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Darwin Correspondence Project

To Asa Gray   4 April [1858]1

Down Bromley Kent

Ap. 4th

My dear Gray

Your kindness to me is really beyond thanks. Believe me that I feel it. By an odd chance yesterday morning, before I got your letter, I had just written down what I had to say on closely allied species in large genera; & I thought that you had forgotten all about your list, & knowing how hard you were worked, to my credit be it said, I firmly resolved that nothing shd. induce me to remind you. Therefore you may believe how delighted I was to get your list, which is now being tabulated.—2

I am, also, particularly obliged for the answer to my question:3 Hooker & several (not all) other Botanists differ from you & think there would be a strong tendency to omit recording actually existing varieties in the smaller genera. None of them pretend they ever thought of this before I asked the question. From what little systematic work I have done myself, I cannot realise their view; & my tables of several local Floras in several respects contradict them in my opinion, & show that Botanists have worked rather more systematically & regularly in recording varieties than could have been anticipated. This is my view, but what Hooker will say, when he reads, as I hope he will, my discussion on this subject I know not. Taking Books as a guide, I find in local Floras & in the only 2 Entomological works, which I have tried, that the rule is almost universal, that the larger genera have more species with varieties (& a greater average number of varieties to the varying species) than the smaller genera.—4

You ask to see my sheets as printed off; I assure you that it will be the highest satisfaction to me to do so: I look at the request as a high compliment. I shall not, you may depend, forget a request, which I look at as a favour.— But (& it is a heavy “but” to me) it will be long before I go to press: I can truly say I am never idle; indeed I work too hard for my much weakened health; yet I can do only 3 hours of work daily, & I cannot at all see, when I shall have finished: I have done eleven long chapters; but I have got some other very difficult ones, as palæontology, classification & embryology &c, & I have to correct & add largely to all those done. I find, alas, each chapter takes me on average three months, so slow I am. There is no end to the necessary digressions. I have just finished a chapter on Instincts, & here I found grappling with such a subject as Bees cells & comparing all my notes made during 20 years took up a despairing length of time.5

But I am running on about myself in a most egotistical style. Yet I must just say how useful I have again & again found your letters, which I have lately been looking over & quoting; but you need not fear that I shall quote anything you would dislike, for I try to be very cautious on this head.— I most heartily hope you may succeed in getting your “incubus” of old work off your hands & be in some degree a free man.

Agassiz has most kindly sent me his Introduction two first Part; but I confess I am disappointed: I cannot realise his rules on the value of the higher groups, & all his prophetic &c &c types.6

Again let me say that I do indeed feel grateful to you & believe me | My dear Gray | Yours most truly | C. Darwin


Dated by the relationship to the letter to Asa Gray, 21 February [1858].
See CD’s annotations on the preceding letter.
CD refers to his question about the likelihood of botanists recording varieties in larger genera more frequently than in small (letter to Asa Gray, 21 February [1858]). Gray’s response, which CD sent to Joseph Dalton Hooker (see letter to J. D. Hooker, 10 April [1858]), has not been found. However, CD cited Gray on the point in Natural selection, p. 161: Dr. A. Gray, whose opinion will be considered by all as of the greatest weight, after deliberation does not believe that he has himself so acted: he at first thought that he might have unfairly recorded a greater number of varieties in the smaller genera…
CD’s results are summarised in Natural selection, pp. 134–67.
CD recorded having completed chapter 10, on the ‘Mental powers and the instincts of animals’ (Natural selection, pp. 466–527), on 9 March 1858 (‘Journal’; Appendix II).
The first volume of Agassiz 1857–62 was presented to CD by Louis Agassiz (see letter to Louis Agassiz, 21 February [1858]). The work is in the Darwin Library–CUL and contains annotations and an abstract by CD. CD presumably refers to Agassiz’s discussion of ‘The gradation of structure among animals’ and ‘Prophetic types among animals’ (Agassiz 1857–62, 1: 26–30, 116–18). The ‘prophetic type’ was the first-appearing representative of a group that reached its full development at a later period.


Discusses the variation of species in large and small genera.

Thanks AG for his list of close species.

Laments the slow progress he makes with his book [Natural selection].

Letter details

Letter no.
Charles Robert Darwin
Asa Gray
Sent from
Source of text
Archives of the Gray Herbarium, Harvard University (25)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 2252,” accessed on 27 April 2017,

Also published in The Correspondence of Charles Darwin, vol. 7