REPORT ON THE TUNICATA. 
69 
The dorsal tubercle is placed very close to the anterior end of the dorsal lamina 
(PL lY. fig. 10, d.t.), and there is no proper peritubercular area. In some cases there is a 
slight bulging posteriorly of the peripharyngeal band at one side of the dorsal lamina, 
thus producing a slight enlargement of the prebranchial zone (PL lY. fig. 10), but this can 
scarcely be regarded as a true peritubercular area. The opaque yellowish-brown mass 
formed by the nerve ganglion and neural gland is clearly 'vdsible through the dorsal 
lamina (PL lY. fig. 10, n.g.). 
The alimentary canal is rather small (PL lY. fig. 7.). The oesophagus runs posteriorly 
with a slight ventral curve. The stomach is ovate in form and decidedly small. It is 
deeply channelled externally, and has a short recurved csecum springing from the anterior 
edge of its intestinal end. The intestine, which is narrower than usual in the Botryllidse, 
runs ventrally for a short distance (PL lY. fig. 7) and then turns anteriorly and dorsally, 
and after running parallel wdth the stomach but not touching it, reaches the oesophagus, 
and then turns anteriorly again to become the short rectum which ends in an anus sur- 
rounded by a prominent lobed margin. The cloacal region of the peribranchial cavity 
into which the anus opens communicates with the common cloaca! aperture of the system 
by a long atrial siphon formed of a prolongation of the mantle and provided with circular 
muscle bands which may be regarded as a diffuse atrial sphincter (PL lY. fig. 7, at.). 
This atrial siphon is sausage-shaped (PL lY. fig. 11), and has not the bulbous form found 
in Pohjcyclus lamarchi. It is lined in its entire extent by an invagination of the test, 
which at the base of the siphon expands in the peribranchial cavity into a disk-like mem- 
brane with lobed or crenated edges (PL lY. fig. 11, t.) 
No ova were found in this species. The reproductive organs are jdaced in the usual 
position (see PL lY. fig. 7), and consist only of rather small irregularly lobed spermatic 
vesicles. It is rather remarkable that while ova were j^i’esent along with the testes in 
such a closely allied species as Polycycliis lamarcki, they should be absent in all the 
Ascidiozooids examined of the present species. Only a very few buds or young Ascidio- 
zooids were discovered. These have masses of young ova placed laterally in the usual 
positions, and have no testes. Hence the probability is that this is a protogynous species 
like others of the Botryllidse. 
Family II. Distomida:. 
Colony rounded and massive, rarely in crusting, either sessile or supported upon 
a long or short peduncle. 
Systems irregular, inconspicuous, or abseiit. 
Ascidiozooids of moderate length and having the body divided into two regions, 
thorax and abdomen ; they may be provided with long vascular ectodermal 
appendages. 
