5. No test; with stalk containing 8
contractile thread

6. No test; with stalk but without Genus _Epistylis_
contractile thread

7. With a test; with or without Genus *_Cothurnia_
a stalk

8. Individuals solitary Genus *_Vorticella_

Individuals colonial; Genus *_Zoothamnium_
entire colony contractile

Individuals colonial; parts Genus _Carchesium_
only of the colony contractile

* Presence at Woods Hole indicated by asterisk.


Genus VORTICELLA (Linnæus 1767) Ehr. '38

(Bell Animalcule Leeuwenhoek 1675; Ehrenberg '38; Dujardin '41; Stein
'51; Cl. & Lach. '58; Greeff '70; Bütschli '88; Kent '81; Stokes '88;
etc.)

Medium-sized ciliates of general bell-like form. They may be
colorless, or yellow and green through the presence of Zoochlorella.
When not contracted, the peristome end is widespread, rarely
narrowed. The adoral zone and peristome agree with the details given