To Robert Ball 26 May 1
Down Farnboro’ Kent
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
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.