tv THE GENEALOGY OF ANIMALS 115 



that the tendency to vary, in a given organism, may 

 have nothing to do with the external conditions to 

 which that individual organism is exposed, but 

 may depend wholly upon internal conditions. No 

 one, I imagine, would dream of seeking for the 

 cause of the development of the sixth finger and 

 toe in the famous Maltese, in the direct influence 

 of the external conditions of his life. 



I conceive that both hereditary transmission 

 and adaptation need to be analysed into their 

 constituent conditions by the further application 

 of the doctrine of the Struggle for Existence. It 

 is a probable hypothesis, that what the world is to 

 organisms in general, each organism is to the 

 molecules of which it is composed. Multitudes of 

 these, having diverse tendencies, are competing 

 with one another for opportunity to exist and 

 multiply ; and the organism, as a whole, is as 

 much the product of the molecules which are 

 victorious as the Fauna, or Flora, of a country is 

 the product of the victorious organic beings in it. 



On this hypothesis, hereditary transmission is 

 the result of the victory of particular molecules 

 contained in the impregnated germ. Adaptation 

 to conditions is the result of the favouring of the 

 multiplication of those molecules whose organising 

 tendencies are most in harmony with such 

 conditions. In this view of the matter, conditions 

 are not actively productive, but are passively 

 permissive ; they do not cause variation in any 



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