KEPOET ON THE TUNICATA. 
73 
This genus is formed for a very striking and remarkable new species, Colella thomsoni, 
obtained near the Philippine Islands and some allied species from other parts of the 
world, but, as will be shown below, a species {Colella pedunculata) described fifty years 
ago by Quoy and Gaimard under the name of Aplidium pedimcidatum also finds its 
place here. The two species, Colella thomsoni and Colella peduncidata, are very different 
in appearance, and at first sight seem to have nothing in common except that both are 
pedunculated Compound Ascidians. A careful examination, however, shows that they 
are really closely related. 
The genus Colella is allied to Oxijcorynia , von Drasche, and to Distaplio:, Della Valle, 
and unites certain of their characters, the result being that it cannot be included in 
either of the older genera. Two courses are open, the first to unite the three groups 
under the generic title first published, Distaplia, 1881 ; the second to consider them as 
three distinct genera. I think there is sufficient difference between them to justify me 
in taking the latter course, but Oxycorynia and Distaplia can no longer be placed in 
distinct families as arranged by von Drasche, consequently I have, as is explained above, 
merged the Chondi'ostaclyddse in the older family, the Distomidse. 
Of the ten species of Colella, two {Colella pedunculata and Colella thomsoni) are 
described in detail. They are good species to take for this purpose, first on account of 
their central position amongst Compound Ascidians, and second on account of the fairly 
large size of the Ascidiozooids, especially in the case of Colella thomsoni. 
The species of this genus may be distinguished by the following characters ; — 
Colella. 
Peduncle not 
branched. 
Peduncle 
branched. 
Peduncle longer 
than the head. 
Peduncle not longer Peduncle long 
than the head. and narrow. 
Colour red. 
C. pulchi'a. 
Tentacles 
large, 
sixteen. 
I 
C. 'pedunculata. 
II I I C. ramulosa. 
Colour Colour bluish. Head narrow Head wide 
greyish- | at top. at top. 
yellow. C. thomsoni. 
I Head longer Head not Colour Colour 
Tentacles than broad, longer than greyish- brown, 
small, I broad. yellow. | 
eight. C. elongata. \ \ C. murrayi, var. 
I C. quoyi. C. murrayi. ruhida. 
C. gaimardi. 
Peduncle short 
and wide. 
C. concreta. 
(ZOOL. CHALL. EXP. PART XXXVIII. 1885.) 
Pp 10 
