222 
THE yOYAGE OE H.M.S. CHALLENGER, 
The Mantle is moderately thick and opaque, but is not very muscular. The muscle 
Ijands are all longitudinal in direction, 
The Branchial Sac is short, and its wall is thick and rather opaque. The transverse 
vessels are vide and all of the same size. The stigmata are rather short and rounded. 
The ciliated cells are distinct. 
The Endostyle is conspicuous ; its course is undulating. 
The Dorsal Lamina is represented by a series of long tapering languets. 
The Alimentary Canal is moderately large and forms a long loop. 
The Post-Abdomen is very large, and is equally wide all the way down. Its end is 
broad and rounded. 
Locality. — Christmas Harbour, Kerguelen Island, January 29, 1874; depth, 50 to 
120 fathoms. 
Five colonies of this species were obtained in Christmas Harbour, Kerguelen Island, 
at depths between 50 and 210 fathoms. They are all of much the same size, the largest 
being 3 cm. and the smallest 2 cm. in greatest length, but they differ somewhat in 
shape. Still they are all more or less elongated, have the upper end broad and rounded, 
and are greatly compressed (PL XXX. fig. 16). They look as if they had grown up 
between stones or in some narrow cleft, which had prevented their expansion laterally. 
The area of attachment is comparatively small. The colour has in places a pale slaty- 
blue tint. 
The Aseidiozooids are distinctly visible from the outside (PL XXX. fig. 16). Their 
long bodies form opaque grey lines upon the flattened sides of the colony and extend 
down to the very base. They are of much the same width in all parts, and the post- 
aljdomen is generally longer than the thorax and abdomen together. 
The test is rather small in amount, and looks shrivelled and contracted. All the usual 
shapes of test cells are found, although the majority are ovate or globular. The branchial 
siphon is rather short, but the sphincter is well developed. The branchial aperture is 
six-lol)ecL The atrial aperture is circular, and is provided with a short pointed languet, 
placed at its anterior edge. 
The branchial sac is usually considerably corrugated. The stigmata are small and 
closely placed. The transverse vessels have well-marked horizontal membranes (PL XXX, 
fig. 17, h.m.). The tentacles are numerous and rather short. The nerve-ganglion is 
large. It is circular in outline. The dorsal languets are very large. 
The stomach is short but wide. Its wall is thrown into a series of well-marked 
longitudinal folds. The rectum is large. The intestinal loop is rather narrow. 
The post-abdomen is as wide as the thorax. It varies greatly in length in the 
different Aseidiozooids. It is of a greyish-yellow colour, and is quite opaque, with 
the exception of a narrow undulating central clear streak which represents the lumen of 
