316 
THE VOYAGE OF H.M.S. CHALLENGER. 
large numbers of bladder cells (PL XLIL fig. 3, hi.). In many places the bladder cells 
are polygonal from mutual pressure. 
The test cells are of two distinct kinds.: (1) the large granular cells, which are very 
conspicuous — these are mostly of spherical or ellipsoidal shapes, but occasionally become 
elongated ; and (2) the ordinary small test cells, which are of fusiform, stellate, or branched 
shapes — these are not numerous, and are inconspicuous on account of their small size 
and clear protoplasm. Vascular ectodermal appendages are found here and there in the 
test. They have short wide terminal bulbs. 
The thorax and abdomen of the Ascidiozooids are of nearly equal size, and they are 
not separated by a marked constriction as in the case of Diplosomoides molle. Some 
parts of the mantle are slightly pigmented, and of a brownish colour. The branchial 
siphon is Amry short, and the aperture is not lobed. The sphincter is, however, distinct. 
The muscle bands of the mantle are very delicate ; they run in various directions. Two 
bands run along the dorsal edge of the thorax. 
The branchial sac is longer antero-posteriorly than dorso-ventrally. The stigmata are 
regularly arranged, and their ciliated cells are distinct (PI. XLIL fig. 4, sg.). The 
muscle bands in the transverse vessels are not strong, and there are no fiibres present 
in the longitudinal interstigmatic vessels (PI. XLIL fig. 4). 
The endostyle is conspicuous ; its course is straight. The dorsal languets are long and 
narrow. The tentacles are long ; they vary a little in number, but are always of two 
sizes, and are arranged regularly. The nerve ganglion and neural gland form an ovate 
opaque mass placed not far from the branchial aperture. 
The oesophagus leads backwards for a short distance from the branchial sac to the 
large globular smooth- walled stomach (PI. XLIL fig. 2). The intestine curves round 
ventrally from the posterior end of the stomach in >a wide open loop, and then crosses 
over to the dorsal side so as to reach the branchial sac close to the oesophagus. The 
intestine throughout the greater part of its length contains a series of round faecal 
pellets of a brown colour (PL XLIL fig. 2). The stomach is also sometimes of a brown 
colour from the contained food matters. 
The reproductive organs were not well developed in any of the Ascidiozooids 
examined. 
