192 NATURAL HISTORY OF OUR SHORES 



together with the young oysters. This is termed the 

 process of " detrogage" 



The little oysters are then washed and placed in cases, 

 which have bottoms of coarse wire gauze raised about 

 six inches from the bottom. The cases are six inches deep, 

 and a lid, also of wire gauze, protects them from enemies. 



The cases are placed in such position that they uncover 

 at least a day or two each fortnight to allow of examination. 

 At first eight or ten thousand are placed in each case. 

 Then, as growth advances, they are thinned, and extra 

 cases brought into service. 



Fig. 85 shows an arrangement of these rearing cases 

 on the coast of Jersey. Here they are in an enclosed area, 

 and their submergence can be controlled by means of some 

 large sluice gates, the supports of which can be seen in the 

 photo, in the distance on the right. 



Growth is rapid, and the first year the " spat " or 

 " brood " oysters will have reached the size of a two'- 

 shilling piece. Growth takes place chiefly in the summer, 

 when a layer of new shell appears around the margin, so 

 that the age of an oyster can be readily ascertained by 

 counting these layers, which are, as a rule, distinctively 

 marked. 



When the oysters have reached a size of two and a 

 half or three inches across they are taken from the cases, 

 and sold by the breeders to the " planters," who place 

 them on such grounds as will best fatten them for market. 

 The chief grounds on our coast are thus " layered " with 

 artificially reared oysters, for the conditions under which 

 oysters best fatten are not those in which the delicate little 

 veligers best develop, and it is only occasionally that in 

 such " fattening grounds " there occurs a " fall of spat." 



The oyster becomes of marketable size when three to 

 four years old, and its age limit is probably from fifteen 

 to twenty years, 



