^889."'] PROCEEDINGS OF THE NATIONAL MUSEUM. 225 



captured and afterward voided on the same spot. It seemed more 

 likely from all the facts that these fishes, after feeding to repletiou, 

 repair in large schools to certain areas to enjoy the pleasures of diges- 

 tion. There would be nothing improbable in the fish of a limited region 

 preferring some special locality for this purpose, and the result might 

 be the accumulation of a veritable bank, of which nearly the whole had 

 at some time or other passed through the intestine of a fish. At all 

 events, whatever explanation be offered of them, it is certain that such 

 accumulations do occur at certain localities, as shown by thedredgings 

 of the Fish Commission off the eastern coast of the United States. 



The last condition remaining to be considered is that of the food sup- 

 ply. It has long since been pointed out that marine vegetation ceases 

 to exist within a limit of 600 feet below the surface. Whatever light 

 exists in the depths it is not of a nature to meet the needs of vegeta- 

 tion. Whether any other factor joins with the absence of light to dis- 

 courage algal growth is yet unknown, but not intrinsically improbable. 

 The mollusks which belong to groups known as phytophagous in shallow 

 water, in the deeps appear to live chiefly on foramiuifera which they 

 swallow in immense quantities. The results of this diet are evident in 

 the greatly increased caliber of the intestine relative to the size of the 

 animal, in the diminution of the masticatory organs, teeth, and jaws, 

 and in the prolongation of the termination of the intestine as a free 

 tube to a length which will carry the faeces out of the nuchal commis- 

 sure, and thus free from their injurious effects the branchial organs, 

 which are usually seated in this space. The quantity of nutriment in 

 the protoplasm of foraminifera is so small that a much larger mass in 

 proportion of these organisms must be swallowed, and their remains 

 consequently ejected afterward, than if the food consisted of the tissues 

 of alga?. 



But the great mass of abyssal mollusks are members of those groups 

 which in shallow waters are normally carnivorous, and to a great ex- 

 tent prey upon one another. In the deeps, however, this reciprocal 

 destruction is unnecessary. 



Those who have become familiar with surface collecting on the sea, 

 alone can realize the immense quantity of organisms which exist in the 

 water on or near the surface. These are frequently numerous enough 

 to reduce the water to the consistency of soup for miles in extent and 

 to a considerable depth. Millions of these creatures are constantly 

 sinking from the region where they naturally beloug, either from injury 

 or exhaustion, and thus raining slowly but constantly upon thebottom. 

 This fact is not new and is admitted to be unquestionable by all biolo- 

 gists. Hence in many regions of the sea bottom the resident fauna have, 

 as it were, only to lie still and hold their mouths open. 



One of the facts r which attracted my attention when I first began to 

 study deep-sea mollusks was the singularly small number which showed 

 signs of having been drilled or attacked by other mollusks. Apart from 

 Proc. N. M. 89 15 



