278 THE SPREAD OF EVOLUTION. [Ch. XIV. 



In the sixth edition my father also referred to the " direct 

 action of the conditions of life" as a subordinate cause of 

 modification in living things : On this subject he wrote to Dr. 

 Moritz Wagner (Oct. 13, 1876) : " In my opinion the greatest 

 error which I have committed, has been not allowing sufficient 

 weight to the direct action of the environment, i.e. food, climate, 

 &c, independently of natural selection. Modifications thus 

 caused, which are neither of advantage nor disadvantage to the 

 modified organism, would be especially favoured, as I can now 

 see chiefly through your observations, by isolation, in a small 

 area, where only a few individuals lived under nearly uniform 

 conditions." 



It has been supposed that such statements indicate a serious 

 change of front on my father's part. As a matter of fact the 

 first edition of the Origin contains the words, "I am con- 

 vinced that natural selection has been the main but not the 

 exclusive means of modification." Moreover, any alteration 

 that his views may have undergone was due not to a change of 

 opinion, but to change in the materials on which a judgment 

 was to be formed. Thus he wrote to Wagner in the above 

 quoted letter : — 



" When I wrote the Origin, and for some years afterwards, I 

 could find little good evidence of the direct action of the 

 environment ; now there is a large body of evidence." 



With the possibility of such action of the environment he 

 had of course been familiar for many years. Thus he wrote to 

 Mr. Davidson in 1861 : — 



" My greatest trouble is, not being able to weigh the direct 

 effects of the long- continued action of changed conditions of 

 life without any selection, with the action of selection on 

 mere accidental (so to speak) variability. I oscillate much on 

 this head, but generally return to my belief that the direct 

 action of the conditions of life has not been great. At least 

 this direct action can have played an extremely small part in 

 producing all the numberless and beautiful adaptations in 

 every living creature." 



And to Sir Joseph Hooker in the following year : — 



"I hardly know why I am a little sorry, but my present 

 work is leading me to believe rather more in the direct action 

 of physical conditions. I presume I regret it, because it 



I went out of my way, and inserted a sentence which seemed to me (and 

 still so seems) to disclose plainly my belief. This was quoted in my 

 Descent of Man. Therefore it is very unjust ... of Mr. Mivart to accuse 

 mo of base fraudulent concealment." 



