ON CORAL llEEFS OF THE INDIAN REGIONS. 401 



small coral colonies, which were evidently a growth of the previous 

 north-east naonsoon. In September these had completely disappeared, 

 having been washed away in the south-west monsoon. At Galle, Talpe, 

 and Weligama numerous recently living colonies of corals, particularly 

 of the genera Porites and Pocillopora, of four to eight months' growth, 

 were found completely silted up with sand and dirt of all sorts. 



A noticeable point about the reefs immediately round Ceylon is the 

 comparative absence of reef-building nuUipores, which are a marked 

 feature of all isolated oceanic reefs. In connection with this an attempt 

 was made to examine the shoals two to six miles off the south and south- 

 west coasts of the island, which indicate with the soundings the possible 

 upgrowth of a barrier reef. The weather, however, at that season was 

 so unfavourable that I was unable to dredge, land, or anchor on any. 



>Subsequent visits to south India and north Ceylon indicated clearly a 

 former land connection between the two. The so-called Adam's Bridge 

 and the islands of Manaar and Ramasserim, which the former joins, 

 appeared indubitably to be the remains of a formerly elevated limestone 

 Hat, which has been more or less cut down by the sea to the low-tide 

 level. The coast lines, too, of Ramasserim and to the north of the Jaffna 

 peninsula were also probably at one time continuous. 



The months of June, July, and August 1899 were spent in Minikoi, 

 an isolated atoll, the most southern of the Laccadive group. Here I 

 was accompanied by Mr. L. A. Borrodaile, who proposed to study various 

 points connected with the Crustacea and Chsetopoda. Unfortunately Mr. 

 Borrodaile, who had been collecting these forms in Ceylon, almost at 

 once succumbed to the climate, and after five weeks returned to Ceylon, 

 whence he was at once ordered home. Every part of the island was 

 visited : a survey was made and numerous cross-sections were run. 

 From these it was clear that there had been an elevation of the original 

 reefs to a height of at least twenty-five feet above low-tide level. 

 Numerous observations were made on the currents at different depths 

 within the lagoon in reference to its shoals, &,c. Work on this point 

 could seldom be carried on outside the reefs, as originally intended, 

 owing to the heavy north-westerly winds which prevailed. The lagoon 

 was dredged to ascertain the distribution of its corals, and a few water 

 samples and temperature observations were taken. 



Considerable attention was paid at Minikoi to the sand-feeding organ- 

 isms, especially Holothuria?, Enteropneusta, and Sipunculida. These forms 

 appear to be largely instrumental in finely triturating the sand, the small 

 particles being subsequently carried out of the lagoon in a state of suspen- 

 sion. The boring organisms, too, are very important in causing the decay 

 of dead coral and rock, especially in the lagoon. These, accordingly, 

 do not form points of attachment for fresh reef growths to arise, and 

 owing to the larger surface exposed are the more readily dissolved by the 

 water. Indeed all evidence collected showed that the lagoons of atolls 

 may be, and are, very generally formed by the solution of the central 

 rock of originally more or less flat reefs. 



In October 1899 I left for the Maldive group, to which I was accom- 

 panied by Mr. Forster Coopei", who assisted me in all the work and very 

 largely took charge of the dredging. The Sultan lent us a schooner of 

 about eighteen tons, which we at once fitted out in Male, subsequently 

 cruising through the northern atolls during the months of November, 

 December, and part of January. About a hundred islands in the atolls 



1900. D jy 



