124 A NURSERY FOR THE MICROSCOPE. 



are no more mysterious than the crystallographic 

 shapes of minerals. The Amoeba is a still commoner 

 object, which will find its way into the aquarium 

 whether we will or no. It is a minute, gelatinous speck, 



Fig 84. 



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Amcela villosa, with diatoms, &c., in its interior. 



possessing the power of protruding any portion of its 

 body in any direction at will. The sarcode of all 

 sponges is usually regarded as made up of a colony of 

 such amoeboid forms. The true A moeba never secretes 

 spicules, although we may frequently see the frustules 

 of diatoms imbedded in its mass (Fig. 84). These, 

 however, are the objects on which it feeds, and over 

 which it has the power of gradually pouring its 

 own flesh until they are enclosed, and await assimila- 

 tion. Then the solid parts are as gradually passed to 

 the outside and extruded. The fresh-water hydras are 

 most interesting aquarium objects. We have two, if 

 not three species, one of which, Hydra vulgar is, is 

 very common. They are each about one-eighth of an 



