22 G REPORT ON ALBATROSS MOLLUSCA DALL. 



those showing the marks of fish teeth, or the dental machinery of echi- 

 noderms, it is extremely rare to find, drilled bivalves or univalves such 

 as make up the great mass of the jetsam on every sandy beach. Such 

 cases occur, but the occurrence is always exceptional and the holes 

 which are most often found in abyssal shells are those which are due 

 either to the friction of some hermit crab or to the erosive properties 

 of the secretions of certain annelids which fix their irregular tubes upon 

 the outer surface of the shell. These injuries can not easily be con- 

 founded with the circular drill-holes of carnivorous gastropods. Having 

 handled more deep-sea mollusks than any other naturalist now living, 

 and spent, probably, more time over material procured by the dredge 

 from shallow water than any one else of my acquaintance, I do not feel 

 that I am presumptuous in affirming the remarkable difference which 

 obtains in this respect between the dead material from the Litoral and 

 from the Extra-Litoral Regions, respectively. 



This brings me to a conclusion which I have elsewhere published 

 with less detail. The animals belonging to the mollnsca which are 

 foun I in the Archibenthal and Abyssal regions, especially the latter, 

 do not live in a perpetual state of conflict with one another. A certain 

 amount of contention and destruction doubtless goes on, but on the 

 whole the struggle for existence is against the peculiarities of the envi- 

 ronment and not between the individual mollusks of the area concerned. 

 It is an industrial community, feeding, propagating, and dying in the 

 persons of its members, and not a scene of carnage where the strong 

 preys upon his molluscan brother who may chance to be weaker. Dep- 

 redations on this community are doubtless committed by deep-sea fishes 

 and echini, perhaps by other organisms, but the iuroads are not so im- 

 portant as to seriously modify the course of evolution and influeuce 

 specific characteristics. 



Ilence 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 m;iy hope to penetrate more deeply into its mysteries 

 with deep sea animals than with those less fortunately situated. In this 

 opportunity, it seems to me, lies the chief importance of research into the 

 biology of deep sea mollusks. Nowhere else may we hope to find the 

 action aud reaction of the contending forces less obscure, and modifica- 

 tion in most cases has not extended so far that we can not 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 instances results sug- 

 gest themselves. 



Deep-sea mollusks, of course, did not originate in the deeps. They 

 are the descendants of those venturesome or unfortunate individuals 

 who, by circumstances carried beyond their usual depth, managed to 

 adapt themselves to their new surroundings, survive, aud propagate. 



