130 
THE VOYAGE OF H.M.S. OHALLENGEE, 
The pigmentation of all of these colonies agrees well with that of Distaplia magnilarva 
as described by Della Valle, and differs from that of Distaplia rosea where there is no dark 
colouring, all the pigment being rose-red. From Distaplia liibrica, on the other hand, our 
species is readily distinguished b}^ the entirely different shape of the colony. From the 
external appearance and colour I should be inclined to refer the Challenger and “Porcupine” 
specimens to Distaplia magnilarva, although in Della Valle’s figures^ the heads are 
relatively larger and more ovate in shape and the peduncles are very much smaller, but 
from the small size of the Ascidiozooids and of the tailed larvae (see below) it is 
impossible that they can belong to that species. The Ascidiozooids are about 2 mm. in 
length,^ and are placed with the long axis extending downwards from the branchial 
aperture towards the peduncle. The branchial aperture, with its conspicuous white 
margin, is less than 0‘5 mm. in diameter, and the centres of adjacent branchial aper- 
tures in the same row are placed about 1 mm. apart (PI. XVIII. fig. l). In the 
“ Porcupine ” specimen the Ascidiozooids and the branchial apertures are a little larger 
(PI. XVIII. fig. 2). 
The test is soft and gelatinous in the centre of the colony. The outer layer is 
firmer, and is very considerably pigmented. The peduncle is the clearest part, but even 
there small patches of opaque white and dark violet or black pigment are found. The 
rosy tint of the upper end of the peduncle is due to the posterior ends of some of the 
Ascidiozooids showing through, and not to red pigment in the test. 
In the head this dark pigment is almost entirely confined to the outer firmer layer 
of the test, the inner part being transparent and of a grey colour. The red and white 
and black pigmented bodies of the Ascidiozooids show through to a certain extent, and 
help to make the head, as a whole, more opaque. In the “Porcupine” specimen some 
parts of the surface layer of test contain a very large amount of red pigment 
(see PI. XVIII. fig. 5, p.c.), resembling in this respect Distaplia rosea. 
In its minute structure the test consists of a homogeneous matrix in which are 
scattered numerous small test cells and larger pigment cells (PI. XVIII. fig. 4). The 
test cells are of all shapes, stellate and branched forms being common. The pigment 
cells are usually ovate or irregularly rounded and very opaque. They show three 
distinct colours : white, red, and very dark violet or black. The red and the white 
ones are evenly pigmented all over (PI. XVIII. fig. 4, r.p.c.), while the black ones have 
the pigment granules usually extending over about one half of the cell, the remainder 
being clear (PI. XVIII. fig. 4, h.p.c.). 
The mantle is fairly strong over the branchial region of the body. On the viscera, how- 
ever, it is very thin, but is deeply pigmented. The muscle bands are nearly all transverse in 
direction, and are more regularly placed than in Della Valle’s figures of the Ascidiozooids of 
1 Nuove Contrilrazioni, &c., Tav. i. figs. 1, 1', 4 and 4'. 
2 Della Valle gives the length of the Ascidiozooid of Distaplia magnilarva as 6 mm. 
