110 ILLINOIS BIOLOGICAL MONOGRAPHS 398] 



size. In transections it is seen to be "concave towards the surface bearing 

 the genital openings" owing to the fact that the ventrally situated isthmus is 

 quite narrow and thick and consequently not well separated from the lobular 

 wings which extend thruout the whole dorsoventral diameter of the medulla 

 and also somewhat enfold the former posteriorly in the median Une. Ova from 

 the isthmus are ISju in diameter, while their nuclei and nucleoli average, re- 

 spectively, 7 and 3fx. The oocapt is quite muscular, and 35m in diameter. The 

 oviduct proceeds dorsally for a short distance only before it is joined by the 

 vagina at a vestibule into which the oviduct itself opens (Fig. 105) by a narrow 

 slit much as in C. crasskeps. The wall of the duct is composed of an epithelium, 

 in which no cell-boundaries could be made out, but provided with ciUa directed 

 towards the uterus. The oviduct continues dorsally for a short distance with 

 the same structure and diameter, nam.ely ISju, to take on the vitelline duct 

 dorsal to the anterior edge of the isthmus. The vitelUne follicles are arranged 

 in the cortical parenchyma in two lateral fields (Fig. 84) which are, however, 

 slightly connected with each other dorsally and ventrally in the median Kne 

 by a few isolated follicles. No large follicle such as that described by Matz in 

 the neighborhood of the ovary was seen in the material studied. The follicles 

 vary somewhat in size, but average 35 to 55/i in diameter, are very closely 

 crowded together — so as to obscure in toto preparations the testes beneath 

 them — and continuous from proglottis to proglottis. The latter fact makes it 

 difficult, if not somewhat umiecessary, to state the number for each genital 

 segment, but using Matz's m.ethod of multiplying the average number seen 

 in transections by that seen in sagittal sections (here the average of several 

 segments was taken), the number varies from 350 to 540, or 440 on the average. 

 Matz gave 490 as the number. Two main vitelUne ducts proceed from opposite 

 sides of the genital segment and unite in the antero -dorsal portion of the genera- 

 tive space to form a very short common duct which from the amount of yolk 

 it usually contains may act as a vitelline reservoir, altho the same function is 

 shared even to a larger degree by the much coiled and distended proximal 

 portions of the separate ducts. A few cases were met with in which small 

 ducts laden with yolk came from foUicles clearly belonging to the genital seg- 

 ment following. This condition is, however, not surprising in view of the con- 

 tinuous arrangement of the follicles themselves. The diameter of the common 

 duct at its point of union with the oviduct is about S/x. The very voluminous 

 shell-gland is situated dorsal to the ovarian isthmus close behind the cirrus-sac, 

 with a depth of 85m and width of 115)u. The uterine duct is quite capacious 

 since it is composed of many coils extending thruout the whole depth of the 

 medulla immediately ahead of the ovary. Proximally it is lined with a syncitial 

 epithelium which distaUy becomes much attenuated. While it is usually 

 situated in the median Kne it may alternate from right to left as a whole accord- 

 ing as the vas deferens does so on the opposite side of the proglottis, the uterus- 

 sac in such cases remaining in the median line. As above noted, the uterus-sacs 

 were called " ovaries " by the early writers. They were seen thru the body wall 

 to be filled with the characteristic dark brown eggs forming dark patches or 



