386 KARM NARAYAN BAHL 
The ventral vessel is the chief distributing channel and, so 
to speak, the arterial trunk of the body. All observers are 
agreed that blood flows backwards in this vessel in the region 
of the body behind the ‘ hearts ’, and that the blood is distri- 
buted to the body-wall and the other organs lying in the body- 
cavity (nephridia (septal and integumentary), nerve-cord, 
prostates, &c.) by means of the pair of ventro-tegumentaries 
in each segment, and to the gut by means of a single unpaired 
ventro-intestinal. Every structure in the body region in fact 
gets its supply from the ventral vessel. 
The subneural vessel collects blood from the ventral part 
of the body-wall and the nerve-cord by means of a pair of small 
branches it receives in each segment. All this blood goes into 
the commissural vessels, from which part of it goes to the 
intestine through the septo-intestinal and the rest to the dorsal 
all along the commissural, the latter receiving the greater 
part of its blood-supply from the capillaries that enter into it 
from the body-wall and the nephridia all along its length. 
The flow in the subneural is therefore from in front backwards. 
This can be easily seen by pinching or cutting the vessel in 
a narcotized worm and watching the direction of blood-flow. 
It should be noted that the intestine has a double supply— 
one from the ventral through the single ventro-intestinal, 
and the other from the subneural through a pair of septo- 
intestinals in each segment; this is what we should expect 
considering the large amount of blood in the extensive network 
of capillaries on the gut-wall, In Lumbricus the only 
source of blood for the gut is the ventral vessel; but there 
the gut receives two or more ventro-intestinal branches in 
each segment, while in Pheretima, there being only 
one unpaired ventro-intestinal vessel in each segment, the 
amount of blood supplied to the gut from the ventral vessel 
is comparatively small, and I suppose it is to supplement this 
that we have blood brought to the gut by the septo-intestinals. 
Both the ventro-intestinals and septo-intestinals bring blood 
to the external intestinal plexus from which the blood passes 
into the internal intestinal plexus. From the internal plexus 
