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Digenetic Trematodes in Japan 
spherical shape. The oesophagus is longer than the prepharynx. The uneven- 
walled intestinal caeca take a winding course but do not branch. 
The excretory vesicle (PI. XXV, figs. 2 and 3) has most remarkable features. 
The pore opens on the dorsal surface near the posterior end, and is connected 
to the vesicle by a short canal. The vesicle has a structure similar to that of 
the Echinostomidae and the Psillostomidae. The median trunk of the vesicle 
runs straight forwards to the posterior border of the shell-gland, where it 
divides into two, each branch running along the lateral margin of the shell- 
gland. At the anterior margin of the gland they unite again into a single tube, 
which runs anteriorly. At the posterior end of the ventral sucker it is con¬ 
tinuous with the lacunae. The lacunae surround all the organs in the interior 
part—the two suckers, the prepharynx, the pharynx, the oesophagus and the 
terminal parts of both genital ducts. Four lateral branches arise on each side 
from the median trunk of the excretory vesicle, two in the region posterior to 
the shell-gland, one from each ramus alongside the shell-gland, and one 
anterior to the shell-glands. There is a closely set network of tubules under 
the cuticle of the entire body surface, which network is continuous with the 
vesicle, morphologically the former being a part of the vesicle. The network 
is more abundant ventrally and anteriorly. 
The vesicula seminalis is very long and takes a peculiar spiral course with 
three turns. At the anterior end of the third turn, it has a caecal appendage 
which runs posteriorly along the wall of the vesicula seminalis proper, and 
terminates near the posterior end of the latter. The walls of these two parts * 
are formed of epithelial cells. Externally they are surrounded by the long 
cirrus-pouch. Almost no space exists between the epithelium and the muscle 
layers of the cirrus-pouch. 
Anterior to the vesicula seminalis with its caecal sac, the cirrus-pouch runs 
directly forwards, passing along the dorsal surface of the ventral sucker. The 
epithelial cells at this part are elongated, and this portion was taken for the 
pars prostatica by Odhner 1 , but his conclusion may be doubted, since, as 
Odhner himself observes, it lacks the glandular cells around it. The real pars 
prostatica lies further forward, in the antero-dorsal region of the ventral 
sucker, and is delimited from the vesicula seminalis by a constriction. 
Numerous cells of the prostate glands lie around it. The pars prostatica is 
continued distally into a relatively long ductus ejaculatorius, which opens 
to the exterior. The wall of the ductus ejaculatorius is armed with stout 
spines. The wall of the cirrus-pouch is closely attached to the male duct, 
contrary to Odhner’s figure. 
This, with other species of Fasciolopsis, has no affinity with the genus 
Fasciola , as has been supposed by previous authors. The following differences 
are presented by the two genera: 
1. Fasciola infests the liver, while Fasciolopsis is found exclusively in the 
intestine. 
1 Odhner, l.c. 
