CD is not surprised at CC's entire rejection of his views. Agrees that there is no direct proof of unlimited variation. Says natural selection should be viewed as comparable to wave theory of light: it is probable because it groups and explains a host of facts in several fields of science.
Agrees Louis Agassiz's review [Am. J. Sci. 2d ser. 30 (1860): 142–55] is not unfair, but Agassiz misunderstands CD. His "categories of thought" are to CD merely empty words.
Down Bromley Kent
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; 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.— 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.
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.— 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. He misunderstands me a good deal.— His ``categories of thought'', ``prophetic types'' & his views on classification are to me merely empty sounds. 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.—
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.—
- f1 3088.f1The identity of the correspondent and the year are based on the reference to CD's having received `several months ago' a pamphlet on representative forms (Collingwood 1860a). See n. 8, below.
- f2 3088.f2Collingwood's letter has not been found. Presumably the letter raised many of the objections to CD's theory discussed in a paper Collingwood delivered before the Literary and Philosophical Society of Liverpool on 10 December 1860. In the paper, Collingwood contrasted Darwin's views on the origin of species with those of Louis Agassiz, as expressed in his critical review of Origin (Agassiz 1860). Collingwood concluded that Agassiz's criticism was `one of the most conclusive and formidable (against Darwin's theory) which had yet appeared.' (Collingwood 1860b, p. 81). Collingwood sent CD a copy of this paper, which is in the Darwin Pamphlet Collection--CUL.
- f3 3088.f3Origin 3d ed., p. 89.
- f4 3088.f4Origin 3d ed., pp. 133--43.
- f5 3088.f5In his paper, Collingwood discussed Agassiz's view that the alternation of generations and other examples of polymorphism within a species were `far more astonishing phenomena, strictly circumscribed between the natural limits of unvarying species, than the slight differences produced by the intervention of men, among domesticated animals' (Agassiz 1860, p. 153). Collingwood then stated that these phenomena had been ignored by CD. See Collingwood 1860b, pp. 92--5. The passages in question are marked in CD's copy of the paper.
- f6 3088.f6Collingwood 1860b was written to defend Agassiz 1860 against the view expressed by Henry Hugh Higgins that Agassiz's review was `quite unworthy of so distinguished a naturalist' (Higgins 1860, p. 42).
- f7 3088.f7In Collingwood 1860b, pp. 83--5, Collingwood attempted to elucidate Agassiz's concept that species, while having no material existence, yet existed as `categories of thought' (Agassiz 1860, p. 142). Agassiz discussed the concept of `prophetic types' in the first volume of Contributions to the natural history of the United States of America (Agassiz 1857--62, 1: 116--18), a copy of which is in the Darwin Library--CUL (see also letter to George Rolleston, 7 March  and n. 4).
- f8 3088.f8A lightly annotated copy of Collingwood 1860a, inscribed `Charles Darwin Esq with the Author's Compts.', is in the Darwin Pamphlet Collection--CUL.
- f9 3088.f9CD may be referring to the 1846 meeting of the British Association for the Advancement of Science, at which Agassiz spoke to a meeting of the Ray Society that CD attended. See Correspondence vol. 4, letter to J. E. Gray, 18 December 1847.