serpentine and with the silicious grains included in the loganite.
Fig. 53 shows such bodies found mixed with fragmental Eozoon and in
separate thin layers at Côte St. Pierre. In Fig. 51, I have shown
some of the singular grains found in the loganite occupying the
chambers of Eozoon from Burgess, and in Fig. 54 some remarkable forms
of this kind found in the limestones of Long Lake and Wentworth. All
these, I think, are essentially of the same nature, namely, chambers
originally invested with a tubulated wall like Eozoon, and aggregated
in groups, sometimes in a linear manner, sometimes spirally, like those
Globigerinæ which constitute the mass of modern deep-sea dredgings and
also of the chalk.
[Illustration: Fig. 54.--_Archæospherinæ from Long Lake Limestone._]
(Magnified.)
(_a_) Single cell, showing tubulated wall. (_b, c_) Portions of same
more highly magnified, (_d_) Casts decalcified, and showing casts of
tubules.
These bodies occur dispersed in the limestone, arranged in thin layers
parallel to the bedding or sometimes in the large chamber-cavities of
Eozoon. They are so variable in size and form that it is not unlikely
they may be of different origins. The most probable of these may be
thus stated. First, they may in some cases be the looser superficial
parts of the surface of Eozoon broken up into little groups of cells.
Secondly, they may be few-celled germs or buds given off from Eozoon.
This would correspond with what Carpenter, and more recently Brady and
Lester, have observed in the case of some of the larger of the modern
Foraminifera. Thirdly, they may be smaller Foraminifera, structurally
allied to Eozoon, but in habit of growth resembling those little
globe-shaped forms which, as already stated, abound in chalk and in the
modern ocean. The latter view I should regard as highly probable in the
case of many of them; and I have proposed for them, in consequence, and
as a convenient name, _Archæospherinæ_ or ancient spherical animals.
Carbonaceous matter is rare in the true Eozoon limestones, and, as
already stated, I would refer the Laurentian graphite or plumbago
mainly to plants.
Dr. Gümbel, the Director of the Geological Survey of Bavaria, is one of
the most active and widely informed of European geologists, combining
European knowledge with an extensive acquaintance with the larger and
in some respects more typical areas of the older rocks in America, and
stratigraphical geology with enthusiastic interest in the microscopic
structures of fossils. He at once, and in a most able manner, took up
the question of the application of the discoveries in Canada to the
rocks of Bavaria. The spirit in which he did so may be inferred from
the following extract:--
"The discovery of organic remains in the crystalline limestones of the
ancient gneiss of Canada, for which we are indebted to the researches
of Sir William Logan and his colleagues, and to the careful microscopic
investigations of Drs. Dawson and Carpenter, must be regarded as
opening a new era in geological science.
"This discovery overturns at once the notions hitherto commonly
entertained with regard to the origin of the stratified primary
limestones, and their accompanying gneissic and quartzose strata,
included under the general name of primitive crystalline schists. It
shows us that these crystalline stratified rocks, of the so-called
primary system, are only a backward prolongation of the chain of
fossiliferous strata; the elements of which were deposited as oceanic
sediment, like the clay-slates, limestones, and sandstones of the
Palæozoic formations, and under similar conditions, though at a time
far more remote, and more favourable to the generation of crystalline
mineral compounds.
"In this discovery of organic remains in the primary rocks, we hail
with joy the dawn of a new epoch in the critical history of these
earlier formations. Already in its light, the primeval geological time
is seen to be everywhere animated, and peopled with new animal forms
of whose very existence we had previously no suspicion. Life, which
had hitherto been supposed to have first appeared in the Primordial
division of the Silurian period, is now seen to be immeasurably
lengthened beyond its former limit, and to embrace in its domain the
most ancient known portions of the earth's crust. It would almost
seem as if organic life had been awakened simultaneously with the
solidification of the earth's crust."
Gümbel has described from limestones of Laurentian age in various parts
of Europe forms referable to Eozoon or to Archæospherinæ, and I have
found fragmental Eozoon in specimens collected by Favre in the supposed
Archæan nucleus of the Alps.
Gümbel also found in the Finnish and Bavarian limestones knotted
chambers, like those of Wentworth above mentioned (Fig. 55), which he
regards as belonging to some other organism than Eozoon; and flocculi
having tubes, pores, and reticulations which would seem to point to the
presence of structures akin to sponges or possibly remains of seaweeds.
These observations Gümbel has extended into other localities in Bavaria
and Bohemia, and also in Silesia and Sweden, establishing the existence
of Eozoon fossils in all the Laurentian limestones of the middle and
north of Europe.
[Illustration: Fig. 55.--_Archæospherinæ from Pargas in Finland._
(After Gümbel.)
(Magnified.)]
Gümbel has further found in beds overlying the older Eozoic series,
and probably of the same age with the Canadian Huronian, a different
species of Eozoon, with smaller and more contracted chambers, and
still finer and more crowded canals. This, which is to be regarded as
a distinct species, or at least a well-marked varietal form, he has
named _Eozoon Bavaricum_ (Fig. 56). Thus this early introduction of
life is not peculiar to that old continent which we sometimes call the
New World, but applies to Europe as well, and Europe has furnished a
successor to Eozoon in the later Eozoic or Huronian period.
[Illustration: Fig. 56.--_Section of Eozoon Bavaricum, with Serpentine,
from the Crystalline Limestone of the Hercynian primitive Clay-slate
Formation at Hohenberg; 25 diameters (probably Huronian)._
(_a_) Sparry carbonate of lime, (_b_) Cellular carbonate of lime, (_c_)
System of tubuli. (_d_) Serpentine replacing the coarser ordinary
variety, (_e_) Serpentine and hornblende replacing the finer variety,
in the very much contorted portions.]
In rocks of this age in America, after long search and much slicing of
limestones, I have hitherto failed to find any decided foraminiferal
remains other than the Tudor and Madoc specimens, which may be of this
age. They are laminated forms resembling Eozoon, but I have reason to
believe that their minute structure more closely resembles that of
Cryptozoon, though it is somewhat obscure. If these are really Huronian
and not Laurentian, the Eozoon from this horizon does not sensibly
differ from that of the Lower Laurentian.
We are indebted to Mr. Matthew, of St. John, New Brunswick, who has so
greatly distinguished himself by his discoveries in the Cambrian of
that region, for some remarkable additions to the contemporaries of
Eozoon. One of these is a laminated body, like Eozoon in its general
appearance, but growing in crowded masses which by mutual pressure
become columnar (Fig. 57). In the best preserved specimens each layer
seems to consist of a thin lamina separated from its neighbours by
a finely granular mass, traversed by innumerable irregular tubes.
This recalls the structure of Cryptozoon of Hall, which, as we have
seen, is found in pre-Cambrian rocks in Colorado, and abounds in the
Upper Cambrian in New York, in Minnesota, and in different parts of
Canada, but Archæozoon differs in its form and habit of growth. If
the Stromatoporæ of the Ordovician and Silurian are hydroids, this
may also be the case with Cryptozoon; but so far as its own structure
is concerned, it approaches most nearly to the fossils known as
Loftusia in the Carboniferous and later formations, and these are
generally regarded as Foraminiferal. We may thus have another giant
Foraminiferal organism which contributed to the building up of rocks in
the Laurentian seas.
[Illustration: Fig. 57.--_Archæozoon Acadiense_, Matthew. _Diagrammatic
transverse and longitudinal sections of a small specimen._
Specimen in Peter Redpath Museum.]
_Pre-Palæozoic Rocks of Southern New Brunswick, as tabulated by
Matthew:--"_
+--+--+------------------------------------------------------------+
| | | Thickness |
| | | Feet. |
| | | Coastal series (or system), 1872.-- |
| | | Grits, hydromicaschists, agillities, etc. |
| | | resembling the Pebidian rocks of Dr. H. |
| | | Hicks 10,000 |
| | | |
| |E | Coldbrook Series (or System), 1865.-- |
| |O | Diorites, felsites, petrosilex, etc.; |
| |Z | resembling the Arvonian rocks of Dr. |
| |O | Hicks. Thickness more than 15,000 |
| |I | |
| |C | Upper series (or system) of Laurentian, 1872. |
|A | | Upper division.--Argillites, |
|R | | limestones, graphitic shales. Fossils. In |
|C | | upper part of the upper limestones of the |
|H | | South basin, fragmental _Eozoon_, observed |
|Æ | | by Sir J. W. Dawson in specimens sent him. In |
|A | | middle of upper limestones in Middle basin, |
|N | | spicules of sponges. In graphitic shale |
| | | of South basin, spicules of _Halichondrites |
| | | graphitiferus_. In lowest limestone of |
| | | the Middle basin, the reef of columnar |
| | | fossils described as Archæozoon 740 |
| | | Middle division.--Quartzites, |
| | | silicious schists, Fossils _Cyathospongia (?) |
| | | eozoica_ near the top of this division 450 |
| | | Lower division.--Limestones and |
| |__| gneisses. No Fossils known 260[41]|
| | | Lower series of Laurentian.-- |
| | | Gneisses, Micaschists, etc ? |
+--+--+------------------------------------------------------------+
[Footnote 41: The above thicknesses are on the authority of Dr. L.
W. Bailey. _Report Progress Geological Survey Canada_, 1879, pp. 10,
D. D., and 21, D. D. Dr. R. W. Ells in the same Report, p. 6, D.,
describes these rocks, sixty miles east of St. John, as one system,
with a thickness of 14,000 feet.]
[Illustration: Fig. 57A.--_Archæozoon Acadiense_, Matthew.
_Horizontal and vertical sections of a group of specimens, reduced._
(From Photographs.)]
This discovery is also of importance as connecting Eozoon through
Cryptozoon with large organisms, probably Protozoa, extending upward to
the top of the Cambrian, and thus forming a link of connection between
the life of the Eozoic and that of the Palæozoic period. Matthew has
also described forms which he regards as spicules of sponges from
the Laurentian of New Brunswick.[42] One of these seems to present
cruciform needles forming square areas, like the Protospongia of
Salter, from the Cambrian. The other has simple elongate needle-like
spicules arranged in bundles. Matthew summarizes the rocks containing
these fossils as in the table on p, 216, in descending order, the
highest bed being below the Etcheminian.[43] The first and second
groups, it will be observed, are equivalent to the Huronian; the third
corresponds to the Grenvillian, and the fourth to the Lower Laurentian.
[Footnote 42: Fuller descriptions of these rocks may be found in _Rep.
Prog. Geol. Surv. of Canada_, 1872, pp. 30, 34, etc.]
[Footnote 43: _Bulletin Nat. Hist. Society of New Brunswick_, 1890
where further details are given as to the fossils.]
_DIFFICULTIES AND OBJECTIONS_
IX
_DIFFICULTIES AND OBJECTIONS_
The active objectors to the animal nature of Eozoon have been few,
though some of them have returned to the attack with a pertinacity and
determination which would lead one to believe that they think the most
sacred interests of science to be dependent on the annihilation of this
proto-foraminifer. I do not propose here to treat of the objections in
detail. I have presented the case of Eozoon on its own merits, and on
these it must stand. I may merely state that the objectors strive to
account for the existence of Eozoon by purely mineral deposition, and
that the complicated changes which they require to suppose are perhaps
the strongest indirect evidence for the necessity of regarding the
structures as organic. The reader who desires to appreciate this may
consult my memoir of 1888.[44]
[Footnote 44: Also Rowney and King's papers in _Journal Geological
Society_, August, 1866; and _Proceedings Irish Academy_, 1870 and
1871.]
I confess that I feel disposed to treat very tenderly the position
of objectors. The facts I have stated make large demands on the
faith of the greater part even of naturalists. Very few geologists
or naturalists have much knowledge of the structure of foraminiferal
shells, or would be able under the microscope to recognise them with
certainty. Nor have they any distinct ideas of the appearances of such
structures under different kinds of preservation and mineralization.
Further, they have long been accustomed to regard the so-called Azoic
or Archæan rocks as not only destitute of organic remains, but as
being in such a state of metamorphism that these could not have been
preserved had they existed. Few, therefore, are able intelligently
to decide for themselves, and so they are called on to trust to the
investigations of others, and on their testimony to modify in a marked
degree their previous beliefs as to the duration of life on our planet.
In these circumstances it is rather wonderful that the researches made
with reference to Eozoon have met with so general acceptance, and
that the resurrection of this ancient inhabitant of the earth has not
aroused more of the sceptical tendency of our age.
It must not be lost sight of, however, that in such cases there may
exist a large amount of undeveloped and even unconscious scepticism,
which shows itself not in active opposition, but merely in quietly
ignoring this great discovery, or regarding it with doubt, as an
uncertain or unestablished point in science. Such scepticism is
especially to be expected on the part of the many enthusiastic students
of petrography who are accustomed to regard rocks merely as mineral
aggregates, and even to have their slices prepared in a manner which
scarcely permits organic remains of present to be distinguished.
Such students should consider that the discovery of Eozoon brings
the rocks of the Laurentian system into more full harmony with the
other geological formations. It explains the origin of the Laurentian
limestones in consistency with that of similar rocks in the later
periods, and in like manner it helps us to account for the graphite
and sulphides and iron ores of these old rocks. It shows us that no
time was lost in the introduction of life on the earth. Otherwise there
would have been a vast lapse of time in which, while the conditions
suitable to life were probably present, no living thing existed to
take advantage of these conditions. Further, it gives a more simple
beginning of life than that afforded by the more complex fauna of the
Cambrian age; and this is more in accordance with what we know of the
slow and gradual introduction of new forms of living things during the
vast periods of Palæozoic time. In connection with this, it opens a
new and promising field of observation in the older rocks; and if this
should prove fertile, its exploration may afford a vast harvest of new
forms to the geologists of the present and coming time. This result
will be in entire accordance with what has taken place before in the
history of geological discovery. I can myself remember a time when the
old and semi-metamorphic sediments constituting the great Cambrian
system were massed together in geological classifications as primitive
or primary rocks, destitute or nearly destitute of organic remains.
The brilliant discoveries of Sedgwick, Murchison, Barrande, and a
host of others, have peopled these once barren regions; and they now
stretch before our wondering gaze in the long vistas of early Palæozoic
life. So we now look out from the Cambrian shore upon the ocean of the
Etcheminian, the Huronian, and the Laurentian--all to us yet almost
tenantless, except for the few organisms which, like stray shells cast
upon the beach, or a far-off land dimly seen in the distance, incite
to further researches, and to the exploration of the unknown treasures
that still lie undiscovered. It would be a suitable culmination of
the geological work of the last half-century, and one within reach at
least of our immediate successors, to fill up this great blank, and to
trace back the Primordial life to the stage of Eozoon, and perhaps even
beyond this, to predecessors which may have existed at the beginning
of the Laurentian, when the earliest sediments of that great formation
were laid down. Vast unexplored areas of Laurentian and Huronian rocks
exist in the Old World and the New. The most ample facilities for
microscopic examination of rocks may now be obtained; and I could wish
that one result of the publication of these pages may be to direct the
attention of some of the younger and more active geologists to these
fields of investigation. It is to be observed also that such regions
are among the richest in useful minerals, and there is no reason why
search for these fossils should not be connected with other and more
practically useful researches. On this subject it will not be out of
place to quote the remarks which I made in one of my earlier papers on
the Laurentian fossils:--
"This subject opens up several interesting fields of chemical,
biological, and geological inquiry. One of these relates to the
conclusions stated by Dr. Hunt as to the probable existence of a
large amount of carbonic acid in the Laurentian atmosphere, and of
much carbonate of lime in the seas of that period, and the possible
relation of this to the abundance of certain low forms of plants and
animals. Another is the comparison already instituted by Professor
Huxley and Dr. Carpenter, between the conditions of the Laurentian and
those of the deeper parts of the modern ocean. Another is the possible
occurrence of other forms of animal life than Protozoa, which I have
stated in my paper of 1864, after extensive microscopic study of the
Laurentian limestones, to be indicated by the occurrence of calcareous
fragments, differing in structure from Eozoon, but at present of
unknown nature. Another is the effort to bridge over, by further
discoveries [similar to those of Cryptozoon and Archæozoon], the gap
now existing between the life of the Lower Laurentian and that of the
Cambrian period. It is scarcely too much to say that these inquiries
open up a new world of thought and investigation, and hold out the
hope of bringing us into the presence of the actual origin of organic
life on our planet, though this may perhaps be found to have been
pre-Laurentian. I would here take the opportunity of repeating that,
in proposing the name Eozoon for the first fossil of the Laurentian,
and in suggesting for the period the name 'Eozoic,' I have by no means
desired to exclude the possibility of forms of life which may have been
precursors of what is now to us the dawn of organic existence. Should
remains of still older organisms be found in those rocks now known to
us only by pebbles in the Laurentian, these names will at least serve
to mark an important stage in geological investigation."
But what if the result of such investigations should be to produce more
sceptics, or to bring to light mineral structures so resembling Eozoon
as to throw doubt upon the whole of the results detailed in these
chapters? I can fancy that this might be the first consequence, more
especially if the investigations were those of persons more conversant
with rocks and minerals than with fossils; but I see no reason to
fear the ultimate results. In any case, no doubt, the value of the
researches hitherto made may be diminished. It is always the fate of
discoverers in Natural Science, either to be followed by opponents who
temporarily or permanently impugn or destroy the value of their new
facts, or by other investigators who push on the knowledge of facts and
principles so far beyond their standpoint that the original discoveries
are cast into the shade. This is a fatality incident to the progress of
scientific work, from which no man can be free; and in so far as such
matters are concerned, we must all be content to share the fate of the
old fossils whose history we investigate, and, having served our day
and generation, to give place to others. If any part of our work should
stand the fire of discussion, let us be thankful. One thing at least
is certain, that such careful surveys as those in the Laurentian rocks
of Canada which led to the discovery of Eozoon, and such microscopic
examinations as those by which it has been worked up and presented to
the public, cannot fail to yield good results of one kind or another.
Already the attention excited by the controversies about Eozoon,
by attracting investigators to the study of various microscopic and
imitative forms in rocks, has promoted the advancement of knowledge,
and must do so still more. For my own part, though I am not content to
base all my reputation on such work as I have done with respect to this
old fossil--which, indeed, was merely an interlude into which I was led
by the urgency of my friend Logan--I am willing at least to take the
responsibility of the results I have announced, whatever conclusions
may be finally reached; and in the consciousness of an honest effort
to extend the knowledge of nature, to look forward to a better fame
than any that could result from the most successful and permanent
vindication of every detail of our scientific discoveries, even if they
could be pushed to a point which no subsequent investigation in the
same difficult line of research would be able to overpass.
Contenting myself with these general remarks, I shall close this
chapter with a short summary of the reasons which may be adduced
in support of the animal nature of Eozoon, prefaced by an ideal
restoration of it in the supposition that it was a rhizopod (Fig. 58).
[Illustration: Fig. 58.--_Restoration of Eozoon as a generalized
Foraminiferal Organism (enlarged)._
Showing endosarc, exosarc, and pseudopods, and the calcareous skeleton
with its canals.]
In doing so, I shall merely sum up the evidence as it has been
presented by Sir W. E. Logan, Dr. Carpenter, Dr. Hunt, and the author,
in a short and intelligible form; and I shall do so under a few brief
heads, with some explanatory remarks:--
1. The Upper Laurentian of Canada, a rock formation whose distribution,
age, and structure have been carefully worked out in several extensive
districts by the Canadian Survey, is found to contain thick and widely
distributed beds of limestone, related to the other beds in the same
way in which limestones occur in the sediments of other geological
formations. There also occur in the same formation, graphite, iron
ores, and metallic sulphides, in such relations as to suggest the idea
that the limestones as well as these other minerals are of organic
origin.
2. In the limestones are found laminated bodies of definite form and
structure, composed of calcite alternating with serpentine and other
minerals. The forms of these bodies suggested a resemblance to the
Silurian Stromatoporæ, and the different mineral substances associated
with the calcite in the production of similar forms showed that these
were not accidental or concretionary.
3. On microscopic examination, it proved that the calcareous laminæ
of these forms were similar in structure to the shells of modern
and fossil Foraminifera, more especially those of the Rotaline and
Nummuline types, and that the finer structures, though usually filled
with serpentine and other hydrous silicates, were sometimes occupied
with calcite, pyroxene, or dolomite, showing that they must when recent
have been empty canals and tubes.
4. The mode of filling thus suggested for the chambers and tubes of
Eozoon is precisely that which takes place in modern Foraminifera
filled with glauconite, and in Palæozoic crinoids and corals filled
with other hydrous silicates, all more or less chemically allied to
serpentine.