292 
THE VOYAGE OF H.M.S. CH ALLEN GEE, 
Locality. — Station 209, January 22, 1875 ; lat. 10° 14' K, long. 123° 54' E.; depth, 
95 fathoms; bottom, blue mud; bottom temperature, 71° F. 
One large colony and several fragments of this well-marked variety were obtained from 
a depth of 95 fathoms at Station 209, oJff Zebu, in the Philippine Islands. It is 
closely allied to Leptoclinum alhidum, Verrill, and in the arrangement of the Ascidio- 
zooids it resembles Yerrill’s variety luteolum, but it has certainly sufficient peculiarities 
of its own to warrant its being considered as a distinct variety, if not a separate species. 
The large colony is a magnificent specimen (see PI. XXXV. fig. 11). It i^ the 
largest of the Didemnidse in the collection. It is an incrusting mass which is attached 
to a large Lamellibranch, over which it has grown so as to completely bury both sides 
of the shell with the exception of a small area at one end of the hinge-line. At the 
opposite end of the colony, corresponding to the ventral edge of the shell, there is a 
narrow line across which the Ascidian is not continuous from side to side. Union has 
evidently been prevented from taking place in this region by the opening and closing 
of the mouth of the shell, so as to form a passage by which water might reach the 
Lamellibranch inside. The upper end of the colony and some parts of the surface are 
prolonged into rounded ridge's and finger-like lobes with blunt ends (PL XXXV. fig. 11). 
The average thickness of the colony is probably about 3 or 4 mm., but in some places 
it is three times as much. 
At the base (the dorsal edge of the shell) for a short distance there is a thin expanded 
edge formed in which no Ascidiozooids are present, and the test is very thin. Over the 
rest of the colony on both sides the Ascidiozooids are exceedingly numerous. They are 
arranged very much as in Leptoclinum alhidum, var. luteolum, so as to form a close 
network of lines over the surface (PI, XXXV. fig. 11). These lines are of a greyer colour 
than that of the test in the meshes, and they are occupied by canal-like extensions from 
the common cloacal cavities. The Ascidiozooids border the lines, but are also placed here 
and there in the meshes, which are not so large as in the specimens of Leptoclinum 
alhidum, var. luteolum from Tangier Bay (p. 290, PI, XL. figs. 10, 11). Consequently, 
although a general view of the colony gives the impression that the Ascidiozooids occupy 
merely the edges of the branching lines (PI. XXXV. fig. 11), a closer examination shows 
that in most places they are really scattered closely all over the surface (PI. XXXV. 
fig. 12), and that the grey lines formed by the cloacal canals wind in and out between 
them. 
The Ascidiozooids are small, and do not extend far into the test. Both thorax 
and abdomen are short. The branchial apertures project slightly above the general 
surface and cause a rough appearance. A surface view of the colony under a low 
power of the microscope shows (PI. XXXV, fig. 12) the numerous open branchial 
apertures of the Ascidiozooids surrounded each by two circles, the outer of which is the 
