CORALS AND THE FORMATION OF CORAL REEFS.* 



By Thomas Wayland Vaughan. 



[With 37 plates.] 



CONTENTS. 



Page, 



Introduction 189 



What are corals 190 



Differences in the corals on the lagoon (quiet water) and on the exposed (rough water) sides of a 



coralreef 194 



Relation of corals to depth of water 197 



Relation of corals to temperature 200 



Relation of corals to sediment 202 



Relation of corals to light 202 



Capacity of corals to withstand exposure in the air 204 



Relation of corals to concentration of salts in the ocean 205 



How corals catch their food and what they eat 206 



Rearing coral larvae 208 



Distribution of corals by marine currents 210 



Rate of growth of corals 210 



Summary of statements on corals 214 



The formation of coral reefs 215 



Definition of the term "coral reef" 215 



Some kinds of limestone that have been confused with coral-reef rock 216 



Geographic distribution of coral reefs 220 



Theories of the formation of coral reefs 222 



Critical examination of the different theories of the formation of coral reefs 225 



Conclusions 237 



INTRODUCTION. 



Corals have long attracted the attention and excited the interest 

 of scientific men, obgervant laymen, and poets. For some hundreds 

 of years they were thought to be marine plants and were termed 

 " Zoophytes," a name said to have been given them in the sixth 

 century by Sextus Empiricus and Isodore of Seville. Notwithstand- 

 ing that Ferrante Imperato in 1599 advocated that corals were ani- 

 mals, naturalists persisted in believing that they were plants until 



* In the present article only a few specific references to the literature on corals and 

 coral reefs have been introduced. However, in my memoir entitled "Fossil corals from 

 Central America, Cuba, and Porto Rico, with an account of the American Tertiary, 

 Pleistocene, and Recent coral reefs," in press as a part of U. S. National Museum Bulletin 

 103, I have given fairly full bibliographic citations and have called attention to certain 

 publications, particularly those by W. M. Davis and R. A. Daly, in which there are 

 elaborate reviews of the literature on coral reefs. 



189 



