ASPIDOGASTER CONCHICOLA. 



173 



whence an elongated pyriform sac, which constitutes the rest 

 of the alimentary canal, is continued. This occupies a great 

 part of the body, and extends nearly to its' posterior end ; but 

 there is no anus. A contractile vacuole placed at the hinder 

 extremity of the body opens outward by a small pore (Fig. 

 41, «), and gives off two lateral contractile non-ciliated canals 

 (6), which pass to the anterior end of the ventral sucker and 

 there end blindly ; but before reaching this termination each 

 gives off a non-contractile ciliated vessel (Fig. 41, c), which, 

 on arriving at the pharynx, turns backward and ramifies 

 through the body. The cilia diminish toward the extremi- 

 ties of these vessels, the terminations of the corresponding 

 canals in the Hotifera being, on the contrary, richly ciliated. 

 No nerves have as yet been found in Aspidogaster. 



Fig. 40.— Aspidogaster conchicola. — A } arrangement of the alimentary and reproduc- 

 tive organs ; profile of the animal in outline : a, mouth ; &, muscular pharynx ; c, 

 stomach ; d, germarium ; e, internal vas deferens ; /, common vitellarian duct ; 

 g, vitellarium ; ^,one of its ducts ; i, k, oviduct ; I, uterus; m, testis ; o, vagina; 

 /?, penis, continuous posteriorly with the external vas deferens ; jB, one of the 

 lateral contractile vessels ; C, ramifications of the ciliated vessels. 



As in most Trematoda, the genitalia (Figs. 40 and 42) 

 form a large part of the viscera, and the structure of the com- 

 plex hermaphrodite apparatus is in some respects so peculiar 

 that it is needful to describe it in detail. It consists of — 

 1. The germarium. 2. The vitellarium. 3. The oviduct. 

 4. The uterus and vagina. 5. The common vestibule. 6. The 

 testis. 7. The vasa deferentia, internal and external. 8. The 

 penis and its sac. The ovary (d) is the anterior of two round- 



