218 
THE VOYAGE OE H.M.S. CHALLENGER. 
The Ascidiozooids are of a pale yellow colour, and are usually quite opaque. The 
5 ’ellowish tint in the colouring of the colony is due to their presence. The brownish tint 
in some of the colonies is, on the other hand, caused by the darker colour of the test in 
these cases, the bodies of the Ascidiozooids showing through as lighter coloured patches 
on the dark brownish-grey ground. 
The small cells in the test vary considerably both in size and shape (PI. XXIX. 
fig. 8, t.c.). In some places they are aggregated to form small clumps which look like 
the terminal knobs of vessels ; they are, however, merely groups of closely-placed test 
cells. Many of the cells have granular contents, but no regular pigment corpuscles were 
noticed except in the case of the brown coloured specimens, where they are abundant. 
These pigment cells are circular in form and of small size. 
The musculature of the mantle is rather regular. The lobes at the branchial aperture 
are six in number, in some cases they are very well marked (PL XXIX. figs. 9, 10, hr.). 
The atrial aperture is provided with a very long narrow atrial languet (PI. XXIX. 
figs. 9, 10, at.l.), which is directed anteriorly and towards the branchial aj)erture. 
The branchial sac in all the Ascidiozooids was considerably corrugated, but whether 
this condition is natural, or the result of contraction on being put into alcohol, I am 
unable to say. There are a good many rows of rather narrow stigmata. The ciliated 
cells are distinct and have pointed free ends. The endostyle is inconspicuous ; its course 
is undulating. 
The alimentary canal is long and narrow (PI. XXIX. fig. 9).. The oesophagus 
runs straight backwards to open into the rather cylindrical stomach, which lie& 
with its long axis directed antero-posteriorly (PI, XXIX. fig. 9, st.). There are about 
fourteen well-marked longitudinal folds, which are seen in transverse sections of the 
abdomen to extend about half-way into the cavity (PL XXIX. fig. 12). The intestine- 
extends for a considerable distance behind the stomach, and then turns abruptly to the 
dorsal edge and then anteriorly, forming a narrow loop. The tube usually becomes 
slightly enlarged in its most posteriorly placed part before turning forwards (see 
PL XXIX. fig. 9, i.). The rectum is long and rather narrow, and in its upper part it is 
very narrow. It lies alongside the intestine, stomach, and oesophagus, and then courses 
along the dorsal edge of the branchial sac. It forms the dorsal edge of the thorax and 
abdomen in their entire length (PL XXIX. fig. 9, r.). 
The post-abdomen is very large, it is usually about twice as long as the thorax and 
abdomen together, and is nearly as wide as the thorax (PL XXIX. fig. 9,p.ahd.). It is 
very opaque except along the middle, where there is a narrow clear line formed by the 
lumen of the douljle septum. This cavity is clearly visible in transverse sections of the 
post-aljdomen (see PL XXIX. fig. 11). There is generally a slight constriction separating 
the abdomen from the post-abdomen. 
In external appearance this species shows some resemblance to ApUdium fuegiense. 
