Genus ACINETA Ehr. '33, Bütschli '88.

(Stein '54, '59; Claparède & Lachman '58; Quennerstedt '67;
Hertwig '76; Mereschowsky '79; Entz '84; Kent '81; Maupas '83;
Gruber '84; Gourret & Roeser '86, and others.)


Fig. 67.—Acineta divisa.
[ ENLARGE ]

Small to medium-sized forms. The distinguishing feature is that the stalk is swollen at the distal extremity to form a cup or basin in which the animal rests. The cup may be developed until the body is nearly inclosed. The macronucleus is spherical or band form. The contractile vacuole is usually single. Budding, so far as known, is endogenous. Fresh and salt water.

Acineta divisa Fraipont '79. Fig. 67.

This extremely graceful form is common on Bryozoa at Woods Hole. The cup is shaped like a wine glass and is specifically characterized by a cup-formed membrane upon which the animal rests. The animal thus has the appearance of being suspended on the edge of the cup. The stalk is slender and about 4 times the length of the body. The tentacles are all capitate and distributed, and about 2-1/2 times the body length. They sway back and forth very slowly. The nucleus is spherical and central in position. The contractile vacuole lies near the periphery.

Length of body 27µ; of stalk 100µ; of extended tentacle 65µ.

Acineta tuberosa Ehr. Fig. 68.