, are veritable magazines of recorded ob-

servation to which workers in the field will, it would seem, find

it profitable to turn for years to come. This remark applies par-

ticularly to the sections dealing with the central nervous sys-

tem of Limulus; with the cutaneous, olfactory, and optical or-

gans of ‘‘Cerachnids’’ and Anthropods; with the dermal skeleton

of Limulus; with the endoskeleton of Arachnids; with the nerve .

***The Evolution of the Vertebrates and their Kin,’’? by Wm.

486 pp. and 309 figures, P: Blakiston’s Son & Co., 1912.

623

624 THE AMERICAN NATURALIST [ Vou. XLVI

supply to the heart of Limulus; and with the general structure

of the Ostracoderms.

The experiments on functions of the brain recorded in Chapter

XI should be a valuable contribution to the interesting prob-

lem of metamerism as expressed through the activities of the

central nervous mechanism.

Two defects in the descriptive matter are likely to interfere

with as extensive a utilization of the book by biologists as it

merits. The first to be mentioned is a want of directness and

definiteness in many of the descriptions that renders their com-

prehension extremely difficult, in some cases almost impossible.

This is due partly to the way references are made to the illus-

trations. Not infrequently a text description of a structure is

given, not very fully, in the course of which one or several

figures are referred to but without specifying the letterings for

the particular parts described. The reader, being in doubt, may

turn to the ‘‘Explanation of lettering’’ at the end of the vol-

ume, only to find that the illustrations in question either have no

letterings for the particular parts, or if sufficient patience in

digging is exercised, to find that the part is labeled with a dif-

ferent name from that used in the description. The account

of the ‘‘middle cord, the lemmatochord and the notochord’’

(Chap. XVIII) is an example of the difficulty here indicated.

Although I have spent much time on this chapter, I have not

been able to get a clear understanding of what is dealt with.

How many distinct structures are in hand? ‘‘The beginning of

the notochord may be recognized in practically all segmented

invertebrates, as the so-called middle cord, or median nerve, and

in its derivative, the lemmatochord,’’ p. 324. This statement is

general, i. e., is not made as applying to any particular animal.

It seems definite to the effect that ‘‘median nerve’’ and ‘‘middle

cord”? are synonymous, and that the structure indicated gives

rise to the lemmatochord. But Fig. 224A, p. 327, representing

the ‘‘nerve cords and lemmatochord of Cecropia,’’ presents to us

the “late pupal stage showing the fully formed lemmatochord,

derived from the condensed sheaths of the median and later

Per ds; also remnants of the median nerve.’’ (Italics by the re-

deto In Limulus the ‘‘middle cord” is said, p. 334, to be

_ arranged in two main lateral cords,” and Fig. 55, l.l.ch., p. 67,

ìs referred to as illustrating this statement. Turning to this fig-

ure and the explanation of letterings, we find that L.l.ch. stands

No. 550] NOTES AND LITERATURE 625.

for ‘‘lateral bands of the lemmatochord.’’ This same figure-

shows a “‘median portion of the lemmatochord”’ distinctly and’

widely separated from the lateral portions. The inference is:

that these lateral and median structures unite somewhere; but

no direct statement to this effect is given, at least in the section

on the middle cord of Limulus.

Again, Fig. 225, p. 328, presents five cross sections of the:

nerve cord of an adult scorpion. Section 5 is said to show the-

“‘merochord.’’ Neither in the description of this figure nor in

the text do we find a direct letter reference to the merochord.

A structure labeled m appears in the figure, but on turning to

the explanation of lettering ‘‘m’’ we find may stand for-

*‘mouth’’ or ‘‘muscle.’? But it is unfair to criticize illustra-

tions and their letterings and labels alone. They must be taken

in connection with the text. By reading a subsection headed

“The Bothroidal Cord or Lemmatochord’’ we find that the-

merochord in section 5 of Fig. 225 is marked l.ch., which stands

for lemmatochord. A sufficiently careful reading of the text

clears up the merely expositive difficulties contained in the figure :

The merochord is the lemmatochord of the ‘‘ posterior thoracic

neuromeres,’’? p. 328. This interpretation is compelled when

Fig. 5 is taken in connection with the text statement indicated.

But then the difficulty becomes substantial and not merely ex-

positive, for on page 328 we read: ‘‘In the scorpion, the median

herve itself is hardly recognizable. .. . The neurilemmas of the:

median and lateral cords form the bothroidal cord of the ab-

domen and the merochord of the posterior thoracic neuromeres.’”

But we have seen above that according to section 5 of Fig. 225

the merochord is a particular part of the lemmatochord. Hence

this part at least of the lemmatochord is formed from the neuro-

lemmas of the median and lateral cords. Under the topic ‘‘De-

velopment of the Lemmatochord’’ we read ‘‘The lemmatochoré

arises, in part, as an axial cord of cells extending forward from.

the primitive streak’’; and nothing under this heading or else-

where so far as I have been able to find, iarmonizes this state-

ment with the indirect assertion above pointed out that the-

lemmatochord is formed from the neurilemmas of the median

and lateral cords. The nearest approach to:such harmonization

is the statement, p. 330, that at the time of hatching, the lem-.

matochord at certain places ‘‘remains permanently attached to:

neurilemma of the middle cord.” As:one-of the many stu--

626 THE AMERICAN NATURALIST [Vou. XLVI

dents who have expended considerable time and ‘‘gray matter’’

on the problem of the forerunner of the vertebrate notochord

the reviewer would heartily welcome a demonstration that the

organ ‘‘may be recognized in practically all segmented inverte-

brates’’; but until a clearer, more convincing description is fur-

nished us of some structure in ‘‘ practically all segmented inver-

tebrates’’ with which the vertebrate notochord is to be com-

pared, the question of homology in the strict sense would not

even be raised were the best interests of comparative anatomy

duly considered.

The other defect in the presentation of matters-of-fact which

a well-wisher for the book may justly fear will tend to prevent

as wide use of it as it deserves, is the circumstance that several

modes of statement occurring over and over again are bound to

give even the fairest-minded reader the impression that many

of the facts were prejudged; that is, were collected and recorded

not primarily on their merits, but in behalf of a theory. The

nomenclature employed in several important connections is

likely to have this effect. The use of the substantive cephalon

with various prefixes in purely descriptive matter dealing with

the thoracic region of arthropods is an example.

In the chapter ‘‘ Minute rig of the Brain and Cord of

Arachnids” we read (p. 8

The more posterior thoracic commissures, and those in the hindbrain,

are shorter, and the neural and hemal fascicles are widely separated,

leaving a space between them, which represents the beginning of the

fourth ventricle (italies by the reviewer).

Such dogmatic and unealled-for statements inserted into

purely descriptive matter are very unfortunate, for they can but

militate against the factual value of the work in the mind of

every candid reader. The feeling of uneasiness engendered in

the reader by these gratuitous dogmatizings, as to the extent to

which facts dealt with have been unconsciously colored by

theory, is not allayed by the author’s avowed attitude toward

the facts of organic structure. On page 469 we find this:

Comparative morphology has no value except in so far as it points

out the historie sequence of organie forms and functions, and reveals to

us the trend of evolution and the causes that direct and control it.

This statement I insist is not true. It may be partly true, but

in the unqualified form given it by the author is not only untrue,

but is provokingly and harmfully untrue. If for Dr. Patten

No. 550] NOTES AND LITERATURE 627

comparative morphology has no value except in the ways indi-

cated, well and good. I neither question nor quarrel with the

assertion. For me, however, comparative morphology has great

value in numerous other ways; and there is much evidence, both

historical and contemporaneous, that it has other values for

many biologists. It is, I submit, a real even though uninten-

tional harm, not only to individuals, but to biological science, for

an able morphologist to make an assertion which carries the

clear implication that the interest in and the valuations placed

upon comparative morphology by the men who devoted them-

selves to it long before anybody knew there was such a thing as

a “‘trend of evolution,’’ were an illusory or spurious interest

and valuation. And I would express my firm conviction that

biologists of this present childhood period of the evolution theory,

as the era from Darwin to the present day may well be called, must

come to see that great as is the value of morphology as a record

of evolution, this is still only one of its values; and further, that

until such perception is attained, just estimation of the facts of

morphology as a record of evolution will be impossible. The in-

terest of the future morphologist in his raw material ought to be,

according to my understanding, that of the pre-evolutionary

morphologist plus that growing out of the later discovery that

the facts of structure mark the ‘historic sequence of organic

forms and functions.’’ It is just because many, indeed all of

the facts dealt with in this work have values for me over and

above those attaching to them as a record of evolution that I re-

gret that they could not have been presented in a fashion less

caleulated to raise doubts in so many instances as to whether

they would appear exactly as they do but for the circumstance

of having been interpreted by the author in the light of his par-

ticular theory of historic sequence.

This consideration will, I trust, give real weight to my words

When I say that the criticisms I am passing on Patten’s mode

of presenting facts is an apology for a work of truly great fac-

tual worth, and not at all an attempt to discredit it. Nor would

I have any one understand me to be an advocate of ‘‘mere facts”?

of morphology; facts, that is, without any reference to their

wider bearings. My point is that all facts of morphology, as of

all other departments of biology, have so many ‘‘wider bear-

ings” that to write down as without value all except some one

set of these bearings, even so important a set as that of evolution,

18 to narrow the horizon of biological science. Against tenden-

628 THE AMERICAN NATURALIST [ Vou. XLVI

cies of this sort, wherever occurring, and unfortunately they

occur in many sections of the vast realm, I am ready at all

times to do battle.

o far this review and commentary has been made entirely

from the standpoint of observed and observable facts dealt with

in the volume. Now the point of view must be shifted to the

theoretical side.

Patten’s central thesis, as is well known, is that vertebrates

have descended from arachnids. The ‘‘arachnid theory of

origin of vertebrates,’’ or, for short, the ‘‘arachnid theory,’

the phraseology used by the author. The theory was first a

nitely set forth in 1889, the title of the original publication being

**On the Origin of Vertebrates from Arachnids.” A somewhat

abbreviated quotation of the author’s outline of the theory will

be justifiable. He writes:

This theory has formed the basis of all my subsequent work, and as

far as it went, is practically the same as the one presented here. In that

paper it was maintained that the vertebrates are descended from the

arachnid division of the arthropods, in which were included the typical

arachnids, the trilobites, and merostomes. The ostracoderms were re-

garded as a separate class, uniting the arachnids with the true verte-

brates. Limulus and the scorpion were the types most carefully studied,

because they were the nearest and most available living representatives

of the now extinct merostomes, or giant sea scorpions, Z were re-

garded as the arachnids standing nearest to the ostracoderm

Other evidence and conclusions were as follows: (1) In die arachnids

a forebrain vesicle is formed by the same process of marginal over-

growth as in the vertebrates. . . . (2)The kidney-shaped compound eye

of arachnids has been transferred to the walls of the cerebral vesicle in

vertebrates, giving rise to the retina, which still shows traces of omma-

tidia in the arrangement of the rod-and-cone cells. . (3) The arach-

nids have a cartilaginous endocranium similar in laine and location to

the primordial cranium of vertebrates. (4) They have an axial, sub-

neural rod comparable with the notochord. (5) In arachnids the brain

contains approximately the same number of neuromeres as in verte-

brates. . . . (6) The segmental sense organs (median and lateral eyes,

olfactory and auditory organs) are comparable with those in vertebrates-

The coxal sense organs are associated with special sensory nerves and

ganglia, comparable with the cranial dorsal-root nerves and ganglia

(suprabranchial sense organs) of verterates. (7) The basal arches of

appendages are comparable with the oral and branchial visceral

arches in vertebrates, (8) The tendency toward concentration of

neuromeres has narrowed the passage way for the stomodeum and

modified the mode of life in the arachnids. This ultimately led to its

No. 550] NOTES AND LITERATURE 629

permanent closure, the infundibulum and adjacent nerve tissues in

vertebrates representing the remnants of the old stomodeum with its

nerves and ganglia. . . .° (12) The process of gastrulation in verte-

brates and arachnids is confined to the procephalie lobes, in the place

where at a later period the primitive stomodeum appears. The so-

ealled “ gastrulation” of vertebrates. and arachnids is an entirely

different and independent process, that is, the process of adding by

apical or teloblastiec growth a segmented, bilaterally symmetrical body to

a primitive radially symmetrical head. (13) The arachnids resemble

the vertebrates in more general ways, as in the minute structure of

cartilage, muscle, nerves, digestive, and sexual organs. (Pp. xvii and

xviii of the Introduction.)

None of the statements in this list, either those quoted or those

not quoted, bring out clearly one of the most striking features of

the theory, namely, the supposition that the ventral surface of

the arachnid became the dorsal surface of the vertebrate. This

is well shown by several series of figures, as, for instance, that

on page eight, of imaginary arthropods and vertebrates with

creatures intermediate between them.

During the twenty years and more that the theory has been

before zoologists it seems to have won very few adherents; in-

deed, to have had little influence on biological thinking of any

sort. Nor does it seem probable that this final marshaling of

the evidence will accomplish much more as regards the main

contention. So far are we still from certainty as to exactly how

and when the back-boned animals originated that even the prob-

able evidence toward such knowledge is not great. Indeed, if

one will consider fully the nature and difficulties of the prob-

lem he will see that the chance of ever reaching certainty is

almost nil.

What would constitute a demonstration of the parenthood of

vertebrates ? Obviously the most indubitable proof, that of

direct observation, is out of the question. The ‘‘supreme canon

of historical evidence that only the statement of contemporaries

can be admitted,” must, in the nature of the case, be completely

ignored here. The best chance of reaching a demonstration is

m finding a series of fossil animals intermediate between some

unmistakably primitive vertebrate and the assumed ancestor,

containing no gaps great enough to raise serious doubt in the

mind of any competent authority as to the genetic relationship

__ “Number nine in this list is absent in the text. Numbers 10 and 11 are

Purposely omitted in the quotation.

630 THE AMERICAN NATURALIST [Von XLVI

of the two forms separated by the gap. The greatness of our

lack of a series connecting any vertebrate with any invertebrate

whatever, must impress one more and more the more he knows

and thinks about the problem. The only other conceivable mode

of demonstration would be to induce, experimentally, the trans-

formation of some living invertebrate into an undoubted verte-

brate. The possibility of accomplishing such a fact is so slight

that no biologist is likely to try it.

This brings us to a point where the transcendent importance

comes to view, of the logic of the interpretation of evolution,

understanding by evolution the transformation of one kind, or

species, of organism into another kind, or species. Except in

the relatively simple and rare cases of proof through direct ob-

servation, experimental or other, the fact that all evidence rests

back absolutely on resemblance—on similarity in form and com-

position of the parts of organisms—is of the utmost importance.

No evolutionist hesitates in either word or intention to accept

this tenet; yet when it comes to the actual ascertainment of like-

nesses and differences, and to speculating on their phylogenetic

significance, the danger of shifting from the inductive to the

deductive mode of reasoning, and of going down before the fal-

lacy known in the logic books as petitio principi, or surreptitious

assumption, is so imminent and subtle that very few of us, even

those most wide awake for pitfalls, avoid it wholly. Almost if

not quite all the numberless hypothetical ancestral organisms

that have been summoned to the aid of speculation on descent

during the last half century and more, are, I am convinced, vic-

tims of this evil, some in greater, some in less degree. The fal-

lacious reasoning usually runs something like this: Assuming

such-or-such an animal once existed, it is easy to see how a par-

ticular organ or part of the animal actually before us may have

arisen from that ancestry. Says Patten:

We have merely to strip off the superficial disguise of our hypothetical

arachnid ancestors and see whether either their underlying structure,

their mode of growth, . . . does or does not harmonize with the assump-

tion that they are the ancestors of the vertebrates (p. 3).

Before this ‘‘mere’’ stripping off begins, would it not be well

to consider ‘our hypothetical arachnid ancestors’’ rather closely?

If such an animal actually once existed, let it be granted for the

moment that it might have undergone such a transformation as

1s conjectured. Surely the first point to be pressed is as to the

No. 550] NOTES AND LITERATURE 631

evidence that the supposed creature did exist. And what is the

evidence? Why, the observed facts of arachnid structure, ex-

actly these and no others, else the ancestor would not be held as

hypothetical. No hypothesis can, of itself, add any new facts.

The hypothetical ancestor has, consequently, done nothing for

the case except to disguise the obvious difficulty there is in seeing

how an actual arachnid can be transformed into an actual verte-

brate.

The only really safe rule for using hypotheses in biology is

that no hypothesis shall be made except to help toward answer-

ing a question by formulating a clear. provisional answer to

that question. The making of hypotheses and using them before

they are themselves proved for the solution of other problems

than those to which they immediately pertain, is perilous busi-

ness. I may without danger, even with profit, construct an

imaginary enteropneust to aid my efforts to answer the question

of how the enteropneustic branchial apparatus or the organ in

this group called a notochord, arose phylogenetically. But be-

fore this imaginary creature can do me real service I must es-

tablish at least a strong probability that such an imaginary ani-

mal once actually existed. Nor must I fail to notice that such

probability can be established only by bringing new evidence

into the case. The facts on which I based the hypothetical ani-

mal can not be used over again to prove the reality of that ani-

mal. But if I must be thus cautious in resorting to an hypothet-

ical enteropneust for the interpretation of actual enteropneusts,

how much more need would there be for caution should I venture

to invoke an hypothetical enteropneust for interpreting actual

vertebrates !

Reflections of this nature opened my eyes several years ago

when I was struggling with the enteropneust hypothesis of verte-

brate descent, to the very slight chance there is of ever solving

the problem of vertebral origin.

Do I then regard all hypotheses on the problem as equal in

value because all alike are equally futile? By no means. I con-

sider each one of them to be of real worth, particularly those

that have been worked out as have Patten’s arachnid hypothesis,

Gaskell’s crustacean hypothesis, the annelid hypothesis and the

enteropneust hypothesis. They are of worth because each shows

quite clearly certain possible developmental courses that may

have been followed in the origin and progress of the great verte-

bral stock. To be explicit, it seems to me that Patten has shown

632 THE AMERICAN NATURALIST [ Vou. XLVI

that in certain structural details there is a similarity between

‘the exoskeletons of Limulus and some of the Ostrachoderms

‘which makes quite possible, not somewhat probable, genetic

relationship between these animals. Similarly the remarkable

likeness between the gills of the enteropneust and amphioxus, if

considered by itself, would make genetic kinship between these

‘animals highly probable; however, when considered along with

‘the whole organization and mode of life of each group, the

probability is much reduced, to such an extent, indeed, as to

become hardly more than a strong possibility.

If we take due cognizance of the extent to which our faith in

the general theory of organic evolution rests on similarities of

form and function among individual organisms which come

under our observation, we are in position to feel the weight of

‘the purely inductive evidence furnished by the many resemb-

lances between vertebrates and invertebrates brought to light by

the investigators in support of the various hypotheses of verte-

brate ancestry, that not only is the theory of evolution true as

applied to the back-boned animals, but that the ancestors of

‘these animals must have been in many respects like certain in-

-vertebrated animals with which we are familiar. The inductive

proof ef the truth of organie evolution, even of the general

‘course of evolution within large provinces of the living world,

approaches much closer to certainty when taken en masse than

‘does, of necessity, that pertaining to any single instance or small

group of instances.

So the moral drawn from examining the theoretical side of

‘the volume before us has this in common with that drawn from

‘examining the factual side: It has real worth, but that worth

would stand forth much more sharply, and probably would be

‘received by biologists with far greater sympathy, had it been

always and clearly distinguished in presentation from pure

‘matters of fact. And the worth would have been greater still

‘had the main and numerous subsidiary and corollary hypotheses

been frankly treated as far from demonstrated or even demon-

‘strable, but as varying in degree of reasonableness from very

possibly true to rather probably true.

Wm. E. RITTER

La JOLLA, CALIF.,

July 26, 1912

. XLVI, NO. 551

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THE

AMERICAN NATURALIST

Vout. XLVI November, 1912 No, 551

THE MENDELIAN NOTATION AS A DESCRIP-

TION OF PHYSIOLOGICAL FACTS

PROFESSOR E. M. EAST

Bussey INSTITUTION, HARVARD UNIVERSITY

As I understand Mendelism! it is a concept pure and

simple. One crosses various animals or plants and re-

cords the results. With the duplication of experiments

under comparatively constant environments these re-

sults recur with sufficient definiteness to justify the use

of a notation in which theoretical genes located in the

germ cells replace actual somatic characters found by

experiment. This is done wholly to simplify the descrip-

tion of the experimental results. If one finds that the

expression DR X DR—1DD+2DR+1RR# adequately

represents the facts in numerous breeding experiments,

he is then able to use the knowledge and the expression

in predicting the results of other similar experiments.

Mendelism is therefore just such a conceptual notation

as is used in algebra or in chemistry. No one objects to

expressing a circle as 2?-+-y?—r*. No one objects to

*I do not speak ES of the new biological facts discovered by Mendel

or by his followers. Facts are always facts. Alternative inheritance and

character recombinations were important facts, but I think no one will deny

that the greatest value of Mendel’s facts arose from the mathematical treat-

ment he gave them. This mathematical notation remains conceptual just

as does the chemical formula, but it must have as much basis of fact as there

are pertinent facts extant.

633

634 THE AMERICAN NATURALIST [ Vou. XLVI

saying that BaCl, + H,SO,—BaSO,+2HCl. No one

should object to saying that DR + RR—1DR-+1RR.

We push things into the germ cells as we place the

dollars in the magician’s hat. Hocuspocus! They dis-

appear! Presto! Out they come again! If we have

marked our money we may find that that which appears

from the magician’s false-bottomed hat is not the same

as that which we put in. But it looks the same and is

good coin of the realm. We have a good right there-

fore to poke our characters into the germ cell and to pull

them out again if by so doing we can develop—not a

true conception of the mechanism of heredity—but a

scheme that aids in describing an inheritance. We may

do this even as we may use algebraical and chemical no-

tations, if we remember that x? + y? does not give us a

circle, that a chemical equation does not represent a true

reaction or prove the atomic theory, that we have not

pulled something new and astonishing out of the germ

cell, that a unit factor represents an idea and not a real-

ity, though it must have a broad basis of reality if it is

to describe a series of genetic facts.

The facts of heredity that one describes in the higher

organisms are the actual somatic characters, variable

things indeed, but still things concrete. Their potential-

ities are transmitted to a new generation by the germ

cells. We know nothing of this germ cell beyond a few

superficial facts, but since a short description of the

breeding facts demands a unit of description, the term

unit factor has been coined. As I hope to show, a factor,”

not being a biological reality but a descriptive term,

must be fixed and unchangeable. If it were otherwise

it would present no points of advantage in describing

varying characters. The only obvious reason for poking

it into the germ cell is to distinguish thus the actual

parent (the cell) from the putative parent (the carrier).

° I hope this statement is not confusing. The term factor represents in &

way a biological reality of whose nature we are ignorant just as a structural

molecular formula represents fundamentally a reality, yet both as they are

used mathematically are concepts.

No. 551] THE MENDELIAN NOTATION 635

If we forget ourselves and begin to speak of unit factors

as particles, only a confusion follows similar to that

caused by Nägeli, Spencer and Weismann. Nothing is

gained and even facts are obscured.

THE Score or MENDELISM

How far may we carry this conceptual notation? My

answer is: just as far as the notation interprets the facts

of breeding and is helpful. Interest in the scope of Men-

delism is now focused on two phases, complete and par-

tial coupling and the interpretation of so-called size char-

acters. Complete coupling in the transmission of char-

acters apparently non-related has been shown in a large

number of cases. Perhaps those best worked out in ani-

mals are the sex-coupled or sex-limited characters ob-

served by Morgan in Drosophila. In plants, cases ob-

served by Emerson and by Bateson and his coworkers

are equally clear. Emerson has shown beyond a rea-

sonable doubt that the characters he describes are inde-

pendent of each other, and can not be represented by one

factor. Bateson has recently corroborated the observa-

tion on other characters. Besides this phenomenon,

Bateson has discovered partially coupled characters.

All three of these writers, have subsidiary hypotheses to

account for their facts. Bateson, when discussing per-

fect couplings, merely says that the characters come out

in F, coupled in the way they went in in the grandpa-

rents, which naturally is only a restatement of the facts.

Morgan and Emerson deal in pictures of carrying bod-

ies. Both of their theories fit their own facts as they

necessarily would. Emerson and, I may say, myself be-

lieve Morgan’s theory incompatible with that of Emer-

Son. Morgan believes his theory adequate for both

cases. Without discussing the merits of these particular

hypotheses I think it is agreed that some characters do

0 into the F, generation and come out from it together

that are in other cases independent. The importance

of the phenomenon is greater than the theory at present.

636 THE AMERICAN NATURALIST [ Vou. XLVI

It has been questioned whether one has the right to con-

tinue to couple characters in large numbers to interpret

facts, because by proper coupling one may interpret

almost any fact, and place himself in a logically unassail-

able position. But this is no reason for not coupling

factors as much as one pleases if it is helpful and if all

of the facts fit. A propos of this statement I might say

that I have recently remade the historical old cross first

made by Kölreuter in 1760, Nicotiana rustica X N icotiana

paniculata. These species differ in many details—habit

of growth, size, shape and hairiness of leaf, inflorescence,

and size and shape of flower and fruit. Both of the pa-

rent species have been reproduced exactly from a par-

tially fertile F, in a total number of less than 200 F,

plants. One may formulate an hypothesis of selective

elimination of gametes combined with selective fertiliza-

tion that helps to describe the facts, but unless large

numbers of factors are coupled together I believe it to

be impossible to account for all the facts by the usual

Mendelian notation.

Before leaving this subject it might be mentioned that

Bateson’s theory, originated to account for partial coup-

ling, keeps the idea of factors segregating from their

absence, but instead of A and a being formed in equal

quantities as in ‘‘regular’’ Mendelian notation, they are

to be formed in series represented by the scheme n—14B:

14B:1aB:n—1ab. I do not believe one should hasten

to accept this description, although Bateson’s F, gen-

eration facts certainly fit and have been recently sup-

ported by Baur. My reason for making this statement

is that as yet Bateson’s F, facts do not fit the theory.

Some of them would even make necessary two or more

different kinds of factorial distribution in the same plant

varieties. On this score the helpfulness of our notation?

*Here is a good illustration of the Mendelian notation as a concept.

Supposing the gametic distribution n —14B:14b:1aB:n—1ab were to

fit all the facts in the case, then no one could object to its use. If it were

to be demonstrated that segregation occurred at the reduction division, how-

ever, the scheme no longer fits the facts and must be abandoned.

No. 551] THE MENDELIAN NOTATION 637

is impaired and this is the only excuse for its existence.

Furthermore, while it has not been proved that the phe-

nomenon we call segregation occurs at the reduction

division, the presumption is in favor of that view. The

work of Webber, Correns, Lock, Emerson and myself on

Xenia in maize indicates that segregation does not take

place immediately after reduction, while the work of the

Marchals on regeneration in mosses indicates that it

does not take place before reduction.

Now to turn to the kinds of variation that may be de-

scribed by the Mendelian notation. Owing to its youth,

we can all remember how we wondered, as each new case

came up, whether Mendelian phraseology would fit.

Since qualitative characters were the ones that could be

divided into definite categories they were the ones at-

tacked. One by one they were analyzed. The phraseol-

ogy did fit. Qualitative characters however form a very

small proportion of the characters in animals and plants.

The numerous characters are the quantitative, the size

characters. If Mendel’s law is to be worth anything as a

generality, therefore, it must describe the inheritance of

these characters. :

To some of us Mendel’s law from the first seemed

destined to be a notation generally useful in describing

inheritance in sexual reproduction. This conclusion was

indicated by the simple fact that Mendel’s law described

many cases in both the animal and the vegetable king-

dom. It was inconceivable that this should be the re-

sult of coincidence. It was therefore still more mecon-

ceivable that only a small portion of the facts in each

kingdom should come under the scope of Mendelism.

A basis for the inclusion of quantitative characters

was obtained when Nilsson-Ehle and the writer showed

that certain qualitative characters gave ratios of 15:1,

63:1, etc., in the F, generation, and in other ways be-

haved so that they might be described only by assuming

more than one independent gametic factor as the germ

cell representative of the character, if the orthodox idea

of segregation were retained. From these phenomena

638 THE AMERICAN NATURALIST [ Vou. XLVI

it was immediately seen that where dominance is ab-

sent and such multiple factors are assumed, size char-

acters can be interpreted as coming under the Mendelian

law. When dominance is complete the mathematical

representation of an F, generation is (3/4+ 1/4)"

where n represents the number of factorial differences

involved; as the manifestation of dominance becomes

less this formula approaches the type (1/2 + 1/2)”.

The difference between the heredity of qualitative char-

acters and quantitative characters is therefore only one

of degree, for there is absence of dominance in cases of

simple monohybrid qualitative characters and there is

presence of multiple factors in cases of qualitative char-

acters showing dominance. But it is manifestly absurd

to expect size characters to appear in natural groups as

do. many qualitative characters. The marked effect of

environment and our ignorance of the exact effect to

attribute to each factor precludes it. One can determine

whether size inheritance compares with the inheritance

of qualitative characters only by the use of arbitrary bio-

metrical methods. In theory, homozygotes with size dif-

ferences when crossed should give an intermediate F,

of low variability and an F, of high variability. Vari-

ous F, populations should differ in their mean and in

their variability. The difference in the variability of

F, over F, should decrease as the heterozygosity of the

parents increases. Sometimes parents of the same size

should differ in the factors they contain and the F, gen-

eration should contain individuals smaller and individ-

uals larger than either of the parents. Each of these re-

quirements has been satisfied by experiment. East and

East and Hayes have tested it for number of rows per

cob, height of plant, length of ear and size of seed in

maize, Shull for number of rows in maize, Emerson for

fruit sizes in maize, beans and gourds, Tammes for

various characters in flax species, Tschermak for time of

blooming in beans, Hayes for number of leaves in to-

bacco, Belling for certain characters in beans, Phillips

for body size in ducks, MacDowell for body size in rab-

No. 551] THE MENDELIAN NOTATION 639

bits. In these investigations every test possible for the

theory has been satisfied. No criticism could be made ex-

cept that certain of the characters used varied consider-

ably in the mother varieties and therefore were pre-

sumably not homozygous for all character factors. This

criticism is apparently answered by a recent investiga-

tion of the writer’s, as yet unpublished, where two

species, Nicotiana forgetiana and Nicotiana alata grandi-

flora were crossed. As seen by the table, the corolla

length is very slightly variable in either species, nor is

it affected to any extent by environment, yet each species

was absolutely reproduced by recombination in the F,

generation.

TABLE I

FREQUENCY DISTRIBUTIONS FOR LENGTH OF COROLLA IN A CROSS BETWEEN

Nicotiana forgetiana (314) anv N. alata grandiflora (321).

: Class Centers in Millimeters

Designation < EEE E SI ; i ; j

20 | 25 | 30 | 35 | 40 45 | 50 | 55 | 6o | 65 | 70 | 75 | 80 | 85 | 90

| meen rt aan ook

314 9 |133| 28 | | |

1/19/50 | 56|32| 9

(314 X321) Fi 3 | 30| 58| 20 | |

— (314 X321) F 5| 27 |79 |136]125|132/ 1021105! 64 |30 15! 6) 2)

Coefficients of variation are: 314 = 8.86 + .33 per cent.; 321 = 6.82 + .25

per cent.; (314 X 321) F, = 8.28 + .38 per cent.; (314 X 321) F, = 22.57 +

39 per cent.

I do not believe that biologists have sufficient facts as

yet to warrant any concrete meaning being given to their

notation as regards germ-cell structure, but I do main-

tain that the Mendelian notation satisfies the facts of

size inheritance as well as it satisfies the facts of quali-

tative inheritance. As a description, it goes the whole

way. If qualitative inheritance is Mendelian, quantita-

tive inheritance is Mendelian; if quantitative inheritance

is not thus described, qualitative inheritance is described

not a whit better.

All writers do not agree with this statement; never-

theless, speaking for myself only, I believe it to be be-

yond question. Castle (Amer. Nart., 46: p. 361) says:

It is quite possible that we are stretching Mendelism too far in

640 THE AMERICAN NATURALIST [Vor. XLVI

making it cover such cases. Dominance is clearly absent and the only

fact suggesting segregation is the increased variability of the second as

compared with the first hybrid generation. This fact however may be

accounted for on other grounds than the existence of multiple units of

unvarying power.

If size differences are due to quantitative variations in special

materials within the cell, it is not necessary to suppose that these

materials are localized in chunks of uniform and unvarying size, or

that they occur in any particular number of chunks, yet the genotype

hypothesis involves one or both of these assumptions. oth are un-

necessary. Variability would result whether the growth-inducing sub-

stances were localized or not, provided only that they were not homo-

geneous in distribution throughout the cell. Crossing would increase

variability beyond the first generation of offspring because it would

inerease the heterogeneity of the zygote in special substances (though

not its total content of such substances) and this heterogeneity of struc-

ture would lead to greater quantitative variation in such materials

among the gametes arising from the heterozygote. Thus greater varia-

bility would appear in the second hybrid generation.

I can not agree with this statement as I understand it,

though this disagreement may be due to my own limita-

tions. We do not stretch Mendelism and we do not make

it cover such cases. The facts of breeding have been ob-

tained and the Mendelian notation expresses them. That

is all that it is necessary to claim. It is not precisely

true, however, to say that increased variability in the

second hybrid generation is the only fact to be expressed.

It is of paramount importance that various F, individ-

uals giving F, populations differing in mean and in

variability, should be included in the Mendelian descrip-

tion. They are included.

Again, Castle states that the genotype conception as-

sumes the localization of the hypothetical factors either

in chunks of uniform and unvarying size, or that they are

carried by a particular number of chunks. I am unaware

of any such assumptions. It is true that some such pic-

ture has been suggested as a diagram helpful to the

imagination in its conception of the scheme as a me-

chanical process, but this is purely and simply a dia-

gram. The real matter under discussion is that the

breeding facts are adequately described in a notation `

essentially Mendelian.

No. 551] THE MENDELIAN NOTATION 641

Of course Castle’s scheme of expressing the facts by

heterogeneity in the germ cell might serve. He pro-

duces increased variability in the second hybrid genera-

tion by greater differentiation among the gametes aris-

ing from the heterozygote. But one can also describe

inheritance of qualitative characters in the same way,

and one gains no system by it. It is a return to the type

of expression used by Nägeli, Naudin and De Lage in

pre-Mendelian days. It is simply a trans-nomination

possessing no advantages.

Before leaving this phase of the subject, I must speak

of Davis’s recent fine paper (Amer. Nart., 46: p. 415) on

his crosses between (Enothera biennis and Cnothera

grandiflora. As I have had the advantage of seeing his

cultures many times in the past two years, I am in a fair

position to draw my own conclusions as to the meaning

of his data. In regard to his F, generation from the

hybrid plant marked 10.30 L b he says:

1. In the immensely greater diversity exhibited by the F, generation

over that of the F, is clearly shown a differentiation of the germ plasm

expressed by the appearance in the F, plants of definite tendencies in

directions toward the two parents of the cross. This seems to the writer

the essential principle of Mendelism and does not necessarily involve

the acceptance of the doctrine of unit characters and their segregation

in either modified or unmodified form.

2. Certain characters of the parent species have appeared in the F,

segregates in apparently pure condition, but the very large range of

intermediate conditions indicates that factors governing the form and

Measurements of organs (if present at all) must in some cases be con-

cerned with characters so numerous and so small that they can not be

Separated from the possible range of fluctuating variations. If this is

true such characters seem beyond the possibility of isolation and analysis

and the unit character hypothesis for these cases has little more than a

theoretical interest.

3. Both cultures certainly showed marked progressive advance in the

range of flower size, the largest flowers having petals somewhat more

than 1 em. longer than those of the grandiflora parent. There 7e

similar advance in the size of the leaves and the extent of their erinkling.

These progressive advances would seem to demand on the unit charaeter

Se either the modification of the old or the creation of new

rs,

4. The absence of classes among the F, hybrids (except for the

642 THE AMERICAN NATURALIST [Vot XLVI

dwarfs) further works against the unit character hypothesis as of

practical value in the analysis of a hybrid generation of this character,

It should be remembered, however, that there were in this cross no

sharply contrasted distinctions of color, anthocyan (stem) coloration

proving most unsatisfactory for the purpose of a genetical study.

These four paragraphs are practically a résumé of

Davis’s genetic facts: I take exception only to some of the

implied conclusions. It is quite evident that Dr. Davis

believes that many breeding facts are expressed in

shorthand by the Mendelian notation. His statements,

however, imply a feeling of loss of caste or something of

the kind if he makes definite use of Mendelian phraseol-

ogy. His F, generation was exactly what would be ex-

pected when several Mendelian units without dominance

segregate and recombine. The advance in size of corolla

was predicted by me in 1910 (Amer. Nar., 44: p. 81) as

a direct consequence of size inheritance. It has since

been demonstrated by Tschermak for time of blossom-

ing of beans and clearly analyzed by Hayes for number

of tobacco leaves. It demands neither modification of

old nor the creation of new factors. It occurs when-

ever AABB (size factors) is crossed with CCDD, and

each factor is allelomorphic to its own absence, to use

the ordinary phraseology.

As to the difficulty of precise analysis into factors, I

agree with Dr. Davis, but that there is no advantage in

showing that this behavior is described in typical Men-

delian terms I can not admit. One holds the same prac-

tical advantage here—though the case is complex—that

one holds in all Mendelian inheritance. He knows that

somatic appearance is not the criterion of breeding ca-

pacity, but that it is determined in some way by gametic

constitution, although no germ cell architecture is pre-

supposed. He knows that recombination of some kind

of factors occurs and has some idea of the number of

progeny to be grown to obtain the desired combination.

In other words, the blend in F, does not indicate com-

plete loss of extremes.

No. 551] THE MENDELIAN NOTATION 643

Menvew’s Law anp Gatton’s Law

The above statement leads into a discussion of Men-

del’s law of heredity as compared with Galton’s law, for

in itself it is almost a statement of the difference. As

Bateson was the first to emphasize, organisms inherit

from parental germ cells only, therefore a law of an-

cestral heredity is a fallacy and a misnomer. The

simple illustration that of two individuals alike in ap-

pearance one is homozygous for a character and the

other heterozygous for the same character, shows the

superficial reasoning that leads to the correlation coeff-

cient as a measure of heredity. Parental and filial pop-

ulations may show correlation, but that is only a matter

of averages and not a measure of the inheritance.

Professor Castle has recently disclosed the probable

Mendelian basis for Galton’s data on coat color of

Bassett hounds by showing the inheritance of tricolor

coat in guinea-pigs, yet he makes the surprising state-

ment that ‘‘as regards height, however, and other size

characters, Galton’s law is quite as good a basis for pre-

dicting the result of particular matings as is Mendel’s.’’

The arch priest of biometry, Karl Pearson, does not

claim that Galton’s law can predict the result of individ-

ual matings. Similarly, Mendel’s law predicts only by

averages. It says that where DR meets DR, there will be

on the average 1DD:2DR:1RR produced. Where the

classes are larger the prediction in increasingly compli-

cated. But the prediction is as good for size characters as

for qualitative characters of the same complication. And

there are such qualitative complications, as is manifest by

Castle’s formula of AACCUUIIYYBBBrBrEE for a

wild rabbit’s coat color. The difference between Gal-

ton’s law and Mendel’s law is that the true criterion of

the germ plasm of any individual is its breeding power

and not the somatic appearance of its back ancestry.

This is as true of size characters as of any other char-

acters.

644 THE AMERICAN NATURALIST [ Vou. XLVI

THE GENOTYPE CONCEPTION or HEREDITY

Expressed in Johannsen’s words, the basis of the

modern conception of heredity is: ‘‘Personal qualities

are the reactions of the gametes joining to form a zygote;

but the nature of the gametes is not determined by the

personal qualities of the parents or ancestors in ques-

tion.” The quotation expresses well the idea that I

have just tried to convey, and from it one sees plainly

that it is the correlation that necessarily appears to a

greater or less extent between the somatic qualities of

two generations when they exist in large numbers that

gave the basis for Galton’s superficial law.

This quotation is Johannsen’s slogan for the geno-

type conception of heredity. As there stated, it is

merely a generalized expression of the essential fea-

tures of the Mendelian notation. Johannsen, therefore,

was the first to admit the broadness of its scope. In his

exposition of his position, however, he adds two sub-

sidiary propositions that we will now discuss; the first

is the perennial question of the possibility of the inherit-

ance of acquired characters, the second is a question

which from its illusivenesg is likely to take on a peren-

nial habit—that of the relative constancy of unit char-

acters, :

In regard to the first question I must be content here

with a mere general statement. Like Osborn I would

emphasize the possibly delusively static condition of

organisms when tested during the infinitesimal time

usually devoted to experiment. The inheritance of ac-

quirements in some subtle way unknown to us may have

been of immense importance in evolution. On the other

hand, some sort of an orthogenesis may account for all

the facts without the inheritance of acquired characters.

It scarcely seems possible that everything is mere chance,

though one who has studied plant teratology is as-

tounded at the almost infinite number of characters that

have appeared that were absolutely dangerous to the

individual in its contest for survival. Be that as it may,

I simply wish to acknowledge unbelief in any so-called

No. 551] THE MENDELIAN NOTATION 645

proof that the inheritance of acquired characters is im-

possible. At the same time one must admit that no un-

questionable proof of such inheritance has ever been

submitted. Experimental evidence is woefully negative.

It seems only reasonable, therefore, considering the

available corroborative evidence, to relegate the expres-

sion of new characters to variations that have affected

the potentialities of the germ cells. We can simply di-

vide variations into the classes inherited and non-in-

herited without any admission as to their cause. We

can call the inherited variations mutations if we will, or

we can give them any other name. We must simply re-

member that they are both large and small.

One can hardly agree with Osborn that large varia-

tions which are not in an orthogenetic line have had

little value in evolution, or that teratological phenom-

ena are of little consequence. The production of iden-

tical quadruplets in the armadillo can scarcely be a grad-

ually perfected character. Zygomorphism in flowers is

lost as a unit and although this does not prove its birth

as a unit, still that is to be presumed. One could fill

pages with such data, but this is hardly the place for it.

We will therefore consider the relative constancy of

what we know as a unit character.

THe Constancy or Unit FACTORS

The first thing one does if he wishes to oppose the

idea of a unit character is to ask for a definition. A per-

fect definition of a unit character is as difficult to formu-

late as for a flower, yet one can obtain an idea of a

flower by proper application. If one describes a unit

character as the somatic expression of a single gametic

- factor or heredity unit, he at once gets into trouble. As

the factor and not the character is the descriptive unit,

a unit factor may affect a character but that character

may never be expressed except when several units co-

operate in ontogeny. I should prefer to disregard the

word character therefore in formulating the problem.

The real problem is: Are the facts of. heredity ade-

646 THE AMERICAN NATURALIST [Vor. XLVI

quately described by unvarying hypothetical factors?

It is my thesis that if they can not be so described, the

Mendelian notation fails.

Johannsen was the first to show the relative constancy

of characters by his beautiful experiments on beans.

Since that time, experiments designed to show change, if

present, have yielded negative results on bisexual animals

such as poultry (Pearl), on plants such as peas (Love),

beans (Johannsen’s later work), maize (Shull, East,

Emerson), on asexual animals such as hydra (Hanel),

paramecium (Jennings) and on asexual plants such as

bacteria (Barber and others), and potatoes (East).

Three critics have appeared. Karl Pearson took up

the gage of battle because Johannsen’s work shows the

utter untenability of the correlation coefficient as a

measure of heredity. He has produced no evidence to

uphold his view. Harris, following Pearson for a like

reason, has concluded against Johannsen, but has not

yet presented his data for public criticism. There re-

mains the work of Castle, which he believes is supported

by the work of Woltereck. The question to consider then

is whether the work of these two investigators justifies

the contention.

Castle states that by selection he has modified a unit

character. No one questions that under certain condi-

tions changes in characters are made manifest by selec-

tion. It has been done again and again. The question

as I see it is the following: Are not the facts presented

by Castle and the facts of the pure-line workers described

most concisely and in a way most helpful to investiga-

tion, by the reactions of fixed and unchanging units? If

they can not be thus described the use of units is an ab-

surdity, for one can not measure or describe by changing

standards.

Castle’s principal work on selection is with a fluctua-

ting black and white coat pattern—the so-called hooded

es, writing of these experiments, Castle says (l. c.,

p. de ¢

No. 551] THE MENDELIAN NOTATION 647

I shall speak first of the case least open to objection from the geno-

type point of view, which requires:

1. That no cross breeding shall attend or shortly precede the selection

experiment, lest modifying units may unconsciously have been intro-

duced, an

2. That only a single unit-character shall be involved i in the experiment.

These requirements are met by a variety of hooded rat which shows a

particular black and white coat pattern. This pattern has been found

to behave as a simple Mendelian unit-character alternative to the self-

condition of all black or of wild gray rats, by the independent investi-

gations of Doncaster, MacCurdy and myself. The pigmentation how-

ever in the most carefully selected race fluctuates in extent precisely as

it does in Holstein or in Dutch Belted cattle. Selection has now been

made by Dr. John C. Phillips and myself through 12 successive genera-

tions without a single out-cross. In one series selection has been made

for an increase in the extent of the pigmented areas; in the other series

the attempt has been made to decrease the pigmented areas. The result

is that the average pigmentation in one series has steadily increased, in

the other it has steadily decreased. The details of the experiment can

not be here presented, but it may be pointed out (1) that with each

selection the amount of regression has grown less, 2. e., the effects of

selection have become more permanent; (2) that advance in the upper

limit of variation has been attended by a like recession of the lower

limit; the total range of variation has therefore not been materially

affected, but a progressive change has been made in the mode about

which variation takes place.

. The plus and minus series have from time to time been crossed

with the same wild race. Each behaves as a simple recessive unit giving

a 3:1 ratio among the grandchildren. But the extracted plus and the

extracted minus individuals are different; the former are the more

extensively pigmented.

e series of animals studied is large enough to have significance.

It ineludes more than 10,000 individuals.

The conclusion seems to me unavoidable that in this ease selection has

modified steadily and permanently a character unmistakably behaving

as a simple Mendelian unit.

This conclusion, from the writer’s standpoint, is not

only avoidable, but unnecessary. No direct or implied

denial of these facts is made, but a shift is made in the

Point of view. It seems to me a logical necessity that

hypothetical units used as measurement or descriptive

Standards be fixed. The problem to be solved is the

simplest means of thus expressing the facts. If the most

648 THE AMERICAN NATURALIST [Vot. XLVI

definite characters—i. e., certain pure-line homozygotes

are sufficiently constant in successive generations to

be expressed by a fixed standard, well and good. The

whole heredity shorthand is then simple. If such is not

the case, the character must still be described by some

fixed standard, but in that case recourse must be had to

complex mathematical expressions and not to a single

unit to describe the most constant somatic expressions.

Furthermore, if these mathematical expressions served

any practical purpose, it would be necessary to prove

that all somatic variability of homozygotes under uni-

form conditions (if there is any) may be expressed by

very few formulas.

Such an attitude does not seem to be in harmony with

the progressive spirit of the times. I believe that we

may describe our results simply and accurately by hold-

ing that unit factors produce identical ontogenetic ex-

pressions under identical or similar conditions. If under

identical conditions the expression is different, then a

new standard, a new unit, must be assumed; that is, fac-

tor A by any change becomes factor B. The results of

the pure-line investigations are the warrant for this in-

terpretation, for they are the investigations of success-

sive generations of somatic expressions with the least

attendant complication. From them one may assume

that a succession of individuals homozygous in all char-

acters and kept under identical conditions will be alike.’

To be sure there are numerous changes in the expression

of characters when external and internal conditions are

not so uniform as the above, but I believe that these

changes can all be described adequately and simply by

ascribing them to modifying conditions both external

and internal. When external we recognize their usual

effect in what we called non-inherited fluctuations, when

internal we recognize their cause in other gametic fac-

tors inherited independently of the primary factor but

* Possibly even under these conditions rare variations that are exceptions

to this rule might occur. In other words, mutations might occur having 20

external cause and therefore to be left for vitalistic interpretation, but this

would not affect the general situation.

No. 551] THE MENDELIAN NOTATION 649

modifying its reaction during development. This is a

physiological conception of heredity, as it recognizes the

great coöperation between factors during development.

It is a very simple conception of heredity, moreover, for

it allows a multitude of individual transmissible differ-

ences with the assumption of a very few factors. Some

illustrations will be given later that will show the idea

underlying this theory. Let us now see whether Castle’s

work can be described properly by it.

Castle started with a peculiar character. It fluctuates

continually and has never been bred to as small a varia-

bility as have many other characters. I have worked

with a somewhat similar character in maize. It is a

variegated pericarp color. In experimenting with it I

have raised over a thousand progeny in one generation,

a thing manifestly impossible with rats. Both solid

colored ears and white ears have been obtained, and

while at present it would be unwise to draw definite con-

clusions, it appears that both solid red ears and white

ears of this kind give again variegated progeny. In

other words, neither the red ear nor the white can be-

have like a normal red or white ear, but as if the pattern

had fluctuated so widely that it can not appear on the

ear (this explanation was suggested by Emerson). At

any rate, we may conclude that the rat pattern fluctuates

widely and is therefore markedly affected by some con-

dition either internal or external.

Castle began therefore with a character in a fluctua-

ting condition, possessed by a race which had not re-

cently been crossed with a different race. This does not

mean, however, that the various individuals forming his

original stock did not differ in several factors that in

their different combinations might have an effect upon

the developing pattern. Suppose for the moment that

this were actually the case. If he had been able to pro-

duce a fraternity by a single mating numbering several

thousands, he would have produced individuals with all

of these combinations of other genes. It is probable

that he would then have obtained his progressive ex-

650 THE AMERICAN NATURALIST [Vou. XLVI

tremes in one generation, extremes that were never seen

when but few individuals were produced. This sort of a

thing is not hypothetical. It is mathematically demon-

strable that with the same variability (a + b)” expanded

gives an increase in the number of classes as the total

number of individuals increases. It is, moreover, sup-

ported by the experimental evidence of De Vries on se-

lecting for higher number of rows in maize. I, myself,

by using greater numbers obtained an increase in protein

in maize in one generation comparable to that obtained

by the Illinois Agricultural Station in three generations.

Castle further argues that decrease in regression

toward the original mean supports his view. On the

other hand, this is exactly what should take place on as-

suming the truth of the fixed factor conception, as has

been shown by Jennings.

Again, the selected races when crossed with wild races

both act as simple recessives, but the extracted plus in-

dividuals are more pigmented. This is what I should

expect. The extracted plus individuals would be more

pigmented when existing in small numbers, because the

modifying factors are several. If several thousand

progeny were grown, however, recombinations would

show a more varied result. And as a matter of fact, ex-

tracted recessives from the plus race are not precisely

comparable in their fluctuation to the selected race with

which the wild was crossed. They are more variable than

the progeny of an inbred hooded individual of the same

grade as the parent used in the cross with the wild. I

do not think that one has a right to say, therefore, that

there were no modifying genes present in various com-

binations in the extracted recessives.

When the selected lines were crossed together, more-

over, the resulting progeny were somewhat intermediate

and variable. The grandchildren were more variable.

This is what should result from our assumptions. The

animals are homozygous as far as having a pattern is

concerned, but they differ in several genes that affect

the development of the pattern.

No. 551] THE MENDELIAN NOTATION 651

Taking into consideration all the facts, no one can

deny that they are well described by terminology which

requires hypothetical descriptive segregating units as

represented by the term factors. What then is the object

of having the units vary at will? There is then no value

to the unit, the unit itself being only an assumption. It

is the expressed character that is seen to vary; and if

one can describe these facts by the use of hypothetical

units theoretically fixed but influenced by environment

and by other units, simplicity of description is gained.

If, however, one creates a hypothetical unit by which to

describe phenomena and this unit varies, he really has

no basis for description.

The facts obtained when working with pied types are

complex. They are evidently not thoroughly understood

as is evidenced by a different interpretation made by

every worker who has investigated them. Doncaster

and Mudge see two types of Irish rat. Why not three or

four? Crampe obtained hooded rats from cross of self-

colored and albino, the hooded coming only from hetero-

zygotes having some white. No adequate explanation

has been given. Cuénot concluded regarding pied mice

with several degrees of piedness that each was recessive

to the other of next higher grade. In fact the behavior

of self colors and spotted colors among mammals as

among plants is pretty well ‘‘confused,”’ as in several

species spotted types dominant to self color are known.

Castle’s other experiments in selection—the forma-

tion of a four-toed race of guinea-pigs starting with one

animal with a rudimentary fourth toe, and the perfec-

tion of a silvered race of guinea-pigs from an animal in

which the character was feebly expressed—need not be

considered here. Both were necessarily crossed with

normals at the start, and gradual isolation of races hav-

ing the proper gene complex for complete expression of

the characters is to be expected. There have been nu-

merous selection experiments of this type—such as those

of De Vries, the Vilmorins, the Illinois Agricultural Ex-

“periment Station, ete.—that have yielded results.

652 THE AMERICAN NATURALIST [ Von. XLVI

But these results, with one possible exception, were

open to the criticism that they probably had to do with

mixed lines and could therefore be described by the no-

tation we have used. The experiments on pure lines have

given no such results. One should not be asked to accept

the results of the unguarded experiments and disregard

the results of the guarded investigations.

The one possible exception alluded to above refers to

the experiments of Woltereck (Deut. Zool. Gesell., 19:

110-173, 1909) on parthenogenetic strains of Hyalo-

daphnia and Daphnia where there can be no question of

gametic recombination. This experiment is not beyond

criticism as will be seen later, but if it were our position

would not be affected. The results would still have to be

described by some fixed standard but the description

would be complicated. Since it is not beyond criticism,

there is yet no reason for such a complication.

Woltereck’s work was primarily to show whether or

not acquired characters are inherited. It was a second-

ary object to find out whether small variations or distinct

sports occurred in the species. Those who use the work

as an argument for unit factor modification, therefore,

should also accept his inheritance of characters acquired.

Woltereck tested the effect of selection on seven char-

acters. Selection gave no results in five cases. The first

supposedly successful case is for difference in head

height. In different pure lines he found an enormous

effect of environment. He therefore endeavored to plot

curves for different kinds of environment, food, tempera-

ture, generation number, etc. By comparing these

curves he makes an argument for the inheritance of

small acquired variations. In the absence of control cul-

tures, and from the fact that culture conditions very

uniform to Dr. Woltereck may have been somewhat ex-

treme to Mr. A. Daphnia, the argument has only the

value of the other numerous scholastic defences of in-

herited acquirements. It is criticized by Tower in a re-

cent publication. Woltereck did obtain one inherited

No. 551] THE MENDELIAN NOTATION 653

head variation. It apparently arose suddenly. He calls

it a mutation.

The only result that can be considered seriously from

the standpoint taken in this paper is the result when se-

lecting for a rudimentary eye. Daphnia has been dis-

tinguished from Hyalodaphnia by the presence of a rudi-

mentary eye. The distinction does not seem to be valid,

for Woltereck noticed rudimentary eyes several times in

pure line cultures of Hyalodaphnia and they have also

been seen by others in wild cultures. He regards the

phenomenon as a reversion to a preexisting condition.

He found that the presence of the rudimentary eye is

periodic. In the spring it appears, in the summer it

again disappears. Wither kind can produce progeny of

the other kind. From this fact it seems reasonable to

believe that environment or generation number has much

to do with the expression of the character, although

Woltereck in one place inclines to the opinion that ex-

ternal factors affect it but little. He performed several

experiments on the effect of light and temperature, how-

ever, and says that provisionally they gave no result

free from objection—‘‘ . . . gegaben einstweilen kein

einwandfreies Resultat.’? Almost any interpretation

can be given this statement. :

From a pure line in which this variable eye spot ap-

peared, he isolated a mother and grandmother with the

character well developed. Ninety per cent. of the

progeny had the eye well developed. The rapidity of his

results and the fact of periodicity in the expression of

the character makes any cumulative effect of selection

exceedingly questionable. One is not justified therefore

in accepting it as proof without corroboration.

CONCLUSION

Tn conclusion, it may be asked if it is not reasonable

to accept simply as a nomenclature the description of

the whole facts of inheritance in sexual reproduction

given by the Mendelian system? Is it wise to turn back-

ward and to give up this handy and helpful notation

654 THE AMERICAN NATURALIST [Vor XLVI

right in the midst of a useful career? The experiments

least open to objection (the pure-line experiments) have

shown the wisdom of assuming a stable unit factor, this

factor being representative of the stability manifested

by a character complex when no interfering conditions

intervene. Let us accept this simple interpretation pro-

visionally, appreciating the fact that the stability of the

characters that have been represented by fixed units may

be only a static appearance due to limited experiments;

but that this appearance justifies our neglecting any

infinitesimal fluency of our factor standards in experi-

ments of like duration, since taking them into account

would necessitate a change of standard, a new fabric of

hypotheses and a more complicated system. Let us take

a physiological view of heredity. Factors are assumed

to be stable. Characters are somewhat unstable owing

to the effect that other factors have upon their expres-

sion. Factor A, for example, is potentially able to pro-

duce a typical expression in ontogeny under certain defi-

nite conditions of environment, but the presence or ab-

sence of B or C or D or B, C, and D are responsible for

slight changes in the expression of A. This conception

gives us a picture of heredity in real accordance with

physiological facts, in contradistinction to the non-bio-

logical and fixed physical conception—the mosaic organ-

ism conception—that critics often say is held by some

geneticists.

One may answer that this conception is all right for

quantitative characters, but do the facts uphold it for

qualitative characters? They do. I will give examples

from my own experiments on the inheritance of the

purple aleurone cells in maize. Here one obtains prog-

eny by the thousands and sees phenomena that are ob-

secured by lesser numbers.

Crosses of the purple variety with three different

whites have given three different results. One shows

that the purple may be represented by the schematic de-

scription PPRRCC. Crossed with pp rr ce it gives

purples, reds and whites in the F, generation, as all three

No. 551] THE MENDELIAN NOTATION 655

factors are necessary for the production of the purple

color. How many other factors (present also in the

whites) may be necessary one can not say. In another

white, the R factor is present and purples and whites in

the ratio of 9:7 result. In another white, both P and R

are present. In another white, both P and C are present.

Both give monohybrid ratios when crossed with the

purple.

This is not the sum total of whites, however; several

others have been found. One has an intensifying factor.

We get darker purples together with the normal purples,

but no one can doubt that the purple is still the same pig-

ment modified in its expression. Another white has a

dominant inhibiting factor. In the heterozygous condi-

tion it does not always inhibit the color entirely, but in

the homozygous condition color never develops. The

dominance of this factor is proved by the fact that ex-

tracted colored recessives are still heterozygous for pres-

ence of color.

In still other whites I have. demonstrated the presence

of at least three modifying genes M,M,M,. They are

independent of each other, yet each and all affect the

purple color. One is dominant, as if it were a partial

inhibitor, the others are recessive, as if they were the loss

of intensifying factors. Purples of all different degrees

can be isolated and breed true. The lightest is such that

the color can be distinguished only with a lens. But they

are all strictly alternative in their transmission and

Somewhere near the expected ratios of darks, lights, very

lights, ete., appear. It is too much to ask that exact ra-

tios be obtained for with this kind of modification all

Shades appear, yet conclusive evidence has been ob-

tained by F, and F, generations. ee :

The qualitative characters do act the same as quanti-

tative characters, therefore, and one can not make a real

distinction between them.

A FIRST STUDY OF THE INFLUENCE OF THE

STARVATION OF THE ASCENDANTS UPON

THE CHARACTERISTICS OF THE DE-

SCENDANTS—IP?

DR. J. ARTHUR HARRIS

CARNEGIE INSTITUTION OF WASHINGTON

III. Presentation oF Data AND COMPARISON OF CoN-

STANTS FoR Navy, WHITE FLAGEOLET AND Ne PLus

LTRA Brans.—Continued

B. Number of Ovules per Pod.

The nature of this and the following character has been

discussed elsewhere.? There the data from which all the

physical constants necessary in this study may be de-

duced, but not the constants themselves, are set forth.

Tables IX-XI give these constants based on countings

of ovules formed and seeds matured in 130,074 pods.

That the starvation of the individual affects not merely

the number of pods which it produces but the character-

istics of these pods as well is evident from a study of

these tables, but is best brought out by a special kind of

graph, _

Reducing absolute to relative frequencies, we take the

difference

Starved less fed

for each ovule grade. Such differences are shown in

Diagram 8 for NDD-NDH, NDDC-NDHC, NHD-NHH,

NHDC-NHHC, USD-USH, USDC-USHC, FSD-FSH

and FSDC-FSHC. The differences for the ancestral

series, which for the moment alone interest us, are shown

*The first part of this paper appeared in this journal, Vol. 46, pp. 313-

343, 1912. The reader must consult it for all questions of purpose, ma-

terials, methods, ete.

* Harris, J. Arthur, ‘‘On the Relationship between Bilateral Asymmetry

and Fertility and Feeundity,’’ Roux’s Archiv. In press.

656

No. 551] INFLUENCE OF STARVATION 657

by the positions of the circles while those for their off-

spring grown upon the comparison field are represented

TABLE IX

Š “Mas pad Probable Standard Deviation Coefficient of Variation

Series and Probable Error and Probable Error

NH 5.7170 = .0106 .7762 = .0075 13.5763 = .1335

NHH 5.4126 = .0049 8569 + .0035 15.8323 + .0653

NHHH 5.3706 = .004 7669 = 0035 14.2803 = .0656

4.7192 + .0080 890 = .0057 18.8383 + .1245

NHDD 4.9985 + .0074 8064 + .0052 16.1313 = .1069

.0034 + .0120 6829 = .0085 17.0587 = .2181

D 4.3503 = .0138 .7695 = .0098 20.1638 + .2340

NDDD 4.7161 + .0163 7083 + .0080 15.0181 + .1630

H 5.1375 = .0070 7957 + .0049 15.4881 = .0980

NDHH 5.1692 + .0067 7057 = .0048 13.6517 = .0936

C 5.6607 + .0109 7852 = .0077 13.8708 = .1389

NHHHC 5.5853 + .0107 8099 = .0076 14.4999 81

Cc 5.6295 + .0137 8466 + .0097 15.0390 + .1762

NHDDC 5.6573 = .0104 .7371 = .0073 13.0289 = .1315

C 5.3701 = .0147 .7409 = .0104 13.7965 + .1969

NDDDC 5.5337 = .0127 .7397 = .0090 13.3674 = .1652

NDHC 5.4800 + .0 .7016 = .0073 12.8031 + .1362

NDHHC 5.4046 = .0096 .7133 = .0068 13.1973 = .1282

TABLE X

i ficient of Variation

Series | Mean ape Probablo | Siar otabieHerot_| ‘and Probable Error

USS 5.5279 = .0072 8694 + .0051 15.7280 + .0945

5. as 8196 + .0067 15.9178 = .1333

USHH 5.2392 + .0116 .7151 = .0082 6483 +

= .020 8705 = .0147 18.2481 + 3174

USDD 4.7991 + .0174 .7531 = .0123 15.6925 = 8

USC 5.5866 = .0093 .6 12.4908 + .1194

USSC 5.6992 = .0109 .6992 + .0077 12.2692 + .1367

USHC 5.5548 + .0125 oy ms 3.2290 =.

USHHC 5.5713 = .0117 .7622 + .0083 13.6816 = .1511

USDC 5.5287 = .0117 .7377 = .0083 13.3431 =+ .15

USDDC 5.5244 + .012 .7236 = .0086 3. = .1579

TABLE XI

of Variation

Beries Mean y Aeg paar sai edges ager yooh ee Pi oe

aridmemesroanesivd sorae E Lt PEATE LRTI

FSS 5 0080 1.0530 = .0057 18.5181 + .1033

5.5580 + .0077 .7639 = .0054 13.7443 + .099

FSHH 5.5150 = .0075 .6873 = .0053 12.4619 + .0974

4.9579 = .0142 8022 = .0101 16.1798 + .2080

FSDD 5.0193 = .0116 .6799 = .008 Sane

60 = .0097 7728 12.6768 + .1145

FSSC 6.1840 + .0106 7816.+ .0075 6390 +.

FSHC 6.0761 = .0121 '8273 = .0086 13.6149 = .1437

FSHHC 6.0245 = . 8173 = .0069 13.5660 + .1168

FSDC 6.0525 = 0137. | .7853 = .00 _ 12.9756 = 1621

—FSDDC | 6.0616 + .0107 18144 = 0076 | 184355 = 1208 __

658 THE AMERICAN NATURALIST [Vor. XLVI

+20

HOP

ojro as TCRA os

—10}- L

NDD—NDH NHD—NHH

AND AND

—29- NDDC—NDHC | NHDC—NHHC

+nob :

+10 :

—l0 i

USD -USH FSD -FSH

—2ol USDC — USHC | FSDC—FSHC

L 1 L L i L L La L L L | i 1 ae FOO

DIAGRAM 8. Differences in the percentage frequencies of various numbers of

ovules per pod in luxuriant and depauperate cultures and in their offspring.

by solid dots. A profound influence of the starvation

conditions is evident from these graphs. Relatively, the

lower grades are much in excess, the higher grades much

in defect in the starvation series.

The same fact is quite patent when one deals with the

means of the series instead of comparing individual

classes in the same lot. Clearly from Diagram 9:

No. 551] INFLUENCE OF STARVATION 659

SCALE OF MAGNITUDE FOR SCALE OF MAGNITUDE FOR

ANCESTRAL SERIES COMPARISON SERIES

so 475 3.00 525 3.50 3.75

= d

oO?

STRAIN AND SERIES OF PLANTS

USDD

FLAGEOLET

FSD ie

FSDD

Diacram 9. Mean number of ovules per pod. „Compare explanation of diagram 6.

(a) The means are in every case conspicuously lower

for the starved than for the fed ancestral series.

(b) The means for the comparison series are closely

Similar: there is no striking superiority of fed over

Starved ancestry.

Here, accordingly, as for number of pods per plant,

we must have recourse to numerical differences and their

Probable errors. The intra-ramal comparisons are made

in Table XII. In three of the four cases, the starved

seeds produce pods with more ovules, but in all ae

Seed was a year older for one generation of ascendan

660

THE AMERICAN NATURALIST

TABLE XII

[Vou. XLVI

Description of Material

Ancestors Starved for

Two Generations

Ancestors Starved for

Three Generations

Ancestors starved for one generation:

USDC series:

SRE OB e be Oe Eee A E Ole ee ak ee

USDDC series:

—2'0101 + 2198

NDDDC series:

= 4291 æ .2571

starvation than for two.

Compare the results for num-

ber of pods per plant, and for seeds per pod.

The inter-ramal differences appear in Tables XII-

XVI. Of the 28 comparisons, direct and cross, of mean

number of ovules, 18 are negative and 10 positive; that

is, in 18 cases, the plants with starved ancestry have a

lower number of ovules per pod. Thus the deviation

TABLE XIII

Description of Material

Ancestors Starved for

One ‘oan

Ancestors Starved for

Two Generations

NHDDC

TSE E ee

Ancestors well fed for one generation:

N. ey ries

eS 8 Se EN a E A ee ga E E E gti

ROW ORR 8 6 6s oy

eh oe te ee ee ee

EE ORES EO aia MA g CR rer Ge WE Te

HON E D

Coefficient = ea aS

NDHHC seri

2 SOS a NE EO Oe ee E ick OS

th we a eta We) ae ee ae

oe 06 heh 8-8 88 E S

Cee ee ae

CS ee eg Rw i gs E eg a Ty

"eee eee eees

+ .1495 = .0172

1450 = .0121

42.2359 + .2297

— .0312 +,

+ .2249 =,

2 = .0174

+ .1773 = .0147

4 5 = .0103

+ .2258 = .1892

— .0034 = .0151

— .0481 + .0106

— .8419 + .1913

+ .2527 + .0141

+ .0238 = .0100

— .1684 =

+ .0720 = .0149

28 = Ol

= 1.4710 = -1908

No. 551] INFLUENCE OF STARVATION 661

from the equality of division, if there were no influence

of the environment of ascendants, is 4+1.79. Of the 28

differences, 16 are thrice their probable errors; 9 are

significantly negative and 7 significantly positive.

Taking averages, regarding signs, we have:

— .0819

Navy, Within Strains, A = + .0150

Ne Plus Ultra,

White Flageolet, A = — .0378

TABLE XIV

Ancestors Starved for | Ancestors Starved for

Description of Material nerations Three Generations

DDO NDDDC

Ancestors well fed for one generation:

NDHC series:

“a AEE ARER cee re eS — .1099 = .0180 + .0. .0164

tandard deviat 7 on oak Puen + .0393 = .0127 + .0381 + .0116

rae Of variston... os. + .9934 = .2394 + .5643 = .2140

ees leh vg for es petals es

ISO Rap Rea geome WE Er ee ott as — .2906 = .0183 — .1270 = .0167

Piandard OES e WA of — .0443 = .0129 — ,0455 = .0118

aent = ais a ee a — .0743 + .2410 — .5034 = .2159

NDHHC se

ick A Ey IE ge cre NR et a oN — .0345 = .0175 + .1291 = .0159

Standard deviation.............. + .0276 = .0124 + .0264 = .0113

Coefficient of moar signee E + .5992 + .2349 -+ A701 = 2000 |

Ancestors well fed for three generations

NHH.

Bo A ec es — .2152 = .0182 — .0516 + .0166

Coefficient of variation.......... — .7034 = .2404 | —1.1325 + .2154 _

TABLE XV

x ES

ved Ancestors Starved

Description of Material D oy Pictish for Two Generations

USDC USDDC

LOE i ate ae

Ancestors well fed for one generation:

USSC series:

WHS iii ivy ee — .1705 = .0160 | — .1748 = .0163

Standard deviation.............. + .0385 = .0113 0244 + .0115

oleae of nena a ia +1.0739 = .2047 | + .8297 = .2088

a we ee ee wl Be were

— 0261 + .0171

+ .0029 + .0121

+ 1141 = .2223

— 0112 + .0123

— 1301 =

USHHC se

MM ee — .0426 = .0166 | — .0469 = .0168

Btandard duviation 222.22. — [9245 = 0117 | — .0386 = .0120

2. Cosficient of ¢ annie ee ae — 3385 = .2145 | — 5827 + .2186

662 THE AMERICAN NATURALIST [ Vou. XLVI

TABLE XVI

Ancestors Starved Ancestors Starved

Description of Material for One Generation for Two Generations

FSDC FSDDC

Ancestors well fed for one generation:

C series:

Ch EN P ee ae ae — .1315 = .0173 — .1224 + .0151

Standard deviation..........3.... + .0037 + .0122 + .0328 + .0107

nr acral of soot un penn + .3366 + .2037 + .7965 1769

aes

oe POG so nee — .0236 = .0183 — .0145 + .0162

Standard deviation eroana eaS — .0420 0130 — .0129 = .0115

Coefficient of variation.......... — .6393 + .2166 — .1794 + .1916

Ancestors at fed for two ‘anata:

parte series:

bE RSE loegepsi eure lye a ee ON ie + .0280 + .0169 + -0371 = .0145

AEE déviation; 04.54.44 a — .0320 = .0119 0029 = .0102

Coefficient of variation.......... 5904 7 1305 = .1723

SCALE OF MAGNITUDE FOR : SCALE OF MAGNITUDE F

ANCESTRAL SERIES COMPARISON pase

250 200 350 400 ino noo 3.50 350 wo

NAVY ee

NHH b

NHD' bera

NHDD' Hien

NAVY

ND E]

NDD.

D oe

eet a

= NDH T

a NDHH Ò

un ULTRA

æ us

A uss Q

a mt ve

USH > J

z USHH -=O

= usD el

a usDD ao th

FLAGEOLET

So pe L -

FSS oo fice ei a

eel

UH remna p= TO Dap S

FSD eoe. F ----} 8

FSDD Ei a EA Re

DIAGRAM 10. Mean number of seeds per pod. Compare explanation of diagram 6.

No. 551] INFLUENCE OF STARVATION 663

The results for Navy are slightly positive, for the other

two varieties more conspicuously negative. The mean

of the four varieties is — .0291.

Regarding only the 10 direct inter-ramal comparisons,

we note that 7 are negative and 3 positive; 3 significantly

negative and none significantly positive. The mean of

the negative differences is —.0771, of the positive

+ .0794, of all — .0316.

The data are available for any one caring to work out

the relationships for variabilities. The discussion of this

point is reserved until further series are gotten.

C. Number of Seeds per Pod

Tables XVII-XIX give the essential biometric con-

stants for number of seeds per pod. Diagram 10 justi-

fies the same general conclusions for the mean number

of seeds as were drawn from Diagram 9 for mean num-

ber of ovules per pod. In one case, however, the average

for seeds is lower on a feeding plot than on the starva-

tion fields.®

Appealing again to constants and their probable

errors, we have the results set forth in the tables of fun-

damental differences, XX—XXIV.

The intra-ramal comparisons, Table XX, show three

positive and one negative difference. Two of the positive

differences are probably and the third possibly statis-

tically significant. Note, however, that the age of the

seed may be a disturbing factor. Compare the results

for number of pods and number of ovules.

Of the 28 inter-ramal comparisons, Tables XXLXXIV,

15 are negative and 13 positive.

In the usual manner, we get for the means:

Navy, Within Strains, A = + .0078

Ne Plus Ultra, A= 0711

White Flageolet, = — .0383

* Why FSS plants did not mature their seeds well I have never been able

to make out. The fact was noticed at harvest time.

664 THE AMERICAN NATURALIST [ Vou. XLVI

For Navy the positive difference is trivial; the negative

difference for Ne Plus Ultra and for White Flageolet is

much larger.

Considering statistical significance to be indicated by

a difference thrice its probable error, we find that 8 are

significantly negative and 4 significantly positive. These

4, and 2 of the 8 significantly negative differences, fall in

the comparisons between the two strains of Navy and

hence can not be given much weight. Of the 20 inter-

ramal comparisons, direct and cross, within the same

strain, 11 are negative and 9 are positive in sign. Of the

10 direct comparisons 5 are positive and 5 negative in

TABLE XVII

Berlen Mean and Probable Standard Deviation Coefficient of Variation

Error and Probable Error and Probable Error

NH 4.2555 = .0193 1.4113 = .0136 33.1634 = .3538

NHH 4.2672 = .0073 1.2893 = .0052 30.2134 = .1323

NHHH 4.277 0082 1.2802 + .0058 29.9268 = .1463

D 3.1269 = .0117 1.2964 + 41.4611 = .306

NHDD 3.7493 = .0116 1.2672 + .0082 33.7974 = .2420

D 3. = .0196 1.1143 + .0139 35.9804 + .5017

DD 3.1872 + .0189 1.1984 = .0134 37.6013 = .4752

NDDD 3.5823 = .0176 1.1709 = .0124 32.6870 = .3823

DH 4.17 0108 1.2363 = .0076 29.5786 = .1982

NDHH 4.2512 = .0112 1.1774 = .0079 27.6963 + .2003

4.0115 + .0194 1.3959 = .0137 34.7973 + .3812

NHHHC 3.8979 + .0181 1.3683 = .0128 35.1028 + .3656

3.9417 + .0221 1.3616 + .0156 34. +

NHDDC 3.9333 = .0191 1.3585 = .0135 34.5397 = .3816

DC 3.7550 + .0254 1.2798 = .0179 34.0838 + .5301

NDDDC 3.8191 = .0227 1.3215 = .0161 34.6033 + .4679

.7333 = .0192 1.2989 + .0136 34.7927 + .4058

NDHHC |_ 3.7751 + .0173 1.2835 + .0123 34.0005 =

TABLE XVIII

Series Mean and Probable Standard Deviation ew ye of Variation

Error and Probable Error d Probable Error

USS 3.8781 = .0114 1.3760 = .0081 35.4817 + .2330

4.0097 = .0146 1.2599 = .0103 31.4219 + .2810

USHH 3.8698 = .0214 1.3253 + .0151 34.2475 + .4347

2.6322 + .0291 2235 = 6 46.4812 = .9367

USDD 3.2268 + .0297 1.2823 = .0210 39.7382 = .7453

4.1269 = .0175 1.3177 = .0124 31.9296 + .3297

USSC 4.2113 = .0204 1.3126 + .0144 31.1673 + .3739

USHC 4.1045 = .0226 1.3280 + .0160 2.3553 + .4283

USHHC 4.0832 =. 1.3333 + .0145 32.6536 = .3899

3.9718 = .0213 1.3403 = .0150 33.7456 + .4192

__USDDC | 4.1619 + .0214 1.2752 = .0151 30.7127 + .3969 __

No. 551] INFLUENCE OF STARVATION 665

TABLE XIX

Mean and Probable Standard Deviation Coefficient of td scree

Series Error and Probable Error and Probable Err.

FSS 3.2918 = .0113 1.4772 = .0080 44.8741 + .2868

H 4.3907. = .0 1.3078 = .0093 29.7865 = .2288

FSHH 4.4563 = .0143 1.3095 = .0101 29.3856 = .2450

D 3.4624 = .0230 1.2993 = .0163 37.5263 + 5323

FSDD 3.8548 = .0021 1.1991 = .0145 31.1063 = .4109

C 4.2865 = .0172 1.3677 = .0122 31.9072 = .3113

FSSC 4.3643 = .0198 1.4532 = .0140 33.2987 = .3541

HC 4.1941 + .0200 1.3610 = .0141 2.4494 + 3701

FSHHC 4.1997 + .0167 1.3941 = .0118 .1948 + .3102

4.1574 + .0236 1.3596 = .0167 32.7024 + «4428

FSDDC 4.2710 = .0178 1.3537. = 0126 31.6950 = .3220

TABLE XxX

SS ` Ancestors Starved for | Ancestors atric ok ag)

Description of Material Generations Three Generatio

Ancestors a for one generation: E

USDC serie: USDD6 series:

ORs ee A Gt Care es oe OS + .1801 + .0302

Standard deviation.............. — .0651 + .0213

anpassa of aeei EE E —3.0329 = .5773

FSDC ser FSDDC series:

DN a a a + .1136 + .0296

Standard deviation.............. — .0059 = .0209

Sop ee of meini, Re a —1.0074 = .5475

HDC se .HDDGE series:

We a os — .0084 = .0292

Biandari d deviation... oc u — .0031 = .0206

fficient of variation.......... — .0047 = .5828

Ancestors era for two generations: :

DDDC series:

i Be ee e a eee + .0641 + .0341

Standard deviation.............. + .0417 + .0241

Coefficient of variation.......... | +.5195 + .7070 _

sign, but none of the positive differences are statistically

Significant, while 3 of the negative differences are from

4 to 8 times their probable errors. The mean of the 5

negative differences is — .1371, of the 5 positive Mier.

ences + .0482, of the whole series — .0445.

D. Weight of Seed

hort the experiments partially described in this

Paper, attention has been given to the weight of the indi-

Vidual seed. From the practical standpoint, the total

weight of the seeds produced by the plant would have

n a more desirable determination, but for several

reasons this was not feasible.

666

THE AMERICAN NATURALIST

[Vou. XLVI

For all the ancestral series, the seeds were weighed

individually in units of .025 gram, but the excessive

labor involved precluded this for the twenty comparison

crops.

Instead, the seeds of each series were mixed

thoroughly among themselves and random drawings

TABLE XXI

neestors Starved Ancestors Starved

Description of Material for One Generation or Two Generations

` NHDC NHDDC

Ancestors well Reg for one generation:

a ie :

RUE iaey he Oa ewe kee + .2084 + .0293 .2000 + .0270

Standard deviation. E eee a + .0627 = .0207 + .0596 = .0192

ont or VATIBUION «sci ccs sis — .2483 = .5989 — .2530 + .5570

isolate well fed for tea pR

E E O rs tie — .0698 = .0294 — .0782 = .0272

Standard deviation 5.2 o1 — .0343 = .0208 — .0374 + .0192

one a i Warintion: 622... — .2529 + .5826 — .2594 + .5394

gr hy

Coy Gime eres aa as + .1666 + .0281 + .1582 0258

Standard aena Rees eee yA + .0781 = .0199 + .0750 + .0183

ib Of Variation «063555 o. + .5439 = .5691 + .5392 + .5248

ies ee fed for si generations

HC series:

BANG. reat se ck Ot -+ .0438 = .0286 + .0354 = .0263

tandard déviation... ..<:.. — .0067 = .0202 — .0098 = .0186

Coefficient of A r E eg — .5584 = .5725 5631 + .5285

TABLE XXII

Ancestors Starved for | Ancestors Starved for

Description of Material Two Generations Three Generations

NDDC NDDDC

Ancestors well fed for one generation:

ND saps ies ë

E T a oak + .0217 = .0318 + .0858 = .0297

Sta aba MSVIALION coo — .0191 + .0225 ti .0226 = .0211

Coefficient of variation.......... -7089 76 1894 + .6194

Ancestors = Sn for ie a generations: e

Mo o — .0256 = .0320 — .1924 + .0299

Standard GOT Cs 1161 = .0225 — .0744 = .0211

cone sa ai BE eee — .7135 = .6529 — .1940 = .6035

ND tami C se

a R a — .0201 = . +. =

or Govindan., ae ae — .0037 + .0217 | + .0380 + .0203

Coefficient of variation.......... + .0833 = + .6028 = .5905

Ancestors well f fed fo or ‘hres generations:

NHHH

Mit a = i =, = = .0290

Standard deviation.............. =+ pobre — .0468 + .0206

Coefficient of variation.......... — .0190 + .6440 4995 = .5938

No. 551] INFLUENCE OF STARVATION 667

TABLE XXIII

Ancestors Starved for | Ancestors Starved for

Description of Material One Ber ages Two 0 Geasrations

Ancestors tie fed for one generation:

U 2” rie

Peder ei E E ew yi — .2395 + .0295 — .0594 + .0296

kadad Geviation 2. E + .0277 = .0208 — .0374 + .0209

Spa o yaristion: i sarr o -+2.5783 + .5617 — 4546 + .5453

tesla

Pa Bites E ene ee ee — .1327 + .0310 +. 0474 + .0311

Standard GeViauon. 62.5035 2a + .0123 + .0219 — .0528 = .0220

Coefficient of variation.......... +1.3903 = .5993 —1.6426 + .5840

Ancestors wel agg or two EA DES

US.

Sen: er i es ee ee ee — .1114 = .0295 + .0687 + .0296

tandard deviation.............. + .0070 = .0209 — .0581 + .0209

Coefficient of variation.......... +1.0920 + .5725 +1.9409 + .5564

TABLE XXIV

Ancestors Starved for | Ancestors Starved for

Description of Material One ph ag Two A

Ancestors well fed for one generation:

FSSC series: ‘ :

RR Bae ek eee un ee — .2069 + .0308 — .0933 = .0266

Standard deviation.............. — .0936 + .0218 — 0995 = .0188

“Symone of variation: : fo i... — .5963 + .5670 — 1.6037 + .4786

FSHC se

nin r a a — .0367 = .0309 | + .0769 = ppan

Standard deviation.............. — .0014 = .0219 — .0073 = .0189

Coefficient of variation.......... + .2530 = .5771 7544 + 4906

Ancestors well fed for two generations:

HHC series:

Reo i hore oh Gh ees ware — .0423 + .0289 + .0713 + .0244

Standard deviation.............. — .0345 + .0204 | — .0404 = .0173

Coefficient of vacation ee eae — A924 + .5406 —1.4998 + .4471

made for mass weighings.t It is on these samples of

2,000 or more seeds (weighed after drying for several

months)* that the averages are based.

Seed weight will be touched rather lightly in this paper.

This is in part due to the fact that the seeds for the com-

Parison series could not be weighed individually, thus

* This was the plan for all but USC and FSC, where 100 seeds, or as

many as were available, were weighed en masse for each line. From these,

the general population mean was calculated. Li

*The plants were harvested and dried in an empty greenhouse in $

early autumn of 1910; stored in an unheated building for the early zak 9

the winter; counted rs uring a period extending from January to

April; and left in the laboratory till weighing, some time in June.

668 THE AMERICAN NATURALIST [Vou. XLVI

affording data from which the variabilities and probable

errors might be calculated. It is in part due to the fact

that (as will be clear later) the starvation conditions

available seem not to have affected seed weight as they

did the other characters with which we deal.

SCALE OF MAGNITUDE FOR SCALE OF MAGNITUDE FOR

100 aso 200 250 3300 35o _.100 JA75 223 27S es

NAVY

NH Q.

NHH ->

NHHH J

NHD a

NHDD o

NAVY

D a

n NDD ---}--@

P A NDAD

< WUDU

a NDH +

S NDHH 2 ee ee ee oe Seen eer es lh a

A ULTRA

n USS Ly EN ae 3

a a

z USH -----+-;-

z USHH EE <a

= La AI

x usp #-4----- ----}--- -iS

n - --

FLAGEOLET

FSS ro es --+-------@

FSH a >

FSHH Ł - A

FSD F- e

r D Fspp a

Ww ee ee eee a

DiacramM 11. Mean weight of seeds. Compare diagrams 6, 9 and 10.

The mean weight for both ancestral and comparison

series are shown in decimals of grams in Table XXV.

That seed weight is a character influenced by environ-

mental conditions is apparent from the scatter of the

means in the ancestral field of Diagram 11 as compared

with their closeness to line in the comparison panel. But

No. 551] INFLUENCE OF STARVATION 669

the diagram also shows at once that* seed weight has not

been influenced by the starvation conditions as other

characters have. Whereas, with a single exception, num-

ber of pods per plant, number of ovules per pod and num-

ber of seeds per pod were all conspicuously reduced, seed

weight is sometimes higher, sometimes lower, on the

starvation plots. Of the 28 differences, 21 are negative

in sign, as compared with 28 for pods per plant and

ovules per pod and 27 for seeds per pod.

Expressing numerically the same differences for the

ancestral series as are usually taken for the comparison

series, we find for comparisons within the strains:

TABLE XXV

Ancestral Series Comparison Series

Series N Mean Series N Mean

F 3,000 19322 FS 7,562 18587

FSS 3,740 15636 FSSC 2,000 18026

2,122 20039 FS ,000 17893

FSHH 1,788 16813 FSHHC 2,000 18145

1,989 16140 FSD 2,000 17816

FSDD 1,643 16783 FSDDC ,000 19027

U 2,391 34491 US 9,879 28450

USS 3,271 35349 USSC 2,000 29933

1,165 34261 USHC 2,000 314

USHH 31642 USHHC 2,000 30147

1,002 25474 USDC 2,000 29170

USDD 29948 USDDC 2,000 29284

7,334 23186 H 2,000 25430

NHHH 5,601 20274 NHHHC 2; 244

6,630 20073 NH. 2,000 26616

NHDD 5,029 22293 NHDDC 2,000 24669

2,362 NDDC 2,000 25849

NDDD 1,946 .20374 NDDDC 2,000 (25207

NDH 3,227 ‘20879 NDHC 2,000 "26248

NDHH 2,433 .20261 NDHHC 2,000 24815

Navy, A = — .0047

Ne Plus Ultra, A= — .0604

White Flageolet, A= — -0103

General Average, A =— 0231

Thus there appears to be a distinct influence of the de-

Ppauperization of the individual upon the weight of the

seeds which it produces. But modification of weight is

very slight indeed as compared with that of the other

characters. :

670 THE AMERICAN NATURALIST [ Vou. XLVI

Considering now the weight of the seeds produced by

the comparison plants, we note that of the 28 differences

which may be taken (within and between strains) be-

tween plants of luxuriant and those of depauperate an-

cestry, 15 are negative and 13 are positive in sign, a devi-

ation of only 1+ 1.79 from the expected 14:14 ratio.

Of the individual differences, the largest is .023 gram,

while most of them fall, towards zero. Averaging we

get:

Positive Differences, + .00915 gr.

Negative Differences, — .00831 gr.

All Differences, — .00020 gr.

Surely values as low as this can not give much weight to

the assertion that depauperization of the parents has

had any influence upon the weight of the seed of the off-

spring plants.

Looked at in a preliminary and superficial way (and

it hardly seems worth while to go into the matter more

minutely until other data are tabled and reduced), the

data seem to indicate that the weight of the seed is a

character much less directly dependent upon cultural

conditions than are the vegetative characters of the

plant. Conditions which reduce these latter may not

materially affect seed weight.

Possibly, the environmental complexes available were

such as to affect certain characteristics of the ancestral

plants, while leaving others, i. e., seed weight, unmodi-

fied. Possibly, seed weight is a character little affected

by external conditions of any kind. These are questions

which can only be solved by further experiments de-

signed to determine whether some environmental com-

plexes regularly affect seed weight while others do not,

and to ascertain what influence, if any, such reduction

has upon the characteristics of offspring seeds.

E. Combination Characters

: Some characteristics are combinations of two or more

individual measurements. Such are, for example, the

No. 551] INFLUENCE OF STARVATION 671

correlation between two dimensions, or the ratio of the

one to the other.

The only case of this kind to be considered here is the.

coefficient of fecundity, which is simply the ratio of the

total seeds matured by a population of pods to the total

ovules formed. The values are given in Table XXVI.

For the ancestral series all but 2 of the 20 compari-

sons within strains show lower fecundity in the starved

series. Taking averages:

Navy, Within Strains, A —— .0790

Ne Plus Ultra, A=—.1178

White Flageolet, A= + .0075

Thus Navy and Ne Plus Ultra mature about 7-11 per

cent. more of their ovules on feeding than on starvation

fields. Apparently, White Flageolet is not affected.

TABLE XXVI

Ancestral Series Comparison Series

Series Pods C.F. Series Pods C.F.

FS — osha FSC 2,876 7387

FSS 7,809 5789 FSSC 2,457 7057

4,541 7899 FSH 2,117 6903

FSHH 3,837 8080 FSHHC 3,180 6971

FSD ; 984 FSD 1,506 86

FSDD 1,556 7680 FSDDC 2,646 .7046

U. —— Sc 2.569 "7032

USS 7015 USSC 1,888 7389

3,406 7787 ‘SH 1,570 7389

USHH 1,743 7386 USHHC 1,936 7329

USD 802 5518 US 1,810 7184

USDD 851 6724 USDDC 1,619 7516

; 78 NHHC 355 7087

NHHH | 11,230 7965 NHHHC 2,614 6979

5,581 6625 1,733 7002

NHDD 5,449 7501 NHDDC 2,308 6953

1,827 .7326 1,159 .6992

NDDD 2,018 7596 NDDDC 1,542 6901

5,955 8136 2,077 6813

NDHH 5,019 (8224 NDHHC 2,494 .6985

For the comparison series grown from these seeds, we

find that of the 20 comparisons, direct and cross, within

the strains, 12 show lower and 8 show higher fecundity

in the offspring of starved plants. The means are:

672 THE AMERICAN NATURALIST [Vou. XLVI

Navy, A = —- .00036

Ne. Plus Ultra, A= — .00615

White Flageolet, A = — .00196

Discussion of such differences is obviously superfluous.

IV. Recaprrunation, Discussion anD TENTATIVE Con-

CLUSIONS

The purpose of the series of investigations, described

in part, is to ascertain whether the depauperization

of the individual through the environmental com-

plexes constituting ‘‘poor’’ agricultural conditions, in-

fluences the characteristics of its offspring, and if so,

how much. The problem of the chemical and physical

‘‘causes”’ of the depauperization has received the most

intensive experimental consideration. The question of

the influence of the surroundings of the ascendants upon

the characteristics of the descendants has been much

more a matter of speculation. Yet the second of these

problems is of obvious importance to the agriculturist

and of interest to the evolutionist concerned with en-

vironmental factors. The time seems ripe, therefore, for

its consideration on the basis of extensive quantitative

experimental data.

Notwithstanding the great progress which has been

made in the investigation of the relationship of the

chemical and physical properties of the substratum to

the characteristics of the plant, the diversity of results

and the clash of theories show that we have only entered

the edge of this field of research. In consideration of

these facts, and especially in view of the all but unsur-

mountable difficulties of controlling in large experiments

the conditions of growth of flowering plants, it has

Seemed necessary in first studies to choose merely good

and bad growing conditions as indicated by yields in

actual cultures. Thus the methods are avowedly and in-

tentionally of the rough and ready sort. If in such ex-

periments an unquestionable influence of the conditions

No. 551] INFLUENCE OF STARVATION 673

of growth of the ascendants upon the characteristics of

the descendants be demonstrated, it will be worth while

to determine the weight to be given to individual physical

and chemical factors in the ascendant environment. If,

on the other hand, there be no detectable effect of ances-

tral depauperization, then the cost of elaborate batter-

ies of experiments had better be devoted to some other

problem.

This first study is based upon three varieties of one

species, Phaseolus vulgaris. The conclusions should not,

therefore, be extended to other forms with different de-

mands upon the soil, habits of growth or type of seed.

This is true not merely on general principles, but is espe-

cially important because of the well-known capacity of

this species for growth under adverse conditions.

The characters considered are number of pods per

_plant, number of ovules formed and number of seeds ma-

_ tured per pod, ratio of total seeds ripened to total ovules

daid down—the coefficient of fecundity—and weight of

eds,

‘astants are based upon the countings of number of

ies and seeds in about 130,000 pods and weighings of

er 110,000 carefully selected seeds. But these obser-

lions were drawn from only 21,000 individual plants.

he results in the body of the paper show, these num-

rs are too small rather than unnecessarily large for

roblem of this delicacy. I believe, however, that they

e sufficiently large to bring the probable errors of

‘random sampling low enough that dangers of erroneous

‘onclusions lie rather in the inevitable experimental

and to a less extent observational) errors.

_ Bearing in mind the difficulties to be surmounted and

the consequent possibilities of error, we draw the fol-

lowing tentative conclusions.

Environmental conditions which greatly reduce num-

ber of pods per plant, number of ovules formed per pod

and number of seeds matured per pod, affect to a less

degree the relative number of seeds matured, i. e., the

674 THE AMERICAN NATURALIST [Vou. XLVI

coefficient of fecundity, and have but little effect upon

seed weight.

_ The influence of the modification of the ascendants

upon the characteristics of the descendants is extremely

slight. There seems, nevertheless, to be a definite reduc-

tion in the number of pods per plant and number of

ovules per pod. There is also a possible lowering of the

absolute and relative number of seeds per pod. Ap-

parently, there is no modification of seed weight.

Cop SPRING HARBOR, N. Y.

STRUCTURAL RELATIONS IN XENOPARASITISM

W. A. CANNON

DESERT BOTANICAL LABORATORY

Ar various times normally independent plants have

been experimentally caused to grow and develop within

the tissues of other independent plants, deriving from

this arrangement food and food-materials and organizing

tissues and organs.! Although in themselves short-lived,

the artificial parasites offer interesting suggestions as to

the possible conditions under which true parasitism may

arise in nature.? Itis clear, for instance, that the mutual

relation of parasite and host is extremely complex, both

from a purely physiological point of view and from a

structural one. On the one hand, it presupposes suitable

osmotic relations and not unfavorable chemical reactions,

and on the other, among other things, the fitting and exact

adjustment of the tissues of the parasite, and it signifies

atrophies as well.

hen we observe the leading structural changes which

normally occur in the growth of a haustorium of a habi-

tual parasite, such, for example, as the mistletoe,’ we find

a course of development which is full of suggestions. A —

young haustorium is composed mainly of undifferentiated

ground tissue, but there are the beginnings of conductive

tissue within, and a protective epidermis without. Upon

the commencement of the parasitic relation the most

marked changes occur. In the first place epithelial cells

*“* Artificial Parasitism, ete.,’’? G. J. Peirce, Bot. Gaz., 38: 214, 1904.

‘‘The Condition of Parasitism in Plants,’’ D. T. MacDougal and W. A.

Cannon, Publ. No. 129 Carnegie Inst. of Wash., 1910. ‘‘An Attempted

Analysis of Parasitism,’’ D. T. MacDougal, Bot. Gaz., 52: 249, 1911.

***An Attempted Analysis of Parasitism,’’ D. T. MacDougal, Bot. Gaz.,

52: 249, 1911.

‘The Anatomy of Phoradendron villosum,’’? W. A. Cannon, Bull. Torr.

Bot. Club, 1901.

675

676 THE AMERICAN NATURALIST [ Vou. XLVI

are formed directly from parenchyma, and then after

penetrating the host, such of the periphery of the haus-

torium as touches non-living cortical host cells, organizes

cork. Finally, upon the attainment by the haustorium of

the woody cylinder the conductive tissue of the hausto-

rium opposes cell for cell the conductive tissue of the host,

and in such parasites as possess sieve-tubes, the sieve-

tubes hold a similar relation to the sieve-tubes of the

host. It happens therefore in habitual parasites that a

portion of the development of the haustoria occurs after

the parasitic relation has been entered into, so that the

direction of the development of much of the tissue of the

haustorium is fortuitous, depending in part on the posi-

tion occupied by the tissues of the host.

DURATION oF THE XENOPARASITIC RELATION

Although induced parasitism means naturally a limited

period during which the artificial relation can be con-

tinued, this period varies greatly with the different nutri-

tive couples. A review of this phase of the subject will

not be given here, as it is completely presented in the

papers referred to above, but two or three of the most

pertinent parasitic relations will be cited. Peirce grew

Pisum sativum on Vicia Faba to maturity (Peirce, ‘‘ Arti-

ficial Parasitism,” l. c.). MacDougal (see above) records

many experiments of which the following may be given:

Cissus laciniata was grown on Opuntia blakeana from

February 1, 1908, until April 19, 1909, and another cul-

ture, which is especially treated in this paper, lasted from

early autumn, 1911, to June 10, 1912. In the instances

where Cissus was employed roots were freely formed, the

stem attained considerable length and organized tendrils

and leaves. From these facts a large capacity for adjust-

ment on the part of the induced parasites is exhibited,

and also a degree of physiological adaptability is shown

which reveals something of the plasticity of such plants

and argues a fair suitability for the dependent relation.

: “On the Structure of the Haustoria of Some Phaneorgamic Parasites, ’’

G. J. Peirce, Ann. Bot., 7: 324, 1893.

No. 551] RELATIONS IN XENOPARASITISM 677

XENOPARASITISM OF Cissus LACINIATA

The induced parasite Cissus laciniata exhibits in the

structure and form of its roots (the shoot was not studied)

certain deviations from the normal which are of signifi-

cance andinterest. A history of the experiments in which

this species was used as a parasite is given in another

place, suffice it to state here that a cutting of the Mexican

grape (Cissus laciniata) was introduced into the tissues of

Opuntia blakeana and allowed to remain several months.

A shoot with leaves and tendrils was formed. After the

culture had been running some time a root of the grape

was seen to emerge from the surface of the cactus, to

grow downwards, and to penetrate the soil. It was sev-

ered so that the Cissus had connections with the cactus

only. On June 10, 1912, the newly organized leaves were

‘seen to be relatively small and the tendrils not to develop.

The culture was thereupon taken down and the roots of

the parasite dissected out so that their relations to the

host tissue might be learned.

All of the roots of Cissus which were situated within

the tissues of the cactus were found to be fleshy. A main

root was traced from the base of the cutting through the

tissues of the cactus for a distance of 3 em. when, as

above mentioned, it issued from the cactus and found its

way into the soil. This root gave off one branch about

1 cm. from its point of origin, which extended for a dis-

tance of 3 cm. into the tissues of the cactus. The root last

mentioned gave rise in turn to a branch which attained a

length of 1.5 cm. In addition to these roots there were

several short ones which reached little belond the surface

of the parent root. All roots except the one especially

mentioned as not behaving in this manner were wholly

enclosed within tissues of the host.

STRUCTURE or FREE-LIVING Roots :

The portion of the roots which are free-living offer

useful points of comparison, for which purpose. the anat-

omy will be briefly reviewed.

678 THE AMERICAN NATURALIST [ Vou. XLVI

A root 2.0 mm. in diameter shows the usual divisions

into central cylinder and cortex. The endodermis is

well marked. The epidermis is discolored and bears the

remains of root-hairs. Cork has not begun to form, how-

ever. The cortex is composed of cubical parenchyma;

the parenchyma of the central cylinder offers no un-

usual features. Little starch or crystals are to be seen.

xin

ih Nab

ANATOMICAL RELATION OF THE Cissus- Opuntia COUPLE. On the left appears

the extra-cortical portion of the root with the limit indicated by the arrow.

On the right is the wound tissue of the cactus, and between this and the root

lies disorganized cactus cells.

STRUCTURE OF THE Parasitic Roots

The roots of Cissus, which developed within the tissues

of the cactus, varied in diameter from 2 to 5 mm. and

showed characteristics which were in certain regards

quite different from those of the free- living roots ex-

amined.

If a cross-section of a root 2 mm. in diameter is studied

the usual differentiation into cortex and central cylinder

will be noted. The cortex is composed of relatively large

cells a few of which contain stellate crystal aggregates

and raphides. A layer of cork, over half dozen cells in

thickness, bounded by the dead remains of the epidermis,

No. 551] RELATIONS IN XENOPARASITISM 679

lies on its periphery. The remains of root-hairs were

looked for but were not found. A well defined endo-

dermis with granular contents, a portion of which is

starch, limits the cortex on its inner surface. The cen-

tral cylinder has relatively wide medullary rays and a

large pith containing much starch. Opposite each

CROSS-SECTION oF Parasitic Root or Cissus laciniata SHOWING THE FORMATION

CORK AND THE DISORGANIZED EPIDERMIS.

bundle, and about 2 cells inside the endodermis, there is

a plate which may be composed of leptome, and which in

some favorable material appears to be thickened wall

only.

A root 5 mm. in diameter has essentially the same

structure as the smaller one above described. The main

differences lie in the heavier cork and the thicker cor-

tex. The plate which lies opposite each fibro-vascular

bundle, also, is heavier. The endodermis is noticeably

poorer in starch.

680 THE AMERICAN NATURALIST [Vou. XLVI

TISSUES oF THE Host

The structure of the flat stems of Opuntia, broadly

speaking, consists of thin-walled, large parenchyma,

through which there course strands of conductive tissue.

Protection of the stem is afforded by a heavy cuticular-

ized epidermis.

When the parasitic relation is entered into, wound

tissue, with heavy outer walls in certain cells similar to

those of the cork, is formed about the injury caused by

the introduction of the cutting. The cutting sends out

adventitious roots which penetrate the parenchymatous

tissue of the host, and sooner or later these roots are

surrounded by wound tissue which the host promptly

organizes as a result of the unusual stimulation. By

this formation the water-storing ground tissue of the

host is separated from the living cells of the parasite.

Tissuz RELATIONS or ParastrE anp Host

In rapidly growing roots, contact is made with the

living parenchyma of the cactus, and the parasite is in

physical position to absorb foods and food materials. In

instances, however, where root growth is slow, wound

tissue is formed by the cactus, and the parasitic relation

is not favorable for absorption. Following the forma-

tion of wound tissue cork is organized by the parasite,

so that the cushion of non-living material separating host

and parasite in the older portions of the culture, comes

to be derived from both species.

When one compares the structural relations of a haus-

torium of a habitual parasite with the analogous absorb-

ing organ of such a xenoparasite as Cissus, several sug-

gestive inferences may be derived. The relation may be

presented briefly in the following parallel:

Xenoparasite Parasite

No special digestive cells, Epithelium - developed.

Root-hairs suppressed. No root-hairs formed.

No. 551]

Foods and food materials enter

haustorial root through epidermis.

Cork formed after establishment,

following organization of wound

tissue by host.

Tissues articulate with the corre-

sponding host tissues.

Meristematic tissue localized.

RELATIONS IN XENOPARASITISM |

681

Foods and food materials enter

haustorium through parenchyma,

sieve-tubes, and vessels.

Terminal portions at least of all

permanent tissues formed after

establishment.

The same.

Meristematic tissue not localized.

The parallel given above suggests, as intimated in an-

other paragraph, that any species which is to become

dependent on another species possesses to a large degree

the power of adaptability and morphological plasticity, so

that the direction of the development of its tissues or

organs can to a degree be modified. Atrophies result, and

the assumption of unaccustomed functions, and tissues

are organized in harmony with tissue formation, or other

physiological activity on the part of the host.

SHORTER ARTICLES AND DISCUSSION

ON TRICOLOR COAT IN DOGS AND GUINEA-PIGS |

AFTER reading Dr. Castle’s short article on this subject I

want to make a few remarks. His explanation of the peculiar

inheritance of the lemon and white and tricolor colors in Gal-

ton’s Bassett hounds will have to be somewhat modified. For it

is impossible to compare tricolor dogs and tricolor guinea-pigs.

Tricolor dogs are never irregularly spotted with black and yel-

low, as tricolor guinea-pigs, cats or rabbits, but they are in .

reality either black and tan, or else sable, spotted with white.

My attention being drawn to the subject of tricolor dogs by

Galton’s paper, I have never neglected an opportunity to ob-

serve dogs of this color, in dog-shows and from illustrations.

Some tricolor breeds, as the fox terrier, are black and tan,

spotted with white, others, as nearly all the hounds, are sable,

still others, such as collies, may be either black and tan or

sable, spotted with white. I have never seen an exception, such

as a dog with a yellow spot on the back and a black foot.

For the rest, I think Dr. Castle’s explanation is quite correct ;

it all depends upon the place of the spots upon a sable dog,

whether these will be yellow or black. A spot on a dog of

sable color, e. g., a fox hound, will always be black if it is on the

animal’s back. If on the muzzle, or on a foot, or far down on

the side, it will always be yellow, a spot, e. g., on the shoulder

may be partially black, partially yellow, shading off from one

color into the other.

It is of course possible that some of the Bassett hounds in

the pack recorded by Galton were real yellow and whites, and

we know from the evidence of breeders of dachshunds that yel-

low can be dominant over black and tan or sable in dogs. So it

may be possible that in that pack two real lemon-and-whites

(e. g., such as had a yellow spot on the back) have sometimes

given tricolor young, but in those cases in which two tricolor

parents gave lemon and white offspring, I feel sure, such young

were of that color only because they happened not to be pig-

mented in a spot where sable dogs show black color.

682 :

No.551] SHORTER ARTICLES AND DISCUSSION 683

It would certainly be interesting to try and find illustrations

of Galton’s hounds, especially of the lemon and white ones of

tricolor parentage.

In rabbits, there exist three wholly different classes of tricolor

animals. In the first place there are the real tricolors, those

animals which, if they were not partially albinistic, would be

irregularly spotted with black, agouti, blue or chocolate on a

yellow ground. They are comparable to the tricolor black-

yellow-white, blue-cream-white, ete., guinea-pigs and to the tri-

color cats. Secondly, there are those animals which are black

and tans, or blue (or chocolate) and tans, spotted with white.

‘These are comparable to the tricolor fox terriers, tricolor goats

and the so-called tricolor mice, which are sable, spotted with

white.t

Thirdly, there are those rabbits which, if not partially albin-

istice, would be ‘‘tortoise-shell,’? and which are comparable to

the spotted ‘‘tortoise’’ mice.

I think Galton’s hounds may have all been alike except for

the distribution of the pigmented patches on the coat. Those

hounds with the less white would then be called black and tan,

or sable; those with much white would be called tricolor, or

lemon and white, or even black and white, according as to where

the colored patches fell.

I am not so sure Galton’s black and tan hounds must neces-

sarily have been partially albinistic, as in dogs the partially

albinistic ones are generally so because of the presence of a

factor (or factors) absent from wholly colored ones. (In other

words, spotting with white is dominant in some dogs.)

The distribution of the colored area over partially albinistic

animals assuredly depends upon the cooperation of so many

factors (amongst which there are very probably some non-

genetic ones) that on our hypothesis the production of tricolor

young from yellow and white parents, and vice versa, becomes

very well possible.

AREND. L. HAGEDOORN

VERRIÈRES LE BUISSON ae

*“¢The Genetic Factors in the Development of the Housemouse,’’ A. L.

pei Zeitschr. f. indukt. Abst. und Vererbungslehre, 1911, Bd. VI,

e. á

NOTES AND LITERATURE

THE CLASSIFICATION OF THE LIVERWORTS

Boranists have long felt that the classification of the liver-

worts was very much in need of revision, and any serious attempt

to establish a classification that will better express the real inter-

relationship of the Hepatice is very welcome. The valuable

series of papers recently published by Dr. Cavers, on the classi-

fication of the Bryophytes, is a distinct contribution to the sub-

ject, and is a decided advance over any classification that has

been proposed hitherto.

Dr. Cavers is well known to students of the liverworts through

a series of papers of exceptional merit, published at intervals

during the past few years. The present publication presents at

length the conclusions he has reached as a result of his studies

on these important plants.

It is still too early to expect a definitive classification of the

liverworts, as there are still a good many important types whose

development is incompletely known, and it is also highly prob-

able that there are still forms awaiting discovery which we may

reasonably expect will throw light upon some relationships which

are still obscure.

Dr. Cavers has made a careful study of the work of the most

recent investigators, as well as of the older standard works, and

while one may take exception to a few of his deductions, still, as

a whole, one will agree with his main conclusions, and will

welcome this contribution of his as a decided advance in our

knowledge of the inter-relationships of the Bryophytes. The

Bryophytes (or “mosses,’’ using this term in its widest sense)

are forms of peculiar interest to students of plant-morphology,

especially to those engaged in the problems of the origin of the

higher types of plants; since the Bryophytes occupy an inter-

mediate place between the aquatic algæ and the ferns which are

typically land plants. While there is decided difference of

opinion as to how the ferns originated, the weight of evidence

1‘‘The Inter-relationships of the Bryophyta,’’ by Frank Cavers, D.Sc.,

sh mi (New Phytologist, Reprint No. 4), Cambridge; at the Botany School,

684

No. 551] NOTES AND LITERATURE 685

is strongly on the side of their direct derivation from some liver-

wort-like ancestor. It is this question that makes a thorough

study of the liverworts of such great importance in seeking for

an explanation of the origin of the vascular plants.

Aside from this, however, the Bryophytes, especially the liver-

worts or Hepatice, are exceptionally interesting, as they show in

a remarkably clear way many adaptations to special environ-

mental influences.

The Bryophytes are divided, usually, into two main groups—

the Liverworts (Hepatice), and the True Mosses (Musci). One

peculiar order, Anthocerotales, the ‘‘Horned Liverworts,’’ is

sometimes considered to represent a third class, coordinate with

the Musci and Hepatic. Cavers does not accept this view, but

considers them to represent an order only of the Hepatice.

Aside from the Anthocerotales, the liverworts usually are

divided thus into two orders, Marchantiales and Jungerman-

niales. There are, however, several genera that to a certain

extent combine characters of both of these orders and sometimes

have been assigned to one, sometimes to the other. Of these

genera Spherocarpus may be cited. This is, on the whole, prob-

ably the simplest known liverwort, and is represented in the

United States by several species in the warmer parts of the

country. Much like Spherocarpus is a peculiar liverwort,

Geothallus, known as yet only from San Diego in Southern Cali-

fornia. A third genus, Riella, evidently related to these, is an

aquatic type, only recently found in America. All of these are

very simple liverworts and probably stand near the base of the

liverwort series. They may, perhaps, be regarded as synthetic

types connected with both of the main series of liverworts.

Cavers proposes to unite them into a special order, Spherocar-

pales, and this conclusion will probably be accepted as repre-

senting best their position in the system. In the Spherocar-

pales, as interpreted by Cavers, the sporophyte or neutral gen-

eration is of simple structure, and the elaters which in the typical

liverworts accompany the spores are represented by undiffer-

entiated sterile cells.

From some form probably not very unlike Sphwrocarpus, but

with perhaps a still simpler sporophyte, it is probable that the

two lines of development, the Marchantiales and the Jungerman-

niales have diverged. Within these two orders the course of

development can be easily traced, as nearly all the stages in the

686 THE AMERICAN NATURALIST [Vov. XLVI

evolution of the two groups are represented by existing genera.

It is hard to say which of the two orders should be considered

the more primitive, as the lower members of each are of about

equal complexity, and can be derived equally well from some

form allied to Sphwrocarpus.

Spherocarpus has been associated most commonly with the

Ricciaceæ, the lowest of the Marchantiales, but there are certain

genera of the Jungermanniales that in many ways show a close

resemblance to the Spherocarpacex, and make it almost certain

that there is a real relationship existing between them. These

similarities are found both in the character of the thallus and

reproductive organs, as well as in the early history of the embryo.

They may be only cases of parallel development, but it is quite

as likely that they are true homologies. Two genera, Petalo-

phyllum and Fossombronia, which have always been placed in

the Jungermanniales, are especially suggestive of a possible con-

nection with the Spherocarpales, and it is by no means impos-

sible that it may turn out that these genera, and possibly some

others, should be removed from their association with the J unger-

manniales and transferred to the Spheerocarpales.

THE MARCHANTIALES

The Marchantiales constitute a very natural order, whose

simplest members, the Ricciacer, are sometimes separated as a

distinct order. There does not seem to be any valid reason for

this, however, as the Ricciacee are connected with the more

n specialized Marchantiaceæ by a number of intermediate

orms.

_ The Marchantiales are comparatively few in number, probably

nee more than three hundred species being known; but their

relatively large size and characteristic appearance make them

the most conspicuous of the liverworts, the common and wide-

spread Marchantia polymorpha being the most familiar liver-

Wort to most students of botany. The dichotomously branched

thallus, with its elaborate systems of tissues, probably may be

said to represent the highest type of a strictly thallose plant.

Within the Marchantiales are many interesting cases of

adaptation, and a very complete series of forms exists showing

the evolution of the elaborate and highly specialized thallus of

Marchantia and similar genera, from the much simpler type

No. 551] NOTES AND LITERATURE 687

found in Riccia. The elaboration of the sporophyte can also be

followed. Riccia, as is well known, has the simplest known sporo-

phyte, in this respect being in a much lower plane than Sphero-

carpus, although the thallus in the latter is much less specialized

than in Riccia.

The evolution of the sporophyte, as every botanist knows, is

associated with a reduction in the amount of tissue devoted to

spore-production, and a corresponding increase in the purely

vegetative or sterile tissue of the sporophyte. The latter, how-

ever, in the Marchantiales always remains relatively simple in

structure.

In the lower Marchantiales the sexual organs are borne upon

the dorsal surface of the unmodified thallus, but in the more

highly specialized types like Fimbriaria or Marchantia, charac-

teristic receptacles are developed, usually composed of a number

of very short branches resulting from the repeated dichotomy of

the original thallus apex. The classification of the Marchan-

tiales has been based largely on the character of the receptacle

and the sporogonium.

Cavers recognizes five families of very unequal size, viz., Ric-

ciacew, Corsiniacex, Targioniacee, Monocleacee and Marchan-

tiacee. The latter, which aside from the Ricciacee, comprises

the greater part of the Marchantiales, was divided by Leitgeb into

three subfamilies, Astropore, Operculate and Composite, but

it is very doubtful whether these can be maintained.

The Ricciaceæ, the great majority of which belong to the

genus Riccia, are undoubtedly the simplest, and probably the

most primitive, members of the order. The extremely simple

sporophyte is almost entirely devoted to spore production, there

being no sterile tissue beyond a very imperfect single outer layer

of cells. No other liverworts approach the Ricciacee in the sim-

plicity of the sporophyte.

The second family, Corsiniacex, is intermediate in the struc-

ture of the sporophyte, between the Ricciacee and the higher

Marchantiales,

The third order, Targioniacex, includes the two small genera,

Targionia and Cyathodium. These are very characteristic liver-

worts represented in the United States by a single species Tar-

gionia hypophylla, common in the coast region of California, but

absent from the eastern states. This species occurs also m

southern and western Europe. Cyathodium includes a few

688 THE AMERICAN NATURALIST [Vou. XLVI

species of delicate liverworts inhabiting dark crevices in rocks,

or shallow caves. All the species show evidences of marked

structural modifications due to their unusual habitat. C. fæti-

dissimum is a characteristic species of the Indo-Malayan region.

The simple genus Monoclea with two species represents very

distinct the family Monocleacee. In his great work on the Hepat-

ice, Leitgeb referred Monoclea to the J ungermanniales, and this

view was adopted by Schiffner in his treatment of the Hepatice

in Engler & Prantl’s ‘‘ Natiirliche Pflanzenfamilien.’’ This asso-

ciation with the Jungermanniales was mainly on account of the

structure of the thallus, which is quite destitute of the air-

chambers which distinguish most of the Marchantiales. There is

also in Monoclea no definite archegonial receptacle, and the soli-

tary sporogonium has a long seta like that of many Jungerman-

niales,

All the more recent students of Monoclea, however, are agreed

that the plant really belongs to the Marchantiales, this being

shown both by the structure of the thallus, and that of the repro-

ductive organs. The absence of air-chambers is with little ques-

tion to be looked upon as a secondary condition, due to the semi-

aquatic habit of the plant. A similar disappearance of the air-

chambers is known in the unmistakable marchantiaceous genus

Dumortiera.

Leitgeb, in his important memoirs on the Hepatice, recognized

three types of archegonial receptacle. Only in one of these was

the receptacle compound in its structure. More recent studies,

including those of Cavers, indicate that this compound or ‘‘com-

posite’’ type is much more general than Leitgeb supposed.

Cavers states that probably all of the genera of the Marchan-

tiaceæ, except Clevea and Plagiochasma, will be found to have

receptacles of the composite type.

In tracing the phylogeny of the Marchantiales, Cavers distin-

guishes two main divergent groups which are connected with the

Ricciaceæ by Corsinia and Boschia, respectively. The first series

includes, among other genera, Clevea, Plagiochasma, Reboulia

= Fimbriaria, the latter representing the culmination of this

series.

The second series, starting with Boschia, shows two main

branches, one including the Targioniacer and Monoclea, the

other the most highly developed genera, like Fegatella, Dumor-

No. 551] NOTES AND LITERATURE 689

tiera and Marchantia. The latter genus is the most highly spe-

cialized of all the Marchantiales.

THE JUNGERMANNIALES

Much the greater number of liverworts belong to the Junger-

manniales. The classification of this large order is very much

in need of revision, as it is at present in a very unsatisfactory

condition.

They are generally divided into two series of very unequal size,

this division being based upon the position of the archegonium

—and are denominated the Anacrogyne and Acrogyne. In the

former the growing point of the shoot persists indefinitely, while

in the latter, in the fertile shoots, it is sooner or later trans-

formed into an archegonium, and the sporogonium is therefore

terminal.

The name Metzgeriacee was later proposed by Underwood, as

a substitute for Leitgeb’s Anacrogyne, the Acrogyne being alone

called Jungermanniacee. Cavers thinks these two divisions are

largely artificial, and it must be admitted that there is much to

be said for his view.

Comparing the Jungermanniales, as a whole, with the Mar-

chantiales, it is seen that in the former specialization has been in

the direction of external differentiation, i. e., in most of them a

more or less definite axis, bearing leaves, is present, but the tis-

sues remain quite uniform. In the Marchantiales, on the other

hand, the plant is a thallus, but the tissues are of various kinds.

The simplest of the Jungermanniales, e. g., Aneura, Pellia,

ete., have a very simple thallus, either composed of quite similar

cells, or with a midrib which may possess a strand of special

conductive tissue. The simplest type of thallus is quite like that

of Spherocarpus, and may very well have originated from some

similar type.

In these thallose Jungermanniales there is frequently a tend-

ency toward the development of marginal lobes, which may bear

a quite definite relation to the primary divisions of the single

apical cell of the thallus. Such marginal lobes are undoubtedly

homologues of the leaves found in the more highly specialized

leafy liverworts—the “ Acrogyne,’’ of Leitgeb. Sometimes these

leaf-like organs of the anacrogynous liverworts are very distinct,

as in Treubia, and the transition to the typical leafy liverworts

690 THE AMERICAN NATURALIST — [Vou. XLVI

like Porella or Frullania, is a very gradual one. It is very clear

that this tendency towards leaf-development has arisen in a

number of quite disconnected genera, and this of course suggests

a multiple origin for the Acrogyne.

Cavers proposes four families of the lower, or anacrogynous,

Jungermanniales, viz., Aneuraceæ, Blyttiaceæ, Codoniacee, Calo-

bryaceæ. He thinks that the first three are more or less arti-

ficial, and it is very certain that it will be necessary when some

of the less known genera are more fully investigated, to make a

radical revision of these families. The Calobryaceæ, on the other

hand, forms a sharply defined and natural family, comprising

two genera, Haplomitrium and Calobryum. Cavers concludes

that there are two main lines of development within the Anacro-

gynæ, one including the Codoniaceæ and Calobryaceæ, the other

the Blyttiaceæ and Aneuraceæ, suggesting that the two latter

families might perhaps be better united into a single one. There

seems to be little question that the two families are closely related

through such forms as Umbraculum and Podomitrium.

There is much uncertainty as to the limits of certain genera.

This is especially the case with the genus Calycularia, to which

have beèn assigned species which further investigation has shown

to belong to quite different families. The writer has had occa-

sion recently to examine carefully the structure of Calycularia

radiculosa, a rare species from Java. Schiffner concluded that

this species should be removed from the genus Calycularia, of

the family Codoniaceæ, and united with Mérkia, a member o

the Blyttiacee. While it is certainly distinct from the true

species of Calycularia, it is equally ‘certain that it can not be

assigned to Mérkia. It will probably have to be separated into

a distinct genus with characters intermediate between those of

the Codoniaceæ and the Blyttiaceew. In short, it is very clear

that at present a satisfactory classification of the group is not

feasible.

The Aneuracee and Blyttiacee show an interesting type of

specialization of the thallus which is wanting in the Codoniacer

and Calobryacexw, where the tendency is toward the development

of leaf-like lobes foreshadowing the leaves of the leafy liver-

worts. In Podomitrium and Umbraculwm, assigned respectively

to the Blyttiacee and Aneuraceæ, the thallus is differentiated

into a prostrate cylindrical rhizome and erect dichotomously

branched fan-shaped shoots, which resemble very closely the deli-

No. 551] NOTES AND LITERATURE 691

cate leaves of certain filmy. ferns, for which these liverworts

might easily be mistaken.

In the development of the sporophyte the Anacrogyne show a

decided advance over the Marchantiales. There may be devel-

oped a considerable amount of sterile tissue in the capsule, aside

from the ordinary elaters, and this sterile tissue sometimes

assumes the form of a sort of columella or ‘‘elaterophore,’’ sug-

gesting the columella found in the Anthocerotacex, and possibly

homologous with it. This elaterophore may be either apical

(Aneura) or basal (Pellia).

While recognizing the entirely independent origin of leaves in

several lines of the Anacrogyne, nevertheless Cavers is inclined

to believe that all of the true leafy liverworts (Acrogyne) can

be traced back to a single type which he thinks is best repre-

sented by Fossombronia, which genus he places at the top of the

series Codoniacew. It may be said, however, that there are some

strong arguments in favor of a polyphyletie origin for the Acro-

gyne—a view which has been defended by several students of

the group.

There are, as we have already stated, good reasons for believing

that Fossombronia should not be associated with Pellia and the

other Codoniacex, but associated with the Spherocarpales, as the

highest member of a series of which Sphwrocarpus and Geothal-

lus are lower members. This interpretation would not interfere

with the acceptance of Cavers’s view that some at least of the

leafy liverworts have been derived from forms like Fossombronia.

The acrogynous Jungermanniales, or leafy liverworts, include

much the larger part of existing liverworts. Of about 250

genera and 4,500 species of known liverworts, all but 60 genera

and 700 species belong to the acrogynous Jungermanniales.

They are nevertheless comparatively uniform in type, and Cavers

believes that they may all be traced back to a common ancestral

type allied to Fossombronia. ;

With very few exceptions they show a single tetrahedral apical

cell and usually three series of leaves corresponding to the three

lateral faces of the apical cell. The ventral leaves (amphigas-

tria) are not infrequently absent, and both dorsal and ventral

leaves often show various modifications, among the most striking

of which are hollow sacs presumably developed for water storage.

The tissues are very simple, and only very rarely is there any

specialization of cells for conduction or other purposes. In size

692 THE AMERICAN NATURALIST [ Von. XLVI

they range from almost microscopic forms like some of the

minute epiphyllous Lejeuniacex, to stout species like some of the

tropical Frullanias, which form pendant masses several feet in

length.

In all the Acrogyne the archegonia are in groups terminating

the fertile branch, whose further growth is arrested by the trans-

formation of the apical cell into an archegonium.

The sporogonium is always well developed, usually showing a

well-marked foot and seta. Perfect elaters are always present.

A small number only of the Acrogyne have been studied crit-

ically with reference to the development of the sporophyte, and

much more work must be done before the real affinities of some

of the genera can be determined satisfactorily.

On the basis of our present knowledge of the group, Cavers

proposes a classification based largely upon the work of Spruce.

He recognizes two main divisions, the first including a single

very large family, Lejeuniaceæ, with nearly 2,000 species; the

second contains seven families, of which three, viz., Porellaceæ,

Pleuroziacee and Radulacex, are regarded as natural families,

the other four as more or less artificial, the limits between them

being difficult to define.

The inter-relationships of the Acrogyne are extremely difficult

to follow. A number of students of the liverworts, notably

Spruce and Schiffner, believe that the group is of polyphyletie

origin, the Lejeuniacew representing a quite distinct line derived

from forms allied to the Aneuracee. There are striking resem-

blances both of gametophyte and sporophyte, the former in some

cases having a protonemal stage of long duration, and very much

resembling one of the simpler thallose liverworts. Cavers be-

lieves, however, that these resemblances are simply parallel devel-

opments, and not true homologies; and, as already stated, that

the Acrogyne represent a single line of development. Of these

forms he states that Lophozia probably comes nearer to the as-

sumed ancestral type.

From the Lophozia type, three branches are traced, one

through Plagiochila developing a large number of genera, among

which Cephalozia, again, is the starting-point for the develop-

ment of a number of specialized genera like Z oopsis, Lepidozia,

and Trichocolea. The second line leads through Marsupiella

and Nardia to a number of genera, of which the highest are

Stephaniella, Gyrothyra and Symphyomitra. The third line,

No. 551] NOTES AND LITERATURE 693

beginning with Lophozia, leads through Sphenolobus to the great

family Lejeuniaceæ, and to the characteristic genera Porella and

Frullania, which may be considered to represent the most per-

fectly developed characters of the whole order.

THE ANTHOCEROTALES

The Anthocerotales, Cavers’s fifth order of Hepatic, com-

prise a comparatively small number of liverworts of very

peculiar structure, and very readily distinguished from all other

plants. The differences between them and the other liverworts

are so marked that they are sometimes considered a class—Antho-

cerotes—coordinate, on the one hand, with all the other liver-

worts, on the other with the true mosses. | :

The structures of the four genera which are comprised in the

order are so much alike that they can all be assigned without

question to a single family, Anthocerotacee.

The gametophyte is of simple structure, and all the cells much

alike, each as a rule containing a single large chromatophore

resembling that of many green alge. The reproductive organs,

both archegonia and antheridia, show certain peculiarities, which

in some ways have their nearest approximation among the lower

ferns, and in connection with the characters of the sporophyte

suggest a real connection between the ferns and the Antho-

cerotalea.

The sporophyte differs much from that of the other liverworts.

In all of thé Anthocerotacea, except possibly some species of

Notothylas, the spore-producing tissue all arises from the outer

region (amphithecium) formed by the first periclinal divisions

in the capsule, and much the greater part of the tissue of the

sporophyte remains sterile. In all cases a large foot is present,

and above it a zone of actively dividing cells is present, which

may retain its activity for several months, so that the sporophyte

may attain a length of 10 centimeters or more. As the outer

tissues are in most cases well provided with chlorophyll, and

sometimes with stomata, a complete photosynthetic apparatus

is established much in advance of anything found in the other

Hepatice.

This long-continued growth of the sporophyte is associated

with a central strand of conducting tissue (columella), which is

reminiscent of the axial vascular bundle of the young sporo-

694 THE AMERICAN NATURALIST [Von XLVI

phyte of some of the lower ferns to which the sporophyte of

Anthoceros shows the closest resemblance known in the Bryo-

phyta.

Within the Anthocerotacer is an interesting series connecting

the small sporophyte of Notothylas with its relatively large

development of sporogenous tissue, and the large sporophyte of

Anthoceros with a small amount of sporogenous tissue and a

highly developed photosynthetic system.

It is, at present, impossible to say whether or not the type of

Notothylas is a reduced one. Cavers believes it is a primitive

type from which the more highly developed genera, culminating

in Anthoceros, have been derived. He is inclined to minimize

the importance of certain striking features, e. g., the peculiar

chloroplasts and the endogenous antheridia, and thinks the dif-

ferences between the Anthocerotales and the other liverworts are

not sufficient to warrant their separation into distinct classes.

He considers the columella of the Anthocerotacee may be con-

nected with the true liverworts through the Spherocarpales,

which they resemble in a number of particulars.

It may be noted, in passing, that there is a possibility of a

connection of the Anthocerotacee with some of the lower Mar-

chantiales. The Targioniacex, especially Cyathodium, for ex-

ample, show some interesting analogies in the sporogonium with

Notothylas, and the gametophytes also agree in the presence of

large lacunæ, and the chromatophores of Cyathodium are also

of unusual size.

Cavers’s conclusions may be summarized as follows: From

some common ancestral form, ‘‘Sphxro-Riccia,’’ two lines of

development diverged, one leading to the Marchantiales, the

other to the Spherocarpales, which in turn gave rise to the lower

Jungermanniales. From some member of the latter, perhaps

Fossombronia, all of the leafy liverworts arose. Somewhere near

the Spherocarpales it is assumed that the Anthocerotales

branched off.

| We are inclined to believe that some modifications of this

arrangement are likely to be made. It is quite possible that

Fossombronia should be removed from the J ungermanniales, and

associated with the Spherocarpales; and if Cavers’s assumption

1s correct, that the leafy liverworts (Acrogyne) have arisen

from a prototype resembling Fossombronia, this would entirely

divorce the two great divisions of the Jungermanniales.

No. 551] NOTES AND LITERATURE 695

It is doubtful whether the derivation of the Anthocerotacese

from the Spherocarpales will be generally accepted. For the

present, at least, the order must be regarded as a very isolated .

one, and perhaps best considered to represent a distinct class,

DovueLtas HOUGHTON CAMPBELL

STANFORD UNIVERSITY

INVERTEBRATES

Unper the able leadership of Professors Zeigler and Woltereck

there is appearing from Klinkhardt’s press in Leipzig a series

of excellent small monographs of familiar animals designed for

the student, teacher, investigator and amateur who desires to

secure a brief but authentic account of the results of systematic,

histological, morphological, anatomical and embryological investi-

gations on representative types of animals. Two volumes have

already appeared, the frog by Dr. Hempelmann, and the rabbit

by Dr. Gerhardt, and the series of invertebrates has been

introduced by two volumes, volume 3 of the series on ‘‘Hydra

und die Hydroiden’”’ by Dr. Steche, of Leipzig, and volume 4 by

Professor Meisenheimer, of Jena, on ‘‘Die Weinbergschnecke.”’

Dr. Steche’s volume is designed not merely as a monograph

on Hydra along the lines on which the series is planned, but

adds to these the features of an introduction to the experimental

treatment of biological problems as offered by the lower ani-

mals. Hydra is an exceptionally favorable subject for this

treatment by virtue of its hardiness, ease of obtaining and of

maintenance, and simplicity of structure. Few invertebrates

have served as a basis of so many and so varied experimental

tests and have been the object of so many investigations as

Hydra. With this wealth of results before him it is not to be

wondered at that this modest volume is open to the charge of

Some sins of omission. The choice of topics treated is, however,

most catholic and this author has wisely avoided controversial

difficulties. The histological and embryological sections are less

1 ‘í Monographien einheimischer Tiere,’’? Herausgegeben von Professor

Dr. H. E. Ziegler, Stuttgart, und Professor Dr. R. Woltereck, Leipzig, Bd. 3;

‘‘ Hydra und die Hydroiden. Zugleich eine Einführung in die experimentelle

Behandlung biologischer Probleme an niederen Tieren,’’ von Dr. Otto Steche,

vi + 162 pp., 65 figs. in text and 2 pls., M. 4, geb. M. 4.80; Bd. 4, “Die

Weibergschnecke, Helix pomatia,’? von Professor Johannes Meisenheimer,

140 pp., 1 pl. and 72 figs. in text, M. 4, geb M. 4.80.

696 THE AMERICAN NATURALIST [Vou. XLVI

developed than seems desirable, but in compensation the sec-

tions on biology and experimental subjects such as regenera-

tion, regulation, grafting, graft hybrids, effects of external fac-

tors on growth and regeneration, polarity and heteromorphosis

are well, though concisely, developed. Several pages of prac-

tical suggestions as to collection, rearing, feeding and preparing

Hydra will be found very useful as will also the key to the

species. ‘The author conservatively clings to the widely current

names viridis, grisea and fusca and rejects the older names of

Pallas which strictly have priority.

Half of the book is given to the hydroids. Noteworthy in this

are several superb figures of hydroid colonies from the Hel- |

goland Nordsee Museum. A brief list of titles closes the volume

from which we note the omission of Nutting’s and Mayer’s

monographs.

The volume by Professor Meisenheimer upon the garden snail

follows closely the program of the series, with perhaps less of

emphasis upon the experimental and physiological aspects and

more space taken for the presentation of the static phases which

are greatly increased necessarily over those of a simple animal

such as Hydra. But there appears still to be call for more

expansion on the dynamic aspects of the subject in the case of

this volume. The chapter upon the relation of the snail to the

environment and to man is a concession in the right direction,

and the prevalence of the biological standpoint throughout the

anatomical chapters in some measure supplies the physiological

data pertinent to the structural phases. These are very clearly

and methodically set forth with abundant illustrations, many

of which are new. A chapter on other land pulmonate mollusks

affords an all too brief basis for comparison of the snail with

other mollusks,

; Both of these volumes will be exceedingly useful to zoologists

in all countries, for the objects with which they deal are cos-

mopolitan. A similar series of monographic booklets on labo-

ratory types based on American material would be of great

value for American students and investigators.

CHARLES ATwoop Kororp

DECEMBER, 1912

. XLVI, NO. 552

VOL

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THE

AMERICAN NATURALIST

Vout. XLVI December, 1912 No. 552

THE MENDELIAN INHERITANCE OF FECUND-

ITY IN THE DOMESTIC FOWL?

DR. RAYMOND PEARL

MAINE AGRICULTURAL EXPERIMENT STATION

Tue investigation here reported was concerned with

the detailed analysis and interpretation of a rather ex-

tensive series of data regarding the inheritance of fe-

cundity in the domestic fowl. The basic data are derived

from trap-nest records extending over a period of years.

They include records from (a) pure Barred Plymouth

Rocks; (b) Cornish Indian Games; (c) the F, individ-

uals obtained by reciprocally crossing these two breeds;

and (d) the F, individuals obtained by matjng the F,’s

inter se and back upon the parent forms in all possible

combinations. The fully-pedigreed material made use of

in the present connection includes something over a

thousand adult females, each of which was trap-nested

for at least one year, and many for a longer period. This

material covers four generations. The birds of the

fifth generation have just completed their winter records

at the time of writing. Besides this fully pedigreed ma-

terial, the collection and study of which has occupied

1 At the request of the editor of the AMERICAN NATURALIST the following

summarized account of the principal results of an investigation carried out _

by the writer has been prepared. A detailed account has been published

in the Journal of Experimental Zoology, Vol. 13, No. 2, pp. 153-268,

August, 1912.

697

698 THE AMERICAN NATURALIST [Vou. XLVI

five years, there was available as a foundation, without

which the results here discussed could not have been

reached, nine years of continuous trap-nest records for

Barred Plymouth Rocks, involving thousands of birds,

which had been subjected during this long period to mass

selection for increased egg production.

Altogether it may fairly be said that the material on

which this work is based is (a) large in amount, (b) ex-

tensive in character, and (c) in quality as accurate as it is

humanly possible to get records of the egg production of

fowls.2 On these accounts the facts presented seem

worthy of careful consideration, and to have a perma-

nent value quite apart from any interpretation which

may be put upon them.

The essential facts brought out in this study of fe-

cundity appear to be the following: ‘

1. The record of fecundity of a hen, taken by and o

itself alone, gives no definite, reliable indication from

which the probable egg production of her daughters may

be predicted. Furthermore mass selection on the basis

_ of the fecundity records of females alone, even though

long continued and stringent in character, failed com-

pletely to produce any steady change in type in the di-

rection of selection. 2

2. Fecundity must, however, be inherited since (a)

there are. widely distinct and permanent (under ordi-

nary breeding) differences in respect of degree of fe-

cundity between different standard breeds of fowls com-

monly kept by poultrymen, and (b) a study of pedigree

records of poultry at once discovers pedigree lines (in

some measure inbred of course) in each of which a defi-

nite, particular degree of fecundity constantly reappears

generation after generation, the ‘‘line’’ thus ‘‘breeding

true’’ in this particular. With all birds (in which such

a phenomenon as that noted under b occurs) kept under

the same general environmental conditions such a result

* Pearl, R., ‘‘On the Accuracy of Trap-nest Records,’’ Me. Agr. Expt.

Sta. Ann. Rept. for 1911, pp. 186-193.

No. 552] INHERITANCE OF FECUNDITY 699

can only mean that the character is in some manner in-

herited.

The facts set forth in paragraphs 1 and 2 have been

presented, and, I believe, fully substantiated by exten-

sive evidence, in previous papers from this laboratory.

It is now further shown that:

3. The basis for observed variations in fecundity is

not anatomical. The number of visible oocytes on the

ovary bears no definite or constant relation to the actu-

ally realized egg production. This is shown by the fig-

ures presented in Table I. These give the counts of the

number of ọocytes on the ovary visible to the unaided eye

in the case of a number of individuals. It will be under-

stood that it is not contended that such counts give an

accurate measure of the total oocyte content of the

ovary. The figures, however, are so greatly in excess of

what a hen actually ever lays that it may be quite safely

concluded that in normal cases (where no accident or

operation has induced regenerative processes in the

ovary) all the eggs which will ever be laid (and usually

more) are included among those visible to the eye, on an

adult fowl’s ovary.

From this table it is evident that when one bird has a

winter record of twice what another bird has it is not

because the first has twice as many oocytes in the ovary.

On the contrary it appears that all birds have an ana-

tomical endowment entirely sufficient for a very high de-

gree of fecundity, and in point of fact quite equal to that

possessed by birds which actually accomplish a high

record of fecundity. Whether or not such high fecund-

ity is actually realized evidently depends then upon the

influence of additional factors beyond the anatomical

basis.

4. This can only mean that observed differences (vari-

ations) in actual egg productions depend upon differ-

ences in the complex physiological mechanism concerned

with the maturation of oocytes and ovulation. ;

THE AMERICAN NATURALIST [Vou. XLVI

700

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No. 552] INHERITANCE OF FECUNDITY 701

5. A study of winter egg production (taken for prac-

tical purposes as that from the beginning of the laying

year in the early fall to March 1) proves that this is the

best available measure of innate capacity in respect to

fecundity, primarily because it represents the laying

cycle in which the widest difference exists between birds

of high fecundity and those of low fecundity.

6. It is found to be the case that birds fall into three

well-defined classes in respect to winter egg production.

These include (a) birds with high winter records, (b)

birds with low winter records, and (c) birds which do

not lay at all in the winter period (as defined above).

The division point between a and b for the Barred

Plymouth Rock stock used in these experiments falls at

a production of about 30 eggs.

7. There is a definite segregation in the Mendelian

sense of the female offspring in respect to these three

fecundity divisions. This is demonstrated by extensive

statistics in the complete report of this work. Here a

single table only may be given by way of illustration, the `

one chosen being taken because all three classes are rep-

resented among the progeny of the particular type of

mating with which it deals.

TABLE II

SHOWING THE RESULTS OF ALL Mares or Crass 4 B.P.R. fd X CLASS

1 B.P.R. 99. GAMETIC CONSTITUTION: fL,L, - ful. X (LL, - Ful,

Numb {ndividual

kavalsi in Matings a Winter Egg Production of Daughters

of this Type

Total Adult

do | vy Class Over 30 | Under 30 Zero | Q Progeny

4 | 17 Observed 21 30 8 59

Expected 22.1 29.5 74

Mean winter egg production of all os ERS A en eas

C O in indicated class... 0.0.5. 3 48.85 eggs 16.34 eggs) 0 eggs

8. High fecundity may be inherited by daughters from

their sire, independent of the dam. This is proved by the

numerous cases presented in the detailed evidence where

the same proportion of daughters of high fecundity are

702 THE AMERICAN NATURALIST [Von XLVI

produced by the same sire, whether he is mated with

dams of low or of high fecundity.

9. High fecundity is not inherited by daughters from

their dam. This is proved by a number of distinct and

independent lines of evidence, of which the most im-

portant are: (a) continued selection of highly fecund

dams does not alter in any way the mean egg production

of the daughters; (b) the proportion of highly fecund

daughters is the same whether the dam is of high or of

low fecundity, provided both are mated to the same

male; (c) the daughters of a fecund dam may show

either high fecundity or low fecundity, depending upon

their sire; (d) the proportion of daughters of low fe-

cundity is the same whether the dam is of high or of low

fecundity, provided both are mated to the same male.

10. A low degree of fecundity may be inherited by the

daughters from either sire or dam or both.

11. The results respecting fecundity and its inherit-

ance stated in paragraphs 3 to 10 inclusive are equally

° Pearl, R., ‘‘The Relation of the Results Obtained in Breeding Poultry

for Increased Egg Production to the Problem of Selection,’’ Rpt. 30th

Meeting Soc. Proc. Agr. Sci., pp. (of reprint) 1-8, 1910; ‘‘Inheritance in

‘Blood Lines’ in Breeding Animals for Perf. ormance, with Special Refer-

ence to the ‘200-egg’ Hen,’’ Ann. Rpt. Amer. Breeders’ Assoc., Vol. 6,

pp. 317-326, 1911; ‘‘Inheritance of Fecundity in the Domestic Fowl,’’

AMER. Nar., Vol. 45, pp. 321-345, 1911; ‘‘Breeding Poultry for Egg

Production,’’? Me. Agr, Expt. Sta. Ann. Rpt. for 1911, pp. 118-176. Pearl,

.„ and Surface, F. M., ‘‘Data on the Inheritance of Fecundity Obtained

from the Records of Egg Production in the Daughters of ‘200-egg’ Hens,’’

Me. Agr. Expt. Sta. Ann. Rpt. for 1909, pp. 49-84 (Bulletin 166), 1909;

**Studies on the Physiology of Reproduction in the Domestic Fowl.

Data on Certain Factors Influencing the Fertility and Hatching of Eggs,’’

Me. Agr. Expt. Sta. Ann. Rpt. for 1909, pp. 105-164, 1909; ‘ʻA Biometrical

Study of Egg Production in the Domestic Fowl. I. Taraka in Ann

Egg Production,’’ U. S. Dept. Agr., Bur. Animal Ind. Bulletin 110, Part I,

pp. apse 1909; ‘‘A Biometrical Study of Egg Production in the Domestic

Fowl. ensonad Distribution of Egg Production,’’ Ibid., Part II, PP.

81-170, Da

‘This is true, of course, only for certain gametic types of low fecundity

females, as will be clear to any one who has studied the detailed evidence.

This limitation, however, in nowise diminishes the force of this particular

evidence in titer of the conclusion standing at the beginning of paragraph 9.

No. 552] INHERITANCE OF FECUNDITY 703

true for Barred Plymouth Rocks, Cornish Indian Games,

and all cross-bred combinations of these breeds in F,

and Fs

The above statements are of definite facts, supported

by a mass of evidence. Their truth is objective and de-

pends in no way upon any theory of inheritance whatso-

ever. With this clearly in mind we may undertake their

interpretation.

It is believed that these general facts, and the detailed

results on which they are based, are completely accounted

for and find their correct interpretation in a simple Men-

delian hypothesis respecting the inheritance of fecund-

ity in the fowl. This hypothesis involves the following

points, each of which is supported by direct and perti-

nent evidence derived either from physiological and

statistical studies of fecundity, or from the detailed data

respecting the mode of inheritance of this character.

It is assumed in this hypothesis that:

1. There are three distinct and separately inherited

factors upon which fecundity in the female fowl depends.

2. The first of these factors (which may be called the

anatomical) determines the presence of an ovary, the

primary organ of the female sex. The letter F is used

throughout to denote the presence of this factor.

3. There are two physiological factors. The first of

these (denoted by L,) is the basic physiological factor,

- which when present alone in a zygote with F brings about

a low degree of fecundity (winter record under 30 eggs).

This factor is under no limitations in gametogenesis, but

may be carried in any gamete, regardless of what other

factors may be also present.

4. The second physiological factor (denoted by L,)

when present in a zygote together with F and L,, leads to

a high degree of fecundity (winter record over 30 eggs).

$ And F,. It was thought wise to delay publication any longer in order

to include the data for F, It may be said, however, that they are in full

accord with those which have been obtained from earlier cross-bred genera-

tions and the parent forms.

704 ‚THE AMERICAN NATURALIST __[Vou. XLVI

When L, is absent, however, and L, is present the zygote

exhibits the same general degree of fecundity (under 30)

which it would if L, were present alone. These two inde-

pendent factors L, and L, must be present together to

cause high fecundity, either of them alone, whether

present in one or two ‘‘ doses,’’ causing the same degree

of low fecundity.

5. The second physiological factor L, behaves as a

sex-limited (sex-correlated or sex-linked) character, in

gametogenesis, according to the following rule: The

factor L, is never borne in any gamete which also carries

F. That is to say, all females which bear L, are hetero-

zygous with reference to it. Any female may be either

homozygous or heterozygous with respect to L, Any

male may be either homozygous or heterozygous with

reference to either L,, L, or both.

TABLE III

CONSTITUTION OF BARRED PLYMOUTH ROCK MALES IN RESPECT TO FECUNDITY

Class Zygote Gametes Produced

ee | LiL , flrla iL

2 fink: . flalz fInLe2, fInle

3 ibe . file JLiLa, flLe

4 JLiz2 . fle fInLe, fLil, f LL, f hl

5 fLi . flale Tals

6 JLi . fhie fLil, fLl

rA ShLle . f hla lIa

8 fhLz . fli fle, fhl

9 fh .fhk fhh

TABLE IV

CONSTITUTION OF BARRED PLYMOUTH Rock FEMALES IN RESPECT

TO FECUNDITY

T ` T Probable Winter Egg

Class Zygote PS irk a ( G Produckag) Pennin ote And

Gametes Gametes Constitution

1 fInLe . Fhie LiLo, f hL? Fle, FLil

2 JLiLl . Flik 5 4 ala m fe 43 eggs

3 Jaiz . Fhe | fLil, fla Fhl, FLil Under 30 eggs

4 flak . Flat || flak FLilə Under 30 eggs

5 Shie . Fuh | Shh Fhill Zero eggs

6 Shi: . Fhe | Sule Fhlz Under 30 eggs

° The reason that gametes of the type fL,l, and fil, are not formed here

will be evident on consideration, Since no gametes of type FL, can, by

No. 552] INHERITANCE OF FECUNDITY 705

The different gametic constitutions in respect to fe-

cundity which are to be expected in Barred Plymouth

Rock males and females are shown in Tables III and IV.

Of these expected types six (1, 2, 3, 4, 7 and 8) were

found and used in the experiments in the case of the

males. In the case of the female class 5 birds were the

only ones not actually tested out in the breeding experi-

ments. Birds undoubtedly belonging to each of the

omitted classes have been reared in the course of the ex-

periments, but not yet submitted tô continued breeding

test.

The gametic constitutions of pure Cornish Indian

Games in respect to fecundity are given in Tables V

and VI.

TABLE V

CONSTITUTION OF CORNISH INDIAN GAME MALES IN RESPECT TO FECUNDITY

Class Zygote Gametes Produced

i fLil . fIale flile

2 fLi . fh flak, fll

3 fl . fll fhk

TABLE VI

CONSTITUTION OF CORNISH INDIAN GAME FEMALES IN RESPECT

“to FECUNDITY

i Probable Winter Egg

f-bearing F-bearing Production of Q

Class Zygote (ð Producing) | (Q Producing) Indicated Zygotic

` Gametes Gametes Constitution

1 JLi . Flak flail Flilk Under 30 eggs

2 Shh . Flak Shia, fLl | Flalz, Flies Under 30 eggs

3 Flak . Fhe flak, f hlk Fh, F Lil Under 30 eggs

4 fhlk . Fhe fli Flilz Zero

It will be noted that C.I.G. 9 classes 2 and 3 are gametically identical.

Both are left in the table, however, since the whole table is so short that no

confusion can be caused, and this example may make clear to some readers

the nature of the compression (by omission of duplicate classes) which was

practised in Tables III and IV.

How well this Mendelian hypothesis agrees with the

facts has been shown in detail in the complete paper. By

hypothesis, be formed this implies that an interchange of the factors E, and

between F and f gametes can not occur. The experimental proof of the

truth of this conviction has been furnished in the case of the inheritance of

the barred color pattern.

706 THE AMERICAN NATURALIST [Vou. XLVI

way of summary the following table shows the accord

between observation and expectation for all matings of

each general type taken together. For reasons set forth

below, the lumped figures do not give an altogether fair

estimate of the matter, but some sort of a summary is

necessary.

TABLE VII

SHOWING THE OBSERVED AND EXPECTED DISTRIBUTIONS OF WINTER EGG

PRODUCTION FOR ALL MATINGS TAKEN TOGETHER

A PENETRAN ROEN PERTRA ENA Pe

Winter Production of Daughters

Mating Class Over 30 | Under 30 | Zero r

A AT A A ee a l a

AN OLG. X O10... 14... FO Oe cicero = io

h a J 1 Gerad 25 | sers | 0.75

All F: and back-crosses.......... { eae a as sn nn

Considering the nature of the material and the char-

acter dealt with it can only be concluded that the agree-

ment between observation and hypothesis is as. close

as could reasonably be expected. The chief point in

regard to which there is a discrepancy is in the tendency,

particularly noticeable in the B. P. R. X B. P. R. and the

F, matings, for the observations to be in defect in the

‘* Over 30 ”’ class and in excess inthe ‘‘ Zero. ”’ class. The

explanation of this is undoubtedly, as has been pointed

out in the detailed paper, to be found in disturbing

physiological factors. The high producing hen, some-

what like the race horse, is a rather finely strung, delicate —

mechanism, which can be easily upset, and prevented

from giving full normal expression to its inherited

capacity in respect to fecundity.

The writer has no desire to generalize more widely

from the facts set forth in this paper than the actual

material experimentally studied warrants. It must be

recognized as possible, if not indeed probable, that other

” With exception of one set of matings discussed in full in the complete

paper.

No. 552] INHERITANCE OF FECUNDITY 707

races or breeds of poultry than those used in the present

experiments may show a somewhat different scheme of

inheritance of fecundity. The directions in which devia-

tions from the plan here found to obtain may, at least

a priori, most probably be expected are two. These are:

(a) differences in different breeds in respect to the abso-

lute fecundity value of the factors which determine the

expression of this character, and (b) gametic schemes

which differ from those here found either in the direction

of more or fewer distinct factors being concerned in the °

determination of fecundity, or in following a totally

different type of germinal reactions.

Regarding the first point, it seems probable from the

evidence in hand that the absolute fecundity value (i. e.,

the degree of actual fecundity determined by the presence

of the gametic factor) may differ for the factor L, in the

case of the Barred Rock as compared with the Cornish

Indian Game breed. It is hoped later to take up a detailed

study of this point, on the basis of the material here pre-

sented, and additional data now in process of collection.

Whenever there is a difference in the absolute fecundity

value of the L, factor, it means that the division point

for the classification of winter productions should be

taken at a point to correspond with the physiological

facts. Similarly, the absolute fecundity value of the

excess production factor L, may be different in different

breeds. In applying the results of this paper to the pro-

duction statistics of other breeds of poultry the possi-

bility of differences of the kind here suggested must

always be kept in mind.

The second point (the possibility of gametic schemes

for fecundity differing qualitatively from that found in

the present study) is one on which it is idle to speculate

in advance of definite investigations. I wish only to

emphasize that nothing is further from my desire or in-

tention than to assert before such investigations have

been made that the results of the present study apply

unmodified to all races of domestic poultry.

708 THE AMERICAN NATURALIST [ Vou. XLVI

It can not justly be urged against the conclusions of

this study that the Mendelian hypothesis advanced to

account for the results is so complicated, and involves

the assumption of so many factors or such complex inter-

actions and limitations of factors, as to lose all signifi-

cance. As a matter of fact the whole Mendelian inter-

pretation here set forth is an extremely simple one,

involving essentially but two factors. This surely does

not indicate excessive complication. To speak in mathe-

matical terms, by way of illustration merely, it may

fairly be said that the formula here used to ‘‘fit’’ the

data has essentially the character of a true graduation

formula. The number of constants (here factors) in the

formula is certainly much less than the number of ordi-

nates to be graduated.

There is no assumption made in the present Mendelian

interpretation which has not been fully demonstrated by

experimental work to hold in other cases. That the ex-

pression of a character may be caused by the coincident

presence of two (or more) separate factors, either of

which alone is unable to bring it about, has been shown

for both plants!! and animals by a whole series of studies

in this field of biology during the last decade. To find

examples one has only to turn to the standard hand-

books summarizing Mendelian work, as for example those

of Bateson and Baur. Again sex-linkage or correlation

of characters in inheritance has been conclusively demon-

strated for several characters in fowls by the careful and

thorough experiments of a number of independent inves-

tigators. Finally it is to be noted that Bateson and

Punnett! have recently shown that the inheritance of the

peculiar pigmentation characteristic of the silky fowl

follows a scheme which in its essentials is very similar to

that here worked out for fecundity.

“ Particularly important here are the brilliant researches of Nilsson-Ehle

on cereals, and of Baur on Antirrhinum.

_ "Bateson, W., and Punnett, R. C., ‘‘The Inheritance of the Peculiar

Pigmentation of the Silky Fowl,’’ Journal of Genetics, Vol. 1, pp. 185-203.

No. 552] INHERITANCE OF FECUNDITY 709

THE SELECTION PROBLEM

The results of the present investigation have an inter-

esting and significant bearing on the earlier selection ex-

periments on fecundity at this station. It is now quite

plain that continued selection of highly fecund females

alone could not even be expected to produce a definite

and steady increase in average flock production. The

gametic constitution of the male (in respect especially to

the L, factor) plays so important a part in determining

the fecundity of the daughters that any scheme of selec-

tion which left this out of account was really not ‘‘ sys-

tematic ’’ at all, but rather almost altogether haphazard.

It is repeatedly shown in the detailed account of these

experiments that the same proportion of daughters of

high fecundity may be obtained from certain mothers of

low fecundity as can be obtained from those of high fe-

cundity provided that both sets of mothers are mated to

males of the same gametic constitution. What gain is to

be expected to accrue from selecting high laying mothers

under such circumstances, at least so far as concerns the

daughters?

‘ Selection ”’ to the breeder means really a system of

breeding. ‘‘ Like produces like,’’ and “‘ breed the best

to get the best ’’; these epitomize the selection doctrine

of breeding. It is the simplest system conceivable. But

its success as a system depends upon the existence of an

equal simplicity of the phenomena of inheritance. If the

mating of two animals somatically a little larger than the

average always got offspring somatically a little larger

than the average, breeding would certainly offer the

royal road to riches. But if, as a matter of fact, as 1m

the present case, a character is not inherited in accord-

ance with this beautiful and childishly simple scheme,

but instead is inherited in accordance with an absolutely

different plan, which is of such a nature that the appli-

cation of the simple selection system of breeding could

not possibly have any direct effect, it would seem idle to

710 THE AMERICAN NATURALIST [ Vou. XLVI

continue to insist that the prolonged application of that

system is bound to result in improvement.

It seems to me that it must be recognized frankly that

whether or not continued selection of somatic variations

can be expected to produce an effect on the race depends

entirely on the mode of inheritance of the character

selected, In other words, any systematic plan for the

improvement of a race by breeding must be based and

operated on a knowledge of the gametic condition and be-

havior of the character in which improvement is sought,

rather than the somatic. Continued mass selection of

somatic variations as a system of breeding, in contrast

to an intelligent plan based on a knowledge of the gametic

basis of a character and how it is inherited, seems to me

to be very much in the same case as a man who, finding

himself imprisoned in a dungeon with a securely locked

and very heavy and strong door with the key on the

inside, proceeded to attempt to get out by beating and

kicking against the door in blind fury, rather than to

take the trouble to find the location of the key and unlock

the door. There is just a possibility that he could finally

get out in a very few instances by the first method, but

even in those cases he would be regarded by sensible men

as rather a fool for his pains.

Of course what has been said is not meant to imply that

selection, on the basis of somatic conditions may not have

a part in a well considered system of breeding for a par-

ticular end. In many cases it certainly will have. Thus

in the case of fecundity in the fowls, selection of mothers

on the basis of fecundity records is essential in getting

male birds homozygous with respect tò L, and L,. But

the point which seems particularly clear in the light of

the present results is that blind mass selection, on the

basis of somatic characters only, is essentially a hap-

hazard system of breeding which may or may not be

successful in changing the type in a particular case.

There is'‘nothing in the method per se which insures such

success, though that there is inherent potency in the

No. 552] INHERITANCE OF FECUNDITY 711

method per se is precisely the burden of a very great

proportion of the teaching of breeding (in whatever form

that teaching is done) at the present time.

It seems to me that it has never been demonstrated, up

to the present time, that continued selection can do any-

thing more than:

1. Isolate pure biotypes from a mixed population,

which contains individuals of different heredity constitu-

tion in respect to the character or characters considered.

2. Bring about and perpetuate as a part of a logical

system of breeding for a particular end, certain combina-

tions of hereditary factors which would never (or very

rarely) have occurred and would have been lost in the

absence of such systematic selection; which combinations

give rise to somatic types which may be quite different

from the original types. In this way a real evolutionary

change (i. e., the formation of a race of qualitatively

different hereditary constitution from anything existing

before) may be brought about. This can unquestionably

be done for fecundity in the domestic fowl. But here

“ selection ” is simply one part of a system of breeding,

which to be successful must be based on a definite knowl-

edge of gametic as well as somatic conditions. It is very

far removed from a blind “ breeding of the best to the

best to get the best.’? The latter plan alone may, as in

the case of fecundity, fail absolutely to bring about any

progressive change whatever.

It has never yet been demonstrated, so far as I know,

that the absolute somatic value of a particular hereditary

factor or determinant (i. e., its power to cause a quanti-

tatively definite degree of somatic development of a char-

acter) can be changed by selection on a somatic basis,

however long continued. To determine, by critical ex-

periments which shall exclude beyond doubt or question

such effects of selection as those noted under 1 and 2

above, whether the absolute somatic value of factors may

be changed by selection, or in any other way, 1s one of

the fundamental problems of genetics.

REFLECTIONS ON THE AUTONOMY OF BIOLOG-

ICAL SCIENCE

PROFESSOR OTTO GLASER

UNIVERSITY OF MICHIGAN

INTRODUCTORY

Ir the knowledge of facts and comprehension of prin-

ciples by certain writers had been adequate, and others

had. freed their minds from the survivals of animism,

the taxonomic position of biology in the scheme of knowl-

edge would appear uncertain to no one. Prolonged and

extensive inkshed however have surrounded this ques-

tion with much unnecessary difficulty and confusion.

Some claim that biology can not properly find a place

among the sciences at all; others, that if our science is

nothing more than physics and chemistry, it can have no

right to independent existence; and finally, the vitalists

postulate an absolute autonomy based on a specific prin-

ciple.

BIoLoGICAL PREDICTION

Merz, Enriques,’ and other present-day writers on the

systematics of biology dwell at length on the fact that

within the realm of the living, very strange and unex-

pected events take place. From the protozoans, human

beings can hardly be inferred: the chromosomal com-

plex, on account of the variations and surprising simi-

larities of its constituent elements, fails to tell us whether

we are dealing with sister species or with forms as re-

mote as snails, frogs, ferns and mice. Because one

crustacean is positively heliotropic, it does not follow

that the next one, even if the species be identical, will re-

spond in like manner, nor because one child in a family

has blue eyes can we conclude that its parents or broth-

ers and sisters have eyes of the same color. A dog or a

* Merz, John Theodore, ‘‘A History of European Thought in the Nine-

teenth Century’’; Enriques, Federigo, ‘‘ Probleme der Wissenschaft.’

712 ;

No. 552] AUTONOMY OF BIOLOGICAL SCIENCE Tic

man may be friendly to-day and vicious to-morrow under

similar external circumstances. Irregularities such as

these, our informants tell us, should quench the ardor of

the dullest, and to convince us still further of the inade-

quacy of our materials for science they point to rational

mechanics, a domain free from ambush, and pervaded by

an order in which only the foreseen and predictable find a

place.

The juxtaposition of these two disciplines is not only

unparliamentary, but unfortunate. Inasmuch as ra-

tional mechanics deals with abstractions and has only

the slightest objective basis, it can have no materials

comparable with the contents of any natural science.

On the contrary, it is a method of thinking. Thinking is

a phenomenon of consciousness; and consciousness, a

biological event. If, therefore, the mechanic produces an

orderly and coherent system in which one thing follows

with certainty from another, this shows nothing else

shan that certain biological events, to wit, mental proc-

esses, are among the most reliable phenomena in nature.

The biologist readily concedes that he is not as weather-

wise as the rational mechanic, but he does not concede

that this is due either to the fundamental disorderliness

of his section of nature, or because his colleague’s oracu-

lar powers differ in origin from his own where he happens

to possess them. As a whole man can not as yet be in-

- ferred from the protozoa, yet from the study of oxida-

tion, secretion and digestion in unicellular organisms we

could readily foresee the existence of these processes

in higher forms. The conditions of the heliotropic re-

sponse are such that an organism must be neither neu-

tral nor alkaline to react positively, and one at variance

with expectation can be made to do the expected by

acidulation. Although half the children of brown-eyed

parents may have blue eyes, this, instead of being a

symptom of disorder, is in strict conformity with a law

which enables us to say that two grandparents, one ma-

ternal, the other paternal, had this eye-color. The same

714 THE AMERICAN NATURALIST [Vou. XLVI

law makes it possible to predict the proportion and sex

of color-blind persons in a family in which this defect is

present. The change from friendliness to viciousness in

dogs and men has been traced to definite chemical and

structural changes so often that it could undoubtedly be

foreseen if these were known. The ‘embryologist fore-

tells the hour of ovulation, the obstetrician the birth of

a child, the entomologist the reappearance of a brood of

locusts, the ornithologist of a flock of birds, and the ichthy-

ologist of a school of fish, with the same reasonable cer-

tainty with which the celestial mechanic predicts the re-

turn of a comet. By the behavior of Convoluta roscoff en-

sis, even though far from its native haunts, it is possible

-= to tell the state of the tides. It should never be forgot-

ten that Weismann predicted the phenomena of matura-

tion in the germ cells.

Because the chromosomes have at present no taxo-

nomic importance, Merz concludes that they never can

have, and that biological events are therefore disorderly.

It so happens that the particular facts which Merz would

like to predict from these bodies are not related to what

we know about them in a manner so intimate that in the

present state of science prediction here would be any

more reasonable than in the absence of wind to judge the

weather from a bonfire. There are no reasons to doubt

that if we knew accurately the chemical structure of the

chromosomes, instead of merely their general composi-

sition, number, size and shape, we could tell the species,

and perhaps predict their composition in related spe-

cies, much as the organic chemist predicts the make-up

of one compound from another. Even now, the physio-

- logical state of the cell, and in numerous instances its

kind, as well as the sex of the individual from which it

was taken, can be determined from the chromosomal

complex.

How the rational mechanic acquired his prophetic

powers can be answered by considering the development

of geometry. Are we expected to believe that from the

No. 552] AUTONOMY OF BIOLOGICAL SCIENCE 715

qualities of a line, the geometrician could predict the

properties of the angle between two lines, if he had yet

to discover the possibility of angles? Knowing angles,

he could probably tell in advance not a few of the proper-

ties of triangles, but can any one imagine, on the basis of

this information alone, the relations which enable us to

measure the heights of trees we have never climbed, or

the distances of sun and moon? On the contrary, the

history of the subject shows that the mechanist is now

able to predict the motions of bodies, and the properties

of configurations, not because he deals exclusively with

prediction, but because he has made certain valid as-

sumptions concerning space, and by deduction has dis-

covered their consequences. He deals with controlled

materials, but the trick of augury has no other secret

than knowledge.

THE SPECIFICALLY BIOLOGICAL PROBLEM

If we reject the classification of biology necessitated

by a belief in the fundamental disorderliness of its phe-

nomena, two mutually exclusive views remain to be con-

sidered. Fortunately for the biologist the discord be-

tween them is quite unnecessary, for biology may be

physics and chemistry and autonomous at the same time.

Some of the most fruitful and illuminating discussions

in recent years have emanated from biological chemists

and physicists, and it is hard to follow the literature on

these subjects without sensing the enormous possibili-

ties with which it is freighted. It must not be supposed, -

however, that proof of the purely physical-chemical na-

ture of vital processes will show that living things are in

any way different than they really are. Whether analy-

sis can subtract qualities from things certainly seems

an idle question, yet we are constantly being told that the

reduction of the phenomena of life to a chemical-physical

basis will demonstrate that living things are, after all,

not alive! ee

Anatomical and histological analysis of a horse is 1m-

716 THE AMERICAN NATURALIST [ Von. XLVI

capable of showing that this animal is a cow. Even if we

reduce its tissues to their constituent chemical elements,

and, not content with this, continue until we have shown

that a horse is entirely composed of electrons, and their

activities, how could this show that a horse is not a horse?

If therefore resolution can detract nothing from the

things analyzed, it is clear that if these are in any way

unique, they will be no less so after this proeess than be-

fore. The only question which can be at issue is whether

living things are, or are not, unique. To this only an

affirmative answer is possible.

To reason with defectives is unprofitable for they have

no organ with which to perceive the qualities by which

we differentiate between the organic and the inorganic.

If we ask ourselves how we make this distinction we

naturally think of the fact that living things are ma-

chines with the power, as Loeb puts it, of automatic self-

preservation and reproduction. All the wonderful proc-

esses for which in the aggregate this simple formula

stands divide animals and plants sharply from matter

not alive and constitute the specific basis for the auton-

omy of our science. This autonomy is nothing meta-

physical, or absolute, but practical, like the autonomy of

physics, chemistry, astronomy and geology.

HistorrcaL BACKGROUND OF THE POSTULATED ABSOLUTE

AUTONOMY

In their analyses of living things, modern biologists

make use of only one practical method, but they apply it

from two distinct points of view, and since the signifi-

cance of phenomena in general depends on the point of

view, the whole meaning of the science hangs in the bal-

ance. The validity of these theoretical standpoints,

therefore, should be tested as carefully as the proposed

site of an observatory.

Unfortunately the issues at stake can not be properly

apprehended without some knowledge of their history.

To begin with Aristotle, and the few Ionians and Eleat-

No. 552] AUTONOMY OF BIOLOGICAL SCIENCE {LT

ics who preceded him, however, does not give us the

needed historical background, for the impression that

Aristotle was a primitive man, or that science was born

in Greece, is surely wrong. Scientific knowledge began

with the human race.

Although the thoughts of early men are for the most

part unrecorded, study of the primitive men living to-day

shows conclusively that the problem of the origin and

nature of life is realized by the savage. In the lore of

medicine men, magicians and seers, scientific knowledge,

theories and beliefs, fuse into an alloy which, despite the

varied conditions of its genesis and growth, presents

remarkable homogeneity. In this cultural amalgam the

attempt is made to explain the difference between a dead

man and a live one, by means of ‘‘a thin unsubstantial

human image, in its nature a sort of vapor, film or

shadow; the cause of life and thought in the individual

it animates; independently possessing the personal con-

sciousness and volition of its corporeal owner, past or

present; capable of leaving the body far behind to flash

swiftly from place to place; mostly impalpable and in-

visible, yet also manifesting physical power, and espe-

cially appearing to men waking or asleep as a phantom

separate from the body of which it bears the likeness;

continuing to exist and appear to men after the death of

that body; able to enter into, possess and act in the bodies

of other men, of animals and even of things.’’ *

These conclusions, drawn from the experience of

dreaming, are not much more primitive than the opin-

ions prevalent during the middle ages and surviving in

the shadows of church spires to-day. Now and again,

however, revolutionary teachings arose, and the most

significant of these for our immediate purposes are the

doctrines of René Descartes.

In his splendid history of biological theories, Rádl?

has traced with considerable detail the fortunes of the

2 Tylor, Edward B., ‘Primitive Culture.’’

? Rádl, Emil, ‘‘Geschichte der Biologischen Theorien.’’

718 THE AMERICAN NATURALIST [ Vou. XLVI

controversy set going in 1644 by the ‘‘Principes de la

Philosophie ’’ at a time when practically all men were

vitalists. During the seventeenth and eighteenth cen-

turies this contest engaged the ablest minds, yet mechan-

ism achieved no decisive victory, but only an increase in

the number of its followers, and the substitution of the

original soul in vitalism by the life force of Müller,

itself destined to elimination in the nineteenth century

by supersession, largely by neglect, and by direct experi-

ments on vital energetics.

Emil du Bois Reymond stands out as the champion of

mechanism during this period, although the limitations

of his materialism led him to classify the problem of life

with six other insoluble riddles. Lotze overthrew the

life force with arguments, substituted a purposeful pre-

formation in the germ, and protected it from further

harm by asserting that to inquire into its origin was un-

scientific. Fechner and Preyer attempted to clear the at-

mosphere by insisting that life is fundamental and the

real problem the origin of the inorganic. Virchow con-

tributed the idea of a mechanism superimposed upon

that already known, and this in the hands of his successor

Rindfleisch became a theory of atomic consciousness. In

the seventies, however, ghostly voices fell upon deaf

ears, for under the leadership of Darwin a seemingly

satisfactory natural explanation of adaptation forced

the mechanistic pendulum to its highest point.

While this period of scientific development proved

fatal to naturalistic vitalism, metaphysical not only sur-

vived, but during the latter-day Darwinian decadence

and reconstruction has again emerged, leaving behind

some of the erudities of its forerunners, and apparently

purged of ghosts. A change of names, however, does

not constitute a change of nature. The ghosts, more

rarefied than ever, are with us still, only to-day we call

them Entelechies, Dominants, Psychoids and Elan Vital.

No. 552] AUTONOMY OF BIOLOGICAL SCIENCE 719

Awnatysts oF Nro-VITALISM

Plate* finds in neo-vitalism four fundamental postu-

lates about which discussion must necessarily center.

These propositions are as follows:

I. Neither now nor in the future can the organism be

explained by chemistry and physics without a remainder.

II. There is an absolute distinction between dead and

living matter; in the inorganic world the law of causa-

tion holds, but in the organic causation holds together

with a unique law.

III. The uniqueness expresses itself in this, that every

organic process is final (teleological), that is, governed

by immanent purposefulness. |

IV. The cause of this finality, in so far as the vitalists

are not agnostic, is (a) a psychical factor; (b) a meta-

physical factor.

PosTULATE I |

Neither now nor in the future can the organism be

explained by chemistry and physics without a remainder.

Nothing could be more physical and chemical than the

analysis of the whole universe into a system of electrons.

When such resolution has been accomplished and every

known chemical element has been shown to be a special

case of corpuscular movement, the organic world and all

that characterizes it will be expressible in terms of elec-

trons if this mode of expression should appear service-

able. Would it not remain true, however, that hydrogen

is hydrogen, and oxygen, oxygen? Even if these gases

were proved to be configurations of essentially similar

corpuscles, they would nevertheless continue to be indi-

vidually different, and those so inclined would find it

possible to found separate sciences of hydrogenology

and of oxygenology, and these subjects would be auton-

omous. Does any one conclude from this that the me-

chanist is not fit to deal with these matters? Or that his

methods are fundamentally inadequate? Yet the argu-

*Plate, Ludwig, tt Darwinsches Selektionsprincip,’’ 3d ed.

720 THE AMERICAN NATURALIST [Vou. XLVI

ment of those who would cast mechanism out of biology

is identical. Resolution leaves intact uniqueness wher-

ever found, and the declaration that this is true of the

organism is a platitude.

PostūLATE IT

There is an absolute distinction between dead and liv-

ing matter; in the inorganic world, the law of causation

holds, but in the organic, causation holds together with

a unique law.

The second part of this proposition will be considered

in connection with postulate III. To the first part the

mechanist subscribes heartily, but adds that in his ex-

perience the distinction between hydrogen and oxygen

is equally absolute.

Postunate IIT

The uniqueness expresses itself in this, that every or-

ganic process is final (teleological) ; that is, governed by

immanent purposefulness.

In discussing postulate ITI, all that is needed is (a) to

sound its logical consequences; (b) to inquire how it

agrees with observations on individual and racial final-

ity; and lastly, (c) to expose the psychology of the teleo-

logical idea itself.

(a) From the harmony between the organic and the

inorganic, Driesch concludes that ‘‘nature is nature for

a purpose.’’ If the whole universe, however, is governed

by immanent purposefulness what becomes of the dis-

tinction between the organic and the inorganic? Ina

purposive system the teleological nature of any particu-

lar event or group of events can not be inferred, for pur-

posefulness can only be recognized by comparison with

purposelessness. Thus general teleology denies the ex-

istence of half the materials for the inference of the very

thing on which it bases itself, and with the best inten-

tions in the world, and without in any way seeming to

sense it, vitalists themselves have not only disarmed

No. 552] AUTONOMY OF BIOLOGICAL SCIENCE 121

teleology in the realm of the living, but have made the

principle scientifically impossible.

(b) Were every organic event final or purposeful,

functional adjustment, training and education would be

unnecessary and impossible. Jennings? tells us:

How the relations that impress us as teleological were brought about,

constitutes undoubtedly a set of most difficult problems. But to keep

us from despairing, we find this process taking place in the lives of

individuals in a manner that can readily be studied. This is in the for-

mation of habits. In the formation of habits, we see that the organism

at first does not react in a way that impresses us as teleological, while

later it does, and we can watch the process change from one condition

to the other, and discover how it is causally determined. Since then a

method of action that appears to us teleological is produced in an

intelligible way under our very eyes, in the lifetime of the individual,

there is no reason why we may not expect to find out how teleological

relations have been brought about in the life of the race when we have

actually made a start in the study of the physiology of racial processes.

past ” reappears again in the future.

The ability to make functional adjustments of this

character is only a special case of automatic self-preser-

vation, and is found in all organisms because those de-

void of it are for this very reason eliminated and conse-

quently remain largely unknown. Paleontology 1s the

science that deals chiefly with these failures. How many

organisms have been unable to make the necessary ad-

justments is attested by the great number of extinct ani-

mals and plants; how many are failing to-day is shown

by every rapidly vanishing species, as well as by many

experiments and special observations. Several of the

mutants of de Vries have for one reason or another

‘c Diverse Ideals and Divergent Conclusions in

i :

Jennings, Herbert S., 1» American Journal Psychol-

the Study of Behavior in Lower Organisms,

ogy, Vol. XXI. :

€ Loeb, Jacques, ‘‘The Mechanistic Conception of Life,

Vol. LXXX.

”? Pop. Sci. Mo.,

722 THE AMERICAN NATURALIST [ Vou. XLVI

proved indurable, whereas Loeb* has pointed out that

faulty organisms must frequently arise, although we only

become aware of them under exceptional conditions.

Moenkhaus found ten years ago that it is possible to fertilize the

egg of each marine bony fish with sperm of practically any other marine

bony fish. His embtyos apparently lived only a very short time. This

year I succeeded in keeping such hybrid embryos between distantly

related bony fish alive for over a month. It is therefore clear that it

is possible to cross practically any marine teleost with any other.

The number of teleosts at present in existence is about 10,000. If

we accomplish all possible hybridization 100,000,000 different crosses

will result. Of these teleosts only a very small proportion, namely,

about one one-hundredth of one per cent., can live. It turned out in

my experiments that the heterogeneous hybrids between bony fishes

formed eyes, brains, ears, fins and pulsating hearts, blood and blood

vessels, but could live only a limited time because no blood circulation

was established at all—in spite of the fact that the heart beat for

weeks—or that the circulation, if it was established at all, did not last

long.

The possibility of hybridization goes much further than we have

thus far assumed. We can cause the eggs of echinoderms to develop

with the sperm of very distant forms, even mollusks and worms

(Kupelwieser) : but such hybridizations never lead to the formation of

durable organisms.

It is therefore no exaggeration to state that the number of species

existing to-day is only an infinitely small fraction of those which can

and possibly occasionally do originate, but which escape our notice

because they can not live and reproduce. Only that limited fraction

of species can exist which possesses no coarse disharmonies in its auto-

matie mechanism of preservation and reproduction. Disharmonies and

faulty attempts in nature are the rule, the harmonically developed

systems the rare exception. But since we only perceive the latter we

gain the erroneous impression that the “ adaptation of the parts to the

plan of the whole” is a general and specifie characteristic of animate

nature, whereby the latter differs from inanimate nature.

the structure and the meclianism of the atoms were known to us

we should probably also get an insight into a world of wonderful

j harmonies and apparent adaptations of the parts to the whole. But in

this case we should quickly understand that the chemical elements are

only the few durable systems among a large number of possible but not

durable combinations.

ties of the assumption, we can be certain that the idea of

No. 552] AUTONOMY OF BIOLOGICAL SCIENCE 123

teleology would never have entered the biologist’s head `

were he not himself a living thing. Since this is the case,

however, his interest in life exceeds all others, and he

attends to the processes that make life possible only be-

cause of their resultant. Inasmuch as the latter occu-

pies the focus of his mind, he wrongfully reasons back-

ward from results to processes, and finding in these none

that might have rendered the cherished product im-

possible, concludes that the processes were all along

aiming at what, from his standpoint, is the end. Clearly

the conclusion has only an anthropocentric basis.

PostuLaTE IV

The cause of this finality, in so far as the vitalists are

not agnostic, is (a) a psychical factor; (b) a metaphys-

ical factor.

Since biological finality is an anthropomorphism, a

discussion of the supposed teleological factors is futile.

Inasmuch, however, as psycho-vitalism has its counter-

part in psycho-mechanism, the fallacy common to both

may be pointed out.

(a) To reflect mind oi the cell, and so reflected to

use it as an explanation of what the cell does, is the

method of primitive animism. Quite apart from the fact

that the existence of mind, so far, at least, has been dem-

onstrated only in the case of certain higher animals, but

not at all for the lower, or the developmental stages of _

the higher, as an explanation it can have no title to

serious consideration since it is itself one of the elements

of the automatic self-preservation which it is the aim of

biology to analyze. To interpret something we do not

understand in terms of something else which at present

we understand even less, may give temporary comfort to

some minds, but the ideals of scientific explanation call

for the reverse process.

(b) The difficulties of Driesch’s style are > such that

many biologists refuse to read his books. For this rea-

ii. Slee THE AMERICAN NATURALIST [ Vou. XLVI

son I have made from one of them’ a series of extracts

to serve as illustrative material. The italics are not

mine.

DriescH’s ENTELECHY

Entelechy or the psychoid has nothing of a “ psychical” nature.

We indeed are in a rather desperate condition with regard to the

real analysis of the fundamental properties of morphogenetic, adaptive,

and instinctive entelechies: for there must be a something in them

that has an analogy, not to knowing and willing in general, as it

may be supposed to exist in the primary faculties of psychoids, but to

the willing of specific unexperienced realities, and to knowing the

specific means of attaining them. (P. 142.

To build up the organism as a combined body of a typical style is

the task of entelechy; entelechy means the faculty of achieving a “ forma

essentialis ”; being and becoming are here united in a most remarkable

manner; time enters into the Timeless, i. e., into the “idea” in the

sense of Plato. (P. 149.) _

There is first the entelechia morphogenetica, and after that the

entelechia psychoidea and the latter may be discriminated as governing

instinets and actions separately. Furthermore the different parts of the

brain, such as the hemispheres and the cerebellum in vertebrates, may

be said to possess their different kinds of entelechy.

In fact we may speak of an order concerning the rank or dignity of

entelechies, comparable with the order of ranks or dignities in an army

or administration. But all entelechies have originated from the pri-

mordial one and in this respect may be said to be one altogether.

Now the primordial entelechy of the egg not only creates derived

entelechies, but also builds up all sorts of arrangements of a truly

mechanical character; the eye, in a great part of its functioning is

nothing but a camera obscura, and the skeleton obeys the laws of inor-

ganie statics. Every part of these organie systems has been placed by

entelechy where it must be placed to act well in the service of the whole,

but the part itself acts like a part of a machine.

So we see finally that the different forms of harmony in the origin

and function of parts that are not immediately dependent on one

another, are in the last resort the consequence of entelechian acts. The

entelechy that created them all was harmonious in its intensive mani-

oldness; the extensive structures which are produced by it are therefore

hiornoniits too. In other words there are many processes in the

organism which are of the statical- teleological type, which go on

ee or purposefully on a fixed machine-like basis, but entelechy

esch, Hans, ‘‘The Science and Philosophy of the Organism,’’ Gif-

ford Teia, 1908.

No. 552] AUTONOMY OF BIOLOGICAL SCIENCE 725

has created this basis, and so statieal teleology has its source in dynam-

ical teleology.

e now see the full meaning of the statement that entelechy is an

“intensive manifoldness” realizing itself extensively; in other words,

we know what it means to say that a body in nature is a living organ-

ism; we have given a full descriptive definition of this concept. (Pp.

150-151.)

Any single spatial occurrence induced or modified by entelechy has its

previous single correlate in a certain single feature of entelechy as far

as it is an intensive manifoldness. (P. 154

Entelechy may be aroused to sipnifeckation by a change in bodily

nature, such as is effected by fertilization, or by some operation, or by

some motor stimulus; on the other hand, entelechy may on its own part

lead to changes in bodily nature. (P. 156.)

It is the essence of an entelechy to manifest itself in an extensive mani-

foldness: all the details of this extensive manifoldness depend upon the

intensive manifoldness of the entelechy, but not upon different spatial

“ causes.” 15

Entelechy lacks all the characteristics of quantity; entelechy is order

of relation and absolutely nothing else; all the quantities concerned in

its manifestations in every case being due to means which are used by

entelechy, or to conditions which ean not be avoided. (P. 169.)

Entelechy, as far as we know, at least, is limited in its acting by many

specificities of inorganie nature, among which are the specificities

included under the phrase “ chemical element.” (P. 179

Entelechy is also unable to cause reactions between chemical compounds

which never are known to react in the inorganic world. In short

entelechy is altogether unable to create differences of intensity of any

kind.

But entelechy is able, so far as we know from the facts concerned in

restitution and adaptation, to suspend for as long a period as it wants

any one of all the reactions which are possible with such compounds as

are present, and which would happen without entelechy. (P. 180.)

Entelechy though not capable of enlarging the amount of diversity of

composition of a given system, is capable of augmenting its diversity

of distribution in a regulatory manner, and it does so by transforming

a system of equally distributed ener into a system of actualities

which are unequally distributed. (P. 1

Entelechy . . . is a factor in nature ia acts teleologically. It is an

intensive manifoldness and on account of its inherent diversities it is

able to augment the amount of diversity in the inorganie world as far

as distribution is concerned. It acts by suspending and setting free

reactions based upon potential differences asi There is noth-

ing like it in inorganic nature. (P. 205

726 THE AMERICAN NATURALIST [ Vou. XLVI

Entelechy is an elemental factor of nature conceived to explain a certain

class of natural phenomena. (P. 206.

You may say if you like that entelechy, when turning a mass particle,

acts upon it at right angles to its path—this kind of action requiring

no energy, but even thus there would be only a pseudo-obedience to the

laws of real mechanics, since entelechy must be regarded here as non-

energetical and as interfering with inertia at the same time. (P. 223.)

Entelechy is affected by the accomplishment of its own performance, in

acting as well as in morphogenesis. (P. 228.

In order that adaptation may happen, the fundamental state of the

organism must be disturbed in its normality; this fact affects or calls

forth entelechy. (P. 229.)

Entelechy is affected and thus called into activity by changes of any

normality governed by it which are due to external causes and these

changes do not affect entelechy as a mere sum of changed singularities,

but as changes of normality as a whole. (P. 232.)

Entelechy is affected by and acts upon spatial causality as if it came

out of an Br dimension; it does not act in space, but it acts

into space. (P. 235.)

Entelechy is an agent acting manifoldly without being itself manifold

in space or extensity. Entelechy then is only an agent that arranges,

but not an agent that possesses quantity. (P. 250.)

Entelechy is something different from matter and altogether opposed to

the causality of matter. (P. 255.)

May not entelechy be called a “substance” in the most general philo-

sophical sense of the word, that is, in the sense of a something irredu-

cible, which remains the always unchangeable bearer of its changeable

qualities. (P. 256.)

Entelechy has the power of preserving its specifie intensive manifold-

ness in spite of being divided into two or more parts. (P. 257.)

Entelechy therefore can not possess a “ seat.”

At present the question whether entelechy is a “ substance ” must remain

as open as the previous question about the relation of entelechy to

causality. . . . Entelechy was a kind of “ quasi” causality, and now

may be said to be an enduring “ quasi-substance.” (P. 260.

Entelechies, though transcending the realm of the Imaginable, do not by

reason of their logical character as such form constituents of meta-

physies in the sense of something absolute and independent of a sub-

ject. (P. 320.)

Entelechy is alien not only to matter but also to its own material

purposes. (P. 336.)

Mir wird vor alle Dem so dumm

Als ging mir ein Mithlrad im Kopf herum!

No. 552] AUTONOMY OF BIOLOGICAL SCIENCE 727

CONCLUSION

I have tried to show that biological events are orderly;

that a distinct problem guarantees the autonomy of the

science; that the application of physical and chemical

methods has no shortcomings specifically different from

those met with when applied to the inorganic, and finally

that vitalism in addition to being unnecessary is absurd.

The question whether the modern outburst of metaphys-

ical biology, a movement which finds favor among phi-

losophers and psychologists, and has no small following

among zoologists and botanists, is not, despite its obvious

faults, sound in motive, remains to be answered. Me-

chanical methods, even if applicable to vital events no

less than to any others, might nevertheless possess an

inherent weakness discoverable only when enlisted in

biological service. The only reply possible to this ques-

tion is that they are the best methods which human

beings can devise, for their excellencies are grounded in

our structure, their deficiencies in that of the world out-

side.

It has been pointed out over and over again that the

explanations of science never amount to more than the

enumeration of the conditions under which the events

in nature take place. With ultimate explanation science

does not deal, not because men of science do not want to,

but because in their experience nature contains nothing

ultimate. The failure, therefore, of science to give us

more than it does can be held up as a fault only by those

who are dissatisfied with the structure of the universe.

For this feeling intellectual hygiene is the only cure.

If the limitations of scientific methods are to be found

in the limitations of a limitless universe, their excellen-

cies, as instruments for the automatic preservation of

life, are to be found in ourselves, for the mechanical

symbols by the aid of which natural phenomena are in-

terpreted are the easiest for us to use. The value of

these symbols depends on our power to visualize, and

728 THE AMERICAN NATURALIST [ Vou. XLVI

visualization depends on sight. Is it without signifi-

cance in this connection that the eye begins in the embryo

earlier than any other receptor of special sense, or that

sight, except perhaps by a few poets and musicians, is

acclaimed the most priceless of all our senses?

If we lived in a world of phantasms, the value of sight

would largely disappear, for, as Berkeley® has pointed

out, it is an organ of anticipatory touch upon which de-

pends our ability to avoid harmful collisions, and to

bring about desirable ones. From the very beginning

of our lives we see and deal with visible objects. Is it

strange then that we should attempt to express all our

experience in terms of the language which by our very

structure and history is the most used and hence the most

efficient medium of interpretation we possess?

Modern energetics has indeed discarded solid mole-

cules and atoms, and has replaced these by constellations

of electrons, yet even if the electrons are nothing more

than electrical charges, they are believed to possess mass,

and to have certain properties in common with visible

things. Does not the physicist still draw pictures on the

wall to make clear what he means? Is nota picture a vis-

ual symbol by the aid of which we understand a less fa-

miliar one? Escape is impossible, for mechanistic sym-

bolism is grounded in our very nature, and for this rea-

son its employment rises to the dignity of amoral act, for

it involves neither more nor less than the application of

our best capabilities to the best of all purposes—the in-

terpretation of nature.

* Berkeley, George, ‘‘An Essay Towards a New Theory of Vision.’’

THE SPAWNING HABITS OF THE SEA LAMPREY,

PETROMYZON MARINUS!

DR. L. HUSSAKOF

AMERICAN Museum or NATURAL HISTORY

THE spawning habits of several species of lamprey are

known from observations which have been made in both

Europe and America.?_ Those of the sea lamprey, Petro-

myzon marinus, however, have not been studied, not-

withstanding that this is the largest of the lampreys and

is common to both sides of the Atlantic. It is merely

known that this species ascends rivers for the purpose of

spawning; and that the ‘‘fish’’ transport stones in build-

ing their nest much like other lampreys (Burroughs,

’83; Holder, ’85). In 1883 a French observer, L. Ferry

(83), noted the development of sea lamprey eggs taken

directly from a female specimen. He concluded that the

eggs must already have been fertilized, and hence that

fertilization in the lampreys is internal. This conclusion,

in the light of the careful observations on the spawning

of various lampreys, especially Petromyzon planeri and

Lampetra wilderi, is undoubtedly erroneous. Moreover,

the discovery that lamprey eggs can develop partheno-

genetically (Bataillon, ’03), affords a simple explana-

tion of the facts recorded by Ferry. None the less the

was very desirable.

The observations recorded in this paper were made by

the writer on Long Island, June 1 and 2, 1911, while col-

lecting material for a group to represent the nesting

habits of the sea lamprey in the American Museum of

Natural History. The locality, Smithtown, on the Nis-

sequogue River, Long Island, was suggested to me by

*Read before the American Society of Zoologists, at Princeton, N. J.,

Dee. 27, 1911.

3 See annotated bibliography at end of paper.

- 129

730 THE AMERICAN NATURALIST [ Vou. XLVI

Professor Bashford Dean, who had learnt of it through

Dr. Tarleton H. Bean.

Locality and Date of Observation.—At the date of

these observations, June 1 and 2, 1911, lampreys had been

seen in the Nissequogue River for several days. A num-

ber of abandoned, partly scattered nests were also to be

found; hence June 1, appears to be toward the end of the

spawning season, which for Long Island must be put

down as the latter half of May.

Fic. 1. SEA LAMPREYS, Petromyzon marinus, on Nest. An exhibition

group, 4 by 5 feet, in the American Museum of Natural itary: prepared under

the piip of the writer.

The Nissequogue is a small stream which empties into

Long Island Sound. At the village of Smithtown, three

and a half miles from its mouth, it is shallow (a foot

or two deep), perfectly clear, and flows over a bed of

large, water-stained pebbles. Here and there are patches

of ‘‘river grass.’? The water is perfectly fresh here,

although still affected by the tide. A quarter of a mile

above and below the village bridge, the river grows

No. 552] THE SEA LAMPREY 731

deeper and muddier; my observations were therefore

confined to the pebbly portion, a stretch of about half a

mile. Here a dozen nests were found, four with lam-

preys on them, the others deserted and partly scattered

by the tide.

Nests——The nest of the sea lamprey is similar to

that of other species, but much larger. It is a circu-

lar depression in the river bed, two to three feet in

diameter. One that was measured was two feet three

inches across, and six inches deep in the center. The

Fie THREE SPECIMENS OF Petromyzon marinus ON A Nest. Instantaneous

photograph taken without special apparatus A bright sunlight, at low tide; with

y three or four inches of water above the “fish.” One male and two females.

(Net EE

nests are easily recognized, eyen at a distance of

several feet, by the large number of whitish quartz peb-

bles which have been uprooted and turned with their

clean faces up. They are built at random anywhere in

the river: near the bank, in the shade of overhanging

trees; in the middle of the stream, exposed to the glare

of the sun; or even, as with the nest shown in the figures

732 THE AMERICAN NATURALIST [Vou. XLVI

(Figs. 1 and 4), partly under a log. Occasionally two

nests adjoin so that their peripheries overlap.

Standing in the water close to a nest, one may observe

minutely every movement the lampreys make. One may

even stroke them or lift them by the tail without disturb-

ing them. A ‘‘fish’’? must be raised to a considerable

angle before it will loosen its hold on the stone to which

it clings, and dart away; and then it will go only a short

distance, fifty or a hundred feet, and seek refuge under

the ‘‘river grass.”

The manner of building the nest is quite like that of the

brook lamprey (Lampetra wilderi), as de-

scribed by Gage (’93), and by Dean and

Sumner (’97). But owing to the large

size of the species all the processes are

writ large, as it were, so that one can see

the purpose of every movement. Build-

ing the nest consists in carrying the

pebbles and stones out of a circular area

until a basin-like depression is formed.

As the work proceeds the finer material

in the interstices between the pebbles

gradually accumulates, so that the bottom

of the nest becomes covered with sand and

fine gravel. The stones are seized with

the circular mouth to which they cling en-

tirely by suction. The ‘‘teeth’’? play no

Fic. 3. Freshly part in this work, as may be proved by ex-

He amprey cdas perimenting with the freshly dead ‘‘fish.’’

the vacuum pro- By pressing the mouth of such a ‘‘fish’’

a agian against a stone, it may be made to hold on

pated i "so tenaciously, that by lifting the stone

one lifts the fish (Fig. 3). A vacuum is

produced inside the buccal funnel, and this is the imme-

diate cause of the hold. In carrying stones out of the

nest, the procedure varies with the size of the stone.

Small stones, an inch or two across, are picked up in the

®©

“

No. 552] THE SEA LAMPREY 733

mouth and carried out. Larger stones, firmly rooted in

the bottom, require considerable effort to be dislodged;

the stone is tugged upward, the lamprey receding back-

ward in a straight line. Sometimes instead of pulling

backward, the lamprey charges head-on and pushes the

stone in front of it up the incline, the body remaining

rigid and acting as a lever, while the tail is lashed vio-

Fie, 4. Sa THREE SPECIMENS AS SHOWN IN FIG. 2, PHOTOGRAPHED

SHORTLY AFTER THEY WERE TAKEN FROM THE Nest. Upper two, females;

lowest one, a male. The stones in lower half of photograph were picked up

just as they were carried by the lampreys out of the nest. The half brick

shown in the picture weighs 840 grams.

lently to gain a firmer support. Some of the larger

stones carried by the lampreys out of the nest (Fig. 4),

were picked up just as they were released from the

mouth; they were found to weigh (in air) from 145 to

840 grams. `

The building and improving of the nest go on continu-

ously between intervals of mating. Both the male and

the female take part in this work. On one nest there

were observed a male and a female; they were joined now

and then, for some minutes, by a second female which

734 THE AMERICAN NATURALIST [ Vou. XLVI

had been for some time by herself on an adjoining nest.

During the time the three ‘‘fish’’ were on the one nest

(Figs. 2 and 5) they all took part in repairing it, in

the intervals between mating—the male apparently not

distinguishing between the female of his own nest and

the intruder. In two other cases there was one indi-

vidual to a nest. After carrying a stone out the lamprey

immediately returns for another. This is repeated a

number of times and then the lamprey clings to a stone

apparently exhausted (Fig. 4). Now and then the tail is

lashed against the sides of the nest to pad it down. When

on a nest by itself, a lamprey occasionally wanders a

distance of some feet—even several hundred feet—but

invariably returns to continue its nest-building. These

wanderings are perhaps for the purpose of finding a

mate.

Mating.—The method of copulation is similar to that

of the brook lamprey, Lampetra wilderi, as described by

Dean and Summer (’97); and it is unnecessary to re-

describe it here. I will merely comment on a few de-

tails. The female must cling to a large stone in the

nest in order that copulation take place. The male

seizes her by the top of the head. In copulo, the two are

arranged so as to form an ellipse. The caudal portion

of the male is applied immediately back of the first dor-

sal of the female, and curved in a loop around her body.

Several authors have referred, in the case of both Amer-

ican and European lampreys, to the vibration of the

posterior portions of the ‘‘fish,’’ in copulo. In the sea

lamprey this vibration may be observed very closely. It

lasts two or three seconds. It begins slowly, gradually

increases in frequency until it reaches an exceeding ra-

pidity of vibration, then subsides by a few slow beats.

The motion strongly suggests the vibration of a rattle-

snake’s tail in the warning pose. Indeed while watching

the lampreys one can hardly keep from imagining the

sound which ought to accompany the lampreys’ vibra-

No. 552] THE SEA LAMPREY 735

tions, so similar is the movement to that of the rattle-

snake’s tail.

As to the length of time ‘‘fish’’ on a nest continue to

spawn, I was able to make some observations. The

nest shown in Figs. 1 and 4 was observed continuously

for over four hours, from 10 a.m. until after 2 p.m.; and

during that time copulation took place at intervals

of from a few to ten minutes; and in all probability

would have continued several hours longer had the

THE SAME NEST AS IN FIG. 2, SHOWING TWO OF THE SPECIMENS in

the female. The second female is seen clinging to a stone. (Not r AE EERE

‘“‘fish”’ been left on the nest. Both became gradually

more and more scarred from seizing each other with

their mouths: round pale wounds stood out clearly

against the blue-black of the head of the female where

the male had repeatedly seized her; and large whitish

wounds could be seen on her back, especially posterior

to the first dorsal fin. The male likewise was scarred in

several places on the head and back. These scars are

736 THE AMERICAN NATURALIST [ Vou. XLVI

greatly augmented through continual rubbing against

stones, padding down the nest, ete.

Fate of Sea Lampreys After Spawning—From the

facts at hand, it appears that lampreys that go up the

river to spawn do not again return to the sea, but die

shortly after spawning. I found two dead, badly

scarred, spent lampreys in the river not far from de-

serted nests. One was in the shade of tall grass near

the bank, the other tangled in weeds and twigs in the

middle of the river. Both had been rasped, apparently

for food, by other lampreys. Burroughs (’83), also re-

cords that it is not unusual to find dead lampreys in

June.

The causes of the death of these lampreys—and in-

deed of all anadromous fishes—are still rather obscure.

Death is probably chiefly due to the cycle of katabolic

processes initiated on the maturing of the gonadial

products. Besides this at least two other causes must

be regarded as contributary: first the greatly lessened

vitality due to the constant exertion in uprooting and

transporting stones. Lampreys thus weakened become

the prey of other lampreys. Secondly, the numerous

sears or wounds which they inflict on one another in

mating allow ‘‘fungus’’ to invade, and ultimately to de-

stroy, their tissues. All three of these causes, probably,

play a part in causing the death of the sea lampreys after

spawning.

Remarks on the Senses and Mentality of the Sea Lam-

prey.—The behavior of the lampreys was carefully noted

to see in how far their senses come into play in building

the nest and in other activities. The general impres-

sion was that the sea lamprey is guided by touch more

than by any other sense. Sound does not disturb them

while on the nest: one may carry on a conversation right

over a nest without in the least affecting them. Indeed

one lamprey that was building a nest under a wooden

bridge was not disturbed by the clattering of automo-

biles over it. This insensitiveness to sound may mean,

No. 552] THE SEA LAMPREY Tal

however, merely absorption in the work of nest-build-

ing, and not that the lampreys are insensible to this

stimulus.

The eyes of lampreys in the water shine like black

beads; but they are not very sensitive. If one meets a

lamprey swimming toward him in the river, it will come

almost right up before it will discover the person and

turn aside.

Many of the movements of the sea lamprey on the

nest are purposeless—as was noted also for the brook

lamprey by Dean and Summer (’97). Thus a lamprey

will sometimes pick up a stone outside the nest, carry

and drop it into the nest; or while carrying out a stone,

will drop it half way up the side of the nest. It will tug

at a large stone which it cannot possibly dislodge, or at

a log, in an effort to drag it out of the nest, and will

repeat this again and again, without profiting in the least

by previous failures. On the whole one has a feeling

that the lamprey possesses a very low mentality even

as compared with fishes.

ANNOTATED BIBLIOGRAPHY

The following list includes all the papers I have been able to find that

deal with the spawning habits of lampreys. Those having to do with the

cytology of fertilization are listed in Ziegler’s text-book referred to below.

Bataillon, E.

1903. La segmentation parthénogénétique expérimentale chez les œufs

de Petromyzon planeri. Comp. Rend. Acad. Sci., Vol. 137, pp.

79-80.

Carried embryos as far as the blastula stage—‘‘en plongeant

et maintenant les œufs dans des solutions de saccharose à 5 ou

6 pour 100 ou dans des solutions isotoniques de NaCl.’’

Burroughs, John.

1888. A lamprey’s nest. The Century Magazine, XXV, p. 457.

Observed Petromyzon marinus spawning in a creek. Describes

their mode of transporting stones; their indifference to an ob-

server at close range; but does not describe the nest, nor appar-

ently recognizes the purpose for which the stones are transported.

The female is the larger of the two. ‘‘In June it is not unusual

to find their dead bodies in the streams they inhabit.’’

738 THE AMERICAN NATURALIST [Von XLVI

Dean, Bashford, and Sumner, Francis B.

1897. otes on the Meroe habits: of the brook lamprey (Petro-

n wilderi).. Trans. N. Y. Acad. Sci., XVI, pp. 321-324,

PL VII.

Detailed observations on manner of building nest, on copula-

ion, and general behavior. Contains the best figure extant o

lampreys on nest.

Ferry, L.

1883. Sur la lamproie marine. Compt. Rend. Acad. Sci., pp. 721-723.

Translated, in part, in Ann. Mag. Nat. Hist., (5), II, p. 388

(May, 1883

A female sea lamprey, taken by a fisherman while i to

his boat, was opened, and its ova put into a large bas It

rained at the time and the basin became partly filled with eae

After twenty days the eggs hatched into perfect larve. Ferry

era ‘‘Il resort de ce fait que les œufs pris dans le ventre

a Lamproie étaient déja ng ndés et avaient dû l’étre dans

‘Sateen de l’animal’’ (p. 722).

Gage, Simon H., and Meek, Seth E.

1886. The lampreys of Cayuga Lake (abstract). Proc. Amer. Assoc.

Adv. Sci, XXXV, p. 269.

Brief tafermnes to nests and to length of breeding season,

which is said to last ally eae months (May and June).

Gage, Simon H.

1893. The lake and brook lampreys of New York, especially those

of Cayuga and Seneca: Lakes. The Wilder Quarter-Century

Book. Ithaca. Pp. 421-493, Pls. I-VII.

Gives extended account of nest building and spawning of the

brook lamprey renee wilderi) and of the lake lamprey

(Petromyzon natar a color); discusses fate of lampreys

after spawning (pp. 4 Man). Figures two lake ATESA on a

nest, carrying aie vii, Fig. 39.

Herfort, Karl.

01.

Die Reifung und Befruchtung des Eies von Petromyzon fluvia-

tilis. Arch. ae mikrosk. Anat. u. Entwickl., Vol. 57, pp. 54-

95, Pis.

ape review ca some European papers on spawning habits

p. 55-57). For his own studies he fertilized the eggs arti-

fici aiy = 57-58).

Holder, Charles Frederick.

1885. The Abi aie eel and nest. In Marvels of Animal Life; 8°; New

York; pp. 5-8

Describes how Petromyzon marinus transports stones, but mis-

takes the mass of stones accumulated outside the nest, for the

nest itself. Quotes from an account of over fifty lampreys build-

ing near a dam in the Saco River, Maine. They dropped the

stones on the dam until it became covered over. This was errone-

ously interpreted to mean that the lampreys had built the dam.

A stone is sometimes carried by two lampreys.

No. 552] THE SEA LAMPREY 739

Kupper, Carl v., and Benecke, B.

1878, Der Vorgang der Befruchtung am Ei der Neunaugen. Fest-

schrift fiir Theodor Schwann. Kénigsberg.

Loman, J. C.

1910. De copulatie van Petromyzon planeri. Tijdschr. nederl. dierk.

ereen, (2), XII, p. vii.

A careful puniki of the spawning of Petromyzon planeri,

observed in a brook near Königsberg.

McClure, Charles F.

1893. Notes on the mad stages of segmentation in Petromyzon

marinus L. (americanus Le S.). Zool. Anz., XVI, pp. 367-

368; 373-376.

Collected thirty specimens from a river near Princeton, New

Jersey, between May 20 and June 1.

Müller, August.

1856. Ueber die Entwickelung der Neunaugen. Ein vorläufiger

ericht. Arch. f. Anatomie, Physiol. u. wissen. Medicin, Jahrg.

1856, pp. 323-339.

This is the earliest account of the breeding habits of the lam-

prey. The observations were made on the brook lamprey; some-

times ten or more were seen together tugging at, and transporting

stones. The object for which the stones were carried was, how-

ever, not made out. He made the discovery, by rearing Ammo-

cœtes, that they are the larve of lampreys.

F, Jaco

1903. An experimental study of the spawning behavior of Lampetra

Science, N. S., XVII, p. 529 (abstract).

“a constant relation between individual fish and indivdual

is determined not by character of

ir natural ee iat

: S. Bureau Fisheries, XXVII, pp. 43-68, Pls. iii-v.

Photograph of four Lampetra wilderi on a nest—P1. iii, Fig. 2.

Vejdovsky, F.

1893. O trenf mihule (Petromyzon planeri) [Die äussere Befruchtung

des Neunauges]. Sitzber. & königl. bohm. Gesell. Wiss. in

Prag. Math.-naturw., 1893, article XLIX, PL xviii.

Observed spawning process In an aquarium containing four

males and one female. Figures two specimens (Pl. xviii) in

ade but this figure does not represent them in their charac-

teristic attitudes.

ay Vieira, Lopes

= 1831. Remarks on the eggs and spawning-season of Petromyzon

| fluviatilis Linn. Ann. de Sciencias Natures, I, pp. ag !

Sea lamprey enters rivers of Portugal at end of December an

beginning of January.

740 THE AMERICAN NATURALIST [ Vou. XLVI

Yarrell, W.

1831. PRE on the Eggs and Spawning-season of Petromyzon

fluvia and P. marinus. Proc. agp ay of Sct. and Cor-

a Zon Soc. London, Part I, pp.

Examined ee es eto aac from March to

middle a ay. U April 19, there were more females than

males; thereafter aa cnbatinionsa females, two to one.

Specimens taken April 26, appeared ready to spawn. By May

10, nearly all examined had spawned. Seven specimens of P.

marinus were taken in the Severn on May 3—‘‘ about Pah time

they ascended that river for the purpose of spawning.’

Young, Robert T., and Cole, Leon J.

1900. On the nesting habits of the eae lamprey (Lampetra wilderi).

Amer, Naturalist, XXXIV, pp. —620.

Notes on nesting observed in pa small tributaries of the

Huron River near Ann Arbor, Michigan. Males precede females

pa beginning the nest. Nests are 74 inches in diameter and

uated anywhere in river.

sae nea Ernst

1902. Lehrbuch dee on Entwickelungsgeschichte der

niederen Wirbelti

Résumé (pp. 14-78) , and bibliography (pp. 74, 89-91).

SHORTER ARTICLES AND DISCUSSION

A SIMPLE TEST OF THE GOODNESS OF FIT OF

MENDELIAN RATIOS

In actual experimentation the so-called Mendelian ratios,

2k, 9:3:3, 9:3:4, 9:7, 15:1, 37:9: 9:9:3:3:3:1, otd, are

never exactly realized because of the errors of sampling TASER

in all statistical work. Notwithstanding this fact, the best the-

oretical formulæ must be selected on the basis of these mislead-

ing experimental results.

Now the test of the validity of any Mendelian formula is two-

fold: the number of individuals found should agree with the

number expected within the limits of experimental error,’ the

assumed germinal composition of the several groups of individ-

uals should be capable of substantiation from a study of the

soma of their offspring.

For the most part, Mondaini have been satisfied to judge

the goodness of fit of the theoretical frequency to the empirical

by inspection merely. More recently, however, attempts have

been made to apply scientific tests to this problem. The first

was that of Weldon,? but Professor Johannsen doubtless de-

serves the credit of having interested the few Mendelian workers

who have taken the pains to calculate probable errors in this

indispensable part of their work.

The test used by Professor Weldon and recommended in a

much extended form by Professor Johannsen? is essentially the

determination of the probable error of the number of individ-

uals in one of the subgroups by the formula

=Va XP X4,

where p is the chance of occurrence of an individual of any

class, g= 1 — p, and n is the number of individuals. Thus the

1 In some cases, valid reasons for discrepancy between calculated and

observed frequencies may be shown. These factors should then be taken

aF account in calculating the theoretical numbers.

n, W. F. R., ‘‘ Mendel’s Laws of Alternative Inheritance in Peas,’?

Sabet J: 228-254, 1902, especially pp. 233-234.

3 Johannsen, W., ‘‘Elemente der Exakten Erblichkeitslehre,’’ pp. 402-

410, 1909.

741

742 THE AMERICAN NATURALIST [Vou. XLVI

‘probable error’’ of the number of individuals of any class,

say p, is

Ep = .67449 \/npgq.

Now while Professor Weldon’s use of this formula for the

simple 3:1 ratios seems quite proper, the same can not be said

for Professor Johannsen’s generalization. This is true for three

reasons:

(a) The formula is valid only when neither n, p nor q is

small. In polyhybrid ratios p or q may be relatively small.*

It is then quite idle to use the probable error suggested, unless

n be large, which unfortunately is generally not the case.

(b) Even when p is not so low as to render the use of the

conventional formula for the probable error open to question,

it is very laborious to calculate the probable errors for the fre-

quency of each class.’

unjustified to test the validity of a given ratio by the determina-

tion of the probable error of one or of all of its individual com-

ponent groups. The random deviations of the class frequencies

are not independent, but correlated. We must have a usable

criterion of the goodness of fit of the theory to the data as a

whole.

Such a criterion was furnished several years ago by Pearson.’

Its applicability to the problem of testing the goodness of fit of

Mendelian ratios seems obvious, but since, as far as I can ascer-

tain, it has nowhere been applied to this problem, it seems

worth while to call the attention of students of genetics to its

usefulness.

xX = S{(0—c)?/c},

where o is observed frequency of any class, c is calculated fre-

quency on the basis of Mendelian theory and S indicates a

_ Summation for the several classes distinguishable in the ratio

under consideration.

P, a measure on the scale of 0 to 1 of the probability that

‘For example, Pap (loc. cit., p. 405) tables values for p = 3/4,

q= 1/4 to p = 63/64, q= 1/6

5 See, for instance, Ka pió given by Johannsen, loc. cit., p. 396

“Pearson, K., ‘On the Criterion that a Given System of Deviations

from the Probable in the Case of a Correlated System of Variables is Such

that it Can be Reasonably Supposed to have Arisen from Random Sampling,’’

Phil. Mag., 50: 157-175, 1900.

No. 552] SHORTER ARTICLES AND DISCUSSION 743 °

the deviations from the theoretical frequencies may be reason-

ably supposed to be due to the errors of sampling, may be cal-

culated from x? by formule which need not concern us here,

since its values for systems of frequency of 3-30 classes have

been tabled.” Hence the Mendelian has only the simple task of

calculating x? and looking up the value of P in Elderton’s tables.

Illustrations will make method of computation and usefulness

most clear.

ILLUSTRATION I, DOUBLENESS AND PLASTID COLOR IN STOCKS

Saunders, Journ. Gen., 1: 349-350, 1911

Obs. Cale. | o-c | (o-c)? (0-c)2/¢

Singles; White .4c...'. 1,666 1,615 51 2,601 1.611

Doubles, White......... 773 807 —34 1,156 1.433

Singles, Cream......... 790 807 = SOE 289 .358

3,229 | 3,229 | rE =3.402

Whence, from the tables in Biometrika, and by interpolation,

m= A P= eee

W238, Cam Pee ig5eso

Diff. = .087795

P = .223130 — .087795 X .402 —.1878.

Thus only in about one case in five would the errors of sampling

lead to divergences from theory as bad as this. The theory is,

as far as this evidence goes, possible, but certainly not demon-

strated.

ILLUSTRATION IJ. SEED FORM AND COLOR IN Pisum

Bateson and Killby, Report Evol. Com., 2: 77, 1905

Obs. | Calc.8 o-¢ | (0-¢)2/e

Round: Yalow- ei eee 4,926 4,883 +43 3787

Tinkled, Yellow. -e 1,656 1,628 +28 4816

Round, Gron: Pare ee 1,621 1,628 —7 .0301

Wimkled, Green.. ... 3.3503. 478 542 —64 7.5572

x? = 8.4476, P= .0384. Thus taking the data as they stand,

it is impossible to regard the 9:3:3:1 ratio as satisfactorily

* Pearson, loc. cit., gives a small table. A much more comprehensive one

is given by W. Palin Elderton, Bogie for Testing the Goodness of Fit of

Theory to Observation,’’ Biometrika, 1: 155-163, 1901.

3 These are not the calculated as given by Bateson and Killby,

but have been recalculated as closely as possible on the 9:3:3:1 ratio.

Theirs are nine seeds short.

744 THE AMERICAN NATURALIST [Vou. XLVI

describing the facts. But the great factor in the magnitude

of x’ is the deficiency in the wrinkled green seeds, and the

authors have suggested a reasonable biological explanation for

this deficiency.

ILLUSTRATION III. COLOR IN OATS

Nillson-Ehle, fide Baur. Einf. Exp. Vererbungsl., pp. 66-67

| Obs. | Cale. | 0-c! | (o-c)?2/e

Schwarsspelsig.................. 418 wo | 0095

Deepa a a 106 ee | 0095

Vepa, o an La 36 Sob ek | 0286

Thus x?=.0476 only. P is not tabled for x? < 1, since the

probabilities of such deviations being due simply to errors of

sampling are so enormously high. Theory and observation

could hardly agree more perfectly.

ILLUSTRATION IV. Bopy COLOR IN Drosophila

Morgan, Journ. Exp. Zool., 13: 35, 1912

obs. Cale. o-c (o-c)2/e

Me E gia a 525 529 —4 .030

Oe oe re 340 265 +75 21.226 -

MN Be a 194 265 -7i 19.023

x? =40.279

Here x? is over 40, the odds against the deviations, being due

to errors of sampling, are so enormously great that it is idle to

express them in figures. In short, the facts do not substantiate

the hypothesis, and Professor Morgan has himself suggested

possible reasons for the disagreement.

ILLUSTRATION V. PARTIAL GAMETIC COUPLING IN SwEET PEAS

Bateson, Saunders and Punnett, Rep. Evol. Com., 4: 11

Observed Calculated on | Calculated on

Number of (OG Bd Ot g ye Be ie d

Cases Basis Bas

Fore boae. o a 493 471 490

Furla, romad a 25 40 20

Red ee 25 40

Red. romid.. a 138 130 151

For the 7:1:1:7 basis, x’ = 12.7699, P=.0053. For the

15:1:1:15 hypothesis, x = 3.6375, P=.3086. Thus the

No. 552] SHORTER ARTICLES AND DISCUSSION 745

chances are about 995:5 or 199:1 against the validity of the

first hypothesis and only 69:31, or about 2:1, against the

second.

ILLUSTRATION VI. COLOR INHERITANCE IN Antirrhinum

Wheldale, Marryat and Sollas, Rep. Evol. Com., 15: 15

| Obs. | Cale. | o-¢ (0-¢)2/e

a CPCS ren ae E E R | 399 361 +38 4.000

E Maisa Genk: oe 122 120 + 2 .033

L RN iG ee ree 131 120 +1 .008

i Cri cola: a a 38 — 2 .100

Toa a cee ee a 88 120 —32 9,075

T ivory DE aa 35 40 — 5 .625

ELS ARES AE a rag 33 40 — 7 1.255

T. aopla aa T rE A us O T 19 14 +5 1.786

| 855 855 x? =16.852

Hence, P==.0185 or the chances are about 980 :20 against such

discrepancies being chance deviations from the theory. Thus

either the theory must be discarded or reasons for the discrep-

ancies found.

A conspicuous advantage of this method of Pearson is that in

its application the deviation of observation from theory for

each class and the amount which this discrepancy contributes

to x’ are under the worker’s eye.

If used with the caution that should be exercised in the draw-

ing of any conclusion from probable errors,® I believe that this

well-known criterion of pen of fit will prove most useful

to Mendelians.

i J. ARTHUR HARRIS

Some biologists apparently seem to feel that the calculation of a statis-

tical ‘‘probable error’’ covers all the biological sins which may be com-

mitted in the collection or manipulation of their data.

NOTES AND LITERATURE

NOTES ON ICHTHYOLOGY

In the Annals of the Carnegie Museum, Vol. VII, 1911, Pro-

fessor Edwin C. Starks gives the result of the survey of San

Juan Island in Puget Sound. Professor Starks regards Hez-

anchus corinus from this region as identical with Hexanchus

griseus, a view already suggested by Mr. Regan. He regards

Raja stellulata as a valid species. Raja.kincaidi is identical

with F. stellulata. New species as follows are described and

figured: Sebastodes deani, S. clavilatus, X. empheus. Xystes

axinophrys is the young of Averruncus emmelane. Xiphistes

ulve is identical with X. chirus. One hundred and fifty-eight

species of fishes are enumerated as known to occur in Puget `

und.

In the Publications of the University of California, Vol. VIII,

1911, Edwin C. Starks and William M. Mann discuss a collec-

tion of fishes from San Diego. A new genus, Orthonopias, based

on O. triacis, a new species of sculpin with a scaly back allied

to Astrolytes, is described.. Another new genus is Rusulus,

related to Clinocottus and based on a new species, R. saburre.

Maynea californica Gilbert is a new species described from Gil-

bert’s manuscript. Valuable notes are given on other rare

species.

In Science, Vol. XXXI, p. 346, Mr. Henry W. Fowler notes

that Coccogenia Cockerell and Callaway (Proc. Biol. Soc. Wash.,

1902, p. 1, 90) is a synonym of Coccotis Jordan (Rept. Geol.

Surv. Ohio, IV, 1882, p. 852) both being based on Hypsilepis

coccogenis Cope.

In the Proc. Ac. Nat. Sci. Phila. for 1910, Mr. Henry W.

Fowler gives a list of little known fishes of New J ersey. He has

also notes on Chimæroid and Ganoid fishes. He recognizes a

number of Gar pikes, instead of the three usually recorded as

valid. The number is certainly greater than three, but such

studies as we have been able to make would not indicate that all

of those noted and figured by Mr. Fowler are really distinct

species. Mr. Fowler describes as new, Cylindrosteus scabriceps

from Leavenworth, Kansas, and C. megalops from Bay Port,

Florida.

In the same proceedings for 1910, Mr. Fowler describes

746

No. 552] NOTES AND LITERATURE 747

Dixonina nemoptera, a remarkable new fish of the family of

Albulide from Santo Domingo.

In the same proceedings Mr. Fowler gives notes on Salmonoid

fishes, describing as new, Stomias bonapartei from Bonaparte’s

collection from Sicily, Synodus dominicensis from Santo

Domingo, and Synodus dermatogenys from Hawaii.

In the same proceedings Mr. Fowler lists the fishes of

Delaware.

In the same proceedings Mr. Fowler describes a new flat

fish from New Jersey under the name Citharichthys micros.

In the same proceedings Mr. Fowler gives notes on the Clupe-

oid fishes. The new genus Heringia is established for Clupea

amazonica Steindachner. Ilisha narrangansette is described

from Narragansett Bay. The subgenus Anchoviella is proposed

for Engraulis perfasciatus. This group includes nearly all the

species of Anchovia, and it is perhaps of generic value as dis-

tinct from Anchovia and from Engraulis. Anchovia scitula is

described from San Diego, Anchovia lepidentostole from Suri-

nam, and Anchovia platyargyrea from St. Martins.

In the same proceedings for 1911, Mr. Fowler describes new

species from Venezuela and Ecuador.

In the Proc. U. S. Nat. Mus. Dr. Jordan and W. F. Thompson

discuss the gold-eye of the northwest, Amphiodon alosoides.

In the Proc. Biol. Soc. of Washington Barton A. Bean and

Alfred C. Weed discuss recent additions to the fish fauna of the

District of Columbia.

In the Bull. Wisconsin Nat. Hist. Xoc., Vol. IX, 1911, George

Wagner describes a new species of cisco from Green Lake, Wis-

consin, under the name of Leucichthys birgei.

In Sctence, Vol. XXXIV, No. 879, Mr. T. D. A. Cockerell

describes a new minnow from Julesburg, Colorado, under the

name of Notropis horatii.

In the Proc. Biol. Soc. Wash. Mr. T. D. A. Cockerell discusses

the scales of various fishes, concluding that the soles are not

degraded flounders but degenerate descendants from some flat

fish from which both have been derived. This conclusion has

also been reached by Professor G. H. Parker from a study of

the optic nerves of the two types. :

In the Bull. Amer. Mus. Nat. Hist., Vol. XXX, 1911, John

Treadwell Nichols has notes on Teleostean fishes. He describes

as new Moxostoma alleghaniense from Marshall, North Carolina.

Menidia audens Hay from Moon Lake, Mississippi, he thinks

748 THE AMERICAN NATURALIST [Von XLVI

identical with Menidia gracilis from Long Island. Blennius

fabbri Nichols, lately described as new from Florida, is the

young of Chasmodes bosquianus. In this paper the curious fish

called Stathmonotus teckla Nichols is figured.

In Science, December 3, 1905, p. 815, the Smooth Hound,

Mustelus mustelus, is recorded from New J ersey. This Euro-

pean species has not been previously known from our coast.

In the Ann. of Mag. Nat. Hist., Vol. VIII, 1911, Mr. C. Tate

Regan publishes a detailed classification of the Siluroidea or cat

hes.

Tn the same annals, Vol. IX, 1912, Mr. Regan gives a classifi-

cation of the Pediculate fishes.

In the same annals Mr. Regan describes the structure of the

Symbranchoid eels.

In the same annals, Vol. XI, 1912, Mr. Regan gives a study of

the Opisthomi.

In the same annals, Vol. VIII, 1911, Mr. Regan gives an

analysis and classification of the Gobioid fishes.

In the same annals, Vol. VIII, 1911, Mr. Regan gives a classi-

fication of the Cyprinoid fishes and their allies.

In the Sitz. Acad. Wiss. Wien, 1911, Dr. Franz Steindachner

describes a number of new fishes from South America.

In the Proc. Biol. Soc. Wash. Dr. R. W. Shufeldt gives a

valuable and interesting account of the rare pelagic fish Ptery-

combus brama. The singular Caristius lately described from

Japan by Dr. Smith, is an ally of Pterycombus, and belongs to

the same family.

n the Memoirs of the Museum of Comparative Zoology at

Harvard Samuel Garman gives a classification of the Chis-

mopnea or Chimeroid fishes. He describes Chimera gilberti

from Hawaii, with valuable notes on all the known species.

In the Mus. Nat. Hist. of Paris Dr. Pellegrin describes nu-

merous fishes from Ecuador, South America.

In the Ann. Carn. Mus., Vol. VII, 1911, John D. Haseman

gives an elaborate catalogue of the Cichlid fishes collected by

the Carnegie Expedition to South America.

In the same annals Mr. Haseman describes and figures numer-

ous new species from South America.

In the same annals; Vol. VII, 1911, Mr. Haseman describes

new species from the Rio Iguassu, an isolated tributary of the

Rio Trabernath, with its peculiar fauna.

In the Sitz. Acad. Wiss. Wien, 1911, Dr. Steindachner dis-

No. 552] NOTES AND LITERATURE 749

cusses the fish fauna of Lake Tanganyika with several new

species and excellent plates.

In the Bull. Soc. Zool. of France Dr. Pellégrin describes a

new Barbus from South Africa, and in the Bull. Soc. Philom.,

Paris, he describes a new Tilapia.

In Arch. Zool. Exper. of Paris Louis Fage discusses the small

codfish of the Mediterranean, showing that capelanus is distinct

from luscus and from minutus.

In the Publ. Dept. Agric. E. W. L. Holt and L. W. Byrne

describe the fishes of the genus Scopelus (earlier and therefore

preferably known as Myctophum).

In the Publ. Zool. Inst. of Lund University Nils Rosen gives

an account of the reptiles and fishes of the Bahamas, an excel-

lent piece of work. New species as follows are described:

Nannocampus nanus from Andros; Garmannia rubra from An-

dros; Gobiesox androsiensis from Andros; Anchenopterus gran-

dicomis from Andros. Mr. Rosen regards Holocentrus siccifer

Cope and Holocentrus puncticulatus Barbour as identical with

H. coruscus. He also suggests the possible identity of the genus

Gymneleotris and Pycnomma with Garmannia. The supposi-

tion is that in the first named genus the ventrals being described

as separated have been simply split apart, the membrane being

very thin.

In the Proc. Roy Soc. of Queensland J. Douglas Ogilby de-

scribes an interesting series of new species.

David G. Stead in the Publications of the Department of

Fisheries of New South Wales gives a valuable account of the

fisheries of that region.

In the Kongl. Sven. Vet. Handl., XLVII, 1911, Professor

Einar Lönnberg gives an account of the reptiles and fishes of

British East Africa.

In a considerable volume published by E. J. Brill, of Leyden,

1911, Dr. Max Weber, of the University of Amsterdam, and

Dr. L. F. de Beaufort give a complete index to the genera or

species described and mentioned by Dr. Pieter Bleeker, the

most voluminous of all writers of ichthyology. In view of the

exceedingly great difficulty in getting exact references to Dr.

Bleeker’s works, this volume of 410 pages of names and refer-

ences is exceedingly useful.

In the Proc. of the New Zealand Institute, 1910, Mr. Edgar

R. Waite gives a record of additions to the fish fauna of that

country with several new genera and species.

750 THE AMERICAN NATURALIST [Vou. XLVI

In the Report of the Scientific Investigations of Shackleton’s

British Antarctic Expedition, Edgar R. Waite describes the new

species obtained.

In the Records of the Canterbury Museum Edgar R. Waite

gives the scientific results of the trawling expedition of the New

Zealand government. Numerous interesting discoveries are

recorded.

In the Publications of the Department of Trade and Com-

merce of Australia, 1911, are given the results of the investiga-

tions of the steamer Endeavour by Mr. Allan R. McCulloch.

Many interesting discoveries are recorded.

In the Proc. U. 8S. Nat. Mus. for 1912 Mr. Radcliffe gives a

most interesting account of new Pediculate fishes taken by the

Albatross in the Philippines.

In the same proceedings Dr. Hugh M. Smith describes the

three Chimeroid fishes taken in the Philippines.

In the same proceedings Dr. Smith describes a new family of

Notidanoid sharks. The genus Pentanchus differs from the

others in having five branchial openings only, like the ordinary

shark. In a note in Science, July 19, 1912, p. 81, Mr. Regan

claims that this shark is merely a Scylliorhinus which has been

deprived of a dorsal fin. é

In the same proceedings Dr. Smith describes numerous Squal-

oid sharks from the Philippines. As to these, Mr. Regan claims

that Nasisqualus is identical with Acanthidium and with Deania.

Squaliolus is a valid genus.

In the same proceedings Mr. Radcliffe describes 15 new

species of Amia (Apogon) and related genera from the Philip-

pines.

In the Abhandl. Senckenberg. Naturf. Ges. Frankfurt, Vol.

XXXIV, 1911, Professor Max Weber gives an account of the

fishes taken in the Aru and Kei Islands with a series of excellent

figures.

In Science, May 12, 1911, Dr. Theodore Gill gives a valuable

review of Professor Thompson’s translation of Aristotle’s ‘‘ His-

tory of Animals.’’

In a volume entitled ‘‘The Freshwater Fishes of the British

Isles” Mr. C. Tate Regan gives a most valuable popular account

of the different river fishes of Great Britain and Ireland. This

is written in such a way that no person of intelligence need have

any difficulty in recognizing the different species found in the

British streams.

No. 552] NOTES AND LITERATURE 751

In the Abhandl. Bayer. Akad. Wiss., Munich, Dr. Victor Franz

publishes a most valuable paper on the bony fishes collected in

Japan by Haberer and Déflein. Many new species are described,

particularly from that richest of all collecting grounds, Sagami

Bay, and contains many notes of value in our study of the

Japanese fauna.

In the Publ. Imp. Univ. Tokyo Mr. Shigeho Tanaka, lecturer

in the Science College, has begun a series of figures and descrip-

tions of the fishes of Japan. This work is extremely well done

and each species is illustrated by excellent plates. There is no

attempt at classification, each of the five parts now issued from

April 15, 1911, to March 10, 1912, containing species valuable

for his purpose, without attempt at orderly arrangement.

In the Sitz. Acad. at Vienna, 1909, Dr. Victor Pietsechmann

describes a new species, Hemilepidotus megapterygius from

Japan.

In the Proc. U. S. Nat. Mus. Professor J. O. Sardor describes

many new species and genera from Japan and from the Riu Kiu

Islands.

In the Ann. Nat. Mus. Wien. Dr. Victor Pietschmann de-

scribes the variations of a frog fish in Japan, and also describes

two species of fishes from Formosa.

In the Journal of the College of Agriculture Dr. K. Kish-

inouye describes new herring from the Bonin Islands, and also

gives an account of prehistoric fishing in Japan.

In the Publ. Roy. Mus. Belgium at Brussels Professor Louis

Dollo has a very interesting discussion of what he calls Ethologie

Paleontology.

In the American Journal of Science Dr. Charles R. Eastman

describes several new sharks from Solenhofen, in the Carnegie

Museum.

In the Bull. Soc. Geol. France Dr. Maurice Leriche describes

eretaceous fishes from the basin of Paris.

In another publication at Lille M. Leriche describes Stampian

fishes of the basin of Paris.

In the Memoirs of the Carnegie Museum, 1911, Dr. Eastman

gives a catalogue of the fossil fishes contained in that museum,

with a description and figure of many species.

In the Mem. Mus. Roy. Belgique Professor Ramsey Traquair

gives an elaborate and valuable account of the fossil fishes of

the Weald from the Bernissart.

In the Proc. Acad. Sci. of Naples Francesco Bassani gives an

752 : THE AMERICAN NATURALIST [Vou. XLVI

elaborate account of the fossil Berycoid fishes (Myripristis

melitensis) from the Miocene at Malta.

In the Annals de Paleontologie M. F. Prien gives a valuable

study of the fossil fishes of the basin of Paris.

In the Conn. Geol. Surv., 1911, Dr. Eastman gives a descrip-

tion of the Triassic fishes known from Connecticut.

In the Geol. Mag. Dr. Louis Hussakof describes several

Arthrodira from Ohio.

In the Publ. Carn. Inst. Wash. Mr. Hussakof describes the

amphibian fishes known from Permian rocks from North

America.

In the Publications of the Fish Commission of Pennsylvania

Dr. David Marine and Dr. C. H. Lenhart describe their observa-

tions on the thyroid carcinoma or goitre of the brook trout, and

the possibility of the relation of this disease to cancer. These

studies are continued in the Journal of Experimental Medicine,

Vol. XIII, 1911. It is concluded that there is no evidence that

goitre is either infectious or contagious, its cause probably

depending on lack of or a disproportion of elements necessary

for proper nutrition. This is also discussed by the authors in

the Johns Hopkins Medical Bulletin, Vol. XXI, 1910.

In the Science Bulletin of the University of Kansas, Professor

Ida H. Hyde gives experiments on the effects of salt injections

on the blood pressure of the skate.

In the Amer. Jour. Anat. William F. Allen describes the

lymphaties in the tail of a large sculpin in California.

In the Trans. Canad. Inst. Professor J. P. MeMurrich gives

an interesting account of the life history of the Pacifice salmon.

In the Proc. Roy. Soc. Canada Professor MeMurrich has an

elaborate study of the marks on the scales of fishes by which the

age of salmon may be known.

In the Publications of Stanford University, 1911, Professor

E. C. Starks gives a detailed account of the osteology of the

mackerel-like fishes. He shows that Leiognathus is a true

Scombroid, and not in any way related to the Percoid family,

Gerride, with which Regan has placed it. In general the rela-

tions of the families on the Scombroid group are fairly deter-

minable by their external appearance.

In the Journal of Comparative N eurology Dr. R. E. Sheldon

discusses the relation of the dogfish to chemical stimuli, and also

the sense of smell among sharks. He shows that the dogfish

No. 552] NOTES AND LITERATURE 753

obtains its food chiefly through the sense of smell, which is com-

parable to that of the higher vertebrates.

In the Internat. Revue Hydrobiol. Leipzig, 1909, Dr. Victor

Franz discusses the effect of light on the movements of Indian

fishes.

In the Journal of Morphology, Dr. J. F. Gudernatsch de-

scribes the thyroid glands of fishes.

In the University of California publications Mr. Asa C.

Chandler describes the lymphoid structure on the brain of the

gar pike.

In the Bull. Bur. Fish. Profesor G. H. Parker describes the

influence of sense organs on the movements of the dogfish.

In the Zool. Jahrb. Wiss. Mr. J. C. Loman describes the nat-

ural history of the European lampreys.

In the Arkiv. fér Zool. Stockholm Nils Rosen describes the

blood-vascular system of the Plectognath fishes.

In the American Journal of Physiology Professor Parker

describes the integumentary nerves of fishes, their reception of

light and their significance in relation to the origin of eyes of

vertebrates.

In the Bull. Bur. Fish. Professor Parker describes the rela-

tion of fishes to sound.

In the Amer. NATUR., 1908, he discusses the origin of the lat-

eral eyes of vertebrates.

In the same bulletin, 1908, he discusses the structure and

function of the ear of the squeteague.

In the Century Magazine, 1910, Mr. Charles H. Townsend

discusses under the head of ‘‘Chameleons of the Sea,’’ the

changes of color among fishes.

In the Bur. of Fish. documents Professor Parker discusses ths

effect of explosive sounds on fishes. These noises are faint under

water and may startle Taia for the moment, but they have no

. permanent effect.

In the Journ. Exper. Zool. Dr. Francis B. Sumner discusses

the color changes of flat fishes with respect to their adaptation

to various backgrounds.

In the Journ. Coll. Sci. Imp. Univ. Tokyo Mr. H. Ohshima

gives an interesting and valuable study of the luminous organs

of different species of fishes.

In the Transactions of the American Fisheries Society Mr.

John P. Babcock describes his experiments in burying the eggs

of salmon and trout in gravel, the result of this being that a

754 THE AMERICAN NATURALIST [Vou. XLVI

much larger number of eggs hatch, and the young are more

vigorous than when hatched in the ordinary way.

If the eggs of salmon are buried beneath five or six inches of sand

and gravel, such eggs will hatch and the young will work their way up

through the sand and gravel to the surface, and by the time they

emerge they have absorbed their sacs and are then exempt from the

attacks of vegetable moulds.

Mr. Babcock thinks that to follow more closely the method of

nature will give more value to artificial fishery hatching.

In the Report of the Fishery Board of Scotland, 1910, Dr. H.

C. Williamson gives a valuable report of the reproductive organs

of different species of Scottish fishes.

In the Bull. Zool. Soc. New York Dr. F. B. Sumner continues

his study on the changes of color of fishes on different bottoms.

The purpose of these changes seems to be simply concealment

from their enemies as well as from those fishes on which they

prey.

In Knowledge, Vol. XXXIII, 1910, Rev. T. R. R. Stebbing

discusses genders in zoology, sharply criticizing the carelessness

with which scientific men have made what he calls ‘“‘ Homeric

blunders,’’ Homer being accustomed to nod when questions of

classical refinement were brought before him. Mr. Stebbing

proposes that in zoology every generic name, whatever its ter-

‘mination, should be recorded as masculine.

In the Philippine Journal of Science Alvin Seale gives a val-

uable account of the fishery resources of the Philippine Islands.

In the Biological Bulletin Victor E. Shelford gives an inter-

esting account of experiments on stream fishes and pond fishes.

In the Bureaus of Fisheries Document 733 William C. Ken-

dall discusses the American fishes, their habits and value.

In Science, October 11, 1911, Professor E. C. Starks discusses

the structure of the air bladder in Ophicephalus.

In Science, Vol. XXXIII, 1911, Mr. Starks discusses the

origin of the gobies. He regards them as somewhat allied to

the sculpins.

In the First Annual Report of the Laguna Marine Laboratory

of Pomona College, Claremont, California, are numerous excel-

lent papers on the local fauna of Laguna Beach in southern

California. Among these papers is an elaborate and well-

planned study of the fishes of the tide pools, by Charles W.

Metz. The report is accompanied by excellent plates.

INDEX

NAMES OF CONTRIBUTORS ARE PRINTED IN SMALL CAPITALS

ABBOTT, JAMES An Unusual

iter tue Relation

Wat and T 5

peters a Seon, Factors in Mice,

A. STURTEVANT, 368; C. C:

LITTLE, 491

Alcohol, Effects not Inherited in

Hydatina senta, D. D. WHITNEY,

fas sit Colors in F, of a Cross

betw n Non-colored Varieties of

. EMERSON, 612; Cells

ize, E. AST, 363

sao in cage

rations, L. R. WALDRON, 463

Allelomorphist, Spurious, and ’Gen-

e Cor p E,

nae Distribution and Origin of

Le fe in, R. F. Scharff, T. Bar-

BOUR, ‘500

American Per vere

Samuel W. Williston, O. P Hay

Asplanchna, Case of ion E

simulating a Mutation, J. H.

Poses 441, 526

Asymmetric Color Resemblance in

the Guinea-pig, JOSEPH H. mash

and G. D. BUCKNER, 505

P eT = Tone Science,

OTTO GLASER, 712

Banta, A. M., The Influence i

Cave Conditions upon

Development in Larvæ of Tabiy

stoma tigrinum, 244

, T., Distribution and Or-

igin of Life in America, R. F.

Scharff, 500

ergs ‘and Punnett ; paise

ir eatin xt W. J. SPIL

Biological, Processes, Physical Anal-

F. CooK, 493; Sci-

ence, Reflections on pp es of,

TO GLASER,

— of the Crayfish, F. E. CHI-

ESTER, 279

sae La and Bie baad HUBERT

LyM. s 139

Bos indic Ev idence of Alterna-

tive Tihotitasen in the F, Genera-

tion cage Crosses = Bos taurus,

wE. r

ns of Paleobotany

oa °F. H. KNOWLTON,

207; Phylogeny and Taxonomy,

JOHN M. COULTER, 215; Morphol-

ogy, EDWAR :

Ecology, ARTHUR

Breeding of Mice, J. FRANK DANIEL,

Bryophyta,

— nk Cav

ON Taon, 684

oleg G. D., Asymmetrie Color

Resemblance in the Guinea- -pig,

eat -relationships of,

D s Hoveu-

Bursa dela Defective Inherit-

ance-Rati , G. H. Shull, wW. J.

EALES, "309

CAMPBELL, DOUGLAS HOUGHTON,

Distribution of Plants

; The Classifi-

ruct

tions in Xenojarasitim, 6

CasTLE, W. E., The Inconstancy of

Uni ohne. Ta On the In-

horitaneo of the Tricolor Coat in

ea-pigs, and its Relation to

Galton s Law of Ancestral Hered-

, 437

Cattle, a -horn, prenien of

LAUG

Col

Cave Conditions and Pigment Devel-

opment in Larve of Amblystoma

. S. JENNINGS, 366

STER, F. E., The Biology of

the Crayfish, 279

Chromosomes, and Particular Char-

acters in Hybrid Echinoid Larve,

NNENT, 68; Sex, E

avp H. E.

B. Wilson, W. J. SPILLMAN, 164

755

Do o

CLARK, HUBERT LYMAN, Biotypes

and Phylogeny, 139

perm of the Liverworts,

AS HOUGHTON ,CAMPBELL,

N., Gametie Coupling

a Cause of Correlations, 569

Color, Celettaate | in Short-horn Cat-

CoLLINS, G.

VELL,

83; Inheritance in the Meatere

Cells of Maize, E. M. East, 363;

mblance, Asymmetric, in the

Guinea-pig, JosepH H. Kast

UCKNER, 505

Colors, Aleurone, in F, of a Cross

between Non- colored Varieties of

Maize, R. A. EMERSON, 612

Characters, HENRY FAIRFIELD

vag 185, 249

C . F., Physical Analogies of

Bi olo ogi cal Processes, 493

ahr genes between piakup osomes

and Particular Speen in Hy-

brid Echinoid Larv Dives H.

TENN paie. 68; Tables, Condensed,

R HARRIS

Correlations, Gametic Coupling as a

of N. COLLINS, 569

DESTER, 279; and Waterbug, Da

usual Symbiotic epen between,

JAMES F. ABBOTT, 5

Cytology, Some kavera of, in rela-

tion to the Study of ‘Genetics,

EpMuND B. Witson, 57

DANIEL, J. FRANK, Mice: Breeding

for § Scientific p aispa , 591

Darwin’s Theory of uh by

the Bolari of Minor Saltations,

AIRFIELD OSBORN, 76

Davenport, C. B., Heredit ity and Fac

ha and Method s of Evolution, 129

a RE, Genetic.

ties o s E daat thera

efective Teheritance- Kation, 0. B

Shull, W. J. Spr 309

THE AMERICAN NATURALIST

G., Problems of :

[Vou. XLVI

Descendants, Starvation of the As-

cendants an Aiono a TIA of,

RTHUR HARRIS, 313, 6

Monee oo Canadian Oyster,

J. Sta x

Differential Mortality with Respect

eed Weight, J. ARTHUR HAR-

of Plants in North

LAS HOUGHTON

and Origin of

in America, R. F. Scharff,

T. BARBOUR, 500

TER r akie, CHARLES

OFOID, 308

ral aud Guinea- -pigs, ilk r

ey in, AREND L. HAGEDOORN,

512

Distr ihotion,

a 2

Dominance, Law of, W. W. STOCK-

ER,

ris ng Begs CHARLES W. HARGITT,

Daali PN F. E. Lutz,

W. J. SPILLMAN

East, E. M., Inheritance of Color

x the Aleurone Cells of Maize,

363; The Mendelian Notation and

Physiological ne 633

East, E. M., and H. K. Hayes, In-

heritaneo | in Maize, Wed, DP

y it

Echinold ot Hybrid, Correla-

tion bet Chromosomes and

Particular Characters in, Davip

TENNENT, 68

Eggs, Double, CHARLES W. HAR-

GITT, 556

Em MERSON, R. A., Aleurone Colors in

Maize , 61 2

Senses ; enetic al bana

and Spurious Allelomorphism

Maize, J. W. LMAN, 119

Evolution, yede Theory o

the Selection of Minor oM ipd

ENRY Pa OSBORN, 76;

Trion Epwin G. CONKLIN,

en Study of

erimental

Heredity, C. B. DAVENPORT, 129;

xperiments with Drosophila Am-

pelophila concerning, F. utz,

W. J. SPILLMAN, 163; of the Ver-

tebrates, William Patten, Wo. E.

RITTER, 623

Fairness in sesh Reviewing, J.

ART 49

Tean in the Domestic Fowl,

OND s 697

Fodevtay's Breeding Experiments

No. 552]

with stig a Pygerd, A. H.

STURTEV

Fertilization, Partial Is the ae

e Sex

HENRY W. 470

Pow, ——, Mendelian coxa

of Fecundity, Ray

Paa ge das

Hra Henry W., Ornamentation

in Fr esh- ici Fishes , 470

Frog, Sex-Ratio and Partial Fertil-

ization? T. H. Morean, 108

Galton’s Law of Ancestral Hered-

ity and Tricolor Coat in Guinea-

pigs, W. E.

Gametic Coupling as a Cause

Correlations, . CoLLINS, 569

Genetic Correlation “and Spurious

PIRE on WS in Maize, A.

daa ” Studies el rial

As er of us

Study of, Ep-

‘ ; oT

app, Relations of Paleobotany

F n papeki a 207

Paaka WALTER B.,

species of rii pi ays

LASER, OTTO, The Autonomy of

Biological Science, 712

Gortner, R. A., Studies in Melanin,

. J. SP PILLMAN, 1

Growth, Nuclear, during Persil De-

S. JEN

A New Sub-

L., 616

velop! oe Nes, 366

Guinea-pigs, Inheritance of the Tri-

1 e STLE, 437;

AREND RN, 682;

Pom a oe EEE p A in,

JOSEPH and G. D.

BUCKNER, oa

HAGEDOORN, AREND. On Tricolor

Coat in Dogs and Guinea-pigs,

Hardi Suce lfalfa

er ae L R N, 463

HARLES W., Double Eggs,

J. A , A First Study

Influence of Starvation of

) a

656; The

Correlation Tables when the Num-

ber of Combinations is large, 477;

On Fairness and Accuracy in Sei-

INDEX

757

entific Reviewing, 498; On Differ-

; Mendelian Ratios,

Harshberger, John Wo, a

graphic Survey of North America,

aE HOUGHTON pa oiea 166

O. merican Permian Ver-

tebaa, “Samuel W. Williston, 561

Hayes, H. K., and E. M. East, In-

heritance in Maize, W. J. SPILL-

MAN,

HENN, ARTHUR W., e Range of

Size in the aie 157

Heredity, W. J. SPILLMAN, 110, stay

309; and Evolution, ; _ DAVE

PORT 29; An cestral, dika’ s

Law, ' W. E. Cas , 437

Heterozygotes, PR of Pure

Homozygotie Organisms by Self-

Ee con, H. S. JENNINGS, 487

HOLLICK, ARTHUR, The Relations of

Paleobotany to ' Botany—Ecology,

Poea porie Organisms, Pure, Pro-

duction from Heterozygotes

Self- Ea aak, H. S. JENNINGS,

487

Honey-bee, Color Sense of, JoHN H.

LOVELL, 83

HUSSAKOF, L., e Spawning Hab-

its of the a Lamprey, 729

Hybrid Echinoid Larve, Chromo-

somes and Partic ular Characters

in, aren H. TENNENT, 68

Hybrids, rnp Defective Inherit-

, G. H. Shull, W. J.

ny 309

Hydra und die Hydroiden, Otto

ar CHARLES Atwoop KOFOID,

Tan pipet Cope, Distribution,

Habits and Variation, C. H. Ric

pe p 5

Ichthyology, Notes on, DAVID STARR

ORDAN,

Inconstancy of betas Characters, W.

E. Cas

gee at og Selection, RAY-

D PEARL,

nina — Studies in, H. M.

ke, W. J. SPILLMAN, 309

nia nla of Color in Shorthorn

ttle, H GHLIN,

Maize, E. an

ayes, W. PILLMAN, 1113; of

Physiognomy, R. N. Sala Ww

SPILLMAN, 116; of Pigmenta-

758

tion, Bateson and Punnett, W. J.

SPILLMAN, 117; Ratios, Defective,

in Bursa Hybrids, G. H. Shull,

. J. SPILLMAN, 311; of ces in

the Aleurone Cells of Mai E.

M. East, 363; re arg om

R ’ NABOURS, grat bed the

Coat in a-pigs,

E. CASTLF, 437; Mansauan,

RAYMOND PEARL, 697

Invertebrates, CHARLES ATWooD

, Korom, 695

JEFFREY, EDWARD C., The Relations

of Paicobotany to Botany—Mor-

pholo 225

JENNINGS, H. S., Nuclear Growth

during "Barly Developmen nt, 366;

Production of Pure Homozygo otie

Organisms fro wi ao aas by

Self- fertilisation, 487

JOHNSON, RoswELL H., The Mal-

thusian Prineiple and Natural

bass 372

AVID STARR, Notes on

Tonor, 756

KASTLE, , Asymmetrie Color

ii i ra "in the Guinea-pig,

Know ton, F. H., The Relations of

Paleobotany Ba Geolo ogy, 20

OFOID, CHAR ATW Proto-

zoa, 308; Tavertebeatie. 695

Lamprey, Sea, Petromyzon marinus

Spawning Habits, L. Husssaxor,

H., The Inheritance

of Color in Short-horn Cattle, 5

ke, 3 :

Cotton, W. J. SPILLMAN, 309

Literary Note on Mendel’s ’ Law, W.

a TOCKBERGER, 15

G: G, Yellow and Agouti

Pate in Mice,

Liverworts Classification of, Doug-

N CAMPBELL, 684

LIVINGSTON Pook E., "Pr t

Problems in Soi Physics as re-

lated to Plant Activities, 294

j e Color Sense

of the Honey-bee, 83

Lutz, E., riments with Dro

sophila Po Sr concerning

Evolution, W. J. SPILLM AN, 163

Maize, Inheritance m, E. M. East

and H, hk. Hayes, W. J. Senz-

THE AMERICAN NATURALIST

[VoL. XLVI

MAN, 111; Genetic S

and ’ Spurious Allelomorphism in

R. A. Emerson, W ILLMAN,

119; Aleurone = of, E

East, 363; R. EMERSON, 612

Malthusian ee and Natural

Selection, ROSWELL H. JOHNSON,

372

Meisenheimer, J poset Die Wein-

bergse hnecke, CHARL ATWOOD

Koro, 695

Melanin, Studies in, R. A. Gortner,

W. J. MAN, 1

Mendel’s Taw, Literary Note on,

W. CKBERGER, 151

Mendelian, Proportions and the In-

siv FRANCIS

697; Ratios, a ARTHUR Higa

741

Mice, the Yellow and Agouti Fac-

tors in, A. H. STURTEVANT, 36

C E. LITTLE, 491; their Poolt

and Rearing for Scientific Pur-

pos J. FRANK x Daxter,

Morean, T. H., Is Change

the Sox. Ratio of tn Fog that is is

affected by External Agents due

pary Relations of Paleobot-

o Botany, EDWARD C. JEF-

oi ly

Mortality, Differential, with Re-

svect to Seed Weig ht, J. ARTHUR

Har 12

Mutation, Case of Polymorphism in

Asplanchna fe a B

Powers, 441, 526

Nasours, Ropert K., Evidence of

Alternative Inheritance in the F,

i from reg

sian seen

North America, Phytogeographie

Survey of, John Ha patina

— E HOUGHTON CAMPBEL

Nota and Literature, 110, 163, 308,

500, 561, 623, 684, 756

Nuclear Size and Cen Size, E. G.

Conklin, H. S, JENNINGS, 366

No. 552]

@nothera, Genetical Studies, BRAD-

LE ORE S, 377

Fresh-water

470

W. ihe

HENRY FAIRFIE "Tar

Baia of Minor Saltationsy 76;

5, 249

Supplementary

Oyster, Canadian,

Observations on Development, J.

STAFFORD, 29

Paleobotany, Modern Aspects t%

elations to G F.

KNOWLTON, 207; AN apie

logeny and Taxonomy, JOH

COULTER, 15; rphology,

Paleontologist, Continuous Orii of

Certain Uni aracters as ob-

serv re by x HENRY FAIRFIELD

OSBORN, 185

Patten, William, The Evolution of

she ‘Vertebrates and their Kin

. E. RITTE

Du. ba Selection Index

Numbers, 302; The endelian

itance of a ay in the

mestie Fowl, 697

Phenolic Substances, Inhibitory ae

tion upon Tyrosinase, . Gort

, W. J. SPILLMAN 117

Phylogeny, and Biotypes, HUBERT

LYMAN CLARK ; and Taxon-

ganie Beings,

mee paaie of Biological

es, O. F. CooK, 493

_Physiognomy, Inheritance = R. A.

Salaman, W. PILL 116

Physiological ce and " Mendelian

Pigment Development in Larvæ o

Amblystoma tigrinum, Influence

of Cave Conditions upon, A.

BANTA, 244

Pigmentation, Inheritance of, Bate-

son and Punnett, W. J. Seri ILL-

117

Plant Activities, Present Problems

hysies as gob to,

veal E. LIVINGSTO , 294

INDEX

759

Pollination of Green Flowers, JOHN

Powers, J. H., A Case of Poly-

ArwooD Ko-

308

Soca, eara Federley’ s sp saat

Experim with, A. H. STUR

VANT, ae

RAMALEY, FRANCIS, Mendelian Pro-

portions and the Increase of Re-

cessives, 34

Recombination, Law of, W. W.

RICHARDSON, H., J2, The Dis-

tribution of Hyla 'arenicolor Cope,

with Notes on its Habits and

Vinnkios, 605

RITTER, ; Patten on the

Origin of Vertebrates, 623

alaman, R. M., Inheritance of

Physiognomy, W. J. SPILLMAN,

Saltations, Minor, Darwin’s Theory

of Evolution by the Selection of,

Origin of Life in America, T.

BARBO 00

sore ine Reviewing, o_o in,

ARTHUR HARRI

Sed Weight, Differential Mortality

occurring in Field Cultures of

Phaseolus vulgaris, J.

HARRIS

Segregation, Law of, W. W. poo

BERGER, 152

— Index Numbers, RAYMOND

PEARL, 302

Self- fertilization,

Production of

ure Homozygotic —

from ee by, S.

JENN 487

= Ratio a the Frog, T. H. Mor-

08; Chromosomes, E. B

Wilo , W. J. SPILLMAN 4.

Shave hora Cattle, Sapien may of

Color, H. H. Lau , 9

Short rter Articles ana gg ee

108, 151, 244, 302, 363, 437, 487,

6 2, 741

. H., Defective Inheritance-

Ratios in Bursa Hybrids, W. J.

AN, 311

Range in De Vertebrates,

ARTHUR W. HENN, 157

760

Soil Physics, ea Problems, as

diman ted to Plant Activities, BUR-

N E. Liv VINGSTON, 294

A ao Habits of the Sea Lam-

etromyzon marinus, L.

om aeth J. ARTHUR HAR-

656

Shakes Otto, Hydra und die H

roiden, CHARLES Atwoop Ko- .

FOID,

STOCKBERGER, W., A Literary

ote on M endel ’s Law, 151

Structural Relations in Xenopara-

sitism, W. A. CANNON,

nA cHe The Yellow and

Factors in 368 ;

eeding Wivethnent,

oth Pygera, 565

i between

ater and a Crayfish,

JAMES F. pi a 553

Tables, Condensed Correlation, For-

mation when the number of Com-

es is large, J. ARTHUR

Harris, 47

Pieni and elas ae argv

of Paleobotany to, M.

COULTER, 215

TENNENT, Pary

tion betwee Chromosom

Particular Characters in Hybrid

Echinoid 68

Tricolor Coat in n Guinea: e pigs, W. E.

ASTLE, A L. HAGE-

DCORN, 682

H. The peirat

and

THE AMERICAN NATURALIST

[Vou. XLVI

Unit Characters, Continuous Origin

of Certain, as 'obse rved by a Pale-

adi 13 HENRY yp pineal Os-

9: Ponnan W.

E. as 352”

Variation, Habits and Distribution

Cope, U. B.

ON, JR., 6

Vertebrates, Range of Size, ARTHUR

NN, 157; Evolution, Will-

iam Patten, Wu. E. RITTER, 623

oN, L. R., Hardiness in Suc-

, Unusual

between,

Weinbergschnecke, y ies Meis-

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por,

WHITNEY . D., The Effects of Al-

ste not pea in Hydatina

Witiston,

Perm

Samuel W., American

n Vertebrates, O. P. Hay

Witson, EDMUND B., Some Aspects

of Cytology in relation to the

Stu tedy of Genetics, 57

Wilson, E. B., Sex Chromo-

somes, W. J. ’ SPILLMAN, 164

Seer hep Structural Rela-

, W. A. Cannon, 675

Yellow and sin. ot Factors in Mice,

A R RTEVANT, 368; C. C.

LITTLE, 491

Zea mays L., New A of,

WALTER B. ’ GERNERT, 616

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The American Naturalist

A Monthly — established i in wae Devoted to the Advancement of the —— Sciences

the Factors

with Special Reference

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CONTENTS not aug NUMBER

A First Study of the Ir of Starvation of the

ants. Dr. J. Arthur Harris,

and the Increase of Recess-

les and Dis : Inheritance of

Color in the Aleurone Cells of Maize: Professor

E. M. East, Nuclear Gro Early De-

nt: Professor H. 8. Jennings. Is

tors in Mice? A. H. Sturtevant, The Malthusian

Principle and Natural Selection. Dr. Roswell H.

SOENT OF JULY NUMBE

tuđi thers, HI. te Bradley

Bridence of nee R F Genera-

from Crosses of = hana ig on Tiao

eog Robert K. Nabo

Shorter Articles and SORE : On the Inheritance

Consens: Correlation Tabl

yten tho Sumber af Combinations pe Dr.

__J, Arthur Harris,

CONTENTS S SEPTEMBER NUMBER

Mortality th Bes t to Seed

woe r Dr.J. Art Field A Culfures of Phaseolus

between

Frofemor James E. Abbott. bonb e Eggs. Pro-

"Grate, De, Or E- Hayy sa Federley s Ere D ae

fe a a

o miaa a Se e ee

CONTENTS OF NOVEMBER NUMBER

E “The Mendelian Notation Description

“"Physiolo naan

ark ti