86 



THE NEXT GENERATION 



be different from the average size and shape of the first 

 group, and in general it is the average that shows itself in 

 the descendants of each new colony. 



32 in. 



FIRST GROUP 

 Average length of beaks in this group is two inches l 



SECOND GROUP 

 Average length of beaks in this group is two and one half inches * 



This, then, explains the short steps that sprang up, one 

 from the other, among the snails of Hawaii. There is an 

 extraordinary number of varieties and species, for two 

 reasons : 



1 The average is found by ad'ding all the lengths together and dividing 

 the sum by the number of beaks. 



