Notes on the morphology of the Tunicata. 523 



animals is more or less filled with disintegrating cells derived from 

 the endothelium of the gland. Posteriorly the duct narrows again 

 and pushes back and to the right side soon bending sharply to return 

 and fuse with the ganglion a little to the right of its posterior end. 

 The recurved portion of the duct is a solid mass of cells continuous 

 with the cells of the ganglion (Fig. 40 /"; cf. Plate 35, Fig. 18 /", 

 which shows a very similar condition in Cynthia cameo). 



A small rapheal nerve arises from the ventral surface of the 

 ganglion, near the posterior end and a little to the right of the 

 median line (Fig. 39). At its upper end it contains a few ganglion 

 cells; further ventralward I cannot distinguish any cells connected 

 with its fibres. 



Botrylloides gascoi Della Valle. 

 Plate 37, Fig. 41. 

 The conditions here so closely resemble those in Botryllus gouldi, 

 that reference to Fig. 41 is sufficient without any further description. 



Poly cy dus renieri Lamk. 

 Plate 37, Fig. 42—44. 



In Folycydus as in Botryllus and Botrylloides the simple funnel- 

 shaped dorsal tubercle leads directly into a spindle-shaped chamber 

 whose lumen contains cells which are disintegrating to form the 

 secretion of the gland (Fig. 43). The duct which leads back from 

 this chamber, over the ganglion, is very delicate and so slender as 

 to show no lumen. It connects behind with a solid mass of peculiar 

 cells (gl" in Fig. 43) in each of which there is an irregular darkly 

 staining^) body lying beside the nucleus (Fig. 44). At one point 

 (not shown in the figures) the membrane that invests this group of 

 cells is wanting, and they are in contact with the cells of the ganglion. 

 I have been unable to determine what is the nature of these cells. 

 I shall soon refer to them again in connection with a comparison of 

 all the compound Ascidians described. Nothing of the sort was seen 

 in Botryllus or Botrylloides. 



A rapheal nerve with occasional gland cells can be seen in the 

 usual position, the only peculiarity being that its point of origin is 

 slightly in front of the mid-ventral point of the ganglion instead of 

 far back as is usual (Fig. 43). 



1) With Delafield's haematoxylin. 



