EFFECTS OF INBREEDING ON BODY WEIGHT 53 



were somewhat heavier at all ages than the animals of the A 

 series. 



5. The males belonging in the seventh to the ninth generations 

 of the two inbred series greatly exceeded the males of the first six 

 inbred generations in body size, and they were, as a rule, much 

 heavier, at all ages, than the males of the subsequent generations 

 (fig. 6). 



6. The females belonging in the first six generations of the two 

 inbred series were considerably smaller, at all ages, than the 

 females of the subsequent generations. Adult females of the 

 seventh to the ninth inbred generations were slightly larger 

 than the females of the later generations (fig. 7). 



7. The unusual size of the intlividuals in the seventh to the 

 ninth inbred generations was probably due, in great part, to the 

 stimulus given to the growth impulse by favorable nutritive 

 conditions following a prolonged period of semi-starvation. 



8. Inbred' males belonging in the seventh to the fifteenth gen- 

 eration inclusive were heavier at all ages than stock albinos. 

 In the adult state the inbred males were, on the average, 18 per 

 cent heavier than the general run of stock albinos and, about 12 

 per cent heavier than males from a selected stock series reared 

 under the same environmental condition (fig. 11). 



9. Inbred females were, as a rule, slightly heavier at any 

 given age than the females of the control series, but the differ- 

 ence between the two groups was much less than in the case of 

 the males. At the 365 day period the average body weight of the 

 inbred females was 3.7 per cent greater than that of the stock 

 females (fig. 12). 



10. Inbred males were more variable in body weight than 

 inbred females, the maximum variability for both sexes coming 

 before the animals were two months old. These results agree 

 with the findings for stock albinos as determined by the inves- 

 tigations of Jackson and of King. 



11. The males of the A series of inbreds were slightly more 

 variable in body weight than the males of the B series, but the 

 females of the two series showed practically the same variability 

 in body weight at corresponding age periods (table 15). 



