350 HANDBOOK OF PROTOZOOLOGY 



phase or by multiple division in the encysted condition, which 

 produces two hundred or more individuals (30 to 45 microns 

 long). Conjugation is also reported. Parasitic in the integument 

 of numerous freshwater fishes in small ponds or especially 

 in aquaria. Widely distributed. 



Ichthyophthirius muUifiliis Fouquet (Fig. 150). Body meas- 

 ures 300 to 800 microns in length. The ciliate attacks the 

 epidermis or gills and forms pustules. When heavily infected, 

 the host fish dies apparently from the infection. 



Genus Enchelys Ehrenberg. The anterior portion is drawn 

 out into flask-shaped body which is obliquely truncated. Peri- 

 stomal cilia are more conspicuous than those of the general 

 body surface. Free-living in fresh water. Several species. 



Enchelys teres (Stokes) (Fig. 151, a). About 170 to 200 

 microns long. In standing water among decaying vegetation. 



Enchelys truncata (Stokes) (Fig. 151, h). About 125 microns 

 long. In fresh water among dead leaves. 



Genus Enchelyodon Claparede and Lachmann. Similar to 

 Enchelys, but with long trichites around the cytopharynx. In 

 salt or fresh water. 



Enchelyodon farctus Claparede and Lachmann (Fig. 13, d). 

 Body about 240 microns long. In marshes. 



Genus Lagynus Quennerstedt. Body elongated ; anterior end 

 sharply truncated. The cytopharynx is rather conspicuous. 

 Encystment observed. In fresh or salt water. 



Lagynus elegans Engelmann (Fig. 151, c). Body about 85 

 to 175 microns long. Fresh water. 



Genus Spathidium Dujardin. Flask- or sack-shaped; an- 

 terior end is slightly narrowed into a neck with a truncate 

 extremity. Cytostome occupies the whole of the end and is or- 

 dinarily closed. Contractile vacuole posterior; elongate macro- 

 nucleus and several micronuclei. Trichites around the cystotome 

 and also scattered throughout the endoplasm (Fig. 13, c). 



Spathidium spathula (Ehrenberg) (Fig. 151, d, e). Body up 

 to 250 microns in length. Fresh water. 



Genus Didinium Stein. Body barrel-shaped. Two girdles of 

 long cilia, but no other cilia. The anterior end possesses a 

 proboscis-like elevation, at the end of which is located an ex- 

 pansible cytostome. Macronucleus is horseshoe-shaped. A 



