REPOKT OX THE TUNICATA. 
315 
Diplosoma macdonaldi, n. sp. (PL XLII. figs. 1-4). 
The Colony is a thin spreading layer of irregular shape, slightly attached by parts of 
its lower surface. The upper surface is uneven but smooth. Tlie colour is grey. 
The length is about 2 '5 cm., and the greatest breadth is 1 cm.; the thickness is 
about 1 mm. 
The Ascidiozooids are moderately large and numerous. They are scattered irregularlj' 
over the surface of the colony, and are not arranged in definite systems. No common 
cloacal apertures are visible. The bodies of the Ascidiozooids are about 1’5 mm. in 
antero-posterior length and O'o mm. in greatest breadth ; they are divided into two 
recrions, thorax and abdomen. 
The Test is very soft and flexible. It is of a clear grey colour and quite transparent. 
The matrix is slightly fibrillated in places, and contains large numbers of bladder cells 
and test cells of various kinds. No calcareous spicules are present. Many of the test 
cells are of large size (0‘075 mm. in diameter) and of rounded form. The}?" are coarsely 
granular. 
The Mantle is rather thin and membranous. Its musculature is feeble. 
The Branchial Sac is large. There are four rows of long stigmata. The transverse 
vessels are narrow, but they are provided with muscle fibres. 
The Dorsal Lamina is represented by a series of long languets. 
The Tentacles are of two sizes, placed alternately. They are about twelve in number. 
The Alimentary Canal forms a wide loop. The stomach is large and smooth-walled. 
Locality. — Off Bahia, Brazil, shallow water. 
The small specimen for ’which this species is formed was found attached to a fragment 
of a Hydroid Zoophyte dredged in shallow water off Bahia. It is loosely attached to the 
branches of the Zoophyte around which it has grown (PI. XLII. fig. 1). Its general colour 
is due to the Ascidiozooids, which are of an opaque grey and show distinctly, while the 
investing test is clear and almost colourless. The colony is exceedingly soft and flexible, 
and the outer layer of test may be readily stripped off, taking the Ascidiozooids with 
it, as in the case of the last species. Figure 2 on Plate XLII. represents such a prepara- 
tion seen from the inner surface. 
The Ascidiozooids lie at various angles to the surface, and are apparently quite irregu- 
larly placed. Their atrial apertures are connected by a system of canals and cavities 
which penetrate the test and greatly reduce its bulk and strength. These doubtless open 
at one or more points on the upper surface of the colony, but no such common cloacal 
apertures were discovered. The upper layer of test to which the Ascidiozooids adhere is 
fairly compact (PL XLII. fig. 2), but the lower parts are greatly vacuolated and contain 
