62 On the Economical Uses of some species of Testacea. 
They are found in the body of the animal, and not confined to 
any particular part. Some contain but one, some a multitude of 
small specimens, known by the name of seed pearls, while in the 
shell itself, and protruding above the surface, are frequently circular 
nodules resembling them ; as these must be cut, and on one side 
are flat, they can only be used for setting, and of course are of less 
value. They are technically termed by jewellers the wens of pearls. 
There is a common opinion that the animal may be forced to 
produce the gems by artificial means. ‘The inhabitants of the shores 
of the Red Sea were said to have wounded them, and returned 
them to the water; and the Chinese we are told insert beads of the 
nacre into the shell, to be covered by the animal with the perlaceous 
substance.* But these accounts from many obvious reasons are im- 
proba and we have not been able to meet in modern histories 
with any authenticated instance of its having been done. In river 
shells it might be more easily effected ; and we shall have to refer to 
it again under the description of Mya margaritifera. They some- 
times grow so large as to hinder the shell from shutting; in which 
case the fish dies, and they are Remeenttcy not uncommon of the 
size of a small bullet. 
On analyzation, perlaceous shells appear to be Gene of animal 
matter, applied stratum upon stratum, with carbonate of lime be- 
* See Rees’ Cyclopedia; Encyelopedia Americana, &c. &c. Art. Peart. 
Beekman, in his History of Inventions, vol. ii. page 5, third Lond. Ed., seems 
to have been the first in more modern times to have given extended publicity to 
this opinion. He quotes as his authority aGerman work, and adds, that “the 
truth of this information cannot be doubted.” That it migit happen, we do not 
mean to deny, but sufficient authority is wanting to prove it, and many powerful 
reasons are against it. How and when does the reader suppose the pearls were 
inserted ? on a string containing five beads; and the clever Chinese caught the 
shell when it rose to the surface in the spring to enjoy itself! Of coursenext year 
it had to be caught again to get at them, but how we are not informed. 
however been servilely coftied by most subsequent writers on this subject, with the 
exception that he expressly says the shells are fluviatile, while his copyists confuse 
or describe them as the present marine species. Beekman confess 
nacre and bruised pearls, and the shell was kept in a basin, to be daily fed on me- 
dicinal and gummy roots. He himself allows that it does not appear probable. 
e Postlethwaite’s Dictionary, vol. ii. Art. Pearl.) It is time however that such 
Ww a and left out of works professedly scientific, and beari 
e of some learned editor, assisted, as we are told, by “ em- 
