HERITAGE OF THE INDIVIDUAL 



305 



mary gene. It would seem however that the effectiveness of 

 selection of this sort should be relatively limited in any par- 

 ticular case, and, in any event, the data thus far secured do 



FiQ. 157. Curves illustrating the relation between pure lines and popu- 

 lations or species. A, a population or 'species' curve, comprising three pure 

 lines; B, the separate elements (pure lines) of A, each with its own average 

 and variability. (After Kellicott.) 



not fundamentally alter the general importance of the pure 

 line concept. 



When all is said, it is clear that the realization of certain 

 categories of variations, taken in connection with the pure 

 line concept, has given new content to the problem of selec- 

 tion. The appreciation of its limitations has but accentuated 

 its possibilities. Selection is not shorn of its importance 

 either practical or theoretical. Artificial selection is useful in 



