THE DEVELOPMENT OF THE TEMNOCEPHALEiE. 429 
and the lumen is occupied by fine filamentous matter that 
might be mistaken for cilia, this occurs in such an irregular 
way that I have little doubt that this appearance is due to a 
rupture or other alteration that has occuri’ed during the 
fixing process. In no case, either in Temnocephala 
no vae-zealan d iae or any other form, is there an epithelium 
with scattered nuclei, as supposed by Wacke. Tn some 
preparations the internal contour appears double, as if the 
cavity of the vesicle possessed an excessively thin cuticular 
lining, but this is always very indefinite, and in many cases 
is not to be detected. The only nuclei in the entii-e organ 
ai-e the two already referred to as the nuclei of the two 
constituent cells. 
Arising from the main excretory trunk at a little distance 
from the vesicle is a special branch of considerable size — the 
vesicular vessel as it may conveniently be termed. This 
runs inwards, and enters the wall of the vesicle on its inner 
side. Here it breaks up (PI. 2.5, fig. 19) into a number of 
branches, which ramify throughout the protoplasmic sub- 
stance of the wall of the sac in all directions. In the course 
of the system of fine intracellular capillaries which is thus 
formed occur numerous ciliary flames of small size, but in 
other respects similar to the ciliaiy flames in the flame-cells 
of other Platodes. I have counted as many as fifty of these 
ciliary flames in movement at one time in the case of 
T. no va3-zealandias, and probably many more than that 
number are actually present. 
In sections of the terminal vesicle in all the Australasian 
species the ramifications of the vesicular vessel are very 
conspicuous, pervading the protoplasmic wall in all direc- 
tions. But the ciliary flames are not to be made out with 
any certainty save in the living animal. 
In most cases the inner part of the protoplasmic wall in 
sections appears regularly divided by fine parallel vertical 
lines, and one might be tempted to suppose that these repre- 
sent a system of vertical canals forming outlets from the 
system of vesicular capillaries into the lumen of the vesicle. 
