Boyal Microscopical Society. 215 



neural wall of the two parts is continuous, without any mark of 

 transition. 



The left lobe is also Hned by flattened cells, which form a 

 tesselated or pavement epithelium. These cells are polygonal in 

 shape, like the flat cells of the right lobe, but differ in each, con- 

 taining a clear round spot resembling a nucleus, the rest of the cell 

 contents being coarsely granular. The shape of these cells varies 

 in different specimens; in some the prevalent form is elongated, 

 pointed at one end and broad at the other, at which part the clear 

 spot is present; but in the greater number they are irregularly 

 polygonal, with the clear spot at or near the centre. 



A profile view of this part of the stomach shows that these 

 cells are slightly elevated above the level of the walls of this viscus, 

 so that the separation between them is formed by a series of 

 channels, which are indicated in a fi'ont view by clear lines of 

 demarcation. 



The colour of these cells is generally darker than in those of the 

 right lobe and of the intestine ; in a few specimens they were of an 

 orange tint, and in one only of a deep purple, the second part of 

 the intestine being of a lighter shade of the same colour. 



The pylorus is placed at the posterior wall of the left lobe, 

 close to the angle between it and the right lobe, so that the greater 

 part of this left lobe forms a cul de sac, which perhaps might be 

 considered as a rudimentary liver; if so, this animal presents 

 another point of resemblance to the amphioxus, inasmuch as it pos- 

 sesses a hver constructed in the form of a blind sac. 



The last-mentioned organ being considered as belonging to the 

 stomach, there only remain two chambers and the rectum as form- 

 ing the intestine ; the first and second of these (which I termed 

 second and third portions of the intestine in my last paper) are oval 

 chambers, which present no apertures except when the fasces are 

 passing; both of them are lined by an epithehiun formed of flat- 

 tened cells, like that of the left lobe of the stomach ; the cells of 

 this epithelimn differ, however, in not containing a clear spot in 

 the centre, or when this is present, as happens in a few cases, 

 it is so indistinct that it is easily overlooked and soon disappears 

 entirely. 



The rectum continues forwards from the second chamber and 

 ends in the anus, which is situated on a distinct papilla in front of 

 the insertion of the tail. This part of the intestine is lined by 

 round cells which project into the cavity. 



That part of the right lobe of the stomach which is lined by 

 flattened epithelium is ciliated, as also is the whole of the left lobe, 

 together with all the intestinal canal except the rectum. 



Nervous System. — The nervous system of these animals is very 

 highly developed, more so even than in their aUies the ascidia. 



