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Darwin Correspondence Project

To Leonard Jenyns   14 February [1845]

Down Bromley Kent

Feb. 14th.

Dear Jenyns.

I have taken my leisure in thanking you for your last letter, & discussion, to me very interesting, on the increase of species. Since your letter, I have met with a very similar view in Richardson, who states that the young are driven away by the old into unfavourable districts, & then mostly perish.—1 When one meets with such unexpected statistical returns on the increase & decrease & proportions of deaths & births amongst mankind & in this well-known country of ours, one ought not to be in the least surprised at ones ignorance, when, where & how, the endless increase of our robins & sparrows is checked.—

Thanks for your hints about terms of “mutation” &c; I had had some suspicions, that it was not quite correct, & yet I do not yet see my way to arrive at any better terms: it will be years before I publish, so that I shall have plenty of time to think of better words— Development wd. perhaps do, only it is applied to the changes of an individual during its growth. I am, however, very glad of your remark, & will ponder over it.

We are all well, wife & children three, & as flourishing as this horrid, house-confining, temper-souring weather permits.—

With thanks, believe me | Your’s very sincerely | C. Darwin


J. Richardson 1829–37, 2: xix–xx. CD recorded this work as having been read on 29 January 1845 (DAR 119; Vorzimmer 1977, p. 133). It is in the Darwin Library–CUL. John Richardson referred to the practice of adult birds driving the young into less favourable breeding grounds but said nothing about the young perishing. For Jenyns’ comments on this subject see Jenyns 1846, pp. 113–17.


Jenyns, Leonard. 1846. Observations in natural history: with an introduction on habits of observing, as connected with the study of that science. Also a calendar of periodic phenomena in natural history; with remarks on the importance of such registers. London: John Van Voorst.

Richardson, John. 1829–37. Fauna Boreali-Americana; or, the zoology of the northern parts of British America. Assisted by William Swainson and William Kirby. 4 vols. London and Norwich: John Murray; Richard Bentley; J. Fletcher.

Vorzimmer, Peter J. 1977. The Darwin reading notebooks (1838-1860). Journal of the History of Biology 10: 107–53.


Discusses checks on growth of species population; use of term "mutation" in his species theory. His belief in species mutability.

Letter details

Letter no.
Charles Robert Darwin
Leonard Jenyns/Leonard Blomefield
Sent from
Source of text
Bath Royal Literary and Scientific Institution
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 828,” accessed on 14 December 2019,

Also published in The Correspondence of Charles Darwin, vol. 3