152 TOKIO KABURAKI 
its ventral side the common duct formed by union of the lateral 
uterine ducts, proceeds backwards as a narrow tube, which 
opens into the median posterior branch of the intestine. To 
me, such frequent occurrence of the genito-intestinal connexion 
appears in favour of the view that this is certainly not abnormal. 
The discovery of the canal m question helps to connect more 
definitely the seminal receptacle of some Polyclads and Triclads 
with parts that occur in other Platodes. It cannot well be 
doubted, it seems to me, that this canal corresponds to the 
similarly named canal in the Heterocotylean Trematodes. 
In this group the duct passes from the oviduct, opposite the 
opening of the yolk-duct, to the right limb of the intestine. 
Now let us proceed to review the arrangement of the terminal 
part of the female genital organ, which is of interest from the 
morphological point of view. The vaginal canal, after almost 
invariably receiving the unpaired common uterine duct, either 
ends blindly, as in Stylochus and some others, or proceeds 
backwards to join the seminal receptacle, as in some Triclads, 
which is unpaired in most, but paired in some, genera (Disco - 
celis, Woodworthia, Shelfordia, and Diploso- 
lenia). This agrees closely with the condition of the duct 
found in the Aspidocotylean Trematodes, which are provided 
with a duet, arising from the oviduct, near or opposite the 
opening of the yolk-duct and leading to the vitelline receptacle. 
On some oceasions the dorsal passage of the vagina, instead of 
swelling into a receptacle and opening into one of the intestinal 
coeca, pursues a course backwards, finally to open to the 
exterior at a certain point of the surface of the body. In 
Cryptophallus and Bergendalia it proceeds back- 
wards and downwards, describing an arched course, and finally 
opens into the female atrium closely behind the vaginal aperture 
and just inside the external female aperture. In the case of 
Trigonoporus, Copidoplana, and Tripylocelis 
the duct terminates behind on the ventral surface of the body by 
the second female aperture. In Polyporus the second female 
opening lies near the hind end of the body, whilein Laidlawia 
it occurs, occupying a position on the dorsal, but not on the 
