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