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 inchvidual men are due in 

 part to heredity, in part to the environment 



-3(5 *2d -d +d *2d +3(5 



Fig. 74. Curve of probability. (After Johannseii.) 



