ECONOMICAL 



147 



It does not matter much to him whether the colour 

 of a pea flower is purple or pink or white. But it 

 does matter whether the plant bears rather larger 

 seeds than usual, or rather more of them. Even a 

 small difference when multiplied by the size of the 

 crop will effect a considerable difference in the profit. 

 It is the general experience of seedsmen and others 

 that differences of this nature are often capable of 

 being developed up to a certain point by a process 



4 6 8 xo 12 14 1 6 18 20 

 Weight of individual seeds 



FIG. 30. 

 Curves to illustrate the influence of selection. 



I 



of careful selection each generation. At first sight 

 this appears to be something very like the gradual 

 accumulation of minute variations through the con- 

 tinuous application of a selective process. Some 

 recent experiments by Professor Johannsen of Copen- 

 hagen set the matter in a different light. One of 

 his investigations deals with the inheritance of the 

 weight of beans, but as an account of these experi- 

 ments would involve us in the consideration of a 

 large amount of detail we may take a simple 

 imaginary case to illustrate the nature of the con- 



