F. J. Meggitt 
40 
the two courses opens the cirrus: the vagina does not enter it until 
its extreme inner end. The openings of the male and female ducts are 
in the same horizontal plane. 
Male Organs. 
With the exception of a narrow anterior strip, the testes occupy the 
whole of the middle field of each proglottis (PI. VI, fig. 3). They lie 
in two layers half-way between the dorsal and ventral surfaces, and 
extend laterally beyond the longitudinal excretory canal: they are most 
numerous in the centre of the segment. Each testis is surrounded by 
a thin but distinct tunica propria, which at one point is drawn out into 
a fine duct, connecting the testis with the nearest vas efferens. The 
vasa efferentia of the one side join together at about one-third the 
width of the proglottis (PL VI, fig. 5) and midway between the anterior 
and posterior borders to form a slender vas deferens. They are 
extremely slender muscular tubes and their small size in view of the large 
size of the spermatozoa is surprising: their walls must obviously be 
capable of great expansion in order to allow of the passage of the male 
elements. 
The vas deferens [v.d.) runs at first towards the lateral margin but 
later bends round in a sweeping curve so as to point towards the anterior 
border. It increases considerably in size, having a diameter of 0'048 mm., 
and presents the appearance more of a vesicula seminalis than of a 
duct {v.s.). It bends round, running posteriorly for a short distance, 
but just posterior to the cirrus-sac it bends anteriorly again and after 
a short course runs laterally to open into the cirrus-sac. From the 
time it runs posteriorly to the time it enters the cirrus-sac, its diameter 
decreases gradually, until at the latter point it is only 0-011 mm. During 
the whole of its course it only occupies the middle third of the proglottis. 
There is no vesicula seminalis, the enlarged portion of the vas deferens 
taking its place. 
The cirrus-sac itself is an oval elongated organ lying near the 
anterior margin of the proglottis and near its dorsal surface. In some 
proglottides it appears to extend internally as far as the longitudinal 
excretory canal, but in the majority of cases it does not reach as far. 
At its outer end it bends towards the dorsal surface, the amount of the 
bend varying in different proglottides. The course of the vas deferens 
in the cirrus-sac is fairly straight, the few bends present appearing to 
be due to contraction caused by fixation. Its opening into the genital 
cloaca has already been described. Unfortunately, owing to some 
Parasitology vnj 
4 
