DETERMINATION OF SEX DONCASTER. 485 



very modern times. Many of them do not concern the point at issue, 

 dealing as they do with possible factors which may influence the 

 sex of a given individual; for we have seen that, whatever the true 

 nature of sex may be, it is conceivable that the proportion of germ 

 cells bearing one or the other sex which come to maturity may 

 possibly be influenced by external conditions. To do justice to what 

 has been written on such subjects would require a book of consider- 

 able size and in the present paper is impossible. The object of 

 this account will have been fulfilled if it indicates the direction in 

 which recent work is leading and if it makes it clear that the prob- 

 abilities are overwhelmingly in favor of the idea that the determina- 

 tion of sex is not consequent on the accidental preponderance of one 

 or other of two nicely balanced tendencies, but is due to fixed and un- 

 alterable characters inherent in the germ cells. 



