496 ORREN LLOYD-JONES AND F. A. HAYS 
lihood of pregnancies should a priori reduce in almost like degree 
the size of those litters which are produced. But table 7 does 
not by any means indicate such a regular and consistent decrease 
in size of litter. In fact, up to the 15th service there is no per- 
ceptible falling off in litter size whatever. It is possible of 
course to form hypotheses to account for this condition of affairs, 
but at this time we know of no sound basis on which this dis- 
crepancy between tables 6 and 7 may be satisfactorily dealt 
with. 
There exists considerable discussion, but so far as the writers 
know, no carefully controlled experimentation to the effect that 
in multiparous animals the male is without influence on litter 
size; the millions of sperm supplied by any ‘normal’ male at a 
single ejaculation will, it is said, be more than ample to impreg- 
nate the ova liberated. Our own work indicates that for rabbits 
there is at least one condition, 1.e., performing twenty services in a 
short time, under which ‘normal’ males may be unable to bring 
about complete development of the full quota of ova liberated 
by the female. It is not inconceivable that the reproductive 
system of supposedly and apparently ‘normal’ males may be 
chronically in a condition analogous to that brought about in 
this experiment by excessive sexual service. 
