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 formule so that maleness 
may not appear simply as the absence of one factor 
for femaleness. Thus, in such formule as FMFM 
(¢) and FMM (32) 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 
