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Darwin Correspondence Project


To Fritz Müller   22 February [1867]

Down Bromley Kent

Feb 22

My dear Sir

Your last letter of Jan. 1. is more valuable to me even than some of your previous ones.1 The fact about the own-pollen being poisonous is quite extraordinary; I will quote your remarks & explanation after giving your former facts.2 Can the cause of the decay be due to parasitic cryptogams?3 I shd be very much obliged to you if you wd. inform me soon whether Oncidium flexuosum is a native of your district.4 These observations of yours will be a most valuable addition to my discussion on self-impotent plants.5 There never was a more curious case than that of the rudimentary condition of the organs in Catasetum. It explains the fact, which I have been assured of, that Catasetum in some countries not rarely produces seed-capsules.6 Your facts also about the sucking in of the pollen-masses & of the dispersal of the seeds in Gesneria are all quite new to me.7 I hope you keep a record of all your miscellaneous observations, for you might thus hereafter publish a wonderful book.

Although you have aided me to so great an extent in many ways, I am going to beg for any information on two other subjects. I am preparing a discussion on “sexual selection”, & I want much to know how low down in the animal scale sexual selection of a particular kind extends.8 Do you know of any lowly organized animals, in which the sexes are separated and in which the male differs from the female in arms of offence, like the horns & tusks of male mammals, or in gaudy plumage & ornaments as with birds & butterflies? I do not refer to secondary sexual characters by which the male is able to discover the female, like the plumed antennæ of Moths, or by which the male is enabled to seize the female, like the curious pincers described by you in some of the lower crustaceans.9 But what I want to know is how low in the scale sexual differences occur which require some degree of self-consciousness in the males, as weapons by which they fight for the female, or ornaments which attract the opposite sex. Any differences between males & females which follow different habits of life wd have to be excluded. I think you will easily see what I wish to learn. A priori it wd never have been anticipated that insects wd have been attracted by the beautiful colouring of the opposite sex, or by the sounds emitted by the various musical instruments of the male Orthoptera.10 I know no one so likely to answer this question as yourself. & shd be grateful for any information however small.

My second subject refers to expression of countenance, to which I have long attended, & in which I feel a keen interest; but to which unfortunately I did not attend when I had the opportunity of observing various races of Man.11 It has occurred to me that you might without much trouble make a few observations for me in the course of some months on Negros, or possibly on native S. Americans; though I care most about Negros. Accordingly I enclose some questions as a guide & if you cd answer me even one or two I shd feel truly obliged. I am thinking of writing a little essay on the origin of Mankind, as I have been taunted with concealing my opinions; & I shd do this immediately after the completion of my present book. In this case I shd add a chapter on the cause or meaning of Expression.12

With gratitude for all your great kindness & sincere admiration of all your powers of observation I remain | my dear Sir yours very | sincerely C. Darwin

PS. | You must not give yourself any great trouble about these questions, but possibly you might in the course of a few months be able to observe for me one or two points.

I have sent copies to other quarters of the world

an answer within 6 or 8 months wd be in time.—13

If you kept the subject occasionally before your mind, an opportunity of observing some few cases, such for instance as (4) or (5) or (13) &c would almost certainly occur.—

But you must not plague yourself on a subject which will appear trifling to you, but has, I am sure, some considerable interest.


Queries about Expression

(1) Is astonishment expressed by the eyes & mouth being opened wide & by the eyebrows being elevated?

(2) Does shame excite a blush, when the colour of the skin allows it to be visible?

(3) When a man is indignant or defiant does he frown, hold his body & head erect, square his shoulders & clench his fists?

(4) When considering deeply on any subject or trying to understand any puzzle does he frown, or wrinkle the skin beneath the lower eyelids?

(5) When in low spirits are the corners of the mouth depressed, & the inner corner or angle of the eybrows raised by that muscle which the French call the ‘grief’ muscle?

(6) When in good spirits do the eyes sparkle with the skin round & under them a little wrinkled & with the mouth a little extended?

(7) When a man sneers or snarls at another is the corner of the upper lip over the canine teeth raised on the side facing the man whom he addresses?

(8) Can a dogged or obstinate expression be recognized, which is chiefly shewn by the mouth being firmly closed, a lowering brow & slight frown?

(9) Is contempt expressed by a slight protrusion of the lips & turning up of the nose with a slight expiration?

(10) Is disgust shewn by everted lower lip, slightly raised upper lip with sudden expiration something like incipient vomiting?

(11) Is extreme fear expressed in the same general manner as with Europeans?

(12) Is laughter ever carried to such an extreme as to bring tears into the eyes?

(13) When a man wishes to shew that he cannot prevent something being done, or cannot himself do something does he shrug his shoulders, turn inwards his elbows, extend outwards his hands & open the palms?

(14) Do the children when sulky pout, or greatly protrude their lips?

(15) Can guilty or sly or jealous expressions be recognized? tho’ I know not how these can be defined.

(16) As a sign to keep silent is a gentle hiss uttered?

(17) Is the head nodded vertically in affirmation, & shaken laterally in negation?

Observations on natives who have had little communications with Europeans would be of course the most valuable, tho’ those made on any natives wd be of much interest to me. General remarks on expression are of comparatively little value. A definite description of the countenance under any emotion or frame of mind wd possess much more value, & an answer to any one of the foregoing questions wd be gratefully accepted.

Ch. Darwin

Down Bromley Kent


See letter from Fritz Müller, 1 January 1867.
See Correspondence vol 14, letter from Fritz Müller, 1 December 1866, and this volume, letter from Fritz Müller, 1 January 1867 and nn. 1, 5, and 8–10.
CD may be recalling John Scott’s observation of fungal threads on the pollen masses of Bletia (see Correspondence vol. 11, letter from John Scott, [1–11] April [1863]). In Variation 2: 134, CD noted that the discoloration and decay were not caused by parasitic cryptogams, which were observed by Müller only once (see letter from Fritz Müller, 1 April 1867).
CD also asked this question in his letter to Müller of 7 February [1867].
See n. 2, above. CD discussed self-impotent plants in Variation 2: 131–40. See also Cross and self fertilisation, pp. 329–47. In Origin 5th ed., p. 333, CD wrote: ‘With plants, so far is cultivation from giving a tendency towards sterility between distinct species, that in several well-authenticated cases …, certain plants … have become self-impotent, whilst still retaining the capacity of fertilising and being fertilised by, other species.’
On the rudimentary nature of some Catasetum organs, see the letter from Fritz Müller, 1 January 1867 and nn. 15 and 16. CD had received letters regarding the production of seed capsules in Catasetum in Trinidad (see Correspondence vol. 11, letter from H. F. Hance, 10 May 1863, and letter from Edward Bradford, 31 July 1863; see also Correspondence vol. 12, letter to Daniel Oliver, 18 March [1864], and ‘Fertilization of orchids’, p. 154 (Collected papers 2: 151)). See also Orchids 2d ed., p. 197 n.
See letter from Fritz Müller, 1 January 1867 and nn. 17–19.
CD had briefly discussed sexual selection in Origin, pp. 87–90, 197–200. He had also discussed sexual selection with Alfred Russel Wallace in 1864, with Charles Lyell in 1865, and with James Shaw in 1866 (see Correspondence vols. 12, 13, and 14). CD was currently collecting material on sexual selection that would ultimately appear in Descent.
For a discussion of secondary sexual characters, see Origin, pp. 150–8. In Für Darwin (F. Müller 1864, pp. 12–17), Müller discussed the chelae in species of crustacea that had two male forms. In one form the chelae were larger; the chelae were used to clasp females (see Dallas trans. 1869, pp. 20–6). Darwin cited Müller on these crustacea in Descent 1: 328 et seq.
CD discussed the colouring of insects throughout Descent 1: 361–423; he discussed the auditory apparatus of Orthoptera in ibid. pp. 352–61.
CD kept notes made during 1837, 1838, and 1839 on human descent and on expression in his M and N notebooks, and in ‘Old and useless notes’ (see Barrett 1980; see also H. E. Gruber 1981, p. 39); he also made careful observations of his children’s expressions (see Correspondence vol. 4, Appendix III). He made occasional observations of the expressions of indigenous peoples while on the Beagle voyage (see Journal of researches, and R. D. Keynes ed. 1988).
CD did not explicitly discuss human descent in Origin; for objections to what his correspondents took to be his opinion on the topic following its publication, see, for example, Correspondence vol. 8, letter from Leonard Jenyns, 4 January 1860, and letter from W. H. Harvey, 24 August 1860. More recently, CD had been deeply disappointed by Charles Lyell’s Antiquity of man (C. Lyell 1863), and had disagreed on ‘minor’ points with Alfred Russel Wallace’s essay on humans and natural selection (A. R. Wallace 1864b; see, respectively, Correspondence vol. 11, and Correspondence vol. 12, letter to A. R. Wallace, 28 [May 1864]). He had only recently decided to write a separate essay on humans instead of devoting a chapter to it in Variation (see letter to William Turner, 11 February [1867]). Ultimately, he published Expression separately from Descent.
CD sent handwritten queries about expression to a number of correspondents at the end of February 1867. CD had earlier sent similar queries on expression to the Falkland Islands (see Correspondence vol. 8, letter to Thomas Bridges, 6 January 1860) and had also evidently sent questions in late 1866 (see Correspondence vol. 14, letter to B. J. Sulivan, 31 December [1866]; see also, this volume, letter from B. J. Sulivan, 11 January 1867 and n. 3). For more on CD’s queries about expression, see Freeman and Gautrey 1970 and 1975, and Freeman 1977. On CD’s research for Expression, see Browne 1985 and Ekman ed. 1998. Müller’s replies, written on 5 October 1867 and sent to CD, have not been found; see letter from Fritz Müller, [8 October 1867], n. 2. See also Expression, pp. 268–9.


Observations on orchid self-sterility.

Wants information on characters that may have originated through sexual selection in lower animals.

Encloses queries on expression.

Letter details

Letter no.
Darwin, C. R.
Müller, J. F. T.
Sent from
Source of text
British Library (Loan 10: 13)
Physical description
5pp, encl 3pp

Please cite as

Darwin Correspondence Project, “Letter no. 5410,” accessed on 26 July 2016,