W. Nicoll 
201 
and is situated behind the middle of the body (0'9 mm. from the 
aiiterior end). The diameter of the ventral sucker is therefore distinctly 
more than twice that of the oral sucker and in some cases it is nearly 
three times. Both suckers are globular. 
The pharynx is contiguous with the oral sucker and measures 
0’07 mm. in diameter. It is succeeded by a short oesophagus, rather 
shorter than the pharynx. The intestinal diverticula are simple, narrow 
and short, terminating some distance in front of the ventral sucker. 
The exci'etory vesicle is a short bulbous sac at the posterior end 
of the body, containing in many cases a hard yellowish green or brown 
concretion of irregular shape. 
The testes are two ovoid bodies sitiaated one over each posterior 
quadrant of the ventral sucker, their posterior borders being just a little 
behind the posterior margin of the sucker. Their long axes are oblique 
and almost tangent to the edge of the sucker. They measure about 
0’25 mm. x 0T2 mm. The cirrus-pouch is a conspicuous arcuate 
structure lying immediately in front of the ventral sucker. In most 
cases it is entirely in front of the sucker, but in some it touches or even 
slightly overlaps it. It contains a bi-partite vesicula seminalis, the 
posterior half being the larger and measuring OT x 0 07 mm., while the 
anterior half is almost globular and has a diameter of 065 mm. In 
front of this is a bulbous pars prostatica which is slightly larger than 
the anterior part of the vesicula (0‘08 mm.). The rest of the cirrus- 
pouch ('3 mm.) is traversed by a long ductus ejaculatorius, the walls 
of which are characteristically crenated or folded. No spines are 
present in the ductus or cirrus. The genital aperture is situated over 
the left intestinal diverticulum near its termination. It is therefore 
not absolutely at the lateral margin of the body. 
The ovary is situated in the middle line, at the posterior border 
of the ventral sucker, between the testes. Sometimes it is a little in 
front of, sometimes a little behind the testes. It is globular and has a 
diameter of 0'09 mm. Alongside the ovary, sometimes dorsal to it, is 
a vei’y small receptaculum seminis, from which passes a short Laurer’s 
canal. The yolk-glands consist of a small compact mass lying near the 
ovary, sometimes on its right side, sometimes behind it. The uterus 
lies almost entirely behind the ventral sucker, although one convolution 
is thrown up along the right side of the sucker. On the left side and 
in front of the sucker the uterus runs into a highly developed and very 
muscular vagina. This lies behind the cirrus-pouch and is considerably 
inflated. The eggs, as in all the members of the family, develop rapidly 
