to
contact. If treatment is not too prolonged, they may be returned to
normal sea water with good prospects of recovery. To stupefy
freshwater mollusks, either chloral hydrate or chlorosone may be
employed, although the latter is expensive to use in great quantity.
Dr. Charles B. Davenport, of the Carnegie Institution, suggests that it
might be well to experiment with pouring ether or chloroform over them.
In Japan the production of these pearly formations in Margaritr ifera martensi, which
is closely related to the Ceylon oyster, has developed into some
prominence since 1890, and the results have been well advertised. The
industry is located in Ago Bay, near the celebrated temple of Ise in
the province of Shima, and gives employment to about one hundred
persons. It is stated that the proprietor, Kokichi Mikimoto, has leased
about one thousand acres of sea bottom, on which are a million oysters
of this species, which yield from 30,000 to 50,000 culture pearls
annually.
As
described by Dr. K. Mitsukuri, the shoal portions of this area are used
for breeding the oysters and raising them to maturity, and in the
deeper parts—covered by several fathoms of water—the oysters are
specially treated for producing the culture pearls. In the former, the
spat is collected on small stones, weighing six or eight pounds each,
placed during May or June. The following November these stones, with
the attached spat or young, are removed, for protection from cold, to
depths greater than five or six feet, where they remain for about
three years. At the end of that period, the growing oysters are taken
from the water, the shells opened slightly, and rounded bits of pearl
shell or nacre are introduced under the mantle without injury to the
mollusks. About 300,000 are thus treated annually, and placed in the
deeper water at the rate of about one to each square foot of bottom
area. After the lapse of about four years more, the oysters are removed
from the water and opened, when a large percentage of the pellets are
found covered on the upper or exposed surface with nacre of good
luster.
Most
of these culture pearls are button-shaped and weigh two or three grains
each. Although somewhat attractive and superior to the culture pearls
of China and other fresh waters, they by no mean's compare favorably
with choice pearls. They are rarely, if ever, spherical, and only the
upper surface is lustrous; consequently they serve only the purpose of
half-pearls. A cross section shows the nacreous growth in a thin
concentric layer, forming a fragile hemispherical cap, the concave
wall of which is covered with a brownish granular secretion which
prevents perfect adhesion. Compared with choice pearls, they are not
only deficient in luster, but are fragile, and are beautiful only on
the upper surface, and not available for neck-
