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Darwin Correspondence Project

From William Preyer   2 December 1880


Dec. 2, 1880

Dear Sir—

I feel very much obliged to you for having sent me your new book, the results of which seem to inaugurate quite a new theory of irritability.1 Besides I think your graphic method may be applied to the chick in the egg. I shall try in spring.2

What you say about the origin of certain instincts which probably must be ascribed to “modifications” or “variations” of the brain, not to experience and habit, was quite new to me and is to a certain degree proved to be true by Brown-Séquards experiments and Westphals observations, which shew that epileptiform-movements may not only be artificially produced in guinea-pigs but that the young of such individuals show the same abnormal phenomena without having been pricked. I remember not exactly when and where this important fact has been published.3 But it confirms not only your theory, it proves also that such instincts which are of no “service to the species” may be inherited. I wish you could find time to write on “the marvellous facts of instinct” as indicated in your ‘Variation of Animals and Plants under domestication’ 1868 vol. 1, p. 8.4 With many thanks I enclose the short notes from ‘Nature’5

I am dear Sir your’s most faithfully | Wm. Preyer


See letter to William Preyer, 27 November 1880. Preyer’s name is on CD’s presentation list for Movement in plants (see Appendix IV). Preyer refers to CD’s theory that sensitivity to irritation was localised in specific areas of plants and transmitted to other parts, which then reacted in variable ways (Movement in plants, pp. 569–73).
In Movement in plants, CD had employed line graphs to represent the circumnutation of different plant organs. Preyer was studying embryonic movement in vertebrates. His conclusions on different causes of embryonic movement were detailed in Specielle Physiologie des Embryo: Untersuchungen ueber Lebenserscheinungen vor der Geburt (Special physiology of the embryo: investigations into phenomena of life before birth; Preyer 1885, pp. 441–60).
Preyer had asked CD for copies of letters on instincts that CD had written to Nature (see letter from William Preyer, 25 November 1880 and n. 2); in one of the letters, CD discussed the possibility that some instincts were the result of modifications of the brain (see Correspondence vol. 21, letter to Nature, [before 3 April 1873]). CD also discussed instincts as modifications of the brain in Descent 2d ed., p. 68. Charles Édouard Brown-Séquard had experimented on the artificial production of epileptic-like convulsions in guinea pigs and the transmission of these to offspring (Brown-Séquard 1860). Carl Westphal had noted further methods of inducing convulsions, but stressed the difference between these induced seizures and those of classical epilepsy in ‘Ueber künstliche Erzeugung von Epilepsie bei Meerschweinchen’ (On artificial production of epilepsy in guinea pigs; Westphal 1871).
CD had proposed to investigate instinct as part of a projected work discussing variation of organisms in a state of nature (Variation 1: 8). He later gave the draft of his work on the subject to George John Romanes, who published it as an appendix to Mental evolution in animals (G. J. Romanes 1883, pp. 355–84).
See letter from William Preyer, 25 November 1880 and n. 2. CD had sent copies of the articles with his letter to Preyer of 27 November 1880.


Brown-Séquard, Charles Édouard. 1860. Hereditary transmission of an epileptiform affection accidentally produced. [Read 2 February 1860.] Proceedings of the Royal Society of London 10 (1859–60): 297–8.

Descent 2d ed.: The descent of man, and selection in relation to sex. By Charles Darwin. 2d edition. London: John Murray. 1874.

Movement in plants: The power of movement in plants. By Charles Darwin. Assisted by Francis Darwin. London: John Murray. 1880.

Preyer, William. 1885. Specielle Physiologie des Embryo. Untersuchungen ueber die Lebenserscheinungen vor der Geburt. Leipzig: Th. Grieben’s Verlag (L. Furnau).

Romanes, George John. 1883a. Mental evolution in animals: with a posthumous essay on instinct by Charles Darwin. London: Kegan Paul, Trench & Co.

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

Westphal, Carl. 1871. Ueber künstliche Erzeugung von Epilepsie bei Meerschweinchen. Berliner Klinische Wochenschrift 8: 449–51; 461–3.


CD’s comment that certain instincts originate as variations of the brain, rather than as habits, is supported by Brown-Séquard’s and C. F. O. Westphal’s work on epileptiform movements.

Letter details

Letter no.
William Thierry (William) Preyer
Charles Robert Darwin
Sent from
Source of text
DAR 174: 72
Physical description
ALS 3pp

Please cite as

Darwin Correspondence Project, “Letter no. 12883,” accessed on 1 October 2023,