Ill 



** (3) destruction by fish, which had got into the tank, 

 and preyed uj)on them ; 



** (4) by excessive agitation of the water in the tank 

 during the south-west monsoon sea ; or, pro- 

 bably, to all these causes combined." 



In March 1886 another experimental tank was made on 

 a more sheltered part of the reef, and 5,000 oysters were 

 placed in it. But, in the following year, all the oysters 

 were found to be dead. The artificial cultivation of the 

 pearl-oyster was attempted some years ago in a nursery 

 mfi.de in the shallow muddy water of the Tuticorin harbour 

 without success ; and, in his final report to the Ceylon 

 Grovernment, Mr. Holdsworth expresses his opinion that 

 there is no ground for thinking that artificial cultivation of 

 the pearl-oyster can be profitably carried out on the Cej'lon 

 coast, as the conditions necessary for the healthy growth 

 of the oysters are not to be found in the very few places, 

 where they could be at all protected or watched. 



On the way to Captain Donnan's tank, which we visited, 

 we rowed over extensive banks of Alcychnans, of the luxu- 

 riant growth and size of which only a very feeble idea is 

 obtained from specimens as seen in museums. On the sandy 

 bottom a large number of Echinoderms, solitary or clustered 

 together, were clearly visible ; and, with the assistance of the 

 divers and the dredge, the following species were procured : — 

 Temnojileurus toreumaficKs, a violet-spined Temnopleuroid^ 

 Oreaster thurstoni, Salmacis bicolor, Lagarium depressum, Fihul' 

 aria voloa, Echinolampas oviformh, Holothuria afra, and Colo- 

 chirus quadrangularis. These species, as also Oreaster linchi 

 and Linckia Ivevigata, which abound on the Muttuwartu Par, 

 are all found on the opposite coast of the Grulf of Mannar, 

 A single young specimen of IlippocampKS was also brought 

 up in the dredge. The tank, washed by the gentle swell, 

 showed no signs of pearl-oysters, which had, doubtless, been 

 smothered and disappeared below the surface of the bottom. 

 But growing from the inner side of the barrier of dead 

 coral which formed the wall of the tank was a fringe of 

 living corals — Monfipora, Pocillopora, Madrepora, &c. As 

 these corals had grown in their present position since the 

 construction of the tank, which was built up entirely of dead 

 blocks of solid coral brought from the shore, the living corals 

 on the reef being found to be too brittle to form a suitable 

 wall, it was obvious that, as the tank was built in March 

 1886, the age of the corals did not exceed three years and 



