CHAPTER II 



ON THE STRUCTURE AND CLASSIFICATION OF CORALS 



" II n'y a dans le Corail ny fleurs, nv feuilles, ny chair, ny graine, 

 ny racine et cela pose, je crois qu'il est bien eloigne du genre des 

 plantes." — Boccone, 1674. 



The large and very heterogeneous assembly of organisms 

 forming the calcareous or horny structures which are com- 

 monly called Corals may be divided into two great divisions : 

 the Animal corals and the Plant corals. 



The Animal corals may be again divided into two 

 groups, namely, those that bear polyps and those that 

 do not bear polyps ; and the Plant corals also into two 

 groups, the Red Seaweed corals and the Green Seaweed 

 corals. 



The polyp-bearing corals must be subdivided into a 

 number of orders according to the anatomical characters 

 presented by the polyps, but before this further sub- 

 division can be made clear to the reader it is necessary 

 to refer very briefly to essential characters presented by 

 these animals. 



There can be no doubt that when the word poulpe or 

 polyp was first introduced in this connexion the important 

 differences between different kinds of polyps, which more 

 modern researches have revealed, were not understood nor 

 even suspected. 



The word has no precise zoological meaning in modern 

 literature, but still retains its utility when applied to animals 

 which present certain superficial external characters in 

 common. It is not a word for which we can find a rigid 

 definition, and the student of zoology must be prepared to 



