"At the request of Sir W. E. Logan, I have submitted to microscopic examination slices of certain peculiar laminated forms, consisting of alternate layers of carbonate of lime and serpentine, and of carbonate of lime and white pyroxene, found in the Laurentian limestone of Canada, and regarded by Sir William as possibly fossils. I have also examined slices of a large number of limestones from the Laurentian series, not showing the forms of these supposed fossils.

"The specimens first mentioned are masses, often several inches in diameter, presenting to the naked eye alternate laminÆ of serpentine, or of pyroxene, and carbonate of lime. Their general aspect, as remarked by Sir W. E. Logan (Geology of Canada, 1863, p. 49), reminds the observer of that of the Silurian corals of the genus Stromatopora, except that the laminÆ diverge from and approach each other, and frequently anastomose or are connected by transverse septa.

"Under the microscope the resemblance to Stromatopora is seen to be in general form merely, and no trace appears of the radiating pillars characteristic of that genus. The laminÆ of serpentine and pyroxene present no organic structure, and the latter mineral is highly crystalline. The laminÆ of carbonate of lime, on the contrary, retain distinct traces of structures which cannot be of a crystalline or concretionary character. They constitute parallel or concentric partitions of variable thickness, enclosing flattened spaces or chambers, frequently crossed by transverse plates or septa, in some places so numerous as to give a vesicular appearance, in others occurring only at rare intervals. The laminÆ themselves are excavated on their sides into rounded pits, and are in some places traversed by canals, or contain secondary rounded cells, apparently isolated. In addition to these general appearances, the substance of the laminÆ, where most perfectly preserved, is seen to present a fine granular structure, and to be penetrated by numerous minute tubuli, which are arranged in bundles of great beauty and complexity, diverging in sheaf-like forms, and in their finer extensions anastomosing so as to form a network (figs. 10 and 28). In transverse sections, and under high powers, the tubuli are seen to be circular in outline, and sharply defined (fig. 29). In longitudinal sections, they sometimes present a beaded or jointed appearance. Even where the tubular structure is least perfectly preserved, traces of it can still be seen in most of the slices, though there are places in which the laminÆ are perfectly compact, and perhaps were so originally.

"With respect to the nature and probable origin of the appearances above described, I would make the following remarks:—

"1. The serpentine and pyroxene which fill the cavities of the calcareous matter have no appearance of concretionary structure. On the contrary, their aspect is that of matter introduced by infiltration, or as sediment, and filling spaces previously existing. In other words, the calcareous matter has not been moulded on the forms of the serpentine and augite, but these have filled spaces or chambers in a hard calcareous mass. This conclusion is further confirmed by the fact, to be referred to in the sequel, that the serpentine includes multitudes of minute foreign bodies, while the calcareous matter is uniform and homogeneous. It is also to be observed that small veins of carbonate of lime occasionally traverse the specimen’s, and in their entire absence of structures other than crystalline, present a striking contrast to the supposed fossils.

"2. Though the calcareous laminÆ have in places a crystalline cleavage, their forms and structures have no relation to this. Their cells and canals are rounded, and have smooth walls, which are occasionally lined with films apparently of carbonaceous matter. Above all, the minute tubuli are different from anything likely to occur in merely crystalline calc-spar. While in such rocks little importance might be attached to external forms simulating the appearances of corals, sponges, or other organisms, these delicate internal structures have a much higher claim to attention. Nor is there any improbability in the preservation of such minute parts in rocks so highly crystalline, since it is a circumstance of frequent occurrence in the microscopic examination of fossils that the finest structures are visible in specimens in which the general form and the arrangement of parts have been obliterated. It is also to be observed that the structure of the calcareous laminÆ is the same, whether the intervening spaces are filled with serpentine or with pyroxene.

"3. The structures above described are not merely definite and uniform, but they are of a kind proper to animal organisms, and more especially to one particular type of animal life, as likely as any other to occur under such circumstances: I refer to that of the Rhizopods of the order Foraminifera. The most important point of difference is in the great size and compact habit of growth of the specimens in question; but there seems no good reason to maintain that Foraminifera must necessarily be of small size, more especially since forms of considerable magnitude referred to this type are known in the Lower Silurian. Professor Hall has described specimens of Receptaculites twelve inches in diameter; and the fossils from the Potsdam formation of Labrador, referred by Mr. Billings to the genus ArchÆocyathus, are examples of Protozoa with calcareous skeletons scarcely inferior in their massive style of growth to the forms now under consideration.

"These reasons are, I think, sufficient to justify me in regarding these remarkable structures as truly organic, and in searching for their nearest allies among the Foraminifera.

"Supposing then that the spaces between the calcareous laminÆ, as well as the canals and tubuli traversing their substance, were once filled with the sarcode body of a Rhizopod, comparisons with modern forms at once suggest themselves.

"From the polished specimens in the Museum of the Canadian Geological Survey, it appears certain that these bodies were sessile by a broad base, and grew by the addition of successive layers of chambers separated by calcareous laminÆ, but communicating with each other by canals or septal orifices sparsely and irregularly distributed. Small specimens have thus much the aspect of the modern genera Carpenteria and Polytrema. Like the first of these genera, there would also seem to have been a tendency to leave in the midst of the structure a large central canal, or deep funnel-shaped or cylindrical opening, for communication with the sea-water. Where the laminÆ coalesce, and the structure becomes more vesicular, it assumes the ‘acervuline’ character seen in such modern forms as Nubecularia.

"Still the magnitude of these fossils is enormous when compared with the species of the genera above named; and from the specimens in the larger slabs from Grenville, in the museum of the Canadian Survey, it would seem that these organisms grew in groups, which ultimately coalesced, and formed large masses penetrated by deep irregular canals; and that they continued to grow at the surface, while the lower parts became dead and were filled up with infiltrated matter or sediment. In short, we have to imagine an organism having the habit of growth of Carpenteria, but attaining to an enormous size, and by the aggregation of individuals assuming the aspect of a coral reef.

"The complicated systems of tubuli in the Laurentian fossil indicate, however, a more complex structure than that of any of the forms mentioned above. I have carefully compared these with the similar structures in the ‘supplementary skeleton’ (or the shell-substance that carries the vascular system) of Calcarina and other forms, and can detect no difference except in the somewhat coarser texture of the tubuli in the Laurentian specimens. It accords well with the great dimensions of these, that they should thus thicken their walls with an extensive deposit of tubulated calcareous matter; and from the frequency of the bundles of tubuli, as well as from the thickness of the partitions, I have no doubt that all the successive walls, as they were formed, were thickened in this manner, just as in so many of the higher genera of more modern Foraminifera.

"It is proper to add that no spicules, or other structures indicating affinity to the Sponges, have been detected in any of the specimens.

“As it is convenient to have a name to designate these forms, I would propose that of Eozoon, which will be specially appropriate to what seems to be the characteristic fossil of a group of rocks which must now be named Eozoic rather than Azoic. For the species above described, the specific name of Canadense has been proposed. It may be distinguished by the following characters:—

“Eozoon Canadense; gen. et spec. nov.

“General form.—Massive, in large sessile patches or irregular cylinders, growing at the surface by the addition of successive laminÆ.

“Internal structure.—Chambers large, flattened, irregular, with numerous rounded extensions, and separated by walls of variable thickness, which are penetrated by septal orifices irregularly disposed. Thicker parts of the walls with bundles of fine branching tubuli.

“These characters refer specially to the specimens from Grenville and the Calumet. There are others from Perth, C. W., which show more regular laminÆ, and in which the tubuli have not yet been observed; and a specimen from Burgess, C. W., contains some fragments of laminÆ which exhibit, on one side, a series of fine parallel tubuli like those of Nummulina. These specimens may indicate distinct species; but on the other hand, their peculiarities may depend on different states of preservation.

“With respect to this last point, it may be remarked that some of the specimens from Grenville and the Calumet show the structure of the laminÆ with nearly equal distinctness, whether the chambers are filled with serpentine or pyroxene, and that even the minute tubuli are penetrated and filled with these minerals. On the other hand, there are large specimens in the collection of the Canadian Survey in which the lower and still parts of the organism are imperfectly preserved in pyroxene, while the upper parts are more perfectly mineralized with serpentine.”

[The following note was added in a reprint of the paper in the Canadian Naturalist, April, 1865.]

“Since the above was written, thick slices of Eozoon from Grenville have been prepared, and submitted to the action of hydrochloric acid until the carbonate of lime was removed. The serpentine then remains as a cast of the interior of the chambers, showing the form of their original sarcode-contents. The minute tubuli are found also to have been filled with a substance insoluble in the acid, so that casts of these also remain in great perfection, and allow their general distribution to be much better seen than in the transparent slices previously prepared. These interesting preparations establish the following additional structural points:—

“1. That the whole mass of sarcode throughout the organism was continuous; the apparently detached secondary chambers being, as I had previously suspected, connected with the larger chambers by canals filled with sarcode.

“2. That some of the irregular portions without lamination are not fragmentary, but due to the acervuline growth of the animal; and that this irregularity has been produced in part by the formation of projecting patches of supplementary skeleton, penetrated by beautiful systems of tubuli. These groups of tubuli are in some places very regular, and have in their axes cylinders of compact calcareous matter. Some parts of the specimens present arrangements of this kind as symmetrical as in any modern Foraminiferal shell.

“3. That all except the very thinnest portions of the walls of the chambers present traces, more or less distinct, of a tubular structure.

“4. These facts place in more strong contrast the structure of the regularly laminated species from Burgess, which do not show tubuli, and that of the Grenville specimens, less regularly laminated and tubulous throughout. I hesitated however to regard these two as distinct species, in consequence of the intermediate characters presented by specimens from the Calumet, which are regularly laminated like those of Burgess, and tubulous like those of Grenville. It is possible that in the Burgess specimens, tubuli, originally present, have been obliterated, and in organisms of this grade, more or less altered by the processes of fossilisation, large series of specimens should be compared before attempting to establish specific distinctions.”

"The careful examination which I have made, in accordance with the request you were good enough to convey to me from Dr. Dawson and to second on your own part, with the structure of the very extraordinary fossil which you have brought from the Laurentian rocks of Canada,[Q] enables me most unhesitatingly to confirm the sagacious determination of Dr. Dawson as to its Rhizopod characters and Foraminiferal affinities, and at the same time furnishes new evidence of no small value in support of that determination. In this examination I have had the advantage of a series of sections of the fossil much superior to those submitted to Dr. Dawson; and also of a large series of decalcified specimens, of which Dr. Dawson had only the opportunity of seeing a few examples after his memoir had been written. These last are peculiarly instructive; since in consequence of the complete infiltration of the chambers and canals, originally occupied by the sarcode-body of the animal, by mineral matter insoluble in dilute nitric acid, the removal of the calcareous shell brings into view, not only the internal casts of the chambers, but also casts of the interior of the ‘canal system’ of the ‘intermediate’ or ‘supplemental skeleton,’ and even casts of the interior of the very fine parallel tubuli which traverse the proper walls of the chambers. And, as I have remarked elsewhere,[R] ‘such casts place before us far more exact representations of the configuration of the animal body, and of the connections of its different parts, than we could obtain even from living specimens by dissolving away their shells with acid; its several portions being disposed to heap themselves together in a mass when they lose the support of the calcareous skeleton.’

"The additional opportunities I have thus enjoyed will be found, I believe, to account satisfactorily for the differences to be observed between Dr. Dawson’s account of the Eozoon and my own. Had I been obliged to form my conclusions respecting its structure only from the specimens submitted to Dr. Dawson, I should very probably have seen no reason for any but the most complete accordance with his description: while if Dr. Dawson had enjoyed the advantage of examining the entire series of preparations which have come under my own observation, I feel confident that he would have anticipated the corrections and additions which I now offer.

"Although the general plan of growth described by Dr. Dawson, and exhibited in his photographs of vertical sections of the fossil, is undoubtedly that which is typical of Eozoon, yet I find that the acervuline mode of growth, also mentioned by Dr. Dawson, very frequently takes its place in the more superficial parts, where the chambers, which are arranged in regular tiers in the laminated portions, are heaped one upon another without any regularity, as is particularly well shown in some decalcified specimens which I have myself prepared from the slices last put into my hands. I see no indication that this departure from the normal type of structure has resulted from an injury; the transition from the regular to the irregular mode of increase not being abrupt but gradual. Nor shall I be disposed to regard it as a monstrosity; since there are many other Foraminifera in which an originally definite plan of growth gives place, in a later stage, to a like acervuline piling-up of chambers.

"In regard to the form and relations of the chambers, I have little to add to Dr. Dawson’s description. The evidence afforded by their internal casts concurs with that of sections, in showing that the segments of the sarcode-body, by whose aggregation each layer was constituted, were but very incompletely divided by shelly partitions; this incomplete separation (as Dr. Dawson has pointed out) having its parallel in that of the secondary chambers in Carpenteria. But I have occasionally met with instances in which the separation of the chambers has been as complete as it is in Foraminifera generally; and the communication between them is then established by several narrow passages exactly corresponding with those which I have described and figured in Cycloclypeus.[S]

"The mode in which each successive layer originates from the one which had preceded it, is a question to which my attention has been a good deal directed; but I do not as yet feel confident that I have been able to elucidate it completely. There is certainly no regular system of apertures for the passage of stolons giving origin to new segments, such as are found in all ordinary Polythalamous Foraminifera, whether their type of growth be rectilinear, spiral, or cyclical; and I am disposed to believe that where one layer is separated from another by nothing else than the proper walls of the chambers,—which, as I shall presently show, are traversed by multitudes of minute tubuli giving passage to pseudopodia,—the coalescence of these pseudopodia on the external surface would suffice to lay the foundation of a new layer of sarcodic segments. But where an intermediate or supplemental skeleton, consisting of a thick layer of solid calcareous shell, has been deposited between two successive layers, it is obvious that the animal body contained in the lower layer of chambers must be completely cut off from that which occupies the upper, unless some special provision exist for their mutual communication. Such a provision I believe to have been made by the extension of bands of sarcode, through canals left in the intermediate skeleton, from the lower to the upper tier of chambers. For in such sections as happen to have traversed thick deposits of the intermediate skeleton, there are generally found passages distinguished from those of the ordinary canal-system by their broad flat form, their great transverse diameter, and their non-ramification. One of these passages I have distinctly traced to a chamber, with the cavity of which it communicated through two or three apertures in its proper wall; and I think it likely that I should have been able to trace it at its other extremity into a chamber of the superjacent tier, had not the plane of the section passed out of its course. Riband-like casts of these passages are often to be seen in decalcified specimens, traversing the void spaces left by the removal of the thickest layers of the intermediate skeleton.

"But the organization of a new layer seems to have not unfrequently taken place in a much more considerable extension of the sarcode-body of the pre-formed layer; which either folded back its margin over the surface already consolidated, in a manner somewhat like that in which the mantle of a Cyproea doubles back to deposit the final surface-layer of its shell, or sent upwards wall-like lamellÆ, sometimes of very limited extent, but not unfrequently of considerable length, which, after traversing the substance of the shell, like trap-dykes in a bed of sandstone, spread themselves out over its surface. Such, at least, are the only interpretations I can put upon the appearances presented by decalcified specimens. For on the one hand, it is frequently to be observed that two bands of serpentine (or other infiltrated mineral), which represent two layers of the original sarcode-body of the animal, approximate to each other in some part of their course, and come into complete continuity; so that the upper layer would seem at that part to have had its origin in the lower. Again, even where these bands are most widely separated, we find that they are commonly held together by vertical lamellÆ of the same material, sometimes forming mere tongues, but often running to a considerable length. That these lamellÆ have not been formed by mineral infiltration into accidental fissures in the shell, but represent corresponding extensions of the sarcode-body, seems to me to be indicated not merely by the characters of their surface, but also by the fact that portions of the canal-system may be occasionally traced into connection with them.

"Although Dr. Dawson has noticed that some parts of the sections which he examined present the fine tubulation characteristic of the shells of the Nummuline Foraminifera, he does not seem to have recognised the fact, which the sections placed in my hands have enabled me most satisfactorily to determine,—that the proper walls of the chambers everywhere present the fine tubulation of the Nummuline shell; a point of the highest importance in the determination of the affinities of Eozoon. This tubulation, although not seen with the clearness with which it is to be discerned in recent examples of the Nummuline type, is here far better displayed than it is in the majority of fossil Nummulites, in which the tubuli have been filled up by the infiltration of calcareous matter, rendering the shell-substance nearly homogeneous. In Eozoon these tubuli have been filled up by the infiltration of a mineral different from that of which the shell is composed, and therefore not coalescing with it; and the tubular structure is consequently much more satisfactorily distinguishable. In decalcified specimens, the free margins of the casts of the chambers are often seen to be bordered with a delicate white glistening fringe; and when this fringe is examined with a sufficient magnifying power, it is seen to be made up of a multitude of extremely delicate aciculi, standing side by side like the fibres of asbestos. These, it is obvious, are the internal casts of the fine tubuli which perforated the proper wall of the chambers, passing directly from its inner to its outer surface; and their presence in this situation affords the most satisfactory confirmation of the evidence of that tubulation afforded by thin sections of the shell-wall.

"The successive layers, each having its own proper wall, are often superposed one upon another without the intervention of any supplemental or intermediate skeleton such as presents itself in all the more massive forms of the Nummuline series; but a deposit of this form of shell-substance, readily distinguishable by its homogeneousness from the finely tubular shell immediately investing the segments of the sarcode-body, is the source of the great thickening which the calcareous zones often present in vertical sections of Eozoon. The presence of this intermediate skeleton has been correctly indicated by Dr. Dawson; but he does not seem to have clearly differentiated it from the proper wall of the chambers. All the tubuli which he has described belong to that canal system which, as I have shown,[T] is limited in its distribution to the intermediate skeleton, and is expressly designed to supply a channel for its nutrition and augmentation. Of this canal system, which presents most remarkable varieties in dimensions and distribution, we learn more from the casts presented by decalcified specimens, than from sections, which only exhibit such parts of it as their plane may happen to traverse. Illustrations from both sources, giving a more complete representation of it than Dr. Dawson’s figures afford, have been prepared from the additional specimens placed in my hands.

"It does not appear to me that the canal system takes its origin directly from the cavity of the chambers. On the contrary, I believe that, as in Calcarina (which Dr. Dawson has correctly referred to as presenting the nearest parallel to it among recent Foraminifera), they originate in lacunar spaces on the outside of the proper walls of the chambers, into which the tubuli of those walls open externally; and that the extensions of the sarcode-body which occupied them were formed by the coalescence of the pseudopodia issuing from those tubuli.[U]

"It seems to me worthy of special notice, that the canal system, wherever displayed in transparent sections, is distinguished by a yellowish brown coloration, so exactly resembling that which I have observed in the canal system of recent Foraminifera (as Polystomella and Calcarina) in which there were remains of the sarcode-body, that I cannot but believe the infiltrating mineral to have been dyed by the remains of sarcode still existing in the canals of Eozoon at the time of its consolidation. If this be the case, the preservation of this colour seems to indicate that no considerable metamorphic action has been exerted upon the rock in which this fossil occurs. And I should draw the same inference from the fact that the organic structure of the shell is in many instances even more completely preserved than it usually is in the Nummulites and other Foraminifera of the Nummulitic limestone of the early Tertiaries.

"To sum up,—That the Eozoon finds its proper place in the Foraminiferal series, I conceive to be conclusively proved by its accordance with the great types of that series, in all the essential characters of organization;—namely, the structure of the shell forming the proper wall of the chambers, in which it agrees precisely with Nummulina and its allies; the presence of an intermediate skeleton and an elaborate canal system, the disposition of which reminds us most of Calcarina; a mode of communication of the chambers when they are most completely separated, which has its exact parallel in Cycloclypeus; and an ordinary want of completeness of separation between the chambers, corresponding with that which is characteristic of Carpenteria.

"There is no other group of the animal kingdom to which Eozoon presents the slightest structural resemblance; and to the suggestion that it may have been of kin to Nullipore, I can offer the most distinct negative reply, having many years ago carefully studied the structure of that stony Alga, with which that of Eozoon has nothing whatever in common.

"The objections which not unnaturally occur to those familiar with only the ordinary forms of Foraminifera, as to the admission of Eozoon into the series, do not appear to me of any force. These have reference in the first place to the great size of the organism; and in the second, to its exceptional mode of growth.

"1. It must be borne in mind that all the Foraminifera normally increase by the continuous gemmation of new segments from those previously formed; and that we have, in the existing types, the greatest diversities in the extent to which this gemmation may proceed. Thus in the GlobigerinÆ, whose shells cover to an unknown thickness the sea bottom of all that portion of the Atlantic Ocean which is traversed by the Gulf Stream, only eight or ten segments are ordinarily produced by continuous gemmation; and if new segments are developed from the last of these, they detach themselves so as to lay the foundation of independent GlobigerinÆ. On the other hand in Cycloclypeus, which is a discoidal structure attaining two and a quarter inches in diameter, the number of segments formed by continuous gemmation must be many thousand. Again, the Receptaculites of the Canadian Silurian rocks, shown by Mr. Salter’s drawings[V] to be a gigantic Orbitolite, attains a diameter of twelve inches; and if this were to increase by vertical as well as by horizontal gemmation (after the manner of Tinoporus or Orbitoides) so that one discoidal layer would be piled on another, it would form a mass equalling Eozoon in its ordinary dimensions. To say, therefore, that Eozoon cannot belong to the Foraminifera on account of its gigantic size, is much as if a botanist who had only studied plants and shrubs were to refuse to admit a tree into the same category. The very same continuous gemmation which has produced an Eozoon would produce an equal mass of independent GlobigerinÆ, if after eight or ten repetitions of the process, the new segments were to detach themselves.

"It is to be remembered, moreover, that the largest masses of sponges are formed by continuous gemmation from an original Rhizopod segment; and that there is no Á priori reason why a Foraminiferal organism should not attain the same dimensions as a Poriferal one,—the intimate relationship of the two groups, notwithstanding the difference between their skeletons, being unquestionable.

"2. The difficulty arising from the zoophytic plan of growth of Eozoon is at once disposed of by the fact that we have in the recent Polytrema (as I have shown, op. cit., p. 235) an organism nearly allied in all essential points of structure to Rotalia, yet no less aberrant in its plan of growth, having been ranked by Lamarck among the Millepores. And it appears to me that Eozoon takes its place quite as naturally in the Nummuline series as Polytrema in the Rotaline. As we are led from the typical Rotalia, through the less regular Planorbulina, to Tinoporus, in which the chambers are piled up vertically, as well as multiplied horizontally, and thence pass by an easy gradation to Polytrema, in which all regularity of external form is lost; so may we pass from the typical Operculina or Nummulina, through Heterostegina and Cycloclypeus to Orbitoides, in which, as in Tinoporus, the chambers multiply both by horizontal and by vertical gemmation; and from Orbitoides to Eozoon the transition is scarcely more abrupt than from Tinoporus to Polytrema.

"The general acceptance, by the most competent judges, of my views respecting the primary value of the characters furnished by the intimate structure of the shell, and the very subordinate value of plan of growth, in the determination of the affinities of Foraminifera, renders it unnecessary that I should dwell further on my reasons for unhesitatingly affirming the Nummuline affinities of Eozoon from the microscopic appearances presented by the proper wall of its chambers, notwithstanding its very aberrant peculiarities; and I cannot but feel it to be a feature of peculiar interest in geological inquiry, that the true relations of by far the earliest fossil yet known should be determinable by the comparison of a portion which the smallest pin’s head would cover, with organisms at present existing."

"Specimens from Long Lake, in the collection of the Geological Survey of Canada, exhibit white crystalline limestone with light green compact or septariiform[W] serpentine, and much resemble some of the serpentine limestones of Grenville. Under the microscope the calcareous matter presents a delicate areolated appearance, without lamination; but it is not an example of acervuline Eozoon, but rather of fragments of such a structure, confusedly aggregated together, and having the interstices and cell-cavities filled with serpentine. I have not found in any of these fragments a canal system similar to that of Eozoon Canadense, though there are casts of large stolons, and, under a high power, the calcareous matter shows in many places the peculiar granular or cellular appearance which is one of the characters of the supplemental skeleton of that species. In a few places a tubulated cell-wall is preserved, with structure similar to that of Eozoon Canadense.

“Specimens of Laurentian limestone from Wentworth, in the collection of the Geological Survey, exhibit many rounded silicious bodies, some of which are apparently grains of sand, or small pebbles; but others, especially when freed from the calcareous matter by a dilute acid, appear as rounded bodies, with rough surfaces, either separate or aggregated in lines or groups, and having minute vermicular processes projecting from their surfaces. At first sight these suggest the idea of spicules; but I think it on the whole more likely that they are casts of cavities and tubes belonging to some calcareous Foraminiferal organism which has disappeared. Similar bodies, found in the limestone of Bavaria, have been described by GÜmbel, who interprets them in the same way. They may also be compared with the silicious bodies mentioned in a former paper as occurring in the loganite filling the chambers of specimens of Eozoon from Burgess.”

These specimens will be more fully referred to under Chapter VI.

I may mention here a peculiar and interesting structure which has been detected in one of my specimens while these sheets were passing through the press. It is an abnormal thickening of the calcareous wall, extending across several layers, and perforated with large parallel cylindrical canals, filled with dolomite, and running in the direction of the laminÆ; the intervening calcite being traversed by a very fine and delicate canal system. It makes a nearer approach to some of the StromatoporÆ mentioned in Chapter VI. than any other Laurentian structure hitherto observed, and may be either an abnormal growth of Eozoon, consequent on some injury, or a parasitic mass of some Stromatoporoid organism overgrown by the laminÆ of the fossil. The structure of the dolomite in this specimen indicates that it first lined the canals, and afterward filled them; an appearance which I have also observed recently in the larger canals filled with serpentine (Plate VIII., fig. 5). The cut below is an attempt, only partially successful, to show the Amoeba-like appearance, when magnified, of the casts of the chambers of Eozoon, as seen on the decalcified surface of a specimen broken parallel to the laminÆ.

It was fortunate for the recognition of Eozoon that Dr. Hunt had, before its discovery, made so thorough researches into the chemistry of the Laurentian series, and was prepared to show the chemical possibilities of the preservation of fossils in these ancient deposits. The following able summary of his views was appended to the original description of the fossil in the Journal of the Geological Society.

"The details of structure have been preserved by the introduction of certain mineral silicates, which have not only filled up the chambers, cells, and canals left vacant by the disappearance of the animal matter, but have in very many cases been injected into the tubuli, filling even their smallest ramifications. These silicates have thus taken the place of the original sarcode, while the calcareous septa remain. It will then be understood that when the replacement of the Eozoon by silicates is spoken of, this is to be understood of the soft parts only; since the calcareous skeleton is preserved, in most cases, without any alteration. The vacant spaces left by the decay of the sarcode may be supposed to have been filled by a process of infiltration, in which the silicates were deposited from solution in water, like the silica which fills up the pores of wood in the process of silicification. The replacing silicates, so far as yet observed, are a white pyroxene, a pale green serpentine, and a dark green alumino-magnesian mineral, which is allied in composition to chlorite and to pyrosclerite, and which I have referred to loganite. The calcareous septa in the last case are found to be dolomitic, but in the other instances are nearly pure carbonate of lime. The relations of the carbonate and the silicates are well seen in thin sections under the microscope, especially by polarized light. The calcite, dolomite, and pyroxene exhibit their crystalline structure to the unaided eye; and the serpentine and loganite are also seen to be crystalline when examined with the microscope. When portions of the fossil are submitted to the action of an acid, the carbonate of lime is dissolved, and a coherent mass of serpentine is obtained, which is a perfect cast of the soft parts of the Eozoon. The form of the sarcode which filled the chambers and cells is beautifully shown, as well as the connecting canals and the groups of tubuli; these latter are seen in great perfection upon surfaces from which the carbonate of lime has been partially dissolved. Their preservation is generally most complete when the replacing mineral is serpentine, although very perfect specimens are sometimes found in pyroxene. The crystallization of the latter mineral appears, however, in most cases to have disturbed the calcareous septa.

"Serpentine and pyroxene are generally associated in these specimens, as if their disposition had marked different stages of a continuous process. At the Calumet, one specimen of the fossil exhibits the whole of the sarcode replaced by serpentine; while, in another one from the same locality, a layer of pale green translucent serpentine occurs in immediate contact with the white pyroxene. The calcareous septa in this specimen are very thin, and are transverse to the plane of contact of the two minerals; yet they are seen to traverse both the pyroxene and the serpentine without any interruption or change. Some sections exhibit these two minerals filling adjacent cells, or even portions of the same cell, a clear line of division being visible between them. In the specimens from Grenville on the other hand, it would seem as if the development of the Eozoon (considerable masses of which were replaced by pyroxene) had been interrupted, and that a second growth of the animal, which was replaced by serpentine, had taken place upon the older masses, filling up their interstices."

[Details of chemical composition are then given.]

"When examined under the microscope, the loganite which replaces the Eozoon of Burgess shows traces of cleavage-lines, which indicate a crystalline structure. The grains of insoluble matter found in the analysis, chiefly of quartz-sand, are distinctly seen as foreign bodies imbedded in the mass, which is moreover marked by lines apparently due to cracks formed by a shrinking of the silicate, and subsequently filled by a further infiltration of the same material. This arrangement resembles on a minute scale that of septaria. Similar appearances are also observed in the serpentine which replaces the Eozoon of Grenville, and also in a massive serpentine from Burgess, resembling this, and enclosing fragments of the fossil. In both of these specimens also grains of mechanical impurities are detected by the microscope; they are however, rarer than in the loganite of Burgess.

"From the above facts it may be concluded that the various silicates which now constitute pyroxene, serpentine, and loganite were directly deposited in waters in the midst of which the Eozoon was still growing, or had only recently perished; and that these silicates penetrated, enclosed, and preserved the calcareous structure precisely as carbonate of lime might have done. The association of the silicates with the Eozoon is only accidental; and large quantities of them, deposited at the same time, include no organic remains. Thus, for example, there are found associated with the Eozoon limestones of Grenville, massive layers and concretions of pure serpentine; and a serpentine from Burgess has already been mentioned as containing only small broken fragments of the fossil. In like manner large masses of white pyroxene, often surrounded by serpentine, both of which are destitute of traces of organic structure, are found in the limestone at the Calumet. In some cases, however, the crystallization of the pyroxene has given rise to considerable cleavage-planes, and has thus obliterated the organic structures from masses which, judging from portions visible here and there, appear to have been at one time penetrated by the calcareous plates of Eozoon. Small irregular veins of crystalline calcite, and of serpentine, are found to traverse such pyroxene masses in the Eozoon limestone of Grenville.

"It appears that great beds of the Laurentian limestones are composed of the ruins of the Eozoon. These rocks, which are white, crystalline, and mingled with pale green serpentine, are similar in aspect to many of the so-called primary limestones of other regions. In most cases the limestones are non-magnesian, but one of them from Grenville was found to be dolomitic. The accompanying strata often present finely crystallized pyroxene, hornblende, phlogopite, apatite, and other minerals. These observations bring the formation of silicious minerals face to face with life, and show that their generation was not incompatible with the contemporaneous existence and the preservation of organic forms. They confirm, moreover, the view which I some years since put forward, that these silicated minerals have been formed, not by subsequent metamorphism in deeply buried sediments, but by reactions going on at the earth’s surface.[Z] In support of this view, I have elsewhere referred to the deposition of silicates of lime, magnesia, and iron from natural waters, to the great beds of sepiolite in the unaltered Tertiary strata of Europe; to the contemporaneous formation of neolite (an aluimino-magnesian silicate related to loganite and chlorite in composition); and to glauconite, which occurs not only in Secondary, Tertiary, and Recent deposits, but also, as I have shown, in Lower Silurian strata.[AA] This hydrous silicate of protoxide of iron and potash, which sometimes includes a considerable proportion of alumina in its composition, has been observed by Ehrenberg, Mantell, and Bailey, associated with organic forms in a manner which seems identical with that in which pyroxene, serpentine, and loganite occur with the Eozoon in the Laurentian limestones. According to the first of these observers, the grains of green-sand, or glauconite, from the Tertiary limestone of Alabama, are casts of the interior of Polythalamia, the glauconite having filled them by ‘a species of natural injection, which is often so perfect that not only the large and coarse cells, but also the very finest canals of the cell-walls and all their connecting tubes, are thus petrified and separately exhibited.’ Bailey confirmed these observations, and extended them. He found in various Cretaceous and Tertiary limestones of the United States, casts in glauconite, not only of Foraminifera, but of spines of Echinus, and of the cavities of corals. Besides, there were numerous red, green, and white casts of minute anastomosing tubuli, which, according to Bailey, resemble the casts of the holes made by burrowing sponges (Cliona) and worms. These forms are seen after the dissolving of the carbonate of lime by a dilute acid. He found, moreover, similar casts of Foraminifera, of minute mollusks, and of branching tubuli, in mud obtained from soundings in the Gulf Stream, and concluded that the deposition of glauconite is still going on in the depths of the sea.[AB] Pourtales has followed up these investigations on the recent formation of glauconite in the Gulf Stream waters. He has observed its deposition also in the cavities of Millepores, and in the canals in the shells of Balanus. According to him, the glauconite grains formed in Foraminifera lose after a time their calcareous envelopes, and finally become ‘conglomerated into small black pebbles,’ sections of which still show under a microscope the characteristic spiral arrangement of the cells.[AC]

“It appears probable from these observations that glauconite is formed by chemical reactions in the ooze at the bottom of the sea, where dissolved silica comes in contact with iron oxide rendered soluble by organic matter; the resulting silicate deposits itself in the cavities of shells and other vacant spaces. A process analogous to this in its results, has filled the chambers and canals of the Laurentian Foraminifera with other silicates; from the comparative rarity of mechanical impurities in these silicates, however, it would appear that they were deposited in clear water. Alumina and oxide of iron enter into the composition of loganite as well as of glauconite; but in the other replacing minerals, pyroxene and serpentine, we have only silicates of lime and magnesia, which were probably formed by the direct action of alkaline silicates, either dissolved in surface-waters, or in those of submarine springs, upon the calcareous and magnesian salts of the sea-water.”

[As stated in the text, the canals of Eozoon are sometimes filled with dolomite, or in part with serpentine and in part with dolomite.]

Since my attention has been directed to this subject, many illustrations have come under my notice of Silurian limestones in which the pores of fossils are infiltrated with hydrous silicates akin to glauconite and serpentine. A limestone of this kind, collected by Mr. Robb, at Pole Hill, in New Brunswick, afforded not only beautiful specimens of portions of Crinoids preserved in this way, but a sufficient quantity of the material was collected for an exact analysis, a note on which was published in the Proceedings of the Royal Irish Academy, 1871.

The limestone of Pole Hill is composed almost wholly of organic fragments, cemented by crystalline carbonate of lime, and traversed by slender veins of the same mineral. Among the fragments may be recognised under the microscope portions of Trilobites, and of brachiopod and gastropod shells, and numerous joints and plates of Crinoids. The latter are remarkable for the manner in which their reticulated structure, which is similar to that of modern Crinoids, has been injected with a silicious substance, which is seen distinctly in slices, and still more plainly in decalcified specimens. This filling is precisely similar in appearance to the serpentine filling the canals of Eozoon, the only apparent difference being in the forms of the cells and tubes of the Crinoids, as compared with those of the Laurentian fossil; the same silicious substance also occupies the cavities of some of the small shells, and occurs in mere amorphous pieces, apparently filling interstices. From its mode of occurrence, I have not the slightest doubt that it occupied the cavities of the crinoidal fragments while still recent, and before they had been cemented together by the calcareous paste. This silicious filling is therefore similar on the one hand to that effected by the ancient serpentine of the Laurentian, and on the other to that which results from the depositions of modern glauconite. The analysis of Dr. Hunt, which I give below, fully confirms these analogies.

I may add that I have examined under the microscope portions of the substance prepared by Dr. Hunt for analysis, and find it to retain its form, showing that it is the actual filling of the cavities. I have also examined the small amount of insoluble silica remaining after his treatment with acid and alkaline solvents, and find it to consist of angular and rounded grains of quartzose sand.

The following are Dr. Hunt’s notes:—

"The fossiliferous limestone from Pole Hill, New Brunswick, probably of Upper Silurian age, is light gray and coarsely granular. When treated with dilute hydrochloric acid, it leaves a residue of 5·9 per cent., and the solution gives 1·8 per cent. of alumina and oxide of iron, and magnesia equal to 1·35 of carbonate—the remainder being carbonate of lime. The insoluble matter separated by dilute acid, after washing by decantation from a small amount of fine flocculent matter, consists, apart from an admixture of quartz grains, entirely of casts and moulded forms of a peculiar silicate, which Dr. Dawson has observed in decalcified specimens filling the pores of crinoidal stems; and which when separated by an acid, resembles closely under the microscope the coralloidal forms of arragonite known as flos ferri, the surfaces being somewhat rugose and glistening with crystalline faces. This silicate is sub-translucent, and of a pale green colour, but immediately becomes of a light reddish brown when heated to redness in the air, and gives off water when heated in a tube, without however, changing its form. It is partially decomposed by strong hydrochloric acid, yielding a considerable amount of protosalt of iron. Strong hot sulphuric acid readily and completely decomposes it, showing it to be a silicate of alumina and ferrous oxide, with some magnesia and alkalies, but with no trace of lime. The separated silica, which remains after the action of the acid, is readily dissolved by a dilute solution of soda, leaving behind nothing but angular and partially rounded grains of sand, chiefly of colourless vitreous quartz. An analysis effected in the way just described on 1·187 grammes gave the following results, which give, by calculation, the centesimal composition of the mineral:—

"A previous analysis of a portion of the mixture by fusion with carbonate of soda gave, by calculation, 18·80 p. c. of protoxide of iron, and amounts of alumina and combined silica closely agreeing with those just given.

"The oxygen ratios, as above calculated, are nearly as 3 : 2 : 1 : 1. This mineral approaches in composition to the jollyte of Von Kobell, from which it differs in containing a portion of alkalies, and only one half as much water. In these respects it agrees nearly with the silicate found by Robert Hoffman, at Raspenau, in Bohemia, where it occurs in thin layers alternating with picrosmine, and surrounding masses of Eozoon in the Laurentian limestones of that region;[AD] the Eozoon itself being there injected with a hydrous silicate which may be described as intermediate between glauconite and chlorite in composition. The mineral first mentioned is compared by Hoffman to fahlunite, to which jollyte is also related in physical characters as well as in composition. Under the names of fahlunite, gigantolite, pinite, etc., are included a great class of hydrous silicates, which from their imperfectly crystalline condition, have generally been regarded, like serpentine, as results of the alteration of other silicates. It is, however, difficult to admit that the silicate found in the condition described by Hoffman, and still more the present mineral, which injects the pores of palÆozoic Crinoids, can be any other than an original deposition, allied in the mode of its formation, to the serpentine, pyroxene, and other minerals which have injected the Laurentian Eozoon, and the serpentine and glauconite, which in a similar manner fill Tertiary and recent shells."

The following on this subject is from a memoir by Dr. Hunt in the Twenty-first Report of the Regents of the University of New York, 1874:—

"Recent investigations have shown that in some cases the dissemination of certain of these minerals through the crystalline limestones is connected with organic forms. The observations of Dr. Dawson and myself on the Eozoon Canadense showed that certain silicates, namely serpentine, pyroxene, and loganite, had been deposited in the cells and chambers left vacant by the disappearance of the animal matter from the calcareous skeleton of the foraminiferous organism; so that when this calcareous portion is removed by an acid there remains a coherent mass, which is a cast of the soft parts of the animal, in which, not only the chambers and connecting canals, but the minute tubuli and pores are represented by solid mineral silicates. It was shown that this process must have taken place immediately after the death of the animal, and must have depended on the deposition of these silicates from the waters of the ocean.

"The train of investigation thus opened up, has been pursued by Dr. GÜmbel, Director of the Geological Survey of Bavaria, who, in a recent remarkable memoir presented to the Royal Society of that country, has detailed his results.

"Having first detected a fossil identical with the Canadian Eozoon (together with several other curious microscopic organic forms not yet observed in Canada), replaced by serpentine in a crystalline limestone from the primitive group of Bavaria, which he identified with the Laurentian system of this country, he next discovered a related organism, to which he has given the name of Eozoon Bavaricum. This occurs in a crystalline limestone belonging to a series of rocks more recent than the Laurentian, but older than the Primordial zone of the Lower Silurian, and designated by him the Hercynian clay slate series, which he conceives may represent the Cambrian system of Great Britain, and perhaps correspond to the Huronian series of Canada and the United States. The cast of the soft parts of this new fossil is, according to GÜmbel, in part of serpentine, and in part of hornblende.

"His attention was next directed to the green hornblende (pargasite) which occurs in the crystalline limestone of Pargas in Finland, and remains when the carbonate of lime is dissolved as a coherent mass closely resembling that left by the irregular and acervuline forms of Eozoon. The calcite walls also sometimes show casts of tubuli…. A white mineral, probably scapolite was found to constitute some tubercles associated with the pargasite, and the two mineral species were in some cases united in the same rounded grain.

"Similar observations were made by him upon specimens of coccolite or green pyroxene, occurring in rounded and wrinkled grains in a Laurentian limestone from New York. These, according to GÜmbel, present the same connecting cylinders and branching stems as the pargasite, and are by him supposed to have been moulded in the same manner…. Very beautiful evidences of the same organic structure consisting of the casts of tubuli and their ramifications, were also observed by GÜmbel in a purely crystalline limestone, enclosing granules of chondrodite, hornblende, and garnet, from Boden in Saxony. Other specimens of limestone, both with and without serpentine and chondrodite, were examined without exhibiting any traces of these peculiar forms; and these negative results are justly deemed by GÜmbel as going to prove that the structure of the others is really, like that of Eozoon, the result of the intervention of organic forms. Besides the minerals observed in the replacing substance of Eozoon in Canada, viz., serpentine, pyroxene, and loganite, GÜmbel adds chondrodite, hornblende, scapolite, and probably also pyrallolite, quartz, iolite, and dichroite."

The following is from a paper by Dr. Hunt in the Report of the Survey of Canada for 1866:—

"In connection with the Eozoon it is interesting to examine more carefully into the nature of the matters which have been called glauconite or green-sand. These names have been given to substances of unlike composition, which, however, occur under similar conditions, and appear to be chemical deposits from water, filling cavities in minute fossils, or forming grains in sedimentary rocks of various ages. Although greenish in colour, and soft and earthy in texture, it will be seen that the various glauconites differ widely in composition. The variety best known, and commonly regarded as the type of the glauconites, is that found in the green-sand of Cretaceous age in New Jersey, and in the Tertiary of Alabama; the glauconite from the Lower Silurian rocks of the Upper Mississippi is identical with it in composition. Analysis shows these glauconites to be essentially hydrous silicates of protoxyd of iron, with more or less alumina, and small but variable quantities of magnesia, besides a notable amount of potash. This alkali is, however, sometimes wanting, as appears from the analysis of a green-sand from Kent in England, by that careful chemist, the late Dr. Edward Turner, and in another examined by Berthier, from the calcaire grossier, near Paris, which is essentially a serpentine in composition, being a hydrous silicate of magnesia and protoxyd of iron. A comparison of these last two will show that the loganite, which fills the ancient Foraminifer of Burgess, is a silicate nearly related in composition.

I. Green-sand from the calcaire grossier, near Paris. Berthier (cited by Beudant, Mineralogie, ii., 178).

II. Green-sand from Kent, England. Dr. Edward Turner (cited by Rogers, Final Report, Geol. N. Jersey, page 206).

III. Loganite from the Eozoon of Burgess.

IV. Green-sand, Lower Silurian; Red Bird, Minnesota.

V. Green-sand, Cretaceous, New Jersey.

VI. Green-sand, Lower Silurian, Orleans Island.

The last four analyses are by myself.

For the best description of ArchÆocyathus, I may refer to The PalÆozoic Fossils of Canada, by Mr. Billings, vol. i. There also, and in Mr. Salter’s memoir in The Decades of the Canadian Survey, will be found all that is known of the structure of Receptaculites. For the American StromatoporÆ I may refer to Winchell’s paper in the Proceedings of the American Association, 1866; to Professor Hall’s Descriptions of New Species of Fossils from Iowa, Report of the State Cabinet, Albany, 1872; and to the Descriptions of Canadian Species by Dr. Nicholson, in his Report on the PalÆontology of Ontario, 1874.

The genus Stromatopora of Goldfuss was defined by him as consisting of laminÆ of a solid and porous character, alternating and contiguous, and constituting a hemispherical or sub-globose mass. In this definition, the porous strata are really those of the fossil, the alternating solid strata being the stony filling of the chambers; and the descriptions of subsequent authors have varied according as, from the state of preservation of the specimens or other circumstances, the original laminÆ or the filling of the spaces attracted their attention. In the former case the fossil could be described as consisting of laminÆ made up of interlaced fibrils of calcite, radiating from vertical pillars which connect the laminÆ. In the latter case, the laminÆ, appear as solid plates, separated by very narrow spaces, and perforated with round vertical holes representing the connecting pillars. These StromatoporÆ range from the Lower Silurian to the Devonian, inclusive, and many species have been described; but their limits are not very definite, though there are undoubtedly remarkable differences in the distances of the laminÆ and in their texture, and in the smooth or mammillated character of the masses. Hall’s genus Stromatocerium belongs to these forms, and D’Orbigny’s genus Sparsispongia refers to mammillated species, sometimes with apparent oscula.

Phillip’s genus Caunopora was formed to receive specimens with concentric cellular layers traversed by “long vermiform cylindrical canals;” while Winchell’s genus Coenostroma includes species with these vermiform canals arranged in a radiate manner, diverging from little eminences in the concentric laminÆ. The distinction between these last genera does not seem to be very clear, and may depend on the state of preservation of the specimens. A more important distinction appears to exist between those that have a single vertical canal from which the subordinate canals diverge, and those that have groups of such canals.

Some species of the Coenostroma group have very dense calcareous laminÆ traversed by the canals; but it does not seem that any distinction has yet been made between the proper wall and the intermediate skeleton; and most observers have been prevented from attending to such structures by the prevailing idea that these fossils are either corals or sponges, while the state of preservation of the more delicate tissues is often very imperfect.

In Canada the principal localities of Eozoon Canadense are at Grenville, Petite Nation, the Calumets Rapids, Burgess, Tudor, and Madoc. At the two last places the fossil occurs in beds which may be on a somewhat higher horizon than the others. Mr. Vennor has recently found specimens which have the general form of Eozoon, though the minute structure is not preserved, at Dalhousie, in Lanark Co., Ontario. One specimen from this place is remarkable from having been mineralized in part by a talcose mineral associated with serpentine.

I have examined specimens from Chelmsford, in Massachusetts, and from Amity and Warren County, New York, the latter from the collection of Professor D. S. Martin, which show the canals of Eozoon in a fair state of preservation, though the specimens are fragmental, and do not show the laminated structure.

In European specimens of limestones of Laurentian age, from Tunaberg and Fahlun in Sweden, and from the Western Islands of Scotland, I have hitherto failed to recognise the characteristic structure of the fossil. Connemara specimens have also failed to afford me any satisfactory results, and specimens of a serpentine limestone from the Alps, collected by M. Favre, and communicated to me by Dr. Hunt, though in general texture they much resemble acervuline Eozoon, do not show its minute structures.

The following summary, given by these authors, may be taken as including the substance of their objections to the animal nature of Eozoon. I shall give them in their words and follow them with short answers to each.

"1st. The serpentine in ophitic rocks has been shown to present appearances which can only be explained on the view that it undergoes structural and chemical changes, causing it to pass into variously subdivided states, and etching out the resulting portions into a variety of forms—grains and plates, with lobulated or segmented surfaces—fibres and aciculi—simple and branching configurations. Crystals of malacolite, often associated with the serpentine, manifest some of these changes in a remarkable degree.

"2nd. The ‘intermediate skeleton’ of Eozoon (which we hold to be the calcareous matrix of the above lobulated grains, etc.) is completely paralleled in various crystalline rocks—notably marble containing grains of coccolite (Aker and Tyree), pargasite (Finland), chondrodite (New Jersey, etc.)

"3rd. The ‘chamber casts’ in the acervuline variety of Eozoon are more or less paralleled by the grains of the mineral silicates in the pre-cited marbles.

"4th. The ‘chamber casts’ being composed occasionally of loganite and malacolite, besides serpentine, is a fact which, instead of favouring their organic origin, as supposed, must be held as a proof of their having been produced by mineral agencies; inasmuch as these three silicates have a close pseudomorphic relationship, and may therefore replace one another in their naturally prescribed order.

"5th. Dr. GÜmbel, observing rounded, cylindrical, or tuberculated grains of coccolite and pargasite in crystalline calcareous marbles, considered them to be ‘chamber casts,’ or of organic origin. We have shown that such grains often present crystalline planes, angles, and edges; a fact clearly proving that they were originally simple or compound crystals that have undergone external decretion by chemical or solvent action.

"6th. We have adduced evidences to show that the ‘nummuline layer’ in its typical condition—that is, consisting of cylindrical aciculi, separated by interspaces filled with calcite—has originated directly from closely packed fibres; these from chrysotile or asbestiform serpentine; this from incipiently fibrous serpentine; and the latter from the same mineral in its amorphous or structureless condition.

"7th. The ‘nummuline layer,’ in its typical condition, unmistakably occurs in cracks or fissures, both in Canadian and Connemara ophite.

"8th. The ‘nummuline layer’ is paralleled by the fibrous coat which is occasionally present on the surface of grains of chondrodite.

"9th. We have shown that the relative position of two superposed asbestiform layers (an upper and an under ‘proper wall’), and the admitted fact of their component aciculi often passing continuously and without interruption from one ‘chamber cast’ to another, to the exclusion of the ‘intermediate skeleton,’ are totally incompatible with the idea of the ‘nummuline layer’ having resulted from pseudopodial tubulation.

"10th. The so-called ‘stolons’ and ‘passages of communication exactly corresponding with those described in Cycloclypeus,’ have been shown to be tabular crystals and variously formed bodies, belonging to different minerals, wedged crossways or obliquely in the calcareous interspaces between the grains and plates of serpentine.

"11th. The ‘canal system’ is composed of serpentine, or malacolite. Its typical kinds in the first of these minerals may be traced in all stages of formation out of plates, prisms, and other solids, undergoing a process of superficial decretion. Those in malacolite are made up of crystals—single, or aggregated together—that have had their planes, angles, and edges rounded off; or have become further reduced by some solvent.

"12th. The ‘canal system’ in its remarkable branching varieties is completely paralleled by crystalline configurations in the coccolite marble of Aker, in Sweden; and in the crevices of a crystal of spinel imbedded in a calcitic matrix from Amity, New York.

"13th. The configurations, presumed to represent the ‘canal systems,’ are totally without any regularity of form, of relative size, or of arrangement; and they occur independently of and apart from other ‘eozoonal features’ (Amity, Boden, etc.); facts not only demonstrating them to be purely mineral products, but which strike at the root of the idea that they are of organic origin.

"14th. In answer to the argument that as all the foregoing ‘eozoonal features’ are occasionally found together in ophite, the combination must be considered a conclusive evidence of their organic origin, we have shown, from the composition, physical characters, and circumstances of occurrence and association of their component serpentine, that they represent the structural and chemical changes which are eminently and peculiarly characteristic of this mineral. It has also been shown that the combination is paralleled to a remarkable extent in chondrodite and its calcitic matrix.

"15th. The ‘regular alternation of lamellÆ of calcareous and silicious minerals’ (respectively representing the ‘intermediate skeleton’ and ‘chamber casts’) occasionally seen in ophite, and considered to be a ‘fundamental fact’ evidencing an organic arrangement, is proved to be a mineralogical phenomenon by the fact that a similar alternation occurs in amphiboline-calcitic marbles, and gneissose rocks.

"16th. In order to account for certain untoward difficulties presented by the configurations forming the ‘canal system,’ and the aciculi of the ‘nummuline layer’—that is, when they occur as ‘solid bundles’—or are ‘closely packed’—or ‘appear to be glued together’—Dr. Carpenter has proposed the theory that the sarcodic extensions which they are presumed to represent have been ‘turned into stone’ (a ‘silicious mineral’) ‘by Nature’s cunning’ (‘just as the sarcodic layer on the surface of the shell of living Foraminifers is formed by the spreading out of coalesced bundles of the pseudopodia that have emerged from the chamber wall’)—‘by a process of chemical substitution before their destruction by ordinary decomposition.’ We showed this quasi-alchymical theory to be altogether unscientific.

"17th. The ‘silicious mineral’ (serpentine) has been analogued with those forming the variously-formed casts (in ‘glauconite,’ etc.) of recent and fossil Foraminifers. We have shown that the mineral silicates of Eozoon have no relation whatever to the substances composing such casts.

"18th. Dr. Hunt, in order to account for the serpentine, loganite, and malacolite, being the presumed in-filling substances of Eozoon, has conceived the ‘novel doctrine,’ that such minerals were directly deposited in the ocean waters in which this ‘fossil’ lived. We have gone over all his evidences and arguments without finding one to be substantiated.

"19th. Having investigated the alleged cases of ‘chambers’ and ‘tubes’ occurring ‘filled with calcite,’ and presumed to be ‘a conclusive answer to’ our ‘objections,’ we have shown that there are the strongest grounds for removing them from the category of reliable evidences on the side of the organic doctrine. The Tudor specimen has been shown to be equally unavailable.

"20th. The occurrence of the best preserved specimens of Eozoon Canadense in rocks that are in a ‘highly crystalline condition’ (Dawson) must be accepted as a fact utterly fatal to its organic origin.

“21st. The occurrence of ‘eozoonal features’ solely in crystalline or metamorphosed rocks, belonging to the Laurentian, the Lower Silurian, and the Liassic systems—never in ordinary unaltered deposits of these and the intermediate systems—must be assumed as completely demonstrating their purely mineral origin.”

1st. This is a mere hypothesis to account for the forms presented by serpentine grains and by Eozoon. Hunt has shown that it is untenable chemically, and has completely exploded it in his recent papers on Chemistry and Geology.[AP] My own observations show that it does not accord with the mode of occurrence of serpentine in the Laurentian limestones of Canada.

2nd. Some of the things stated to parallel the intermediate skeleton of Eozoon, are probably themselves examples of that skeleton. Others have been shown to have no resemblance to it.

3rd. The words “more or less” indicate the precise value of this statement, in a question of comparison between mineral and organic structures. So the prismatic structure of satin-spar may be said “more or less” to resemble that of a shell, or of the cells of a Stenopora.

4th. This overlooks the filling of chamber casts with pyroxene, dolomite, or limestone. Even in the case of loganite this objection is of no value unless it can be applied equally to the similar silicates which fill cavities of fossils[AQ] in the Silurian limestones and in the green-sand.

5th. Dr. GÜmbel’s observations are those of a highly skilled and accurate observer. Even if crystalline forms appear in “chamber casts,” this is as likely to be a result of the injury of organic structures by crystallization, as of the partial effacement of crystals by other actions. Crystalline faces occur abundantly in many undoubted fossil woods and corals; and crystals not unfrequently cross and interfere with the structures in such specimens.

6th. On the contrary, the Canadian specimens prove clearly that the veins of chrysotile have been filled subsequently to the existence of Eozoon in its present state, and that there is no connection whatever between them and the Nummuline wall.

7th. This I have never seen in all my examinations of Eozoon. The writers must have mistaken veins of fibrous serpentine for the nummuline wall.

8th. Only if such grains of chondrodite are themselves casts of foraminiferal chambers. But Messrs. King and Rowney have repeatedly figured mere groups of crystals as examples of the nummuline wall.

9th. Dr. Carpenter has shown that this objection depends on a misconception of the structure of modern Foraminifera, which show similar appearances.

10th. That disseminated crystals occur in the Eozoon limestones is a familiar fact, and one paralleled in many other more or less altered organic limestones. Foreign bodies also occur in the chambers filled with loganite and other minerals; but these need not any more be confounded with the pillars and walls connecting the laminÆ than the sand filling a dead coral with its lamellÆ. Further, it is well known that foreign bodies are often contained both in the testa and chambers even of recent Foraminifera.

11th. The canal system is not always filled with serpentine or malacolite; and when filled with pyroxene, dolomite, or calcite, the forms are the same. The irregularities spoken of are perhaps more manifest in the serpentine specimens, because this mineral has in places encroached on or partially replaced the calcite walls.

12th. If this is true of the Aker marble, then it must contain Eozoon; and specimens of the Amity limestone which I have examined, certainly contain large fragments of Eozoon.

13th. The configuration of the canal system is quite definite, though varying in coarseness and fineness. It is not known to occur independently of the forms of Eozoon except in fragmental deposits.

14th. The argument is not that they are “occasionally found together in ophite,” but that they are found together in specimens preserved by different minerals, and in such a way as to show that all these minerals have filled chambers, canals, and tubuli, previously existing in a skeleton of limestone.

15th. The lamination of Eozoon is not like that of any rock, but a strictly limited and definite form, comparable with that of Stromatopora.

16th. This I pass over, as a mere captious criticism of modes of expression used by Dr. Carpenter.

17th. Dr. Hunt, whose knowledge of chemical geology should give the greatest weight to his judgment, maintains the deposition of serpentine and loganite to have taken place in a manner similar to that of jollyte and glauconite in undoubted fossils: and this would seem to be a clear deduction from the facts he has stated, and from the chemical character of the substances. My own observations of the mode of occurrence of serpentine in the Eozoon limestones lead me to the same result.

18th. Dr. Hunt’s arguments on the subject, as recently presented in his Papers on Chemistry and Geology, need only be studied by any candid and competent chemist or mineralogist to lead to a very different conclusion from that of the objectors.

19th. This is a mere statement of opinion. The fact remains that the chambers and canals are sometimes filled with calcite.

20th. That the occurrence of Eozoon in crystalline limestones is “utterly fatal” to its claims to organic origin can be held only by those who are utterly ignorant of the frequency with which organic remains are preserved in highly crystalline limestones of all ages. In addition to other examples mentioned above, I may state that the curious specimen of Coenostroma from the Guelph limestone figured in Chapter VI., has been converted into a perfectly crystalline dolomite, while its canals and cavities have been filled with calcite, since weathered out.

21st. This limited occurrence is an assumption contrary to facts. It leaves out of account the Tudor specimens, and also the abundant occurrence of the Stromatoporoid successors of Eozoon in the Silurian and Devonian. Further, even if the Eozoon were limited to the Laurentian, this would not be remarkable; and since all the Laurentian rocks known to us are more or less altered, it could not in that case occur in unaltered rocks.

I have gone over these objections seriatim, because, though individually weak, they have an imposing appearance in the aggregate, and have been paraded as a conclusive settlement of the questions at issue. They have even been reprinted in the year just past in an English journal of some standing, which professes to accept only original contributions to science, but has deviated from its rule in their favour. I may be excused for adding a portion of my original argument in opposition to these objections, as given more at length in the Transactions of the Irish Academy.

1. I object to the authors‘ mode of stating the question at issue, whereby they convey to the reader the impression that this is merely to account for the occurrence of certain peculiar forms in ophite.

With reference to this, it is to be observed that the attention of Sir William Logan, and of the writer, was first called to Eozoon by the occurrence in Laurentian rocks of definite forms resembling the Silurian StromatoporÆ, and dissimilar from any concretions or crystalline structures found in these rocks. With his usual sagacity, Sir William added to these facts the consideration that the mineral substances occurring is these forms were so dissimilar as to suggest that the forms themselves must be due to some extraneous cause rather than to any crystalline or segregative tendency of their constituent minerals. These specimens, which were exhibited by Sir William as probably fossils, at the meeting of the American Association in 1859, and noticed with figures in the Report of the Canadian Survey for 1863, showed under the microscope no minute structures. The writer, who had at the time an opportunity of examining them, stated his belief that if fossils, they would prove to be not Corals but Protozoa.

In 1864, additional specimens having been obtained by the Survey, slices were submitted to the writer, in which he at once detected a well-marked canal-system, and stated, decidedly, his belief that the forms were organic and foraminiferal. The announcement of this discovery was first made by Sir W. E. Logan, in Silliman’s Journal for 1864. So far, the facts obtained and stated related to definite forms mineralised by loganite, serpentine, pyroxene, dolomite, and calcite. But before publishing these facts in detail, extensive series of sections of all the Laurentian limestones, and of those of the altered Quebec group of the Green Mountain range, were made, under the direction of Sir W. E. Logan and Dr. Hunt, and examined microscopically. Specimens were also decalcified by acids, and subjected to chemical examination by Dr. Sterry Hunt. The result was the conviction that the definite laminated forms must be organic, and further, that there exist in the Laurentian limestones fragments of such forms retaining their structure, and also other fragments, probably organic, but distinct from Eozoon. These conclusions were submitted to the Geological Society of London, in 1864, after the specimens on which they were based had been shown to Dr. Carpenter and Professor T. R. Jones, the former of whom detected in some of the specimens an additional foraminiferal structure—that of the tubulation of the proper wall, which I had not been able to make out. Subsequently, in rocks at Tudor, of somewhat later age than those of the Lower Laurentian at Grenville, similar structures were found in limestones not more metamorphic than many of those which retain fossils in the Silurian system. I make this historical statement in order to place the question in its true light, and to show that it relates to the organic origin of certain definite mineral masses, exhibiting, not only the external forms of fossils, but also their internal structure.

In opposition to these facts, and to the careful deductions drawn from them, the authors of the paper under consideration maintain that the structures are mineral and crystalline. I believe that in the present state of science such an attempt to return to the doctrine of “plastic-force” as a mode of accounting for fossils would not be tolerated for a moment, were it not for the great antiquity and highly crystalline condition of the rocks in which the structures are found, which naturally create a prejudice against the idea of their being fossiliferous. That the authors themselves feel this is apparent from the slight manner in which they state the leading facts above given, and from their evident anxiety to restrict the question to the mode of occurrence of serpentine in limestone, and to ignore the specimens of Eozoon preserved under different mineral conditions.

2. With reference to the general form of Eozoon and its structure on the large scale, I would call attention to two admissions of the authors of the paper, which appear to me to be fatal to their case:—First, they admit, at page 533 [Proceedings, vol. x.], their “inability to explain satisfactorily” the alternating layers of carbonate of lime and other minerals in the typical specimens of Canadian Eozoon. They make a feeble attempt to establish an analogy between this and certain concentric concretionary layers; but the cases are clearly not parallel, and the laminÆ of the Canadian Eozoon present connecting plates and columns not explicable on any concretionary hypothesis. If, however, they are unable to explain the lamellar structure alone, as it appeared to Logan in 1859, is it not rash to attempt to explain it away now, when certain minute internal structures, corresponding to what might have been expected on the hypothesis of its organic origin, are added to it? If I affirm that a certain mass is the trunk of a fossil tree, and another asserts that it is a concretion, but professes to be unable to account for its form and its rings of growth, surely his case becomes very weak after I have made a slice of it, and have shown that it retains the structure of wood.

Next, they appear to admit that if specimens occur wholly composed of carbonate of lime, their theory will fall to the ground. Now such specimens do exist. They treat the Tudor specimen with scepticism as probably “strings of segregated calcite.” Since the account of that specimen was published, additional fragments have been collected, so that new slices have been prepared. I have examined these with care, and am prepared to affirm that the chambers in these specimens are filled with a dark-coloured limestone not more crystalline than is usual in the Silurian rocks, and that the chamber walls are composed of carbonate of lime, with the canals filled with the same material, except where the limestone filling the chambers has penetrated into parts of the larger ones. I should add that the stratigraphical researches of Mr. Vennor, of the Canadian Survey, have rendered it probable that the beds containing these fossils, though unconformably underlying the Lower Silurian, overlie the Lower Laurentian of the locality, and are, therefore, probably Upper Laurentian, or perhaps Huronian, so that the Tudor specimens may approach in age to GÜmbel’s Eozoon Bavaricum.[AR]

Further, the authors of the paper have no right to object to our regarding the laminated specimen as “typical” Eozoon. If the question were as to typical ophite the case would be different; but the question actually is as to certain well-defined forms which we regard as fossils, and allege to have organic structure on the small scale, as well as lamination on the large scale. We profess to account for the acervuline forms by the irregular growth at the surface of the organisms, and by the breaking of them into fragments confusedly intermingled in great thicknesses of limestone, just as fragments of corals occur in PalÆozoic limestones; but we are under no obligation to accept irregular or disintegrated specimens as typical; and when objectors reason from these fragments, we have a right to point to the more perfect examples. It would be easy to explain the loose cells of Tetradium which characterize the bird’s-eye limestone of the Lower Silurian of America, as crystalline structures; but a comparison with the unbroken masses of the same coral, shows their true nature. I have for some time made the minute structure of PalÆozoic limestones a special study, and have described some of them from the Silurian formations of Canada.[AS] I possess now many additional examples, showing fragments of various kinds of fossils preserved in these limestones, and recognisable only by the infiltration of their pores with different silicious minerals. It can also be shown that in many cases the crystallization of the carbonate of lime, both of the fossils themselves and of their matrix, has not interfered with the perfection of the most minute of these structures.

The fact that the chambers are usually filled with silicates is strangely regarded by the authors as an argument against the organic nature of Eozoon. One would think that the extreme frequency of silicious fillings of the cavities of fossils, and even of silicious replacement of their tissues, should have prevented the use of such an argument, without taking into account the opposite conclusions to be drawn from the various kinds of silicates found in the specimens, and from the modern filling of Foraminifera by hydrous silicates, as shown by Ehrenberg, Mantell, Carpenter, Bailey, and Pourtales.[AT] Further, I have elsewhere shown that the loganite is proved by its texture to have been a fragmental substance, or at least filled with loose debris; that the Tudor specimens have the cavities filled with a sedimentary limestone, and that several fragmental specimens from Madoc are actually wholly calcareous. It is to be observed, however, that the wholly calcareous specimens present great difficulties to an observer; and I have no doubt that they are usually overlooked by collectors in consequence of their not being developed by weathering, or showing any obvious structure in fresh fractures.

3. With regard to the canal system, the authors persist in confusing the casts of it which occur in serpentine with “metaxite” concretions, and in likening them to dendritic crystallizations of silver, etc., and coralloidal forms of carbonate of lime. In answer to this, I think it quite sufficient to say that I fail to perceive the resemblance as other than very imperfectly imitative. I may add, that the case is one of the occurrence of a canal structure in forms which on other grounds appear to be organic, while the concretionary forms referred to are produced under diverse conditions, none of them similar to those of which evidence appears in the specimens of Eozoon. With the singular theory of pseudomorphism, by means of which the authors now supplement their previous objections, I leave Dr. Hunt to deal.

4. With respect to the proper wall and its minute tubulation, the essential error of the authors consists in confounding it with fibrous and acicular crystals, and in maintaining that because the tubuli are sometimes apparently confused and confluent they must be inorganic. With regard to the first of these positions, I may repeat what I have stated in former papers—that the true cell-wall presents minute cylindrical processes traversing carbonate of lime, and usually nearly parallel to each other, and often slightly bulbose at the extremity. Fibrous serpentine, on the other hand, appears as angular crystals, closely packed together, while the numerous spicular crystals of silicious minerals which often appear in metamorphic limestones, and may be developed by decalcification, appear as sharp angular needles usually radiating from centres or irregularly disposed. Their own plate (Ophite from Skye, King and Rowney’s Paper, Proc. R. I. A., vol. x.), is an eminent example of this; and whatever the nature of the crystals represented, they have no appearance of being true tubuli of Eozoon. I have very often shown microscopists and geologists the cell-wall along with veins of chrysotile and coatings of acicular crystals occurring in the same or similar limestones, and they have never failed at once to recognise the difference, especially under high powers.

I do not deny that the tubulation is often imperfectly preserved, and that in such cases the casts of the tubuli may appear to be glued together by concretions of mineral matter, or to be broken or imperfect. But this occurs in all fossils, and is familiar to any microscopist examining them. How difficult is it in many cases to detect the minute structure of Nummulites and other fossil Foraminifera? How often does a specimen of fossil wood present in one part distorted and confused fibres or mere crystals, with the remains of the wood forming phragmata between them, when in other parts it may show the most minute structures in perfect preservation? But who would use the disintegrated portions to invalidate the evidence of the parts better preserved? Yet this is precisely the argument of Professors King and Rowney, and which they have not hesitated in using in the case of a fossil so old as Eozoon, and so often compressed, crushed, and partly destroyed by mineralization.

I have in the above remarks confined myself to what I regard as absolutely essential by way of explanation and defence of the organic nature of Eozoon. It would be unprofitable to enter into the multitude of subordinate points raised by the authors, and their theory of mineral pseudomorphism is discussed by my friend Dr. Hunt; but I must say here that this theory ought, in my opinion, to afford to any chemist a strong presumption against the validity of their objections, especially since it confessedly does not account for all the facts, while requiring a most complicated series of unproved and improbable suppositions.

The only other new features in the communication to which this note refers are contained in the “supplementary note.” The first of these relates to the grains of coccolite in the limestone of Aker, in Sweden. Whether or not these are organic, they are apparently different from Eozoon Canadense. They, no doubt, resemble the grains referred to by GÜmbel as possibly organic, and also similar granular objects with projections which, in a previous paper, I have described from Laurentian limestones in Canada. These objects are of doubtful nature; but if organic, they are distinct from Eozoon. The second relates to the supposed crystals of malacolite from the same place. Admitting the interpretation given of these to be correct, they are no more related to Eozoon than are the curious vermicular crystals of a micaceous mineral which I have noticed in the Canadian limestones.

The third and still more remarkable case is that of a spinel from Amity, New York, containing calcite in its crevices, including a perfect canal system preserved in malacolite. With reference to this, as spinels of large size occur in veins in the Laurentian rocks, I am not prepared to say that it is absolutely impossible that fragments of limestone containing Eozoon may not be occasionally associated with them in their matrix. I confess, however, that until I can examine such specimens, which I have not yet met with, I cannot, after my experience of the tendencies of Messrs. Rowney and King to confound other forms with those of Eozoon, accept their determinations in a matter so critical and in a case so unlikely.[AU]

If all specimens of Eozoon were of the acervuline character, the comparison of the chamber-casts with concretionary granules might have some plausibility. But it is to be observed that the laminated arrangement is the typical one; and the study of the larger specimens, cut under the direction of Sir W. E. Logan, shows that these laminated forms must have grown on certain strata-planes before the deposition of the overlying beds, and that the beds are, in part, composed of the broken fragments of similar laminated structures. Further, much of the apparently acervuline Eozoon rock is composed of such broken fragments, the interstices between which should not be confounded with the chambers: while the fact that the serpentine fills such interstices as well as the chambers shows that its arrangement is not concretionary. Again, these chambers are filled in different specimens with serpentine, pyroxene, loganite, calcareous spar, chondrodite, or even with arenaceous limestone. It is also to be observed that the examination of a number of limestones, other than Canadian, by Messrs. King and Rowney, has obliged them to admit that the laminated forms in combination with the canal-system are “essentially Canadian,” and that the only instances of structures clearly resembling the Canadian specimens are afforded by limestones Laurentian in age, and in some of which (as, for instance, in those of Bavaria and Scandinavia) Carpenter and GÜmbel have actually found the structure of Eozoon. The other serpentine-limestones examined (for example, that of Skye) are admitted to fail in essential points of structure; and the only serpentine believed to be of eruptive origin examined by them is confessedly destitute of all semblance of Eozoon. Similar results have been attained by the more careful researches of Prof. GÜmbel, whose paper is well deserving of study by all who have any doubts on this subject.

"In the Proceedings of the Royal Irish Academy, for July 12, 1869, Messrs. King and Rowney have given us at length their latest corrected views on various questions connected with Eozoon Canadense. Leaving to my friend, Dr. Dawson, the discussion of the zoological aspects of the question, I cannot forbear making a few criticisms on the chemical and mineralogical views of the authors. The problem which they had before them was to explain the occurrence of certain forms which, to skilled observers, like Carpenter, Dawson, and Rupert Jones, appear to possess all the structural character of the calcareous skeleton of a foraminiferal organism, and moreover to show how it happens that these forms of crystalline carbonate of lime are associated with serpentine in such a way as to lead these observers to conclude that this hydrous silicate of magnesia filled and enveloped the calcareous skeleton, replacing the perishable sarcode. The hypothesis now put forward by Messrs. King and Rowney to explain the appearances in question, is, that all this curiously arranged serpentine, which appears to be a cast of the interior of a complex foraminiferal organism, has been shaped or sculptured out of plates, prisms, and other solids of serpentine, by “the erosion and incomplete waste of the latter, the definite shapes being residual portions of the solid that have not completely disappeared.” The calcite which limits these definite shapes, or, in other words, what is regarded as the calcareous skeleton of Eozoon, is a ‘replacement pseudomorph’ of calcite taking the place of the wasted and eroded serpentine. It was not a calcareous fossil, filled and surrounded by the serpentine, but was formed in the midst of the serpentine itself, by a mysterious agency which dissolved away this mineral to form a mould, in which the calcite was cast. This marvellous process can only be paralleled by the operations of that plastic force in virtue of which sea-shells were supposed by some old naturalists to be generated in the midst of rocky strata. Such equivocally formed fossils, whether oysters or Foraminifers, may well be termed pseudomorphs, but we are at a loss to see with what propriety the authors of this singular hypothesis invoke the doctrines of mineral pseudomorphism, as taught by Rose, Blum, Bischof, and Dana. In replacement pseudomorphs, as understood by these authors, a mineral species disappears and is replaced by another which retains the external form of the first. Could it be shown that the calcite of the cell-wall of Eozoon was once serpentine, this portion of carbonate of lime would be a replacement pseudomorph after serpentine; but why the portions of this mineral, which on the hypothesis of Messrs. King and Rowney have been thus replaced, should assume the forms of a foraminiferal skeleton, is precisely what our authors fail to show, and, as all must see, is the gist of the whole matter.

"Messrs. King and Rowney, it will be observed, assume the existence of calcite as a replacement pseudomorph after serpentine, but give no evidence of the possibility of such pseudomorphs. Both Rose and Bischof regard serpentine itself as in all cases, of pseudomorphous origin, and as the last result of the changes of a number of mineral species, but give us no example of the pseudomorphous alteration of serpentine itself. It is, according to Bischof, the very insolubility and unalterability of serpentine which cause it to appear as the final result of the change of so many mineral species. Delesse, moreover, in his carefully prepared table of pseudomorphous minerals, in which he has resumed the results of his own and all preceding observers, does not admit the pseudomorphic replacement of serpentine by calcite, nor indeed by any other species.[AV] If, then, such pseudomorphs exist, it appears to be a fact hitherto unobserved, and our authors should at least have given us some evidence of this remarkable case of pseudomorphism by which they seek to support their singular hypothesis.

"I hasten to say, however, that I reject with Scheerer, Delesse and Naumann, a great part of the supposed cases of mineral pseudomorphism, and do not even admit the pseudomorphous origin of serpentine itself, but believe that this, with many other related silicates, has been formed by direct chemical precipitation. This view, which our authors do me the honour to criticise, was set forth by me in 1860 and 1861,[AW] and will be found noticed more in detail in the Geological Report of Canada, for 1866, p. 229. I have there and elsewhere maintained that ‘steatite, serpentine, pyroxene, hornblende, and in many cases garnet, epidote, and other silicated minerals, are formed by a crystallization and molecular re-arrangement of silicates, generated by chemical processes in waters at the earth’s surface.’[AX]

"This view, which at once explains the origin of all these bedded rocks, and the fact that their constituent mineral species, like silica and carbonate of lime, replace the perishable matter of organic forms, is designated by Messrs. King and Rowney ‘as so completely destitute of the characters of a scientific hypothesis as to be wholly unworthy of consideration,’ and they speak of my attempt to maintain this hypothesis as ‘a total collapse.’ How far this statement is from the truth my readers shall judge. My views as to the origin of serpentine and other silicated minerals were set forth by me as above in 1860-1864, before anything was known of the mineralogy of Eozoon, and were forced upon me by my studies of the older crystalline schists of North America. Naumann had already pointed out the necessity of some such hypothesis when he protested against the extravagances of the pseudomorphist school, and maintained that the beds of various silicates found in the crystalline schists are original deposits, and not formed by an epigenic process (Geognosie, ii., 65, 154, and Bull. Soc. Geol. de France, 2, xviii., 678). This conclusion of Naumann’s I have attempted to explain and support by numerous facts and observations, which have led me to the hypothesis in question. GÜmbel, who accepts Naumann’s view, sustains my hypothesis of the origin of these rocks in a most emphatic manner,[AY] and Credner, in discussing the genesis of the Eozoic rocks, has most ably defended it.[AZ] So much for my theoretical views so contemptuously denounced by Messrs. King and Rowney, which are nevertheless unhesitatingly adopted by the two geologists of the time who have made the most special studies of the rocks in question,—GÜmbel in Germany, and Credner in North America.

“It would be a thankless task to follow Messrs. King and Rowney through their long paper, which abounds in statements as unsound as those I have just exposed, but I cannot conclude without calling attention to one misconception of theirs as to my view of the origin of limestones. They quote Professor Hull’s remark to the effect that the researches of the Canadian geologists and others have shown that the oldest known limestones of the world owe their origin to Eozoon, and remark that the existence of great limestone beds in the Eozoic rocks seems to have influenced Lyell, Ramsay, and others in admitting the received view of Eozoon. Were there no other conceivable source of limestones than Eozoon or similar calcareous skeletons, one might suppose that the presence of such rocks in the Laurentian system could have thus influenced these distinguished geologists, but there are found beneath the Eozoon horizon two great formations of limestone in which this fossil has never been detected. When found, indeed, it owes its conservation in a readily recognisable form to the fact, that it was preserved by the introduction of serpentine at the time of its growth. Above the unbroken Eozoon reefs are limestones made up apparently of the debris of Eozoon thus preserved by serpentine, and there is no doubt that this calcareous rhizopod, growing in water where serpentine was not in process of formation, might, and probably did, build up pure limestone beds like those formed in later times from the ruins of corals and crinoids. Nor is there anything inconsistent in this with the assertion which Messrs. King and Rowney quote from me, viz., that the popular notion that all limestone formations owe their origin to organic life is based upon a fallacy. The idea that marine organisms originate the carbonate of lime of their skeletons, in a manner somewhat similar to that in which plants generate the organic matter of theirs, appears to be commonly held among certain geologists. It cannot, however, be too often repeated that animals only appropriate the carbonate of lime which is furnished them by chemical reaction. Were there no animals present to make use of it, the carbonate of lime would accumulate in natural waters till these became saturated, and would then be deposited in an insoluble form; and although thousands of feet of limestone have been formed from the calcareous skeletons of marine animals, it is not less true that great beds of ancient marble, like many modern travertines and tufas, have been deposited without the intervention of life, and even in waters from which living organisms were probably absent. To illustrate this with the parallel case of silicious deposits, there are great beds made up of silicious shields of diatoms. These during their lifetime extracted from the waters the dissolved silica, which, but for their intervention, might have accumulated till it was at length deposited in the form of schist or of crystalline quartz. In either case the function of the coral, the rhizopod, or the diatom is limited to assimilating the carbonate of lime or the silica from its solution, and the organised form thus given to these substances is purely accidental. It is characteristic of our authors, that, rather than admit the limestone beds of the Eozoon rocks to have been formed like beds of coralline limestone, or deposited as chemical precipitates like travertine, they prefer, as they assure us, to regard them as the results of that hitherto unheard-of process, the pseudomorphism of serpentine; as if the deposition of the carbonate of lime in the place of dissolved serpentine were a simpler process than its direct deposition in one or the other of the ways which all the world understands!”

"That I have not troubled myself to reply to the reiterated arguments in favour of the doctrine [of mineral origin] advanced by Professors King and Rowney on the strength of the occurrence of undoubted results of mineralization in the Canadian Ophite, and of still more marked evidences of the same action in other Ophites, has been simply because these arguments appeared to me, as I thought they must also appear to others, entirely destitute of logical force. Every scientific palÆontologist I have ever been acquainted with has taken the best preserved specimens, not the worst, as the basis of his reconstructions; and if he should meet with distinct evidence of characteristic organic structure in even a very small fragment of a doubtful form, he would consider the organic origin of that form to be thereby substantiated, whatever might be the evidence of purely mineral arrangement which the greater part of his specimen may present,—since he would regard that arrangement as a probable result of subsequent mineralization, by which the original organic structure has been more or less obscured. If this is not to be our rule of interpretation, a large part of the palÆontological work of our time must be thrown aside as worthless. If, for example, Professors King and Rowney were to begin their study of Nummulites by the examination of their most mineralized forms, they would deem themselves justified (according to their canons of interpretation) in denying the existence of the tubulation and canalization which I described (in 1849) in the N. lÆvigata preserved almost unaltered in the London Clay of Bracklesham Bay.

"My own notions of Eozoic structure have been formed on the examination of the Canadian specimens selected by the experienced discrimination of Sir William Logan, as those in which there was least appearance of metamorphism; and having found in these what I regarded as unmistakable evidence of an organic structure conformable to the foraminiferal type, I cannot regard it as any disproof of that conformity, either to show that the true Eozoic structure has been frequently altered by mineral metamorphism, or to adduce the occurrence of Ophites more or less resembling the Eozoon of the Canadian Laurentians at various subsequent geological epochs. The existence of any number or variety of purely mineral Ophites would not disprove the organic origin of the Canadian Eozoon—unless it could be shown that some wonderful process of mineralization is competent to construct not only its multiplied alternating lamellÆ of calcite and serpentine, the dendritic extensions of the latter into the former, and the ‘acicular layer’ of decalcified specimens, but (1) the pre-existing canalization of the calcareous lamellÆ, (2) the unfilled nummuline tubulation of the proper wall of the chambers, and (3) the peculiar calcarine relation of the canalization and tubulation, here described and figured from specimens in the highest state of preservation, showing the least evidence of any mineral change.

"On the other hand, Professors King and Rowney began their studies of Eozoic structure upon the Galway Ophite—a rock which Sir Roderick Murchison described to me at the time as having been so much ‘tumbled about,’ that he was not at all sure of its geological position, and which exhibits such obvious evidences of mineralization, with such an entire absence of any vestige of organic structure, that I should never for a moment have thought of crediting it with an organic origin, but for the general resemblance of its serpentine-grains to those of the ‘acervuline’ portion of the Canadian Eozoon. They pronounced with the most positive certainty upon the mineral origin of the Canadian Eozoon, before they had subjected transparent sections of it to any of that careful comparison with similar sections of recent Foraminifera, which had been the basis of Dr. Dawson’s original determination, and of my own subsequent confirmation, of its organic structure.