140 Life and Death, Heredity and Evolution 



equally cases in which by any physiological test that can 

 be applied, there is no diversity of sex. 



The only doctrine of sex diversity that appears to offer 

 possibilities of general application is one that holds, not 

 that there is always a definite positive characteristic 'for 

 each sex, but only that there is some relative difference be- 

 tween the two mates, one of them being somewhat more 

 developed in a certain direction than the other. It would 

 not be inconsistent, on this view, if a given individual or 

 cell or chromosome could play the part of male in some 

 matings ; of female in others, depending on the relative de- 

 velopment of the two mates. But such a doctrine is cer- 

 tainly not established; and for the mating of the chromo- 

 somes it has not a particle of evidence. 



It is most important not to commit the error common in 

 evolutionary thought, of identifying the question of the 

 primitive nature of a phenomenon with that of its physio- 

 logical significance where it is developed in a marked degree. 

 The question whether all organisms have sex has little to do 

 with the question as to what the nature and results of sex 

 are, in organisms that are divided into two sexes. In such 

 organisms in man for example the fundamental chemical 

 processes that make up life are in the two sexes diverse in 

 every cell of the body, for the nuclei on which these processes 

 depend are diverse. There is no ground therefore for sup- 

 posing that the characteristic differences in the activities of 

 the two sexes are mere matters of different education or en- 

 vironment. 



