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Darwin Correspondence Project

From A. R. Wallace   23 July 1876

Rosehill, Dorking.

July 23rd. 1876

My dear Darwin

I should have replied sooner to your last kind and interesting letters, but they reached me in the midst of my packing previous to removal here, & I have only just now got my books & papers in a get-at-able state.1

And first, many thanks for your close observation in detecting the two absurd mistakes in the tabular headings.2

As to the former greater distinction of the North & South American faunas I think I am right.3 The Edentata being proved (as I hold) to have been mere temporary migrants into North America in the Post-Pliocene epoch, form no part of its Tertiary fauna. Yet in South America they were so enormously developed in the Pliocene epoch that we know, if there is any such thing as Evolution &c., that strange ancestral forms must have preceeded them in Miocene times.4

Mastodon on the other hand, represented by one or two sp. only, appears to have been a late immigrant into S. America from the North.5

The immense development of Ungulates (in varied families, genera, & species) in North America during the whole Tertiary Epoch is however the great feature, which assimilates it to Europe & contrasts it with S. America. True Camels, hosts of Hog-like animals, true Rhinoceroses, & hosts of ancestral Horses, all bring N. America much nearer to the Old World than it is now. Even the horse, represented in all S. America by Equus only, was probably a temporary immigrant from the N.6

As to extending too far the principle (yours) of the necessity of comparatively large areas for the development of varied faunas, I may have done so, but I think not.7 There is I think every probability that most islands &c. where a varied fauna now exists have been once more extensive,—e.g. N. Zealand Madagascar,— Where there is no such evidence (e.g. Galapagos) the fauna is very restricted.

Lastly as to want of references; I confess the justice of your criticism.8 But I am dreadfully unsystematic. It is my first large work involving much of the labour of others. I began with the intention of writing a comparatively short sketch,—enlarged it, and added to it, bit by bit; remodeled the tables, the headings, & almost everything else, more than once, & got my materials in such confusion that it is a wonder it has not turned out far more crooked & confused than it is. I no doubt ought to have given references; but in many cases I found the information so small & scattered, & so much had to be combined & condensed from conflicting authorities, that I hardly knew how to refer to them or where to leave off. Had I referred to all authors consulted for every fact, I should have greatly increased the bulk of the book,—while a large portion of the references would be valueless in a few years owing to later & better authorities. My experience of refering to references has generally been most unsatisfactory. One finds, nine times out of ten, the fact as stated, and nothing more; or a reference to some third work not at hand!

I wish I could get into the habit of giving chapter & verse for every fact & extract, but I am too lazy & generally in a hurry, having to consult books against time when in London for a day.

However I will try & do something to mend this matter shd. I have to prepare another edition.9

I return you Forel’s letter.10 It does not advance the question much, neither do I think it likely that even the complete observation he thinks necessary would be of much use;—because it may well be that the ova or larvæ or imagos of the beetles are not carried systematically by the ants, but only occasionally owing to some exceptional circumstances. This might produce a great effect in distribution yet be so rare as never to come under observation.

Several of your remarks in previous letters I shall carefully consider. I know that, compared with the extent of the subject, my book is in many parts crude & ill-considered;—but I thought & still think, it better to make some generalizations wherever possible, as I am not at all afraid of having to alter my views in many points of detail. I was so overwhelmed with zoological details, that I never went through the Geological Soc. Journal11 as I ought to have done, & as I mean to do before writing more on the subject.

With best wishes | Believe me | Yours very faithfully | Alfred R Wallace

C. Darwin F.R.S.


See letters to A. R. Wallace, 17 June 1876 and 25 June 1876. Wallace had just moved from the house he built, ‘The Dell’, which was sold by auction on 15 June 1876 (sale poster, Thurrock Library, folder no. 205;, accessed 12 September 2014). For more on Wallace’s move, see Raby 2001, p. 216.
See letter to A. R. Wallace, 25 June 1876 and nn. 5 and 6. CD had detected the errors in Wallace’s Geographical distribution of animals (Wallace 1876a). The bird family Sittidae had no entry under the Ethiopian region in the table, but should have had; Rhinochetidae (now Rhynochetidae) was entered under the neotropical instead of the Australian subregion (see Wallace 1876a, 2: 265 and 359).
Edentata is a former order of mammals that included armadillos, anteaters, and sloths; it has been replaced by the modern orders Cingulata (armadillos) and Pilosa (anteaters and sloths). The Tertiary period is a former geologic period equivalent to the Paleogene and Neogene periods and the first stage of the Pleistocene in the Cenozoic era. The Pliocene is the younger epoch of the Neogene period; it formerly included the Gelasian stage, which is now included in the Pleistocene epoch. The Miocene is the older epoch of the Neogene period. For more on the revision of the geologic time scale, see Ogg et al. 2008.
Mastodons are an extinct group of mammals related to elephants; Mastodon is a synonym of Mammut.
Equus, the only surviving genus of the family Equidae, appeared in the early Pleistocene epoch.
See letter to A. R. Wallace, 25 June 1876. CD had pointed out that several species of the same genus often developed on small islands.
No second edition of Wallace 1876a was produced.
CD had written to Auguste Forel about Wallace’s theory about how Coleoptera that inhabited the nests of ants might colonise a new nest (see letter to Auguste Forel, 19 June 1876). CD mentioned he had written to Forel in his letter to Wallace of 25 June 1876 and evidently sent Forel’s reply of 23 June 1876 to Wallace.
CD had referred Wallace to a paper in the Quarterly Journal of the Geological Society of London (see letter to A. R. Wallace, 17 June 1876 and n. 6).


Raby, Peter. 2001. Alfred Russel Wallace: a life. London: Chatto & Windus.


Responds to CD’s comments and criticism of Geographical distribution.

Letter details

Letter no.
Alfred Russel Wallace
Charles Robert Darwin
Sent from
Source of text
DAR 106: B126–9
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 10564,” accessed on 24 September 2021,

Also published in The Correspondence of Charles Darwin, vol. 24