STRUCTURE AND GROWTH OF ZOOPHYTES. 51 



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 penetrating the solid parts in minute ramifi- 

 cations. Coral is also secreted between the radiating fleshy 

 lamellse of the internal cavity of the polyp, producing the radia- 

 ted calcareous lamellae which constitute the star of a cell. In 

 the corallum of a Madrepora 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 too long a 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 grace- 

 fully 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 cling- 

 ing to the rock, and the fungus in all its varieties, have their nu- 

 merous representatives. Besides these forms imitating vegeta- 

 tion, there are gracefully modelled vases, some of which are three 

 or four feet in diameter, made up of a network of branches and 

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

 spheres like domes among the vases and shrubbery, occasionally 

 ten, or even twenty feet in diameter, whose symmetrical sur- 

 face is gorgeously decked with polyp-stars of purple and eme- 

 rald green.* 



All the many shapes proceed in each instance from a single 

 germ, which grows and buds under a few simple laws of devel-. 

 opment, and thus gives origin either to the branch, the broad 

 leaf, the column, or the hemisphere. 



e. Life and Death in Concurrent Progress. — But the more 

 massy forms would not exist, and others would be of diminutive 



* See Report on Zoophytes, pp. 29 and 59-61. 



