LETTER 103. TO J.D. HOOKER.

(103/1. This letter is of interest as containing a strong expression upon the overwhelming importance of selection.)

Down [1860].

Many thanks for Harvey's letter (103/2. W.H. Harvey had been corresponding with Sir J.D. Hooker on the "Origin of Species."), 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 I 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. (103/3. 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.) My blessed little Scaevola 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.