STUDIES ON THE DIGENETIC TREMATODES. 463 
generally accepted conclusion. There is evidently scope for 
further investigation on the matter. 
The foregoing observations apply mainly to the ventral 
sucker. In the oral sucker the cells are more closely packed 
and not so easily differentiated. It is also worth mentioning 
that in some specimens the marginal cells, to which I have 
ascribed a glandular function, can hardly be distinguished. 
These are generally highly contracted specimens. In most 
cases, however, these cells stand out with striking distinct- 
ness and give sections of the sucker an entirely unique 
appearance. 
In spite of their large size the suckers are not particularly 
muscular, The fibres are widely separated and the interspaces 
are filled with a large amount of loose tissue. The radial 
fibres have a diameter of about ‘001 mm. in the case of 
the ventral sucker. ‘Two layers of circular fibres are present 
under both the external and internal surfaces. 
The surface of the body is covered with a fairly uniform 
cuticle, -002—004 mm. thick; Jacoby says ‘0113, but that is 
certainly too high a figure. There are no spines, but the 
cuticle is covered throughout its whole extent with curious 
little rod-like bodies, measuring ‘004 by ‘001 mm. (fig. 13, Cu.). 
These are regularly arranged, close together, and stand out 
straight from the surface, not sloped backwards in the manner 
of spines. They are purely superficial outgrowths and do 
not penetrate the cuticle. It is strange that no mention is 
made of these by Jacoby, for their appearance is certainly 
remarkable enough. It may be that they are of transitory 
occurrence, but they were present in every specimen which I 
sectioned. ‘he cuticle lining the suckers and the pharynx 
also shows these rod-like bodies in many specimens. 
In the anterior part of the body the cuticle is thrown into 
numerous small transverse wrinkles. These are not the ir- 
regular wrinkles so commonly met with in other species ; they 
are fairly uniform in size, and in longitudinal section present 
the appearance of a series of regular furrows. Of this, again, 
no mention is made by Jacoby. In the posterior part of 
