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Excretory System in Diyenea 
The Excretory System. 
In studying C. macrostoma I noticed numerous flame cells connected with 
the ultimate capillaries of the excretory system but was unable to work out 
the pattern on account of the large portion of the body occupied by the mature 
genital complex. In C. stephanocauda I was able to count eight main groups 
of collecting tubules on each side of the body and in some of these groups 
I made but sixteen flame cells to each group. Cercaria pekinensis has proved 
very favourable for working out the entire excretory system, not only in the 
mature cercaria but in typical stages of development and in the sporocyst as 
well. 
In the cercaria, the bladder at the posterior end of the body is compressed 
oval in shape with a dorsal pore. From the bladder a median trunk extends 
into the tail, dividing into two trunks somewhat anterior to the bifurcation 
of that organ. Each of these furcal branches runs to the end of the furcus 
where it opens to the exterior through a conspicuous pore. These caudal canals 
receive no lateral branches. They are drainage channels. Coming into the 
bladder from the anterior side is a single median canal which, when traced 
forward, divides about two-thirds the distance toward the acetabulum, the 
two branches of which run toward the oral sucker. They cross over the trans¬ 
verse portion of the corresponding coecum to the side of the oral sucker, in the 
mid-plane of which they turn back on themselves. As the secondary tubules 
they are recurrent the entire length of the body (see figures). 
In its reversed course the secondary tubule receives eight main (tertiary) 
branches. The first, third, fifth, and seventh of these provide for excretory 
drainage of the dorsal portion of the worm, while the alternate ones care for 
the ventral side. Each of these tertiary tubules, when traced a short distance 
distad, is found to bifurcate, each fork of which has a definite field of function. 
This fork in turn receives four tubules at a common centre, and, finally, each 
of these receives four capillaries, for each of which there is a single solenocyte 
or flame-cell. Where each group of four tubules unites in a common centre 
to form the tubule of next higher rank there is a definite polygonal enlarge¬ 
ment (see Fig. 6). This is, however, devoid of any concrement. 
The anterior four main branches (tertiary tubules) are preacetabular, the 
fifth is acetabular, the sixth and seventh are postacetabular but within the 
body, while the eighth provides for drainage of the tail. This latter has an 
interesting distribution. One ramus cares for the anterior half of the tail trunk 
(Fig. 1) while the other not only drains the remainder of the tail trunk, but also 
the flapper of the corresponding side. This elaborate provision for ridding the 
tail of excretory wastes is apparently unique among cercariae. The furco- 
cercariae have an analogous derivative from the posterior end of the body 
excretory system but there is no record of such an elaboration of the furcal 
branch in that group. The condition in the cystocercariae is probably explained 
by the extraordinary size of the tail common to all described species of the group. 
