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Darwin Correspondence Project

To W. H. Dallinger   [after 10 January 1876]1

Down, | Beckenham, Kent. | Railway Station | Orpington. S.E.R.

My dear Sir

You will find at p. 404 of my Insectivorous Plants the reasons why I think that it is not a main function of the bladders to serve as floats.2 I might have added that very young plants or branches with bladders not containing air float. The terminal buds separate in the autumn from the decaying branches, & as you no doubt know well know sink to the bottom, & I imagine this is due to the absence of air in the intercellular passages, which is present there in the summer.

I am very glad to hear that you intend to investigate Drosera in the spring.3

Allow me to add that I have read all your & Dr. Drysdale’s papers, & they seem to me to possess higher value than anything which has been published on such subjects, though I am too ignorant to have any right to express such an opinion, but I have a full right to say that they are extremely interesting.4

With sincere respect for your labours, I remain | Dear Sir


The date is established by the relationship between this letter and the letter from W. H. Dallinger, 10 January 1876.
See letter from W. H. Dallinger, 10 January 1876. CD had argued that the purpose of the bladders on Utricularia (bladderwort) was to catch insects rather than to serve as floats; he pointed out that branches with no bladders, or from which the bladders had been removed, also floated owing to air in the intercellular spaces (Insectivorous plants, p. 404).
Dallinger had collaborated with John James Drysdale on a series of experiments on flagellate protozoa that demonstrated that their spores could survive at temperatures above boiling point, thus undermining evidence for the spontaneous generation of life in supposedly sterile liquids. CD had sent Ernst Haeckel his copy of the first in a series of papers published by Dallinger and Drysdale in the Monthly Microscopical Journal between 1873 and 1875 (Dallinger and Drysdale 1873; see Correspondence vol. 21, letter to Ernst Haeckel, 25 September 1873). Copies of two later papers in the series (Dallinger and Drysdale 1874 and Dallinger and Drysdale 1875) are in the Darwin Pamphlet Collection–CUL, but these, which were sent with the authors’ compliments, were probably received in 1878 (see letter from W. H. Dallinger, 29 June 1878 (Calendar no. 11576)). For Dallinger’s career, and the significance of his discoveries with Drysdale, see Haas 2000 and Strick 2000.


Calendar: A calendar of the correspondence of Charles Darwin, 1821–1882. With supplement. 2d edition. Edited by Frederick Burkhardt et al. Cambridge: Cambridge University Press. 1994.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Insectivorous plants. By Charles Darwin. London: John Murray. 1875.

Strick, James. 2000. Sparks of life: Darwinism and the Victorian debates over spontaneous generation. Cambridge, Mass.: Harvard University Press.


CD has read all of WHD’s and J. J. Drysdale’s papers [on spontaneous generation, monads, and the origin of life] and finds them the best work on the subject.

The function of bladders in Utricularia is not to float the plant.

Letter details

Letter no.
Charles Robert Darwin
William Henry Dallinger
Sent from
Source of text
Royal Institution of Great Britain (RI MS CG/u/3)
Physical description
damaged incomplete

Please cite as

Darwin Correspondence Project, “Letter no. 10354,” accessed on 6 August 2020,

Also published in The Correspondence of Charles Darwin, vol. 24