606 FRANK A. HAYS 
number of the other 5th-service litters were born during ex- 
tremely hot weather when the mortality was very high even 
among the older animals. The 10th-service group shows a 
higher death rate than the Ist-service group. In all these cases 
the percentage of mortality during the first five days does not 
seem to depend upon the number of services that the male is 
required to make. 
Table 5 shows that there is very little consistency between the 
mortality percentages as revealed in the first part of the table 
and between the percentages of deaths that occurred between 
five and ninety days. The first five days is a very critical 
time in the life of the young rabbit and very slight exposure may 
bring disaster. When this period is over the deaths usually re- 
sult from bowel disorders or from septicaemia. Bowel disorders 
are most common during the very hot weather of summer in the 
stock, and it is very unfortunate that a large number of the ani- 
mals in the 5th-service groups should have been so attacked. 
The 10th-service progeny also show a higher death rate than the 
Ist-service progeny, even though these 10th-service litters were 
housed under more favorable conditions than were the majority 
of the Ist-service litters. The mortality percentage of the 15th- 
service offspring is the highest of any of the service groups dur- 
ing the first five days of life, but it falls below that of all other 
service groups between the age of five and ninety days. Practi- 
cally one-fourth of the 20th-service rabbits died between ‘the 
fifth and the ninetieth day of postnatal life. An outbreak of 
septicaemia happened to occur among a number of these litters. 
This being the case, we are inclined to believe that this sudden 
outbreak of disease rather than any inherent weakness of the 
progeny resulting from heavy sexual service of the sire is here 
operating to cause the high percentage of mortalities. 
6G. Relation of number of services made to sex of offspring . 
A study of the relation of sex of the offspring to the amount 
of sexual service the male is required to perform is important 
because such data will show if either male or female producing 
