192 UTILIZATION OF MINUTE LIFE. 



common enough in England, Wales, Scotland, Ger- 

 many, etc. It has a large bivalve shell, which, when 

 clean, is of a peculiar yellowish-brown colour, with 

 a wide blue band round the edges. The species has 

 been known for ages in Scotland, where it produces 

 pearls (sometimes called ' ' Scotch pearls ") that are 

 now and then quite equal to the Oriental pearl of 

 the Avicula. Old writers assure us that it was these 

 English jewels that tempted Julius Cassar to renew 

 his visit to our island. 



Unio margaritiferus is as common in Germany as 

 with us. Very fine specimens are seen in the brooks 

 and rivulets of the Bavarian woods and the moun- 

 tains Fichtelgebirge. Its pearls have likewise 

 attracted attention, and although they are not equal 

 to the Oriental pearl, they are held in certain esti- 

 mation by the jewellers ; and the rich collection of 

 Bavarian pearls that figured some years ago at the 

 Industrial Exhibition of Munich, proved that in 

 Germany the culture of the pearl may one day 

 become a considerable branch of industry. A step 

 has indeed been taken already in this direction. 

 An accomplished geologist, Dr. Von Hessling, of 

 Munich, was directed, a few years back, by the 

 King of Bavaria, to make minute investigations into 

 the manner in which these pearl mussels live, and 

 under what circumstances they produce their jewels, 

 for all the shells do not contain pearls. Dr. Von 



