MUSEUM OF COMPAKATTVE ZOOLOGY. 127 



little of coral reefs from their own observations, some of whom have 

 ignored or flatly denied facts which can hardly be dealt with in so sum- 

 mary a fashion. 



According to Reade, 1 it seems very evident that if we accept the dis- 

 solution theory for the origin of coral lagoons, it seems impossible to 

 believe in the building up of calcium carbonate, or volcanic platforms, or 

 other peaks, from varying and unknown depths to the levels necessary 

 for the growth of coral reefs. If, on the other hand, we believe that 

 platforms are so built up, it appears equally destructive of the dissolu- 

 tion theory of lagoons. 



In "Nature" of September 21, 1880, Mr. Reade says: "I think the 

 theory Mr. Murray sets forth, — that the cones or peaks on which he con- 

 siders atolls have been formed have been levelled up by pelagic deposits, 

 and thus brought within the limits of reef-building coral growth, — a 

 very far-fetched idea." 



In the same journal, Darwin says : " I am not a fair judge, but I agree 

 with you exactly that Murray's view is far-fetched. It is astonishing 

 that there should be rapid dissolution of cai'bonate of lime at great 

 depths and near the surface, but not at intermediate depths, where he 

 places his mountain peaks." 



It is surprising that Reade 2 should have attempted to throw doubt on 

 the existence of calcareous submarine banks. The submarine banks are 

 not, as Mr. Reade seems to think, due tp the tests of the pelagic fauna 

 alone. A submarine peak is not built up by the pelagic fauna, but it is 

 built up by the carcasses of the Invertebrates that live upon it, and for 

 which the pelagic fauna serves in part as food. Certainly, the amount 

 of limestone and shells of pteropods alone in some regions is very much 

 larger than any estimate made by Mr. Reade. The large number of 

 well known limestone banks of great thickness and extent should make 

 such a discussion unnecessary. 



The " pelagic cemetery " is farther down, and not on the surface, and 

 I would refer Mr. Reade to my article on the Florida Reefs, in the 

 Memoirs of the American Academy of Arts and Sciences, 1883, as well as 

 to the " Three Cruises of the Blake," for such proof as has thus far been 

 obtained regarding the existence of these huge masses of limestone 

 banks, eminently fitted, as I think I have shown, to form the base of 

 such coral reefs as those of the "West Indies, of Florida, of the shores of 

 Cuba, and of the great Alacran and other reefs on the Yucatan Bank. 



i T. Mallard Reade, Nature, March 22, 1888, p. 489. 

 2 Nature, April 5, 1888, p. 535. 



