42 A. CO. OUDEMANS. 
downwards, coalesce beneath the proboscidian sheath, com- 
municate with the median dorsal vessel in the sheath, remain 
a moment in their places, and descend still further behind the 
lower brain commissure, to unite with the lacunz, which have 
now totally enclosed the large posterior lobes, and seem to 
come from above, whilst the circular muscular layer, which 
has always followed all the movements of the lacune, now 
closes again (figs. 45, 46, 47, 48). A little further backwards the 
posterior lobes gradually become smaller, and two short diver- 
ticula of the cesophagus, directed forwards and terminating 
blindly, now become visible (figs. 49 and 50). What in 
Valencinia I saw only once I here saw continually, even on 
the lateral nerve trunks, viz. club-shaped ganglionic masses 
projecting into the lacune. Behind the mouth the lacune 
again coalesce and embrace the cesophagus, but next to the 
proboscidian sheath two distinct uninterrupted lacunar spaces 
are always visible (fig. 51). But these latter extend beyond 
the point where the median vessel leaves the proboscidian 
sheath, whilst already the number of the lacune round the 
cesophagus diminishes, and two lacune present themselves 
constantly at the same places beneath the intestine, so that 
we have here again a figure of five longitudinal blood-spaces. I 
have not seen in Polia curta that these five longitudinal blood- 
spaces are united by transverse vessels. At first, when the 
two proboscidian sheath lacune have disappeared, and thus 
when there are only three vessels, transverse uniting vessels 
become visible, one over each diverticulum. The communica- 
cation of the three longitudinal vessels in the tail is the same 
as in Valencinia. . 
Just behind the lower brain-commissure the first longitu- 
dinal muscular fibres occur within the circular muscular coat. 
I have not seen a longitudinal fibre in the precerebral region. 
This is very anomalous. 
As to the internal coating of the lacune and vessels, it is 
the same as in Valencinia; also here the median dorsal 
vessel, when it lies in the proboscidian sheath, shows its dorsal 
side formed otherwise than its ventral arch; also here it is 
