Revietvs — Agassis' s Coral Beefs of the Pacific. 365' 



Semper also suggests that marine animals may build up a 

 foundation for the growth of reef-corals from far greater depths 

 than those at which corals can thrive. 



This writer also first called attention to the effect of solution in 

 removing material from an atoll, but it is to Sir John Murray 

 (1889-90, Proc. Koy. Soc. Edinb., xvii, p. 79) that we owe those 

 careful experiments to determine the amount of lime removed by 

 solution, and the suggestion of its importance as a factor in the 

 formation of lagoons. Semper even considers the effect of solution 

 in removing lime from the lagoon of an atoll as balancing the 

 constructive agencies proved by the growth of corals in it. 



Agassiz points out that Professor Dana was the principal 

 supporter of Darwin's theory of the formation of coral reefs, and 

 that the areas which these eminent naturalists and explorers covered 

 in their investigations seemed to include all that was essential to 

 satisfy the demands of Darwin's theory. 



The author gives a summary of each important group of coral 

 islands visited, with their chief characteristics, describing in detail 

 the structure of the Sandwich and Samoan Islands ; the Paumotu 

 Archipelago ; the Ellice, Marshall, and Gilbert Islands ; the 

 Gloucester Islands, and Marquesas ; the Cook Archipelago ; the 

 Tonga Archipelago ; the Haapai group to the north of Tongatabu. 



"Groups like the Ellice, Gilbert, and Marshall Islands give us 

 the means of studying the many modes of formation of the land-rims 

 in a most satisfactory manner. Nowhere have we been able to 

 follow as clearly the results of the various agencies at work in 

 shaping the endless variation produced in the islands and islets of 

 the land-rims of the different atolls of these groups ; changes due 

 either to slight elevation or to the incessant handling and rehandling 

 of the older material in place, or of the fresh material added from 

 the disintegration of the sea or lagoon faces of the land-rim, or of 

 the corals on the outer and inner slopes. It has been most 

 interesting to trace the ever -changing conditions which have 

 produced so many variations in the appearance and structure of 

 the islands, islets, and of the land-rims of the different groups. 



"In the Fiji, as in the Society Islands, the wider fringing reef- 

 flats often pass gradually into barrier-reefs with a narrow lagoon 

 between the outer edge of the reef platform and the shore line. The 

 rotten condition of the inner part of a wide fringing reef is most 

 favourable to its removal by solution or mechanically, and leads to 

 the formation of narrow lagoons, which may, as is the case in 

 Tahiti, become wide and deep barrier-reef lagoons. The small 

 number of islands and islets of the outer barrier-reef in Fiji atolls 

 contrast strongly with the well-wooded islands and islets on the 

 encircling belt of the Society Islands. 



" The disintegration of the masses of corals growing upon a reef 

 is due to the boring Echini, Mollusks, Annelids, Crustacea, and 

 sponges, which infect the large masses ; as these become weakened, 

 they are torn off by the waves and rapidly reduced to shingle. The 

 smaller fragments are then still further disintegrated by boring 



