No. 2.] FRESH-WATER PROTOZOA. 2$ 



Not flexible or only slightly so; with a thick cuticle ii 



8. Without a lorica 9 



With a lorica lO 



9. With one flagellum ; both ends contracted Euglena* 



With one flagellum; anterior end rounded; usually 



in a jelly-like envelope, and attached by a branched 



stalk ; ectoparasites Colacium 



With two flagella Etitreptia* 



10. In a beaker-shaped or tube-like lorica Ascoglena 



In a hard, smooth or spiny, spherical or cylindrical, 



brownish shell Trachelomonas* 



11. Ellipsoidal or slightly flattened; pharynx in body 



axis, and a short, pointed caudal process. .Lepocinclis* 

 Ellipsoidal, not flattened ; with rows of tubercles and 



a pointed caudal process Chloropeltis* 



Usually asymmetrical, flattened. Mouth on back; 



pharynx oblique ; evident, pointed caudal process 



12. Not flexible 13 



Flexible 14 



13. Elongated, somewhat crescentic ; rounded posterior 



end Menoidium 



Straight, spindle- formed ; acute posterior end 



Atractonema* 



Cylindrical, slightly bent; both ends rounded 



Rhabdomonas 

 Much flattened, with one or more keels upon dorsal 

 surface; large mouth at base of flagellum, P(?fa/owoa>y 



14. Long, needle-shaped; frequently spiral Astasia psis 



Oval, flattened ; mouth at base of flagellum ; an evi- 

 dent pharynx and a rod-like organ Peranema* 



Flask-shaped ; neck-like anterior end, with pharynx 



extending to middle; rod-like organ present 



Urceolus'* 



Like Urceolus, but covered with sand grains 



Urceolopsis 



15. Flexible 16 



Not flexible 17 



