EFFECTS OF INBREEDING AND CROSSBREEDING. 21 



1906 

 /OO 



60 



1908 /9/0 1912 1914 1916 1918 1920 



^ 60 



20 









Fig. 1.— The percjentage born alive among the inbreds {A ) and controls (-B) in successive years 1906 to 1920. 

 Correction made for effect of size of litter by assigning weights of 1, 3, 4, and 2 to the averages for litters 

 of 1, 2, 3, and 4, respectively. 



1906 

 JOG 



/908 1910 1912 1914 1916 1918 1920 



60 



^ 60 



I 



iJi 40 



20 



I 



Fig. 2.-The percentage raised of those born alive. Inbreds {A ) and controls (S), 1906 to 1920. Corrected 

 for efiect of size of litter as in Figure 1. 



