ILLUSTRATIONS (7). CORAL-REEFS. 259 



attention of naturalists to coral-animalcules," they say, "we 

 hope to be able to prove that all which has been hitherto 

 affirmed or believed up to the present time, regarding the 

 immense structures they are capable of raising, is for the 

 most part inexact, and in all cases very greatly exaggerated. 

 We are rather of opinion that coral-animalcules, instead of 

 rearing -perpendicular walls from the depths of the Ocean, only 

 form strata or incrustrations of some few toises in thick- 

 ness." Quoy and Gaimard (p. 289) have also expressed an 

 opinion, that Atolls (coral walls inclosing a lagoon) owe 

 their origin to submarine volcanic craters. They have 

 undoubtedly underrated the depth at which animals who 

 construct coral-reefs (as for example the Astraea) can exist, as 

 they place the extreme limits at from 26 to 32 feet below 

 the level of the sea. Charles Darwin, a Laturalist, who 

 has known how to enhance the value of his own observa- 

 tions by a comparison with those of others in many parts of 

 the world, places the region of living coral-animals at a depth 

 of 20 or 30 fathoms,* which corresponds with that in which 

 Professor Edward Forbes found the greatest number of corals 

 in the 2Egean Sea. This is Professor Forbes's fourth region 

 of marine-animals, as given in his ingenious memoir on the 

 Provinces of Depth, and the geographical distribution of Mol- 

 lusca at perpendicular distances from the surface. f It would 

 appear, however, that the depth at which corals live is very 

 different in the different species, especially in the more 

 delicate ones which do not form such considerable struc- 

 tures. 



Sir James Ross, in his Antarctic expedition, brought up 

 corals from a great depth with the lead ; and these he remitted 

 for accurate examination to Mr. Stokes and Professor Forbes. 

 Westward of Victoria Land, in the neighbourhood of the 

 Coulman Island, in 72 31' south lat., and at a depth of 

 270 fathoms, Retepora cellulosa, a Hornera, and Prymnoa 

 Rossii, (the latter very similar to a species common to the 

 coasts of Norway,) were found alive and in a perfectly 



* See Darwin's Journal, 1845, p. 467, also his Structure of Coral 

 Reefs, pp. 8487; and Sir Robert Schomburgk, Hist, of Barbadoes, 

 1848, p. 636. 



t Report on JEgean Invertebrata in the Report of the Thirteenth 

 Meeting of the British Association, held at Cork in 1843, pp. 151, 161 



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