CHAPTER II. 



CORHL-REEFS, THEIR GENERAL STRUCTURE, HND THEORIES OF ORIGIN, 



SLIGHT deviation is here made from the original intention to pro- 

 ceed forthwith with a description of the structural features of the 

 Great Barrier Reef of Australia, together with an examination of the 

 conditions under which, apparently, this vast coral edifice was primarily 

 produced. In order to make the general reader able to follow the 

 details given, and to assist him towards forming a clearer judgment 

 concerning the evidence hereafter to be submitted, it has been thought 

 !i desirable to devote a short preliminary chapter to a brief outline of 

 the more generally recognised elements and modifications oi coral-reef structure, supplementing 

 such details with a precis of the newer interpretations that have of late years been associated 

 with coral-reef formation. 



For the information of those by whom the subject of corals and coral animals is approached 

 for the first time in this volume, it is necessary to begin with a descent into elementary 

 details, which the accomplished specialist will of necessity skip. In the first instance, it is, 

 perhaps, incumbent to define the correct significance of the terms "corals" and "coral animals." 

 Notwithstanding the wide diffusion of knowledge, which includes a smattering of many "'ologies," 

 it is astonishing to find how tenacious an influence ancient tradition concerning coral organisation 

 still exerts on the public mind. The poetic fallacy of coral-reefs being built up by an associa- 

 tion of "insects" between which there subsists a relationship analogous to that which obtains 

 between " the busy bee and its waxen cell " is frequently enunciated from the pulpit, and in 

 the pages of the daily newspapers. 



Doubtless, there is a large section of the public whose zoological lore will ever 

 remain restricted to the narrow limits of that of Piiiic/i's railway porter, who, puzzled as to 

 the classification of the old lady's tortoise, declared that, being "neither a dawg nor a bird, 

 it must needs be a hinsec." There is also a very large multitude to whom the term 

 "insect" includes everything not distinctly referable to the category of "flesh, fowl, or 



