PHYSIOLOGY OF THE INVERTEBRATA. 



253 



Their experiments prove that " there is very great diversity 

 as to the amount of carbonate of lime that will pass into solu- 

 tion in sea water from various calcareous structures in a given 

 time." The more dense varieties of coral are less soluble 

 than the porous varieties. " The rate of solution is also 

 much greater when the water is constantly renewed than 

 when the same water remains in contact with the coral, and 

 the solution approaches to saturation." 



(i) Prom the investigations and observations of Murray 

 and Irvine " it is evident that a very large quantity of car- 

 bonate of lime is in a continual state of flux in the ocean, nOw 

 existing in the form of shells and corals, but after the death 

 of the animals passing slowly into solution, to go again 

 through the same cycle." 



" On the whole, however, the quantity of carbonate of lime 

 that is secreted by animals must exceed what is re-dissolved 

 by the action of sea-water, and at the present time there is a 

 vast accumulation of carbonate of lime going on in the ocean. 

 It has been the same in the past, for with a few insignificant 

 exceptions all the carbonate of lime in the geological series 

 of the rocks has been secreted from sea water, and owes its 

 origin to organisms in the same way as the carbon of the car- 

 boniferous formations. The extent of these deposits appears 



