12 BIOLOGICAL SOCIETY OF WASHINGTON. 



other factor joins with the absence of light to discourage 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 foramini- 

 fera which they swallow in immense quantities. The results 

 of this diet are evident in the greatly increased caliber of the 

 intestine relatively to the size of the animal, in the diminution 

 of the masticatory organs, teeth and jaws, and in the prolonga- 

 tion of the termination of the intestine as a free tube to a 

 length which will carry the effete matters out of the nuchal com- 

 missure, 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 algae. 



But the great mass of abyssal mollusks are members of those 

 groups which in shallow waters are normally carnivorous, and 

 to a great extent prey upon one another. In the deeps how- 

 ever this reciprocal destruction is unnecessary. 



Those who have become familiar with surface collection 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 consist- 

 ency of soup, for miles in extent and to a considerable depth. 

 Millions of these creatures are constantly sinking from the 

 region where they naturally belong, either from injury or ex- 

 haustion, and thus raining slowly but constantly upon the 

 bottom. This fact is not new and is admitted to be unques- 

 tionable by all biologists. Hence in many regions of the sea 

 bottom the resident fauna have, as it were, only to lie still and 

 hold their mouths open. 



