DARWIN. r.EFOIlE AND AFTER 175 



Following as an addendum to the ideas of the action 

 of srinmUis on the organism, we may mention R. Semon's 

 "Die ]\[neme" (1004). He considers that such stimula- 

 tive action leaves a more or less permanent trace of such 

 a nature as to modify the subsequent action of the or- 

 ganism. Others have regarded memory as a function of 

 all organised matter. A very good treatment of the 

 subject of memory and heredity is given by E. Rignano 

 (1906), who accepts the transmissibility of acquired 

 characters, relying on what he calls " specific nervous 

 accumulators '' to explain experimental embryology. 



With views somewhat allied to these, we may note the 

 materialistic vitalism of Driesch, derived from studies 

 on embryology and regeneration, and the profound in- 

 tuitionalism of Bergson. 



A large number of other contributors to the theory of 

 evolution — many of them only speculative — might be 

 mentioned. Thus, Spencer and Romanes have made most 

 interesting contributions to the subject, but time does 

 not permit of details. 



Summarising, we may state that of the various hypo- 

 theses xjut forward to account for the method of the 

 origin of specific differences, the most important are 

 four in number, namely, those of Lamarck and Darwin, 

 the Mutation hypothesis and the Hormone hypothesis, 

 and I hope that I have indicated that these hypotheses 

 are not antagonistic to each other, but rather that they 

 explain different aspects of this wade and complicated 

 problem, forming complements to each other. 



Again, we may briefly consider the influence of Darwin 

 in some spheres other than those of strict biology. As 

 Huxley w^rote in 1885: "Whatever be the ultimate verdict 

 of posterity upon this or that opinion w^hich Mr. Darwin 

 has propounded ; whatever adumbration or anticipations 

 of his doctrines may be found in the w^ri tings of his pre- 

 decessors; the broad fact remains that, since the publica- 

 tion and by jeason of the publication of "The Origin of 



