Physiology of Trichodina pediculus. 423 
Fig. 10. A dorsal view of an individual whose peristome (d’, d?) is inrolled, 
and with it the vibratory crown (4), which hangs down into the 
enclosed space about the partially raised boss-like bottom (c) of 
the disk. The contractile vesicle (cv) is in partial diastole. The 
nucleus (7) lies next the back. The principal feature in this 
figure is the adherent apparatus (i, h, 0, l'), which is copied whilst 
in the act of embracing a highly convex surface, and has 
therefore an inverted saucer-shaped contour. The radii (7) are in 
the extreme distance; the hooks (4) project in the opposite direc- 
tion; the striated membrane shows its breadth in the profile (7), 
and exhibits its milled edge (/') and the coarser striz where it 
projects toward the observer. The velum (f) is at its fullest 
expansion, and allows its thickened margin (f1) to be seen very 
distinctly where it overlies the gaps between the groups of 
vibrating cilia (g). The cilia of the basal vibratory crown are 
represented as they appear sometimes when moving in groups or 
successive waves, and when they most resemble a torn, undulating 
membrane. 6.9 diam. 
Fig. 11. A bird’s-eye viev of the left side and of the anterior end of the 
body, partially exposing the depressed face (c*) of the cupuliform 
disk. The vibratory crown (4) is displayed throughout its length, 
from its beginning (6') on the right side, over its spiral sweep by 
the ventral and dorsal sides, and thence to its downward coil into 
the mouth (m) of the vestibule. The peristome follows the same 
course as the vibratory crown, and appears as a distinct rim (d%, 
d®) just outside the base of the cilia, until, after descending along 
the edge (d*) of the inclined plane (c*), it vanishes on the left of 
the mouth (m). The false vestibular lash (e) or lumen of the 
vibrating tips of the cilia. The velum (f, f), shown very clearly 
in the profile (f), projecting like a tongue, and undulating m- 
dependently of the vibratory cilia (g). The circle (h) of hooks 
and the striated membrane are drawn but just distinct enough to 
show their position. The mouth (m) of the vestibule appears as 
an oval aperture, lying between the first (d°) and second (d*) coils 
of the peristome. The cesophagus (0) is very much expanded at 
its bottom by a fully formed nutritive pellet, just at the moment 
when the latter is about to be passed into the digestive cavity. 
The nucleus (n, n') lies fully in view, with its left end (n) nearest 
the observer, and its right half in the distance beyond the con- 
tractile vesicle (cv). 650 diam. 
PLATE IX. 
Fig. 12. A bird’s-eye view of the ventral side and front of a slightly re- 
tracted individual, exposing the dorsal flank (c?) of the eupuliform 
disk. The anus (qa) appears as a distinct opening (when the feces 
are making their exit) at the right side of the vestibule, whose 
interior is here partially exposed in the full-face view of the 
gaping mouth (m). The descent of the vibratory crown along 
the edge (d*) of the inclined plane (ct) is its most noteworthy 
feature in this view. Its beginning (6!) on the right side of the 
front is also clearly brought out. The dorsal flank (c%) of the 
cup-shaped disk presents an unobstructed view, but its bottom (¢) 
is seen in profile through the side of the body. Its extension in 
the form of the inclined plane (c*) has already been noticed. 
The contractile vesicle (cv) is represented in partial systole, a 
very marked feature when contrasted with its hemidiastole 
