WHAT DETERMINES SEX? Ill 



in the castrated male, without there being 

 much to show for it. It would be interesting 

 to experiment with some exceptional case, 

 such as the Red-necked Phalarope, where the 

 female bird looks the more masculine of the two. 



POSSIBLE INFLUENCE OF THE ENVIRONMENT 

 IN DETERMINING THE RELATIVE NUMBERS OF 

 MALE - PRODUCING AND FEMALE - PRODUCING 

 GERM-CELLS. Recent observations have gone 

 much against the view that the sex of the young 

 offspring can be affected by peculiar nurture. 

 It is possible, however, that nurtural condi- 

 tions, such as the nutrition of the parents, may 

 be influential at any earlier date, e. g. in deter- 

 mining the relative numbers of male-producing 

 or female-producing ova, or in determining 

 the percentage of survival of one kind or 

 the other, for there is often a struggle for 

 existence among germ-cells. We recall, for 

 instance, the green flies which produce females 

 all the summer through, but suddenly pro- 

 duce males on the advent of autumn. It may 

 be that the seasonal change, acting on the 

 nutritive condition of the maternal body, 

 brings about the production of ova that 

 develop into males. 



The careful experiments that Cuenot and 

 Schultze made on mice with a view of testing 

 whether altered nutrition affected the ordinary 

 proportion of males and females, gave no 

 support to that view. Schultze extended his 

 experiments over three generations ; but the 

 high feeding of grandparents, as well as 

 parents, did not seem to have any influence 

 on the proportion of the sexes among the 

 offspring. 



