A NEW MAMMALIAN CESTODE. 1047 
the younger and more spherical cirrus-sacs of earlier segments 
the cirrus is coiled. It perforates the muscle-layers of the 
cirrus-sac to become continuous with the vas deferens without 
any change of diameter. 
The ovary of this worm is ventral in position, as in Shipleya 
inermis. In horizontal sections it forms with the vitelline gland 
almost a complete ring, since the ovary is semicircular and the 
smaller vitelline gland serves to close the semicircle posteriorly. 
The ovary is larger than the vitelline gland, and lies, of course, 
more anteriorly in the segment. In transverse sections the ovary 
is Seen to possess a longitudinal and tubular form, the greater 
part of the cavity being empty. This is illustrated in text-fig. 2 
(p. 1041). It is there seen to be pressed closely against the 
transverse muscular layer bounding the medulla, and thus to lie 
below the receptaculum seminis and also, to some extent, the 
vitelline gland. The remarkable tubular form of the ovary in 
young proglottids might lead to its being confused with the 
commencing uterus, which, however, lies above it and on a level 
with the receptaculum ovorum. The ovary has thus a flattened 
form when viewed in its entirety. It is near to the middle of the 
proglottid verging towards the pore side. The young cells, which 
will become ova, are chiefly massed at the two ends right and left 
of the tubular ovary, and this region, as shown in the figure 
referred to, is somewhat dilated on both sides, forming an oval 
sac. The course of the tube when viewed in transverse sections 
is quite straight from side to side. 
§ Vagina. 
A careful inspection of the horizontal sections shows that, 
although no vagina opens into the so far isolated receptaculum 
seminis, the equivalent of a vagina would appear to be present. 
I cannot otherwise interpret a narrow straight duct which opens 
on to the exterior beside, and in front of, the cirrus-sac. This 
duct passes towards the interior of the body, up to a point ona 
level with the end of the outer half of the cirrus-sac; it is 
therefore of very. limited extent. It ends at this spot in a 
dilatation, an oval sac. I have seen this tube ending blindly in 
a sac in four or five segments. There is thus no question of its 
normal presence; but I have seen it in the more anterior seg- 
ments only, but which are nevertheless well provided with gonads, 
and a cirrus-sac as large as it is in the more posteriorly situated 
segments. The slender character of the duct and the delicate 
chamber into which it expands, remind me greatly of the conditions 
obtaining in my genus Diplopylidium *. But in the latter worm 
* P.Z.S. 1913, p. 562. The illustration depicting the vagina of Diplopylidium 
(text-fig. 92, p. 563) may be compared with my description of the present species. 
In the text of that paper I have remarked that only in Tetrabothrius is this reversed 
position of pores. ‘This is an obvious lapsus calami for Tetradiscotyla. 
