File:Heredity and sex (1913) (14578211468).jpg

Identifier: hereditysex00morg (find matches)
Title: Heredity and sex
Year: 1913 (1910s)
Authors: Morgan, Thomas Hunt, 1866-1945
Subjects: Heredity Sex
Publisher: New York, N.Y. : Columbia University Press
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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Goodale also removed the ovary from very youngchicks. He found that the female developed thesecondary sexual plumage of the cock. How shall we interpret these cases ? It is clear thatthe female has the potentiality of producing the fullplumage of the male, but she does not do so as long asthe ovary is present. The ovary must therefore besupposed to prevent, or inhibit, the development ofsecondary sexual characters that appear therefore onlyin the male. The converse operation — the removal of the maleglands from the male — is an operation that is verycommon among poultry men. The birds grow largerand fatter. They are known as capons. In this case THE EFFECTS OF CASTRATION 143 the male assumes his full normal plumage with all ofhis secondary male sexual characters. It is said thatthe comb and wattles and to some extent the spurs areless developed in the capon than in the normal male.But aside from this it is quite certain that the de-velopment of the secondary sexual plumage in the
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Fig. 73. — Male and female Seabright. Note short neck feathers andincomplete tail cover in male. In the Seabright cock the sickle feathers onback at base of tail are like those of the hen. (After Reliable Poultry-Journal.) male is largely independent of the presence of the sexglands. The method of inheritance of the secondary sexualcharacters in birds has been little studied. Daven-port has reported one case, But I am not sure of his in-terpretation.^ I have begun to study the question byusing Seabright bantams, in which the male lacks some 1 Because it is not evident whether the secondary sexual char-acters as such are involved or only certain general features ofcoloration. 144 HEREDITY AND SEX of the secondary sexual characters of the domesticraces, notably the saddle feathers, as shown in Fig. 73. When a female Seabright was mated to a black-breasted game male the sons had the secondary sexualplumage of the father. In the second generation, however, some of the malesshowed imperf

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