218 



MICROSCOPY FOR BEGINNERS. 



two eye-spots. The foot is long, tail-like, very flexible, 

 and apparently formed of narrow rings. It 

 can be withdrawn entirely into the carapace, 

 and the Rotifer seems to take pleasure in 

 doing so. It has no tail, but is terminated 

 by a small sucker bordered by a circle of 

 tine cilia. The Rotifer is often seen among 



Ceratophyllum leaflets. 



11. DINOCHARIS (Fig. 151). 



The transparent, glassy carapace is rather squarely 

 vase-shaped and somewhat flattened. It gen- 

 erally has a tooth-like projection on each side 

 of the posterior border. The Rotifer can al- 

 ways be recognized by its two very long toes, 

 in one common species one toe being very 

 much longer than the other. The foot is 

 formed of two joints slightly enlarged at the 

 ends. 



12. POLYARTHRA (Fig. 152). 



The form of the carapace is somewhat like an egg, 

 with both ends cut squarely off. The character, how- 

 ever, by which the Rotifer may always be 

 known is the presence of the twelve long, 

 serrated fins which project backward from 

 the front part of the upper and lower sur- 

 faces. They are arranged in clusters of 

 three fins each, one cluster being on each 

 side below, and one on each side above. By them the 



Fig. 151. 

 Diu6charis. 



