138 MICROSCOPY FOR BEGINNERS. 



Las also been recommended for this purpose, but its ac- 

 tion is similar to that of the iodine solution, and not 

 more satisfactory. 



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

 monest Infusoria in fresh water and vegetable infusions. 

 To include a tithe of those most frequently seen in such 

 places is an impossibility. When the beginner learns 

 that there are fifty known species of Yorticella alone, 

 and about thirty of Monad, he will see that it is possi- 

 ble to refer in the most superficial way to only a very 

 few of these abundant and attractive creatures. 



Key to some Genera of Infusoria. 



1. Free-swimming (f). 



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



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



lorica (&). 



a. Stem much branched, neither it nor the animals 

 contractile. Dendromonas, 1. 



a. Stem much branched, both it and the animals con- 

 tractile. Carchesiitm, 2. 



a. Stern much branched, only the animals contrac- 

 tile. Epistylis, 3. 



a. Stem not branched, contracting into spirals. Vor- 



ticella, 4. 



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

 5. Loricee soft, granular, brownish (e). 



c. Attached to each other to form colonies. Dino- 



bryon, 5. 



