Physiology of Trichodina pediculus. 409 
organ, and is more or less elevated above the annular peristome 
whereas in the Trichodina before us the peristome (d, d', d’, d*, d®) 
is not a closed circle, but is blended with the spiral margin of 
the disk (ce, cl, c?, ct); or rather the disk, instead of projecting 
beyond the rest of the body, is sunken (c, c!)—invaginated, as 
it were—and has a deep cyathiform contour, and its margin 1s 
only separated from the peristome (fig. 15, d!) by the slight 
furrow (0?) in which the cilia (6) of the vibratory crown are im- 
planted. This relationship is strikingly exemplified in another 
way ; for when the animal is contracted (fig. 10) and the peri- 
stome (d', d?) rolled inwardly, the vibratile row of cilia (b) 1s not 
to be found at the bottom of the enclosed space, as is the case 
when the like phenomena occurs in Vorticella, Zodthamnium, 
Carchesium, and Epistylis, but hangs down into that space, 
like a fringed curtain, from the inrolled edge of the peristome. 
The distinction between disk and peristome is therefore no more 
marked than in Stentor; and, in consequence of the relation of 
the two, the peristome, instead of traversing the-ventral side 
and forming a complete ring as in the true Vorticellide, de- 
scends, with the vibratile organ, to the mouth of the vestibule, 
and then vanishes in the general surface of the body. 
The vibratile cilia (6) of this organ are very long and slender 
thread-like bodies, which stand in close rank, in a single row. 
They arise from the bottom of a slight furrow (fig. 15, 5°) 
which extends along the inner side of the peristome (d'), from 
its beginning (d') on the right, throughout its first turn (d’), 
and thence to its termination (d) at the left margin of the aper- 
ture of the vestibule. They usually incline in the direction 
which leads toward the mouth and along the margin of the 
disk (2. e., throughout the extent of the first turn of the spiral), 
and they at the same time spread outwardly as if m continua- 
tion of the curve of the cup; but occasionally they incline to- 
ward the centre of the depressed disk, and produce a vortex 
therein by their combined action. 
The esophageal cilia—The vibratile cilia which line the ceso- 
phagus (0, o') and seem to be continuous with those of the 
vibratory crown (b) which enter the vestibule, are much more 
delicate and shorter than they; and although they perform an 
analogous duty in the preparation of the food before it is finally 
taken into the general cavity of the body, yet, inasmuch as they 
are occupied in the more special office of moulding the intus- 
suscepted matter into nutritive pellets, they in all probability 
are to be looked upon as belonging to a separate system from 
those of the vibratory organ. 
The so-called bristle of the vestibule of Vorticellide, which 
was first described as such by Lachmann (Mull. Archiv, 1856, 
