AGASSIZ: FIJI ISLANDS AND CORAL REEFS. 9 



building up columnar masses which may eventually reach the surface 

 forming mushroom- or even bell-shaped structures, of which enlarging 

 rims may meet, " resulting in the formation of a connected reef surface 

 supported by many upright pillars underneath from forty to fifty feet 

 high," the so called " chapeiroes" of the Portuguese. These patches fre- 

 quently occur near the shore along the margin of a fringing reef, but are 

 hest developed in the deeper water of the Abrolhos regions and between 

 these and the city of Bahia, growing upon the submerged rocky ledge. 

 The number of reef building corals in Brazil is quite small, and Xulli- 

 pores seem according to Rathbun to play a very important part in the 

 building up of the limestone reefs. 



Professor Bonney ^ summarizes the position of the theory of coral reefs 

 as now left (1889) in the following terms : " That this theory may have 

 been expressed in terms a little too comprehensive, that there may be a 

 larger number of exceptional cases than was at first supposed, is quite 

 possible. ... It may very possibly be found that, as remarked by 

 !Mr. Bourne, the history of coral reefs is more varied and complicated 

 than was at first supposed, but it seems to me that, as the evidence at 

 present stands, it is insufiicient to justify a decision adverse to Mr. Dar- 

 win's theory as a general explanation." 



Professor Bouney, in spite of his intention to present an absolutely 

 unbiassed expression, has, in common with most geologists not familiar 

 with coral reefs, retained the view of the correctness of Darwin's theory.^ 

 It can scarcely be said that the earlier examinations of coral reefs were 

 made with the detail which has characterized the later explorations. 

 The original work of Darwin was limited to a narrow field, and sup- 

 plemented by data derived from charts and descriptions. Its con'ect- 

 ness depends wholly upon the existence of masses of coral reefs of great 

 thickness, where coral reefs exist as barrier reefs or atolls, and having 

 ■assumed this the rest naturally followed. For no one will deny that sub- 

 sidence is one of the possible modes of formation of masses of limestone 

 of great thickness. But subsequent observers showed most distinctly 

 that both atolls and barrier reefs occurred in regions of elevation. These 

 exceptions are not limited to a single area. They occur in regions of 

 the globe widely separated. "While it undoubtedly is true, as remarked 



1 Loc. cit., p. 332. 



2 Dana's support of Darwin's theory, based as it was upon very great ex- 

 perience among coral reefs, has probably been the principal cause of the gen- 

 eral acceptance of tlie theory in late years, in spite of the attacks of recent 



investigators. 



