294 



ROBERT M. YERKES 



TABLE 5 

 Summary of Results for First Generation Hybrids, P, (Wide X Wild) 



6F, 



females 



43 



40-46 

 da. 



4.00 



3-5 



Distribution of rats in 

 grades 0-5. 



4. 







1 

 

 

 2 

 3 



2.5 



2 

 

 



1 

 3 

 



3.33 



4.33 





 

 



2 

 



4 



2.83 







•j 







1 



3 

 



3.67 



3.83 





 

 2 

 

 1 

 3 



2.5 







1 

 1 

 4 

 

 



3.17 





 

 2 



1 

 3 

 



rats. There is no very marked constant difference for the sex 

 groups. The modal grade ranges from o to 4. It is most fre- 

 quently either 2 or 3. This apparently indicates that savage- 

 ness, wildness, and timidity are of lower grade development in 

 the second generation than in the first generation of wide by 

 wild individuals. 



Finally, in table 7 are presented the results for the F t as 

 contrasted with the F 2 narrow by wild hybrids, the sex groups 

 having been combined. In this table, the averages for the 

 first test alone are given. This test appears to be in all respects 

 the most reliable measurement of the several traits. As ap- 

 pears, the first generation hybrids approximate the average 

 grade of 4 in savageness, wildness, and timidity, whereas the 

 second generation hybrids approximate the average grade of 2. 

 The modal grade for the first generation individuals is 5 in the 

 case of all three traits. For the second generation individuals 

 it is o in the case of savageness and 2 in the cases of wildness 

 and timidity. 



