24 HISTORY OF THE OYSTER. 



the number of young in it (2500). The total weight of 

 the whole was 72 gr., which, multiplied by 10, and 

 again by 2500, gives 1,800,000 as the total number 

 of young oysters in one old one. I do not mean to 

 say that this calculation is precisely correct, there pro- 

 bably having been some loss ; but, at all events, it is 

 a pretty near approximation. 



The growth of the oyster depends very much upon 

 the locality, and some grounds feed much faster than 

 others, particularly where there is an admixture of 

 fresh water. As the animal increases, the functions 

 of the mantle are called into operation for the purpose 

 of adding a fresh layer to the shell. Some have 

 imagined that the age of the oyster can be computed 

 by the rings of growth on the shell ; but that such is 

 not the case, a very short examination will suffice to 

 show. The immense oysters that are dredged at 

 Llandudno and other places are from beds that have 

 not been much broken up, and from water where 

 there is often a strong current : no doubt, if dredged, 

 and deposited in a proper situation, the spat, with 

 care, would produce good oysters. 



Plate VI. represents the oysters from one year old 

 to five, fig. 1 having been deposited as spat the year 

 before. Oysters are found in almost all countries ; 

 but not always of the same species as the British one, 

 Ostrea edulis. 



