(Bütschli '88; Maupas '83.)
The general form is oval, slightly compressed laterally with the
dorsal side strongly arched. The ventral side is slightly incurved.
The anterior end is somewhat smaller than the posterior end, which is
broadly rounded. The mouth is placed some distance from the anterior
end in an oral depression and opens into a tubular oesophagus. There
are usually two undulating membranes which do not extend beyond the
mouth borders. The right undulating membrane extends down into the
oesophagus and appears to be attached to the walls of the latter. The
body stripes in front of the mouth are twisted to the left. The anus
is terminal and the contractile vacuole may be terminal or situated
forwards in the dorsal region. The macronucleus is spherical and
has one micronucleus attached. Food consists mainly of bacteria.
Movement rapid, but interrupted.
Fresh and salt water, common in infusions.
Colpidium colpoda Ehr., sp. Fig. 38.
Synonyms: _Colpidium cucullus_ Kent '81; _C. striatus_ Stokes '85;
_Kolpoda cucullus_ Duj. '41; _Paramoecium colpoda_ Ehr. '38,
Quennerstedt '67; _Plagyiopyla nasula_ Kent '81, G. & R. '86;
_Glaucoma pyriformis_ G. & R. '86; _Tillina campyla_ Stokes '85, '88.
The body is oval, somewhat larger posteriorly, and a little
compressed dorso-ventrally. The anterior end is twisted a little from
the right to the left (more evident in fresh-water forms), and leans
somewhat toward the ventral side. Under this portion, on the ventral
side, lies the mouth in a large depression just above the middle of
the body. The entire body is covered with uniform and delicate cilia,
which are placed in longitudinal rows. These rows are almost straight
on the dorsal side, but bend on the ventral surface, following
the contour of the twisted anterior portion. The endoplasm is
finely granular; the oesophagus leading into it is very distinct.
Schewiakoff ('89) describes two membranes, an inner and an outer;
Maupas ('83) describes them as right and left. In the present species
I was able to make out only one. The macronucleus is central,
spherical in form, and bears a single minute micronucleus. The
contractile vacuole is posterior and dorsal to the long axis of the
body. The anus is ventral to this axis and also posterior. Length
45µ, width 20µ. Common.
This marine variety is much smaller than the fresh-water form and the
form differs in a number of respects, viz, in the anterior torsion
and in the structure of the mouth. These may be, however, only
individual variations of a widely spread species, and I believe it is
perfectly safe to describe this as _Colpidium colpoda_.
[Illustration: Fig. 38.--_Colpidium colpoda_.]
Genus URONEMA Duj. '41.
(Quennerstedt '69; Cohn '66; Kent '81; Bütschli '81; Schewiakoff '89;
Shevyakov '96.)
Minute forms; colorless and constant in body form. The form is oval,
slightly compressed on the ventral side, while the dorsal side is
distinctly arched. The membrane is distinctly marked by rather widely
separated striæ. These occasionally have a spiral course about the
body; in all cases they can be easily counted. The mouth is large
and placed near the center of the ventral surface. It is sometimes
approached by a very shallow depression or peristome from the
anterior end, and marked by two rows of cilia. An undulating membrane
extends down the mouth. Oesophagus absent. A long, stiff bristle
extends outwards from the posterior end. The contractile vacuole is
terminal or subterminal and near the anal opening. The macronucleus
is spherical, centrally placed, and with one micronucleus closely
applied. Movement is rapid and usual forwards in a straight line,
often found resting, however, with outstretched cilia in contact with
some foreign body. Food mainly bacteria. Fresh and saltwater, usually
in decomposing vegetable substances.
Uronema marina Duj. Fig. 39.
Synonyms: _Enchelys triquetra_ Dujardin; _E. corrugata_ Duj.;
_Cryptochilum griseolum_ Maupas '83; _Philaster digitiformis_
Fabre-Domergue '85.
Small animals with ellipsoidal form and about twice as long as
broad. The mouth lies in the upper half of the body and bears a
well-developed undulating membrane upon its left edge. The membrane
is longitudinally striped and covered with long and vibratile cilia.
The right edge of the mouth bears cilia which are about the same in
size as the body cilia, but are more closely inserted (Schewiakoff).
The most characteristic feature is the long caudal bristle, which
is extremely delicate and about two-thirds the length of the body.
Schewiakoff thinks this bristle has a sensory function. I could not
make this out, for although other protozoa ran against this bristle,
often bending it well over to one side, the animal showed no sign
of irritability but lay quiescent. A spherical macronucleus with
attached micronucleus lies in the center of the body. The contractile
vacuole is posterior in front of the bristle. The macronucleus was
found to be double, as though just divided, in a large percentage of
cases. This may be a precocious division of the nucleus long before
signs of the body division are evident. Such a phenomenon, however,
is rare, the macronucleus usually dividing at a late stage of cell
division. Length 30 to 50µ; width 15 to 20µ. Common in decomposing
algæ.
[Illustration: FIG. 39.--_Uronema marina_.]