Chapter 5

Body colorless, elongate, and with the general form of a cucumber, the posterior end being somewhat pointed. The mouth and relatively small peristome are situated in the lower third of the body. The peristome begins as a shallow furrow at the center of the ventral surface and dips sharply into the buccal depression, which is deep and turned toward the posterior end. The left edge of the peristome bears a high undulating membrane, which extends anteriorly only as far as the center of the body; posteriorly it passes around to the right edge of the peristome, thus forming the characteristic membranous pocket. Inside the oral depression is a second undulating membrane, running down to the mouth. This is small and without an oesophagus. The body is clothed with long setose cilia which are frequently fully outstretched when the animal is resting, a slight tremor of the large membrane alone indicating vitality. Posteriorly these appendages are drawn out into long filiform setæ, the number varying in different individuals from three to nine or ten. These are extremely fine and difficult to see without a high power (_e.g._ 1/12 oil) and careful focussing of the substage condensor. Like _P. chrysalis_, the resting periods are terminated by sudden springs, otherwise the movements are steady and forward. The macronucleus is central, and the contractile vacuole posterior and terminal. Length 45µ to 50µ; greatest diameter 17µ. In decaying algæ.

It was this form, I believe, that Peck '95 described as a "ciliate."

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 zoogloea 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.

_L. infusionum_ resembles _L. elongatus_ in its general form and in its mode of life, for it excavates a retreat in zoogloea masses and lies there for considerable periods perfectly quiet. It differs from _L. elongatus_ and from _L. velifer_ (probably the same as _L. elongatus_ of 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 resembles _Lembus verminus_ (Müller) as described by Kent (_Proboscella vermina_), and _L. intermedius_ as described by Gourret & Roeser (_Lembus verminus_ syn.)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 pusillus Quennerstedt 1869. Fig. 43.

Synonym: _L. subulatus_ Kent 81.

This species is much smaller than the preceding, and might easily be mistaken for _Uronema marina_. It is subcylindrical in form, the anterior end bluntly pointed, the posterior end rounded. The oral apparatus is quite different from _Uronema_. 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 in _L. 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 of _L. infusionum_, in zoogloea masses. Length 26 to 30µ; diameter 7 to 8µ.

Although Quennerstedt's description of _L. pusillus_ makes 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 Genus *_Anoplophrya_ cylindrical; tapering

Anterior end pointed; body elongate; Genus _Opalinopsis_ cylindrical; tapering

* Presence at Woods Hole indicated by asterisk.

Genus ANOPLOPHRYA Stein '60.

(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 oesophagus, the animals being parasitic in the digestive tract of various annelids. Parasites, salt-water forms.

Anoplophrya branchiarum. Stein '52. Fig. 44.

_A. circulans_ Balbiani.

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.

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, the _Opalinidæ_. As the name indicates, however, this species is an ectoparasite upon the gills, and Stein gave the name _branchiarum_ to a fresh-water form parasitic upon _Gammarus pulex_. The Woods Hole form is so strikingly similar to the figure of _G. branchiarum_ that, 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 body 1

Cilia reduced to certain 2 localized areas

1. _Polytrichina_.

a. The mouth terminates a long Family _Plagiotomidæ_ peristomial furrow having an adoral zone along the entire left edge

b. Peristomial area a broad Family _Bursaridæ_ triangular area ending in mouth

c. Peristomial depression short; Family _Stentoridæ_ limited to the anterior end; its plane at right angles to the long axis of body; surface of peristome striated and ciliated; no undulating membranes

2. _Oligotrichina_.

a. Peristome without cilia; cilia Family _Halteriidæ_ limited to one or more girdles about body

One marine genus *_Strombidium_

b. Thecate forms; the body is Family _Tintinnidæ_ attached by a stalk to the cup; within the adoral zone is a ring of cilia.

c. The peristomial depression is Family _Ophryoscolecidæ_ deep and funnel-like; cuticle thick, with posterior spine-like processes.

* 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; Genus _Metopus_ peristome long and turns sharply to the left at the extremity

2. No torsion in the peristome; Genus _Blepharisma_ undulating membrane is confined to the posterior part of peristome

3. No peristomial torsion; Genus _Spirostomum_ body highly contractile; no undulating membrane

KEY 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 Genus _Balantidium_ tapers to nearly a point in front; the peristome is narrowest at the apex; the mouth is the entire peristome base.

2. The anterior end does not taper; Genus *_Condylostoma_ the peristome is widest at the end of the body; the mouth is clearly defined.

* Presence at Woods Hole indicated by asterisk.

Genus CONDYLOSTOMA (KONDYLOSTOMA Bory de St. Vincent 1824) Dujardin '41

(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 oesophagus. 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 patens Müller. 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.

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; Genus _Stentor_ limited to the anterior end

2. The peristome is drawn out into two Genus _Folliculina_ wing-like processes; tube-dwelling

Genus STROMBIDIUM Cl. & Lach. '58.

(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 like _Astasia_; 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 oesophagus, 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 caudatum Fromentel '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.

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 as _S. 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 Genus _Tintinnidium_ less covered by foreign particles

2. The test is chitinous and clear. Genus _Tintinnus_ No foreign particles.

3. The test is chitinous; covered by Genus *_Tintinnopsis_ foreign particles, growth rings frequent

4. The test is chitinous, often Genus _Codonella_ covered by foreign particles. The test is marked by discoid, circular, or hexagonal spots.

5. The test is perforated by pores Genus _Dictyocysta_ of circular or hexagonal form.

* Presence at Woods Hole indicated by asterisk.

Genus TINTINNOPSIS Stein '67.

(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 genus _Tintinnus_, 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 oesophagus 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 and _Tintinnus_ is 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 beroidea Stein, var. plagiostoma Daday. Fig. 47.

Synonym: _Codonella beroidea_ Entz '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 davidoffi Daday. 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.

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 Family _Peritromidæ_ ventral surface uniform and not One genus, *_Peritromus_ differentiated into cirri

b. Peristome more or less indistinct; Family _Oxytrichidæ_ cilia reduced to a few rows on the ventral surface; anal and frontal cirri present

c. Cilia entirely reduced; frontal Family _Euplotidæ_ and anal cirri present or reduced; macronucleus band-formed or spherical

d. Peristome reduced to left edge and Family _Aspidiscidæ_ does not reach over the anterior One genus, *_Aspidisca_ margin

* Presence at Woods Hole indicated by asterisk.

Genus PERITROMUS Stein '62.

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