THE ASCIDIANS 229 



of the endostyle, with which it is nearly parallel. Anus hardly as far 

 forward as the anterior end of the loop (p1. xxvii, fig. 3). The clear 

 ' renal vesicles ' very abundant along the entire length of the intestine, 

 and extending on the mantle to some extent, but not covering up and 

 obscvxring the intestine. 



Reproductive organs. — In the intestinal loop, not very voluminous. 

 Vas deferens large and distinct, running along the dorsal side of the 

 rectum. 



This Ascidia has so many characters in common with Ascidia 

 koreana Traustedt that in a former paper (1900) I identified, with con- 

 siderable hesitation, a few specimens from Puget Sound with Trau- 

 stedt's species ; but now, with ample material at hand, it is clear that 

 the American and Asiatic forms are distinct, though closely related. 



Traustedt says of the general form of A. koreana : " Corpus ut conus 

 inversus formatum est, infra subacuminatum et supra pi"aecisum." ^ 

 This is so different from that of A. adkcerens and the differences in the 

 intestinal tract and the dorsal lamina are so great that it is impossible 

 to regard them as belonging to the same species. The intestinal loop 

 of koreana is neither so long relatively, nor so nearly parallel with the 

 endostylic edge of the sac as that of adhcerens ; and apparently since 

 Traustedt makes no mention of the point, the folding of the stomach- 

 wall does not occur in his species. The irregular serration of the edge 

 of the dorsal lamina in A. koreana does not occur in the American 

 species, as the description and figure show. 



A word should be said with regard to the intermediate papilla of 

 the branchial sac; i. e., papilla on the internal longitudinal vessels in 

 the intervals between the crossings of the transverse vessels. These 

 apparently exist, as a rule, but they may or may not be present even in 

 different portions of the same sac. It may be, however, that their 

 presence, as actual intermediate papillce, is sometimes apparent rather 

 than real, and that when present, this may be due to the suppression of 

 transverse vessels corresponding to them. In regions where they are 

 present (p1. xxvii, fig. 5) the alternate transverse vessels are much 

 smaller than the others, and one and the same vessel maybe interrupted 

 for a considerable distance while the papills corresponding to it remain. 

 On the other hand by carefully examining an area in which the inter- 

 mediate papillae are present, fragments of vessels corresponding to them 

 are found here and there (pi. xxvii, fig. 5), so that it may be doubted 

 whether the papillae are ever present except where transverse vessels 

 actually do cross the longitudinal ones, or where they have existed, or 

 are going to develop. 



^Vidensk. Meddel. fra den naturh. Foren, p. 49, 1884. 



