STUDIES ON THE DIGENETIC TREMATODES. 409 
separated by a narrow space occupied by yolk-glands, 
Their outline is shghtly irregular, but not lobed. The 
anterior testis is often hollowed out in front and transversely 
elongated; it varies in size and shape much more than the 
posterior testis does. The antero-posterior axis measures 
-21—28 mm., the transverse axis *26—-44 mm. ‘The corre- 
sponding measurements of the posterior testis are ‘28-43 mm 
and *29--39 mm. ‘The average is about *27 by 54 mm. for 
the anterior, and *34 by °35 mm. for the posterior. Thus 
the diameter is rather less than one tenth of the body length. 
This result is in close agreement with the figures of Olsson 
and Linton. Olsson, however, states that the testis exceeded 
the ventral sucker in size. That was certainly never the 
case in ‘any of my specimens, nor does it appear to be so from 
Linton’s figure. 
There is no sinus genitalis, or at most it is represented 
merely by a shallow depression, in which the male and female 
ducts open separately but contiguously, the former in front 
and to the left of the latter. In total preparations, however, 
only one aperture is sometimes seen. Its position is invariably 
median and exactly ventral to the posterior end of the 
pharynx. In Olsson’s representation of the species (PI: IV, 
fig. 52) the apertures are shown widely separate,-but this is 
evidently the result of an erroneous observation, which I shall 
endeavour to make clear. The apertures are figured behind 
the intestinal bifurcation, between it and the ventral sucker, 
and they appear to be separated by a distance of nearly 2 mm. 
Further, from the supposed male aperture a long penis is 
represented stretching straight forwards to about the middle 
of the pharynx, while the cirrus-pouch shows a somewhat 
elongated oval outline quite different from the pear shape of 
my specimens. ‘To me it appears that the structures marked 
p and b in fig. 52 are really portions of the cirrus-pouch, } 
being the thicker posterior part and p the narrow anterior 
part or neck running forward to the genital aperture near 
the posterior end of the pharynx. The erroneous position of 
the female genital aperture is probably due to the fact that 
