Genus LIONOTUS Wrzesniowski '70.

(Incorrectly called Litonotus by many. Entz '84; Gruber '84;
Bütschli '88; Kent '81; Schewiakoff '89; Shevyakov '96.)

The body is elongate and somewhat lance-shaped, widest at the central part and tapering to a point at the anterior end. The posterior end may be similarly tapered or rounded. The anterior end frequently proboscis-like, flat, and flexible, while the entire body is more or less elastic and contractile. The right side is flattened and alone provided with cilia, while the left side of the body proper is arched; on the left side of the proboscis is a row of coarse cilia resembling an adoral zone, and a row of trichocysts. A long peristome stretches down the thin, ventral side of the proboscis, and the mouth proper is situated at the junction of the proboscis and body; the mouth, as a rule, is invisible. The ciliated right side alone is striated in the majority of species. The contractile vacuole may be single or multiple, usually in the posterior region of the body and dorsal in position. The macronucleus is usually double, rarely single or quadruple, but may occasionally break into numerous smaller pieces. Movement, free-swimming or gliding, with especial tendency to get under clumps of foreign matter.

Fresh and salt water.

Lionotus fasciola Ehr. Fig. 33.

Synonyms. Amphileptus fasciola Ehr. '38; Dujardin '41; Lachmann '56; Cohn '66, Diesing '65.
Loxophyllum fasciola Claparède & Lachmann '58; Balbiani '61.
Loxophyllum duplostriatum Maupas '83. Shevyakov '96.

Body frequently brown or brilliant yellow in color, somewhat sigmoid in form with tapering anterior end, the extremity of which is turned dorsally. The proboscis is about half the entire length and is not sharply marked from the rest of the body but tapers gradually, its base being equal to the diameter of the body at its middle point. The body is slightly contractile and the posterior end is carried to a rounded point, but not into a distinct tail. Unlike the fresh-water variety, this one has no hyaline margin nor hyaline caudal region, and the contractile vacuole is double or multiple on the dorsal side near the posterior end. Cilia are present only on the under (right) side, with, however, a row of large cilia marking the course of the elongate mouth, upon its left side. The right side is striated, the left arched and without markings. The endoplasm is finely granular with, however, larger food particles in the process of digestion, while specimens are occasionally seen with the natural form completely lost through distortion caused by over-large captures (Cf. also Wrzesniowski '70, p. XXIII, fig. 32). Movement continuous, slow, and gliding; very little tendency to jerking movements. Macronucleus double, both parts spherical, and placed in about the center of the larger part of the body; closely approximated but not, as Schewiakoff described, connected. In conjugation, a large form unites with a smaller one, the mouth parts being connected. Details of conjugation and macronuclei not made out. Length 200µ to 600µ.


Fig. 33.—Lionotus fasciola. [ ENLARGE ]

Key to marine genera of Chlamydodontidæ.
Diagnostic characters: Form usually ellipsoid, never very elongate. Transverse section of body circular or elliptical. The mouth is usually some distance from the anterior end and may be in the posterior part. Sometimes it is in the center of the ventral surface, again on the right side. The œsophagus invariably has a well-developed buccal armature, or a smooth peculiarly built œsophageal tube. Food particles of large size.
1. Body cylindrical. Cilia about entire body Genus *[Nassula]
Body flat 2
2. a. Without a caudal process 3
b. With a caudal process 5
3. a. Anterior end angular 4
b. Anterior end rounded Genus Chlamydodon
4. a. Dorsal striæ and cilia present, ventral cilia longer Genus Orthodon
b. Dorsal striæ and cilia absent; posterior end not pointed Genus *[Chilodon]
c. Dorsal striæ and cilia absent; posterior end pointed Genus Scaphidiodon
5. a. Caudal spine with posterior bristle-like cilia 6
b. Caudal spine without posterior bristle-like cilia; ventral cilia reduced Genus Trochilia
6. a. With pigment spot on anterior angle Genus Ægyria
b. Without such pigment spot Genus Onychodactylus
c. Cilia on right edge only of greatly reduced ventral surface Genus *[Dysteria]
* Presence at Woods Hole indicated by asterisk.