368 KARM NARAYAN BAHL 
is the strict parallelism which obtains throughout between 
“artery? and “‘ vein”’’. In serial sections it is very interesting 
to follow pairs of parallel capillaries in the body-wall, and one 
can invariably trace them to their afferent and efferent vessels. 
Fig. 4, reconstructed from three sections of 6 thickness, 
serves to illustrate the parallelism obtained in sections, while 
fig. 4a gives an accurate camera lucida drawing of part 
of the body-wall mounted flat after the removal of longitudinal 
muscles. The strict parallelism between an ‘artery’ and 
a vein together with the capillary loops connecting them are 
very clearly displayed. 
3. The Nephridial Blood-system.—The blood-supply 
of the three kinds of nephridia in Pheretima has already 
been described by me elsewhere (8), and I have nothing further 
to add here. 
(d) The Dorso-intestinals and the Ventro- 
intestinals. 
The Dorso-intestinals.—I have referred to these 
vessels already in describing the dorsal vessel. The dorso- 
intestinals form, so to speak, the efferert vessels (veins) of 
the intestinal blood-plexus, as all the blood in the intestine 
is returned to the dorsal vessel through these dorso-intestinals. 
There is a single pair of them in the fourteenth segment and in 
all the segments of the rectal (post-typhlosolar) region, while 
in the remaining large part of the intestine we have two pairs 
to each segment. We have already noted that the dorso- 
intestinals communicate with the external plexus in the rectal 
region but with the internal plexus in the first and second 
regions. At the place where the dorso-intestinal leaves the 
gut, it also receives a branch from the typhlosolar vessel 
(fig. 2). 
The Ventro-intestinals.—These single unpaired 
vessels in each segment have also been referred to above. 
They form the afferent vessels (arteries) of the gut, and are 
present in all the three regions. 
