252 VIEWS, kc. PHYSIOGNOMY OF PLAXTS. 



loporec especially produce mural coral-reefs,) are inhabited 

 and invested by animalcules, •which were long supposed to 

 be allied to the Nereids belonging to Cuvier's Annelida 

 (jointed worms). The anatomy of these gelatinous animalcules 

 has been made known by the acute and comprehensive re- 

 searches of Cavolini, Savigny, and Ehrenberg. We have 

 learned that, in order to understand the whole organism of the 

 (so-called) rock-building animals, we must not considei the 

 scaffolding which remains after their death, namelv, the iavers 

 of lime formed into delicate lamellae by a vital function of 

 secretion, as foreign to the soft membranes of the food- 

 receiving animal. 



Besides our increased knowledge of the wonderful for- 

 mation of the living coral-stocks, a more correct view has 

 gradually gained ground respecting the extensive influence 

 which the coral world has exercised on the appearance of low 

 island groups above the level of the sea, on the migration of 

 land-plants, and the successive extension of the domain of the 

 Floras, and, indeed, in some parts of the ocean, on the distri- 

 bution of the human race and of languages. 



As minute social organisms the corals play an import- 

 ant part in the general economy of nature, although they do 

 not, as people began to believe after Capt. Cook's voyages of 

 discovery, build up islands or enlarge continents from almost 

 unfathomable depths of the ocean. They excite the liveliest 

 interest, whether regarded as physiological objects, and as 

 illustrating the various gradations of animal form, or in con- 

 nection with the geography of plants, and the geognostic 

 relations of the earth's crust. According to the comprehen- 

 sive views of Leopold von Buch, the whole Jura-formation 

 consists of " large elevated coral-banks of the ancient world, 

 surrounding at a certain distance the old mountain chains." 



According to Ehrenberg" s classification,-'' coral- animals, (in 

 English works often incorrectly termed coral-insects,) are 

 separable into the monostomous Anthozoa, which are either 

 free and with the power of detaching themselves, as Animal- 

 corals; or are attached in the manner of plants, as Phyto-corals. 

 To the first order (Zoocorallia) belong the Hydras or Arm- 

 polyps of Trembley, the Actinia?, radiant with the most 



* Abhandlungen der Akad. der Wiss. zu Berlin aus dem J. 1832, 

 s. 393—432. 



