286 WILLIAM BLAXLAND BENHAM. 
to determine, so that whether the blood enters it, or leaves it by 
the branches mentioned, is uncertain; but it seems probable, 
from the consideration of the arrangement of these branches, 
and the supply of the neighbouring organs by the dorsal trunk, 
that it receives blood from the septa and from the alimentary 
tract, carrying some of it forwards to the pharynx. 
(d) The Typhlosolar Trunk.—This is an ill-defined vessel, 
as seen in sections, lying in the typhlosole, and commencing 
in somite x11 (7). It communicates, frequently, in each 
somite with the dorsal trunk, and receives a branch from the 
wall of the intestine (¢.2n¢.) in each somite, near the posterior 
septum. ‘This intestinal vessel receives anterior and posterior 
branches, which help to form the capillary network on the wall 
of the intestine, contributed to also by similar fore-and-aft 
branches from the intestinal vessel of the dorsal trunk. 
These intestinal vessels of the typhlosolar trunk are veins, 
pouring blood into the typhlosole, whence it passes into the 
dorsal trunk by small vertical vessels. 
The Course of the Blood (figs. 17, 19, 20).—Perrier 
has described minutely the course of the blood in Urocheta 
(28), and probably the main points are the same for most 
Earthworms, but in Microcheta the absence of a subneural 
trunk causes some variation. As is well known, the blood 
in the dorsal trunk passes from behind forwards, as it also 
does in the typhlosolar trunk. 
The blood is directed out of the dorsal trunk, through the 
intestinal branches, by means of the valves placed at the exits of 
these. In the posterior region the following is what appears 
to be the course: by the intestinal vessels the blood is carried 
to the network on the wall of the intestine; from this net- 
work the blood passes by means of other intestinal vessels into 
the typhlosolar trunk and thence forwards. 
In this region, also, the blood is passing backwards in the 
very contractile ventral trunk, from which it passes by the 
septal branches to the septa, nephridia, and body wall; from 
the various networks on these structures the blood is col- 
lected by branches, which, in each somite, enter the dorsal 
