250	Pearls.
	fresh-water mussels of Russia and of France. In 1849, Dr. Adolphe de Bauran performed numerous experiments on the production of Pearls by the mussels {Unto margaritifer) of the torrential stream of Vianz, near Rhoder, in the department of Aveyron. His experiments were not followed by any striking success. Even less successful were the attempts to produce Pearls in the Unio littoralis, of the Touch, near Toulouse, as conducted by MM. Mouquin-Tandon and Jules Cioquet, who, in 1858, read a paper on this subject before the Société drAcclimatation of Paris.
	American River Pearls. In many of the rivers flowing through the northern part of the American Continent, the Pearl-mussel is abundant. Dr. Isaac Lea, of Philadelphia, has catalogued many hundreds of species of American river-mussels belonging to the genera Unio, Marga-ritana and Anadon. Yet the occurrence of good Pearls in these shells does not appear to be frequent. - *At any rate, the business of Pearl-fishing, involving as it does, great expense in a country where the value of labour is high, has not hitherto been a very remunerative industry. River-Pearls have been systematically fished in the Miami river, in Warren county, Ohio. The