_THE DAWN OF LIFE_
Do we know the first animal? Can we name it, explain its structure,
and state its relations to its successors? Can we do this by inference
from the succeeding types of being; and if so, do our anticipations
agree with any actual reality disinterred from the earth's crust? If we
could do this, either by inference or actual discovery, how strange it
would be to know that we had before us even the remains of the first
creature that could feel or will, and could place itself in vital
relation with the great powers of inanimate nature. If we believe in a
Creator, we shall feel it a solemn thing to have access to the first
creature into which He breathed the breath of life. If we hold that all
things have been evolved from collision of dead forces, then the first
molecules of matter which took upon themselves the responsibility of
living, and, aiming at the enjoyment of happiness, subjected themselves
to the dread alternatives of pain and mortality, must surely evoke
from us that filial reverence which we owe to the authors of our own
being; if they do not involuntarily draw forth even a superstitious
adoration. The veneration of the old Egyptian for his sacred animals
would be a comparatively reasonable idolatry, if we could imagine any
of these animals to have been the first that emerged from the domain
of dead matter, and the first link in a reproductive chain of being
that produced all the population of the world. Independently of any
such hypotheses, all students of nature must regard with surpassing
interest the first bright streaks of light that break on the long reign
of primeval night and death, and presage the busy day of teeming animal
existence.
No wonder, then, that geologists have long and earnestly groped in
the rocky archives of the earth in search of some record of this
patriarch of the animal kingdom. But after long and patient research
there still remained a large residuum of the oldest rocks destitute
of all traces of living beings, and designated by the hopeless name
"Azoic,"--the formations destitute of remains of life, the stony records
of a lifeless world. So the matter remained till the Laurentian rocks
of Canada, lying at the base of these old Azoic formations, afforded
forms believed to be of organic origin. The discovery was hailed
with enthusiasm by those who had been prepared by previous study to
receive it. It was regarded with feeble and not very intelligent faith
by many more, and was met with half-concealed or open scepticism by
others. It produced a copious crop of descriptive and controversial
literature, but for the most part technical, and confined to scientific
transactions and periodicals, read by very few except specialists.
Thus, few even of geological and biological students have clear ideas
of the real nature and mode of occurrence of these ancient organisms,
if organisms they are, and of their relations to better known forms of
life; while the crudest and most inaccurate ideas have been current in
lectures and popular books, and even in text-books.
This state of things has long ceased to be desirable in the interests
of science, since the settlement of the questions raised is in the
highest degree important to the history of life. We cannot, it is
true, affirm that Eozoon is in reality the long-sought prototype of
animal existence; but it was for us, at least until recently, the last
organic foothold, on which we can poise ourselves, that we may look
back into the abyss of the infinite past, and forward to the long
and varied progress of life in geological time. Now, however, we
have announcements to be referred to in the sequel of other organisms
discovered in the so-called Archæan rocks; and it is not improbable
that these will rapidly increase. The discussion of its claims has
also raised questions and introduced new points, certain, if properly
entered into, to be fruitful of interesting and valuable thought, and
to form a good introduction to the history of life in connection with
geology.
As we descend in depth and time into the earth's crust, after passing
through nearly all the vast series of strata constituting the monuments
of geological history, we at length reach the Eozoic or Laurentian
rocks,[47] deepest and oldest of all the formations known to the
geologist, and more thoroughly altered or metamorphosed by heat and
heated moisture than any others. These rocks, at one time known as
Azoic, being supposed destitute of all remains of living things, but
now more properly Eozoic, are those in which the first bright streaks
of the dawn of life make their appearance.
[47] Otherwise named "Archæan."
The name Laurentian, given originally to the Canadian development of
these rocks by Sir William Logan, but now applied to them throughout
the world, is derived from a range of hills lying north of the
St. Lawrence valley, which the old French geographers named the
Laurentides. In these hills the harder rocks of this old formation rise
to considerable heights, and form the highlands separating the St.
Lawrence valley from the great plain fronting on Hudson's Bay and the
Arctic Sea. At first sight it may seem strange that rocks so ancient
should anywhere appear at the surface, especially on the tops of
hills; but this is a necessary result of the mode of formation of our
continents. The most ancient sediments deposited in the sea were those
first elevated into land, and first altered and hardened. Upheaved in
the folding of the earth's crust into high and rugged ridges, they have
either remained uncovered with newer sediments, or have had such as
were deposited on them washed away; and being of a hard and resisting
nature, they have remained comparatively unworn when rocks much more
modern have been swept off by denuding agencies.[48]
[48] This implies the permanence of continents in their main features,
a doctrine the writer has maintained for thirty years, and which is
discussed elsewhere.
But the exposure of the old Laurentian skeleton of mother earth is not
confined to the Laurentide Hills, though these have given the formation
its name. The same ancient rocks appear in the Adirondack mountains
of New York, and in the patches which at lower levels protrude from
beneath the newer formations along the American coast from Newfoundland
to Maryland. The older gneisses of Norway, Sweden, and the Hebrides,
of Bavaria and Bohemia, of Egypt, Abyssinia and Arabia, belong to the
same age, and it is not unlikely that similar rocks in many other parts
of the old continent will be found to be of as great antiquity. In no
part of the world, however, are the Laurentian rocks more extensively
distributed or better known than in Canada; and to this as the grandest
and most instructive development of them we may more especially devote
our attention.
The Laurentian rocks, associated with another series only a little
younger, the Huronian, form a great belt of broken and hilly country,
extending from Labrador across the north of Canada to Lake Superior,
and thence bending northward to the Arctic Sea. Everywhere on the lower
St. Lawrence they appear as ranges of billowy rounded ridges on the
north side of the river, and as viewed from the water or the southern
shore, especially when sunset deepens their tints to blue and violet,
they present a grand and massive appearance, which, in the eye of
the geologist, who knows that they have endured the battles and the
storms of time longer than any other mountains, invests them with the
dignity which their mere elevation would fail to give. (Fig. 1.) In the
isolated mass of the Adirondacks, south of the Canadian frontier, they
rise to a still greater elevation, and form an imposing mountain group,
almost equal in height to their somewhat more modern rivals, the White
Mountains, which face them on the opposite side of Lake Champlain.
The grandeur of the old Laurentian ranges is, however, best displayed
where they have been cut across by the great transverse gorge of the
Saguenay, and where the magnificent precipices, known as Capes Trinity
and Eternity, look down from their elevation of 1,500 feet on the
fiord, which at their feet is more than 100 fathoms deep. The name
Eternity applied to such a mass is geologically scarcely a misnomer,
for it dates back to the very dawn of geological time, and is of hoar
antiquity in comparison with such upstart ranges as the Andes and the
Alps. (See Frontispiece.)
On a nearer acquaintance, the Laurentian country appears as a broken
and hilly upland and highland district, clad in its pristine state
with magnificent forests, but affording few attractions to the
agriculturist, except in the valleys, which follow the lines of its
softer beds, while it is a favourite region for the angler, the
hunter, and the lumberman. Many of the Laurentian townships of Canada
are, however, already extensively settled, and the traveller may pass
through a succession of more or less cultivated valleys, bounded by
rocks or wooded hills and crags, and diversified by running streams and
romantic lakes and ponds, constituting a country always picturesque
and often beautiful, and rearing a strong and hardy population. To
the geologist it presents in the main immensely thick beds of gneiss,
bedded diorite and quartzite, and similar crystalline rocks, contorted
in the most remarkable manner, so that if they could be flattened out
they would serve as a skin much too large for mother earth in her
present state, so much has she shrunk and wrinkled since those youthful
days when the Laurentian rocks were her outer covering.
[Illustration: Fig. 1.--Laurentian Hills opposite Kamouraska, Lower St.
Lawrence. The islands in front are Cambro-Silurian.]
[Illustration: Fig. 2.--Section from Petite Nation Seigniory to St.
Jerome (60 miles). After Sir W. E. Logan.
(_a b_) Upper Laurentian. (_c_) Fourth Gneiss. (_d´_) Third Limestone.
(_d_) Third Gneiss. (_e´_) Second Limestone. (_x_) Porphyry. (_y_)
Granite.]
I cannot describe such rocks, but their names, as given in the section,
Fig. 2, will tell something to those who have any knowledge of the
older crystalline materials of the earth's crust. To those who have
not, I would advise a visit to some cliff on the lower St. Lawrence,
or the Hebridean coasts, or the shore of Norway, where the old hard
crystalline and gnarled beds present their sharp edges to the ever
raging sea, and show their endless alternations of various kinds
and colours of strata, often diversified with veins and nests of
crystalline minerals. He who has seen and studied such a section of
Laurentian rock cannot forget it.
The elaborate stratigraphical work of Sir William Logan has proved
that these old crystalline rocks are bedded or stratified, and that
they must have been deposited in succession by some process of aqueous
action. They have, however, through geological ages of vast duration
been subjected to pressure and chemical action, which have, as stated
in a previous chapter, much modified their structure, while it is also
certain that they must have differed originally from the sands, clays
and other materials laid down in the sea in later times.
It is interesting to notice here that the Laurentian rocks thus
interpreted show that the oldest known portions of our continents were
formed in the waters. They are oceanic sediments deposited perhaps when
there was no dry land, or very little, and that little unknown to us,
except in so far as its _débris_ may have entered into the composition
of the Laurentian rocks themselves. Thus the earliest condition of the
earth known to the geologist is one in which old ocean was already
dominant on its surface; and any previous condition when the surface
was heated, and the water constituted an abyss of vapours enveloping
its surface, or any still earlier condition in which the earth was
gaseous or vaporous, is a matter of mere inference, not of actual
observation. The formless and void chaos is a deduction of chemical and
physical principles, not a fact observed by the geologist. Still we
know, from the great dykes and masses of igneous or molten rock which
traverse the Laurentian beds, that even at that early period there
were deep-seated fires beneath the crust; and it is quite possible
that volcanic agencies then manifested themselves, not only with quite
as great intensity, but also in the same manner, as at subsequent
times. It is thus not unlikely that much of the land undergoing
waste in the earlier Laurentian time was of the same nature with
recent volcanic ejections, and that it formed groups of islands in an
otherwise boundless ocean.
However this may be, the distribution and extent of these
pre-Laurentian lands is, and probably ever must be, unknown to us; for
it was only after the Laurentian rocks had been deposited, and after
the shrinkage and deformation of the earth's crust in subsequent times
had bent and contorted them, that the foundations of the continents
were laid. The rude sketch map of America given in Fig. 3 will show
this, and will also show that the old Laurentian mountains mark out the
future form of the American continent.
[Illustration: Fig. 3.--The Laurentian Nucleus of the American
Continent, after Dana.]
Some subsequent writers have, it is true, treated with disbelief
Logan's great discoveries; but no competent geologist who has traced
the regularly bedded limestones and other rocks of his original fields
of investigation could continue to doubt. On this subject I may quote
from my friend Dr. Bonney, one of the most judicious of the builders
who undertake hypothetically to lay the foundation stones of the
earth's crust for our enlightenment in these later days. In an address
delivered at the Bath meeting of the British Association he says:--
"The first deposits on the solidified crust of the earth would
obviously be igneous. As water condensed from the atmosphere on the
cooling surface, aqueous waste or condensation would begin, and
stratified deposits in the ocean would become possible in addition
to detrital volcanic material. But at that time the crust itself, and
even later stratified deposits would often be kept for a considerable
period at a high temperature. Thus, not only rocks of igneous origin
(including volcanic ashes) would predominate in the lowest foundation
stones, but also secondary changes would occur more readily, and even
the sediments or precipitates might be greatly modified. As time went
on, true sediments would predominate over volcanic materials, and these
would be less and less affected by chemical changes, and would more and
more retain their original character. Thus we should expect that as we
retraced the earth's course through 'the corridor of time' we should
arrive at rocks which, though crystalline in structure, were evidently
in great part sedimentary in origin, and should behind them find rocks
of more coarsely crystalline texture and more dubious character, which,
however, probably were in part of a like origin, and should at last
reach coarsely crystalline rocks, in which, while occasional sediments
would be possible, the majority were originally igneous, though
modified at a very early period of their history. This corresponds with
what we find in nature, when we apply, cautiously and tentatively,
the principles of interpretation which guide us in stratigraphical
geology."[49]
[49] "The Foundation Stones of the Earth's Crust," 1888. The extract is
slightly condensed.
This expresses very well the general result of the patient
stratigraphical and chemical labours of Logan and Sterry Hunt, as
applied to the vast areas of old crystalline stratified rocks in
Canada, and which I have had abundant opportunities to verify on the
ground. Under the undoubted Cambrian beds of Canada lies the Huronian,
a formation largely of hardened sands, clays and gravels, now forming
sandstones, slates, and conglomerates, but with great beds of igneous
or volcanic rock, and hardened and altered ash beds. Under this, in
the upper portion of the Laurentian, we have regularly bedded rocks,
quartzites, limestones, and quartzose, and graphitic and ferruginous
gneisses, evidently altered aqueous sediments; but intermixed with
other rocks, as diorites and hornblendic gneisses, which are plainly
of different origin. Lastly, on the bottom of all, we have nothing but
coarse crystalline gneiss, representing perhaps the earliest crust
of a cooling globe. Broadly, and without entering into details or
theoretical views as to the precise causes of formation and alteration
of these rocks, this is the structure of the Archæan or Eozoic system
in Canada; and it corresponds with that of the basement or foundation
stones of our continents in every country that I have been able to
visit, or of which I have trustworthy accounts.
In the lower or fundamental gneiss, and in the igneous beds which
succeed it, we need not look for any indications of living beings; but
so soon as the sea began to deposit sand, mud, limestone, iron ore,
carbon, there would be nothing to exclude the presence of some forms of
marine life; while, as land must have already existed, there would be a
possibility of life on it. This, therefore, we may begin to look for so
soon as we ascend to those beds of the Laurentian in which limestone,
iron ore, and quartzite appear; and it is precisely at this point in
the Laurentian of Canada that indications of life are supposed to have
been found. Certain it is that if we cannot find some sign of life in
the Laurentian or Huronian, we shall have to face as the beginnings of
life the swarms of marine creatures that appear all over the globe at
once, in the early Cambrian age.
Is it likely, then, that such rocks should afford any traces of living
beings, even if any such existed when they were formed? Geologists who
had traced organic remains back to the lowest Cambrian might hope for
such remains, even in the Laurentian; but they long looked in vain
for their actual discovery. Still, as astronomers have suspected the
existence of unknown planets from observing perturbations not accounted
for, and as voyagers have suspected the approach to unknown regions
by the appearance of floating wood or stray land birds, anticipations
of such discoveries have been entertained and expressed from time to
time. Lyell, Dana, and Dr. Sterry Hunt more especially have committed
themselves to such speculations. The reasons assigned may be stated
thus:--
Assuming the Laurentian rocks to be altered sediments, they must, from
their great extent, have been deposited in the ocean; and if there had
been no living creatures in the waters, we have no reason to believe
that they would have consisted of anything more than such sandy and
muddy _débris_ as may be washed away from wasting rocks originally of
igneous origin. But the Laurentian beds contain other materials than
these. No formations of any geological age include thicker or more
extensive limestones. One of the beds measured by the officers of the
Geological Survey is stated to be 1,500 feet in thickness, another is
1,250 feet thick, and a third, 750 feet; making an aggregate of 3,500
feet.[50] These beds may be traced, with more or less interruption,
for hundreds of miles. Whatever the origin of such limestones, it
is plain that they indicate causes equal in extent, and comparable
in power and duration, with those which have produced the greatest
limestones of the later geological periods. Now, in later formations,
limestone is usually an organic rock, accumulated by the slow gathering
from the sea-water, or its plants, of calcareous matter, by corals,
foraminifera, or shell fish, and the deposition of their skeletons,
either entire or in fragments, in the sea bottom. The most friable
chalk and the most crystalline limestones have alike been formed in
this way. We know of no reason why it should be different in the
Laurentian period. When, therefore, we find great and conformable
beds of limestone, such as those described by Sir William Logan in
the Laurentian of Canada, we naturally imagine a quiet sea bottom, in
which multitudes of animals of humble organization were accumulating
limestone in their hard parts, and depositing this in gradually
increasing thickness from age to age. Any attempts to account otherwise
for these thick and greatly extended beds, regularly interstratified
with other deposits, have so far been failures, and have arisen either
from a want of comprehension of the nature and magnitude of the
appearances to be explained, or from the error of mistaking the true
bedded limestones for veins of calcareous spar.
[50] Logan: "Geology of Canada," p. 45.
The Laurentian rocks contain great quantities of carbon, in the form of
graphite or plumbago. This does not occur wholly, or even principally,
in veins or fissures, but in the substance of the limestone and gneiss,
and in regular layers. So abundant is it, that I have estimated the
amount of carbon in one division of the Lower Laurentian of the Ottawa
district at an aggregate thickness of not less than twenty to thirty
feet, an amount comparable with that in the true coal formation itself.
Now we know of no agency existing in present or in past geological
time capable of deoxidizing carbonic acid, and fixing its carbon as
an ingredient in permanent rocks, except vegetable life. Unless,
therefore, we suppose that there existed in the Laurentian age a vast
abundance of vegetation, either in the sea or on the land, we have no
means of explaining the Laurentian graphite.
The Laurentian formation contains great beds of oxide of iron,
sometimes seventy feet in thickness. Here, again, we have an evidence
of organic action; for it is the deoxidizing power of vegetable matter
which has in all the later formations been the efficient cause in
producing bedded deposits of iron. This is the case in modern bog and
lake ores, in the clay ironstones of the coal measures, and apparently,
also, in the great ore beds of the Silurian rocks. May not similar
causes have been at work in the Laurentian period?
Any one of these reasons might, in itself, be held insufficient to
prove so great and, at first sight, unlikely a conclusion as that of
the existence of abundant animal and vegetable life in the Laurentian;
but the concurrence of the whole in a series of deposits unquestionably
marine, forms a chain of evidence so powerful that it might command
belief even if no fragment of any organic and living form or structure
had ever been recognised in these ancient rocks.
Such was the condition of the matter until the existence of supposed
organic remains was announced by Sir W. Logan, at the American
Association for the Advancement of Science, in Springfield, in 1859;
and we may now proceed to narrate the manner of this discovery, and how
it has been followed up.
Before doing so, however, let us visit Eozoon in one of its haunts
among the Laurentian Hills. One of the most noted repositories of
its remains is the great Grenville band of limestone; and one of the
most fruitful localities is at a place called Côte St. Pierre on this
band. Leaving the train at Papineauville, we find ourselves on the
Laurentian rocks, and pass over one of the great bands of gneiss for
about twelve miles, to the village of St. André Avelin. On the road we
see on either hand abrupt rocky ridges, partially clad with forest, and
sometimes showing on their flanks the stratification of the gneiss in
very distinct parallel bands, often contorted, as if the rocks, when
soft, had been wrung as a washerwoman wrings clothes. Between the hills
are little irregular valleys, from which the wheat and oats have just
been reaped, and the tall Indian corn and yellow pumpkins are still
standing in the fields. Where not cultivated, the land is covered with
a rich second growth of young maples, birches, and oaks, among which
still stand the stumps and tall scathed trunks of enormous pines, which
constituted the original forest. Half way we cross the Nation River,
a stream nearly as large as the Tweed, flowing placidly between wooded
banks, which are mirrored in its surface; but in the distance we can
hear the roar of its rapids, dreaded by lumberers in their spring
drivings of logs. Arrived at St. André, we find a wider valley, the
indication of the change to the limestone band, and along this, with
the gneiss hills still in view on either hand, and often encroaching
on the road, we drive for five miles more to Côte St. Pierre. At this
place the lowest depression of the valley is occupied by a little pond,
and, hard by, the limestone, protected by a ridge of gneiss, rises in
an abrupt wooded bank by the roadside, and a little farther forms a
bare white promontory, projecting into the fields.
[Illustration: Fig. 4.--Attitude of Limestone at St. Pierre, (_a_)
Gneiss band in the Limestone, (_b_) Limestone with Eozoon. (_c_)
Diorite and Gneiss.]
The limestone is here highly inclined and much contorted, and in all
the excavations a thickness of about 100 feet of it may be exposed.
It is white and crystalline, varying much, however, in coarseness in
different bands. It is in some layers pure and white; in others it
is traversed by many grey layers of gneissose and other matter, or
by irregular bands and nodules of pyroxene and serpentine, and it
contains subordinate beds of dolomite. In one layer only, and this
but a few feet thick, does the Eozoon occur in abundance in a perfect
state, though fragments and imperfectly preserved specimens abound
in other parts of the bed. It is a great mistake to suppose that it
constitutes whole beds of rock in an uninterrupted mass. Its true mode
of occurrence is best seen on the weathered surfaces of the rock, where
the serpentinous specimens project in irregular patches of various
sizes, sometimes twisted by the contortion of the beds, but often too
small to suffer in this way. On such surfaces the projecting patches
of the fossil exhibit laminæ of serpentine so precisely like the
_Stromatoporæ_ of the Silurian rocks, that any collector would pounce
upon them at once as fossils. In some places these small weathered
specimens can be easily chipped off from the crumbling surface of the
limestone; and it is perhaps to be regretted that they have not been
more extensively shown to palæontologists, with the cut slices which
to many of them are so problematical. One of the original specimens,
brought from the Calumet, and now in the Museum of the Geological
Survey of Canada, was of this kind, and much finer specimens from
Côte St. Pierre are now in that collection and in my own. A very fine
example is represented on the plate facing this chapter, which is taken
from an original photograph. In some of the layers are found other
and more minute vesicular forms, which may be organic, and these,
together with fragmental remains, as ingredients in the limestone, will
be discussed in the sequel. We may merely notice here that the most
abundant layer of Eozoon at this place occurs near the base of the
great limestone band, and that the upper layers, in so far as seen,
are less rich in it. Further, there is no necessary connection between
Eozoon and the occurrence of serpentine, for there are many layers
full of bands and lenticular masses of that mineral without any Eozoon
except occasional fragments, while the fossil is sometimes partially
mineralised with pyroxene, dolomite, or common limestone. The section
in Fig. 4 will serve to show the attitude of the limestone at this
place, while the more general section, Fig. 2, page 101, taken from
Sir William Logan, shows its relation to the other Laurentian rocks.
We may now notice the manner in which the specimens discovered in this
and other places in the Laurentian country came to be regarded as
organic.
It is a trite remark that most discoveries are made, not by one
person, but by the joint exertions of many, and that they have their
preparations made often long before they actually appear. For this
reason I may be excused here for introducing some personal details in
relation to the discovery of Eozoon, and which are indeed necessary in
vindication of its claims. In this case the stable foundations were
laid years before the discovery of Eozoon, by the careful surveys made
by Sir William Logan and his assistants, and the chemical examination
of the rocks and minerals by Dr. Sterry Hunt, which established beyond
all doubt the great age and truly bedded character of the Laurentian
rocks and their probable original nature, and the changes which they
have experienced in the course of geological time. On the other hand,
Dr. Carpenter and others in England were examining the structure of the
shells of the humbler inhabitants of the modern ocean, and the manner
in which the pores of their skeletons become infiltrated with mineral
matter when deposited in the sea bottom. These laborious and apparently
dissimilar branches of scientific inquiry were destined to be united by
a series of happy discoveries, made not fortuitously but by painstaking
and intelligent observers. The discovery of the most ancient fossil
was thus not the chance picking up of a rare and curious specimen. It
was not likely to be found in this way; and if so found, it would have
remained unnoticed and of no scientific value, but for the accumulated
stores of zoological and palæontological knowledge, and the surveys
previously made, whereby the age and distribution of the Laurentian
rocks and the chemical conditions of their deposition and metamorphism
were ascertained.
The first specimens of Eozoon ever procured, in so far as known, were
collected at Burgess, in Ontario, by a veteran Canadian mineralogist,
Dr. Wilson, of Perth, and were sent to Sir William Logan as mineral
specimens. Their chief interest at that time lay in the fact that
certain laminæ of a dark green mineral present in the specimens were
found, on analysis by Dr. Hunt, to be composed of a new hydrous
silicate, allied to serpentine, and which he named loganite. The form
of this mineral was not suspected to be of organic origin. Some years
after, in 1858, other specimens, differently mineralized with the
minerals serpentine and pyroxene, were found by Mr. J. McMullen, an
explorer in the service of the Geological Survey, in the limestone
of the Grand Calumet on the River Ottawa. These seem to have at once
struck Sir W. E. Logan as resembling the Silurian fossils known as
_Stromatopora_, and he showed them to Mr. Billings, the palæontologist
of the survey, and to the writer, with this suggestion, confirming
it with the sagacious consideration that inasmuch as the Ottawa and
Burgess specimens were mineralized by different substances, yet were
alike in form, there was little probability that they were merely
mineral or concretionary. Mr. Billings was naturally unwilling to risk
his reputation in affirming the organic nature of such specimens;
and my own suggestion was that they should be sliced, and examined
microscopically, and that if fossils, as they presented merely
concentric laminæ and no cells, they would probably prove to be
protozoa rather than corals. A few slices were accordingly made, but
no definite structure could be detected. Nevertheless, Sir William
Logan took some of the specimens to the meeting of the American
Association at Springfield, in 1859, and exhibited them as possibly
Laurentian fossils; but the announcement was evidently received with
some incredulity. In 1862 they were exhibited by Sir William to some
geological friends in London, but he remarks that "few seemed disposed
to believe in their organic character, with the exception of my friend,
Professor Ramsay." In 1863 the general Report of the Geological Survey,
summing up its work to that time, was published, under the name of the
"Geology of Canada," and in this, at page 49, will be found two figures
of one of the Calumet specimens, here reproduced, and which, though
unaccompanied with any specific name or technical description, were
referred to as probably Laurentian fossils. (Figs. 5 and 6.)
[Illustration: Fig. 1.--Small specimen of Eozoon, weathered out,
natural size, from a photograph.
Fig. 2.--Canal System of Eozoon injected with serpentine (magnified).
Fig. 3.--Very fine Canals and Tubuli filled with Dolomite (magnified).
(From Micro-photographs.)]
[Illustration: Fig. 5.--Weathered Specimen of Eozoon from the Calumet.
(Collected by Mr. McMullen.)]
[Illustration: Fig. 6.--Cross Section of the Specimen represented in
Fig. 8. The dark parts are the laminæ of calcareous matter converging
to the outer surface.]
About this time Dr. Hunt happened to mention to me, in connection with
a paper on the mineralization of fossils which he was preparing, that
he proposed to notice the mode of preservation of certain fossil woods
and other things with which I was familiar, and that he would show me
the paper in proof, in order that I might give him any suggestions that
occurred to me. On reading it, I observed, among other things, that
he alluded to the supposed Laurentian fossils, under the impression
that the organic part was represented by the serpentine or loganite,
and that the calcareous matter was the filling of the chambers. I took
exception to this, stating that though in the slices I had examined no
structure was apparent, still my impression was that the calcareous
matter was the fossil, and the serpentine or loganite the filling. He
said--"In that case, would it not be well to re-examine the specimens,
and try to discover which view is correct?" He mentioned, at the same
time, that Sir William had recently shown him some new and beautiful
specimens collected by Mr. Lowe, one of the explorers on the staff of
the Survey, from a third locality, at Grenville, on the Ottawa. It
was supposed that these might throw further light on the subject; and
accordingly Dr. Hunt suggested to Sir William to have additional slices
of these new specimens made by Mr. Weston, of the Survey, whose skill
as a preparer of these and other fossils has often done good service to
science. A few days thereafter some slices were sent to me, and were
at once put under the microscope. I was delighted to find in one of
the first specimens examined a beautiful group of tubuli penetrating
one of the calcite layers. Here was evidence, not only that the
calcite layers represented the true skeleton of the fossil, but also
of its affinities with the foraminifera, whose tubulated supplemental
skeleton, as described and figured by Dr. Carpenter, and represented
in specimens in my collection, presented by him, was apparently of the
same type with that preserved in the canals of these ancient fossils.
Fig. 7 is an accurate representation of the group of canals first
detected by me.
[Illustration: Fig. 7.--Group of Canals in the Supplemental Skeleton of
Eozoon. Taken from the specimen in which they were first recognised.
Magnified. (Camera tracing by Mr. H. S. Smith.)]
On showing the structures discovered to Sir William Logan, he entered
into the matter with enthusiasm, and had a great number of slices, as
well as decalcified specimens, prepared, which were placed in my hands
for examination.
Feeling that the discovery was most important, but that it would be
met with determined scepticism by a great many geologists, I was
not content with examining the typical specimens of Eozoon, but had
slices prepared of every variety of Laurentian limestone, of altered
limestones from the Primordial and Silurian, and of serpentine
marbles of all the varieties furnished by our collections. They were
examined with ordinary and polarized light, and with every variety of
illumination. They were also examined as decalcified specimens, after
the carbonate of lime had been removed by acids. An extensive series of
notes and camera tracings were made of all the appearances observed;
and of some of the more important structures beautiful drawings
were executed by the late Mr. H. S. Smith, the then palæontological
draughtsman of the Survey. The result of the whole investigation was a
firm conviction that the structure was organic and foraminiferal, and
that it could be distinguished from any merely mineral or crystalline
forms occurring in these or other limestones.
At this stage of the matter, and after exhibiting to Sir William all
the characteristic appearances, in comparison with such concretionary,
dendritic and crystalline structures as most resembled them, and also
with the structure of recent and fossil Foraminifera, I suggested
that the further prosecution of the matter should be handed over to
Mr. Billings, as palæontologist of the Survey. I was engaged in other
researches, not connected with the Survey or with this particular
department, and I knew that no little labour must be devoted to the
work and to its publication, and that some controversy might be
expected. Mr. Billings, however, with his characteristic caution and
modesty, declined. His hands were full of other work. He had not given
any special attention to the microscopic appearances of Foraminifera or
of mineral substances. It was finally arranged that I should prepare
a description of the fossil, which Sir William would take to London,
along with the more important specimens, and a detailed list stating
all the structures observed in each. Sir William was to submit the
manuscript and specimens to Dr. Carpenter, or, failing him, to Prof.
T. Rupert Jones, in the hope that these eminent authorities would
confirm my conclusions, and bring forward new facts which I might
have overlooked or been ignorant of. Sir William saw both gentlemen,
who gave their testimony in favour of the organic and foraminiferal
character of the specimens; and Dr. Carpenter, in particular, gave much
attention to the subject, and worked out more in detail many of the
finer structures, besides contributing valuable suggestions as to the
probable affinities of the supposed fossil.
Dr. Carpenter thus contributed in a very important manner to the
perfecting of the investigations begun in Canada, and on him fell the
greater part of their illustration and defence,[51] in so far as Great
Britain is concerned.
[51] In _Quarterly Journal of Geological Society_, vol. xxii.; _Proc.
Royal Society_, vol. xv.; _Intellectual Observer_, 1865. _Annals and
Magazine of Natural History_, 1874; and other papers and notices.
The immediate result was a composite paper in the _Proceedings of the
Geological Society_, by Sir W. E. Logan, Dr. Carpenter, Dr. Hunt, and
myself, in which the geology, palæontology and mineralogy of _Eozoon
Canadense_ and its containing rocks were first given to the world.[52]
It cannot be wondered at that when geologists and palæontologists
were thus required to believe in the existence of organic remains in
rocks regarded as altogether Azoic and hopelessly barren of fossils,
and to carry back the dawn of life as far before those Primordial
rocks, which were supposed to contain its first traces, as these are
before the middle period of the earth's life history, some hesitation
should be felt. Further, the accurate appreciation of the evidence
for such a fossil as Eozoon required an amount of knowledge of
minerals, of the more humble types of animals, and of the conditions
of mineralization of organic remains, possessed by few even of
professional geologists. Thus Eozoon has met with some scepticism and
not a little opposition,--though the latter has been weaker than we
might have expected when we consider the startling character of the
facts adduced, and has mostly come from men imperfectly informed.
[52] _Journal Geological Society_, February, 1865.
But what is Eozoon, if really of animal origin? The shortest answer
to this question is, that this ancient fossil is supposed to be the
skeleton of a creature belonging to that simple and humbly organized
group of animals which are known by the name Protozoa. If we take as a
familiar example of these the gelatinous and microscopic creature found
in stagnant ponds, and known as the _Amœba_[53] (Fig. 8), it will form
a convenient starting-point. Viewed under a low power, it appears as
a little patch of jelly, irregular in form, and constantly changing
its aspect as it moves, by the extension of parts of its body into
finger-like processes or pseudopods which serve as extempore limbs.
When moving on the surface of a slip of glass under the microscope,
it seems, as it were, to flow along rather than creep, and its body
appears to be of a semi-fluid consistency. It may be taken as an
example of the least complex forms of animal life known to us, and is
often spoken of by naturalists as if it were merely a little particle
of living and scarcely organized jelly or protoplasm. When minutely
examined, however, it will not be found so simple as it at first sight
appears. Its outer layer is clear and transparent, and more dense than
the inner mass, which seems granular. It has at one end a curious
vesicle which can be seen gradually to expand and become filled with
a clear drop of liquid, and then suddenly to contract and expel the
contained fluid through a series of pores in the adjacent part of
the outer wall. This is the so-called pulsating vesicle, and is an
organ both of circulation and excretion. In another part of the body
may be seen the nucleus, which is a little cell capable, at certain
times, of producing by its division new individuals. Food, when taken
in through the wall of the body, forms little pellets, which become
surrounded by a digestive liquid exuded from the enclosing mass into
rounded cavities or extemporised stomachs. Minute granules are seen
to circulate in the gelatinous interior, and may be substitutes for
blood-cells, and the outer layer of the body is capable of protrusion
in any direction into long processes, which are very mobile, and used
for locomotion and prehension. Further, this creature, though destitute
of most of the parts which we are accustomed to regard as proper to
animals, seems to exercise volition, and to show the same appetites
and passions with animals of higher type. I have watched one of these
animalcules endeavouring to swallow a one-celled plant as long as its
own body; evidently hungry and eager to devour the tempting morsel, it
stretched itself to its full extent, trying to envelope the object of
its desire. It failed again and again; but renewed the attempt, until
at length, convinced of its hopelessness, it flung itself away as if in
disappointment, and made off in search of something more manageable.
With the Amœba are found other types of equally simple Protozoa, but
somewhat differently organized. One of these, _Actinophrys_ (Fig. 9),
has the body globular and unchanging in form, the outer wall of greater
thickness; the pulsating vesicle like a blister on the surface, and the
pseudopods long and thread-like. Its habits are similar to those of the
Amœba, and I introduce it to show the variations of form and structure
possible even among these simple creatures.
[53] The alternating animal, alluding to its change of form.
[Illustration: Fig. 8. Amœba. Fig. 9. Actinophrys.
From original sketches.]
The Amœba and Actinophrys are fresh-water animals, and are destitute
of any shell or covering. But in the sea there exist swarms of similar
creatures, equally simple in organization, but gifted with the power of
secreting around their soft bodies beautiful little shells or crusts of
carbonate of lime, having one orifice, and often in addition multitudes
of microscopic pores through which the soft gelatinous matter can ooze,
and form outside finger-like or thread-like extensions for collecting
food. In some cases the shell consists of a single cavity only, but in
most, after one cell is completed, others are added, forming a series
of cells or chambers communicating with each other, and often arranged
spirally or otherwise in most beautiful and symmetrical forms. Some of
these creatures, usually named Foraminifera, are locomotive, others
sessile and attached. Most of them are microscopic, but some grow by
multiplication of chambers till they are a quarter of an inch or more
in breadth.
The original skeleton or primary cell wall of most of these creatures
is seen under the microscope to be perforated with innumerable pores,
and is extremely thin. When, however, owing to the increased size of
the shell, or other wants of the creature, it is necessary to give
strength, this is done by adding new portions of carbonate of lime to
the outside, and to these Dr. Carpenter has given the appropriate name
of "supplemental skeleton"; and this, when covered by new growths,
becomes what he has termed an "intermediate skeleton." The supplemental
skeleton is also traversed by tubes, but these are often of larger
size than the pores of the cell wall, and of greater length, and
branched in a complicated manner. Thus there are microscopic characters
by which these curious shells can be distinguished from those of
other marine animals; and by applying these characters we learn that
multitudes of creatures of this type have existed in former periods of
the world's history, and that their shells, accumulated in the bottom
of the sea, constitute large portions of many limestones. The manner in
which such accumulation takes place we learn from what is now going on
in the ocean, more especially from the result of the recent deep-sea
dredging expeditions. The Foraminifera are vastly numerous, both near
the surface and at the bottom of the sea, and multiply rapidly; and as
successive generations die, their shells accumulate on the ocean bed,
or are swept by currents into banks, and thus, in process of time,
constitute thick beds of white chalky material, which may eventually
be hardened into limestone. This process is now depositing a great
thickness of white ooze in the bottom of the ocean; and in times past
it has produced such vast thicknesses of calcareous matter as the chalk
and nummulitic limestone of Europe and the orbitoidal limestone of
America. The chalk which alone attains a maximum thickness of 1,000
feet, and, according to Lyell, can be traced across Europe for 1,100
geographical miles, may be said to be entirely composed of shells of
Foraminifera imbedded in a paste of smaller calcareous bodies, the
Coccoliths, which are probably products of marine vegetable life, if
not of some animal organism still simpler than the Foraminifera.
Lastly, while we have in such modern forms as the masses of
Polytrema attached to corals, and the Loftusia of the Eocene and the
carboniferous, large fossil foraminiferal species, there is some reason
to believe that in the earlier geological ages there existed much
larger animals of this grade than are found in our present seas; and
that these, always sessile on the bottom, grew by the addition of
successive chambers, in the same manner with the smaller species.[54]
[54] I refer to some of the Stromatoporæ of the Silurian and the
_Cryptozoon_ of the Cambrian. See note appended to this chapter.
Let us, then, examine the structure of Eozoon, taking a typical
specimen, as we find it in the limestone of Grenville or Petite Nation.
In such specimens the skeleton of the animal is represented by a white
crystalline marble, the cavities of the cells by green serpentine, the
mode of whose introduction we shall have to consider in the sequel.
The lowest layer of serpentine represents the first gelatinous coat
of animal matter which grew upon the bottom, and which, if we could
have seen it before any shell was formed upon its surface, must have
resembled a minute patch of living slime. On this primary layer grew
a delicate calcareous shell, perforated by innumerable minute tubuli,
and resting on the slimy matter of the animal, though supported also
by some perpendicular plates or septa. Upon this again was built up,
in order to strengthen it, a thickening or supplemental skeleton,
more dense, and destitute of fine tubuli, but traversed by branching
canals, through which the soft gelatinous matter could pass for the
nourishment of the skeleton itself, and the extension of pseudopods
beyond it. (Figs. 11, 12.) So was formed the first layer of Eozoon,
which probably was at its beginning only of very small dimensions. On
this the process of growth of successive layers of animal sarcode and
of calcareous skeleton was repeated again and again, till in some cases
even a hundred or more layers were formed (nature-print, Chap. VI.)
As the process went on, however, the vitality of the organism became
exhausted, probably by the deficient nourishment of the central and
lower layers making greater and greater demands on those above, and so
the succeeding layers became thinner, and less supplemental skeleton
was developed. Finally, toward the top, the regular arrangement in
layers was abandoned, and the cells became a mass of rounded chambers,
irregularly piled up in what Dr. Carpenter has termed an "acervuline"
manner, and with very thin walls unprotected by supplemental skeleton.
Then the growth was arrested, and possibly these upper layers gave
off reproductive germs, fitted to float or swim away and to establish
new colonies. We may have such reproductive germs in certain curious
globular bodies, like loose cells, found in connection with Eozoon in
many of the Laurentian limestones.[55] At St. Pierre, on the Ottawa,
these bodies occur on the surface of layers of the limestone in vast
numbers, as if they had been growing separately on the bottom, or had
been drifted over it by currents. They may have served as reproductive
buds or germs to establish new colonies of the species. Such was the
general mode of growth of Eozoon, and we may now consider more in
detail some questions as to its gigantic size, its precise mode of
nutrition, the arrangement of its parts, its relations to more modern
forms, and the effects of its growth in the Laurentian seas.
[55] It would be interesting to compare these bodies with the forms
recently found by Barrois and Cayeux in the "Azoic" quartzite of
Brittany, which should certainly now be called Eozoic.
[Illustration: Fig. 10.--Minute Foraminiferal forms from the Laurentian
of Long Lake. Highly magnified, (_a_) Single cell, showing tubulated
wall. (_b, c_) Portions of same more highly magnified. (_d_) Serpentine
cast of a similar chamber, decalcified, and showing casts of tubuli.]
With respect to the size of Eozoon, this was rivalled by some
succeeding animals of the same humble type in later geological ages;
and, as a whole, foraminiferal animals have been diminishing in
size in the lapse of geological time. This is indeed a fact of so
frequent occurrence that it may almost be regarded as a law of the
introduction of new forms of life, that they assume in their early
history gigantic dimensions, and are afterwards continued by less
magnificent species. The relations of this to external conditions,
in the case of higher animals, are often complex and difficult to
understand; but in organisms so low as Eozoon and its allies, they lie
more on the surface. Such creatures may be regarded as the simplest and
most ready media for the conversion of vegetable matter into animal
tissues, and their functions are almost entirely limited to those
of nutrition. Hence it is likely that they will be able to appear
in the most gigantic forms under such conditions as afford them the
greatest amount of pabulum for the nourishment of their soft parts
and for their skeletons. There is reason to believe, for example,
that the occurrence, both in the chalk and the deep-sea mud, of
immense quantities of the minute bodies known as Coccoliths along with
Foraminifera, is not accidental. The Coccoliths appear to be grains
of calcareous matter formed in minute plants adapted to a deep-sea
habitat; and these, along with the vegetable and animal _débris_
constantly being derived from the death of the living things at the
surface, afford the material both of sarcode and shell. Now if the
Laurentian graphite represents an exuberance of vegetable growth in
those old seas proportionate to the great supplies of carbonic acid
in the atmosphere and in the waters, and if the Eozoic ocean was even
better supplied with salts of lime than those Silurian seas whose vast
limestones bear testimony to their richness in such material, we can
easily imagine that the conditions may have been more favourable to a
creature like Eozoon than those of any other period of geological time.
Growing, as Eozoon did, on the floor of the ocean, and covering wide
patches with more or less irregular masses, it must have thrown up from
its whole surface its pseudopods to seize whatever floating particles
of food the waters carried over it. There is also reason to believe,
from the outline of certain specimens, that it often grew upward
in conical or club-shaped forms, and that the broader patches were
penetrated by large pits or oscula, admitting the sea-water deeply into
the substance of the masses. In this way its growth might be rapid and
continuous; but it does not seem to have possessed the power of growing
indefinitely by new and living layers covering those that had died,
in the manner of some corals. Its life seems to have had a definite
termination, and when that was reached, an entirely new colony had to
be commenced. In this it had more affinity with the Foraminifera, as
we now know them, than with the corals, though practically it had the
same power with the coral polyps of accumulating limestone in the sea
bottom--a power indeed still possessed by its foraminiferal successors.
In the case of coral limestones we know that a large proportion of
these consist not of continuous reefs, but of fragments of coral mixed
with other calcareous organisms, spread usually by waves and currents
in continuous beds over the sea bottom. In like manner we find in the
limestones containing Eozoon, layers of fragmental matter which show
in places the characteristic structures, and which evidently represent
the _débris_ swept from the Eozoic masses and reefs by the action of
the waves. It is with this fragmental matter that the small rounded
organisms already referred to most frequently occur; and while they
may be distinct animals, they may also be the fry of Eozoon, or small
portions of its acervuline upper surface floated off in a living state,
and possibly capable of living independently and of founding new
colonies.
It is only by a somewhat wild poetical licence that Eozoon has been
represented as a "kind of enormous composite animal stretching from the
shores of Labrador to Lake Superior, and thence northward and southward
to an unknown distance, and forming masses 1,500 feet in depth." We
may, it is true, readily believe in the composite nature of masses or
Eozoon, and we see in the corals evidence of the great size to which
composite animals of a higher grade can attain. In the case of Eozoon
we must imagine an ocean floor more uniform and level than that now
existing. On this the organism would establish itself in spots and
patches. These might finally become confluent over large areas, just
as massive corals do. As individual masses attained maturity and died,
their pores would be filled up with limestone or silicious deposits,
and thus could form a solid basis for new generations, and in this way
limestone to an indefinite extent might be produced. Further, wherever
such masses were high enough to be attacked by the breakers, or where
portions of the sea bottom were elevated, the more fragile parts of the
surface would be broken up and scattered widely in beds of fragments
over the bottom of the sea, while here and there beds of mud or sand,
or of volcanic _débris_ would be deposited over the living or dead
organic mass, and would form the layers of gneiss and other schistose
rocks interstratified with the Laurentian limestone. In this way, in
short, Eozoon would perform a function combining that which corals and
Foraminifera perform in the modern seas; forming both reef limestones
and extensive chalky beds, and probably living both in the shallow and
the deeper parts of the ocean. If in connection with this we consider
the rapidity with which the soft, simple, and almost structureless
sarcode of these Protozoa can be built up, and the probability that
they were more abundantly supplied with food, both for nourishing
their soft parts and skeletons, than any similar creatures in later
times, we can readily understand the great volume and extent of the
Laurentian limestones which they aided in producing. I say aided in
producing, because I would not care to commit myself to the doctrine
that the Laurentian limestones are wholly of this origin. There may
have been other limestone builders than Eozoon, and there may have been
limestones formed by plants like the modern Nullipores, or by merely
mineral deposition.
[Illustration: Fig. 11.--Section of a Nummulite, from Eocene Limestone
of Syria. Showing chambers, tubuli, and canals. Compare this and Fig.
12 with Fig. 7 and Nature-print of Eozoon.]
Its relations to modern animals of its type have been very clearly
defined by Dr. Carpenter. In the structure of its proper wall and its
fine parallel perforations, it resembles the _Nummulites_ and their
allies; and the organism may therefore be regarded as an aberrant
member of the Nummuline group, which affords some of the largest and
most widely distributed of the fossil Foraminifera. This resemblance
may be seen in Fig. 11. To the Nummulites it also conforms in its
tendency to form a supplemental or intermediate skeleton with canals,
though the canals themselves in the arrangement more nearly resemble
Calcarina, which is represented in Fig. 12. In its superposition
of many layers, and in its tendency to a heaped up or acervuline
irregular growth it resembles _Polytrema_ and _Tinoporus_, forms of a
different group in so far as shell-structure is concerned. It may thus
be regarded as a composite type, combining peculiarities now observed
in two groups, or it may be regarded as representing one of these in
another series. At the time when Dr. Carpenter stated these affinities,
it might be objected that Foraminifera of these families are in the
main found in the modern and Tertiary periods. Dr. Carpenter has since
shown that the curious oval Foraminifer called _Fusulina_, found in
the coal formation, is allied to both Nummulites and Rotalines; and
Mr. Brady has discovered a true Nummulite in the Lower Carboniferous
of Belgium. I have myself found small Foraminifera in the Silurian and
Cambro-Silurian of Canada. This group being now brought down to the
Palæozoic, we may hope to trace it to the Primordial, and thus to bring
it still nearer to Eozoon in time.
[Illustration: Fig. 12.--Portion of shell of Calcarina. Magnified,
after Carpenter, (_a_) Cells. (_b_) Original cell wall with tubuli.
(_c_) Supplementary skeleton with canals.]
Though Eozoon was probably not the only animal of the Laurentian seas,
yet it was in all likelihood the most conspicuous and important as
a collector of calcareous matter, filling the same place afterwards
occupied by the reef-building corals. Though probably less efficient
than these as a constructor of solid limestones, from its less
permanent and continuous growth, it formed wide floors and patches
on the sea bottom, and when these were broken up, vast quantities of
limestone were formed from their _débris_. It must also be borne in
mind that Eozoon was not everywhere infiltrated with serpentine or
other silicious minerals; quantities of its substance were merely
filled with carbonate of lime, resembling the chamber wall so closely
that it is nearly impossible to make out the difference, and thus is
likely to pass altogether unobserved by collectors, and to baffle
even the microscopist. Although, therefore, the layers which contain
well characterised Eozoon are few and far between, there is reason to
believe that in the composition of the limestones of the Laurentian it
bore no small part, and as these limestones are some of them several
hundred feet in thickness, and extend over vast areas, Eozoon may be
supposed to have been as efficient a world-builder as the Stromatoporæ
of the Silurian and Devonian, the Globigerinæ and their allies in
the chalk, or the Nummulites and Miliolites in the Eocene. It is a
remarkable illustration of the constancy of natural causes and of
the persistence of animal types, that these humble Protozoans, which
began to secrete calcareous matter in the Laurentian period, have been
continuing their work in the ocean through all the geological ages,
and are still busy in accumulating those chalky muds with which recent
dredging operations in the deep sea have made us so familiar. (See Note
appended.)
All this seems sufficiently reasonable, more especially since
no mineralogist has yet succeeded in giving a feasible inorganic
explanation of the combination of canals, laminæ, tubulation and varied
mineral character existing in Eozoon. But then comes the strange fact
of its apparent isolation without companions in highly crystalline
rocks, and with apparently no immediate successors. This has staggered
many, and it certainly, if taken thus baldly, seems in some degree
improbable. Recent discoveries, however, are removing this reproach
from Eozoon. The Laurentian rocks have yielded other varieties, or
perhaps species of the genus, those which I have described as variety
Acervulina, and variety Minor, and still another form, more like a
Stromatopora, which I have provisionally named _E. latior_, from
the breadth and uniformity of its plates.[56] There are also in the
Laurentian limestone cylindrical bodies apparently originally tubular,
and with the sides showing radiating markings in the manner of corals,
or of the curious Cambrian Archæocyathus. Matthew, a most careful
observer, has found in the Laurentian limestone of New Brunswick
certain laminated bodies of cylindrical form, constituting great reefs
in the limestone, and in the slates linear flat objects resembling
Algæ or Graptolites, and spicular structures resembling those of
sponges.[57] Britton has also described from the Laurentian limestone
of New Jersey certain ribbon-like objects of graphite which he regards
as vegetable, and names _Archæophyton Newberryii_.[58] Should these
objects prove to be organic, Eozoon will no longer be alone. Besides
this the peculiar bodies named Cryptozoum by Hall, and which are
intermediate in structure between Eozoon and Loftusia, have now been
found as low as the Lower Cambrian.[59] Barrois has also recently
announced the discovery of forms which he regards as akin to the modern
Radiolaria, creatures of a little higher grade than the Foraminifera,
in the "Archæan" rocks of Brittany.[60] Thus Eozoon is no longer
isolated, but has companions of the same great age with itself. The
progress of discovery is also daily carrying the life of the Cambrian
to lower beds, and thus nearer to the Laurentian. It is not unlikely
that in a few years a pre-Cambrian fauna will force itself on the
attention of the most sceptical geologists.
[56] Notes on Specimens of Eozoon, "Memoirs of Peter Redpath Museum,"
1888.
[57] _Bul. Nat. Hist. New Brunswick, No. IX._, 1890.
[58] _Annals N. Y. Academy of Science_, 1888.
[59] Walcott, Lower Cambrian, 1892.
[60] _Natural Science_, Oct., 1892.
References:--"Life's Dawn on Earth," London, 1875. (Now out of
print.) "Specimens of Eozoon Canadense in the Peter Red path
Museum, Montreal," 1888. (This memoir contains reference to
previous papers.)
Appended Notes.
1. _Stromatoporæ._ It has been usual of late to regard these as allies
of the modern Millepores and Hydractineæ; but careful study of large
series of specimens has convinced me that some species, notably the
_Stromatocerium_ of the Cambro-Silurian and the _cryptozoum_ of the
Cambrian, cannot be so referred. I hope to establish this in the
future, if time permit.
2. Modern Foraminifera. The discovery by Brady and Lister of
reproductive chamberlets at the margin of the modern _orbitolites_,
tends to connect this with Eozoon. The gigantic foraminiferal species
discovered by Agassiz at the Gallipagos, has points of affinity
with Eozoon; and its arenaceous nature does not affect this, as we
know sandy species in this group closely allied to others that are
calcareous.
_WHAT MAY BE LEARNED FROM EOZOON._
DEDICATED TO THE MEMORY OF
DR. WILLIAM B. CARPENTER,
Who, among his many Services to Science,
devoted much Time and Labour to the Investigation
of Eozoon, and by his Knowledge of Foraminifera
and unrivalled Power of unravelling difficult
Structures
did much to Render it intelligible.
The Microscope in Geology--Contributions of the Study of Eozoon to
our Knowledge of the Mode of Preservation of Fossils--Its Teaching
Relatively to the Origin of Life and the Laws of its Introduction and
Progress
[Illustration: Specimen of Eozoon Canadense (Dawson), showing General
Form and Osculiform Tubes. (Reproduced from Photograph.)]