■REPORT OIST THE TUNICATA. 
203 
zooicls partly ejected from the test and in a decomposed condition, while large areas 
of test occur in which no x4.scidiozooids are present. Hence it is probable that this 
is the oldest part of the colony, and that at the time when the specimen was collected 
many of the xA.scidiozooids in this region had died and were being removed from the 
colony. 
The branchial aperture is distinctly six-lobed, and the sphincter is well developed. 
Equidistant muscle bands are found running longitudinally in the mantle over the 
alimentary and reproductive viscera to the posterior end of the body. 
The branchial sac is very long. It has in some cases at least fifteen rows of 
stigmata, with nearly twenty in each row. The stigmata are long and narrow 
(PI. XXVII. fig. 5), and the stigmatic cells are convex on their free surfaces (PI. XXVII. 
fig. 6) and richly ciliated. The transverse vessels (PI. XXVII. fig. 5, tr.) are excep- 
tionally wide for a Compound Ascidian. 
The tentacles are large, and their bases, which are rather swollen, touch one 
another. The long tentacles are at least twice the size of the smaller intermediate 
ones (PI. XXVII. fig. 8, ^w.,, tn'.). The dorsal- languets are large and numerous. They 
are of the usual shape (PI. XXVII. fig. 7, 1.). The median dorsal line between them is 
occupied by a strong band of muscle fibres. 
The ahmentary canal forms a narrow loop, the elongated stomach and intestine lying 
close together. The wall of the stomach is very much folded, the longitudinal ridges 
projecting into the interior. The rectum is large, and is alw'ays filled with dark coloured 
faecal matter. 
The reproductive organs are of moderate size. They form a mass placed behind the 
intestinal loop, and continuing the abdomen posteriorly for a short distance, and then 
ending in a point. Thus no very distinct post-abdomen is formed. In most of the 
Ascidiozooids examined one or two large ova were found, more or less surrounded by a 
mass of small, ovate spermatic vesicles of an opaque dull yellow colour. The vas deferens 
is long and conspicuous. The spermatic vesicles and the vas deferens readily stain deep 
red with picro-carmine. 
This species closely resembles Pohjclinuni molle in the external appearance (compare 
PI. XXV. fig. 7, and PI. XXVII. fig. 3), and also in the structure of the test, but they 
differ notably in the form of the Ascidiozooids and in the structure of the branchial sacs. 
In the condition of the post-abdomen the present species shows some resemblance to 
Polyclinum fungosum, but differs from it in the structure of the stomach. 
Aplidium fuscum, n. sp. (PI. XX VIII. figs. 8-10). 
The Colony consists of a hemispherical mass, slightly compressed laterally, and 
attached by a small area in the middle of the lower surface. The upper end is broad 
