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| Transcriber’s note: |
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| This book was published in two volumes, of which this is the |
| second. The first volume was released as Project Gutenberg ebook |
| #40472, available at https://www.gutenberg.org/ebooks/40472 |
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| Numbers enclosed in square brackets, e.g. [1], relate to |
| footnotes, which have been placed at the end of the text. |
| Numbers enclosed in parentheses, e.g. (1), relate to works |
| referred to in the text and listed at the end of this volume. |
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| In the text versions of these two volumes, words in _italics_ |
| are enclosed in underscores, +bold+ words are enclosed in plus |
| signs, and words in =Gothic script= are enclosed in equal signs. |
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THE HISTORY OF CREATION.
[Illustration: Hypothetical Sketch of the Monophyletic Origin of Man.]
THE
HISTORY OF CREATION:
_OR THE DEVELOPMENT OF THE EARTH AND ITS
INHABITANTS BY THE ACTION OF NATURAL CAUSES._
A POPULAR EXPOSITION OF
THE DOCTRINE OF EVOLUTION IN GENERAL, AND OF THAT OF
DARWIN, GOETHE, AND LAMARCK IN PARTICULAR.
FROM THE GERMAN OF
ERNST HAECKEL,
PROFESSOR IN THE UNIVERSITY OF JENA.
THE TRANSLATION REVISED BY
PROFESSOR E. RAY LANKESTER, M.A., F.R.S.,
FELLOW OF EXETER COLLEGE, OXFORD.
_IN TWO VOLUMES._
VOL. II.
NEW YORK:
D. APPLETON AND COMPANY,
1, 3, AND 5 BOND STREET.
1880.
A sense sublime
Of something far more deeply interfused,
Whose dwelling is the light of setting suns,
And the round ocean, and the living air,
And the blue sky, and in the mind of man;
A motion and a spirit that impels
All thinking things, all objects of all thought,
And rolls through all things.
In all things, in all natures, in the stars
Of azure heaven, the unenduring clouds,
In flower and tree, in every pebbly stone
That paves the brooks, the stationary rocks,
The moving waters and the invisible air.
WORDSWORTH.
CONTENTS OF VOL. II.
CHAPTER XV.
PAGE
PERIODS OF CREATION AND RECORDS OF CREATION.
Reform of Systems by the Theory of Descent.—The Natural System
as a Pedigree.—Palæontological Records of the
Pedigree.—Petrifactions as Records of Creation.—Deposits of the
Neptunic Strata and the Enclosure of Organic Remains.—Division
of the Organic History of the Earth into Five Main Periods:
Period of the Tangle Forests, Fern Forests, Pine Forests,
Foliaceous Forests, and of Cultivation.—The Series of Neptunic
Strata.—Immeasurable Duration of the Periods which have elapsed
during their Formation.—Deposits of Strata only during the
Sinking, not during the Elevation of the Ground.—Other Gaps in
the Records of Creation.—Metamorphic Condition of the most
Ancient Neptunic Strata.—Small Extent of Palæontological
Experience.—Small proportion of Organisms and of Parts of
Organisms Capable of Petrifying.—Rarity of many Petrified
Species.—Want of Fossilised Intermediate Forms.—Records of the
Creation in Ontogeny and in Comparative Anatomy 1
CHAPTER XVI.
PEDIGREE AND HISTORY OF THE KINGDOM OF THE PROTISTA.
Special Mode of Carrying out the Theory of Descent in the
Natural System of Organisms.—Construction of Pedigrees.—Descent
of all Many-celled from Single-celled Organisms.—Descent of
Cells from Monera.—Meaning of Organic Tribes, or Phyla.—Number
of the Tribes in the Animal and Vegetable Kingdoms.—The
Monophyletic Hypothesis of Descent, or the Hypothesis of one
Common Progenitor, and the Polyphyletic Hypothesis of Descent,
or the Hypothesis of many Progenitors.—The Kingdom of Protista,
or Primæval Beings.—Eight Classes of the Protista Kingdom:
Monera, Amœbæ, or Protoplastæ; Whip-swimmers, or Flagellata;
Ciliated-balls, Cili Catallacta; Labyrinth-streamers, or
Labyrinthuleæ; Flint-cells, or Diatomeæ; Mucous-moulds, or
Myxomycetes; Root-footers (Rhizopoda).—Remarks on the General
Natural History of the Protista: Their Vital Phenomena,
Chemical Composition, and Formation (Individuality and
Fundamental Form).—Phylogeny of the Prostista Kingdom 36
CHAPTER XVII.
PEDIGREE AND HISTORY OF THE VEGETABLE KINGDOM.
The Natural System of the Vegetable Kingdom.—Division of the
Vegetable Kingdom into Six Branches and Eighteen Classes.—The
Flowerless Plants (Cryptogamia).—Sub-kingdom of the Thallus
Plants.—The Tangles, or Algæ (Primary Algæ, Green Algæ, Brown
Algæ, Red Algæ).—The Thread-plants, or Inophytes (Lichens and
Fungi).—Sub-kingdom of the Prothallus Plants.—The Mosses, or
Muscinæ (Water-mosses, Liverworts, Leaf-mosses,
Bog-mosses).—The Ferns, or Filicinæ (Leaf-ferns, Bamboo-ferns,
Water-ferns, Scale-ferns).—Sub kingdom of Flowering Plants
(Phanerogamia).—The Gymnosperms, or Plants with Naked Seeds
(Palm-ferns = Cycadeæ; Pines = Coniferæ).—The Angiosperms, or
Plants with Enclosed Seeds.—Monocotylæ.—Dicotylæ.—Cup-blossoms
(Apetalæ).—Star-blossoms (Diapetalæ).—Bell-blossoms
(Gamopetalæ) 77
CHAPTER XVIII.
PEDIGREE AND HISTORY OF THE ANIMAL KINGDOM.
I. ANIMAL-PLANTS AND WORMS.
The Natural System of the Animal Kingdom.—Linnæus’ and Lamarck’s
Systems.—The Four Types of Bär and Cuvier.—Their Increase to
Seven Types.—Genealogical Importance of the Seven Types as
Independent Tribes of the Animal Kingdom.—Derivation of
Zoophytes and Worms from Primæval Animals.—Monophyletic and
Polyphyletic Hypothesis of the Descent of the Animal
Kingdom.—Common Origin of the Four Higher Animal Tribes out of
the Worm Tribe.—Division of the Seven Animal Tribes into
Sixteen Main Classes, and Thirty-eight Classes.—Primæval
Animals (Monera, Amœbæ, Synamœbæ), Gregarines, Infusoria,
Planæades, and Gastræades (Planula and Gastrula).—Tribe of
Zoophytes.—Spongiæ (Mucous Sponges, Fibrous Sponges, Calcareous
Sponges).—Sea Nettles, or Acalephæ (Corals, Hood-jellies,
Comb-jellies).—Tribe of Worms 117
CHAPTER XIX.
PEDIGREE AND HISTORY OF THE ANIMAL KINGDOM.
II. MOLLUSCA, STAR-FISHES, AND ARTICULATED ANIMALS.
Tribe of Molluscs.—Four Classes of Molluscs: Lamp-shells
(Spirobranchia); Mussels (Lamellibranchia); Snails (Cochlides);
Cuttle-fish (Cephalopoda).—Tribe of Star-fishes, or
Echinoderma.—Their Derivation from Ringed Worms (Mailed Worms,
or Phracthelminthes).—The Alternation of Generation in the
Echinoderma.—Four Classes of Star-fish: Sea-stars (Asteridea);
Sea-lilies (Crinoidea); Sea-urchins (Echinidea); Sea-cucumbers
(Holothuridea).—Tribe of Articulated Animals, or
Arthropoda.—Four Classes of Articulated Animals: Branchiata, or
Crustacea, breathing through gills; Jointed Crabs; Mailed
Crabs; Articulata Tracheata, breathing through Air
Tubes.—Spiders (Long Spiders, Round
Spiders).—Myriopods.—Insects.—Chewing and Sucking
Insects.—Pedigree and History of the Eight Orders of Insects 154
CHAPTER XX.
PEDIGREE AND HISTORY OF THE ANIMAL KINGDOM.
III. VERTEBRATE ANIMALS.
The Records of the Creation of Vertebrate Animals (Comparative
Anatomy, Embryology, and Palæontology).—The Natural System of
Vertebrate Animals.—The Four Classes of Vertebrate Animals,
according to Linnæus and Lamarck.—Their Increase to Nine
Classes.—Main Class of the Tube-hearted, or Skull-less Animals
(the Lancelet).—Blood Relationship between the Skull-less Fish
and the Tunicates.—Agreement in the Embryological Development
of Amphioxus and Ascidiæ.—Origin of the Vertebrate Tribe out of
the Worm Tribe.—Main Class of Single-nostriled, or
Round-mouthed Animals (Hag and Lampreys).—Main Class of
Anamnionate Animals, devoid of Amnion.—Fishes (Primæval Fish,
Cartilaginous Fish, Osseous Fish).—Mud-fish, or Dipneusta.—Sea
Dragons, or Halisauria.—Frogs and Salamanders, or Amphibia
(Mailed Amphibia, Naked Amphibia).—Main Class of Amnionate
Animals, or Amniota.—Reptiles (Primary Reptiles, Lizards,
Serpents, Crocodiles, Tortoises, Flying Reptiles, Dragons,
Beaked Reptiles).—Birds (Feather-tailed, Fan-tailed,
Bush-tailed) 192
CHAPTER XXI.
PEDIGREE AND HISTORY OF THE ANIMAL KINGDOM.
IV. MAMMALS.
The System of Mammals according to Linnæus and
Blainville.—Three Sub-classes of Mammals (Ornithodelphia,
Didelphia, Monodelphia).—Ornithodelphia, or Monotrema.—Beaked
Animals (Ornithostoma).—Didelphia, or Marsupials.—Herbivorous
and Carnivorous Marsupials.—Monodelphia, or Placentalia
(Placental Animals).—Meaning of the Placenta.—Tuft
Placentalia.—Girdle Placentalia.—Disc
Placentalia.—Non-deciduates, or Indeciduata.—Hoofed
Animals.—Single and Double-hoofed Animals.—Whales.—Toothless
Animals.—Deciduates, or Animals with
Decidua.—Semi-apes.—Gnawing Animals.—Pseudo-hoofed
Animals.—Insectivora.—Beasts of Prey.—Bats.—Apes 231
CHAPTER XXII.
ORIGIN AND PEDIGREE OF MAN.
The Application of the Theory of Descent to Man.—Its Immense
Importance and Logical Necessity.—Man’s Position in the Natural
System of Animals, among Disco-placental Animals.—Incorrect
Separation of the Bimana and Quadrumana.—Correct Separation of
Semi-apes from Apes.—Man’s Position in the Order of
Apes.—Narrow-nosed Apes (of the Old World) and Flat-nosed Apes
(of America).—Difference of the two Groups.—Origin of Man from
Narrow-nosed Apes.—Human Apes, or Anthropoides.—African
Human-apes (Gorilla and Chimpanzee).—Asiatic Human-apes (Orang
and Gibbon).—Comparison between the different Human Apes and
the different Races of Men.—Survey of the Series of the
Progenitors of Man.—Invertebrate Progenitors (Prochordata) and
Vertebrate Progenitors 263
CHAPTER XXIII.
MIGRATION AND DISTRIBUTION OF MANKIND. HUMAN SPECIES AND HUMAN
RACES.
Age of the Human Race.—Causes of its Origin.—The Origin of
Human Language.—Monophyletic or Single, Polyphyletic or
Multiple Origin of the Human Race.—Derivation of Man from many
Pairs.—Classification of the Human Races.—System of Twelve
Species of Men.—Woolly-Haired Men, or Ulotrichis.—Bushy-Haired
(Papuans, Hottentots).—Fleecy-haired (Caffres,
Negroes).—Straight-haired Men, or Lissotrichi.—Stiff-haired
(Australians, Malays, Mongols, Arctic, and American
Tribes).—Curly-haired (Dravidas, Nubians, Midlanders).—Number
of Population.—Primæval Home of Man (South Asia, or
Lemuria).—Nature of Primæval Men.—Number of Primæval Languages
(Monoglottists and Polyglottists).—Divergence and Migration of
the Human Race.—Geographical Distribution of the Human Species 296
CHAPTER XXIV.
OBJECTIONS AGAINST, AND PROOFS OF THE TRUTH OF, THE THEORY OF
DESCENT.
Objections to the Doctrine of Filiation.—Objections of Faith
and Reason.—Immeasurable Length of the Geological
Periods.—Transition Forms between Kindred Species.—Dependence
of Stability of Form on Inheritance, and of the Variability of
Form on Adaptation.—Origin of very Complicated Arrangement of
Organisation.—Gradual Development of Instincts and Mental
Activities.—Origin of à priori Knowledge from Knowledge a
posteriori.—The Knowledge requisite for the Correct
Understanding of the Doctrine of Filiation.—Necessary
Interaction between Empiricism and Philosophy.—Proofs of the
Theory of Descent.—Inner Causal-Connection between all the
Biological Series of Phenomena.—The Direct Proof of the Theory
of Selection.—Relation of the Theory of Descent to
Anthropology.—Proofs of the Animal Origin of Man.—The Pithecoid
Theory as an Inseparable Part of the Theory of
Descent.—Induction and Deduction.—Gradual Development of the
Human Mind.—Body and Mind.—Human Soul and Animal Soul.—A Glance
at the Future 334
LIST OF WORKS REFERRED TO IN THE TEXT 371
APPENDIX (Explanation of the Plates) 379
INDEX 402
LIST OF ILLUSTRATIONS.
PLATES.
XV.—Hypothetical Sketch of the Monophyletic Origin
of Man _Frontispiece_
IV.—Hand of Nine different Mammals _To face page_ 34
V.—Single-Stemmed, or Monophyletic, Pedigree of the
Vegetable Kingdom ” 112
VI.—Historical Growth of the Six Great Stems of Animals ” 122
VII.—Animal Plants, or Zoophytes ” 140
VIII.—Star Fishes—First Generation _Between pp._ 170, 171
IX.—Star Fishes—Second Generation ” ” ”
X.—Nauplius-Youth-Form of Six Crab Fish ” 174, 175
XI.—Adult-Form of the same Six Crab Fish ” ” ”
XII.—Ascidia and Amphioxus ” 201, 202
XIII.—Ascidia and Amphioxus ” ” ”
XIV.—Single, or Monophyletic, Pedigree of Back-boned
Animals _To face page_ 222
FIGURES.
8.—Protamœba Primitiva 52
9.—Bathybius Hæckelii 53
10.—Amœba Sphærococcus 54
11.—Euglena Striata 57
12.—Magosphæra Planula 58
13.—Labyrinthula Macrocystis 59
14.—Navicula Hippocampus 60
15.—Physarum Albipes 61
16.—Cyrtidosphæra Echinoides 66
17.—Caulerpa Denticulata 87
18.—Euastrum Rota 88
19.—Fucus Vesiculosus (egg of) 90
THE HISTORY OF CREATION.
CHAPTER XV.
PERIODS OF CREATION AND RECORDS OF CREATION.
Reform of Systems by the Theory of Descent.—The Natural System
as a Pedigree.—Palæontological Records of the
Pedigree.—Petrifactions as Records of Creation.—Deposits of the
Neptunic Strata and the Enclosure of Organic Remains.—Division
of the Organic History of the Earth into Five Main Periods:
Period of the Tangle Forests, Fern Forests, Pine Forests,
Foliaceous Forests, and of Cultivation.—The Series of Neptunic
Strata.—Immeasurable Duration of the Periods which have elapsed
during their Formation.—Deposits of Strata only during the
Sinking, not during the Elevation of the Ground.—Other Gaps in
the Records of Creation.—Metamorphic Condition of the most
Ancient Neptunic Strata.—Small Extent of Palæontological
Experience.—Small proportion of Organisms and of Parts of
Organisms Capable of Petrifying.—Rarity of many Petrified
Species.—Want of Fossilised Intermediate Forms.—Records of the
Creation in Ontogeny and in Comparative Anatomy.
The revolutionary influence which the Theory of Descent must exercise
upon all sciences, will in all probability affect no branch of science,
excepting Anthropology, so much as the descriptive portion of natural
history, that which is known as systematic Zoology and Botany. Most
naturalists who have hitherto occupied themselves with arranging the
different systems of animals and plants, have collected, named, and
arranged the different species of these natural bodies with much the
same interest as antiquarians and ethnographers collect the weapons and
utensils of different nations. Many have not even risen above the degree
of intelligence with which people usually collect, label, and arrange
crests, stamps, and similar curiosities. In the same manner as some
collectors find their pleasure in the similarity of forms, the beauty or
rarity of the crests or stamps, and admire in them the inventive art of
man, so many naturalists take a delight in the manifold forms of animals
and plants, and marvel at the rich imagination of the Creator, at His
unwearied creative activity, and at His curious fancy for forming, by
the side of so many beautiful and useful organisms, also a number of
ugly and useless ones.
This childlike treatment of systematic Zoology and Botany is completely
annihilated by the Theory of Descent. In the place of the superficial
and playful interest with which most naturalists have hitherto regarded
organic structures, we now have the much higher interest of the
intelligent understanding which detects in the _related forms_ of
organisms their true _blood relationships_. The _Natural System of
animals and plants_, which was formerly valued either only as a registry
of names, to facilitate the survey of the different forms, or as a table
of contents for the short expression of their degrees of similarity,
receives from the Theory of Descent the incomparably higher value of a
true _pedigree of organisms_. This pedigree is to disclose to us the
genealogical connection of the smaller and larger groups. It has to show
us in what way the different classes, orders, families, genera, and
species of the animal and vegetable kingdoms correspond with the
different branches, twigs, and groups of twigs of the pedigree. Every
wider and higher category or stage of the system (for example a class,
or an order) comprises a number of larger and stronger branches of the
pedigree; every narrower and lower category (for example a genus, or a
species) only a smaller and thinner group of twigs. It is only when we
thus view the natural system as a pedigree that we perceive its true
value. (Gen. Morph. ii. Plate XVII. p. 397.)
Since we hold fast this genealogical conception of the Organic System,
to which alone undoubtedly the future of classificatory Zoology and
Botany belongs, we should now turn our attention to one of the most
essential, but also one of the most difficult, tasks of the
“non-miraculous history of creation,” namely, to the actual construction
of the Organic Pedigree. Let us see how far we are already able to point
out all the different organic forms as the divergent descendants of a
single or of some few common original forms. But how can we construct
the actual pedigree of the animal and vegetable group of forms from our
knowledge of them, at present so scanty and fragmentary? The answer to
this question lies in what we have already remarked of the parallelism
of the three series of development—in the important causal relation
which connects the palæontological development of all organic tribes
with the embryological development of individuals, and with the
systematic development of groups.
In order to accomplish our task we shall first have to direct our
attention to _palæontology_, or _the science of petrifactions_. For if
the Theory of Descent is really true, if the petrified remains of
formerly living animals and plants really proceed from the extinct
primæval ancestors and progenitors of the present organisms, then,
without anything else, the knowledge and comparison of petrifactions
ought to disclose to us the pedigree of organisms. However simple and
clear this may seem in theory, the task becomes extremely hard and
complicated when it is actually taken in hand. Its practical solution
would be very difficult even if the petrifactions were to any extent
completely preserved. But this is by no means the case. The obvious
records of creation which lie buried in petrifactions are imperfect
beyond all measure. Hence it is necessary critically to examine these
records, and to determine the value which petrifactions possess for the
history of the development of organic tribes. As I have previously
discussed the general importance of petrifactions as the records of
creation, when we were considering Cuvier’s merits in the science of
fossils, we may now at once examine the conditions and circumstances
under which the remains of organic bodies became petrified and preserved
in a more or less recognizable form.
As a rule we find petrifactions or fossils enclosed only in those stones
which have been deposited in layers as mud by water, and which are on
that account called neptunic, stratified, or sedimentary rocks. The
deposition of such strata could of course only commence after the
condensation of watery vapour into liquid water had taken place in the
course of the earth’s history. After that period, which we considered in
our last chapter, not only did life begin on the earth, but also an
uninterrupted and exceedingly important transformation of the rigid
inorganic crust of the earth. The water began that extremely important
mechanical action by which the surface of the earth is perpetually,
though slowly, transformed. I may surely presume that it is generally
known what an extremely important influence, in this respect, is even
yet exercised by water at every moment. As it falls down as rain,
trickling through the upper strata of the earth’s crust, and flowing
down from heights into hollows, it chemically dissolves different
mineral parts of the ground, and mechanically washes away the loose
particles. In flowing down from mountains water carries their debris
into the plains, or deposits it as mud in stagnant lakes. Thus it
continually works at lowering mountains and filling up valleys. In like
manner the breakers of the sea work uninterruptedly at the destruction
of the coasts and at filling up the bottom of the sea with the debris
they wash down. The action of water alone, if it were not counteracted
by other circumstances, would in time level the whole earth. There can
be no doubt that the mountain masses—which are annually carried down as
mud into the sea, and deposited on its floor—are so great that in the
course of a longer or shorter period, say a few millions of years, the
surface of the earth would be completely levelled and become enclosed by
a continuous sheet of water. That this does not happen is owing to the
perpetual volcanic action of the fiery-fluid centre of the earth. The
surging of the melted nucleus against the firm crust necessitates
continual alternations of elevation and depression on the different
parts of the earth’s surface. These elevations and depressions for the
most part take place very slowly; but, as they continue for thousands of
years, by the combined effect of small, interrupted movements, they
produce results no less grand than does the counteracting and levelling
action of water.
Since the elevations and depressions of the different parts of the
earth alternate with one another in the course of millions of years,
first this and then that part of the earth’s surface is above or below
the level of the sea. I have already given examples of this in the
preceding chapter (vol. i. p. 361). Hence, in all probability, there is
no part of the outer crust of the earth which has not been repeatedly
above and also below the level of the sea. This repeated change explains
the variety and the different composition of the numerous neptunic
strata of rocks, which in most places have been deposited one above
another in considerable thickness. In the different periods of the
earth’s history during which these deposits took place there lived
various and different populations of animals and plants. When their dead
bodies sank to the bottom of the waters, the forms of the bodies
impressed themselves upon the soft mud, and imperishable parts, such as
hard bones, teeth, shells, etc., became enclosed in it uninjured. These
were preserved in the mud, which condensed them into neptunic rock, and
as petrifactions they now serve to characterise the respective strata.
By a careful comparison of the different strata lying one above another,
and the petrifactions preserved in them, it has become possible to
decide the relative age of the strata and groups of strata, and to
establish, by direct observation, the principal eras of phylogeny, that
is to say, the stages in history of the development of animal and
vegetable tribes.
The different strata of neptunic rocks deposited one above another,
which are composed in very various ways of limestone, clay, and sand,
geologists have grouped together into an ideal System or Series, which
corresponds with the whole course of the organic history of the earth,
or with that portion of the earth’s history during which organic life
existed. Just as so-called “universal history” falls into larger and
smaller periods, which are characterized by the conditions of
development of the most important nations at the respective epochs, and
are separated from one another by great events, so we also divide the
infinitely longer organic history of the earth into a series of greater
and less periods. Each of these periods is distinguished by a
characteristic flora and fauna, and by the specially strong development
of certain vegetable or animal groups, and each is separated from the
preceding and succeeding period by a striking change in the character of
its animal and vegetable inhabitants.
In relation to the following survey of the historical course of
development which the large animal and vegetable tribes have passed
through, it will be desirable to say a few words first as to the
systematic classification of the neptunic groups of strata, and the
larger and smaller periods corresponding to them. As will be seen
directly, we are able to divide the whole of the sedimentary rocks lying
one above another into five main groups or periods, each period into
several subordinate groups of strata or _systems_, and each system of
strata again into still smaller groups or _formations_; finally, each
formation can again be divided into stages or sub-formations, and each
of these again into still smaller layers or beds. Each of the five great
rock-groups was deposited during a great division of the earth’s
history, during a long _era_ or _epoch_; each system during a shorter
_period_; each formation during a still shorter _period_. In thus
reducing the periods of the organic history of the earth, and the
neptunic strata containing petrifactions deposited during those periods
into a connected system, we proceed exactly like the historian who
divides the history of nations into the three main divisions of
Antiquity, the Middle Ages, and Modern Times, and each of those sections
again into subordinate periods and epochs. But the historian by this
sharp systematic division, and by fixing the boundary of the periods by
particular dates, only seeks to facilitate his survey, and in no way
means to deny the uninterrupted connection of events and the development
of nations. Exactly the same qualification applies to our systematic
division, specification, or classification of the organic history of the
earth. Here, too, a continuous thread runs through the series of events
unbroken. We must therefore distinctly protest against the idea that by
sharply bounding the larger and smaller groups of strata, and the
periods corresponding with them, we in any way wish to adopt Cuvier’s
doctrine of terrestrial revolutions, and of repeated new creations of
organic populations. That this erroneous doctrine has long since been
completely refuted by Lyell, I have already mentioned. (Compare vol. i.
p. 127.)
The five great main divisions of the organic history of the earth, or
the palæontological history of development, we call the primordial,
primary, secondary, tertiary, and quaternary epochs. Each is distinctly
characterized by the predominating development of certain animal and
vegetable groups in it, and we might accordingly symbolically designate
the five epochs, on the one hand by the names of the groups of the
vegetable kingdom, and on the other hand by those of the different
classes of vertebrate animals. In this case the _first_, or primordial
epoch, would be the era of the Tangles (Algæ) and skull-less
Vertebrates; the _second_, or primary epoch, that of the Ferns and
Fishes; the _third_, or secondary epoch, that of Pine Forests and
Reptiles; the _fourth_, or tertiary epoch, that of Foliaceous Forests
and of Mammals; finally, the _fifth_, or quaternary epoch, the era of
Man, and his Civilization. The divisions or _periods_ which we
distinguish in each of the five _long eras_ (p. 14) are determined by
the different _systems_ of strata into which each of the five great
_rock-groups_ is divided (p. 15). We shall now take a cursory glance at
the series of these systems, and at the same time at the populations of
the five great epochs.
The first and longest division of the organic history of the earth is
formed by the _primordial epoch_, or _the era of the Tangle Forests_. It
comprises the immense period from the first spontaneous generation, from
the origin of the first terrestrial organism, to the end of the Silurian
system of deposits. During this immeasurable space of time, which in all
probability was much longer than all the other four epochs taken
together, the three most extensive of all the neptunic systems of strata
were deposited, namely, the _Laurentian_, upon that the _Cambrian_, and
upon that the _Silurian_ system. The approximate thickness or size of
these three systems together amounts to 70,000 feet. Of these about
30,000 belong to the Laurentian, 18,000 to the Cambrian, and 22,000 to
the Silurian system. The average thickness of all the four other rock
groups, the primary, secondary, tertiary, and quaternary, taken
together, may amount at most to 60,000 feet; and from this fact alone,
apart from many other reasons, it is evident that the duration of the
primordial period was probably much longer than the duration of all the
subsequent periods down to the present day. Many thousands of millions
of years were required to deposit such masses of strata. Unfortunately,
by far the largest portion of the primordial group of strata is in the
metamorphic state (which we shall directly explain), and consequently
the petrifactions contained in them—the most ancient and most important
of all—have, to a great extent, been destroyed and become
unrecognisable. Only in one portion of the Cambrian strata have
petrifactions been preserved in a recognizable condition and in large
quantities. The most ancient of all distinctly preserved petrifactions
has been found in the lowest Laurentian strata (in the Ottawa
formation), which I shall afterwards have to speak of as the “Canadian
Life’s-dawn” (Eozoon canadense).
Although only by far the smaller portion of the primordial or
archilithic petrifactions are preserved to us in a recognizable
condition, still they possess the value of inestimable documents of the
most ancient and obscure times of the organic history of the earth. What
seems to be shown by them, in the first place, is that during the whole
of this immense period there existed only inhabitants of the waters. As
yet, at any rate, among all archilithic petrifactions, not a single one
has been found which can with certainty be regarded as an organism which
has lived on land. All the vegetable remains we possess of the
primordial period belong to the lowest of all groups of plants, to the
class of Tangles or Algæ, living in water. In the warm primæval sea,
these constituted the forests of the period, of the richness of which in
forms and density we may form an approximate idea from their present
descendants, the tangle forests of the Atlantic Sargasso sea. The
colossal tangle forests of the archilithic period supplied the place of
the forest vegetation of the mainland, which was then utterly wanting.
All the animals, also, whose remains have been found in archilithic
strata, like the plants, lived in water. Only crustacea are met with
among the animals with articulated feet, as yet no spiders and no
insects. Of vertebrate animals, only a very few remains of fishes are
known as having been found in the most recent of all primordial strata,
in the upper Silurian. But the headless vertebrate animals, which we
call _skull-less_, or _Acrania_, and out of which fishes must have been
developed, we suppose to have lived in great numbers during the
primordial epoch. Hence we may call it after the _Acrania_ as well as
after the _Tangles_.
The _primary epoch_, or _the era of Fern Forests_, the second main
division of the organic history of the earth, which is also called the
palæolithic or palæozoic period, lasted from the end of the Silurian
formation of strata to the end of the Permian formation. This epoch was
also of very long duration, and again falls into three shorter periods,
during which three great systems of strata were deposited, namely,
first, the _Devonian_ system, or the old red sandstone; upon that, the
_Carboniferous_, or coal system; and upon this, the _Permian_ system.
The average thickness of these three systems taken together may amount
to about 42,000 feet, from which we may infer the immense length of time
requisite for their formation.
The Devonian and Permian formations are especially rich in remains of
fishes, of primæval fish as well as enamelled fish (Ganoids), but the
bony fish (Teleostei) are absent from the strata of the primary epoch.
In coal are found the most ancient remains of animals living on land,
both of articulated animals (spiders and insects) as well as of
vertebrate animals (amphibious animals, like newts and frogs). In the
Permian system there occur, in addition to the amphibious animals, the
more highly-developed reptiles, and, indeed, forms nearly related to our
lizards (Proterosaurus, etc.). But, nevertheless, we may call the
primary epoch that of _Fishes_, because these few amphibious animals and
reptiles are insignificant in comparison with the immense mass of
palæozoic fishes. Just as Fishes predominate over the other vertebrate
animals, so _Ferns_, or Filices, predominate among the plants of this
epoch, and, in fact, real ferns and tree ferns (leafed ferns, or
Phylopteridæ), as well as bamboo ferns (Calamophytæ) and scaled ferns
(Lepidophytæ). These ferns, which grew on land, formed the chief part of
the dense palæolithic island forests, the fossil remains of which are
preserved to us in the enormously large strata of coal of the
Carboniferous system, and in the smaller strata of coal of the Devonian
and Permian systems. We are thus justified in calling the primary epoch
either the era of _Ferns_ or that of _Fishes_.
The third great division of the palæontological history of development
is formed by the _secondary epoch_, or the _era of Pine Forests_, which
is also called the mesolithic or mesozoic epoch. It extends from the end
of the Permian system to the end of the Chalk formation, and is again
divided into three great periods. The stratified systems deposited
during this period are, first and lowest, the _Triassic_ system, in the
middle the _Jura_ system, and at the top the _Cretaceous_ system. The
average thickness of these three systems taken together is much less
than that of the primary group, and amounts as a whole only to about
15,000 feet. The secondary epoch can accordingly in all probability not
have been half so long as the primary epoch.
Just as Fishes prevailed in the primary epoch, _Reptiles_ predominated
in the secondary epoch over all other vertebrate animals. It is true
that during this period the first birds and mammals originated; at that
time, also, there existed important amphibious animals, especially the
gigantic Labyrinthodonts, in the sea the wonderful sea-dragons, or
Halisaurii, swam about, and the first fish with bones were associated
with the many primæval fishes (Sharks) and enamelled fish (Ganoids) of
the earlier times; but the very variously developed kinds of reptiles
formed the predominating and characteristic class of vertebrate animals
of the secondary epoch. Besides those reptiles which were very nearly
related to the present living lizards, crocodiles, and turtles, there
were, during the mesolithic period, swarms of grotesquely shaped
dragons. The remarkable flying lizards, or Pterosaurii, and the colossal
land-dragons, or Dinosaurii, of the secondary epoch, are peculiar, as
they occur neither in the preceding nor in the succeeding epochs. The
secondary epoch may be called the era of _Reptiles_; but on the other
hand, it may also be called the era of _Pine Forests_, or more
accurately, of the _Gymnosperms_, that is, the epoch of _plants having
naked seeds_. For this group of plants, especially as represented by the
two important classes—the pines, or _Coniferæ_, and the palm-ferns, or
_Cycadeæ_—during the secondary epoch constituted a predominant part of
the forests. But towards the end of the epoch (in the Chalk period) the
plants of the pine tribe gave place to the leaf-bearing forests which
then developed for the first time.
SURVEY
_Of the Palæontological Periods, or of the Greater Divisions of the
Organic History of the Earth._
I. _First Epoch_: ARCHILITHIC ERA. _Primordial Epoch._
(Era of Skull-less Animals and Forests of Tangles.)
1. Older Primordial Period or Laurentian Period.
2. Middle Primordial Period ” Cambrian Period.
3. Later Primordial Period ” Silurian Period.
II. _Second Epoch_: PALÆOLITHIC ERA. _Primary Epoch._
(Era of Fish and Fern Forests.)
4. Older Primary Period or Devonian Period.
5. Mid Primary Period ” Coal Period.
6. Later Primary Period ” Permian Period.
III. _Third Epoch_: MESOLITHIC ERA. _Secondary Epoch._
(Era of Reptiles and Pine Forests.)
7. Older Secondary Period or Trias Period.
8. Middle Secondary Period ” Jura Period.
9. Later Secondary Period ” Chalk Period.
IV. _Fourth Epoch_: CÆNOLITHIC ERA. _Tertiary Epoch._
(Era of Mammals and Leaf Forests.)
10. Older Tertiary Period or Eocene Period.
11. Newer Tertiary Period ” Miocene Period.
12. Recent Tertiary Period ” Pliocene Period.
V. _Fifth Epoch_: ANTHROPOLITHIC ERA. _Quaternary Epoch._
(Era of Man and Cultivated Forests.)
13. Older Quaternary Period or Ice or Glacial Period.
14. Newer Quaternary Period ” Post Glacial Period.
15. Recent Quaternary Period ” Period of Culture.
(The Period of Culture is the Historical Period, or the Period of
Tradition.)
SURVEY
_Of the Palæontological Formations, or those Strata of the Earth’s Crust
containing Petrifactions._
--------------------+-------------------+----------------------+--------------
_Rock-Groups._ | _Systems._ | _Formations._ | _Synonyms of
| | | Formations._
--------------------+-------------------+----------------------+-------------
V. _Quaternary { |
Group_, { XIV. Recent { 36. _Present_ | Upper alluvial
or { (Alluvium) { 35. _Recent_ | Lower alluvial
Anthropolithic { |
(Anthropozoic) { XIII. Pleistocene { 34. _Post glacial_ | Upper diluvial
groups of { (Diluvium) { 33. _Glacial_ | Lower diluvial
strata { |
IV. _Tertiary { XII. Pliocene { 32. _Arvernian_ | Upper pliocene
Group_, { (Late tertiary) { 31. _Sub-Appenine_ | Lower pliocene
or { |
Cænolithic { XI. Miocene { 30. _Falunian_ | Upper miocene
(Cænozoic) { (New tertiary) { 29. _Limburgian_ | Lower miocene
groups of { |
strata { { 28. _Gypsum_ | Upper eocene
{ X. Eocene { 27. _Nummulitic_ | Mid eocene
{ (Old tertiary) { 26. _London clay_ | Lower eocene
{ { 25. _White chalk_ | Upper cretaceous
{ IX. Cretaceous { 24. _Green sand_ | Mid cretaceous
{ { 23. _Neocomian_ | Lower cretaceous
III. _Secondary { { 22. _Wealden_ | The Kentish Weald
Group_, {
or { { 21. _Portlandian_ | Upper oolite
Mesolithic { VIII. Jura { 20. _Oxfordian_ | Mid oolite
(Mesozoic) { { 19. _Bath_ | Lower oolite
groups of { { 18. _Lias_ | Lias formation
strata {
{ { 17. _Keuper_ | Upper trias
{ VII. Trias { 16. _Muschel-kalk_ | Mid trias
{ { 15. _Bunter sand_ | Lower trias
{ VI. Permian { 14. _Zechstein_ | Upper Permian
II. _Primary { { 13. | Lower Permian
Group_, { { 12. _Carboniferous |
or { V. Carbonic sandstone_ | Upper carbonic
Palæolithic { (coal) { 11. _Carboniferous |
(Palæozoic) { { limestone_ | Lower carbonic
groups of { IV. Devonian { 10. _Pilton_ | Upper Devonian
strata {(Old red sandstone){ 9. _Ilfracombe_ | Mid Devonian
{ 8. _Linton_ | Lower Devonian
I. _Primordial { { 7. _Ludlow_ | Upper Silurian
Group_, { III. Silurian { 6. _Llandovery_ | Mid Silurian
or { { 5. _Llandeilo_ | Lower Silurian
Archilithic {
(Archizoic) { II. Cambrian { 4. _Potsdam_ | Upper Cambrian
groups of { { 3. _Longmynd_ | Lower Cambrian
strata {
{ I. Laurentian { 2. _Labrador_ | Upper Laurentian
{ { 1. _Ottawa_ | Lower Laurentian
The fourth main division of the organic history of the earth, the
_tertiary epoch_, or _era of Leafed Forests_, is much shorter and less
peculiar than the three first epochs. This epoch, which is also called
the cænolithic or cænozoic epoch, extended from the end of the
cretaceous system to the end of the pliocene system. The strata
deposited during it amount only to a thickness of about 3000 feet, and
consequently are much inferior to the three first great groups. The
three systems also into which the tertiary period is subdivided are very
difficult to distinguish from one another. The oldest of them is called
_eocene_, or old tertiary; the newer _miocene_, or mid tertiary; and the
last is the _pliocene_, or later tertiary system.
The whole population of the tertiary epoch approaches much nearer, on
the whole as well as in detail, to that of the present time than is the
case in the preceding epochs. From this time the class of _Mammals_
greatly predominates over all other vertebrate animals. In like manner,
in the vegetable kingdom, the group—so rich in forms—of the
_Angiosperms_, or _plants with covered seeds_, predominates, and its
_leafy forests_ constitute the characteristic feature of the tertiary
epoch. The group of the Angiosperms consists of the two classes of
single-seed-lobed plants, or _Monocotyledons_, and the double-seed-lobed
plants, or _Dicotyledons_. The Angiosperms of both classes had, it is
true, made their appearance in the Cretaceous period, and mammals had
already occurred in the Jurassic period, and even in the Triassic
period; but both groups, the mammals and the plants with enclosed seeds,
did not attain their peculiar development and supremacy until the
tertiary epoch, so that it may justly be called after them.
The fifth and last main division of the organic history of the earth is
the _quaternary epoch, or era of Civilization_, which in comparison with
the length of the four other epochs almost vanishes into nothing, though
with a comical conceit we usually call its record the “history of the
world.” As the period is characterized by the development of _Man_ and
his _Culture_, which has influenced the organic world more powerfully
and with greater transforming effect than have all previous conditions,
it may also be called the era of Man, the anthropolithic or anthropozoic
period. It might also be called the era of Cultivated Forests, or
Gardens, because even at the lowest stage of human civilization man’s
influence is already perceptible in the utilization of forests and their
products, and therefore also in the physiognomy of the landscape. The
commencement of this era, which extends down to the present time, is
geologically bounded by the end of the pliocene stratification.
The neptunic strata which have been deposited during the comparatively
short quaternary epoch are very different in different parts of the
earth, but they are mostly of very slight thickness. They are reduced to
two “systems,” the older of which is designated the _diluvial_, or
_pleistocene_, and the later the _alluvial_, or _recent_. The diluvial
system is again divided into two “formations,” the older _glacial_ and
the more recent _post glacial_ formations. For during the older diluvial
period there occurred that extremely remarkable decrease of the
temperature of the earth which led to an extensive glaciation of the
temperate zones. The great importance which this “ice” or “glacial
period” has exercised on the geographical and topographical distribution
of organisms has already been explained in the preceding chapter (vol.
i. p. 365). But the _post glacial period_, or the more recent diluvial
period, during which the temperature again increased and the ice
retreated towards the poles, was also highly important in regard to the
present state of chorological relations.
The biological characteristic of the quaternary epoch lies essentially
in the development and dispersion of the human organism and his culture.
Man has acted with a greater transforming, destructive, and modifying
influence upon the animal and vegetable population of the earth than any
other organism. For this reason, and not because we assign to man a
privileged exceptional position in nature in other matters, we may with
full justice designate the development of man and his civilization as
the beginning of a special and last main division of the organic history
of the earth. It is probable indeed that the corporeal development of
primæval man out of man-like apes took place as far back as the earlier
pliocene period, perhaps even in the miocene tertiary period. But the
actual development of _human speech_, which we look upon as the most
powerful agency in the development of the peculiar characteristics of
man and his dominion over other organisms, probably belongs to that
period which on geological grounds is distinguished from the preceding
pliocene period as the pleistocene or diluvial. In fact the time which
has elapsed from the development of human speech down to the present
day, though it may comprise many thousands and perhaps hundreds of
thousands of years, almost vanishes into nothing as compared with the
immeasurable length of the periods which have passed from the beginning
of organic life on the earth down to the origin of the human race.
The tabular view given on page 15 shows the succession of the
palæontological rock-groups, systems, and formations, that is, the
larger and smaller neptunic groups of strata, which contain
petrifactions, from the uppermost, or Alluvial, down to the lowest, or
Laurentian, deposits. The table on page 14 presents the historical
division of the corresponding eras of the larger and smaller
palæontological periods, and in a reversed succession, from the most
ancient Laurentian up to the most recent Quaternary period.
Many attempts have been made to make an approximate calculation of the
number of thousands of years constituting these periods. The thickness
of the strata has been compared, which, according to experience, is
deposited during a century, and which amounts only to some few lines or
inches, with the whole thickness of the stratified masses of rock, the
succession of which we have just surveyed. This thickness, on the whole,
may on an average amount to about 130,000 feet; of these 70,000 belong
to the primordial, or archilithic; 42,000 to the primary, or
palæolithic; 15,000 to the secondary, or mesolithic; and finally only
3,000 to the tertiary, or cænolithic group. The very small and scarcely
appreciable thickness of the quaternary, or anthropolithic deposit
cannot here come into consideration at all. On an average, it may at
most be computed as from 500 to 700 feet. But it is self evident that
all these measurements have only an average and approximate value, and
are meant to give only a rough survey of the _relative_ proportion of
the systems of strata and of the spaces of time corresponding with them.
Now, if we divide the whole period of the organic history of the
earth—that is, from the beginning of life on the earth down to the
present day—into a hundred equal parts, and if then, corresponding to
the thickness of the systems of strata, we calculate the relative
duration of the time of the five main divisions or periods according to
percentages, we obtain the following result:—
I. Archilithic, or primordial period 53.6
II. Palæolithic, or primary period 32.1
III. Mesolithic, or secondary period 11.5
IV. Cænolithic, or tertiary period 2.3
V. Anthropolithic, or quaternary period 0.5
-----
Total 100.0
According to this, the length of the archilithic period, during which no
land-living animals or plants as yet existed, amounts to more than one
half, more than 53 per cent.; on the other hand the length of the
anthropolithic era, during which man has existed, amounts to scarcely
one-half per cent. of the whole length of the organic history of the
earth. It is, however, quite impossible to calculate the length of these
periods, even approximately, by years.
The thickness of the strata of mud at present deposited during a
century, and which has been used as a basis for this calculation, is of
course quite different in different parts of the earth under the
different conditions in which these deposits take place. It is very
slight at the bottom of the deep sea, in the beds of broad rivers with a
short course, and in inland seas which receive very scanty supplies of
water. It is comparatively great on the sea-shores exposed to strong
breakers, at the estuaries of large rivers with long courses, and in
inland seas with copious supplies of water. At the mouth of the
Mississippi, which carries with it a considerable amount of mud, in the
course of 100,000 years about 600 feet would be deposited. At the bottom
of the open sea, far away from the coasts, during this long period only
some few feet of mud would be deposited. Even on the sea-shores where a
comparatively large quantity of mud is deposited the thickness of the
strata formed during the course of a century may after all amount to no
more than a few inches or lines when condensed into solid stone. In any
case, however, all calculations based upon these comparisons are very
unsafe, and we cannot even approximately conceive the enormous length of
the periods which were requisite for the formation of the systems of
neptunic strata. Here we can apply only relative, not absolute,
measurements of time.
Moreover, we should entirely err were we to consider the size of these
systems of strata alone as the measure of the actual space of time which
has elapsed during the earth’s history. For the elevations and
depressions of the earth’s crust have perpetually alternated with one
another, and the mineralogical and palæontological difference—which is
perceived between each two succeeding systems of strata, and between
each two of their formations at any particular spot—corresponds in all
probability with a considerable intermediate space of many thousands of
years, during which that particular part of the earth’s crust was raised
above the water. It was only after the lapse of this intermediate
period, when a new depression again laid the part in question under
water, that there occurred a new deposit of earth. As, in the mean time,
the inorganic and organic conditions on this part had undergone a
considerable transformation, the newly-formed layer of mud was
necessarily composed of different earthy constituents and enclosed
different petrifactions.
IV. Tertiary Group of |
Strata, 3,000 feet. | Eocene, Miocene, Pliocene.
---------------------------------+------------------------------
| IX. Chalk System.
III. Mesolithic Group of Strata. |
|
Deposits of the | VIII. Jura System.
Secondary Epoch, about |
15,000 feet. |
| VII. Trias System.
---------------------------------+------------------------------
|
| VI. Permian System.
II. Palæolithic Group of Strata. |
|
Deposits of the | V. Coal System.
Primary Epoch, about |
42,000 feet. | IV. Devonian System.
---------------------------------+------------------------------
|
| III. Silurian System, about
| 22,000 feet.
I. Archilithic Group of Strata. |
|
Deposits of the | II. Cambrian System, about
Primordial Epoch, about | 18,000 feet.
70,000 feet. |
| I. Laurentian System, about
| 30,000 feet.
The striking differences which so frequently occur between the
petrifactions of two strata, lying one above another, are to be
explained in a simple and easy manner by the supposition that the same
part of the earth’s surface has been exposed to _repeated depressions
and elevations_. Such alternating elevations and depressions take place
even now extensively, and are ascribed to the heaving of the fiery fluid
nucleus against the rigid crust. Thus, for example, the coast of Sweden
and a portion of the west coast of South America are constantly though
slowly rising, while the coast of Holland and a portion of the east
coast of South America are gradually sinking. The rising as well as the
sinking takes place very slowly, and in the course of a century
sometimes only amounts to some few lines, sometimes to a few inches, or
at most a few feet. But if this action continues uninterruptedly
throughout hundreds of thousands of years it is capable of forming the
highest mountains.
It is evident that elevations and depressions, such as now can be
measured in these places, have uninterruptedly alternated one with
another in different places during the whole course of the organic
history of the earth. This may be inferred with certainty from the
geographical distribution of organisms. (Compare vol. i. p. 350.) But to
form a judgment of our palæontological records of creation it is
extremely important to show that permanent strata can only be deposited
during a slow sinking of the ground under water, but not during its
continued rising. When the ground slowly sinks more and more below the
level of the sea, the deposited layers of mud get into continually
deeper and quieter water, where they can become condensed into stone
undisturbed. But when, on the other hand, the ground slowly rises, the
newly-deposited layers of mud, which enclose the remains of plants and
animals, again immediately come within the reach of the play of the
waves, and are soon worn away by the force of the breakers, together
with the organic remains which they on close. For this simple but very
important reason, therefore, abundant layers, in which organic remains
are preserved, can only be deposited during a continuous sinking of the
ground. When any two different formations or strata, lying one above the
other, correspond with two different periods of depression, we must
assume a long period of rising between them, of which period we know
nothing, because no fossil remains of the then living animals and plants
could be preserved. It is evident, however, that those _periods of
elevation_, which have passed without leaving any trace behind them,
deserve a no less careful consideration than the greater or less
alternating _periods of depression_, of whose organic population we can
form an approximate idea from the strata containing petrifactions.
Probably the former were not of shorter duration than the latter.
From this alone it is apparent how imperfect our records must
necessarily be, and all the more so since it can be theoretically proved
that the variety of animal and vegetable life must have increased
greatly during those very periods of elevation. For as new tracts of
land are raised above the water, new islands are formed. Every new
island, however, is a new centre of creation, because the animals and
plants accidentally cast ashore there, find in the new territory, in
the struggle for life, abundant opportunity of developing themselves
peculiarly, and of forming new species. The formation of new species has
evidently taken place pre-eminently during these intermediate periods,
of which, unfortunately, no petrifactions could be preserved, whereas,
on the contrary, during the slow sinking of the ground there was more
chance of numerous species dying out, and of a retrogression into fewer
specific forms. The intermediate forms between the old and the
newly-forming species must also have lived during the periods of
elevation, and consequently could likewise leave no fossil remains.
In addition to the great and deplorable gaps in the palæontological
records of creation—which are caused by the periods of elevation—there
are, unfortunately, many other circumstances which immensely diminish
their value. I must mention here especially the _metamorphic state of
the most ancient formations_, of those strata which contain the remains
of the most ancient flora and fauna, the original forms of all
subsequent organisms, and which, therefore, would be of especial
interest. It is just these rocks—and, indeed, the greater part of the
primordial, or archilithic strata, almost the whole of the Laurentian,
and a large part of the Cambrian systems—which no longer contain any
recognizable remains, and for the simple reason that these strata have
been subsequently changed or metamorphosed by the influence of the fiery
fluid interior of the earth. These deepest neptunic strata of the crust
have been completely changed from their original condition by the heat
of the glowing nucleus of the earth, and have assumed a crystalline
state. In this process, however, the form of the organic remains
enclosed in them has been entirely destroyed. It has been preserved only
here and there by a happy chance, as in the case of the most ancient
petrifactions known, the _Eozoon canadense_, from the lowest Laurentian
strata. However, from the layers of crystalline charcoal (graphite) and
crystalline limestone (marble), which are found deposited in the
metamorphic rocks, we may with certainty conclude that petrified animal
and vegetable remains existed in them in earlier times.
Our record of creation is also extremely imperfect from the circumstance
that only a small portion of the earth’s surface has been accurately
investigated by geologists, namely, England, Germany, and France. But we
know very little of the other parts of Europe, of Russia, Spain, Italy,
and Turkey. In the whole of Europe, only some few parts of the earth’s
crust have been laid open, by far the largest portion of it is unknown
to us. The same applies to North America and to the East Indies. There
some few tracts have been investigated; but of the larger portion of
Asia, the most extensive of all continents, we know almost nothing; of
Africa nothing, excepting the Cape of Good Hope and the shores of the
Mediterranean; of Australia almost nothing; and of South America but
very little. It is clear, therefore, that only quite a small portion,
perhaps scarcely the thousandth part of the whole surface of the earth,
has been palæontologically investigated. We may therefore reasonably
hope, when more extensive geological investigations are made, which are
greatly assisted by the constructions of railroads and mines, to find a
great number of other important petrifactions. A hint that this will be
the case is given by the remarkable petrifactions found in those parts
of Africa and Asia which have been minutely investigated,—the Cape
districts and the Himalaya mountains. A series of entirely new and very
peculiar animal forms have become known to us from the rocks of these
localities. But we must bear in mind that the vast bottom of the
existing oceans is at the present time quite inaccessible to
palæontological investigations, and that the greater part of the
petrifactions which have lain there from primæval times will either
never be known to us, or at best only after the course of many thousands
of years, when the present bottom of the ocean shall have become
accessible by gradual elevation. If we call to mind the fact that
three-fifths of the whole surface of the earth consists of water, and
only two-fifths of land, it becomes plain that on this account the
palæontological record must always present an immense gap.
But, in addition to these, there exists another series of difficulties
in the way of palæontology which arises from the nature of the organisms
themselves. In the first place, as a rule only the hard and solid parts
of organisms can fall to the bottom of the sea or of fresh waters, and
be there enclosed in the mud and petrified. Hence it is only the bones
and teeth of vertebrate animals, the calcareous shells of molluscs, the
chitinous skeletons of articulated animals, the calcareous skeletons of
star-fishes and corals, and the woody and solid parts of plants, that
are capable of being petrified. But soft and delicate parts, which
constitute by far the greater portion of the bodies of most organisms,
are very rarely deposited in the mud under circumstances favourable to
their becoming petrified, or distinctly impressing their external form
upon the hardening mud. Now, it must be borne in mind that large classes
of organisms, as for example the Medusæ, the naked molluscs without
shells, a large portion of the articulated animals, almost all worms,
and even the lowest vertebrate animals, possess no firm and hard parts
capable of being petrified. In like manner the most important parts of
plants, such as the flowers, are for the most part so soft and tender
that they cannot be preserved in a recognizable form. We therefore
cannot expect to find any petrified remains of these important
organisms. Moreover, all organisms at an early stage of life are so soft
and tender that they are quite incapable of being petrified.
Consequently all the petrifactions found in the neptunic stratifications
of the earth’s crust comprise altogether but a very few forms, and of
these for the most part only isolated fragments.
We must next bear in mind that the dead bodies of the inhabitants of the
sea are much more likely to be preserved and petrified in the deposits
of mud than those of the inhabitants of fresh water and of the land.
Organisms living on land can, as a rule, become petrified only when
their corpses fall accidentally into the water and are buried at the
bottom in the hardening layers of mud. But this event depends upon very
many conditions. We cannot therefore be astonished that by far the
majority of petrifactions belong to organisms which have lived in the
sea, and that of the inhabitants of the land proportionately only very
few are preserved in a fossil state. How many contingencies come into
play here we may infer from the single fact that of many fossil mammals,
in fact of all the mammals of the secondary, or mesozoic epoch, nothing
is known except the lower jawbone. This bone is in the first place
comparatively solid, and in the second place very easily separates
itself from the dead body, which floats on the water. Whilst the body is
driven away and dissolved by the water, the lower jawbone falls down to
the bottom of the water and is there enclosed in the mud. This explains
the remarkable fact that in a stratum of limestone of the Jurassic
system near Oxford, in the slates of Stonesfield, as yet only the lower
jawbones of numerous pouched animals (Marsupials) have been found. They
are the most ancient mammals known, and of the whole of the rest of
their bodies not a single bone exists. The opponents of the theory of
development, according to their usual logic, would from this fact be
obliged to draw the conclusion that the lower jawbone was the only bone
in the body of those animals.
Footprints are very instructive when we attempt to estimate the many
accidents which so arbitrarily influence our knowledge of fossils; they
are found in great numbers in different extensive layers of sandstone;
for example, in the red sandstone of Connecticut, in North America.
These footprints were evidently made by vertebrate animals, probably by
reptiles, of whose bodies not the slightest trace has been preserved.[1]
The impressions which their feet have left on the mud alone betray the
former existence of these otherwise unknown animals.
The accidents which, besides these, determine the limits of our
palæontological knowledge, may be inferred from the fact that we know of
only one or two specimens of very many important petrifactions. It is
not ten years since we became acquainted with the imperfect impression
of a bird in the Jurassic or Oolitic system, the knowledge of which
has been of the very greatest importance for the phylogeny of the whole
class of birds. All birds previously known presented a very uniformly
organized group, and showed no striking transitional forms to other
vertebrate classes, not even to the nearly related reptiles. But that
fossil bird from the Jura possessed not an ordinary bird’s tail, but a
lizard’s tail, and thus confirmed what had been conjectured upon other
grounds, namely, the derivation of birds from lizards. This single
fossil has thus essentially extended not only our knowledge of the age
of the class of birds, but also of their blood relationship to reptiles.
In like manner our knowledge of other animal groups has been often
essentially modified by the accidental discovery of a single fossil. The
palæontological records must necessarily be exceedingly imperfect,
because we know of so very few examples, or only mere fragments of very
many important fossils.
Another and very sensible gap in these records is caused by the
circumstance that the _intermediate forms_ which connect the different
species have, as a rule, not been preserved, and for the simple reason
that (according to the principle of divergence of character) they were
less favoured in the struggle for life than the most divergent
varieties, which had developed out of one and the same original form.
The intermediate links have, on the whole, always died out _rapidly_,
and have but rarely been preserved as fossils. On the other hand, the
most divergent forms were able to maintain themselves in life for a
longer period as independent species, to propagate more numerously, and
consequently to be more readily petrified. But this does not exclude the
fact that in _some_ cases the connecting intermediate forms of the
species have been preserved so perfectly petrified, that even now they
cause the greatest perplexity and occasion endless disputes among
systematic palæontologists about the arbitrary limits of species.
An excellent example of this is furnished by the celebrated and very
variable fresh-water snail from the Stuben Valley, near Steinheim, in
Würtemburg, which has been described sometimes as _Paludina_, sometimes
as _Valvata_, and sometimes as _Planorbis multiformis_. The snow-white
shells of these small snails constitute more than half of the mass of
the tertiary limestone hills, and in this one locality show such an
astonishing variety of forms, that the most divergent extremes might be
referred to at least twenty entirely different species. But all these
extreme forms are united by such innumerable intermediate forms, and
they lie so regularly above and beside one another, that Hilgendorf was
able, in the clearest manner, to unravel the pedigree of the whole group
of forms. In like manner, among very many other fossil species (for
example, many ammonites, terebratulæ, sea urchins, lily encrinites,
etc.) there are such masses of connecting intermediate forms, that they
reduce the “dealers in fossil species” to despair.
When we weigh all the circumstances here mentioned, the number of which
might easily be increased, it does not appear astonishing that the
natural accounts or records of creation formed by petrifactions are
extremely defective and incomplete. But nevertheless, the petrifactions
actually discovered are of the greatest value. Their significance is of
no less importance to the natural history of creation than the
celebrated inscription on the Rosetta stone, and the decree of Canopus,
are to the history of nations—to archæology and philology. Just as it
has become possible by means of these two most ancient inscriptions to
reconstruct the history of ancient Egypt, and to decipher all
hieroglyphic writings, so in many cases a few bones of an animal, or
imperfect impressions of a lower animal or vegetable form, are
sufficient for us to gain the most important starting-points in the
history of the whole group, and in the search after their pedigree. A
couple of small back teeth, which have been found in the Keuper
formation of the Trias, have of themselves alone furnished a sure proof
that mammals existed even in the Triassic period.
Of the incompleteness of the geological accounts of creation, Darwin,
agreeing with Lyell, the greatest of all recent geologists, says:—
“I look at the geological record as a history of the world imperfectly
kept, and written in a changing dialect; of this history we possess the
last volume alone, relating only to two or three countries. Of this
volume, only here and there a short chapter has been preserved; and of
each page, only here and there a few lines. Each word of the
slowly-changing language, more or less different in the successive
chapters, may represent the forms of life which are entombed in our
consecutive formations, and which falsely appear to us to have been
abruptly introduced. On this view, the difficulties above discussed are
greatly diminished, or even disappear.”—_Origin of Species_, 6th
Edition, p. 289.
If we bear in mind the exceeding incompleteness of palæontological
records, we shall not be surprised that we are still dependent upon so
many uncertain hypotheses when actually endeavouring to sketch the
pedigree of the different organic groups. However, we fortunately
possess, besides fossils, other records of the history of the origin of
organisms, which in many cases are of no less value, nay, in several
cases are of much greater value, than fossils. By far the most important
of these other records of creation is, without doubt, _ontogeny_, that
is, the history of the development of the organic individual (embryology
and metamorphology). It briefly repeats in great and marked features the
series of forms which the ancestors of the respective individuals have
passed through from the beginning of their tribe. We have designated the
palæontological history of the development of the ancestors of a living
form as the history of a tribe, or _phylogeny_, and we may therefore
thus enunciate this exceedingly important _biogenetic fundamental
principle_: “_Ontogeny is a short and quick repetition, or
recapitulation, of Phylogeny, determined by the laws of Inheritance and
Adaptation_.” As every animal and every plant from the beginning of its
individual existence passes through a series of different forms, it
indicates in rapid succession and in general outlines the long and
slowly changing series of states of form which its progenitors have
passed through from the most ancient times. (Gen. Morph. ii. 6, 110,
300.)
It is true that the sketch which the ontogeny of organisms gives us of
their phylogeny is in most cases more or less obscured, and all the more
so the more Adaptation, in the course of time, has predominated over
Inheritance, and the more powerfully the law of abbreviated inheritance,
and the law of correlative adaptation, have exerted their influence.
However, this does not lessen the great value which the actual and
faithfully preserved features of that sketch possess. _Ontogeny is of
the most inestimable value for the knowledge of the earliest
palæontological conditions of development_, just because no petrified
remains of the most ancient conditions of the development of tribes and
classes have been preserved. These, indeed, could not have been
preserved on account of the soft and tender nature of their bodies. No
petrifactions could inform us of the fundamental and important fact
which ontogeny reveals to us, that the most ancient common ancestors of
all the different animal and vegetable species were quite simple cells
like the egg-cell. No petrifaction could prove to us the immensely
important fact, established by ontogeny, that the simple increase, the
formation of cell-aggregates and the differentiation of those cells,
produced the infinitely manifold forms of multicellular organisms. Thus
ontogeny helps us over many and large gaps in palæontology.
[Illustration: Hand of Nine different Mammals. Pl. IV.
_1. Man_, _2. Gorilla_, _3. Orang_, _4. Dog_, _5. Seal_, _6. Porpoise_,
_7. Bat_, _8. Mole_, _9. Duck-bill_.]
To the invaluable records of creation furnished by palæontology and
ontogeny are added the no less important evidences for the blood
relationship of organisms furnished by _comparative anatomy_. When
organisms, externally very different, nearly agree in their internal
structure, one may with certainty conclude that the agreement has its
foundation in Inheritance, the dissimilarity its foundation in
Adaptation. Compare, for example, the hands and fore paws of the nine
different animals which are represented on Plate IV., in which the bony
skeleton in the interior of the hand and of the five fingers is visible.
Everywhere we find, though the external forms are most different, the
same bones, and among them the same number, position, and connection. It
will perhaps appear very natural that the hand of _man_ (Fig. 1) differs
very little from that of the _gorilla_ (Fig. 2) and of the
_orang-outang_ (Fig. 3), his nearest relations. But it will be more
surprising if the fore feet of the _dog_ also (Fig. 4), as well as the
breast-fin (the hand) of the _seal_ (Fig. 5), and of the _dolphin_ (Fig.
6), show essentially the same structure. And it will appear still more
wonderful that even the wing of the _bat_ (Fig. 7), the shovel-feet of
the _mole_ (Fig. 8), and the fore feet of the _duck-bill_
(Ornithorhynchus) (Fig. 9), the most imperfect of all mammals, is
composed of entirely the same bones, only their size and form being
variously changed. Their number, the manner of their arrangement and
connection has remained the same. (Compare also the explanation of Plate
IV., in the Appendix.) It is quite inconceivable that any other cause,
except the common inheritance of the part in question from common
ancestors, could have occasioned this wonderful homology or similarity
in the essential inner structure with such different external forms.
Now, if we go down further in the system below the mammals, and find
that even the wings of birds, the fore feet of reptiles and amphibious
animals, are composed of essentially the same bones as the arms of man
and the fore legs of the other mammals, we can, from this circumstance
alone, with perfect certainty, infer the common origin of all these
vertebrate animals. Here, as in all other cases, the degree of the
internal agreement in the form discloses to us the degree of blood
relationship.