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Darwin Correspondence Project

To Robert Ball   26 May [1851]1

Down Farnboro’ Kent

May 26th

My dear Sir

I am very much obliged to you for your kindness in writing to me on the several curious points, specified in your letter, touching the Cirripedia.

I think I certainly know the large species, attached to turtles’ backs & sometimes penetrating even their bones; it is the Chelonobia of Leach & Astrolepas of Gray.2 I have not yet particularly attended to this genus.3 I have dissected with care Coronula & Tubicinella & the only conclusion which I was able to arrive at was, that the cirripedes did not in fact penetrate the skin, but that the surrounding parts of the skin of the cetacea grow upwards, the part immediately under the cirripede not growing or even being absorbed by the action of the downward pressure of the cirripede which grows at its base.—4 I always have felt some doubt regarding this, & especially in regard to Chelonobia.—5 It is quite new to me that this genus should make burrows or move at all laterally, if I understand you rightly: but I do not think a cast wd. be worth sending,6 though I shd. have much liked to have examined the real specimens.

I have a vast number of specimens in the Turtle-shell, & these hereafter I will closely inspect: Lithotrya, Alcippe of Hancock & a nov. genus,7 have an undoubted power of mechanical burrowing, but this is different from anything which Chelonobia could possess.—

If you wd. take the trouble to send me the S. American Balanus, the growth of which is known to have been under 7 weeks, I shd be very much obliged in order to measure it & see what species it is.— I have plenty of specimens, which are impressed with the various markings of the shells & other objects to which they have been attached.

Very many thanks for your offers of sending me notes of the occurrence of species of Anatifa on the Irish Coasts; but having had Mr. W. Thompson’s of Belfast8 & several other collections for examination, I do not think it likely there would be anything new. Of the six species of Anatifa, I know of 5 as being British; & the 6th is antarctic.

With my sincere thanks. Believe me | My dear Sir | Yours sincerely | C. Darwin


The year is established from the mourning border of the stationery used by CD after the death of Anne Darwin.
Darwin did not begin working on this genus of Balanidae until 1852 (‘Journal’; Correspondence vol. 5, Appendix I).
CD described this attachment of Chelonobia in Living Cirripedia (1854): 390–2.
A reference to Cryptophialus. The three genera are mentioned in Living Cirripedia (1854): 512 as the only three to which CD attributed mechanical powers of excavation. He based his opinion on his examination, especially in Lithotrya, of the serrated structure of the lowest scales of the peduncle (see Living Cirripedia (1851): 337).


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

Living Cirripedia (1851): A monograph of the sub-class Cirripedia, with figures of all the species. The Lepadidæ; or, pedunculated cirripedes. By Charles Darwin. London: Ray Society. 1851.

Living Cirripedia (1854): A monograph of the sub-class Cirripedia, with figures of all the species. The Balanidæ (or sessile cirripedes); the Verrucidæ, etc. By Charles Darwin. London: Ray Society. 1854.


Obliged for letter about cirripedes attached to turtles’ backs. Genus is Chelonobia, Leach. Cirripedes do not penetrate skin, but surrounding tissue grows up around them.

Asks RB to send S. American Balanus. Already has specimens from Irish coast.

Letter details

Letter no.
Charles Robert Darwin
Robert Ball
Sent from
Source of text
Christ’s College Library, Cambridge (Fellows’ Papers 54.ii)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 1429,” accessed on 27 October 2021,

Also published in The Correspondence of Charles Darwin, vol. 5