EFFECTS OF INBREEDING AND CROSSBREEDING. 27 



1906 /SOS /SIO /Sia 1914 /9/6 19/6 1920 



^ 2 



\ 







« 



% 

 ■0 » 



* 

 ». 









^^ 





V 







'*x 



» 

 1 



B 

 A 











^ 



V 



^ 



































































Fig. 8.— The average size of litter. Inbreds {A ) and controls (B), 1906 to 1920. 



1906 1908 /9/0 1912 /9M /9/6 /9/6 1920 

 5 



k 

 ^ 2 



I 



/ 



I' 



Fig. 9.— The average number of litters produced per year by mature matings. Inbreds (^ ) and controls 



(£), 1906 to 1920. 



