122 



EVOLUTION AND GENETICS 



of the beans, will appear as shown in figure 54. An 

 imaginary line running over the tops of the piles 

 will give a curve (fig, 55) that corresponds to the 

 curve of probability (fig. 56). 



Fig. 54. — Beans put into cylin- 

 ders according to size of beans. 

 The cylinders are arranged ac- 

 cording to the size of the con- 

 tained beans. (After DeVries.) 



If we stand men in lines according to their height 

 we get a similar arrangement. 



The differences in size shown by the individual 

 beans or by the individual men are due in part to 

 heredity, in part to the environment in which they 

 have developed. This is a familiar fact of almost 

 every-day observation. It is well shown in the fol- 



