OSTREA EDULIS. 



they can move from place to place by suddenly closing their 

 shells, and thus ejecting the water contained between them 

 with sufficient force to throw themselves backward or in a lat- 

 eral direction. 



The principal breeding-time of the common oyster is in 

 April or May, when their spawn is usually cast ; this appears 

 at first like little spots of grease, which fasten upon rocks, 

 stones, or other hard substances that happen to be near. 

 Very commonly they adhere to adult shells, and thus are 

 formed the large masses termed oyster-banks. In about a 

 year and a half they attain a size fit for the table, when they 

 are taken by dredging, and stored in pits formed for the pur- 

 pose, furnished with sluices, through which, in spring, the 

 water is suffered to flow. In these receptacles they acquire 

 a green tinge, which arises from the confervce and other ma- 

 rine vegetable matter on which they feed. The powers of 

 multiplication which oysters possess are so wonderful, that the 

 banks or beds which they form occupy portions of the sea, in 

 shallow parts extending for miles, and in some places (partic- 

 ularly along the alluvial shores of the Atlantic Southern 

 States) walls of living oysters literally counteract the other- 

 wise resistless force of the tide. Oysters are consequently 

 particularly plentiful, and form a most important article of 

 commerce. The breeding and fattening of them for market 

 forms a separate and considerable branch of business. (For 

 more details, see Spratt's History of the Royal Society, p. 307.) 



From the spawning time till about June the oysters are 

 said to be sick; but by the end of August they become per- 

 fectly recovered. In England the oyster fisheries are regu- 

 lated by a court of admiralty, and after the month of May it 

 is felony to carry away the cultch (which means any sub- 

 stance the oysters adhere to), and otherwise punishable to 

 take any oyster between whose shells when closed a shilling 

 will rattle. 



The oyster is a very entertaining object to those who are 

 fond of microscopic investigation. In the clear liquid around 

 the animal many minute, round, living animalcules have been 

 found, whose bodies, being unjoined, form spherical figures 

 with tails, not changing their place otherwise than by sinking 

 to the bottom, being heavier than the fluid ; these have been 

 frequently seen separating, and coming together again. In 

 other oysters animalcules of the same kind were found, not 



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