HEREDITY 



white hairs on the under surface of the body 

 only. By inbreeding, a homozygous strain of 

 the silvered animals was soon obtained, one in 



43 



+ 2 



-2 



gen 



FIG. 41. Chart showing effects of selection in eight successive 

 generations upon the color-pattern of hooded rats. A, 

 average condition of the selected parents in the plus series; 

 B, average condition of their offspring. A 1 , average condi- 

 tion of the selected parents in the minus series; B 1 , average 

 condition of their offspring. 



which all the offspring were silvered to a 

 greater or less extent. Selection was now 

 directed toward two ends, (1) to secure ani- 

 mals which were free from spots of red or 

 white, a condition which was present in the 



122 



