300 ALFRED GIBBS BOURNE. 
These vessels and their main branches are covered, as is 
frequently the case, with yellowish-brown celomic epithelium 
cells, which make them look very large and very different 
from the other branches of the dorsal vessel (dorso-tegumen- 
tary vessels) which are not covered by pigmented cells. 
The connection of these dorso-intestinal vessels with the 
intestinal capillaries has been described above. 
Ventro-intestinal Vessels.—These are branches of the 
ventral vessel running from it to the intestinal walls. There 
is one pair in every segment from Segment vi (at any rate) 
backwards, arising immediately posterior to the septum, ex- 
cept in Segments vi, viI, vii1, and 1x, where they arise imme- 
diately in front of the hearts. They are the sole afferent 
vessels of the intestinal walls. There are no such vessels in 
Megascolex ceruleus, their function is performed by the 
intestino-tegumentary vessels. 
Ventro-tegumentary Vessels.—These are branches of 
the ventral vessel connecting it with the peripheral networks. 
There is a pair of these vessels in every segment except the 
first, in which there is a branch of that belonging to the 2nd 
segment on each side, and except in those segments in which 
the ventral vessel is joined by hearts, viz. Segments vi, vil, 
vull, and rx, and in Segment x. 
In Segments vi, viz, and vii1 the place of ventro-tegumen- 
tary vessels is taken by vessels which come off from a bulbous 
dilatation, which is interposed between the heart proper and 
the ventral vessel. The limit of the heart proper is marked 
by a sphincter, and between this sphincter and the ventral 
vessel is the bulbous dilatation. 
In Segment viii, in addition to the ventro-tegumentary 
vessels belonging to that segment, there is a second pair of 
vessels arising from the bulbous dilatations which run back- 
wards through Septum vitt-1x, and form the ventro-tegumen- 
tary vessels, or rather the vessels which correspond to them, of 
Segments 1x and x, 
Ordinarily these ventro-tegumentary vessels come off from 
the ventral vessel immediately in front of the septum which 
