THE SEA 23 



The lighted zone along the shore has a fauna unlike 

 that at a hundred fathoms, while at a thousand 

 fathoms another world is seen, and so on with 

 increasing depth. 



The variety of marine plants and animals is so 

 great that it is only possible to consider the subject 

 briefly here. The largest and smallest animals and 

 the tallest and smallest plants live in the sea, and 

 an amazing number and variety of both plants and 

 animals are found there. Even the surface water 

 collected in mid-ocean, which is seemingly devoid of 

 life, is teeming with minute living organisms. 



Life is most abundant in the relatively shallow 

 water close to shore, and it is from these waters 

 that most of the products of economic importance 

 come. The fish, lobsters, shrimp, crabs, oysters, clams, 

 mussels, abalones, sponges, turtles, terrapins, squid, 

 and algae utilized by man are all taken in fairly 

 shallow water close to shore or on the banks — areas 

 of shallow water farther from shore, which are exten- 

 sions of the continental shelves. The largest animals 

 found in the sea are whales, which are not fish but 

 mammals especially adapted for life in the ocean. 

 Many other mammals are found in the ocean, the 

 most important of which are the seals, walruses, sea- 

 lions, porpoises, and dolphins. Whaling and sealing 

 are important marine industries. Approximately 

 nineteen thousand different species of fish exist, 

 many of which are found in enormous numbers. The 

 various species of fish differ greatly in size, form, 

 color, and habits. 



Nearly all marine plants require light for their 



