(Dujardin '41; Stein '67; Cienkowsky '55; Cohn '66; Clap. et Lach.
'58; Kent '81; Maupas '83; Entz '84; Fabre-Domergue '88; Bütschli
'88; Shevyakov '96.)
The body is ovoid or cylindrical, with well-rounded ends, and in
some cases slightly flattened. The mouth is ventral and placed some
distance from anterior end (1/4 to 1/3 total length). A slight
depression on the ventral surface marks the mouth region, which is
further indicated by larger and more powerful cilia. The rest of the
body is uniformly ciliated. The entire body is marked by clearly
defined spiral stripes. The mouth is circular and the oesophagus is
supported by a considerable armature, which usually extends dorsally
and to the left, rarely to the right. In some cases the structure of
this armature is indistinct; again it can be clearly seen to consist
of definite rods (Stäbchen). The anus is probably always terminal.
Contractile vacuoles are variable in different species. In some cases
there is but one, which is placed at the posterior end or centrally
on the ventral side; in others there may be four--two dorsal and
two ventral. In many cases trichocysts are uniformly distributed.
Sometimes the body is colorless; again, and more often, it is
brightly colored with red, blue, brown, or black pigment. The
macronucleus is globular and central, occasionally band-form and
with numerous attached micronuclei. Food substance varied, usually
vegetable matter, see, however, below. Cysts are globular. Movement
is a steady progression, combined with rolling.
Nassula microstoma Cohn '66. Fig. 34.
Synonyms: _Paramoecium microstomum_ Cl. et Lach. '58, Gourret et
Roeser '88; _Isotricha microstomum_ Kent '81.
Body subcylindrical, rounded at each extremity, not quite twice as
long as broad. A slight depression on one surface marks the position
of the mouth, this depression being indicated by a row of longer
cilia. The mouth is extremely small and is surrounded by a curious
buccal armature. This is not made up of bars or rods, as in most
species of _Nassula_, but appears perfectly smooth and uniform
except for the considerable swelling at the inner end. The cuticle is
firm and unyielding and marked by longitudinal and somewhat spiral
rows of cilia and trichocysts. Under the microscope this is one of
the most pleasing forms found at Woods Hole. Its color is yellowish
brown from the presence of brilliant particles of coloring matter
held in the cortical plasm, and, as it slowly rolls along, these
particles and the black trichocysts give to the organism a peculiar
sparkling effect. The macronucleus is almost central; the contractile
vacuole posterior. The endoplasm appears well filled with food
bodies, some of which could be distinguished as _Amphidinium_ and
_Glenodinium_.
Length 55µ; greatest diameter 30µ.
[Illustration: Fig. 34.--_Nassula microstoma_.]
Genus CHILODON Ehr.
(Dujardin '41; Engelmann '78; Stein '54, '58; Kent '81; Bütschli '88;
Gruber '83; Cienkowsky '55; Möbius '88; Clap. et Lach '58;
Wrzesniowksi '65; Shevyakov '96.)
Small forms, greatly flattened dorso-ventrally and almost egg-form in
outline. The anterior end is bent distinctly to the left and forms a
characteristic process, which, together with the entire margin of the
body, is soft and flexible. The posterior end is, as a rule, broadly
rounded. The ventral surface is finely striate, and this surface
alone is ciliated. The lines of cilia converge at the mouth, and at
this region the cilia are somewhat larger and more distinct, thus
forming a functional adoral zone. The mouth is median and is situated
in the anterior half of the body. It is surrounded by a well-defined
armature, composed usually of from 10 to 16 rods. The contractile
vacuoles are quite varied and from one to many in number, the
number increasing with the size of the individual. The macronucleus
is usually single, elliptical in form, and centrally placed;
one micronucleus. Reddish granular pigment and trichocysts are
occasionally present.
Chilodon cucullulus Müll., sp. Fig. 35.
Synonyms; _Colpoda cucullus_ O. F. Müller; _Loxodes cucullulus_;
_Chilodon uncinatus_ Ehr. '58, Perty '52, Dujardin '41; _L. dentatus_
Duj., etc.
This extremely variable form has received so many different names
that it hardly pays to enumerate them. It is one of the commonest
and most widely spread ciliates known, although at Woods Hole I was
surprised to see it so rarely. It is the type species of the genus
and needs no further description. The specimens observed at Woods
Hole had numerous contractile vacuoles and were 42 to 45µ long and
from 28 to 32µ wide.
[Illustration: Fig. 35.--Ventral and dorsal aspects of _Chilodon
cucullulus_.]
Genus DYSTERIA Huxley '57.
(Cl. et Lach. '58; Entz '84; Möbius '88; Shevyakov '96.)
Small forms, firm in outline, and colorless or slightly colored. The
body is somewhat clam-shaped, flattened, slightly curved or straight
on the right side, the other more convex. The true ventral side is
only a narrow strip along the right and anterior edge of the body,
the apparent ventral side being a fold of the very large dorsal
surface which comes around ventrally, forming a valved structure
somewhat analogous to a clam shell. Cilia are limited to the outer
edge of the small ventral surface, which also bears a peculiar spine
at the posterior end. Behind this spine are larger cilia. The mouth
opening lies in the anterior widened portion of the ventral surface
and is connected with a smooth tubular pharynx. The right half of the
dorsal side, _i.e._, the apparent dorsal side, is arched and bears
longitudinal ridges. Two to four contractile vacuoles are placed on
the ventral side. The macronucleus is usually dorsal, elliptical, and
cleft, with one micronucleus attached. Fresh and salt water.
Dysteria lanceolata Cl. et Lach. Fig. 36.
Synonym: _Cypridium lanceolatum_ Kent '81.
Outline of the flattened body ovoid; body consists of two valve-like
portions; the edge of the right valve is nearly straight, that of the
left valve more or less sinuous; anteriorly it is cut away, obliquely
and posteriorly it has a deep indentation in which the seizing spine
rests. The cilia are confined to the ventral surface, here reaching,
however, from the anterior dorsal extremity to below the posterior
indentation. Posteriorly the cilia become larger, corresponding to
the larger cirri of _D. armata_, which are posterior to the spine.
The mouth lies between the two valves and is surrounded by a long
and smooth buccal armature which passes downward and backward to
the left a distance equal to about half the entire body length. The
macronucleus is situated in the dorsal region in the central part of
the body. There are two contractile vacuoles, one behind the center
of the buccal armature, the other near the inner end of this organ.
Movement is in circles, the animal moving around quite rapidly when
not attached by its posterior process. It is colorless and measures
45µ in length by 27µ in width. Claparède & Lachmann and Shevyakov
describe it as 70µ long.
[Illustration: Fig. 36.--_Dysteria lanceolata_.]