150 HALOMENIA GRAVIDA. 



wall. Opposite the anterior end of the shell gland the ventral sinus enlarges, 

 and divides, each branch passing dorsally, then posteriorly along the sides of 

 the rectum. Upon arriving at the bases of the cloacal folds they break up into 

 numerous branches each of which enters a fold, passes through it to the neighbor- 

 hood of the body wall whereupon it makes its way forward to enter the heart. 



In appearance, position, and extent the gonad is nowise peculiar. The 

 reproductive elements in the anterior third are wholly male, and in the neigh- 

 borhood of the pericardium also are great accumulations of spermatozoa while 

 in an intermediate position the great ova, 0.26 mm. in diameter, are most con- 

 spicuous objects. Correlated with their great size the ducts leading into the 

 pericardial cavity are of unusually large calibre, being 0.175 mm. in their greatest 

 diameter. The lining cells are low and heavily ciliated. 



From the postero-lateral borders of the pericardiimi the coelomoducts 

 arise, extend outward and forward and enlarging somewhat unite with the shell 

 gland (Plate 3, fig. 5). In the early part of their course the cells, like those 

 lining the pericardium, are low, but more outwardly they become more columnar 

 and form longitudinal ridges of considerable height. At the anterior limits 

 of the shell gland is the opening of the seminal receptacle, which is a simple 

 unbranched tube, empty in the present instance, and is provided with a high 

 ridge extending, like a typhlosole, throughout its length. The cells composing 

 this latter organ are slender, triangular elements which when combined form a 

 fan-shaped structure in cross section. A heavy layer of circular muscles en- 

 sheaths the seminal receptacle, and a few radiating bands extend from it chiefly 

 to the body wall. 



As usual the shell gland is U-shaped and in the present example is fully 

 functional. In the neighborhood of the seminal receptacle its cells are rather 

 low and their secretion small in amount, but half way down toward the mid line 

 they become greatly elongated, and distally contain a finely granular secretion 

 which escapes in large quantities into the lumen of the duct. Upon the fusion 

 of these tubes in the mid line the dorsal wall of the undivided section is composed 

 of cells, also high in form, which during the early stages of glandular activity 

 are filled with a darkly staining vacuolated secretion (Plate 15, fig. 8 and Plate 22, 

 fig. 6). This condition of affairs, mucous cells dorsal and albumen forming 

 elements below, continues to the single m.edian opening in the cloacal cavity. 



As noted previously this species broods its young. The eggs, about two 

 dozen in number, have been retained in spaces between the great branchial 

 folds in the cloacal wall and evidently they have come down at different periods 



