Conchology. 237 



no pearl in the shell. The pearl fish, he supposes, is attacked by- 

 two classes of enemies. One is what he calls the anger ivorm 

 which penetrates into the inside, near the edge of the valve, by 

 making a longitudinal passage, between the layers of the shell. 

 The length of the channel is one inch, or one inch and a half, when 

 it doubles back in a hne parallel to the first. At the inner extrem- 

 ity there is a small circular portion formed by the worm in turning 

 round. These excavations are in the pearly part of the shell. The 

 pearly juice extravasating, forms protuberances in the same direc- 

 tion; and the cyhndrical bodies which are thus formed, may be 

 considered as elongated pearls, adhering to the internal surface. 

 When several worms of this kind, unite their labors, by penetrat- 

 ing near each other, the result is a kind of pearls, even with irreg- 

 ular protuberances. 



Another sea worm, which he says belongs to the multivalves, a 

 species ofpholas, also attacks the pearl shells. The shell of this 

 species of pholas has a hinge in the form of a crooked bill, as he 

 saw in some species of oyster, which he examined, from the coast 

 of Guinea. The hole was of the shape of a pear. Pearls of this 

 shape have been found, and have been held in great estimation. 

 Observing this circumstance, artificial perforations are made in the 

 shell, and this forces the animal to produce pearls. In some shells 

 brought from China, this artificial hole has been observed filled up 

 with brass wire, rivetted on the outside like a nail, and the inner 

 extremity of the wire with a well-formed pearl, which seemed as if 

 soddered to its extremity. 



Pearls are also produced by another artificial process. The 

 shell is opened with great care, to avoid injuring the animal, and a 

 small portion of the internal surface of the shell is scraped off. In 

 its place is inserted a spherical piece of mother-of-pearl, about the 

 size of a small grain of lead shot. This serves as a nucleus, on 

 which is deposited the pearly fluid, and in time fonus a pearl. 

 Experiments of this kind have been made in Finland, and have 

 been repeated in other countries. 



A remarkable discovery has been ascribed to Linnaeus respect- 

 ing the generation of pearls. This was a method which he found 

 out, by putting the pearl muscle [JS'Iya margaritifera) into a state 

 ot producing pearls at his pleasure. It was some years, before 

 the final efl^ect could take place; but in five or six years after the 

 operation, the pearl, it is said, had acquired the size of a vetch. 

 But it does not seem to be known in what this operation consisted. 

 Whether it consisted in imitating the process of insects, by wound- 

 ing the shell from the outside, or by following the other process, 

 by scraping away part of the inner layer; nor is it much known 



