W. Nicoll 
191 
usually presents a distinct terminal protuberance and this marks the 
aperture of the excretory vesicle. 
The cuticular spines are more extensive than was originally supposed 
and in some specimens they can be traced almost to the posterior end 
of the body. The cephalic spines could be counted in only two specimens, 
in one of which they numbered 30, in the other 29, in each row. In 
addition, occasionally, intercalary spines were observed much smaller 
than the normal spines and having apparently no definite arrangement. 
The spines of the anterior row measure 0'033 mm., and those in the 
posterior row 0 039 mm., in length. 
A feature which passed unnoticed in the original specimen was the 
presence of two crescentic eye-spots situated midway between the oral 
sucker and the pharynx. They are probably persistent in all species of 
the genus. Owing to the fact that the original specimen was somewhat 
contracted the neck appeared somewhat shorter than is normally the 
case. On an average it is about one-third of the body length (0‘88 mm.). 
The oral sucker is of very variable size and shape. Sometimes it 
appears as a shallow cup with a wide mouth, at other times as a deeper 
structure with a comparatively narrow aperture. Its average diameter 
is 021 mm., but it varies from 015 mm. to 0'27 mm. The ventral 
sucker, which is approximately globular, is of much more constant size, 
its average diameter being 027 mm. The sucker ratio is therefore 
about 7 : 9. 
The pre-pharynx varies in length, with the state of extension, 
from 0 07 mm. to 0'3 mm., the average being 0'25 mm. Similarly 
the oesophagus varies from 0 03 mm. to 0T7 mm., with an average of 
008 mm. The pharynx measures 0'2x0T3mm. 
The testes are usually contiguous or separated by a very small space. 
They measure 0‘29 x 0’26 mm. and the post-testicular space is usually 
equal to the long diameter of the testes. As a rule the axis of the 
testes is slightly oblique, the anterior end being displaced a little to 
the right side. This is more marked in the case of the anterior 
testis. 
The ovary lies a little in front of the anterior testis from which it is 
usually separated by a number of yolk follicles. It is displaced 
somewhat to the right side and is nearly globular with a diameter 
of 016 mm. The yolk glands are uninterrupted and extend from the 
posterior border of the ventral sucker to the end of the body but they 
do not fuse in the post-testicular space. The follicles surround the 
intestinal diverticula except on the inner side. There is a small yolk 
