and the nucleus of the Pearl, if of inorganic matter, after having been
the cause of infinite annoyance to its unfortunate captor, is returned
to the place from whence it came. In Fig. 4, p. 95, we have a
representation of the oyster shell after the Pearl has been passed
through the substance.
may be urged that the layers of shell enveloping the Pearl or blister,
are laid equally upon the top of it and at the sides ; and that an
unnatural excrescence would still remain on the inner surface of the
shell long after the original cause of it has passed away ; but this is
not so. It must be remembered that the laws of development by which
creatures are adapted to cope with the surrounding conditions and
difficulties of their existence, are as applicable to an oyster as to
any other form of life, and the same power that taught the oyster to
protect itself against the inveterate attacks of its enemy, the "
borer," by increasing the thickness of its shell at the point of
danger, might also teach it to rid itself of an uncomfortable tenant in
its bed, by exactly the reverse process.