Dear Sir

I am much obliged for your long letter, as I always like to know how naturalists view the subject. I feel not a shade of surprise at your entirely rejecting my views;²   my surprise is that I have been successful in converting some few eminent Botanists, Zoologists, & Geologists. In several cases the conversion has been very slow & that is the only sort of conversion which I respect.— I entirely agree with you that there is no more direct proof of variation being unlimited in amount than there is that it is strictly limited.— In a new & corrected Edit. of the Origin, which will appear in about a week or two, I have pointed this as emphatically as I could.—³ I did not formerly explicitly say this (but indirectly in several places) because I thought it was obvious.

The manner in which I wish to approach the whole subject, & in which it seems to me it may fairly be approached, I can best illustrate by the case of Light.— The Ether is hypothetical, as are its undulations; but as the undulatory hypothesis groups together & explains a multitude of phenomena, it is universally now admitted as the true theory. The undulations in the ether are considered in some degree probable, because sound is produced by undulations in air. So natural selection, I look at as in some degree probable, or possible, because we know what artificial selection can do.— But I believe in Nat. Selection, not because, I can prove in any single case that it has changed one species into another, but because it groups & explains well (as it seems to me) a host of facts in classification, embryology, morphology, rudimentary organs, geological succession & Distribution.—

I have no space to discuss the many points alluded to in your letter.— I cannot see such perfection in structure as you do. In the new Edit. I have attempted to explain how it is that many low forms have not progressed to a higher grade of organisation.⁴

I did not allude to the very curious subject of “alternate generations”, because I did not, & do not yet, see, how it has any special bearing on my views.—⁵ I look at alternate generations, as not essentially differing from various stages in any one individual larva—a form of gemmation being merely added at some stage. Under this point of view I see no essential difference between alternative generation & metamorphosis: you, I presume, take some very different view.—

I forget what Agassiz says on subject.— I quite agree with you that Agassiz’s Review is not in the least unfair.⁶ He misunderstands me a good deal.— His “categories of thought”, “prophetic types” & his views on classification are to me merely empty sounds.⁷ To others they seem full of meaning.—

I received several months ago, & thank you for, a very curious pamphlet on representative forms, (or some such title) which interested me very much.—⁸

With my best thanks, I remain | Dear Sir | Yours very faithfully | Charles Darwin

I am much pleased at & grateful for the sentence which you kindly copy from a recent letter from Agassiz.— I once saw him, & was charmed with him.—⁹