430 WILLIAM ' NICOLL. 
The mouth opens into a short but wide pre-pharynx. 
From the ventral side of this there arises a well-marked 
pre-pharyngeal diverticulum (fig. 8), which passes back- 
wards ventral to the pharynx, and may extend a short 
distance beyond it. This diverticulum forms part of the pre- 
pharynx and there is no difference in its structure ; its 
occurrence, however, is constant. Such a structure appears 
to be absent in Br. palliatum, and was not observed by 
Braun or Poirier. Its function is not very apparent, but it 
is a curious fact that in each of three specimens which | 
examined a number of ova were found in the diverticulum. 
Ova, however, were found in one case in the intestinal 
diverticula, and were probably accidentally swallowed. The 
width of this pre-pharyngeal pouch is ‘13-18 mm., but at its 
junction with the pre-pharynx it is only (09 mm. Its walls 
are in some cases thrown into irregular folds, but they are 
not muscular. 
The pharynx is somewhat flask-shaped, narrowest in front 
and with its anterior end projecting far into the pre-pharynx. 
The extreme freedom of movement of the pharynx is evident 
from the fact that its anterior end may be found directed 
ventrally, dorsally or towards either side. Its length in a 
5°) mm. specimen is ‘36 mm.; breadth *22 mm. and thickness 
20 mm. It is, therefore, a comparatively large structure, and 
is narrower than that of Br. palliatum and larger in 
proportion to the size of the animal. The histological 
structure is the same as that of the suckers. The myoblasts 
measure ‘008-011 mm., with minute reddish eccentric 
nucleoli. 
The cesophagus arises from the posterior end of the 
pharynx as a narrow tube, transversely oval in section, with 
a diameter of "10 mm. It gradually increases in diameter to 
‘15 mm., where, at a distance of ‘(05 mm. behind the pharynx, 
there is a small dilatation on the left which causes the width 
to increase to ‘20 mm. The bifucation takes place at a 
distance of 115 mm. behind the pharynx. ‘This, however, is 
not a bifurcation in the usual sense of the term, when the 
