Selection of Elementary Species 93 



duction of sugar. He must have made some 

 choice among the numerous available sorts of 

 beets, or chance must have placed in his hands 

 one of the most appropriate forms. On this 

 point however, no evidence is at hand. 



Since the work of Vilmorin the selection-prin- 

 ciple has increased enormously in importance, 

 for practical purposes as well as for the the- 

 oretical aspect of the subject. It is now being 

 applied on a large scale to nearly all ornamental 

 plants. It is the one great principle now in 

 universal practice as well as one of preeminent 

 scientific value. Of course, the main argu- 

 ments of the evolution theory rest upon mor- 

 phologic, systematic, geographic and pale- 

 ontologic evidence. But the question as to how 

 we can coordinate the relation between 

 existing species and their supposed ancestors 

 is of course one of a physiologic nature. Di- 

 rect observation or experiments were not avail- 

 able for Darwin and so he found himself con- 

 strained to make use of the experience of breed- 

 ers. This he did on a broad scale, and with 

 such success that it was precisely this side of 

 his arguments that played the major part in 

 convincing his contemporaries. 



The work of the breeders previous to Dar- 

 win's time had not been very critically per- 

 formed. Eecent analyses of the evidence ob- 



