| Key to families of Heterotrichida. | |||
| Cilia cover the body | 1 | ||
| Cilia reduced to certain localized areas | 2 | ||
| 1. | Polytrichina. | ||
| a. | The mouth terminates a long peristomial furrow having an adoral zone along the entire left edge | Family [Plagiotomidæ] | |
| b. | Peristomial area a broad triangular area ending in mouth | Family [Bursaridæ] | |
| c. | 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 membranes | Family [Stentoridæ] | |
| 2. | Oligotrichina. | ||
| a. | Peristome without cilia; cilia limited to one or more girdles about body | Family Halteriidæ | |
| One marine genus | *[Strombidium] | ||
| b. | Thecate forms; the body is attached by a stalk to the cup; within the adoral zone is a ring of cilia. | Family [Tintinnidæ] | |
| c. | The peristomial depression is deep and funnel-like; cuticle thick, with posterior spine-like processes. | Family Ophryoscolecidæ | |
| * 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 extremity | Genus Metopus |
| 2. | No torsion in the peristome; undulating membrane is confined to the posterior part of peristome | Genus Blepharisma |
| 3. | No peristomial torsion; body highly contractile; no undulating membrane | Genus Spirostomum |
| 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 tapers to nearly a point in front; the peristome is narrowest at the apex; the mouth is the entire peristome base. | Genus Balantidium |
| 2. | 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. | ||
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 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 patens Müller. Fig. 45.