
JOHNSTON AND BECKWITH—LARVAL TREMATODES 567 
the fureae (fig. 8). There are five or six irregular pairs of large clear cells, 
variable in shape, within the tail-stem, These ‘‘caudal bodies” are anchored to the 
sides of the tail-stem by fine strands of tissue, and are also attached to the central 
excretory canal of the tail. Numerous small stalked cells line the sides of the 
tail-stem, their bodies projecting inwards and moving freely. Longitudinal and 
transverse muscle fibres are well-developed. 
The body of the bladder (fig. 2) is rounded, with a bulge on either side from 
which the main collecting tube passes forward to the level of the posterior border 
of the yentval sucker. Here ittakes a sharp bend posteriad, continuing for a short 
distance as a greatly convoluted tube which receives two secondary tubules, one 
from the anterior part of the body, draining one pair of flame-cells, the other 
from the posterior part of the body, draining two pairs of flame-cells in the body 
aud a single flame-cell in the anterior extremity of the tail-stem, the formula 
being 2{(2) + (24+ 2-+ (1))] =14. 
Where the main exeretory tube bends posteriad, it receives two transverse 
commissures, one anterior to, the other posterior to, the ventral sucker. The 
extent to which these commissnres are developed varies considerably in different 
specimens. The commissures arise as a pair of branches growing out from the 
main excretory duct on either side, at the point where this duct turus posteriad. 
The posterior brauch from each sidle grows towards the mid-lme; the anterior 
pass forward by the side of the ventral sueker before growing inward to meet. 
In any one cerearia, both pairs of commissural outgrowths, or one only (either 
the anterior ov the posterior), or neither, may meet and fuse, the point of fusion 
being as 4 rule the point of origin of a short, blindly-ending vessel. Thus four 
stages of fusion have been observed, and in cases where fusion has not ocenrred, 
the degree of development of the commissures is very variable (fig, 6). 
Posterior to the bladder is an island of Cort, ancl from this the excretory canal 
of the tail passes posteriad along the tail-stem, branching at the origin of the 
furene into two tubes, cach of which opens by a pore to the exterior halfway along 
the anterior border of the furea. 
SPOROCYST. 
Upon dissection of a host Planorbis, the liver was found to be almost ecom- 
pletely replaced by narrow, elongate, colourless sporocysts with rounded ends 
(fig, 4). The length of the longest sporoeyst dissected out entire was 3 mm. 
(preseryed in formalin), ie. they are relatively small. No birthpore was 
observed; cercariae and germ-balls are scattered without order along the length 
of the parasite, The wall of the sporocys( is studded with cells which stain with 
haematoxylin; the enticle is yellowish and faintly wrinkled. Living sporoeysts 
are capable of slight movement. 
