S. O. Yosiiida 
•281 
and the transverse canals is peculiar, the outer end of the latter dividing 
into two halves and each of the halves passing respectively dorsally and 
ventrally on each side of the dorsal canal, and opening separately into 
the ventral vessel. This unusual mode of connexion was recently 
observed and described by Beddard (1912) in Urocystidiiiin gemmipartmi. 
The male reproductive organs consist of the testes, the vas deferens, 
the cirrus pouch, and the cirrus. The testes are oval or sometimes 
globular in shape arranged in two or three rows and fairly equally 
distributed in all three wings. In normal specimens of T. crassicollis 
the testes are confined to the dorsal side of the segment, but this is not 
the case in the tri-radiate form (fig. 8). 
The vas deferens (fig. 9) is much coiled, and, though small in 
diameter, it forms a voluminous mass when fully distended with sperma¬ 
tozoa. Entering the cirrus pouch at its base the male duct coils once 
or twice upon itself, then runs directly outward to open into the genital 
cloaca. The distal straight portion of the male duct in the cixTus pouch 
is termed the cirrus; its wall is more muscular than in any other part of 
the male duct. The cirrus pouch is a long, slender, cylindrical sac 
surrounded by muscular walls and its base reaches nearly to the 
excretory canals which are situated dorsally and ventrally of it. 
The female organs consist of ovary, yolk-gland, shell-gland, vagina, 
and uterus. The ovary is irregularly lobed, situated on the basal portion 
of each wing near to the posterior end of each segment (fig. 6, ov.). 
The shell-gland is spherical in shape and occupies the centre of the axis 
at about the same level as the ovary (fig. 6, sg.). The yolk-gland lies 
a little behind the shell-gland. 
In the anterior younger segments, the uterus consists of a mere 
longitudinal cavity running anteriorly from the shell-gland, in the axis 
of the worm ; in the mature segments, not only does the main axial 
trunk of the uterus become extended, but it sends out laterally long and 
numerous branches into all three wings. Such branched lateral portions 
of the uterus may be easily distinguished from the radiating, transverse 
commissures of the excretory system by the presence of the uterine eggs 
in their cavity (figs. 7 and 8). 
From the common genital cloaca, the vagina runs straight inwards 
parallel with the cirrus pouch and the vas deferens to the inner end 
of a wing, where it bends posteriorly to run to the region of the segment 
where the ovary lies. The vagina is small in diameter, but with thicker 
muscular walls than the vas deferens, and they are easily distinguished 
from one another even in the same part of the body. 
Parasitology vi 
19 
