38 University of California Publications in Zoology. [VOL. 4 



There is considerable variation from the typical structure of 

 the branchial sac as this is given in the diagnosis, and in the 

 figure (pi. 3, fig. 38). The secondary or smaller transverse ves- 

 sels are frequently absent. The primary transverse vessels while 

 undoubtedly to be regarded as " internal' : ' since they usually 

 cross the stigmata, are as a rule less raised above the surface of 

 the membrane than the figure gives the impression that they are. 

 Furthermore there are considerable stretches on some of the 

 stigmatic series where the primary vessels are absent. 



The distally lobulated, enlarged, curved papillae deserve 

 special notice. It will be seen that in general a single smaller 

 projection occurs on the side of the papilla underneath the larger 

 terminal lobe, or bent-over end of the papilla. In many cases 

 there are two or even three of these lateral processes. The 

 internal longitudinal vessels are distinctly more " internal " than 

 are any of the transverse ones. It is interesting to notice that 

 the longitudinal vessels are connected with the papillae some 

 distance from their bases, and quite independently of any of the 

 secondary lobes of the papillae. The interest in this fact lies in 

 its possible bearing- on the question of the secondary lobes at- 

 tached to the papillae of some other ascidians, notably Pcrophcra. 

 It has been suggested that the secondary lobes in that genus are 

 the remnants of internal longitudinal vessels. In the species 

 now under examination we have the longitudinal vessels in full 

 development, and secondary lobes on the papillae besides. I do 

 not mean to imply by this that I should regard the secondary 

 papillae in Pcropltcra and in the present species as homologous. 

 The condition now described does, however, show the possibility 

 of secondary lobes on the papillae quite independently of the 

 internal vessels. 



The dorsal lan</n<lx, about fifteen in number, are as shown in 

 fig. 36 much broadened transversely and flattened antero-poste- 

 riorly at their bases. They are considerably farther apart toward 

 the posterior end of the row than at the anterior. They are not 

 situated on a membrane or other prominence. 



From the posterior extremity of the long meandering endo- 

 style, a shallow but distinct gutter continues on, nearly or quite 

 to the esophageal opening. 



