EFFECTS OF INBREEDING AND CROSSBREEDING. 



11 



crossbreeding experiment is shown in Table 3 by percentages. These 

 percentages can be applied to the differences between each inbred 

 family and the total inbred stock as shown in Table 2 in order to iind 

 the extent to which the ancestry of the various crossbreeding experi- 

 ments was above or below the average. 



Table 4. — The estmiated superiority {-\-) or inferiority ( — ) of the inbred ancestors of the 

 a'ossbreds to the total inbred stock. 



[ The figures are based on the percentages given in Table 2 and may be compared with the actual superiority 

 of the crossbreds over the inbreds as shown in that table.] 



Experi- 

 ment. 





Pern 







Per 

 cent 

 born 

 aUve. 



cent 

 of 

 those 

 born 

 alive. 



Per 



cent 



raised. 



Birth 

 weight 

 (total). 



+0.6 



-1.0 



-0.8 



0.0 



-0.2 



-0.9 



-1.3 



+0.1 



+0.1 



-1.0 



-1.0 



-0.7 



-0.6 



-1.1 



-1.5 



+ 1.0 



+0.4 



-0.5 



-0.2 



+0.3 



0.0 



-0.8 



-0.9 



-1.5 



+1.1 



-1.9 



-1.2 



+0.9 



+0.8 



-1.8 



-1.4 



+ 1.0 



+0.8 



-1.6 



-1.2 



+0.5 



+1.1 



-2.1 



-1.4 



+0.5 



Birth 

 weight 



of 

 those 

 raised. 





Weight 



Size 



Litters 



Young 



Gain. 



at 33 



of 



per 



per 





days. 



litter. 



year. 



year. 



-0.6 



-0.5 



-0.4 



-3.3 



-3.7 



+0.3 



+0.3 



+0.4 



-2.0 



-1.6 



+0.1 



-0.1 



+0.6 



-0.3 



+0.3 



+3.7 



+ 2.9 



+ 1.4 



+3.9 



+5.2 



+2.3 



+1.5 



+ 1.0 



+3.0 



+4.1 



-2.2 



-1.8 



-0.2 



-0.3 



-0.6 



+2.1 



+ 1.5 



+0.5 



-5.5 



-4.9 



+2.6 



+2.0 



+1.1 



-5.7 



-4.6 



+1.2 



+0.9 



+0.4 



-5.0 



-4.6 



-0.3 



-0.2 



-0.8 



-7.6 



-8.3 



Young 



raised 



per 



year. 



CO: 



CA: 



Sire... 

 Dam. . 



AC: 



Sire.... 

 Dam.. . 



CC: 



Sire... 

 Dam. . 



CI. 

 C2. 



Sire... 

 Dam. . 



-0.4 

 +0.4 



-0.3 

 +1.9 



+0.4 

 -1.2 



+or6 



+1.0 

 +0.3 

 -0.1 



- 4.9 



- 3.3 



- 1.2 

 + 3.1 



+ 3.0 



- 1.6 



- 7.4 

 -7.4 



- 6.7 

 -10.5 



The results are shown in Table 4. It will be seen that while the 

 ancestors of the crossbreds were slightly above the average in some 

 respects, as in weight and percentage born alive, in other respects 

 they were below the average, notably in frequency of litter and the 

 characteristics which depend on it. 



In all important cases the corrections which might be made are 

 small compared with the actual differences among the experiments. 

 It is clear that these differences are not due to selection of superior 

 inbred families in making the crosses. 



In the case of the selection experiments CG and CL, the most 

 important consideration relative to ancestry is the degree to which 

 they were derived from different crossbreeding experiments. This 

 is shown in Table 5. 



Table 5. — The origin of the inales and females used in experiments CL and CG, in per- 

 centages. 



[Each mating weighted by the number of litters produced through 1919.] 



Experiment. 



CL. 



CG. 



■Experiment. 



CL. 



CG. 



Sire. 



Dam. 



Sire. 



Dam. 



Sire. 



Dam. 



Sire. 



Dam. 



Inbred 



5.2 

 9.0 

 33.6 

 3.7 

 2.2 



4.5 





 32.1 

 11.9 











3.0 

 5.9 

 26.7 

 7.9 



1.0 



9.4 



20.8 



21.8 







AC. 



12.7 

 15.7 

 17.9 

 



16.4 

 16.4 

 18.7 

 



1.5 

 18.8 





 36.1 



11.4 



02 



cc 



12.9 



Cl 



CL 







CO 



CG 



22.8 



CA 







