g. 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
45 mu, width 20 mu. 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; Buetschli '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 striae. 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