ON JULINIA. 9 



distance, while the ventral wall stops short of this and becomes 

 continuous with the band of glandular tissue. The columnar 

 epithelium lining the duct is reflected at its mouth over the 

 *' dorsal tubercle," and in the interior of the duct bears the 

 usual long cilia, one to each cell. 



It is interesting to note that the extreme degeneracy of the 

 gland itself (carried to a greater degree, I think, than has been 

 described in any other Ascidian) is not associated with any 

 corresponding reduction in the size of the duct. Indeed, even 

 in other cases where the gland is much better developed (e. g. 

 Fragaroides), the duct, both in respect to size and to the 

 richness of its ciliation, seems out of all proportion to any 

 secretory function we can ascribe to the gland. 



Circulatory System. — The heart in its pericardium lies 

 on the ventral side of the intestinal loop (PI. 1, fig. 4; 

 PI. 2, fig. 16). It is a thin-walled, somewhat fusiform tube, 

 but I was unable to trace any vessels connected with it. 

 A space lined by endothelium and lying to the left of the peri- 

 cardium may possibly represent a vestige of the epicardial 

 system. A large blood-sinus runs along the dorsal edge of the 

 branchial sac (PI. 2, figs. 14 and 22) ; in its lateral walls 

 run strongly developed longitudinal muscle-bands, while in the 

 middle of its dorsal wall runs the ganglionic nerve-cord above 

 alluded to. 



The "vascular process" arises near the hinder end of the 

 abdomen, a little to the left side. In the substance of the 

 test these processes branch and probably anastomose, and 

 finally end in club-shaped dilatations (PI. 1, fig. 6). In 

 section (PI. 3, fig. 32) each is seen to consist of a simple 

 tube of ectoderm divided into two by a median partition of 

 thin and apparently structureless membrane. No internal 

 layer of connective tissue, as described by Herdman in Col ell a, 

 could be distinguished, the processes appearing to be exclusively 

 ectodermal, like the ''stolons'' of Botryllus (Hjort, 'Mitt. 

 Zool. Stat. Neap.,' x, p. 589), a point which is of interest in 

 connection with the probable origin of buds from them. 

 Numerous blood-corpuscles occur in the cavity of these tubes. 



