F . D. Wei dm an 
269 
equator. The venter is flat transversely in its mesial portion, curved 
laterally, and strongly curved longitudinally. When fresh, the worms 
were pinkish grey and showed slight vermicular movement upon gentle 
warming; the movements were most marked in the anterior extremity 
and probably were responsible for the variations in the degree of 
attenuation noted in fixed specimens. When fixed in formalin they 
are of a grey green colour. 
The oral orifice is terminal, directed ventrally, small, circular, 
unarmed, without papillae or other specializations, and measures 0-25 mm. 
in diameter. The genital pore lies T15 mm. 1 posterior to it, is circular, 
measures 0-1 mm. in diameter and carries a low broad papilla in the 
depths of the very small atrium into which it leads. I could not find 
a suctorial muscle around it other than the continuation of the general 
body muscles. Otto and Duff state that there is a suctorial muscle, 
but my examination of Duff’s material strengthens me in the belief 
that there is no such muscle. Fischoeder, moreover, states that there 
is none. The centre of the acetabular orifice is 3-0 mm. posterior to 
the genital pore and 1-8 mm. 1 from the posterior extremity. Its orifice 
is large (070 mm. in diameter), circular, and tilted obliquely ventrally. 
The triangular form, due to dorsal ridging, originally ascribed to 
the worm by Rudolphi, could doubtfully be made out microscopically 
in the specimens at hand and not at all grossly. The histological cross 
sections vary in form at different levels, but are never fairly subtriangular. 
Anteriorly they are subcircular, with an inconstant gentle dorsal de¬ 
pression at the right of the mid-line. This shortly disappears, the 
intercaecal portion of the dorsum becoming flat, and at the level of the 
genital pore strongly concave. Below this point the venter in turn 
becomes markedly flattened and now a gentle median dorsal swelling 
appears, to disappear at the anterior border of the acetabulum. Between 
the genital pore and the latter level the transverse diameter of the worm 
is to the dorso-ventral as 3 : 2. The venter between the acetabular orifice 
and the anterior acetabular margin is now strongly concave (obliquity 
of plane of section due to tilting of acetabulum). At the level of the 
acetabular orifice the venter resumes its convexity (and maintains it 
to the terminus) the section here appearing subcircular with flat or 
concave dorsum. Below this level a distinct median dorsal swelling 
appears, which continues a short distance (0-2 mm.), disappears for 
a distance of 0-064 mm. to re-appear for a. second (0-2 mm.) course. 
After this one of the declivities gradually disappears, the other forming 
1 Measurements taken from the entire specimen 5-95 mm. long. 
Parasitology x 
IS 
