Oyster Culture in Europe and Japan 85 



would be required to provide a means of livelihood for 

 the most unambitious eleveur, and his initial expense 

 would be considerable. But, properly cared for, these 

 boxes serve for many seasons. If carefully tarred each 

 year, they may be kept in use for ten, or sometimes 

 twenty years. Occasionally more elaborate boxes are 

 constructed that hold a number of trays, but all are built 

 on essentially the same plan. 



Not only are these cases necessary as a protection 

 against mud, but there is great advantage in their posi- 

 tion* on the flats between tide lines; for, being exposed 

 at low water, oysters may readily be placed in them, 

 sorted from time to time, and finally removed. The 

 cases, also, may be repaired with ease. When cases 

 are used in enclosed parks, it of course is necessary that 

 the surrounding walls should be high enough to hold 

 sufficient water to cover them. 



The young oysters that have been removed from tile 

 collectors are at first spread evenly, but closely, in the 

 bottom of the cases, and as they increase in size, are re- 

 moved a few at a time and placed in other cases in order 

 that all may haye food and a sufficient amount of water 

 for aeration. The number of food organisms brought 

 to the growing young varies in different localities along 

 the shore, and for this reason there is a difference in the 

 length of time during which they must be kept. In some 

 localities, two years are sufficient, while in many others 

 they must be cared for during a third, a fourth, or even 

 a fifth year, before attaining marketable size. 



It sometimes happens that lamellibranchs of various 

 species, living in certain localities, collect in the gills and 

 in parts of the mantle, a quantity of chlorophyl, the 

 green coloring matter characteristic of most plants. 



