Down Farnborough Kent
April 1st
My dear Sir
I am very much obliged to you for the specimens on the Slate & Old Red Sandstone: they certainly show no boring, as I anticipated wd be the case:1 as you have examined many specimens I will venture to quote you.2 I shd. be still very glad to get some on limestone, especially on impure limestone. I fully believe verruca burrows to the very slight degree it ever does, by some solvent; & it has ducts opening on its under side which might emit some solvent or carbonic acid gas as you suggest. In the only 3 other known, & much more effective, burrowing cirripedes;3 I think the evidence is quite sufficient to show that it is mechanical. Perhaps you may think it worth while to read what I have said under Lithotrya:4 the points being worn, (& then periodically renewed) shows to demonstration that there is friction.
If you go on, (as I do not doubt) with your microscopic investigations, I wish I cd. persuade you to reinvestigate, what I have described on the Complemental Males of Scalpellum vulgare, so common on your coasts:—5 You must, however, dissect a good deal under the simple microscope: in all probability you would find out something new, & the subject in my (perhaps prejudiced) eyes seems very curious.— In your researches do you use boiling strong caustic potash for of an hour? it is really beautiful the way it dissolves every thing, except the external integument (leaving them like glass) of the articulata.6
With very many thanks | Believe me Your’s truly | C. Darwin
Please cite as “DCP-LETT-1511,” in Ɛpsilon: The Charles Darwin Collection accessed on