MOLLUSC A 157 



have been found in the Philippine Islands and on the coasts of 

 Venezuela and Pacific Mexico. Black pearls from the " pearl 

 oyster " of the Gulf of Mexico are extremely valuable. The fresh 

 water mussels, besides furnishing pearl buttons, also produce a 

 fine quality of pinkish pearls. The abalones {Haliotis) found in the 

 Pacific Ocean produce very few good blister pearls but the shells are 

 valuable for mother of pearl. Pink pearls are sometimes secured 

 from the large West Indian conch shell, Strombus gigas^ one of them 

 having sold for five thousand dollars. 



True pearls increase in value notably according to the size. If 

 a one-grain pearl is worth ^10.00, a two-grain pearl is worth ^40.00, 

 while a ten-grain pearl is valued at ^1,000.00. 



Culture Pearls. — The nucleus of a pearl may be a parasite, an 

 ovum, a fragment of tissue, or a bit of shell or other hard material. 

 Investigators have found Cestode larvae, Trematode worms, and 

 even small Crustacea and Hydrachnids as the nuclei of pearls. 

 Centuries ago the Chinese discovered that if foreign substances were 

 placed between the mantle and shell of a mussel, in many cases a 

 coating of " mother-of-pearl " was laid down over the insert. 



The Japanese developed the earlier work of the Chinese to a 

 great enterprise under the guidance of the late Prof. Mitsukuri, 

 opening the oysters slightly and inserting bits of sand, images, and 

 bits of mother of pearl, with the result that blister or culture pearls 

 were produced. In 1892, Kokichi Mikimoto, the " Pearl King," 

 following the suggestions made to him by Professor Mitsukuri, 

 began the cultivation of pearls on a large scale. Mikimoto's oyster 

 beds extend over 40,000 acres. According to Jordan (1927) he 

 employs one thousand people. The divers are all young women who, 

 it is reported, can remain two minutes under water. 



Culture pearls with a spherical mother-of-pearl nucleus are just 

 as aesthetic as a natural pearl, which may be the " sarcophagus " 

 of a tape-worm. In spite of attempts to bar them from the market 

 as genuine, they are now sold for as much as $200 each. Chemically 

 and biologically they are true pearls. 



Coated Glass Substitutes for Pearls. — Alabaster or glass beads 

 are now coated with pearl essence secured by the extraction of 

 guanin crystals from herring and other fishes (see page 254) and are 

 sold as artificial pearls. 



