[8] 
(op) 
nt 
EdmundB. Wilson: 
It is, however, also clear, that the factor represented by 
the Y-chromosome is not indispensable, for sex-produetion is not 
affected by its absence. In my later discussions, accordingly, I 
found it simpler to confine the statement to the quantitative mass- 
relation of the X-chromosomes, learing Y out of account. If, in 
cases where the female is homogametic, we assume simply that 
XX stands for the female condition and X for the male, the 
diffieulties mentioned under the first interpretation disappear. 
"In ordinary sexual reproduction all the unfertilized eggs 
should, after maturation, bear the male tendency, because one 
X-element is left in the egg after reduction. If capable of 
parthenogenesis with the reduced or haploid number of chromo- 
somes, such eggs should produce males (as appears to be the 
case in the bees and ants). If fertilized by a spermatozoon that 
contains this element, the egg produces a female because of the 
introduction, not of a dominant "female tendency‘ but of a second 
X-element.‘‘ (1909 e.) 
”Accepting this view, we may designate the female as the 
plus sex, the male as the minus. In current Mendelian terms, the 
female Protenor or Anasa is cytologically "homozygous‘, arising 
by the union of like plus gametes; while the male is ’"heterozygous'‘, 
arising by the union of a plus and a minus gamete, and produeing 
these two classes in equal numbers. To employ a more recent, 
and perhaps in this case preferable terminology, in respect to 
the X-element the female is of ’duplex‘ constitution, the male 
of ’simplex‘.““ (1910a.) 
These statements of course hold true whether a Y-chromo- 
some be present or absent, and are independent of any particular 
theory regarding the difference between this element and X. 
In my last ”Study‘‘ (1911) the question of the Y-chromosome is 
again taken up, and a view is adopted that is akin to one 
suggested by Stevens in 1906. This postulates a true quali- 
tative difference between X and Y, not merely one of degree of 
activity. Specifically, this view is that the XY pair of the male 
may be consideered to represent (or originally to have been) an 
ordinary pair of chromosomes (YY pair) with one member of 
which a specific ”X-chromatin‘ is associated. 
”The primary sexual differentiation is thus traceable to a 
eondition of plus or minus in this pair, accompanied by a corre- 
