THE DEEP SEA ANIMALS 



In the open ocean there is abundant plant Hfe at the sur- 

 face, almost entirely composed of microscopic types upon 

 which feed minute animals endowed with remarkable repro- 

 ductive powers through which the organic matter is passed 

 on to larger creatures. There are also floating sea-weeds torn 

 from the rocks and drifting with the currents, growing more 

 or less though never fruiting, which serve to some extent to 

 feed the smaller creatures. The gulf-weed or sargassum, so 

 common in the north Atlantic, is the most familiar and im- 

 portant type. 



Far below the surface in the twilight zone where the daylight 

 gradually fades to darkness and plant life disappears, in the 

 levels to which most of the surface animals, at least in the 

 clearer and more sunUt portions of the seas, retreat during the 

 day, lurk many predaceous forms which never rise above it. 

 Still further down, in the cold perpetual night where the mo- 

 tion of the waves is never felt, the creatures of the twilight 

 zone pass over into other types, all of medium size or rather 

 small, all good swimmers, and all or nearly all with phosphor- 

 escent lights like fire-flies — strange fishes, squids, crustaceans, 

 jelly-fish, etc. — which, becoming fewer and fewer, reach 

 probably to the bottom, those of each level feeding upon the 

 animals from the zone above, and all being supported by the 

 creatures of the twilight zone which at night feed upon the 

 plants. In the north and in the south where the cold water, 

 filled with living particles, is less transparent, and the sun's 

 rays strike it at an angle and do not penetrate so deeply the 

 twilight zone comes almost to the surface and there is little 

 difference between night and day conditions. 



Along the shores there is a greater or lesser abundance of 



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