388 
Digenetic Trematodes in Japan 
The cirrus-pouch lies in the region antero-dorsal to the ventral sucker and 
opens slightly posterior to the place of bifurcation of the intestine. The pouch 
contains a tubular, winding vesicula seminalis, a short pars prostatica and 
a long ductus ejaculatorius. The latter may be evaginated exteriorly as the 
penis. 
The ovary lies posterior to the left testis, near the median line. It has an 
ellipsoid or slightly lobate form, 0*2 mm. in diameter. The oviduct rises at 
the postero-lateral margin of the ovary. The receptaculum seminis is a small 
round sac, 0-06 mm. in diameter. Laurer’s canal is slender and ends blindly 
near the dorsal surface. The vitellaria lie exteriorly to the intestine, extending 
longitudinally in the middle third of the body length. The uterus lies between 
the intestinal caeca and runs posteriorly. As it approaches the posterior end 
of the body it turns forwards and passing between the testes, and the ventral 
sucker, the uterus is continued to the vagina, which opens to the exterior, 
alongside the male genital pore. Along the course of the uterus numerous 
smaller loops are met with. The uterus occupies almost the entire space 
between the ovary and the intestinal caeca. 
The eggs are numerous; they measure 0*042-0-045 mm. long by 0*025 mm. 
wide and each has a relatively thick elliptical shell. 
Here it may be desirable to state the probable affinities of this and other 
species. There are seven genera of mammalian Dicrocoeliinae: Athesmia , 
Lyperosomum, Brodenia, Eurytrema, Platynosomum , Paradistomum , and 
Dicrocoelium. Of these, three genera ( Athesmia, Lyperosomum and Brodenia ) 
may readily be distinguished, one from another, by the following charac¬ 
teristics : 
1. In Athesmia, the vitellaria are absent on one side. 
2. In Lyperosomum the body is elongate, and the testes are situated 
mesially one behind the other. 
3. Brodenia has a remarkable serration in the middle part of the bodv. 
In the remaining four genera, the differential characters are as follows: 
1. In Eurytrema, the body is broad and the testes lie side by side at the 
same level. 
2. In Platynosomum, the body is lancet-shaped and the widest portion is 
situated in the middle of the body. Both the testes and the ovary are also 
found in the widest part. The former are disposed symmetrically. 
3. Dicrocoelium is lancet-shaped, and the widest portion is situated rather 
posteriorly. One of the testes lies a little anterior to the other. 
4. Paradistomum is oval in outline, broadest near the posterior end, and 
the testes lie side by side. 
All the above four genera have a smooth cuticle, excepting Dicrocoelium 
concinnum Braun, whose cuticle is armed with spines. Looss considers this 
species as belonging to a new genus, because of the spined cuticle. 
In some specimens of Dicrocoelium macaci the widest portion is at the 
