THE AMCBBA, HYDRA, AND OTHER SIMPLE ANIMALS 119 



division. An occasional generation must be produced 

 by the method in which conjugation precedes division. 



Other kinds of one-celled animals, or Protozoa, are 

 common in stagnant water, and under the microscope a 

 variety of forms may be seen swimming quickly about. 

 Locomotion is effected usually by many fine cilia or by 

 fewer, usually two, longer whiplash-like processes called 



Fig. 82. — Sun animalcule, a fresh-water protozoan with a siliceous skele- 

 ton, and long thread-like protoplasmic prolongations. (Greatly magni- 

 fied; from life.) 



flagella. Some have the soft body inclosed in a tiny shell, 

 as is the case with the sun animalcule shown in fig. 82. 



Ocean 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, the herring, and 

 the mackerel. Those who have been on the seashore 



