294 
THE VOYAGE OF H.M.S. CHALLENGER. 
This is a small incrusting species, a specimen of which was found attached to the test 
of a large Simple Ascidian from Kerguelen Island. It is quite flat (PI. XXXVIII. 
fig. 14), and the edges are expanded. The colour is a warm yellowish-grey. 
The Ascidiozooids are conspicuous (PL XXXVIII. fig. 14). They form slight rounded 
elevations all over the surface, and are closely placed. Their bodies are nearly 1 mm. 
in greatest breadth. They are divided into two regions, thorax and abdomen 
(PI. XXXVIII. fig. 15). 
The test cells are mostly of very large size. In some places smaller ones occur 
aggregated together in spherical or ellipsoidal clumps. All these cells stain deeply with 
carmine, and so give the test a minutely dotted appearance under a low power. A few 
vascular appendages are found in the test ; they are narrow and straight, and have long 
ovate swellings at their ends. 
The spicules are fairly abundant. They are more numerous near the upper and 
lower surfaces than in the deeper parts of the test, and are of most irregular form 
(PI. XXXVIII. fig. 16). The smaller ones are usually more or less rounded. The 
larger ones, which attain to 0’3 mm. in length, are discoid or ellipsoidal or lobed. No 
regular spherical or stellate spicules were discovered. Many of the larger spicules are 
marked by radiating and concentric lines (PL XXXVIII. fig. 16) like those seen still 
more distinctly in the large discoid spicules of Cystodytes. 
The mantle is rather opaque, and is fairly muscular. The branchial siphon is large 
(PL XXXVIII. fig. 15), and the sphincter is well developed. In addition to the delicate 
longitudinal and transverse muscle bands, which are closely placed all round the body, 
there are two strong bands which run longitudinally down the dorsal edge of the thorax. 
They are separated by a narrow clear space which is the median dorsal line, and from 
which the dorsal languets project inwards. 
The branchial sac is rather strong, the stigmata being narrow and the vessels rather 
vdde (PL XXXVIII. figs. 15, 17). The transverse vessels are provided with bundles of 
muscle fibres (PL XXXVIII. fig. 17, m.f.). The stigmata vary greatly in length. In 
some cases they are much longer than those represented in the figure (PL XXXVIII. 
fig. 17, sg.). 
The tentacles are irregular. None of them are long, but some are larger than others 
(PL XXXVIII. fig. 18). They are not arranged according to size, and they vary also 
in number in the different Ascidiozooids. 
The alimentary canal forms a rounded mass placed close behind the branchial sac 
(PL XXXVIII. fig. 15), so that the body, as a whole, is short and compact. The stomach 
is not large ; it is smooth-walled. The intestine is short but wide. 
The reproductive organs were not well developed in any of the Ascidiozooids 
examined. The vas deferens coils spirally around the testis. 
