126 EVOLUTION AND GENETICS 



left the same kind of corn has had more room to 

 develop and is taller. 



Darwin knew that if selection of particular kinds 

 of individuals of a population takes place the next 

 generation is affected. If the taller men of a com- 

 munity are selected, the average of their offspring 

 will be taller than the average of the former popula- 

 tion. If selection for tallness again takes place, still 

 taller men will on the average arise. If selection again 

 makes a choice, the process may continue {jig. 60) . 



Fig. go. — Curves showing (hyi)othetically) how 

 selection might be supposed to bring about pro- 

 gress in the direction of selection. {After Gold- 

 schmidt.) 



Now while we recognize that this statement con- 

 tains an imj^ortant truth, it has been found that it 

 contains only a part of the truth. Any one who re- 

 peats for himself this kind of selection experiment 

 will find that while the average class will often at 

 first change in the direction of selection, the pro- 

 cess slows down as a rule rather suddenly {fig. 61) . 

 He finds, moreover, that the limits of variability 

 are not necessarily transcended as the process con- 



