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Darwin Correspondence Project

To J. S. Henslow   11 October [1860]

15 Marine Parade | Eastbourne

Oct 11.

My dear Henslow

Very many thanks for your pleasant letter just received from Down, with many things which interested me.1 I am particularly obliged for answer about contracting & expanding red thick fluid substance. I have been observing it with great care. & it really is a most curious phenomenon.—   It all takes place within the same cell. & is, I now find certainly not from endosmose or exosmose from any external fluid;2 for a hair cut off & put dry between two slips of glass, shows the phenomenon splendidly. I have outline of a whole series of changes; which are infinitely varied & never cease. The movement can never be seen until after the hairs have contracted over a Fly or other substance.3 But I shall write a paper on the subject: so will not trouble you any more.—

You have told me what I wanted to know, whether it was some well phenomenon.—4

Yours affect | C. Darwin

Dr. Bree “pitches” into me handsomely.—5


Henslow’s letter has not been found. It was evidently a reply to the letter to J. S. Henslow, 28 [September 1860].
CD discussed the phenomenon of ‘aggregation’ in Insectivorous plants, chapter 3. He stated that at first he believed the ‘movements of the masses might be due to the absorption of water’ (ibid., p. 41).
CD later found that the process of aggregation was independent of the inflexion of the hairs (ibid., pp. 43, 54–5).
Henslow interlined ‘known’ after ‘well’.


Sends further details on the movement of the red fluid substance in Drosera. Will write a paper on it.

"Dr [C. R.] Bree ""pitches"" into me handsomely."

Letter details

Letter no.
Charles Robert Darwin
John Stevens Henslow
Sent from
Source of text
DAR 93: A79–80
Physical description
ALS 3pp

Please cite as

Darwin Correspondence Project, “Letter no. 2945,” accessed on 22 July 2024,

Also published in The Correspondence of Charles Darwin, vol. 8