BY JAS. P. HILL. 
33 
dorsal vessel retains its lumen to near the posterior end of the 
body. 
As Spengel has found in Ft. minuta, the place of the ventral 
vessel is taken by the keel-shaped process of the gut epithelium. 
As in Ft. minuta, a very delicate musculature is found on the gut 
in this region, and as in that species a distinct sphincter derived 
from the circular musculature exists round the anus. 
V a s cular S y st e m. — Dorsal vessel : In the post-branchial 
region the dorsal vessel is related essentially as in Ft. minuta. 
It can be traced as a vessel with a distinct lumen to near the 
posterior end of the body; it appears, however, to end as a solid 
structure at its extreme posterior end just as in Ft. minuta. In 
the branchial region the dorsal vessel may occupy the whole of 
the mesentery or only its dorsal portion. Between the perihsemal 
spaces the dorsal vessel usually occupies the whole extent of the 
partition wall, but just as in Ft. minuta it may only occupy the 
dorsal half of it, and the ventral part of the wall may then either 
persist as a low wall of partition below the vessel, or it may 
disappear entirely and place the two perihsemal spaces in com- 
munication. 
At the anterior end of the perihsemal spaces, the dorsal vessel 
opens, as in the described species, into a lacuna (figs. 11, 12, 14, 
cl.) between the organs in the proboscis neck and which stands in 
connection with the central blood space of the proboscis by a 
narrow cleft. From the lacuna there passes away dorsally a vessel 
(fig. 10, oav.), the afferent skin vessel, which Spengel regards as 
carrying blood to the capillary net of the proboscis. Where two 
proboscis canals are present it passes between them (fig. 10); 
where there is only one canal, along one side of that. It then 
passes into the limiting membrane and runs in that anteriorly for 
a short distance, finally dividing as in the described species into 
two branches which divide up again to form the capillary net of 
the proboscis. 
Proboscis glomerulus: The glomerulus of this species essentially 
resembles that of Ft. minuta. It covers the anterior ends of the 
c 
