Flints of the Upper or White Chalk. 179 



themselves (whether we bury our heads and call it spiculin'^, 

 or glairinef, or acanthine J, or even Bathi/bine ^) , if all 

 absolutely " dissijyated,^^ or " extricated^'' should leave any 

 }3seudomorphic forms behind at all? If pseudomorphs, the 

 pseudomorph must represent something that has been re- 

 placed. But under the extraordinary conditions assumed by 

 Mr, Sollas they can represent nothing — a logical situation 

 from which I shall certainly not attempt to dislodge them, for 

 most obvious reasons. 



I may here mention another of the reasons which induce 

 me to reject the replacement theory as applicable to the true 

 flint. It is the fact that, were no powerful restraining influ- 

 ence at work on the sea-bed wherever the calcareous deposits 

 occur, such as arises out of the nearly absohite insolubility in 

 sea-water of sponge and Foraminiferal protoplasm, and of the 

 now gelatinous and colloid silica in combination with it, instead 

 of well-defined strata of chalk alternating with nodular and 

 tabular layers of flint, the stratum of the one substance never 

 encroaching upon or becoming deeply fused into the stratum 

 of the other so as to render it doubtful where chalk entirely 

 ends and silica begins (evidence being in this wise furnished 

 of their insulation from each other being dependent on some 

 chemical or molecular agency present in the one which is 

 absent in the other), the replacement process would have had 

 no definite limits, and must have been exerted indetermi- 

 nately. This would have resulted in the production, in lieu 

 of stratified chalk with intercalated and conformable layers of 

 flint, of siliceous limestone, either with or without concre- 

 tionary masses of chert distributed through it, probably with- 

 out any regard to regularity. And, lastly, we should certainly 

 not meet with nodular flints bearing unmistakable evidence of 

 a highly colloidal origin. Nay, it is perhaps not going too 

 far to say that, in such a case, the entire mass of organic rock 

 known as chalk would, through the replacement of tlie whole 

 of its carbonate of lime by silica, which had penetrated in a 

 state of very dilute aqueous solution into every nook and 



'* Prof. Sollas's paper, p. 445. 



t Alexis Julieii, iu ditto, p. 457. 



X ' The Atlantic,' by Sir Wyville Thomson, vol. i. p. 340. 



§ G. C. Wallich, stipra. I would repeat here what I stated iu a 

 footnote at p. 73 of my paper on the FUuts, that I used the word " protu- 

 2)1(18111' only because it is less specialized than either sarcode ur alhiinien. 

 It will be time enough to give it a distinctive name, as applied to 

 enveloping albmninoid substance of the sponges or the basal organic 

 substance of their siliceous parts, when we really know in what the 

 distinction between the various guises under which protoplasm appears 

 shall be more precisely determined than it has hitherto been. 



