90 INFLUENCE OF HORMONES 



life of the individual. According to Mendelism the 

 structure and development of each part of the soma 

 is due to the constitution of the chromosomes of 

 the nuclei in that part. The effects of castration 

 show that the development of certain characters is 

 greatly influenced in some way by the presence of 

 the testes in a distant part of the body. The 

 Mendelians used to say it was impossible to believe in 

 the heredity of somatic modifications due to external 

 conditions, because it was impossible to conceive of 

 any means by which such modifications could affect 

 the constitution of the chromosomes in the gametes 

 within the modified body. It would have been just 

 as logical to deny the proved effects of castration, 

 because it was impossible to conceive of any means 

 by which the testes could affect the development of a 

 distant part of the body. 



But this is not all. The supposed fact that female 

 secondary characters in Vertebrates are absent in the 

 male is completely disproved for Mammals by the 

 presence of rudimentary mammary glands in the 

 male. It is true that secondary sex-characters are 

 usually positive in the male, while those of the 

 female are apparently negative, but in tlie case of 

 the mammary glands the opposite is the case. There 

 is no room for doubt that the mammary glands are 

 an essentially female somatic sex-character, not only 

 in their function but in the relation between the 

 periodicity of that function and those of the 

 ovaries and uterus, and it is equally certain from 

 their presence in rudimentary condition in the 

 male that they are not absent from the male 

 constitution. 



