56 ANTHOZOA. 



removed from the future influence of the animal. Such a supposition 

 is, however, at variance with the facts above stated, and incompatible 

 with many circumstances connected with the history of the lithophytous 

 polyps. On trying to detach the soft envelope from the surface of the 

 skeleton, the firmness of their adherence would render such a want of 

 connexion improbable they appear to be, as it were, incorporated 

 with each other ; and, besides, the separation of the Fungia from the 

 peduncle whereby it was joined to the parent Fungia during its earlier 

 growth necessarily supposes a power of removing the calcareous par- ' 

 tides after their deposition. It is therefore demonstrable that the 

 earthy matter secreted by the polyp is deposited in the tissue of its 

 substance, and still remains, in a greater or less degree, subject to 

 absorption and removal ; of this, however, we shall have fuller evidence 

 hereafter. 



(119.) Cortical compound ANTHOZOA. The compound polyps consist 

 of a mass of gelatinous matter, which indicates, by its power of con- 

 traction upon the application of stimuli, a degree of sensation, and of 

 a great number of polyps, or flower-like mouths, which spring from the 

 surface of the common body, and are individually capable of seizing and 

 digesting prey, the nutriment thus gained being appropriated to the 

 nourishment of the general mass. 



(120.) Although essentially similar in their habits, the compound 

 polyps present various modifications of structure, which naturally causes 

 them to be grouped in distinct families. Sometimes the central common 

 mass is entirely soft and gelatinous, its surface being covered with 

 minute cells in which the polyps are lodged : such are the Alcyonidce. 

 Sometimes the common body secretes large quantities of calcareous 

 matter in the same manner as the Fungia, which, being deposited in its 

 interior, forms arborescent masses, presenting upon their surface multi- 

 tudes of cells, generally distinguishable after the removal of the outer 

 crust, in each of which when alive a polyp was lodged : these form the 

 family of Madreporidce. The central axis is not unfrequently quite solid 

 and smooth upon the surface, offering no cells for the lodgment of the 

 polyps being either composed of hard and dense calcareous substance, 

 or else flexible and horny in its texture : such are the Corallidce, or 

 family of corals, properly so called. The internal central axis is more- 

 over, in another family, composed of several pieces united together by 

 the living crust that secretes them ; and being free and unattached, 

 such forms are probably able to change their position at pleasure : these 

 constitute the family of Pennatulidce, or swimming polyps. They are, 

 however, all merely modifications of the same general type of structure, 

 although differing in certain minor points of their organization, so as to 

 render an examination of each form needful for our purpose. 



(121.) ALCYOKLDJE. This family includes several genera, known by 

 the names of Alcyonium, Lobttlaria, Cydonium, &c., being charac- 



