92 SEX INHERITANCE 



Since genetics has at present nothing to offer that, 

 will decide the question as to whether another set of 

 sex differentiators is present, or whether the same 

 differentiators with a different setting are involved 

 in these two cases, discussion is quite certain to be 

 futile. 



It may seem inconsistent to use the name of the 

 chromosome as the symbol for the sex factor when 

 dealing with the inheritance of sex, while in all other 

 cases a factor representing a point in the chromosome 

 is used to designate the special character under con- 

 sideration. No doubt with this idea in mind, several 

 writers have followed the practice of indicating the 

 sex factor by a significant letter, such as F for female- 

 ness and M for maleness. As the use of such letters 

 often involves a question of interpretation, a brief 

 consideration may be given to this matter. In the 

 discussion that follows reference is made always to 

 the Drosophila type, but exactly the same arguments 

 apply to the Abraxas type. 



1. It has been suggested, for example, that a factor 

 for the male be added to the formulae so that maleness 

 may not appear simply as the absence of one factor 

 for femaleness. Thus, in such formula as FMFM 

 ( $ ) and FMM ( $ ) the factor for maleness is added 

 to indicate that when a single amount of F is present 

 the male factors produce the male. But since M's 

 are distributed everywhere, the formula is little more 

 than a concession to male vanity, for M is not here 

 a differentiator. Moreover, the use of the letters 

 MM is here unjustifiable because there is no ground 



