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Show ANNOTATIONS A D ADDITIONS. 267 and according to Biot the purity of the air would appear to depend on the depth at which the fish live. (Memoires de Physique et de Chimie de la Societe d' Arcueil, t. i. 1807, pp. 252-281.) (1) p. 230.-" The collective labors of united Lithophytes." Following Linnreus and Ellis, the calcareous zoophytes-among which Madrepores, l\ieondrinre, Astrere, and Pocilloporre, especially, produce wall-like coral reefs-are inhabited by living creatures, which were long believed to be allied to the Nereids belonging to Cuvier's Annelidre. The anatomy of these gelatinous little creatures has been elucidated by the ingenious and extensive researches of Cavolini, Savigny, and Ehrenberg. We have learnt that in order to understand the entire organization of what are called the rock-building coral animals, the scaffolding which survives them, i.e. the layers of lime, which in the form of thin, delicate plates, or lamellre, are elaborated by vital functions, must not be regarded as something extraneous to the soft membranes of the food-receiving animal. Besides the more extended knowledge of the wonderful formation of the animated coral stocks, there have been gradually established more accurate views respecting the influence exercised by corals on other departments of nature-on the elevation of groups of low islands above the level of the sea-on the migrations of land-plants and the successive extension of the domains of particular Florasand, lastly, in some parts of the ocean, on the diffusion of races of men, and the spread of particular languages. As minute organic creatures living in society, corals do indeed perform an important part in the general economy of nature, although they do not, as was begun to be believed at the time of Cook's voyages, enlarge continents and build up islands from fathomless depths of the ocean. They excite the liveliest interest, whether considered as subjects of physiology and of the study of the gradation of animal forms, or whether they are regarded in reference to their influence on the geography of plants, and on the geological relations of the crust of the earth. According to the great views of Leopold von Buch, the whole formation of the Jura consi ts of "large raised coral-banks of the ancient world, surrounding the ancient mountain chains at a certain distance." |