9152 Mollusks. 
Pholades make holes for their habitations in rocks by some solvent 
fluid, and not by rasping with the tubercles of their shells ; and our 
dear friend’s note in reply is so interesting, and shows so much clear- 
ness and vigour of mind at this his late period of life, that I think you 
will be pleased with it; I therefore enclose it with this. I have never 
had an opportunity of observing how the Pholades make their holes: 
Have we now any reason to suppose that the tubercles of the Pholas 
shell are used for rasping, when we find that the smooth-shelled Helix 
and the Patella can make their habitation in rocks with their solvent 
acid only? I think we have not. I enclose some lithmus paper acted 
on by Helix hortensis and nemoralis, which are your aspersa and 
wood snail, also Limax cinereus. The green stains are produced by 
the froth or slime of hortensis, procured by irritating the animal with 
a feather. I am somewhat surprised to find the different secretions. 
‘Robert Anstice io William Baker. 
August 5, 1842. 
My Dear Mr. Baker,—I never doubted that the animals of most sea 
shells had the power of dissolving calcareous bodies, by means of 
some acid which would not act injuriously on their living structure 
till the powers of life had escaped. Without such a provision how 
can we account for the powers of many, if not all, of those Testacea in 
removing the varices and spines, which would otherwise stand in the 
way of the periodical enlargement of their dwelling; and that the 
limpet has a like power to make himself a sunken and therefore more 
fixed dwelling in the rock is, I think, certain. This acid being found 
also in the land snails goes far to convince me that your opinion con- 
cerning their hybernacula-making is correct. Respecting the boring 
of the Pholades, I recollect it has been the subject of our discussion 
often, and believe we agreed in opinion that their operations were the 
effect of the joint action of an acid and the finishing off with their 
rasp-like shells. The only apparent difficulty in comprehending this 
to be so, arises from the action of the acid not seeming to act on the 
shell itself, and that the rock being harder than the shell, that 
that also should not act injuriously upon it; but I think both these 
may be solved as difficulties, by considering that the acid may be so 
applied to the rock as to be withheld from the shell till it became 
neutralised and inoperative before the animal began its turnings and 
raspings ; and any wearing it must be easy for the animal to repair, 
endowed as it is with the power of making the shell itself. I would 
gladly enlarge, but am not up to it to-day. I hope we may yet talk 
