W. G. Van Name — Bermuda Ascidkms. :^51 



amount of shrinkage. This is very likely to occur in preserved 

 specimens, as the tissues of the zooids are exceedingly delicate. 

 Well-expanded individuals are beautiful objects, and the internal 

 structure can be made out with greater ease than in any other of the 

 Bermuda ascidians. The mantle is but slightly muscular, the fibers 

 running chiefly ol)liquely and transversely. It is often more or less 

 pigmented, at other times nearly colorless. The stomach and 

 duodenum are always orange in fresh specimens. The largest and 

 best preserved zooids measure over ■',""" in length, and about 1.2'""^ 

 across the thorax. 



The branchial sac has four rows of more than twenty long narrow 

 stigmata on each side, which become shorter as the ends of the rows 

 are approached. A very narrow intermediate transverse vessel 

 crosses the stigmata half way between each principal transverse 

 vessel. This is visible even in quite young buds, where the number 

 of stigmata in a row is still much less than in the adult. The struc 

 ture of the branchial sac agrees exactly with Herdman's (6) descrip- 

 tion of D. rosea and J), vallil. 



The branchial orifice has an irregularly toothed margin. This is 

 not apparent when the aperture is much contracted. The atrial 

 opening is placed well back from the anterior end and is very large, 

 with the anterior lip produced into a long pointed languet. There 

 are about 16 tentacles of two sizes placed alternately, but their 

 arrangement and number is not always exactly the same. 



As already mentioned, the stomach-wall is not pitted nor folded, 

 but is smooth within and without. 



The zooids are usually hermaphroditic, well-developed testes and 

 eggs of considerable size being present at the same time. (Fig. 15.) 

 Some, however, appear to have the organs of only one sex. Some 

 colonies contain great numbers of buds and embryos, the latter 

 usually contained in the long incubatory pouch, which eventually 

 becomes detached from the zooid. I have not observed more than 

 three embryos in a pouch. 



Family POLYCLINIDiE Giard, 1872. 



Colony usually massive, sometimes incrusting, sometimes lobed or 

 pedunculated. Sj'^stems of various shapes, occasionally irregular or 

 wanting. 



Zouids elongated antero-posteriorly, and usually divided into three 

 distinct regions ; the thorax, abdomen, and post-abdomen. 



