270 
Cladorchis subtriquetrus Rud. 
one side of a cleft which indents the worm fairly deeply. The cleft 
gradually becomes shallower, finally disappearing toward the posterior 
extremity. 
From the above description it will be seen that the dorsal ridge of 
Rudolphi (1814) is represented in the specimen here studied by a short, 
low, rounded median discontinuous ridge extending 0-4 mm. over the 
dorsum of the worm, i e. only about one-sixth of its length. To the 
writer it seems to be a very inconspicuous character on which to name 
the species. 
The surface is smooth and glistening except near the genital pore, 
where the cuticle is thrown into deep transverse ridges. There are no 
spines, tubercles or ridges anywhere. 
The acetabulum is large, subterminal, tilted obliquely ventrally, and 
measures 1-45 mm. laterally, TO mm. dorso-ventrally and 0-92 mm. 
antero-posteriorly. 
The cuticle agrees in general structure with that of other trematodes; 
it shows no spines or other specializations. Duff discusses the sub¬ 
cuticular cells and their function with considerable detail; she considers 
the “large cells” in the suctorial muscles as embryonic remnants rather 
than nervous elements. 
The Alimentary System. 
The oral orifice leads into a roomy oral cavity of subglobular shape 
measuring 0-6 mm. in width, 0-22 mm. dorso-ventrally and 0-384 mm. 
antero-posteriorly. From its postero-lateral portion, two blind tubular 
evaginations, one on each side and each 0-2 mm. long, extend into, but 
not through, the muscle of the oral sucker. Fischoeder takes issue 
with Otto here. The former found the oral cavity very small, of tri¬ 
angular shape in cross section with one angle directed ventrally and the 
two pockets springing from the other two angles. The latter describes 
the cavity as a cleft (Spaltformig). It seems possible that the varia¬ 
tion might depend upon different degrees of rigor mortis in the oral 
suctorial muscle or to the kind of preservative used. The oral cavity 
is surrounded by a muscle 0-25 mm. thick in the form of a much flattened 
sphere measuring T1 mm. dorso-ventrally, 1-1 mm. in width and 0-9 mm. 
antero-posteriorly. At its most anterior portion its fibres are arranged 
into two closely placed sphincters, the more anterior being the heavier. 
They do not lie at the oral orifice, but well (fully 0-25 mm.) internal 
thereto. The beginning of the oral cavity thus assumes a broad, short, 
tubular form lined by cuticle and not surrounded by special muscle. 
