398 
Digenetic Trematodes in Japan 
short oesophagus is recognisable postero-dorsal to the pharynx, which soon 
bifurcates into two intestinal caeca which turn laterally at right angles and 
for a certain distance show the same structure as the oesophagus, being lined 
by cuticle. This part corresponds to the crop of Distomum ampullaceum as de¬ 
scribed by von Buttel-Reepen 1 . Ultimately, each caecum widens into a sac-like 
portion, the glandular stomach (Driisenmagen of the German author), which 
has special epithelium; each cell of which bears long flagella-like appendages, 
longest in the posterior portion, and measuring 0-06 mm. in length. The 
epithelium of the glandular stomach is continuous with the ordinary epithe¬ 
lium of the intestine. Both the caeca turn posteriorly and run along the lateral 
body margins with characteristic windings, some five turns; and then termi¬ 
nate near the posterior end of the body, where each approaches to the median 
line. The first turn of the intestine occurs near the anterior margin of the 
ventral sucker; the remaining four turns are situated posterior to the ventral 
sucker. The first turn is most remarkable and in some cases the caeca almost 
meet in the median plane. 
The excretory pore opens at the posterior end of the body. The vesicle 
has the form of an exceedingly elongate Y, the stem and the two arms of 
which bend laterally several times. In young specimens the stem is straight 
or slightly curved, while in mature specimens it bends at right angles at the 
level of the ovary to the right and forms a spindle-shaped broad tube, which 
becomes abruptly narrower and runs laterally and anteriorly, with two or 
three transverse bends, in between the intestinal caeca. Its anterior end 
reaches the middle part of the body and divides into two arms at the median 
plane. Each arm has a similar course to the stem, and after bending once or 
twice it reaches the level of the testes and passes over the intestinal caeca, 
then runs anteriorly along the lateral body margin and reaches as far as the 
pharynx. At this place it continues into the collecting vessels. The winding 
course is more marked in large and mature specimens, while in younger 
examples the entire vesicle usually takes a slightly undulating course. 
Both the testes lie at the posterior lateral margin of the ventral sucker, 
immediately mesial to the intestinal caeca. Each of them has a somewhat 
*/ 
round shape, and is 0-7 mm. in diameter. From their antero-mesial border 
the vasa efferentia arise. They run antero-medially and unite at the antero- 
dorsal margin of the ventral sucker to form the vas deferens. The vas deferens 
widens slightly to form the tube-like vesicula seminalis. In the mature speci¬ 
men it bends 3-4 times, while in the younger form it remains straight. Anteriorly 
the vesicula seminalis enters into a cirrus-pouch-like muscular organ and 
continues into the ductus ejaculatorius. Both structures make several wind¬ 
ings. The distal end of the ductus ejaculatorius is united with the vagina and 
forms the ductus hermaphroditicus. The cirrus-pouch-like organ is situated 
midway between the two suckers; it has an elliptical shape and measures 
1 Buttel-Reepen, H. von (1902). Zur Kenntniss der Gruppe des Distomum, clavatum, etc. 
Zool. Jahrb. Ab. Syst. etc. xvii. 
