CREATURES PRODUCING PEARLS. 285 



on which is deposited the pearly fluid, and in time forms 

 pearl." 



Linnaeus was persuaded that pearls could be pro- 

 duced at pleasure by simply puncturing the shell with 

 a pointed wire ; and pearls formed in this manner are 

 preserved in the Hunterian Museum. 



But enough as to the mode in which pearls may be 

 formed. The process of their artificial formation is so 

 simple that it deserves to be the subject of further 

 experiment. 



What are the creatures by which pearls are pro- 

 duced? They are chiefly bivalved molluscs the edible 

 mussel, the fresh- water mussel, and what is improperly 

 termed the pearl-oyster. Pearls are also found in the 

 oyster of the British coasts ; and we have three found in 

 an oyster presented at table in Edinburgh. The great- 

 est pearl-fishery in the world is off Ceylon, which at 

 present is of especial interest, owing to Government 

 having resorted to the formation of artificial oyster- 

 banks, suggested by the method recently introduced 

 along the shores of France for repeopling the wellnigh 

 ruined banks of the edible oyster. It is necessary to 

 have recourse to artificial banks, it being found that a 

 remunerative annual fishery cannot be obtained, owing 

 to the banks being exposed to the violence of ocean 

 currents, which, by washing sand into the interstices 

 of the rocks, often destroy the young oysters over a 

 considerable area. The oysters, moreover, are exposed 

 to the pernicious influence of the soorum, a species of 

 modiola like a mussel with a swollen face. The Tinne- 

 velly pearl-banks, which in 1861 yielded 15,874,500 

 shells, realising a profit of more than 20,000, were in 

 1863 found to be in so unpromising a condition that no 

 fishery was attempted. It is to remedy the uncertainty 

 of this valuable fishery that Dr Kelaart, after investi- 

 gating the nature of the pearl-oyster (Meleagrina mar- 

 garitifera), declares it as his opinion that he " sees no 

 reason why pearl-oysters should not live and breed in 



