94 
THE VOYAGE OE H.M.S. CHALLENGER. 
On the other hand, after a certain period the power of reproducing by gemmation will 
probably decrease, and, as a result, the colony will dwindle away and finally disappear, 
new ones being doubtless formed by the free swimming tailed larvae which escape from 
the incubatory pouches of the adult Ascidiozooids. 
Colella thomsoni, n. sp. (Pis. X.-XIIL). 
The Colony is somewhat club-shaped, and is attached by the base of an irregular 
peduncle which does not increase in size as it is traced upwards. The head, in which 
the Ascidiozooids are placed, is of an elongated ellipsoidal shape. The surface is smooth. 
The colour of the head is bluish- violet, of the stalk white. 
Size — head 0‘9 to 6'5 cm. in length, and 0’7 to 3 cm. in greatest breadth; stalk 
7 '2 to 13 cm. in length, 8 mm. in average diameter. 
The Ascidiozooids are of very large size and are imbedded in the common test. The 
body of each is composed of thorax and abdomen with a long vascular appendage. 
The Test is soft and gelatinous in the head, and considerably harder in the peduncle. 
The Mantle is thin, but is fairly muscular. 
The Branchial Sac is large, and has many rows of stigmata on each side. The 
transverse vessels are all of the same size. The stigmata are long and narrow, and are 
arranged with regularity. 
The Dorsal Lamina is represented by a series of long triangular languets. 
The Tentacles are eight in number, and are all of the same size. 
The Dorsal Tubercle has a simple circular aperture. 
The Alimentary Canal is large, and extends for a considerable distance behind the 
branchial sac. • 
The Reproductive Organs are not large, and lie alongside the alimentary canal. The 
testes are well developed ; they are arranged in a grape-like manner. 
The Incubatory Pouch is small, and is not coiled spirally. 
Locality. — Station 212, January 30, 1875 ; lat. 6° 54' N., long. 122° 18' E.; depth, 
10 fathoms ; bottom, sand. 
About a dozen specimens of this remarkable species were obtained off the south 
coast of the Philippine Islands, in shallow water. It resembles somewhat in external 
appearance Oxycorynia fascicularis, von Drasche,^ from the Caroline Islands, and a 
Compound Ascidian figured by Gould,^ and named “ Nephtheis {?),” from the Sulu Sea, 
but differs from both. Besides other points of distinction, Oxycorynia fascicularis has 
the Ascidiozooids projecting at their anterior ends, while in Gould’s species the peduncle 
is branched and the colour is green. 
* Verhandl. d. Jc. Ic. zool.-hot. Gesellsch. Wien, Jahrg. 1882, Bd. xxxii. p. 175. 
“ United States Exploring Expedition, 1856, Mollusca, pi. lii. fig. 621. 
