INCISUEA (sCISSURELLA) LYTTELTONENSTS. 15 



I may amplify this account by saying that the right kidney 

 of Incisura is a structure of considerable size and importance 

 which may be described as consisting of three lobes. The 

 most anterior lobe, varies considerably in size : it lies in the 

 roof of the mantle-cavity to the right of the rectum (figs. 4 

 and 10) and somewhat posterior to the left kidne3\ It opens 

 by a simple slit-shaped apertui-e (fig. 10, h.r.o.) into the mantle- 

 cavity, and a few sections further back than the one figured 

 it extends over to the right, forming a considerable projection 

 into the posterior part of the mantle-cavity. Posteriorly it 

 gives oif two lobes. That on the right runs nearly vertically 

 downwards close to the right side of the vertical loop of the 

 intestine and passes inward among the viscera, curving round 

 the floor of the middle part of the stomach and eventually 

 coming in contact with the gonad, but it does not effect any 

 communication with this organ. The left posterior lobe 

 passes below the rectum and overlies the anterior c^cal end 

 of the stomach. 



The exci-etory cells of the depuratory kidney of Gastropods 

 are notoriously difficult to preserve, and in my specimens 

 were too much macerated to admit of a satisfactory study of 

 their structure. For the same reason I have been unable to 

 satisfy myself completely as to the relations of the right reno- 

 pericardial canal. For some time I was uncertain whether 

 any communication existed between the right kidney and the 

 pericardium, but the series of sections represented in figs. 22 

 to 26 demonstrate that this connection does exist, and that, as 

 in Trochus, there is an intimate connection between the right 

 reno-pericardial canal and the gonaduct. In fig. 22 the ovi- 

 duct {od.) is seen lying close to the right side of the anterior 

 lobe of the kidney, and from it a narrow canal leads upwards 

 and inwards. The histological features of this canal are not 

 well preserved in any of my specimens, but its walls appear 

 to be formed by cubical epithelial cells containing small, deeply 

 staining nuclei, whose characters as shown in figs. 22 and 23, 

 suggest that they bear cilia and form a ciliated funnel open- 

 ing into the pericardium. The connection between the canal 



