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Lectures and Essays

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Title: Lectures and Essays

Author: Thomas Henry Huxley


        
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Lectures and Essays

BY

THOMAS HENRY HUXLEY

MACMILLAN AND CO., LIMITED

ST. MARTIN'S STREET, LONDON

1910




THE WORKS OF THOMAS HENRY HUXLEY.


THE LIFE AND WORKS OF THOMAS HENRY HUXLEY, F.R.S. _Eversley Series_.

Twelve vols. Globe 8vo, 4s. net each.

VOL. I. METHOD AND RESULTS.
    II. DARWINIANA.
   III. SCIENCE AND EDUCATION.
    IV. SCIENCE AND HEBREW TRADITION.
     V. SCIENCE AND CHRISTIAN TRADITION.
    VI. HUME, WITH HELPS TO THE STUDY OF BERKELEY.
   VII. MAN'S PLACE IN NATURE.
  VIII. DISCOURSES, BIOLOGICAL AND GEOLOGICAL.
    IX. EVOLUTION AND ETHICS, AND OTHER ESSAYS.
     X. }
    XI. } THE LIFE AND LETTERS OF PROFESSOR HUXLEY.
   XII. }

       *       *       *       *       *

APHORISMS AND REFLECTIONS FROM THE WORKS OF T.H. HUXLEY. Selected by
HENRIETTA A. HUXLEY. With Portrait. Pott 8vo, _2s. 6d._ net. Also cloth
elegant, _2s. 6d._ net. Limp Leather, _3s. 6d._ net. _Golden Treasury
Series_.

AMERICAN ADDRESSES. 8vo, _6s. 6d._

CRITIQUES AND ADDRESSES. 8vo, _10s. 6d._

LESSONS IN ELEMENTARY PHYSIOLOGY. F'cap 8vo, _4s. 6d._ QUESTIONS.
Pott 8vo, _1s. 6d._

LAY SERMONS, ADDRESSES, AND REVIEWS. 8vo, _7s. 6d._

INTRODUCTORY PRIMER OF SCIENCE. Pott 8vo, _1s._

PHYSIOGRAPHY: AN INTRODUCTION TO THE STUDY OF NATURE. Crown 8vo,
_6s._

PHYSIOGRAPHY. A New Edition. Revised and partly re-written by R.A.
GREGORY. Globe 8vo, _4s. 6d._

SOCIAL DISEASES AND WORSE REMEDIES. Crown 8vo. Sewed, _1s._ net.

LECTURES AND ESSAYS. 8vo. Sewed. _6d._

ESSAYS: ETHICAL AND POLITICAL. 8vo, Sewed. _6d._

LIFE OF HUME. Crown 8vo. Library Edition. _2s._ net. Popular Edition,
_1s. 6d._ Sewed. _1s._ F'cap 8vo. Pocket Edition. _1s._ net. _English
Men of Letters._


By Prof. T.H. HUXLEY, assisted by Prof. H.N. MARTIN.

A COURSE OF ELEMENTARY INSTRUCTION IN PRACTICAL BIOLOGY. Revised and
extended by G.B. HOWES and D.H. SCOTT. Crown 8vo, _10s. 6d._

MACMILLAN AND CO., LTD., LONDON.




LECTURES AND ESSAYS


BY

THOMAS HENRY HUXLEY




MACMILLAN AND CO., LIMITED ST. MARTIN'S STREET, LONDON 1910




CONTENTS.
                                                  PAGE

AUTOBIOGRAPHY                                       5

LECTURES ON EVOLUTION                              11

ON THE PHYSICAL BASIS OF LIFE                      45

NATURALISM AND SUPERNATURALISM                     57

THE VALUE OF WITNESS TO THE MIRACULOUS             71

AGNOSTICISM                                        83

THE CHRISTIAN TRADITION IN RELATION TO JUDAIC
  CHRISTIANITY                                     96

AGNOSTICISM AND CHRISTIANITY                      108


_First Edition, February_ 1902.
_Reprinted, December_ 1902, 1903, 1904, 1910.




AUTOBIOGRAPHY


I was born about eight o'clock in the morning on the 4th of May, 1825,
at Ealing, which was, at that time, as quiet a little country village
as could be found within half-a-dozen miles of Hyde Park Corner. Now it
is a suburb of London with, I believe, 30,000 inhabitants. My father was
one of the masters in a large semi-public school which at one time had a
high reputation. I am not aware that any portents preceded my arrival in
this world, but, in my childhood, I remember hearing a traditional
account of the manner in which I lost the chance of an endowment of
great practical value. The windows of my mother's room were open, in
consequence of the unusual warmth of the weather. For the same reason,
probably, a neighbouring beehive had swarmed, and the new colony,
pitching on the window-sill, was making its way into the room when the
horrified nurse shut down the sash. If that well-meaning woman had only
abstained from her ill-timed interference, the swarm might have settled
on my lips, and I should have been endowed with that mellifluous
eloquence which, in this country, leads far more surely than worth,
capacity, or honest work, to the highest places in Church and State. But
the opportunity was lost, and I have been obliged to content myself
through life with saying what I mean in the plainest of plain language,
than which, I suppose, there is no habit more ruinous to a man's
prospects of advancement.

Why I was christened Thomas Henry I do not know; but it is a curious
chance that my parents should have fixed for my usual denomination upon
the name of that particular Apostle with whom I have always felt most
sympathy. Physically and mentally I am the son of my mother so
completely--even down to peculiar movements of the hands, which made
their appearance in me as I reached the age she had when I noticed
them--that I can hardly find any trace of my father in myself, except an
inborn faculty for drawing, which unfortunately, in my case, has never
been cultivated, a hot temper, and that amount of tenacity of purpose
which unfriendly observers sometimes call obstinacy.

My mother was a slender brunette, of an emotional and energetic
temperament, and possessed of the most piercing black eyes I ever saw in
a woman's head. With no more education than other women of the middle
classes in her day, she had an excellent mental capacity. Her most
distinguishing characteristic, however, was rapidity of thought. If one
ventured to suggest she had not taken much time to arrive at any
conclusion, she would say, "I cannot help it, things flash across me."
That peculiarity has been passed on to me in full strength; it has often
stood me in good stead; it has sometimes played me sad tricks, and it
has always been a danger. But, after all, if my time were to come over
again, there is nothing I would less willingly part with than my
inheritance of mother wit.

I have next to nothing to say about my childhood. In later years my
mother, looking at me almost reproachfully, would sometimes say, "Ah!
you were such a pretty boy!" whence I had no difficulty in concluding
that I had not fulfilled my early promise in the matter of looks. In
fact, I have a distinct recollection of certain curls of which I was
vain, and of a conviction that I closely resembled that handsome,
courtly gentleman, Sir Herbert Oakley, who was vicar of our parish, and
who was as a god to us country folk, because he was occasionally visited
by the then Prince George of Cambridge. I remember turning my pinafore
wrong side forwards in order to represent a surplice, and preaching to
my mother's maids in the kitchen as nearly as possible in Sir Herbert's
manner one Sunday morning when the rest of the family were at church.
That is the earliest indication I can call to mind of the strong
clerical affinities which my friend Mr. Herbert Spencer has always
ascribed to me, though I fancy they have for the most part remained in a
latent state.

My regular school training was of the briefest, perhaps fortunately, for
though my way of life has made me acquainted with all sorts and
conditions of men, from the highest to the lowest, I deliberately affirm
that the society I fell into at school was the worst I have ever known.
We boys were average lads, with much the same inherent capacity for good
and evil as any others; but the people who were set over us cared about
as much for our intellectual and moral welfare as if they were
baby-farmers. We were left to the operation of the struggle for
existence among ourselves, and bullying was the least of the ill
practices current among us. Almost the only cheerful reminiscence in
connection with the place which arises in my mind is that of a battle I
had with one of my classmates, who had bullied me until I could stand it
no longer. I was a very slight lad, but there was a wild-cat element in
me which, when roused, made up for lack of weight, and I licked my
adversary effectually. However, one of my first experiences of the
extremely rough-and-ready nature of justice, as exhibited by the course
of things in general, arose out of the fact that I--the victor--had a
black eye, while he--the vanquished--had none, so that I got into
disgrace and he did not. We made it up, and thereafter I was unmolested.
One of the greatest shocks I ever received in my life was to be told a
dozen years afterwards by the groom who brought me my horse in a
stable-yard in Sydney that he was my quondam antagonist. He had a long
story of family misfortune to account for his position, but at that time
it was necessary to deal very cautiously with mysterious strangers in
New South Wales, and on inquiry I found that the unfortunate young man
had not only been "sent out," but had undergone more than one colonial
conviction.

As I grew older, my great desire was to be a mechanical engineer, but
the fates were against this, and, while very young, I commenced the
study of medicine under a medical brother-in-law. But, though the
Institute of Mechanical Engineers would certainly not own me, I am not
sure that I have not all along been a sort of mechanical engineer _in
partibus infidelium_. I am now occasionally horrified to think how very
little I ever knew or cared about medicine as the art of healing. The
only part of my professional course which really and deeply interested
me was physiology, which is the mechanical engineering of living
machines; and, notwithstanding that natural science has been my proper
business, I am afraid there is very little of the genuine naturalist in
me. I never collected anything, and species work was always a burden to
me; what I cared for was the architectural and engineering part of the
business, the working out the wonderful unity of plan in the thousands
and thousands of diverse living constructions, and the modifications of
similar apparatuses to serve diverse ends. The extraordinary attraction
I felt towards the study of the intricacies of living structure nearly
proved fatal to me at the outset. I was a mere boy--I think between
thirteen and fourteen years of age--when I was taken by some older
student friends of mine to the first _post-mortem_ examination I ever
attended. All my life I have been most unfortunately sensitive to the
disagreeables which attend anatomical pursuits, but on this occasion my
curiosity overpowered all other feelings, and I spent two or three hours
in gratifying it. I did not cut myself, and none of the ordinary
symptoms of dissection-poison supervened, but poisoned I was somehow,
and I remember sinking into a strange state of apathy. By way of a last
chance, I was sent to the care of some good, kind people, friends of my
father's, who lived in a farmhouse in the heart of Warwickshire. I
remember staggering from my bed to the window on the bright spring
morning after my arrival, and throwing open the casement. Life seemed to
come back on the wings of the breeze, and to this day the faint odour of
wood-smoke, like that which floated across the farm-yard in the early
morning, is as good to me as the "sweet south upon a bed of violets." I
soon recovered, but for years I suffered from occasional paroxysms of
internal pain, and from that time my constant friend, hypochondriacal
dyspepsia, commenced his half century of co-tenancy of my fleshly
tabernacle.

Looking back on my "Lehrjahre," I am sorry to say that I do not think
that any account of my doings as a student would tend to edification. In
fact, I should distinctly warn ingenuous youth to avoid imitating my
example. I worked extremely hard when it pleased me, and when it did
not--which was a very frequent case--I was extremely idle (unless making
caricatures of one's pastors and masters is to be called a branch of
industry), or else wasted my energies in wrong directions. I read
everything I could lay hands upon, including novels, and took up all
sorts of pursuits to drop them again quite as speedily. No doubt it was
very largely my own fault, but the only instruction from which I ever
obtained the proper effect of education was that which I received from
Mr. Wharton Jones, who was the lecturer on physiology at the Charing
Cross School of Medicine. The extent and precision of his knowledge
impressed me greatly, and the severe exactness of his method of
lecturing was quite to my taste. I do not know that I have ever felt so
much respect for anybody as a teacher before or since. I worked hard to
obtain his approbation, and he was extremely kind and helpful to the
youngster who, I am afraid, took up more of his time than he had any
right to do. It was he who suggested the publication of my first
scientific paper--a very little one--in the _Medical Gazette_ of 1845,
and most kindly corrected the literary faults which abounded in it,
short as it was; for at that time, and for many years afterwards,
I detested the trouble of writing, and would take no pains over it.

It was in the early spring of 1846, that having finished my obligatory
medical studies and passed the first M.B. examination at the London
University--though I was still too young to qualify at the College of
Surgeons--I was talking to a fellow-student (the present eminent
physician, Sir Joseph Fayrer), and wondering what I should do to meet
the imperative necessity for earning my own bread, when my friend
suggested that I should write to Sir William Burnett, at that time
Director-General for the Medical Service of the Navy, for an
appointment. I thought this rather a strong thing to do, as Sir William
was personally unknown to me, but my cheery friend would not listen to
my scruples, so I went to my lodgings and wrote the best letter I could
devise. A few days afterwards I received the usual official circular of
acknowledgment, but at the bottom there was written an instruction to
call at Somerset House on such a day. I thought that looked like
business, so at the appointed time I called and sent in my card, while I
waited in Sir William's ante-room. He was a tall, shrewd-looking old
gentleman, with a broad Scotch accent--and I think I see him now as he
entered with my card in his hand. The first thing he did was to return
it, with the frugal reminder that I should probably find it useful on
some other occasion. The second was to ask whether I was an Irishman. I
suppose the air of modesty about my appeal must have struck him. I
satisfied the Director-General that I was English to the backbone, and
he made some inquiries as to my student career, finally desiring me to
hold myself ready for examination. Having passed this, I was in Her
Majesty's Service, and entered on the books of Nelson's old ship, the
_Victory_, for duty at Haslar Hospital, about a couple of months after I
made my application.

My official chief at Haslar was a very remarkable person, the late Sir
John Richardson, an excellent naturalist, and far-famed as an
indomitable Arctic traveller. He was a silent, reserved man, outside the
circle of his family and intimates; and, having a full share of youthful
vanity, I was extremely disgusted to find that "Old John," as we
irreverent youngsters called him, took not the slightest notice of my
worshipful self either the first time I attended him, as it was my duty
to do, or for some weeks afterwards. I am afraid to think of the lengths
to which my tongue may have run on the subject of the churlishness of
the chief, who was, in truth, one of the kindest-hearted and most
considerate of men. But one day, as I was crossing the hospital square,
Sir John stopped me, and heaped coals of fire on my head by telling me
that he had tried to get me one of the resident appointments, much
coveted by the assistant-surgeons, but that the Admiralty had put in
another man. "However," said he, "I mean to keep you here till I can get
you something you will like," and turned upon his heel without waiting
for the thanks I stammered out. That explained how it was I had not been
packed off to the West Coast of Africa like some of my juniors, and why,
eventually, I remained altogether seven months at Haslar.

After a long interval, during which "Old John" ignored my existence
almost as completely as before, he stopped me again as we met in a
casual way, and describing the service on which the _Rattlesnake_ was
likely to be employed, said that Captain Owen Stanley, who was to
command the ship, had asked him to recommend an assistant surgeon who
knew something of science; would I like that? Of course I jumped at the
offer. "Very well, I give you leave; go to London at once and see
Captain Stanley." I went, saw my future commander, who was very civil to
me, and promised to ask that I should be appointed to his ship, as in
due time I was. It is a singular thing that, during the few months of my
stay at Haslar, I had among my messmates two future Directors-General of
the Medical Service of the Navy (Sir Alexander Armstrong and Sir John
Watt-Reid), with the present President of the College of Physicians and
my kindest of doctors, Sir Andrew Clark.

Life on board Her Majesty's ships in those days was a very different
affair from what it is now, and ours was exceptionally rough, as we were
often many months without receiving letters or seeing any civilised
people but ourselves. In exchange, we had the interest of being about
the last voyagers, I suppose, to whom it could be possible to meet with
people who knew nothing of fire-arms--as we did on the south Coast of
New Guinea--and of making acquaintance with a variety of interesting
savage and semi-civilised people. But, apart from experience of this
kind and the opportunities offered for scientific work, to me,
personally, the cruise was extremely valuable. It was good for me to
live under sharp discipline; to be down on the realities of existence by
living on bare necessaries; to find out how extremely well worth living
life seemed to be when one woke up from a night's rest on a soft plank,
with the sky for canopy and cocoa and weevilly biscuit the sole prospect
for breakfast; and, more especially, to learn to work for the sake of
what I got for myself out of it, even if it all went to the bottom and I
along with it. My brother officers were as good fellows as sailors ought
to be and generally are, but, naturally, they neither knew nor cared
anything about my pursuits, nor understood why I should be so zealous in
pursuit of the objects which my friends, the middies, christened
"Buffons," after the title conspicuous on a volume of the "Suites à
Buffon," which stood on my shelf in the chart room.

During the four years of our absence, I sent home communication after
communication to the "Linnean Society;" with the same result as that
obtained by Noah when he sent the raven out of his ark. Tired at last of
hearing nothing about them, I determined to do or die, and in 1849 I
drew up a more elaborate paper and forwarded it to the Royal Society.
This was my dove, if I had only known it. But owing to the movements of
the ship, I heard nothing of that either until my return to England in
the latter end of the year 1850, when I found that it was printed and
published, and that a huge packet of separate copies awaited me. When I
hear some of my young friends complain of want of sympathy and
encouragement, I am inclined to think that my naval life was not the
least valuable part of my education.

Three years after my return were occupied by a battle between my
scientific friends on the one hand and the Admiralty on the other, as to
whether the latter ought, or ought not, to act up to the spirit of a
pledge they had given to encourage officers who had done scientific work
by contributing to the expense of publishing mine. At last the
Admiralty, getting tired, I suppose, cut short the discussion by
ordering me to join a ship, which thing I declined to do, and as
Rastignac, in the "Père Goriot," says to Paris, I said to London, "_à
nous deux_." I desired to obtain a Professorship of either Physiology or
Comparative Anatomy, and as vacancies occurred I applied, but in vain.
My friend, Professor Tyndall, and I were candidates at the same time, he
for the Chair of Physics and I for that of Natural History in the
University of Toronto, which, fortunately, as it turned out, would not
look at either of us. I say fortunately, not from any lack of respect
for Toronto, but because I soon made up my mind that London was the
place for me, and hence I have steadily declined the inducements to
leave it, which have at various times been offered. At last, in 1854, on
the translation of my warm friend Edward Forbes, to Edinburgh, Sir Henry
De la Beche, the Director-General of the Geological Survey, offered me
the post Forbes vacated of Paleontologist and Lecturer on Natural
History. I refused the former point blank, and accepted the latter only
provisionally, telling Sir Henry that I did not care for fossils, and
that I should give up Natural History as soon as I could get a
physiological post. But I held the office for thirty-one years, and a
large part of my work has been paleontological.

At that time I disliked public speaking, and had a firm conviction that
I should break down every time I opened my mouth. I believe I had every
fault a speaker could have (except talking at random or indulging in
rhetoric), when I spoke to the first important audience I ever
addressed, on a Friday evening: at the Royal Institution, in 1852. Yet,
I must confess to having been guilty, _malgré moi_, of as much public
speaking as most of my contemporaries, and for the last ten years it
ceased to be so much of a bugbear to me. I used to pity myself for
having to go through this training, but I am now more disposed to
compassionate the unfortunate audiences, especially my ever-friendly
hearers at the Royal Institution, who were the subjects of my oratorical
experiments.

The last thing that it would be proper for me to do would be to speak of
the work of my life, or to say at the end of the day whether I think I
have earned my wages or not. Men are said to be partial judges of
themselves. Young men may be; I doubt if old men are. Life seems
terribly foreshortened as they look back, and the mountain they set
themselves to climb in youth turns out to be a mere spur of immeasurably
higher ranges when, with failing breath, they reach the top. But if I
may speak of the objects I have had more or less definitely in view
since I began the ascent of my hillock, they are briefly these: To
promote the increase of natural knowledge and to forward the application
of scientific methods of investigation to all the problems of life to
the best of my ability, in the conviction which has grown with my growth
and strengthened with my strength, that there is no alleviation for the
sufferings of mankind except veracity of thought and of action, and the
resolute facing of the world as it is when the garment of make-believe
by which pious hands have hidden its uglier features is stripped off.

It is with this intent that I have subordinated any reasonable, or
unreasonable, ambition for scientific fame which I may have permitted
myself to entertain to other ends; to the popularisation of science; to
the development and organisation of scientific education; to the
endless series of battles and skirmishes over evolution; and to untiring
opposition to that ecclesiastical spirit, that clericalism, which in
England, as everywhere else, and to whatever denomination it may belong,
is the deadly enemy of science.

In striving for the attainment of these objects, I have been but one
among many, and I shall be well content to be remembered, or even not
remembered, as such. Circumstances, among which I am proud to reckon the
devoted kindness of many friends, have led to my occupation of various
prominent positions, among which the Presidency of the Royal Society is
the highest. It would be mock modesty on my part, with these and other
scientific honours which have been bestowed upon me, to pretend that I
have not succeeded in the career which I have followed, rather because I
was driven into it than of my own free will; but I am afraid I should
not count even these things as marks of success if I could not hope that
I had somewhat helped that movement of opinion which has been called the
New Reformation.




LECTURES AND ESSAYS

LECTURES ON EVOLUTION

[NEW YORK; 1876]


I

THE THREE HYPOTHESES RESPECTING THE HISTORY OF NATURE

We live in and form part of a system of things of immense diversity and
perplexity, which we call Nature; and it is a matter of the deepest
interest to all of us that we should form just conceptions of the
constitution of that system and of its past history. With relation to
this universe, man is, in extent, little more than a mathematical point;
in duration but a fleeting shadow; he is a mere reed shaken in the winds
of force. But as Pascal long ago remarked, although a mere reed, he is a
thinking reed; and in virtue of that wonderful capacity of thought, he
has the power of framing for himself a symbolic conception of the
universe, which, although doubtless highly imperfect and inadequate as a
picture of the great whole, is yet sufficient to serve him as a chart
for the guidance of his practical affairs. It has taken long ages of
toilsome and often fruitless labour to enable man to look steadily at
the shifting scenes of the phantasmagoria of Nature, to notice what is
fixed among her fluctuations, and what is regular among her apparent
irregularities; and it is only comparatively lately, within the last few
centuries, that the conception of a universal order and of a definite
course of things, which we term the course of Nature, has emerged.

But, once originated, the conception of the constancy of the order of
Nature has become the dominant idea of modern thought. To any person who
is familiar with the facts upon which that conception is based, and is
competent to estimate their significance, it has ceased to be
conceivable that chance should have any place in the universe, or that
events should depend upon any but the natural sequence of cause and
effect. We have come to look upon the present as the child of the past
and as the parent of the future; and, as we have excluded chance from a
place in the universe, so we ignore, even as a possibility, the notion
of any interference with the order of Nature. Whatever may be men's
speculative doctrines, it is quite certain that every intelligent person
guides his life and risks his fortune upon the belief that the order of
Nature is constant, and that the chain of natural causation is never
broken.

In fact, no belief which we entertain has so complete a logical basis as
that to which I have just referred. It tacitly underlies every process
of reasoning; it is the foundation of every act of the will. It is based
upon the broadest induction, and it is verified by the most constant,
regular, and universal of deductive processes. But we must recollect
that any human belief, however broad its basis, however defensible it
may seem, is, after all, only a probable belief, and that our widest and
safest generalisations are simply statements of the highest degree of
probability. Though we are quite clear about the constancy of the order
of Nature, at the present time, and in the present state of things, it
by no means necessarily follows that we are justified in expanding this
generalisation into the infinite past, and in denying, absolutely, that
there may have been a time when Nature did not follow a fixed order,
when the relations of cause and effect were not definite, and when
extra-natural agencies interfered with the general course of Nature.
Cautious men will allow that a universe so different from that which we
know may have existed; just as a very candid thinker may admit that a
world in which two and two do not make four, and in which two straight
lines do inclose a space, may exist. But the same caution which forces
the admission of such possibilities demands a great deal of evidence
before it recognises them to be anything more substantial. And when it
is asserted that, so many thousand years ago, events occurred in a
manner utterly foreign to and inconsistent with the existing laws of
Nature, men who without being particularly cautious are simply honest
thinkers, unwilling to deceive themselves or delude others, ask for
trustworthy evidence of the fact.

Did things so happen or did they not? This is a historical question, and
one the answer to which must be sought in the same way as the solution
of any other historical problem.

       *       *       *       *       *

So far as I know, there are only three hypotheses which ever have been
entertained, or which well can be entertained, respecting the past
history of Nature. I will, in the first place, state the hypotheses, and
then I will consider what evidence bearing upon them is in our
possession, and by what light of criticism that evidence is to be
interpreted.

Upon the first hypothesis, the assumption is, that phenomena of Nature
similar to those exhibited by the present world have always existed; in
other words, that the universe has existed, from all eternity, in what
may be broadly termed its present condition.

The second hypothesis is that the present state of things has had only a
limited duration; and that, at some period in the past, a condition of
the world, essentially similar to that which we now know, came into
existence, without any precedent condition from which it could have
naturally proceeded. The assumption that successive states of Nature
have arisen, each without any relation of natural causation to an
antecedent state, is a mere modification of this second hypothesis.

The third hypothesis also assumes that the present state of things has
had but a limited duration; but it supposes that this state has been
evolved by a natural process from an antecedent state, and that from
another, and so on; and, on this hypothesis, the attempt to assign any
limit to the series of past changes is, usually, given up.

It is so needful to form clear and distinct notions of what is really
meant by each of these hypotheses that I will ask you to imagine what,
according to each, would have been visible to a spectator of the events
which constitute the history of the earth. On the first hypothesis,
however far back in time that spectator might be placed, he would see a
world essentially, though perhaps not in all its details, similar to
that which now exists. The animals which existed would be the ancestors
of those which now live, and similar to them; the plants, in like
manner, would be such as we know; and the mountains, plains, and waters
would foreshadow the salient features of our present land and water.
This view was held more or less distinctly, sometimes combined with the
notion of recurrent cycles of change, in ancient times; and its
influence has been felt down to the present day. It is worthy of remark
that it is a hypothesis which is not inconsistent with the doctrine of
Uniformitarianism, with which geologists are familiar. That doctrine was
held by Hutton, and in his earlier days by Lyell. Hutton was struck by
the demonstration of astronomers that the perturbations of the planetary
bodies, however great they may be, yet sooner or later right themselves;
and that the solar system possesses a self-adjusting power by which
these aberrations are all brought back to a mean condition. Hutton
imagined that the like might be true of terrestrial changes; although no
one recognised more clearly than he the fact that the dry land is being
constantly washed down by rain and rivers and deposited in the sea; and
that thus, in a longer or shorter time, the inequalities of the earth's
surface must be levelled, and its high lands brought down to the ocean.
But, taking into account the internal forces of the earth, which,
upheaving the sea bottom, give rise to new land, he thought that these
operations of degradation and elevation might compensate each other; and
that thus, for any assignable time, the general features of our planet
might remain what they are. And inasmuch as, under these circumstances,
there need be no limit to the propagation of animals and plants, it is
clear that the consistent working-out of the uniformitarian idea might
lead to the conception of the eternity of the world. Not that I mean to
say that either Hutton or Lyell held this conception--assuredly not;
they would have been the first to repudiate it. Nevertheless, the
logical development of some of their arguments tends directly towards
this hypothesis.

The second hypothesis supposes that the present order of things, at some
no very remote time, had a sudden origin, and that the world, such as it
now is, had chaos for its phenomenal antecedent. That is the doctrine
which you will find stated most fully and clearly in the immortal poem
of John Milton--the English _Divina Commedia_--"Paradise Lost." I
believe it is largely to the influence of that remarkable work, combined
with the daily teachings to which we have all listened in our childhood,
that this hypothesis owes its general wide diffusion as one of the
current beliefs of English-speaking people. If you turn to the seventh
book of "Paradise Lost," you will find there stated the hypothesis to
which I refer, which is briefly this: That this visible universe of ours
came into existence at no great distance of time from the present; and
that the parts of which it is composed made their appearance, in a
certain definite order, in the space of six natural days, in such a
manner that, on the first of these days, light appeared; that, on the
second, the firmament, or sky, separated the waters above, from the
waters beneath, the firmament; that, on the third day, the waters drew
away from the dry land, and upon it a varied vegetable life, similar to
that which now exists, made its appearance; that the fourth day was
signalised by the apparition of the sun, the stars, the moon, and the
planets; that, on the fifth day, aquatic animals originated within the
waters; that, on the sixth day, the earth gave rise to our four-footed
terrestrial creatures, and to all varieties of terrestrial animals
except birds, which had appeared on the preceding day; and, finally,
that man appeared upon the earth, and the emergence of the universe from
chaos was finished. Milton tells us, without the least ambiguity, what a
spectator of these marvellous occurrences would have witnessed. I doubt
not that his poem is familiar to all of you, but I should like to recall
one passage to your minds, in order that I may be justified in what I
have said regarding the perfectly concrete, definite, picture of the
origin of the animal world which Milton draws. He says:--

    "The sixth, and of creation last, arose
    With evening harps and matin, when God said,
    'Let the earth bring forth soul living in her kind,
    Cattle and creeping things, and beast of the earth,
    Each in their kind!' The earth obeyed, and, straight
    Opening her fertile womb, teemed at a birth
    Innumerous living creatures, perfect forms,
    Limbed and full-grown. Out of the ground uprose,
    As from his lair, the wild beast, where he wons
    In forest wild, in thicket, brake, or den;
    Among the trees in pairs they rose, they walked;
    The cattle in the fields and meadows green;
    Those rare and solitary; these in flocks
    Pasturing at once, and in broad herds upsprung.
    The grassy clods now calved; now half appears
    The tawny lion, pawing to get free
    His hinder parts--then springs, as broke from bonds,
    And rampant shakes his brinded mane; the ounce,
    The libbard, and the tiger, as the mole
    Rising, the crumbled earth above them threw
    In hillocks; the swift stag from underground
    Bore up his branching head; scarce from his mould
    Behemoth, biggest born of earth, upheaved
    His vastness; fleeced the flocks and bleating rose
    As plants; ambiguous between sea and land,
    The river-horse and scaly crocodile.
    At once came forth whatever creeps the ground,
    Insect or worm.

There is no doubt as to the meaning of this statement, nor as to what a
man of Milton's genius expected would have been actually visible to an
eye-witness of this mode of origination of living things.

The third hypothesis, or the hypothesis of evolution, supposes that, at
any comparatively late period of past time, our imaginary spectator
would meet with a state of things very similar to that which now
obtains; but that the likeness of the past to the present would
gradually become less and less, in proportion to the remoteness of his
period of observation from the present day; that the existing
distribution of mountains and plains, of rivers and seas, would show
itself to be the product of a slow process of natural change operating
upon more and more widely different antecedent conditions of the mineral
framework of the earth; until, at length, in place of that framework, he
would behold only a vast nebulous mass, representing the constituents of
the sun and of the planetary bodies. Preceding the forms of life which
now exist, our observer would see animals and plants, not identical with
them, but like them, increasing their differences with their antiquity
and, at the same time, becoming simpler and simpler; until, finally, the
world of life would present nothing but that undifferentiated
protoplasmic matter which, so far as our present knowledge goes, is the
common foundation of all vital activity.

The hypothesis of evolution supposes that in all this vast progression
there would be no breach of continuity, no point at which we could say
"This is a natural process," and "This is not a natural process;" but
that the whole might be compared to that wonderful operation of
development which may be seen going on every day under our eyes, in
virtue of which there arises, out of the semi-fluid comparatively
homogeneous substance which we call an egg, the complicated organisation
of one of the higher animals. That, in a few words, is what is meant by
the hypothesis of evolution.

I have already suggested that, in dealing with these three hypotheses,
in endeavouring to form a judgment as to which of them is the more
worthy of belief, or whether none is worthy of belief--in which case our
condition of mind should be that suspension of judgment which is so
difficult to all but trained intellects--we should be indifferent to all
_a priori_ considerations. The question is a question of historical
fact. The universe has come into existence somehow or other, and the
problem is, whether it came into existence in one fashion, or whether it
came into existence in another; and, as an essential preliminary to
further discussion, permit me to say two or three words as to the nature
and the kinds of historical evidence.

The evidence as to the occurrence of any event in past time may be
ranged under two heads which, for convenience' sake, I will speak of as
testimonial evidence and as circumstantial evidence. By testimonial
evidence I mean human testimony; and by circumstantial evidence I mean
evidence which is not human testimony. Let me illustrate by a familiar
example what I understand by these two kinds of evidence, and what is to
be said respecting their value.

Suppose that a man tells you that he saw a person strike another and
kill him; that is testimonial evidence of the fact of murder. But it is
possible to have circumstantial evidence of the fact of murder; that is
to say, you may find a man dying with a wound upon his head having
exactly the form and character of the wound which is made by an axe,
and, with due care in taking surrounding circumstances into account, you
may conclude with the utmost certainty that the man has been murdered;
that his death is the consequence of a blow inflicted by another man
with that implement. We are very much in the habit of considering
circumstantial evidence as of less value than testimonial evidence, and
it may be that, where the circumstances are not perfectly clear and
intelligible, it is a dangerous and unsafe kind of evidence; but it must
not be forgotten that, in many cases, circumstantial is quite as
conclusive as testimonial evidence, and that, not unfrequently, it is a
great deal weightier than testimonial evidence. For example, take the
case to which I referred just now. The circumstantial evidence may be
better and more convincing than the testimonial evidence; for it may be
impossible, under the conditions that I have defined, to suppose that
the man met his death from any cause but the violent blow of an axe
wielded by another man. The circumstantial evidence in favour of a
murder having been committed, in that case, is as complete and as
convincing as evidence can be. It is evidence which is open to no doubt
and to no falsification. But the testimony of a witness is open to
multitudinous doubts. He may have been mistaken. He may have been
actuated by malice. It has constantly happened that even an accurate man
has declared that a thing has happened in this, that, or the other way,
when a careful analysis of the circumstantial evidence has shown that it
did not happen in that way, but in some other way.

We may now consider the evidence in favour of or against the three
hypotheses. Let me first direct your attention to what is to be said
about the hypothesis of the eternity of the state of things in which we
now live. What will first strike you is, that it is a hypothesis which,
whether true or false, is not capable of verification by any evidence.
For, in order to observe either circumstantial or testimonial evidence
sufficient to prove the eternity of duration of the present state of
nature, you must have an eternity of witnesses or an infinity of
circumstances, and neither of these is attainable. It is utterly
impossible that such evidence should be carried beyond a certain point
of time; and all that could be said, at most, would be, that so far as
the evidence could be traced, there was nothing to contradict the
hypothesis. But when you look, not to the testimonial evidence--which,
considering the relative insignificance of the antiquity of human
records, might not be good for much in this case--but to the
circumstantial evidence, then you find that this hypothesis is
absolutely incompatible with such evidence as we have; which is of so
plain and simple a character that it is impossible in any way to escape
from the conclusions which it forces upon us.

[Illustration: FIG. 1.--IDEAL SECTION OF THE CRUST OF THE EARTH.]

You are, doubtless, all aware that the outer substance of the earth,
which alone is accessible to direct observation, is not of a homogeneous
character, but that it is made up of a number of layers or strata, the
titles of the principal groups of which are placed upon the accompanying
diagram. Each of these groups represents a number of beds of sand, of
stone, of clay, of slate, and of various other materials.

On careful examination, it is found that the materials of which each of
these layers of more or less hard rock are composed are, for the most
part, of the same nature as those which are at present being formed
under known conditions on the surface of the earth. For example, the
chalk, which constitutes a great part of the Cretaceous formation in
some parts of the world, is practically identical in its physical and
chemical characters with a substance which is now being formed at the
bottom of the Atlantic Ocean, and covers an enormous area; other beds of
rock are comparable with the sands which are being formed upon
sea-shores, packed together, and so on. Thus, omitting rocks of igneous
origin, it is demonstrable that all these beds of stone, of which a
total of not less than seventy thousand feet is known, have been formed
by natural agencies, either out of the waste and washing of the dry
land, or else by the accumulation of the exuviæ of plants and animals.
Many of these strata are full of such exuviæ--the so-called "fossils."
Remains of thousands of species of animals and plants, as perfectly
recognisable as those of existing forms of life which you meet with in
museums, or as the shells which you pick up upon the sea-beach, have
been imbedded in the ancient sands, or muds, or limestones, just as they
are being imbedded now, in sandy, or clayey, or calcareous subaqueous
deposits. They furnish us with a record, the general nature of which
cannot be misinterpreted, of the kinds of things that have lived upon
the surface of the earth during the time that is registered by this
great thickness of stratified rocks. But even a superficial study of
these fossils shows us that the animals and plants which live at the
present time have had only a temporary duration; for the remains of such
modern forms of life are met with, for the most part, only in the
uppermost or latest tertiaries, and their number rapidly diminishes in
the lower deposits of that epoch. In the older tertiaries, the places of
existing animals and plants are taken by other forms, as numerous and
diversified as those which live now in the same localities, but more or
less different from them; in the mesozoic rocks, these are replaced by
others yet more divergent from modern types; and, in the palæozoic
formations the contrast is still more marked. Thus the circumstantial
evidence absolutely negatives the conception of the eternity of the
present condition of things. We can say, with certainty, that the
present condition of things has existed for a comparatively short
period; and that, so far as animal and vegetable nature are concerned,
it has been preceded by a different condition. We can pursue this
evidence until we reach the lowest of the stratified rocks, in which we
lose the indications of life altogether. The hypothesis of the eternity
of the present state of nature may therefore be put out of court.

We now come to what I will term Milton's hypothesis--the hypothesis that
the present condition of things has endured for a comparatively short
time; and, at the commencement of that time, came into existence within
the course of six days. I doubt not that it may have excited some
surprise in your minds that I should have spoken of this as Milton's
hypothesis, rather than that I should have chosen the terms which are
more customary, such as "the doctrine of creation," or "the Biblical
doctrine," or "the doctrine of Moses," all of which denominations, as
applied to the hypothesis to which I have just referred, are certainly
much more familiar to you than the title of the Miltonic hypothesis. But
I have had what I cannot but think are very weighty reasons for taking
the course which I have pursued. In the first place, I have discarded
the title of the "doctrine of creation," because my present business is
not with the question why the objects which constitute Nature came into
existence, but when they came into existence, and in what order. This is
as strictly a historical question as the question when the Angles and
the Jutes invaded England, and whether they preceded or followed the
Romans. But the question about creation is a philosophical problem, and
one which cannot be solved, or even approached, by the historical
method. What we want to learn is, whether the facts, so far as they are
known, afford evidence that things arose in the way described by Milton,
or whether they do not; and, when that question is settled, it will be
time enough to inquire into the causes of their origination.

In the second place, I have not spoken of this doctrine as the Biblical
doctrine. It is quite true that persons as diverse in their general
views as Milton the Protestant and the celebrated Jesuit Father Suarez,
each put upon the first chapter of Genesis the interpretation embodied
in Milton's poem. It is quite true that this interpretation is that
which has been instilled into every one of us in our childhood; but I do
not for one moment venture to say that it can properly be called the
Biblical doctrine. It is not my business, and does not lie within my
competency, to say what the Hebrew text does, and what it does not
signify; moreover, were I to affirm that this is the Biblical doctrine,
I should be met by the authority of many eminent scholars, to say
nothing of men of science, who, at various times, have absolutely denied
that any such doctrine is to be found in Genesis. If we are to listen to
many expositors of no mean authority, we must believe that what seems so
clearly defined in Genesis--as if very great pains had been taken that
there should be no possibility of mistake--is not the meaning of the
text at all. The account is divided into periods that we may make just
as long or as short as convenience requires. We are also to understand
that it is consistent with the original text to believe that the most
complex plants and animals may have been evolved by natural processes,
lasting for millions of years, out of structureless rudiments. A person
who is not a Hebrew scholar can only stand aside and admire the
marvellous flexibility of a language which admits of such diverse
interpretations. But assuredly, in the face of such contradictions of
authority upon matters respecting which he is incompetent to form any
judgment, he will abstain, as I do, from giving any opinion.

In the third place, I have carefully abstained from speaking of this as
the Mosaic doctrine, because we are now assured upon the authority of
the highest critics, and even of dignitaries of the Church, that there
is no evidence that Moses wrote the Book of Genesis, or knew anything
about it. You will understand that I give no judgment--it would be an
impertinence upon my part to volunteer even a suggestion--upon such a
subject. But, that being the state of opinion among the scholars and the
clergy, it is well for the unlearned in Hebrew lore, and for the laity,
to avoid entangling themselves in such a vexed question. Happily, Milton
leaves us no excuse for doubting what he means, and I shall therefore be
safe in speaking of the opinion in question as the Miltonic hypothesis.

Now we have to test that hypothesis. For my part, I have no prejudice
one way or the other. If there is evidence in favour of this view, I am
burdened by no theoretical difficulties in the way of accepting it; but
there must be evidence. Scientific men get an awkward habit--no, I won't
call it that, for it is a valuable habit--of believing nothing unless
there is evidence for it; and they have a way of looking upon belief
which is not based upon evidence, not only as illogical, but as immoral.
We will, if you please, test this view by the circumstantial evidence
alone; for, from what I have said, you will understand that I do not
propose to discuss the question of what testimonial evidence is to be
adduced in favour of it. If those whose business it is to judge are not
at one as to the authenticity of the only evidence of that kind which is
offered, nor as to the facts to which it bears witness, the discussion
of such evidence is superfluous.

But I may be permitted to regret this necessity of rejecting the
testimonial evidence the less, because the examination of the
circumstantial evidence leads to the conclusion, not only that it is
incompetent to justify the hypothesis, but that, so far as it goes, it
is contrary to the hypothesis.

The considerations upon which I base this conclusion are of the simplest
possible character. The Miltonic hypothesis contains assertions of a
very definite character relating to the succession of living forms. It
is stated that plants, for example, made their appearance upon the third
day, and not before. And you will understand that what the poet means
by plants are such plants as now live, the ancestors, in the ordinary
way of propagation of like by like, of the trees and shrubs which
flourish in the present world. It must needs be so; for, if they were
different, either the existing plants have been the result of a separate
origination since that described by Milton, of which we have no record,
nor any ground for supposition that such an occurrence has taken place;
or else they have arisen by a process of evolution from the original
stocks.

In the second place, it is clear that there was no animal life before
the fifth day, and that, on the fifth day, aquatic animals and birds
appeared. And it is further clear that terrestrial living things, other
than birds, made their appearance upon the sixth day and not before.
Hence, it follows that, if, in the large mass of circumstantial evidence
as to what really has happened in the past history of the globe we find
indications of the existence of terrestrial animals, other than birds,
at a certain period, it is perfectly certain that all that has taken
place, since that time, must be referred to the sixth day.

In the great Carboniferous formation, whence America derives so vast a
proportion of her actual and potential wealth, in the beds of coal which
have been formed from the vegetation of that period, we find abundant
evidence of the existence of terrestrial animals. They have been
described, not only by European but by your own naturalists. There are
to be found numerous insects allied to our cockroaches. There are to be
found spiders and scorpions of large size, the latter so similar to
existing scorpions that it requires the practised eye of the naturalist
to distinguish them. Inasmuch as these animals can be proved to have
been alive in the Carboniferous epoch, it is perfectly clear that, if
the Miltonic account is to be accepted, the huge mass of rocks extending
from the middle of the Palæozoic formations to the uppermost members of
the series, must belong to the day which is termed by Milton the sixth.
But, further, it is expressly stated that aquatic animals took their
origin on the fifth day, and not before; hence, all formations in which
remains of aquatic animals can be proved to exist, and which therefore
testify that such animals lived at the time when these formations were
in course of deposition, must have been deposited during or since the
period which Milton speaks of as the fifth day. But there is absolutely
no fossiliferous formation in which the remains of aquatic animals are
absent. The oldest fossils in the Silurian rocks are exuviæ of marine
animals; and if the view which is entertained by Principal Dawson and
Dr. Carpenter respecting the nature of the _Eozoön_ be well-founded,
aquatic animals existed at a period as far antecedent to the deposition
of the coal as the coal is from us; inasmuch as the _Eozoön_ is met with
in those Laurentian strata which lie at the bottom of the series of
stratified rocks. Hence it follows, plainly enough, that the whole
series of stratified rocks, if they are to be brought into harmony with
Milton, must be referred to the fifth and sixth days, and that we cannot
hope to find the slightest trace of the products of the earlier days in
the geological record. When we consider these simple facts, we see how
absolutely futile are the attempts that have been made to draw a
parallel between the story told by so much of the crust of the earth as
is known to us and the story which Milton tells. The whole series of
fossiliferous stratified rocks must be referred to the last two days;
and neither the Carboniferous, nor any other, formation can afford
evidence of the work of the third day.

Not only is there this objection to any attempt to establish a harmony
between the Miltonic account and the facts recorded in the fossiliferous
rocks, but there is a further difficulty. According to the Miltonic
account, the order in which animals should have made their appearance in
the stratified rocks would be this: Fishes, including the great whales,
and birds; after them, all varieties of terrestrial animals except
birds. Nothing could be further from the facts as we find them; we know
of not the slightest evidence of the existence of birds before the
Jurassic, or perhaps the Triassic, formation; while terrestrial animals,
as we have just seen, occur in the Carboniferous rocks.

If there were any harmony between the Miltonic account and the
circumstantial evidence, we ought to have abundant evidence of the
existence of birds in the Carboniferous, the Devonian, and the Silurian
rocks. I need hardly say that this is not the case, and that not a trace
of birds makes its appearance until the far later period which I have
mentioned.

And again, if it be true that all varieties of fishes and the great
whales, and the like, made their appearance on the fifth day, we ought
to find the remains of these animals in the older rocks--in those which
were deposited before the Carboniferous epoch. Fishes we do find, in
considerable number and variety; but the great whales are absent, and
the fishes are not such as now live. Not one solitary species of fish
now in existence is to be found in the Devonian or Silurian formations.
Hence we are introduced afresh to the dilemma which I have already
placed before you: either the animals which came into existence on the
fifth day were not such as those which are found at present, are not the
direct and immediate ancestors of those which now exist; in which case,
either fresh creations of which nothing is said, or a process of
evolution, must have occurred; or else the whole story must be given up,
as not only devoid of any circumstantial evidence, but contrary to such
evidence as exists.

I placed before you in a few words, some little time ago, a statement of
the sum and substance of Milton's hypothesis. Let me now try to state,
as briefly, the effect of the circumstantial evidence bearing upon the
past history of the earth which is furnished, without the possibility of
mistake, with no chance of error as to its chief features, by the
stratified rocks. What we find is, that the great series of formations
represents a period of time of which our human chronologies hardly
afford us a unit of measure. I will not pretend to say how we ought to
estimate this time, in millions or in billions of years. For my purpose,
the determination of its absolute duration is wholly unessential. But
that the time was enormous there can be no question.

It results from the simplest methods of interpretation, that leaving out
of view certain patches of metamorphosed rocks, and certain volcanic
products, all that is now dry land has once been at the bottom of the
waters. It is perfectly certain that, at a comparatively recent period
of the world's history--the Cretaceous epoch--none of the great physical
features which at present mark the surface of the globe existed. It is
certain that the Rocky Mountains were not. It is certain that the
Himalaya Mountains were not. It is certain that the Alps and the
Pyrenees had no existence. The evidence is of the plainest possible
character, and is simply this:--We find raised up on the flanks of these
mountains, elevated by the forces of upheaval which have given rise to
them, masses of Cretaceous rock which formed the bottom of the sea
before those mountains existed. It is therefore clear that the elevatory
forces which gave rise to the mountains operated subsequently to the
Cretaceous epoch; and that the mountains themselves are largely made up
of the materials deposited in the sea which once occupied their place.
As we go back in time, we meet with constant alternations of sea and
land, of estuary and open ocean; and, in correspondence with these
alternations, we observe the changes in the fauna and flora to which I
have referred.

But the inspection of these changes give us no right to believe that
there has been any discontinuity in natural processes. There is no
trace of general cataclysms, of universal deluges, or sudden
destructions of a whole fauna or flora. The appearances which were
formerly interpreted in that way have all been shown to be delusive, as
our knowledge has increased and as the blanks which formerly appeared to
exist between the different formations have been filled up. That there
is no absolute break between formation and formation, that there has
been no sudden disappearance of all the forms of life and replacement of
them by others, but that changes have gone on slowly and gradually, that
one type has died out and another has taken its place, and that thus, by
insensible degrees, one fauna has been replaced by another, are
conclusions strengthened by constantly increasing evidence. So that
within the whole of the immense period indicated by the fossiliferous
stratified rocks, there is assuredly not the slightest proof of any
break in the uniformity of Nature's operations, no indication that
events have followed other than a clear and orderly sequence.

That, I say, is the natural and obvious teaching of the circumstantial
evidence contained in the stratified rocks. I leave you to consider how
far, by any ingenuity of interpretation, by any stretching of the
meaning of language, it can be brought into harmony with the Miltonic
hypothesis.

There remains the third hypothesis, that of which I have spoken as the
hypothesis of evolution; and I purpose that, in lectures to come, we
should discuss it as carefully as we have considered the other two
hypotheses. I need not say that it is quite hopeless to look for
testimonial evidence of evolution. The very nature of the case precludes
the possibility of such evidence, for the human race can no more be
expected to testify to its own origin, than a child can be tendered as a
witness of its own birth. Our sole inquiry is, what foundation
circumstantial evidence lends to the hypothesis, or whether it lends
none, or whether it controverts the hypothesis. I shall deal with the
matter entirely as a question of history. I shall not indulge in the
discussion of any speculative probabilities. I shall not attempt to show
that Nature is unintelligible unless we adopt some such hypothesis. For
anything I know about the matter, it may be the way of Nature to be
unintelligible; she is often puzzling, and I have no reason to suppose
that she is bound to fit herself to our notions.

I shall place before you three kinds of evidence entirely based upon
what is known of the forms of animal life which are contained in the
series of stratified rocks. I shall endeavour to show you that there is
one kind of evidence which is neutral, which neither helps evolution nor
is inconsistent with it. I shall then bring forward a second kind of
evidence which indicates a strong probability in favour of evolution,
but does not prove it; and, lastly, I shall adduce a third kind of
evidence which, being as complete as any evidence which we can hope to
obtain upon such a subject, and being wholly and strikingly in favour of
evolution, may fairly be called demonstrative evidence of its
occurrence.


II

THE HYPOTHESIS OF EVOLUTION. THE NEUTRAL AND THE FAVOURABLE EVIDENCE

In the preceding lecture I pointed out that there are three hypotheses
which may be entertained, and which have been entertained, respecting
the past history of life upon the globe. According to the first of these
hypotheses, living beings, such as now exist, have existed from all
eternity upon this earth. We tested that hypothesis by the
circumstantial evidence, as I called it, which is furnished by the
fossil remains contained in the earth's crust, and we found that it was
obviously untenable. I then proceeded to consider the second
hypothesis, which I termed the Miltonic hypothesis, not because it is of
any particular consequence whether John Milton seriously entertained it
or not, but because it is stated in a clear and unmistakable manner in
his great poem. I pointed out to you that the evidence at our command as
completely and fully negatives that hypothesis as it did the preceding
one. And I confess that I had too much respect for your intelligence to
think it necessary to add that the negation was equally clear and
equally valid, whatever the source from which that hypothesis might be
derived, or whatever the authority by which it might be supported. I
further stated that, according to the third hypothesis, or that of
evolution, the existing state of things is the last term of a long
series of states, which, when traced back, would be found to show no
interruption and no breach in the continuity of natural causation. I
propose, in the present and the following lecture, to test this
hypothesis rigorously by the evidence at command, and to inquire how far
that evidence can be said to be indifferent to it, how far it can be
said to be favourable to it, and, finally, how far it can be said to be
demonstrative.

From almost the origin of the discussions about the existing condition
of the animal and vegetable worlds and the causes which have determined
that condition, an argument has been put forward as an objection to
evolution, which we shall have to consider very seriously. It is an
argument which was first clearly stated by Cuvier in his criticism of
the doctrines propounded by his great contemporary, Lamarck. The French
expedition to Egypt had called the attention of learned men to the
wonderful store of antiquities in that country, and there had been
brought back to France numerous mummified corpses of the animals which
the ancient Egyptians revered and preserved, and which, at a reasonable
computation, must have lived not less than three or four thousand years
before the time at which they were thus brought to light. Cuvier
endeavoured to test the hypothesis that animals have undergone gradual
and progressive modifications of structure, by comparing the skeletons
and such other parts of the mummies as were in a fitting state of
preservation, with the corresponding parts of the representatives of the
same species now living in Egypt. He arrived at the conviction that no
appreciable change had taken place in these animals in the course of
this considerable lapse of time, and the justice of his conclusion is
not disputed.

It is obvious that, if it can be proved that animals have endured,
without undergoing any demonstrable change of structure, for so long a
period as four thousand years, no form of the hypothesis of evolution
which assumes that animals undergo a constant and necessary progressive
change can be tenable; unless, indeed, it be further assumed that four
thousand years is too short a time for the production of a change
sufficiently great to be detected.

But it is no less plain that if the process of evolution of animals is
not independent of surrounding conditions; if it may be indefinitely
hastened or retarded by variations in these conditions; or if evolution
is simply a process of accommodation to varying conditions; the argument
against the hypothesis of evolution based on the unchanged character of
the Egyptian fauna is worthless. For the monuments which are coeval with
the mummies testify as strongly to the absence of change in the physical
geography and the general conditions of the land of Egypt, for the time
in question, as the mummies do to the unvarying characters of its living
population.

The progress of research since Cuvier's time has supplied far more
striking examples of the long duration of specific forms of life than
those which are furnished by the mummified Ibises and Crocodiles of
Egypt. A remarkable case is to be found in your own country, in the
neighbourhood of the falls of Niagara. In the immediate vicinity of the
whirlpool, and again upon Goat Island, in the superficial deposits
which cover the surface of the rocky subsoil in those regions, there are
found remains of animals in perfect preservation, and among them, shells
belonging to exactly the same species as those which at present inhabit
the still waters of Lake Erie. It is evident, from the structure of the
country, that these animal remains were deposited in the beds in which
they occur at a time when the lake extended over the region in which
they are found. This involves the conclusion that they lived and died
before the falls had cut their way back through the gorge of Niagara;
and, indeed, it has been determined that, when these animals lived, the
falls of Niagara must have been at least six miles further down the
river than they are at present. Many computations have been made of the
rate at which the falls are thus cutting their way back. Those
computations have varied greatly, but I believe I am speaking within the
bounds of prudence, if I assume that the falls of Niagara have not
retreated at a greater pace than about a foot a year. Six miles,
speaking roughly, are 30,000 feet; 30,000 feet, at a foot a year, gives
30,000 years; and thus we are fairly justified in concluding that no
less a period than this has passed since the shell-fish, whose remains
are left in the beds to which I have referred, were living creatures.

But there is still stronger evidence of the long duration of certain
types. I have already stated that, as we work our way through the great
series of the Tertiary formations, we find many species of animals
identical with those which live at the present day, diminishing in
numbers, it is true, but still existing, in a certain proportion, in the
oldest of the Tertiary rocks. Furthermore, when we examine the rocks of
the Cretaceous epoch, we find the remains of some animals which the
closest scrutiny cannot show to be, in any important respect, different
from those which live at the present time. That is the case with one of
the cretaceous lamp-shells (_Terebratula_) which has continued to exist
unchanged, or with insignificant variations, down to the present day.
Such is the case with the _Globigerinæ_, the skeletons of which,
aggregated together, form a large proportion of our English chalk. Those
_Globigerinæ_ can be traced down to the _Globigerinæ_ which live at the
surface of the present great oceans, and the remains of which, falling
to the bottom of the sea give rise to a chalky mud. Hence it must be
admitted that certain existing species of animals show no distinct sign
of modification, or transformation, in the course of a lapse of time as
great as that which carries us back to the Cretaceous period; and which,
whatever its absolute measure, is certainly vastly greater than thirty
thousand years.

There are groups of species so closely allied together, that it needs
the eye of a naturalist to distinguish them one from another. If we
disregard the small differences which separate these forms, and consider
all the species of such groups as modifications of one type, we shall
find that, even among the higher animals, some types have had a
marvellous duration. In the chalk, for example, there is found a fish
belonging to the highest and the most differentiated group of osseous
fishes, which goes by the name of _Beryx_. The remains of that fish are
among the most beautiful and well-preserved of the fossils found in our
English chalk. It can be studied anatomically, so far as the hard parts
are concerned, almost as well as if it were a recent fish. But the genus
_Beryx_ is represented, at the present day, by very closely allied
species which are living in the Pacific and Atlantic Oceans. We may go
still farther back. I have already referred to the fact, that the
Carboniferous formations, in Europe and in America, contain the remains
of scorpions in an admirable state of preservation and, that those
scorpions are hardly distinguishable from such as now live. I do not
mean to say that they are not different, but close scrutiny is needed in
order to distinguish them from modern scorpions.

More than this. At the very bottom Of the Silurian series, in beds which
are by some authorities referred to the Cambrian formation, where the
signs of life begin to fail us--even there, among the few and scanty
animal remains which are discoverable, we find species of molluscous
animals which are so closely allied to existing forms that, at one time,
they were grouped under the same generic name. I refer to the well known
_Lingula_ of the _Lingula_ flags, lately, in consequence of some slight
differences, placed in the new genus _Lingulella_. Practically, it
belongs to the same great generic group as the _Lingula_, which is to be
found at the present day upon your own shores and those of many other
parts of the world.

The same truth is exemplified if we turn to certain great periods of the
earth's history--as, for example, the Mesozoic epoch. There are groups
of reptiles, such as the _Ichthyosauria_ and the _Plesiosauria_, which
appear shortly after the commencement of this epoch, and they occur in
vast numbers. They disappear with the chalk and, throughout the whole of
the great series of Mesozoic rocks, they present no such modifications
as can safely be considered evidence of progressive modification.

Facts of this kind are undoubtedly fatal to any form of the doctrine of
evolution which postulates the supposition that there is an intrinsic
necessity, on the part of animal forms which have once come into
existence, to undergo continual modification; and they are as distinctly
opposed to any view which involves the belief, that such modification as
may occur, must take place, at the same rate, in all the different types
of animal or vegetable life. The facts, as I have placed them before you
obviously directly contradict any form of the hypothesis of evolution
which stands in need of these two postulates.

But, one great service that has been rendered by Mr. Darwin to the
doctrine of evolution in general is this: he has shown that there are
two chief factors in the process of evolution: one of them is the
tendency to vary, the existence of which in all living forms may be
proved by observation; the other is the influence of surrounding
conditions upon what I may call the parent form and the variations which
are thus evolved from it. The cause of the production of variations is a
matter not at all properly understood at present. Whether variation
depends upon some intricate machinery--if I may use the phrase--of the
living organism itself, or whether it arises through the influence of
conditions upon that form, is not certain, and the question may, for the
present, be left open. But the important point is that granting the
existence of the tendency to the production of variations; then, whether
the variations which are produced shall survive and supplant the parent,
or whether the parent form shall survive and supplant the variations, is
a matter which depends entirely on those conditions which give rise to
the struggle for existence. If the surrounding conditions are such that
the parent form is more competent to deal with them, and flourish in
them than the derived forms, then, in the struggle for existence, the
parent form will maintain itself and the derived forms will be
exterminated. But if, on the contrary, the conditions are such as to be
more favourable to a derived than to the parent form, the parent form
will be extirpated and the derived form will take its place. In the
first case, there will be no progression, no change of structure,
through any imaginable series of ages; in the second place there will be
modification of change and form.

Thus the existence of these persistent types, as I have termed them, is
no real obstacle in the way of the theory of evolution. Take the case of
the scorpions to which I have just referred. No doubt, since the
Carboniferous epoch, conditions have always obtained, such as existed
when the scorpions of that epoch flourished; conditions in which
scorpions find themselves better off, more competent to deal with the
difficulties in their way, than any variation from the scorpion type
which they may have produced; and, for that reason, the scorpion type
has persisted, and has not been supplanted by any other form. And there
is no reason, in the nature of things, why, as long as this world
exists, if there be conditions more favourable to scorpions than to any
variation which may arise from them, these forms of life should not
persist.

Therefore, the stock objection to the hypothesis of evolution, based on
the long duration of certain animal and vegetable types, is no objection
at all. The facts of this character--and they are numerous--belong to
that class of evidence which I have called indifferent. That is to say,
they may afford no direct support to the doctrine of evolution, but they
are capable of being interpreted in perfect consistency with it.

There is another order of facts belonging to the class of negative or
indifferent evidence. The great group of Lizards, which abound in the
present world, extends through the whole series of formations as far
back as the Permian, or latest Palæozoic, epoch. These Permian lizards
differ astonishingly little from the lizards which exist at the present
day. Comparing the amount of the differences between them and modern
lizards, with the prodigious lapse of time between the Permian epoch and
the present age, it may be said that the amount of change is
insignificant. But, when we carry our researches farther back in time,
we find no trace of lizards, nor of any true reptile whatever, in the
whole mass of formations beneath the Permian.

Now, it is perfectly clear that if our palæontological collections are
to be taken, even approximately, as an adequate representation of all
the forms of animals and plants that have ever lived; and if the record
furnished by the known series of beds of stratified rock covers the
whole series of events which constitute the history of life on the
globe, such a fact as this directly contravenes the hypothesis of
evolution; because this hypothesis postulates that the existence of
every form must have been preceded by that of some form little different
from it. Here, however, we have to take into consideration that
important truth so well insisted upon by Lyell and by Darwin--the
imperfection of the geological record. It can be demonstrated that the
geological record must be incomplete, that it can only preserve remains
found in certain favourable localities and under particular conditions;
that it must be destroyed by processes of denudation, and obliterated by
processes of metamorphosis. Beds of rock of any thickness, crammed full
of organic remains, may yet, either by the percolation of water through
them, or by the influence of subterranean heat, lose all trace of these
remains, and present the appearance of beds of rock formed under
conditions in which living forms were absent. Such metamorphic rocks
occur in formations of all ages; and, in various cases, there are very
good grounds for the belief that they have contained organic remains,
and that those remains have been absolutely obliterated.

I insist upon the defects of the geological record the more because
those who have not attended to these matters are apt to say, "It is all
very well, but, when you get into a difficulty with your theory of
evolution, you appeal to the incompleteness and the imperfection of the
geological record;" and I want to make it perfectly clear to you that
this imperfection is a great fact, which must be taken into account in
all our speculations, or we shall constantly be going wrong.

You see the singular series of footmarks, drawn of its natural size in
the large diagram hanging up here (Fig. 2), which I owe to the kindness
of my friend Professor Marsh, with whom I had the opportunity recently
of visiting the precise locality in Massachusetts in which these tracks
occur. I am, therefore, able to give you my own testimony, if needed,
that the diagram accurately represents what we saw. The valley of the
Connecticut is classical ground for the geologist. It contains great
beds of sandstone, covering many square miles, which have evidently
formed a part of an ancient sea-shore, or, it may be, lake-shore. For a
certain period of time after their deposition, these beds have remained
sufficiently soft to receive the impressions of the feet of whatever
animals walked over them, and to preserve them afterwards, in exactly
the same way as such impressions are at this hour preserved on the
shores of the Bay of Fundy and elsewhere. The diagram represents the
track of some gigantic animal, which walked on its hind legs. You see
the series of marks made alternately by the right and by the left foot;
so that, from one impression to the other of the three-toed foot on the
same side, is one stride, and that stride, as we measured it, is six
feet nine inches. I leave you, therefore, to form an impression of the
magnitude of the creature which, as it walked along the ancient shore,
made these impressions.

[Illustration: FIG. 2.--TRACKS OF BRONTOZOUM.]

Of such impressions there are untold thousands upon these sandstones.
Fifty or sixty different kinds have been discovered, and they cover vast
areas. But, up to this present time, not a bone, not a fragment, of any
one of the animals which left these great footmarks has been found; in
fact, the only animal remains which have been met with in all these
deposits, from the time of their discovery to the present day--though
they have been carefully hunted over--is a fragmentary skeleton of one
of the smaller forms. What has become of the bones of all these animals?
You see we are not dealing with little creatures, but with animals that
make a step of six feet nine inches; and their remains must have been
left somewhere. The probability is, that they have been dissolved away,
and completely lost.

I have had occasion to work out the nature of fossil remains, of which
there was nothing left except casts of the bones, the solid material of
the skeleton having been dissolved out by percolating water. It was a
chance, in this case, that the sandstone happened to be of such a
constitution as to set, and to allow the bones to be afterward dissolved
out, leaving cavities of the exact shape of the bones. Had that
constitution been other than what it was, the bones would have been
dissolved, the layers of sandstone would have fallen together into one
mass, and not the slightest indication that the animal had existed would
have been discoverable.

I know of no more striking evidence than these facts afford, of the
caution which should be used in drawing the conclusion, from the absence
of organic remains in a deposit, that animals or plants did not exist at
the time it was formed. I believe that, with a right understanding of
the doctrine of evolution on the one hand, and a just estimation of the
importance of the imperfection of the geological record on the other,
all difficulty is removed from the kind of evidence to which I have
adverted; and that we are justified in believing that all such cases are
examples of what I have designated negative or indifferent
evidence--that is to say, they in no way directly advance the hypothesis
of evolution, but they are not to be regarded as obstacles in the way of
our belief in that doctrine.

I now pass on to the consideration of those cases which, for reasons
which I will point out to you by and by, are not to be regarded as
demonstrative of the truth of evolution, but which are such as must
exist if evolution be true, and which therefore are, upon the whole,
evidence in favour of the doctrine. If the doctrine of evolution be
true, it follows, that, however diverse the different groups of animals
and of plants may be, they must all, at one time or other, have been
connected by gradational forms; so that, from the highest animals,
whatever they may be, down to the lowest speck of protoplasmic matter in
which life can be manifested, a series of gradations, leading from one
end of the series to the other, either exists or has existed.
Undoubtedly that is a necessary postulate of the doctrine of evolution.
But when we look upon living Nature as it is, we find a totally
different state of things. We find that animals and plants fall into
groups, the different members of which are pretty closely allied
together, but which are separated by definite, larger or smaller,
breaks, from other groups. In other words, no intermediate forms which
bridge over these gaps or intervals are, at present, to be met with.

To illustrate what I mean: Let me call your attention to those
vertebrate animals which are most familiar to you, such as mammals,
birds, and reptiles. At the present day, these groups of animals are
perfectly well-defined from one another. We know of no animal now living
which, in any sense, is intermediate between the mammal and the bird, or
between the bird and the reptile; but, on the contrary, there are many
very distinct anatomical peculiarities, well-defined marks, by which the
mammal is separated from the bird, and the bird from the reptile. The
distinctions are obvious and striking if you compare the definitions of
these great groups as they now exist.

The same may be said of many of the subordinate groups, or orders, into
which these great classes are divided. At the present time, for example,
there are numerous forms of non-ruminant pachyderms, or what we may call
broadly, the pig tribe, and many varieties of ruminants. These latter
have their definite characteristics, and the former have their
distinguishing peculiarities. But there is nothing that fills up the gap
between the ruminants and the pig tribe. The two are distinct. Such also
is the case in respect of the minor groups of the class of reptiles. The
existing fauna shows us crocodiles, lizards, snakes, and tortoises; but
no connecting link between the crocodile and lizard, nor between the
lizard and snake, nor between the snake and the crocodile, nor between
any two of these groups. They are separated by absolute breaks. If,
then, it could be shown that this state of things had always existed,
the fact would be fatal to the doctrine of evolution. If the
intermediate gradations, which the doctrine of evolution requires to
have existed between these groups, are not to be found anywhere in the
records of the past history of the globe, their absence is a strong and
weighty negative argument against evolution; while, on the other hand,
if such intermediate forms are to be found, that is so much to the good
of evolution; although for reasons which I will lay before you by and
by, we must be cautious in our estimate of the evidential cogency of
facts of this kind.

It is a very remarkable circumstance that, from the commencement of the
serious study of fossil remains, in fact from the time when Cuvier began
his brilliant researches upon those found in the quarries of Montmartre,
palæontology has shown what she was going to do in this matter, and what
kind of evidence it lay in her power to produce.

I said just now that, in the existing Fauna, the group of pig-like
animals and the group of ruminants are entirely distinct; but one of the
first of Cuvier's discoveries was an animal which he called the
_Anoplotherium_, and which proved to be, in a great many important
respects, intermediate in character between the pigs on the one hand,
and the ruminants on the other Thus, research into the history of the
past did, to a certain extent, tend to fill up the breach between the
group of ruminants and the group of pigs. Another remarkable animal
restored by the great French palæontologist, the _Palæotherium_,
similarly tended to connect together animals to all appearance so
different as the rhinoceros, the horse, and the tapir. Subsequent
research has brought to light multitudes of facts of the same order;
and, at the present day, the investigations of such anatomists as
Rütimeyer and Gaudry have tended to fill up, more and more, the gaps in
our existing series of mammals, and to connect groups formerly thought
to be distinct.

But I think it may have an especial interest if, instead of dealing with
these examples, which would require a great deal of tedious osteological
detail, I take the case of birds and reptiles; groups which, at the
present day, are so clearly distinguished from one another that there
are perhaps no classes of animals which, in popular apprehension, are
more completely separated. Existing birds, as you are aware, are covered
with feathers; their anterior extremities, specially and peculiarly
modified, are converted into wings, by the aid of which most of them are
able to fly; they walk upright upon two legs; and these limbs, when they
are considered anatomically, present a great number of exceedingly
remarkable peculiarities, to which I may have occasion to advert
incidentally as I go on, and which are not met with, even approximately,
in any existing forms of reptiles. On the other hand, existing reptiles
have no feathers. They may have naked skins, or be covered with horny
scales, or bony plates, or with both. They possess no wings; they
neither fly by means of their fore-limbs, nor habitually walk upright
upon their hind-limbs; and the bones of their legs present no such
modifications as we find in birds. It is impossible to imagine any two
groups more definitely and distinctly separated, notwithstanding certain
characters which they possess in common.

As we trace the history of birds back in time, we find their remains,
sometimes in great abundance, throughout the whole extent of the
tertiary rocks; but, so far as our present knowledge goes, the birds of
the tertiary rocks retain the same essential characters as the birds of
the present day. In other words, the tertiary birds come within the
definition of the class constituted by existing birds, and are as much
separated from reptiles as existing birds are. Not very long ago no
remains of birds had been found below the tertiary rocks, and I am not
sure but that some persons were prepared to demonstrate that they could
not have existed at an earlier period. But, in the course of the last
few years, such remains have been discovered in England; though,
unfortunately, in so imperfect and fragmentary a condition, that it is
impossible to say whether they differed from existing birds in any
essential character or not. In your country the development of the
cretaceous series of rocks is enormous; the conditions under which the
later cretaceous strata have been deposited are highly favourable to the
preservation of organic remains; and the researches, full of labour and
risk, which have been carried on by Professor Marsh in these cretaceous
rocks of Western America, have rewarded him with the discovery of forms
of birds of which we had hitherto no conception. By his kindness, I am
enabled to place before you a restoration of one of these extraordinary
birds, every part of which can be thoroughly justified by the more or
less complete skeletons, in a very perfect state of preservation, which
he has discovered. This _Hesperornis_ (Fig. 3), which measured between
five and six feet in length, is astonishingly like our existing divers
or grebes in a great many respects; so like them indeed that, had the
skeleton of _Hesperornis_ been found in a museum without its skull,
improbably would have been placed in the same group of birds as the
divers and grebes of the present day.[1] But _Hesperornis_ differs from
all existing birds, and so far resembles reptiles, in one important
particular--it is provided with teeth. The long jaws are armed with
teeth which have curved crowns and thick roots (Fig. 4), and are not set
in distinct sockets, but are lodged in a groove. In possessing true
teeth, the _Hesperornis_ differs from every existing bird, and from
every bird yet discovered in the tertiary formations, the tooth-like
serrations of the jaws in the _Odontopteryx_ of the London clay being
mere processes of the bony substance of the jaws, and not teeth in the
proper sense of the word. In view of the characteristics of this bird we
are therefore obliged to modify the definitions of the classes of birds
and reptiles. Before the discovery of _Hesperornis_, the definition of
the class Aves based upon our knowledge of existing birds might have
been extended to all birds; it might have been said that the absence of
teeth was characteristic of the class of birds; but the discovery of an
animal which, in every part of its skeleton, closely agrees with
existing birds, and yet possesses teeth, shows that there were ancient
birds, which, in respect of possessing teeth, approached reptiles more
nearly than any existing bird does, and, to that extent, diminishes the
_hiatus_ between the two classes.

[Illustration: FIG. 3--HESPERORNIS REGALIS (Marsh).]

The same formation has yielded another bird _Ichthyornis_ (Fig. 5),
which also possesses teeth; but the teeth are situated in distinct
sockets, while those of _Hesperornis_ are not so lodged. The latter also
has such very small, almost rudimentary wings, that it must have been
chiefly a swimmer and a diver like a Penguin; while _Ichthyornis_ has
strong wings and no doubt possessed corresponding powers of flight.
_Ichthyornis_ also differed in the fact that its vertebræ have not the
peculiar characters of the vertebræ of existing and of all known
tertiary birds, but were concave at each end. This discovery leads us to
make a further modification in the definition of the group of birds, and
to part with another of the characters by which almost all existing
birds are distinguished from reptiles.

[Illustration: FIG. 4.--HESPERORNIS REGALIS (Marsh).

Side and upper views of half the lower jaw; side and end views of a
vertebra and a separate tooth.]

Apart from the few fragmentary remains from the English greensand, to
which I have referred, the Mesozoic rocks, older than those in which
_Hesperornis_ and _Ichthyornis_ have been discovered have afforded no
certain evidence of birds, with the remarkable exception of the
Solenhofen slates. These so-called slates are composed of a fine grained
calcareous mud which has hardened into lithographic stone, and in which
organic remains are almost as well preserved as they would be if they
had been imbedded in so much plaster of Paris. They have yielded the
_Archæopteryx_, the existence of which was first made known by the
finding of a fossil feather, or rather of the impression of one. It is
wonderful enough that such a perishable thing as a feather, and nothing
more, should be discovered; yet for a long time, nothing was known of
this bird except its feather. But by and by a solitary skeleton was
discovered which is now in the British Museum. The skull of this
solitary specimen is unfortunately wanting, and it is therefore
uncertain whether the _Archæopteryx_ possessed teeth or not.[2] But the
remainder of the skeleton is so well preserved as to leave no doubt
respecting the main features of the animal, which are very singular. The
feet are not only altogether bird-like, but have the special characters
of the feet of perching birds, while the body had a clothing of true
feathers. Nevertheless, in some other respects, _Archæopteryx_ is unlike
a bird and like a reptile. There is a long tail composed of many
vertebræ. The structure of the wing differs in some very remarkable
respects from that which it presents in a true bird. In the latter, the
end of the wing answers to the thumb and two fingers of my hand; but the
metacarpal bones, or those which answer to the bones of the fingers
which lie in the palm of the hand, are fused together into one mass; and
the whole apparatus, except the last joints of the thumb, is bound up in
a sheath of integument, while the edge of the hand carries the principal
quill feathers. In the _Archæopteryx_, the upper-arm bone is like that
of a bird; and the two bones of the fore-arm are more or less like those
of a bird, but the fingers are not bound together--they are free. What
their number may have been is uncertain; but several, if not all, of
them were terminated by strong curved claws, not like such as are
sometimes found in birds, but such as reptiles possess; so that, in the
_Archæopteryx_, we have an animal which, to a certain extent, occupies a
midway place between a bird and a reptile. It is a bird so far as its
foot and sundry other parts of its skeleton are concerned; it is
essentially and thoroughly a bird by its feathers; but it is much more
properly a reptile in the fact that the region which represents the hand
has separate bones, with claws resembling those which terminate the
fore-limb of a reptile. Moreover, it had a long reptile-like tail with a
fringe of feathers on each side; while, in all true birds hitherto
known, the tail is relatively short, and the vertebræ which constitute
its skeleton are generally peculiarly modified.

[Illustration: FIG. 5.--ICHTHYORNIS DISPAR (Marsh).

(Side and upper views of half the lower jaw; and side and end views of a
vertebra.)]

Like the _Anoplotherium_ and the _Palæotherium_, therefore,
_Archaopteryx_ tends to fill up the interval between groups which, in
the existing world, are widely separated, and to destroy the value of
the definitions of zoological groups based upon our knowledge of
existing forms. And such cases as these constitute evidence in favour of
evolution, in so far as they prove that, in former periods of the
world's history, there were animals which overstepped the bounds of
existing groups, and tended to merge them into larger assemblages. They
show that animal organisation is more flexible than our knowledge of
recent forms might have led us to believe; and that many structural
permutations and combinations, of which the present world gives us no
indication, may nevertheless have existed.

But it by no means follows, because the _Palæotherium_ has much in
common with the horse, on the one hand, and with the rhinoceros on the
other, that it is the intermediate form through which rhinoceroses have
passed to become horses, or _vice versa_; on the contrary, any such
supposition would certainly be erroneous. Nor do I think it likely that
the transition from the reptile to the bird has been effected by such a
form as _Archæopteryx_. And it is convenient to distinguish these
intermediate forms between two groups, which do not represent the actual
passage from the one group to the other, as _intercalary_ types, from
those _linear_ types which, more or less approximately, indicate the
nature of the steps by which the transition from one group to the other
was effected.

I conceive that such linear forms, constituting a series of natural
gradations between the reptile and the bird, and enabling us to
understand the manner in which the reptilian has been metamorphosed into
the bird type, are really to be found among a group of ancient and
extinct terrestrial reptiles known as the _Ornithoscelida_. The remains
of these animals occur throughout the series of Mesozoic formations,
from the Trias to the Chalk, and there are indications of their
existence even in the later Palæozoic strata.

Most of these reptiles, at present known, are of great size, some having
attained a length of forty feet or perhaps more. The majority resembled
lizards and crocodiles in their general form, and many of them were,
like crocodiles, protected by an armour of heavy bony plates. But, in
others, the hind-limbs elongate and the fore-limbs shorten, until their
relative proportions approach those which are observed in the
short-winged, flightless, ostrich tribe among birds.

The skull is relatively light, and in some cases the jaws, though
bearing teeth, are beak-like at their extremities and appear to have
been enveloped in a horny sheath. In the part of the vertebral column
which lies between the haunch bones and is called the sacrum, a number
of vertebræ may unite together into one whole, and in this respect, as
in some details of its structure, the sacrum of these reptiles
approaches that of birds.

But it is in the structure of the pelvis and of the hind limb that some
of these ancient reptiles present the most remarkable approximation to
birds, and clearly indicate the way by which the most specialised and
characteristic features of the bird may have been evolved from the
corresponding parts in the reptile.

In Fig. 6, the pelvis and hind-limbs of a crocodile, a three-toed bird,
and an ornithoscelidan are represented side by side; and, for facility
of comparison, in corresponding positions; but it must be recollected
that, while the position of the bird's limb is natural, that of the
crocodile is not so. In the bird, the thigh-bone lies close to the body,
and the metatarsal bones of the foot (ii., iii., iv., Fig. 6) are,
ordinarily, raised into a more or less vertical position; in the
crocodile, the thigh-bone stands out at an angle from the body, and the
metatarsal bones (i., ii., iii., iv., Fig. 6) lie flat on the ground.
Hence, in the crocodile, the body usually lies squat between the legs,
while, in the bird, it is raised upon the hind legs, as upon pillars.

In the crocodile, the pelvis is obviously composed of three bones on
each side: the ilium (_Il._), the pubis (_Pb._), and the ischium
(_Is._). In the adult bird there appears to be but one bone on each
side. The examination of the pelvis of a chick, however, shows that
each half is made up of three bones, which answer to those which remain
distinct throughout life in the crocodile. There is, therefore, a
fundamental identity of plan in the construction of the pelvis of both
bird and reptile; though the difference in form, relative size, and
direction of the corresponding bones in the two cases are very great.

[Illustration: FIG. 6.--BIRD. ORNITHOSCELIDAN. CROCODILE.

(The letters have the same signification in all the figures. _Il._,
Ilium; _a_, anterior end; _b_, posterior end _Is._, ischium; _Pb._,
pubis; _T_, tibia; _F_, fibula; _As._, astragalus; _Ca._, calcaneum;
_i_, distal portion of the tarsus; i., ii., iii., iv., metatarsal
bones.)]

But the most striking contrast between the two lies in the bones of the
leg and of that part of the foot termed the tarsus, which follows upon
the leg. In the crocodile, the fibula _(F)_ is relatively large and its
lower end is complete. The tibia _(T)_ has no marked crest at its upper
end, and its lower end is narrow and not pulley-shaped. There are two
rows of separate tarsal bones _(As., Ca., &c.)_ and four distinct
metatarsal bones, with a rudiment of a fifth.

In the bird the fibula is small and its lower end diminishes to a point.
The tibia has a strong crest at its upper end and its lower extremity
passes into a broad pulley. There seem at first to be no tarsal bones;
and only one bone, divided at the end into three heads for the three
toes which are attached to it, appears in the place of the metatarsus.

In a young bird, however, the pulley-shaped apparent end of the tibia is
a distinct bone, which represents the bones marked _As., Ca._, in the
crocodile; while the apparently single metatarsal bone consists of three
bones, which early unite with one another and with an additional bone,
which represents the lower row of bones in the tarsus of the crocodile.

In other words it can be shown by the study of development that the
bird's pelvis and hind limb are simply extreme modifications of the same
fundamental plan as that upon which these parts are modelled in
reptiles.

On comparing the pelvis and hind limb of the ornithoscelidan with that
of the crocodile, on the one side, and that of the bird, on the other
(Fig. 6), it is obvious that it represents a middle term between the
two. The pelvic bones approach the form of those of the birds, and the
direction of the pubis and ischium is nearly that which is
characteristic of birds; the thigh bone, from the direction of its head,
must have lain close to the body; the tibia has a great crest; and,
immovably fitted on to its lower end, there is a pulley-shaped bone,
like that of the bird, but remaining distinct. The lower end of the
fibula is much more slender, proportionally, than in the crocodile. The
metatarsal bones have such a form that they fit together immovably,
though they do not enter into bony union; the third toe is, as in the
bird, longest and strongest. In fact, the ornithoscelidan limb is
comparable to that of an unhatched chick.

[Illustration: FIG. 7.--RESTORATION OF COMPSOGNATHUS LONGIPES.]

Taking all these facts together, it is obvious that the view, which was
entertained by Mantell and the probability of which was demonstrated by
your own distinguished anatomist, Leidy, while much additional evidence
in the same direction has been furnished by Professor Cope, that some of
these animals may have walked upon their hind legs, as birds do,
acquires great weight. In fact, there can be no reasonable doubt that
one of the smaller forms of the _Ornithoscelida, Compsognathus_, the
almost entire skeleton of which has been discovered in the Solenhofen
slates, was a bipedal animal. The parts of this skeleton are somewhat
twisted out of their natural relations, but the accompanying figure
gives a just view of the general form of _Compsognathus_ and of the
proportions of its limbs; which, in some respects, are more completely
bird-like than those of other _Ornithoscelida_.

We have had to stretch the definition of the class of birds so as to
include birds with teeth and birds with paw-like fore-limbs and long
tails. There is no evidence that _Compsognathus_ possessed feathers;
but, if it did, it would be hard indeed to say whether it should be
called a reptilian bird or an avian reptile.

As _Compsognathus_ walked upon its hind legs, it must have made tracks
like those of birds. And as the structure of the limbs of several of the
gigantic _Ornithoscelida_, such as _Iguandon_, leads to the conclusion
that they also may have constantly, or occasionally, assumed the same
attitude, a peculiar interest attaches to the fact that, in the Wealden
strata of England, there are to be found gigantic footsteps, arranged in
order like those of the _Brontozoum_, and which there can be no
reasonable doubt were made by some of the _Ornithoscelida_, the remains
of which are found in the same rocks. And, knowing that reptiles that
walked upon their hind legs and shared many of the anatomical characters
of birds did once exist, it becomes a very important question whether
the tracks in the Trias of Massachusetts, to which I referred some time
ago, and which formerly used to be unhesitatingly ascribed to birds may
not all have been made by Ornithoscelidan reptiles; and whether, if we
could obtain the skeletons of the animals which made these tracks, we
should not find in them the actual steps of the evolutional process by
which reptiles gave rise to birds.

The evidential value of the facts I have brought forward in this Lecture
must be neither over nor under estimated. It is not historical proof of
the occurrence of the evolution of birds from reptiles, for we have no
safe ground for assuming that true birds had not made their appearance
at the commencement of the Mesozoic epoch. It is in fact, quite possible
that all these more or less aviform reptiles of the Mesozoic epoch are
not terms in the series of progression from birds to reptiles at all,
but simply the more or less modified descendants of Palæozoic forms
through which that transition was actually effected.

[Illustration: FIG. 8.--PTERODACTYLUS SPECTABILIS (Von Meyer).]

We are not in a position to say that the known _Ornithoscelida_ are
intermediate in the order of their appearance on the earth between
reptiles and birds. All that can be said is that, if independent
evidence of the actual occurrence of evolution is producible, then these
intercalary forms remove every difficulty in the way of understanding
what the actual steps of the process, in the case of birds, may have
been.

That intercalary forms should have existed in ancient times is a
necessary consequence of the truth of the hypothesis of evolution; and,
hence, the evidence I have laid before you in proof of the existence of
such forms, is, so far as it goes, in favour of that hypothesis.

There is another series of extinct reptiles which may be said to be
intercalary between reptiles and birds, in so far as they combine some
of the characters of these groups; and which, as they possessed the
power of flight, may seem, at first sight, to be nearer representatives
of the forms by which the transition from the reptile to the bird was
effected, than the _Ornithoscelida_.

These are the _Pterosauria_, or Pterodactyles, the remains of which are
met with throughout the series of Mesozoic rocks, from the lias to the
chalk, and some of which attain a great size, their wings having a span
of eighteen or twenty feet. These animals, in the form and proportions
of the head and neck relatively to the body, and in the fact that the
ends of the jaws were often, if not always, more or less extensively
ensheathed in horny beaks, remind us of birds. Moreover, their bones
contained air cavities, rendering them specifically lighter, as is the
case in most birds. The breast-bone was large and keeled, as in most
birds and in bats, and the shoulder girdle is strikingly similar to that
of ordinary birds. But it seems to me that the special resemblance of
pterodactyles to birds ends here, unless I may add the entire absence of
teeth which characterises the great pterodactyles (_Pteranodon_)
discovered by Professor Marsh. All other known pterodactyles have teeth
lodged in sockets. In the vertebral column and the hind-limbs there are
no special resemblances to birds, and when we turn to the wings they are
found to be constructed on a totally different principle from those of
birds.

There are four fingers. These four fingers are large, and three of them,
those which answer to the thumb and two following fingers in my
hand--are terminated by claws, while the fourth is enormously prolonged
and converted into a great jointed style. You see at once, from what I
have stated about a bird's wing, that there could be nothing less like a
bird's wing than this is. It was concluded by general reasoning that
this finger had the office of supporting a web which extended between it
and the body. An existing specimen proves that such was really the case,
and that the pterodactyles were devoid of feathers, but that the fingers
supported a vast web like that of a bat's wing; in fact, there can be no
doubt that this ancient reptile flew after the fashion of a bat.

Thus, though the pterodactyle is a reptile which has become modified in
such a manner as to enable it to fly, and therefore, as might be
expected, presents some points of resemblance to other animals which
fly; it has, so to speak, gone off the line which leads directly from
reptiles to birds, and has become disqualified for the changes which
lead to the characteristic organisation of the latter class. Therefore,
viewed in relation to the classes of reptiles and birds, the
pterodactyles appear to me to be, in a limited sense, intercalary forms;
but they are not even approximately linear, in the sense of exemplifying
those modifications of structure through which the passage from the
reptile to the bird took place.


III

THE DEMONSTRATIVE EVIDENCE OF EVOLUTION

The occurrence of historical facts is said to be demonstrated, when the
evidence that they happened is of such a character as to render the
assumption that they did not happen in the highest degree improbable;
and the question I now have to deal with is, whether evidence in favour
of the evolution of animals of this degree of cogency is, or is not,
obtainable from the record of the succession of living forms which is
presented to us by fossil remains.

Those who have attended to the progress of palæontology are aware that
evidence of the character which I have defined has been produced in
considerable and continually-increasing quantity during the last few
years. Indeed, the amount and the satisfactory nature of that evidence
are somewhat surprising, when we consider the conditions under which
alone we can hope to obtain it.

It is obviously useless to seek for such evidence except in localities
in which the physical conditions have been such as to permit of the
deposit of an unbroken, or but rarely interrupted, series of strata
through a long period of time in which the group of animals to be
investigated has existed in such abundance as to furnish the requisite
supply of remains; and in which, finally, the materials composing the
strata are such as to ensure the preservation of these remains in a
tolerably perfect and undisturbed state.

It so happens that the case which, at present, most nearly fulfils all
these conditions is that of the series of extinct animals which
culminates in the horses, by which term I mean to denote not merely the
domestic animals with which we are all so well acquainted, but their
allies, the ass, zebra, quagga, and the like. In short, I use "horses"
as the equivalent of the technical name _Equidæ_, which is applied to
the whole group of existing equine animals.

The horse is in many ways a remarkable animal; not least so in the fact
that it presents us with an example of one of the most perfect pieces of
machinery in the living world. In truth, among the works of human
ingenuity it cannot be said that there is any locomotive so perfectly
adapted to its purposes, doing so much work with so small a quantity of
fuel, as this machine of Nature's manufacture--the horse. And, as a
necessary consequence of any sort of perfection, of mechanical
perfection as of others, you find that the horse is a beautiful
creature, one of the most beautiful of all land animals. Look at the
perfect balance of its form, and the rhythm and force of its action. The
locomotive machinery is, as you are aware, resident in its slender fore
and hind limbs; they are flexible and elastic levers, capable of being
moved by very powerful muscles; and, in order to supply the engines
which work these levers with the force which they expend, the horse is
provided with a very perfect apparatus for grinding its food and
extracting therefrom the requisite fuel.

Without attempting to take you very far into the region of osteological
detail, I must nevertheless trouble you with some statements respecting
the anatomical structure of the horse; and, more especially, will it be
needful to obtain a general conception of the structure of its fore and
hind limbs, and of its teeth. But I shall only touch upon those points
which are absolutely essential to our inquiry.

Let us turn in the first place to the fore-limb. In most quadrupeds, as
in ourselves, the fore-arm contains distinct bones called the radius and
the ulna. The corresponding region in the horse seems at first to
possess but one bone. Careful observation, however, enables us to
distinguish in this bone a part which clearly answers to the upper end
of the ulna. This is closely united with the chief mass of the bone
which represents the radius, and runs out into a slender shaft which may
be traced for some distance downwards upon the back of the radius, and
then in most cases thins out and vanishes. It takes still more trouble
to make sure of what is nevertheless the fact, that a small part of the
lower end of the bone of the horse's fore-arm, which is only distinct in
a very young foal, is really the lower extremity of the ulna.

What is commonly called the knee of a horse is its wrist. The "cannon
bone" answers to the middle bone of the five metacarpal bones, which
support the palm of the hand in ourselves. The "pastern," "coronary,"
and "coffin" bones of veterinarians answer to the joints of our middle
fingers, while the hoof is simply a greatly enlarged and thickened nail.
But if what lies below the horse's "knee" thus corresponds to the middle
finger in ourselves, what has become of the four other fingers or
digits? We find in the places of the second and fourth digits only two
slender splint-like bones, about two-thirds as long as the cannon-bone,
which gradually taper to their lower ends and bear no finger joints, or,
as they are termed, phalanges. Sometimes, small bony or gristly nodules
are to be found at the bases of these two metacarpal splints, and it is
probable that these represent rudiments of the first and fifth toes.
Thus, the part of the horse's skeleton which corresponds with that of
the human hand contains one overgrown middle digit, and at least two
imperfect lateral digits; and these answer, respectively, to the third,
the second, and the fourth fingers in man.

Corresponding modifications are found in the hind limb. In ourselves,
and in most quadrupeds, the leg contains two distinct bones, a large
bone, the tibia, and a smaller and more slender bone, the fibula. But in
the horse, the fibula seems, at first, to be reduced to its upper end; a
short slender bone united with the tibia, and ending in a point below,
occupying its place. Examination of the lower end of a young foal's
shin-bone, however, shows a distinct portion of osseous matter, which
is the lower end of the fibula; so that the apparently single lower end
of the shin-bone is really made up of the coalesced ends of the tibia
and fibula, just as the apparently single lower end of the fore-arm bone
is composed of the coalesced radius and ulna.

The heel of the horse is the part commonly known as the hock. The hinder
cannon-bone answers to the middle metatarsal bone of the human foot, the
pastern, coronary, and coffin bones, to the middle toe bones; the hind
hoof to the nail, as in the fore-foot. And, as in the fore-foot, there
are merely two splints to represent the second and the fourth toes.
Sometimes a rudiment of a fifth toe appears to be traceable.

The teeth of a horse are not less peculiar than its limbs. The living
engine, like all others, must be well stoked if it is to do its work;
and the horse, if it is to make good its wear and tear, and to exert the
enormous amount of force required for its propulsion, must be well and
rapidly fed. To this end, good cutting instruments and powerful and
lasting crushers are needful. Accordingly, the twelve cutting teeth of a
horse are close-set and concentrated in the fore-part of its mouth, like
so many adzes or chisels. The grinders or molars are large, and have an
extremely complicated structure, being composed of a number of different
substances of unequal hardness. The consequence of this is that they
wear away at different rates; and, hence, the surface of each grinder is
always as uneven as that of a good millstone.

I have said that the structure of the grinding teeth is very
complicated, the harder and the softer parts being, as it were,
interlaced with one another. The result of this is that, as the tooth
wears, the crown presents a peculiar pattern, the nature of which is not
very easily deciphered at first; but which it is important we should
understand clearly. Each grinding tooth of the upper jaw has an _outer
wall_ so shaped that, on the worn crown, it exhibits the form of two
crescents, one in front and one behind, with their concave sides turned
outwards. From the inner side of the front crescent, a crescentic _front
ridge_ passes inwards and backwards, and its inner face enlarges into a
strong longitudinal fold or _pillar_. From the front part of the hinder
crescent, a _back ridge_ takes a like direction, and also has its
_pillar_.

The deep interspaces or _valleys_ between these ridges and the outer
wall are filled by bony substance, which is called _cement_, and coats
the whole tooth.

The pattern of the worn face of each grinding tooth of the lower jaw is
quite different. It appears to be formed of two crescent-shaped ridges,
the convexities of which are turned outwards. The free extremity of each
crescent has a _pillar_, and there is a large double _pillar_ where the
two crescents meet; The whole structure is, as it were, imbedded in
cement, which fills up the valleys, as in the upper grinders.

If the grinding faces of an upper and of a lower molar of the same side
are applied together, it will be seen that the apposed ridges are
nowhere parallel, but that they frequently cross; and that thus, in the
act of mastication, a hard surface in the one is constantly applied to a
soft surface in the other, and _vice versa_. They thus constitute a
grinding apparatus of great efficiency, and one which is repaired as
fast as it wears, owing to the long-continued growth of the teeth.

Some other peculiarities of the dentition of the horse must be noticed,
as they bear upon what I shall have to say by and by. Thus the crowns of
the cutting teeth have a peculiar deep pit, which gives rise to the
well-known "mark" of the horse. There is a large space between the outer
incisors and the front grinder. In this space the adult male horse
presents, near the incisors on each side, above and below, a canine or
"tush," which is commonly absent in mares. In a young horse, moreover,
there is not unfrequently to be seen in front of the first grinder, a
very small tooth, which soon falls out. If this small tooth be counted
as one, it will be found that there are seven teeth behind the canine on
each side; namely, the small tooth in question, and the six great
grinders, among which, by an unusual peculiarity, the foremost tooth is
rather larger than those which follow it.

I have now enumerated those characteristic structures of the horse which
are of most importance for the purpose we have in view.

To any one who is acquainted with the morphology of vertebrated animals,
they show that the horse deviates widely from the general structure of
mammals; and that the horse type is, in many respects, an extreme
modification of the general mammalian plan. The least modified mammals,
in fact, have the radius and ulna, the tibia and fibula, distinct and
separate. They have five distinct and complete digits on each foot, and
no one of these digits is very much larger than the rest. Moreover, in
the least modified mammals, the total number of the teeth is very
generally forty-four, while in horses, the usual number is forty, and in
the absence of the canines, it may be reduced to thirty-six; the incisor
teeth are devoid of the fold seen in those of the horse: the grinders
regularly diminish in size from the middle of the series to its front
end; while their crowns are short, early attain their full length, and
exhibit simple ridges or tubercles, in place of the complex foldings of
the horse's grinders.

Hence the general principles of the hypothesis of evolution lead to the
conclusion that the horse must have been derived from some quadruped
which possessed five complete digits on each foot; which had the bones
of the fore-arm and of the leg complete and separate; and which
possessed forty-four teeth, among which the crowns of the incisors and
grinders had a simple structure; while the latter gradually increased in
size from before backwards, at any rate in the anterior part of the
series, and had short crowns.

And if the horse has been thus evolved, and the remains of the different
stages of its evolution have been preserved, they ought to present us
with a series of forms in which the number of the digits becomes
reduced; the bones of the fore-arm and leg gradually take on the equine
condition; and the form and arrangement of the teeth successively
approximate to those which obtain in existing horses.

Let us turn to the facts, and see how far they fulfil these requirements
of the doctrine of evolution.

In Europe abundant remains of horses are found in the Quaternary and
later Tertiary strata as far as the Pliocene formation. But these
horses, which are so common in the cave-deposits and in the gravels of
Europe, are in all essential respects like existing horses. And that is
true of all the horses of the latter part of the Pliocene epoch. But, in
deposits which belong to the earlier Pliocene and later Miocene epochs,
and which occur in Britain, in France, in Germany, in Greece, in India,
we find animals which are extremely like horses--which, in fact, are so
similar to horses, that you may follow descriptions given in works upon
the anatomy of the horse upon the skeletons of these animals--but which
differ in some important particulars. For example, the structure of
their fore and hind limbs is somewhat different. The bones which, in the
horse, are represented by two splints, imperfect below, are as long as
the middle metacarpal and metatarsal bones; and, attached to the
extremity of each, is a digit with three joints of the same general
character as those of the middle digit, only very much smaller. These
small digits are so disposed that they could have had but very little
functional importance, and they must have been rather of the nature of
the dew-claws, such as are to be found in many ruminant animals. The
_Hipparion_, as the extinct European three-toed horse is called, in
fact, presents a foot similar to that of the American _Protohippus_
(Fig. 9), except that, in the _Hipparion_, the smaller digits are
situated farther back, and are of smaller proportional size, than in the
_Protohippus_.

The ulna is slightly more distinct than in the horse; and the whole
length of it, as a very slender shaft, intimately united with the
radius, is completely traceable. The fibula appears to be in the same
condition as in the horse. The teeth of the _Hipparion_ are essentially
similar to those of the horse, but the pattern of the grinders is in
some respects a little more complex, and there is a depression on the
face of the skull in front of the orbit, which is not seen in existing
horses.

In the earlier Miocene, and perhaps the later Eocene deposits of some
parts of Europe, another extinct animal has been discovered, which
Cuvier, who first described some fragments of it, considered to be a
_Palæotherium_. But as further discoveries threw new light upon its
structure, it was recognised as a distinct genus, under the name of
_Anchitherium_.

In its general characters, the skeleton of _Anchitherium_ is very
similar to that of the horse. In fact, Lartet and De Blainville called
it _Palæotherium equinum_ or _hippoides_; and De Christol, in 1847, said
that it differed from _Hipparion_ in little more than the characters of
its teeth, and gave it the name of _Hipparitherium_. Each foot possesses
three complete toes; while the lateral toes are much larger in
proportion to the middle toe than in _Hipparion_, and doubtless rested
on the ground in ordinary locomotion.

The ulna is complete and quite distinct from the radius, though firmly
united with the latter. The fibula seems also to have been complete. Its
lower end, though intimately united with that of the tibia, is clearly
marked off from the latter bone.

There are forty-four teeth. The incisors have no strong pit. The canines
seem to have been well developed in both sexes. The first of the seven
grinders, which, as I have said, is frequently absent, and, when it does
exist, is small in the horse, is a good-sized and permanent tooth, while
the grinder which follows it is but little larger than the hinder ones.
The crowns of the grinders are short, and though the fundamental pattern
of the horse-tooth is discernible, the front and back ridges are less
curved, the accessory pillars are wanting, and the valleys, much
shallower, are not filled up with cement.

Seven years ago, when I happened to be looking critically into the
bearing of palæontological facts upon the doctrine of evolution, it
appeared to me that the _Anchitherium_, the _Hipparion_, and the modern
horses, constitute a series in which the modifications of structure
coincide with the order of chronological occurrence, in the manner in
which they must coincide, if the modern horses really are the result of
the gradual metamorphosis, in the course of the Tertiary epoch, of a
less specialised ancestral form. And I found by correspondence with the
late eminent French anatomist and palæontologist, M. Lartet, that he had
arrived at the same conclusion from the same data.

That the _Anchitherium_ type had become metamorphosed into the
_Hipparion_ type, and the latter into the _Equine_ type, in the course
of that period of time which is represented by the latter half of the
Tertiary deposits, seemed to me to be the only explanation of the facts
for which there was even a shadow of probability.[3]

And, hence, I have ever since held that these facts afford evidence of
the occurrence of evolution, which, in the sense already defined, may be
termed demonstrative.

All who have occupied themselves with the structure of _Anchitherium_,
from Cuvier onwards, have acknowledged its many points of likeness to a
well-known genus of extinct Eocene mammals, _Palæotherium_. Indeed, as
we have seen, Cuvier regarded his remains of _Anchitherium_ as those of
a species of _Palæotherium_. Hence, in attempting to trace the pedigree
of the horse beyond the Miocene epoch and the Anchitheroid form, I
naturally sought among the various species of Palæotheroid animals for
its nearest ally, and I was led to conclude that the _Palæotherium
minus_ (_Plagiolophus_) represented the next step more nearly than any
form then known.

I think that this opinion was fully justifiable; but the progress of
investigation has thrown an unexpected light on the question, and has
brought us much nearer than could have been anticipated to a knowledge
of the true series of the progenitors of the horse.

You are all aware that, when your country was first discovered by
Europeans, there were no traces of the existence of the horse in any
part of the American continent. The accounts of the conquest of Mexico
dwell upon the astonishment of the natives of that country when they
first became acquainted with that astounding phenomenon--a man seated
upon a horse. Nevertheless, the investigations of American geologists
have proved that the remains of horses occur in the most superficial
deposits of both North and South America, just as they do in Europe.
Therefore, for some reason or other--no feasible suggestion on that
subject, so far as I know, has been made--the horse must have died out
on this continent at some period preceding the discovery of America. Of
late years there has been discovered in your Western Territories that
marvellous accumulation of deposits, admirably adapted for the
preservation of organic remains, to which I referred the other evening,
and which furnishes us with a consecutive series of records of the fauna
of the older half of the Tertiary epoch, for which we have no parallel
in Europe. They have yielded fossils in an excellent state of
conservation and in unexampled number and variety. The researches of
Leidy and others have shown that forms allied to the _Hipparion_ and the
_Anchitherium_ are to be found among these remains. But it is only
recently that the admirably conceived and most thoroughly and patiently
worked-out investigations of Professor Marsh have given us a just idea
of the vast fossil wealth, and of the scientific importance, of these
deposits. I have had the advantage of glancing over the collections in
Yale Museum; and I can truly say that, so far as my knowledge extends,
there is no collection from any one region and series of strata
comparable, for extent, or for the care with which the remains have been
got together, or for their scientific importance, to the series of
fossils which he has deposited there. This vast collection has yielded
evidence bearing upon the question of the pedigree of the horse of the
most striking character. It tends to show that we must look to America,
rather than to Europe, for the original seat of the equine series; and
that the archaic forms and successive modifications of the horse's
ancestry are far better preserved here than in Europe.

Professor Marsh's kindness has enabled me to put before you a diagram,
every figure in which is an actual representation of some specimen which
is to be seen at Yale at this present time (Fig. 9).

The succession of forms which he has brought together carries us from
the top to the bottom of the Tertiaries. Firstly, there is the true
horse. Next we have the American Pliocene form of the horse
(_Pliohippus_); in the conformation of its limbs it presents some very
slight deviations from the ordinary horse, and the crowns of the
grinding teeth are shorter. Then comes the _Protohippus_, which
represents the European _Hipparion_, having one large digit and two
small ones on each foot, and the general characters of the fore-arm and
leg to which I have referred. But it is more valuable than the European
_Hipparion_, for the reason that it is devoid of some of the
peculiarities of that form--peculiarities which tend to show that the
European _Hipparion_ is rather a member of a collateral branch, than a
form in the direct line of succession. Next, in the backward order in
time, is the _Miohippus_, which corresponds pretty nearly with the
_Anchitherium_ of Europe. It presents three complete toes--one large
median and two smaller lateral ones; and there is a rudiment of that
digit, which answers to the little finger of the human hand.

[Illustration: FIG. 9.]

The European record of the pedigree of the horse stops here; in the
American Tertiaries, on the contrary, the series of ancestral equine
forms is continued into the Eocene formations. An older Miocene form,
termed _Mesohippus_, has three toes in front, with a large splint-like
rudiment representing the little finger; and three toes behind. The
radius and ulna, the tibia and the fibula, are distinct, and the short
crowned molar teeth are anchitherold in pattern.

But the most important discovery of all is the _Orohippus_, which comes
from the Eocene formation, and is the oldest member of the equine series
as yet known. Here we find four complete toes on the front limb, three
toes on the hind-limb, a well-developed ulna, a well-developed fibula,
and short-crowned grinders of simple pattern.

Thus, thanks to these important researches, it has become evident that,
so far as our present knowledge extends, the history of the horse-type
is exactly and precisely that which could have been predicted from a
knowledge of the principles of evolution. And the knowledge we now
possess justifies us completely in the anticipation, that when the still
lower Eocene deposits, and those which belong to the cretaceous epoch,
have yielded up their remains of ancestral equine animals, we shall
find, first, a form with four complete toes and a rudiment of the
innermost or first digit in front, with probably a rudiment of the fifth
digit in the hind foot;[4] while, in still older forms, the series of
the digits will be more and more complete, until we come to the
five-toed animals, in which, if the doctrine of evolution is well
founded, the whole series must have taken its orgin.

That is what I mean by demonstrative evidence of evolution. An inductive
hypothesis is said to be demonstrated when the facts are shown to be in
entire accordance with it. If that is not scientific proof, there are no
merely inductive conclusions which can be said to be proved. And the
doctrine of evolution, at the present time, rests upon exactly as secure
a foundation as the Copernican theory of the motions of the heavenly
bodies did at the time of its promulgation. Its logical basis is
precisely of the same character--the coincidence of the observed facts
with theoretical requirements.

The only way of escape, if it be a way of escape, from the conclusions
which I have just indicated, is the supposition that all these different
equine forms have been created separately at separate epochs of time;
and, I repeat, that of such an hypothesis as this there neither is, nor
can be, any scientific evidence; and, assuredly so far as I know, there
is none which is supported, or pretends to be supported, by evidence or
authority of any other kind. I can but think that the time will come
when such suggestions as these, such obvious attempts to escape the
force of demonstration, will be put upon the same footing as the
supposition made by some writers, who are I believe not completely
extinct at present, that fossils are mere simulacra, are no indications
of the former existence of the animals to which they seem to belong; but
that they are either sports of Nature, or special creations,
intended--as I heard suggested the other day--to test our faith.

In fact, the whole evidence is in favour of evolution, and there is none
against it. And I say this, although perfectly well aware of the seeming
difficulties which have been built up upon what appears to the
uninformed to be a solid foundation. I meet constantly with the argument
that the doctrine of evolution cannot be well founded, because it
requires the lapse of a very vast period of time; while the duration of
life upon the earth thus implied is inconsistent with the conclusions
arrived at by the astronomer and the physicist. I may venture to say
that I am familiar with those conclusions, inasmuch as some years ago,
when President of the Geological Society of London, I took the liberty
of criticising them, and of showing in what respects, as it appeared to
me, they lacked complete and thorough demonstration. But, putting that
point aside, suppose that, as the astronomers, or some of them, and some
physical philosophers, tell us, it is impossible that life could have
endured upon the earth for as long a period as is required by the
doctrine of evolution--supposing that to be proved--I desire to be
informed, what is the foundation for the statement that evolution does
require so great a time? The biologist knows nothing whatever of the
amount of time which may be required for the process of evolution. It is
a matter of fact that the equine forms which I have described to you
occur, in the order stated, in the Tertiary formations. But I have not
the slightest means of guessing whether it took a million of years, or
ten millions, or a hundred millions, or a thousand millions of years, to
give rise to that series of changes. A biologist has no means of
arriving at any conclusion as to the amount of time which may be needed
for a certain quantity of organic change. He takes his time from the
geologist. The geologist, considering the rate at which deposits are
formed and the rate at which denudation goes on upon the surface of the
earth, arrives at more or less justifiable conclusions as to the time
which is required for the deposit of a certain thickness of rocks; and
if he tells me that the Tertiary formations required 500,000,000 years
for their deposit, I suppose he has good ground for what he says, and I
take that as a measure of the duration of the evolution of the horse
from the _Orohippus_ up to its present condition. And, if he is right,
undoubtedly evolution is a very slow process and requires a great deal
of time. But suppose, now, that an astronomer or a physicist--for
instance, my friend Sir William Thomson--tells me that my geological
authority is quite wrong; and that he has weighty evidence to show that
life could not possibly have existed upon the surface of the earth
500,000,000 years ago, because the earth would have then been too hot to
allow of life, my reply is: "That is not my affair; settle that with the
geologist, and when you have come to an agreement among yourselves I
will adopt your conclusion." We take our time from the geologists and
physicists; and it is monstrous that having taken our time from the
physical philosopher's clock, the physical philosopher should turn round
upon us, and say we are too fast or too slow. What we desire to know is,
is it a fact that evolution took place? As to the amount of time which
evolution may have occupied, we are in the hands of the physicist and
the astronomer, whose business it is to deal with those questions.

I have now, ladies and gentlemen, arrived at the conclusion of the task
which I set before myself when I undertook to deliver these lectures. My
purpose has been, not to enable those among you who have paid no
attention to these subjects before, to leave this room in a condition to
decide upon the validity or the invalidity of the hypothesis of
evolution; but I have desired to put before you the principles upon
which all hypotheses respecting the history of Nature must be judged;
and furthermore, to make apparent the nature of the evidence and the
amount of cogency which is to be expected and may be obtained from it.
To this end, I have not hesitated to regard you as genuine students and
persons desirous of knowing the truth. I have not shrunk from taking you
through long discussions, that I fear may have sometimed tried your
patience; and I have inflicted upon you details which were
indispensable, but which may well have been wearisome. But I shall
rejoice--I shall consider that I have done you the greatest service
which it was in my power to do--if I have thus convinced you that the
great question which we have been discussing is not one to be dealt with
by rhetorical flourishes, or by loose and superficial talk; but that it
requires the keen attention of the trained intellect and the patience of
the accurate observer.




ON THE PHYSICAL BASIS OF LIFE

[1868]


In order to make the title of this discourse generally intelligible, I
have translated the term "Protoplasm," which is the scientific name of
the substance of which I am about to speak, by the words "the physical
basis of life." I suppose that, to many, the idea that there is such a
thing as a physical basis, or matter, of life may be novel--so widely
spread is the conception of life as a something which works through
matter, but is independent of it; and even those who are aware that
matter and life are inseparably connected, may not be prepared for the
conclusion plainly suggested by the phrase, "_the_ physical basis or
matter of life," that there is some one kind of matter which is common
to all living beings, and that their endless diversities are bound
together by a physical, as well as an ideal, unity. In fact, when first
apprehended, such a doctrine as this appears almost shocking to common
sense.

What, truly, can seem to be more obviously different from one another,
in faculty, in form, and in substance, than the various kinds of living
beings? What community of faculty can there be between the
brightly-coloured lichen, which so nearly resembles a mere mineral
incrustation of the bare rock on which it grows, and the painter, to
whom it is instinct with beauty, or the botanist, whom it feeds with
knowledge?

Again, think of the microscopic fungus--a mere infinitesimal ovoid
particle, which finds space and duration enough to multiply into
countless millions in the body of a living fly; and then of the wealth
of foliage, the luxuriance of flower and fruit, which lies between this
bald sketch of a plant and the giant pine of California, towering to the
dimensions of a cathedral spire, or the Indian fig, which covers acres
with its profound shadow, and endures while nations and empires come and
go around its vast circumference. Or, turning to the other half of the
world of life, picture to yourselves the great Finner whale, hugest of
beasts that live, or have lived, disporting his eighty or ninety feet of
bone, muscle, and blubber, with easy roll, among waves in which the
stoutest ship that ever left dockyard would flounder hopelessly; and
contrast him with the invisible animalcules--mere gelatinous specks,
multitudes of which could, in fact, dance upon the point of a needle
with the same ease as the angels of the Schoolmen could, in imagination.
With these images before your minds, you may well ask, what community of
form, or structure, is there between the animalcule and the whale; or
between the fungus and the fig-tree? And, _a fortiori_, between all
four?

Finally, if we regard substance, or material composition, what hidden
bond can connect the flower which a girl wears in her hair and the blood
which courses through her youthful veins; or, what is there in common
between the dense and resisting mass of the oak, or the strong fabric of
the tortoise, and those broad disks of glassy jelly which may be seen
pulsating through the waters of a calm sea, but which drain away to
mere films in the hand which raises them out of their element?

Such objections as these must, I think, arise in the mind of every one
who ponders, for the first time, upon the conception of a single
physical basis of life underlying all the diversities of vital
existence; but I propose to demonstrate to you that, notwithstanding
these apparent difficulties, a threefold unity--namely, a unity of
power or faculty, a unity of form, and a unity of substantial
composition--does pervade the whole living world.

No very abstruse argumentation is needed, in the first place, to prove
that the powers, or faculties, of all kinds of living matter, diverse as
they may be in degree, are substantially similar in kind.

Goethe has condensed a survey of all powers of mankind into the
well-known epigram:--

  "Warum treibt sich das Volk so und schreit?
                Es will sich ernähren
    Kinder zeugen, und die nähren so gut es vermag.

         *       *       *       *       *

    Weiter bringt es kein Mensch, stell' er
                sich wie er auch will."

In physiological language this means, that all the multifarious and
complicated activities of man are comprehensible under three categories.
Either they are immediately directed towards the maintenance and
development of the body, or they effect transitory changes in the
relative positions of parts of the body, or they tend towards the
continuance of the species. Even those manifestations of intellect, of
feeling, and of will, which we rightly name the higher faculties, are
not excluded from this classification, inasmuch as to every one but the
subject of them, they are known only as transitory changes in the
relative positions of parts of the body. Speech, gesture, and every
other form of human action are, in the long run, resolvable into
muscular contraction, and muscular contraction is but a transitory
change in the relative positions of the parts of a muscle. But the
scheme which is large enough to embrace the activities of the highest
form of life, covers all those of the lower creatures. The lowest plant,
or animalcule, feeds, grows, and reproduces its kind. In addition, all
animals manifest those transitory changes of form which we class under
irritability and contractility; and, it is more than probable, that when
the vegetable world is thoroughly explored, we shall find all plants in
possession of the same powers, at one time or other of their existence.

I am not now alluding to such phænomena, at once rare and conspicuous,
as those exhibited by the leaflets of the sensitive plants, or the
stamens of the barberry, but to much more widely spread, and at the same
time, more subtle and hidden, manifestations of vegetable contractility.
You are doubtless aware that the common nettle owes its stinging
property to the innumerable stiff and needle-like, though exquisitely
delicate, hairs which cover its surface. Each stinging-needle tapers
from a broad base to a slender summit, which, though rounded at the end,
is of such microscopic fineness that it readily penetrates, and breaks
off in, the skin. The whole hair consists of a very delicate outer case
of wood, closely applied to the inner surface of which is a layer of
semi-fluid matter, full of innumerable granules of extreme minuteness.
This semi-fluid lining is protoplasm, which thus constitutes a kind of
bag, full of a limpid liquid, and roughly corresponding in form with the
interior of the hair which it fills. When viewed with a sufficiently
high magnifying power, the protoplasmic layer of the nettle hair is seen
to be in a condition of unceasing activity. Local contractions of the
whole thickness of its substance pass slowly and gradually from point to
point, and give rise to the appearance of progressive waves, just as the
bending of successive stalks of corn by a breeze produces the apparent
billows of a cornfield.

But, in addition to these movements, and independently of them, the
granules are driven, in relatively rapid streams, through channels in
the protoplasm which seem to have a considerable amount of persistence.
Most commonly, the currents in adjacent parts of the protoplasm take
similar directions; and, thus, there is a general stream up one side of
the hair and down the other. But this does not prevent the existence of
partial currents which take different routes; and sometimes trains of
granules may be seen coursing swiftly in opposite directions within a
twenty-thousandth of an inch of one another; while, occasionally,
opposite streams come into direct collision, and, after a longer or
shorter struggle, one predominates. The cause of these currents seems to
lie in contractions of the protoplasm which bounds the channels in which
they flow, but which are so minute that the best microscopes show only
their effects, and not themselves.

The spectacle afforded by the wonderful energies prisoned within the
compass of the microscopic hair of a plant, which we commonly regard as
a merely passive organism, is not easily forgotten by one who has
watched its display, continued hour after hour, without pause or sign of
weakening. The possible complexity of many other organic forms,
seemingly as simple as the protoplasm of the nettle, dawns upon one; and
the comparison of such a protoplasm to a body with an internal
circulation, which has been put forward by an eminent physiologist,
loses much of its startling character. Currents similar to those of the
hairs of the nettle have been observed in a great multitude of very
different plants, and weighty authorities have suggested that they
probably occur, in more or less perfection, in all young vegetable
cells. If such be the case, the wonderful noonday silence of a tropical
forest is, after all, due only to the dulness of our hearing; and could
our ears catch the murmur of these tiny Maelstroms, as they whirl in the
innumerable myriads of living cells which constitute each tree, we
should be stunned, as with the roar of a great city.

Among the lower plants, it is the rule rather than the exception, that
contractility should be still more openly manifested at some periods of
their existence. The protoplasm of _Algæ_ and _Fungi_ becomes, under
many circumstances, partially, or completely, freed from its woody case,
and exhibits movements of its whole mass, or is propelled by the
contractility of one, or more, hair-like prolongations of its body,
which are called vibratile cilia. And, so far as the conditions of the
manifestation of the phænomena of contractility have yet been studied,
they are the same for the plant as for the animal. Heat and electric
shocks influence both, and in the same way, though it may be in
different degrees. It is by no means my intention to suggest that there
is no difference in faculty between the lowest plant and the highest, or
between plants and animals. But the difference between the powers of the
lowest plant, or animal, and those of the highest, is one of degree, not
of kind, and depends, as Milne-Edwards long ago so well pointed out,
upon the extent to which the principle of the division of labour is
carried out in the living economy. In the lowest organism all parts are
competent to perform all functions, and one and the same portion of
protoplasm may successfully take on the function of feeding, moving, or
reproducing apparatus. In the highest, on the contrary, a great number
of parts combine to perform each function, each part doing its allotted
share of the work with great accuracy and efficiency, but being useless
for any other purpose.

On the other hand, notwithstanding all the fundamental resemblances
which exist between the powers of the protoplasm in plants and in
animals, they present a striking difference (to which I shall advert
more at length presently), in the fact that plants can manufacture fresh
protoplasm out of mineral compounds, whereas animals are obliged to
procure it ready made, and hence, in the long run, depend upon plants.
Upon what condition this difference in the powers of the two great
divisions of the world of life depends, nothing is at present known.

With such qualification as arises out of the last-mentioned fact, it may
be truly said that the acts of all living things are fundamentally one.
Is any such unity predicable of their forms? Let us seek in easily
verified facts for a reply to this question. If a drop of blood be drawn
by pricking one's finger, and viewed with proper precautions, and under
a sufficiently high microscopic power, there will be seen, among the
innumerable multitude of little, circular, discoidal bodies, or
corpuscles, which float in it and give it its colour, a comparatively
small number of colourless corpuscles, of somewhat larger size and very
irregular shape. If the drop of blood be kept at the temperature of the
body, these colourless corpuscles will be seen to exhibit a marvellous
activity, changing their forms with great rapidity, drawing in and
thrusting out prolongations of their substance, and creeping about as if
they were independent organisms.

The substance which is thus active is a mass of protoplasm, and its
activity differs in detail, rather than in principle, from that of the
protoplasm of the nettle. Under sundry circumstances the corpuscle dies
and becomes distended into a round mass, in the midst of which is seen a
smaller spherical body, which existed, but was more or less hidden, in
the living corpuscle, and is called its _nucleus_. Corpuscles of
essentially similar structure are to be found in the skin, in the lining
of the mouth, and scattered through the whole framework of the body.
Nay, more; in the earliest condition of the human organism, in that
state in which it has but just become distinguishable from the egg in
which it arises, it is nothing but an aggregation of such corpuscles,
and every organ of the body was, once, no more than such an aggregation.

Thus a nucleated mass of protoplasm turns out to be what may be termed
the structural unit of the human body. As a matter of fact, the body, in
its earliest state, is a mere multiple of such units; and in its perfect
condition, it is a multiple of such units, variously modified.

But does the formula which expresses the essential structural character
of the highest animal cover all the rest, as the statement of its powers
and faculties covered that of all others? Very nearly. Beast and fowl,
reptile and fish, mollusk, worm, and polype, are all composed of
structural units of the same character, namely, masses of protoplasm
with a nucleus. There are sundry very low animals, each of which,
structurally, is a mere colourless blood-corpuscle, leading an
independent life. But at the very bottom of the animal scale, even this
simplicity becomes simplified, and all the phænomena of life are
manifested by a particle of protoplasm without a nucleus. Nor are such
organisms insignificant by reason of their want of complexity. It is a
fair question whether the protoplasm of those simplest forms of life,
which people an immense extent of the bottom of the sea, would not
outweigh that of all the higher living beings which inhabit the land put
together. And in ancient times, no less than at the present day, such
living beings as these have been the greatest of rock builders.

What has been said of the animal world is no less true of plants.
Embedded in the protoplasm at the broad, or attached, end of the nettle
hair, there lies a spheroidal nucleus. Careful examination further
proves that the whole substance of the nettle is made up of a repetition
of such masses of nucleated protoplasm, each contained in a wooden case,
which is modified in form, sometimes into a woody fibre, sometimes into
a duct or spiral vessel, sometimes into a pollen grain, or an ovule.
Traced back to its earliest state, the nettle arises as the man does, in
a particle of nucleated protoplasm. And in the lowest plants, as in the
lowest animals, a single mass of such protoplasm may constitute the
whole plant, or the protoplasm may exist without a nucleus.

Under these circumstances it may well be asked, how is one mass of
non-nucleated protoplasm to be distinguished from another? why call one
"plant" and the other "animal"?

The only reply is that, so far as form is concerned, plants and animals
are not separable, and that, in many cases, it is a mere matter of
convention whether we call a given organism an animal or a plant. There
is a living body called _Æthalium septicum_, which appears upon decaying
vegetable substances, and, in one of its forms, is common upon the
surfaces of tan-pits. In this condition it is, to all intents and
purposes, a fungus, and formerly was always regarded as such; but the
remarkable investigations of De Bary have shown that, in another
condition, the _Æthalium_ is an actively locomotive creature, and takes
in solid matters, upon which, apparently, it feeds, thus exhibiting the
most characteristic feature of animality. Is this a plant; or is it an
animal? Is it both; or is it neither? Some decide in favour of the last
supposition, and establish an intermediate kingdom, a sort of biological
No Man's Land for all these questionable forms. But, as it is admittedly
impossible to draw any distinct boundary line between this no man's land
and the vegetable world, on the one hand, or the animal, on the other,
it appears to me that this proceeding merely doubles the difficulty
which, before, was single.

Protoplasm, simple or nucleated, is the formal basis of all life. It is
the clay of the potter: which, bake it and paint it as he will, remains
clay, separated by artifice, and not by nature, from the commonest brick
or sun-dried clod.

Thus it becomes clear that all living powers are cognate, and that all
living forms are fundamentally of one character. The researches of the
chemist have revealed a no less striking uniformity of material
composition in living matter.

In perfect strictness, it is true that chemical investigation can tell
us little or nothing, directly, of the composition of living matter,
inasmuch as such matter must needs die in the act of analysis,--and upon
this very obvious ground, objections, which I confess seem to me to be
somewhat frivolous, have been raised to the drawing of any conclusions
whatever respecting the composition of actually living matter, from that
of the dead matter of life, which alone is accessible to us. But
objectors of this class do not seem to reflect that it is also, in
strictness, true that we know nothing about the composition of any body
whatever, as it is. The statement that a crystal of calc-spar consists
of carbonate of lime, is quite true, if we only mean that, by
appropriate processes, it may be resolved into carbonic acid and
quicklime. If you pass the same carbonic acid over the very quicklime
thus obtained, you will obtain carbonate of lime again; but it will not
be calc-spar, nor anything like it. Can it, therefore, be said that
chemical analysis teaches nothing about the chemical composition of
calc-spar? Such a statement would be absurd; but it is hardly more so
than the talk one occasionally hears about the uselessness of applying
the results of chemical analysis to the living bodies which have yielded
them.

One fact, at any rate, is out of reach of such refinements, and this is,
that all the forms of protoplasm which have yet been examined contain
the four elements, carbon, hydrogen, oxygen, and nitrogen, in very
complex union, and that they behave similarly towards several reagents.
To this complex combination, the nature of which has never been
determined with exactness, the name of Protein has been applied. And if
we use this term with such caution as may properly arise out of our
comparative ignorance of the things for which it stands, it may be truly
said, that all protoplasm is proteinaceous, or, as the white, or
albumen, of an egg is one of the commonest examples of a nearly pure
proteine matter, we may say that all living matter is more or less
albuminoid.

Perhaps it would not yet be safe to say that all forms of protoplasm are
affected by the direct action of electric shocks; and yet the number of
cases in which the contraction of protoplasm is shown to be affected by
this agency increases every day.

Nor can it be affirmed with perfect confidence, that all forms of
protoplasm are liable to undergo that peculiar coagulation at a
temperature of 40°-50° centigrade, which has been called
"heat-stiffening," though Kühne's beautiful researches have proved this
occurrence to take place in so many and such diverse living beings, that
it is hardly rash to expect that the law holds good for all.

       *       *       *       *       *

Enough has, perhaps, been said to prove the existence of a general
uniformity in the character of the protoplasm, or physical basis, of
life, in whatever group of living beings it may be studied. But it will
be understood that this general uniformity by no means excludes any
amount of special modifications of the fundamental substance. The
mineral, carbonate of lime, assumes an immense diversity of characters,
though no one doubts that, under all these Protean changes, it is one
and the same thing.

And now, what is the ultimate fate, and what the origin, of the matter
of life?

Is it, as some of the older naturalists supposed, diffused throughout
the universe in molecules, which are indestructible and unchangeable in
themselves; but, in endless transmigration, unite in innumerable
permutations, into the diversified forms of life we know? Or, is the
matter of life composed of ordinary matter, differing from it only in
the manner in which its atoms are aggregated? Is it built up of ordinary
matter, and again resolved into ordinary matter when its work is done?

Modern science does not hesitate a moment between these alternatives.
Physiology writes, over the portals of life--

     "Debemur morti nos nostraque,"

with a profounder meaning than the Roman poet attached to that
melancholy line. Under whatever disguise it takes refuge, whether fungus
or oak; worm or man, the living protoplasm not only ultimately dies and
is resolved into its mineral and lifeless constituents, but is always
dying, and, strange as the paradox may sound, could not live unless it
died.

In the wonderful story of the "Peau de Chagrin," the hero becomes
possessed of a magical wild ass' skin, which yields him the means of
gratifying all his wishes. But its surface represents the duration of
the proprietor's life; and for every satisfied desire the skin shrinks
in proportion to the intensity of fruition, until at length life and the
last hand-breadth of the _peau de chagrin_, disappear with the
gratification of a last wish.

Balzac's studies had led him over a wide range of thought and
speculation, and his shadowing forth of physiological truth in this
strange story may have been intentional. At any rate, the matter of life
is a veritable _peau de chagrin_, and for every vital act it is somewhat
the smaller. All work implies waste, and the work of life results,
directly or indirectly, in the waste of protoplasm.

Every word uttered by a speaker costs him some physical loss; and, in
the strictest sense, he burns that others may have light--so much
eloquence, so much of his body resolved into carbonic acid, water, and
urea. It is clear that this process of expenditure cannot go on for
ever. But, happily, the protoplasmic _peau de chagrin_ differs from
Balzac's in its capacity of being repaired, and brought back to its full
size, after every exertion.

For example, this present lecture, whatever its intellectual worth to
you, has a certain physical value to me, which is, conceivably,
expressible by the number of grains of protoplasm and other bodily
substance wasted in maintaining my vital processes during its delivery.
My _peau de chagrin_ will be distinctly smaller at the end of the
discourse than it was at the beginning. By and by, I shall probably have
recourse to the substance commonly called mutton, for the purpose of
stretching it back to its original size. Now this mutton was once the
living protoplasm, more or less modified, of another animal--a sheep. As
I shall eat it, it is the same matter altered, not only by death, but by
exposure to sundry artificial operations in the process of cooking.

But these changes, whatever be their extent, have not rendered it
incompetent to resume its old functions as matter of life. A singular
inward laboratory, which I possess, will dissolve a certain portion of
the modified protoplasm; the solution so formed will pass into my veins;
and the subtle influences to which it will then be subjected will
convert the dead protoplasm into living protoplasm, and transubstantiate
sheep into man.

Nor is this all. If digestion were a thing to be trifled with, I might
sup upon lobster, and the matter of life of the crustacean would undergo
the same wonderful metamorphosis into humanity. And were I to return to
my own place by sea, and undergo shipwreck, the crustacean might, and
probably would, return the compliment, and demonstrate our common nature
by turning my protoplasm into living lobster. Or, if nothing better were
to be had, I might supply my wants with mere bread, and I should find
the protoplasm of the wheat-plant to be convertible into man, with no
more trouble than that of the sheep, and with far less, I fancy, than
that of the lobster.

Hence it appears to be a matter of no great moment what animal, or what
plant, I lay under contribution for protoplasm, and the fact speaks
volumes for the general identity of that substance in all living beings.
I share this catholicity of assimilation with other animals, all of
which, so far as we know, could thrive equally well on the protoplasm of
any of their fellows, or of any plant; but here the assimilative powers
of the animal world cease. A solution of smelling-salts in water, with
an infinitesimal proportion of some other saline matters, contains all
the elementary bodies which enter into the composition of protoplasm;
but, as I need hardly say, a hogshead of that fluid would not keep a
hungry man from starving, nor would it save any animal whatever from a
like fate. An animal cannot make protoplasm, but must take it ready-made
from some other animal, or some plant--the animal's highest feat of
constructive chemistry being to convert dead protoplasm into that living
matter of life which is appropriate to itself.

Therefore, in seeking for the origin of protoplasm, we must eventually
turn to the vegetable world. A fluid containing carbonic acid, water,
and nitrogenous salts, which offers such a Barmecide feast to the
animal, is a table richly spread to multitudes of plants; and, with a
due supply of only such materials, many a plant will not only maintain
itself in vigour, but grow and multiply until it has increased a
million-fold, or a million million-fold, the quantity of protoplasm
which it originally possessed; in this way building up the matter of
life, to an indefinite extent, from the common matter of the universe.

Thus, the animal can only raise the complex substance of dead protoplasm
to the higher power, as one may say, of living protoplasm; while the
plant can raise the less complex substances--carbonic acid, water, and
nitrogenous salts--to the same stage of living protoplasm, if not to the
same level. But the plant also has its limitations. Some of the fungi,
for example, appear to need higher compounds to start with; and no known
plant can live upon the uncompounded elements of protoplasm. A plant
supplied with pure carbon, hydrogen, oxygen, and nitrogen, phosphorus,
sulphur, and the like, would as infallibly die as the animal in his bath
of smelling-salts, though it would be surrounded by all the
constituents of protoplasm. Nor, indeed, need the process of
simplification of vegetable food be carried so far as this, in order to
arrive at the limit of the plant's thaumaturgy. Let water, carbonic
acid, and all the other needful constituents be supplied except
nitrogenous salts, and an ordinary plant will still be unable to
manufacture protoplasm.

Thus the matter of life, so far as we know it (and we have no right to
speculate on any other), breaks up, in consequence of that continual
death which is the condition of its manifesting vitality, into carbonic
acid, water, and nitrogenous compounds, which certainly possess no
properties but those of ordinary matter. And out of these same forms of
ordinary matter, and from none which are simpler, the vegetable world
builds up all the protoplasm which keeps the animal world a-going.
Plants are the accumulators of the power which animals distribute and
disperse.

But it will be observed, that the existence of the matter of life
depends on the pre-existence of certain compounds; namely, carbonic
acid, water, and certain nitrogenous bodies. Withdraw any one of these
three from the world, and all vital phænomena come to an end. They are
as necessary to the protoplasm of the plant as the protoplasm of the
plant is to that of the animal. Carbon, hydrogen, oxygen, and nitrogen
are all lifeless bodies. Of these, carbon and oxygen unite in certain
proportions and under certain conditions, to give rise to carbonic acid;
hydrogen and oxygen produce water; nitrogen and other elements give rise
to nitrogenous salts. These new compounds, like the elementary bodies of
which they are composed, are lifeless. But when they are brought
together, under certain conditions, they give rise to the still more
complex body, protoplasm, and this protoplasm exhibits the phænomena of
life.

I see no break in this series of steps in molecular complication, and I
am unable to understand why the language which is applicable to any one
term of the series may not be used to any of the others. We think fit to
call different kinds of matter carbon, oxygen, hydrogen, and nitrogen,
and to speak of the various powers and activities of these substances as
the properties of the matter of which they are composed.

When hydrogen and oxygen are mixed in a certain proportion, and an
electric spark is passed through them, they disappear, and a quantity of
water, equal in weight to the sum of their weights, appears in their
place. There is not the slightest parity between the passive and active
powers of the water and those of the oxygen and hydrogen which have
given rise to it. At 32° Fahrenheit, and far below that temperature,
oxygen and hydrogen are elastic gaseous bodies, whose particles tend to
rush away from one another with great force. Water, at the same
temperature, is a strong though brittle solid, whose particles tend to
cohere into definite geometrical shapes, and sometimes build up frosty
imitations of the most complex forms of vegetable foliage.

Nevertheless we call these, and many other strange phænomena, the
properties of the water, and we do not hesitate to believe that, in some
way or another, they result from the properties of the component
elements of the water. We do not assume that a something called
"aquosity" entered into and took possession of the oxidated hydrogen as
soon as it was formed, and then guided the aqueous particles to their
places in the facets of the crystal, or amongst the leaflets of the
hoarfrost. On the contrary, we live in the hope and in the faith that,
by the advance of molecular physics, we shall by and by be able to see
our way as clearly from the constituents of water to the properties of
water, as we are now able to deduce the operations of a watch from the
form of its parts and the manner in which they are put together.

Is the case in any way changed when carbonic acid, water, and
nitrogenous salts disappear, and in their place, under the influence of
pre-existing living protoplasm, an equivalent weight of the matter of
life makes its appearance?

It is true that there is no sort of parity between the properties of the
components and the properties of the resultant, but neither was there in
the case of the water. It is also true that what I have spoken of as the
influence of pre-existing living matter is something quite
unintelligible; but does anybody quite comprehend the _modus operandi_
of an electric spark, which traverses a mixture of oxygen and hydrogen?

What justification is there, then, for the assumption of the existence
in the living matter of a something which has no representative, or
correlative, in the not living matter which gave rise to it? What better
philosophical status has "vitality" than "aquosity"? And why should
"vitality" hope for a better fate than the other "itys" which have
disappeared since Martinus Scriblerus accounted for the operation of the
meat-jack by its inherent "meat-roasting quality," and scorned the
"materialism" of those who explained the turning of the spit by a
certain mechanism worked by the draught of the chimney.

If scientific language is to possess a definite and constant
signification whenever it is employed, it seems to me that we are
logically bound to apply to the protoplasm, or physical basis of life,
the same conceptions as those which are held to be legitimate elsewhere.
If the phenomena exhibited by water are its properties, so are those
presented by protoplasm, living or dead, its properties.

If the properties of water may be properly said to result from the
nature and disposition of its component molecules, I can find no
intelligible ground for refusing to say that the properties of
protoplasm result from the nature and disposition of its molecules.

But I bid you beware that, in accepting these conclusions, you are
placing your feet on the first rung of a ladder which, in most people's
estimation, is the reverse of Jacob's, and leads to the antipodes of
heaven. It may seem a small thing to admit that the dull vital actions
of a fungus, or a foraminifer, are the properties of their protoplasm,
and are the direct results of the nature of the matter of which they are
composed. But if, as I have endeavoured to prove to you, their
protoplasm is essentially identical with, and most readily converted
into, that of any animal, I can discover no logical halting-place
between the admission that such is the case, and the further concession
that all vital action may, with equal propriety, be said to be the
result of the molecular forces of the protoplasm which displays it. And
if so, it must be true, in the same sense and to the same extent, that
the thoughts to which I am now giving utterance, and your thoughts
regarding them, are the expression of molecular changes in that matter
of life which is the source of our other vital phænomena.

Past experience leads me to be tolerably certain that, when the
propositions I have just placed before you are accessible to public
comment and criticism, they will be condemned by many zealous persons,
and perhaps by some few of the wise and thoughtful. I should not wonder
if "gross and brutal materialism" were the mildest phrase applied to
them in certain quarters. And, most undoubtedly, the terms of the
propositions are distinctly materialistic. Nevertheless two things are
certain; the one, that I hold the statements to be substantially true;
the other, that I, individually, am no materialist, but, on the
contrary, believe materialism to involve grave philosophical error.

This union of materialistic terminology with the repudiation of
materialistic philosophy I share with some of the most thoughtful men
with whom I am acquainted. And, when I first undertook to deliver the
present discourse, it appeared to me to be a fitting opportunity to
explain how such a union is not only consistent with, but necessitated
by, sound logic. I purposed to lead you through the territory of vital
phænomena to the materialistic slough in which you find yourselves now
plunged, and then to point out to you the sole path by which, in my
judgment, extrication is possible.

An occurrence of which I was unaware until my arrival here last night
renders this line of argument singularly opportune. I found in your
papers the eloquent address "On the Limits of Philosophical Inquiry,"
which a distinguished prelate of the English Church delivered before the
members of the Philosophical Institution on the previous day. My
argument, also, turns upon this very point of the limits of
philosophical inquiry; and I cannot bring out my own views better than
by contrasting them with those so plainly and, in the main, fairly
stated by the Archbishop of York.

But I may be permitted to make a preliminary comment upon an occurrence
that greatly astonished me. Applying the name of the "New Philosophy" to
that estimate of the limits of philosophical inquiry which I, in common
with many other men of science, hold to be just, the Archbishop opens
his address by identifying this "New Philosophy" with the Positive
Philosophy of M. Comte (of whom he speaks as its "founder"); and then
proceeds to attack that philosopher and his doctrines vigorously.

Now, so far as I am concerned, the most reverend prelate might
dialectically hew M. Comte in pieces, as a modern Agag, and I should not
attempt to stay his hand. In so far as my study of what specially
characterises the Positive Philosophy has led me, I find therein little
or nothing of any scientific value, and a great deal which is as
thoroughly antagonistic to the very essence of science as anything in
ultramontane Catholicism. In fact, M. Comte's philosophy, in practice,
might be compendiously described as Catholicism _minus_ Christianity.

But what has Comtism to do with the "New Philosophy," as the Archbishop,
defines it in the following passage?

     "Let me briefly remind you of the leading principles of this new
     philosophy.

     "All knowledge is experience of facts acquired by the senses. The
     traditions of older philosophies have obscured our experience by
     mixing with it much that the senses cannot observe, and until these
     additions are discarded our knowledge is impure. Thus metaphysics
     tell us that one fact which we observe is a cause, and another is
     the effect of that cause; but, upon a rigid analysis, we find that
     our senses observe nothing of cause or effect: they observe, first,
     that one fact succeeds another, and, after some opportunity, that
     this fact has never failed to follow--that for cause and effect we
     should substitute invariable succession. An older philosophy
     teaches us to define an object by distinguishing its essential from
     its accidental qualities: but experience knows nothing of essential
     and accidental; she sees only that, certain marks attach to an
     object, and, after many observations, that some of them attach
     invariably, whilst others may at times be absent.... As all
     knowledge is relative, the notion of anything being necessary must
     be banished with other traditions." [5]

There is much here that expresses the spirit of the "New Philosophy," if
by that term be meant the spirit of modern science; but I cannot but
marvel that the assembled wisdom and learning of Edinburgh should have
uttered no sign of dissent, when Comte was declared to be the founder of
these doctrines. No one will accuse Scotchmen of habitually forgetting
their great countrymen; but it was enough to make David Hume turn in his
grave, that here, almost within ear-shot of his house, an instructed
audience should have listened, without a murmur, while his most
characteristic doctrines were attributed to a French writer of fifty
years later date, in whose dreary and verbose pages we miss alike the
vigour of thought and the exquisite clearness of style of the man whom I
make bold to term the most acute thinker of the eighteenth century--even
though that century produced Kant.

But I did not come to Scotland to vindicate the honour of one of the
neatest men she has ever produced. My business is to point out to you
that the only way of escape out of the "crass materialism" in which we
just now landed, is the adoption and strict working out of the very
principles which the Archbishop holds up to reprobation.

Let us suppose that knowledge is absolute, and not relative, and
therefore, that our conception of matter represents that which it really
is. Let us suppose, further, that we do know more of cause and effect
than a certain definite order of succession among facts, and that we
have a knowledge of the necessity of that succession--and hence, of
necessary laws--and I, for my part, do not see what escape there is from
utter materialism and necessarianism. For it is obvious that our
knowledge of what we call the material world is, to begin with, at least
as certain and definite as that of the spiritual world, and that our
acquaintance with law is of as old a date as our knowledge of
spontaneity. Further, I take it to be demonstrable that it is utterly
impossible to prove that anything whatever may not be the effect of a
material and necessary cause, and that human logic is equally
incompetent to prove that any act is really spontaneous. A really
spontaneous act is one which, by the assumption, has no cause; and the
attempt to prove such a negative as this is, on the face of the matter,
absurd. And while it is thus a philosophical impossibility to
demonstrate that any given phænomenon is not the effect of a material
cause, any one who is acquainted with the history of science will admit,
that its progress has, in all ages, meant, and now, more than ever,
means, the extension of the province of what we call matter and
causation, and the concomitant gradual banishment from all regions of
human thought of what we call spirit and spontaneity.

I have endeavoured, in the first part of this discourse, to give you a
conception of the direction towards which modern physiology is tending;
and I ask you, what is the difference between the conception of life as
the product of a certain disposition of material molecules, and the old
notion of an Archæus governing and directing blind matter within each
living body, except this--that here, as elsewhere, matter and law have
devoured spirit and spontaneity? And as surely as every future grows out
of past and present, so will the physiology of the future gradually
extend the realm of matter and law until it is co-extensive with
knowledge, with feeling, and with action.

The consciousness of this great truth weighs like a nightmare, I
believe, upon many of the best minds of these days. They watch what they
conceive to be the progress of materialism, in such fear and powerless
anger as a savage feels, when, during an eclipse, the great shadow
creeps over the face of the sun. The advancing tide of matter threatens
to drown their souls; the tightening grasp of law impedes their freedom;
they are alarmed lest man's moral nature be debased by the increase of
his wisdom.

If the "New Philosophy" be worthy of the reprobation with which it is
visited, I confess their fears seem to me to be well founded. While, on
the contrary, could David Hume be consulted, I think he would smile at
their perplexities, and chide them for doing even as the heathen, and
falling down in terror before the hideous idols their own hands have
raised.

For, after all, what do we know of this terrible "matter," except as a
name for the unknown and hypothetical cause of states of our own
consciousness? And what do we know of that "spirit" over whose
threatened extinction by matter a great lamentation is arising, like
that which was heard at the death of Pan, except that it is also a name
for an unknown and hypothetical cause, or condition, of states of
consciousness? In other words, matter and spirit are but names for the
imaginary substrata of groups of natural phænomena.

And what is the dire necessity and "iron" law under which men groan?
Truly, most gratuitously invented bugbears. I suppose if there be an
"iron" law, it is that of gravitation; and if there be a physical
necessity, it is that a stone, unsupported, must fall to the ground. But
what is all we really know, and can know, about the latter phænomena?
Simply, that, in all human experience, stones have fallen to the ground
under these conditions; that we have not the smallest reason for
believing that any stone so circumstanced will not fall to the ground;
and that we have, on the contrary, every reason to believe that it will
so fall. It is very convenient to indicate that all the conditions of
belief have been fulfilled in this case, by calling the statement that
unsupported stones will fall to the ground, "a law of Nature." But when,
as commonly happens, we change _will_ into _must_, we introduce an idea
of necessity which most assuredly does not lie in the observed facts,
and has no warranty that I can discover elsewhere. For my part, I
utterly repudiate and anathematise the intruder. Fact I know; and Law I
know; but what is this Necessity, save an empty shadow of my own mind's
throwing?

But, if it is certain that we can have no knowledge of the nature of
either matter or spirit, and that the notion of necessity is something
illegitimately thrust into the perfectly legitimate conception of law,
the materialistic position that there is nothing in the world but
matter, force, and necessity, is as utterly devoid of justification as
the most baseless of theological dogmas. The fundamental doctrines of
materialism, like those of spiritualism, and most other "isms," lie
outside "the limits of philosophical inquiry," and David Hume's great
service to humanity is his irrefragable demonstration of what these
limits are. Hume called himself a sceptic and therefore others cannot be
blamed if they apply the same title to him; but that does not alter the
fact that the name, with its existing implications, does him gross
injustice.

If a man asks me what the politics of the inhabitants of the moon are,
and I reply that I do not know; that neither I, nor any one else, has
any means of knowing; and that, under these circumstances, I decline to
trouble myself about the subject at all, I do not think he has any right
to call me a sceptic. On the contrary, in replying thus, I conceive that
I am simply honest and truthful, and show a proper regard for the
economy of time. So Hume's strong and subtle intellect takes up a great
many problems about which we are naturally curious, and shows us that
they are essentially questions of lunar politics, in their essence
incapable of being answered, and therefore not worth the attention of
men who have work to do in the world. And he thus ends one of his
essays:--

     "If we take in hand any volume of Divinity, or school metaphysics,
     for instance, let us ask, _Does it contain any abstract reasoning
     concerning quantity or number?_ No. _Does it contain any
     experimental reasoning concerning matter of fact and existence?_
     No. Commit it then to the flames; for it can contain nothing but
     sophistry and illusion." [6]

Permit me to enforce this most wise advice. Why trouble ourselves about
matters of which, however important they may be, we do know nothing, and
can know nothing? We live in a world which is full of misery and
ignorance, and the plain duty of each and all of us is to try to make
the little corner he can influence somewhat less miserable and somewhat
less ignorant than it was before he entered it. To do this effectually
it is necessary to be fully possessed of only two beliefs: the first,
that the order of Nature is ascertainable by our faculties to an extent
which is practically unlimited; the second, that our volition[7] counts
for something as a condition of the course of events.

Each of these beliefs can be verified experimentally, as often as we
like to try. Each, therefore, stands upon the strongest foundation upon
which any belief can rest, and forms one of our highest truths. If we
find that the ascertainment of the order of nature is facilitated by
using one terminology, or one set of symbols, rather than another, it is
our clear duty to use the former; and no harm can accrue, so long as we
bear in mind, that we are dealing merely with terms and symbols.

In itself it is of little moment whether we express the phænomena of
matter in terms of spirit; or the phænomena of spirit in terms of
matter: matter may be regarded as a form of thought, thought may be
regarded as a property of matter--each statement has a certain relative
truth. But with a view to the progress of science, the materialistic
terminology is in every way to be preferred. For it connects thought
with the other phænomena of the universe, and suggests inquiry into the
nature of those physical conditions, or concomitants of thought, which
are more or less accessible to us, and a knowledge of which may, in
future, help us to exercise the same kind of control over the world of
thought, as we already possess in respect of the material world;
whereas, the alternative, or spiritualistic, terminology is utterly
barren, and leads to nothing but obscurity and confusion of ideas.

Thus there can be little doubt, that the further science advances, the
more extensively and consistently will all the phænomena of Nature be
represented by materialistic formulæ and symbols.

But the man of science, who, forgetting the limits of philosophical
inquiry, slides from these formulæ and symbols into what is commonly
understood by materialism, seems to me to place himself on a level with
the mathematician, who should mistake the _x_'s and _y_'s with which he
works his problems, for real entities--and with this further
disadvantage, as compared with the mathematician, that the blunders of
the latter are of no practical consequence, while the errors of
systematic materialism may paralyse the energies and destroy the beauty
of a life.




NATURALISM AND SUPERNATURALISM

[FROM PROLOGUE TO CONTROVERTED QUESTIONS, 1892.]


There is a single problem with different aspects of which thinking men
have been occupied, ever since they began seriously to consider the
wonderful frame of things in which their lives are set, and to seek for
trustworthy guidance among its intricacies.

Experience speedily taught them that the shifting scenes of the world's
stage have a permanent background; that there is order amidst the
seeming contusion, and that many events take place according to
unchanging rules. To this region of familiar steadiness and customary
regularity they gave the name of Nature. But at the same time, their
infantile and untutored reason, little more, as yet, than the playfellow
of the imagination, led them to believe that this tangible, commonplace,
orderly world of Nature was surrounded and interpenetrated by another
intangible and mysterious world, no more bound by fixed rules than, as
they fancied, were the thoughts and passions which coursed through their
minds and seemed to exercise an intermittent and capricious rule over
their bodies. They attributed to the entities, with which they peopled
this dim and dreadful region, an unlimited amount of that power of
modifying the course of events of which they themselves possessed a
small share, and thus came to regard them as not merely beyond, but
above, Nature.

Hence arose the conception of a "Supernature" antithetic to
"Nature"--the primitive dualism of a natural world "fixed in fate" and a
supernatural, left to the free play of volition--which has pervaded all
later speculation, and, for thousands of years, has exercised a profound
influence on practice. For it is obvious that, on this theory of the
Universe, the successful conduct of life must demand careful attention
to both worlds; and, if either is to be neglected, it may be safer that
it should be Nature. In any given contingency, it must doubtless be
desirable to know what may be expected to happen in the ordinary course
of things; but it must be quite as necessary to have some inkling of the
line likely to be taken by supernatural agencies able, and possibly
willing, to suspend or reverse that course. Indeed, logically developed,
the dualistic theory must needs end in almost exclusive attention to
Supernature, and in trust that its over-ruling strength will be exerted
in favour of those who stand well with its denizens. On the other hand,
the lessons of the great school-master, experience, have hardly seemed
to accord with this conclusion. They have taught, with considerable
emphasis, that it does not answer to neglect Nature; and that, on the
whole, the more attention paid to her dictates the better men fare.

Thus the theoretical antithesis brought about a practical antagonism.
From the earliest times of which we have any knowledge, Naturalism and
Supernaturalism have consciously, or unconsciously, competed and
struggled with one another; and the varying fortunes of the contest are
written in the records of the course of civilisation from those of Egypt
and Babylonia, six thousand years ago, down to those of our own time and
people.

These records inform us that, so far as men have paid attention to
Nature, they have been rewarded for their pains. They have developed the
Arts which have furnished the conditions of civilised existence; and the
Sciences, which have been a progressive revelation of reality, and have
afforded the best discipline of the mind in the methods of discovering
truth. They have accumulated a vast body of universally accepted
knowledge; and the conceptions of man and of society, of morals and of
law, based upon that knowledge, are every day more and more, either
openly or tacitly, acknowledged to be the foundations of right action.

History also tells us that the field of the supernatural has rewarded
its cultivators with a harvest, perhaps not less luxuriant, but of a
different character. It has produced an almost infinite diversity of
Religions. These, if we set aside the ethical concomitants upon which
natural knowledge also has a claim, are composed of information about
Supernature; they tell us of the attributes of supernatural beings, of
their relations with Nature, and of the operations by which their
interference with the ordinary course of events can be secured or
averted. It does not appear, however, that supernaturalists have
attained to any agreement about these matters or that history indicates
a widening of the influence of supernaturalism on practice, with the
onward flow of time. On the contrary, the various religions are, to a
great extent, mutually exclusive; and their adherents delight in
charging each other, not merely with error, but with criminality,
deserving and ensuing punishment of infinite severity. In singular
contrast with natural knowledge, again, the acquaintance of mankind with
the supernatural appears the more extensive and the more exact, and the
influence of supernatural doctrines upon conduct the greater, the
further back we go in time and the lower the stage of civilisation
submitted to investigation. Historically, indeed, there would seem to
be an inverse relation between supernatural and natural knowledge. As
the latter has widened, gained in precision and in trustworthiness, so
has the former shrunk, grown vague and questionable; as the one has more
and more filled the sphere of action, so has the other retreated into
the region of meditation, or vanished behind the screen of mere verbal
recognition.

Whether this difference of the fortunes of Naturalism and of
Supernaturalism is an indication of the progress, or of the regress, of
humanity; of a fall from, or an advance towards, the higher life; is a
matter of opinion. The point to which I wish to direct attention is that
the difference exists and is making itself felt. Men are growing to be
seriously alive to the fact that the historical evolution of humanity
which is generally, and I venture to think not unreasonably, regarded as
progress, has been, and is being, accompanied by a co-ordinate
elimination of the supernatural from its originally large occupation of
men's thoughts. The question--How far is this process to go?--is in my
apprehension, the Controverted Question of our time.

Controversy on this matter--prolonged, bitter, and fought out with the
weapons of the flesh, as well as with those of the spirit--is no new
thing to Englishmen. We have been more or less occupied with it these
five hundred years. And, during that time, we have made attempts to
establish a _modus vivendi_ between the antagonists, some of which have
had a world-wide influence; though, unfortunately, none have proved
universally and permanently satisfactory.

In the fourteenth century, the controverted question among us was,
whether certain portions of the Supernaturalism of mediæval Christianity
were well-founded. John Wicliff proposed a solution of the problem
which, in the course of the following two hundred years, acquired wide
popularity and vast historical importance: Lollards, Hussites,
Lutherans, Calvinists, Zwinglians, Socinians, and Anabaptists, whatever
their disagreements, concurred in the proposal to reduce the
Supernaturalism of Christianity within the limits sanctioned by the
Scriptures. None of the chiefs of Protestantism called in question
either the supernatural origin and infallible authority of the Bible, or
the exactitude of the account of the supernatural world given in its
pages. In fact, they could not afford to entertain any doubt about these
points, since the infallible Bible was the fulcrum of the lever with
which they were endeavouring to upset the Chair of St. Peter. The
"freedom of private judgment" which they proclaimed, meant no more, in
practice, than permission to themselves to make free with the public
judgment of the Roman Church, in respect of the canon and of the meaning
to be attached to the words of the canonical books. Private
judgment--that is to say, reason--was (theoretically, at any rate) at
liberty to decide what books were and what were not to take the rank of
"Scripture"; and to determine the sense of any passage in such books.
But this sense, once ascertained to the mind of the sectary, was to be
taken for pure truth--for the very word of God. The controversial
efficiency of the principle of biblical infallibility lay in the fact
that the conservative adversaries of the Reformers were not in a
position to contravene it without entangling themselves in serious
difficulties; while, since both Papists and Protestants agreed in taking
efficient measures to stop the mouths of any more radical critics, these
did not count.

The impotence of their adversaries, however, did not remove the inherent
weakness of the position of the Protestants. The dogma of the
infallibility of the Bible is no more self-evident than is that of the
infallibility of the Pope. If the former is held by "faith," then the
latter may be. If the latter is to be accepted, or rejected, by private
judgment, why not the former? Even if

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