608 FRANK A. HAYS 
TABLE 7 
Sex as related to mortality. Percentage mortality of the sexes 
SERVICE 
PERIOD SEX: 
5th 10th 15th 20th 
BITS MivienteeyeRene ss. cic ss Sec wisgttdaces aoclaeks of 8.69 7.14 0 9.09 
9 6.85 | 11.90] 17.74] -9.09 
Between five and ninety days............| o& 6.52 8.93 9.09 | 27.27 
Q 12.33 | 15.47 | 11.29 | 24.24 
In table 6 we considered the relation of sexual service to the sex 
of the offspring and found that .a predominance of females to 
males is the rule in the heavy service groups. In table 7 we 
shall consider sex of the offspring dying before the close of the 
observation period at ninety days. | 
Table 7 shows that up to the 15th-service group there is a 
higher death rate among the female offspring than among the 
male offspring. In the 20th-service group, however, the fact 
will be noted that females are just as likely to survive as males 
for the first five days of postnatal life. Between the fifth and 
the ninetieth day there‘is a slightly lower death rate of females 
than males in the 20th-service group. These facts seem to 
indicate that in comparison with males of the same class, female 
offspring from the 20th-service are in respect of their ability so 
survive superior to ordinary offspring from the less advanced 
service groups. The fact still seems evident that these female 
offspring in the 20th-service group are slightly more likely to 
die than ordinary offspring. 
SUMMARY OF FACTS 
1. Body weight of the rabbit is a measure of growth that is 
subject to considerable variations largely brought about by slight 
changes in the environment. 
2. The rate of increase in body weight continues at a uniformly 
rapid rate for the first ninety days of the rabbit’s life. 
3. The factors that appear to govern the weight of the young 
at birth are age of mother, state of health of mother, weight of 
