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Darwin Correspondence Project

To Nature   [21? May 1878]1


Transplantation of shells

It is well known that animals and plants inhabiting freshwater have, as a general rule, a very wide distribution; yet each river system, with all the pools and lakes in connection with it, seems completely cut off from every other system of the same country. Still more complete is the separation between the freshwaters of distinct continents or of islands; nevertheless they often possess freshwater species in common. In my “Origin of Species” I have suggested various means of transportal;2 but as few facts on this head are positively known, the case given in the adjoined letter of a living Unio, which had caught one of the toes of a duck’s foot between its valves, and was secured in the act of being transported, seems to me well worth recording.3

charles darwin


The date is conjectured from the relationship between this letter and the letter to J. N. Lockyer, 21 May [1878]. This letter may have been enclosed in the letter to J. N. Lockyer, 21 May [1878]; alternatively, Lockyer may have asked CD later to write an introduction to the letter from A. F. Gray, 8 May [1878], but no other correspondence on the subject has been found.
See Origin, pp. 383–88.
CD enclosed the letter from A. F. Gray, 8 May [1878]. Gray had sent a sketch of a freshwater mussel, Unio complanatus (a synonym of Elliptio complanata, eastern elliptio), attached to the foot of a duck.


Origin: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. By Charles Darwin. London: John Murray. 1859.


CD’s letter on wide distribution of freshwater plants and animals introduces a letter to him from Arthur H. Gray [see 11497].

Letter details

Letter no.
Charles Robert Darwin
Sent from
Source of text
Nature, 30 May 1878, pp. 120–1

Please cite as

Darwin Correspondence Project, “Letter no. 11520,” accessed on 1 October 2023,