CIRCULATORY APPARATUS OF THE NEMERTEA. 27 
canal becomes larger, also the cells, the nuclei in their base, 
and the cilia at their top. By-and-by it moves away from the 
vessel, descends, and finally is partly situated in the longi- 
tudinal muscular layer (fig. 33). A little further backwards a 
second canal suddenly appears on the side of the vessel, which 
soon divides into two canals, the upmost of which gradually 
goes upwards till above the level of the nerve-stems, then goes 
to the periphery, piercing the basilar membrane and the skin, 
and communicates with the exterior. The second undermost 
canal of the two coalesces further backwards with the chief 
canal beneath the blood-vessel. It is thus a branch which, 
rising from a certain branch of the nephridial canal, goes for- 
wards, then a little backwards, and communicates with the 
exterior above the nerve-trunk (see fig. 5: fig. 84 is an ideal 
transverse section cut along the dotted line in fig. 5). There 
are thus a few slices which show six cut canals, on each side 
three, then a larger number with four canals (fig. 35). This 
point of rising of the branch we see in fig. 36. Still further 
backwards the canal again lies close to the vessel, and is finally 
connected with it (figs. 5 and 37), thus forming the hindmost 
open communication with the vascular system. 
Let us now compare the nephridial system of Carinoma 
with that of Carinella. We find a striking resemblance in 
their design, but an extraordinary progress in the structure 
of that of the former. Both have in front and behind an open 
communication with the blood-vessel, both have one single 
excretory duct ou each side, which rises from the hindmost 
part of the nephridial canal, goes directly outwards in Cari- 
nella, and in Carinoma first tends forwards a little before 
communicating with the exterior. Both have the excretory 
ducts lying above the nerve-stems. In Carinella the 
nephridial canal has occasion to communicate from time to 
time with the nephridial gland, which lies in the blood-vessel ; 
in Carinoma it is connected in its whole course once with the 
blood-vessel, thus forming a third direct communication. The’ 
nephridial gland is absent in Carinoma, but we may perhaps 
suggest that its function has passed over to the cells of the 
