MOLLUSCS AS FOOD 



291 



growth proceeds, sorting from time to time becomes necessary, 

 so as to give increased room. The cases are placed in oyster 

 " parks ", which are simply enclosed areas of shallow water, with 

 boundaries of the most various character, from lines of waving 

 saplings to solid masonry pierced by flood-gates (fig. 1211). 

 When the oysters have attained a fair size they may be trans- 



rig. 121 r. A Norwegian Oyster-Park 



ferred from the cases to the floor of the park, which sometimes 

 has to be specially prepared for their reception. 



There are still two more stages which some French oysters 

 have to go through before they reach the market. One is the 

 process of " greening", as at Marennes, the products of which 

 are greatly esteemed. The oysters are here kept for a long time 

 in small and muddy salt ponds (claires), where they gradually 

 acquire a green colour owing to the nature of the food avail- 

 able, which consists of minute algae. At the same time a pecu- 

 liarly delicate flavour is imparted. Healthy British oysters from 

 the estuaries of the Roach and Crouch, in Essex, may also be 



