349] PSEUDOFHYLLIDEA FROM FISHES— COOPER 61 



the medulla just ahead of the isthmus where it is formed by the union of a right 

 and left duct as in C. truncatus. Thruout its dorsoventral course the vitelline 

 duct is expanded to form a viteUine reservoir which may reach a diameter of 

 40m- Immediately outside of the longitudinal muscles the vitelline follicles 

 form a compact layer from 70 to 90^ in thickness (152ju in C. truncatus), con- 

 tinuous from proglottis to proglottis and broken only iimnediately around the 

 reproductive openings. They range in diameter from 30 to 85ju, while their 

 number in transverse sections varies from 20 to 35, 45 being given by Kraemer. 

 From its point of origm to a short distance beyond the entrance of the vitelline 

 duct, the oviduct is lined with epithelial cells showing prominent nuclei but 

 indistinct boundaries, the whole being thus of the nature of a syncitium.. But 

 soon this epithehum becomes modified in that, as the duct continues with a 

 few coils to the opposite side of the proglottis, its cytoplasmic portion gets quite 

 thin, while the nuclei remain more nearly the same size relatively speaking. 

 Then as it further enlarges dorsally the oviduct is surrounded by an incon- 

 spicuous shell-gland. However, no shell-gland such as described by Kraemer 

 was found in this species. Beyond the ootype the duct, in reaUty the beginning 

 of the uterus, is enveloped for a considerable distance by numerous unicellular 

 glands which at first sight appear to constitute a second and voluminous shell- 

 gland. This mass of glandular tissue is so extensive in fact, that it occupies in 

 frontal sections about one-half of the posterior half of the uterine rosette (Fig. 

 93). The individual cells, of which it is composed, are comparatively short, 

 stout and well defined, their nuclei being large and the nucleoplasm clear like 

 the cytoplasm. Most of the coils of this tubular uterus, which may attain a 

 diameter of 0.10mm. or more when filled with eggs (0.038mm. in C. truncatus), 

 are situated just behind the cirrus-sac. Before reaching the opening, the 

 position of which has been stated above, the tube narrows down quickly. 

 Thruout its course it is lined with a much attenuated epithelium, the nuclei of 

 which, however, stand out prominently towards the lumen. In this species 

 there is no muscular sac surrounding the uterus, as described and figured 

 by Kraemer. 



The largest eggs in the uterus not in a collapsed state were found to be 

 ellipsoidal in shape and 40 by 30fi in size. Linton gave their size when pre- 

 served in acetic acid as 50 by 32ijl; while the measurements for C. truncatus 

 have been given as 95 by 76/i (Kraemer) and 44 to 51 by 33 to 36^ (Liihe, 1910). 

 Since most of the eggs seen in the uteri of the sections made were quite young, 

 many of them not having gone thru the first cleavage as yet, the writer is of 

 the opinion that the size of the egg of this species is probably about the same 

 as that given by Liihe for C. truncatus in Europe. 



Altho evidently no one has as yet studied the early stages in the develop- 

 ment of C. truncatus, Wolf (1906) discovered that the intermediate host is 

 Gammarus pulex and that the transfer to the final hosts is a direct one. As re- 

 gards the life history of C. americanus the writer can only say that he is of the 

 opinion that Pontoporeia hoyi (Stimpson Mss.) may later be found to be the 

 intermediate host at least in Georgian Bay, Lake Huron, where it constitutes 

 practically the only food of Coregonus clupeiformis. 



