164 CORAL AND ATOLLS 



portions from time to time. During the early months of the 

 year, at the eastern extremity of Pulu Tikus, a spit composed 

 of rock fragments and sand, will form and extend far out into 

 the lagoon, only to wane gradually during the next few 

 months, with the deposition of sandy beaches at the western 

 end of the island. 



The barrier is the home of a myriad forms of life, but 

 only those need be mentioned here which have an influence 

 on its architecture, and so on the formation of the atoll. 

 Fish in thousands live in its pools, and come and go with the 

 rise and fall of the surf- line; and one of the strangest and 

 most beautiful sights of the barrier is the crowd of brightly 

 coloured fish seen mirrored in every oncoming wave. As you 

 stand on the coral beach it seems that every wave must wash 

 ashore these wonderful fish, and yet, as the sea sucks back 

 and the foam clears, they are still quietly feeding in the clear 

 water where there is only just enough depth for them to 

 swim. Many of these fish are amongst the most important 

 agents in the making of the coral sand which forms the cement 

 of the island and the silt of the lagoon, and the most active 

 of them all are the beautiful Kakatua (Scams, sp.), the most 

 conspicuous of the barrier fish. Darwin and Forbes, during 

 their visits to the islands, watched these fish, and asserted 

 that they fed on the living coral ; but this is certainly not the 

 case. As these bright green, or cobalt -blue, Kakatua go 

 slowly along head downwards, and with a frequent flapping of 

 their bright tails above the water as the wash flows back, they 

 seem to be grazing among the corals as beasts among herbage ; 

 and if their stomachs are opened they are found to contain 

 coral ground down to a very fine sand. But the coral from 

 which this sand is made is dead, and has long been dead ; for 

 it is the coral of the cemented breccia, and it is only scraped 

 off by the fishes' hard beaks as they rasp the boulders for 

 their covering film of algse. 



If the feeding-spot of the bright fish be noted, and the 

 boulders over which they have fed be examined, it will be 

 seen that on every rock is the characteristic bite where the 



