Length 60µ from disk to extremity of the peristomial disk.

Fig. 58.—
Lichnophora macfarlandi.
[ ENLARGE ]

This form does not agree in all respects with Stevens's species, but the agreement is so close in other respects that I believe it can be safely identified as L. macfarlandi. The mode of life is different, and the macronucleus is different, there being from 25 to 30 fragments in Stevens's form and only 5 or 6 in the present one. There is, however, the same evidence of chain formation in both of them. The length of the oral cilia in Stevens's form is 18µ in fixed and 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 permanent around an attaching disk 3
2. Posterior ciliated girdle, temporary during motile stage 4
3. Body cylindrical:
(a) With ring of stiff bristles above the ciliated girdle Genus Cyclochæta
(b) Without accessory ring of bristles; with velum Genus Trichodina
Body conical; general surface ciliated Genus Trichodinopsis
4. No test and no stalk Genus Scyphidia
5. No test; with stalk containing contractile thread 8
6. No test; with stalk but without contractile thread Genus Epistylis
7. With a test; with or without a stalk Genus *[Cothurnia]
8. Individuals solitary Genus *[Vorticella]
Individuals colonial; entire colony contractile Genus *[Zoothamnium]
Individuals colonial; parts only of the colony contractile Genus Carchesium
* 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.)