OYSTERS. 



367 



various ages, attached to a piece of wood : A being oysters of twelve to 

 fifteen months, B fi ve*br six months, c three to four months, D one to 

 two months, and E oysters twenty days after birth. 



Fig. 171. Groups of Oysters of different ages attached to a block of wood. 



The species of oysters usually eaten are the common oyster (Ostrea 

 edulis, Linn.) of our own coasts and the opposite shore, and the 



different ages ; but it is necessary to state that the specimens were artificially attached 

 to the block by means of glue for exhibition. Oysters always attach themselves by 

 the back of the rounded shell near to the hinge, as stated at p. 363. 



