HOLOTRICHA 569 



encyst on the bottom of aquarium; the cytostome is absorbed; the 

 body protoplasm divides into 100-1000 small spherical ciliated 

 cells, 18-22/x in diameter, which presently metamorphose into 

 elongated forms, measuring about 40^ by lO/x. These young ciliates 

 break through the cyst wall and seek new host fish by active swim- 

 ming. The young ciliates are able to attack the fish integument for at 

 least 96 hours, though their infectivity decreases markedly after 48 

 hours. 



Genus Bursella Schmidt. Oval; anterior end broadly and ob- 

 liquely truncate where a large ciliated groove-like pit occurs; ridges 

 of pit contractile; cilia short; macronucleus, spherical to ellipsoidal; 

 several micro nuclei; endoplasm reticulated; with symbiotic algae; 

 ectoplasm with tricho cysts; fresh water. 



B. spumosa S. 240-560^1 long; freshwater pond. 



Genus Spasmostoma Kahl. Somewhat similar to Holophrya; 

 cytostome with flaps which beat alternately; ciliation uniform. 



S. viride K. (Fig. 271, c). Spherical or oval; always with green food 

 vacuoles containing Euglena and allied flagellates; cytostome at 

 anterior end; cytopharynx with trichocysts, which are extensible 

 at the time when food is taken in; cilia on about 20 rows, near cyto- 

 stome somewhat longer; macronucleus round; body 50-75/i long; 

 sapropelic. 



Genus Urotricha Clarapar^de and Lachmann {Balanitozoon 

 Stokes), Body oval to ellipsoidal or conical; with 1 or more longer 

 caudal cilia; ciliation uniform, except in posterior region which may 

 be without cilia; cytostome at or near anterior end, surrounded by 

 ring of heavier cilia; contractile vacuole, posterior; macronucleus 

 spherical; fresh water. 



U. agilis (Stokes) (Fig. 271, d). Body small; about 15-20m long; 

 swimming as well as leaping movement; standing fresh water with 

 sphagnum, 



U. farda C. and L. (Fig. 271, e). Body 20-30^ long; fresh water. 

 Kahl considers U. parvula Penard and Balanitozoon gyrans Stokes 

 are identical with this species. 



Genus Plagiocampa Schewiakoff. Ovoid, spindle-form or cylin- 

 drical; slightly asymmetrical; cytostome at anterior end in a slit; 

 right ridge thickened and lip-like, with about 8 long cilia; with or 

 without long caudal cilium; fresh or salt water. Several species. 



P. marina Kahl (Fig. 271, /, g). Cylindrical; oval macronucleus 

 central; contractile vacuole terminal; a caudal cilium; 55-90/i long; 

 salt water; Florida (Noland). 



Genus Chilophrya Kahl. Ovoid or ellipsoid ; cytostome at anterior 



