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Darwin Correspondence Project

To Fritz Müller   12 May 1870

Down Beckenham | Kent

May 12. 1870

My dear Sir

I thank you for your two letters of Dec 15 & Mar 29, both abounding with curious facts.1 I have been particularly glad to hear in yr last about the Escholtzia; for I am now rearing crossed & self-fertilized plants, in antagonism to each other, from your semi-sterile plants, so that I may compare their comparative growth with that of the offspring of English fertile plants.2 I have forwarded your post script about Passiflora with the seeds, to Mr Farrer, who I am sure will be greatly obliged to you; the turning up of the pendant flower plainly indicates some adaptation.3 When I next go to London I will take up the specimens of butterflies & shew them to Mr Butler of the British Museum, who is a learned lepidopterist & interested on the subject.4 This reminds me to ask you whether you received my letter about the ticking butterfly described at p. 33 of my Journal of researches; viz whether the sound is in any way sexual? Perhaps the species does not inhabit yr island.5

The case described in yr last letter of the trimorphic monocot. Pontederia is grand. I wonder whether I shall ever have time to recur to this subject; I hope I may, for I have a good deal of unpublished material.6

I thank you for telling me about the first-formed flowers having additional petal, stamens, carpels &c; for it is a possible means of transition of form: it seems also connected with the fact on which I have insisted of peloric flowers being so often terminal.7 As pelorism is strongly inherited (I have just got a curious case of this in a legum. plant from India); would it not be worth while to fertilise some of your early flowers having additional organs with pollen from a similar flower, & see whether you cd not make a race thus characterised? Some of yr abutilons have germinated, but I have been very unfortunate with most of your seed.8 You will remember having given me in a former letter an account of a very curious popular belief in regard to the subsequent progeny of asses, which have borne mules; & now I have another case almost exactly like that of Lord Morton’s mare, in which it is said the shape of the hoofs in the subsequent progeny are affected.9

(Pangenesis will turn out true some day!)10

A few months ago I recd an interesting letter & paper from yr brother, who has taken up a new & good line of investigation, viz the adaptation in insects for the fertilisation of flowers.11

The only scientific man I have seen for several months is Kölliker who came here with Günther & whom I liked extremely.12

I am working away very hard at my book on man & on sexual selection, but I do not suppose I shall go to press till late in the autumn13

Believe me my dear Sir | with many thanks for all yr kindness | yours sincerely | Ch. Darwin


See letters from Fritz Müller, 18 December 1869 (Correspondence vol. 17) and 29 March 1870. CD evidently wrote ‘15’ in error.
In his letter of 29 March 1870, Müller had reported his most recent results with plants of Eschscholzia californica raised from seeds sent by CD. CD reported the results of his experiments in Cross and self fertilisation, pp. 109–17; 262–3.
For the postscript referred to, see the letter from Fritz Müller, 16 February 1870. Müller had enclosed seeds of Passiflora. Thomas Henry Farrer had been studying the fertilisation mechanisms of Passiflora (see Correspondence vol. 17).
No letter from Müller mentioning specimens of butterflies has been found. CD refers to Arthur Gardiner Butler.
See Correspondence vol. 17, letter to Fritz Müller, 8 September [1869] and n. 2. The ticking butterfly was Papilio feronia (now Hamadryas feronia, the blue cracker), which is found where Müller lived in Santa Catarina province (now state), Brazil. See Journal of researches 2d ed., p. 33. Müller moved to the mainland in 1867, but had previously lived at Destêrro (now Florianópolis) on Santa Catarina Island.
See Correspondence vol. 17, letter from Fritz Müller, 18 December 1869 and n. 3. Müller published on the three forms of Pontederia (now Eichhornia, the water hyacinth) in F. Müller 1871. CD discussed it in Forms of flowers, pp. 183–7.
In his letter of 18 December 1869 (Correspondence vol. 17), Müller had described peloric flowers of Agapanthus and Jussiaea, a synonym of Ludwigia. In Variation 2: 345–7, CD discussed the tendency of terminal or central flowers to be peloric.
Müller had sent seeds of Abutilon with his letter of 18 October 1869 (Correspondence vol. 17; see ibid., letter to Fritz Müller, 1 December [1869]).
The letter in which Müller discussed the offspring of asses has not been found, but see the letter to J. J. Weir, 17 March [1870], in which CD quoted a passage from Müller on the topic. See also the letter from J. J. Weir, 17 March 1870 and n. 1 for more on the mare of Lord Morton (George Sholto Douglas).
CD refers to his hypothesis of pangenesis, a theory of heredity described in Variation 2: 357–404.
CD refers to Descent, which went to press on 30 August 1870 (see CD’s ‘Journal’ (Appendix II)).


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

Cross and self fertilisation: The effects of cross and self fertilisation in the vegetable kingdom. By Charles Darwin. London: John Murray. 1876.

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

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

Journal of researches 2d ed.: Journal of researches into the natural history and geology of the countries visited during the voyage of HMS Beagle round the world, under the command of Capt. FitzRoy RN. 2d edition, corrected, with additions. By Charles Darwin. London: John Murray. 1845.

Müller, Fritz. 1871. Ueber den Trimorphismus der Pontederien. Jenaische Zeitschrift für Medicin und Naturwissenschaft 6: 74–8.

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


Crossing experiments and self-sterility [in Eschscholzia].


Hermann Müller on insect adaptations for fertilisation of flowers.

CD working on book on man and sexual selection.

Letter details

Letter no.
Charles Robert Darwin
Johann Friedrich Theodor (Fritz) Müller
Sent from
Source of text
The British Library (Loan MS 10 no 32)
Physical description
LS(A) 4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 7184,” accessed on 19 April 2024,

Also published in The Correspondence of Charles Darwin, vol. 18