Growth^ and Habits of Coral Zoophytes. 41 



general nature of coral secretions. These secretions, it 

 should be further observed, increase within simultaneously 

 with growth, and every new animal adds to those previously 

 formed. They go on throughout the sides and base of each 

 polyp, excepting generally the exterior skin, as above stated ; 

 and the whole forms a calcareous framework penetrated by 

 the animal tissues, some of these tissues corresponding to 

 and occupying the cellules of the corallum, and others pene- 

 trating the solid parts in minute ramifications. Coral is also 

 secreted between the radiating fleshy lamellse of the internal 

 cavity of the polyp, producing the radiated calcareous lamellsa 

 which constitute the star of a cell. In the corallum of a Ma- 

 drepora or an Astrsea, each surface cell or star belonged to 

 a separate polyp, and the star was formed as here explained. 



It would lead to a too long digression from the main topic 

 before us, to explain the principles upon which the forms of 

 zoophytes depend. They are dwelt upon at length in another 

 volume. In this place we may briefly allude to the principal 

 varieties of form proceeding from the budding process, and 

 to a single point in their mode of growth, upon which much 

 of their importance in reef-making depends. 



d. Forms of Actinoid Zoophytes, — Zoophytes imitate nearly 

 every variety of vegetation. Trees of coral are well known ; 

 and although not emulating in size the oaks of our forests — 

 for they do not exceed six or eight feet in height — they are 

 gracefully branched, and the whole surface blooms with coral 

 polyps in place of leaves and flowers. Shrubbery, tufts of 

 rushes, beds of pinks, and feathery mosses, are most exactly 

 imitated. Many species spread out in broad leaves or folia, 

 and resemble some large leaved plant just unfolding ; when 

 alive, the surface of each leaf is covered with polyp flowers. 

 The cactus, the lichen clinging to the rock, and the fungus in 

 all its varieties, have their numerous representatives. Be- 

 sides these forms imitating vegetation, there are grace- 

 fully modelled vases, some of which are three or four feet in 

 diameter, made up of a net work of branches and branchlets, 

 and sprigs of flowers. There are also solid coral hemi- 

 spheres like domes among the vases and shrubbery, occasion- 

 ally ten, or even twenty feet in diameter, whose symmetrieal 



