EFFECTS OF INBREEDING ON BODY WEIGHT 



37 



TABLE 15 



Showing the coefficients of variation, with their probable error, for the body weights 

 at different ages of the two series of inbred rats (seventh to the fifteenth generation 

 inclusive) 



were somewhat more variable in body weight than the males 

 during the early stages of development up to sixty days of age, 

 and that beyond this point the males were the more variable. 

 In each series, also, the maximum variability in body weight 

 came at the same age for both sexes: but this maximum was at 

 the sixty day period in the A series of inbreds and at the thirty 

 day period in the B series. The coefficients indicate, moreover, 

 that there was a pronounced tendency in each sex for the vari- 

 bility to diminish after the period of rapid growth was ended. 

 Guinea-pigs show a similar decrease in variability in body 

 weight with advancing age, as was noted by Minot ('91). 



The average coefficient for the male groups of the A series, 

 taking all ages together, was about two points higher than the 

 corresponding coefficient for the females of this series. This dif- 



