SEXUAL ACTIVITY OF MALE RABBITS 609 
mother, weight of sire, character of food of mother, and num- 
ber of individuals born in the litter. 
4. The factors that govern the rate of postnatal growth of the 
young for the first ninety days are weight at birth, number in 
litter, milk supply furnished by the mother, and, after weaning, 
the character of the food supplied to the young and general 
character of the quarters. 
5. No inferiority in the offspring from the heavy service groups 
is revealed by comparing the body weights with those of the 
light service groups. 
6. The average litter coefficient of variability in body weight 
at birth at thirty days and at ninety days is no greater in the 
progeny in the heavy service groups than in the light service 
groups. Greater variability might be expected if a part of the 
offspring are made genetically inferior by inferiority of the male 
element in the advanced service groups. 
7. The service group coefficients of variability indicate greater 
variability in the weight of the general population than within 
the litters, but do not indicate that heavy service produces ‘weak’ 
litters. 
8. Body development seems to progress at the maximum rate 
during the first twenty days of postnatal life, after. which time 
there is a rather marked decline in the rate of increase in head 
length and breadth of ilial expanse. 
9. No inferiority in the offspring from the advanced services 
is revealed from a study of body growth by measurement. 
10. Offspring in the more advanced service groups do not 
show a significantly higher percentage of mortality during the 
first five days of life than do the offspring in the light service 
groups. 
11. A higher mortality does not seem to exist in offspring from 
the advanced service groups as compared with the light service 
groups between the ages of five and ninety days. 
12. Heavy sexual service of males gives a decrease in the 
proportion of male to female offspring that is very perceptible. 
13. Female offspring are to some degree more likely to suc- 
cumb than male offspring in all service groups except the 
twentieth. 
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