332 CEYLON PEARL OYSTER REPORT. 



(' Mitth. Naturh. Mus., Hamburg,' 1904), into the genus Diandrocarpa, Van Name, 

 and agrees fairly well in details of structure with the species D. hrakenhielmi, 

 Michaelsen. It shows a single hermaphrodite gonad (fig. 12) on each side of the 

 body, and the spermatic sacs are deeply cleft into lobes (fig. 15). There are, however, 

 some points of difference. There are only about 12 folds in the stomach-wall, 

 certainly not so many as 14 or 15, the ducts from the spermatic cseca are certainly 

 longer than MiCHAELSEisr represents, and, finally, the Ceylon species appears to be 

 more transparent and does not in life, at least, show the bluish grey and other colours 

 noted in the described forms of D. hrakenhielmi. I do not attach much importance 

 to the last point, since it is probable that Michaelsen's specimens from the Berlin 

 and Hamburg Museums were preserved colonies which had lost their transparency 

 and changed their colour. And as I find that individuals vary somewhat in the folds 

 of the stomach wall, in the proportions of the tentacles, and in other details of 

 structure, I think it best to refer this to the described species with which it closely 

 agrees, calling it the Ceylon variety and figuring its peculiarities. I have specimens 

 in the collection from three localities, and my field-notes in regard to two of these are 

 as follows : 



(1) North end of Periya Paar, Station LXIL, 12 fathoms. " (?) Polystyelid on 

 young pearl oyster shell, translucent grey with lemon-yellow pigmentation, especially 

 along a line (? endostyle) between the apertures, and also around the atrial siphon. 

 Line of red around the edge of each aperture. Under low power of microscope 

 surface is seen to have a reticulum of yellow, pale-blue and red-brown lines which are 

 sinuses tilled with pigment corpuscles." 



(2) Cheval Paar, 6 fathoms, several colonies. "A very thin transparent (?) Poly- 

 styelid with large ascidiozooids up to 4 millims. long, with very conspicuous branchial 

 sac because the vessels are all engorged with coloured corpuscles. One colony covers 

 a large area in the interior of an old pearl oyster shell and allows the nacre to show 

 through distinctly. Ascidiozooids slightly grey, test between transparent, with a few 

 meandering coloured lines which are vessels." 



The third locality is Attached to oyster cages suspended from the ship on the 

 Cheval Paar ; about 20 colonies ranging from 1 centim. x 1 centim. to 7 centims. x 

 6 centims. over all. 



These specimens, although differing a little in appearance, are clearly the same 

 species, and figs. 10 to 18, on Plate VII., show the leading points in structure. 

 There are 10 to 12 rows of stigmata in the branchial sac, and the transverse vessels 

 are very conspicuous from being filled with coloured corpuscles. The vessels in the 

 test, and especially in the marginal parts of the colony, are a conspicuous feature 

 (figs. 11 and 17). There are 12 oral tentacles of three orders, which show, however, 

 some variation in arrangement (figs. 14 and 18). They may be 1, 3, 2, 3. 1, &c, or 

 1, 3, 3, 3, 1, 3, 2, 3, 3, 3, 2, 3, or 1, 3, 3, 2, 3, 3, 1, &c. There are about 20 much 



