598 FRANK A. HAYS 
weight of their offspring because it will bring to light occasional 
litters in which every individual is inferior. For example, table 
3 shows that there is not an occasional inferior individual in the 
advanced service progeny. This fact does not remove the pos- 
sibility of some entire litters being inferior because it is possible 
to conceive that at one time a male rabbit might sire an excep- 
tionally good litter on the 15th or the 20th service because of 
extra high reserve, but the majority of his progeny might be 
inferior in growth as entire litters. By table 4 we shall attempt 
to discover if litters as a whole are inclined to be more variable 
in any particular service group. 
Table 4 shows that at birth there is less variability in the 1st- 
service progeny than in any other progeny. This implies that 
the individual mean weight of the Ist-service litters more nearly 
represents the mean of every litter in the service group than is 
the case in any of the other four service groups. There appears 
to be little tendency for variability to increase as the amount of 
service increases as shown in the other four service groups at 
birth. 
Concerning the variability between litters at thirty days of 
age, practically the same relationship exists between the progeny 
of the different service groups as has been already noted in con- 
sidering the progeny at birth. The table shows us one additional 
fact at the thirty-day age; namely, that the greatest variability 
in weight during the ninety days of the observation exists at 
weaning time or thirty days. This fact is additional evidence 
that the nutrition furnished by the mother while suckling the 
young may vary in absolute amount or may be distributed in 
limited quantities because of the large number of individuals that 
she may suckle. 
At the age of ninety days there is a striking uniformity in the 
coefficients for all five service groups. Only in the case of the 
20th-service group is there any noticeable digression, and this is 
probably due to the small number of litters concerned. 
Table 4 as a whole does not in any way indicate that inferior 
litters exist more frequently in any one service group than in any 
other, and the fact has already been pointed out in connection 
