1. _Gymnostomina_.

a. Mouth terminal or subterminal. Family _Enchelinidae_ Food is swallowed and not introduced by currents

b. Mouth terminal or subterminal; Family _Trachelinidae_ body frequently drawn out into long process; mouth may have specialized framework.

c. Mouth central or posterior; Family _Chlamydodontidae_ pharynx with supporting framework

2. _Trichostomina_.

a. Mouth anterior or central; Family _Chiliferidae_ pharynx short or absent; peristomial depression faint or absent

b. Mouth central; pharynx long, Family _Urocentridae_ tubular; cilia in two broad zones

c. Mouth posterior; form Family _Microthoracidae_ asymmetrical; cilia dispersed or limited to oral region

d. Mouth anterior or central. _Paramoecidae_ Peristomial depression (One genus, _Paramoecium_) clearly marked.

e. Mouth at end of long peristome Family _Pleuronemidae_ running along ventral side; body dorso-ventrally or laterally compressed; left edge of peristome with great, sail- like undulating membrane

f. Mouth and pharynx distinct, Family _Isotrichidae_ posterior; cilia uniform.

Parasites in ruminants.

g. Mouth absent; body vermiform, Family _Opalinidae_ cilia uniform. Usually parasites.

KEY TO MARINE GENERA OF ENCHELINIDae

Diagnostic characters: Form ellipsoid or ovoid; the mouth is invariably terminal and is usually round--more rarely slit-formed; it is closed except when food is taken. An oesophagus when present is a short, invariably non-ciliated tube which is usually surrounded by a more or less clearly defined buccal armature. The a.n.u.s is usually terminal. Large food particles are swallowed, never introduced by currents.

1. Body naked 3

2. Body inclosed in a sh.e.l.l or coat 7

3. a. Cilia uniform about the entire 4 body; body symmetrical

b. Cilia in the mouth region 5 longer than the others; body symmetrical

c. Bristles, or tentacles, in 6 addition to cilia

4. Mouth terminal; body ellipsoidal Genus _Holophrya_ to ovoid

5. a. Mouth terminal; body elongate, Genus _Chaenia_ flexible, and elastic

b. Mouth terminal; "neck" highly Genus *_Lacrymaria_ elastic; entire body flexible; conical "head"

c. Mouth terminal; "neck" highly Genus *_Trachelocerca_ elastic; entire body flexible; "head" square

d. Mouth terminal; "neck" highly Genus _Lagynus_ elastic; no separate mouth-bearing portion

6. a. Body asymmetrical; bristles Genus _Stephanopogon_ in addition to cilia

b. Body symmetrical; 4 small Genus *_Mesodinium_ tentacles from mouth; cilia and cirri in girdles

7. Sh.e.l.l composed of small Genus *_Tiarina_ sculptured pieces; cilia long, uniform

* Presence at Woods Hole indicated by asterisk.

Genus LACRYMARIA Ehr. '30.

(Ehrenberg, C. G., 1838; Perty '52; Claparede & Lachmann '58; Stein 59-83; Quennerstedt '66, '67; Fromentel '74; Kent '81; Gruber '84; Gourret & Roeser '86; Butschli '88; Schewiakoff '89.)

Body short to very long flask-shape; for the most part contractile, especially in the neck region. The posterior end is rounded or pointed. The main character is the mouth-bearing apex, which "sets like a cork in the neck of the flask." One or more circles of long cilia at the base of the mouth portion or upon it. The body is spirally striped. Contractile vacuole terminal, with sometimes one or two further forward. Macronucleus central, globular to elongate, sometimes double. Food mainly bacteria. Fresh and salt water.

Lacrymaria lagenula Clap. & Lach. Fig. 28, a, b.

Synonym: _L. tenuicula_ Fromentel '74.

Body more or less flask-shape, two or three times as long as broad, with conical apex, which is slightly elastic and protrusible; surface obliquely striate, with well-defined lines, 14 to 16 in number; cilia uniform on the body, with a crown of longer ones at the base of the conical proboscis. The body cilia are not thickly placed except around the proboscis. The endoplasm is thickly packed with large granules (food particles) in the anterior half and with finely granular particles in the posterior half. The elongate macronucleus lies a little above the center among the larger granules; the contractile vacuole is double, one on each side of the median line and at the posterior end of the body among the finer granules. The a.n.u.s is posterior. Length 90 to 160; greatest width a.s.sumed 65.

When fully expanded the posterior end a.s.sumes a curious polyhedral form. (Fig. 28 b.)

This form differs slightly from others of the same species as described by different observers, the most striking difference being the presence of two contractile vacuoles in place of the usual one.

These are very slow to fill and grow to a large size before diastole.

The membrane is very tough and retains its form easily under pressure of the cover gla.s.s. Another characteristic feature is the flattening of the surfaces between the striae. Decaying algae.

[Ill.u.s.tration: Fig. 28.--_Lacrymaria lagenula_.]

Lacrymaria coronata Cl. & Lach. '58. Fig. 29.

Synonyms: _L. lagenula_ Cohn '66; Mobius '88; _L. cohnii_ ? Kent '81; _L. versatilis_ Quen. '67.

Form flask-like and similar to _L. lagenula_, contractile but tough.

The contractile vacuole is terminal, the proboscis is short, slightly raised and separated from the body by a deep cleft; the buccal cilia are inserted part way up on the proboscis. Form changeable, from short, sac-like to elongate and vermiform. Length 85.

This species is not very different from _L. lagenula_, but I noted that in addition to the elongate nucleus, the body striae are much more apparent here and seem to sink into the cuticle, giving the periphery, especially at the collar region, a curious crenulated effect. The endoplasm is very densely granular and colored a blue-green, probably from food particles. The number of striae is much larger than in the preceding species. The membrane is very tough and retains the shape of the body, even with the full pressure of the cover gla.s.s. Micronucleus and trichocysts were not observed.

[Ill.u.s.tration: Fig. 29.--_Lacrymaria coronata_.]

Genus TRACHELOCERCA (Ehr. '83) Cohn '66.

(Quennerstedt '67; Gruber '87; Entz '84; Kent '81; Gourret & Roeser '88; Butschli '88; Schewiakoff '89; Shevyakov '96.)

The only well-known representative is very elongate, large (up to 3 mm. Van Beneden), and very contractile. The main feature of importance in distinguishing it is the 4-part structure of the mouth region, which, however, may not be obvious. Pharynx faint and smooth.

Contractile vacuole terminal. Macronucleus in one central body or in numerous pieces scattered throughout the cell. Salt water.