214 Henry Lestıe OsBorn, 
it is neither forked nor branched. Its wall continues the lines of 
the oesophagus unbroken. It lies in the center of the animal and 
extends nearly to its posterior end. Its wall consists of two distinct 
layers, an inner epithelium and an outer muscular coat. The epi- 
thelium is composed of cells that are attached at the base only, 
and are entirely free from each other. They are very tall and 
slender, some measuring 105 « in length and 10 u across the base. 
Others are shorter and broader and have an appearance of con- 
traction, perhaps owing to the action of reagents. They are frequently 
swollen at the free end, as in Fig. 19, and are always blunt and 
never acute at the tip, as indicated by Monticerrı (1892) fig. 15, 
for Cotylogaster michaelis. They are essentially alike in all parts of 
the intestine, and not sharply pointed at the anterior end and much 
shorter posteriorly, as in Macraspis according to JAGERSKIOLD (1899). 
In life these long cells sway about with the motions of the animal; 
at times those in front run out into the oesophagus as in Fig. 18 
and at other times they point posteriorly. The cytoplasm is always 
minutely vacuolated throughout in addition to which there are large 
vacuoles most constantly one in the free end of the cell. Each cell 
has a large nucleus generally located near its base, of a diameter of 
5—7 u, presenting a distinct membrane, a large deeply staining 
nucleolus and a small amount of chromatine in scattered grains. In 
a few instances I saw nuclei manifesting indications of activity, in 
which the nuclear membrane was wanting and in place of a clear 
nucleus there was a densely stained granular mass. The muscular 
coat of the intestine does not call for special remark. It consists 
of two layers, an inner circular layer and an outer longitudinal one 
(see Fig. 20). The fibers are scanty, especially those of the longi- 
tudinal layer. 
i) The Excretory System. 
The general arrangement of the parts of the excretory system 
is shown on the right side of Fig. 5. The main parts are: — a 
median single terminal pore, two globular bladders, almost entirely 
separate from one another on each side, a collecting vessel running 
forward from the bladder to the level of the pharynx, a recurrent 
vessel running posteriorly to the level of the ventral sucker, an 
anterior and a posterior branch from the recurrent vessel, and 
capillaries running to the ultimate flame cells. All these parts are 
visible in living compressed specimens, but the flame cells are very 
