SEXUAL HORMONES AND MORPHOGENESIS 453 



D. EVOLVED CHARACTERS OF THE ASEXUAL 

 EMBRYONIC SOMA. 



Besides persistence of characters after castration due to 

 former fixation there is still another kind of persistence to 

 which this explanation does not apply. Instances of such a 

 persistence of characters are the plumage and the spurs of the 

 capon. Feminization experiments with castrated cocks supply 

 evidence that these characters can be changed by an ovarian 

 graft; there is a fixation of plumage only up to the next moult. 

 These persistent characters in the cock develop independently 

 of sexual hormones, but they may be considered as the result 

 of the development of characters of an asexual soma common to 

 both sexes. The fact that certain sex characters are really 

 independent of sexual hormones is not contrary to our theory 

 of an asexual embryonic soma. There is no need to explain 

 persistence of certain sex characters by the assumption that they 

 are already present as such in the embryo, for the persistence is due 

 rather to the fact that the characters of the asexual embryonic soma 

 are not influenced during their development by the hormones of one 

 sex, but are changed by those of the opposite sex. 



As already mentioned, Pezard and Goodale were the first 

 to make an assumption of this kind. Later on Goodale (1918) 

 changed his original view somewhat after observing certain 

 new facts. He found that the spurs may be well developed in 

 castrated hens even when there is afterwards a regeneration 

 of the ovary, and that in spite of this organ they may even 

 continue to grow. In the feminization experiments spurs 

 developed, though the plumage was a female one. To explain 

 these results Goodale (1918, p. 391) assumed that the germinal 

 factors in the various individuals differ from one another; he 

 suggested further that additional germinal factors may be 

 present, owing to which the reaction to sexual hormones or to 

 the removal of the latter may become modified. This assump- 

 tion is not necessary, for the variability as observed by Goodale 

 can be explained on our theory that the sensitiveness of a given 

 tissue to sex hormones is a function of time. 



The question here discussed seems to be of great importance 

 also in connection with the theory of intersexuality in mammals. 

 It seems likely, as I have pointed out already in Chapter IX., 



