72 A. C. OUDEMANS. 
Of higher development is the nephridial system of Cari- 
noma. The function of removing the waste products is here 
transferred to the canals of the system itself. Here we no 
more find a nephridial gland. The canals, however, are coated 
with an epithelium, consisting of pure glandular cells. The 
removal of the secretion outwards would seem not to happen 
periodically but permanently, as each cell is provided with a 
long cilium directed outwards, The system, though changed 
so much that it cannot possibly be confounded with the 
vascular system, in Carinoma, however, still shows its 
primitive relation to it. There are three open connections on 
each side, and the whole lower arch of the blood-vessel 
between the first and the second communication is changed 
into a tissue which closely resembles that of which the 
nephridial canal consists. Thus, we have here also a por- 
tion of the nephridium, which is, as it were, separated from 
the blood-vessel, of which the traces are still present! The 
two excretory ducts here lie also in the same transverse 
plane. 
In the Schizo-type the nephridium lies wholly in the lacunar 
spaces of the cesophageal region. In some species it extends 
still a little further into the intestinal region. The whole 
system is generally situated against the inner side of the 
inner longitudinal muscular coat. There are, however, types 
where it seems to float in the lacune (Langia). In most 
species I could not distinguish the exact arrangement. In 
Valencinia, however, the form is that of a ladder, and on the 
level of each step there is an excretory duct. Thus there are 
two longitudinal canals and numerous transverse ones. They 
are, however, all of the same size. The whole indicates a seg- 
mental arrangement. The same is found in Polia and 
Lineus. In these two genera I could not, however, trace the 
form of the system, but it seems to me that here too the canals 
are all of the same size. In Cerebratulus and Langia, 
however, a thicker longitudinal canal is distinctly seen, and 
several thinner ones. Here I could not find more than one 
single pair of excretory ducts. Thus, the lower the types the 
