infus6ria. 147 



animals to thrive. Its finely divided leaves afford 

 shelter for innumerable forms of life. They are ex- 

 cellent places to seek for Diatoms and for various Algae; 

 indeed among them are to be. found representatives of 

 most of the fresh-water microscopic creatures, both 

 vegetable and animal. Ceratophyllum comes next so 

 far as desirability is concerned, and after it there is 

 little choice among the larger aquatic plants. 



The following Key refers to only a few of the com- 

 monest Infusoria in fresh water and in vegetable in- 

 fusions. To include a tithe of those most frequently 

 seen in such places is an impossibility. When the be- 

 ginner learns that there are about seventy known 

 species of Vorticdlla alone, and about thirty of Monad, 

 he will perceive that it is possible to refer even in the 

 most superficial way to but few of these abundant and 

 attractive creatures. 



Key to sonie Genera of Infusoria. 

 'I. Free-swimming (/). 



2. Not free-swimming; singly or in clusters on a 



stem (a). 



3. Not free-swimming; in a transparent or a granular 



lorica (/5). 



a. Stem much branched, neither it nor the animals 

 contractile. Dendrdmonas, i. 



a. Stem much branched, both it and the animals 

 contractile. CarcMsium, 2. 



a. Stem much branched, only the animals contrac- 

 tile. Epistylis, 3. 



a. Stem not branched, but contracting into a spiral 



coil. Vorticdla, 4. 



b. Loricse vase-shaped, transparent (c). 

 b. Loricse soft, granular, brownish (e). 



