150 



THEORY OF EVOLUTION 



in whic'li they have developed. This is a famil- 

 iar fact of almost eveiy-day observation. It 

 is well shown in the following example. In 

 figure 76 the two boys and the two varieties of 



10 1 



22 25 26 



17 11 17 1 4 1 



:!n 4:11 5,0 5:1 S:2 3:3 5:4 S:S 3:0 5:7 5:8 5:9 5:10 3:11 6:0 6:1 <i:2 



Fig. 75. Students arranged according to size. (After 

 Blakeslee.) 



corn, which they are holding, differ in height. 

 The pedigrees of the boys (fig. 77) make it 

 probable that their height is largely inherited 

 and the two races of corn are known to belong 

 to a tall and a short race respective^. Here, 

 then, the chief effect or difference is due to 

 heredit3^ On the other hand, if individuals of 

 the same race develop in a favorable environ- 

 ment the result is different from the develop- 



