VASCULAR SYSTEM OF PHERETIMA 879 
other two genera. Moreover, while in Lumbricus and 
Allolobophora the subneural goes right up to the anterior 
end of the body, in Pheretima it passes into the lateral 
oesophageals in the fourteenth, as it also does in Monili- 
gaster (2), being absent in the first thirteen segments. The 
venous branches of the dorsal vessel bringing blood into it 
behind the ‘hearts’ are the ‘ dorso-intestinals’ and the 
‘commissurals ’, The latter, while they lie completely in one 
segment in Pheretima, occupy two segments in Lum- 
bricus and Allolobophora. In these the ventral 
portions of the commissurals lie on the posterior face of 
a septum in one segment, while the dorsal portions lie on the 
anterior face of the same septum in the segment in front. 
In this way, while the commissural vessel enters the dorsal 
vessel in front of a septum, it enters the subneural imme- 
diately behind that septum; but in Pheretima, both the 
ends of the commissural and, in fact, the whole of the com- 
missural, lies on the posterior face of a septum. 
The ventro-tegumentaries in all the three genera arise in the 
segment anterior to the one they supply ; but while in Phere- 
tima and Allolobophora the ventro-tegumentary runs 
along the middle line of a segment (fig. 8), it runs very near 
the anterior septum alongside the commissural in Lum- 
bricus. The parallelism. between an artery and vein shown 
in fig. 4 in Pheretima in the body-wall is not found in 
Lumbricus, in which the arterial branch lying inside the 
muscular layers of the body-wall takes a dip towards the 
epidermis, runs beneath this layer for a short distance, and 
runs back to the muscular layers to be continued as a venous 
branch to the commissural into which it enters (6). 
As regards the blood-vessels in connexion with the gut we 
may notice the absence of septo-intestinal vessels in the 
Lumbricidae, whereas in Pheretima the gut has 
a double source of blood-supply (the ventro-intestinals and the 
septo-intestinals) ; in the other two genera it gets all its blood 
from the ventral vessel only. ‘he typhlosopar vessel of 
Pheretima, unlike that of the Lumbricidae, is only 
