VASCULAR SYSTEM OF PHERETIMA 355 
distance, it pierces the septum and gets into the succeeding 
segment (vt.v., fig. 1). Here it lies on the inner surface of the 
body-wall near the middle line of the segment just in front of 
the row of setal sacs, going right up near the mid-dorsal line 
(figs. 1 and 2). As it ascends along the body-wall transversely, 
the ventro-tegumentary vessel (vt.v.) gives off backwards and 
forwards capillaries that supply blood to the body-wall 
(epidermis and the muscles) and the integumentary nephridia. 
Besides, the septal nephridia and the prostates also receive 
their blood-supply from the ventro-tegumentaries. The septal 
nephridia are supplied by a septo-nephridial branch (sn.b., 
fig. 1) of the ventro-tegumentary given off in each segment 
at the place where it pierces the septum; while the prostate 
glands in the segments sixteen to twenty-one receive small 
branches from the ventro-tegumentary in each of these 
segments. 
Besides the paired ventro-tegumentary branches the ventral 
vessel gives off dorsally a single unpaired ventro-intestinal 
vessel in each segment (vi.v., fig. 1). This vessel originates 
from the ventral a little behmd the middle of each segment, 
and runs forward to enter the ventral wall of the intestine, 
by three or four branches, close to the anterior intersegmental 
septum. The ventro-intestinal, though generally overlooked 
in this worm, 1s, however, an important vessel, and measures 
as much as 1-5 mm. in length in some worms from its place of 
origin on the ventral vessel to its place of entrance into the 
intestinal wall. It puts the ventral vessel into communication 
with the intestinal plexus. There are no valves anywhere along 
the course of the ventral vessel. 
The ventral vessel is the main and, in fact, the only distribut- 
ing channel in the intestinal region of the body. All parts 
in this region get their supply of blood from the ventral 
vessel. 
3. The subneural vessel.—The subneural vessel runs 
along the mid-ventral line of the body-wall, bemg intimately 
attached to it, and hes, as its name indicates, beneath the 
nerve-cord. It is a very slender vessel and extends from the 
NO, 259 Bb 
