Discusses capacity of some cirripedes to bore into rock. Describes progress of his research.
Down Farnborough Kent
My dear Sir
As you have attended with such eminent success to the boring of animals into
rocks, you will perhaps like to hear that I believe I now
understand the boring of Lithotrya, thanks to the enclosed
drawing [SYMBOL HERE] (which please return) sent me by Steenstrup without text. I suppose the same explanation is applicable to Arthrobalanus,
& I sh
Since receiving this same Plate, I have had a good deal of rock, bored by
L. dorsalis, given me, & I now
find out for the first time the following important facts, (1)
In the drawing you will at once understand how the animal travels, by imagining a set of ghosts or exuvia attached to each of the little discs one above the other.— I have seen a rows of disc extending an inch in length. (The teeth on the valves and on the beads on the peduncle, with their exuviations sufficiently explain the mere increase in diameter of the burrow.)
I cannot explain in a letter how the discs are fixed; but it is as in all other Cirripedia, by a cement or tissue (for I hardly know which to call it), which primarily debouches at the penultimate segment of the prehensile antennæ of the larva (this cement is formed by a gland, strange to say, which is certainly part of the branching ovaria) & subsequently during life, in different cirripedia, either through these 2 same orifices, or out of two fresh or only one fresh aperture placed symmetrically or irregularly or again through numerous apertures placed in a regular circle; so that it is nothing unusual in Lithotrya for the discs to be fixed symmetrically in a straight line. In Scalpellum the peduncle is attached to the thin stem of the Coralline by apertures, through which the cement debouches, placed quite symmetrically in a straight row along the ventral side, a new one being opened at each exuviation.—
But I must stop, & not weary you.— I think the drawing will make you understand what I mean, better than my perhaps ill-expressed explanations.
I have not yet looked at Alcippe! But do not suppose that I
undervalue your kindness in having sent me the specimens; but I have been working like a
wretched slave at mere species & have many more months' work,
& till I have completed this slavery, I have not heart to begin work of
interest, for I think I sh
Believe me my dear Sir, | Your's sincerely | C. Darwin
P.S. The accompanying spec., of as I suppose, a Cliona, you can throw in the fire if of no interest to you.— from Northern part of Patagonia.
- f1 1378.f1A. Hancock 1848 and 1849a.
- f2 1378.f2See the earlier correpondence which discusses the boring mechanism of Lithotrya, especially letters to Albany Hancock, 29 September , 25 December , and [26 January – March 1850].
- f3 1378.f3See letter to J. J. S. Steenstrup, 20 May , in which CD acknowledged receipt of the drawing. The drawing is reproduced in Living Cirripedia (1851), Plate VIII, figs. 2 and 2a', copied from Reinhardt 1850. The memoir accompanying the drawing, which CD had requested in his letter to J. J. S. Steenstrup, 1 September , was not received until after CD's own description had been set in type. See Living Cirripedia (1851): 346 n., in which CD discussed the differences in the two descriptions.
- f4 1378.f4CD believed that Arthrobalanus (Cryptophialus) and Alcippe also burrowed into hard surfaces by mechanical means (Living Cirripedia (1854): 568, 570; 549). In Clisia (renamed Verruca), however, he believed the powers of burrowing were chemical rather than mechanical, effected by means of a solvent exuded by the cement ducts (ibid., p. 496).
- f5 1378.f5Probably by Hugh Cuming (Living Cirripedia (1851): 344).
- f6 1378.f6CD did not examine Alcippe until early in 1853 (see Correspondence vol. 5).
- f7 1378.f7A sponge which bores into the shells of molluscs. Hancock had previously described the excavating powers of Cliona in A. Hancock 1849a.