EEPORT ON THE TUNICATA. 
321 
The branchial apertures are conspicuous over the greater part of the surface of the 
colony (PL XXXVII. fig. 1 ; PI. XXXVIII. fig. 2). They are more regularly placed 
and more widely open on the inner walls of the cavity than on the outside. They are 
nearly circular in shape, and are surrounded by five short blunt lobes (PI. XXXVIII. 
fig. 3), each of which is strengthened at its base by a clump of calcareous spicules, 
which forms a small opaque white dot \fisible to the eye (PI. XXXVIII. figs. 2, 3). 
The test is soft, and is to a great extent cut up by canals and spaces which are 
prolongations of the common cloaca! cavity and serve to connect the atrial apertures of 
the various Ascidiozooids (shown diagrammatically in fig. 10, B, on p. 320). The clear 
matrix contains delicate fibres stretching in all directions. The test cells are large and 
granular ; they are mostly rounded in form, but fusiform and branched shapes also 
occur. No spicules are present in the deeper parts of the test, and even in the super- 
ficial layers they are not very abundant. They are exactly like the spicules of a 
typical Lejptoclinum (see PI. XXXVII. fig. 4). The rays vary in thickness, but are 
generally very sharp at the points. No spherical forms were found. 
In a section through the wall of the colony the large Ascidiozooids are seen projecting 
inwards from both surfaces, and occupying the greater part of the test (see PI. XXXVII. 
fig. 3). The intestine, containing a row of faecal pellets, is usually visible to the eye. 
It lies to a great extent alongside the branchial sac, and the thoracic and abdominal 
regions of the body are not distinctly separated. 
The mantle is thin and transparent, but has a considerable number of muscle bands. 
They run mainly in a longitudinal direction, occasionally branching and anastomosing 
(PI. XXXVII. fig. 5). The branchial sphincter is rather feeble. It is a narrow band of 
muscle, encircling the wide branchial aperture at the bases of the rounded lobes (see 
PI. XXXVIII. fig. 3). The clumps of spicules which strengthen the lobes are usually 
placed on the line of the sphincter. 
The branchial sac is large but delicate. The transverse vessels are narrow 
(PI. XXXVII. fig. 6, tr.), and the stigmata are of great length but are arranged with 
regularity (PL XXXVII. figs. 6, 7). The ciliated cells are well developed (PL XXXVII. 
fig. 7). 
The endostyle is not wide; its course is rather undulating. The dorsal languets are 
large. They taper to narrow points. The tentacles are very narrow, and the larger 
ones are of considerable length. They are closely placed round the base of the wide 
branchial siphon. The dorsal tubercle has a large ovate aperture immediately in front 
of the convoluted peripharyngeal band. The aperture leads into the usual infundibulum 
(PL XXXVIII. fig. 4, inf.), which rapidly tapers into a short narrow canal, leading to 
the neural gland (PL XXXVIII. fig. 4, n.gl.). This gland is an elongated curved body 
which lies along the ventral surface of the ellipsoidal nerve ganglion (PL XXXVIII. 
fig. 4, ng.). 
(ZOOL. CHALL. EXP. — PART XXXVIII. — 1886.) 
Pp 41 
