360 KARM NARAYAN BAHL 
well developed. The internal plexus is a dense network of 
capillaries appearing as a sort of blood-sinus interrupted at 
places by the foldings of the gut epithelium (fig. 2). The 
typhlosolar vessel, which should be regarded as part of the 
internal plexus, communicates with it at two places in each 
segment. The external blood-plexus, which is not continuous 
from segment to segment, has capillaries of varying diameters. 
The blood apparently passes from the external to the internal 
plexus, as, like the case in Megascolex (1), we can see the 
capillaries of the external network communicating with the 
capillaries of the internal network at numerous places in 
sections. 
In the first region we have only a well-developed internal 
plexus but no external one. Neither is there a typhlosole, 
although, of the specially large mid-dorsal and mid-ventral 
capillaries, the mid-dorsal one simulates the typhlosolar 
vessel. 
(1) Alimentary plexus in the first region (fourteenth to 
twenty-sixth segment). 
In this region of the gut the internal blood-plexus is best 
developed. The network is very dense, almost a blood-sinus 
interrupted at certain places; the interspaces in the dorsal 
half of the plexus are very small indeed, even less than one- 
fourth the size of the vessels which surround them. ‘The 
capillaries run parallel to one another transversely to the 
length of the gut, and towards the ventral half break up into 
capillaries of smaller calibre, so that in the ventral half of the 
gut a continuous blood-sinus gives place to a coarse network 
of capillaries. In a freshly-opened worm this region of the 
out presents a very bloody appearance. 
Besides the richness in capillaries of this region we have 
a pair of well-marked vessels lying on the dorso-lateral aspect. 
These begin ventrally in the intestinal plexus about the four- 
teenth segment, and incline gradually dorsalwards up to the 
twenty-sixth segment, where they join the posterior pair of 
dorso-intestinal vessels of that segment at the mner angles of 
the roots of the intestinal coeca, and also communicate at that 
