SUMMARY AND CONCLUSIONS.
1. The two principal results obtained were: (_a_) that castration of
hen-feathered Sebright males causes them to develop the full plumage
characteristic of the cock-bird; (_b_) that complete hen-feathering is
due to two dominant Mendelian genes.
2. A striking change takes place when the Sebright male is castrated
(plate 1, figs. 3, 4; plate 3, fig. 1). The new feathers on the upper
surface of the head, neck, back, wings, rump, and tail-coverts assume a
different color and distribution of their pigment; they take on a new
shape, and in those regions where in the cock the barbules are absent
from a part of the margin of the feather, the same absence occurs in the
castrated birds. Such feathers are present on the neck, back, wing-bow,
and rump. The transition is shown in the figures in plate 6, where for
comparison one of the old and one of the new feathers lie side by side.
The tail-coverts in the hen-feathered bird are short, and like those in
the hen do not cover the true tail. After castration they become
excessively long--longer, in fact, than in many cocks--and cover the
true tail feathers. The tail feathers themselves, moreover, become
increased in length, as do the posterior row of feathers of the
wing-coverts. On the breast and sides the change is less marked. The
castrated Sebright loses his erect carriage, but how far this is due to
the changes in his plumage and how far is real (as a result of a new
balance due possibly to the lengthening tail and its coverts) I can not
decide.
3. While castration causes the hen-feathered male to make additions in
color, length, and size of many feathers, it causes at the same time the
other retrogressive changes characteristic of the capon (a castrated
cock-feathered bird); the comb and wattles shrink and become pale, the
birds almost cease crowing, and become timid. They do not make much
effort to mate with the hens, but when they do they show the usual
copulatory reactions.
4. If feathers are removed at the time of castration, the new feathers
show the full effect of the removal of the testes, although they must
have begun to develop immediately afterward. It is suggested that by
means of this delicate test the time relations of the internal secretion
can be profitably studied.
5. Feathers that may have started their development at the time of the
operation show the old influence at the tip of the feathers (plate 10)
and the new one in the rest of the feather. The change is abrupt,
although the transition is perfect.
6. Incomplete castration of the hen-feathered male leads to smaller
changes in the same direction than those following complete castration.
Where such small pieces of the testis were left that complete
cock-feathering followed, the bird slowly changed back to
hen-feathering as the testes began to regenerate. When the regenerated
pieces were removed the bird became cock-feathered again.
7. One Sebright male whose testes appear to have been completely removed
did not change the character of the plumage. No testes were found on
autopsy. It is suggested that some other endocrine organs have taken
over the function of the testes, but as yet none such can be indicated.
8. In one case an old hen-feathered (F₁) male began to change over to
cock-feathering. It was found that his testes had dwindled (probably
through disease) to very small size (10 by 5 mm.).
9. The F₁ male of the cross between the Sebright and game is also
hen-feathered (plate 2, fig. 1). After castration he becomes
cock-feathered (plate 2, fig. 4) and shows thereby the genetic type of
the heterozygous cock-feathered class in which his hen belongs. The
change in this male is even more striking than that in the Sebright. The
change in the individual feathers is shown in plate 7, figs. 1 and 1_a_.
10. Three types of F₂ hen-feathered castrated males are shown in plate
2, figure 3, and plate 3, figure 3 and figure 4. The first was a dark
bird that changed to a lighter red above. The third a gray bird that
became bright red; the second was a light yellow that became deep
yellow, etc. The class of hens to which such males belong, as
cock-feathered birds, can thus be found out by castration. In this way
the F₂, and back-cross, hen-feathered cocks can be classified with the
corresponding F₂ cock-feathered males.
11. In the F₂ generation, made up of birds from the direct and
reciprocal crosses taken together, there were 29 hen-feathered and 26
cock-feathered males. In the back-cross (F₁ hen by game male) the
classes were 2 and 7. The results seem in better accord with the
assumption that two factors are present in the Sebright that stand for
hen-feathering; that either alone will give hen-feathered birds
(intermediate type?), but that both together give the extreme type of
hen-feathering seen in the Sebright.
12. The difference in color in the two races (Sebright and Black
Breasted Game bantams) is very great. The former have almost uniformly
laced feathers, while the latter has the varied plumage of the
jungle-fowl. The game is strongly dimorphic in color and color-pattern;
the Sebright has the same type of coloration and pattern both in the
male and female, but this is deceptive, as castration shows, because the
castrated male is as strikingly different from the normal Sebright
female as is the cock of other birds from the hen. The resemblance of
male and female in this race is due to the suppression of the true male
plumage by something produced in the testes. Therefore the heredity of
dimorphism resolves itself here into the problem of the heredity of
hen-feathering. That the female Sebright has the same genetic factors as
the male is shown by the fact that she transmits hen-feathering in the
same way as does the male, and also by the fact, as Darwin pointed out,
that an old female Sebright whose ovaries had degenerated developed not
the hen-feathered plumage of her own cock, but cock-feathered plumage
like that of most male poultry.
13. The color of the F₁ birds is shown in plate 2, figs. 1 and 2. In
general, the feathers are stippled, black and light yellow being the two
most conspicuous ingredients. Since hen-feathering dominates, the
dimorphism is absent, or at least is so slight as to not attract
attention--little more, in fact, than in the Sebright race. The carriage
of the male is like that of the Sebright male. The F₁ male and female
are alike in the direct cross and the reciprocal, or at least no
conspicuous difference is found between the two classes of hens,
indicating that no important sex-linked factors are involved in the
cross.
14. The F₂ birds show a great variety of color and pattern, but those
obtained can be approximately grouped into 16 classes. The classes are,
however, admittedly not uniform, indicating minor factors not here
reckoned with. The classification of the hens is easiest; the F₂
hen-feathered males can then in many cases be referred to the proper
classes; the F₂ cock-feathered males can not be accurately classified
with their corresponding hens, except in the case of those that resemble
the two P₁ males, the F₁ male, and those that castration experiments of
the hen-feathered males have shown to belong to certain hen types.
15. Despite the admitted difficulties of classification, it is suggested
that three factor-pairs of differences will cover the main color classes
seen in the F₂ and in the back-cross. One or two of these seem to be
incompletely dominant, since the F₁ birds are not like either parent in
any single character, nor are they like the wild type in so far as this
is represented by the game.
16. A histological examination of the testis of the male Sebright by
Boring and Morgan has shown that it contains cells like those present in
the ovary of all breeds of poultry. These cells are called luteal cells
by Pearl and Boring, from their resemblance to the cells of that name
found in the corpora lutea of mammals. In the mammals similar cells are
supposed to produce internal secretions that act as hormones. Their
function in the female bird is unknown, but the fact that after the
removal of the ovary the female develops the secondary sexual plumage of
the male suggests that some secretion from these cells performs this
function. Their occurrence in the male Sebright and their complete
absence, or paucity, in the males of other races supports strongly the
view that these cells are concerned with the suppression of the
secondary sexual plumage.
17. While in mammals the interstitial cells have been supposed to
produce an internal secretion that causes the development of some of the
secondary sexual characters of the male, and the fuller elaboration of
others, in birds no such connection exists, if we except the case of
the Sebright. Castration of ordinary males does not affect deleteriously
the secondary sexual plumage (although it does the comb, behavior,
etc.), in fact may even enhance their effects. But, while in the mammal
a secretion is necessary for the full development of the secondary
sexual characters, in the Sebright a secretion inhibits certain of them.
What element in the ordinary bird and in the Sebright causes the full
development of the comb, wattles, sexual behavior, etc., is not known.
Possibly it is the sexual elements themselves, but possibly it is a
secondary influence of the luteal cells producing a contrary effect on
these parts from its effects on the feathers; but possibly more than one
kind of secretory cell is present in the testis of the cock.
18. The causes of the development of the secondary sexual characters are
seen to be of such diverse physiological kinds that one may well
hesitate to apply the same explanation as to their evolution. In fact,
it is pointed out that several of the theories that have been suggested
run counter to the conditions that bring about the development of the
secondary sexual characters.
19. An attempt is made to give a critical review of Darwin’s theory of
sexual selection in the light of the modern genetic and operative
results on the secondary sexual characters of the vertebrates. It is
pointed out that far from extending the general theory in its
applications, the modern work has shown in the first place that the
underlying conditions that call forth the development of the secondary
sexual differences are so diverse in the different groups of animals
that it is a priori very unlikely that this evolution can have been
directed by the same external agent, such as the choice of the female,
for such an assumption carries with it in several cases other
implications concerning the causes of the suppression of these same
characters in the female herself, etc. In the second place, it is
pointed out that the problem of the excessive development of certain
characters in the male whose genes are present in both sexes no longer
oppresses us as it did Darwin, for it has been shown both by the genetic
and by the operative work that a single factorial difference may be at
the root of exceedingly great differences in the individual. Such
results, while they admittedly do not _in most cases_ tell us that the
differences involved have arisen at a single progressive step, show us
nevertheless that such differences may depend on very simple initial
differences, and if so, the entire problem becomes enormously
simplified. To Darwin the excessive development of color and
ornamentation appeared due to a long, slow process of evolution
laboriously brought about by the female through selection of those males
a little more ornamented than their fellows. To-day we have found out
that in many cases the genetic composition of a male with such
ornamentation and of a female without it may be almost identical, except
that the genes in one chromosome are duplex in one sex and simplex in
the other. Owing to this initial difference, the female in birds
produces an internal secretion that suppresses in her the ornamentation
shown by the male, and in the mammal an internal secretion produced by
the testes causes the full development in the male of the secondary
sexual characters. If, as seems probable, these secretions are some
particular kind of substance, the condition that led to their appearance
historically need not have been very complex; and if not, the problem
appears simplified. It still remains to give some reasonable explanation
as to why such substances should continue to be produced if their
products--the secondary sexual characters--possess no “beauty” for the
female. Here more work is necessary, but the modern genetic point of
view may possibly give an important clue. We are coming to realize more
fully that the hereditary genes generally have more than a single effect
on the characters of the animal. The secondary sexual characters may,
then, be only by-products of genes whose important function lies in some
other direction. If, for example, the secretion produced by the cells of
the male have an important influence on his output of energy, or
strength, or activity, their secondary influence over certain parts of
the body would not call for any further explanation on the modern view
of natural selection. If the secretions of the ovary of the female bird
have some direct relation to her physiological processes that are
important in the development of the oviduct, for instance, it would be a
matter of no importance from an evolutionary point of view if that same
secretion suppresses in her the development of the high color shown by
the male.
BIBLIOGRAPHY.
ALCOCK, A., 1892. On the habits of _Galasimus annulipes_. An. Mag.
Nat. Hist., VI.
ANCEL, P., ET BOUIN, 1906. Sur l’effet des injections d’extrait de
glande interstitielle du testicule sur la croissance. Compt. Rend.
Acad. Sc. Paris, CXLII.
ARKELL, T. R., 1912. Some data on the inheritance of horns in
sheep. N. H. Agr. Exp. Sta. Bull., 160.
--------, 1912. The nature of the inheritance in sheep. Science, n.
s., XXXV.
--------, and C. B. DAVENPORT, 1912. Horns in sheep as a typical
sex-limited character. Science, n. s., XXXV.
BATESON, W., and E. R. SAUNDERS, 1902. Experiments with poultry.
Reports Evol. Committee, I, Part II.
--------, E. R. SAUNDERS, and R. C. PUNNETT, 1905. Experimental
studies in the physiology of heredity. Reports Evol. Committee, II.
--------, 1906. Poultry. Reports Evol. Committee, III.
--------, 1908. Experimental studies in the physiology of heredity.
Reports Evol. Committee, IV.
--------, and R. C. PUNNETT, 1911. The inheritance of the peculiar
pigmentation of the silky fowl. Jour. of Genetics, III.
--------, 1913. Mendel’s principles of heredity. Cambridge.
BAUR, E., 1914. Einführung in die experimentelle Vererbungslehre,
Berlin.
BEEBE, C. W., 1908. Preliminary report on an investigation of the
seasonal changes of color in birds. Amer. Nat., XLII.
BERGENDAL, D., 1888. Über abnorme Formen der ersten abdominalen
Anhänge bei einigen Krebsweibschen. Bihang till K. Svenska
Vet.-Akad. Handlingar, XIV.
BERTKAU, P., 1891. Beschreibung eines Arthropodenzwitters. Arch. f.
Nat. ges., LVII.
BOND, C. J., 1913. Some points of genetic interest in regeneration
of the testis after experimental orchectomy in birds. Jour. of
Gen., III.
--------, 1914. On a case of unilateral development of secondary
male characters in a pheasant, with remarks on the influence of
hormones in the production of secondary sexual characters. Jour. of
Gen., III.
BORING, ALICE M., 1912. The interstitial cells and the supposed
internal secretion of the chicken testis. Biol. Bull., XXIII.
--------, and RAYMOND PEARL, 1917. Sex studies, IX. Interstitial
cells in the reproductive organs of the chicken. Anat. Record,
XIII.
--------, 1918. Sex studies, X. Hermaphrodite birds. Jour. Exp.
Zool., XXV.
--------, and T. H. MORGAN, 1918. Lutear cells and hen-feathering.
Jour. of General Physiology, I.
BOURNE, A. G., 1884. On certain abnormalities of the common frog.
Quart. Jour. Micro. Science, XXIV.
BRANDT, A., 1889. Anatomisches und Allgemeines über die sogenannte
Hahnenfedrigkeit und über anderweitige Geschlechtsanomalien bei
Vögeln. Zeits. f. wiss. Zool., XLVIII.
BRESCA, G., 1910. Experimentelle Untersuchungen über die sekundären
Sexualcharaktere der Tritonen. Arch. Entw.-mech., XXIX.
CASTLE, W. E., 1912. Are horns in sheep a sex-limited character?
Science, n. s., XXXV.
CHIDESTER, F. E., 1911. The mating habits of four species of the
Brachyura. Biol. Bull., XXI.
CHOLODOWSKY, N., 1908. Über den Hermaphroditismus bei
Chermes-Arten. Zool. Anz., XXV.
CILLEULS DES, J., 1912. A propos du determinisme des caractères
sexual secondaires chez les oiseaux. Compt. Rend. Soc. Biol.,
LXXIII.
CUNNINGHAM, J. T., 1908. The heredity of secondary sexual
characters in relation to hormones, a theory of the heredity of
somatogenic characters. Arch. Ent. Med., XXVI.
DARWIN, CHARLES, 1868. Animals and plants under domestication.
DAVENPORT, C. B., 1906. Inheritance in poultry. Carnegie Inst.
Wash. Pub. No. 52, 1908.
--------, 1909. Inheritance of characteristics in domestic fowl.
Carnegie Inst. Wash. Pub. No. 121, 1909.
--------, 1911. Another case of sex-limited heredity in poultry.
Proc. Soc. Exp. Biol., Med., IX.
--------, 1912. Sex-limited inheritance in poultry. Jour. Exp.
Zool., XIII. 1912.
DITTRICH, V. R., 1888. Über Andrena praecox ♀ und _Astacus
fluviatilis_ ♀ mit teilweise männlichen Kennzeichen. Zeit. f. Ent.,
XIII.
DURHAM, F. M., and D. C. E. MARRYAT., 1908. Note on the inheritance
of sex in canaries. Reports Evol. Committee, IV.
FOGES, ARTHUR, 1903. Zur Lehre von den secundären
Geschlechtscharakteren. Arch. f. Phys., 93.
FOWLER, C. H., 1894. Notes on some specimens of antlers of the
fallow deer, showing continuous variation and the effects of total
or partial castration. Proc. Zool. Soc. London.
GEDDES, A. C., 1910. Abnormal bone growth in the absence of
functioning testicles. Proc. Roy. Soc. of Edinburgh, XXXI.
GIARD, A., 1904. Comme la castration agit-elle sur les caractères
sexuels secondaires? Compt. Rend. Soc. Biol., LVI.
GISSLER, C. F., 1881. Description of a hermaphroditic phyllopod
crustacean (_Eubranchipus_). Am. Nat., XV.
GOODALE, H. D., 1909. Sex and its relation to the barring factor in
poultry. Science, XXIX.
--------, 1910. Some results of castration in ducks. Biol. Bull.,
XX.
--------, 1910. Breeding experiments with poultry. Proc. Soc. Exp.
Biol. Med., VII.
--------, 1911. Studies in hybrid ducks. Journ. Exp. Zool., XX.
--------, 1913. Castration in relation to the secondary sexual
characters of Brown Leghorns. Am. Nat., XLVII.
--------, 1916. A feminized cockerel. Journ. Exp. Zool., XX.
--------, 1916. Gonodectomy. Carnegie Inst. Wash. Pub. No. 243.
--------, 1917. Crossing-over in the sex chromosome of the male
fowl. Science, XLVI.
GURNEY, J. H., 1888. On the occasional assumption of the male
plumage by female birds. Ibis, VI.
GUYER, M. F., 1909. The spermatogenesis of the domestic guinea
(_Numida meleagris_ dom.) Anat. Anz., XXXIV.
--------, 1909. The spermatogenesis of the domestic chicken
(_Gallus gallus_ dom.). Anat. Anz., XXXIV.
--------, 1909. On the sex of hybrid birds. Biol. Bull., XVI.
--------, 1909. La livré e du plumage chez les hybrids de pinta de
et de poule. Bull. du Museum. d’hist. Nat. No. 1.
--------, 1910. Accessory chromosome in man. Biol. Bull., XIX.
GUTHRIE, C. C., 1911. On evidence of some influence in offspring
from engrafted ovarian tissue. Science, XXXIII.
HADLEY, P. B., 1913. Studies on inheritance in poultry. 1. The
constitution of the White Leghorn breed. Bull. Agr. Exp. Station of
the Rhode Island State College, No. 155.
--------, 1914. 11. The factor for the black pigmentation in the
White Leghorn breed. Bull. Agr. Exp. Station of the Rhode Island
State College, No. 161.
HALBAN, J., 1903. Die Entstehung der Geschlechtscharaktere. Arch.
f. Gynäkologie, LXX.
HANAU, A., 1897. Versuche über den Einfluss der Geschlechtsdrüsen
und die secundären Sexualcharactere. Arch. f. ges. Phys., LXV.
HARRIS, J. A., A. F. BLAKESLEE, and W. E. KIRKPATRICK, 1918. The
correlation between egg production during various periods of the
year in domestic fowl. Genetics, III.
HEGAR, A., 1903. Korrelation der Keimdrüsen und
Geschlechtsbestimmung. Beiträge zur Geburtshilfe und Gynäkologie,
VII.
HEINROTH, O. VON, 1909. Ein lateral hermaphroditisch gefärbter
Gimpel (_Pyrrhula pyrrhula europaea_). Ges. Nat. Freunde zu Berlin.
HERBST, C., 1901. Formative Reize in der tierischen Ontogenese.
Leipzig.
HERLITZKA, A., 1899. Sul trapiantamento dei testicoli. Arch. f.
Ent.-mec., IX.
HOLMES, S. J., 1908. Phototaxis in fiddler crabs and its relation
to theories of orientation. Journ. Comp. Neurol., XVIII.
HUDSON, W. H., 1892. The naturalist in La Plata. London.
HULL, J. E., 1918. Gynandry in arachnids. Jour. of Genetics, VII.
HUNTER, JOHN, 1780. Account of an extraordinary pheasant. Phil.
Trans. Royal Soc. London., LXX.
HURST, C. C., 1905. Experiments with poultry. Reports Evol.
Committee, II.
JONES, E. L., 1914. The Campine Club, 1914, Year Book (see also
Farm Poultry, June, 1914, page 113).
KELLOGG, V. L., 1904. Influence of the primary reproductive organs
on the secondary sexual characters. Jour. Exp. Zool., I.
KNAPPE, E., 1886. Das biddersche Organ. Morph. Jahrb., XI.
KOPĚC, S., 1913. Nochmals über die Unabhängigkeit der Ausbildung
sekundärer Geschlechtscharaktere von den Gonaden bei Lepidopteren.
Zool. Anz., XLIII.
KURZ, W., 1874. Über androgyne Missbildung bei Cladoceren. Sitz. d.
math.-nat.-wiss. Klasse. d. Akadem. Wissensch., Wien., LXIX.
LEFEVRE, G. Sex-limited inheritance in poultry. Aust. Record, XI,
p. 499, 1916-17.
LILLIE, F. R., 1917. The free-martin; a study of the action of
sex-hormones in the fœtal life of cattle. Jour. Exp. Zool., XXIII.
LIPPINCOTT, W. A., 1918. The case of the blue Andalusian. Amer.
Nat., LII.
LOEWY, A., 1903. Neuere Untersuchungen zur Physiologie der
Geschlechtsorgane. Ergebn. d. Phys. II. Jabrg., 1. Abt., Biochemie.
LOIBEL, 1901. Grenouille femelle presentent toutes les caractères
sexuels secondaires du male. Comptes Rend. Soc. Biol.
MCEWEN, R. S., The reactions to light and to gravity in
_Drosophila_ and its mutants. Jour. Exp. Zool., XXV.
MARSHALL, A. M., 1884. On certain abnormal conditions of the
reproductive organs of the frog. Jour. Anat. and Physiol., VIII.
MARSHALL, F. H. A., 1910. The physiology of reproduction. London.
--------, 1910. Physiology of Reproduction. New York.
DE MEIJERE, J. C. H., 1911. Über getrennte Vererbung der
Geschlechter. Arch. Rass. Gesell. VIII.
MAYER, A. G., 1897. A new hypothesis of seasonal-dimorphism in
Lepidoptera. Psyche, VIII.
--------, 1900. On the mating instinct in moths. Psyche, IX.
MAZZETTI, L., 1916. I Caretteri sessuali secondari e le cellule
interstitiali del testicolo. Anat. Anz. XXXVIII.
MEISENHEIMER, J., 1909. Experimentelle Studien zur Soma- und
Geschlechtsdifferenzierung. Jena.
--------, 1911. Über die Wirkung von Hoden-und Ovarial-substanz auf
die sekundären Geschlechtsmerkmale des Frosches. Zool. Anz.,
XXXVIII.
MÖBIUS, P. J., 1906. Über die Wirkungen der Kastration. Halle.
MONTGOMERY, T. H., JR., 1909. Further studies on the activities of
Araneads, II. Proc. Acad. Nat. Sci., Philadelphia.
MONTGOMERY, T. H., Jr., 1910. The significance of the courtship and
secondary sexual characters of Araneads. Amer. Nat., XLIV.
MORGAN, T. H., 1905. An alternative interpretation of the origin of
gynandromorphous insects. Science, XXI.
--------, 1907. Experimental Zoology. New York.
--------, 1909. A biological and cytological study of sex
determination in phylloxerans and aphids. Journ. Expr. Zool., VII.
--------, 1913. Heredity and sex. New York.
--------, 1914. Mosaics and gynandromorphs in _Drosophila_. Proc.
Soc. Biol. and Med., XI.
--------, 1914. Sex-limited and sex-linked inheritance. Amer.
Natur., XLVIII.
--------, 1915. Demonstration of the appearance after castration of
cock-feathering in a hen-feathered cockerel. Proc. Soc. Exp. Biol.
and Med., XIII.
--------, 1917. The theory of the gene. Amer. Natur., LI.
--------, 1918. A critique of the theory of evolution. New York.
--------, 1918. Concerning the mutation theory. Scientific Monthly,
May.
--------, 1918. Changes in factors through selection. Scientific
Monthly, June.
--------, 1918. Evolution by mutation. Scientific Monthly, July.
MORGAN, T. H., and H. D. GOODALE, 1912. Sex-linked inheritance in
poultry. Annals New York Acad. Science, XXII.
MÜLLER, R., 1907. Sexualbiologie. Berlin.
--------, 1908. Das Problem der sekundären Geschlechtsmerkmale und
die Tierzucht.
MYERS, B. D., 1916. Histological changes in testes following
vasectomy. Anat. Record X, 1916.
NICHOLLS, F., 1731. An account of the hermaphrodite lobster. Phil.
Trans. London, XXXVI.
NUSSABAUM, M., 1905. Einfluss des Hodensekrets auf die Entwicklung
der Brunstorgane des Landfrosches. Verhandl. d. Naturhist. Vereins.
f. Rheinl.-Westfalen, LXII.
--------, 1905. Innere Sekretion und Nerveneinfluss. Ergebn. Anat.
und Ent.-ges., XV.
--------, 1909, Hoden und Brunstorgane des braunen Landfrosches
(_Rana fusca_). Arch. f. d. gesamte Phys., CXXVI.
OUDEMANS, H. TH., 1899. Falter aus kastrierten Raupen, wie sie
aussehen und wie sie sich benehmen. Zoolog. Jahrb., Abt. Syst.,
XII.
PACKARD, A. S., 1875. On gynandromorphism in the Lepidoptera. Mem.
Boston Soc. Nat. Hist., II.
PAINTER, T. S., 1913. On the dimorphism of the males of _Mœvia
vittata_, a jumping spider. Zool. Jahrb. Abt., Syst., XXXV.
PEARL, R., and M. R. CURTIS, 1909. Studies on the physiology of
reproduction in the domestic fowl. Biol. Bull., XVII.
--------, 1910. Studies on hybrid poultry. Rept. Maine Agri. Exp.
Station.
--------, and F. M. SURFACE, 1910. On the inheritance of the barred
color pattern in poultry. Arch. Ent.-mech., XXX.
--------,--------, 1910. Further data regarding the sex-limited
inheritance of the barred colored pattern in poultry. Science,
XXXII.
--------, and A. M. BORING, 1917. Sex studies. Anat. Rec., XIII.
--------, 1917. The corpus luteum in the ovary of the domestic
fowl. Am. Journ. of Anat., XXIII.
PEARSE, A. S., 1912. The habits of fiddler crabs. Philippine Journ.
Science, VII.
--------, 1914. On the habits of _Uca pugna_ and _Uca pugilator_.
Wiscon, Acad. Sci., XVII.
PETRUNKEWITCH, A., 1911. Sense of sight, courtship, and mating in
_Dugesiella hentzi_, a theraphosid spider from Texas. Zool. Jahrb.,
Abst. Syst., XXXI.
POCOCK, R. I., 1905. The effects of castration on the horns of the
prongbuck. Proc. Zool. Soc., London.
POLL, H., 1909. Zur Lehre von den sekundären Sexualcharakteren.
Sitz. Ges. Nat. Fr. zu Berlin.
PONCET, A., 1903. De l’influence de la castration sur le
developpement du squelette. Compt. Rend. Soc. Biol., LV.
PORTER, J. P., 1906. The habits, instincts and mental powers of
spiders. Jour. Phys., XVII.
POTTS, F. A., 1906. The modification of the sexual characters of
the hermit crab caused by the parasite _Peltogaster_. Q. J. M. Sc.,
L.
PUNNETT, R. C., 1915. Mimicry in butterflies. Cambridge.
PUNNETT, R. C., and P. G. BAILEY, 1914. On inheritance of weight in
poultry. Journ. of Genetics, IV.
RASMUSSEN, A. T., 1917. Seasonal changes in the interstitial cells
of the testis in the woodchuck, _Marmota monax_. Am. Jour. of
Anat., XXII.
REAGAN, E. P., 1916. Some results and possibilities of early
embryonic castration. Anat. Record, II.
REEVES, T. P., 1915. On the presence of interstitial cells in the
chicken’s testis. Anat. Record, IX, 1915.
ROGEN, J., 1909. Kastration und ihre Folgeerscheinungen bei
_Gryllus campestris_ L. Zool. Anz., XXXIV.
--------, 1910. Kastration und ihre Folgeerscheinungen bei _Gryllus
campestris_ L. Zool. Anz., XXXV.
RIBBERT, 1897. Über Veränderungen transplantierter Gewebe. Arch. f.
Ent.-mec., VI.
--------, 1898. Über Transplantation von Ovarium, Hoden und Mamma.
Arch. f. Ent. mech., VII.
ROMANES, G. J., 1892. Darwin, and after Darwin, Chicago.
RÖRIG, A., 1899. Welche Beziehungen bestehen zwischen den
Reproduktionsorganen der Cerviden and der Geweihbildung derselben?
Arch. Entw.-mech., VIII.
--------, 1901. Korrelationen zwischen gewissen Organen der
Cerviden und den Geweihen derselben. Verhandl. internat. Zoolog.
Kongress, Berlin.
SHATTOCK, S. G., and C. G. SELIGMANN, 1906. An example of true
hermaphroditism in the domestic fowl with remarks on the phenomenon
of allopterotism. Trans. Pathol. Soc. of London.
SMITH, GEOFFREY, 1910-1912. Studies in the experimental analysis of
sex. Q. J. Micro. Sci., LIV-LVIII.
--------, 1913. On the effect of castration on the thumb of the
frog, _Rana fusca_. Zool. Anz., XLI.
SMITH, GEOFFREY and Mrs. HAIG THOMAS, 1913. On sterile and hybrid
pheasants. Jour. Gen., III.
SPENGEL, J. W., 1876. Das Urogenitalsystem der Amphibien. Arbeit.
Zool. Zootom. in Würzburg, III.
SPENGEL, J. W., 1889. Zwitterbildung bei Amphibien. Biol.
Centralbl., IV.
SPILLMAN, W. J., 1908. Spurious allelomorphism. Am. Nat., XLII.
--------, 1909. Barring in barred Plymouth Rocks. Poultry, V.
STAMATI, G., 1888. Sur l’opération de la castration chez
l’écrevisse. Bull. Soc. Zool. France, XIII.
STEINACH, E., 1910. Geschlechtstrieb und echt sekundäre
Geschlechtsmerkmale als Folge der innersekretorischen Funktion der
Keimdrüsen. Zeit. f. Phys., XXIV.
--------, 1912. Willkürliche Umwandlung von Säugetier-Männchen in
Tieren mit ausgeprägt weiblichen Geschlechtscharakteren und
weiblicher Psyche. Archiv. ges. Phys., CXXXXIIII.
STEPHAN, P., 1902. De l’hermaphoditisme chez les vertébrés. Annal.
de la faculté des sciences de Marseille, XII.
STOCKARD, C. R., 1911. The fate of the ovarian tissues when planted
on different organs. Arch. f. Ent. Mech., XXXII.
--------, and G. N. PAPANICOLAU, 1917. The existence of a typical
œstrous cycle in the guinea-pig. With a study of its histological
and physiological changes. Am. Jour. of Anat., XXII.
STOTSENBURG, J. M., 1913. The effect of spaying and semi-spaying
young albino rats (_Mus norvegicus albinus_) on the growth in body
weight and body length. Anat. Rec., VII.
STURTEVANT, A. H., 1911. Another sex-limited character in fowls,
Science, XXXIII.
--------, 1912. An experiment dealing with sex-linkage in fowls.
Journ. Exp. Zool., XII.
--------, 1915. Experiments on sex recognition and the problem of
sexual selection in _Drosophila_. Journ. of Animal Behav., V.
SWIFT, C. H., 1914. Origin and early history of the germ cells of
the chick. Amer. Jour, of Anat., XV.
TANDLER, J., und K. KELLAR. Die Körperform der weiblichen
Fruehkastraten des Rindes. Archiv Entw-mech., XXXI.
--------, und S. GROSZ, 1909, 1910. Ueber den Einfluss der
Castration auf den Organismus. Archiv f. Entw-mech., XXVII, XXIX,
XXX, 1909.
--------, und S. GROSZ, 1913. Die biologischen Grundlagen der
sekundären Geschlechtscharaktere. Berlin.
V. LA VALETTE ST. GEORGE, 1895. Zwitterbildung beim kleinen
Wassermolch. Arch. Mik. Anat., XLV.
WALKER, C. E., 1908. The influence of the testis upon the secondary
sexual characters of fowls. Proc. Royal Soc. of Med.
WALLACE, A. R., 1891. Darwinism: An exposition of the theory of
natural selection. London.
--------, 1891. Natural selection and tropical nature. London.
WEBER, M., 1890. Über einen Fall von Hermaphroditismus bei
_Fringilla coelebs_, Zool. Anz., XIII.
YARRELL, W., 1827. On the changes in the plumage of some
hen-pheasants, Phil. Trans., 117.
--------, 1857. On the influence of the sexual organ in modifying
external character. Journ. Proc. Linn. Soc., I.
DESCRIPTION OF PLATES.
PLATE 1.
FIG. 1. Black-Breasted Game bantam cock. He is typically
cock-feathered, but, as in all games, his hackles and tail-coverts
are shorter than in the cocks of other breeds. The comb was dubbed
by the breeder.
FIG. 2. Black-Breasted Game bantam hen. The great contrast in color
between the cock and hen is practically the same as that in the
Brown Leghorn, in most races of Tosa fowls, and in the wild type
_Gallus bankiva_.
FIG. 3. Sebright cock, “hen-feathered.” The short hackles, the
rounded feathers of the back and saddle, and the shortness of the
tail-coverts are characteristic features of these males. For
details of individual feathers from different regions see plates 6
and 8.
FIG. 4. A castrated Sebright male. The drawing was made about a
year after the operation. This particular bird developed a lighter
color than did other castrated Sebrights (see plate 3, fig. 1). The
entire dorsal region has changed its color, and the feathers have
also changed in shape, length, etc. Note especially the very long
hackle and saddle feathers (for details see plate 6, fig. 1_a_) and
the change in the wing-bow. The tail-coverts have also grown long.
PLATE 2.
FIG. 1. F₁ hen-feathered male out of Game by Sebright. The
hen-feathering in this bird is as complete as in the Sebright.
FIG. 2. F₁ female out of Game by Sebright.
FIG. 3. Castrated male originally hen-feathered (292), nearly black
in color, as shown by the individual feathers of plate 7, figure 2.
After castration the bird has become red above, with black
iridescent tail-coverts, and deeper yellow (or red) below.
FIG. 4. Castrated F₁ male, originally like figure 1. Note
especially the change in color of the whole upper surface that has
become red, like that of the jungle-fowl. The tail-coverts have
grown long and are now iridescent black. The breast has changed
least, but is a richer yellow. The comb and wattles and ear lobes
are shrunken, as in all capons.
PLATE 3.
FIG. 1. A castrated Sebright male. The operation was performed on a
juvenile bird; the drawing was made a year later. The bird is
typical as to the change in color that takes place in the Sebright.
He was darker red than the bird shown in plate 1, figure 4. The red
was more mahogany than the picture shows. The original feathers
were like those in plate 6, fig. 2 (there erroneously referred to
as those of light-colored Sebright).
FIG. 2. An F₂ hen-feathered very dark male. The condition of his
plumage at the time of the operation is shown in this figure. The
change that took place after castration is shown in the next
figure.
FIG. 3. The change that took place in the bird drawn in figure 2 is
shown here. The whole upper surface has become red, except the
tail-coverts, which are iridescent black. Note also the change in
color on the wing-bow. For the details of the feathers see plate 9,
figures 1, 1_a_.
FIG. 4. A castrated F₂ bird that had been hen-feathered and had
changed over to cock-feathering, as shown here. The color and the
details of the original hen-feathering are shown in plate 9,
figures 2 and 2_a_.
PLATE 4.
FIG. 1. One of the original Black-Breasted Game males used in the
breeding experiments. Compare with colored drawing, plate 1, figure
1.
FIG. 2. A Black-Breasted Game hen used in the breeding experiments.
Compare with colored drawing, plate 1, figure 2.
FIG. 3. A Sebright male. The bird was used in the later
back-crosses and not in the original experiments. He is typical of
his breed.
FIG. 4. A Sebright female. One of the birds used in the original
experiments.
FIG. 5. An F₁ male. This bird had just reached maturity and was
younger than the one drawn in plate 2, figure 1.
FIG. 6. An F₁ hen of the same age as the last. The pattern changed
a little as the bird became older.
PLATE 5.
FIG. 1. An adult Sebright male for comparison with the next figure.
FIG. 2. A castrated Sebright male. This photograph shows the same
bird from which the drawing, plate 1, figure 4, was made. It is the
lighter colored bird referred to in the text.
FIG. 3. One of the two F₁ castrated birds. For comparison see the
colored drawing in plate 2, figure 4.
FIG. 4. A castrated Sebright. This bird is darker, and in this
sense more typical than figure 2.
FIG. 5. One of the castrated Sebright males which at one time after
castration was as extremely cock-feathered as figure 2, but slowly
“went back” towards hen-feathering, as the figure shows especially
in the hackle and saddle. The details are much better shown in the
feathers photographed in plate 8, figures 1, 2, 3, 4, 1_a_, 2_a_,
3_a_, 4_a_, 1_b_, 2_b_, 3_b_, 4_b_.
FIG. 6. The same bird was opened and the regenerated pieces of the
testis removed. He returned later, as shown here, to full
cock-feathering.
PLATE 6.
FIGS. 1, 1A. Typical old (1) and new (1_a_) feathers (after
castration) of the same bird. This is the “lighter” male drawn in
plate 1, figure 4, and photographed in plate 5, figure 2.
FIGS. 2, 2A. Typical old (2) and new (2_a_) (after castration)
feathers of another Sebright. This bird developed after castration
darker feathers than did the last bird. Its feathers were more like
those that other castrated Sebrights developed. Legend on plate 6
erroneous as far as 2 and 2a are concerned.
PLATE 7.
FIGS. 1, 1A. Typical old (1) and new (1_a_) (after castration)
feathers of an F₁ bird. (See plate 2, figures 1 and 4.)
FIGS. 2, 2A. Typical old (2) and new (2A) (after castration)
feathers of bird shown in plate 3, figures 2 and 3 (No. 292).
PLATE 8.
Typical feathers of “dark” Sebright (1, 2, 3, 4) that after
incomplete castration changed to cock-feathering (1_a_, 2_a_, 3_a_,
4_a_), then later, as pieces of the testes that had been left
behind in the old situs regenerated, began to go back towards
hen-feathering (1_b_, 2_b_, 3_b_, 4_b_). The bird was then opened
again, and the regenerated pieces removed, when it again became
cock-feathered (1_c_, 2_c_, 3_c_, 4_c_), and has so remained for
more than a year.
PLATE 9.
FIGS. 1, 1A. Typical feathers of hackle and saddle from
hen-feathered bird (No. 68) plate 3, figure 2, that changed over to
the cock-feathered bird of plate 3, figure 3.
FIGS. 2, 2A. Typical feathers of an F₁ male (2) that changed over
partly as a result of degeneration of his testes, into a
cock-feathered bird (2A). The change was not so great as it is
after castration.
FIGS. 3, 3A. Typical feathers of Sebright male that slightly
changed towards cock-feathering (old hackle feather missing).
PLATE 10.
FIGS. 1, 1A. Old (1) and new (1A) wing-coverts of normal Sebright
(1) and castrated (1A).
FIGS. 2A, 2B. Upper row, to right, “Transitional” hackle feathers
(2A), and a slightly later changed-over feather from wing-bow (2A),
and from back (2B). Second row, to left, old (2), transitional
(2_a_), and changed-over feather (2_b_), from saddle of Sebright.
FIG. 3. Three feathers (tail-covert, wing-bow, and saddle) of an F₂
hen-feathered game-like male.
FIG. 4. A series of breast feathers from an F₂ bird. At one end of
the series (the left) the feather is spangled, at the other barred.
FIG. 5. A series of breast feathers from another F₂ bird. At one
end of the series (the left) the feathers are penciled, at the
other end they are barred.
[Illustration:
T. H. MORGAN PLATE 1
JULIUS BIEN, N.Y.
1. Black Breasted Game Bantam male.
2. Female.
3. Sebright male.
4. Castrated Sebright male.
]
[Illustration:
T. H. MORGAN PLATE 2
JULIUS BIEN, N.Y.
1. Hen-feathered F₁ male.
2. F₁ female.
3. Castrated F₂ male.
4. Castrated F₁ male (Fig. 1).
]
[Illustration:
T. H. MORGAN PLATE 3
JULIUS BIEN, N.Y.
1. Castrated Sebright male.
2. F₂ Hen-feathered male.
3. Same castrated.
4. F₂ Castrated male.
]
[Illustration:
MORGAN PLATE 4
1. Black-Breasted Game male.
2. Black-Breasted Game female.
3. Sebright male.
4. Sebright female.
5. Hybrid male.
6. Hybrid female.
]
[Illustration:
MORGAN PLATE 5
1. Adult Sebright male.
2. Castrated Sebright male.
3. Castrated F₁ male.
4. Another castrated Sebright male.
5. Castrated Sebright male with testes regenerating.
6. Same as 5 after second removal of testes.
]
[Illustration:
T. H. MORGAN PLATE 6
JULIUS BIEN, N.Y.
Feathers of “light” colored Sebright (1, 2) that changed to
cock-feathers after castration (1ªa, 2ª).]
[Illustration:
T. H. MORGAN PLATE 7
JULIUS BIEN, N.Y.
Feathers of F₁ hen-feathered male before (1), and after (1ª) castration.
Feathers of a darker hen-feathered male before (2), and after (2ª)
castration.]
[Illustration:
T. H. MORGAN PLATE 8
JULIUS BIEN, N.Y.
Feathers from hen-feathered male Sebright (1, 2, 3, 4) that changed to
cock-feathered male (1ª, 2ª, 3ª, 4ª) after castration; and then began to
go back as the testes regenerated (1ᵇ, 2ᵇ, 3ᵇ, 4ᵇ); then changed again
to cock-feathering after castration (1ᶜ, 2ᶜ, 3ᶜ, 4ᶜ).]
[Illustration:
T. H. MORGAN PLATE 9
JULIUS BIEN, N.Y.
Feathers showing complete (1) or incomplete (2 and 3) change from
hen-feathering to cock-feathering (1ª, 2ª, 3ª) after castration.]
[Illustration:
T. H. MORGAN PLATE 10
JULIUS BIEN, N.Y.
Normal. 1, 2; transitional, 1ª, 2ª, and changed-over feathers, 2ᵇ, of
Sebright, 3, 4 and 5. Feathers from F₂ birds.]
FOOTNOTES:
[1] The expectation for 1 dominant and 1 recessive factor is so nearly
the same as for 1 dominant alone that for the numbers obtained no
difference between the two cases could be detected.
[2] There is one other bird, not given in the above list, that is
pure Sebright except that his legs are yellow. Until I find out by
further breeding of the Sebright stock whether yellow legs are present
in it, this case must remain doubtful. On the basis of a two factor
color-difference one Sebright (as to color) is expected in 16 birds,
and one in 64 on a three factor basis. Some Sebrights had been raised
along with the back cross, hence the possibility of contamination.
[3] Provided that the blue classification was based on the adult
plumage and not on down color.
[4] If the recessive mutation occurs first in the Z chromosome of an
egg of the female it will not appear in the next generation; then if
it has passed into a male, half his daughters will show it. The single
factor-pair involved is carried by the sex chromosomes ZZ.
[5] One may be either sex-linked or sex-limited so far as the evidence
goes.
[6] No mention is made by Baur that a heterozygous male instead of a
pure silver male was used, although the male is made heterozygous in
the formulæ.
[7] For activity and pugnacity in hummingbirds, see Tropical Nature,
pp. 130, 213.
[8] The Naturalist in La Plata, W. H. Hudson, London, 1892, pp. 269-270.
[9] Proceedings of the Zoological Society of London, 1885, p. 431,
Quelques remarques sur le dimorphisme sexuel. Jean Stolzmann.
[10] George W. and Elizabeth G. Peckham. Observations on Sexual
Selection in Spiders of the Family Attidæ. Nat. Hist. Soc. of
Wisconsin, Vol. I, 1889, pp, 46, 47.
[11] _Loddigesia mirabilis_ has the tail about three times as long
as the body. Similar modifications are found in the genera _Sappho_,
_Cynanthus_, _Lesbia_, _Stegnura_, _Discura_, _Gouldia_, _et al._
[12] Among the most remarkable of this wonderful family are the nine
species of coquettes (_Lophornis_), which have elongated feathers,
with metallic tips, springing from the sides of the neck; some have
also beautiful crests. (George W. and Elizabeth G. Peckham, Additional
Observations on Sexual Selection in Spiders of the Family Attidæ, Nat.
Hist. Soc. of Wisconsin, 1889, vol. I, pp. 141, 142.)
[13] Tropical Nature, p. 210. The italics are ours.
[14] A. H. Sturtevant, Experiments on Sex Recognition and the Problem
of Sexual Selection in _Drosophila_. Journ. Animal Behavior, Sept.-Oct.
1915, vol. 5, No. 5, pp. 352, 353.
[15] In the eland as well as in the reindeer, in which both sexes have
horns that begin in the latter at least to develop before the gonads
ripen, it is stated that castration does not prevent the development of
the horns in the male, but whether they are as large as in the normal
male is apparently not definitely stated.
[16] Yarrell also states that after the fallow buck has reached the
height of its maturity and has 6 prongs in its antler, removal of one
testis causes the next antler to have but 5 prongs.
[17] It might be supposed that this bird was really a cock which had
been changed for a hen; but the following facts put this matter beyond
a doubt: First, there was no other pyed pea-fowl in the country.
Secondly, the hen had knobs on her toes, which were the same after
her change. Thirdly, she was as small after the change as before,
therefore too small for a cock. Fourthly, she was a favorite bird, and
was generally fed by the lady, and used to come for her meat, which she
still continued to do after the change in the feathers.
[18] See the latter also for references to _Lacertilia_ and _Chelonia_.
[19] Carnegie Inst. Wash. Pub. No. 278, 1918.