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GENESIS OF PEARLS
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and systematic arrangement of surface wave edges, has not been reached.
A
sectional view as seen in a half pearl would lead one to infer that a
free pearl in the beginning lies stationary in the oyster; is turned
or partially rolled as it grows larger; and finally, on attaining about
a one grain size, is kept in constant motion with a concentric rolling
in the nacreous exudations of the mantle which are deposited upon it.
The
nuclei of pearls were long thought to be grains of sand, but late and
careful research has shown that in the majority of cases they are
minute parasitic or domiciliary worms.
Professor
Herdman and James Hornell, after three consecutive inspections of the
oyster banks in the Gulf of Manaar in 1902-3, stated in a paper
contributed to the British Association for the advancement of science,
that after examining many hundreds of oysters and decalcifying a large
number of pearls, they had come to the conclusion, that grains of sand
and other inorganic particles formed the nuclei of pearls only under
exceptional circumstances, as for instance, when the shell was injured
by the
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