The latter are perhaps the most valuable of all the offerings of animate nature, and are the results of the efforts of the bivalve to protect itself from injury. A parasite bores into the shell of the pearl bearer, and when felt by the animal it immediately fortifies itself by covering up the spot with its pearly secretion; the parasite pushes on, the oyster piling up until an imperfect pearl attached to the shell is the result. The clear oval pearls are formed in a similar way, only in this case a bit of sand has become lodged in the folds of the creature, and in its efforts to protect itself from the sharp edges, the bit becomes covered, layer by layer, and assumes naturally an oval shape. This growth of the pearl, as it is incorrectly termed, can be seen by breaking open a $500 gem, when the nacre will be seen in layers, resembling the section of an onion. The Romans were particularly fond of pearls, and, according to Pliny, the wife of Caius Caligula possessed a collection valued at over $8,000,000 of our money.

Julius Caesar presented a jewel to the mother of Brutus valued at $250,000, while the pearl drank by Cleopatra was estimated at $400,000. Tavernier, the famous traveler, sold a pearl to the Shah of Persia for $550,000. A twenty-thousand-dollar pearl was taken from American waters in the time of Philip II. It was pear-shaped, and as large as a pigeon's egg. Another, taken from the same locality, is now owned by a lady in Madrid who values it at $30,000.

Fresh water pearls are often of great value. The streams of St. Clair County. Ill., and Rutherford County, Tenn., produce large quantities, but the largest one was found near Salem, N. J. It was about an inch across, and brought $2,000 in Paris. The pearls from the Tay, Doon, and Isla rivers, in Scotland, are preferred by many to the Oriental, and in one summer $50,000 worth of pearls have been taken from these localities by men and children. Mother-of-pearl used in the arts is sold by the ton, from $50 to $700 being average prices. The last year's pearl fisheries in Ceylon alone realized $80,000, to obtain which more than 7,000,000 pearl oysters were brought up.