376 Mr. L. Reeve on the Re-calcification of the Shell in Cyprea. 
The animal does not quit the shell as Lamarck supposed, but dis- 
solves the outer portion with its acetous juices. All visible trace 
of the shell may be thus removed without weakening M. Deshayes’ 
proposition, founded on the circumstance of the mantle being the 
only organ charged with the secretive fluid. The mantle 1s always 
capable of extension over the shell; and the same power which 
furnishes the adult with its last coating of enamel can be exerted 
to the formation of as many superincumbent layers as may be 
necessary to replace all that has been decomposed. That a dis- 
solution takes place there can be no doubt ; the shell gradually 
swells, says Lieut. Hankey, and cracks, becomes thinner and 
duller in colour, and finally disappears; a circumstance which 
may be easily credited when it is remembered that the Murex 
possesses the faculty of removing spines, or any similar obstacles 
to its advancement of growth, and that the Pholades and other 
terebrating mollusks exercise a power of absorbing which enables 
them to penetrate the hardest limestone rocks. The microscopical 
structure of the Cowry shell is, moreover, of a nature peculiarly 
tenacious of absorption; it 1s composed of a large quantity of 
carbonate of lime in proportion to the amount of membranous 
substance; and this accounts for its surface becoming vitrified, 
as it were, to such a highly polished state of enamel, in contact 
with the acidity of the soft parts. 
There is another circumstance in Lieut. Hankey’s narrative to 
which attention should be given, respecting the formation of the 
new shell:—the glutmous matter which has the appearance of 
shell-lac, and is so fragile that it yields to the touch, does not 
assume the narrow cylindrical Bulla form,—it does not follow the 
original plan of revolving round a columellar axis, but is of the 
wide ventricose shape of a Cymba, and rapidly consolidates into 
the adult shell. : 
With these generalizations I think it may be assumed that 
the Cyprea possesses the faculty of decomposing, during one or 
more periods of its existence, any portion of the shell that is 
liable to resist its advancement of growth; that the renewal of 
the shell is accomplished withm a comparatively short space of 
time ; and that the columella with its imternal spiral partitions 
remains undisturbed. It may, however, be inferred that it is an 
operation of extremely rare occurrence, and one which only hap- 
pens under peculiar conditions. 
Nore. 
Since writing the above, I have observed that Mr. Gray’s opi- 
nion on the subject at the time of the publication of his “ (tei: 
graph on the Cypreidee ” ran as follows :— 
“Tn this family I have often observed full-grown specimens of 
