188 UTILIZATION OP MINUTE LIFE. 



will perceive what a vast field for amelioration is 

 offered here, and what a great improvement it 

 would be to do away not only with the barbarous 

 mode of diving, by breeding the Avicula in appro- 

 priate places, but with the unwholesome process of 

 extracting the pearls and shells from the putrid 

 heaps of mollusca. 



There is no doubt, from the experiments already 

 made with the common oyster, that the pearl 

 oyster might be easily submitted to culture ; as it 

 is, the pearl banks in Ceylon, according to Sir 

 Emerson Tennent, were, from 1834 to 1854, an 

 annual charge, instead of producing an income to 

 the colony. Seven years is the period required, in 

 the present state of things, before the pearl oyster 

 arrives at perfection, and can be sought with ad- 

 vantage ! Diving-bells, or the diving apparatus 

 used in constructing bridges, would be a protection 

 against sharks, etc., though accidents from this 

 cause seldom or ever occur ; the noise of the boats 

 seems to scare the sharks away. 



According to Dr. Kelaart, the pearl oyster can 

 sever its byssus and change its place, so as to 

 migrate to some distance in search of food, or to 

 escape from impurities in the water, and so moor 

 itself again in more favourable situations. This 

 may account somewhat for their disappearance at 

 intervals, and the bad crops yielded by localities 



