no Transactions of the Royal Canadian Institute, [vol. x. 



secretion is to be seen mostly opposite the glands and that the ductlets 

 have very thin but distinct walls. 



The uterine tube ("Uteringang") is usually considered to 

 commence immediately beyond the shell-glands, but in this species its 

 first portion so closely resembles the oviduct posterior to the latter that 

 the writer is inclined to place the region of demarcation somewhat 

 farther ahead. The circular muscles are better and more uniformly 

 developed, but what appears to be a decided augmentation in the number 

 of cilia is probably a continuation of the threads of material secreted by 

 the shell-glands. While the shell-gland region of the tube is directed 

 dorsally, anteriorly and generally to the right of the proglottis, the be- 

 ginning of the uterine tube makes a sharp turn and then passes backward 

 again or expands immediately into what might be called the second 

 division of the uterus, (Fig. 27). But this is not the second division of 

 the uterus according to Braun ('00), since he does not seem to recognize 

 in the "Uteringang", or uterine duct, two divisions, differing histolo- 

 gically; his second division is the uterus-sac, or "Uterushohle". In 

 this species it is in the form of a tube from 25 to 55/^ in diameter, the walls 

 of which are very thin and composed of a greatly extended epithelium 

 in which quite flattened nuclei appear at irregular intervals. Commen- 

 cing in the dorsal portion of the generative space, it courses forward in 

 the median line above the ovarian isthmus as a somewhat flattened spiral, 

 and in ripe proglottides often narrows down appreciably before entering 

 the uterus-sac tangentially. It is usually filled with young eggs, each 

 composed of many yolk-cells surrounding the "egg" (fertilized ovum) 

 or a small number of cells resulting from the first divisions, all enveloped 

 by a thin shell. In development the uterine duct is quite similar to the 

 other ducts, possessing in the earliest stages a syncitial epithelium devel- 

 oped from an axial strand of cells surrounded by another layer of several 

 cells in thickness, between which the basement membrane appears. 



The uterus-sac (" Uterushohle") arises in the same way from 

 the middle piece of the elongated anlage (Figs. 15 and 16), but is from 

 the outset distinctly separate from the uterine tube, the latter opening 

 into it dorsally and slightly ahead of its posterior end. Beneath this 

 opening the uterus-sac sends a diverticulum ventrally to the point where 

 the aperture will later appear, while the remainder of the organ is directed 

 forward in the median line some distance from the ventral surface, at 

 first as a narrow tube, later as an elongated sac (Fig. 10). At this stage 

 the wall of the uterus resembles, in general, that of the generative ducts. 

 It is composed of a syncitial epithelium with scattered nuclei, a well- 

 defined basement membrane, and outside of the latter a thin layer of 

 parenchymatous cells. All of these parts are thinned out considerably 



