life is dawn on the earth 21

life is dawn on the earth 21

(_a._) Specimens dissolved out by acid. The lower one showing interior

septa. (_b._) Specimens seen in section.]

 

[Illustration: Fig. 33. _Archæospherinæ from Burgess Eozoon._

 

Magnified.]

 

[Illustration: Fig. 34. _Archæospherinæ from Wentworth Limestone._

 

Magnified.]

 

It is different, however, with the round cells infiltrated with

serpentine and with the silicious grains included in the loganite. I

have already referred to and figured (fig. 18) the remarkable rounded

bodies occurring at Long Lake. I now figure similar bodies found mixed

with fragmental Eozoon and in separate thin layers at St. Pierre (fig.

32), also some of the singular grains found in the loganite occupying

the chambers of Eozoon from Burgess (fig. 33), and a beaded body set

free by acid, with others of irregular forms, from the limestone of

Wentworth (fig. 34). All these I think are essentially of the same

nature, namely, chambers originally invested with a tubulated wall

like Eozoon, and aggregated in groups, sometimes in a linear manner,

sometimes spirally, like those Globigerinæ which constitute the mass

of modern deep-sea dredgings and also of the chalk. These bodies occur

dispersed in the limestone, arranged in thin layers parallel to the

bedding or sometimes in the large chamber-cavities of Eozoon. They

are so variable in size and form that it is not unlikely they may be

of different origins. The most probable of these may be thus stated.

First, they may in some cases be the looser superficial parts of the

surface of Eozoon broken up into little groups of cells. Secondly,

they may be few-celled germs or buds given off from Eozoon. Thirdly,

they may be smaller Foraminifera, structurally allied to Eozoon, but

in habit of growth resembling those little globe-shaped forms which,

as already stated, abound in chalk and in the modern ocean. The latter

view I should regard as highly probable in the case of many of them;

and I have proposed for them, in consequence, and as a convenient name,

_Archæospherinæ_, or ancient spherical animals.

 

Carbonaceous matter is rare in the true Eozoon limestones, and, as

already stated, I would refer the Laurentian graphite or plumbago

mainly to plants. With regard to the worm-burrows referred to in 1865,

there can be no doubt of their nature, but there is some doubt as to

whether the beds that contain them are really Lower Laurentian. They

may be Upper Laurentian or Huronian. I give here figures of these

burrows as published in 1866[AG] (fig. 35). The rocks which contain

them hold also fragments of Eozoon, and are not known to contain other

fossils.

 

[Footnote AG: _Journal of Geological Society._]

 

[Illustration: Fig. 35. _Annelid Burrows, Laurentian or Huronian._

 

Fig 1. _Transverse section of Worm-burrow_--magnified, as a transparent

object. (_a._) Calcareo-silicious rock. (_b._) Space filled with

calcareous spar. (_c._) Sand agglutinated and stained black. (_d._)

Sand less agglutinated and uncoloured. Fig. 2. _Transverse section of

Worm-burrow on weathered surface_, natural size. Fig. 3. _The same_,

magnified.]

 

If we now turn to other countries in search of contemporaries of

Eozoon, I may refer first to some specimens found by my friend Dr.

Honeyman at Arisaig, in Nova Scotia, in beds underlying the Silurian

rocks of that locality, but otherwise of uncertain age. I do not vouch

for them as Laurentian, and if of that age they seem to indicate a

species distinct from that of Canada proper. They differ in coarser

tubulation, and in their canals being large and beaded, and less

divergent. I proposed for these specimens, in some notes contributed to

the survey of Canada, the name _Eozoon Acadianum_.

 

Dr. Gümbel, the Director of the Geological Survey of Bavaria, is

one of the most active and widely informed of European geologists,

combining European knowledge with an extensive acquaintance with the

larger and in some respects more typical areas of the older rocks in

America, and stratigraphical geology with enthusiastic interest in the

microscopic structures of fossils. He at once and in a most able manner

took up the question of the application of the discoveries in Canada

to the rocks of Bavaria. The spirit in which he did so may be inferred

from the following extract:--

 

"The discovery of organic remains in the crystalline limestones of the

ancient gneiss of Canada, for which we are indebted to the researches

of Sir William Logan and his colleagues, and to the careful microscopic

investigations of Drs. Dawson and Carpenter, must be regarded as

opening a new era in geological science.

 

"This discovery overturns at once the notions hitherto commonly

entertained with regard to the origin of the stratified primary

limestones, and their accompanying gneissic and quartzose strata,

included under the general name of primitive crystalline schists. It

shows us that these crystalline stratified rocks, of the so-called

primary system, are only a backward prolongation of the chain of

fossiliferous strata; the elements of which were deposited as oceanic

sediment, like the clay-slates, limestones, and sandstones of the

palæozoic formations, and under similar conditions, though at a time

far more remote, and more favourable to the generation of crystalline

mineral compounds.

 

"In this discovery of organic remains in the primary rocks, we hail

with joy the dawn of a new epoch in the critical history of these

earlier formations. Already in its light, the primeval geological time

is seen to be everywhere animated, and peopled with new animal forms

of whose very existence we had previously no suspicion. Life, which

had hitherto been supposed to have first appeared in the Primordial

division of the Silurian period, is now seen to be immeasurably

lengthened beyond its former limit, and to embrace in its domain the

most ancient known portions of the earth's crust. It would almost

seem as if organic life had been awakened simultaneously with the

solidification of the earth's crust.

 

"The great importance of this discovery cannot be clearly understood,

unless we first consider the various and conflicting opinions

and theories which had hitherto been maintained concerning the

origin of these primary rocks. Thus some, who consider them as the

first-formed crust of a previously molten globe, regard their apparent

stratification as a kind of concentric parallel structure, developed

in the progressive cooling of the mass from without. Others, while

admitting a similar origin of these rocks, suppose their division

into parallel layers to be due, like the lamination of clay-slates,

to lateral pressure. If we admit such views, the igneous origin of

schistose rocks becomes conceivable, and is in fact maintained by many.

 

"On the other hand, we have the school which, while recognising the

sedimentary origin of these crystalline schists, supposes them to

have been metamorphosed at a later period; either by the internal

heat, acting in the deeply buried strata; by the proximity of eruptive

rocks; or finally, through the agency of permeating waters charged with

certain mineral salts.

 

"A few geologists only have hitherto inclined to the opinion that

these crystalline schists, while possessing real stratification,

and sedimentary in their origin, were formed at a period when the

conditions were more favourable to the production of crystalline

materials than at present. According to this view, the crystalline

structure of these rocks is an original condition, and not one

superinduced at a later period by metamorphosis. In order, however,

to arrange and classify these ancient crystalline rocks, it becomes

necessary to establish by superposition, or by other evidence,

differences in age, such as are recognised in the more recent

stratified deposits. The discovery of similar organic remains,

occupying a determinate position in the stratification, in different

and remote portions of these primitive rocks, furnishes a powerful

argument in favour of the latter view, as opposed to the notion which

maintains the metamorphic origin of the various minerals and rocks of

these ancient formations; so that we may regard the direct formation of

these mineral elements, at least so far as these fossiliferous primary

limestones are concerned, as an established fact."

 

His first discovery is thus recorded, in terms which show the very

close resemblance of the Bavarian and Canadian Eozoic.

 

"My discovery of similar organic remains in the serpentine-limestone

from near Passau was made in 1865, when I had returned from my

geological labours of the summer, and received the recently published

descriptions of Messrs. Logan, Dawson, etc. Small portions of this

rock, gathered in the progress of the Geological Survey in 1854,

and ever since preserved in my collection, having been submitted

to microscopic examination, confirmed in the most brilliant manner

the acute judgment of the Canadian geologists, and furnished

palæontological evidence that, notwithstanding the great distance which

separates Canada from Bavaria, the equivalent primitive rocks of the

two regions are characterized by similar organic remains; showing at

the same time that the law governing the definite succession of organic

life on the earth is maintained even in these most ancient formations.

The fragments of serpentine-limestone, or ophicalcite, in which I first

detected the existence of Eozoon, were like those described in Canada,

in which the lamellar structure is wanting, and offer only what Dr.

Carpenter has called an acervuline structure. For further confirmation

of my observations, I deemed it advisable, through the kindness of

Sir Charles Lyell, to submit specimens of the Bavarian rock to the

examination of that eminent authority, Dr. Carpenter, who, without any

hesitation, declared them to contain Eozoon.

 

"This fact being established, I procured from the quarries near Passau

as many specimens of the limestone as the advanced season of the year

would permit; and, aided by my diligent and skillful assistants,

Messrs. Reber and Schwager, examined them by the methods indicated by

Messrs. Dawson and Carpenter. In this way I soon convinced myself of

the general similarity of our organic remains with those of Canada.

Our examinations were made on polished sections and in portions etched

with dilute nitric acid, or, better, with warm acetic acid. The most

beautiful results were however obtained by etching moderately thin

sections, so that the specimens may be examined at will either by

reflected or transmitted light.

 

"The specimens in which I first detected Eozoon came from a quarry

at Steinhag, near Obernzell, on the Danube, not far from Passau. The

crystalline limestone here forms a mass from fifty to seventy feet

thick, divided into several beds, included in the gneiss, whose general

strike in this region is N.W