1. 5 8 MANUAL OF ZOOLOGY. 



covered with minute spines, All the Antipathida form colo- 

 nies, which are rooted by the base to some foreign object, and 

 which consist of numerous minute polypes united by a fleshy 

 ccenosarc (fig. 72). The corallum is secreted by the ccenosarc, 



Fig. 72. Part of the living stem of Antipathes anguina, of the natural size. 

 (After Dana.) 



and thus forms an axis or stem which is completely covered 

 during life by the soft parts of the colony, just as the trunk of 

 a tree is covered by the bark. Owing, further, to the fact that 

 the skeleton is produced wholly by the ccenosarc, the corallum 

 is wholly outside the polypes, which are themselves entirely 

 destitute of hard structures. Various other Actinozoa (such as 

 the Gorgonida) possess, as we shall see, a similar axial skele- 

 ton, secreted by the ccenosarc ; and all such coralla are said 

 to be " sclerobasic." As coralla of this nature are not formed 

 by hard structures deposited within the tissues of the polypes, 

 the general name of "foot- secretion" has been applied to them 

 by Prof. Dana. 



SUB-ORDER III. ZOANTHARIA SCLERODERMATA OR MADRE- 

 PORARIA. The members of this sub-order include the great 

 bulk of coral-producing or " coralligenous " zoophytes (Madre- 

 porarid] of recent seas. They are defined by the possession of 

 a corallum which is partially or wholly developed within the 

 tissues of the polypes themselves (" sclerodermic"), which does not 

 consist simply of scattered spicules, and in which the parts are 

 very generally disposed in multiples of six. The actinosoma may 

 be simple, consisting of a single polype only, or composite, consist- 

 ing of many polypes united by a ccenosarc. 



As regards the anatomy of their soft parts, the simple Zoan- 

 tharia sclerodermata may be regarded as essentially Sea-anem- 

 ones, whilst the compound forms are simply colonies of Actin- 

 oid polypes united by a common flesh or ccenosarc. It is, 

 therefore, only necessary to consider the nature of the skeleton 

 or corallum of these forms, since the leading peculiarities of 

 the sub- order are to be found in this. 



If we examine first a simple coral of this group, we find that 

 we have to deal with an animal in all important respects iden- 

 tical with an ordinary Sea-anemone, but having a more or less 



