106 
THE VOYAGE OF H.M.S. CHALLENGEE. 
side, but does not seem to have any supporting transverse fibres sucb as are present in 
some Ascidian larvae. The single pigmented sense organ of the larva is placed very far 
back in the body. 
Colella pulchra, n. sp. (PL XV. figs. 1-13). 
The Colony has the form of a somewhat elongated mass, the head, borne on the 
summit of a long narrow peduncle. The head is not flattened laterally, and its upper 
end is usually rather wider than the lower, which tapers into the top of the peduncle. 
The widest part is about the middle of the head. The peduncle is thickest at the top, 
where it joins the head, and from that point tapers downwards to the point of attachment, 
where it usually expands again slightly. The surface is even and smooth. The colour 
is a dull red. The peduncle is rather paler than the head. 
The length of the head is 10 mm., the greatest breadth or thickness 4 mm. The 
length of the peduncle is about 2'5 cm., and its thickness about the middle 0‘5 mm. 
The Ascidiozooids are small, less than 1 mm. in length. They are slightly elongated 
antero-posteriorly, and are placed nearly at right angles to the surface ; they incline some- 
what inwards and downwards towards the base of the colony. They are arranged in 
regular vertical rows, which are more or less distinctly placed in pairs. 
The Test in the head is soft and gelatinous, that of the peduncle is firmer. The 
transparent homogeneous matrix contains bladder cells of moderate size, and also the 
usual small fusiform and stellate cells. The latter are not numerous. The test is to a 
very great extent occupied by the Ascidiozooids and the embryos, which are numerous 
and closely placed. 
The Mantle is very delicate. The muscle bands are very thin, and they are not 
numerous. They run chiefly in a transverse direction over the thoracic region of 
the body. 
The Branchial Sac is short, and of a more or less quadrangular form. The transverse 
vessels are moderately wide, and are all of the same size. The stigmata are long and 
narrow, they are regularly arranged. The ciliated cells bounding them are convex at 
their free ends. 
The Dorsal Lamina is formed of a series of short blunt triangular languets. 
The Tentacles are about twelve in number. They are long and narrow. 
Locality. — Station 187, September 9, 1874 ; lat. 10° 36' S., long. 141° 55' R; depth, 
6 fathoms ; bottom, coral mud. 
About a dozen specimens of this beautiful little species were dredged in Torres Strait 
between Australia and New Guinea, from a depth of 6 fathoms. The dimensions given 
above are those of the largest colony. An average sized one has the head about 7 mm. 
