COLLEGE OF AGRICULTURE
DAVIS. CALIFORNIA

INHERITANCE IN POULTRY

BY

C. B. DAVENPORT

WASHINGTON, D. C.

Published by the Carnegie Institution of Washington
1906

UNIVERSITY OF CALIFORNIA

LIBRARY

COLLEGE OF AGRICULTURE
DAVIS

PUBLICATIONS OF'tHE CA'RNgGIE INSTITUTION OF
WA.SHJNG JON; Np. >.-,

PAPERS OF THE STATION FOR EXPERIMENTAL
EVOLUTION, No. 7

PRESS OF

JUDD & DETWEILER, INC.
WASHINGTON, D. C.

TABLE OF CONTENTS.

Page

A. Statement of Problem I

B. Method and Material 5

C. Results of Crossing 6

Series I. Single-comb Black Minorca and

White-crested Black Polish 6

Statement of Problem 6

The Races as a Whole 6

Table of Characteristics 6

Remarks on the Characteristics 7

i. Comb, 7 ; 2. Nostrils, 7 ; 3. Form
of Skull, 8 ; 4. Crest, 9 ; 5. Color
of Crest, 10.

Material 10

Results 10

i. Comb, 10 ; 2. Nostrils, 12; 3.
Cerebral Hernia, 13 ; 4. Crest,
14 ; 5. Color of Top of Head, 15 ;
6. Cor relation of Characters, 16.

Conclusions 17

Series II. Single-comb White Leghorn and

Houdau 18

Statement of Problem 18

The Races as a Whole 18

Table of Characteristics 19

Discussion of Characteristics 19

i. General Plumage Color, 19 ;

2. Color of Upper Mandible, 19 ;

3. Nostrils, 19 ; 4. Comb, 19 ;

5. Whiskers or Muff, 20 ;

6. Beard, 20 ; 7, 8. Crest ; Cere-
bral Hernia, 20 ; 9. Foot Color,
20; 10. Number of ''Iocs, 20.

Previous Investigations 21

Material 21

Results 21

i. General Plumage Color, 21; 2.
Color of Upper Mandible, 22 ;
3. Nostrils, 22 ; 4. Comb, 22 ; 5.
Face Feathering, 23 ; 6. Beard,
24 ; 7. Cerebral Hernia, 24 ; 8.
Crest, 24 ; 9. Foot Color, 24 ; 10.
Number of Toes, 25 ; n. Corre-
lation of Characters, 25.

Conclusions 26

Series III. Houdau and Single-comb Black

Minorca 27

Statement of Problem 27

The Races as a Whole 27

Table of Characteristics 27

Material 28

Results 28

i. General Plumage Color, 28 ;
2. Comb, 28; 3. Nostril Form,
28; 4. Crtst, 28; 5. Cerebral Her-
nia, 28 ; 6. 7. Muff and Beard,
28 ; 8. Foot Color, 28; 9. Toes, 28.
Conclusions 2g

Page
Series IV. Single-comb White Leghorn and

Rose-comb Black Minorca 29

Statement of Problem 29

The Races as a Whole 29

Table of Characteristics 29

Remarks on the Characteristics 29

i. General Plumage Color, 29 ;
2. Comb Form, 29; 3. Foot
Color, 29.

Material 29

Results 30

i. Plumage Color, 30; 2. Comb
Form, 30 ; 3. Foot Color, 31.

Conclusions 31

Series V. Single-comb Black Minorca and

Dark Brahma 31

Statement of Problem 31

The Races as a Whole 31

Table of Characteristics 32

Remarks on the Characteristics 32

i. General Plumage Color, 32;

2. Wiug Bars, 32 ; 3. Comb, 32 ;
4. Earlobe Color, 33 ; 5. Iris
Color, 33 ; 6. Foot Color, 33 ;

7. Foot Feathering, 34 ; 8. Vul-
ture Hock, 34.

Material 34

Results 34

i. General Plumage Color, 34 ; 2.
Wing Coverts, 35 ; 3. Comb,
35 ; 4. Earlobe Color, 35 ; 5. Iris
Color, 35 ; 6. Beak and Foot
Color, 35 ; 7. Foot Feathering,
35 ; 8. Vulture Hock, 35.

Conclusions 36

Series VI. White Leghorn and Dark

Brahma 36

Statement of Problem 36

The Races as a Whole 36

Table of Characteristics 36

Remarks on the Characteristics 36

i. Hackle Color, 36; 3. Wing
Bow, 37.

Material 37

Results 37

i. General Plumage Color, 37 ;

3. Wing Coloration, 37; 4. Tail
Color, 38 ; 5. Comb Form, 38 ; 6.
Earlobe, 38 ; 7. Iris Color, 38 ;

8. Vulture Hock, 38 ; 9. Foot
Feathering, 38.

Conclusions 38

Series VII. Black Cochin Bantam and

White Leghorn Bantam 39

Statement of Problem 39

The Races as a Whole 39

Table of Characteristics 39

(III)

IV

TABLE OF CONTENTS.

Page

Remarks on the Characteristics 39

i. General Plumage Color, 39 ;
2. Earlobe Color, 39 ; 3. Vul-
ture Hock, 39.

Material 39

Results 40

i. General Plumage Color, 40 ; 2.
Earlobe Color, 40 ; 3. Vulture
Hock, 46 ; 4. Foot Feathering,
40.

Conclusions 40

Series VIII. White Leghorn Bantam and

Buff Cochin Bantam 40

Statement of Problem 40

The Races as a Whole 40

Table of Characteristics 41

Remarks on the Characteristics 41

i. General Plumage Color 41

Material .'... 42

Results 42

i. General Plumage Color, 42 ; 2.
Earlobe Color, 43 ; 3. Vulture
Hock,43; 4. Foot Feathering^.

Conclusions 43

Series IX. Tosa Fowl (Yokohama) and

White Cochin Bantam 43

Statement of Problem 43

The Races as a Whole 43

Table of Characteristics 44

Remarks on the Characteristics 44

i. General Plumage Color, 44;
2. Tail, 44; 3. Foot Feather-
ing, 48 ; 4. Foot Color, 48.

Material 48

Results 49

i. General Plumage Color, 49 ;
2. Tail Length, 49 ; 3. Foot
Feathering, 50 ; 4. Foot Color,
50 ; 5. Correlation of Character-
istics, 51.

Conclusions 51

Series X. Dark Brahma and Tosa Fowl 51

Statement of Problem 51

The Races as a Whole 51

Table of Characteristics 52

Remarks on the Characteristics 52

r. Shafting, 52 ; 2. Hackle Lac-
ing, 52; 3- Body Lacing, 52;
4. Penciling, 53 ; 5. Red Wing-
Bar, 53 ; 6. White Wing-Bows,
53 ; 8. White Earlobe, 53 ; 9.
Iris Color, 53.

Material 53

Results 54

i. Shafting, 54; 2. Hackle Lac-
ing, 54 ; 3- Body Lacing, 54 ;
4. Penciling, 54; 5. Red Wing-
Bar, 54; 6. White Wing-Bow,
54; 7- Comb, 54; 8. Earlobe
Color, 54 ; 9. Iris Color, 54 ;
10. Foot Color, 54; ii. Vulture
Hock, 54 ; 12. Foot Feathering,
55 ; 13. Tail Feathers, 55.

Conclusions

Method of Inheritance, 55 ; Sex in
Inheritance, 55.

Series XI. Frizzle and Silky

Statement of Problem

The Races as a Whole

Table of Characteristics

Remarks on the Characteristics

i. Plumage Color, 57 ; 2. Comb
Form, 57; 3-5. Feather Form,
57 ; 6. Number of Toes, 59 ; 7.
Skin Color, 59.

Material

Results

i. Plumage Color, 59 ; 2. Comb,
59 ; 3-5- Curving of Shaft, Barb
Length, and Barb Form, 59 ;
6. Number of Toes, 60 ; 7. Skin
Color, 60 ; 8. Crest, 60.

Conclusions

Series XII. Single-comb White Leghorn
Bantam and Black-breasted Red Rump-
less Game

Statement of Problem

The Races as a Whole

Table of Characteristics

Remarks on the Characteristics

4. Uropygium

Material

Results

i. General Plumage Color, 62 ; 2.
Beak Color, 63; 3. Uropygium,
63 ; 4. Foot Color, 63.

Conclusions

Series XIII. Black Cochin Bantam and

Black-breasted RedRumpless Game

Statement of Problem

The Races as a Whole

Table of Characteristics

Material

Results

i. General Plumage Color, 64; 2.
Uropygium, 64; 3. Iris Color,
64 ; 4. Vulture Hock, 64 ; 5. Foot
Feathering, 64.

Conclusions

D. General Discussion

Inheritance of Particular Characteristics...

Comb Form

Nostril Form

Cerebral Hernia

Crest

Whiskers, or Muff.

Beard

Feather Form...

Uropygium

Tail-Length

Vulture Hock

Foot Feathering

Extra Toes

Skin Color

Mandible Color

Foot Color

Page
55

55
55
55
57
57

60

61
61
61
61
61
61
62
62

63

63
63
63
63
63
64

64
65
65
65
68
69
69
70
70
70
71
71
71
72
72
73
74
74

TABLE OF CONTENTS.

Page

Iris Color 74

Earlobe Color 74

General Plumage Color 74

White vs. Dark 75

Dominance of White 75

Barring 75

Andalusian Coloration 76

White vs. Buff. 76

Black vs. Red 76

Color of Top of Head 76

Color of Hackles— Hackle Lacing 77

Wing Color— Red Wing Coverts 77

Tail Color 77

Shafting 77

Body Lacing 78

Penciling 78

General Topics in Inheritance 78

Unit Characters 78

Alternative, Particulate (Mosaic), and

Blending Inheritance 81

Inheritance of Specific vs. Varietal

Characteristics 82

Inheritance of Positive vs. Negative

Varietal Characteristics 83

Inheritance of Old vs. New Character-
istics 84

Dominance and Recessiveness 84

Page
Dependence of Dominance on the Races

Crossed 86

Prepotency and Dominance 87

Hybrid Forms 88

Reversion 90

Purity of Gametes 91

Comparison of Reciprocal Crosses 93

Inheritance of Sexually Dimorphic
Characteristics and Sexual Dimor-
phism in the Hybrids 93

Black Minorca and Dark Brahma... 94

White Leghorn and Dark Krahma.. 94

White Leghorn and Houdan 94

White Leghorn and Rose-comb

Black Minorca 95

Tosa Fowl and White Cochiu Ban-
tam 95

Dark Brahma (female) and Tosa

Fowl (male) 95

Transfer of Sexually Dimorphic Char-
acteristics from One Sex to the Other. 95

Sex in Hybrids 97

Correlation of Characteristics 97

The Mutation Theory in its Relation to

the Origin of Domesticated Animals.. 98

E. Summary of Conclusions 100

F. Literature Cited 101

INHERITANCE IN POULTRY.

By C. B. DAVENPORT.

Evolution proceeds by steps. These steps are measured by the character-
istics of organisms. When in the evolution of a race a characteristic is
added a progressive step is taken. When a characteristic drops out a retro-
gressive step is made. Since the characteristic is the unit of evolution, it
deserves careful study. The present work is a first study of the method
of inheritance of characteristics.

A. STATEMENT OF PROBLEM.

When by some abnormal process a single, fertilized egg develops into two
individuals they are, and continue throughout life to be, almost indistin-
guishable. This holds true even when the conditions of life of the two are
dissimilar. This case is exemplified by ' ' identical twins ' ' as they occur in
man.* The great similarity of such identical twins teaches that environ-
ment plays a small part in determining adult characteristics as compared
with heredity. Consequently more confidence can be felt that the results
of hybridization experiments are directly due to inheritance ; they are little
affected by varying environment.

The children of the ordinary family are not identical in appearance,
although showing marked family traits. Certain characteristics may be
common, but others are peculiar to each individual child. This proves that
the fertilized eggs of the same two parents have not the same hereditary
potentialities. It indicates also that we cannot predict the characteristics
of the offspring from those of the parents. The proportion of qualities
derived from either one of the two parents will differ in different children,
or new qualities may appear. This is because the offspring do not inherit
from the visible part of the parents' bodies but from their hidden germ
cells or ' ' gametes. ' ' And the characteristics of the soma are never through-
out the same as those of the ripe gametes it carries.

When the parents belong to different races having markedly dissimilar
characteristics there is not merely the question of dissimilarity of the off-
spring but of the inheritance of the antagonistic characteristics. Until

* Gal ton, F., 1883, pp. 216-243. Compare also for a critical study of resemblance in
twins, Thorndike, 1905.

2 INHERITANCE IN POULTRY.

recently the law has been commonly accepted which is thus expressed by
Darwin (1876, Chapter XV) : "When two breeds are crossed their char-
acters usually become intimately fused together." Many cases of non-
fusing inheritance are now known and it is important to ascertain the rela-
tive .frequency of the different kinds of inheritance and their relation to one
another'.. :. /

. . IiU<?as: ( 1 856-,. p. 194) recognizes three methods of inheritance, which he
tails respectively that of election, of mixture, and of combination. They
are thus defined : Election results in imprinting on some or all parts of the
organism the characteristics of the father exclusively or those of the mother.
Mixture results in a mixed or simultaneous representation of the father and
of the mother on some or all of the parts of the organism. Its extreme is
fusion of characteristics. Combination results in the substitution of a new
characteristic in the place of any representative in a part or over the whole
of the organism. This new characteristic results from the interaction of
the two antagonistic ones just as a chemical combination often differs wholly
from the elements which have been united in its manufacture.

Darwin (1876, Chapter XV) seems to recognize only two classes of inherit-
ance, viz. , one in which characteristics blend and one in which they refuse
to blend. Of the latter class, however, there are two cases ; either the
hybrid receives all its characters from one of its parents only, or the hybrid
receives part of its characters from one parent, the rest from the other.

Nageli (1884 ; 1898, p. 17) describes the different forms of inheritance
very clearly, thus :

In the idioplasm of a germ cell arising from the crossing of unlike individuals the
micellar rows of the individual Anlagen have sometimes an intermediate constitution
and produce characteristics in the organism which are intermediate between the char-
acteristics of the parents. Sometimes the micellar rows derived from the father and the
mother respectively lie side by side interchanged in the idioplasm of the offspring in
distinct groupings and may reproduce in the organism their respective characteristics
side by side, or only one of them may develop, while the other remains latent. (Clark's
translation.)

Galton (1889, pp. 7, 12, 14) distinguishes three kinds of inheritance, as
follows: (i) Particulate, or inheritance "bit by bit, this element from one
progenitor, that from another ; " (2) blending, as in human skin color ; this
may "be none the less ' particulate ' in its origin, but the result maybe
regarded as a fine mosaic too minute for its elements to be distinguished in
a general view;" and (3) exclusive, as in human eye color; although
"there are probably no heritages that perfectly blend or that absolutely
exclude one another, but all heritages have a tendency in one or the other
direction, and the tendency is often a very strong one."

The different types of inheritance are thought by various authors to be
characteristic of particular sorts of crossing. Isidore Geoffrey St.-Hilaire
insisted ' ' that the transmission of characters without fusion occurs very

STATEMENT OF PROBLEM. 3

rarely when species are crossed." De Vries (1905, pp. 253, 280) concludes
that blending and participate inheritance of qualities characterize the
offspring of crossed species, whereas an alternative inheritance of qualities
is characteristic of the offspring of a species crossed with a variety * or of
two varieties crossed inter se.

In the case of alternative inheritance there often is exhibited an extremely
suggestive phenomenon. When hybrids showing such inheritance are
crossed inter sc there is a segregation of the various alternative character-
istics into different individual offspring. This is the discovery of Mendel
(i866).f The attempt has naturally been made to generalize Mendel's
law — to make it apply universally. In my own study the applicability of
this law has been kept constantly in mind.

* It is to be recalled that in the De Vries system a variety differs from its parent
species either in that a characteristic of the species has become latent in the variety or
in that a characteristic which was latent in the species has reappeared in the variety. A
new species, on the other hand, differs from its parent species in the acquisition of one
or more wholly new characteristics. "In normal fertilization and in the intercrossing
of varieties all characters are paired." Hence the paired characters struggle together in
the zygote and the stronger one of the pair dominates or covers over the weaker one.
Thus inheritance is alternative or exclusive. "In crosses between elementary species
the differentiating marks are not mated." Hence there is no such struggle between
characteristics ; consequent!}' those of both parents reappear in the offspring, interdigi-
tating.

fThe rediscovery of Mendel's work simultaneously by De Vries and by Correns in
1900 will always rank as one of the interesting coincidences in the history of science.
There is evidence that others had independently discovered this law in their own work
in the last third of the nineteenth century, but the history of this law is still to be written.
I may note that Haacke, in 1893, as a result of extensive breeding of animals, expresses
the law of purity of the germ cells. He has the theoretical idea that inheritance is con-
veyed both by the plasma (P) and the nucleus (Kern, K). In the union of dissimilar
races two kinds of plasma (P and P') and two kinds of nuclear material (K and K') may
be distinguished. On page 236 he says :

Die beideti verschiedenen Plasmen P und P' die sich bei der Befruchtung vereinigt haben, trennen
sich wieder bei der Reductionsteiluug der Keimzelle, und dasselbe gilt von den beideu Kernstoffe K
und K'. Diese Trennutig ist in manchen Fallen, wie es scheint, eine vollige, so dass die Plasmen und
die Kernstoffe, abaesehen von deu mehr oder minder weitgehenden, aber niemals vollkommenen
Ausgleichungen ihrer Eigenschaften, die durch gegenseitige Beeinflussung stattfinden mfissen, ebenso
rein aus der Vereinigung hervorgehen, als sie in diese hineingetreten sind.

Still further Haacke recognizes that in the separation of qualities that occur in the
reduction period of the hybrid germ cells, those from different parents may gather into
one germ cell. Since this occurs in accordance with the laws of chance (worked out in
an example by Haacke), we have various combinations of characteristics in the second
hybrid generation. Because of the purity of the germ cells it will often happen that
mice having certain qualities will, when bred together, produce only those qualities,
however complex their ancestry. For example, white dancing-mice bred together will
produce nothing but white dancing-mice. Haacke's results seem to have been overlooked
by recent experimenters.

4 INHERITANCE IN POULTRY.

In typical Mendelian cases not only do the qualities segregate in the second
hybrid generation, but in addition, in the first generation, when two con-
trasted characteristics are bred together one of the two is patent in the
offspring ; the other does not appear. The first is the dominant quality ; the
second is recessive.

It seems at first to have been assumed that when one of two antagonistic
characteristics was dominant over the other it was so in all cases. Recent
studies have, however, greatly expanded our notion of dominance and reces-
siveness. Even in alternative inheritance we have to admit various addi-
tional phenomena of which the following are examples : Prepotency of a
character, elsewhere recessive, in some individual or strain. Latency, as
Castle (1905, p. 24) uses the term, or the inactive persistence of a normally
dominant characteristic in a recessive individual or gamete. When the
recessive is cross-bred the latent characteristic may appear as a dominant.
Reversion, or the assumption of an atavistic character by a heterozygote.
This is illustrated by the case of the cross between albino and black-and-
white mice which throw gray. However, this instance may be one of
latency. In this study attention will be paid to these phenomena.

What determines dominance in any case? This is a disputed point.
De Vries (1905, pp. 278, 280) suggests "that hybrids between a species and
its retrograde variety will bear the aspect of the species," and "that the
older character dominates the younger one." However, he says it is not
the systematic relation of the two parents of a cross that is decisive, but only
the occurrence of the same quality, in the one in an active, and in the other
in an inactive condition. Hence, whenever this relation occurs between the
parents of a cross the active quality prevails in the hybrid, even when the
parents differ from each other in other respects so as to be distinguished as
systematic species. Correns (1905) also cites cases in which the active
allelomorph dominates. In my studies constant attention is directed toward
this matter.

To recapitulate : This study has been undertaken to determine the differ-
ent forms of inheritance (alternative, particulate, blending) occurring in
poultry, and to study especially the phenomena of alternative inheritance as
exhibited in this group in order to see in how far they accord with Mendel's
law and in how far the accessory phenomena of dominance, latency, and
reversion occur.

METHOD AND MATERIAL. 5

B. METHOD AND MATERIAL.

To answer in the shortest time the foregoing questions about inheritance
it was necessary to use some rapid and fecund breeder and to interbreed
both varieties and species. But species-breeding is slower and more diffi-
cult and not more important than breeding races ; for while on the one hand
it may be urged that races are artificial, having arisen under domestication,
on the other hand hybridization between established species probably plays
little part in nature. What must occur again and again in nature is the
mating of a mutation or newly arisen race with the parent species. It has
been urged that, in such cases, the rare mutation must be swamped by
intercrossing with the numerous representatives of the species. But if new
characters do not blend in breeding we can see that a new characteristic
once arisen may not be swamped. Consequently the study of inheritance
in races assumes first importance, and domestic races afford the best material
for such study.

Again, if we accept the doctrine that man is a single species, all the mo-
mentous questions of human inheritance are questions of race inheritance.
The outcome of such an admixture of races as is going on in America is a
question of race inheritance. The offspring of a man and a woman having
one or more diverse characteristics will follow the laws deduced from a study
of crossed races. These are practical problems of human evolution, and
experiments made with domesticated races can throw light upon them.

The main material utilized has been, as stated, poultry. Poultry offer
these great advantages : That they are easily bred in great numbers, that two
generations can be reared to maturity in a year, that they stand much
inbreeding without loss of fertility, and that the number of well-defined
characteristics in the group is very great.

In my experiments I have kept 29 pens, each with its cock and one or
more hens. To separate the eggs of the different females, trap nests were
used in the later experiments to hold the hen until she is released. Her
number is read and written, with date, upon the egg. Before placing the
eggs in the incubator, a list is made of them. Before hatching, eggs of
each of the different parentages are separated into a compartment by them-
selves, so that the exact parents of each chick may be known. A legband
is applied to the chick the moment it is removed from the pedigree tray of
the incubator. By these means I have gained in one year 1,500 offspring
derived from known parents, and have reared about 500 of them to a period
when their adult plumage characters were distinguishable. For keeping
records I have used a field pocketbook and a day book at my work-table.
" Loose leaf" forms were used for the description of each of the stock, for
its egg record, for a chart of its plumage, and for its photographs. Finally,
the results of each set of experiments are kept in a large book, posted nearly
to date.

INHERITANCE IN POUI/TRY.

In treating of my experiments I propose first to give the results by the
races crossed, and, secondly, to discuss in order the problems that were set
at the beginning. My experiments led me to lay little stress on the races
as named by fanciers. In fact it is not races that have been crossed but
characteristics. However, as the breeders' names have a utility in bringing
to the mind a certain combination of characteristics, they have been freely
employed. The different races whose offspring are discussed in this paper
are given below in the order adopted in Wright's Poultry Book.

Buff Cochin (Bantam).
Black Cochin (Bantam).
Dark Brahma (Bantam).
Black-breasted Red Game.
Single-comb Black Minorca.
Rose-comb Black Minorca.
Single-comb White Leghorn.

White-crested Black Polish.

Houdan.

Frizzle.

Silky.

Tosa fowl, or Yokohama.

Rumpless Game Bantam.

C. RESULTS OF CROSSING.

Series I.— Single-comb Black Minorca and White-crested Black Polish.
STATEMENT OF PROBLEM.

The cross was undertaken primarily to learn the method of inheritance of
the crest, cerebral hernia, and comb of the remarkable Polish fowl.

THE RACES AS A WHOI^E.

The Black-crested White Polish (figs, i and 2) belongs to a class — Polish
fowl — which is one of the fundamental types of poultry. The origin of the
Polish fowl is obscure. They were mentioned by Aldrovandi in the six-
teenth century. They are found to-day in most parts of the world, and their
most characteristic feature may, indeed, have originated independently many
times. This feature is a cerebral hernia and its associated crest of large
feathers.

The Single-comb Black Minorca (figs. 3 and 4) is a typical representative
of the Mediterranean class of poultry — tall, stately, close- feathered, non-
broody fowl, — modern representatives of the ancient Egyptian poultry.
They seem, indeed, to have come from Spain, those imported to England
having, according to Wright (1902, p. 391), come from the island whose
name they bear. The single-combed form is the original and typical variety.

TABI<E OP CHARACTERISTICS.

No.

Characteristic.

Single-comb Black
Minorca.

White-crested Black
Polish.

I

Comb

Single, very large ....

Two papillae.

2

Nostrils

Narrow

Wide or high

•I

Top of head — skull

Normal

Cerebral hernia.

4

Top of head — plumage form . .

Plain

Crested.

f.

Top of head — plumage color. .

Black

White and black.

SINGLE-COMB MINORCA AND WHITE-CRESTED POLISH. 7

REMARKS ON THE CHARACTERISTICS.

1 . COMB. — The single comb of the Minorca (fig. 4) is derived from the primi-
tive wild ancestor, for all the four feral species of Gallus have a single comb.
What is remarkable about the comb of the Minorca is, however, its enormous
size, gaining in many fowls a length of 150 mm. and a height of 100 mm.
This seems to have been brought about by selection of extreme variants in
fluctuating variability ; at any rate, English breeders have gone further than
American breeders have thought wise in the production of enormous combs.

The Polish comb (fig. 7, PI. II) is a remarkable structure and is a phylo-
genetically new form. Some breeders try to eliminate it altogether ; others
retain it as a pair of horns. I quote from some of the "Standards" and
descriptions of authors. Mr. P. Jones in Tegetmeier (1867, p. 176) says:
" There should be no appearance of comb." Darwin (1876, Chapter VII)
says : ' ' Comb absent or small and of crescentic shape. ' ' According to Wright
(1902, p. 443), "The comb should be practically absent, but on close inspec-
tion two very small horns can generally be discerned." Baldamus (1896,
p. 149) states : " Kamm nicht oder kaum bemerklich, hochstens 2 kleine
Spitzen zulassig." The American Standard of Perfection (1905, p. 152)
announces : ' ' Comb V-shaped, of small size, the smaller the better ; set evenly
on head, retreating into crest ; natural absence of comb is preferred." My
parental stock (fig. 7) had two large papillae of irregular form and large
confluent base. Further discussion of this type of comb will be deferred to
page 65.

2. NOSTRILS. — In the Minorca, as in the Jungle fowl, each of the external
nares is a horizontal slit bounded above and laterally by a fold of cornified
skin (compare fig. 22). The slit leads into the outer ethmoid cavity. By
removing the membrane the outer fold of the ethmoid can be seen as a ridge
that extends well distad (Fig. A). In the Polish fowl the outer membrane

L~ — — j

1 2 3

PIG. A. — i. Cross-section of beak of Polish fowl through wide nostril;
a. e., outer ethmoidal fold. 2. Cross-section of beak of Minorca fowl through
narrow nostril; p. w.,premaxillary bone ; «, nasal bone. 3. Cross-section
of beak of fowl behind nostril ; o. e., outer ethmoidal fold.

is so short that the narial aperture is very wide and the outer ethmoidal fold is
exposed to view. The nostril may be said to be wide or " high " (figs. 7, 12).
Sometimes the upper margin of the nostril may even be elevated above the
level of the culmen of the beak, and in this case a transverse fold crosses the
culmen from nostril to nostril. This I call the culminal fold.

The morphology of the nostril of the Polish fowl seems to be little under-
stood. The term "cavernous" is applied to this form by the American

8 INHERITANCE IN POULTRY.

Standard of Perfection (1905, p. 13), which speaks of the hollow protruding
nostrils. Wright (1902, p. 441) in treating of the cranial dome says :
' ' Excess in one part being often connected with defect in some other, as
Mr. Darwin pointed out, the skulls with this peculiarity usually show a
chasm in the intermaxillary bones, which in other fowls support the roof of
the nostrils ; owing to which deficiency in bony support the nostrils of all
heavily crested fowls appear flattened and depressed and yet cavernous in
character. ' ' Darwin (1876, Chapter VII) attributes the width of the nostrils
to the circumstance that the branches of the premaxillary and of the inner
processes of the nasal bone are somewhat upturned.

Comparing the skull of a Polish fowl with that of a Minorca, I find the
following relations :

First, the nasal bone has in the Minorca as in most other fowl the form of
the Greek A ; the single stem (processus frontalis) projects caudad and lies
as a flat plate above the frontal bone by which, also, it is cut off from contact
with most of the lachrymal bone. The two anterior branches enclose between
them the olfactory space. The processus maxillaris runs nearly perpendic-
ular to the maxillary bone ; the processus premaxillaris is a slender stylet
terminating over the middle of the olfactory space and embracing the nasal
process of the premaxillary bone (Fig. A, 2, ri). In the Polish fowl the pro-
cessus frontalis is relatively shorter and broader. The whole central nasal
area is greatly depressed, forming a cavity in front of the cranial dome — a
cavity that is filled with the cartilaginous foundation of the rudimentary
comb. In front of this depression of the skull the processus premaxillaris
rises, reaching about the normal height of this part of the nasal bone, and
stops there in the posterior quarter of the nasal space. Thus the bony
nasal space is posteriorly of normal height. What is peculiar in the skull
of the Polish fowl is that the processes premaxillaris are very short and slender
and do not embrace the nasal process of the premaxillary, but instead the
cartilaginous dorsal edge of the orbitosphenoid or mesethmoid. This thick-
ened dorsal edge continues anteriorly as the edge of the internasal septum, and
it replaces the nasal processes of the premaxillary. Anteriorly the septum
abuts upon the premaxillary. At this point there is adhering to the premax-
illary a mass of tissue in the median plane which seems to be the rudiment
of the nasal process of the premaxillary.

In criticism of Darwin' s explanation of the wide nostril based on the ground
that the nasal process is upturned, it may be said that the wide nostril lies in
front of the upturned nasal bone and in a part of the nasal space that is not
higher (nor wider) than in the normal skull. I think it must be concluded
that the wide nostril is independent of the width of the nasal space. As we
shall see later, the wide nostril is never found in connection with a single comb.

3. FORM OP SKUU,. — Polish fowl have long been noted for the remarkable
form of their skull. This was referred to by Bovelli (1670, cent. 2, p. 157,

SINGLE-COMB MINORCA AND WHITE-CRESTED POLISH. 9

teste Hagenbach) and has been studied by Blumenbach (1812), Hagenbach
(1839), Tegetmeier (1856), Darwin (1876), and others. A dome rises from
the front of the nasal bone often to a height of 15 or 18 cm. (figs. 7, 10,
PI. II). This dome is the secondary bony covering of a cerebral hernia
whose dura mater has become ossified. Such cerebral hernias are not un-
common among poultry. Roughly, i per cent of the chicks (outside of the
crested races) that failed to hatch in my incubations and were examined by
me had such a hernia. In one or two instances Polish chicks that died
before hatching were affected by incomplete closure of the cerebrum, the
top of the head not being covered by bone or skin. Such an abnormality
has been described by Hagenbach (1839, pp. 324-326) also. So profound a
modification of the brain would naturally be associated with mental pecul-
iarities. My own Polish have shown themselves very slow of movement,
and two male Houdans (having the same sort of abnormal skull) were
affected by some trouble in the head which led them to move backward,
turn somersaults, and move otherwise abnormally. Hagenbach states that
the Polish fowl are subject to apoplexy and epilepsy. It is remarkable
that formerly the hens alone had the cerebral hernia (Darwin, 1876, Chap.
VII), while now it occurs in both sexes.

4. CREST. — This consists of a number of large white feathers arising from
the frontal region of the skull (figs. 1,2, and 7). Structurally, they, like
normal feathers from the top of the head, have the barbules of the distal
portion of the barbs reduced so that the barbs do not interlock. This con-
dition is seen in the hackles of all breeds. The form of the feathers resem-
bles that of the hackle, being more attenuated in the male than the female.
The great size of the crest feather, like that of the hackle, is largely due to
its long period of growth. After molting, the new crest feathers are char-
acterized by long and stout sheaths in which the feather develops. These
persist after most of the other contour feathers no longer possess sheaths
and consequently have stopped growing.

The cause of the crest is a matter of much interest. Hagenbach (1839,
p. 329) raises the question and says : 4

Nicht ohne Bedeutung scheint mir iibrigens eine auf die Hemicephalie beziigliche
Beobachtung von Meckel* zu sein, welche so lautet : "Sehr merkwiirdig ist die haufig
vorkommende regelwidrige starke Entwicklung von Haaren an ungewohnten Stellen.
So finde ieh bei einigen von deneii, welche ich vor mir babe, und gerade bei denen, wo
der Hauptmangel am grossten ist, fast den ganzen Korper, besonders aber den Riicken,
die Hiiften und die obern Extremitaten, mit Haaren von 6 L/inien bedeckt."

Whether or not the developmental disturbance is the cause of the pro-
longed growth of feathers, it is certain that the immediate cause is the
unusual and prolonged nutrition of the feathers. The skin from which they
arise is thick and rich in blood-vessels. Whether the cerebral hernia is a

* Handbuch der pathologischen Anatomic, Tom. I, p. 195-260.

IO INHERITANCE IN POULTRY.

necessary antecedent of the increased nutrition of the feathers or not can be
tested by hybridization, which will show whether or not crest and dome are
absolutely correlated.

5. COLOR OP CREST. — In our race this is white, in striking contrast with
the rest of the plumage. This color is not necessarily associated with the
crest. Wholly gold- spangled, silver- spangled, buff, white, and even black
Polish have been created. On the other hand, since normal poultry with the
top only of the head white are unknown, it seems probable that the color of
the crest has dissociated itself from that of the other parts of the body as an
independent unit character. Consequently it is not strange to find a black-
crested white breed of Polish (Wright, 1902, p. 448). It will be of interest
in our experiments to see how far color and crest are dissociable.

MATERIAL.

The mothers in this experiment were partly Polish, partly Minorca. The
Polish mothers, Nos. 6 and 7,* were good representatives of their breed,
with perfectly black plumage except for the well-developed white crest.
The Minorca mothers, Nos. 13 and 14, were also typical birds without trace
of mealiness in feathers.

The father Minorca (No. 12, fig. 4) had a great red comb, 150 mm. long,
with seven points, one of which rose to 100 mm. above the level of the
head. Its plumage was perfectly black. The paternal Polish (fig. 2) had
as representative of the comb a pair of papillae. The crest anteriorly con-
tained some black feathers with white base or tip ; next came feathers 75 to
loo mm. long, at first largely, then wholly white. At the posterior end of
the crest, where it passes into the nape, black gradually makes its appearance
until the exclusively black feathers of the neck are reached. White and
black do not blend on any feather, but coexist in a particulate fashion.

RESULTS.

i. COMB. — First gerieration. Of 88 hybrids between single-combed and
Polish-combed all follow a single type, which is, however, very variable.
The comb is single anteriorly but bifurcated behind. This may be called
the Y-shaped comb. The point of splitting occupies a variety of positions.
Usually it lies in the middle third of the whole comb (fig. 8). In some
cases, such as Nos. 67 £ (fig. 8), 1769, 350?, and 4089, the splitting
point is close to the anterior end, so that the comb is cup-shaped. f In other
cases the point of division may be so far posteriad that only the last or the
last few serrations are split. Indeed, in one case (No. 324, which died five
weeks after hatching) , the comb was apparently perfectly single. I regard,
this as the last term of the series and suspect that there existed, even in this

* Bought July i, 1904 ; No. 7 died October 17, 1904.

fSuch a comb is mentioned by Darwin (1876, Chap. VII) as formed when the two ends
of a double comb are cemented together.

SINGLE-COMB MINORCA AND WHITE-CRESTED POLISH.

II

case, a repressed potentiality toward splitting of the comb at its posterior end.
In general, then, the hybrid condition between single comb and supranasal
papillae is a Y-shaped comb* and there is an absence of dominance.

Second generation. When the birds with Y-shaped combs were interbred
the 101 offspring were of three types, as follows :

Characteristic.

No. of

individuals.

Percentages.

Actual.

Expected.

Single comb

30
47
24

29.7
46.5
23-8

a
25
5°
25

ft

18.75

56-25
25.00

Cleft comb

Papillae or "absent"

Total

101

IOO.O

ZOO

100.00

Expectation in this case depends on the theoretical view we take of the
nature of the unit characters involved. We may assume that single comb and
V-comb are the allelomorphs and split comb a heterozygous type, constantly
reproducing itself. On this assumption we should expect the proportion
given in column a of the foregoing table. On the other hand, following the
method of interpretation suggested by Cuenot (1903) and Correns (1905) in
such cases, we may assume two pairs of allelomorphs, namely, (i#) median
comb and (id*) no median, and (20) no splitting and (2^) splitting. Taking
median comb and splitting as dominant, the single comb combines the two
characters : median comb, no splitting ; the V comb combines : no median
comb, splitting. In generation F, the four characters are combined : median
(no median), splitting (no splitting), and the comb is Y-shaped, the char-
acteristics put in parenthesis being recessive. The F2 generation follows
the law of inheritance in dihybrids :

Per cent. Class.

( Splitting X splitting 6# ) yS3/ - , .

25 % (Median X median}. . 1 2 (Splitting x no-splitting) . . E2# / I0/* '°

( No-splitting x no-splitting. . 6% (b)

Relative
frequency.

dian ) .

No-splitting X no-splitting. . 12% (d)

f

' ' ( No-splitting x no-splitting. .. 6% ( /)

Summing up, out of every 16 individuals we should expect:

Characteristic and class.

Relative
frequency.

Per cent.

Median and split comb (a) -\- (c)

">6.2";

Median and unsplit comb (b) -f- (d)

7

18.75

No-median and split comb (ei

i

1

No-median and no-split comb (_/")

I

| 25.00

* For further discussion of the Y-shaped comb see page 65

12

INHERITANCE IN POULTRY.

On account of the difficulty of deciding in the case of any young chicks
whether ' no-median and no-splic comb ' is present, the last two classes are
combined in the right-hand column of this table and in columns a and p of the
table above.

In comparing the fit of the expected percentages on the two hypotheses
with the actual, it is seen that hypothesis a is the better. However, the real
test will come in the F3 generation. On hypothesis a the single-combed
individuals bred together should produce only median-combed offspring. On
hypothesis /? they should produce some without median comb.*

first generation hybrids crossed with Minorca. When the Y-shaped comb is
crossed back on the single comb of the Minorca (No. 26 $ ) the following
distribution of comb characters was obtained :

Characteristic.

Frequency.

Per cent.

Single comb

21

52.5

Cleft comb

f 19

47-5

Papillae or " absent "

o

o.o

This result accords well with the expectation that 50 per cent of the
combs shall be of the pure Minorca type and 50 per cent of the heterozy-
gous type.

2. NOSTRILS. — First generation. No case occurred of a typical high nostril;
this characteristic is dominated by the narrow nostril ; but this dominance
is imperfect. In three cases (5 per cent) the nostril is recorded as one-half
high, i. e., having an aperture one-half as high as the extreme. In the
other cases, placed in class 2, the breadth was less, but still evidently influ-
enced by the germinal representative of the ' ' high ' ' characteristic. In two
skulls that were dissected the processus nasalis of the premaxillary bone
was present.

Class.

Characteristic.

First generation.

Class.

Characteristic.

Second generation.

/•

Per cent.

/

Per cent.

•{

3

I ^
( I0

0

83
17

0

:{

3

Narrow

I ^
1 "
18

52-9
25-9

21.2

a. One-third high 7
b. One-half high 3
High

a. One-third high 16
b. One-half high 6
High or nearly high

Total

Total

57

100

85

IOO.O

Second generation. In the second generation the high nostril appears again
in full or nearly full size in 2 1 per cent of the cases. Class 3 includes two

* This topic is discussed again, generally, at page 68.

f Including one thick comb with a median ridge in addition to the cleft comb, forming
a typical pea comb. Seen in unhatched chick XVIII, 103.

SINGLE-COMB MINORCA AND WHITE-CRESTED POLISH.

cases iu which the records read three- fourths high ; but even in the Polish
fowl the high nostril varies somewhat. Theoretically, we should expect 25
per cent of the second generation to have the recessive high nostril. The
deficiency may indicate merely insufficient numbers, or perhaps some of
the " one-half high " group truly belong in " class 3." The essential facts
are, first, that high and narrow are segregated, and that in the second
generation also dominance is frequently imperfect.

First generation hybrid crossed with Minorca. The heterozygous mothers all
had narrow nostrils, as of course had the Minorca father. No true case of
high nostril occurred. The recorded distribution is as follows :

Class.

Nostril.

No of
individuals.

i

Narrow

12

2

One-third to one-half high

H

It seems probable that the 12 individuals with narrow nostrils belong to
homogametous birds and the 13 individuals of class 2 to heterogametous
birds.

3. CEREBRAL HERNIA. — First hybrid gene ration. Every bird was without a
typical cerebral hernia. Nevertheless some of them showed clear traces of
their mixed ancestry. On the frontal bone of all fowl is the so-called
frontal eminence which is covered by fascia and the thickened skin of the
crest. The profile of the skull from the apex of this eminence to the
parietal is nearly straight, except for a slight concavity limiting the frontal
eminence. In hybrids this concavity is frequently still more marked, the
eminence being higher. Indeed, in one case (No. 405 $ ) the concavity is
so marked that, as far as one can judge from the living bird, there is a
slight hernia. We see, then, that though plain head is dominant it is incom-
pletely so.

Second hybrid generation. The following is the distribution of this char-
acteristic when the hybrids are bred inter se. Expectation is: 75 per cent
without hernia, 25 per cent with hernia. The result agrees closely with
expectation.

Characteristic.

Frequency.

Per cent.

75

76.5

23

23.5

Total

98

IOO.O

First hybrid generation crossed with Minorca. Since the first generation is
DR and Minorca is D, half of the offspring will be pure dominants and half

INHERITANCE IN POULTRY.

heterozygous, both halves showing the dominant "absence of hernia."
The result agrees with expectation.

Characteristic.

Frequency.

Per cent.

Hernia absent

T.A

IOO

Hernia present

o

Total

4. CREST. — First hybrid generation. The crest is present in every hybrid
old enough to show a crest, yet always in reduced size. Crest is dominant,
but the dominance is imperfect. The crest is larger in the females (fig. 5)
than in the males (fig. 6).

Characteristic.

Frequency.

Per cent.

Crest absent

o

o

Crest present

7o

IOO

Total

7o

Second hybrid generation. All records, from embryo chicks as well as
adults, give :

Characteristic.

Frequency.

Per cent.

Crest absent

21

*^O.7

Crest present

C.2

6Q.";

Total

75

IOO O

*Fig. ii.

Expectation is that crest will be absent in 25 per cent of the cases. The
excess is probably due to the fact that, since crest develops late, it was noted
as absent when it would have appeared in adult life. To test this I give a
table based on hatched chicks only :

Characteristic.

Frequency.

Per cent.

Crest absent . ...

ii

21 2

Crest present

41

788

Total

62

IOO O

This gives a close approximation to expectation, with a slight excess of
crested individuals. The exact statistical proportion, with its possible errors

SINGLE-COMB MINORCA AND WHITE-CRESTED POLISH.

of classification, is less essential than the fact of reappearance in about one-
fourth of the cases of the recessive characteristic.

First hybrid generation crossed with Minorca. Since plain-head is R, the
cross is of the order DR X R ; from which we should expect an equal number
of heterozygous (crested) and pure recessive (plain-headed) offspring. The
result, though based on small numbers, accords with expectation.

Characteristic.

All records.

Hatched
chicks only.

Crest absent (RR)

12

6

Crest present (DR)

8

6

Total . .

20

12

5. COLOR OF TOP OF HEAD. — First hybrid generation. All records give :

Characteristic.

Frequency.

Per cent.

Wholly black

36

64.';

Black and white

20

7C.7

Total

56

IOO.O

It is to be noted, first, that the white of the crest tends to disappear in the
later molts, some birds which showed it at 2 months losing it by 6 months,
or showing white at the tip only of the crest feathers. Further, with two
exceptions, all crests with white feathers belong to females (which have
larger crests than males). The two exceptional males are still young and
have only a trace of white remaining ; this will probably disappear in the
next molt. Third, the proportion of white to black in the crest is always
small — much smaller than in the Polish crest. Tne result looks like an
imperfect dominance of black.

Second hybrid generation. Hatched chicks only give :

Characteristic.

Frequency.

Per cent.

Wholly black

24

47.1

Black and white

27

52 Q

Total

CI

IOO.O

I interpret this irregular result to be due to the imperfect dominance of
black. Twenty-five per cent of the individuals have wholly black gametes
and 25 per cent wholly black-and-white, or mosaic, gametes. The 50 per
cent with mixed gametes tend to be black, but contain white in varying pro-
portions. Something more than one-fourth of the black-and-white headed
individuals are males.

1 6 INHERITANCE; IN POULTRY.

First hybrid crossed with Minorca. All records give :

Characteristic.

Frequency.

Per cent.

Wholly black

21

QI.7

Black and white

2

8.7

Total

21.

IOO O

Expectation, assuming complete dominance of black, is 100 per cent of
black individuals. Result shows incomplete dominance. Of the black-and-
white headed individuals, one is a female ; the other died too early for the
sex to be determined. Here, again, dominance is less perfect in the female.

6. CORRELATION OF CHARACTERS. — In the Single-comb Black Minorca
and in the White- crested Black Polish there is an assemblage of characters
that are nearly always associated in those races. The first hybrids have
another constant association unlike either of the parents, viz., split comb,
black crest (in the male) without cerebral hernia, and low to medium nos-
trils (fig. 6). In the second generation of hybrids, on the other hand, occur
combinations of characters both of the parental species and also of the first
generation of hybrids. These combinations are of the most varied sort, so
that characteristics always found associated in one parent species may here
be found dissociated. When hybrids are bred inter se the following com-
binations are obtained :

No.

Comb.

Crest.

Hernia.

Nostril.

Number of cases.

Actual.

Calcu-
lated.

I

2

3
4
5
6

7
8

9

10

II
12
13
14
15

16

17
18

19

20
21
22

23

24

Y

i r
i i

r

- 0 0 J

J I

Present
Absent ....
Present. . ..
Absent
Present
Absent
Present . . .
Absent ....
Present.. . .
Absent
Present
Absent ....

Absent . . -j
Absent . . <
Present . j
Present.. j
Absent . . •<
Absent . . -j
Present. . •<
Present. . s
Absent . . -j
Absent . . -|
Present. . 1
Present . . s

Narrow ....
High

17
o
8
o

i
o

3
o
8
o

12
O
2
O
O
O
I

8
o

i
4
5
o
o

15
5
5
1.6

5
1.6
1.6
o.5
7-3
2.5
2-5
0.8

2-5

0.8
0.8
o-3
7-3
2.8

2-5

0.8

2.5
0.8
0.8
o.o

Narrow ....
High

Narrow ....
High

Narrow. . . .
High
Narrow ....
High

Narrow ....
High . ..
Narrow ....
High

Narrow ....
High

Narrow ....
High

Narrow
High
Narrow . .
High..

Narrow ....
High

SINGLE-COMB MINORCA AND WHITE-CRESTED POLISH.

This table gives the distribution of characteristics in 70 individuals.
Grouping the individuals under certain alternative characters, we have the
following relations of actual and calculated frequency of occurrence of each
characteristic :

Characteristic.

Actual.

Expected.

Characteristic.

Actual.

Expected.

Split comb

2Q

^S-o

Hernia present ....

16

17.5

Single comb

22

17.5

Hernia absent

SA

52.5

Papillae

10

17.5

Nostril high

14

17.5

Crest present

4Q

C2.S

Nostril low

56

52.5

21

17.5

The actual never deviates far from the expected.

If, however, we compare the actual number of cases of each of the combi-
nations with the calculated the result is instructive. For example, in the
absence of correlation of characters we should expect a high nostril to be
associated with a single comb in 5 or 6 of the 22 cases ; but it is never found so
associated. In fact a high nostril never occurs in this cross dissociated jrom a
rudimentary comb. On the other hand, it appears that a low nostril may be
associated with a rudimentary comb, but in unexpectedly few cases, 4 instead
of about 14. Two of the 4 records are from embryos in the shell, in which
therefore adult characteristics were not fully developed and the other two
cases are recorded as one-half high. It is quite possible that an atypical
nostril and absence of true comb are always associated (fig. u).

In order not to complicate the table too much, the correlation between
crest and color of the crest feathers was omitted. A subsidiary table is con-
sequently given here :

Crest present.
Crest absent .

(Black .......................... 18

\ White and black . ........... 23

/Black .......................... 9

\ White and black ................ 6

Whether crest is present or absent white occurs on the head ; but it is more
apt than not to occur when the crest is present and less apt than not when
the crest is absent.

CONCLUSIONS.

In the cross under consideration no characteristic is inherited in strictly
Mendelian fashion, for in no case is dominance complete. The nearest ap-
proach to typical Mendelian dominance is exhibited, in the present cross, only
when crest is crossed with no crest. The new additive characteristic — crest —

1 8 INHERITANCE IN POULTRY.

is dominant. But the crest of the first generation hybrids is always of small
size. likewise, plain head is dominant over cerebral hernia, but some of
the hybrids have exceptionally high frontal prominences. The white color
of crest is recessive in the male hybrids, but is not entirely shut out from the
females. The high nostril is recessive, yet the presence of its representative
in the hybrid gives the latter abnormally wide nostrils. Finally, the comb
affords us a case of an organ in which neither parental form can be said to
be dominant without such an extension of the term as to render it quite
vague. Every individual shows a modified comb — the Y or 0 shaped comb.
This is a new form — a heterozygous form — that probably reappears in the
heterozygotes of each generation.

The facts of correlation show that crest is by no means dependent on
cerebral hernia. At the same time I doubt if the absence of present corre-
lation disproves the hypothesis that the crest was the result of the hernia. It
is at least conceivable that a characteristic that arose as a response to the
stimulus of an abnormal ontogenesis should become hereditary and inde-
pendent of the stimulus. As for white color on the top of the head, it is
dissociable from the crest, for wholly black-crested second hybrids occur.

Series II.— Single-comb White Leghorn and Houdan.
STATEMENT OF PROBIvEM.

This cross was undertaken for comparison with that between Minorca and
Polish, and to test the inheritance of plumage color, extra toe, and face
feathering.

THE RACES AS A WHOLE.

The Leghorn (fig. 15) is typical of the Mediterranean class of poultry-
slender, tall-legged, close-feathered, nervous, and non-broody — the same class
as that to which the Minorca belongs. The white Leghorns came originally
from northern Italy.* They have been bred in America since 1834. The
single-comb variety is one of the most widely bred of our races and has the
reputation of being the greatest egg-producer. Considering its white
plumage, its transparent skin, with a trace of yellow, and its red iris, it
conies very near to being an albino race, but the retina is pigmented.

The Houdan (fig. 16) comes from France. It, like the Dorking, has
doubtless descended from the 5-toed fowls of the Romans, described by
Columella, which they probably carried to Gaul in their conquest of that

* Wright, 1902, p. 385; Wyckoff, 1904, p. 788.

SINGLE-COMB WHITE LEGHORN AND HOUDAN.

country. This may have been crossed with ' ' the old crested race of Caux."*
The Houdan may be regarded as one of the fundamental types.

TABI.E OF CHARACTERISTICS.

No.

Characteristic.

Single-comb White Leghorn.

Houdan.

i

General plumage color ....

White

Black white-tipped

2

Color of upper mandible. . . .

Yellow

L-ight horn.

a

Nostrils . .

Narrow

High

A

Cotnb

Single (rarelv cleft behind

2-pronged or V

<;

Face feathering

No. n.)
Plain

Whiskered

6

Chin feathering

Plain

Bearded

7

Dorsal head plumage

Plain

Crested.

8

Dorsum of cranium

Plain

Domed

q

Foot color

Yellow

White.

10

Number of toes .

Four . .

Five.

comb

DISCUSSION OF CHARACTERISTICS.

1. GENERAL PLUMAGE COLOR. — In the Leghorn this is typically white,
and the most highly selected birds are without trace of black specks or
yellowish lacing. The yellow lacing is hard to get rid of. The Houdan
color consists typically of black feathers occasionally

tipped with white (fig. 16).

2. COLOR OF UPPER MANDIBLE. — The clear yellow
of the mandible of the white Leghorn is part of the
general pigmentation of the skin. Much yellow pig-
ment is deposited over the body. It shows prominently
in the tarsal scutes. The Houdan mandible is clear
black.

3. NOSTRILS. — The high nostrils of the Houdan
(fig. 12) are like those of the Polish fowl (page 7).

4. COMB. — The comb of the Houdan in America is
the so-called V-comb. It differs from the Polish comb
(page 7) in that the two horns arise from the sides of
a median swelling (Fig. B). In England the Houdan
is cultivated with a leaf comb consisting of two broad,
flat expansions of the horns arising from a median

ridge like ' ' a butterfly with open wings. " f It thus resembles the posterior
part of a Y-comb (fig. 8). The single comb of the Leghorn is very large
and lops in the female to the right or left side of the head.

*Petersen, C. E., 1905, p. 961, quoting P. Megnin : "ijleVage et engraissement des
volailles."

f Hurst, C. C., 1905, p. 132.

•« — nostril
c.f

FiG. B. — Dorsal view of
beak of Houdan 9A</
showing pail of clublike
papillse, c, that represent
the v-comb, c. f., cul-
mitial fold.

2O INHERITANCE IN POULTRY.

5. WHISKERS, OR MUFF. — This is a bunch of long feathers growing from
the sub-orbital and post-orbital region of the head. This characteristic, of
whose origin nothing is known, has been engrafted on several of the other
French breeds : the Crevecoeur, the Faverolle, the Du Mante, the Cossack,
the Bourbourg, etc. The muff occurs also on breeds which have little in
common with the French fowl, e. g. , the Sultan and the Orlaff and Pavaloff of
Russia.

6. BEARD. — This consists of a number of long feathers growing from the
middle of the chin and upper throat region (fig. 16). There is a fold of
skin here from which the feathers arise. Such a beard is usually associated
with the muff. The fold of skin, "dewlap," is found in some Indian Games
and, less marked, in the Dark Brahma male.

7. 8. CREST ; CEREBRAL HERNIA. — These are indistinguishable from
those of the Polish (pp. 8-10).

9. FOOT COLOR. — The brilliant yellow color of the tarsus of the Leghorn is
strikingly different from the colorless or dirty gray tarsus of the Houdan.
There must be a special yellow pigment in the skin of the former which is
absent in the latter.

10. NUMBER OF TOES. — The possession of an extra toe (fig. 13) is an ancient
characteristic of poultry. The Latin author Columella, speaking of the fowl
kept by the Romans, says : ' ' Those hens are reckoned of the purest breed
which are 5-clawed, but so placed that no cross-spurs arise from the legs."
Since the tendency to extra toes must have arisen spontaneously once, there
is always a possibility that it has done so several times, and it is by no
means certain, although probable, that the extra toe of the Polish is genet-
ically connected with that of the Roman fowl referred to. The following
record of occurrence of extra toes in poultry is interesting, since in this case
no relation to the Roman fowl is probable. A writer* in Der Zoologische
Garten states that Carl Bock in his " Reich desweissen Elefant," p. 267, re-
lates that he, in a journey from Tschengmai, on the third day reached
Muang Hawt, a way station on the road to Mulmen. This village is dis-
tinguished for its 6-toed fowl. Again, the Silky fowl, which certainly have
little in common with the Dorking, have extra toes (page 59) . The extra toe
is to be regarded as a sport which has appeared at different times and which
is easily maintained as a racial characteristic. The question of the inher-
itance of such a sport is always interesting. The Houdan has typically
only one extra toe, making 5 in all ; it is occasionally found with 6.
Bateson andSaunders (1902, p. 98) sometimes got 6 toes in hybrids between
Leghorns and Dorkings. The length of the extra toe and the completeness
of bifurcation are very variable.

* Langkavel, B. 1886, p. 35.

SINGLE- COMB WHITE LEGHORN AND HOUDAN. 21

PREVIOUS INVESTIGATIONS.

During the progress of my experiments appeared the second report to
the Evolution Committee of the Royal Society by Bateson and others.
This contains a paper by Hurst (1905, p. 133) giving his results with White
Leghorn male X Houdan female. These will be considered in comparison
with my results.

MATERIAL.

The mothers were two Houdan hens* (fig. 16) purchased from a dealer
as pure stock. They agreed well with the standard requirements. When
bred with a Houdan male they produced only typical Houdans.

"£\i£. father was a Single-comb White Leghorn f likewise of unknown
ancestry. The plumage of No. I3A is devoid of black pigment, and mated
with White Leghorn hens it has produced only White Leghorn offspring.

RESULTS.

i. GENERAL PLUMAGE COLOR. — First hybrid generation. Of 41 individuals
all were white in plumage (fig. 17), but almost without exception both in
down plumage and that of the adult there were traces of black on one or
more feathers, particularly those of the back ; more especially was this true
of the females than of the males.

Hurst (1905, p. 133) got ii black chicks out of 105 offspring and in the
first plumage these developed into 6 black (all pullets) and 5 barred (all
cockerels). Here also females have more pigment than males. Of the white
chicks all except two developed black ticking. Doubtless these two were
males.

Second hybrid generation. When these hybrids were crossed inter se, out of
50 individuals 9 were markedly pigmented like the Houdan. This is 18 per
cent of all cases, expectation being 25 per cent. With larger numbers
Hurst (1905, p. 138) got 24.3 per cent black. Equally striking is the
occurrence of many pure white individuals along with the impure whites.
The pure whites that were reared to maturity proved to be males ; the impure
whites were females.

First hybrid ( No. <?/ $ ) crossed with white Leghorn {No. 71 $ ). The father
was pure white ; the mother was speckled with black. Of 22 offspring all were
white, but some had single pigmented feathers. All males (9) are pure white,
excepting No. 562, which has some black on two feathers of the left wing
coverts, and No. 649, which has one-half of one right wing covert black.
My only certain female has a score of partly black feathers. Hurst (1905,
p. 139) obtained 66 clear white chicks and 69 white, ticked with black. I

*Nos. 8 and n, received July i, 1904, from Geo. C. Ely.
f No. I3A., received Sept. 15, 1904, from a farmer.

22

INHERITANCE IN POULTRY.

judge this equality to indicate a difference of color in sex ; or else the pig-
mented individuals are heterozygotes. Possibly the females are the hetero-
zygous forms — the males homozygous.

2. COLOR OF UPPER MANDIBLE. — This assumes its final condition so late in
life that definite statistics will not be given now.

First hybrid generation. A few young are recorded as showing yellow.
The rest are white ; this is probably the young condition of the light horn
of the adult Houdan. I/ight horn seems dominant.

Second hybrid generation. A few cases of black mandible are recorded,
even in the young, where pigment is less developed.

First hybrid (87) crossed with white Leghorn. All older chicks have white
mandibles ; there are no blacks.

3. NOSTRILS. — First hybrid generation. Of 25 individuals, all but one have a
nostril of one-half width or less — thus approaching the white Leghorn type.
The exceptional individual (No. 386 9 ) has a typical high nostril and is
peculiar in respect to comb also. Only one individual is recorded as having
as narrow a nostril as the Minorca.

Second hybrid generation. Forty-nine individuals give :

Characteristic.

Frequency.

Per cent.

Narrow (24) and intermediate (8)

T.2

65.5

High

17

14 c

Total

4Q

IOO O

On the assumption that " narrow and intermediate " includes pure- narrow
and heterozygous individuals, while " high " includes recessive, pure-high
individuals, we should expect 75 per cent and 25 per cent in the two classes
respectively — only an approximate agreement with the actual.

First hybrid {No. 87$} crossed with white Leghorn (//$). The father
has a "one-fourth" nostril; the mother, of course, a typical "narrow"
one. Of 24 individuals 12 are recorded as narrow; 12 as intermediate of
some grade. This gives the ratio 1:1, which we expect, assuming the inter-
mediate nostril to be the heterozygous type ; the narrow, the pure type.

4. COMB. — First hybrid generation. Of 41 individuals 40 have the Y-shaped
comb in some form (fig. 17). This comb resembles that of the Minorca
X Polish hybrid. There is no case of a single comb in this generation, but
there are two cases in which the posterior end of the comb is merely much
thickened. On the whole the present series of cleft combs differs from the
former in that a smaller proportion of the comb is split — no cases of wholly
split or cup combs occur, although in one important case (87 $ ) two-thirds

SINGLE-COMB WHITE LEGHORN AND HOUDAN.

of the comb is cleft. A new characteristic of this series of cleft combs is
the occasional appearance of a median comb lying between the two wings of
the cleft comb — a posteriad continuation of the single part of the comb.
This condition appears in three cases (258 $ , 259 $ , 448 $ ). It is important
for the interpretation of the cleft comb. It gives the posterior part of the
hybrid comb the triple condition characteristic of English Houdans.

The one case that lacks the Y-shaped comb is No. 386 9 (with high
nostrils). She has only a pair of papillae. Hurst (1905, p. 133) got no
single comb in 105 offspring.

Second hybrid generation. Fifty- five individuals show the following dis-
tribution of comb forms :

Characteristic.

Frequency.

Per cent.

Actual.

Expected.

Single

17
23
15

30.9
41.8

27-3

2*5 (18-75)
50 (56.25)
25 (25.00)

Y comb .....

o o or absent.

Total

55

IOO.O

IOO (lOO.OO)

The Y comb being the heterozygous form should appear in 50 per cent of
the cases ; each of the other forms in 25 per cent. The deviation from
expectation is of the same character as in Series I. That the approximation
to theory is less close is probably due to the smaller total number. Hurst
(1905, p. 138) obtained 56 ordinary single combs in 226, or 24.8 per cent.

First hybrid (Sy $ ) crossed with white Leghorn (jr 9 ). The Y-shaped comb
crossed with single gives, in 26 individuals :

Characteristic.

/•

Per cent.

Single

15
ii

57-7
42.3

Cleft, etc. (se
Total .

? Remarks)

26

IOO.O

REMARKS: Including two cases in which a median ridge runs through
the cleft comb. Of these one is a nearly typical pea comb except that
the side lobes are higher than the median one. Including, furthermore,
one case of an arrow-shaped comb, two parallel V 's occurring in front
and behind, respectively, being joined by a median ridge. Including,
finally, two cases of cup-comb.

Here the expected equality is approached. Hurst (1905, p. 139) obtained
60 ordinary single combs in 135 individuals of this cross, or 44.4 per cent.

5. FACE FEATHERING. — First hybrid generation. Of 24 recorded cases all
show the muff (fig. 17).

24 INHERITANCE; IN POULTRY.

Second hybrid generation. All individuals (26) whose face feathering was
observed are recorded as muffed; concerning a greater number (35) the
record is silent. What has become of the expected 25 per cent of muffless
individuals ? It is possible, but on strict chance hardly probable, that the
muffless individuals all died young. A decisive answer to our question
must await further experimentation.

First hybrid (87 $ ) crossed with white Leghorn (71 $ ) . Only one parent is
muffed. Muffed and non-muffed offspring occur in approximate equality ;
but even in the adult muffing is not full in amount. This cross confirms the
result of the first that muffing is dominant, but it is not perfectly so.

6. BEARD. — In Mb& first hybrid generation all individuals are bearded. When
these hybrids are crossed with the white Leghorn about half of the offspring
are beardless. Beard is dominant.

7. CEREBRAL HERNIA. — \-n.\h& first hybrid generation all (24) individuals
were without external evidence of the cerebral hernia. In the second hybrid
generation out of 45 individuals 11 had the hernia (fig. 14) and 34 had
none, or 24.4 per cent and 75.6 per cent respectively. When the hybrid
was crossed with the white Leghorn (71?) no individual with the hernia
appeared. The cerebral hernia is a recessive characteristic. However, the
height of the frontal dome is variable, even in the pure-bred Houdans, and
on at least one occasion the cerebral prominence in an unhatched hybrid
was so high that it was doubtful whether or not it might represent a hernia.
Here, as in Series I, plain-headedness, though clearly dominant, is imper-
fectly so.

8. CREST. — First hybrid generation. Of 2 5 individuals all are crested. Hurst
(1905, p. 134) gets the same result. Second hybrid generation. Of 19 indi-
viduals 6 are non-crested, or 31.6 per cent, approaching the expected 25 per
cent. The remainder are crested. First hybrid (87$} crossed with ivhite
Leghorn (7/9). Of 15 individuals 6, or 40 per cent, are without crest.
Expectation is 50 per cent. Crest is clearly dominant, yet in the first hybrid
it is never so large as in the Houdan. This fact is, I take it, due to imperfect
dominance. It may, however, be associated physiologically with the absence
of a cerebral hernia.

9 . FOOT COLOR. — In the first hybrid generation this always becomes white in
the adult, although sometimes yellow in young birds. In the second genera-
tion of hybrids bred inter sc or with the White Leghorn stock, yellow reappears
as leg color. Statistics would be misleading on this point, as permanent leg
color is reached only on maturity. It may be concluded that white is domi-
nant over yellow.

SINGLE-COMB WHITK LEGHORN AND HOUDAN.

10. NUMBER OF TOES. — First hybrid generation. Among 37 individuals the
following distribution appears :

Number of toes.

/.

Per cent.

4-4 .

6

16.2

4 - 5

81

c - c

23 I31

83.8

Total

VI

IOO O

Hurst (1905, p. 133) got among 105 birds 103 with trace of extra toe
(including duplication of nail and hyperphalangia) and two without any such
trace. The difference in the proportions of extra and normal toes between
Hurst's and my results is partly a matter of classification and perhaps partly
due to the real difference in potency of the extra-toe characteristic in the
two strains.

Second hybrid generation. To learn if the individuals with 4-4 toes were
merely imperfect dominants or true recessives I mated two of them (Nos.
84 9 and 86 9 ) with their brother, a 4-toed cock (No. 83 $ ) . Of 23 offspring,
17 were normal-toed and 6 had extra toes on one or both feet, or nearly 25
per cent with extra toes. Expectation, on the other hand, was either («)
if the 4~4-toed were recessives there should be no extra toes, or else (£) if
extra toe here merely fails to dominate there should be 75 per cent with
extra toes. Hurst (1905, p. 150) mated together two 4~4-toed hybrids and
got 14 extra-toed to 8 normal, or 63.6 per cent extra-toed. He also mated
the same 4-4 hybrid cock with a 4-toed Hamburg Cochin hen, and about
half the offspring had extra toes. He concludes : ' ' These results prove that
the apparently recessive feet with no trace of extra toe .... are in reality
DR's, as both birds gave chicks with e. t. when bred together and with pure
recessives. ' ' I am inclined to doubt if this is the whole story, for one of my
two 4~4-toed hybrid hens, namely, No. 86, mated with 83 $ , gave 12 offspring
with 4-4 toes and no certain offspring without normal toes. This looks as
though 86 9 and 83 $ were both truly recessive. No. 84 9 , on the other
hand, produces extra-toed and normal-toed individuals in about equal pro-
portions. Furthef experiments with 83, 84, and 86 are planned for 1906.

Second hybrid (87 $ ) mated with white Leghorn (7^9). The father (87)
has an extra toe on the left side only. Of 25 offspring 17 have 4 toes
on each side, 6 have 5 toes on each side, and 2 have an extra toe on one
side only.

ii. CORRELATION OF CHARACTERS. — The first hybrids between white
L,eghorns and Houdans show a fairly constant association of characteristics,
a white plumage flecked with black, white mandible, narrowish nostrils,
Y-shaped comb, muffed and bearded face, reduced crest on a domeless head ,

26

INHERITANCE IN POULTRY.

white legs, and toes that are usually but not always meristically abnormal.
When the hybrids are bred inter se we get varied combinations of char-
acteristics, as follows (D meaning dominant and R, recessive) :

Comb.

Nostril.

Hernia.

Toes.

Plumage.

Actual No.
of cases.

f

Low (D) .

Absent (D)

Normal (R)

White (D)

6

LOW

Absent

Normal

Black and white

i

Low

Absent

Extra

White

a

Low

Present . .

Normal. . . .

o

Y -{

Low

Present

Extra ....

I

High . .

Absent. . .

Normal ....

White

I

High

Absent

Normal

Black and white. . .

I

High

Absent . .

Extra

o

1

High

Present

o

f

Low

Absent

Normal ....

White

6

Low

Absent . .

Normal ....

Black and white

o

Low

Absent ....

Extra

White

3

Low

Absent

Extra

Black and white ....

o

Low

Present

Normal. . . .

*2

1

Low

Present

Extra

O

High . .

Absent

Normal ....

O

High.

Absent . . .

Extra

o

High . .

Present

Normal ....

o

High .

Present .....

Extra

o

r

Low .... .

Absent

Normal . .

White

o

Absent

Normal . . .

Black and white

0

Low

Absent

Extra

o

Low

Present

Normal. . . .

I

Low

Present

Extra

0

High

Absent

Normal ,

White

4

High .

Absent . . .

Normal ....

Black and white

I

High

Absent

Extra

White

3

High.

Absent

Extra

Black and white

i

High.

Present ....

Normal

White

3

High . .

Present ....

Normal ....

Black and white

i

1

High

Present

Extra ....

o

38

*Fig. 14.

CONCLUSIONS.

In the series of crosses between the White L/eghorn and Houdan, Mendelian
results were obtained as in the first series. Dominance, however, is frequently
imperfect. The plumage color of the offspring of a pure homogametous white-
and-black and a white are rarely pure white. Likewise in the second hybrid
generation impure whites occur. Also, nostril-height exhibits imperfect
dominance of the narrow type. The muff, beard, arid crest, though always
present in the first hybrid generation, are apparently alwaj^s reduced. The
cerebral hernia, though recessive, affects the dominant normal skull.

A heterozygous form results from hybridizing the single and V-shaped comb.
The cleft comb is a neomorph, of which more will be said in the sequel
(page 65).

Polydactylism does not readily fall into the Mendelian formula. Hurst's
results, although suggestive, need support from other experiments.

HOUDAN AND SINGLE- COMB BLACK MINORCA.

27

Few characters are correlated ; the second hybrid generation exhibits all
combinations, except that high nostril and single comb do not occur together
here any more than they do in the Minorca-Polish hybrids.

Among heterozygous individuals, with Y-shaped comb, the combination
of dominant characteristics (narrow nostril, no hernia, and white plumage)
is the commonest, forming nine-thirteenths of all. These are also, apart
from the Y-comb, all Leghorn characteristics. It appears, too, with the given
parentage, that normal toes are usually present. The low nostril and cerebral
hernia combination occurs several times with or without extra toe. The
combination refutes the notion of Wright (quoted at page 8) that there is any
necessary relation between cerebral hernia and "cavernous" nostril. A
high nostril was in two instances (both of which died very young, one before
hatching) associated with a Y-cornb, but it is doubtful if the median portion
would have developed.

The single comb may occur associated with a hernia (e.g., No. 443,
fig. 14), with extra toes and with mottled plumage, but in my records so
far it is never associated with a high nostril.

The V-shaped comb is commonly associated with high nostril, but rarely
with a low one, despite the fact that low nostril is dominant. It occurs on
white individuals thrice as frequently as on black-and-white ones ; it shows
no preference for the extra toe.

The hernia is never found dissociated from the crest ; but the crest occurs
three times as often as the hernia.

Series III.— Houdan and Single-comb Black Minorca.
STATEMENT OF PROBLEM.

This series was undertaken to compare the behavior of the Houdan with
that of the Polish (vSeries I, page 6) when crossed with the Minorca.

THE RACES AS A WHOLE.

The Houdan is described at page 18 and the Black Minorca at page 6.
Both of the races are fundamental and old. The Houdan contains the
larger assemblage of new characteristics.

TABLE OF CHARACTERISTICS.

Characteristic.

Houdan.

Discussed
at page —

Single-comb Black
Minorca.

Discussed
at page —

Black and white

IQ

Black

2Q

V

IQ

I

7

T. Nostril fortn . . .

Wide

IQ

Narrow

7

4 Crest

Present

2O

Absent

c Cerebral lieniia

Present ...

2O

Absent

6 Muff

Present

IQ

Absent

7 Beard . •

Present

2O

Absent

8 Foot color

White

2O

Black

29

c-e .

2O

4-4

28 INHERITANCE IN POULTRY.

MATERIAL,.

As mothers, Nos. 8 and 1 1 (page 21), original Houdan stock, and later their
daughters, Nos. 60 and 81, were used. No trap nests were employed in
this series and consequently mothers are not exactly known.

Father: No. 27, bred at the station, August, 1904, son of No. 12,
Minorca cock (page 6) and a Minorca hen.

RESULTS.

1 . GENERAL PLUMAGE COLOR. — The young hybrids, like the young black
Minorcas, contain much white on the belly and primaries. In later molt-
ings the white is replaced by black, but even at five months the primaries
are sometimes mealy or white-spangled. Except for this the hybrids have
lost the Houdan white and are of the Minorca color. Minorca uniform
black is dominant over the Houdan mottling.

2. COMB. — First hybrid generation. Of 20 offspring 18 have a Y-shaped comb
like the hybrids of Polish and Minorcas. In two cases (of egg embryos) the
comb was recorded as single, but this is probably only the limiting condi-
tion of the Y-shaped comb, which is here also the heterozygous form.

3. NOSTRIL FORM. — First hybrid generation. In no case does the nostril
width exceed one-half. As in Series I and II, there is imperfect dominance
of the narrow form. However, the nostril in this cross runs lower than in
the Leghorn X Houdan cross.

4. CREST. — This is present in all first hybrids reared to a sufficient age to
render an opinion possible.

5. CEREBRAL HERNIA. — Fj. Always absent. One egg embryo, which died
at about 17 days of incubation, had a vesicle protruding, uncovered by
skin, from the top of the head at the usual position of the hernia. Such a
teretological case is not uncommon in straight- bred Houdans. It is note-
worthy to find it here where the cerebral hernia is recessive.

6. 7. MUFF AND BEARD. — f^ Present in all older hybrids.

8. FOOT COLOR. — Fj. Always black as in the Minorca.

9. TOES. — Of 21 hybrids, 12 have 5-5 toes, 3 have 5-4 toes, and 6 have 4-4
toes. The proportion without extra toes is higher than in the Leghorn x
Houdan first cross, being there 16.2 per cent, here 28.6 per cent.

CONCLUSIONS.

The following characteristics apparently exhibit alternative inheritance:
Plumage color, nostril form, crest, cerebral hernia, muff and beard, leg
color, and number of toes. Dominant are: Uniform black plumage color
(imperfect), narrow nostril (imperfect), crest (imperfect), cerebral hernia
(imperfect), muff and beard (imperfect), and black leg color. Of these the
crest, muffling, and black leg color are positive characters in de Vries' sense
and are dominant. The color pattern of the Houdan yields here to black

SINGLE COMB LEGHORN AND ROSE-COMB MINORCA.

29

as it does in Series II to white ; mottling is recessive to solid color. The
comb, crest, muffling, and extra toe are inherited essentially as in Series II.
Striking is the nearly universal imperfection of dominance.

Series IV. —Single-comb White Leghorn and Rose-comb Black Minorca.
STATEMENT OF PROBLEM.

This cross was undertaken to learn the inheritance in these races of the
characteristics described below.

THE RACES AS A WHOLE.

The Leghorn has been described at page 18 ; the Minorca at page 6.
TABLE OF CHARACTERISTICS.

No.

Characteristic.

Single-comb
White Leghorn.

Discussed
at page—

Rose-comb
Black Minorca.

Discussed
at page —

I

General plumage color. .

White

10

Black

2O

2

Comb form

Single . . .

TO

Rose

2O

•i

Foot color

Yellow

2O

Blue-black'.

2Q

REMARKS ON THE CHARACTERISTICS.

1. GENERAL PLUMAGE COLOR. — Black is one of the constituents of the
color of Gallus bankiva, being the chief color of the breast. Just how a
wholly black condition of plumage was attained is of course not exactly
known ; there are, however, many instances known of melanic sports among
birds. It is probable that wholly black varieties have arisen as a result of
excessive production of the black pigment, melanin.

2. COMB FORM. — The rose comb is a broad mass of erectile tissue replacing
the single comb. Anteriorly it overhangs the nostrils and extends over and
back of the eyes. The upper surface is covered by numerous tubercles.
These do not, in young birds and females, run wholly at random but tend to
lie in five or more parallel lines. Posteriorly the rose comb ends in a finger-
like process or spike. The rose comb is the last term of the series starting
at the single comb and having the triple or pea comb for its middle term.

3. FOOT COLOR. — The dense black color of the scutes of the foot of the
Minorca constitutes a positive or additive characteristic as contrasted with
the pigmeutless condition of the yellow-footed White Leghorn.

MATERIAL-

As mothers three White Leghorns were used, of unknown ancestry but
reputed pure. They had fair Leghorn points except as noted in the descrip-
tions given below. When mated with White Leghorn I3A# they produced
only white offspring.

IOA. Feathers all white ; comb strictly single.

30 INHERITANCE IN POULTRY.

IIA. Feathers mostly white, but some are sooty. The single comb is
cleft behind for about one- fourth of its total length.

1 2 A. Feathers all white ; comb strictly single.

The father, No. QA, also of unknown parentage, has a large rose comb
90 mm. long by 44 mm. broad at its widest part. The tubercles are very
irregular, but five rows of them can be discerned. The plumage is prevail-
ingly black, but many feathers of the back are tipped with white and several
primaries are almost or quite white.

RESULTS.

This series of experiments has been carried as yet through only the first
hybrid generation.

1 . PLUMAGE COLOR. — Eighty-three first hybrids were obtained of which 74
were white, either pure or with some black feathers, and 9 were deeply pig-
mented. Females A and C yielded only white offspring. Female B, on the
other hand, produced chiefly dark birds, recorded as "blue" or "black-
and-white." She was the mother of the 9 pigmeuted birds just mentioned.
B's germ cells are probably mixed. The only two of B's offspring reared
to maturity are blue like the so-called "Andalusian breed " (fig. 54, pi. xvii).
Now blue is a combination of black and white and is a " heterozygous form."
If blue birds, one of which is male, the other female, breed together, both
pure black and impure white, as well as blues again, are to be expected in
the proportions of 1:1:2 respectively.* Of the white offspring of both A
and C it is noteworthy that the males are mostly pure white (i. e. , without
trace of black, although often suffused with yellow), while the females are
always specked with black.

2. COMB FORM. — Of 80 first hybrids 40 have single comb and 40 rose comb.
This result indicates first that the cock is a heterozygote and consequently
produces in its germ glands two kinds of germ cells, viz, those with the single-
comb and those with the rose-comb determinants and second, that rose comb
is dominant. Then : R single X DR rose gives 50 per cent DR rose and 50
per cent RR single.

Batesou and Saunders (1902, pp. 102, 103) find rose comb of Wyandotte
or White Dorking dominant over single comb of the Leghorn. Hurst
( 1905, p. 134) crossed a White Leghorn with a Black Hamburgh (rose comb)

*Tegetmeier (1867, p. 185) states that blue Polish bred together throw cuckoo, white or
speckled produce. Wright (1902, pp. 399-401) states that "Andalusians " constantly throw
black and also white chicks. Blue chicks are frequently produced by crossing black and
white. Wright (1902) mentions such a result from crossing black and white Langshans
(p. 291) and Wyandottes (p. 318). Such blues also throw whites and blacks. Inher-
itance of blue is discussed by Bateson and Saunders (1902, pp. 131-132) and by Bateson
and Punnett (1905, pp. 118-119). ^n the latter paper it is stated that of 75 offspring of
Andalusians 17 were " white splashed, 36 blues, 22 blacks." A blue bred to awhitepro-
dnced 34 blue and 20 white splashed ; bred to a black it gave 27 blue and 19 black.

SINGLE COMB MINORCA AND DARK BRAHMA. 31

aud got rose combs in all of the offspring. Here, too, rose comb is domi-
nant over single comb.

Rose comb is a positive variation. It behaves in Mendelian fashion.
Although a neomorph, it is dominant.

3. FOOT COLOR. — Excluding from consideration all but the older hybrids,
40 showed foot coloring as follows :

Black, bluish, willow, or greeii 9

White 7

Yellow 24

Total 40

This result indicates that one of the parents (probably the male) is a
heterozygote containing traces of some white-legged ancestor. Yellow
appears to be dominant over white and black, but to be imperfectly so. The
black x yellow gives green or willow; the whitened yellow is "white."
Hurst (1905, p. 137) finds that when blue-footed and yellow footed individ-
uals are crossed, the offspring have light-blue feet. Yellow is in his case
recessive.

CONCLUSIONS.

In general, plumage color, foot color, and comb form are inherited in
Mendelian fashion. White plumage is dominant, although imperfectly so ;
wherefore we have spotted whites and even blues. Rose comb is dominant ;
whether perfectly so can not be determined until later. Yellow foot color
seems to be dominant, but is imperfectly so, even the yellow legs showing
traces of black.

Series V,— Single-comb Black Minorca and Dark Brahma.
STATEMENT OP PROBLEM.

This cross was made to see the result of uniting two races as unlike as
possible in origin and general form.

THE RACES AS A WHOLE.

The Minorcas have been already described at page 6. The Dark Brahma
race was originally imported from India near the home of Gallus bankiva ;
yet it differs from it as much as does the Minorca. It is a blocky, short,
stout-legged bird, is fluffy in plumage, and has a small pea comb and small
wattles. It is, moreover, sexually dimorphic. The male (fig. 19, pi. v)
has much more black in its plumage and is very differently marked from
the penciled or barred female (fig. 18). The Dark Brahma has so many
characters unlike those of the Jungle fowl that it is now thought to be
chiefly derived from a different ancestor, namely, that of the Aseel and
Indian races.

INHERITANCE IN POULTRY.
TABLE OF CHARACTERISTICS.

No.

Characteristic.

Single-comb
Black Minorca.

Dark Brahma.

I

General color

Black in both sexes

Complex black red and

2

Wing coverts (wing bar)

Black

white pattern ; sexes
dissimilar.
Black, white, and red.

•3.

Comb

Single

Pea.

4

Earlobe color

White, red mottling.

Red

<:

Iris color

Brown

Yellow

6

Foot and beak color

Blue-black

Yellow.

7

Foot feathering

Absent

Present and heavy

8

Vulture hock. .

Absent

Present.

Wing coverts

Black

Black white and red

REMARKS ON THE CHARACTERISTICS.

1 . GENERAL, PLUMAGE COLOR. — The adult Minorca has a completely glossy
black plumage. In the chick of two weeks the whole ventral surface is
covered with a white down, and certain of the primaries, especially those at
the distal end of the series, are partly or wholly white. The coverts over-
lying these reminges are usually white also. The white on the wing grad-
ually disappears in successive molts.

The adult Dark Brahma has a sexual dimorphism of color. The female
(fig. 1 8) is nearly uniformly penciled black and straw color. The hackles
have a broad whitish margin and the inner half of the vane is solid black.
The male (fig. 19) has solid glossy greenish-black feathers in the tail, white
feathers on top of the head, in the middle of the back and upper wing
coverts ; below black. Feathers with narrow black central stripe and broad
white margin (lacing) constitute nape, hackle, and saddle. Red occurs on
wing bar and humeral patch. In the down plumage Brahmas of both sexes
are longitudinally striped buff and black.

2. WING BARS. — The wing bar of the male Dark Brahma depends upon
the fact that the wing coverts of the second and third rows (which are black
at the base) have a white tip and a transverse band of red in the middle
between black and white. In the higher coverts and on the shoulder the
red still occurs, but it is reduced in extent.

3. COMB. — The single comb is found on Callus bankiva and has sometimes
been regarded as the only ancestral form. The pea comb is a distinct type,
consisting of a median comb bordered on each side by an accessory comb.
The origin of the pea comb is obscure but certainly ancient. Wright (1902,
pp. 265, 330, 339) contends that it arose in the Aseel, a type of oriental fowl
regarded as the ancestor of the Malays and Indian Games and believed not
to have originated from Callus bankiva, but to represent a distinct species.
According to this view the pea comb has not arisen from the single, but is
coordinate with it and of equal age. From the ancestral breed it has become

SINGLE-COMB MINORCA AND DARK BRAHMA. 33

fixed upon others. Although not typical of the Malay breed (which has a
small ' ' walnut ' ' conib) , it often appears when two walnut combs are bred
together.* The pea comb is found also in certain derived races, particu-
larly in the Brahma, and from this it has been engrafted on various other
breeds, notably on the Plymouth Rock of America and on the so-called
"Buckeyes." f

4. EARLOBE COLOR. — Two main color types of earlobes are found in poul-
try, red and white. The former occurs in the Jungle fowl, Aseels, Indian
Games, Javas, Dorkings, Cochins, Brahmas, and other foundation stock ; con-
sequently it must be regarded as the more primitive. The white earlobe
seems to have arisen in the Mediterranean type. It finds its highest expres-
sion in the White-faced Black Spanish. It has become a constituent of the
Houdans and L,a Fleche among the French breeds and of the Hamburghs.

5. IRIS COLOR. — Among poultry this ranges from a gray or pearl through
yellow to orange, red and bright red on the one hand, or through a dirty
red or bay to brown and black on the other. The red type seems to belong
to the descendants of the Jungle fowl ; it is found in the Jungle fowl, in
most Games, in most Mediterranean breeds, in most French fowl, in the
Dorkings, and in many of their derivatives. The lighter colors, yellow and
pearl, are found in the Aseels, Malays, Indian Games, often in the Brahmas,
attesting their origin from the Aseel group, also in many Cochins, where it
is said to be "very hereditary " (Wright, 1902, p. 320). The dark colors —
hazel, brown, and black — are found in certain Game fowl of dark plumage,
the Brown-Red Games, the Birchen Games and the Black Sumatras. They
are found also in the Black Javas of America, in the L,angshans, and sometimes
the^ Orpingtons. Both the Langshans and Orpingtons have derived their
eye color from the Java. Dark-brown eyes are found among the Mediter-
ranean fowl only in the Black Minorca which we have to do with here.
Whence acquired by the Minorca is uncertain ; possibly indirectly from the
Java. Finally, a perfectly black iris is found in the Silkies, where it is
probably due to the melanic sport that has made also skin and connective
tissue black.

6. FOOT COLOR. — This varies with the general skin color. The primitive
color of the Gallus bankiva group is an olive, commonly called ' ' willow. ' '
This is found in ordinary Game fowl. The Aseel- Malay-Indian type has
yellow feet. To this type belong the yellow feet of the Brahma and the
Cochin and doubtless also of the American Dominiques, which have trans-
mitted it to the Plymouth Rocks and Wyandottes. Finally, the Leghorns
have bright yellow feet.

By increase of the black pigment in certain birds of dark plumage there
have been produced from the willow foot the blue, blue-black, and leaden blue

* Wright, 1902, p. 325.

t American Standard of Perfection, 1905, p. 79.

34 INHERITANCE IN POULTRY.

feet of numerous races, e.g., Black Cochins, Black Wyandottes, Black Java,
Black Leghorn, Black Minorca, White-faced Black Spanish, Hamburgh, the
French fowl, black and dark-colored Games, and the Silky. By decrease of
pigment are derived the white feet of the Dorkings and Houdans. This
loss of pigment may be regarded as a mutation. It is associated with red
or yellow eyes.

Considering the Aseel type and the bankiva type as specifically distinct,
the cross of the yellow foot and the blue-black foot in the present series is
a cross between specific characteristics.

7. FOOT FEATHERING. — In Gallus bankiva and in the Aseel-Malay group
the. feet are without boots. The same is true of the Game fowl, although
minute feathers are sometimes found on their feet. Foot feathering is
found among various species of birds ; among scratching birds, in grouse,
ptarmigans (Tctrco, Bruasia, Lagopus), among some pigeons, and the owls.
Typically absent from the Gallinse, it has cropped out in the Brahma, Cochin,
and, probably independently, in the Silky and Sultan. In these groups it
has been preserved because of its importance in brooding or because it has
struck the fancier's eye.

8. VULTURE HOCK. — This consists of long stiff quill feathers projecting
backward at the heel joint. It is found among poultry only in the Cochin-
Brahma group and its derivatives. This characteristic is a good example of
a progressive variation.

MATERIAL.

The cock used in this cross, No. 122 (fig. 19), was a bantam Dark Brahma,
weighing 1,900 grams, received (February, 1905) from F. H. Hodges,*
Red Bank, New Jersey, who is a successful breeder of this variety. The
cock is typical of his kind.

The hens were four Single-comb Black Minorcas, Nos. 14 (fig. 3), 16, 18,
and 28, of which the three former were purchased of Mr. George C. Ely in
July, 1904, and No. 28 was hatched at the station in August, 1904, from
one of the purchased hens mated with the full-blooded Minorca cock No. 12.

RESULTS.

Only the first generation of hybrids has been reared up to the time of
writing.

i. GENERAL PLUMAGE COLOR. — In all cases (41) the hybrids are prevail-
ingly black. Usually the feathers of the occiput and nape are laced with
white, much more in the males than in the females, and the hackles of the
male are obscurely barred or splashed with white (fig. 21). Evidently the
white lacing of the Dark Brahma is trying to assert itself. The color of the
wing coverts is considered in the next paragraph. The down of the young

* Foot marked "F. H. H., 164."

SINGLE-COMB MINORCA AND DARK BRAHMA. 35

is dead-black, being without the longitudinal stripes of the Dark Brahma
young, and, for the most part, without the white wing feathers and ventral
aspect of the young Minorca. Nevertheless, exceptionally, one finds the
chin and part of the throat of the young white, the head feathers may be
tipped with white, and in one or two instances a little white occurs on the
wing. The young plumage seems to be a ueomorph, but on the whole it
belongs rather to the Minorca type than to the more primitive Game type
of juvenile coloration.

2. WING COVERTS. — In 14 grown male hybrids of which I have records, a
more or less prominent wing bar, formed by black, red, and straw-colored
feathers in the third or fourth row of wing coverts, occurs (figs. 20, 21).
The five females are wholly black, but even in these the wing coverts are
barred with an iridescent purple black ; consequently a disturbance of the
coloration of the wing coverts may be said to be typical of the hybrids. The
wing bar of the Dark Brahma male dominates over the black wing of the
Minorca, but it dominates imperfectly.

3 . COMB. — In all cases the pea comb of the Brahma dominates over the single
comb. Critical examination shows, however, that the pea comb of the
hybrid is not always typical. Frequently the whole structure, and espe-
cially the median ridge, is abnormally high (fig. 21), and, on the other hand,
in a few cases the lateral ridges are hard to make out. The dominance is
imperfect.*

4. EARLOBE COLOR. — The earlobe in every case contains both white and
red. The result is not a blend, however, but is particulate, the white
appearing at the center. As red is rarely wholly absent from the Minorca's
earlobes, whereas white is wholly absent from that of the Dark Brahma, it
may be possible to bring inheritance of earlobe color under the general
formula and speak of the white earlobe as being imperfectly dominant.

5. IRIS COLOR. — The iris of the hybrid is yellow, rarely with a trace of red
or reddish brown. The type of the Dark Brahma is dominant, but imper-
fectly so.

6. BEAK AND FOOT COLOR. — This is always black in the hybrid. However,
the black is rarely the blue-black of the Minorca, but it is usually a brownish
black frequently tinged with yellow, particularly on the under side of the
toes. Black is imperfectly dominant.

7. FOOT FEATHERING. — In all cases the hybrids have feathering on the feet.
In many cases this is clearly reduced in amount from what is found in the
Dark Brahma. Foot feathering is imperfectly dominant (fig. 20).

8. VULTURE HOCK. —This is absent in every case, although about a quarter
of the cases show the feathers of the heel much larger and more removed

* The inheritance of the pea comb of the Dark Brahma has not been considered in the
recent studies of others. The pea comb of the Indian Game is found by Bateson and
Saunders (1902, p. 94) to be imperfectly dominant over the single comb of the White
Leghorn.

36 INHERITANCE IN POULTRY.

from the foot than in the Minorca. Plain feathered heel is dominant, but
not perfectly so.

CONCLUSIONS.

This series of experiments is only begun. Conclusions as to dominance
are tentative until tested in the second hybrid generation. The Minorca
characteristics appear to dominate in (i) general black color, (4) white ear-
lobes, (6) black foot and beak, and (8) absence of vulture hock. Dark
Brahma characteristics appear to dominate in (2) wing bar, (3) pea comb,
(5) yellow iris, and (7) foot feathering. In every case, however, dominance
is imperfect. In some cases, at any rate, (5, 7), it is the new, additional,
or positive characteristic that dominates.

Series VI.— White Leghorn and Dark Brahma.

STATEMENT OF PROBLEM.

THE RACES AS A WHOLE.

It is proposed to investigate the behavior of characteristics when the heavy-
bodied, short and stout legged, loose-feathered, dark-colored Asiatic type is
crossed with the slender, tall-legged, close-feathered, white Mediterranean
type. Both types are ancient, but the Brahma must be regarded as nearer
its ancestral form, Aseel-Malay-Indian, than the Leghorn is to the Jungle
fowl.

TABI^E OF CHARACTERISTICS.

No.

Characteristic.

White Leghorn.

Dark Brahma, female.

Dark Brahma,
male.

i

2

3
4
5
6

8
9

10

Hackle color
Wing bar

White

Straw, black-penciled. . .
Buff, black -penciled . . .

Buff, black -penciled .
Black, straw-penciled. . .
Pea (see page
Red (see page

Yellow (see p.
Present (see p
Present (see p
Broad, chunk

Black, straw-
laced.
Black, red, and
white.
Black and white.
Greenish black.
32).
33).

ige 33).
age 34)-
age 34).
7-

White

Wing bow

White

Tail color

White

Comb

Single (page 19) .
White, red-edged
(page 33).
Red (page 33) ...
Absent

Earlobe

Iris color ...

Vulture hock
Foot feathering. .
General form. . . .

Absent
Narrow, slender. .

REMARKS ON THE CHARACTERISTICS.

i. HACKLE COLOR. — Among most poultry that are of broken color the
hackle feathers are unlike those of the rest of the plumage. They have a
dark center and a lighter lacing. In the Malays and Indians they have a
red center edged with green. In the Gallus bankiva female the hackles have
a black center (with straw-colored shafting) and straw-colored lacing. This
is the type of hackle feather found in the male Dark Brahma. It is found,

WHITE LEGHORN AND DARK BRAHMA.

37

in both sexes, among many other breeds. The hackle of the female Dark
Brahma (fig. 18) differs from that of the male in that the broad black center
is barred, or penciled, with straw color.

3. WING Bow. — The wing bar is described for the male at page 32. In the
male Dark Brahma the feathers of the fourth and higher rows of wing coverts
have their distal halves white forming the wing bow. No such distinct wing
bar and wing bow occur in the female, the feathers of this region being
uniformly penciled like the others.

MATERIAL.

There are two sets of experiments in this series. In the first sefC&e. mothers
were White Leghorn Bantams, Nos. 127 and 128, probably heterozygotes
with black, further discussed at page 39. The paternal Dark Brahma,
No. 122, has been already referred to at page 34. In the second set the
mother was Dark Brahma, No. 121. She has the same history as No. 122.
She is a prettily penciled bird (fig. 18). The father was White Leghorn
Bantam, No. 126, described at page 39.

RESULTS.

Of the first set 19 offspring are recorded, including 8 in the shell. Females
8, males 5. Of the second set 27 are recorded, including 8 in the shell.
Females 14, males 4.

i. GENERAL PLUMAGE COLOR. — The result differs in the two sets and the
two sexes, and it is otherwise variable.

Plumage color.

Females.

Males.

Unknown sex.

Total.

First
set.

Second

set.

Total.

First
set.

Second
set.

Total.

First

set.

Second
set.

Total.

Nearly pure white
White + much black
and red pigment as
barring

4
o

3
o

7
o

3

2

2
O

5

2

7

ii

2

18

2

3°

4

7
5
5

Like Dark Brahma fe-
male

4

0

°

3
3
5

*7
3
5

0
O
0

0
2
0

O

2
0

Barred

Black or nearly so

The results are explicable on the hypothesis that all of the White Leg-
horn Bantams, Nos. 126 <? , 127 9, and 128 9, contain white gametes and
also gametes bearing red pigment, black pigment, and the barred pattern.

3. WING COLORATION. — In the first set the wing coloration is like that of
the plumage in general, except that in the females marked like the Dark
Brahma the coverts contain much red (fig 23).

Second set. Of 7 prevailingly white hybrids three show red or buff on the
wings ;j of the 5 black-and-white (penciled) birds all but one show red or
purple on the wings ; of two adult black hybrids one shows buff. Three other

*Fig. 23.

f Fig. 25, Plate vm.

38 INHERITANCE IN POULTRY.

females are marked like the Dark Brahma female. Red pigment is com-
moner in this set, with White Leghorn father, than in the first set, with
Dark Brahma father. This speaks for the hypothesis that red has come
from the White Leghorn, as, according to usual e xperience, the father tends
to determine coloration.

4. TAIL COLOR. — First set. Of 1 1 offspring, 8 have a white tail, the prevail-
ing color of the body ; in one case the tail is white except for one black
feather, and in two cases it, like the body in general, agrees with the Dark
Brahma female in being black with buff penciling (fig. 23).

Second set. Of 15 hybrids, 6 are nearly or wholly white on the tail, one
has two black feathers, 5 are black, two are black-and-white barred, and
one is black with buff, as in the Dark Brahma female. The tail color tends
to resemble that of the general body.

5. COMB FORM. — In all cases of adult hybrids of either set, the comb is pea
(fig. 24). Pea comb is consequently here also dominant over single comb.

6. EARLOBE. — Both the Brahma solid red and the White Leghorn white,
red-margined earlobes appear in about equal numbers. It is probable that
my heterozygous White Leghorn bantams have been early crossed with some
red-lobed race.

7. IRIS COLOR. — This is definitely established only in mature birds. All
eyes show more red than the Dark Brahma and the tendency is to redden with
age ; consequently red is probably dominant.

8. VULTURE HOCK. — This is absent in all cases (fig. 22). One hybrid
has the hock feathers a little elongated. Short feathering at the heel is
dominant.

9. FOOT FEATHERING. — Pirst set. Of 19 hybrids having the Dark Brahma
father, 3 unhatched chicks are recorded as non-booted. Of the remainder, 8
are slightly or very slightly booted. Three adults have a medium covering
of feathers on the foot. The Brahma tendency toward booting has been
diluted by the cross with the Leghorn.

Second set. Of 24 offspring of Dark Brahma mother, all have well-devel-
oped boots. This constitutes a striking case of a difference in reciprocal
crosses. Booting is probably here, as elsewhere, dominant, but frequently
very imperfectly so.

CONCLUSIONS.

Of the nine characteristics, the following exhibit clear alternative inherit-
ance, the dominant characteristic being printed in italics :
Pea comb vs. single comb.
No vulture hock vs. vulture hock.
Booted foot vs. unbooted (when Brahma is mother) .

The other characteristics can not for one reason or another be so easily
classified. The red of the wing bar seems to behave like a unit character
and is independent of the coloration of the rest of the body.

BLACK COCHIN AND WHITE LEGHORN.

39

The inheritance of booting is peculiar in that in the first set, Leghorn
mother and Brahma father, the booting fails to show that clear dominance
which is almost universal ; yet I can hardly suspect the purity of the Dark
Brahma male. It would seem that in this series also the mother transmits
booting more strongly than the father.

Series VII.— Black Cochin Bantam and White Leghorn Bantam.
STATEMENT OF PROBLEM.

This experiment was undertaken to learn the method of inheritance where
one parent is pure white and the other pure black.

THE RACES AS A WHOLE.

The Black Cochin Bantam, also called Black Pekin, is a diminutive of the
Cochin (fig. 26). It is stated by Wright (1902, p. 499) that the Pekins
came in 1860 from the city of that name. The original color was buff ; the
black has probably been engrafted on the race by a cross with some small
black race. The Cochins are closely allied to the Brahmas and share with
them a chunky form, stout and densely feathered feet and red face and ear-
lobes. The White Leghorn has been discussed at page 18.

TABLE OF CHARACTERISTICS.

No.

Characteristic.

Black Cochin
Bantam.

White Leghorn
Bantam.

I

General plumage color.

Black

White.

2

Ear lobe color

Red

White, with trace of red.

7

Vulture hock

Present

Absent.

A

Foot feathering

Present

Absent.

REMARKS ON THE CHARACTERISTICS.

1. GENERAL PLUMAGE COLOR. — In the Black Cochin this is a deep
greenish black. No trace of white appears anywhere.

2. EARLOBE COLOR. — In the Black Cochin this is of the dark red or bay
characteristic of all the Aseel- Malay group.

3. VULTURE HOCK. — This is well developed in the Black Cochin (see
page 34).

MATERIAL.

The mothers were four Black Cochin Bantams,* very similar, each heavily
booted and weighing about 600 grams apiece. Trap nests were not used,
but owing to special peculiarities the eggs of the separate mothers were dis-
tinguished as A, B, C, and D.

The father was a White Leghorn Bantam, No. 126, purchased January,
1905, from the Cyphers Incubator Company, together with two hens (Nos.

*Nos. 129, 130, 131, 132, received February, 1905, from Mr. H. B. Kutschbach (fig.
26, pi. ix).

4O INHERITANCE IN POULTRY.

127, 128). Mated with the hens, nine young were produced. Four of
these were typical White Leghorns without black ; three others were white
except that black feathers occasionally appeared. One (No. 213) was
nearly solid black and one (No. 229) was black with nearly every feather
barred with white. It is plain that the strain I have has not been wholly
purified of black. This is indicated also by the fact that No. 128 has every
feather peppered with black — a heterozygous form of coloration.

RESULTS.

1 . GENERAL PLUMAGE COLOR. — Of 26 hybrids, 1 1 were pure white or had
only a little black ; 7 were black, sometimes with a little white, and 8 were
barred black and white (fig. 27). The results confirm the view that White
Leghorn Bantan No. 126^ has black germ cells. The barred condition is
unexpected and is probably recessive in the White L/eghorns.

2. EARLOBE COLOR. — In all cases ( 10) of adults but two, the earlobe is red ;
in the remaining two some white is mixed with the red. The red earlobe
is probably dominant, but imperfectly so.

3. VULTURE HOCK. — Out of 13 cases n have clearly no vulture hock and
two show a slight enlargement of the heel feathers. Vulture hock is prob-
ably recessive.

4. FOOT FEATHERING. — Every hybrid is booted, but the booting is less
heavy than in the Dark Brahma (fig. 27). Booting may be dominant, but
it is not perfectly so.

CONCLUSIONS.

The male parent is heterozygous and probably contains at least three sorts
of gametes, viz, pure black, pure white, and barred, the last being a mosaic.*
The black of the mother is recessive to all of these. The occurrence of barred
mosaic is of interest, but it is of unknown origin. The ancestral red ear-color
and the new " booting" are both dominant. Dominance is, however, im-
perfect.

Series VIII. — White Leghorn Bantam and Buff Cochin Bantam.

STATEMENT OF PROBLEM.

This series was undertaken to determine the method of inheritance of
buff when combined with a white plumage coloration.

THK RACES A.S A WHOLE.

The White Leghorn Bantam has been described at page 39. The Buff
Cochin Bantam (fig. 28) is a diminutive Buff Cochin, which resembles in
form the Black Cochin (p. 39). Cochins as we know them to-day (the
name was formerly applied to a different, now extinct, race) seem to have
been imported into this country and also into England from eastern China

* Castle and Allen, 1903, p. 606.

WHITE LEGHORN AND BUFF COCHIN.

41

According to

in the year 1847. The earliest importations were buff.
McGrew (1904, p. 526) :

In many of these retreats, mi-au^ or monasteries, thousands of specimens of Buff and
Partridge China (Cochin) fowls are annually raised, and in other places the colors are
mixed. The Kinkee (gold flower) colored birds are the most esteemed, both as regards
antiquity and purity. . . . Hoangho is the oldest [of the] wi-aus, and its records show
that this same race of fowls was cultivated by the brotherhood 1,500 years ago.

Buff and Partridge Cochins are indigenous to the temperate and more southerly por-
tions of the empire. This is corroborated by naturalists and travelers. Mr. Gabb, the
well-known English naturalist, says : "According to my view, a black or white Cochin is
an improbability, if not an impossibility, as a natural product of a tropical or subtropical
region. The natural color of the feathers of the poultry in the zone of Cochin China
would be buff or yellow, or some of the varieties of these colors, but never black or
white, except by accidental variation."

Other testimony presented by the same author is of the same sort and
establishes the fact that Buff Cochins are a primitive, foundation race of

great antiquity.

TABLE OF CHARACTERISTICS.

No.

Characteristic.

White Leghorn.

Discussed
at page —

Buff Cochin.

Discussed
at page —

i

General color

White... .

IQ

Buff

41

2

Earlobe color

White

•IT.

Red

17

7

Vulture hock..

Absent

Present. . . .

T.A

A

Foot feathering

Absent. . . .

Present. . . .

T.A

REMARKS ON THE CHARACTERISTICS.

i. GENERAL PLUMAGE COLOR. — The buff color of the Cochin is, as has
been shown above, of high antiquity. From the Buff Cochin it has been
transferred to many other breeds by crossing. Thus there are Buff Wyan-
dottes, of which McGrew says (1901, p. 24): " Two distinct lines were pro-
duced under different methods. One was formed from Wyandotte-Buff
Cochin cross ; the other came through the Rhode Island Red-Wyandotte
cross." The Rhode Island Red is, however, as is well known, a direct
descendant of the Buff Cochin. The Buff Plymouth Rocks were derived
directly or indirectly from the Buff Cochin (McGrew, 1901, p. 25). The
history of the Buff Leghorn is the same — the offspring of a yellow Danish
Leghorn cock and Buff Cochin pullets mated with a yellow Leghorn hen.
The produce, three-fourths Yellow Leghorn and one- fourth Buff Cochin,
gave* "the first Buff Leghorns ever shown." The Buff " Orpingtons " —
a highly modern and mongrel breed — have a similar history, being chiefly
Buff Cochin and Dorking (Wright, 1902, p. 296).

The origin of the buff as it occurs in the Cochins can only be guessed at ;
but there are important facts to be considered. First, it appears that the
buff color is very inconstant even in China. Says a traveler : ' ' No two can

*Wyckoff, 1904, p. 527.

42

INHERITANCE IN POULTRY.

be found of exactly the same color ; some are a chestnut color, others darker,
and some quite light " (McGrew, 1901, p. 527). Of the Buff Cochins as
first imported to England, Wright (1902, p. 245) says: " The buff colors
were much subdivided, ranging from the lightest silver buff and silver cin-
namons through lemons and buffs to the deep colored cinnamons which
would now be called almost red. Originally, also, the birds were not
uniformly buff over the whole body ; even prize-winners were such as would
now be called ' tricolored,' the breast being lemon or orange buff, the
hackles and saddle much darker, and the wing darker still, even a red."
From all of this it is plain that buff is only a diluted form of red — a color
that is abundant in the plumage of the Malay and Indian breeds, and the
replacement of all black by this buff is probably due, originally, to a xanthic
"sport."

MATERIAL.

The mother was the White L/eghorn Bantam No. 128, a heterogametous
bird, already discussed at page 40. The father was a Buff Cochin Bantam,
No. 545 (fig. 28), original stock, of whose ancestry nothing is known.

RESULTS.

i. GENERAL PLUMAGE COLOR. — Thirty-one offspring show the following
distribution of color : White, 9 ; white and buff, 9 ; white and black, 4 ;
white, black, and buff, 2 ; black and buff, 4 ; black (all juvenile), 3.

Calling the germ cells of the mother equally white and white- and-black
and regarding the buff as (imperfectly) recessive when paired with white,
we have —

Characteristic.

/

Percentages.

Actual.

Expecta-
tion.

White (and buff)

18
13

58.1
41.9

50
So

White-and-black (and buff)

Total

3i

IOO.O

IOO

Of the white and buff heterozygotes, white only appears in 9 ; the remainder
show some buff. White is dominant, but imperfectly so.*

Wright (1902, p. 244) states in regard to crosses between white and buff
Cochins that io the early days they "bred most amazingly in regard to
color. . . . From one brood of ten chickens of this cross two pullets were
pure black ; two pullets and three cockerels black with more or less gold in
the hackles, and marked wings ; the other three darkly penciled birds."

Hurst (1905, p. 134) finds that crosses between White Leghorn female
and Buff Cochin male (essentially the same crosses as mine) gave 60 chicks —

* But see fuller discussion of the heterozygous nature of my White Leghorns, page 40.

TOSA FOWL AND WHITE COCHIN. 43

"53 whites and 7 buffs. Of these 2 were apparently clear whites and 5 1 white
patched with buff and brown, chiefly on the head, neck, and breast (18 of
these were also oddly black-ticked) ; the 7 buffs were all more or less patched
white." Hurst concludes that the white plumage color of the Leghorn is
dominant over the Cochin buff, but that this dominance is incomplete in the
majority of cases. He adds : " In F, the dominance of both white and black
over buff is much less complete than that of white over black."

2. EARLOBE COLOR. — In all recorded cases the hybrids have a red earlobe,
sometimes with a lighter colored, even yellowish, center.

3. VULTURE HOCK. — This is always absent in the hybrids. However, two
cases show an elongation of the heel feathers.

4. FOOT FEATHERING. — In all cases the ' ' boot ' ' of the hybrid was reduced
as compared with the Cochin parent. In 3 cases out of 31 no trace of
feathers could be detected on the tarsus.

CONCLUSIONS.

Buff- is recessive toward white, but the dominance of white is very im-
perfect, so that we may have various degrees of buffness in the hybrids.
Black, or the mosaic black-white, appears to dominate over buff, but here
again the dominance is frequently imperfect. Imperfect dominance is not
revealed by a blending, but by sprinkling of the red pigment.

The earlobe color of the Cochins ( A.seel type) dominates over that of the
Leghorn, but not perfectly. Vulture Jwck is recessive, but not always per-
fectly so. Foot feathering may be said to be imperfectly dominant. But
this case is of special interest because the result is practically a blend.
Hurst (1905, p. 134) similarly states that out of 60 chicks from his cross, all
had feathered ' ' shanks, " " but in every case the length or number of feathers
was reduced to about one-half."

Series IX. — Tosa Fowl (Yokohama) and White Cochin Bantam.
STATEMENT OF PROBLEM.

This series of experiments was undertaken in the first instance to test the
inheritance of the long-tailed characteristic of the Japanese long-tailed fowl
(variously called Tosa fowl, Yokohama, Phoenix fowl, Japanese Game
Shinowara-to, etc.).

THE RACES AS A WHOLE.

The Tosa fowl* (figs. 29, 31) has long been bred in Japan and plays a

* Professor Mitsukuri on the occasion of a recent visit to the Station for Experimental
Evolution informed me that in Japan these birds are known as Tosa fowl, since they were
originally bred in the province of that name, particularly at Shinowara. He further re-
marked that the feudal chief, or daimio, of that province had as his emblem or insignia
a spear with a long cock's feather on it, and he made the interesting suggestion that the
activity of the fanciers had been stimulated, not only by their satisfaction in long-tailed
birds, but also by the desire of meeting the ever-increasing ideals of their chief as to the
length of the feather of his insignia.

44

INHERITANCE IN POULTRY.

prominent part in Japanese art. On the authority of Chamberlain (1900),
" as great a length of tail as 18 feet has been reached in the tail feathers,
but even 12 feet is a rarity. From 7 to 8 or n feet is the usual length."
Aside from the tail, the fowl has remarkably long hackle and saddle feathers
of a golden color. Otherwise it closely approaches the European black-
breasted Red Game, having, like it, retained most of the coloration of Gallus
bankiva.

The Cochin fowl was used in the mating because its tail feathers are
notoriously short and consequently afford a strongly opposed allelomorph.

TABLK OF CHARACTERISTICS.

No.

Characteristic.

Tosa fowl.

White Cochin
Bantam.

I

General color

Dark

White.

2

Tail

L/ong . . . .

Short.

7

Foot feathering

Absent

Present.

4

Foot color

Willow

White.

REMARKS ON THE CHARACTERISTICS.

1 . GENERAL PLUMAGE COLOR. — The colors of the male Tosa fowl* are very
striking. The head is black ; the feathers of the nape and the hackles are
black proximately, but the exposed portion is red, becoming a deep mahogany
on the middle of the back. The long saddle feathers are green laced with
mahogany. The tail feathers are solid greenish-black. The breast, belly,
and under tail coverts are black. The remiges are black, edged exteriorly
with red. The coverts are black tipped with mahogany in varying amount,
but so as to produce a marked red wing bar. The female Tosa fowl (fig. 30)
has a black head and nape and golden hackles. The feathering of the back
and saddle and the wing coverts are black mossed with rusty and have a
straw-colored shaft. The breast is strongly tinged with buff. The White
Cochin, on the other hand, is pure white (fig. 32).

2. TAIL. — The question of the origin of the long tail is of great importance.
Any light on this question would illuminate the problem of specific differ-
entiation and the origin of specific characteristics in general.

Hypotheses. In accordance with current theories of specific differentiation
we have to recognize that this characteristic may have arisen :

(1) As a mutation. As such it would be brought into the same category
with frizzled feathers or the cerebral hernia of Polish fowl. Professor E. Ray
L/ankester has referred to the condition as a sport.

(2) As the result of selection. This would be the most popular explana-
tion. Romanes (1901, p. 302, fig. 95) includes this case as one of a number
of typical proofs of the efficiency of artificial selection. Weismann (1904,
11, pp. 124, 326) states definitely that the long tail is due to selection. The

* Fig. 29, Plate X.

TOSA FOWL AND WHITE COCHIN. 45

underlying assumption in both cases is that the selection has been of minute
favorable fluctuations rather than the conservation of sports. This is a
conceivable hypothesis.

(3) As a result of functional hypertrophy of the feather follicle. By
artificial treatment the blood supply to the follicles might be stimulated so
as to make the feather grow longer. Such an effect might be inherited or
not, as could be determined by breeding. If the offspring of the long-tailed
fowl have a long tail, though untreated, then we would have, on the third
hypothesis, an inheritance of an acquired character. Cunningham (1903)
believes that the Tosa fowl is a demonstration of such inheritance.

Growth of tail feathers. The study of the long tail of the Tosa fowl leads
us to consider the whole matter of feather growth and of the anatomy of the
tail. In early months of their life chicks are constantly losing old feathers
and gaining new ones built on a larger scale to meet the needs of the enlarg-
ing body. Later, these feathers
are all molted during one period ./

in the autumn. During develop- A'^

ment, the tip of the feather is O c?, (§

formed first and growth continues **O O ZQ ,

at the base, within a sheath, for a
shorter or longer period, depending "^ ^M O
on the eventual size of the feather. O Q

The reason why some feathers, like ^'?Q
the contour feathers, are short is

O

O

-9

o
*£>

because growth quickly ceases.
The feathers of the hackle, saddle, T

' FIG. C.— Diagram of arrangement of the tail feathers,
and tail of the male are long be- A^-A&, feathers of right anterior row; A'l-A's, feathers

cause the growth period is in them of if anfe?r ™T : M^^ M'r%"»**?*Z °f

right and left middle rows; P\-P* and P'\-F*z, feathers
prolonged. The Sickle feathers Of of right and left posterior rows; o. g., oil gland;

the Leghorn are still growing for D~ v' dors°-ventral Une = *• ri*M ' L< left-
three months after the molting period ; consequently they attain a length of
300 to 400 mm. If the period of drying up of the growth sheath at the
base of the sickle feathers could be delayed in the Leghorn for an entire
year they would become each a meter long. The reason for the great length
of the tail feathers of the Tosa fowl is that they do not cease growing. In
this respect they resemble the long hair of Angora guinea pigs, rabbits and
cats, and the head hair of man.

Morphology of the tail. As just intimated, only certain feathers of the tail
of the Tosa fowl grow indefinitely. It is now necessary to describe the
structure of the tail. The feathers have the following arrangement :

The posterior row (P) consists of broad feathers with rounded ends and
constitutes the characteristic ' ' fan ' ' of the tail. The middle row ( M) con-
tributes the characteristic long growing feathers, those nearest the median

46 INHERITANCE IN POULTRY.

line being longest. The sickle feathers (S) may belong to either row, so
far as the adult position indicates ; but, as growing feathers, they belong
physiologically to the middle series. The anterior row (A) is, at the same
time, the posterior row of tail coverts. The lateral feathers of this row are
the smallest, owing to a late and brief growth. The long tail of the Tosa
fowl is thus produced by the prolonged growth period of the middle row of
feathers including the sickle, together with the more median feather of the
anterior row.

Catisc of excessive growth of tail ; Cunningham 's experiments. The cause
of this prolonged growth of the median and sickle feathers is the crucial
point. The latest student of the subject, Cunningham (1903, p. 232),
quotes Mr. John Sparks as stating : "In order to ensure very great length

of tail, the cocks ought to be kept on a perch and the tail-feathers

should be pulled gently every morning." Cunningham adds: "My own

experiments tend to show that this mechanical treatment of the

feathers is the whole secret of the mystery. ' ' He describes in great detail
how he stroked the tail of one of two cocks daily ; the other not at all.
When a feather stopped growing he pulled it out. He concludes (p. 248) :

In the cock whose feathers were stimulated by pulling, growth did not go on at a
more rapid rate, but continued for a longer time and produced a longer feather. Thus
in cock A [not stroked] no growth took place after April i, and the maximum length
was 2 feet 4/^ inches ; while in cock B [stroked] growth continued till July 13, and the
maximum length was 2 feet 9^ inches.

Half a page farther on Cunningham sums up thus :

The long-tailed cock in its perfection, therefore, is neither a sport nor a breed, but
the product of artificial cultivation ; and the excessive growth of the feathers is the result
of stimulation applied to the individual. The more important part of the stimulation is
not the mere pulling of the feathers, but the extraction of it which causes the growth of
its successor.

One can not but remark that Cunningham here contradicts himself. After
having laboriously pulled the feathers for over a year and found that the
feathers are stimulated by pulling, he states : ' ' The most important part of
the stimulation is not the pulling but the extraction of the feather causing
the growth of its successor. ' ' Does Cunningham indeed think that, origi-
nally, by extraction of a feather its follicle was so stimulated that it there-
after produced feathers which neither ceased to grow nor molted and,
moreover, so affected the germ plasm as to produce a race with a tendency
toward excessive growth of feathers ? Certainly such a conclusion seems
past belief.

Author's experiments. To see what influence, if any, stroking the tail
feathers has upon their growth, I experimented upon two cocks. One
(No. 3, "Admiral Togo") was stroked twice daily by passing the feathers
of the middle and anterior row between the thumb and forefinger. The

TOSA. FOWL AND WHITE COCHIN.

47

other (No. 7, " General Oyatna ") did not have its tail stroked. The two
birds were treated similarly, except that Admiral Togo was confined to his
perch during all but about two to six hours per day, while General Oyama
had free run with the hens. The experiment was begun July 20, 1904,
when the cocks were 103 days old, and was continued until March, 1905,
when " Oyama " died of roup.

The relative growth of the corresponding feathers of the two males is
shown in a series of curves (text figure D). The full line is the curve of

600
500
400
300
ZOO
100
0
600
500
400
300
£00
100
0

Aug. Sept. Oct.

Nov. Deo. Jan. Aug. Sept. Oct.

Nov. Dec. Jan.

/

3
'' 7

/<

//

f3

M,

"/

#'

^

S

^

,''

'/

/

/^7

3

/,

,

7

s'

X

/

3

'Ma

7

f

7/

^

/

/

<i

T

X

>

/3

^3

/

/

, 7

/

/

M2

/

(X

Mg

^

/.

7

x"

/

,''

S -,*

*/

/

\,'

•

*

s~-~

'.7 •

FIG. D.— Curves of growth of certain tail feathers of Togo (No. 3, full line) and Oyama (No. 7, dotted
line). MI, first right middle tail feather; Ms, M'j, second right and left middle tail feathers; M«,
third right tail feather ; S, right sickle.

the stroked feather ; the dotted line that of the unstroked. These curves
show several things.

First, the average rate of growth of one of the tail feathers in the Tosa
fowl is about 3 mm. per day, or an inch a week. Consequently, if growth
is uninterrupted and the feather does not break, it should come to be over a
meter long by the end of one year. The extremely long feathers — 5 meters
or more — on record are acquired by (a) rapid growth, (3) continuous growth,
O) preservation of the tail from breakage, and (d) long life of the individual.
If stroking has any effect it must be by altering one or more of these elements.

Second, the curves show fluctuations in the rate of growth due to fluctua-
tions in the condition of the fowl.

Third, in the case of those feathers that were studied during the greatest

48 INHERITANCE IN POULTRY.

period, viz, Mj, M2, M'2, the stroked feather grew more rapidly than the
correspouding unstroked.

Fourth, the unstroked feathers of No. 7 ceased growing earlier than the
corresponding stroked feathers of No. 3.

Whether the third and fourth items are due to differences in treatment
or to other peculiarities of the fowl can not be asserted definitely. In any
case the feathers all eventually, at about six months, ceased to grow.
Owing to the death of No. 7 soon after, the comparison had to be abandoned.
The result agrees with Cunningham's in that stroking prolongs the period
of growth ; but the result, depending on three feathers, can hardly be
generalized. It would not be surprising, in view of what we know of
functional hypertrophy, if it were some day demonstrated that stroking
always prolongs the growing period of a feather. This is, however, an
entirely different matter from proving that the origin of the long-tailed con-
dition of the Tosa fowl was due to, and its maintenance in some way depends
upon, stroking.

A few further cipeiiments iiave been made with Admiral Togo (fig. 31).
I have found, in confirmation of Cunningham, that if a feather that has
ceased to grow be forcibly removed it is quickly replaced by another that
continues to grow. Thus a feather pulled out January i, 1905, had grown
steadily to November i ; but as the bird was needed for breeding and could
not be confined, the tail has repeatedly broken off. In September, 1905, it
measured over 900 mm.

As a further criterion of the value of manipulation in causing this great
growth of the tail feathers of the Tosa fowl, it becomes important to see
how this physiological characteristic is inherited when crossed with a short-
tailed individual. This consideration led to the present series of experiments.

The tail of the Cochin fowl is the shortest of all races of poultry. Thus
Wright (1902, p. 245) expresses the ideal of the fancier : " The tail of the
cock should be as short as possible."

3. FOOT FEATHERING. — While the Cochin is very heavily feathered on the
foot, the Tosa fowl is typically clean-legged. However, No. 3, which is
not the father of any of my hybrids, shows a few bunches of rudimentary
feathers or hairs on the tarsus.

4. FOOT COLOR. — The willow foot of the Tosa fowl is derived directly
from the Jungle fowl. The white foot of the White Cochin seems to be an
albinic form of the yellow foot derived from its Indian-Malay ancestry.

MATERIAL.

FIRST GENERATION. — The mother was a White Cochin Bantam, No. 35^
(fig. 32), of unknown origin, but apparently pure in respect to the four
characteristics here under consideration. The father was imported from
Japan, having been purchased in New York city, January, 1904. It has a
dark Game coloration (fig. 29).

TOSA FOWL AND WHITE COCHIN.

49

SECOND GENERATION. — Two hybrid cocks, Nos. 53 (fig. 34) and 95 (fig.
35), were successively bred to their sisters, Nos. 58 (fig. 33), 94, 96, and 98.

RESULTS.

i . GENERAL PLUMAGE COLOR. — First hybrid generation. Of 7 offspring,
3 cocks and 3 hens developed their adult plumage. The males were all of the
male Tosa-fowl coloration except that every feather was repeatedly barred
with white (figs. 34, 35, 37A). The females were all of the female Tosa-fowl
coloration except that the shafting was much broadened (fig. 37) ; also the
saddle feathers and the proximal secondaries were obscurely barred black -
and-buff.

Second hybrid generation. Among 57 individuals we have the following
distribution of plumage color :

Color.

No.

Per cent.

White

16

28 i

Pigmented

41

71. Q

The original white color has reappeared in about one-fourth of the cases
(fig. 38) ; plumage color segregates in the germ cells of the first hybrid
generation in true Mendelian fashion. Of the 16 whites, only 5 were without
trace of reddish pigment. Such pigment occurred on the breast, top of
head, and remiges. The purity of the germ cells from which these whites
sprang — the completeness of segregation — is not always perfect.

The 41 pigmented individuals show a curiously mixed lot of coloration.
Of 14 mature females, 6 are like the female Tosa fowl, without barring, but
sometimes with wider shafting than male Tosa fowl. The remainder have
feathers of the back and wing coverts barred with lighter, even with white —
a condition not found in the female first hybrids. One of these (No. 659)
shows a mixture of female Tosa and female Partridge Cochin coloration. As
no Partridge Cochin is involved in the immediate ancestry, this looks like a
' ' reversion ; ' ' the characteristic has probably lain latent in the White
Cochin. Of 10 males, two show no trace of white, and may, consequently,
be considered as homozygous. The remainder are more or less barred with
white. One bird (No. 646) shows a remarkable mixture of Tosa and male
Partridge Cochin coloration.

2. TAIL LENGTH. — First hybrid generation. All the three males reared
developed abnormally long middle tail feathers. One of these birds died
young. The second bird (No. 53, fig. 34) lived to be exactly one year old.
Its sickles were 427 mm. long and had stopped growing. It had suffered a
severe paralytic stroke four months before its death. The remaining cock
(No. 95, fig. 35) had at n}£ months sickle feathers 360 mm. long and still
growing. These feathers had thus grown at a rate of about i mm. a day, or
4

INHERITANCE IN POULTRY.

only one-third that of its father. The long-tailed characteristic of the male
has been inherited, but in a reduced form.
Second hybrid generation. Still immature.

3. FOOT FEATHERING. — First hybrid generation. Of the 7 individuals all
have the feet feathered (" booted ") and the females are provided with a
"vulture hock." The feathering is usually less than in the Cochin.

Second hybrid generation. Among the 55 individuals of this generation all
degrees of foot feathering were obtained. Bight cases are recorded as
"heavily booted," 27 as "booted," 13 as slightly booted, and 7 as non-
booted. The classification is arbitrary and therefore the exact proportions
not significant. The important outcome is that a good share of this genera-
tion is essentially clean-legged like the Tosa-fowl ancestor, and an approxi-
mately equal proportion is heavily booted like the Cochin ancestor, while
the rest are feathered to an intermediate degree like the parents.

4. FOOT COLOR. — This has a curious way of changing during the early
months of the individual. White is often represented in the young by
yellow. A "slate blue " or " bluish black " occurs ; this may be a form of
the willow from which yellow has been extracted.

First hybrid generation. Of 5 individuals two are recorded as white, one
as yellow, one as willow, and one as slate blue. Here is practically equal
frequency of the light and dark types.

Second hybrid generation. Fifty-three individuals give the following dis-
tribution of foot color :

Color.

/.

Per cent.

White

ii

20.8)

Yellow

16

30 2 [51

Willow

20

^7.7 1

Slate or bluish

6

** ' >4Q

II. 3 I v

Total

53

IOO

This shows a practical equivalence of light and dark foot colors as in the
first generation. The interpretation of this result must be left for later
studies.

5. CORRELATION OF CHARACTERISTICS. — Considering only the three
characteristics of plumage color, booting, and foot color, and assuming that
game color and boot are dominant and light and dark feet equally apt to
occur, we find the following calculated and actual frequency of each combi-
nation (actual percentage is in italics) :

P Booted 56.3$ 58.5$

Non-booted 18.7$

98.3$

Game plumage 75$ 69.8$

(Booted 18.7$
Non-booted 6.2$

Li<?htfeet 28.1$

Dark feet 28.1$

Light feet 9.4$

Dark feet 9.4$

Litfhtfeet 9.4$

Dark feet 9.4$

Light feet 3.1$

Dark feet 3.1$

so.e$

5.7%
5.7$
!S.g$
15.1$
0.0$
1.9$

DARK BRAHMA AND TOSA FOWL. 51

Considering the intrinsic difficulties of classification due to the partial
blending of characteristics, there is a fairly close correspondence between the
calculated and the actual. This result proves that there is little if any
necessary correlation between the characteristics in question ; they may
combine in a chance fashion in the second hybrid generation.

CONCLUSIONS.

The inheritance of color in this cross between a white and a game-colored
breed is remarkable in that white is not dominant — as is usually the case —
nor recessive ; but inheritance is particulate in the heterozygote, producing
barred offspring. Segregation nevertheless occurs in the second hybrid
generation, but the extracted whites and game colored birds are, for the
most part, no longer as pure in color as their grandparents were. The
germ cells are no longer perfectly pure — they have become infected by con-
tact with the opposite quality.

The long-tailed characteristic behaves in inheritance like a unit character —
in no wise different from plumage color. One can not help doubting whether
it originated by any different method from that in which the diverse colors
of poultry have arisen.

Foot feathering is dominant here as in many other cases ; yet the domi-
nance is incomplete. The germ cells of the second hybrid generation are
no longer pure.

The White Cochin has no sexual dimorphism in plumage color, while the
Tosa fowl is strongly dimorphic. Every one of the first hybrids is dimorphic
in plumage coloration, the two sexes resembling, except for the white,
respectively the female and the male Tosa fowl It is striking to see how
from a germ cell of the male Tosa fowl either a bird colored like a male
Tosa or a bird colored like a female Tosa may arise. The male germ cells
contain the Anlagen not only of the male characteristic but also of the
female characteristic (Darwin, 1876, Chapter XIII).

Series X. — Dark Brahma and Tosa Fowl.
STATEMENT OF PROBLEM.

This series was undertaken primarily to test inheritance of secondary sexual
characteristics and the possibility of transferring them from one sex to
another.

THE RACES AS A WHOLE.

The Dark Brahma male and female have been described at page 32 ; the
Tosa fowl, male and female, at pages 43, 44. Each race has a strongly
marked sexual dimorphism in plumage color. The males have feathers of a
more uniform color ; the female Dark Brahma has penciled feathers ; the
female Tosa fowl has mossy feathers with prominent light shafting.

INHERITANCE IN POULTRY.
TABLE OF CHARACTERISTICS.

No.

Characteristic.

Tosa fowl.

See
page—

Dark Brahma.

See
page—

Female.

Male.

Female.

Male.

I

2

3
4
5
6

7
8

9

10

ii

12
13

Shafting

Present
Present
Absent .
Absent ,
Absent.
Absent.
Single
White,
Red

Absent .
Present
Absent.
Absent.
Present
Absent .

32
33
33
48
48

44-48

Absent .
Present
Absent .
Present
Absent ,
Absent.
Pea .
Red or
Yellow
Yellow
Presen
Presen
Short

Absent.
Present
Present
Absent .
Present
Present

bav.

32
33
33
33
34
34

I/acing on hackle . .
Lacing elsewhere. .
Penciling

Red wing-bar

White wing bow. .
Comb

Earlobe

red edge. .

Iris color

Foot color

Willow
Absent
Absent

LOH£T

Vulture hock

Foot feathering
Tail feathers . . .

REMARKS ON THE CHARACTERISTICS.

1. SHAFTING. — In plumage, shafting is a light streak on the shaft and adja-
cent parts of the vane. Of the two parental races it occurs only in the
female Tosa fowl (fig. 30). The light shaft-stripe is, however, widespread
among females of certain dark or silvered races — e, g., Silver Wyandottes,
Silver-gray and Dark Dorkings, Silver Duckwing Games, and Silver Penciled
Hamburghs. It crops out in many individ uals where its o ccurrence is regarded
by the " fancy " as a " defect." It is an original characteristic of poultry
introduced from Gallus bankiva, whose female exhibits it conspicuously

(fig- 39)-

2. HACKLE LACING. — Among most broken-colored poultry the hackle
feathers are unlike those of the rest of the plumage. Usually the hackle has
a dark band in the center and is margined or laced by white — more rarely by
yellow or red. In the female Jungle fowl (fig. 39) the feathers of nape and
hackle have a black center (with broad, straw-colored shafting) and are laced
with straw color. The male Jungle fowl has hackle feathers of a solid red
color. In the descent of the domestic poultry, hackle lacing seems to have
been transferred to the male sex also.

3. BODY L,ACING. — Few races of poultry exhibit lacing elsewhere than on
the hackles. It is very prominent on the Indian female, but is not found on the
Jungle fowl of either sex. In the Dark Brahma male (fig. 19) it occurs only
on the saddle feathers. Whether its laced saddle is derived from the Indian
or is due to a spreading, through correlation, from the hackles can not be
said. Lacing is found on the breast of Game fowl and over much of the
body of the female Dark Dorking. Among certain derived races, such as
the Spangled Polish and the Laced Wyandottes, it affects nearly the whole
plumage and is very conspicuous.

DARK BRAHMA AND TOSA FOWL. 53

4. PENCILING. — This may be defined as a concentric repetition on the
feather of alternating bands of the lacing and the ground color. In the hackle
of the female Jungle fowl the straw color of the lacing is repeated in the center,
the two light areas being separated by a black band. In the female Indian
fowl the feathers of the throat are laced, but lower down on the larger back-
feathers and on the wing bows, there is a second or inner lacing — i. e. , the
wing is penciled ; * consequently penciling may be said to be a fundamental
form of coloration in the genus Gallus. Penciling occurs widespread among
the derived or secondary races of poultry, particularly in the " partridge "
varieties. A. curious modification of penciling is the straight transverse
barring of the feather familiar in the Barred Plymouth Rock and Penciled
Hamburghs.

5. RED WING-BAR. — The wing-bar is formed by the lower wing coverts,
usually the first to third rows above the remiges or flight feathers. In the
male of many races of fowl these differ from the more proximal rows. In
the Dark Brahma male they have white and red in addition to black. The
wing-bar has probably been derived by the Dark Brahma male from the
Indian fowl. In the male Tosa fowl the lower wing coverts are tipped with
red, but they show no white.

6. WHITE WiNG-Bows. — The wing-bow is formed by the upper or proximal
rows of wing coverts — i. e., above the third. These coverts are frequently
of a different color from the wing bar. They are red in the male Indian
and Malay, but they are white f in the male Aseel.I The white wing-bow
of the Dark Brahma has probably been derived from this source. The wing-
bow of the male Tosa fowl, like that of the Jungle fowl and Games, is red.

8. WHITE EARLOBE is a derived color, the primitive condition being red
(page 33).

9. IRIS COLOR. — The origin of the yellow eye of the Brahma has been dis-
cussed at page 33. The red eye of the Tosa fowl is found in most Games
and is the prevailing color among domestic poultry.

MATERIAL.

Mother.— No. 121, Dark Brahma Bantam (fig. i8).§ She is a beautifully
penciled bird, with horn-colored beak, pearl-colored iris, prominent vulture
hocks, and booted down to the outer two toes. To test her purity, she was
bred for a month to No. 122, Dark Brahma male, also from Mr. Hodges.
Their offspring died before hatching except one (No. 146 £), which is a
typical Dark Brahma.

* Compare Wright, 1902, p. 334, and American Standard of Perfection, 1905, p. 207, figure.

f According to Ludlow's painting in Wright, 1902, opposite p. 326.

t Since the above was written I have purchased a male Aseel which has dark coverts
tipped with white.

§ Weight 1,300 grams, received February, 1905, from Mr. F. H. Hodges Red Bank,
New Jersey, marked F. H. H., No. 66, also No. 338.

54 INHERITANCE IN POULTRY.

Father. — A Tosa fowl bred at the station, No. 8A, "General Oyama,"
referred to at page 46.

RESULTS.

The produce was 5 females and 16 males (fig. 40). They are all blocky
birds, very different from the Tosa fowl, but longer than the Brahma. The
maternal or Brahma type is, however, predominant. Only the first genera-
tion of hybrids has been reared.

r . SHAFTING. — The male hybrids are mostly without shafting on the feath-
ers of the back and the wing coverts. Two, however, show clear yellow
shafting on these feathers, and in two others the shafting is a light buff
color. The female hybrids have these feathers shafted. Shafting is domi-
nant in the female hybrids. It is doubtfully transferred to some males.

2. HACKLE LACING. — This showed on all hybrids of both sexes.

3. BODY LACING. — In the male hybrids the saddle feathers and sometimes
the tail coverts are laced with yellow as in the Brahma. Such lacing does
not appear on the female. Lacing in the male sex appears to be dominant.

4. PENCILING. — This appears as typical penciling or as barring on the back
and saddle and on the exposed parts of the secondaries of the female hybrids.
It does not appear on the males. Penciling seems to be dominant over
mossiness and to be confined to the female sex.

5. RED WING-BAR. — This is present in all of the first hybrid males, but the
red is deeper and spreads farther over each feather than in the Dark Brahma,
the red of the Tosa fowl having its effect. The female is without wing-bar
as in the female parents.

6. WHITE WiNG-Bow. — Of 13 hybrid males four show no white in the
upper wing coverts (fig. 40) ; but one of these has a light buff bow — a tendency
toward white. The others have a small amount of white, which is derived
from the Dark Brahma. The white has, however, been clearly reduced in
amount. The interpretation of this result must await further breeding.

7. COMB. — In every hybrid the comb is pea, proving the dominance of that
form over the single. The pea is, however, often atypical, the lateral ridges
being rudimentary. Dominance is not always perfect,

8. EARLOBE COLOR. — Every hybrid shows some white, as in the Tosa fowl ;
but this white tends toward yellow — a much diluted red. White seems to
dominate, but, if so, the dominance is imperfect.

9. IRIS COLOR. — This is red in the hybrids; but in two cases the red ap-
proaches orange. The iris color of the Tosa fowl is dominant, but imper-
fectly so.

10. FOOT COLOR. — Of 21 hybrids, all males (i6)show yellow feet and all
females (5) willow feet. This dimorphism is not found in the parent races.

11. VULTURE HOCK. — The hybrids show a tendenc}^ toward long feathers
hanging over the heel (fig. 40). In one case these had reached a length of
105 mm. by six months ; in another, about 90 mm. In other cases these

FRIZZLE AND SILKY. 55

feathers are much reduced from the Brahma type, and in one or two cases it
is doubtful if they are present. We have to do here either with a blending
characteristic or else a very imperfect dominance of the vulture hock.

12. FOOT FEATHERING. — This is always present in the hybrids, but is
usually less heavy than in the Dark Brahma (fig. 40). Booting is dominant,
but is imperfectly so.

13. TAIL FEATHERS. — As none of the hybrids are over six months old, it
is impossible to report fully on the inheritance of this characteristic. While
in some male hybrids the tail feathers already surpass in length the middle
tail feathers of the adult Brahma parent and are still growing, in no case
have they made the extraordinary growth of the Tosa fowl.

CONCLUSIONS.

METHOD OF INHERITANCE. — The color characteristic of shafting and
penciling in the female, and body lacing, red wing bar, and white wing bow
in the male, appear to dominate in the respective sexes ; but dominance, if
such it is, is always imperfect, in that traces of the opposite allelomorph are
sometimes found. Furthermore :

Red eye color dominates over yellow (not always perfectly) .

Booting is dominant over clean leg.

Earlobe color is something of a mixture.

Vulture hock is sometimes very imperfectly " dominant."

The length of tail feathers is perhaps a blend.

SEX IN INHERITANCE. — For the most part a sexually dimorphic charac-
teristic is inherited only by the proper sex. In the hybrids of this series,
however, shafting seems to have been partially transferred from the female
to some males. Most peculiar is the inheritance of foot color, where all the
female hybrids show the willow foot of their father, and all male hybrids
the yellow foot of their mother.

Series XI.— Frizzle and Silky.
STATEMENT OF PROBLEM.

This series of crossings was made to learn the inheritance of the allelo-
morphs given below.

THE RACES AS A WHOI.E.

The origin of the Frizzle fowl (figs. 41 and 42) is not definitely known.
Darwin (1876, Chapter VII) states that they are not uncommon in India,
and Temminck states that they are domesticated also in Java, Sumatra, and
all the Philippine Islands, being prevailingly white. They must have been
brought to Europe early, since they are described by Aldrovandus in 1645
from a specimen sent him from Parma. Willoughby, in his Ornithology
(1676), says that he had seen them in England. The recurving of feathers
is found in many species of birds. It usually occurs on the neck, where it
forms a ruff ; more rarely over the entire body. Frizzled canary birds are

56 INHERITANCE IN POULTRY.

occasionally exhibited. Frizzling is probabty morphologically related to
' ' rough coat ' ' in mammals. The frizzled characteristic is a typical sport.

The Silky fowl (fig. 43) is likewise of great antiquity. Marco Polo saw
it in Asia in the thirteenth century (teste, Diirigeu, 1886, p. 298). Gesner
described it in 1555. It is a native of eastern India, coming, according to
Blyth (Tegetmeier, 1867, p. 221), from China, Malacca, and Singapore. A
condition allied to silkiuess (described below at page 57) is found in other
races of poultry, particularly, as the following statements show, in the
Cochins.

Tegetmeier (1867, p. 46) says :

The singular variety known as Silky Cochins, or sometimes as Emu fowls, is simply
an accidental variation of plumage which occasionally occurs and which may be perpetu-
ated by careful breeding. The cause of the coarse fluffy appearance of these remarkable
fowls is to be discovered in the fact that the barbs of the feathers instead of being held
together by a series of hooked barbules (so as to constitute a plane surface, as occurs in
all ordinary feathers) are perfectly distinct, and this occasions the loose fibrous silky
appearance from which the fowl obtains its name.

An engraving of such a feather is given by that author at page 224.

Wright (1902, p. 255) states that he has seen no Emu fowl "now for
twenty years, ' ' and makes the suggestion that this entire ' ' silkiness ' ' of
feather is the extreme limit, perhaps, of the kind of plumage which gives
fluffiness to the leg region of American Buff Cochins.

The fluff of Cochins and Brahmas has indeed many points of similarity in
structure with the feathers of the Silky. In one feather from the abdomen
of a Brahma hen, whose shaft is 35 mm. long, I find the barbs very long (up
to 30 mm. ) and not connected together. Each barb bears, proximally, two
rows of short, flat, hook-shaped barbules alike on the two sides. Beyond,
there are a few short barbules that taper to a hair-like apex. Still more
distally on the barb the barbules may attain a length of 5 mm., be altogether
devoid of booklets, but show a segmented condition as in the Silky Far
from my preconceived notion, I find few intergrades between the short barb-
ules and the others. The more proximal of the long barbules are the longest
of all, and the short barbules (which rarely exceed 0.5 mm. in length) also
occur here scattered among the long ones. There thus seems to be a dis-
continuity between the two kinds of barbules, and this harmonizes with the
view that the long barbule is a mutational form of the more typical short
barbule.

As to the relation of the plumage of the Silky fowl to the fluff of Cochins,
I have formulated the following hypothesis : Long and short barbules are
two dimorphic forms found among birds. This dimorphism has been recog-
nized in the terminology ' ' down feathers ' ' and ' ' contour " -f- ' ' quill ' '
feathers. Down feathers may or may not have a shaft ; they have barbs,
and usually barbules, the latter being long and devoid of cilia or booklets.
In the contour and quill feathers of most birds the short barbules alone are

FRIZZLK AND SILKY.

57

present. But in some birds the barbules are long and devoid of cilia or hook-
lets as in the Ralitae (ostrich, emu, cassowary, etc.). In poultry the down
feathers are characterized by absence of hooklets, and the ventral abdominal
feathers of poultry belong to this category. In the Silky fowl the contour
feathers, in the strict sense, are absent, or rather they have gained long
bookless barbs, and consequently have become in so far down feathers.
But the feathers of the Silky fowl have one new characteristic not found in
any other long-barbed forms, namely, the bifurcation and anastomosis of
the barbs (page 58).

TABLE OF CHARACTERISTICS.

No.

Characteristic.

Frizzle fowl (Game).

Silky fowl.

I

Plumage color

Dark, black, red and buff

White

2

Comb form

Rose

Single.

3

Shaft of contour feather.

Recurved

Straight

4

Barb length .

Short. . .

Loncr

5
6

Barb form
Number of toes

Twisted about long axis . . .
Four

Straight.
Five or six.

7

Skin color

White

Black

8

Crest

Absent

Present.

REMARKS ON THE CHARACTERISTICS.

1 . PLUMAGE COLOR. — This characteristic is very variable in Frizzles, owing
to the fact that fanciers have established no color ' ' varieties, ' ' although an
effort is now being made in that direction.* As stated below in detail, my
Frizzles were of varied and mixed colors.

2. COMB FORMS. — The "American Standard " calls for single comb in the
Frizzle and rose, or rather strawberry, comb in the Silkies. My Frizzles
have, on the contrary, a rose comb, and my Silkies either a single comb or a
rose comb, the Silky being impure in respect to this characteristic.

3-5. FEATHER FORM. — In the Frizzles the contour feathers have the shaft
curved so that its outer surface becomes concave. This is most striking in
the neck region, where a ruff is formed (fig. 41). The wing primaries are
modified in another direction, since in them the barbs, in groups of 4 to 8,
are twisted in corkscrew fashion about their own axis and through 180° or
more ; consequently the gray surface, which is normally next the body,
comes to lie outermost. Such a twisting of the barbs sometimes occurs in
primaries of non-frizzled races ; particulary I have found it in the eighth
primary of some Houdans. The barbs of the remiges of the Frizzles are
mostly short, and in some cases are lacking altogether, being easily broken off.

The feathers of the Silky fowl are remarkable in all parts of the plumage.
The contour feathers, as already stated, are down feathers, whose shaft is

*The new "American Standard of Perfection," published by the American Poultry
Association, 1905, p. 248, directs that color should be " solid — black, white, red, and bay
admissible, provided the birds match when shown in pairs, trios, and pens."

58 INHERITANCE IN POUI/TRY.

usually delicate but not otherwise atypical. The barbs are, on the other
hand, remarkably long. Thus in a contour feather, from the middle of the
dorsal region, whose shaft is 25 mm. long, the prevailing length of barb is
35 to 45 mm. The barbs are, moreover, remarkable in that they frequently
bifurcate, even repeatedly. In a feather before me, one barb, taken at
random, undergoes bifurcation four times. As the branches are not all in
one plane, the feather becomes exceedingly fluffy. At the proximal end of
the shaft the barbs arise parallel and produce an imperfect web close to the
shaft, but marginally the web is lost. Distally on the shaft the barbs arise
more irregularly from the shaft, often bifurcating almost immediately, so
that no web or vane is formed. The barbs may also anastomose.

The barbules are not less strikingly modified than the barbs. They attain
a length of from i to 2 mm. Moreover, it is not possible here, as in other
races, to distinguish between a distal series of barbules carrying a row of
booklets or cilia and a proximal series without booklets but with a folded
edge into which the hooklets of the distal barbules catch. This impossibility
is due, first, to the fact that the barbules are not in two series merely, but may
arise in three planes, or irregularly ; also, morphologically, all the barbules
on the barb are alike. They are all segmented like the ordinary distal barbule,
and the hooklets are represented by minute thickenings at the end of each
segment. As a consequence of this structure the barbs do not hang together
to form a vane and the fluffiness is still further exaggerated.

The quill feathers of the wing (rerniges) and tail (rectrices) of the Silky
are modified, but to a less degree. Primaries, secondaries, and coverts are
all affected. The proximal part of the vane is nearly normal ; the distal part
has barbs of twice to thrice the normal length. The barbs may bifurcate
repeatedly and even anastomose in the plane of the vane. The barbules also
are modified, being much shortened. Proximal as well as distal barbules
may carry hooklets, as is seen in the middle part of the feather. In the
proximal part of the feather, on the other hand, the proximal barbules are
without hooklets. The feathers of the tail have the web even more broken
up than those of the wing.

The silky condition of the feather is a characteristic that is either entirely
new (progressive in deVries's sense) or possibly latent (in de Vries' s sense)
in typical fowl, so that its appearance in the Silky is a case of "degression "
(de Vries). If the former, we should expect, according to de Vries, the
offspring between a Silky and a non-Silky to show a mosaic of the parental
feather characteristics and a non-Mendelian inheritance of silkiness ; if the
latter, a recessiveness of the varietal characteristic of silkiness and its Men-
delian inheritance.*

* De Vries, 1905, p. 280 : " The character of the species is dominant in the hybrid, while
that of the variety is recessive." On the latter of the two assumptions made above, plain
plumage is the species eharacter ; silky plumage, the varietal.

FRIZZLE AND SILKY. 59

6. NUMBER OF TOES. — This is constantly four in pure-bred Frizzles. In
Silkies a fifth toe is always present. The extra toe frequently has a double
nail, or the division may be complete, resulting in six toes.

7. SKIN COLOR. — In the case of the Frizzle the skin is white, sometimes
tinged with yellow pigment. The skin of the Silky is notoriously blue-black.
This is a clear case of melanism, and since early times has been associated
with the other peculiarities of the Silky. The melanic condition affects the
periosteum also. It is remarkable that despite this excess of pigment ren-
dering black the internal tissues, skin, leg scutes, comb, and wattles, the
plumage should be always white.

MATERIAL.

Mothers. — Four Frizzles (Nos. I4A, i8A, IQA, and 2OA), hatched May,

1904, from eggs obtained from Dr. A. G. Phelps, of Glen Falls, N. Y. All
have rose combs and slightly booted feet. No. i8A is peculiar in that the
feathers on head and neck are sparse and small (fig. 42). In general color
the hens vary ; I4A is prevailingly dark brown ; i8A is yellowish ; igA. is light
brown, and 2OA is mixed black, yellow, and red. A male Frizzle from the
same lot of eggs was highly colored red and black.

Father. — A white Silky cock (No. 24A, fig. 43), likewise hatched from
eggs sent in May, 1904, by Dr. Phelps.

The Silky cock and Frizzle hens were mated from January 16 to April 14,

1905. Trap nests were not used, so that I could distinguish mothers only
by the form of the eggs. The egg of i8A was very peculiar and was early
identified. A certain proportion of the offspring can not be assigned to any
particular mother.

RESULTS.

Only the first hybrid generation has been obtained.

1. PLUMAGE COLOR. — Of 32 hybrids, 7 (2 2. 6 per cent) are white (showing
some buff in six cases) and 25 (77.4 per cent) are dark. No. i8A appar-
ently produced only dark birds, largely dead-black. The others produced
in part white hybrids (fig. 44), but mostly piginented ones. The result is
not what we should have expected. If white were recessive, o to 50 per cent,
if dominant, 100 per cent, of the offspring should be white. Moreover, the
Silky is doubtless homozygous in respect to color, since (i) Silky fowls are
carefully bred for white color, and (2), bred to a hen of its own strain, it has
produced only white birds. I conclude, therefore, that the white plumage
color is not always dominant over the black, red, and yellow of the Frizzle.
The matter will be further investigated.

2. COMB. — In all cases the rose comb of the Frizzle dominated over the
single comb of the Silky (fig. 44).

3-5. CURVING OF SHAFT, BARB LENGTH, AND BARB FORM. — These are all
correlated in the first generation. Of 10 mature birds, 6 are typically frizzled

6o

INHERITANCE IN POULTRY.

and 4 have flat feathers. Assuming frizzling to be dominant, non-frizzling
recessive, and that all my Frizzle fowls are heterozygous, we should expect
50 per cent frizzled offspring. The result accords well with these hypotheses.
None of the hybrids show an)r trace of silkiness. Silkiness is recessive as
against non-silkiness.

This result is striking and has been observed by others. Tegetmeier
(1867, p. 224) bred Silkies to other varieties and found that " the chickens
produced seldom had the silky feathers, but were clothed in plumage of the.
ordinary character." Mating these hybrids together he got among plain
feathered offspring " one covered with feathers like those of the Silk fowl,"
but with black plumage. Darwin (1876, Chapter VII) had previously bred
a white Silk hen to a Spanish cock; "none inherited the so-called silky
feathers."

6. NUMBER OF TOES. — Thirty hybrids gave the following distribution of
characteristics :

Characteristic.

/•

Per cent.

4 toes, both feet

7

23.3

4 and 5 toes

q

V>.o

5 toes, both feet

14

46.7

Total

•*o

IOO.O

Here, as elsewhere in this paper, the inheritance of extra toe is difficult to
account for on the Mendelian principle of dominance.

7. SKIN COLOR. — All hybrids have a black skin. Tegetmeier (1867,
p. 224) got the same result.

8. CREST. — So far as noted, all mature hybrids have a well-marked crest,
but it is somewhat smaller than that of the Silky.

CONCLUSIONS.

A final conclusion as to dominance must await the production of the second
generation of hybrids. The following (in italics) appear to show Mendelian
dominance over the corresponding allelomorphs :

Rose comb vs. Single comb.

Frizzle feathers vs. Plain feathers.
Black skin vs. White skin.

Crest vs. Plain head.

Plumage color and number of toes are unit characters, but behave pe-
culiarly. The dominance of the crest is imperfect.

LEGHORN AND RUMPI.ESS GAME.

6l

Series XII.— Single-comb White Leghorn Bantam and Black-breasted Red Rumpless Game.
STATEMENT OF PROBLEM.

This cross was undertaken primarily to test the inheritance of rumplessness,
and secondarily of the more primitive game coloration against white plumage
color.

THE RACES AS A WHOIyE.

The White Leghorns have been described at pages 37 and 39. The Black-
breasted Red Game closely resembles the wild Jungle fowl in color (figs.
45 and 46).

TABLE OF CHARACTERISTICS.

No.

Characteristic.

Single-combed
White Leghorn.

Discussed
at page—

Black-breasted Red
Rumpless Game.

Discussed
at page :

I

General color ....

White

18

Black and red.

2

Beak color

Yellow

iq

Black . .

3

Uropygium .

Present

Absent . .

4

Foot color

Yellow

20

Willow

48

REMARKS ON THE CHARACTERISTICS.

UROPYGIUM. — The absence of uropygium is a characteristic that has long
been known among fowl, but there seems to be little knowledge of its mor-
phology. In ordinary fowl there are five free caudal vertebrae, followed by
a. fused portion — the uropygial bone. In the case of a rumpless Game female
(No. 119, fig. 45) dissected by me, there are two unsymmetrically formed
and intimately fused vertebrae behind the fifteenth synsacral — the posterior
limit of the sacral vertebrae. That there are two is shown by distinct trans-
verse processes with spaces of the passage of the nerves. Behind these is a
knob of bone about i mm. in diameter. These three elements constitute
the entire caudal skeleton. It is profoundly reduced from the normal.

Rumplessness may be found in any race. It has cropped out in two of
the 800 fowl bred at this station in the past year — hybrids derived from the
Minorca- Polish and the Leghorn- Houdan crosses. It seems like a misuse
of the term breed to speak of a " Rumpless breed," as poultry books do.

The characteristic is referred to by Aldrovandus in 1645, by Temminck,
and by other early writers. Its origin has been ascribed to Persia, to Cey-
lon, and to China ; doubtless it occurs in all these places as well as in many
others. Taillessness early appeared among fowls in America. Clayton
(1693, P- 992) asserted that he had observed that in "Virginia " most of the
cocks and hens were without tails, and Wright states that he was informed
by a West Indian in 1872 "that the greater number of fowls in his own
neighborhood had no tails." Darwin (1876, Chapter VII) refers to this
characteristic and states that one bird he examined had no oil gland; the
same is true of the three rumpless Games that I have had. Among the

62 INHERITANCE IN POULTRY.

poultry books that describe the "breed " quite fully are Tegetmeier (1867,
pp. 230-232), Baldatnus (1896, pp. 170-172, " Kaul oder Kliitthuhner " ),
Diirigen (1886, pp. 98-100), Wright (1902, p. 481), and Weir-Johnson-
Brown (1905, pp. 1016-1017).

Regarding the inheritance of this characteristic, statements are not in
accord. Tegetmeier (p. 231) says:

A friend of mine purchased a successful pen [of Rumpless fowl] at a poultry show,
taking them away to a walk where no other fowls ever trespassed, and yet the chickens
were, in a considerable number of instances, furnished with fully developed tail feathers,
being not rumpless. On inquiry of the previous owner, he stated: "Mine have always
done so from the first time I kept them; but the tailed birds will very probably produce
rumpless chickens." Three such birds were purposely retained, and they produced the
next year more than twenty youngsters, all of which but one were rumpless and destitute
of tail feathers.

The foregoing experiment would seem to prove that the rumpless parents
were heterogametous, and that while rumplessness is dominant the recessive
condition of tail is here prepotent (Castle, 1905). Darwin (1876, Chapter VII)
possessed a rumpless bird which "came from a family where, as I was told,
the breed had kept true for twenty years; but" he adds, " rumpless fowls
often produce chickens with tails." The breeding true of a character may
mean either that it is dominant and homogametous in this respect or that it
is recessive. Diirigen (1886, p. 99) states that a rumpless cock mated with
a tailed hen produces not exclusively rumpless, but a fair percentage of them,
and Wright (1902, p. 481) says that ' ' a Rumpless fowl crossed with any other
generally produces a large majority of Rumpless birds." All of the fore-
going results are consonant with the conclusion that rumplessness is typically
dominant, but that the recessive full tail may be prepotent.

MATERIAL.

The mother was the White Leghorn bantam No. 127 discussed at page 39.
She is heterozygous and contains black gametes.

The father (No. 117, fig. 46) was one of three rumpless bantams obtained
from Dr. A. H. Phelps, of Glen Falls, New York. Two of these were
typical Black-breasted Red Games; they lack oil glands and weigh about
1,000 grams each.

RESULTS.

Only the first generation of hybrids has been so far obtained.

GENERAL PLUMAGE COLOR. — Of 24 hybrids 12 were white or prevailingly
so (fig. 47). Usually, however, more or less black and more rarely some
buff was present. The other 12 were either black-and-white barred (and
these were all males) or black with more or less reddish. As we have seen,
the white mother contains recessive black or black-and-white, so that the
result accords with the expectation of only 50 per cent white.

BLACK COCHIN AND RUMPLESS GAME.

BEAK COLOR. — In the hybrids the beak is sometimes yellow, sometimes
black, sometimes black-and-yellow streaked.

UROPYGIUM. — Of 24 hybrids the uropygium is normal in 23 (fig. 47).
One chick taken from the egg is recorded as without tail, though tail gland
is present. It is doubtful if much stress may be laid on this record, as the
uropygium is always very small in the unhatched bird. We may exclude it
from present consideration. This whole result was unexpected because
opposed to the earlier observations. It leads to the provisional hypothesis
that rumplessness is recessive in my strain. If full tail is recessive, then in
my strain the recessive condition is prepotent. Further discussion must be
deferred until the second hybrids have been bred.

FOOT COLOR. — This was yellow in about half of the cases and willow or
dark in the other half. Recalling that the White Leghorn is heterozygous,
the result favors the hypothesis that yellow is dominant over willow.

CONCLUSIONS.

White plumage color seems to be dominant over game color. The hy-
potheses seem to be warranted that yellow beak and foot color are dominant,
and that rumplessness is recessive in this strain.

Series XIII.— Black Cochin Bantam and Black Breasted Red Rumpless Game,
STATEMENT OF PROBLEM.

This cross was primarily to test the inheritance of rumplessness, and
secondarily of black against red plumage color.

THE RACES AS A WHOLE.

Concerning the Rumpless Game see page 61. The Black Cochins are
discussed at page 39.

TABLE OF CHARACTERISTICS.

No.

Characteristic.

Black Cochin
Bantam.

Discussed
at page —

Black-breasted Red
Rumpless Game.

Discussed
at page —

i

2

3

4
5

General color

Black

39
63

39

34

Red with some black.
Absent

62
63

Present

"Iris color

Dark brown . .
Present

Red streaked with

Vulture hock . . .
Foot feathering . .

Absent

••

MATERIAL.

Mothers.— The Black Cochin Bantams Nos. 129 (fig. 26), 130, 131, and
132 were the same as those referred to at page 39.
Father. — The Rumpless Game is No. 1 17, referred to at page 62 (fig. 46).

64 INHERITANCE IN POULTRY.

RESULTS.

Only the first hybrid generation has been produced.

GENERAL PLUMAGE COLOR. — Of 24 hybrids all were prevailingly black.
Among 1 8 of those that hatched 8 showed some red. This red is chiefly
found as a lacing on the hackle feathers or a peppering on the wing coverts,*
throat, f and outer margins of the remiges.J This seems to point to the
hypotheses that while black dominates over red the dominance is sometimes
imperfect. When red occurs it occurs on those feathers that normally con-
tain red in the Game, and on that part of the feather that is red in the Game.

UROPYGIUM. — This is invariably present, apparently fully developed.

IRIS COLOR. — All the hybrids have dark-brown eyes; only one shows a
trace of red. The hypothesis seems justified that in this case dark-brown
iris pigment is dominant over red and yellow.

VULTURE HOCK. — This is always absent. In only a single case§ are the
feathers slightly elongated on the hock.

FOOT FEATHERING. — Every chick that hatched has the foot and at least
one toe booted. In some cases this booting is much reduced as compared
with the Cochin parent. Booting is dominant, but not always completely so.

CONCLUSIONS.

In this cross of black vs. red, black appears to be dominant, although im-
perfectly so. The two colors do not blend, however, but red appears in a
particulate fashion, usually in the parts of the plumage that have normally
least black pigment. It is as if there were a struggle between the two
pigments and red overcame black where black was weakest.

The presence of tail in the first hybrid generation is confirmatory of the
results of the preceding series. Rumplessness is apparently recessive.

Brown iris color appears to dominate over the older red, and booting
dominates over the ancestral clean- footed condition.

* Nos. 589 tf and 798 <?. f No. 587 9 . J No. 577 $ . § No. 651 tf.

GENERAL DISCUSSION. 65

D. GENERAL DISCUSSION.

INHERITANCE OF PARTICULAR CHARACTERISTICS.

COMB FORM.

The coinb is a characteristic that has had its origin in the genus Callus.
It consists of a mass of uncovered erectile tissue — a tissue present in many
species of birds. The primitive form of the comb is the single comb seen
in the wild species of the genus Gallus, and in most domestic races. This
may be modified in two directions : First, in the direction of lateral repetition
of the comb giving rise to the pea comb,* and, in an extreme case, to the
rose comb (of which the walnut comb of the Malays is a special modifica-
tion); second, in the direction of reduction of the modified comb producing
the races with mere papillae (Houdan, Polish, La Fleche, etc.) or that are
entirely combless (Breda fowl). That the rose comb is a modification of the
same sort as the pea comb but carried to a greater extreme is indicated by
the fact that the rose comb often shows five parallel ridges (instead of the
more usual irregularly scattered papillae) and that in the female the rose
comb sometimes consists of three ridges as in the male pea comb.

When single comb (Minorca, fig. 4) and pea comb (Brahma, fig. 19) are
crossed, pea comb is dominant (p. 35). The median ridge is, however, in
the hybrid high for a pea comb and the lateral ridges are usually reduced
(figs. 20, 21). When single comb (Leghorn) and rose comb (Minorca) are
crossed, rose comb is dominant (p. 30). When single comb (Minorca or
Leghorn) is crossed with the paired rudiments of a comb found in the Polish
and Houdan fowl, a Y-shaped comb results (pages 10, 22, 28, fig. 8). This
Y comb is of great interest. It was obtained by Bateson and Punnett (1905,
pp. 108, 112-114) in some of the offspring of (single-comb Leghorn x rose-
comb Dorking), crossed with (single-comb Leghorn x walnut- comb Indian) ;
and also in one of the offspring of a single-comb Leghorn crossed with
[(single-comb Leghorn x walnut-comb Indian) x (single-comb Leghorn
X rose-comb Dorking)]. In Bateson and Punnett's cases the splitting was
evidently nearly complete, forming an 0-shaped comb, or the "cup comb"
of Darwin (1876, Chapter VII). The Y comb was obtained also by Hurst
(1905, pp. 133, 135, 138, 140, 146). This was a single split comb when
Leghorn and Houdan were crossed, and a rose split comb when rose-comb
Hamburgh and Houdan were mated.

The interrelation of the different forms of comb — single, pea, walnut,
Y, and V may, I think, be expressed in the following hypothesis : The pea
comb and the walnut comb are composed of two elements — a median single
comb and a pair of lateral combs. This hypothesis is supported by the

*The pea comb was doubtless a characteristic of the unknown feral ancestor of the
Aseel-Indian group. But as the single comb is the dominant type in the known wild
Jungle fowls the pea comb probably evolved from it.
5

66 INHERITANCE IN POULTRY.

following evidence. First, of teratology. Extraneous paired papillae occa-
sionally occur on the sides of the single comb in pure-bred races. These are
known as ' ' side springs, ' ' and are considered by fanciers as grave ' ' defects. ' '
Now such side springs are morphologically equivalent to the lateral ridges of
the pea comb. Second, there is the evidence of hybrid forms. Bateson and
Punnett (1905 a) show that when pea comb and rose comb are crossed the
second hybrid generation (F2) gives single comb, as well as pea and rose combs.
This result may be interpreted as due to the fact that the gametes of a pea-
combed bird have either a tendency toward side- springs (= pea comb) or
they have no such tendency (= single comb) ; and the gametes of a rose-
comb bird have a tendency to produce two pairs of side combs (= rose comb)
or else they have no such tendency (= single comb). When two gametes
without the side-comb tendency come together in F2 a single comb is pro-
duced. The necessity of assuming absence and presence of lateral combs
strengthens the view that the pea comb is made up of two elements — median
and lateral. If median comb and side-springs are distinct elements, then
they should be independently inheritable. This result is realized on the one
hand in the single comb, and, I think, on the other hand, in the cup comb
(fig. 6), which consists of two side-springs without median comb. It is
realized also in the V comb of the Polish fowl, which is a cup comb of
which the anterior portion is typically not developed.

That the V comb represents the posterior portion of a cup comb is supported
by the fact that it is not uncommon to find not one pair of papillae merely,
but two, three, or four pairs of papillae in Polish fowl and in second-genera-
tion hybrids. A row of three' or four papillae on each side of the head is a
close approach to a typical cup comb.

The incompleteness of the cup comb where a V comb is produced may be
due to various causes. In the Polish fowl the upturned nasal process and
absence of a bony ridge over the nostrils appear to be the cause of the absence
of a comb there, and we have seen (p. 17) that the only undissociable char-
acteristics in the second- generation hybrids of Minorca and Polish are
those of high nostril and rudimentary comb. The second cause restricting
the development of the cup comb to its posterior limits is the presence of a
median comb anteriorly ; this is the case of the ordinary Y comb. The Y comb
is found in hybrids between single and V comb ; the anterior portion of the
comb is not suppressed here, because the bony roof of the culmen is com-
pletely developed, and the very presence of a large median comb there prevents
the development of the side-springs at the same niveau. In the development
of the comb of the hybrid there is, as it were, a struggle between the two
elements of median and lateral combs. The Y comb assumes a great variety
of forms, running the entire gamut from a single comb on the one hand to
(i) a cup comb or to (2) a pair of papillae on the other. I have already
(p. 10) referred to the variation of the length of the stem of the Y, series

INHERITANCE OP PARTICULAR CHARACTERISTICS. 67

( i ), f rom ioo per cent to nearly zero. The second hybrids of Polish or Houdans
crossed with single combs illustrate series (2). We begin with a single comb
having its posterior one-sixth split ; next conies a comb having its posterior
one-sixth split and anterior five-sixths single, but greatly reduced in height
(fig. 50) ; next the same with the anterior portion reduced to an irregular
carunculated mass having a slight median elevation (fig. 49) , and finally a
pair of papillae only (fig. 48). In this series we have a fading out of the
median portion, pari passu with the enlargement of the nostril, but the
persistence of the side combs unimpaired. The side combs have been unable
to enter the territory from which the median comb has been driven, because
that territory is likewise untenable for it. These two series sufficiently
demonstrate that the V comb represents the posterior portion of the cup comb.

That the cup comb represents merely the greatly enlarged lateral combs
or side-springs is proven by the occasional presence of both median and cup
comb on the same individual. In some races, as in the English type of Hou-
dans, the median comb typically appears lying between the pair of cup-like
side-springs, resembling the trunk of a butterfly between its wings. Among
the heterozygous combs of the second generation of Minorca x Houdan or
Minorca x Polish hybrids, instructive examples of persistence of both single
comb and side-springs are especially apt to occur. Figure 52 shows this
condition ; there is a median comb anteriorly and a nearly typical pea comb
posteriorly, except that the lateral ridges are atypically high. Thus the
Y comb becomes explained as due to the presence of both single and lateral
combs.

The question now arises, Is it possible to explain on Mendelian principles
the production of a Y comb when median comb and lateral comb are crossed ?
In accordance with such principles we should have to picture the gametes
of the single-comb and V-comb parents as follows :

Single comb.

V-comb.

Median element

No median elements.

No lateral elements . .

Lateral elements.

The allelomorphs are then median and no median, no lateral and lateral,
and the positive characteristics are dominant. In the second hybrid gen-
eration the two dominant characters should be combined in nine-sixteenths
of all cases ; the two recessive in one-sixteenth, and one dominant with one
recessive in three-sixteenths + three-sixteenths of the cases.

Another hypothesis is possible. Granting that the Y comb is no neomorph,
but the sum of single and lateral comb, then the Y comb may be a case of
particulate inheritance, the median comb being produced on the anterior and
the lateral on the posterior part of the frontal region. In cases of particulate

68

INHERITANCE IN POULTRY.

hybrids bred inter se, the offspring exhibits one or the other of the parental
conditions each in 25 per cent of the cases and the heterozygous condition
in 50 per cent. To decide between these rival hypotheses we have to appeal
to the statistics of occurrence of the different forms of comb. All cases
(Series I and II) are combined in the following table, showing distribution
in the second hybrid generation :

Comb characteristic.

Expected.

Actual.

On hypothesis
of dominance.

On hypothesis
of participate
inheritance.

Single comb

Per cent.
18.75
56.00

•SS)*"

Per cent.
25
5-1
25
o

Per cent.
3O.I

44-9
25.00

0?

Y comb

Lateral comb

No comb

The foregoing table reveals several things. First, the actual distribution
of comb form in the second generation accords better with the hypothesis of
particulate inheritance than that of dominance of both single and lateral
comb. That there is an excess of single comb and deficiency of Y comb is
partly accounted for by occasionally counting a potentially Y comb but
actually single (or nearly single) comb as a true single. Secondly, the
hypothesis of dominance demands the occurrence of a fourth form — pre-
sumably no comb — in 6^ per cent of the cases. No combless fowl was
raised to maturity, and the only possible cases were seen in still very young
or unhatched chicks. Probably no true combless bird appeared. From
both of these considerations I conclude, provisionally, in favor of the theory
that the Y comb is reproduced from the median and the lateral by particular
inheritance.

NOSTRIL FORM.

The sum of results in Series I, II, and III (narrow x high nostril) gives :

Generation.

Narrow and intermediate.

High.

/.

Actual.

Expected.

/.

Actual.

Expected.

PI...,

IO2

99

33

Per cent.
99.0
73-9
51-5

Per cfnt.

100

75
50

I
35
3i

Per cent.
1.0
26.1

48.5

Per cent.

O

25
50

F2

F! X narrow

A close agreement exists between the percentage obtained in each genera-
tion and the expectation on the Mendelian theory, assuming that narrow
nostril is dominant. The statistics do not, however, tell the whole story.
In 36 per cent of the cases in the F: generation the nostril was wider than in

INHERITANCE OF PARTICULAR CHARACTERISTICS.

69

the ' ' narrow ' ' ancestor. Even in the F2 generation nearly half of the ' ' nar-
row and intermediate ' ' were of the intermediate sort. This intermediate
form is evidence that dominance is imperfect and segregation is incomplete.

CEREBRAL HERNIA.

Cerebral hernia is, as already pointed out, a typical monstrosity. The
distribution of its occurrence in crossing is as follows :

*

I-

F

«•

FiX ]

•>lain.

Plain.

Hernia.

Plain.

Hernia.

Plain.

Hernia.

Minorca X Polish

66

o

75

2\

•*4

o

White Leghorn X Houdan. .
Houdan X Minorca

^4
16

o
*o

34

ii

25

to

Total

106

o

109

34

19

o

Percentage .

IOO

o

76.1

2VQ

IOO

o

* Excluding one case of egg embryo with cerebral vesicle,
t Excluding one egg embryo recorded as doubtful.

Cerebral hernia is inherited in Mendelian fashion with plain head domi-
nant. Nevertheless, many of the plain-headed hybrids have the frontal
eminence abnormally high — dominance is imperfect.

CREST.

The crest is independent of the cerebral hernia (pages 16-18). It is a
widespread characteristic among birds, so common that it is not readily
thought of as pathological but usually as ornamental. The distribution of
its occurrence in crossing is as follows :

F

F

F,X

plain.

Plain.

Crested.

Plain.

Crested.

Plain.

Crested.

Minorca X Polish

o

7°

ii

41

6

6

White Leghorn X Houdan . .
Houdan X Minorca

o
o

25
9

6

13

6

9

Frizzle X Silky

o

5

Total

o

IOQ

17

54

12

15

Percentage

o

IOO

24

76

44-5

55-5

Crest is inherited in Mendelian proportions, and is dominant over crestless
head. Even when the Silky is crossed with Callus bankiva its crest is domi-
nant (fig. 53). In this case the new characteristic, a positive variant, domi-
nates over the ancient one ; but the crest is diminished in the first genera-
tion ; dominance is imperfect.

INHERITANCE IN POULTRY.

WHISKERS OR MUFF.

This is certainly a new character and a positive variant. The distribution
of its occurrence in crossing is as follows :

F

k

F

*iX

alain.

Absent.

Present.

Absent.

Present.

Absent.

Present.

Leghorn X Houdan

o

24

f

26

1 1

Houdan X Minorca

o

ii

Total

o

-I?

f

26

ii

Muffling is apparently dominant.

BEARD.

This is also a new, positive, variant. The distribution of its occurrence
is as follows :

F

F

!•

PiX

plain.

Absent.

Present.

Absent.

Present.

Absent.

Present.

leghorn X Houdan

o

21

f

12

8

Houdan X Minorca

0

10

Total

o

7.7.

i>

12

7

8

Beard is apparently dominant, but often imperfectly so.

FEATHER FORM.

Silkiness is a new characteristic and, approximating as it does the juvenile
down condition, a negative one. When a Silky is crossed with a Jungle fowl
the offspring are plain. Silkiness is recessive to non-silkiness — the retrograde
to the progressive type.

Frizzling is likewise a new characteristic — a positive character added to
the perfect feather. The distribution of the occurrence of silkiness and friz-
zling is as follows :

F,.

No silkiness.

Silkiness.

Non-frizzling.

Frizzling.

Frizzle X Silky

f.

The Frizzle fowl used were doubtless heterozygous. When non-frizzled
birds are crossed inter sc they produce only plain offspring. Frizzling is
dominant over non-frizzling — the progressive over the primitive.

INHERITANCE OF PARTICULAR CHARACTERISTICS.

UROPYGIUM.

Rumplessness is a new characteristic and a typical negative variant. The
distribution of its occurrence is as follows :

Fr

Non-rumpless.

Rumpless.

Leghorn X Rumpless Game

27.

*o

Cochin X Rumpless Game

IQ

Frizzle X Rumpless Game

7

Nankin X Rumpless Game

7

o

Total

C2

o

Percentage

IOO

* One egg embryo doubtfully rumpless.

The new, negative characteristic is here completely recessive.

TAIL-LENGTH.

The long tail of the male Tosa fowl is a new, positive variant. The dis-
tribution of its occurrence in male hybrids is as follows :

F

I-

F

V

Crosses.

Short.

Long.

Short.

Long.

Tosa X Cochin

o

7

?

?

Brahma X Tosa

o

*i6

Total

o

IQ

* The tails are, perhaps, more properly intermediate. While still growing at date of record, they
grow slowly.

The new, positive characteristic is doubtfully dominant, possibly inter-
mediate (cf. fig. 34).

VULTURE HOCK.

This bundle of strong feathers constitutes a new, positive characteristic.
The distribution of its occurrence is as follows :

Crosses.

F,.

F,.

Absent.

Present.

Absent.

Present.

Minorca X Brahma . ...

7

12
12
9

t3
All j

til

*o
(Small) i

0

A t3

grades,
o

16

J 20

Leghorn X Bralima

Black Cochin X Leghorn

Leghorn X Buff Cochin. . . .

Tosa X White Cochin

Brahma X Tosa

Black Cochin X Rumpless Game.

* One shows trace of enlargement of leathers,
t Females with vulture hock ; males without it.

J Seven recorded as slight.

\ One case of trace of elongation of feathers.

INHERITANCE IN POULTRY.

The result is peculiar. Usually the vulture hock is absent in the first
hybrids, indicating its recessiveness. In crosses with a particular race —
Tosa fowl — however, there is no recessiveness. It is probable that the Tosa
fowl is heterozygous in respect of this characteristic. The new character-
istic is recessive, but imperfectly so.

FOOT FEATHERING.

Foot feathering, as the discussion on page 34 indicated, is a positive vari-
ation, new to Galltis, but not of a pathological sort. Common among wild,
scratching birds, its occurrence in Gallus may be regarded as a case of de-
gressive variation (de Vries). The distribution of its occurrence is as follows :

I

» _

I

V

Non-
booted.

Booted.

Non-
booted.

Booted.

Minorca X Dark Brahma

i

4°

Leghorn female X Dark Brahma
male

4

15

Dark Brahma female X Leg-
horn male

o

25

Black Cochin X Leghorn

o

20

Leghorn X Buff Cochin ....

•\

26

Tosa X White Cochin
Dark Brahma X Tosa

o
o

7

22

7

48

Frizzle X Silky

•*

15

Black Cochin X Rumpless Game .

o

21

••

••

Total

II

IQI

7

48

The foregoing statistics tell only a part of the story. Booting, when
present, is frequently much reduced ; one may regard absence of booting as
the extreme condition. Booting is dominant, but usually imperfectly so.

EXTRA TOES.

The extra toe is a positive variation of a teratological sort,
tion of its occurrence is as follows :

The distribu-

F

i

F

f

F! X t

lormal.

Crosses.

No extra
toe.

Extra
toe.

No extra
toe.

Extra
toe.

No extra
toe.

Extra
toe.

Houdan X Leghorn

6

ii

17

6

17

8

Houdan X Minorca

6

1C

Frizzle X Silky

7

2*

Total

IQ

6q

17

6

17

8

Percentage

21.6

78 A.

11 O

26 i

68 o

72 O

INHERITANCE OF PARTICULAR CHARACTERISTICS. 73

These results are peculiar. If both normal-toed and extra-toed ancestors
were heterozygous in respect to toes, we should expect the result obtained in
F,. It is quite possible, though not probable, that this is true. Then extra
toe would be dominant, although sometimes so imperfectly so as not to
appear. In F2 the parents were normal-toed, either because "normal" is
recessive or because it is imperfectly dominant. All offspring should be
normal-toed in the one case or give 100 per cent to 75 per cent extra-toed
in the other. The result is not in accordance with either hypothesis. If
there is any dominance in this generation it is of the normal toe. Bateson
and Saunders (1902, p. 124), while concluding that extra toe is dominant,
find "that the recessive foot character may sometimes dominate." Hurst
(1905, p. 150) also got, in a cross between Leghorn and Houdaii, some
normal -toed offspring which, interbred, produced extra-toed progeny. He
concludes that a usually dominant character may recede in certain individ-
uals. There is danger here of straining Mendel's law. It is better to hold
' ' explanations ' ' in abeyance until the matter of inheritance of polydactylism
has been more thoroughly investigated. Certainly the facts of inheritance
of polydactylism in man can hardly be explained on Mendelian principles
(Davenport, 1904). Polydactylism is at least not recessive. The new, posi-
tive, pathological characteristic holds its own against the older one.

SKIN COLOR.

The epidermis of poultry is everywhere covered by feathers except on the
beak, face, and feet. The naked portions may, however, have a different
color from the covered ones ; consequently the correlation between general
skin, beak, and foot color, although not absent, is not close. Thus, although
the yellow beak and foot of the Leghorn are correlated with its yellow skin,
the black legs and beak of the Black Minorca are not accompanied by a
black skin. Not all exposed parts, even of the skin, are of one color, for the
face, at least, may be red or white when the legs are black. Color of beak
and foot are, on the other hand, closely correlated, individual variations of
the one being usually associated with corresponding variations of the other.
This correlation is doubtless the result of the similar cornification of the skin
of beak and foot, whereas (excepting races with opaque white face) the
vascular face and earlobes are white or red, according to a less or greater
blood supply in them.

The pigmentation of the epidermis of poultry falls into three classes : (a)
Without pigment or white ; (b) yellow ; (c) black. White skin is the com-
monest, even among poultry with black plumage and feet. Yellow skin is
found in the Asiatics, derived from the Aseel- Malay ancestry, and is a char-
acteristic of the White Leghorn. Black pigment occurs in the skin of the
Silky fowl and the Negro fowl. Black pigment is to be regarded as a new
variant and of the nature of a pathological sport — melanism. When black

74 INHERITANCE IN POULTRY.

skin is crossed with white, black — the new, positive, pathological character-
istic— is dominant (page 60).

MANDIBLE COLOR.

The prevailing types are black, willow, yellow, and white. Black is the
primitive color on the Jungle side ; yellow, on the Aseel group. When horn
(Houdan) and yellow (Leghorn) mandible colors are crossed, the first genera-
tion shows the yellow of the Leghorn, which is dominant. When, however,
the black beak of the Minorca was crossed with the yellow beak of the
Brahma, the dark color dominated. The potency in the hybrid of beak color
seems to follow this series: Black, yellow, horn. The most positive char-
acter, black, dominates all.

FOOT COLOR.

Four principal types are to be distinguished — willow, black, yellow, and
white. Willow is primitive and white the most aberrant. The results are
based on still insufficient data, but so far as they go they indicate that willow
is dominated by yellow (p. 54), yellow by white (p. 24), and white by black
(p. 28). The newer, negative characteristic, white, is dominant over the
older yellow, but the new, positive characteristic of melanism dominates all.

IRIS COLOR.

Of the various forms, pearl to yellow is characteristic of the Aseel type ;
red, of the Game or Gallus bankiva type. Black has become associated with
black plumage. The results, subject to revision, indicate that in poultry,
as in man, iris color rarely blends, that red dominates pearl (page 38), and
that dark brown dominates red. The new, positive variation of melanism
seems to dominate all, although not always perfectly.

EARLOBE COLOR.

Red is primitive in both groups. White is a new variation, which is prob-
ably due to fat or other particles in the skin, and is consequently positive.
Only in extreme cases is red wholly eliminated from the earlobe. In three
series of crosses (V, VI, and X) of the red-lobed Dark Brahma and a white
(and red) lobed race the earlobes were prevailingly red, but had some white
at their centers. Likewise, in two series of crosses (VII and VIII) of the
red-lobed Cochin and a white-lobed Leghorn, red dominated in the hybrids,
but did not always perfectly exclude white. Red is apparently dominant,
but very imperfectly so ; some cases rather indicate particulate inheritance.

GENERAL PLUMAGE COLOR.

The original plumage as exhibited in the Jungle fowl is largely black and
red ; that of the Aseel type sometimes contains much white ; but the pure
white plumage must be regarded as a new negative variant. The outcome
of crossing is complex.

INHERITANCE OF PARTICULAR CHARACTERISTICS. 75

WHITE vs. DARK — Three different results may be, under differing condi-
tions, obtained.

Dominance of White. — This is the usual result. Two White Leghorns
crossed by a black Minorca produced only white hybrids, but the female
hybrids, at least, had some black feathers. White Leghorns crossed with
Houdans gave only white. White Leghorns crossed with a Red-backed
Game had white offspring with some buff on breast. On the other hand,
the white color of the Silky dominates over the dark color of the Frizzle
(Series XI) in about only 23 percent of the hybrids. Bateson andSaunders
(1902, pp. 108-109), dividing all hybrids between black and white parents
into those of light type and those of dark type, conclude that the former
are to the later as 3.1 to i. Bateson and Punnett (1905, p. 117) conclude
that offspring of a pure white parent with colored or heterozygous (mixed)
birds are practically always prevailingly white. Hurst (1905, pp. 146-149)
gets chiefly white birds from crosses of White Leghorn hens with black or
mottled males. The exceptions may be due to the impurity of one of the
females.

Barring. — No barring resulted from crossing White Leghorn withHoudan
or black Minorca, or Silky with Frizzle. On the other hand, all males, and
only males, were barred in the hybrids of Tosa x White Cochin, and in the
hybrids of White Leghorn Bantam and Rumpless Game barring occurred,
but among males only. Of 26 hybrids between Black Cochin and White
Leghorn, 8 were barred black and white, and these belonged equally to the
two sexes. Of n dark hybrids obtained by Hurst (1905, p. 133) from
White Leghorn x Houdan, 6 developed into black females and 5 into cuckoo
males. Apparently barring ("cuckoo marking" of the English) is asso-
ciated with maleness. This result is curious enough, for, as Darwin pointed
out, in the ancestors of domestic poultry barring (or rather penciling) is
confined to the female sex.

Barring is a heterozygous condition found in hybrids from a white and
a black parent. It is provisionally regarded as a form of particulate inherit-
ance as opposed to the alternative inheritance of the Leghorn x Minorca
cross. This heterozygous condition when interbred usually breaks up into
white, uniformly pigmented, and barred again, as in the case of the Tosa
X White Cochin hybrids (p. 49). This form has in certain cases, as in the
Cuckoo Dorkings and in the Dominiques — ancestors to the Plymouth Rocks —
become truly mosaic, transmitting the mixture of qualities pure. The
method of fixing a heterozygous quality is still unknown to science.*

* The experience of breeders of mice and guinea-pigs shows that white may be due to
the absence of an oxidizing ferment necessary to the bringing out of the color potential in a
chroinogenic substance (cf. von Fiirth, 1903). If the chromogen is present the addition
(by crossing with a pigmented individual) of the ferment will reveal in the hybrid off-
spring the colors and pattern latent in the white parent. Working on this hypothesis,
we can judge of the latent patterns in the White Leghorn bantams and draw conclusions

76 INHERITANCE IN POULTRY.

Andalusian Coloration. — Among the offspring of a White Leghorn and a
Black Minorca two adult blue fowls were reared (fig. 54) . The coloration
was that of the Andalusian "breed." It consisted of a minute patchwork
of black and white pigment. Such a blue coloration is common in barn-yard
fowls. It results, according to the testimony of breeders,! from crossing
black and white.

The special conditions which determine whether the offspring of a white
and a black parent shall be all white or barred or blue have not yet been
determined. The solution of thn problem offers one of the most interesting
fields for future investigation (p. 30).

WHITE vs. BUFF. — Both colors are novel ; the former is probably a nega-
tive mutation ; the latter has been extracted from the original game colora-
tion of fowls. The hybrids are prevailingly white, and white may be
regarded as dominant. Nevertheless, this dominance is imperfect, for in
half of the offspring buff is more or less evident. It is found diffused over
the back, wings, and breast as in " pile" Games. On the whole, white is
less strongly dominant over buff than it is over black (Hurst, 1905, p. 134).

BLACK vs. RED. — The red coloration is ancestral ; the solid black is novel
and positive — a melanic condition. The hybrids between Black Cochin and
Red-breasted Game are prevailingly black, but about half of them show red
lacing on the hackle feathers or a red peppering in those places where red is
displayed by the Game. Black is dominant over red, but imperfectly so.

COLOR OF TOP OF HEAD.

In the white-crested Black Polish the feathers of the top of the head are
in striking contrast to those over the rest of the body. That the crest is not
necessarily white is proven by the existence of a black-crested race. Hybrids
between the Minorca, whose head is wholly black, and the Polish give (p.
15) chiefly black feathers in the males, the females, however, still showing

as to what pigmented ancestors they may have had. They were used in five crosses, as
follows : (i) Black Cochin X White Leghorn ; (2) White Leghorn X Buff Cochin ; (3)
White Leghorn X Black-breasted Red-backed Game ; (4) White Leghorn X Dark
Brahma ; (5) Dark Brahma X White Leghorn.

Taking all offspring together, about 50 per cent (48.5) are white or nearly so. All
crosses exhibit barring, together in about one-quarter (26.5) of the cases, and also black
and buff or red. It seems probable that all of these pigments and the barred pattern
are latent in my White Leghorn bantams. These conclusions are supported by breed-
ing the White Leghorns inter se, when, in addition to white offspring, a black and a
barred were obtained (p. 40). Similarly among the second hybrids between the Tosa and
White Cochin Bantam there appeared^ male and a female resembling in plumage colora-
tion the Partridge Cochins (p. 49). This coloration probably lay latent in the gametes
of the White Cochin.

t Compare Darwin (1876, I, Chapter VII ; 1894, I, p. 270) ; Wright (1902, pp. 291, 292,
3^7, 3OI» 399. 4OI> etc.) ; Bateson and Saunders (1902, p. 131) ; Bateson and Punnett
(I9°5, P- 126). When blues are interbred, the offspring are either white or black or blue.
Even in the Andalusian " breed " the blue coloration has never become fixed.

INHERITANCE OF PARTICULAR CHARACTERISTICS. 77

white in their crests. The hybrids crossed back on the Minorca give nearly
100 per cent black heads. Black is dominant, but imperfectly so ; the nega-
tive characteristic is recessive. The dominant character is less perfectly
dominant in the female sex than in the male.

COI.OR OK HACKLES— HACKLE LACING.

The color of the hackle feathers and the correlated saddle feathers in
birds of broken color usually differs from that of the rest of the plumage.
This peculiarity of the hackle coloration is an old character, since it is
exhibited by the Jungle fowl, and was probably in the ancestor of the
Aseel-Malay group. The feathers are laced with a lighter color than the
center.

In crosses between Minorca and Dark Brahma, and White Leghorn and
Dark Brahma the solid color (black or white) , the new, positive character-
istic, dominates over the lacing. Nevertheless, in the Minorca X Dark
Brahma hybrids the feathers of the nape are frequently faintly laced with
gray. The black is imperfectly dominant.

WING COLOR— RED WING COVERTS.

The male Jungle fowl has red on the upper wing coverts, and doubtless
the male of the ancestors of the Aseel-Malay group had also.

The male hybrids between the Dark Brahma and the Black Minorca on
the one hand and the White Leghorn on the other usually show red on the
wing coverts, although there is no other red in the plumage. Red on the
wing coverts is probably dominant, but it is much reduced.

TAIL COLOR.

Although the tail feathers are derived from a distinct feather tract, and in
broken-colored birds are usually without the red of the wing, yet tail color
does not seem to be a unit character ; in inheritance it follows the rest of the
body plumage. On the other hand, in breeding buff varieties black persists
in the tail feathers longer than in the others. This case resembles the per-
sistence of black at the extremities of the legs of white or red rabbits
(Castle, 1905).

SHAFTING.

The female Jungle fowl has a light shaft to the feather. The same is
true of the Tosa fowl and some Games. Light shafting is a primitive
characteristic of the female.

In the female hybrids between the Tosa fowl and White Cochin the shaft-
ing is greatly broadened, and this is the principal modification of the plumage
color. In female hybrids of the Tosa fowl and Dark Brahmas the shafting
of the feathers of the back and wing coverts is striking, and some shafting
appears in two of the males, probably transferred from the female (p. 54).
Apparently shafting is dominant.

78 INHERITANCE IN POULTRY.

BODY LACING.

This character is not found in the Jungle fowl, but may have been derived
from the penciling of the Aseel-Malay group. In male hybrids between
the Tosa fowl and the Dark Brahma it occurs, derived from the latter (p. 54).
It appears to be dominant.

PENCILING.

This is an ancient feminine characteristic, best marked in the Aseel- Indian
group (p. 53). It is found particularly well developed in the Dark Brahma
female. In the female hybrids between that race and the Tosa fowl penciling
is well developed ; it is dominant.

GENERAL TOPICS IN INHERITANCE.

UNIT CHARACTERS.

Taxonomic descriptions of plants and animals give a list of their specific
characteristics (Merkmale, caracteres). These comprise for the most part
only the external characteristics, but a similar list might be made for internal
characteristics. In addition to specific characteristics, those of a higher
order (such as generic, etc.) and those of a lower order (such as varietal) may
be enumerated. Such characteristics are, in first approximation, unit char-
acters. They are of prime importance, because the whole problem of evolution
is that of the origin and significance of the various unit characters of the
body.

The theory of the unit character is associated with that of its bearer in
inheritance. Darwin (1876) and later de Vries (1889) designated as such
bearers particles of the nuclear material named " pangenes." "Changed
numerical relation of pangenes is the basis of fluctuating variability ; dis-
placement (Umlagerung) of pangenes in the nucleus conditions retrogressive
and degressive mutations ; while the formation of new kinds of pangenes is
necessary to the explanation of progressive mutations ' ' (i. c. , those exhibit-
ing altogether new characteristics).

The two main hypotheses of the origin of unit character ire that of de Vries
and that of Weismann. De Vries sets forth his hypothesis at the very begin-
ning of his great work, " Die Mutationstheorie. " His words may be thus
translated :

As mutation theory I designate the doctrine that the characteristics of organisms are
built up of units that are sharply separable one from another. These units can be united
into groups, and in related species the same units and groups recur. Transitions, such
as the external forms of plants and animals exhibit in such numbers, exist between the

units as little as between the molecules of chemistry In the realm of the doctrine

of descent this principle leads to the conviction that species have proceeded from one
another not continuously but by steps [nicht fliessend, aber stufetiweise]. Each new unit
added to the older ones constitutes a step and separates the new form, as an independent

species, sharply and fully from the species whence it arose Die neue Art ist somit

mit eiuetn Male da ; sie entsteht aus der friiheren ohne sichtbare Vorbereitung, ohne
Ubergange.

GKNiJRAI, TOPICS IN INHERITANCE. 79

Weismanu, on the other hand, is only less clear in expressing his hypoth-
esis. He accepts, of course, the idea of unit characters, each of which is rep-
resented in the germ cells by a " determinant. " " We called, ' ' he says (1904,
I. P- 369), ' ' determinants those parts of the germ-substance which determine
an ' hereditary character ' of the body ; that is, whose presence in the germ
determines that a particular part of the body, whether it consists of a group
of cells, a single cell, or a part of a cell, shall develop in a specific manner,
and whose variations cause the variations of these particular parts alone."
The " hereditary parts " may be small or " large regions, whole cell masses
of the body, which in all probability vary only en bloc, as, for instance, the
milliards of blood cells in man, the hundreds of thousands or millions of cells
in the liver and other glandular organs, the thousands of fibers in a muscle,
or of the sinews or fascia, the cells of a cartilage or a bone, and so on. In
all these cases a single determinant, or at least a few in the germ plasm, may
be enough." For Weismann (1904, II, p. 151) the ultimate source of all
hereditary variations is the variation of the representatives of the unit char-
acters in the germ plasm. " If I mistake not," he says, " we may at least
say so much, that all variations are, in ultimate instance, quantitative and
that they depend on the increase or decrease of the vital particles, or their
constituents, the molecules What appears to us a qualitative varia-
tion is, in reality, nothing more than a greater or less different mingling of
the constituents which make up the higher unit ; an unequal increase or
decrease of these constituents, the lower units." The cell changes its consti-
tution when the proportion of its component parts " is disturbed, when, for
instance, the red pigment granules which were formerly present, but scarcely
visible, increase so that the cell looks red. If there had previously been no
red granules present, they might have arisen through the breaking up of
certain other particles — of protoplasm, for instance, in the course of metab-
olism —so that, among other substances, red granules of uric acid or some
other red stuff were produced. In this case, also, the qualitative change
would depend on an increase or decrease of certain simpler molecules and
atoms constituting the protoplasm-molecule."

In criticism of the foregoing it may be said that a variation in the number
of atoms in a protoplasmic molecule is certainly also a qualitative change —
a mutation. The only real difference between Weismann and de Vries
depends on the extent of the mutative modification, whether progressive or
complete from the beginning; but this is a real difference, for the latter
view is required by the theory of immutable unit characters. The former
view is not in harmony with such a theory. Conversely, if it appears that
there are immutable unit characters, then the theory of evolution by saltation
is necessary ; if unit characters are modifiable, then species may have arisen
gradually.

80 INHERITANCE IN POULTRY.

The result of the breeding experiments described herein bears upon this
discussion. No other group, I imagine, exhibits so many characteristics as
poultry ; of the comb alone there are half a dozen forms. The forms of
feathers and their color patterns are numerous. These forms are sharply
marked off from one another for the most part ; moreover, when two char-
acteristics are crossed the result is rarely a blend. This was a great surprise
to me, as I had anticipated that blends would be the rule ; and, overwhelmed
by the facts, I embraced at once the theory of immutable characteristics.

That there are unit characters in poultry can not be doubted. When single
and V comb are crossed and progeny obtained all writh a Y comb, how con-
vincingly do the second hybrids reproduce the single comb in some individuals
and the V comb in others ! Though the cerebral hernia and its associated
great crest may disappear in the first generation of hybrids, how beautifully
do they reappear in one-fourth of the offspring of such hybrids ! How in-
structive is it to see perfectly plain feathered offspring arising from a frizzled
pair, or in a Black Minorca X Dark Brahma white-laced hackles appearing
in an otherwise dead- black plumage ! Truly we may hope, as in chemistry,
to make various kinds of molecules by the proper admixture of our atoms —
the characteristics. Even in man such non-blending characteristics are evi-
dent. One of the most famous is the Hapsburg lip or chin, which from the
fifteenth century has persisted to the present day despite infusion of new
blood during fifteen generations.* Another striking case is that of Irypo-
phalangia in man, described by Farabee (1905). In the four or five gener-
ations studied, there has, he states, "never been a single instance of partial
inheritance, but in all cases all extremities have been affected in precisely
the same way."

While admitting, thus, the reality of unit characters, the further study of
the evidence of hybridization in poultry has led me away from the conception
that they are rigid and immutable as atoms are, which may be combined
and recombined in various way and always come out of the process in their
pristine purity. This is by no means the case. Very frequently, if not
always, the character that has been once crossed has been affected by its
opposite with which it was mated and whose place it has taken in the hybrid.
It rnay be extracted therefrom to use in a new combination, but it will be
found to be altered. This we have seen to be true for almost every char-
acteristic sufficiently studied — for the comb form, the nostril form, cerebral
hernia, crest, muff, tail length, vulture hock, foot- feathering, foot color, ear-
lobe, and both general and special plumage color. Everywhere unit char-
acters are changed by hybridizing.

How does this fact bear on the rival theories of evolution ? It has an im-
portant bearing on them. It is not in accord with the statements of de Vries

* Cf. F. A. Woods, 1902-03.

GENERAL TOPICS IN INHERITANCE. 8 1

quoted above : ' ' The characteristics of organisms are built up of units that
are sharply separable one from another," and " Transitions exist between
the unit as little as between the molecules." Single comb is one unit and
pea comb is a different unit, but they are not sharply separable. Crest and
no crest are units, but they run into each other in hybridizing. Unit char-
acters ma}7 show transitions, and, if so, they may have originated gradually,
so far as I see. It does not follow that they must have originated gradually.

ALTERNATIVE, PARTICULATE (MOSAIC), AND BLENDING INHERITANCE.

Doubtless Darwin's statement that crossed characters usually blend is
still the prevalent view. Much if not most biometric work in heredity has
been made on this basal assumption. I may say that I began my experi-
ments prejudiced in favor of this view.

The results that have been recorded in the foregoing pages indicate that
probably in general typical blending of characters is rare. Excepting char-
acters like general form of the body, which are doubtless not units, but
complex, I have, indeed, seen no single case of a typical blend. A fusion
of characters is a rather rare phenomenon. Human skin color is the one
striking case. One can but wish we had more careful data on inheritance
of human skin color in successive generations. Other human characteristics
show alternative inheritance. This is strikingly true in Farabee's family of
hypodactyls cited above. It is said to be true of eye color and probably
of the states of general pigmentation known as blonde and brunette.
The following characters of poultry show alternative inheritance :

Comb form. Uropygium. Earlobe color.

Nostril form. Tail length. General plumage color

Cerebral hernia. Vulture hock. (sometimes).

Crest. Booting. Color of hackles.

Muff. Extra toe. Wing bar.

Beard. Color of mandible Shafting.

Frizzling. aiid foot. Body lacing.

Silkiness. Iris color. Penciling.

The following characteristics show particulate inheritance :

Iris color (sometimes?).

White and black, producing barring (Series VI, VII, IX, XII).

White and black, producing blue (fig. 54) (a fine mosaic of white and

black).

It is too early yet to interpret the cases of particulate inheritance. It is a
striking fact that, excepting the Tosa X White Cochin cross, all my barred
birds reared to maturity had the White Leghorn Bantams as mother or
father. Now, as repeatedly observed, these bantams were heterogametous.
It is possible that they contain barred blood in the "fixed" condition.
Aside from the fact that they throw a certain proportion of barred birds, this
conclusion gains support from the fact that the wing coverts of the male are
6

82 INHERITANCE IN POULTRY.

obscurely barred with dusty bands, although, on the other hand, this barring
may be merely the badge of heterozygotism. It is possible, therefore, that
the barring in the plumage of the White Leghorn Bantams is transmitted as
an alternative characteristic. The case of the barred descendants of the
Tosa X White Cochin is more difficult. I am not yet prepared to go so far
as Correns (1905*, p. 13, note) when he says: "Wo Mosaikbildung als
Regel bei einem Bastard auftritt, war sie schon in einem der Kltern oder in
beiden, aktiv oder latent, vorhanden."

Naturally, attention was directed chiefly toward evident qualitatively
marked characteristics. Such do not blend. The fact that for the most
part a characteristic does not blend when crossed with its allelomorph is of
the highest importance for the theory of evolution. If blending were uni-
versal a new characteristic must inevitably become quickly swamped by
intercrossing with the parental characteristic. Since the new quality does
not blend, it need not be swamped, even when there is no special isolation.

INHERITANCE OF SPECIFIC VS. VARIETAL CHARACTERISTICS.

A distinction between specific and varietal characteristics is made by
Nageli (1884, P- 247) and by de Vries (1902, p. 141 ; 1905, p. 141). Fol-
lowing de Vries, a. specific characteristic is a wholly novel one acquired by the
race — one which stamps its possessor as an elementary species. A varietal
characteristic is sometimes positive (/. <?., additional), in which case it is
found also in closely allied species, and may be regarded as the becoming
patent of a characteristic all the time latent in the variety. It is, on the
other hand, sometimes negative, this condition being marked by the disap-
pearance (becoming latent) of a characteristic patent in the ancestral species.
Specific and varietal characteristics are thought by de Vries to be inherited
very differently. When two elementary species are crossed the character-
istics of both parents appear, fully developed, side by side ; Mendel's law is
not followed. When a species is crossed with a variety a Mendelian result
is obtained and the patent characteristic is dominant over the latent.

L,et us now see in how far the results gained in breeding poultry accord
with de Vries' s law. It is not easy to make the classification in an unpreju-
diced way ; an attempt, however, will be made.

First, the comb is a specific characteristic of the genus Gallus. It is absent
in other Gallinae. Also pea comb and rose comb are each wholly new, posi-
tive variations from the primitive single comb. Muff and beard seem to be
novel ; so also the long tail of the Tosa fowl, the extra toe, and the melanic
feet and beak.

Clear cases of negative variations are : L,oss of the nasal process of inter-
maxillary and consequent high nostril; failure of cerebral plate to close and
consequent cerebral hernia ; loss of uropygium ; loss of red and black pig-
ment in feathers (albinism, partial or complete) ; loss of dark pigment in
crest feathers ; loss of wing bar ; loss of primitive shafting.

GENERAL TOPICS IN INHERITANCE.

Now, by hypothesis we should expect a difference in inheritance in these
characteristics as indicated below :

Expected non-Mendelian.

Expected Mendelian.

1. Pea and rose comb vs. single comb.

2. Muff and beard vs. plain head.

3. Long tail vs. normal.

4. Extra toe vs. normal.

5. Melanic feet and beak vs. willow or

yellow.

1. High nostril vs. low.

2. Cerebral hernia vs. normal.

3. Taillessness vs. normal tail.

4. Albinism in plumage vs. pigment.

5. Absence of wing bar vs. presence.

6. Absence of shafting vs. presence.

Of the five cases where, on de Vries's theory, we should expect non- Men-
delian results, No. 4 is apparently not Mendelian, No. 5 gives often a
mixture of characters, Nos. i and 2 apparently give true Mendelian domi-
nance and recessiveness, No. 3 is still doubtful. Of the six cases in which
a Mendelian inheritance is looked for, we certainly find it in three cases and
less certainly in the others. On the whole, there is a slight but not a striking
difference in transmission between the two sets of characteristics, and I can
only conclude that for poultry, so far as I can see at present, de Vries's
formula does not hold universally.

INHERITANCE OF POSITIVE VS. NEGATIVE VARIETAL CHARACTERISTICS.

According to de Vries, when an individual having a certain characteristic
patent is crossed with one in which it is latent the patent characteristic is
dominant, the latent recessive. Do results with poultry confirm this law ?

In the following table the patent characteristic is given in the left-hand
column and the dominant characteristic in italics :

Patent.

Latent.

1. Nasal process of premaxillary, narrow

nostril.

2. Closure of cerebrum completed ; plain

head.

3. Crest ; black crest feathers

4. Complete development of the feather ..

5- Tail

6. Pigmented plumage

7. Red wing bar

8. Shafting ,

High nostril.

Failure of cerebrum to close ; cerebral

hernia.

Smooth head ; white crest feathers.
Interrupted development of the feather ;

silky feather.
Taillessness.
Albinism in plumage.
Uniformly colored wing.
Plain feather.

Of the foregoing eight characters, seven clearly follow the law that patent
characteristics dominate over latent. No. 6 is a clear exception, for since
all the wild Gallinae are deeply pigmented birds it can hardly be doubted
that white is a negative variation in which color is latent. However, the
exception (No. 6) is not universal, for white plumage does not always domi-

84

INHERITANCE IN POULTRY.

nate over pigmented plumage. It appears, then, that the patent character
is, in general, but with some exceptions, dominant over the corresponding
latent character.

INHERITANCE OF OI,D VS. NEW CHARACTERISTICS.

Standfuss ( 1 896, p. 1 1 1 ) , as a result of his hybridization of moths, concluded
that hybrids resemble the older species. De Vries (1902, pp. 33-42, and
1905, pp. 280, 281) cites several instances of the prepotency of the phyloge-
netically older characteristic. Bateson and Saunders (1902, p. 137), how-
ever, point out that younger characteristics sometimes dominate, and cite
pea and rose comb, extra toe, and the polled condition of cattle as examples.
Correns (1905, p. 463 et seq.) describes a case of petaloid calyx — a new
characteristic — which is dominant over the normal form. Correns (i9O5d,
p. 13), indeed, concludes that in general the phylogenetically more advanced
characteristic — the later originated, younger characteristic — dominates.

Let us see what evidence poultry hybrids have to offer bearing on this point.

Old characteristics.

New characteristics.

Old characteristics.

New characteristics.

i. Single comb. .. .

Rose comb.

ii. White skin. . . .

Black skin

2. Low nostril. . . .

High nostril.

12. Red iris.,

Black iris.

3. No hernia, . . .
4. Plain head

Hernia.
Crest.

13. Red ear lobe. . . .
14 Pigmented. .

White earlobe.
White (sometimes

5. No muffling. . . .
6. Plain feathers. .
7. Plain feathers. .

Muffling.
Frizzled feathers.
Silky feathers.

15. Red pigmented.
1 6. Black head. ....

dominates).
Black ; no red.
White head.

8. Tailed (?)

Non-tailed.

17 Hackle lacing.

Solid black

9. Tail feathers lim-
ited in growth .
10. Four toes

Tail unlimited.
Five toes

1 8. Red wing bar. .
19. Shafting

20. Penciling .

No wing bar.
No shafting.
No penciling

This table shows that of nineteen characteristics (No. 10 being left out of
consideration) , nine old ones are dominant and ten new ones. Clearly, dom-
inance of characteristics in poultry is not determined by the age of the
characteristic.

DOMINANCE AND RECESSIVENESS.

Mendelian dominance and recessiveness with segregation of characteristics
in the gametes are not universal concomitants of hybridization. Mendel knew
it (Correns, 1905") ; de Vries founds his system on the fact ; Correns lays
stress on it ; Bateson and Saunders (1902, p. 152) recognize it, but consider
the exceptions insufficiently known. The characteristics that I have crossed
show always segregation excepting extra toe and perhaps also melanic foot
and beak color. These are among the positive variations of de Vries, which,
in accordance with his system, we should not expect to " meudelize." As
stated, other positive variations, however (pea comb and muff), seem to
mendelize.

GENERAI, TOPICS IN INHERITANCE. 85

Of the varietal characteristics, the positive or patent characteristics almost
always are dominant, white plumage forming an occasional exception. On
the other hand, phylogenatically old characters are not more apt to be domi-
nant than ' ' new ' ' ones. Some evident sports, such as crest, frizzling of
feathers, unlimited growth of tail, and black skin (of Silky), are dominant.
Other sports — hernia, shortened premaxillary, silkiness, and rumplessness —
are recessive ; the novelty or antiquity of the characteristic has nothing to
do with its dominance. Dominance of a character in hybridization is deter-
mined by the same causes as determine the appearance in the race of a posi-
tive variation. A progressive variation, one which means a further stage in
ontogeny, will be dominant ; a variation that is due to abbreviation of the
ontogenetic process, which depends on something having dropped out, will
be recessive.

This conclusion, however satisfactory, must be regarded as tentative. It
is doubtful if it is of general validity ; for while long tail and crest feathers
are dominant in poultry, long hair (equally due to prolonged life of the fol-
licle) is recessive in mammals (Castle, 1903 ; 1905, pp. 64-67, 73-74; Hurst,
1904). White is usually recessive to pigment in flowers and mammals, but
it is usually dominant over pigment in poultry. It is still too early to regard
the conclusions expressed in the last paragraph as anything but an hypothesis.

While dominance and recessiveness are typically found in Mendelian in-
heritance, yet they may be absent even in cases when segregation of charac-
teristics occurs in the second hybrid generation. Thus, the barred offspring
of the black-and-red Tosa fowl and the white Cochin throw in the F2 gener-
ation 25 per cent black and red and 25 per cent white, but the remainder,
like all of Fn is barred with white, and no one can say which plumage color
is dominant. The same is true of some black-and-white barred hybrids. It
is also true of hybrids between single and V comb. The phenomena of domi-
nance and recessiveness do not always accompany segregation.

Another modification of the law of dominance and recessiveness must be
recognized, namely, that they are by no means always complete. Even in
the first hybrid generation the dominant characteristic is more or less inter-
mediate. The antagonistic characteristics a and a' of the two parent types
are not only united in the zygote, but they pass in the development of the or-
ganism into all the tissues of the body, and particularly into the cells out
of which the organ A is developed. The dominant characteristic, a, and
the recessive characteristic, a', each works to determine the quality of the
organ A, If a dominates, it is because it is more active than a'. It does
not dominate by excluding a'. Sometimes, as in the case of barred feathers,
it appears that a and a' in ontogeny alternate in their activities. The cells
of a certain zone of the feather manufacture only black pigment ; in the next
zone black is wanting ; then comes a zone of black, and so on, in many repe-
titious. Dominance as contrasted with recessiveness is a matter of degree
and not of kind.

86 INHERITANCE IN POULTRY.

Various authors refer to the imperfection of the dominant or recessive
characteristic in the hybrid. Batesou and Saunders (1902, p. 23) say :

Although the offspring resulting from a cross between any two of the forms (of Datura]
employed is usually indistinguishable from the type which is dominant as regards the
particular character crossed, yet in other cases the intensity of a dominant character may
be more or less diminished either in particular individuals or in particular parts of one
individual.

Hurst (1905, pp. 145-154) records many cases of imperfect dominance in
poultry and estimates the incomplete dominants to be twice as numerous as
the complete dominants.

DEPENDENCE OF DOMINANCE ON THE RACES CROSSED.

Is one of a pair of allelomorphs that shows itself dominant when varieties
A and B are crossed likewise dominant when any other varieties, M and N,
are crossed,, or is the relative potency of the allelomorphs dependent upon
the varieties in which they happen to reside ?

Data for an answer to this question are to be found in the experiments where
the same pair of allelomorphs were crossed , using different varieties. We may
except from this list the Minorca x Polish and the Leghorn x Houdau crosses,
as the races involved are very closely related. The following allelomorphs
remain for consideration :

(1) Crest vs. crestlessness. (6) Extra vs. normal toes.

(2) Silkiness vs. non-silkiness. (7) Black vs. white skin.

(3) Rumplessness vs. tail. (8) Black vs. yellow beak.

(4) Vulture hock vs. plain hock. (9) White vs. dark plumage.

(5) Boot vs. clean foot.

Crest. — This is dominant when Polish or Houdau is crossed with the
Mediterranean breeds and when the Silky is crossed with the Frizzle or with
the Jungle fowl. Crest is uniformly dominant over crestlessness, no matter
which of these races are used.

Silkiness is recessive to non-silkiness when crossed with Frizzle or the
Jungle fowl. Non-silkiness is probably always dominant.

Rumplessness in a Game fowl was recessive to the tailed condition of Leg-
horn, Cochin, Frizzle, and Nankin. The tailed condition seems always to
dominate.

Vulture hock is recessive when an Asiatic race is crossed with any Med-
iterranean breed or a Game, and probably, in general, plain hock dominates.

Booting is dominant when the booted form is the mother, no matter what
the race. Booting is much reduced and sometimes altogether absent in the
first generation of hybrids when it is derived from the father. Inheritance
of booting is independent of race but not of sex (p. 38).

Extra toe seems not to Mendelize. The excess of extra toes in the first
hybrid generation holds for all the races crossed and is probably independent
of race.

GENERAL TOPICS IN INHERITANCE. 87

Black skin of the Silky dominates over the colorless skin of the Frizzle
and of the Jungle. It probably dominates throughout.

Yellow vs. black beak and foot color. — Yellow of the White Leghorn domi-
nates over black of the Minorca, but yellow of the Dark Brahma is domi-
nated by the Minorca. Here yellow behaves differently, according as it is
in the Leghorn or Dark Brahma race. It is quite possible that the yellow
is not identical in the two groups, but that, while it is ancestral in the Dark
Brahma, it is secondary and a progressive character in the Leghorn. The
lack of uniformity in dominance of yellow may be due to essential dissimi-
larity of the character in different races.

White vs. dark plumage. — Aside from cases of barring and Andalusian
coloration, white usually dominates over dark plumage. This is true in all
cases where White Leghorn is employed as white race, whether the other
race is Game, Dark Brahma, Houdan, or Minorca. When the Silky is used
as the white race white is sometimes recessive (fig. 53), but it must be ac-
knowledged that the dark parents were not the same as were used with the
Leghorn, but were a Game, Frizzle, and Jungle fowl ; consequently the
results in the two series are not strictly comparable. However, Darwin
found the white of the Silky recessive to the black of the Minorca. It is
hardly conceivable that the white of the Silky is different from that of the
Leghorn ; so it must be concluded that white inherited as a solid color is
sometimes dominant and sometimes recessive, depending on the race in which
it inheres.

Summarizing the foregoing evidence, it appears, first, that (except in
certain obviously complex color characters) when one of a pair of allelo-
morphs is dominant it is so regardless of the races crossed. This shows
that dominance and recessiveness depend upon a relation of the character-
istics per se and not upon any relation of the races into which they have
been introduced. This is in accord with the conclusion reached above, that
dominance is determined by ib& positive nature of the characteristic (p. 84).

PREPOTENCY AND DOMINANCE.

Prepotency was a much used and probably abused term in the period pre-
ceding the revival of Mendelism. In the new era all of the old terms have
been subjected to reexamination as to their significance. Bateson and Saun-
ders ( 1 902 , p. 1 2 1 ) use the term ' ' as signifying determination of dominance , ' '
i. <?., whether the normally dominant or the normally recessive character
shall be in any case actually dominant. Castle (1905, pp. 58-64) shows that
although rough coat is dominant over smooth coat, a few smooth-coated
mothers will, when crossed with rough males, produce partial-rough young.
The normally recessive character here partially dominates. In my own
experiments the most remarkable case of dominance is exhibited by a gamete
from the maternal side that produced the Houdan x White Leghorn hybrid

88 INHERITANCE IN POULTRY.

No. 386 9 ; for this hybrid has a high nostril and a pair of papillae like
the Houdan mother, both of which characters are recessive. Out of 41 in-
dividuals No. 386 is the only one that exhibits them. It appears, then, that
" prepotency " in its modern sense can not be neglected.

HYBRID FORMS.

It sometimes happens when two dissimilar characteristics are crossed that
neither appears in the offspring, but they are replaced by a new character.
This fact has been long known. Mendel obtained such hybrid forms (cf.t
Correns, 1905, p. 232). Several cases are cited by Focke (1881, pp. 473, 474).
He refers particularly to the blue hybrid of the white Datura Jcrox crossed
with the likewise white D. laevis and D. strammonium Bertolonii.

As a result of more recent work it appears probable that hybrid forms are
of two kinds. First, such as are atavistic or due to the becoming patent of
a latent characteristic ; * and, second, such as are due to a particulate inher-
itance of the two characteristics crossed. In the latter case all that is novel
in the hybrid is the replacement of either single character by a combination
of characteristics.

Atavistic hybrid forms have been carefully investigated of late, especially
by Correns (1902) and Cuenot (1903), who have applied a method of inter-
pretation to particular cases. When albino mice are crossed inter sc they
produce only albinos. But if such an albino is crossed with a pigmented
(e . g. , a black) mouse its latent pigment appears and the offspring may be
all gray, or perhaps yellow and gray or yellow and black. The same holds
exactly true for albino rabbits, as Hurst (1905, pp. 306-310) has shown.
Cuenot' s interpretation depends on the principle that pigments result from
the action of an oxidizing diastase (tryosinase) upon a chromogenic sub-
stance. Both of these elements are present in a pigmented mouse, but he
assumes the chromogenic substance alone is present in the albino. The sperm
from the pigmented male brings to the egg of an albino the diastase necessary
to the production of pigment in the offspring. Correns (1905°) finds that
the hybrid of Mirabilis jalapa alba (white flowers) and M. jalapa gilva (yel-
low flowers) has rose-colored flowers that are, moreover, striped with red.
His experiments lead to the conclusion that the alba variety forms no pig-
ment, but does produce a pigment-changing (reddening) enzyme. The^-zYzvz
variety forms pigment, but not the reddening enzyme. When alba sperm
unites with the gilva egg the pigment of the latter, under the influence of
the reddening enzyme, becomes rose. Similarly with striping. There is
evidence that this is only partly latent in alba and completely latent in gilva.
Now if we assume a factor that permits the development of the striping
determinant to be active in gilva but to be latent in alba, the imperfect

*Tschermak (1904, p. 95) would add as another kind that in which an originally patent
character becomes latent.

GENERAL TOPICS IN INHERITANCE.

89

development in alba of the striping determinant is accounted for. When the
sperm of gilva, bringing the active principle for striping, fertilizes the egg
of alba with its striping determinant, the striping makes its full appearance.
These two or three examples from both plant and animals indicate a method
of explaining hybrid forms that is probably of wide applicability.

Are the hybrid forms of poultry to be explained on the atavistic or the
participate inheritance theory? Take first the case of barring. Three
tests can be applied : First, inherent probability from the ancestry of the fowl
crossed ; second, general distribution of barring among the offspring ; third,
proportion of different forms of plumage pattern in generations beyond the
first. The cross between Tosa fowl and White Cochin gave barred birds.
If the barring were latent it must have lain in the Cochins — the form without
visible pattern. It is fairly certain that neither of the ancestors of domestic
fowl was barred ; hence if the barring determinant existed in the Cochin
bantam it must have been introduced by a recent cross. Bantatnizing of
Cochins is effected by crossing with some bantam race, but until recently
no barred bantams have been created. It is therefore highly improbable
that a barred bird was used to bantamize the Cochins. While it is possible,
it is improbable that the White Cochin contained a barred determinant.
Second, barred races have the two sexes equally barred, but our hybrids
are barred in the male only ; consequently barring here acts like a neomorph.
Third, on the theory of atavism we should expect to get in the second hybrid
generation :

Coloration of second generation.

Atavism
theory.

Participate
theory.

Actual.

White ...

Per cent.
25.OO

Per cent.
25

Per cent.
28

Pigmented and barred

56 25

CQ

48

Pigmented and not barred

18 75

2?

24.

The actual proportions of the three types accord much better with the
particulate inheritance theory than with that of atavism, but the total number
of offspring is insufficient to give certainty. It may be concluded that while
the evidence does not exclude the atavism theory of the cropping out of
barring, it favors the theory of particulate inheritance.

The case of the hybrid between single and V comb rests on more extensive
data. These are set forth on pages 10-12, and are less favorable to the ata-
vistic theory than to the particulate theory.

The other heterozygous forms have been less carefully studied. They are
the blue, Andalusian (fig. 54, pi. xvn), plumage color resulting from a
white and a black crossed, and the case of the down of the hybrid Minorca X
Dark Brahma chicks. This is black like the Minorca, but lacks the white
of the chicks both of that race and of the Dark Brahma. The Andalusian

9O INHERITANCE IN POULTRY.

breed has been discussed by Bateson and Punnett (1905, p. 126), and they
find, what is the universal testimony of breeders, that (as stated also at page
76) the blues bred inter se produce some white and some blacks, but still
more blues. Until more complete statistics have been gained on the pro-
portions of colors in the offspring, the interpretation of blue must remain
uncertain.

Hybrid forms are, then, frequently cases of particulate inheritance in
which the hybrid gametes are not mosaic ; consequently whenever ' ' pure ' '
offspring are produced, as in Fa, these reassurne the character of the pure
race. In some cases, as in the cuckoo Dorking and the Dominique (from
which our barred Plymouth Rock has been derived), the heterozygous form
of barred plumage has become fixed, so that only barred offspring are pro-
duced. A mosaic gamete has been created. The blue coloration has never
yet been fixed as a permanent hybrid form. The method of fixing a hj'brid
form is urgently in need of investigation.

REVERSION.

This term has been used rather loosely in the past for the appearance in
hybrids of characteristics not visible in the immediate parents of the hybrids
and often belonging to remote ancestors. Darwin (1876) made much use
of this term in describing his results. He believed that the occurrence of
" reversion " gave a useful key to ancestry. It is worth while to consider
his observations and experiments. He mentions the fact that " purely bred
Game, Malay, Cochin, Dorking, Bantam, and Silk fowls may fre-
quently or occasionally be met with, which are almost identical in plumage
with the wild G. bankiva. ' ' But does this indicate anything else than that
this type of coloration has persisted in certain primitive races, like the Game,
and has been transplanted from them to the new races ? Darwin crossed a
black Spanish cock with various white and white- and-black hens of pure
breed. The offspring of this cock crossed with a silver-spangled Polish hen
and with a white Cochin hen showed no sign of reversion to the red color of
G. bankiva. The male offspring of a spangled or silver Hamburgh hen
showed white in the hackles and a reddish yellow on the saddle. Darwin
regarded this as a " first sympton of reversion ; " but in the first of these
peculiarities the hybrid resembles G. bankiva less than the Dark Brahma.
The offspring of a white Game hen with the Spanish cock was at first snow
white, but eventually produced the "pile" coloration. Darwin regards
this as a partial reversion to G. bankiva ; but it is equally possible that the
reversion is only to a pile coloration that is latent in the white from an earlier
cross and is brought out when the white is crossed with a dark color. But
Darwin's most remarkable hybrid was the offspring of a white Silky hen.
Of two cockerels one was black (with light laced hackles) ; the other resem-
bled closely a Jungle cock. Darwin admits that the case is extraordinary,

GENERAL TOPICS IN INHERITANCE. 91

but it was duplicated by Mr. Tegetmeier. This experiment certainly should
be repeated, and I have arranged to repeat it next season.

One of the best cases of reversion is the gray coat of a hybrid between a
white and a black mouse. We now know, however, that even a "pure
race" of white mice may carry gray as a latent characteristic that first be-
comes patent on crossing. In view of such facts cases of " reversion " to a
remote ancestor must be critically examined. If the " reversion " be not a
neomorph, it must have been handed down without break in the germ
plasm from an ancestor possessing the characteristic.

PURITY OF GAMETES.

The dogma of purity of the gametes, the second corner-stone of Mendelism,
asserts that while the unripe germ cells of a hybrid having antagonistic or
alternative characteristics A and A' contain representatives of both A and
A', yet the ripe germ cells of such a hybrid contain representatives of either
A or A' > and not of both. Thus the ripe germ cells (gametes) are pure in
respect to a given characteristic. They gain this purity, it is supposed, dur-
ing the maturation period, the period when the reduction division of the
chromosomes occurs, and when in each cell division one-half of each chro-
mosome moves bodily to one daughter cell and one- half to the other. The
theory assumes, of course, that characteristics A and A', being derived from
different parents, inhere in different chromosomes. I/et us assume that our
hybrid has eight chromosomes, four derived from each parent, thus :

in which the black dots represent chromosomes of maternal origin ; the
circles chromosomes of paternal origin. If all maternal chromosomes contain
the determinant a then purity of the gametes demands that all such go to
one gamete and all of the chromosomes of paternal origin go to the other,
and that such is their behavior has in fact been assumed by Cannon (1902).
But that would result in the extracted pure individuals of the second hybrid
generation being like their grandmother or their grandfather in all charac-
teristics, which is not the case. If we assume that some only of the maternal
chromosomes, such as are represented by the small dots, contain the deter-
minant a, then these may be associated with any of the paternal chromo-
somes excepting those that contain the determinant a'. Such a selection of
chromosomes so as to exclude from the ripe gamete chromosomes containing
both the alternative characteristics is quite possible, owing to the fact of
synapsis, in which the homologous chromosomes from the two parents unite
in pairs, as shown in the figure, in such a way that both can not pass to the
same gamete.

The foregoing hypothesis of Button (1902, 1903) and Boveri (1902) would
account for perfect purity of gametes. But it is clear that gametes are not

92 INHERITANCE IN POULTRY.

wholly pure, since the characteristics in second generation hybrids are rarely
exactly like those of their grandparents ; consequently various additional
hypotheses have been offered accounting for this feature. Hacker (1904)
points out that chromosomes do not pass from cell to cell unchanged except
for their growth and division. During the resting stage "of the nucleus it
disappears. The new nucleus which arises in the position of the old is at
first small ; it arises inside of the old chromosome as a spore arises in the
mother cell ; its material has been derived from a part only of that of the
mother chromosome ; the remainder goes to form part of the cytoplasm.
Though chromosomes from different parents tend to separate to distinct
gametes, still all gametes are infected by each kind of characteristic."
McClung (1905, p. 329) assumes, more vaguely, a mutual influence of synap-
tically paired chromosomes in the prophase of ths first spermatocyte.

A different suggestion is offered by Ziegler (1905). He assumes that each
chromosome of maternal or of paternal origin carries determinants of all
characteristics. After maturation all gametes contain the same number of
chromosomes, but the proportion in them of chromosomes of paternal and
of maternal origin varies. Gametes rarely contain exclusively maternal or
paternal chromosomes, but whenever the proportion from one parent is high
the gamete acts as though it contains exclusively the gametes of that one
ancestor. If two gametes that are prevailingly paternal unite in a zygote
the resulting hybrids (of the second generation) show all the grand-paternal
characteristics. The difficulty with this hypothesis is that, like Cannon's,
it does not account (any better than the first hypothesis) for the diverse
combinations of characteristics shown in the second hybrid generation.

Still another suggestion has been made by Morgan (1905). It is that the
gametes are not pure, but contain determinants of both allelomorphs a and
a', and that one of these dominates in half of the gametes and the other in
the remaining half. The advantage of this hypothesis is that it accounts
for latent dominant characters in recessive individuals. This hypothesis
assumes that the gametes of hybrids are always impure, and that this im-
purity can not be got rid of. This seems to me to be contrary to experience.
Moreover, except for the explanation that it offers of latency — which has
been accounted for on other grounds by Cuenot — it offers no practical advan- .
tage over the theory of pure gametes.

From the foregoing diversity of hypotheses it is evident that we lack a fully
satisfactory cytological explanation of the facts other than that of purity—
the fact of imperfect dominance and the fact of particulate inheritance com-
bined with purity in the second hybrid generation. Perhaps it will suffice
to suppose a restricted purity of gametes such that the determinant of a
characteristic may become infected to a slight degree by the presence of its
allelomorph.

GENERAL, TOPICS IN INHERITANCE. 93

COMPARISON OF RECIPROCAL CROSSES.

There is a notion among breeders of poultry that the father and the mother
contribute different qualities to the offspring ; and if the cytoplasm carries
any hereditary tendencies this result is to be expected, for the female trans-
mits more cytoplasm than the male. Certainly the hybrid between a large
hen and a bantam cock starts life on a very different plane of size from the
hybrid between a bantam hen and a large cock. A writer in Wright's
Poultry Book (1902) says in respect to breeding Houdans that the male bird
is more responsible for the outside qualities — color, size of crest, beard, tail
carriage, color of legs, and so on. The hen determines laying qualities and
general size.

I have made only one extensive experiment on this matter. I crossed a
single-comb White Leghorn bantam and a Dark Brahma both ways. The
offspring of the Dark Brahma hen (weight, 1,300 grams) are a little heavier
than those of the White Leghorn bantam hen (weight, 700 grams). Two
males descended from the one and the other mother, respectively, weighed
at 3^2 months 720 and 550 grams. The average of three pullets from the
Dark Brahma at 3 months 22 days is 655 grams ; of three pullets from the
White Leghorn at 3 months 23 days is 626 grams. The proportional differ-
ence in the weight of the young of about 3 to 4 months is less than that of
their parents, but is in the same sense.

The booting of the offspring of the White Leghorn hen is much reduced
as compared with the booting of the offspring of the Dark Brahma hen, the
father in the first cross not differing from the mother in the second cross
in its heavy booting. In plumage color the 19 offspring of the White Leg-
horn female were all white except four. Of the 19 offspring of the Dark
Brahma female, only six were white, the others resembling the Dark Brahma.
Thus we see that in these three characters of weight, booting, and plumage
color the offspring tended to ' ' take after ' ' the mother.

INHERITANCE OP SEXUALLY DIMORPHIC CHARACTERISTICS AND SEXUAL
DIMORPHISM IN THE HYBRIDS.

Most species of vertebrates exhibit certain characteristics peculiar to one or
the other sex, and it is well known that, for example, a female peculiarity
can be transmitted through a son to a granddaughter. Thus the good
milking quality of a cow is transmitted through her son to his daughters.
Whenever femaleness crops out in the history of the germ plasm the good
milking quality, or whatever other quality it may be, also appears. The
inheritance of dimorphic characters is most strikingly seen in hybridization.
Thus I crossed a male Tosa fowl (which has self-colored feathers) with a
white Cochin.* The male hybrids are barred with white, but the female
hybrids closely resemble in color the female Tosa fowl in having white

* See Series IX.

94 INHERITANCE IN POULTRY.

shafting on the contour feathers, although the white shafting is much
broadened. When the barred male and broad-shafted females of this first
hybrid generation were crossed the pure plumage of the Tosa fowl tends to
reappear. The males have contour feathers without white and with much
red ; the females have the shafted feather without any red. With maleness
or femaleness go the proper secondary attributes.

What is true of the Tosa fowl is true generally, and there is much oppor-
tunity to test this matter in poultry, for sexual dimorphism is widespread.
In all "dark" or "partridge," silvered, and golden races as found in
Brahmas, Cochins, Wyandottes, Dorkings, Haaiburghs, Games, and Oriental
fowl, the plumage of the two sexes is conspicuously different ; and to pro-
duce sexual dimorphism in a race that is without it the use of one male
bird of a dimorphic race may suffice. Again, in the male, comb and wattles
are generally larger than in the female. The rose comb of the male becomes
often a modified pea comb in the female. The simple comb of the Minorca,
Spanish, and Dorking fowl is erect in the male, drooping to one side (equally
to the right and left side) in the female. The form of the hackle and saddle
feathers constitutes one of the most constant differences between the two
sexes. These are long, narrow, and pointed in the male ; short, broad, and
rounded in the female. The tail feathers differ similarly. The sickle feathers
and those of the middle row especially continue to grow in the male long after
their growth has ceased in the female. Similarly the crest feathers of Polish
and Houdans grow longer in the male than in the female, but on account of
their greater breadth in the female her crest appears larger and fuller. Lastly,
the greater development of the spurs in the male over six to eight months
old is a well-marked dimorphic character. Of these characters I have paid
most attention to plumage and skin color, and will take up in review the
results gained in crossing dimorphic species.

Black Minorca and Dark Brahma. — The male Dark Brahma has white-
laced hackles and black, white, and red wing bars. In the female the lacing
on the hackles is less conspicuous, and there are no wing bars or bows.
Red is wholly absent. All hybrids are prevailingly black. All males, how-
ever, show a more or less prominent wing-bar formed of black, straw, and
red colored feathers. No females show any trace of a wing bar unless it be a
slight iridescence in the wing coverts.

White Leghorn and Dark Brahma. — The male hybrids are typically white,
with some red on wing coverts. Apart from some black individuals, the
female hybrids are either white, with some buff on wing, or else they resem-
ble the female Dark Brahma, having the penciling modified into mossiness.
There is no well-defined wing-bar, but the middle wing is suffused with red.
White Leghorn and Houdan. — Neither of these races exhibits a marked
dimorphism in plumage color. Nevertheless, the coloration of the hybrids
is dissimilar in the two sexes, the males being of a much purer white than

GENERAL TOPICS IN INHERITANCE. 95

the females (p. 21), and this is true not only in the first generation, but also
in the extracted whites of a later generation.

White Leghorn and Rose-comb Black Minorca. — In the first generation the
male hybrids were almost without exception pure white ; the female hybrids
invariably show some black-speckled feathers.

Tosa fowl and White Cochin Bantam. — In the first hybrid generation, as
stated, the males had all feathers of male Tosa coloration, but barred with
white. The females had the Tosa hen coloration, but with shafting broad-
ened. Here each sex inherits the corresponding characteristic plumage of
the Tosa fowl modified by the white of the Cochin, but in different fashion
for each sex. Barring or cuckoo marking seems, indeed, a prevailingly male
characteristic. Hurst (1905, p. 133), in crosses of White Leghorn and
Houdan, got, in addition to white hybrids, n dark birds ; of these the 6
pullets were black ; the 5 cockerels were barred.

In the F, generation I obtained extracted pure (?) male and female Tosa-
fowl plumage as well as pure whites (p. 49).

Dark Brahma {female} and Tosa Jowl (male~}. — Here both races are
dimorphic. The female hybrids closely resembled in coloration the female
Tosa fowl, except that the contour feathers were penciled as in the Brahma.
The male hybrids closely resembled in coloration the male 'Dark Brahma,
except that much more red and less white appeared on the wing bars and
wing bows. Both sexes inherit some qualities from the corresponding sex
of each of the parent species. Again, the males have a yellow foot like their
mother, whereas the females have a willow foot like their father. The hybrids
of either sex inherit foot-color from the opposite sex of their parents (p. 54).

TRANSFER OF SEXUALLY DIMORPHIC CHAR ACT KRISTICS FROM ONE SEX TO THE OTHER.

Secondary sexual characters, such as have been referred to in the last sec-
tion, seem indissolubly associated with their corresponding sex. The reason
for such an association is obscure, but it is known that it is not due to the
absence in the protoplasm of the characteristics of the opposite sex, for these
may develop in the individual when the germ glands are removed. The germ
glands, then, control the latency of the one set of characters and the patency
of the other set. In poultry the removal of the sex glands from a young
cock, in the process of caponizing, results in loss of the crowing instinct and
failure of comb, wattles, spurs, hackle, saddle, and sickles to acquire the
size characteristic of a cock. If in the fowl the germ glands fail to develop,
the secondary sex characters are ambiguous .

Despite this apparently physiological dependence of secondary characters
in the germ gland, it seems improbable that the association is a necessary
one. Almost all characters can be dissociated ; why not also sex and second-
ary characters? There is reason to think much can be done in this way,
because something has already been accomplished. For example, the cereb-

96 INHERITANCE IN POULTRY.

ral hernia which now is found equally in both sexes of the Polish fowl was
formerly a female secondary sexual characteristic. Bechstein (1793) states
that he never observed the cranial dome in male Polish fowl. Blumenbach
(1813), who made numerous dissections of the cranium of this fowl, states
' ' of this deformity very slight traces indeed are found in the cocks, and
these but seldom." * Consequently it must be concluded that the female
secondary characteristic of cerebral hernia has been gradual^ transferred
to the male sex also. A case of which the history is known even more defi-
nitely is that of the Sebright Bantam. This bird is characterized by the
fact that in the male the hackle, saddle, and sickle feathers are of the same
form as in the female ; consequently the tail is short and truncate as in a
hen. Here, apparently, female characteristics have become attached to a
male. Fortunately we have the history of the race from the mouth of the
son of the maker, Sir Thomas Sebright. Dr. Horner, who obtained the state-
ment from Sebright, published it in Tegetmeier's Poultry Book (1868, pp.
241, 242).

It was about the year 1800 that the late Sir John Sebright began to fashion the Sebright
Bantam. The first cross was between a common Kantamf and the Polish fowl, j The
chickens resulting from this alliance were bred in-and-in until the required markings
and size were secured. Sir John then accidentally found a hen-tailed Bantam cock in
the country where he was traveling. This short-tailed bird he in-bred with his newly
manufactured Bantams, thereby giving their progeny the present form of the square tail.

The essential characteristic of the race was thus gained from a mutative
modification of a polymorphic characteristic. §

In my own experiments I have hardly proceeded far enough to get results ;
yet already evidence of transference of color characteristics from one sex
to the other is appearing. Thus in the second hybrid generation of the
Cochin X Tosa cross at least one bird (No. 659 9. ) has hackles of a plain
buff color like those of the male Tosa fowl, and entirely unlike the hackles
of the female Tosa fowl or the female of the dark variety of the Cochin.
Again, the female hybrids between the Dark Brahma hen and White Leghorn
cock have much red on the wing coverts. This is foreign to the Dark Brahma
hen, and must, so far as I can see, have been derived from the red on the
wings of the male SPesa fowl. Finally, two male hybrids between the Tosa
fowl and Dark Brahma show the feminine shafting. Experiments in con-
tinuance of this investigation are, naturally, in progress.

* Translation quoted by Tegetmeier, 1867, p. 173.

f Doubtless Game Bantam is here meant.

J The Golden Spangled Polish are undoubtedly referred to, whence the spangling of the
feather was obtained. The combination gave the small size and gold-spangled plumage.

§ As might be anticipated from the notoriously sterile quality of hen-feathered cocks,
Sebright Bantams are inclined to be sterile, and one is advised not to try to breed from
the best show stock, i. e., cocks with the shortest tails (Wright, 1902, p. 598).

GENERAL TOPICS IN INHERITANCE. 97

SEX IN HYBRIDS.

There is a widely held and frequently expressed opinion that hybrids show
an excessive proportion of males. Bateson and Saunders (1902, p. 139)
probably have this in mind in their statement — "the statistical distribution
of sex among first crosses shows great departure from the normal propor-
tions." I have therefore been interested to tabulate the sex proportions
in my hybrids. Without giving the full table, I may state that the totals
are : Males, 204 ; females, 173 ; sex undetermined, 573. There is here an
excess of males ; but in view of the large early death rate, this may well be
due to a difference in the death rate of the two sexes. Taking the different
series of hybrids separately, most of them gave an approximation to equality
of the sexes. One of the most striking departures is the series of Dark
Brahma (121 9) X Tosa (8A tf) hybrids. Of 22 individuals that developed
to 18 days in the incubator, all but one grew to maturity. Of these 21, 16
are males and 5 females. The first egg laid by the Dark Brahma after she
was put with the Tosa fowl developed into a female ; the next nine that
hatched were males ; also her last six young were males. The exceptions
to the law of equality of sexes in hybrid offspring are thus individual and
not of general significance.

CORRELATION OF CHARACTERISTICS.

Every taxonomic description testifies to the fact that a certain set of
characteristics is usually found associated in each species or variety. The
prevailing theory has been that this association is a necessary one, maintained
because all the characters are necessary to the success of the species in its
relations to external environment, or else that they were physiologically inter-
dependent. Modern work in hybridizing is establishing the fact that few of
the specific characteristics are interdependent. Their association is, so far
as interaction goes, mostly accidental. Thus in my experiments with poultry
I have merely reached the same conclusions as have been gained by Johannsen
(1899, P- JSs), de Vries (1903, p. 494), and indeed all recent workers. I
find, namely, that of the scores of evident external characteristics of poultry
that are inherited in alternative fashion scarcely two can be found that are
always associated. The most striking exception is the association of high
nostril and absence of single comb.

What, then, is the meaning of correlation in nature ? Clearly it is only
rarely due to physiological interdependence. It may often be due to an
unrelated association of characters independently advantageous to the organ-
ism. It is doubtless due to an accidental association of characters brought
into the race by successive mutations or by hybridizations and never disturbed ,
because not prejudicial to the well-being of the species.

98 INHERITANCE IN POULTRY.

THE MUTATION THEORY IN ITS RELATION TO THE ORIGIN OF DOMESTICATED ANIMALS.

While the mutation theory of de Vries has received widespread adherence
among botanists, many students of animals, and especially of domesticated
races, have appeared as its opponents. Foremost among these are Professors
Keller, of Zurich (1905), and Plate (1905), of Berlin. I think that the essence
of the mutation theory is too little apprehended. It rests on the funda-
mental theory of heritable unit characters and assumes their very limited
mutability. It recognizes the important results wrought by artificial selec-
tion, but considers them as arising from two processes — first, the selection of
minute favorable variations of the fluctuating sort, and, secondly, the preser-
vation of new unit characters suddenly appearing. Such unit characters can
usually be not only maintained but much improved by subsequent selective
breeding.

Now, it is true that breeders nowadays do not regularly wait for favorable
qualities to crop out. The process is too slow, uncertain, and expensive. If
one had scores of thousands of individuals, desired mutations would come
more frequently ; but even then they would rarely be of a desirable sort.
Every breeder can, on the other hand, improve any characteristic by selec-
tion, and that is for the most part the only method of improving a quality
that is open to him. Of course he can make new combinations of qualities
by crossing, but this does not, typically, result in new qualities.

The question of the permanence of the improvement wrought by selection
of minute variations is the first point of difference between de Vries and
Keller. De Vries asserts that such improvement persists only so long as
selection is maintained. Keller adduces some interesting cases on the other
side, and the cogency of some of his evidence must be admitted. He traces
the gradual evolution in Egypt of long lop-eared hounds from straight-eared
ones. Ear length in rabbits, as Castle (1905, pp. 125-126) has shown, is not a
unit character ; at least, it blends in hybridization and consequently exhibits
any desired intermediate condition. The same is probably due for dogs ;
consequently this character may well have arisen by summation of minute
variations. Yet Keller goes on to show the long-eared condition has per-
sisted in central Africa, where selective breeding no longer occurs. Hence
one characteristic originated by selection of fluctuations has not retrogressed
on removal of selection.

The preceding method of proof is not, however, of general validity.
Evidence that a characteristic arisen in domestication does not disappear
when the race becomes feral again is not evidence against the permanence
of fluctuations unless it is also proven that the characteristic arose by selec-
tion of fluctuations. This is usually not the case. The instance of long
ears would seem to be peculiar. Some of the other examples offered by
Keller of persistence of characteristics despite discontinuance of selection
avail little, since the precise origin of the unit characters concerned is un-

GENERA.I, TOPICS IN INHERITANCE. 99

known. If, unconsciously or not, a unit character arising as a sport has
been preserved under domestication, it will persist even though the race
bearing it become feral.

Positive support for the mutation theory is gained from a consideration of
the characteristics of poultry. Our study has shown them to be, for the
most part, of the order of integral unit characters. As such they could
hardly have been " gradually built up." Being indivisible they must have
appeared at once, roughly in their present form. The very existence of unit
characters is proof of the mutation theory.

That many characteristics of organisms have not bean built up, but have
suddenly appeared complete, may be inferred from peculiarities of the char-
acters other than their integral nature. For, first, not all kinds of charac-
teristics have been evolved in domestic poultry, but for the most part only
such as occur elsewhere among wild races. Thus, for example, booted feet,
as found in the grouse ; crest on head, as seen in the umbrella bird (Cc[>halop-
teriis}, and long tail, as seen also in the widow bird (Chera). Secondly,
many of the characteristics of domestic poultry are of the order of mutations
in so far as they are almost pathological, e. ^., taillessness, rose comb, silky
and frizzled feathers, cerebral hernia, polydactyl feet, albinism. These char-
acters, cropping out in the sporting organism and not being prejudicial to
its well-being, have been preserved by the fancier ; they doubtless arose sud-
denly, as we find arising suddenly to-day other characters, which we discard
because incompatible with a healthy stock — such as featherlessness, cross-bill,
and imperfect development of toes. If these characteristics appeared sud-
denly and not by being "built up," as we know is the case, then so, doubt-
less, have others. The evidence that many, if not most, characteristics of
poultry have arisen .suddenly, without having been sought and laboriously
built up by man, is convincing, and there can hardly be any escape from the
conclusion that here evolution has been largely, though not exclusively, by
mutation.

100 INHERITANCE IN POULTRY.

E. SUMMARY OF CONCLUSIONS.

(1) Poultry exhibit numerous unit characteristics which do not blend in
hybridization, but are inherited in alternative fashion. The unit characters
are not immutable things in hybrids, but subject to modification — perhaps
permanent — by interaction of the alternative characters.

(2) Although the great majority of characteristics of poultry are inherited
alternatively, yet a few cases of color characters show a particulate inher-
itance. The comparative rarity of blending of characters makes it easier to
see how new characters will not be ' ' swamped by intercrossing with the
parent form " (page 82).

(3) Specific and varietal characteristics in de Vries's sense are not inherited
in a markedly different fashion, although in two cases progressive variants
do not Mendelize typically.

(4) The patent characteristic is usually dominant over its latent allelo-
morph.

(5) Old and new characteristics are equally dominant.

(6) Dominance and recessiveness of characteristics are not always accom-
paniments of their segregation in the germ cells ; both, moreover, are fre-
quently incomplete.

(7) Dominance is usually, but not always, independent of the races crossed.

(8) Prepotency is as truly important in inheritance as dominance.

(9) Many first hybrids exhibit special forms, due to the interaction of the
two allelomorphs. These may become fixed as new characteristics.

(10) Reversion is being explained by the persistence in a "latent"
condition of the latent character.

(n) An adequate theory of gametic purity has not only to explain the
simple Mendelian formula, but also the facts of imperfect dominance, im-
purity of extracted forms, latency and atavism, and occasional particulate
inheritance.

(12) Reciprocal crosses exhibit differences due to the fact that the father
and the mother transmit different kinds of characteristics.

(13) When the parent races are dimorphic each sex in the hybrids exhibits
the respective sex characteristic of both of the species. In many cases a
new form of sexual dimorphism appears in the hybrids.

(14) Certain characteristics of one sex may become transferred to the
other by hybridization, owing to lack of complete correlation between primary
and secondary sex characters.

(15) The proportion of the two sexes in hybrids is normal.

(16) With few exceptions, correlated characteristics easily separate as a
result of hybridization so that any conceivable combination may be effected.

CARNEGIE INSTITUTION,

STATION FOR EXPERIMENTAL EVOLUTION,

COLD SPRING HARBOR, February 12, 1906,

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1900. Note on a long-tailed breed of fowls in Tosa. Trans. Asiatic Soc. Japan,

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102 INHERITANCE IN POUI/TRY.

CUENOT, L.

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1903. Observations and experiments on Japanese long-tailed fowls. Pror. Zool. Soc.

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1904. Wonder horses and Mendelism. Science, xix, 151-152. Jan. 22.

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1839. Untersuchungen iiber den Hirn-und Schadelbau der sogenannten Hollen-

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104 INHERITANCE IN POULTRY.

EXPLANATION OF PLATES.

PI.ATB I.

PlG. I. — White Crested Black Polish, $ 5. One of the females crossed with the Single-
combed Black Minorca (cf. fig. 3) to produce the female hybrid shown in
fig. 5. (H.A. H.)

FlG. 2. — White Crested Black Polish, $ 30. To show the male type of the Polish race,
which, when crossed with the Minorca (fig. 4), produces male hybrids like
fig. 6. (H. A. H.)

FlG. 3. — Single Comb Black Minorca, 9 13- The mother of the hybrids, Minorca X Polish,
represented by fig. 5.

FlG. 4. — Single Comb Black Minorca, rf 12. The father of various Polish X Minorca
crosses, of which a male is represented in fig. 6.

FlG. 5. — First Hybrid between Polish and Minorca, pullet. Compare the females of the
parental races, figs, i and 3.

FlG. 6. — First Hybrid between Polish and Minorca, cockerel. Compare the males of the
parental races, figs. 2 and 4.

The figures marked H. A. H. are from photographs made by Mr. H. A. Hackett.

PLATE

106 INHERITANCE IN POULTRY.

PIRATE II.

FlG. 7. — The head of a Polish fowl, tf 3, with skin on left half of head dissected away.
Shows cerebral heruia, and the relation to it of the thick skin and crest
feathers lying above. Note also the culminal fold, high nostril, and rudi-
mentary comb. The latter lies at the base of the comb and shows as a
mottled area against the deep black of the anterior crest feathers.
(H. A. H.)

FlG. 8. — Head of a hybrid, tf 50, between Minorca £ 13 (fig. 3) and Polish ^ 3 (fig. 7).
Shows the Y-shaped comb lying in front of the crest. The comb is double
behind, single in front.

FIG. 9. — Head of a Minorca X Polish hybrid of the second generation. The son of such a
pair as are represented in figs. 5 and 6. Note the reappearance of a large
crest, high nostril, and rudimentary comb. (H. A. H.)

FIG. 10. — Side of cranium of Polish fowl. Shows bony dome covering cerebral hernia.

PLAT'

10

108 INHERITANCE IN POULTRY.

PLATE III.

FiG. ii. — Head of hybrid of the second generation, Minorca X Polish, 371 <$ — the son
of such a pair as are represented in figs. 5 and 6. Note the absence (imper-
fect) of crest, the high nostril, and the rudimentary comb. (H. A. H.)

FiG. 12. — Head of Houdan (cf 9). Shows crest, high nostril, and rudimentary comb.

FIG. 13. — Foot of Houdan (<$• 9). Shows the two toes (in place of one) situated imme-
diately below the spur.

FIG. 14. — Head of second generation White I/eghorn x Houdan hybrid, its father being
like fig. 17. Shows the occurrence of both cerebral hernia and single comb
on the same individual. (H. A. H.)

PLATE

N

no INHERITANCE; IN POULTRY.

PLATE IV.

FIG. 15. — Single Comb White Leghorn (^ 74). Note high single coinb, plain head, clean
feet with four toes, and white plumage. (H. A. H.)

FIG. 16. — Houdan ( 9 8). Note crest, high nostril, rudimentary comb, mottled plumage,
and muff and beard.

FIG. 17. — First hybrid (tf 87) between White Leghorn and Houdan. Note crest, Y comb,
white plumage, muff, and double toe behind on left foot.

PLATE IV.

17

16

112 INHERITANCE IN POULTRY.

PLATE v.

FIG. 18. — Dark Brahma hen (121). Note uniformity of plumage coloration, except that
hackles are laced -with whit?, and wing coverts, back, and breast are penciled.
Comb of pea tyt>e. Feet booted. Vulture hock. (H. A. H.)

FIG. 19. — Dark Brahma cock (122). Note laced hackles and saddles, prominent white
wing bow, pea comb, and booted feet.

PLATE V.

19

114 INHERITANCE IN POULTRY.

PLATE VI.

PiG. 20. — First generation hybrid, $ 607, between Black Minorca (fig. 6) and Dark
Brahma (fig. 19). Note prevailingly black plumage, with trace of white
wing bow, irregular pea comb, slightly booted feet, and absence of vulture
hock and of lacing on hackles. (H. A. H.)

PlC. 21. — First generation hybrid, cf 603, between Black Minorca and Dark Brahma.
Brother to fig. 20. Note almost complete absence of white wing bow, but
presence of white lacing on hackles. Note also high, though pea, comb, and
long tail. Form of trunk like Dark Brahma, neck like Minorca. (H. A. H.)

PLATE VI.

Il6 INHERITANCE IN POULTRY.

PLATE VII.

FIG. 22. — First generation hybrid, $ 387, between White Leghorn Bantam (resembling
fig. 15) and Dark Brahma (fig. 18). Note the new type of plumage colora-
tion. Hackles broadly laced as in male, rest of plumage mottled, with much
red. Booting rudimentary. (H. A. H. )

FlG. 23. — First generation hybrid, $ 395, between White Leghorn and Dark Brahma.
Shows reappearance of the Dark Brahma $ type of coloration. (H. A. H.)

PLATE VII.

22

Il8 INHERITANCE IN POULTRY.

PLATE VIII.

FiG. 24. — First generation hybrid, tf 270, between White Leghorn and Dark Brahma.
Shows the pure white t3'pe, i. e., dominance of White Leghorn coloration.
Note slight booting, absence of vulture hock and the erect, Leghorn tail.
(H. A. H.)

FiG. 25. — First generation hybrid, <^ 409 A, between White Leghorn and Dark Brahma.
Shows the type with red on the wing coverts. (H. A. H.)

PLATE VIII.

V

NT

24

120 INHERITANCE IN POULTRY.

PLATE IX.

PiG. 26. — Black Cochin Bantam, 9 129. Shows short tail and heavily booted feet. The
mother of the barred bird, fig. 27. (H. A. H.)

FiG. 27. — First hybrid, $ 365, between Black Cochin Bantam (fig. 26) and White I/eghorn
(cf. fig. 15). Note barred plumage coloration, red earlobe, and booted feet.
(H. A. H.)

PiG. 28. — Buff Cochin Bantam, ^ 545. >T^te short tail, heavily booted feet, red earlobe,
and single comb.

PLATE IX.

28

122 INHERITANCE IN POULTRY.

X.

FIG. 29. — Tosa fowl, rf IA, imported from Japan. Long tail feathers had been recently
pulled out.

FIG. 30. — Tosa fowl, 9 2A, imported from Japan. Note the light shafting.

FIG. 31. — Tosa fowl, (J*3A, "Admiral Togo," son of IA and 2A. Photographed Septem-
ber 7, 1905. Note length of tail. (H. A. H.)

FIG. 32. — White Cochin Bantam, $ 35A. This bird was crossed with fig. 29 and gave
hybrids represented on plate XI.

PLATE X.

124 INHERITANCE IN POULTRY.

Pr,ATE XI.

FIG. 33. First generation hybrid, 9 5$, between White Cochin (fig. 32) and Tosa fowl
(fig. 29). Note a slight broadening of shaft stripe as compared with female
Tosa fowl.

FIG. 34. — First hybrid, (J 53, between White Cochin and Tosa fowl (fig. 29). Note white
barring on feathers, and long tail. (H. A. H.)

FIG. 35. — First hybrid, <$ 95, between White Cochin and Tosa fowl, younger brother to
fig. 34. Note barring and growth of saddle and tail feathers. (H. A. H.)

FIG. 36. — Second generation hybrid, 9 3I2i between White Cochin and Tosa fowl. Note
pure white plumage color, like Cochin grandmother, fig. 32, combined with
long tail of Tosa, fig. 30. (H. A. H.)

PLATE XI.

126 INHERITANCE IN POULTRY.

PLATE XII.

FIG. 37. — Plumage chart of F, (White Cochin X Tosa), 9 58, at about 5 months, pi, to
of head ; 2, hackle ; 3, middle of back ; 4, throat ; 5, breast ; 6, middle tail ;
7, saddle ; 8, wing, secondary.

FIG. yja. — Plumage chart of Fx (White Cochin X Tosa), $ 53, at about 5 months. Signifi-
cation of figures same as in fig. 37. Shows barring of feathers.

FIG. 38. — Second hybrid generation (White Cochin XTosa), $ 315. Note reappearance
of pure white like Cochin grandmother (fig. 32, plate X) ; form intermediate,
feet booted. (H. A. H.)

PLATE XII.

37a

37

;. "

128 INHERITANCE IN POULTRY.

PLATE XIII.

FIG. 39. — Jungle fowl, 9 2. Taken after death to show shafting on breast, nape, back,
and wing coverts.

FIG. 40. — First generation hybrid, $ 358, between Dark Brahma (fig. 19, plate V ) and Tosa
fowl (fig. 29). Note white laced hackles and saddles, vulture hock, boot,
and pea comb of Brahma aud white earlobe and elongated head of Tosa.
(H. A. H.)

PLATE XIII.

39

40

INHERITANCE IN POULTRY.

PLATE XIV.

FlC. 41. — Frizzle fowl, tf 15. Note rose comb and feathers that turn forward, forming a
ruff on the neck. On the exposed vanes of the upper secondaries the twist-
ing of the barbs may be seen.

FIG. 42. — Frizzle fowl, ? i8A. Note extreme curling of feathers, the absence of barbs on

part of the secondaries, leaving the shaft quite naked, and the absence of

plumage on the back of the head.
FIG. 43. — Silky fowl, cT 2IA- Note single comb, small crest, the downy condition of the

contour feathers, and the elongated aud disconnected barbs of the wing

secondaries and tail feathers.

FIG. 44. — First hybrid between Frizzle and Silky, $ 219. Note the white plumage, rose
comb, trace of crest, frizzled feathers (ruff !), and absence of elongated barbs
on the wing, secondaries, or other evidence of silkiness. The booted feet and
extra toe are derived from the Silky. (H. A. H.)

PLATE XIV.

132 INHERITANCE IN POULTRY.

PLATE XV.

FIG. 45. — Rumpless Game, $ 49.

FiG. 46. — Rumpless Game, tf 117. The hackles and saddles and wing bars are red ; other-
wise the plumage is largely black. (H. A. H.)

FiG. 47. — First hybrid between White Leghorn (cf. fig. 15, plate IV) and Rumpless Game,
1^516. Note dominance of white (except for a trace of red on the wing
coverts) and long tail. The comb is intermediate between that of a Game
and that of a White Leghorn. (H. A. H.)

PLATE XV.

46

47

134 INHERITANCE IN POULTRY.

PLATE XVI.

FIG. 48. — Head of second generation Minorca X Polish hybrid, <^ 474. Shows last term
of series, beginning with fig. 50 and passing through fig. 49, of reduction
of median component of Y comb, leaving only two papillae remaining.
(H. A. H.)

FIG. 49. — Head of second generation Minorca X Polish hybrid. Shows middle term of
series passing from Y comb to V comb. The median portion of the comb is
represented by a carunculated mass at the base of the papillae. (H. A. H.)

FlG. 50.— Head of second generation Minorca X Polish hybrid, tf 259. Shows beginning
degeneration of median component of Y comb, which ends in the V comb
(fig. 48). (H. A. H.)

FlG. 51. — Head of second generation Minorca X Polish hybrid. Shows 2 pairs of papillae,
high nostrils and rudimentary crest, indicating that the first two character-
istics are independant of the third. H. A. H.)

FlG. 52 — Dorsal view of head of (Minorca X Polish) X Minorca hybrid. Shows Y comb
in which the median component extends between the arms of the Y, the
whole resembling a pea comb. (H. A. H.)

PLATE XVI.

136 INHERITANCE IN POULTRY.

PLATE XVII.

FIG. 53. — First generation hybrid between Silky and Jungle fowl, tf 156. Shows domi-
nance of Jungle-fowl plumage color and the extra toe and crest of the Silky.
(H. A. H.)

FIG. 54. — First generation hybrid between White Leghorn and Rose Corrb Black Mi-
norca, $ 138. One of the two birds that exhibit the blue, Andalusian type
of coloration, all others being white. (H. A. H.)

PLATE XVII.

53

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LIBRARY, COLLEGE OP AGRICULTURE, DAVIS
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LIBRARY, COLLEGE OP AGRICULTURE, DAVIS
UNIVERSITY OF CALIFORNIA