VASCULAR SYSTEM OF PHERETIMA 365 
also lies in exactly the same position. Its dorsal part with its 
connexions with both the dorsal vessel and the body-wall 
would correspond to the ‘ dorso-tegumentary ’, and its lateral 
part together with the septo-intestinal having connexions 
with the body-wall on the one hand and the intestinal plexus 
on the other would correspond to the ‘ intestino-tegumentary ’ 
of Megascolex. There being no subneural vessel in the 
latter genus, there is nothing in its blood-system corresponding 
to the ventral part of the commissural of Pheretima. 
Again, the ‘dorso-tegumentary’ of Moniligaster (2) 
and Lumbricus (8) corresponds to the commissural vessel 
of Pheretima minus the septo-intestinal. Unlike Mega- 
scolex, these two genera (Moniligaster and Lumbricus) 
possess a subneural vessel like Pheretima, and we have 
a loop or commissural vessel connecting the dorsal with the 
subneural, which has been described by Jaquet (9) in Luin- 
bricus as the ‘ branche dorso-sous-nervienne ’, a term adopted 
by Bourne for the same structure in Moniligaster. Jaquet 
also describes a ‘branche tégumentaire’ from the dorso- 
tegumentary ; but I have examined the tegumentary (com- 
missural or parietal) of Lumbricus and do not find 
a special ‘ branche tégumentaire’ as Jaquet makes out. Of 
course, there are several branches from the body-wall (tegu- 
mentary branches) joining the commissural all along its 
course as in Pheretima, to which the term ‘ branche 
tégumentaire’ can be applied; but the real point in which 
the commissural of Lumbricus and Moniligaster 
differs from that of Pheretima is that in the former two 
genera it has no connexion with the intestinal plexus, there 
being nothing corresponding to the ‘septo-intestinal’ of 
Pheretima. 
From the comparisons made above it seems reasonable to 
deduce that the commissural vessel of Pheretima is a com- 
pound vessel which combines in itself the ‘ dorso-tegumentary ° 
(commissural or parietal) of Lumbricus and Moniligaster 
(the dorso-tegumentary of Megascolex corresponding only 
to one of the tegumentary branches joining the commissural 
