THE HORMONE THEORY 157 



The left and larger gonad had a quite similar 

 structure, but at its lower end were found two ova 

 enclosed within a follicular epithelium. 



With regard to the last case it is to be remarked 

 that though the gonad on the right side was entirely 

 male, there was no unilateral development of male 

 characters. With regard to the other two cases it 

 must be pointed out (1) that the difference between 

 the two somatic sex-characters on the two sides is 

 chiefly a difference of colour, except the difference in 

 the spurs in Bond's pheasant ; (2) that the evidence 

 already cited shows that in fowls castration does not 

 prevent the development of the colour and form 

 of the male plumage, nor of the spurs : that in 

 drakes, although castration does not seem to have 

 been carried out on young specimens before the male 

 plumage was developed, when performed on the 

 mature bird it prevents the eclipse, and does not 

 cause the male to resemble the hen. Castration, 

 then, tends to prove that in Birds the development 

 of the male characters is not so closely dependent on 

 the stimulation of testicular hormone as in Mammals. 

 The characters must therefore be developed by 

 heredity in the soma, which impHes that the soma 

 must itself be differentiated in the two sexes. The 

 development must therefore be more in the natm'c 

 of gametic coupling. It does not follow that the 

 primary sex-character or the somatic characters are 

 exclusive in either sex. We may suppose that the 

 zygote contains both sexes, one or other of which is 

 dominant, and that dominance of one primary sex 

 involves dominance of the corresponding sexual 

 characters. This does not, however, agree with the 

 result of removal of the ovaries in ducks, for this 



