of Tetrastemma graecense, Béhmig. 325 
network of canals, as well as into the finer one in the cephalic 
region, there open numerous fine straight canalicules, upon 
which lie the terminal organs, which are easily recognizable 
owing to the active movements of their cilia-flames. Infor- 
mation as to the finer structure of the excretory organs is 
afforded by microscopical sections. In these may be observed 
on each side, chiefly towards the dorsal surface and laterally 
to the intestine, a ramifying cord of cells of varying size, 
from which, however, isolated branches also pass over to the 
ventral side. There is no communication at any point 
between the two lateral cords of cells, although they some- 
times approach so closely as almost to come into contact. 
For the sake of clearness it appears to me to be advan- 
tageous from a descriptive point of view to distinguish three 
sections in the excretory organs—namely, the end-canalicules, 
upon which lie the terminal organs, the connecting canals, 
and the main canals. 
The first-mentioned lie for the most part close beneath the 
dermo-muscular tube, and further on in immediate proximity 
to the wall of the intestine ; their transverse diameter amounts 
to about 3to5y. Their wall consists of flat cells, which 
take but a slight stain, and the respective limits of which can 
only be made out with difficulty. The cell-plasma is homo- 
geneous in character or else finely granular, not infrequently 
of greater density on the outer and inner surfaces, a fact to 
which the somewhat greater stainability of these cells is 
probably also to be ascribed. I never observed cilia or more 
strongly developed single flagella in the case of these cells. 
The connecting canals which join the end-canalicules are 
distinguished from the latter not only by greater thickness, 
but also by the fact that the cells forming their boundaries 
possess a cylindrical shape and a more strongly granular, not 
infrequently finely vacuolate, protoplasm, which is capable of 
taking a more intense stain. ‘These cells appear always to 
bear cilia, though I have succeeded in recognizing the delicate 
fringe of cilia only in certain preparations. 
Lastly, if we examine sections through the main portion of 
the organ, we observe, in the first place, a complex of cells 
which is traversed by canals in all directions. Closer study, 
however, shows us that even here each canal has its own 
cellular wall, but that the cells of the different canals often 
lie extracrdinarily close together, and that there are tracts 
where the limits of the cells are not recognizable. These 
cells vary considerably in size, but they are always larger 
than those of the connecting portions. Their plasma is 
granular and very frequently interspersed with a large number 
of vacuoles; they, too, in life probably possess a clothing of 
