THE PAST CONDITION OF ORGANIC NATURE.

In the lecture which I delivered last Monday evening, I endeavoured to

sketch in a very brief manner, but as well as the time at my disposal

would permit, the present condition of organic nature, meaning by

that large title simply an indication of the great, broad, and general

principles which are to be discovered by those who look attentively at

the phenomena of organic nature as at present displayed. The general

result of our investigations might be summed up thus: we found that the

multiplicity of the forms of animal life, great as that may be, may be

reduced to a comparatively few primitive plans or types of construction;

that a further study of the development of those different forms

revealed to us that they were again reducible, until we at last brought

the infinite diversity of animal, and even vegetable life, down to the

primordial form of a single cell.

We found that our analysis of the organic world, whether animals or

plants, showed, in the long run, that they might both be reduced into,

and were, in fact, composed of, the same constituents. And we saw

that the plant obtained the materials constituting its substance by

a peculiar combination of matters belonging entirely to the inorganic

world; that, then, the animal was constantly appropriating the

nitrogenous matters of the plant to its own nourishment, and returning

them back to the inorganic world, in what we spoke of as its waste; and

that finally, when the animal ceased to exist, the constituents of its

body were dissolved and transmitted to that inorganic world whence they

had been at first abstracted. Thus we saw in both the blade of grass and

the horse but the same elements differently combined and arranged. We

discovered a continual circulation going on,--the plant drawing in the

elements of inorganic nature and combining them into food for the animal

creation; the animal borrowing from the plant the matter for its own

support, giving off during its life products which returned immediately

to the inorganic world; and that, eventually, the constituent materials

of the whole structure of both animals and plants were thus returned to

their original source: there was a constant passage from one state of

existence to another, and a returning back again.

Lastly, when we endeavoured to form some notion of the nature of the

forces exercised by living beings, we discovered that they--if

not capable of being subjected to the same minute analysis as the

constituents of those beings themselves--that they were correlative

with--that they were the equivalents of the forces of inorganic

nature--that they were, in the sense in which the term is now used,

convertible with them. That was our general result.

And now, leaving the Present, I must endeavour in the same manner to put

before you the facts that are to be discovered in the Past history of

the living world, in the past conditions of organic nature. We have,

to-night, to deal with the facts of that history--a history involving

periods of time before which our mere human records sink into utter

insignificance--a history the variety and physical magnitude of whose

events cannot even be foreshadowed by the history of human life and

human phenomena--a history of the most varied and complex character.

We must deal with the history, then, in the first place, as we should

deal with all other histories. The historical student knows that his

first business should be to inquire into the validity of his evidence,

and the nature of the record in which the evidence is contained, that

he may be able to form a proper estimate of the correctness of the

conclusions which have been drawn from that evidence. So, here, we must

pass, in the first place, to the consideration of a matter which may

seem foreign to the question under discussion. We must dwell upon the

nature of the records, and the credibility of the evidence they contain;

we must look to the completeness or incompleteness of those records

themselves, before we turn to that which they contain and reveal. The

question of the credibility of the history, happily for us, will not

require much consideration, for, in this history, unlike those of human

origin, there can be no cavilling, no differences as to the reality and

truth of the facts of which it is made up; the facts state themselves,

and are laid out clearly before us.

But, although one of the greatest difficulties of the historical student

is cleared out of our path, there are other difficulties--difficulties

in rightly interpreting the facts as they are presented to us--which

may be compared with the greatest difficulties of any other kinds of

historical study.

What is this record of the past history of the globe, and what are the

questions which are involved in an inquiry into its completeness or

incompleteness? That record is composed of mud; and the question which

we have to investigate this evening resolves itself into a question

of the formation of mud. You may think, perhaps, that this is a

vast step--of almost from the sublime to the ridiculous--from the

contemplation of the history of the past ages of the world's existence

to the consideration of the history of the formation of mud! But,

in nature, there is nothing mean and unworthy of attention; there

is nothing ridiculous or contemptible in any of her works; and this

inquiry, you will soon see, I hope, takes us to the very root and

foundations of our subject.

How, then, is mud formed? Always, with some trifling exception, which

I need not consider now--always, as the result of the action of water,

wearing down and disintegrating the surface of the earth and rocks with

which it comes in contact--pounding and grinding it down, and carrying

the particles away to places where they cease to be disturbed by this

mechanical action, and where they can subside and rest. For the ocean,

urged by winds, washes, as we know, a long extent of coast, and every

wave, loaded as it is with particles of sand and gravel as it breaks

upon the shore, does something towards the disintegrating process. And

thus, slowly but surely, the hardest rocks are gradually ground down to

a powdery substance; and the mud thus formed, coarser or finer, as the

case may be, is carried by the rush of the tides, or currents, till it

reaches the comparatively deeper parts of the ocean, in which it can

sink to the bottom, that is, to parts where there is a depth of about

fourteen or fifteen fathoms, a depth at which the water is, usually,

nearly motionless, and in which, of course, the finer particles of this

detritus, or mud as we call it, sinks to the bottom.

Or, again, if you take a river, rushing down from its mountain sources,

brawling over the stones and rocks that intersect its path, loosening,

removing, and carrying with it in its downward course the pebbles and

lighter matters from its banks, it crushes and pounds down the rocks and

earths in precisely the same way as the wearing action of the sea waves.

The matters forming the deposit are torn from the mountain-side and

whirled impetuously into the valley, more slowly over the plain, thence

into the estuary, and from the estuary they are swept into the sea. The

coarser and heavier fragments are obviously deposited first, that is,

as soon as the current begins to lose its force by becoming amalgamated

with the stiller depths of the ocean, but the finer and lighter

particles are carried further on, and eventually deposited in a deeper

and stiller portion of the ocean.

It clearly follows from this that mud gives us a chronology; for it is

evident that supposing this, which I now sketch, to be the sea bottom,

and supposing this to be a coast-line; from the washing action of the

sea upon the rock, wearing and grinding it down into a sediment of mud,

the mud will be carried down, and at length, deposited in the deeper

parts of this sea bottom, where it will form a layer; and then, while

that first layer is hardening, other mud which is coming from the same

source will, of course, be carried to the same place; and, as it is

quite impossible for it to get beneath the layer already there, it

deposits itself above it, and forms another layer, and in that way you

gradually have layers of mud constantly forming and hardening one above

the other, and conveying a record of time.

It is a necessary result of the operation of the law of gravitation that

the uppermost layer shall be the youngest and the lowest the oldest, and

that the different beds shall be older at any particular point or spot

in exactly the ratio of their depth from the surface. So that if they

were upheaved afterwards, and you had a series of these different layers

of mud, converted into sandstone, or limestone, as the case might be,

you might be sure that the bottom layer was deposited first, and that

the upper layers were formed afterwards. Here, you see, is the first

step in the history--these layers of mud give us an idea of time.

The whole surface of the earth,--I speak broadly, and leave out minor

qualifications,--is made up of such layers of mud, so hard, the majority

of them, that we call them rock whether limestone or sandstone, or other

varieties of rock. And, seeing that every part of the crust of the earth

is made up in this way, you might think that the determination of the

chronology, the fixing of the time which it has taken to form this crust

is a comparatively simple matter. Take a broad average, ascertain how

fast the mud is deposited upon the bottom of the sea, or in the estuary

of rivers; take it to be an inch, or two, or three inches a year, or

whatever you may roughly estimate it at; then take the total thickness

of the whole series of stratified rocks, which geologists estimate at

twelve or thirteen miles, or about seventy thousand feet, make a sum

in short division, divide the total thickness by that of the quantity

deposited in one year, and the result will, of course, give you the

number of years which the crust has taken to form.

Truly, that looks a very simple process! It would be so except for

certain difficulties, the very first of which is that of finding how

rapidly sediments are deposited; but the main difficulty--a difficulty

which renders any certain calculations of such a matter out of the

question--is this, the sea-bottom on which the deposit takes place is

continually shifting.

Instead of the surface of the earth being that stable, fixed thing that

it is popularly believed to be, being, in common parlance, the very

emblem of fixity itself, it is incessantly moving, and is, in fact,

as unstable as the surface of the sea, except that its undulations are

infinitely slower and enormously higher and deeper.

Now, what is the effect of this oscillation? Take the case to which

I have previously referred. The finer or coarser sediments that are

carried down by the current of the river, will only be carried out a

certain distance, and eventually, as we have already seen, on reaching

the stiller part of the ocean, will be deposited at the bottom.

(FIGURE 4. Section through deposits on sea-bottom and shore.)

Let C y (Figure 4) be the sea-bottom, y D the shore, x y the sea-level,

then the coarser deposit will subside over the region B, the finer over

A, while beyond A there will be no deposit at all; and, consequently, no

record will be kept, simply because no deposit is going on. Now, suppose

that the whole land, C, D, which we have regarded as stationary, goes

down, as it does so, both A and B go further out from the shore, which

will be at yl; x1, y1, being the new sea-level. The consequence will be

that the layer of mud (A), being now, for the most part, further than

the force of the current is strong enough to convey even the finest

'debris', will, of course, receive no more deposits, and having attained

a certain thickness will now grow no thicker.

We should be misled in taking the thickness of that layer, whenever it

may be exposed to our view, as a record of time in the manner in which

we are now regarding this subject, as it would give us only an imperfect

and partial record: it would seem to represent too short a period of

time.

Suppose, on the other hand, that the land (C D) had gone on rising

slowly and gradually--say an inch or two inches in the course of a

century,--what would be the practical effect of that movement? Why, that

the sediment A and B which has been already deposited, would eventually

be brought nearer to the shore-level, and again subjected to the wear

and tear of the sea; and directly the sea begins to act upon it, it

would of course soon cut up and carry it away, to a greater or less

extent, to be re-deposited further out.

Well, as there is, in all probability, not one single spot on the whole

surface of the earth, which has not been up and down in this way a great

many times, it follows that the thickness of the deposits formed at any

particular spot cannot be taken (even supposing we had at first obtained

correct data as to the rate at which they took place) as affording

reliable information as to the period of time occupied in its deposit.

So that you see it is absolutely necessary from these facts, seeing that

our record entirely consists of accumulations of mud, superimposed one

on the other; seeing in the next place that any particular spots on

which accumulations have occurred, have been constantly moving up and

down, and sometimes out of the reach of a deposit, and at other times

its own deposit broken up and carried away, it follows that our record

must be in the highest degree imperfect, and we have hardly a trace

left of thick deposits, or any definite knowledge of the area that they

occupied, in a great many cases. And mark this! That supposing even

that the whole surface of the earth had been accessible to the

geologist,--that man had had access to every part of the earth, and had

made sections of the whole, and put them all together,--even then his

record must of necessity be imperfect.

But to how much has man really access? If you will look at this Map you

will see that it represents the proportion of the sea to the earth: this

coloured part indicates all the dry land, and this other portion is the

water. You will notice at once that the water covers three-fifths of the

whole surface of the globe, and has covered it in the same manner ever

since man has kept any record of his own observations, to say nothing of

the minute period during which he has cultivated geological inquiry.

So that three-fifths of the surface of the earth is shut out from us

because it is under the sea. Let us look at the other two-fifths,

and see what are the countries in which anything that may be termed

searching geological inquiry has been carried out: a good deal of

France, Germany, and Great Britain and Ireland, bits of Spain, of

Italy, and of Russia, have been examined, but of the whole great mass of

Africa, except parts of the southern extremity, we know next to nothing;

little bits of India, but of the greater part of the Asiatic continent

nothing; bits of the Northern American States and of Canada, but of

the greater part of the continent of North America, and in still larger

proportion, of South America, nothing!

Under these circumstances, it follows that even with reference to that

kind of imperfect information which we can possess, it is only of about

the ten-thousandth part of the accessible parts of the earth that has

been examined properly. Therefore, it is with justice that the most

thoughtful of those who are concerned in these inquiries insist

continually upon the imperfection of the geological record; for, I

repeat, it is absolutely necessary, from the nature of things, that

that record should be of the most fragmentary and imperfect character.

Unfortunately this circumstance has been constantly forgotten. Men of

science, like young colts in a fresh pasture, are apt to be exhilarated

on being turned into a new field of inquiry, to go off at a hand-gallop,

in total disregard of hedges and ditches, losing sight of the real

limitation of their inquiries, and to forget the extreme imperfection of

what is really known. Geologists have imagined that they could tell us

what was going on at all parts of the earth's surface during a given

epoch; they have talked of this deposit being contemporaneous with

that deposit, until, from our little local histories of the changes at

limited spots of the earth's surface, they have constructed a universal

history of the globe as full of wonders and portents as any other story

of antiquity.

But what does this attempt to construct a universal history of the globe

imply? It implies that we shall not only have a precise knowledge of the

events which have occurred at any particular point, but that we shall

be able to say what events, at any one spot, took place at the same time

with those at other spots.

(FIGURE 5. Section through two beds of mud.)

Let us see how far that is in the nature of things practicable. Suppose

that here I make a section of the Lake of Killarney, and here the

section of another lake--that of Loch Lomond in Scotland for instance.

The rivers that flow into them are constantly carrying down deposits of

mud, and beds, or strata, are being as constantly formed, one above the

other, at the bottom of those lakes. Now, there is not a shadow of

doubt that in these two lakes the lower beds are all older than the

upper--there is no doubt about that; but what does 'this' tell us about

the age of any given bed in Loch Lomond, as compared with that of any

given bed in the Lake of Killarney? It is, indeed, obvious that if

any two sets of deposits are separated and discontinuous, there is

absolutely no means whatever given you by the nature of the deposit of

saying whether one is much younger or older than the other; but you may

say, as many have said and think, that the case is very much altered if

the beds which we are comparing are continuous. Suppose two beds of mud

hardened into rock,--A and B--are seen in section. (Figure 5.)

Well, you say, it is admitted that the lowermost bed is always the

older. Very well; B, therefore, is older than A. No doubt, 'as a whole',

it is so; or if any parts of the two beds which are in the same vertical

line are compared, it is so. But suppose you take what seems a very

natural step further, and say that the part 'a' of the bed A is younger

than the part 'b' of the bed B. Is this sound reasoning? If you find any

record of changes taking place at 'b', did they occur before any events

which took place while 'a' was being deposited? It looks all very plain

sailing, indeed, to say that they did; and yet there is no proof of

anything of the kind. As the former Director of this Institution, Sir

H. De la Beche, long ago showed, this reasoning may involve an entire

fallacy. It is extremely possible that 'a' may have been deposited ages

before 'b'. It is very easy to understand how that can be. To return

to Figure 4; when A and B were deposited, they were 'substantially'

contemporaneous; A being simply the finer deposit, and B the coarser

of the same detritus or waste of land. Now suppose that that sea-bottom

goes down (as shown in Figure 4), so that the first deposit is carried

no farther than 'a', forming the bed Al, and the coarse no farther

than 'b', forming the bed B1, the result will be the formation of two

continuous beds, one of fine sediment (A A1) over-lapping another of

coarse sediment (B Bl). Now suppose the whole sea-bottom is raised up,

and a section exposed about the point Al; no doubt, AT THIS SPOT, the

upper bed is younger than the lower. But we should obviously greatly err

if we concluded that the mass of the upper bed at A was younger than

the lower bed at B; for we have just seen that they are contemporaneous

deposits. Still more should we be in error if we supposed the upper bed

at A to be younger than the continuation of the lower bed at Bl; for

A was deposited long before B1. In fine, if, instead of comparing

immediately adjacent parts of two beds, one of which lies upon another,

we compare distant parts, it is quite possible that the upper may be any

number of years older than the under, and the under any number of years

younger than the upper.

Now you must not suppose that I put this before you for the purpose of

raising a paradoxical difficulty; the fact is, that the great mass of

deposits have taken place in sea-bottoms which are gradually sinking,

and have been formed under the very conditions I am here supposing.

Do not run away with the notion that this subverts the principle I

laid down at first. The error lies in extending a principle which is

perfectly applicable to deposits in the same vertical line to deposits

which are not in that relation to one another.

It is in consequence of circumstances of this kind, and of others that I

might mention to you, that our conclusions on and interpretations of

the record are really and strictly only valid so long as we confine

ourselves to one vertical section. I do not mean to tell you that there

are no qualifying circumstances, so that, even in very considerable

areas, we may safely speak of conformably superimposed beds being older

or younger than others at many different points. But we can never be

quite sure in coming to that conclusion, and especially we cannot

be sure if there is any break in their continuity, or any very great

distance between the points to be compared.

Well now, so much for the record itself,--so much for its

imperfections,--so much for the conditions to be observed in

interpreting it, and its chronological indications, the moment we pass

beyond the limits of a vertical linear section.

Now let us pass from the record to that which it contains,--from the

book itself to the writing and the figures on its pages. This writing

and these figures consist of remains of animals and plants which, in the

great majority of cases, have lived and died in the very spot in which

we now find them, or at least in the immediate vicinity. You must all of

you be aware--and I referred to the fact in my last lecture--that there

are vast numbers of creatures living at the bottom of the sea. These

creatures, like all others, sooner or later die, and their shells and

hard parts lie at the bottom; and then the fine mud which is being

constantly brought down by rivers and the action of the wear and tear of

the sea, covers them over and protects them from any further change

or alteration; and, of course, as in process of time the mud becomes

hardened and solidified, the shells of these animals are preserved

and firmly imbedded in the limestone or sandstone which is being thus

formed. You may see in the galleries of the Museum up stairs specimens

of limestones in which such fossil remains of existing animals are

imbedded. There are some specimens in which turtles' eggs have been

imbedded in calcareous sand, and before the sun had hatched the young

turtles, they became covered over with calcareous mud, and thus have

been preserved and fossilized.

Not only does this process of imbedding and fossilization occur with

marine and other aquatic animals and plants, but it affects those land

animals and plants which are drifted away to sea, or become buried in

bogs or morasses; and the animals which have been trodden down by their

fellows and crushed in the mud at the river's bank, as the herd have

come to drink. In any of these cases, the organisms may be crushed or be

mutilated, before or after putrefaction, in such a manner that perhaps

only a part will be left in the form in which it reaches us. It is,

indeed, a most remarkable fact, that it is quite an exceptional case

to find a skeleton of any one of all the thousands of wild land animals

that we know are constantly being killed, or dying in the course of

nature: they are preyed on and devoured by other animals or die in

places where their bodies are not afterwards protected by mud. There are

other animals existing in the sea, the shells of which form exceedingly

large deposits. You are probably aware that before the attempt was made

to lay the Atlantic telegraphic cable, the Government employed vessels

in making a series of very careful observations and soundings of the

bottom of the Atlantic; and although, as we must all regret, up to the

present time that project has not succeeded, we have the satisfaction

of knowing that it yielded some most remarkable results to science.

The Atlantic Ocean had to be sounded right across, to depths of several

miles in some places, and the nature of its bottom was carefully

ascertained. Well, now, a space of about 1,000 miles wide from east to

west, and I do not exactly know how many from north to south, but at

any rate 600 or 700 miles, was carefully examined, and it was found that

over the whole of that immense area an excessively fine chalky mud is

being deposited; and this deposit is entirely made up of animals whose

hard parts are deposited in this part of the ocean, and are doubtless

gradually acquiring solidity and becoming metamorphosed into a chalky

limestone. Thus, you see, it is quite possible in this way to preserve

unmistakable records of animal and vegetable life. Whenever the

sea-bottom, by some of those undulations of the earth's crust that I

have referred to, becomes upheaved, and sections or borings are made,

or pits are dug, then we become able to examine the contents and

constituents of these ancient sea-bottoms, and find out what manner of

animals lived at that period.

Now it is a very important consideration in its bearing on the

completeness of the record, to inquire how far the remains contained

in these fossiliferous limestones are able to convey anything like an

accurate or complete account of the animals which were in existence

at the time of its formation. Upon that point we can form a very clear

judgment, and one in which there is no possible room for any mistake.

There are of course a great number of animals--such as jelly-fishes,

and other animals--without any hard parts, of which we cannot reasonably

expect to find any traces whatever: there is nothing of them to

preserve. Within a very short time, you will have noticed, after they

are removed from the water, they dry up to a mere nothing; certainly

they are not of a nature to leave any very visible traces of their

existence on such bodies as chalk or mud. Then again, look at land

animals; it is, as I have said, a very uncommon thing to find a land

animal entire after death. Insects and other carnivorous animals very

speedily pull them to pieces, putrefaction takes place, and so, out of

the hundreds of thousands that are known to die every year, it is the

rarest thing in the world to see one imbedded in such a way that its

remains would be preserved for a lengthened period. Not only is this the

case, but even when animal remains have been safely imbedded, certain

natural agents may wholly destroy and remove them.

Almost all the hard parts of animals--the bones and so on--are composed

chiefly of phosphate of lime and carbonate of lime. Some years ago, I

had to make an inquiry into the nature of some very curious fossils

sent to me from the North of Scotland. Fossils are usually hard bony

structures that have become imbedded in the way I have described, and

have gradually acquired the nature and solidity of the body with which

they are associated; but in this case I had a series of 'holes' in some

pieces of rock, and nothing else. Those holes, however, had a certain

definite shape about them, and when I got a skilful workman to make

castings of the interior of these holes, I found that they were the

impressions of the joints of a backbone and of the armour of a great

reptile, twelve or more feet long. This great beast had died and got

buried in the sand; the sand had gradually hardened over the bones, but

remained porous. Water had trickled through it, and that water being

probably charged with a superfluity of carbonic acid, had dissolved all

the phosphate and carbonate of lime, and the bones themselves had thus

decayed and entirely disappeared; but as the sandstone happened to have

consolidated by that time, the precise shape of the bones was retained.

If that sandstone had remained soft a little longer, we should have

known nothing whatsoever of the existence of the reptile whose bones it

had encased.

How certain it is that a vast number of animals which have existed

at one period on this earth have entirely perished, and left no trace

whatever of their forms, may be proved to you by other considerations.

There are large tracts of sandstone in various parts of the world, in

which nobody has yet found anything but footsteps. Not a bone of any

description, but an enormous number of traces of footsteps. There is no

question about them. There is a whole valley in Connecticut covered with

these footsteps, and not a single fragment of the animals which made

them has yet been found. Let me mention another case while upon that

matter, which is even more surprising than those to which I have yet

referred. There is a limestone formation near Oxford, at a place called

Stonesfield, which has yielded the remains of certain very interesting

mammalian animals, and up to this time, if I recollect rightly, there

have been found seven specimens of its lower jaws, and not a bit of

anything else, neither limb-bones nor skull, or any part whatever; not

a fragment of the whole system! Of course, it would be preposterous

to imagine that the beasts had nothing else but a lower jaw!

The probability is, as Dr. Buckland showed, as the result of his

observations on dead dogs in the river Thames, that the lower jaw, not

being secured by very firm ligaments to the bones of the head, and being

a weighty affair, would easily be knocked off, or might drop away from

the body as it floated in water in a state of decomposition. The jaw

would thus be deposited immediately, while the rest of the body would

float and drift away altogether, ultimately reaching the sea, and

perhaps becoming destroyed. The jaw becomes covered up and preserved

in the river silt, and thus it comes that we have such a curious

circumstance as that of the lower jaws in the Stonesfield slates. So

that, you see, faulty as these layers of stone in the earth's crust

are, defective as they necessarily are as a record, the account of

contemporaneous vital phenomena presented by them is, by the necessity

of the case, infinitely more defective and fragmentary.

It was necessary that I should put all this very strongly before you,

because, otherwise, you might have been led to think differently of the

completeness of our knowledge by the next facts I shall state to you.

The researches of the last three-quarters of a century have, in truth,

revealed a wonderful richness of organic life in those rocks. Certainly

not fewer than thirty or forty thousand different species of fossils

have been discovered. You have no more ground for doubting that these

creatures really lived and died at or near the places in which we find

them than you have for like scepticism about a shell on the sea-shore.

The evidence is as good in the one case as in the other.

Our next business is to look at the general character of these fossil

remains, and it is a subject which it will be requisite to consider

carefully; and the first point for us is to examine how much the

extinct 'Flora' and 'Fauna' as a 'whole'--disregarding altogether

the 'succession' of their constituents, of which I shall speak

afterwards--differ from the 'Flora' and 'Fauna' of the present day;--how

far they differ in what we 'do' know about them, leaving altogether out

of consideration speculations based upon what we 'do not' know.

I strongly imagine that if it were not for the peculiar appearance that

fossilised animals have, any of you might readily walk through a museum

which contains fossil remains mixed up with those of the present forms

of life, and I doubt very much whether your uninstructed eyes would

lead you to see any vast or wonderful difference between the two. If

you looked closely, you would notice, in the first place, a great many

things very like animals with which you are acquainted now: you would

see differences of shape and proportion, but on the whole a close

similarity.

I explained what I meant by ORDERS the other day, when I described the

animal kingdom as being divided in sub-kingdoms, classes and orders. If

you divide the animal kingdom into orders, you will find that there are

about one hundred and twenty. The number may vary on one side or the

other, but this is a fair estimate. That is the sum total of the orders

of all the animals which we know now, and which have been known in past

times, and left remains behind.

Now, how many of those are absolutely extinct? That is to say, how many

of these orders of animals have lived at a former period of the world's

history, but have at present no representatives? That is the sense in

which I meant to use the word "extinct." I mean that those animals did

live on this earth at one time, but have left no one of their kind

with us at the present moment. So that estimating the number of extinct

animals is a sort of way of comparing the past creation as a whole with

the present as a whole. Among the mammalia and birds there are none

extinct; but when we come to the reptiles there is a most wonderful

thing: out of the eight orders, or thereabouts, which you can make among

reptiles, one-half are extinct. These diagrams of the plesiosaurus,

the ichthyosaurus, the pterodactyle, give you a notion of some of these

extinct reptiles. And here is a cast of the pterodactyle and bones of

the ichthyosaurus and the plesiosaurus, just as fresh as if it had been

recently dug up in a churchyard. Thus, in the reptile class, there are

no less than half of the orders which are absolutely extinct. If we turn

to the 'Amphibia', there was one extinct order, the Labyrinthodonts,

typified by the large salamander-like beast shown in this diagram.

No order of fishes is known to be extinct. Every fish that we find in

the strata--to which I have been referring--can be identified and placed

in one of the orders which exist at the present day. There is not known

to be a single ordinal form of insect extinct. There are only two orders

extinct among the 'Crustacea'. There is not known to be an extinct order

of these creatures, the parasitic and other worms; but there are

two, not to say three, absolutely extinct orders of this class, the

'Echinodermata'; out of all the orders of the 'Coelenterata' and

'Protozoa' only one, the Rugose Corals.

So that, you see, out of somewhere about 120 orders of animals, taking

them altogether, you will not, at the outside estimate, find above ten

or a dozen extinct. Summing up all the orders of animals which have left

remains behind them, you will not find above ten or a dozen which cannot

be arranged with those of the present day; that is to say, that the

difference does not amount to much more than ten per cent.: and the

proportion of extinct orders of plants is still smaller. I think that

that is a very astounding, a most astonishing fact, seeing the enormous

epochs of time which have elapsed during the constitution of the surface

of the earth as it at present exists; it is, indeed, a most astounding

thing that the proportion of extinct ordinal types should be so

exceedingly small.

But now, there is another point of view in which we must look at this

past creation. Suppose that we were to sink a vertical pit through the

floor beneath us, and that I could succeed in making a section right

through in the direction of New Zealand, I should find in each of the

different beds through which I passed the remains of animals which I

should find in that stratum and not in the others. First, I should come

upon beds of gravel or drift containing the bones of large animals, such

as the elephant, rhinoceros, and cave tiger. Rather curious things to

fall across in Piccadilly! If I should dig lower still, I should come

upon a bed of what we call the London clay, and in this, as you will see

in our galleries upstairs, are found remains of strange cattle, remains

of turtles, palms, and large tropical fruits; with shell-fish such as

you see the like of now only in tropical regions. If I went below

that, I should come upon the chalk, and there I should find something

altogether different, the remains of ichthyosauri and pterodactyles, and

ammonites, and so forth.

I do not know what Mr. Godwin Austin would say comes next, but probably

rocks containing more ammonites, and more ichthyosauri and plesiosauri,

with a vast number of other things; and under that I should meet with

yet older rocks, containing numbers of strange shells and fishes; and in

thus passing from the surface to the lowest depths of the earth's crust,

the forms of animal life and vegetable life which I should meet with

in the successive beds would, looking at them broadly, be the more

different the further that I went down. Or, in other words, inasmuch

as we started with the clear principle, that in a series of

naturally-disposed mud beds the lowest are the oldest, we should come

to this result, that the further we go back in time the more difference

exists between the animal and vegetable life of an epoch and that which

now exists. That was the conclusion to which I wished to bring you at

the end of this Lecture.

End of The Past Condition of Organic Nature.

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

In the two preceding lectures I have endeavoured to indicate to you the

extent of the subject-matter of the inquiry upon which we are engaged;

and now, having thus acquired some conception of the Past and Present

phenomena of Organic Nature, I must now turn to that which constitutes

the great problem which we have set before ourselves;--I mean, the

question of what knowledge we have of the causes of these phenomena of

organic nature, and how such knowledge is obtainable.

Here, on the threshold of the inquiry, an objection meets us. There are

in the world a number of extremely worthy, well-meaning persons, whose

judgments and opinions are entitled to the utmost respect on account of

their sincerity, who are of opinion that Vital Phenomena, and especially

all questions relating to the origin of vital phenomena, are questions

quite apart from the ordinary run of inquiry, and are, by their very

nature, placed out of our reach. They say that all these phenomena

originated miraculously, or in some way totally different from the

ordinary course of nature, and that therefore they conceive it to be

futile, not to say presumptuous, to attempt to inquire into them.

To such sincere and earnest persons, I would only say, that a question

of this kind is not to be shelved upon theoretical or speculative

grounds. You may remember the story of the Sophist who demonstrated to

Diogenes in the most complete and satisfactory manner that he could not

walk; that, in fact, all motion was an impossibility; and that Diogenes

refuted him by simply getting up and walking round his tub. So, in the

same way, the man of science replies to objections of this kind, by

simply getting up and walking onward, and showing what science has done

and is doing--by pointing to that immense mass of facts which have been

ascertained and systematized under the forms of the great doctrines of

Morphology, of Development, of Distribution, and the like. He sees an

enormous mass of facts and laws relating to organic beings, which

stand on the same good sound foundation as every other natural law; and

therefore, with this mass of facts and laws before us, therefore,

seeing that, as far as organic matters have hitherto been accessible and

studied, they have shown themselves capable of yielding to scientific

investigation, we may accept this as proof that order and law reign

there as well as in the rest of nature; and the man of science says

nothing to objectors of this sort, but supposes that we can and shall

walk to a knowledge of the origin of organic nature, in the same way

that we have walked to a knowledge of the laws and principles of the

inorganic world.

But there are objectors who say the same from ignorance and ill-will. To

such I would reply that the objection comes ill from them, and that the

real presumption, I may almost say the real blasphemy, in this matter,

is in the attempt to limit that inquiry into the causes of phenomena

which is the source of all human blessings, and from which has sprung

all human prosperity and progress; for, after all, we can accomplish

comparatively little; the limited range of our own faculties bounds us

on every side,--the field of our powers of observation is small enough,

and he who endeavours to narrow the sphere of our inquiries is only

pursuing a course that is likely to produce the greatest harm to his

fellow-men.

But now, assuming, as we all do, I hope, that these phenomena are

properly accessible to inquiry, and setting out upon our search into the

causes of the phenomena of organic nature, or, at any rate, setting out

to discover how much we at present know upon these abstruse matters, the

question arises as to what is to be our course of proceeding, and what

method we must lay down for our guidance. I reply to that question,

that our method must be exactly the same as that which is pursued in any

other scientific inquiry, the method of scientific investigation being

the same for all orders of facts and phenomena whatsoever.

I must dwell a little on this point, for I wish you to leave this room

with a very clear conviction that scientific investigation is not, as

many people seem to suppose, some kind of modern black art. I say that

you might easily gather this impression from the manner in which

many persons speak of scientific inquiry, or talk about inductive and

deductive philosophy, or the principles of the "Baconian philosophy."

I do protest that, of the vast number of cants in this world, there are

none, to my mind, so contemptible as the pseudoscientific cant which is

talked about the "Baconian philosophy."

To hear people talk about the great Chancellor--and a very great man he

certainly was,--you would think that it was he who had invented science,

and that there was no such thing as sound reasoning before the time of

Queen Elizabeth. Of course you say, that cannot possibly be true; you

perceive, on a moment's reflection, that such an idea is absurdly wrong,

and yet, so firmly rooted is this sort of impression,--I cannot call it

an idea, or conception,--the thing is too absurd to be entertained,--but

so completely does it exist at the bottom of most men's minds, that this

has been a matter of observation with me for many years past. There

are many men who, though knowing absolutely nothing of the subject with

which they may be dealing, wish, nevertheless, to damage the author of

some view with which they think fit to disagree. What they do, then,

is not to go and learn something about the subject, which one would

naturally think the best way of fairly dealing with it; but they abuse

the originator of the view they question, in a general manner, and wind

up by saying that, "After all, you know, the principles and method

of this author are totally opposed to the canons of the Baconian

philosophy." Then everybody applauds, as a matter of course, and agrees

that it must be so. But if you were to stop them all in the middle of

their applause, you would probably find that neither the speaker nor his

applauders could tell you how or in what way it was so; neither the

one nor the other having the slightest idea of what they mean when they

speak of the "Baconian philosophy."

You will understand, I hope, that I have not the slightest desire to

join in the outcry against either the morals, the intellect, or the

great genius of Lord Chancellor Bacon. He was undoubtedly a very great

man, let people say what they will of him; but notwithstanding all that

he did for philosophy, it would be entirely wrong to suppose that the

methods of modern scientific inquiry originated with him, or with his

age; they originated with the first man, whoever he was; and indeed

existed long before him, for many of the essential processes of

reasoning are exerted by the higher order of brutes as completely and

effectively as by ourselves. We see in many of the brute creation the

exercise of one, at least, of the same powers of reasoning as that which

we ourselves employ.

The method of scientific investigation is nothing but the expression of

the necessary mode of working of the human mind. It is simply the mode

at which all phenomena are reasoned about, rendered precise and

exact. There is no more difference, but there is just the same kind of

difference, between the mental operations of a man of science and those

of an ordinary person, as there is between the operations and methods of

a baker or of a butcher weighing out his goods in common scales, and the

operations of a chemist in performing a difficult and complex analysis

by means of his balance and finely-graduated weights. It is not that

the action of the scales in the one case, and the balance in the other,

differ in the principles of their construction or manner of working; but

the beam of one is set on an infinitely finer axis than the other, and

of course turns by the addition of a much smaller weight.

You will understand this better, perhaps, if I give you some familiar

example. You have all heard it repeated, I dare say, that men of science

work by means of Induction and Deduction, and that by the help of these

operations, they, in a sort of sense, wring from Nature certain other

things, which are called Natural Laws, and Causes, and that out of

these, by some cunning skill of their own, they build up Hypotheses and

Theories. And it is imagined by many, that the operations of the common

mind can be by no means compared with these processes, and that they

have to be acquired by a sort of special apprenticeship to the craft.

To hear all these large words, you would think that the mind of a man of

science must be constituted differently from that of his fellow men; but

if you will not be frightened by terms, you will discover that you are

quite wrong, and that all these terrible apparatus are being used by

yourselves every day and every hour of your lives.

There is a well-known incident in one of Moliere's plays, where the

author makes the hero express unbounded delight on being told that he

had been talking prose during the whole of his life. In the same way, I

trust, that you will take comfort, and be delighted with yourselves, on

the discovery that you have been acting on the principles of inductive

and deductive philosophy during the same period. Probably there is not

one here who has not in the course of the day had occasion to set in

motion a complex train of reasoning, of the very same kind, though

differing of course in degree, as that which a scientific man goes

through in tracing the causes of natural phenomena.

A very trivial circumstance will serve to exemplify this. Suppose you

go into a fruiterer's shop, wanting an apple,--you take up one, and, on

biting it, you find it is sour; you look at it, and see that it is hard

and green. You take up another one, and that too is hard, green, and

sour. The shopman offers you a third; but, before biting it, you examine

it, and find that it is hard and green, and you immediately say that you

will not have it, as it must be sour, like those that you have already

tried.

Nothing can be more simple than that, you think; but if you will take

the trouble to analyze and trace out into its logical elements what

has been done by the mind, you will be greatly surprised. In the first

place, you have performed the operation of INDUCTION. You found that,

in two experiences, hardness and greenness in apples go together with

sourness. It was so in the first case, and it was confirmed by the

second. True, it is a very small basis, but still it is enough to make

an induction from; you generalize the facts, and you expect to find

sourness in apples where you get hardness and greenness. You found upon

that a general law, that all hard and green apples are sour; and that,

so far as it goes, is a perfect induction. Well, having got your natural

law in this way, when you are offered another apple which you find is

hard and green, you say, "All hard and green apples are sour; this

apple is hard and green, therefore this apple is sour." That train of

reasoning is what logicians call a syllogism, and has all its various

parts and terms,--its major premiss, its minor premiss, and its

conclusion. And, by the help of further reasoning, which, if drawn out,

would have to be exhibited in two or three other syllogisms, you arrive

at your final determination, "I will not have that apple." So that, you

see, you have, in the first place, established a law by Induction, and

upon that you have founded a Deduction, and reasoned out the special

conclusion of the particular case. Well now, suppose, having got your

law, that at some time afterwards, you are discussing the qualities

of apples with a friend: you will say to him, "It is a very curious

thing,--but I find that all hard and green apples are sour!" Your friend

says to you, "But how do you know that?" You at once reply, "Oh, because

I have tried it over and over again, and have always found them to be

so." Well, if we were talking science instead of common sense, we should

call that an Experimental Verification. And, if still opposed, you go

further, and say, "I have heard from the people in Somersetshire and

Devonshire, where a large number of apples are grown, that they have

observed the same thing. It is also found to be the case in Normandy,

and in North America. In short, I find it to be the universal experience

of mankind wherever attention has been directed to the subject."

Whereupon, your friend, unless he is a very unreasonable man, agrees

with you, and is convinced that you are quite right in the conclusion

you have drawn. He believes, although perhaps he does not know he

believes it, that the more extensive Verifications are,--that the more

frequently experiments have been made, and results of the same kind

arrived at,--that the more varied the conditions under which the same

results have been attained, the more certain is the ultimate conclusion,

and he disputes the question no further. He sees that the experiment has

been tried under all sorts of conditions, as to time, place, and people,

with the same result; and he says with you, therefore, that the law you

have laid down must be a good one, and he must believe it.

In science we do the same thing;--the philosopher exercises precisely

the same faculties, though in a much more delicate manner. In scientific

inquiry it becomes a matter of duty to expose a supposed law to every

possible kind of verification, and to take care, moreover, that this is

done intentionally, and not left to a mere accident, as in the case of

the apples. And in science, as in common life, our confidence in a law

is in exact proportion to the absence of variation in the result of our

experimental verifications. For instance, if you let go your grasp of

an article you may have in your hand, it will immediately fall to

the ground. That is a very common verification of one of the best

established laws of nature--that of gravitation. The method by which men

of science establish the existence of that law is exactly the same as

that by which we have established the trivial proposition about

the sourness of hard and green apples. But we believe it in such an

extensive, thorough, and unhesitating manner because the universal

experience of mankind verifies it, and we can verify it ourselves at any

time; and that is the strongest possible foundation on which any natural

law can rest.

So much by way of proof that the method of establishing laws in science

is exactly the same as that pursued in common life. Let us now turn

to another matter (though really it is but another phase of the same

question), and that is, the method by which, from the relations of

certain phenomena, we prove that some stand in the position of causes

towards the others.

I want to put the case clearly before you, and I will therefore show you

what I mean by another familiar example. I will suppose that one of you,

on coming down in the morning to the parlour of your house, finds that a

tea-pot and some spoons which had been left in the room on the previous

evening are gone,--the window is open, and you observe the mark of a

dirty hand on the window-frame, and perhaps, in addition to that, you

notice the impress of a hob-nailed shoe on the gravel outside. All these

phenomena have struck your attention instantly, and before two minutes

have passed you say, "Oh, somebody has broken open the window, entered

the room, and run off with the spoons and the tea-pot!" That speech is

out of your mouth in a moment. And you will probably add, "I know there

has; I am quite sure of it!" You mean to say exactly what you know; but

in reality what you have said has been the expression of what is, in all

essential particulars, an Hypothesis. You do not 'know' it at all; it is

nothing but an hypothesis rapidly framed in your own mind! And it is an

hypothesis founded on a long train of inductions and deductions.

What are those inductions and deductions, and how have you got at this

hypothesis? You have observed, in the first place, that the window

is open; but by a train of reasoning involving many Inductions and

Deductions, you have probably arrived long before at the General

Law--and a very good one it is--that windows do not open of themselves;

and you therefore conclude that something has opened the window. A

second general law that you have arrived at in the same way is, that

tea-pots and spoons do not go out of a window spontaneously, and you are

satisfied that, as they are not now where you left them, they have been

removed. In the third place, you look at the marks on the window-sill,

and the shoemarks outside, and you say that in all previous experience

the former kind of mark has never been produced by anything else but

the hand of a human being; and the same experience shows that no other

animal but man at present wears shoes with hob-nails on them such as

would produce the marks in the gravel. I do not know, even if we could

discover any of those "missing links" that are talked about, that they

would help us to any other conclusion! At any rate the law which states

our present experience is strong enough for my present purpose.--You

next reach the conclusion, that as these kinds of marks have not been

left by any other animals than men, or are liable to be formed in any

other way than by a man's hand and shoe, the marks in question have been

formed by a man in that way. You have, further, a general law, founded

on observation and experience, and that, too, is, I am sorry to say, a

very universal and unimpeachable one,--that some men are thieves;

and you assume at once from all these premisses--and that is what

constitutes your hypothesis--that the man who made the marks outside and

on the window-sill, opened the window, got into the room, and stole your

tea-pot and spoons. You have now arrived at a 'Vera Causa';--you have

assumed a Cause which it is plain is competent to produce all the

phenomena you have observed. You can explain all these phenomena only by

the hypothesis of a thief. But that is a hypothetical conclusion, of the

justice of which you have no absolute proof at all; it is only rendered

highly probable by a series of inductive and deductive reasonings.

I suppose your first action, assuming that you are a man of ordinary

common sense, and that you have established this hypothesis to your own

satisfaction, will very likely be to go off for the police, and set

them on the track of the burglar, with the view to the recovery of your

property. But just as you are starting with this object, some person

comes in, and on learning what you are about, says, "My good friend,

you are going on a great deal too fast. How do you know that the man who

really made the marks took the spoons? It might have been a monkey that

took them, and the man may have merely looked in afterwards." You would

probably reply, "Well, that is all very well, but you see it is contrary

to all experience of the way tea-pots and spoons are abstracted; so

that, at any rate, your hypothesis is less probable than mine." While

you are talking the thing over in this way, another friend arrives, one

of that good kind of people that I was talking of a little while ago.

And he might say, "Oh, my dear sir, you are certainly going on a great

deal too fast. You are most presumptuous. You admit that all these

occurrences took place when you were fast asleep, at a time when you

could not possibly have known anything about what was taking place. How

do you know that the laws of Nature are not suspended during the night?

It may be that there has been some kind of supernatural interference in

this case." In point of fact, he declares that your hypothesis is one

of which you cannot at all demonstrate the truth, and that you are by no

means sure that the laws of Nature are the same when you are asleep as

when you are awake.

Well, now, you cannot at the moment answer that kind of reasoning. You

feel that your worthy friend has you somewhat at a disadvantage. You

will feel perfectly convinced in your own mind, however, that you are

quite right, and you say to him, "My good friend, I can only be guided

by the natural probabilities of the case, and if you will be kind enough

to stand aside and permit me to pass, I will go and fetch the police."

Well, we will suppose that your journey is successful, and that by good

luck you meet with a policeman; that eventually the burglar is found

with your property on his person, and the marks correspond to his hand

and to his boots. Probably any jury would consider those facts a very

good experimental verification of your hypothesis, touching the cause

of the abnormal phenomena observed in your parlour, and would act

accordingly.

Now, in this supposititious case, I have taken phenomena of a very

common kind, in order that you might see what are the different steps in

an ordinary process of reasoning, if you will only take the trouble to

analyse it carefully. All the operations I have described, you will

see, are involved in the mind of any man of sense in leading him to

a conclusion as to the course he should take in order to make good a

robbery and punish the offender. I say that you are led, in that case,

to your conclusion by exactly the same train of reasoning as that which

a man of science pursues when he is endeavouring to discover the origin

and laws of the most occult phenomena. The process is, and always must

be, the same; and precisely the same mode of reasoning was employed by

Newton and Laplace in their endeavours to discover and define the causes

of the movements of the heavenly bodies, as you, with your own common

sense, would employ to detect a burglar. The only difference is, that

the nature of the inquiry being more abstruse, every step has to be most

carefully watched, so that there may not be a single crack or flaw in

your hypothesis. A flaw or crack in many of the hypotheses of daily life

may be of little or no moment as affecting the general correctness of

the conclusions at which we may arrive; but, in a scientific inquiry,

a fallacy, great or small, is always of importance, and is sure to be

constantly productive of mischievous, if not fatal results.

Do not allow yourselves to be misled by the common notion that an

hypothesis is untrustworthy simply because it is an hypothesis. It is

often urged, in respect to some scientific conclusion, that, after

all, it is only an hypothesis. But what more have we to guide us in

nine-tenths of the most important affairs of daily life than hypotheses,

and often very ill-based ones? So that in science, where the evidence of

an hypothesis is subjected to the most rigid examination, we may rightly

pursue the same course. You may have hypotheses and hypotheses. A man

may say, if he likes, that the moon is made of green cheese: that is an

hypothesis. But another man, who has devoted a great deal of time and

attention to the subject, and availed himself of the most powerful

telescopes and the results of the observations of others, declares that

in his opinion it is probably composed of materials very similar to

those of which our own earth is made up: and that is also only an

hypothesis. But I need not tell you that there is an enormous difference

in the value of the two hypotheses. That one which is based on sound

scientific knowledge is sure to have a corresponding value; and that

which is a mere hasty random guess is likely to have but little value.

Every great step in our progress in discovering causes has been made

in exactly the same way as that which I have detailed to you. A person

observing the occurrence of certain facts and phenomena asks, naturally

enough, what process, what kind of operation known to occur in nature

applied to the particular case, will unravel and explain the mystery?

Hence you have the scientific hypothesis; and its value will be

proportionate to the care and completeness with which its basis had been

tested and verified. It is in these matters as in the commonest affairs

of practical life: the guess of the fool will be folly, while the guess

of the wise man will contain wisdom. In all cases, you see that the

value of the result depends on the patience and faithfulness with

which the investigator applies to his hypothesis every possible kind of

verification.

I dare say I may have to return to this point by-and-by; but having

dealt thus far with our logical methods, I must now turn to something

which, perhaps, you may consider more interesting, or, at any rate,

more tangible. But in reality there are but few things that can be more

important for you to understand than the mental processes and the means

by which we obtain scientific conclusions and theories.* ([Footnote]

*Those who wish to study fully the doctrines of which I have endeavoured

to give some rough and ready illustrations, must read Mr. John Stuart

Mill's 'System of Logic'.) Having granted that the inquiry is a proper

one, and having determined on the nature of the methods we are to pursue

and which only can lead to success, I must now turn to the consideration

of our knowledge of the nature of the processes which have resulted in

the present condition of organic nature.

Here, let me say at once, lest some of you misunderstand me, that I have

extremely little to report. The question of how the present condition of

organic nature came about, resolves itself into two questions. The first

is: How has organic or living matter commenced its existence? And the

second is: How has it been perpetuated? On the second question I shall

have more to say hereafter. But on the first one, what I now have to say

will be for the most part of a negative character.

If you consider what kind of evidence we can have upon this matter, it

will resolve itself into two kinds. We may have historical evidence and

we may have experimental evidence. It is, for example, conceivable, that

inasmuch as the hardened mud which forms a considerable portion of the

thickness of the earth's crust contains faithful records of the past

forms of life, and inasmuch as these differ more and more as we go

further down,--it is possible and conceivable that we might come to

some particular bed or stratum which should contain the remains of those

creatures with which organic life began upon the earth. And if we did

so, and if such forms of organic life were preservable, we should have

what I would call historical evidence of the mode in which organic life

began upon this planet. Many persons will tell you, and indeed you will

find it stated in many works on geology, that this has been done, and

that we really possess such a record; there are some who imagine that

the earliest forms of life of which we have as yet discovered any

record, are in truth the forms in which animal life began upon the

globe. The grounds on which they base that supposition are these:--That

if you go through the enormous thickness of the earth's crust and get

down to the older rocks, the higher vertebrate animals--the quadrupeds,

birds, and fishes--cease to be found; beneath them you find only the

invertebrate animals; and in the deepest and lowest rocks those remains

become scantier and scantier, not in any very gradual progression,

however, until, at length, in what are supposed to be the oldest rocks,

the animal remains which are found are almost always confined to four

forms--'Oldhamia', whose precise nature is not known, whether plant or

animal; 'Lingula', a kind of mollusc; 'Trilobites', a crustacean animal,

having the same essential plan of construction, though differing in

many details from a lobster or crab; and Hymenocaris, which is also a

crustacean. So that you have all the 'Fauna' reduced, at this period,

to four forms: one a kind of animal or plant that we know nothing about,

and three undoubted animals--two crustaceans and one mollusc.

I think, considering the organization of these mollusca and crustacea,

and looking at their very complex nature, that it does indeed require a

very strong imagination to conceive that these were the first created of

all living things. And you must take into consideration the fact that

we have not the slightest proof that these which we call the oldest beds

are really so: I repeat, we have not the slightest proof of it. When you

find in some places that in an enormous thickness of rocks there are but

very scanty traces of life, or absolutely none at all; and that in other

parts of the world rocks of the very same formation are crowded with the

records of living forms, I think it is impossible to place any reliance

on the supposition, or to feel oneself justified in supposing that these

are the forms in which life first commenced. I have not time here

to enter upon the technical grounds upon which I am led to this

conclusion,--that could hardly be done properly in half a dozen lectures

on that part alone;--I must content myself with saying that I do not at

all believe that these are the oldest forms of life.

I turn to the experimental side to see what evidence we have there.

To enable us to say that we know anything about the experimental

origination of organization and life, the investigator ought to be able

to take inorganic matters, such as carbonic acid, ammonia, water, and

salines, in any sort of inorganic combination, and be able to build them

up into Protein matter, and that that Protein matter ought to begin to

live in an organic form. That, nobody has done as yet, and I suspect it

will be a long while before anybody does do it. But the thing is by no

means so impossible as it looks; for the researches of modern chemistry

have shown us--I won't say the road towards it, but, if I may so say,

they have shown the finger-post pointing to the road that may lead to

it.

It is not many years ago--and you must recollect that Organic Chemistry

is a young science, not above a couple of generations old,--you must not

expect too much of it; it is not many years ago since it was said to be

perfectly impossible to fabricate any organic compound; that is to say,

any non-mineral compound which is to be found in an organized being. It

remained so for a very long period; but it is now a considerable number

of years since a distinguished foreign chemist contrived to fabricate

Urea, a substance of a very complex character, which forms one of the

waste products of animal structures. And of late years a number of other

compounds, such as Butyric Acid, and others, have been added to the

list. I need not tell you that chemistry is an enormous distance from

the goal I indicate; all I wish to point out to you is, that it is by no

means safe to say that that goal may not be reached one day. It may be

that it is impossible for us to produce the conditions requisite to the

origination of life; but we must speak modestly about the matter, and

recollect that Science has put her foot upon the bottom round of the

ladder. Truly he would be a bold man who would venture to predict where

she will be fifty years hence.

There is another inquiry which bears indirectly upon this question,

and upon which I must say a few words. You are all of you aware of the

phenomena of what is called spontaneous generation. Our forefathers,

down to the seventeenth century, or thereabouts, all imagined, in

perfectly good faith, that certain vegetable and animal forms gave

birth, in the process of their decomposition, to insect life. Thus,

if you put a piece of meat in the sun, and allowed it to putrefy, they

conceived that the grubs which soon began to appear were the result

of the action of a power of spontaneous generation which the meat

contained. And they could give you receipts for making various animal

and vegetable preparations which would produce particular kinds of

animals. A very distinguished Italian naturalist, named Redi, took up

the question, at a time when everybody believed in it; among others our

own great Harvey, the discoverer of the circulation of the blood. You

will constantly find his name quoted, however, as an opponent of the

doctrine of spontaneous generation; but the fact is, and you will see it

if you will take the trouble to look into his works, Harvey believed

it as profoundly as any man of his time; but he happened to enunciate a

very curious proposition--that every living thing came from an 'egg'; he

did not mean to use the word in the sense in which we now employ it, he

only meant to say that every living thing originated in a little rounded

particle of organized substance; and it is from this circumstance,

probably, that the notion of Harvey having opposed the doctrine

originated. Then came Redi, and he proceeded to upset the doctrine in a

very simple manner. He merely covered the piece of meat with some very

fine gauze, and then he exposed it to the same conditions. The result

of this was that no grubs or insects were produced; he proved that the

grubs originated from the insects who came and deposited their eggs in

the meat, and that they were hatched by the heat of the sun. By

this kind of inquiry he thoroughly upset the doctrine of spontaneous

generation, for his time at least.

Then came the discovery and application of the microscope to scientific

inquiries, which showed to naturalists that besides the organisms which

they already knew as living beings and plants, there were an immense

number of minute things which could be obtained apparently almost at

will from decaying vegetable and animal forms. Thus, if you took some

ordinary black pepper or some hay, and steeped it in water, you would

find in the course of a few days that the water had become impregnated

with an immense number of animalcules swimming about in all directions.

From facts of this kind naturalists were led to revive the theory

of spontaneous generation. They were headed here by an English

naturalist,--Needham,--and afterwards in France by the learned Buffon.

They said that these things were absolutely begotten in the water of

the decaying substances out of which the infusion was made. It did not

matter whether you took animal or vegetable matter, you had only to

steep it in water and expose it, and you would soon have plenty of

animalcules. They made an hypothesis about this which was a very fair

one. They said, this matter of the animal world, or of the higher

plants, appears to be dead, but in reality it has a sort of dim life

about it, which, if it is placed under fair conditions, will cause it

to break up into the forms of these little animalcules, and they will go

through their lives in the same way as the animal or plant of which they

once formed a part.

The question now became very hotly debated. Spallanzani, an Italian

naturalist, took up opposite views to those of Needham and Buffon, and

by means of certain experiments he showed that it was quite possible to

stop the process by boiling the water, and closing the vessel in which

it was contained. "Oh!" said his opponents; "but what do you know you

may be doing when you heat the air over the water in this way? You may

be destroying some property of the air requisite for the spontaneous

generation of the animalcules."

However, Spallanzani's views were supposed to be upon the right side,

and those of the others fell into discredit; although the fact was

that Spallanzani had not made good his views. Well, then, the subject

continued to be revived from time to time, and experiments were made by

several persons; but these experiments were not altogether satisfactory.

It was found that if you put an infusion in which animalcules would

appear if it were exposed to the air into a vessel and boiled it, and

then sealed up the mouth of the vessel, so that no air, save such as

had been heated to 212 degrees, could reach its contents, that then no

animalcules would be found; but if you took the same vessel and exposed

the infusion to the air, then you would get animalcules. Furthermore, it

was found that if you connected the mouth of the vessel with a red-hot

tube in such a way that the air would have to pass through the tube

before reaching the infusion, that then you would get no animalcules.

Yet another thing was noticed: if you took two flasks containing the

same kind of infusion, and left one entirely exposed to the air, and

in the mouth of the other placed a ball of cotton wool, so that the air

would have to filter itself through it before reaching the infusion,

that then, although you might have plenty of animalcules in the first

flask, you would certainly obtain none from the second.

These experiments, you see, all tended towards one conclusion--that the

infusoria were developed from little minute spores or eggs which

were constantly floating in the atmosphere, which lose their power of

germination if subjected to heat. But one observer now made another

experiment which seemed to go entirely the other way, and puzzled

him altogether. He took some of this boiled infusion that I have been

speaking of, and by the use of a mercurial bath--a kind of trough used

in laboratories--he deftly inverted a vessel containing the infusion

into the mercury, so that the latter reached a little beyond the level

of the mouth of the 'inverted' vessel. You see that he thus had a

quantity of the infusion shut off from any possible communication with

the outer air by being inverted upon a bed of mercury.

He then prepared some pure oxygen and nitrogen gases, and passed them

by means of a tube going from the outside of the vessel, up through the

mercury into the infusion; so that he thus had it exposed to a perfectly

pure atmosphere of the same constituents as the external air. Of course,

he expected he would get no infusorial animalcules at all in that

infusion; but, to his great dismay and discomfiture, he found he almost

always did get them.

Furthermore, it has been found that experiments made in the manner

described above answer well with most infusions; but that if you fill

the vessel with boiled milk, and then stop the neck with cotton-wool,

you 'will' have infusoria. So that you see there were two experiments

that brought you to one kind of conclusion, and three to another; which

was a most unsatisfactory state of things to arrive at in a scientific

inquiry.

Some few years after this, the question began to be very hotly discussed

in France. There was M. Pouchet, a professor at Rouen, a very learned

man, but certainly not a very rigid experimentalist. He published a

number of experiments of his own, some of which were very ingenious, to

show that if you went to work in a proper way, there was a truth in

the doctrine of spontaneous generation. Well, it was one of the most

fortunate things in the world that M. Pouchet took up this question,

because it induced a distinguished French chemist, M. Pasteur, to take

up the question on the other side; and he has certainly worked it out

in the most perfect manner. I am glad to say, too, that he has published

his researches in time to enable me to give you an account of them. He

verified all the experiments which I have just mentioned to you--and

then finding those extraordinary anomalies, as in the case of the

mercury bath and the milk, he set himself to work to discover their

nature. In the case of milk he found it to be a question of temperature.

Milk in a fresh state is slightly alkaline; and it is a very curious

circumstance, but this very slight degree of alkalinity seems to have

the effect of preserving the organisms which fall into it from the

air from being destroyed at a temperature of 212 degrees, which is the

boiling point. But if you raise the temperature 10 degrees when you boil

it, the milk behaves like everything else; and if the air with which

it comes in contact, after being boiled at this temperature, is passed

through a red-hot tube, you will not get a trace of organisms.

He then turned his attention to the mercury bath, and found on

examination that the surface of the mercury was almost always covered

with a very fine dust. He found that even the mercury itself was

positively full of organic matters; that from being constantly exposed

to the air, it had collected an immense number of these infusorial

organisms from the air. Well, under these circumstances he felt that the

case was quite clear, and that the mercury was not what it had appeared

to M. Schwann to be,--a bar to the admission of these organisms; but

that, in reality, it acted as a reservoir from which the infusion was

immediately supplied with the large quantity that had so puzzled him.

But not content with explaining the experiments of others, M. Pasteur

went to work to satisfy himself completely. He said to himself: "If

my view is right, and if, in point of fact, all these appearances of

spontaneous generation are altogether due to the falling of minute germs

suspended in the atmosphere,--why, I ought not only to be able to show

the germs, but I ought to be able to catch and sow them, and produce

the resulting organisms." He, accordingly, constructed a very ingenious

apparatus to enable him to accomplish this trapping of this "germ dust"

in the air. He fixed in the window of his room a glass tube, in the

centre of which he had placed a ball of gun-cotton, which, as you all

know, is ordinary cotton-wool, which, from having been steeped in strong

acid, is converted into a substance of great explosive power. It is also

soluble in alcohol and ether. One end of the glass tube was, of course,

open to the external air; and at the other end of it he placed an

aspirator, a contrivance for causing a current of the external air to

pass through the tube. He kept this apparatus going for four-and-twenty

hours, and then removed the 'dusted' gun-cotton, and dissolved it in

alcohol and ether. He then allowed this to stand for a few hours, and

the result was, that a very fine dust was gradually deposited at

the bottom of it. That dust, on being transferred to the stage of a

microscope, was found to contain an enormous number of starch grains.

You know that the materials of our food and the greater portion of

plants are composed of starch, and we are constantly making use of it in

a variety of ways, so that there is always a quantity of it suspended

in the air. It is these starch grains which form many of those bright

specks that we see dancing in a ray of light sometimes. But besides

these, M. Pasteur found also an immense number of other organic

substances such as spores of fungi, which had been floating about in the

air and had got caged in this way.

He went farther, and said to himself, "If these really are the things

that give rise to the appearance of spontaneous generation, I ought to

be able to take a ball of this 'dusted' gun-cotton and put it into one

of my vessels, containing that boiled infusion which has been kept away

from the air, and in which no infusoria are at present developed, and

then, if I am right, the introduction of this gun-cotton will give rise

to organisms."

Accordingly, he took one of these vessels of infusion, which had been

kept eighteen months, without the least appearance of life, and by a

most ingenious contrivance, he managed to break it open and introduce

such a ball of gun-cotton, without allowing the infusion or the cotton

ball to come into contact with any air but that which had been subjected

to a red heat, and in twenty-four hours he had the satisfaction of

finding all the indications of what had been hitherto called spontaneous

generation. He had succeeded in catching the germs and developing

organisms in the way he had anticipated.

It now struck him that the truth of his conclusions might be

demonstrated without all the apparatus he had employed. To do this, he

took some decaying animal or vegetable substance, such as urine, which

is an extremely decomposable substance, or the juice of yeast, or

perhaps some other artificial preparation, and filled a vessel having a

long tubular neck with it. He then boiled the liquid and bent that

long neck into an S shape or zig-zag, leaving it open at the end. The

infusion then gave no trace of any appearance of spontaneous generation,

however long it might be left, as all the germs in the air were

deposited in the beginning of the bent neck. He then cut the tube close

to the vessel, and allowed the ordinary air to have free and direct

access; and the result of that was the appearance of organisms in it, as

soon as the infusion had been allowed to stand long enough to allow

of the growth of those it received from the air, which was about

forty-eight hours. The result of M. Pasteur's experiments proved,

therefore, in the most conclusive manner, that all the appearances of

spontaneous generation arose from nothing more than the deposition of

the germs of organisms which were constantly floating in the air.

To this conclusion, however, the objection was made, that if that were

the cause, then the air would contain such an enormous number of these

germs, that it would be a continual fog. But M. Pasteur replied that

they are not there in anything like the number we might suppose, and

that an exaggerated view has been held on that subject; he showed that

the chances of animal or vegetable life appearing in infusions, depend

entirely on the conditions under which they are exposed. If they are

exposed to the ordinary atmosphere around us, why, of course, you may

have organisms appearing early. But, on the other hand, if they are

exposed to air from a great height, or from some very quiet cellar, you

will often not find a single trace of life.

So that M. Pasteur arrived at last at the clear and definite result,

that all these appearances are like the case of the worms in the piece

of meat, which was refuted by Redi, simply germs carried by the air and

deposited in the liquids in which they afterwards appear. For my own

part, I conceive that, with the particulars of M. Pasteur's experiments

before us, we cannot fail to arrive at his conclusions; and that the

doctrine of spontaneous generation has received a final 'coup de grace'.

You, of course, understand that all this in no way interferes with the

POSSIBILITY of the fabrication of organic matters by the direct method

to which I have referred, remote as that possibility may be.

End of The Origination of Living Beings.