monogenetic trematodes are faulty and appear as a result of inattentive 

 study of the copulatory organs of Capsalidae in which the penis really re- 

 sembles a cirrus but nevertheless, as will be seen later on, is fashioned 

 along the type common for Monogenoidea (see however, page 476 ). Gener- 

 ally the corresponding schemes of structures of copulatory organs of 

 Rhabdocoela can be applied wholly also to such monogenetic trematodes. 



a02n 



Fig. 92. Anclyodiscoides magnus Bychowsky and Nagibina, cross section 

 in the region of the prostate glands. 



In a more simple (from a morphological point of view) case the 

 ductus ejaculatorius , representing a slightly more muscular direct ex- 

 tension of the seminal duct, opens directly into the sex atrium; at the same 

 time, the role of the copulatory organ can be played by various formations 

 not connected with these ducts and related to the sex atrium as has been 

 indicated above. Thus, for instance, similar relations are characteristic 

 for a number of Microcotylidae. Generally in isolated cases the sperm which 

 falls into the sex atrium is ejected by its contraction without any special 

 copulatory contrivances. A small muscular sucker at the end of the seminal 

 ejaculatory canal (ductus ejaculatorius) appears as the most primitive but 

 already isolated copulatory organ, (for instance among Microcotyle caudata p. 63 

 Goto, Fig. 93). This sucker is separated from the surrounding tissues by 

 a special fold and can be extended into the sex atrium and beyond its limits 

 through the sex pore. Morphologically it is little delineated from the sur- 

 rounding tissue but has a more powerfully developed musculature, circular 

 as well as longitudinal, further we can observe more and more the growth 

 of the penis and also its giadual delineation from the surrounding tissues. 

 All in ill in the most complicated case (Benedenia, Fig. 196) the penis is 

 completely separated by a special membrane, its upper part really lies in 

 a spherical pocket emanating from the sex atrium and the lower part is 

 usually spherical and inflated--or flask-shaped, in the thickness of the 

 parenchynna. The internal structure of such a penis is sufficiently complex. 

 The ductus eiaculatorius which passes through its center usually forms a 

 more or less well-developed interior seminal vesicle (vesicula seminalls 



58 



