EEPOET ON THE TUNICATA. 
47 
of them containing more pigmented corpuscles than others. The common cloacal aper- 
tures are usually slightly stellate or lobed in form when not opened to the full extent. 
Their membranous edges are richly provided with purplish-brown pigment corpuscles 
(PL I. fig. 5). 
The cells of the test are small and inconspicuous. The matrix though generally 
homogeneous is in some places finely fibrillated. The vessels form a very prominent 
feature (see PI. III. figs. 9, 10) with their numerous branches and large globular 
terminal knobs. The pigment corpuscles are large, circular, ovate, or elliptical in 
shape, and contain (PI. III. fig. 12) fine reddish-brown pigment particles which are 
frequently placed entirely, or almost entirely, in one half of the cell. 
The mantle, although it appears very thin and slight, contains many muscle bands, 
but they are very fine. The large pigmented cells form almost a continuous layer in 
some parts of the mantle and agree exactly in structure with those found in the vessels 
of the test (PI. III. fig. 12). They are particularly well seen in sections stained in 
aniline blue, where the red-brown cells stand out well against the blue ground formed 
by the remainder of the mantle. 
The branchial sac (PI. III. fig. 11) is long and narrow, and is of a brown colour, 
due to the pigmented corpuscles. The transverse A^essels are considerably broader than 
in the last species [BotryJloides 2 '>urpureiirn), and contain muscle fibres. In one young 
specimen examined there were three internal longitudinal bars on the one side of the sac 
and four on the other. This specimen had fourteen rows of stigmata on each side, that 
is, there were thirteen transverse vessels. Another specimen, fully developed, but young, 
showed thirteen rows of stigmata oh a side. There are usually ten to twelve stigmata in 
a row about the middle of the sac. 
The endostyle is narrow and not very prominent. Its groove is deep and 
the columnar cells are fairly long. As usual, a series of very long cilia projects from 
the centre of the groove (see PL III. fig. 13). The dorsal tubercle is placed rather 
further forward than is usual. Directly behind it lies a large elliptical opaque yellowish- 
brown mass, formed by the nerve ganglion and the neural gland. In some specimens 
the smaller tentacles are absent, so that the number is reduced to four ; while in others, 
although eight are present, they are all very short. 
The alimentary canal is confined to the posterior region of the Ascidiozooid. The 
oesophagus runs posteriorly and ventrally and is moderately long (PL III. fig. 14, n?). 
It has no marked angle. The stomach is large and is strongly ribbed externally, 
especially at the oesophageal end, which is truncated and much wider than the opposite 
end where the stomach tapers somewhat suddenly into the intestine. There are usually 
five projecting folds on each side of the stomach. The intestine (PL III. fig. 14, i) 
curves anteriorly, and then dorsally, and a little posteriorly to touch the anterior edge 
of the stomach. It then turns dorsally and anteriorly to become the rectum, which, after 
