MOLLUSC A. 169 



nexion of the oyster with the pearl is one of the interesting 

 circumstances connected with its history. Moore, with his 

 usual felicity, has referred to the Eastern fable of 



" That rain from the sky 



That turns into pearls as it falls in the sea." 



The real facts, as at present known, arc scarcely less won- 

 derful. The shell is pierced by some worm, and the oyster 

 deposits the "nacre," or mother-of-pearl, on the perforated 

 part; or grains of sand or gravel gain admission into the 

 substance of the mantle, and become encrusted by a similar 

 deposit. This would appear to be, in many instances, the 

 origin of the pearls, so highly prized, and still so eagerly 

 sought for. The Romans were extravagantly fond of these 

 ornaments, which they ranked .next 

 to the diamond, and are said to have 

 given almost incredible prices for 

 them. "Julius Caesar presented 

 Servilia, the mother of M. Brutus, 

 with a pearl worth 48,417 10s.; 

 and Cleopatra, at a feast with 

 Antony, of which Pliny has given 

 a long and interesting account, 

 swallowed one dissolved in vinegar 

 of the value of 80,729 3s. 4d." 

 Such statements are generally re- Fig l 

 garded by naturalists of the present 

 day with distrust, as exaggerated or erroneous. 



The shell (Avicula margaritacca, Fig. 160) from which 

 the greater number of pearls and the largest quantity of 

 mother-of-pearl is obtained, is not an oyster strictly so called, 

 but belongs to an allied genus. It is not our intention to 

 enter into any history of the pearl fisheries of Ceylon or the 

 Persian Gulf, which annually give employment to some 

 hundreds of boats and many thousand men. But we would 

 mention, that a very exaggerated idea prevails as to the 

 length of time a pearl-diver is in the habit of staying under 

 water. The usual period on the Aripo banks, is stated by 

 Captain Stcunrt, to be 53 to 57 seconds; when paid for the 



