Alfred Russel Wallace 



individual adaptation cannot meet the requirements, then 

 Natural Selection rapidly brings about a permanent adapt- 

 ation which is inherited. In plants these two forms of 

 adaptation are well marked and easily tested, and we 

 shall soon have a large body of evidence upon it. In the 

 higher animals I imagine that individual adaptation is 

 small in amount, as indicated by the fact that even slight 

 varieties often breed true. 



In Lepidoptera we have the two forms of colour-adapta- 

 bility clearly shown. Many species are, in all their stages, 

 permanently adapted to their environment. Others have 

 a certain power of individual adaptation, as of the pupae 

 to their surroundings. If this last adaptation were strictly 

 inherited it would be positively injurious, since the progeny 

 would thereby lose the power of individual adaptability, 

 and thus we should have light pupre on dark surroundings, 

 and vice versa. Each kind of adaptation has its own sphere, 

 and it is essential that the one should be non-inheritable, the 

 other heritable. The whole thing seems to me quite har- 

 monious and ''as it should be." 



Thiselton-Dyer tells me that H. Spencer is dreadfully 

 disturbed on the question. He fears that acquired charac- 

 ters may not be inherited, in which case the foundation of 

 his whole philosophy is undermined ! — Yours very truly, 



Alfred R. Wallace. 



P.S. — I am afraid you are partly responsible for that 

 kindly meant but too personal manifestation which dis- 

 turbed the solemnity of the Royal Society meeting on 

 Thursday! . . . 



To Prof. Poulton 



Parkstone, Dorset. September 25, 1893. 

 My dear Poulton, — I suppose you were not at Notting- 

 ham and did not get the letter, paper, and photographs I 



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