PREFACE 



For nearly three quarters of a century the occurrence of evohi- 

 tion among organisms has been widely accepted by scientists. 

 It is only natural that the work of Darwin, which made possible 

 this acceptance, should have colored the beliefs of the period 

 thi'ough which we have since been passing, and that the apparent 

 opposition of his views and those of Lamarck should establish 

 the basis for theoretical consideration of the processes of evolution. 

 Initial views in any subject are likely to determine the trend of 

 human thought upon that subject. 



In the case of evolution it was obvious even when the Origin of 

 Species was published that there were many difficulties to be 

 surmounted before we could know even approximately how the 

 wonderful adjustments of evolution were consummated. It was 

 possible then as now to recognize the existence of natiu-al selec- 

 tion, and to some a wider application of this principle appeared 

 logical then than now seems justified. The Lamarckians offered 

 their explanations as opposed to the Darwinian point of view 

 and vice versa, and there is nothing so stimulating as confhct, al- 

 though it is of doubtful productiveness. 



When Mendel's discoveries were taken up early in the twentieth 

 century and the new science of genetics arose it seemed that we 

 might expect new concrete information regarding evolution, for 

 in genetics we come as near as possible to the raw materials of 

 evolution. The bearing of genetics on the larger problem of evo- 

 lutionary processes is, indeed, of the utmost importance, but in 

 the first quarter of the century it has made little if any unpression 

 upon the established treatment of evolutionary problems. The 

 Lamarckian and Darwinian points of view still determine the 

 course of a vast majority of writings on this subject. 



It is difficult for most people to depart entirely from a point 

 of view once learned as true. The printed page is probably the 

 most potent influence in establishing an initial belief. Give a 

 class a textbook which leans ever so slightly toward one opinion 

 and no matter how vigorously an instructor may assert the op- 



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