120 
THE VOYAGE OF H.M.S. CHALLENGER. 
rows. The ends of the Ascidiozooids at the surface are very small, and show merely as 
small dark brown points. No common cloacal apertures are visible in any part of the 
colony. The Ascidiozooids are largest at the top and smallest near the base of the head. 
Their vascular appendages can be faintly seen in a very good light as dark streaks 
running down the peduncle. 
Sections show at once that the brown colour of the colony is due to a very large 
number of small clear yellowish-brown pigment corpuscles of a rounded shape whieh 
are scattered through nearly all the tissues of the body. In the test, which is other- 
wise very mueh the same as in Colella murrayi. they are present in the outer layers 
scattered through the matrix between the bladder cells. They are present in large 
quantities in some parts of the mantle, especially along the dorsal line and round the 
base of the branchial siphon. The musculature of the mantle is remarkably feeble, and, 
where pigment cells are absent, this membrane is perfectly transparent. The branchial 
aperture is distinctly six-lobed, and the siphon is fairly strong. 
In the branchial sac the transverse vessels do not seem quite so wide as in Colella 
murrayi. The stigmata are regular. They are long, with rounded ends, and are 
usually considerably wider than the fine longitudinal vessels between them (PL XVII. 
fig. 14, l.v). The ciliated cells are distinct. 
The endostyle is conspicuous. It is long and straight. The tentacles are short and 
stout. There are eight, four longer and four shorter placed alternately (PI. XYII. 
fig. 13, tn., tn'.). 
Altogether the main difference between the colony under consideration and those 
belonging to Colella murrayi is in the pigmentation. The latter are entirely free from 
yellowish-brown pigment corpuscles, and are very remarkably coloured in places by 
opaque white granules, while in the former no white pigmentation is present, and the 
entire colony is coloured by small round clear yellowish-brown pigment corpuscles. 
This produces such an entirely different aspect, not only in the colony as a whole, but 
also in the various organs separately, that I think the specimen is worthy of being 
regarded as a marked variety, but certainly not as a distinct species. 
Colella ramulosa, n. sp. (PL XV. figs. 14-17). . 
The Colony is composed of one or more rounded masses borne on long branched 
peduncles. The rounded mass or head is usually irregularly flattened in one direction. 
The peduncle is very irregular in its course and in its thickness. The colour of the head 
varies from light to very dark grey. The peduncle is always of a straw yellow colour. 
The surface is uneven but smooth. No common cloacal apertures are visible. 
The length of the head is 12 mm., the breadth 9 mm., and the thickness 4 mm. 
The length of the peduncle is about 5 cm., and the thickness 2 mm. 
