My dear Hooker

Thank you for your last note with news of Richmond Hill, which I have been studying on the map. I have been trying to do a little about aberrants, but before I tell you, (thinking that you might possibly like to hear) I must beg you to thank M^r. Bentham particularly for the Historical notes,¹ which by chance I had see referred to but 2 days before, & wished much to see in regard to Figs.—²

In Shoenherrs Catalogue of Curculionidum,³ the 6717 species are on average 10.17 to genus. Waterhouse, (who knows the group well) (& who has published on fewness of species in aberrant genera)⁴ has given me a list of 62 aberrant genera,⁵ & these have on average 7.6 species; & if 1 single genus be removed (& which I cannot yet believe ought to be considered aberrant) then the 61 aberrant genera w^d. have only 4.91 species on average.— I tested these results in another way. I found in Schoenherr 9 Families including only 11 genera, & these genera (9 of which were in Waterhouses list) I found included only 3.36 species on an average.⁶

This last result led me to Lindleys Vegetable Kingdom⁷ in which I find (excluding Thallogens & Acrogens) that the genera include each 10.46 species (how near by chance to the Curculionidæ) & I find 21 orders including single genera, & these 21 genera have on average 7.95 species; but if Lindley is right that Erythroxylon (with its 75 species) ought to be amongst the Malpighiads, then the average w^d. be only 4.6 per genus.

But here comes, as it appears to me, an odd thing, (—I hope I shall not quite weary you out,)—there are 29 other orders, each with 2 genera & these 58 genera have on average 15.07 species: this great number being owing to the 10 genera in the ¹Smilaceæ, ²Salicaceæ (with 220 spec.^s) ³Begoniaceæ, ⁴Balsaminaceæ ⁵Grossulariaceæ, without which, the remaining 48 genera, w^d have on average only 5.91 species.—

This case of the orders with only 2 genera, the genera, notwithstanding having 15.07 species each, seems to me very perplexing, & upsets almost the conclusion deducible from the orders with single genera.

I have gone higher, & tested the Alliances⁸ with 1, 2, & 3 Orders, & in these cases, I find both the genera few in each alliance, & the species, less than average of whole kingdom, in each genus.—

All this has amused me,⁹ but I daresay you will have a good sneer at me, & tell me to stick to my Barnacles. By the way you agree with me that sometimes one gets despondent, for instance when theory & facts will not harmonise; but what appears to me even worse, & makes me despair, is, when I see from the same great class of facts, men, like Barrande deduce conclusions, such as his Colonies¹⁰ & his agreement with E. de Beaumonts lines of Elevation,¹¹ or such men as Forbes with his Polarity;¹² —I have not a doubt that before many months are over I shall be longing for the most dishonest species as being more honest than the honestest theories.— One remark more, if you feel any interest, or can get anyone else to feel any interest on the aberrant genera question, I sh^d. think the most interesting way w^d be to take aberrant genera in any great natural Family, & test the average number by the number of species to the genera in that Family.—

How I wish we lived near each other; I sh^d. so like a talk with you on geograph. distribution, taken in its greatest features; I have been trying from land productions to take a very general view of world, & I sh^d. so like to see how far it agrees with plants.

But adios for the present. Ever your’s very truly. C. Darwin

Comfort has got the place. many thanks to you & M^rs Hooker.—¹³