THEORY OF EVOLUTION 149 



Fig. 73. A curve resulting from arrangement of beans 

 according to size. (After de Vries.) 



The differences in size shown by the individ- 

 ual beans or by the individual men are due in 

 part to heredity, in part to the environment 



-3d *2<J -d *6 



Fig. 74. Curve of probability. 



*2(5 



♦3(3 



