234 
THE VOYAGE OF H.M.S. CHALLENGER. 
Tlie test of the head is not soft, but it is not so firm as that of the peduncle. 
It is of a dark grey colour and is only slightly transparent. The dull yellowish 
Ascidiozooids show through the superficial layer of test as lighter grey patches with a 
slight yellowish tinge. No common cloacal apertures are visible in the colony. 
The Ascidiozooids are evidently arranged in vertical lines, which are, however, some- 
what irregular in parts (PL XXVII. fig. 9). Their bodies are not placed at right angles 
to the surface, but dip inwards at various angles. Consequently in many cases the 
greater part of the body is visible through the surface layer of test, and measures up to 
nearly 2 mm. in its greatest extent {i.e., antero-posteriorly). The central region of the 
head is occupied by the posterior prolongations of the Ascidiozooids, which run chiefly in 
a lonsfitudinal direction. 
O 
The test is fairly tough, and does not show a great many cells in its matrix. The* 
cells are of the usual forms, but are of small size. 
The mantle is rather opaque, but is not strongly muscular. Over the post- 
abdomen it contains a number of longitudinal bands of muscle fibres. The branchial 
aperture is small, but is distinctly six-lobed. The endostyle is wide, and undulates 
greatly from side to side in its course. The branchial sac contains few stigmata, but 
they are of a fair size (PL XXVII. fig. 10, sg.). The transverse vessels are wide. 
The alimentary viscera form an opaque mass placed close against the branchial region 
of the body and continuous with it ; the stomach is folded longitudinally. The repro- 
ductive organs are contained in the very long and narrow post-abdomen, upon which 
they produce a fusiform swelling (PL XXVII. fig. 11). They consist of one or two large 
yellow ova and a number of small spermatic vesicles. The vas deferens is a conspicuous 
object (PL XXVII. fig. 11, v.d.). It has a remarkably undulating course. 
A considerable number of tailed larvae are present in the colony. They have the 
body much elongated antero-posteriorly (PL XXVII. fig. 12), and provided -with three 
adhering organs in front which have a somewhat remarkable form. Two pigmented 
sense-organs are present ; they are placed very far posteriorly (PL XXVII. fig. 12). 
Amaroucium albidum, n. sp. (PL XXVI. figs. 11-12). 
The Colony is an irregularly elongated mass of considerable size, attached by the lower 
end, and slightly compressed laterally. The widest part is about the middle, and the 
upper end is obtusely pointed. The surface is irregular but fairly smooth. The colour is 
dull white. 
The length is 7 cm., the greatest breadth 4 cm., and the greatest thickness 3 cm. 
The Aseidiozooids are small and inconspicuous. They are long but narrow, and are 
very numerous. The thorax and abdomen are short, but the post-abdomen is of great 
