DB} 
abnormal sex-limited transmission and sterility. 309 
sterility. If the sterility is due, directly or indirectly, to the 
failure of sex-limited transmission on the part of one of the 
parents, we should expect other cases in which there is an ex- 
ception to the normal sex-limited transmission to be sterile also, 
and this summer I have bred two specimens of this kind in 
tye moth Abraxas grossulariata. Usually the grossulariata 
female transmits the gross. character only to her sons, so that 
when mated with a lacticolor male (from which the gross. charac- 
ter is absent), the male offspring are gross., the females Jlact. 
I have had very rare exceptions to this rule in preceding years, 
but none in which I could entirely exclude the possibility that the 
gross. females were really wild females of which the larvae had 
accidentally been introduced with the food. This year, however, I 
have in one family from the mating gross. 2 x lact. f in addition to 
21 gross. males and 14 lact. females, two gross. females to which it 
is impossible to ascribe such an accidental origin, for they have 
peculiar features which I have only seen in the strain to which the 
family belongs. I intend to discuss elsewhere the importance of 
these exceptions to the normal sex-Jimited transmission; in 
the present connexion, the interesting fact about them is that 
hoth were quite sterile. Both paired normally; one laid no 
eggs at all, and the other laid only 22 eggs, none of which 
developed. Sterility in the strain to which they belong is not 
very tare; this summer, in 56 matings with females more or less 
related to the moths in question, 10 were nearly or quite sterile. 
On the other hand, I paired four normal sisters of the exceptional 
females, and all were fully fertile. It is thus not very probable 
that both the exceptional females should have been sterile, if the 
sterility had no connexion with their abnormal hereditary consti- 
tution. The facts, therefore, seem to indicate that when, by 
failure of sex-limited transmission, an individual arises which 
receives from one parent a character which it normally receives 
only from the other, that individual tends to be sterile. 
21—2 
