610 FRANK A. HAYS 
14. The high percentage of deaths of female progeny is largely 
due to the predominance of females to males in the litters. 
15. By no means thus far used has any inferiority of progeny 
from heavy sexual service been discovered. They are fully 
equal if not superior to progeny from very light service of male. 
DISCUSSION 
The amount of sexual service that the male performs has a 
marked effect upon the physical properties of his spermatozoa 
(Lloyd-Jones and Hays, ’17); the whole basis of this work is to 
discover if these effects are in any way made manifest in the 
offspring. 
Growth in body weight must be assumed to be due to a com- 
plex of stimuli acting upon every living cell of the organism. If 
it were possible to modify the contribution of growth stimuli 
from the male germ cell by extreme sexual use of the male, an 
effect should be produced upon every cell of the body in his 
offspring and a reduction of these stimuli would thus result in a 
decreased body growth. The sum total of the body increase in 
the offspring from the heavy service series is fully equal and 
even superior to the increase in the offspring in the light service 
groups. This apparent superiority has been attributed to vari- 
ous factors, largely environmental and possibly to superior male 
reproductive cell. After these factors are corrected for, which 
we have found impossible to do, we believe that the rate of growth 
in body weight would be identical in all five service groups. A 
study of body weight as reported here will only reveal the char- 
acter of the total population and will not reveal the occurrence 
of an occasional inferior individual. 
The coefficient of variability of litters, on the other hand, is 
valuable in that it will reveal the occasional inferior individual 
in the litter. If only a part of the offspring in the heavy serv- 
ice groups are inferior as far as rate of growth is concerned, 
there should be a greater coefficient of variability in the litters 
from heavy service than among the light service litters. No 
such evidence appears in our data, and this fact we feel warrants 
the assumption that not even a part of the offspring in the 
