ARTIFICIAL OYSTER CULTURE. 1065 



reef. In our own waters there is usually a strip along the 

 shore where no oysters are found, as the depth of water is 

 not great enough to protect them in winter. The whole of 

 the hard belt is not uniformly covered with oysters, but it 

 is divided up into separate oyster rocks, between which 

 comparatively few can be found. . . . When such a 

 bed is carefully examined, it will be found that most of the 

 rock is made up of empty shells, and a little examination 

 will show that the crowding is so great that the growth of 

 one oyster prevents adjacent ones from opening their 

 shells, and thus crowds them out and exterminates them. 

 The most significant characteristic of a bed of 

 this kind is the sharpness of its boundaries. . . . and 

 between these beds are areas where not a single oyster can 

 be found. The intervening area is perfectly adapted for 

 the oyster, and when a few bushels of shells are scattered 

 upon it they are soon covered with young, and in a year or 

 two a new oyster rock is established upon them ; but when 

 they are left to themselves the rocks remain sharply defined. 



What is the reason for this sharp limitation of a natural 

 bed? 



Those who know the oyster only in its adult condition 

 may believe that it is due to the absence of powers of loco- 

 motion, and may hold that the young oysters grew up 

 among the old ones, just as young oak trees grow up 

 where the acorns fall from the branches. This cannot be 

 the true explanation, for the young oysters are swimming 

 animals, and they are discharged into the water in count- 

 less numbers, (g) to be swept away to great distances by 

 the currents. (/*) As they are too small to be seen at this 



(g) Oyster spat may be said to swarm like bees, and it has been 

 said to be as uncertain in its choice of locality. 



(h] See the account of Lim Fiord. 



