152 EVOLUTION [CHAP. HI 



Letter 103 To J. D. Hooker. 



This letter is of interest as containing a strong expression upon the 

 overwhelming importance of selection. 



Down [1860]. 



Many thanks for Harvey's letter, 1 which I will keep a 

 little longer and then return. I will write to him and try to 

 make clear from analogy of domestic productions the part 

 which I believe selection has played. I have been reworking 

 my pigeons and other domestic animals, and 1 am sure that 

 any one is right in saying that selection is the efficient 

 cause, though, as you truly say, variation is the base of all. 

 Why I do not believe so much as you do in physical agencies 

 is that I see in almost every organism (though far more 

 clearly in animals than in plants) adaptation, and this 

 except in rare instances, must, I should think, be due to 

 selection. 



Do not forget the Pyrola* when in flower. My blessed 

 little Sccevola has come into flower, and I will try artificial 

 fertilisation on it. 



I have looked over Harvey's letter, and have assumed (I 

 hope rightly) that he could not object to knowing that you 

 had forwarded it to me. 



Letter 104 To Asa Gray. 



Down, June 8th [1860]. 



I have to thank you for two notes, one through Hooker, 

 and one with some letters to be posted, which was done. 

 I anticipated your request by making a few remarks on 

 Owen's review. 3 Hooker is so weary of reviews that I do not 

 think you will get any hints from him. I have lately had 

 many more " kicks than halfpence." A review in the last 



1 W. H. Harvey had been corresponding with Sir J. D. Hooker on 

 the Origin of Species. A biographical note on Harvey is given as a 

 note to Letter 95. 



2 In a letter to Hooker, May 22nd, 1860, Darwin wrote : " Have you 

 Pyrola at Kew ? if so, for heaven's sake observe the curvature of the 

 pistil towards the gangway to the nectary." The fact of the stigma in 

 insect-visited flowers being so placed that the visitor must touch it on 

 its way to the nectar, was a point which early attracted Darwin's attention 

 and strongly impressed him. 



3 The Edinburgh Review, April, 1860. 



