338 HEREDITY AND ENVIRONMENT 



from the testes or the ovary, which stimulate or 

 inhibit the formation of these characters. If 

 the ovary is removed from a young hen she de- 

 velops the larger size, the more brilliant plum- 

 age and the peculiar comb, wattles and spurs 

 of the cock. These secondary sexual charac- 

 ters of the male are potential in the female 

 but are kept from developing or are inhibited 

 by the activity of the ovary. On the other 

 hand the castration of the young cock does not 

 prevent the development of most of the sec- 

 ondary sexual characters of the male. In the 

 case of mammals removal of the ovaries of a 

 young female or of the testes of a young male 

 does not lead to the development of the sec- 

 ondary sexual characters of the other sex, but 

 both sexes remain in a sexually undeveloped 

 or infantile condition, that is, the presence of 

 ovaries or testes serves as stimulus to call forth 

 the development of the secondary sexual char- 

 acters in mammals, and not as inhibitors to 

 prevent the development of the secondary 

 sexual characters of the opposite sex, as in the 

 female fowl. If bits of the ovary of a guinea- 

 pig are inserted under the skin of a young 



