Axial Canals of Sponge Spicules, &e. By Prof. Duncan. 571 



and whicli in the case of the carbonates resulted in a formation of 

 soluble bicarbonates. In some of the deep-sea deposits calcareous 

 fossil forms have been dredged up, but their delicate structures have 

 not been dissolved. Many of the corals which Pourtales, Moseley, 

 and I have described and which were from great depths, are marvels 

 of perfection of structure. Yet they and the fossils are presumed to 

 be under such chemical conditions that after death they must rapidly 

 disintegrate and be dissolved ; that is to say, they have been subjected 

 to enormous pressure of sea water containing considerable amounts 

 of carbon dioxide. That there is solution of silica and carbonate of 

 lime going on in the depths and on the surface of the sea, is evident 

 enough, but it takes place very slowly and minutely, and not in the 

 degree or amount which it ought, did the deep and surface sea hold 

 a little free carbonic acid gas in suspension. The quantity of 

 dissolved sihca and carbonate and bicarbonate of lime in the sea 

 is really very small. 



It will be a boon when chemists inform us what are the results 

 of pressure assisted by bicarbonates and carbonates in solution, 

 leaving out the free carbonic acid gas, upon organic silica, and on the 

 calcareous tests of invertebrata. Until that occurs we must demur 

 to the belief in the existence of that free carbonic acid which, acting 

 during the whole history of the globe, has permitted calcareous sea 

 floors to be perpetuated as rocks, and the most delicate ornamen- 

 tation of fossils to be preserved, and plenty of visible carbonate of 

 lime to exist on sea floors. Probably the very slow and slight 

 process of solution depends upon the presence of atmospheric air 

 and of oxygen gas in water with or without pressure. An oxyge- 

 nating process is quite as credible as the other, and indeed is more 

 so, for it has a greater scientific basis than that propounded by the 

 believers in a sea whose waters resemble those of a gazogene.* 



Beautiful and symmetrical as are the spaces and cavities within 

 the spicula, they must be acknowledged to be enlargements of 

 normal axial canals, and to be evidences and tokens that even the 

 siliceous spicule obeys the inevitable laws of change, death, and 

 dissolution. The spicule which has lived, has to decay, and may 

 live again in another form. And this new one will have, by-and-by, 

 to illustrate in its turn, the aesthetics of destroying nature — of that 

 environment which develops the grand outlines of the hills as their 

 rocks crumble away, and which condescends to beautify the tiny 

 microcosm as it passes away and plays its little part in the scheme 

 of evolution. 



[Since this communication was read I have found sponge spicula 



* On the evening of the reading of this communication the Society received 

 the admirable work on the ' Chemistry of the Norwegian North Atlantic Expe- 

 dition,' by Tomo. That able chemist disproves the hypothesis which has been 

 so useful to Sir Wy ville Thomson, and which maintains the existence of important 

 quantities of carbonic acid gas in a free state in the sea. 



