THEORIES OF ORGANIC EVOLUTION 



on this phase of the subject, expounding the Lamarck- 

 ian conceptions of the direct influence of the environ- 

 ment (an idea which had especially appealed to Buff on 

 and to Geoffrey Saint-Hilaire) , and of effort in response 

 to environment and stimulus as modifying the individ- 

 ual organism, and thus supplying the basis for the op- 

 eration of natural selection. Haeckel also became an 

 advocate of this idea, and presently there arose a so- 

 called school of neo-Lamarckians, which developed 

 particular strength and prominence in America under 

 the leadership of Professors A. Hyatt and E. D. Cope. 



But just as the tide of opinion was turning strongly 

 in this direction, an utterly unexpected obstacle ap- 

 peared in the form of the theory of Professor August 

 Weismann, put forward in 1883, which antagonized 

 the Lamarckian conception (though not touching the 

 Darwinian, of which Weismann is a firm upholder) by 

 denying that individual variations, however acquired 

 by the mature organism, are transmissible. The 

 flurry which this denial created has not yet altogether 

 subsided, but subsequent observations seem to show 

 that it was quite disproportionate to the real merits of 

 the case. Notwithstanding Professor Weismann's ob- 

 jections, the balance of evidence appears to favor the 

 view that the Lamarckian factor of acquired variations 

 stands as the complement of the Darwinian factor of 

 natural selection in effecting the transmutation of 

 species. 



Even though this partial explanation of what Pro- 

 fessor Cope calls the "origin of the fittest" be ac- 

 cepted, there still remains one great life problem which 

 the doctrine of evolution does not touch. The origin 



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