208 MICROSCOPY FOR BEGINNERS. 



c. Sheath formed of rounded brownish pellets. Meli- 

 certa, 5. , 



c. Sheath membranous, brownish or colorless. Lim- 



nias, C. 



d. Ciliary disk horse-shoe shaped. Megalotrocha, 7. 



e. "With carapace (g). 



e. Without carapace ; ciliary disks two (/"). 

 f. With ten or twelve short, scattered, recurved 



spines ; toes three. Philodina, 14. 

 f. Without spines; foot with telescopic joints, toes 



two. Rotifer, 8. 



f. Without spines ; foot with telescopic joints, toes 



three, the middle one longest. Actinurus, 4. 



g. Carapace with a vizor - like projection in front. 



Stephanops, 9. 

 g. Carapace circular ; foot long, cylindrical, retractile. 



Pterodina, 10. 

 g. Carapace vase - shaped ; foot long, with two very 



long toes. Dinocharis, 11. 

 g. Carapace with six long, narrow, movable fins on 



each side. Polydrthra, 12. 

 g. Carapace with several tooth-like spines on the front 



border. Brachionus, 13. 



1. LACDTDLARIA. 



The clusters contain numerous individuals secreting 

 a common, soft, colorless, or pale yellowish short sheath 

 without any special shape ; it surrounds only the poste- 

 rior part of the colony and can serve as a very slight 



