120 THE ANIMALS AND MAN 



Marine Protozoa. — One usually thinks of the ocean as 

 the home of the whales and the seals and the sea-lions, and 

 of the countless fishes, the cod, and the herring, and the 

 mackerel. Those who have been on the seashore will 

 recall the sea-urchins and starfishes and the sea-anemones 

 which live in the tide-pools. On the beach there are the 

 innumerable shells, too, each representing an animal which 

 has lived in the ocean. But more abundant than all of 

 these, and in one way more important than all, are the 

 myriads of the marine Protozoa. 



Although the water at the surface of the ocean appears 

 clear and on superficial examination seems to contain no 

 animals, yet in certain parts of the ocean (especially in the 

 southern seas) a microscopical examination of this water 

 shows it to be swarming with Protozoa. And not only is 

 the water just at the surface inhabited by one-celled animals, 

 but they can be found in all the water from the surface to a 

 great depth below it. In a pint of this ocean-water there 

 may be millions of these minute animals. In the oceans of 

 the world the number of them is inconceivable. And these 

 myriads of Protozoa represent a great host of different species 

 grouped in various families and orders. All of this wealth of 

 animal life was unknown to the earlier naturalists, for but few 

 of the Protozoa are visible without the aid of the microscope. 



Among all these ocean Protozoa none are more interesting 

 than those belonging to the two orders Foraminifera (fig. 48) 

 and Radiolaria. The many kinds belonging to these orders 

 secrete a tiny shell (of lime in the Foraminifera, of silica 

 in the Radiolaria) which encloses most of the one-celled 

 body. These minute shells present a great variety of shape 

 and pattern, many being of the most exquisite symmetry 

 and beauty. The shells are perforated by many small 

 holes through which project long, delicate, protoplasmic 

 pseudopodia. These fine pseudopodia often interlace and 

 fuse when they touch each other, thus forming a sort of 



