160 THE MICROSCOPICAL NEWS. 
which appears to have been overlooked by previous observers. In 
the specimens which presented it most favourably for examination 
it was composed of two knife-like blades working laterally, and 
coming in contact with each other by their points only. Outside 
the wall of the sac, the blades pass into handles in the form of the 
letter S. The blades, of which there are sometimes three on 
each side, appear to me to correspond with the mallei of the mas- 
tax of the rotifera, the handle being comparable with the manubria. 
The short cesophagus is somewhat dilated about the middle of its 
length, Fig. 43 @s, and passes into the intestine, ze, which divid- 
ing into two branches immediately in front of the uterus, u/s, 
passes along its sides, just beneath the dorsal surface, and termi- 
nates ccecally, the ends of the two branches being applied to each 
other, cze, and resting on the ovary. ‘The intestine is composed 
of two layers, the outer one being thin and structureless, the 
inner being much thicker, and consisting of ill-defined and granu- 
lar cells. On either side of the pharyngeal sac a group of cells, 
very variable in number and size, are situated, Fig. 43 wg. These 
are the so-called unicellular glands. Each cell possesses a nucleus 
and nucleolus, and from each a filamentous duct passes to the 
cephalic lobe of the same side, where it becomes much dilated, fd. 
The ducts are irregular in thickness, and are bound together in a 
spherical bundle. Wagener states that these glands secrete a yel- 
lowish oily fluid, which may sometimes be seen exuding from the 
ducts which open upon the cephalic lobes. ‘Two much smaller 
groups of cells may often be seen on either side; one, containing 
three or four cells being situated close to the anterior border of 
the pharyngeal sac, Fig. 47 a, the other occurring at the base of the 
cephalic lobe, and containing from six to nine cells, 0. 
In contact with the unicellular glands, on either side of the 
cesophagus, there is a spherical contractile sac, containing a clear 
fluid, Fig. 43 wus. In some specimens only one sac is to be 
seen, while others possess more than two, all of which may be 
situated on the same side of the body. The two sacs always con- 
tract at the same moment, frequently when the animal is moving 
actively, less often when it is at rest. Contraction is accompanied 
and apparently aided by a spasmodic contraction of the surround- 
ing tissues, and results in complete obliteration of the cavity of 
the sacs. Ina few seconds they become fully dilated again, and 
remain in this condition from one to three minutes. 
Up to the present time I have not succeeded in tracing any 
connection between these sacs and any other structures, but they 
probably form part of a system of vessels described by Wagener, 
consisting of four principal trunks lying in pairs on either side of the 
body, near the ventral surface, and a number of minor branches, 
some of which are ciliated. These vessels contain a clear fluid. 
