82 New York State Museum 



animals are particularly characteristic of the shore. 

 The number of kinds of animals between tides is rela- 

 tively small ; greater, however, nearer low tide mark. 

 There is a marked increase in variety below low water 

 mark. With increase in depth certain forms disappear 

 and others take their places. Some of the shore forms 

 disappear at about a depth of 50 feet or so. The great- 

 est variety of animal types is found at depths of 600 to 

 1200 feet, on the bottom. The waters are cool and 

 quiet, the light dim to almost absent, and the waters 

 above and the detrital material washed from the shore 

 furnish an abundant food supply. Animals of very 

 large size are found in this zone including huge crabs, 

 urchins and starfishes. Plants, that is, seaweeds, do 

 not grow beyond depths to which sufficient light pene- 

 trates — the 100-fathom line. 



The open sea is characterized by floating and swim- 

 ming types. This pelagic life consists to a large ex- 

 tent of microscopic plants and animals, such as dia- 

 toms, foraminifera and radiolarians. The microscopic 

 plant life is very abundant and serves as food for the 

 microscopic animals which reproduce very prolifically 

 and in turn serve as food for larger creatures. The 

 micro-organisms of the surface therefore constitute the 

 basis of all life in the sea, the fundamental food sup- 

 ply. The chance for diversity in the pelagic life is 

 very small because of the simplicity of the environ- 

 ment. Conditions of life are very easy so there is no 

 fierce competition, as at the shore. Far below the 

 surface is the twilight zone where are found predace- 

 ous forms which, however, do not rise above this zone. 

 Below this zone, again, is the region of perpetual night 

 and cold, where the motion of the waves is never felt. 



