30 ILLINOIS BIOLOGICAL MONOGRAPHS [30 



the vagina may disappear or is very thin and difficult to determine. In 

 Proteocephalus macrocephalus and a few other species the vagina is 

 ciliated throughout almost its entire length. Just after the long tube of 

 the vagina enters the interovarial space or in some species just anterior 

 to the mid-piece of the ovary the vagina broadens out slightly and this 

 is followed by a sudden diminution in diameter and a change in the 

 histological structure of the tube. This broadened part is known as the 

 receptaculum seminis, the presence of which Riggenbach (1896) denied. 

 Since it is somewhat different histologically and also since it serves the 

 function of a receptaculum it may well be called a receptaculum. The 

 writer has already presented his views on this matter in his description 

 of the organ in Ophiotaenia filaroides (La Rue 1909). Since that time 

 he has observed the structure in several other species and sees no reason 

 for changing his view. From the receptaculum seminis to its junction 

 with the oviduct the vagina may be spoken of as the lower vagina. This 

 part is characterized by its small diameter, thick muscular walls and 

 rich investment of gland cells. It is not ciliated in any part of its course 

 in any species studied by the writer. The lower vagina frequently de- 

 scribes a long loop or several coils within the interovarial space. 



The ovary as in other Tetraphyllideans is situated in the posterior 

 end of the proglottid, is bilobed and the lobes are connected by a mid- 

 piece. The lobes are thin, alate or club-shaped, branched or made up of 

 several slender blind pouches, or the branches may anastomose. Rarely 

 or never is the lobe a solid mass but it seems to be made up of more or 

 less anastomosing branches or tubes. The whole ovary is closely in- 

 vested with a thin membrane. The organs of the interovarial region are 

 taken up as nearly as possible in the order of occurrence, beginning with 

 the oocapt. The general relations of these structures are shown in draw- 

 ings which have been reproduced (Figs. 99, 104). The oocapt is a funnel- 

 shaped muscular organ attached to the mid-piece of the ovary and pres- 

 ent in all the species examined. It is made up of circular and longitudi- 

 nal muscle fibers and is surrounded by scattered gland cells. In action 

 it is a gulping organ which by its rhythmic contractions forces the ova 

 down the oviduct. The oviduct is a thick-walled tube made up of epi- 

 thelial cells and around these are circular and longitudinal muscle fibers. 

 Some gland cells are scattered along its entire length and it is lined with 

 numerous long cilia. In its course from the oocapt it describes one or 

 more loops or coils and then it receives the lower vagina which here pours 

 the sperms upon the ova. The oviduct from this point on should be 

 known as a fertilization passage. This passage, which is relatively short, 

 discharges into the ootype. However, just before entering into the 

 ootype the oviduct receives the unpaired vitelline duct which pours out 



