INVESTIGATIONS IN THE INDIAN 0CP:AN. 



^33'' 



ordinary paucity of animal life. Green weed, too, of every sort is prac- 

 tically absent. However, this barrenness is amply compensated for by the 

 enormous quantity of Nullipores [Lithothamnia, kc), incrusting, massive, 

 mammillated, columnar and branching. The outgrowing seaward edges 

 of the reefs are practically formed by their growths, and it is not too 

 much to say that, were it not for the abundance and large masses of these 

 organisms, there would be no atolls with surface reefs in the Chagos. 

 The lagoon shoals of Egmont are covered by them, and are the only lagoon 

 reefs in the Chagos that reach the surface ; having once done so, they die 

 and become hollowed out, finally resembling miniature atolls. 



In such a large group as the Chagos the conditions of the encircling 

 reefs against the lagoons naturally vary very considerably. In general 

 their inner edges reach the surface, and in the more open atolls the lagoon 

 slope to 10 fathoms closely resembles the seaward slope. The bottoms of 

 the lagoons are bare rock, hard sand, or mud, with shoals arising pre- 

 cipitously here and there, built up by a few species of coral, but largely 

 covered by Xenia and Sarcojyliytum (as are also the only two submerged 

 banks, Wight and Centurion, which we examined). Diego Garcia lagoon 

 differs somewhat owing to its being almost completely surrounded by 

 land. It has, perhaps, the most varied fauna in the group, and gives 

 definite evidence of enlarging in every direction. The land everywhere 

 is entirely of coral origin. Diego Garcia shows signs of a recent elevation 

 of a few feet, the present single island having been formed by the joining 

 up of a series of separate islets on an elongated reef. The kuli, or 

 barachois (large shallow lakes) of the same island owe their origin to the 

 same elevation, though elsewhere in the group they are sometimes due to 

 the successive washing up of beaches from the sea, enclosing areas of the 

 reef. On the whole, there is singularly little change since the survey in 

 1837, and my impression is that Chagos has been for a long time an area 

 of rest, and that the present condition of its reefs is mainly due to 

 agencies still in action. 



We further examined the marine fauna in Salomon, Pcros Banhos, 

 Diego Garcia and Egmont, and we would lay stress on its comparative 

 paucity and lack of variety as compared with the Maldives, Fiji and 

 Funafuti, though many of tlie forms are very common. In short, its 

 general character is rather that of the temperate than of the tropical 



zone. 



The land fauna is largely dependent on the flora, and the latter, except 

 on small isolated islets and selected positions, has been destroyed to allow 

 of coconuts being planted. The shores are everywhere fringed with 

 Sccevola koenigii and Tournejortia argentea, both covered with a climbing 

 bean. Behind these there was originally a forest formed of immense 

 mapou (Pisonia ca^ndia) and takamaka [Calophyllum inophyllum), with 

 a few coconuts, Barringtonia, banyans, and other smaller trees, and an 

 undergrowth largely consisting of immense Asplenium and other fei-ns 

 and Psilotum, herbaceous dicotyledons being confined to the more open, 

 dry, sandy and stony parts ; mangroves and Fandani are, curiously 

 enough, not found. With the assistance of Dr. Simpson we collected the 

 flora of each of the atolls, obtaining more than 600 specimens (about 140 

 species), of which probably only half are indigenous. 



Of mammals there are only rats aiid mice, but there are traditions of 

 dugong as well. Of birds, the cardinal, sparrow, and mina have doubt- 

 .lesa been introduced ; noddies, frigates, and terns were breeding in 



