34 University of California Publications in Zoology. L^ol. 4 



ulation. Testis branched, situated on and immediately behind 

 the stomach. Both oviduct and vas deferens following the course 

 of the intestine to open into the atrial chamber near the atrial 

 orifice (fig. 32, ov. and t.) 



Several rather important variations from the type here diag- 

 nosed have been observed. 



In some individuals the ribbing of the dorsal lamina, and the 

 corresponding toothing of its edge, pertain to only the posterior 

 half, or even less, of the membrane. 



The great transverse pipes, or vessels of the branchial sac, are 

 far less conspicuous in some specimens than in the one here 

 figured. Again the plications of the branchial membrane are but 

 feebly developed in some specimens. Finally, the renal vesicles 

 are much less in volume in some than in others. 



As the specimens in which I have observed these less pro- 

 nounced expression of characters, as set forth in the diagnosis, 

 were both considerably smaller than that from which the figures 

 and diagnosis were made, it is possible that the differences are 

 age or growth differences. This however, judging from our 

 knowledge of life stages in some other ascidians, is hardly prob- 

 able. It is more likely that we have to do with true individual 

 variations. 



It is probable that a genus will ultimately have to be formed 

 to receive the species represented by the animal here described, 

 but until more material can be examined it has seemed the wiser 

 course to place it provisionally in the central genus of the ascidia 

 group. The presence of a voluminous renal organ in the mantle 

 is, of course, a violent shock to the best established character- 

 ization of the genus Ascidia. This, however, is the only character 

 that favors an alliance with Ascidiella, the other recognized 

 genus that calls for consideration in connection with it. In the 

 distance of the ganglion and gland from the hypophysis mouth ; 

 the presence of a post esophageal extension of the dorsal lamina ; 

 and of intermediate papillae on the internal longitudinal vessels, 

 the Ascidia as opposed to the Ascidiella affinities are clear enough, 

 particularly if the count is to be on a numerical basis alone. As 

 a matter of fact I am of the opinion that considerably more 

 weight should be given to the position of the renal organ than to 



