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Mexican pearl-oyster (Margaritifera margaritifera mazatlanica) with adherent pearl

Group of encysted pearls in shell of Australian pearl-oyster (Margaritifera maxima)

American Museum of Natural History

Mexican pearl-oyster (Margaritifera margaritifera mazatlanica) with encysted fish

American Museum of Natural History

Group of encysted pearls (Oriental)

Reverse of same group, showing outline of the individual pearls

The discovery of the parasitic origin of pearls was extended to the pearl-oysters and to other parasites by Küchenmeister^[57] in 1856, by Möbius^[58] in 1857, and by several other investigators. Prominent among these were E. F. Kelaart and his assistant Humbert, who, in 1859^[59] disclosed the important relation which the presence of vermean parasites bears to the origin of pearls in the Ceylon oysters. These naturalists found “in addition to the Filaria and Cercaria, three other parasitical worms infesting the viscera and other parts of the pearl-oyster. We both agree that these worms play an important part in the formation of pearls.” Dr. Kelaart likewise found eggs from the ovarium of the oyster coated with nacre and forming pearls, and also suggested that the silicious internal skeletons of microscopic diatoms might possibly permeate the mantle and become the nuclei of pearls. Unfortunately, Dr. Kelaart’s investigations were terminated by his death a few months thereafter.