I20 



MANUAL OF ZOOLOGY. 



dermic corallum each polype has a complete skeleton of its 

 own, and the entire coral may consist of one such skeleton, or 

 of several such united by the calcareous matter of the ccenosarc 



Fig. 32. — Morphology of Corals a Cup of Acervitlnria ananas, showing calicular 

 gemmation, enlarged ; i> Diagram of Rugose Coral {Polyccelia profunda), showing 

 the quadripartite arrangement of the septa; c Diagram of a recent coral, showing 

 the sextuple arrangement of the septa ; rf Vertical section of Campophyllimi flexuo- 

 sitm, showing tabulae. 



A sclerodermic corallum, therefore, like tne animal which pro- 

 duces it, may be simple or composite, according as it is pro- 

 duced by a single polype or by several united by a ccenosarc. 

 It consists, therefore, of a single calcareous cup, or " corallite;" 

 or of several such united by a common calcareous bond or basis, 

 the "ccenenchyma." Taking a single "corallite" (fig. 32, d) 

 as the type, we find that it shows its origin and nature plainly 

 in its form. It consists of a cylindrical or conical tube of car- 

 bonate of lime, the outer wall of which is called the "theca." 

 The upper part of the space included by the "theca" is vacant, 

 and it is termed the cup or "calice;" but the lower part is sub- 

 divided into a series of chambers, or " lociili," by a series of 

 radiating, vertical, calcareous plates, which are called the 

 "septa" (fig. 32, li). The septa extend from the inner surface 

 of the theca towards its centre, where they usually unite to 

 form an axial column, called the "columella." Many of the 

 septa, however, do not reach the centre, but stop short at 

 some distance from the columella, often being broken up into 

 upright pillars, called "pali." The parts thus described as 

 essentially composing a corallite in a typical sclerodermic 

 corallum are related in the most obvious manner to the soft 

 structures of the animal by which they are secreted. Thus, 

 the " theca " clearly corresponds to the " column-wall," or the 

 general wall of the body ; the " columella," when present, cor- 



