30µ in living forms. In the Woods Hole form the cilia are not more
than half that length.


KEY TO THE MARINE GENERA OF VORTICELLIDÆ.

Diagnostic characters: Attached or unattached forma of peritrichous
ciliates in which the adoral zone seen from above forms a right-wound
spiral. A secondary circlet of cilia around the posterior end may be
present either permanently or periodically.

1. Posterior ciliated girdle 3
permanent around an attaching disk

2. Posterior ciliated girdle, 4
temporary during motile stage

3. Body cylindrical:

(a) With ring of stiff bristles Genus _Cyclochæta_
above the ciliated girdle

(b) Without accessory ring of Genus _Trichodina_
bristles; with velum

Body conical; general Genus _Trichodinopsis_
surface ciliated

4. No test and no stalk Genus _Scyphidia_