398 INTERNAL SECRETIONS 



gland on intersexuality in frogs has lately been discussed from 

 a general point of view by Witschi (1921) and by Crew (1921), 

 whose papers may be referred to here. The most important 

 points are the following. Though there is in frogs a great 

 variability as to the degree of intersexuality, it may be said that 

 somatic intersexuality corresponds to that of the gonad. All 

 transitions between female and male as to the development 

 of the ducts of Miiller and \No\ii have been observed, and it 

 can be stated that the Miillerian ducts are the better developed 

 the more the ovary is developed, and vice versa in regard to the 

 Wolffian ducts and the testicle. The ]\Iiillerian ducts of an 

 intersexual or a male individual are the better developed the 

 longer the gonads remained female, and the later the time at 

 which the gonad changed to maleness. There is a change of 

 somatic sex characters parallel to that of the gonads, but the 

 change of the former takes place somewhat later. If there is an 

 ovary only on one side, the Miillerian duct will be found reduced 

 on the other side, whereas the male pads and the seminal vesicle 

 are normally developed in the same individual on both sides, 

 notwithstanding that only one testicle is present. Witschi 

 concludes from these observations that there is a sex specific 

 dependence of the somatic sex characters upon the sex gland, 

 but that this dependence is not an endocrine one. This latter 

 conclusion is founded on Witschi's observations on asymmetrical 

 hermaphrodites. On the contrarj^, Crew concludes that ''the 

 mechanism by which the individual is thus transformed is one 

 which acts through the internal secretion of the gonads." 



In my view there is one weak point in Witschi's arguments. 

 The influence which the gonad has on such sex characters as 

 the excretory ducts need not necessarily be an endocrine one, 

 as we shall show in some detail in Chapter XI. But on the 

 other hand certain facts mentioned by Witschi are contrary 

 to his conclusion that there is no morphogenetic endocrine 

 influence of the sex glands on the sex characters, since in his 

 asymmetrical hermaphrodites there was at the same time a 

 symmetrical development of male sex characters, though the 

 testicle was present only on one side. When making these 

 objections against Witschi's conclusions, I do not say that 

 there is necessarily only an endocrine basis for intersexuality in 

 frogs. What I wish to point out is merely that the observations 

 available are not sufficient for drawing definite conclusions in 



