342 CEYLON PEARL OYSTER REPORT. 



The green colour is due to immense numbers of small round bodies which are probably 

 symbiotic Algse. They have a central clear space (fig. 35), while around that is a 

 finely granular pigmented layer. These pigmented cells are specially abundant in the 

 outer layers of the test ; they are also around the bodies of the ascidiozooids, and 

 they extend more sparsely scattered through the loose lacunar test that occupies the 

 centre of the colony (fig. 40). Vessels with swollen terminal knobs (fig. 36) are a 

 conspicuous feature in the thin expanded margin of the colony. 



Diplosoma crystallinum (GiARD). 



A number of small colonies of a grey semi-transparent Diplosoma which were found 

 encrusting pearl oysters and sponges, &c. , in the oyster cages suspended from the ship 

 at the Cheval Paar, are indistinguishable from the common European D. crystallinum. 

 There are long pointed lobes to the branchial siphon, the ascidiozooids have large 

 eggs, and many tailed-larvse are embedded in the test (taken in April). Ten colonies 

 range from 1 centim. to 3 centims. in length. 



Diplosoma, sp. (?) Plate VIII., fig. 44. 



Four small reddish-brown colonies were dredged from Muttuvaratu Paar 

 (Station LIX.), 9 fathoms, which resemble D. viride, from Galle, in structure, but 

 have pigment spherules of a different colour in the test. The colony is fixed by a 

 small base, has overhanging edges and a flat upper surface with a little central tubercle 

 which probably marks the position of the common cloacal aperture (fig. 44). The 

 ascidiozooids show as dots on the surface, and in profile on the margin. The test is 

 very tough, is vacuolated as in the case of D. viride, and contains many rounded 

 pigment masses of a reddish colour. 



FAMILY: SALPID^. 

 Salpa cylindrica, CUVIER. 



Some individuals of both the solitary and the aggregated forms of this species were 

 obtained in tow-net gatherings on the West Cheval and the Periya paars, and in 

 Palk Bay. The solitary forms extend up to 29 millims. in length, and single 

 members of the chain form up to 14 millims. 



My " Field-notes" contain some observations on the specimens of this species taken|in 

 Palk Bay. " The body is nearly cylindrical, when alive, with projecting ridges along 

 the sides. The ' nucleus ' is marked with yellow, brown, and red. The stomach is 

 brown with yellow caeca around it. When swimming, the tubular orifices are drawn 

 in and shot out again almost simultaneously. They certainly do not alternate. 

 If not quite simultaneous the order is : oral, atrial, long pause, oral, &c. The 

 aggregated forms are arranged longitudinally in chains and are iridescent when in 

 movement, and look pale blue on a black background.'' 



