SEX INHERITANCE 107 



ing, that the machinery of sex determination may be 

 upset is not an argument against the sex chromosome 

 theory. It is not a refutation of the factorial hy- 

 pothesis of sex determination, for in such a case there 

 would only be a substitution of an environmental 

 factor for a genetic one. Opponents and advocates 

 of the chromosome theory of sex determination have 

 often failed to realize that ^ ^factor for sex" is not 

 used in an absolute sense, but as the best known or 

 most usual factor-difference among any number of 

 possible theoretical ones; and in consequence the 

 identification of sex as a character with the factor 

 for sex determination has led to needless confusion. 

 If the factor for sex were identified with sex itself, 

 i.e., if it alone would produce sex, there would be of 

 course only one form of sex determination possible. 

 But, as no one maintains such an interpretation of sex 

 determination, this view can not be properly advanced 

 as an argument against the sex chromosome theory. 



