Genus LIONOTUS Wrzesniowski '70.

(Incorrectly called _Litonotus_ by many. Entz '84; Gruber '84; Butschli '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 coa.r.s.e 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_ Claparede & 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 200 to 600.

[Ill.u.s.tration: Fig. 33.--_Lionotus fasciola_.]

KEY TO MARINE GENERA OF CHLAMYDODONTIDae.

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 oesophagus invariably has a well-developed buccal armature, or a smooth peculiarly built oesophageal tube. Food particles of large size.

1. Body cylindrical. Cilia about Genus *_Na.s.sula_ entire body

Body flat 2

2. a. Without a caudal process 3

b. With a caudal process 5

3. a. Anterior end angular 4 on left side

b. Anterior end rounded Genus _Chlamydodon_

4. a. Dorsal striae and cilia present, Genus _Orthodon_ ventral cilia longer

b. Dorsal striae and cilia absent; Genus *_Chilodon_ posterior end not pointed

c. Dorsal striae and cilia absent; Genus _Scaphidiodon_ posterior end pointed

5. a. Caudal spine with posterior 6 bristle-like cilia

b. Caudal spine without posterior Genus _Trochilia_ bristle-like cilia; ventral cilia reduced

6. a. With pigment spot on anterior Genus _aegyria_ angle

b. Without such pigment spot Genus _Onychodactylus_

c. Cilia on right edge only of Genus *_Dysteria_ greatly reduced ventral surface

* Presence at Woods Hole indicated by asterisk.

Genus Na.s.sULA Ehr. '33

(Dujardin '41; Stein '67; Cienkowsky '55; Cohn '66; Clap. et Lach.

'58; Kent '81; Maupas '83; Entz '84; Fabre-Domergue '88; Butschli '88; Shevyakov '96.)

The body is ovoid or cylindrical, with well-rounded ends, and in some cases slightly flattened. The mouth is ventral and placed some distance from anterior end (1/4 to 1/3 total length). A slight depression on the ventral surface marks the mouth region, which is further indicated by larger and more powerful cilia. The rest of the body is uniformly ciliated. The entire body is marked by clearly defined spiral stripes. The mouth is circular and the oesophagus is supported by a considerable armature, which usually extends dorsally and to the left, rarely to the right. In some cases the structure of this armature is indistinct; again it can be clearly seen to consist of definite rods (Stabchen). The a.n.u.s is probably always terminal.

Contractile vacuoles are variable in different species. In some cases there is but one, which is placed at the posterior end or centrally on the ventral side; in others there may be four--two dorsal and two ventral. In many cases trichocysts are uniformly distributed.

Sometimes the body is colorless; again, and more often, it is brightly colored with red, blue, brown, or black pigment. The macronucleus is globular and central, occasionally band-form and with numerous attached micronuclei. Food substance varied, usually vegetable matter, see, however, below. Cysts are globular. Movement is a steady progression, combined with rolling.

Na.s.sula microstoma Cohn '66. Fig. 34.

Synonyms: _Paramoecium microstomum_ Cl. et Lach. '58, Gourret et Roeser '88; _Isotricha microstomum_ Kent '81.

Body subcylindrical, rounded at each extremity, not quite twice as long as broad. A slight depression on one surface marks the position of the mouth, this depression being indicated by a row of longer cilia. The mouth is extremely small and is surrounded by a curious buccal armature. This is not made up of bars or rods, as in most species of _Na.s.sula_, but appears perfectly smooth and uniform except for the considerable swelling at the inner end. The cuticle is firm and unyielding and marked by longitudinal and somewhat spiral rows of cilia and trichocysts. Under the microscope this is one of the most pleasing forms found at Woods Hole. Its color is yellowish brown from the presence of brilliant particles of coloring matter held in the cortical plasm, and, as it slowly rolls along, these particles and the black trichocysts give to the organism a peculiar sparkling effect. The macronucleus is almost central; the contractile vacuole posterior. The endoplasm appears well filled with food bodies, some of which could be distinguished as _Amphidinium_ and _Glenodinium_.

Length 55; greatest diameter 30.

[Ill.u.s.tration: Fig. 34.--_Na.s.sula microstoma_.]

Genus CHILODON Ehr.

(Dujardin '41; Engelmann '78; Stein '54, '58; Kent '81; Butschli '88; Gruber '83; Cienkowsky '55; Mobius '88; Clap. et Lach '58; Wrzesniowksi '65; Shevyakov '96.)

Small forms, greatly flattened dorso-ventrally and almost egg-form in outline. The anterior end is bent distinctly to the left and forms a characteristic process, which, together with the entire margin of the body, is soft and flexible. The posterior end is, as a rule, broadly rounded. The ventral surface is finely striate, and this surface alone is ciliated. The lines of cilia converge at the mouth, and at this region the cilia are somewhat larger and more distinct, thus forming a functional adoral zone. The mouth is median and is situated in the anterior half of the body. It is surrounded by a well-defined armature, composed usually of from 10 to 16 rods. The contractile vacuoles are quite varied and from one to many in number, the number increasing with the size of the individual. The macronucleus is usually single, elliptical in form, and centrally placed; one micronucleus. Reddish granular pigment and trichocysts are occasionally present.

Chilodon cucullulus Mull., sp. Fig. 35.

Synonyms; _Colpoda cucullus_ O. F. Muller; _Loxodes cucullulus_; _Chilodon uncinatus_ Ehr. '58, Perty '52, Dujardin '41; _L. dentatus_ Duj., etc.

This extremely variable form has received so many different names that it hardly pays to enumerate them. It is one of the commonest and most widely spread ciliates known, although at Woods Hole I was surprised to see it so rarely. It is the type species of the genus and needs no further description. The specimens observed at Woods Hole had numerous contractile vacuoles and were 42 to 45 long and from 28 to 32 wide.

[Ill.u.s.tration: Fig. 35.--Ventral and dorsal aspects of _Chilodon cucullulus_.]

Genus DYSTERIA Huxley '57.