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Darwin Correspondence Project

To Raphael Meldola   23 January [1872]1

Down Beckenham | Kent

Jan 23. 1871

Dear Sir

The point to which you refer seems to me a very difficult one.2 1st the comparison of the amount of variability in itself wd be difficult. 2ndly. Of all characters, colour seems to be the most variable, as we see in domesticated productions. (3) I fully agree that selection if long continued gives fixity to characters. We see the reverse of this in the great variability of fancy races, now being selected by man. But to give fixity, selection must be continued for a very long period: pray consider on this head what I have said in the Origin about the variability of characters developed in an extraordinary manner, in comparison with the same characters in allied species.3 The selection must also be for a definite object, & not for any thing so vague as beauty, or for the superiority of one male in its weapons over another male, which can in like manner be modified. This at least seems to me partly to account for the general variability of secondary sexual characters. In the case of mimetic insects, there is another element of doubt, as the imitated form may be undergoing change which will be followed by the imitating form. This latter consideration seems to me, as remarked in my “Descent of man”, to throw much light on how the process of imitation first began—4

I enclose a letter from Fritz Müller which I think is well worth reading, & which please to return to me.5

You will see he lays much stress on the difficulty of several remotely allied forms all imitating some one species. Mr Wallace did not think that there was so much weight in this objection as I do.6 It is however possible that a few species in widely different groups, before they had diverged much, shd have accidentally resembled, to a certain extent, some one species. You will also see in this letter a strange speculation, which I shd not dare to publish, about the appreciation of certain colours being developed in those species which frequently behold other forms similarly ornamented. I do not feel at all sure that this view is as incredible as it may at first appear. Similar ideas have passed through my mind when considering the dull colours of all the organisms which inhabit dull-coloured regions, such as Patagonia & the Galapagos Ids7 I suppose you know Mr Riley’s excellent essay on mimicry in the last report on the noxious insects of Missouri or some such title.8

I hope your work may be in every way successful & I remain | dear Sir | yours faithfully | Charles Darwin

Footnotes

The year is established by the postmark. The amanuensis wrote ‘1871’ in error.
See letter from Raphael Meldola, 21 January [1872].
See Origin 5th ed., pp. 185–9: ‘A part developed in any species in an extraordinary degree or manner, in comparison with the same part in allied species, tends to be highly variable.’ CD’s point was that a part highly developed in one species but not in other species of the same genus must have been developed relatively recently, and that the tendency to vary that underlay the development was probably still active.
In Descent 1: 412, CD suggested that imitation might begin with two forms that resembled each other, one of which was protected by a noxious taste or odour, the other not. Natural selection would favour closer imitation of the protected species by the other, and if the protected species changed its colours as a result of sexual selection, the imitator would follow the same course.
CD enclosed the letter from Fritz Müller, 14 June 1871 (Correspondence vol. 19).
CD had forwarded Müller’s letter to Alfred Russel Wallace; for Wallace’s comments, see Correspondence vol. 19, letter from A. R. Wallace, 7 August 1871.
CD had wondered whether the generally dull coloration he had noticed in animals in the Galàpagos and in Patagonia arose because animals in that environment had not learned to appreciate bright colours; he added a note to this effect to the second edition of Descent (Descent 2d ed, p. 422 n. 34). See also Correspondence vol. 19, letter to Fritz Müller, 2 August [1871].
The third volume of Charles Valentine Riley’s Annual reports on the noxious, beneficial and other insects in the state of Missouri (Riley 1869–77) was published in 1871; the essay is on pages 159 to 172. See also Correspondence vol. 19, letter to C. V. Riley, 1 June [1871].

Summary

Discusses the problems of mimicry as related to natural selection; the general variability of colour as a character; and the conditions necessary for natural selection to fix firmly a character.

Encloses a Fritz Müller letter speculating that organisms respond to certain colours because of the prevalence of those colours in their environment.

Please cite as

Darwin Correspondence Project, “Letter no. 8172,” accessed on 24 February 2017, http://www.darwinproject.ac.uk/DCP-LETT-8172

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