ROTIFERS. 



235 



toes. The foot is formed of two joints slightly enlarged 

 at the ends. The Rotifer is not very common. 



14. PolyjSrthra (Fig. 167). 



The contour of the lorica is somewhat like that of 

 ^" 6gg> with both ends cut squarely off. The char- 

 acter, however, by which the Rotifer may always be 

 known is the presence of the twelve long, serrated oar- 

 like appendages which project backward from the. front 

 part of the upper, and 

 lower surfaces, from 

 near what may perhaps 

 be called the shoulders. 

 They are arranged in 

 clusters of three each, 

 one group being on each 

 side below, and one on 

 each side above, only six 

 being shown in the figijre. 

 By them the Rotifer _ ^'s le/.-Poijinhra. 



makes long, quick, sudden leaps, often jumping so rap- 

 idly that it can hardly be seen; it appears to spread the 

 appendages and to vanish. Occasionally it turns a com- 

 plete somersault. The cilia are arranged in a row 

 along the front border. There is no foot. The mas- 

 tax is pear-shaped and large, but its structure is diffi- 

 cult to make out. The Rotifer has only one eye, 

 which appears to be near the center of the upper front 

 surface. The little creature has been called by some 

 writers the "sword-bearer," and is said to be quite 

 common in some localities, but I have never been 

 fortunate enough to find it in the waters near my 

 home. It is not rare in New York. 



