MONILIGASTER GRANDIS, A. G.B. 349 
networks of vessels, the branches of which all repeatedly sub- 
divide until they become capillaries, some of which, i. e. those 
in one particular region of the body, are continuous with the 
capillaries formed by an artery, and others with those formed 
by an ordinary vein. 
I shall speak of these last-mentioned veins collectively as a 
portal system.} 
The most important distinction which I find between the 
vascular system of one worm and that of another lies in the 
presence or absence of a “ portal system.’ Where a portal 
system is present there are no intestinal arteries; the blood is 
brought to the capillaries of the intestine from the peripheral 
capillaries by means of the portal system. 
Where there is no portal system the intestine receives intes- 
tinal arteries (ventro-intestinal vessels), while the blood in the 
peripheral networks is carried by ordinary veins (latero-longi- 
tudinal and subneural vessels) direct to the main trunks (dorsal 
vessel, supra-intestinal vessel, or hearts). 
There is no portal system in Moniligaster or Lumbri- 
cus, while on the other hand I have observed such a system in 
all the Perichzetide which I have examined, in Perionyx and 
Acanthodrilus, and from facts recorded by Perrier and 
Benham, I have no doubt but that such is present in Uro- 
cheta, Pontodrilus, Microcheta, Rhinodrilus, Plu- 
tellus, Digaster, and Titanus. 
The character which seems to me to come next to the presence 
or absence of a portal system in order of importance is the 
presence or absence of a subneural trunk. 
Where a subneural is present in addition to a portal system, 
as in Urocheta and Pericheta (sensu restrictu) it appears 
to take some of the blood more directly into a main trunk (a 
conclusion to which I am led by a study of Perichzta). 
Where a subneural is present without a portal system it 
1 As the term “portal” is now in general use to designate veins other 
than that to which it was originally applied, there seems to be no objection 
to its use for all vessels having similar relationships with regard to capillary 
networks, 
