By the way, there is another subject which I shall introduce in my essay, namely, expression of countenance. Now, do you happen to know by any odd chance a very good-natured and acute observer in the Malay Archipelago, who you think would make a few easy observations for me on the expression of the Malays when excited by various emotions? For in this case I would send to such person a list of queries. I thank you for your most interesting letter, and remain, Yours very sincerely, CH. DARWIN.
CHARLES DARWIN TO A.R. WALLACE.
Down, March [1867].
My dear Wallace, I thank you much for your two notes. The case of Julia Pastrana (A bearded woman having an irregular double set of teeth. 'Animals and Plants,' volume ii. page 328.) is a splendid addition to my other cases of correlated teeth and hair, and I will add it in correcting the press of my present volume. Pray let me hear in the course of the summer if you get any evidence about the gaudy caterpillars. I should much like to give (or quote if published) this idea of yours, if in any way supported, as suggested by you. It will, however, be a long time hence, for I can see that sexual selection is growing into quite a large subject, which I shall introduce into my essay on Man, supposing that I ever publish it. I had intended giving a chapter on man, inasmuch as many call him (not QUITEtruly) an eminently domesticated animal, but I found the subject too large for a chapter. Nor shall I be capable of treating the subject well, and my sole reason for taking it up is, that I am pretty well convinced that sexual selection has played an important part in the formation of races, and sexual selection has always been a subject which has interested me much. I have been very glad to see your impression from memory on the expression of Malays. I fully agree with you that the subject is in no way an important one; it is simply a "hobby-horse" with me, about twenty-seven years old; and AFTER thinking that I would write an essay on man, it flashed on me that I could work in some "supplemental remarks on expression." After the horrid, tedious, dull work of my present huge, and I fear unreadable, book ['The Variation of Animals and Plants'], I thought I would amuse myself with my hobby-horse. The subject is, I think, more curious and more amenable to scientific treatment than you seem willing to allow. I want, anyhow, to upset Sir C. Bell's view, given in his most interesting work, 'The Anatomy of Expression,' that certain muscles have been given to man solely that he may reveal to other men his feelings. Iwant to try and show how expressions have arisen. That is a good suggestion about newspapers, but my experience tells me that private applications are generally most fruitful. I will, however, see if I can get the queries inserted in some Indian paper. I do not know the names or addresses of any other papers.
...My two female amanuenses are busy with friends, and I fear this scrawl will give you much trouble to read. With many thanks, Yours very sincerely, CH. DARWIN.
[The following letter may be worth giving, as an example of his sources of information, and as showing what were the thoughts at this time occupying him:]
CHARLES DARWIN TO F. MULLER.
Down, February 22 [1867].
...Many thanks for all the curious facts about the unequal number of the ***es in Crustacea, but the more I investigate this subject the deeper Isink in doubt and difficulty. Thanks also for the confirmation of the rivalry of Cicadae. I have often reflected with surprise on the diversity of the means for producing music with insects, and still more with birds.
We thus get a high idea of the importance of song in the animal kingdom.
Please to tell me where I can find any account of the auditory organs in the Orthoptera. Your facts are quite new to me. Scudder has described an insect in the Devonian strata, furnished with a stridulating apparatus. Ibelieve he is to be trusted, and, if so, the apparatus is of astonishing antiquity. After reading Landois's paper I have been working at the stridulating organ in the Lamellicorn beetles, in expectation of finding it sexual; but I have only found it as yet in two cases, and in these it was equally developed in both ***es. I wish you would look at any of your common lamellicorns, and take hold of both males and females, and observe whether they make the squeaking or grating noise equally. If they do not, you could, perhaps, send me a male and female in a light little box. How curious it is that there should be a special organ for an object apparently so unimportant as squeaking. Here is another point; have you any toucans? if so, ask any trustworthy hunter whether the beaks of the males, or of both ***es, are more brightly coloured during the breeding season than at other times of the year...Heaven knows whether I shall ever live to make use of half the valuable facts which you have communicated to me! Your paper on Balanus armatus, translated by Mr. Dallas, has just appeared in our 'Annals and Magazine of Natural History,' and I have read it with the greatest interest. I never thought that I should live to hear of a hybrid Balanus! I am very glad that you have seen the cement tubes; they appear to me extremely curious, and, as far as I know, you are the first man who has verified my observations on this point.
With most cordial thanks for all your kindness, my dear Sir, Yours very sincerely, C. DARWIN.
CHARLES DARWIN TO A. DE CANDOLLE.
Down, July 6, 1868.