REPORT ON THE TUNICATA. 
99 
languets, which are attached to the muscular band running along the dorsal edge of the 
branchial sac. This band is seen best from the outside, and is of considerable breadth. 
A languet springs from it at its intersection with each of the transverse vessels of the 
sac (PI. XL fig. 9). Each languet has the form of a greatly drawn out isosceles triangle, 
and at the base its edges are in connection vdth the ends of the internal transverse 
vessels running along the inner surface of the branchial sac (PI. XL fig. 10). The edges 
of the languet are composed of columnar cells bearing short cilia, continuous with those 
on the internal transverse vessel. The languets are about 0'2 mm. in length, and are 
generally thrown into one or more curves. The rather blunt aj)ex of each extends to the 
base of the next below, and sometimes beyond it, when they are placed pointing 
posteriorly. 
Tentacles. — Eight is the normal number of tentacles in this species, but seven and 
nine have been also observed. They are all of the same length, and are placed in a 
circle in the usual position anterior to the periphai^mgeal band (PL XII. figs. 1, 2). 
They are rather shorter and stouter than those of the last species arid are placed much 
closer to the peripharyngeal band, but are othei'vdse very similar in appearance and 
minute structure. 
The Peripharyngeal Band requires no special description, as in structure and relations 
it exactly resembles that already described in the last species. The same may be said of 
the prebranchial zone and the ciliated band at the base of the tentacles, but a structure 
placed above or anterior to the tentacular circlet requires a short notice. It presents the 
appearance of a number of curiously shaped tentacles of different sizes arranged in a 
circle and directed outwards so as to meet and be overlapped by the true tentacles 
(PI. XII. fig. l). They form a series of irregular finger-like processes depending from 
the edge of a zone-like thickening of the mantle near the base of the siphon, and forming 
a sort of rudimentary diaphragm (PL XII. fig. 2). A similar structure is seen at the 
base of the atrial siphon, where, however, it is more rudimentary, being present only as a 
thickened undulating line (PL XII. fig. 3). 
Neural Gland and Dorsal Tubercle. — Here, as in the last species, these obscure 
organs are difficult to distiuguish on account of their oj)acity. On the ventral and 
anterior surfaces of the nerve ganglion there is a small oval or pyriform opaque yellowish- 
brown body (PL XII. fig. 1), which is, there can lie little doulit, the neural gland. 
Continued from its anterior end towards the circlet of tentacles is a somewhat conical or 
funnel-shaped opaque body with the wider end anterior. Its walls in an optical section 
are seen to be formed of columnar cells, and the interior is occupied by large cilia point- 
ing posteriorly. This is the neural duct, and its anterior end seems to be a simple 
circular aperture as in Colella p>edunculata. 
The Nerve Ganglion is of small size and is elliptical in shape. It is placed nearer to 
the branchial than to the atrial aperture (PL XII. fig. 3), and gives off nerves at its ends. 
