ILLUSTRATIONS (7). COHAL ANIMALS. 253 



splendid colours, and tbe mushroom-corals; and to the second 

 order belong the Madrepores, the AstraeaB, and the Ocellinae. 

 The Polyps of the second order are those which from their 

 cellular, wave-resisting, Avail-works are the principal subject 

 of this illustration. The wall-work is composed of the aggre- 

 gate of the coral-trunks, which, however, do not suddenly lose 

 their combined vitality, like a dead forest tree. 



Every coral-trunk arises by a process of gemmation in ac- 

 cordance with certain laws, and forms one complete structure, 

 each portion being formed by a great number of organically 

 distinct individual animals. In the group of Phyto-corals these 

 cannot separate themselves spontaneously, but remain united 

 with one another by lamellae of carbonate of lime. Hence 

 each coral-trunk by no means possesses a central point of 

 common vitality.* 4 The propagation of coral-animals, accord- 

 ing to the difference of the orders, is by eggs, spontaneous 

 division or gemmation. This last kind of propagation 

 presents the greatest variety of forms in the development of 

 individuals. 



The Coral-reefs (or, as Dioscorides designates them, sea- 

 plants, a forest of stony-trees, Lithodendra), are of three 

 kinds; namely, Coast-reefs, (shore-reefs, fringing-reefs), which 

 are directly connected with continental or insular coasts, as 

 on the north-east coast of New Holland, between Sandy Cape 

 and the dreaded Torres Straits, and almost all the coral-banks 

 of the Red Sea examined for eighteen months by Ehrenberg 

 and Hemprich; Island-surrounding reefs (barrier-reefs, encir- 

 cling-reefs), as at Vanikoro in the small archipelago of Santa 

 Cruz, north of the New Hebrides, and at Puynipete, one of 

 the Carolinas ; and Coral-banks surrounding lagoons (Atolls or 

 Lagoon-islands). This very natural division and nomencla- 

 clature have been introduced by Charles Darwin, and are 

 most intimately connected with the very ingenious explana- 

 tion which this intellectual naturalist has given of the gradual 

 origin of these wonderful forms. While, on the one hand, 

 Cavolini, Ehrenberg, and Savigny have completed the scientific 

 anatomical knowledge of the organization of coral-animals, on 

 the other, the geographical and geological relations of coral- 

 islands have been investigated, first by Reinhold and George 

 Forster in Cook's second voyage, and then, after a long 

 * Ehrenberg ; Op. cit., s. 419. 



