460 FRANK E. BEDDARD. 
dense mass of small nucleated cells, enveloped in a thin fibrous 
sheath ; sometimes the centre of the acinus was hollow and 
contained a blood-clot (fig. 9a) ; most of the acini (? all) were 
connected with two blood-vessels, generally, but not always, 
empty of blood. The walls of these are tolerably thick, and 
there is a continuous lining of cells, which gives them a certain 
resemblance to ducts. These blood-vessels form a series of 
branching tubes, the acini being simply dilatations, in which 
the lining epithelium has undergone so vigorous a growth as 
almost to obliterate the cavity. 
In Pericheta aspergillum (probably also in P. Houl- 
leti, though my material is not sufficiently well preserved to 
allow me to speak with certainty) these acini are closely 
packed together (fig. 8) and surrounded with a sheath of 
chloragogen cells; these cells also form a branching network, 
variable in the amount of its development between the indi- 
vidual vessels and the large dilatation. A compact organ, or 
rather a series of organs, is thus formed, which consists of a 
capillary network, with numerous large dilatations and a coat- 
ing of modified peritoneal cells. These organs show a meta- 
meric arrangement, which is perhaps rather more conspicuous 
in P. Houlleti than in P. aspergillum. 
The occurrence of identical organs in Acanthodrilus is 
interesting, as it tends to strengthen the evidence of near re- 
lationship between these two genera. It is very possible, how- 
ever, that they will be found to occur elsewhere. 
Tt is well known that in the nephridia of Lumbricus the 
capillaries are here and there dilated, the dilatation being filled 
with free nuclei. These structures are comparable to those 
which have been just described in the anterior segments of Peri- 
cheeta, but they are scattered here and there among the coils 
of the nephridium, and are not compacted into large masses, as 
in the “ blood-glands.” The dilatation occurring on the capil- 
laries of the nephridia are also of smaller size than those which 
make up the “ blood-glands,”’ though in the latter small dila- 
tations, just like those of the nephridia, are also found. 
The fact that these dilatations are always crowded with 
