INFUSORIA. 153 



animal uses them for swimming, or it walks about the 

 slide or climbs among aquatic plants by resting part of 

 its weight on their tips as if they were legs. When the 

 creature happens to be turned on its back, these large 

 cilia can be seen pattering irregularly against the cover- 

 glass. They vary in number from ten to 

 twelve. The front border has a row of 

 finer but still large cilia extending down the 

 side of the flat surface to the mouth near the 

 centre of the body. Four straight, stiff hairs 

 project from the posterior margin, two of P 16tes - 

 them often being divided into fine branches. The back 

 of the Infusorium has no cilia, but is a hard surface, al- 

 most like a shell. The animal is very active. There 

 are several species common among Ceratophyllum and 

 Myriophyllum. 



19. STTLONYCHIA (Fig. 127). 



To the beginner the members of this genus will quite 

 closely resemble Euplotes, as all the cilia are confined 

 to the frontal border, the part about the 

 mouth, and irregularly distributed over one 

 side of the flat lower surface as walking or- 

 gans. It can easily be distinguished from 

 Euplotes by its shape, being much more ob- 

 long. Sometimes it is quite long and nar- 



i -i -n i i i i 



row, while Luplotes is always more or less 

 circular. It has no cilia on the back, which is usually 

 hard and shell-like. The species are several, being espe- 

 cially common in vegetable infusions. 



