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

In the last Lecture I endeavoured to prove to you that, while, as a

general rule, organic beings tend to reproduce their kind, there is

in them, also, a constantly recurring tendency to vary--to vary to a

greater or to a less extent. Such a variety, I pointed out to you, might

arise from causes which we do not understand; we therefore called it

spontaneous; and it might come into existence as a definite and marked

thing, without any gradations between itself and the form which preceded

it. I further pointed out, that such a variety having once arisen,

might be perpetuated to some extent, and indeed to a very marked extent,

without any direct interference, or without any exercise of that process

which we called selection. And then I stated further, that by such

selection, when exercised artificially--if you took care to breed only

from those forms which presented the same peculiarities of any variety

which had arisen in this manner--the variation might be perpetuated, as

far as we can see, indefinitely.

The next question, and it is an important one for us, is this: Is there

any limit to the amount of variation from the primitive stock which can

be produced by this process of selective breeding? In considering this

question, it will be useful to class the characteristics, in respect of

which organic beings vary, under two heads: we may consider structural

characteristics, and we may consider physiological characteristics.

In the first place, as regards structural characteristics, I endeavoured

to show you, by the skeletons which I had upon the table, and by

reference to a great many well-ascertained facts, that the different

breeds of Pigeons, the Carriers, Pouters, and Tumblers, might vary in

any of their internal and important structural characters to a very

great degree; not only might there be changes in the proportions of the

skull, and the characters of the feet and beaks, and so on; but that

there might be an absolute difference in the number of the vertebrae of

the back, as in the sacral vertebrae of the Pouter; and so great is the

extent of the variation in these and similar characters that I pointed

out to you, by reference to the skeletons and the diagrams, that these

extreme varieties may absolutely differ more from one another in their

structural characters than do what naturalists call distinct SPECIES

of pigeons; that is to say, that they differ so much in structure that

there is a greater difference between the Pouter and the Tumbler than

there is between such wild and distinct forms as the Rock Pigeon or

the Ring Pigeon, or the Ring Pigeon and the Stock Dove; and indeed

the differences are of greater value than this, for the structural

differences between these domesticated pigeons are such as would be

admitted by a naturalist, supposing he knew nothing at all about their

origin, to entitle them to constitute even distinct genera.

As I have used this term SPECIES, and shall probably use it a good deal,

I had better perhaps devote a word or two to explaining what I mean by

it.

Animals and plants are divided into groups, which become gradually

smaller, beginning with a KINGDOM, which is divided into SUB-KINGDOMS;

then come the smaller divisions called PROVINCES; and so on from a

PROVINCE to a CLASS from a CLASS to an ORDER, from ORDERS to FAMILIES,

and from these to GENERA, until we come at length to the smallest

groups of animals which can be defined one from the other by constant

characters, which are not sexual; and these are what naturalists call

SPECIES in practice, whatever they may do in theory.

If, in a state of nature, you find any two groups of living beings,

which are separated one from the other by some constantly-recurring

characteristic, I don't care how slight and trivial, so long as it is

defined and constant, and does not depend on sexual peculiarities, then

all naturalists agree in calling them two species; that is what is meant

by the use of the word species--that is to say, it is, for the practical

naturalist, a mere question of structural differences.* ([Footnote] * I

lay stress here on the PRACTICAL signification of "Species." Whether

a physiological test between species exist or not, it is hardly ever

applicable by the practical naturalist.)

We have seen now--to repeat this point once more, and it is very

essential that we should rightly understand it--we have seen that

breeds, known to have been derived from a common stock by selection, may

be as different in their structure from the original stock as species

may be distinct from each other.

But is the like true of the physiological characteristics of animals?

Do the physiological differences of varieties amount in degree to those

observed between forms which naturalists call distinct species? This is

a most important point for us to consider.

As regards the great majority of physiological characteristics, there

is no doubt that they are capable of being developed, increased, and

modified by selection.

There is no doubt that breeds may be made as different as species in

many physiological characters. I have already pointed out to you very

briefly the different habits of the breeds of Pigeons, all of which

depend upon their physiological peculiarities,--as the peculiar habit of

tumbling, in the Tumbler--the peculiarities of flight, in the "homing"

birds,--the strange habit of spreading out the tail, and walking in a

peculiar fashion, in the Fantail,--and, lastly, the habit of blowing

out the gullet, so characteristic of the Pouter. These are all due

to physiological modifications, and in all these respects these birds

differ as much from each other as any two ordinary species do.

So with Dogs in their habits and instincts. It is a physiological

peculiarity which leads the Greyhound to chase its prey by sight,--that

enables the Beagle to track it by the scent,--that impels the Terrier to

its rat-hunting propensity,--and that leads the Retriever to its

habit of retrieving. These habits and instincts are all the results of

physiological differences and peculiarities, which have been developed

from a common stock, at least there is every reason to believe so.

But it is a most singular circumstance, that while you may run through

almost the whole series of physiological processes, without finding a

check to your argument, you come at last to a point where you do find

a check, and that is in the reproductive processes. For there is a most

singular circumstance in respect to natural species--at least about some

of them--and it would be sufficient for the purposes of this argument if

it were true of only one of them, but there is, in fact, a great number

of such cases--and that is, that, similar as they may appear to be

to mere races or breeds, they present a marked peculiarity in the

reproductive process. If you breed from the male and female of the same

race, you of course have offspring of the like kind, and if you make the

offspring breed together, you obtain the same result, and if you breed

from these again, you will still have the same kind of offspring; there

is no check. But if you take members of two distinct species, however

similar they may be to each other and make them breed together, you will

find a check, with some modifications and exceptions, however, which I

shall speak of presently. If you cross two such species with each other,

then,--although you may get offspring in the case of the first cross,

yet, if you attempt to breed from the products of that crossing, which

are what are called HYBRIDS--that is, if you couple a male and a female

hybrid--then the result is that in ninety-nine cases out of a hundred

you will get no offspring at all; there will be no result whatsoever.

The reason of this is quite obvious in some cases; the male hybrids,

although possessing all the external appearances and characteristics

of perfect animals, are physiologically imperfect and deficient in the

structural parts of the reproductive elements necessary to generation.

It is said to be invariably the case with the male mule, the cross

between the Ass and the Mare; and hence it is, that, although crossing

the Horse with the Ass is easy enough, and is constantly done, as far as

I am aware, if you take two mules, a male and a female, and endeavour to

breed from them, you get no offspring whatever; no generation will take

place. This is what is called the sterility of the hybrids between two

distinct species.

You see that this is a very extraordinary circumstance; one does not see

why it should be. The common teleological explanation is, that it is

to prevent the impurity of the blood resulting from the crossing of one

species with another, but you see it does not in reality do anything of

the kind. There is nothing in this fact that hybrids cannot breed with

each other, to establish such a theory; there is nothing to prevent the

Horse breeding with the Ass, or the Ass with the Horse. So that this

explanation breaks down, as a great many explanations of this kind do,

that are only founded on mere assumptions.

Thus you see that there is a great difference between "mongrels," which

are crosses between distinct races, and "hybrids," which are crosses

between distinct species. The mongrels are, so far as we know, fertile

with one another. But between species, in many cases, you cannot succeed

in obtaining even the first cross: at any rate it is quite certain that

the hybrids are often absolutely infertile one with another.

Here is a feature, then, great or small as it may be, which

distinguishes natural species of animals. Can we find any approximation

to this in the different races known to be produced by selective

breeding from a common stock? Up to the present time the answer to that

question is absolutely a negative one. As far as we know at present,

there is nothing approximating to this check. In crossing the breeds

between the Fantail and the Pouter, the Carrier and the Tumbler, or any

other variety or race you may name--so far as we know at present--there

is no difficulty in breeding together the mongrels. Take the Carrier and

the Fantail, for instance, and let them represent the Horse and the Ass

in the case of distinct species; then you have, as the result of their

breeding, the Carrier-Fantail mongrel,--we will say the male and female

mongrel,--and, as far as we know, these two when crossed would not be

less fertile than the original cross, or than Carrier with Carrier.

Here, you see, is a physiological contrast between the races produced

by selective modification and natural species. I shall inquire into the

value of this fact, and of some modifying circumstances by and by; for

the present I merely put it broadly before you.

But while considering this question of the limitations of species, a

word must be said about what is called RECURRENCE--the tendency of races

which have been developed by selective breeding from varieties to return

to their primitive type. This is supposed by many to put an absolute

limit to the extent of selective and all other variations. People say,

"It is all very well to talk about producing these different races,

but you know very well that if you turned all these birds wild, these

Pouters, and Carriers, and so on, they would all return to their

primitive stock." This is very commonly assumed to be a fact, and it is

an argument that is commonly brought forward as conclusive; but if you

will take the trouble to inquire into it rather closely, I think you

will find that it is not worth very much. The first question of course

is, Do they thus return to the primitive stock? And commonly as the

thing is assumed and accepted, it is extremely difficult to get anything

like good evidence of it. It is constantly said, for example, that if

domesticated Horses are turned wild, as they have been in some parts of

Asia Minor and South America, that they return at once to the primitive

stock from which they were bred. But the first answer that you make to

this assumption is, to ask who knows what the primitive stock was; and

the second answer is, that in that case the wild Horses of Asia Minor

ought to be exactly like the wild Horses of South America. If they are

both like the same thing, they ought manifestly to be like each other!

The best authorities, however, tell you that it is quite different. The

wild Horse of Asia is said to be of a dun colour, with a largish head,

and a great many other peculiarities; while the best authorities on

the wild Horses of South America tell you that there is no similarity

between their wild Horses and those of Asia Minor; the cut of their

heads is very different, and they are commonly chestnut or bay-coloured.

It is quite clear, therefore, that as by these facts there ought to

have been two primitive stocks, they go for nothing in support of the

assumption that races recur to one primitive stock, and so far as this

evidence is concerned, it falls to the ground.

Suppose for a moment that it were so, and that domesticated races, when

turned wild, did return to some common condition, I cannot see that this

would prove much more than that similar conditions are likely to produce

similar results; and that when you take back domesticated animals into

what we call natural conditions, you do exactly the same thing as if you

carefully undid all the work you had gone through, for the purpose of

bringing the animal from its wild to its domesticated state. I do not

see anything very wonderful in the fact, if it took all that trouble to

get it from a wild state, that it should go back into its original state

as soon as you removed the conditions which produced the variation to

the domesticated form. There is an important fact, however, forcibly

brought forward by Mr. Darwin, which has been noticed in connection with

the breeding of domesticated pigeons; and it is, that however different

these breeds of pigeons may be from each other, and we have already

noticed the great differences in these breeds, that if, among any of

those variations, you chance to have a blue pigeon turn up, it will be

sure to have the black bars across the wings, which are characteristic

of the original wild stock, the Rock Pigeon.

Now, this is certainly a very remarkable circumstance; but I do not see

myself how it tells very strongly either one way or the other. I think,

in fact, that this argument in favour of recurrence to the primitive

type might prove a great deal too much for those who so constantly

bring it forward. For example, Mr. Darwin has very forcibly urged,

that nothing is commoner than if you examine a dun horse--and I had an

opportunity of verifying this illustration lately, while in the islands

of the West Highlands, where there are a great many dun horses--to find

that horse exhibit a long black stripe down his back, very often stripes

on his shoulder, and very often stripes on his legs. I, myself, saw

a pony of this description a short time ago, in a baker's cart, near

Rothesay, in Bute: it had the long stripe down the back, and stripes on

the shoulders and legs, just like those of the Ass, the Quagga, and the

Zebra. Now, if we interpret the theory of recurrence as applied to

this case, might it not be said that here was a case of a variation

exhibiting the characters and conditions of an animal occupying

something like an intermediate position between the Horse, the Ass, the

Quagga, and the Zebra, and from which these had been developed? In the

same way with regard even to Man. Every anatomist will tell you that

there is nothing commoner, in dissecting the human body, than to meet

with what are called muscular variations--that is, if you dissect

two bodies very carefully, you will probably find that the modes of

attachment and insertion of the muscles are not exactly the same in

both, there being great peculiarities in the mode in which the muscles

are arranged; and it is very singular, that in some dissections of the

human body you will come upon arrangements of the muscles very similar

indeed to the same parts in the Apes. Is the conclusion in that case to

be, that this is like the black bars in the case of the Pigeon, and that

it indicates a recurrence to the primitive type from which the animals

have been probably developed? Truly, I think that the opponents of

modification and variation had better leave the argument of recurrence

alone, or it may prove altogether too strong for them.

To sum up--the evidence as far as we have gone is against the argument

as to any limit to divergences, so far as structure is concerned; and

in favour of a physiological limitation. By selective breeding we can

produce structural divergences as great as those of species, but we

cannot produce equal physiological divergences. For the present I leave

the question there.

Now, the next problem that lies before us--and it is an extremely

important one--is this: Does this selective breeding occur in nature?

Because, if there is no proof of it, all that I have been telling you

goes for nothing in accounting for the origin of species. Are natural

causes competent to play the part of selection in perpetuating

varieties? Here we labour under very great difficulties. In the last

lecture I had occasion to point out to you the extreme difficulty of

obtaining evidence even of the first origin of those varieties which we

know to have occurred in domesticated animals. I told you, that almost

always the origin of these varieties is overlooked, so that I could only

produce two of three cases, as that of Gratio Kelleia and of the Ancon

sheep. People forget, or do not take notice of them until they come to

have a prominence; and if that is true of artificial cases, under our

own eyes, and in animals in our own care, how much more difficult it

must be to have at first hand good evidence of the origin of varieties

in nature! Indeed, I do not know that it is possible by direct evidence

to prove the origin of a variety in nature, or to prove selective

breeding; but I will tell you what we can prove--and this comes to the

same thing--that varieties exist in nature within the limits of species,

and, what is more, that when a variety has come into existence in

nature, there are natural causes and conditions, which are amply

competent to play the part of a selective breeder; and although that

is not quite the evidence that one would like to have--though it is

not direct testimony--yet it is exceeding good and exceedingly powerful

evidence in its way.

As to the first point, of varieties existing among natural species, I

might appeal to the universal experience of every naturalist, and of any

person who has ever turned any attention at all to the characteristics

of plants and animals in a state of nature; but I may as well take a few

definite cases, and I will begin with Man himself.

I am one of those who believe that, at present, there is no evidence

whatever for saying, that mankind sprang originally from any more than a

single pair; I must say, that I cannot see any good ground whatever, or

even any tenable sort of evidence, for believing that there is more than

one species of Man. Nevertheless, as you know, just as there are numbers

of varieties in animals, so there are remarkable varieties of men. I

speak not merely of those broad and distinct variations which you see at

a glance. Everybody, of course, knows the difference between a Negro and

a white man, and can tell a Chinaman from an Englishman. They each

have peculiar characteristics of colour and physiognomy; but you must

recollect that the characters of these races go very far deeper--they

extend to the bony structure, and to the characters of that most

important of all organs to us--the brain; so that, among men belonging

to different races, or even within the same race, one man shall have a

brain a third, or half, or even seventy per cent. bigger than another;

and if you take the whole range of human brains, you will find a

variation in some cases of a hundred per cent. Apart from these

variations in the size of the brain, the characters of the skull vary.

Thus if I draw the figures of a Mongul and of a Negro head on the

blackboard, in the case of the last the breadth would be about

seven-tenths, and in the other it would be nine-tenths of the total

length. So that you see there is abundant evidence of variation among

men in their natural condition. And if you turn to other animals there

is just the same thing. The fox, for example, which has a very large

geographical distribution all over Europe, and parts of Asia, and on the

American Continent, varies greatly. There are mostly large foxes in the

North, and smaller ones in the South. In Germany alone, the foresters

reckon some eight different sorts.

Of the tiger, no one supposes that there is more than one species; they

extend from the hottest parts of Bengal, into the dry, cold, bitter

steppes of Siberia, into a latitude of 50 degrees,--so that they may

even prey upon the reindeer. These tigers have exceedingly different

characteristics, but still they all keep their general features, so that

there is no doubt as to their being tigers. The Siberian tiger has a

thick fur, a small mane, and a longitudinal stripe down the back, while

the tigers of Java and Sumatra differ in many important respects from

the tigers of Northern Asia. So lions vary; so birds vary; and so, if

you go further back and lower down in creation, you find that fishes

vary. In different streams, in the same country even, you will find the

trout to be quite different to each other and easily recognisable by

those who fish in the particular streams. There is the same differences

in leeches; leech collectors can easily point out to you the differences

and the peculiarities which you yourself would probably pass by; so with

fresh-water mussels; so, in fact, with every animal you can mention.

In plants there is the same kind of variation. Take such a case even as

the common bramble. The botanists are all at war about it; some of

them wanting to make out that there are many species of it, and others

maintaining that they are but many varieties of one species; and they

cannot settle to this day which is a species and which is a variety!

So that there can be no doubt whatsoever that any plant and any

animal may vary in nature; that varieties may arise in the way I have

described,--as spontaneous varieties,--and that those varieties may be

perpetuated in the same way that I have shown you spontaneous varieties

are perpetuated; I say, therefore, that there can be no doubt as to the

origin and perpetuation of varieties in nature.

But the question now is:--Does selection take place in nature? is there

anything like the operation of man in exercising selective breeding,

taking place in nature? You will observe that, at present, I say nothing

about species; I wish to confine myself to the consideration of the

production of those natural races which everybody admits to exist. The

question is, whether in nature there are causes competent to produce

races, just in the same way as man is able to produce by selection, such

races of animals as we have already noticed.

When a variety has arisen, the CONDITIONS OF EXISTENCE are such as to

exercise an influence which is exactly comparable to that of artificial

selection. By Conditions of Existence I mean two things,--there are

conditions which are furnished by the physical, the inorganic world,

and there are conditions of existence which are furnished by the organic

world. There is, in the first place, CLIMATE; under that head I include

only temperature and the varied amount of moisture of particular places.

In the next place there is what is technically called STATION, which

means--given the climate, the particular kind of place in which an

animal or a plant lives or grows; for example, the station of a fish

is in the water, of a fresh-water fish in fresh water; the station of a

marine fish is in the sea, and a marine animal may have a station higher

or deeper. So again with land animals: the differences in their stations

are those of different soils and neighbourhoods; some being best adapted

to a calcareous, and others to an arenaceous soil. The third condition

of existence is FOOD, by which I mean food in the broadest sense, the

supply of the materials necessary to the existence of an organic being;

in the case of a plant the inorganic matters, such as carbonic acid,

water, ammonia, and the earthy salts or salines; in the case of the

animal the inorganic and organic matters, which we have seen they

require; then these are all, at least the two first, what we may

call the inorganic or physical conditions of existence. Food takes a

mid-place, and then come the organic conditions; by which I mean the

conditions which depend upon the state of the rest of the organic

creation, upon the number and kind of living beings, with which an

animal is surrounded. You may class these under two heads: there are

organic beings, which operate as 'opponents', and there are organic

beings which operate as 'helpers' to any given organic creature. The

opponents may be of two kinds: there are the 'indirect opponents', which

are what we may call 'rivals'; and there are the 'direct opponents',

those which strive to destroy the creature; and these we call 'enemies'.

By rivals I mean, of course, in the case of plants, those which require

for their support the same kind of soil and station, and, among animals,

those which require the same kind of station, or food, or climate; those

are the indirect opponents; the direct opponents are, of course, those

which prey upon an animal or vegetable. The 'helpers' may also be

regarded as direct and indirect: in the case of a carnivorous animal,

for example, a particular herbaceous plant may in multiplying be an

indirect helper, by enabling the herbivora on which the carnivore preys

to get more food, and thus to nourish the carnivore more abundantly;

the direct helper may be best illustrated by reference to some parasitic

creature, such as the tape-worm. The tape-worm exists in the human

intestines, so that the fewer there are of men the fewer there will be

of tape-worms, other things being alike. It is a humiliating reflection,

perhaps, that we may be classed as direct helpers to the tape-worm, but

the fact is so: we can all see that if there were no men there would be

no tape-worms.

It is extremely difficult to estimate, in a proper way, the importance

and the working of the Conditions of Existence. I do not think there

were any of us who had the remotest notion of properly estimating them

until the publication of Mr. Darwin's work, which has placed them before

us with remarkable clearness; and I must endeavour, as far as I can in

my own fashion, to give you some notion of how they work. We shall find

it easiest to take a simple case, and one as free as possible from every

kind of complication.

I will suppose, therefore, that all the habitable part of this

globe--the dry land, amounting to about 51,000,000 square miles,--I will

suppose that the whole of that dry land has the same climate, and that

it is composed of the same kind of rock or soil, so that there will be

the same station everywhere; we thus get rid of the peculiar influence

of different climates and stations. I will then imagine that there shall

be but one organic being in the world, and that shall be a plant. In

this we start fair. Its food is to be carbonic acid, water and ammonia,

and the saline matters in the soil, which are, by the supposition,

everywhere alike. We take one single plant, with no opponents, no

helpers, and no rivals; it is to be a "fair field, and no favour". Now,

I will ask you to imagine further that it shall be a plant which shall

produce every year fifty seeds, which is a very moderate number for a

plant to produce; and that, by the action of the winds and currents,

these seeds shall be equally and gradually distributed over the whole

surface of the land. I want you now to trace out what will occur, and

you will observe that I am not talking fallaciously any more than a

mathematician does when he expounds his problem. If you show that the

conditions of your problem are such as may actually occur in nature and

do not transgress any of the known laws of nature in working out your

proposition, then you are as safe in the conclusion you arrive at as

is the mathematician in arriving at the solution of his problem. In

science, the only way of getting rid of the complications with which a

subject of this kind is environed, is to work in this deductive method.

What will be the result, then? I will suppose that every plant requires

one square foot of ground to live upon; and the result will be that,

in the course of nine years, the plant will have occupied every single

available spot in the whole globe! I have chalked upon the blackboard

the figures by which I arrive at the result:--

Plants. Plants

1 x 50 in 1st year = 50

50 x 50 " 2nd " = 2,500

2,500 x 50 " 3rd " = 125,000

125,000 x 50 " 4th " = 6,250,000

6,250,000 x 50 " 5th " = 312,500,000

312,500,000 x 50 " 6th " = 15,625,000,000

15,625,000,000 x 50 " 7th " = 781,250,000,000

781,250,000,000 x 50 " 8th " = 39,062,500,000,000

39,062,500,000,000 x 50 " 9th " = 1,953,125,000,000,000

51,000,000 sq. miles--the dry surface of the earth x 27,878,400--the

number of sq. ft. in 1 sq. mile = sq. ft. 1,421,798,400,000,000 being

531,326,600,000,000 square feet less than would be required at the end

of the ninth year.

You will see from this that, at the end of the first year the single

plant will have produced fifty more of its kind; by the end of the

second year these will have increased to 2,500; and so on, in succeeding

years, you get beyond even trillions; and I am not at all sure that I

could tell you what the proper arithmetical denomination of the total

number really is; but, at any rate, you will understand the meaning of

all those noughts. Then you see that, at the bottom, I have taken the

51,000,000 of square miles, constituting the surface of the dry land;

and as the number of square feet are placed under and subtracted from

the number of seeds that would be produced in the ninth year, you can

see at once that there would be an immense number more of plants than

there would be square feet of ground for their accommodation. This is

certainly quite enough to prove my point; that between the eighth and

ninth year after being planted the single plant would have stocked the

whole available surface of the earth.

This is a thing which is hardly conceivable--it seems hardly

imaginable--yet it is so. It is indeed simply the law of Malthus

exemplified. Mr. Malthus was a clergyman, who worked out this

subject most minutely and truthfully some years ago; he showed quite

clearly,--and although he was much abused for his conclusions at the

time, they have never yet been disproved and never will be--he showed

that in consequence of the increase in the number of organic beings in

a geometrical ratio, while the means of existence cannot be made to

increase in the same ratio, that there must come a time when the number

of organic beings will be in excess of the power of production of

nutriment, and that thus some check must arise to the further increase

of those organic beings. At the end of the ninth year we have seen that

each plant would not be able to get its full square foot of ground, and

at the end of another year it would have to share that space with fifty

others the produce of the seeds which it would give off.

What, then, takes place? Every plant grows up, flourishes, occupies its

square foot of ground, and gives off its fifty seeds; but notice this,

that out of this number only one can come to anything; there is thus,

as it were, forty-nine chances to one against its growing up; it depends

upon the most fortuitous circumstances whether any one of these fifty

seeds shall grow up and flourish, or whether it shall die and perish.

This is what Mr. Darwin has drawn attention to, and called the "STRUGGLE

FOR EXISTENCE"; and I have taken this simple case of a plant because

some people imagine that the phrase seems to imply a sort of fight.

I have taken this plant and shown you that this is the result of the

ratio of the increase, the necessary result of the arrival of a time

coming for every species when exactly as many members must be destroyed

as are born; that is the inevitable ultimate result of the rate of

production. Now, what is the result of all this? I have said that there

are forty-nine struggling against every one; and it amounts to this,

that the smallest possible start given to any one seed may give it an

advantage which will enable it to get ahead of all the others; anything

that will enable any one of these seeds to germinate six hours before

any of the others will, other things being alike, enable it to choke

them out altogether. I have shown you that there is no particular in

which plants will not vary from each other; it is quite possible

that one of our imaginary plants may vary in such a character as the

thickness of the integument of its seeds; it might happen that one of

the plants might produce seeds having a thinner integument, and that

would enable the seeds of that plant to germinate a little quicker

than those of any of the others, and those seeds would most inevitably

extinguish the forty-nine times as many that were struggling with them.

I have put it in this way, but you see the practical result of the

process is the same as if some person had nurtured the one and destroyed

the other seeds. It does not matter how the variation is produced, so

long as it is once allowed to occur. The variation in the plant once

fairly started tends to become hereditary and reproduce itself; the

seeds would spread themselves in the same way and take part in the

struggle with the forty-nine hundred, or forty-nine thousand, with which

they might be exposed. Thus, by degrees, this variety, with some slight

organic change or modification, must spread itself over the whole

surface of the habitable globe, and extirpate or replace the other

kinds. That is what is meant by NATURAL SELECTION; that is the kind of

argument by which it is perfectly demonstrable that the conditions of

existence may play exactly the same part for natural varieties as man

does for domesticated varieties. No one doubts at all that particular

circumstances may be more favourable for one plant and less so for

another, and the moment you admit that, you admit the selective power of

nature. Now, although I have been putting a hypothetical case, you must

not suppose that I have been reasoning hypothetically. There are plenty

of direct experiments which bear out what we may call the theory of

natural selection; there is extremely good authority for the statement

that if you take the seed of mixed varieties of wheat and sow it,

collecting the seed next year and sowing it again, at length you will

find that out of all your varieties only two or three have lived, or

perhaps even only one. There were one or two varieties which were best

fitted to get on, and they have killed out the other kinds in just

the same way and with just the same certainty as if you had taken the

trouble to remove them. As I have already said, the operation of nature

is exactly the same as the artificial operation of man.

But if this be true of that simple case, which I put before you, where

there is nothing but the rivalry of one member of a species with others,

what must be the operation of selective conditions, when you recollect

as a matter of fact, that for every species of animal or plant there

are fifty or a hundred species which might all, more or less, be

comprehended in the same climate, food, and station;--that every plant

has multitudinous animals which prey upon it, and which are its direct

opponents; and that these have other animals preying upon them,--that

every plant has its indirect helpers in the birds that scatter abroad

its seed, and the animals that manure it with their dung;--I say, when

these things are considered, it seems impossible that any variation

which may arise in a species in nature should not tend in some way or

other either to be a little better or worse than the previous stock;

if it is a little better it will have an advantage over and tend to

extirpate the latter in this crush and struggle; and if it is a little

worse it will itself be extirpated.

I know nothing that more appropriately expresses this, than the phrase,

"the struggle for existence"; because it brings before your minds, in a

vivid sort of way, some of the simplest possible circumstances connected

with it. When a struggle is intense there must be some who are sure to

be trodden down, crushed, and overpowered by others; and there will be

some who just manage to get through only by the help of the slightest

accident. I recollect reading an account of the famous retreat of

the French troops, under Napoleon, from Moscow. Worn out, tired, and

dejected, they at length came to a great river over which there was

but one bridge for the passage of the vast army. Disorganised and

demoralised as that army was, the struggle must certainly have been a

terrible one--every one heeding only himself, and crushing through the

ranks and treading down his fellows. The writer of the narrative, who

was himself one of those who were fortunate enough to succeed in getting

over, and not among the thousands who were left behind or forced into

the river, ascribed his escape to the fact that he saw striding onward

through the mass a great strong fellow,--one of the French Cuirassiers,

who had on a large blue cloak--and he had enough presence of mind to

catch and retain a hold of this strong man's cloak. He says, "I caught

hold of his cloak, and although he swore at me and cut at and struck me

by turns, and at last, when he found he could not shake me off, fell to

entreating me to leave go or I should prevent him from escaping, besides

not assisting myself, I still kept tight hold of him, and would not quit

my grasp until he had at last dragged me through." Here you see was

a case of selective saving--if we may so term it--depending for its

success on the strength of the cloth of the Cuirassier's cloak. It is

the same in nature; every species has its bridge of Beresina; it has

to fight its way through and struggle with other species; and when well

nigh overpowered, it may be that the smallest chance, something in its

colour, perhaps--the minutest circumstance--will turn the scale one way

or the other.

Suppose that by a variation of the black race it had produced the white

man at any time--you know that the Negroes are said to believe this to

have been the case, and to imagine that Cain was the first white man,

and that we are his descendants--suppose that this had ever happened,

and that the first residence of this human being was on the West Coast

of Africa. There is no great structural difference between the white man

and the Negro, and yet there is something so singularly different in the

constitution of the two, that the malarias of that country, which do not

hurt the black at all, cut off and destroy the white. Then you see there

would have been a selective operation performed; if the white man had

risen in that way, he would have been selected out and removed by means

of the malaria. Now there really is a very curious case of selection of

this sort among pigs, and it is a case of selection of colour too.

In the woods of Florida there are a great many pigs, and it is a very

curious thing that they are all black, every one of them. Professor

Wyman was there some years ago, and on noticing no pigs but these black

ones, he asked some of the people how it was that they had no white

pigs, and the reply was that in the woods of Florida there was a root

which they called the Paint Root, and that if the white pigs were to eat

any of it, it had the effect of making their hoofs crack, and they died,

but if the black pigs eat any of it, it did not hurt them at all. Here

was a very simple case of natural selection. A skilful breeder could not

more carefully develope the black breed of pigs, and weed out all the

white pigs, than the Paint Root does.

To show you how remarkably indirect may be such natural selective

agencies as I have referred to, I will conclude by noticing a case

mentioned by Mr. Darwin, and which is certainly one of the most curious

of its kind. It is that of the Humble Bee. It has been noticed that

there are a great many more humble bees in the neighbourhood of towns,

than out in the open country; and the explanation of the matter is this:

the humble bees build nests, in which they store their honey and deposit

the larvae and eggs. The field mice are amazingly fond of the honey and

larvae; therefore, wherever there are plenty of field mice, as in the

country, the humble bees are kept down; but in the neighbourhood of

towns, the number of cats which prowl about the fields eat up the field

mice, and of course the more mice they eat up the less there are to prey

upon the larvae of the bees--the cats are therefore the INDIRECT HELPERS

of the bees!* Coming back a step farther we may say that the old maids

are also indirect friends of the humble bees, and indirect enemies of

the field mice, as they keep the cats which eat up the latter! This is

an illustration somewhat beneath the dignity of the subject, perhaps,

but it occurs to me in passing, and with it I will conclude this

lecture. ([Footnote] *The humble bees, on the other hand, are direct

helpers of some plants, such as the heartsease and red clover, which are

fertilized by the visits of the bees; and they are indirect helpers of

the numerous insects which are more or less completely supported by the

heartsease and red clover.)

End of The Conditions of Existence.

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

In the preceding five lectures I have endeavoured to give you an account

of those facts, and of those reasonings from facts, which form the data

upon which all theories regarding the causes of the phenomena of organic

nature must be based. And, although I have had frequent occasion to

quote Mr. Darwin--as all persons hereafter, in speaking upon these

subjects, will have occasion to quote his famous book on the "Origin of

Species,"--you must yet remember that, wherever I have quoted him,

it has not been upon theoretical points, or for statements in any way

connected with his particular speculations, but on matters of fact,

brought forward by himself, or collected by himself, and which appear

incidentally in his book. If a man WILL make a book, professing to

discuss a single question, an encyclopaedia, I cannot help it.

Now, having had an opportunity of considering in this sort of way the

different statements bearing upon all theories whatsoever, I have to lay

before you, as fairly as I can, what is Mr. Darwin's view of the matter

and what position his theories hold, when judged by the principles which

I have previously laid down, as deciding our judgments upon all theories

and hypotheses.

I have already stated to you that the inquiry respecting the causes of

the phenomena of organic nature resolves itself into two problems--the

first being the question of the origination of living or organic beings;

and the second being the totally distinct problem of the modification

and perpetuation of organic beings when they have already come into

existence. The first question Mr. Darwin does not touch; he does

not deal with it at all; but he says--given the origin of organic

matter--supposing its creation to have already taken place, my object is

to show in consequence of what laws and what demonstrable properties of

organic matter, and of its environments, such states of organic nature

as those with which we are acquainted must have come about. This, you

will observe, is a perfectly legitimate proposition; every person has a

right to define the limits of the inquiry which he sets before himself;

and yet it is a most singular thing that in all the multifarious, and,

not unfrequently, ignorant attacks which have been made upon the 'Origin

of Species', there is nothing which has been more speciously criticised

than this particular limitation. If people have nothing else to urge

against the book, they say--"Well, after all, you see, Mr. Darwin's

explanation of the 'Origin of Species' is not good for much, because, in

the long run, he admits that he does not know how organic matter began

to exist. But if you admit any special creation for the first particle

of organic matter you may just as well admit it for all the rest; five

hundred or five thousand distinct creations are just as intelligible,

and just as little difficult to understand, as one." The answer to these

cavils is two-fold. In the first place, all human inquiry must stop

somewhere; all our knowledge and all our investigation cannot take us

beyond the limits set by the finite and restricted character of our

faculties, or destroy the endless unknown, which accompanies, like its

shadow, the endless procession of phenomena. So far as I can venture

to offer an opinion on such a matter, the purpose of our being

in existence, the highest object that human beings can set before

themselves, is not the pursuit of any such chimera as the annihilation

of the unknown; but it is simply the unwearied endeavour to remove its

boundaries a little further from our little sphere of action.

I wonder if any historian would for a moment admit the objection, that

it is preposterous to trouble ourselves about the history of the Roman

Empire, because we do not know anything positive about the origin and

first building of the city of Rome! Would it be a fair objection to

urge, respecting the sublime discoveries of a Newton, or a Kepler,

those great philosophers, whose discoveries have been of the profoundest

benefit and service to all men,--to say to them--"After all that you

have told us as to how the planets revolve, and how they are maintained

in their orbits, you cannot tell us what is the cause of the origin of

the sun, moon, and stars. So what is the use of what you have done?"

Yet these objections would not be one whit more preposterous than the

objections which have been made to the 'Origin of Species.' Mr. Darwin,

then, had a perfect right to limit his inquiry as he pleased, and the

only question for us--the inquiry being so limited--is to ascertain

whether the method of his inquiry is sound or unsound; whether he has

obeyed the canons which must guide and govern all investigation, or

whether he has broken them; and it was because our inquiry this evening

is essentially limited to that question, that I spent a good deal of

time in a former lecture (which, perhaps, some of you thought might

have been better employed), in endeavouring to illustrate the method

and nature of scientific inquiry in general. We shall now have to put in

practice the principles that I then laid down.

I stated to you in substance, if not in words, that wherever there

are complex masses of phenomena to be inquired into, whether they be

phenomena of the affairs of daily life, or whether they belong to the

more abstruse and difficult problems laid before the philosopher, our

course of proceeding in unravelling that complex chain of phenomena with

a view to get at its cause, is always the same; in all cases we must

invent an hypothesis; we must place before ourselves some more or less

likely supposition respecting that cause; and then, having assumed an

hypothesis, having supposed cause for the phenomena in question, we must

endeavour, on the one hand, to demonstrate our hypothesis, or, on the

other, to upset and reject it altogether, by testing it in three ways.

We must, in the first place, be prepared to prove that the supposed

causes of the phenomena exist in nature; that they are what the

logicians call 'vera causae'--true causes;--in the next place, we

should be prepared to show that the assumed causes of the phenomena are

competent to produce such phenomena as those which we wish to explain by

them; and in the last place, we ought to be able to show that no other

known causes are competent to produce those phenomena. If we can succeed

in satisfying these three conditions we shall have demonstrated our

hypothesis; or rather I ought to say we shall have proved it as far as

certainty is possible for us; for, after all, there is no one of our

surest convictions which may not be upset, or at any rate modified by

a further accession of knowledge. It was because it satisfied these

conditions that we accepted the hypothesis as to the disappearance of

the tea-pot and spoons in the case I supposed in a previous lecture; we

found that our hypothesis on that subject was tenable and valid, because

the supposed cause existed in nature, because it was competent to

account for the phenomena, and because no other known cause was

competent to account for them; and it is upon similar grounds that any

hypothesis you choose to name is accepted in science as tenable and

valid.

What is Mr. Darwin's hypothesis? As I apprehend it--for I have put

it into a shape more convenient for common purposes than I could find

'verbatim' in his book--as I apprehend it, I say, it is, that all the

phenomena of organic nature, past and present, result from, or are

caused by, the inter-action of those properties of organic matter,

which we have called ATAVISM and VARIABILITY, with the CONDITIONS OF

EXISTENCE; or, in other words,--given the existence of organic matter,

its tendency to transmit its properties, and its tendency occasionally

to vary; and, lastly, given the conditions of existence by which organic

matter is surrounded--that these put together are the causes of the

Present and of the Past conditions of ORGANIC NATURE.

Such is the hypothesis as I understand it. Now let us see how it will

stand the various tests which I laid down just now. In the first place,

do these supposed causes of the phenomena exist in nature? Is it the

fact that in nature these properties of organic matter--atavism and

variability--and those phenomena which we have called the conditions of

existence,--is it true that they exist? Well, of course, if they do not

exist, all that I have told you in the last three or four lectures

must be incorrect, because I have been attempting to prove that they do

exist, and I take it that there is abundant evidence that they do exist;

so far, therefore, the hypothesis does not break down.

But in the next place comes a much more difficult inquiry:--Are the

causes indicated competent to give rise to the phenomena of organic

nature? I suspect that this is indubitable to a certain extent. It is

demonstrable, I think, as I have endeavoured to show you, that they

are perfectly competent to give rise to all the phenomena which are

exhibited by RACES in nature. Furthermore, I believe that they are

quite competent to account for all that we may call purely structural

phenomena which are exhibited by SPECIES in nature. On that point also

I have already enlarged somewhat. Again, I think that the causes assumed

are competent to account for most of the physiological characteristics

of species, and I not only think that they are competent to account

for them, but I think that they account for many things which

otherwise remain wholly unaccountable and inexplicable, and I may say

incomprehensible. For a full exposition of the grounds on which this

conviction is based, I must refer you to Mr. Darwin's work; all that I

can do now is to illustrate what I have said by two or three cases taken

almost at random.

I drew your attention, on a previous evening, to the facts which are

embodied in our systems of Classification, which are the results of

the examination and comparison of the different members of the animal

kingdom one with another. I mentioned that the whole of the animal

kingdom is divisible into five sub-kingdoms; that each of these

sub-kingdoms is again divisible into provinces; that each province may

be divided into classes, and the classes into the successively smaller

groups, orders, families, genera, and species.

Now, in each of these groups, the resemblance in structure among the

members of the group is closer in proportion as the group is smaller.

Thus, a man and a worm are members of the animal kingdom in virtue of

certain apparently slight though really fundamental resemblances which

they present. But a man and a fish are members of the same sub-kingdom

'Vertebrata', because they are much more like one another than either of

them is to a worm, or a snail, or any member of the other sub-kingdoms.

For similar reasons men and horses are arranged as members of the

same Class, 'Mammalia'; men and apes as members of the same Order,

'Primates'; and if there were any animals more like men than they

were like any of the apes, and yet different from men in important

and constant particulars of their organization, we should rank them as

members of the same Family, or of the same Genus, but as of distinct

Species.

That it is possible to arrange all the varied forms of animals into

groups, having this sort of singular subordination one to the other, is

a very remarkable circumstance; but, as Mr. Darwin remarks, this is a

result which is quite to be expected, if the principles which he lays

down be correct. Take the case of the races which are known to be

produced by the operation of atavism and variability, and the conditions

of existence which check and modify these tendencies. Take the case

of the pigeons that I brought before you; there it was shown that

they might be all classed as belonging to some one of five principal

divisions, and that within these divisions other subordinate groups

might be formed. The members of these groups are related to one

another in just the same way as the genera of a family, and the groups

themselves as the families of an order, or the orders of a class;

while all have the same sort of structural relations with the wild

rock-pigeon, as the members of any great natural group have with a real

or imaginary typical form. Now, we know that all varieties of pigeons of

every kind have arisen by a process of selective breeding from a common

stock, the rock-pigeon; hence, you see, that if all species of animals

have proceeded from some common stock, the general character of their

structural relations, and of our systems of classification, which

express those relations, would be just what we find them to be. In other

words, the hypothetical cause is, so far, competent to produce effects

similar to those of the real cause.

Take, again, another set of very remarkable facts,--the existence of

what are called rudimentary organs, organs for which we can find no

obvious use, in the particular animal economy in which they are found,

and yet which are there.

Such are the splint-like bones in the leg of the horse, which I here

show you, and which correspond with bones which belong to certain toes

and fingers in the human hand and foot. In the horse you see they are

quite rudimentary, and bear neither toes nor fingers; so that the horse

has only one "finger" in his fore-foot and one "toe" in his hind foot.

But it is a very curious thing that the animals closely allied to the

horse show more toes than he; as the rhinoceros, for instance: he has

these extra toes well formed, and anatomical facts show very clearly

that he is very closely related to the horse indeed. So we may say that

animals, in an anatomical sense nearly related to the horse, have those

parts which are rudimentary in him, fully developed.

Again, the sheep and the cow have no cutting-teeth, but only a hard

pad in the upper jaw. That is the common characteristic of ruminants in

general. But the calf has in its upper jaw some rudiments of teeth which

never are developed, and never play the part of teeth at all. Well, if

you go back in time, you find some of the older, now extinct, allies of

the ruminants have well-developed teeth in their upper jaws; and at

the present day the pig (which is in structure closely connected with

ruminants) has well-developed teeth in its upper jaw; so that here

is another instance of organs well-developed and very useful, in one

animal, represented by rudimentary organs, for which we can discover

no purpose whatsoever, in another closely allied animal. The whalebone

whale, again, has horny "whalebone" plates in its mouth, and no teeth;

but the young foetal whale, before it is born, has teeth in its jaws;

they, however, are never used, and they never come to anything.

But other members of the group to which the whale belongs have

well-developed teeth in both jaws.

Upon any hypothesis of special creation, facts of this kind appear to me

to be entirely unaccountable and inexplicable, but they cease to be so

if you accept Mr. Darwin's hypothesis, and see reason for believing that

the whalebone whale and the whale with teeth in its mouth both sprang

from a whale that had teeth, and that the teeth of the foetal whale are

merely remnants--recollections, if we may so say--of the extinct whale.

So in the case of the horse and the rhinoceros: suppose that both have

descended by modification from some earlier form which had the normal

number of toes, and the persistence of the rudimentary bones which no

longer support toes in the horse becomes comprehensible.

In the language that we speak in England, and in the language of the

Greeks, there are identical verbal roots, or elements entering into the

composition of words. That fact remains unintelligible so long as we

suppose English and Greek to be independently created tongues; but when

it is shown that both languages are descended from one original, the

Sanscrit, we give an explanation of that resemblance. In the same way

the existence of identical structural roots, if I may so term them,

entering into the composition of widely different animals, is striking

evidence in favour of the descent of those animals from a common

original.

To turn to another kind of illustration:--If you regard the whole

series of stratified rocks--that enormous thickness of sixty or seventy

thousand feet that I have mentioned before, constituting the only record

we have of a most prodigious lapse of time, that time being, in all

probability, but a fraction of that of which we have no record;--if you

observe in these successive strata of rocks successive groups of animals

arising and dying out, a constant succession, giving you the same kind

of impression, as you travel from one group of strata to another, as

you would have in travelling from one country to another;--when you find

this constant succession of forms, their traces obliterated except to

the man of science,--when you look at this wonderful history, and ask

what it means, it is only a paltering with words if you are offered the

reply,--'They were so created.'

But if, on the other hand, you look on all forms of organized beings as

the results of the gradual modification of a primitive type, the facts

receive a meaning, and you see that these older conditions are the

necessary predecessors of the present. Viewed in this light the facts of

palaeontology receive a meaning--upon any other hypothesis, I am unable

to see, in the slightest degree, what knowledge or signification we are

to draw out of them. Again, note as bearing upon the same point, the

singular likeness which obtains between the successive Faunae and

Florae, whose remains are preserved on the rocks: you never find any

great and enormous difference between the immediately successive Faunae

and Florae, unless you have reason to believe there has also been a

great lapse of time or a great change of conditions. The animals, for

instance, of the newest tertiary rocks, in any part of the world, are

always, and without exception, found to be closely allied with those

which now live in that part of the world. For example, in Europe,

Asia, and Africa, the large mammals are at present rhinoceroses,

hippopotamuses, elephants, lions, tigers, oxen, horses, etc.; and if

you examine the newest tertiary deposits, which contain the animals

and plants which immediately preceded those which now exist in the same

country, you do not find gigantic specimens of ant-eaters and kangaroos,

but you find rhinoceroses, elephants, lions, tigers, etc.,--of different

species to those now living,--but still their close allies. If you turn

to South America, where, at the present day, we have great sloths and

armadilloes and creatures of that kind, what do you find in the newest

tertiaries? You find the great sloth-like creature, the 'Megatherium',

and the great armadillo, the 'Glyptodon', and so on. And if you go to

Australia you find the same law holds good, namely, that that condition

of organic nature which has preceded the one which now exists, presents

differences perhaps of species, and of genera, but that the great types

of organic structure are the same as those which now flourish.

What meaning has this fact upon any other hypothesis or supposition than

one of successive modification? But if the population of the world, in

any age, is the result of the gradual modification of the forms which

peopled it in the preceding age,--if that has been the case, it is

intelligible enough; because we may expect that the creature that

results from the modification of an elephantine mammal shall be

something like an elephant, and the creature which is produced by the

modification of an armadillo-like mammal shall be like an armadillo.

Upon that supposition, I say, the facts are intelligible; upon any

other, that I am aware of, they are not.

So far, the facts of palaeontology are consistent with almost any

form of the doctrine of progressive modification; they would not be

absolutely inconsistent with the wild speculations of De Maillet, or

with the less objectionable hypothesis of Lamarck. But Mr. Darwin's

views have one peculiar merit; and that is, that they are perfectly

consistent with an array of facts which are utterly inconsistent with

and fatal to, any other hypothesis of progressive modification which

has yet been advanced. It is one remarkable peculiarity of Mr. Darwin's

hypothesis that it involves no necessary progression or incessant

modification, and that it is perfectly consistent with the persistence

for any length of time of a given primitive stock, contemporaneously

with its modifications. To return to the case of the domestic breeds

of pigeons, for example; you have the Dove-cot pigeon, which closely

resembles the Rock pigeon, from which they all started, existing at the

same time with the others. And if species are developed in the same way

in nature, a primitive stock and its modifications may, occasionally,

all find the conditions fitted for their existence; and though they come

into competition, to a certain extent, with one another, the derivative

species may not necessarily extirpate the primitive one, or 'vice

versa'.

Now palaeontology shows us many facts which are perfectly harmonious

with these observed effects of the process by which Mr. Darwin supposes

species to have originated, but which appear to me to be totally

inconsistent with any other hypothesis which has been proposed. There

are some groups of animals and plants, in the fossil world, which have

been said to belong to "persistent types," because they have persisted,

with very little change indeed, through a very great range of time,

while everything about them has changed largely. There are families of

fishes whose type of construction has persisted all the way from the

carboniferous rock right up to the cretaceous; and others which have

lasted through almost the whole range of the secondary rocks, and from

the lias to the older tertiaries. It is something stupendous this--to

consider a genus lasting without essential modifications through all

this enormous lapse of time while almost everything else was changed and

modified.

Thus I have no doubt that Mr. Darwin's hypothesis will be found

competent to explain the majority of the phenomena exhibited by species

in nature; but in an earlier lecture I spoke cautiously with respect to

its power of explaining all the physiological peculiarities of species.

There is, in fact, one set of these peculiarities which the theory of

selective modification, as it stands at present, is not wholly competent

to explain, and that is the group of phenomena which I mentioned to you

under the name of Hybridism, and which I explained to consist in the

sterility of the offspring of certain species when crossed one with

another. It matters not one whit whether this sterility is universal,

or whether it exists only in a single case. Every hypothesis is bound

to explain, or, at any rate, not be inconsistent with, the whole of the

facts which it professes to account for; and if there is a single one of

these facts which can be shown to be inconsistent with (I do not merely

mean inexplicable by, but contrary to) the hypothesis, the hypothesis

falls to the ground,--it is worth nothing. One fact with which it is

positively inconsistent is worth as much, and as powerful in negativing

the hypothesis, as five hundred. If I am right in thus defining the

obligations of an hypothesis, Mr. Darwin, in order to place his

views beyond the reach of all possible assault, ought to be able to

demonstrate the possibility of developing from a particular stock by

selective breeding, two forms, which should either be unable to cross

one with another, or whose cross-bred offspring should be infertile with

one another.

For, you see, if you have not done that you have not strictly fulfilled

all the conditions of the problem; you have not shown that you can

produce, by the cause assumed, all the phenomena which you have in

nature. Here are the phenomena of Hybridism staring you in the face, and

you cannot say, 'I can, by selective modification, produce these same

results.' Now, it is admitted on all hands that, at present, so far as

experiments have gone, it has not been found possible to produce this

complete physiological divergence by selective breeding. I stated this

very clearly before, and I now refer to the point, because, if it could

be proved, not only that this HAS not been done, but that it CANNOT

be done; if it could be demonstrated that it is impossible to breed

selectively, from any stock, a form which shall not breed with another,

produced from the same stock; and if we were shown that this must be

the necessary and inevitable results of all experiments, I hold that Mr.

Darwin's hypothesis would be utterly shattered.

But has this been done? or what is really the state of the case? It is

simply that, so far as we have gone yet with our breeding, we have

not produced from a common stock two breeds which are not more or less

fertile with one another.

I do not know that there is a single fact which would justify any one

in saying that any degree of sterility has been observed between breeds

absolutely known to have been produced by selective breeding from a

common stock. On the other hand, I do not know that there is a single

fact which can justify any one in asserting that such sterility cannot

be produced by proper experimentation. For my own part, I see every

reason to believe that it may, and will be so produced. For, as Mr.

Darwin has very properly urged, when we consider the phenomena of

sterility, we find they are most capricious; we do not know what it is

that the sterility depends on. There are some animals which will not

breed in captivity; whether it arises from the simple fact of their

being shut up and deprived of their liberty, or not, we do not know, but

they certainly will not breed. What an astounding thing this is, to

find one of the most important of all functions annihilated by mere

imprisonment!

So, again, there are cases known of animals which have been thought

by naturalists to be undoubted species, which have yielded perfectly

fertile hybrids; while there are other species which present what

everybody believes to be varieties* which are more or less infertile

with one another. ([Footnote] *And as I conceive with very good reason;

but if any objector urges that we cannot prove that they have been

produced by artificial or natural selection, the objection must be

admitted--ultrasceptical as it is. But in science, scepticism is a

duty.) There are other cases which are truly extraordinary; there is

one, for example, which has been carefully examined,--of two kinds of

sea-weed, of which the male element of the one, which we may call A,

fertilizes the female element of the other, B; while the male element of

B will not fertilize the female element of A; so that, while the former

experiment seems to show us that they are 'varieties', the latter leads

to the conviction that they are 'species'.

When we see how capricious and uncertain this sterility is, how unknown

the conditions on which it depends, I say that we have no right to

affirm that those conditions will not be better understood by and

by, and we have no ground for supposing that we may not be able to

experiment so as to obtain that crucial result which I mentioned

just now. So that though Mr. Darwin's hypothesis does not completely

extricate us from this difficulty at present, we have not the least

right to say it will not do so.

There is a wide gulf between the thing you cannot explain and the thing

that upsets you altogether. There is hardly any hypothesis in this

world which has not some fact in connection with it which has not been

explained, but that is a very different affair to a fact that entirely

opposes your hypothesis; in this case all you can say is, that your

hypothesis is in the same position as a good many others.

Now, as to the third test, that there are no other causes competent to

explain the phenomena, I explained to you that one should be able to say

of an hypothesis, that no other known causes than those supposed by it

are competent to give rise to the phenomena. Here, I think, Mr. Darwin's

view is pretty strong. I really believe that the alternative is either

Darwinism or nothing, for I do not know of any rational conception or

theory of the organic universe which has any scientific position at all

beside Mr. Darwin's. I do not know of any proposition that has been

put before us with the intention of explaining the phenomena of organic

nature, which has in its favour a thousandth part of the evidence which

may be adduced in favour of Mr. Darwin's views. Whatever may be the

objections to his views, certainly all others are absolutely out of

court.

Take the Lamarckian hypothesis, for example. Lamarck was a great

naturalist, and to a certain extent went the right way to work; he

argued from what was undoubtedly a true cause of some of the phenomena

of organic nature. He said it is a matter of experience that an

animal may be modified more or less in consequence of its desires and

consequent actions. Thus, if a man exercise himself as a blacksmith,

his arms will become strong and muscular; such organic modification is a

result of this particular action and exercise. Lamarck thought that by a

very simple supposition based on this truth he could explain the

origin of the various animal species: he said, for example, that the

short-legged birds which live on fish had been converted into the

long-legged waders by desiring to get the fish without wetting their

bodies, and so stretching their legs more and more through successive

generations. If Lamarck could have shown experimentally, that even races

of animals could be produced in this way, there might have been some

ground for his speculations. But he could show nothing of the kind, and

his hypothesis has pretty well dropped into oblivion, as it deserved

to do. I said in an earlier lecture that there are hypotheses and

hypotheses, and when people tell you that Mr. Darwin's strongly-based

hypothesis is nothing but a mere modification of Lamarck's, you will

know what to think of their capacity for forming a judgment on this

subject.

But you must recollect that when I say I think it is either Mr. Darwin's

hypothesis or nothing; that either we must take his view, or look upon

the whole of organic nature as an enigma, the meaning of which is

wholly hidden from us; you must understand that I mean that I accept it

provisionally, in exactly the same way as I accept any other hypothesis.

Men of science do not pledge themselves to creeds; they are bound by

articles of no sort; there is not a single belief that it is not a

bounden duty with them to hold with a light hand and to part with it

cheerfully, the moment it is really proved to be contrary to any fact,

great or small. And if, in course of time I see good reasons for such

a proceeding, I shall have no hesitation in coming before you, and

pointing out any change in my opinion without finding the slightest

occasion to blush for so doing. So I say that we accept this view as

we accept any other, so long as it will help us, and we feel bound

to retain it only so long as it will serve our great purpose--the

improvement of Man's estate and the widening of his knowledge. The

moment this, or any other conception, ceases to be useful for these

purposes, away with it to the four winds; we care not what becomes of

it!

But to say truth, although it has been my business to attend closely

to the controversies roused by the publication of Mr. Darwin's book,

I think that not one of the enormous mass of objections and obstacles

which have been raised is of any very great value, except that

sterility case which I brought before you just now. All the rest are

misunderstandings of some sort, arising either from prejudice, or want

of knowledge, or still more from want of patience and care in reading

the work.

For you must recollect that it is not a book to be read with as much

ease as its pleasant style may lead you to imagine. You spin through it

as if it were a novel the first time you read it, and think you know

all about it; the second time you read it you think you know rather less

about it; and the third time, you are amazed to find how little you have

really apprehended its vast scope and objects. I can positively say that

I never take it up without finding in it some new view, or light,

or suggestion that I have not noticed before. That is the best

characteristic of a thorough and profound book; and I believe this

feature of the 'Origin of Species' explains why so many persons have

ventured to pass judgment and criticisms upon it which are by no means

worth the paper they are written on.

Before concluding these lectures there is one point to which I must

advert,--though, as Mr. Darwin has said nothing about man in his book,

it concerns myself rather than him;--for I have strongly maintained on

sundry occasions that if Mr. Darwin's views are sound, they apply

as much to man as to the lower mammals, seeing that it is perfectly

demonstrable that the structural differences which separate man from the

apes are not greater than those which separate some apes from others.

There cannot be the slightest doubt in the world that the argument which

applies to the improvement of the horse from an earlier stock, or of ape

from ape, applies to the improvement of man from some simpler and lower

stock than man. There is not a single faculty--functional or structural,

moral, intellectual, or instinctive,--there is no faculty whatever that

is not capable of improvement; there is no faculty whatsoever which does

not depend upon structure, and as structure tends to vary, it is capable

of being improved.

Well, I have taken a good deal of pains at various times to prove this,

and I have endeavoured to meet the objections of those who maintain,

that the structural differences between man and the lower animals are of

so vast a character and enormous extent, that even if Mr. Darwin's views

are correct, you cannot imagine this particular modification to take

place. It is, in fact, easy matter to prove that, so far as structure is

concerned, man differs to no greater extent from the animals which

are immediately below him than these do from other members of the same

order. Upon the other hand, there is no one who estimates more highly

than I do the dignity of human nature, and the width of the gulf in

intellectual and moral matters, which lies between man and the whole of

the lower creation.

But I find this very argument brought forward vehemently by some. "You

say that man has proceeded from a modification of some lower animal, and

you take pains to prove that the structural differences which are

said to exist in his brain do not exist at all, and you teach that all

functions, intellectual, moral, and others, are the expression or the

result, in the long run, of structures, and of the molecular forces

which they exert." It is quite true that I do so.

"Well, but," I am told at once, somewhat triumphantly, "you say in the

same breath that there is a great moral and intellectual chasm between

man and the lower animals. How is this possible when you declare that

moral and intellectual characteristics depend on structure, and yet tell

us that there is no such gulf between the structure of man and that of

the lower animals?"

I think that objection is based upon a misconception of the real

relations which exist between structure and function, between

mechanism and work. Function is the expression of molecular forces and

arrangements no doubt; but, does it follow from this, that variation

in function so depends upon variation in structure that the former is

always exactly proportioned to the latter? If there is no such relation,

if the variation in function which follows on a variation in structure,

may be enormously greater than the variation of the structure, then, you

see, the objection falls to the ground.

Take a couple of watches--made by the same maker, and as completely

alike as possible; set them upon the table, and the function of

each--which is its rate of going--will be performed in the same manner,

and you shall be able to distinguish no difference between them; but let

me take a pair of pincers, and if my hand is steady enough to do it,

let me just lightly crush together the bearings of the balance-wheel, or

force to a slightly different angle the teeth of the escapement of one

of them, and of course you know the immediate result will be that

the watch, so treated, from that moment will cease to go. But what

proportion is there between the structural alteration and the functional

result? Is it not perfectly obvious that the alteration is of the

minutest kind, yet that slight as it is, it has produced an infinite

difference in the performance of the functions of these two instruments?

Well, now, apply that to the present question. What is it that

constitutes and makes man what he is? What is it but his power

of language--that language giving him the means of recording

his experience--making every generation somewhat wiser than its

predecessor,--more in accordance with the established order of the

universe?

What is it but this power of speech, of recording experience, which

enables men to be men--looking before and after and, in some dim

sense, understanding the working of this wondrous universe--and which

distinguishes man from the whole of the brute world? I say that this

functional difference is vast, unfathomable, and truly infinite in

its consequences; and I say at the same time, that it may depend upon

structural differences which shall be absolutely inappreciable to us

with our present means of investigation. What is this very speech that

we are talking about? I am speaking to you at this moment, but if you

were to alter, in the minutest degree, the proportion of the nervous

forces now active in the two nerves which supply the muscles of my

glottis, I should become suddenly dumb. The voice is produced only so

long as the vocal chords are parallel; and these are parallel only so

long as certain muscles contract with exact equality; and that again

depends on the equality of action of those two nerves I spoke of. So

that a change of the minutest kind in the structure of one of these

nerves, or in the structure of the part in which it originates, or of

the supply of blood to that part, or of one of the muscles to which it

is distributed, might render all of us dumb. But a race of dumb men,

deprived of all communication with those who could speak, would be

little indeed removed from the brutes. And the moral and intellectual

difference between them and ourselves would be practically infinite,

though the naturalist should not be able to find a single shadow of even

specific structural difference.

But let me dismiss this question now, and, in conclusion, let me say

that you may go away with it as my mature conviction, that Mr. Darwin's

work is the greatest contribution which has been made to biological

science since the publication of the 'Regne Animal' of Cuvier, and since

that of the 'History of Development' of Von Baer. I believe that if you

strip it of its theoretical part it still remains one of the greatest

encyclopaedias of biological doctrine that any one man ever brought

forth; and I believe that, if you take it as the embodiment of

an hypothesis, it is destined to be the guide of biological and

psychological speculation for the next three or four generations.

End of A Critical Examination of "On The Origin of Species".