VASCULAR SYSTEM OF PHERETIMA 363 
from the longitudinal capillaries and the typhlosolar vessel 
(which we may regard as a specialized longitudinal capillary 
lying in the mid-dorsal line), and convey it to the dorsal vessel 
by means of the two pairs of dorso-intestinals in the same 
way as the ring-vessels of the oesophagus convey its blood to 
the supra-oesophageal vessel there (vide infra). It would 
be interesting to note here that, although the typhlosole is 
absent in the segments fourteen to twenty-six, there is 
a prominent blood-vessel in the mid-dorsal line of the gut- 
epithelium, the vessel corresponding to the typhlosolar behind, 
with which it is directly continuous. 
(3) The blood-plexus in the third region (last twenty-three 
to twenty-eight segments). 
In the last twenty-three to twenty-eight segments of the 
worm where the typhlosole in the gut is absent, and which 
region Beddard (8, p. 18) has referred to as the ‘rectum’, 
the intestinal plexus is different from what we have seen in the 
first two regions. The whole of the plexus is external, i.e. lies 
outside the muscular coats, there being no internal plexus. 
The regular and rectangular arrangement of capillaries in the 
typhlosolar (second) region at once changes into a branching 
tree-like plexus as shown in fig. 3. There is only one pair of 
dorso-intestinals in this rectal region in place of two pairs 
in the first two regions. Since there is no internal plexus 
the dorso-intestinals change their connexions and communicate 
in this region with the external blood-plexus. 
The blood coming to the rectum from the ventro-intestinals 
and septo-intestinals goes to the external plexus, from where 
it passes to the dorsal through the dorso-intestinals, the part 
of the course involving the internal plexus having been cut 
out (vide infra). 
(c) The Commissural, Integumentary, and 
Nephridial Vessels. 
1. The Commissural Vessel.—As already mentioned, 
there is a pair of commissural vessels (parietal vessels) in each 
segment connecting the dorsal with the subneural vessel 
