62 CONTRIBUTIONS TO AMERICAN HELMINTHOLOGY. 
without distorting some part of it. The only way to obtain a correct 
view of the structure of the suckers, is to examine them in the first 
place with incident light before they have been subjected to pressure. 
I believe that Fig. 8 conveys a correct interpretation of the disposition 
of the parts of the framework. 
The suckers have short muscular pedicels and an oval aperture, 
the long axis of which is directed transversely to the caudal disc, and 
which has a nearly continuous chitinous ring. This ring is interrupted 
by hinges at four points in its course, viz., the middle points of the 
outer and inner borders, from each of which a hook arches over the 
aperture of the sucker, and the middle points of the anterior and 
posterior borders, where it meets with a mesial piece which traverses 
the concave floor of the sucker. I have never been able to establish 
the continuity of this with the anterior border of the ring, and am 
inclined to believe that they do not meet. 
The aperture of the sucker may be narrowed so as only to leave a 
chink between its approximated anterior and posterior borders. This 
is effected by the outer and inner hinges, and the appearance of the 
framework is changed by the greater curvature thus given to the 
mesial piece, and by the free hooks being pressed backwards toward 
the posterior border. I believe that Leuckart’s figure is drawn 
from the framework in this position ; in which case it is possible to 
identify the pieces shown in both figures. 
The aperture of the sucker may also be narrowed in a direction at 
right angles to the above, in which case the hinges from which the 
free hooks project become more apparent. This seems to agree better 
with Olsson’s figures (loc. cit.) of the suckers in various species of 
Octobothrium. 
The mouth-suckers are somewhat peculiarly formed, the muscular 
tissue being interrupted at the inner margin of each (Fig. 20, Pl. EL). 
The intestinal coeca are invested throughout by a thick layer of 
vitelligenous glands, forming two dark-coloured stripes in the body, 
on each side of and between which a somewhat more translucent area 
is to be seen. 
The abundance and opacity of these glands, render the examination 
of the genital organs difficult; the following points were, however, 
made out. 
The only genital orifice detected is situated 0.78 mm. from the 
anterior end. It is a circular sucker of 0.1385 mm. diameter, which, 
