1911] Watson: The Genus Gyrocotyle. 397 



(oot.) then becomes the uterus, passing to the left of the recep- 

 taculum seminis and around it to the ventral surface, across the 

 ventral surface and forward, at once increasing in size. The first 

 two or three coils of the uterus, as above described,_may be 

 regarded as an ootype. They are surrounded by shell-glands, and 

 within them the compound eggs are formed. In the dorsal 

 (proximal) part of the first coil, and to the left of the receptac- 

 ulum seminis, the yolk-cells are seen to be aggregating about 

 a single ovum and the uterus is full of droplets of a yellow homo- 

 geneous material, which form a coating around the combined 

 ovum and yolk-cells. The uterus contains fully formed eggs in 

 the convolutions anterior to the receptaculum seminis. It winds 

 back and forth across the median third of the body through 

 from fifteen to twenty convolutions, the duct increasing steadily 

 in size, ending finally in a greatly dilated pouch which opens 

 to the exterior by a large aperture on the dorsal surface in the 

 median line posterior to the opening of penis and vagina. 



The uterus is lined at its inception and throughout its course 

 by a thin fibrillated layer, increasing in thickness from the pos- 

 terior coils forward. This layer is covered with fine cilia, in 

 the first five or six coils of the uterus. These cilia are connected 

 with scattered nuclei beneath the cuticula, by means of delicate 

 fibrils strongly suggesting those figured by Lonnberg (1891) 

 for the cilia lining the excretory canals. Their direction is in 

 general at right angles to the course of the uterus. These fibres 

 lie in a nucleated meshwork of parenchymal fibres, which pass 

 indistinguishably into the cuticular lining of the duct. Further 

 forward, the nucleated circular muscle fibres disappear, and a 

 typical subcuticular layer of cells appears coincidently with the 

 appearance of a typical cuticular musculature, suggesting very 

 strongly a structural connection between subcuticular and cuti- 

 cular musculature. 



The shell-glands (sh. gl., pi. 39, fig. 42) are an aggregation of 

 large cells, with characteristic nuclei, lying close to the recepta- 

 culum seminis on its dorsal, ventral, and posterior surfaces. 

 This relation to the receptaculum seminis is of course due to the 

 fact that the earliest convolutions of the uterus lie on these sur- 

 faces of the receptaculum. The greatest mass of cells lies to the 



