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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 havethough it
is not direct testimonyyet 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 deeperthey extend to the bony structure； and to the
characters of that most important of all organs to usthe 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 meansgiven 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
globethe 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
in