The macronucleus is centrally placed and globular to ovoid in form.

The contractile vacuole is usually single. Reproduction takes place by division; the distal half developing cilia and becoming a swarm-spore. Fresh and salt water.

Podophrya gracilis, n. sp. Fig. 65.

Of all the _Podophrya_ that have been described not one approaches this minute form in the relative length of the stalk. The body is spherical and is covered with short capitate tentacles. The stalk is extremely slender, bent, and without obvious structure. There are one or two contractile vacuoles in the distal half of the body. The nucleus is small and is situated near the insertion-point of the stalk. Reproduction not observed. Diameter of body 8; length of stalk 40. Only one specimen seen.

[Ill.u.s.tration: Fig. 65.--_Podophrya gracilis_.]

Genus EPHELOTA Str. Wright '78.

(Butschli '88; Ishikawa '96; Sand '98.)

Small to medium-sized and large forms; colorless to brown. The body is globular or oval or wedge-shape, sometimes quadrangular. The stalk is variable, sometimes 1 mm. in length. The diameter of the stalk increases from the point of attachment to the body of the animal; it is usually striated either longitudinally or transversely, or both. The tentacles are of two kinds and are usually confined to the anterior half of the body. Some are long and sharp-pointed and adapted for piercing; others are short, cylindrical, usually retracted and capitate, adapted for sucking. Contractile vacuoles vary from one to many. The macronucleus is nearly central in position and usually of horseshoe shape, but is frequently branched and irregular. Reproduction is accomplished by external multiple budding, usually from the anterior half of the body. Salt water.

Ephelota coronata Str. Wright. Fig. 66.

Synonyms: _Hemiophrya gemmipara_ S. K.; _Podophrya gemmipara_ Hertwig.

The body is spheroidal, ovate, or pyriform, with numerous sharp-pointed tentacles and a few straight, uniform tentacles. The stalk is about three times the length of the body and tapers from its widest part at the insertion in the body to the narrowest part at the point of attachment. It may or may not be longitudinally striated.

This is one of the commonest of the _Suctoria_ found at Woods Hole.

It is usually present on Campanularian hydroids, but may be found on algae and Bryozoa.

Length of body 90 to 200.

[Ill.u.s.tration: Fig. 66.--_Ephelota coronata_.]

Genus ACINETA Ehr. '33, Butschli '88.

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

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 gla.s.s 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 27; of stalk 100; of extended tentacle 65.

[Ill.u.s.tration: Fig. 67.--_Acineta divisa_.]

Acineta tuberosa Ehr. Fig. 68.

Large forms of _Suctoria_ with tentacles arranged in fascicles. The stalk is variable in length and the cup is frequently so delicate that it can barely be made out. A specific characteristic is the break in continuity of the cup at different points, and through these places the tentacles emerge in bundles. The tentacles are capitate and in the Woods Hole form, 15 in number in each of the two bundles.

The endoplasm is granular and yellowish in color. The coloring matter is frequently arranged in patterns. The nucleus is spheroidal. The contractile vacuole is in the anterior third of the body about midway between the bundles of tentacles. Reproduction not observed.

Length of body 330.

[Ill.u.s.tration: Fig. 68.--_Acineta tuberosa_.]

Genus TRICHOPHRYA Clap. & Lach. '58.

(See Kent '81; Entz '84; Butschli '88; Sand 1901.)

Small forms to medium size; no cups or stalks. The body is spherical to elongate, usually, however, more or less irregularly lobed and changeable. The tentacles are in fascicles which are usually borne upon lobed or swollen places. The body is always more or less spread out. Contractile vacuoles variable. The macronucleus is spherical, elongate, band-formed or horseshoe-shaped. Reproduction takes place by endogenous budding, and the swarm spores are flat or lenticular with a distinct ciliary girdle. They are frequently parasitic. Fresh and salt water.

Trichophrya salparum Entz '84. Fig. 69.

Butschli '88; Schewiakoff '93; _Trichophrya ascidiarum_ Lachmann '59; Rene Sand 1901.

The body is somewhat cup-form, with a large, flat base. The anterior border is rounded, each of the ends being somewhat truncate and carrying a bundle of tentacles all capitate and similar. These may be continued internally as far as the nucleus (Sand). The cytoplasm is uncolored, but may contain some brilliant granules. The nucleus is granular, and spherical, band or horseshoe formed.

[Ill.u.s.tration: Fig. 69.--_Trichophrya salparum_.]

This species was found by Dr. G. Hunter on the branchial bars of the Ascidian _Molgula manhattensis_, where great numbers of them are often parasitic.