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DISCOURSES ^^^

BIOLOGICAL AND GEOLOGICAL ^^

ESSAYS

BY

THOMAS H. HUXLEY

NEW YORK
D. APPLETON AND COMPANY

1896

Authorized Edition.

rHEFACE

The contents of the present volume, with three
exceptions, are either popular lectures, or addresses
delivered to scientific bodies with which I have
been officially connected. I am not sure which
gave me the more trouble. For I have not been
one of those fortunate persons who are able to
regard a popular lecture as a mere hers dCceuvre,
unworthy of being ranked among the serious efforts
of a philosopher; and who keep their fame as
scientific hierophants unsullied by attempts — at
least of the successful sort — to be understanded
of the people.

On tlie contrary, I found that the task of
putting the truths learned in the field, the
laboratory and the museum, into language which,
without bating a jot of scientific accuracy shall be
generally intelligible, taxed such scientific and
literary faculty as I possessed to the uttermost;
indeed my experience has furnished me with no
better corrective of the tendency to scholastic
pedantry Avhich besots all those who are absorbed

VI PREFACE

in pursuits remote from the common ways of men,
and become habituated to think and speak in the
technical dialect of their own little world, as if
there were no other.

If the popular lecture thus, as I believe,
finds one moiety of its justification in the self-
disciphne of the lecturer, it surely finds the
other half in its effect on the auditory. For
though various sadly comical experiences of the
results of my own efforts have led me to entertain
a very moderate estimate of the purely intellectual
value of lectures ; though I venture to doubt if
more than one in ten of an average audience
carries away an accurate notion of what the
speaker has been driving at ; yet is that not
equally true of the oratory of the hustings, of the
House of Commons, and even of the pulpit ?

Yet the children of this world are wise in their
generation ; and both the politician and the priest
are justified by results. The living voice has an
influence over human action altogether indepen-
dent of the intellectual worth of that which it
utters. Many years ago, I was a guest at a great
City dinner. A famous orator, endowed with a
voice of rare flexibihty and power ; a born actor,
ranging with ease through every part, from refined
comedy to tragic unction, was called upon to reply
to a toast. The orator was a very busy man, a
charming conversationalist and by no means
despised a good dinner; and^I imagine, rose with-

PREFACE VU

out having given a thouglit to what he was going
to say. The rhythmic roll of sound was admirable,
the gestures perfect, the earnestness impressive;
nothing was lacking save sense and, occasionally,
grammar. When the speaker sat down the
applause was terrific and one of my neighbours
was especially enthusiastic. So when he had
quieted down, I asked him what the orator had
said. And he could not tell me.

That sagacious person John Wesley, is reported
to have replied to some one who questioned the
propriety of his adaptation of sacred words to
extremely secular airs, that he did not see why the
Devil should be left in possession of all the best
tunes. And I do not see why science should not
turn to account the peculiarities of human nature
thus exploited by other agencies : all the more
because science, by the nature of its being, can-
not desire to stir the passions, or profit by the
weaknesses, of human nature. The most zealous
of popular lecturers can aim at nothing more
than the awakening of a S3mipathy for abstract
truth, in those who do not really follow his argu-
ments ; and of a desii*e to know more and better in
the few who do.

At the same time it must be admitted that the
popularization of science, whether by lecture or
essay, has its drawbacks. Success in this depart-
ment has its perils for those who succeed. The
" people who fail " take their revenge, as we have

nil PREFACE

recently had occasion to observe, by ignoring all
the rest of a man's work and glibly labelling him
a mere popularizer.- If the falsehood were not too
glaring, they would say the same of Faraday and
Helmholtz and Kelvin.

On the other hand, of the affliction caused by
persons who think that what they have picked up
from popular exposition qualifies them for discuss-
ing the great problems of science, it may be said,
as the Radical toast said of the power of the Crown
in bygone days, that it " has increased, is increas-
ino-, and ouscht to be diminished." The oddities
of " English as she is spoke " might be abundantly
paralleled by those of " Science as she is misunder-
stood " in the sermon, the novel, and the leading
article; and a collection of the grotesque trav-
esties of scientific conceptions, in the shape of
essays on such trifles as " the Nature of Life " and
the " Origin of All Things," which reach me, from
time to time, might well be bound up with them.

The tenth essay in this volume unfortunately
brought me, I will not say into collision, but into
a position of critical remonstrance with regard
to some charges of physical heterodoxy, brought
by my distinguished friend Lord Kelvin, against
British Geology. As President of the Geological
Society of London at that time (1869), I thought
I might venture to plead that we were not such
heretics as we seemed to be; and that, even if

PREFACE IX

we were, recantation would not affect the
question of evolution.

I am glad to see that Lord Kelvin has just
reprinted his reply to my plea,^ and I refer the
reader to it. I shall not presume to question any-
thing, that on such ripe consideration, Lord Kelvin
has to say upon the physical problems involved.
But I may remark that no one can have asserted
more strongly than I have done, the necessity
of looking to physics and mathematics, for help
in regard to the earhest history of the globe.
(See pp. 108 and 109 of this volume.)

And I take the opportunity of repeating the
opinion, that, whether what we call geological
time has the lower limit assigned to it by Lord
Kelvin, or the higher assumed by cth3r philoso-
phers; whether the germs of all living things
have originated in the globe itself, or whether
they have been imported on, or in, meteorites
from without, the problem of the origin of those
successive Faunae and Florae of the earth, the
existence of which is fully demonstrated by
paleontology remains exactly where it was.

For I think it will be admitted, that the germs
brought to us by meteorites, if any, were not ova
of elephants, nor of crocodiles ; not cocoa-nuts nor
acorns ; not even eggs of shell-fish and corals ;
but only those of the lowest forms of animal and
vegetable life. Therefore, since it is proved that,
^ Popular Lectures and Addresses. II. Macmillan and Co. 1894,

Z PREFACE

from a very remote epoch of geological time, the
earth has been peopled by a continual succession
of the higher forms of animals and plants, these
either must have been created, or they have arisen
by evolution. And in respect of certain groups of
animals, the well-established facts of paleontology
leave no rational doubt that they arose by the
latter method.

In the second place, there are no data what-
ever, which justify the biologist in assigning
any, even approximately definite, period of time,
either long or short, to the evolution of one
species from another by the process of variation
and selection. In the ninth of the following
essays, I have taken pains to prove that the change
of animals has gone on at very different rates in
different groups of living beings ; that some types
have persisted with little change from the paleo-
zoic epoch till now, while others have changed
rapidly within the limits of an epoch. In 1862
(see below p. 303, 304) in 1863 (vol. IL, p. 461)
and again in 1864 {ibid., p. 89 — 91) I argued, not
as a matter of speculation, but, from paleonto-
logical facts, the bearing of which I believe, up to
that time, had not been shown, that any ade-
quate hypothesis of the causes of evolution must
be consistent with progression, stationariness and
retrogression, of the same type at different epochs ;
of different types in the same epoch ; and that
Dal'^vin's hypothesis fulfilled these conditions.

PREFACE XI

According to that hypothesis, two factors are at
work, variation and selection. Next to nothing is
known of the causes of the former process ; nothing
whatever of the time required for the production
of a certain amount of deviation from the existing
type. And, as respects selection, which operates
by extinguishing all but a small minority of
variations, we have not the slightest means of
estimating the rapidity with which it does its
work. All that we are justified in saying is that
the rate at which it takes place may vary almost
indefinitely. If the famous paint-root of Florida,
which kills white pigs but not black ones, were
abundant and certain in its action, black pigs
might be substituted for white in the course of
two or three years. If, on the other hand, it was
rare and uncertain in action, the white pigs might
linger on for centuries.

T. H. Huxley.

HoDESLEA, Eastbourne,
April. 1894.

CONTENTS

I

PAGE

ON A PIECE OF CHALK [1868] 1

(A Lecture delivered to the working men of
Norwich during the meeting of the British
Association.)

II

THE PROBLEMS OF THE DEEP SEA [1873] 37

III

on rome of the "results of the expedition of h.m.s,

•'challenger" [1875] 69

IV

YEAST [1871] 110

XIV CONTENTS

V

PAGE

ON THE FORMATION OF COAL [1870] 137

(A Lecture delivered at the Philosophical
Institute, Bradford. )

VI

ON THE BORDER TERRITORY BETWEEN THE ANIMAL AND

THE VEGETABLE KINGDOMS [1876] 162

(A Friday evening Lecture delivered at the
Koyal Institution.)

VII

A LOBSTER ; OR, THE STUDY OF ZOOLOGY [1861] .... 196

(A Lecture delivered at the South Kensington
Museum.)

VIII

BIOGENESIS AND ABIOGENESIS [1870] 229

(The Pi-esidential Address to the Meeting of
the British Association for the Advance-
ment of Science at Liverpool.)

IX

GEOLOGICAL CONTEMPORANEITY AND PERSISTENT TYPES

OF LIFE [1862] 272

(Address to the Geologi^^al Society on behalf
of the President by one of the Secretaries, )

CONTENTS XV

X

PACK

GEOLOGICAL EEFORM [1869] 305

(Presidential Address to the Geological
Society.)

XI

FAL^)NTOLOGY AND THE DOCTRINE OF EVOLUTION [1870] 340

(Presidential Address to the Geological
Societ J'. )

ON A PIECE OF CHALK

[1868]

If a well were sunk at our feet in the midst of
the city of Norwich, the diggers would very soon
find themselves at work in that white substance
almost too soft to be called rock, with which we
are all familiar as " chalk."

Not only here, but over the whole county of
Norfolk, the well-sinker might carry his shaft
down many hundred feet without comiug to the
end of the chalk ; and, on the sea-coast, where
the waves have pared away the face of the land
which breasts them, the scarped faces of the high
cliffe are often wholly formed of the same material.
Northward, the chalk may be followed as far as
Yorkshire ; on the south coast it appears abruptly
in the picturesque western bays of Dorset, and
breaks into the Needles of the Isle of Wight ;
while on the shores of Kent it supplies that long

187

2 ON A PIECE OF CHALK 1

line of white cliffs to which England owes her
name of Albion.

Were the thin soil which covers it all washed
away, a curved band of white chalk, here broader,
and there narrower, might be followed diagonally
across England from Lulworth in Dorset, to Flam-
borough Head in Yorkshire — a distance of over
280 miles as the crow flies. From this band to
the North Sea, on the east, and the Channel, on
the south, the chalk is largely hidden by other
deposits ; but, except in the Weald of Kent and
Sussex, it enters into the very foundation of all
the south-eastern counties.

Attaining, as it does in some places, a thickness
of more than a thousand feet, the English chalk
must be admitted to be a mass of considerable
magnitude. Nevertheless, it covers but an insig-
nificant portion of the whole area occupied by the
chalk formation of the globe, much of which has
the same general characters as ours, and is found
in detached patches, some less, and others more
extensive, than the English. Chalk occurs in
north-west Ireland ; it stretches over a large part
of France, — the chalk which underlies Paris being,
in fact, a continuation of that of the London basin ;
it runs through Denmark and Central Europe, and
extends southward to North Africa; while east-
ward, it appears in the Crimea and in Syria, and
may be traced as far as the shores of the Sea of
Aral, in Central Asia. If all the points at which

I ON A PIECE OF CHALK 3

true clialk occurs were circumscribed, they would
lie within an irregular oval about 3,000 miles in
long diameter — the area of which would be as
great as that of Europe, and would many times
exceed that of the largest existing inland sea —
the Mediterranean.

Thus the chalk is no unimportant element in
the masonry of the earth's crust, and it impresses
a peculiar stamp, varying with the conditions to
which it is exposed, on the scenery of the districts
in which it occurs. The undulating downs and
rounded coombs, covered with sweet-grassed turf,
of our inland chalk country, have a peacefully
domestic and mutton-suggesting prettiness, but
can hardly be called either grand or beautiful.
But on our southern coasts, the wall-sided cliffs,
many hundred feet high, with vast needles and
pinnacles standing out in the sea, sharp and
solitary enough to serve as perches for the wary
cormorant, confer a wonderful beauty and grandeur
upon the chalk headlands. And, in the East,
chalk has its share in the formation of some of
the most venerable of mountain ranges, such as
the Lebanon.

What is this wide-spread component of the
surface of the earth ? and whence did it come ?

You may think this no very hopeful inquiry.
You may not unnaturally suppose that the
attempt to solve such problems as these can lead

4 ON A riECE OF CHALK I

to no result, save that of entangling the inquirer
in vague speculations, incapable of refutation and
of verification. If such were really the case, I
should have selected some other subject than a
" piece of chalk " for my discourse. But, in truth,
after much deliberation, I have been unable to
think of any topic which would so well enable me
to lead you to see how solid is the foundation
upon which some of the most startling conclusions
of ph3'sical science rest.

A great chapter of the history of the world is
written in the chalk. Few passages in the history
of man can be supported by such an overwhelm-
ing mass of direct and indirect evidence as that
which testifies to the truth of the fragment of the
history of the globe, which I hope to enable you
to read, with your own eyes, to-night. Let me
add, that few chapters of human history have a
more profound significance for ourselves. I weigh
my words well when I assert, that the man who
should know the true history of the bit of chalk
which every carpenter carries about in his
breeches-pocket, though ignorant of all other
history, is likely, if he will think his knowledge
out to its ultimate results, to have a truer, and
therefore a better, conception of this wonderful
universe, and of man's relation to it, than the
most learned student who is deep-read in the
records of humanity and ignorant of those of
Nature.

I ON A PIECE OF CHALK 5

The language of the chalk is not hard to learn,
not nearly so hard as Latin, if you only want to
get at the broad features of the story it has to
tell ; and I propose that we now set to work to
spell that story out together.

We all know that if we " burn " chalk the
result is quicklime. Chalk, in fact, is a compound
of carbonic acid gas, and lime, and when you
make it very hot the carbonic acid flies away and
the Kme is left. By this method of procedure
we see the lime, but we do not see the carbonic
acid. If, on the other hand, you were to powder
a little chalk and drop it into a good deal of strong
vinegar, there would be a great bubbling and
fizzing, and, finally, a clear liquid, in which no
sign of chalk would appear. Here you see the
carbonic acid in the bubbles ; the lime, dissolved
in the vinegar, vanishes from sight. There are a
great many other ways of showing that chalk is
essentially nothing but carbonic acid and quick-
lime. Chemists enunciate the result of all the
experiments which prove this, by stating that
chalk is almost wholly composed of "carbonate
of lime."

It is desirable for us to start from the knowledge
of this fact, though it may not seem to help us
very far towards what we seek. For carbonate
of lime is a widely-spread substance, and is met
with under very various conditions. All sorts of
limestones are composed of more or less pure

6 ON A PIECE OF CHALK I

carbonate of lime. The cinist which is often
deposited by waters which have drained through
limestone rocks, in the form of what are called
stalagmites and stalactites, is carbonate of lime.
Or, to take a more familiar example, the fur on
the inside of a tea-kettle is carbonate of lime ;
and, for an}i}hing chemistry tells us to the con-
trary, the chalk might be a kind of gigantic fur
upon the bottom of the earth-kettle, which is
kept pretty hot below.

Let us try another method of making the chalk
tell us its own history. To the unassisted eye
chalk looks simply hke a very loose and open
kind of stone. But it is possible to grind a slice
of chalk down so thin that you can see through
it — until it is thin enough, in fact, to be examined
with any magnifying power that may be thought
desirable. A thin slice of the fur of a kettle
might be made in the same way. If it were
examined microscopically, it would show itself to
be a more or less distinctly laminated mineral sub-
stance, and nothing more.

•But the slice of chalk presents a totally different
appearance when placed under the microscope.
The general mass of it is made up of very minute
granules ; but, imbedded in this matrix, are in-
numerable bodies, some smaller and some larger,
but, on a rough average, not more than a
hundredth of an inch in diameter, having a well-
defined shape and structure. A cubic inch of

I ON A PIECE OF CHALK 7

some specimens of chalk may contain hundreds of
thousands of these bodies, compacted together
with incalculable millions of the granules.

The examination of a transparent slice gives a
good notion of the manner in which the com-
ponents of the chalk are arranged, and of their
relative proportions. But, by rubbing up some
chalk with a brush in water and then pouring off
the milky fluid, so as to obtain sediments of
different degrees of fineness, the gi^anules and
the minute rounded bodies may be pretty well
separated from one another, and submitted to
microscopic examination, either as opaque or as
transparent objects. By combining the views
obtained in these various methods, each of the
rounded bodies may be proved to be a beautifully-
constructed calcareous fabric, made up of a
number of chambers, communicating freely with
one another. The chambered bodies are of
various forms. One of the commonest is some-
thing like a badly-grown raspberry, being formed
of a number of nearly globular chambers of
different sizes congregated together. It is called
Glohigerina, and some specimens of chalk consist
of little else than Globigerhim and granules. Let
us fix our attention upon the Glohigerina. It is
the spoor of the game we are tracking. If we can
learn what it is and what are the conditions of its
existence, we shall see our way to the origin and
past history of the chalk

8 ON A PIECE OF CHALK I

A suggestion which may naturally enough pre-
sent itself is, that these curious bodies are the
result of some process of aggregation which has
taken place in the carbonate of lime ; that, just
as in winter, the rime on our windows simulates
the most delicate and elegantly arborescent foliage
— proving that the mere mineral water may,
under certain conditions, assume the outward
form of organic bodies — so this mineral substance,
carbonate of lime, hidden away in the bowels of
the earth, has taken the shape of these chambered
bodies. I am not raising a merely fanciful and
unreal objection. Very learned men, in former
days, have even entertained the notion that all the
formed things found in rocks are of this nature ;
and if no such conception is at present held to be
admissible, it is because long and varied ex-
perience has now shown that mineral matter
never does assume the form and structure we find
in fossils. If any one were to try to persuade
you that an oyster-shell (which is also chiefly
composed of carbonate of lime) had crystallized
out of sea-water, I suppose you would laugh at
the absurdity. Your laughter would be justified
by the fact that all experience tends to show that
oyster-shells are formed by the agency of oysters,
and in no other way. And if there were no better
reasons, we should be justified, on like grounds,
in believing that Glohigerina is not the product of
anything but vital activity.

I ON A PIECE OF CHALK 9

Happily, however, better evidence in proof of
the organic nature of the GlohigerincB than that
of analogy is forthcoming. It so happens that
calcareous skeletons, exactly similar to the
Glohigerince of the chalk, are being formed, at
the present moment, by minute hving creatures,
which flourish in multitudes, Hterally more
numerous than the sands of the sea-shore, over a
large extent of that part of the earth's surface
which is covered by the ocean.

The history of the discovery of these living
Glohigerince, and of the part which they play in
rock building, is singular enough. It is a
discovery which, like others of no less scientific
importance, has arisen, incidentally, out of work
devoted to very different and exceedingly practical
interests. When men first took to the sea, they
speedily learned to look out for shoals and rocks ;
and the more the burthen of their ships increased,
the more imperatively necessary it became for
sailors to ascertain with precision the depth of
the waters they traversed. Out of this necessity
grew the use of the lead and sounding line ; and,
ultimately, marine-surve3dng, which is the re-
cording of the form of coasts and of the depth
of the sea, as ascertained by the sounding-lead,
upon charts.

At the same time, it became desirable to ascer-
tain and to indicate the nature of the sea-bottom,
since this circumstance gi'catly affects its goodness

10 ON A PIECE OF CHALK I

as holding ground for anchors. Some ingenious
tar, whose name deserves a better fate than the
oblivion into which it has fallen, attained this
object by "arming" the bottom of the lead with
a lump of grease, to which more or less of the
sand or mud, or broken shells, as the case might
be, adhered, and was brought to the surface. But,
however well adapted such an apparatus might
be for rough nautical purposes, scientific accuracy
could not be expected from the armed lead, and
to remedy its defects (especially when applied to
sounding in great depths) Lieut. Brooke, of the
American Navy, some years ago invented a most
ingenious machine, by which a considerable por-
tion of the superficial layer of the sea-bottom can
be scooped out and brought up from any depth to
which the lead descends. In 1853, Lieut. Brooke
obtained mud from the bottom of the North
Atlantic, between Newfoundland and the Azores,
at a depth of more than 10,000 feet, or two miles,
by the help of this sounding apparatus. The
specimens were sent for examination to Ehrenberg
of Berlin, and to Bailey of West Point, and those
able microscopists found that this deep-sea mud
was almost entirely composed of the skeletons of
living organisms — the greater proportion of these
being just like the Glchigerinm aheady known to
occur in the chalk.

Thus far, the work had been carried on simply
in the interests of science, but Lieut. Brooke's

I ON A PIECE OF CHALK 11

method of sounding acquired a high commercial
value, when the enterprise of laying down the
telegraph-cable between this country and the
United States was undertaken. For it became a
matter of immense importance to know, not only
the depth of the sea over the whole line along
which the cable was to be laid, but the exact
nature of the bottom, so as to guard against
chances of cutting or fraying the strands of that
costly rope. The Admiralty consequently ordered
Captain Dayman, an old friend and shipmate of
mine, to ascertain the depth over the whole line
of the cable, and to bring back specimens of the
bottom. In former days, such a command as this
might have sounded very much like one of the
impossible things which the young Prince in the
Fairy Tales is ordered to do before he can obtain
the hand of the Princess. However, in the months
of June and July, 1857, my friend performed the
task assigned to him with great expedition and
precision, without, so far as I know, having met
with any reward of that kind. The specimens of
Atlantic mud which he procured were sent to me
to be examined and reported upon.^

^ See Appendix to Captain Dayman's Deep-sea SotmcUngs in
the North Atlantic Ocean hetioeen Ireland and Ncvfoundland,
made in H.M.S. " Cyclops." Publislied by order of the Lords
Conrimissioners of the Admiralty, 1858. They have since
formed the subject of an elaborate Memoir by Messrs. Parker
and Jones, published in the Philosophical Transactions foi
1865.

12 ON A PIECE OF CHALK I

The result of all these operations is, that we
know the contours and the nature of the surface-
soil covered by the North Atlantic for a distance
of 1,700 miles from east to west, as well as we
know that of any part of the dry land. It is a
prodigious plain — one of the widest and most even
plains in the world. If the sea were drained off,
you might drive a waggon all the way from
Valentia, on the west coast of Ireland, to Trinity
Bay, in Newfoundland. And, except upon one
sharp incline about 200 miles from Valentia, I am
not quite sure that it would even be necessary to
put the skid on, so gentle are the ascents and
descents upon that long route. From Valentia
the road would lie down-hill for about 200 miles
to the point at which the bottom is now covered
by 1,700 fathoms of sea-water. Then would come
the central plain, more than a thousand miles wide,
the inequalities of the surface of which would be
hardly perceptible, though the depth of water
upon it now varies from 10,000 to 15,000 feet;
and there are places in which Mont Blanc might
be sunk without showing its peak above water.
Beyond this, the ascent on the American side
commences, and gradually leads, for about 300
miles, to the Newfoundland shore.

Almost the whole of the bottom of this central
plain (which extends for many hundred miles in a
north and south direction) is covered by a fine
mud, which, when brought to the surface, dries

I ON A PIECE OF CHALK 13

into a greyish white friable substance. You can
write with this on a blackboard, if you are so
inclined ; and, to the eye, it is quite Hke very soft,
gra3rish chalk. Examined chemically, it proves to
be composed almost wholly of carbonate of lime ;
and if you make a section of it, in the same way
as that of the piece of chalk was made, and view
it with the microscope, it presents innumerable
Globigerince embedded in a granular matrix. Thus
this deep-sea mud is substantially chalk. I say
substantially, because there are a good many
minor differences ; but as these have no bearing on
the question immediately before us, — which is the
nature of the Glchigerince of the chalk, — it is un-
necessary to speak of them.

Glcbigerince of every size, from the smallest to
the largest, are associated together in the Atlantic
mud, and the chambers of many are filled by a soft
animal matter. This soft substance is, in fact, the
remains of the creature to which the Glohigerina
shell, or rather skeleton, owes its existence — and
which is an animal of the simplest imaginable
description. It is, in fact, a mere particle of living
jelly, without defined parts of any kind — without
a mouth, nerves, muscles, or distinct organs, and
only manifesting its vitaHty to ordinary observa-
tion by thrusting out and retracting from all parts of
its surface, long filamentous processes, which serve
for arms and legs. Yet this amorphous particle,
devoid of everything which, in the higher animals,

14 ON A PIECE OF CHALK 1

we call organs, is capable of feeding, growing, and
multipljdng ; of separating from tlie ocean the
small proportion of carbonate of lime which is
dissolved in sea-water ; and of building up that
substance into a skeleton for itself, according to a
pattern which can be imitated by no other known
agency.

The notion that animals can live and flourish in
the sea, at the vast depths from which apparently
living GlGhigerinm have been brought up, does
not agree very well with our usual conceptions re-
specting the conditions of animal life ; and it is not
so absolutely impossible as it might afc first sight
appear to be, that the Globigerince of the Atlantic
sea-bottom do not live and die where they are
found.

As I have mentioned, the soundings from the
great Atlantic plain are almost entirely made up
of Glohigermce, with the granules which have been
mentioned, and some few other calcareous shells ;
but a small percentage of the chalky mud — per-
haps at most some five per cent, of it — is of a
different nature, and consists of shells and skele-
tons composed of silex, or pure flint. These
silicious bodies belong partly to the lowly vege-
table organisms which are called Diatomacccc, and
partly to . the minute, and extremely simple,
animals, termed Badiolaria. It is quite certain
that these creatures do not live at the bottom of
the ocean, but at its surface — where they may be

I ON A PIECE OF CHALK 15

obtained in prodigious numbers by the use of a
properly constructed net. Hence it follows that
these silicious organisms, though they are not
heavier than the lightest dust, must have fallen,
in some cases, through fifteen thousand feet of
water, before they reached their final resting-
place on the ocean fioor. And considering how
large a surface these bodies expose in proportion
to their weight, it is probable that they occupy a
great length of time in making their burial
journey from the surface of the Atlantic to the
bottom.

But if the Radiolaria and Diatoms are thus
rained upon the bottom of the sea, from the
superficial layer of its waters in which they pass
their lives, it is obviously possible that the
GlobigerincB may be similarly derived ; and if they
were so, it would be much more easy to under-
stand how they obtain their supply of food than
it is at present. Nevertheless, the positive and
negative evidence all points the other way. The
skeletons of the full-grown, deep-sea Glohigerince
are so remarkabl}^ solid and heavy in proportion to
their surface as to seem Httle fitted for floating ;
and, as a matter of fact, they are not to be found
along with the Diatoms and Badiolaria in the
uppermost stratum of the open ocean. It has
been observed, again, that the abundance of
Glohigerince, in proportion to other organisms, of
like kind, increases with the depth of the sea ; and

16 ON A PIECE OF CHALK I

that deep-water Globigerince are larger than those
which Hve in shallower parts of the sea ; and such
facts negative the supposition that these organisms
have been swept by currents from the shallows
into the deeps of the Atlantic. It therefore seems
to be hardly doubtful that these wonderful
creatures live and die at the depths in which they
are found.^

However, the important points for us are, that
the living Glohigerince are exclusively marine
animals, the skeletons of which abound at the
bottom of deep seas ; and that there is not a
shadow of reason for believing that the habits of
the Globigerince of the chalk differed from those
of the existing species. But if this be true, there
is no escaping the conclusion that the chalk itself
is the dried mud of an ancient deep sea.

In working over the soundings collected by
Captain Dayman, I was surprised to find that
many of what I have called the " granules " of that
mud were not, as one might have been tempted

^ During the cruise of H.M.S. Bulldog, commanded by Sir
Leopold M'Clmtock, in 1860, living star-fish were brought uj),
clinging to the lowest part of the sounding-line, from a depth
of 1,260 fathoms, midway between Cape Farewell, in Green-
land, and the Rockall banks. Dr. Wallich ascertained that
the sea-bottom at this point consisted of the ordinary Globi-
geriim ooze, and that the stomachs of the star-fishes were full
of Globigerince. This discovery removes all objections to the
existence of living Globigerince at great depths, which are based
upon the supposed diffictilty of maintaining animal life under
snch conditions ; and it throws the burden of proof upon those
■who object to the supposition that the Globigerince live and
die where they are found.

I ON A PIECE OF CHALK 17

to think at first, the mere powder and waste of
Globigerinm, but that they had a definite form and
size. I termed these bodies " coccoliths" and
doubted their organic nature. Dr. WalHch verified
my observation, and added the interesting dis-
covery that, not unfrequently, bodies similar to
these " coccoliths " were aggregated together into
spheroids, which he termed " ccccjspheres." So far
as we knew, these bodies, the nature of which
is extremely puzzling and problematical, were
peculiar to the Atlantic soundings. But, a few
years ago, Mr. Sorby, in making a careful examina-
tion of the chalk by means of thin sections and
otherwise, observed, as Ehrenberg had done before
him, that much of its granular basis possesses a
definite form. Comparing these formed particles
with those in the Atlantic soundings, he found
the two to be identical ; and thus proved that the
chalk, like the surroundings, contains these mys-
terious coccoliths and coccospheres. Here was a
further and most interesting confirmation, from
internal evidence, of the essential identity of the
chalk with modem deep-sea mud. Glohigerince,
coccoliths, and coccospheres are found as the chief
constituents of both, and testify to the general
similarity of the conditions under which both have
been formed.^

The evidence furnished by the hewing, facing,

^ I have recently traced out the development of the "cocco-
lith:3 " fi cm a diameter of T-oVij-th of an inch up to their largest

188

18 ON A PIECE OF CHALK I

and superposition of the stones of the Pyramids,
that these structures were built by men, has no
greater weight than the evidence that the chalk
was built by Glchigerince ; and the belief that
those ancient pyramid-builders were terrestrial
and air-breathing creatures hke ourselves, is not
better based than the conviction that the chalk-
makers lived in the sea. But as our belief in the
building of the Pyramids by men is not only
grounded on the internal evidence afforded by
. these structures, but gathers strength from multi-
tudinous collateral proofs, and is clinched by the
total absence of any reason for a contrary belief;
so the evidence drawn jfrom the Glchigerince that
the chalk is an ancient sea-bottom, is fortified by
innumerable independent lines of evidence ; and
our belief in the truth of the conclusion to which
all positive testimony tends, receives the like
negative justification from the fact that no other
hypothesis has a shadow of foundation.

It may be worth while briefly to consider a few
of these collateral proofs that the chalk was de-
posited at the bottom of the sea. The great
mass of the chalk is composed, as we have seen,
of the skeletons of Glchigerince, and other simple
organisms, imbedded in granular matter. Here
and there, however, this hardened mud of the

size (which is about rsVoth), and no longer doubt that they
are produced by independent organisms, which, like the Globi-
gerince, live and die at the bottom of the sea.

I ON A PIECE OF CHALK ' 19

ancient sea reveals tlie remains of higher aniraals
which have hved and died, and left their hard
parts in the mud, just as the oysters die and
leave their shells behind them, in the mud of the
present seas.

There are, at the present day, certain groups of
animals which are never found in fresh waters,
being unable to live anywhere but in the sea.
Such are the corals ; those corallines which are
called Polyzoa ; those creatures which fabricate
the lamp-shells, and are called Brachicpcda ; the
pearly Nautilus, and all animals allied to it ; and
all the forms of sea-urchins and star-fishes. Not
only are all these creatures confined to salt water
at the present day ; but, so far as our records of
the past go, the conditions of their existence have
been the same : hence, their occurrence in any
deposit is as strong evidence as can be obtained,
that that deposit was formed in the sea. Now
the remains of animals of all the kinds which have
been enumerated, occur in the chalk, in greater or
less abundance ; while not one of those forms of
shell-fish which are characteristic of fresh water
has yet been observed in it.

When we consider that the remains of more
than three thousand distinct species of aquatic
animals have been discovered among the fossils of
the chalk, that the great majority of them are of
such forms as are now met with only in the sea,
and that there is no reason to believe that any

20 ON A PIECE OF CHALK I

one of them inhabited fresh water — the collateral
evidence that the chalk represents an ancient sea-
bottom acquires as great force as the proof
derived from the nature of the chalk itself I
think you will now allow that I did not overstate
my case when I asserted that we have as strong
grounds for believing that all the vast area of
dry land, at present occupied by the chalk, was
once at the bottom of the sea, as we have for any
matter of history whatever; while there is no
justification for any other belief

No less certain it is that the time during which
the countries we now call south-east England,
France, Germany, Poland, Russia, Eg}^t, Arabia,
Syria, were more or less completely covered by a
deep sea, was of considerable duration. We have
already seen that the chalk is, in places, more
than a thousand feet thick. I think you will
agi^ee with me, that it must have taken some
time for the skeletons of animalcules of a
hundredth of an inch in diameter to heap up
such a mass as that. I have said that through-
out the thickness of the chalk the remains of
other animals are scattered. These remains are
often in the most exquisite state of preservation.
The valves of the shell-fishes are commonly
adherent; the long spines of some of the sea-
urchins, which would be detached by the smallest
jar, often remain in their places. In a word, it is
certain that these animals have lived and died

I ON A PIECE OF CHALK 21

when the place which they now occupy was the
surface of as much of the chalk as had then been
deposited ; and that each has been covered up by
the layer of Globigcrina mud, upon which the
creatures imbedded a little higher up have, in
like manner, lived and died. But some of these
remains prove the existence of reptiles of vast
size in the chalk sea. These lived their time,
and had their ancestors and descendants, which
assuredly implies time, reptiles being of slow
growth.

There is more curious evidence, again, that the
process of covering up, or, in other words, the
deposit of Glohigerina skeletons, did not go on
very fast. It is demonstrable that an animal of
the cretaceous sea might die, that its skeleton
might lie uncovered upon the sea-bottom long
enough to lose all its outward coverings and
appendages by putrefaction ; and that, after this
had happened, another animal might attach itself
to the dead and naked skeleton, might giow to
maturity, and might itself die before the calcareous
mud had buried the whole.

Cases of this kind are admirably described by
Sir Charles Lyell. He speaks of the frequency
with which geologists find in the chalk a fossilized
sea-urchin, to which is attached the lower valve of
a Crania. This is a kind of shell-fish, with a shell
composed of two pieces, of which, as in the oyster,
one is fixed and the other free.

22 ON A PIECE OF CHALK i

" The upper valve is almost invariably wanting,
though occasionally found in a perfect state of
presei-vation in the white chalk at some distance.
In this case, we see clearly that the sea-urchin
first Hved from youth to age, then died and lost
its spines, which were carried away. Then the
young Crania adhered to the bared shell, grew
and perished in its turn ; after which, the upper
valve was separated from the lower, before the
Echinus became enveloped in chalky mud."^

A specimen in the Museum of Practical
Geology, in London, still further prolongs the
period which must have elapsed between the
death of the sea-urchin, and its burial by the
Glchigerinm. For the outward face of the valve
of a Crania, which is attached to a sea-urchin,
{Micraster), is itself overrun by an incrusting
coralline, which spreads thence over more or less
of the surface of the sea-urchin. It follows that,
after the upper valve of the Crania fell off, the
surface of the attached valve must have remained
exposed long enough to allow of the growth of
the Avhole coralline, since corallines do not live
embedded in mud.^

The progress of knowledge may, one day, enable
us to deduce from such facts as these the maxi-
mum rate at which the chalk can have ac-
cumulated, and thus to arrive at the minimum

1 Elements of Geology, by Sir Charles Lyell, Bart. r.E.S.,
p. 23.

I ON A PIECE OF CHALK 23

duration of the chalk period. Suppose that the
valve of the Crania upon which a coralline has
fixed itself in the way just described, is so attached
to the sea-urchin that no part of it is more than an
inch above the face upon which the sea-urchin
rests. Then, as the coralline could not have fixed
itself, if the Crania had been covered up with
chalk mud, and could not have lived had itself
been so covered, it follows, that an inch of chalk
mud could not have accumulated within the time
between the death and decay of the soft parts of
the sea-urchin and the growth of the coralline to
the full size which it has attained. If the decay
of the soft parts of the sea-urchin ; the attachment,
growth to maturity, and decay of the Crania ; and
the subsequent attachment and growth of the
coralline, took a year (which is a low estimate
enough), the accumulation of the inch of chalk
must have taken more than a year: and the
deposit of a thousand feet of chalk must, conse-
quently, have taken more than twelve thousand
years.

The foundation of all this calculation is, of
course, a knowledge of the length of time the
Crania and the coralline needed to attain their
full size ; and, on this head, precise knowledge is
at present wanting. But there are circumstances
which tend to show, that nothing like an inch of
chalk has accumulated during the life of a Crania ;
and, on any probable estimate of the length of

24 ON A PIECE OF CHALK i

that life, the chalk period must have had a much
longer duration than that thus roughly assigned
to it.

Thus, not only is it certain that the chalk
is the mud of an ancient sea-bottom ; but it is no
less certain, that the chalk sea existed during an
extremely long period, though we may not be
prepared to give a precise estimate of the length
of that period in years. The relative duration is
clear, though the absolute duration may not be
definable. The attempt to affix any precise date
to the period at which the chalk sea began, or
ended, its existence, is baffled by difficulties of the
same kind. But the relative age of the cretaceous
epoch may be determined with as great ease
and certainty as the long duration of that epoch.

You will have heard of the interesting dis-
coveries recently made, in various parts of Western
Europe, of flint implements, obviously worked into
shape by human hands, under circumstances which
show conclusively that man is a very ancient
denizen of these regions. It has been proved that
the whole populations of Europe, whose existence
has been revealed to us in this way, consisted of
savages, such as the Esquimaux are now ; that, in
the country which is now France, they hunted the
reindeer, and were familiar with the ways of the
mammoth and the bison. The physical geography
of France was in those days different from what it

I ON A PIECE OF CHALK 25

is now — the river Somme, for instance, having cut
its bed a hundred feet deeper between that time
and this ; and, it is probable, that the cUmate was
more Hke that of Canada or Siberia, than that of
Western Europe.

The existence of these jDeople is forgotten even
in the traditions of the oldest historical nations.
The name and fame of them had utterly vanished
until a few years back ; and the amount of physical
change which has been eifected since their day
renders it more than probable that, venerable as
are some of the historical nations, the workers of
the chipped flints of Hoxne or of Amiens are to
them, as they are to us, in point of antiquity. But,
if we assign to these hoar relics of long- vanished
generations of men the greatest age that can
possibly be claimed for them, they are not older
than the drift, or boulder clay, which, in com-
parison with the chalk, is but a very juvenile
deposit. You need go no further than your own
sea-board for evidence of this fact. At one of the
most charming spots on the coast of Norfolk,
Cromer, you will see the boulder clay forming a
vast mass, which lies upon the chalk, and must
consequently have come into existence after it.
Huge boulders of chalk are, in fact, included in
the clay, and have evidently been brought to the
position they now occupy by the same agency as
that which has planted blocks of syenite from
Norway side by side with them.

26 ON A PIECE OF CHALK i

The chalk, then, is certainly older than the
boulder clay. If you ask how much, I will again
take you no further than the same spot upon 3^our
own coasts for evidence. I have spoken of the
boulder clay and drift as resting upon the chalk.
That is not strictly true. Interposed between the
chalk and the drift is a comparatively insignifi-
cant layer, containing vegetable matter. But that
layer tells a wonderful history. It is full of stumps
of trees standing as they grew. Fir-trees are there
with their cones, and hazel-bushes with their
nuts ; there stand the stools of oak and yew trees,
beeches and alders. Hence this stratum is appro-
priately called the " forest-bed."

It is obvious that the chalk must have been
upheaved and converted into dry land, before the
timber trees could grow upon it. As the bolls of
some of these trees are from two to three feet in
diameter, it is no less clear that the dry land thus
formed remained in the same condition for long
ages. And not only do the remains of stately
oaks and well-grown firs testify to the duration of
this condition of things, but additional evidence to
the same effect is afforded by the abundant re-
mains of elephants, rhinoceroses, hippopotamuses,
and other great wild beasts, which it has yielded
to the zealous search of such men as the Rev, Mr.
Gunn. When you look at such a collection as he
has formed, and bethink you that these elephan-
tine bones did veritably carry their owners about,

I ox A PIECE OF CHALK 27

and these great grinders crunch, in the dark woods
of which the forest-bed is now the only trace, it is
impossible not to feel that they are as good
evidence of the lapse of time as the annual rings
of the tree stumps.

Thus there is a writing upon the wall of cliffs
at Cromer, and whoso runs may read it. It tells
us, with an authority which cannot be impeached,
that the ancient sea-bed of the chalk sea was
raised up, and remained dry land, until it was
covered with forest, stocked with the great game the
spoils of which have rejoiced your geologists. How
long it remained in that condition cannot be said ;
but " the whirligig of time brought its revenges '*
in those days as in these. That dry land, with
the bones and teeth of generations of long-lived
elephants, hidden away among the gnarled roots
and dry leaves of its ancient trees, sank gradually
to the bottom of the icy sea, which covered it with
huge masses of drift and boulder clay. Sea-beasts,
such as the walrus, now restricted to the extreme
north, paddled about where birds had twittered
among the topmost twigs of the fir-trees. How
long this state of things endured we know not,
but at length it came to an end. The upheaved
glacial mud hardened into the soil of modern
Norfolk. Forests gi-ew once more, the wolf and
the beaver replaced the reindeer and the elephant ;
and at length what we call the history of England
dawned.

Thus you have, within the limits of your own

28 ON A PIECE OF CHALK I

county, proof that the chalk can justly claim a
very much greater antiquity than even the oldest
physical traces of mankind. But we may go fur-
ther and demonstrate, by evidence of the same
authority as that which testifies to the existence
of the father of men, that the chalk is vastly older
than Adam himself The Book of Genesis informs
us that Adam, immediately upon his creation, and
before the aj^pearance of Eve, was placed in the
Garden of Eden. The problem of the geographical
position of Eden has greatly vexed the spirits of
the learned in such matters, but there is one
point respecting which, so far as I know, no com-
mentator has ever raised a doubt. This is, that
of the four rivers which are said to run out of it,
Euphrates and Hiddekel are identical with the
livers now known by the names of Euphrates and
Tigris. But the whole country in which these
mighty rivers take their origin, and through
which they run, is composed of rocks which are
either of the same age as the chalk, or of later
date. So that the chalk must not only have been
formed, but, after its formation, the time required
for the deposit of these later rocks, and for their
upheaval into dry land, must have elapsed, before
the smallest brook which feeds the swift stream
of " the great river, the river of Babylon," began
to flow.

Thus, evidence which cannot be rebutted, and
which need not be strengthened, though if time

I ON A PIECE OF CHALK 29

permitted I might indefinitely increase its quantity,
compels you to believe that the earth, from the
time of the chalk to the present day, has been the
theatre of a series of changes as vast in their
amount, as they were slow in their progress. The
area on which we stand has been first sea and
then land, for at least four alternations ; and has
remained in each of these conditions for a period
of great length.

Nor have these wonderful metamorphoses of sea
into land, and of land into sea, been confined to one
corner of England. During the chalk period, or
" cretaceous epoch," not one of the present great
physical features of the globe was in existence.
Our great mountain ranges, Pyrenees, Alps,
Himalayas, Andes, have all been upheaved since
the chalk was deposited, and the cretaceous sea
flowed over the sites of Sinai and Ararat. All
this is certain, because rocks of cretaceous, or still
later, date have shared in the elevatory movements
which gave rise to these mountain chains; and
may be found perched up, in some cases, many
thousand feet high upon their flanks. And evi-
dence of equal cogency demonstrates that, though,
in Norfolk, the forest-bed rests directly upon the
chalk, yet it does so, not because the period at
which the forest grew immediately followed that
at which the chalk was formed, but because an
immense lapse of time, represented elsewhere by
thousands of feet of rock, is not indicated at Cromer

so ON A PIECE OF CHALK 1

I must ask you to believe that there is no less
conclusive proof that a still more prolonged suc-
cession of similar changes occurred, before the
chalk was deposited. Nor have we any reason to
think that the first term in the series of these
changes is known. The oldest sea-beds preserved
to us are sands, and mud, and pebbles, the wear
and tear of rocks which were formed in still older
oceans.

But,* great as is the magnitude of these physical
changes of the world, they have been accompanied
by a no less striking series of modifications in its
living inhabitants. All the great classes of
animals, beasts of the field, fowls of the air,
creeping things, and things which dwell iq the
waters, flourished upon the globe long ages before
the chalk was deposited. Very few, however, if
any, of these ancient forms of animal life were
identical with those which now Kve. Certainly
not one of the higher animals was of the same
species as any of those now in existence. The
beasts of the field, in the da3's before the chalk,
were not our beasts of the field, nor the fowls of
the air such as those which the eye of men has
seen flying, unless his antiquity dates infinitely
further back than we at present surmise. If we
could be carried back into those times, we should
be as one suddenly set down in AustraHa before it
was colonized. We should see mammals, birds,
reptiles, fishes, insects, snails, and the like, clearly

r ON A PIECE OF CHALK 81

recognizable as such, and yet not one of them
would be just the same as those with which we
are familiar, and many would be extremely
different.

From that time to the present, the population
of the world has undergone slow and gradual, but
incessant, changes. There has been no grand
catastrophe — no destroyer has swept away the
forms of life of one period, and replaced them by
a totally new creation : but one species has
vanished and another has taken its place ;
creatures of one tjrpe of structure have diminished,
those of another have increased, as time has
passed on. And thus, while the differences be-
tween the living creatures of the time before the
chalk and those of the present day appear
startling, if placed side by side, we are led from
one to the other by the most gradual progress, if
we follow the course of Nature through the
whole series of those relics of her operations which
she has left behind. It is by the population of
the chalk sea that the ancient and the modem
inhabitants of the world are most completely con-
nected. The groups which are d3dng out flourish,
side by side, with the groups which are now the
dominant forms of Hfe. Thus the chalk contains
remains of those strange flying and swimming
reptiles, the pterodactyl, the ichthyosaurus, and
the plesiosaurus, which are found in no later
deposits, but abounded in preceding ages. The

32 ON A PIECE OF CHALK I

chambered shells called ammonites and belemnites,
which are so characteristic of the period pre-
ceding the cretaceous, in like manner die with it.
But, amongst these fading remainders of a
previous state of things, are some very modem
forms of life, looking like Yankee pedlars among
a tribe of Red Indians. Crocodiles of modem
type appear; bony fishes, many of them very
similar to existing species, almost supplant the
forms of fish which predominate in more ancient
seas; and many kinds of living shell-fish first
become known to us in the chalk. The vegetation
acquires a modern aspect. A few living animals
are not even distinguishable as species, from those
which existed at that remote epoch. The Glchi-
gerina of the present day, for example, is not
different specifically from that of the chalk ; and
the same may be said of many other Foraminifera.
I think it probable that critical and unprejudiced
examination will show that more than one species
of much higher animals have had a similar lon-
gevity; but the only example which I can at
present give confidently is the snake's-head lamp-
shell {Terehrahdina caput serpentis), which lives in
our English seas and abounded (as Tcrehratulina
striata of authors) in the chalk.

The longest line of human ancestry must hide
its diminished head before the pedigree of this
insignificant shell-fish. We Englishmen are proud
to have an ancestor who was present at the

I ON A PIECE OF CHALK 33

Battle of Hastings. The ancestors of Tcrebratulina
caput serpentis may have been present at a battle
of Ichthyosauria in that part of the sea which,
when the chalk was forming, flowed over the site
of Hastings. While all around has changed, this
Terehratulina has peacefully propagated its species
from generation to generation, and stands to this
day, as a living testimony to the continuity of the
present with the past history of the globe.

Up to this moment I have stated, so far as I
know, nothing but well-authenticated facts, and
the immediate conclusions which they force upon
the mind. But the mind is so constituted that it
does not willingly rest in facts and immediate
causes, but seeks always after a knowledge of the
remoter links in the chain of causation.

Taking the many changes of any given spot of
the earth's surface, from sea to land and from land
to sea, as an established fact, we cannot refrain
from asking ourselves how these changes have
occurred. And when we have explained them —
as they must be explained — by the alternate slow
movements of elevation and depression which
have affected the crust of the earth, we go still
further back, and ask. Why these movements ?

I am not certain that any one can give you a
satisfactory answer to that question. Assuredly I
cannot. All that can be said, for certain, is, that
such movements are part of the ordinary course

189

34 ON A PIECE OF CHALK T

of nature, inasmuch as they are going on at the
present time. Direct proof may be given, that
some parts of the land of the northern hemisphere
are at this moment insensibly rising and others
insensibly sinking ; and there is indirect, but per-
fectly satisfactory, proof, that an enormous area
now covered by the Pacific has been deepened
thousands of feet, since the present inhabitants of
that sea came into existence. Thus there is not
a shadow of a reason for believing that the
physical changes of the globe, in past times, have
been effected by other than natural causes. Is
there any more reason for beHeving that the con-
comitant modifications in the forms of the living
inhabitants of the globe have been brought about
in other ways ?

Before attempting to answer this question, let
us try to form a distinct mental picture of what
has happened in some special case. The crocodiles
are animals which, as a group, have a very vast
antiquity. They abounded ages before the chalk
was deposited ; they throng the rivers in warm
climates, at the present day. There is a difference
in the form of the joints of the back-bone, and in
some minor particulars, between the crocodiles of
the present epoch and those which lived before
the chalk ; but, in the cretaceous epoch, as I have
already mentioned, the crocodiles had assumed
the modern t}^e of structure. Notwithstand-
ing this, the crocodiles of the chalk are not

I ON A PIECE OF CHALK 35

identically the same as those which lived in the
times called " older tertiary," which succeeded the
cretaceous epoch ; and the crocodiles of the older
tertiaries are not identical with those of the
newer tertiaries, nor are these identical with
existing forms. I leave open the question whether
particular species may have lived on from epoch
to epoch. But each epoch has had its peculiar
crocodiles; though all, since the chalk, have
belonged to the modern t}'pe, and differ simply in
their proportions, and in such structural particulars
as are discernible only to trained eyes.

How is the existence of this long succession of
different species of crocodiles to be accounted for ?
Only two suppositions seem to be open to us —
Either each species of crocodile has been specially
created, or it has arisen out of some pre-existing
form by the operation of natural causes. Choose
your hypothesis ; I have chosen mine. I can find
no warranty for believing in the distinct creation
of a score of successive species of crocodiles in the
course of countless ages of time. Science gives
no countenance to such a wild fancy ; nor can
even the perverse ingenuity of a commentator
pretend to discover this sense, in the simple words
in which the writer of Genesis records the pro-
ceedings of the fifth and six days of the Creation.

On the other hand, I see no good reason for
doubting the necessary alternative, that all these
varied species have been evolved from pre-existing

36 ON A PIECE OF CHALK I

crocodilian forms, by tlie operation of causes as
completely a part of the common order of nature
as those which have efifected the changes of the
inorganic world. Few will venture to affirm that
the reasoning which applies to crocodiles loses its
force among other animals, or among plants. If
one series of species has come into existence by
the operation of natural causes, it seems folly to
deny that all may have arisen in the same way.

A small beginning has led us to a great ending.
If I were to put the bit of chalk with which we
started into the hot but obscure flame of burning
hydrogen, it would presently shine Hke the sun.
It seems to me that this physical metamorphosis
is no false image of what has been the result of
our subjecting it to a jet of fervent, though no-
wise brilliant, thought to-night. It has become
luminous, and its clear rays, penetrating the abyss
of the remote past, have brought within our ken
some stages of the evolution of the earth. And
in the shifting " without haste, but without rest "
of the land and sea, as in the endless variation of
the forms assumed by living beings, we have
observed nothing but the natural product of the
forces originally possessed by the substance of the
universe.

n

THE PROBLEMS OF THE DEEP SEA

[1873]

ONthe21stofDecember,1872,H.M.S.(7^6fZ/e7i(7^r,an
eighteen gun corvette, of 2,000 tons burden, sailed
from Portsmouth harbour for a three, or perhaps four,
years' cruise. No man-of-war ever left that famous
port before with so singular an equipment. Two of
the eighteen sixty-eight pounders of the Chcdlengers
armament remained to enable her to speak with
effect to sea-rovers, haply devoid of any respect
for science, in the remote seas for which she is
bound ; but the main-deck was, for the most part,
stripped of its war-like gear, and fitted up with
physical, chemical, and biological laboratories;
photography had its dark cabin ; while apparatus
for dredging, trawling, and sounding ; for photo-
meters and for thermometers, filled the space
formerly occupied by guns and gun-tackle, pistols
and cutlasses.

38 THE PROBLEMS OF THE DEEP SEA n

The crew of the Challenger match her fittings.
Captain Nares, his officers and men, are ready to
look after the interests of hydrography, work the
ship, and, if need be, fight her as seamen should ;
while there is a staff of scientific civilians, under
the general direction of Dr. Wjrvdlle Thomson,
F.R.S. (Professor of Natural History in Edinbm^gh
University by rights, but at present detached for
duty in partihcs), whose business it is to turn all
the wonderfully packed stores of appliances to
account, and to accumulate, before the ship returns
to England, such additions to natural knowledge
as shall justify the labour and cost involved in the
fitting out and maintenance of the expedition.

Under the able and zealous superintendence of
the Hydrographer, Admiral Richards, every pre-
caution which experience and forethought could
devise has been taken to provide the expedition
with the material conditions of success; and it
would seem as if nothing short of wreck or pesti-
lence, both most improbable contingencies, could
prevent the Challenger from doing splendid work,
and opening up a new era in the history of scien-
tific voyages.

The dispatch of this expedition is the culmina-
tion of a series of such enterprises, gradually in-
creasing in magnitude and importance, which the
Admiralty, greatly to its credit, has carried out for
some years past ; and the history of which is given
by Dr. Wyrille Thomson in the beautifully illus-

n THE PROBLEMS OF THE DEEP SEA 39

trated volume entitled " The Depths of the Sea,"
published since his departure.

" In the spring of the year 1868. my friend Dr. W. B. Car-
penter, at that time one of the Vice-Presidents of the Royal
Society, was with me in Ireland, where we were working out
together the structure and development of the Crinoids. I had
long previously had a profound conviction that the land of
promise for the naturalist, the only remaining region where
there were endless novelties of extraordinary interest ready to
the hand which had the means of gathering them, was the
bottom of the deep sea. I had even had a glimpse of some of
these treasures, for I had seen, the year before, with Prof. Sars,
the forms which I have already mentioned dredged by his son
at a depth of 300 to 400 fathoms off the Loffoten Islands. I
propounded my views to my fellow-labourer, and we discussed
the subject many times over our microscojies. I strongly urged
Dr. Carpenter to use his influence at head-quarters to induce the
Admiralty, probably through the Council of the Royal Society,
to give us the use of a vessel properly fitted with dredging gear
and all necessary scientific apparatus, that many heavy questions
as to the state of things in the depths of the ocean, which were
still in a state of uncertainty, might be definitely settled.
After full consideration, Dr. Carpenter ])romised his hearty co-
operation, and we agreed that I should write to him on his
return to London, indicating generally the results which I an-
ticipated, and sketching out what I conceived to be a promising
line of inquiry. The Council of the Royal Society warmly
supported the proposal ; and I give here in chronological order
the short and eminently satisfactory correspondence which led
to the Admiralty placing at the disposal of Dr. Carpenter and
myself the gunboat Lightning, under the command of Staff-
Comraauder May, R N., in the summer of 1868, for a trial
cruise to the North of Scotland, and afterwards to the much
wider surveys in H.M.S. Porcupine, Captain Calver, R.N.,
which were made with the additional association of Mr. Gwyu
Jeffreys, in the summers of the years 1869 and 1870." ^

1 The Depths of the Sea, pp. 49-50.

40 THE PROBLEMS OF THE DEEP SEA ii

Plain men may be puzzled to understand why
Dr. Wyville Thomson, not bemg a cynic, should
relegate the " Land of Promise " to the bottom of
the deep sea : they may still more wonder what
manner of " milk and honey " the Challenger
expects to find ; and their perplexity may Avell
rise to its maximum, when they seek to divine the
manner in which that milk and honey are to be
got out of so inaccessible a Canaan. I will, there-
fore, endeavour to give some answer to these
questions in an order the reverse of that in which
I have stated them.

Apart from hooks, and lines, and ordinary nets,
fishermen have, from time immemorial, made use
of two kinds of implements for getting at sea-
creatures which live beyond tide-marks — these are
the " dreds^e " and the " trawl." The dredo-e is
used by oyster-fishermen. Imagine a large bag,
the mouth of which has the shape of an elongated
parallelogram, and is fastened to an iron frame of
the same shape, the two long sides of this rim
being fashioned into scrapers. Chains attach the
ends of the frame to a stout rope, so that when
the bag is dragged along by the rope the edge of one
of the scrapers rests on the ground, and scrapes
whatever it touches into the bag. The oyster-
dredger takes one of these machines in his boat,
and when he has reached the oyster-bed the
dredge is tossed overboard ; as soon as it has sunk
to the bottom the rope is paid out sufficiently

It THE PROBLEMS OF THE DEEP SEA 41

to prevent it from pulling the dredge directly
upwards, and is then made fast while the boat
goes ahead. The dredge is thus dragged along
and scrapes oysters and other sea-animals and
plants, stones, and mud into the bag. When the
dredger judges it to be full he hauls it up, picks
out the oysters, throws the rest overboard, and
begins again.

Dredging in shallow water, say ten to twenty
fathoms, is an easy operation enough ; but the
deeper the dredger goes, the heavier must be his
vessel, and the stouter his tackle, while the opera-
tion of hauling up becomes more and more
laborious. Dredging in 150 fathoms is very hard
work, if it has to be carried on by manual labour ;
but by the use of the donkey-engine to supply
power,^ and of the contrivances kno\vn as " accumu-
lators," to diminish the risk of snapping the dredge
rope by the rolling and pitching of the vessel, the
dredge has been worked deeper and deeper, until
at last, on the 22nd of July, 1869, H.M.S. Pormpine
being in the Bay of Biscay, Captain Calver, her
commander, performed the unprecedented feat of
dredging in 2,435 fathoms, or 14,610 feet, a depth

^ The emotional side of the scientific nature has its singulari-
ties. Many persons will call to mind a certain philosopher's
tenderness over his watch — "the little creature" — which was
so singularly lost and found again. But Dr. Wyville Thomson
surpasses the owner of the watch in his loving-kindness towards
a donkey-engine. "This little engine was the comfort of our
lives. Once or twice it was overstrained, and then we pitied tho
Willing little thing, panting like an overtaxed horse."

42 THE PROBLEMS OF THE DEEP SEA n

nearly equal to the height of Mont Blanc. The
dredge " was rapidly hauled on deck at one o'clock
in the morning of the 23rd, after an absence of
7i hours, and a journey of upwards of eight statute
miles," with a hundred weight and a half of solid
contents.

The trawl is a sort of net for catching those fish
which habitually live at the bottom of the sea,
such as soles, plaice, turbot, and gurnett. The
mouth of the net may be thirty or forty feet wide,
and one edge of its mouth is fastened to a beam
of wood of the same length. The two ends of the
beam are supported by curved pieces of iron,
which raise the beam and the edge of the net
which is fastened to it, for a short distance, while
the other edge of the mouth of the net trails upon
the ground. The closed end of the net has the
form of a great pouch; and, as the beam is
dragged along, the fish, roused from the bottom
by the sweeping of the net, readily pass into its
mouth and accumulate in the pouch at its end.
After drifting with the tide for six or seven hours
the trawl is hauled up, the marketable fish are
picked out, the others thrown away, and the trawl
sent overboard for another operation.

More than a thousand sail of well-found trawlers
are constantly engaged in sweeping the seas
around our coast in this way, and it is to them
that we owe a very large proportion of our supply
of fish. The difficulty of trawhng, like that of

II THE PROBLEMS OF THE DEEP SEA 43

dredging, rapidly increases with the depth at
which the operation is performed ; and, until the
other day, it is probable that trawling at so great
d depth as 100 fathoms was something unheard of.
But the first news from the Challenger opens up
new possibilities for the traAvl.

Dr. W3rviUe Thomson writes (" Nature," March
20, 1873) :—

"For the first two or three hauls in very deep water off the
coast of Portugal, the dredge came up filled with the usual
'Atlantic ooze,' tenacious and uniform throughout, and the
work of hours, in sifting, gave the very smallest possible result.
We were extremely anxious to get some idea of the general
character of the Fauna, and particularly of the distribution of
the higher groups ; and after various suggestions for modification
of the dredge, it was proposed to try the ordinary trawl. We
had a compact trawl, with a 15-feet beam, on Iward, and we
sent it down off Cape St. Vincent at a depth of 600 fathoms.
The experiment looked hazardous, but, to our great satisfaction,
the trawl came up all right and contained, with many of the
larger invertebrata, several fishes, . . . After the first attempt
we tried the trawl several times at depths of 1090, 1525, and,
finally, 2125 fathoms, and always with success,"

To the coral-fishers of the Mediterranean, who
seek the precious red coral, which grows firmly
fixed to rocks at a depth of sixty to eighty
fathoms, both the dredge and the trawl would be
useless. They, therefore, have recourse to a sort
of frame, to which are fastened long bundles of
loosely netted hempen cord, and which is lowered
by a rope to the depth at which the hempen cords
can sweep over the surface of the rocks and break

44 THE PROBLEMS OF THE DEEP SEA

II

off the coral, which is brought up entangled in the
cords. A similar contrivance has arisen out of the
necessities of deep-sea exploration.

In the course of the dredging of the Forcupine,
it was frequently found that, while few objects of
interest were brought up within the dredge, many
living creatures came up sticking to the outside of
the dredge-bag, and even to the fii^t few fathoms
of the dredge-rope. The mouth of the dredge
doubtless rapidly filled with mud, and thus the
things it should have brought up were shut out.
To remedy this inconvenience Captain Calver
devised an arrangement not unlike that employed
by the coral-fishers. He fastened half a dozen
swabs, such as are used for drying decks, to the
dredge. A swab is something like what a birch-
broom would be if its twigs were made of long,
coarse, hempen yarns. These dragged along after
the dredge over the surface of the mud, and en-
tangled the creatures living there — multitudes of
which, twisted up in the strands of the swabs,
were brought to the surface with the dredge. A
ftirther improvement was made by attaching a
long iron bar to the bottom of the dredge bag, and
fastening large bunches of teased-out hemp to the
end of this bar. These " tangles " bring up
immense quantities of such animals as have long
arms, or spines, or prominences which readily
become caught in the hemp, but they are very
destructive to the fragile organisms which they

n THE PROBLEMS OF THE DEEP SEA 45

imprison ; and, now that the trawl can be success-
fully worked at the greatest depths, it may be
expected to supersede them ; at least, wherever
the ground is soft enough to permit of trawling.

It is obvious that between the dredge, the trawl,
and the tangles, there is little chance for any
organism, except such as are able to burrow
rapidly, to remain safely at the bottom of any part
of the sea which the ChcdlengeT undertakes to
explore. And, for the first time in the history of
scientific exploration, we have a fair chance of learn-
ing what the population of the depths of the sea is
like in the most widely different parts of the world.

And now arises the next question. The means
of exploration being fairly adequate, what forms
of life may be looked for at these vast depths ?

The systematic study of the Distribution of
living beings is the most modern branch of Biolo-
gical Science, and came into existence long after
Morphology and Physiology had attained a con-
siderable development. This naturally does not
imply that, from the time men began to observe
natural phenomena, they were ignorant of the fact
that the animals and plants of one part of the
world are different from those in other regions ; or
that those of the hills are different from those of
the plains in the same region; or finally that
some marine creatures are found only in the
shallows, while others inhabit the deeps. Never-
theless, it was only after the discovery of America

46 THE PROBLEMS OF THE DEEP SEA n

that tli8 attention of naturalists was powerfully
drawn to the wonderful differences between the
animal population of the central and southern
parts of the new world and that of those parts of
the old world which lie under the same parallels of
latitude. So far back as 1667 Abraham Mylius,
in his treatise " De Animalium origine et migratione
poj)ulorum," argues that, since there are innumer-
able species of animals in America which do not
exist elsewhere, they must have been made and
placed there by the Deity : Buffon no less forcibly
insists upon the difference between the FaunoB of
the old and new world. But the first attempt to
gather facts of this order into a whole, and to co-
ordinate them into a series of generalizations, or
laws of Geogi^aphical Distribution, is not a century
old, and is contained in the " Specimen Zoologic?
Geographicoe Quadrupedum Domicilia et Migra-
tiones sistens," published, in 1777, by the learned
Brunswick Professor, Eberhard Zimmermann, who
illustrates his work by what he calls a " Tabula
Zoographica," which is the oldest distributional
map known to me.

In regard to matters of fact, Zimmermann's
chief aim is to show that among terrestrial
mammals, some occur all over the world, while
others are restricted to .particular areas of gi^eater
or smaller extent ; and that the abundance of
species follows temperature, being greatest in warm
and least in cold climates. But marine animals

II THE PROBLEMS OF THE DEEP SEA 47

he thinks, obey no such law. The Arctic and
Atlantic seas, he says, are as full of fishes and
other animals as those of the tropics. It is, there-
fore, clear that cold does not affect the dwellers
in the sea as it does land animals, and that this
must be the case follows from the fact that sea
water, "propter varias quas continet bituminis
spiritusque particulas," freezes with much more
difficulty than fresh water. On the other hand,
the heat of the Equatorial sun penetrates but a
short distance below the surface of the ocean.
Moreover, according to Zimmermann, the incessant
disturbance of the mass of the sea by winds and
tides, so mixes up the warm and the cold that
life is evenly diffused and abundant throughout
the ocean.

In 1810, Risso, in his work on the Ichthyology
of Nice, laid the foundation of what has since been
termed " bath}Txietrical " distribution, or distribu-
tion in depth, by showing that regions of the sea
bottom of different depths could be distinguished
by the fishes which inhabit them. There was the
littoral region between tide marks with its sand-
eels, pipe fishes, and blennies : the scaivced region,
extending from lowwater-mark to a depth of 450
feet, with its wrasses, rays, and flat fish ; and the
deep-sea region, fi:om 450 feet to 1500 feet or more,
with its file-fish, sharks, gurnards, cod, and sword-
fish.

More than twenty years later, MM. Audouin and

48 THE PROBLEMS OF THE DEEP SEA n

Milne Edwards carried out the principle of distin-
guishing the FaunsG of different zones of depth
much more minutely, in their " Recherches pour
servir a I'Histoire Naturelle du Littoral de la
France," pubhshed in 1832.

They divide the area included between high-
water-mark and lowwater-mark of spring tides
(which is very extensive, on account of the great
rise and fall of the tide on the Normandy coast
about St, Malo, where their observations were
made) into four zones, each characterized by its
peculiar invertebrate inhabitants. Beyond the
fourth region they distinguish a fifth, which is
never uncovered, and is inhabited by oysters,
scallops, and large starfishes and other animals.
Beyond this they seem to think that animal life
is absent.^

Audouin and Milne Edwards were the first to
see the importance of the bearing of a knowledge
of the manner in which marine animals are
distributed in depth, on geology. They suggest
that, by this means, it will be possible to judge
whether a fossiliferous stratum was formed upon
the shore of an ancient sea, and even to determine
whether it was deposited in shallower or deeper
water on that shore ; the association of shells of
animals which live in different zones of depth will

^ ". Enfin plus bas encore, c'est-k-dire alors loin des cotes, le
fond des eaux ne paraii plus etre habite, du moins dans nos
mers, par aucun de ces animaux" (1. c. torn. i. p. 237). The
*'ces animaux " leaves the meaning of the authors doubtluL

II THE PROBLEMS OF THE DEEP SEA 49

prove that the shells have been transported into
the position in which they are found ; while, on
the other hand, the absence of shells in a deposit
will not justify the conclusion that the waters in
which it was formed were devoid of animal in-
habitants, inasmuch as they might have been only
too deep for habitation.

The new line of investigation thus opened by
the French naturalists was followed up by the
Norwegian, Sars, in 1835, by Edward Forbes, in
our own country, in 1840,^ and by (Ersted, in
Denmark, a few years later. The genius of
Forbes, combined wdth his extensive knowledge of
botany, invertebrate zoology, and geology, enabled
him to do more than any of his compeers, in
bringing the importance of distribution in depth
into notice ; and his researches in the iEgean Sea,

^ In the paper in the Memoirs of the Survey cited further on,
Forbes writes : —

"In an essay 'On the Association of Mollusca on the
British Coasts, considered with reference to Pleistocene
Geology,' printed in [the Edinhurcfh Academic Anvuciliox] 1840,
I described the mollusca, as distributed on our shores and seas,
in four great zones or regions, usually denominated ' The Lit-
toral Zone,' 'The region of Laminarine,' ' The region of Coral-
lines,' and 'The region of Corals.' An extensive series of
re earches, chiefly conducted by the members of the committee
appointed by the British Association to investigate the nsarine
geology of Britain by means of the dredge, have not invalidati-d
this classification, and the researches of Professor Loven, in the
Norwegian and Lapland seas, have borne out their correctness.
The first two of the regions above mentioned had been previ-
ously noticed by Lamouroux, in his account of the distribution
(vertically) of sea-weeds, by Audouin and Milne Edwards in •
their ObiiervcUions on the Natural History of the coast of France^
ami by Sai's in the preface to his Bcskriielssr og Jagttajelser.'*

190

50 THE PROBLEMS OF THE DEEP SEA il

and still more his remarkable paper " On the Geo-
logical Relations of the existing Fauna and Flora of
the British Isles," published in 1846, in the first
volume of the " Memoirs of the Geological Survey
of Great Britain," attracted universal attention.

On the coasts of the British Islands, Forbes
distinguishes four zones or regions, the Littoral
(between tide marks), the Laminarian (between
lowwater-mark and 15 fathoms), the Coralline
(from 15 to 50 fathoms), and the Deep sea
or Coral region (from 50 fathoms to beyond 100
fathoms). But, in the deeper waters of the ^Egean
Sea, between the shore and a depth of 300
fathoms, Forbes was able to make out no fewer
than eight zones of life, in the course of which the
number and variety of forms gi^adually diminished ;
until, beyond 300 ikthoms, life disappeared alto-
gether. Hence it appeared as if descent in the
sea had much the same effect on life, as ascent
on land. Recent investigations appear to show
that Forbes was right enough in his classification
of the facts of distribution in depth as they are to
be observed in the iEgean ; and though, at the
time he wrote, one or two observations were
extant which might have warned him not to
generalize too extensively from his ^gean ex-
perience, his own dredging work was so much
more extensive and systematic than that of any
other naturalist, that it is not wonderful he should
have felt justified in building upon it. Never*

n THE PROBLEMS OF THE DEEP SEA 51

theless, so far as the limit of the range of life in
depth goes, Forbes' conclusion has been completely-
negatived, and the greatest depths yet attained
show not even an approach to a " zero of life " : — ■

" During the several cruises of H. M. ships Lightning and
Porcwpine in the years 1868, 1869, and 1870," says Dr. Wyville
Thomson, "fifty-seven hauls of the dredge were taken in the
Atlantic at depths beyond 500 fathoms, and sixteen at depths
beyond 1,000 fathoms, and, in all cases, life was abundant. In
1869, we took two casts in depths greater than 2,000 fathoms.
In both of these life was abundant ; and with the deepest cast,
2,435 fathoms, off the mouth of the Bay of Biscay, we took
living, well-marked and characteristic examples of all the five
invertebrate sub kingdoms. And thus the question of the
existence of abundant animal life at the bottom of the sea has
been finally settled and for all depths, for there is no reason
to suppose that the depth anywhere exceeds bettveen three and
four thousand fathoms ; and if there be nothing in the condi-
tions of a depth of 2,500 fathoms to prevent the full develop-
ment of a varied Fauna, it is impossible to suppose that even an
additional thousand fathoms would make any gi'eat difference,"^

As Dr. Wyville Thomson's recent letter, cited
above, shows, the use of the trawl, at great depths,
has brought to light a still greater diversity of life.
Fishes came up from a depth of 600 to more than

1 The Depths of the Sea, p. 30. Results of a similar kind,
obtained by previous observers, are stated at length in the sixth
chapter, pp. 267-280. The dredgings carried out by Count
Pourtales, under the authority of Professor Peirce, the Super-
intendent of the United States Coast Survey, in the years
1867, 1868, and 1869, are particularly noteworthy, and it is
probably not too much to say, in the words of Professor
Agassiz, "that we owe to the coast survey the first broad and
comprehensive basis for an exploration of the sea bottom on a
large scale, opening a new era in zoolodcal and geological
research."

52 THE PROBLEMS OF THE DEEP SEA ii

1,000 fathoms, all "in a peculiar condition from
the expansion of the air contained in their bodies.
On their relief from the extreme pressure, their
eyes, especially, had a singular appearance, pro-
truding like great globes from their heads."
Bivalve and univalve mollusca seem to be rare at
the greatest depths; but starfishes, sea urchins,
and other echinoderms, zoophytes, sponges, and
protozoa abound.

It is obvious that the Challenger has the
privilege of opening a new chapter in the history
of the living world. She cannot send down her
dredges and her trawls into these virgin depths of
the great ocean without bringing up a discovery.
Even though the thing itself may be neither
" rich nor rare," the fact that it came from that
depth, in that particular latitude and longitude,
will be a new fact in distribution, and, as such,
have a certain importance.

But it may be confidently assumed that the
things brought up will very frequently be zoo-
logical novelties; or, better still, zoological
antiquities, which, in the tranquil and little-
changed depths of the ocean, have escaped the
causes of destruction at Avork in the shallows, and
represent the predominant population of a past
age.

It has been seen that Audouin and Milne
Edwards foresaw the general influence of the
Btudy of distribution in depth upon the interpreta-

n THE PROBLEMS OF THE DEEP SEA 53

tion of geological phenomena. Forbes connected
the two orders of inquiry still more closely ; and
in the thoughtful essay " On the connection be-
tween the distribution of the existing Fauna and
Flora of the British Isles, and the geological
changes which have affected their area, especially
during the epoch of the Northern drift," to which
reference has already been made, he put forth a
most pregnant suggestion.

In certain parts of the sea bottom in the imme-
diate vicinity of the British Islands, as in the
Clyde district, among the Hebrides, in the Moray
Firth, and in the German Ocean, there are de-
pressed areae, forming a kind of submarine valleys,
the centres of which are from 80 to 100 fathoms,
or more, deep. These depressions are inhabited
by assemblages of marine animals, which differ
from those found over the adjacent and shallower
region, and resemble those which are met with
much farther north, on the Norwegian coast.
Forbes called these Scandinavian detachments
" Northern outliers."

How did these isolated patches of a northern
population get into these deep places? To
explain the mystery, Forbes called to mind the
fact that, in the epoch which immediately pre-
ceded the present, the climate was much colder
(whence the name of " glacial epoch " applied to
it) ; and that the shells which are found fossil, or
sub-fossil, in deposits of that age are precisely such

54 THE PROBLEMS OF THE DEEP SEA ii

as are now to be met with only in the Scandinavian,
or still more Arctic, regions. Undoubtedly, during
the glacial epoch, the general population of our
seas had, universally, the northern aspect which
is now presented only by the " northern outliers ";
just as the vegetation of the land, do^vn to the
sea-level, had the northern character which is, at
present, exhibited only by the plants which live
on the tops of our mountains. But, as the glacial
epoch passed away, and the present climatal con-
ditions were developed, the northern plants were
able to maintain themselves only on the bleak
heio-hts, on which southern forms could not com-
pete with them. And, in like manner, Forbes sug-
gested that, after the glacial epoch, the northern
animals then inhabiting the sea became restricted
to the deeps in which they could hold their
own against invaders from the south, better fitted
than they to flourish in the warmer waters of the
shallows. Thus depth in the sea corresponded in
its effect upon distribution to height on the
land.

The same idea is applied to the explanation of
a similar anomaly in the Fauna of the ^gean : —

" In the deepest of the regions of depth of the MgesLU, the
representation of a Northern Fauna is maintained, partly by
iilentical and partly by representative forms. . . . The presence
of the latter is essentially due to the law (of representation of
parallels of latitude by zones of depth), whilst that of the
former species depended on their transmission from their parent
seas during a former epoch, and subsequent isolation. That

ir THE PROBLEMS OF THE DEEP SEA 55

epoch was doubtless the newer Pliocene or Glacial Era., when the
Mya tricnc da and other northern forms now extinct in the
Mediterranean, and found fossil in the Sicilian tertiaries,
ranged into tliat sea. The changes which there destroyed the
shallow water glacial forms, did not affect those living in the
depths, and which still survive." ^

The conception that the inhabitants of local
depressions of the sea bottom might be a remnant
of the ancient population of the area, which had
held their own in these deep fastnesses against an
invading Fauna, as Britons and Gaels have held
out in Wales and in Scotland against encroaching
Teutons, thus broached by Forbes, received a
wider application than Forbes had dreamed of
when the sounding machine first brought up
specimens of the mud of the deep sea. As I have
pointed out elsewhere,^ it at once became obvious
that the calcareous sticky mud of the Atlantic
was made up, in the main, of shells of Glohigerina
and other Foraminifera, identical with those of
which the true chalk is composed, and the identity
extended even to the presence of those singailar
bodies, the Coccoliths and Coccospheres, the true
nature of which is not yet made out. Here then
were organisms, as old as the cretaceous epoch,
still alive, and doing their work of rock-making at
the bottom of existing seas. What if GloUgerina

^ Memoirs of the Geological Survey of Great Britain, Yol i
p. 390.
^ See above, "On a Piece of Chalk," p. 13.

56 THE PROBLEMS OF THE DEEP SEA ii

and the Coccoliths should not be the only sur-
vivors of a world passed away, Avhich are hidden
beneath three miles of salt water? The letter
which Dr. Wyville Thomson wrote to Dr. Car-
penter in May, 1868, out of which all these expe-
ditions have grown, shows that this query had
become a practical problem in Dr. Thomson's
mind at that time ; and the desirableness of
solving the problem is put in the foregTound of
his reasons for urging the Government to under-
take the work of exploration : —

** Two years ago, M. Sars, Swedish Government Inspector of
Fisheries, had an opportunity, in his official capacity, of dredg-
ing off the Loffoten Islands at a depth of 300 fathoms. I
visited Norway shortly after his return, and had an opportunity
of studying with his father, Professor Sars, some of his results.
Animal forms were abundant; many of them were new to
science ; and among them was one of surpassing interest, the
small crinoid, of which you have a specimen, and which we at
once recognised as a degraded type of the Apiocrinidoi, an order
hitherto regarded as extinct, which attained its maximum in
the Pear Encrinites of the Jurassic period, and whose latest
representative hitherto known was the Bourgurftocrinus of the
chalk. Some years previously, Mr. Absjornsen, dredging in 200
fathoms in the Hardangerfjord, procured several examples of a
Starfish {Brisinga), which seems to find its nearest ally in the
fossil genus Protaster. These observations place it beyond a
doubt that animal life is abundant in the ocem at depths
varying from 200 to 300 fathoms, that the forms at these great
depths differ greatly from those met within ordinary dredgings,
and that, at all events in some cases, these animals are closely
allied to, and would seem to be directly descended from, the
Fauna of the early tertiaries.

"I think the latter result might almost have been antici-

ri THE PROBLEMS OF THE DEEP SEA 57

pated ; and, probably, further investigation will largely add to
this class of data, and will give us an opportunity of testing
our determinations of the zoological position of some fossil
types by an examination of the soft parts of their recent
representatives. The main cause of the destruction, the migra-
tion, and the extreme modification of animal types, appear to
be change of climate, chiefly depending upon oscillations of the
earth's crust. These oscillations do not appear to have ranged,
in the Northern portion of the Northern Hemisphere, much
beyond 1,000 feet since the commencement of the Tertiary
Epoch. The temperature of deep waters seems to be constant
for all latitudes at 39" ; so that an immense area of the North
Atlantic must have had its conditions unaffected by tertiary or
post- tertiary oscillations." ^

As we shall see, the assumption that the tem-
perature of the deep sea is everywhere 39° F. (4°
Cent.) is an error, which Dr. Wyville Thomson
adopted from eminent physical writers ; but the
general justice of the reasoning is not affected by
this circumstance, and Dr. Thomson's expectation
has been, to some extent, already verified.

Thus besides Glohigerina, there are eighteen
species of deep-sea Foraminifera identical with
species found in the chalk. Imbedded in the
chalky mud of the deep sea, in many locali-
ties, are innumerable cup-shaped sponges, pro-
vided with six-rayed silicious spicula, so disposed
that the wall of the cup is formed of a
lace work of flinty thread. Not less abundant,
in some parts of the chalk formation, are the
fossils known as Ventriculites, well described by

1 The Depths of the Sea, pp. 51-52,

58 THE PROBLEMS OF THE DEEP SEA n

Dr. Thomson as " elegant vases or cups, with
branching root-hke bases, or groups of regularly
or irregularly spreading tubes delicately fretted
on the surface with an impressed network like
the finest lace " ; and he adds, " When we com-
pare such recent forms as Aphrocallistes, IpMtcon,
Holtmia, and Askonema, with certain series of the
chalk Ventriculites, there cannot be the slightest
doubt that they belong to the same family — in
some cases to very nearly allied genera." ^

Professor Duncan finds " several corals from the
coast of Portugal more nearly allied to chalk forms
than to any others."

The Stalked Crinoids or Feather Stars, so
abundant in ancient times, are now exclusively
confined to the deep sea, and the late explorations
have yielded forms of old afiinity, the existence
of which has hitherto been unsuspected. The
general character of the group of star fishes
imbedded in the white chalk is almost the same
as in the modern Fauna of the deep Atlantic.
The sea urchins of the deep sea, while none of
them are specifically identical with any chalk
form, belong to the same general groups, and
some closely approach extinct cretaceous genera.

Taking these facts in conjunction with the

positive evidence of the existence, during the

Cretaceous epoch, of a deep ocean where now lies

the dry land of central and southern Europe,

1 The Depths of the Sea, p. 484.

II THE PROBLEMS OF THE DEEP SEA 59

northern Africa, and western and southern Asia ;
and of the gradual diminution of this ocean
during the older tertiary epoch, until it is
represented at the present day by such teacup-
fuls as the CasjDian, the Black Sea, and the
Mediterranean; the supposition of Dr. Thomson
and Dr. Carpenter that what is now the deep
Atlantic, was the deep Atlantic (though merged
in a vast easterly extension) in the Cretaceous
epoch, and that the Glohigerina mud has been
accumulating there from that time to this, seems
to me to have a great degree of probability. And
I agree with Dr. Wyville Thomson against Sir
Charles Lyell (it takes two of us to have any
chance against his authority) in demurring to the
assertion that " to talk of chalk having been
uninterruptedly formed in the Atlantic is as
inadmissible in a geographical as in a geological
sense."

If the word " chalk " is to be used as a
stratigraphical term and restricted to Glohigerina
mud deposited during the Cretaceous epoch, of
course it is improper to call the precisely similar
mud of more recent date, chalk. If, on the other
hand, it is to be used as a mineralogical term, I
do not see how the modem and the ancient
chalks are to be separated — and, looking at the
matter geographically, I see no reason to doubt
that a boring rod driven from the surface of the
mud which forms the floor of the mid-Atlantic

60 THE PROBLEMS OF THE DEEP SEA II

would pass through one continuous mass of
GloUgerina mud, first of modern, then of tertiary,
and then of mesozoic date ; the " chalks " of
different depths and ages being distinguished
merely by the different forms of other organisms
associated with the Glohigerince.

On the other hand, I think it must be admitted
that a belief in the continuity of the modern with
the ancient chalk has nothing to do with the
proposition that we can, in any sense whatever,
be said to be still living in the Cretaceous epoch.
When the Challengers trawl brings up an Ich-
thyosaurtcs, along with a few Hving specimens
of Belemnites and Tumlites, it may be admitted
that she has come upon a cretaceous " outlier."
A geological period is characterized not only
by the presence of those creatures which lived
in it, but by the absence of those which have
only come into existence later; and, however
large a proportion of true cretaceous fonns may
be discovered in the deep sea, the modem types
associated with them must be abolished before
the Fauna, as a whole, could, with any propriety,
be termed Cretaceous.

I have now indicated some of the chief lines of
Biological inquiry, in which the Challenger has
special opportunities for doing good service, and
in following which she will be carrying out the
work already commenced by the Lightning and

n THE PROBLEMS OF THE DEEP SEA 61

Porcu]pine in their cruises of 1868 and subsequent
years.

But biology, in the long run, rests upon physics,
and the first condition for arriving at a sound
theory of distribution in the deep sea, is the
precise ascertainment of the conditions of life;
or, in other words, a full knowledge of all those
phenomena which are embraced under the head
of the Physical Geogi^aphy of the Ocean.

Excellent work has already been done in this
direction, chiefly under the superintendence of Dr.
Carpenter, by the Lightning and the Porcupine}
and some data of fundamental importance to the
physical geography of the sea have been fixed
beyond a doubt.

Thus, though it is true that sea-water steadily
contracts as it cools doA\Ti to its freezing point,
instead of expanding before it reaches its freezing
point as fresh water does, the truth has been
steadily ignored by even the highest authorities
in physical geography, and the erroneous con-
clusions deduced from their erroneous premises
have been widely accepted as if they were
ascertained facts. Of course, if sea-water, like
fresh water, were heaviest at a temperature of
39° F. and got lighter as it approached 32° R,
the water of the bottom of the deep sea could not
be colder than 39°. But one of the first results
s>f the careful ascertainment of the temperature
* FroGcedings of the Royal Society, 1870 and 1872.

62 THE PROBLEMS OF THE DEEP SEA n

at different depths, by means of thermometers
specially contrived for the avoidance of the errors
produced by pressure, was the proof that, below
1000 fathoms in the Atlantic, down to the greatest
depths yet sounded, the water has a temperature
always lower than 38° Fahr., whatever be the
temperature of the water at the surface. And
that this low temperature of the deepest water
is probably the universal rule for the depths of
the open ocean is sho^vn, among others, by Captain
Chimmo's recent observations in the Indian ocean,
between Ceylon and Sumatra, where, the surface
water ranging from 85° — 81° Fahr., the tempera-
ture at the bottom, at a depth of 2270 to 2656
fathoms, was only from 34° to 32° Fahr.

As the mean temjDerature of the superficial
layer of the crust of the earth may be taken at
about 50° Fahr., it follows that the bottom layer
of the deep sea in temperate and hot latitudes,
is, on the average, much colder than either of the
bodies with which it is in contact ; for the tem-
perature of the earth is constant, while that of
the air rarely falls so low as that of the bottom
water in the latitudes in question ; and even when
it does, has time to affect only a comparatively
thin stratum of the surface water before the
return of warm weather.

How does this apparently anomalous state of
things come about ? If we suppose the globe to
be covered with a universal ocean, it can hardly

II THE PROBLEMS OF THE DEEP SEA 63

be doubted that the cold of the regions towards
the poles must tend to cause the suj)erficial water
of those regions to contract and become specifically
heavier. Under these circumstances, it would
have no alternative but to descend and spread
over the sea bottom, while its place would be
taken by warmer water drawn from the adjacent
regions. Thus, deep, cold, polar-equatorial currents,
and superficial, warmer, equatorial-polar currents,
would be set up ; and as the former would have
a less velocity of rotation from west to east than
the regions towards which they travel, they would
not be due southerly or northerly currents, but
south-westerly in the northern hemisphere, and
north-westerly in the southern ; while, by a parity
of reasoning, the equatorial-polar warm currents
would be north-easterly in the northern hemi-
sphere, and south-easterly in the southern. Hence,
as a north-easterly cuiTent has the same direction
as a south-westerly wind, the direction of the
northern equatorial-polar current in the extra-
tropical part of its course would pretty nearly
coincide with that of the anti-trade winds. The
freezing of the surface of the polar sea would not
interfere with the movement thus set up. For,
however bad a conductor of heat ice may be, the
unfrozen sea-water immediately in contact with
the undersurface of the ice must needs be colder
than that further off ; and hence will constantly tend
to descend through the subjacent warmer water.

64 THE PROBLEMS OF THE DEEP SEA ii

111 this way, it would seem inevitable that the
surface waters of the northern and southern frigid
zones must, sooner or later, find their way to the
bottom of the rest of the ocean; and there ac-
cumulate to a thickness dependent on the rate at
which they absorb heat from the crust of the earth
below, and from the surface water above.

If this hypothesis be correct, it follows that, if
any part of the ocean in warm latitudes is shut
off from the influence of the cold polar underflow,
the temperature of its deeps should be less cold
than the temperature of corresponding depths in
the open sea. Now, in the Mediterranean, Nature
ofters a remarkable experimental proof of just the
kind needed. It is a landlocked sea which runs
nearly east and west, between the twenty-ninth
and forty-fifth 23arallels of north latitude. Roughly
speaking, the average temperature of the air over
it is 75° Fahr. in July and 48° in January.

This great expanse of water is divided by the
peninsula of Italy (including Sicily), continuous
with which is a submarine elevation carrying less
than 1,200 feet of water, which extends from
Sicily to Cape Bon in Africa, into two great pools
■ — an eastern and a western. The eastern pool
rapidly deepens to more than 12,000 feet, and
sends off to the north its comparatively shallow
branches, the Adriatic and the ^gean Seas. The
western pool is less deep, though it reaches some
10,000 feet. And, just as the western end of the

n THE PROBLEMS OF THE DEEP SEA 65

eastern pool communicates by a shallow passage,
not a sixth of its greatest depth, with the western
pool, so the western pool is separated jfrom the
Atlantic by a ridge which runs between Capes
Trafalgar and Spartel, on which there is hardly
1,000 feet of water. All the water of the Mediter-
ranean which lies deeper than about 150 fathoms,
therefore, is shut off from that of the Atlantic,
and there is no communication between the cold
layer of the Atlantic (below 1,000 fathoms) and
the Mediterranean. Under these circumstances,
what is the temperature of the Mediterranean ?
Every^vhere below 600 feet it is about 55° Fahr. ;
and consequently, at its greatest depths, it is some
20° warmer than the corresponding depths of the
Atlantic.

It seems extremely difficult to account for this
difference in any other way, than by adopting
the views so strongly and ably advocated by Dr.
Carpenter, that, in the existing distribution of
land and water, such a circulation of the water of
the ocean does actually occur, as theoretically must
occur, in the universal ocean, with which we
started.

It is quite another question, however, whether
this theoretic circulation, true cause as it may be,
is competent to give rise to such movements of
sea-water, in mass, as those currents, which have
commonly been regarded as northern extensions of
the Gulf-stream. I shall not venture to touch

191

6Q THE PROBLEMS OF THE DEEP SEA n

upon this complicated problem ; but I may take
occasion to remark that tbe cause of a much
simpler phenomenon — the stream of Atlantic
water which sets through the Straits of Gibraltar,
eastward, at the rate of two or three miles an hour
or more, does not seem to be so clearly made out
as is desirable.

The facts appear to be that the water of the
Mediterranean is very slightly denser than that of
the Atlantic (1-0278 to 1-0265), and that the deep
water of the Mediterranean is slightly denser than
that of the surface ; while the deep water of the
Atlantic is, if anything, Hghter than that of the
surface. Moreover, while a rapid superficial cur-
rent is setting in (always, save in exceptionally
violent easterly winds) through the Straits of
Gibraltar, from the Atlantic to the Mediterranean,
a deep undercurrent (together with variable side
currents) is setting out through the Straits, from
the Mediterranean to the Atlantic.

Dr. Carpenter adopts, without hesitation, the
view that the cause of this indraught of Atlantic
water is to be sought in the much more rapid
evaporation which takes place from the surface of
the Mediterranean than from that of the Atlantic ;
and thus, by lowering the level of the former, gives
rise to an indraught from the latter.

But is there any sound foundation for the three
assumptions involved here? Firstly, that the
evaporation from the Mediterranean, as a whole,

n THE PROBLEMS OF THE DEEP SEA 67

is mucli greater tlian that from the Atlantic under
corresponding parallels ; secondly, that the rainfall
over the Mediterranean makes up for evaporation
less than it does over the Atlantic ; and thirdly,
supposing these two questions answered affirm-
atively; Are not these sources of loss in the
Mediterranean fully covered by the prodigious
quantity of fresh water which is poured into it by
great rivers and submarine springs ? Consider
that the water of the Ebro, the Rhine, the Po, the
Danube, the Don, the Dnieper, and the Nile, all
flow directly or indirectly into the Mediterranean ;
that the volume of fresh water which they pour
into it is so enormous that fresh water may some-
times be baled up from the surface of the sea off
the Delta of the Nile, while the land is not yet in
sight ; that the water of the Black Sea is half fresh,
and that a current of three or four miles an hour
constantly streams from it Mediterraneanwards
through the Bosphorus; — consider, in addition,
that no fewer than ten submarine springs of fresh
water are known to burst up in the Mediterranean,
some of them so large that Admiral Smyth calls
them " subterranean rivers of amazing volume and
force " ; and it would seem, on the face of the
matter, that the sun must have enough to do to
keep the level of the Mediterranean down ; and
that, possibly, we may have to seek for the cause
of the small superiority in saline contents of the
Mediterranean water in some condition other than
solar evaporation.

68 THE PROBLEMS OF THE DEEP SEA n

Again, if tlie Gibraltar indraught is the effect of
evaporation, why does it go on in Avinter as well
as in summer ?

All these are questions more easily asked than
answered ; but they must be answered before we
can accept the Gibraltar stream as an example
of a current produced by indraught with any
comfort.

The Mediterranean is not included in the
Challengers route, but she will visit one of the
most promising and little explored of hydro-
graphical regions — the North Pacific, between
Pol3rQesia and the Asiatic and American shores ;
and doubtless the store of observations upon the
currents of this region, which she will accumulate,
when compared with what we know of the North
Atlantic, will throw a powerful light upon the
present obscurity of the Gulf-stream problera.

Ill

ON SOME OF THE RESULTS OF THE
EXPEDITION OF H.M.S. CHALLENGER

[1875]

In May, 1873, I drew attention^ to the im-
portant problems connected with the physics
and natural history of the sea, to the solu-
tion of which there was every reason to hope
the cruise of H.M.S. Challenger would furnish
important contributions. The expectation then
expressed has not been disappointed. Reports to
the Admiralty, papers communicated to the Royal
Society, and large collections which have already
been sent home, have shown that the Challengers
staff have made admirable use of their gxeat
opportunities; and that, on the return of the
expedition in 1874, their performance will be fully
up to the level of their promise. Indeed, I am
disposed to go so far as to say, that if nothing
more came of the Challengers expedition than
^ See the preceding Essay.

70 EXPEDITION OF THE "CHALLENGER" m

has hitherto been yielded by her exploration of
the nature of the sea bottom at great depths, a
fall scientific equivalent of the trouble and ex-
pense of her equipment would have been obtained.
In order to justify this assertion, and yet, at the
same time, not to claim more for Professor Wyville
Thomson and his colleagues than is their due, I
must give a brief history of the observations which
have preceded their exploration of this recondite
field of research, and endeavour to make clear
what was the state of knowledge in December,
1872, and what new facts have been added by the
scientific staff of the Challenger. So far as I have
been able to discover, the first successful attempt
to bring up from great depths more of the sea
bottom than would adhere to a sounding-lead, was
made by Sir John Ross, in the voyage to the
Arctic regions which he undertook in 1818. In
the Appendix to the narrative of that voyage,
there will be found an account of a very ingenious
apparatus called " clams " — a sort of double scoop
— of his own contrivance, which Sir John Eoss
had made by the ship's armourer ; and by which,
being in Baffin's Bay, in 72° 30' N. and 77° 15' W.,
he succeeded in bringing up from 1,050 fathoms
(or 6,300 feet), " several pounds " of a " fine green
mud," which formed the bottom of the sea in this
region. Captain (now Sir Edward) Sabine, who
accompanied Sir John Ross on this cruise, says of
this mud that it was " soft and greenish, and that

in EXPEDITION OF THE "CHALLENGER" 71

the lead sunk several feet into it." A similar
" fine green mud " was found to compose the sea
bottom in Davis Straits by Goodsir in 1845.
Nothing is certainly kno^vn of the exact nature of
the mud thus obtained, but we shall see that the
mud of the bottom of the Antarctic seas is de-
scribed in curiously similar terms by Dr. Hooker,
and there is no doubt as to the compiDsition of this
deposit.

In 1850, Captain Penny collected in Assistance
Bay, in Kingston Bay, and in Melville Bay,
which lie between 73° 45' and 74° 40' N., speci-
mens of the residuum left by melted surface ice,
and of the sea bottom in these localities. Dr.
Dickie, of Aberdeen, sent these materials to
Ehrenberg, who made out ^ that the residuum of
the melted ice consisted for the most part of the
silicious cases of diatomaceous plants, and of the
silicious spicula of sponges ; while, mixed with
these, were a certain number of the equally
silicious skeletons of those low animal organisms,
which were termed Polycistinece by Ehrenberg, but
are now known as Radiolaria.

In 1856, a very remarkable addition to our
knowledo'e of the nature of the sea bottom in high
northern latitudes was made by Professor Bailey
of West Point. Lieutenant Brooke, of the United
States Navy, who was employed in surveying the

^ Uebcr ncue AnscJiauungen des klcinsicn vordlichen Polar*
lebens. — Monatsberichte d. K. Akad. Berlin, 1853.

72 EXPEDITION OF THE "CHALLENGER" in

Sea of Kamschatka, had succeeded in obtaining
specimens of the sea bottom from gi'eater depths
than any hitherto reached, namely from 2,700
fathoms (16,200 feet) in 56° 46' N., and 168° 18' E. ;
and from 1,700 fathoms (10,200 feet) in 60° 15' N-
and 170° 53' E. On examining these microscopically,
Professor Bailey found, as Ehrenberg had done in
the case of mud obtained on the opj^osite side of
the Arctic region, that the fine mud was made up
of shells of Biatcmacce, of spicula of sponges, and
of Radiolaria, with a small admixture of mineral
matters, but without a trace of any calcareous
organisms.

Still more complete information has been ob-
tained concerning the nature of the sea bottom
in the cold zone aroimd the south pole. Between
the years 1839 and 1843, Sir James Clark Boss
executed his famous Antarctic expedition, in the
course of which he penetrated, at two widely dis-
tant points of the Antarctic zone, into the high
latitudes of the shores of Victoria Land and of
Graham's Land, and reached the parallel of 80° S.
Sir James Boss was himself a naturalist of no
mean acquirements, and Dr. Hooker,^ the present
President of the Boyal Society, accompanied him
as naturalist to the expedition, so that the obser-
vations upon the fauna and flora of the Antarctic
reo^ions made during- this cruise were sure to have
a peculiar value and importance, even had not the
* [Now Sir Joseph Hooker. 1894.]

Iir EXPEDITION OF THE " CHALLENGER " 73

attention of the voyagers been particularly directed
to the importance of noting the occurrence of the
minutest forms of animal and vegetable hfe in the
ocean.

Among the scientific instiiictions for the voyage
drawn up by a committee of the Royal Society,
however, there is a remarkable letter from Von
Humboldt to Lord Minto, then First Lord of the
Admiralty, in which, among other things, he
dwells upon the significance of the researches into
the microscopic composition of rocks, and the dis-
covery of the great share which microscopic organ-
isms take in the formation of the crust of the earth
at the present day, made by Ehrenberg in the years
1836-39. Ehrenberg, in fact, had shown that the
extensive beds of " rotten-stone " or " TripoH '*
which occur in various parts of the world, and
notably at Bilin in Bohemia, consisted of accumu-
lations of the silicious cases and skeletons of Biato-
macecB, sponges, and Radiolaria ; he had proved
that similar deposits were being formed by
Diatoonacem, in the pools of the Thiergarten in
Berlin and elsewhere, and had pointed out that, if
it were commercially worth while, rotten-stone
might be manufactured by a process of diatom-
culture. Observations conducted at Cuxhaven in
1839, had revealed the existence, at the surface of
the waters of the Baltic, of living Diatoms and
Badiolaricb of the same species as those which, in

74 EXPEDITION OF THE " CHALLENGER " m

a fossil state, constitute extensive rocks of tertiary
age at Caltanisetta, Zante, and Oran, on the
shores of the Mediterranean.

Moreover, in the fresh-water rotten-stone beds
of Bilin, Ehrenberg had traced out the metamor-
phosis, effected apparently by the action of perco-
lating water, of the primitively loose and friable
deposit of organized particles, in which the silex
exists in the hydrated or soluble condition. The
silex, in fact, undergoes solution and slow redepo-
sition, until, in ultimate result, the excessively
fine-grained sand, each particle of which is a
skeleton, becomes converted into a dense opaline
stone, with only here and there an indication of an
organism.

From the consideration of these facts, Ehren-
berg, as early as the year 1839, had arrived at the
conclusion that rocks, altogether similar to those
which constitute a large part of the crust of the
earth, must be forming, at the present day, at the
bottom of the sea ; and he threw out the sugges-
tion that even where no trace of organic structure
is to be found in the older rocks, it inay have been
lost by metamorphosis.^

^ Ucherdie nuch jrtzt znUlrcich Irheiirltt Thicrarten dcr Krcide-
hildnnq und den Organisvins der Polythnhtmirn. Jbhandlungen
der K'on. Al'ad. dcr Wissnichaften. 1839. Berlin. 1841, I am
afraid that this remarkable paper has been somewhat overlooked
in the recent discussious of the relation of ancient rocks to
modern deposits.

Ill EXPEDITION OF THE " CHALLENGER " 75

The results of the Antarctic exploration, as
stated by Dr. Hooker in the " Botany of the Ant-
arctic Voyage," and in a paper which he read
before the British Association in 1847, are of the
greatest importance in connection with these
views, and they are so clearly stated in the former
work, which is somewhat inaccessible, that I make
no apology for quoting them at length —

*' The waters and the ice of the South Polar Ocean were alike
fonnd to abound with microscopic vegetables belonging to the
order D iatomacece. Though much too small to be discernible
by the naked eye, they occurred in such countless myriads as
to stain the berg and the pack ice wlierever they were washed by
the swell of the sea ; and, when enclosed in the congealing
surface of the water, they imparted to the brash and pancake
ice a pale ochreous colour. In the open ocean, northward of
the frozen zone, this order, though no doubt almost universally
present, generally eludes the search of the naturalist; except
when its species are congregated amongst that mucous scum
which is sometimes seen floating on the waves, and of whose
real nature we are ignorant ; or when the coloured contents of
the marine animals who feed on these Algse are examined. To
the south, however, of the belt of ice which encircles the globe,
between the parallels of f 0° and 70° S., and in the waters com-
prised between that belt and the highest latitude ever attained by
man, this vegetation is very conspicuous, from the contrast
between its colour and the white snow and ice in which it is
imbedded. Insomuch, that in the eightieth degree, all the
surface ice carried along by the currents, the sides of every
berg, and the base of the great Victoria Barrier itself, within
reach of the swell, were tinged brown, as if the polar waters
were charged with oxide of iron.

" As the majority of these plants consist of very simple vege-
table cells, enclosed in indestructible silex (as other Algae are in
carbonate of lime), it is obvious that the death and decomposi-

76 EXPEDITION OF THE " CHALLENGER " III

tiou of such multitudes must form sedimentary deposits, propor-
tionate in their extent to the k'ngth and exposure of the coast
against which they are washed, in thickness to the power of
such agents as the winds, currents, and sea, which sweej)
them more energetically to certain positions, and in purity, to
the depth of the water and nature of the bottom. Hence we
detected their remains along every icebound shore, in the depths
of the adjacent ocean, between 80 and 400 fathoms. Off
Victoria Barrier (a jierpendicular wall of ice between one and
two hundred feet above the level of the sea) the bottom of the
ocean was covered with a stratum of pure white or green mud,
composed principally of the silicious shells of the Diatomaccce.
These, on being put into water, rendered it cloudy like milk,
and took many hours to subside. In the very deep water off
Victoria and Graham's Land, this mud was particularly pure and
fine ; but towards the shallow shores there existed a greater or
less admixture of disintegrated rock and sand ; so that the
organic compounds of the bottom frequently bore but a small
proportion to the inorganic." . . .

" The universal existence of such an invisible vegetation as
that of the Antarctic Ocean, is a truly wonderful fact, and the
more from its not being accompanied by plants of a high order.
During the years we spent there, I had been accustomed to
regard the phenomena of life as difl'ering totally from what obtains
throughout all other latitudes, for everything living appeared
to be of animal origin. The ocean swarmed with Mollusca, and
particularly entomostracous Ci-uHacca, small whales, and por-
poises ; the sea abounded with penguins and seals, and the air
with birds ; the animal kingdom was ever present, the larger
creatures preying on the smaller, and these again on smaller
still ; all seemed carnivorous. The herbivorous were not recog-
nised, because feeding on a microscopic herbage, of whose true
nature I had formed an erroneous impression. It is, therefore,
with no little satisfaction that I now class the Diafomacece with
plants, probably niaintainiiig in the South Polar Ocean that
balance between the vegetable and the animal kingdoms whifjh
prevails over the surface of our globe. Nor is the sustenance
and nutrition of the animal kingdom the only function these

Ill

EXPEDITION OF THE " CHALLENGER '' 77

minute productions may perform ; they may also be the purifiers
of the vitiated atmosphere, and thus execute in the Antarctic
latitudes the office of our trees and grass turf in the temperate
regions, and the broad leaves of the palm, &c., in the
tropics." ....

With respect to the distribution of tlie
DiatGmaccm, Dr. Hooker remarks : — ■

** There is probably no latitude between that of Spitzbergen
and Victoria Land, where some of the species of either country
do not exist : Iceland, Britain, the Mediterranean Sea, North and
South America, and the South Sea Islands, all possess Antarctic
Diatomacece. The silicious coats of species only known living
in the waters of the South Polar Ocean, have, during past
ages, contriliuted to the formation of rocks ; and thus they out-
live several successive creations of organized beings. The
phonolite stones of the Ehine, and the Tripoli stone, contain
species identical with Avhat are now contributing to form a sedi-
mentary deposit (and perhaps, at some future period, a bed of
rock) extending in one continuous stratum for 400 measured
miles. I allude to the shores of the Victoria Barrier, along
whose coast the soundings examined were invariably charged
with diatomaceous remains, constituting a bank which stretches
200 miles north from the base of Victoria Barrier, while the
average depth of water above it is 300 fathoms, or 1,800 feet.
Again, some of the Antarctic species have been detected floating
in the atmosphere which overhangs the wide ocean between
Africa and America. The knowledge of this marvellous fact we
owe to Mr. Darwin, who, when he was at sea off the Cape de
Verd Islands, collected an impalpable powder which fell on
Captain Fitzroy's ship. He transmitted this dust to Ehrenberg,
who ascertained it to consist of the silicious coats, chiefly of
American Diatomacece, which were being wafted through the
•upper region of the air, when some meteorological phenomena
checked them in their course and deposited them on the ship
and surface of the ocean.

*' The existence of the remains of many species of this order

78 EXPEDITION OF THE " CHALLENGER m

(and amongst them some Antarctic ones) in the volcanic ashes,
pumice, and scoriae of active and extinct volcanoes (those of the
Mediterranean Sea and Ascension Island, for instance) is a fact
hearing immediately upon the present subject. Mount Erebus,
a volcano 12,400 feet high, of the first class in dimensions and
energetic action, rises at once from the ocean in the seventy-
eighth degree of south latitude, and abreast of the Diatomacece
bank, ^vhich reposes in part on its base. Hence it may not
appear preposterous to conclude that, as Vesuvius receives the
waters of the Mediterranean, with its fish, to eject them by its
crater, so the subterranean and subaqueous forces which maintain
Mount Ei-ebns in activity may occasionally receive organic
matter from the bank, and disgorge it, together with those
volcanic products, ashes and pumice.

"Along the shores of Graham's Land and the South Shetland
Islands, we have a parallel combination of igneous and aqueous
action, accompanied with an equally copious supply o^ Diatom-
accoe. In the Gulf of Erebus and Terror, fifteen degrees north
of Victoria Land, and placed on the opposite side of the globe,
the soundings were of a similar nature with those of the Victoria
Land and Barrier, and the sea and ice as full of Diatomacece,
This was not only proved by the deep sea lead, but by the
examination of bergs which, once stranded, had floated off" and
become reversed, exposing an accunmlation of white friable mud
frozen to their bases, which abounded with these vegetable
remains. "

The Challenger has explored the Antarctic seas
in a region intermediate between those examined
by Sir James Ross's expedition ; and the observa-
tions made by Dr. Wyville Thomson and his
colleagues in every respect confirm those of Dr.
Hooker :—

"On the 11th of February, lat. 60° 52' S., long. 80° 20' E.,
and March 3, lat. 53° 55' S., long. 108° 35' E., the sounding

ni EXPEDITION OF THE "CHALLENGER" 79

instrument came up filled with a very fine cream-coloured paste,
which scarcely effervesced with acid, and dried into a very lighl;,
impalpable, white powder. This, when examined under the
microscope, was found to consist almost entirely of the frustulea
of Diatoms, some of them wonderfully perfect in all the details
of their ornament, and many of them broken up. The species
of Diatoms entering into this deposit have not yet been worked
up, but they appear to be referable chiefly to the genera Fragil-
laria, Coscinodisc^cs, Chcctoceros, A.^teromphahis, and Didyocha,
with fragments of the separated roils of a singular silicious
organism, with which we were unacquainted, and which made
up a large proportion of the finer matter of this deposit. Mixed
with the Diatoms there were a few small Glohigerince, some of the
tests and spicules of Radiolarians, and some sand particles ; but
these foreign bodies were in too small proportion to affect the
formation as consisting practically of Diatoms alone. On the
4th of February, in lat. 52°, 29' S., long., 71° 36' E., a little to
the north of the Heard Islands, the tow-net, dragging a few
fathoms b-low the surface, came up nearly filled with a pale yellow
gelatinous mass This was found to consist entirely of Diatoms
of the same species as those found at the bottom. By far the
most abundant was the little bundle of silicious rods, fastened
together loosely at one end, separating from one another at the
other end, and the whole bundle loosely twisted into a spindle.
The rods are hollow, and contain the characteristic endochrome
of the Diatomacece. Like the Glohigcrina ooze, then, which it
succeeds to the southward in a band apparently of no gi-eat
width, the materials of this silicious deposit are derived entirely
from the surface and intermediate depths. It is somewhat
singular that Diatoms did not appear to be in such large num-
ber on the surface over the Diatom ooze as they were a little
further north. This may perhaps be accounted for by our not
having struck their belt of depth with the tow-net ; or it is
possible that when we found it on the 11th of February the bottom
deposit was really shifted a little to the south by the warm
current, the excessively fine flocculent debris of the Diatoms
taking a certain time to sink. The belt of Diatom ooze is
certainly a little further to the southward in long. 83° E., in

80 EXPEDITION OF THE " CHALLENGER '* ni

the patli of the reflux of the Agiilhas current, than in long.
108° E.

"All along the edge of the ice-pack — everywhere, in fact, to
the south of the two stations— on the 11th of February on our
southward voyage, and on the 3rd of March on our return, we
brought up fine sand and grayish mud, with small pebbles of
quartz and felspar, and small fragments of mica-slate, chlorite-
slate, clay-slate, gneiss, and granite. This deposit, I have no
doubt, was derived from the surface like the others, but in this
case by the melting of icebergs and the precipitation of foreign
matter contained in the ice.

"We never saw any trace of gravel or sand, or any material
necessarily derived from land, on an iceberg. Several showed
Tertical or irregular fissures filled with discoloured ice or snow ;
but, when looked at closely, the discoloration proved usually to
be very slight, and the effect at a distance was usually due to
the foreign material filling the fissure reflecting light less per-
fectly than the general surface of the berg. I conceive that
the upper surface of one of these great tabular southern ice-
bergs, including by far the greater part of its bulk, and culmin-
ating in the portion exposed above the surface of the sea, was
formed by the piling up of successive layers of snow during the
period, amounting perhaps to several centuries, during which
the ice-cap was slowly forcing itself over the low land and out
to sea over a long extent of gentle slope, until it reached a depth
considerably above 200 fathoms, when the lower specific weight
of the ice caused an upward strain which at length overcame the
cohesion of the mass, and portions were rent off and floated
away. If this be the true histoiy of the formation of these
icebergs, the absence of all land debris in the portion exposed
above tlie surface of the sea is readily understood. If any such
exist, it must be confined to the lower part of the berg, to that
pai-t which has at one time or other moved on the floor of the
ice-cap.

" The icebergs, when they are first dispersed, float in from
200 to 250 fathoms. When, therefore, they have been drifted
to latitudes of 65° or 64° S., the bottom of the berg just reaches
the layer at which the temperature of the water is distinctly

in EXPEDITION OF THE "CHALLENGER" 81

rising, and it is rapidly melted, and the mud and pebbles with
which it i? more or less charged are precipitated. That this
precipitation takes place all over the area where the icebergs are
breaking up, constantly, and to a considerable extent, is evident
from the fact of the soundings being entirely composed of such
deposits ; for the Diatoms, Globu/erince, and radiolarians are
present on the surface in large numbers ; and unless the deposit
from the ice were abundant it would soon be covered and
masked by a layer of the exuvia of surface organisms."

The observations wliich have been detailed
leave no doubt that the Antarctic sea bottom,
from a little to the south of the fiftieth parallel,
as far as 80'' S., is being covered by a fine deposit of
silicious mud, more or less mixed, in some parts,
with the ice-borne debris of polar lands and with
the ejections of volcanoes. The silicious particles
which constitute this mud, are derived, in part,
from the diatomaceous plants and radiolarian
animals which throng the surface, and, in part,
from the spicula of sponges which live at the
bottom. The evidence respecting the correspond-
ing Arctic area is less complete, but it is sufficient to
justify the conclusion that an essentially similar
silicious cap is being formed around the northern
pole.

There is no doubt that the constituent particles
of this mud may agglomerate into a dense rock,
such as that formed at Oran, on the shores of the
Mediterranean, which is made up of similar
materials. Moreover, in the case of freshwater
deposits of this kind, it is certain that the action

192

82 EXPEDITION OF THE "CHALLENGER" m

of percolating water may convert the originally
soft and friable, fine-grained sandstone into a
dense, semi-transparent opaline stone, the silicious
organized skeletons being dissolved, and the siiex
re-deposited in an amorphous state. Whether
such a metamorphosis as this occurs in submarine
deposits, as well as in those formed in fresh water,
does not appear; but there seems no reason to
doubt that it may. And hence it may not be
hazardous to conclude that very ordinary meta-
morphic agencies may convert these polar caps into
a form of quartzite.

In the great intermediate zone, occupying some
110° of latitude, which separates the circumpolar
Arctic and Antarctic areas of silicious deposit, the
Diatoms and Badiolaria of the surface water and
the sponges of the bottom do not die out, and, so
far as some forms are concerned, do not even
appear to dimmish in total number ; though, on a
rough estimate, it would appear that the propor-
tion of Badiolaria to Diatoms is much greater than
in the colder seas. Nevertheless the composition
of the deep-sea mud of this intermediate zone is
entirely different from that of the circumpolar
regions.

The first exact information respecting the
nature of this mud at depths greater than 1,000
fathoms was given by Ehrenberg, in the account
which he published in the " Monatsberichte " of

Ill

EXPEDITION OF THE "CHALLENGER" 83

the Berlin Academy for the year 1853, of the
soundings obtained by Lieut. Berr3rtnan, of the
United States Navy, in the North Atlantic,
between Newfoundland and the Azores.

Observations which confirm those of Ehrenberg
in all essential respects have been made by
Professor Bailey, myself, Dr. Wallich, Dr. Car-
penter, and Professor Wyville Thomson, in their
earlier cruises; and the continuation of the
Glohigerina ooze over the South Pacific has been
proved by the recent work of the Challenger, by
which it is also shown, for the first time, that, in
passing from the equator to high southern lati-
tudes, the number and variety of the Foramimfera
diminishes, and even the Glchigerince become
dwarfed. And this result, it will be observed, is
in entire accordance with the fact already men-
tioned that, in the sea of Kamschatka, the deep-
sea mud was found by Bailey to contain no cal-
careous organisms.

Thus, in the whole of the " intermediate zone,"
the silicious deposit which is being formed there,
as elsewhere, by the .accumulation of sponge-
spicula, Radiolaria, and Diatoms, is obscured and
overpowered by the immensely greater amount of
calcareous sediment, which arises fi:om the ags^re-
gation of the skeletons of dead Foraminifera. The
similarity of the deposit, thus composed of a
large percentage of carbonate of lime, and a small
percentage of silex, to chalk, regarded merely as a

84 EXPEDITION OF THE " CHALLENGER " m

kind of rock, whicli Avas first pointed out by
Ehrenberg,^ is now admitted on all bands ; nor
can it be reasonably doubted, that ordinary meta-
morphic agencies are competent to convert the
" modern chalk " into hard limestone or even into
crystalline marble.

Ehrenberg appears to have taken it for granted
that the' Glohigcrince and other Fcraminifcra which
are found in the deep-sea mud, live at the gi'eat
depths in which their remains are found ; and he
supports this opinion by producing evidence that
the soft parts of these organisms are preserved,
and may be demonstrated by removing the cal-
careous matter with dilute acids. In 1857, the

^ The following passages in Elirenberg's memoir ob The
Organis'ms in the Chalk which are still living (1839), are con-
clusive : —

* ' 7. The dawning period of the existing living organic creation,
if such a period is distinguishable (which is doubtful), can only
be supposed to have existed on the other side of, and below, the
chalk formation ; and thus, either the chalk, with its wide-
spread and thick beds, must enter into the series of newer
formations ; or some of the accepted four great geological periods,
the quaternary, teitiary, and secondary formations, contain
organisms which still live. It is more probable, in the propor-
tion of 3 to 1, that the transition or primary period is not
different, but that it is only more difficult to examine and
understand, by reason of the gradual and prolonged chemical
decomposition and metamorphosis of many of its organic
constitttents."

"10. By the mass-forming Infusoria and Polythalamia,
secondary are not distinguishable from tertiary formations ; and,
from what has been said, it is possible that, at this very day,
rock masses are forming in the sea, and being raised by volcanic
agencies, the constitution of which, on the whole, is altogether
similar to that of the chalk. The chalk remains distinguishable
by its organic remains as a formation, btit not as a kind of
rock."

Ill

EXPEDITION OF THE "CHALLENGER*' 85

evidence for and against this conclusion appeared
to me to be insufficient to warrant a positive con-
clusion one way or the other, and I expressed
myself in my report to the Admiralty on Captain
Da3nnan's soundings in the following terms : —

" When we consider the immense area over which this
deposit is spread, the de[)th at which its formation is going on,
and its similarity to chalk, and still more to such rocks as the
marls of Caltanisetta, the question, whence are all these organ-
isms derived ? becomes one of high scientific interest.

"Three answers have suggested themselves : —

" In accordance with the prevalent view of the limitation of
life to comparatively small depths, it is imagined either : 1, that
these organisms have drifted into their present position from
shallower waters ; or 2, that they habitually live at the surface
of the ocean, and only fall down into their present position.

** 1. I conceive that the first supposition is negatived by the
extremely marked zoological peculiarity of the deep-sea fauna.

" Had the Globigerince been drifted into their present position
from shallow water, we should find a very large proportion of
the characteristic inhabitants of shallow watei-s mixed with
them, and this would the more certainly be the case, as the
large Globigerince, so abundant in the deep-sea soundings, are,
in proportion to their size, more solid and massive than almost
any other Fcraminifcra. But the fact is that the proportion of
other Fornminifera is exceedingly small, nor have I found as
yet., in the deep-sea deposits, any such matters as fragments
of molluscous shells, oi Echini, &c., which abound in shallow
waters, and are quite as likely to be drifted as the heavy Glohi-
gerince. Again, the relative proportions of young and fully
formed Globigerince seem inconsistent with the notion that they
have travelled far. And it seems difficult to imagine why, had
the deposit been accumulated in this way, Coscinodisci should
so almost entirely represent the Diatomacece.

"2. The second hypothesis is far more feasible, and is
strongly supported by the fact that many Polifcisti7iece[Radicla'

86 EXPEDITION OF THE " CHALLENGER " in

ria] and Coseinodisci are well known to live at the surface of the
ocean. Mr. Macdonald, Assistant-Surgeon of H.M.S. Herald,
now in the South- Western Pacific, has lately sent home some
very valuable observations on living forms of this kind, met
with in the stomachs of oceanic mollusks, and therefore certainly
inhabitants of the superficial layer of the ocean. But it is a
singular circumstance that only one of the forms figured by Mr.
Macdonald is at all like a Glohigerina, and there are some
peculiarities about even this which make me greatly doubt its
affinity with that genus. The form, indeed, is not unlike
that of a Glohigerina, but it is provided with long radiating
processes, of which I have never seen any trace in Glohigerina.
Did they exist, they might explain what otherwise is a great
objection to this view, viz. , how is it conceivable that the heavy
Glohigerina should maintain itself at the surface of the
water ?

" If the organic bodies in the deep-sea soundings have neither
been drifted, nor have fallen from above, there remains but one
alternative — they must have lived and died where they are.

*' Important objections, however, at once suggest themselves
to this view. How can animal life be conceived to exist
under such conditions of light, temperature, pressure, and
aeration as must obtain at these vast depths ?

" To this one can only reply that we know for a certainty
that even very highly-organized animals do continue to live at
a depth of 300 and 400 fathoms, inasmuch as they have been
dredged up thence ; and that the diflference in the amount of
light and heat at 400 and at 2,000 fathoms is probably, so to
speak, very far less than the diff"erence in complexity of organi-
sation between these animals and the humbler Protozoa and
Protophyta of the deep-sea soundings.

" I confess, though as yet far from regarding it proved that
the Glohigerinoi live at these depths, the balance of probabilities
saems to me to incline in that direction. And there is one
circumstance which weighs strongly in my mind. It may be
taken as a law that any genus of animals which is found far
back in time is capable of living under a great variety of circum-
stances as regards light, temperature, and pressure. Now, the

Ill EXPEDITION OF THE "CHALLENGER" 87

genus Glohigerina is abundantly represented in the cretaceous
epoch, and perhaps earlier.

"1 abstain, however, at present from drawing any positive
conclusions, preferring rather to await the result of more
extended observations." ^

Dr. Wallich, Professor Wyville Thomson, and
Dr. Carpenter concluded that the Glchigei^inm hve
at the bottom. Dr. WalHch writes in 1862—" By
sinking very fine gauze nets to considerable depths,
I have repeatedly satisfied myself that Glchigerina
does not occur in the superficial strata of the
ocean." "^ Moreover, having obtained certain living
star-fish from a depth of 1,260 fathoms, and found
their stomachs full of " fresh-looking Glohigerince "
and their ddhris — he adduces this fact in support
of his belief that the Glohigerina^ live at the
bottom.

On the other hand, MuUer, Haeckel, Major
O.ven, Mr. Gwyn Jeffries, and other observers,
found that Glohigerinx, with the allied genera
Orhidina and Fidvimdina, sometimes occur abund-
antly at the surface of the sea, the shells of these
pelagic forms being not unfrequently provided
with the long spines noticed by Macdonald ; and
in 1865 and 1866, Major Owen more especially
insisted on the importance of this fact. The
recent work of the Challenger fully confirms Major
Owen's statement. In the paper recently pub-

^ Appendix to Report on Deep-sea Soundings in the Atlantic
Ocean, by Lieut. -Commander Joseph Dayman. 1857.
- The No}'th Atlantic Sea bed, p. 137.

88 EXPEDITION OF THE "CHALLENGER" III

lished in the proceedings of the Royal Society,^
from which a quotation has already been made,
Professor Wyville Thomson says : —

" I had formed and expressed a very strong opinion on the
matter. It seemed to me that the evidence was conclusive that
the Foraminifera which formed the Globigcrma ooze lived on
the bottom, and that the occurrence of individuals on the surface
was accidental and exceptional ; but after going into the thing
carefully, and considering the mass of evidence which has been
accumulated by Mr. Murray, I now admit that I was in error ;
and I agree with him that it may be taken as proved that all
the materials of such deposits, with the exception, of course, of
the remains of animals which we now know to live at the
bottom at all depths, which occur in the deposit as foreign
bodies, are derived from the surface.

"Mr. Murray has combined with a careful examination of the
sounding's a constant use of the tow net, usually at the surface,
but also at depths of from ten to one hundred fathoms ; and he
hnds the closest relation to exist between the surface fauna of
any particular locality and the deposit which is taking place at
the bottom. In all seas, from the equator to the polar ice, the
tow-net contains Globigtrince. They are more abundant and of
a larger size in warmer seas ; several varieties, attaining a large
size and presenting marked varietal characters, are found in the
intertropical area of the Atlantic. In the latitude of Kerguelen
they are less numerous and smaller, while further south they are
still more dwarfed, and only one variety, the typical Glohigcrina
hulloides, is represented. The living Glohigcrince from the tow-
net are singularly different in appearance from the dead shells
we find at the bottom. The shell is clear and transparent, and
each of the pores which penetrate it is surrounded by a raised
crest, the crest round adjacent pores coalescing into a roughly

1 "Preliminary Notes on the Nature of the Sea-bottom pro-
cured by the soundings of H.M.S. Challenger during her cruise
in the Southern Seas, in the early pait of the year 1874."—
Froceedings of the lloyal Society, Nov, 26, 1874.

m EXPEDITION OF THE "CHALLENGER" 89

hexagonal network, so that the pores appear to lie at the
bottom of a hexagonal pit. At each angle of this hexagon the
crest gives off a delicate flexible calcareous spine, which is some-
times four or five times the diameter of the shell in length.
The spines radiate symmetrically from the direction of the
centre of each chamber of the shell, and the sheaves of long
transparent needles crossing one another in different directions
have a very beautiful effect. The smaller inner chambers of the
shell are entirely filled with an orange-yellow granular sarcode ;
and the large terminal chamber usually contains only a small
irregular mass, or two or three small masses run together, of
the same yellow sarcode stuck against one side, the remainder of
the chamber being empty. No definite arrangement and no
approach to structure was observed in the sarcode, and no
differentiation, with the exception of round bright-yellow oil-
globules, very much like those found in some of the radiolarians,
which are scattered, apparently iiregularly, in the sarcode. We
never have been able to detect, in any of the large number of
Glohigerince which we have examined, the least trace of pseudo-
podia, or any extension, in any form, of the sarcode beyond the
shell.

"In specimens taken with the tow-net the spines are very
usually absent ; but that is probably on account of their extreme
tenuity ; they are broken off by the slightest touch. In fresh
examples from the surface, the dots indicating the oiigin of the
lost spines may almost always be made out with a high power.
There are never sjiines on the Glohigerince from the bottom,
even in the shallowest water."

There can now be no douht, therefore, that
Glohigerince live at the top of the sea ; but the
question may still be raised whether they do not
also live at the bottom. In favour of this view, it
has been urged that the shells of the Glohigerince
of the surface never possess such thick walls as

90 EXPEDITION OF THE " CHALLENGER" ill

those which are found at the bottom, but I confess
that I doubt the accuracy of this statement.
Again, the occurrence of minute Glohigerince in all
stages of development, at the gToatest depths, is
brought forward as evidence that they live in situ.
But considering the extent to which the surface
organisms are devoured, without discrimination of
young and old, by Salpce and the like, it is not
wonderful that shells of all ages should be among
the rejectamenta. Nor can the presence of the
soft parts of the body in the shells which form
the Glohigerina ooze, and the fact, if it be one,
that animals living at the bottom use them as
food, be considered as conclusive evidence that
the Glohigerince live at the bottom. Such as die
at the surface, and even many of those which are
swallowed by other animals, may retain much of
their protoplasmic matter when they reach the
depths at which the temperature sinks to 34° or
32° Fahrenheit, where decomposition must become
exceedingly slow.

Another consideration appears to me to be in
favour of the view that the Glohigerince and their
allies are essentially surface animals. This is the
fact brought out by the Challenger s work, that
they have a southern limit of distribution, which
can hardly depend upon anything but the tem-
perature of the surface water. And it is to
be remarked that this southern limit occurs at a
lower latitude in the Antarctic seas than it does

ni EXPEDITION OF THE '' CHALLENGER " 91

in tlie North Atlantic. According to Dr. Wallicli
(" The North Atlantic Sea Bed," p. 157) Glohi-
gerina is the prevailing form in the deposits
between the Faroe Islands and Iceland, and be-
tween Iceland and East Greenland — or, in other
words, in a region of the sea-bottom which lies
altogether north of the parallel of 60° N. ; while
in the southern seas, the Glohigerince become
dwarfed and almost disappear between 50^ and
55° S. On the other hand, in the sea of
Kamschatka, the GlohigerincB have vanished in
56° N., so that the persistence of the GloMgerina
0')ze in high latitudes, in the North Atlantic,
would seem to depend on the northward curve of
the isothermals peculiar to this region ; and it is
difficult to understand how the formation of
Glchigerina ooze can be affected by this climatal
peculiarity unless it be effected by surface animals.
Whatever may be the mode of life of the
Foraminifera, to which the calcareous element of
the deep-sea " chalk " owes its existence, the fact
that it is the chief and most widely spread
material of the sea-bottom in the intermediate
zone, throughout both the Atlantic and Pacific
Oceans, and the Indian Ocean, at depths from a
few hundred to over two thousand fathoms, is
established. But it is not the only extensive
deposit which is now taking place. In 1853,
Count Pourtales, an officer of the United States
Coast Survey, which has done so much for

92 EXPEDITION OF THE " CHALLENGER " m

scientific hydrography, observed, that the mud
forming the sea-bottom at depths of one hundred
and fifty fathoms, in 31° 32' N, 79° 35' W., off
the Coast of Florida, was " a mixture, in about
equal proportions, of Glohigerince and black sand,
probably greensand, as it makes a green mark
when crushed on paper." Professor Bailey,
examining these grains microscopically, found
that they were casts of the interior cavities of
Foraminifera, consisting of a mineral known as
Glauconite, which is a silicate of iron and alumina.
In these casts the minutest cavities and finest
tubes in the Foraminifer were sometimes repro-
duced in solid counterparts of the glassy mineral,
while the calcareous original had been entirely
dissolved away.

Contemporaneously with these observations,
the indefatigable Ehrenberg had discovered that
the "greensands" of the geologist were largely
made up of casts of a similar character, and proved
the existence of Foraminifera at a very ancient
geological epoch, by discovering such casts in a
greensand of Lower Silurian age, which occurs
near St. Petersburg.

Subsequently, Messrs Parker and Jones dis-
covered similar casts in process of formation, the
original shell not having disappeared, in specimens
of the sea-bottom of the Australian seas, brought
home by the late Professor Jukes. And the
Challenger has observed a deposit of a similar

Ill EXPEDITION OF THE "CHALLENGER" 93

character in the course of the Agulhas current,
near the Cape of Good Hope, and in some othei
locaHties not yet defined.

It would appear that this infiltration of Fora-
minifera shells with Glauconite does not take place
at great depths, but rather in what may be
termed a sublittoral region, ranging from a
hundred to three hundred fathoms. It cannot be
ascribed to any local cause, for it takes place, not
only over large areas in the Gulf of Mexico and
the Coast of Florida, but in the South Atlantic
and in the Pacific. But what are the conditions
which determine its occurrence, and whence the
silex, the iron, and the alumina (with perhaps
potash and some • other ingredients in small
quantity) of which the Glauconite is composed,
proceed, is a point on which no light has yet been
thrown. For the present we must be content
with the fact that, in certain areas of the
" intermediate zone," greensand is replacing and
representing the primitively calcareo-silicious
ooze.

The investigation of the deposits which are
now being formed in the basin of the Mediterra-
nean, by the late Professor Edward Forbes, by
Professor Williamson, and more recently by Dr.
Carpenter, and a comparison of the results thus
obtained with what is known of the surface fauna,
have brought to light the remarkable fact, that
while the surface and the shallows abound with

94 EXPEDITION OF THE "CHALLENGER*" m

Foraminifera and other calcareous shelled organ-
isms, the indications of life become scanty at
depths beyond 500 or 600 fathoms, while almost
all traces of it disappear at greater depths, and at
1,000 to 2,000 fathoms the bottom is covered with
a fine clay.

Dr. Carpenter has discussed the significance of
this remarkable fact, and he is disposed to attri-
bute the absence of life at great depths, partly
to the absence of any circulation of the water of
the Mediterranean at such depths, and partly to
the exhaustion of the oxygen of the water by the
organic matter contained in the fine clay, which
he conceives to be formed by the finest particles
of the mud brought down by the rivers which
flow into the Mediterranean.

However this may be, the explanation thus
offered of the presence of the fine mud, and of the
absence of organisms which ordinarily live at the
bottom, does not account for the absence of
the skeletons of the organisms which undoubtedly
abound at the surface of the Mediterranean ; and
it would seem to have no application to the re-
markable fact discovered by the Challenger, that
in the open Atlantic and Pacific Oceans, in the
midst of the great intermediate zone, and
thousands of miles away from the embouchure of
any river, the sea-bottom, at depths approaching
to and beyond 3,000 fathoms, no longer consists of
GloUgerina ooze, but of an excessively fine red clay.

in EXPEDITION OF THE "CHALLENGER'* 95

Professor Thomson gives the following account
of this capital discovery : —

" According to our present experience, the deposit of Glohi-
gerina ooze is limited to water of a certain depth, the extreme
limit of the pure characteristic formation being placed at a depth
of somewhere about 2,250 fathoms. Crossing from these shal-
lower regions occupied by the ooze into deeper soundings, we
find, universally, that the calcareous formation gradually passes
into, and is finally replaced by, an extremely fine pure clay,
which occupies, speaking generally, all depths below 2,500
fathoms, and consists almost entirely of a silicate of the red
oxide of iron and alumina. The transition is very slow, and
extends over several hundred fathoms of increasing depth ; the
shells gradually lose their sharpness of outline, and assume a
kind of ' rotten ' look and a brownish colour, and become more
and more mixed with a fine amorphous red- brown powder,
which increases steadily in proportion until the lime has almost
entirely disappeared. This brown matter is in the finest possible
state of subdivision, so fine that when, after sifting it to separate
any organisms it might contain, we put it into jars to settle, it
remained for days in suspension, giving the water very much
the appearance and colour of chocolate.

*' In indicating the nature of the bottom on the charts, we
came, from experience and without any theoretical considera-
tions, to use three terms for soundings in deep water. Two of
these, Gl. oz. and r. cl., were very definite, and indicated
strongly-marked formations, with apparently but few characters
in common ; but we frequently got soundings which we could
not exactly call ' Glohigerina ooze ' or ' red clay, ' and before we
were fully aware of the nature of these, we were in the habit of
indicating them as ' grey ooze ' (gr. oz. ) We now recognise the
' grey ooze ' as an intermediate stage between the Glohigerina
ooze and the red clay ; we find that on one side, as it were, of
an ideal line, the red clay contains more and more cf the material
of the calcareous ooze, while on the other, the ooze is mixed
with an increasing proportion of 'red clay.'

96 EXPEDITION OF THE "CHALLENGER m

" Although we have met with the same phenomenon so
frequently, that we were at length able to predict the nature of
the bottom from the depth of the soundings with absolute cer-
tainty for the Atlantic and the Southern Sea, we had, perhaps,
the best opportunity of observing it in our first section across
'tlie Atlantic, between Teneriffe and St. Thomas. The first four
stations on this section, at depths from 1,525 to 2,220 fathoms,
show Gluhigeriva ooze. From the last of these, which is about
300 miles from Teneriffe, the depth gradually increases to 2,740
fathoms at 500, and 2,950 fathoms at 750 miles from Teneriffe
The bottom in these two soundings might have been called
* grey ooze,' for although its nature has altered entirely from the
Glohigerina ooze, the red clay into which it is rapidly j)assing
still contains a considerable admixture of carbonate of lime.

" The depth goes on increasing to a distance of 1,150 miles
from Teneriffe, when it reaches 3,150 fathoms ; there the clay
is pure and smooth, and contains scarcely a trace of lime. From
this great depth the bottom gradually rises, and, with decreas-
ing depth, the grey colour and the calcareous composition of the
ooze return. Three soundings in 2,050, 1,900, and 1,950 fathoms
on the ' Dolphin Rise ' gave highly characteristic examples of
the Glohigerina formation. Passing from the middle plateau of
the Atlantic into the western trough, with depths a little over
3,000 fathoms, the red clay returned in all its purity ; and our
last sounding, in 1,420 fathoms, before reaching Sombrero,
restored the Glohigerina ooze with its peculiar associated fauna.

"This section shows also the wide extension and the vast
geological importance of the red clay formation. The total
distance from Teneriffe to Sombrero is about 2,700 miles. Pro-
ceeding from east to west, we have —

About 80 miles of volcanic mud and sand.

„ 350

Glohigerina ooze,

„ 1,050

red clay,

„ 330

Glohigerina ooze,

■ „ 850

red clay.

40

Glohigerina ooze ;

giving a total of 1,900 miles of red clay to 720 miles of GlohU

gerina ooze.

til EXPEDITION OF THE " CHALLENGER " 97

** The nature and origin of this vast deposit of clay is a ques-
tion of the very greatest interest ; and although I think there
can be no doubt that it is in the main solved, yet some matters
of detail are still involved in difficulty. My first impression
was that it might be the most minutely divided material, the
ultimate sediment produced by the disintegration of the land,
by rivers and by the action of the sea on exposed coasts, and
held in suspension and distributed by ocean currents, and only
making itself manifest in places unoccupied by the Globigerina
ooze. Several circumstances seemed, however, to negative this
mode of origin. The formation seemed too uniform : wherever
we met with it, it had the same character, and it only varied in
composition in containing less or more carbonate of lime.

"Again, we were gradually becoming more and more con-
vinced that all the important elements of the Globigerina ooze
lived on the surface, and it seemed evident that, so long as the
condition on the surface remained the same, no alteration of
contour at the bottom could possibly prevent its accumulation ;
and the surface conditions in the Mid -Atlantic were very
uniform, a moderate current of a very equal temperature passing
continuously over elevations and depressions, and everywhere
yielding to the tow-net the ooze-forming Foraniinifera in the
same proportion. The Mid-Atlantic swarms with pelagic
Mollusca, and, in moderate depths, the shells of these are con-
stantly mixed with the Globigerina ooze, sometimes in number
sufficient to make up a considerable portion of its bulk. It is
clear that these shells must fall in equal numbers upon the red
clay, but scarcely a trace of one of them is ever brought up by
the dredge on the red clay area. It might be possible to explain
the absence of shell-secreting animals living on the bottom, on
the supposition that the nature of the deposit was injurious to
them ; but then the idea of a current suflSciently strong to
sweep them away is negatived by the extreme fineness of the*
sediment which is being laid doAvn ; the absence of surface
shells appears to be intelligible only on the supposition that they
are in some way removed,

"We conclude, therefore, that the 'red clay' is not an addi-
tional substance introduced from without, and occupying certain

193

98 EXPEDITION OF THE "CHALLENGER" m

depressed regions on account of some law regulating its deposi-
tion, but that it is produced by the removal, by some means or
other, over these areas, of the carbonate of lime, which forms
probably about 98 per cent, of the material of the Globigerina
ooze. We can trace, indeed, every successive stage in the
removal of the carbonate of lime in descending the slope of the
ridge or plateau where the Globigerina ooze is forming, to
the region of the clay. We find, first, that the shells of
pteropods and other surface Mollusca which are constantly
falling on the bottom, are absent, or, if a few remain, they
are brittle and yellow, and evidently decaying rapidly. These
shells of Mollusca decompose more easily and disappear sooner
than the smaller, and apparently more delicate, shells of
rhizopods. The smaller Foraminifera now give way, and are
found in lessening proportion to the larger ; the coccoliths first
lose their thin outer border and then disappear ; and the clubs
of the rhabdoliths get worn out of shape, and are last seen,
under a high power, as infinitely minute cylinders scattered over
the field. The larger Foraminifera are attacked, and instead
of being vividly white and delicately sculptured, they become
brown and worn, and finally they break up, each according to
its fashion ; the chamber-walls of Globigerina fall into wedge-
shaped pieces, wliich qixickly disappear, and a thick rough crust
breaks away from the surface of Orbulina, leaving a thin inner
sphere, at first beautifully transparent, but soon becoming
opaque and crumbling away.

"In the meantime the proportion of the amorphous 'red
clay' to the calcareous elements of all kinds increases, until
the latter disappear, with the exception of a few scattered shells
of the larger Foraminifera, which are still found even in the
most characteristic samples of the 'red clay.'

"There seems to be no room left for doubt that the red clay
is essentially the insoluble residue, the ash, as it were, of the
calcareous organisms which form the Globigerina ooze, after the
calcareous matter has been by some means removed. An
ordinary mixture of calcareous Foraminifera with the shells of
pteropods, forming a fair sample of Globigerina ooze from near
St. Thomas, was carefully washed, and subjected by Mr.

in EXPEDITION OF THE "CHALLENGER" 99

Buchanan to the action of weak acid ; and he found that there
remained after the carbonate of lime had been removed, about
1 per cent, of a reddish mud, consisting of silica, alumina, and
the red oxide of iron. This experiment has been frequently
repeated with different samples of Globigerin% ooze, and always
with the result that a small proportion of a red sediment re-
mains, which possesses ail the characters of the red clay."
♦ ♦ * « «

" It seems evident from the observations here recorded, that
clay, which we have hitherto looked upon as essentially the
product of the disintegration of older rocks, may be, under
certain circumstances, an organic formation like chalk ; that, as
a matter of fact, an area on the surface of the globe, which we
have shown to be of vast extent, although we are still far from
having ascertained its limits, is being covered by such a deposit
at the present day.

" It is impossible to avoid associating such a formation with
the fine, smooth, homogeneous clays and schists, poor in fossils,
but showing worm-tubes and tracks, and bunches of doubtful
branching things, such as Oldhamia, silicious sponges, and
thin-shelled peculiar shrimps. Such formations, more or less
metamorphosed, are very familiar, especially to the student of
palaeozoic geology, and they often attain a vast thickness. One
is inclined, from the great resemblance between them in com-
position and in the general character of the included fauna, to
suspect that these may be organic formations, like the modem
red clay of the Atlantic and Southern Sea, accumulations of the
insoluble ashes of shelled creatures.

"The dredging in the red clay on the 13th of March was
unusually rich. The bag contained examples, those with cal-
careous shells rather stunted, of most of the characteristic deep-
water groups of the Southern Sea, including Uonhcllularia,
Eupledella, PtcrocriniLS, Brisinga, Ophioglypha, Pourtalesia,
and one or two Mullusca. This is, however, very rarely the
case. Generally the red clay is barren, or contains only a very-
small number of forms.

It must be admitted that it is very diflScult, at

100 EXPEDITION OF THE "CHALLENGER" m

present, to frame any satisfactory explanation of
the mode of origin of this singular deposit of red
clay.

I cannot say that the theory put forward
tentatively, and with much reservation by Pro-
fessor Thomson, that the calcareous matter is
dissolved out by the relatively fresh water of the
deep currents from the Antarctic regions, appears
satisfactory to me. Nor do I see my way to the
acceptance of the suggestion of Dr. Carpenter, that
the red clay is the result of the decomposition of
previously-formed greensand. At present there is
no evidence that greensand casts are ever formed
at great depths; nor has it been proved that
Glauconite is decomposable by the agency of water
and carbonic acid.

I think it probable that we shall have to wait
some time for a sufficient explanation of the origin
of the abyssal red clay, no less than for that of the
sublittoral greensand in the intermediate zone.
But the importance of the establishment of the
fact that these various deposits are being formed
in the ocean, at the present day, remains the same,
whether its rationale be understood or not.

For, suppose the globe to be evenly covered with
sea, to a depth say of a thousand fathoms — then,
whatever might be the mineral matter composing
the sea-bottom, little or no deposit would be
formed upon it, the abrading and denuding action
of water, at such a depth, being exceedingly sHght

Ill EXPEDITION OF THE "CHALLENGER" 101

Next, imagine sponges, Radiolaria, Foraminifera,
and diatcmaceous plants, such as those which now
exist in the deep-sea, to be introduced : they
would be distributed according to the same laws
as at present, the sponges (and possibly some of
the Formninifera) covering the bottom, while other
Foraminifera, with the Radiolaria and Diatomacew,
would increase and multiply in the surface waters.
In accordance with the existing state of thino-s,
the Radiolaria and Diatoms would have a universal
distribution, the latter gathering most thickly in
the polar regions, while the Foraminifera would
be largely, if not exclusively, confined to the inter-
mediate zone ; and, as a consequence of this distri-
bution, a bed of " chalk " would begin to form in
the intermediate zone, while caps of silicious rock
would accumulate on the circumpolar regions.

Suppose, further, that a part of the intermediate
area were raised to within two or three hundred
fathoms of the surface — for an3rthing that we know
to the contrary, the change of level might deter-
mine the substitution of greensand for the
" chalk " ; while, on the other hand, if part of
the same area were depressed to three thousand
fathoms, that change might determine the substi-
tution of a different silicate of alumina and iron — •
namely, clay — for the " chalk " that would other-
wise be formed.

If the Challenger hypothesis, that the red
clay is the residue left by dissolved Foraminiferous

102 EXPEDITION OF THE "CHALLENGER" m

skeletons, is correct, then all these deposits ahke
would be directly, or indirectly, the product of
living organisms. But just as a silicious deposit
may be metamorphosed into opal or quartzite, and
chalk into marble, so known metamorphic agencies
may metamorphose clay into schist, clay-slate, slate,
gneiss, or even granite. And thus, by the agency
of the lowest and simplest of organisms, our
imaginary globe might be covered with strata, of
all the chief kinds of rock of which the known
crust of the earth is composed, of indefinite thick-
ness and extent.

The bearing of the conclusions which are now
either estabhshed, or highly probable, respecting
the origin of silicious, calcareous, and clayey rocks,
and their metamorphic derivatives, upon the
archaeology of the earth, the elucidation of which
is the ultimate object of the geologist, is of no
small importance.

A hundred years ago the singular insight of
Linnseus enabled him to say that " fossils are not
the children but the parents of rocks," ^ and the

1 "Petrificata montium calcariorum non filii sed parentes
snnt, cum omnis calx oriatiir ab anima]ibus." — Sy sterna Naiurce,
YA. xii., t. iii., p. 154. It must be recollected that Linnjeus
included silex, as "well as limestone, under the name of " calx,"
and that he would probably have arranged Diatoms among
animals, as part of "chaos." Ehrenberg quotes another even
more pithy passage, which I have not been able to find in any
edition of the Systema accessible to me: **Sic lapides ab
animalibus, nee \ice versa. Sic rupes saxei non primaevi, sed
temporis filiaa."

m EXPEDITION OF THE " CHALLENGER " 103

whole efifect of the discoveries made since his time
has been to compile a larger and larger comment-
ary upon this text. It is, at present, a perfectly-
tenable hypothesis that all silicious and calcareous
rocks are either directly, or indirectly, derived from
material which has, at one time or other, formed
part of the organized framework of living organ-
isms. Whether the same generalization may be
extended to aluminous rocks, depends upon the
conclusion to be drawn from the facts respecting
the red clay areas brought to light by the
Challenger. If we accept the view taken by
Wyville Thomson and his colleagues — that the
red clay is the residuum left after the calcareous
matter of the Globigerinm ooze has been dissolved
away — then clay is as much a product of life as
limestone, and all known derivatives of clay may
have formed part of animal bodies.

So long as the Glohigerinoe, actually collected at
the surface, have not been demonstrated to con-
tain the elements of clay, the Challenger hypo-
thesis, as I may term it, must be accepted with
reserve and provisionally, but, at present, I cannot
but think that it is more probable than any other
suggestion which has been made.

Accepting it provisionally, we arrive at the
remarkable result that all the chief known con-
stituents of the crust of the earth may have
formed part of living bodies ; that they may be
the " ash " of protoplasm ; that the " riLpes saxei "

104 EXPEDITION OF THE "CHALLENGER" iii

are not only " temporis," but " vitce filice *' ; and,
consequently, that the time during which life has
been active on the globe may be indefinitely
greater than the period, the commencement of
which is marked by the oldest known rocks,
whether fossiliferous or unfossiliferous.

And thus we are led to see where the solution
of a great problem and apparent paradox of
geology may lie. Satisfactory evidence now exists
that some animals in the existing world have been
derived by a process of gradual modification from
pre-existing forms. It is undeniable, for example,
that the evidence in favour of the derivation of
the horse from the later tertiary Hipparion, and
that of the Hipparion from AncJiithermm, is as
complete and cogent as such evidence can reason-
ably be expected to be ; and the further investiga-
tions into the history of the tertiary mammalia are
pushed, the greater is the accumulation of evidence
having the same tendency. So far from palae-
ontology lending no support to the doctrine of
evolution — as one sees constantly asserted — that
doctrine, if it had no other support, would have
been irresistibly forced upon us by the palseonto-
logical discoveries of the last twenty years.

If, however, the diverse forms of life which now
exist have been produced by the modification ©f
previously-existing less divergent forms, the recent
and extinct species, taken as a whole, must fall
into series which must converge as we go back in

Ill EXPEDITION OF THE "challenger" 105

time. Hence, if the period represented by the
rocks is greater than, or co-extensive with, that
during which hfe has existed, we ought, some-
where among the ancient formations, to an'ive at
the point to which all these series converge, or
from which, in other words, they have diverged — -
the primitive undifferentiated protoplasmic living
things, whence the two great series of plants and
animals have taken their departure.

But, as a matter of fact, the amount of conver-
gence of series, in relation to the time occupied by
the deposition of geological formations, is extra-
ordinarily small. Of all animals the higher
Vertehrata are the most complex ; and among
these the carnivores and hoofed animals ( Ungulata)
are highly differentiated. Nevertheless, although
the different lines of modification of the Carnivora
and those of the Ungidata, respectively, approach
one another, and, although each group is repre-
sented by less differentiated forms in the older
tertiary rocks than at the present day, the oldest
tertiary rocks do not bring us near the primitive
form of either. If, in the same way, the conver-
gence of the varied forms of reptiles is measured
against the time during which their remains are
preserved — which is represented by the whole of
the tertiary and mesozoic formations — the amount
of that convergence is far smaller than that of the
lines of mammals, between the present time and
the beginning of the tertiary epoch. And it is a

106 EXPEDITION OF THE "CHALLENGER" m

broad fact that, the lower we go in the scale of

organization, the fewer signs are there of con-
vergence towards the primitive form from whence
all must have diverged, if evolution be a fact.
Nevertheless, that it is a fact in some cases, is
proved, and I, for one, have not the courage to
suppose that the mode in which some species have
taken their origin is different from that in which
the rest have originated.

What, then, has become of all the marine
animals which, on the h}^othesis of evolution,
must have existed in myriads in those seas, wherein
the many thousand feet of Cambrian and Lauren-
tian rocks now devoid, or almost devoid, of any
trace of life were deposited ?

Sir Charles Lyell long ago suggested that the
azoic character of these ancient formations might
be due to the fact that they had undergone
extensive metamorphosis ; and readers of the
" Principles of Geology " will be familiar with the
ingenious manner in which he contrasts the theory
of the Gnome, who is acquainted only with the
interior of the earth, with those of ordinaiy
philosophers, who know only its exterior.

The metamorphism contemplated by the great
modern champion of rational geology is, mainly,
that brought about by the exposure of rocks to
subterranean heat ; and where no such heat could
be sho^vn to have operated, his opponents as-
sumed that no metamorphosis could have taken

Ill EXPEDITION OF THE "CHALLENGER** 107

place. But the formation of greensand, and still
more that of the "red clay" (if the Challenger
hypothesis be correct) affords an insight into a
new kind of metamorphosis — not igneous, but
aqueous — by which the primitive nature of a
deposit may be masked as completely as it can be
by the agency of heat. And, as Wyville Thomson
suggests, in the passage I have quoted above (p.
17), it further enables us to assign a new cause
for the occurrence, so puzzling hitherto, of
thousands of feet of unfossiliferous fine-grained
schists and slates, in the midst of formations
deposited in seas which certainly abounded in life.
If the great deposit of " red clay " now forming in
the eastern valley of the Atlantic were meta-
morphosed into slate and then upheaved, it would
constitute an " azoic " rock of enormous extent.
And yet that rock is now forming in the midst of
a sea which swarms with living beings, the great
majority of which are provided with calcareous or
silicious shells and skeletons ; and, therefore, are
such as, up to this time, we should have termed
eminently preservable.

Thus the discoveries made by the Challenger
expedition, like all recent advances in our
knowledge of the phenomena of biology, or
of the changes now being effected in the
structure of the surface of the earth, are in
accordance with, and lend strong support to,
that doctrine of Uniformitarianism, which, fifty

108 EXPEDITION OF THE "CHALLENGER" m

years ago, was held only by a small minority of
English geologists — Lyell, Scrope, and De la Beche
• — but now, thanks to the long-continued labours
of the first two, and mainly to those of Sir Charles
Lyell, has gradually passed from the position of a
heresy to that of catholic doctrine.

Applied within the limits of the time registered
by the known fraction of the crust of the earth,
I believe that uniformitarianism is unassailable.
The evidence that, in the enormous lapse of time
between the deposition of the lowest Laurentian
strata and the present day, the forces which have
modified the surface of the crust of the earth were
different in kind, or greater in the intensity of
their action, than those which are now occupied in
the same work, has yet to be produced. Such
evidence as we possess all tends in the contrary
direction, and is in favour of the same slow and
gradual changes occurring then as now.

But this conclusion in nowise conflicts with the
deductions of the physicist from his no less clear
and certain data. It may be certain that this
globe has cooled down from a condition in which
life could not have existed ; it may be certain that,
in so cooling, its contracting crust must have
undergone sudden convulsions, which were to our
earthquakes as an earthquake is to the vibration
caused by the periodical eruption of a Geyser ; but
in that case, the earth must, like other respectable
parents, have sowed her wild oats, and got through

Ill EXPEDITION OF THE "CHALLENGER" 109

her turbulent youth, before we, her children, have
any knowledge of her.

So far as the evidence afforded by the super-
ficial crust of the earth goes, the modern geologist
can, ex animo, repeat the saying of Hutton, " We
find no vestige of a beginning — no prospect of an
end." However, he will add, with Hutton, " But
in thus tracing back the natural operations which
have succeeded each otter, and mark to us the
course of time past, we come to a period in which
we cannot see any further." And if he seek to
peer into the darkness of this period, he will
welcome the light proffered by physics and
mathematics.

IV

YEAST

[1871]

It has been known, from time immemorial, that
the sweet liquids which may be obtained by ex-
pressing the juices of the fruits and stems of
various plants, or by steeping malted barley in hot
water, or by mixing honey with water — are liable
to undergo a series of very singular changes, if
freely exposed to the air and left to themselves, in
warm weather. However clear and pellucid the
liquid may have been when first prepared, however
carefully it may have been freed, by straining and
filtration, from even the finest visible impurities,
it will not remain clear. After a time it will
become cloudy and turbid ; little bubbles will be
seen rising to the surface, and their abundance will
increase until the liquid hisses as if it were sim-
mering on the fire. By degrees, some of the solid
particles which produce the turbidity of the liquid

IV YEAST 111

collect at its surface into a scum, which is blown
up by the emerging air-bubbles into a thick, foamy
froth. Another moiety sinks to the bottom, and
accumulates as a muddy sediment, or " lees."

When this action has continued, with more or
less violence, for a certain time, it gradually
moderates. The evolution of bubbles slackens,
and finally comes to an end ; scum and lees alike
settle at the bottom, and the fluid is once more
clear and transparent. But it has acquired
properties of which no trace existed in the
original liquid. Instead of being a mere sweet
fluid, mainly composed of sugar and water, the
sugar has more or less completely disappeared ; and
it has acquired that peculiar smell and taste which
we call " spirituous." Instead of being devoid of
any obvious effect upon the animal economy, it
has become possessed of a very wonderful influence
on the nervous system ; so that in small doses it
exhilarates, while in larger it stupefies, and may
even destroy life.

Moreover, if the original fluid is put into a still,
and heated moderately, the first and last product
of its distillation is simple water ; while, when the
altered fluid is subjected to the same process, the
matter which is first condensed in the receiver is
found to be a clear, volatile substance, which is
hghter than water, has a pungent taste and smell,
possesses the intoxicating powers of the fluid in
an eminent degree, and takes fire the moment it

112 YEAST

IV

is brought in contact with a flame. The Al-
chemists called this volatile liquid, which they
obtained from wine, " spirits of wine," just as they
called hydrochloric acid " spirits of salt," and as
we, to this day, call refined turpentine " spirits of
turpentine." As the " spiritus," or breath, of a
man was thought to be the most refined and
subtle part of him, the intelligent essence of man
was also conceived as a sort of breath, or spirit ;
and, by analogy, the most refined essence of any-
thing was called its " spirit." And thus it has
come about that we use the same word for the
soul of man and for a glass of gin.

At the present day, however, we even more
commonly use another name for this peculiar
liquid — namely, " alcohol," and its origin is not
less singular. The Dutch physician, Van Helmont,
lived in the latter part of the sixteenth and the
beginning of the seventeenth century — in the
transition period between alchemy and chemistry
— and was rather more alchemist than chemist.
Appended to his " Opera Omnia," published in 1707,
there is a very needful " Clavis ad obscuriorum
sensum referendum," in which the following
passage occurs : —

"Alcohol. — Chymicis est liquor ant pulvis siimme subtili-
satns, vocabulo Oiientalibus quoque, cum primis Habessinis,
familiari, quibus cohol speciatim pulverem impalpabilem ex
antimonio pro oculis tingendis denotat . . . Hodie autem, ob
analogiam, quivis pulvis tenerior, ut pulvis oculorum cancri

IV

YEAST 113

summ^ subtilisatus alcohol audit, haud aliter ac spiritus rectifi-
catissimi alcolisati dicuntur."

Similarly, Robert Boyle speaks of a fine powder
as " alcohol " ; and, so late as the middle of the
last century, the English lexicographer, Nathan
Bailey, defines " alcohol " as " the pure substance
of anything separated from the more gross, a very
fine and impalpable powder, or a very pure, well-
rectified spirit." But, by the time of the publi-
cation of Lavoisier's " Traite Elementaire de
Chimie,"in 1789, the term "alcohol," " alkohol,"
or " alkool " (for it is spelt in all three ways), which
Van Helmont had applied primarily to a fine
powder, and only secondarily to spirits of wine, had
lost its primary meaning altogether; and, from
the end of the last century until now, it has, I
believe, been used exclusively as the denotation of
spirits of wine, and bodies chemically allied to that
substance.

The process which gives rise to alcohol in a
saccharine fluid is known to us as " fermentation " ;
a term based upon the apparent boiling up or
'' effervescence " of the fermenting liquid, and of
Latin origin.

Our Teutonic cousins call the same process
"giihren," "gasen," "goschen," and "gischen";
but, oddly enough, we do not seem to have
retained their verb or their substantive denot-
ing the action itself, though we do use names
identical with, or plainly derived fi:om, theirs for

194

114 YEAST IV

the scum and lees. These are called, in Low
German, " giischt " and " gischt " ; in Anglo-Saxon,
"gest," "gist," and "yst," whence our "yeast."
Again, in Low German and in Anglo-Saxon there
is another name for yeast, having the form " barm,"
or " beorm " ; and, in the Midland Counties,
" barm " is the name by which yeast is still best
known. In High German, there is a third name
for yeast, " hefe," which is not represented in
English, so far as I know.

All these words are said by philologers to be
derived from roots expressive of the intestine
motion of a fermenting substance. Thus " hefe "
is derived from " heben," to raise ; " barm " from
" beren " or " baren," to bear up ; " yeast," " yst,"
and " gist," have all to do with seething and foam,
with " yeasty " waves, and " gusty " breezes.

The same reference to the swelling up of the
fermenting substance is seen in the Gallo-Latin
terms " levure " and " leaven."

It is highly creditable to the ingenuity of our
ancestors that the peculiar property of fermented
liquids, in virtue of which they " make glad the
heart of man," seems to have been known in the
remotest periods of which we have any record.
All savages take to alcoholic fluids as if they
were to the manner bom. Our Vedic forefathers
intoxicated themselves with the juice of the
" soma " ; Noah, by a not unnatural reaction
against a superfluity of water, appears to have

IV

YEAST 115

taken the earliest practicable opportunity cf
qualifying that which he was obliged to drink;
and the ghosts of the ancient Egyptians were
solaced by pictures of banquets in which the
wine-cup passes round, graven on the walls of
their tombs. A knowledge of the process of
fermentation, therefore, was in all probability
possessed by the prehistoric populations of the
globe ; and it must have become a matter of great
interest even to primgeval wine-bibbers to study
the methods by which fermented liquids could
be surely manufactured. No doubt it was soon
discovered that the most certain, as well as
the most expeditious, way of making a sweet juice
ferment was to add to it a little of the scum, or
lees, of another fermenting juice. And it can
hardly be questioned that this singular excitation
of fermentation in one fluid, by a sort of infection,
or inoculation, of a little ferment taken from some
other fluid, together with the strange swelling,
foaming, and hissing of the fermented substance,
must have always attracted attention from the
more thoughtful. Nevertheless, the commence-
ment of the scientific analysis of the phenomena
dates from a period not earlier than the first half
of the seventeenth century.

At this time, Van Helmont made a first step,
by pointing out that the peculiar hissing and
bubbling of a fermented liquid is due, not to the
evolution of common air (which he, as the inventoi

116 YEAST IV

of the term " gas," calls " gas ventosum "), but to
that of a peculiar kind of air such as is occasionally
met with in caves, mines, and wells, and which
he calls " gas sylvestre."

But a century elapsed before the nature of this
"gas sylvestre," or, as it was afterwards called,
"fixed air," was clearly determined, and it was
found to be identical with that deadly " choke-
damp " by which the lives of those who descend
into old wells, or mines, or brewers' vats, are
sometimes suddenly ended ; and with the poisonous
aeriform fluid which is produced by the combus-
tion of charcoal, and now goes by the name of
carbonic acid gas.

During the same time it gradually became
evident that the presence of sugar was essential to
the production of alcohol and the evolution of
carbonic acid gas, which are the two great and
conspicuous products of fermentation. And finally,
in 1787, the ItaHan chemist, Fabroni, made the
capital discovery that the yeast ferment, the
presence of which is necessary to fermentation,
is what he termed a " vegeto-animal " substance ;
that is, a body which gives off ammoniacal salts
when it is burned, and is, in other ways, similar
to the gluten of plants and the albumen and
casein of animals.

These discoveries prepared the way for the
illustrious Frenchman, Lavoisier, who first ap-
proached the problem of fermentation with a

IV

YEAST 11'

complete conception of the nature of the work to
be done. The words in which he expresses this
conception, in the treatise on elementary chemistry
to which reference has already been made, mark
the year 1789 as the commencement of a revolu-
tion of not less moment in the world of science
than that which simultaneously burst over the
political world, and soon engulfed Lavoisier himself
in one of its mad eddies.

"We may lay it down as an incontestable axiom that, in all
the operations of art and nature, nothing is created ; an equal
quantity of matter exists both before and after the experiment :
the quality and quantity of the elements remain precisely the
same, and nothing takes place beyond changes and modifications
in the combinations of these elements. Upon this principle the
whole art of performing chemical experiments depends ; we
must always suppose an exact equality between the elements of
the body examined and those of the products of its analysis.

"Hence, since from must of grapes we procure alcohol arid
carbonic acid, I have an undoubted right to suppose that must
consists of carbonic acid and alcohol. From these premisses we
have two modes of ascertaining what passes during vinous fer-
mentation : either by determining the nature of, and the elements
which compose, the fermentable substances ; or by accurately ex-
amining the products resulting from fermentation ; and it is evi-
dent that the knowledge of either of these must lead to accurate
conclusions concerning the nature and composition of the other.
From these considerations it became necessary accurately to
determine the constituent elements of the fermentable sub-
stances ; and for this purpose I did not make use of the com-
pound juices of fruits, the rigorous analysis of which is perhaps
impossible, but made choice of sugar, which is easily analysed,
and the nature of which I have already explained. This sub-
Btance is a true vegetable oxyd, with two bases, composed of

118 YEAST IV

li3'drogen and carbon, brought to the state of an oxyd by means
of a certain proportion of oxygen ; and these three elements are
combined in such a way that a very slight force is sufficient to
destroy the equilibrium of their connection."

After giving the details of his analysis of sugar
and of the products of fermentation, Lavoisier
continues : —

"The effect of the vinous fermentation upon sugar is thus
reduced to the mere separation of its elements into two portions ;
one part is oxygenated at the expense of the other, so as to form
carbonic acid ; while the other part, being disoxygenated in
favour of the latter, is converted into the combustible substance
called alkohol ; therefore, if it were possible to re-unite alkohol
and carbonic acid together, we ought to form sugar." ^

Thus Lavoisier thought he had demonstrated
that the carbonic acid and the alcohol which are
produced by the process of fermentation, are
equal in weight to the sugar which disappears;
but the application of the more refined methods
of modem chemistry to the investigation of the
products of fermentation by Pasteur, in 1860,
proved that this is not exactly true, and that
there is a deficit of from 5 to 7 per cent, of the
sugar which is not covered by the alcohol and
carbonic acid evolved. The greater part of this
deficit is accounted for by the discovery of two
substances, glycerine and succinic acid, of the
existence of which Lavoisier was unaware, in the

^ Elements of ChemUtry. By M. Lavoisier. Translated by
Robert Kerr. Second Edition, 1793 (pp. 186—196).

rv

YEAST 119

fermented liquid. But about IJ per cent, still
remains to be made good. According to Pasteur,
it has been appropriated by the yeast, but the
fact that such appropriation takes place cannot
be said to be actually proved.

However this may be, there can be no doubt
that the constituent elements of fully 98 per
cent, of the sugar which has vanished during
fermentation have simply undergone rearrange-
ment ; like the soldiers of a brigade, w^ho at the
word of command divide themselves into the
independent regiments to which they belong.
The brigade is sugar, the regiments are carbonic
acid, succinic acid, alcohol, and glycerine.

From the time of Fabroni, onwards, it has been
admitted that the agent by which this surprising
rearrangement of the particles of the sugar is
effected is the yeast. But the first thoroughly
conclusive evidence of the necessity of yeast for
the fermentation of sugar was furnished by
Appert, whose method of preserving perishable
articles of food excited so much attention in
France at the beginning of this century. Gay-
Lussac, in his " Memoire sur la Fermentation," ^
alludes to Appert's method of preserving beer-
wort unfermented for an indefinite time, by
sim23ly boiling the wort and closing the vessel
in which the boiling fluid is contained, in such
a way as thoroughly to exclude air; and he
^ Annates de Chimie, 1810.

120 YEAST IV

shows that, if a little yeast be introduced into
such wort, after it has cooled, the wort at once
begins to ferment, even though every precaution
be taken to exclude air. And this statement has
since received full confirmation from Pasteur.

On the other hand, Schwann, Schroeder and
Dusch, and Pasteur, have amply proved that air
may be allowed to have free access to beer-wort,
without exciting fermentation, if only efficient
precautions are taken to prevent the entry of
particles of yeast along with the air.

Thus, the truth that the fermentation of a
simple solution of sugar in water depends upon
the presence of yeast, rests upon an unassailable
foundation; and the inquiry into the exact
nature of the substance which possesses such a
wonderful chemical influence becomes profoundly
interesting.

The first step towards the solution of this
problem was made two centuries ago by the patient
and painstaking Dutch naturalist, Leeuwenhoek,
who in the year 1680 wrote thus : —

"Ssepissime examinavi fermentum cerevisise. semperqne hoc
ex globulis per materiam pellncidam fluitantibiis, qnam cere-
visiam esse censiii, constare observavi : vidi etiara evider_tissime,
unumqueinque hujus fermenti globiilnra denuo ex sex distinctis
globulis constare, accurate eidem quantitate et fornise, cui
globulis sanguinis nostri, respondentibns.

*' Verum talis mihi de horam origine et formatione conceptus
formabara ; globulis nempe ex qnibus farina Tritici, Hordei,
Avenee, Fagotritici, se constat aquae calore dissolvi et aquse com.

rv

YEAST 121

misceii ; hac, vero aqua, quam cere vis iam vocare licet, refriges-
cente, multos ex minimis particulis in cerevisiacoadunaii, et hoc
pacto efficere particulam sive globuliim, qiise sexta pars est
globuli faecis, et iterum sex ex hisce globulis conjungi." ^

Thus Leeuwenhoek discovered that yeast con-
sists of globules floating in a fluid ; but he thought
that they were merely the starchy particles of the
grain from which the wort was made, rearranged.
He discovered the fact that yeast had a definite
structure, but not the meaning of the fact. A
century and a half elapsed, and the investigation
of yeast was recommenced almost simultaneousl}?
by Cagniard de la Tour in France, and by Schwann
and Ktitzing in Germany. The French observer
was the first to publish his results ; and the sub-
ject received at his hands and at those of his
colleague, the botanist Turpin, full and satisfactory
investigation.

The main conclusions at which they arrived are
these. The globular, or oval, corpuscles which
float so thickly in the yeast as to make it muddy,
though the largest are not more than one two-
thousandth of an inch in diameter, and the
smallest may measure less than one seven-
thousandth of an inch, are living organisms. They
multiply with great rapidity by giving off minute
buds, which soon attain the size of their parent,
and then either become detached or remain
united, forming the compound globules of which
^ Leeuwenhoek, Arcana Naturce Detecta. Ed. Nov., 1721.

122 YEAST IV

Leeuwenhoek speaks, thougli the constancy of
their arrangement in sixes existed only in the
worthy Dutchman's imagination.

It was very soon made out that these yeast
organisms, to which Turpin gave the name of
Torula cerevisicv, were more nearly allied to the
lower Fungi than to an}i:hing else. Indeed
Turpin, and subsequently Berkeley and Hoffmann,
believed that they had traced the development of
the Torula into the well-known and very common
mould — the Penicillium glaucuin. Other observers
have not succeeded in verifying these statements ;
and my own observations lead me to believe, that
while the connection between Torula and the
moulds is a very close one, it is of a different
nature from that which has been supposed. I
have never been able to trace the development of
Torula into a true mould ; but it is quite easy to
prove that species of true mould, such as Peni-
cillium, when sown in an appropriate nidus, such
as a solution of tartrate of ammonia and yeast-
ash, in water, with or without sugar, give rise to
Torulce, similar in all respects to T. cerevisicc,
except that they are, on the average, smaller.
Moreover, Bail has observed the development of a
Torula larger than T. ccrevisice, from a Mucor, a
mould allied to Penicillium.

It follows, therefore, that the Torulce, or
organisms of yeast, are veritable plants ; and con-
clusive experiments have proved that the powei

IV YEAST 123

which causes the rearrangement of the molecules
of the sugar is intimately connected with the life
and growth of the plant. In fact, w^hatever arrests
the vital activity of the plant also prevents it
from exciting fermentation.

Such being the facts with regard to the nature
of yeast, and the changes which it effects in
sugar, how are they to be accounted for ? Before
modern chemistry had come into existence, Stahl,
stumbling, with the stride of genius, upon the con-
ception which lies at the bottom of all modern views
of the process, put forward the notion that the
ferment, being in a state of internal motion, com-
municated that motion to the sugar, and thus
caused its resolution into new substances. And
Lavoisier, as we have seen, adopts substantially
the same view. But Fabroni, full of the then
novel conception of acids and bases and double
decompositions, propounded the hypothesis that
sugar is an oxide with two bases, and the ferment
a carbonate with two bases ; that the carbon of
the ferment unites with the oxygen of the sugar,
and gives rise to carbonic acid ; while the sugar,
uniting with the nitrogen of the ferment, pro-
duces a new substance analogous to opium. This
is decomposed by distillation, and gives rise to
alcohol. Next, in 1803, Thenard propounded a
hypothesis which partakes somewhat of the nature
of both Stahl's and Fabroni's views. " I do not
believe with Lavoisier," he says, " that all the

1 24 YEAST

IV

carbonic acid formed proceeds from tlie sugar.
How, in that case, could we conceive the action of
the ferment on it ? I think that the first por-
tions of the acid are due to a combination of the
carbon of the ferment with the oxygen of the
sugar, and that it is by carrying ofif a portion of
oxygen from the last that the ferment causes the
fermentation to commence — the equilibrium be-
tween the principles of the sugar being disturbed,
they combine afresh to form carbonic acid and
alcohol."

The three views here before us may be familiarly
exemplified by supposing the sugar to be a card-
house. According to Stahl, the ferment is some-
body who knocks the table, and shakes the card-
house down; according to Fabroni, the ferment
takes out some cards, but puts others in their
places ; according to Thenard, the ferment simply
takes a card out of the bottom story, the result
of which is that all the others fall.

As chemistry advanced, facts came to light
which put a new face upon Stahl's h}^othesis, and
gave it a safer foundation than it previously pos-
sessed. The general nature of these phenomena
may be thus stated : — A body. A, without giving
to, or taking from, another body B, any material
particles, causes B to decompose into other sub-
stances, G, D, E, the sum of the weights of which
is equal to the weight of B, which decomposes.

Thus, bitter almonds contain two substances,

IV YEAST 125

amygdalin and synaptase, which can be extracted,
in a separate state, from the bitter almonds. The
amygdaUn thus obtained, if dissolved in water,
undergoes no change ; but if a little synaptase be
added to the solution, the amygdalin sphts up
into bitter almond oil, prussic acid, and a kind of
sugar.

A short time after Cagniard de la Tour dis-
covered the yeast plant, Liebig, struck with the
similarity between this and other such processes
and the fermentation of sugar, put forward the
hypothesis that yeast contains a substance which
acts upon sugar, as synaptase acts upon amygdalin.
And as the synaptase is certainly neither organized
nor alive, but a mere chemical substance, Liebig
treated Cagniard de la Tour's discovery with no
small contempt, and, from that time to the pre-
sent, has steadily repudiated the notion that the
decomposition of the sugar is, in any sense, the
result of the vital activity of tiie Tcnda. But,
though the notion that the Torula is a creature
which eats sugar and excretes carbonic acid and
alcohol, which is not unjustly ridiculed in the
most surprising paper that ever made its appear-
ance in a grave scientific journal,^ may be un-

^ " Das entrathselte Geheimniss der geistigen Gahrung (Vor-
laufige briefliche Mittheilung)" is the title of an anonymous
contiibiition to Wohler and Liebig's Jnnahn der Pharmacia
for 1839, in which a somewhat Rabelaisian imaginary descrip-
tion of the organisation of the "yeast animals" and of the
manner in which their functions are performed, is given with a

126 YEAST IV

tenable, the fact that the Toridm are alive, and
that yeast does not excite fermentation unless it
contains living Toridoe., stands fast. Moreover, of
late years, the essential participation of living
organisms in fermentation other than the alcoholic,
has been clearly made out by Pasteur and other
chemists.

However, it may be asked, is there any necessary
opposition between the so-called " vital " and the
strictly physico-chemical views of fermentation ?
It is quite possible that the living Torula may
excite fermentation in sugar, because it constantly
produces, as an essential part of its vital manifes-
tations, some substance which acts upon the sugar,
just as the synaptase acts upon the amygdalin.
Or it may be, that, without the formation of any
such special substance, the physical condition of
the living tissue of the yeast plant is sufficient to
effect that small disturbance of the equilibrium of
the particles of the sugar, which Lavoisier thought
sufficient to effect its decomposition.

Platinum in a very fine state of division —
known as platinum black, or noir de platine — has

circumstantiality worthy of the author of GulUv'rs Travels.
As a specimen of the writer's humour, his account of what
happens when fermentation comes to an end may suftice.
"Sobald namlich die Thiere keinen Zucker mehr vorfinden, so
fressen sie sich gegenseitio: selbst auf, was durch eine eigene
Manipulation geschieht ; alles wird verdant his auf die Eier,
weiche unverandert durch den Darmkanal hineingehen ; man
hat zuletzt wieder gahrungsfahige Het'e, namlich den Saamen
der Thieie, der iibrig bleibt"

IV

YEAST 127

the very singular property of causing alcohol to
change into acetic acid with great rapidity. The
vinegar plant, which is closely allied to the yeast
plant, has a similar effect upon dilute alcohol,
causing it to absorb the oxygen of the air, and
become converted into vinegar ; and Liebig's
eminent opponent, Pasteur, who has done so much
for the theory and the practice of vinegar-making,
himself suggests that in this case —

*'La cause du phenomene physique qui accompagne la vie de
la plante reside dans un etat physique propre, analogue k celui
du noir de platine. Mais il est essentiel de remarquer que cet
etat physique de la plante est etroitement lie avec la vie de
cette plante." ^

Now, if the vinegar plant gives rise to the oxi-
dation of alcohol, on account of its merely phy-
sical constitution, it is at any rate possible that
the physical constitution of the yeast plant may
exert a decomposing influence on sugar.

But, without presuming to discuss a question
which leads us into the very arcana of chemistry,
the present state of speculation upon the modus
operandi of the yeast plant in producing fermenta-
tion is represented, on the one hand, by the
Stahlian doctrine, supported by Liebig, according
to which the atoms of the sugar are shaken into
new combinations, either directly by the Torulce^
or indirectly, by some substance formed by them ;

* Mvdes mr Us Mycodfrmes, Comptcs-Rendus, liv., 1862.

128 YEAST TV

and, on the other hand, by the Thunardian doc-
trine, supported by Pasteur, according to which
the yeast plant assimilates part of the sugar, and,
in so doino^, disturbs the rest, and determines its
resolution into the products of fermentation. Per-
haps the two views are not so much opposed as
they seem at first sight to be.

But the interest which attaches to the influence
of the yeast plants upon the medium in which
they live and grow does not arise solely from its
bearing upon the theory of fermentation. So long
ago as 1838, Turpin compared the Torulce to the
ultimate elements of the tissues of animals and
plants — " Les organes elementaires de leurs tissus,
comparables aux petits veg^taux des levures
ordinaires, sont aussi les decompositeurs des sub-
stances qui les environnent."

Almost at the same time, and, probably, equally
guided by his study of yeast, Schwann was en-
gaged in those remarkable investigations into the
form and development of the ultimate structural
elements of the tissues of animals, Avhich led him
to recognise their fundamental identity with the
ultimate structural elements of vegetable organ-
isms.

The yeast plant is a mere sac, or " cell," con-
taining a semi-fluid matter, and Schwann's micro-
scopic analysis resolved all living organisms, in the
long run, into an aggregation of such sacs or cells,
variously modified ; and tended to show, that all,

rv

YEAST 129

whatever their ultimate complication, begin their
existence in the condition of such simple cells.

In his famous "Mikroskopische Untersuchun-
gen " Schwann speaks of Torula as a " cell " ; and,
in a remarkable note to the passage in which he
refers to the yeast plant, Schwann says : —

**I have been unable to avoid mentioning fermentation,
because it is the most fully and exactly known operation of cells,
and represents, in the simplest fashion, the process which is
repeated by every cell of the living body. "

Jn other words, Schwann conceives that every
cell of the living body exerts an influence on the
matter which surrounds and permeates it, ana-
logous to that which a Tcrula exerts on the
saccharine solution by which it is bathed. A
wonderfully suggestive thought, opening up views
of the nature of the chemical processes of the
living body, which have hardly yet received all
the development of which they are capable.

Kant defined the special peculiarity of the living
body to be that the parts exist for the sake of the
whole and the whole for the sake of the parts.
But when Turpin and Schwann resolved the living
body into an aggregation of quasi-independent
cells, each, like a Torula, leading its own life and
having its own laws of growth and development,
the aggregation being dominated and kept work-
ing towards a definite end only by a certain
harmony among these units, or by the superaddition

196

130 YEAST IV

of a controlling apparatus, such as a nervous system,
this conception ceased to be tenable. The cell
lives for its own sake, as well as for the sake of
the whole organism ; and the cells ivhich float in
the blood, live at its expense, and profoundly
modify it, are almost as much independent organ-
isms as the Torulce which float in beer-wort.

Schwann burdened his enunciation of the " cell
theory" with two false suppositions; the one,
that the structures he called " nucleus " ^ and " cell-
wall " are essential to a cell ; the other, that cells
are usually formed independently of other cells ;
but, in 1839, it was a vast and clear gain to arrive
at the conception, that the vital functions of all
the higher animals and plants are the resultant of
the forces inherent in the innumerable minute cells
of which the}^ are composed, and that each of them
is, itself, an equivalent of one of the lowest and
simplest of independent living beings — the Torula,

From purely morphological investigations, Tur-
pin and Schwann, as we have seen, arrived at the
notion of the fundamental unity of structure of
living beings. And, before long, the researches of
chemists gradually led up to the conception of the
fundamental unity of their composition.

So far back as 1803, Thenard pointed out, in

^ [Later investigations have thrown an entirely new light
npon the structure and the functional importance of the
nucleus ; and have proved that Schwann did not over-estimate
Its iraportam^e. 1894.]

rv YEAST 131

most distinct terms, the important fact that yeast
contains a nitrogenous " animal " substance ; and
that such a substance is contained in all ferments.
Before him, Fabroni and Fourcroy speak of the
" vegeto-animal " matter of yeast. In 1844 Mulder
endeavoured to demonstrate that a peculiar sub-
stance, which he called " protein," was essentially
characteristic of living matter.
In 1846, Payen writes : —

"Enfin, une loi sans exception me semLle apparaitre dans
les faits nombreux que j'ai observes et conduire a envisager sous
un nouveau jour la vie vegetale ; si je ne m'abuse, tout ce que
dans les tissus vegetaux la vue directe ou amplitiee nous permet
de discerner sous la forme de cellules et de vaisseaux, ne represente
autre chose que les enveloppes protectrices, les reservoirs et les
conduits, a I'aide desquels les corps animes qui les secretent et les
faQonnent, se logent, puisent et charrient leurs aliments, deposent
et isolent les matieres excretees. "

And again : —

" Afin de completer aujourd'hui I'^nonce du fait general, je
rappellerai que les corps, dou^ des fonctions accomplies dans
les tissus des plantes, sont formes des elements qui constituent,
en proportion peu variable, les organismes animaux ; qu'ainsi
Ton est conduit a reconnaitre une immense unite de composition
^lementaire dans tous les corps vivants de la nature." ^

In the year (1846) in which these remarkable
passages were published, the eminent German
botanist, Yon Mohl, invented the word " proto-
plasm," as a name for one portion of those nitro-
genous contents of the cells of living plants, the

^ "Mem. sur les Developpements des Vegetaux,' &c. — Mim.
Pri&cnUrs. ix. 1846.

132 YEAST IV

close chemical resemblance of which to the essen-
tial constituents of living animals is so strongly
indicated by Payen. And through the twenty-
five years that have passed, since the matter of
life was first called protoplasm, a host of investi-
gators, among whom Cohn, Max Schulze, and
Kiihne must be named as leaders, have accum-
ulated evidence, morphological, physiological, and
chemical, in favour of that " immense unite de
composition elementaire dans tous les corps vivants
de la nature," into which Payen had, so early, a
clear insight.

As far back as 1850, Cohn wrote, apparently
without any knowledge of what Payen had said
before him : —

" The protoplasm of the botanist, and the contractile sub-
stance and sarcode of the zoologist, must be, if notiientical, yet
in a high degree analogous substances. Hence, fvom this point
of view, the difference between animals and plants consists in
this ; that, in the latter, the contractile substance, as a primordial
utricle, is enclosed within an inert cellulose membrane, which
permits it only to exhibit an internal motion, expressed by the
phenomena of rotation and circulation, while, in the former, it
is not so enclosed. The protoplasm in the form of the primordial
utricle is, as it were, the animal element in the plant, but
which is imprisoned, and only becomes free in the animal ; or,
to strip off the metaphor which obscures simple thought, the
energy of organic vitality which is manifested in movement is
especially exhibited by a nitrogenous contractile substance,
which in plants is limited and fettered by an inert membrane,
in animals not so." ^

^ Cohn, "Ueber Protococcus pluvialis, " m the Nova Acta for
1850.

IV YEAST 183

In 1868, thinking that an untechnical state-
ment of the views current among the leaders of
biological science might be interesting to the
general public, I gave a lecture embodpng them in
Edinburgh. Those who have not made the mis-
take of attempting to approach biology, either by
the high d, priori road of mere philosophical specu-
lation, or by the mere low a posteriori lane offered
by the tube of a microscope, but have taken the
trouble to become acquainted with well-ascertained
facts and with their history, will not need to
be told that in what I had to say " as regards
protoplasm " in my lecture " On the Physical
Basis of Life " (Vol. I. of these Essays, p. 130),
there was nothing new; and, as I hope, no-
thing that the present state of knowledge does
not justify us in believing to be true. Under these
circumstances, my surprise may be imagined, when
I found, that the mere statement of facts and of
views, long familiar to me as part of the common
scientific property of Continental workers, raised a
sort of storm in this country, not only by exciting
the wrath of unscientific persons whose pet pre-
judices they seemed to touch, but by giving rise to
quite superfluous explosions on the part of some
who should have been better informed.

Dr. Stirling, for example, made my essay the
subject of a special critical lecture,^ which I have

1 Subsequently published under the title of "As regards
Protoplasm."

134 YEAST IV

read with mucli interest, though, I confess, the
meaning of much of it remains as dark to me as
does the " Secret of Hegel " after Dr. Stirhng's
elaborate revelation of it. Dr. Stirhng's method
of dealing with the subject is peculiar. " Proto-
plasm " is a question of history, so far as it is a
name ; of fact, so far as it is a thing. Dr. Stirling
has not taken the trouble to refer to the original
authorities for his history, which is consequently a
travesty ; and still less has he concerned himself
with looking at the facts, but contents himself
with taking them also at second-hand. A most
amusing example of this fashion of dealing with
scientific statements is furnished by Dr. Stirling's
remarks upon my account of the protoplasm of the
nettle hair. That account was drawn up from
careful and often-repeated observation of the facts.
Dr. Stirling thinks he is offering a valid criticism,
when he says that my valued friend Professor
Strieker gives a somewhat different statement
about protoplasm. But why in the world did not
this distinguished Hegelian look at a nettle hair for
himself, before venturing to speak about the matter
at all ? Why trouble himself about what either
Strieker or I say, when any t}TO can see the facts
for himself, if he is provided with those not rare
articles, a nettle and a microscope ? But I suppose
this would have been '' Avfkldrung " — a recurrence
to the base common-sense philosophy of the
eighteenth century, which liked to see before it

IV YEAST 135

believed, and to understand before it criiicised
Dr. Stirling winds up his paper with the following
paragraph : —

"In shovt, the whole position of Mr. Huxley, (1) that all
organisms consist alike of the same life-matter, (2) which life-
matter is, for its part, due only to chemistry, must be pro-
nounced untenable — nor less untenable (3) the materialism he
•would found on it."

The paragraph contains three distinct assertions
concerning my views, and just the same number of
utter misrepresentations of them. That which I
have numbered (1) turns on the ambiguity of the
word " same," for a discussion of which I would
refer Dr. Stirling to a great hero of ''Aufkldrung"
Archbishop Whately ; statement number (2) is,
in my judgment, absurd, and certainly I have never
said anything resembling it ; while, as to number
(3), one great object of my essay was to show that
what is called " materialism " has no sound philo-
sophical basis !

As we have seen, the study of yeast has led in-
vestigators face to face with problems of immense
interest in pure chemistry, and in animal and
vegetable morphology. Its physiology is not less
rich in subjects for inquiry. Take, for example,
the singular fact that yeast will increase indefin-
itely when grown in the dark, in water containing
only tartrate of ammonia, a small percentage of
mineral salts, and sugar. Out of these materials
the Torulce will manufacture nitrogenous proto-

136 YEAST IV

plasm, cellulose, and fatty matters, in any quantity,
although they are wholly deprived of those rays of
the sun, the influence of which is essential to the
growth of ordinary plants. There has been a
great. deal of speculation lately, as to how the
living organisms buried beneath two or three
thousand fathoms of water, and therefore in all
probability almost deprived of light, live. If any
of them possess the same powers as yeast (and
the same capacity for living without light is ex-
hibited by some other fungi) there would seem to
be no difficulty about the matter.

Of the pathological bearings of the study of
yeast, and other such organisms, I have spoken
elsewhere. It is certain that, in some animals,
devastating epidemics are caused by fungi of low
order — similar to those of which Too-ula is a sort
of offshoot. It is certain that such diseases are
propagated by contagion and infection, in just
the same way as ordinary contagious and infectious
diseases are propagated. Of course, it does not
follow from this, that all contagious and infectious
diseases are caused by organisms of as definite
and independent a character as the Toritla ; but,
I think, it does follow that it is prudent and wise
to satisfy one's self in each particular case, that the
"germ theory" cannot and will not explain the
facts, before having recourse to hypotheses which
have no equal support from analogy.

ON THE FORMATION OF COAL

[1870]

The lumps of coal in a coal-scuttle very often
have a roughly cubical form. If one of them be
picked out and examined with a little care, it wiU
be found that its six sides are not exactly alike.
Two opposite sides are comparatively smooth and
shining, while the other four are much rougher,
and are marked by lines which run parallel with
the smooth sides. The coal readily splits along
these lines, and the split surfaces thus formed
are parallel with the smooth faces. In other
words, there is a sort of rough and incomplete
stratification in the lump of coal, as if it were a
book, the leaves of which had stuck together very
closely.

Sometimes the faces along which the coal splits
are not smooth, but exhibit a thin layer of dull,
charred-looking substance, which is known a3
" mineral charcoal"

138 ON THE FORMATION OF COAL v

Occasionally one of tlie faces of a lump of coal
will present impressions, which are obviously
those of the stem, or leaves, of a plant ; but
though hard mineral masses of p}Tites, and even
fine mud, may occur here and there, neither sand
nor pebbles are met with.

When the coal burns, the chief ultimate
products of its combustion are carbonic acid,
water, and ammoniacal products, which escape
up the chimney ; and a greater or less amount
of residual earthy salts, which take the form of
ash. These products are, to a great extent, such
as would result from the burning of so much
wood.

These properties of coal may be made out
without any very refined appliances, but the
microscope reveals something more. Black and
opaque as ordinary coal is, slices of it become
transparent if they are cemented in Canada
balsam, and rubbed dovni very thin, in the
ordinary way of making thin sections of non-
transparent bodies. But as the thin slices, made
in this way, are very apt to crack and break
into fragments, it is better to employ marine
glue as the cementing material. By the use of
this substance, slices of considerable size and
of extreme thinness and transparency may be
obtained.^

^ My assistant in the Museum of Practical Geolo^, Mr.
Newton, invented this excellent method of obtaining thin slices
of coal.

V ON THE FORMATION OF COAL 139

Now let us suppose two such slices to be
prepared from our lump of coal — one parallel
with the bedding, the other perpendicular to it ;
and let us call the one the horizontal, and the
other the vertical, section. The horizontal section
will present more or less rounded yellow patches
and streaks, scattered irregularly tlirough the
dark brown, or blackish, ground substance ; while
the vertical section will exhibit mere elongated
bars and granules of the same yellow materials,
disposed in lines which correspond, roughly, with
the general direction of the bedding of the coal.

This is the microscopic structure of an ordinary-
piece of coal. But if a great series of coals, from
different locahties and seams, or even from
different parts of the same seam, be examined,
this structure will be found to vary in two
directions. In the anthracitic, or stone-coals, which
burn like coke, the yellow matter diminishes,
and the ground substance becomes more pre-
dominant, blacker, and more opaque, until it be-
comes impossible to grind a section thin enough
to be translucent ; while, on the other hand, in
such as the " Better-Bed " coal of the neigfhbour-
hood of Bradford, which burns with much flame,
the coal is of a far lighter colour, and transparent
sections are very easily obtained. In the browner
parts of this coal, sharp eyes will readily detect
multitudes of curious little coin-shaped bodies,
of a yellowish brown colour, embedded in the

140 ON THE FORMATION OF COAL v

dark brown ground substance. On the average,
these httle brown bodies may have a diameter of
about one-twentieth of an inch. They he with
their flat surfaces nearly parallel with the two
smooth faces of the block in which they are con-
tained ; and, on one side of each, there may be
discerned a figure, consisting of three straight
linear marks, which radiate from the centre of
the disk, but do not quite reach its circumference.
In the horizontal section these disks are often
converted into more or less complete rings ; while
in the vertical sections they appear hke thick
hoops, the sides of which have been pressed to-
gether. The disks are, therefore, flattened bags ;
and favourable sections show that the three-rayed
marking is the expression of three clefts, which
penetrate one wall of the bag.

The sides of the bags are sometimes closely
approximated ; but, when the bags are less
flattened, their cavities are, usually, filled wdth
numerous, irregularly rounded, hollow bodies,
having the same kind of wall as the large ones,
but not more than one seven-hundredth of an
inch in diameter.

In favourable specimens, again, almost the
whole ground substance appears to be made up
of similar bodies — more or less carbonized or
blackened — and, in these, there can be no doubt
that, with the exception of patches of mineral
charcoal, here and there, the whole mass of the

V ON THE FORMATION OF COAL 141

coal IS made up of an accumulation of the larger
and of the smaller sacs.

But, in one and the same slice, every transition
can be observed from this structure to that which
has been described as characteristic of ordinary
coal. The latter appears to rise out of the
former, by the breaking-up and increasing car-
bonization of the larger and the smaller sacs.
And, in the anthracitic coals, this process appears
to have gone to such a length, as to destroy the
original structure altogether, and to replace it by
a completely carbonized substance.

Thus coal may be said, speaking broadly, to be
composed of two constituents : firstly, mineral
charcoal ; and, secondly, coal proper. The nature
of the mineral charcoal has long since been
determined. Its structure shows it to consist of
the remains of the stems and leaves of plants,
reduced a little more than their carbon. Again,
some of the coal is made up of the crushed and
flattened bark, or outer coat, of the stems of plants,
the inner wood of which has completely decayed
away. But what I may term the "saccular
matter " of the coal, which, either in its primary
or in its degraded form, constitutes by far the
greater part of all the bituminous coals I have
examined, is certainly not mineral charcoal ; nor
is its structure that of any stem or leaf Hence
its real nature is, at first, by no means appai-ent,
and has been the subject of much discussion.

142 ON THE FORMATION OF COAL v

The first person who threw any light upon the
problem, as far as I have been able to discover,
was the well-known geologist, Professor Morris.
It is now thirty-four years since he carefully
described and figured the coin-shaped bodies, or
larger sacs, as I have called them, in a note
appended to the famous paper " On the Coal-
brookdale Coal-Field," published at that time,
by the present President of the Geological Society,
Mr. Prestwich. With much sagacity, Professor
Morris divined the real nature of these bodies.
and boldly affirmed them to be the spore-cases
of a plant allied to the living club-mosses.

But discovery sometimes makes a long halt ;
and it is only a few years since Mr. Carruthers
determined the plant (or rather one of the plants)
which produces these spore-cases, by finding the
discoidal sacs still adherent to the leaves of the
fossihzed cone which produced them. He gave
the name of Flemingites gracilis to the plant of
which the cones form a part. The branches
and stem of this plant are not yet certainly
known, but there is no sort of doubt that it was
closely allied to the Leioidcdcndron, the remains
of which abound in the coal formation. The
Zepidodendra were shrubs and trees which put
one more in mind of an Araucaria than of any
other familiar plant ; and the ends of the fruiting
branches were terminated by cones, or catkins,
somewhat like the bodies so named in a fir, or a

y ON THE FORMATION OF COAL .143

willow. TheS3 conical fruits, however, did not
produce seeds ; but the leaves of which they
were composed bore upon their surfaces sacs full
of spores or sporangia, such as those one sees on
the under surface of a bracken leaf Now, it is
these sporangia of the Lepidodendroid plant
Flemingites which were identified by Mr. Carruthers
with the free sporangia described by Professor
Morris, which are the same as the large sacs of
which I have spoken. And, more than this,
there is no doubt that the small sacs are the
spores, which were originally contained in the
sporangia.

The living club-mosses are, for the most part,
insignificant and creeping herbs, which, super-
ficially, very closely resemble true mosses, and
none of them reach more than two or three feet
in height. But, in their essential structure, they
very closely resemble the earliest Lepidodendroid
trees of the coal : their stems and leaves are
similar ; so are their cones ; and no less hke are
the sporangia and spores ; while even in their
size, the spores of the Lepidodendron and those of
the existing Lycopodium, or club-moss, very closely
approach one another.

Thus, the singular conclusion is forced upon us,
that the greater and the smaller sacs of the
"Better-Bed" and other coals, in which the
primitive structure is well preserved, are simply
the sporangia and spores of certain plants, many

144 ON THE FORMATION OF COAL v

of whicli were closely allied to tlie existing club-
mosses. And if, as I believe, it can be demon-
strated that ordinary coal is nothing but
" saccular " coal which has undergone a certain
amount of that alteration which, if continued,
would convert it into anthracite ; then, the con-
clusion is obvious, that the great mass of the
coal we burn is the result of the accumulation of
the spores and spore-cases of plants, other parts of
which have furnished the carbonized stems and
the mineral charcoal, or have left their impressions
on the surfaces of the layer.

Of the multitudinous speculations which, at
various times, have been entertained respecting
the origin and mode of formation of coal, several
appear to be negatived, and put out of court, by
the structural facts the significance of which I
have endeavoured to explain. These facts, for
example, do not permit us to suppose that coal is
an accumulation of peaty matter, as some have
held.

Again, the late Professor Quekett was one of
the first observers who gave a correct description
of what I have termed the " saccular " structure
of coal ; and, rightly perceiving that this structure
was something quite different from that of any
known plant, he imagined that it proceeded fi-om
some extinct vegetable organism which was
peculiarly abundant amongst the coal-forming
plants. But this explanation is at once shown to

V ON THE FORMATION OF COAL 145

be untenable when the smaller and the larger sacs
are proved to be spores or sporangia.

Some, once more, have imagined that coal was
of submarine origin; and though the notion is
amply and easily refuted by other considerations,
it may be worth while to remark, that it is
impossible to comprehend how a mass of light
and resinous spores should have reached the
bottom of the sea, or should have stopped in that
position if they had got there.

At the same time, it is proper to remark that I
do not presume to suggest that all coal must
needs have the same structure ; or that there may
not be coals in which the proportions of wood and
spores, or spore-cases, are very different from those
which I have examined. All I repeat is, that
none of the coals which have come under my
notice have enabled me to observe such a dif-
ference. But, according to Principal Dawson, who
has so sedulously examined the fossil remains
of plants in North America, it is otherwise
with the vast accumulations of coal in that
country.

"The true coal.," says Dr. Dawson, "consists principally of
the flattened bark of Sigillarioid and other trees, intermixed
with leaves of Ferns and Cordaites, and other herbaceous debris,
and with fragments of decayed wood, constituting ' mineral char-
coal,' all these materials having manifestly alike grown and
accumulated where we find them." ^

^ Acadian Geology, 2nd edition, p. 138.
196

146 ON THE FORMATION OF COAL y

When I had the pleasure of seeing Principal
Dawson in London last summer, I showed him
my sections of coal, and begged him to re-examine
some of the American coals on his return to
Canada, with an eye to the presence of spores and
sporangia, such as I was able to show him in our
English and Scotch coals. He has been good
enough to do so ; and in a letter dated September
26th, 1870, he informs me that —

" Indications of spore-cases are rare, except in certain coarse
shaly coals and portions of coals, and in the roofs of the seams.
The most marked case I have yet met with is the shaly coal
referred to as containing Sporavgitrs in my paper on the con-
ditions of accumulation of coal ('* Journal of the Geological
Society," vol. xxii. pp. 115, 139, and 165). The purer coals cer-
tainly consist principally of cubical tissues with some true woody
matter, and the spore-cases, &c., are chiefly in the coarse and
shaly layers. This is my old doctrine in my two papers in the
" Journal of the Geological Society," and I see nothing to modify
it. Your observations, however, make it probable that the
frequent dear s2Juts in the cannels are spore-cases. "

Dr. Dawson's results are the more remarkable,
as the numerous specimens of British coal, from
various localities, which I have examined, tell one
tale as to the predominance of the spore and
sporangium element in their composition ; and as
it is exactly in the finest and purest coals, such as
the "Better-Bed" coal of Lowmoor, that the
spores and sporangia obviously constitute almost
the entire mass of the deposit.

Coal, such as that which has been described, is

V ON THE FORMATION OF COAL 147

always found in sheets, or " seams," varying from
a fraction of an inch to many feet in thickness,
enclosed in the substance of the earth at very
various depths, between beds of rock of different
kinds. As a rule, every seam of coal rests upon a
thicker, or thinner, bed of clay, which is known
as " under-clay." These alternations of beds of
coal, clay, and rock may be repeated many times,
and are known as the " coal-measures " ; and in
some regions, as in South Wales and in Nova
Scotia, the coal-measures attain a thickness of
twelve or fourteen thousand feet, and enclose
eighty or a hundred seams of coal, each with its
under-clay, and separated from those above and
below by beds of sandstone and shale.

The position of the beds which constitute the
coal-measures is infinitely diverse. Sometimes
they are tilted up vertically, sometimes they are
horizontal, sometimes curved into gi^eat basins;
sometimes they come to the surface, sometimes
they are covered up by thousands of feet of rock.
But, whatever their present position, there is
abundant and conclusive evidence that every
under-clay was once a surface soil. Not only do
carbonized root-fibres frequently abound in these
under-clays ; but the stools of trees, the trunks of
which are broken off and confounded with the bed
of coal, have been repeatedly found passing into
radiating roots, still embedded in the under-clay.
On many parts of the coast of England, what are

148 ON THE FORMATION OF COAL v

commonly known as " submarine forests " are to
be seen at low water. They consist, for the most
part, of short stools of oak, beech, and fir-trees,
still fixed by their long roots in the bed of blue
clay in which they originally grew. If one of
these submarine forest beds should be gradually
depressed and covered up by new deposits, it
would present just the same characters as an
under-clay of the coal, if the Sigillaria and
LcioiclGdendron of the ancient world were sub-
stituted for the oak, or the beech, of our own
times.

In a tropical forest, at the present day, the
trunks of fallen trees, and the stools of such trees
as may have been broken by the violence of
storms, remain entire for but a short time. Con-
trary to what might be expected, the dense wood
of the tree decays, and suffers from the ravages of
insects, more swiftly than the bark. And the
traveller, setting his foot on a prostrate trunk,
finds that it is a mere shell, which breaks under
his weight, and lands his foot amidst the insects,
or the reptiles, which have sought food or refuge
within.

The trees of the coal forests present parallel
conditions. When the fallen trunks which have
entered into the composition of the bed of coal
are identifiable, they are mere double shells of
bark, flattened together in consequence of the
destruction of the woody core; and Sir Charles

V ON THE FORMATION OF COAL 149

Lyell and Principal Dawson discovered, in the
hollow stools of coal trees of Nova Scotia, the
remains of snails, millipedes, and salamander-like
creatures, embedded in a deposit of a different
character from that which surrounded the exterior
of the trees. Thus, in endeavouring to compre-
hend the formation of a seam of coal, we must try
to picture to ourselves a thick forest, formed for
the most part of trees like gigantic club-mosses,
mares'-tails, and tree-ferns, with here and there
some that had more resemblance to our existing
yews and fir-trees. We must suppose that, as the
seasons rolled by, the plants grew and developed
their spores and seeds; that they shed these in
enormous quantities, which accumulated on the
ground beneath ; and that, every now and then,
they added a dead frond or leaf; or, at longer
intervals, a rotten branch, or a dead trunk, to
the mass.

A certain proportion of the spores and seeds no
doubt fulfilled their obvious function, and, car-
ried by the wind to unoccupied regions, ex-
tended the limits of the forest ; many might be
washed away by rain into streams, and be lost ;
but a large portion must have remained, to
accumulate like beech-mast, or acorns, beneath
the trees of a modern forest.

But, in this case, it may be asked, why does
not our English coal consist of stems and leaves
to a much greater extent than it does ? What is

150 ON THE FORMATION OF COAL >

the reason of the predominance of the spores and
spore-cases in it ?

A ready answer to this question is afforded hy
the study of a h ving full-grown club-moss. Shake it
upon a piece of paper, and it emits a cloud of fine
dust, which falls over the paper, and is the well-
known Lycopodium powder. Now this powder
used to be, and I believe still is, employed for two
objects which seem, at first sight, to have no par-
ticular connection with one another. It is, or was,
employed in making lightning, and in making
pills. The coats of the spores contain so much
resinous matter, that a pinch of Lycopodium pow-
der, thrown through the flame of a candle, burns
with an instantaneous flash, which has long done
duty for lightning on the stage. And the same
character makes it a capital coating for pills ; for
the resinous powder prevents the drug from being
wetted by the saliva, and thus bars the nauseous
flavour from the sensitive papillae of the tongue.

But this resinous matter, which lies in the walls
of the spores and sporangia, is a substance not
easily altered by air and water, and hence tends
to preserve these bodies, just as the bituminized
cerecloth preserves an Egyptian mummy ; while,
on the other hand, the merely woody stem and
leaves tend to rot, as fast as the wood of the
mummy's coffin has rotted. Thus the mixed heap
of spores, leaves, and stems in the coal-forest would
be persistently searched by the long-continued

y ON THE FORMATION OF COAL 151

action of air and rain ; the leaves and stems would
gradually be reduced to little but their carbon, or,
in other words, to the condition of mineral char-
coal in which we find them ; while the spores and
sporangia remained as a comparatively unaltered
and compact residuum.

There is, indeed, tolerably clear evidence that
the coal must, under some circumstances, have
been converted into a substance hard enough to
be rolled into pebbles, while it yet lay at the
surface of the earth; for in some seams of coal,
the courses of rivulets, which must have been
living water, while the stratum in which their
remains are found was still at the surface, have
been observed to contain rolled pebbles of the
very coal through which the stream has cut its
way.

The structural facts are such as to leave no
alternative but to adopt the view of the origin
of such coal as I have described, which has just
been stated ; but, happily, the process is not
without analogy at the present day. I possess a
specimen of what is called "white coal" from
Australia. It is an inflammable material, burning
with a bright flame, and having much the con-
sistence and appearance of oat-cake, which, I am
informed, covers a considerable area. It consists,
almost entirely, of a compacted mass of spores and
spore-cases. But the fine particles of blown sand
which are scattered through it, show that it must

152 ON THE FORMATION OF COAL y

have accumulated, subaerially, upon the surface
of a soil covered by a forest of cryptogamous
plants, probably tree-ferns.

As regards this important point of the subaerial
region of coal, I am glad to find myself in entire
accordance with Principal Dawson, who bases his
conclusions upon other, but no less forcible,
considerations. In a passage, which is the con-
tinuation of that already cited, he writes : —

*''(3) The microscopical structure and chemical composition
of the beds of cannel coal and earthy bitumen, and of the more
highly bituminous and carbonaceous shale, show them to have
been of the nature of the fine vegetable mudwliich accumulates
in the ponds and shallow lakes of modern swamps. "When such
fine vegetable sediment is mixed, as is often the case, with clay,
it becomes similar to the bituminous limestone and calcareo-
bituminous shales of the coal-measures. (4) A few of the under-
clays, which support beds of coal, are of the nature of the vege-
table mud above referred to ; but the greater part are argillo-
arenaceous in composition, with little vegetable matter, and
bleaclied by the drainage from them of water containing the
products of vegetable decay. They are, in short, loamy or clay
soils, and must have been sufficiently above water to admit of
drainage. The absence of sul[>hurets, and the occurrence of
carbonate of iron in connection with them, prove that, when
they existed as soils, rain-water, and not sea-water, percolated
them. (5) The coal and the fossil forests present many evi-
dences of subaerial conditions. Most of the erect and prostrate
trees had become hollow shells of bark before they were finally
embedded, and their wood had broken into cubical pieces of
mineral charcoal. Land-snails and galley-worms (Xyl(>h!us)
crept into them, and they became dens, or traps, for reptiles.
Large quantities of mineral charcoal occur on the surface of all
the large beds of coal. None of these appearances could have
been produced by subaqueous action. (6) Though the roots of

V ON THE FORMATION OF COAL 153

the Sigillaria bear more resemblance to the rhizomes of certain
aquatic plants ; yet, structurally, they are absolutely identical
with the roots of Cycads, which the stems also resemble.
Further, the Sigillarice grew on the same soils which supported
Conifers, Lrpidodendra, Cordaites, and Ferns — plants which
could not have grown in water. Again, with the exception
perhaps of some Pinnularice and Aster ophyllites, there is a
remarkable absence from the coal measures of any form of
properly aquatic vegetation. (7) The occurrence of marine, or
brackish -water animals, in the roofs of coal-beds, or even in the
coal itself, affords no evidence of subaqueous accumulation,
since the same thing occurs in the case of modern submarine
forests. For these and otlier reasons, some of which are more
fully stated in the papers already referred to, while I admit that
the areas of coal accumulation were frequently submerged, I
must maintain that the true coal is a subaerial accumulation by
vegetable growth on soils, wet and swampy it is true, but not
submerged. "

I am almost disposed to doubt whether it is
necessary to make the concession of "wet and
swampy " ; otherwise, there is nothing that I know
of to be said against this excellent conspectus of
the reasons for believinoj in the subaerial orimn of
coal.

But the coal accumulated upon the area covered
by one of the great forests of the carboniferous
epoch would, in course of time, have been wasted
away by the small, bt fc constant, wear and tear of
rain and streams, had the land which supported it
remained at the same level, or been gradually
raised to a greater elevation. And, no doubt, aa
much coal as now exists has been destroyed, after
its formation, in this way. What are now known

154 ON THE FORMATION OF COAL v

as coal districts owe their importance to the fact
that they were areas of slow depression, during a
greater or less portion of the carboniferous epoch ;
and that, in virtue of this circumstance, Mother
Earth was enabled to cover up her vegetable
treasures, and preserve them from destruction.

Wherever a coal-field now exists, there must
formerly have been free access for a great river, or
for a shallow sea, bearing sediment in the shape of
sand and mud. When the coal-forest area became
slowly depressed, the waters must have spread
over it, and have deposited their burden upon the
surface of the bed of coal, in the form of layers,
which are now converted into shale, or sandstone.
Then followed a period of rest, in which the
superincumbent shallow waters became completely
filled up, and finally replaced, by fine mud, which
settled down into a new under-clay, and furnished
the soil for a fresh forest growth. This flourished,
and heaped up its spores and wood into coal, until
the stage of slow depression recommenced. And,
in some localities, as I have mentioned, the process
was repeated until the first of the alternating
beds had sunk to near three miles below its
oriofinal level at the surface of the earth.

In reflecting on the statement, thus briefly
made, of the main facts connected with the
orimn of the coal formed durinor the carboniferous
epoch, two or three considerations suggest them-
selves.

V ON THE FORMATION OF COAL 155

In the first place, tlie great phantom of geo-
logical time rises before the student of this, as of
all other, fragments of the history of our earth —
springing irrepressibly out of the facts, like the
Djin from the jar which the fishermen so incau-
tiously opened ; and like the Djin again, being
vaporous, shifting, and indefinable, but unmis-
takably gigantic. However modest the bases of
one's calculation may be, the minimum of time
assignable to the coal period remains something
stupendous.

Principal Dawson is the last person likely
to be guilty of exaggeration in this matter, and
it will be well to consider what he has to say
about it : —

" The rate of accumulation of coal was very slow. The
climate of the period, in the northern temperate zone, was of
such a character that the true conifers show rings of growth,
not larger, nor much less distinct, than those of many of their
modern congeners. The Sigillarim and Calamites were not, as
often supposed, composed wholly, or even principally, of lax
and soft tissues, or necessarily short-lived. The former had, it
is tme, a very thick inner bark ; but their dense woody axis,
tlieir thick and nearly imperishable outer bark, and their scanty
and rigid foliage, would indicate no very rapid growth or decay.
In the case of the Sigillarice, the variations in the leaf-scars in
different parts of the trunk, the intercalation of new ridges at
the surface representing that of new woody wedges in the axis,
the transverse marks left by the stages of upward growth, all
indicate that several years must have teen required for the
growth of stems of njoderate size. The enormous roots of these
trees, and the condition of the coal-swamps, must have exemj>ted
them from the danger of being overthrown by violence. They

156 ON THE FORMATION OF COAL v

probably fell in successive generations from natural decay ; and
making every allowance for other materials, we may safely assert
that every foot of thickness of pure bituminous coal implies the
qniet growth and fall of at least fifty generations of Sigillarice,
and therefore an undisturbed condition of forest growth enduring
through many centuries. Further, there is evidence that an
immense amount of loose parenchymatous tissue, and even of
wood, perished by decay, and we do not know to what extent
even the most durable tissues may have disappeared in this way ;
so that, in many coal-seams, we may have only a very small
part of the vegetable matter produced. "

Undoubtedly the force of these reflections is not
diminished when the bituminous coal, as in Britain,
consists of accumulated spores and spore-cases,
rather than of stems. But, suppose we adopt
Principal Dawson's assumption, that one foot of
coal represents fifty generations of coal plants ;
and, further, make the moderate supposition that
each generation of coal plants took ten years to
come to maturity — then, each foot-thickness of
coal represents five hundred years. The super-
imposed beds of coal in one coal-field may amount
to a thickness of fifty or sixty feet, and therefore
the coal alone, in that field, represents 500 X 50
= 25,000 years. But the actual coal is but an
insignificant portion of the total deposit, which, as
has been seen, may amount to between two and
three miles of vertical thickness. Suppose it be
12,000 feet — which is 240 times the thickness of
the actual coal — is there any reason why we should
believe it may not have taken 240 times as long to
form? I know of none. But, in this case, the

V ox THE FORMATION OF COAL 157

time which the coal-field represents would be
25,000 X 240 = 6,000,000 years. As affording a
definite chronology, of course such calculations as
these are of no value ; but they have much use in
fixing one's attention upon a possible minimum.
A man may be puzzled if he is asked how long
E-ome took a-building ; but he is proverbially safe
if he affirms it not to have been built in a day ;
and our geological calculations are all, at present,
pretty much on that footing.

A second consideration which the study of the
coal brings prominently before the mind of any one
who is familiar with palaeontology is, that the
coal Flora, viewed in relation to the enormous
period of time which it lasted, and to the still
vaster period which has elapsed since it flourished,
underwent little change while it endured, and in
its peculiar characters, differs strangely little from
that which at present exist.

The same species of plants are to be met with
throughout the whole thickness of a coal-field, and
the youngest are not sensibly different from the
oldest. But more than this. Notwithstanding
that the carboniferous period is separated from us
by more than the whole time represented by the
secondary and tertiary formations, the great t}^es
of vegetation were as distinct then as now. The
structure of the modern club-moss furnishes a
complete explanation of the fossil remains of the
Zepid:de7idra, and the fronds of some of the ancient

158 ON THE FORMATION OF COAL v

ferns are hard to distinguish from existing ones.
At the same time, it must be remembered, that
there is nowhere in the world, at present, any
forest which bears more than a rough analogy with
a coal-forest. The types may remain, but the
details of their form, their relative proportions,
their associates, are all altered. And the tree-fern
forest of Tasmania, or New Zealand, gives one only
a faint and remote image of the vegetation of
the ancient world.

Once more, an invariably-recurring lesson of
geological history, at whatever point its study is
taken up : the lesson of the almost infinite slow-
ness of the modification of living forms. The
lines of the pedigrees of living things break o^
almost before they begin to converge.

Finally, yet another curious consideration. Let
us suppose that one of the stupid, salamander-like
Labyrinthodonts, which pottered, with much belly
and little leg, like Falstaff in his old age, among
the coal-forests, could have had thinking power
enough in his small brain to reflect upon the
showers of spores which kept on falling through
years and centuries, while perhaps not one in ten
million fulfilled its apparent purpose, and repro-
duced the organism which gave it birth : surely
he might have been excused for moralizing upon
the thoughtless and wanton extravagance which
Nature displayed in her operations.

But we have the advantage over our shovel-

V ON THE FOEMATION OF COAL 159

headed predecessor — or possibly ancestor — and can
perceive that a certain vein of thrift runs through
this apparent prodigahty. Nature is never in a
hurry, and seems to have had always before her eyes
the adage, " Keep a thing long enough, and you
will find a use for it." She has kept her beds of
coal many millions of years without being able to
find much use for them ; she has sent them down
beneath the sea, and the sea-beasts could make
nothing of them ; she has raised them up into dry
land, and laid the black veins bare, and still, for
ages and ages, there was no living thing on the
face of the earth that could see any sort of value
in them ; and it was only the other day, so to
speak, that she turned a new creature out of her
v^rorkshop, who by degrees acquired sufiicient wits
to make a fire, and then to discover that the black
rock would burn.

I suppose that nineteen hundred years ago,
when Julius Caesar was good enough to deal with
Britain as we have dealt with New Zealand, the
primaeval Briton, blue with cold and woad, may
have known that the strange black stone, of
which he found lumps here and there in his
wanderings, would burn, and so help to warm his
body and cook his food. Saxon, Dane, and
Norman swarmed into the land. The English
people grew into a powerful nation, and Nature
still waited for a full return of the capital she

160 ON THE FORMATION OF COAL v

had invested in the ancient club-mosses. The
eighteenth century arrived, and with it James
Watt. The brain of that man was the spore out of
which was developed the modem steam-engine, and
all the prodigious trees and branches of modern in-
dustry which have grown out of this. But coal is
as much an essential condition of this growth and
development as carbonic acid is for that of a club-
moss. Wanting coal, we could not have smelted
the iron needed to make our engines, nor have
worked our engines when we had got them. But
take away the engines, and the great towns of
Yorkshire and Lancashire vanish like a dream.
Manufactures give place to agTiculture and
pasture, and not ten men can live where now ten
thousand are amply supported.

Thus, all this abundant wealth of money and of
vivid hfe is Nature's interest upon her investment
in club-mosses, and the like, so long ago. But
what becomes of the coal which is burnt in }aeld-
inof this interest ? Heat comes out of it, lio^ht
comes out of it ; and if we could gather together
all that goes up the chimney, and all that remains
in the grate of a thoroughly-burnt coal-fire, we
should find ourselves in possession of a quantity
of carbonic acid, water, ammonia, and mineral
matters, exactly equal in weight to the coal. But
these are the very matters with which Nature
supplied the club-mosses which made the coal

V ON THE FORMATION OF COAL 161

She is paid back principal and interest at the
same time ; and she straightway invests the car-
bonic acid, the water, and the ammonia in new
forms of life, feeding with them the plants that
now live. Thrifty Nature ! Surely no prodigal,
but most notable of housekeepers !

19":

VI

ON THE BORDER TERRITORY BETWEEN
THE ANIMAL AND THE VEGETABLE
KINGDOMS

[1876]

In the whole history of science there is nothing
more remarkable than the rapidity of the growth
of biological knowledge within the last half-
century, and the extent of the modification which
has thereby been effected in some of the funda-
mental conceptions of the naturalist.

In the second edition of the " Regno Animal,"
published in 1828, Cuvier devotes a special section
to the " Division of Organised Beings into Animals
and Vegetables," in w^hich the question is treated
with that comprehensiveness of knowledge and
clear critical judgTiient which characterise his
writings, and justify us in regarding them as re-
presentative expressions of the most extensive,
if not the profoundest, knowledge of his time.
He tells us that living beings have been sub-

VI ANIMALS AND PLANTS 163

divided from the earliest times into animated
heings, which possess sense and motion, and inani-
mated beings, which are devoid of these functions
and simply vegetate.

Although the roots of plants direct themselves
towards moisture, and their leaves towards air and
light, — although the parts of some plants exhibit
oscillating movements without any perceptible
cause, and the leaves of others retract when
touched, — yet none of these movements justify the
ascription to plants of perception or of will. From
the mobility of animals, Cuvier, with his charac-
teristic partiality for teleological reasoning, de-
duces the necessity of the existence in them of an
alimentary cavity, or reservoir of food, whence
their nutrition may be drawn by the vessels, which
are a sort of internal roots ; and, in the presence
of this alimentary cavity, he naturally sees the
primary and the most important distinction be-
tween animals and plants.

Followinof out his teleoloofical aro^ument, Cuvier
remarks that the organisation of this cavity and
its appurtenances must needs vary according to
the nature of the aliment, and the operations
which it has to undergo, before it can be converted
into substances fitted for absorption ; while the
atmosphere and the earth supply plants with
juices ready prepared, and which can be absorbed
immediately. As the animal body required to be
independent of heat and of the atmosphere, there

164 ANIMALS AND PLANTS VI

were no means by which the motion of its fluids
could be produced by internal causes. Hence
arose the second great distinctive character of
animals, or the circulatory system, which is less
important than the digestive, since it was un-
necessary, and therefore is absent, in the more
simple animals.

Animals further needed muscles for loco-
motion and nerves for sensibility. Hence, says
Cuvier, it was necessary that the chemical compo-
sition of the animal body should be more compli-
cated than that of the plant ; and it is so, inasmuch
as an additional substance, nitrogen, enters into it
as an essential element ; while, in plants, nitrogen
is only accidentally joined with the three other
fundamental constituents of organic beings —
carbon, hydrogen, and oxygen. Indeed, he after-
wards affirms that nitrogen is peculiar to animals ;
and herein he places the third distinction between
the animal and the plant. The soil and the
atmosphere supply plants with water, composed of
hydrogen and oxygen ; air, consisting of nitrogen
and oxygen ; and carbonic acid, containing carbon
and oxygen. They retain the hydrogen and the
carbon, exhale the superfluous oxygen, and absorb
little or no nitrogen. The essential character of
vegetable life is the exhalation of oxygen, which
is effected through the agency of light. Animals,
on the contrary, derive their nourishment either
directly or indirectly from plants. They get rid of

VI ANIMALS AND PLANTS 165

the superfluous liydrogen and carbon, and accumu-
late nitrogen. The relations of plants and
animals to the atmosphere are therefore inverse.
The plant withdraws water and carbonic acid from
the atmosphere, the animal contributes both to it.
Respiration — that is, the absorption of oxygen and
the exhalation of carbonic acid — is the specially
animal function of animals, and constitutes their
fourth distinctive character.

Thus wi'ote Cuvier in 1828. But, in the fourth
and fifth decades of this century, the greatest and
most rapid revolution which biological science has
ever undergone was effected by the application of
the modern microscope to the investigation of
organic structure; by the introduction of exact
and easily manageable methods of conducting the
chemical analysis of organic compounds; and
finally, by the emplo}Tiient of instruments of pre-
cision for the measurement of the physical forces
which are at work in the living economy.

That the semi-fluid contents (which we now
term protoplasm) of the cells of certain plants,
such as the Charm ^ are in constant and regular
motion, was made out by Bonaventura Corti a
century ago ; but the fact, important as it was,
fell into obhvion, and had to be rediscovered by
Treviranus in 1807. Robert Brown noted the
more complex motions of the protoplasm in the
cells of Tradescantia in 1831 ; and now such move*
ments of the living substance of plants are well

166 ANIMALS AND PLANTS vi

known to be some of the most widely-prevalent
phenomena of vegetable life.

Agardh, and other of the botanists of Cuvier's
generation, who occupied themselves with the
lower plants, had observed that, under particular
circumstances, the contents of the cells of certain
water-weeds were set free, and moved about with
considerable velocity, and with all the appearances
of spontaneity, as locomotive bodies, which, from
their similarity to animals of simple organisation,
were called " zoospores." Even as late as 1845,
however, a botanist of Schleiden's eminence dealt
very sceptically with these statements; and his
scepticism was the more justified, since Ehren-
berg, in his elaborate and comprehensive work on
the Infusoria, had declared the greater number of
what are now recognised as locomotive plants to
be animals.

At the present day, innumerable plants and free
plant cells are known to pass the whole or part of
their lives in an actively locomotive condition, in
no wise distinguishable from that of one of the
simpler animals ; and, while in this condition, their
movements are, to all appearance, as spontaneous
— as much the product of volition — as those of
such animals.

Hence the teleological argument for Cuvier's
first diagnostic character — the presence in animals
of an alimentary cavity, or internal pocket, in
which they can carry about their nutriment — has

n ANIMALS AND PLANTS 167

broken down, so far, at least, as his mode of stating
it goes. And, with the advance of microscopic
anatomy, the universaHty of the fact itself among
animals has ceased to be predicable. Many
animals of even complex structure, which live
parasitically within others, are wholly devoid of an
alimentary cavity. Their food is provided for
them, not only ready cooked, but ready digested,
and the alimentary canal, become superfluous,
has disappeared. Again, the males of most
Rotifers have no digestive apparatus ; as a German
naturalist has remarked, they devote themselves
entirely to the " Minnedienst," and are to be
reckoned among the few realisations of the
Byronic ideal of a lover. Finally, amidst the
lowest forms of animal life, the speck of gelatinous
protoplasm, which constitutes the whole body, has
no permanent digestive cavity or mouth, but takes
in its food anywhere ; and digests, so to speak, all
over its body.

But although Cuvier's leading diagnosis of the
animal from the plant will not stand a strict test,
it remains one of the most constant of the dis-
tinctive characters of animals. And, if we sub-
stitute for the possession of an alimentary cavity,
the power of taking solid nutriment into the body
and there digesting it, the definition so changed
will cover all animals, except certain parasites,
and the few and exceptional cases of non-parasitic
animals which do not feed at all. On the other

168 ANIMALS AND PLANTS vi

hand, the definition thus amended will exclude all
ordinary vegetable organisms.

Cuvier himself practically gives up his second
distinctive mark when he admits that it is want-
ing in the simpler animals.

The third distinction is based on a completely
erroneous conception of the chemical differences
and resemblances between the constituents of
animal and vegetable organisms, for which Cuvier
is not responsible, as it was current among con-
temporary chemists. It is now established that
nitrogen is as essential a constituent of vegetable
as of animal hving matter ; and that the latter is,
chemically speaking, just as complicated as the
former. Starchy substances, cellulose and sugar,
once supposed to be exclusively confined to plants,
are now known to be regular and normal products
of animals. Amylaceous and saccharine substances
are largely manufactured, even by the highest
animals ; cellulose is widespread as a constituent
of the skeletons of the lower animals ; and it is
probable that amyloid substances are universally
present in the animal organism, though not in the
precise form of starch.

Moreover, although it remains true that there
is an inverse relation between the green plant in
sunshine and the animal, in so far as, under these
circumstances, the green plant decomposes car-
bonic acid and exhales oxygen, while the animal
absorbs oxygen and exhales carbonic acid ; yet

VI ANIMALS AND PLANTS 169

the exact researches of the modern chemical in-
vestigators of the physiological processes of plants
have clearly demonstrated the fallacy of attempt-
ing to draw any general distinction between
animals and vegetables on this ground. In fact,
the difference vanishes with the sunshine, even in
the case of the gi^een plant ; which, in the dark,
absorbs oxygen and gives out carbonic acid like
any animal.^ On the other hand, those plants,
such as the fungi, which contain no chlorophyll
and are not green, are always, so far as respiration
is concerned, in the exact position of animals.
They absorb oxygen and give out carbonic acid.

Thus, by the progress of knowledge, Cuvier's
fourth distinction between the animal and the
plant has been as completely invah dated as the
third and second ; and even the first can be re-
tained only in a modified form and subject to
exceptions.

But has the advance of biology simply tended
to break down old distinctions, without establish-
ing new ones ?

With a qualification, to be considered presently,
the answer to this question is undoubtedly in the
affirmative. The famous researches of Schwann

1 There is every reason to believe that living plants, like living
animals, always respire, and. in respiring, absorb oxygen and
give off carbonic acid ; but, that in green plants exposed
to daylight or to the electric light, the quantity of oxygen
evolved in consequence of the decomposition of carbonic acid
by a special aiq)aratus which greeii plants possess exceeds that
absorbed in the concurrent respiratory process.

170 ANIMALS AND PLANTS VI

and Sclileiden in 1837 and the following years,
founded the modern science of histology, or that
branch of anatomy which deals with the ultimate
visible structure of organisms, as revealed by the
microscope ; and, from that day to this, the rapid
improvement of methods of investigation, and the
energy of a host of accurate observers, have given
greater and greater breadth and firmness to
Schwann's great generalisation, that a fundamental
unity of structure obtains in animals and plants ;
and that, however diverse may be the fabrics, or
tissues, of which their bodies are composed, all
these varied structures result from the meta-
morphosis of morphological units (termed cells, in
a more general sense than that in which the word
" cells " was at first employed), which are not only
similar in animals and in plants respectively, but
present a close resemblance, when those of animals
and those of plants are compared together.

The contractility which is the fundamental con-
dition of locomotion, has not only been discovered
to exist far more widely among plants than was
formerly imagined ; but, in plants, the act of con-
traction has been found to be accompanied, as Dr.
Burdon Sanderson's interesting investigations have
sho^vn, by a disturbance of the electrical state of
the contractile substance, comparable to that
which was found by Du Bois Bepnond to be a
concomitant of the activity of ordinary muscle in
animals.

TI ANIMALS AND PLANTS 171

Again, I know of no test by which the reaction
of the leaves of the Sundew and of other plants to
stimuli, so fully and carefully studied by Mr.
Darwin, can be distinguished from those acts of
contraction following upon stimuli, which ai'e
called " reflex " in animals.

On each lobe of the bilobed leaf of Venus's fly-
trap {Dioncea muscijpula) are three delicate filaments
which stand out at right angle from the surface of
the leaf Touch one of them with the end of a
fine human hair and the lobes of the leaf instantly
close together ^ in virtue of an act of contraction
of part of their substance, just as the body of
a snail contracts into its shell when one of its
" horns " is irritated.

The reflex action of the snail is the result of the
presence of a nervous system in the animal. A
molecular change takes place in the nerve of the
tentacle, is propagated to the muscles by which the
body is retracted, and causing them to contract,
the act of retraction is brought about. Of course
the similarity of the acts does not necessarily in-
volve the conclusion that the mechanism by
which they are effected is the same; but it
suggests a suspicion of their identity which needs
careful testing.

The results of recent inquiries into the structure
of the nervous system of animals converge towards
the conclusion that the nerve fibres, which we
^ Darwin, Insectivoroibs Plants, p. 289.

172 ANIMALS AND PLANTS vi

have hitherto regarded as ultimate elements of
nervous tissue, are not such, but are simply the
visible aggregations of vastly more attenuated
filaments, the diameter of which dwindles down to
the limits of our present microscopic vision, greatly
as these have been extended by modern improve-
ments of the microscope ; and that a nerve is, in
its essence, nothing but a linear tract of specially
modified protoplasm between two points of an
organism — one of which is able to affect the other
by means of the communication so established.
Hence, it is conceivable that even the simplest
living being may possess a nervous system. And
the question whether plants are provided with a
nervous system or not, thus acquires a new aspect,
and presents the histologist and physiologist with
a problem of extreme difficulty, which must be
attacked jfrom a new point of view and by the aid
of methods which have yet to be invented.

Thus it must be admitted that plants may be
contractile and locomotive ; that, while locomotive,
their movements may have as much appearance of
spontaneity as those of the lowest animals ; and
that many exhibit actions, comparable to those
which are brought about by the agency of a
nervous system in animals. And it must be
allowed to be possible that further research may
reveal the existence of something comparable to a
nervous system in plants. So that I know not
where we can hope to find any absolute distinction

VI ANIMALS AND PLANTS 173

between animals and plants, unless we return to
their mode of nutrition, and inquire whether
certain differences of a more occult character than
those imagined to exist by Cuvier, and which cer-
tainly hold good for the vast majority of animals
and plants, are of universal application.

A bean may be supplied with water in which
salts of ammonia and certain other mineral salts
are dissolved in due proportion ; with atmospheric
air containing its ordinary minute dose of carbonic
acid ; and with nothing else but sunlight and heat.
Under these circumstances, unnatural as they are,
with proper management, the bean will thrust
forth its radicle and its plumule ; the former will
grow down into roots, the latter grow up into
the stem and leaves of a vigorous bean-plant ; and
this plant will, in due time, flower and produce its
crop of beans, just as if it were grown in the
garden or in the field.

The weight of the nitrogenous protein com-
pounds, of the oily, starchy, saccharine and woody
substances contained in the full-grown plant and its
seeds, will be vastly greater than the weight of the
same substances contained in the bean from which it
sprang. But nothing has been suppHed to the bean
save water, carbonic acid, ammonia, potash, lime,
iron, and the like, in combination with phosphoric,
sulphuric, and other acids. Neither protein, nor
fat, nor starch, nor sugar, nor any substance in the
slightest degree resembling them, has formed part

174 ANIMALS AND PLANTS VI

of the food of the bean. But the weights of the
carbon, hydrogen, oxygen, nitrogen, phosphorus,
sulphur, and other elementary bodies contained in
the bean-plant, and in the seeds which it produces,
are exactly equivalent to the weights of the same
elements which have disappeared from the
materials supplied to the bean during its growth.
Whence it follows that the bean has taken in only
the raw materials of its fabric, and has manu-
factured them into bean-stuffs.

The bean has been able to perform this great
chemical feat by the help of its green colouring
matter, or chlorophyll; for it is only the green
parts of the plant which, under the influence of
sunlight, have the marvellous power of decom-
posing carbonic acid, setting free the oxygen and
laying hold of the carbon which it contains. In
fact, the bean obtains two of the absolutely in-
dispensable elements of its substance from two
distinct sources ; the watery solution, in which its
roots are plunged, contains nitrogen but no carbon ;
the air, to which the leaves are exposed, contains
carbon, but its nitrogen is in the state of a free
gas, in which condition the bean can make no use
of it ; ^ and the chlorophyll ^ is the apparatus by

1 I purposely assume that the air with which the bean is
supplied in the case stated contains no aninioniacal salts.

- Tlie recent researches of Pringsheim have raised a host of
questions as to the exact share taken hy chlorophyll in the
chemical operations which are eftected by the green parts of
plants. It may be that the chlorophyll is only a constant con-
comitant of the actual deoxidising apparatus.

VI

ANIMALS AND PLANTS 175

which the carbon is extracted from the atmo-
spheric carbonic acid — the leaves being the chief
laboratories in which this operation is effected.

The great majority of conspicuous plants are, as
everybody knows, green ; and this arises from the
abundance of their chlorophyll. The few which
contain no chlorophyll and are colourless, are un-
able to extract the carbon which they require from
atmospheric carbonic acid, and lead a parasitic
existence upon other plants ; but it by no means
follows, often as the statement has been repeated,
that the manufacturing power of plants depends
on their chlorophyll, and its interaction with the
rays of the sun. On the contrary, it is easily
demonstrated, as Pasteur first proved, that the
lowest fungi, devoid of chlorophyll, or of any sub-
stitute for it, as they are, nevertheless possess the
characteristic manufacturing powers of plants in a
very high degree. Only it is necessary that they
should be supplied with a different kind of raw
material ; as they cannot extract carbon from car-
bonic acid, they must be furnished with something
else that contains carbon. Tartaric acid is such a
substance ; and if a single spore of the commonest
and most troublesome of moulds — Penicillium — be
sown in a saucerful of water, in which tartrate of
ammonia, with a small percentage of phosphates
and sulphates is contained, and kept warm, whether
in the dark or exposed to light, it will, in a
short time, give rise to a thick crust of mould,

176 ANIMALS AND PLANTS vi

which contains many million times the weight of
the original spore, in protein compounds and
cellulose. Thus we have a very wide basis of fact
for the generalisation that plants are essentially
characterised by their manufacturing capacity — by
their power of working up mere mineral matters
into complex organic compounds.

Contrariwise, there is a no less wide foundation
for the generalisation that animals, as Cuvier puts
it, depend directly or indirectly upon plants for
the materials of their bodies ; that is, either they
are herbivorous, or they eat other animals which
are herbivorous.

But for what constituents of their bodies are
animals thus dependent upon plants ? Certainly
not for their horny matter ; nor for chondrin, the
proximate chemical element of cartilage ; nor for
gelatine ; nor for syntonin, the constituent of
muscle; nor for their nervous or biliary sub-
stances; nor for their amyloid matters; nor,
necessarily, for their fats.

It can be experimentally demonstrated that
animals can make these for themselves. But that
which they cannot make, but must, in all known
cases, obtain directly or indirectly from plants, is
the peculiar nitrogenous matter, protein. Thus
the plant is the ideal proUtaire of the living
world, the worker who produces ; the animal, the
ideal aristocrat, who mostly occupies himself in
consuming, after the manner of that noble repre-

VI ANIMALS AND PLANTS 177

sentative of the line of Zahdarm, whose epitaph is
written in " Sartor Resartus."

Here is our last hope of finding a sharp line of
demarcation between plants and animals; for, as
I have already hinted, there is a border territory
between the two kingdoms, a sort of no-man's-
land, the inhabitants of which certainly cannot
be discriminated and brought to their proper
allegiance in any other way.

Some months ago. Professor Tyndall asked me
to examine a drop of infusion of hay, placed
under an excellent and powerful microscope, and
to tell him what I thought some organisms
visible in it were. I looked and observed, in the
first place, multitudes of Bacteria moving about
with their ordinary intermittent spasmodic
wriggles. As to the vegetable nature of these
there is now no doubt. Not only does the close
resemblance of the Bacteria to unquestionable
plants, such as the Oscillatorice and the lower forms
of Ficngi, justify this conclusion, but the manu-
facturing test settles the question at once. It
is only needful to add a minute drop of fluid
containing Bacteria, to water in which tartrate,
phosphate, and sulphate of ammonia are dissolved ;
and, in a very short space of time, the clear fluid
becomes milky by reason of their prodigious
multiplication, which, of course, implies the
manufacture of living Bacterium-stufif out of
these merely saline matters,

198

178 ANIMALS AND PLANTS vi

But other active organisms, very much larger
than the Bacteria^ attaining in fact the com-
paratively gigantic dimensions of -g-oVo ^^ ^^
inch or more, incessantly crossed the field of view.
Each of these had a body shaped like a pear, the
small end being slightly incurved and produced
into a long curved filament, or cilmm, of extreme
tenuity. Behind this, from the concave side of
the incurvation, proceeded another long cilium,
so delicate as to be discernible only by the use of
the highest powers and careful management of
the light. In the centre of the pear-shaped
body a clear round space could occasionally be
discerned, but not always; and careful watching
showed that this clear vacuity appeared gradually,
and then shut up and disappeared suddenly, at
regular intervals. Such a structure is of common
occurrence among the lowest plants and animals,
and is known as a contractile vacuole.

The little creature thus described sometimes
propelled itself with great activity, with a curious
rolling motion, by the lashing of the front cilium,
while the second cilium trailed behind; some-
times it anchored itself by the hinder cilium and
was spun round by the working of the other, its
motions resembling those of an anchor buoy in a
heavy sea. Sometimes, when two were in full
career towards one another, each would appear
dexterously to get out of the other's way ; some-
times a crowd would assemble and jostle one

VI ANIMALS AND PLANTS 179

anotlier, with as much semblance of individual
effort as a spectator on the Grands Mulets might
observe with a telescope among the specks repre-
senting men in the valley of Chamounix.

The spectacle, though always surprising, was
not new to me. So my reply to the question put
to me was, that these organisms were what
biologists call Monads, and though they might be
animals, it was also possible that they might,
like the Bacteria, be plants. My friend received
my verdict with an expression which showed a
sad want of respect for authority. He would as
soon believe that a sheep was a plant. Naturally
piqued by this want of faith, I have thought a
good deal over the matter ; and, as I still rest in
the lame conclusion I originally expressed, and
must even now confess that I cannot certainly
say whether this creature is an animal or a plant,
I think it may be well to state the grounds of my
hesitation at length. But, in the first place, in
order that I may conveniently distinguish this
" Monad " from the multitude of other things
which go by the same designation, I must give it
a name of its own. I think (though, for reasons
which need not be stated at present, I am not
quite sure) that it is identical with the species
Mooias lens, as defined by the eminent French
microscopist Dujardin, though his magnifying
power was probably insufficient to enable him
to see that it is curiously like a much larger

180 ANIMALS AND PLANTS vi

form of monad whicli lie has named Hcteromita.
I shall, therefore, call it not Monas, but Hetcrcmita
lens.

I have been unable to devote to my Heteromita
the prolonged study needful to work out its whole
history, which would involve weeks, or it may be
months, of unremitting attention. But I the less
regret this circumstance, as some remarkable
observations recently published by Messrs. Dal-
linger and Drysdale ^ on certain Monads, relate,
in part, to a form so similar to my Hdcrcmita
lens, that the history of the one may be used to
illustrate that of the other. These most patient
and painstaking observers, who employed the
highest attainable powers "of the microscope and,
relieving one another, kept watch day and night
over the same individual monads, have been
enabled to trace out the whole history of their
Heteromita ; which they found in infusions of the
heads of fishes of the Cod tribe.

Of the four monads described and figured by
these investigators, one, as I have said, very
closely resembles Heteromita lens in every
particular, except that it has a separately dis-
tinguishable central particle or " nucleus," which
is not certainly to be made out in Heteromita
lens ; and that nothing is said by Messrs. DaUinger

^ *' Researclies in the Life history of a Cercomonad : a Lesson
In Biogenesis"; and "Furtlier Ecsearches in the Life-histoi7
of the Monads." — Monthly Micruscopkal Journal, 1S73.

VI ANIMALS AND PLANTS 181

and Diysdale of the existence of a contractile
vacuole in this monad, though they describe it in
another.

Their Heteromita, however, multiplied rapidly
by fission. Sometimes a transverse constriction
appeared ; the hinder half developed a new cilium,
and the hinder cilium gradually split from its
base to its free end, until it was divided into
two ; a process which, considering the fact that
this fine filament cannot be much more than
To 0^0 0 0 ^f ^^ 'vcioh. in diameter, is wonderful
enough. The constriction of the body extended
inwards until the two portions were united by a
narrow isthmus ; finally, they separated and each
swam away by itself, a complete Heteromita,
provided with its two cilia. Sometimes the con-
striction took a longitudinal direction, with the
same ultimate result. In each case the process
occupied not more than six or seven minutes.
At this rate, a single Heteromita would give rise
to a thousand like itself in the course of an hour,
to about a million in two hours, and to a number
greater than the generally assumed number of
human beings now living in the world in three
hours ; or, if we give each Heteromita an hour's
enjoyment of individual existence, the same result
will be obtained in about a day. The apparent
suddenness of the appearance of multitudes of
such organisms as these, in any nutritive fluid to
which one obtains access, is thus easily explained.

182 ANIMALS AND PLANTS

VI

' During these processes of multiplication by-
fission, the Heteromita, remains active ; but some-
times another mode of fission occurs. The body
becomes rounded and quiescent, or nearly so ; and,
while in this resting state, divides into two
portions, each of which is rapidly converted into
an active Hctercmita.

A still more remarkable phenomenon is that
kind of multiplication which is preceded by the
union of two monads, by a process which is termed
conjugation. Two active Hetcromitce become applied
to one another, and then slowly and gradually coa-
lesce into one body. The two nuclei run into one ;
and the mass resulting from the conjugation of the
two Heteromitm, thus fused together, has a tri-
angular form. The two pairs of cilia are to be
seen, for some time, at two of the angles, which
answer to the small ends of the conjoined monads ;
but they ultimately vanish, and the twin organ-
ism, in which all visible traces of organisation
have disappeared, falls into a state of rest.
Sudden wave-like movements of its substance
next occur; and, in a short time, the apices of
the triangular mass burst, and give exit to a
dense yellowish, glairy fluid, filled with minute
granules. This process, which, it will be observed,
involves the actual confluence and mixture of the
substance of two distinct organisms, is effected in
the space of about two hours.

The authors whom I quote say that they

VI

ANIMALS AND PLANTS 183

" cannot express " tlie excessive minuteness of ttie
granules in question, and they estimate their
diameter at less than o-owo "o ^f ^^ inch. Under
the highest powers of the microscope, at present
apphcable, such specks are hardly discernible.
Nevertheless, particles of this size are massive
when compared to physical molecules; whence
there is no reason to doubt that each, small as it
is, may have a molecular structure sufficiently
complex to give rise to the phenomena of life.
And, as a matter of fact, by patient watching of
the place at which these infinitesimal living
particles were discharged, our observers assured
themselves of their growth and development into
new monads. In about four hours from their
being set free, they had attained a sixth of the
length of the parent, with the characteristic ciHa,
though at first they were quite motionless ; and,
in four hours more, they had attained the dimen-
sions and exhibited all the activity of the adult.
These inconceivably minute particles are therefore
the germs of the Hetercmita ; and from the
dimensions of these germs it is easily shown that
the body formed by conjugation may, at a low
estimate, have given exit to thirty thousand of
them ; a result of a matrimonial process whereby
the contracting parties, without a metaphor, " be-
come one flesh," enough to make a Malthusian
despair of the future of the Universe.

I am not aware that the investigators firora

184 ANIMALS AND PLANTS vi

whom I have borrowed this history have en-
deavoured to ascertain whether their monads take
sohd nutriment or not ; so that though they help
•QS very much to fill up the blanks in the history
of my Heteromita, their observations throw no
light on the problem we are trying to solve — Is it
an animal or is it a plant ?

Undoubtedly it is possible to bring forward
very strong arguments in favour of regarding
Heteromita as a plant.

For example, there is a Fungus, an obscure and
almost microscopic mould, termed Peroncspcra
infestans. Like many other Fungi, the Perono-
sporce are parasitic upon other plants; and this
particular Peronospora happens to have attained
much notoriety and pohtical importance, in a way
not without a parallel in the career of notorious
politicians, namely, by reason of the frightful
mischief it has done to mankind. For it is this
Fungus which is the cause of the potato disease ;
and, therefore, Peronospora infestans (doubtless of
exclusively Saxon origin, though not accurately
known no be so) brought about the Irish famine.
The plants afflicted with the malady are found to
be infested by a mould, consisting of fine tubular
filaments, termed hyphce, which burrow through
the substance of the potato plant, and appropriate
to themselves the subs^n^i^e of their host; while,
at the same time, directly or indirectly, they set
up chemical changes by which even its woody

VI ANIMALS AND PLANTS 185

framework becomes blackened, sodden, and
withered.

In structure, however, the Peronosiwra is as
much a mould as the common Penicillium ; and
just as the Penicillium multiplies by the breaking
up of its hj^hge into separate rounded bodies, the
spores; so, in the Peronospora, certain of the
hyphse grow out into the air through the interstices
of the superficial cells of the potato plant, and
develop spores. Each of these hj^phse usually
gives off several branches. The ends of the
branches dilate and become closed sacs, which
eventually drop off as spores. The spores falling
on some part of the same potato plant, or carried
by the wind to another, may at once germinate,
throAving out tubular prolongations which become
h}^h8e, and burrow into the substance of the
plant attacked. But, more commonly, the con-
tents of the spore divide into six or eight separate
portions. The coat of the spore gives way, and
each portion then emerges as an independent
organism, which has the shape of a bean, rather
narrower at one end than the other, convex on one
side, and depressed or concave on the opposite.
From the depression, two long and delicate ciha
proceed, one shorter than the other, and directed
forwards. Close to the origin of these cilia, in the
substance of the body, is a regularly pulsating,
contractile vacuole. The shorter cihum vibrates
actively, and effects the locomotion of the organ-

186 ANIMALS AND PLANTS vi

ism, while the other trails behind; the whole
body rolling on its axis with its pointed end
forwards.

The eminent botanist, De Bary, who was not
thinking of our problem, tells us, in describing the
movements of these "Zoospores," that, as they
swim about, " Foreign bodies are carefully avoided,
and the whole movement has a deceptive likeness
to the voluntary changes of place which are
observed in microscopic animals."

After swarming about in this way in the
moisture on the surface of a leaf or stem (which,
film though it may be, is an ocean to such a fish)
for half an hour, more or less, the movement of
the zoospore becomes slower, and is limited to a
slow turning upon its axis, without change of
place. It then becomes quite quiet, the ciha dis-
appear, it assumes a spherical form, and surrounds
itself with a distinct, though dehcate, membranous
coat. A protuberance then grows out from one
side of the sphere, and rapidly increasing in length,
assumes the character of a hy]Dha. The latter
penetrates into the substance of the potato plant,
either by entering a stomate, or by boring through
the wall of an epidermic cell, and ramifies, as a
mycelium, in the substance of the plant, destroying
the tissues with which it comes in contact. As
these processes of multiplication take place very
rapidly, millions of spores are soon set free from a
single infested plant ; and, from their minuteness,

VI

ANIMALS AND PLANTS 187

they are readily transported by the gentlest
breeze. Since, again, the zoospores set free from
each spore, in virtue of their powers of locomotion,
swiftly disperse themselves over the surface, it is
no wonder that the infection, once started, soon
spreads from field to field, and extends its ravages
over a whole country.

However, it does not enter into my present
plan to treat of the potato disease, instructively as
its history bears upon that of other epidemics ;
and I have selected the case of the Peroncsi^orcb
simply because it affords an example of an organ-
ism, which, in one stage of its existence, is truly a
" Monad," indistinguishable by any important
character from our Hderomita, and extraordinarily
like it in some respects. And yet this " Monad "
can be traced, step by step, through the series of
metamorphoses which I have described, until it
assumes the features of an organism, which is as
much a plant as is an oak or an elm.

Moreover, it would be possible to pursue the
analogy farther. Under certain circumstances, a
process of conjugation takes place in the Ferono-
spora. Two separate portions of its protoplasm
become fused together, surround themselves with
a thick coat, and give rise to a sort of vegetable
Qgg called an oospore. After a period of rest, the
contents of the oospore break up into a number of
zoospores like those already described, each of
which, after a period of activity, germinates in the

188 ANIMALS AND PLANTS VI

ordinary way. This process obviously corresponds
with the conjugation and subsequent setting free
of germs in the Heteromita.

But it may be said that the Peronospora is,
after all, a questionable sort of plant ; that it seems
to be wanting in the manufacturing power, selected
as the main distinctive character of vegetable
life ; or, at any rate, that there is no proof that
it does not get its protein matter ready made
from the potato plant.

Let us, therefore, take a case which is not open
to these objections.

There are some small plants known to botanists
as members of the genus Coleochccte, which, with-
out being truly parasitic, grow upon certain
water-weeds, as lichens grow upon trees. The
little plant has the form of an elegant green star,
the branching arms of which are divided into
cells. Its greenness is due to its chlorophyll, and
it undoubtedly has the manufacturing power in
full degree, decomposing carbonic acid and setting
oxygen free, under the influence of sunlight. But
the protoplasmic contents of some of the cells of
which the plant is made up occasionally divide, by
a method similar to that which effects the division
of the contents of the Peronospora spore ; and the
severed portions are then set free as active monad -
like zoospores. Each is oval and is provided at
one extremity with two long active ciHa. Pro-
pelled by these, it swims about for a longer or

VI ANIMALS AND PLANTS 189

shorter time, but at length comes to a state of
rest and gradually grows into a Coleochcete.
Moreover, as in the Peroiiospora, conjugation may
take place and result in an oospore ; the contents
of which divide and are set free as monadiform
germs.

If the whole history of the zoospores of Perono-
spora and of Goleochcete were unknown, they would
undoubtedly be classed among " Monads " with
the same right as Hcteromita ; why then may not
Heteromita be a plant, even though the cycle of
forms through which it passes shows no terms
quite so complex as those which occur in Perono-
spora and Coleoclimte .^ And, in fact, there are
some green organisms, in every respect charac-
teristically plants, such as Chlamydomonas,
and the common Volvox, or so-called " Globe
animalcule," which run through a cycle of forms
of just the same simple character as those of
Heteromita.

The name of CMamyclomonas is applied to certain
microscopic green bodies, each of which consists of
a protoplasmic central substance invested by a
structureless sac. The latter contains cellulose, as
in ordinary plants; and the chlorophyll which
gives the green colour enables the Chlamydomonas
to decompose carbonic acid and fix carbon as they
do. Two long cilia protrude through the cell-wall,
and effect the rapid locomotion of this " monad,"
which, in all respects except its mobility, is

190 ANIMALS AND PLANTS VI

characteristically a plant. Under ordinary cir-
cumstances, the Chlainydomonas multiplies by
simple fission, each splitting into two or into four
parts, which separate and become independent
organisms. Sometimes, however, the Clilamy-
domonas divides into eight parts, each of which is
provided with four instead of two cilia. These
"zoospores" conjugate in pairs, and give rise to
quiescent bodies, which multiply by division, and
eventually pass into the active state.

Thus, so far as outward form and the general
character of the cycle of modifications, through
which the organism passes in the course of its
life, are concerned, the resemblance between
Chlamy domonas and HeUromita is of the closest
description. And on the face of the matter there
is no ground for refusing to admit that Heteromita
may be related to Chlamy domonas, as the colourless
fungus is to the green alga. Volvox may be com-
pared to a hollow sphere, the wall of which is
made up of coherent Chlamydomonads ; and which
progresses with a rotating motion effected by the
paddling of the multitudinous pairs of cilia which
project from its surface. Each Volvox-m.ona,d,
moreover, possesses a red pigment spot, like the
simplest form of eye known among animals. The
methods of fissive multiplication and of conjugation
observed in the monads of this locomotive globe
are essentially similar to those observed in Chlamy-
domonas; and, though a hard battle has been

VT ANIMALS AND PLANTS 191

fought over it, Volvox is now finally surrendered to
the Botanists.

Thus there is really no reason why Hderonnita
may not be a plant; and this conclusion would be
very satisfactory, if it were not equally easy to
show that there is really no reason why it should
not be an animal. For there are numerous
organisms presenting the closest resemblance to
Heteromita, and, like it, grouped under the general
name of " Monads," which, nevertheless, can be
observed to take in solid nutriment, and which,
therefore, have a virtual, if not an actual, mouth
and digestive cavity, and thus come under Cuvier's
definition of an animal. Numerous forms of such
animals have been described by Ehrenberg,
Dujardin, H. James Clark, and other writers on
the Infusoria. Indeed, in another infusion
of hay in which my Heteromita lens occurred,
there were innumerable such infusorial animalcules
belonging to the well-known species Colpcda
cucullus}

Full-sized specimens of this animalcule attain a
length of between -g-J-g- or -^^^ of an inch, so that it
may have ten times the length and a thousand
times the mass of a Heteromita. In shape, it is
not altogether unlike Heteromita, The small end,
however, is not produced into one long cilium,
but the general surface of the body is covered with

* Excellently described by Stein, almost all of whose state-
ments I have verified.

192 ANIMALS AND PLANTS vi

small actively vibrating ciliary organs, which are
only longest at the small end. At the point
which answers to that from which the two cilia
arise in Heteromita, there is a conical depression,
the mouth ; and, in young specimens, a tapering
filament, which reminds one of the posterior cilium
of Heteromita, projects from this region.

The body consists of a soft granular proto-
plasmic substance, the middle of which is occupied
by a large oval mass called the " nucleus " ; while,
at its hinder end, is a " contractile vacuole," con-
spicuous by its regular rh}iihmic appearances and
disappearances. Obviously, although the Colpoda
is not a monad, it differs from one only in subor-
dinate details. Moreover, under certain conditions,
it becomes quiescent, incloses itself in a delicate
case or cyst, and then divides into two, four, or
more portions, which are eventually set free and
swim about as active Colpodce.

But this creature is an unmistakable animal,
and full-sized Col])odce may be fed as easily as one
feeds chickens. It is only needful to diffuse very
finely ground carmine through the water in which
they hve, and, in a very short time, the bodies of
the Colpcdce are stuffed mth the deeply-coloured
granules of the pigment.

And if this were not sufficient evidence of the
animahty of Colpoda, there comes the fact that it
is even more similar to another well-knowm
animalcule, Paramcecium; than it is to a monad.

n ANIMALS AND PLANTS 193

But Paramcecium is so huge a creature compared
with those hitherto discussed — it reaches y^-g- of
an inch or more in length — that there is no diffi-
culty in making out its organisation in detail;
and in proving that it is not only an animal, but
that it is an animal which possesses a somewhat
compHcated organisation. For example, the sur-
face layer of its body is different in structure from
the deeper parts. There are two contractile
vacuoles, from each of which radiates a system of
vessel-hke canals ; and not only is there a conical
depression continuous with a tube, which serve as
mouth and gullet, but the food ingested takes a
definite course, and refuse is rejected from a
definite region. Nothing is easier than to feed
these animals, and to watch the particles of indigo
or carmine accumulate at the lower end of the
gullet. From this they gradually project, sur-
rounded by a ball of water, which at length passes
with a jerk, oddly simulating a gulp, into the
pulpy central substance of the body, there to cir-
culate up one side and down the other, until its
contents are digested and assimilated. Neverthe-
less, this complex animal multiplies by division, as
the monad does, and, like the monad, undergoes
conjugation. It stands in the same relation to
Heteromita on the animal side, as ColeccJicete does
on the plant side. Start from either, and such an
insensible series of gradations leads to the monad
that it is impossible to say at any stage of the

199

194 ANIMALS AND PLAXTS

VI

progress where the line between the animal and
the plant must be drawn.

There is reason to think that certain organisms
which pass through a monad stage of existence,
such as the Myxomycetcs, are, at one time of their
lives, dependent upon external sources for their
protein matter, or are animals; and, at another
period, manufacture it, or are plants. And seeing
that the whole progress of modern investigation is
in favour of the doctrine of continuit}^, it is a fair
and probable speculation — though only a specu-
lation— that, as there are some plants which can
manufacture protein out of such apparently in-
tractable mineral matters as carbonic acid, water,
nitrate of ammonia, metaUic and earthy salts ; while
others need to be supplied with their carbon and
nitrogen in the somewhat less raw form of tartrate
of ammonia and allied compounds ; so there may be
yet others, as is possibly the case with the true
parasitic plants, which can only manage to put
together materials still better prepared — still more
nearly approximated to protein — until we arrive at
such organisms as the Psorospermice and the Pan-
Msto2ohyton, which are as much animal as vegetable
in structure, but are animal in their dependence
on other organisms for their food.

The singular circumstance observed by Meyer,
that the Tomtla of yeast, though an indubitable
plant, still flourishes most vigorously when supplied
with the complex nitrogenous substance, pepsin ;

VI ANIMALS AND PLANTS 195

the probability that the PeronosiJora is nourished
directly by the protoplasm of the potato-plant;
and the wonderful facts which have recently been
brought to Hght respecting insectivorous plants, all
favour this view ; and tend to the conclusion that
the difference between animal and plant is one of
degree rather than of kind, and that the problem
whether, in a given case, an organism is an
animal or a plant, may be essentially insoluble.

vn

A LOBSTER; OR, THE STUDY OF

ZOOLOGY

[1861]

Natural History is the name familiarly applied
to the study of the properties of such natural
bodies as minerals, plants, and animals; the
sciences which embody the knowledge man has
acquired upon these subjects are commonly termed
Natural Sciences, in contradistinction to other so-
called " physical " sciences ; and those who devote
themselves especially to the pursuit of such
sciences have been and are commonly termed
" Naturalists."

Linnaeus was a naturalist in this wide sense,
and his " Systema Naturae " was a work upon
natural history, in the broadest acceptation of the
term ; in it, that great methodising spirit em-
bodied all that was known in his time of the
distinctive characters of minerals, animals, and

VII TUE STUDY OF ZOOLOGY 197

plants. But the enormous stimulus which
Linnaeus gave to the investigation of nature soon
rendered it impossible that any one man should
write another " Systema Naturae," and extremely
difficult for any one to become even a naturalist
such as Linnaeus was.

Great as have been the advances made by all
the three branches of science, of old included
under the title of natural history, there can be no
doubt that zoology and botany have grown in an
enormously greater ratio than mineralogy; and
hence, as I suppose, the name of " natural history "
has gradually become more and more definitely
attached to these prominent divisions of the
subject, and by " naturalist " people have meant
more and more distinctly to imply a student of
the structure and function of living beings.

However this may be, it is certain that the
advance of knowledge has gradually widened the
distance between mineralogj^ and its old associates,
while it has drawn zoology and botany closer to-
gether; so that of late years it has been found
convenient (and indeed necessary) to associate the
sciences which deal with vitality and all its phe-
nomena under the common head of " biology " ;
and the biologists have come to repudiate any
blood-relationship with their foster-brothers, the
mineralogists.

Certain broad laws have a general application
throughout both the animal and the vej^etable

198 THE STUDY OF ZOOLOGY vil

worlds, but the ground common to these kingdoms
of nature is not of very wide extent, and the
multiplicity of details is so great, that the student
of living beings finds himself obliged to devote his
attention exclusively either to the one or the
other. If he elects to study plants, under any
aspect, we know at once what to call him. He is
a botanist, and his science is botany. But if the
investigation of animal life be his choice, the name
generally applied to him will vary according to
the kind of animals he studies, or the particular
phenomena of animal life to which he confines his
attention. If the study of man is his object, he is
called an anatomist, or a physiologist, or an ethno-
logist ; but if he dissects animals, or examines
into the mode in which their functions are per-
formed, he is a comparative anatomist or com-
parative physiologist. If he turns his attention to
fossil animals, he is a palaeontologist. If his mind
is more particularly directed to the specific de-
scription, discrimination, classification, and distri-
bution of animals, he is termed a zoologist.

For the purpose of the present discourse, how-
ever, I shall recognise none of these titles save the
last, which I shall employ as the equivalent of
botanist, and I shall use the term zoology as
denoting the whole doctrine of animal life, in con-
tradistinction to botany, which signifies the whole
doctrine of vegetable life.

Employed in this sense, zoology, like botany, is

VII THE STUDY OF ZOOLOGY 199

divisible into three great but subordinate sciences,
morphology, physiology, and distribution, each of
which may, to a very great extent, be studied in-
dependently of the other.

Zoological morphology is the doctrine of animal
form or structure. Anatomy is one of its branches ;
development is another ; while classification is the
expression of the relations which different animals
bear to one another, in respect of their anatomy
and their development.

Zoological distribution is the study of animals in
relation to the terrestrial conditions which obtain
now, or have obtained at any previous epoch of
the earth's history.

Zoological physiology, lastly, is the doctrine of
the functions or actions of animals. It regards
animal bodies as machines impelled by certain
forces, and performing an amount of work which
can be expressed in terms of the ordinary forces of
nature. The final object of physiology is to
deduce the facts of morphology, on the one hand,
and those of distribution on the other, from the
laws of the molecular forces of matter.

Such is the scope of zoology. But if I were to
content myself with the enunciation of these dry
definitions, I should ill exem^phfy that method of
teaching this branch of physical science, which it is
my chief business to-night to recommend. Let us
turn away then from abstract definitions. Let us
take some concrete living thing, some animal, tho

200 THE STUDY OF ZOOLOGY vil

commoner the better, and let us see how the appli-
cation of common sense and common logic to the
obvious facts it presents, inevitably leads us into
all these branches of zoological science.

I have before me a lobster. When I examine
it, what appears to be the most striking character it
presents ? Why, I observe that this part which we
call the tail of the lobster, is made up of six distinct
hard rings and a seventh terminal piece. If I
separate one of the middle rings, say the third, I
find it carries upon its under surface a pair of
Hmbs or appendages, each of which consists of a
stalk and two terminal pieces. So that I can re-
present a transverse section of the ring and its
appendages upon the diagram board in this way.

If I now take the fourth ring, I find it has the
same structure, and so have the fifth and the second ;
so that, in each of these divisions of the tail, I find
parts which correspond with one another, a ring
and two appendages ; and in each appendage a
stalk and two end pieces. These corresponding
parts are called, in the technical language of
anatomy, "homologous parts." The ring of the
third division is the " homologue " of the ring of
the fifth, the appendage of the former is the homo-
logue of the appendage of the latter. And, as
each division exhibits corresponding parts in
corresponding places, we say that all the divisions
are constructed upon the same plan. But now let
us consider the sixth division. It is similar to,

Til THE STUDY OF ZOOLOGY 201

and yet diflferent from, the others. The ring is
essentially the same as in the other divisions ; but
the appendages look at first as if they were very
different ; and yet when we regard them closely,
what do we find ? A stalk and two terminal
divisions, exactly as in the others, but the stalk is
very short and very thick, the terminal divisions
are very broad and flat, and one of them is divided
into two pieces.

I may say, therefore, that the sixth segment is
like the others in plan, but that it is modified in
its details.

The first segment is like the others, so far as its
ring is concerned, and though its appendages differ
from any of those yet examined in the simphcity
of their structure, parts corresponding with the
stem and one of the divisions of the appendages
of the other segments can be readily discerned in
them.

Thus it appears that the lobster's tail is com-
posed of a series of segments which are funda-
mentally similar, though each presents peculiar
modifications of the plan common to all. But
when I turn to the forepart of the body I see, at
first, nothing but a great shield-like shell, called
technically the " carapace," ending in front in a
sharp spine, on either side of which are the curious
compound eyes, set upon the ends of stout movable
stalks. Behind these, on the under side of the
body, are two pairs of long feelers, or antennae.

202 THE STUDY OF ZOOLOGY vn

followed by six pairs of jaws folded against one
another over the mouth, and five pairs of legs, the
foremost of these being the great pinchers, or
claws, of the lobster.

It looks, at first, a little hopeless to attempt to
find in this complex mass a series of rings, each
with its pair of appendages, such as I have shown
you in the abdomen, and yet it is not difiicult to
demonstrate their existence. Strip off the legs,
and you will find that each pair is attached to a
very definite segment of the under wall of the
body; but these segments, instead of being the
lower parts of free rings, as in the tail, are such
parts of rings which are all solidly united and
bound together ; and the like is true of the jaws,
the feelers, and the eye-stalks, every pair of which
is borne upon its own special segment. Thus the
conclusion is gradually forced upon us, that the
body of the lobster is composed of as many rings
as there are pairs of appendages, namely, twenty in
all, but that the six hindmost rings remain free
and movable, while the fourteen front rings be-
come firmly soldered together, their backs forming
one continuous shield — the carapace.

Unity of plan, diversity in execution, is the
lesson taught by the study of the rings of the body,
and the same instruction is given still more em-
phatically by the appendages. If I examine the
outermost jaw I find it consists of three distinct
portions, an inner, a middle, and an outer, mounted

VII THE STUDY OF ZOOLOGY 203

upon a common stem ; and if I compare this jaw
with the legs behind it, or the jaws in front of it,
I find it quite easy to see, that, in the legs, it is
the part of the appendage which corresponds with
the inner division, which becomes modified into
what we know familiarly as the " leg," while the
middle division disappears, and the outer division
is hidden under the carapace. Nor is it more
difficult to discern that, in the appendages of the
tail, the middle division appears again and the
outer vanishes ; while, on the other hand, in the
foremost jaw, the so-called mandible, the inner
division only is left ; and, in the same way, the
parts of the feelers and of the eye-stalks can be
identified with those of the legs and jaws.

But whither does all this tend ? To the very
remarkable conclusion that a unity of plan, of the
same kind as that discoverable in the tail or
abdomen of the lobster, pervades the whole organ-
isation of its skeleton, so that I can return to the
diagram representing any one of the rings of the
tail, which I drew upon the board, and by adding a
third division to each appendage, I can use it as a
sort of scheme or plan of any ring of the body. I
can give names to all the parts of that figure, and
then if I take any segment of the body of the
lobster, I can point out to you exactly, what modi-
fication the general plan has undergone in that
particular segment ; what part has remained
movable, and what has become fixed to another ;

204 THE STUDY OF ZOOLOGY tii

what has been excessively developed and metamor-
phosed and what has been suppressed.

But I imagine I hear the question, How is all
this to be tested ? No doubt it is a pretty and
ingenious way of looking at the structure of any
animal ; but is it anything more ? Does Nature
acknowledge, in any deeper way, this unity of plan
we seem to trace ?

The objection suggested by these questions is a
very vahd and important one, and morphology was
in an unsound state so long as it rested upon the
mere perception of the analogies which obtain
between fully formed parts. The unchecked in-
genuity of speculative anatomists proved itself
fully competent to spin any number of contradic-
tory hypotheses out of the same facts, and endless
morphological dreams threatened to supplant
scientific theory.

Happily, however, there is a criterion of mor-
phological truth, and a sure test of all homologies.
Our lobster has not always been what we see it ;
it was once an egg, a semifluid mass of 3'olk, not so
big as a pin's head, contained in a transparent
membrane, and exhibiting not the least trace of
any one of those organs, the multiplicity and
complexity of which, in the adult, are so surprising.
After a time, a delicate patch of cellular membrane
appeared upon one face of this yolk, and that
patch was the foundation of the whole creature,
the clay out of which it would be moulded.

vn THE STUDY OF ZOOLOGY 205

Gradually investing the yolk, it became subdivided
by transverse constrictions into segments, the
forerunners of the rings of the body. Upon the
ventral surface of each of the rings thus sketched
out, a pair of bud-like prominences made their ap-
pearance— the rudiments of the appendages of the
ring. At first, all the appendages were alike, but,
as they grew, most of them became distinguished
into a stem and two terminal divisions, to which,
in the middle part of the body, was added a third
outer division ; and it was only at a later period,
that by the modification, or absorption, of certain
of these primitive constituents, the limbs acquired
their perfect form.

Thus the study of development proves that the
doctrine of unity of plan is not merely a fancy,
that it is not merely one way of looking at the
matter, but that it is the expression of deep-seated
natural facts. The legs and jaws of the lobster
may not merely be regarded as modifications of a
common type, — in fact and in nature they are so,
— the leg and the jaw of the young animal being,
at first, indistinguishable.

These are wonderful truths, the more so because
the zoologist finds them to be of universal appHca-
tion. The investigation of a pol}^e, of a snail, of
a fish, of a horse, or of a man, would have led us,
though by a less easy path, perhaps, to exactly the
same point. Unity of plan everjrvs^here Kes hidden
under the mask of diversity of structure — the

206 THE STUDY OF ZOOLOGY vii

complex is ever^^vhere evolved out of the simple.
Every animal has at first the form of an egg, and
every animal and every organic part, in reaching
its adult state, passes through conditions common
to other animals and other adult parts ; and this
leads me to another point. I have hitherto
spoken as if the lobster were alone in the world,
but, as I need hardly remind you, there are
m3rriads of other animal organisms. Of these,
some, such as men, horses, birds, fishes, snails,
slugs, oysters, corals, and sponges, are not in the
least Hke the lobster. But other animals, though
they may differ a good deal from the lobster, are
yet either very hke it, or are hke something that
is hke it. The cray fish, the rock lobster, and the
pra^vn, and the shrimp, for example, however
different, are yet so hke lobsters, that a child
would group them as of the lobster kind, in contra-
distinction to snails and slugs ; and these last again
would form a kind by themselves, in contradis-
tinction to cows, horses, and sheep, the cattle kind.

But this spontaneous grouping into " kinds " is
the first essay of the human mind at classification,
or the calhng by a common name of those things
that are ahke, and the arranging them in such a
manner as best to suggest the sum of their hke-
nesses and unhkenesses to other things.

Those kinds which include no other subdivisions
than the sexes, or various breeds, are called, in
techni<;al language, species. The Enghsh lobster

VII THE STUDY OF ZOOLOGY 207

is a species, our cray fish is another, our prawn is
another. In other countries, however, there are
lobsters, cray fish, and prawns, very Hke ours, and
yet presenting sufficient differences to deserve dis-
tinction. Naturahsts, therefore, express this re-
semblance and this diversity by grouping them as
distinct species of the same "genus." But the
lobster and the cray fish, though belonging to dis-
tinct genera, have many features in common, and
hence are grouped together in an assemblage which
is called a family. More distant resemblances
connect the lobster with the prawn and the crab,
which are expressed by putting all these into the
same order. Again, more remote, but still very
definite, resemblances unite the lobster with the
woodlouse, the king crab, the water flea, and the
barnacle, and separate them firom all other animals ;
whence they collectively constitute the larger
group, or class, Crustacea. But the Cintstacea
exhibit many pecuHar features in common with
insects, spiders, and centipedes, so that these are
grouped into the still larger assemblage or " pro-
vince" Articulata; and, finally, the relations
which these have to worms and other lower
animals, are expressed by combining the whole vast
aggregate into the sub-kingdom of Annulosa.

If I had worked my way from a sponge instead
of a lobster, I should have found it associated, by
like ties, with a great number of other animals
into the sub-kingdom Protozoa ; if I had selected
a fresh-water pol^^e or a coral, the members of

208 THE STUDY OF ZOOLOGY vii

what naturalists term the sub-kingdom Ccelenterata,
would have grouped themselves around my type ;
had a snail been chosen, the inhabitants of all
univalve and bivalve, land and water, shells, the
lamp shells, the squids, and the sea-mat would
have gradually linked themselves on to it as mem-
bers of the same sub-kingdom of Mollusca ; and
finally, starting from man, I should have been com-
pelled to admit first, the ape, the rat, the horse,
the dog, into the same class ; and then the bird,
the crocodile, the turtle, the frog, and the fish,
into the same sub-kingdom of Vertehrata.

And if I had followed out all these various Hues
of classification fully, I should discover in the end
that there was no animal, either recent or fossil,
which did not at once fall into one or other of
these sub-kingdoms. In other words, every animal
is organised upon one or other of the five, or more,
plans, the existence of which renders our classifi-
cation possible. And so definitely and precisely
marked is the structure of each animal, that, in
the present state of our knowledge, there is not
the least evidence to prove that a form, in
the slightest degree transitional between any of
the two groups Vertehrata, AnmUosa, Mollusca,
and Codenterata, either exists, or has existed,
during that period of the earth's history which is
recorded by the geologist.^ Nevertheless, you
must not for a moment suppose, because no such

P The different grouping necessitated by later knowledge
does not affect the principle of the argument. — 1894.]

vn THE STUDY OF ZOOLOGY 209

transitional forms are known, that the members of
the sub-kingdoms are disconnected from, or inde-
pendent of, one another. On the contrary, in
their earliest condition they are all similar, and the
primordial germs of a man, a dog, a bird, a fish, a
beetle, a snail, and a polype are, in no essential
structural respects, distinguishable.

In this broad sense, it may with truth be said,
that all Hving animals, and all those dead faunae
which geology reveals, are bound together by an
all-pervading unity of organisation, of the same
character, though not equal in degree, to that
which enables us to discern one and the same plan
amidst the twenty different segments of a lobster's
body. Truly it has been said, that to a clear eye
the smallest fact is a window through which the
Infinite may be seen.

Turning from these purely morphological con-
siderations, let us now examine into the manner in
which the attentive study of the lobster impels us
into other lines of research.

Lobsters are found in all the European seas ;
but on the opposite shores of the Atlantic and in
the seas of the southern hemisphere they do not
exist. They are, however, represented in these
regions by very closely allied, but distinct forms —
the Hcmarus Amcricaniis and the Homarus
Capensis : so that we may say that the European
has one species of Homarus; the American,
another; the African, another; and thus the

200

210 THE STUDY OF ZOOLOGY vn

remarkable facts of geographical distribution begin
to dawn upon us.

Again, if we examine the contents of the earth's
crust, we shall find in the latter of those deposits,
which have served as the great burjdng groimds of
past ages, numberless lobster-hke animals, but
none so similar to our living lobster as to make
zoologists sure that they belonged even to the
same genus. If we go still further back in time,
we discover, in the oldest rocks of all, the remains
of animals, constructed on the same general plan
as the lobster, and belonging to the same great
group of Crustacea; but for the most part
totally different from the lobster, and indeed from
any other living form of crustacean ; and thus we
gain a notion of that successive change of the
animal population of the globe, in past ages,
which is the most striking fact revealed by
geology.

Consider, now, where our inquiries have led us.
We studied our type morphologically, when we
determined its anatomy and its development, and
when comparing it, in these respects, with other
animals, we made out its place in a system of
classification. If we were to examine every
animal in a similar manner, we should estabhsh a
complete body of zoological morphology.

Again, we investigated the distribution of our
type in space and in time, and, if the Hke had
been done with every animal, the sciences of geo-

ril THE STUDY OF ZOOLOGY 211

graphical and geological distribution would have
attained their hmit.

But you will observe one remarkable circum-
stance, that, up to this point, the question of the
life of these organisms has not come under con-
sideration. Morphology and distribution might be
studied almost as well, if animals and plants were
a peculiar kind of crystals, and possessed none of
those functions which distinguish living beings so
remarkably. But the facts of morphology and
distribution have to be accounted for, and the
science, the aim of which it is to account for
them, is Physiolog}'.

Let us return to our lobster once more. If we
watched the creature in its native element, we
should see it climbing actively the submerged
rocks, among which it delights to live, by means
of its strong legs ; or swimming by powerful strokes
of its great tail, the appendages of the sixth
joint of which are spread out into a broad fan-like
propeller : seize it, and it will show you that its
great claws are no mean weapons of offence ; sus-
pend a piece of carrion among its haunts, and it
will greedily devour it, tearing and crushing the
flesh by means of its multitudinous jaws.

Suppose that we had known nothing of the
lobster but as an inert mass, an organic crystal, if
I may use the phrase, and that we could suddenly
see it exerting all these powers, what wonderful
new ideas and new questions would arise in our

212 THE STUDY OF ZOOLOGY vii

minds ! The great new question would be, " How
does all this take place ? " the chief new idea would
be, the idea of adaptation to purpose, — the notion,
that the constituents of animal bodies are not
mere unconnected parts, but organs working
together to an end. Let us consider the tail of
the lobster again from this point of view.
Morphology has taught us that it is a series
of segments composed of homologous parts,
which undergo various modifications — beneath
and through which a common plan of formation
is discernible. But if I look at the same part
physiologically, I see that it is a most beautifully
constructed organ of locomotion, by means of
which the animal can swiftly propel itself either
backwards or forwards.

But how is this remarkable propulsive machine
made to perform its functions ? If I were sud-
denly to kill one of these animals and to take out
all the soft parts, I should find the shell to be per-
fectly inert, to have no more power of moving
itself than is possessed by the machinery of a mill
when disconnected from its steam-engine or water-
wheel. But if I were to open it, and take out the
viscera only, leaving the white flesh, I should per-
ceive that the lobster could bend and extend its
tail as well as before. If I were to cut off the
tail, I should cease to find any spontaneous motion
in it ; but on pinching any portion of the flesh,
I should observe that it underwent a very curious

vn THE STUDY OF ZOOLOGY 213

change — each fibre becoming shorter and thicker.
By this act of contraction, as it is termed, the
parts to which the ends of the fibre are attached
are, of course, approximated ; and according to the
relations of their points of attachment to the
centres of motions of the different rings, the
bending or the extension of the tail results. Close
observation of the newly-opened lobster would
soon show that all its movements are due to the
same cause — the shortening and thickening of
these fleshy fibres, which are technically called
muscles.

Here, then, is a capital fact. The movements
of the lobster are due to muscular contractiHty.
But why does a muscle contract at one time and
not at another ? Why does one whole group of
muscles contract when the lobster wishes to ex-
tend his tail, and another group when he desires
to bend it ? What is it originates, directs, and
controls the motive power ?

Experiment, the great instrument for the ascer-
tainment of truth in physical science, answers this
question for us. In the head of the lobster
there lies a small mass of that pecuHar tissue
which is known as nervous substance. Cords of
similar matter connect this brain of the lobster,
directly or indirectly, with the muscles. Now, if
these communicating cords are cut, the brain
remaining entire, the power of exerting what we
call voluntary motion in the parts below the sec-

214 THE STUDY OF ZOOLOGY Til

tion is destroyed ; and, on the other hand, if, the
cords remaining entire, the brain mass be destroyed,
the same voluntary mobihty is equally lost.
Whence the inevitable conclusion is, that the
power of originating these motions resides in
the brain and is propagated along the nervous
cords.

In the higher animals the phenomena which
attend this transmission have been investigated,
and the exertion of the pecuhar energy which
resides in the nerves has been found to be accom-
panied by a disturbance of the electrical state of
their molecules.

If we could exactly estimate the signification
of this disturbance ; if we could obtain the value
of a given exertion of nerve force by determining
the quantity of electricity, or of heat, of which it
is the equivalent; if we could ascertain upon
what arrangement, or other condition of the
molecules of matter, the manifestation of the
nervous and muscular energies depends (and
doubtless science wiU some day or other ascertain
these points), physiologists would have attained
their ultimate goal in this direction ; they would
have determined the relation of the motive force
of animals to the other forms of force found in
nature ; and if the same process had been success-
fully performed for all the operations which are
carried on in, and by, the animal frame, physiology
would be perfect, and the facts of morphology

VII THE STUDY OF ZOOLOGY 215

and distribution would be deducible from the
laws which physiologists had established, com-
bined with those determining the condition of the
surrounding universe.

There is not a fragment of the organism of this
humble animal whose study would not lead us
into regions of thought as large as those which I
have briefly opened up to you ; but what I have
been saying, I trust, has not only enabled you to
form a conception of the scope and purport of
zoology, but has given you an imperfect example
of the manner in which, in my opinion, that
science, or indeed any physical science, may be
best taught. The great matter is, to make
teaching real and practical, by fixing the atten-
tion of the student on particular facts; but at
the same time it should be rendered broad and
comprehensive, by constant reference to the
generalisations of which all particular facts are
illustrations. The lobster has served as a type
of the whole animal kingdom, and its anatomy
and physiology have illustrated for us some of
the greatest truths of biology. The student who
has once seen for himself the facts which I have
described, has had their relations explained to
him, and has clearly comprehended them, has,
so far, a knowledge of zoology, which is real and
genuine, however limited it may be, and which is
worth more than all the mere reading knowledge
of the science he could ever acquire. His zoologi*

216 THE STUDY OF ZOOLOGY vii

cal information is, so far, knowledge and not mere
hearsay.

And if it were my business to fit you for the
certificate in zoological science granted by this
department, I should pursue a course precisely
similar in principle to that which I have taken
to-night. I should select a fresh- water sponge,
a fresh-water pol}^e or a Cyancea, a fi:esh-water
mussel, a lobster, a fowl, as tj^es of the five
primary divisions of the animal kingdom. I
should explain their structure very fully, and
show how each illustrated the great principles of
zoology. Having gone very carefully and fully
over this ground, I should feel that you had a
safe foundation, and I should then take you in
the same way, but less minutely, over similarly
selected illustrative types of the classes ; and then
I should direct your attention to the special
forms enumerated under the head of types, in
this syllabus, and to the other facts there men-
tioned.

That would, speaking generally, be my plan.
But I have undertaken to explain to you the best
mode of acquiring and communicating a know-
ledge of zoology, and you may therefore fairly ask
me for a more detailed and precise account of the
manner in which I should propose to furnish you
with the information I refer to.

My own impression is, that the best model for
aU kinds of training in physical science is that

vu TnE STUDY OF ZOOLOGY 217

afforded by the method of teaching anatomy, in
use in the medical schools. This method con-
sists of three elements — lectures, demonstrations,
and examinations.

The object of lectures is, in the fimh place, to
awaken the attention and excite the enthusiasm
of the student; and this, I am sure, may be
effected to a far greater extent by the oral dis-
course and by the personal influence of a respected
teacher than in any other way. Secondly, lectures
have the double use of guiding the student to
the salient points of a subject, and at the same
time forcing him to attend to the whole of it, and
not merely to that part which takes his fancy.
And lastly, lectures afford the student the oppor-
tunity of seeking explanations of those difficulties
which will, and indeed ought to, arise in the
course of his studies.

What books shall I read ? is a question con-
stantly put by the student to the teacher. My
reply usually is, " None : write your notes out
carefully and fully ; strive to understand them
thoroughly; come to me for the explanation of
anything you cannot understand ; and I would
rather you did not distract your mind by reading."
A properly composed course of lectures ought to
contain fully as much matter as a student can
assimilate in the time occupied by its delivery;
and the teacher should always recollect that his
business is to feed, and not to cram the intellect.

218 THE STUDY OF ZOOLOGY vn

Indeed, I believe that a student who gains
from a course of lectures the simple habit of
concentrating his attention upon a definitely
limited series of facts, until they are thoroughly
mastered, has made a step of immeasurable
importance.

But, however good lectures may be, and how-
ever extensive the course of reading by which
they are followed up, they are but accessories to
the great instrument of scientific teaching —
demonstration. If I insist unweariedly, nay
fanatically, upon the importance of physical
science as an educational agent, it is because
the study of any branch of science, if properly
conducted, appears to me to fill up a void left
by all other means of education. I have the
greatest respect and love for literature; nothing
would grieve me more than to see hterary train-
ing other than a very prominent branch of
education : indeed, I wish that real literarj^ dis-
cipline were far more attended to than it is ;
but I cannot shut my eyes to the fact, that there
is a vast difference between men who have had a
purely literary, and those who have had a sound
scientific, training.

Seeking for the cause of this difference, I
imagine I can find it in the fact that, in the
world of letters, learning and knowledge are one,
and books are the source of both; whereas in
science, as in life, learning and knowledge are

vil THE STUDY OF ZOOLOGY 219

distinct, and the study of things, and not of
books, is the source of the latter.

All that literature has to bestow may be obtained
by reading and by practical exercise in writing
and in speaking ; but I do not exaggerate when
I say, that none of the best gifts of science are to
be won by these means. On the contrary, the
great benefit w^hich a scientific education bestows,
whether as training or as knowledge, is dependent
U23on the extent to w^hich the mind of the student
is brought into immediate contact with facts — •
upon the degree to which he learns the habit of
appealing directly to Nature, and of acquiring
through his senses concrete images of those pro-
perties of things, which are, and always wiU be,
but approximatively expressed in human language.
Our way of looking at Nature, and of speaking
about her, varies from year to year; but a fact
once seen, a relation of cause and effect, once
demonstratively apjDrehended, are possessions
which neither change nor pass away, but, on the
contrary, form fixed centres, about which other
truths aggregate by natural afiinity.

Therefore, the great business of the scientific
teacher is, to imprint the fundamental, irrefragable
facts of his science, not only by words upon the
mind, but by sensible impressions upon the eye,
and ear, and touch of the student, in so complete
a manner, that every term used, or law enunciated,
should afterwards call up vivid images of tho

220 THE STUDY OF ZOOLOGY vii

particular structural, or other, facts which furnished
the demonstration of the law, or the illustration
of the term.

Now this important operation can only be
achieved by constant demonstration, which may
take place to a certain imperfect extent during a
lecture, but which ought also to be carried on
independently, and which should be addressed to
each individual student, the teacher endeavouring,
not so much to show a thing to the learner, as to
make him see it for himself

I am well aware that there are great practical
difficulties in the way of effectual zoological
demonstrations. The dissection of animals is not
altogether pleasant, and requires much time ; nor
is it easy to secure an adequate supply of the
needful specimens. The botanist has here a
great advantage ; his specimens are easily ob-
tained, are clean and wholesome, and can be
dissected in a private house as well as anywhere
else ; and hence, I believe, the fact, that botany
is so much more readily and better taught than
its sister science. But, be it difficult or be it
easy, if zoological science is to be properly studied,
demonstration, and, consequently, dissection, must
be had. Without it, no man can have a reall}^
sound knowledge of animal organisation.

A good deal may be done, however, without
actual dissection on the student's part, by demon-
stration upon specimens and preparations ; and in

vn THE STUDY OF ZOOLOGY 221

all probability it would not be very difficult, were
the demand sufficient, to organise collections of
such objects, sufficient for all the purposes of
elementary teaching, at a comparatively cheap
rate. Even without these, much mis^ht be
effected, if the zoological collections, which are
open to the public, were arranged according to
what has been termed the " typical principle " ;
that is to say, if the specimens exposed to public
view were so selected that the public could learn
something from them, instead of being, as at
present, merely confused by their multiplicity.
For example, the grand ornithological gallery at
the British Museum contains between two and
three thousand species of birds, and sometimes
five or six specimens of a species. They are
very pretty to look at, and some of the cases are,
indeed, splendid ; but I will undertake to say,
that no man but a professed ornithologist has
ever gathered much information from the col-
lection. Certainly, no one of the tens of thousands
of the general public who have walked through
that gallery ever knew more about the essential
peculiarities of birds when he left the gallery
than when he entered it. But if, somewhere in
that vast hall, there were a few preparations,
excmphfying the leading structural peculiarities
and the mode of development of a common fowl ;
if the types of the genera, the leading modifica-
tions in the skeleton, in the plumage at various

222 THE STUDY OF ZOOLOGY vil

ages, in the mode of nidification, and the hke,
among birds, were disj^layed ; and if the other
specimens were put away in a place where the
men of science, to whom they are alone useful,
could have free access to them, I can conceive
that this collection might become a great instru-
ment of scientific education.

The last implement of the teacher to which I
have adverted is examination — a means of educa-
tion now so thoroughly understood that I need
hardly enlarge upon it. I hold that both written
and oral examinations are indisj^ensable, and, by
requiring the description of specimens, they may
be made to supplement demonstration.

Such is the fullest reply the time at m}^ dis-
posal will allow me to give to the question — how
may a knowledge of zoology be best acquired and
communicated ?

But there is a previous question which may
be moved, and which, in fact, I know many
are inclined to move. It is the question, why
should teachers be encouraged to acquire a know-
ledge of this, or any other branch of physical
science ? What is the use, it is said, of attempt-
ing to make physical science a branch of primary
education ? Is it not probable that teachers, in
pursuing such studies, will be led astray from the
acquirement of more important but less attractive
knowledge ? And, even if they can learn some-
thing of science without prejudice to their useful-

VII

THE STUDY OF ZOOLOGY 223

ness, what is the good of their attempting to
instil that knowledge into boys whose real busi-
ness is the acquisition of reading, writing, and
arithmetic ?

These questions are, and will be, very commonly
asked, for they arise from that profound ignorance
of the value and true position of physical science,
which infests the minds of the most highly edu-
cated and intelligent classes of the community.
But if I did not feel well assured that they are
capable of being easily and satisfactorily answered ;
that they have been answered over and over again ;
and that the time will come when men of Hberal
education will blush to raise such questions — I
should be ashamed of my position here to-night.
Without doubt, it is your great and very important
function to carry out elementary education ; with-
out question, anything that should interfere with
the faithful fulfilment of that duty on your part
would be a great evil ; and if I thought that your
acquirement of the elements of physical science,
and your communication of those elements to your
pupils, involved any sort of interference with your
proper duties, I should be the first person to pro-
test against your being encouraged to do anything
of the kind.

But is it true that the acquisition of such a
knowledge of science as is proposed, and the com-
munication of that knowledge, axe calculated to
weaken your usefulness ? Or may I not rather

224 THE STUDY OF ZOOLOGY vil

ask, 18 it possible for you to discharge youi
functions properly without these aids ?

What is the purpose of primary intellectual
education ? I apprehend that its first object is to
train the young in the use of those tools where-
with men extract knowledge from the ever-shift-
ing succession of phenomena which pass before
their eyes ; and that its second object is to inform
them of the fundamental laws which have been
found by experience to govern the course of things,
so that they may not be turned out into the world
naked, defenceless, and a prey to the events they
might control.

A boy is taught to read his own and other
languages, in order that he may have access to
infinitely wider stores of knowledge than could
ever be opened to him by oral intercourse with his
fellow men ; he learns to write, that his means of
communication with the rest of mankind may be
indefinitely enlarged, and that he may record and
store up the knowledge he acquires. He is taught
elementary mathematics, that he may understand
all those relations of number and form, upon which
the transactions of men, associated in compHcated
societies, are built, and that he may have some
practice in deductive reasoning.

All these operations of reading, writing, and
ciphering, are intellectual tools, whose use should,
before all things, be learned, and learned thor-
oughly; so that the youth may be enabled to

vn THE STUDY OF ZOOLOGY 225

make his life that which it ought to be, a con-
tinual progress in learning and in wisdom.

But, in addition, primary education endeavours
to fit a boy out with a certain equipment of
positive knowledge. He is taught the great laws
of morality; the religion of his sect; so much
history and geography as wiU tell him where the
great countries of the world are, what they are,
and how they have become what they are.

Without doubt all these are most fitting and
excellent things to teach a boy ; I should be very
sorry to omit any of them from any scheme of
primary intellectual education. The system is
excellent, so far as it goes.

But if I regard it closely, a curious reflection
arises. I suppose that, fifteen hundred years ago,
the child of any well-to-do Roman citizen was
taught just these same things ; reading and writing
in his own, and, perhaps, the Greek tongue ; the
elements of mathematics ; and the religion, moral-
ity, history, and geography current in his time.
Furthermore, I do not think I err in affirming,
that, if such a Christian Roman boy, who had
finished his education, could be transplanted into
one of our public schools, and pass through its
course of instruction, he would not meet with a
single unfamiliar line of thought ; amidst all the
new facts he would have to learn, not one would
suggest a different mode of regarding the universe
from that current in his own tima

201

226 THE STUDY OF ZOOLOGY vii

And yet surely there is some great difterence
between the civihsation of the fourth century and
that of the nineteenth, and still more between the
intellectual habits and tone of thought of that
day and this ?

And what has made this difference ? I answer
fearlessly — The prodigious development of physi-
cal science within the last two centuries.

Modern civilisation rests upon physical science ;
take away her gifts to our own country, and our
position among the leading nations of the world
is gone to-morrow; for it is physical science only
that makes intelligence and moral energy stronger
than brute force.

The whole of modem thought is steeped in
science; it has made its way into the works of
our best poets, and even the mere man of letters,
who affects to ignore and despise science, is un-
consciously impregnated with her spirit, and in-
debted for his best products to her methods. I
beheve that the greatest intellectual revolution
mankind has yet seen is now slowly taking place
by her agency. She is teaching the world that
the ultimate court of appeal is observation and
experiment, and not authority ; she is teaching it
to estimate the value of evidence ; she is creating
a firm and hving faith in the existence of immut-
able moral and physical laws, perfect obedience to
which is the highest possible aim of an intelligent
beincr.

VII

THE STUDY OF ZOOLOGY 227

But of all this your old stereot}^ed system of
education takes no note. Physical science, its
methods, its problems, and its difficulties, will
meet the poorest boy at every turn, and yet we
educate him in such a manner that he shall enter
the world as ignorant of the existence of the
methods and facts of science as the day he was
born. The modern world is full of artillery ; and
we turn out our children to do battle in it,
equipped with the shield and sword of an ancient
gladiator.

Posterity will cry shame on us if we do not
remedy this deplorable state of things. Nay, if
we live twenty years longer, our own consciences
will cry shame on us.

It is my firm conviction that the only way to
remedy it is to make the elements of physical
science an integral part of primary education. I
have endeavoured to show you how that may be
done for that branch of science which it is my
business to pursue; and I can but add, that I
should look upon the day when every schoolmaster
throughout this land was a centre of genuine,
however rudimentary, scientific knowledge, as an
epoch in the history of the country.

But let me entreat you to remember my last
words. Addressing myself to you, as teachers, I
would say, mere book learning in physical science
is a sham and a delusion — what you teach, unless
you wish to be impostors, that you must first

228 THE STUDY OF ZOOLOGY vn

know; and real knowledge in science means
personal acquaintance with the facts, be they
few or many.^

^ It has "been suggested to me that these words may be taken
to imply a discouragement on my part of any sort of scientific
instruction which does not give an acquaintance with the facts
at first hand. But this is not my meaning. The ideal of
scientific teaching is, no doubt, a system by which the scholar
sees every fact for himself, and the teacher supplies only the
explanations. Circumstances, however, do not often allow of
the attainment of that ideal, and we must put up with the
next best system — one in which the scholar takes a good deal on
trust from a teacher, who, knowing the facts by his own know-
ledge, can describe them with so much vividness as to enable
his audience to form competent ideas concerning them. The
system which I repudiate is that which allows teachers who
have not come into direct contact with the leading facts of a
science to pass their second-hand information on. The scientific
virus, like vaccine lymph, if passed through too long a succes-
sion of organisms, will lose all its effect in protecting the young
against the intellectual epidemics to which they are exposed.

[The remarks on p. 222 applied to the Natural History Collec-
tion of the British Museum in 1861. ■ The visitor to the Natural
History Museum in 1894 need go no further than the Great Hall
to see the realisation of my hopes by the present Director.]

VIII
BIOGENESIS AND ABIOGENESIS

(the presidential address to the BRITISH

ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE

FOR 1870)

It has long been the custom for the newly
installed President of the British Association for
the Advancement of Science to take advantage of
the elevation of the position in which the suffrages
of his colleagues had, for the time, placed him, and,
casting his eyes around the horizon of the scientific
world, to report to them what could be seen from
his watch-tower ; in what directions the multitu-
dinous divisions of the noble army of the improvers
of natural knowledge were marching; what
important strongholds of the great enemy of us
all, ignorance, had been recently captured; and,
also, with due impartiality, to mark where the
advanced posts of science had been driven in, or a
long-continued siege had made no progress.

230 BIOGENESIS AND ABIOGENESIS vili

1 propose to endeavour to follow this ancient
precedent, in a manner suited to the limitations of
my knowledge and of my capacity I shall not
presume to attempt a panoramic survey of the
world of science, nor even to give a sketch of what
is doing in the one great province of biology, with
some portions of which my ordinary occupations
render me familiar. But I shall endeavour to put
before you the history of the rise and progress of
a single biological doctrine; and I shall try to
give some notion of the fruits, both intellectual
and practical, which we owe, directly or indirectly,
to the working out, by seven generations of
patient and laborious investigators, of the
thought which arose, more than two centuries
ago, in the mind of a sagacious and observant
Italian naturalist.

It is a matter of everyday experience that it is
difficult to prevent many articles of food from
becoming covered with mould ; that fruit, sound
enough to all appearance, often contains grubs at
the core ; that meat, left to itself in the air, is
apt to putrefy and swarm with maggots. Even
ordinary water, if allowed to stand in an open
vessel, sooner or later becomes turbid and full of
living matter.

The philosophers of antiquity, interrogated as to
the cause of these phenomena, were provided with
a ready and a plausible answer. It did not enter
their minds even to doubt that these low forms of

Vlir BIOGENESIS AND ABIOGENESIS 231

life were generated in the matters in which they
made their appearance. Lucretius, who had drunk
deeper of the scientific spirit than any poet of
ancient or modern times except Goethe, intends to
speak as a philosopher, rather than as a poet, when
he writes that "with good reason the earth has
gotten the name of mother, since all things are
produced out of the earth. And many living
creatures, even now, spring out of the earth, taking
form by the rains and the heat of the sun." ^ The
axiom of ancient science, " that the corruption of
one thing is the birth of another," had its popular
embodiment in the notion that a seed dies before
the young plant springs from it ; a belief so wide-
spread and so fixed, that Saint Paul appeals to
it in one of the most splendid outbursts of his
fervid eloquence : —

" Thou fool, that which thou sowest is not
quickened, except it die."^

The proposition that life may, and does, proceed
from that which has no Hfe, then, was held alike
by the philosophers, the poets, and the people, of

' It is thus that Mr. Munro renders

" Linqnitur, ut merito maternum nomen adepta
Terra sit, e terra quoniam sunt cuncta creata.
Multaque nunc etiam exsistant animalia terris
Imbribus et calido solis concreta vapore."

De Rerum Natura, lib. v. 793—796.

But would not the meaning of the last line be better
rendered " Developed in rain-wat3r and in the warm vapours
raised by the sun " ? ^ I Corinthians xv. 36.

232 BIOGENESIS AND ABIOGENESIS vni

the most enlightened nations, eighteen hundred
years ago ; and it remained the accepted doctrine
of learned and unlearned Europe, through the
Middle Ages, down even to the seventeenth
century.

It is commonly counted among the many merits
of our great countryman, Harvey, that he was the
first to declare the opposition of fact to venerable
authority in this, as in other matters ; but I can
discover no justification for this widespread
notion. After careful search through the " Exer-
citationes de Generatione," the most that appears
clear to me is, that Harvey believed all animals
and plants to spring from what he terms a " prim-
ordium vegetale," a phrase which may nowadays be
rendered " a vegetative germ " ; and this, he says,
is " oviforme^' or " egg-like " ; not, he is careful to
add, that it necessarily has the shape of an egg, but
because it has the constitution and nature of one.
That this "|9Wm(5?'<fi2t?7i cmforrm " must needs, in
all cases, proceed from a living parent is nowhere
expressly maintained by Harvey, though such an
opinion may be thought to be imphed in one or two
passages ; while, on the other hand, he does, more
than once, use language which is consistent only
with a full belief in spontaneous or equivocal
generation.^ In fact, the main concern of Harvey's

^ See tlie following passage in Exercitatio I. : — "Item sipnnU
nasccntia dicuntur ; non quod ex pntredine oviunda sint, sed
q^uod casu, naturae sponte, et isquivGca (ut aiunt) generatione, a

Vin BIOGENESIS AND ABIOGENESIS 233

wonderful little treatise is not with generation, in
the physiological sense, at all, but with develop-
ment ; and his great object is the establishment of
the doctrine of epigenesis.

The first distinct enunciation of the h}^othesis
that all living matter has sprung from pre-existing
living matter, came from a contemporary, though a
junior, of Harvey, a native of that country, fertile
in men great in all departments of human activity,
which was to intellectual Europe, in the sixteenth
and seventeenth centuries, what Germany is in the
nineteenth. It was in Italy, and from Italian
teachers, that Harvey received the most import-
ant part of his scientific education. And it was
a student trained in the same schools, Francesco
Redi — a man of the widest knowledge and most
versatile abilities, distinguished alike as scholar,
poet, physician, and naturalist — who, just two
hundred and two years ago, pubhshed his " Esper-
ienze intorno alia Generazione degl' Insetti," and
gave to the world the idea, the growth of which it
is my purpose to trace. Redi's book went through
five editions in twenty years; and the extreme

parentibns sui dissimilibus proveniant." Again, in Dc Uteri
Mcmbrmiis :—'' In cunctorum viventium generatione (sicut
diximus) hoc solenne est, ut ortum ducunt a primordio alifjuo,
quod turn materiani turn efficiendi potestatem in se habet :
sitque adeo id, ex quo et a quo quicqiiid nascitur, ortum suum
ducat. Tale piimordium in animalibus {sivc ab aliis gcnerantibus
proveniant, sivc sponte, aut ex pntredi.nc nascentttr) est humor
in tunica aliqua aut putami ne conchisus." Compare also
what Redi has to say respecting Harvey's opinions, Ei'2)erienzef
p. 11.

234 BIOGENESIS AND ABIOGENESIS vill

simplicity of his experiments, and the clearness
of his arguments, gained for his views, and
for their consequences, almost universal accept-
ance.

Redi did not trouble himself much with specu-
lative considerations, but attacked particular cases
of what was supposed to be " spontaneous genera-
tion" experimentally. Here are dead animals, or
pieces of meat, says he ; I expose them to the air
in hot weather, and in a few days they swarm with
maggots. You tell me that these are generated
in the dead flesh; but if I put similar bodies,
while quite fresh, into a jar, and tie some fine
gauze over the top of the jar, not a maggot makes
its appearance, while the dead substances, never-
theless, putrefy just in the same way as before.
It is obvious, therefore, that the maggots are not
generated by the corruption of the meat ; and that
the cause of their formation must be a some-
thing which is kept away by gauze. But gauze
will not keep away aeriform bodies, or fluids.
This something must, therefore, exist in the
form of solid particles too big to get through
the gauze. Nor is one long left in doubt
what these solid particles are ; for the blow-
flies, attracted by the odour of the meat, swarm
round the vessel, and, urged by a powerful
but in this case misleading instinct, lay eggs out
of which maggots are immediately hatched, upon
the gauze. The conclusion, therefore, is un-

VIII BIOGENESIS AND ABIOGENESIS 235

avoidable ; the maggots are not generated by the
meat, but the eggs which give rise to them are
brought through the air by the flies.

These experiments seem almost childishly
simple, and one wonders how it was that no one
ever thought of them before. Simple as they are,
however, they are worthy of the most careful study,
for every piece of experimental work since done,
in regard to this subject, has been shaped upon
the model furnished by the Italian philosopher.
As the results of his experiments were the same,
however varied the nature of the materials he
used, it is not wonderful that there arose in Redi's
mind a presumption, that, in all such cases of the
seeming production of life from dead matter,
the real explanation was the introduction of
hving germs from without into that dead matter.^

^ " Pure contentandomi semprein questa ed in ciascuna altro
cosa, da eiascuno piu savio, la dove io difettuosamente ])arlassi,
e.sser corretto ; nontaceio, cheper molteosservazioni molti volti
da nie fatte, mi sento inclinato a credere che la terra, da quelle
prime piaute, e da quel primi aniiuali in poi, che ella nei primi
giorni del mondo produsse per comandemento del sovrano ed
omnipotente Fattore, non abbiamaipiii prodotto da se medesima
lie erba ne albero, ne animale alcuno porfetto o imperfetto che
ei se fosse ; e che tutto quello, che ne' tempi trapassati e nato
e che ora nascere in lei, o da lei veggiamo, venga tutto dalla
semenza reale e vera delle piante, e degli animali stessi, i quali
col mezzo del proprio seme la loro spezie conservano. E se hene
tutto giorno scorghiamo da' cadaveri degli animali, e da tutte
quante le maniere dell' erbe, e de' fiori, e dei frutti imputriditi,
e corrotti nascere vermi infiniti —

' Nonne vides qusecunque mora, fluidoque calore

Corpora tabescunt in parva animalia verti ' —

Io mi sento, dico, inclinato, a credere che tutti quel vermi si

236 BIOGENESIS AND ABIOGENESIS vm

And thus the hypothesis that living matter always
arises by the agency of pre-existing Hving matter,
took definite shape ; and had, henceforward, a
right to be considered and a claim to be refuted, in
each particular case, before the production of Hving
matter in any other way could be admitted by
careful reasoners. It will be necessary for me to
refer to this h}^othesis so frequently, that, to save
circumlocution, I shall call it the hypothesis of
Biogenesis ; and I shall term the contrary doctrine
— that living matter may be produced by not
living matter — the h}^othesis of Abio genesis.

In the seventeenth century, as I have said, the
latter was the dominant view, sanctioned ahke by
antiquity and by authority; and it is interesting
to observe that Redi did not escape the customary
tax upon a discoverer of having to defend himself
against the charge of impugning the authority of
the Scriptures ; ^ for his adversaries declared that

generino dal seme paterno ; e che le carni, e T erbe, e 1' altre
cose tutte putrefatte, o putrefattibili non facciano altra parte,
re abbiano altro ufizio nella generazione degl' insetti, se non
•d'apprestare un luogo o un nido proporzionato, in cui dagli
aniraali nel tempo della figliatura sieno portati, e partoriti i
vermi, o 1' nova o 1' altre semenze del vermi, i quali tosto che
nati sono, trovano in esso nido nn suflBciente alimento abilissimo
per nutricarsi : e se in queUo non son portate dalle madri queste
suddette semenze, niente mai, e replicatameute niente, vis'in-
gegnevi e nasca." — Redi, Espcricnzc, pp. 14-16.

^ " ilolti, e molti altri aneora vi potrei annoverare, se non
fossi chiamato a rispondere alle rampogne di alcuni, che brusca-
mente mi rammentano cio, che si legge nel capitolo qnattor-
dicesimo del sacrosanto Libro de' giudici. . . ." — Redi, loc. cit,
p. 45.

VIII BIOGENESIS AND ABIOGENESIS 237

the generation of bees from the carcase of a dead
lion is affirmed, in the Book of Judges, to have
been the origin of the famous riddle with which
Samson perplexed the Philistines : —

" Out of the eater came fortli meat,
And out of the strong came forth sweetness."

Against all odds, however, Redi, strong with
the strength of demonstrable fact, did splendid
battle for Biogenesis; but it is remarkable that
he held the doctrine in a sense which, if he had
lived in these times, would have infallibly caused
him to be classed among the defenders of " spon-
taneous generation." " Omne vivum ex vivo,"
*' no life without antecedent life," aphoristically
sums up Redi's doctrine ; but he went no further.
It is most remarkable evidence of the philosophic
caution and impartiality of his mind, that although
he had speculatively anticipated the manner in
which grubs really are deposited in jfruits and in
the galls of plants, he deliberately admits that the
evidence is insufficient to bear him out; and he
therefore prefers the supposition that they are
generated by a modification of the living substance
of the plants themselves. Indeed, he regards
these vegetable growths as organs, by means of
which the plant gives rise to an animal, and looks
upon this production of specific animals as the
final cause of the gaUs and of, at any rate, some
fruits. And he proposes to explain the occurrence

238 BIOGENESIS AND ABIOGENESIS vill

of parasites within the animal body in the same
way.^

1 The passage {Espericnze, p. 129) is worth quoting in full :—
" Se dovessi palesarvi il mio sentimento crederei che i frutti,
i logumi, gli alberi e le foglie, in due nianiere inverminassero.
Una, perche venendo i bachi ])er di fuora, e cercando 1' alimento,
col rodere ci aprono la strada, ed arrivano alia \>i\x interna
midolla de' frutti e de' legni. L'altra nianiera si e, che io ptr
me stimerei, che non fosse gran fatto disdicevole il credere, che
queir anima o quella virt'i la quale genera i fiori ed i frutti
nelle piante viventi, sia quella stessa che generi ancora i bachi
di esse piante. E chi sa forse, che molti frutti degli alberi non
sieno prodotti, non per un fine primario e principale, ma bensi
per un uffizio secondario e servile, destinato alia generazione di
que' vermi, servendo a lore in vece di matrice, in cui dimorino
un prefisso e determiuato tempo ; 11 quale arrivato escan fuora a
godere il sole.

** Io m' immagino, che questo mio pensiero non viparra total-
mente un paradosso ; mentre farete riflessione a quelle tante
sorte di galle, di gallozzole, di coccole, di ricci, di calici, di
cornetti ed i lappole, che son produtte dalle quercel, dalle farnie,
da' cerri, da' su.heri, da' lecci e da altri simili alberi da ghianda ;
imperciocche in quelle gallozzole, e jtarticolarmente nelle piii
grosse, che si chiamano coronati, ne" ricci capelluti, che ciuttbli
da' nostri contadini son detti ; nei ricci legnosi del cerro, iie'
ricci stellati della querela, nelle galluzze della foglia del leccio si
vede eviilentissimameute, che la prima e principale intenzione
della natura e formare dentro di quelle un animale volante ;
vedendosi nel centro della gallozzola un novo, che col crescere e col
maturarsi di essa gallozzola va crescendo e maturando anch'
egli, e cresce altresi a suo tempo quel vermc, chn nell' novo si
racchiude ; il qual verme, quando la gallozzola e tinita di matu-
rare e che e venuto il termine destinato al suo nascimento,
diventa, di verme che era, una mosca. . . . Io vi confesso in-
genuamente, che prima d'aver fatte queste mie esperienze intorno
alia generazione degl' insetti mi dava a credere, o per dir meglio
sospettava, che forse la gallozzola nascesse, perche arrivando la
mosca nel tempo della primavera, e facendo una }>iccolissima
fessura ne' rami piu teneri dt-lla querela, in quella fessura nas-
condesse uno de suol semi, 11 quale fosse cagione che sbocciasse
fuora la gallozzola ; e che mai non si vedessero galle o gallozzole
o ricci o cornetti o calici o coccole, se non in que' rami, ne' quali
le mosche avessero depositate le lore semenze ; e ml dava ad
intendere, che le gallozzole fossero una malattla cagiouata nelle

VIII BIOGENESIS AND ABIOGENESIS 239

It is of great importance to apprehend Redi's
position rightly ; for the hnes of thought he laid
down for us are those upon which naturalists have
been working ever since. Clearly, he held Bio-
genesis as against Abio genesis ; and I shall imme-
diately proceed, in the first place, to inquire how
far subsequent investigation has borne him out in
so doing.

But Redi also thought that there were two
modes of Biogenesis. By the one method, which
is that of common and ordinary occurrence, the
living parent gives rise to offspring which passes
through the same cycle of changes as itself — like
gives rise to like ; and this has been termed
Hcmogenesis. By the other mode, the living
parent was supposed to give rise to offspring
which passed through a totally different series of
states from those exhibited by the parent, and
did not return into the cycle of the parent ; this
is what ought to be called Hetero genesis, the off-
spring being altogether, and permanently, unlike
the parent. The term Heterogenesis, however,
has unfortunately been used in a different sense,
and M. Milne-Edwards has therefore substituted
for it Xenogenesis, which means the generation of
something foreign. After discussing Redi's hypo-
thesis of universal Biogenesis, then, I shall go

qiierce dalle punture delle mosche, in quella giusa stessa che
dalle puuture d' altri animaletti simiglievoli veggiamo crescere
de' tumori ue' coi-pi degli animali."

240 BIOGENESIS AND ABIOGENESIS vill

on to ask how far the growth of science justifies
his other hypothesis of Xenogenesis.

The progress of the hypothesis of Biogenesis
was triumphant and unchecked for nearly a
century. The apphcation of the microscope to
anatomy in the hands of Grew, Leeuwenhoek,
Swammerdam, Lyonnet, Vallisnieri, Reaumur, and
other illustrious investigators of nature of that
day, disjDlayed such a complexity of organisation
in the lowest and minutest forms, and everywhere
revealed such a prodigahty of provision for their
multiplication by germs of one sort or another,
that the hypothesis of Ahiogenesis began to
appear not only untrue, but absurd ; and, in the
middle of the eighteenth century, when Needham
and Buffon took up the question, it was almost
universally discredited.^

But the skill of the microscope makers of the
eighteenth century soon reached its limit. A
microscope magnifying 400 diameters was a chef
d'ceuvre of the opticians of that day; and, at the
same time, by no means trustworthy. But a
magnifying power of 400 diameters, even when

^ Needham, writing in 1750, says : —

" Les naturalistes modernes s'accordent nnaninenient aetablir,
comme nne verite certaine, que toute plante vient de sa semence
specihque, tout animal d'un ceuf ou de quelque chose d'analogue
pieexistant dans la plante, ou dans Tanimal de meme espece qui
I'a produit." — Nouvdles Observations, p. 169.

"Les naturalistes ont generalemente era que les animaux
microscopiques etaient engendres par des oeufs transportes dans
I'air, ou deposes dans des eaux donnantes par des insectes
volans," — Ihid. p. 176,

VIII BIOGENESIS AND ABIOGENESIS 241

definition ]:eaclies the exquisite perfection of our
modem achromatic lenses, hardly suffices for the
mere discernment of the smallest forms of life.
A speck, only gV^^ ^^ ^^ ii^ch in diameter, has, at
ten inches from the eye, the same apparent size
as an object looooth of an inch in diameter,
when magnified 400 times; but forms of living
matter abound, the diameter of which is not more
than xo-o-cro-^^ of an inch. A filtered infusion of
hay, allowed to stand for two days, will swarm
with living things among which, any which
reaches the diameter of a human red blood-
corpuscle, or about 3^0*^^ ^f ^n inch, is a giant.
It is only by bearing these facts in mind, that we
can deal fairly with the remarkable statements
and speculations put forward by Bufifon and
Needham in the middle of the eig^hteenth
century.

When a portion of any animal or vegetable
body is infused in water, it gradually softens and
disintegrates; and, as it does so, the water is
found to swarm with minute active creatures, the
so-called Infusorial Animalcules, none of which
can be seen, except by the aid of the microscope ;
while a large proportion belong to the category of
smallest things of which I have spoken, and
which must have looked like mere dots and lines
under the ordinary microscopes of the eighteenth
century.

Led by various theoretical considerations which
202

242 BIOGENESIS AND ABIOGENESIS viil

I cannot now discuss, but which looked promising
enouofh in the lio-hts of their time, Buffon and
Needham doubted the applicabihty of Redi's
hypothesis to the infusorial animalcules, and
Needham very properly endeavoured to put the
question to an experimental test. He said to
himself, If these infusorial animalcules come from
germs, their germs must exist either in the sub-
stance infused, or in the water with which the
infusion is made, or in the superjacent air. Now
the vitality of all germs is destroyed by heat.
Therefore, if I boil the infusion, cork it up care-
fully, cementing the cork over with mastic, and
then heat the whole vessel by heaping hot ashes
over it, I must needs kill whatever germs are
present. Consequently, if Redi's hypothesis hold
good, when the infusion is taken away and allowed
to cool, no animalcules ought to be developed in
it ; whereas, if the animalcules are not dependent
on pre-existing germs, but are generated from the
infused substance, they ought, by and by, to make
their appearance. Needham found that, under
the circumstances in which he made his experi-
ments, animalcules always did arise in the
infusions, when a sufficient time had elapsed to
allow for their development.

In much of his work Needham was associated
with BufiPon, and the results of their experiments
fitted in admirably with the great French natural-
ist's hypothesis of " organic molecules," according

VIII BIOGENESIS AND ABIOGENESIS 243

to which, Kfe is the indefeasible property of certain
indestructible molecules of matter, which exist in
all livinor thino^s, and have inherent activities
by which they are distinguished from not hving
matter. Each individual living organism is
formed by their temporary combination. They
stand to it in the relation of the particles of
water to a cascade, or a whirlpool ; or to a mould,
into which the water is poured. The form of the
organism is thus determined by the reaction
between external conditions and the inherent
activities of the organic molecules of which it is
composed; and, as the stoppage of a whirlpool
destroys nothing but a form, and leaves the
molecules of the water, with all their inherent
activities intact, so what we call the death and
putrefaction of an animal, or of a plant, is merely
the breaking up of the form, or manner of asso-
ciation, of its constituent organic molecules, which
are then set free as infusorial animalcules.

It will be perceived that this doctrine is by no
means identical with Abiogenesis, with which it is
often confounded. On this h\^othesis, a piece of
beef, or a handful of hay, is dead only in a limited
sense. The beef is dead ox, and the hay is dead
grass ; but the " organic molecules " of the beef or
the hay are not dead, but are ready to manifest
their vitality as soon as the bovine or herbaceous
shrouds in which they are imprisoned are rent by
the macerating action of water. The h3rpothesi3

244 BIOGENESIS AND ABIOGENESIS \m

therefore must be classified under Xenogenesis,
rather than under Abiogenesis. Such as it was, I
think it will appear, to those who will be just
enough to remember that it was propounded
before the birth of modern chemistry, and of the
modern optical arts, to be a most ingenious and
suggestive speculation.

But the great tragedy of Science — the slaying of
a beautiful hypothesis by an ugly fact — which is so
constantly being enacted under the eyes of philo-
sophers, was played, almost immediately, for the
benefit of Buff on and Needham.

Once more, an Italian, the Abbt^ Spallanzani, a
worthy successor and representative of Redi in his
acuteness, his ingenuity, and his learning, sub-
jected the experiments and the conclusions of
Needham to a searching criticism. It might be
true that Needham's experiments yielded results
such as he had described, but did they bear out
his arguments ? Was it not possible, in the first
place, he had not completely excluded the air by his
corks and mastic ? And was it not possible, in the
second place, that he had not sufficiently heated
his infusions and the superjacent air ? Spallan-
zani joined issue with the English naturalist on
both these pleas, and he showed that if, in the first
place, the glass vessels in which the infusions were
contained were hermetically sealed by fusing their
necks, and if, in the second place, they were ex-
posed to the temperature of boiling water for

vm BIOGENESIS AND ABIOGENESIS 245

three-quarters of an hour/ no animalcules ever
made their appearance within them. It must be
admitted that the experiments and arguments of
Spallanzani furnish a complete and a crushing
reply to those of Needham. But we all too often
forget that it is one thing to refute a proposition,
and another to prove the truth of a doctrine which,
imphcitly or explicitly, contradicts that propo-
sition ; and the advance of science soon showed
that though Needham might be quite wrong, it
did not follow that Spallanzani was quite right.

Modern Chemistry, the birth of the latter half
of the eighteenth century, grew apace, and soon
found herself face to face with the great problems
which biology had vainly tried to attack without
her help. The discovery of oxygen led to the lay-
ing of the foundations of a scientific theory of
respiration, and to an examination of the marvel-
lous interactions of organic substances with
oxygen. The presence of free oxygen appeared to
be one of the conditions of the existence of life,
and of those singular changes in organic matters
which are known as fermentation and putrefaction.
The question of the generation of the infusory
animalcules thus passed into a new phase. For
what might not have happened to the organic
matter of the infusions, or to the oxygen of the
air, in Spallanzani's experiments ? What security
was there that the development of life which ought

* See Spallanzani, Opere, vi. pp. 42 and 51.

246 BIOGENESIS AND ABIOGENESIS viil

to have taken place had not been checked or pre-
vented by these changes ?

The battle had to be fought again. It was need-
ful to repeat the experiments under conditions
which would make sure that neither the oxygen of
the air, nor the composition of the organic matter,
was altered in such a manner as to interfere with
the existence of life.

Schulze and Schwann took up the question from
this point of view in 1836 and 1837. The passage
of air through red-hot glass tubes, or through
strong sulphuric acid, does not alter the propor-
tion of its oxygen, while it must needs arrest, or
destroy, any organic matter which may be con-
tained in the air. These experimenters, therefore,
contrived arrangements by which the only air
which should come into contact with a boiled in-
fusion should be such as had either passed through
red-hot tubes or through strong sulphuric acid.
The result which they obtained was that an in-
fusion so treated developed no living things, while,
if the same infusion was afterwards exposed to the
air, such things appeared rapidly and abundantly.
The accuracy of these experiments has been
alternately denied and affirmed. Supposing them
to be accepted, however, all that they really proved
was that the treatment to which the air was
subjected destroyed something that was essential
to the development of life in the infusion. This
" something " might be gaseous, fluid, or solid ;

VIII BIOGENESIS AND ABIOGENESIS 247

that it consisted of germs remained only an hypo-
thesis of greater or less probability.

Contemporaneously with these investigations a
remarkable discovery was made by Cagniard de la
Tour. He found that common yeast is com-
posed of a vast accumulation of minute plants.
The fermentation of must, or of wort, in the
fabrication of wine and of beer, is always accom-
panied by the rapid growth and multiplication of
these Torulce. Thus, fermentation, in so far as it
was accompanied by the development of micro-
scopical organisms in enormous numbers, became
assimilated to the decomposition of an infusion of
ordinary animal or vegetable matter ; and it was
an obvious suggestion that the organisms were, in
some way or other, the causes both of fermentation
and of putrefaction. The chemists, with Berzelius
and Liebig at their head, at first laughed this idea
to scorn ; but in 1843, a man then very young,
who has since performed the unexampled feat of
attaining to high eminence alike in Mathematics,
Physics, and Physiology — I speak of the illustrious
Helmholtz — reduced the matter to the test of
experiment by a method alike elegant and con-
clusive. Helmholtz separated a putrefying or a
fermenting liquid from one which was simply
putrescible or fermentable by a membrane Avhich
allowed the fluids to pass through and become
intermixed, but stopped the passage of solids.
The result was, that while the putrescible or the

248 BIOGENESIS AND ABIOGENESIS VIII

fermentable liquids became impregnated with the
results of the putrescence or fermentation which
was sfoins: on on the other side of the membrane,
they neither putrefied (in the ordinary way) nor
fermented ; nor were any of the organisms which
abounded in the fermenting or putrefying liquid
generated in them. Therefore the cause of the
development of these organisms must lie in some-
thing which cannot pass through membranes ; and
as Helmholtz's investigations were long antecedent
to Graham's researches upon colloids, his natural
conclusion was that the agent thus intercepted
must be a solid material. In point of fact.
Helmholtz's experiments narrowed the issue to
this : that which excites fermentation and putre-
faction, and at the same time gives rise to living
forms in a fermentable or putrescible fluid, is not
a ofas and is not a diffusible fluid ; therefore it is
either a colloid, or it is matter divided into very
minute solid particles.

The researches of Schroeder and Dusch in 1854,
and of Schroeder alone, in 1859, cleared up this
point by experiments which are simply refine-
ments upon those of Redi. A lump of cotton-wool
is, physically speaking, a pile of many thicknesses
of a very fine gauze, the fineness of the meshes of
which depends upon the closeness of the compres-
sion of the wool. Now, Schroeder and 'Dusch
found, that, in the case of all the putrefiable
materials which they used (except milk and yolk

VIII BIOGENESIS AND ABIOGENESIS 249

of egg), an infusion boiled, and then allowed to
come into contact with no air but such as had
been filtered through cotton-wool, neither putre-
fied, nor fermented, nor developed Hving forms.
It is hard to imagine what the fine sieve formed
by the cotton-wool could have stopped except
minute soHd particles. Still the evidence was
incomplete until it had been positively sho^^Ti,
first, that ordinary air does contain such particles ;
and, secondly, that filtration through cotton-wool
arrests these particles and allows only physically
pure air to pass. This demonstration has been
furnished within the last year by the remarkable
experiments of Professor Tyndall. It has been a
common objection of Abiogenists that, if the
doctrine of Biogeny is true, the air must be thick
with germs ; and they regard this as the height of
absurdity. But nature occasionally is exceedingly
unreasonable, and Professor TjTidall has proved
that this particular absurdity may nevertheless be
a reality. He has demonstrated that ordinary air
is no better than a sort of stirabout of excessively
minute solid particles; that these particles are
almost wholly destructible by heat ; and that they
are strained off, and the air rendered optically
pure, by its being passed through cotton -wool

It remains yet in the order of logic, though
not of history, to show that among these solid
destructible particles, there really do exist germs
capable of giving rise to the development of living

250 BIOGENESIS AND ABIOGENESIS viii

forms in suitable menstrua. This piece of work was
done by M. Pasteur in those beautiful researches
which will ever render his name famous; and
which, in spite of all attacks upon them, appear
to me now, as they did seven years ago,^ to be
models of accurate experimentation and logical
reasoning. He strained air through cotton-wool,
and found, as Schroeder and Dusch had done, that
it contained nothing competent to give rise to the
development of life in fluids highly fitted for that
purpose. But the important further links in the
chain of evidence added by Pasteur are three. In
the first place he subjected to microscopic exam-
ination the cotton-wool which had served as
strainer, and found that sundry bodies clearly
recognisable as germs, were among the solid
particles strained off. Secondly, he proved that
these germs were competent to give rise to living
forms by simply sowing them in a solution fitted
for their development. And, thirdly, he showed
that the incapacity of air strained through cotton-
wool to give rise to life, was not due to any occult
change effected in the constituents of the air by
the wool, by proving that the cotton-wool might
be dispensed with altogether, and perfectly free
access left between the exterior air and that in the
experimental flask. If the neck of the flask is
dra^vn out into a tube and bent downwards ; and

' Lectures to Working Men on the Caicses of the Phenomena of
Organic Nature^ 1863. (See Vol. II. of these Essays.)

VIII BIOGENESIS AND ABIOGENESIS 251

if, after the contained fluid has been carefully
boiled, the tube is heated sufficiently to destroy
any germs which may be present in the air which
enters as the fluid cools, the apparatus may be
left to itself for any time and no life will appear
in the fluid. The reason is plain. Although there
is free communication between the atmosphere
laden with germs and the germless air in the flask,
contact between the two takes place only in the
tube ; and as the germs cannot fall upwards, and
there are no currents, they never reach the interior
of the flask. But if the tube be broken short off
where it proceeds from the flask, and free access
be thus given to germs falling vertically out of
the air, the fluid, which has remained clear and
desert for months, becomes, in a few days, turbid
and full of life.

These experiments have been repeated over and
over again by independent observers with entire
success; and there is one very simple mode of
seeing the facts for one's self, which I may as well
describe.

Prepare a solution (much used by M. Pasteur,
and often called " Pasteur's solution " ) composed
of water with tartrate of ammonia, sugar, and
yeast-ash dissolved therein.^ Divide it into three
portions in as many flasks; boil all three for a

^ Infusion of hay treated in the same way yields similar
results ; but as it contains organic matter, the argument wliich
follows cannot be based upon it.

252 BIOGENESIS AND ABIOGENESIS Tin

quarter of an hour ; and, while the steam is passing
out, stop the neck of one with a large plug of
cotton-wool, so that this also may be thoroughly
steamed. Now set the flasks aside to cool, and,
when their contents are cold, add to one of the open
ones a drop of filtered infusion of hay which has
stood for twenty-four hours, and is consequently
full of the active and excessively minute organisms
known as Bacteria. In a couple of days of ordinary
warm weather the contents of this flask will be
milky from the enormous multij)lication of Bacteria.
The other flask, open and exposed to the air, will,
sooner or later, become milky with Bacteria, and
patches of mould may appear in it ; while the liquid
in the flask, the neck of which is plugged with
cotton-wool, will remain clear for an indefinite
time. I have sought in vain for any explanation
of these facts, excejDt the obvious one, that the air
contains germs competent to give rise to Bacteria,
such as those with which the first solution has
been knowingly and purposely inoculated, and to
the m.OM\di-Fungi. And I have not yet been able
to meet with any advocate of Abiogenesis who
seriously maintains that the atoms of sugar, tar-
trate of ammonia, yeast-ash, and water, under no in-
fluence but that of free access of air and the ordinary
temperature, re-arrange themselves and give rise
to the protoplasm of Bacterium. But the alterna-
tive is to admit that these Bacteria arise from
germs in the air ; and if they are thus propagated,

VIII BIOGENESIS AND ABIOGENESIS 253

the burden of proof that other Kke forms are
generated in a different manner, must rest with
the assertor of that proposition.

To sum up the effect of this long chain of
evidence : —

It is demonstrable that a fluid eminently fit for
the development of the lowest forms of life, but
which contains neither germs, nor any protein
compound, gives rise to living things in great
abundance if it is exposed to ordinary air ; while
no such development takes place, if the air with
which it is in contact is mechanically freed from
the solid particles which ordinarily float in it, and
which may be made visible by appropriate means

It is demonstrable that the great majority of
these particles are destructible by heat, and that
some of them are germs, or living particles, capable
of giving rise to the same forms of life as those
which appear when the fluid is exposed to un-
purified air.

It is demonstrable that inoculation of the ex-
perimental fluid with a drop of Hquid known to
contain living particles gives rise to the same
phenomena as exposure to unpurified air.

And it is further certain that these hvino*

o

particles are so minute that the assumption of
their suspension in ordinary air presents not the
slightest difliculty. On the contrary, considering
their lightness and the wide diffusion of the
organisms which produce them, it is impossible to

254 BIOGENESIS AND ABICGENESIS viii

conceive that they should not be suspended in the
atmosphere in myriads.

Thus the evidence, direct and indirect, in favour
of Biogenesis for all known forms of life must, I
think, be admitted to be of great weight.

On the other side, the sole assertions worthy
of attention are that hermetically sealed fluids,
which have been exposed to great and long-con-
tinued heat, have sometimes exhibited living
forms of low organisation when they have been
opened.

The first reply that suggests itself is the prob-
ability that there must be some error about these
experiments, because they are performed on an
enormous scale every day with quite contrary
results. Meat, fruits, vegetables, the very ma-
terials of the most fermentable and putrescible
infusions, are preserved to the extent, I suppose I
may say, of thousands of tons every year, by a
method which is a mere application of Spallan-
zani's experiment. The matters to be preserved
are well boiled in a tin case provided with a small
hole, and this hole is soldered up when all the air
in the case has been replaced by steam. By this
method they may be kept for years without
putrefying, fermenting, or getting mouldy. Now
this is not because oxygen is excluded, inasmuch
as it is now proved that free oxygen is not neces-
sary for either fermentation or putrefaction. It
is not because the tins are exhausted of air, for

VIII BIOGENESIS AND ABIOGENESIS 255

Vihriones and Bacteria live, as Pasteur has shown,
without air or free oxygen. It is not because the
boiled meats or vegetables are not putrescible or
fermentable, as those who have had the misfortune
to be in a ship supplied with unskilfully closed
tins well know. What is it, therefore, but the
exclusion of germs ? I think that Abiogenists are
bound to answer this question before they ask us
to consider new experiments of precisely the same
order.

And in the next place, if the results of the
experiments I refer to are really trustworthy, it
by no means follows that Abiogenesis has taken
place. The resistance of living matter to heat is
known to vary within considerable limits, and to
depend, to some extent, upon the chemical and
physical qualities of the surrounding medium.
But if, in the present state of science, the alter-
native is offered us, — either germs can stand a
greater heat than has been supposed, or the mole-
cules of dead matter, for no valid or intellimble
reason that is assigned, are itble to re-arrange
themselves into living bodies, exactly such as can
be demonstrated to be frequentl}' produced in
another way, — I cannot understand how choice
can be, even for a moment, doubtful.

But though I cannot express this conviction of
mine too strongly, I must carefully guard myself
against the supposition that I intend to suggest
that no such thing as Abiogenesis ever has taken

256 BIOGENESIS AND ABIOGENESIS vill

place in the past, or ever will take place in
the future. With organic chemistry, molecular
physics, and physiology yet in their infancy, and
every day making prodigious strides, I think it
would be the height of presumption for any man
to say that the conditions under which matter
assumes the properties we call " vital " may not,
some day, be artificially brought together. All I
feel justified in affirming is, that I see no reason
for believing that the feat has been performed
yet.

And looking back through the prodigious vista
of the past, I find no record of the commencement
of life, and therefore I am devoid of any means of
forming a definite conclusion as to the conditions
of its appearance. Belief, in the scientific sense
of the word, is a serious matter, and needs strong
foundations. To say, therefore, in the admitted
absence of evidence, that I have any belief as to
the mode in which the existing forms of life have
originated, would be using words in a wrong sense.
But expectation is permissible where belief is
not ; and if it were given me to look beyond the
abyss of geologically recorded time to the still
more remote period when the earth was passing
through physical and chemical conditions, which
it can no more see again than a man can recall
his infancy, I should expect to be a witness of the
evolution of living protoplasm from not living
matter. I should expect to see it appear under

V'lir BIOGENESIS AND ABIOGENESIS 257

forms of great simplicity, endowed, like existing
fungi, with the power of determining the formation
of new protoplasm from such matters as ammonium
carbonates, oxalates and tartrates, alkaline and
earthy phosphates, and water, without the aid of
light. That is the expectation to which analogi-
cal reasoning leads me ; but I beg you once more
to recollect that I have no right to call my
opinion anything but an act of philosophical
faith.

So much for the history of the progress of
Redi's great doctrine of Biogenesis, which appears
to me, with the limitations I have expressed, to
be victorious along the whole line at the present
day.

As regards the second problem offered to us by
Redi, whether Xenogenesis obtains, side by side
with Homogenesis, — whether, that is, there exist
not only the ordinary living things, giving rise to
offspring which run through the same cycle as
themselves, but also others, producing offspring
which are of a totally different character from
themselves, — the researches of two centuries have
led to a different result. That the grubs found
in galls are no product of the plants on
which the galls grow, but are the result of the
introduction of the eggs of insects into the sub-
stance of these plants, was made out by Vallisnieri,
Reaumur, and others, before the end of the first
half of the eighteenth century. The tapeworms,

203

258 BIOGENESIS AXD ABIOGENESIS viii

bladderworms, and flukes continued to be a
stronghold of the advocates of Xenogenesis for a
much longer period. Indeed, it is only within the
last thirty years that the splendid patience of Von
Siebold, Van Beneden, Leuckart, Kuchenmeister,
and other helminthologists, has succeeded in
tracing every such parasite, often through the
strangest wanderings and metamorphoses, to an
egg derived from a parent, actually or potentially
like itself; and the tendency of inquiries else-
where has all been in the same direction. A
plant may throw off bulbs, but these, sooner or
later, give rise to seeds or spores, which develop
into the original form. A poh^pe may give rise
to Medusae, or a pluteus to an Echinoderm, but
the Medusa and the Echinoderm give rise to eggs
which produce polypes or plutei, and they are
therefore only stages in the cycle of life of the
species.

But if we turn to pathology, it offers us some
remarkable approximations to true Xenogenesis.

As I have already mentioned, it has been
known since the time of Vallisnieri and of
Reaumur, that galls in plants, and tumours in
cattle, are caused by insects, which lay their eggs
in those parts of the animal or vegetable frame of
which these morbid structures are outgrowths.
Again, it is a matter of familiar experience to
everybody that mere pressure on the skin will
give rise to a corn. Now the gall, the tumour.

Viir BIOGENESIS AND ABIOGENESIS 259

and the corn are parts of the living body, which
have become, to a certain degree, independent and
distinct organisms. Under the influence of cer-
tain external conditions, elements of the body,
which should have developed in due subordination
to its general plan, set up for themselves and
apply the nourishment which they receive to their
own purposes.

From such innocent productions as corns and
warts, there are all gradations to the serious
tumours which, by their mere size and the
mechanical obstruction they cause, destroy the
organism out of which they are developed ; while,
finally, in those terrible structures known as
cancers, the abnormal growth has acquired powers
of reproduction and multiplication, and is only
morphologically distinguishable from the parasitic
worm, the life of which is neither more nor less
closely bound up with that of the infested
organism.

If there were a kind of diseased structure, the
histological elements of which were capable of
maintaining a separate and independent existence
out of the body, it seems to me that the shadowy
boundary between morbid growth and Xeno-
genesis would be effaced. And I am inclmed to
think that the progress of discovery has almost
brought us to this point already. I have been
favoured by Mr. Simon with an early copy of the
last published of the valuable " Reports on the

260 BIOGENESIS AND ABIOGENESIS viii

Public Health," wliich, in his capacity of their
medical officer, he annually presents to the Lords
of the Privy Council. The appendix to this
report contains an introductory essay " On the
Intimate Pathology of Contagion," by Dr. Burdon-
Sanderson, which is one of the clearest, most
comprehensive, and well-reasoned discussions of a
great question which has come under my notice
for a long time. I refer you to it for details and
for the authorities for the statements I am about
to make.

You are familiar with what happens in vaccina-
tion A minute cut is made in the skin, and an
infinitesimal quantity of vaccine matter is mserted
into the wound. Within a certain time a vesicle
appears in the place of the wound, and the fluid
which distends this vesicle is vaccine matter, in
quantity a hundred or a thousandfold that which
was originally inserted. Now what has taken
place in the course of this operation ? Has the
vaccine matter, by its irritative property, produced
a mere blister, the fluid of which has the same
irritative property? Or does the vaccine matter
contain living particles, which have grown and
multiplied where they have been planted ? The
observations of M. Chauveau, extended and con-
firmed by Dr. Sanderson himself, appear to leave
no doubt upon this head. Experiments, similar
in principle to those of Helmholtz on fermentation
and putrefaction, have proved that the active

VIII BIOGENESIS AND ABIOGENESIS 261

element in the vaccine lympli is non-diffusible,
and consists of minute particles not exceeding
Yoooo^^ of an inch in diameter, which are made
visible in the lymj)h by the microscope. Similar
experiments have proved that two of the most
destructive of epizootic diseases, sheep-pox and
glanders, are also dependent for their existence
and their propagation upon extremely small living
soHd particles, to which the title of microzymes is
appHed. An animal suffering under either of
these terrible diseases is a source of infection and
contagion to others, for precisely the same reason
as a tub of fermenting beer is capable of pro-
pagating its fermentation by "infection," or
"contagion," to fresh wort. In both cases it is
the solid living particles which are efficient ; the
liquid in which they float, and at the expense of
which they live, being altogether passive.

Now arises the question, are these microzjTnes
the results of Homogenesis^ or of Xcnogenesis ? are
they capable, like the Tm^ulce of yeast, of arising
only by the development of pre-existing germs?
or may they be, hke the constituents of a nut-gall,
the results of a modification and individuahsation
of the tissues of the body in which they are
found, resulting from the operation of certain
conditions ? Are they parasites in the zoological
sense, or are they merely what Virchow has called
" heterologous growths " ? It is obvious that this
question has the most profound importance.

262 BIOGENESIS AND ABIOGENESIS vin

whether we look at it from a practical or from a
theoretical point of view. A parasite may be
stamped out by destroying its germs, but a patho-
logical product can only be annihilated by
removing the conditions which give rise to it.

It appears to me that this great problem will
have to be solved for each z}Tnotic disease
separately, for analogy cuts two ways. I have
dwelt upon the analogy of pathological modifi-
cation, which is in favour of the xenogenetic
origin of microzymes; but I must now speak
of the equally strong analogies in favour of the
origin of such pestiferous particles by the ordinary
process of the generation of like from like.

It is, at present, a well-established fact that
certain diseases, both of plants and of animals,
which have all the characters of contagious and
infectious epidemics, are caused by minute organ-
isms. The smut of wheat is a weU-known instance
of such a disease, and it cannot be doubted that
the grape-disease and the potato-disease fall
under the same category. Among animals,
insects are wonderfully liable to the ravages of
contagious and infectious diseases caused by
microscopic Fungi.

In autumn, it is not uncommon to see flies
motionless upon a window-pane, with a sort of
magic circle, in white, drawn round them. On
microscopic examination, the magic circle is found
to consist of innumerable spores, which have been

Viir BIOGENESIS AND ABIOGENESIS 263

thrown off in all directions by a minute fungus
called Empitsa muscce, the spore -forming filaments
of which stand out like a pile of velvet from the
body of the fly. These spore-forming filaments
are connected with others which fill the interior
of the fly's body like so much fine wool, having
eaten away and destroyed the creature's viscera.
This is the full-grown condition of the Unijmsa.
If traced back to its earliest stages, in flies which
are still active, and to all appearance healthy, it
is found to exist in the form of minute corpuscles
which float in the blood of the fly. These multiply
and lengthen into filaments, at the expense of
the fly's substance ; and when they have at last
killed the patient, they grow out of its body and
give off spores. Healthy flies shut up with
diseased ones catch this mortal disease, and
perish like the others. A most competent
observer, M. Cohn, who studied the development
of the Emimsa very carefully, was utterly unable
to discover in what manner the smallest germs
of the Emintsa got into the fly. The spores
could not be made to give rise to such germs by
cultivation ; nor were such germs discoverable in
the air, or in the food of the fly. It looked
exceedingly like a case of Abiogenesis, or, at any
rate, of Xenogenesis ; and it is only quite recently
that the real course of events has been made out.
It has been ascertained, that when one of the
spores falls upon the body of a fly, it begins to

264 BIOGENESIS AND ABIOGENESIS vill

germinate, and sends out a process which bores
its way through the fly's skin ; this, having
reached the interior cavities of its body, gives
off the minute floating corpuscles which are the
earhest stage of the EmjDUsa. The disease is
" contagious," because a healthy fly coming in
contact with a diseased one, from which the
spore-bearing filaments protrude, is pretty sure
to carry off a spore or two. It is " infectious "
because the spores become scattered about all
sorts of matter in the neighbourhood of the slain
flies.

The silkworm has long been known to be
subject to a very fatal and infectious disease
called the Muscardine. Audouin transmitted it
by inoculation. This disease is entirely due to
the development of a fungus, Botrytis Bassiana,
in the body of the caterpillar ; and its contagious-
ness and infectiousness are accounted for in the
same way as those of the fly-disease. But, of
late years, a still more serious epizootic has
appeared among the silkworms ; and I may
mention a few facts which will give you some
conception of the gravity of the injury which it
has inflicted on France alone.

The production of silk has been for centuries
an important branch of industry in Southern
France, and in the year 1853 it had attained
such a magnitude that the annual produce of the
French sericulture was estimated to amount to a

VIII BIOGENESIS AND ABIOGENESIS 265

tenth of that of the whole world, and represented a
money- value of 117,000,000 francs, or nearly five
millions sterling. What may be the sum which
would represent the money-value of all the in-
dustries connected with the working up of the
raw silk thus produced, is more than I can
pretend to estimate. Suffice it to say, that the
city of Lyons is built upon French silk as much
as Manchester was upon American cotton before
the civil war.

Silkworms are liable to many diseases ; and,
even before 1853, a peculiar epizootic, frequently
accompanied by the appearance of dark spots
upon the skin (whence the name of " Pebrine "
which it has received), had been noted for its
mortality. But in the years following 1853 this
malady broke out with such extreme violence,
that, in 1858, the silk -crop was reduced to a third
of the amount which it had reached in 1853 ;
and, up till within the last year or two, it has
never attained half the yield of 1853. This
means not only that the great number of people
engaged in silk growing are some thirty millions
sterling poorer than they might have been; it
means not only that high prices have had to be
paid for imported silkworm eggs, and that, after
investing his money in them, in pajdng for mul-
berry-leaves and for attendance, the cultivator has
constantly seen his silkworms perish and himself
plunged in ruin; but it means. that the looms of

2G6 BIOGENESIS AND ABIOGENESIS vrii

Lyons have lacked employment, and that, for
years, enforced idleness and misery have been
the portion of a vast population which, in former
days, was industrious and well-to-do.

In 1858 the gravity of the situation caused the
French Academy of Sciences to appoint Com-
missioners, of whom a distinguished naturalist,
M. de Quatrefages, was one, to inquire into the
nature of this disease, and, if possible, to devise
some means of staying the plague. In reading
the Report ^ made by M. de Quatrefages in 1859,
it is exceedingly interesting to observe that his
elaborate study of the Pebrine forced the convic-
tion upon his mind that, in its mode of occurrence
and propagation, the disease of the silkworm is, in
every respect, comparable to the cholera among
mankind. But it differs from the cholera, and so
far is a more formidable malady, in being here-
ditary, and in being, under some circumstances,
contagious as well as infectious.

The Italian naturalist, Filippi, discovered in the
blood of the silkworms affected by this strange
disorder a multitude of cyHndrical corpuscles, each
about 6 oVo^ii of ^^ i^^^^ long. These have been
carefully studied by Lebert, and named by him
Fanhistophyton ; for the reason that in subjects in
which the disease is strongly developed, the cor-
puscles swarm in every tissue and organ of the
body, and even pass into the undeveloped eggs of

1 Et'ides sur les Maladiea actuelles des Vers d Soie, p. 53.

Vin BIOGENESIS AND ABIOGENESIS 267

the female moth. But are these corpuscles
causes, or mere concomitants, of the disease ?
Some naturalists took one view and some another ;
and it was not until the French Government,
alarmed by the continued ravages of the malady,
and the inefficiency of the remedies which had
been suggested, despatched M. Pasteur to study it,
that the question received its final settlement ; at
a great sacrifice, not only of the time and peace of
mind of that eminent philosopher, but, I regret to
have to add, of his health.

But the sacrifice has not been in vain. It is
now certain that this devastating, cholera-like,
Pebrine, is the effect of the growth and multiplica-
tion of the Fanhisto'phyton in the silkworm. It is
contagious and infectious, because the corpuscles
of the Parihisto'phyton pass away from the bodies
of the diseased caterpillars, directly or indirectly,
to the alimentary canal of healthy silkworms in
their neighbourhood ; it is hereditary because the
corpuscles enter into the eggs while they are being
formed, and consequently are carried within them
when they are laid ; and for this reason, also, it
presents the very singular peculiarity of being
inherited only on the mother's side. There is
not a single one of all the apparently capricious
and unaccountable phenomena presented by the
Pebrine, but has received its explanation from the
fact that the disease is the result of the presence
of the microscopic organism Panhistojphyton.

268 BIOGENESIS AND ABIOGENESIS viii

Such being the facts with respect to the Pebrine,
v/hat are the indications as to the method of pre-
venting it ? It is obvious that this depends upon
the way in which the Panhistcphyton is generated.
If it may be generated by Abiogenesis, or by
Xenogenesis, within the silkworm or its moth, the
extirpation of the disease must depend upon the
prevention of the occurrence of the conditions
under which this generation takes place. But if,
on the other hand, the Paiihistophytcn is an inde-
pendent organism, which is no more generated by
the silkworm than the mistletoe is generated by
the apple-tree or the oak on which it grows,
though it may need the silkworm for its develop-
ment in the same way as the mistletoe needs the
tree, then the indications are totally different.
The sole thing to be done is to get rid of and keep
away the germs of the Fanhistophyton. As might
be imagined, from the course of his previous inves-
tigations, M. Pasteur was led to believe that the
latter was the right theory ; and, guided by that
theory, he has devised a method of extirpating the
disease, which has proved to be completely success-
ful wherever it has been properly carried out.

There can be no reason, then, for doubting that,
among insects, contagious and infectious diseases,
of great malignity, are caused by minute organisms
which are produced from pre-existing germs, or by
homogenesis ; and there is no reason, that I know
of, for believing that what happens in insects may

VIII BIOGENESIS AND ABIOGENESIS 269

not take place in the highest animals. Indeed,
there is already strong evidence that some diseases
of an extremely malignant and fatal character to
which man is subject, are as much the work of
minute organisms as is the Pebrine. I refer for
this evidence to the very striking facts adduced
by Professor Lister in his various well-known
pubHcations on the antiseptic method of treat-
ment. It appears to me impossible to rise from
the perusal of those publications without a strong
conviction that the lamentable mortality which so
frequently dogs the footsteps of the most skilful
operator, and those deadly consequences of wounds
and injuries which seem to haunt the very walls
of great hospitals, and are, even now, destroying
more men than die of bullet or bayonet, are due
to the importation of minute organisms into
wounds, and their increase and multiplication ; and
that the surgeon who saves most lives will be he
who best works out the practical consequences of
the hypothesis of Redi.

■ I commenced this Address by asking you to
follow me in an attempt to trace the path which
has been followed by a scientific idea, in its long
and slow progress from the position of a probable
hypothesis to that of an established law of nature.
Our survey has not taken us into very attractive
regions ; it has lain, chiefly, in a land flowing with
the abominable, and peopled with mere grubs and
mouldiness. And it may be imagined with what

270 BIOGENESIS AND ABIOGENESIS vill

smiles and shrugs, practical and serious contempo-
raries of Redi and of Spallanzani may have com-
mented on the waste of their high abilities in
toiling at the solution of problems which, though
curious enough in themselves, could be of no con-
ceivable utility to mankind.

Nevertheless, you will have observed that before
we had travelled very far upon our road, there
appeared, on the right hand and on the left,
fields laden with a harvest of golden grain,
immediately convertible into those things which
the most solidly practical men will admit to have
value — viz., money and life.

The direct loss to France caused by the Pebrine
in seventeen years cannot be estimated at less
than fifty milHons sterling; and if we add to
this what Redi's idea, in Pasteur's hands, has
done for the wine-grower and for the vinegar-
maker, and try to capitalise its value, we shall
find that it will go a long way towards repairing
the money losses caused by the frightful and
calamitous war of this autumn. And as to the
equivalent of Redi's thought in Hfe, how can we
over-estimate the value of that knowledge of the
nature of epidemic and epizootic diseases, and
consequently of the means of checking, or eradi-
cating them, the da^vn of which has assuredly
commenced ?

Looking back no further than ten years, it is
possible to select three (1863, 1864, and 1869) in

VIII BIOGENESIS AND ABIOGENESIS 271

which the total number of deaths from scarlet-
fever alone amounted to ninety thousand. That
is the return of killed, the maimed and disabled
being left out of sight. Why, it is to be hoped
that the list of killed in the present bloodiest
of all wars will not amount to more than this 1
But the facts which I have placed before you
must leave the least sanguine without a doubt
that the nature and the causes of this scourge
will, one day, be as well understood as those
of the Pebrine are now; and that the long-
suffered massacre of our innocents will come to
an end.

And thus mankind will have one more admoni-
tion that " the people perish for lack of know-
ledge " ; and that the alleviation of the miseries,
and the promotion of the welfare, of men must
be sought, by those who will not lose their pains,
in that diligent, patient, loving study of all the
multitudinous aspects of Nature, the results of
which constitute exact knowledge, or Science.
It is the justification and the glory of this great
meeting that it is gathered together for no other
object than the advancement of the moiety of
science which deals with those phenomena of
nature which we call physical. May its en-
deavours be crowned with a full measure of
success I

IX

GEOLOGICAL CONTEMPORANEITY AND
PERSISTENT TYPES OF LIFE

[1862]

Merchants occasionally go through a wholesome,
though troublesome and not always satisfactory,
process which they term " taking stock." After
aU the excitement of speculation, the pleasure of
gain, and the pain of loss, the trader makes up his
mind to face facts and to learn the exact quantity
and quality of his solid and reliable possessions.

The man of science does well sometimes to
imitate this procedure ; and, forgetting for the
time the importance of his own small winnings,
to re-examine the common stock in trade, so that
he may make sure how far the .stock of bullion in
the cellar — on the faith of whose existence so
much paper has been circulating — is really the
solid gold of truth.

The Anniversary Meeting of the Geological

IX

GEOLOGICAL CONTEMPORANEITY 273

Society seems to be an occasion well suited for an
undertaking of this kind — for an inquiry, in fact,
into the nature and value of the present results
of palaeontological investigation ; and the more
so, as all those who have paid close attention to
the late multitudinous discussions in which
palaeontology is implicated, must have felt the
urgent necessity of some such scrutiny.

First in order, as the most definite and unques-
tionable of all the results of palaeontology, must
be mentioned the immense extension and impulse
given to botany, zoology, and comparative an-
atomy, by the investigation of fossil remains.
Indeed, the mass of biological facts has been so
greatly increased, and the range of biological
speculation has been so vastly widened, by the
researches of the geologist and palaeontologist,
that it is to be feared there are naturalists in
existence who look upon geology as Brindley
regarded rivers. " Rivers," said the great engineer,
" were made to feed canals ; " and geology, some
seem to think, was solely created to advance com-
parative anatomy.

Were such a thought justifiable, it could
hardly expect to be received with favour by this
assembly. But it is not justifiable. Your favourite
science has her own great aims independent of all
others ; and if, notwithstanding her steady devotion
to her own progress, she can scatter such rich
alms among her sisters, it should be remembered

204

274 GEOLOGICAL CONTEMPORANEITY is

that her charity is of the sort that does not
impoverish, but "blesseth him that gives and him
that takes."

Regard the matter as we will, however, the
facts remain. Nearly 40,000 species of animals
and plants have been added to the S3^stema
Naturae by palseontological research. This is a
living population equivalent to that of a new
continent in mere number ; equivalent to that of
a new hemisphere, if we take into account the
small population of insects as yet found fossil, and
the large proportion and peculiar organisation of
many of the Yertebrata.

But, beyond this, it is perhaps not too much
to say that, except for the necessity of interpreting
palaeontological facts, the laws of distribution
would have received less careful study; while
few comparative anatomists (and those not of the
first order) would have been induced by mere
love of detail, as such, to study the minutiae of
osteology, were it not that in such minutiae lie the
only keys to the most interesting riddles offered
by the extinct animal world.

These assuredly are great and solid gains. Surely
it is matter for no small congratulation that in
half a century (for palaeontology, though it dawned
earlier, came into full day only with Cuvier) a
subordinate branch of biology should have doubled
the value and the interest of the whole group
of sciences to which it belongs.

IX

GEOLOGICAL CONTEMPORANEITY 275

But this is not all. Allied with geology,
palaeontology has established two laws of inestim-
able importance : the first, that one and the same
area of the earth's surface has been successively
occupied by very different kinds of Hving beings ;
the second, that the order of succession established
in one locality holds good, approximately, in all.

The first of these laws is universal and iiTe-
versible ; the second is an induction from a vast
number of observations, though it may possibly,
and even probably, have to admit of exceptions.
As a consequence of the second law, it follows
that a peculiar relation frequently subsists between
series of strata containing organic remains, in dif-
ferent localities. The series resemble one another
not only in virtue of a general resemblance of the
orsfanic remains in the two, but also in virtue of a
resemblance in the order and character of the
serial succession in each. There is a resemblance
of arrangement ; so that the separate terms of
each series, as well as the whole series, exhibit a
correspondence.

Succession implies time ; the lower members
of an undisturbed series of sedimentary rocks are
certainly older than the upper; and when the
notion of age was once introduced as the equiva-
lent of succession, it was no wonder that corres-
pondence in succession came to be looked upon as
a correspondence in age, or "contemporaneity."
And, indeed, so long as relative age only is spoken

276 GEOLOGICAL CONTEMPORANEITY ix

of, correspondence in succession is correspondence
in age ; it is relative contemporaneity.

But it would have been very mucti better for
geology if so loose and ambiguous a word as
"contemporaneous" had been excluded from her
terminology, and if, in its stead, some term
expressing similarity of serial relation, and ex-
cluding the notion of time altogether, had been
employed to denote correspondence in position
in two or more series of strata.

In anatomy, Avhere such correspondence of posi-
tion has constantly to be spoken of, it is denoted
by the word " homology " and its derivatives ; and
for Geology (which after all is only the anatomy
and physiology of the earth) it might be well to
invent some single word, such as "homotaxis"
(similarity of order), in order to express an essen-
tially similar idea. This, however, has not been
done, and most probably the inquiry will at once
be made — To what end burden science with a new
and strange term in place of one old, familiar, and
part of our common language ?

The reply to this question will become obvious
as the inquiry into the results of palaBontology is
pushed further.

Those whose business it is to acquaint themselves
specially with the works of palaeontologists, in fact,
will be fully aware that very few, if any, would rest
satisfied with such a statement of the conclusions

IX GEOLOGICAL CONTEMPORANEITY 277

of their branch of biology as that which has just
been given.

Our standard repertories of palaeontology profess
to teach us far higher things — to disclose the
entire succession of living forms upon the surface
of the globe ; to tell us of a wholly different dis-
tribution of climatic conditions in ancient times ;
to reveal the character of the first of all hving
existences ; and to trace out the law of progi'ess
from them to us.

It may not be unprofitable to bestow on these
professions a somewhat more critical examination
than they have hitherto received, in order to
ascertain how far they rest on an irrefragable
basis ; or whether, after all, it might not be well
for palaeontologists to learn a little more carefully
that scientific " ars artium," the art of saying '•' I
don't know." And to this end let us define some-
what more exactly the extent of these pretensions
of palaeontology.

Every one is aware that Professor Bronn's " Un-
tersuchungen " and Professor Pictet's " Traite de
Paleontologie " are works of standard authority,
familiarly consulted by every working palaeontolo-
gist. It is desirable to speak of these excellent
books, and of their distinguished authors, with the
utmost respect, and in a tone as far as possible re-
moved from carping criticism ; indeed, if they are
specially cited in this place, it is merely in justifi-
cation of the assertion that the following proposi-

278 GEOLOGICAL CONTEMPORANEITY ix

tions, which may be found implicitly, or explicitly,
in the works in question, are regarded by the mass
of palieontologists and geologists, not only on the
Continent but in this country, as expressing some
of the best-established results of palseontology.
Thus :—

Animals and plants began their existence to-
gether, not long after the commencement of the
deposition of the sedimentary rocks ; and then
succeeded one another, in such a manner, that
totally distinct faunae and florae occupied the whole
surface of the earth, one after the other, and dur-
ing distinct epochs of time.

A geological formation is the sum of all the
strata deposited over the whole surface of the
earth during one of these epochs : a geolo-
gical fauna or flora is the sum of all the
species of animals or plants which occupied the
whole surface of the globe, during one of these
epochs.

The population of the earth's surface was at first
very similar in all parts, and only from the middle
of the Tertiary epoch onwards, began to show a
distinct distribution in zones.

The constitution of the original population, as
well as the numerical proportions of its members,
indicates a warmer and, on the whole, somewhat
tropical climate, which remained tolerably equable
throughout the year. The subsequent distribution
of living beings in zones is the result of a gradual

IX GEOLOGICAL CONTEMPORANEITY 279

lo\srering of the general temperature, which first
began to be felt at the poles.

It is not now proposed to inquire whether these
doctrines are true or false ; but to direct your
attention to a much simpler though very essential
preliminary question — What is their logical basis ?
what are the fundamental assumptions upon which
they all logically depend ? and what is the evidence
on which those fundamental propositions demand
our assent ?

These assumptions are two : the first, that the
commencement of the geological record is coeval
with the commencement of life on the globe ; the
second, that geological contemporaneity is the
same thing as chronological s}Tichrony. Without
the first of these assumptions there would of
course be no ground for any statement respecting
the commencement of life ; without the second, all
the other statements cited, every one of which
implies a knowledge of the state of different parts
of the earth at one and the same time, will be no
less devoid of demonstration.

The first assumption obviously rests entirely on
negative evidence. This is, of course, the only
evidence that ever can be available to prove the
commencement of any series of phenomena ; but,
at the same time, it must be recollected that the
value of negative evidence depends entirely on the
amount of positive corroboration it receives. If A.K

280 GEOLOGICAL CONTEMPORANEITY ix

wishes to prove an alibi, it is of no use for him to
get a thousand witnesses simply to swear that
they did not see him in such and such a place,
unless the witnesses are prepared to prove that
they must have seen him had he been there. But
the evidence that animal life commenced with the
Lingula-flags, e.g., would seem to be exactly of this
unsatisfactory uncorroborated sort. The Cambrian
witnesses simply swear they " haven't seen any-
body their way " ; upon which the counsel for the
other side immediately puts in ten or twelve
thousand feet of Devonian sandstones to make
oath they never saw a fish or a mollusk, though
all the world knows there were plenty in their
time.

But then it is urged that, though the Devonian
rocks in one part of the world exhibit no fossils,
in another they do, while the lower Cambrian
rocks nowhere exhibit fossils, and hence no living
being could have existed in their epoch.

To this there are two replies : the first that the
observational basis of the assertion that the lowest
rocks are nowhere fossiliferous is an amazingly
small one, seeing how very small an area, in com-
parison to that of the whole world, has yet been
fully searched ; the second, that the argument is
good for nothing unless the unfossiliferous rocks
in question were not only contemporaneous in the
geological sense, but synchronous in the chronolo-
gical sense. To use the alibi illustration again.

rx GEOLOGICAL CONTEMPORANEITY 281

If a man wislies to prove he was in neither of
two places, A and B, on a given day, his witnesses
for each place must be prepared to answer for the
whole day. If they can only prove that he was
not at A in the morning, and not at B in the
afternoon, the evidence of his absence from both
is nil, because he might have been at B in the
morning and at A in the afternoon.

Thus everything depends upon the validity of
the second assumption. And we must proceed to
inquire what is the real meaning of the word
" contemj)oraneous " as employed by geologists.
To this end a concrete example may be taken.

The Lias of England and the Lias of Germany,
the Cretaceous rocks of Britain and the Cretaceous
rocks of Southern India, are termed by geologists
" contemporaneous " formations ; but whenever
any thoughtful geologist is asked whether he
means to say that they were deposited synchron-
ously, he says, " No, — only within the same great
epoch." And if, in pursuing the inquiry, he is
asked what may be the approximate value in time
of a " great epoch " — whether it means a hundred
years, or a thousand, or a million, or ten million
years — his reply is, " I cannot tell."

If the further question be put, whether physical
geology is in possession of any method by which
the actual synchrony (or the reverse) of any two
distant deposits can be ascertained, no such
method can be heard of; it being admitted by all

282 GEOLOGICAL CON rEMPORANEITY ix

the best authorities that neither similarity of
mineral composition, nor of physical character,
nor even direct continuity of stratum, are absolute
proofs of the synchronism of even approximated
sedimentary strata : while, for distant deposits,
there seems to be no kind of physical evidence
attainable of a nature competent to decide
whether such deposits were formed simultan-
eously, or whether they possess any given differ-
ence of antiquity. To return to an example
already given : All competent authorities will
probably assent to the proposition that physical
geology does not enable us in any way to rejDly to
this question — Were the British Cretaceous rocks
deposited at the same time as those of India, or
are they a million of years younger or a million of
3^ears older ?

Is palaeontology able to succeed where physical
geology fails ? Standard writers on palaeontology,
as has been seen, assume that she can. They
take it for granted, that deposits containing
similar organic remains are synchronous — at any
rate in a broad sense ; and yet, those who will
study the eleventh and twelfth chapters of Sir
Henry De La Beche's remarkable " Researches
in Theoretical Geology," published now nearly
thirty j^ears ago, and will carry out the arguments
there most luminously stated, to their logical
consequences, may very easily convince them-
selves that even absolute identity of organic

IX

GEOLOGICAL CONTEMPORANEITY 283

contents is no proof of the s}Tichrony of deposits,
while absolute diversity is no proof of difference
of date. Sir Henry De La Beche goes even
further, and adduces conclusive evidence to show
that the different parts of one and the same
stratum, having a similar composition throughout,
containing the same organic remains, and having
similar beds above and below it, may yet differ
to any conceivable extent in age.

Edward Forbes was in the habit of asserting
that the similarity of the organic contents of
distant formations was primd facie evidence, not
of their similarity, but of their difference of age ;
and holding as he did the doctrine of single
specific centres, the conclusion was as legitimate
as any other ; for the two districts must
have been occuj^ied by migration from one of
the two, or from an intermediate spot, and the
chances against exact coincidence of migration
and of imbedding are infinite.

In point of fact, however, whether the hypo-
thesis of single or of multiple specific centres
be adopted, similarity of organic contents cannot
possibly afford any proof of the synchrony of
the deposits which contain them ; on the con-
trary, it is demonstrably compatible with the
lapse of the most prodigious intervals of time,
and. with the interposition of vast changes in the
organic and inorganic worlds, between the epochs
in which such deposits were formed.

284 GEOLOGICAL CONTEMPORANEITY ix

On what amount of similarity of their faunae
is the doctrine of the contemporaneity of the
European and of the North American Silurians
based ? In the last edition of Sir Charles Lyell's
"Elementary Geology" it is stated, on the
authority of a former President of this
Society, the late Daniel Sharpe, that between
30 and 40 per cent, of the species of Silurian
Mollusca are common to both sides of the
Atlantic. By way of due allowance for further
discovery, let us double the lesser number and
suj)pose that 60 per cent, of the species are
common to the North American and the British
Silurians. Sixty per cent, of species in common
is, then, proof of contemporaneity.

Now sujDpose that, a million or two of years
hence, when Britain has made another dip
beneath the sea and has come up again, some
geologist appHes this doctrine, in comparing the
strata laid bare by the upheaval of the bottom,
say, of St. George's Channel with what may then
remain of the Suffolk Crag. Reasoning in the
same way, he will at once decide the Suffolk
Crag and the St. George's Channel beds to be
contemporaneous ; although we happen to know
that a vast period (even in the geological sense)
of time, and physical changes of almost unpre-
cedented extent, separate the two.

But if it be a demonstrable fact that strata
containing more than 60 or 70 per cent, of species

IX GEOLOGICAL CONTEMPOEANEITY 285

of MoUusca in common, and comparatively close
together, may yet be separated by an amount
of geological time sufficient to allow of some
of the greatest physical changes the world has
seen, what becomes of that sort of contem-
poraneity the sole evidence of which is a simi-
larity of facies, or the identity of half a dozen
species, or of a good many genera ?

And yet there is no better evidence for the
contemporaneity assumed by all who adopt the
hypothesis of universal faunae and florse, of a
universally uniform climate, and of a sensible
cooling of the globe during geological time.

There seems, then, no escape from the admis-
sion that neither physical geology, nor palaeonto-
logy, possesses any method by which the absolute
synchronism of two strata can be demonstrated.
All that geology can prove is local order of succes-
sion. It is mathematically certain that, in any
given vertical linear section of an undisturbed
series of sedimentary deposits, the bed which lies
lowest is the oldest. In many other vertical
Hnear sections of the same series, of course, cor-
responding beds will occur in a similar order;
but, however great may be the probability, no
man can say with absolute certainty that the
beds in the two sections were synchronously
deposited. For areas of moderate extent, it is
doubtless true that no practical evil is likely to
result from assuming the corresponding beds to

286 GEOLOGICAL CONTEMPORANEITY ix

be synchronous oi strictly contemporaneous ; and
there are multitudes of accessory circumstances
which may fully justify the assumption of such
synchrony. But the moment the geologist has
to deal with large areas, or with completely
separated deposits, the mischief of confounding
that " homotaxis " or " similarity of arrangement,"
which can be demonstrated, with " synchron}^ " or
"identity of date," for which there is not a
shadow of proof, under the one common term
of " contemporaneity " becomes incalculable, and
proves the constant source of gratuitous specu-
lations.

For anything that geology or pala3ontology are
able to show to the contrary, a Devonian fauna
and flora in the British Islands may have been
contemporaneous with Silurian life in North
America, and with a Carboniferous fauna and flora
in Africa. Geographical provinces and zones may
have been as distinctly marked in the Palaeozoic
epoch as at present, and those seemingly sudden
appearances of new genera and species, which we
ascribe to new creation, may be simple results of
migration.

It may be so; it may be otherwise. In the
present condition of our knowledge and of our
methods, one verdict — "not proven, and not
provable" — must be recorded against all the
grand hypotheses of the palaeontologist respecting
the general succession of Hfe on the globa The

IX GEOLOGICAL COXTEMPORANEITY 287

order and nature of terrestrial life, as a whole,
are open questions. Geology at present provides
us with most valuable topographical records, but
she has not the means of working them into a
universal history. Is such a universal history,
then, to be regarded as unattainable ? Are all
the grandest and most interesting problems which
offer themselves to the geological student, essenti-
ally insoluble ? Is he in the position of a scientific
Tantalus — doomed always to thirst for a knowledge
which he cannot obtain ? The reverse is to be
hoped ; nay, it may not be impossible to indicate
the source whence help Avill come.

In commencing these remarks, mention wa8
made of the great obligations under which the
naturalist lies to the geologist and palaeontologist.
Assuredly the time will come when these obliga-
tions will be repaid tenfold, and when the maze of
the world's past history, through which the pure
geologist and the pure palaeontologist find no
guidance, will be securely threaded by the clue
furnished by the naturalist.

All who are competent to express an opinion on
the subject are, at present, agreed that the mani-
fold varieties of animal and vegetable form have
not either come into existence by chance, nor
result from capricious exertions of creative power ;
but that they have taken place in a definite order,
the statement of which order is what men of
science term a natural law. Whether such a law

288 GEOLOGICAL CONTEMPORANEITY ix

is to be regarded as an expression of the mode of
operation of natural forces, or whether it is simply
a statement of the manner in which a super-
natural power has thought fit to act, is a secondary
question, so long as the existence of the law and
the possibility of its discovery by the human
intellect are granted. But he must be a half-
hearted philosopher who, believing in that possi-
bility, and having watched the gigantic strides
of the biological sciences during the last twenty
years, doubts that science will sooner or later
make this further step, so as to become possessed
of the law of evolution of organic forms — of the
unvarying order of that great chain of causes and
effects of which all organic forms, ancient and
modern, are the links. And then, if ever, we
shall be able to begin to discuss, with profit, the
questions respecting the commencement of life,
and the nature of the successive populations of
the globe, which so many seem to think are
already answered.

The preceding arguments make no particular
claim to novelty ; indeed they have been floating
more or less distinctly before the minds of geo-
logists for the last thirty years ; and if, at the
present time, it has seemed desirable to give them
more definite and systematic expression, it is be-
cause palaeontology is every day assuming a greater
importance, and now requires to rest on a basis

IX GEOLOGICAL CONTEMPORANEITY 289

the firmness of which is thoroughly well assured.
Among its fundamental conceptions, there must
be no confusion between what is certain and what
is more or less probable.^ But, pending the con-
struction of a surer foundation than palseontology
now possesses, it may be instructive, assuming
for the nonce the general correctness of the
ordinary hypothesis of geological contemporaneity,
to consider whether the deductions which are
ordinarily drawn from the whole body of palse-
ontological facts are justifiable.

The evidence on which such conclusions are
based is of two kinds, negative and positive. The
value of negative evidence, in connection with this
inquiry, has been so fully and clearly discussed in
an address from the chair of this Society ,2 which
none of us have forgotten, that nothing need at
present be said about it ; the more, as the con-
siderations which have been laid before you have
certainly not tended to increase your estimation
of such evidence. It will be preferable to turn to
the positive facts of palseontology, and to inquire
what they tell us.

We are all accustomed to speak of the number
and the extent of the changes in the living popu-
lation of the globe during geological time as

1 " Le plus grand service qn'on piiisse rendre k la science est
d'y faire place nette avant d'y rien construire." — Cuvier.

- Anniversary Address for 1851, Quart. Joitrn. Geol. Soc.
vol. vii.

205

290 GEOLOGICAL CONTEMPORANEITY ix

something enormous . and indeed they are so, if
we regard only the negative differences which
separate the older rocks from the more modem,
and if we look upon specific and generic changes
as great changes, which from one point of view,
they truly are. But leaving the negative differ-
ences out of consideration, and looking only at the
positive data furnished by the fossil world from a
broader point of view — from that of the compara-
tive anatomist who has made the study of the
greater modifications of animal form his chief
business — a surprise of another kind dawns upon
the mind ; and. under this aspect the smallness of
the total change becomes as astonishing as was its
greatness under the other.

There are two hundred known orders of plants ;
of these not one is certainly known to exist ex-
clusively in the fossil state. The whole lapse of
geological time has as yet yielded not a single new
ordinal type of vegetable structure.^

The positive change in passing from the recent
to the ancient animal world is greater, but still
sinonlarly small. No fossil animal is so distinct
from those now living as to require to be arranged
even in a separate class from those which contain
existing forms. It is only when we come to the
orders, which may be roughly estimated at about
a hundred and thirty, that we meet with fossil

1 See Hooker's Introductory Essay to the Flora of Tasmania^
p. xxiii

IX GEOLOGICAL CONTEMPORANEITY 291

animals so distinct from those now living as to
require orders for themselves; and these do not
amount, on the most liberal estimate, to more than
about 10 per cent, of the whole.

There is no certainly known extinct order of
Protozoa ; there is but one among the Coelenterata
— that of the rugose corals ; there is none among
the MoUusca; there are three, the Cystidea,
Blastoidea, and Edrioasterida, among the Echino-
derms; and two, the Trilobita and Eurypterida,
among the Crustacea ; making altogether five for
the great sub-kingdom of Annulosa. Among
Vertebrates there is no ordinally distinct fossil
fish : there is only one extinct order of Amphibia
— the Labyrinthodonts ; but there are at least four
distinct orders of Reptilia, viz. the Ichthyosauria,
Plesiosauria, Pterosauria, Dinosauria, and perhaps
another or two. There is no known extinct order
of Birds, and no certainly known extinct order of
Mammals, the ordinal distinctness of the " Toxo-
dontia " being doubtful.

The objection that broad statements of this
kind, after all, rest largely on negative evidence is
obvious, but it has less force than may at first be
supposed ; for, as might be expected from the cir-
cumstances of the case, we possess more abundant
positive evidence regarding Fishes and marine
Mollusks than respecting ' any other forms of
animal life ; and yet these offer us, through the
whole range of geological time, no species ordinally

292 GEOLOGICAL CONTEMPORANEITY ix

distinct from those now living ; while the far less
numerous class of Echinoderms presents three, and
the Crustacea two, such orders, though none of these
come down later than the Palseozoic age. Lastty,
the Reptilia present the extraordinary and excep-
tional phenomenon of as many extinct as existing
orders, if not more ; the four mentioned maintain-
ing their existence from the Lias to the Chalk
inclusive.

Some years ago one of your Secretaries pointed
out another kind of positive palaeontological
evidence tending towards the same conclusion —
afforded by the existence of what he termed
" persistent types " of vegetable and of animal
life.^ He stated, on the authority of Dr. Hooker,
that there are Carboniferous plants which appear
to be generically identical with some now Hving ;
that the cone of the Oolitic Araiicaria is hardly
distinguishable from that of an existing species ;
that a true Pinus appears in the Purbecks and a
Jicglans in the Chalk ; while, from the Bagshot
Sands, a Banksia, the wood of which is not
distinguishable from that of species now living
in Australia, had been obtained.

Turning to the animal kingdom, he affirmed
the tabulate corals of the Silurian rocks to be
wonderfully like those which now exist; while

^ See the abstract of a Lecture "On the Persistent Types of
Animal Life," in the Notices of the Meetings of the Royal
Institution of Great Britain. — June 3, 1859, vol. iii. p. 151.

IX GEOLOGICAL CONTEMPORANEITY 293

even the families of the Aporosa were all repre-
sented in the older Mesozoic rocks.

Among the Mollusca similar facts were adduced.
Let it be borne in mind that Avicula, Mytilus^
Chiton, Natica, Patella, Trochus, Discina, Orhictda^
Lingida, Bhynchonella, and Nautilus, all of which
are existing genera, are given without a doubt as
Silurian in the last edition of " Siluria " ; while
the highest forms of the highest Cephalopods
are represented in the Lias by a genus Belemno^
teuthis, which presents the closest relation to the
existing Loligo.

The two highest groups of the Annulosa, the
Insecta and the Arachnida, are represented in the
Coal, either by existing genera, or by forms
differing from existing genera in quite minor
peculiarities.

Turning to the Yertebrata, the only palaeozoic
Elasmobranch Fish of which we have any complete
knowledge is the Devonian and Carboniferous
PleuracaiitJius, which differs no more from existing
Sharks than these do from one another.

Again, vast as is the number of undoubtedly
Ganoid fossil Fishes, and great as is their range
in time, a large mass of evidence has recently
been adduced to show that almost all those
respecting which we possess sufficient information,
are referable to the same sub-ordinal groups as
the existing Lepidcstcus, Polyptcrus, and Sturgeon ;
and that a singular relation obtains between the

294 GEOLOGICAL CONTEMPORANEITy ix

older and the younger Fishes ; the former, the
Devonian Ganoids, being almost all members of
the same sub-order as Polypterus, while the
Mesozoic Ganoids are almost all similarly allied
to Zepidosfeus}

Again, what can be more remarkable than the
singular constancy of structure preserved through-
out a vast period of time by the family of the
Pycnodonts and by that of the true Coelacanths :
the former persisting, with but insignificant
modifications, from the Carboniferous to the
Tertiary rocks, inclusive; the latter existing,
with still less change, from the Carboniferous
rocks to the Chalk, inclusive ?

Among Reptiles, the highest living gi'oup, that
of the Crocodilia, is represented, at the early part
of the Mesozoic epoch, by species identical in the
essential characters of their organisation with
those now living, and differing from the latter
only in such matters as the form of the articular
facets of the vertebral centra, in the extent to
which the nasal passages are separated fi'om the
cavity of the mouth by bone, and in the pro-
portions of the limbs.

And even as regards the Mammalia, the scanty
remains of Triassic and Oolitic species afford no
foundation for the supposition that the organisa-

1 ** Memoirs of the Geological Survey of the United Kingdom.
—Decade x. Preliminary Essay upon the Systematic Arrange-
ment of the Fishes of the Devonian Epoch."

IX GEOLOGICAL CONTEMPORANEITY 295

tion of the oldest forms differed nearly so much
from some of those which now live as these differ
from one another.

It is needless to multiply these instances;
enough has been said to justify the statement
that, in view of the immense diversity of known
animal and vegetable forms, and the enormous
lapse of time indicated by the accumulation of
fossiliferous strata, the only circumstance to be
wondered at is, not that the changes of Hfe, as
exhibited by positive evidence, have been so gi'eat,
but that they have been so small.

Be they great or small, however, it is desirable
to attempt to estimate them. Let us, therefore,
take each great division of the animal world in
succession, and, whenever an order or a family can
be shown to have had a prolonged existence, let us
endeavour to ascertain how far the later members
of the group differ from the earlier ones. If these
later members, in all or in many cases, exhibit a
certain amount of modification, the fact is, so far,
evidence in favour of a general law of change ;
and, in a rough way, the rapidity of that change
will be measured by the demonstrable amount of
modification. On the other hand, it must be
recollected that the absence of any modification,
while it may leave the doctrine of the existence of
a law of change without positive support, cannot
possibly disprove all forms of that doctrine, though

29G GEOLOGICAL CONTEMPORANEITY ix

it may afiford a sufficient refutation of many of
them.

The Protozoa. — The Protozoa are represented
throughout the whole range of geological series,
from the Lower Silurian formation to the present
day. The most ancient forms recently made
known hy Ehrenberg are exceedingly like those
which now exist : no one has ever pretended that
the difference between any ancient and any modern
Foraminifera is of more than generic value, nor
are the oldest Foraminifera either simpler, more
embryonic, or less differentiated, than the existing
forms.

The Ccelenterata. — The Tabulate Corals have
existed from the Silurian epoch to the present
day, but I am not aware that the ancient Hcliolitcs
possesses a single mark of a more embryonic or
less differentiated character, or less high organisa-
tion, than the existing Helicpora. As for the
Aporose Corals, in what respect is the Silurian
FalceGcyclus less highly organised or more embry-
onic than the modern Fungia, or the Liassic
Aporosa than the existing members of the same
families ?

The Mollusca. — In what sense is the living
Waldheimia less embryonic, or more specialised,
than the palaeozoic B^irifer ; or the existing
Bhynchonellce, Cranioe, Fiscince, Lingulce, than the
Silurian species of the same genera ? In what
sense can Loligo or Sjoinda be said to be more

IX GEOLOGICAL CONTEMPOEANEITY 297

specialised, or less embryonic, than Belcmnites ;
or the modern species of Lamelhbranch and
Gasteropod genera, than the Silurian species of
the same genera ?

The Annulosa. — The Carboniferous Insecta
and Arachnida are neither less specialised, nor
more embryonic, than these that now live, nor are
the Liassic Cnripedia and Macrura ; while several
of the Brachyura, which appear in the Chalk,
belong to existing genera; and none exhibit
either an intermediate, or an embryonic,
character.

The Vertebrata. — Among fishes I have
referred to the Coelacanthuii (comprising the
genera Gmlacanthus, HolopJiagus, Undina, and
Macropoma) as affording an example of a persistent
type ; and it is most remarkable to note the
smallness of the differences between any of these
fishes (affecting at most the proportions of the
body and fins, and the character and sculpture
of the scales), notwithstanding their enormous
range in time. In ail the essentials of its
very peculiar structure, the Macropoma of the
Chalk is identical with the Cmlacanthus of the
Coal. Look at the genus Lepidotus, again, per-
sisting without a modification of importance
from the Liassic to the Eocene formations in-
clusivly.

Or among the Teleostei — in what respect is
the Beryx of the Chalk more embryonic, or

298 GEOLOGICAL CONTEMPORANEITY ix

less differentiated, than Beryx lincatus of King
George's Sound ?

Or to turn to the higher Vertebrata — in what
sense are the Liassic Chelonia inferior to those
which now exist ? How are the Cretaceous
Ichthyosauria, Plesiosauria, or Pterosauria less
embryonic, or more differentiated, species than
those of the Lias ?

Or lastly, in what circumstance is the PJiasco-
lotherium more embryonic, or of a more genera-
lised type, than the modern Opossum; or a
ZoijhiGdoi, or a Fala3othermmj than a modern
Taijirus or Hyrax'^

These examples might be almost indefinitely
multiplied, but surely they are sufficient to prove
that the only safe and unquestionable testimony
we can procure — positive evidence — fails to dem-
onstrate any sort of progressive modification
towards a less embryonic, or less generahsed, type
in a great many groups of animals of long-
continued geological existence. In these groups
there is abundant evidence of variation — none of
what is ordinarily understood as progression ; and,
if the known geological record is to be regarded
as even any considerable fragment of the whole,
it is inconceivable that any theory of a necessarily
progressive development can stand, for the numer-
ous orders and families cited afford no trace of
such a process.

But it is a most remarkable fact, that, while the

IX

GEOLOGICAL CONTEMPORANEITY 299

groups which have been mentioned, and many
besides, exhibit no sign of progressive modification,
there are others, co-existing with them, under the
same conditions, in which more or less distinct
indications of such a process seems to be traceable.
Among such indications I may remind you of the
predominance of Holostome Gasteropoda in the
older rocks as compared with that of Siphonostone
Gasteropoda in the later. A case less open to the
objection of negative evidence, however, is that
afforded by the Tetrabranchiate Cephalopoda, the
forms of the shells and of the septal sutures
exhibiting a certain increase of complexity in the
newer genera. Here, however, one is met at once
with the occurrence of Orthoceras and Baculites at
the two ends of the series, and of the fact that
one of the simplest genera. Nautilus^ is that
which now exists.

The Crinoidea, in the abundance of stalked
forms in the ancient formations as compared with
their present rarity, seem to present us with a
fair case of modification from a more embryonic
towards a less embryonic condition. But then, on
careful consideration of the facts, the objection
arises that the stalk, caljrx, and arms of the palae-
ozoic Crinoid are exceedingly different from the
corresponding organs of a larval Comahda ; and it
might with perfect justice be argued that Actino-
crinus and Eucalyptccrinus, for example, depart to
the full as widely, in one direction, from the stalked

800 GEOLOGICAL CONTEMPORANEITY jx

embryo of Comahda, as Comatula itself does in
the other.

The Echinidea, again, are frequently quoted as
exhibiting a gradual passage from a more genera-
lised to a more specialised type, seeing that the
elongated, or oval, Spatangoids appear after the
spheroidal Echinoids. But here it might be
argued, on the other hand, that the spheroidal
Echinoids, in reality, depart further from the
general plan and from the embryonic form than
the elongated Spatangoids do ; and that the
peculiar dental apparatus and the pedicellarige of
the former are marks of at least as great differ-
entiation as the petaloid ambulacra and semitse of
the latter.

Once more, the prevalence of Macrurous before
Brachyurous Podophthalmia is, apparently, a fair
piece of evidence in favour of progressive modifi-
cation in the same order of Crustacea; and yet
the case will not stand much sifting, seeing that
the Macrurous Podophthalmia depart as far in one
direction from the common type of Podophthalmia,
or from any embryonic condition of the Brachjoira,
as the Brachyura do in the other ; and that the
middle terms between Macrura and Brachyura —
the Anomura — are little better represented in the
older Mesozoic rocks than the Brachyura are.

None of the cases of progressive modification
which are cited from among the Invertebrata
appear to me to have a foundation less open to

IX GEOLOGICAL CONTEMPORANEITY 3Ul

criticism than these ; and if this be so, no careful
reasoner would, I think, be inclined to lay very
great stress upon them. Among the Vertebrata,
however, there are a few examples which appear to
be far less open to objection.

It is, in fact, true of several groups of Verte-
brata which have lived through a considerable
range of time, that the endoskeleton (more par-
ticularly the spinal column) of the older genera
presents a less ossified, and, so far, less differ-
entiated, condition than that of the younger
genera. Thus the Devonian Ganoids, though
almost all members of the same sub-order as
Polypterus, and presenting numerous important re-
semblances to the existing genus, which possesses
biconclave vertebrae, are, for the most part, wholly
devoid of ossified vertebral centra. The Mesozoic
Lepidosteidse, again, have, at most, biconcave
vertebrae, while the existing Lepidosteus has
Salamandroid, opisthocoelous, vertebrae. So, none
of the Palaeozoic Sharks have shown themselves
to be possessed of ossified vertebrae, while the
majority of modern Sharks possess such vertebrae.
Again, the more ancient Crocodilia and Lacertilia
have vertebrae with the articular facets of their
centra flattened or biconcave, while the modern
members of the same group have them procoelous.
But the most remarkable examples of progressive
modification of the vertebral column, in corre-
spondence with geological age, are those afforded

302 GEOLOGICAL CONTEMPORANEITY m

by the Pycnodonts among fish, and the Labyrin-
thodonts among Amphibia.

The late able ichthyologist Heckel pointed out
the fact, that, while the Pycnodonts never possess
true vertebral centra, they differ in the degi^ee of
expansion and extension of the ends of the bony
arches of the vertebrae upon the sheath of the
notochord ; the Carboniferous forms exhibiting
hardly any such expansion, while the Mesozoic
genera present a greater and greater development,
until, in the Tertiary forms, the expanded ends
become suturally united so as to form a sort of
false vertebra. Hermann von Meyer, again, to
whose luminous researches we are indebted for
our present large knowledge of the organisation of
the older Labyrinthodonts, has proved that the
Carboniferous Archegosaurus had very imperfectly
developed vertebral centra, while the Triassic
Mastodonsaurus had the same parts completely
ossified.^

The regularity and evenness of the dentition of
the Ano2)Iotherium, as contrasted with that of exist-
in o- Artiodactyles, and the assumed nearer approach
of the dentition of certain ancient Carnivores to
the typical arrangement, have also been cited as
exemplifications of a law of progressive develop-
ment, but I know of no other cases Based on

^ As this Address is passing through the press (March 7,
1862), evidence lies before me of the existence of a new Laby-
rinthodont {Pholvh'jnstrr), from the Edinburgh coal-field with
well-ossified vertebral centra.

IX GEOLOGICAL CONTEMPORANEITY 803

positive evidence which are worthy of particular
notice.

What then does an impartial survey of the
positively ascertained truths of palaeontology testify
in relation to the common doctrines of progressive
modification, which suppose that modification to
have taken place by a necessary progress from
more to less embryonic forms, or from more to
less generalised types, within the limits of the
period represented by the fossiliferous rocks ?

It negatives those doctrines ; for it either
shows us no evidence of any such modification, or
demonstrates it to have been very slight ; and as
to the nature of that modification, it yields no
evidence whatsoever that the earlier members of
any long-continued group were more generalised
in structure than the later ones. To a certain
extent, indeed, it may be said that imperfect
ossification of the vertebral column is an em-
bryonic character; but, on the other hand, it
would be extremely incorrect to suppose that the
vertebral columns of the older Yertebrata are in
any sense embryonic in their whole structure.

Obviously, if the earliest fossiliferous rocks now
known are coeval with the commencement of life,
and if their contents give us any just conception
of the nature and the extent of the earliest fauna
and flora, the insignificant amount of modification
which can be demonstrated to have taken place in
any one group of animals, or plants, is quite in-

304 GEOLOGICAL CONTEMPORANEITY ix

compatible with the hypothesis that all living
forms are the results of a necessary process of
progressive development, entirely comprised within
the time represented by the fossiliferous rocks.

Contrariwise, any admissible hypothesis of pro-
gressive modification must be compatible with
persistence without progression, through indefi-
nite periods. And should such an hypothesis
eventually be proved to be true, in the only
way in which it can be demonstrated, viz.
by observation and experiment upon the
existing forms of life, the conclusion will
inevitably present itself, that the Palaeozoic
Mesozoic, and Cainozoic faunae and florae, taken
together, bear somewhat the same proportion to
the whole series of living beings which have
occupied this globe, as the existing fauna and
flora do to them.

Such are the results of palaeontology as they
appear, and have for some years appeared, to the
mind of an inquirer who regards that study simply
as one of the applications of the great biological
sciences, and who desires to see it placed upon the
same sound basis as other branches of physical
inquiry. If the arguments which have been
brought forward are valid, probably no one, in view
of the present state of opinion, will be inclined to
think the time wasted which has been spent upon
their elaboration.

X

GEOLOGICAL REFORM

[1869]

•' A great reform in geological speculation seems now to ha'/e
become necessary."

" It is quite certain that a great mistake has been made— that
British popular geology at the present time is in direct opposi-
tion to the principles of Natural Philosopliy." ^

In reviewing the course of geological thought
during the past year, for the purpose of discovering
those matters to which I might most fitly direct
your attention in the Address which it now
becomes my duty to deliver from the Presidential
Chair, the two somewhat alarming sentences
which I have just read, and which occur in an
able and interesting essay by an eminent natural
philosopher, rose into such prominence before my
mind that they eclijDsed everything else.

It surely is a matter of paramount importance

1 On Geological Time. By Sir W. Thomson, LL.D. Trans*
actions of the Geological Society of Glasgow, vol. iii.

206

306 GEOLOGICAL REFORM X

for the British geologists (some of them very
popular geologists too) here in solemn annual
session assembled, to inquire whether the severe
judgment thus passed upon them by so high an
authority as Sir William Thomson is one to which
they must plead guilty sans phrase, or whether
they are prepared to say " not gnilty/' and appeal
for a reversal of the sentence to that higher
court of educated scientific opinion to which we
are all amenable.

As your attorney-general for the time being,
I thought I could not do better than get up the
case with a view of advising you. It is true that
the charges brought forward by the other side
involve the consideration of matters quite foreign
to the pursuits with w^hich I am ordinarily occu-
pied ; but, in that respect, I am only in the
position which is, nine times out of ten, occupied
by counsel, who nevertheless contrive to gain
their causes, mainly by force of mother- wit and
common-sense, aided by some training in other
intellectual exercises.

Nerved by such precedents, I proceed to put
my pleading before you.

And the first question with w^hich I propose to
deal is, What is it to which Sir W. Thomson
refers when he speaks of " geological speculation "
and " British popular geology " ?

I find three, more or less contradictory, systems
of geological thought, each of which might fairly

X GEOLOGICAL REFORM 307

enough claim these appellations, standing side by
side in Britain. I shall call one of them Cata-
STROPHISM, another UNiFORMiTARiANlSM,the third
Evolutionism ; and I shall try briefly to sketch
the characters of each, that you may say whether
the classification is, or is not, exhaustive.

By Catastrophism, I mean any form of geo-
logical speculation which, in order to account for
the phenomena of geology, supposes the operation
of forces different in their nature, or immeasur-
ably different in power, from those which we at
present see in action in the universe.

The Mosaic cosmogony is, in this sense, cata-
strophic, because it assumes the operation of
extra-natural power. The doctrine of violent
upheavals, d^hddcs, and cataclysms in general, is
catastrophic, so far as it assumes that these were
brought about by causes which have now no
parallel. There was a time when catastrophism
might, pre-eminently, have claimed the title of
" British popular geology " ; and assuredly it has
yet many adherents, and reckons among its sup-
porters some of the most honoured members of
this Society.

By Uniformitarianism, I mean especially, the
teaching of Hutton and of Lyell.

That gi^eat though incomplete work, " The
Theory of the Earth," seems to me to be one of
the most remarkable contributions to geology
which is recorded in the annals of the science.

308 GEOLOGICAL REFORM X

So far as the not-living world is concerned, uni-
formitarianism lies there, not only in germ, but in
blossom and fruit.

If one asks how it is that Hutton was led
to entertain views so far in advance of those
prevalent in his time, in some respects ; while, in
others, they seem almost curiously Hmited, the
answer appears to me to be plain.

Hutton was in advance of the geological specu-
lation of his time, because, in the first place, he
had amassed a vast store of knowledge of the
facts of geology, gathered by personal observation
in travels of considerable extent ; and because, in
the second place, he was thoroughly trained in
the physical and chemical science of his day, and
thus possessed, as much as any one in his time
could possess it, the knowledge which is requisite
for the just interpretation of geological pheno-
mena, and the habit of thought which fits a man
for scientific inquiry.

It is to this thorough scientific training that I
ascribe Hutton's steady and persistent refusal to
look to other causes than those now in operation,
for the explanation of geological phenomena.

Thus he writes : — " I do not pretend, as he
[M. de Luc] does in his theory, to describe the
beginning of things. I take things such as I find
them at present ; and from these I reason with
regard to that which must have been." ^

1 The Theory of the Earth, vol. i. p. 173, note.

X GEOLOGICAL REFORM 809

And again : — " A theory of the earth, which
has for object truth, can have no retrospect to
that which had preceded the present order of the
world ; for this order alone is what we have to
reason upon ; and to reason without data is
nothing but delusion. A theory, therefore, which
is limited to the actual constitution of this earth
cannot be allowed to proceed one step beyond the
present order of things." ^

And so clear is he, that no causes beside such
as are now in operation are needed to account for
the character and disposition of the components
of the crust of the earth, that he says, broadly
and boldly: — ^* . . . There is no part of the
earth which has not had the same origin, so
far as this consists in that earth being collected
at the bottom of the sea, and afterwards pro-
duced, as land, along with masses of melted
substances, by the operation of mineral causes." ^

But other influences were at work upon Hutton
beside those of a mind logical by nature, and
scientific by sound training; and the pecuHar
turn which his speculations took seems to me
to be unintelligible, unless these be taken into
account. The arguments of the French astro-
nomers and mathematicians, which, at the end
of the last century, were held to demonstrate
the existence of a compensating arrangement
among the celestial bodies, whereby all perturba-

1 The Theory of the EartJi, vol. i. p. 281. - Ibid. p. 3/1.

810 GEOLOGICAL REFORM X

tions eventually reduced themselves to oscilla-
tions on each side of a mean position, and the
stability of the solar system was secured, had
evidently taken strong hold of Hutton's mind.

In those oddly constructed periods which seem
to have prejudiced many persons against reading
his works, but which are full of that peculiar, if
unattractive, eloquence which flows from mastery
of the subject, Hutton says : —

" We have now got to the end of our reasoning ;
we have no data further to conclude immediately
from that which actually is. But we have got
enough; we have the satisfaction to find, that
in Nature there is wisdom, system, and consist-
ency. For having, in the natural history of this
earth, seen a succession of worlds, we may from
this conclude that there is a system in Nature ;
in like manner as, from seeing revolutions of the
planets, it is concluded, that there is a system by
which they are intended to continue those revolu-
tions. But if the succession of worlds is estab-
lished in the system of nature, it is in vain to
look for anything higher in the origin of the
earth. The result, therefore, of this physical
inquiry is, that we find no vestige of a beginning,
— no prospect of an end." ^

Yet another influence worked strongly upon
Hutton. Like most philosophers of his age, he
coquetted with those final causes which have
» The Theory of the Earth, vol. i. p. 200.

X GEOLOGICAL REFORM 311

been named barren virgins, but which might
be more fitly termed the hetairce of philosophy,
so constantly have they led men astray. The
final cause of the existence of the world is, for
Hutton, the production of life and intelligence.
"We have now considered the globe of this
earth as a machine, constructed upon chemical
as well as mechanical principles, by which its
different parts are all adapted, in form, in quality,
and in quantity, to a certain end ; an end at-
tained with certainty or success ; and an end
from which we may perceive wisdom, in contem-
plating the means employed.

" But is this world to be considered thus
merely as a machine, to last no longer than its
parts retain their present position, their proper
forms and qualities ? Or may it not be also
considered as an organised body? such as has
a constitution in which the necessary decay of
the machine is naturally repaired, in the exertion
of those productive powers by which it had
been formed.

" This is the view in which we are now to
examine the globe ; to see if there be, in the
constitution of this world, a reproductive opera-
tion, by which a ruined constitution may be
again repaired, and a duration or stability thus
procured to the machine, considered as a world
sustaining plants and animals."^

» Th^ Theory of the Earth, vol. i. pp. 16, 17.

312 GEOLOGICAL REFORM X

Kirwan, and the other Philistines of the day,
accused Hutton of declaring that his theory
implied that the world never had a beginning,
and never differed in condition from its present
state. Nothing could be more gi'ossly unjust, as
he expressly guards himself against any such
conclusion in the following terms : — ■

" But in thus tracing back the natural opera-
tions which have succeeded each other, and mark
to us the course of time past, we come to a period
in which we cannot see any farther. This, how-
ever, is not the beginning of the operations which
proceed in time and according to the wise
economy of this world ; nor is it the establishing
of that which, in the course of time, had no
beginning; it is only the hmit of our retrospec-
tive view of those operations which have come
to pass in time, and have been conducted by
supreme intelligence." ^

I have spoken of Uniformitarianism as the doc-
trine of Hutton and of Lyell. If I have quoted
the older wi^iter rather than the newer, it is be-
cause his works are little known, and his claims
on our veneration too frequently forgotten, not
because I desire to dim the fame of his eminent
successor. Few of the present generation of
geologists have read Playfair's " Illustrations,"
fewer still the original " Theory of the Earth " ; the
more is the pity ; but which of us has not thumbed

1 The Theory of the Earth, vol. i. p. 223.

X GEOLOGICAL REFORM 313

every page of the " Principles of Geology " ? I
think that he who writes fairly the history of his
own progress in geological thought, will not be
able to separate his debt to Hutton from his
obligations to Lyell ; and the history of the pro-
gress of individual geologists is the history of

No one can doubt that the influence of uniform-
itarian views has been enormous, and, in the
main, most beneficial and favourable to the
progress of sound geology.

Nor can it be questioned that Uniformitarianism
has even a stronger title than Catastrophism to
call itself the geological speculation of Britain, or,
if you will, British popular geology. For it is
eminently a British doctrine, and has even now
made comparatively little progress on the con-
tinent of Europe. Nevertheless, it seems to me
to be open to serious criticism upon one of its
aspects.

I have sho"v\Ti how unjust was the insinuation
that Hutton denied a beginning to the world.
But it would not be unjust to say that he persist-
ently in practice, shut his eyes to the existence
of that prior and different state of things which,
in theory, he admitted ; and, in this aversion to
look beyond the veil of stratified rocks, Lyell
follows him.

Hutton and Lyell alike agree in their indis-
position to carry their speculations a step beyond

814 GEOLOGICAL REFORM X

the period recorded in the most ancient strata
now open to observation in the crust of the earth.
This is, for Hutton, " the point in which we can-
not see any farther " ; while Lyell tells us, —

" The astronomer may find good reasons for
ascribing the earth's form to the original fluidity
of the mass, in times long antecedent to the first
introduction of living beings into the planet ; but
the geologist must be content to regard the earliest
monuments which it is his task to interpret, as
belonging to a period when the crust had already
acquired great solidity and thickness, probably as
great as it now possesses, and when volcanic rocks,
not essentially differing from those now produced,
were formed from time to time, the intensity of
volcanic heat being neither greater nor less than
it is now." ^

And again, " As geologists, we learn that it is
not only the present condition of the globe which
has been suited to the accommodation of myriads
of living creatures, but that many former states
also have been adapted to the organisation and
habits of prior races of beings. The disposition of
the seas, continents and islands, and the climates,
have varied ; the species likewise have been
changed ; and yet they have all been so modelled,
on types analogous to those of existing plants and
animals, as to indicate, throughout, a perfect
harmony of design and unity of purpose. To
* Principles of Geology, vol. ii. p. 211.

X (GEOLOGICAL REFORM 315

assume that the evidence of the beginning, or end,
of so vast a scheme lies within the reach of our
philosophical inquiries, or even of our speculations,
appears to be inconsistent with a just estimate of
the relations which subsist between the finite
powers of man and the attributes of an infinite
and eternal Being." ^

The limitations implied in these passages appear
to me to constitute the weakness and the logical
defect of Uniformitarianism. No one will impute
blame to Hutton that, in face of the imperfect
condition, in his day, of those physical sciences
which furnish the keys to the riddles of geology,
he should have thought it practical wisdom to
limit his theory to an attempt to account for " the
present order of things " ; but I am at a loss to
comprehend why, for all time, the geologist must
be content to regard the oldest fossiiiferous rocks
as the ultima Thide of his science ; or what there
is inconsistent with the relations between the
finite and the infinite mind, in the assumption,
that we may discern somewhat of the beginning,
or of the end, of this speck in space we call our
earth. The finite mind is certainly competent to
trace out the development of the fowl within the
Qgg ; and I know not on what ground it should
find more difficulty in unravelling the complexities
of the development of the earth. In fact, as Kant

^ Princijjles of Geology, vol. ii. p. 613.

316 GEOLOGICAL REFORM X

has well remarked,^ the cosmical process is really
simpler than the biological.

This attempt to limit, at a particular point, the
progress of inductive and deductive reasoning
from the things which are, to those which were —
this faithlessness to its own logic, seems to me to
have cost Uniformitarianism the place, as the
j)ermanent form of geological speculation, which
it might otherwise have held.

It remains that I should put before you what
I understand to be the third phase of geological
speculation — namely, Evolutionism.

I shall not make what I have to say on this
head clear, unless I divero^e, or seem to divero^e, for a
while, from the direct path of my discourse, so far
r.s to explain what I take to be the scope of geology
itself I conceive geology to be the history of the
earth, in precisely the same sense as biology is
the history of living beings ; and I trust you will
not think that I am overpowered by the influence
of a dominant pursuit if I say that I trace a close
analogy between these two histories.

If I study a living being, under what heads
does the knowledge I obtain fall ? I can learn its
structure, or what we call its Anatomy ; and its

^ "Mandarfes sicli also nicht befremden lassen, wenn ich
mich unterstehe zu sacfen, dass elier die Bildung aller Plimmels-
korper, die Ursache ihrer Bewegungen, knrz der Ursprnng der
ganzen gegenwriitigen Verfassimg des Weltbaiies werdenkonnen
eingeseheii wevden, elie die Erzengung eines einzigen Kiautes odei
einer Raiij^eans rnechanischon Gniiideri, dcutlichuud voDstandig
kund vverden wird." — Kant's iSdmmdiche Werke, Bd, i. p. 220.

X GEOLOGICAL REFORM 317

Development, or the series of changes which it
passes through to acquire its complete structure.
Then I find that the living being has certain
powers resulting from its own activities, and the
interaction of these with the activities of other
things — the knowledge of which is Physiology.
Beyond this the living being has a position in
space and time, which is its Distribution. All
these form the body of ascertainable facts which
constitute the status quo of the hving creature.
But these facts have their causes ; and the
ascertainment of these causes is the doctrine of
Etiology.

If we consider what is knowable about the
earth, we shall find that such earth-knowledofe —
if I may so translate the word geology — falls into
the same categories.

What is termed stratigraphical geology is neither
more nor less than the anatomy of the earth ; and
the history of the succession of the formations is
the history of a succession of such anatomies, or
corresponds with development, as distinct from
generation.

The internal heat of the earth, the elevation
and depression of its crust, its belchings forth
of vapours, ashes, and lava, are its activities, in as
strict a sense as are warmth and the movements
and products of respiration the activities of an
animal. The phenomena of the seasons, of the
trade mnd's, of the Gulf-stream, are as much the

818 GEOLOGICAL REFORM X

results of the reaction between these inner
activities and outward forces, as are the budding
of the leaves in spring and their falling in autumn
the effects of the interaction between the organ-
isation of a plant and the solar light and heat.
And, as the study of the activities of the hving being
is called its physiology, so are these phenomena
the subject-matter of an analogous telluric physio-
logy, to which we sometimes give the name of
meteorology, sometimes that of physical geography,
sometimes that of geology. Again, the earth has
a place in space and in time, and relations to
other bodies in both these respects, which con-
stitute its distribution. This subject is usually
left to the astronomer; but a knowledge of its
broad outlines seems to me to be an essential
constituent of the stock of geological ideas.

All that can be ascertained concerning the
structure, succession of conditions, actions, and posi-
tion in space of the earth, is the matter of fact of its
natural history. But, as in biology, there remains
the matter of reasoning from these facts to their
causes, which is just as much science as the other,
and indeed more ; and this constitutes geological
aetiology.

Having regard to this general scheme of geo-
logical knowledge and thought, it is obvious that
geological speculation may be, so to speak, ana-
tomical and developmental speculation, so far as it
relates to points of stratigraphical arrangement

X GEOLOGICAL REFORM 319

which are out of reach of direct observation ; or,
it may be physiological speculation so far as it
relates to undetermined problems relative to the
activities of the earth ; or, it may be distributional
speculation, if it deals with modifications of the
earth's place in space ; or, finally, it will be aetio-
logical speculation if it attempts to deduce the
history of the world, as a whole, from the known
properties of the matter of the earth, in the con-
ditions in which the earth has been placed.

For the purposes of the present discourse I may
take this last to be what is meant by " geological
speculation."

Now Uniformitarianism, as we have seen, tends
to ignore geological speculation in this sense
altogether.

The one point the catastrophists and the uni-
formitarians agreed upon, when this Society was
founded, was to ignore it. And you will find, if
you look back into our records, that our revered
fathers in geology plumed themselves a good deal
upon the practical sense and wisdom of this
proceeding. As a temporary measure, I do not
presume to challenge its wisdom ; but in all
organised bodies temporary changes are apt to
produce permanent effects ; and as time has
slij)ped by, altering all the conditions which may
have made such mortification of the scientific flesh
desirable, I think the effect of the stream of cold
water which has steadily flowed o^er geological

320 GEOLOGICAL REFORM x

speculation within these walls has been of doubtful
beneficence.

The sort of geological speculation to which I am
now referring (geological aetiology, in short) was
created, as a science, by that famous philosopher
Immanuel Kant, when, in 1775, he wrote his
"General Natural History and Theory of the
Celestial Bodies ; or an Attempt to account for
the Constitutional and the Mechanical Origin of
the Universe upon Newtonian principles." ^

In this very remarkable but seemingly little-
known treatise,^ Kant expounds a complete cosmo-
gony, in the shape of a theory of the causes which
have led to the development of the universe
from diffused atoms of matter endowed with simple
attractive and repulsive forces.

" Give me matter," says Kant, " and I will build
the world ; " and he proceeds to deduce from the
simple data from which he starts, a doctrine in all
essential respects similar to the well-known
" Nebular Hypothesis " of Laplace.^ He accounts
for the relation of the masses and the densities of
the planets to their distances from the sun, for the
eccentricities of their orbits, for their rotations, for

* Grant {History of Physical Astronomy, p. 674) makes but
the briefest reference to Kant.

- " Allgemeine Naturgesehichte und Theorie des Himmels :
oder Yersuch von der Vevfassung und dem mechanischen
Urspvunge des ganzen Weltgebaudes nach Newton'schen Grund-
satzen abgeliandelt. " — Kant's Sdmmtliche JVerke, Bd. i. p.
207. ^ Systeme du Mondc^ tome ii. chap. 6.

X GEOLOGICAL REFORM 821

their satellites, for the general agreement in the
direction of rotation among the celestial bodies, for
Saturn's ring, and for the zodiacal Hght. He finds
in each system of worlds, indications that the
attractive force of the central mass will eventually
destroy its organisation, by concentrating upon
itself the matter of the whole system ; but, as the
result of this concentration, he argues for the
development of an amount of heat which will
dissipate the mass once more into a molecular
chaos such as that in which it began.

Kant pictures to himself the universe as once
an infinite expansion of formless and diffused
matter. At one point of this he supposes a single
centre of attraction set up ; and, by strict deduc-
tions from admitted d}T2amical principles, shoAvs
how this must result in the development of a
prodigious central body, surrounded by systems
of solar and planetary worlds in all stages of
development. In vivid language he depicts the
giaat world-maelstrom, widening the margins of its
prodigious eddy in the slow progress of millions of
ages, gradually reclaiming more and more of the
molecular waste, and converting chaos into cosmos.
But what is gained at the margin is lost in the
centre ; the attractions of the central systems
bring their constituents together, which then, by
the heat evolved, are converted once more into
molecular chaos. Thus the worlds that are, lie
between the ruins of the worlds that have been,

207

822 GEOLOGICAL EEFORM x

and the chaotic materials of the worlds that shall
be; and in spite of all waste and destruction,
Cosmos is extending his borders at the expense of
Chaos.

Kant's further application of his views to the
earth itself is to be found in his " Treatise on
Physical Geography"^ (a term under which the
then unkno^vn science of geology was included), a
subject which he had studied with very great
care and on which he lectured for many years.
The fourth section of the first part of this Treatise
is called " History of the great Changes which
the Earth has formerly undergone and is still
undergoing," and is, in fact, a brief and pregnant
essay upon the principles of geology. Kant gives
an account first " of the gradual changes which
are now taking place " under the heads of such as
are caused by earthquakes, such as are brought
about by rain and rivers, such as are effected by
the sea, such as are produced by winds and frost ;
and, finally, such as result from the operations of
man.

The second part is devoted to the " Memorials
of the Changes which the Earth has undergone in
remote Antiquity." These are enumerated as : —
A. Proofs that the sea formerly covered the whole
earth. B. Proofs that the sea has often been
changed into dry land and then again into sea.
C. A discussion of the various theories of the
* Kaki's Sdmmtli-che Werke, Bd. viii. p. 145.

X GEOLOGICAL REFORM 823

earth put forward by Scheuchzer, Moro, Bonnet,
Woodward, White, Leibnitz, Linnaeus, and Buffon.

The third part contains an " Attempt to give a
sound explanation of the ancient history of the
earth."

I suppose that it would be very easy to pick
holes in the details of Kant's speculations, whether
cosmological, or specially telluric, in their appli-
cation. But for all that, he seems to me to have
been the first person to frame a complete system
of geological speculation by founding the doctrine
of evolution.

With as much truth as Hutton, Kant could say,
" I take things just as I find them at present, and,
from these, I reason with regard to that which
must have been." Like Hutton, he is never tired
of pointing out that " in Nature there is wisdom,
system, and consistency." And, as in these great
principles, so in believing that the cosmos has a
reproductive operation " by which a ruined consti-
tution may be repaired," he forestalls Hutton;
while, on the other hand, Kant is true to science.
He knows no bounds to geological speculation
but those of the intellect. He reasons back to a
beginning of the present state of things; he
admits the possibility of an end.

I have said that the three schools of geological
speculation which I have termed Catastrophism,
tJniformitarianism, and Evolutionism, are com-
monly supposed to be antagonistic to one another ;

32-i GEOLOGICAL REFORM x

and I presume it will have become obvious that
in my belief, the last is destined to swallow up
the other two. But it is proper to remark that
each of the latter has kept alive the tradition of
precious truths.

Catastrophism has insisted upon the existence
of a practically unlimited bank of force, on which
the theorist might draw; and it has cherished the
idea of the development of the earth from a state
in which its form, and the forces which it exerted,
were very different from those we now know.
That such difference of form and power once
existed is a necessary part of the doctrine of
evolution.

Uniformitarianism, on the other hand, has with
equal justice insisted upon a practically unlimited
bank of time, ready to discount any quantity of
hypothetical paper. It has kept before our eyes
the power of the infinitely little, time being
granted, and has compelled us to exhaust known
causes, before flying to the unknown.

To my mind there appears to be no sort of
necessary theoretical antagonism between Cata-
strophism and Uniformitarianism, On the contrary,
it is very conceivable that catastrophes may be
part and parcel of uniformity. Let me illustrate
my case by analog}^ The working of a clock is a
model of uniform action ; good time-keeping
means uniformity of action. But the striking
of the clock is essentially a catastrophe; the

X GEOLOGICAL REFORM 325

hammer might he made to blow up a barrel of
gunpowder, or turn on a deluge of water ; and, by
proper arrangement, the clock, instead of marking
the hours, might strike at all sorts of irregular
periods, never twice alike, in the intervals, force,
or number of its blows. Nevertheless, all these
irregular, and apparently lawless, catastrophes
would be the result of an absolutely uniformitarian
action ; and we might have two schools of clock-
theorists, one studying the hammer and the other
the pendulum.

Still less is there any necessary antagonism
between either of these doctrines and that of
Evolution, which embraces all that is sound in
both Catastrophism and Uniformitarianism, while
it rejects the arbitrary assumptions of the one and
the, as arbitrary, hmitations of the other. Nor is
the value of the doctrine of Evolution to the philo-
sophic thinker diminished by the fact that it applies
the same method to the hving and the not-living
world ; and embraces, in one stupendous analogy,
the growth of a solar system from molecular chaos,
the shaping of the earth from the nebulous cub-
hood of its youth, through innumerable changes
and immeasurable ages, to its present form ; and
the development of a living being from the shape-
less mass of protoplasm we term a germ.

I do not know whether Evolutionism can claim
that amount of currency which would entitle it
to be called British popular geology ; but, more

326 GEOLOGICAL REFOKM X

or less vaguely, it is assuredly present in the
minds of most geologists.

Such being the three phases of geological
speculation, we are now in position to inquire
which of these it is that Sir William Thomson
calls upon us to reform in the passages which I
have cited.

It is obviously Uniformitarianism which the
distinguished physicist takes to be the representa-
tive of geological speculation in general. And
thus a first issue is raised, inasmuch as many
persons (and those not the least thoughtful among
the younger geologists) do not accept strict Uni-
formitarianism as the final form of geological
speculation. We should say, if Hutton and
Playfair declare the course of the world to have
been always the same, point out the fallacy by all
nxeans ; but, in so doing, do not imagine that
you are proving modern geology to be in opposi-
tion to natural philosophy. I do not suppose
that, at the present day, any geologist would be
found to maintain absolute Uniformitarianism,
to deny that the rapidity of the rotation of the
earth may be diminishing, that the sun Tnay be
waxing dim, or that the earth itself may be
cooling. Most of us, I suspect, are GalHos, " who
care for none of these things," being of opinion
that, true or fictitious, they have made no prac-
tical difference to the earth, during the period

X GEOLOGICAL REFORM 827

of which a record is preserved in stratified
deposits.

The accusation that we have been running
counter to the princiiolcs of natural philosophy,
therefore, is devoid of foundation. The only
question which can arise is whether we have, or
have not, been tacitly making assumptions which
are in opposition to certain conclusions which
may be drawn from those principles. And this
question subdivides itself into two : — the first,
are we really contravening such conclusions ? the
second, if we are, are those conclusions so firmly
based that we may not contravene them ? I reply
in the negative to both these questions, and I
will give you my reasons for so doing. Sir
Wilham Thomson believes that he is able to
prove, by physical reasonings, " that the existing
state of things on the earth, life on the earth — all
geological history showing continuity of life
— must be limited within some such jDcriod
of time as one hundred million years " {Ice.
cit. p. 25).

The first inquiry which arises plainly is, has it
ever been denied that this period inay be enough
for the purposes of geology ?

The discussion of this question is greatly
embarrassed by the vagueness with which the
assumed limit is, I will not say defined, but
indicated, — " some such period of past time as
one hundred million years." Now does this mean

328 GEOLOGICAL REFORM X

that it may have been two, or three, or four
hundred million years? Because this really
makes all the difference.^

I presume that 100,000 feet may be taken as a
full allowance for the total thickness of stratified
rocks containing traces of life ; 100,000 divided
by 100,000,000 = O'OOl. Consequently, the deposit
of 100,000 feet of stratified rock in 100,000,000
years means that the deposit has taken place
at the rate of xgVo ^^ ^ ^^^t, or, say, qV of an
inch, per annum.

Well, I do not know that any one is prepared
to maintain that, even making all needful allow-
ances, the stratified rocks may not have been
formed, on the average, at the rate of ^^ of an
inch per annum. I suppose that if such could be
shown to be the limit of world-gTowth, we could
put up with the allowance without feeling that
our speculations had undergone any revolution.
And perhaps, after all, the qualifjang phrase
*' some such period " may not necessitate the
assumption of more than y^^ or g-J^ or -g^ of
an inch of deposit per year, which, of course,
would give us still more ease and comfort.

But, it may be said, that it is biology, and not
creolooy, which asks for so much time — that the
succession of life demands vast intervals ; but

^ Sir William Thomson implies {Joe. cit. p, 16) that the pre-
cise time is of no consequence : "the principle is the same":
hut, as the principle is admitted, the whole discussion turns on
its practical results.

X GEOLOGICAL KEFORM 329

this appears to me to be reasoning in a circle.
Biology takes her time from geology. The only
reason we have for believing in the slow rate of
the change in living forms is the fact that they
jDcrsist through a series of deposits which, geology
informs us, have taken a long while to make.
If the geological clock is wrong, all the naturalist
will have to do is to modify his notions of the
-apidity of change accordingly. And I venture
to point out that, when we are told that the
limitation of the period during which living
beings have inhabited this planet to one, two, or
three hundred million years requires a complete
revolution in geological speculation, the onus
prchandi rests on the maker of the assertion,
who brings forward not a shadow of evidence
in its support.

Thus, if we accept the limitation of time placed
before us by Sir W. Thomson, it is not obvious,
on the face of the matter, that we shall have to
alter, or reform, our ways in any appreciable
degree ; and we may therefore proceed with much
calmness, and indeed much indifference, as to the
result, to inquire whether that hmitation is
justified by the arguments employed in its
support.

These argum_ents are three in number: —
I. The first is based upon the undoubted fact
that the tides tend to retard the rate of the
earth's rotation upon its axis. That this must

330 GEOLOGICAL REFORM X

be so is obvious, if one considers, roughly, that
the tides result from the pull which the sun
and the moon exert upon the sea, causing it
to act as a sort of break upon the rotating solid
earth.

Kant, who was by no means a mere " abstract
philosopher," but a good mathematician and well
versed in the physical science of his time, not
only proved this in an essay of exquisite clear-
ness and intelligibility, now more than a century
old, ^ but deduced from it some of its more im-
portant consequences, such as the constant turn-
ing of one face of the moon towards the earth.

But there is a long step from the demonstration
of a tendency to the estimation of the practical
value of that tendency, which is all with which
we are at present concerned. The facts bearing
on this point appear to stand as follows : —

It is a matter of observation that the moon's
mean motion is (and has for the last 3,000 years
been) undergoing an acceleration, relatively to
the rotation of the earth. Of course this may
result from one of two causes : the moon may
really have been moving more swiftly in its orbit ;
or the earth may have been rotating more slowly
on its axis.

^ " Untersuchung der Frage ob die Erde in ihrer Umdrehung
um die Achse, wodurch sie die Abwechselung des Tages \;nd der
Naclit liervorbringt, einige Vevanuening seit den ersten Zeiten
ihres Ursprunges erlitten habe, kc." — Kant's Sdmmtlicht
IVerke, Bd. i. p. 178.

X GEOLOGICAL REFORM 831

Laplace believed he had accounted for this phe-
nomenon by the fact that the eccentricity of the
earth's orbit has been diminishing throughout
these 3,000 years. This would produce a diminu-
tion of the mean attraction of the sun on the
moon; or, in other words, an increase in the
attraction of the earth on the moon; and, con-
sequently, an increase in the rapidity of the orbital
motion of the latter body. Laplace, therefore,
laid the responsibility of the acceleration upon
the moon, and if his views were correct, the tidal
retardation must either be insignificant in amount,
or be counteracted by some other agency.

Our great astronomer, Adams, however, appears
to have found a flaw in Laplace's calculation, and
to have shown that only half the observed re-
tardation could be accounted for in the way he
had suggested. There remains, therefore, the
other half to be accounted for ; and here, in the
absence of all positive knowledge, three sets of
hypotheses have been suggested.

(a.) M. Delaunay suggests that the earth is at
fault, in consequence of the tidal retardation.
Messrs. Adams, Thomson, and Tait work out this
suggestion, and, "on a certain assumption as to
the proportion of retardations due to the sun and
moon," find the earth may lose twenty -two seconds
of time in a century from this cause.^

(h.) But M. Dufour suggests that the retardation

^ Sir W. Thomson, loe. cit. p. 14.

832 GEOLOGICAL REFORM X

of the earth (which is hypothetically assumed to
exist) may be due in part, or wholly, to the increase
of the moment of inertia of the earth by meteors
falling upon its surface. This suggestion also
meets with the entire approval of Sir W. Thomson,
who shows that meteor-dust, accumulating at the
rate of one foot in 4,000 years, would account for
the remainder of retardation.^

(c.) Thirdly, Sir W. Thomson brings forward an
h3^othesis of his own with respect to the cause
of the hypothetical retardation of the earth's
rotation : —

" Let us suppose ice to melt from the polar
regions (20° round each pole, we may say) to the
extent of something more than a foot thick,
enough to give 1"1 foot of water over those areas,
or 0'006 of a foot of water if spread over the whole
globe, which would, in reality, raise the sea-level
by only some such undiscoverable difference as
three-fourths of an inch or an inch. This, or the
reverse, which we believe might happen any year,
and could certainly not be detected without far
more accurate observations and calculations for
the mean sea-level than any hitherto made, would
slacken or quicken the earth's rate as a timekeeper
by one -tenth of a second per year." ^

I do not presume to throw the slightest doubt
upon the accuracy of any of the calculations made
by such distinguished mathematicians as those
1 Sir W. Thomson, loc. cit. p. 27. ^ /jj^?.

X GEOLOGICAL REFORM 883

who have made the suggestions I have cited. On
the contrary, it is necessary to my argument to
assume that they are all correct. But I desire to
point out that this seems to be one of the many
cases in which the admitted accuracy of mathe-
matical process is allowed to throw a wholly
inadmissible appearance of authority over the
results obtained by them. Mathematics may be
compared to a mill of exquisite workmanship,
which grinds you stuff of any degree of fineness ;
but, nevertheless, what you get out depends upon
what you put in ; and as the grandest mill in the
world will not extract wheat-flour from peascods,
so pages of formulae will not get a definite result
out of loose data.

In the present instance it appears to be
admitted : —

1. That it is not absolutely certain, after all,
whether the moon's mean motion is underofoinof
acceleration, or the earth's rotation retardation.^
And yet this is the key of the whole position.

2. If the rapidity of the earth's rotation is
diminishing, it is not certain how much of that
retardation is due to tidal friction, how much to
meteors, — how much to possible excess of melting
over accumulation of polar ice, during the period
covered by observation, which amounts, at the
outside, to not more than 2,600 years.

^ It will be understood that I do not wish to deny that the
earth's rotation may he undergoing retardation.

834 GEOLOGICAL REFORM X

3. The effect of a different distribution of land
and water in modifying the retardation caused by
tidal friction, and of reducing it, under some cir-
cumstances, to a minimum, does not appear to be
taken into account.

4. During the Miocene epoch the polar ice was
certainly many feet thinner than it has been dur-
ing, or since, the Glacial epoch. Sir W. Thomson
tells us that the accumulation of something more
than a foot of ice around the poles (which implies
the withdrawal of, say, an inch of water from the
general surface of the sea) will cause the earth
to rotate quicker by one-tenth of a second per
annum. It would appear, therefore, that the earth
may have been rotating, throughout the whole
period which has elapsed from the commencement
of the Glacial epoch down to the present time, one,
or more, seconds per annum quicker than it
rotated during the Miocene epoch.

But, according to Sir W. Thomson's calculation,
tidal retardation will only account for a retardation
of 22" in a century, or y%%- (say i) of a second per
annum.

Thus, assuming that the accumulation of polar
ice since the Miocene epoch has only been suffi-
cient to produce ten times the effect of a coat of
ice one foot thick, we shall have an accelerating
cause which covers all the loss from tidal action,
and leaves a balance of 4 of a second per annum
in the way of acceleration.

X GEOLOGICAL REFORM 335

If tidal retardation can be thus checked and
overthrown by other temporary conditions, what
becomes of the confident assertion, based upon the
assumed uniformity of tidal retardation, that ten
thousand million years ago the earth must have
been rotating more than twice as fast as at
present, and, therefore, that we geologists are
" in direct opposition to the principles of Natural
Philosophy " if we spread geological history over
that time ?

II. The second argument is thus stated by Sir
W. Thomson : — " An article, by myself, published
in ' Macmillan's Magazine ' for March 1862, on the
age of the sun's heat, explains results of investiga-
tion into various questions as to possibilities
regarding the amount of heat that the sun could
have, dealing with it as you would with a stone, or a
piece of matter, only taking into account the sun's
dimensions, which showed it to be possible that
the sun may have already illuminated the earth
for as many as one hundred million years, but at
the same time rendered it almost certain that he
had not illuminated the earth for five hundred
millions of years. The estimates here are neces-
sarily very vague ; but yet, vague as they are, I do
not know that it is possible, upon any reasonable
estimate founded on known properties of matter,
to say that we can believe the sun has really ilium •
inated the earth for five hundred million years." ^
* I/^. ciL p. 20.

336 GEOLOGICAL REFORM X

I do not wish to " Hansardise " Sir William
Thomson by laying much stress on the fact that,
only fifteen years ago he entertained a totally differ-
ent view of the origin of the sun's heat, and
believed that the energy radiated from year to
year was supphed from year to year — a doctrine
which would have suited Hutton perfectly. But
the fact that so eminent a physical philosopher
has, thus recently, held views opposite to those
which he now entertains, and that he confesses his
own estimates to be " very vague," justly entitles
us to disregard those estimates, if any distinct
facts on our side go against them. However, I am
not aware that such facts exist. As I have already
said, for anything I know, one, two, or three hun-
dred millions of years may serve the needs of
geologists perfectly well.

III. The third line of argument is based upon
the temperature of the interior of the earth. Sir
W. Thomson refers to certain investigations which
prove that the present thermal condition of the
interior of the earth implies either a heating of
the earth within the last 20,000 years of as much
as 100' F., or a greater heating all over the surface
at some time further back than 20,000 years, and
then proceeds thus : —

" Now, are geologists prepared to admit that, at
some time within the last 20,000 years, there has
been all over the earth so high a temperature as
that ? I presume not ; no geologist — no w.odern

X GEOLOGICAL REFORM 837

geologist — would for a moment admit tlie hypo-
thesis that the present state of underground heat
is due to a heating of the surface at so late a
period as 20,000 years ago. If that is not admitted
we are driven to a greater heat at some time more
than 20,000 years ago. A greater heating all
over the surface than 100° Fahrenheit would kill
nearly all existing plants and animals, I may
safely say. Are modern geologists prepared to
say that all life was killed off the earth 50,000,
100,000, or 200,000 years ago ? For the uniformity
theory, the further back the time of high surface-
temperature is put the better ; but the further
back the time of heating, the hotter it must have
been. The best for those who draw most largely
on time is that which puts it furthest back ; and
that is the theory that the heating was enough to
melt the whole. But even if it was enough to
melt the whole, we must still admit some limit,
such as fifty million years, one hundred million
years, or two or three hundred million years ago.
Beyond that we cannot go." ^

It will be observed that the " limit " is once
again of the vaguest, ranging from 50,000,000
years to 300,000,000. And the reply is, once
more, that, for anjrfching that can be proved to the
contrary, one or two hundred million years might
serve the purpose, even of a thoroughgoing Hut-
tonian uniformitarian, very well.
^ Loc. cit. p. 24.
208

338 GEOLOGICAL REFORM X

But if, on the other hand, the 100,000,000 or
200,000,000 years appear to be insufficient for
geological purposes, we must closely criticise the
method by which the limit is reached. The
argument is simple enough. Assuming the earth
to be nothing but a cooling mass, the quantity of
heat lost per year, siippcsi7ig the rate of cooling to
have been uniform, multipHed by any given
number of years, will be given the minimum
temperature that number of years ago.

But is the earth nothing but a cooling mass,
"like a hot-water jar such as is used in carriages,"
or " a globe of sandstone," and has its cooling
been uniform ? An affirmative answer to both
these questions seems to be necessary to the
validity of the calculations on which Sir W.
Thomson lays so much stress.

Nevertheless it surely may be urged that such
affirmative answers are purely hypothetical, and
that other suppositions have an equal right to
consideration.

For example, is it not possible that, at the
prodigious temperature which would seem to
exist at 100 miles below the surface, aU the
metallic bases may behave as mercury does at a
red heat, when it refuses to combine with oxygen ;
while, nearer the surface, and therefore at a lower
temperature, they may enter into combination (as
mercury does with oxygen a few degrees below its
boiling-point), and so give rise to a heat totally

X GEOLOGICAL REFORM 889

distinct from that which they possess as cooHng
bodies ? And has it not also been proved by
recent researches that the quahty of the atmo-
sphere may immensely affect its permeability to
heat ; and, consequently, profoundly modify the
rate of cooling the globe as a whole ?

I do not think it can be denied that such con-
ditions may exist, and may so greatly affect the
supply, and the loss, of terrestrial heat as to
destroy the value of any calculations which leave
them out of sight.

My functions as your advocate are at an end. I
speak with more than the sincerity of a mere
advocate when I express the belief that the case
against us has entirely broken down. The cry for
reform which has been raised without, is super-
fluous, inasmuch as w"e have long been reforming
from within, with all needful speed. And the
critical examination of the grounds upon which
the very grave charge of opposition to the principles
of Natural Philosophy has been brought against
us, rather shows that we have exercised a wise
discrimination in declining, for the present, to
meddle with our foundations.

XI

PALEONTOLOGY AND THE DOCTRINE
OF EVOLUTION

[1870]

It is now eight years since, in the absence of
the late Mr. Leonard Horner, who then presided
over us, it fell to my lot, as one of the Secretaries
of this Society, to draw up the customary Annual
Address. I availed myself of the opportunity to
endeavour to " take stock " of that yjortion of the
science of biology, which is commonly called
" palaeontology," as it then existed ; and, dis-
cussing one after another the doctrines held by
palseontologists, I put before you the results of
my attempts to sift the well-established from
the h3^pothetical or the doubtful. Permit me
briefly to recall to your minds what those results
were : —

1. The Hving population of all parts of the
earth's surface which have yet been examined

XI PALEONTOLOGY AND EVOLUTION 341

has undergone a succession of changes which,
upon the whole, have been of a slow and gradual
character.

2. When the fossil remains which are the
evidences of these successive changes, as they
have occurred in any two more or less distant
parts of the surface of the earth, are com-
pared, they exhibit a certain broad and general
parallelism. In other words, certain forms of
life in one locality occur in the same general
order of succession as, or are homotaxicd with,
similar forms in the other locahty.

3. Homotaxis is not to be held identical with
synchronism wdthout independent evidence. It
is possible that similar, or even identical, faunse
and flor« in two different locahties may be of
extremely diiBferent ages, if the term " age " is
used in its proper chronological sense. I stated
that " geographical provinces, or zones, may have
been as distinctly marked in the Palaeozoic epoch
as at present ; and those seemingly sudden ap-
pearances of new genera and species which we
ascribe to new creation, may be simple results
of migration."

4. The opinion that the oldest known fossils
are the earhest forms of hfe has no sohd founda-
tion.

5. If we confine ourselves to positively ascer-
tained facts, the total amount of change in the
forms of animal and vegetable life, since the

842 PALAEONTOLOGY AND EVOLUTION xi

existence of such forms is recorded, is small.
When compared with the lapse of time since
the first appearance of these forms, the amount
of change is wonderfully small. Moreover, in
each great group of the animal and vegetable
kingdoms, there are certain forms which I termed
Persistent Types, which have remained, with
but very little apparent change, from their first
appearance to the present time.

6. In answer to the question " What, then, does
an impartial survey of the positively ascertained
truths of palaeontology testify in relation to the
common doctrines of progressive modification,
which suppose that modification to have
taken place by a necessary progress from more
to less embryonic forms, from more to less general-
ised types, within the limits of the period
represented by the fossiliferous rocks ? " I reply,
" It negatives these doctrines ; for it either
show us no evidence of such modification, or
demonstrates such modification as has occurred
to have been very slight ; and, as to the nature
of that modification, it yields no evidence what-
soever that the earlier members of any long-con-
tinued group were more generalised in structure
than the later ones."

I think that I cannot employ my last opportu-
nity of addressing you, officially, more properly — >
I may say more dutifully — than in revising these
old judgments with such help as further know-

XI PALEONTOLOGY AND EVOLUTION 343

ledge and reflection, and an extreme desire to get
at the truth, may afford me.

1. With respect to the first proposition, I may-
remark that whatever may be the case among the
physical geologists, catastrophic palaeontologists
are practically extinct. It is now no part of
recognised geological doctrine that the species of
one formation all died out and were replaced by a
brand-new set in the next formation. On the
contrary, it is generally, if not universally, agreed
that the succession of life has been the result of a
slow and gradual replacement of species by species ;
and that all appearances of abruptness of change
are due to breaks in the series of deposits, or other
changes in physical conditions. The continuity of
living forms has been unbroken from the earliest
times to the present day.

2, 3. The use of the word " homotaxis " instead
of " synchronism " has not, so far as I know, found
much favour in the eyes of geologists. I hope,
therefore, that it is a love for scientific caution,
and not mere personal affection for a bantling of
my own, which leads me still to think that the
change of phrase is of importance, and that
the sooner it is made, the sooner shall we get rid
of a number of pitfalls which beset the reasoner
upon the facts and theories of geology.

One of the latest pieces of foreign intelligence
which has reached us is the information that the
Austrian geologists have, at last, succumbed to

844 PALEONTOLOGY AND EVOLUTION xi

fche weighty evidence which M. Barrande has
accumulated, and have admitted the doctrine of
colonies. But the admission of the doctrine of
colonies implies the further admission that even
identity of organic remains is no proof of the
synchronism of the deposits which contain
them.

4. The discussions touching the Eozoon, which
commenced in 1864, have abundantly justified the
fourth proposition. In 1862, the oldest record of
life was in the Cambrian rocks ; but if the Eozoon
be, as Principal Dawson and Dr. Carpenter have
shown so much reason for believing, the remains
of a living being, the discovery of its true nature
carried life back to a period which, as Sir William
Logan has observed, is as remote from that during
which the Cambrian rocks were deposited, as the
Cambrian epoch itself is from the tertiaries. In
other words, the ascertained duration of life upon
the globe was nearly doubled at a stroke.

5. The significance of persistent types, and of
the small amount of change which has taken place
even in those forms which can be shown to have
been modified, becomes greater and greater in my
eyes, the longer I occupy myself with the biology
of the past.

Consider how long a time has elapsed since the
Miocene epoch. Yet, at that time there is reason
to believe that every important group in every
order of the Mammalia was represented. Even the

XI PALEONTOLOGY AND EVOLUTION 845

comparatively scanty Eocene fauna 3delds examples
of the orders Cheiroptera, Insectwora, Rodentia, and
Pcrissodactyla ; of Articdactyla under both the
Ruminant and the Porcine modifications ; of Carni-
vora, Cetacea, and Marsupialia.

Or, if we go back to the older half of the Meso-
zoic epoch, how truly surprising it is to find
every order of the Re][)tilia, except the Ophidia,
represented ; while some groups, such as the
Omithoscelida and the Pterosauria, more specialised
than any which now exist, abounded.

There is one division of the Amphibia which
offers especially important evidence upon this
point, inasmuch as it bridges over the gap between
the Mesozoic and the Palaeozoic formations (often
supposed to be of such prodigious magnitude), ex-
tending, as it does, from the bottom of the Car-
boniferous series to the top of the Trias, if not
into the Lias. I refer to the LabjTinthodonts.
As the Address of 1862 was passing through the
press, I was able to mention, in a note, the
discovery of a large Labyrinthodont, with well-
ossified vertebrse, in the Edinburgh coal-field.
Since that time eight or ten distinct genera of
Labyrinthodonts have been discovered in the
Carboniferous rocks of England, Scotland, and
Ireland, not to mention the American forms
described by Principal Dawson and Professor
Cope. So that, at the present time, the Labpin-
thodont Fauna of the Carboniferous rocks is moie

846 PALEONTOLOGY AND EVOLUTION xi

extensive and diversified than that of the Trias,
while its chief types, so far as osteology enables
us to judge, are quite as highly organised. Thus
it is certain that a comparatively highly organised
vertebrate type, such as that of the Labyiintho-
donts, is capable of persisting, with no considerable
change, through the period represented by the
vast deposits which constitute the Carboniferous,
the Permian, and the Triassic formations.

The very remarkable results which have been
brought to light by the sounding and dredging
operations, which have been carried on with such
remarkable success by the expeditions sent out by
our own, the American, and the Swedish Govern-
ments, under the supervision of able naturalists,
have a bearing in the same direction. These in-
vestigations have demonstrated the existence, at
great depths in the ocean, of living animals in
some cases identical with, in others very similar
to, those which are found fossilised in the white
chalk. The G-loligcrince, Cyatholiths, Cocco-
spheres, Discoliths in the one are absolutely
identical with those in the other ; there are
identical, or closely analogous, species of Sponges,
Echinoderms, and Brachiopods. Off the coast of
Portugal, there now lives a species of Bcryx, which,
doubtless, leaves its bones and scales here and
there in the Atlantic ooze, as its predecessor left
its spoils in the mud of the sea of the Cretaceous
epoch.

XI PALJEONTOLOGY" AND EVOLUTION 847

Many years ago^ I ventured to speak of the
Atlantic mud as " modern chalk," and I know of
no fact inconsistent with the view which Professor
Wyville Thomson has advocated, that the modem
chalk is not only the Kneal descendant of the
ancient chalk, but that it remains, so to speak, in
the possession of the ancestral estate; and that
from the Cretaceous period (if not much earlier)
to the present day, the deep sea has covered a
large part of what is now the area of the Atlantic.
But if Glchigerina, and Terebratula caput-serpentis
and Beryx, not to mention other forms of animals
and of plants, thus bridge over the interval
between the present and the Mesozoic periods, is
it possible that the majority of other living things
underwent a " sea-change into something new and
strange " all at once ?

6. Thus far I have endeavoured to expand and
to enforce by fresh arguments, but not to modify
in any important respect, the ideas submitted to
you on a former occasion. But when I come to
the propositions touching progressive modifica-
tion, it appears to me, with the help of the new
light which has broken from various quarters, that
there is much ground for softening the somewhat
Brutus-like severity with which, in 1862, I dealt
with a doctrine, for the truth of which I should
have been glad enough to be able to find a good

^ See an article in the Saturday Eevicia, for 1858, on " Chalk,
Ancient and Modem."

348 PALAEONTOLOGY AND EVOLUTION xi

foundation. So far, indeed, as the Invertehrata and
the lower Vertehrata are concerned, the facts and
the conclusions which are to be drawn from them
appear to me to remain what they were. For
anything that, as yet, appears to the contrary, the
earhest known Marsupials may have been as
highly organised as their living congeners ; the
Permian Hzards show no signs of inferiority to
those of the present day; the Labyrinthodonts
cannot be placed below the living Salamander and
Triton ; the Devonian Ganoids are closely related
to Poly'pteTiiS and to Lejndosiren.

But when we turn to the higher Verfxhratay
the results of recent investigations, however we
may sift and criticise them, seem to me to leave a
clear balance in favour of the doctrine of the
evolution of Hving forms one from another.
Nevertheless, in discussing this question, it is
very necessary to discriminate carefully between
the different kinds of evidence from fossil re-
mains which are brought forward in favour of
evolution.

Every fossil which takes an intermediate place
between forms of life already known, may be said,
so far as it is intermediate, to be evidence in
favour of evolution, inasmuch as it shows a possible
road by which evolution may have taken place.
But the mere discovery of such a form does not,
in itself, prove that evolution took place by and
through it, nor does it constitute more than pre-

XI

PALEONTOLOGY AND EVOLUTION 349

sumptive evidence in favour of evolution in
general. Suppose A, B, C to be three forms,
while B is intermediate in structure between A
and C. Then the doctrine of evolution offers four
possible alternatives. A may have become C by
way of B ; or C may have become A by way of B ;
or A and C may be independent modifications of
B ; or A, B, and C may be independent modifica-
tions of some unknown D. Take the case of the
Pigs, the Ancplotheridcc, and the Ruminants.
The AnoplotJieridce are intermediate between the
first and the last ; but this does not tell us whether
the Ruminants have come from the Pigs, or the
Pigs from Ruminants^ or both from Anajylotheridce,
or whether Pigs, Ruminants, and Anoplotheridce
alike may not have diverged from some common
stock.

But if it can be shown that A, B, and C exhibit
successive stages in the degree of modification, or
specialisation, of the same tjipe ; and if, farther, it
can be proved that they occur m successively
newer deposits, A being in the oldest and C in
the newest, then the intermediate character of B
has quite another importance, and I should accept
it, without hesitation, as a link in the genealogy
of C. I should consider the burden of proof to be
thrown upon any one who denied C to have been
derived from A by way of B, or in some closely
analogous fashion ; for it is always probable that
one may not hit upon the exact line of filiation,

350 PALEONTOLOGY AND EVOLUTION xi

and, in dealing with fossils, may mistake uncles
and nephews for fathers and sons.

I think it necessary to distinguish between the
former and the latter classes of intermediate forms,
as intercalary types and linear types. When I
apply the former term, I merely mean to say that
as a matter of fact, the form B, so named, is inter-
mediate between the others, in the sense in which
the Anoplotherium is intermediate between the
Pigs and the Ruminants — without either affirming,
or denying, any direct genetic relation between
the three forms involved. When I apply the
latter term, on the other hand, I mean to express
the opinion that the forms A, B, and C constitute
a line of descent, and that B is thus part of the
lineage of C

From the time when Cuvier's wonderful re-
searches upon the extinct Mammals of the Paris
gypsum first made intercalary types known, and
caused them to be recognised as such, the number
of such forms has steadily increased among the
higher Mammalia. Not only do we now know
numerous intercalary forms of Ungulata, but M.
Gaudry's great monograph upon the fossils of
Pikermi (which strikes me as one of the most
perfect pieces of palseontological work I have seen
for a long time) shows us, among the Primates,
Mesopithecus as an intercalary form between the
Semnopitheci and the Macaci ; and among the
Carnivora, Hycenictis and Iditherium as intercalary,

XI PALEONTOLOGY AND EVOLUTION 351

or, perhaps, linear types between the Viverridne
and the Hycenidce.

Hardly any order of the higher Mammalia
stands so apparently separate and isolated from
the rest as that of the Cdacea ; though a careful
consideration of the structure of the pinnipede
Carnivora, or Seals, shows, in them, many an
approximation towards the still more completely
marine mammals. The extinct Zeuglcclon, how-
ever, presents us with an intercalary form between
the t}q)e of the Seals and that of the Whales.
The skull of this great Eocene sea-monster, in
fact, shows by the narrow and prolonged inter-
orbital region ; the extensive union of the parietal
bones in a sagittal suture ; the well-developed
nasal bones ; the distinct and large incisors
implanted in premaxillary bones, which take a
full share in bounding the fore part of the gape ;
the two-fano-ed molar teeth with triangular and
serrated crowns, not exceeding five on each side
in each jaw ; and the existence of a deciduous
dentition — its close relation with the Seals.
While, on the other hand, the produced rostral
form of the snout, the long symphysis, and the
low coronary process of the mandible are approxi-
mations to the cetacean form of those parts.

The scapula resembles that of the cetacean
Hyperoodon, but the supra-spinous fossa is larger
and more seal-like ; as is the humerus, which
differs from that of the Cdacea in presenting true

352 PALAEONTOLOGY AND EVOLUTION xi

articular surfaces for the free jointing of the
bones of the fore-arm. In the apparently com-
plete absence of hinder limbs, and in the characters
of the vertebral column, the Zeuglodon lies on the
cetacean side of the boundary line ; so that upon
the whole, the Zeuglodonts, transitional as they
are, are conveniently retained in the cetacean
order. And the publication, in 1864, of M. Van
Beneden's memoir on the Miocene and Pliocene
Squalcdon, furnished much better means than
anatomists previously possessed of fitting in
another link of the chain which connects the
existing Cctacca with Zcuglcdon. The teeth are
much more numerous, although the molars exhibit
the zeuglodont double fang ; the nasal bones are
very short, and the upper surface of the rostrum
presents the groove, filled up during life by the
prolongation of the ethmoidal cartilage, which is
so characteristic of the majority of the Cetacea.

It appears to me that, just as among the
existing Carnivora, the walruses and the eared
seals are intercalary forms between the fissipede
Carnivora and the ordinary seals, so the Zeuglo-
donts are intercalary between the Carnivora, as a
whole, and the Cetacea. Whether the Zeuglodonts
are also linear types in their relation to these two
groups cannot be ascertained, until we have more
definite knowledge than we possess at present,
respecting the relations in time of the Carnivora
and Cetacea.

XI PAL^OXTOLOGY AND EVOLUTION 358

Thus far we have been concerned with the
intercalary types which occupy the intervals
between Families or Orders of the same class ;
but the investigations which have been carried
on by Professor Gegenbaur, Professor Cope, and
myself into the structure and relations of the
extinct reptiUan forms of the Ornithoscelida (or
Dinosauricb and CGmpsognatha) have brought to
light the existence of intercalary forms betv/een
what have hitherto been always regarded as very
distinct classes of the vertebrate sub-kino^dom,
namely Beptilia and Aves. Whatever inferences
may, or may not, be drawn from the fact, it is
now an estabhshed truth that, in many of these
Ornithoscelida, the hind limbs and the pelvis are
much more similar to those of Birds than they
are to those of Reptiles, and that these Bird-
reptiles, or Reptile-birds, were more or less com-
pletely bipedal.

When I addressed you in 1862, I should have
been bold indeed had I suggested that palaeon-
tology would before long show us the possibility
of a direct transition from the type of the lizard
to that of the ostrich. At the present moment,
we have, in the Ornithoscelida, the intercalary t}^e,
which proves that transition to be something
more than a possibility; but it is very doubtful
whether any of the genera of Ornithoscelida with
which we are at present acquainted are the actua]
linear types by which the transition from the

209

854 PALEONTOLOGY AND EVOLUTION xi

lizard to the bird was effected. These, very prob-
ably, are still hidden from us in the older for-
mations.

Let us now endeavour to find some cases of
true linear types, or forms which are intermediate
between others because they stand in a direct
genetic relation to them. It is no easy matter to
find clear and unmistakable evidence of filiation
among fossil animals; for, in order that such
evidence should be quite satisfactory, it is necessary
that we should be acquainted with all the most
important features of the organisation of the
animals which are supposed to be thus related, and
not merely with the fragments upon which the
genera and species of the palaeontologist are so
often based. M. Gaudry has arranged the species
of HycenidcB, Prohoscidea, Bhinccerotidce, and Equidce
in their order of filiation from their earliest appear-
ance in the Miocene epoch to the present time, and
Professor Riitimeyer has drawn up similar schemes
for the Oxen and other Ungulata — with what, I
am disposed to think, is a fair and probable approxi-
mation to the order of nature. But, as no one is
better aware than these two learned, acute, and
philosophical biologists, all such arrangements
must be regarded as provisional, except in those
cases in which, by a fortunate accident, large
series of remains are obtainable from a thick and
widespread series of deposits. It is easy to
accumulate probabilities — hard to make out somB

XI PALEONTOLOGY AND EVOLUTION 855

particular case in such a way that it will stand
rigorous criticism.

After much search, however, I think that such
a case is to be made out in favour of the pedigree
of the Horses.

The genus Equus is represented as far back as
the latter part of the Miocene epoch; but in
deposits belonging to the middle of that epoch its
place is taken by two other genera, ffijyjmrion and
Anchitlierium ; ^ and, in the lowest Miocene and
upper Eocene, only the last genus occurs. A
species of Anchitlierium was referred by Cuvier to
the Palceotheria under the name of P. aurelianense.
The grinding-teeth are in fact very similar in
shape and in pattern, and in the absence of any
thick layer of cement, to those of some species of
Paloeotherium, especially Cuvier's Palceotherium
minus, which has been formed into a separate
genus, Plagiolophus, by Pomel. But in the fact
that there are only six full-sized grinders in the
lower jaw, the first premolar being very small;
that the anterior grinders are as large as, or
rather larger than, the posterior ones ; that the

^ Heniiann von Meyer gave the name of Anchitherium to A.
Ezquerrce ; and in his paper on the subject he takes great pains
to distinguish the latter as the type of a new genus, from
Cuvier's Palceothe?'iu7n d' Orleans. But it is precisely the
Palceotherium d'Orleans Avhich is the type of Christol's genus
Hipparitherhcm ; and thus, though Hipi'^riihcrium is of later
date than Anchitherium, it seemed to me to have a sort of
equitable right to recognition when this Address was written.
On the whole, however, it seems most convenient to adopt
Anchitherium.

856 PALiEONTOLOGY AND EVOLUTION xi

second premolar has an anterior prolongation ; and
that the posterior molar of the lower jaw has, as
Cuvier pointed out, a posterior lobe of much
smaller size and different form, the dentition of
Anchitherium departs from the type of the
Palceotherium, and approaches that of the Horse.

Again, the skeleton of Anchitherium is ex-
tremely equine. M. Christol goes so far as to
say that the description of the bones of the horse,
or the ass, current in veterinary works, would fit
those of AncJiitherium. And, in a general way,
this may be true enough ; but there are some most
important differences, which, indeed, are justly
indicated by the same careful observer. Thus the
ulna is complete throughout, and its shaft is not a
mere rudiment, fused into one bone with the
radius. There are three toes, one large in the
middle and one small on each side. The femur is
quite like that of a horse, and has the character-
istic fossa above the external condyle. In the
British Museum there is a most instructive
specimen of the leg-bones, showing that the fibula
was represented by the external malleolus and by
a flat tongue of bone, which extends up from it
on the outer side of the tibia, and is closely
ankylosed with the latter bone.^ The hind toes

^ I am indebted to M. Gervais for a specimen which indicates
that the fibula v/as complete, at any rate, in some cases ; and
for a very interesting ramus of a mnndible, -which shows that,
as in the Palccothcria, the hindermost milk-molar of the lowei

XI PALEONTOLOGY AXD EVOLUTION 857

are three, like those of the fore leg; and the
middle metatarsal bone is much less compressed
from side to side than that of the horse.

In the Hi^ppariorij the teeth nearly resemble
those of the Horses, though the crowns of the
grinders are not so long ; like those of the Horses,
they are abundantly coated with cement. The
shaft of the ulna is reduced to a mere style, anky-
losed throughout nearly its whole length with the
radius, and appearing to be little more than a
ridge on the surface of the latter bone until it is
carefully examined. The front toes are still three,
but the outer ones are more slender than in
Anchitherium, and their hoofs smaller in proportion
to that of the middle toe ; they are, in fact, re-
duced to mere dew-claws, and do not touch the
ground. In the leg, the distal end of the fibula is
so completely united with the tibia that it appears
to be a mere process of the latter bone, as in the
Horses.

In Equus, finally, the crowns of the grinding-
teeth become longer, and their patterns are slightly
modified ; the middle of the shaft of the ulna
usually vanishes, and its proximal and distal ends
ankylose with the radius. The phalanges of the
two outer toes in each foot disappear, their meta-
carpal and metatarsal bones being left as the
« sphnts."

jaw was devoid of the posterior lobe which exists in the hinder*
most triie molar.

358 PALEONTOLOGY AND EVOLUTION xi

The Hipparion has large depressions on the
face in front of the orbits, Hke those for the
" larmiers " of many ruminants ; but traces of these
are to be seen in some of the fossil horses from
the Sewalik EQlls; and, as Leidy's recent re-
searches show, they are preserved in Anchi-
therium.

When we consider these facts, and the further
circumstance that the Hipparions, the remains of
which have been collected in immense numbers,
were subject, as M. Gaudry and others have
pointed out, to a great range of variation, it
appears to me impossible to resist the conclusion
that the types of the Anchithcriiim, of the
Jlipparion, and of the ancient Horses consti-
tute the Hneage of the modern Horses, the Jlip-
parion being the intermediate stage between the
other two, and answering to B in my foiTQer
illustration.

The process by which the Anchitherium has
been converted into Equus is one of specialisation,
or of more and more complete deviation from what
might be called the average form of an ungulate
mammal. In the Horses, the reduction of some
parts of the limbs, together with the special modi-
fication of those which are left, is carried to a
greater extent than in any other hoofed mammals.
The reduction is less and the specialisation is less
in the Hipparion, and still less in the Anchi-
therium ; but yet, as compared with other mam-

XI PALEONTOLOGY AND EVOLUTION 359

mals, the reduction and specialisation of parts in
the Anchitherium remain great.

Is it not probable then, that, just as in the
Miocene epoch, we find an ancestral equine form
less modified than Uqtms, so, if we go back
to the Eocene epoch, we shall find some quadruped
related to the Anchitherium, as Hipparion is re-
lated to Eqious, and consequently departing less
from the average form ?

I think that this desideratum is very nearly, if
not quite, supplied by Flagiolophtts, remains of
which occur abundantly in some parts of the
Upper and Middle Eocene formations. The
patterns of the grinding-teeth of Plagiolcphus are
similar to those of Anchitherium, and their crowns
are as thinly covered with cement; but the
grinders diminish in size forwards, and the last
lower molar has a large hind lobe, convex outwards
and concave inwards, as in Falceotherium.. The
ulna is complete and much larger than in any of
the Equidce, while it is more slender than in most
of the true Palceotheria ; it is fixedly united, but
not ankylosed, with the radius. There are three
toes in the fore limb, the outer ones being slender,
but less attenuated than in the Equiclce. The
femur is more like that of the Palceotheria than
that of the horse, and has only a small depression
above its outer condyle in the place of the gTeat
fossa which is so obvious in the Pquidce. The fibula
is distinct, but very slender, and its distal end is

360 PALEONTOLOGY AND EVOLUTION XI

ankjdosed with the tibia. There are three toes
on the hind foot having similar proportions to
those on the fore foot. The principal metacarpal
and metatarsal bones are flatter than they are in
any of the Equidce ; and the metacarpal bones are
longer than the metatarsals, as in the Palceothcria.
■ In its general form, PlagioloijJius resembles a
very small and slender horse,^ and is totally unlike
the reluctant, pig-like creature depicted in Cuvier's
restoration of his Palceotlurium minus in the
" Ossemens Fossiles."

It would be hazardous to say that PlagiolopTius
is the exact radical form of the Equine quadru-
peds; but I do not think there can be any
reasonable doubt that the latter animals have
resulted from the modification of some quadruped
similar to Plagiolophus.

We have thus arrived at the Middle Eocene
formation, and yet have traced back the Horses
only to a three-toed stock ; but these three-toed
forms, no less than the Equine quadrupeds them-
selves, present rudiments of the two other toes
which appertain to what I have termed the
" average " quadruped. If the expectation raised
by the splints of the Horses that, in some ancestor
of the Horses, these splints would be found to
be complete digits, has been verified, we are fur-

^ Such, at least, is the conclusion sugo^ested by the proportions
of the skeleton figured by Cuvier and De Blainville ; but per-
haps something between a Horse and an Agouti would be nearest
the mark.

XI PALAEONTOLOGY AND EVOLUTION 861

nished with very strong reasons for looking for a
no less complete verification of the expectation
that the three-toed FlagiolojjJitcs-like " avus " of the
horse must have had a five-toed " atavus " at some
earlier period.

No such five-toed " atavus," however, has yet
made its appearance among the few middle and
older Eocene Mammalia which are known.

Another series of closely affiliated forms, though
the evidence they afford is perhaps less complete
than that of the Equine series, is presented to
us by the Diclwhune of the Eocene epoch, the
Cainctherium of the Miocene, and the Tragulidce,
or so-called " Musk-deer," of the present day.

The Tragulidm have no incisors in the upper
jaw, and only six grinding-teeth on each side of
each jaw ; while the canine is moved up to the
outer incisor, and there is a diastema in the lower
jaw. There are four complete toes on the hind
foot, but the middle metatarsals usually become,
sooner or later, ankylosed into a cannon bone.
The navicular and the cuboid unite, and the
distal end of the fibula is ankylosed with the
tibia.

In Cainctherium and Dichchune the upper
incisors are fully developed. There are seven
grinders ; the teeth form a continuous series with-
out a diastema. The metatarsals, the navicular
and cuboid, and the distal end of the fibula,
remain free. In the Cainctheriicm, also, the second

362 PALEONTOLOGY AND EVOLUTION xi

metacarpal is developed, but is much shorter than
the third, while the fifth is absent or rudimentary.
In this respect it resembles Anoplotherium secimda^
rium. This circumstance, and the peculiar pattern
of the upper molars in Caincthcrium, lead me to
hesitate in considering it as the actual ancestor
of the modern Tragulidce. If Diclioliune has a
fore-toed fore foot (though I am inclined to
suspect that it resembles Caincther,iu7n), it will
be a b'etter representative of the oldest forms of
the Traguline series ; but Dichchune occurs in the
Middle Eocene, and is, in fact, the oldest known
artiodactyle mammal. Where, then, must we
look for its five-toed ancestor ?

If we follow down other lines of recent and
tertiary Ungidata, the same question presents
itself. The Pigs are traceable back through the
Miocene epoch to the Upper Eocene, where they
appear in the two well-marked forms of Hyopopo-
tamus and Chmropotamus ; but Hyojpotamus appears
to have had only two toes.

Again, all the great groups of the Ruminants,
the Bovidoe, Antilcpidoe, Camelopardcdidce, and
Cewidce, are represented in the Miocene epoch, and
so are the Camels. The Upper Eocene Anc^jlo'
therium, which is intercalary between the Pigs
and the Tragulidce, has only two, or, at most,
three toes. Among the scanty mammals of the
Lower Eocene formation we have the perisso-
dactyle Ungulata rej)resented by Coryphcdon^

XI PALEONTOLOGY AND EVOLUTION 863

Kyracotherium, and Fliolophus. Suppose for a
moment, for tlie sake of following out the
argument, that Flioloj^htcs represents the primary
stock of the Perissodactyles, and Dichohune that
of the Artiodactyles (though I am far from saying
that such is the case), then we find, in the earliest
fauna of the Eocene epoch to which our investiga-
tions carry us, the two divisions of the Ungulata
completely differentiated, and n) trace of any
common stock of both, or of hve-toed predecessors
to either. With the case of the Horses before us,
justifying a belief in the production of new
animal forms by modification of old ones, I see no
escape from the necessity of seeking for these
ancestors of the Ungulata beyond the limits of
the Tertiary formations.

I could as soon admit special creation, at
once, as suppose that the Perissodactyles and
Artiodactyles had no five- toed ancestors. And
when we consider how large a portion of the
Tertiary period elapsed before Anchithermm was
converted into Uquus, it is difficult to escape the
conclusion that a large proportion of time anterior
to the Tertiary period must have been expended
in converting the common stock of the Ungulata
into Perissodactyles and Artiodactyles.

The same moral is inculcated by the study
of every other order of Tertiary monodelphous
Mammalia. Each of these orders is represented
in the Miocene epoch : the Eocene formation, as

864 PALiEONTOLOGY AND EVOLUTION xi

I have already said, contains Cheircptera, Inscdi-
vora, Bodentia, Ungulata, Carnivora, and Cetacea,
But the CheivGiJtera are extreme modifications
of the Insectivora, just as the Cdacea are extreme
modifications of the Carnivorous t}^e ; and there-
fore it is to my mind incredible that monodelphous
Inscctivora and Carnivora should not have been
abundantly developed, along with Ungidata, in
the Mesozoic epoch. But if this be the case,
how much further back must we go to find the
common stock of the monodelphous Mainmalia?
As to the Didelphia, if we may trust the evidence
which seems to be afforded by their very scanty
remains, a Hypsiprymnoid form existed at the
epoch of the Trias, contemporaneously with a
Carnivorous form. At the epoch of the Trias,
therefore, the Marsiiiyialia must have already
existed long enough to have become differentiated
into carnivorous and herbivorous forms. But the
Monotremata are lower forms than the Didelphia
which last are intercalary between the Ornitho-
delphia and the Moncddphia. To what point of
the Palaeozoic epoch, then, must we, upon any
rational estimate, relegate the origin of the
Monotremata ?

The investigation of the occurrence of the
classes and of the orders of the Sauropsida in time
points in exactly the same direction. If, as there
is great reason to believe, true Birds existed in
the Triassic epoch, the ornithoscelidous forms by

XI PALEONTOLOGY AND EVOLUTION 865

whicti Reptiles passed into Birds must have pre-
ceded them. In fact there is, even at present,
considerable ground for suspecting the existence
of Binoscmria in the Permian formations ; but, in
that case, lizards must be of still earlier date.
And if the very small differences which are
observable between the Crocodilia of the older
Mesozoic formations and those of the present day
furnish any sort of approximation toAvards an
estimate of the average rate of change among the
Sauropsida, it is almost appalling to reflect how far
back in Palaeozoic times we must go, before we
can hope to arrive at that common stock from
which the Crocodilia, Lacertilia, Ornithoscdida,
and Flesiosauria, which had attained so great a
development in the Triassic epoch, must have
been derived.

The Amphibia and Pisces tell the same story.
There is not a single class of vertebrated animals
which, when it first appears, is represented by
analogues of the lowest known members of the
same class. Therefore, if there is any truth in
the doctrine of evolution, every class must be vastly
older than the first record of its appearance upon
the surface of the globe. But if considerations of
this kind compel us to place the origin of ver-
tebrated animals at a period sufficiently distant
from the Upper Silurian, in which the first Elas-
mobranchs and Ganoids occur, to allow of the
evolution of such fishes as these firom a Vertebrate

366 PALEONTOLOGY AND EVOLUTION xi

as simple as the Ampliioxus, I can only repeat
that it is appalling to speculate upon the extent
to which that origin must have preceded the
epoch of the first recorded appearance of verte-
brate life.

Such is the further commentary which I have
to offer upon the statement of the chief results of
palseontology which I formerly ventured to lay
before you.

But the growth of knowledge in the interval
makes me conscious of an omission of considerable
moment in that statement, inasmuch as it contains
no reference to the bearings of palseontology upon
the theory of the distribution of Hfe; nor takes
note of the remarkable manner in which the facts
of distribution, in present and past times, accord
with the doctrine of evolution, especially in regard
to land animals.

That connection between palseontology and
geology and the present distribution of terrestrial
animals, which so strikingly impressed Mr. Darwin,
thirty years ago, as to lead him to speak of a " law
of succession of types," and of the wonderful re-
lationship on the same continent between the
dead and the living, has recently received much
elucidation from the researches of Gaudry, of
Rutimeyer, of Leidy, and of Alphonse Milne-
Edwards, taken in connection with the earlier
labours of our lamented colleague Falconer; and

XI PALEONTOLOGY AND EVOLUTION 867

it has been instructively discussed in the thought-
ful and ingenious work of Mr. Andrew Murray
" On the Geographical Distribution of Mammals." ^

I propose to lay before you, as briefly as I can,
the ideas to which a long consideration of the
subject has given rise in my mind.

If the doctrine of evolution is sound, one of its
immediate consequences clearly is, that the present
distribution of life upon the globe is the product
of two factors, the one being the distribution
which obtained in the immediately preceding
epoch, and the other the character and the extent
of the changes which have taken place in physical
geography between the one epoch and the other ;
or, to put the matter in another way, the Fauna
and Flora of any given area, in any given epoch,
can consist only of such forms of life as are directly
descended from those which constituted the Fauna
and Flora of the same area in the immediately
preceding epoch, unless the physical geography
(under which I include climatal conditions) of
the area has been so altered as to give rise to
immigration of living forms from some other
area.

The evolutionist, therefore, is bound to grapple

^ The paper * ' On the Form and Distribution of the Land-
tracts during the Secondary and Tertiary Periods respectively ;
and on the Effect upon Animal Life M'hich great Changes m
Geograpliical Configuration have probably produced," by Mr.
Searles V. Wood, jun., which was published in th.Q Philosophical
Magazine, in 1862, was unknown to me when this Address
Was written. It is well worthy of the most careful study.

368 PALEONTOLOGY AND EVOLUTION xi

with the following problem whenever it is clearly
put before him : — Here are the Faunae of the same
area during successive epochs. Show good cause
for believing either that these Faunae have been
derived from one another by gradual modification,
or that the Faunae have reached the area in ques-
tion by migration from some area in which they
have undergone their development.

I propose to attempt to deal with this problem,
so far as it is exemplified by the distribution of
the terrestrial Vertchrata, and I shall endeavour
to show you that it is capable of solution in a
sense entirely favourable to the doctrine of evo-
hition.

I have elsewhere ^ stated at length the reasons
which lead me to recognise four primary distribu-
tional provinces for the terrestrial Vertchrata in
the present world, namely, — first, the Ncvozelanian,
or New-Zealand province ; secondly, the Austra-
lian province, including Australia, Tasmania, and
the Negrito Islands ; thirdly, Aitstro-Cohtnibia, or
South America plus North America as far as
Mexico ; and fourthly, the rest of the world, or
Ardoga^a, in which province America north of
Mexico constitutes one sub-province, Africa south
of the Sahara a second, Hindostan a third, and the
remainder of the Old World a fourth.

Now the truth which Mr. Darwin perceived and

1 " On the Classification and Distribution of the Alectoro-
morphfe ; " Proceedings of the Zoological itociriy, 1868.

XI PALEONTOLOGY AND EVOLUTION 369

promulgated as "the law of tlie succession of
types " is, that, in all these provinces, the animals
found in Pliocene or later deposits are closely
affined to those which now inhabit the same pro-
vinces ; and that, conversely, the forms character-
istic of other provinces are absent. North and
South America, perhaps, present one or two
exceptions to the last rule, but they are readily
susceptible of explanation. Thus, in Australia, the
later Tertiary mammals are marsupials (possibly
with the exception of the Dog and a Rodent or two,
as at present). In Austro-Columbia, the later
Tertiary fauna exhibits numerous and varied forms
of Platyrrhine Apes, Rodents, Cats, Dogs, Stags,
Edentata, and Opossums ; but, as at present, no
Catarrhine Apes, no Lemurs, no Insectivora, Oxen,
Antelopes, Rhinoceroses, nor Didelphia other than
Opossums. And in the widespread Arctogseal
province, the Pliocene and later mammals belong
to the same gi'oups as those which now exist in
the province. The law of succession of types^
therefore, holds good for the present epoch as
compared with its predecessor. Does it equally
well apply to the Pliocene fauna when we com-
pare it with that of the Miocene epoch ? By
great good fortune, an extensive mammalian fauna
of the latter epoch has now become known, in
four very distant portions of the Arctogseal pro-
vince which do not differ greatly in latitude.
Thus Falconer and Cautley have made known the

210

370 PALEONTOLOGY AND EVOLUTION xi

fauna of the sub-Himalayas and the Perim Islands ;
Gaudry that of Attica ; many observers that of
Central Europe and France ; and Leidy that of
Nebraska, on the eastern flank of the Rocky
Mountains. The results are very striking. The
total Miocene fauna comprises many genera and
species of Catarrhine Apes, of Bats, of Insectivora ;
of Arctog^eal t}^es of Pvodentia ; oi Frohoscidea ; of
equine, rhinocerotic, and tapirine quadrupeds ; of
cameline, bovine, antilopine, cervine, and traguline
Ruminants; of Pigs and Hippopotamuses; of
Viverridcc and Hycenidce among other Carnivora ;
with Edentata allied to the Arctogseal Oryderopus
and Maiiis, and not to the Austro-Columbian
Edentates. The only type present in the Miocene
but absent in the existing, fauna of Eastern Arc-
togaea, is that of the Dideli^liidce, which, however,
remains in North America.

But it is very remarkable that while the
Miocene fauna of the Arctog^al province, as
a whole, is of the same character as the existing
fauna of the same province, as a whole, the com-
ponent elements of the fauna were differently as-
sociated. In the Miocene epoch. North America
possessed Elephants, Horses, Rhinoceroses, and a
great number and variety of Ruminants and Pigs,
which are absent in the present indigenous fauna;
Europe had its Apes, Elephants, Rhinoceroses,
Tapirs, Musk-deer, Giraffes, Hyaenas, great Cats,
Edentates, and Opossum-like Marsupials, which

XI

PALJiONTOLOGY AND EVOLUTION 371

have equally vanished from its present fauna ;
and in Northern India, the African types of Hippo-
potamuses, Giraffes, and Elephants were mixed
up with what are now the Asiatic ty^es of the
latter, and with Camels, and Semnopithecine and
Pithecine Apes of no less distinctly Asiatic forms.
In fact the Miocene mammalian fauna of
Europe and the Himalayan regions contains, asso-
ciated together, the types which are at present
separately located in the South- African and
Indian sub-provinces of Arctogsea. Now there
is every reason to believe, on other grounds, that
both Hindostan, south of the Ganges, and Africa,
south of the Sahara, were separated by a wide
sea from Europe and North Asia during the
Middle and Upper Eocene epochs. Hence it
becomes highly probable that the well-known
similarities, and no less remarkable differences
between the present Faunae of India and South
Africa have arisen in some such fashion as the
following. Some time during the Miocene epoch,
possibly when the Himalayan chain was ele-
vated, the bottom of the nummulitic sea was
upheaved and converted into dry land, in the
direction of a line extending from Abyssinia to
the mouth of the Ganges. By this means, the
Dekhan on the one hand, and South Africa on
the other, became connected with the Miocene
dry land and with one another. The Miocene
mammals spread gradually over this intermediate

872 PALAEONTOLOGY AND EVOLUTION xi

dry land ; and if the condition of its eastern and
western ends offered as wide contrasts as the
valleys of the Ganges and Arabia do now, many
forms which made their way into Africa must
have been different from those which reached
the Dekhan, while others might pass into both
these sub-provinces.

That there was a continuity of dry land between
Europe and North America during the Miocene
epoch, appears to me to be a necessary consequence
of the fact that many genera of terrestrial
mammals, such as Castor, Hystrix, Mephas,
Mastodon, Uquus, Hipparion, AncMtJieriitm, Rhino-
ceros, Cervus, AmpMcyon, Hycenarctos, and Machair-
odus, are common to the Miocene formations of
the two areas, and have as yet been found (except
perhaps Anchitherium) in no deposit of earlier age.
Whether this connection took place by the east,
or by the west, or by both sides of the Old
World, there is at present no certain evidence, and
the question is immaterial to the present argu-
ment; but, as there are good grounds for the
belief that the Australian province and the Indian
and South- African sub-provinces were separated
by sea from the rest of Arctogsea before the
Miocene epoch, so it has been rendered no less
probable, by the investigations of Mr. Canick
Moore and Professor Duncan, that Austro-Columbia
was separated by sea from North America during
a large part of the Miocene epoch.

XI PALEONTOLOGY AND EVOLUTION 873

It is unfortunate that we have no knowledge oF
the Miocene mammalian fauna of the Australian
and Austro-Columbian provinces ; but, seeing that
not a trace of a Platyrrhine Ape, of a Procyonine
Carnivore, of a characteristically South-American
Rodent, of a Sloth, an Armadillo, or an Ant-eater
has yet been found in Miocene deposits of Arc-
tog^a, I cannot doubt that they already existed in
the Miocene Austro-Columbian province.

. Nor is it less probable that the characteristic
types of Australian Mammalia were already de-
veloped in that region in Miocene times.

But Austro-Columbia presents difficulties from
which Australia is free ; Camelidce and Tapiridce
are now indigenous in South America as they are
in Arctogsea; and, among the Pliocene Austro-
Columbian mammals, the Arctoggeal genera
Equus, Mastodon, and Machairodus are numbered.
Are these Postmiocene immigrants, or Praemio-
cene natives ?

Still more perplexing are the strange and in-
teresting forms Toxodon, Macrauchenm, Typo-
therium, and a new Anoplotherioid mammal
{Homalodotherium) which Dr. Cunningham sent
over to me some time ago from Patagonia. I con-
fess I am strongly inclined to surmise that these
last, at any rate, are remnants of the popula-
tion of Austro-Columbia before the Miocene
epoch, and were not derived from Arctogaea by
way of the north and east

874 PALEONTOLOGY AND EVOLUTION XI

The fact that this immense fauna of Miocene
Arctogaea is now fully and richly represented only
in India and in South Africa, while it is shrunk
and depauperised in North Asia, Europe, and
North America, becomes at once intelligible, if we
suppose that India and South Africa had but a
scanty mammalian population before the Miocene
immigration, while the conditions were highly
favourable to the new comers. It is to be supposed
that these new regions offered themselves to the
Miocene Ungulates, as South America and Australia
offered themselves to the cattle, sheep, and horses
of modern colonists. But, after these great areas
were thus peopled, came the Glacial epoch, during
which the excessive cold, to say nothing of depres-
sion and ice-covering, must have almost depopu-
lated all the northern parts of Arctogsea, destroying
all the higher mammalian forms, except those
which, like the Elephant and Rhinoceros, could
adjust their coats to the altered conditions. Even
these must have been driven away from the
greater part of the area; only those Miocene
mammals which had passed into Hindostan and
into South Africa would escape decimation by such
changes in the physical geography of Arctogsea.
And when the northern hemisphere passed into its
present condition, these lost tribes of the Miocene
Fauna were hemmed by the Himalayas, the
Sahara, the Red Sea, and the Arabian deserts,
within their present boundaries.

XI

PALEONTOLOGY AND EVOLUTION 875

Now, on the hypothesis of evolution, there is no
sort of difficulty in admitting that the differences
between the Miocene forms of the mammalian
Fauna and those which exist at present are the
results of gradual modification; and, since such
differences in distribution as obtain are readily
explained by the changes which have taken place
in the physical geography of the world since the
Miocene epoch, it is clear that the result of the
comparison of the Miocene and present Faunae is
distinctly in favour of evolution. Indeed I may
go further. I may say that the hypothesis of
evolution explains the facts of Miocene, Pliocene,
and Recent distribution, and that no other sup-
position even pretends to account for them. It is,
indeed, a conceivable supposition that every species
of Rhinoceros and every species of Hya3na, in the
long succession of forms between the Miocene and
the present species, was separately constructed out
of dust, or out of nothing, by supernatural power ;
but until I receive distinct evidence of the fact, I
refuse to run the risk of insulting any sane man
by supposing that he seriously holds such a
notion.

Let us now take a step further back in time,
and inquire into the relations between the Miocene
Fauna and its predecessor of the Upper Eocene
formation.

Here it is to be regretted that our materials for
forming a judgment are nothing to be compared

876 PALEONTOLOGY AND EVOLUTION xi

in point of extent or variety with those which are
yielded by the Miocene strata. However, what we
do know of this Upper Eocene Fauna of Europe
gives sufficient positive information to enable us
to draw some tolerably safe inferences. It has
yielded representatives of Inscdivora, of Cheir-
o'pUra, of Bodentia, of Carnivora, of artiodactyle
and perissodactyle Ungulata, and of opossum-like
Marsupials. No Australian type of Marsupial has
been discovered in the Upper Eocene strata, nor
any Edentate mammal. The genera (except per-
haps in the case of some of the Inscdivora, Cheir-
cptera, and Rodentia) are different from those of
the Miocene epoch, but present a remarkable
general similarity to the Miocene and recent
genera. In several cases, as I have already shown,
it has now been clearly made out that the relation
between the Eocene and Miocene forms is such
that the Eocene form is the less specialised ; while
its Miocene ally is more so, and the specialisation
reaches its maximum in the recent forms of the
same type.

So far as the Upper Eocene and the Miocene
Mammalian Faunae are comparable, their relations
are such as in no way to oppose the hypothesis
that the older are the progenitors of the more
recent forms, while, in some cases, they distinctly
favour that h}^othesis! The period in time and
the changes in physical geography represented by
the nummulitic dejiosits are undoubtedly very

XI PALEONTOLOGY AXD EVOLUTION 377

great, while the remains of Middle Eocene and
Older Eocene Mammals are comparatively few.
The general facies of the Middle Eocene Fauna,
however, is quite that of the Upper. The Older
Eocene pre-nummulitic mammalian Fauna con-
tains Bats, two genera of Carnivora, three genera
of Ungidatcc (probably all perissodactyle), and a
didelphid Marsupial; all these forms, except
perhaps the Bat and the Opossum, belong to
genera which are not known to occur out of the
Lower Eocene formation. The Coryphodcn appears
to have been allied to the Miocene and later
Tapirs, while PliolopJius, in its skull and dentition,
curiously partakes of both artiodactyle and perisso-
dactyle characters; the third trochanter upon
its femur and its three-toed hind foot, however,
appear definitely to fix its position in the latter
division.

There is nothing, then, in what is known of the
older Eocene mammals of the Arctogseal province
to forbid the supposition that they stood m an
ancestral relation to those of the Calcaire Grossier
and the Gypsum of the Paris basin, and that our
present fauna, therefore, is directly derived from
that which already existed in Arctogsea at the
commencement of the Tertiary period. But if
we now cross the firontier between the Cainozoic
and the Mesozoic faunae, as they are preserved
within the Arctoggeal area, we meet with an
astounding change, and what appears to be a

378 PALiEONTOLOGY AND EVOLUTION XT

complete and unmistakable break in the line of
biological continuity.

Among the twelve or fourteen species of Mam-
malia which are said to have been found in the
Parbecks, not one is a member of the orders
Cheiroptera, Bodentia, Ungulata, or Carnivora,
which are so well represented in the Tertiaries.
No Tnsectivora are certainly known, nor any
opossum-like Marsupials. Thus there is a vast
negative difference between the Cainozoic and
the Mesozoic mammalian faunae of Europe. But
there is a still more important positive difference,
inasmuch as all these Mammaha appear to be
Marsupials belonging to Australian groups, and
thus appertaining to a different distributional
province from the Eocene and Miocene marsupials,
which are Austro-Columbian. So far as the im-
perfect materials which exist enable a judgment
to be formed, the same law appears to have held
good for all the earlier Mesozoic Mammalia. Of
the Stonesfield slate mammals, one, Amphither-
ium, has a definitely Australian character; one,
Fhascolotherium, may be either Dasyurid or
Didelphine ; of a third, Stereo goiathus, nothing
can at present be said. The two mammals
of the Trias, also, appear to belong to Australian
groups.

Every one is aware of the many curious points
of resemblance between the marine fauna of the
European Mesozoic rocks and that which now

XI

PALEONTOLOGY AND EVOLUTION 879

exists in Australia. But if there was this
Australian facies about both the terrestrial and
the marine faunae of Mesozoic Europe, and if
there is this unaccountable and immense break
between the fauna of Mesozoic and that of
Tertiary Europe, is it not a very obvious sugges-
tion that, in the Mesozoic epoch, the Australian
province included Europe, and that the Arctogseal
province was contained within other limits ? The
Arctogseal province is at present enormous, while
the Austrahan is relatively small. Why should
not these proportions have been different during
the Mesozoic epoch ?

Thus I am led to think that by far the simplest
and most rational mode of accounting for the
great change which took place in the living
inhabitants of the European area at the end of
the Mesozoic epoch, is the supposition that it
arose from a vast alteration of the physical
geography of the globe ; whereby an area long
tenanted by Cainozoic forms was brought into
such relations with the European area that
migration from the one to the other became
possible, and took place on a great scale.

This supposition relieves us, at once, from the
difficulty in which we were left, some time ago,
by the arguments which I used to demonstrate
the necessity of the existence of all the great
types of the Eocene epoch in some antecedent
period.

880 PIL^ONTOLOGT AND EVOLUTION xi

It is this Mesozoic continent (which may well
have lain in the neighbourhood of what are now
the shores of the North Pacific Ocean) which I
suppose to have been occupied by the Mesozoic
Monodeljpliia ; and it is in this region that I con-
ceive they must have gone through the long
series of changes by which they were specialised
into the forms which we refer to different orders.
I think it very probable that what is now South
America may have received the characteristic
elements of its mammalian fauna during the
Mesozoic epoch ; and there can be httle doubt
that the general nature of the change which took
place at the end of the Mesozoic epoch in Europe
was the upheaval of the eastern and northern
regions of the Mesozoic sea-bottom into a west-
ward extension of the Mesozoic continent, over
which the mammalian fauna, by which it was
already peopled, gradually spread. This invasion
of the land was prefaced by a previous invasion of
the Cretaceous sea by modem forms of mollusca
and fish.

It is easy to imagine how an analogous change
might come about in the existing world. There
is, at present, a great difference between the fauna
of the Polynesian Islands and that of the west
coast of America. The animals which are leaving
their spoils in the deposits now forming in these
localities are widely different. Hence, if a gradual
shifting of the deep sea, which at present bars

xr PALEONTOLOGY AND EVOLUTION 381

migration between the easternmost of these islands
and America, took place to the westward, while
the American side of the sea-bottom was gradually
upheaved, the palaeontologist of the future would
find, over the Pacific area, exactly such a change
as I am supposing to have occurred in the North-
Atlantic area at the close of the Mesozoic period.
An Australian fauna would be found underl}?ing
an American fauna, and the transition from the
one to the other would be as abrupt as that
between the Chalk and lower Tertiaries ; and as
the drainage-area of the newly formed extension
of the American continent gave rise to rivers and
lakes, the mammals mired in their mud would
differ from those of like deposits on the Australian
side, just as the Eocene mammals differ from those
of the Purbecks.

How do similar reasonings apply to the other
great change of hfe — that which took place at the
end of the Palaeozoic period ?

In the Triassic epoch, the distribution of the
diy land and of terrestrial vertebrate life appears
to have been, generally, similar to that which
existed in the Mesozoic epoch ; so that the Triassic
continents and their faunae seem to be related to the
Mesozoic lands and their faunae, just as those of the
Miocene epoch are related to those of the present
day. In fact, as I have recently endeavoured to
prove to the Society, there was an Arctogaeal con-
tinent and an Arctogaeal province of distribution
in Triassic times as there is now ; and the Saurcp-

382 PALEONTOLOGY AND EVOLUTION il

sida and Marsu2ncdia which constituted that fauna
were, I doubt not, the progenitors of the Sauropsida
and Marsuinalia of the whole Mesozoic epoch.

Looking at the present terrestrial fauna of
Australia, it appears to me to be very probable
that it is essentially a remnant of the fauna of the
Triassic, or even of an earlier, age ; ^ in which case
Australia must at that time have been in continuity
with the Arctogseal continent.

But now comes the further inquiry, Where was
the highly differentiated Sauropsidan fauna of the
Trias in Palaeozoic times ? The supposition that
the Dinosaurian, Crocodilian, Dicynodontian, and
Plesiosaurian types were suddenly created at the
end of the Permian epoch may be dismissed, with-
out further consideration, as a monstrous and un-
warranted assumption. The supposition that all
these types were rapidly differentiated out of
Lacertilia in the time represented by the passage
from the Palaeozoic to the Mesozoic formation,
appears to me to be hardly more credible, to say
nothing of the indications of the existence of
Dinosaurian forms in the Permian rocks which
have already been obtained.

For my part, I entertain no sort of doubt that
the Reptiles, Birds, and Mammals of the Trias are
the direct descendants of Reptiles, Birds, and
Mammals which existed in the latter part of the

^ Since this Address was read, Mr. Krefft has sent us news of
the discovery in Australia of a freshwater fish of straugily
Palaeozoic aspect, and apparently a Ganoid intermediate between
Dipterus and Lepidosiren. [The now well-known Ceratodus. 189 'L.]

XI PALEONTOLOGY AND EVOLUTION 383

Palaeozoic epoch, but not in any area of the present
dry land which has yet been explored by the
geologist.

This may seem a bold assumption, but it will
not appear unwarrantable to those who reflect
upon the very small extent of the earth's surface
which has hitherto exhibited the remains of the
great Mammalian fauna of the Eocene times. In this
respect, the Permian land Vertebrate fauna appears
to me to be related to the Triassic much as the
Eocene is to the Miocene. Terrestrial reptiles
have been found in Permian rocks only in three
localities ; in some spots of France, and recently
of England, and over a more extensive area in
Germany. Who can suppose that the few fossils
yet found in these regions give any sufficient re-
presentation of the Permian fauna ?

It may be said that the Carboniferous forma-
tions demonstrate the existence of a vast extent
of dry land in the present dry-land area, and that
the supposed terrestrial Palaeozoic Vertebrate
Fauna ought to have left its remains in the Coal-
measures, especially as there is now reason to
believe that much of the coal was formed by the
accumulation of spores and sporangia on dry land.
But if we consider the matter more closely, I
think that this apparent objection loses its force.
It is clear that, during the Carboniferous epoch,
the vast area of land which is now covered by
Coal-measures must have been undergoing a
gradual depression. The dry land thus depressed

884 PALEONTOLOGY AND EVOLUTION xi

must, therefore, have existed, as such, before the
Carboniferous epoch — in other words, in Devonian
times — and its terrestrial population may never
have been other than such as existed during the
Devonian, or some previous epoch, although much
higher forms may have been develoiDed else-
where.

Again, let me say that I am making no
gratuitous assumption of inconceivable changes.
It is clear that the enormous area of Polynesia is,
on the whole, an area over which depression has
taken place to an immense extent ; consequently
a great continent, or assemblage of subcontinental
masses of land must have existed at some former
time, and that at a recent period, geologically
speaking, in the area of the Pacific. But if that
continent had contained Mammals, some of them
must have remained to tell the tale ; and as it is
well known that these islands have no indigenous
Mammalia, it is safe to assume that none existed.
Thus, midway between AustraHa and South
America, each of which possesses an abundant
and diversified mammahan fauna, a mass of land,
which may have been as large as both put together,
must have existed ^vithout a mammalian in-
habitant. Suppose that the shores of this great
land were fringed, as those of tropical Australia are
now, with belts of mangroves, which would extend
landwards on the one side, and be buried beneath
littoral deposits on the other side, as depression
went on; and great beds of mangrove lignite

XI PALEONTOLOGY AND EVOLUTION 885

might accumulate over the sinking land. Let
upheaval of the whole now take place, in such a
manner as to bring the emerging land into con-
tinuity with the South- American or Austrahan
continent, and, in course of time, it would be
peopled by an extension of the fauna of one of
these two regions — ^just as I imagine the European
Permian dry land to have been peopled.

I see nothing whatever against the supposition
that distributional provinces of terrestrial life
existed in the Devonian epoch, inasmuch as M.
Barrande has proved that they existed much
earlier. I am aware of no reason for doubting
that, as regards the grades of terrestrial life
contained in them, one of these may have been
related to another as New Zealand is to Australia,
or as Australia is to India, at the present day.
Analogy seems to me to be rather in favour of,
than against, the supposition that while only
Ganoid fishes inhabited the fresh waters of our
Devonian land, Amiohibia and Reptilia, or even
higher forms, may have existed, though we have
not yet found them. The earliest Carboniferous
AmpJiihia now known, such as Anthraccsaurus,
are so highly specialised that I can by no means
conceive that they have been developed out of
piscine forms in the interval between the Devonian
and the Carboniferous periods, considerable as that
is. And I take refuge in one of two alternatives ;
either they existed in our own area during the
Devonian epoch and we have simply not yet found

211

386 PALEONTOLOGY AND EVOLUTION xi

them; or they formed part of the population of
some other distributional province of that day,
and only entered our area by migration at the end
of the Devonian epoch. Whether Be2:)tilia and
Mammalia existed along with them is to me, at
present, a perfectly open question, which is just
as likely to receive an affirmative as a negative
answer from future inquirers.

Let me now gather together the threads of my
argumentation into the form of a connected hypo-
thetical view of the manner in w^hich the dis-
tribution of living and extinct animals has been
brought about.

I conceive that distinct provinces of the distribu-
tion of terrestrial life have existed since the earliest
period at which that life is recorded, and possibly
much earlier; and I suppose, with Mr. Darwin,
that the progress of modification of terrestrial
forms is more rapid in areas of elevation than in
areas of depression. I take it to be certain that
Labyrinthodont Amphibia existed in the distribu-
tional province which included the dry land
depressed during the Carboniferous epoch ; and
I conceive that, in some other distributional
provinces of that day, which remained in the
condition of stationary or of increasing dry land,
the various types of the terrestrial Sattrcjysida
and of the Mavimalia were gradually developing.

The Permian epoch marks the commencement
of a new movement of upheaval in our area, which
attained its maximum in the Triassic epoch, when

XI PAX^ONTOLOGY AND EVOLUTION 387

dry land existed in North Ameiica, Europe, Asia,
and Africa, as it does now. Into this great new
continental area the Mammals, Birds, and Rejjtiles
developed during the Palaeozoic epoch spread, and
formed the great Triassic Arctoga^al province.
But, at the end of the Triassic period, the move-
ment of depression recommenced in our area,
though it was doubtless balanced by elevation
elsewhere ; modification and development, checked
in the one province, went on in that " elsewhere " ;
and the chief forms of Mammals, Birds and Rep-
tiles, as we know them, were evolved and peopled
the Mesozoic continent. I conceive Australia to
have become separated from the continent as early
as the end of the Triassic epoch, or not much
later. The Mesozoic continent must, I conceive,
have lain to the east, about the shores of the
North Pacific and Indian Oceans ; and I am
inclined to believe that it continued along the
eastern side of the Pacific area to what is now the
province of Austro-Columbia, the characteristic
fauna of which is probably a remnant of the popu-
lation of the latter part of this period.

Towards the latter part of the Mesozoic
period the movement of upheaval around the
shores of the Atlantic once more recommenced,
and was very probably accompanied by a de-
pression around those of the Pacific. The Verte-
brate fauna elaborated in the Mesozoic continent
moved westward and took possession of the new

388 PAL^:ONTOLOGY AND EVOLUTION jj

lands, which gradually increased in extent up to,
and in some directions after, the Miocene epoch.

It is in favour of this hypothesis, I think,
that it is consistent with the persistence of a
general uniformity in the positions of the great
masses of land and water. From the Devonian
period, or earlier, to the present day, the four
great oceans, Atlantic, Pacific, Arctic, and Antarc-
tic, may have occupied their present positions,
and only their coasts and channels of communi-
cation have undergone an incessant alteration.
And, finally, the hypothesis I have put before you
requires no supposition that the rate of change in
organic life has been either greater or less in
ancient times than it is now ; nor any assumption,
either physical or biological, which has not its
justification in analogous phenomena of existing
nature.

I have now only to discharge the last duty
of my office, which is to thank you, not only
for the patient attention with which vou have
listened to me so long to-day, but also for the
uniform kindness with which, for the past two
years, you have rendered my endeavours to per-
form the important, and often laborious, functions
of your President a pleasure instead of a burden.

END OF VOLUME VII I.

:l^->:;