218 HENRY LESLIE OSBORN 



bounded by a thin non-cellular membrane, which encloses cells, 

 some of which, near the opening to the oviduct, are much larger 

 than the rest and are about to descend to the ootype. 



Oviduct and uterus. The oviduct passes inwardly from the 

 ovary and crosses to the opposite side of the body. Its wall is 

 composed of cubical epithelium and circular muscle fibers. At a 

 point near the ovary there is a small sack, the spermatic receptacle, 

 opening from the oviduct, this narrows dorsally to a tube — 

 Laurer's canal — runs to the dorsal surface of the body (fig. 4 G) , 

 and opens to the exterior. The epithelium of the oviducal wall is 

 replaced by cuticle in Laurer's canal, which becomes continuous 

 with that of the general surface of the body. The oviduct, at a 

 point a little farther to the left, meets the duct coming from the 

 yolk receptacle. There is no marked change in the diameter of 

 the oviduct at this point but it is surrounded by glandular cells 

 and doubtless serves as the ootype. The duct from this point 

 continues as the uterus, at first without change in diameter or 

 direction, next with several loops it recrosses toward the ovary, 

 then abru]:)tly bends again and runs a straight course, passes 

 externally to the anterior testis on its left side and runs forward 

 to enter a large sack which we may call the uterine sack. The 

 relation of the uterus to this sack is shown in fig. 3; it passes on its 

 dorsal wall for a distance and opens into it at about the center of 

 its dorsal surface. 



Uterine sack. The uterine sack is a large cavity capable of 

 considerable distension; in the case of mature worms it is filled 

 with eggs, as in fig. 1 ; in bass worms (fig. 2) the cavity is merely 

 a narrow slit. The form of the cavity in transverse section is 

 shown in fig. 4 D. It extends posteriorly to a point near the an- 

 terior border of the anterior testis ; anteriorly it does not reach the 

 ventral sucker. The outlet from the sack is located at its pos- 

 terior end. The histological structure of the wall of the sack is 

 quite unlike that of the uterus. In the latter there is a nucleated 

 epithelium and a coat of muscle fibers. In the sack the cavity 

 is lined with cuticle and there is a muscular coat consisting of cir- 

 cular and longitudinal fibers. In addition to these there is a 

 condensation of the parenchyma immediately surrounding the 

 uterus. The nuclei of these parenchyma cells lie in definite 



