REPORT ON THE TUNICATA. 307 



The branchial sac is notable on account of the large size 

 of the stigmata compared with that of the interstigmatic 

 vessels (PI. V, fig. 7). The narrow horizontal membranes 

 which divide the meshes transversely, in some places inter- 

 rupt the stigmata (see PI. V, fig. 8). On the right side of 

 the branchial sac, there are four longitudinal folds, while on 

 the left side three only are present. The internal longi- 

 tudinal bars are strong (PL V, fig. 7, id). In some places 

 on the folds they are corrugated. 



The small size of the tentacles (see PL V, fig. 5), is 

 remarkable, and forms one of the most noteworthy charac- 

 teristics of the species. There are betv/een twenty and thirty 

 altogether. They are placed far apart, and the two sizes 

 alternate with regularity. 



The oesophagus is short (PL V, fig. 6, ce). It runs 

 ventrally and posteriorly to open into the stomach, which 

 has its long axis directed dorso-ventrally. The intestine 

 runs at first ventrally and then turns anteriorly, then dorsally 

 so as to form a narrow loop. After running along the 

 anterior edge of the stomach, it turns forward to become the 

 long straight rectum, which terminates close to the atrial 

 aperture. The anus (PL V, fig. 6, a) has a white thickened 

 edge. The polycarps are not numerous. They occur on 

 both sides of the body, and are ovate, and of a pale yellow 

 colour. Each polycarp is hermaphrodite. 



Family. — Molgulid^. 



Molgula occulta, Kupffer. (PL VI, fig. 6.) 

 A large number of specimens of the genus Molgula were 

 dredged during August, off the south end of the Isle of Man, 

 chiefly between Port Erin and the Calf, and off Spanish 

 Head, from depths of ten to twenty fathoms. They differ 

 considerably in external appearance, some being coated with 

 small stones and fragments of Nullipores and shells, while 



