TUNICATA OF THE PRIBILOF ISLANDS. 



517 



it. (Fig. 13.) Branchial sac with four folds on each side, the development of these 

 folds varying with the size (age?) of the specimen. In smaller (younger?) specimens 

 the folds on the left side more strongly developed than those on the right. In speci- 

 mens 3.1 to 6.7 cm. (including peduncle), pair of folds next the endostyle had about 

 12 bars and those next dorsal lamina about 20. In specimen 0.85 to 1,8 cm. folds 

 next endostyle had about G and those next dorsal lamina about 12 bars. Folds closely 

 j)laced, only 3 to 5 bars between them. Transverse vessels of three sizes, a wide one 

 (Tri, fig. 11) occurring at irregular intervals, and two narrower ones (Tr2 and Trs), 

 which usually alternate with each other. Intermediate transverse vessels (Trj) some- 

 times present, often dividing the series of stigmata into two. Meshes nearly square 

 or longitudinally elongated with 4 to 6 (usually 5) long narrow stigmata. (Fig. 11.) 



Dorsal lamina ribbed 

 on one side by the ves- '^ 



sels passing round the 

 oesophagus. 



Digestive tract. — 

 Situated on the left 

 side of branchial sac 

 and making a narrow 

 turn. CEsophagus 

 short, opening from 

 the dorsal side of the 

 branchial sac near its 

 posterior end. Stom- 

 ach long and narrow, with numerous in- 

 ternal folds which show on the surface 

 as longitudinal markings. Anal open- 

 ing bilobed, each half cut into about six 

 lobes. (Fig. 12.) 



Sexual organs. — Gonads on each side 



of the body. Ovaries long, sausage 



shaped, ending in a short oviduct, those 



on the right side longer than those on 



the left. One of those on the left side 



placed in the loop of the intestine, the other beginning higher up and extending down 



under the stomach. Testis small, clustered in bunches over the ovaries. Endocarps 



rather numerous on the mantle. 



The genus Styela is naturally divided into two sections — those in which the 

 species are pedunculated, and those in which they are not. The species here described, 

 of course, belongs to the first section. In this section S. greeleyi finds its nearest 

 allies in 8. montereyensis of the coast of California, and S. clava, Herdman, of the 

 North Pacific. But it is quite distinct from either of these. So far as can be judged 

 from the specimens at hand, it is a much smaller species than either of them, x In 

 general form it differs from 8. montereyensis in its considerably more abrupt transition 

 from body to peduncle; while from 8. clava it differs distinctly by its lack of the prom- 

 inent irregular tubercles of the test of the latter species. The collection contains 17 



