PHYSIOLOGY OF THE INVERTEBRATA. 249 



" The vast organic accumulations known as coral reefs are 

 undoubtedly among the most striking phenomena of tropical 

 oceanic waters. The picturesque beauty of coral atolls and 

 barrier reefs, with their shallow placid lagoons, and their 

 wonderful submarine zoological and botanical gardens, fixed 

 at once the attention of the early voyagers into the seas of 

 equatorial regions of the ocean." 



What delight and pleasure a " Captain Nemo," with his 

 submarine boat,* would have in visiting these zoological and 

 botanical gardens, witnessing (among a hundred or more 

 interesting phenomena, not dreamt of in man's philosophy) 

 the Holotlmrim and Scari feeding upon coral-polypes, &c., 

 and grinding the coral, into such a fine mud that it may be 

 more easily re-dissolved in sea water, and thus furnish a 

 new generation of lime-secreting animals with the necessary 

 lime. 



It is not our object to describe the theories of Darwin f and 

 Murray { on the origin and formation of coral reefs and 

 islands ; but to give the chief points of interest concerning 

 the recent investigations of Dr. J. Murray and Mr. E. Irvine § 

 on the " function of corals and other lime-secreting organisms, 

 and the accumulation of their shells and skeletons on the 

 floor of the great oceans." The conclusions arrived at are 

 the following :- — 



(a) " Coral reefs are developed in greatest perfection in 

 those ocean waters where the temperature is highest and the 



animal range is least Throughout the temperate 



and polar regions there are no coral reefs. This is all the 

 more remarkable, seeing that organisms belonging to the 

 same orders, families, and even genera as those which build 

 up coral reefs, flourish throughout colder, and even in polar, 

 seas. In these colder seas the representatives of the reef- 



* Jules Verne's Twenty Tlixmsand Leagues under the Sea. 

 t The Structwre and Distribution of Coral Beefs, 

 t Proceedings of Moyal Societij of Edinburgh, vol. 10, p. 505. 

 § Ibid., vol. 17, p. 79. 



