THE PHYSIOLOGY OF DEEP-SEA LIFE. 313 



in the food supply of shore aiihuals ; vegetable life forms the 

 basis of all life ; for while many animals are carnivorous, yet 

 those they feed upon depend in a measure for their sustenance 

 upon plants. It is therefore an interesting problem to ascer- 

 tain how far vegetable life extends into the depths of the sea. 

 Its disappearance in comparatively shallow regions is a remark- 

 able phenomenon, when we remember that all animal life is 

 ultimately dependent upon vegetable life for its own existence. 



The discovery gf the carcasses of pelagic animals at the bot- 

 tom of the ocean, still fresh enough to supply a large amount 

 of food for the animals constituting the deep-sea fauna, solves 

 the problem at once. The pelagic animals derive a large part 

 of their food supply from the swarms of large and small pelagic 

 algai covering the surface of the sea in all oceans. On dying, 

 both surface animals and plants drop to the bottom, and still 

 retain an amount of nutritive matter sufficient to serve as food 

 for the carnivorous annuals living on the bottom. The pelagic 

 fauna thus becomes the medium of transfer to the bottom of a 

 large quantity of vegetable matter living at the surface. This 

 transfer takes place rapidly. Moseley says Salpse will sink two 

 thousand fathoms in less than three days. 



The larger carnivorous animals of course prey upon one an- 

 other, but foraminifera, sponges, and their allies, cannot feed 

 upon each other, as do the mollusks, annelids, polyps, and the 

 like. They need vegetable substances, or diluted organic mat- 

 ter, such as they find in abundance on the bottom. 



A sort of " broth," as it has been called by Carpenter, collects 

 on the bottom of the ocean, from which the lower types may 

 possibly be able to obtain theii* sustenance directly, and transfer 

 it for their uses, as they do the silex and lime which they get 



careous algae are found at that depth, Boring algaj have been dredged in deep 



would prove conclusively that some kind water (over 1,000 fathoms), 



of light penetrates to this depth. Some At a depth of 270 fathoms off Havana, 



of the organisms which have been de- Pourtalfes dredged a single specimen of 



scribed as single-chambered foraminifera a minvite alga, Centroceras clavulatum 



are in reality calcareous algae, allied to Aghard, which Harvey says is common 



the green spore-bearing algae, the Dasy- at low-water mark at Key West. Di- 



cladse of Harvey. atoms were also brought up from the 



same locality. 



