mind.
Blister Pearls are generally hollow nacreous bodies, of irregular
shape, and are often due to the deposition of nacre at some point where
the shell has been attacked by a parasite from without.
That
the oyster does not work magic may be taken for granted, and the
following explanation of the vexed question of the formation of Pearls
is now submitted to practical pearlers and conchologists. The principle
involved is applicable to all molluscs, but due consideration in each
case must be given to the natural position of the shell, and its
owner's habits.
The oyster lies at the bottom of the sea at an
angle more or less considerable, but is generally
inclined to the sea bottom at about 20* to 25* The
shell is usually open about 1-1/2 inches, to admit the
entrance of water, its owner's natural sustenance,
and the mantle is spread out over the horny outside
lips of the shell. Respiration is carried on by means
of the gills, and any organic particles in the water
which bathes these vascular organs are transferred
to the mouth. Scientists have taught us that
" haemoglobin," or the colouring matter of the blood
in the animal kingdom, is the agent, that owing to
its great affinity for oxygen, extracts that supporter
of life from the air inhaled. Of the agent that
