352 HANDBOOK OF PROTOZOOLOGY 



Dinidium nasutum (Miiller) (Fig. 151, f-j). Body length 

 80 to 200 microns. Cysts common. In fresh water; often abun- 

 dantly found in Paramecium cultures. 



Genus Monodinium Fabre. Body somewhat similar to 

 Didinium, but with a single girdle of cilia located at the an- 

 terior end. 



Monodinium balbianii (Biitschli) (Fig. 151, k). About 70 

 microns long. Fresh water. 



Genus Mesodinium Stein. Body spherical with a deep con- 

 striction, in which are located strong cilia. Anterior end is 

 conical. Cytostome is connected with a cytopharynx. Four 

 tentacle-like retractile processes occur around the cytostome. 

 Nuclei similar to those of Didinium. Fresh or marine water. 



Mesodinium pulex Claparede and Lachmann (Fig. 151, /). 

 Length about 35 microns. In salt water. 



Genus Dinophrya Biitschli. Body elongate; posterior end 

 drawn out. Anterior end conical with a cytostome at its ex- 

 tremity. Besides being ciliated on general body surface, several 

 girdles of long cilia near the anterior end. Ellipsoidal macro- 

 nucleus central; a contractile vacuole posterior. Fresh water. 



Dinophrya lieberkuhni Biitschli (Fig. 151, m). Length 70 

 to 80 microns. In fresh water. 



Family 3 Tracheliidae Kent 



Cilia occur uniformly over the entire body surface except 

 in a few forms in which they are considerably reduced. An- 

 terior end is drawn out into a proboscis. The location of the 

 cytostome is not constant, it may be on the proboscis, dorsal 

 side, or ventral side. 



Genus Trachelius Schrank. Body large, spherical to ellip- 

 soidal. The anterior region is drawn out into a massive dorsally 

 bent moveable proboscis. The cytostome is located on the 

 ventral side at the base of the proboscis. Cytopharynx basket- 

 like. Contractile vacuoles numerous; macronucleus central and 

 simple or band-form. Movement slow. With spherical cyst. 



Trachelius ovum Ehrenberg (Fig. 152, a). Body about 350 

 microns long. Fresh water. 



Genus Dileptus Dujardin. Body much elongated, anterior 

 end is drawn out into a long proboscis, on the ventral side of 



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