186 Dr. Wallich on the Origin of the 



also shown bj Graham {loc. cit. p. 337) to be greatly assisted 

 by the presence of alkaline salts and more particularly of 

 carbonate of lime. 



According to Mr. Sollas's statement already referred to, 

 silicic acid forms, with albumen and gelatin, chemical com- 

 pounds, silicate of albumen^ and silicate of gelatin [ant^y 

 p. 163, note), and Mr. Sollas reasons upon it as if it were an 

 indisputable fact. It may be so ; but, until I have some sub- 

 stantial proofs of the fact, I confess I shall continue disin- 

 clined to believe that any chemical compound, such as silicic 

 acid, or protoplasm, can be broken up into its elements by 

 simple mechanical means, such as solution or diffusion. Thus 

 glycerine and water may be mixed in any quantities without 

 losing their chemical identity. So may two gelatinous and 

 colloidal substances, as in the case of silicic acid and proto- 

 plasm, as soon after the death of the parent organism as the 

 purely material forces step into the field to cause a combina- 

 tion of the silica, which had, in the first instance only, yielded 

 so far^ but no further, to the quasi-c\\Qm.\Q,fi\ action by which 

 silicic acid, in the presence of a powerful colloid, exchanged 

 one unstable condition in which it can exist without chemical 

 disruption, for another unstable condition in which it can also 

 do so. 



On these grounds I contend that the union of these two 

 substances is a purely mechanical combination or intermix- 

 ture, whereby they become amalgamated, as it were, into an 

 organic alloy, capable of retaining just sufficient " combined 

 water" not to interfere, in the least degree, with their mutual 

 insolubility in the surrounding water. Organic silica, or, in 

 other words, silicic hydrate, in the presence of protoplasm only, 

 passes into its gelatinous phase as soon as the preservative 

 action of the living organism ceases with its death. " Decom- 

 position " at the sea-bed, in the presence of the various saline 

 preservative substances contained in sea-water, the low tem- 

 perature prevailing, and the stupendous pressure (which, in all 

 probability, prevents any gaseous body from existing, save in 

 its fluid condition), must necessarily be an extremely slow 

 process. In the combined state of colloidal silica and proto- 

 plasm their insolubility helps still further to protect them from 

 decomposition by excluding substances which might otherwise 

 enter into chemical combination with them. They constitute 

 an independent regnum in regno, the permanence of which is 

 interfered with only by the inherent and powerful tendency of 



from the chalk rock. This would appear to be in some way related to 

 its retaining its permanent minute residuary quantity of water only until 

 its exposure to the action of the atmosphere. 



