Beaches 19 



waters, live more or less both in air and in water. Marine animals 

 thus have opportunity to become adjusted to life on land, and land 

 animals may gain some ability to endure life under water. Many 

 thoughtful, beach-haunting biologists have suggested ocean shores 

 as one route through which old marine stocks of animals have 

 reached land (Flattely, 1920, 1921). 



The moving littoral water contains myriads of small organisms 

 which serve as food for animals. The accumulations which have 

 been left along the drift line above high-tide mark furnish food 

 and shelter for both terrestrial and aquatic animals. There is keen 

 competition for places to live between tide marks. The plants and 

 animals on beaches are arranged in zones. Various factors con- 

 tribute to enforce such zonal arrangement: the height of tides, the 

 slope of the beach, the character of the bottom, etc. On most 

 beaches zones are clearly defined by characteristic littoral plants. 

 These in turn furnish protection and food for animals. At one 

 locality on Long Island, N. Y., for example, there are about five 

 zones of plants: (1) the plankton (peridinians, diatoms, etc.) in the 

 littoral water, (2) the attached bottom vegetation (Ulva, Entero- 

 morpha, Fucus, Chondrus, etc.), (3) a mid-littoral belt (Spartina, 

 Fucus, Ascophyllum, Bostrichia, etc.) , (4) an upper littoral belt 

 which has rather varied vegetation (Spartina, Scirpus, Salicornia, 

 filamentous algae, etc.) , and (5) supra-littoral belt containing a 

 great variety of plants (Johnson & York, 1915). Similar zonal 

 arrangement of animals is characteristic on all ocean beaches 

 (Harms, 1929; Huntsman, 1918a; Pearse, 1914, 1914a, 1929, 1931; 



Fig. 3. Zones on a rocky shore at Nahant, Mass 



From above downward: Barnacles, and the algae 



Ascophyllum, Fucus, and Chondrus. (From Pearse 

 1914.) 



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