446 WILLIAM NICOLL. 
suckers, just over the intestinal bifurcation. In most speci- 
mens it is approximately median, but in many it is displaced a 
little to the left side, and in a few a little to the right. The 
normal position may therefore be regarded as median, but 
with variations, and this probably indicates one of the initial 
stages of the transformation to a distinctly lateral position 
as in Podocotyle. The only other members of the ALo- 
CREADIINH, as at present recognised, which have a lateral 
genital aperture, are A. tumidulum (Rud.) and A. angus- 
ticolle (Hausmann), in the former of which the aperture is 
well to the left, in the latter only slightly. In all the other 
species it is median, and it is surprising that more forms have 
not been described showing intermediate stages of this dis- 
placement, for it is evident that it can only have occurred by a 
gradual series of changes. It would be interesting to dis- 
cover the reason of the transposition and why it is to the left. 
A small genital sinus is present, into which the male duct 
opens on the right, the female on the left. 
The ovary is situated immediately in front and to the right 
side of the anterior testis, with which it is contiguous. It 
also lies close beside the intestinal diverticulum, and is 
separated from the ventral sucker by a distance equal to the 
diameter of the ovary. It is a round, almost globular body, 
with entire margin and measures ‘16—"17 mm. in diameter. 
The ovarian cells are largest anteriorly, being about ‘01 mm. 
in size. The oviduct arises from the anterior dorsal surface 
of the ovary, and passes in a curved course towards the 
receptaculum seminis. This is a large oval sac, measuring 
‘1-16 mm., attached to the oviduct without the intervention of 
a pedicle. Laurer’s canal arises directly from the receptaculum 
and runs almost straight in towards the middle line of the 
body. The exact position of its opening could not be 
ascertained. The receptaculum lies dorsal to the ovary, but 
its position is variable, being sometimes in front of the ovary, 
sometimes behind it. In fig. 12 it is shown in the latter 
position. From the receptaculum the oviduct passes across 
the ovary to the shell-gland, before entering which it is 
