xn 



XI 



IX 



vin 



VII 



VI 



V 



IV 



II 



FIG. 31. Diagram showing the ineffectiveness of selection through 

 twelve generations within a homozygous strain in the case of 

 the Colorado potato-beetle (Leptinotarsa). In each genera- 

 tion extremely dark specimens were selected as the parents of 

 the succeeding generation but the progeny always swung back 

 to the type. After Tower. 



144 



