NO. 1989. A8CIDIAN8 FROM NORTHEASTERN PACIFIC— RITTER. 473 



Alimentary system. — On the left side of the body the intestinal 

 canal as a whole forming a reversed S as seen from the outer surface, 

 the ventral or gastric portion of the S being considerably broader 

 than the dorsal or rectal portion. Esophagus short; stomach spin- 

 dle-shaped, about a third longer than thick, wall closely and deeply 

 folded, the folds about 30 in number; intestine of quite uniform 

 diameter throughout; anal border with a series of distinct, somewhat 

 bead-like lobes, in some specimens these extending all the way 

 around, while in others they are restricted to scarcely more than one- 

 half of the circumference, the other portion being occupied by a single 

 projecting j^ointed lobe or lip (fig. 23). 



Reproductive system. — On both sides of the body. Ovary consist- 

 ing of a much elongated, evenly cylindrical mass, two or one on each 

 side, on the left crossing the rectal part of the intestinal loop, and in 

 some individuals reaching back across the gastric portion of the loop 

 also. Testes consisting of fully separated bodies of unequal size and 

 irregular shaj^e arranged along both sides of each ovarian cylinder, 

 but sharply separated from it. Both ovaries and testes adhering 

 closely to the mantle, the testes seeming to be without common sperm 

 ducts, each lobe discharging its sperm independently (fig. 23). 



The great individual variation among the animals strongly sug- 

 gests at fu'st sight that we are dealing with two quite distinct specific 

 groups. The difference in shape, for example, as shown by the photo- 

 graphs, and as indicated in the diagnosis by the terms ''flat form," 

 and "pyramidal form" is striking indeed, and when taken in con- 

 junction with other external differences, particularly the tubercula- 

 tion of the test in the pyramidal form and the evenness of the surface 

 in the flat form, would lead one to say without hesitation that the 

 two styles make two well-separated species. 



Such an internal difference, too, as the presence of two ovaries on 

 each side in some individuals and of only one in others would, accord- 

 ing to our usual notions about species in the genus Styela, strongly 

 incline one to believe we have to do here with two species. The 

 several differences do not, however, correlate with one another in 

 such way as to make a specific grouping possible at least within the 

 limits of the specimens examined. For example, some of the py- 

 ramidal forms pcssess double ovarian cylinders on both sides of the 

 body while others have single cylinders on both sides, and the same 

 variation occurs among the "flat" animals. Again, the differences 

 in the number of longitudinal vessels of the branchial sac between 

 the branchial folds are sufficient to serve as specific marks, as these 

 structures usually go ; but here a correlation between either the 

 maximum or the minimum number of the vessels with the extreme of 

 variation in other particulars is not obvious. I conclude, therefore, 

 that no other course is open than to assign the specimens all to one 



