CD now acknowledges that the sometimes very great sexual, i.e., ornamental, differences in fishes offer a difficulty to the view that females are not brightly coloured on account of the danger to propagation of the species.
6 Queen Anne | St W
My dear Wallace
I return by this post the journal. Your resumé of glacier action seems to me very good and has interested my brother much and as the subject is new to him he is a better judge. That is quite a new & perplexing point which you specify about the Freshwater fishes during the glacial period— I have also been very glad to see the article on Lyell which seems to me to be done by some good man.
I forgot to say when with you, but I then indeed did not know so much as I do now, that the sexual i.e. ornamental differences in fishes, which differences are sometimes very great, offer a difficulty on the wide extension of the view that the female is not brightly coloured on account of the danger which she would incur in the propagation of the species.
I very much enjoyed my long conversation with you; and today we return home & I to my horrid dull work correcting proof sheets.
Believe me, my dear Wallace | yours very sincerely | Charles Darwin
P.S. I had arranged to go & see your collection on Saturday evening, but my head suddenly failed after luncheon & I was forced to lie down all the rest of day.—
- f1 5404.f1The date is established by the relationship between this letter and the letter from A. R. Wallace, [19 June 1867]. The first Monday after 19 June 1867 was 24 June.
- f2 5404.f2CD refers to the Quarterly Journal of Science and to Wallace's article `Ice marks in north Wales', which appeared in the January 1867 issue (A. R. Wallace 1867d); see Correspondence vol. 14, letter from A. R. Wallace, 19 November 1866. While in London, CD stayed with his brother, Erasmus Alvey Darwin.
- f3 5404.f3Wallace had argued that the presence of so many peculiar species of freshwater fishes in some North American lakes could be explained only if these lakes were formed through glacial action (A. R. Wallace 1867d, pp. 50--1).
- f4 5404.f4The unsigned article, `Sir Charles Lyell and modern geology' (Quarterly Journal of Science 4 (1867): 1--19), was a review of Lyell's services to geology.
- f5 5404.f5CD may have met Wallace on 21 June 1867, after failing to see him earlier (see letter from A. R. Wallace, [19 June 1867]). In notes for Descent written on that date (DAR 82: B5--6), CD mentioned Wallace's view that protective coloration in fishes could be analogous to that in birds, where the nesting parent of either sex was the least conspicuous (see letter from A. R. Wallace, 26 April ). In Descent 2: 12--23, CD discussed colour differences in fish depending on gender, age (juvenile or adult), and spawning times. He concluded that while both sexes of some fish species might have developed protective colouring, there were no examples of females alone having colours or other characters modified for protection.
- f6 5404.f6CD was correcting proof-sheets of Variation.
- f7 5404.f7The reference is to an exhibition of Wallace's collection of bird skins and butterflies (see letter from A. R. Wallace, [19 June 1867] and n. 3).