246 THE THEORIES OF EVOLUTION 



those researches which, after all, aim at finding a 

 mechanical explanation for life's phenomena, have 

 brought us near the solution of the problem of the 

 process by which the organism reacts against the influ- 

 ence of its environment. Still this research work is 

 not exclusively done by Lamarckians nor from a 

 purely Lamarckian point of view. Weismann him- 

 self had recourse to a Lamarckian explanation when he 

 discovered that Vanessa levana and Vanessa prorsa, 

 which had always been regarded as two distinct varie- 

 ties of butterflies presented only a case of seasonal 

 dimorphism due to differences in temperature. Neo- 

 Darwinians have accomplished as much in that direc- 

 tion as Neo-Lamarckians, but the path was blazed by 

 the Neo-Lamarckians. 



It is difficult to state which of the two theories is 

 the more popular at the present day. We shall not 

 be far from the truth when we say that the biologists 

 who call themselves Lamarckians are less numerous 

 than those who proclaim their allegiance to Darwin. 

 But Lamarckism is making great strides and is influ- 

 encing even its professed opponents. An official 

 census of the scientific world would reveal more Dar- 

 winians than Lamarckians, but many of the scientists 

 who follow the Darwinian flag are in reality Lamarck- 

 ians who lack the courage of their convictions. 



