Submarine Appliances And Their Uses
Deep Sea Diving, &c., &c.

But the more valuable pearl is that which is found loose inside the mantle of the oyster, or perhaps but very slightly attached to it. Sometimes one of the ova is life- less, and is not exuded with the rest at spawning time. Although infertile, it is still supplied with nutriment from the parent body, and gradually increases in size. It then hardens, and so becoming- a source of irritation, the mollusc covers it with nacre, and thus a pearl—perhaps of great price—is formed. The pear-shaped pearl acquires its form through the connecting link or pedicel between the stranded ovum and the body being also coated with nacre. Amongst the Chinese and Japanese very clever methods have been used for com- pelling the oysters to produce pearls. Several of the live shells are collected and put in a pond of clear sea water. A wedge of steel is slipped into the open lips (oysters live with their lips open) to prevent them shutting, then a small hole is drilled through the shell from the inside ; a small mother-of-pearl button is fixed into this hole, with a round knob projecting inside the shell ; the steel wedge is then removed from the lips, which quickly come together, and the mollusc inside soon feels this uncomfortable button pressing into its body. Squirting from one of the cells in its mantle the liquid nacre over the button, it gradually lessens the uneven inside surface, and so produces a pearl over the button. Month by month the shell is examined until at length a pearl is formed over the intruded button. When it is ready the oyster is destroyed, the pearl is cut out of the shell and set in some ornament where the artificial foundation can be hidden in the set- ting, and only the perfect top of an apparently perfect pearl is shewn. Photo No. 78. Pearling Lugger. (Western Australia.)