342 ANNUAL OF SCIENTIFIC DISCOVERY. 



stomachs. In some species the coalescence is confined to the lower 

 half of the polyps, or to a still less part ; and in this case the animals 

 project above the general living surface. Polyps thus clustered, 

 spreading at summit a star of tentacles, constitute the flowering 

 zoophytes of coral reefs. Those coral animals which do not bud are 

 to all external appearance true actiniae. The existence of coral in the 

 living coral zoophyte is nowhere apparent, and would not be suspected 

 if not previously known ; for, as before stated, it is wholly internal, 

 and the visible exterior is the fleshy skin of the polyp. Prof. Jas, 

 D. Dana, Geology of the U. S. Exploring Expedition. 



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, 

 l)eds 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 repre- 

 sentatives. Besides these forms imitating vegetation, there are grace- 

 fully 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 hemispheres, like domes among the vases and 

 shrubbery, occasionally ten, or even twenty feet in diameter, whose 

 symmetrical surface is gorgeously decked with polyp-stars of purple 

 and emerald green. All the many shapes proceed in each instance 

 from a single germ, which grows and buds under a few simple laws of 

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

 leaf, the column, or the hemisphere. 



But the more massy forms would not exist, and others would be of 

 diminutive size, were it not for a peculiar mode of growth which 

 characterizes most coral zoophytes. Life and death are here in con- 

 current or parallel progress, a condition favored by the existence of 

 coral secretions. In some instances, a simple polyp, while growing at 

 top and constantly lengthening itself upward, is dying at its lower 

 extremity, leaving the base of the coral bare, and destitute of any 

 living tissues. The polyp thus continues rising in height, and death 

 progresses below at the same rate, till at last the live polyp may be at 

 the extremity of a coral stem many times its own length. In species 

 which bud and form large groups, the same operation takes place. In 

 some instances the summit polyp or polyps bud and groAV, while, at a 

 certain distance below the summit, the work of death is going on, and 

 polyps are gradually disappearing. There is thus a certain interval of 

 life, the length of which interval is different for different species. The 

 death of the polyps about the base of a coral tree would expose it seem- 

 ingly to immediate wear from the waters around it, and especially as 



