210 THE VOYAGE OF H.M.8. CHALLENGED. 



Ascidia nigra, Savigny. 



Phallusia nigra, Savigny, M6m. sur les Anim. sans Vert., part ii., 1" fasc. p. 163, pL ii. 



fig. 2, pi. ix. fig. 1, 1816. 

 Ascidia atra, Lesueur, Descr. of several new species of Ascidia, Jour. Acad. Nat. Sc. Philadel., 



vol. iii. part 1, p. 2, pi. i. fig. 2, 1823. 

 Ascidia nigra, Herdman, Prelim. Rep., Proc. Eoy. Soc. Edin., 1880-81, p. 466. 

 Phallusia atra, Traustedt, Vestindiske Ascidia; Simplices, Vid. Medd. Nat. For. Kj0benh., 



p. 278, 1881. 



At the time when the first part of the Preliminary Eeport was written, I had only 

 examined a single specimen, from Bermuda, of this curious species. Since then I have 

 received from the Challenger Office three large specimens, probably from Station 142 (off 

 the Cape of Good Hope). They are joined into a single mass by the fusion of the tests, 

 chiefly at the posterior end, so that the appearance of a colony is produced. There seems 

 to me no doubt that these Challenger specimens are the same species as Savigny's Phal- 

 lusia nigra and Lesueur's Ascidia atra, although Traustedt (loc. cit.) appears to think 

 otherwise. I have seen a considerable number of specimens, as in addition to those of the 

 Challenger expedition, Mr. Moore, the curator of the Liverpool Free Public Museum, has 

 kindly allowed me to examine the specimens in the collection made by the Rev. H. H. 

 Higgins during the " Argo " expedition. Some of these, which were collected at Antigua 

 and Tucacas, are very large. 



One of the most striking features of this species is the test, which varies considerably 

 in shape, and especially in the length and direction of the siphons, but is always of a 

 very deep blue colour, almost black, and quite opaque. Sections show that this is due to 

 the presence of very large numbers of rounded pigment corpuscles, each well filled with 

 small dark blue pigment granules. 



The apertures are distinct and prominent, but sometimes there are one or two super- 

 numerary lobes. The test is thick and strong, but rather brittle ; it contains numerous 

 blood- vessels. The mantle is fairly muscular on the right side of the body, and the 

 muscle bands are of a dark colour. 



The branchial sac is long, and tapers to a point at the posterior extremity ; it is 

 plicated longitudinally, and is in some respects rather like that of Ascidia tra7islucida. 

 The transverse vessels are alternately wider and narrower, and occasional still wider 

 transverse vessels are present, alternating with from five to nine of the smaller size. The 

 internal longitudinal bars are strong, and bear each a series of large curved papillae at 

 the angles of the meshes, and smaller intermediate ones, which are only present in some 

 parts of the sac. The papilla? are somewhat like those in the branchial sac of Ascidia 

 falcigera. A number of the blood corpuscles found in the vessels are of a deep indigo 

 blue colour. This gives a bluish tinge to the whole sac, and to most of the other organs 

 of the body. 



