238 ANNUAL REPOET SMITHSONIAN INSTITUTION, 1917. 



(3) Recent rise of sea level because of deglaciation lias made con- 

 ditions favorable for coral reef formation over enormous areas, and 

 it is one of the important factors in causing the great development 

 of coral reefs at the present time. But in some areas, as in the Fijis, 

 the flats on which the reefs are growing are coastal flats that have 

 been brought below sea level by tilting, as described by Andrews and 

 Foye. 



(4) The theoretic possibility of the progressive change of a 

 fringing reef into a barrier and later into an atoll, according to the 

 Darwin-Dana hypothesis, may not be denied, but no instance of such 

 . a transformation has as yet been discovered. 



(5) The results of the investigation of coral reefs are valuable to 

 geology not so much because of discoveries immediately concerning 

 corals as because of the additions to knowledge obtained through 

 a study of great complexes of geologic phenomena among which 

 corals and coral reefs are only incidents. Further investigations of 

 the phenomena associated with coral reefs are among the pressing 

 desiderata of geologic research. 



