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.
[Illustration: Fig. 45.--_Condylostoma patens_.]