BERKELEY

.URARY

JNWERS1TY OF
CALIFORNIA ^

EARTH

SCIENCES

LIBRARY

EARTH
SCIENCES

LIFE ON THE EAKTH.

KNOWN UNTO GOD ARE ALL HIS WORKS,
FROM THE BEGINNING OF THE WORLD.

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LIFE' ON THE EARTH

ITS'

OKIGIN AND SUCCESSION.

JOHN PHILLIPS, M.A. LL.D. F.K.S.

LATE PRESIDENT OF THE GEOLOGICAL SOCIETY OF LONDON, PEOFESSOE OF GEOLOGY
IN THE UNIVERSITY OF OXFOED.

MACMILLAN AND CO.

Cambrfoge :

AND 23, HENRIETTA STREET, COVENT GARDEN,

Honfcon.

I860.

The right of Translation it reserved.

EARTH
8C

PRINTED BY C. J. CLAY, M.A.
AT THE UNIVERSITY PRESS

TO THE HON. AND EEV.

LATIMEE NEVILLE, M.A.,

VICE-CHANCELLOR OF THE UNIVERSITY OF CAMBRIDGE,

THIS VOLUME

WHICH CONTAINS THE SUBSTANCE OF THE REDE LECTURE,
DELIVERED UNDER HIS AUSPICES IN MAY, 1860,

IS BY PERMISSION
MOST RESPECTFULLY DEDICATED.

PKEFACE.

IN the following pages, the three great divisions of
Strata, and the three great portions of Geological
Time, are termed Palseozoic, Mesozoic, and Cseno-
zoic ; these designations having fairly won their way,
and being really preferable, while treating of the
Succession of Life, to such titles as Primary, Se-
condary, and Tertiary, which express something more
than the knowledge we actually possess, and some-
thing different from the idea we wish to convey.

While speaking of the Lower Palseozoic Strata
and the beautiful system of Life which they contain
— a system of the highest importance in the inquiry
now on hand — I find it convenient to employ the
combination of Siluro-Cambrian, or Cambro-Silurian,
as the occasion suggests ; and have pleasure in thus
commemorating in my phrase the gigantic labours,
sometimes independent, sometimes associated, but
always successful, by which, first of all men, Mur-
chison and Sedgwick laid open for us these deeply-
buried monuments of the earliest Life on the Earth.

Vlll PEEFACE.

Under the title Csenozoic, I wish the reader to
comprehend with me not only the Eocene, Meiocene,
and Pleiocene of Lyell, but the whole series of Supra-
cretaceous deposits; the latest geological age being
chiefly distinguishable by the presence and activity of
MAN, for whom the Book of the Strata, inscribed with
the earlier Wonders of Nature, has been given to be
opened with care and deciphered with reverence, by
the help of comparison with the living inhabitants of
the Land and Sea.

OXFOBD,

Oct. 1860.

CONTENTS.

PAGE

Essential Conditions of Life 5

Influence of Climate on the Distribution of Life . .11
Influence of Depth on the Distribution of Life jn the Sea . 15

Provinces of Life 18

Types of Life Structure 25

Adaptations of Life Structure 31

System of Life Coeval with Man 45

^Successive Systems of Life ....... 53

^Variety of the Forms of Life in Successive Periods . . 59

Origin of Life on the Earth 67

} Earliest Systems of Life 70

- ^Successive Systems of Marine Invertebral Life ... 81
Changes of Marine Animals with Elapsed Time , . .84

Freshwater Life . . 109

Terrestrial Life 115

Antiquity of the Earth 119

Changes of Climate 142

Physical Aspects of the Earth 165

THEORIES AND OPINIONS.

Formed Stones 175

Cataclysms 178

All Life derived from the Sea . 180

X CONTENTS.

PAGB

Germs of Life 182

Strata identified by Organic Remains 187

Development 188

Constancy of Species . . 191

Primitive Types 194

Distinction of Species 196

Natural Selection 200

General Reflections . 204

LIFE ON THE EARTH.

MR VICE-CHANCELLOR,

THE subject which, by your command, I have
the gratification of bringing before the notice of
the University of Cambridge, is not offered as new,
though, in consequence of being at the present time
subjected to that scrutiny which always arises on
the production of new evidence, it wears a somewhat
novel aspect. For certainly the history of life is a
theme which can never have been absent from the
mind of a contemplative naturalist. It never can
have been absent, because in all the classifications,
in all the systems by which we vainly task ourselves
to represent the divine idea of nature, we have inva-
riably looked for a beginning, a progress, and a pos-
sible end. Standing by the stream of life, we have
surveyed the variations in its course, and appealed
to history and experience, for the data which might
guide us to a right view of its incessant fluctuations,
and its recurring uniformities. \Ye have thus found
all nature, organic and inorganic, to be harmoniously
combined in mutual dependence; the worlds of
R. L. B

' LIFE ON THE EARTH.

ai<Ji''Qf .life linked together by peculiar asso-
ciations, which endure through long time amid vary-
ing phenomena, all suggestive of appointed succes-
sion and definite purpose. Perceiving that every
one thing exists as part of a system, that all effects
are parts of a series, and that the whole is com-
pacted together and kept in perpetual movement by
some determinate and general principles, we are con-
strained to believe that so perfect a plan must be
permanent and subject to no material change. Nor
is this inference much disturbed by the fact that in
every stage we perceive vicissitudes from the greater
to the less, and from the less to the greater : from
the simple to the complex, and from the complex to
the simple. For the changes which thus manifest
themselves appear, by sufficient experience, to be
often repeated in cycles of measurable duration, and
governed by laws which appear of perpetual efficacy.
Thus amidst all the diversity of nature nothing
appears accidental, nothing indefinite, nothing unfore-
seen, and it is this consideration which makes the
study of creation hopeful. We may never fathom
the mystery of the origin of life or the inner con-
stitution of matter, but every step we take in ac-
cordance with sound reason and reverent feeling
brings us nearer to a better understanding of the
problem, and is a step in the right direction. Let us,

LIFE ON THE EARTH. 3

then, bring into view the facts discovered in relation
to the Origin and Succession of Life on the Earth,
not with the expectation that we can altogether
penetrate the ' scheme of creation,' but to get a
further insight into it, and a clearer perception of the
appointed laws of nature, by the use of those senses
with which the Almighty has endowed us. Let us l
hope that while we study the external world, and,
perhaps in vain, strive to master its wonderful history,
we shall at least enlarge and correct our ideas, and
truly perform the part assigned to us in the large
field of creation which we are enabled and invited
to contemplate.

Nature, in a large sense, is the expression of
a DIVINE IDEA, the harmonious whole of this
world of matter and life. Man, included in this
whole, is endowed with the sacred and wonderful
power of standing in some degree apart, so as to
observe the course, investigate the laws, and measure
and direct the inexhaustible powers which surround
him and penetrate him. The knowledge thus slowly
gathered is contained in two great HUMAN IDEAS,
the idea of force, as producing phenomena, and of
time as determining the succession and duration of
these. The ideas of constant force and perpetual
time are suggested to us in various ways by the
repeated occurrences of nature; uniform measures

B2

4 LIFE ON THE EARTH.

of force and time are obtained by observation of
the earth's constant force of attraction toward its
centre, and unchanging velocity of rotation on its
axis. By comparing phenomena with uniform mea-
sures of force, and uniform measures of time, we
obtain, or strive to obtain, for each natural effect,
a correct numerical valuation in terms of the force
employed and the time consumed in the production
of the effect.

There are, or appear to be, different kinds of
force, producing different kinds of effects— as magnet-
ism and gravitation ; — but they are often comparable,
and capable of valuation under the one comprehensive
idea of relative magnitude. Thus all natural effects
known to us are measured or conceived to be
measurable, by units of force, operating through
units of space in units of time. And nature appears
to us to be the sum of these effects combined
into a ' System,' harmonious, mutually dependent,
and preserved entire amidst an endless succession
of limited vicissitudes. In expressing our concep-
tions of this well-adjusted 'System of Nature' we
employ the term 'Laws;' and the more compre-
hensive these are, — the higher the abstractions
which they represent — the less do we conceive them
to be variable ; so that the most general laws which
we reach or strive to reach, are conceived to be,

LIFE ON THE EARTH. 5

like their Divine Author, independent of time and
exempt from change.

ESSENTIAL CONDITIONS OF LIFE.

The Forces of Nature are constant ; we do not
conceive of them as beginning, or changing, or end-
ing ; the Laws of Nature appear to us invariable ;
but the forces and the laws are manifested only in
relation to particular conditions. Thus in the case
of life, regarded as a manifestation of forces accord-
ing to laws, we find it to be limited to f organic'
structures composed of certain sorts, and certain
combinations of matter1. Much of the matter which
composes living bodies is capable of assuming the
gaseous form, as Carbon, Hydrogen, Oxygen, Nitro-
gen. Other parts are capable of appearing in
solution, as Phosphate of Lime, Carbonate of Lime,
&c. All the substances named exist in nearly all
plants and animals ; and it appears, though we do
not know how, necessary to the exhibition of vital
phenomena, that they should be present — necessary,
I mean, according to this actual plan of creation,
the only one we are acquainted with, or can justly

1 In modern language matter is said to be known to us only
by effects cognizable by our senses; these effects are due to
forces ; matter is the seat of these forces ; or, if we will, it is a
collection of centres of force.

6 LIFE ON THE EARTH.

conceive of as possible. For though it may be urged,
and cannot be doubted, that other elements, other
forces, and other laws might be employed for other
systems of life ; that is a conjecture which may be
useful when thinking of the possible inhabitants of
other planets, as Mercury, or Jupiter, or Neptune, but
is not suited to the Land, Sea, and Air, with which our
History of Life is connected. Deprive the atmosphere
of its carbonic acid, — plants disappear ; let phosphate
of lime be absent — not only vertebrate animals vanish,
but a large part of both the animal and vegetable
races would languish and become unproductive1.
Without supposing oxygen or the other elements
to be entirely absent, any material change in their
relative quantity must greatly affect the relative
abundance of different races of living beings whose
dependence on these elements is different in degree.
Life is dependent on a continual loss and restora-
tion of parts in its organic fabric. One great part in
this process is maintained by the atmosphere, from
which all plants and all animals draw supplies of
gaseous elements suited to their constitution. Plants
absorb the carbonic acid, which exists in the at-
mosphere to the extent of nnroth part by weight,

1 Phosphate of Lime occurs in so many animals, and in so
many plants, in some part or other, as to be regarded by eminent
writers as an invariable accompaniment of life.

LIFE ON THE EARTH. 7

and yield oxygen in return ; while on the other
hand, animals inspire this oxygen, and evolve in
exchange carbonic acid. Thus appears a real and
necessary relation between the atmosphere as it is,
and the double system of life which is in operation.
If we change the constitution of the atmosphere,
all the relations in which it is so important must
be changed also, and amongst the most obvious of
these are the reciprocally dependent races of plants
and animals. It has been conjectured by Brong-
niart, that the very rich series of vegetable forms,
including many ferns, in the old carboniferous de-
posits, may have been favoured in their amazing
growth, not only by high temperature and humid
atmosphere, but by a greater proportion of carbonic
acid in the air. Dr Daubeny has submitted this
to a trial, in vessels properly supplied with a regu-
lated artificial atmosphere, and the result is not
unfavourable to the speculation.

Again, animal life depends upon the previous
exercise of vegetable life; for ultimately all animals
subsist upon plants, as these feed upon the atmo-
sphere. Perhaps nothing is more surprising than the
immense diversity of the forms and qualities of
the plants, coupled with the almost equal depend-
ence of all vegetative life upon the same atmosphere
chemically everywhere almost identical. Upon this

8 LIFE ON THE EARTH.

vast variety of plants, innumerable hosts of herbivo-
rous animals feed, and they minister to the appetites
of the Garni vora. It is conceivable that while the
plants remain unchanged, the Herbivora might
vary, or might become the prey of different flesh-
eaters ; but it is perhaps not conceivable that with
such an atmosphere as ours, under such conditions
as now obtain, there could be generally any great
variation in the relative total amount of vital energy
in plants, compared with animals. There seems also
a high degree of permanence in the relation of
Herbivora compared with Carnivora. Our marine
Cetacea might be replaced by Enaliosaurians ; our
Gasteropoda by Crustacea ; our fishes by Cephalo-
poda ; but the researches of geology seem to shew that
from the earliest periods, carnivora and herbivora,
plants and animals, have been combined into the same
general relations of mutual dependence as at present.
Subject to these conditions, life appears in all
the habitable spaces of the land, sea and air, filling
each with beings capable of enjoying their own
existence, and of ministering to the bodily wants
and intellectual longings of the one observing and
reflecting being to whom God has committed the
wonderful gift of thoughts which reach back beyond
the origin of his race, and stretch forward to a
brighter futurity.

LIFE ON THE EARTH. 9

In the elements of land, air, and water, both
plants and animals are fitted to live by means of
contrivances varied in almost every individual case,
but always to be conceived of as elegant adapta-
tions to some conditions of matter — adaptations to
gravity, to force of wind, to depth of water, to
degrees of light, to periodicity of seasons, and even
to local and limited occurrences. Regard the eye
which in its perfect state, as in man, is destined
to feel the presence or absence of light, to dis-
tinguish the colours of the several rays, and to per-
ceive the forms of the luminous surfaces. What is
it but a triple photographic lens with six curved
surfaces calculated for three different media ; calcu-
lated for achromaticity and spherical aberration ;
provided with a variable self-adjusting aperture, and
a variable self-adjusting focal length, adapted to
something better and more sensitive than a collodion-
plate — the beautifully expanded and guarded retina,
which after the fraction of a second of time is ready
to receive a new impression with undiminished
energy. Regard the two eyes, the natural stereo-
scope, by whose beautiful joint action solids take
their proper aspect, distance is estimated, and the
landscape acquires that instructive composition which
our artists delight to imitate.

Again, regard this wonderful organ, modified to

10 LIFE ON THE EARTH.

suit the sunny flight of the eagle, the twilight
mousing of the owl, the brousing of the ruminant,
the nocturnal watch of the lion ; the watery life
of the whale, or the fish, where the different re-
fractive power of the fluid in which they live is
accompanied by modifications, not alike in each,
but yet alike in the manifestation of intentional
adaptation. Consider in the same point of view
the large orbit of Ichthyosaurus with its broad cir-
clet of sclerotic bones ; or the reticulated lenses
of the Trilobite ; or finally, the black or red spots
sensitive only to light in the Mollusca and Radiata ;
or scrutinize in the same way any other organ of
sense, in the animals of every age, and inquire with
the Psalmist:

He who planted the ear, shall He not hear?
He who made the eye, shall He not see?

Life runs always the same course of growth,
decay and death, in the individual — always the same
course of renewal by offspring, after a definite mode
which varies with the different kinds of living beings.
One of these modes seems to deserve separation from
the rest, under the title of fissiparism, because in
it the individual seems divided, and so the number
of individuals multiplied. This obtains among the
Polyparian Zoophyta, and may be paralleled among
many plants, and artificially exemplified by cuttings.

LIFE ON THE EARTH. 11

But in general, there is the preparation of egg or
seed, the development of these in connection with
nutritive matter prepared in each, and the passage
through several stages before the complete state
of individual life is attained ; then recurs the separa-
tion of parts impressed with the wonderful power,
and subject to the inconceivable restraint, of so
acting on and being acted on by the elementary
powers around, as to grow, reproduce and decay,
in forms and through periods corresponding to those
appointed for their ancestral races since time began.

INFLUENCE OF CLIMATE ON THE DISTRIBUTION
OF LIFE.

Not the whole surface of the earth is occupied
by living beings. Notwithstanding the perpetual
struggle to diffuse their seed, plants do not cover all
the regions of the land ; nor is the amazing fertility
of many marine animals able to carry life into all
parts of the sea. The geographical distribution of I
plants and animals, a subject of great richness and
instruction, offers some general facts which must
not be neglected in reasoning on the ancient forms
of life which fill the stratified rocks.

Among the most influential of all the causes
which limit the ranges of life is temperature. The

12 LIFE ON THE EARTH.

annual mean temperature, the extremes of yearly and
daily heat and cold, and the humidity of the atmo-
sphere, in a good degree dependent on temperature,
are conditions to which life in general, and special
forms of life in particular, are adjusted.

For example, proceeding from the equator to
the north, along the land in the new or the old
world, we find the number of the forms of life con-
tinually grow less and less. According to an esti-
mate of some date, if we count in the warm zones
of Asia the plants which range northwards from the
equator with a temperature of 80°, so as to reach the
latitude where the annual mean temperature of 64°
prevails, we shall find 4500 species ; between 64° and
48° the number is reduced to 1500, while between
32° and 0° the total sinks to 500, till in Walden
Island, lat. 80J north, only ten species occur ; and
finally, the whole series becomes extinct.

So if we estimate the land mammalia of the Tropical
zone at 800 species, the proportionate number for
the Temperate zone is 200, and for the Polar zone
twenty. But the reverse holds in regard to the
Cetacea, which increase towards the Polar oceans.

It may be further observed that the earth seems
to have the two extremes of life, the hot extreme
in the deserts of Africa, the cold extreme toward
either pole, and toward the summits of high moun-

LIFE ON THE EARTH. 13

tains. The American Flora is richer than that of the
old world. If 13000 be the number of phaneroga-
mous plants in Tropical America, 4000 may be taken
to represent the flora in the Temperate zone. If
2000 plants can be collected within a radius of ten
miles in India, about 500 can be found in an equal
space of the surface of England1.

In Mr Watson's interesting work on the Geogra-
phical Distribution of British Plants, we find the
Highland plants of Scotland grouped in three divi-
sions according to elevation — 1000 to 2000 ft., 2000 to
3000ft. and 3000 to 4000ft. above the sea. The num-
bers are : —

273 species — 183 species — 85 species
48 orders — 38 orders — 25 orders,

shewing clearly the reduction of vegetative energy
with increased elevation.

Equally positive is the limitation fixed by climate
upon the geographical range of the different natural
groups of plants. Proceeding northward from the
equator we pass through the fruitful equatorial re-
gion of the bananas and palms, the tropical zone of
arborescent ferns and figs, the sub-tropical zone of

1 Humboldt; Hooker, Indian Flora; Watson's British
Plants; Balfour's Class Book; Somerville's Phys. Geography,
Meyen, Botanical Geography.

14 LIFE ON THE EARTH.

myrtles and laurels, the warm temperate zone of
evergreen trees, the cold temperate zone of deciduous
trees, the sub-arctic zone of pines, the arctic zone of
rhododendra, and finally, the polar zone where the
last relics of vegetable life expire1.

The same succession of plants is found in ascend-
ing the lofty mountains of the equatorial zone, as
Chimborazo in South America, and Popocatepetl in
North America, whose summits have the polar climates,
and their slopes the plants and animals of different
latitudes. The ranges are equally definite on Etna,
but there the palm zone is only at the very base ;
and on Mont Blanc, which has none of the lower and
warmer zones.

In a diagram, Fig. 1, the distribution in latitude

•

of several races of mammalia is traced by lines. If we
regard the two halves of the circle divided by the
central meridian as representing the old and new
world, we shall find in each the same laws prevail
for the same groups ; though none of the species
are the same in the two regions, except toward the
north pole, where there is almost a connection of the
two countries by islands and ice.

Thus the Platyrhine Monkeys of the new world
are balanced by the Catarhine Quadrumana of the
old world ; the Feline races of Asia and Africa, the
1 Humboldt.

FIG. i, to face p. 14.

NEW WORLD.

Alpaca Llama.

Armadillo.

Sloth.

Peccary.

Tapir.

Ocelot. Jaguar. Puma.

Platyrhine Monkeys.

Elk.

Beaver.

Catarhine Monkeys.
Lion. Leopard. Tiger.
Khinoceros. Tapir.

Beaver.
Fox. Wolf. Gulo

OLD WORLD.

LIFE ON THE EARTH. 15

Lion and Leopard, are copied so to speak by the
Puma and Jaguar of tropical America ; the Tapir
of Mexico mimics the congeneric animal of Sumatra ;
the Sloth, Armadillo, and Myrmecophaga of Brazil,
find relatives in the Manis and Orycteropus of Asia
and Africa.

These parallels might be extended by many ex-
amples from Struthious and other birds, and from
Crocodiles and other reptiles, tending to shew in
two large separated regions, two distinct but ana-
logous groups of life, subject to similar limitations
by climate.

In like manner, reef-making Corals in the sea, and
the large molluscous families of Cones, Cowries, and
Volutes, might be mentioned as characterizing the
warmer waters ; but a more curious and interest-
ing law of distribution of marine life, is founded on
investigation of the contents of the sea at different
depths.

INFLUENCE OF DEPTH ON THE DISTRIBUTION OF LIFE
IN THE SEA.

One example, the best known, is the Survey of
the JEgean sea-depths by the late excellent naturalist,
Edward Forbes. Dividing the depths from the sur-
face to 230 fathoms into eight unequal zones, he finds

16

LIFE ON THE EARTH.

the distribution of testaceous mollusca in them to be
as under :

I.

0 to 2

2

147

735

II.

2 to 10

8

291

161

III.

10 to 20

10

124

124

IV.

20 to 35

15

142

91

V.

35 to 55

20

141

70

VI.

55 to 79

24

119

50

VII.

79 to 105

26

85

33

VIII.

105 to 230

125

66

6

The first column gives the zones in succession
downwards.

The second gives the limits of the zone in depth
by fathoms.

The third, the depth in thickness of each zone in
fathoms.

The fourth the number of species found in each
zone.

The fifth is a column which I have calculated by
dividing the fourth by the third, to shew the relative
productiveness of each zone. (For the sake of avoid-
ing decimals, the quotient is multiplied by 10.)

Thus it appears that the relative fertility of the
several zones decreases downwards toward zero :
and it is believed that at 300 fathoms life is extinct.

If we consider that at and near the surface of the
sea all the influences favourable to both vegetable

Fm. i, to face p. 17.

-32° 16000

15000

Lichens.

-38

i

I

1

1-

.1

i Khododendra.

-44

\
\

\

\

\

\

|

\ Pines.

%

\

£ "3

\

•5o -s £ i oooo

\

Hi

\

i J

\

^ «

\ Amentaceee.

5 5

\

O

v

"aS ^

i

-56 g |

\ Wheat.

£ <W

I

2 £

V

1

v Vines.

s

\

£ I

\
\

X-

1

v Myrtles.

\

\

5000

Xx Tree Ferns.

-68

\

The Space \

in this \

direction is \

\

proportionate \ Palms.

-74

to the Variety \
of Life. \

t

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0 r,O <-l

\ SEA LEVEL.

-oO o

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2OOO

LIFE ON THE EARTH. 17

and animal life must have their greatest effect, here
being the greatest mixture of air with the water ; the
greatest motion of the water, to give full effect to that
mixture ; the greatest amount of stimulating light,
and the greatest change of daily temperature ; we
shall readily conceive that near the surface the forms
of life should be both more varied and more abund-
ant ; while, on the other hand, in the deeper and
calmer water, less light, less motion, less air and less
change of air, should correspond to fewer and less
varied inhabitants. Only a few of the Mollusca are,
like the Argonaut of the Poet, who tilts along the
Atlantic waves —

But if a breath of danger sound,

With sails quick-furled she dives profound,

And far below the tempest's path

In coral grots defies the foe,

That never broke, in heaviest wrath,

The sabbath of the deeps below.

In a Diagram, Fig. 2, we may represent the limits
of life above and below the level of the sea by
setting off on the vertical line a scale of heights,
and depths, and drawing at right angles to this, for
each selected zone of height and depth, lines repre-
senting the ratios of abundance of life. Thus shall
we have, in a general form, an expression of the
apparent dependence of life on elevation above and
depression below the general level of the surface
of the sea. The real dependence on the land is
B. L. c

18 LIFE ON THE EARTH.

ascertained by the temperatures placed opposite the
several elevations.

PROVINCES OF LIFE.

We have been speaking of the climatal distribu-
tion of life-forms in general, and of the larger groups
and families. The distribution of genera and of species
seems to obey the same general laws of co-ordination
to climate, elevation, and depth ; but it also often
suggests the dependence on existing purely local
conditions, on ancient geological revolutions, or even
on locality considered alone and without regard to
conditions.

The great group of Ferns occurs in nearly all
latitudes ; Arborescent Ferns, excluded from cold and
fluctuating climates, extend further to the south than
to the north of the equator. Thus, Aspidium is arbo-
rescent on the shores of Auckland and Campbell, as
far as 52^ S. Lat.;,Alsophila and Cybotium in Aus-
tralia and Van Diemen; Cyathea and Dicksonia are
conspicuous in the vegetation of New Zealand.

An example of the limitation of a race to terres-
trial conditions is afforded by the Gorilla ; that mon-
strous anthropoid animal of the eastern coast of
Africa, whose residence seems limited by the forests
which supply it with food.

On the contrary, it is to ancient geological revo-

LIFE ON THE EARTH. 19

lutions that we must ascribe the detached aspect
of the distribution of many plants and animals ;
these great changes having divided what was once
a continuous area, and interrupted what was once
a free communication between the regions in which
the species occur. Thus we may comprehend the
occurrence of Scandinavian plants in the mountains
of Scotland, and the north of England ; as Myosotis
alpestris, on Micklefell 2400 ft. high, in Yorkshire ;
Cornus Suecica on the eastern moorland, and Tri-
entalis Europa3a, in the western part of the same
county. We must suppose land once continuous
between Scotland and Norway, and a climate more
severe than the present. Under such circumstances
the plants might spread southward ; and afterwards,
when the countries were divided and the climate
became milder, they might remain in a few and
especially cold or elevated situations1.

In the same way we may attempt to explain the
remarkable fact that not only a very considerable
number of European plants is found in the Himalaya
mountains, but also many of the accompanying birds.

The late Dr Royle long since called attention to

this remarkable fact, and Dr Hooker, recently, has

stated that no less than 222 species of British plants

extend to India, and oblige us to look to a common

1 E. Forbes, in Memoirs of Geological Survey, Vol. I.

C2

20 LIFE ON THE EARTH.

origin for the species found in both these regions,
and to seek for causes no longer in operation for
their distribution over so extended an area1. It is
remarkable that these 222 species include no less
than 154 genera. Among them are the plants which
flower in fields and meadows, in woods and wastes,
in marshes and in water — trees and herbs, climbers
and parasites, reproduce before us the familiar aspect
of European vegetation. The water-plants include
Ranunculus aquatilis, Nympheea alba, Myriophyllum
verticillatum, Hippuris vulgaris, Alisma plantago,
Sagittaria sagittifolia, Butomus umbellatus, Acorus
calamus, and several species of Potamogeton. East
of Kumaoon, the European admixture of plants gives
place to a Chinese and Malayan flora. West of
the Himalaya, mountain-plants of the European type
occur at several points, ideally connecting this range
with the coasts of the Levant and the Black Sea,
and really indicative of the anciently connected flora
and the continuous means of communication.

Another inference from such facts is of equal
importance. The species of plants thus shewn to
be identical in the regions of the Himalaya and the
Islands of the West, have retained their characters
during all the time of the existence of each race ;
these characters have survived the chances of long
1 Flora Indica. Introductory Essay, 108.

LIFE ON THE EARTH. 21

migration, have traversed large tracts without hy-
bridism, and have been subject to various physical
influences without suffering any sensible change.
Ranunculus aquatilis in India and Britain every
where retains the little nectary at the base of each
petal, to mark the genus, still spreads its white
blossoms on the water, and extends its filmy leaves
beneath. Still Ranunculus lingua distinguishes itself
by its leaves, and Ranunculus arvensis by its prickly
seeds.

Instances of purely local species of plants are
very common ; sometimes defined by impassable
boundaries — as broad oceans or crested mountains ; —
but not unfrequently contracted to small areas from
a once wider distribution, or confined to such areas
by the successful rivalry of other and more pros-
perous races. Thus the huge cypresses in the Sierra
Nevada of Upper California, known to us as Welling-
tonia1, are now confined to a small district, and
indeed rear their prodigious heads 400 ft. high, mostly
in one valley, where they have lived for a thousand
years and more near the head-waters of the Stanis-
laus and St Antonio rivers, lat. 38° N., long. 120°
10' W.2 So in the valley of the Cherwell, in Ox-
fordshire, the Fritillaria adorns but a few meadows,

1 Sequoia Wellingtoniana is perhaps the right appellation.

2 Seemann, Ann. Nat. Hist. March, 1859.

22 LIFE ON THE EARTH.

and the Snow-flake is equally local. Gagea lutea
is a rare plant of the Oxfordshire hills, yet it re-
appears in the Himalaya ; Gentiana lutea is found
on the high slopes of the Puy de Dome, but it is
deficient over the greater part of central France, and
is rare even in the direction of the Alps till we reach
the mountains where it occurs more frequently. In-
stances like these which have been now enumerated,
seem to be satisfactory in proof that the actual dis-
tribution of any given species is the final result of
many long periods of general effort to extend, and
of some particular influences to restrain, its diffusion.

Remarkable examples are recorded by botanists
of plants having sprung up unexpectedly in the
course of cultivation, in spots where such had not
been growing for very long periods. Perhaps the
well-known case of the upspringing of white clover
on the burnt surface of the heaths of Yorkshire,
when lime has been added, is one of the most strik-
ing. The heath thus displaced has been growing
there for many centuries ; the little clover is rarely
seen in the district ; yet no sooner is the heath ex-
pelled and the calcareous element added, than it
grows and covers the surface.

The distribution of particular groups of animals
is quite as limited as that of plants, and this is true
not only for land-animals but for the inhabitants of

LIFE ON THE EARTH. 23

the sea and the free wanderers of the air. While
some genera are of very wide occurrence in the sea,
as the little Spirula, and the huge Physeter ; while
some birds pass from arctic to temperate, and from
temperate to torrid zones, and some quadrupeds
annually migrate over large breadths of land in
quest of food, the far greater number appear to be
restrained by necessity or limited by choice to narrow
tracts and definite associations of life.

It is not by conformity of climate or physical
conditions, or oceanic currents, that the few existing
genera of Brachiopoda are now allowed representa-
tives in almost all seas, for each particular species
of these genera is usually limited to one small area,
or zone of ocean. Rhynchonella psittacea to the
circumpolar seas ; Terebratula vitrea to the Medi-
terranean ; and Waldheimia australis to the shore
of New Holland1.

Reptilia in a general sense depend for their
distribution on favourable climate; but when we
examine any certain group, as the Crocodilidse, one
species is found to belong to the Nile, another to
the Ganges, a third to the North American rivers.
Struthious birds wander over the dry lands of several

1 See on questions of Distribution of Mollusca, Woodward's
Rudimentary Treatise on Recent and Fossil Shells, — an excel-
lent work.

24 LIFE ON THE EARTH.

parts of the world, but the Rhea is found in South
America, the Ostrich in Africa and Arabia, the
Cassowary in the Indian Islands, and the Emeu in
Australia.

The Condor clings to the summits of the Cor-
dillera, the Lammergeyer haunts the Alps — the Stork
knoweth her abiding place. In a word, every living
race of plants and animals exists in a province of
space ; over which by natural conditions it has been
diffused, within which by natural conditions it has
been restrained, and beyond which it only passes
by a change of these conditions. Thus one place of
origin is indicated for each species of plant and
animal — one locality where it first appeared, whether
it still remain there confined to a limited region, or
have wandered far away, without losing its prominent
characters, through length of time, change of con-
ditions, mixture with other races, or any of the
innumerable incidents of the ' struggle for existence.'

I have thus, Mr Vice-Chancellor, recapitulated
some of the laws regarding the Conditions and
Limitations of Life, which are commonly accepted
among naturalists, and must be observed by geolo-
gists who desire to work out the problem of the
succession of ancient created being. I propose them
as the very reverse of novelties, and regard them

LIFE ON THE EARTH. 25

as truths generally admitted. Here in Cambridge,
I know that these and other great results of the
contemplation of nature are well comprehended,
since you have all long had the advantage of hearing
them from the eloquent lips of the noblest of English
Geologists, your pride and my pride — Professor
Sedgwick. Assuming, then, definite limits and con-
ditions for every living form ; a definite local origin,
and a longc-ontinued permanence of structure and
habits for each species of plant and animal, I may
now turn to the appointed purpose of this lecture,
and trace the history of the changes of life in the
ancient lands and seas.

TYPES OF LIFE STRUCTURE.

One of the most arduous of all the enterprises of
science is the attempt to classify the variously allied
objects of organic and inorganic nature, according
to their prevalent structures and qualities — to place
them in such relations to each other as they really
have — to represent, in short, the plan of these parts
of creation — according to the leading ideas of which
it is, or seems to us to be, the expression. Not that
so great a purpose was at first conceived by Aristotle
and his followers, or even by Linnseus, or Cuvier ; it
was at first intended to group together things which
resembled each other, — as crystals — herbs — trees; —
residents in the water— animals of the land. Pro-

26 LIFE ON THE EARTH.

ceeding from such analogies to stricter inquiries,
other and firmer divisions were founded on the
organs of motion, prehension, food, respiration and
circulation, — the organs of sense, and the internal
arrangements of the nervous system. In the course
of these inquiries we have detected, under many dis-
guises, some general rules of structure and function
— patterns or types so to speak to each of which a
vast number of specific forms can be referred, as if
they were so many examples of one general structure,
modified in an almost infinite variety of ways to suit
appointed habits of life. The general characters of
agreement we often call typical, the special characters
of difference are often called adaptive — terms which
imply the recognition of law and modification, mind
and choice — a Creator who works by rule, and who
has provided for wonderful diversity in his works and
for the persistence through them all of some firm
general principles of construction, which can be
traced out in their operation by the human mind-
process of observation, comparison, and inference.

When reduced to the smallest number of great
primary types, we find Plants to be ranked in two
divisions : —

Phanerogamous or flowering and seed-bearing,
and Cryptogamous or flowerless plants deficient of
true seeds.

LIFE ON THE EARTH.

27

These may be again subdivided so as to make four
great groups : viz.

X

1. Dicotyledones. Embryo
with two seed-lobes, stem
growth outward, leaves reticu-
lated, symmetry quinary or
quaternary (as Ranunculacece,
Rosacece, Labiatce, Coniferce).

2. Monocotyledones. Em-
bryo with one seed-lobe, stem
growth internal, leaves usually
with parallel veins, symmetry
ternary (as Liliacece, Aracece,
Gramineoe).

Phanerogamous plants
with stamens and pistils,
spiral vessels, and seeds.

Cryptogamous plants,
without flowers, true sta-
mens, pistils, spiral vessels,
or seeds.

3. Acrogens. Stem, with
leaves and branches, mostly
traversed by vessels (as Filices,
Lycopodiacece, Equisetacem).

4. Thallogens. No distinct
stem or leaves, or vessels, but
cellular expansions (as Liche-
nes, Algce, Fungi).

In like manner Animals may be collected in four
great groups : —

I. Yertebrata. Brain protected by bony (or cartilaginous)

case, and, proceeding from it, a nervous trunk car-
ried along the upper side of a chain of articulated
bones (vertebrae) or a corresponding cartilaginous
axis. Symmetry bilateral.

II. Articulata. Body jointed or ringed across. A double

28 LIFE ON THE EARTH.

nervous cord, ganglionated at intervals, proceeding
along the body. Symmetry bilateral.

III. Mollusca. Body not jointed or ringed across : ner-

vous cord encircling the alimentary canal, and rami-
fying through the body. Symmetry bilateral or
spiral.

IV. Radiata. Nervous system absent or reduced to a

ring round the alimentary canal with few radiating
threads. Symmetry radiate round an axis.

There are some forms of plants and animals so
slightly adapted to special purposes of life, as far as
we have yet discovered, that life may be thought to
reside in them only in a general form; the type of
which — if that can be called typical which seems
rather to be marked by absence of all but elementary
organization — may be called cellular or rudimentary.
This group, however, is but provisional, and will pro-
bably be hereafter better divided according as the
nutritive and reproductive systems are more surely
analysed by the microscope.

Under the great types of vegetable and animal
structure which have been mentioned, naturalists find
it convenient to adopt many classes, orders, families,
genera, species and varieties. These are not so set-
tled in any case as to be altogether free from change
by fresh inquiries and discoveries: they have been
augmented and modified by the discoveries of palae-
ontology; which have filled several void spaces in

LIFE ON THE EARTH. 29

the series of affinities, and illustrated modern types
by ancient parallels.

The adherence of plants and animals to the several
leading types is sufficient in most cases to leave no
doubt of the place of each; the typical peculiarity
influences all parts of their structure, — the leaves,
flowers and fruit of a plant — the limbs, dermal cover-
ing, composition, colour and temperature of the blood
in an animal. So that a single leaf will generally
decide the place of a plant in the three great divi-
sions— a single drop of circulating fluid, the eye, a
bone, a shell or crust, that of an animal. As an
exception among plants we may mention those of
the family Smilacese which yield Sarsaparilla, whose
leaves are veined with the net-work of Dicotyledones,
but whose seeds are formed on the model of Monoco-
tyledones. Among animals the Polyzoa or Bryozoa
were long ranked as Radiate animals, and there is
now a difference of opinion regarding the place of
the conspicuous family of Echinodermata, which
some place at the head of the Radiata, but others
join with Annulose animals.

Each great type comprehends several considerable
subdivisions, in each of which a reigning idea may
often be traced in the structure, and exemplified in
the function. These are again subdivided in a man-
ner suggestive of other ideas. For example, Mam-

30 LIFE ON THE EARTH.

malia are separated from all other animals by their
mode of rearing their young.

Among Mammalia quadrupedal motion on land
appears to be the reigning idea, which determines the
complete type ; but the Cetacea, destined for aquatic
life, are bipedal, and have their two legs altered to
perform the work of pectoral fins, and the tail ex-
panded to a propulsive instrument. Thus ideas are
expressed which seem borrowed from fishes, to which
in general form suited for easy motion in water the
Cetaceans also correspond. So in early geological
times we find Ichthyosaurus assuming that sort of
conformity to fish-structure and form, which belongs
to what Mac Leay calls analogy, while the real affinity
of the whale is to ordinary Mammalia, and the real
affinity of the Ichthyosaurus is to ordinary Reptilia.

In a different manner the quadrupedal mammal
is modified for flight in the air. The Bat takes up the
extended interdigital membrane, and the sternal keel,
by analogy with birds—as in older periods of the
world, the Pterodactyle spread its wings and worked
its pectoral muscles under the same peculiarities1.
Instances of this kind might be greatly multiplied,
but these may be sufficient to shew that each great
type or subtype of structure admits of variations of

1 See the evidence of the sternal keel of Pterodactylus in the
fine collection of Green Sand Fossils in the Cambridge Museum.

LIFE ON THE EARTH. 31

high importance, by adopting means, if we may so
speak, to express the ideas which are prevalent in
another division. Though each great type seems to
have in a general sense one mam destiny marked out
for it by structure, place of residence, and habits, yet
each of the three higher types (Mollusca, Articulata,
Vertebrata) admits of modifications to suit some of
them for watery, and others for aerial life ; some for
swimming, others for flying, some for climbing,
others for burrowing into earth or wood or mud or
stone. Thus every thing that lives, is especially con-
structed for its life1, in conformity with general types
which admit of much modification, to suit particular
purposes.

ADAPTATIONS OF LIFE STEUCTUEE.

Some idea may be formed of the rich variety of
adaptations of animal structures to the conditions
under which they are appointed to live by a mere
enumeration of a few well-known cases, such as the
following variations in respect of the powers of
attachment or locomotion.

Life in water is maintained in objects which
exhibit a vast diversity of forms and magnitudes, and

1 La moindre facette d'os, la moindre apophyse a un carac-
tere determine, relatif a la classe, a 1'ordre, au genre et a Pespece
auxquels elle appartient.— Cuvier, Ossemens Fossiles, Disc. prel.

32 LIFE ON THE EARTH.

various contrivances are employed to adapt them to
the specific gravity of the liquid. Among those not
so adjusted are a large portion of the shell-covered
Mollusca, which by reason of the weight of the shell
are for the most part collected on the beds of lakes,
rivers or the sea. Within reach of the tidal agitation,
where the water is well charged with air, several races
of Mollusca attach themselves — as the young oyster
by its lower shell fixes itself permanently and fur-
nishes support to others. Anomia is attached by
a sort of plug, Pinna and the young Mytilus by a
byssus spun through the agency of a muscular organ
called the foot, which in all the races mentioned loses
its usual function of locomotion.

The attachment of Actinia by its broad base, and
of Patella by its circular mantle, is not of so perma-
nent a character. Perhaps this is also the case with
the suspensional ligament of Lingula and Terebratula.
More curious examples are furnished by the cusps
for adhesion which cover the arms of Cephalo-
poda1, both recent and fossil, and the sucking sur-
faces of Remora.

Flotation is accomplished in some of the marine

races by very obvious contrivances. In the large

Medusidse whose figure is hemispherical, a steady

position with the mouth downward is maintained by

1 The Polypus of Aristotle and Homer.

LIFE ON THE EARTH. 33

the help of fringes dependent from the edge; in
Physalia and Yelella, an air-bladder is raised above
the general mass and catches the wind; in Nautilus
the complicated air-chambers of the shell with a pipe
through them all, appears to be another and more
remarkable contrivance, which belonged to the group
through all geological time; the air-bladder of fishes
has been often celebrated in this respect; and we
may add the thick oily integument of the Cetacea
which at once balances their heavy bones, maintains
the heat of their bodies in the polar oceans, and
gives the boat-like form which fits them for motion
in water.

Swimming, though chiefly exhibited by the Arti-
culated and Yertebrated divisions of animals, is some-
times exercised by the other types. Some of the
Infusoria swim by the aid of cilia on the periphery,
or about the mouth, others by altering the form of
the body. Some of the Cephalopoda employ the
hinder expansion of the body as well as the arms and
hydraulic funnel, for motion. But it is in the Arti-
culata with jointed feet and among the Vertebrata,
that swimming by special organs arrives at the most
curious and diversified excellence.

We may remark in regard to nearly all of these
special organs that the general idea carried out in
them is that of striking the water forcibly with an

B.L.

34 LIFE ON THE EARTH.

expanded organ, which can again be drawn through
the water more slowly and with less surface to be
again expanded and presented for a fresh effort.

Thus whales and fishes, the Triton and the
young Frog, all work the expanded tail after the
manner which men use in sculling a boat ; while the
beautiful boat-beetle (Notonecta) floating on his back
rows himself with long jointed, flattened oars, fringed
with stiff bristles. When he strikes for motion, the
oars extend themselves, and the bristles catch the
water and widen the instrument; but in returning
the oar is bent, and turned edgeways, and the bristles
pass easily through the liquid — Oav^a l$eo-0ai — a
wonderful thing to behold.

The paddles of the Turtle and the pectoral fins of
the Whale are instruments having the same general
property of varying the extent of surface exposed to
the water. A similar result is obtained by the very
different contrivance of the webbed feet of the Swan
and the Otter — and that remarkable organ for back-
ward swimming or rather leaping in the water, the
bending tail of the Lobster and Crawfish, which
besides has its five plates endowed with lateral
motion, so as to fold up into a small area.

It is interesting to observe this same structure
in the Lobsters (Glyphia) of the ancient oolites, and
to note in the Speeton clay and the London clay the

LIFE ON THE EARTH. 35

flexible tail of the Crayfish (Palinurus), distinct from
that of the true Astacidse in those remote ages as
it is still found to be in the corresponding groups
living together in the ocean. Equally curious to
notice in the Ichthyosaurus and Teleosaurus of the
Lias the same principles of watery propulsion, by the
tail and lateral paddles, as in the Fish, Turtles and
Alligators of the present period. One general idea
runs through the whole series, the propulsive power
is worked by a system of leverage placed more or less
retrally, aided by a directing power placed forward.
If Plesiosaurus appear to be an exception, the ano-
maly may be regarded as compensated by the exten-
sion of the neck, for thus in fact the dynamic centre
is really retral, as to the general figure, while the
approximation of the paddles gives remarkable power
of quick turning, suitable to its way of life.

Diving. The same backward position of the
propulsive organs is even more remarkable in the
case of the diving birds, such as Colymbus, Uria,
Aptenodytes, whose general form resembles that
given by mechanicians to ships constructed for swift
motion, and suggests to every observer the idea of
the solid of least resistance in water. The same
peculiarities appear in a different manner in the very
different group of diving insects, such as Dytiscus,
Colymbetes, and Hydrophilus, and may be found

D 2

36 LIFE ON THE EARTH.

again in some of the ciliated Infusoria like Trichoda
anas. But nowhere does it reach so high a degree
of perfection in air-breathing animals, as in the water-
birds alluded to ; in which if we examine the form of
the head, the texture and arrangement of the fea-
thers, and the elegant bony apparatus of the chest,
admitting of much expansion and much contraction,
we see how well, in every part, the whole living ma-
chine is fitted for its peculiar purpose, and calculated
to follow with success even the fishes which glide so
easily through their native element.

Boring into solid substances, by which, in con-
trast with all these cases, some marine tribes exca-
vate for themselves a dwelling, which they can never
leave, is accomplished by several quite different con-
trivances. Digging into sand is effected by some bi-
valve Mollusca, as Lutraria and Mya, by the action of
the same muscular mass called a foot, which enables
the Cockle to spring some distance, and the Unio to
cut its way through the slime. Pholades bore into
chalk and much harder limestone by turning round
their body and its sharply serrated shelly covering
on the pivot of the foot ; Teredines in a similar
manner destroy the substance of ships, and Limnoria
terebrans, a Crustacean, eats its way into the wooden
piles of harbours. So in early geological times, per-
forating Modiolse and Pholades are traced by their

LIFE ON THE EARTH. 37

work into the substance of coral, and Teredines are
found to have rasped their way through the masses
of drift wood in the Portland oolite, the Woburn
sand, the Chalk and London clay.

Movements in air are accomplished by animals
of the articulated and vertebrated types with a con-
siderable variety of organization, curiously engrafted
on the original structure by modification of some of
its parts. If we consider the mechanism for flight in
its completeness, the general idea appears to be the
employment of two anterior limbs for rowing through
the air by an expanded elastic wing, and employing
some retral instrument for steerage. Thus the ge-
neral arrangement is in a considerable degree the
inverse of that employed for swimming. The wing
or air-fin is in like manner distinct in principle of
construction from the paddle or water-fin. Its an-
terior edge is always strongly fortified — by bones in
Birds, by strong tracheal tubes in Insects—the sur-
face is made flexible by feathers in Birds, by clear or
scaly membranes in Insects. Thus a yielding blade
is presented to the air, and this yielding is so ma-
naged in Birds as to be nothing anteriorly but great
retrally, very little on the stroke, very great on the
return. This is managed (1) by the tile-like arrange-
ment of the feathers as a whole ; for thus they are
strongly compacted in one direction, and feeble in

38 LIFE ON THE EAKTil.

the other; (2) by the bending of the jointed wing to
extend or reduce the surface, and increase or dimi-
nish the flexibility; and (3) by the construction of
each effective wing-feather. For each of these is
so made, both in regard to the axis of the plume,
and in regard to the smaller elements of the feather,
as to be strong in the direction in which the whole
wing-arrangement is strong, and yielding in the di-
rection in which the whole wing is yielding.

This remarkable concurrence of the individual
strength of the feather in all its parts with the me-
chanical conditions of the problem is secured by the
general shape and also by a change of the substance
of the feather on the opposite faces ; the upper con-
vex face of the wing-feather having the compact
quill-sheath extended along it to the very extremity
and giving origin to the plume, while below it is a
thick mass of cellular substance, not so covered, in
which extension and contraction take place advan-
tageously. This is exactly the arrangement indicated
by the experiments of engineers, and the theories of
mechanicians, for the employment of the least weight
of such elastic materials in the production of the
required result1; but no human hands could make
an apparatus embodying so perfectly the abstract

1 Hodgkinson and Fairbairn, in Reports of the British Asso-
ciation* Barlow, On Strength of Materials.

LIFE ON THE EAKTH. 39

truths of mechanical science, nor could the human
mind with the materials given have predicted by any
theory the arrangement which is found to be so com-
plete. Into the other wonders of the feather, its
hollow quill basis, its implantation, the relation of
the directions of its axis and plane to the axes and
planes of the plumose elements I cannot now enter,
though by this means the impression that the whole
is an ingenious and profound piece of mechanism
would surely be strengthened.

The scheme of feather structure and arrange-
ment is altered in the tails of Birds to suit the very
different mechanical purposes of that instrument —
altered in the construction of the individual feathers
— in the direction of their planes — in the resultant
of their strength. Hence the resemblance of the
steering-tails of the swift Falconidae, and Hirundines,
and Sternidse — in contrast with the stiff prop of the
Picidae, and the almost extinction of the apparatus
and suppression of the function in the acuminated
tails of the Diving-birds. Every feather is altered
when the work is different.

Among Insects the Lepidoptera, with their ex-
panded wings, shew the same principle, differently
carried out; what in human contrivances is called
1 feathering the oar' being largely employed in na-
ture; and in Coleoptera we may cite the curious

40 LIFE ON THE EARTH.

doubling and cross-folding of the membranous wings
under their waterproof horny elytra, as a singular
and expressive example of a purely mechanical ope-
ration, performed on an organ for its conservation,
more ingenious than the putting-up of a fan in its
varnished case, or a parapluie into its oiled sheath.

The same mechanical principles may be traced in
the wings of the Bat, carried out in practice in such
a manner as to suit the Mammalian type of bones
and dermal covering. The fluttering collapse of the
soft skin of the Vespertilionidse is however a much
lower order of movement in air than the rapid sweep
of the elastic feather-wing of the bird ; nor need we
suppose for the flying Lizards of the Mesozoic ages a
very rapid or very sustained flight, notwithstanding
the hollowness of their elongated digital bones, the
carinated sternum, and the devotion of a large part
of the muscular energy to the anterior limbs. But
there is no reason whatever for comparing the Pte-
rodactyle with such parachute-bearing Mammals as
Petaurus, and Pteromys, and still less with the Lizard
called Draco volans. The membranes extended be-
tween the limbs of the former creatures, and beyond
the ribs of the latter, serve only to retard their fall,
and thus to allow of their making longer leaps, espe-
cially among trees, just as the flying-fish makes long
leaps by the sustaining power of its expanded pec-

LIFE ON THE EARTH. 41

toral fins. Pterodactylus, by its large and pointed
wings, retractile neck and snapping long-toothed
jaws, seems to realize all that can be supposed of a
reptile accustomed to flap the air rather heavily not
far above shallow waters, and occasionally to snatch
from them fishes swimming near enough to the sur-
face to come within reach.

Life in Trees presents us with a considerable
variety of contrivances for holding to the surface,
grasping the branches, or making incisions into the
bark and wood. To say nothing of the sucker
feet of Dipterous Insects, and the Gecko Lizard, we
may remark on the prevalent idea of climbing and
holding on by opposable fingers which appear among
the Reptilia in Chamseleon, among the Birds in the
Parrot and Woodpecker, and among the Mammalia
in the whole race of the Quadrumana. Perhaps the
prehensile tail of the Platyrhine Monkeys, and the
suspensorial claws of the Sloth, may be quoted
among the singular provisions of animals of the New
World. It is even more curious to notice with re-
spect to some of these climbing animals, the other
adjustments which complete their equipment. Thus
the feeding of the Woodpecker is provided for not
only by its scansorial foot, its supporting tail, and
its perforating beak, which makes the forests ring
around. We have further to notice the singular

42 LIFE ON THE EARTH.

piece of mechanism by which its long tongue is sud-
denly projected, and suddenly retracted, a mechanism
of elastic bone, the hyoid or tongue-bone greatly
lengthened backward, the horns turned upward in a
groove of the cranium and planted in the right nos-
tril. Inexplicable on any view but that of a wise
co-ordination of the different parts of the structure
to answer an appointed end. With this view in our
minds we no longer wonder at the long spirally
wrapped muscles which govern this elastic bone, or
at the terminal armature of the tongue.

Nor under such an aspect are we confounded by
the sudden outrush of the Chamseleon's tongue,
which seizes instantly, by its moistened extremity,
the fly so patiently watched ; the result of a com-
bined mechanism whereby the soft mass is straight-
ened, directed, and shot forth like an arrow flying to
its mark, and then retracted and folded within the
jaws which otherwise could not have received it1.

Life on land presents no less variety of appro-
priate adjustments, by which the general types of
the Vertebrata and Articulata are made to answer a
great diversity of requirements. TO take examples
from Mammalia. For pure motion what can be con-
ceived more complete than the whole frame, and

1 These peculiarities of the Woodpecker and Chamseleon and
other animals were some of my pleasant studies of Natural His-
tory 30 years since.

LIFE ON THE EARTH. 43

especially the unidigital limbs of the horse? The
predaceous habits of the Feline races are indicated
by their sharp curved claws, retractile into sheaths ;
the Mole is strengthened for digging by the approx-
imation of the scapulae, and the outward-turned
broad anterior feet; even for suspension during hy-
bernation the Bat has a hooked finger prepared;
and thus, to close this part of the subject, we find
everywhere in rich profusion, what would be regarded
as remarkable inventions, if they were due to human
minds and hands, and which cannot be removed
from the list of intelligent adaptations because they
are frequent in nature, and are of higher perfection
and greater beauty than any work of man.

On the whole it is evident that in the several
great types of animals very similar mechanical func-
tions are performed by means of organizations which
depend on the type, and have only analogical resem-
blances in the different types.

In each great type the variations of the several
organs may be such that, while the homologies are
not to be doubted, the employment of the organs
varies much. In some cases parts of the fabric
dwindle to mere representatives, as the wing-bones
of the Ostrich and the pelvic bones of the Whale ; in
others they die out altogether, as the hind-limbs of
the Cetacea.

44 LIFE ON THE EARTH.

These gradations and modifications of the parts
constituting a general type may be represented by
one of three suppositions : — First, that the structure
is what we see because that portion of the general
type, and that state of the organ or constituent part
of the type was selected as suitable for the life of the
creature; Secondly, that the structure has become
what it is by degradation from a fuller type through
the reduction or suppression of certain parts by want
of exercise of their functions; Thirdly, that the
typical structure is incompletely manifested because
some of the functions have been unexercised, and
the organs which belong to them consequently re-
main undeveloped.

Each of these views may be thought to be so far
founded on observation of nature as to be allowed in
an hypothesis for comparison with more observations.
The choice between them can only be justified by
reference to phenomena, which by their number,
consistency and critical character, may furnish a basis
for sound judgment. Without such reference a
choice no doubt will be often made, but it can then
be little better than prejudice, and must be expected
to differ in different persons, according to the pre-
vious training of their minds. It is consoling to
believe that each may be connected, indeed will be
connected, by minds accustomed

LIFE ON THE EARTH. 45

To look through Nature up to Nature's God,

with reverential thoughts of the GREAT MAKER. No
sincere inquirer for truth will be likely to expect
success in the search,

unde queat res quaeque creari,

Et quo quseque modo fiant, opera sine Divom ;

and no one who has advanced so far in Philosophy
as to have thought of one thing in relation to an-
other will ever be satisfied with Laws which had no
Author, Works which had no Maker, Co-ordinations
which had no Designer. In this as in other cases,

An undevout philosopher is mad.
SYSTEM OF LIFE COEVAL WITH MAN.

The Living creation then, as we see it, is found
to exist only in a fabric of certain sorts and certain
combinations of matter, in the presence of the atmo-
sphere, subject to continual loss and restoration of
parts, suffering death in every individual, and renewed
by birth of other individuals; adapted to the ele-
ments of water, land, and air; limited by tempera-
ture and physical conditions; called into being at
certain points of origin, and spread over certain areas
of occupation.

Thus the visible creation presents itself as a cal-

46 LIFE ON THE EARTH.

culated whole; the parts co-ordinated; the condi-
tions adjusted; the origin defined; and a long du-
ration secured. Looking at it in this aspect we may
conceive it to be all of one age — the result of one
act of power and wisdom, — the expression of one
will at one epoch of time, and in this sense employ
for the whole the term, Creation, which admits of
no explanation in human language, because it refers
to an act of God's power, transcending all human
thought and experience.

How completely the life of to-day represents the
life of the earliest historic times, in the same coun-
tries, may be ascertained by the slightest examina-
tion of the books, sculptures and buried skeletons,
which speak of those times. The Swallows, whose
twittering disturbed Anacreon, still break the slum-
bers of the luxurious poets of our day, and still ex-
cite the wonder of naturalists by their long flight to
Memphis1; the Ibis still wanders by Egyptian rivers;
Philomela still charms us with her song of love;
still clang the Cranes, and soar aloft the Eagles;
still dance in air the summer-loving Flies as in the
days of Homer; and still the Polypus and Sponge,
and all the inhabitants of the sea, exhibit in the
Mediterranean the peculiar properties noticed in
them by Aristotle. Various as are the races of
1 Anac. 12. 33,

LIFE ON THE EAIITH. 47

horses, dogs, and cattle now, they seem to have been
as various in the earlier times, and associated then
as now with particular tracts of country and fami-
lies of mankind1; nor even in regard to man do we
find much change in the African, Caucasian, or Mon-
golian races, which seem to have been from remote
antiquity separate, and still are distinguishable by
the characters assigned to them in the pages of Am-
mianus Marcellinus and Herodotus, and in the an-
cient sculptures of Egypt.

The interval of time which has elapsed since the
present races of created life came into being cannot
be known by any kind of research practicable for
mankind, unless Geology can solve the problem. As
far as human experience goes — a few thousand
years — there appears too little change in individual
character, or in the combination of the whole series,
to furnish any data for inferences touching the epoch
of the ' creation.' If we are able to say these races
of plants and animals were not eternal, nor the ear-
liest of created things, but had predecessors and a
date of origin, it is not Zoology, nor History, nor
Tradition which tells us so; but Geology, which,
agreeing with the authority of Scripture in the late
date of man, and the races of beings associated with
him, adds its own testimony of Pre-adamitic beings.

1 Oppian. KTNHF. i. 116.

48 LIFE ON THE EARTH.

If we take as the first of the problems to be exa-
mined on this subject, that which seems the most
likely to be answered on satisfactory evidence, viz.
the geological antiquity of the human race, wre find
clear though incomplete testimony leading to a sure
and definite conclusion. Man and the works of man
have been preserved in natural repositories of higher
antiquity than all the mausoleums, and tumuli, and
vTroyaid', in caverns, peat-bogs, lacustrine and river-
sediments, which derived their characteristic features
from the operation of physical conditions long since
passed away. Thus deep in the sediments of many
of our British valleys left by the rivers in some
earlier period, we find the canoe of the primitive
inhabitant, hollowed by fire and rude stone chisels
from the trunk of the native oak. In Caverns near
Swansea, and near Narbonne, skeletons of the early
people have been found ; in those of Kent's hole and
Brixham and Sicily, and deep in the gravel of Amiens
and Abbeville, the flint instruments which served for
rude workmen in wood, rude diggers of the ground,
or rude warriors in the field. According to such
observations as we can make these facts can only be
explained by supposing a long period of time to
have elapsed since their occurrence. To heap twenty
or more feet of sediment over the buried canoes by
the ordinary operation of a river like the Yorkshire

LIFE ON THE EARTH. 49

Aire, would require thousands of years ; if it were
not accumulated under the ordinary circumstances
now in operation, but under different geographical
conditions, this would perhaps require the hypothesis
of still longer time. In the alluvial sediments of this
same valley lie nearly complete skeletons of the ex-
tinct Hippopotamus major1; in another place jaws
and horns of the deer, and hazel wood and nuts, some
of them petrified2. Perhaps man was contemporary
with this extinct Hippopotamus, which has also been
found in the Peat deposits of Lancashire.

The gravel of Amiens and Abbeville appears to
furnish evidence of higher antiquity for the flint
implements found there, for they lie at the bottom
of the deposit, 20 ft. or more in depth. The deposit
is of fluviatile origin, but it is not in the bed of the
actual valley. It lies in what must have been the
course of the great floods of some earlier time, under
other geographical conditions, before the actual river-
channel was sunk to its present level. In this gravel
have been found remains of Elephas primigenius,
now extinct. Man may have been contemporary with
that animal in Europe ; nor will this appear a very
startling inference, if we remember the discovery of
the entire specimen covered with flesh and hair at
the mouth of the Lena.

1 British Association Reports, 1853. 2 Phil Mag. 1827,

R. L. E

50 LIFE ON THE EARTH.

But how many soever of centuries we allow for
the accumulation of the gravel, the filling of the
caves, or the deposition of the alluvium, this period
thus indicated is as nothing compared to those which
have passed away before it began. In a general sum-
mary we may affirm that the human period of the
earth's history is a very short one on the geological
scale, the latest of all, and yet the most important,
since independent of the interest conferred on it by
the presence of our race, it is by evidence collected
from this period that we are to judge of the earlier
ages of nature.

If we put as our second question the geological
antiquity of the races of plants and animals which
are directly and specially associated with man, as the
valuable Pomaceous Plants and Ruminant Animals,
the answer is of the same kind. They are of recent
date — their remains are found only in deposits near
the surface, which belong to the existing order of
physical conditions, the later effects of geological
agencies. The creatures most useful to him appear
to be of contemporaneous origin ; and may be em-
ployed as marks of the human period, in cases where
no traces of man or his works remain. The relation
of this to earlier periods will appear in the following
scale of geological time, the length of the periods
being not perhaps exactly proportioned to the thick-

LIFE ON THE EAETH.

51

Geological Scale of Time.

Periods, Systems. Life.

2
Csenozoic.

~ OS

Pleistocene.

Man.

Placental
Mammals.

Pleiocene.

Meiocene.

Eocene.

- 00

Mesozoic.
~ £••

- &

Cretaceous.

Marsupial
Mammals.

Oolitic.

Triassic.

- ^j
- -*

Palaeozoic.

- <M

- iH

Permian.

Reptiles.

Land Plants.
Fishes.

Monomy. Echinod.
Pterop. Heterop.
Dimy. Gasterop.
Annel. Polyzoa.
Zooph. Brach. Crust.

Carboniferous.

Devonian.

Siluro-
Cambrian.

52 LIFE ON THE EARTH.

nesses of the systems of strata, but yet (as will be
shewn hereafter) undoubtedly to some extent repre-
sented by them.

In this scale the total thickness of the Fossil-
iferous strata, down to the Lingula beds of Wales,
is assumed to be 10 miles, 52800 ft. That is not the
maximum thickness, which in Britain is supposed by
Ramsay to be 72584 ft. In his estimate the Palae-
ozoic beds are taken much above the average, and
the Csenozoic beds much below the average of
Europe, Morris gives the maximum numbers thus,
Caanozoic 2830, Mesozoic 6170, Palaeozoic 49460.
D'Orbigny's general statement gives 21260 metres
= 69750 ft., the Tertiary occupying 9842 ft., while in
England they are supposed to be 2240. The figures
on the left may be used to mark miles of depth, thick-
ness of deposits, or periods of unknown duration,
according to the purpose in view.

The Geological Scale of Time thus constituted by
the succession of marine strata, is liable to the objec-
tion which applies to almost every scale of historical
time, that it is not complete in any one region, no
one oceanic basin having been yet discovered which
has received marine sediments continuously through
all geological periods. The remedy is the same as in
ordinary history — the scales of different regions are
combined by means of common terms, which in one

LIFE ON THE EARTH. 53

district appear in the upper part of one series, and
in another district in the lower part of another.
Thus in several parts of England the Permian system
is unconformed to the Coal series, but on the borders
of the Staffordshire Coal-field it seems otherwise, and
the sequence appears to be nearly complete. Again,
the passage of the Permian strata into the Triassic
group is more full in the south of Yorkshire than
elsewhere, and the passage of the Trias into Lias is
best exhibited (in England) in the Vale of the
Severn. The uppermost chalk of Maestricht and
the region of Bayonne softens the break which in
England appears so decisive at the base of the Cseno-
zoic strata ; and thus, with few exceptions, by taking
our data from different regions we acquire nearly but
not quite a complete series of the strata of marine
origin, and the means of accurately placing the monu-
ments of the life which has passed away for ever.

SUCCESSIVE SYSTEMS OF LIFE.

Passing from the limited consideration of man
and his works, and the animals and plants specially
associated with him, to examine as a third problem
how far into antiquity we can trace the forms of the
numerous species of existing plants and animals, we
find in deposits of old, but perhaps not prehistoric

54 LIFE ON THE EARTH.

or at least prehuman date—peat bogs — subterranean
forests — sea-beaches — lacustrine m arls — river-sedi-
ments— many examples of the plants, shells, insects,
birds and quadrupeds now existing, together with a
few no longer living in the same regions, as the Wolf
and Beaver in England, or not now living any where,
as the Irish Elk, Rhinoceros, Hippopotamus major,
Elephas primigenius, and large Lion. Below these, in
the deposits called Pleistocene, the proportion of
extinct species mixed with species still living in-
creases. In the Pleiocene tertiaries it is great, still
greater in the Meiocene, and quite predominant in
the Eocene, below which, in all the Mesozoic and
Palaeozoic Strata, there is hardly a fossil specimen of
a living species — though it is held by several writers
that Terebratulina striata of the Cretaceous Strata is
both fossil and living, and it is not possible to dis-
tinguish some forms of fossil and living Foramini-
fera1.

With the exceptions already noted, if they be
really such, the whole living creation, examined by
species, as we understand this term, ceases below
the Tertiary Strata. For this reason, to indicate the
real affinity of their organic contents to the living
creation, I have elsewhere called them Cvenozoic.
The following table will illustrate this statement
1 Auct. Ehrenberg, Jones, Parker.

LIFE ON THE EARTH.

55

by a few examples of living species selected from
marine animals only1.

d

1

i

i

1

a

vermicul

|

1

I

cS

P3

i

1

Pes Peli

1

1

1

8

1

|

a
!

%

1

a

1

£

1

£

1

1

a

3

«

E.

A.

Cr.

P.

B.

M.

D.

G.

Cet.

In Modern Oceans

—

—

In Ceenozoic Strata. Pleistocene

<*

*

-X-

*

*

Pleiocene

*

•X-

-X-

•*

•5C-

#

*

*

Meiocene

_

_

Eocene

__

In Mesozoic Strata

But if we examine the fossil and living races by
genera instead of species, the result is different.
For instance, some existing genera of Mollusca occur
in the Mesozoic, and perhaps even in the PalsDozoic
Strata, though in these latter the genera Avicula,
Modiola, Nucula, &c., among Conchifera, are by
some writers thought to be distinguishable from
their living analogues.

The subjoined table is meant to illustrate this

1 The asterisk indicates in what deposits the living species
occur. E. Echinodermata ; A. Annelida ; Cr. Crustacea ; P. Poly^
zoa or Bryozoa ; B. Brachiopoda ; M. Monomyaria ; D. Dimyaria j
G. Gasteropoda ; Cet. Cetacea.

LIFE ON THE EARTH.

statement by examples taken from the same classes
as in the former table, with the exception of Fishes
(F), which are here substituted for Cetacea.

»3

o
E.

£
A.

£ Palinurus.

TO Cellepora.

to Terebratula.

a
M.

d

1

fc

D.

.1

£
G.

eg

1
F.

In modern Oceans

*

In Csenozoic Strata

•X-

*

*

*

*

*

-X-

*

*

In Mesozoic Strata

*

*•

*

t

*

*

*

#

•x-

In Palaeozoic Strata . .

%

•

*

•

#

•

For comparison with the tables just given of
species and genera still living traced backward in
time, we may in like manner select species and
genera living in the older strata, and trace them up-
ward in the rocks, or forward in time, as in the
following examples. There being no Fishes in the

tn

3

.

1

1

r

'S3

1

1

o

•2

1

d

.S

8

•§

c2

0

JJB

H

1

0

|

B

02

$

J«

^

c8
|

3

i

So

M

§

P

a

g

I

I

'g

1

fe

f

1

"3

P<

§

1

01

•«

«

3

1

6

d

0

z.

E.

A.

Cr.

P.

B.

M.

D.

G.

Cc.

In modern Oceans

In Csenozoic Strata

—

—

—

—

—

—

—

—

—

In Palaeozoic Strata

*

*

*

*

*

*

*

*

*

*

LIFE ON THE EARTH.

57

lower parts of the Palaeozoic Strata, Zoophytes are
introduced (Z) instead. We have added also a column
for the Cephalopoda (Cc).

In the same manner we may select genera which
occur in the older strata, and trace upward those
which have the greatest range in the strata, in other
words, the longest duration in time.

d

1

3

o

1

i

o

t

.2

1

1

1

N

&

i

0

3

2

5

*

fc

K

Z.

E.

A.

Cr.

p.

Br.

M.

D.

G.

Get.

In modern Oceans

*

*

•«$•

*

*

In Csenozoic Strata

—

In Mesozoic Strata

*

In Palseozoic Strata

Again, if we consider not genera but greater
groups as families, their extension is greater, their
antiquity higher ; while some classes of the radiated
and molluscous and articulated divisions occur in
all the strata. Thus the general result is to shew
that only one general plan of creation is to be traced
in all the range of geological time, though the terms
in which this plan is expressed vary from period to
period. There is a succession of the forms of life to
be traced in the strata ; we shall shew hereafter that
the relative proportions of the families, orders, and

58

LIFE ON THE EARTH.

classes vary so as, in this limited sense, to justify our
speaking of different systems or combinations of
life ; but they are all included in one general plan of
the Omniscient mind, comprehending the past, the
present, and the future.

Perhaps this subject may be yet further illus-
trated by means of tables shewing on the one hand
the numerical distribution in time of some genera of
marine animals now living and remarkably prevalent
in the sea, and of others as abundant in the more
ancient strata. In each case the relative abundance
of species is intended to be shewn by the numerals
corresponding to each period. I confine the illustra-
tions to the Molluscous animals, because of their
being the most uniformly plentiful in all periods,
and to the British Islands, as affording the best or
most convenient terms of comparison.

Nwmerous in a living state.

j

rf

1

i

rf

^

y

|

»•

|

|

.

cS

*O

B

•S

£

f|

c5

^

s

2

3

g

5

3

£

o

Q

S

1

§

1

Recent ....

200

200

100

100

170

60

117

269

430

70

350

150

Csenozoic..

22

34

43

32

14

1

3

9

50

32

8

14

Mesozoic . .

34

5

7

9?

2

Palaeozoic .

~~

•-_

LIFE ON THE EARTH.

The numbers representing the several genera in
the Csenozoic groups of strata would bear a much
nearer proportion to those of the now living species
if we had employed the data of Deshayes, and in-
cluded European species. The analogy of the Cse-
nozoic to the living marine fauna, and the contrast
between these and the older systems of life are espe-
cially striking in regard to the Gasteropodous genera
placed to the right.

Numerous in a fossil state.

.

of

1

§

4

i

.

i

<&

B

4

S

§

eS

:£

&

2

2

%

«2

&

a

"S

0

I

0

Q

§

I

I

1

g

I

S

1

1

|

1

0

Recent ....

~~~

'

~~

Csenozoic..

—

—

—

2

—

1

—

—

—

—

—

Mesozoic ..

—

—

5

70

45

29

30

18

—

280

36

1

Palaeozoic •

69

51

84

6

—

—

54

—

41

—

—

97

VARIETY OF THE FORMS OF LIFE IN SUCCESSIVE
PERIODS.

If we select among the marine classes of animals
those which are represented in all the great periods
of Geology, count the number of species yet disco-
vered in them in the British strata1, and refer

1 See Morris's excellent Catalogue of British Fossils, 2nd
Edit.

60

LIFE ON THE EARTH.

them at present to only three great periods, we have
the following result :

1

ci

4

§

1

t

I

I

1

1

I

g

.3

1

i

§

ft

s

|

1

3

i

3

o

«

g

a

o

5

H

Csenozoic ...

27

41

15

8

63

394

662

12

1222

Mesozoic . . .

103

245

65

165

308

499

389

396

2170

Palaeozoic . . .

379

225

218

632

196

342

401

336

2729

The absolute number of marine species appears
thus to be greatest in the Palaeozoic Strata; but
when the thickness of the deposits — which represents
elapsed time — is taken into account, the variety of
forms in a given thickness or given period of time is
very much less.

For if we take account of the thickness according
to the maximum scale for Britain proposed by Ram-
say, on data collected by the Geological Survey, the
following table may be constructed : —

Total

Species
in 8 classes.

Maxim.
Thickness.

Eelative number of
Species to 1000 ft.

Csenozoic Strata

1222

2240

KAK

Mesozoic Strata

2170

23190

164

Palaeozoic Strata

2729

57154

41

The ratio thus found by dividing the number of
species by the maximum thickness, represents . the

LIFE ON THE EARTH.

61

variety of life by the relative number of species to be
expected on an average in searching a given thick-
ness of strata in each of the great periods. Also
since it is known that the species are not uniformly
arranged through the deposits of each period, but
occupy many distinct stages in each, we may say that
on the average, they represent the rate of change in
the forms of marine life, or the number of different
species to be expected in searching successive equal
thicknesses in each of these systems of strata. Accord-
ing to Morris's estimates of thickness (p. 52), the
relative numbers would have been 432, 251, 59.

Had we instead of the figures which represent
the thicknesses and number of species found in
Britain employed the data given by D 'Orbigny1,
counting all the species in all the classes of Mollusca
and Radiata, viz.

Species.

Thickness in
metres.

Eatio.

Csenozoic

6042

3000

201

Mesozoic

9064

6010

150

Palaeozoic

3180

12250

26

we should have nearly the same result as with
Morris's numbers ; a nearer approximation of the
Mesozoic and Caenozoic ratios, but the same remark-
able inferiority of the Palaeozoic series.

1 PalcBontologie et Geologic, 11.

62 LIFE ON THE EAETH.

Thus it appears certain that the variety of life,
estimated by the marine tribes existing in a given
period, is greater in the more recent periods; but
the number of individuals, or the abundance of life,
is not measured by the same proportions. Periods
of extraordinary abundance alternate in every great
series of strata with other periods of comparative
scarcity; and though sometimes this may be ex-
plained by the well-known fact that red peroxide of
iron in sedimentary strata is very unfavourable to
marine invertebral life, while grey protoxidated rocks
of the same series contain organic remains in abund-
ance ; and sometimes requires attention to the un-
equal conservative conditions, or originally unequal
feeding circumstances of Calcareous, Argillaceous and
Arenaceous sea-bottom ; still it is a very impressive
phenomenon in the continuously grey Cambrians
and Silurians, in the continuously grey Carboniferous
rocks, in the continuously protoxidated Oolitic strata,
and in the almost uniform deposits of Lias, Oxford
Clay, Kimmeridge Clay, Gault, London Clay and
Barton Clay. An illustration is subjoined from the
Lower Palaeozoic Strata of Britain. Fig. 3.

LIFE ON THE EARTH.

63

PASSAGE.
LUDLOW.

WENLOCK.
LLANDOVEEY.

CABADOC.

LLANDEILO.

LINGULA.

Fig. 3-

3
114

123

78

49

15

64 LIFE ON THE EARTH.

In this diagram the Passage Beds are taken at
500 ft. with 13 species, Ludlow 2000 ft. with 228 spe-
cies, Wenlock 2500 ft. with 322 species, Llandovery
2500 ft. with 196 species, Caradoc 6800 ft. with 335
species, Llandeilo 6800 ft. with 104 species, Lingula
beds 4000 ft. with 14 species. The area of the spaces
corresponds to the number of species, thus shewing
at a glance the relative richness in species of the
several groups for equal thicknesses. This richness
(expressed by numbers on the right side) rises from
almost zero in the Lingula beds to a maximum in
the upper part of the Wenlock series, and dies out
almost to zero in the beds of Passage to the Old Red
Sandstone system above.

What is here said of the Siluro-Cambrian or
Lower Palaeozoic Strata may be repeated with equal
truth in reference to each of the systems of associated
deposits : for in each the characteristic and prevalent
fauna begins at a minimum, rises to a maximum, and
dies away to a final minimum, to be followed by an-
other system having similar phases. The most remark-
able and prevalent of these surfaces or zones of least
life are those two which separate the Palaeozoic from
the Mesozoic, and these from the Caenozoic Series.
The Palaeozoic Series dies out through the Permian
system, and the Mesozoic rises slowly in the Trias;
so the Mesozoic Series dies away in the uppermost

LIFE ON THE EARTH. 65

beds of the Cretaceous system, and the Csenozoic
Series grows slowly through the lowest Eocene to a
maximum in the later tertiaries.

A depression in the maximum occurs in the Palae-
ozoic Series of Britain corresponding to the Devonian
period, here so largely represented by peroxidated
sediments ; another in the Mesozoic period, in the
uppermost Oolites, which are poor in comparison with
the richer series of Oxford and Bath. These pecu-
liarities are represented in the following diagram by
a continuous curve, which corresponds to the nu-
merical prevalence of life, and represents its rise
and fall. Fig. 4.

R. L,

66 LIFE ON THE EARTH.

C^NOZOIC LIFE.

MESOZOIC LIFE.

PALAEOZOIC i

LIFE. /

Fig. 4.

LIFE ON THE EARTH. 67

ORIGIN OF LIFE ON THE EARTH.

We have found by this mode of inquiry that the
abundance of the forms of life in the sea has been
very unequal at different periods, and that race has
followed race so as to match the words of the poet —

Augescunt alise gentes, aliae minuuntur,

Inque brevi spatio mutantur ssecla animantum,

Et quasi cursores vita'i lampada tradunt.

Can we trace back this system to an origin, or do
we discover only cycles of perpetual change, system
following system, with 'no trace of a beginning, no
prospect of an end'? Perhaps the following consi-
derations will incline the reader to adopt the opinion
which ascribes a definite origin in time to life on
the earth.

1. It is ascertained that, in passing downward
through the lower Palaeozoic Strata, the forms of
life grow fewer and fewer, until in the lowest Cam-
brian Rocks they vanish entirely. In the thick series
of these strata in the Longmynd (supposed to be
20000ft. thick or more) hardly any traces of life
occur. Yet these strata are of a kind such as might
be expected to yield them ; for they are not in general
peroxidated, nor conglomeritic, nor much affected
by metamorphic action, nor so much confused by

F2

68 LIFE ON THE EARTH.

slaty cleavage as to render the search for fossils
ineffectual by any of these circumstances. The ma-
terials are fine-grained or arenaceous, with or with-
out mica, in laminae and beds quite distinct and of
various thickness, by no means unlikely to retain
impressions of a delicate nature, such as those left
by Graptolites, or Mollusks, or Annulose crawlers.
Indeed, one or two such traces are supposed to have
been recognized, so that the almost total absence of
the traces of life in this enormous series is best
understood by the supposition that in these parts of
the sea little or no life existed. But the same re-
mark of the excessive rarity of life in the lower de-
posits is made in North America, in Norway, and in
Bohemia, countries well searched for this very pur-
pose, so that all our observations lead to the conviction
that the lowest of all the strata are quite deficient of
organic remains. The absence is general — it appears
due to a general cause. Is it not probable that during
these very early periods the ocean and its sediments
were nearly devoid of plants and animals, and in
the earliest time of all which is represented by sedi-
ments, quite deprived of such ?

2. The variety of life in the sea continually aug-
ments from the lower Cambrian rocks upwards, in
such a way as to leave no doubt of the richer fauna
of the Llandeilo series being a part of the same

LIFE ON THE EARTH. 69

natural system as that of the Lingula flags below,
and of the Caradoc beds above. Thus in tracing
backward the series of Siluro-Cambrian life it ap-
pears to diminish, and disappear in a few forms, if
not in a single form, before we reach the base of the
strata. Thus we seem to have, as nearly as can be
had, the evidence of the beginning of the earliest
traceable life after the commencement of the earliest
non-metamorphic strata.

3. In tracing downwards the various classes of
marine animals, we find them to disappear separately
at several successive zones of strata, so that for each
class we have reason to think the origin in time is
reached, or at least approached. Thus Fishes are
not found below the Ludlow Rocks; Rhynchonella
and Avicula hardly pass below Caradoc beds ; Dimy-
aria and Cephalopoda grow very rare in the Llandeilo
Rocks ; and Lingula is almost the solitary occupant
of the lowest laminae of the fossiliferous beds of
Wales.

No doubt it is open to any one to compare this
approach to a Hypozoic Zero, with the reductions of
life to a minimum above the Palaeozoic and above
the Mesozoic deposits; and to suppose that below
the Palaeozoics were other earlier strata and earlier
systems of life, though they are now all lost in the
general metamorphism which has produced the

70 LIFE ON THE EARTH.

Gneiss and Mica Schist. No one is likely to believe
this however who attends seriously to the facts re-
garding the successive appearance of the classes,
orders, families, genera and species, as we search the
records of Geological time.

EARLIEST SYSTEMS OF LIFE.

The earliest system of life of which comments
remain is found in that very low part of the fossil-
iferous rocks of Wales, to which Professor Sedgwick
first directed attention, now called the Lingula Zone.
Perhaps the fossils of Bray, in the county of Wick-
low, may belong to an older group of the strata, but
this is assumed rather than proved. Of the two
generic forms there discovered, Oldhamia may be a
plant; Histioderma is an Annelid, probably of the
Cephalobranchiate order. Taking our stand on the
now well-explored Lingula Zone, but including in
our Survey the forms just mentioned, we find the
following characters of marine life, for no trace of
terrestrial or of Fresh-water organization has been
observed.

Zoophyta 1 One genus. Oldhamia, 2 species.
Annelida 2 genera. Histioderma — Arenicolites—

2 species.

LIFE ON THE EAKTH. 71

Crustacea 7 genera. Agnostus — Conocephalus —

Ellipsocephalus — Hyme-
nocaris — Olenus — Para-
doxides — Protichniites —
11 species.

Polyzoa One genus. Dictyonema — 1 species.

Brachiopoda 2 genera. Lingula — Orthis. 3 species.

The list is taken from a valuable catalogue of the
Lower Palaeozoic Fossils of the British Isles, in Mur-
chison's Siluria, Ed. n. 1859 \ The Crustacea belong
mostly to the great family of Trilobitidse. Norway
and North America yield each a series of the same
general character. A larger number of species has
been detected by M. Barrande in Bohemia, with the
same general aspect. Individuals of the Oleni, Lin-
guise and Oldhamise are abundant in certain layers,
but a large portion of the strata of this ' Primor-
dial ' Zone is devoid of all traces of life.

Small as is this series of generic forms, we re-
cognize representatives of each of the three great
branches of the Invertebrata — there are carnivorous
feeders as well as creatures nourished by cellular or
vegetable food — and Fucoids are traced both in
Norway and Malvern, in beds below the Oleni. In

1 Three species of Oleni found by myself in the black shales of
Malvern are included in this zone, though in the Catalogue re-
ferred to they are placed in the Caradoc formation. Murchison,
however, assigns these black shales to the early date here adopted
for them. Siluria, 45 et seq.

72 LIFE ON THE EARTH.

what sense a system of life restricted to these few
and mostly small elements can be regarded as the
ancestral type of the races now living in the sea,

gentis cunabula nostrse,

will perhaps appear as we proceed. Lingula is
henceforward always present in every great group of
strata till we reach the Tertiaries.

The next combination which attracts attention
occurs in the superincumbent group of strata, called
the Llandeilo formation. The following summary will
be sufficient for our purpose :

Zoophyta 4 genera 4 species.

Crustacea

jj
16

34

Polyzoa

6

22

Bradiiopoda

5

18

*]V[onomyaria

I

. . 1

*Dimyaria

2

2

* Gasteropoda

3

3

*Heteropoda . . .

1 „ ...

2

* P t eropoda

2

6

*Oer>}ia1oT)oda .

2

4

The classes of Invertebrata are now augmented
to eleven : the new classes, all Molluscous, marked by
the asterisk, being very poor in species, while the pre-
viously existing classes have become much more fertile.

The Annelida include both Cephalobranchiate and
Dorsibranchiate tribes.

LIFE ON THE EARTH. 73

The Crustacea are nearly all Trilobites.

Among the Brachiopoda is no Rhynchonella or
Terebratula.

The single Monomyarian is Ambonychia Triton,
from Bird-hill, near Llandeilo, of the family Avicu-
lacese.

The two Dimyarians are Ctenodonta Isevis and
Cucullella Anglica (of the family Arcadse).

These two families stand near to one another in
the methods of naturalists.

Among the characters of this period is the rela-
tive prevalence of Pteropod and Polyzoan species,
and the absence of Echinodermata, if indeed the
Haverfordwest Strata which yield Echinosphserites and
Sphseronites, be rightly removed from this formation.

The Carnivorous tribes are augmented by the
Cephalopoda, which henceforward are found to sus-
tain a very important part in the economy of the
sea, and in a less degree by the Pteropoda and Hete-
ropoda.

A third combination may be examined in the
Caradoc formation, which indeed is scarcely to be
separated from the Llandeilo series, but is much
richer in species.

*Amorphozoa ... 2 genera 3 species.

Zoophyta 11 „ 23 „

^Echinodermata.. 8 ..20

74 LIFE ON THE EARTH.

Annelida 6 genera 8 species.

Crustacea 28 „ 82* „

Polyzoa 9 „ 27 „

Brachiopoda ... 12 „ 67 „

Monomyaria ... 2 ,, 7 „

Dimyaria 10 „ 31 „

Gasteropoda ... 10 „ 25 ,,

Heteropoda 1 „ 7 ,,

Pteropoda 4 ,, 7 „

Cephalopoda ... 4 ,, 26 „

Two new classes, Amorphozoa and Echinodermata,
appear among the lower groups of the Invertebrata.
Crustacea ascend to a great predominance, both in
number, variety, and magnitude, still belonging to
the same divisions; Cephalopoda, Gasteropoda and
Dimyaria grow to be numerous. Thus the aspect of
the marine Fauna is greatly altered.

Brachiopoda abound, and now Rhynchonella, an
existing genus, appears, but without Terebratula,
which is also living. Among the Dimyaria, Pleuro-
rhynchus is recorded, but Arcadse and Mytilidse are
the predominant races, Aviculidse still the only Mo-
nomyarian group. Among the Gasteropoda Murchi-
sonia prevails. Orthoceras, comparatively rare in
Llandeilo rocks, is here abundant. Star-fishes appear
among Echinodermata.

The series of strata next above is regarded by
Murchison as a transitional or intermediate group

LIFE ON THE EARTH. 75

between the Caradoc and Wenlock formations, and
receives from him the name of Llandoveiy Rocks.
Hardly a single genus (Mdulites may perhaps be
one exception), but as many as 71 out of 193 species
seem to have been found exclusively in these deposits.

Plants. Fucoids.

Amorphozoa 2 genera 2 species.

Zoophyta 14 „ 26 „

Echinodermata 5 „ 6 „

Annelida 2 „ 3 ,,

Crustacea 11 „ 16 „

Polyzoa 3 „ 5 „

Brachiopoda ... 13 „ 69 „

Monomyaria ... 2 „ 5 „

Dimyaria 8 „ 13 „

Gasteropoda ... 13 „ 26 „

Heteropoda ... 1 „ 6 ,,

Pteropoda 3 „ 3 „

Cephalopoda ... 5 „ 13 „

We find in the Upper Silurian Strata the system
of life unequally represented in the different parts
of the series, most full in the Wenlock and Ludlow
groups, and reduced almost to nothing in the upper-
most beds. In the Wenlock group, which contains
the principal calcareous mass of the Silurian Strata,
we find :

Amorphozoa ... 3 genera 3 species.

Zoophyta 29 „ 66 „

76 LIFE ON THE EARTH.

Echinodermata 20 genera 34 species.

Annelida 4 „ 6 „

Crustacea 16 „ 36 „

Polyzoa 12 „ 25 „

Brachiopoda ... 17 „ 79 „

Monomyaria ... 2 „ 12 „

Dimyaria 7 „ 15 „

Gasteropoda ... 8 „ 18 „

Heteropoda 1 „ 3 „

Pteropoda 2 „ 3 „

Cephalopoda ... 3 „ 22 „

The prevalence of Zoophyta is connected with
the great abundance of limestone in this Zone, a
circumstance less favourable to Crustaceans, though
these are still numerous ; all Entomostracous, mostly
Trilobites. The Monomyarians are all Aviculoid, the
Dimyarians mostly Arcaceee and MytilacesG.

In the Ludlow Zone which follows, we have to
remark a general analogy to the Caradoc deposits,
both being for the most part arenaceous and muddy
deposits, with only partial expansions of the calca-
reous element. Hence fewer Zoophyta and Echino-
dermata, more Monomyaria and Dimyaria, these bi-
valves being still of the same natural families. In
the uppermost layer Land-plants and Fishes appear
for the first time in the History of Life.

Plants probably terrestrial 1 genus 1 species.

marine... 2 genera 5 „

Amorphozoa (none)

LIFE ON THE EARTH. 77

Zoophyta 8 genera 10 species.

Echinodermata ... 11 „ 17 „

Annelida 6 „ 8 „

Crustacea 15 „ 39 „

Polyzoa 1 „ 1 „

Brachiopoda 10 „ 30 „

Monomyaria 2 „ 17 „

Dimyaria 10 „ 41 ,,

Gasteropoda 10 „ 27 „

Heteropoda 1 „ 4 „

Pteropoda 3 „ 4 „

Cephalopoda 5 „ 30 „

! Fishes 5 „ 7 „

The decline of the whole series is very marked in
the Passage-beds, which yield only the following
meagre list.

Plants probably terrestrial — Lycopodiaceae ?

Crustacea ... 5 genera 11 species.

Brachiopoda... 1 „ 1 „

Gasteropoda... 1 „ 1 „

! Fishes 5 „ 7 „

Of the few species here noted, three Fishes, the
two Mollusks, and six of the Crustacea, are also
found in the upper Ludlow beds, of which indeed
these are merely the capping. This decline of the
Silurian species may be compared with the dawn of
the series in the Lingula Zone ; the analogy of con-
ditions is maintained by the Crustacea and Brachio-

78

LIFE ON THE EARTH.

poda, but difference of time is marked by Gastero-
poda and Fishes.

From the data thus collected we may compile
one general table representing the numerical preva-
lence in time of each of the classes of Marine Inver-
tebrata in the Lower Palaeozoic Strata as at present
known.

o

j

4

|

3

,

4

|

,

|

1

»s

f

•3

•y,

M

"o

g

§

0

•S

1

o

^»

i

2

0*

5

1

I

!

1

§

|

i

M

1

S

1

1

1

JL

,,

1

1

Ludlow

1

10

17

18

39

i

30

17

41

27

4

4

30

Wenlock

3

66

34

6

36

25

79

12

15

18

3

3

22

Llandovery ...

2

—

26

6

3

16

5

69

5

13

26

6

3

13

Caradoc

3

__

23

20

8

82

27

67

7

31

25

7

7

26

Llandeilo

—

4

7

34

22

18

1

2

3

2

6

4

Lingula

_

— -.. .

V,?

2

11

1

By inspection of this table it appears that the
earliest system of marine life contained a few exam-
ples of five great classes; viz. Zoophyta, Annelida,
Crustacea, Polyzoa, Brachiopoda.

In the next period all the ordinary classes of
Mollusca are added, in small numbers.

In the third period, Echinodermata appear, and
perhaps Amorphozoa, for this seems, to me at least,
still somewhat doubtful.

Thus excepting Cirripedia which up to this time

LIFE ON THE EAETH. 79

have not been certainly recognized, all the important
classes of Marine Invertebrata are traced into the
Lower Paleozoic Strata, beginning in each case with
few species and very few genera. The progress of
the several classes is very unequal. Crustacea, rela-
tively abundant in every stage, reach a maximum in
the third period. Brachiopoda, also a very abundant
group, reach the maximum in the fifth period with
Zoophyta and Echinodermata, while the Monomyaria,
Dimyaria, Gasteropoda, and Cephalopoda increase,
though not uniformly, upwards to the sixth period.
The seventh period is everywhere marked by a zone
of sterility, the local extinction of most of the classes,
and the introduction of a new order of sediments,
brought by a new set of watery currents. Arranging
the classes according to their priority of appearance,
including Fishes, and giving to each in the successive
strata a space proportioned to the number of species,
we construct the scheme of proportionate life for the
Lower Palaeozoic Strata, represented in Fig. 5.

80

LIFE ON THE EARTH.

LIFE ON THE EARTH. 81

SUCCESSIVE SYSTEMS OF MARINE IN VERTEBRAL
LIFE.

The system of life thus constituted in the seas of
the most ancient period so far resembles the system
now established in modern oceans as to contain the
same classes with similar functions and dependen-
cies. But there are great differences in the relative
proportions of the classes, and of the tribes which
are included in them. And these differences are to
a certain extent dependent on the elapsed time;
classes at first very small have grown very large,
others once predominant have been greatly dimi-
nished. To make this evident it will be useful to
give up the mere enumeration of species in each
class, and to adopt as a basis of representation the
proportions in which the classes stand to each other
in each period.

This can be easily done by equating the sum of
the species in each period to 1000, and the number
of species in each class to its proportion of the
whole. Choosing for this purpose eight principal
classes or assemblages, and tracing their relative
proportions in successive periods, we arrive at the
result represented in the parallelogram, Fig. 6.

In this representation of the relative proportions
of the several classes in successive geological periods,
R. L. G

82 LIFE ON THE EARTH.

the arrangement is purposely made to shew by the
blue tint those classes which suffer diminution with
time, and by the red tint those which from small
beginnings grow to great preponderance, — while the
yellow tint is assigned to classes which scarcely ap-
pear in the early period, but swell out in the middle
of the scale so as to equal or overmatch either of
the other classes Thus appears in a striking light
the great difference between the systems of oceanic
life in earlier and later periods, the nature of this
difference, and something of the method of varia-
tion which binds the whole into one plan, and con-
nects the dawn of created life with this our breathing
world.

In all the great periods the numerically prevalent
life among the Invertebrata of the Sea appears in the
Molluscous division1.

In the three grand periods the order of preva-
lence is thus found.

Caenozoic Period . . . Gasteropoda, Dimyaria, Monomyaria,
Echinodermata, Zoophyta, Crustacea,
Cephalopoda, Brachiopoda.

Mesozoic Period ... Dimyaria, Cephalopoda, Gasteropoda,
Monomyaria, Echinodermata, Brachio-
poda, Zoophyta, Crustacea.

1 Only in the very earliest zone, Crustacea appear to predomi-
nate over Brachiopoda.

LIFE ON THE EARTH. 83

Palaeozoic Period ... Brachwpodu, Gasteropoda, Zoophyta,
Dimyaria, Cephalopoda, Echinodermata,
Crustacea, Monomyaria.

Taken in the order of their total numerical su-
periority, the classes range thus :

Caenozoic. Mesozoic. Palaeozoic. Total.

Gasteropoda 662+ 389 401 1452

Dimyaria 394 499+ 342 1235

Brachiopoda 8 165 632+ 805

Cephalopoda 12 396+ 336 744

Monomyaria 63 308+ 196 567

Echinodermata ... 41 245+ 225 511

Zoophyta 27 103 379+ 509

Crustacea 15 65 218+ 298

The sign + is placed to the maximum number
in each class, shewing that the maximum is attained
in the

Caenozoic Period, by Gasteropoda.

Mesozoic Period, by Dimyaria, Cephalopoda, Monomyaria,

Echinodermata.
Palaeozoic Period, by Brachiopoda, Zoophyta, Crustacea.

These results afford but slight encouragement to
the speculation of the inferiority of the earlier and
superiority of the later systems, and of continual
progress upward in the organization of animals. In
proportion to the elapsed time the changes make
progress, but these changes are not always in the
sense of uninterrupted advance from inferior to
superior forms.

G2

84 LIFE ON THE EARTH.

For example, Cephalopoda, by universal consent,
stand at the head of the Molluscous kingdom of
animals; but their origin is of the same date as
that of the Mollusca generally : they rapidly rise to
importance, but pass the maximum in the Mesozoic
period, and are now but a small and scattered part of
the inhabitants of the sea, enormously outnumbered
by the inferior races of Gasteropoda and Dimyaria.
Thus, starting from an equal basis, the superior class
has lost in the 'struggle for existence.' But we
must examine this subject on other occasions, after
gathering additional data.

CHANGES IN MARINE ANIMALS WITH ELAPSED
TIME.

The principal classes of marine fossil Invertebrata
have now been traced from what seems to be their
origin, to or beyond the epoch of their greatest
prevalence. We have, in fact, taken the census of
our marine inhabitants at several periods. It re-
mains to examine them with reference to their
structure and grade of organization in these periods ;
to compare, for instance, the Crustacea and Mollusca
of one period with those of another, and thus to
learn the amount of variation in this respect from
period to period, and what is the method of varia-
tion. We may include in this inquiry Fishes, which

LIFE ON THE EARTH. 85

to the extent of 736 species have been recorded in
the British strata, Marine Reptiles, which are less
numerous, and Cetacea, which are rare.

Amorphozoa offer in this respect little for remark.
Belonging to the lowest grade of animal organiza-
tion— by some naturalists of eminence counted among
plants — Sponges are nowhere very abundant except
in the Cretaceous Strata, where some forms occur
much like existing tribes, and similarly furnished
with siliceous spicula, and in some cases with a net-
work of anastomozing fibres.

Foraminifera. — These minute cellular structures
occur perhaps in most of the limestones and clays,
but at present the greater number are quoted from
the Upper Mesozoic and Csenozoic Strata. In ge-
neral they correspond much and even remarkably to
existing kinds. Some fossil groups, extremely vari-
able in form, appear quite undistinguishable from
recent examples; so that by this tribe of animals
there appears a continuity of some specific forms
from Mesozoic through Csenozoic to recent times1.

Zoophyta. — The fossil groups are principally of
the kinds which secrete the stony support known as
Coral, and belong to the division of Zoantharia.
With hardly an exception (Gorgonia?) the numerous

1 Carpenter, Proc. of Roy. Soc. 1855—60. Jones and Parker,
Journal of the Geological Society of London, 1860.

86 LIFE ON THE EARTH.

genera of the Palaeozoic systems belong to this divi-
sion; the same is true for the Mesozoic series; and
even in the Caenozoie strata Alcyonoid Zoophyta are
rare. Here, then, is one great order of Zoophyta
continuous through the whole series. The genera
change with the successive deposits, but there is one
remarkable law of structure which is characteristic
of period. The radiating plates of the Coral are in
a young state pretty regular in number and in the
mode of division. In all the Palaeozoic Strata the
primary or principal plates are four, or some multiple
of four; in all the Mesozoic and Caenozoic Strata
they are six, or some multiple of six. This striking
generalization, due to Milne Edwards and the late
Jules Haime, is thought to be subject to no more
than solitary exceptions. It suggests the reflec-
tion that the persistence of characters which we
observe in modern living nature was quite as re-
markable in ancient organizations, and throws a
heavy weight into the scale against the doctrine of
the later forms of life being derived from earlier
types, through natural variations integrated by time.

Echinodermata. — Six fossil groups represent this
beautiful class of animals, viz. Crinoidea, Blastoidea,
Cystoidea, Ophiuroidea, Asteroidea, Echinoidea. Of
these, two are only known fossil (Blastoidea and
Cystoidea), and they belong to the Palaeozoic Strata.

LIFE ON THE EARTH. 87

Crinoidea are very rare in a living state, Echinoidea
plentiful. Now 29 species of Crinoidea occur in the
Lower Palaeozoic, 15 in Middle Palaeozoic, and 105 in
Upper Palaeozoic Strata. After this they grow com-
paratively rare, though still 29 species occur in Me-
sozoic Strata, and 5 in the Caenozoic series. One
recent species ! On the other hand, Echinoidea are
represented in the Palaeozoic series by 12 species, in
the Mesozoic by 173, and in the Caenozoic by 25.

All the Echinoidea of the Palaeozoic series belong
to the regular division, with the openings of the
alimentary canal opposite (E. endocyclida). The
same group occurs in the Mesozoic Series, but in ad-
dition we have a second equally large group with
these openings not opposite (E. exocyclida), and this
is continued in the modern ocean.

The Echinoidea of the Palaeozoic Series have
such peculiarities in the series of plates and pores
as to claim to be enrolled in separate families (Pa-
laechinidae and Archaeocidaridae), or even to consti-
tute an order (Perischoechinoidea) equal to that of
the Echinoidea.

The contrasts which have thus been stated be-
tween the Palaeozoic and later forms of Radiated
Animals may be represented in the following tabular
view; where the word Neozoic is used to include
Mesozoic and Caenozoic ages.

88

LIFE ON THE EARTH.

OQ

-2

O*

Q c« P3

m

EH

-, '• —
^

pq

IS

.JN O
0 W

EH

w

m
Q

a

o

0
0

O

5

g

3

LIFE ON THE EARTH. 89

Annelida. — In the modern seas we find two great
groups, Cephalobranchiate and Dorsibranchiate An-
nelida. The same two orders exist in the Lower
Palaeozoic Strata, sometimes containing species of
very large dimensions, and they seem to have been,
as now, mostly prevalent on muddy shores.

Cirripedia— These beautiful animals are not re-
cognized in Palaeozoic Strata.

Crustacea. — Dividing them into two groups we
find one (Entomostraca) extremely prevalent in the
Palaeozoic periods; the other (Malacostraca) not yet
certainly discovered therein.

Among the Entomostraca the large groups of
Trilobitidae and Eurypteridae are peculiar to the
Palaeozoic ages.

The relations to time which thus appear among
the Articulata are represented in the following
Table.

90

LIFE ON THE EARTH.

3

o

I

11

II

^ a

p-^ V2

§* o

-fi

II

Polyzoa, or Bryozoa. — These abnormal, often
compound mollusks, in their mode of growth and
membranous or stony parts much resembling Zoo-
phyta, occur in all the groups of Strata, and except-
ing Reteporidse, which are almost confined to Palseo-

LIFE ON THE EARTH. 91

zoic Strata, their families are pretty equally dif-
fused.

Tunicata, another somewhat less abnormal group,
not covered by shell, is not recognized in a fossil
state.

Brachiopoda abound in the Strata, and are scat-
tered through the modern Seas in somewhat greater
numbers than was formerly supposed, when dredging
at considerable depths was not practised. They are
rare in the Csenozoic Strata. Of nearly forty genera
and subgenera upwards of twenty appear limited to
the Palaeozoic Series ; only two are mentioned among
the Csenozoic fossils of Britain; but twelve at least
occur in various modern oceans. The families of
Spiriferidse, Orthidse, and Productidse are confined
to the Palaeozoic Strata; Terebratulidse, Rhyncho-
nellidse, Craniadse, Discinidse, and Lingulidse may be
regarded as of all periods ; Lingula, Discina, Crania,
Rhynchonella, Thecidium, Argiope, Terebratella,
Waldheimia, Terebratulina, Terebratula, are both
fossil and recent. Of these, Terebratula, Rhyncho-
nella, Crania, Discina, Lingula, pass through all the
great periods of Geology and still exist, with pecu-
liarities of structure and association very like those
which belonged to them in the earliest periods.
For example, the Lingulse of every age always shew
almost exactly equal, delicate, depressed, nearly

92 LIFE ON THE EARTH.

smooth or slightly striated valves, accuminated at the
beaks. The shells of Terebratulse of every age ma-
nifest the beautiful punctation to which Dr Carpen-
ter called attention, and are usually smooth; while,
in marked contrast with its associate through the
immensity of time, Rhynchonella is deficient of this
punctation, and is commonly ridged in radiating
folds.

If we place before us a series of Lingulse accord-
ing to their antiquity, and include the recent species,
we remark the absence of the genus from the British
Tertiaries, and the abundance of it in Palaeozoic
ages, the greater comparative breadth of some of
the older species (Lingula Davisii, L. granulata), the
more elliptical contour of particular examples (L.
elliptica from the Carboniferous rocks, L. Beanii
from the Inferior Oolite), but upon the whole a uni-
formity from one end of the series to the other,
which suggests very strongly the idea of very narrow
limits imposed on the tendency to variety in this
genus of mollusks.

If we take in like manner a series of Terebratulse,
such as T. hastata, from the oldest known forms in
Devonian and Carboniferous rocks, T. elongata of
the Permian, T. punctata of the Lias, T. ornitho-
cephala of the Inferior Oolite and Fullers' Earth
Rocks, and T. digona of the Great Oolite, or another

LIFE ON THE EARTH. 93

series such as T. sacculus of the Carboniferous, T.
sufflata of the Permian, T. perovalis of the Fullers'
Earth, T. intermedia of the Cornbrash, T. biplicata
of the Green Sand, T. semiglobosa of the Chalk,
T. grandis of the Crag, and T. vitrea of the existing
ocean, — illustrate each largely by examples with sinu-
ated or even margins, more or less prominent beaks,
greater or smaller foramina, we shall be amazed at
the small amount of real diiferences which divide
these species so far — how very far! — removed from
one another in order of time. If we try on a min-
gled series of Terebratulse of all ages the sharpest
powers of our differentiating naturalists, the same
result may happen to them as has happened to older
palaeontologists, — to confound species differing in age
from the Devonian Limestones to the Upper Green
Sand; from the Chalk to the Bath Oolite; from the
Lias to the Mountain Limestone. Little difference
appears between T. striata of the Chalk and T. caput
serpentis of the Sea, nor is T. fimbria of the Inferior
Oolite very unlike the recent T. Australis.

If we choose among Rhynchonellse a series such as

R. decemplicata, Silurian ; R. anisodenta, Devonian ;
R. pleurodon, Carboniferous ; R. variabilis, Lias ; R. tetrae-
dra, Marlstone j R. media, Fullers' Earth ; R. obsoleta, Great
Oolite; R. inconstans, Kimmeridge Clay; —

or compare

94 LIFE ON THE EARTH.

R. Wilsoni of the Silurians; R concinna of the Oolite;
R. octoplicata of the Chalk ; with R. psittacea of the Nor-
wegian Seas ;

we shall perceive how very small is the amount of
change which all the lapse of time has witnessed in
the forms of what seem to be among the most varia-
ble as well as the most numerous of fossil shells.

Rudista are not known below the Cretaceous
Series.

Monomyaria. — Classing these in four great fa-
milies, Aviculidee, Pectinidse, Limidse, and Ostreidse,
which are all found both fossil and recent, we remark
in the first place the constancy of the general charac-
ters of each. Thus Ostreidse shew always rudely
laminated shells ; PectinidsB and limidse are nearly
equivalvular, neat, and radiated; the former nearly
equilateral, the latter more oblique ; but in this
respect yielding to the Aviculidae, which are more
frequently smooth externally, and pearly within, and
have very unequal valves. No true oysters occur
below the Mesozoic strata. Pecten and Lima are
not known below the Carboniferous Limestone ; Avi-
culidoe belong to every geological age.

Dimyaria. — Two great divisions constitute this
large group of shells. To the Asiphonida, which ap-
proach nearest to Monomyaria, and include three
marine groups, Mytilidse, Arcadse, Trigoniadse, and one

LIFE ON THE EARTH. 95

freshwater group, Unionidse, belong nearly all the
equivalved bivalves of the Lower Palaeozoic, and the
larger portion of those found in the Upper Palaeozoic
formations. They are numerous in the later strata,
and excepting Trigoniadae still remain so. The larger
group of Siphonida begins to be plentiful in the
Oolitic and Cretaceous rocks, and is much more
abundant in the tertiary strata and existing oceans.

Two conspicuous fossil genera, Trigonia and Pho-
ladomya, are represented by one living species to
each. The former is confined in a fossil state to
Mesozoic Strata, and in a recent state to the Austra-
lian shore ; the latter, a constant companion in
Mesozoic Strata, is found also in the Eocene beds,
and has been discovered living off the Island of
Tortosa. The recent species is in each case judged
to be distinct from the fossils. What strong affinities,
however, obtain in each case between the fossil and
the living races will appear by attending to the form,
surface ornament, commissure of valves, hinge, um-
bones, and muscular impressions.

Pholadomya in every age preserves a striking con-
formity of characters — radiating ribs on a part of
the surfaces, usually swollen at intervals by pro-
minent laminae of growth, a thin tumid oblong
shell, prominent beaks, gaping posterior end, ob-
scure hinge-teeth. The recent species differs but

96 LIFE ON THE EARTH.

slightly from fossils which might be selected from
the Oolites.

Trigonia exhibits more diversity of form and or-
nament, but preserves the essential characters ; a
thick shell, ribbed or tuberculated with beaks bend-
ing toward the posterior side, which is angular, and
bears a prominent ligament often preserved in the
fossils. Internally the shell is nacreous, with deep
muscular impressions; the hinge-teeth are strong,
radiating, and transversely striated. If we place in
the order of their existence the following species of
Trigonia, we shall perceive at once the general affinity
and the special diversity which runs through this
genus. The recent species is the only one with ridges
radiating from the beak over all the surface.

Recent Trig, pectinata.

Chalk T. sulcata.

Cretaceous T. dsedalea.

)T. clavellata.
T. costata.
T. striafca.
Lias T. literata.

Pteropoda. — These floating mollusks are few in
the stratified deposits of every age ; more frequent in
the sea. Conularia, Theca, and Pterotheca, belong to
the Palaeozoic Strata ; Hyalsea, Cleodora, and Cuvieria,
are both recent and tertiary.

LIFE OX THE EARTH. 97

Heteropoda. — The symmetrically convolute Belle-
rophon, and its allies Cyrtolites and Porcellia, are
confined to Palaeozoic Strata. The recent Carinarise
are represented by one tertiary Italian fossil.

Gasteropoda. — The marine kinds — all breathing
by gills and freely swimming in their embryonic
state by help of two ciliated fins, retractile with the
body into a convolute shell — grow by constant laws
of development into shells of various forms, usually
spiral, though examples occur in which this character
is insensible (e. g. Patella). The most numerous order
both in the recent and fossil state receives the title
of Prosobranchiata, from the anterior position of the
gills. This character cannot be recognized in fossils,
but the forms of the shells are always sufficient to
identify the order. It may be divided into two sub-
orders : Holostomata with entire aperture to the
shell, Siphonostomata with the aperture notched or
canaliculate. The former are for the most part
feeders on vegetables, the latter, for the most part
carnivorous. The late Mr Dillwyn remarked the
prevalence of the siphonostomatous shells in the Ter-
tiary Strata, and the extreme rarity of them in older
strata. This curious generalization is found to be
of much importance in general views regarding the
succession of Molluscous life.

No siphonostomatous shell has yet been found
R. L. H

98 LIFE ON THE EARTH.

in the Palaeozoic Strata. If we place the Mesozoic
fossil shells, formerly called Rostellaria (now Alaria),
and Cerithium, in the holostomatous division— as
Morris and Woodward do—there will remain but few
exceptions to the rule that the Palaeozoic and Meso-
zoic Gasteropoda belong to the herbivorous division.
Euomphalus and Murchisonia are Palaeozoic; Alaria
and Nerinsea, Mesozoic. The function of the Carnivora
was in the earliest of these periods principally exer-
cised by Cephalopoda ; in the later period Fishes and
Reptiles were effective as allies, or opponents.

Cephalopoda, among the most abundant as well
as highest in organization of all the fossil mollusca,
are much less numerous in the modern than they
were in the older periods. If we class them by the
organs usually called arms or feet, as Octopod, Deca-
pod, and Polypod, we find no trace of the first in the
Strata of the British Isles, though Argonauta is fossil
in the Italian Tertiaries. Decapod fossil genera more
or less allied to the recent Loligo, which includes a
long horny pen ; to the recent Sepia, which contains a
broad calcareous plate, thickly fibrous in front, con-
cave behind, and ending in a solid apex ; and to the
fossil Belemnite, which is of a long conical figure,
concave and chambered in front, fibrous behind, and
sometimes mucronated. These are all absent from
the Palaeozoic Strata, and Belemnites, by far the

LIFE ON THE EARTH. 99

most numerous group, are peculiar to the Oolitic and
Cretaceous formations. The recent genera have an
ink-bag containing black pigment; this organ is
recognized in several of the fossil races, filled with
the fossil ink, which retains its good colour, and has
been successfully employed in drawings.

The Polypod genera were (unlike all those pre-
viously mentioned except Argonauta) protected by
an external shell ; in these it was concamerated, the
chambers formed by transverse plates which were
pierced by a pipe opening to the last or outer cham-
ber, into which the whole or principal part of the
animal could be retracted.

It is usual to rank them in three families — Ortho-
ceratidae, Nautilidae, Ammonitidse. Of these, the first
did not pass1 the Palaeozoic period ; Ammonitidse did
not pass the Mesozoic period ; but Nautilidae, which
began in the earliest ages, lived in all the subsequent
seas, and still adorn, though not plentifully, the
modern ocean. Among the Nautilidae, however, Cly-
menia ceased before the close of the Palaeozoic age.
The geological range of the Ammonitidae is still more

1 Unless in the single case of the Triassic beds of Saint Cassian,
which contain what seem to be Orthoceratites, and also very pecu-
liar Ammonitidse having the numerous gradually diminishing
lobes of Ceratites, with the highly ramified sutures of the Oolitic
Ammonites.

II 2

100

LIFE ON THE EARTH.

curious, for the earliest group, Goniatites, ceases with
the upper Palaeozoic Strata; Ceratites occurs* in
Muschelkalk, but does not enter the Lias ; Ammonites
begins at some height in the Lias, and dies out
before reaching the upper Chalk, being accompanied
in decline by Hamites, Scaphites, Turrilites and
Baculites. These distributions appear in the follow-
ing Table.

Ammonites sublsevis,

t

Ceratites nodosus.

f

Goniatites striatus.

LIFE ON THE EARTH. 101

Recent.

102 LIFE ON THE EARTH.

Having so limited a total range in time, but

. including some hundreds of well-marked specific

; for, ws, a^d bejng widely diffused in geographical space,

Ammonites furnish to the Palaeontologist admirable

data for fixing the chronological succession of the

secondary strata, in cases when these strata are not

continuously traceable. Taking some well-known

forms, including Ceratites, and placing them in the

order of their superposition, we obtain the following

series of geological epochs in the great Mesozoic

Period.

No Ammonites or Ceratites or Goniatites in Caenozoic Strata.

f Amm.Rhotomagensis Lower Chalk.

A. varians Upper Green Sand.

Cretaceous Period •{ «lu

A. auritus Gault.

[A. Deshaysii Lower Green Sand.

UpperOolitio Age ( A' ^ntens Portland Oolite.

\ A. biplex Kimmendge Clay.

( A. vertebralis . . . .Oxford Oolite.and below.
Middle Oolitic Age I. _ .. ' .

\ A. calloviensis Kelloways Rock.

A. macrocephalus Cornbrash, and below.

A. gracilis Great Oolite.

A. Parkinsoni Inf. Oolite upper part.

A. Humphreysianus ...Inf.Oolite middle part.
A. Murchisonae Inf. Oolite lower part.

•83

II

Lower Oolitic Age

P

A. Jurensis Sand.

{A. bifrons Upper Lias.
A. Conybeari Lias Limestone.
A. planorbis Lowest Lias.

Triassic Period Ceratites nodosus Muschelkalk.

No Ammonites or Ceratites in the Palaeozoic Strata.

LIFE ON THE EARTH. 103

Fishes commencing, as already stated, in the
upper Silurian Strata, become from that point highly
important in geological history — more important than
even their numerous remains at first seem to indicate ;
for though teeth, scales, and fin-rays of these animals
are not scarce in the strata, these, the most conservable
of the hard parts of fishes, are scattered irregularly,
and, until studied after the method of Agassiz, give
but slight information. Under the hands of this great
naturalist and his disciples, Egerton and Enniskillen,
we have seen the history of fossil fishes grow to em-
brace many hundreds of distinct forms, very interesting
in physiology, always very valuable in geological rea-
soning. The method of Agassiz is no doubt in some
degree conventional, and specially framed for the study
of fossils, yet the characters derived from the dermal
covering are always of high value in the classification
of the vertebrata, and specially influential in fishes.

Two great orders of fishes have enamelled scales
e. g. Placoid and Ganoid Fishes — the latter have ena-
mel externally, bone internally for each scale, and
the scales so closely packed as to constitute a real
dermo-skeleton. These orders occur in all the strata
above the Silurians, and still exist : they are the
only orders which occur in the Palaeozoic rocks ; in
the existing ocean and in the Tertiary Strata they
are comparatively the least abundant.

104 LIFE ON THE EARTH.

Two other orders have horny scales, neither bony
nor enamelled — viz. Cycloid and Ctenoid Fishes;
and these, beginning their courses with the Mesozoic
Strata, constitute by far the largest portion of the
existing race of fishes. Here again we perceive the
strong contrast between the Palaeozoic and Neozoic
inhabitants.

Existing marine Fishes have tails formed on
different models, as the forked tail of the Salmon, the
rounded tail of the Wrasse, the elongate pointed
tail of the Conger, arid the unequally lobed tail of the
Shark. The three former tails may be called regular
or symmetrical, the latter unsymmetrical ; or if we
please, the fishes possessing the former may be called
Homocercal, while the latter may be called Hetero-
cercal. In existing nature the Homocercal fishes are
by far the most numerous; they are plentiful in
Caenozoic and Mesozoic Strata, but they are unknown
in the Palaeozoic rocks, where Heterocercal fishes
alone occur. This is the more remarkable because
both in the Palaeozoic and Mesozoic rocks Ganoid
fishes abound ; still Palaeozoic races are all hetero-
cercal, Mesozoic are mostly homocercal. In all pe-
riods Placoid fishes were heterocercal.

The group of Placoid Fishes is the only one
which has existed through all geological periods to
the present day ; it includes a large range and gra-

LIFE'ON THE EARTH. 105

dation of structure, so that while some races may
probably be regarded as of the highest type in the
class, others (if we include Myxine) can only just
claim to be vertebrata. The fossil races belong gene-
rally to the higher types. The skeleton being cartila-
ginous or mainly so, it often happens that the verte-
bral column is not preserved : indeed very frequently
only a few scattered teeth and fin-rays remain to
attest the existence and magnitude of these ancient
mostly shark-like creatures. Singular to say, one
group of these fishes, represented in a living state
by one Australian species (Cestracion Philippi), has
been traced through all these periods (except Cseno-
zoic) by its teeth and fin-rays, abounding in Palaeozoic
and Mesozoic ages; while, on the other hand, the
ordinary sharks of the modern seas are represented
in the Tertiary strata plentifully, in the Mesozoic
sparingly, in the Palaeozoic not at all. The Cestra-
ciontidee have, besides pointed teeth in front, some
very large and broad behind, not pointed but suited
for crushing and grinding hard and solid substances,
such as shell-covered Mollusca, Crustacea, Echino-
dermata, or even Ganoid fishes1.

Reptilia according to Owen2 may be arranged in
thirteen orders, of which five, viz. i. Batrachia (Frogs),

1 Buckland, Br. Tr. PI. 41.

2 Reports of British Association, 1859.

106 LIFE ON THE EARTH.

II. Chelonida (Turtles), in. Ophidia (Snakes), iv. La-
certilia (Lizards), and v. Crocodilia (Crocodiles), are
both recent and fossil ; and eight, viz. vi. Deinosauria,
vir. Thecodontia, vm. Pterosauria, ix. Anomodontia,
x. Sauropterygia, xi. Ichthyopterygia, xn. Labyrinth-
odontia, xm. Ganocephala are only found in a fossil
state. Among the marine tribes are some of the
Chelonida, all the fossil Ichthyopterygia, Sauropte-
rygia, some of the Crocodilia and Lacertilia, possi-
bly the Thecodontia1, omitting the Chelonida. They
stand in the following order of time :

Mososaurus Chalk.

Leiodon Chalk.

Pleiosaurus Kimmeridge Clay.

Cetiosaurus Great Oolite and upwards to Wealden.

Teleosaurus Lias and upwards to Chalk.

Ichthyosaurus Lias and upwards to Chalk.

Plesiosaurus Bone Bed, Aust, and upwards to Chalk.

Stagonolepis2 Triassic Sandstone of Elgin.

Thecodontosaurus. Conglomerate, Bristol.

It will be seen hereafter that Terrestrial and
Freshwater Reptilia appear to be of higher antiquity
than the marine tribes yet discovered. Remains of
Chelonida appear to be about of the same antiquity
as the marine Saurians; they occur in the Red

1 The fossil Crocodilia may perhaps have visited rivers and
the land ; their legs might allow of this, and their feet are not
unsuitable.

2 Huxley, Geol Soc. Journal, 1859.

LIFE ON THE EARTH. 107

Sandstone of Lochmaben in Dumfriesshire, with va-
rious undetermined Ichnites.

Cetacea appear to be totally absent from any of
the deposits older than the Tertiary Strata, a cir-
cumstance more remarkable since the discovery of
terrestrial Mammalia in the Oolitic Strata of Pur-
beck and Stonesfield, and the Bone-bed of Wiirtem-
berg. The Crag of Suffolk (Pleiocene) is the oldest
tertiary deposit in our Islands containing Cetacea.
In no district of Europe do they reach downward
even to the earliest series of Tertiary Strata. Above
this D'Orbigny counts four genera in the Parisian,
seven in the Falunian, five in the sub-Apennine strata
— fifteen, the maximum, in the modern seas. In a
general point of view, the Cetacea, Great Reptiles,
and Great Fishes,

Csenozoic Cetacea,

Mesozoic
Palaeozoic

Great Reptiles,

Placoid and Ganoid Fishes,

may be regarded as successively the dominant races
of the Sea, the Cetacea taking up the functions
which had been exercised by the Enaliosaurians.
The earlier races of Cestraciont Fishes, with their
crushing teeth, may be thought very well suited
to such food as the shelly Mollusca, the strongly-
walled Encrinites, and the cuirassed Crustacea of
the early periods might furnish; and when their

108

LIFE ON THE EARTH.

influence declined in the Tertiary Seas, the skates and
rays, furnished with a suitable pavement of teeth, may
be supposed to have assumed some of their duties.

I

ERESHWATEK LIFE.

The stratified rocks on which we base the general
scale of elapsed time being marine, and the occur-
rence of freshwater deposits among such being ne-
cessarily limited, it is not surprising that our history
of freshwater life is marked by many lacunae.
Rather may we be surprised that the nature of the
movements of the earth in ancient times was such
that marine deposits were covered by lakes, or estu-
aries, at several epochs, and sometimes for long
periods of time. In the following brief catalogue,
suited to the British Isles, we find what may be
termed Freshwater zones in all the great systems
of Strata.

LIFE ON THE EARTH. 109

Postglacial shelly marls, &c.
Preglacial shelly marls, &c.
Csenozoic Period..

Alternating freshwater and marine

Strata of the Isle of Wight.

Mesozoic Period . . . The deposits of the Weald of Sussex.

The deposits of Whitbyand Scarborough.

Palaeozoic Period ... The Coal-formation.

The Upper part of the Old Bed Sand-
stone of Ireland.

And besides, there are several cases of the inter-
mixture of land-plants and insects and sea-shells,
only to be explained by the flowing of currents
from the land, as at Stonesfield, Westbury Cliff, &c.

The forms of life in the Fresh waters of the Earth
differ from those in the Sea in all cases; but the
difference can seldom be traced to any physiological
necessity, arising from the difference of the fluids.
Amorphozoa, Zoophyta, Mollusca, Annelida, Crustacea,
Fishes, Reptiles and Mammalia, occur in both, under
shapes not indeed identical, but fashioned on the
same general models. The salmon migrates from
one water to the other, and experiments appear to
shew that by long continuance of favourable circum-
stances other fishes and some Mollusca might be
made to exchange elements, or to subsist for a time
in brackish water, a fluid of intermediate character.
But, on a large scale, the provisions of nature keep

110 LIFE ON THE EARTH.

separate the denizens of lakes and rivers from those
of the lagoons, bays, and currents of the sea.

This fact, which is observed in all countries, is
connected with another of much significance, the
comparative fewness of the freshwater races, and
their great affinity over large tracts of the earth.
Unionidse and Cycladeo are the prevailing family of
Dimyarian Mollusks ; Paludinadse and Limnseadee,
reinforced by Ancylus, Melania, Neritina, &c. the
most frequent of Gasteropoda. How these fresh-
water genera have been so widely diffused as in fact
we find them ; how some particular species have be-
come common to so many rivers and lakes, are ques-
tions of much interest. For as neither the animals
nor their ova could pass through the salt water,
and retain vitality, we must ascribe to changes in
physical geography and the accidents of mixed oc-
cupation of a country, the transference from one
river to another, of the germs of life ; or regard the
existing fresh waters, now unconnected, as formerly
somehow connected; or suppose a creation of the
same species or the same genera at many separate
points. Rejecting this last, we may venture to prefer,
as a general explanation, the transfer of the germs
of life by natural events, specially by birds carrying
spawn from one river to another, even as now we
are transferring by experimental means the Crawfish,

LIFE ON THE EARTH. Ill

the Trout, and other valued creatures, to rivers which
have never yet been visited by them.

The results arrived at by tracing some of the
successive groups of freshwater life, from the earliest
date to their eventual distribution, are veiy instruc-
tive in regard to what may, with reference to human
ideas, be termed the Theory of Creation. Taking
first the molluscous classes and remembering that
Brachiopoda ahd Monomyaria are absent from fresh
waters, we may fix our attention on the Dimyarian
family of UnionidaB and Cycladse. They occur fossil
according to the following scale:

Caenozoic^-Unio, and Cyclas, not very plentiful, with Gas-
teropoda and land-plants.

Mesozoic — Wealden Unio and Cyclas, with Cyprides

and Gasteropoda and land-
plants.

„ Purbeck Unio and Cyclas, with Cyprides

and Gasteropoda and land-plants
(Cycadacese).

„ Yorkshire Oolitic. Unio not common, with land-
plants (Cycadacese, &c.)

Palaeozoic — Coal-formations. Unio, several species, common,

with land-plants, Lepidoden-
dron, &c. Cyprides, <kc.
„ Upper Old Red. Unio, in one locality, with Ferns.

Here we have the remarkable fact of decided
affinity in the successive groups of freshwater bi-

112 LIFE ON THE EARTH.

valves, through the vast series of deposits which ex-
tends from the Devonian rocks to the present ocean
— similar forms, similar accompaniments, and similar
exclusions of other forms, such as Brachiopoda,
Monomyaria, &c. So that the law of segregation (if
we may use this term) which separates the few
freshwater from the many marine races, operates
now as it did operate in the Palaeozoic ages, and
similar races are subjected to its influence. During
all this time Unionidse have maintained their cha-
racteristic structure and associations. Taking next
the Gasteropoda we remark in living nature two
groups,- one separating air from water by means of
gills like fishes, the other breathing air by lungs.
Of the former, the living examples cluster round the
genera, Paludina, Yalvata, Ancylus, Neritina, the
former are represented by Planorbis, Limnsea, Physa,
Melania. In a fossil state these forms are recog-
nized at several stages, but not at so early a period
as the Dimyarians. They are not known to occur
below the Purbeck Strata.

Csenozoic . . . Paludina, Neritina, Planorbis, Physa, Limnsea, Me-
lania, &c. several zones in the Fluvio-marines
of the Isle of Wight.

"Wealden ...Paludina, Melania, Melanopsis.

Purbeck ...Paludina, Valvata, Melania, Physa, Limiisea,
Planorbis,

LIFE ON THE EARTH. 113

The freshwater Mollusca altogether appear of
later origin than the marine tribes, and the Gaste-
ropoda appear to be of later origin than the Dimy-
aria, in fresh waters as well as in the sea. If we
compare the fossil and living Paludinse, Physse, Lim-
nseae and Planorbes, we are struck by the great re-
semblance in each case; Physa in each case has the
sinistral spire, Planorbis is discoidally depressed,
Paludina rises in tumid whorls, Limnsea extends
from a large aperture to an acute point. Here
again is the evidence of long duration of even slight
peculiarities, persistence of type, and restraint of
variation.

If in either of these cases — the Unionidse — the
Paludinadse — the Limnseadse — Planorbes — Phy sae,
&c., — the modern forms are derived from the ancient,
we have the full measure of the whole variation —
the differentials of change are all integrated by time,
and we behold the sum — how little! But if not so,
if the modern and ancient species have sprung from
different branches of a stem still older than either,
how much stronger, if possible, is this decisive tes-
timony against the doctrine of indefinite change
through time and circumstance ! Circumstances have
varied, ages have passed away, and yet every generic
group exhibits at every step the same essential cha-
racters, and many of the little peculiarities, such as

K. L. I

114 LIFE ON THE EARTH.

eroded beaks, plications on the surface, reflexions of
the lip, carinations of the whorls, which cannot be
consistent with accumulated tendencies to change.

If in the same spirit we look at the few Insects,
Crustaceans and Reptilia, the only other freshwater
groups which occur at several stages in the series
of strata, very similar results appear, much resem-
blance in the components of the several groups from
whatever age we take the examples, and much ad-
herence to generic, or family type. The series of
freshwater Reptiles considered in this respect offers
the largest variations, but the structure of some of
the earlier forms, even in regard to the limbs, is too
uncertain to allow of a satisfactory view of their
history. True Crocodiles with vertebrae concave in
front, occur above the Chalk1; Crocodilians with bi-
concave vertebrae— an indication of aquatic, but not
necessarily of marine life— are frequent in the Oolites
and Lias2, and are found in the Trias3, with a La-
certian fossil*. Batrachians with deciduous gills are
mostly of Tertiary date5, but allies of the Menopoma
and Triton appear in the Coal Strata, and in Strata
above them6. Freshwater Chelonians are recognized
in the Strata of Purbeck and in Tertiary deposits.

1 Croc. Harsingsise. 2 Teleosaurus and Steneosaurus.

3 The Stagonolepis of Elgin. 4 Rhynchosaurus of Shropshire.

5 In the Paper Coal of the Rhine.

6 Archegosaurus— Labyrinthodon.

LIFE ON THE EARTH. 115

TERRESTRIAL LIFE.

The information afforded by freshwater deposits,
and the effects of freshwater currents flowing into
the sea, is strongly reflected in the history of the
ancient land. As the stream flows down from its
parent mountains, gathering air and penetrated by
light, it soon begins to swarm with infusoria, feeding
among the immersed and marginal vegetation; Pla-
norbes, Limnseadse, Cycladse, appear in its sparkling
or quiescent water; Gammarinso and Daphnise, Insects
and Argyronetse, furnish delicate diet to the watch-
ful Trout ; and thus race follows race, till finally Uni-
onidse prevail and occupy the bed of the current as it
slowly winds toward the estuary, which, itself almost
deserted, divides the fluviatile from the oceanic
worlds of life.

When in the Coal-formation we find an abun-
dance of Unionidse, often buried in colonies as they
lived, in layers of fine sediment, alternating with
Coal Strata, accumulated towards the margin of the
sea, we may easily connect in imagination this
marshy savannah with rivers descending from the
interior, and suppose on their banks many races of
animals whose remains, if rare., may nevertheless
occur to diligent search on favourable occasions.

By such scrupulous attention to the contents of
Ironstone nodules at Coalbrook Dale Mr Anstice

12

116 LIFE ON THE EARTH.

discovered two species of Coleoptera (Curculionidse),
and a Neuropterous Insect (Cerydalis)1. But the
most remarkable illustration of the utility of this
kind of hopeful search is afforded by the discovery
of a landshell, allied to if not identical with Pupa,
in the interior of a fossil tree (Sigillaria), in the
Coal-formation of Nova Scotia, by Sir C. Lyell and
Dr Dawson. Remains of Land Reptiles (Dendrer-
peton and Hylonomus), and a Chilognathous Myria-
pod (Xylobius). An airbreathing Gasteropod of a
modern genus, airbreathing Reptiles, Insects of two
recognized orders, and a Myriapod, these suggest
and indeed imply the existence of many more forms
of terrestrial animals so as to constitute a Fauna of
the Carboniferous age. Precarboniferous we might
perhaps say, for plants of the family (Lepidodendra)
with which these insects and reptiles and shells are
associated occur in earlier strata, being first noticed
in the uppermost bands of the Silurian system.

Terrestrial plants are scattered at intervals
through most of the Marine Strata, above the Silu-
rian Rocks, thus indicating the force and frequency
of affluents from the land. They were collected in
considerable quantity in estuarine and lacustrine de-
posits of the Carboniferous and Oolitic eras, and in
lagoons of salt water, as at Stonesfield, having been?

1 Prestwich, On Cocfbrook Dale Coalfield, Geol Trans.

LIFE ON THE EARTH. 117

perhaps, blown into these latter situations with Neur-
opterous and Coleopterous Insects, among the lat-
ter, Bupresticbe and Curculionidse. In the Palaeozoic
ages are no Cycadaceae; in the Neozoic no Lepido-
dendra; Ferns abound in several of the deposits in
and above the Upper Devonian Strata.

In the lowest beds of the Lias and passage-beds
from the Trias, Insects have been collected at the
Cliffs of Aust, Westbury and Wainlode, and at several
other places in the Vale of the Severn, probably
blown into shallow salt water, a common circum-
stance on the coasts. Others occur more abundantly
in the Vale of Wardour and Pur beck1. The census
of the fossil orders of Insects runs thus :

Csenozoic. . .Coleoptera (Copris, Donacia, Harpalus,) in Pleisto-
cene beds, at Mundsley, Norfolk.
(In France most of the Orders of Insects are
found in freshwater beds at Aix in Provence).
Mesozoic ...Purbeck beds, Coleoptera, Neuroptera, Ortho-

ptera, Homoptera, Diptera.
Oolite of Stonesfield, Coleoptera, Neuroptera.
Lias of Severn Vale, Coleoptera, Neuroptera,

Orthoptera, Homoptera, Diptera.
Palaeozoic... Coal-formation, Coleoptera, Neuroptera.

Terrestrial Saurian Reptiles acquired extraordi-
nary magnitude in the Oolitic period, and exhibit as

1 Brodie, On Fossil Insects. Westwood has determined many
of the orders and genera.

118 LIFE ON THE EARTH.

high a grade of organization in Megalosaurus and
Iguanodon as the aquatic Crocodilians, of the same
ages, Teleosaurus, Steneosaurus, Cetiosaurus and their
allies. The earliest traces of Land Saurians are those
already alluded to as found in the Nova Scotia coal-
field, one of which is supposed to be of Lacertian,
the other of Ganocephalic affinity. Perhaps in re-
gard to most of the Saurian fossils we may prudently
wait for further information before confidently as-
signing them to marine, fluviatile, or terrestrial life.
Ichthyosaurus is no doubt truly marine, Megalo-
saurus truly terrestrial; regarding many others we
may reserve an opinion.

Of fossil birds our evidence is mostly in footsteps,
sometimes, as in Connecticut1 and near Hastings2,
of such extraordinary magnitude as to match the
stride of the Moa of New Zealand. In general the
footprints are of the Cursorial order of Birds ; marks
of their movements are found in the sandy shores
of the Permian, Triassic, and Oolitic Seas.

Mammalia of the Marsupial order appear to have
the priority in time. The most ancient fossils of
this kind yet traced are the small insectivorous
teeth found in the Trias of Wurtemburg3. Next

1 Hitchcock, Mem. American Academy ', Vol. m.
8 Beckles, Journal of Geol. Soc.
3 Lyell, Elem. of Geol. p. 343.

LIFE ON THE EARTH. 119

come the Insectivora of Stonesfield, which in part
belong to the Marsupialia1, and one, the latest of
the discoveries there, the Stereognathus Ooliticus,
which belongs to an artiodactylous order2. Next
come the Insectivora and Rodentia of Purbeck3, also
in part Marsupial. Then as far as yet discovered
a blank follows; there is no Mammal known of the
Cretaceous period, but the Tertiary Strata reveal
several successive groups. The whole series stands
thus, if we include more than the British Fauna:

Pleistocene and Pleiocene. Full series of orders of mammalia.
Meiocene...Pachydermata and other families.

Eocene Pachydermatous prevail.

Purbeck ...Marsupial Insectivora, Rodentia.
Stonesfield. .Marsupial Insectivora, Artiodactylous genus.
Trias Marsupial Insectivora.

ANTIQUITY OF THE EARTH.

Geologists have been much censured for vainly
endeavouring to assign measures of time to the
seemingly vague and shadowy ages of the Trilobites
and Belemnites; nor have they escaped censure for

1 Buckland, Bridgewater Treatise and Owen, Brit. Foss. Mam-
malia.

2 See for the latest Classification of Mammalia the Rede Lec-
ture by Prof. Owen, 1859.

3 The capital discovery of Mr Beckles.

120 LIFE ON THE EARTH.

countenancing speculations which assign to the hu-
man race a period very much longer than that
hitherto adopted on historical grounds. They de-
serve no rebuke, however, for the endeavour to force
their way into the citadel of natural truth, if they
undertake the siege after a sufficient survey of the
difficulties of the enterprise, which in this case are
not slight. Let any one acquainted with the modern
aspect of Astronomy, consider well the nature of
that problem which, omitting all previous cosmical
changes, would count the years since the planet be-
came a terraqueous globe — let him then look at the
Mosaic narrative, and be satisfied with the truth,
that 'In the beginning God created the heavens
and the Earth,' for no measures of time conceivable
by man will reach back to that remote epoch in the
history of our solar system. That, however, is the
starting-point of physical geography, for then began
the movements and changes in land, water, and air,
which it is the business of geology to register and in-
terpret. As already explained, the gift of life on this
earth is limited by conditions within which alone it is
possible: until these conditions were attained — that
is to say, arrived at in the pre-ordained course of
nature — the earth might be well described by the
words ' without form, and void.' For the rocky mo-
numents of this period, which we have endeavoured

LIFE ON THE EARTH. 121

to trace, the terms 'Azoic' and 'Hypozoic' have been
suggested. Thus arises the second great epoch in
geological chronology — the epoch of Life on the Earth
— the starting-point of Palaeontology. How shall we
proceed to collect evidence which may bring that
remote event into a scale of solar time? What na-
tural phenomena can be found, so much alike in all
past periods of time, and so related to years and
cycles of years, as to be safely employed in estimat-
ing, not only the relative antiquity of the several
races of plants and animals, but the absolute anti-
quity of the earliest inhabitants of the earth?

The Geological Scale of Time is founded on the
series of the strata deposited in the ancient sea; if
the forces tending to produce such deposits have
always been productive of equal effects in equal
times, the thicknesses of the strata are exact mea-
sures of the times ; the thickness added in a certain
historical time to the modern sea-bed, will bear the
same proportion to the total thickness which has
been added in geological time as the historical time
ascertained to the geological time required. This
view of the uniformity of natural effects, in the
strict terms here assigned, is perhaps held by none
of the followers of Hutton, however nearly some
expressions of the eminent author of the Principles
of Geology may seem to approach it. It cannot be

122 LIFE ON THE EARTH.

held consistently by any speculator who is unpre-
pared with proof, that the conditions under which
the laws of nature operate have always been the
same ; not indeed at each moment of time or at
each point of space, but when a cycle of time or
the average of such cycles is taken as the unit of
proportion, and the area of the globe is the field of
experiment. Now this proof requires that the pro-
portion of land and water and atmosphere should
be always cyclically the same, the land equally ele-
vated, the water equally deep — that terrestrial climate
should on the whole have been unchanged — atmo-
spheric precipitations always equal in total effect —
the surface of the globe always equally destructible, —
besides other conditions on which equality in the
rate of deposition of sediments depends. Still, in spite
of all these difficulties, the short measure of modern
physical effects in a given time is the only standard
to be applied to the immensity of past duration.

They who reject the uniformity of natural effects,
as a principle of computation of past geological time,
do so on the ground that the earth has gone
through a series of different conditions since it be-
came a terraqueous globe; that the effect of such
different conditions may be perfectly seen in dif-
ferent parts of the globe at present, giving to one
quarter more rapid waste of the land and more rapid

LIFE ON THE EARTH. 123

accumulation in the sea ; that some of these changes
of conditions can be traced to vast and ancient move-
ments in the crust of the earth, perhaps the accu-
mulated consequence of slow variation in the con-
dition of the interior, but certainly productive of
great derangement of rate in the accumulation of
earthy sediments at the surface. In the full an-
nouncement of this view of the earth being subject
to great disturbance from within, — disturbance grow-
ing less and less with time — no one has been more
explicit than Leibnitz, who conceived the idea of a
globe once fluid with heat, then slowly cooling, chang-
ing its dimensions, and breaking up its surface in
confusion; ' donee, quiescentibus causis atque equi-
libratis, consistentior emergeret rerum status.' The
two theoretical views thus strongly contrasted may
be represented by a few letters — any known natural
effect or amount of work performed (E), is a product
of the power operating (P), and the time con-
sumed (T), or E = PT. If P can be determined, T
becomes known. If P is assumed with uncertainty,
as by the Uniformitarians, T is equally uncertain.
The really useful problem then is to find the
limits of the power, which can only be done by a
knowledge of the law according to which the con-
ditions influencing its value depend. Such a law
is supposed to be discoverable in the decreasing

124 LIFE ON THE EAKTH.

temperature of the surface of the globe; with this
decrease the disturbances from the interior are sup-
posed to diminish, and the action of the atmosphere
to be more and more approaching to a uniform rate.
I propose to consider the computations which may
be founded on these different views.

Nothing can be simpler in aspect than the pro-
blem of the age of the stratified crust of the globe
on the Uniformitarian hypothesis. We have only
to find out the rate of accumulation of sediment in
the sea — the thickness of deposits produced in a
year, or century, or some long historic period — and
apply this measure or rate to the ancient deposits.
This modern rate of progress of deposits is very un-
equal ; great along some shores, which thus are
stretching outwardly to contract the domain of the
sea, insensible on others, especially where sea-cur-
rents sweep the coast and carry away the sediments to
other situations. But so it was in ancient times, for
none of our strata have more than a limited range,
and some of those that are most extensive may be
reasonably thought to have acquired their large
breadths by oceanic currents which disturbed and
redistributed sediments over areas greater than those
of original deposition.

The distance to which fine sediments brought by
rivers are carried in the ocean is found much to ex-

LIFE ON THE EARTH. 125

ceed the expectation of scientific navigators. The
fine sediments of the Maranon were still discoverable
by Sabine at the discoloured surface of the sea 300
miles from the mouth, so that in fact even the deep
central valleys and gulphs of the Atlantic may be
receiving sediments from the Western Chains of
America, mixed with, perhaps alternating with other
particles from the interior of Africa. The extent of
modern oceanic deposits may thus be admitted as equal
to that of the ancient Strata; if so, the Uniformitarian
calculation becomes of easy application.

Take any large surface of the land, which yields
to the atmospheric agency unequally in different
parts, because granite, limestone, and sandstone, are
unequally acted on by rains, and frosts, and carbonic
acid; observe and measure what is carried away by
one or more rivers from this surface to the sea in
one year. Assume this to be a fair average for the
whole surface of the land, and, to save trouble, sup-
pose the whole of the sediment to be spread out on
the sea-bed, over an area equal to that from which
it was derived. The thickness wasted from the land,
in one year, is thus the same as that added to the
sea-bed in one year. Divide by this thickness the
measured thickness of the sedimentary strata, the
result is the number of Uniformitarian years em-
ployed in depositing the strata, if the materials were

126 LIFE ON THE EARTH.

all derived in this manner from atmospheric waste
of the land, as some suppose.

For example, the Ganges, which drains 300,000
square miles of plains, hills, and mountains, con-
taining a great variety of rocky and earthy masses,
delivers annually to the Bay of Bengal 6,368,077,440
cubic feet of sediment, which is equal to TTTtn °f
an inch in a year. The maximum thickness of the
strata is supposed to be about 72,000 feet = 864,000
inches, and dividing this by TiT^h we nave the
calculated antiquity of the base of the stratified
rocks = 95,904,000 years. But here two things are
to be allowed for. The thickness of the old strata
is taken at a maximum, and the new deposit is
supposed to spread over a much larger space of sea-
bed than it really does, so that the period found is
something too large. On the other hand, the Ganges
carries very much more sediment than some other
great rivers, — nearly twenty times as much as the
Rhine ; — it has the character of tropical or excessive
effect, and on this account the period may be much
too short.

In whatever way we try the question of the
antiquity of the fossiliferous strata, whatever class
of phenomena we bring under examination, the re-
sults are always the same, always indicative of
periods too vast, and we must add too vague, for

LIFE ON THE EARTH. 127

conception. If for the purpose of arriving at more
definite ideas we select from the pile of strata some
part whose origin is clear, and whose formation was
continuous, the time still comes out enormous. The
Coal-formation, in South Wales, is 12,000 feet thick,
and through a great part of its thickness there, gives
proof after proof that this whole series of strata was
deposited bed by bed at or nearly at the level of the
sea; the estuarine alveus continually sinking, and
continually receiving additions of fresh sediment.
Many beds of Coal, amounting to one hundred and
twenty feet in thickness, alternate with these sedi-
ments. Not a single bed of limestone occurs in the"
series; towards the bottom are marine shells, above 4
only freshwater shells and land-plants; the whole
mass agreeing with the facts of estuarine accumu-
lation at the mouth of a great river. If the growth
of the sediment were at the same rate as the waste
of the land, 12,000 x 12 x 111 =the years employed i
the production of the sediments = 15,984,000 years.

But there are circumstances in the Coal-formation
which greatly modify this result. It is evidently a
deposit in quiet water — quiet as compared with the
agitation of the open ocean. In such a case the ad-
dition of sediment would not follow the law of open
sea-deposits but rather that of lakes, and so the
strata would be for the most part accumulated in

128 LIFE ON THE EARTH.

a sort of delta, or along a limited range of coast-
line. The Coal-field of South Wales is connected by
the character and succession of the Strata with those
of the Forest of Dean, Kingswood, and Somerset-
shire. This gives a length of 125 miles and a maxi-
mum breadth of 50, which may be assumed to have
been one great deposit, on the southern side of one
line of coast. If the 6250 square miles thus cal-
culated were all deposited from the spoils of one
great river equal to the Ganges, something less than
half an inch would be deposited in a year, and 12,000
feet in 333,000 years.

If we vary the computation by taking what may
be thought a fairer basis of comparison, and suppose
a stream equal to the great Indian river to have
produced the Wealden deposits — 3000 square miles
and 1000 feet thick — twelve thousand years would
accomplish ,he work, but the Wealden deposits pro-
bably extended to more than four times the area,
though with a less average thickness.

But the sea also attacks the land, often very
strenuously, and along the vast line which it beats
with restless energy, many parts of the coast yield
much, all yield something, to the watery hammers.
The rate at which the sea wastes the land depends
on the nature of the coast, and the force and direc-
tion of the currents. A cliff of shale or glacial de-

LIFE ON THE EARTH. 129

tritus falls away very rapidly in consequence of the
decay of its base. On the coasts of Yorkshire the
fertile lands of Holderness have lost from this cause
2j yards per annum, during the whole period since
it has been carefully noted. So the feeble shores of
Norfolk, Suffolk and Essex have suffered enormous
loss. The picturesque cliffs of the southern coast of
England, from Dover to Devonshire included, com-
posed of chalk, sand, sandstone, and indurated
clays, are suffering rapid displacement. Look at the
many arched rocks and island-peaks in the Purbeck
beds about Lulworth ; contemplate the Chalk Needles
of the Isle of Wight ; consider the vast heap of peb-
bles in the Chesil bank ; climb the sliding Lias cliffs
of Charmouth; everywhere signs of recent, daily,
destruction. Stand on the high ridge of the chalk
where it fronts the sea in Warburro^ * Bay ; mark
the incomplete ring of the fortifications which shel-
tered British or Saxon warriors, — incomplete because
since that comparatively modern date the sea has
reclaimed a part of his ancient domain, — and you
will have a true idea of the real recession of our
island boundary. Measure on the lofty summit of
Golden Cap, near Lyme Regis, the fissures prepared
for many yards to yield at once along the pre-
cipitous face; look at the Preventive stations on
the cliffs at Lulworth and in sight of Kimmeridge
E. L. K

130 LIFE ON THE EARTH.

which threaten to fall, and must soon be removed ;
see this, which is a fair specimen of the average waste
of English coasts, and specially of the south coast,
before adopting an estimate of the rate of annual
loss. In his recent work, On the Origin of Species,
Mr Darwin assumes the rate of waste for the Weal-
den coast to be one inch in a century; I should
have preferred, and do prefer, an estimate of one
inch in a year, that is to say, one hundred times as
great, and I suppose that by most observers this
will be thought too low an estimate for all but the
most invincible coasts. Still the effect of all this
violence of the waves on the production of materials
for the sea to deposit in new strata is not great,
compared to the powerful action of the atmosphere
on the broad surfaces of the land.

For example, assume an extravagantly high rate
of waste, such as that on the coasts of England,
which certainly cannot equal 1 foot in a year ; apply
it to the whole of the sea-coasts of the world ; assume
these to be equal to four circuits of the globe, that
is to say, 100,000 miles in extent, and 100 feet high.

.,, , 100000 x 100 x 1
The annual waste will be - . - = 0*4 cubic

miles of sediment. The area of the land being as
before assumed equal to the area of new deposits,
we have 50,000,000 sq. miles covered 2 oVoth inch

LIFE ON THE EAETH. 131

deep with these spoils won by the sea from the land.
The quantity of sediment derived from cliffs, al-
though computed on exaggerated data, being so very
much less than that obtained by the universal waste
of the surface of the land, may be neglected in •
future calculations.

Keeping still the same purpose in view, the at-
tainment of some probable estimate of the time
which was consumed in the production of some de-
finite part, if not the whole, of our stratified depo-
sits, we may take as a new basis of computation the
rate of growth and duration of life of some races of
fossil plants and animals. Thus at several stages in
the Coal-formation of Yorkshire and Derbyshire
occur beds of shale some inches or one foot in thick-
ness which are full of Unionidse. The area over
which these shells in their peculiar beds can be
traced is sometimes as much as 40 miles long in
one direction, parallel to the edge of the coal-field;
the breadth is considerable, may be as great, indeed,
but can be proved for a few miles. They have not
been spread over this area by drifting, but by na-
tural distribution of the young, as we see happen in
the lower parts of rivers approaching the sea and
the beds of lakes. Modem Unionidse live some
years. Suppose only the period of one life, say five
years, to have passed during the distribution of the

K2

132 LIFE ON THE EARTH.

species over the area, and that during this period
one foot of shale was accumulated, we have the
years consumed in depositing the strata of this coal-
field, 3000 to 5000ft. thick; =15,000 to 25,000 years.
But several layers of the shells lie in the thickness of
one foot. In the same coal-field, near the base, we find
one or more thin beds of shale and calcareous balls,
abounding in Goniatites Listen, and some other ma-
rine shells. These Goniatites are of every magnitude,
from the youngest not larger than mustard-seed, to
specimens three inches in diameter. This fact leads
to an inference of the same order, and indicates a
period only to be expressed in tens of thousands of
years.

These inferences apply only to the rate of accu-
mulation of shales ; we cannot adopt the same esti-
mates for the sandstones, which may have been
more rapidly, or for the coal-beds which may have
been more slowly aggregated. For these latter de-
posits, fortunately, Liebig and modern agricultural
Chemistry have supplied a different and independent
basis of computation.

It is now very generally admitted that our coal-
strata are derived from the accumulation of trees, and
other kinds of plants, on or very near to the places
of their growth ; at all events the greater part can have
been moved but small distances. Plants after their

LIFE ON THE EARTH. 133

germination draw from the atmosphere the Carbon
which is fixed in their tissues, and combined with
Oxygen, Hydrogen, and in some cases Mtrogen,
constitutes the main part of their substance. The
chemical composition of the atmosphere is every-
where nearly the same; the stimulus of light which
is the great determinant of the chemical processes
in plants, and which specially governs the absorption
of carbonic acid by them, acts with much equality
on the various races of plants. Hence much equa-
lity in the amount of Carbon taken from the atmo-
sphere, and fixed in the substance of plants in a
given time. Liebig has found that the annual pro-
duct of Carbon fixed in plants so different as Fir-
wood, Hay, Beet-roots, and Straw, is the same in
weight, for the same extent of ground. This quan-
tity is about 1000 Hessian Ibs. for 40,000 square feet
of surface1; in English weight and measure 10 Ibs.
for 244 square feet.

Supposing the whole of this quantity to be stored
up year by year, and converted to Anthracite, the
variety of Coal richest in Carbon, such as occurs in
South Wales and North America, it would amount
to about one inch in 170 years. If converted to or-
dinary Coal, with about 75 per cent, of Carbon, it
would yield one inch in 127*5 years. In South Wales
1 * Organic Chemistry, 1840.

134 LIFE ON THE EARTH.

the total thickness of Coal, some beds being Anthra-
citic and some ordinary Coal, is 120 feet. To produce
this thickness of ordinary Coal, by vegetables growing
on the spot, would require 120 x 12 x 127'5 = 183,600
years. The same thickness of Anthracitic Coal would
require 120x12x170 = 244,800 years. Add to either
of these periods the lowest number of years found
for the deposition of the sediments in the same
coal-field, 333,000, and we have as the probable
length of time required for the production of the
Strata of Coal, Sandstone, Shale, and Ironstone in
South Wales, half a million of years.

If now we turn to the Leibnitzian Theory, and
apply it to the same problems, we must first settle
the limits of the atmospheric power to waste the
surface in the early geological periods. This limit
at the origin of the oceans needs not to be inquired
into ; there would indeed be a mighty power in ac-
tion— perpetually falling floods — the fountains of
heaven — wasting a hot and friable surface1. Coming
down to the base of the Palaeozoic System, and
adopting as high a limit for the temperature of the
surface of the globe as might be possible to suit
the races of Mollusca and Crustacea then coming
into view, we may allow 20° higher mean tempera-
ture than at present. From this point it must be
1 Babbage. Ninth Bridgewater Treatise.

LIFE ON THE EARTH. 135

supposed to have declined to the actual condition,
and with the depression of temperature the atmo-
spheric wasting power to have declined also, and in
a more rapid progression. For the quantity of mois-
ture sustained in air of different temperatures freely
in contact with water diminishes more rapidly than
the temperatures1; so that if we take 56° for the
present mean temperature of the surface of the
earth, and suppose it to have been formerly 76°, the
quantity of moisture held up by the atmosphere
formerly may be taken at nearly double that now
supported in it.

This being the case, and the causes of rain and
vicissitudes of seasons the same in kind, we may
admit the atmospheric power in wasting the earth's
surface to have been double what it is now, and
that from that time to the present it has sunk in
geometrical progression. Under these conditions the
time consumed in the production of the same total
effect as that already stated, under the actual
powers of the atmosphere, could not be so little as
two-thirds of that computed on the hypothesis of
uniform action, viz. 63,936,000 years.

But according to the same hypothesis the action
of the sea and atmosphere in early times must have
been more effective than at present, because of the

1 It varies in geometrical proportion to the temperature.

136 LIFE ON THE EARTH.

greater frequency, or greater violence, of movements
in the crust of the earth: for thus it would yield
more easily to the assaults of the waves and atmo-
spheric vicissitudes. During the earlier periods,
land rising through the waves was subject to more
rapid erosion by the sea and the atmosphere; short
seras of enormous waste productive of conglomerates,
longer periods of strong action yielding large masses
of sandstone, still longer periods of more equable
decay producing more extended beds of clay since
indurated to shale and slate.

During the same periods land was sunk in one
tract as well as raised in another, perhaps to as
great a depth here as the elevation there; while
it was sinking, fresh edges were exposed to the
sea, and thus the waste was quickened. How are
these effects to be calculated ? Strictly they cannot
be. But, as an illustration, let us suppose that by
these operations the resisting power of the rocky
masses of the earth's crust was weaker than at pre-
sent— only one-half as great — so that combining this
ratio to resist with that already allowed for the
power to destroy, we shall have the earlier atmo-
spheric waste effectively four times as great as at
present. This allowed, we shall find the whole time,
as given by the Uniformitarian hypothesis, cannot
be reduced to so little as f , or 38,000,000 years.

LIFE ON THE EARTH. 137

The same hypothesis applied to the formation of
the Coal Strata leads to very similar results. Higher
mean temperature, a greater quantity of moisture,
a larger dose of carbonic acid in the air,— these things
must be allowed to have been active in accelerating
the growth of the plants in Palaeozoic ages. If it is
conceivable that the growth was then twice as rapid
as now, that only halves the immense period already
assigned by the calculation; and besides it takes
no account of the probably serious objection that
very rapid growth under these conditions would
be in some degree balanced by very rapid decay
and dissipation of the constituent elements of the
plants.

From all that has been said we may learn that
by no hypothesis founded on probability, or consist-
ent even in a small degree with actual phenomena,
and the course of natural events, can we assign for
the deposition of the fossiliferous strata so short a
period as that last mentioned. It is rather to be
supposed very much longer, if reduction of tempe-
rature is to be taken as the mainly influential con-
dition of deviation from uniform action. For if this
reduction of temperature were taken at 20° it must
have required ages of ages to be accomplished by
the excess of radiation into space over the heat
received from the sun; the period may not elude

138 LIFE ON THE EARTH.

calculation, but it lies quite beyond the power of the
mind to contemplate with steadiness.

Abandoning all further attempts to determine the
probable antiquity of the Strata, and the several
races of Life, in measures of solar time, we may re-
fer to some more limited trials to assign a date to
the origin of the present physical aspect of nature —
the present action of the sea on its coasts, and of the
rivers on their beds. In the speculations of De Luc
concerning natural chronometers this period is de-
scribed as posterior to the existence of our conti-
nents, and as having a fixed chronology; it is now
regarded as the latest of the Pleistocene periods ; in
the northern zones of the world it is the Postglacial
period; and it includes, according to all observation
and opinion, the age of the human race.

Herodotus, the first author who ventured an
estimate of this kind, was naturally conducted to it
by his inquiries regarding the ancient history of
Egypt. This fertile country, 'the gift of the Nile,'
offered him, in the real and fabulous narrative of its
governors, a long series of centuries of elapsed time,
and in the periodical floods and corresponding rise
of its surface and growth of its delta, natural chro-
nometers by which in some degree to check the tra-
ditions of the priests.

The conclusion of Herodotus does not however

LIFE ON THE EARTH. 139

directly apply to the land of Egypt. The statement
is to the effect that if the Mle were turned into the
Arabian gulf, that part of the sea would be filled
up by sediments in 20,000 years ; indeed, according
to his own opinion, in 10,000 years. Such being the
present tendency of the river to deposit sediment,
he justly concluded that, in the long lapse of earlier
time, the Nile may have filled up the greater Egyp-
tian gulf which lay in its course.

De Luc, one of the most ingenious and labo-
rious geologists at the close of the last century and
the commencement of the present, devoted much
attention to those operations of the sea and rivers
which promised to afford some measures of effect
applicable to the problems of past time. The growth
of new land on the sea-shore, the waste of the old
surfaces by the waves, the filling up of lakes and the
wearing away of valleys, — these, diligently studied,
led him to the general conclusion that the actual
state of our continents is not ancient ; that it is
not very long since they were given to the dominion
of men ; that not many ages have elapsed since the
continental parts of our globe were abandoned by
the ocean.

The limited growth of new lands — still yearly on
the increase by deposition of sediment — the small
extent to which lakes have been filled up by the

140 LIFE ON THE EARTH.

rivers which enter them, and the truncation of hills
sloping to the sea by cliffs not far from the point
where the slope once met the sea-level, may be men-
tioned as data of this kind. Undoubtedly they all
tend to convince us of the comparatively short period
of time which has elapsed since the sea began to
waste, or to be filled up, and the rivers began to wear
away the upper parts and to fill up the lower parts
of the valleys ; but it is difficult to translate this con-
clusion into centuries or thousands of years. Per-
haps such a case as that of the Derwent River
flowing into the Lake of the same name in Cumber-
land, and augmenting year by year the mass of sedi-
ments at the upper end, may be found worthy of
special attention, because of the abundance of rains
on the slaty mountains around, the shortness of the
course of the river, and the very slight degree in
which cultivation, quarrying, and mining, have, till
within a few years, altered the natural character of
the surface. The requisite measures of the lake, the
delta, and the sediment brought by the river, would
present no great difficulty.

Perhaps it may be sufficient to take one example,
the best at present known, to which computation has
been applied, for determining the number of years
in which a river has been running and excavating
for itself a channel in rocks of one definite charac-

LIFE ON THE EARTH. 141

ter. This example is found in the recession of the
Falls of Niagara1.

The river St Lawrence, in traversing the space
of 32 miles between Lake Erie and Lake Ontario,
has a fall of 330 feet. The general floor of the whole
country is limestone resting on shale ; the limestone
appears in the stream, covered in the banks on
each side by alluvial sand from 10 to 140 feet thick
for the first 25 miles. At this point the great Falls
occur; the river being precipitated over the solid
and projecting rock of limestone, in one tremendous
cascade 158 to 164 feet deep, into the subjacent
shale, which is deeply excavated below the general
level of the channel, and also worn into a recess
forty feet within, a perpendicular line dropped from
the limestone edge of the cataract. Below this point
the river flows in the deep chasm which it has
worn for itself, seven miles, to Queenstown and Lake
Ontario.

The Falls recede, not regularly, but by sudden
steps, in proportion as the subjacent shale is worn
away, and leaves the crown of limestone unsupported.
In the course of forty years they have thus receded
fifty yards/ Adopting this as the rate of recession
for the whole of the channel below the Falls, we
have 9856 years for the time which has elapsed
1 Lyell, Principles of Geology, I. 277.

142 LIFE ON THE EARTH.

since the epoch when the Falls began their back-
ward progress from Lake Ontario.

This epoch, however, is not of necessity the same
as that of the origin of the river action, which may
have gone on for some unknown time previously.
It does not then give us the desired information of
the length of the Postglacial period, or the date, as
De Luc might have expressed it, of the birth of our
continents. But it seems to point in the same direc-
tion as all the other natural chronometers, and to
compress within a few thousand years the later part
of the Pleistocene Period, when the main features of
the Land, the Rivers and Lakes, and Plains and
Mountains, had been finally redeemed from the power
of the sea, and peopled by the now existing races
of plants and animals.

CHANGES OF CLIMATE.

Few inferences have obtained a more general
assent among geologists than that which affirms the
change of climate during the progress of life on the
globe. The evidence on which reliance has been
placed has been sometimes adopted on light grounds,
sometimes rejected for fresh and better testimony;
but the conviction of almost every writer has been
deliberately recorded in favour of the prevalence of
much higher temperatures during early geological

LIFE ON THE EARTH. 143

periods in the northern zones of the earth, varied
by at least one great interval of remarkable cold in
later times. Before proceeding to consider how such
variations of climate might be possible, it will be
useful to collect some points of the evidence which
may be regarded as establishing the fact of their
having really taken place.

There is only one kind of evidence — that to be
obtained from organic remains ; and as in existing
nature some groups are more definitely related to
and indicative of climate than others, so in the fossil
world. In some modern genera and families the
species are distributed over different latitudes ; some
being intra-tropical, others extra-tropical, some in
the temperate, others in the arctic zones.

Such genera and families can only be employed
in arguments on ancient climate, where they contain
species which are both recent and fossil, and this
occurs only in the Csenozoic Strata. But there are
other fossil genera, families, and even larger natural
groups, which on proper questioning yield satisfac-
tory answers in regard to the main characters of the
climate to which they were appointed, whether on
land or in the sea.

To take our first examples from the vegetable
kingdom, we may inquire what climate is indicated
by the characteristic forms of land-plants buried in

144 LIFE ON THE EARTH.

the Coal-formation. Ferns are usually in fragments,
distributed by water on the successive surfaces of
deposition. It can seldom be ascertained whether
they belonged to arborescent or repent kinds, but
two or three species of the former division under
the title of Caulopteris are recognized in the Coal-
measures. The great abundance of Ferns is a fur-
ther and good argument for great warmth and damp-
ness. If Lepidodendra belong to the natural order
of Lycopodiaceee, their extraordinary size may be
held to demand the extreme of the conditions fa-
vourable to that race, heat and moisture; if they
include strong analogies to Araucarise, that is an
indication in the same direction. Sigillarise, now
commonly placed among the Gymnospermous Pha-
nerogamia, near Cycadacese, have also been thought
allied to Cacteaceae, and to Tree-ferns, and thus
follow on the same side as their companions the
Lepidodendra.

Calamites, no longer referred to Equisetacese,
but with Asterophyllites classed among Coniferce,
give no independent testimony to climate ; but a few
Palms (Flabellaria, Palmacites, Trigonocarpum), and
Musacese (Musocarpum), concur with the Tree-ferns
in requiring for the low shores of early time, where
now extend the coal-deposits of America and Europe,
a mean temperature of 64°, which is 16° above that

LIFE ON THE EARTH. 145

now experienced in the centre of the Coal-basin of
Scotland, 20° higher than that of the Coal-field of
Michigan, and not less than 30° above that of the
northern part of Newfoundland, to which the American
Coal-basin extends.

Again, in the Oolitic period, we find Ferns still
the prevalent vegetation, with gigantic Equiseta,
and stems and fronds of Zamioid and Cycadeoid
plants and Pandanacese, all indications of an equally
warm climate, prevalent as far north as Yorkshire
and Bornholm. Thus a difference of 16° or more
appears in favour of the ancient temperature.

In Csenozoic Strata, the natural orders of Cucur-
bitacese, Anonacese, and Mpadaceae in the London
basin, and Palmacere in that of Paris, carry on the
inference to times nearer our own; but there is rea-
son to suspect the influence of drift — like that of the
modern gulf-stream — in transporting the numerous
fruits now found in the clay of Sheppey1.

Coral growing into masses comparable to modern
reefs affords a valuable illustration of marine climate
at several geological epochs ; for reefs having this
origin, whether rising perpendicularly in the waters,
or accumulated under the influence of sea-currents,
are confined in modern nature to a limited breadth
on either side of the equator. The Corals which fall

1 Bowerbank, Fossil Fruits and Seeds of Sheppey.
E. L. L

146 LIFE ON THE EARTH.

under this designation in the West Indian Archi-
pelago are for the most part not of the same species
as those which occur in the Indian and Pacific
Oceans, and thus the argument acquires a gene-
rality and independence of specific forms and pecu-
liarities ; which suits it for application to the extinct
races, and the earlier reefs constructed often by dif-
ferent genera, in the Silurian, Carboniferous, and
Oolitic periods.

Keeping in mind that light, warmth, and proxi-
mity to the surface of pure sea-water, are essentials
for the life of the reef-making animals, we shall
understand the complete segregation of these re-
mains from the great mass of argillaceous and are-
naceous sediments in the several formations. The
limestones of Wenlock and Aymestry, of Plymouth, of
Mendip, Flintshire, Derbyshire, and Yorkshire, all of
Palaeozoic ages and full of Coral-beds and bands of
corals in place and attitude of growth, appear to be
little else than the accumulations of Polypean and
Crinoidal reliquiae, augmented by the shells and
other exuviae of the sea-animals naturally attracted
to the growing calcareous accretion. Each of these
limestones indicates an interval of rest in the accu-
mulation of sediments, a pause of the depression of
the sea-bed1.

1 Memoirs ofMalvern in Memoirs of Geological Survey, n. 1.

LIFE ON THE EARTH. 147

The Crinoidea mentioned in connexion with the
Coral-reefs may perhaps be quoted independently
as favouring the opinion of a prevalent high tem-
perature in these northern regions in the Palaeozoic
periods, for the living Pentacrinite, very similar to
the fossil groups in the London Clay and Mesozoic
Strata, has been found only in the West Indian
Seas. If we look at a map of isothermal lines, it
will appear that a mean temperature like that to be
inferred for the land of the Coal-measures from
the evidence of Plants, ought to be assigned to the
sea of the same period from the evidence of the
Marine Radiata.

This inference, according to discoveries in the
northern parts of America, would seem to carry the
warmth of ancient times very much beyond the ex-
perience of geologists in Europe — even to the shores
of the Arctic Sea — where mean temperatures below
that of congelation now prevail.

The Mollusca of Tertiary Strata in Europe may
sometimes be appealed to for evidence of the former
connexion of the basins in which they were collected
with the ocean, in such a manner as to allow of at
least occasional communication ; so that Voluta,
Conus, Cyprsea, Nautilus, &c. might be introduced
among the fossils of the basins of London and Paris.
But in earlier geological periods, evidence of this

L 2

148 LIFE ON THE EAETH.

kind is very faint; and a very large proportion of
the fossil shells of all orders must be passed over as
yielding no sufficient data for a sound conclusion.
If we may trust to the few species of the recent
genus Nautilus, as indicative of a warm climate, and
include all the fossil groups in the same inference,
the conclusion already obtained as to the Palaeozoic
and Mesozoic seas of the north temperate zone would
be confirmed.

With much confidence we may appeal to the class
of Reptiles for proof of the warm climates of the
land, sea, and fresh water of the whole Mesozoic
period, for this whole class, as represented in modern
times, has such a dependence on temperature as to
diminish rapidly in number and dwindle to small
size beyond the tropics, and to require special pro-
visions for enduring the winter cold. Not that it
seems necessary to suppose, for their comfortable life,
a climate heated above ordinary temperatures, in the
same proportion that their magnitude exceeds that
of recent species. The living Crocodilia are con-
fined to rivers which open into warm seas, and their
own geographical range does not pass the isothermal
of 64° mean annual temperature. Within this range
are most of the races of Serpents and Batrachians on
land, and of Turtles in the sea; except that now
and then some species wander beyond their usual

LIFE ON THE EARTH. 149

bounds ; as we may perhaps suppose the marine
Turtles and Saurians of the Mesozoic and Cainozoic
periods occasionally to have done. In migrations of
this kind it is difficult to assign the limits ; indivi-
duals may arrive and live, where the race would soon
perish in the struggle with unfavourable natural con-
ditions.

In the earlier Tertiary periods, the excessive pre-
dominance of Pachydermatous Genera, allied to Tapir,
Rhinoceros, Hippopotamus, Elephas, and the occur-
rence of their remains in old lakes and marshes, &c.
seem to require the hypothesis of their having lived
through long ages in the latitudes of Paris, the
Rhine-land, and England. Granting that they in-
dicate a warmer climate then prevailing, we may
confirm it by the remains of Serpents and Monkeys
found in the London clay at Kyson near Ipswich1.
But in the later Tertiary epochs, the frequent mixture
of Rhinoceros and Hippopotamus and Elephant with
Horse, Ox, Deer, Wolf, Bear and other quadrupeds,
whose relatives are found in various climates, and are
known by experience to prosper in the climates now
prevalent where their remains occur, renders inferences
as to climate from them too vague and indecisive to
be trusted. With these mixed land quadrupeds lie
in several situations, in old Pleistocene lakes, shells
1 Owen in British Fossil Mammalia.

150 LIFE ON THE EARTH.

of the, land and fresh waters, which are identical with
those now living in the same neighbourhood, un-
mixed with any from latitudes further south, or
further north ; so that here we have a decisive test,
and must admit in these cases that the climate was
nearly the same as now. This applies to the Post-
glacial period, in some part of which we place the
commencement of the History of Man.

The Glacial period itself— marked over a great
part of the north temperate zone in America and
Europe, by marine deposits heaped over what had
been dry land — covering sometimes the lacustrine
and peaty layers of that earlier (Preglacial) land, — this
period was one of considerable refrigeration, within
the large areas mentioned, for the shells found in
the deposits are of the colder arctic types ; and the
deposits are found to be consistent with the idea of
icebergs floating in deep water over all but the
mountainous tracts, (these being covered with ice and
snow, the source of glaciers and icebergs,) and not
consistent with any other probable condition of things.

Thus we have one well-marked period, at least,
of considerably greater cold in the northern tempe-
rate regions, succeeding many periods of greater
warmth in these same regions. It has been supposed
that toward the close of the Palaeozoic period, a very
early glacial sea was spread round several of our

LIFE ON THE EARTH. 151

British and Scottish mountains, and that the remark-
able conglomerate of the Malvern and Abberley hills,
now supposed to be of Permian age, is due to the
floating and stranding of icebergs along the edge of
the sea which washed the Longmynd, Abberley, and
Malvern hills1; and a more comprehensive conjecture
was once proposed by Agassiz, that the ancient cli-
mate was subject to several sudden depressions,
coincident with great destructions of life, followed by
some rise of temperature, and a renewal of life.

Admitting that such great changes have happened
in the climate of our north temperate zones, how are
they to be accounted for?

If in agreement with the conclusions of Herschel2
we admit the earth's orbit to be only in a small
degree variable, and so the sun's influence nearly
constant; and decline to accept the hypothesis of
Poisson3 that the solar system in its wandering
through space has encountered various temperatures ;
we shall find our power of explaining the great dif-
ferences of climate, on the same area in ancient and
modern times, reduced to estimating the effect of
variations proper to the planet. It has been sup-

1 See Memoirs of the Geological Survey, n. 1 for my descrip-
tion of this conglomerate. Professor Ramsay is the author of the
hypothesis referred to.

2 Geological Transactions, Ser. 2, Vol. n.

3 Whewell in Reports of British Association, 1835.

152 LIFE ON THE EARTH.

posed that the mass of the Earth has grown alto-
gether colder, since the earliest times, by radiation
of its heat into and beyond the cold starry spaces
of the universe. It has been conjectured that the
Earth's axis has been displaced, so that parts once
under the more direct action of the sun have lost
much of his beneficent influence; and it has been
thought that the differences in question might arise
from a different distribution of land and water, which
is a known cause of considerable inequality of tem-
perature in the same latitudes.

In considering this subject we may remark that
inequalities of temperature in the same parallel of
latitude may be observed when an area of water is
compared with a surface of land; and when land
varies in elevation, and the nature of its surface. Sir
Charles Lyell has founded on these facts the sup-
position that if a tract of land, equal to and of the
same form as our existing continents and islands and
rising to the same height, were collected round the
poles, while the equatorial zones were occupied by an
encircling sea, the whole earth would be cooler than
it is now. There is no doubt that this would be the
case, but it happens not to agree with the observed
facts regarding the glacial deposits, for these require
deep ocean over much of what is now land in circum-
polar zones.

LIFE ON THE EARTH. 153

On the other hand, he supposes that if all the
land, similarly shaped, were collected along the
equator, while the poles were overflowed, the whole
earth would be warmer than it is now. This ap-
pears somewhat doubtful; for though the equatorial
regions of land might gather more heat from the
sun, and the polar regions receive more warmth by
oceanic communications, still these polar surfaces of
warmed water might lose more heat by radiation
into space than equal surfaces of snowy land ; and
thus the whole ocean might be cooler, as well as
more equal in temperature. Whatever changes we
suppose possible in the distribution of land and sea
must fall short of these extreme suppositions, which
besides do not so well match the phenomena of any
geological period, as to prevent our turning to other
causes of change — not in the temperature of the
whole surface of the globe, but in the climates of
particular parts, still following the guidance of Lyell.
Of these two are very prominent ; the flowing of
oceanic currents, and the course of the winds ; and to
these a great and real influence is justly attributed,
in heating some parts of the earth above the average,
and in cooling other parts below it. Thus the well-
known broad and constant stream which flows from
the Gulf of Florida up the North Atlantic, carries a
vast body of warmed water from the tropical shores

154 LIFE ON THE EARTH.

of North America, to the Arctic circle, the North Cape
of Scandinavia, and the icy shores of Spitzbergen.
Along the line of this current the isothermal lines
are inflected to the northward, beyond the points
which they reach in the midst of the continents of
Asia and America 10, 15, and even 20 degrees; in
other words the northern parts of Europe have their
winter climate in particular so mitigated by the aid
brought to them over 2000 miles of sea, as to make
the yearly average of temperature higher by 10° or
15° than places in the corresponding latitudes in the
United States. Conceive that by some movement of
the solid earth-crust, this current were entirely pre-
vented from flowing up the Atlantic, then 10° or 15°
would be lost to the climate; suppose other un-
favourable circumstances arising from the new dis-
tribution of land and water, such as a cold current
from the north ; perpetual snows would gather on the
mountains of Scotland, Cumberland, Wales, and Ire-
land; glaciers would be formed in suitable situations;
icebergs would be floating on the sea; Arctic shells
might be encouraged in growth, and the phenomena
of the glacial period be repeated1.

It appears from these considerations, that by a
change of the oceanic currents, quite within geolo-
gical probability, the warmest meridional band in the
1 Hopkins in Geol. Soc. Journal, Vol. vm.

LIFE ON THE EARTH. 155

northern hemisphere might lose its singular advant-
ages of climate, so that glaciers might spread over its
valleys now fertile of corn. Changes in the earth's
physical features will account for a local augmen-
tation of cold, and explain to us the glacial epoch,
the phenomena of the boulder drift, and the Arctic
fauna which accompanies it. Can we by processes of
the same order, taken in another direction, account for
the opposite effect of greater heat in the same regions
in earlier times?

The hypothesis of Sir C. Lyell already alluded to,
which attributes change of climate to an alteration
in the distribution of land and water, though appa-
rently not of much efficacy in exalting the mean
temperature of the whole surface of the globe, opens
beyond doubt a source of real power to change the
local climate of any part, and especially to augment
the warmth of a tract lying far from the equator.
We see this to be strikingly the fact in the case of
the gulf-stream running up the Atlantic; and in a
less degree in the bending of the isothermals north-
ward to Behring's Strait. The maximum effect of
such currents, according to the present arrangement
of land and water, is seen in the beneficial action of
the gulf-stream on the western coasts of the British
Islands and Norway: and unless we can imagine a
position of the continents more favourable for the

156 LIFE ON THE EARTH.

distribution of water wanned between the tropics,
we must conclude that no material elevation of mean
temperature can be effected by means of oceanic
currents, beyond that imparted by the gulf-stream
and winds which blow in the same direction.

What appears to be the most favourable distribu-
tion of land and water for the diffusion of heat, is
neither an equatorial nor a polar position of large
continents; nor indeed of large continents at all,
but low islands scattered over the area of the globe,
amidst large breadths of water1. By this means
the watery communications being everywhere easy,
the whole ocean would acquire the greatest uni-
formity of which it is capable, the lands would par-
take in this equality, and the general temperature
would be something exalted by the absence of the
cooling effect on the atmosphere of the lofty moun-
tain-ridges, for these intercept and mix the aerial
currents, and chill the winds which cross their
snowy tops and afterwards traverse the lower
ground. The thermometric range of mean temper-
ature on the surface of the earth (the Pole not being
in the coldest zone) is about 100° Fahr.; that of the
sea, where most warmed by the Atlantic currents,
even to the Pole, probably not above 80° Fahr.

1 Prof. Hennessy has suggested a similar view of the subject.
Atlantis, Jan. 1859.

LIFE ON THE EARTH.

157

In the following Table the temperatures accord-
ing to latitudes are represented (1) for the whole
Northern Hemisphere, (2) for the warmest band of
water up the Atlantic1, (3) the difference of these or
the warming influence exerted by the sea-currents
and winds.

Pole.

I.

II.

III.

80°

—

__

__

70

17°

36°

19°

60

30

46

16

50

41

54

13

40

56

62

6

30

68

68

0

20

76

76

0

10

79

79

0

0

79

79

0

As already observed the temperatures, even in
the warm North Atlantic band, are not high enough
to suit the case of the Coral growths in Palaeozoic
and Mesozoic ages, which demand in lat. 60° about
34°, in addition to the average temperature, or 18°
above the highest observed temperature.

To meet this necessity we may suppose a more
effective distribution of the equatorial temperature
into the basins of the North. We may further sup-
pose, for the sake of calculation, the average result
1 From Dove's Maps of Temperature.

158

LIFE ON THE EAETH.

for each zone of latitude to be an increase of warmth
proportioned to the difference of area between that
zone and the equatorial zone. On this supposition
the following calculation is made1.

The addition to mean temperature in lat. 60°
being taken at 30°, the scale of augmentations for the
whole series of latitudes will be nearly as in Col. I.,
and, the equatorial temperature remaining the same,
the temperature for each latitude up to 70° will be as
in Col. II.

Pole.

I.

II.

80°

—

—

70

39°

56°

60

30

60

50

22

63

40

14

70

30

8

76

20

4

80

10

1

80

0

0

80

These temperatures would meet the geological
requirement; but it seems very doubtful whether
there is enough of probability about the hypotheses
on which they are founded, to meet the two objec-
tions which follow. 1. The augmentation, here attri-

1 The formula is merely this. Augmentation = A (rad. — cos.
lat.).

LIFE ON THE EARTH. 159

buted to a considerable part at least of the hemi-
sphere, is twice as great in amount as in the most
favourable example now to be found on any part
of the globe. 2. The average temperature of the
whole area affected must be augmented by about
13°. Though neither of these conditions may be ac-
cepted as very probable, we can hardly avoid be-
lieving the varying distribution of land and water to
be an important element in a just explanation of
ancient high climate in northern zones.

There is indeed a further consideration which
deserves much attention. One characteristic of the
climates not very far from the equator is the small
range of the annual temperature, only a few degrees
being the full amount of vicissitude in this respect
through the year. Some weight must be allowed to
this in forming our scale of required additional tem-
perature; perhaps a considerable weight. Under
the conditions assumed in the last calculation the
whole of the oceanic temperatures would become
remarkable for very small variations from one part
of the year to another; and thus one characteristic
requisite in the life of the plants and animals of the
warm regions being perfectly fulfilled, it seems very
probable that so high an average temperature as that
assumed might not be required. If we allow full
force to this idea, and conceive the equatorial tern-

160 LIFE ON THE EAKTH.

perature to be lowered (as it would be) by an effec-
tive distribution of part of its warmth by currents
directed toward the poles, the difficulty would be
much reduced.

For those who are not satisfied with the proba-
bility of the explanation just examined, another hy-
pothesis is ready, the displacement of the axis of
the earth. Though this is refused by the proper
authorities, the astronomers, it may be worth while
to mention that the centre of gravity of the earth
cannot be regarded as having been always absolutely
fixed when we remember the irregular distribution
of the axes of elevation of different periods, the
very considerable mass of the elevated mountain-
chains, and the great amount of subsidence by which
the areas of deposition have been affected at different
times. But if the centre of gravity of the earth be
allowed to be thus inconstant in position, the axis
of rotation must be subject to change from the same
cause. Such minute variations, however, would be
of small efficacy in regard to the matter in hand, if
we are to judge by the actual distribution of the
masses of elevated land, and the direction of the
depths of the sea. Even if we could place an extra
load on one meridian between the pole and the
equator, and thus cause an angular deviation of the
axis, this is a process requiring long perseverance

LIFE ON THE EARTH. 161

and many repetitions in the economy of nature to
produce a sensible effect1.

Passing without remark conjectures regarding the
limits of the precession of the equinoxes, and the ob-
liquity of the ecliptic, and estimates of the variation
of the diameter of the earth's orbit, by which it has
been attempted to meet the difficulties of ancient
geological climate, a few words may be added re-
garding one speculation which has justly received
more serious consideration. The interior tempera-
ture of the earth is observed to augment sensibly
as we descend; the figure of the earth indicates ori-
ginal fluidity; the lowest rocks agree with the opi-
nion that great heat has been an essential agent in
giving to them their present appearance. The earth
is hotter within than at the surface; receives a cur-
rent of heat from the interior, and dissipates it into
space; grows cooler, and has been always growing
cooler, from the earliest times. Why not suppose
the greater surface-heat of early times to have been
caused by the then greater and nearer influence of
the interior much heated masses? The influence of
such a flow of heat outward to all parts of the sur-
face, independent of latitude, is exactly of such a kind

1 Col. Sir H. James has attributed a great effect to this cause,
AthencBum, Sept. 1860. Remarks have followed by Professor
Airy, Professor Jukes, and Professor Hennessy, which agree
with the views expressed in this work.

K. L. M

162 LIFE ON THE EARTH.

as our problem seems to require. "What are the ob-
jections to it?

Two, principally. First. The rate of increase of
temperature, as we go downward, is proportioned to
the quantity of heat flowing out and influencing the
climate by increase of sensible or thermometric tem-
perature. To augment by 10°, 20°, or 30° the existing
temperature of the surface would require an aug-
mentation of heat from the surface downward, in
the same proportion as the measure of warmth to
be communicated (say 10°) to the measure of warmth
(say gV^h of a degree) actually communicated. In
the case supposed, 200 times as great as now, the
heat of boiling water would be attained at about 50
feet of depth ! How under such circumstances could
the Mollusca and other creatures live in the sea, or
plants grow on the land?

Secondly. The rate of cooling of the earth by
radiation into space is so slow at present, that to
reduce the actual effect (say gVth of a degree) to
half that amount would require, according to the
calculation of Poisson, the period of one hundred
thousand millions of years1. In earlier times, the
flow of heat outward being much greater, the rate
of cooling would have been much more rapid; still
the period of time which must have elapsed in the

1 Hopkins, Address to Geol Soc. 1851.

LIFE ON THE EARTH. 163

reduction of the surface temperature by only 10°
is so vast and even inconceivable, that the adoption
of the hypothesis to that extent seems to require
something more than courage. But even ten degrees
of added warmth in lat. 60° would not be sufficient
to meet the case of the Corals in the sea, or the
Palms, Ferns, or Cycadacese on the land.

These objections have been urged as fatal to the
opinion that the internal heat of the earth, now
hardly sensible among the elements of surface climate,
was formerly a real and efficient, if not the principal,
cause of the superior mean temperature of the sea
and lands in extra-tropical countries. They have
even been urged by geologists, who accept the same
heat as real and very influential in that general
metamorphosis of the lowest rocks, which is observed
in every country, and in those disturbances of the
strata, which are equally universal, and of various
ages. It appears to me, however, that in these ob-
jections one thing is forgotten — the state of the at-
mospheric mantle which envelopes the terraqueous
globe, mitigates solar heat and stellar radiation, and,
like the clothing of a steam cylinder, prevents ex-
cessive waste of the warmth treasured within. For
nothing can be advanced to justify the supposition
that this important element in the economy of nature
was always of the same total weight, always identical

M 2

164 LIFE ON THE EARTH.

in chemical composition, and always on the average
charged to the same degree with aqueous vapour.
On the contrary, to take an example which appears
decisive, from the accumulation of the Coal Strata,
there is good reason to adopt positively the opinion
that the chemical constitution (if that may be
termed a chemical constitution which is only a me-
chanical mixture) of the atmosphere has been greatly
altered. For if the Carbon, fixed in the thick and
extensive beds of coal since the Palaeozoic ages,
were again restored to the atmosphere from which
it was taken, the weight of Carbonic acid now in
the atmosphere (_J^.th part) would be more than
doubled. Those who think the proportion of the
three main constituents of the atmosphere must ever
have been as they are now, may if they please
double also the Oxygen and Nitrogen, and thus aug-
ment the total barometric pressure of the early
Palaeozoic ages to 60 inches ! But without adopting
such an extreme view, there is really no reason to
limit our theory of the ancient atmosphere in respect
of Oxygen or Nitrogen any more than in regard to
Carbonic acid. The whole atmosphere may have
weighed more ; if so its measured depth must have
been greater, and its effect in restraining the waste
of heat, and, what is equally important, in reducing
the extremes of climatal difference, also greater.

LIFE ON THE EARTH. 165

Moreover, a warmer atmosphere, whether of
greater total mass or not, would hold more moisture
in suspension, and thus the tendency to equalize
temperatures might probably be augmented, both
by the transport of aqueous vapour to the coolest
parts, and by the wider canopy of clouds which are
well known to be effective in preventing the waste-
ful radiation of heat from the surface of the earth.
Thus all these inquiries — into the greater diffusion
of warmth over the surface by oceanic currents — the
greater flow of heat from the interior of the earth,
and the greater resistance to the escape and waste
of this heat, by the surrounding atmosphere — concur
in shewing that causes really founded in nature, and
still operating, may be appealed to for solution of
the interesting questions regarding ancient climate.
Neither perhaps is fully sufficient singly to explain
the phenomena, but they are of a nature to be com-
bined without improbability into a general and satis-
factory solution of the problem.

PHYSICAL ASPECTS OF THE EARTH.

The rich variety of the earth's surface, as it is
now possessed by man, is the legacy of many long
ages of busy nature, labouring to upheave the moun-
tains, and depress the seas, and carefully storing up
the treasures of those distant years for the enjoy-

166 LIFE ON THE EARTH.

ment of the present period. No Coal-fields, to last
even a single century, are now growing at the mouths
of our rivers ; no metallic veins are spreading
through the rocks that we can explore ; no great
catastrophe breaks down the barriers of seas, or
opens picturesque glens through the ridges of the
mountains. Yet the forces whose accumulated effects
seem to us so mighty are still alive, and still give
proof of their power to make further change in the
condition of the globe.

If we trace back the physical history of the parts
of the earth best known to us, we shall be surprised
at the permanence of many of the great features
of the land and sea ; where these have changed we
can often clearly see the mode and almost the
mechanism of change, and not unfrequently discover
somewhat of the effect of these variations on the
distribution of ancient life, its mutation and dis-
continuity.

The German Ocean is what remains of a wider
Tertiary Sea, which spread over a large part of the
country north of the Carpathians, extending east-
ward across the plains of Southern Russia, and north
of the Caucasus, but probably closed to the west-
ward. The Mediterranean of the Tertiary ages
stretched northward up the Adriatic gulf, to in-
clude the basin of the Po ; eastward and southward

LIFE ON THE EARTH. 167

into Syria, Egypt and Africa, and communicated with
the Atlantic by a strait, where now is the valley of
the Garonne and the basin of Bordeaux. The Black
Sea was connected to a long gulf up the vale of
the Danube. Land stood up in this large tract of
ocean only in small islands or much ramified masses,
where now appear the mountains in the centre of
France, in Germany, on the borders of Bohemia
and Moravia, in the Hartz, and Carpathians. The
British Isles formed almost a complete western
boundary, while small points and narrow ridges of
land marked the rising Alps and Apennines, and
the mountains of Dalmatia and Croatia.

In a far earlier period, after the deposition of the
Carboniferous Strata, many of the great features of
the British Isles and Scandinavia had been firmly
fixed by the axes of elevation which range north-
eastward from Ireland, through Scotland to the
Norwegian Alps, and eastward along the south of
Ireland and the south of England, through Belgium,
and across the Valley of the Rhine ; this last tract
was afterwards sunk again and partly covered up
by secondary and tertiary deposits, but the former
was never again wholly submerged.

But in the still earlier Cambro-Silurian period, the
broad ocean flowed over nearly every part of the area
now occupied by land in the whole of the northern

168 LIFE ON THE EARTH.

zones, most probably here and there diversified by
primitive islands, whose situation, however, and con-
stitution are merely conjectural, till we arrive at
the series of Wenlock rocks in the Malvern hills.
Here is proof of land situated where now is the
ridge of the Worcester Beacon ; land from which fell,
into the sea of that period, rocky fragments precisely
the same in nature as the variable Syenites of that
ridge ; fell into tranquil and slightly agitated water
of small depth, and were there cemented together with
Corals, Crinoids, Shells and Trilobites, a venerable
and interesting mark of the ancient limit of the old
and populous sea, against the old perhaps uninha-
bited land. Accustomed, in this way, to regard the
northern seas of our time as the shrunk and rami-
fied remainders of wider tracts of ocean, and the
lands as amplified by comparatively modern desicca-
tion round primitive peaks and ridges, we naturally
turn to consider whether the forms of life in the
sea manifest any special affinity to the fossils of the
neighbouring tracts from which it has withdrawn ;
and in what degree the plants and animals which
now cover the land are related to those which
occupied smaller spaces in the same regions.

Taking for a favourable illustration the Germanic
Ocean, and comparing its Mollusca with those of the
adjoining Pleiocene Crag, on the eastern coast of

LIFE ON THE EARTH. 169

England, Deshayes found about 40 per cent, of the
Crag shells identical with living species, and of these
nearly all occur in the neighbouring ocean1. In like
manner, the Tertiary fossils of the sub-Apennine region
of Italy are successfully compared with those of the
modern epoch, yielding, according to Deshayes, 41*8
per cent, of living species, a large proportion of them
from the neighbouring seas2. By observations of this
kind, the Tertiary Series is linked in easy harmony
with the actual period ; but if we make the same
kind of comparison of the Tertiary with preceding
Mollusca, but little of direct affinity can be traced ;
and the same remark applies to the common bound-

1 See Lyell's Principles of Geology ; Wood, in Pal. Soc.
Memoirs.

2 ' From the copious fauna which now tenants the Mediterra-
nean waters, a series of changes may be traced, through older
sea-beds of the same area, far back into bygone ages. Nowhere
do we find better illustration than here of the nature of the
changes which a fauna may undergo in time : the evidence is
consecutive. It is possible, however, that the Mediterranean
series, recent and fossil, may be imperfect, and that the earliest
periods of our European marine fauna are not represented there.
A comparison of the contents of the older Italian deposits, and
their equivalents containing the remains of the existing Atlan-
tic species of Testacea, with those of the Faluns of Bordeaux
and Touraine, suggests the probability that in these last we have
an earlier stage still in the history of our fauna, referable to the
time when the Mediterranean depression had not yet been opened
to the Atlantic waters.' — Forbes and Godwin- Austen, Nat. Hist.
of European Seas, 1859.

170 LIFE ON THE EARTH.

ary of the Mesozoic and Paleozoic Deposits, not many
closely related forms passing the limits in either case.
The present age is in fact a part of the great
Csenozoic period.

The attention of Linnaeus was drawn to the other
question regarding the succession of forms on the
land, and in the Amoenitates Academicce, which con-
tain some essays from his own hand, and many con-
tributed by his pupils, we find an interesting dis-
course on the subject of the extension of life from
the centres of mountainous districts1. It is easy to
find examples of parallel forms of Mammalia now
living, with some of the Tertiary quadrupeds once
denizens of the same regions, or regions formerly
connected by land ; the affinities thus traced being
feebler in proportion to the antiquity of the earlier
forms. Thus, in England the Beaver is extinct, but
yet lives in Germany ; our Red Deer is apparently
the same as some Pleistocene fossils, and very similar
to others of earlier date ; and our European Wolf
is found in the ossiferous caverns of England, Ger-
many and France. Sometimes, without this close
affinity, a considerable resemblance is found between
special tribes now living and others fossil in the same
region. In a part of the Continent of America this
is remarkable, among the Edentata, which thougli

1 De telluris orbis increment*).

LIFE ON THE EARTH. 171

not quite confined to that region, are more plentiful
there than elsewhere, and are successors of fossil
races also found almost exclusively in that country.
Thus the fossil Megatherium has been compared with
the Sloth, the Glyptodon with the Armadillo ; nor
does the enormous bulk of the fossils hinder the re-
ception of them into the same natural families. The
same lands then have been in successive periods
peopled by analogous races, and thus we have mani-
fested ' a wonderful relationship on the same conti-
nent between the dead and the living1.' Still this
succession of similar forms is limited to Csenozoic

One other example must suffice. The marsupial
peculiarity of Australian Mammalia is not of modern
date ; the Australian caves contain evidence of the
same character in the races whose remains are there
preserved. The peculiarity indeed is of far earlier
origin, for it occurs in the Eocene deposits of the
basin of Paris, in the Lacustrine deposits over the
upper Oolite in Purbeck, in the lagoon of the great
Oolite at Stonesfield, and probably in the Trias of

1 Darwin. This author does not suppose the living Edentata

of the same region to be the dwarfed descendants of these mon-

* strous beasts, but speaks of some others, their contemporaries in

time and companions in the same caverns, which may be regarded

as the progenitors of the living species.

172 LIFE ON THE EARTH.

Wiirtemberg. In respect of the Stonesfield fossils,
this is not the only evidence presented by that curious
deposit of similarity of Mesozoic life in the north,
and Csenozoic life in the antipodal region of the south.
It extends to other groups, both of the land and sea,
and almost justifies the notion of some affinity even
in the systems of life. For just as at Stonesfield, so
in Australia, small insectivorous marsupial mammals
are associated with Cycadaceous Plants and Ferns;
as now in the seas surrounding Australia, Terebratula
and Rhynchonella, Trigonia and Cucullsea, consort with
Turtles and the Cestraciont Sharks, near reefs of
Coral, and rivers tenanted by Gavialian Crocodiles,
so at Stonesfield in the older time, similar animals
in similar combination.

What does this teach us ? Are we looking upon
two partially similar but really separate creations
suited to partially similar conditions in very different
periods of time ? Or is the life-system of the modern
Australian land and sea truly derived in some of its
components by descent with modification from the
older periods of the world, and preserved to this
our day, notwithstanding displacement over half the
circumference of the globe, and all the vicissitudes
of an immensity of time ?

Whoever has the courage to adopt the latter
view, must accept with it the obvious inference that

LIFE ON THE EAKTH. 173

in all the countless ages which have rolled away
since the branches of Zamia were blown into the
lagoon of Stonesfield, the amount of organic change
has been small in each group of plants and animals ;
that a similar amount of change affected the unlike
inhabitants of land and sea ; that Mollusca and
Sharks, and Turtles and Crocodiles, have all been
modified by differences of a small description in pass-
ing from Oolitic to modern times, while not only hosts
of Ammonites and Belemnites have perished in the
experiment, but many new forms, as Oliva, Mitra,
Triton, Struthiolaria, unknown in the earlier period,
have come into view in the latter! But let it be
adopted. What follows? These small differences
then, accomplished in all that prodigious range of
elapsed time, under all that variety of physical
changes and removals, these are all the mutations
which have been possible under the constant ten-
dency of hereditary descent to perpetuate similar
forms with modification.

One of these genera, that of Trigonia, is known
to be in the fossil state rich in species ; supposing
them to have all come from one original typical form,
the differences which they shew in strata of the same
system, deposited within the same grand period, and
under much similarity of conditions, argues a facility
in giving variations ; let this operation be supposed

174 LIFE ON THE EARTH.

to be continued in the interval between the epoch
of Stonesfield and that of Australia, and the effects
summed by natural selection, the result is the modern
Trigonia, scarcely differing more in appearance from
the fossil species than they differ one from another.

But if not so derived, by continual descent, but
sprung from separate contemporaneous branches of
one stem of life, arriving at a given standard of
excellence at such enormously different epochs,
how should it happen that Plants and, Quadrupeds
on land, Sharks and Mollusks in the sea, should in
each of these two cases pass with equal advance
along the streams of change, moving in one case so
fast, in the other so slow? But if the branches
sprang at different times and led to these similar
results, would this double origin in time, for several
similar forms, in similar associations, fit with the
hypothesis of continual development ?

LIFE ON THE EARTH. 175

THEOKIES AND OPINIONS.

FORMED STONES.

THKEE centuries have glided by since Bernard
Palissy, the philosophic potter of Xaintonge, revived
the ancient opinion of Herodotus1 and Pythagoras2,
and wrote the simple words,

* Je t'ay monstre plusieurs coquilles reduites en pierre.'

France may well be proud of him, for he was among
the first who ever uttered in modern Europe sensible
remarks on the subject of Palaeontology8, and they
fell on incredulous ears.

Two centuries only remove us from Agostino
Scilla4, the worthy Italian painter, who strove to
dissipate false speculations regarding petrified marine
exuvise, by excellent drawings of recent and fossil
teeth, Echinida and shells, from the Tertiary Strata
of Messina and Malta. What these false speculations
were, is too well known to the readers of our earliest
English authors, Plot, Llwydd, Lister, Ray, and Wood-

1 Euterpe, 12. 2 Ovid, Metam.

3 The first of Palissy's Essays is dated 1557 ; the complete
work 1580 ; Gessner's work, De omni rerum fossilium genere, &c.,
was printed at Zurich in 1565.

4 La vana speculazione disingannata. Earliest Edition, 1670.

176 LIFE ON THE EARTH.

ward, who consumed the latter part of the seventeenth
century in wrangling about l formed stones/ ' plastic
forces,' and 'lusus natune.'

The learned Dr Robert Plot, the first Keeper of
the Ashmolean Museum in Oxford, in that valuable
Natural History of Oxfordshire (1677), which was
the model for many goodly volumes in other counties
of England, after carefully describing many Ophio-
morphites, Ostracites, Belemnites, and Cockles lying
in their stony sepulchres, is brought to consider the
great question then so much controverted in the
world.

1 Whether the stones we find in the form of shell-
fish, be lapides sui generis, naturally produced by
some extraordinary plastic virtue latent in the earth
or quarries where they are to be found? Or whether
they rather owe their form and figuration to the shells
of the fishes they represent, brought to the places
where they are now found by a deluge, earthquake,
or some other such means, and there being filled
with mud, clay, and petrifying juices, have in tract
of time been turned into stones, as we now find
them, still retaining the same shape on the whole,
with the same lineations, sutures, eminences, cavities,
orifices, points, that they had whilst they were shells.

'In the handling whereof (he tells us), 'though
I intend not any peremptory decision, but a friendly

LIFE ON THE EAKTH. 177

debate; yet having according to the wishes and ad-
vice of those eminent virtuosi, Mr Hook and Mr
Ray, made some considerable collections of these
kind of things, and observed many particulars and
circumstances concerning them; upon mature con-
sideration, I must confess I am inclined rather to
the opinion of Mr Lister, that they are lapides sui
generis; than to theirs, that they are thus formed in
an animal mould. The latter opinion appearing at
present to be pressed with far more and more in-
superable difficulties than the former. For they that
hold these stones were thus formed in the shells of
fishes, must suppose either with Steno, that they
were brought hither by the Deluge in the days of
Noah; or by some other more particular and per-
haps national flood, such as the Ogygean or Deu-
calionian in Greece, than either of which there is
nothing more improbable.'

His argument against the Noachian origin of the
figured stones is very complete; first, that it was not
universal, but confined to the continent of Asia; and
next, that if it were universal it could not have
produced the effects which require to be explained,
whether it were occasioned by rain, or the breaking
up of the sea, and whether it were violent or gradual.

E. L.

178 LIFE ON THE EARTH,

CATACLYSMS.

Sufficient as they were, and satisfactory as they
ought to have been, these arguments against the
diluvial origin of the ' figured stones,' did not
prevent the adoption of it by many writers who
had gained the right faith in regard to their
nature and origin. Woodward, the great founder of
the Chair, which has been so worthily filled by
Mitchell and Sedgwick, who ransacked the British
Islands for fossils, and devoted all his mind to
" observation of the present state of the earth, and
of the site and condition of the marine bodies which
are lodged in and upon it," adopts the hypothesis
which Plot rejected, to account for phenomena which
that author had not rightly valued. His Natural
History of the Earth (1695), contains these propo-
sitions and reflections:

1. 'That the marine bodies were borne forth of
the sea by the universal deluge; and that upon the
return of the water back again from off the earth,
they were left behind at land.7

2. 'That during the time of the deluge, whilst
the water was out upon and covered the terrestrial
globe, all the stone and marble of the antediluvian
earth ; all the metals of it ; all mineral concretions ;
and in a word all fossils whatever that had before

LIFE ON THE EARTH. 179

obtained any solidity, were totally dissolved, and
their constituent corpuscles all disjoined, their co-
hesion perfectly ceasing. That the said corpuscles
of these solid fossils, together with the corpuscles
of those which were not before solid, such as sand,
earth and the like; as also all animal bodies and
parts of animals, bones, teeth, shells, vegetables and
parts of vegetables, trees, shrubs, herbs; and to be
short, all bodies whatsoever, that were either upon
the earth or that constituted the mass of it, if not
quite down to the abyss, yet at least to the greatest
depths we ever dig ; all these were assumed up pro-
miscuously into the water, and bodies in it, and
made up one common confused mass.'

3. 'That at length all the mass that was thus
borne up in the water, was again precipitated and
subsided toward the bottom — according to the laws
of gravity — forming the strata, including the organic
fossils according to their specific gravity/

He then goes on to explain the solidification of the
strata, their original parallelism, their subsequent
dislocation by a force from within, and the produc-
tion by this means of the irregularities of the surface
of the earth, and makes these explanations on the
whole :

'Here was, we see, a mighty revolution; and
that attended with accidents very strange and amaz-

N2

180 LIFE ON THE EARTH.

ing; the most horrible and portentous catastrophe
that nature ever yet saw; an elegant, orderly, and
habitable earth, quite unhinged, shattered all to
pieces, and turned into a heap of ruins : convulsions
so exorbitant and unruly; a change so exceedingly
great and violent, that the very representation alone
is enough to startle and shock a man.'

ALL LIFE DERIVED FEOM THE SEA.

By degrees, however, the great truth fixed by ge-
ology, that we stand on the dried bed of the ancient
sea, began to influence the ingenious writers who
followed close upon Plot and Scheuchzer. Among
these De Maillet, in the singular work called ' Tellia-
medj (his own name reversed,) is conspicuous for the
perverse resolution with which he follows out the
evil consequences of an ' inappropriate idea1' on
this subject. Believing that the old sea-beds were
laid dry by the retirement and diminution of the
water, about three feet in a thousand years, he
feels no hesitation in deriving all the plants and
animals of the land from prior productions of like
nature in the sea, though at present circumstances
may fail which contributed formerly to spontaneous

1 See Whewell's Inductive Sciences for examples of ' appro-
priate ideas.'

LIFE ON THE EARTH. 181

generation, and that the earth is reduced to ordi-
nary propagation.

Jamque adeo fracta est setas, ecfoetaque tellus
Vix animalia parva creat, quse cuncta creavit
Saecla, deditque ferarum ingentia corpora partu.

Tlie germs of life he supposes to be everywhere
provided through the universe — in air, food, water —
ready to be developed into species by the warmth of
the sun, in water or mud disposed to fecundity, so
that all life has proceeded from the sea. Whether
this constitution of things be ascribed to laws of
nature or the design of the Creator, he regards with
indifference, being satisfied that such a condition of
things is real.

The difficulty of the change from watery life to
aerial life, he regards lightly.

'A hundred millions of individuals must have
perished, without being able to assume the new
habit of life, but it is enough if two have survived
the trial, to give permanence to the race.'

Here is one example of the process :

'It may have happened, as indeed we know it
often does happen, that flying-fishes fell into bram-
bles or pastures, from which it was impossible to
return to the sea by the effort which brought them
from it, and that in this state they acquired a
greater power of flight. Their large fins, no longer

182 LIFE ON THE EARTH.

bathed by the waters of the sea, divided and opened
in drying; the separated fin-rays prolonged them-
selves, and became covered with barbs, or to speak
exactly, the membranes which had previously held
them together were metamorphosed. The barb form-
ed of these separated pellicles, lengthened itself;
the skin gradually covered itself with a down of
the same colour, and this down increased. The
subventral fins, which, as well as the large fins,
assisted their promenade in the sea, became feet,
and served them for walking on the earth. Some
other small changes took place in their shape. The
beak and neck of some were lengthened, of others
shortened; and so of the other parts of the body.
But still the conformity of the original figure remains
on the whole; and it is and always will be easy to
recognize.'

So much for the origin of Birds ! By processes
equally easy and satisfactory, the sea is shewn to be
the parent of quadrupeds and men.

GERMS OF LIFE.

Buffon adopted similar views as to the deriva-
tion of the forms of life, and was followed by one
greatly superior in real knowledge of nature, who

LIFE ON THE EARTH. 183

has given to the dreams of De Maillet a regular
form and delusive symmetry1.

Lamarck supposes all the phenomena of life may
be accounted for upon electro-chemical principles,
and that the higher and more intelligent races of
animals may have been gradually formed by the
plastic power of nature, out of the smallest and
simplest. By nature, we are to understand a certain
order of causes and effects, constituted by the will
of the Supreme Author of all things, and appointed
to produce all the phenomena of the material world.
In obedience to this secondary power he supposes
that the attractive force of matter is sufficient to pro-
duce small portions of gelatinous substance, capable of
being acted on by these powerful agents, caloric and
electricity, and that when thus acted on they exhibit
vital energies ; in other words, that caloric and elec-
tricity acting on appropriate dead matter may convert
it into living organic matter. Further, that the mo-
difying influence of circumstances has caused these
indefinite organic living masses to be extended into
various animal forms; that first were produced the
more simple, from these, by methods of reproduction,
aided by the continued action of the same vital fluids
and under the influence of changed circumstances

1 Philosophic Zoologique and Introduction to Animaux sans
Vertebres.

184 LIFE ON THE EARTH.

and acquired habits and desires, other different and
superior races of animals may have been formed.

In this hypothesis we have three assumptions:

First, that some of the inferior tribes of plants
and animals are producible by the agency of caloric
and electricity from dead matter, and that loco-
motion in some of these is accomplished by the ex-
ternal influence of these exciting fluids, and not by
the inherent power of the creature.

Secondly, that the organic beings thus originating
are capable of indefinite change of form and struc-
ture from the force of external circumstances.

Thirdly, that new habits of life are acquired with
the new structures ; that individual desires or long-
ings have influence in the further development; and
that the acquisition and exercise of the senses, in-
stinct, reason, hope and fear, memory of the past,
and expectation of the future, is a part of this stu-
pendous chain of metamorphism with a tendency to
progressive improvement.

Neither of these assumptions is proved, or ren-
dered probable; but rather becomes less and less
acceptable the more we consider the illustrations
suggested by the author, which are scarcely less sur-
prising than the instance already quoted from Telli-
amed.

The foundation in truth for this hypothesis is

LIFE ON THE EARTH. 185

the unquestionable power of adaptation which living
creatures possess, through exercise of the organs of
life, by which some change is possible in structure
and some change in function also, the new qualities
being in some degree transmitted to the descendants.

There is no need to mention in detail the views
of other and later continental writers, for none have
been more ingenious, more plausible, or more ex-
plicit; nor has the proof which is wanting to sus-
tain the propositions of Lamarck been supplied by
his followers in any country.

The speculations of Lamarck have met with a
full and fair examination in Ly ell's Principles of
Geology, leading to a deliberate rejection of the hy-
pothesis, and a decisive affirmation of the reality of
species in nature. The following is his recapitula-
tion of the result of the inquiry.

'For the reasons therefore detailed in this and
the two preceding chapters, we may draw the follow-
ing inferences in regard to the reality of species in
nature :

1 1. That there is a capacity in all species to
accommodate themselves, to a certain extent, to a
change of external circumstances, this extent varying
greatly, according to the species.

' 2. When the change of situation which they can
endure is great, it is usually attended by some mo-

186 LIFE ON THE EARTH.

dification of the form, colour, size, structure, or other
particulars ; but the mutations thus superinduced are
governed by constant laws, and the capability of so
varying forms part of the specific character.

' 3. Some acquired peculiarities of form, struc-
ture, and instinct are transmissible to the offspring;
but these consist of such qualities and attributes
only as are intimately related to the natural wants
and propensities of the species.

' 4. The entire variation from the original type,
which any given kind of change can produce, may
usually be effected in a brief period of time, after
which no farther deviation can be attained by con-
tinuing to alter the circumstances, though ever so
gradually; indefinite divergence, either in the way
of improvement or deterioration, being prevented,
and the least possible excess beyond the definite
limits being fatal to the existence of the individual.

'5. The intermixture of the distinct species is
guarded against by the aversion of the individuals
composing them to sexual union, or by the sterility
of the mule offspring. It does not appear that true
hybrid races have ever been perpetuated for several
generations, even by the assistance of man ; for the
cases usually cited relate to the crossing of mules
with individuals of pure species, and not to the
intermixture of hybrid with hybrid.

LIFE ON THE EARTH. 187

'6. From the above considerations, it appears
that species have a real existence in nature; and
that each was endowed, at the time of its creation,
with the attributes and organization by which it is
now distinguished1.'

STEATA IDENTIFIED BY OEGANIC EEMAINS.

The discovery by William Smith of the successive
stages of the stratification of Britain, each contain-
ing the remains of the organic beings then living
in the waters or distributed through their agency,
each stratum having been in succession the bed of
the sea, gave the basis of a true Palaeontology, and
a true history of the succession of life on the globe.
Almost every geologist and naturalist who has read
this history by the light of these discoveries has
arrived at the conclusion that many separate acts of
creation are required to explain the successive ap-
pearances of the various races of animals and plants*
In a few instances, of late years, the attempt has
been made to adapt the hypothesis of Lamarck to
the facts of Geology, and to combine two really dis-
tinct ideas — to derive all the observed variety of
organization from one or a few original germs, by
steps continually ascending on the whole to higher

1 Principles of Geology, Book in. conclusion of Chap. rv.

188 LIFE OX THE EARTH.

grades and greater perfection as a physiological
problem; and to shew that in the buried worlds of
life this continual expansion of the general funda-
mental form, with a continual tendency to higher
and higher development, can be placed in evidence
as a matter of history. It is important to keep this
distinction in mind.

DEVELOPMENT.

The author of the Vestiges of Creation placed
before the English reader some sketches of the as-
pect of the animated world in successive geological
ages, and has proposed in relation to the vegetable
and animal kingdoms a full hypothesis of develop-
ment to fit the gradation from the simple Lichen and
Animalcule respectively up to the highest order of
Dicotyledonous trees and the Mammalia. He attri-
butes a great amount of change to the necessary
effect of variations in the physical conditions which
are influential on life: this change being progressive
from lower to higher grades, and unlimited except
by the range of physical conditions.

'While the external forms of the various verte-
brate animals are so different, the whole are, after
all, variations of a fundamental plan, which can be
traced as a basis through the whole, the variations
being merely modifications of that plan to suit the

LIFE ON THE EARTH. 189

particular conditions in which each particular animal
has been designed to live. Starting from the pri-
meval germ, which is the representative of a par-
ticular order of full-grown animals, we find all others
to be merely advances from that type, with the ex-
tension of endowments and modification of forms
which are required in each particular case: each
form, also, retaining a strong affinity to that which
precedes it, and tending to impress its own features
on that which succeeds.

'The various organic forms of our world are
bound up in one — a fundamental unity pervades and
embraces them all, collecting them, from the hum-
blest lichen up to the highest mammifer, in one sys-
tem, the whole creation of which must have depended
upon one law or decree of the Almighty, though it
did not all come forth at one time. The idea of a
separate creation for each must appear totally inad-
missible. The single fact of abortive or rudimentary
organs condemns it ; for these, on such a supposition,
could be regarded in no other light than as blemishes
or blunders, the thing of all others most irreconcile-
able with that idea of Almighty Perfection which a^
general view of nature so irresistibly conveys. On
the other hand, when the organic creation is ad-
mitted to have been effected by a general law, we
see nothing in these abortive parts but harmless

190 LIFE ON THE EARTH.

peculiarities of development, and interesting evi-
dences of the manner in which the Divine Author
has been pleased to work,

'The whole train of animated beings, from the
simplest and oldest up to the highest and most
recent, are thus to be regarded as a series of ad-
vances of the principle of development, which have
depended upon external physical circumstances to
which the resulting animals are appropriate. I con-
template the whole phenomena,' he says, 'as having
been in the first place arranged in the councils of
the Divine Wisdom, to take place, not only upon
this sphere, but upon all the others in space, under
necessary modifications, and as being carried on,
from first to last, here and elsewhere, under imme-
diate favour of the creative will or energy. We are
drawn to the supposition that the first step in the
creation of life upon this planet was a chemico-
electric operation, by which simple germinal vesicles
were produced' After this it is suggested, 'as an
hypothesis already countenanced by much that is
ascertained, and likely to be farther sanctioned by
much that remains to be known, that the first step
was an advance under favour of peculiar condi-
tions, from the simplest forms of being, to the next
more complicated, and this through the medium of
the ordinary process of generation'

LIFE ON THE EARTH.

I ain relieved from the necessity of pointing out
on how slight a basis these bold assumptions are
rashly poised, by the opportunity of referring to the
full and complete examination of the whole argu-
ment, in the Discourse on the Studies of the Univer-
sity of Cambridge, by Professor Sedgwick. In this
luminous treatise, the hypothesis of development has
been met at every point, on physiological and geo-
logical evidence; palaeontology has been surveyed
from a high point of view; the latest discoveries of
Forbes, Falconer, and Owen, bearing on the subject,
have been ascertained; and the true succession of
physical phenomena has been traced through the long
periods of time embraced by geology. From this
large investigation, the general conclusion is that
'Geology, not seen through the mists of any theory,
but taken as a plain succession of monuments and
facts, offers one firm cumulative argument against
the hypothesis of development1/

CONSTANCY OF SPECIES.

It is curious to contrast with these views of the
unlimited mutability of species, the conclusions of
an anatomist and naturalist, who is so little fettered
by ordinary formulae, as to admit in the genus Homo,

1 Studies of the University of Cambridge. Preface, p cxxviii
edit. 5.

192 LIFE ON THE EARTH.

sixteen distinct species. In discussing the geogra-
phical distribution of these families of men, and
the animals associated with them, M. Charles Des-
moulins1 takes occasion to affirm in the strongest
manner the constancy of specific forms, unimpaired
by time and physical changes:

' In future it will be vain to contest the inalter-
ability of species, by means of the thousand and one
suppositions suggested by ignorance or deception.
For example, the carp and the barbel, which differ
much less one from the other than a Negro and a
Frenchman, have the central parts of their nervous
system, different in number, differently arranged and
shaped. Evidently cold, heat, light, obscurity, ex-
ercise, repose, more or less food, &c. have had no
influence on that.

1 A single objection has been offered to the
certainty of these results, and this objection is merely
a supposition. It is supposed that the actual diver-
sity of species depends on an alteration of primitive
forms, either by climate, or by the crossing of allied
species, which would thus have multiplied differences,
which were afterwards strengthened by time, so that
the actual species would be for the most part only
accidental varieties rendered definite, one knows not
how.

1 Hist. Nat. des Races Humaines, 1826.

LIFE ON THE EAETH. 193

'These assertions are purely gratuitous. At the
present time such deviations are not producible even
by means of art, and it is known by examination of
the fossils of the later formations, as well as by the
comparison of the most ancient examples with their
living analogues, that the forms remain unalterable/

So Agassiz, after that complete survey of Fossil
Fishes, which has earned him the perpetual gratitude
of geologists, says on the question of the diversity of
species due to development: 'We must necessarily
rise to a higher cause, and recognize more powerful
influences, exercising on the whole of nature a more
direct action, if one wishes not always to move in a
vicious circle. For my part, I am convinced that
species have been created successively at different
epochs; and that the changes which they have
suffered during a geological period are but of second-
ary importance, and depend only on their greater
or less fecundity, and on migrations subordinated to
the influences of the period.'

On the same side must be ranked the great
authority of Cuvier,

clarum et yenerabile nomen.

'There is no proof that all the differences which
now distinguish organized beings are of such a nature
as to have been produced by circumstances. All that
has been advanced on this subject is hypothetical;

Ii. L. n

194 LIFE ON THE EARTH.

experience appears to shew on the contrary, that, in
the actual state of the globe, varieties are restrained
within rather narrow limits, and as far back as we
ascend into antiquity we see that these limits were
the same then as now.

' We are therefore obliged to admit certain forms,
which have been perpetuated since the origin of
things without exceeding these limits; and all the
beings which appertain to one of these forms con-
stitute what is called a species. Varieties are the
accidental subdivisions of the species.

' Generation being the only means of knowing the
limits to which varieties can extend, a species may
be defined, as comprising the individuals, descended
one from another or from common parents, and those
which resemble them as much as they resemble each
other.

' These forms do not produce or change them-
selves ; life supposes their existence ; it can only be
kindled in organizations ready prepared for it; and
the most profound meditations, as well as the most
delicate observations, reach no further than to the
mystery of the pre-existence of germs.'

PRIMITIVE TYPES.

The illustrious author of the Systema Naturce
permitted his accurate and richly stored mind some-

LIFE ON THE EAETH. 195

times to wander into general contemplation of the
origin of the large series of living beings which he
had subjected to classification. Perhaps no man who
ever lived was more entitled to pronounce an opinion
on the affinities and sequences of the hosts of
'specific' forms which he had characterized. His
Natural Orders of Plants are among the most real
and consistent groups yet assembled; many of his
divisions of plants and animals are the clearest and
most satisfactory. What was the deliberate opinion
of this gifted man? I take it from the 13th and
best edition of his great work, 1767. It applies to
plants only.

' Suppose that in the beginning the Almighty
proceeded from the simple to the compound; from
few to many; and thus from a primary vegetable
principle, created so many different plants as there
are natural orders. Then that HE mixed these
orders of plants in generation, so that as many plants
should arise as now are distinct genera. Next that
nature mixed these generic plants, by ambigenous
generations (which change not the structure of the
flower), and multiplied them into species, as many as
possible, excluding however hybrids, as sterile.'

Without too minutely criticising the distinction
here drawn between the work of the Almighty, and
the performance of nature, — which apparently may

o2

196 LIFE ON THE EARTH.

be held to mean independent permanency of genus,
and dependent mutability of species — we remark in
this passage the recognition of general 'primary
types,' the 'struggle for existence' and the final
'limitation of species,' which have often been ap-
pealed to in later speculations.

DISTINCTION OF SPECIES.

Ever since the days of Linnaeus the tendency of
naturalists has been toward a nicer discrimination
of species and a more thorough appreciation of the
affinities which constitute natural assemblages. The
former analytical process has been pushed very far
in Botany, Zoology and Palaeontology, so that what
Linnaeus and his immediate followers regarded as
mere varieties have since been freely admitted to
rank as 'good' species. This decision in regard to
the majority of plants and animals has been quite
independent of and without any reference to proof
of the descent of the objects from a common
parentage which is the original ground of specific
identity, or from different parents which should con-
stitute specific difference. In the case of a very
large majority of the living invertebrata, no proof
of this sort has been looked for; a definite pecu-
liarity of structure, however slight, if often repeated,

LIFE ON THE EARTH. 197

so as to appear to be hereditary, has seldom been
rejected as a specific character; even colour and
magnitude are not despised in this analysis.

But in Palaeontology the list of species is even less
satisfactory. For here the question of descent is
seldom to be insisted on at all; very often we have
only the knowledge of one age of the fossils, some-
times only one specimen — occasionally only the sur-
face of that. For the purpose of diminishing these
sources of error, and of determining in regard to
each species the two most important parts of its
history, viz.

1. Its geographical province, the area which it

occupies, in one stratum or in several strata ;

2. Its geological range in differents parts of this

area;

nothing is so effectual as those monographs of par-
ticular well selected districts, which are founded on
accurate observations of the localities of fossils, and
of the conditions under which they are observed.
But these observations lose all their value if the
species of fossils be not precisely and certainly de-
termined, and this amidst the conflict of classifica-
tions, and unequal estimates of specific agreements
and differences, is a condition of success not always
easy to be secured. If for example we wish to trace
the geographical province or geological range of a

198 LIFE ON THE EARTH.

common shell like Spirifera striata, we find two
difficulties — one practical — arising from the want of
an adequate public collection, to which reference
might always be made, for foreign as well as British
fossils, for varieties of race, and examples of the
young and the aged, and of stunted, deformed, or
gigantic growth. The best figures and the best de-
scriptions will never suffice for determining specific
distinctions in particular cases of very variable
groups. This practical difficulty, of becoming per-
fectly acquainted with the accepted nomenclature,
is aggravated by the cloud of theoretical obscurity
which has been for some time condensing round the
origin and character of species. Are the groups
which we call species united by characters which
vary only within definable limits? Are these limits
of variation for a given species constant for all the
area of its province, and for all the period of its
geological range? Palaeontologists generally answer
in the affirmative, and the type-specimens in our
Museums appear to confirm it. But if instead of
these selections to exemplify differences we make
large collections to illustrate agreements, the species
(so-called) seem to lose their distinctness, and a
second, or even a third or fourth group of forms may
be fairly united to the first, before arriving at a real
circumscription available for space and for time.

LIFE ON THE EARTH. 199

This process, in the careful hands of Mr Davidson,
has already reduced the number of species in several
groups of Brachiopoda; and augmented the geogra-
phical area of the groups. When fully carried out, I
expect it will be found that the Brachiopoda of the
Carboniferous limestones, so remarkably allied over
all Europe, have a much larger agreement with those
of North America than is at present allowed in our
Catalogues.

In this process of reducing the admitted number
of species we are following in the track of great
botanists like Bentham and Hooker, whose researches
in modern nature have brought them into view of
similar difficulties.

But what if, as naturalists of no mean fame have
told us, the limits we thus draw round species are
arbitrary functions of our own minds, not real
boundaries set by nature; limits which are not
chosen alike by different minds, nor surely and firmly
retained by the same mind, at different times? If
such an opinion, whether true or not, were accepted
by physiologists from a survey of existing nature,
how would it affect our view of the succession of
life on the globe? Those who maintain it to be
true, usually assume some hypothesis which involves
the operation of long time, and thus brings the
question within the judgment of Geology.

200 LIFE ON THE EARTH.

NATUKAL SELECTION.

Moved by such considerations, an eminent natu-
ralist and geologist of our day has quitted the high
road of the Systema Natura, and is seeking for
the history of species1 by a path which takes the
same general direction as that already explored by
Lamarck toward the primitive germs and primordial
forms of life. Nature, he affirms, in successive ge-
nerations gives varieties; these in the struggle for
existence have unequal fortune, those most adapted
to the circumstances of the time and place prosper,
and give origin to descendants which run the same
risks, and under the same principle of ' natural selec-
tion' acquire more and more the character of distinct-
ness and of superiority. Following out these ideas, he
has arrived at results which are thus expressed:

'Although much remains obscure, and will long
remain obscure, I can entertain no doubt, after the
most deliberate study and most dispassionate judg-
ment of which I am capable, that the view which
most naturalists entertain, and which I formerly
entertained, namely, that each species has been in-
dependently created, is erroneous. I am fully con-
vinced that species are not immutable; but that
those belonging to what are called the same genera

1 Darwin, Origin of Species, 1859.

LIFE ON THE EARTH. 201

are lineal descendants of some other and generally
extinct species, in the same way as the acknowledged
varieties of any one species are the descendants of
that species. Furthermore, I am convinced that
natural selection has been the main but not the
exclusive means of modification.7

If asked how far he extends the doctrine of the
mutability of species, he replies :

'The question is difficult to answer, because the
more distinct the forms are which we may consider,
by so much the arguments fall away in force. But
some arguments of the greatest weight extend very
far. All the members of whole classes can be con-
nected together by chains of affinities, and all can
be classified on the same principle, in groups sub-
ordinate to groups. Fossil remains sometimes tend
to fill up very wide intervals between existing orders.
Organs in a rudimentary condition plainly show that
an early progenitor had the organs in a fully deve-
loped state; and this in some instances necessarily
implies an enormous amount of modification in the
descendants. Throughout whole classes various
structures are formed on the same pattern, and at
an embryonic age the species closely resemble each
other. Therefore I cannot doubt that the theory
of descent with modification embraces all the mem-
bers of the same class. I believe that animals have

202 LIFE ON THE EARTH.

descended from at most only four or five progenitors,
and plants from an equal or lesser number.

'Analogy would lead me one step further, namely,
to the belief that all animals and plants have de-
scended from one prototype. But analogy may be
a deceitful guide. Nevertheless all living things
have much in common, in their chemical composition,
their germinal vesicles, their cellular structure, and
their laws of growth and reproduction. We see this
even in so trifling a circumstance as that the same
poison often similarly affects plants and animals; or
that the poison secreted by the gall-fly produces
monstrous growths on the wild rose or oak-tree.
Therefore I should infer from analogy that probably
all the organic beings which have ever lived on this
earth have descended from some one primordial
form into which life was first breathed.

* As all the living forms of life are the lineal de-
scendants of those which lived long before the Si-
lurian epoch, we may feel certain that the ordinary
succession by generation has never once been broken,
and that no cataclysm has desolated the whole world.
Hence we may look with some confidence to a secure
future of equally inappreciable length. And as
natural selection works solely by and for the good
of each being, all corporeal and mental endowments
will tend to progress toward perfection.

LIFE ON THE EARTH. 203

( It is interesting to contemplate an entangled
bank, clothed with many plants of many kinds, with
birds singing on the bushes, with various insects
flitting about, and with worms crawling through the
damp earth, and to reflect that these elaborately
constructed forms, so different from each other, and
dependent on each other in so complex a manner,
have all been produced by laws acting around us.
These laws, taken in the largest sense, being growth
with reproduction; inheritance which is almost im-
plied by reproduction; variability from the indirect
and direct action of the extemal conditions of life,
and from use and disuse ; a ratio of increase so high
as to lead to a struggle for life, and as a consequence
to natural selection, entailing divergence of charac-
ter, and the extinction of less improved forms. Thus,
from the war of nature, from famine and death, the
most exalted object which we are capable of con-
ceiving, namely, the production of the higher animals,
directly follows. There is grandeur in this view of
life, with its several powers having been originally
breathed into a few forms or into one; and that,
whilst this planet has gone cycling on according to
the fixed law of gravity, from so simple a beginning
endless forms most beautiful and most wonderful
have been, and are being, evolved1/

1 Professor Sedgwick has communicated to the Cambridge
Philosophical Society an examination of the evidence bearing on

204 LIFE ON THE EARTH.

GENERAL REFLECTIONS.

These various speculations on the subject of
Fossil plants and animals, and the origin and pro-
gress of life, may perhaps, to the student of exact
science, appear little more than the chase of a phan-
tom, a wandering after unattainable truth. There is,
however, something seductive in the problem of the
origin of life, and one who has entered on this
charmed path, will seldom leave it without reluctance.
Vain and ill-judged as are some of these attempts,
they ought perhaps not to be visited with the heavy
condemnation which sometimes has been heaped
upon them. Men may have mistaken views about
the diluvial catastrophe ; false conceptions regarding
electricity as the agent of imparting life ; wrong notions
about the nature of atoms, and yet not reason, at
least intentionally, as ' atheists', denying the incessant
watchfulness of God over the arrangements which he
has appointed. It is hard to believe this of any
serious thinker, even of Lucretius, however strongly
he may contend for the regular operation of natural
laws, in opposition to the capricious meddling of
those monstrous personifications of human passions,

the Darwinian hypothesis, not less searching than that formerly
directed by the same hand into the doctrine contained in the
work entitled Vestiges of Creation, and with the same result, a
decided rejection of the hypothesis.

LIFE ON THE EARTH, 205

which were accepted for deity by the ' too superstitious'
men of Athens and Rome. Erroneous opinions have
but their day, and are, perhaps, less mischievous than
the indolence which acquiesces in dull and incurious
conformity with whatever may reign for the moment.
Truth, or what appears such to human reason, ope-
rating on real facts and just inferences, this is the
end of scientific research ; while we seek it, let us
not be too much troubled if some run in courses
wide of our own, and ask questions we think not
likely to be answered. If we do not ourselves believe
the origin of created life to be discoverable by a
creature limited to the observation of sensible phe-
nomena, why should we restrain the enterprise of
those who, vainly striving after something that is
unattainable or fabulous, may yet win much that is
accessible, valuable and real?

According to most of the hypotheses we have
been considering, the forms, structures and habits
of life, which we now circumscribe by specific cha-
racters, however distinct these may seem to be, are
only constant for this moment, slowly varying through
this period, as they have varied in preceding periods,
possibly then at 'a greater rate than now. The forms
that now are have had a long series of progenitors,
gradually changing from the earliest times ; many of
the earlier races of a great common stock having

206 LIFE ON THE EARTH.

died out, while others came into view; the whole
theatre of life always full of action, but the actors
continually changing, however slow the process of
change.

But, as already observed, the evidence of most
value for deciding the probability of such a pro-
gressive change in the forms of life is to be furnished
by geology. That it does not furnish good evidence
in favour of gradual and indefinite change is perhaps
generally allowed ; but that it does furnish evidence
of interrupted and limited change, and that the
changes mark steps of progress, is a prevalent opinion.
It is the opinion of Mr Darwin, that if the record
of life in the fossiliferous strata were complete, those
changes which now appear interrupted and sudden
would be found to have been continuous, and the
progress by steps would become an inclined plane
of easy ascent. This incompleteness he assumes to
be enormous ; so much so that the traces of whole
periods of immense duration, including the first
period, are lost ; what we possess being merely frag-
ments of the record, which indeed never was com-
plete, owing to the character of some kinds of
deposits. Thus we must not expect to be able to
arrange the fossil remains in a real however broken
series, since the true order and descent may be, and
for the most part is, irrecoverably lost. .

LIFE ON THE EARTH. 207

Surely this imperfection of the geological record
is overrated. With the exceptions of the two great
breaks at the close of the Palaeozoic and Mesozoic
periods, the series of strata is nearly if not quite com-
plete, the series of life almost equally so. Not indeed
in one small tract or in one section ; but on a com-
parison of different tracts and several sections. For
example, the marine series of Devonian life cannot
be found in the districts of Wales or Scotland, but
must be collected in Devonshire, Bohemia, Russia
and America. When so gathered it fills very nearly
if not entirely the whole interval between the Upper
Silurian and the Carboniferous Fauna. So in England
the marine intermediaries of the Oolitic and Creta-
ceous ages are not given : but the Neocomian Strata
supply the want. We have no Meiocene Strata in
England, but their place is marked in France and
America.

Even the great breaks alluded to are bridged.
The Permian series of life contains some Mesozoic
interpolations ; and the Lias contains reliquiae of
some Palaeozoic genera. The upper chalk of Maes-
tricht and the South of France extends toward the
Tertiaries the reign of the Upper Mesozoic beds.

On the whole, it appears that there exist ample
materials for testing any hypothesis of the sequence
of life which includes the marine races ; and that

208 LIFE ON THE EARTH.

there is inuch ground for believing, in regard to the
chasms which do exist in the series of freshwater
and terrestrial races, that if filled, they would not
lead to other inferences than such as appear con-
sistent with the records of the sea. If the monu-
ments of the earlier life of the globe are essential
witnesses, but too few and independent for a satis-
factory test of a given hypothesis of the sequence
of life, it is unfortunately ineligible for admission
among accepted truths.

Caloric, electricity, chemical action, are all in-
fluential on life ; elevating and depressing it, carry-
ing it on or bringing it to a close, according to the
measure and mode of application of these powers of
nature. Employed as they are in the current of life,
and at every moment acting on and being acted on
by it, nothing has seemed easier to speculation than
to conceive these agencies so operating on appro-
priate matter as to make the vital machine which
could not be kept in motion without them. The
only thing wanting is the due co-ordination of these
powers, in the appropriate matter. Here unfortu-
nately is the difficulty — due co-ordination of inde-
pendent powers in matter rightly adapted implies
the directing mind of the Master of power and matter.
The formula is imperfect —

We start, for LIFE is wanting there !

LIFE ON THE EARTH. 209

Given, however, the appropriate matter, and the
stroke of life upon it, what have we — no living
thing — but vitalized matter. Capable of what ? Self-
development ? Into what simple organic form ? The
answer seems to have been an Infusory Animalculum,
before the scrutiny of the microscope had shewn the
real complexity of most of these children of unknown
fathers, the transition stages of others, the definite
course of life of all. At present the first hopeful
product of the cryptogamy of electricity and carbu-
retted moisture would be a fertile cell, for cells are
the ultimate term of the mechanical analysis of or-
ganic beings.

Given then a cell with walls ; composed of
carbon, hydrogen and oxygen ; capable of self-divi-
sion and so of increasing in number. Let it be born
in the sea according to Telliamed, or, in moisture,
or slime, according to Lamarck, or if it suit better
the following phenomena, in the air. What follows?
An aggregation of cells. Plant or animal ? Perhaps
neither, but a living being, capable not of moving,
but of being moved, says Lamarck, by the external
powers influential on life, like Volvox. What next ?
Reproduction of other Yolvoces by self-division, or
the growth of new individuals within the parent.

Here the process, so far as our knowledge and
observation go, at present, must stop — the aggregate

B.L. p

210 LIFE ON THE EARTH.

of cells breaks up into smaller aggregates, or is re-
solved into solitary cells again, and our little circle
of discovery is completed.

Given, therefore, something more; a current of
water guided by cilia through the mass ; removal and
renewal of cells; addition of a new substance to
line the canals, in forms determined by these cur-
rents ; the growth of germs capable of being sepa-
rated and going through the same series of events;
in short a sponge, for the possession of which Botany
and Zoology have had a long conflict, and which
seems placed at the very lowest limit of specific life.

What is the next step, or rather leap, is hard to
say; for if we go to the minute Foraminifera, that is
a group of aggregated and perforated cells, with cilia,
which helps us very little or not at all in the advance-
ment of animalization ; but if we ascend per saltum
to the Zoophyta most allied to Spongiadse, and claim
affinity with Alcyonium, we require the large postu-
lates of freely moving polypi, with eight arms round
the contractile mouth, a complete digestive cavity,
and ova of definite character.

Then again is another hiatus between the Alcyo-
nidse and the Mollusca, which neither fossil nor
recent life can fill; and thus in what seem to be
the first and easiest steps we can imagine, nothing
but postulate upon postulate will bring us on our

LIFE ON THE EARTH. 211

way. But postulates in the sense here used are
equivalent to special endowments, not in the least
easier to conceive of than separate creations; for
what are these but endowments, and has not every
special structure its appropriate germ and mode of
growth?

If it is not possible in the existing ocean, among
the innumerable and variable radiated, amorphozoan,
and foraminiferous animals, to construct one chain
of easily graduated life, from the fertile cell to the
prolific ovarium and digestive stomach, it must be
quite in vain to look for such evidence in the fossil
state. In the face of the assumptions requisite to
imagine such a chain, we cannot venture to adopt
it as a probable hypothesis, and thus the idea of
one general oceanic germ of life, whether we like
it or not, must be abandoned. Reasoning of the
same kind will convince us that to derive by any
probable steps any one great division of the animal
kingdom from another, involves too much of hazard-
ous assumption to be adopted by a prudent in-
quirer.

Take therefore the hypothesis in an easier shape,
and accept as primary structures in general forms
all the great invertebral divisions which reside in
water; let us suppose them capable of indefinite
variation, and inquire what is the geological evidence

P2

212 LIFE ON THE EARTH.

in proof of each later group being derived from some
earlier one by descent with modification. Take the
least incomplete series of forma, viz. the Mollusca,
and undoubtedly the most favourable of all the marine
groups for the application of hypothesis.

The earliest known Mollusk is the Brachiopod
Lingula; which, as already observed, recurs in all
the systems of strata, and is still living. It gives
no generic branches. The next earliest are the Dimy-
arian genera, Ctenodonta and Cucullella, which can-
hot be regarded as descended from any conceivable
Brachiopod, or accepted as progenitors of Modiola,
Orthonota, Cardiola or Pleurorhynchus ; still less of
their Monomyarian companions, Ambonychia, Avicula
and Pterinea. It is inconceivable that from these or
any thing like them could be derived the Gaste-
ropod, Euomphali, Loxonemee, &c., or that the He-
teropod Bellerophon, the Pteropod Theca, or the
Cephalopod Orthoceras, are consanguineous, any one
of them with any other. All these great classes then
are according to the evidence equally aboriginal,
though not of equal antiquity.

Without bringing in similar results from the other
invertebral classes we may boldly affirm that the
later series of Cambro-Silurian life cannot possibly
be derived from the earlier series, according to the
evidence preserved to us; but on the contrary re-

LIFE ON THE EARTH. 213

quires absolutely the admission of separate stemmata,
certainly for every principal group, apparently and
probably so for every genus or natural assemblage
of much resembling forms with similar structures.

The explanation offered by most palaeontologists
is that these several stemmata are of independent
origin, separate creations in fact, using this term
to indicate a process unknown to us, by which the
Creator has provided for the appearance of new
forms and structures at definite times, and in certain
places, which it is in the province of palaeontology
to search out. The explanation offered in the hy-
pothesis of Mr Darwin, is that the groups of life
which appear to be and really are distinct, in the
Cambro-Silurian rocks, are not aboriginal forms ; but
derived from progenitors of far earlier date, belong-
ing to few types or to one; the original form, and
the transition forms being unknown to us.

Now they are not unknown to us by any im-
possibility of being preserved, for the strata of the
Cambro-Silurian series are of a kind in which organic
remains of great delicacy are often preserved, and
indeed such are preserved in these very strata; and
by the hypothesis the life-structures which are lost
must have only gradually differed in their nature
from those which are preserved. It follows, there-
fore, that the earlier living progenitors of the Cam-

214 LIFE ON THE EARTH.

bro-Silurian series, not only lived long before but
must have lived somewhere else. But as in all the
known examples of this series of strata, wherever
found, we have everywhere animals of the same
general type, and nowhere the traces of earlier pro-
genitors, it is clear that everywhere we are required
by the hypothesis to look somewhere else; which
may fairly be interpreted to signify, that the hypo-
thesis everywhere fails in the first and most im-
portant step. How is it conceivable that the second
stage should be everywhere preserved, but the first
nowhere?

This difficulty occurs again and again, not only
at the great breaks of the series of strata accom-
panied with much disturbance and change of sea-
bed, but during the ordinary and least interrupt-
ed accumulations of deposit, for example, in the
Silurian and Oolitic systems, in each of which new
families and genera, new types of structure in short,
make their appearance frequently at definite stages,
and always compel the hypothesis to the same an-
swer— look elsewhere for the progenitor— the father
is never buried with his children.

Is there not at the base of all these hypotheses
of one continuously branching stream of variable life,
some trace of the common errors of assuming that to
be true without limits, which is acknowledged to be

LIFE ON THE EAETH. 215

true in a restricted sense ; of employing infinite time
to integrate quantities which are subject to no law
of varying magnitude; and of assigning a resultant
to unknown and inconstant directions? Do we not
find the 'mutability of species' illustrated by ex-
amples of limited change, effected by the directing
agency of man ; and then what stands for an infer-
ence that unlimited changes have been effected or
are in progress by the undirected combination of
external conditions? Are we sure that varieties
which are given by nature in successive generations,
can be summed in one direction by the variable
preponderant of a number of concomitant variable
conditions of life? Can we remove 'natural selec-
tion' from the large synonymy of 'chance,' except
by giving to one of the variable conditions of which
it is the sum, direction, definite value or effect ? Is
it not the one acknowledged possession by every
species of an inherent tendency to propagate its
like? Would not the effect of this one constant
among any number of variables without law, be to
preserve the characters of the species for ever ? And
if 'natural selection' were regarded as giving direc-
tion to these variables, in combination with that
constant tendency, what would be the final result
but that which has always been recognized, viz. a
species varying within limits which are to be sought

216 LIFE ON THE EARTH.

out by experience ? But, finally, if Natural Selection
be thus gifted with the power of continually acting
for the good of its subject, — encouraging it, or rather
compelling it to continual advancement, —

Atct a/Horevetv /cat vTrep/xopov e)a/x,€vat aAAa>v,

how is this beneficent personification to be sepa-
rated from an ever watchful providence ; which once
brought into view sheds a new light over the whole
picture of causes and effects?

It may be thought that, while professing to
keep to the old and safe method of reasoning on
known causes and ascertained effects, we deviate
from this principle in regard to the origin of life,
and introduce an unknown cause for phenomena
not understood, by calling to our aid an act of
'creation.' Be it so, let the word stand for a con-
fession of our ignorance of the way in which the
governing mind has in this case acted upon matter;
we are equally ignorant in every other instance
which brings us face to face with the idea of forces
not manifested in acts. We see the stream of life
flowing onward in a determined course, in harmony
with the recognized forces of nature, and yielding
a great amount of enjoyment, and a wonderful di-
versity of beautiful and instructive phenomena, in
which MIND speaks to mind. Life through many

LIFE ON THE EARTH. 217

long periods has been manifested in a countless
host of varying structures, all circumscribed by one
general plan, each appointed to a definite place, and
limited to an appointed duration. On the whole the
earth has been thus more and more covered by the
associated life of plants and animals, filling all ha-
bitable space with beings capable of enjoying their
own existence or ministering to the enjoyment of
others; till finally, after long preparation, a 'being
was created capable of the wonderful power of mea-
suring and weighing all the world of matter and
space which surrounds him, of treasuring up the
past history of all the forms of life, and of consi-
dering his own relation to the whole. When he
surveys this vast and co-ordinated system, and in-
quires into its history and origin, can he be at a
loss to decide whether it be a work of Divine thought
and wisdom, or the fortunate offspring of a few atoms
of matter, warmed by the anima mundi, a spark of
electricity, or an accidental ray of sunshine

INDEX.

Acorus calamus, 20.

Acrogens, 27.

Actinia, 32.

Agassiz on constancy of specific

forms, 193.

Aire, Yorkshire river, 48.
Algae, 27.

Alisma plantago, 20.
American Flora, richness of, 13.
Amiens and Abbeville, flint instru-
ments found at, 48.
Ammonites sublsevis, 100.

distribution of, 102.

Amorphozoa, 85.

Animals collected in four great

groups, 27.
Annelida, 89.
Anomia, 32.
Anonaceae, 145.
Anstice, Mr, discoveries at Coalbrook

Dale, 116.

Antiquity of the Earth, 119.
Aptenodytes, propulsive organs of,35.
Araceae, 27.
Araucariae, 144.

Aristotle's classification of Nature, 25.
Articulata, 27 ; jointed feet, 33.
Astacidae distinct from Palinurus, 35.
Asterophyllites, 144.
Atmosphere supplies gaseous ele-
ments, 6; changes of, 163.

Australian Life compared to the

Stonesfield Fossils, 171.
Axis of earth, change of, 160.

B.

Barrande, species of fossils detected
in Bohemia, 71.

Bat,affinity of the, 30 ; hooked finger,
43.

Birds, Struthious, 23; fossil, 118.

Boring into solid substances by ani-
mals, 36.

Brachiopoda, 23, 91.

Bray Fossils, 70.

Brodie, Fossil Insects, 117.

Brongniart on carboniferous Flora, 7.

Bryozoa, 29.

Buffon on the germs of life, 182.

Butomus umbellatus, 20.

C.

Cacteacea?, 144.

Cambro- Silurian Life, 212—214.

Caradoc formation, 73.

Carnivora in relation to Herbivora,

8.
Carpenter's description of Terebra-

tula?, 92.

Cassowary, the, 24.
Cataclysms, 178.
Catarhine Quadrumana, 14.
Jaulopteris, 144.

220

INDEX.

Centre of gravity of the Earth, 160.
Cephalopoda, 8, 32, 84, 98, 101.
Ceratites nodosus, 100.
Cetacea, 8, 12, 30.

oily integument, 33.

hind limbs, 43.

earliest traces of, 107.

Chamaeleon, toes, 41 ; tongue, 42.
Cirripedia, 89.

Climate and the distribution of Life,
11.

changes, 142.

Tables, 157, 158.

Clover on the Yorkshire heaths, 22.
Coal formation of Yorkshire and

Derbyshire, probable age of, 132.

of South Wales, 133.

Coalbrook Dale, Ironstone nodules

at, 115.

Cockle, foot of, 36.
Coleoptera membranous wing, 40.
Colymbetes, propulsive organs, 35.
Colymbus, propulsive organs, 35.
Condor, the, 24.
Coniferae, 27.
Corals, 145.

Crawfish, bending tail of, 34.
Crinoidea, 147.
Crocodilidae, 23.
Crustacea, 8, 89, 90.
Cryptogam ous plants, 26.
Cucurbitaceaj, 145.
Cuvier's classification of nature, 25.

on constancy of specific form, 193.

Cycadeoid Plants, 145.

D.

Darwin's computation of waste on
Wealden coast, 130.

on Natural Selection, 200.

theoretical views, 206, 213.

Daubeny, experiments on plants, 7.

Davidson's, Mr, investigation of Bra-
chiopoda, 199.

Dawson, Dr, fossil tree found by, 116.

De Luc's speculations concerning na-
tural chronometers, 139.

De Maillet's Telliamed, 180.

Derwent River, 140.

Deshayes on crag-shells, 169.

Desmoulins on constancy of specific
forms, 192.

Development theory, 188, 208.

Dicotyledones, 27.

Dillwyn, his remarks on siphonosto-
matous shells, 97.

Dimyaria, 94, 212.

Diving movements in animals, 35.

Draco volans, the, 40.

Dytiscus, propulsive organs, 35.

E.

Echinodermata, 29, 86.

Edentata, fossil and recent, 171 .

Enaliosaurians, 8.

Equiseta, 145.

Equisetaceae, 27.

Eyes, structure of, 9, 10.

F.

Falconidae, steering tails, 39.

Filices, 27.

Fishes, earliest traces of, 103.

Flabellaria, 144.

Flotation of the marine races,

Foraminifera, 85, 210.

Forbes, Edward, JEgean researches,

15.

Freshwater Life, 108.
Fritillaria, 21.

s,32.

INDEX.

221

Frog, motion of the, 34.
Fungi, 27.

G.

Gagea lutea, 22.

Ganges, sediment annually delivere<

by, 126.

Gasteropoda, 8, 97.
Gentiana lutea, 22.
Geological Scale of Time, 51.
Glacial Period, 150.
Glyphia of the ancient oolites, 34.
Goniatites Listen, 132.
Goniatites striatus, 100.
Gramineae, 27.
Gymnospermous Phanerogamia, 144.

H.

Haime (Jules), his generalization of

the Palaeozoic Corals, 86.
Heat of Interior of Earth, 161.
Herbivora, 8.

Herodotus's estimate of time, 138.
Herschel on climate, 151.
Heteropoda, 97.
Himalaya range, British Plants in the,

20.

Hippuris vulgaris, 20.
Hirundines, steering tails, 39.
Histioderma found at Bray, 70.
Hooker, Dr, on Himalayan Flora, 19.
Hydrophilus, propulsive organs, 35.

Ichthyosaurus, 10; sclerotic bones,
18 — 22; affinity of, 30; propulsion
of, 35.

Infusoria swim by aid of cilia, 33.

origin of, 209.

Insects, census of the fossil orders,117.

(dipterous) sucker feet, 41.

Invertebrata, 82.

J.

Jones and Parker, on Foraminifera,
85.

K.

Kyson clay, remains of monkeys
found in, 149.

L.

Labiataa, 27.

Lamarck's proposition on germs of

life, 185.

Lammergeyer, the, 24.
Lancashire peat deposits, 49.
Leibnitz's conception of a globe fluid

with heat, 123.
Lena, remains of Elephas primige-

nius at, 49.
Lepidodendra, 144.
Lepidoptera, movements, 39.
Lichenes, 27.

Life, essential conditions of, 5 ; pro-
vinces of, 18.
ratios of abundance, 17.

— in water, 31.

— structure, adaptations, 31.
- in trees, 41.

— on land, 42.

system coeval with man, 45.

successive systems of, 53.

variety of forms in successive

periods, 59.

origin of, on the Earth, 67.

earliest systems, 70.

fresh-water, 108.

~— terrestrial, 115.
germs, 182.

222

INDEX.

Liebig's computation of carbon in

plants, 133.
Liliaceae, 27.

Limnoria terebrans in harbours, 36.
Lingula, 32, 212.
Lingula Zone of Wales, 70.
Linnaeus' classification of nature, 25.
essays in the Amoenitates Aca-

demicae, 170.

on Primitive Types, 195.

Lizard (Gecko), sucker-feet, 41.

Llandeilo formation, 72.

Llandovery Rocks, 75.

Lobster, bending tail of the, 34.

Ludlow zone, 76.

Lutraria digging into sand, 36.

Lycopodiaceae, 27, 144.

Lyell, Sir C., shell in fossil tree found

by, 116.

on Climate, 152.

on the Germs of Life, 187.

M.

Malvern, antiquity of land, 168.
Mammalia, numerical distribution, 12.

rearing their young, 30.

Marine animals, changes with elapsed

time, 84.
-^inver tebral life, successive systems,

81.
invertebrata in Lower Palaeozoic

Strata, table, 78.
Marsupialia fossil, 119.
Medusidae, 32.
Milne Edwards, his generalization of

the Palaeozoic Corals, 86.
Moa of New Zealand, 118.
Modiolae traced in coral, 36.
Mole, claws of the, 43.
Mollusca, eye-spots, 10; description

of, 28.

Mollusca, shell-covered, 32.
Monkeys, remains of, 149.
Monocotyledones, 27.
Monomyaria, 94.
Morris, estimate of thickness of strata,

52.

Movements in air by animals, 37.
Murchison's Siluria, 71.
Musaceae, 144.
Mya digging into sand, 36.
Myriophyllum verticillatum, 20.
Mytilus, 32.

N.

Narbonne, early human remains at,

48.

Natural Selection, 200, 215, 216.
Nature, the expression of a Divine

Idea, 3.

the forces of, 5.

the laws of, 5.

Nautilus (Argonauta), 33.

Niagara Falls, computation of time

by recession of, 140.
Nipadaceae, 145.
Notonecta, motion of the, 34.
Nova Scotia, Sigillaria (fossil tree)

found in, 116.
Nymphaea alba, 20.

O.

Oldhamia found at Bray, 70.
Olenus, 71.
Ostrich, the, 24.

wing bones, 43.

Otter, webbed feet of the, 34.

P.

Palinurus, flexible tail of, 35.
Palissy's observations, 175,

INDEX.

223

Palmacites, 144.

Pandanaceae, 145.

Paris basin, Eocene deposits in, 171.

Patella, 32.

Petaurus, the, 40.

Phanerogamous plants, 13, 26.

Pholades bore into chalk, 36 ; traced

in coral, 37.
Physalia, 33.
Physeter, 23.
Picidse, stiff tail prop, 39.
Pinna, 32.
Plants and animals, relations of, 7;

geographical distribution, 11.

ranked in two divisions, 26.

Platyrhine monkeys, 15, 41.
Pleiocene the oldest tertiary deposit

in our Island, 107.
Pleistocene period, 138.
Plot's Natural History of Oxfordshire,

176.

Poisson's hypothesis of climate, 151.
Polyparian Zoophyta, 10.
Polyzoa, 29, 91.
Postglacial period, 138.
Potamogeton, 20.

Prestwich on Co%lbrook Dale, 116.
Primitive Types, 194.
Pterodactyle, the, 30, 40.
Pteromys, the, 40.
Pteropoda, 96.

Purbeck Oolite, Lacustrine deposits
in, 171.

Q.

Quadrumana, opposable fingers, 41.

R.

Radiata, eye -spots, 10; description of,

28.
Ramsay's estimate of the thickness of

strata, 52.

Ranunculus aquatilis, 20, 27.

Remora, 32.

Reptilia depend on climate for distri-
bution, 23, 148.

. earliest traces of, 105.

Rhea, 24.

Rhynchonella, 23, 93.

Rosaceae, 27.

Royle, Dr, on Himalayan Flora, 19.

Rudista, 94.

S.

Sabine's observations on the Maranon,
125.

Sagittaria sagittifolia, 20.

Sarsaparilla, 29.

Scilla, Agostino, on marine exuviae,
175.

Sea's depth and the distribution of
life, 15.

— encroachments in England, 129.

all life derived from, 180.

Sedgwick, Professor, 25.

Discourse on University Studies,

191.

Sediment derived from sea-coasts, an-
nual estimate, 130.

Sequoia "Wellingtonia of California,
21.

Sheppey Clay, numerous fruits found
in, 145.

Smilaceae, 29.

Smith, William, discovery of stages
of strata, 187.

Species, constancy of, 191.

distinction of, 196.

Spirula, 23.
Spongiadse, 210.
Sternidae, steering tails, 39.
Stonesfield, intermixture of land-
plants, insects, and sea-shells, 109.

Oolite, lagoon of, 171.

224

INDEX.

Strata identified by organic remains,

187 ; thickness of, 52.
Swan, webbed feet of the, 34.
Swansea, early human remains at, 48.
Swimming of the marine races, 33.
movements in animals, 33.

T. /'
Table of comparison of irVing species

with fossil, 55.
Table of comparison of Irving genera

with fossil, 56.

Table of comparison of living Mol-
luscous animals and those of the
ancient strata, 58.

Table of Temperature on the Earth,
157.

Teleosaurus, propulsion of the, 35.

Temperature the limit of the ranges
of life, 12.

Terebratula, 23, 32, 92.

Teredines destroy ships, 36 ; in drift-
wood, 37.

Thallogens, 27.

Time, geological scale of, 51.

Trichoda anas, propulsive organs, 36.

Trigonia, 96, 172.

Trigonocarpum, 144.

Trilobite, eyes of, 10.

Triton, motion of the, 34.

Tunicata, 91.

Turt!*» paddles of the, 34.

Types of life structure, 25.

U.

Uniformitarian hypothesis of the age
of the globe's crust, 124.

Unio, foot of, 36.

Una, propulsive organs of, 35.

f

V.

Velella, 33.

Vertebrata, 27 ; swimming of, 33.
Vespertilionidae, skin of, 40.
"Vestiges of Creation," the author's

hypothesis of development, 188.
Volvox, 209.

W.

Waldheimia australis, 23.
Wales, Lingula beds, 52.
Wales, probable age of coal, &c., in,

134.
Warmth of ancient and modern times,

147.

Watson on British Plants, 13.
Wealden deposits, probable age of,

128.

Wenlock group, 75.
Westbury Cliff, intermixture of land.

plants, insects, and sea-shells, 109.
Westwood, Fossil Insects, 117.
Whale, fins of the, 34.
— pelvic bones, 43.
Woodward's Natural History of the

Earth, 178.

on Mollusca, 23.

Wiirtemburg, the Trias of, 118.

Z.

Zamioid Plants, 145.
Zoophyta, 85.

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