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Letter 2627

Wallace, A. R. to Darwin, C. R.

[Dec? 1860]

    Summary Add

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    Gives an extract from L. von Buch on the flora of the Canaries [Physikalische Beschreibung der Canarische Inseln (1825)].

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    Natural selection does not explain why animals of different groups in the same place often resemble each other.

Transcription

From ``Von Buch on the Flora of the Canaries''. ``On continents the individuals of one kind of plant disperse themselves very far, and by the difference of stations of nourishment & of soil produce varieties which at such a distance not being crossed by other varieties and so brought back to the primitive type, become at length permanent and distinct species. Then if by chance in other directions they meet with an other variety equally changed in its march, the two are become very distinct species and are no longer susceptible of intermixture.''

P.S. ``Natural Selection'' explains almost everything in Nature, but there is one class of phenomena I cannot bring under it,—the repetition of the forms & colours of animals in distinct groups, but the two always occurring in the same country & generally on the very same spot. These are most striking in insects, & I am constantly meeting with fresh instances. Moths resemble butterflies of the same country—Papilios in the east resemble Euplœ as, in America Heliconias. At Amboyna I took on the same tree at the same time two longicorns of distinct genera, but so alike in colour & markings that I only separated them after some days—   Here also & at Macassar occurs together a Malacoderm & an Elater of exactly the same tints of metallic blue & soft orange & also similarly striate,— yet there is no affinity between them. A few days ago only I took a new & curious little Cicindela which so closely resembles in size & markings a Therates occurring with it, that I never know which it is till I take it out of my net;—yet there is no sign of a change in the structural characters which separate these genera. It seems to shew that colour, markings & texture of surface depend strictly on local conditions—   Home Entomologists might do something in experiments on breeding insects, varying conditions of food light heat &c as much as they will bear. In domestic vars. have you discovered what tends to produce white, black, or particular coloured variations? or what tends to produce spots rather than stripes.

ARW.

    Footnotes Add

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    f1 2627.f1
    The date is suggested by Wallace's itinerary during the final years of his expedition in Malaysia. The letter clearly precedes the formulation of either Wallace's or Henry Walter Bates's views on insect mimicry and probably falls in the period between Wallace's receiving a copy of Origin in February 1860 and the autumn of 1861, when Bates read a paper in which he explained mimicry in terms of CD's views (Bates 1861). Wallace had collected insects from areas around Macassar on the island of Celebes in 1856 (see Wallace 1869, 1: 334 et seq.) and from Amboina in 1857 and 1859 (see Wallace 1869, 1: 460 et seq.). During 1860, having left Amboina in February, Wallace visited the islands of Ceram, Goram, and Waigiou, any of which might have yielded the beetles mentioned. When he returned to Ternate in December 1860, he was `stupefied' by his `year's letters, accounts, papers, magazines, and books' (Wallace 1905, 1: 373). In 1861, Wallace visited Timor and its neighbouring islands, all of which were very poor in beetles (Wallace 1869, 1: 296 et seq.).
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    f2 2627.f2
    Buch 1825, later translated into French as Buch 1836. The passage Wallace translates is given in Buch 1825, pp. 132--3, and in Buch 1836, pp. 147--8. From the extract given here, Wallace may be responding to CD's comments in the letter to A. R. Wallace, 18 May 1860, about people who had anticipated his theory. Christian Leopold von Buch was not, however, cited in the historical sketch that CD added to the third edition of Origin published in April 1861.
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    f3 2627.f3
    In his published account of his travels in Malaysia, Wallace described how he had noticed that some species of insects, predominantly butterflies and beetles, imitated each other in their shape and colouring. It was while he was on the island of Bourn, in the Moluccas, during May and June 1861, that he first noted mimicry among birds (Wallace 1869, 2: 150--3). At the time this letter was written, Wallace evidently did not believe that the phenomenon was explicable by natural selection. Later, after considering the case of birds and the work of Bates (Bates 1861), he came to believe that mimicry supplied powerful support for natural selection operating in nature. See Wallace 1866 and also Wallace 1905, 1: 401--2.
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    f4 2627.f4
    Coloration of animals had been mentioned in previous correspondence between Wallace and CD. See Correspondence vol. 6, letter to A. R. Wallace, 1 May 1857, and vol. 7, letter to A. R. Wallace, 25 January [1859].
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    f5 2627.f5
    The annotation refers to the third chapter in CD's `big book' on species, `On the possibility of all organic beings occasionally crossing' (Natural selection, pp. 33--91).
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    f6 2627.f6
    h IV` refers to the chapter in Origin entitled 'Natural selection` (Origin, pp. 80--130).
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    f7 2627.f7
    CD's comment relates to his regarding the origin of the electric organs of fishes as a particular difficulty for the theory of natural selection (Origin, pp. 192--3). Not only was it hard to envisage an intermediate form of electric organ, but it was also difficult to account for the organs occurring in species widely remote in their affinities, for then the organs could not be explained as a product of inheritance from a common ancestor. In Origin, pp. 193--4, CD suggested that the case could perhaps be explained by independent adaptations.
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    f8 2627.f8
    CD cited the independently developed adaptations of some plant species to disseminate their seeds by plumes and hooks in the fourth edition of Origin (see Peckham ed. 1959, p. 357).
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