EFFECTS OF INBREEDING ON BODY WEIGHT 



93 



their probable error, were calculated from the data summarized 

 in tables 8, 9, and 10 according to the formulae given by Daven- 

 port ('14) ; they are shown in table 12. 



During early postnatal life, as the coefficients in table 12 

 show, the females in both inbred series were shghtly more vari- 

 able in body weight than were the males, but after thirty days 

 of age the males, as a rule, were the more variable. Variability 



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

 at different ages of the two series of inbred rats {sixteenth to the twenty- 

 fifth generations, inclusive) 



was at its maximum for both sexes at the sixty-day period, and 

 then tended to decrease with advancing age for some time. In 

 table 12 the average coefficient for the male group in each of the 

 two inbred series, taking all ages together, exceeds that for the 

 corresponding group of females by over two points. Since this 

 difference is over three times the probable error, it is sufficiently 

 large to indicate that the males had a greater range of vari- 



