412 BIOLOGY OF THE PROTOZOA 



Tribe 1. Contractilia, Biitschli. 



Note. — Individuals are often detached from their stalks under labora- 

 tory conditions and beconie free-swimming; such detached forms always 

 have a posterior girdle of cilia, one genus — Opisthonecta — has them per- 

 manently. 



1. Solitary; a single highly contractile stalk 



Genus Vorticella 

 Colonial; colonies dichotomously branched 2 



2. Individual stalks contract separately; not 



connected Genus Carchesium 



Entire colony contracts; stalk threads con- 

 nected Genus Zoothamnmm 



Tribe 2. Acontradilia, Biitschli. 



1. Colonial forms; colonies often enormous. . 2 

 Solitary forms 4 



2. Individuals of huge colony embedded in 



jelly Genus Ophrydium 



Individuals not embedded in jelly 3 



3. Peristome disc not stalked; feather-like 



colonies (Fig. 210, p. 502) Genus Epistylis 



Peristome disc stalked ; feather-like colonies 



Genus Opercularia 



4. Individuals free-swimming or creeping. ... 5 

 Individuals attached 6 



5. No stalk; posterior cilia girdle permanent 



Genus Opisthonecta 

 Vorticella-like ; two posterior bristles; no 



stalk Genus Astylozoon 



Posterior end broad, ringed near Ijase, no 



bristles Genus Gerda 



6. Solitary, in delicate cup; peristome cup-like 



Genus Ophrydiopsis 

 Cylindrical, with attaching disc; cross- 

 ringed Genus Scyphidia 



Vorticella-like; with or without short stalk 7 



7. Undulating membrane enormously devel- 



oped Genus Glossatella 



Undulating membrane inconspicuous ; stalk 



short Genus Rhabdostyla 



Tribe 3. Cothurnina, Biitschli. 



1. Upright; attachment posterior; with or 



without stalk Genus Cotkurnia 



Attachment lateral or lengthwise; recum- 

 bent 2 



2. Peristome disc with stalk, operculum-like 



Genus Lagenophrys 

 Peristome disc not stalked Genus Vagiyiicola 



Cl.\ss II. SUCTORIA, Butschli. 



1 . Cilia absent except on embryos 2 



Body permanently ciliated Family Hypocomid.e 



2. Suctorial tentacles alone present 3 



Prehensile tentacles in addition to suctorial 



Family Ephelotid^ 



