6o 



Heredity and Eugenics 



new stock was at any other time introduced in either series, 

 the two remaining distinct at all times except in the second 

 generation. It will be observed that a change in the aver- 

 age grade of the parents is attended by a corresponding 

 change in the average of the offspring, and likewise in the 

 range of variation in the offspring. The amount of varia- 

 bility of the offspring is not materially affected by the 

 selection, but the average about which variation occurs is 

 steadily changed, as are also the limits of the range of 

 variation. 



TABLE I 



Results of Selection for Modification of the Color-Pattern of 



Hooded Rats 



The interesting feature of this experiment is the pro- 

 duction, as a result of selection, of wholly new grades, in 

 the narrow series of animals having less pigment than any 

 known type other than the albino; in the wide series, of 



