232 Stephanochasmus Looss 
which pass forward to the region of the oral sucker. The median 
trunk is a wide canal which extends forward to the space between the 
ovary and the anterior testis, or in much contracted specimens to that 
between the ovary and the dorsal body-wall. In the region of the 
testes it lies, as a flattened tube about 0-1 mm. wide, between these 
bodies and the dorsal body-wall. The two paired excretory canals 
are narrow tubes about 0-012 mm. wide which pass forward, one to 
the right and the other to the left of the ovary along the ventral surface 
of the intestinal trunks to the extreme forward end of the body. In 
front of the acetabulum they are much convoluted. 
The genital pore (Fig. 1, 18) is median in position, being situated in 
the narrow space between the acetabulum and the transverse intestinal 
trunks, and opens into a long cylindrical genital sinus (Fig. 2). This 
structure, in a worm in which the cirrus is not extended (Fig. 2) and the 
body is much contracted, measures about 0-13 mm. in length : in a worm, 
however, the body of which is not contracted the genital sinus may be 
several times this length. It extends posteriorly either dorsal to the 
acetabulum or around one side of it. 
The wall of the genital sinus (Fig. 5) is made up of a cuticula bounded 
by muscle fibres. The cuticula is continuous with that of the outer 
surface of the body, but is very different in structure. Instead of 
forming a smooth surface with large spines it is thickly set with short, 
perpendicular bristle-like projections (10) which arise near the outer 
surface of the cuticula and extend through it into the lumen of the 
sinus. These bristles may be compared with the spines of the outer 
cuticula. The muscle fibres consist of delicate circular fibres (4) sur¬ 
rounding the cuticula and powerful longitudinal fibres (22) which show 
a more or less rectangular cross section. 
Joining the posterior end of the genital sinus are the cirrus sac 
(Figs. 1 and 2, 6) and the metraterm (24) which are extremely long, 
more or less cylindrical structures of about the same length, extending 
posteriorly to a point from a half to two-tliirds the distance between 
the acetabulum and the ovary. Their actual position is dependent 
upon the condition of contraction of the body and whether the cirrus 
is extended or not. In Fig. 1, in which the cirrus (5) is extended and 
the body but little contracted, the cirrus sac is straight and not coiled 
and, not including the extended cirrus, about 1 mm. long, reaching back 
of the acetabulum to a point about half-way between it and the ovary, 
while the metraterm (24) is but slightly coiled and extends a short 
distance back of the cirrus sac. In Fig. 2, on the other hand, in which 
