To Alfred Russel Wallace   22 January 1866

Down. | Bromley. | Kent. S.E.

Jan 22. 1866

My dear Wallace

I thank you for your paper on Pigeons, which interested me, as every thing that you write does.1 Who wd ever have dreamed that monkeys influenced the distribution of pigeons & parrots!2

But I have had a still higher satisfaction; for I finished yesterday your paper in Linn. Trans.3 It is admirably done. I cannot conceive that the most firm believer in Species cd read it without being staggered. Such papers will make many more converts among naturalists than long-winded books such as I shall write if I have strength.

I have been particularly struck with your remarks on Dimorphism; but I cannot quite understand one point (p. 22) & shd be grateful for an explanation for I want fully to understand you.

How can one female form be selected & the intermediate forms die out, without also the other extreme form also dying out from not having the advantages of the first selected form; for as I understand, both female forms occur on the same Island.4 I quite agree with your distinction between dimorphic forms & varieties; but I doubt whether your criterion of dimorphic forms not producing intermediate offspring will suffice; for I know of a good many varieties which must be so called, that will not blend or intermix, but produce offspring quite like either parent.5

I have been particularly struck with your remarks on Geog. Distrib. in Celebes. It is impossible that any thing cd be better put, & wd give a cold shudder to the immutable naturalists.6

And now I am going to ask a question which you will not like. How does yr Journal get on?7 It will be a shame if you do not popuralize your researches. my health is so far improved that I am able to work one or 2 hours a day—

Believe me dear Wallace | yours very sincerely | Ch. Darwin

LS

1
The reference is to A. R. Wallace 1865. A lightly annotated copy is in the Darwin Archive–CUL (DAR 133: 11).
2
CD marked the passage in which Wallace noted that the largest populations of pigeons, and of parrots, occurred in a part of the Malay archipelago from which monkeys and squirrels were absent (A. R. Wallace 1865, p. 366; see also ML 1: 265). Wallace suggested that the birds consumed fruits that formed part of the diets of these mammals; he also noted the monkeys’ habits of destroying eggs and young birds (A. R. Wallace 1865, p. 366).
3
The reference is to A. R. Wallace 1864b, a paper on variation and geographical distribution as illustrated by butterflies of the family Papilionidae in the Malayan region. CD was aware of its theme through the summary printed in the Reader in 1864; however, the paper was not published in full until 1865. CD’s unbound, annotated, copy is in the Darwin Archive–CUL. For CD’s earlier favourable impressions of its content, see Correspondence vol. 12, letter to A. R. Wallace, 28 [May 1864] and n. 4. CD referred to the content of A. R. Wallace 1864b in considering taxonomic distinctions between variable forms, local forms, geographical races or subspecies, and true species in Origin 4th ed., pp. 53–4; CD also referred to Wallace’s work on polymorphic butterflies in the chapter on pangenesis in Variation 2: 399–400. See also Descent, chapter 11.
4
The passage to which CD refers concerns Wallace’s interpretation of the origins of dimorphism and polymorphism in Papilio (A. R. Wallace 1864b, p. 22). In observing wing patterns in P. memnon, Wallace had noted three different forms of female, two of which occurred in Java. One form (plate 1, fig. 4, in A. R. Wallace 1864b) was a mimic of P. coon. Wallace argued that such polymorphic variants resulted from natural selection and conferred various advantages on females in particular, since, being slower than males, they were more vulnerable to predation. Wallace wrote that natural selection thus explained the development of the differently camouflaged wing colours and patterns in female forms, as well as the phenomenon of mimicry. In his own copy of A. R. Wallace 1864b, CD wrote on page 22: ‘just like neuters’. See also A. R. Wallace 1905, 1: 401–3.
5
Wallace urged that it was important to distinguish between varieties, which he defined as producing intermediate offspring when crossed, and dimorphic forms, the progeny of which he claimed would resemble one parent (A. R. Wallace 1864b, p. 10). However, CD had earlier written of varieties producing offspring that were not intermediate but resembled one parent (Origin, pp. 273–5). CD described this phenomenon in greater detail in Variation 2: 92–4.
6
Compared with other islands of the archipelago, Celebes had many more species of Papilionidae that were unique to it. Celebes also had 3 unique species of mammals, 5 unique species of birds and 190 unique hymenopterous species. Furthermore, Wallace observed that members of the Papilionidae on Celebes exhibited certain common characteristics that distinguished them from their counterparts on other islands. Wallace used this information to argue for the mutability of species and against the notion that all species had been created exactly as and where they were found (A. R. Wallace 1864b, pp. 30–2).
7
Four months earlier, CD had enquired about progress on Wallace’s ‘journal’ (Correspondence vol. 13, letter to A. R. Wallace, 22 September [1865] and n. 3). After his return from Malaya in 1862, Wallace spent five years organising his collections and writing articles. It was not until 1867 that he began in earnest to write The Malay Archipelego, his most popular book; it was published in 1869 (A. R. Wallace 1905, 1: 385–408). There is an annotated copy inscribed by the author in the Darwin Library–CUL (see Marginalia 1: 840–2), and the first volume bears a printed dedication testifying to Wallace’s personal friendship for CD and to his ‘deep admiration for his genius and works’.

Please cite as “DCP-LETT-4982,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-4982