612 FRANK A. HAYS 
female offspring in multiparous animals at birth is slightly less 
than that of the males. If this is true for the rabbit, it may 
render the females less able to compete with the male offspring 
for nourishment during their early life when food supply is of 
such vital importance in determining the survival of the young. 
The fact that the great majority of the offspring dying in early 
life have been females seems to warrant the assumption that 
females are actually less able to compete with the males during 
the early part of life. The data do not justify the conclusion 
that there is any higher rate of mortality in the advanced service 
groups than in the lighter service groups after the first five days 
of postnatal life. If inferiority of offspring exists in the advanced 
service groups because of the predominance of females, which we 
may assume under all ordinary conditions are less able to survive 
than males, it is apparent that no real inferiority exists, but 
that the mortality is greater because the percentage of females 
is greater in the heavy service groups. 
In conclusion, it may be noted 1) that the methods used for 
measuring the character of offspring from different degrees of 
sexual service of sires fail to show that any inferiority of the 
offspring can be induced by using a male excessively; 2) that the 
male in heavy sexual service furnishes germ cells that are fully 
the equal in their contribution to his offspring of those elaborated 
by a male in very moderate sexual service. 
ACKNOWLEDGMENTS 
The writer wishes to express his high appreciation to Dr. 
Orren Lloyd-Jones for his constant codperation and helpful ad- 
vice, to Dr. H. 8S. Murphey for assistance in making a study of 
the male and female genitalia, and to Prof. G. M. Turpin and 
Prof. H. D. Hughes for furnishing quarters for this work for a 
time. 
