Some Salient Points in the Science of the Earth

CHAPTER V.

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.

Fig. 1.—Laurentian Hills opposite Kamouraska, Lower St. Lawrence. The islands in front are Cambro-Silurian.

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.

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.

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.)

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.)

Fig. 5.—Weathered Specimen of Eozoon from the Calumet. (Collected by Mr. McMullen.)

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.

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 Amoeba[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 Amoeba 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 Amoeba, 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.

Fig. 8. Amoeba. Fig. 9. Actinophrys.
From original sketches.

The Amoeba 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.

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.

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.

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.

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