96 THE UNFINISHED BOOK. [1857. 



of the now very prevalent doctrine of all our domestic animals 

 having descended from several wild stocks ; though I do not 

 doubt that it is so in some cases. I think there is rather 

 better evidence on the sterility of hybrid animals than you 

 seem to admit : and in regard to plants the collection of 

 carefully recorded facts by Kolreuter and Gaertner (and 

 Herbert) is enormous. I most entirely agree with you on the 

 little effects of " climatal conditions," which one sees referred 

 to ad nauseam in all books : I suppose some very little effect 

 must be attributed to such influences, but I fully believe that 

 they are very slight. It is really impossible to explain my 

 views (in the compass of a letter), on the causes and means of 

 variation in a state of nature ; but I have slowly adopted a 

 distinct and tangible idea, whether true or false others must 

 judge ; for the firmest conviction of the truth of a doctrine by 

 its author, seems, alas, not to be the slightest guarantee of 

 truth ! . . . 



C. Darwin to J. D. Hooker. 



Moor Park, Saturday [May 2nd, 1857], 



MY DEAR HOOKER, You have shaved the hair off the 

 Alpine plants pretty effectually. The case of the Anthyllis 

 will make a " tie " with the believed case of Pyrenees plants 

 becoming glabrous at low levels. If I do find that I have 

 marked such facts, I will lay the evidence before you. 

 I wonder how the belief could have originated ! Was it 

 through final causes to keep the plants warm ? Falconer in 

 talk coupled the two facts of woolly Alpine plants and 

 mammals. How candidly and meekly you took my Jeremiad 

 on your severity to second-class men. After I had sent 

 it off, an ugly little voice asked me, once or twice, how much 

 of my noble defence of the poor in spirit and in fact, was 

 owing to your having not seldom smashed favourite notions 

 of my own. I silenced the ugly little voice with contempt, 

 but it would whisper again and again. I sometimes despise 



