BRANCHIURA SOWERBYI BEDDARD. 297 
leave the ventral surface altogether and reach the dorsal side of the cesophagus in viil. 
The vessel is surrounded by chloragogen cells, and is situated in close contact with the 
intestinal wall, as far forwards as ix; it then separates from the alimentary tube and 
becomes free in the body-cavity. It is contractile throughout its length. 
BEDDARD (3) mentions a ventral position of the dorsal vessel as a rare peculiarity 
among the Oligochzeta, which is found in the genera Branchiwra and Dero. It isa 
curious coincidence that these two worms were found in association with the species 
under description, as related previously. 
The swpra-intestinal vessel can be traced in the living animal as well as in sections 
as far forwards as the anterior part of segment v. It is covered by chloragogen cells 
throughout its course ; in the anterior part of its extent it appears in transverse sections 
as a fusiform space, a special channel of the gut plexus ; it is large in segment vil; in 
segment viii it may, in the living specimen, be hardly visible (perhaps from accidental 
causes), or, on the other hand, it may be large and conspicuous ; in sections it is here 
larger than either the dorsal or the ventral vessel. 
In the anterior part of segment ix, situated transversely like a half ring on the 
dorsal side of the intestine, is a sinus-like blood-space, with the following connections 
(figs. 12, 13). Posteriorly it dissolves into a close network of small vessels in the 
intestinal wall. On the right side it is in open communication with a large vessel in 
the gut wall, which runs along the right side of the alimentary tube, gradually dying 
away, and becoming indistinguishable posteriorly at about segment xxi, while anteriorly 
it ceases as a distinct vessel in segment vill; this, again, though a perfectly distinct, and 
indeed a very conspicuous, vessel in the living animal, is covered by chloragogen 
cells, and appears in sections as a special channel of the intestinal plexus. Anteriorly 
the sinus in segment ix may in favourable cases in the living worm be seen to be 
connected with the supra-intestinal vessel, though the channel of communication 
through septum & seems as a rule to be of inconsiderable width. ‘The above (descrip- 
tion is confirmed by sections; the supra-intestinal can be traced as a well-marked 
vessel up to the septum, where all blood-channels are constricted ; on the other side 
of the septum there is no longer a supra-intestinal vessel, but a sinus encircling 
the upper half of the gut, from which, on the right side, the vessel described above 
takes origin. 
The intestinal plexus, which has already been referred to, extends throughout the 
length of the intestine, and reaches as far forwards as segment iv. For some distance 
behind the genital segments it is fed on the left side by a conspicuous series of branches, 
one in the anterior part of each segment, from the dorsal vessel ; and on the right side 
by twigs from the channel described above as running along the right side of the in- 
testine (fig. 14). 
The hearts (figs. 12, 13) are a single pair of vessels, which arise from the supra- 
intestinal anteriorly in viii, pass obliquely downwards and backwards, pierce septum $ 
and gradually converge, to unite about the middle of segment ix. When full of blood 
