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Darwin Correspondence Project

From John Davy   10 January 1856

[Reports the results of experiments on the vitality of impregnated fish ova carried out in November and December 1855. The ova of Charr were exposed to temperatures ranging from 70o F to 84o F for various periods of time. Ten experiments to ascertain the maximum temperature at which the ova will stay alive were carried out. A second series of experiments was also performed in which a trial of the vitality of the ova was made by packing them in wet wool and sending them a distance by post. Considers it as proved that the power of resisting an undue temperature is possessed in a higher degree by the ova in an advanced, than in an early stage of development; and that the power of retaining life in moist air in like degree increases with age. It may further be inferred that the ova of other species of the Salmonidæ, were they similarly exposed, would afford similar results.]1


The letter was intended to be communicated by CD to the Royal Society of London in the same way that CD had sent an earlier letter from Davy to be published in the Philosophical Transactions of the Royal Society of London (see Correspondence vol. 5, letter from John Davy, 21 March 1855).


On the vitality of the ova of the Salmonidae at different stages of development.

Letter details

Letter no.
John Davy
Charles Robert Darwin
Sent from
Source of text
Proceedings of the Royal Society of London 8 (1856–7): 27–33

Please cite as

Darwin Correspondence Project, “Letter no. 1819A,” accessed on 25 June 2019,

Also published in The Correspondence of Charles Darwin, vol. 6