STUDIES ON THE DIGENETIC TREMATODES. 429 
ally diminishing forwards and backwards. Around the oral 
sucker they are ‘019 mm. long with a base measurement of 
‘0045 mm. The maximum size about the middle of the body 
is ‘058 by ‘014 mm. ‘Towards the posterior end they measure 
‘037 by ‘012 mm. ‘They are thus much shorter than the spines 
of Br. palliatum. The spines are deeply embedded in the 
cuticle, penetrating its whole thickness and causing bulging 
of the basement membrane. Immediately beneath the latter 
he the usual three layers of muscle-fibres. The circular fibres 
have a diameter of ‘0019 mm., and are separated by spaces 
equal to their diameter. The longitudinal fibres measure 
‘003—'004 mm., and are separated by spaces of ‘006-01 mm. 
The diagonal fibres measure ‘0035—"0055 mm., and are widely 
separated by spaces of ‘04 mm. ‘Those passing in opposite 
directions make an angle of 125° with each other, but this 
varies with the state of contraction. The longitudinal and 
diagonal fibres run for the most part in pairs, which are in 
more or less intimate contact. Sometimes they are indistin- 
guishable ; sometimes a distinct interval separates them. 
This corresponds with the condition described by Looss in 
Br. palliatum. In both species the circular fibres run singly. 
The suckers are small in comparison with the size of the 
animal. Both are globular with circular apertures, and 
present no peculiar feature. The oral sucker is subterminal 
and has a diameter of *33 mm. ‘The ventral sucker is 
situated at a distance of rather more than a quarter of the 
body length from the anterior end, and has a diameter of 
‘43-46 mm, The diameters are therefore in the propor- 
tion of 3: 4, and are respectively about one sixteenth and one 
twelfth of the body length (taking the average as 5°5 mm.). 
This agrees fairly well with Braun’s measurements. 
The radial fibres of the oral sucker are ‘015 mm. thick ; 
those of the ventral sucker ‘025 mm., the circular fibres about 
‘(019 mm. The wall of the oral sucker has a thickness of 
‘078 mm., that of the ventral sucker ‘09 mm. The cuticular 
lining of the suckers is thinner than the cuticle covering the 
body, being only about ‘004 mm. thick. 
