CHAPTER IV. 



CORSLS END CORSL-ANIMALS. 



ONCERNING the nature and organisation of the living animals by 

 whose agency, direct and indirect, the vast edifice of the Great Barrier 

 and all kindred coral-reefs are chiefly fabricated, much has been already 

 said in the opening paragraphs of Chapter II. It was there distinctly 

 demonstrated that the hard-dying, popular notion of an industrious 

 coral insect that lived independently of the coral, and, with consummate 

 skill and patience, built up the reef on the same principle as ants 

 or bees construct their nests or waxen cells, had no foundation in fact, 

 and should be permanentl}- consigned to the limbo of exploded fallacies. It was also fully explained 

 that coral-animals, in the restricted sense of the term, were organisms that agreed essentially in 

 structure with ordinary polyps or sea-anemones, with the exception that they possessed the pro- 

 perty of secreting within their tissues a distinct calcareous skeleton. It is proposed in this chapter 

 to devote some space to a detailed account of the leading modifications of the innumerable species 

 that are included b}' biologists in the coral-producing polyp class, associating such account with 

 descriptions and illustrations of the more typical and attractive varieties which are comprised 

 in the marine fauna of the Great Barrier Reef. 



It is scarcely necessary, perhaps, to reiterate here that the main mass of the Great Barrier, 

 and of all other coral-reefs, is chiefly composed, not of the perfect polyparies or coralla of growing 

 corals, but of a sort of indurated concrete, built out ot the broken-up and reconsolidated debris ot 

 coral-stocks that have either undergone natural disintegration, or have been forcibly torn by storms 

 from their original position on the reefs. This indurated reef-rock, as previously remarked, may 

 vary in texture from a fine, close-grained limestone, that rings under the hammer, to coarse, 

 loosely-constructed conglomerate, in which coralla of every size and description, and every possible 

 condition of conservation or of erosion, are bound together by a fine calcareous cement. Sufficient 

 prominence, however, has not been previously given to the fact that the entire, or more or 

 less fragmentary, calcareous skeletons of a large number of organisms, in addition to those of 

 coral polyps, enter into the composition of the reef limestone or conglomerate. The class of the 



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