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 in the family characteristics. The chief character is the attachment of the posterior end by means of a single, longer or shorter, stalk, which contains a highly contractile thread easily distinguished in the living animal. Another character is the absence of colony formation. Contractile vacuole, single or double, usually connected with a sac-like reservoir. The macronucleus is invariably long and band-formed, with attached micronucleus. Fresh and salt water.

So many species of Vorticella have been described that the task of collecting data and of arranging the synonyms is extremely irksome and difficult. Stokes enumerates 66 species, inhabiting fresh and salt water, and several other new species have been added since his work. I am impressed with the fact that new species have been created without proper regard for the manifold variations which nearly all of the Ciliata show, and I believe the 66 species might be safely reduced to 12 or 15.

Vorticella patellina Müller. Fig. 59.

Body campanulate, widest at anterior border, from which it tapers directly to the pedicle. The diameter of the peristome is a little larger than the length of the body. The ciliary disk is but little elevated. The cuticle is not striated and the body plasm is quite transparent. Length 52µ.

Fig. 59.—
Vorticella patellina.
[ ENLARGE ]

Vorticella marina Greeff. Fig. 60.

The body is conical but variable, and may he short or elongate, so that relative length and breadth offer no chance of identification. In general the body is campanulate. The distinguishing feature is the transverse annulation of the bell.

Small, but common, and grows in small social groups. Length 35µ.

Fig. 60.—
Vorticella marina.
[ ENLARGE ]