SEX INHERITANCE 95 



the case of some other characters, however, it is 

 conceivable that the sex factors co-operate in their 

 production, and yet have the same effect whether 

 present in single or double amount. Such characters 

 would not be sex limited. 



As in the case of sex limited characters, so in the 

 case of sex itself there must be many factors in the 

 fertilized egg that are as essential to the development 

 of sex as are the sex factors themselves, but as they 

 are distributed to all individuals alike, they are not 

 thought of as differentiators, but as forming the 

 chemical background on which the single or the 

 double amount of the sex factor gives its result. It 

 is quite conceivable that one or more of these other 

 factors might so change that the sex differentiators 

 would become inoperative or even change so that 

 these other factors themselves become the differen- 

 tiators that determine sex. 



The environment — the outer world — is also one of 

 the components that enters into the development of 

 every individual. A specific environment is one of 

 the conditions of development. Why then, it may 

 be asked, may not the environment turn the scale 

 and determine sex? As a general proposition this 

 must be acceded to at once — it is entirely a matter of 

 proof. If there is an internal mechanism to de- 

 termine sex in a normal environment it is quite con- 

 ceivable that it might be supplanted in a new world. 

 It is a question of evidence as to how often, if ever, 

 this occurs. It is furthermore quite conceivable that 

 some animals have no internal mechanism to regulate 



