STUDIES ON THE DIGENETIC TREMATODES. 465 
end of the testes. Anteriorly their width is about *2 mm. 
but further back they dilate to *5 mm. They are situated 
just below the dorsal surface of the body. The intestinal 
epithelium is exceptionally well marked. It is cubical or 
columnar in type, but the cells are all of different sizes and 
shapes, projecting to various degrees into the lumen. Towards 
the posterior end of the diverticula the cells are usually 
flatter. It is evident that these cells are capable of consider- 
able pseudopodial movement, for they contain varying amounts 
of bile which they have ingested (fig. 14, z). The extended 
cells contain a large amount of bile surrounded by a vacuole. 
As the bile becomes metabolised and absorbed the cell 
contracts and the vacuole disappears. Two neighbouring 
cells may thus present a great contrast, one being highly 
extended and packed full of bile, the other small, flat and 
without any trace of bile. From this there can hardly be 
any doubt that the cells actually engulph the intestinal 
contents. In their extended state they may reach a length 
of (04 mm. They possess small round nuclei situated basally. 
The hair-like or thread-like processes so frequently described 
in other species are entirely absent in this, and it appears as 
it the character of the epithelium and the manner of food 
absorption in this species were different from that in most 
other species. Here, however, the dark-green colour of the 
intestinal contents renders its presence within the epithelial 
cells a matter of easy observation—a fact which is by no means 
so easy to demonstrate in those species in which the intestinal 
contents are colourless or nearly so. It appears highly pro- 
bable that in many cases a certain restricted pseudopodial 
movement of the epithelial cells does really take place, but it 
is a quite as well attested fact that in many other cases no 
such movement occurs, and that the process of assimilation 
of material, partially metabolised in the lumen of the intes- 
tine, is effected by a capillary action of the hair-like processes 
of the epithelial cells. 
Excretory System.—The vesicle is of the Y-shaped type. 
The main stem is short and almost diamond-shaped, its length 
