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Darwin Correspondence Project

To Fritz Müller   30 January [1868]1

Down Bromley Kent

Jan 30

My dear Sir

I send by this post, by French packet, my new book, the publication of which has been much delayed.2 The greater part, as you will see, is not meant to be read; but I shd very much like to hear what you think of “Pangenesis”, tho’ I fear it will appear to every one far too speculative.3

I am very much obliged for yr answers, tho’ few in number (Oct 5th) about expression. I was especially glad to hear about shrugging the shoulders.4 You say that an old negro woman, when expressing astonishment, wonderfully resembled a Cebus when astonished; but are you sure that the Cebus opened its mouth?? I ask because the Chimpanzee does not open its mouth when astonished or when listening.5 Please have the kindness to remember that I am very anxious to know whether any monkey when screaming violently partially or wholly closes its eyes.6

Many thanks for your answers about the Planariæ, & about conspicuous seeds.7 By the way one of your seeds of the Pavonia has germinated.8 I sent the Solanum-like flower to Hooker, & I believe he has written to you.9 How strange it is that the same anomalous reduction of one leaf shd occur in several families! Gesneria pendulina (this is the sp. name) is certainly not dimorphic.10 Your Plumbago is Zeylanica an Indian species, I suppose naturalized with you; it shed its first flower-buds but it is now producing others, & I think it will turn out dimorphic.11 The flowers of Escholzia when crossed with pollen from a distinct plant produced 91 per cent of capsules; when self-fertilized the flowers produced only 66 per cent of capsules. An equal number of crossed & self-fertilized capsules contained seed by weight in the proportion of 100 to 71.12

Nevertheless the self-fert. flowers produced an abundance of seed. I enclose a few crossed seeds in hopes that you will raise a plant, cover it with a net, & observe whether it is self-fertile; at the same time allowing several uncovered plants to produce capsules; for the sterility formerly observed by you seems to me very curious.

With sincere thanks for your never failing kindness believe me my dear Sir | yours very faithfully | Charles Darwin

You will find your most valuable observations on self-sterile Orchids given in the second volume.—13


The year is established by the reference to the publication of Variation (see n. 2, below).
The reference is to Variation. Müller’s name appears on the presentation list for the book (see Correspondence vol. 16, Appendix IV). On delays to publication caused by the preparation of the index, see the letter from W. S. Dallas, 8 January 1868.
CD refers to his chapter ‘Provisional hypothesis of pangenesis’ (Variation 2: 357–404).
Müller’s reply to CD’s queries on the expression of emotions was probably in the missing portion of his letter to CD of [8 October 1867] (Correspondence vol. 15). Müller is cited once in Expression pp. 268–9, on the shrugging of shoulders by ‘negroes in Brazil’.
Cebus is a genus of South American monkeys. CD included chimpanzees and other primates in his discussion of the expression of astonishment in Expression, pp. 144–5, remarking that ‘in no case did any monkey keep its mouth open when it was astonished’. CD suggested that this might be because monkeys breathed more freely through their nostrils than humans did.
CD’s letter to Müller containing this query has not been found.
CD had asked Müller about brightly coloured Planaria (flatworms) in his letter of 31 July [1867] (Correspondence vol. 15; see also Descent 1: 322); Müller’s reply was probably in the missing portion of his letter of [8 October 1867] (ibid.). Müller sent information about plants in the family Amarantaceae (now Amaranthaceae) producing conspicuous seeds that attracted the attention of birds in his letter of [8 October 1867] (ibid.).
Pavonia is a genus in the family Malvaceae. It is mentioned in a list of genera containing cleistogamic species in Forms of flowers, p. 313. However, CD may refer to Adenanthera pavonina (Leguminosae). Joseph Dalton Hooker had identified the plant from its brightly coloured seeds, which had been sent to CD by Fritz Müller in 1866 (see Correspondence vol. 14, letter from J. D. Hooker, 14 December [1866]).
In his letter to Müller of 2 November 1867 (Correspondence vol. 15), CD reported that Gesneria appeared to be dimorphic. His observations were made on plants that had been raised from seeds sent by Müller. Gesneria pendulina is a synonym of Sinningia aggregata
Müller first reported on a dimorphic species of Plumbago in his letter to CD of [2 November 1866] (Correspondence vol. 14), and later sent CD seeds of the plant (see Correspondence vol. 15, letter to Fritz Müller, 25 March [1867]).
Müller had observed self-sterility in Eschscholzia californica (Correspondence vol. 14, letter from Fritz Müller, 2 August 1866), and sent further observations in his letter of [2 November 1866] (ibid.). CD reported that he had found the species to be self-fertile (Correspondence vol. 15, letter to Fritz Müller, 2 November 1867). CD reported the results of further experiments, made over several generations, in Cross and self fertilisation.
Müller’s observations of Oncidium, Epidendrum, and Notylia are reported in Variation 2: 134–5. See also Correspondence vols. 14 and 15.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

Descent: The descent of man, and selection in relation to sex. By Charles Darwin. 2 vols. London: John Murray. 1871.

Expression: The expression of the emotions in man and animals. By Charles Darwin. London: John Murray. 1872.

Forms of flowers: The different forms of flowers on plants of the same species. By Charles Darwin. London: John Murray. 1877.

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.


Sends Variation and would like to hear what FM thinks of Pangenesis.

Thanks for information on expression.

Dimorphic plants;

differences in seed production in cross- and self-fertilised plants.

Letter details

Letter no.
Charles Robert Darwin
Johann Friedrich Theodor (Fritz) Müller
Sent from
Source of text
The British Library (Loan MS 10 no 20)
Physical description
LS(A) 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 5816,” accessed on 22 March 2023,

Also published in The Correspondence of Charles Darwin, vol. 16