THEORY OF EVOLUTION 157 



If I have made several statements here that 

 appear dogmatic let me now attempt to justify 

 them, or at least give the evidence which seems 

 to me to make them prohahle. 



The work of the Danish botanist, Johannsen, 

 lias given us the most carefully analyzed case 

 of selection that has ever been obtained. There 

 are, moreover, special reasons why the mater- 

 ial that he used is better suited to give definite 

 information than any other so far studied. 

 Joliannsen worked with the common bean, 

 weighing tlie seeds or else measuring them. 

 These beans if taken from many plants at ran- 

 dom give the typical curve of probability (fig. 

 74) . The plant multiplies by self-fertilization. 

 Taking advantage of this fact Johannsen kept 

 the seeds of each plant separate from the 

 others, and raised from them a new generation. 

 When curves were made from these new groups 

 it was found that some of them had different 

 modes from tliat of the original general popula- 

 tion (fig. 81 A-E, bottom group). They 

 are shown in the upper groups (A, B, C, D, 

 E) . But do not understand me to say that the 

 offspring of each bean gave a different mode. 



