On the so-called “Eozoonal” Rock
Authors: King W. , Rowney T. H. 
Published: October 2009

Abstract

T
he
authors noticed that, since the reading of their former communication in 1866, further descriptions of
Eozoon
have been published by Hochstetter, Gümbel, Carpenter, Dawson, and Logan; and after a few words on those by the first two, they proceeded to criticise the others more fully, intimating that the English and Canadian observers have by no means mastered all the difficulties of the subject, nor answered the objections brought forward by them. In the course of these remarks, Messrs. King and Rowney, objecting to the specimen from Tudor, of which they have seen the photograph, and which was described and figured in 1867*, suggested that it is nothing more than the result of infiltration of carbonate of lime, with entangled impurities, between two layers of the sandy limestone. They also stated their belief that the term “Eozoonal” is applicable to any of the ophites they describe, inasmuch as, it was contended, the 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 infilling. Fourthly, reiterating their observations on the so-called “canal-system,” they suggested that the globoso-vermicular bodies noticed by Dawson and Gümbel 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, coecolite, &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 ophites, though some are wanting in other ophites, just as they are not always present in the Eozoonal rock of Canada.

Serpentine has been described as having been deposited in the cavities of Eozoon, and having taken the place of its sarcode; but the authors criticised all the quoted analogies of such a precipitation of any siliceo-magnesian substance, which they disbelieve, and put aside glauconitic infiltration as beside the question.

Considered
geologically
, with referrenee to its occurrence in a metamorphic rock, the authors regarded the
Eozoon
as an organic impossibility; and they asked why it should never be found in anything but crystalline or semicrystalline rocks—in ophites or ophicalcites of widely different ages. Particularly they found eozoonal structure in the Liassie ophite of Skye; and this they described in full. They criticised Sterry Hunt's change of opinion, who used to think that the serpentinous rocks of Canada were once earthy amorphous silicates, and afterwards metamorphosed, but who now supposes they were deposited in a crystalline state; and they asked why, if so, may not all the Laurentian rocks have been so deposited? In conclusion, they totally denied that Eozoonal structure has anything to do with any organism, and repeated that, like all analogous conditions of serpentine, chondrodite, &c., it is of purely mineral origin.