220 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 10, 



and of their minute filamentous prolongations, by a siliceous deposit 

 in the cavities and tubes which they occupied, was effected by some 

 process at present in operation upon the sea-bottom. And whatever 

 view we may take of the nature of this process, — whether we suppose 

 these chambers and tubes to have filled when empty by infiltration, 

 or regard the animal matter which originally occupied them to have 

 given place to the siliceous deposit by a process of chemical suh- 

 stitutio7i*, — the fact remains, that an undoubted internal cast of a 

 recent Poraminifer presents the exact parallel to the model of the 

 animal body of Eozoon obtained by the removal of its calcareous 

 skeleton. Indeed it was in consequence of the suggestion afforded 

 by this specimen of Ampliistegina, that I was led to look for the 

 corresponding structure in the decalcified Eozoon ; the discovery of 

 which affords no slight confirmation of the view previously arrived 

 at by the examination of thin transparent sections. 



My observations upon the Nummuline structure of the proper walls 

 of the chambers have been fully confirmed by Dr. Dawson, who 

 thus speaks in an Appendix to the Canadian reprint of his paper on 

 Eozoon, " Since the above was published, I have had opportunities 

 of examining sKces and decalcified specimens of Eozoon from Petite 

 Nation, the locality which afforded the specimens referred to by 

 Dr. Carpenter ; and I have much pleasure in adding my testimony 

 to his observation of the distinctness of the proper wall of the 

 chambers from the supplemental or intermediate skeleton, as ex- 

 hibited in these specimens." 



This iN'ummuhne tubulated stracture comes to be of special im- 

 portance, now that the organic nature of the Eozoic serpentine- 

 limestone has been formally called in question. For even if it be 

 admitted that the peculiar arrangement of the calcareous and siliceous 

 components of the Eozoic limestone, and the remarkable dendritic 

 passages hollowed out in the calcareous layers, are capable of being 



* Notwithstanding that this idea has been designated by Profs. King and 

 Eowney as so completely destitute of the characters of a scientific hypothesis as 

 to be wholly unworthy of consideration, I believe it to be the one commonly 

 entertained by those who have given most thought to the mode in which the si- 

 licification of Woods and of the soft tissues of Sponges and other organisms has 

 been effected, so as to preserve the minutest features of their structures. And 

 those eminent geologists who were present with me at the discussion which took 

 place in Paris upon the subject of the Abbeville Jaw, will recollect that no less 

 an authority than Prof. Milne-Edwards stated that he believed that infiltration 

 of bones and teeth was more likely to take place when their cavities were occu- 

 pied by animal matter at the time they were imbedded, than when those cavities 

 had been emptied by its decay ; the minute tubuli being, in his view, more readily 

 and completely filled by the process of substitution, during the decomposition of 

 their animal contents, than they could be by mere percolation. This suggestion 

 was thrown out to account for the fact mentioned by M. Ijartet, that completely 

 infiltrated and non-infiltrated bones are often found in the same stalagmitic 

 deposit. My own early investigations into the structure of Nummulites had long 

 before led me to the conclusion that among those fovmd imbedded in the clay 

 of Bracklesham Bay, the specimens most completely infiltrated with carbonate 

 of Hme had their chambers occupied with animal matter at the time when this 

 fossilizing process commenced (see Quart. Journ. Geol. Soc. vol. vi. p. 23, 

 Plate iii. fig. 2) ; traces of it being distinguishable even to the very centre of 

 the spire. 



