]40 
THE VOYAGE OF H.M.S, CHALLENGER. 
The branchial aperture is distinctly six-lobed, and the whole branchial siphon is 
considerably pigmented of a reddish-brown colour (PL XIX. fig. 10). The atrial aperture 
is prolonged into a long narrow siphon which opens into the common cloacal cavity 
(PI. XIX. fig. 11, at.). 
The branchial sac is thick and opaque. The stigmata are small and not very 
numerous. The endostyle is large and has a serpentine course (PI. XIX. fig. 3, en.). 
The tentacles are very numerous, remarkably so for a Compound Ascidian, and are 
also, some of them, singularly long and narrow. Their bases are closely placed 
(PL XIX. fig. 12). They have all the appearance of being extensile and retractile, as 
some portions of them have a stretched out appearance (PL XIX. figs. 12, 13). Some of 
the epithelial cells on the surface of the tentacles are large and fusiform, with very large 
central ovate projecting nuclei. These cells are placed generally in little groups, with 
their long axes pointing along the tentacle. On the edges of the tentacle, as seen under 
a high magnification (about 1000 diameters), the nuclei form rounded projections of 
considerable size (PL XIX. fig. 13). At the extreme tip of the tentacle these cells are 
much more numerous, and cover almost the whole surface, the nuclear projections giving 
it quite a rough knobbed appearance (PL XIX. fig. 14). 
The alimentary canal occupies the broad rounded posterior end of the Ascidiozooid. 
The stomach is large and globular, and is smooth on the outer surface. The intestine is 
short. A few tailed larvae were found in the colony; the single pigmented sense organ is 
placed near the posterior end of the body, the endostyle is large, and they are in many 
ways very like those of Colella pulchra (compare PL XIX. fig. 15, and PL XV. fig. 12). 
Cystodytes pJiilippinensis, n. sp. (PL XX. figs. 1-12). 
The Colony is of irregular form, fiat and incrusting, and of moderate thickness. 
The colour is dark brownish- grey, rather lighter round the edges. The surface is 
uneven but fairly smooth. The common cloacal apertures are inconspicuous. 
The length is 4 cm., the greatest breadth is 3 cm., and the thickness about 5 mm. 
The Ascidiozooids are elongated antero-posteriorly, and are usually placed at right 
angles to the surface. The usual size is 2 ‘5 mm. antero-posteriorly, and slightly more 
than 1 mm. in greatest breadth. The anterior end is slightly narrower, and terminates 
in the branchial siphon, while the atrial projects from its dorsal extremity. The posterior 
end of the body is broad and rounded. The posterior half or three-fourths of the 
Ascidiozooid is concealed by a calcareous capsule formed of disk-shaped spicules. The 
anterior end projects from this capsule and is quite unprotected. 
The Test is firm and rather stiff. It is smooth on the upper surface, and is 
moderately transparent. It does not vary much in thickness, and the edges are pro- 
minent and rounded. The matrix is clear and homogeneous, but it is greatly reduced and 
