510 A. H. STURTEVANT 
Pink & bM bM 
Black @ BM bm 
BMbM —black o& 30 
bMabmy—pinikas Ons 
black @ 4 
It is the last class of four black females which is of interest in 
this connection, and is inexplicable on the current scheme. I see 
only two explanations of this class—either the sire was, through 
some mistake, really black-eyed, which I mention only because 
it presents itself as a possible way out of the difficulty; or else, 
as I think probable, we have here an example of partial sex-linkage, 
B ordinarily being coupled with M. If this coupling be incom- 
plete, then black females are to be expected from the last mating, 
as the following analysis will show: 
Gametes of pink @ bM bM 
Gametes of black 9 BMbm (BmbM) 
BM bM —black &@ 
bm bM —pink 
(bM bM —pink @ ) 
(Bm bM —black ¢ ) 
This hypothesis could be easily tested. If itis correct, then the 
cross just discussed should, if large enough numbers be reared, 
produce as many pink males as black females. Furthermore, 
if these black females be bred to pink males, there should arise 
a race which would be dimorphic—black-eyed females and pink- 
eyed males—except for the occasional ‘crossing’ back of B, which 
would now be coupled with m, and m occurs only in the female. 
Such a relation, if it be shown to exist, would be highly interesting 
in its bearing upon the problem of secondary sexual characters. 
The third case which I have interpreted as partial sex-linkage 
is that of the moth Aglia tau reported by Standfuss (’96), and 
discussed by Castle (03). The variety lugens of this species 
is dominant to the type. Its gene may be designated L. My 
interpretation of this case is that L and M are associated in such 
degree that ‘crossing over’ occurs in about one-third, instead 
of the usual one-half of the cases. The analysis of the matings 
