CHAPTER XXIX 



ORDER 2 HE'TEROTRICHIDA STEIN 



THIS ORDER includes those Euciliata which possess an adoral 

 zone that is wound to the left. The adoral zone is composed 

 either of strong cilia or membranellae. As a rule, the body is 

 covered by delicate cilia which, however, may be reduced in 

 some forms. The cytopharynx possesses a conspicuous undulat- 

 ing membrane. In one group Tintinnoinea, the animal secretes 

 a lorica. Free-living or parasitic. 



Following an extensive study of Kofoid and Campbell, the 

 Euciliata which were formerly placed in the family Tintinnidae, 

 are removed from Oligotrichida into the present order. The 

 Heterotrichida are, therefore, divided into two suborders as 

 follows: 



Without a lorica Suborder 1 Gymnoheterotrichina 



With a lorica Suborder 2 Tintinnoinea 



Suborder 1 Gymnoheterotrichina 



The group will be divided into six families: 



Adoral zone parallel to the main body axis 



Peristome is narrow and long Family 1 Plagiotomidae 



Peristome is wide, triangular, and deep Family 2 Bursariidae 



Adoral zone not parallel to the main body axis 

 Body funnel-shaped; adoral zone strong 



Cytopharynx tubular; free-living Family 3 Stentoridae 



Cytostome not permanently open; ectoparasitic . . . . Family 4 Boveriidae 



Body form medusoid Family 5 Caenomorphidae 



Body asymmetrical; sapropelic; cilia reduced Family 6 Epalcidae 



Family 1 Plagiotomidae Poche 



Genus Plagiotoma Dujardin. Body form constant, ovoid; 

 convex dorsally, flattened ventrally. Peristome extends from 

 the anterior end to the middle of the body, where a cytostome 

 is located. Cytopharynx distinct. There is a single bristle ex- 

 tending out of the cytostome. Parasitic. 



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