may exert a gametocidal effect on the ova. A third pos- 
sibility was that eggs might have been fertilized normally 
ke pee pre-oviposital embryonic death which was not 
etected. 
A final instance where factors in the oviduct might 
inhibit the fertilizing capacity of sperm is illustrated in 
recent work of Grigg and Skaller (1958). In a flock of 350 hens, 
they found three that were repeatedly sterile on artificial 
insemination. When these were inseminated intraperitoneally, 
90% of their eggs were fertile. They considered that the block 
to normal fertilization could have been due to failure of the 
active mechanism of the oviduct in transporting sperm, or to 
an exaggeration of the restrictive function of the utero-«= 
vaginal junction. Since this study was completed, the authors 
have adopted a new insemination technique, depositing semen near 
the utero=vaginal junction, and have found no hens to be sterile 
&®s a result. They consider this as evidence in favor of the 
idea of super-restriction of the utero-vaginal junction caus= 
ing sterility, and hence an example of inhibition of fertility 
attributable to adverse conditions in the oviducal environment. 
c) Control of sex. 
Positive control of sex has not yet been obtained in 
either mammals or birds. Perhaps such control would be easier 
to obtain in mammals since the male is the heterogametic sex, 
having both X=bearing and Y-bearing sperm; by eliminating one 
kind of sperm, presumably only offspring of one sex would be 
produced following insemination; the factor making such control 
in mammals easier being that the sperm are readily available 
for manipulation. 
The situation in birds is made somewhat more dife 
ficult because the female is the heterogametic sex, males having 
no part in determining gender of offspring. Thus, to achieve 
control of the sex of progeny, a means must be found to elim-= 
inate either X=bearing or Y-bearing (or O-bearing) ova before 
fertilization. 
One possibility that comes to mind is the use of the 
antigen-antibody phenomenon. Theoretically, it might be pose 
sible to immunize males against the Y= or O=-chromosome; upon 
insemination, the X=-bearing sperm would react against Y-bearing 
ova with resultant infertility, but the sperm would unite readily 
with the X=bearing ova; the end result would be production of 
males only, but unfortunately the fertility of eggs so treated 
would be less than 50%. McCartney (1923) was able to inhibit 
fertility by injecting rooster sperm into laying hens; the period 
of infertility lasted from 12 to 67 days after injection. 
Lamoreux (1940) was unable to repeat these results. No doubt, 
present techniques will require considerable refinement before 
this theory of artificial control of sex in birds could be 
tested experimentally. 
14 
