SEXUAL ACTIVITY OF MALE RABBITS 589 
Rares T T T al T T saat en oe u T =e T T toa 
nas CHarat NO XML | 
an Grano Averace Grown Coeves =} 
Act Service Groves 
= 
#70 | ——_—_—_ = 
» 
= 
x 
ig 
o 
- 
3£ 
2) 
iw 
Ss 
may not be made with absolute justice because, as will be shown 
later, the litters in the advanced service groups tend to be 
smaller. A rough comparison of all progeny may be made in 
this way, however. 
Charts 1 to 12, inclusive, present the results in a form that 
may be easily grasped by the reader, but there are a few points 
revealed by a study of these graphs that require some discussion. 
With but few exceptions, the 20th-service graph lies above all 
other graphs. This is a striking and surprising result and the 
question at once arises as to the cause of the almost uniform 
heavier birth weight and more rapid growth of the 15th- and 
20th-service litters compared with litters of the same size from 
less advanced services. The results are in direct contrast to 
what, according to the traditions of breeders, would be expected. 
On their face they actually show that the heavier the service of 
the male, the more thrifty the offspring. It seems best to here 
consider the possible factors that may play a part in causing the 
superiority of these advanced service litters over litters from the 
Ist, 5th, and 10th service. 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 25, NO. 2 
