4 INTERNAL SECRETIONS 



Not until we have built up a genetic system of sexual characters 

 on this basis will it be possible for us to approach the second 

 great problem, the investigation of the manner in which the 

 other parts of the organism influence the sexual gland and 

 through them the sexual characters. Meanwhile we must also 

 leave the question open as to whether the other endocrine 

 glands and parts of the organism influence the development of 

 the sexual characters directly, and if so, how this is effected. 

 We have so far tacitly assumed that the two sexes are 

 definitely distinguishable by morphological, physiological and 

 psychical characters, that male and female are, as it were, like 

 two opposite poles within the same species. But we know 

 that there are in reality transitions between ''male" and 

 "female," and what is still more important, that "male" and 

 "female" organs are not mutually exclusive even in the same 

 individual. Moreover, these matters must be taken into con- 

 sideration in discussing a genetic system of sexual characters. 



