432 WILLIAM NICOLL. 
coats of the cesophagus are well marked but those of the 
diverticula are thin. 
As already noted the excretory aperture opens on a large 
pit-like depression at the posterior end of the body; 
whether this depression is an intrinsic part of the excretory 
system or not | am at a loss to say. Small cuticular spines 
penetrate a short distance within it, and the rest of its surface 
is hned by a thin membrane which appears like cuticle but is 
much thinner than the body cuticle. It may be either an 
invagination of the posterior end of the body, or a dilatation 
of the terminal part of the excretory duct, or both combined. 
A similar condition has not been observed in the other species 
of the genus, and as it is only visible on section Braun was 
not able to observe it. It was present in each of my speci- 
mens. Its significance is not apparent. 
A narrow tube with muscular walls leads from the aperture 
to the vesicle. Several muscle-fibres are grouped round the 
aperture in the form of a sphincter. The vesicle itself is of 
simple structure. It is lined throughout by a thin, delicate 
membrane, in which small scattered epithelial cells can be 
observed. The wall is extremely irregular, being thrown into 
innumerable little wrinkles and folds. There is a deposition 
of muscle-fibres, both annular and longitudinal, but they are 
very fine. ‘The vesicle les ina mass of very loose connective 
tissue, and it extends as far forward as the posterior border 
of the ovary, passing dorsally to the testes, by which it is com- 
pressed, but expanding in the spaces between the testes and 
‘ovary. The anterior end is flattened and broadened and into 
it the two lateral tubules enter. These pass forwards and are 
distributed in the manner which Looss has fully described in 
Br. palliatum.! 
The genital aperture is median, close in front of the ventral 
sucker. It is a narrow transverse slit with sphincter and 
radiating muscle-fibres. The genital sinus is of small size. 
The male duct opens into it on the right, the female on the 
left. ‘lhe radial fibres of the genital aperture pass into the 
1 Op. cit., p. 405 
