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ON THE

ORIGIN OF SPECIES:

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THE CAUSES OF THE PHENOMENA

OF

ORGANIC NATURE.

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BY

THOMAS H. HUXLEY, F.R.S., F.L.S.,

rnoFESson of natural history in the jerjjyn street school of mines.

NEW YORK:
D. APPLETON AND COMPANY

443 & 445 BROADWAY.
1863.

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PREFACE TO THE AMERICAN EDITIOK

The publication of Mr. Darwin's work on the
u Origin of Species," whether we consider the import-
ance of the questions it raises, the ability w T ith which
he treats them, the boldness and originality of his
speculations, or the profound and universal interest
which the book awakened, must be looked upon as
marking an era in the progress of science. But while
it called forth a due share of candid discussion and
intelligent criticism, it has been vehemently and per-
sistently assailed by many who understood nothing of
its real character ; and the subject has hence been so
overloaded with prejudice and perversion that unscien-
tific people hardly know what to think or believe about
it. In these circumstances, those who disencumber the
subject of its difficulties, simplify its statements, relieve
it of technicalities, and bring it so distinctly within the
horizon of ordinary apprehension that persons of com-
mon sense may judge for themselves, perform an in-

4 PREFACE TO THE AMERICAN EDITION.

valuable service. Such is the character of the present
volume.

Prefixed to the English edition, is the following
note from Professor Huxley : " Mr. J. Aldous Mays,
who is taking shorthand notes of my ' Lectures to
Working Men,' has asked me to allow him, on his own
account, to print those notes for the use of my audience.
I willingly accede to this request, on the understanding
that a notice is prefixed to the effect that I have no
leisure to revise the Lectures, or to make alterations
in them, beyond the correction of any important error
in a matter of fact."

The reader will not regret that the Lectures appear
in this form. Taken from the lips of the distinguished
naturalist, as he addressed an audience of ' Working
Men,' they have a clearness, a directness, and a sim-
plicity which belonged to the circumstances of their
delivery. In this respect, the following Lectures are
incomparable. Dealing w T ith the most abstruse and
fundamental questions of mind and organization, these
subjects are nevertheless presented in so lucid and at-
tractive a manner as to impress vividly the commonest
imagination.

The gift of translating the high questions of science
into popular forms of expression, without sacrificing ac-
curacy and introducing error, is a very rare one among
scientific men, but Professor Huxley possesses it in an
eminent degree : his lectures are models of their class.

CONTENTS.

— • —

NO. PAGE

I. The Present Condition of Organic Nature ... 7

II. The Past Condition of Organic Nature . . . .29

III. The Method by which the Causes of the Present and
Past Conditions of Organic Nature are to be Discov-
ered. — The Origination of Living Beings . . .52

IT. The Perpetuation of Living Beings, Hereditary Trans-
mission and Variation 80

V. The Conditions of Existence as affecting the Perpetua-
tion of Living Beings 102

VI. A Critical Examination of the Position of Mr. Darwin's
"Work, " On the Origin of Species," in relation to the
complete Theory of the Causes of the Phenomena of
Organic Nature 127

LECTUKE I.

THE PPwESENT CONDITION OF ORGANIC NATURE.

"When it was my duty to consider what subject I
would select for the six lectures which I shall now
have the pleasure of delivering to you, it occurred to
me that I could not do better than endeavour to put
before you in a true light, or in what I might perhaps
with more modesty call, that which I conceive myself
to be the true light, the position of a book which has
been more praised and more abused, perhaps, than
any book which has appeared for some years ; — I mean
Mr. Darwin's work on the " Origin of Species." That
work, I doubt not, many of you have read ; for I know
the inquiring spirit which is rife among you. At any
rate, all of you will have heard of it, — some by one kind
of report and some by another kind of report ; the
attention of all and the curiosity of all have been prob-
ably more or less excited on the subject of that work.
All I can do, and all I shall attempt to do, is to put
before you that kind of judgment which has been
formed by a man, who, of course, is liable to judge
erroneously ; but at any rate, of one whose business
and profession it is to form judgments upon questions
of this nature.

8 THE PRESENT CONDITION

And here, as it will always happen when dealing
with an extensive subject, the greater part of my course
— if, indeed, so small a number of lectures can be prop-
erly called a course — must be devoted to preliminary
matters, or rather to a statement of those facts and of
those principles which the work itself dwells upon, and
brings more or less directly before us. I have no right
to suppose that all or any of you are naturalists ; and
even if you were, the misconceptions and misunder-
standings prevalent even among naturalists on these
matters would make it desirable that I should take the
course I now propose to take, — that I should start from
the beginning, — that I should endeavour to point out
what is the existing state of the organic world — that
I should point out its past condition — that I should
state what is the precise nature of the undertaking
which Mr. Darwin has taken in hand ; that I should
endeavour to show you what are the only methods by
which that undertaking can be brought to an issue,
and to point out to you how far the author of the work
in question has satisfied those conditions, how far he has
not satisfied them, how far they are satisfiable by man,
and how far they are not satisfiable by man. And for
to-night, in taking up the first part of this question,
I shall endeavour to put before, you a sort of broad
notion of our knowledge of the condition of the living
world. There are many ways of doing this. I might
deal with it pictorially and graphically. Following
the example of Humboldt in his " Aspects of Nature,"
I might endeavour to point out the infinite variety of
organic life in every mode of its existence, with refer-
ence to the variations of climate and the like ; and such
an attempt would be fraught with interest to us all ;

OF ORGANIC NATURE. V

but considering the subject before us, such a course
would not be that best calculated to assist us. In an
argument of this kind we must go further and dig
deeper into the matter; we must endeavour to look
into the foundations of living Nature, if I may so say,
and discover the principles involved in some of her
most secret operations. I propose, therefore, in the
first place, to take some ordinary animal with which
you are all familiar, and, by easily comprehensible and.
obvious examples drawn from it, to show what are the
kind of problems which living beings in general lay
before us ; and I shall then show vou that the same
problems are laid open to us by all kinds of living
beings. But, first, let me say in what sense I have
used the words " organic nature." In speaking of the
causes which lead to our present knowledge of organic
nature, I have used it almost as an equivalent of the
word " living," and for this reason, — that in almost all
living beings you can distinguish several distinct por-
tions set apart to do particular things and work in a
particular way. These are termed " organs," and the
whole together is called " organic." And as it is
universally characteristic of them, this term " organic "
has been very conveniently employed to denote the
whole of living nature, — the whole of the plant world,
and the whole of the animal world.

Few animals can be more familiar to you than that
whose skeleton is shown on this diagram. You need
not bother yourselves with this " Equus caballus "
written under it ; that is only the Latin name of it,
and does not make it any better. It simply means the
common Horse. Suppose we wish to understand all
about the Horse. Our first object must be to study
1*

10 THE PRESENT CONDITION

the structure of the animal. The whole of his body
is inclosed within a hide, a skiu covered with hair ; and
if that hide or skin be taken off, we find a great mass
of flesh, or what is technically called muscle, being
the substance which by its power of contraction enables
the animal to move. These muscles move«the hard
parts one upon the other, and so give that strength
and power of motion which renders the Horse so useful
to us in the performance of those services in which we
employ him.

And then, on separating and removing the whole
of this skin and flesh, you have a great series of bones,
hard structures, bound together with ligaments, and
forming the skeleton which is represented here.

In that skeleton there are a number of parts to be
recognized. This long series of bones, beginning from
the skull and ending in the tail, is called the spine, and
these in front are the ribs ; and then there are two pairs
limbs, one before and one behind ; and these are what
we all know as the fore-legs and the hind-legs. If we
pursue our researches into the interior of this animal,
we find within the framework of the skeleton a great
cavity, or rather, I should say, two great cavities — one
cavity beginning in the skull and running through the
neck-bones, along the spine, and ending in the tail,
containing the brain and the spinal marrow, which are
extremely important organs. The second great cavity,
commencing with the mouth, contains the gullet, the
stomach, the long intestine, and all the rest of those
internal apparatus which are essential for digestion ;
and then in the same great cavity, there are lodged the
heart and all the great vessels going from it ; and, be-
sides that, the organs of respiration — the lungs ; and

OF ORGANIC NATURE.

11

then the kidneys, and the organs of reproduction, and
so on. Let us now endeavor to reduce this notion of a
horse that we now have, to some such kind of simple
expression as can be at once, and without difficulty, re-
tained in the mind, apart from all minor details. If I
make a transverse section, that is, if I were to saw a dead
horse across, I should find that, if I left out the details,
and supposing I took my section through the anterior
region, and through the fore-limbs, I should have here
this kind of section of the body (Fig. 1). Here would
be the upper part of the
animal — that great mass
of bones that we spoke
of as the spine (a, Fig.
1). Here I should have
the alimentary canal (5,
Fig. 1). Here I should
have the heart (<?, Fig. 1) ;
and then you see, there
would be a kind of double
tube, the whole being in- i
closed within the hide ;
the spinal marrow would be placed in the upper tube
(a, Fig. 1), and in the lower tube (J, Fig. 1), there would
be the alimentary canal and the heart ; and here I
shall have the legs proceeding from each side. For
simplicity's sake, I represent them merely as stumps
(e e, Fig. 1). Now that is a horse — as mathematicians
would say — reduced to its most simple expression.
Carry that in your minds, if you please, as a simplified
idea of the structure of the Horse. The considerations
which I have now put before you belong to what we
technically call the ' Anatomy ' of the Horse. Now,

Fig. 1.

12 THE PRESENT CONDITION

suppose we go to work upon these several parts — flesh
and hair, and skin and bone, and lay open these vari-
ous organs with our scalpels, and examine them by
means of our magnifying-glasses, and see what we can
make of them. "We shall iind that the flesh is made
up of bundles of strong fibres. The brain and nerves,
too, we shall find, are made up of fibres, and these
queer-looking things that are called ganglionic cor-
puscles. If we take a slice of the bone and examine
it, we shall find that it is very like this diagram of a
section of the bone of an' ostrich, though differing, of
course, in some details ; and if we take any part what-
soever of the tissue, and examine it, we shall find it
all has a minute structure, visible only under the
microscope. All these parts constitute microscopic
anatomy or 'Histology.' These parts are constantly
being changed ; every part is constantly growing, de-
caying, and being replaced during the life of the animal.
The tissue is constantly replaced by new material ; and
if you go back to the young state of the tissue in the
case of muscle, or in the case of skin, or any of the
organs I have mentioned, you will find that they all
come under the same condition. Every one of these
microscopic filaments and fibres (I now speak merely
of the general character of the whole process) — every
one of these parts — could be traced down to some
modification of a tissue which can be readily divided
into little particles of fleshy matter, of that substance
which is composed of the chemical ele-
ments, carbon, hydrogen, oxygen, and ni-
trogen, having such a shape as this (Fig.
2). These particles, into which all primi-
tive tissues break up, are called cells. FioX

OF ORGANIC NATURE. 13

If I were to make a section of a piece of the skin of
my hand, I should find that it was made np of these
cells. If I examine the fibres which form the various
organs of all living animals, I should find that all of
them, at one time or other, had been formed out of a
substance consisting of similar elements ; so that you
see, just as we reduced the whole body in the gross to
that sort of simple expression given in Fig. 1, so we
may reduce the whole of the microscopic structural
elements to a form of even greater simplicity ; just as
the plan of the whole body may be so represented in a
sense (Fig. 1), so the primary structure of every tissue
may be represented by a mass of cells (Fig. 2).

Having thus, in this sort of general way, sketched
to you what I may call, perhaps, the architecture of
the body of the Horse (what we term technically its
Morphology), I must now turn to another aspect. A
horse is not a mere dead structure : it is an active,
living, working machine. Hitherto we have, as it
were, been looking at a steam-engine with the fires out,
and nothing in the boiler ; but the body of the living
animal is a beautifully-formed active machine, and
every part has its different work to do in the working
of that machine, which is what we call its life. The
Horse, if you see him after his day's work is done, is
cropping the grass in the fields, as it may be, or munch-
ing the oats in his stable. What is he doing ? His
jaws are working as a mill — and a very complex mill
too — grinding the corn, or crushing the grass to a pulp.
As soon as that operation has taken place, the food is
passed down to the stomach, and there it is mixed with
the chemical fluid called the gastric juice, a substance
which has the peculiar property of making soluble and

14 THE PRESENT CONDITION

dissolving out the nutritious matter in the grass, and
leaving behind those parts which are not nutritious ;
so that you have, first, the mill, then a sort of chemical
digester ; and then the food, thus partially dissolved,
is carried back by the muscular contractions of the in-
testines into the hinder parts of the body, while the
soluble portions are taken up into the blood. The
blood is contained in a vast system of pipes, spreading
through the whole body, connected with a force-pump,
— the heart, — which, by its position and by the con-
tractions of its valves, keeps the blood constantly cir-
culating in one direction, never allowing it to rest ;
and then, by means of this circulation of the blood,
laden as it is with the products of digestion, the skin,
the flesh, the hair, and every other part of the body,
draws from it that which it wants, and every one of
these organs derives those materials which are neces-
sary to enable it to do its work.

The action of each of these organs, the performance
of each of these various duties, involve in their opera-
tion a continual absorption of the matters necessary for
their support, from the blood, and a constant formation
of waste products, which are returned to the blood, and
conveyed by it to the lungs and the kidneys, which are
organs that have allotted to them the ofhce of extract-
ing, separating, and getting rid of these waste products ;
and thus the general nourishment, labour, and repair
of the whole machine is kept up with order and reg-
ularity. Bat not only is it a machine which feeds and
appropriates to its own support the nourishment neces-
sary to its existence — it is an engine for locomotive
purposes. The Horse desires to go from one place to
another ; and to enable it to do this, it has those strong

OF ORGANIC NATURE. 15

contractile bundles of muscles attached to the bones of
its limbs, which are put in motion by means of a sort
of telegraphic apparatus formed by the brain and the
great spinal cord running through the spine or back-
bone ; and to this spinal cord are attached a number
of fibres termed nerves, which proceed to all parts
of the structure. By means of these the eyes, nose,
tongue, and skin — all the organs of perception — trans-
mit impressions or sensations to the brain, which acts
as a sort of great central telegraph-office, receiving
impressions and sending messages to all parts of the
body, and putting in motion the muscles necessary to
accomplish any movement that may be desired. So
that here you have an extremely complex and beauti-
fully-proportioned machine, with all its parts working
harmoniously together towards one common object —
the preservation of the life of the animal.

Now, note this : the Horse makes up its waste by
feeding, and its food is grass or oats, or perhaps other
vegetable products ; therefore, in the long run, the
source of all this complex machinery lies in the vege-
table kingdom. But where does the grass, or the oat,
or any other plant, obtain this nourishing food-pro-
ducing material ? At first it is a little seed, which
soon begins to draw into itself from the earth and the
surroundiuo; air matters which in themselves contain
no vital properties whatever ; it absorbs into its own
substance water, an inorganic body ; it draws into its
substance carbonic acid, an inorganic matter ; and am-
monia, another inorganic matter, found in the air ; and
then, by some wonderful chemical process, the details
of which chemists do not yet understand, though they
are near foreshadowing them, it combines them* into

16 THE PRESENT CONDITION

one substance, which is known to us as " Protein," a
complex compound of carbon, hydrogen, oxygen, and
nitrogen, which alone possesses the property of mani-
festing vitality and of permanently supporting animal
life. So that, you see, the waste products of the ani-
mal economy, the effete materials which are contin-
ually being thrown off by all living beings, in the
form of organic matters, are constantly replaced by
supplies of the necessary repairing and rebuilding
materials drawn from the plants, which in their turn
manufacture them, so to speak, by a mysterious com-
bination of those same inorganic materials.

Let us trace out the history of the Horse in another
direction. After a certain time, as the result of sick-
ness or disease, the effect of accident, or the conse-
quence of old age, sooner or later, the animal dies.
The multitudinous operations of this beautiful me-
chanism flag in their performance, the Horse loses its
vigour, and after passing through the curious series of
changes comprised in its formation and preservation,
it finally decays, and ends its life by going back into
that inorganic world from which all but an inappre-
ciable fraction of its substance was derived. Its bones
become mere carbonate and phosphate of lime ; the
matter of its flesh, and of its other parts, becomes, in
the long run, converted into carbonic acid, into water,
and into ammonia. You will now, perhaps, under-
stand the curious relation of the animal with the plant,
of the organic with the inorganic world, which is
shown in this diagram.

The plant gathers these inorganic materials together
and makes them up into its own substance. The ani-
mal eats the plant and appropriates the nutritious por-

OF ORGANIC NATURE

17

INORGANIC WORLD.

Carbonic Acid. "Wnt^r. Ammonia.

Salines.

VEGETABLE WORLD.

(Fig. 3.)

ANIMAL WORLD.

tions to its own sustenance, rejects and gets rid of
the useless matters ; and, finally, the animal itself dies,
and its whole body is decomposed and returned into
the inorganic world. There is thus a constant circula-
tion from one to the other, a continual formation of
organic life from inorganic matters, and as constant a
return of living bodies to the inorganic world ; so that
the materials of which our bodies are composed are
largely, in all probability, the substances which con-
stituted the matter of long extinct creations, but which
have in the interval constituted a part of the inorganic
world.

Thus we come to the conclusion, strange at first
sight, that the Matter constituting the living world is
identical with that wdiich forms the inorganic world.
And not less true is it, that, remarkable as are the
powers or, in other words, as are the Forces which are
exerted by living beings, yet all these forces are either
identical with those which exist in the inorganic world,
or they are convertible into them ; I mean in just the
same sense as the researches of physical philosophers
have shown that heat is convertible into electricity,

18 THE PRESENT CONDITION

that electricity is convertible into magnetism, magne-
tism into mechanical force or chemical force, and any
one of them with the other, each being measurable in
terms of the other, — even so, I say, that great law is
applicable to the living world. Consider why is the
skeleton of this horse capable of supporting the masses
of flesh and the various organs forming the living body,
unless it is because of the action of the same forces of
cohesion which combines together the particles of mat-
ter composing this piece of chalk ? What is there in
the muscular contractile power of the animal but the
force which is expressible, and which is in a certain
sense convertible, into the force of gravity which it
overcomes ? Or, if you go to more hidden processes,
in what does the process of digestion differ from those
processes which are carried on in the laboratory of the
chemist ? Even if we take the most recondite and
most complex operations of animal life — those of the
nervous system, these of late years have been shown to
be — I do not say identical in any sense with the elec-
trical processes — but this has been shown, that they
are in some way or other associated with them ; that is
to say, that every amount of nervous action is accom-
panied by a certain amount of electrical disturbance in
the particles of the nerves in which that nervous action
is carried on. In this way the nervous action is re-
lated to electricity in the same way that heat is re-
lated to electricity ; and the same sort of argument
which demonstrates the two latter to be related to one
another shows that the nervous forces are correlated to
electricity ; for the experiments of M. Dubois Rey-
mond and others have shown that whenever a nerve
is in a state of exeiment, sending a message to the

OF ORGANIC NATURE. 19

muscles or conveying an impression to the brain, there
is a disturbance of the electrical condition of that nerve
which does not exist at other times ; and there are a
number of other facts and phenomena of that sort ; so
that we come to the broad conclusion that not only as
to living matter itself, but as to the forces that matter
exerts, there is a close relationship between the organic
and the inorganic world — the difference between them
arising from the diverse combination and disposition
of identical forces, and not from any primary diver-
sity, so far as we can see.

I said just now that the Horse eventually died and
became converted into the same inorganic substances
from whence all but an inappreciable fraction of its
substance demonstrably originated, so that the actual
wanderings of matter are as remarkable as the trans-
migrations of the soul fabled by Indian tradition. But
before death has occurred, in the one sex or the other,
and in fact in both, certain products or parts of the
organism have been set free, certain parts of the organ-
ism of the two sexes have come into contact with one
another, and from that conjunction, from that union
which then takes place, there results the formation of a
new being. At stated times the mare, from a particu-
lar part of the interior of her body, called the ovary,
gets rid of a minute particle of matter comparable in
all essential respects with that which we called a cell a
little while since, which cell contains a kind of nucleus
in its centre, surrounded by a clear space and by a vis-
cid mass of protein substance (Fig. 2) ; and though it
is different in appearance from the eggs which we are
mostly acquainted with, it is really an egg. After a
time this minute particle of matter, which may only be

20 THE PRESENT CONDITION

a small fraction of a grain in weight, undergoes a series
of changes, — wonderful, complex changes. Finally,
upon its surface there is fashioned a little elevation,
which afterwards becomes divided and marked by a
groove. The lateral boundaries of the groove extend
upwards and downwards, and at length give rise to a
double tube. In the upper smaller tube the spinal
marrow and brain are fashioned ; in the lower, the ali-
mentary canal and heart, and at length two pairs of
buds shoot out at the sides of the body, which are the
rudiments of the limbs. In fact a true drawing of a
section of the embryo in this state would in all essen-
tial respects resemble that diagram of a horse reduced
to its simplest expression, which I first placed before
you (Fig. 1).

Slowly and gradually these changes take place.
The whole of the body, at first, can be broken up into
" cells," which become in one place metamorphosed
into muscle, — in another place into gristle and bone,
— in another place into fibrous tissue, — and in another
into hair ; every part becoming gradually and slowly
fashioned, as if there were an artificer at work at each
of these complex structures that we have mentioned.
This embryo, as it is called, then passes into other con-
ditions. This diagram represents the embryo of a dog ;
and I should tell vou that there is a time when the
embryos of neither dog, nor horse, nor porpoise, nor
monkey, nor man, can be distinguished by any essen-
tial feature one from the other ; there is a time when
they each and all of them resemble this one of the Dog.
But as development advances, all the parts acquire
their speciality, till at length you have the embryo
converted into the form of the parent from which it

OF ORGANIC NATURE. 21

started. So that you see, this living animal, this horse,
begins its existence as a minute particle of introgenous
matter, which, being supplied with nutriment (derived,
as I have shown, from the inorganic world), grows up
according to the special type and construction of its
parents, works and undergoes a constant waste, and
that waste is made good by nutriment derived from
the inorganic world ; the waste given off in this way
being directly added to the inorganic world ; and
eventually the animal itself dies, and, by the process
of decomposition, its whole body is returned to those
conditions of inorganic matter in which its substance
originated.

This, then, is that which is true of every living
form, from the lowest plant to the highest animal — to
man himself. You might define the life of every one
in exactly the same terms as those which I have now
used ; the difference between the highest and the
lowest being simply in the complexity of the develop-
mental changes, the variety of the structural forms,
the diversity of the physiological functions which are
exerted by each.

If I were to take an oak tree as a specimen of the
plant world, I should find that it originated in an acorn,
which, too, commenced in a cell ; the acorn is placed
in the ground, and it very speedily begins to absorb
the inorganic matters I have named, adds enormously
to its bulk, and we can see it, year after year, extend-
ing itself upward and downward, attracting and ap-
propriating to itself inorganic materials, which it vivi-
fies, and eventually, as it ripens, gives off its own
proper acorns, which again run the same course. But
I need not multiply examples — from the highest to the

22 THE PRESENT CONDITION

lowest the essential features of life are the same, as I
have described in each of these cases.

So much, then, for these particular features of the
organic world, which you can understand and compre-
hend so long as you confine yourself to one sort of
living being, and study that only.

But, as you know, horses are not the only living
creatures in the world; and again, horses, like all
other animals, have certain limits— are confined to a
certain area on the surface of the earth on which we
live— and, as that is the simpler matter, I may take
that first. In its wild state, and before the discovery
of America, when the natural state of things was inter-
fered with by the Spaniards, the Horse was only to be
found in parts of the earth which are known to geo-
graphers as the Old World ; that is to say, you might
meet with horses in Europe, Asia, or Africa ; but there
were none in Australia, and there were none whatso-
ever in the whole continent of America, from Labrador
down to Cape Horn. This is an empirical fact, and
it is what is called, stated in the way I have given it
you, the " Geographical Distribution " of the Horse.

Why horses should be found in Europe, Asia, and
Africa, and not in America, is not obvious ; the expla-
nation that the conditions of life in America are un-
favorable to their existence, and that, therefore, they
had not been created there, evidently does not apply ; for
when the invading Spaniards, or our own yeomen farm-
ers, conveyed horses to these countries for their own
use, they were found to thrive well and multiply very
rapidly ; and many are even now running wild in those
countries, and in a perfectly natural condition. Now,
suppose we were to do for every animal what we have

OF OEGANIC SPECIES. 23

here done for the Horse — that is, to mark off and dis-
tinguish the particular district or region to which each
belonged ; and supposing we tabulated all these results,
that would be called the Geographical Distribution of
animals, while a corresponding study of plants would
yield as a result the Geographical Distribution of plants.

I pass on from that now, as I merely wished to
explain to you what I meant by the use of the term
" Geographical Distribution." As 1 said, there is another
aspect, and a much more important one, and that is,
the relations of the various animals to one another.
The Horse is a very well defined matter-of-fact sort of
animal, and we are all pretty familiar with its structure.
I dare say it may have struck you, that it resembles
very much no other member of the animal kingdom,
except perhaps the Zebra or the Ass. But let me ask
you to look along these diagrams. Here is the skeleton
of the Horse, and here the skeleton of the Dog. You
will notice that we have in the Horse a skull, a back-
bone and ribs, shoulder-blades and haunch-bones. In
the fore-limb, one upper arm-bone, two fore arm-bones,
wrist-bones (wrongly called knee), and middle hand-
bones, ending in the three bones of a finger, the last
of which is sheathed in the horny hoof of the fore-foot :
in the hind-limb, one thigh-bone, two leg-bones, ankle-
bones, and middle foot-bones, ending in the three bones
of a toe, the last of which is encased in the hoof of the
hind-foot. Now turn to the Dog's skeleton. We find
identically the same bones, but more of them, there
being more toes in each foot, and hence more toe-bones.

Well, that is a very curious thing ! The fact is
that the Dog and the Horse — when one gets a look at
them without the outward impediments of the skin —

24 THE PKESENT CONDITION

are found to be made in very much the same sort of
fashion. And if I were to make a transverse section
of the Dog, I should find the same organs that I have
already shown you as forming parts of the Horse.
"Well, here is another skeleton — that of a kind of Lemur
— you see he has just the same bones ; and if I were
to make a transverse section of it, it would be just the
same again. In your mind's eye turn him around, so
as to put his backbone in a position inclined obliquely
upwards and forwards, just as in the next three dia-
grams, which represent the skeletons of an Orang, a
Chimpanzee, a Gorilla, and you find you have no
trouble in identifying the bones throughout ; and lastly
turn to the end of the series, the diagram representing
a man's skeleton, and still you find no great structural
feature essentially altered. There are the same bones
in the same relations. From the Horse we pass on
and on, with gradual steps, until we arrive at last at
the highest known forms. On the other hand, take
the other line of diagrams, and pass from the Horse
downwards in the scale to this fish ; and still, though
the modifications are vastly greater, the essential frame-
work of the organization remains unchanged. Here,
for instance, is a Porpoise ; here is its strong backbone,
with the cavity running through it, which contains the
spinal cord; here are the ribs, here the shoulder-blade;
here is the little short upper-arm bone, here are the
two forearm bones, the wrist-bone, and the finger-bones.
Strange, is it not, that the Porpoise should have in
this queer looking affair — its flapper (as it is called),
the same fundamental elements as the fore-leg of the
Horse or the Dog, or the Ape or Man ; and here you
will notice a very curious thing — the hinder limbs are

OF ORGANIC NATURE. 25

absent. Now, let us make another jump. Let us go
to the Codfish : here you see is the forearm, in this
large pectoral fin — carrying your mind's eye onward
from the flapper of the Porpoise. And here you have
the hinder limbs restored in the shape of these ventral
fins. If I were to make a transverse section of this, I
should find just the same organs that we have before
noticed. So that, you see, there comes out this strange
conclusion as the result of our investigations, that the
Horse, when examined and compared with other ani-
mals, is found bv no means to stand alone in nature ;
but that there are an enormous number of other crea-
tures which have backbones, ribs, and legs, and other
parts arranged in the same general manner, and in all
their formation exhibiting the same broad peculiarities.

I am sure that you cannot have followed me even
in this extremely elementary exposition of the struc-
tural relations of animals, without seeing what I have
been driving at all through, which is to show you that,
step by step, naturalists have come to the idea of a
unity of plan, or conformity of construction, among
animals which appeared at first sight to be extremely
dissimilar.

And here you have evidence of such a unity of plan
among all the animals which have backbones, and
which we technically call Yertebrata. But there are
multitudes of other animals, such as crabs, lobsters,
spiders, and so on, which we term Annulosa. In these
I could not point out to you the parts that correspond
with those of the Horse — the backbone, for instance —
as they are constructed upon a very different principle,
which is also common to all of them ; that is to say,
the Lobster, the Spider, and the Centipede, have a
2

26 THE PKESENT CONDITION

common plan running through their whole arrange-
ment, in just the same way that the Horse, the Dog,
and the Porpoise assimilate to each other.

Yet other creatures — whelks, cuttlefishes, oysters,
snails, and all their tribe (Mollusca) — resemble one
another in the same way, but differ from both Verte-
brata and Annulosa ; and the like is true of the ani-
mals called Coelenterata (Polypes) and Protozoa (ani-
malcules and sponges).

Now by pursuing this sort of comparison, naturalists
have arrived at the conviction that there are — some
think five, and some seven — but certainly not more
than the latter number — and perhaps it is simpler to
assume five — distinct plans or constructions in the
whole of the animal world ; and that the hundreds of
thousands of species of creatures on the surface of the
earth, are all reducible to those five, or, at most, seven,
plans of organization.

But can we go no further than that ? When one
has got so far, one is tempted to go on a step and in-
quire whether we cannot go back yet further and bring
down the whole to modifications of one primordial
unit. The anatomist cannot do this ; but if he call to
his aid the study of development, he can do it. For
we shall find that, distinct as those plans are, whether
it be a porpoise or man, or lobster, or any of those
other kinds I have mentioned, every one begins its ex-
istence with one and the same primitive form, — that of
the egg, consisting, as we have seen, of a introgenous
substance, having a small particle or nucleus in the
centre of it. Furthermore, the earlier changes of each
are substantially the same. And it is in this that lies
that true " unity of organization " of the animal king-

OF ORGANIC NATURE. 27

dom which has been guessed at and fancied for many
years ; but which it has been left to the present time
to be demonstrated by the careful study of develop-
ment. But is it possible to go another step further
still, and to show that in the same way the whole of
the organic world is reducible to one primitive con-
dition of form ? Is there among the plants the same
primitive form of organization, and is that identical
with that of the animal kingdom ? The reply to that
question, too, is not uncertain or doubtful. It is now
proved that every plant begins its existence under the
same form ; that is to say, in that of a cell — a particle
of introgenous matter having substantially the same
conditions. So that if you trace back the oak to its
first germ, or a man, or a horse, or lobster, or oyster,
or any other animal you choose to name, you shall find
each and all of these commencing their existence in
forms essentially similar to each other : and, further-
more, that the first processes of growth, and many of
the subsequent modifications, are essentially the same
in principle in almost all.

In conclusion, let me, in a few words, recapitulate
the positions -which I have laid down. And you must
understand that I have not been talking mere theory ;
I have been speaking of matters which are as plainly
demonstrable as the commonest propositions of Euclid
—of facts that must form the basis of all speculations
and beliefs in Biological science. We have gradually
traced down all organic forms, or, in other words, we
have analyzed the present condition of animated na-
ture, until we found that each species took -its origin in
a form similar to that under which all the others com-
mence their existence. We have found the whole of

28 PRESENT CONDITION OF ORGANIC NATURE.

the vast array of living forms, with which we are sur-
rounded, constantly growing, increasing, decaying, and
disappearing ; the animal constantly attracting, modify-
ing, and applying to its sustenance the matter of the
vegetable kingdom, which derived its support from the
absorption and conversion of inorganic matter. And
so constant and universal is this absorption, waste, and
reproduction, that it may be said with perfect certainty
that there is left in no one of our bodies at the present
moment a millionth part of the matter of which they
were originally formed ! We have seen, again, that
not only is the living matter derived from the inor-
ganic world, but that the forces of that matter are all
of them correlative with and convertible into those of
inorganic nature.

This, for our present purposes, is the best view of
the present condition of organic nature which I can lay
before you : it gives you the great outlines of a vast
picture, which you must fill up by your own study.

In the next lecture I shall endeavour in the same
way to go back into the past, and to sketch in the same
broad manner the history of life in epochs preceding
our own.

LECTUKE II.

THE PAST CONDITION OF ORGANIC NATURE.

In the lecture which I delivered' last Monday even-
ing, I endeavoured to sketch in a very brief manner,
but as well as the time at my disposal would permit,
the present condition of organic nature, meaning by
that large title simply an indication of the great, broad,
and general principles which are to be discovered by
those who look attentively at the phenomena of or-
ganic nature as at present displayed. The general re-
sult of our investigations might be summed up thus :
we found that the multiplicity of the forms of animal
life, great as that may be, may be reduced to a com-
paratively few primitive plans or types of construction ;
that a further study of the development of those dif-
ferent forms revealed to us that they were again re-
ducible, until we at last brought the infinite diversity
of animal, and even vegetable life, down to the primor-
dial form of a single cell.

AVe found that our analysis of the organic world,
whether animals or plants, showed, in the long run,
that they might both be reduced into, and were, in
fact, composed of the same constituents. And we saw
that the plant obtained the materials constituting its

30 THE PAST CONDITION

substance by a peculiar combination of matters belong-
ing entirely to the inorganic world ; that, then, the
animal was constantly appropriating the nitrogenous
matters of the plant to its own nourishment, and re
turning them back to the inorganic world, in what we
spoke of as its waste ; and that, finally, when the
animal ceased to exist, the constituents of its body
were dissolved and transmitted to that inorganic world
whence they had been at first abstracted. Thus we
saw in both the blade of grass and the horse but the
same elements differently combined and arranged. We
discovered a continual circulation going on, — the plant
drawing in the elements of inorganic nature and com-
bining them into food for the animal creation ; the ani-
mal borrowing from the plant the matter for its own
support, giving off during its life products which re-
turned immediately to the inorganic world ; and that,
eventually, the constituent materials of the whole struc-
ture of both animals and plants were thus returned to
their original source : there was a constant passage
from one state of existence to another, and a returning
back again.

Lastlv, when we endeavoured to form some notion
of the nature of the forces exercised by living beings,
we discovered that they — if not capable of being sub-
jected to the same minute analysis as the constituents
of those beings themselves — that they were correlative
with — that they were the equivalents of the forces of
inorganic nature — that there were, in the sense in
which the term is now used, convertible with them.
That was our general result.

And now, leaving the Present, I must endeavour
in the same manner to put before you the facts that

OF ORGANIC NATURE. 31

are to be discovered in the Past history of the living
world, in the past conditions of organic nature. We
have, to-night, to deal with the facts of that history —
a history involving periods of time before which our
mere human records sink into utter insignificance — a
history the variety and physical magnitude of whose
events cannot even be foreshadowed by the history of
human life and human phenomena — a history of the
most varied aud complex character.

We must deal with the history, then, in the first
place, as we should deal with all other histories. The
historical student knows that his first business should
be to inquire into the validity of his evidence, and the
nature of the record in which the evidence is contain-
ed, that he may be able to form a proper estimate of
the correctness of the conclusions which have been
drawn from that evidence. So, here, we must pass, in
the first place, to the consideration of a matter which
may seem foreign to the question under discussion.
We must dwell upon the nature of the records, and
the credibility of the evidence they contain ; we must
look to the completeness or incompleteness of those
records themselves, before we turn to that which they
contain and reveal. The question of the credibility of
the history, happily for us, will not require much con-
sideration, for, in this history, unlike those of human
origin, there can be no cavilling, no differences as to
the reality and truth of the facts of which it is made
up ; the facts state themselves, and are laid out clearly
before us.

But, although one of the greatest difficulties of the
historical student is cleared out of our path, there are
other difficulties — difficulties in rightly interpreting the

32 THE PAST CONDITION

facts as they are presented to us — which may be com-
pared with the greatest difficulties of any other kinds
of historical study.

What is this record of the past history of the globe,
and what are the questions which are involved in an
inquiry into its completeness or incompleteness ? That
record is composed of mud ; and the question which
we have to investigate this evening resolves itself into
a question of the formation of mud. You may think,
perhaps, that this is a vast step — of almost from the
sublime to the ridiculous — from the contemplation of
the history of the past ages of the world's existence to
the consideration of the history of the formation of
mud ! But, in nature, there is nothing mean and un-
worthy of attention ; there is nothing ridiculous or con-
temptible in any of her works ; and this inquiry, you
will soon see, I hope, takes us to the very root and
foundations of our subject.

How, then, is mud formed ? Always, with some
trifling exception, which I need not consider now —
always, as the result of the action of water, wearing
down and disintegrating the surface of the earth and
rocks with which it comes in contact — pounding and
grinding it down, and carrying the particles away to
places where they cease to be disturbed by this me-
chanical action, and where they can subside and rest.
For the ocean, urged by winds, washes, as we know,
a long extent of coast, and every wave, loaded as it is
with particles of sand and gravel as it breaks upon the
shore, does something towards the disintegrating pro-
cess. And thus, slowly but surely, the hardest rocks
are gradually ground down to a powdery substance ;
and the mud thus formed, coarser or liner, as the case

OF ORGANIC NATURE. 33

may be, is carried by the rush of the tides, or currents,
till it reaches the comparatively deeper parts of the
ocean, in which it can sink to the bottom, that is, to
parts where there is a depth of about fourteen or fifteen
fathoms, a depth at which the water is, usually, nearly
motionless, and in which, of course, the finer particles
of this detritus, or mud, as we call it, sinks to the
bottom.

Or, again, if you take a river, rushing down from
its mountain sources, brawling over the stones and
rocks that intersect its path, loosening, removing, and
carrying with it in its downward course the pebbles
and lighter matters from its banks, it crushes and
pounds down the rocks and earths in precisely the
same way as the wearing action of the sea w T aves. The
matters forming the deposit are torn from the mountain-
side and w T hirled impetuously into the valley, more
slowly over the plain, thence into the estuary, and from
the estuary they are swept into the sea. The coarser
and heavier fragments are obviously deposited first,
that is, as soon as the current begins to lose its force
by becoming amalgamated with the stiller depths of
the ocean, but the finer and lighter particles are carried
further on, and eventually deposited in a deeper and
stiller portion of the ocean.

It clearly follows from this that mud gives us a
chronology ; for it is evident that supposing this, which
I now sketch, to be the sea bottom, and supposing this
to be a coast-line ; from the washing action of the sea
upon the rock, wearing and grinding it down into a
sediment of mud, the mud will be carried clown, and
at length, deposited in the deeper parts of this sea bot-
tom, where it will form a layer ; and then, while that
2*

34 THE PAST CONDITION

first layer is hardening, other mud which is coming
from the same source will, of course, be carried to the
same place ; and, as it is quite impossible for it to get
beneath the layer already there, it deposits itself above
it, and forms another layer, and in that way you grad-
ually have layers of mud constantly forming and hard-
ening one above the other, and conveying a record of
time.

It is a necessary result of the operation of the law
of gravitation that the uppermost layer shall be the
youngest and the lowest the oldest, and that the differ-
ent beds shall be older at any particular point or spot
in exactly the ratio of their depth from the surface.
So that if they were upheaved afterwards, and you had
a series of these different lay ere of mud, converted into
sandstone, or limestone, as the 3ase might be, you might
be sure that the bottom layer was deposited first, and
that the upper layers were formed afterwards. Here,
you see, is the first step in the history — these layers of
mud give us an idea of time.

The whole surface of the earth — I speak broadly,
and leave out minor qualifications — is made up of such
layers of mud, so hard, the majority of them, that we
call them rock, whether limestone or sandstone, or
other varieties of rock. And, seeing that every part
of the crust of the earth is made up in this way, you
might think that the determination of the chronology,
the fixing of the time which it has taken to form this
crust is a comparatively simple matter. To take a broad
average, ascertain how fast the mud is deposited upon
the bottom of the sea, or in the estuary of rivers ; take
it to be an inch, or two, or three inches a year, or what-
ever you may roughly estimate it at ; then take the

OF ORGANIC NATURE. 35

total thickness of the whole series of stratified rocks,
which geologists estimate at twelve or thirteen miles,
or about seventy thousand feet, make a sum in short
division, divide the total thickness by that of the quan-
tity deposited in one year, and the result will, of course,
give you the number of years which the crust has taken
to form.

Truly, that looks a very simple process ! It would
be so except for certain difficulties, the very first of
which is that of finding how rapidly sediments are de-
posited ; but the main difficulty — a difficulty which
renders any certain calculations of such a matter out
of the question — is this, the sea-bottom on which the
deposit takes place is continually shifting.

Instead of the surface of the earth being that stable,
fixed thing that it is popularly believed to be, being,
in common parlance, the very emblem of fixity itself,
it is incessantly moving, and is, in fact, as unstable as
the surface of the sea, except that its undulations are
infinitely slower and enormously higher and deeper.

JS r ow, what is the effect of this oscillation ? Take
the case to which I have previously referred. The finer
or coarser sediments that are carried down by the
current of the river, will only be carried out a certain
distance, and eventually, as we have already seen, on
reaching the stiller part of the ocean, will be deposited
at the bottom.

Let C y (Fig. 4) be the sea-bottom, y T> the shore,
x y the sea-level, then the coarser deposit will subside
over the region B, the finer over A, while beyond A
there will be no deposit at all ; and, consequently, no
record will be kept, simply because no deposit is going
on. Now, suppose that the whole land, C, D, which

36

THE PAST CONDITION

we have regarded as stationary, goes down, as it does
so, both A and B go further out from the shore, which

Fig. 4.

will be at y\ x 1 y\ being the new sea-level. The con-
sequence will be that the layer of mud (A), being now,
for the most part, further than the force of the current
is strong enough to convey even the finest debris, will,
of course, receive no more deposits, and having attained
a certain thickness will now grow no thicker.

We should be misled in taking the thickness of that
layer, whenever it may be exposed to our view, as a
record of time in the manner in which we are now
regarding this subject, as it would give ns only an
imperfect and partial record it would seem to repre-
sent too short a period of time.

Suppose, on the other hand, that the land (C D)
had gone on rising slowly and gradually — say an inch
or two inches in the conrse of a century, — what would
be the practical effect of that movement ? Why, that
the sediment A and B which has been already depos-
ited, would eventually be brought nearer to the shore-
level, and again subjected to the wear and tear of the
sea ; and directly the sea begins to act upon it, it would
of course soon cut up and carry it away, to a greater
or less extent, to be re-deposited further out.

OF ORGANIC NATURE. 37

"Well, as there is, in all probability, not one single
spot on the whole surface of the earth, which has not
been up and down in this way a great many times, it
follows that the thickness of the deposits formed at
any particular spot cannot be taken (even supposing
we had at first obtained correct data as to the rate at
which they took place), as affording reliable informa-
tion as to the period of time occupied in its deposit.
So that you see it is absolutely necessary from these
facts, seeing that our record entirely consists of accumu-
lations of mud, superimposed one on the other ; seeing
in the next place that any particular spots on which
accumulations have occurred, have been constantly
moving up and down, and sometimes out of the reach
of a deposit, and at other times its own deposit broken
up and carried away, it follows that our record must
be in the highest degree imperfect, and we have hardly
a trace left of thick deposits, or any definite knowledge
of the area that they occupied in a great many cases.
And mark this! That supposing even that the whole
surface of the earth had been accessible to the geolo-
gist, — that man had had access to every part of the
earth, and had made sections of the whole, and put
them all together, — even then his record must of neces-
sity be imperfect.

But to how much has man really access ? If you
will look at this Map you will see that it represents
the proportion of the sea to the earth : this coloured
part indicates all the dry land, and this other portion
is the water. You will notice at once that the water
covers three-fifths of the whole surface of the globe,
and has covered it in the same manner ever since man
has kept any record of his own observations, to say

38 THE PAST CONDITION

nothing of the minute period during which he has cul-
tivated geological inquiry. So that three-fifths of the
surface of the earth is shut out from us because it is
under the sea. Let us look at the other two-fifths, and
see what are the countries in which anything that may
be termed searching geological inquiry has been carried
out : a good deal of France, Germany, and Great Brit-
ain and Ireland, bits of Spain, of Italy, and of Russia,
have been examined, but of the whole great mass of
Africa, except parts of the southern extremity, we know
next to nothing ; little bits of India, but of the greater
part of the Asiatic continent nothing ; bits of the
Northern American States and of Canada, but of the
greater part of the continent of North America, and
in still larger proportion, of South America, nothing !

Under these circumstances, it follows that even with
reference to that kind of imperfect information which
we can possess, it is only about the ten thousandth part
of the accessible parts of the earth that has been exam-
ined properly. Therefore, it is with justice that the
most thoughtful of those who are concerned in these
inquiries insist continually upon the imperfection of
the geological record ; for, I repeat, it is absolutely
necessary, from the nature of things, that that record
should be of the most fragmentary and imperfect char-
acter. Unfortunately this circumstance has been con-
stantly forgotten. Men of science, like young colts
in a fresh pasture, are apt to be exhilarated on being
turned into a new field of inquiry, and to go off at a
hand-gallop, in total disregard of heriges and ditches,
losing sight of the real limitation of their inquiries,
and to forget the extreme imperfection of what is really
known. Geologists have imagined that they could tell

OF ORGANIC NATURE. 39

us what was going on at all parts of the earth's surface
during a given epoch ; they have talked of this deposit
being contemporaneous with that deposit, until, from
our jfittle local histories of the changes at limited spots
of the earth's surface, they have constructed a universal
history of the globe as full of wonders and portents as
any other story of antiquity.

But what does this attempt to construct a universal
history of the globe imply ? It implies that we shall
not only have a precise knowledge of the events which
have occurred at any particular point, but that we shall
be able to say what events, at any one spot, took place
at the same time with those at other spots.

Let us see how far that is in the nature of things
practicable. Suppose that here I make a section of
the Lake of Killarney, and here the section of another
lake — that of Loch Lomond in Scotland for instance.
The rivers that flow into them are constantly carrying
down deposits of mud, and beds, or strata, are being as
constantly formed, one above the other, at the bottom
of those lakes. Now, there is not a shadow of doubt
that in these two lakes the upper beds are all older than
the lower — there is no doubt about that ; but what does
this tell us about the age of any given bed in Loch
Lomond, as compared with that of any given bed in
the Lake of Killarney? It is, indeed, obvious that if
any two sets of deposits are separated and discontinu-
ous, there is absolutely no means whatever given you
by the nature of the deposit of saying whether one is
much younger or older than the other ; but you may
say, as many have said and think, that the case is very
much altered if the beds which we are comparing are

40

THE PAST CONDITION

continuous. Suppose two beds of mud hardened into
rock, — A and B are seen in section. (Fig. 5.)

Well, you say, it is admitted that the lowermost
bed is always the older. Very well ; B, therefore, is
older than A. No doubt, as a tchole, it is so ; or if

Fig. 5.

any parts of the two beds which are in the same verti-
cal line are compared, it is so. But suppose you take
what seems a very natural step further, and say that
the part a of the bed A is younger than the part b of
the bed B. Is this sound reasoning ? If you find any
record of changes taking place at b, did they occur be-
fore any events which took place while a was being
deposited ? It looks all very plain sailing, indeed, to
say that they did ; and yet there is no proof of any-
thing of the kind. As the former Director of this In-
stitution, Sir II. De la Beche, long ago showed, this
reasoning may involve an entire fallacy. It is extremely
possible that a may have been deposited ages before b.
It is very easy to understand how that can be. To
return to Fig. 4 ; when A and B were deposited, they
w T ere substantially contemporaneous; A being simply
the finer deposit, and B the coarser of the same detritus
or waste of land. Now suppose that the sea-bottom
goes down (as shown in Fig. 4), so that the first deposit

O'v ORGANIC NATURE. 41

is carried no farther than <?, forming the bed A 1 , and
the coarse no farther than b, forming the bed B 1 , the
result will be the formation of two continuous beds,
one of line sediment (AA 1 ) over-lapping another of
coarse sediment (BB 1 ). Now suppose the whole sea-
bottom is raised up, and a section exposed about the
point A 1 ; no doubt, at this sjiot, the upper bed is
younger than the lower. But we should obviously
greatly err if we concluded that the mass of the upper
bed at A was younger than the lower bed at B ; for
we have just seen that they are contemporaneous de-
posits. Still more should we be in error if we supposed
the upper bed at A to be younger than the continu-
ation of the lower bed at B 1 ; for A was deposited long
before B 1 . In fine, if, instead of comparing imme-
diately adjacent parts of two beds, one of which lies
upon another, we compare distant parts, it is quite pos-
sible that the upper may be any number of years older
than the under, and the under any number of years
younger than the upper.

Now you must not suppose that I put this before
you for the purpose of raising a paradoxical difficulty ;
the fact is, that the great mass of deposits have taken
place in sea-bottoms which are gradually sinking, and
have been formed under the very conditions I am here
supposing.

Do not run away with the notion that this subverts
the principle I laid down at first. The error lies in
extending a principle which is perfectly applicable to
deposits in the same vertical line to deposits which are
not in that relation to one another.

It is in consequence of circumstances of this kind,
and of others that I might mention to you, that our

42 THE PAST CONDITION

conclusions on and interpretations of the record are
really and strictly only valid so long as we confine our-
selves to one vertical section. I do not mean to tell
you that there are no qualifying circumstances, so
that, even in very considerable areas, we may safely
speak of conformably superimposed beds being older
or younger than others at many different points. But
we can never be quite sure in coming to that con-
clusion, and especially we cannot be sure if there is
any break in their continuity, or any very great dis-
tance between the points to be compared.

"Well now, so much for the record itself, — so much
for its imperfections, — so much for the conditions to be
observed in interpreting it, and its chronological indi-
cations, the moment we pass beyond the limits of a
vertical linear section.

Now let us pass from the record to that which it
contains, — from the book itself to the writing and the
figures on its pages. This writing and these figures
consist of remains of animals and plants which, in the
great majority of cases, have lived and died in the very
spot in which we now find them, or at least in the im-
mediate vicinity. You must all of you be aware —
and I referred to the fact in last Monday's lecture —
that there are yast numbers of creatures living at the
bottom of the sea. These creatures, like all others,
sooner or later die, and their shells and hard parts lie
at the bottom ; and then the fine mud which is being
constantly brought down by rivers and the action of
the wear and tear of the sea, covers them over and
protects them from any further change or alteration ;
and, of course, as in process of time the mud becomes
hardened and solidified, the shells of these animals are

OF ORGANIC NATURE. 43

preserved and firmly imbedded in the limestone or
sandstone which is being thus formed. You may see
in the galleries of the Museum upstairs specimens of
limestones in which such fossil remains of existing
animals are imbedded. There are some specimens in
which turtle's eggs have been imbedded in calcareous
sand, and before the sun had hatched the young turtles,
they became covered over with calcareous mud, and
thus have been preserved and fossilized.

Kot only does this process of imbedding and fos-
silization occur with marine and other aquatic animals
and plants, but it aiFects those land animals and plants
which are drifted away to sea, or become buried in
bogs or morasses ; and the animals which have been
trodden down by their fellows and crushed in the mud
at the river's bank, as the herd have come to drink.
In any of these cases, the organisms may be crushed
or be mutilated, before or after putrefaction, in such a
manner that perhaps only a part will be left in the
form in which it reaches us. It is, indeed, a most re-
markable fact, that it is quite an exceptional case to
find a skeleton of any one of all the thousands of wild
land animals that we know are constantly being kill-
ed, or dying in the course of nature : they are preyed
on and devoured by other animals, or die in places
where their bodies are not afterwards protected by
mud. There are other animals existing in the sea, the
shells of which form exceedingly large deposits. You
are probably aware that before the attempt was made
to lay the Atlantic telegraphic cable, the Government
employed vessels in making a series of very careful ob-
servations and soundings of the bottom of the Atlantic ;
and although, as we must all regret, that up to the

44 THE PAST CONDITION

present time that project has not succeeded, we have
the satisfaction of knowing that it yielded some most
remarkable results to science. The Atlantic Ocean
had to be sounded right across, to depths of several
miles in some places, and the nature of its bottom was
carefully ascertained. Well, now, a space of about
1,000 miles wide from east to west, and I do not ex-
actly know how many from north to south, but at any
rate 600 or TOO miles, was carefully examined, and it
was found that over the whole of that immense area
an excessively fine chalky mud is being deposited ; and
this deposit is entirely made up of animals whose hard
parts are deposited in this part of the ocean, and are
doubtless gradually acquiring solidity and becoming
metamorphosed into a chalky limestone. Thus, you
see, it is quite possible in this way to preserve unmis-
takable records of animal and vegetable life. "When-
ever the sea-bottom, by some of those undulations of
the earth's crust that I have referred to, becomes up-
heaved, and sections or borings are made, or pits are
dug, then we become able to examine the contents and
constituents of these ancient sea-bottoms, and find out
what manner of animals lived at that period.

Now it is a very important consideration in its bear-
ing on the completeness of the record, to inquire how
far the remains contained in these fossiliferous lime-
stones are able to convey anything like an accurate
or complete account of the animals which were in ex-
istence at the time of its formation. Upon that point
we can form a very clear judgment, and one in which
there is no possible room for any mistake. There are
of course a great number of animals — such as jelly-
fishes, and other animals — 'without any hard parts,

OF ORGANIC NATURE. 45

of which we cannot reasonably expect to find any
traces whatever : there is nothing of them to preserve.
Within a very short time, you will have noticed, after
they are removed from the water, they dry up to a
mere nothing ; certainly* they are not of a nature to
leave any very visible traces of their existence on such
bodies as chalk or mud. Then again, look at land ani-
mals ; it is, as I have said, a very uncommon thing to
find a land animal entire after death. Insects and
other carnivorous animals very speedily pull them to
pieces, putrefaction takes place, and so, out of the hun-
dreds of thousands that are known to die every year,
it is the rarest thing in the world to see one imbedded
in such a way that its remains would be preserved for
a lengthened period. Not only is this the case, but
even when animal remains have been safely imbedded,
certain natural agents may wholly destroy and remove
them.

Almost all the hard parts of animals — the bones
and so on — are composed chiefly of phosphate of lime
and carbonate of lime. Some years ago, I had to make
an inquiry into the nature of some very curious fossils
sent to me from the North of Scotland. Fossils are
usually hard bony structures that have become imbed-
ded in the way I have described, and have gradually
acquired the nature and solidity of the body with
which they are associated ; but in this case I had a
series of holes in some pieces of rock, and nothing else.
Those holes, however, had a certain definite shape
about them, and when I got a skilful workman to make
castings of the interior of these holes, I found that they
were the impressions of the joints of a back-bone anc*
of the armour of a great reptile, twelve or more feet

46 THE PAST CONDITION

long. This great beast had died and got buried in the
sand, the sand had gradually hardened over the bones,
but remained porous. Water had trickled through it,
and that water being probably charged with a super-
fluity of carbonic acid, had dissolved all the phosphate
and carbonate of lime, and the bones themselves had
thus decayed and entirely disappeared ; but as the
sandstone happened to have consolidated by that time,
the precise shape of the bones was retained. If that
sandstone had remained soft a little longer, we should
have known nothing whatsoever of the existence of the
reptile whose bones it had encased.

How certain it is that a vast number of animals
which have existed at one period on this earth have
entirely perished, and left no trace whatever of their
forms, may be proved to you by other considerations.
There are large tracts of sandstone in various parts of
the world, in which no body has yet found anything
but footsteps. Not a bone of any description, but an
enormous number of traces of footsteps. There is no
question about them. There is a whole valley in Con-
necticut covered with these footsteps, and not a single
fragment of the animals which made them have yet
been found. Let me mention another case while upon
that matter, which is even more surprising than those
to which I have yet referred. There is a limestone
formation near Oxford, at a place called Stonesfield,
which has yielded the remains of certain very inter-
esting mammalian animals, and up to this time, if I
recollect rightly, there have been found seven speci-
mens of its lower jaws, and not a bit of anything else,
neither limb-bones nor skull, or any part whatever ;
not a fragment of the whole system ! Of course, it

OF ORGANIC NATURE. 47

would be preposterous to imagine that the beasts had
nothing else but a lower jaw ! The probability is, as
Dr. Buckland showed, as the result of his observations
on dead dogs in the river Thames, that the lower jaw,
not being secured by very firm ligaments to the bones
of the head, and being a weighty affair, would easily
be knocked off, or might drop away from the body as
it floated in water in a state of decomposition. The
jaw would thus be deposited immediately, while the
rest of the body would float and drift away altogether,
ultimately reaching the sea, and perhaps becoming de-
stroyed. The jaw becomes covered up and preserved
in the river silt, and thus it comes that we have such
a curious circumstance as that of the lower jaws in
the Stonesfield slates. So that, you see, faulty as these
layers of stone in the earth's crust are, defective as they
necessarily are as a record, the account of contempora-
neous vital phenomena presented by them is, by the
necessity of the case, infinitely more defective and frag-
mentary.

It was necessary that I should put all this very
strongly before you, because, otherwise, you might
have been led to think differently of the completeness
of our knowledge by the next facts I shall state to you.

The researches of the last three-quarters of a century
have, in truth, revealed a wonderful richness of organic
life in those rocks. Certainly not fewer than thirty or
forty thousand different species of fossils have been dis-
covered. You have no more ground for doubting that
these creatures really lived and died at or near the
places in which we find them than you have for like
scepticism about a shell on the sea-shore. The evidence
is as good in the one case as in the other.

48 THE PAST CONDITION

Our next business is to look at the general charac-
ter of these fossil remains, and it is a subjeet which will
be requisite to consider carefully ; and the first point
for us is to examine how T much the extinct Flora and
Fauna as a whole — disregarding altogether the succes-
sion of their constituents, of which I shall speak after-
wards — differ from the Flora and Fauna of the present
day ; — how far they differ in what we do know about
them, leaving altogether out of consideration specula-
tions based on what we do not know.

I strongly imagine that if it were not for the pecu-
liar appearance that fossilized animals have, that any
of you might readily walk through a museum which
contains fossil remains mixed up with those of the pres-
ent forms of life, and I doubt very much whether your
un instructed eyes would lead you to see any vast or
wonderful difference between the two. If you looked
closely, you would notice, in the first place, a great
many things very like animals with wdiich you are
acquainted now : you would see differences of shape
and proportion, but on the whole a close similarity.

I explained what I meant by Orders the other day,
when I described the animal kingdom as being divided
into sub-kingdoms, classes, and orders. If you divide
the animal kingdom into orders, you will find that
there are above one hundred and twenty. The num-
ber may vary on one side or the other, but this is a
fair estimate. That is the sum total of the orders of
all the animals which we know now, and which have
been known in past times, and left remains behind.

Kow, how many of those are absolutely extinct ?
That is to say, how many of these orders of animals
have lived at a former period of the world's history,

OF ORGANIC NATURE. 49

but have at present no representatives ? That is the
sense in which I meant to use the word " extinct." I
mean that those animals did live on this earth at one
time, but have left no one of their kind with us at the
present moment. So that estimating the number of
extinct animals is a sort of way of comparing the past
creation as a whole with the present as a whole. To
make that clear, I have written in red ink on these
diagrams the names of all those extinct orders, and in
black ink the names of the rest. Among the mammalia
and birds there are none extinct ; but when we come
to the reptiles there is a most wonderful thing : out of
the eight orders, or thereabouts, which you can make
among reptiles, one-half are extinct. These diagrams
of the plesiosaurus, the ichthyosaurus, the pterodactyle,
give you a notion of some of these extinct reptiles.
And here is the cast of the pterodactyle and bones of
the ichthyosaurus and the plesiosaurus, just as fresh as
if it had been recently dug up in a churchyard. Thus,
in the reptile class, there are no less than half of the
orders which are absolutely extinct. If we turn to the
Amphibia, there was one extinct order, the Labyrintho-
donts, typified by the large salamander-like beast shown
in this diagram.

No order of fishes is known to be extinct. Every
fish that we find in the strata — to which I have been
referring — can be identified and placed in one of the
orders which exist at the present day. There is not
known to be a single ordinal form of insect extinct.
There are only two orders extinct among the Crustacea.
There is not known to be an extinct order of these crea-
tures, the parasitic and other worms ; but there are two,
not to say three, absolutely extinct orders of this class,
3

50 THE PAST CONDITION

the Eehinodermata / out of all the orders of the Coden-
terata and Protozoa only one, the Rugose Corals.

So that, you see, out of somewhere about 120 orders
of animals, taking them altogether, you will not, at the
outside estimate, find above ten or a dozen extinct.
Summing up all the order of animals which have left
remains behind them, you will not find above ten or
a dozen which cannot be arranged with those of the
present day ; that is to say, that the difference does
not amount to much more than ten per cent. ; and the
proportion of extinct orders of plants is still smaller.
I think that that is a very astounding, a most astonish-
ing fact, seeing the enormous epochs of time which
have elapsed during the constitution of the surface of
the earth as it at present exists; it is, indeed, a most
astounding thing that the proportion of extinct ordinal
types should be so exceedingly small.

But now, there is another point of view in which
w r e must look at this past creation. Suppose that we
were to sink a vertical pit through the floor beneath
us, and that I could succeed in making a section right
through in the direction of New Zealand, I should find
in each of the different beds through which I passed
the remains of animals which. I should find in that
stratum and not in the others. First, I should come
upon beds of gravel or drift containing the bones of
large animals, such as the elephant, rhinoceros, and
cave tisrer. Rather curious things to fall across in
Piccadilly ! If I should dig lower still, I should come
upon a bed of what we call the London clay, and in
this, as you will see in our galleries up-stairs, are found
remains of strange cattle, remains of turtles, palms, and
large tropical fruits ; with shell-fish such as you see the

OF ORGANIC NATURE. 51

like of now only in tropical regions. If I went below
that, I should come upon the chalk, and there I should
find something altogether different, the remains of
ichthyosauri and pterodactyles, and ammonites, and
so forth.

I do not know what Mr. Godwin Austin would say
comes next, but probably rocks containing more am-
monites, and more ichthyosauri and plesiosauri, with
a vast number of other things ; and under that I should
meet with yet older rocks, containing numbers of strange
shells and fishes ; and in thus passing from the surface
to the lowest depths of the earth's crust, the forms of
animal life and vegetable life which I should meet with
in the successive beds would, looking at them broadly,
be the more different the further that I went down.
Or, in other words, inasmuch §s we started with the
clear principle, that in a series of naturally-disposed
mud beds the lowest are the oldest, we should come
to this result, that the further we go back in time the
more difference exists between the animal and vege-
table life of an epoch and that which now exists. That
was the conclusion to which I wished to bring you at
the end of this Lecture.

LECTUKE III.

THE METHOD BY WHICH THE CAUSES OF THE PRES-
ENT AND PAST CONDITIONS OF ORGANIC NATURE
ARE TO BE DISCOVERED.— THE ORIGINATION OF
LIVING BEINGS.

In the two preceding lectures I have endeavoured
to indicate to you the extent of the subject-matter of
the inquiry upon which we are engaged ; and now,
having thus acquired some conception of the Past and
Present phenomena of Organic Nature, I must turn, to-
night, to that which constitutes the great problem which
w r e have set before ourselves ; — I mean, the question
of what knowledge we have of the causes of these
phenomena of organic nature, and how such knowl-
edge is obtainable.

Here, on the threshold of inquiry, an objection
meets us. There are in the world a number of ex-
tremely worthy, well-meaning persons, whose judg-
ments and opinions are entitled to the utmost respect
on account of their sincerity, who are of opinion that
Yital Phenomena, and especially all questions relating
to the origin of vital phenomena, are questions quite
apart from the ordinary run of inquiry, and are, by
their very nature, placed out of our reach. They say

METHOD OF DISCOVERY. 53

that all these phenomena originated miraculously, or
in some way totally different from the ordinary course
of nature, and that therefore they conceive it to be
futile, not to say presumptuous, to attempt to inquire
into them.

To such sincere and earnest persons, I would only
say, that a question of this kind is not to be shelved
upon theoretical or speculative grounds. You may
remember the story of the Sophist who demonstrated
to Diogenes in the most complete and satisfactory man-
ner that he could not walk ; that, in fact, all motion
was an impossibility ; and that Diogenes refuted him
by simply getting up and walking round his tub. So,
in the same way, the man of science replies to objec-
tions of this kind, by simply getting up and walking
onward, and showing what science has done and is
doing, — by pointing to that immense mass of facts
which have been ascertained and systematized under the
forms of the great doctrines of Morphology, of Develop-
ment, of Distribution, and the like. He sees an enor-
mous mass of facts and laws relating to organic beings,
which stand on the same good sound foundation as
every other natural law ; and, therefore, with this mass
of facts and laws before us, seeing that, as far as organic
matters have hitherto been accessible and studied, they
have shown themselves capable of yielding to scientific
investigation, we may accept this as proof that order
and law reign there as well as in the rest of nature ;
and the man of science says nothing to objectors of
this sort, but supposes that we can and shall walk to
the origin of organic nature, in the same way that we
have walked to a knowledge of the laws and manciples
of the inorganic world.

54: METHOD OF DISCOVERY.

But there are objectors who say the same from
ignorance and ill-will. To such I would reply that the
objection comes ill from them, and that the real pre-
sumption, I may almost say the real blasphemy, in this
matter, is in the attempt to limit that inquiry into the
causes of phenomena which is the source of all human
blessings, and from which has sprung all human pros-
perity and progress ; for, after all, we can accomplish
comparatively little ; the limited range of our own
faculties bounds us on every side, — the field of our
powers of observation is small enough, and he who en-
deavours to narrow the sphere of our inquiries is only
pursuing a course that is likely to produce the greatest
harm to his fellow-men.

But now, assuming, as we all do, I hope, that these
phenomena are properly accessible to inquiry, and set-
ting out upon our search into the causes of the phe-
nomena of organic nature, or, at any rate, setting out to
discover how much we at present know upon these
abstruse matters, the question arises as to what is to be
our course of proceeding, and what method we must
lay down for our guidance. I reply to that question,
that our method must be exactly the same as that
which is pursued in any other scientific inquiry, the
method of scientific investigation being the same for
all orders of facts and phenomena whatsoever.

I must dwell a little on this point, for I wish you
to leave this room with a very clear conviction that
scientific investigation is not, as many people seem to
suppose, some kind of modern black art. I say that
you might easily gather this impressson from the man-
ner in which many persons speak of scientific inquiry,
or talk about inductive and deductive philosophy, or

METHOD OF DISCO VERY. 55

the principles of the " Baconian philosophy." I do
protest that, of the vast number of cants in this world,
there are none, to my mind, so contemptible as the
pseudo-scientific cant which is talked about the " Ba-
conian philosophy."

To hear people talk about the great Chancellor,-^
and a very great man he certainly was, — you would
think that it was he who had invented science, and
that there was no such thing as sound reasoning before
the time of Queen Elizabeth ! Of course, you say,
that cannot possibly be true ; you perceive, on a mo-
ment's reflection, that such an idea is absurdly wrong ;
and yet, so firmly rooted is this sort of impression, — I
cannot call it an idea, or conception, — the thing is too
absurd to be entertained, — but so completely does it
exist at the bottom of most men's minds, that this has
been a matter of observation with me for many years
past. There are many men who, though knowing ab-
solutely nothing of the subject with which they may
be dealing, wish, nevertheless, to damage the author
of some view with which they think fit to disagree.
What they do, then, is not to go and learn something
about the subject, which one would naturally think the
best way of fairly dealing with it ; but they abuse the
originator of the view they question, in a general man-
ner, and wind up by saying that, " After all, you know,
the principles and method of this author are totally
opposed to the canons of the Baconian philosophy."
Then everybody applauds, as a matter of course, and
agrees that it must be so. But if you were to stop
them all in the middle of their applause, you would
probably find that neither the speaker nor his ap-
plauders could tell you how or in what way it was so ;

56 METHOD OF DISCO YEET.

neither the one nor the other having the slightest idea
of what they mean when they speak of the i* Baconian
philosophy."

You will understand, I hope, that I have not the
slightest desire to join in the outcry against either the
morals, the intellect, or the great genius of Lord Chan-
cellor Bacon. He was undoubtedly a very great man,
let people say what they will of him ; but notwith-
standing all that he did for philosophy, it would be
entirely wrong to suppose that the methods of modern
scientific inquiry originated with him, or with his age ;
they originated with the first man, whoever he w T as ;
and indeed existed long before him, for many of the
essential processes of reasoning are exerted by the
higher order of brutes as completely and effectively as
by ourselves. We see in many of the brute creation
the exercise of one, at least, of the same powers of
reasoning as that wmich we ourselves employ.

The method of scientific investigation is nothing
but the expression of the necessary mode of working
of the human mind. It is simply the mode at which
all phenomena are reasoned about, rendered precise
and exact. There is no more difference, but there is
just the same kind of difference, between the mental
operations of a man of science and those of an ordinary
person, as there is between the operations and methods
of a baker or of a butcher weighing out his goods in com-
mon scales, and the operations of a chemist in perform-
ing a difficult and complex analysis by means of his
balance and finely-graduated weights. It is not that
the action of the scales in the one case, and the balance
in the other, differ in the principles of their construc-
tion or manner of working ; but the beam of one is set

METHOD OF DISCOVERY. 57

on an infinitely finer axis than the other, and of course
turns by the addition of a much smaller weight.

You will understand this better, perhaps, if I give
you some familiar example. You have all heard it re-
peated, I dare say, that men of science work by means
of Induction and Deduction, and that by the help of
these operations, they, in a sort of sense, wring from
Nature certain other things, which are called Natural
Laws, and Causes, and that out of these, by some cun-
ning skill of their own, they build up Hypotheses and
Theories. And it is imagined by many, that the opera-
tions of the common mind can be by no means com-
pared with these processes, and that they have to be
acquired by a sort of special apprenticeship to the craft.
To hear all these large words, you would think that
the mind of a man of science must be constituted dif-
ferently from that of his fellow-men ; but if you will
not be frightened by terms, you will discover that you
are quite wrong, and that all these terrible apparatus
are being used by yourselves every day and every hour
of your lives.

There is a well-known incident in one of Moliere's
plays, where the author makes the hero express un-
bounded delight on being told that he had been talk-
ing prose during the whole of his life. In the same
way, I trust, that you will take comfort, and be de-
lighted with yourselves, on the discovery that you
have been acting on the principles of inductive and
deductive philosophy during the same period. Prob-
ably there is not one here to-night who has not in the
course of the day had occasion to set in motion a com-
plex train of reasoning, of the very same kind, though
differing of course in degree, as that which a scientific
3*

58 METHOD OF DISCOVERT.

man goes through in tracing the causes of natural phe-
nomena.

A very trivial circumstance will serve to exemplify
this. Suppose you go into a fruiterer's shop, wanting
an apple, — you take up one, and, on biting it, you find
it is sour ; you look at it, and see that it is hard and
green. You take up another one, and that too is hard,
green, and sour. The shopman offers you a third ;
but, before biting it, you examine it, and find that it is
hard and green, and you immediately say that you
will not have it, as it must be sour, like those that you
have already tried.

Nothing can be more simple than that, you think ;
but if you will take the trouble to analyze and trace
out into its logical elements what has been done by
the mind, you will be greatly surprised. In the first
jilace, you have performed the operation of Induc-
tion. You found that, in two experiences, hardness
and greenness in apples go together with sourness. It
was so in the first case, and it was confirmed by the
second. True, it is a very small basis, but still it is
enough to make an induction from ; you generalize
the facts, and you expect to find sourness in apples
where you get hardness and greenness. You found
upon that a general law, that all hard and green apples
are sour ; and that, so far as it goes, is a perfect induc-
tion. Well, having got your natural law in this way,
when you are offered another apple which you find is
hard and green, you say, " All hard and green apples
are sour ; this apple is hard and green, therefore this
apple is sour." That train of reasoning is what logi-
cians call a syllogism, and has all its various parts and
terms, — its major premiss, its minor premiss, and its

METHOD OF DISCOVERY. 59

conclusion. And, by the help of further reasoning,
which, if drawn ont, wonld have to be exhibited in
two or three other syllogisms, you arrive at your final
determination, " I will not have that* apple." So that,
you see, you have, in the first place, established a law
by Induction, and upon that you have founded a De-
duction, and reasoned out the special conclusion of the
particular case. Well now, suppose, having got your
law, that at some time afterwards, you are discussing
the qualities of apples with a friend : you will say to
him, "It is a very curious thing, — but I find that all
hard and green apples are sour ! " Your friend says
to you, " But how do you know that ? " You at once
reply, " Oh, because I have tried it over and over
again, and have always found them to be so." Well,
if we were talking science instead of common sense, we
should call that an Experimental Verification. And, if
still opposed, you go further, and say, " I have heard
from the people in Somersetshire and Devonshire,
where a large number of apples are grown, that they
have observed the same thing. It is also found to be
the case in Normandy, and in North America. In
short, I find it to be the universal experience of man-
kind wherever attention has been directed to the sub-
ject." Whereupon, your friend, unless he is a very
unreasonable man, agrees with you, and is convinced
that you are quite right in the conclusion you have
drawn. He believes, although perhaps he does not
know he believes it, that the more extensive Verifica-
tions are, — that the more frequently experiments have
been made, and results of the same kind arrived at, —
that the more varied the conditions under which the
same results have been attained, the more certain is

60 METHOD OF DISCOVERY.

the ultimate conclusion, and he disputes the question
no further. He sees that the experiment has been
tried under all sorts of conditions, as to time, place,
and people, with the same result ; and he says with
you, therefore, that the law you have laid down must
be a good one, and he must believe it.

In science we do the same thing ; — the philosopher
exercises precisely the same faculties, though in a much
more delicate manner. In scientific inquiry it becomes
a matter of duty to expose a supposed law to every
possible kind of verification, and to take care, more-
over, that this is done intentionally, and not left to a
mere accident, as in the case of the apples. And in
science, as in common life, our confidence in a law is
in exact proportion to the absence of variation in the
result of our experimental verifications. For instance,
if you let go your grasp of an article you may have in
your hand, it will immediately fall to the ground. That
is a very common verification of one of the best estab-
lished laws of nature — that of gravitation. The method
by which men of science establish the existence of that
law is exactly the same as that by which we have estab-
lished the trivial proposition about the sourness of hard
and green apples. But we believe it in such an exten-
sive, thorough, and unhesitating manner because the
universal experience of mankind verifies it, and we can
verify it ourselves at any time ; and that is the strongest
possible foundation on which any natural law can rest.

So much by way of proof that the method of estab-
lishing laws in science is exactly the same as that pur-
sued in common life. Let us now turn to another
matter (though really it is but another phase of the
same question), and that is, the method by which, from

METHOD OF DISCOVERY. 61

the relations of certain phenomena, we prove that some
stand in the position of causes towards the others.

I want to put the case clearly "before you, and I will
therefore show you what I mean by another familiar
example. I will suppose that one of you, on coming
down in the morning to the parlour of your house, finds
that a tea-pot and some spoons which had been left in
the room on the previous evening are gone, — the win-
dow is open, and you observe the mark of a dirty hand
on the window-frame, and perhaps, in addition to that,
you notice the impress of a hob-nailed shoe on the
gravel outside. All these phenomena have struck your
attention instantly, and before two minutes have passed
you say, '* Oh, somebody has broken open the window,
entered the room, and run off with the spoons and the
tea-pot ! ' That speech is out of your mouth in a mo-
ment. And you will probably add, " I know there
has ; I am quite sure of it ! " You mean to say exactly
what you know ; but in reality what you have said has
been the expression of what is, in all essential particu-
lars, a Hypothesis. You do not 1c now it at all ; it is
nothing but a hypothesis rapidly framed in your own
mind ! And it is a hypothesis founded on a long train
of inductions and deductions.

What are those inductions and deductions, and how
have you got at this hypothesis? You have observed,
in the first place, that the window is open ; but by a
train of reasoning involving many Inductions and De-
ductions, you have probably arrived long before at the
General Law — and a very good one it is — that windows
do not open of themselves ; and you therefore conclude
that something has opened the window. A second
general law that you have arrived at in the same way

62 METHOD OF DISCOVERY.

is, that tea-pots and spoons do not go out of a window
spontaneously, and you are satisfied that, as they are
not now where you left them, they have been removed.
In the third place, you look at the marks on the win-
dow-sill, and the shoe-marks outside, and you say that
in all previous experience the former kind of mark
has never been produced by anything else but the
hand of a human being ; and the same experience shows
that no other animal but man at present wears shoes
with hob-nails on them such as would produce the
marks in the gravel. I do not know, even if we could
discover any of those " missing links " that are talked
about, that they would help us to any other conclusion !
At any rate the law which states our present experience
is strong enough for my present purpose. You next
reach the conclusion, that as these kinds of marks have
not been left by any other animals than men, or are
liable to be formed in any other way than by a man's
hand and shoe, the marks in question have been formed
by a man in that w T ay. You have, further, a general
law, founded on observation and experience, and that,
too, is, I am sorry to say, a very universal and unim-
peachable one, — that some men are thieves ; and you
assume at once from all these premisses — and that is
what constitutes your hypothesis — that the man who
made the marks outside and on the window-sill, opened
the window, got into the room, and stole your tea-pot
and spoons. You have now arrived at a Vera Causa ;
— you have assumed a Cause which it is plain is com-
petent to produce all the phenomena you have observed.
You can explain all these phenomena only by the hy-
pothesis of a thief. But that is a hypothetical conclu-
sion, of the justice of which you have no absolute proof

METHOD OF DISCOVERY. 63

at all ; it is only rendered highly probable by a series
of inductive and deductive reasonings.

I suppose your first action, assuming you are a man
of ordinary common sense, and that you have estab-
lished this hypothesis to your own satisfaction, will
very likely be to go off for the police, and set them on
the track of the burglar, with the view to the recovery
of your property. But just as you are starting with
this object, some person comes in, and on learning what
you are about, says, " My good friend, you are going
on a great deal too fast. How do you know that the
man who really made the marks took the spoons ? It
might have been a monkey that took them, and the
man may have merely looked in afterwards." You
would probably reply, " Well, that is all very well,
but you see it is contrary to all experience of the way
tea-pots and spoons are abstracted ; so that, at any rate,
your hypothesis is less probable than mine." While
you are talking the thing over in this way, another
friend arrives, one of that good kind of people that I
was talking of a little while ago. And he might say,
" Oh, my dear sir, you are certainly going on a great
deal too fast. You are most presumptuous. You ad-
mit that all these occurrences took place when you
were fast asleep, at a time when you could not possibly
have known anything about what was taking place.
How do you know that the laws of Nature are not sus-
pended during the night ? It may be that there has
been some kind of supernatural interference in this
case." In point of fact, he declares that your hypoth-
esis is one of which you cannot at all demonstrate the
truth, and that you are by no means sure that the

64: METHOD OF DISCOVERY.

laws of Nature are the same when you are asleep as
when you are awake.

"Well, now, you cannot at the moment answer that
kind of reasoning. You feel that your worthy friend
has you somewhat at a disadvantage. You will feel
perfectly convinced in your own mind, however, that
you are quite right, and you say to him, " My good
friend, I can only be guided by the natural probabili-
ties of the case, and if you will be kind enough to stand
aside and permit me to pass, I will go and fetch the
police." "Well, we will suppose that your journey is
successful, and that by good luck you meet with a
policeman ; that eventually the burglar is found with
your property ou his person, and the marks correspond
to his hand and to his boots. Probably any jury would
consider those facts a very good experimental verifica-
tion of your hypothesis, touching the cause of the ab-
normal phenomena observed in your parlour, and would
act accordingly.

Now, in this supposititious case I have taken phe-
nomena of a very common kind, in order that you
might see what are the different steps in an ordinary
process of reasoning, if you will only take the trouble
to analyze it carefully. All the operations I have de-
scribed, you will see, are involved in the mind of any
man of sense in leading him to a conclusion as to the
course he should take in order to make good a robbery
and punish the offender. I say that you are led, in
that case, to your conclusion by exactly the same train
of reasoning as that which a man of science pursues
when he is endeavouring to discover the origin and
laws of the most occult phenomena. The process is,
and always must be, the same ; and precisely the same

METHOD OF DISCOVERY. 65

mode of reasoning was employed by Newton and
Laplace in their endeavours to discover and define the
causes of the movements of the heavenly bodies, as you,
with your own common sense, would employ to detect
a burglar. The only difference is, that the nature of
the inquiry being more abstruse, every step has to be
most carefully watched, so that there may not be a
single crack or flaw in your hypothesis. A flaw or
crack in many of the hypotheses of daily life may be
of little or no moment as affecting the general correct-
ness of the conclusions at which we may arrive ; but
in a scientific inquiry a fallacy, great or small, is always
of importance, and is sure to be constantly productive
of mischievous, if not fatal, results in the long run.

Do not allow yourselves to be misled by the com-
mon notion that a hypothesis is untrustworthy simply
because it is a hypothesis. It is often urged, in respect
to some scientific conclusion, that, after all, it is only
a hypothesis. But what more have we to guide us in
nine-tenths of the most important affairs of daily life
than hypotheses, and often very ill-based ones? So
that in science, where- the evidence of a hypothesis is
subjected to the most rigid examination, we may rightly
pursue the same course. You may have hypotheses
and hypotheses. A man may say, if he likes, that the
moon is made of green cheese : that is a hypothesis.
But another man, who has devoted a great deal of time
and attention to the subject, and availed himself of the
most powerful telescopes and the results of the observa-
tions of others, declares that in his opinion it is prob-
ably composed of materials very similar to those of
which our own earth is made up : and that is also only a
hypothesis. But I need not tell you that there is an

66 METHOD OF DISCOVERY.

enormous difference in the value of the two hypotheses.
That one which is based on sound scientific knowledge
is sure to have a corresponding value ; and that which
is a mere hasty random guess is likely to have but little
value. Every great step in our progress in discovering
causes has been made in exactly the same way as that
which I have detailed to you. A person observing the
occurrence of certain facts and phenomena asks, natu-
rally enough, what process, what kind of operation
known to occur in nature applied to the particular
case, will unravel and explain the mystery? Hence
you have the scientific hypothesis : and its value will
be proportionate to the care and completeness with
which its basis had been tested and verified. It is in
these matters as in the commonest affairs of practical
life : the guess of the fool will be folly, while the guess
of the wise man will contain wisdom. In all cases,
you see that the value of the result depends on the
patience and faithfulness with which the investigator
applies to his hypothesis every possible kind of verifi-
cation.

I dare say I may have to return to this point by-
and-by ; but having dealt thus far with our logical
methods, I must now turn to something which, perhaps,
you may consider more interesting, or, at any rate,
more tangible. But in reality there are but few things
that can be more important for you to understand than
the mental processes and the means by which we obtain
scientific conclusions and theories.* Having granted
that the inquiry is a proper one, and having determined

* Those who wish to study fully the doctrines of which I have en-
deavoured to give some rough and ready illustrations, must read Mr. John
Stuart Mill's " System of Logic."

ORIGINATION OF LIVING BEINGS. 67

on the nature of the methods we are to pursue and
which only can lead to success, I must now turn to the
consideration of our knowledge of the nature of the
processes which have resulted in the present condition
of organic nature.

Here, let me say at once, lest some of you misun-
derstand me, that I have extremely little to report.
The question of how the present condition of organic
nature came about, resolves itself into two questions.
The first is : How has organic or living matter com-
menced its existence ? And the second is : How has it
been perpetuated ? On the second question I shall
have more to say hereafter. But on the first one, what
I now have to say will be for the most part of a nega-
tive character.

If you consider what kind of evidence we can have
upon this matter, it will resolve itself into two kinds.
We may have historical evidence and we may have ex-
perimental evidence. It is, for example, conceivable,
that inasmuch as the hardened mud which forms a
considerable portion of the thickness of the earth's
crust contains faithful records of the past forms of life,
and inasmuch as these differ more and more as we go
further down, — it is possible and conceivable that we
might come to some particular bed or stratum which
should contain the remains of those creatures with
which organic life began upon the earth. And if we
did so, and if such forms of organic life were pre-
servable, we should have what I would call historical
evidence of the mode in which organic life began upon
this planet. Many persons will tell you, and indeed
you will find it stated in many works on geology, that
this has been done, and that we really possess such a

68 ORIGINATION OF LIVING BEINGS.

record ; there are some who imagine that the earliest
forms of life of which we have as yet discovered any
records, are in truth the forms in which animal life be-
gan upon the globe. The grounds on which they base
that supposition are these : — That if you go through
the enormous thickness of the earth's crust and get
down to the older rocks, the higher vertebrate animals
— the quadrupeds, birds, and fishes — cease to be found ;
beneath them you find only the invertebrate animals ;
and in the deepest and lowest rocks those remains be-
come scantier and scantier, not in any very gradual
progression, however, until, at length, in what are sup-
posed to be the oldest rocks, the animal remains which
are found are almost always confined to four forms, —
Old/ia?nia, whose precise nature is not known, whether
plant or animal ; Lingula, a kind of mollusc ; Trilo-
bites, a crustacean animal, having the same essential
plan of construction, though differing in many details
from a lobster or crab ; and Hymenocaris, which is
also a crustacean. So that you have all the Fauna re-
duced, at this period, to four forms : one a kind of ani-
mal or plant that we know nothing about, and three
undoubted animals — two crustaceans and one mollusc.
I think, considering the organization of these mol-
lusca and Crustacea, and looking at their very complex
nature, that it does indeed require a very strong ima-
gination to conceive that these were the first created of
all living things. And you must take into considera-
tion the fact that we have not the slightest proof that
these which we call the oldest beds are really so : I re-
peat, we have not the slightest proof of it. When you
find in some places that in an enormous thickness of
rocks there are but very scanty traces of life, or abso-

ORIGINATION OF LIVING BEINGS. 69

lutely none at all ; and that in other parts of the world
rocks of the very same formation are crowded with
the records of living forms ; I think it is impossible to
place any reliance on the supposition, or to feel oneself
justified in supposing that these are the forms in which
life first commenced. I have not time here to enter
upon the technical grounds upon which I am led to
this conclusion, — that could hardly be done properly
in half a dozen lectures on that part alone ; — I must
content myself with saying that I do not at all believe
that these are the oldest forms of life.

I turn to the experimental side to see what evidence
we have there. To enable us to say that we know any-
thing about the experimental origination of organiza-
tion and life, the investigator ought to be able to take
inorganic matters, such as carbonic acid, ammonia, wa-
ter, and salines, in any sort of inorganic combination,
and be able to build them up into Protein matter, and
that that Protein matter ought to begin to live in an
organic form. That, nobody has done as yet, and I
suspect it will be a long while before anybody does
do it. But the thing is by no means so impossible as
it looks ; for the researches of modern chemistry have
shown us — I won't say the road towards it, but, if I
may so say, they have shown the finger-post pointing
to the road that may lead to it.

It is not many years ago — and you must recollect
that Organic Chemistry is a young science, not above
a couple of generations old, — you must not expect too
much of it ; it is not many years ago since it was said
to be perfectly impossible to fabricate any organic
compound ; that is to say, any non-mineral compound
which is to be found in an organized being. It re-

70 ORIGINATION OF LIVING BEINGS.

mained so for a very long period ; but it is now a con-
siderable number of years since a distinguished foreign
chemist contrived to fabricate Urea, a substance of a
very complex character, which forms one of the waste
products of animal structures. And of late years a
number of other compounds, such as Butyric Acid,
and others, have been added to the list. I need not
tell you that chemistry is an enormous distance from
the goal I indicate ; all I wish to point out to you is,
that it is by no means safe to say that that goal may
not be reached one day. It may be that it is impos-
sible for us to produce the conditions requisite to the
origination of life ; but we must speak modestly about
the matter, and recollect that Science has put her foot
upon the bottom round of the ladder. Truly he would
be a bold man who would venture to predict where she
will be fifty years hence.

There is another inquiry which bears indirectly
upon this question, and upon which I must say a few
words. You are all of you aware of the phenomena
of what is called spontaneous generation. Our fore-
fathers, down to the seventeenth century, or there-
abouts, all imagined, in perfectly good faith, that cer-
tain vegetable and animal forms gave birth, in the
process of their decomposition, to insect life. Thus, if
you put a piece of meat in the sun, and allowed it to
putrefy, they conceived that the grubs which soon be-
gan to appear were the result of the action of a power
of spontaneous generation which the meat contained.
And they could give you receipts for making various
animal and vegetable preparations which would pro-
duce particular kinds of animals. A very distinguish-
ed Italian naturalist, named Redi, took up the ques-

ORIGINATION OF LIVING BEINGS. 71

tion, at a time when everybody believed in it ; among
others our own great Harvey, the discoverer of the
circulation of the blood. You will constantly find his
name quoted, however, as an opponent of the doctrine
of spontaneous generation ; but the fact is, and you
will see it if you will take the trouble to look into his
works, Harvey believed it as profoundly as any man
of his time ; but he happened to enunciate a very cu-
rious proposition — that every living thing came from
an egg ; he did not mean to use the word in the sense
in which we now employ it, he only meant to say that
every living thing originated in a little rounded par-
ticle of organized substance ; and it is from this cir-
cumstance, probably, that the notion of Harvey having
opposed the doctrine originated. Then came Redi,
and he proceeded to upset the doctrine in a very simple
manner. He merely covered the piece of meat with
some very fine gauze, and then he exposed it to the
same conditions. The result of this was that no grubs
or insects were produced ; he proved that the grubs
originated from the insects who came and deposited
their eggs in the meat, and that they were hatched
by the heat of the sun. By this kind of inquiry he
thoroughly upset the doctrine of spontaneous genera-
tion, for his time at least.

Then came the discovery and application of the
microscope to scientific inquiries, which showed to
naturalists that besides the organisms which they
already knew as living beings and plants, there were
an immense number of minute things which could be
obtained apparently almost at will from decaying vege-
table and animal forms. Thus, if you took some or-
dinary black pepper or some hay, and steeped it in

72 ORIGINATION OF LIVING BEINGS.

water, you would find in the course of a few days that
the water had become impregnated with an immense
number of animalcules swimming about in all direc-
tions. From facts of this kind naturalists were led to
revive the theory of spontaneous generation. They
were headed here by an English naturalist, — Needham,
— and afterwards in France by the learned Buffon.
They said that these things were absolutely begotten
in the water of the decaying substances out of which
the infusion was made. It did not matter whether you
took animal or vegetable matter, you had only to steep
it in water and expose it, and you would soon have
plenty of animalcules. They made a hypothesis about
this which was a very fair one. They said, this matter
of the animal world, or of the higher plants, appears to
be dead, but in reality it has a sort of dim life about it,
which, if it is placed under fair conditions, will cause it
to break up into the forms of these little animalcules,
and they will go through their lives in the same way as
the animal or plant of which they once formed a part.

The question now became very hotly debated.
Spallanzani, an Italian naturalist, took up opposite
views to those of Needham and Buffon, and by means
of certain experiments he showed that it was quite pos-
sible to stop the process by boiling the water, and clos-
ing the vessel in which it was contained. " Oh ! " said
his opponents ; " but what do you know you may be
doing when you heat the air over the water in this way ?
You may be destroying some property of the air requi-
site for the spontaneous generation of the animalcules."

However, Spall anzani's views were supposed to be
upon the right side, and those of the others fell into
discredit ; although the fact was that Spallanzani had

ORIGINATION OF LIVING BEINGS. 73

not made good his views. Well, then, the subject con-
tinued to be revived from time to time, and experiments
were made by several persons ; but these experiments
were not altogether satisfactory. It was found that if
you put an infusion in which animalcules would appear
if it were exposed to the air into a vessel and boiled
it, and then sealed up the mouth of the vessel, so that
no air, save such as had been heated to 212°, could
reach its contents, that then no animalcules would be
found ; but if you took the same vessel and exposed
the infusion to the air, then you would get animalcules.
Furthermore, it was found that if you connected the
mouth of the vessel with a red-hot tube in such a way
that the air would have to pass through the tube be-
fore reaching the infusion, that then you would get
no animalcules. Yet another thing was noticed : if
you took two flasks containing the same kind of infu-
sion, and left one entirely exposed to the air, and in
the mouth of the other placed a ball of cotton wool,
so that the air would have to filter itself through it
before reaching the infusion, that then, although you
might have plenty of animalcules in the first flask, you
would certainly obtain none from the second.

These experiments, you see, all tended towards one
conclusion — that the infusoria were developed from little
minute spores or eggs which were constantly floating
in the atmosphere, which lose their power of germi-
nation if subjected to heat. But one observer now made
another experiment, which seemed to go entirely the
other way, and puzzled him altogether. He took some
of this boiled infusion that I have been speaking of,
and by the use of a mercurial bath — a kind of trough
used in laboratories — he deftly inverted a vessel con-
4

74 ORIGINATION OF LIVING BEINGS.

*

taining the infusion into the mercury, so that the latter
reached a little beyond the level of the mouth of the
inverted vessel. You see that he thus had a quantity
of the infusion shut oif from any possible communica-
tion with the outer air by being inverted upon a bed of
mercury.

He then prepared some pure oxygen and nitrogen
gases, and passed them by means of a tube going from
the outside of the vessel, up through the mercury into
the infusion ; so that he thus had it exposed to a per-
fectly pure atmosphere of the same constituents as the
external air. Of course, he expected he would get no
infusorial animalcules at all in that infusion ; but, to
his great dismay and discomfiture, he found he almost
always did get them.

Furthermore it has been found that experiments
made in the manner described above answer well with
most infusions ; but that if you fill the vessel with
boiled milk, and then stop the neck with cotton-wool,
you will have infusoria. So that you see there were
two experiments that brought you to one kind of con-
clusion, and three to another ; which was a most un-
satisfactory state of things to arrive at in a scientific
inquiry.

Some few years after this, the question began to be
very hotly discussed in France. There was M. Pouchet,
a professor at Rouen, a very learned man, but certainly
not a very rigid experimentalist. He published a num-
ber of experiments of his own, some of which were very
ingenious, to show that if you went to work in a proper
way, there was a truth in the doctrine of spontaneous
generation. Well, it was one of the most fortunate
things in the world that M. Pouchet took up this ques-

ORIGINATION OF LIVING BEINGS. 75

tion, because it induced a distinguished French chemist,
M. Pasteur, to take up the question on the other side ;
and he has certainly worked it out in the most perfect
manner. I am glad to say, too, that he has published
his researches in time to enable me to give you an ac-
count of them. He verified all the experiments which
I have just mentioned to you — and then finding those
extraordinary anomalies, as in the case of the mercury
bath and the milk, he set himself to w T ork to discover
their nature. In the case of milk he found it to be a
question of temperature. Milk in a fresh state is
slightly alkaline ; and it is a very curious circumstance,
but this very slight degree of alkalinity seems to have
the effect of preserving the organisms which fall into
it from the air from being destroyed at a temperature
of 212°, which is the boiling point. But if you raise
the temperature 10° when you boil it, the milk behaves
like everything else ; and if the air with which it comes
in contact, after being boiled at this temperature, is
passed through a red-hot tube, you will not get a trace
of organisms.

He then turned his attention to the mercury bath,
and found on examination that the surface of the mer-
cury was almost always covered with a very fine dust.
He found that even the mercury itself was positively
full of organic matters; that from being constantly
exposed to the air, it had collected an immense num-
ber of these infusorial organisms from the air. Well,
under these circumstances he felt that the case was
quite clear, and that the mercury was not what it had
appeared to M. Schwann to be — a bar to the admission
of these organisms ; but that, in reality, it acted as a
reservoir from which the infusion was immediately

76 ORIGINATION OF LIVING BEINGS.

supplied with the large quantity that had so puzzled
him.

But not content with explaining the experiments
of others, M. Pasteur went to work to satisfy himself
completely. He said to himself: " If my view is right,
and if, in point of fact, all these appearances of spon-
taneous generation are altogether due to the falling of
minute germs suspended in the atmosphere, — why, I
ought not only to be able to show the germs, but I
ought to be able to catch and sow them, and produce
the resulting organisms." He, accordingly, constructed
a very ingenious apparatus to enable him to accomplish
this trapping of this " germ dust " in the air. He fixed
in the window of his room a glass tube, in the centre
of which he had placed a ball of gun-cotton, which,
as you all know, is ordinary cotton-wool, which, from
having been steeped in strong acid, is converted into
a substance of great explosive power. It is also solu-
ble in alcohol and ether. One end of the glass tube
was, of course, open to the external air; and at the
other end of it he placed an aspirator, a contrivance
for causing a current of the external air to pass through
the tube. He kept his apparatus going for four-and-
twenty hours, and then removed the dusted gun-cot-
ton, and dissolved it in alcohol and ether. He then al-
lowed this to stand for a few hours, and the result was,
that a very fine dust was gradually deposited at the
bottom of it. That dust, on being transferred to the
stage of a microscope, was found to contain an enor-
mous number of starch grains. You know that the
materials of our food and the greater portion of plants
are composed of starch, and we are constantly making
use of it in a variety of ways, so that there is always

ORIGINATION OF LIVING- BEINGS. 77

a quantity of it suspended in the air. It is these starch
grains which form many of those bright specks that
we see dancing in a ray of light sometimes. But be-
sides these, M. Pasteur found also an immense number
of other organic substances such as spores of fungi,
which had been floating about in the air and had got
caged in this way.

He went farther, and said to himself, "If these
really are the things that give rise to the appearance
of spontaneous generation, I ought to be able to take
a ball of this dusted gun-cotton and put it into one of
my vessels, containing that boiled infusion which has
been kept away from the air, and in which no in-
fusoria are at present developed, and then, if I am right,
the introduction of this gun-cotton will give rise to
organisms."

Accordingly, he took one of these vessels of infu-
sion, which had been kept eighteen months, without
the least appearance of life, and by a most ingenious
contrivance, he managed to break it open and intro-
duce such a ball of gun-cotton, without allowing the
infusion or the cotton ball to come into contact with
any air but that which had been subjected to a red
heat, and in twenty-four hours he had the satisfaction
of finding all the indications of what had been hitherto
called spontaneous generation. He had succeeded in
catching the germs and developing organisms in the
way he had anticipated.

It now struck him that the truth of his conclusions
might be demonstrated without all the apparatus he
had employed. To do this, he took some decaying
animal or vegetable substance, such as urine, which is
an extremely decomposable substance, or the juice of

78 ORIGINATION OF LIVING BEINGS.

yeast, or perhaps some other artificial preparation, and
filled a vessel having a long tubular neck, with it. He
then boiled the liquid and bent that long neck into an
S shape or zig-zag, leaving it open at the end. The
infusion then gave no trace of any appearance of spon-
taneous generation, however long it might be left, as
all the germs in the air were deposited in the beginning
of the bent neck. He then cut the tube close to the
vessel, and allowed the ordinary air to have free and
direct access ; and the result of that was the appearance
of organisms in it, as soon as the infusion had been
allowed to stand long enough to allow of the growth
of those it received from the air, which was about forty-
eight hours. The result of M. Pasteur's experiments
proved, therefore, in the most conclusive manner, that all
the appearances of spontaneous generation arose from
nothing more than the deposition of the germs of or-
ganisms which were constantly floating in the air.

To this conclusion, however, the objection was
made, that if that were the cause, then the air would
contain such an enormous number of these germs, that
it would be a continual fog. But M. Pasteur replied
that they are not there in anything like the number we
might suppose, and that an exaggerated view has been
held on that subject ; he showed that the chances of
animal or vegetable life appearing in infusions, depend
entirely on the conditions under which they are ex-
posed. If they are exposed to the ordinary atmosphere
around us, why, of course, you may have organisms
appearing early. But, on the other hand, if they are
exposed to air from a great height, or from some very
quiet cellar, you will often not find a single trace of
life.

ORIGINATION OF LIVING BEINGS. 79

So that M. Pasteur arrived at last at the clear and
definite result, that all these appearances are like the
case of the worms in the piece of meat, which was re-
futed by Redi, simply germs carried by the air and
deposited in the liquids in which they afterwards ap-
pear. For my own part, I conceive that, with the
particulars of M. Pasteur's experiments before us, we
cannot fail to arrive at his conclusions ; and that the
doctrine of spontaneous generation has received a final
coup de grace.

You, of course, understand that all this in no way
interferes with the possibility of the fabrication of or-
ganic matters by the direct method to which I have
referred, remote as that possibility may be.

LECTUEE IT.

THE PERPETUATION OF LIVING BEINGS, HEREDITARY
TRANSMISSION AND VARIATION.

The inquiry which we undertook, at our last meet-
ing, into the state of our knowledge of the causes of
the phenomena of organic nature, — of the past and of
the present, — resolved itself into two subsidiary in-
quiries : the first was, whether we know anything,
either historically or experimentally, of the mode of
origin of living beings ; the second subsidiary inquiry
was, whether, granting the origin, we know anything
about the perpetuation and modifications of the forms
of organic beings. The reply which I had to give to
the first question was altogether negative, and the chief
result of my last lecture was, that, neither historically
nor experimentally, do we at present know anything
whatsoever about the origin of living forms. We saw
that, historically, we are not likely to know anything
about it, although we may perhaps learn something ex-
perimentally ; but that at present we are an enormous
distance from the goal I indicated.

I now, then, take up the next question, What do
we know of the reproduction, the perpetuation, and the
modifications of the forms of living beings, supposing

*

THE PEKPETUATION OF LIVING BEINGS. 81

that we Lave put the question as to their origination on
one side, and have assumed that at present the causes
of their origination are beyond us, and that Ave know
nothing about them ? Upon this question the state of
our knowledge is extremely different ; it is exceedingly
large, and, if not complete, our experience is certainly
most extensive. It would be impossible to lay it all
before you, and the most I can do, or need do to-night,
is to take up the principal points and put them before
you with such prominence as may subserve the pur-
poses of our present argument.

The method of the perpetuation of organic beings
is of two kinds, — the asexual and the sexual. In the
first the perpetuation takes place from and by a par-
ticular act of an individual organism, which sometimes
may not be classed as belonging to any sex at all. In
the second case, it is in consequence of the mutual ac-
tion and interaction of certain portions of the organisms
of usually two distinct individuals, — the male and the
female. The cases of asexual perpetuation are by no
means so common as the cases of sexual perpetuation ;
and they are by no means so common in the animal as
in the vegetable world. You are all probably familiar
with the fact, as a matter of experience, that you can
propagate plants by means of what are called " cut-
tings ; " for example, that by taking a cutting from a
geranium plant, and rearing it properly, by supply-
ing it with light and warmth and nourishment from
the earth, it grows up and takes the form of its parent,
having all the properties and peculiarities of the ori-
ginal plant.

Sometimes this process, which the gardener per-
forms artificially, takes place naturally ; that is to say,
4*

82 THE PERPETUATION OF LIVING BEINGS,

a little bulb, or portion of the plant, detaches itself,
drops off, and becomes capable of growing as a separate
thing. That is the case with many bulbous plants,
which throw off in this way secondary bulbs, which
are lodged in the ground and become developed into
plants. This is an asexual process, and from it results
the repetition or reproduction of the form of the ori-
ginal being from which the bulb proceeds.

Among animals the same thing takes place. Among
the lower forms of animal life, the infusorial animal-
culse we have already spoken of throw off certain por-
tions, or break themselves up in various directions,
sometimes transversely or sometimes longitudinally ;
or they may give off buds, which detach themselves
and develop into their proper forms. There is the
common fresh-water Polype, for instance, which multi-
plies itself in this way. Just in the same w r ay as the
gardener is able to multiply and reproduce the pecu-
liarities and characters of particular plants by means
of cuttings, so can the physiological experimentalist,
— as was shown by the Abbe Trembley many years
ago, — so can he do the same thing with many of the
lower forms of animal life. M. de Trembley showed
that you could take a polype and cut it into two, or
four, or many pieces, mutilating it in all directions,
and the pieces would still grow up and reproduce com-
pletely the original form of the animal. These are all
cases of asexual multiplication, and there arc other in-
stances, and still more extraordinary ones, in which
this process takes place naturally, in a more hidden, a
more recondite kind of way. You are all of you fa-
miliar with those little green insects, the Aphis or
blight, as it is called. These little animals, during

HEREDITARY TRANSMISSION AND VARIATION. 83

a very considerable part of their existence, multiply
themselves by means of a kind of internal budding, the
buds being developed into essentially asexual animals,
which are neither male nor female ; they become con-
verted into young Aphides, which repeat the process,
and their offspring after them, and so on again ; you
may go on for nine or ten, or even twenty or more suc-
cessions ; and there is no very good reason to say how
soon it might terminate, or how long it might not go
on if the proper conditions of warmth and nourishment
were kept up.

Sexual reproduction is quite a distinct matter.
Here, in all these cases, what is required is the detach-
ment of two portions of the parental organisms, which
portions we know as the egg or the spermatozoon. In
plants it is the ovule and the pollen-grain, as in the
flowering plants, or the ovule and the antherozooid, as
in the nowerless. Among all forms of animal life, the
spermatozoa proceed from the male sex, and the egg is
the product of the female. Now, what is remarkable
about this mode of reproduction is this, that the egg
by itself, or the spermatozoa by themselves, are unable
to assume the parental form ; but if they be brought
into contact with one another, the effect of the mixture
of organic substances proceeding from two sources ap-
pears to confer an altogether new vigour to the mix-
ed product. This process is brought about, as we all
know, by the sexual intercourse of the two sexes, and
is called the act of impregnation. The result of this
act on the part of the male and female is, that the
formation of a new being is set up in the ovule or egg ;
this ovule or egg soon begins to be divided and sub-
divided, and to be fashioned into various complex or-

84: THE PERPETUATION OF LIVING BEINGS,

ganisms, and eventually to develop into the form of
one of its parents, as I explained in the first lecture.
These are the processes by which the perpetuation of
organic beings is secured. Why there should be the
two modes — why this re-invigoration should be re-
quired on the part of the female element we do not
know ; but it is most assuredly the fact, and it is pre-
sumable, that, however long the process of asexual
multiplication could be continued, — I say there is good
reason to believe that it w r ould come to an end if a new
commencement were not obtained by a conjunction of
the two sexual elements.

That character which is common to these two dis-
tinct processes is this, that, whether we consider the
reproduction, or perpetuation, or modification of or-
ganic beings as they take place asexually, or as they
may take place sexually, — in either case, I say, the off-
spring has a constant tendency to assume, speaking
generally, the character of the parent. As I said just
now, if you take a slip of a plant, and tend it with care,
it will eventually grow up and develop into a plant
like that'' from which it had sprung ; and this tendency
is so strong that, as gardeners know, this mode of mul-
tiplying by means of cuttings is the only secure mode
of propagating very many varieties of plants ; the pecu-
liarity of the primitive stock seems to be better pre-
served if you propagate it by means of a slip than if
you resort to the sexual mode.

Again, in experiments upon the lower animals, such
as the polype, to which I have referred, it is most ex-
traordinary that, although cut up into various pieces,
each particular piece will grow up into the form of the
primitive stock ; the head, if separated, will reproduce

HEREDITARY TRANSMISSION AND VARIATION. 85

the body and the tail ; and if you cut off the tail, you
will find that that will reproduce the body and all the
rest of the members, without in any way deviating
from the plan of the organism from which these por-
tions have been detached. And so far does this go,
that some experimentalists have carefully examined
the lower orders of animals, — among them the Abbe
Spallanzani, who made a number of experiments upon
snails and salamanders, — and have found that they
might mutilate them to an incredible extent ; that you
might cut off the jaw or the greater part of the head,
or the leg or the tail, and repeat the experiment sev-
eral times, perhaps, cutting off the same member again
and again ; and yet each of those types would be
reproduced according to the primitive type : nature
making no mistake, never putting on a fresh kind of
leg, or head, or tail, but always tending to repeat and
to return to the primitive type.

It is the same in sexual reproduction : it is a mat-
ter of perfectly common experience, that the tendency
on the part of the offspring always is, speaking broadly,
to reproduce the form of the parents. The proverb
has it that the thistle does not bring forth grapes ; so,
among ourselves, there is always a likeness, more or
less marked and distinct, between children and their
parents. That is a matter of familiar and ordinary ob-
servation. We notice the same thing occurring in the
cases of the domestic animals — dogs, for instance, and
their offspring. In all these cases of propagation and
perpetuation, there seems to be a tendency in the off-
spring to take the characters of the parental organisms.
To that tendency a special name is given — and as I
may very often use it, I will write it up here on this

86 THE PERPETUATION OF LIVING BEINGS,

black-board that you may remember it — it is called
Atavism; it expresses this tendency to revert to the
ancestral type, and comes from the Latin word atavus,
ancestor.

Well, this Atavism which I shall speak of, is, as I
said before, one of the most marked and striking ten-
dencies of organic beings ; but, side by side with this
hereditary tendency, there is an equally distinct and
remarkable tendency to variation. The tendency to
reproduce the original stock has, as it were, its limits,
and side by side with it there is a tendency to vary in
certain directions, as if there were two opposing pow-
ers working upon the organic being, one tending to
take it in a straight line, and the other tending to make
it diverge from that straight line, first to one side and
then to the other.

So that you see these two tendencies need not pre-
cisely contradict one another, as the ultimate result
may not always be very remote from what would have
been the case if the line had been quite straight.

This tendency to variation is less marked in that
mode of propagation which takes place asexual ly ; it is
in that mode that the minor characters of animal and
vegetable structures are most completely preserved.
Still, it will happen sometimes, that the gardener,
when he has planted a cutting of some favourite plant,
will find, contrary to his expectation, that the slip
grows up a little different from the primitive stock —
that it produces flowers of a different colour or make,
or some deviation in one way or another. This is what
is called the " sporting " of plants.

In animals the phenomena of asexual propagation
are so obscure, that at present we cannot be said to

HEREDITARY TRANSMISSION AND VARIATION. 87

know much about them ; but if we turn to that mode
of perpetuation which results from the sexual process,
then we find variation a perfectly constant occurrence,
to a certain extent ; and, indeed, I think that a certain
amount of variation from the primitive stock is the
necessary result of the method of sexual propagation
itself ; for, inasmuch as the thing propagated proceeds
from two organisms of different sexes and different
makes and temperaments, and as the offspring is to be
either of one sex or the other, it is quite clear that it
cannot be an exact diagonal of the two, or it would be
of no sex at all ; it cannot be an exact intermediate
form between that of each of its parents — it must de-
viate to one side or the other. You do not find that
the male follows the precise type of the male parent,
nor does the female always inherit the precise charac-
teristics of the mother, — there is always a proportion
of the female character in the male offspring, and of
the male character in the female offspring. That must
be quite plain to all of you who have looked at all at-
tentively on your own children or those of your neigh-
bours ; you will have noticed how very often it may
happen that the son shall exhibit the maternal type of
character, or the daughter possess the characteristics
of the father's family. There are all sorts of intermix-
tures and intermediate conditions between the two,
where complexion, or beauty, or fifty other different
peculiarities belonging to either side of the house, are
reproduced in other members of the same family. In-
deed, it is sometimes to be remarked in this kind of
variation, that the variety belongs, strictly speaking,
to neither of the immediate parents ; you will see a
child in a family who is not like either its father or its

88 THE PERPETUATION OF LIVING BEINGS,

mother ; but some old person who knew its grand-
father or grandmother, or, it may be, an ancle, or, per-
haps, even a more distant relative, will see a great
similarity between the child and one of these. In this
way it constantly happens that the characteristic of
some previous member of the family comes out and
is reproduced and recognized in the most unexpected
manner.

But apart from that matter of general experience,
there are some cases which put that curious mixture in
a very clear light. You are aware that the offspring of
the Ass and the Horse, or rather of the he-Ass and the
Mare, is what is called a Mule ; and, on the other hand,
the offspring of the Stallion and the she-Ass is what is
called a Ilinny. It is a very rare thing in this country
to see a Hinny. I never saw one myself; but they
have been very carefully studied. Now, the curious
thing is this, that although you have the same elements
in the experiment in each case, the offspring is entirely
different in character, according as the male influence
comes from the Ass or the Horse. Where the Ass is
the male, as in the case of the Mule, you find that the
head is like that of the Ass, that the ears are long, the
tail is tufted at the end, the feet are small, and the
voice is an unmistakable bray ; these are all points
of similarity to the Ass ; but, on the other hand, the
barrel of the body and the cut of the neck are much
more like those of the Mare. Then, if you look at the
Hinny, — the result of the union of the Stallion and
the she-Ass, then you find it is the Horse that has the
predominance ; that the head is more like that of the
Horse, the ears are shorter, the legs coarser, and the
type is altogether altered ; while the voice, instead

HEREDITARY TRANSMISSION AND VARIATION. 89

of being a bray, is the ordinary neigh of the Horse.
Here, yon see, is a most curions thing : yon take ex-
actly the same elements, Ass and Horse, but yon com-
bine the sexes in a different manner, and the result is
modified accordingly. Yon have in this case, however,
a result which is not general and universal — there is
usually an important preponderance, but not always
on the same side.

Here, then, is one intelligible, and, perhaps, neces-
sary cause of variation : the fact, that there are two
sexes sharing in the production of the offspring, and
that the share taken by each is different and variable,
not only for each combination, but also for different
members of the same family.

Secondly, there is a variation, to a certain extent, — ■
though in all probability the influence of this cause has
been very much exaggerated — but there is no doubt
that variation is produced, to a certain extent, by what
are commonly known as external conditions, — such as
temperature, food, w T armth, and moisture. In the long
run, every variation depends, in some sense, upon ex^
ternal conditions, seeing that everything has a cause
of its own. I use the term " external conditions " now
in the sense in which it is ordinarily employed : cer-
tain it is, that external conditions have a definite effect.
You may take a plant which has single flowers, and
by dealing with the soil, and nourishment, and so on,
you may by-and-by convert single flowers into double
flow T ers, and make thorns shoot out into branches.
You may thicken or make various modifications in the
shape of the fruit. In animals, too, you may produce
analogous changes in this way, as in the case of that
deep bronze colour which persons rarely lose after

SO THE PERPETUATION OF LIVING BEINGS,

having passed any length of time in tropical countries.
You may also alter the development of the muscles
very much, by dint of training ; all the world knows
that exercise has a great effect in this way ; we always
expect to find the arm of a blacksmith hard and wiry,
and possessing a large development of the brachial
muscles. No doubt, training, which is one of the forms
of external conditions, converts what are originally
only instructions, teachings, into habits, or, in other
words, into organizations, to a great extent ; but this
second cause of variation cannot be considered to be
by any means a large one. The third cause that I
have to mention, however, is a very extensive one. It
is one that, for want of a better name, has been called
" spontaneous variation ; " which means that when we
do not know anything about the cause of phenomena,
we call it spontaneous. In the orderly chain of causes
and effects in this world, there are very few things of
which it can be said with truth that they are spon-
taneous. Certainly not in these physical matters, — in
these there is nothing of the kind, — everything depends
on previous conditions. But when we cannot trace the
cause of phenomena, we call them spontaneous.

Of these variations, multitudinous as they are, but
little is known with perfect accuracy. I will mention
to you some two or three cases, because they are very
remarkable in themselves, and also because I shall
want to use them afterwards. Reaumur, a famous
French naturalist, a great many years ago, in the essay
which he wrote upon the art of hatching chickens, —
which was indeed a very curious essay, — had occasion
to speak of variations and monstrosities. One very re-
markable case had come under his notice of a variation

HEREDITARY TRANSMISSION AND VARIATION. 91

in the form of a human member, in the person of a
Maltese, of the name of Gratio Kelleia, who was born
with six fingers upon each hand, and the like number
of toes to each of his feet. That was a case of spon-
taneous variation. Nobody knows why he was born
with that number of fingers and toes, and as we don't
know, we call it a case of " spontaneous " variation.
There is another remarkable case also. I select these,
because they happen to have been observed and noted
very carefully at the time. It frequently happens that
a variation occurs, but the persons who notice it do not
take any care in noting down the particulars, until at
length, when inquiries come to be made, the exact cir-
cumstances are forgotten ; and hence, multitudinous as
may be such " spontaneous " variations, it is exceed-
ingly difficult to get at the origin of them.

The second case is one of which you may find the
whole details in the " Philosophical Transactions " for
the year 1813, in a paper communicated by Colonel
Humphrey to the President of the Royal Society, —
" On a new Variety in the Breed of Sheep," giving an
account of a very remarkable breed of sheep, which
at one time was well known in the northern states of
America, and which went by the name of the Ancon
or the Otter breed of sheep. In the year 1791, there
was a farmer of the name of Seth Wright in Massa-
chusetts, who had a flock of sheep, consisting of a ram
and, I think, of some twelve or thirteen ewes. Of this
flock of ewes, one at the breeding-time bore a lamb
which was very singularly formed ; it had a very long
body, very short legs, and those legs were bowed ! I
will tell you by-and-by how this singular variation in
the breed of sheep came to be noted, and to have the

92 THE PERPETUATION OF LIVING BEINGS,

prominence that it now lias. For the present, I men-
tion only these two cases ; but the extent of variation
in the breed of animals is perfectly obvious to any one
who has studied natural history with ordinary atten-
tion, or to any person who compares animals with
others of the same kind. It is strictly true that there
are never any two specimens which are exactly alike ;
however similar, they will always differ in some cer-
tain particular.

Now let us go back to Atavism, — to the hereditary
tendency I spoke of. What will come of a variation
when you breed from it, when Atavism comes, if I
may say so, to intersect variation ? The two cases of
which I have mentioned the history, give a most excel-
lent illustration of what occurs. Gratio Kelleia, the
Maltese, married when he was twenty-two years of age,
and, as I suppose there were no six-fingered ladies in
Malta, he married an ordinary five-fingered person.
The result of that marriage was four children ; the
first, who was christened Salvator, had six fingers
and six toes, like his father; the second was George,
who had five fingers and toes, but one of them was
deformed, showing a tendency to variation ; the third
was Andre ; he had five fingers and five toes, quite
perfect ; the fourth was a girl, Marie ; she had five
fingers and five toes, but her thumbs were deformed,
showing a tendency towards the sixth.

These children grew up, and when they came to
adult years, they all married, and of course it hap-
pened that they all married five-fingered and five-toed
persons. Now let us see what w T ere the results. Sal-
vator had four children ; they were two boys, a girl,
and another boy : the first two boys and the girl were

HEREDITARY TRANSMISSION AND VARIATION. 93

six-fingered and six-toed like their grandfather ; the
fourth boy had only five fingers and five toes. George
had only four children : there were two girls with six
fingers and six toes; there was one girl with six fingers
and five toes on the right side, and five fingers and five
toes on the left side, so that she was half and half.
The last, a boy, had five fingers and five toes. The
third, Andre, you will recollect, was perfectly well-
formed, and he had many children whose hands and
feet were all regularly developed. Marie, the last,
who, of course, married a man who had only five fin-
gers, had four children : the first, a boy, was born with
six toes, but the other three were normal.

Now observe what very extraordinary phenomena
are presented here. You have an accidental variation
arising from what you may call a monstrosity; you
have that monstrosity tendency or variation diluted in
the first instance by an admixture with a female of
normal construction, and you would naturally expect
that, in the results of such an union, the monstrosity,
if repeated, would be in equal proportion with the
normal type ; that is to say, that the children would
be half and half, some taking the peculiarity of the
father, and the others being of the purely normal type
of the mother ; but you see we have a great prepon-
derance of the abnormal type. Well, this comes to be
mixed once more with the pure, the normal type, and
the abnormal is again produced in large proportion,
notwithstanding the second dilution. Now what would
have happened if these abnormal types had intermar-
ried with each other ; that is to say, suppose the two
boys of Salvator had taken it into their heads to marry
their first cousins, the two first girls of George, their

94: THE PERPETUATION OF LIVING BEINGS,

uncle? You will remember that these are all of the
abnormal type of their grandfather. The result would
probably have been, that their offspring would have
been in every case a further development of that ab-
normal type. You see it is only in the fourth, in the
person of Marie, that the tendency, when it appears
but slightly in the second generation, is washed out
in the third, while the progeny of Andre, who escaped
in the first instance, escape altogether.

"We have in this case a good example of nature's
tendency to the perpetuation of a variation. Here it
is certainly a variation which carried with it no use
or benefit ; and yet you see the tendency to perpetu-
ation may be so strong, that, notwithstanding a great
admixture of pure blood, the variety continues itself
up to the third generation, which is largely marked
with it. In this case, as I have said, there was no
means of the second generation intermarrying with any
but five-fingered persons, and the question naturally
suggests itself, What would have been the result of
such marriage? Heaumur narrates this case only as
far as the third generation. Certainly it would have
been an exceedingly curious thing if Ave could have
traced this matter any further ; had the cousins inter-
married, a six-fingered variety of the human race might
have been set up.

To show you that this supposition is by no means
an unreasonable one, let me now point out what took
place in the case of Seth Wright's sheep, where it hap-
pened to be a matter of moment to him to obtain a
breed or raise a flock of sheep like that accidental va-
riety that I have described — and I will tell you why.
In that part of Massachusetts where Seth Wright was

HEREDITARY TRANSMISSION AND VARIATION. 95

living, the fields were separated by fences, and the
sheep, which were very active and robust, would roam
abroad, and without much difficulty jump over these
fences into other people's farms. As a matter of course,
this exuberant activity on the part of the sheep con-
stantly gave rise to all sorts of quarrels, bickerings and
contentions among the farmers of the neighbourhood ;
so it occurred to Seth Wright, who was, like his suc-
cessors, more or less 'cute, that if he could get a stock
of sheep like those with the bandy legs, they would not
be able to jump over the fences so readily, and he acted
upon that idea. He killed his old ram, and as soon as
the young one arrived at maturity, he bred altogether
from it. The result was even more striking than in the
human experiment which I mentioned just now. Col-
onel Humphreys testifies that it always happened that
the offspring were either pure Ancons or pure ordinary
sheep ; that in no case was there any mixing of the
Ancons with the others. In consequence of this, in
the course of a very few years, the farmer was able to
get a very considerable flock of this variety, and a large
number of them were spread throughout Massachusetts.
Most unfortunately, however — I suppose it was because
they were so common — nobody took enough notice of
them to preserve their skeletons ; and although Colonel
Humphreys states that he sent a skeleton to the presi-
dent of the Royal Society at the same time that he
forwarded his paper, and I am afraid that the variety
has entirely disappeared ; for a short time after these
sheep had become prevalent in that district, the Merino
sheep were introduced ; and as their wool was much
more valuable, and as they were a quiet race of sheep,
and showed no tendency to trespass or jump over fences,

96 THE PERPETUATION OF LIVING BEINGS,

the Otter breed of sheep, the wool of which was infe-
rior to that of the Merino, was gradually allowed to die
out.

You see that these facts illustrate perfectly well

what may be done if you take care to breed from stocks
that are similar to each other. After having got a
variation, if, by crossing a variation with the original
stock, you multiply that variation, and then take care
to keep that variation distinct from the original stock,
and make them breed together, — then you may almost
certainly produce a race whose tendency to continue
the variation is exceedingly strong.

This is what is called " selection ; " and it is by exactly
the same process as that by which Seth Wright bred his
Ancon sheep, that our breeds of cattle, dogs, and fowls,
are obtained. There are some possibilities of excep-
tion, but still, speaking broadly, I may say that this is
the way in which all our varied races of domestic ani-
mals have arisen ; and you must understand that it is
not one peculiarity or one characteristic alone in which
animals may vary. There is not a single peculiarity
or characteristic of any kind, bodily or mental, in which
offspring may not vary to a certain extent from the
parent and other animals.

. Among ourselves this is well known. The simplest
physical peculiarity is mostly reproduced. I know a
case of a man whose wife has the lobe of one^lier ears
a little flattened. An ordinary observer might scarcely
notice it, and yet every one of her children has an
approximation to the same peculiarity to some ex-
tent.

If you look at the other extreme, too, the gravest
diseases, such as gout, scrofula, and consumption, may

HEREDITARY TRANSMISSION AND VARIATION. 97

be handed down with just the same certainty and per-
sistence as we noticed in the perpetuation of the bandy
legs of the Ancon sheep.

However, these facts are best illustrated in animals,
and the extent of the variation, as is well known, is
very remarkable in dogs. For example, there are
some dogs very much smaller than others ; indeed, the
variation is so enormous that probably the smallest dog
would be about the size of the head of the largest ;
there are very great variations in the structural forms
not only of the skeleton but also in the shape of the
skull, and in the proportions of the face and the dis-
position of the teeth.

The Pointer, the Retriever, Bulldog, and the Ter-
rier, differ very greatly, and yet there is every reason
to believe that every one of these races has arisen from
the same source, — that all the most important races
have arisen by this selective breeding from accidental
variation.

A still more striking case of what may be done by
selective breeding, and it is a better case, because there
is no chance of that partial infusion of error to which
I allude, has been studied very carefully by Mr. Dar-
win, — the case of the domestic pigeons. I dare say
there may be some among you who may be pigeon
fanciers, and I wish you to understand that in ap-
proaching the subject, I would speak with all humility
and hesitation, as I regret to say that I am not a pigeon
fancier. I know it is a great art and mystery, and a
thing upon which a man must not speak lightly ; but
I shall endeavour, as far as my understanding goes, to
give you a summary of the published and unpublished
information which I have gained from Mr. Darwin.
5

98 THE PERPETUATION OF LIVING BEINGS,

Among the enormous variety, — I believe there are
somewhere about a hundred and fifty kinds of pigeons,
— there are four kinds which may be selected as repre-
senting the extremest divergences of one kind from an-
other. Their names are the Carrier, the Pouter, the
Fantail, and the Tumbler. In these large diagrams
that I have here they are each represented in their
relative sizes to each other. This first one is the Car-
rier ; you will notice this large excrescence on its
beak ; it has a comparatively small head ; there is a
bare space round the eyes ; it has a long neck, a very
long beak, very strong legs, large feet, long wings, and
so on. The second one is the Pouter, a very large bird,
with very long legs and beak. It is called the Pouter
because it is in the habit of causing its gullet to swell
up by inflating it with air. I should tell you that all
pigeons have a tendency to do this at times, but in the
Pouter it is carried to an enormous extent. The birds
appear to be quite proud of their power of swelling
and puffing themselves out in this way ; and I think it
is about as droll a sight as you can well see to look at
a cage full of these pigeons puffing and blowing them-
selves out in this ridiculous manner.

This diagram is a representation of the third kind
I mentioned — the Fantail. It is, you see, a small bird,
with exceedingly small legs and a very small beak.
It is most curiously distinguished by the size and ex-
tent of its tail, which, instead of containing fourteen
feathers, may have many more, — say thirty, or even
more — I believe there are some with as many as forty-
tw r o. This bird has a curious habit of spreading out
the feathers of its tail in such a way that they reach
forward, and touch its head ; and if this can be accom-

HEREDITARY TRANSMISSION AND VARIATION. 99

plished, I believe it is looked upon as a point of great
beauty.

But here is the last great variety, — the Tumbler ;
and of that great variety, one of the principal kinds,
and one most prized, is the specimen represented here
— the short-faced Tumbler. Its beak, you see, is re-
duced to a mere nothing. Just compare the beak of
this one and that of the first one, the Carrier — I believe
the orthodox comparison of the head and beak of a
thoroughly well-bred Tumbler is to stick an oat into a
cherry, and that will give you the proper relative pro-
portions of the head and beak. The feet and legs are
exceedingly small, and the bird appears to be quite a
dwarf when placed side by side with this great Carrier.

These are differences enough in regard to their ex-
ternal appearance ; but these differences are by no
means the whole or even the most important of the dif-
ferences which obtain between these birds. There is
hardly a single point of their structure which has not
become more or less altered ; and to give you an idea
of how extensive these alterations are, I have here some
very good skeletons, for which I am indebted to my
friend Mr. Tegetmeier, a great authority in these mat-
ters ; by means of which, if you examine them by-and-
by, you will be able to see the enormous difference in
their bony structures.

I had the privilege, some time ago, of access to
some important MSS. of Mr. Darwin, who, I may tell
you, has taken very great pains and spent much valu-
able time and attention on the investigation of these
variations, and getting together all the facts that bear
upon them. I obtained from these MSS. the follow-
ing summary of the differences between the domestic

100 THE PERPETUATION OF LIVING BEINGS,

breeds of pigeons ; that is to say, a notification of the
various points in which their organization differs. In
the first place, the back of the skull may differ a good
deal, and the development of the bones of the face may
vary a great deal ; the back varies a good deal ; the
shape of the lower jaw varies ; the tongue varies very
greatly, not only in correlation to the length and size
of the beak, but it seems also to have a kind of inde-
pendent variation of its own. Then the amount of
naked skin round the eyes, and at the base of the beak,
may vary enormously ; so may the length of the eye-
lids, the shape of the nostrils, and the length of the
neck. I have already noticed the habit of blowing out
the gullet, so remarkable in the Pouter, and compara-
tively so in the others. There are great differences,
too, in the size of the female and the male, the shape
of the body, the number and width of the processes of
the ribs, the development of the ribs, and the size,
shape, and development of the breastbone. "We may
notice, too, — and I mention the fact because it has
been disputed by what is assumed to be high author-
ity, — the variation in number of the sacral vertebrae.
The number of these varies from eleven to fourteen,
and that without any diminution in the number of the
vertebrae of the back or of the tail. Then the number
and position of the tail-feathers may vary enormously,
and so may the number of the primary and secondary
feathers of the wings. Again, the length of the feet
and of the beak, — although they have no relation to
each other, yet appear to go- together, — that is, you
have a long beak wherever you have long feet. There
are differences also in the periods of the acquirement of
the perfect plumage, — the size and shape of the eggs, —

HEREDITARY TRANSMISSION AND VARIATION. 101

the nature of flight, and the powers of flight, — so-call-
ed " homing " birds having enormous flying powers ;*
while, on the other hand, the little Tumbler is so called
because of its extraordinary faculty of turning head
over heels in the air, instead of pursuing a distinct
course. And, lastly, the dispositions and voices of the
birds may vary. Thus the case of the pigeons shows
you that there is hardly a single particular, — whether
of instinct, or habit, or bony structure, or of plumage,
— of either the internal economy or the external shape,
in which some variation or change may not take place,
which, by selective breeding, may become perpetuated,
and form the foundation of, and give rise to, a new
race.

If you carry in your mind's eye these four varieties
of pigeons, you will bear with you as good a notion as
you can have, perhaps, of the enormous extent to which
a deviation from a primitive type may be carried by
means of this process of selective breeding.

* The " Carrier" I learn from Mr. Tegetmeier, does not carry ;
a high-bred bird of this breed being but a poor flier. The birds
which fly long distances, and come home, — " homing " birds, —
and are consequently used as carriers, are not " carriers " in the
fancy sense.

LECTUEE V.

THE CONDITIONS OF EXISTENCE AS AFFECTING THE
PERPETUATION OF LIVING BEINGS.

In the last Lecture I endeavoured to prove to you
that, while, as a general rule, organic beings tend to
reproduce their kind, there is in them, also, a constantly
recurring tendency to vary — to vary to a greater or to
a less extent. Such a variety, I pointed out to you,
might arise from causes which we do not understand ;
we therefore called it spontaneous ; and it might come
into existence as a definite and marked thing, without
any gradations between itself and the form which pre-
ceded it. I farther pointed out, that such a variety
having once arisen, might be perpetuated to some ex-
tent, and indeed to a very marked extent, without any
direct interference, or without any exercise of that pro-
cess which we called selection. And then I stated
further, that by such selection, when exercised artifi-
cially — if you took care to breed only from those forms
which presented the same peculiarities of any variety
which had arisen in this manner — the variation might
be perpetuated, as far as we can see, indefinitely.

The next question, and it is an important one for
us, is this : Is there any limit to the amount of varia-

PERPETUATION OF LIVING BEINGS. 103

tion from the primitive stock which can be produced
by this process of selective breeding ? In considering
this question, it will be useful to class the character-
istics, in respect of which organic beings vary, under
two heads : we may consider structural characteristics,
and we may consider physiological characteristics.

In the first place, as regards structural characteris-
tics, I endeavoured to show you, by the skeletons which
I had upon the table, and by reference to a great many
well-ascertained facts, that the different breeds of
Pigeons, the Carriers, Pouters, and Tumblers, might
vary in any of their internal and important structural
characters to a very great degree ; not only might there
be changes in the proportions of the skull, and the char-
acters of the feet and beaks, and so on ; but that there
. might be an absolute difference in the number of the
vertebrae of the back, as in the sacral vertebrae of the
Pouter ; and so great is the extent of the variation in
these and similar characters that I pointed out to you,
by reference to the skeletons and the diagrams, that
these extreme varieties may absolutely differ more from
one another in their structural characters than do what
naturalists call distinct Species of pigeons; that is to
say, that they differ so much in structure that there is
a greater difference between the Pouter and the Tum-
bler than there is between such wild and distinct forms
as the Pock Pigeon or the Ping Pigeon, or the Ping
Pigeon and the Stock Dove ; and indeed the differences
are of greater value than this, for the structural differ-
ences between these domesticated pigeons are such as
would be admitted by a naturalist, supposing he knew
nothing at all about their origin, to entitle them to
constitute even distinct genera.

104: CONDITIONS AFFECTING THE

As I have used this term Species, and shall proba-
bly use it a good deal, I had better perhaps devote a
word or two to explaining what I mean by it.

Animals and plants are divided into groups, which
become gradually smaller, beginning with a Kingdom,
which is divided into Sub-Kingdoms ; then come the
smaller divisions called Provinces ; and so on from a
Province to a Class, from a Class to an Order, from
Orders to Families, and from these to Genera, until
we come at length to the smallest groups of animals
which can be denned one from the other by constant
characters, which are not sexual ; and these are what
naturalists call Species in practice, whatever they may
do in theory.

If in a state of nature you rind any two groups of
living beings, which are separated one from the other
by some constantly-recurring characteristic, I don't
care how slight and trivial, so long as it is denned and
constant, and does not depend on sexual peculiarities,
then all naturalists agree in calling them two species ;
that is what is meant by the use of the word species —
that is to say, it is, for the practical naturalist, a mere
question of structural differences.*

We have seen now — to repeat this point once more,
and it is very essential that we should rightly under-
stand it — we have seen that breeds, known to have
been derived from a common stock by selection, may
be as different in their structure from the original stock
as species may be distinct from each other.

But is the like true of the physiological charac-

* I lay stress here on the practical signification of " Species." Wheth-
er a physiological test between species exist or not, it is hardly ever ap-
plicable by the practical naturalist.

PEKPETUATION OF LIVING BEINGS. 105

teristics of animals ? Do the physiological differences
of varieties amount in degree to those observed between
forms which naturalists call distinct species? This is
a most important point for us to consider.

As regards the great majority of physiological char-
acteristics, there is no doubt that they are capable of
being developed, increased, and modified by selection.

There is no doubt that breeds may be made as dif-
ferent as species in many physiological characters. I
have already pointed out to you very briefly the differ-
ent habits of the breeds of Pigeons, all of which depend
upon their physiological peculiarities, — as the peculiar
habit of tumbling, in the Tumbler, — the peculiari-
ties of flight, in the "homing" birds, — the strange
habit of spreading out the tail, and walking in a pecu-
liar fashion, in the Fantail, — and, lastly, the habit of
blowing out the gullet, so characteristic of the Pouter.
These are all due to physiological modification, and in
all these respects these birds differ as much from each
other as any two ordinary species do.

So with Dogs in their habits and instincts. It is
a physiological peculiarity which leads the Greyhound
to chase its prey by sight, — that enables the Beagle to
track it by the scent, — that impels the Terrier to its
rat-hunting propensity, — and that leads the Retriever
to its habit of retrieving. These habits and instincts
are all the results of physiological differences and pecu-
liarities, which have been developed from a common
stock, at least there is every reason to believe so. But
it is a most singular circumstance, that while you may
run through almost the whole series of physiological
processes, without finding a check to your argument,
you come at last to a point where you do find a check,

106 CONDITIONS AFFECTING THE

and that is in the reproductive processes. For there
is a most singular circumstance in respect to natural
species — at least about some of them — and it would be
sufficient for the purposes of this argument, if it were
true of only one of them, but there is, in fact, a great
number of such cases — and that is, that similar as they
may appear to be to mere races or breeds, they present
a marked peculiarity in the reproductive process. If
you breed from the male and female of the same race,
you of course have offspring of the like kind, and if
you make the offspring breed together, you obtain the
same result, and if you breed from these again, you
will still have the same kind of offspring ; there is no
check. But if you take members of two distinct spe-
cies, however similar they may be to each other, and
make them breed together, you will find a check, with
some modifications and exceptions, however, which I
shall speak of presently. If you cross two such species
with each other, then, — although you may get offspring
in the case of the first cross, yet, if you attempt to breed
from the products of that crossing, which are what are
called Hybrids — that is, if you couple a male and a
female hybrid — then the result is that in ninety-nine
cases out of a hundred you will get no offspring at all :
there will be no result whatsoever.

The reason of this is quite obvious in some cases ;
the male hybrids, although possessing all the external
appearances and characteristics of perfect animals, are
physiologically imperfect and deficient in the structural
parts of the reproductive elements necessary to gener-
ation. It is said to be invariably the case with the
male mule, the cross between the Ass and the Mare ;
and hence it is, that, although crossing the Horse with

PERPETUATION OF LIVING BEINGS. 107

the Ass is easy enough, and is constantly done, as far
as I am aware, if you take two mules, a male and a
female, and endeavour to breed from them, you get
no offspring whatever ; no generation will take place.
This is what is called the sterility of the hybrids be-
tween two distinct species.

You see that this is a very extraordinary circum-
stance ; one does not see why it should be. The com-
mon teleological explanation is, that it is to prevent the
impurity of the blood resulting from the crossing of
one species with another, but you see it does not in
reality do anything of the kind. There is nothing in
this fact that hybrids cannot breed with each other, to
establish such a theory ; there is nothing to prevent
the Horse breeding with the Ass, or the Ass with the
Horse. So that this explanation breaks down, as a
great many explanations of this kind do, that are only
founded on mere assumptions.

Thus you see that there is a great difference be-
tween " mongrels," which are crosses between distinct
races, and " hybrids," which are crosses between dis-
tinct species. The mongrels are, so far as we know,
fertile with one another. But between species, in many
cases, you cannot succeed in obtaining even the first
cross : at any rate it is quite certain that the hybrids
are often absolutely infertile one with another.

Here is a feature, then, great or small as it may be,
which distinguishes natural species of animals. Can
we find any approximation to this in the different races
known to be produced by selective breeding from a
common stock? Up to the present time the answer
to that question is absolutely a negative one. As far
as we know at present, there is nothing approximating

108 CONDITIONS AFFECTING THE

to this check. In crossing the breeds between the Fan-
tail and the Pouter, the Carrier and the Tumbler, or
any other variety or race you may name — so far as we
know at present — there is no difficulty in breeding to-
gether the mongrels. Take the Carrier and the Fantail,
for instance, and let them represent the Horse and the
Ass in the case of distinct species ; then you have, as
the result of their breeding, the Carrier-Fantail mon-
grel, — we will say the male and female mongrel, — and,
as far as we know, these two when crossed would not
be less fertile than the original cross, or than Carrier
with Carrier. Here, you see, is a physiological con-
trast between the races produced by selective modifica-
tion and natural species. I shall inquire into the value
of this fact, and of some modifying circumstances, by
and by ; for the present I merely put it broadly before

you.

But while considering this question of the limita-
tions of species, a word must be said about what is
called Recurrence — the tendency of races which have
been developed by selective breeding from varieties to
return to their primitive type. This is supposed by
many to put an absolute limit to the extent of selective
and all other variations. People say, " It is all very
well to talk about producing these different races, but
you know very well that if you turned all these birds
wild, these Pouters, and Carriers, and so on, they would
all return to their primitive stock." This is very com-
monly assumed to be a fact, and it is an argument that
is commonly brought forward as conclusive ; but if
you will take the trouble to inquire into it rather closely,
I think you will find that it is not worth very much.
The first question of course is, Do they thus return to

PERPETUATION OF LIVING BEINGS. 109

the primitive stock ? And commonly as the thing is
assumed and accepted, it is extremely difficult to get
anything like good evidence of it. It is constantly said,
for example, that if domesticated Horses are turned
wild, as they have been in some parts of Asia Minor
and South America, that they return at once to the
primitive stock from which they were bred. But the
first answer that you make to this assumption is, to
ask who knows what the primitive stock was ; and the
second answer is, that in that case the wild Horses of
Asia Minor ought to be exactly like the wild Horses
of South America. If they are both like the same
thing, they ought manifestly to be like each other !
The best authorities, however, tell you that it is quite
different. The wild Horse of Asia is said to be of a
dun colour, with a largish head, and a great many
other peculiarities ; while the best authorities on the
wild Horses of South America tell you that there is
nothing of this sort in the wild Horses there ; the cut
of their heads is very different, and they are commonly
chestnut or bay-coloured. It is quite clear, therefore,
that as by these facts there ought to have been two
primitive stocks, they go for nothing in support of the
assumption that races recur to one primitive stock, and
so far as this evidence is concerned, it falls to the
ground.

Suppose for a moment that it were so, and that
domesticated races, when turned wild, did return to
some common condition, I cannot see that this would
prove much more than that similar conditions are likely
to produce similar results; and that when you take
back domesticated animals into what we call natural
conditions, you do exactly the same thing as if you

110 CONDITIONS AFFECTING THE

carefully undid all the work you liad gone through,
for the purpose of bringing the animal from its wild
to its domesticated state. I do not see anything very
wonderful in the fact, if it took all that trouble to get
it from a wild state, that it should go back into its
original state as soon as you remove the conditions
which produced the variation to the domesticated form.
There is an important fact, however, forcibly brought
forward by Mr. Darwin, which has been noticed in
connection with the breeding of domesticated pigeons ;
and it is, that however different these breeds of pigeons
may be from each other, and we have already noticed
the great differences in these breeds, that if, among
any of those variations, you chance to have a blue
pigeon turn up, it will be sure to have the black bars
across the wings, which are characteristic of the origi-
nal wild stock, the Rock Pigeon.

Now, this is certainly a very remarkable circum-
stance ; but I do not see myself how it tells very
strongly either one way or the other. I think, in fact,
that this argument in favour of recurrence to the primi-
tive type might prove a great deal too much for those
who so constantly bring it forward. For example, Mr.
Darwin has very forcibly urged, that nothing is com-
moner than if you examine a dun horse — and I had an
opportunity of verifying this illustration lately, while
in the islands of the West Highlands, where there are
a great many dun horses — to find that horse exhibit
a long black stripe down his back, very often stripes
on his shoulder, and very often stripes on his legs. I,
myself, saw a pony of this description a short time ago,
in a baker's cart, near Rothesay, in Bute : it had the
long stripe down the back, and stripes on the shoulders

PERPETUATION OF LIVING BEINGS. Ill

and legs, just like those of the Ass, the Quagga, and
the Zebra. Now, if we interpret the theory of recur-
rence as applied to this case, might it not be said that
here was a case of a variation exhibiting the characters
and conditions of an animal occupying something like
an intermediate position between the Horse, the Ass,
the Quagga, and the Zebra, and from which these had
been developed ? In the same way with regard even
to Man. Every anatomist will tell you that there is
nothing commoner, in dissecting the human body, than
to meet with what are called muscular variations — that
is, if you dissect two bodies very carefully, you will
probably find that the modes of attachment and inser-
tion of the muscles are not exactly the same in both,
there being great peculiarities in the mode in which
the muscles are arranged ; and it is very singular, that
in some dissections of the human body you will come
upon arrangements of the muscles very similar indeed
to the same parts in the Apes. Is the conclusion in
that case to be, that this is like the black bars in the
case of the Pigeon, and that it indicates a recurrence
to the primitive type from which the animals have been
probably developed? Truly, I think that the oppo-
nents of modification and variation had better leave
the argument of recurrence alone, or it may prove alto-
gether too strong for them.

To sum up, — the evidence as far as we have gone
is against the argument as to any limit to divergences,
so far as structure is concerned ; and in favour of a
physiological limitation. By selective breeding we
can produce structural divergences as great as those
of species, but we cannot produce equal physiological
divergences. For the present I leave the question
there.

112 CONDITIONS AFFECTING THE

Now, the next problem that lies before us — and it
is an extremely important one — is this : Does this selec-
tive breeding occur in nature ? Because, if there is no
proof of it, all that I have been telling you goes for
nothing in accounting for the origin of species. Are
natural causes competent to play the part of selection
in perpetuating varieties ? Here we labour under very
great difficulties. In the last lecture I had occasion
to point out to you the extreme difficulty of obtaining
evidence even of the first origin of those varieties which
we know to have occurred in domesticated animals.
I told you, that almost always the origin of these varie-
ties is overlooked, so that I could only produce two
or three cases, as that of Gratio Kelleia and of the
Ancon sheep. People forget, or do not take notice of
them until they come to have a prominence ; and if
that is true of artificial cases, under our own eves, and
in animals in our own care, how much more difficult
it must be to have at first hand good evidence of the
origin of varieties in nature! Indeed, I do not know
that it is possible by direct evidence to prove the origin
of a variety in nature, or to prove selective breeding ;
but I will tell you what we can prove — and this comes
to the same thing — that varieties exist in nature within
the limits of species, and, what is more, that when a
variety has come into existence in nature, there are
natural causes and conditions, which are amply com-
petent to play the part of a selective breeder ; and al-
though that is not quite the evidence that one would
like to have — though it is not direct testimony — yet it
is exceeding good and exceedingly powerful evidence
in its way.

As to the first point, of varieties existing among

PERPETUATION OF LIVING BEINGS. 113

natural species, I might appeal to the universal experi-
ence of every naturalist, and of any person who has
ever turned any attention at all to the characteristics
of plants and animals in a state of nature ; but I may
as well take a few definite cases, and I will begin with
Man himself.

I am one of those who believe that, at present, there
is no evidence whatever for saying, that mankind sprang
originally from any more than a single pair ; I must say,
that I cannot see any good ground whatever, or even
any tenable sort of evidence, for believing that there
is more than one species of Man. Nevertheless, as you
know, just as there are numbers of varieties in animals,
so there are remarkable varieties of men. I speak not
merely of those broad and distinct variations which
you see at a glance. Everybody, of course, knows the
difference between a Negro and a white man, and can tell
a Chinaman from an Englishman. They each have pecu-
liar characteristics of colour and physiognomy ; but you
must recollect that the characters of these races go very
far deeper — they extend to the bony structure, and to
the characters of that most important of all organs to
ns — the brain ; so that, among men belonging to differ-
ent races, or even within the same race, one man shall
have a brain a third, or half, or even seventy per cent,
bigger than another ; and if you take the whole range
of human brains, you will find a variation in some cases
of a hundred per cent. Apart from these variations
in the size of the brain, the characters of the skull vary.
Thus if I draw the figures of a Mongul and a Negro
head on the blackboard, in the case of the last the
breadth would be about seven-tenths, and in the other
it would be nine-tenths of the total length. So

114: CONDITIONS AFFECTING THE

that you see there is abundant evidence of variation
among men in their natural condition. And if you
turn to other animals there is just the same thing. The
fox, for example, which has a very large geographical
distribution all over Europe, and parts of Asia, and on
the American Continent, varies greatly. There are
mostly large foxes in the North, and smaller ones in
the South. In Germany alone, the foresters reckon
some eight different sorts.

Of the tiger, no one supposes that there is more than
one species; they extend from the hottest parts of
Bengal, into the dry, cold, bitter steppes of Siberia,
into a latitude of 50°, — so that they may even prey
upon the reindeer. These tigers have exceedingly dif-
ferent characteristics, but still they all keep their gen-
eral features, so that there is no doubt as to their being
tigers. The Siberian tiger has a thick fur, a small
mane, and a longitudinal stripe down the back, while
the tigers of Java and Sumatra differ in many impor-
tant respects from the tigers of Northern Asia. So
lions vary ; so birds vary ; and so, if you go further
back and lower down in creation, you find fishes vary.
In different streams, in the same country even, you
will find the trout to be quite different to each other
and easily recognizable by those who fish in the par-
ticular streams. There is the same differences in
leeches ; leech collectors can easily point out to you
the differences and the peculiarities which you your-
self would probably pass by ; so with fresh-water mus-
sels ; so, in fact, with every animal you can mention.

In plants there is the same kind of variation. Take
such a case even as the common bramble. The bota-
nists are all at war about it ; some of them wanting to

PERPETUATION OF LIVING BEINGS. 115

make out that there are many species of it, and others
maintaining that they are but many varieties of one
species ; and they cannot settle to this day which is a
species and which is a variety !

So that there can be no doubt whatsoever that any
plant and any animal may vary in nature ; that varie-
ties may arise in the way I have described, — as sponta-
neous varieties, — and that those varieties may be per-
petuated in the same way that I have shown you
spontaneous varieties are perpetuated ; I say, therefore,
that there can be no doubt as to the origin and per-
petuation of varieties in nature.

But the question now is : — Does selection take place
in nature ? is there anything like the operation of man
in exercising selective breeding, taking place in nature ?
You will observe that, at present, I say nothing about
species ; I wish to confine myself to the consideration
of the production of those natural races which every-
body admits to exist. The question is, whether in na-
ture there are causes competent to produce races, just
in the same way as man is able to produce, by selec-
tion, such races of animals as we have already noticed.

When a variety has arisen, the Conditions of Exist-
ence are such as to exercise an influence which is
exactly comparable to that of artificial selection. By
Conditions of Existence I mean two things, — there are
conditions which are furnished by the physical, the in-
organic world, and there are conditions of existence
which are furnished by the organic world. There is,
in the first place, Climate ; under that head I in-
clude only temperature and the varied amount of
moisture of particular places. In the next place
there is what is technically called Station, which

116 CONDITIONS AFFECTING THE

means — given the climate, the particular kind of
place in which an animal or a plant lives or grows ; for
example, the station of a fish is in the water, of a fresh
water fish in fresh water ; the station of a marine fish
is in the sea, and a marine animal may have a station
higher or deeper. So again with land animals : the
differences in their stations are those of different soils
and neighbourhoods ; some being best adapted to a
calcareous, and others to an arenaceous soil. The
third condition of existence is Food, by which I mean
food in the broadest sence, the supply of the materials
necessary to the existence of an organic being ; in the
case of a plant the inorganic matters, such as carbonic
acid, water, ammonia, and the earthy salts or salines ;
in the case of the animal the inorganic and organic
matters, which we have seen they require ; then these
are all, at least the two first, what we may call the
inorganic or physical conditions of existence. Food
takes a mid-place, and then come the organic condi-
tions ; by which I mean the conditions which depend
upon the state of the rest of the organic creation, upon
the number and kind of living beings, with which an
animal is surrounded. You may class these under two
heads : there are organic beings, which operate as
opponents, and there are organic beings which operate
as helpers to any given organic creature. The oppo-
nents may be of two kinds : there are the indirect op-
ponents, which are what we may call rivals / and there
are the direct opponents, those which strive to destroy
the creature ; and these we call enemies. By rivals I
mean, of course, in the case of plants, those which
require for their support the same kind of soil and
station, and, among animals, those which require the

PERPETUATION OF LIVING BEINGS. 117

same kind of station, or food, or climate ; those are the
indirect opponents ; the direct opponents are, of course,
those which prey upon an animal or vegetable. The
helpers may also be regarded as direct and indirect : in
the case of a carnivorous animal, for example, a particu-
lar herbaceous plant may in multiplying be an indirect
helper, by enabling the herbivora on which the carni-
vore preys to get more food, and thus to nourish the
carnivore more abundantly ; the direct helper may be
best illustrated by reference to some parasitic creature,
such as the tape- worm. The tape-worm exists in the
human intestines, so that the fewer there are of men
the fewer there will be of tape-worms, other things
being alike. It is a humiliating reflection, perhaps,
that we may be classed as direct helpers to the tape-
worm, but the fact is so : we can all see that if there
were no men there would be no tape-worms.

It is extremely difficult to estimate, in a proper way,
the importance and the working of the Conditions of
Existence. I do not think there were any of us who
had the remotest notion of properly estimating them
until the publication of Mr. Darwin's work, which has
placed them before us with remarkable clearness ; and
I must endeavour, as far as I can in my own fashion, to
give you some notion of how they work. We shall find
it easiest to take a simple case, and one as free as possi-
ble from every kind of complication.

I will suppose, therefore, that all the habitable part of
this globe — the dryland, amounting to about 51,000,000
square miles, — I will suppose that the whole of that dry
land has the same climate, and that it is composed of
the same kind of rock or soil, so that there will be the

118 CONDITIONS AFFECTING THE

same station everywhere ; we thus get rid of the pecu-
liar influence of different climates and stations. I will
then imagine that there shall be but one organic being
in the world, and that shall be a plant. In this we
start fair. Its food is to be carbonic acid, water and
ammonia, and the saline matters in the soil, which are,
by the supposition, everywhere alike. We take one
single plant, with no opponents, no helpers, and no
rivals ; it is to be a " fair field and no favour." Now,
I will ask you to imagine further that it shall be a plant
which shall produce every year fifty seeds, which is a
very moderate number for a plant to produce ; and
that, by the action of the winds and currents, these
seeds shall be equally and gradually distributed over the
whole surface of the land. I want you now to trace
out what will occur, and you will observe that I am not
talking fallaciously any more than a mathematician
does when he expounds his problem. If you show that
the conditions of your problem are such as may actually
occur in nature, and do not transgress any of the known
laws of nature in working out your proposition, then
you are as safe in the conclusion you arrive at, as is the
mathematician in arriving at the solution of his problem.
In science, the only way of getting rid of the complica-
tions with which a subject of this kind is environed, is
to work in this deductive method. What will be the
result then ? I will suppose that every plant requires
one square foot of ground to live upon ; and the result
will be that, in the course of nine years, the plant will
have occupied every single available spot in the whole
globe ! I have chalked upon the blackboard the figures
by which I arrive at the result : —

PERPETUATION OF LIVING BEINGS. 119

Plants.

Plants.

1 x 50 in 1st

year

50

50 x 50 " 2nd

(i

=

2,500

2,500 x 50 " 3rd

u

=

125,000

125,000 x 50 " 4th

u

=

6,250,000

6,250,000 x 50 " 5th

u

=

312,500,000

312,500,000 x 50 " 6th

u

=

15,625,000,000

15,625,000,000 x 50 " 7th

((

=

781,250,000,000

781,250,000,000 x 50 " 8th

it

=

39,062,500,000,000

39,062,500,000,000 x 50 " 9th

u

=

1,953,125,000,000,000

51,000,000 sq. miles — the dry sur-

)

face of the earth x 27,878,400—

=l

sq. ft.

1,421,798,400,000,000

the number of sq. ft. in 1 sq. mile

)

•

bein

g 531,326,600,000,000

square feet less than would be required at the end of the ninth year.

You will see from this that, at the end of the first
year the single plant will have produced fifty more of its
kind ; by the end of the second year these will have
increased to 2,500 ; and so on, in succeeding years, you
get beyond even trillions ; and I am not at all sure that
I could tell you what the proper arithmetical denomina-
tion of the total number really is ; but, at any rate, you
will understand the meaning of all those noughts.
Then you see that, at the bottom, I have taken the
51,000,000 of square miles, constituting the surface of
the dry land ; and as the number of square feet are
placed under and abstracted from the number of seeds
that would be produced in the ninth year, you can see
at once that there would be an immense number more
of plants than there would be square feet of ground for
their accommodation. This is certainly quite enough
to prove my point ; that between the eighth and ninth
year after being planted, the single plant would have
stocked the whole available surface of the earth.

This is a thing which is hardly conceivable — it seems

120 CONDITIONS AFFECTING THE

hardly imaginable — yet it is so. It is indeed simply
the law of Maltlms exemplified. Mr. Malthus was a
clergyman, who worked out this subject most minutely
and truthfully some years ago ; he showed quite clearly,
— and although he was much abused for his conclusions
at the time, they have never yet been disproved and
never will be — he showed that in consequence of the
increase in the number of organic beings in a geometri-
cal ratio, while the means of existence cannot be made
to increase in the same ratio, that there must come a
time when the number of organic beings will be in
excess of the power of production of nutriment, and that
thus some check must arise to the further increase of
those organic beings. At the end of the ninth year we
have seen that each plant would not be able to get its
full square foot of ground, and at the end of another
year it would have to share that space with fifty others
the produce of the seeds which it would give off.

What, then, takes place ? Every plant grows up,
flourishes, occupies its square foot of ground, and gives
off its fifty seeds ; but notice this, that out of this num-
ber only one can come to anything ; there is thus, as it
were, forty-nine chances to one against its growing up ;
it depends upon the most fortuitous circumstances
whether any one of these fifty seeds shall grow up and
flourish, or whether it shall die and perish. This is
what Mr. Darwin has drawn attention to, and called the
" Struggle fob Existence ; " and I have taken this
simple case of a plant because some people imagine that
the phrase seems to imply a sort of fight.

I have taken this plant and shown you that this is
the result of the ratio of the increase, the necessary re-
sult of the arrival of a time coming for every species

PERPETUATION OF LIVING BEINGS. 121

when exactly as many members must be destroyed as
are born ; that is the inevitable ultimate result of the
rate of production. Now, what is the result of all this ?
I have said that there are forty-nine struggling against
every one ; and it amounts to this, that the smallest
possible start given to any one seed may give it an
advantage which will enable it to get ahead of all the
others ; anything that will enable any one of these seeds
to germinate six hours before any of the others will,
other things being alike, enable it to choke them out
altogether. I have show you that there is no particu-
lar in which plants will not vary from each other ; it is
quite possible that one of our imaginary plants may
vary in such a character as the thickness of the integu-
ment of its seeds. It might happen that one of the
plants might produce seeds having a thinner integu-
ment, and that would enable the seed of that plant to
germinate a little quicker than those of any of the
others, and those seeds would most inevitablv extin-
guish the forty-nine times as many that were strug-
gling with them.

I have put it in this way, but you see the practical
result of the process is the same as if some person had
nurtured the one and destroyed the other seeds. It does
not matter how the variation is produced, so long as it
is once allowed to occur. The variation in the plant
once fairly started, tends to become hereditary and
reproduce itself ; the seeds would spread themselves in
the same way and take part in the struggle with the
forty-nine hundred, or forty-nine thousand, with which
they might be exposed. Thus, by degrees, this variety,
with some slight organic change or modification, must
spread itself over the whole surface of the habitable
6

122 CONDITIONS AFFECTING THE

globe, and extirpate or replace the other kinds. That
is what is meant by Natural Selection ; that is the
kind of argument by which it is perfectly demonstrable
that the conditions of existence may play exactly the
same part for natural varieties as man does for domesti-
cated varieties. No one doubts at all that particular
circumstances may be more favorable for one plant and
less so for another, and the moment you admit that, you
admit the selective power of nature. Now, although I
have been putting a hypothetical case, you must not
suppose that I have been reasoning hypothetically.
There are plenty of direct experiments which bear out
what we may call the theory of natural selection ; there
is extremely good authority for the statement that if you
take the seed of mixed varieties of wheat and sow it,
collecting the seed next year and sowing it again, at
length you will find that out of all your varieties, only
two or three have lived, or perhaps even only one.
There were one or two varieties which were best fitted
to get on, and they have killed out the other kinds in
just the same way and with just the same certainty as
if you had taken the trouble to remove them. As I
have already said, the operation of nature is exactly the
same as the artificial operation of man.

But if this be true of that simple case, which I put
before you, where there is nothing but the rivalry of one
member of a species with others, what must be the
operation of selective conditions, when you recollect as
a matter of fact, that for every species of animal or
plant there are fifty or a hundred species which might
all, more or less, be comprehended in the same climate,
food, and station ; — that every plant has multitudinous
animals which prey upon it, and which are its direct

PERPETUATION OF LIVING BEINGS. 123

opponents ; and that these have other animals preying
upon them, — that every plant has its indirect helpers in
the birds that scatter abroad its seed, and the animals
that manure it with their dung ; — I say, when these
things are considered, it seems impossible that any
variation which may arise in a species in nature should
not tend in some way or other, either to be a little
better or worse than the previous stock ; if it is a little
better it will have an advantage over and tend to extir-
pate the latter in this crush and struggle ; and if it is a
little worse it will itself be extirpated.

I know nothing that more appropriately expresses
this, than the phrase, " the struggle for existence ; " be-
cause it brings before your minds, in a vivid sort of
way, some of the simplest possible circumstances con-
nected with it. When a struggle is intense, there must
be some who are sure to be trodden down, crushed, and
overpowered by others ; and there will be some who
just manage to get through only by the help of the
slightest accident. I recollect reading an account of the
famous retreat of the French troops, under Napoleon,
from Moscow. Worn out, tired, and dejected, they at
length came to a great river over which there was but
one bridge for the passage of the vast army. Disorgan-
ized and demoralized as it was, the struggle must cer-
tainly have been a terrible one — everyone heeding only
himself, and crushing through and treading down his
fellows. The writer of the narrative, who was himself
one of those who were fortunate enough to succeed in
getting over, and not among the thousands who were
left behind or forced into the river, ascribed his escape
to the fact that he saw striding onward through the
mass a great strong fellow, — one of the French Cuiras-

124 CONDITIONS AFFECTING THE

siers, who had on a large blue cloak — and he had
enough presence of mind to catch and retain a hold of
this strong man's cloak. He says, " I caught hold of
his cloak, and although he swore at me and cut at and
struck me by turns, and at last, when he found he could
not shake me off, fell to entreating me to leave go or I
should prevent him from escaping, besides not assisting
myself, I still kept tight hold of him, and would not
quit my grasp until he had at last dragged me through."
Here you see was a case of selective saving — if we may
so term it — depending for its success on the strength of
the cloth of the Cuirassier's cloak. It is the same in
nature ; every species has its Beresina ; it has to fight
its way through and struggle with other species ; and
when well nigh overpowered, it may be that the
smallest chance, something in its colour, perhaps — the
minutest circumstance — will turn the scale one way or
the other.

Suppose that by a variation of the black race it had
produced the white man at any time — you know that
the Negroes are said to believe this to have been the
case, and to imagine that Cain was the first white man,
and that we are his descendants — suppose that this had
ever happened, and that the first residence of this
human being was on the West Coast of Africa. There
is no great structural difference between the white man
and the Negro, and yet there is something so singularly
different in the constitution of the two, that the malarias
of that country, which do not hurt the black at all, cut
off and destroy the white, thus you see there would
have been a selective operation performed. If the white
man had risen in that way, he would have been selected
out and removed by means of the malaria. Now there

PERPETUATION OF LIVING BEINGS. 125

really is a very curious case of selection of this sort
among pigs, and it is a case of selection of colour, too.
In the woods of Florida there are a great many pigs,
and it is a very curious thing that they are all black,
every one of them. Professor Wyman was there some
years ago, and on noticing no pigs but these black ones,
he asked some of the people how it was that they
had no white pigs, and the reply was that in the woods
of Florida there was a root which they called the
Paint Boot, and that if the white pigs were to eat any
of it, it had the effect of making their hoofs crack, and
they died, but if the black pigs eat any of it, it did not
hurt them at all. Here was a very simple case of
natural selection. A skilful breeder could not more
carefully develop the black breed of pigs, and weed out
all the white pigs, than the Paint Hoot does.

To show you how remarkably indirect may be such
natural selective agencies as I have referred to, I will
conclude by noticing a case mentioned by Mr. Darwin,
and which is certainly one of the most curious of its
kind. It is that of the Humble Bee. It has been
noticed that there are a great many more humble bees
in the neighbourhood of towns, than out in the open
country ; and the explanation of the matter is this : the
humble bees build nests, in which they store their honey
and deposit the larvoe and eggs. The field mice are
amazingly fond of the honey and larvae ; therefore,
wherever there are plenty of field mice, as in the coun-
try, the humble bees are kept down ; but in the neigh-
bourhood of towns, the number of cats which prowl
about the fields eat up the field mice, and of course the
more mice they eat up the less there are to prey upon
the larvse of the bees — the cats are therefore the indi-

126 CONDITIONS, ETC.

eect helpers of the bees.* Coming back a step farther
we may say that the old maids are also indirect friends
of the humble bees, and indirect enemies of the field
mice, as they keep the cats which eat up the latter !
This is an illustration somewhat beneath the dignity of
the subject, perhaps, but it occurs to me in passing, and
with it I will conclude this lecture.

* The humble bees, on the other hand, are direct helpers of
some plants, such as the heartsease and red clover, which are
fertilized by the visits of the bees; and they are indirect helpers
of the numerous insects which are more or less completely sup-
ported by the heartsease and red clover.

LECTUBE VI.

A CRITICAL EXAMINATION OF THE POSITION OF
MR. DARWIN'S WORK, " ON THE ORIGIN OF
SPECIES," IN RELATION TO THE COMPLETE
THEORY OF THE CAUSES OF THE PHENOME-
NA OF ORGANIC NATURE.

In the preceding five lectures I have endeavoured to
give you an account of those facts, and of those reason-
ings from facts, which form the data upon which all
theories regarding the causes of the phenomena of or-
ganic nature must be based. And, although I have had
frequent occasion to quote Mr. Darwin — as all persons
hereafter, in speaking upon these subjects, will have
occasion to quote his famous book on the " Origin of
Species," — you must yet remember that, wherever I
have quoted him, it has not been upon theoretical
points, or for statements in any way connected with his
particular speculations, but on matters of fact, brought
forward by himself, or collected by himself, and which
appear incidentally in his book. If a man will make
a book, professing to discuss a single question, an en-
cyclopaedia, I cannot help it.

Now, having had an opportunity of considering in
this sort of way the different statements bearing upon
all theories whatsoever, I have to-night to lay before

128 me. darwin's woek and

you, as fairly as I can, what is Mr. Darwin's view of the
matter and what position his theories hold, when judged
by the principles which I have previously laid down as
deciding our judgments upon all theories and hypotheses.
I have already stated to you that the inquiry respect-
ing the causes of the phenomena of organic nature re-
solves itself into two problems — the first being the
question of the origination of living or organic beings ;
and the second being the totally distinct problem of the
modification and perpetuation of organic beings when
they have already come into existence. The first ques-
tion Mr. Darwin does not touch ; he does not deal with
it at all ; but he says — given the origin of organic mat-
ter — supposing its creation to have already taken place,
my object is to show in consequence of what laws and
what demonstrable properties of organic matter, and of
its environments, such states of organic nature as those
with which we are acquainted must have come about.
This, you will observe, is a perfectly legitimate propo-
sition ; every person has a right to define the limits of
the inquiry which he sets before himself ; and yet it is
a most singular thine* that in all the multifarious, and
not unfrequently, ignorant attacks which have been made
upon the " Origin of Species," there is nothing which has
been more speciously criticised than this particular limi-
tation. If people have nothing else to urge against the
book, they say— " "Well, after all, you see Mr. Darwin's
explanation of the ' Origin of Species' is not good for
much, because, in the long run, he admits that he does
not know how organic matter began to exist. But if
you admit any special creation for the first particle of
organic matter you may just as well admit it for all the
rest ; five hundred or five thousand distinct creations

THE PHENOMENA OF ORGANIC NATURE. 120

are just as intelligible, and just as little difficult to
understand, as one." The answer to these cavils is
two-fold. In the first place, all human inquiry must
stop • somewhere ; all our knowledge and all our inves-
tigation cannot take us beyond the limits set by the
finite and restricted character of our faculties, or de-
stroy the endless unknown, which accompanies, like
its shadow, the endless procession of phenomena. So
far as I can venture to offer an opinion on such a
matter, the purpose of our being in existence, the
highest object that human beings can set before them-
selves, is not the pursuit of any such chimera as the
annihilation of the unknown ; but it is simply the un-
wearied endeavour to remove its boundaries a little
further from our little sphere of action.

I wonder if any historian would for a moment admit
the objection, that it is preposterous to trouble ourselves
about the history of the Roman Empire, because we do
not know anything positive about the origin and first
building of the city of Rome ! Would it be a fair ob-
jection to urge respecting the sublime discoveries of a
Newton, or a Kepler, those great philosophers, whose
discoveries have been of the profoundest benefit and
service to all men, — to say to them — " After all that
you have told us as to how the planets revolve, and how
they are maintained in their orbits, you cannot tell us
what is the cause of the origin of the sun, moon, and
stars. So what is the use of what you have clone ? "
Yet these objections would not be one whit more pre-
posterous than the objections which have been made to
the " Origin of Species." Mr. Darwin, then, had a
perfect right to limit his inquiry as he pleased, and the
only question for us — the inquiry being so limited — is
6*

130 mr. darwin's work and

to ascertain whether the method of his inquiry is sound
or unsound ; whether he has obeyed the canons which
must guide and govern all investigation, or whether he
has broken them ; and it was because our inquiry this
evening is essentially limited to that question that I
spent a good deal of time in a former lecture (which,
perhaps some of you thought might have been better
employed) in endeavouring to illustrate the method and
nature of scientific inquiry in general. We shall now
have to put in practice the principles that I then laid
down.

I stated to you in substance, if not in words, that
wherever there are complex masses of phenomena to be
inquired into, whether they be phenomena of the affairs
of daily life, or whether they belong to the more abstruse
and difficult problems laid before the philosopher, our
course of proceeding in unravelling that complex chain
of phenomena with a view to get at its cause, is always
the same ; in all cases we must invent a hypothesis ; we
must place before ourselves some more or less likely
supposition respecting that cause ; and then, having
assumed a hypothesis, having supposed a cause for the
phenomena in question, we must endeavour, on the one
hand, to demonstrate our hypothesis, or, on the other, to
upset and reject it altogether, by testing it in three
ways. We must, in the first place, be prepared to
prove that the supposed causes of the phenomena
exist in nature ; that they are what the logicians
call vera causae — true causes ; — in the next place, we
should be prepared to show that the assumed causes of
the phenomena are competent to produce such pheno-
mena as those which we wish to explain by them ; and
in the last place, we ought to be able to show that no

THE PHENOMENA OF ORGANIC NATURE. 131

other known causes are competent to produce these
phenomena. If we can succeed in satisfying these
three conditions, we shall have demonstrated our hypo-
thesis ; or rather I ought to say, we shall have proved
it as far as certainty is possible for us ; for, after all,
there is no one of our surest convictions which may not
be upset, or at any rate modified by a further accession
of knowledge. It was because it satisfied these con-
ditions that we accepted the hypothesis as to the dis-
appearance of the tea-pot and spoons in the case I sup-
posed in a previous lecture ; we found that our hypo-
thesis on that subject was tenable and valid, because
the supposed cause existed in nature, because it was
competent to account for the phenomena, and because
no other known cause was competent to account for
them ; and it is upon similar grounds that any hypo-
thesis you choose to name is accepted in science as
tenable and valid.

What is Mr. Darwin's hypothesis ? A I apprehend
it — for I have put it into a shape more convenient for
common purposes than I could find verbatim in his book
— as I apprehend it, I say, it is, that all the phenome-
na of organic nature, past and present, result from,
or are caused by, the inter-action of those properties of
organic matter, which we have called Atavism and
Variability, with the Conditions of Existence ; or,
in other words, — given the existence of organic matter,
its tendency to transmit its properties, and its tendency
occasionally to vary ; and, lastly, given the conditions
of existence by which organic matter is surrounded —
that these put together are the causes of the Present
and of the Past conditions of Organic Nature.

Such is the hypothesis as I understand it. Now

132 mr. darwin's work and

let us see how it will stand the various tests which I laid
down just now. In the first place, do these supposed
causes of the phenomena exist in nature ? Is it the
fact that in nature these properties of organic matter
— atavism and variability — and those phenomena which
we have called the conditions of existence, — is it true
that they exist ? Well, of course, if they do not exist,
all that I have told you in the last three or four lec-
tures must be incorrect, because I have been attempting
to prove that they do exist, and I take it that there is
abundant evidence that they do exist ; so far, therefore,
the hypothesis does not break down.

But in the next place comes a much more difficult
inquiry : — Are the causes indicated competent to give
rise to the phenomena of organic nature ? I suspect
that this is indubitable to a certain extent. It is de-
monstrable, I think, as I have endeavoured to show
you, that they are perfectly competent to give rise to all
the phenomena which are exhibited by Races in nature.
Furthermore, I believe that they are quite competent
to account for all that we may call purely structural
phenomena which are exhibited by Species in nature.
On that point also I have already enlarged somewhat.
Again, I think that the causes assumed are competent
to account for most of the physiological characteristics
of species, and I not only think that they are competent
to account for them, but I think that they account for
many things which otherwise remain wholly unaccount-
able and inexplicable, and I may say incomprehensible.
For a full exposition of the grounds on which this con-
viction is based, I must refer you to Mr. Darwin's
work ; all that I can do now is to illustrate what I have
said by two or three cases taken almost at random.

THE PHENOMENA OF ORGANIC NATURE. 133

I drew your attention, on a previous evening, to the
facts which are embodied in our systems of Classifi-
cation, which are the results of the examination and
comparison of the different members of the animal
kingdom one with another. I mentioned that the
whole of the animal kingdom is divisible into five sub-
kingdoms ; that each of these sub-kingdoms is again
divisible into provinces ; that each province may be
divided into classes, and the classes into the successively
smaller groups, orders, families, genera, and species.

Now, in each of these groups, the resemblance in
structure among the members of the group is closer in
proportion as the group is smaller. Thus, a man and
a worm are members of the animal kingdom in virtue
of certain apparently slight though really fundamental
resemblances which they present. But a man and a
fish are members of the same Sub-kingdom Yertebrata,
because they are much more like one another than
either of them is to a worm, or a snail, or any member
of the other sub-kingdoms. For similar reasons men
and horses are arranged as members of the same Class,
Mammalia / men and apes as members of the same
Order, Primates / and if there were any animals more
like men than they were like any of the apes, and yet
different from men in important and constant particu-
lars of their organization, we should rank them as
members of the same Family, or of the same Genus,
but as of distinct Species.

That it is possible to arrange all the varied forms of
animals into groups, having this sort of singular subor-
dination one to the other, is a very remarkable circum-
stance ; but, as Mr. Darwin remarks, this is a result
which is quite to be expected, if the principles which he

134 mr. darwin's work and

lays down be correct. Take the case of the races which
are known to be produced by the operation of atavism
and variability, and the conditions of existence which
check and modify these tendencies. Take the case of
the pigeons that I brought before you : there it was
shown that they might be all classed as belonging to
some one of five principal divisions, and that within
these divisions other subordinate groups might be
formed. The members of these groups are related to
one another in just the same way as the genera of a
family, and the groups themselves as the families of an
order, or the orders of a class ; while all have the same
sort of structural relations with the wild Rock-pigeon,
as the members of any great natural group have with a
real or imaginary typical form. Now, we know that
all varieties of pigeons of every kind have arisen by a
process of selective breeding from a common stock, the
Rock-pigeon ; hence, you see, that if all species of ani-
mals have proceeded from some common stock, the gen-
eral character of their structural relations, and of our
systems of classification, which express those relations,
would be just what we find them to be. In other
words, the hypothetical cause is, so far, competent to
produce effects similar to those of the real cause.

Take, again, another set of very remarkable facts, —
the existence of what are called rudimentary organs,
organs for which we find no obvious use, in the par-
ticular animal economy in which they are found, and
yet which are there.

Such are the splint-like bones in the leg of the
horse, which I here show you, and which correspond
with bones which belong to certain toes and fingers
in the human hand and foot. In the horse you see

THE PHENOMENA OF ORGANIC NATURE. 135

they are quite rudimentary, and bear neither toes nor
fingers ; so that the horse has only one " finger " in
his fore-foot and one " toe " in his hind-foot. But it
is a very curious thing that the animals closely allied
to the horse show more toes than he ; as the rhinoceros,
for instance : he has these extra toes well formed, and
anatomical facts show very clearly that he is very closely
related to the horse indeed. So we may say that ani-
mals, in an anatomical sense nearly related to the
horse, have those parts which are rudimentary in him,
fully developed.

Again, the sheep and the cow have no cutting-teeth,
but only a hard pad in the upper jaw. That is the
common characteristic of ruminants in general. But
the calf has in its upper jaw some rudiments of teeth
which never are developed, and never play the part
of teeth at all. Well, if you go back in time, you find
some of the older, now extinct, allies of the ruminants
have well-developed teeth in their upper jaws ; and at
the present day the pig (which is in structure closely
connected with ruminants) has well-developed teeth in
its upper jaws ; so that here is another instance of
organs well developed and very useful, in one animal,
represented by rudimentary organs, for which we can
discover no purpose whatsoever, in another closely
allied animal. The whalebone whale, again, has horny
" whalebone " plates in its mouth, and no teeth ; but
the young foetal whale, before it is born, has teeth in
its jaws ; they, however, are never used, and they never
come to anything. But other members of the group to
which the whale belongs have well-developed teeth in
both jaws.

Upon any hypothesis of special creation, facts of this

136 mr. darwin's work and

kind appear to me to be entirely unaccountable and
inexplicable, but they cease to be so if you accept Mr.
Darwin's hypothesis, and see reason for believing that
the whalebone whale and the whale with teeth in its
mouth both sprang from a whale that had teeth, and
that the teeth of the foetal whale are merely remnants
— recollections, if we may so say — of the extinct whale.
So in the case of the horse and the rhinoceros : suppose
that both have descended by modification from some
earlier form which had the normal number of toes, and
the persistence of the rudimentary bones which no
longer support toes in the horse becomes compre-
hensible.

In the language that we speak in England, and in
the language of the Greeks, there are identical verbal
roots, or elements entering into the composition of
words. The fact remains unintelligible so long as we
suppose English and Greek to be independently created
tongues ; but when it is shown that both languages are
descended from one original, the Sanscrit, we give an
explanation of that resemblance. In the same way the
existence of identical structural roots, if I may so term
them, entering into the composition of widely different
animals, is striking evidence in favour of the descent
of those animals from a common original.

To turn to another kind of illustration : — If you
regard the whole series of stratified rocks — that enor-
mous thickness of sixty or seventy thousand feet that
1 have mentioned before, constituting the only record
we have of a most prodigious lapse of time, that time
being, in all probability, but a fraction of that of which
we have no record ; — if you observe in these successive
strata of rocks successive groups of animals arising and

THE PHENOMENA OF OEGANIC NATUEE. 137

dying out, a constant succession, giving you the same
kind of impression, as you travel from one group of
strata to another, as you would have in travelling from
one country to another ; — when you find this constant
succession of forms, their traces obliterated except to
the man of science, — when you look at this wonderful
history, and ask what it means, it is only a paltering
with words if you are offered the reply, — " They were
so created."

But if, on the other hand, you look on all forms of
organized beings as the results of the gradual modifi-
cation of a primitive type, the facts receive a meaning,
and you see that these older conditions are the necessary
predecessors of the present. Yiewed in this light the
facts of palaeontology receive a meaning — upon any
other hypothesis, I am unable to see, in the slightest
degree, what knowledge or signification we are to draw
out of them. Again, note as bearing upon the same
point, the singular likeness which obtains between the
successive Faunae and Florae, whose remains are pre-
served on the rocks : you never find any great and
enormous difference between the immediately successive
Faunas and Floras, unless you have reason to believe
tli ere has also been a great lapse of time or a great
change of conditions. The animals, for instance, of the
newest tertiary rocks, in any part of the world, are
always, and without exception, found to be closely allied
with those which now live in that part of the world.
For example, in Europe, Asia, and Africa, the large
mammals are at present rhinoceroses, hippopotamuses,
elephants, lions, tigers, oxen, horses, &c. ; and if you
examine the newest tertiary deposits, which contain the
animals and plants which immediately preceded those

138 MR. DARWIN 'S WORK AND

which now exist in the same country, yon do not find
gigantic specimens of ant-eaters and kangaroos, but you
find rhinoceroses, elephants, lions, tigers, &c, — of differ-
ent species to those now living, — but still their close
allies. If you turn to South America, where, at the
present day, we have great sloths and armadilloes and
creatures of that kind, what do you find in the newest
tertiaries ? You find the great sloth-like creature, the
Megatherium, and the great armadillo, the Glyptodon,
and so on. And if you go to Australia you find the
same law holds good, namely, that that condition of or-
ganic nature which has preceded the one which now
exists, presents differences perhaps of species, and of
genera, but that the great types of organic structure
are the same as those which now flourish.

What meaning has this fact upon any other hypo-
thesis or supposition than one of successive modifica-
tion ? But if the population of the world, in any age,
is the result of the gradual modification of the forms
which peopled it in the preceding age, — if that has been
the case, it is intelligible enough ; because we may ex-
pect that the creature that results from the modification
of an elejmantine mammal shall be something like an
elephant, and the creature which is produced by the
modification of an armadillo-like mammal shall be like
an armadillo. Upon that supposition, I say, the facts
are intelligible ; upon any other, that I am aware of,
they are not.

So far, the facts of palaeontology are consistent with
almost any form of the doctrine of progressive modifi-
cation ; they would not be absolutely inconsistent with
the wild speculations of De Maillet, or with the less
objectionable hypothesis of Lamarck. But Mr. Dar-

THE PHENOMENA OF ORGANIC NATURE. 139

win's views have one peculiar merit ; and that is, that
they are perfectly consistent with an array of facts which
are utterly inconsistent with and fatal to, any other
hypothesis of progressive modification which has yet
been advanced. It is one remarkable peculiarity of
Mr. Darwin's hypothesis that it involves no necessary
progression or incessant modification, and that it is
perfectly consistent with the persistence for any length
of time of a given primitive stock, contemporaneously
with its modifications. To return to the case of the
domestic breeds of pigeons, for example ; you have the
Dove-cot pigeon, which closely resembles the Rock
pigeon, from which they all started, existing at the
same time with the others. And if species are devel-
oped in the same way in nature, a primitive stock and
its modifications may, occasionally, all find the con-
ditions fitted for their existence ; and though they
come into competition, to a certain extent, with one
another, the derivative species may not necessarily ex-
tirpate the primitive one, or vice versa.

Now palaeontology shows us many facts which are
perfectly harmonious with these observed effects of the
process by which Mr. Darwin supposes species to have
originated, but which appear to me to be totally in-
consistent with any other hypothesis which has been
proposed. There are some groups of animals and
plants, in the fossil world, which have been said to
belong to " persistent types," because they have per-
sisted, with very little change indeed, through a very
great range of time, while everything about them has
changed largely. There are families of fishes whose
type of construction has persisted all the way from the
carboniferous rock right up to the cretaceous ; and

140 MR. darwin's work and

others which have lasted through almost the whole
range of the secondary rocks, and from the lias to the
older tertiaries. It is something stupendous this — to
consider a genus lasting without essential modifications
through all this enormous lapse of time while almost
everything else was changed and modified.

d CD CD

Thus I have no doubt that Mr. Darwin's hypothesis
will be found competent to explain the majority of
the phenomena exhibited by species in nature ; but in
an earlier lecture I spoke cautiously with repect to its
power of explaining all the physiological peculiarities
of species.

There is, in fact, one set of these peculiarities which
the theory of selective modification, as it stands at
present, is not wholly competent to explain, and that is
the group of phenomena which I mentioned to you
under the name of Hybridism, and which I explained
to consist in the sterility of the offspring of certain spe-
cies when crossed one with another. It matters not one
whit whether this sterility is universal, or whether it
exists only in a single case. Every hypothesis is bound
to explain, or, at any rate, not be inconsistent with, the
whole of the facts which it professes to account for ; and
if there is a single one of these facts which can be shown
to be inconsistent with (I do not merely mean inexpli-
cable by, but contrary to,) the hypothesis, the hypothesis
falls to the ground, — it is worth nothing. One fact with
which it is positively inconsistent is worth as much, and
as powerful in negativing the hypothesis, as five hun-
dred. If I am right in thus defining the obligations of
a hypothesis, Mr. Darwin, in order to place his views
beyond the reach of all possible assault, ought to be
able to demonstrate the possibility of developing from

THE PHENOMENA OF ORGANIC NATURE. 141

a particular stock by selective breeding, two forms,
which should either be unable to cross one with
another, or whose cross-bred offspring should be infer-
tile with one another.

For, you see, if you have not done that you have not
strictly fulfilled all the conditions of the problem ; you
have not shown that you can produce, by the cause
assumed, all the phenomena which you have in nature.
Here are the phenomena of Hybridism staring you in
the face, and you cannot say, " I can, by selective
modification, produce these same results." Now, it is
admitted on all hands that, at present, so far as experi-
ments have gone, it has not been found possible to pro-
duce this complete physiological divergence by selective
breeding. I stated this very clearly before, and I now
refer to the point, because, if it could be proved, not
only that this has not been done, but that it cannot be
done ; if it could be demonstrated that it is impossible
to breed selectively, from any stock, a form which shall
not breed with another, produced from the same stock ;
and if we were shown that this must be the necessary
and inevitable result of all experiments, I hold that
Mr. Darwin's hypothesis would be utterly shattered.

But has this been done ? or what is really the state
of the case ? It is simply that, so far as we have gone
yet with our breeding, we have not produced from a
common stock two breeds which are not more or less
fertile with one another.

I do not know that there is a single fact which
would justify any one in saying that any degree of ster-
ility has been observed between breeds absolutely
known to have been produced by selective breeding
from a common stock. On the other hand, I do not

142 mr. dakwin's woek and

know that there is a single fact which can justify any-
one in asserting that such sterility cannot be produced
by proper experimentation. For my own part, I see
every reason to believe that it may, and will be so pro-
duced. For, as Mr. Darwin has very properly urged,
when we consider the phenomena of sterility, we find
they are most capricious ; we do not know what it is
that the sterility depends on. There are some animals
which will not breed in captivity ; whether it arises
from the simple fact of their being shut up and deprived
of their liberty, or not, we do not know, but they
certainly will not breed. What an astounding thing
this is, to find one of the most important of all functions
annihilated by mere imprisonment !

So, again, there are cases known of animals which
have been thought by naturalists to be undoubted spe-
cies, which have yielded fertile hybrids ; while there
are other species which present what everybody believes
to be varieties' 55 ' which are more or less infertile with
one another. There are other cases which are truly
extraordinary ; there is one, for example, which has
been carefully examined, — of two kinds of sea-w T eed,
of which the male element of the one, which we may
call A, fertilizes the female element of the other, B ;
while the male element of B w r ill not fertilize the female
element of A ; so that, while the former experiment
seems to show us that they are varieties, the latter
leads to the conviction that they are species.

* And as I conceive with very good reason ; but if any objec-
tor urges that we cannot prove that they have been produced by
artificial or natural selection, the objection must be admitted —
ultra-sceptical as it is. But in science, scepticism is a duty.

THE PHENOMENA OF ORGANIC NATURE. 143

When we see how capricious and uncertain this
sterility is, how unknown the conditions on which it
depends, I say that we have no right to affirm that
those conditions will not be better understood by and
by, and we have no ground for supposing that we may
not be able to experiment so as to obtain that crucial
result which I mentioned just now. So that though
Mr. Darwin's hypothesis does not completely extricate
us from this difficulty at present, we have not the least
right to say it will not do so.

There is a wide gulf between the thing you cannot
explain and the thing that upsets you altogether.
There is hardly any hypothesis in this world which
has not some fact in connection with it which has not
been explained, but that is a very different affair to a
fact that entirely opposes your hypothesis ; in this case
all you can say is, that your hypothesis is in the same
position as a good many others.

Now, as to the third test, that there are no other
causes competent to explain the phenomena, I explained
to you that one should be able to say of a hypothesis,
that no other known causes than those supposed by it
are competent to give rise to the phenomena. Here,
I think, Mr. Darwin's view is pretty strong. I really
believe that the alternative is either Darwinism or
nothing, for I do not know of any rational conception
or theory of the organic universe which has any scien-
tific position at all beside Mr. Darwin's. I do not
know of any proposition that has been put before us
with the intention of explaining the phenomena of
organic nature, which has in its favor a thousandth
part of the evidence which may be adduced in favour
of Mr. Darwin's views. Whatever may be the objec-

144 mb. dakwin's wokk and

tions to his views, certainly all others are absolutely out
of court.

Take the Lamarckian hypothesis, for example. La-
marck was a great naturalist, and to a certain extent
went the right way to work ; he argued from what was
undoubtedly a true cause of some of the phenomena of
organic nature. He said it is a matter of experience
that an animal may be modified more or less in conse-
quence of its desires and consequent actions. Thus, if
a man exercise himself as a blacksmith, his arms will
become strong and muscular ; such organic modifica-
tion is a result of this particular action and exercise.
Lamarck thought that by a very simple supposition
based on this truth he could explain the oirgin of the
various animal species : he said, for example, that the
short-legged birds which live on fish, had been converted
into the long-legged waders by desiring to get the fish
without wetting their feet, and so stretching their legs
more and more through successive generations. If
Lamarck could have shown experimentally, that even
races of animals could be produced in this way, there
might have been some ground for his speculations.
But he could show nothing of the kind, and his hy-
pothesis has pretty well dropped into oblivion, as it de-
served to do. I said in an earlier lecture that there are
hypotheses and hypotheses, and when people tell you
that Mr. Darwin's strongly-based hypothesis is nothing
but a mere modification of Lamarck's, you will know
what to think of their capacity for forming a judgment
on this subject.

But you must recollect that when I say I think it
is either Mr. Darwin's hypothesis or nothing ; that
either we must take his view, or look upon the whole

THE PHENOMENA OF ORGANIC NATURE. 145

of organic nature as an enigma, the meaning of which
is wholly hidden from us ; you must understand that I
mean that I accept it provisionally, in exactly the same
way as I accept any other hypothesis. Men of science
do not pledge themselves to creeds ; they are bound by
articles of no sort ; there is not a single belief that it
is not a bounden duty with them to hold with a light
hand and to part with it, cheerfully, the moment it is
really proved to be contrary to any fact, great or small.
And if in course of time I see good reasons for such a
proceeding, I shall have no hesitation in coming before
you, and pointing out any change in my opinion without
finding the slightest occasion to blush for so doing. So
I say that we accept this view as we accept any other,
so long as it will help us, and we feel bound to retain it
only so long as it will serve our great purpose — the
improvement of Man's estate and the widening of his
knowledge. The moment this, or any other conception,
ceases to be useful for these purposes, away with it to
the four winds ; we care not what becomes of it !

But to say truth, although it has been my business
to attend closely to the controversies roused by the
publication of Mr. Darwin's book, I think that not one
of the enormous mass of objections and obstacles which
have been raised is of any great value, except that
sterility case which I brought before you just now.
All the rest are misunderstandings of some sort, arising
either from prejudice, or want of knowledge, or still
more from want of patience and care in reading the
work.

For you must recollect that it is not a book to be
read with as much ease as its pleasant style may lead
you to imagine. You spin through it as if it were a

146 mr. darwin's work and

novel the first time you read it, and think you know all
about it ; the second time you read it you think you
know rather less about it ; and the third time, you are
amazed to find how little you have really apprehended
its vast scope and objects. I can positively say that I
never take it up without finding in it some new view,
or light, or suggestion that I have not noticed before.
That is the best characteristic of a thorough and pro-
found book ; and I believe this feature of the " Origin
of Species " explains why so many persons have ven-
tured to pass judgment and criticisms upon it which
are by no means worth the paper they are written on.

Before concluding these lectures there is one point
to which I must advert, — though, as Mr. Darwin has
said nothing about man in his book, it concerns myself
rather than him ; — for I have strongly maintained on
sundry occasions that if Mr. Darwin's views are sound,
they apply as much to man as to the lower mammals,
seeing that it is perfectly demonstrable that the struc-
tural differences w T hich separate man from the apes are
not greater than those wdiich separate some apes from
others. There cannot be the slightest doubt in the
world that the argument which applies to the improve-
ment of the horse from an earlier stock, or of ape from
ape, applies to the improvement of man from some
simpler and lower stock than man. There is not a
single faculty — functional or structural, moral, intel-
lectual, or instinctive, — there is no faculty whatever
that is not capable of improvement ; there is no faculty
whatsoever which does not depend upon structure, and
as structure tends to vary, it is capable of being im-
proved.

Well, I have taken a good deal of pains at various

THE PHENOMENA OF ORGANIC NATURE. 147

times to prove this, and I have endeavoured to meet
the objections of those who maintain, that the structural
differences between man and the lower animals are of
so vast a character and enormous extent, that even if
Mr. Darwin's views are correct, you cannot imagine this
particular modification to take place. It is, in fact,
easy matter to prove that, so far as structure is con-
cerned, man differs to no greater extent from the ani-
mals which are immediately below him than these do
from other members of the same order. Upon the
other hand, there is no one who estimates more highly
than I do the dignity of human nature, and the width
of the gulf in intellectual and moral matters, which lies
between man and the whole of the lower creation.

But I find this very argument brought forward
vehemently by some. " You say that man has pro-
ceeded from a modification of some lower animal, and
you take pains to prove that the structural differences
which are said to exist in his brain do not exist at all,
and you teach that all functions, intellectual, moral,
and others, are the expression or the result, in the long
run, of structures, and of the molecular forces which
they exert." It is quite true that I do so.

" Well, but," I am told at once, somewhat triumph-
antly, " you say in the same breath that there is a great
moral and intellectual chasm between man and the
lower animals. How is this possible when you declare
that moral and intellectual characteristics depend on
structure, and yet tell us that there is no such gulf be-
tween the structure of man and that of the lower ani-
mals ? "

I think that objection is based upon a misconception
of the real relations which exist between structure and

'/

148 mr. darwin's work and

function, between mechanism and work. Function is
the expression of molecular forces and arrangements no
doubt ; but, does it follow from this, that variation in
function so depends upon variation in structure that the
former is always exactly proportioned to the latter ? If
there is no such relation, if the variation in function
which follows on a variation in structure may be enor-
mously greater than the variation of the structure, then,
you see, the objection falls to the ground.

Take a couple of watches — made by the same -maker,
and as completely alike as possible ; set them upon the
table, and the function of each — which is its rate of
going — will be performed in the same manner, and you
shall be able to distinguish no difference between them ;
but let me take a pair of pincers, and if my hand is
steady enough to do it, let me just lightly crush to-
gether the bearings of the balance-wheel, or force to a
slightly different angle the teeth of the escapement of
one of them, and of course you know the immediate
result will be that the watch, so treated, from that mo-
ment will cease to go. But what proportion is there
between the structural alteration and the functional
result ? Is it not perfectly obvious that the alteration
is of the minutest kind, yet that slight as it is, it has
produced an infinite difference in the performance of
the functions of these two instruments ?

Well, now, apply that to the present question.
What is it that constitutes and makes man what he is ?
What is it but his power of language — that language
f. giving him the means of recording his experience —
making every generation somewhat wiser than its
predecessor, — more in accordance with the established
order of the universe ?

THE PHENOMENA OF ORGANIC NATURE. 149

What is it but this power of speech, of recording
experience, which enables men to be men — looking
before and after and, in some dim sense, understanding
the working of this wondrous universe — and which dis-
tinguishes man from the whole of the brute world ? I
say that this functional difference is vast, unfathomable,
and truly infinite in its consequences ; and I say at the
same time, that it may depend upon structural differ-
ences which shall be absolutely inappreciable to us with
our present means of investigation. "What is this very
speech that we are talking about ? I am speaking to
you at this moment, but if you were to alter, in the
minutest degree, the proportion of the nervous forces
now active in the two nerves which supply the muscles
of my glottis, I should become suddenly dumb. The
voice is produced only so long as the vocal chords are .
parallel ; and these are parallel only so long as certain
muscles contract with exact equality ; and that again
depends on the equality of action of those two nerves I
spoke of. So that a change of the minutest kind in the
structure of one of these nerves, or in the structure of
the part in which it originates, or of the supply of blood
to that part, or of one of the muscles to which it is dis-
tributed, might render all of us dumb. But a race of
dumb men, deprived of all communication with those
who could speak, would be little indeed removed from
the brutes. And the moral and intellectual difference
between them and ourselves would be practically in-
finite, though the naturalist should not be able to find
a single shadow of even specific structural difference.

But let me dismiss this question now, and, in con-
clusion, let me say that you may go away with it as my
mature conviction, that Mr. Darwin's work is the

150 mr. darwin's work, etc.

greatest contribution which has been made to biological
science since the publication of the " Regne Animal "
of Ciivier, and since that of the " History of Develop-
ment," of Yon Baer. I believe that if you strip it of
its theoretical part it still remains one of the greatest
encyclopaedias of biological doctrine that any one man
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marked by however slight, but favorable peculiarities.

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