290 



UTILITARIAN ZOOLOGY 



with a thin layer of a mixture of hme and sand (or mud), and 

 it is the under surfaces which, under ordinary circumstances, serve 

 for the attachment of the larval oysters when these give up a 

 free-swimming existence for a sedentary life. It may be added 

 that in some localities it has been found possible to construct large 

 spawning-ponds instead of relying on the supply of spat from 

 the oyster-banks off the shore. 



Fig. i2?o,— The Gahar<^t Collector Ruche in position (at Arcachon). Yonng oysters are seen attacheti to 

 the tile which is being lifted, and to another that is up-ended on the right. The collectors are covered with 

 sea-weed, so that when left by the tide they are kept moist, and protected from heat and light. 



A " set " of spat having been secured on the collectors, the 

 tender molluscs are left till about October, by which time they 

 have grown to the size of a finger-nail, and are known as " seed- 

 oysters ". They are then flaked off the tiles (or boards), which 

 the thin layer of lime renders possible with trifling loss, and 

 carefully packed. This ends the stage of production {produc- 

 tion), and the little oysters are now committed to the care of 

 another set of specialists, who rear them to a marketable size. 

 This process of ^levage is much more difficult. The ileveitr 

 places the seed in rectangular rearing-cases, the upper and 

 lower sides of which are chiefly made of wire-o-auze. As 



