494 BIOLOGY OF THE PROTOZOA 



Family 1. Holophryidae Perty 1852. 



21. Elongate to worm-like species, usually 



more or less distensible 22 



Short or flask-shape species; little disten- 

 sible; ectoplasm without warts 24 



22. Head region narrowed ; somewhat contrac- 



tile, longitudinal or slightly spiral stripes 23 

 No spiral stripes; head region not nar- 

 rowed; no tuft of oral cilia, pellicle warty, 

 exclusively marine worm-like or flask- 

 shape usually very large Genus Trachelocerca Ehr. 



23. Without caudal thread; tuft of cilia di- 



rected forwards (Fig. 191) Genus Chaenea Quennerstedt 



With two caudal threads Genus Urochaenea Savi 



24. Gullet opens to outside with a distinct 



dome-like process Genus Enchelydon C. and L. 



Gullet mouth round to slit-form; with 

 cross or obliquely truncate anterior end . 25 



25. Gullet mouth appears like long cross-cut 



of anterior end; posterior end with tuft 



of cilia Genus Crobylura Andre 



Gullet mouth not clean-cut section in ap- 

 pearance; no anal tuft of cilia. . . .Genus Enchelys Hill 

 Family 2. Actinobolinidae Kent 1880. 



Only 1 genus Actinobolina Strand 1926 (Actinobolus Stein pre-occupied) 

 Family 3. Metacystidae Kahl 1926. 



1. Animals ovoid, without end vesicle; with 



caudal cilia Genus Vasicola Tatem 



Animals not ovoid 2 



2. Spindle-form ; no caudal cilia ; closely annu- 



late . Genus Pelatractus Kahl 



Cylindrical; usually one, rarely more, 

 caudal cilia, with globular, swollen end 



vesicle Genus Metacystis Cohn 



Family 4. Didiniidae Poche 1913. 



1 . No gullet; special polar area for food-taking 



(Fig. 191) Genus Cyclotrichium Meunier 



Distinct gullet, opening in center on a defi- 

 nite mound 2 



2. Body with one or more circlets of cirri .... 3 

 Body with circlet of pectinelles 4 



3. With circlet of pectinelles about oral 



mound outside of which is circlet of cirri 



Genus Askenasia Blochmann 

 With circlet of cirri around oral mound 



Genus Mesodinium Stein 



4. In addition to pectinelles, body uniformly 



ciliated Genus Acropisthium Perty 



With one to several circlets of pectinelles, 



otherwise without cilia Genus Didinium Stein 



Family 5. Colepidae Clap, and Lach. 1858. 

 1. Body rounded posteriorly; plates separate 



on pressure Genus Coleps Nitsch 



Body pointed posteriorly, plates firm 



Genus Tiarina Bergh 



