190 THE AMERICAN MONTHLY [July 
line, having a projection on the left side opposite the buc- 
‘cal cavity. The ventral side is depressed centrally and 
posteriorly, the dorsal side convex laterally and posteri- 
orly, but continuous with the neck anteriorly. The width 
of the disc varies from 33°5 micron to 57 microns in fixed 
material, and was 72 microns in the large living specimen 
cited above. | 
The oral ciliary band begins just above the pharynx on 
the left side, curves about the posterior extremity and 
right side, and passes with a twist under the upper lip of 
the mouth, where it broadens out and covers the roof of 
the pharynx into which its cilia descend. The band is 
made up of about one hundred and twenty-five transverse 
rows of fine long cilia which are usually twisted together 
in action so as to appear under low power as so many 
stout membranelle, but under Abbé homogeneous apo- 
chromatic oil immersion 1:5 mm., oc. 8, the individual] 
cilia are plainly seen in the living specimen, hundreds of 
them in each row forming a flat brush or a stout twist. 
The transverse width of these flat brushes, i. e., the width 
of the band, is least at the beginning of the band and is 
increased one-half or more in the pharynx, the average 
width outside of the mouth being 10 microns in large liv- 
ing specimens. The cilia of the several rows on the left 
side are most often seen untwisted in the living animal 
at rest ; while those on the right side, where the band 
turns toward the mouth, are often divided, one portion 
extending outward, the other curving toward or into the 
mouth. 
In sections fixed in Hermann’s or Flemming’s fluid and 
stained with Heidenhain’s iron-hamatoxylin, the oral band 
is seen to have a complicated internal structure. At the 
base of each row of cilia is a deeply stained basal band 
whose ends are connected by fine fibres with an internal, 
deeply staining fibre. A cross-section of the band pre- 
sents a triangular appearance with deeply stained basal 
