630 



THE AMERICAN NATURALIST [Vol.L 



adduced evidences to show that females which have borne young 

 are heavier than unmated controls. Whether the effect of bear- 

 ing young is cumulative in such a way as to influence the corre- 

 lations in Captain Lloyd 's series is not yet evident. 



Taking these various factors into account, there seems little 

 ground for Moving that there is any material correlation be- 

 tween the fertility of a mammalian female and her measurable 

 somatic characters. 



There is an obvious physiological and morphogenetic interest 

 attaching to the correlations between the number of individuals 

 horn in a litter and the characteristics of these individuals. 



Consider first the correlations between number of pigs in the 

 litter and number of nipples, in swine. For Parker's 10 and Dul- 

 lard's data the values are: 



For males, r = .0810 ± .0121, 

 For females, r=.0324 ± .0124. 20 



These are numerically low, but both are positive, and may pos- 

 sibly be significant in comparison with their probable errors. 

 They may indicate morphogenetic relationships between the 

 vigor of the mother as indicated by the number of her young 

 and the characteristics of these young. 



These positive correlations for number per litter and number 

 of nipples are of interest in connection with the negative corre- 

 lation for number in the litter and mean weight of individuals 

 suggested many years ago by Minot, 21 who states that in guinea 

 pigs the size of the animals at birth depends to a considerable 

 degree upon the number of young in a litter: the larger the 



given data from which approximate- values of the correlation 



cence and Kejuvenatie-n. I. On the Weight of 



lies in the fact that his Tables VII and VIII do 



