14 BIOLOGICAL SOCIETY OF WASHINGTON. 



chance to be weaker. Depredations on this community are 

 doubtless committed by deep sea fishes and echini, perhaps 

 by other organisms, but the inroads are not so important as to 

 seriously modify the course of evolution and influence specific 

 characteristics. 



Hence the course of evolution and modification, though still 

 complex, is certainly much less so than in the shallower parts 

 of the ocean. For this reason we may hope to penetrate more 

 deeply into its mysteries with deep sea animals than with those 

 less fortunately .situated. In this opportunity, to me, lies the 

 chief importance of research into the biology of deep sea mol- 

 lusks. Nowhere else may we hope to find the action and reac- 

 tion of the contending forces less obscure, and modification in 

 most cases has not extended so far that we cannot compare the 

 deep sea forms with their shallow-water analogues and draw 

 valuable conclusions. 



While we are not yet in a position to formulate conclusions 

 covering all the details of abyssal mollusk-life in certain in- 

 stances results suggest themselves. 



Deep sea mollusks of course did not originate in the depths. 

 They are the desceudents of those venturesome or unfortunate 

 individuals who, by circumstances carried beyond their depth, 

 managed to adapt themselves to their new surroundings, sur- 

 vive and propagate. Many species must have been eliminated 

 to begin with. Others more plastic, or more numerous in in- 

 dividuals, survived the shock and have gradually spread over 

 great areas of the oceanic floor. In accordance with these not 

 unreasonable assumptions we should expect to find among the 

 newer comers at least some characters which were assumed un- 

 der the stress of the struggle for existence in the shallows, and 

 which, through specific inertia, have not become wholly obso- 

 lete in the new environment. We should also expect to find a 



