268 
FRANK E. BEDDARD. 
appear to be at any rate largely isolated from each other and 
from the pair of large nepliridia ; and I have not found a 
longitudinal duct passing from the large nephridia of successive 
segments and connecting them. Neither can I discover evi- 
dence of any nepliridial network uniting the tufts of minute 
tubules of successive segments. In all these points the 
nephridia of P. armata are different from those of Mega- 
scolides. I shall refer again to the nephridia of P. armata 
and to Professor Spencer’s description of Megascolides (see 
below. 
Comparison of the Nephridia of Perichaeta, Mega- 
scolides, Acanthodrilus multiporus, Deinodrilus, 
Dicliogaster. 
Before attempting to draw any conclusions as to the path 
of development of the excretory system in Earthworms, it will 
be convenient to briefly review the facts already known con- 
cerning the nephridia of those genera in which there is a 
greater or less development of a network with numerous 
external pores in each segment. 
It appears to be possible to separate those genera into two 
groups: the first group contains Perichaeta and Mega- 
scolides; the second, the remaining genera enumerated above. 
I am at present uncertain as to the relations of Typliaeus, 
which has not yet been properly investigated. 
The principal character which distinguishes the nephridia of 
these two groups is the size of the tubules. 
In Perichaeta, and apparently also in Megascolides, the 
greater part of the nepliridial system (the whole of it in the 
anterior segments of the body) is made of tubules having an 
excessively fine lumen ; the entire diameter of the tubules is 
not inconsiderable, but the perforation of the cells which form 
the duct is much less than the thickness of its walls. Besides 
the network of fine tubules, both these genera possess coils of 
tubules of a much greater diameter which are more or less 
closely connected with the network of fine tubules ; that is to 
