ANNOTATIONS AND 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.) 



( 7 ) p. 230. "The collective labors of united Lithophytes." 

 Following Linnaeus and Ellis, the calcareous zoophytes among 

 which Madrepores, Meandrinae, Astreae, and Pocilloporae, 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 Annelidae. 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-build- 

 ing coral animals, the scaffolding which survives them, i. e. the layers 

 of lime, which in the form of thin, delicate plates, or lamellae, are 

 elaborated by vital functions, must not be regarded as something ex- 

 traneous 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 Floras 

 and, 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 grada- 

 tion of 'animal forms, or whether they are regarded in reference to 

 their influence on the geography of plants, and on the geological re- 

 lations of the crust of the earth. According to the great views of 

 Leopold von Buch, the whole formation of the Jura consists of 

 " large raised coral-banks of the ancient world, surrounding the 

 ancient mountain chains at a certain distance." 



