珍珠历来受到人们的喜爱和赞赏，名贵的珍珠可以与最尊贵的宝石相提并论。光是汉语中和珍珠有关的词汇就有很多，比如“珠圆玉润”，“玉貌珠颜”，“珠光宝气”等等等等。天然珍珠的产量是十分稀少的，因此人们开创了养殖珍珠的方法。下面这篇短文将为您介绍珍珠是如何养殖的。 

    About 4,000 years ago the Chinese discovered pearls in oysters. The inside of an oyster's shell is covered with a smooth shiny coating called mother-of-pearl. When an irritant, such as a grain of sand, gets caught inside the oyster's shell it secretes layers of mother-of-pearl to protect its body by coating the irritant. The coated grain of sand becomes a pearl. 

    Man can force the oyster to produce a pearl by inserting an irritant into the shell. It takes the oyster two to three years to produce a good size pearl. 

    Cultured pearls are usually not perfect, but the Japanese have discovered that if you surgically insert an irritant directly into the body of the oyster this will produce a perfect pearl. 

    Historically, pearl divers dove up to 80 feet with equipment no more sophisticated than nose clips. The divers could stay under water for about a minute and they scooped up the shells with their hands and put them in tubs that would float to the surface. The largest pearl ever found is reported to be four inches around and two inches long. 

    oysters: 牡蛎

    irritant: 刺激物