192 
THE VOYAGE OF H.M.S. CHALLENGER. 
they are flat-topped and do not project as in the case of Colella pedunculata and some 
other species. 
The endostyle is long and narrow, but conspicuous ; its course is nearly straight. 
The languets (PL XIV. fig. 19, 1 .) are well ‘developed. The tentacles are very long and 
thin. Their bases form a rather small circle (PI. XIV. fig. 20) and are closely placed. 
There are about two dozen large tentacles and some smaller intermediate ones. The 
peripharyngeal band is very distinct, it does not form a peritubercular area. The mass 
formed by the nerve ganglion and neural gland is large and of an elliptical shape 
(PL XIV. fig. 20, n.g.). From its anterior end projects a very large and conspicuous 
neural duct with thick walls, which runs forward under the peripharyngeal band to open 
in the prebranchial zone, not far behind the base of the tentacles (PL XIV. fig. 20, d.t.). 
In all probability this very distinct neural tube really corresponds to the funnel-shaped 
enlargement, lined by columnar ciliated cells which is found in other forms (see 
Botrylloides fulgurale, PL III. fig. 8), and not to the more delicate part of the duct 
lying behind that. 
The alimentary canal is relatively not very large. The oesophagus is a narrow tube 
which runs from the dorsal edge of the posterior part of the branchial sac backwards 
and dorsally to open into the irregularly globular stomach (PL XIV. fig. 21). The 
oesophagus does not enter at the anterior end of the stomach, but a little way back on 
the inner edge. The stomach is thick walled, but has no folds in its interior. At the 
posterior end of the stomach the intestine commences by a very narrow passage which 
soon expands into a somewhat quadrate thick-walled dilatation (PL XIV. fig. 21); from 
this cavity the intestine continues backwards as a wide tube which turns round ventrally 
and then anteriorly to become the rectum. From this point forward the tube contains a 
series of ovate faecal pellets of a dark colour, which are just visible to the naked eye 
(PL XIV. fig. 21, r). The rectum is very long; it crosses the oesophagus, and is then 
continued up the dorsal edge of the branchial sac for a very considerable distance. 
The anus is small but has a prominent margin (PL XIV. fig. 21, a.). 
The reproductive organs are large, and form an ovate mass (PL XIV. fig. 22) extending 
for a considerable distance behind the alimentary canal. They thus agree with the 
arrangement seen in the other Polyclinidse, where there is always more or less of a post- 
abdomen developed, in which the genital glands are situated. In the development of this 
region of the body the present species is intermediate between Colella and the Distomidse 
on the one hand, and most of the Polyclinidse on the other. 
The mature Ascidiozooids are hermaphrodite. Ova of various sizes and ages are found 
along with fully developed spermatic vesicles (PL XIV. fig. 22, o. and t.v.). The ova form 
a clump upon one side of the genital mass, while the ovate spermatic vesicles are grouped 
in front and at the sides, and especially behind, where they form the most posterior 
part of the body of the Ascidiozooid. The vas deferens is large and is always a 
