28 
CHARLES BADHAM. 
vessels is very similar to that found in Ozobranchus (Oka, 
1904, Fig. 1). The second pair of lateral vessels (L.v.2), 
is given off in somite 9 ; these branches run ventrally and 
anteriorly, and unite with the ventral vessel just behind the 
spot where the first pair join. The third pair of lateral 
vessels (L.v. 3) are given off in somite 10 ; the two branches 
run at first posteriorly to the end of somite 1 1 ; then they 
curve sharply and, running forward, enter the ventral vessel, 
just behind the point of entry of the second pair of lateral 
vessels. 
Immediately in front of the first valve the dorsal vessel 
gives off the proboscis branch (P. v. 1.) which runs to the apex 
of the proboscis and there bifurcates. The two vessels thus 
formed unite almost at once to form the efferent proboscis 
branch (P. v. 2), which runs to join the ventral vessel, just 
behind the point where the second pair of lateral vessels enter 
into it. After emerging from its intimate relations with the 
•caeca of the thick-walled intestine posteriorly (J. s.), the dorsal 
vessel divides in two at the beginning of the 24th somite. 
These branches extend in such a way as to form a vessel 
running round the periphery of the posterior sucker. This 
part of the dorsal vessel gives off on each side four or five 
.short-looped vessels, which communicate with a ring vessel 
(P. v.) running right round the periphery of the posterior 
sucker. This ring vessel receives on each side seven branches 
of the ventral vessel. A certain degree of anastomosis is 
.seen in these branches before they unite to form the ventral 
vessel. I have followed the course of this ring vessel in 
living leeches obtained from different places. 
As stated in the account of the coelomic system, the dorsal 
blood-vessel lies in the dorsal lacuna, or its extension the 
intestinal lacuna, for almost the whole extent of these lacunae. 
Anteriorly the dorsal vessel passes out of the lacuna at 
somite 13. PI. 2, fig. 12, shows the vessels in the 11th 
somite shortly after the dorsal blood-vessel has left the lacuna. 
The ventral vessel is lying free in the dilated lacuna which 
.surrounds the accessory male glands. 
