656 THE PHYSIOLOGY OF REPRODUCTION 



sexual potency. But it has been shown that castration, while 

 tending in certain cases to favour the development of characters 

 belonging to the opposite sex, results frequently in a distinctive 

 sexual type, as the experiments of Sellheim and others have 

 shown. Moreover, in certain forms of life (e.g. insects) the 

 secondary sexual characters are developed independently of 

 the essential organs of reproduction (see p. 307), the sexual 

 characteristics of the different tissues, although clearly correlated 

 to a large extent in most individuals, being independent of one 

 another when once they have been laid down in embryonic life. 

 This fact is demonstrated by Crampton's experiment in grafting 

 the heads of caterpillars from individuals of one sex on to those 

 of the other sex. 



It would appear possible, therefore, that in exceptional in- 

 dividuals, whose sex has been assigned to them on account of 

 the presence of testicles or ovaries, the sexual complement is to 

 be found actually on their own side of the sexual line that is 

 to say, on the side on which they are reckoned, although in 

 reality they may belong to the other. 1 In the terms of 

 Weininger's hypothesis, such individuals would be regarded as 

 possessing more arrhenoplasm than thelyplasm (or conversely), 

 although the particular kind of plasma that predominates in 

 the soma is unrepresented in the organs of generation. 



Lastly, Weininger's theory helps to explain why it is that 

 transplantation of gonads on animals of the opposite sex is 

 usually attended by failure, a fact which has been noted by 

 Ribbert and others, including the present writer. The internal 

 secretions of the ovaries or testicles, on this view, are operative 

 only in an appropriate environment of thelyplasm or arrheno- 

 plasm, or, to speak physiologically, in the existence of a re- 

 sponsive metabolism, and without this their influence on the 

 organism is ineffective, even though they succeed in becoming 

 attached. 



In criticism of Weininger's morphological hypothesis, it 

 must be pointed out again that there is no real evidence that 

 any sort of character, whether sexual or otherwise, is at any 

 time definitely located in a special kind of material or plasma 

 (not even in the accessory chromosome, since this probably 

 1 Weininger, loc. cit. 



