CIRCULATORY APPARATUS OF THE NEMERTEA. 59 
vessel in the proboscidian sheath (No. 47). Meanwhile, I saw 
all at once, on the sides of the sheath and above the ganglia 
(No. 42 and No. 46), a vessel cut transversally. There, then, 
are two branches, terminating blindly forwards (see fig. 9). 
The two vessels, after having communicated with the median 
vessel, go directly towards these little branches, coalesce, and 
go back to their former place between the brain-masses and the 
proboscidian sheath, leaving no trace of these peculiar blood- 
spaces (Nos. 49—51). The median vessel soon leaves the pro- 
boscidian sheath. It remains in the sheath only in five sections 
of +, mm. Ina younger specimen only three sections. The 
two lateral vessels remain on the inner side of the lateral 
nerves, but swing up and down, now being above and then 
beneath their level. I have twice closely examined the 800 
slices, made through the whole animal, and I have nowhere 
seen a transverse vessel. In a tail-portion, horizontally cut, 
however, they were present. The communication of the three 
longitudinal vessels in Amphiporus lactifloreus I saw 
very distinctly. It occurred again before the anal commissure, 
and above the intestine. 
With respect to the nephridial system, I may mention the 
following points. It lies, as all other organs in this species, 
free in the gelatinous stroma, in which I could nowhere observe 
nuclei. It begins in the cerebral region (slice No. 42), just 
there where I saw the foremost point of the strange branches 
of the vascular system (figs. 9 and 39). The first canal I saw 
lay so close to this branch that it will not surprise me if another 
naturalist finds there an open communication between the two 
systems. At all events, 1 have not seen it myself, though I 
believe I have seen that the tissues were here intimately 
jomed. The canals showed the well-known structure. They 
swung very irregularly round the lateral nerves, remaining 
always next tothem. I have found here again more than one 
pair of excretory ducts. These lay in the following sections. 
