j-Q HALOMKNIA GRAVIDA. 



wall. OiMH.sito tin- anteri..r en<l of tho sh.-ll sland the ventral sinus enlarses, 

 a.ul (livid.^s, cnrl. branch passins dorsally, then posteriorly along the sides of 

 the reclmn. Upon arriving at Ihe leases of the eloaeal f.^lds they break up into 

 numerous branchc-s eacli of which enters a iohl, passes through it to the neighbor- 

 hood of tlie body wall whereuix).! it makes its way forward to enter the heart. 



In api)earance, position, and extent the gonad is nowise peculiar. The 

 reproductive elem<>nts in the anterior third are wholly male, an.l in the neigh- 

 borhood of the iKM-icardium also are great accumulations of spermatozoa while 

 in an intermediate position the great ova, ().2(i nun. 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 ciliatetl. 



From the postero-latcral borders of the pericardium the coelomotlucts 

 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 l^ecome more colunnuu- 

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

 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 ami in the present exam]ile is fully 

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

 low and their secretion snuill 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 ciuantities into the lumen of the duct. Upon the fusion 

 of these tubes in the mid line the tlorsal 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 an)umen forming 

 elemcTits below, continues to the single median opening in the cloacal cavity. 



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

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

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



