STUDIES ON THE DIGENETIC TREMATODES. A411 
reach this level, but seldom, if ever, exceeds it. Its length is 
45-55 mm.; the maximum diameter is ‘12 mm., and the 
average diameter of the neck is ‘(05 mm. 
The pouch is a true muscular cirrus-pouch, and its wall 
consists of the frequently described internal annular layer 
and external longitudinal layer. It thus differs essentially 
from that of Bunodera nodulosa (Zed.), in which the wall 
is purely membranous. 
The structures contained within the cirrus-pouch conform 
to the common type, e.g. that of the ALLocrEApINa”, but 
they are simple and less complicated. The vesicula seminalis 
is an undivided elongated oval sac (fig. 3), measuring *2 by 
‘04mm. It is not in the slightest degree convoluted. It is 
surrounded on all sides by the cells of the prostate glands, 
except towards the posterior end, where it is contiguous with 
the wall of the cirrus-pouch. The length of the ductus 
between the vesicula and the pars prostatica is about ‘15 mm. 
For the first two thirds of that length it has a diameter of 
‘015 mm.; it then somewhat suddenly widens to ‘023 mm., 
which diameter it retains till it passes into the pars prostatica. 
The latter has a length of (05 mm., and a maximum diameter 
of 035 mm. It has a globose shape, and into it open the 
ducts of the numerous prostatic cells. These are entirely 
confined to the part of the cirrus-pouch behind the pars 
prostatica, so that their ducts all pass forward. They are 
large tear-shaped cells elongated in the long axis of the 
cirrus-pouch, and having an average size of ‘027 by 012 
mm. ‘Their outline may be more or less quadrilateral owing 
to compression. They stain deep purple with hemalum-eosin, 
and have distinct round, rather small (‘004—005) nuclei. 
The terminal part of the ductus ejaculatorius, which, although 
not extended in any of my specimens, functions as an ex-sertile 
cirrus, is shghtly convoluted. As a rule it describes only 
one turn, a little in front of the pars prostatica, but its 
position is not constant. ‘The length of this part is about ‘1 
mm, and its diameter is °02—025 mm. Between this part and 
the wall of the cirrus-pouch are numerous small, round cells. 
