260 NATURAL HISTORY OF PRECIOUS STONES, &c.
be
found in the Description of Parthia by Isidorus of Charace: "In the
Persian Sea is a certain island* where great plenty of the pearl-oyster
is to be found. Wherefore rafts of reeds (bamboos) are stationed all
around the island, from off which the divers, jumping into the sea to
the depth of 20 fathoms, bring up two shells at a time. They assert
that when there are continuous thunderstorms and falls of rain (the
Monsoon), the Pinna then breeds more freely, and the pearl becomes most
plentiful and of good size. In winter the shèll-fish are wont to retire
into their holes in the deep, but in summer they swim about with their
valves gaping wide open by night, but keep them closed by day. All that
grow close to rocks or stones put forth roots, and abiding there
fixedly breed the Pearl. They (the Pearls) are born alive, and are
nourished through the part attached to the flesh. The latter is firmly
fixed to the mouth of the shell, and is furnished with claws and
catches food. This part is exactly like the little crab called the
Pinnophylax. From this the fleshy part extends as far as the middle of
the shell like a root, along which the Pearls are bred, and grow
through the solid part of the shell, and increase in size as long as
they remain attached thereto. But when the fish recedes along the
length of its projection, and gently cuts off and severs the pearl from
the shell, though it envelopes the pearl it no longer nourishes it,
only renders it more polished, more transparent, and purer. The pinna
of the deep water produces the most lustrous, and clear, and largest
pearl; that which swims near the surface is spoilt by the rays of the
sun, and gives those of bad colour and smaller size. Those that fish
for Pearls run a danger when they thrust their hands straight into the
gaping shell, for then it shuts
* The Bahrein Islands in the Persian Gulf.
