REPOKT THE THNICATA. 
147 
stigmata (PL XVIII. figs. 10, 12). The transverse vessels vary a little in size, but are 
always very narrow. In some cases they are so small as to be reduced to an undulating 
vessel winding between the ends of the adjacent interstigmatic vessels (PL XVIII. 
fig. 11, tr.). 
The stigmata are rather long and narrow in the fully developed sac (PL XVIII. 
fig. 10, sg.). In the young state they are short and rounded (PL XVIII. fig. 12, sg.), and aU 
intermediate forms may be found. In some places the branchial sac is of an opaque green 
colour from the numbers of blood-corpuscles contained in the vessels. The endostyle 
is long and narrow, and takes a straight course. It is not very conspicuous. 
The dorsal lamina is remarkable on account of its having no languets. It is a 
perfectly plain and rather narrow membrane (PL XVIII. fig. 13, cZ.L), which is formed 
anteriorly by the junction of the right and left halves of the peripharyngeal band 
(PL XVIII. fig. 13,p.p.). The dorsal lamina is exactly like the internal longitudinal 
bars of the branchial sac, but is a good deal wider. 
The tentacles are like those of some species of Colella. They are not numerous, and 
are all of one size. They are attached to a very thick muscular band which encircles the 
base of the branchial siphon, and bounds the prebranchial zone anteriorly (PL XVIII. 
fig. 13, spli.), while it forms the posterior end of the branchial sphincter. 
The aperture of the dorsal tubercle is small, but has a thick lip surrounding it. It is 
placed nearly at the angle of a very deep triangular peritubercular area (PL XVIII. 
fig, 13, d.t.), which is formed by the peripharyngeal bands bending posteriorly to join 
the anterior end of the dorsal lamina. 
The alimentary and reproductive viscera form an opaque yellowish mass placed 
alongside the posterior part of the branchial sac and projecting very little beyond it. 
The oesophagus is narrow. The stomach (PL XVIII. fig. 14, st.) is large and globular. 
It lies with its long axis directed dorso-ventrally. It is ridged internally and has a small 
curved horn-like caecum (PL XVIII. fig. 14, ccb.) projecting from the anterior part of its 
ventral end. The intestine is wide. It curves ventraUy and anteriorly, and then after 
running for a short distance dorsally it crosses the oesophagus, and turning anteriorly 
again becomes the rectum, which runs up the dorsal edge of the branchial sac to open 
into the peribranchial cavity near to the atrial aperture. 
In structure and course, as well as in position, the alimentary canal resembles that of 
some of the Botryllidae. The reproductive organs are hermaphrodite, and consist of one 
or two large clear yellow ova and an irregular mass of small spermatic vesicles. 
A number of tailed larvae were found in the colony. They are rather small, and have 
short rounded bodies. Two pigmented sense organs are present. 
