Genus LEMBUS Cohn '66.

(Cohn '66; Quennerstedt '69; Kent '81; Fabre-Domergue '85;Gourret & Roeser '88; Bütschli '88; Shevyakov '96.)

Free-swimming animals of elongate form, more or less elastic, and flexible, bending readily to avoid obstacles, etc. The anterior half is usually drawn out into a slightly curved neck-like portion. The peristome is a small groove leading from the anterior end to the mouth about midway down the ventral side of the body. Bütschli, following Quennerstedt, describes an undulating membrane on each side of the peristome groove. Other observers, however, usually describe but one, the left, which is clearly defined and stretches out some distance from the body, while the right border is described as having smaller but very active cilia. The general body surface is clothed with fine, uniform cilia, and body striæ are usually absent. One or more caudal bristles may be present. The contractile vacuole is posterior and terminal, and may be multiple. The macronucleus is spherical and perhaps double (Kent). Food is chiefly bacteria, and the animals are frequently found with the anterior end embedded in zooglœa masses. Salt water, usually in infusions.

Lembus infusionum, n. sp. Fig. 42.

The body is elongate, lancet-shaped, with a tapering anterior extremity. The dorsal outline is concave through the bending of the anterior end, while the ventral outline presents an even, convex curve. The mouth lies slightly above the center of the body and marks the posterior limit of the ventral peristomial groove, which curves slightly from the anterior extremity. Each side of this groove bears an undulating membrane, the left being much larger and conspicuously striated. The general form of this left membrane is triangular, the widest part is anterior, the narrowest at the mouth. The right membrane is similar in form, but smaller and more active. The endoplasm is colorless and finely granular, not regionally differentiated. The ectoplasm consists of a relatively thick cortical plasm specially noticeable in the posterior half of the body and a delicate cuticle which bears almost imperceptible longitudinal markings—the insertion points of the fine cilia. The body is covered with uniform cilia except at the anterior extremity. Here they are much larger and bristle-like. I was unable to find any cilia in the peristome. One long caudal bristle, one-quarter of the length of the body, trails out behind. The macronucleus is spheroidal and placed near the center of the body; a conspicuous micronucleus lies near it. A row of contractile vacuoles extends from the posterior end. I have seen as many as six of nearly equal size and one or two smaller ones. The intervals of contraction are quite long. Length 70 to 75µ; greatest diameter 10 to 12µ.

Lembus infusionumFig. 42.—Lembus infusionum.ENLARGE

L. infusionumresemblesL. elongatusin its general form and in its mode of life, for it excavates a retreat in zooglœa masses and lies there for considerable periods perfectly quiet. It differs fromL. elongatusand fromL. velifer(probably the same asL. elongatusof Claparède & Lachmann) in the presence of the caudal bristle, in the absence of annular markings, number of contractile vacuoles, and in the slightly smaller size. It resemblesLembus verminus(Müller) as described by Kent (Proboscella vermina), andL. intermediusas described by Gourret & Roeser (Lembus verminussyn.)in the absence of annular markings and in the presence of a caudal bristle. It differs from the former, however, in the absence of a tentacle-like process, and from both in the absence of a double nucleus and in the presence of many vacuoles. These features are so characteristic of all the specimens examined that I have concluded, somewhat reluctantly, to give it a specific name. It is common in old infusions of algæ, especially after decomposition is well advanced. Its food consists of bacteria.

Lembus pusillusQuennerstedt 1869. Fig. 43.

Synonym:L. subulatusKent 81.

This species is much smaller than the preceding, and might easily be mistaken forUronema marina. It is subcylindrical in form, the anterior end bluntly pointed, the posterior end rounded. The oral apparatus is quite different fromUronema. The mouth, as in the preceding species, is at the end of a long peristomial groove extending from the anterior end to the middle of the body. The edges of the peristome bear undulating membranes as inL. infusionum. Like the latter, there is one caudal bristle, but unlike it there is only one posterior contractile vacuole, while the endoplasm is filled with large granules or food balls. The cuticle is distinctly striated with longitudinal markings, and the cilia are uniform in length.

Habitat similar to that ofL. infusionum, in zooglœa masses. Length 26 to 30µ; diameter 7 to 8µ.

Lembus pusillusFig. 43.—Lembus pusillus.ENLARGE

Although Quennerstedt's description ofL. pusillusmakes no mention of a caudal bristle, the size and other characters are so closely similar that I hesitate to make a new species. The bristle is extremely delicate, scarcely thicker than a cilium, and easily overlooked, yet with proper focussing of the condenser I found it on every specimen examined.

Key to marine genera of Opalinidæ.Diagnostic characters:The form is oval, and the body may be short or drawn out to resemble a worm. They are characterized mainly by the absence of mouth and pharynx.Anterior end not pointed; body cylindrical; taperingGenus *AnoplophryaAnterior end pointed; body elongate; cylindrical; taperingGenusOpalinopsis* Presence at Woods Hole indicated by asterisk.

(Stein '60; Claparède '60; Leidy '77; Vejdovsky '79;Kent '81; Balbiani '85; Bütschli '88; Shevyakov '96.)

The general form is elongate, cylindrical or slightly flattened, with rounded ends, the posterior end tapering. The body is striated with clearly defined, often depressed lines, which run longitudinally and sometimes spirally. The contractile vacuoles are usually placed in rows upon the edges. The macronucleus is almost always long and band-formed, rarely oval, and generally extending through the entire length of the body. Micronuclei have been made out in one case. Reproduction is effected by simple cross division or by budding at the posterior end, and is frequently combined with chain formation. The main characteristic is the entire absence of mouth and œsophagus, the animals being parasitic in the digestive tract of various annelids. Parasites, salt-water forms.

Anoplophrya branchiarum. Stein '52. Fig. 44.

A. circulansBalbiani.

The body is cylindrical to pyriform, in the latter case broadened anteriorly. Cuticle distinctly marked by longitudinal striations which take the form of depressions and give to the body a characteristic melon shape. The endoplasm contains a number of large refringent granules—probably body products. The nucleus is elongate, somewhat curved, and coarsely granular. A micronucleus lies in the concavity. The cilia are long, inserted rather widely apart along the longitudinal markings. The contractile vacuole is single and is located at the pointed end, which is directed backwards during locomotion. One specimen found free swimming among some algæ.

Length 104µ; greatest diameter 36µ.

Anoplophrya branchiarumFig. 44.—Anoplophrya branchiarum.ENLARGE

I was much surprised to find this form swimming about freely in the water; its mouthless condition showed it to belong to the family of parasites, theOpalinidæ. As the name indicates, however, this species is an ectoparasite upon the gills, and Stein gave the namebranchiarumto a fresh-water form parasitic uponGammarus pulex. The Woods Hole form is so strikingly similar to the figure ofG. branchiarumthat, although the name was given to a fresh-water form, it obviously applies to this marine variety. One important difference is the presence of only one contractile vacuole in the marine form.

Key to families of Heterotrichida.Cilia cover the body1Cilia reduced to certain localized areas21.Polytrichina.a.The mouth terminates a long peristomial furrow having an adoral zone along the entire left edgeFamilyPlagiotomidæb.Peristomial area a broad triangular area ending in mouthFamilyBursaridæc.Peristomial depression short; limited to the anterior end; its plane at right angles to the long axis of body; surface of peristome striated and ciliated; no undulating membranesFamilyStentoridæ2.Oligotrichina.a.Peristome without cilia; cilia limited to one or more girdles about bodyFamilyHalteriidæOne marine genus*Strombidiumb.Thecate forms; the body is attached by a stalk to the cup; within the adoral zone is a ring of cilia.FamilyTintinnidæc.The peristomial depression is deep and funnel-like; cuticle thick, with posterior spine-like processes.FamilyOphryoscolecidæ* Presence at Woods Hole indicated by asterisk.Key to the marine genera of Plagiotomidæ.Diagnostic characters:The peristome is a narrow furrow which begins, as a rule, close to the anterior end and runs backward along the ventral side, to the mouth, which is usually placed between the middle of the body and the posterior end. A well-developed adoral zone stretches along the left side of the peristome, and is usually straight.1.Body cylindrical; size medium; peristome long and turns sharply to the left at the extremityGenusMetopus2.No torsion in the peristome; undulating membrane is confined to the posterior part of peristomeGenusBlepharisma3.No peristomial torsion; body highly contractile; no undulating membraneGenusSpirostomumKey to the marine genera of Bursaridæ.Diagnostic characters:The body is usually short and pocket-like, but may be elongate. The chief characteristic is the peristome, which is not a furrow, but a broad triangular area deeply insunk and ending in a point at the mouth. The adoral zone is usually confined to the left peristome edge, or it may cross over to the right anterior edge.1.The anterior half of the body tapers to nearly a point in front; the peristome is narrowest at the apex; the mouth is the entire peristome base.GenusBalantidium2.The anterior end does not taper; the peristome is widest at the end of the body; the mouth is clearly defined.Genus *Condylostoma* Presence at Woods Hole indicated by asterisk.

(Dujardin '41; Claparède & Lachmann '58; Stein '59, '67; Cohn '66; Quennerstedt '67;Wrzesniowski '70; Bütschli '76, '88; Kent '81; Maupas '83; Shevyakov '96.)

Colorless and more or less flexible animals of medium size. The general form is elongate and cylindrical or somewhat smaller anteriorly. The posterior end is broadly rounded, the anterior end somewhat truncate and oblique. The peristome is broad and triangular, the base of the triangle being the entire anterior end of the body. The entire length of the peristome is one-fourth or less of the body length. The mouth is large and placed at the apex of the peristomial triangle and opens into a comparatively small œsophagus. The right edge of the peristome is lamellate and bears a clearly defined undulating membrane. The adoral zone is well developed upon the left edge of the peristome, from which it passes around anteriorly to the right edge. The surface of the peristome is free from cilia, but the rest of the body is uniformly coated with small active cilia. Contractile vacuoles are not safely determined. Bütschli thinks there is probably one terminal vacuole, but some observers deny this (e.g.Maupas). Others describe them on the dorsal side of the posterior end (Quennerstedt). The macronucleus is long and beaded and placed upon the right side. Micronuclei are numerous and scattered along the macronucleus. The anus is terminal and dorsal. Food consists of large and small particles. Movement rapid, free swimming, alternating with resting periods; in some cases an undulating or wriggling movement is seen, showing clearly the flexibility of the body. Fresh and salt water.

Condylostoma patensMüller. Fig. 45.

The body is elongate, somewhat sac-like, five or six times as long as broad, plastic, and frequently contains brightly colored food granules. The triangular peristome takes up the greater part of the anterior end, and the mouth is situated at the sharper angle of the triangle, about one-fourth of the total length from the anterior end. The cuticle is longitudinally striated, the lines having a slightly spiral course. They are not closely set, and fine cilia are thickly inserted along their edges. The endoplasm is granular and viscous. The motile organs consist of an adoral zone of membranelles, which stretch along the left edge of the peristome and the front edge of the body. The right edge of the peristome supports an undulating membrane. The nucleus is moniliform and extends the full length of the left side; a number of micronuclei are distributed along its course (Maupas).

Length 400µ; diameter at widest part 105µ. Maupas gives the length from 305µ to 495µ; and Stein 376µ to 564µ. Very common.

For a more extended account of the structures, see the excellent description by Maupas '83.

Condylostoma patensFig. 45.—Condylostoma patens.ENLARGE

Key to the marine genera of Stentoridæ.Diagnostic characters:The peristome is relatively short and limited to the front end of the animal, so that its plane is nearly at right angles to that of the longitudinal axis of the body. The adoral zone of cilia either passes entirely around the peristome edge or ends at the right-hand edge. The surface of the peristome is spirally striated and provided with cilia. Undulating membranes are absent.1.Peristome circular in outline; limited to the anterior endGenusStentor2.The peristome is drawn out into two wing-like processes; tube-dwellingGenusFolliculina

(Stein '67; Bütschli '73; Fromentel '74; Kent '81;Gruber '84; Entz '84; Maupas '83. Bütschli '88.)

Small, colorless (except for ingested food) animals with characteristic springing movements. The form is usually constant, but in some cases may be plastic likeAstasia; it is usually globular or conical, the posterior end being more or less pointed, the anterior end broadest. The latter is surrounded by a complete circle of the adoral zone, the oral end of which passes into a peristomial depression which extends deep into the middle of the body. The mouth, with a very small œsophagus, lies at the bottom of the inturned peristome. The region surrounded by the adoral zone is frequently drawn out into an anterior process, occasionally bearing a pigment mass. The ventral surface in some cases bears cilia, which may be distributed or restricted to a row of large cilia. Trichocysts are usually present and may be widely spread, limited to the posterior region, or arranged in a girdle about the middle. The contractile vacuole is simple, and posterior in position. The macronucleus is spherical and usually central in position. Movement is rapid swimming, combined with resting and floating periods, the latter usually terminated by a sudden leap.

Fresh and salt water; more common in the latter.

Strombidium caudatumFromentel '74. Fig. 46, a, b, c.

Fromentel described a fresh-water form of this genus with a caudal appendage. The body is pyriform, broadly truncate on the anterior end, in the middle of which rises a papilliform process (Schnabel). On this process is a heap of pigment granules, which, however, are not constant. A ring of long cirri surround the anterior end and pass into the peristome, and from the left edge of this line of cirri a large adoral zone continues down to the mouth. The peristome is elongate and sac-form, and the mouth lies at the posterior extremity. With the exception of a caudal filament there are no other motile organs; this is about half as long as the body, structureless, hyaline, and sharply pointed. It splits up into a bundle of fine fibers upon treatment with caustic potash (c). The cirri emerge from minute hollows in the edge of the anterior border. The cortical plasm contains peculiar rod-like bodies, which look more like lines or markings than like rods or trichocysts. The nucleus is large, spherical, and placed in the center of the body. The contractile vacuole is posterior.

Length without appendage is about 35µ; greatest diameter 15 to 18µ. In decaying vegetable matter. Common.

Strombidium caudatumFig. 46.—Strombidium caudatum.ENLARGE

Although Fromentel's species is incompletely described, it is very evident that the organism corresponds fairly well with the Woods Hole variety. His was a fresh-water type; this is marine, but the caudal filament and the contractile vacuole are similar. Certainly in this case the organism can not be regarded as a Vorticella broken off its stalk, as Kent '81 suspected. The anterior process with its pigment spot; the cirri, the spherical nucleus, the position of the vacuole, etc., are all opposed to such an interpretation which Kent applied to the original species. Neither can it be a Tintinnoid. I place it provisionally asS. caudatum.

Key to the marine genera of Tintinnidæ.Diagnostic characters:Body attached by a stalk to a cup. Inside the zone of membranelles is a ring of cilia (par-oral).1.The test is gelatinous and more or less covered by foreign particlesGenusTintinnidium2.The test is chitinous and clear. No foreign particles.GenusTintinnus3.The test is chitinous; covered by foreign particles, growth rings frequentGenus *Tintinnopsis4.The test is chitinous, often covered by foreign particles. The test is marked by discoid, circular, or hexagonal spots.GenusCodonella5.The test is perforated by pores of circular or hexagonal form.GenusDictyocysta* Presence at Woods Hole indicated by asterisk.

(Stein '67; Kent '81; Daday '87; Bütschli '88.)

Medium-sized ciliates, inclosed in a chitinous lorica with embedded sand crystals. The form of the house, or lorica, varies greatly. In some cases the mouth opening is wide, giving the lorica a bell form; it may be long and tubular, short and spherical, or variously indented. The animal is attached, as in the closely allied genusTintinnus, by a peduncle to the bottom of the lorica. The anterior end of the animal is inclosed by two complete circles of cilia; one, the outer, forming the adoral zone, is composed of thick tentacle-like membranelles, the other consists of shorter cilia within the adoral zone. The mouth leads into a curved œsophagus containing rows of downward-directed cilia (Daday). The entire body is covered with cilia, but as the lorica is always opaque these can be made out only when the animal is induced to leave the house. The only difference between this genus andTintinnusis the covering of foreign bodies—usually sand crystals. Movement is rapid and restless, and peculiarly vibratory, owing to the apparent awkwardness in moving the house. Salt water.

Tintinnopsis beroideaStein, var. plagiostoma Daday. Fig. 47.

Tintinnopsis beroideaFig. 47.—Tintinnopsis beroidea.ENLARGE

Synonym:Codonella beroideaEntz '84.

The shell is colorless, thimble-shaped, with a broadly rounded posterior end. The body is cylindrical. The internal organs were not observed. Membranelles 24 in number. Length 50µ; greatest diameter 40µ.

Var. compressa Daday '87.

The posterior end of the shell is pointed, the lower third of the shell is swollen, the upper third is uniform in diameter and without oral inflation or depression. Nucleus not seen.

Length 70µ; greatest diameter 48µ.

Tintinnopsis davidoffiDaday. Fig. 48.

The shell is large, elongated, and provided with a considerable spine. The chitin of the shell is covered with silicious particles of diverse size. The internal structures were not observed.

Length of shell and spine 230µ; diameter of the oral aperture 54µ.

Tintinnopsis davidoffiFig. 48.—Tintinnopsis davidoffi.ENLARGE

The variations of these species are considerable, and as the internal structures, such as the nucleus, are essential in fixing their systematic position, I place them as above, provisionally, and until further observations can be made.

Key to families of Hypotrichida.a.Peristome indistinct; cilia on ventral surface uniform and not differentiated into cirriFamilyPeritromidæOne genus, *Peritromusb.Peristome more or less indistinct; cilia reduced to a few rows on the ventral surface; anal and frontal cirri presentFamilyOxytrichidæc.Cilia entirely reduced; frontal and anal cirri present or reduced; macronucleus band-formed or sphericalFamilyEuplotidæd.Peristome reduced to left edge and does not reach over the anterior marginFamilyAspidiscidæOne genus, *Aspidisca* Presence at Woods Hole indicated by asterisk.

(Stein '62, '67; Maupas '83.)

The body is flat, colorless or tinged with yellow, and contractile. It is elliptical in outline, with broadly rounded ends; in some cases the left edge is slightly incurved, the right edge convex. The ventral surface is flat, the dorsal surface is arched in the middle region of the body. The edges being flat are somewhat more transparent than the remainder of the body. The ventral surface is striated by longitudinal straight or slightly curved lines, the dorsal surface is smooth and without cilia. (Maupas describes bristles on the back, but this is not corroborated.) The adoral zone is fairly well developed, but not distinctly marked off from the remaining ventral surface. It begins on the right side and extends entirely around the frontal margin and down the left side below the middle of the body, where it turns suddenly to the right, entering the slightly insunk peristome. The mouth leads into a short, indistinct œsophagus. One contractile vacuole is situated in the dorsal swelling at the posterior end of the animal. Macronucleus double, one in each side of the dorsal swelling. Movement is slow and creeping, with a peculiar method of contracting the more hyaline edge, which may turn upward or around a foreign object.

Fresh (?) and salt water.

Peritromus emmæStein. Fig. 49.

With the characters of the genus.

Peritromus emmae, ventral and lateral aspects.Fig. 49.—Peritromus emmæ,ventral and lateral aspects.ENLARGE

Key to the marine genera of Oxytrichidæ.Diagnostic characters:The peristome is not always marked off from the frontal area. In the most primitive forms the cilia on the ventral surface are similar to those of the preceding family (Peritromidæ). Usually some of the anterior and some of the posterior cilia are fused into cirri, distinguished as the frontal and anal cirri, respectively. In the majority of forms all of the cilia are thus differentiated; strong marginal cirri are formed in perfect rows, and ventral cirri in imperfect rows. In addition to the adoral zone there is an undulating membrane on the right side of the peristome, and in some cases a row of cilia between the membrane and the adoral zone. These are the par-oral cilia and they form the par-oral zone.1.The posterior end is pointed or tail-like2The posterior end is rounded; not tail-like52.The front end is pointed3The front end is rounded43.Frontal and anal cirri absent; often tube-formingGenusStichotrichaEight frontal and 3 caudal cirri; not tubiculousGenusGonostomum4.Anal cirri present; with or without short lateral bristlesGenus *EpiclintesAnal cirri absent; no bristlesGenusUroleptus5.With frontal cirri6No frontal cirri; 2 to 3 rows of ventral cirri; anal cirri smallGenusHolosticha6.Right margin of peristome straight as far as the anterior end; 5 rows ventral cirri; 5 anal cirriGenusOxytrichaRight margin of peristome curved77.Five rows or less of ventral cirri8More than 5 rows of ventral cirriGenusUrostyla8.Membranelles normal; 5-10 anal cirri; no caudal cirriGenus *AmphisiaMembranelles normal; 5 to 10 anal cirri; 3 caudal cirriGenusStylonychiaMembranelles very large and powerful; adoral zone not continued to mouth; 5 anal cirriGenusActinotricha* Presence at Woods Hole indicated by asterisk.

(Stein '62, '64, '67; Mereschowsky '79; Gruber '87; Bütschli '88.)

Very active, contractile, colorless forms of rather small size. In the fully expanded condition the body is oval and long, with its greatest width in the center or at the front half of the body. The posterior end is always drawn out into a relatively long tail, which is extremely elastic. The peristome is short and stretches around the front end of the animal. In the frontal region are from one to three rows of cirri. The ventral surface is covered with longitudinal rows of cilia, the number of rows being in dispute (6 to 7 according to Stein; 9 according to Mereschowsky and Rees) Some of these cilia project from the lateral edges and from the posterior end, where they are slightly elongated. The anus is dorsal and placed at the beginning of the posterior process. Macronucleus probably double. Movement is rapid and restless, the tail process contracting to jerk the body backward. Salt water.

Epiclintes radiosaFig. 50.—Epiclintes radiosa.ENLARGE

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