Chapter 3

The body is somewhat triangular and bears three horns, two of which are shorter than the other one and slightly curved upward.

Length, including the horns, 290µ.

Ceratium fusus Ehr. Fig. 26.

Synonym: _Peridinium fusus_ Ehr.

The animal is very elongate, due to the presence of two long horns at the extremities of the body. Color, yellow with chromatophores. Length 285µ; width 23µ.

Both of these species are common in the tow and in the algæ at the edge of the wharf. Both of them are mentioned by Peck in '93 and '95.

Genus AMPHIDINIUM Clap. & Lach.

The body is ovoid to globular and usually much flattened dorso-ventrally. The anterior portion is very much reduced and is somewhat head-like or cap-like. The longitudinal furrow extends through the entire posterior body length and is apparently capable of widening and narrowing. It is probably naked (see here Klebs, Pouchet, Bütschli), although Stein maintained that there is a delicate cuticle-like shell. Chromatophores of brown or green colors present and usually grouped radially about a central amylum granule. The nucleus is posterior.

Fresh and salt water.

Amphidinium operculatum Clap. & Lach. Fig. 27.

The body is oval and flattened. The transverse furrow is at the extremity (posterior) of the body and the small portion, which is thus apparently cut off, is the cap-like or operculum-like structure which gives the name to the species. Klebs maintains that the two furrows are not connected, but in this he is certainly mistaken, provided we have the same species under consideration. Very common about Woods Hole.

Length from 40 to 50µ; width 30µ; thickness 15µ.

KEY TO INFUSORIA.

1. With cilia Subclass _Ciliata_. 3

2. Without cilia (in adult state) Subclass _Suctoria_ tentacles

3. a. Without a specialized fringe of Order _Holotrichida_ large cilia (ad. zone)

b. With general covering of cilia Order _Heterotrichida_ + adoral zone

c. With cilia on ventral side Order _Hypotrichida_ + adoral zone

d. With cilia in region of adoral Order _Peritrichida_ zone, and about mouth only

KEY TO FAMILIES OF THE HOLOTRICHIDA.

A. Mouth closed except during food 1 ingestion; no undulating membrane

Mouth always open; with undulating 2 membrane

1. _Gymnostomina_.

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

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

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

2. _Trichostomina_.

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

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

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

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

e. Mouth at end of long peristome Family _Pleuronemidæ_ 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 _Isotrichidæ_ posterior; cilia uniform. Parasites in ruminants.

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

KEY TO MARINE GENERA OF ENCHELINIDÆ

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 anus is usually terminal. Large food particles are swallowed, never introduced by currents.

1. Body naked 3

2. Body inclosed in a shell 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 _Chænia_ 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. Shell 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; Claparède & Lachmann '58; Stein 59-83; Quennerstedt '66, '67; Fromentel '74; Kent '81; Gruber '84; Gourret & Roeser '86; Bütschli '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 anus is posterior. Length 90µ to 160µ; greatest width assumed 65µ. When fully expanded the posterior end assumes 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 glass. Another characteristic feature is the flattening of the surfaces between the striæ. Decaying algæ.

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

Synonyms: _L. lagenula_ Cohn '66; Möbius '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 85µ.

This species is not very different from _L. lagenula_, but I noted that in addition to the elongate nucleus, the body striæ 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 striæ 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 glass. Micronucleus and trichocysts were not observed.

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

(Quennerstedt '67; Gruber '87; Entz '84; Kent '81; Gourret & Roeser '88; Bütschli '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.

Trachelocerca phoenicopterus Cohn '66. Fig. 30.

Synonyms: _T. sagitta_ Ehr. '40, Stein '59; _T. tenuicollis_ Quennerstedt '67, Kent '81; _T. minor_ Gruber '87, Shevyakov '96.

The body is extremely elongate and ribbon-like, and this, combined with its wonderful power of extension and retraction, makes it one of the most curious and interesting of microscopic forms. The anterior end is square or cylindrical; the type species has a four-sided mouth, but many specimens may be found which have a plain cylindrical mouth region. One reason for this may be the fact that the extremity gets broken off. In one instance I noticed a very large form with the anterior end under some debris, which evidently held it tight, for the body of the ciliate was thrashing back and forth and twisting itself into knots, etc., like a nematode worm. Finally, the anterior end broke off with about one-tenth of the body; the remainder, in an hour, had regenerated a new anterior end with long cilia, but with no indication of four sides. The small anterior piece was also very lively, moving about and eating like the normal animal; its history, however; was not followed. This species appears to be variable in other ways as well; thus, in some cases the posterior end is rounded (cf. Entz '84); in others it is pointed (cf. Kent '81, Cohn '66, et al.).

Again, the macronucleus may be a single round body (Entz '84, Bütschli '88) or in two parts (Kent '81), or in many parts scattered about the body (Gruber). In the Woods Hole forms the tail is distinctly pointed and turned back sharply, forming an angle at the extremity. The cilia on this angular part are distinctly longer than the rest. The function of this posterior part is apparently to anchor the animal while it darts here and there upon the tail as a pivot, contracting and expanding the while. The body is finely striated with longitudinal markings; when contracted there are no transverse markings nor annulations. The nucleus is in the form of many fragments scattered throughout. Length of large specimen 1.7 mm.

Genus MESODINIUM Stein '62.

(Maupas '82, '84; Entz '84; Shevyakov '96.)

The main part of the body is globular or conical, with a short, platform-like oral region, and a deep annular groove about the middle of the body. The oesophagus is rather long, and smooth or longitudinally striped. One or more rings of cirri rise in the groove. If more than one ring of cirri are present, the anterior set usually point forward and lie close to the anterior part of the body. The posterior set, on the other hand, cling close to the posterior region of the body and give to it a peculiar encapsuled appearance. The most characteristic feature is the presence of four short tentacle-like processes which can be protracted and retracted from the oral region. (Mereschowsky says that the entire anterior half is more or less contractile.) The macronucleus is horseshoe-shaped or ovoid and is situated in the posterior half of the body. The contractile vacuole is also posterior.

Movement consists in rapid swimming, with rotation on its axis, or in creeping by means of its anterior cirri, or in sudden jumping, by which it apparently clears a distance of 20 times its diameter in one bound. Mouth parts may also be used for attachment to foreign bodies. The moving periods alternate with quiescent periods, during which the organisms with their outstretched and radiating cirri resemble the heliozoön _Actinophrys_.

Mesodinium cinctum, n. sp. Fig. 31.

Body spherical to pyriform, constricted near the middle, the constriction dividing the body into dissimilar parts. The anterior part is broadly pyriform, somewhat plastic and hyaline, with an oral extremity which is sometimes hollow, sometimes evaginated and convex. Upon this flexible anterior part there are four short but distensible tentacles. The posterior part is granular and usually filled with food particles; it is well rounded and holds the nucleus and contractile vacuole. The entire body is surrounded by a fine cuticle. The nucleus is elongate and extends through the greater part of the posterior half. The contractile vacuole lies on one side, near the girdle. The mouth is on the anterior pole in the tentacle region. The motile organs are cirri and cilia, all inserted in the constriction. There are two sets of cirri and one of cilia; the latter stand out radially from the girdle and are usually in motion. The cirri of one set, the anterior, extend forward about twice the length of the anterior half; those of the posterior set closely engirdle the lower half, reaching not quite to the posterior extremity. These are somewhat hyaline and are closely approximated, giving the impression of a tight-fitting crenulate casing about the lower half. The cirri are sharply pointed, much broader at the base, and the two sets are so placed that, looked at from above, they have the appearance of a twisted cord. (Fig. 31 b.) Movement erratic; sometimes the animal swims steadily forward with mouth in front; again it shoots across the field of the microscope, either backward or forward or sideways, through the action of its powerful cirri. It is often quiet, usually mouth downward, and is held in place by adhesion of the tentacles. In this position it looks strikingly like a heliozoön.

Length 35µ; greatest width 30µ. Not uncommon.

The chief features by which this species is distinguished from the frequently described _M. pulex_ of Europe are the number of anterior cirri and the ring of true cilia in place of the central girdle of cirri. The European form is described with four anterior bristles; the present form has from 28 to 32. The radial cilia differ decidedly from the more powerful cirri and they are not in one plane, so that counting is difficult; they are not closely set. The presence of tentacles makes these forms of especial theoretical interest, especially in the light of the origin of _Suctoria_.

Genus TIARINA R. S. Bergh '79.

(Claparède & Lachmann '58.)

Body subcylindrical, pointed posteriorly, two and one-half times as long as broad; encased in covering composed of separate pieces arranged in five girdles. The pieces bear processes which rest against neighboring pieces of the girdle. Mouth large, anus terminal near contractile vacuole. The macronucleus is simple and round. Salt water.

Tiarina fusus (Cl. & Lach.) emend R. S. Bergh.

Synonyms: _Coleps fusus_ Cl. & Lach. '58; Daday '86; Möbius '88, Lauterborn '94; Shevyakov '86.

This form, which resembles _Coleps_ rather closely, was placed as a separate genus by R. S. Bergh. The skeletal parts consist of five zones of needles composed of an organized substance and embedded in the cortical plasm, the last zone coming to a point at the posterior end. The needles have lateral processes, which give a latticed appearance to the casing. The cilia are long, with a specialized crown of still longer ones at the oral end; they arise outside of the skeletal elements and do not pass between them, as in _Coleps_.

KEY TO MARINE GENERA OF TRACHELINIDÆ.

Diagnostic characters: Body bilateral, or asymmetrical by local prolongations; usually compressed or flattened laterally, the left side more convex than the right. The essential feature is the position and character of the mouth. This is either a long slit extending from the anterior end well down the ventral surface, or the posterior part only of a ventral furrow remains open as a round or elongate mouth some distance from the anterior end. The entire mouth region of the body is usually drawn out into an elongate tapering proboscis which is generally curved dorsally at the extremity. An oesophagus is short or absent altogether; when present it is supported by a stiff buccal armature. Cilia are uniform about entire body or limited to the flat right side. Food is swallowed.

1. a. Proboscis easily distinguished 2 from the main body

b. Proboscis not marked off from Genus *_Loxophyllum_ main body; body flat; both surfaces striated

2. a. Mouth runs the entire length Genus _Amphileptus_ of proboscis; entire body uniformly ciliated

b. Mouth runs the entire length Genus *_Lionotus_ of proboscis; body flat; right side only is ciliated

c. Proboscis much drawn out, Genus _Dileptus_ flexible; mouth at its base

* Presence at Woods Hole indicated by asterisk.

Genus LOXOPHYLLUM Dujardin '41.

(Duj. '41; Wrzesniowski '69; Quennerstedt '65; '67; Cohn '66; Entz '84; Gourret & Roeser '88; Bütschli '88; Shevyakov '96.)

The body is flat and somewhat leaf-shape, flexible, and elastic. The anterior end is somewhat proboscis-like and flexible, but is not sharply demarcated as in _Lionotus_. The central portion of the body is developed into a more or less arched dorsal mass, which usually contains the nuclei and contractile vacuoles. As a result of this local thickening, the body is surrounded by a thin hyaline margin. This, however, may be absent on the right side in some species. The mouth reaches from the anterior extremity to a short distance from the end, and usually approaches the left edge. An anus is present near the posterior end of the dorsal swelling. Trichocysts are numerous on the ventral surface, and often on the dorsal surface, where they are inclosed in minute papilla-like swellings. Cilia-distribution controverted. Maupas and Bütschli hold that ventral surface alone is ciliated; others (Kent and Dujardin) that cilia are uniformly distributed. The entire body, dorsal and ventral surfaces alike, are uniformly striated. The contractile vacuole lies posteriorly, on the right side and in the dorsal swelling. In the fresh-water form _L. meleagris_, it is connected with a long canal whose swellings are frequently taken for additional contractile vesicles (Bütschli); in the marine form described below the canal is not developed and a series of vacuoles takes its place; these are all contractile. The macronucleus may be single, double, quadruple, band-formed, or rosette-formed. Movement is steadily progressive and peculiarly gliding. Fresh and salt water.

Loxophyllum setigerum Quenn. '67.

Synonyms: _Litosolenus armatus_ Stokes '93; _Litosolenus verrucosa_ Stokes '93.

The body is flattened, irregular in outline, obtusely pointed anteriorly, the point being turned to the right; rounded posteriorly. The left edge is nearly straight, the right considerably arched with a few setæ on the posterior half. Contractile vacuoles are numerous, dorsal in position and on the right side. The macronueleus is beaded, the several spheres connected.

Variety armatum (Cl. & Lach.) Fig. 32.

Under the name _Litosolenus armatus_, Stokes described a form from brackish water near New York, which should unquestionably be referred to the genus _Loxophyllum_, and I believe to Quennerstedt's species _setigerum_. While the latter possesses only a few setæ, the former has a number of them, and Stokes described his species as having a variable number. For this reason I include the Woods Hole form under the tentative name _armatum_, as a variety of Quennerstedt's _L. setigerum_. The flat margins are distinctly striated longitudinally, and faintly marked radially, on the dorsal surface. Longitudinal elevated striæ also run the length of the dorsal hump and upon the entire ventral surface. The ventral surface is alone ciliated. Upon the edges of the flat border are sharp-pointed, colorless, spine-like processes, situated at equal distances around the entire periphery except at the anterior end. Each spine is thick at the base and tapers to a full point which is curved upward--_i. e._, dorsally (fig. 32, a, b). The entire body is plastic and contractile, turning its leaf-like edge readily over objects upon which it creeps. The cilia are fine and uniform, with a tendency to lengthen in the oral region.

Length 100µ; greatest width assumed on contraction 85µ; when normal about 50µ.

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.