28 ILLINOIS BIOLOGICAL MONOGRAPHS [308 



and possess a distinct nucleus and nucleolus. Their ducts could not be 

 traced to the ejaculatory duct but in many cases appear to lead to the 

 body wall near the margin of the genital sinus. In P. orhiculare, P. 

 opacum and P. megacotyle the cirrus sac is large and many nuclei are 

 present around the ejaculatory duct in the dorsal part of the sac. These 

 nuclei are large, with distinct nucleoli, and are surrounded by a deeply 

 staining area of granular or flaky substance, but no cell boundries could 

 be made out. 



Female Reproductive System. — In all known species but one, the 

 ovary is oval or comma shaped. In P. kachugae it is described by Stew- 

 art as a "curved sausage-shaped organ, the curve forming all but a com- 

 plete circle. The fundus is somewhat bulbous." This structure is 

 usually not more than one half the size of the testis, is situated a short 

 distance anterior to that organ, and in a given species may lie on either 

 side of the body. In all the species studied by the writer it is comma 

 shaped, the larger part is ventral, anterior, and lateral, and terminal 

 region is dorsal, posterior, and mesal. The ova are formed in the large 

 part and the ovary is divided into zones of growth, ova of increasing size 

 being present in each succeeding zone (Fig. 23). 



In the species described in this paper the viteUaria consist of masses 

 of foUicles occupying the dorsal and lateral regions of the body. Each 

 follicle consists of several cells which may vary much in appearance ; the 

 difference is due to the phase of secretory activity of the cells. In the 

 peripheral part of the gland the ceUs are usually small, with granular or 

 flaky protoplasm, a distinct nucleus and nucleolus; whereas those more 

 centrally located may be two or three times their size, the extra-nuclear 

 area being either vacuolated or filled with droplets of a yellow substance 

 (Figs. 19, 20). In some cells the secretory droplets are scattered uni- 

 formly thruout the cell. The presence of the material in the cells often 

 renders the body so opaque that the diverticula can not be seen. The 

 glandular secretion is apparently identical with that which forms the shell 

 of the egg, and this observation further confirms the statement of Gold- 

 schmidt (1909) that the so-called vitellaria secrete the shell of the egg. 

 Small ducts from the follicles (Fig. 11) unite and discharge into longi- 

 tudinal collecting ducts. These extend along the sides of the body, later- 

 al to the ceca and dorsal to the excretory tubules ; on either side of the 

 body there is an anterior and a posterior branch which unite just behind 

 the level of the ovary and the common duct discharges into the external 

 end of the vitello-vaginal canal. In P. hulliense, Johnston reports : ' ' The 

 lateral vaginal swellings are formed by a large number of papillae, per- 

 forated by fine canals, which after a very short course, open into a fairly 

 wide sperm reservoir, situated one on either side, just under the swell- 



