268 PHYSIOGNOMY OF PLANTS. 



In Ehrenberg's Classification (Abhandlungen der Akad der Wiss. 

 zu Berlin aus dem, J. 1832, s. 393-432), Coral-animals (often im- 

 properly called, in English works, Coral-insects) are divided into two 

 great classes : the single- mouthed Anthozoa, which are either free or 

 capable of detaching themselves, being the animal-corals, Zooco- 

 rallia; and those in which the attachment is permanent and plant- 

 like, being the Phyto-corals. To the first order, the Zoocorallia, 

 belong the Hydras or Arm-polypi of Trembley, the Actiniae decked 

 with beautiful colors, and the mushroom-corals; to the second order 

 or Phyto-corals belong the Madrepores, the Astraeids, and the Ocel- 

 linaa. The Polypi of the second order are those which, by the cel- 

 lular wave-defying ramparts which they construct, are the principal 

 subject of the present note. These ramparts consist of an aggregate 

 of coral trunks, which, however, do not instantly lose their common 

 vitality as does a forest-tree when cut down. 



Every coral-trunk is a whole which has arisen by a formation of 

 buds taking place according to certain laws, the parts of which the 

 whole consists forming a number of organically distinct individuals. 

 In the group of Phyto-corals these individuals- cannot detach them- 

 selves at pleasure, but remain united with each other by thin plates 

 of carbonate of lime. It is not, therefore, by any means the case 

 that each trunk of coral has a central point of common vitality or 

 life. (See Ehrenberg's Memoir, above referred to, s. 419.) The 

 propagation of coral-animals takes place, in the one order, by eggs 

 or by spontaneous division; and in the other order, by the formation 

 of buds. It is the latter mode of propagation which, in the deve- 

 lopment of individuals, is the "most rich in variety of form. 



Coral-reefs (according to the definition of Dioscorides, sea-plants, 

 a forest of stone-trees, Lithodendra) are of three kinds; coast-reefs, 

 called by the English "shore or fringing reefs," which are imme- 

 diately connected with the coasts of continents or islands, as almost 

 all the coral banks of the Red Sea seen during an eighteen months' 

 examination by Ehrenberg and Hemprich; "barrier-reefs," "en- 

 circling-reefs," as the great Australian barrier-reef on the north-east 

 coast of New Holland, extending from Sandy Cape to the dreaded 

 Torres Strait; and as the encircling-reefs surrounding the islands of 

 Yanikoro (between the Santa Cruz group and the New Hebrides) 



