56 
Billiarziasis 
spicules. The circular oral sucker opens into a short muscular pharynx. No more of the alimentary 
canal can be made out, and according to Looss, this is absent. The remainder of the body is occu¬ 
pied by eight pairs of large cephalic glands whose numerous ducts open into the mouth cavity. 
Situated in the posterior sixth is an oval structure with cellular outline and an absence of a mus¬ 
cular rim; this was thought by Sonsino to be the ventral sucker, but Looss pointed out (op. cit. 
p. 209) that it represents the excretory vesicle and that the cercaria is probably the larval form of 
some monostome. In front of this excretory vesicle is situated a round well-marked collection of 
genital cells. The tail is long and tapering and in the more mature forms is provided with a lateral 
cuticular expansion as is shown in the Plate. 
Therediae are sausage-shaped striking objects, 1 *055 mm. in length and 0-150 mm. broad, and 
possess a muscular anterior sucker. They are granular in appearance and contain a number of 
cercariae in all stages. 
Plate I V, fig. 4. Distome cercaria from liver of Cleopatra bulimoides commonly found at el 
Marg and at Tel-el-Kebir. This is evidently the Cercaria distomatosa of Sonsino (1895). Rediae of 
this species are large and pigmented and form very prominent objects. The whole body appears 
granular, so occupied is it with cystogenous cells that it is only with difficulty that the finer points 
of internal structure can be made out. The ventral sucker (acetabulum) is muscular and pro¬ 
minent; the oral sucker is pitted round its margin with numerous small orifices, said by Looss to 
be the openings of many small ducts. The pharynx is continued into a muscular oesophageal 
bulb. Posterior to this, the two blind sacs of the intestinal canal branch off and run into the 
posterior end of the body. The excretory system is represented by two fine excretory ducts, 
which run from the ventral sucker and open into a vesicle at the posterior end of the body. The 
tail is blunt-endecl and does not move independently when the animal is alive. The extremity of 
the tail is rounded and is split for a short distance at its termination. The excretory canals open 
bilaterally on the anterior portion of the tail. 
Plate IV, fig. 5. Very active amphistome cercaria commonly found in Bullinus, Planorbis and 
once in Physa ; apparently not described by Looss. In the former snail from el Marg as well as 
from Tel-el-Kebir 31 % were found to be naturally infested. The body is full of cystogenous 
cells. The oral sucker is round with an oval termination. There is a large muscular pharynx 
which imparts a lobulated appearance to the anterior end of the body. This is bordered 
on one side by a string of glands, the canals of which run forwards and open laterally into 
the mouth. There is a straight oesophagus which branches into two ill-defined alimentary 
caeca anterior to the ventral sucker. The branches of the alimentary canal run far forward, and 
also for a short distance towards the posterior end of the body. The ventral sucker is large, promi¬ 
nent and muscular; on its anterior margin there opens a small duct derived from a collection of 
cells (probably genital) situated at its posterior border. The tail which is equal in length to the 
body, is long and tapering, and contains the efferent excretory canal. This cercaria is often found 
encysted in the liver of Bullinus and Planorbis, especially in the winter months (Plate IV, fig. 6). 
The redia and cercariae appear to resemble those described by Gilchrist who has worked out 
their life history in S. Africa and finds them to be the larval stages of Distomuw luteum in the intes¬ 
tine of the frog, but our measurements are considerably larger than his. 
This is possibly also the Cercaria pigmentata described by Sonsino. 
Plate IV, fig. 7. The redia is a very striking object. The infested livers in which they are found 
are of a bright orange colour, and the organ appears to be packed with them. Directly the shell 
of such an infested snail in incised, these prominent objects can be seen floating out of the breach. 
The body wall of the redia is studded with bright orange pigment granules. The length is about 
1-43 mm. There is a large anterior muscular sucker, and near the posterior end there is generally 
a lateral protrusion or appendix. The interior of the redial sac is filled with young and active cer¬ 
cariae. (Corresponds with that of Distomum luteum of Gilchrist.) 
For compiling this section the works of Cort on N. American Cercariae and 
of Faust on those of S. Africa have been consulted. 
