SEXUAL ACTIVITY OF MALE RABBITS 605 
TABLE 5 
Percentage mortality in offspring during the first five days of life and between the 
fifth and the ninetieth day of life 
SERVICE 
ist + 5th | toth | 15th | 20th 
Numberof animals |borniess.... sites. alee 180 119 /|139 84 77 
Number dying first five days.................. 16 15 16 11 7 
Rericent dying first five days:....4.+...0..04- 8.89) 12.61} 11.51) 13.09) 9.09 
Number dying between 5 and 90 daa ,:| 2 36 17 9 19 
Per cent dying between 5 and 90 fee rasta aracrene 11.67| 30.25) 12.23) 10.71) 24.68 
Summarizing the results of the measurement studies, we note 
that there is very close proximity of the graphs for the different 
service groups. This points very strikingly to the probable fact 
that heavy service of males has no effect upon the growth of their 
offspring in the length of head and in the breadth of ilial expanse. 
In table 5 the progeny are grouped by services and the num- 
ber and the percentage mortality is given for each service group. 
Under the row marked ‘‘Number dying first five days” are in- 
cluded all animals dead at birth as well as those that died dur- 
ing the first five days of life. The other row of the table in- 
cludes only animals actually dying between the fifth and the 
ninetieth day of postnatal life. 
The percentage of mortality during the first five days shows 
a slight increase as the number of services increases up to the 
15th-service group. Comparing the Ist-service group with the 
20th-service group, we note that the percentage mortality in the 
first five days is practically the same in both groups. Since the 
environment has been more favorable for the 20th-service litters 
than for the 1st-service litters, as previously pointed out, there 
is no indication that twenty copulations by a male do in any way 
tend to reduce the percentage of his progeny that will survive the 
first five days of postnatal life. The table shows practically the 
same percentage of mortality during the first five days in both the 
5th- and the 15th-service groups. The explanation for the 
rather high percentage of mortality in the 5th-service group is 
that two litters were destroyed outright by the mother and a 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 25, NO. 2 
