skip to content

Darwin Correspondence Project

From H. C. Watson   11 October 1855

Thames Ditton,

Oct 11. 1855

My dear Sir,

Posted with this sheet, but apart; is a copy of the London Catalogue of British plants. In the 3rd. paragh. within the Wrapper (ii) it is stated that the vars. there retained are (with few exceptions) the species of some botanists. By striking out those exceptions in the copy sent, we get the foundation for a list of debateable species (dubieties: i.e. varieties or species).1 I have run over the last editions of Babington’s Manual2 & Newman’s Ferns,3 & have added in [mg] their varieties (species of some authors), which are not given in London Catalogue; partly, on account of its earlier publication; chiefly, because slighter varieties. I have further marked in the Catalogue the names of those species (so standing there) which come nearest to the varieties in debateability.—

These 3 categories,—the more debateable species of the Catalogue, plus the vars. of the Catalogue, plus Babington’s & N’s Vars.,—will give you a very full list of debateables for the flora of the British Islands;—all of them being species of some botanists, vars. of other botanists. For the moment, taking all these to be true species, they do not wholly consist of those absolutely the most like some other species in the list. There are in the list several pairs of species perhaps more closely alike, but which have been long distinguished, & are always received for species, because they have some one or two characters by which they can be readily recognized & distinguished one from the other.

I look upon the words ‘Orders, genera, species (of books), & varieties,’ only as terms to indicate passably well the grades of resemblance between objects. Mutatis mutandis, a general rule or fact of the one, would thus be expected to hold good with the other grades. But in this view, perhaps the strictly logical series of comparisons (assuming your rule) would be, that varieties are closer in species having many varieties,—species (not necessarily also vars.) are closer in genera having many species,—genera (not necessarily species) are closer in orders having many genera. If so, the debateable species are not the best to be taken for your purpose; because they may all be varieties rather than species, or a mixture of the two grades.— I don’t see how to mend the selection, however, by a better test of closeness; & the varieties which are occasionally or frequently deemed species, must be at least very near that grade of difference, which would constitute them items in genera, rather than items in species. Perhaps you will think this too metaphysical.

Do not mistake me about the difference between small & large areas for your quest. In taking the whole known Flora of the Earth, you could distinguish the genera absolutely into small & large (those with fewer, those with more, than the average number of species), as at present existing. Any fact or rule deduced from a comparison between these two divisions of existing genera, would be an absolute truth pro tempore. In doing the same with the Flora of a small section of the Earth, you would only reach an absolute truth pro loco. It seems to me that the larger the area, the nearer would the local truth correspond with the temporal one. And that you might even lessen the area so far as to destroy & reverse the correspondence, thro’ the large genera becoming locally the small genera, & the small genera relatively the large ones.

In reference to a remark of your letter, closely following the name of E. Forbes. I claim no property in what I may write during such a correspondence as ours. I simply comment on your ideas, & you are fully at liberty to use or apply such comments in any way you like. You probably deem me touchy or tenacious of aught that has been my own, because I fell foul of Forbes in regard to certain geographical groupings of British plants.—4 Forbes did not re-examine these groupings,—ascertain their correctness,—& then apply them to his further object. Had he done so, they would have become his also; & I should have said nothing (or little) about his mere omission to state that such groupings were not original with him. But he practised a fraud on the British Association5 & general public of science, by giving on his sole personal authority the results of long investigations & comparisons which he had neither made, nor repeated, nor imitated,—simply misappropriated, & without clearly understanding them. Not any evidence drawn from the animal kingdom was given in his own printed reports of the communication to the B.A. The “facts” afterwards found from the animal world, were found under water by a man not remarkably conscientious, & to whom it had become a sort of necessity to find them.6 I shall believe them when confirmed by some other naturalist, conscientious & uncommitted.

I am not sure of clearly understanding “the imagined rule of individuals of one or more species in a genus varying in those characters by which the species of the same genus differ”.7 Usually, botanists avoid those characters which are inconstant in the same species, when they seek to frame a diagnosis between different species. Is this it? diag Ranunculus hederaceus — Leaves all lobed, never multipartite. ——– circinatus — Leaves never lobed, all multipartite. ——– aquatilis — Leaves, upper lobed, lower multipartite;—but

frequently all multipartite. ramme

In Saxifraga, one section has the capsule “inferior”, another section has it “superior”. This is a technical difference usually held to warrant the reference of genera to different orders. The two sections of Saxifraga differ much in other respects also. Recently a new species has been described, from a single plant flowering in a garden, which had the inferior capsule of the one section, tho’ the rest of its characters would have associated it with the other section;—indeed, judging by figure & description only, without specimen, I might say, with a given species of the other section. This peculiar Saxifrage is named S. Andrewsii, & is kept apart, only by its inferior capsule, from the section of the genus which seems to connect the West of Ireland with the Pyrenees botanically.

Yours very truly | Hewett C. Watson C. Darwin | Esq

CD annotations

double scored pencil
double scored brown crayon; ‘very true, but impossible to ascertain.—’ added pencil
3.9 varieties rather than species,] ‘This assumes something essentially different between varieties & species.’ added pencil
4.3 genera absolutely] ‘at one time’ interl pencil
double scored pencil; ‘certainly better’added pencil
4.11 the large ones.] ‘but yet in such peculiar areas I shd expect law to hold.’ added pencil
crossed pencil
‘Yes this is case.—’added pencil
Top of first page: ‘London Catague Correspondence’brown crayon
Top of last page (6.1): ‘Ch 7’8 pencil, circled pencil


In Natural selection, pp. 148, 149, CD summarised the information provided by Watson’s markings as part of his evidence for believing that varieties may be incipient species. Watson apparently sent the marked catalogue twice, the second time after he better understood CD’s purpose. See letters from H. C. Watson, 17 August 1855 and 23 August 1855.
Babington 1851.
Newman 1854.
Watson had accused Edward Forbes of plagiarism (see Correspondence vol. 3, letter from J. D. Hooker, [before 3 September 1846], n. 2). The controversy concerned priority in the description of the distribution of British plants.
Forbes’s work had first been announced at the meeting of the British Association for the Advancement of Science held in Cambridge in 1845 (Forbes 1845).
Watson refers to Forbes’s contention in Forbes 1851 that the distribution of molluscs confirmed his land-bridge hypothesis: ‘the marine mollusks would seem to point to the submergence of a tract of land probably linking Africa with South America, before the elevation of St. Helena’ (p. 77).
Chapter seven of Natural selection, ‘Laws of variation’.


Sends London catalogue of British plants with close species marked.

Charges E. Forbes with fraudulent appropriation of others’ work.

Comments on, and cites possible cases of, CD’s imagined rule that individuals of one or more species in a genus vary in some of those characters by which the species of that genus are distinguished.

Letter details

Letter no.
Hewett Cottrell Watson
Charles Robert Darwin
Sent from
Thames Ditton
Source of text
DAR 47: 163a–b
Physical description
4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 1764,” accessed on 24 March 2019,

Also published in The Correspondence of Charles Darwin, vol. 5