SEXUAL HORMONES AND MORPHOGENESIS 443 



position on experimental work, came to conclusions similar to 

 mine. 



Zawadowsky (1922), who has performed a great many 

 experiments on fowls, also came to the conclusion that the 

 soma of the male and female is essentially identical, and that 

 sexual differentiation of the soma is caused by the influence 

 of specific sex hormones. He likewise speaks of an asexual 

 type which develops after removal of the sex glands. The 

 term '^equipotentiality of the soma," which is also used by 

 Zawadowsky, seems to me more convenient, as it leaves the 

 door open for adopting our view in regard to possible new facts 

 which might not conform wholly with the original and more 

 radical meaning implied by the term " identity." Zawadowsky 

 mentions some facts which are opposed to the idea of an 

 absolute identity of male and female soma; absence of spurs 

 in castrated female pheasants may be taken as an example. 

 But on the other hand in every such case the question must be 

 put as to how far the deviation from the common neutral or 

 asexual type after castration is caused by the removal of the 

 sex glands having been performed late. We shall discuss this 

 question again below. 



Zawadowsky has drawn similar conclusions as to the existence 

 of an identical soma from observations made on the results of 

 castration on mammals. In the antelope Portax pictus the 

 grey hair of the male is transformed more or less into the 

 brown hair characteristic of the female; the transformation 

 takes place at the first moult after castration. He made 

 similar observations about other species, fully confirming the 

 view developed by Tandler and his fellow workers many years 

 ago. 



For amphibians, Aron, as well as Champy, who made 

 detailed investigations as to the dependence of the sex characters 

 on the sex gland, have accepted the hypothesis of the asexuality 

 of the soma. Aron (1922) says that the male and female 

 triton are morphologically identical except in the gonads: 

 " Whereas the soma apparently remains for a longer or shorter 

 time asexual, the gonad is differentiated very early and without 

 doubt is fixed from the beginning of development. At a 

 different time, which varies according to the classes and species 

 of vertebrates, the testicle most likely becomes, by inter- 

 mediation of an endocrine tissue, the starting point of the 



