EVOLUTION 9 



his Autobiography in which, with reference to the same 

 article of 1852, he says : — 



' It seems strange that, having long entertained a belief 

 in the development of species through the operation of 

 natural causes, I should have failed to see that the truth 

 indicated [in the article quoted] must hold, not of man- 

 kind only, .but of aU animals, and must ever5rwhere be 

 working changes among them. If when human beings 

 are subjected by pressure of poptilation to a competition 

 for the means of subsistence, it results that on the average 

 the tendency is for the select of their generation to 

 survive, so, little by little, producing a better adapted 

 tj^e, then the like must happen with every other kind 

 of living thing similarly subjected to the " struggle for 

 existence ". And if so, .this must be in all cases a cause 

 for modification. Yet I completely overlooked this 

 obvious corollary — was blind to the fact that here was 

 a universally-operative factor in the development of 

 species. There were, I think, two causes for this over- 

 sight. 



' One was my espousal of the belief that the inheritance 

 of functionally produced modifications suffices to explain 

 the facts. Recognizing this as a sufficient cause for 

 many orders of changes in organisms, I concluded that it 

 was a sufficient cause for all orders of change. There are, 

 it is true, various phenomena which did not seem recon- 

 cilable with this conclusion ; but I lived in the faith that 

 some way of accounting for them would eventually be 

 found. Had I looked more carefully into the evidence and 

 observed ho\y multitudinous these inexplicable facts are — 

 had I not slurred over the difficulties, but deliberately 

 contemplated them, I might perhaps have seen that here 

 was the additional factor wanted. 



' A further cause was that I knew little or nothing about 

 the phenomena of variation. Though aware that devia- 

 tions of structure, in most cases scarcely appreciable but 

 occasionally constituting monstrosities, occur among all 

 organisms, yet I had never been led to think about them. 

 Hence there lacked an indispensable idea. Even had I 

 become distinctly conscious that the principle of the 

 survival of the select must hold of all species, and tend to 

 modify them, yet, not recognizing the universal tendency 

 to vary in structure, I should have failed to recognize 

 a chief reason why divergence and re-divergence must 



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