18 
CHARLES BADHAM. 
extension as tubes iti place of the row of vesicles found in 
allied genera. They possess, as shown in PI. 2, fig. 9 ( C . 1), 
the character of a series of pouches ; their walls are 
furnished with delicate muscle fibres. Anteriorly the con- 
tractile lacunae cease to be contractile at the level of the 
neck but are continued forward as non-contractile parts to 
the anterior sucker. I have not determined their course past 
this point, but they certainly do not appear to break up into 
capillaries. 
Posteriorly their relations are more important. At the 
level of the posterior sucker they curve sharply, and, passing 
ventral to the two branches of the dorsal vessel, open into 
the lacuna in the anal region. They receive on either side 
of each segment the two openings of the segmental lacunae 
(PL 2, fig. 8, C. 1.). Dorsally in each segment they give 
off three or four pairs of capillaries (PI. 2, fig 8, Cap. 1.) ; 
these run parallel to one another, just outside the muscle 
layer. In one living specimen I observed these opening into 
the dorsal lacuna, but was unable to demonstrate this in 
other specimens. 
In Callobdella Johansson has seen three or four pairs 
of capillaries in each segment going from the dorsal lacuna 
and stretching into the surrounding tissue. 
The Circulation of the Lymph. 
In the description of the circulation of blood in the vessels 
mention will be made of the contraction of the pouches of 
the thick-walled intestinal region. By these contractions a 
space is produced between the wall of the intestinal sinus 
and the wall of the intestinal lacuna, which is immediately 
filled by the lymph flowing in from the lacuna formed in the 
anal region by the fusion of the dorsal and ventral lacunas. 
When the intestinal sinus is again in the condition of diastole, 
the lymph is seen to be forced out of the dorsal lacuna and 
to flow into the segmental lacunae. At the spot where the 
dorsal and ventral extensions of the segmental lacunae join a 
great deal of regurgitation takes place. The lymph corpuscles 
