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Darwin Correspondence Project

From Searles Valentine Wood   18 February 1862

Brentwood | Essex

My dear Sir

I am much obliged by your very friendly note & for your commendatory remark upon my monogh.1 I have been waiting to see if I cod procure any information you require but I fear after all my delay I shall not be able to give a very satisfactory answer to your question.2

As a general rule among the Mollusca I may say that the Genus most abundant in species & the species most abundant in individuals will present the greatest variation as we might naturally expect altho this rule like most others is not without exceptions   I have found some species of fossils which are but rare or sparingly exhibited present very great diversity of character   this possibly may have arisen from a paucity of individuals in one locality—while another locality which has not been examined or perhaps removed might have furnished them more abundantly & the apparently rare species might not in reality have been so altho no doubt some animals have a greater tendency to change than others or possess a less adaptability to altered conditions by which of course greater permanence of character will be maintained. In regard to the the special genus Lucina there is I believe every possible variation between what are called sectional divisions & the line of demarkation is extremely shadowy fading away in a most evanescent manner. The same may I believe be said of any other extensive Genus such as Helix, Unio, Cerithium, Conus Cypræa &c &c which have been divided into sections but which merge imperceptibly the one into the other

I presume that you are still employed collecting & arranging data for your work of which the essay published is you tell us but an outline   I hope that I may live to see it & that you may have health & strength to complete the work you have begun3   I may add in reference to your remark about the obloquy thrown upon it that it has been a great surprise to me that so much toleration has been accorded to you as seems to me to have been the case   I admired your courage in so boldly avowing your opinions

The mistake into which Authors like that of the vestiges4 fell by treating the organic world as a chain of developement in a continuous line instead of as an ever diverging ramification of being had furnished the opponents of the Theory of the origin of beings by the natural process of production out of a preexisting form with the means of an easy victory & it was in the midst of the general gratulation at this “scotching of the snake” that your sounder views came upon the world & backed by the reputation that you had previously so justly acquired   they cod not be so easily poohpoohed as might have been the case had they emanated from a less known man. I think that your thus boldly coming forwar⁠⟨⁠d⁠⟩⁠ is a merit of itself (apart from that attaching to the lucid developement of your argument⁠⟨⁠)⁠⟩⁠ & I rather suspect that there are other naturalists who have by their studies been forced to regard this natural origin of being as the true one but have not the confidence to avow their conviction in the face of the opprobrium which has been attached to such opinions

Believe me Dear Sir | Yours very truly | Searles Wood

Feb. 18. 62

Chas Darwin Esq

CD annotations

2.1 Genus … without 2.3] scored brown crayon
3.1 I presume … production 4.4] crossed brown crayon
Top of first page: ‘S. Wood | Feb 18 | 1862’ ink


CD’s letter has not been found. The reference is to the first part of Wood’s monograph on Eocene bivalves, which was published in December 1861 (S. V. Wood 1861–77).
Evidently CD’s question concerned whether species belonging to large genera of molluscs were more variable and wider ranging than those from small genera; this had a bearing on his principle of divergence, first outlined in Origin, pp. 111–30 (see also Kohn 1985). In order to demonstrate the connection between large genera and variable species, CD had already given the results of his extensive tabulation of the genera listed in the floras of various countries in Origin, pp. 54–8. For a discussion of CD’s objective in relation to his botanical work, see Browne 1980 and 1983.
In the introduction to Origin (pp. 1–6), CD explained that he regarded the work as an abstract of a larger work yet to be completed. The only part of this larger work that was published during CD’s lifetime was Variation (1868). The remaining draft chapters of what CD called his ‘big book’ were published posthumously as Natural selection.
The first edition of Vestiges of the natural history of creation was published anonymously in 1844 ([Chambers] 1844). It argued for a designed progressive evolution of life, and aroused a storm of protest and criticism. Robert Chambers was thought by many to be the author of the work, but this was not confirmed publicly until 1884, well after his death. See Secord 1989 and Secord ed. 1995.


Browne, Janet. 1980. Darwin’s botanical arithmetic and the ‘principle of divergence’, 1854–1858. Journal of the History of Biology 13: 53–89.

[Chambers, Robert.] 1844. Vestiges of the natural history of creation. London: John Churchill.

Kohn, David. 1985. Darwin’s principle of divergence as internal dialogue. In The Darwinian heritage, edited by David Kohn. Princeton: Princeton University Press in association with Nova Pacifica (Wellington, NZ).

Natural selection: Charles Darwin’s Natural selection: being the second part of his big species book written from 1856 to 1858. Edited by R. C. Stauffer. Cambridge: Cambridge University Press. 1975.

Origin: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. By Charles Darwin. London: John Murray. 1859.

Secord, James A. 1989. Behind the veil: Robert Chambers and Vestiges. In History, humanity and evolution: essays for John C. Greene, edited by James R. Moore. Cambridge: Cambridge University Press. [Vols. 8,10]

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.

Wood, Searles Valentine. 1861–77. A monograph of the Eocene Mollusca, or, descriptions of shells from the older Tertiaries of England. Bivalves. 3 pts. and supplement. London.


Variation in Mollusca. The most abundant forms vary most.

Letter details

Letter no.
Searles Valentine Wood
Charles Robert Darwin
Sent from
Source of text
DAR 181: 144
Physical description
6pp †

Please cite as

Darwin Correspondence Project, “Letter no. 3452,” accessed on 27 October 2021,

Also published in The Correspondence of Charles Darwin, vol. 10