THEORIES OF WEISMA.W AXD DIC VRII-:s 403 



and that it has given a i^rcat stimulus to expcrimcnlal slucHes. 

 Experiment was Hkewise a dominant feature in Darwin's 

 work, Init that seems to lia\e ])een almost overlooked in 

 the discussions aroused by his conclusions; I)e Wies, by 

 building upon experimental evidence, has led naturalists to 



Fig. 115. — Hugo de Vries. 



realize tliat the metliod of evolution is not a subject for 

 argumentatixe discussion, Ijut for experimental in\estigation. 

 This is most commendable. 



Dc Vries's theory tends also lo widen llie field of explo- 

 ration. J>)a\enport, Tower, and others ha\e made it clear 

 that sj^ecies ma\- arise by slow accumulations of trixial \aria- 

 tions, and that, while the formation of S})ccies 1)\ mutation 



