41 



inferior mantle cavity, which liad evidently been drawn 

 in by the inward current. It is plain in this case that very 

 mild means may become effective as prehensile and de- 

 structive agents, so as to bring remotely related types into 

 intimate vital relation. Though an animal may be ap- 

 parently invulnerable on account of the effectiveness of 

 its covering, it cannot emancipate itself from the abiding 

 struggle it has to make to obtain food, no matter how pas- 

 sively it may apj)ear to conduct itself. Tlie oyster has 

 such a charactei', yet it has been apparent from what has 

 been observed before, that it is entirely dependent for a 

 vigorous existence upon the f avorableness of surrounding- 

 conditions. The beds and banks in a true sense are inter- 

 dependent comnumities, whose vigor may no doubt be 

 impaired by the removal pf a single one of its members. 

 Suppose we should take away the algae, diatoms, oyster 

 crabs, vibriones, bacteria, infusoria, in fact all the minute 

 life, Ave should greatly impair if not destroy tlie vitality 

 of the beds. While it is true that many of even the 

 smallest forms may destroy food which should properly 

 be consumed by the oyster, that were it net for the pres- 

 ence of these same small forms some destructive element 

 might attain such a development as to be more injurious 

 still. There is therefore no doubt ]>ut that a delicate bal- 

 ance of power is maintained by these rivals which is best 

 for the health of the community. The stability of perma- 

 nent oyster beds, it must be remembered, furnishes the 

 right conditi(ms for the survival of nuiny tyx)es. It is a 

 place where they find both a home and x)lenty of food. It 

 is the very f avorableness offered by these places which 

 tends to induce them to congregate and multiply, and it 

 becomes a serious question whether the artiiicial establish- 

 ment of banks will not in time cause the proper types to 

 congregate and multii>iy so as to afford the needed food 

 sup])ly for the oysters. That destructive members of 

 the community may also be attracted is admitted, but if 

 the beds are established in shallow writers, as I have 



