No. 2.] STRUCTURE OF TWO FISH TAPEWORMS. 351 



passes down the median line of the proglottis near the ventral 

 side, forming a number of turns and coils (PI. XVI, Fig. 9). The 

 inner portion is slightly larger in diameter. The mass of the 

 coils is just anterior to the ovaries, differing in this respect from 

 other described species, in all of which the coils are further pos- 

 terior. The end of this portion of the vagina is marked by a 

 minute receptaculum seminis (PI. XVI, Fig. 10, r.sem). From 

 this region the vagina continues as a heavy-walled duct of 

 decreased diameter, supplied with a layer of gland cells, and 

 more heavily ciliated than before. This heavy-walled portion 

 of the vagina by a series of curves reaches nearly to the poste- 

 rior end of the proglottis, and there unites with the oviduct (PL 

 XVI, Fig, 10). Further investigation will probably show that 

 in Proteocephalus the vagina usually opens into the oviduct and 

 not into the ootype. Such is undoubtedly the case in P.fili- 

 collis, although Kraemer ('92) describes the vagina as entering 

 the ootype. P. abscissa and P. fossata Riggenbach ('96) both 

 show the former condition. 



The presence of spermatozoa can be plainly seen in most 

 specimens ; in some cases the vaginal chamber near the 

 sphincter will be packed with them ; other specimens show 

 this portion with walls collapsed and lumen empty, while the 

 coils near the ovary are distended. 



The ovary lies in the posterior end of the proglottis, close to 

 the ventral surface. It is a bi-lobed organ, each half extending 

 from the median line, where they are joined together, to the 

 vitellarian glands on the side. Each half is somewhat retort- 

 shaped, with the small end inward, whether viewed in frontal 

 or transverse section (PI, XVI, Fig, 9, ^,), 



The ovary is surrounded by a delicate epithelial layer ; the 

 ova are closely packed together, those at the extreme outer end 

 being clearly less developed than those toward the center. The 

 ova are .01 mm. in diameter, with a nucleus measuring .005 

 mm., and containing a very prominent nucleolus. The ovary 

 is penetrated by a few delicate sheets of tissue, which divide 

 the eggs into irregular groups, extending from dorsal to ventral 

 surface, but all open at the inner end, thus leaving the passage 

 free into the oviduct. The two lateral wings of the ovary are 



