So ELEMENTARY ZOOLOGY 



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 it is necessary that these Protozoa 

 exist in such great numbers, for they and the marine one- 

 celled plants (Protophyta) supply directly or indirectly 

 the food for all the other animals of the ocean. 

 /Among all these ocean Protozoa none are more in- 

 teresting than those belonging to the two orders Forami- 

 nifera (fig. 1 1) and Radiolaria. The many kinds belong- 

 ing to these orders secrete a tiny shell (of lime in 

 the Foraminifera, of silica in the Radiolaria) which en- 

 closes 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 



