NATURAL SELECTION SINCE DARWIN 75 



fingers or hare lips would have long ago become the 

 specific characters of entire races. 



Observation shows on the contrary that frequency 

 of reversion to the normal type is in inverse ratio to 

 the degree of variation. Breeders and agriculturists 

 have noticed that, while it is relatively easy in the 

 first generation to make certain characters constant 

 through selection, the task becomes harder in the suc- 

 ceeding generations when the character seems to 

 reach the limits which have been assigned to it by 

 nature. Galton, a naturalist who gathered statistical 

 data as to variations and their laws, and who origi- 

 nated the new branch of biology known as biometrics 

 (application of statistical methods to biological 

 studies), formulated a law according to which when 

 parents diverge to a certain degree from the average 

 (from the "mode," in biometrical parlance) the off- 

 spring diverge in the same direction but to a lesser 

 degree; the result is that, after several generations, a 

 species, instead of engendering an entirely new spe- 

 cies reverts to the original average type. 



We must also note that in amphimixia, the mode 

 of reproduction which requires two parents for the 

 procreation of offspring, the characters inherited by 

 both sides become blended and the variation is gen- 

 erally attenuated in the first generation in which it 

 appears. 



