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Darwin Correspondence Project


To J. S. Henslow   28 [September 1860]

15 Marine Parade | Eastbourne.


My dear Henslow

Just before coming here for our poor girl’s health (I am glad to say that she has benefitted decidedly from sea-air) I received your little note, telling me that you were not quite satisfied on antiquity of the Celts.1

I fear that this truly dreadful weather will give me no chance of my weed-seeds.—2

My object in writing now is to beg for a bit of information; & I cannot think of any one else to apply to, otherwise I would not have troubled you.—

I have been making a great number of observations on the leaves of Drosera, & have come to some curious results about their power of discriminating nitrogenised compounds.—

When the viscid hairs contract or become inflected; they pour out much fluid & the contents of the cells in the footstalks, instead of being a thin pink homogeneous fluid, becomes a broken mass of dark red, thick fluid. When the cells are in this condition, the particles circulate round the cell, as if driven by ciliæ. I believe that this is not an uncommon circumstance: is it? But what has surprised me is that the globules & cylinders of the thick dark red fluid or substance keeps on an incessant slow contracting & expanding movement: they often coalesce & then separate again; they often send out buds, which rapidly increase at the expence of the larger parent mass; in short endless slow changes in form.3 These slow incessant movements, which are quite independent of the circulation, resemble the movements of sarcode in the protozoa.4

Is any such phenomenon known? it may be quite common, as I am so ignorant of vegetable physiology.—   It has surprised me much. Will you be so very kind, whenever you have a little leisure, to let me hear—

I hope you have returned well & strong after your tour.

What a wonderful start this of Hooker’s.!—5

My dear Henslow | Yours affectionately | C. Darwin

P.S. Though I cannot conceive how it can be effected, I presume that the movement in the red matter must be due to slow absorption of water. Yet how this should make the globules coalesce, divide, coalesce again & bud out into new globules, it is hard to understand.—


The letter from Henslow has not been found. Henslow’s interest in the question of the antiquity of man had been stimulated by the recent discovery of flint implements known as celts in various deposits in Europe and Britain. He examined the finds at a site in Hoxne, Suffolk, in 1859 and discussed his views in a letter to the Athenæum, 19 November 1859, p. 668. He had just returned to England from France, where he visited the celebrated gravel pits near Amiens and Abbeville in which many celts had been found. In a letter to the Athenæum dated 14 October 1860, Henslow stated his conviction ‘that the facts I have witnessed do not of necessity support the hypothesis of a pre-historic antiquity for these works of man.’ (Athenæum, 20 October 1860, p. 516). See also letters to J. S. Henslow, 26 October [1860] and 10 November [1860].
It is not known for what purpose CD wished to obtain weed seeds. It may have been in connection with his study of the digestive powers of Drosera (see Insectivorous plants, pp. 127–8). Henslow had previously supplied CD with the seeds of many native plants, some of them collected by the little girls who attended Henslow’s elementary botanical classes in Hitcham (see Correspondence vols. 5 and 6). In 1857, CD made observations on weed seedlings naturally appearing in a cleared patch of ground, noting the proportion that perished (see Experimental book, p. 25 (DAR 157a), and Correspondence vol. 6, letter to J. D. Hooker, [21 March 1857] and n. 5). He cited his results in Origin, pp. 67–8.
This phenomenon, which CD called ‘aggregation of protoplasm’, is described in Insectivorous plants, chapter 3. His notes recording observations made in the autumn of 1860 are in DAR 60.1: 77–81.
The French naturalist Félix Dujardin coined the term ‘sarcode’ to denote the homogeneous, glutinate substance found in Protozoa. He further noted that this substance was endowed with the ability of self-contraction. See Dujardin 1841, pp. 35–42.
CD refers to Joseph Dalton Hooker’s botanical expedition to Syria.


Has been observing Drosera. Asks JSH whether a curious motion in the red fluid poured out from the viscid hairs is a known or common phenomenon. It surprised him, but he is "so ignorant of vegetable physiology".

Letter details

Letter no.
Darwin, C. R.
Henslow, J. S.
Sent from
Source of text
DAR 93: 76–8
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 2932,” accessed on 28 August 2016,