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