Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/210

 structure of the latter is similar to that of the Canadian rock containing the so-called Eozoon.

The authors then proceeded to treat of the supposed foraminiferal characters of "Eozoon." First, as to the " cell-wall" or "nummuline layer," they advanced repeated evidence of the value of their former proofs that the typical form is due to aciculate serpentine (or modified chrysotile) of inorganic origin — having examined, besides others, a Canadian specimen presented by Dr. Carpenter. Secondly, nothing new was adduced with regard to the mineral structure of the so-called " intermediate skeleton." Thirdly, in proof that the " chamber- casts" are not of organic origin, the authors referred to their former work, and stated that chondrodite and pyrallolite may be added to the list of minerals that occur, as such, disseminated in limestones. They thought it strange that a carbonate, as well as a silicate, should not have been found filling the so-called chambers ; and they decidedly refused to accept the Tudor specimen having some tubuli filled with calcite, to which they suppose Dawson refers when speaking of chambers filled with calcite, as a case in point ; they were unacquainted with any published instances of this mineral being an infillng. Fourthly, reiterating their observations on the so-called " canal- system," they suggested that the globoso-vermicular bodies noticed by Dawson and Gumbel may be metaxite ; and they insisted on the difficulty of explaining the presence of isolated unbroken tube- casts in patches of pure limestone. The Madoc specimen, described by Dawson as having its "canals" and " chambers " filled with calcite, was next referred to ; and it was argued that the so-called calcite, both in this and in another specimen, described by Carpenter, is doubtful and not proved ; for the authors had not been able to confirm the accuracy of the observations in these cases, having examined a Canadian specimen, presented by Dr. Carpenter as an example of the kind, which had in it " homogeneous and structureless forms of the canal-system " that were not dissolved in the decalcification. Fifthly, the organic nature of the so-called " stolons " was regarded as quite disproved. Mineralogical considerations of Eozoonal rocks were next entered upon ; and from the study of Canadian specimens, and of others from Connemara and Bavaria, described in full, the authors concluded that they fully prove the " canal-system," " chamber-casts," and " nummuline layer" to be structural and inorganic modifications of serpentine — that the whole have originated from the change or waste of granules, plates, &c. of serpentine ; and they incline to the belief that the calcite of the " intermediate skeleton " is pseudomorphic after one or other form of serpentine by infiltration and replacement. The rounded form of the granular masses of chondrodite, coccolite, &c. in some limestones was also referred by the authors to the gradual removal of their surfaces by deep-seated hydrothermal agency.

It was then argued that the organic nature of Eozoon cannot be supported by the cumulative evidence afforded by the combination of foraminiferal features ; for these features, combined and due to purely mineral paragenesis, had occurred to the authors in certain