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Darwin Correspondence Project

To J. D. Hooker   11 [December 1854]1

Down Farnborough Kent

Monday 11

My dear Hooker

I shd. have less scruple in troubling you, if I had any confidence what my work would turn out; sometimes I think it will be good; at other times I really feel as much ashamed of myself, as the Author of the Vestiges ought to be of himself. I know well that your kindness & friendship would make you do a great deal for me, but that is no reason that I shd. be unreasonable: I cannot & ought not to forget that all your time is employed in work certain to be valuable. It is superfluous in me to say that I enjoy exceedingly writing to you, & that your answers are of the greatest possible service to me.—

I return with many thanks the Proof on Aquilegia:2 it has interested me much: it is exactly like my Barnacles:3 but for my particular purpose, most unfortunately both Kolreuter4 & Gærtner5 have worked chiefly on A. vulgaris & Canadensis & atro-purpurea; & these are just the species, that you seem not to have studied.— (N.B. Why do you not let me buy the Indian Flora? you are too magnificent.)6 With respect to splitting Australia we are in a “Muddle”; I do not think I quite understood you & you me; I am pretty sure I do not quite understand or remember what I wrote myself; & I doubt whether you quite understand or remember what you wrote; for in first letter you say “Under this view disruption produces similarity of Botanical features”: in your second letter, you say that “three-fourths would be killed, & that a greater proportion of those species common to both (islands) would be killed, than of those peculiar to each”; but this wd. produce dis similarity.—7

Now for a short ride on my chief (at present) Hobby-Horse, viz aberrant genera: what you say under your remarks on Lepidodendron seems just the case, viz that I want to give some sort of evidence of what we both believe in, viz how groups come to be anomalous or aberrant. And I think some sort of proof is required; for I do not believe very many naturalists would at all admit our view. Thank you for caution on large anomalous genera first catching attention. I do not quite agree with your “grave objection to the whole process” which is “that if you multiply the anomalous species by 100, & divide the normal by the same, you will then reverse the names”… — For, to take an example, ornithoryhnchus & Echidna8 would not be less aberrant if each had a dozen (I do not say 100, because we have no such cases in animal kingdom) species instead of one. What would really make these 2 genera less anomalous, would be the creation of many genera & sub-families round & radiating from them on all sides. Thus if Australia were destroyed Didelphys in S. America wd be wonderfully anomalous (this is your case with Proteaceæ—), whereas now there are so many genera & little sub-families of Marsupiata, that the group cannot be called aberrant or anomalous. Sagitta9 (& the Earwig) is one of the most anomalous animals in world, & not a bit the less because there are a dozen species.— Now my point (which I think is a slightly new point of view) is, if it is extinction which has made the genus anomalous, as a general rule , the same causes of extinction would allow the existence of only a few species in such genera.

Whenever we meet (which will be on 23d. Club)10 I shall much like to hear whether this strikes you as sound; I feel all the time on the borders of a circle of truism.— Of course I could not think of such a request, but you might possibly, if Bentham does not think the whole subject rubbish, ask him sometime to pick out the dozen most anomalous genera in the Leguminosæ,11 or any great order of which there is a monograph, by which I could calculate the ordinary percentage of species to genera. I am the more anxious as the more I enquire, the fewer are the cases in which it can be done: it cannot be done in Birds or I fear Mammifers. I doubt much whether in any other class of Insects.—

I saw your nice notice of poor Forbes in Gardeners Chron; & I see in Athenæum a notice of meeting on last Saturday of his friends:12 of course I shall wish to subscribe as soon as possible to any memorial.

Farewell you most goodnatured of men. C. Darwin.—

I have just been testing practically what disuse does in reducing parts; I have made skeletons of wild & tame Duck (oh the smell of well-boiled, high Duck!!)13 & I find the tame-duck wing, ought according to scale of wild prototype to have its two wings 360 grams in weight, but it has it only 317 or 43 grams too little or 17th of own two wings too little in weight: this seems rather interesting to me.—14

P.S. I do not know whether you will think this worth reading over; I have worked it out since writing my letter. & tabulated the whole.—15 diag 21 orders with 1 genus, having 7.95 species (or 4.6?)

29 orders — 2 genera, having 15.05 species on average.

23 orders each with 3 genera; & these genera include on average 8.2 species

20 orders each with 4 genera, & these genera include on average 12.2 species

27 orders each with above 50 genera (altogether 4716 genera) & these genera

on average have 9.97 species.ramme

From this I conclude whether there be many or few genera in an Order, the number of species in genus is not much affected; but perhaps when only 1 genus in order it will be affected; & this will depend whether on Erythroxylon be made a Family of.—16


J. D. Hooker and Thomson 1855 (see letter from J. D Hooker, 5 December [1854], n. 4).
CD made this point again in Natural selection, p. 101: For example look at the case of Aquilegia vulgaris, as worked out by Dr. Hooker in his Flora Indica, who devoted weeks to the examination of specimens from all parts of Asia & Europe, & who ends in uniting about 16 species of other authors into one. I may state, as I know that similar cases have occurred with others, that in Lepas anatifera & Balanus tintinnabulum, I … finally concluded, that it was impossible to separate them!
Kölreuter 1761–6, Dritte Fortsetzung, pp. 119–24. CD’s annotated copy is in the Darwin Library–CUL. At the bottom of p. 119, CD wrote: ‘I see Gartner (p. 865) experimented much on Aquilegia, & nearly all (i a;) (but no K s) with many species: Now Hooker thinks all one species; has he published?’ ‘Now Hooker … published?’ was subsequently deleted in pencil. CD’s reference is to Gärtner 1849, (actually p. 685). The references to ‘i’, ‘a’, and ‘K’ were to Karl Friedrich von Gärtner’s symbols for indicating degrees of fertility in hybrid offspring; ‘K’ indicated normal fertility.
Gärtner 1849, p. 685, listed the results of Gärtner’s cross-fertilisation experiments between varieties of Aquilegia. CD’s copy is in the Darwin Library–CUL. Beside these results CD wrote, ‘Hooker thinks that probably Canadensis & atropurpurea, are merely synonyms; Hooker thinks Canadensis & vulgaris distinct’.
In the letter from J. D. Hooker, 5 December [1854], Hooker proposed giving CD a copy of J. D. Hooker and Thomson 1855. A presentation copy, inscribed ‘To Charles Darwin, Esq. F.R.S. With the best regards of the Authors.’, is in the Darwin Library–CUL. It is lightly annotated by CD.
See letters from J. D. Hooker, [15 November 1854] and 5 December [1854].
See CD’s memorandum attached to the letter from J. D. Hooker, 5 December [1854].
CD was speaking from experience. In his paper ‘Observations on the structure and propagation of the genus Sagitta’ (Collected papers 1: 177–82), he considered the ‘obscurity of their affinities’ and reported how the species of this genus were to be found in ‘infinite numbers’ in the inter-tropical and temperate seas (p. 177).
The Philosophical Club of the Royal Society.
The Leguminosae were one of George Bentham’s special interests. For Bentham’s list, see letter from J. D. Hooker, [after 11 December 1854].
Athenæum, no. 1415, 9 December 1854, p. 1496: ‘a meeting of friends and admirers was held at King’s College, when a resolution was adopted to place a bust of the deceased in the large hall … and a subscription was opened for the purpose of defraying all expenses.’ Other friends met at the Museum of Practical Geology to ‘determine upon some form of memorial’. For the notice in the Gardeners’ Chronicle and Agricultural Gazette, see letter to J. D. Hooker, 4 December [1854], n. 5.
CD later described his experiences of skeletonising birds in Expression, p. 259: I wished to clean the skeleton of a bird, which had not been sufficiently macerated, and the smell made my servant and myself (we not having had much experience in such work) retch so violently, that we were compelled to desist. During the previous days I had examined some other skeletons, which smelt slightly; yet the odour did not in the least affect me, but, subsequently for several days, whenever I handled these same skeletons they made me retch.
CD had recorded his intention to carry out this experiment in his Questions & experiments notebook, p. 3 (Notebooks): ‘Weigh skeleton of Tame Duck & Wild Duck, & then weigh their wing bones & see if relation is same good, avoids effects of fatness.—’. CD made the same point in Origin, p. 11, and, in greater statistical detail, in Variation 1: 284–6.
CD’s results are drawn up from the list of genera and species in Lindley 1846; his calculations are in DAR 205.9 (iii): 305–10.
CD is repeating a point made in letter to J. D. Hooker, 15 November [1854]. The genus Erythroxylon, which at that time was believed to have 75 species, was considered by John Lindley to belong to the order Malpighiaceae; if it were to be made a family, it would alter CD’s calculations on the average number of species in each genus.


Debates aberrant species, e.g., Ornithorhynchus and Echidna, with JDH. CD argues they are result of extinction having removed intermediate links to allied forms.

Studying effects of disuse in wings of tame and wild ducks.

Tabulations showing that number of species in a genus is not correlated with number of genera in an order.

Letter details

Letter no.
Charles Robert Darwin
Joseph Dalton Hooker
Sent from
Source of text
DAR 114: 148
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 1612,” accessed on 29 June 2017,

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