1915.] A. Oxa : The Tunicata of the Indian Museum. 9 
thin all over and can be peeled off as a fine, moderately tough membrane. The 
hairs are outgrowths of this layer and are seen to spring densely from the surface in 
an oblique direction. Each hair is nearly of the same thickness throughout and is 
never branched ; the surface is rugged and is covered with fine mud particles. The 
inner layer or the test proper is soft, cartilaginous, almost colourless and trans- 
parent. Its thickness varies considerably in different parts, so that the internal body, 
taken out of the test, has quite a different shape compared with the entire animal 
(Pl. II, fig. 12). It is thickest in the region lying between the branchial and atrial 
apertures where it is nearly 5 mm. thick, while at the opposite end of the body it is 
less than 0°5 mm. thick. The inner surface is even and smooth, and is of the same 
colour as the substance of the test proper. A thin continuation of the test extends 
for some distance inwards from the branchial aperture. 
The internal body has avery peculiar shape. It consists of a globular trunk 
from the anterior end of which two large siphons are projecting. One of these, the 
atrial, exhibits no striking character, being simply a long, conical, slightly curved 
tube directed anteriorly and ending in a small four-lobed aperture, but the other, 
the branchial, is modified in a most extraordinary manner, and its shape is quite 
unique among the whole group of the Ascidiacea. Roughly speaking, it may be 
compared with a very short but wide tube bent in a curve, with one end compressed 
so as to represent a bilabiate mouth, and the wall on the convex side puffed out in. 
the form of a hemispherical dome. The branchial aperture is directed ventrally, 
the rounded dome-like surface looks anteriorly, and the whole structure is placed at 
the ventral edge of the anterior end of the trunk. The branchial siphon is nearly 
as large as the trunk itself, and as there isa slight constriction looking like a neck 
between the trunk and the siphon, one is reminded of a bird’s head with a dispropor- 
tionally wide mouth. Strangely enough, there is nothing in the external appearance 
of the animal suggestive of this peculiar configuration of the internal body. 
The Mantle is very thin and transparent in the trunk region, and scarcely any 
muscle bands are visible in this part of the body. On the siphons, on the contrary, 
both the connective tissue and the muscular bands constituting the mantle are well 
developed. There are strong muscle bands forming the rim of the branchial aper- 
ture, and a number of concentric annular bands are seen running parallel with the 
former. The longitudinal muscle bands are also numerous; they all start at the 
margin of the aperture, and run on the inner side of the transverse bands, cutting 
them at right angles so as to form a regular network with rectangular meshes. On 
the anterior surface of the body the longitudinal bands disappear gradually, being 
lost in the connective tissue, but on the ventral side they all terminate rather 
abruptly in a line marking the posterior boundary of the branchial siphon. Each 
of the tentacle-like lobes surrounding the branchial aperture is provided with a 
bundle of strong muscle fibres which fill up the axial portion of the stem. On reach- 
ing the base of the process just inside the rim of the branchial aperture, these fibres 
diverge and are either mixed up with the longitudinal and transverse bands of the 
branchial siphon proper or are gradually lost in the connective tissue (Pl. III, fig. 1). 
