EFFECTS OF INBREEDING AND CROSSBREEDING. 



21 



1906 



too 



80 



!> 60 



20 



1908 /9I0 1912 1914 1916 1918 1920 





Fig. 1.— The percentage born alive among the inbreds (^i) and controls (£) 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. 



/906 /908 1910 I9J2 1914 1916 1916 1920 



/OO 





80 



^ 60 



% 



20 



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

 for effect of size of litter as in Figure 1. 



