STRUCTURE OF UROCH^ITA AND DICHOGASTER. 269 
say, they form a more or less independent nephridium opening 
internally in Megascolides and Perichueta armata by a 
single funnel. 
In Deinodrilus, Acanthodrilus, and Dicliogaster, 
the general nephridial network is made up of tubules, the 
lumen of which is greater than in Perichseta; the diameter 
of the cells is not greater, but the lumen occupies a greater 
proportion of the cell. These tubules resemble in fact very 
closely the finer portion of the nephridium of Lumbricus. 
In Deinodrilus (at any rate in those segments of the body 
which I have investigated — some of the more posterior ones) 
the nephridial network appears to be entirely made up of 
tubules of this kind. In the other two genera, however, 
part of the nephridial network is composed of tubules of a 
much greater calibre, equal in size to the larger tubules of P. 
armata, or of such Earthworms (e. g. Allurus, Pontodrilus, 
Eudrilus, Acanthodrilus no vse-zeal audite) as possess 
but a single pair of nepliridia in each segment of the body. 
In Acanthodrilus multiporus the larger tubules are 
not independent of the smaller tubules, and the network opens 
into the ccelom by numerous funnels, as in Perichseta asper- 
gillum. In Dicliogaster, in the anterior segments, this 
specialisation of the network is not seen; in the posterior 
segments, on the other hand, there is not much beyond the 
coil of large nephridial tubules, which have to a great extent 
the characters of a single nephridium, such as that of Lum- 
bricus, &c., and open into the coelom by a single funnel borne 
at the end of a duct which traverses the intersegmental septum. 
We have therefore a parallel series in the nepliridia of 
these two groups which may be expressed in the following 
Table : 
