REPORT ON THE THNICATA. 
179 
is rather remarkable that this form, so closely allied to other species of the Polyclinidse, 
should differ from them in the number of lobes surrounding the branchial aperture, a 
feature which is in most Ascidians a diagnostic character of great importance and 
constancy. 
The brauchial sac is of considerable length, and may have as many as fourteen rows of 
stigmata upon each side. In most cases the anterior half of the sac is narrower than the 
posterior, and the stigmata in the wider part are rather larger than elsewhere. There 
are as many as eighteen stigmata in the larger rows, and they are usually wider than the 
fine longitudinal vessels between them. The transverse vessels are provided with muscle 
fibres, and are usually very regular and uniform, but in one sac I found a transverse 
vessel bifurcating (PI. XXIV. fig. 18) so as to produce a new row of stigmata, a 
condition frequently seen in some Simple Ascidians, but exceedingly rare amongst 
Compound Ascidians. The ciliated cells bounding the stigmata are large and 
distinct. 
The endostyle is large. The dorsal languets are tentacular in shape and rather 
blunt. 
The oesophagus is a gradually widening tube which leads from the posterior end of 
the branchial sac directly backwards to the large stomach (PI. XXIV. fig. 20, ce.). The 
stomach is irregularly pear-shaped, and its wall in place of being thrown into ridges as 
in Amaroucium variahile and other allied forms, is raised into a series of knobs 
projecting from the surface, on which the epithelium is greatly thickened. These 
knobs are placed in irregular rows extending antero-posteriorly along the stomach 
(PI. XXIV. fig. 20, cce.). There can be no doubt that this peculiar condition is simply 
the result of the breaking up of the longitudinal folds or ridges so common in the 
stomachs of Compound Ascidians into rows of detached knobs. The intestine extends 
for a considerable distance beyond the stomach and then turns sharply towards the 
dorsal side and anteriorly, to form a very narrow loop. It then becomes the thin- 
walled wide rectum, which runs forwards along^ the dorsal edafe of the abdomen and 
thorax. The post-abdomen varies considerably in size, usually it is rather narrow. Its 
prolongation to form ectodermal tubes or vessels which branch through the test (PL 
XXIV. fig. 17, v.ap.) is remarkable, since it is a condition very rarely seen in the 
Polyclinidee. 
Reproductive organs were not developed in many of the Ascidiozooids examined. 
When they are present, the vas deferens is large and conspicuous. Its course is very 
undulating. 
