THE PHILOSOPHY OF BIOLOGY
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THE PHILOSOPHY
OF
BIOLOGY
BY
JAMES JOHNSTONE, D.Sc.
Cambridge :
at the University Press
1914
331
INTRODUCTION
It has been suggested that some reference, of an
apologetic nature, to the title of this book may be
desirable, so I \^dsh to point out that it can really be
justified. Science, says Driesch, is the attempt to
describe Givenness, and Philosophy is the attempt to
understand it. It is our task, as investigators of
nature, to describe what seems to us to happen there,
and the knowledge that we so attain — that is, our per-
ceptions, thinned out, so to speak, modified by our
mental organisation, related to each other, classified
and remembered — constitutes our Givenness. This is
only a description of what seems to us to be nature.
But few of us remain content with it, and the impulse
to go beyond our mere descriptions is at times an
irresistible one. Fettered by our habits of thought,
and by the limitations of sensation, we seem to look
out into the dark and to see only the shadows of things.
Then we attempt to turn round in order that we
might discover what it is that casts the shadows, and
what it is in ourselves that gives shape to them. We
seek for the Reality that we feel is behind the shadows.
That is Philosophy.
The Physics of a generation earlier than our own
thought that it had discovered Reality in its conception
of an Universe consisting of atoms and molecules in
ceaseless motion. What it described were only motions
and transformations, but it understood these motions
and transformations as matter and energy. Yet more
vi INTRODUCTION
subtle minds than the great physicists of the beginning
of the nineteenth century had already seen that
sensation might mislead us. There was something in
us that continually changed — ^that was our conscious-
ness, and it was all that we knew. If external things
did exist they existed only because we thought them.
But we ourselves exist, for we are not only a stream of
consciousness that continually changes, but there is in
us a personality, or identity, which has remained the
same throughout all the vicissitudes of our conscious-
ness. If the things that exist for us exist only because
we think them, and if we also exist, then we must exist
in the thought of an Absolute Mind that thinks us.
Physical Science, studying only motions and trans-
formations, understood that there was something that
moved and transformed — this was matter and energy.
Mental Science, studying only thought, understood
that nature was only the thought of an Universal
Mind. Either conclusion was equally valid Philosophy
(or metaphysics), and neither could be proved or dis-
proved by the methods of Science. The speculative
game is drawn, said Huxley, let us get to practical
work !
Both Physics and Biology did get to work, with the
results that we know. But Physics advanced far
beyond the acquirement of the results that stimulated
Biology to formulate our present hypotheses of evolu-
tion and heredity. As its knowledge accumulated, it
began to doubt whether matter and energy, atoms and
molecules, mass and inertia — all those things which
it thought at first were so real — were anything else
after all than ways in which our mental organisation
dealt with crude sensations. They might, as Bergson
said later on, be the moulds into which we pour our
perceptions. Physics set up a test of Reality, the law
INTRODUCTION vii
of the conservation of matter and energy. There are
existences which may or may not persist. Visions
and phantasms and dreams are existences while they
last. They are true for the mind in which they occur.
But they seem to arise out of nothing, and to dis-
appear into nothing, and physical Science cannot
investigate them. They are existences which are not
conserved. On the other hand those images which we
call moving matter and transforming energy can be
investigated by the methods of physics. Molecules
change, but something in them, the atoms, remain
constant. Energy becomes transformed, and it may
even seem to cease to exist, but if it disappears, then
something is changed so that the lost energy can be
traced in the nature of the change. Matter and
energy are conserved and therefore they are the only
Realities. But the test is obviously one that has an
a priori basis, and we may doubt whether it is a test
of Reality.
Thus Physics constructed a dynamical Universe,
that is, one which consisted of atoms which attracted
or repelled each other with forces which were functions
of the distances between them. Even now this con-
ception of a dynamical, Nev/tonian Universe is a use-
ful one, though we recognise that it is only symbolism.
But it was not a conception with which Physics could
long remain content. How could atoms separated
from each other by empty space act on each other,
that is, how could a thing act where it was not ?
There must be something between the atoms. The
Universe could not be a discontinuous one, and so
Physics invented an Universe that was full. It was
an immaterial, homogeneous, imponderable, con-
tinuous Universe. That which existed behind the
appearances of atoms and molecules and energy was
viii INTRODUCTION
the ether of space. It must be admitted that the
conception appears to the layman to involve only
contradictions : heterogeneous, discontinuous, ponder-
able atoms are only singularities in a homogeneous,
continuous, imponderable medium, or ether. Yet it is
easy to see that this contradiction arises in our mind
only because we had previously thought of the Universe
in terms of matter and energy, and in spite of ourselves
we attempt to think of the new Reality in terms of the
old one. In its attempt to understand all its later
results Physics had therefore to invent a new Philo-
sophy—that of the ether of space.
It is only in our own times that Biology has become
sceptical and has begun to doubt whether its earlier
Philosophy is a sound one. That which it describes—
the object-matter of its Science— is not that which
Physics describes. There are two domains of Given-
ness, the organic and the inorganic. Biology, leaning
on Physics, studied motions and transformations, just
as Physics did, though the motions which it studied
were more complex and the transformations more
mysterious. But borrowing the methods of investiga-
tion of Physics it borrowed also its Philosophy, and so it
placed behind its Givenness the Reality that Physics
at first postulated and then abandoned. The organism
was therefore a material system actuated by energy.
The notion, it should be noted, is not a deduction from
the results of Biology, but only from its methods.
Did Physiology, that is, the Physiology of the
Schools, ever really investigate the organism ? A
muscle-nerve preparation, an excised kidney through
which blood is perfused, an exposed salivary gland
which is stimulated, even a frog deprived of its cerebral
hemispheres— these things are not organisms. They
are not permanent centres of action, autonomous
INTRODUCTION ix
physico-chemical constellations capable of independent
existence, and capable of indefinite growth by dis-
sociation. They are parts of the organism, which,
having received the impulse of life, an impulse which
soon becomes exhausted, exhibit for a time some of the
phenomena of the organism. What Physiology did
attain in such investigations was an analytical descrip-
tion of some of the activities of the organism. It did
not describe life, but rather the physico-chemical
reactions in which life is manifested. The description,
it should be noted, is all-important for the human race
in its effort to acquire mastery over its environment ;
and there is no other way in which it may be carried
further but by the methods of physical Science. Given-
ness is one, though we arbitrarily divide it into the
domains of the organic and the inorganic, and there
can be only one way of describing it. That is the
mechanistic method.
Nevertheless ail this is only a description, and our
Philosophy must be the attempt to understand our
description. The mechanistic biologist, in the attempt
to identify his Philosophy with that of a former genera-
tion of physicists, says that he is describing a physico-
chemical aggregate — an assemblage of molecules of a
high degree of complexity — actuated by energy, and
undergoing transformations. But our scepticism as
to the validity of this conclusion is aroused by reflect-
ing on its origin. If it was borrowed from the Philo-
sophy of a past Physics, and if the more penetrating
analysis of the Physics of our own time has made a
new Philosophy desirable, should not Biology also
revise its understanding of its descriptions ? For
Biology has not stood still any more than Physics,
and the Physiology of our own day has become different
from that of the times when the mechanistic Philosophy
X INTRODUCTION
of life took origin. The embryologists and the natura-
lists of our own generation have studied the whole
organism in its normal functioning and behaviour, and
have obtained results which cannot easily be under-
stood as physico-chemical mechanism. Life is not the
activities of the organism, but the integration of the
activities of the organism, just as Reality for Physics
is not the atoms and molecules of gross matter, but
the integration of these in the ether of space.
This, then, is all that we mean by the philosophy of
Biology — the attempt to understand the descriptions
of the Science in the light of its later investigations.
Philosophy, in the academic sense, we have not con-
sidered in relation to the subject-matter of our science,
though there is much in the classic systems that is
of absorbing interest, even to the working investigator
of the nineteenth century. The biological education is
not, however, such as to predispose one towards these
studies. The reader will recognise that the point of
view, and the methods of treatment, adopted in this
book are those suggested by Driesch and Bergson,
even if no references are given. He may, perhaps,
appreciate this limitation ; for, influenced by the
modern scientific training, he may be inclined to
regard Philosophy as Mark Twain regarded his Egyptian
mummy : if he is to have a corpse it might as well be
a real fresh one.
J. J-
Liverpool
November 191 3
CONTENTS
CHAPTER I
PAGE
THE CONCEPTUAL WORLD ...... 1
Argument. — The conscious organism is one that acts. Its
consciousness of an external world is not simply the result of
the stimuU made by that world on its organs of sense, for it becomes
fully aware only of those stimuh which result in deliberated bodily
activity. This awareness of an outer world on which it acts is the
perception of the organism. Its consciousness is an intensive
multiplicity. This multiplicity is arbitrarily dissociated, for con-
venience' sake, by the mental organisation, which confers extension
and magnitude and succession on those aspects of consciousness
which it arbitrarily dissociates from each other. Our notion of
space is an intuitive one and depends on our modes of bodily
exertion. Our notions of motion and continuity are also intuitive
ones, and they cannot be represented intellectually, but we can
approximate to them by the methods of the infinitesimal calculus.
Mathematical time is only a series of standard events which punc-
tuate our duration. Duration is the accumulated existence and
experience of the organism. We cannot prove intellectually that
there is a world external to our consciousness, but that this world
exists is a conviction intuitively held.
CHAPTER n
THE ORGANISM AS A MECHANISM ..... 49
Argument. — If the organism is a physico-chemical mechanism its
activities must conform to the two principles of energetics : the law
of conservation of energy and matter, and the law of entropy-
increase. They conform strictly to the law of conservation.
The law of the degradation of energy is true of our experience
of inorganic nature, but we can show that it cannot be universally
true. Inorganic processes are irreversible ones, and they proceed
xii CONTENTS
PAGE
in one direction only, and in them energy is degrade*. Organic
processes, that is, the processes carried on in the generaUsed
organism, are irreversible ; or, at least, there is a tendency for
them to be carried on v.'ithout necessary dissipation of energy.
CHAPTER III
THE ACTIVITIES OF THE ORGANISM ..... 83
Argument. — If the organism is investigated by the methods of
physical and chemical science, nothing but physico-chemical
activities can be discovered. This is necessarily the case, since
methods which yield physico-chemical results only are employed.
The physiologist makes an analysis of the activities of the organism,
and he reduces these activities to certain categories ; although all
attempts completely to describe the functioning of the organism
solely in terms of physical and chemical reactions fail. In addition
to the reactions which make up the functioning of an organ or
organ-system, there is direction and co-ordination of these reactions.
The individual physico-chem-ical reactions which occur in the
functioning of the organism are integrated, and life is not merely
these reactions, but also their integration.
CHAPTER IV
THE VITAL IMPETUS ....... 120
Argument. — The notion of the organism as a physico-chemical
mechanism is a deduction from the methods of physiology, and
not from its results. The notion of vitalism is a natural or
intuitive one. The historic systems of vitalism assumed the
existence of a spiritual agency in the organism, or of a form of
energy which was peculiar to the activities of the organism.
Modern investigation lends no support to either belief. But the
study of the organism as a whole, that is, the study of developmental
processes, or that of the organism acting as a whole, afford a
logical disproof of pure mechanism. It show^s that there cannot
be a functionality, in the mathematical sense, between the inorganic
agencies that affect the whole organism and the behaviour or
functioning of the whole organism. Mechanism is only suggested
in the study of isolated parts of the organism. We are compelled
toward the belief that there is an agency operative in the activities
of the organism which does not operate in purely inorganic becom-
ing. This is the Vital Impetus of Bergson, or the Entelechy of
Driesch.
CONTENTS xiii
CHAPTER V
PAG8
THE INDIVIDUAL AND THE SPECIES 162
Argument. — The concept of the organic individual is one which
is arbitrary, and is convenient only for purposes of description.
Life on the earth is integrally one. Personality is the intuition of
the conscious organism that it is a centre of action, and that all the
rest of the universe is relative to it. The individual organism,
regarded objectively, is an isolated, autonomous constellation,
capable of indefinite growth bj' dissociation, differentiation, and
re- integration. This growth is reproduction. The dissociated
part reproduces the form and manner of functioning of the indi-
vidual organism from which it has proceeded. The offspring varies
from the parent organism, but it resembles it much more than it
varies from it. There are therefore categories of organisms in
nature the individuals of which resemble each other more than they
resemble the individuals belonging to other categories : these are
the elementary species. Hypotheses of heredity are corpuscular
ones, and are based on the physical analogy of molecules and
atoms. The concept of the species is a logical one. The organism
is a phase in an evolutionary or a developmental fiux, and the idea
of the species is attained by arresting this flux.
CHAPTER VI
TRANSFORMISM ........ 208
Argument. — A reasoned classification of organisms suggests that
a process of evolution has taken place. It suggests logical relation-
ships between organisms, while the results of embryology and
paleontology suggest chronological relationships. Yet this kin-
ship of organisms might only be a logical, and not a material
one. Evolution may have occurred somewhere, but it might be
argued that the ideas of species have generated each other in a
Creative Thought. But transformism may be produced experi-
mentally, and so science has adopted a mechanistic hypothesis of
the nature of the process. Transformism of species depends on
the occurrence of variations, but these arise spontaneously and
independently of each other, and they must be co-ordinated.
This co-ordination of variations cannot be the work of the environ-
ment. Variations are cumulative, and they exhibit direction, and
this direction is either an accidental one, or it is the expression of
an impetus or directing agency in the varying organism itself.
The problem of the cause of variation is only a pseudo-problem.
xiv CONTENTS
CHAPTER VII
PAGE
THE MEANING OF EVOLUTION 245
Aygument. — If we assume the existence of an evolutionary
process, the results of morphology, embryology, and palaeontology
ought to enable us to trace the directions followed during this
process. But these results are still so uncertain that they indicate
only a few main lines of transformism. Phylogenetic trees are
largely conjectural in matters of detail. Evolution has resulted in
the establishment of several dominant groups of organisms — the
metatrophic bacteria, the chlorophyllian organisms, the arthro-
pods, and the vertebrates. Each of these groups displays certain
characters of morphology, energy-transformation, and behaviour ;
and a certain combination of characters is concentrated in each of
the groups. But there is a community of character in all organisms
wliich have arisen during the evolutionary process. The trans-
formation of kinetic into potential energy is characteristic of the
chlorophyllian organisms. The utilisation of potential energy,
and its conversion into the kinetic energy of regulated bodily
activity, by means of a sensori-motor system, is characteristic of
the animal. The bacteria carry to the limit the energy-transforma-
tions begun in the tissues of the plants and animals. Immobility
and unconsciousness characterise the plant, mobility and con-
sciousness the animal. Animals indicate two types of actions —
intelligent actions and instinctive actions. Instinctive activity
involves the habitual exercise of modes of action that have been
inherited. Intelligent activities involve the exercise of modes of
action that are not inherited, but which are acquired by the
animal during its own lifetime, and are the results of perceptions
which show the animal that its activity is relative to an outer
environment.
CHAPTER VIII
THE ORGANIC AND THE INORGANIC ..... 289
Argument. — A strictly mechanistic hypothesis of evolution
compels us to regard the organic world, and the inorganic environ-
ment with which it interacts, as a physico-chemical system. All
the stages of an evolutionary process must therefore be equally
complex : they are simply phases, or rearrangements, of the
elements of a transforming system. The physics on which these
mechanistic hypotheses were based was that of a discontinuous,
granular, Newtonian universe, that is, one consisting of discrete
particles, cr mass-points, attracting or repelling each other with
CONTENTS XV
PAGE
forces which are functions of the distances betrween them. It was
a spatially extended system of parts. Therefore at all stages in
an evolutionary process, or one of individual development, the
elements of the system constitute an extensive manifoldness, and
the obligation of mechanistic hypotheses of evolution and develop-
ment to accept this view has shaped modern theories of heredity.
Life is an intensive manifoldness, but in individual or racial evolu-
tion this intensive manifoldness becomes an extensive manifold-
ness. Life is a bundle of tendencies which can co-exist, but which
cannot all be fully manifested, in the same material constellation,
therefore these tendencies become dissociated in the evolutionary
process. In this dissociation there is direction and co-ordination,
which are the Vital Impetus of Bergson, or the Entelechy of
Driesch.
Entelechy is an elemental agency in nature which we are
compelled to postulate because of the failure of mechanism. It is
not spirit, nor a form of energy, but the direction and co-ordination
of energies. There is a sign, or direction of inorganic happening
which absolutely characterises the processes which are capable of
analysis by physico-chemical methods of investigation, and the
result of this direction of inorganic happening is material inertia.
Yet this direction cannot be universal : it must be evaded some-
where in the universe. It is evaded by the organism.
The problem of the nature of life is only a pseudo-problem.
APPENDIX
MATHEMATICAL AND PHYSICAL NOTIONS .... 342
Infinity and the notion of the limit. Functionality. Frequency
distributions and probability. Matter, force, mass, and inertia.
Energy-transformations. Isothermal and adiabetic transforma-
tions. The Carnot engine and cycle. Entropy. Inert matter.
Index 377
THE PHILOSOPHY OF BIOLOGY
CHAPTER I
THE CONCEPTUAL WORLD
Let us suppose that we are walking along a street in
a busy town ; that we are familiar with it, and all
the things that are usually to be seen in it, so that
our attention is not likely to be arrested by anything
unusual ; and let us further suppose that we are
thinking about something interesting but not intel-
lectually difficult. In these circumstances all the
sights of the town, and all the turmoil of the traffic
fail to impress us, though we are, in a vague sort of
way, conscious of it all. Electric trams approach and
recede with a grinding noise ; a taxicab passes and
we hear the throb of the engine and the hooting of the
horn, and smell the burnt oil ; a hansom comes down
the street and we hear the rhythmic tread of the horse's
feet and the jingle of the bells ; we pass a florist's
shop and become aware of the colour of the flowers
and of their odour ; in a cafe a band is playing " rag-
time." There are policemen, hawkers, idlers, ladies
with gaily coloured dresses and hats, newsboys, a crowd
of people of many characteristics. It is all a flux of
experience of which we are generally conscious without
analysis or attention, and it is a flux which is never
for a moment quite the same, for everything in it
melts and flows into everything else. The noise of
the tram-cars is incessant, but now and then it becomes
2 THE PHILOSOPHY OF BIOLOGY
louder ; the music of the orchestra steals imperceptibly
on our ears and as imperceptibly fades away ; the
smell of the flowers lingers after we pass the shop,
and we do not notice just when we cease to be conscious
of it ; the rhythm of the ragtime continues to irritate
after we have ceased to hear the band — all the sense-
impressions that we receive melt and flow over into
each other and constitute our stream of consciousness,
and this changes from moment to moment without
gap or discontinuity. It is not a condition of " pure
sensation," but it is as nearly such as we can experience
in our adult intellectual life.
It is easy to discover that many things must have
occurred in the street which did not affect our full
consciousness. We may learn afterwards that we
have passed several friends without recognising them ;
we may read in the newspapers about things that
happened that we might have seen, but which we did
not see ; we may think we know the street fairly well,
but we find that we have difficulty in recalling the
names of three contiguous shops in it ; if we happen
to see a photograph which was taken at the time we
passed through the street we are usually surprised to
find that there were many things there that we did
not see. Why is it, then, that so much that might have
been perceived by us was not really perceived ? We
cannot doubt that everything that came into the
visual fields of our eyes must have affected the termin-
ations of the optic nerves in the retinas; the complex
disturbances of the air in the street must have set our
tympanic membranes in motion ; and all the odori-
ferous particles inhaled into our nostrils must have
stimulated the olfactory mucous membranes. In all
these cases the stimulation of the receptor organs
must have initiated nervous impulses, and these must
THE CONCEPTUAL WORLD 3
have been propagated along the sensory nerves, and
must have reached the brain, affecting masses of
nerve cells there. Nothing in physiology seems to
indicate that we can inhibit or repress the activity
of the distance sense-receptors, visual, auditory, and
olfactory, with their central connections in the brain ;
they must have functioned, and must have been
physically affected by the events that took place out-
side ourselves, and yet we were unconscious, in the
fullest sense of this term, of all this activity. Why
is it, then, that our perception was so much less than
the actual physical reception of external stimuli that we
must postulate as having occurred ? Sherlock Holmes
would have said that we really saw and heard all these
things although we did not observe them, but the full
explanation involves a much more careful consideration
of the phenomena of perception than this saying
indicates.
There is, of course, no doubt that we did see and
hear and smell all the things that occurred in the street
during our aimless peregrination, that is, all the things
which so happened that they were capable of affecting
our organs of sense. This is true if we mean by seeing
and hearing and smelling merely the stimulation of
the nerve-endings of the visual, auditory, and olfactory
organs, and the conduction into the brain of the
nervous impulses so set up. But merely to be stimu-
lated is only a part of the full activity of the brain ; the
stimulus transmitted from the receptor organs must
result in some kind of bodily activity if it is to affect
our stream of consciousness. Two main kinds of
activity are induced by the stimulation of a receptor
organ and a central ganglion, (i) those which we call
reflex actions, and (2) those actions which we re-
cognise as resulting from deliberation. We must now
4 THE PHILOSOPHY OF BIOLOGY
consider what are the processes that are involved in
these kinds of neuro-muscular activity.
The term " reflex action " is one that denotes rather
a scheme of sensori-motor activity than anything that
actually happens in the animal body ; it is a concept
that is useful as a means of analysis of complex pheno-
mena. In a reflex three things happen, (i) the
stimulation of a receptor organ and of the nerve
connecting this with the brain, (2) the reflection, or
shunting, of the nervous impulse so initiated from the
terminus ad quern of the afferent or sensory nerve, to
the terminus a quo of the efferent or motor nerve,
and (3) the stimulation of some effector organ, say
a motor organ or muscle, by the nervous impulse so
set up. The simplest case, perhaps, of a reflex is the
rapid closure of the eyelids when something, say a few
drops of water, is flicked into the face. Stated in the
way we have stated it the simple reflex does not exist.
In the first place, it is a concept based on the structural
analysis of the complex animal where the body is
differentiated to form tissues — receptor organs, nerves,
muscles, glands, and so on. But a protozoan animal,
a Paramcecium for instance, responds to an external
stimulus by some kind of bodily activity, and yet it is
a homogeneous, or nearly homogeneous, piece of pro-
toplasm, and this simple protoplasm acts at the same
time as receptor organ, conducting tissue or nerve,
and effector organ. In the higher animal certain parts
of the integument are differentiated so as to form
visual organs, and the threshold of these for light
stimuli is raised while it is lowered for other kinds of
physical stimuli. Similarly other parts of the in-
tegument are modified for the reception of auditory
stimuli, becoming more susceptible for these but less
susceptible for other kinds of stimuli than the adjacent
THE CONCEPTUAL WORLD 5
parts of the body. Within the body itself certain
tracts of protoplasm are differentiated so that they
can conduct molecular disturbances set up in the
receptor organs in the integument better than can the
general protoplasm ; these are the nerves. Other
parts are modified so that they can contract or secrete
the more easily ; these are the muscles and glands.
The conception of a reflex action, as it is usually stated
in books on physiology, therefore includes this idea
of the differentiation of the tissues, but all the pro-
cesses that are included in the typical reflex are pro-
cesses which can be carried on by undifferentiated
protoplasm.
It is also a schematic description that assumes a
simplicity that does not really exist. As a rule a
reflex is initiated by the stimulation of more than one
receptor organ, and the impulses initiated may thus
reach the central nervous system by more than one
path. There is no simple shunting of the afferent
impulse from the cell in which it terminates into
another nerve, when it becomes an efferent impulse ;
but, instead of this, the impulse ma}^ " zigzag " through
a maze of paths in the brain or spinal cord connecting
together afferent and efferent nerves and ganglia.
Further, the final part of the reflex, the muscular
contraction, is far from being a simple thing, for
usually a series of muscles are stimulated to contract,
each of them at the right time and with the right
amount of force, and every contraction of a muscle
is accompanied by the relaxation of the antagonistic
muscle. There are muscles which open the eyelids and
others which close them, and the cerebral impulse
which causes the levators to contract at the same time
causes the depressors to relax.
It is quite necessary to remember that the simple
6 THE PHILOSOPHY OF BIOLOGY
reflex is really a process of much complexity and may
involve many other parts and structures than those
to which we immediately direct our attention. But
leaving aside these qualifications we may usefully
consider the general characters of the reflex, regarding
it as a common, automatically performed, restricted
bodily action, involving receptor organ, central nervous
organ, and effector organ. There are certain kinds of
external stimuli that continually affect our organs of
sense, and there are certain kinds of muscular and
glandular activity that occur " as a matter of course,"
when these stimuli fall on our organs of sense. The
emanation from onions or the vapour of ammonia
causes our eyes to water; the smell of savoury food
causes a flow of saliva ; and anything that approaches
the face very rapidly causes us to close the eyes.
Reflexes are, in a way, commonly occurring, purposeful
and useful actions, and their object is the maintenance
of a normal condition of bodily functioning.
We dare hardly say that the simple reflex is an un-
consciously performed action, although we are not
conscious, in the fullest sense of the term, of the
reflexes that habituahy take place in ourselves. But
even in the decapitated frog, which moves its limbs
when a drop of acid is placed on its back, something,
it has been said, akin to consciousness may flash out
and light up the automatic activity of the spinal cord.
We must not think of consciousness as that state of
acute mentality which we experience in the perform-
ance of some difficult task, or in some keenly apprec-
iated pleasure, or in some condition of mental -or bodily
distress ; it is also that dimly felt condition of normality
that accompanies the satisfactory functioning of the
parts of the bodily organism. But this dim and
obscure feeling of the awareness of our actions is easily
THE CONCEPTUAL WORLD 7
inhibited whenever what we call intellectual activity
proceeds.
Much of the stimulation of our receptor organs is of
this generally occurring nature, and we are not aware
of it although the stimuli received are such as to induce
useful and purposeful bodily activity. In walking
along the street we automatically avoid the people,
and the other obstacles that we encounter, by means
of regulated movements of the body and limbs, but
this is activity that has become so habitual and easy
that we are hardly aware of it, and not at all, perhaps,
of the physical stimuli which induce it. But not only
do we receive stimuli which are reflected into bodily
actions without our being keenly aware of this reception,
but we also receive stimuli which do not become re-
flected into bodily activity. It is, Bergson suggests,
as if we were to look out into the street through a
sheet of glass held perpendicularly to our line of sight ;
held in this way we see perfectly all that happens in
front of us, but when we incline the glass at a certain
angle it becomes a perfect reflector and throws back
again the rays of light that it receives. This is, of
course, a physical analogy, and no comparison of
material things with psychical processes can go very
far, but in a way it is more than an analogy. In our
indolent absorbed state of mind we do not as a rule
see the objects which we are not compelled to avoid,
and which do not, in any way, influence our immediate
condition of bodily activity. The optical images of
all these things are thrown upon our retinas and are,
in some way, thrown or projected upon the central
ganglia, but there the series of events comes to an end,
for the images are not reflected out towards the
periphery of the body as muscular actions. We
cannot doubt that this is why we do not perceive all
8 THE PHILOSOPHY OF BIOLOGY
the stimulation of our organs of sense that we are
sure that take place. These stimuli pass through us,
as it were, unless they are reflected out again as
actions. In this reflection, or translation of neutral
into muscular activity, perceptions arise.
But even then perception need not arise. It does
not, as a rule, accompany the automatically per-
formed reflex action, because the latter is the result of
intra-cerebral activities that have become so habitual
that they proceed withotd friction. There are innumer-
able paths in the brain along which impulses from the
receptor organs may pass into the motor ganglia, but
in the habitually performed reflex actions these paths
have been worn smooth, so to speak. The images
of objects which are perceived over and over again by
the receptor organs glide easily through the brain and
as easily translate themselves into muscular, or some
other kind of activity. The things that matter in the
life of an animal which lives " according to nature "
are cyclically recurrent events in which, after a time,
there is nothing new. Most of them proceed just as
well in the animal deprived of its cerebral hemispheres
by operation as in the intact cerebrate animal. In
the performance of actions of this kind the organism
becomes very much of an automaton.
Let something unusual happen in the street while
w^e are walking through it — a runaway horse, or the
fall of an overhead " live " wire, for instance, something
that has seldom or never formed part of our experience,
and something that may have an immediate effect on
us as living organisms. Then perception arises at
once because the stimulation of our organs of sense
presents us with something which is unfamiliar, and yet
not so unfamiliar that it does not recall from memorv,
or from derived experience, reminiscences of the
THE CONCEPTUAL WORLD 9
images of somewhat similar things, and of the effects
of these. The train of events that now proceeds in our
central nervous system becomes radically different
from that which proceeded in our former, rather aim-
less, series of actions. The stimuli no longer pass easily
through the " lower " ganglia of the brain, but flash
upwards into the cortical regions, where they become
confronted with the possibility of innumerable alterna-
tive paths and connections \\dth all the parts of the
body. They waver, so to speak, before adopting one or
other, or a combination of these paths ; there is hesita-
tion, deliberation, and finally choice of a path, with the
result that a series of muscular organs become inervated
and motor actions, of a type more or less competent
to the situation in which we find ourselves, are set up.
In this hesitation and deliberation perception arises.
It is when the animal may act in a certain way as the
result of a stimulus which is not a continually recurrent
one, but at the same time may refrain from acting,
or may act in one of several different ways, that
perception of external things and their relations arises.
That is to say, we perceive and think because we
act. We do not look out on the environment in which
we are placed in a speculative kind of way, merely
receiving the images of things, and classifying and
rem.embering them, while all the time we are passive
in so far as our bodily activities are concerned. If
the results of modern physiology teach us anything
in an unequivocal way they teach us this — that the
organs of activity, muscles, glands, and so on, and the
organs of sense and communication, are integrally
one series of parts, and that apart from motor activity
nervous activity is an aimless kind of thing. It is
because we act that we think and disentangle the images
of things presented to us by our organs of sense, and
10 THE PHILOSOPHY OF BIOLOGY
subject ail that is in tlie stream of consciousness to
conceptual analysis.^
That is to say, in thinking about the flux of con-
sciousness we decompose it into what we regard as its
constituent parts, and we confer upon these parts
separate existence in space and time. But it is clear
that none of the things which we thus regard as the
elements of our consciousness has anv real existence
apart from the others. The smell of the flowers and
that of the burnt oil interpenetrate in our consciousness
of the stimulation of our olfactory organs just as do
the jingle of the cab bells, the music of the orchestra,
and the throb of the motor car in the impressions
transmitted by our auditory organs. It is difflcult
to see that all these things, with the multitude of other
things which we perceive, constitute a " multiplicity
in unity," that is an assemblage of things which are
separate things, but which do not lie alongside each
other in space and mutually exclude each other, but
which are all jammed into each other, so to speak.
It is easy to see that we are conscious of a heterogeneity,
and whenever we think of this multitude of things
it seems natural that we should separate them from
each other. The stream of our consciousness is so
complex that we cannot attend to it all at once, not
even to the few things that we have picked out in
our example. If we concentrate our attention on
any part, or rather aspect of it, all the rest ceases to
exist, or rather we agree to ignore it, and this very
concentration of thought upon one part of our experi-
ence isolates it from all the rest. To a certain extent
the analysis of the complex of sensation is the result
of the work of different receptor organs ; certain
1 All this is, of course, the argument of Bergson's earlier books, Mati^re et
Menioire and Donnees immediates de la Conscience.
THE CONCEPTUAL WORLD
11
fields of energy, which we call light, radiation, etc.,
affect the nerve-endings in the retina ; chemically
active particles in the atmosphere affect the nerve-
endings in the olfactory membranes ; and rapidly
repeated changes of pressure in the atmosphere
(sound vibrations) affect the auditory organs in the
internal ear, and so on. But this reception of different
stimuli by different receptor organs exists only in the
higher animal ; there are no specialised sense organs
in a Paramoecium, for instance, and the whole periphery
of the animal must receive
all these different kinds of
external stimuli at once.
The specialisation of its
receptor organs in the
y
Fig. I.
the consciousness of the
higher animal is rather
the means whereby the
organism becomes more ji
receptive of its environ-
ment, than the means
whereby it analyses that
environment. This ana-
lysis is the work of
animal.
Suppose that we draw a curve AB freehand with a
single undivided sweep of the pencil. By making a
certain assumption — that the curve which we drew
was one that might be regarded as cyclical, that is,
might be repeated over and over again — we can subject
it to harmonic analysis. We can decompose it into a
number of other curves (CD, EF, etc.), each of which
is a separate " wave " rising above and falling below
the axis OX in a symmetrical manner. If we draw
any vertical line MN cutting these curves, we shall
find that the distance between the axis OX and the
12 THE PHILOSOPHY OF BIOLOGY
main curve AB is always equal to the algebraic sum
of the distances between the axis and the other curves.
These latter we call the harmonic constituents of the
curve AB, supposing them to " add up " so as to form
it. But AB was something quite simple and elemental
and its constituents cannot be said to have existed
in it when we drew it freehand ; it was only by an
artifice of practical utility in mathematical computa-
tions that we constructed them. It may be, of course,
that the harmonic constituents of a curve had actual
existence apart from the curve itself, but, in the case
that we take, they certainly had not. Now we must
think of our stream of consciousness in much the same
way. It is something immediately experienced and
elementary ; it is the concomitant, if we choose so to
regard it, of the external processes that go on outside
our bodies. We can investigate it by thinking about
it, and attending to one aspect of it after another,
thus arbitrarily detaching one " part " of it from all
the rest, but immediately we do this we rise above
the flux of experience into the region of intellectual
concepts. We have converted a multiplicity of states
of consciousness, all of which co-exist along with each
other, and in each other, and which have no spatial
existence, into a multiplicity of states, visual, auditory,
olfactory, etc., which have become separated from
each other and have therefore acquired extension.
This dissociation of the flux of experience is the process
of conceptual analysis carried out by thought.
If we dissociate the stream of consciousness in this
way, breaking it up into states which we choose to
regard as separate from each other, we shall see that
of the elements which we thus isolate many are like
each other and can be associated. Obviously there
is a greater resemblance between different smells
THE CONCEPTUAL WORLD 18
than between smells and sounds. Different musical
sounds are more like each other than are sounds, and
feelings of heat and cold. There is a greater likeness
between the states of consciousness which arise from
the stimulation of the same receptor organ, than
between those that arise from the stimulation of
different receptors. Those differences of sensation
accompanying the stimulation of different sense organs
we regard as different in kind ; there is absolutely
no resemblance between a colour and a sound, we
say, however much the modern annotator of concert
programmes may suggest the analogy. But we say
that there may be different degrees of stimulation of
the same sense organ, and that the sensations that we
thus receive are of the same kind though they differ
in intensity. The whistle of a railway engine becomes
louder as the train approaches, that is to say, more
intense, and if we study the physical conditions that
are concomitant with the stimulation of our tympanic
membranes we shall see that waves of alternate rare-
faction and compression are set up in the atmosphere
outside our ears. All the time that the train approaches
the frequency of these weaves remains the same, that
is, just as many occur in a second when the train is
distant as when it is near. But the amplitude of the
waves has been increasing, and the velocity with
which the molecules of air strike against the tympanic
membranes becomes greater the nearer is the source
of sound. We can represent this by means of a
diagram which shows that the amplitude of the waves — ■
\\hich represents the loudness of the sound — increases
while the frequency — which represents the pitch —
remains the same. The amplitude is represented by
the straight vertical lines, ii, 22, 33, etc., which are
of increasing magnitude. Thus we represent the
14
THE PHILOSOPHY OF BIOLOGY
physical cause of the increasing loudness of the sound
by space-magnitudes, and then we transfer these
magnitudes to the states of consciousness concomitant
with the vibrating molecules of air. Suppose that we
knew nothing at all about the cause of the differences
of pitch of musical sounds and that we Hsten to the
notes of the octave, C, D, E, C, sounded by an
organ ; all that we should experience would be that
the sounds were different. If we were to sing the
notes we might
attain the intui-
tion that the
notes G, A, B were
"higher" than
the notes C, D, E,
because a greater
effort was re-
quired in order
to produce these
sounds, but ob-
FlG. 2.
\ viously this is
a different thing
from saying that
the notes themselves were " higher " or " lower."
But let us match the notes by striking tuning-forks,
and then having selected forks which give the notes
of the octave let us fix them so that they will
make a tracing, while still vibrating, on a revolving
strip of paper. We shall then find that the fork
emitting the note C makes (say) 256 vibrations per
second, the fork D I 256 vibrations, the fork E
T 256 vibrations, and so on. Thus we associate the
notes of the octave together and we say that their
quality was the same but that their pitch differed,
and since the pitch depends on the frequency of
THE CONCEPTUAL WORLD 15
vibration of the fork, or of the air in its vicinity, we
say that pitch differences are quantitative ones, and
that the states of consciousness which accompany these
physical events are also quantitatively different.
So also with colour. If we had no such apparatus
as prisms or diffraction gratings, which enable us to
find what is the wave length of light, should we have
any idea of the spectral hues, red, yellow, orange, green,
etc., as differing from each other quantitatively? It
is certain that we should not. But observation and
experiment have shown that the nerve-endings of the
optic nerve in the retina are stimulated by vibrations
of something which we agree to call the ether of space,
and that the frequency of vibration of light which we
call red is less than that which we call orange, while
the frequency of vibration of orange light is less again
than that of blue light, and so on. To our conscious-
ness red, orange, yellow, and blue light are absolutely
different, but we disregard this intuition and we say
that our perceptions of light are similar in kind but
differ, in some of them are more intense than are
some others. Again, have we any intuitive knowledge
of increasing temperature ? If we dip our hands into
ice-cold water the sensation is one of pain, if the water
has a temperature of 5° C. it feels cold, if it is at 15° C.
we have no particular appreciation of temperature, if
at 25° C. it feels very warm, if it is at 60° it is very hot,
and if it is at 90° we are probably scalded and the
feeling is again one of pain. If we place a thermometer
in the water we notice that each sensation in turn is
associated with a progressive lengthening of the
mercury thread, and if we investigate the physical
condition of the water we find that at each stage the
velocity of movement of the molecules was greater
than that at the preceding stage. We say, then, that
16 THE PHILOSOPHY OF BIOLOGY
our different perceptions were those of heat of different
degrees of intensity, so transferring to the perceptions
themselves the notions of space-magnitudes acquired
by a study of the expansion of the mercury in the
thermometer, or by the adoption of the physical
theory of the kinetic structure of the water. Yet it is
quite certain that what we experienced were quite
different things or conditions, cold, warmth, heat,
and pain, and indeed, in this series of perceptions
different receptor organs are involved.
Suppose we listen to the note emitted by a syren
which is sounding with slowly increasing loudness but
with a pitch which remains constant. We do not
notice at first that the sound is becoming louder, but
after a little time we do notice a difference. Let us
call the amplitude of vibration of the air when the syren
first sounds E, and then, when we notice a difference,
let us call the amplitude ^E + E, AE being the in-
crement of amplitude. Let us call our sensation when
the syren first sounds S, and our sensations when
the sound has become louder S + AS, AS being the
" increment of sensation." Then the relation holds : —
aE
P^ = constant.
That is to say, the louder is the sound the greater must
be the increase of loudness before we notice a difference.
Let us assume now that the successive sensations of
loudness that we receive as the syren blows louder and
louder are, each of them, just the same amount louder
than the preceding sound ; that is to say, let us assume
that what we experience are " minimal perceptible
differences " of sensation — that they are " elements
of loudness " — thus we construct a series of sounds
each of which differs from that preceding it by an
elemental increment of loudness. Now things that
THE CONCEPTUAL WORLD
17
cannot be further decomposed are necessarily equal
to each other ; if, for instance, the atoms represent
the ultimate units into which we break up the matter
called oxygen, then these atoms are all equal to each
other. Therefore the increments of loudness are
equal to each other.
If we plot these equal increments of loudness as
the dependent variable S in a graph, and the amplitude
of the vibrations of the atmosphere as the independent
variable E, we can obtain the following curve If we
investigate this we
shall find that a cer-
tain relation exists be-
tween the " values "
of the sensation and
the values of the stim-
uli that correspond to
them ; a regular in-
crease in the loudness
of the sensation cor-
responds to a regular
increase in the log-
arithms of the strength of the stimuli. Let S = the
sensation, E the stimulus, and C and Q constants ;
then
E
S = Clog g ;
so that we seem to establish a mathematical relation
between the intensity of our sensations and the
intensity of the stimuli that give rise to those sensations,
but this relation depends on the assumption that what
we call " minimal perceptible differences " of sensation
are numerical differences that are equal to each other,
and this is, of course, an assumption that cannot
possibly be proved.
Fig. 3.
18 THE PHILOSOPHY OF BIOLOGY
Thus we decompose our stream of consciousness
into a series of quantitatively different and qualitatively
different things, upon each of which we confer in-
dependent existence. We attribute to these different
aspects of our consciousness extension, but the ex-
tension is due only to our analysis ; for the qualities
of pitch, loudness, colour, odour, etc., which we dis-
entangle from each other, did not exist apart from each
other, any more than do the sine and cosine curves
into which we decompose an arbitrarily drawn curved
line. The multiplicity of our consciousness is intensive,
like the multiplicity that we see to exist in the abstract
number ten. This number stands for a group of things,
but its multiplicity is intensive and only exists because
we are able to subdivide anything in thought to an
indefinite extent. Now, so far we have only separated
what we agree to regard as the elemental parts of our
general perception of the environment, but it is to be
noted that we have not given to these elements anything
like spatial extension.
We may, if we like, regard our intuition of space
as that of an indefinitely large, homogeneous, empty
medium which surrounds us and in which we may,
in imagination, place things. So regarded it is difficult
to see in what way our notion of space differs from our
idea of " nothing," a pseudo-idea incapable of analysis,
except into the idea of something which might be
somewhere else. The more we think about it the more
we shall become convinced that space, that is the
" form " of space, represents our actual or potential
modes of motion, that is, our powers of exertional
activity. Space, we say, has three dimensions ; in
all our analysis of the universe, and of the activities
that we can perceive in it, this idea of movement in
three dimensions, forward and backward, up and down.
THE CONCEPTUAL WORLD 19
and right and left, occurs ; and we have to recognise
that in it there is something fundamental, as funda-
mental as the intuitive knowledge that we possess of
the direction of right and left. It is because we can
move in such a way that any of our motions, no
matter how complex, can be resolved into the com-
ponents of backward and forward, right and left,
and up and down, these directions all being at right
angles to each other, that we speak of our movements
as three-dimensional ones. Our geometry is founded,
therefore, on concepts derived from our modes of
activity ; and there is nothing in the universe, apart
from our own activity, that makes this the only
geometry possible to us. Euclidean geometry does
not depend on the constitution of the external universe,
but on the nature of the organism itself.
There is a little Infusorian which lives, in its adult
phase, on the surface of the spherical ova of fishes.
These ova float freely in sea water, and the Infusorian
crawls on their surfaces, moving about by means of
ciliary appendages. It does not swim about in the
water, but adheres closely to the surface of the ovum
on which it lives. Let us suppose that it is an in-
telligent animal and that it is able to construct a
geometry of its own ; if so, this geometry would be
very different from our OAvn.
It would be a two-dimensional geometry, for the
animal can move backward and forward, and right
and left, but not up and down ; it is a stereotropic
organism, as Jacques Loeb would say, that is, it is
compelled by its organisation to apply its body closely
to the surface on which it lives. But its two-dimen-
sional geometry would, on this account, be different
from ours. Our straight lines are really the directions
in which we move from one point to another point in
20 THE PHILOSOPHY OF BIOLOGY
such a way as to involve the least exertion ; they are
the shortest distances between two points, and if we
deviate from them we exert a greater degree of activity
than if we had moved along them. For us there is
only one straight line that can be drawn between
two points, but this is not necessarily true for our
Infusorian, and its straight line need not be the shortest
distance between two points. It might be either the
longest or the shortest distance between the points,
for the latter can always be placed on a great circle
passing through the two points and the poles of the
egg, and in moving from a point on which it is placed
the animal could reach the other point by moving
in two directions, just as we could go round the earth
along the equator by moving to the east or to the west.
Therefore the straight line of the Infusorian would be
not only a scalar quantity but a vector quantity, that
is, it would represent, not only a quantity of energy,
but a quantity of energy that has direction. For us
only one straight line can be drawn between two
given points, but this limitation would not exist in
the two-dimensional geometry of a curved surface.
Suppose that the two points are situated on a great
circle and that they are exactly i8o° apart ; then the
Infusorian could move from one pole to another pole
along an infinite number of straight lines or meridians
all of which had a different direction, but all of
which were of the same length ; that is to say, in
this geometry an infinite number of straight lines can
be drawn between the same two points. Again, its
triangles inight be different from ours ; our triangles
are figures formed by drawing straight lines between
three points, and on a plane surface the sum of the
angles of the triangle are together equal to two right
angles, though on a curved surface they may be greater
THE CONCEPTUAL WORLD 21
or less than two right angles. But our Infusorian could
not imagine a triangle in which the sum of the angles
was not greater than two right angles, for all its figures
would be drawn on a convex surface.
Our three-dimensional geometry depends, therefore,
on our modes of activity and the concepts with which
it operates ; points, straight lines, etc. are conceptual
limits to those modes of activity. We can imagine
a straight line only as a direction along which we can
move without deviating to the right or the left, or up
or down. But even if we draw such a line on paper
with a fine pencil the trace would still have some width,
and we can imagine ourselves small enough to be able
to deviate to the right or the left within the width of
the line drawn on the paper. We might make a very
small mark on the paper, but no matter how small
this mark is it would still have some magnitude ;
otherwise we should be unable to see it. If the straight
line had no width and the point no magnitude they
would have no perceptual existence. Our perceptual
triangles are not figures, the angles of which are
necessarily equal to two right angles. If we drive
three walking sticks into a field and then measure
the angles between them by means of a sextant we
shall find that the sum is nearly i8o°, but in general not
that amount. If we stick a darning needle into the
heads of each of the walking sticks and then remeasure
the angles by means of a theodolite we shall obtain
values which are nearer to that of two right angles,
but we should not, except by " accident," obtain
exactly this value. We do not, therefore, get the
" theoretical " result, and we say this is because of the
errors of our methods of observation ; but why do we
suppose that there is such a theoretical result from
which our observations deviate, if our observations
22 THE PHILOSOPHY OF BIOLOGY
themselves do not in general give this ideal result ?
We might accumulate a great series of measurements
of the angles of our triangle, and we should then find
that these results would tend to group themselves
symmetrically round a certain value which would be
i8o°. Some of the results would be considerably
less than the ideal, and some of them would be con-
siderably more ; but these relatively great deviations
would be small in number and most of the results
would be a very little less than i8o° or a very little
more, and there would be as many which would be a
little less as those that were a little more. We should
have formed a " frequency distribution " ^ with its
" mode " at i8o°.
But by " reasoning " about the " properties "
of these lines and triangles in plane two-dimensional
space, we should arrive at the conclusion that the
angles of a triangle were equal to i8o°, and neither
more nor less. We should then think of a straight
line as still a path along which we move in imagination,
and a path which still has some width. But we
imagine the width of the path to become less and less,
so that, even if we imagine ourselves to become thinner
and thinner, we should be unable to deviate either to
the right or left in moving along the path, because the
thinner we make ourselves the thinner becomes also
the path. We imagine our intuition of a deviation
to the right or left becoming keener and keener, so
that, no matter how small the deviation we should still
be able to appreciate it by the extra exertion which it
would involve. We think of a point as a little spot,,
and we think of ourselves as being very small indeed,
so that we can move about on this spot. But we can
reduce the area of the spot more and more, until it
^ See appendix, p. 350.
THE CONCEPTUAL WORLD
23
becomes " infinitesimally " small ; and at the same
time we think of ourselves as becoming smaller and
smaller, so that we can still move about on the spot.
But we think of the area of the spot as becoming so
small that no matter how small we make ourselves
we are unable to move on it.
This means that we substitute conceptual lines
and points and triangles for the perceptual ones of our
experience, and then we operate in imagination with
these concepts. That is to say, we carry our modes
of exertional activity to their limits,^ in the way which
we have tried to indicate above — a process of thought
which is the foundation of the reasoning of the in-
finitesimal calculus.
What we call space, therefore, depends on our
intuition of bodily exertion. This intuition includes
the knowledge that a certain change has occurred as
the consequence of the expenditure of a certain amount
of bodily energy, and that, as the result of this change,
the relation of the rest of the universe to our body
has become different. We think of our body as the
origin, or centre, of a system of co-ordinates : —
y
^ See appendix, p. 346.
y
Fig. 4.
24 THE PHILOSOPHY OF BIOLOGY
We imagine three lines at right angles to each other
to extend indefinitely out into space, and we think
of ourselves as being situated at the point of intersection
of these three straight lines. If anything moves in
the universe outside ourselves we can resolve this
motion into three components, each of which is to be
measured along one of the axes of our system of co-
ordinates. But any motion whatever in the universe
outside ourselves can be represented equally well by
supposing that the origin of the system of co-ordinates
has been changed ; that is, by supposing that we
have changed our position relative to the rest of the
universe. Therefore motion outside ourselves is not
to be distinguished from a contrary motion of our own
body — a statement of the "principle of relativity" —
except that any change outside ourselves may be
distinguished from that compensatory change in the
position of our body which appears to be the same
thing, by the absence of the intuition that we have
expended a certain quantity of energy in producing
the change. Conscious motion of our own body is
something absolute ; all other motion is relative.
So far we have been speaking of our crude bodily
motion, but a very little consideration will show that
our knowledge of space attained by scientific measure-
ments depends just as much on our intuition of our
bodily activity, and its direction ; the measurement
of a stellar parallax, or that of the meridian altitude
of the sun, for instance, by astronomical instruments,
involves bodily exertion, though of a refined kind.
Three-dimensional space, that is our space, therefore
represents the manner of our activity, just as convex
two-dimensional space represents the manner of the
activity of the Infusorian, and one-dimensional space
would represent the manner of activity of an animal
THE CONCEPTUAL WORLD 25
which was compelled to live in a tube, the sides of
which it fitted closely, so that it could move only in one
direction — up and down. A parasite, living attached
to some fixed object, and the movements of which were
represented only by the growth of its tissues, could
not form any idea of space ; and the " higher " forms
of geometry, that is, space of four or more dimensions,
present no clear notion to our minds, even although
we regard the operations included in mathematics
of this kind as pure symbolism, because we cannot
relate this imaginary space to any form of bodily
exertion. Geometry, then, represents the manner in
which our bodily exertion cuts up the homogeneous
medium in which we live.
Motion, whether it be that of our own body in
controlled muscular activity, or that imaginary motion
of the environment which we call giddiness, or a sensibly
perceived motion of some part of the environment,
that is, a motion which we can compensate by some
actual or imaginary change in the position of our own
body produced by our own exertion, is an intuitively
felt change, and is incapable of intellectual representa-
tion. It is not clearly conceived either in ancient or
in modern geometry. Euclidean geometry is, as we
have seen, based directly on our intuition of bodily
exertion, but it is essentially static in treatment.
Let it be admitted that we can draw a straight line
of any length and in any direction, and so on ; then
we regard these straight lines, etc., as motionless,
abstract things, and we proceed to discuss their relation-
ships. Cartesian geometry, and the methods of the
infinitesimal calculus, do not treat of real motion, and
the concept, if it is introduced at all, is introduced
illegitimately and surreptitiously. Consider what we
do when we " plot a curve." Let the latter be a
26
THE PHILOSOPHY OF BIOLOGY
parabola having the equation y=h x. Now a parabola
is defined as " the locus of a point which moves, so that
its distance from a fixed point is in a constant relation
to its distance from a fixed straight line." How do
we construct such a curve ?
y
y/t2
yo5
We proceed to fix the positions of a series of points
in this way : there are two straight lines, OX and OY,
at right angles to each other, and we measure off certain
steps along the line OX ; these steps are OXq.^, OXi,
0X15, 0X2, and so on, the small numerals indicating
the distance of each point (OXo-s, etc.) from the origin
0. We then draw lines perpendicular to the X-axis
through these points. We have now to calculate one-
half of the square of each of these lengths OX 05, OX^
etc., and then we mark off these calculated lengths
along the perpendicular lines. The point A, for
instance, is ^(0.5)2 from the point Xo-^, B is \(iY from
Xi, and so on. In this way we obtain a series of points,
A,B,C, D, E, etc., and these are points on the locus of
the " moving " point.
THE CONCEPTUAL WORLD 27
There is nothing at all about motion here. All
that we have done is to measure lengths. We have
made a kind of counterpoint, X-points against Y-points,
but we have not even made a curve. We connect the
points A, B, C, D, E, etc., by means of short, straight
lines, and then we may connect together these short
lines, and, if we plot a number of intermediate points
between those that we have already obtained and join
these, the points may be so close together that they
may seem to be indistinguishable from a curve. Yet,
no matter how numerous they may be, they can never
be connected together so as to form a curve ; we there-
fore draw a curved
line freehand through
them, and at once,
in so doing, we aban-
don our intellectual
methods, for our curve
depends on our intui-
tion of continuously p^^ ^
changing direction.
But if we think about it we shall find that we can
form no clear intellectual notion of continuity and we
can onl}^ measure the curvature of a line at a point in
the line by drawing a tangent to the curve at this
point, and then by measuring the slope of the tangent.
The curve itself we obviously leave out of considera-
tion.
We cannot conceive of the point moving along the
locus OD. We can think of it only as at the places
0, A, B, C, D, E, etc., but we must neglect the intervals
OA, AB, BC, CD, DE, and so on, or we can divide them
into smaller intervals by supposing the point to have
occupied the positions /, g, i, j, between the points
A and B, for instance. Yet, no matter how many these
28 THE PHILOSOPHY OF BIOLOGY
intervals may be, we can only think of the point as
being at the places 0,A,B, C, D, E, or at /, g, i, j, and so
on. We never think of the intervals themselves, and, if
all we think about is the position of the point, we do
not really think of it as in motion at all. We can see
it in motion, but we cannot form an intellectual concept
of its motion. It is not really necessary that we should
in the affairs of everyday life, but for the adequate
treatment of problems involving rates of change
science had to wait for the invention of the methods of
the infinitesimal calculus before this disability of the
human mind could be circumvented.
But the moving point occupies successively a number
of different positions in space. If it is a material
point that we observe to move from one place to
another, we perceive that a certain interval of our
duration corresponds with the change of position
of the point. Duration was not used up in the
occupancy of the different positions 0, A, B, C, D, E,
and so on, nor in that of the occupancy of the inde-
finitely numerous other positions in which we may
place the moving point, but in the intervals themselves.
We have said " duration " and not " time," using
Bergson's term. By duration and time we understand
different things.
Time is, for us, only a series of standard events
which punctuate, so to speak, our experienced duration.
The unit of time is the sidereal day, that is, the interval
of time between two successive transits of a fixed star
across the arbitrary meridian. But if we try to con-
ceptualise this interval we find that we can do so only
by breaking it up into smaller intervals, and this we
do by using a pendulum of a certain length which
makes a certain number of swings (86,400) during
the interval between the two transits of the star.
THE CONCEPTUAL WORLD 29
Thus we obtain a smaller interval of duration and we
call this a second of time. But for many purposes
this interval is too long, and we can again sub-divide
it by making use of a tuning-fork which makes, say,
1000 complete vibrations in a second ; in this way
we obtain still smaller intervals of duration— the
sigmata of the ph3^siologists. A sigma, therefore,
represents the interval between the beginning and end
of one complete vibration of a certain kind of tuning-
fork; a second, that between the beginning and end
of one complete swing of a pendulum of a certain
length, placed at certain parts of the earth's surface ;
and a day, that between two successive transits of a
fixed star across a selected meridian, after all the
necessary corrections have been made to the obser-
vation. These actual occurrences, the positions of
the prongs of the tuning-fork, or those of the bob of
the pendulum, or those of the fixed star do not involve
duration. We consider the meridian of Greenwich
as an imaginary line drawn across the celestial sphere,
and the star as a point of light, so that the actual
transit is, in the limit, an occurrence which occupies
only an " infinitesimal" interval of duration. So also
with the pendulum and the tuning-fork ; the positions
of these things do not " use up " time, and even if the
intervals into which we divide astronomical time are
indefinitely numerous no real quantity of duration is
taken up by their occurrence. We know that the
interval between two successive transits of a fixed
star are not really constant, that is, the astronomical
day is lengthening by an incredibly small part of a
second each year, but how do w^e know this ? It is
not that we can feel the increments of duration, but
just that we assume that Newton's laws of motion are
true ; and hence that the tidal friction due to the
30
THE PHILOSOPHY OF BIOLOGY
motions of the earth, sun, and moon must retard the
period of rotation of the earth so that the intervals
between two successive transits of a star must become
greater.
Thus we do not conceptuahse the actual intervals
of duration of which we are able to mark the end-
points ; they are lived by us, and they are real absolute
things independent of our wills. Suppose we come in
from a long walk, tired and thirsty, and ask the maid
to get tea ready at once. She puts the kettle on the
gas stove and then sits down to read. The water takes,
say, five minutes to boil. What do we mean by this ?
This is what we mean : —
Time
The pendulum of
the clock has al-
ready swung
M times
1
and it has
now swung
M + n times .
1
and now
M + 2n times
1
and so on
The time
elapses
P swings
Tempera-,
TURE
1
' The water in the
kettle is at
T" . .
The volume of
1
it is now at
T° + t° .
1
it is now
1
and now
T^+-2t°
1
and now
and so on
the kettle
boils
It is
mercury in the
thermometer is
^ v . .
V + v .
V-j
-2V
and so on
\
V
What we call time here is only a series of simul-
taneously occurring events. The standard events are
the positions of the hands of the clock on the clock
face, that is, lengths of arc recording the number of
swings of the pendulum that have occurred since the
beginning of the operation of the boiling of the kettle.
When this began, the hands of the clock were at, say,
4.30, and the temperature of the water was then, say,
17° C. ; and, when it ended, the hands of the clock were
at 4.35 and the temperature of the water was 100° C.
It is only the simultaneities of these events that we
have recorded and not the interval of duration that
they mark. It does not matter how many times we
THE CONCEPTUAL WORLD 31
might have looked at the hands of the clock and the
thermometer, we should still have observed only
simultaneities.
But we had to wait for the kettle to boil, and the
temperature ioo° was attained after the temperature
90°, and so on. What does this mean ? While we
were waiting, the water seemed to take an intolerably
long time to boil. But the maid was reading one of
Mr Charles Garvice's novels, and " before she knew
where she was " the kettle boiled over. There was a
certain interval of duration experienced by her, and
another, but different, interval of duration experienced
by us. In each case there was a stream of conscious-
ness. We felt fatigue, thirst, a lack of satisfaction,
wandering attention, and irritation — all that was our
duration. But the maid was identifying herself with
Lady Mary, who had sprained an ankle and was being
helped along by the new, young gamekeeper, and that
was her duration.
There need not be any succession of events in the
conceptual representation of a physical process. There
is, for instance, no succession in such a conception as
is represented by the following diagram — a conception
well worth analysis : —
Jif shock '1 SS, 4-2
Bnd shock
Fig. 7.
32 THE PHILOSOPHY OF BIOLOGY
The figure represents a tracing made by a muscle-
nerve preparation. A living muscle taken from an
animal has been attached to a light lever, the end of
which makes a scratch on a piece of smoked paper.
The paper is fastened on a revolving cylinder and so
long as the muscle is motionless the end of the lever
marks a horizontal line on the paper. But if the
muscle is stimulated so that it contracts and then re-
laxes again the lever is puUed up and is then lowered,
and so its point makes a curve on the paper. The
nerve going to the muscle can be stimulated electrically
and the moment of the stimulation can be recorded by
another lever, which makes a mark on the paper below
the trace made by the lever which is attached to the
muscle. Two such shocks have been applied to the
nerve and they have elicited two contractions of the
muscle and these two contractions have fused together.
In the actual experiment the operators could see
that the muscle moved, and they could feel that a
certain interval of their own duration coincided with
the interval between the first and second depressions
of the key that made the electric shocks. But the
extent of motion of the muscle was too small, and the
depressions of the key succeeded each other too rapidly
to be easily observed, and therefore all these events
were made to record themselves on the myogram.
The series of little notches at the base of the figure
represent the movements of the time-lever, that is,
they are scratches made on the paper by a little lever
which moves up and down at a rate fixed beforehand.
Nov/ when this time lever had made ten notches on
the paper the first shock was applied to the nerve,
and at the eleventh the muscle began to contract.
At the seventeenth notch the second shock was applied
and the muscle continued to contract. At the twenty-
THE CONCEPTUAL WORLD 33
fifth notch the muscle ceased to contract and began to
relax, and at the forty-second notch the muscle had
ceased to contract. Everything now becomes clear
and easy to represent mentally ; the time-lever makes
100 notches on the paper in a second, so that there was
an interval of 0.07 seconds between the two stimuli,
and these two stimuli produced a compound contraction
of the muscle lasting for o.i second. This is what the
experimenters might have perceived, had human un-
aided senses been sufficiently acute. But they are
not, and so the crude perception of the results of the
experiment is replaced by a conception of the train
of events involved in the operation. Duration and
succession disappear and the myogram represents only
a series of simultaneous events of this nature ; the
first stimulus occurs simultaneously with the tenth
movement of the time-lever ; the second stimulus
with the seventeenth, and so on. In seeing the ex-
periment the operators had to wait for one phase to
be completed before they could observe another one,
but in reasoning about it all the phases are spread out
and are present in the conception at once. The
duration was in the operators but not in the experi-
ment : it was experienced, but it disappears when the
results of the experiment are conceptualised.
A succession of events is in ourselves and not in
the events observed. If a point is said to move along
the locus OD through the positions A , B, C, it is we
that have the feeling of succession, and the whole
trajectory, or locus, or path of the point corresponds
with a portion of our duration. The operation of
boiling the kettle corresponds with a portion of our
duration, which in its turn corresponds with that part
of our duration which was marked by the positions
of the hands of the clock. Thus we perceive a simul-
34 THE PHILOSOPHY OF BIOLOGY
taneity in these two trains of events, and this enables
us to assign a certain period of astronomical time to
the operation of raising the temperature of the water,
in the conditions of the experiment, from 17° C. to
100° C. But there is nothing absolute in this interval
of astronomical time : what is absolute is that certain
successions of events always correspond with other
successions of events. A certain number of swings of
a seconds-pendulum always corresponds with a certain
rise in temperature of a definite mass of water which
is in thermal contact with an indefinitely large reservoir
of heat at a certain temperature, and, no matter how
often we repeat this experience, the same simultaneity
is always to be observed. Thus what the ph^/sicist
considers is not intervals of his own duration but series
of correspondences — that is, correspondences of certain
standard events with the events which he is studying.
In reality time, in the sense of the astronomer's
time, does not enter into the methods of the mathema-
tical physicist. Let us suppose that he is investigating
the change that occurs in a material system between
the two moments of tim.e /i and 4, these moments
being separated from each other by a period of duration
that we can feel. Let the system be, say, the earth
and moon ; the first body being supposed to be
motionless, and the second being supposed to have
a certain tangential velocity of movement. If the
interval t^ to ti is really an interval of astronomical
time, the problem, what is the difference of position
of the moon owing to the gravitation of the earth, is
incapable of solution, and even if we reduce the interval
of time indefinitely while still supposing that it is a
finite interval, the mathematical difficulty remains.
We then replace the finite interval ^ to 4 by the
differential dt, which means that the two phases of
THE CONCEPTUAL WORLD 35
the system, motionless earth and moving moon at the
time ti, and motionless earth and moving moon at the
time ^2, are separated by an interval of time dt, which
is smaller than any finite interval that we can conceive.
We must then integrate the differential of the position
difference so as to obtain the real difference in the
condition of the system after the finite interval of time
ti to ^2 has elapsed. Thus mathematics, incapable
of dealing with real intervals of time, evades this diffi-
culty by considering tendencies, not real occurrences.
Things that happen in a part of inorganic nature
arbitrarily detached from the rest, and investigated by
the methods of mathematical physics, do not endure.
Let us suppose that we take some silver and add nitric
acid to it : the metal dissolves. We can then add
hydrochloric acid to the solution and precipitate the
metal in the form of chloride ; and we can then fuse
this chloride with carbonate of soda, or some other
substance, and so obtain the metal again. If we work
carefully enough we can repeat this series of operations
again and again and the original portion of silver will
remain unchanged both in nature and in mass. All
the chemical reactions into which it has entered have
not affected it in any way ; that is to say, these reactions
have not endured.
If we inject a serum, containing a toxin, into the
blood stream of a susceptible animal, certain things
happen. The animal will become ill, but, provided
that the amount of serum which has been injected was
not too great, it will recover. If the toxin be again
injected a reaction occurs, but the animal does not
become so ill as on the first occasion, and after a number
of injections the dose administered may be so great as
to kill a susceptible animal but may yet produce no
effect on the animal which is the subject of the process
36 THE PHILOSOPHY OF BIOLOGY
of immunisation : immunity has been conferred on it.
Now can we compare the two operations, that of the
solution and precipitation of the metal and that of
the immunisation of the animal ? We can to some
extent, but the analogy soon fails, and indeed we should
not attempt to formulate a theory of immunity on a
physico-chemical basis if we did not start with the
assumption that the series of operations was one in
which only physico-chemical reactions were involved,
that is to say, there is nothing in the phenomena of
immunisation that suggests that what occurs in the
animal body is similar to what we can cause to occur
in inorganic materials outside the tissues of the living
organism. We start with the assumption that the
administration of the toxin causes the formation of an
antitoxin in very much the same sort of way as the
administration of hydrochloric acid to a solution of
nitrate of silver causes the formation of chloride of
silver. This antitoxin then neutralises the dose of
toxin which may be administered after the process of
immunisation has been effected, very much in the same
sort of way as a certain amount of some acid can be
neutralised by an equivalent amount of some base with
which the acid can combine. If the reader will analyse
any of the theories of immunisation current at the
present day he will find that these are the physical
ideas that are involved in it.^ But physiological
science has the much more formidable task of explain-
ing the persistence of the immunity. The animal
rendered immune to the toxins produced by certain
species of bacteria may remain so for many years, that
is, for a very long time after the antitoxins origin-
ally produced by the reaction of the tissues to the
^ Except that, of course, the reactions that are supposed to occur are
very complex ones.
THE CONCEPTUAL WORLD 37
toxins first administered have disappeared. We must
imagine, therefore, that the anti-substances produced
originally by the reaction of the toxin are produced
again and again by the tissues of the susceptible
animal, for the latter may resist repeated infections,
that is, repeated doses of toxin, without illness. But
then the tissues of the animal body are transitory
substances and they do not persist unchanged.
Muscles, glands, connective tissues, even nerve-fibres
and nerve-cells undergo metabolism, and the chemical
substances of which they are composed break down
into the excretory products, pass out into the blood
stream, and are eliminated from the body ; while at
the same time these tissues are continually being
renewed from the nutritive substances in the blood
and lymph. It is the organisation of the tissues —
their form and modes of reaction — that endure, but
the material substances of which they are composed
are in a state of continual flux. Yet the organisation
of these tissues does not persist unchanged, for it is
continually responding to new conditions experienced
by it. The reactions that occur when a toxin is
administered to a susceptible animal affect the organis-
ation of its tissues in such a way that the latter acquire
the capability of producing antitoxins which may — if
we like to say so — neutralise the toxins that enter
into them when they become infected. The reaction
endures. But this is a different thing from saying that
the process is a physico-chemical one alone.
This is what we must understand by the duration
of the organism. Everything that it experiences for
the first time persists in its organisation. It acquires
the ability of responding to some stimulus by a definite,
purposeful reaction, the effect of which is to aid it in
its struggle for existence ; and this reaction, once
38 THE PHILOSOPHY OF BIOLOGY
carried out, becomes a " motor habit " or the basis of
a reflex, or in some other way, as in the process of
immunisation, remains a part of the modes of function-
ing of the animal. In our behaviour certain cerebral
nerve tracts become laid down and continue to exist
throughout life, modifying all our future experience.
Our past experience accumulates. There must be
direct continuity in our flux of consciousness, for no
perception seem.s ever to fade absolutely from memory.
This continual addition of perceptions to those that
already exist makes our consciousness ever become
more complex, so that a perception experienced for
the first time is never quite the same when it is again
experienced. The first time that we go up and down
in an elevator, or sit on a " joy-wheel," or ascend in a
balloon or an aeroplane, or become intoxicated, con-
stitutes an unique event in our lives, and we experience
a " new sensation." What the blase man of the world
complains of is this accumulation, or rather persistence,
of his experiences. A repetition of the same stimulus
never again begets the same perception. The first
hearing of a modern drawing-room song may be
enjoyable, but the next time we hear it we are not
interested, and by-and-bye it becomes very tiresome.
The first hearing of a great symphony usually perplexes
us, and we are perhaps repelled by unusual harmonies,
or progressions, or strange modulations, but subsequent
hearings afford increasing pleasure. We say that there
was " so much in it " that we did not understand it,
yet precisely the same series of external stimuli affected
our auditory membranes on each occasion, and the
same molecular disturbances were transmitted along
our afferent nerves to the central nervous system,
where the same physical effects must have been pro-
duced. The difference in all these cases between the
THE CONCEPTUAL WORLD 39
repetitions of the same stimuli was that the later ones
became added to the earlier ones, so that the state of
consciousness produced by, or which was concomitant
with, these external stimuli was a different state in
each case.
This is the duration of the intelligently acting
animal : it is not merely memory, but memory and the
accumulation of all its past modes of responding to
changes in its environment, whether these modes of
response were conscious ones (as in the case of an
intelligently performed or " learned " action), or un-
conscious ones (as, for instance, in the case of the ac-
quirement of immunity by an animal which had become
able to resist disease). It is not merely the experience
of the individual organism, but also all the experience
of those things which were done or experienced by
the ancestry of the organism, and which were trans-
mitted by heredity to the progeny. Motor habits are
formed, so that much the same series of muscular
actions are carried out when a stimulus formerly
experienced is again experienced. Pure memory
remains, so that the images of past things and actions
somehow persist in our consciousness. Physical
analogy suggests that these images are inscribed on the
substance of the brain or are stored away in some
manner ; but, apart from the incredible difficulty of
imagining a mechanism competent for this purpose, it
is obvious that we thus apply to the investigation of
our consciousness (which is an intensive multiplicity),
the concept of extension which can only apply in all
its strictness to the things outside ourselves on which
we are able to act. All these motor habits, functional
reactions, and memory images are our duration or
accumulated experience. The motor habits and those
functional habitual reactions of other parts of the body
40 THE PHILOSOPHY OF BIOLOGY
than the sensori-motor system are the basis of our
actions, but the memory images are, so to speak,
pressed back into that part of our organisation which
does not emerge into consciousness. Only so much of
them as bear on the situation in which we, for the
moment, find ourselves and which may therefore
influence our actions, flash out into consciousness.
As " dreamers " we indulge ourselves in the luxury
of becoming conscious of these memory images, but
as " men of action " we sternly repress them, or so
much of them as do not assist us in the actions that
we are performing. Yet it is in the experience of each
of us that, in spite of this continual inhibition, parts of
our memories slip through the barriers of utility and
surreptitiously remind us of all that we have been
and thought.
Thus we simplify the stream of our consciousness.
That of which we are conscious at any time is never
more than a part of our crude sensation : we never
perceive more, than a small part of all that our organs
of sense transmit to our central nervous system.
But even these chosen perceptions of the external
world are so rich, so chaotic and confused, that we
are unable to attend to them all at once and we there-
fore " skeletonise " the contents of our consciousness.
We think about it a bit at a time. It is an unitary
thing, unable to be broken up, but we look at it from
a great number of different points of view, so to speak ;
and then, fixing our attention on some aspect of it, we
agree to ignore all the rest. We thus detach parts of
it from the rest and, having thus arbitrarily decomposed
it, we call these separate aspects the elements of our
perceptions, and confer upon them separate existence
THE CONCEPTUAL WORLD 41
in space and time. We remember and classify things
and group together all those that seem to resemble
€ach other. We form genera, agreeing to ignore all
but the most general characteristics of the things which
we tr}^ to conceptualise. W^e do not think separately
about all the dogs or horses or fishes that we have ever
seen, but we group all these animals into species, and
it is usually the species that we think about when the
idea of a dog or a horse or a herring emerges into our
consciousness. When we think about a tramcar we
do not think about all the separate vehicles that we
have seen, nor about their colours, nor the advertise-
ments on the boards outside, nor the people hanging on
to the straps inside. Just so much of the experience
of what is relevant to the purpose of our thought
enters into our idea of the tramcar : it is a conceptual
vehicle that we think about. Such is the nature of
the concepts that form the basis of our reasoning :
they are generalised aspects of our experience of
nature, usually poorer in content than were the actually
perceived things, except when it is necessary that some
individual thing seen or otherwise experienced should
be investigated or reasoned about. All our descrip-
tions of nature are conceptual schemes. The world
of perception, says William James, is too rich to be
attended to all at once, but in conceptualising it we
spread it out and make it thinner, and we mark out
boundaries and division lines in it that do not really
exist. It is this generalised nature that is the subject
matter of our reasoning of pure science ; and it is
these concepts that form the matter of all our descrip-
tions. We do not describe nature " as we see it," it
is our conceptions that we write about. Genera and
species and varieties do not really exist in the animate
world : all these are logical categories generated by
42 THE PHILOSOPHY OF BIOLOGY
our thought, concepts that facihtate our descriptions.
When an anatomist gives an account of the structure
of an animal he does not say what it looks like, nor as
a rule does he content himself by making a photograph
of his dissections. For him the animal is a complex of
muscles, skeleton, nerves, glands, and so on, and in his
drawings all these things are given an individuality
that they do not really possess. In the living creature
there were no such sharply-distinguished organs as a
good drawing represents : all are bound together and
are continuous. But for practical convenience in
description — that is, in the long run, that we may
act upon these things, we isolate from each other aspects
that are in realit}^ one unitary Vv^hole.
The universe, that is, all that is given to us, presents
itself as immediately perceived phenomena which are
then conceptually transformed. It is an aggregate of
things — gross matter, particles, molecules, atoms, and
electrons. These things have separate existence and
shape, so that each of them lies outside all other things
— we apply to them the category of extension. They
possess properties — that is, they are hard, or heavy, or
hot, or cold, or they are coloured, or they smell, and
so on — we thus apply to them the category of in-
herence. They are not things that are immutable, for
they change in place, or are transformed in other ways,
that is, they are acted upon by energies. But beneath
the properties of the things, or the transformations
that they undergo, we imagine something that has
properties and which transforms : it is not convenient
that we speak solely of attributes or transformations
as entities in themselves, for we think of things as
THE CONCEPTUAL WORLD 4a
having properties and being subject to transformations.
Thus we apply the category of substance.
Has this universe that we construct from the data
of sensation objective reahty ? We are led quite
naturaUy by our study of physiology to the notion of
idealism. We see that our perception of things, that
is, our knowledge of the universe, depends on the
integrity of functioning of certain bodily structures,
and upon the condition that in men in general this
integrity of functioning is normal, that is, common to
the great majority of mankind.
To say that a thing exists is to say that it is perceived
in some way ; that immediately or remotely it affects
our state of consciousness. To say that the star
Sirius exists is to say that the stimulation of the retina
by a minute spot of light transmits certain molecular
disturbances along the optic nerve, and that other
molecular disturbances are set up in the tissues of the
central nervous system. Even if we do not see those
dark stars that we know to exist, there are still evidences
of their being that in some way affect the instrum.ents
of the astronomer and lead to their being perceived.
Even if we do not actually see the emanations from a
radio-active substance, we can cause these emanations
to produce changes in something that we can see. We
speak of the star as a minute spot of coloured light.
But if we are short-sighted the spot becomes a little
flare, and if we are colour-blind the hue of the star is
different from what it is to normal persons. If we put a
drop of atropine into one eye and then close the other,
objects appear to lose their distinctness, but if we close
this eye and then open the other, the original sharpness
of vision returns. When we are bilious, wisps and spots
may appear on a sheet of white paper that at other
times was blank. If we take an overdose of quinine.
44 THE PHILOSOPHY OF BIOLOGY
rustlings and singing noises become apparent even in
conditions that ought to preclude all sensation of
sound. If we have a bad cold, we do not smell sub-
stances which at other times strongly affect our olfac-
tory membranes. When we become intoxicated, a host
of aberrations of sense displace our normal perceptions
of things.
Our perception of the universe, therefore, depends
on the normal functioning of our organs of sense, that
is, such modes of functioning as we can describe and
communicate to others, and which are thus common
to the majority of other men and women. These
perceptions resulting from the normal functioning of
the organs of sense constitute givenness, and we
enlarge, or conceptualise this givenness and call it the
subject matter of science. But what is this reality
that we say is external to us ? It is, we see, our inner
consciousness. If we walk along a road in the dark
we can feel what is the nature of the path on which
we tread, whether stones or gravel, or sand or grass.
But this feeling is obviously not in the soles of our
boots, and neither is it in the skin of the feet, for we
should feel nothing if the afferent nerves in the legs
were severed. Is it then in the brain ? It would
appear to be there, but it disappears if certain tracts
in the brain are injured.
All that we can say is that the appearance of reality
of things outside ourselves is only the ever-changing
condition of our consciousness. This is all that we
immediately know, and if we say that there is an
universe external to ourselves we thus project outside
our own minds what is in them ; and we construct
an environment which may or may not exist, but
which we have no right to say does exist. A philosophy
based on the science of the organism would appear to be
THE CONCEPTUAL WORLD 45
restricted to this idealistic view of the universe. When
we come across it for the first time when we are young
it appeals to us with all the force of exact reasoning,
and yet it has all the charm of paradox. There is no
part of our intuitive knowledge which appears to us
to be more certain than this distinction between
ourselves and an outer environment : we know that our
conscious Ego is something different from our body—
and we know that outside our body there is something
else. Yet the idealistic view so appeals to the intellect
that we cannot think speculatively about it without,
at times, almost convincing ourselves of the unreality
and shadowiness of all that at other times seems most
real and tangible ; and we indulge in these speculations
all the more readily because we know that whenever
we begin to act, the intuitively felt body and outer
world will return to us with all their original conviction
of reality.
Some such system of idealism must generally
characterise a system of philosophy founded on pure
reasoning. We cannot but feel that the universe that
we construct is one that depends on our perceptions :
it is our perceptions. The essence of a thing is that
it is perceived. If there were no mind to perceive it,
would it exist ? The universe is our thought, and we,
that is our thought, exist only in the Thought of an
absolute Mind which we call God. Such is the meta-
physics to which the study of sensation led Berkeley.
The metaphysics of science has taken another turn.
It is true that men and women see something outside
themselves which differs slightly in different individuals
— these differences are due to what w^e call the "personal
equation." The image of the universe seen by some
individuals may differ profoundly from the image
seen by some others, or most others ; but a well-
46 THE PHILOSOPHY OF BIOLOGY
marked gap separates these slight individual deviations
in the images seen by normal individuals from the
large deviations seen by those whose perceptions are
what we call pathological ones. The normal universe
common to the majority of men and women is an
aggregate of molecules in motion. But this is a
conclusion with which modern physics has been unable
to remain content, for molecules must be able to act
on each other across empty space, and this is incon-
ceivable. The universe therefore consists of a homo-
geneous immaterial medium, the ether of space, and
this is the true substantia physica. Molecules and
radiation are conditions of the ether, and for the
physicist it is the only reality. The " materialism "
of our own time is therefore the belief in the existence,
unconditioned by time or anything else, of the ether,
or physical continuum ; a homogeneous medium, of
which matter and energy, and the consciousness of
the organism, are only states or conditions.
The materialism of the twentieth century, like the
idealism of Berkeley, thus finds that there is something
outside our own consciousness that possesses absolute
existence. To the materialist it is the ether of space,
and to Berkeley it is the existence of absolute Mind.
But if our desire to avoid metaphysics is a genuine one,
we must reject the notion of the universal ether no
less than we must reject the notion of an absolute
Mind, and we must rest content with pure phenomenal-
ism. For each of us there can be no existence except
that which is perceived or conceptualised. There is
nothing but our own consciousness ; there cannot even
be an Ego which perceives ; there is only perception.
We never do really believe this in spite of our profes-
sions of reason. We find on strict self-analysis that
we believe that there is an Ego that perceives and
THE CONCEPTUAL WORLD 47
that there are other Egos that perceive, and that the
universe which our Ego perceives is also the same
universe that other Egos perceive. If we did not
beheve that there were other men and women that
perceived — other consciousnesses hke our owti, all that
part of our own behaviour that we call morality would
be meaningless. In a philosophy of pure idealism
other men and women are only phenomena ; only
bodies moving in nature. Why, then, should these
elements of our consciousness influence the rest of our
consciousness as if they were men and women like
ourselves. All this amounts to saying that while our
speculative thought suggests to us that all that exists
is our stream of consciousness, our actions must
convince us that there are other thinking individuals
like ourselves.!
Even if we do surrender ourselves to phenomenal-
ism and try to believe that all that exists is our own
consciousness, the fact of our duration would suggest
to us that this present consciousness is not all. Our
reality is not only that which is present in our minds
now, but all that was ever present in our mind. All
that we have ever thought and done persists and forms
our conscious and unconscious experience. This past
of ours is something that is ever being added to, or
becoming incorporated with, our present state of con-
sciousness ; and if it is something other than that which
we now perceive and conceptualise, it is something that
has an existence of its own.
We must believe that there is something that we
perceive, and not that we merely perceive. For the
phases of our immediate givenness, that is, those things
which were present in our minds from moment to
1 The reader may recognise in this argument that of Driesch's Three
Windows into the Absolute.
48 THE PHILOSOPHY OF BIOLOGY
moment of the past were connected together and had
direction, and this direction was something that could
not be influenced by our will, and may even have been
contrary to our will. Something that is very hot
always cools, a wheel that is revolving of itself always
comes to a stop, a pendulum ceases to swing, a stone
that is rolling down a hill continues to roll. Let us look
back at a fire that was going out : it is now nearly
dead ; let us start a pendulum to swing and then go
away : when we come back the pendulum is still
swinging but the amplitude of its vibrations is now
less than it was ; let us look away from the stone that
was falling : when we look again it is still falling but
it is not where it was. In all our givenness, in all the
phenomena that we perceive, there is something that
is determined and unequivocal, something that goes
its own way apart from our consciousness of it.
Above all, we have the conviction of absoluteness in
our sense of personal identity. We, that is our Ego,
are something that endures, and we can trace no
beginning to our identity, and we have no intuition
that it will cease to exist. Our Ego is now the same
Ego that it was in the past, and round it something has
accumulated — the memories of our former perceptions,
and the habits that these have engendered. Did our
Ego create this from itself ? Was it not rather a
centre of action which, residing in an existence other
than itself— the absolute which we call the universe —
modified that existence and continually acquired new
relationships to it ?
CHAPTER II
THE ORGANISM AS A MECHANISM
We propose now to consider the organism purely as a
physico-chemical mechanism, but before doing so it
may be useful to summarise the results of the discus-
sions of the last chapter. Let us, for the moment,
cease to regard the organism as a structure — a " con-
stellation of parts " — and think of it as the physiologist
does : it is a machine ; it is essentially " something
happening." What, then, is the object of its activity ?
Whatever else the study of natural history shows us,
it shows us this, that the immediate object of the
activity of the organism is to adapt itseli-to-its-sur-
roundings. It must master its environment, and
subdue, or at least avoid whatever in the latter is
inimical. It must avoid accident, disease, and death,
it must find food and shelter ; it must seek for those
conditions of the environment which are most favour-
able to its prolonged existence. Ultimate aims — the
preservation of its race, ethical ideals — do not concern
us in the meantime. The main object of the function-
ing of the individual organism is that it may dominate
its environment, and obtain mastery over inert matter.
Consciously or unconsciously it acts towards this end.
All those actions which we call reflex, or automatic,
or instinctive, have this in common, that the organism
in performing them comes into relation with only a very
limited region of its environment. But knowing that
n 49
50 THE PHILOSOPHY OF BIOLOGY
region intuitively, its actions have a completeness that
an intelligent action does not exhibit until it has
become so habitual as to approach to automatic acting.
The relations between the organism and that part of
its world on which it acts, intuitively or instinctively,
is something like that between a key and the lock to
which it is fitted : it opens this lock, perhaps one or
two others which resemble it, but no more. Now
just because of this perfect, but restricted, adjust-
ment of the instinctive or automatically acting
organism to the objects on which it operates, know-
ledge of all else in the environment becomes of little
consequence.
It is clear that intelligent acting involves delibe-
ration. The almost inevitable motor response to a
stimulus, which is characteristic of the reflex or in-
stinct, does not occur in the intelligent action : instead
of this we find that we choose between two or more
responses to the same stimulus. We reply to the latter
by doing this now, and that another time ; and we see
at once what results flow from acting differently upon
the same part of our environment, or acting in the same
way upon different parts. Perception, that is, know-
ledge of the world, arises from acting ; and as our
actions, when carried out intelligently, become almost
infinitely varied, the environment appears to us in
very many aspects. In every action we modify that
part of our surroundings on which we operate. We
can produce many modifications that are of no use to
us : these we do not attend to. We produce others
that are useful, and then we note the sequences of
events involved in our actions. Thus v/e discover or
invent natural law — an environment which is an orderly
one. We can calculate and predict what will happen :
we produce, for instance, a Nautical Almanac, at
THE ORGANISM AS A MECHANISM 51
once the type of useful knowledge and of knowledge
of sequences of events rigidly determined — knowledge
in short that is mechanistic ; and which has been
engendered by the necessity for acting on our en-
vironment in our own interests.
All this, the reader may note, is Bergson's theory
of intellectual knowledge, a theory which, new and
paradoxical at first, becomes more and more convinc-
ing the longer we think about it, until at last it seems
so obvious that we wonder that it ever seemed new.
Our modes of thinking become constrained into certain
grooves, just because these modes of thinking have
been those that were generated by our modes of acting.
So long as our thinking relates only to our acting, its
exercise is legitimate. But if its object is pure specula-
tion its results may be illusory, for a method has been
applied to objects other than those for which it was
evolved. Let us now extend our intellectual methods
to the investigation of the organism. Necessarily we
must reason about the latter as a mechanism if we
reason about it at all.
If it is a mechanism it must conform to the laws
of energetics, for science, so far as it is quantitative,
whether its results are expressed in the form of equa-
tions or inequalities, is based on these principles.
The first principle of energetics,^ or the first law of
thermodynamics, is that of the conservation of energy.
Let us think of an isolated system of parts such as the
sun with its assemblage of planets, satellites, and other
bodies : in reality these do not form an isolated system,
but we can regard them as such by supposing that
just as much energy is received by them from the rest
of the universe as is radiated off by them to the rest
of the universe. In this system, then, the sum of a
1 See appendix, p. 356.
52 THE PHILOSOPHY OF BIOLOGY
certain entity remains constant, and no conceivable
process can diminish or increase its quantity. We call
this entity energy, and we usually extend the principle
of its absolute conservation to matter, though this
extension is unnecessary, for we must think of matter
in terms of energy. Stated more generally the principle
is that whatever exists must continue to exist, if we
are to regard this existence as a real one.^
It is not at all self-evident to the mind that energy
must be conserved, for we see that, to all appearance,
it may disappear. A golf -ball driven up the side of
a hill possesses energy while in flight, kinetic energy
or the energy of motion ; but this apparently is lost
when the ball alights on the hill-top and comes to rest.
We say, however, that it now possesses potential
energy in virtue of its position ; for if the hill is a
steep one a little push wdll start the ball rolling down
with increasing velocity, and when it reaches the spot
from which it was originally impelled it possesses
kinetic energy. This is described as one-half of the
mass of the ball multiplied by the square of its velocity.
Now the kinetic energy of the ball at the instant when
it left the head of the driver ought to be equal to its
kinetic energy when it reached the same horizontal
level on its downward roll. Yet it can easily be shown
that this is not the case, and we account for the lost
kinetic energy by saying that it has been dissipated
by the friction of the ball against the atmosphere in
its flight, and against the side of the hill on its roll
back. We cannot verify this quantitatively, but we
are quite certain that it is the case. If we take a
clock-spring and wind it up, the energy expended
becomes potential in the spring, and when the latter
^ The principal reason why we do not beUeve in phantasms is that these
appearances are not conserved.
I
THE ORGANISM AS A MECHANISM 53
is released most of it is recovered. But we may
dissolve the spring in weak acid without allowing it
to uncoil. What then becomes of the energy imparted
to it ? We are compelled to say that it has changed
the physical condition of the solution into which it
passes, either becoming potential in this solution, or
becoming dissipated in some way. Yet again we cannot
trace this transformation experimentally though we
may be quite sure that all the energy potential in the
coiled spring is conceivably traceable. Suppose, again,
we bum some hundredweights of coal in a steam-
boiler furnace. Heat is evolved which raises steam
in the boiler, and the steam actuates an engine, and
the latter exhibits measurable kinetic energy. Where
did this come from ? It was potential in the coal,
we say, though no method known to physics enables
us to prove this by mere inspection of the coal. W^e
must cause the latter to undergo some transformation.
But by rigid methods we can estimate very exactly
the potential energy of the coal, and we can calculate
the kinetic energy equivalent to this. Yet again
we find that the kinetic energy of the steam-engine is
only a fraction of that which calculation shows us is
the equivalent of the kinetic energy of the coal. What
becomes of the balance ? W^e can be quite certain that
it has been dissipated in friction, radiation, loss of
heat by conduction, loss of heat in the condenser,
and so on, although we cannot prove this rigidly by
experimental methods.
Think of the universe as an isolated system. It
contains an invariable quantity of energy. This
energy may be that of bodies in motion — suns, planets,
cosmic dust, molecules, etc. — when it is kinetic energy ;
or it may be the energy of electric charges at rest or in
motion ; or any one of the many kinds of potential
54 THE PHILOSOPHY OF BIOLOGY
energy. It may pass through numerous transfor-
mations— the chemical potential energy of coal may
be transformed into the kinetic energy of water
molecules (steam at high temperature), and this into
the kinetic energy of the revolving armature of a
dynamo, and this again into the energy of moving
electrons (the current of electricity in the circuit of
the dynamo) , and then again into the energy of ethereal
vibration (light, heat, X-rays, or other electro-magnetic
waves), and these again into mechanical or kinetic
energy, and so on. When we say that we can control
energy we say that we can produce these transfor-
mations ; we can cause things to happen, we bring
becoming into being. In this sense energy is causalit3^
But while the sum-total of energy in the universe
remains constant, the sum of causality continually
diminishes. Energy is the power, or condition, of
producing diversity, but while energy can suffer no
diminution of quantity, diversity tends continually
to decrease.
In the last two sentences we state, in one way,
the second law of thermodynamics — in some respects
the most fundamental result of our experience
in the physical investigation of the universe. In
its most technical form, as enunciated by Clausius,
this law states that the value of a certain mathe-
matical function, called entropy,^ tends continually
towards a maximum, when it is applied to the
universe as a whole. When we say the " universe,"
we mean all that comes within our power of physical
investigation. Let us now see what this statement
means.
^ See appendix, p. 369. Entropy is a shadowy kind of concept, difficult
to grasp. But again we may point out that the reader who would extend
the notion of mechanism into life simply must grasp it.
THE ORGANISM AS A MECHANISM 55
The energy of the solar system is in part the kin-
etic energy of those parts of it which are in motion —
planets, planetesimals/ and satellites. This quantity
of energy is enormously great. In the case of our earth
it is hmv'^, m being the mass of the earth, and v its
velocity. Translated into numerical symbols we find
this quantity almost inconceivable. The greater part
of this energy is unavailable, that is, it can undergo no
transformations. But because the earth is in rotation
at the same time as it revolves round the sun, and
because the moon revolves round the earth, there are
tides in the watery and atmospheric envelopes of the
earth. The energy of the tides is the kinetic energy
of water or air in motion, and we can employ this
energy in the production of transformations, and it is
therefore available. But well-known investigations
have shown that the tides produce friction, and that
the period of rotation of the earth is slowly becoming
greater. Ultimately the earth will rotate on its ov/n
axis in the same time that it revolves round the sun —
then a year and day will be of the same length. When
that occurs, the sun, earth, and moon will be in equi-
librium, and tidal phenomena due to the sun will cease.
The kinetic energy of the earth, rotating once in 24
hours is obviously greater than its kinetic energy when
rotating in the period which will then be its year.
What has become of the balance ? It has been
transformed into the mechanical friction of the tides
against the surface of the earth,- and this friction has
been transformed into low-temperature heat, and this
heat has been radiated off into space.
1 Meteorites, cosmic dust, and other small particles moving in the solar
system within influence of the sun's gravity.
* Not entirely, of course, but whatever be the transformation it ends in
heat production.
56 THE PHILOSOPHY OF BIOLOGY
The solar system also contains energy in the form
of the heated sun and planets, and in the form of
chemical potential energy of the substances of which
those bodies are composed. Let us think of the system,
sun and earth. The sun contains enormous heat
energy, its temperature being some 6000° C. absolute. ^
It contains enormous chemical energy in the shape
of compounds existing beneath its outer envelopes,
and it contains energy in the form of its own gravity —
its contraction together produces heat. But this heat
is being continually radiated away : chemical reactions
must occur in which the potential chemical energy
of its substances must become transformed into heat,
and this heat is also radiated away ; contraction of its
mass must occur up to a point when the materials are
as closely packed together as possible ; heat is developed
during the contraction, and this also passes away by
radiation. Suppose that modern speculations are well
founded and that radio-active substances are present
in the sun : in the atomic disintegration of these
substances heat is produced and again radiated.
Therefore in whatever form energy exists in the sun,
it transforms into heat and this radiates. The ultimate
fate of the sun is to cool down and solidify. It will
then move through space as a body having a cool,
solid crust, and an intensely heated interior. Slowly,
very slowly, this heated interior will cool down by
the conduction of its heat from the core to the outer
shell, and by the radiation of this heat from the shell
into space. For incredibh^ long periods radio-active
substances in the interior must generate heat, but
even this process must reach an end.
The energy received by the earth is that of solar
^ Absolute temperature is Centigrade temperature + 273. This is, of
course not a lull definition, but it is sufficient for our present discussion.
THE ORGANISM AS A MECHANISM 57
and stellar radiation. Stellar radiation is minute, the
absolute temperature of cosmic space (or ether) being
about - 263° C. The absolute temperature of the earth
is about +17° C, so that it radiates off more heat into
space (other than that represented by the sun) than
it receives. All energy-transformations on the earth
(except tidal effects, and energy-conduction from
the heated core, and possibly radio-active effects) are
transformations of this solar energy received by
radiation. We see these in oceanic and atmospheric
circulations (currents, winds, rainfall, etc.). We see
them also in the transformations of the chemical
potential energy of coal and other products of life —
products in which the contained potential energy has
been absorbed from solar radiation.
Let us follow the transformations of this energy.
Oceanic currents transport heat from the equatorial
sea-areas to the colder temperate and polar areas,
and compensatory polar currents flow towards the
equator, absorbing heat from the waters of temperate
and equatorial areas. Winds act in an analogous way.
Water is evaporated where the solar radiation is intense,
and heat is absorbed in the transformation of water
into aqueous vapour. Then this water vapour is
transported in the winds into regions where it becomes
condensed and precipitated as rain or snow, heat being
emitted in this condensation. In all these movements
there is friction, and this friction transforms to heat.
In all the effect is the general distribution over the earth
of the heat which the equatorial regions receive in
excess of that which the polar regions receive. Other
mechanical effects are also produced by oceanic and
atmospheric circulations — the denudation of the coasts
by tides and storms, the erosion of the land by rivers,
rains, snow, and ice, the transport of dust in winds, etc.
58 THE PHILOSOPHY OF BIOLOGY
In all these friction is produced, and this friction passes
into heat.
The potential chemical energy which results from
absorption of solar radiation by plants is principally
accumulated as coal. Apart from the interference of
man, this coal would slowly accumulate, perhaps it
would more slowly disappear by bacterial action, or by
physical transformations. In these transformations
the energy of the coal would become heat energy
and the potential energy of the gas produced by
bacterial activity. By man's agency the coal suffers
other transformations, and in the present phase of
civilisation it is his chief source of energy. It is
available for doing work of many kinds, and in all these
forms of work it becomes transformed by chemical
action (burning) into high temperature heat.
We can cause this potential energy of coal to trans-
form into mechanical energy of machines, vehicles,
and ships in motion by causing it to pass into heat.
In the steam-engine, or gas-engine, a highly heated gas
(steam, or the mixture resulting from the explosion of
coal gas and air in the cylinder of the engine) expands
and propels a piston or rotates a turbine. (Obviously
in the petrol engine the same essential process takes
place.) We employ this kinetic energy directly in
transport, or we cause it to undergo other transfor-
mations. In the dynamo, kinetic energy of machinery
in motion transforms to electrical energy ; and this
may transform to radiant energy (light, heat in electric
radiators, wireless telegraphy radiations), or it may
transform to chemical energy (the manufacture of
carborundum in the electric furnace, for instance),
or it may transform again to the kinetic energy of
bodies in motion (electric traction). In innumerable
ways the human power of direction causes trans-
THE ORGANISM AS A MECHANISM 59
formation of this accumulated potential energy, and
the reader will notice the analogy of all this with the
essential, unconsciously expressed activity of the animal
organism in its own metabolism — a point to which
we return later.
Notice now that all the energy-transformations
we have noticed are irreversible. This is a matter of
deep philosophical importance, and we must devote
some time to it. Consider first of all the working of
the steam-engine ; what occurs is this — coal is burned
in the boiler-furnace, that is to say, potential chemical
energy passes into heat and this vaporises water in
the boiler, producing a gas at high temperature (steam.) .
This gas expands in the high-pressure cylinder of the
engine, driving forward a piston ; it expands further in
the intermediate cylinder, propelling its piston also,
and again in the low-pressure cylinder. It is then
cooled by passing through the condenser, and in the
contraction further mechanical energy is obtained.
The train of events thus begins with a gas at a high
temperature and ends with the same gas at the tem-
perature of the water in the condenser. The heat
lost is transformed into the mechanical energy of the
engine. But not all of it. A certain quantity is lost
by radiation from the boiler walls, the walls of the
steam-pipes, the cylinders, and other parts of the engine ;
also some of the energy is transformed to friction,
and this again to heat. In this way a very considerable
part of the energy contained in the coal is frittered
away in unavoidable heat-conduction and radiation,
and a last residue of it goes down the drain, so to speak,
with the condenser water. This loss is inherent in the
nature of the mechanism of the engine.
Suppose that the energy of the engine is employed
to drive a dynamo. The armature of the latter rotates
60 THE PHILOSOPHY OF BIOLOGY
against the constraint of powerful electro-magnets, and
in so doing a current of electricity is generated. By
the law of conservation this current should contain
as much energy as was put into the rotation of the
armature ; as a matter of fact it does not, and the
deficiency is represented by the friction of the parts
of the machine against each other, by imperfect con-
ductivity of electricity in the wires, and by imperfect
insulation of the current. Friction, imperfect con-
ductivity, and imperfect insulation all transform to
heat, and this radiates away. Suppose now that the
current is used for lighting purposes : to do this it
must heat the metallic filaments in the lamps, or the
points of the carbons in an arc. This heat then trans-
forms to light, but along with the light, which was
the object of the transformation, heat is produced,
and this heat radiates away.
The actual process in which the particular form
of energy required is generated may or may not be
reversible in theory. That employed in the steam-
engine is not, for if we start with a cold boiler and then
work the engine backwards we could not raise steam.
The process in the dynamo is theoretically reversible :
if we send a current of electricity into a dynamo the
machine will begin to rotate, and become a motor,
so that we can obtain mechanical work from it. Now
in theory all forms of energy are mutually convertible,
and all can be expressed in terms of a common unit.
The unit of mechanical energy is called the erg : let
a current, the energy of which is equal to N ergs, be
sent into the dynamo, then we ought to obtain from
the latter mechanical energy equal to A^ ergs. Con-
versely, if N ergs of mechanical energy be employed
to rotate the dynamo, we should obtain electrical
energy equal to this amount. Now as a matter of
THE ORGANISM AS A MECHANISM 61
fact we do not obtain these theoretical conversions,
for some of the electrical energy is dissipated when we
employ the machine as a motor, and some of the
mechanical energy is likewise dissipated when we
employ it as a dynamo.
The entity that we call energy is the product of
two factors, a capacity-factor and an intensity-factor.
Thus : —
Mechanical energy of water power = quantity of water x height at which it is
situated above the water-motor.
Energy of an electric current = quantity of electricity x electrical potential.
Chemical energy = equivalent weight of the substance x
chemical potential.
What is it that determines whether or not an
energy-transformation will occur ? It is the condition
that a difference of the intensity-factors of the energy
in different parts of a system exists. Water will flow
from a higher to a lower level, doing work as it flows,
if it is directed through a motor. Electricity will flow
if there is a difference of electrical potential. A
chemical reaction will occur if two substances before
interacting possess greater chemical potential than do
the products which may possibly be formed during
the interaction. Coal and oxygen possess greater
chemical potential than do carbon dioxide and water,
therefore they will combine, forming carbon dioxide
and water. Energy-transformations will therefore
occur wherever it is possible that differences of intensity
or potential can become abolished. The energy that
may thus flow from a condition of high to a condition
of low potential, undergoing a transformation as it
flows, is the available energy of the system of bodies
in which it is contained. A closed vessel surrounded
by an envelope impervious to heat, and containing a
mixture of oxygen and hydrogen, is an isolated system
62 THE PHILOSOPHY OF BIOLOGY
containing available energy. Let the mixture be
fired by an electric spark, and heat is evolved. The
total energy of the system is unaltered in amount, but
the available energy has disappeared, since the heated
water vapour is incapable of undergoing further trans-
formations while it forms part of its isolated system.^
All physical processes are therefore irreversible,
that is to say, proceed in one direction only. Either
a process is irreversible in the sense that it cannot
proceed both in the positive and negative directions
(a steam-engine, for instance), or it is irreversible
in the sense that while it proceeds the energy in-
volved in it becomes less capable of being transformed
into other conditions. (In the theoretically reversible
dynamo, energy becomes dissipated in the form of
heat.) The following statements may be regarded
as axioms - : —
(i) " If a system can undergo an irreversible change,
it will do so."
(2) "A perfectly reversible change cannot take
place by itself."
In the phenomena studied by physics we see only
^ It is really necessary to lay stress on the distinction between available
and unavailable energy, as it is one which many biologists appear to ignore.
Thus, a popular book on the making of the earth attempts to argue that
essential distinctions between living and inorganic matter are non-existent.
One of these distinctions is that organisms absorb energy, and this author
points to the absorption of " latent heat " by melting ice as an example of
the absorption of energy in a purely physical process. Consider a system
consisting of a block of ice and a small steam boiler. We can obtain work
from this by the melting of the ice — that is, its " absorption of latent heat."
The system, ice at 0° C.-l- steam at 100° C, possesses available energy, but the
system, melted ice + condensed steam, both at the same temperature, contains
none. The molecules of water at o" C. " absorb energy," that is to saj', their
kinetic energy becomes greater, but their available energy in the system has
disappeared. In saying that the organism absorbs energy, we mean, of
course, that it accumulates available energy, that is, the power of producing
physical transformations. (See further, appendix, p. 366.)
* Bryan, Thermodynamics : Teubner, Leipzig, 1907, p. 40.
THE ORGANISM AS A MECHANISM 63
irreversible changes. In all these processes energy
descends the incline, and some (considerable) fraction
of the amount involved passes into conditions in which
it is incapable of further transformation ; in all, energy-
becomes less and less available. Expressed in its most
technical form, the second law of thermodynamics
states that entropy tends continually to increase.
Every such process as we can study in physics " leaves
an indelible imprint somewhere or other on the progress
of events in the universe considered as a whole." ^
We cannot observe a truly isolated system. The
earth itself is part of the solar system, and the latter
receives energy from., and radiates it to the rest of, the
universe. Our only isolated system is the whole
universe. We must think of it, in so far as we regard
it as physical, as a finite system : if it is infinite,
our speculations become meaningless. The universe
therefore is a system in which energy tends continually
towards degradation. In every process that occurs
in it — that is to say every purely physical process —
heat is evolved, and this heat is distributed by conduc-
tion and radiation, and tends to become universally
diffused throughout all its parts. When this ultimate,
uniform distribution of energy will have been attained,
all physical phenomena will have ceased. It is useless
to argue that universal phenomena are cyclical. We
vainly invoke the speculations (founded on rather
prematurely developed cosmical physics) of stellar
collisions, light-radiation pressure, the distribution of
cosmic dust, etc. to support our notions of alternate
phases of dissipation and concentration of energy ;
close analysis will show that all these processes must
be irreversible. The picture physics exhibits to us is
that of the universe as a clock running down ; of an
^ Bryan, Thermodynamics, p. 195.
64 THE PHILOSOPHY OF BIOLOGY
ultimate extinction of all becoming ; an universal
physical death.
In this conclusion there is nothing that is specu-
lative. It is the least metaphysical of the great
generalisations of science. It represents simply
our experience of the direction in which physical
changes are proceeding. Based upon the most exact
methods of science known to us, nothing seems more
certain and more capable of rigorous mathematical
investigation.
And yet we are certain that it is not universally
true. For there must always have been an universe —
at least our intellect is incapable of conceiving begin-
ning. If we suppose a beginning, an unconditioned
creation, at once we leap from science into the rankest
of metaphysics. Holding, then, that the duration of
our physical universe is an infinite one, we see that the
ultimate attainment of energy — dissipation — must have
occurred if our physics is true. It does not matter
what new sources of energy modern investigation has
shown to us ; nor do the incredibly great lapses of
duration necessary for the depletion of these sources
matter. We have eternity to draw upon. Every-
where in the universe we see diversity and becoming.
Is then the whole problem a transcendental one, or is
the second law untrue ? We refuse to regard the
problem as insoluble, and we must think of the second
law as true of our physical experience only. But our
conception of the universe shows that it cannot be
true, and so we have to seek for an influence com-
pensatory to it.
If the organism is a mechanism of the physico-
chemical kind, it should therefore conform to the two
great principles of energetics established by the
physicists. Now there can be no doubt that the law of
THE ORGANISxM AS A MECHANISM 65
energy-conservation does apply to all the processes
observed in animals and plants. Let us consider the
" calorimetric experiments." An animal, together with
the food and oxygen supplied to it, and the various
substances excreted by it, constitutes a physical system.
This system can be approximately isolated so that no
heat enters it from outside, while the heat that leaves
it can be determined quantitatively. The animal is
made to perform mechanical work, and this is measured.
The energy- value of the food ingested by it, and that
of the excreta, can be estimated. All the physical
conditions can thus be controlled, and the results of
such experiments show that energy is conserved. The
energy contained in the food is greatly in excess of
the energy contained in the excreta, but the deficit is
quantitatively represented by the work done by the
animal, and by the heat lost in conduction and radiation
from its body. The difference between the observed
results and the theoretical ones are within the limits
of error of the experiment. The metabolism of the
animal as a whole, then, conforms to the law of con-
servation, and the general results of physiology all go
to show that this is also true of chemico-physical
changes considered in detail.
It cannot be shown that the second law, that of the
dissipation of energy, applies to the organism with all
the strictness in which it applies to purely physical
systems. If we consider only the warm-blooded
animal we do indeed find that its general metabolism
does proceed in one direction, and that irreversible
changes occur. In the mammal and bird we have
organisms which present a superficial resemblance to
the heat-engine, with respect to their chemico-physical
processes, a resemblance, however, which is rather an
analogy than an identity of processes. In the heat-
E
66 THE PHILOSOPHY OF BIOLOGY
engine we have (i) a mechanism of parts which do
not change in material and relationships to each other
(boiler, cylinder, pistons, cranks, slide-valves, etc.) ;
and (2) a working substance (the steam).
Energy in the form of the chemical potential of coal
and oxygen is supplied to the mechanism. The coal
is oxidised, producing heat. The heat then expands
the working substance (the water in the boiler), and
this working substance — now a gas at high tempera-
ture and pressure — propels the piston and confers
kinetic energy on the engine. Note the essential steps
in this process : substances of high chemical potential
(coal and oxygen) suffer transformation into substances
of low chemical potential (carbon dioxide and water),
and the difference of energy appears as high-tempera-
ture heat (increased kinetic energy of water molecules,
to be more precise). This heat is then transformed
into mechanical work (the kinetic energy of the mole-
cules of steam is imparted to the piston of the engine).
But in this transformation only a relatively small
proportion (10% to 20%) of the energy available
is transformed into mechanical work : the rest is
dissipated as irrecoverable low-temperature heat, by
radiation from boiler, steam-pipes, engine, and as the
heat which passes into the condenser water.
In the organism in general there is no distinction
between the fixed parts of the mechanism and the
working substance. The organism itself (its muscles,
nerves, glands, etc.) is the working substance. Further,
it is not quite certain that there is a necessary trans-
formation of chemical energy into heat. The source
of energy in the case of the warm-blooded animal is
the chemical energy of the food substances and oxygen
taken into its body. These chemical substances
undergo transformations in the alimentary canal and
THE ORGANISM AS A MECHANISM 67
in the metabolic tissues. The proteids of the food
are broken down into animo-substances in the aU-
mentary canal, and these animo-sabstances are
synthesised into the specific proteids of the animal's
body. Corresponding changes occur with the carbo-
hydrates and fats ingested. These rearrangem.ents of
the molecular structure of the foodstuffs are the
object of the processes of digestion and assimilation ;
and when they are concluded, a certain proportion of
the food taken into the body has become incorporated
with, or has actually become a part of, the living tissues
(muscles, nerves, etc.) of the animal body. This living
substance, compounds of high chemical potential
(proteids, carbohydrates, and fats) undergoes trans-
formation into compounds of low chemical potential
(water, carbon dioxide, and urea). There is a difference
of energy, and this appears as mechanical energy, as
the chemical energy required for glandular activity,
and as heat.
We must not, however, conclude that this heat of
the warm-blooded animal is comparable with the waste
heat of the steam-engine. The homoiothermic animal
maintains its body at a constant temperature, which is
usually higher than that of the medium in which it
lives, and this constancy of temperature obviously
confers many advantages. Chemical reactions proceed
with a velocity which varies with the temperature, so
that in the warm-blooded animal the processes of life
go on almost unaffected by changes in the medium.
The animal exhibits complete activity throughout all
the seasons of the year. It does not, or need not,
hibernate, and it can live in climates which are widely
different. We therefore find that the most widely-
distributed groups of land-animals are the warm-
blooded mammals and birds, while the largest and most
68 THE PHILOSOPHY OF BIOLOGY
cosmopolitan marine animals are the warm-blooded
whales. Heat-production in the mammals and birds
is therefore a direct object of the metabolism of the
animal ; it is a means whereby the latter acquires a
more complete mastery over its environment. That it
is not necessarily a step in the transformation of
chemical into mechanical energy we see by consider-
ing the metabolism of the cold-blooded animals. In
these poikilothermic organisms the body preserves
the temperature of the medium. The temperature in
such animals may be a degree, or a fraction of a degree,
higher than that of the environment, but, in the absence
of exact calorimetric experiments, we cannot say what
proportion of the energy of the food of these animals
passes into unav^ailable food energy. Probably it is
a very sm.all fraction of the whole, and we are thus
justified in saying that in the cold-blooded animal
chemical energy does not, to a significant extent,
become transformed into heat. The result is, of course,
that the vital processes in these organisms keep pace,
so to speak, with the temperature of the environment,
since the chemical reactions of their metabolism are
affected by the external temperature. We find there-
fore that hibernation, the formation of resting stages,
and a general slowing down of metabolic processes
are more characteristic of the cold-blooded animal
during the colder seasons than of the warm-blooded
animal. The former has not that mastery over the
environment attained by the mammal or bird.
The metabolism of the animal therefore resembles
the energy process of the heat-engine only in the
general way, that in both series of transformations
chemical energy descends from a condition of high
potential to a condition of low potential, transforming
into mechanical energy in so doing, and thus perform-
THE ORGANISM AS A MECHANISM 69
ing work. In the heat-engine chemical energy trans-
forms to heat, and then to mechanical energy, and of
the total quantity transformed a certain large pro-
portion supers dissipation by conversion into low-
temperature heat. In the animal organism chemical
energy transforms directly to mechanical energy with-
out passing through the phase of heat. If heat is
produced it is because it is, in a way, available energy,
inasmuch as it permits of the continuance of chemical
reactions at a normal rate. The analogy of the animal
with the heat-engine is therefore a false one. It
suggests oxidation of the food-stuffs and heat produc-
tion, whereas it is not at ail certain that any significant
proportion of the energy of the organism is the result
of oxidation : many animal organisms indeed function
in the entire absence of free oxygen. Further, the
proportion of energy dissipated is always small com-
pared with the heat-engine, and tends to vanish. The
second law of thermodynamics does not, then, restrict
the energ},'-transformations of the animal organism to
the same extent that it restricts the energy-transform-
ations of the physico-chemical mechanism.
The processes involved in the plant organism
differ still more in their direction from those of a
" purely physical " train. To see this clearly we must
consider the imaginary mechanism known as a Carnot
heat-engine."^ This is a system in which we have (i) a
heat-reservoir at a constant high temperature, (2) a
refrigerator at a constant low temperature, and (3) a
working substance which is a gas. Energy is drawn
from the reservoir in the form of heat, and this heat
expands the gas, doing work. The gas contracts, and
its heat is then given up to the refrigerator. The
work done is equal to the difference between the amount
1 See appendix, p. 363.
70 THE PHILOSOPHY OF BIOLOGY
of heat taken from the reservoir and the amount given
to the refrigerator.
This series of operations is called a direct Carnot
cycle. But the mechanism can be worked backwards.
In this case heat passes from the refrigerator into the
working substance, which was at a lower temperature.
The working substance, or gas, is then compressed,
as the result of which operation it is heated to just
above the temperature of the reservoir. The heat it
thus acquires is then given up to the reservoir.
In the direct Carnot cycle, therefore, energy passes
from a state of high potential to a state of low potential
and work is done hy the mechanism. In the reversed
Carnot cycle energy passes from a state of low potential
to a state of high potential and work is done on the
mechanism. The Carnot engine is thus perfectly
reversible. No energy is dissipated in its working.
It is, of course, a purely imaginary mechanism.
In the metabolism of the green plant carbon dioxide
and water are taken into the tissues of the leaf and
are transformed into starch. But the energy of the
compounds, carbon dioxide and water, is much less
than that of the same compounds when built up into
starch. Energy must therefore be derived from
some source, and this source is said to be the ether.
Solar radiation is absorbed by the green leaf, and this
energy is employed to produce the chemical trans-
formation. Just how this is effected we do not
positively know, in spite of much investigation. It
is possible that formaldehyde is formed from carbon
dioxide and water, polymerized, and then converted
into starch. It is possible that the absorbed electro-
magnetic vibrations are converted into electricity in
the chlorophyll bodies of the leaf, though when
radiation is absorbed in physical experiments it is
THE ORGANISM AS A MECHANISM 71
converted into heat. We do not know just what are
the steps in the transformation, though it is clear that
solar radiation is absorbed and that the chlorophyll of
the leaf is instrumental in converting this energy of
radiation into chemical potential energy. But the im-
portant thing to notice is, that we have here a process
closely analogous to that of a reversed Carnot engine.
Energy (that of the carbon dioxide and water) passes
from a state of low potential to a state of high potential
(that of the energy of starch) , and work is done on the
plant in producing this transformation.
Work is not done hy the green plant. This state-
ment is not, of course, quite rigidly true, for a certain
amount of mechanical work is done by the plant.
Flowers open and close ; tendrils may move and clasp
other objects ; there is a circulation of protoplasm in
the plant cells, and a circulation of sap in the vessels
of stems, etc. Also work is done against gravity in
raising the tissues of the plant above the soil, while
work is also done by the roots in penetrating the soil.
But when compared with the work done by radiation
in producing the chemical transformations referred
to above, these other expenditures of energy must be
insignificant. Speaking generally, then, we may describe
the green plant as a system in which available energy
is accumulated in the form of chemical compounds of
high potential. It is, further, a system in which energy
becomes transformed without doing mechanical work,
except to a trifling extent, and in which there is no
formation of heat, or at least in which the quantity of
heat dissipated is only perceptible during very re-
stricted phases, is relatively small during the other
phases, and tends to vanish.
Let us now combine the processes of plant and
animal ; we start with the latter. In it we have a
72 THE PHILOSOPHY OF BIOLOGY
mechanism which does work. The source of its
energy is the potential chemical energy of its food-
stuffs, which latter reduce down to those substances
known as proteids, fats, and carbohydrates. The
energy- value of these compounds is considerable, that
is to say, if they are burned in a stream of oxygen
a large quantity of heat is obtained from their com-
bustion. They are ingested by the animal, broken
down chemically, and rearranged. The proteids eaten
by the animal (say those of beef or mutton or vv^heat)
are acted upon by the enzymes of the alimentary canal
and are decomposed into their immediate constituents,
animo-acids, and then other enzymes rearrange these
animo-acids so as to form proteid again, but proteids
of the same kinds as those characteristic of the tissues.
This decomposition and re-synthesis is carried out also
with respect to the fats and carbohydrates ingested.
The result is that the food taken into the alimentary
canal, or at least a part of it, is built up into the living
substance of the animal's body. The energy expended
upon these processes of digestion and assimilation is
probably inconsiderable. During these processes the
animal absorbs available chemical energy.
The energy thus taken into the animal is then
transformed. The major part of it appears as mechani-
cal energy — that of bodily movement, the movements
of heart, lungs, blood, etc. — and heat. Some part of
it becomes nervous energy, by which rather vague term
we mean the energy involved in the propagation of
nervous impulses. Some of it is used in glandular
reactions, in the formation of the digestive juices, for
instance. The most of it, however, transforms to
mechanical energy and heat. Just how these energy
transformations are effected we do not know. The
heat is, of course, the result of chemical changes, oxida-
THE ORGANISM AS A MECHANISM 73
tions, decompositions, or changes of the same kind as
that of the dilution of sulphuric acid by water, but
the mechanical energy appears to result directly from
chemical change without the intermediation of heat.
We shall return to this point in a later chapter, and
content ourselves with saying here that the chemical
compounds contained in the metabolic tissues of the
animal bod}^ undergo transformation from a state of
high to a state of low chemical potential, and that this
difference of potential is represented by the work done
and the heat generated. The proteid, fat, and carbo-
hydrate of the tissues represent the condition of
high potential ; and the carbon dioxide, the water,
and the urea, into which these substances are trans-
formed, represent the condition of lov/ potential.
Let us suppose a Carnot heat-engine in which the
temperature of the reservoir of heat is (say) I20°C.,
and that of the refrigerator 5o°C. The heat of the
refrigerator can still be made a further source of energy
by constituting it the heat reservoir of another Carnot
engine which has a refrigerator at a temperature of
o°C. Our animal organism may be compared with a
Carnot cycle ; its energy reservoir is the proteid, fat,
and carbohydrate ingested, and its refrigerator (or
energy sink) is the carbon dioxide and urea excreted.
Now the urea of the higher mammal becomes infected
with certain bacteria, which convert it into ammonium
carbonate. Another species of bacteria converts the
ammonia into nitrite, and yet another turns the nitrite
into nitrate. The main process of the animal is there-
fore combined with several subsidiary ones.
74 THE PHILOSOPHY OF BIOLOGY
Carbohydrate, fat, proteid'\ Metabolism
break down into /of the animal
Carbon dioxide
Water
Urea Urea metabolism of
Chemical 4 / urea bacteria
Energy at passes into
high potential ammonium
carbonate ammonium j metabolism
carbonate \ of nitrifying
^ I bacteria
oxidises to
nitrite Nitrite \ Metm. of
ttrUe ^ Metm. o
■^ y nitrify-
oxidises | ing
to nitratej bacteria
V, chemical energy
at low potential
The arrows show that energy is descending the incline
indicated by a direct Camot cycle. There is no more
work to be obtained from the carbon dioxide and water
excreted by the mammal, but more work can be ob-
tained from the urea when it is used by bacteria, and
" ferments " to ammonia. Work can again be obtained
from the ammonia by bacteria, which convert it into
nitrite, and yet again from the nitrite by other bacteria,
which convert it into nitrate. The nitrate represents
the energy-zero so far as the organisms considered are
concerned.
Other nitrogenous residues are contained in the
urine of animals, and several other excretory products
may be formed. But in all these cases we can easily
find subsidiary energy-transformations effected by
bacteria, as in the above scheme. This, then, is the
positive, or direct half, of that reversible Carnot cycle
with which we are comparing life. In it energy falls
in potential (or intensity, or level), and in this fall of
potential transformations are produced — exhibit them-
selves, is perhaps a better way of putting it. We will
consider these transformations later ; in the meantime
THE ORGANISM AS A MECHANISM 75
it should be noted that in this fall of potential is a
degradation of chemical energy. Compounds, carbon
dioxide, water, and nitrate are produced which are
chemically inert. It is no use to sa}^ that carbon
dioxide may react with (say) glowing magnesium,
water with metallic sodium, and nitrate with (say)
glowing carbon. A condition of chemical equilibrium
would result from purely inorganic becoming on
our earth in which there was no metallic sodium or
magnesium or incandescent carbon ; in which the
metals would become inert oxides, and the carbon
would become dioxide. The formation of these com-
pounds represents a limit to energy-transformations.
Note also that all these energy-transformations are
conservative ; the total quantity remains unchanged
throughout, and is the same at the end as at
the beginning. But entropy has been augmented :
unavailable energy has increased at the expense of
available energy.
Consider now the indirect, or reversed, Carnot cycle.
We begin with the inert matter, resulting from the
metabolism of the animal, carbon dioxide, water,
nitrate, and a few more mineral substances. We have
the energy of solar radiation. By virtue of the living
chlorophyll plastid in the cells of the green plant, this
solar radiation uses the carbon dioxide and water as
raw materials in the elaboration of starch. At the same
time it absorbs nitrate, with some other inert mineral
substances from the soil, and takes these into its
tissues. The starch formed in the chlorophyll is
converted into soluble sugar, which circulates through
the vessels of the plant and is associated with the
nitrogenous salt in the elaboration of proteid. Proteid,
oils, fats and resins, and to a greater extent carbo-
hydrates, are thus built up by the plant and accumulate,
76 THE PHILOSOPHY OF BIOLOGY
for mechanical work is not done by it, nor is heat
dissipated — or at least these processes occur to an
insignificant extent.
are synthesised to —
(proteid
fat
carbohydrate
Carbon dioxide \ Metabolism
Water - of the green
Nitrate J plant
Chemical energy
at high potential.
Chemical energy at \\'ott "^ c^vste'D^
low potential
The " working substance " of our organic cycle has
therefore returned to its original state.
We have considered the process of metabolism
in two categories of organisms, the typical animal
and the green plant, and we have combined these so
as to obtain a picture of a reversible cycle of physico-
chemical processes. When w^e speak of the " organism "
in the most general sense, we mean that it exhibits
these two modes of metabolism. This is, of course,
not the case in any actual organism which we can
investigate, or at least the typical modes of be-
haviour which characterise animal and plant life
are not seen in any one individual. But we find that
there is no absolute distinction between the two
kingdoms. The plant may exhibit a mode of nutrition
closely resembling that of the animal (as in the
insectivorous plants), and it is possible that photo-
synthetic process, in the general sense, may be present
in the metabolism of some animals. Certain lower
plants, the zoospores of algae, exhibit movements
identical in character with those of lower animals.
At the base of both kingdoms are organisms, the
THE ORGANISM AS A MECHANISM 77
Peridinians, for instance, which have much of the
structure of tiie animal (though cellulose is present
in their skeleton), which possess motile organs, but
which also possess a photo-synthetic apparatus, and
exhibit the typical plant mode of nutrition. Further,
there are symbiotic partnerships, that is, associations
of plant and animal in one " individual " form (as,
for instance, among the lower worms, Echinoderms,
polyzoa, molluscs, and other groups of animals). In
these cases green algal cells, capable of forming starch
from carbon dioxide and water under the influence of
light, become intercalated among the tissues of the
animal. We find, also, that with regard to some
fundamental characters, plant and animal display
close similarities : the structure of the cell, for ex-
ample, and the highly special mode of conjugation
of the germ-nuclei in sexual reproduction. We must
regard all the distinctive characters of the plant as
represented in the animal and vice versa. Wh}'' they
have become specialised in different directions is a
question that we discuss later.
The organism, then, in so far as we regard it
as a physico-chemical mechanism, as the theatre of
energetic happenings, exhibits the following general
characters : —
(i) It slowly accumulates available energy in the
form of chemical compounds of high potential,
work being done upon it.
(2) It liberates this energy in relatively rapid, con-
trolled, " explosive reactions," transforming
into movements carried out by a sensori-
motor system of parts, work being done by it.
(3) In all these transformations the amount of
energy which is dissipated is relatively small,
and tends to vanish.
78 THE PHILOSOPHY OF BIOLOGY
From the point of view, then, of energetic processes
these are the characters of hfe, using the term in the
general sense indicated above. ^
Is there an absolute distinction between the organic
mechanism and the inorganic one ? Let us note, for
the first time, that the actual physico-chemical trans-
formations themselves, which we study in inorganic
matter, are identical with those which we study in the
organism. Molecules of carbon dioxide, water, nitrate,
sodium chloride, potassium chloride, phosphate, and
so on, are just the same in inert matter as in the
organism. Chemical transformations, such as the
hydrolysis of starch, the inversion of cane sugar, or
the splitting of a neutral fat, are certainly just the same
processes, whether v/e carry them out in the glass
vessels of the laboratory, or observe them to proceed
in the living tissues of the animal body. The same
molecular rearrangements, and the same transfers
of energy, occur in both series of events. This, however,
is not the material of a distinction : what we have to
find is, whether the direction of a group of physico-
chemical reactions is the same in the organism and in
a series of inorganic processes.
Let us return to the Carnot cycle. This is a series
of operations which occur in an imaginary mechanism
in such a manner that the whole series can be easilj^
reversed. Heat is supplied to the imaginary engine,
which then performs work and yields up its heat to a
refrigerator. Work is then performed on the engine,
which thereupon takes heat from the refrigerator and
returns it to the source. The work done hy the engine
in the direct cycle is equal to the work done on it in
^ This is, of course, the argument of part of Chapter II. of Bergson's Creative
Evolution. The reader will not find the essential differences between plants
and animals stated so clearly anywhere else in biological literature.
THE ORGANISM AS A MECHANISM 79
the indirect cycle. The heat taken from the source
and given to the refrigerator in the direct cycle is
equal to the heat taken from the refrigerator and given
to the source in the indirect cycle. But it is a purely
imaginary mechanism, and all experience shows not
only that it has not been realised in practice, but that
it cannot so be realised. If it could be realised, we
should show that the second law of thermo-dynamics
is not physically true.
Do the energy processes of life realise such a
perfectly reversible cycle of operations ? In order to
answer this question we must consider the fate of the
energy which is absorbed in the plant metabolic cycle,
and that which is given out in the animal one. Does
all the energy of solar radiation which is absorbed by
the plant pass into the form of the potential chemical
energy of the carbohydrates and other substances
manufactured ? Does any of the energy of the animal
which results from the metabolism of its body pass
into the unavailable form — that is, into a form in which
it cannot be utilised by other organisms ? That is to
say, is energy dissipated by the organism ?
Undoubtedly it is to some extent, but to a far less
extent than in the inorganic train of processes. Some
of the energy of solar radiation absorbed by the plant
must become transformed, by the friction of whatever
movements occur, into low-temperature heat, and
some quantity of heat, however small, is generated by
the metabolism of the plant. Again, some of the heat
of the warm-blooded animal must be radiated into
space, or conducted away from its body ; and this
energy becomes dissipated — let us assume, at least,
that it is so dissipated in the physical sense. Probably
also some quantity of heat is generated by the meta-
bolism of the cold-blooded animal, though this must
80 THE PHILOSOPHY OF BIOLOGY
be a very small proportion of the total energy trans-
formed. We see, then, that the distinction is one of
degree, though the difference between inorganic and
organic energetic processes is very great in this respect ;
so great that we must regard it as constituting a funda-
mental difference, and as indicative of the limitation
of the second law when extended to the functioning
of the organism.
But we have also to consider the effect of the work
done by the organism. We consider the nature and
meaning of the evolutionary process in a later chapter,
but in the meantime we may state this thesis : that
the process of evolution leads up to man and his
activity. It leads, if we regard the process as a directed
one ; but even if we regard it as a fortuitous process
we still find that man, far more than any other organism,
is the result of it. All the facts of biology and history
show that man dominates the organic world, plant or
animal ; that the whole trend of his activity is to
eliminate whatever organisms are inimical, and to
foster those that are useful. Already, during the brief
period of his rational activity, the wolf has disappeared
from civilised lands while the dog has been produced.
Species after species of hostile or harmful organisms
have been, or are being, destroyed or changed, while
numerous other species have been preserved and
altered for his benefit. In the future we see an organic
world subservient to him either entirely or to an
enormous extent.
So also in the inorganic world. Rivers which
formerly rushed down through rapids, dissipating
their energy of movement in waste irrecoverable heat,
now pour through turbines and water wheels, generating
electricity and accumulating available energy. Winds
which " naturally " dissipated their mechanical energy
THE ORGANISM AS A MECHANISM 81
in waste heat now propel ships and windmills. Tides,
with their incredibly great mechanical energy, now
simply warm up the crust of the earth by an infini-
tesimal fraction of a degree daily, and produce heat
which at once radiates into space. Who doubts that
by and by this energy too will become accumulated
for human use ? Multitudes of chemical reactions
were potential, so to speak, in the molecules of
petroleum, while the energy which might have pro-
duced them ran to waste. But under human activity
this energy became directed and made to produce
chemical reactions formerly existing only in their
possibilit3^ and ail the substances of modem organic
chemistry came into existence.
The energ}^ then, of human activity has been directed
towards averting or retarding the progress towards
dissipation, or irrecoverable waste, of cosmic energy —
that of the sun's radiation, and of the motions of
earth and moon. Human activity has accumulated
available energy. The difference of water-level
between Niagara and the rapids below represents
available mechanical energy. A few years ago an
enormous quantity of this energy became irredeemably
lost in waste heat every twenty-four hours : now it
remains available for work ; and this quantity of work
retained is enormously greater than is the human
energy which was expended on erecting the water-
power installation there.
The processes studied by physics and chemistry
are therefore irreversible ones. We can conceive a
perfectly reversible process, as in the Carnot heat-
engine, but this is a purely intellectual conception,
formed as the limit to a series of operations which
approximate closer and closer to an ideal reversibility.
It is a conception that has no physical reality — a
82 THE PHILOSOPHY OF BIOLOGY
guide to reasoning only. On the other hand we see
that all naturally occurring physical processes are
irreversible and in their sum tend to complete degrad-
ation of energy. Mechanistic biology isolates physico-
chemical processes in the functioning of the organism,
and sees that they conform to the law of dissipation,
as well as to that of the conservation of energy.
Yet the organism as a whole, that is, life as a whole,
on the earth, does not conform to the law of dissipation.
That which is true of the isolated processes into which
physiology decomposes life is not true of life. In all
inorganic happenings energy becomes unavailable for
the performance of v/ork. Solar radiation falling on
sea and land fritters itself away in waste irrecoverable
heat, but falling on the green plant accumulates in the
form of available chemical energy. The total result
of life on the earth in the past has been the accumula-
tion of enormous stores of energy in the shape of
coal and other substances. By its agency degradation
has been retarded. Whenever, says Bergson, energy
descends the incline indicated by Camot's law, and
where a cause of inverse direction can retard the
descent, there we have life.
CHAPTER III
THE ACTIVITIES OF THE ORGANISM
The rather lengthy discussion of the last chapter was
necessary in order to show just how far the principles
of energetics established by the physicists applied to
the organism. We have seen that the first law of
thermodynamics does so apply with all its exclusive-
ness. The more carefully a physiological experiment
is made ; the more closely do its results correspond
with those which theorv demands. It is true that
relatively few experimental investigations can be
controlled in this way, but in those that can be checked
by calculation (as, for instance, in the well-known
calorimetric experiments) everything tends to show
that precisely the same quantities of matter and
energy enter the body of an organism in the form of
food-stuff, that leave it as radiated and conducted
heat, as work done, and as the potential chemical
energy of the excretions. Even when we are unable
(as in most investigations) to apply the test of corre-
spondence with theory, we have the conviction that the
law of conservation holds with all its strictness.
Then, whenever it was possible to apply the
methods of chemistry and physics to the study of the
organism, it was seen that the processes at work were
chemical and physical. The substance of the living
body was seen to consist of a large (though limited)
number of chemical compounds, differing mainly
8S
84 THE PHILOSOPHY OF BIOLOGY
from those which exist in inorganic nature in their
greater complexity. It was also seen that physico-
chemical reactions occurred in living substance ana-
logous with, or quite similar to, those which could be
studied in non-living substance. The conclusion, then,
was irresistible that the life of the organism was merely
a phase in the evolution of matter and energy, and
differed in no essential respect from the physico-
chemical activities that could be observed in the non-
living world.
These conclusions were stated so well by Huxley
in his famous lecture on " The physical basis of life,"
over forty years ago, that all subsequent utterances
have been merely reiterations of this thesis in a less
perfect form. The existence of the matter of life,
Huxley said, depended on the pre-existence of cer-
tain chemical compounds — carbonic acid, water, and
ammonia. Withdraw any one of them from the world
and vital phenomena come to an end. They are the
antecedents of vegetable protoplasm, just as the latter
is the antecedent of animal protoplasm. They are all
lifeless substances, but when brought together under
certain conditions they give rise to the complex body
called protoplasm ; and this protoplasm exhibits the
phenomena of life. There is no apparent break in the
series of increasingly complex compounds between
water, carbon dioxide, and ammonia, on the one hand,
and protoplasm on the other. We decide to call
differen tkinds of matter carbon, oxygen, hydrogen,
and nitrogen and to speak of their activities as their
physico-chemical properties. Why, then, should we
speak otherwise of the activities of the substance
protoplasm ?
" When hydrogen and oxygen are mixed in certain
proportions and an electric spark is passed through
THE ACTIVITIES OF THE ORGANISM 85
them they disappear, and a quantity of water, equal
in weight to the sum of their weights, appears in their
place. There is not the slightest parity between the
passive and active powers of the water and those of
the oxygen and hydrogen that have given rise to it.
. . . We call these and many other phenomena, the
properties of water, and we do not hesitate to believe
that in some way they result from the properties of
the component elements of the w^ater. We do not
assume that a something called " aquosity " entered
into and took possession of the oxide of hydrogen as
soon as it was formed and guided the aqueous particles
to their places in the facets of the crystal, or among
the leaflets of the hoar frost."
" Is the case in any way changed when carbonic
acid, water, and ammonia disappear, and in their place,
under the influence of pre-existing protoplasm, an
equivalent weight of the matter cf life makes its
appearance ? "
" It is true that there is no sort of parity between
the properties of the components and the properties of
the resultant. But neither was there in the case of
water. It is also true that the influence of pre-existing
protoplasm is something quite unintelligible. But
does anyone quite understand the modus operandi of
an electric spark which traverses a mixture of oxygen
and hydrogen ? What justification is there, then, for
the assumption of the existence in the living matter
of a something which has no representative or correla-
tive in the non-living matter which gave rise to it ? "
All the investigations of over forty years leave
nothing to be added to this statement of what, in
Huxley's days, was called materialistic biolog;^^ It
was a very unpopular statement to make then, but it
has become rather fashionable now. Let the reader
86 THE PHILOSOPHY OF BIOLOGY
compare it with all that has been spoken and written
since 1869, even with the utterances of the British
Association of the year 1912, and he will find that it
expresses the point of view of mechanistic biology far
better than all the subsequent restatements. The
only difference he wall find is that the latter have
become (as William James has said about academic
philosophies), rather shop-soiled. They have been
reached down and shown so often to the enquiring
public, that each display has taken away something
of their freshness.
Now Huxley's example leads up so well to the
consideration of the differences between the chemical
activities of the organ-
ism and those of in-
organic matter that we
may consider it in some
Fig. 8. detail. What, then, is
the difference between
the explosion of a mixture of oxygen and hydrogen,
and the photo-synthesis of starch by the green plant ?
In the case of the synthesis of water we have an
example of an exothermic chemical reaction. We are
to think of the mixture of oxygen and hydrogen as
existing in a condition of " false equilibrium." It
may be compared with a weight resting on an inclined
plane.
Suppose that the plane is a sheet of smoothly
polished glass, and that the weight is a smooth block of
glass. By canting the plane more and more an angle will
be found at which the slightest push starts the weight
sliding down. Now in the case of the explosive mixture
of oxygen and hydrogen we have a chemical analogue.
Either the gases do not combine at all at the ordinary
temperature or they combine " infinitely slowly."
THE ACTIVITIES OF THE ORGANISM 87
But the slightest impulse, an electric spark requiring
an almost infinitesimally small quantity of energy,
starts the combination of the gases, and this continues
until all is changed into water vapour. In this reaction
a large quantity of energy is liberated in the form of
heat. This heat becomes transformed into the kinetic
energy of the water particles which condense from the
steam formed in the explosion, and these particles
assume the temperature of their surroundings. The
energy which was potential in the explosive mixture,
and which was capable of doing work, still exists as
the kinetic energy of the water formed, but it has
become unavailable for any natural process of work.
We have seen what is the general character of the
reaction series in the course of which carbon dioxide
and water become starch ; and then this, becoming
first soluble, and becoming associated with the ammonia
or nitrate taken into the plant, becomes protoplasm.
It is a reaction which differs from that just described,
in that available energy becomes absorbed and
accumulated, and retains the power of doing work.
It is not a reaction which can be initiated by an in-
finitesimal stimulus, but one in which just as much
energy is required in order that it may happen as is
represented in the energy'' which becomes potential in
the living substance generated. The first reaction
is one which may take place by itself ; ^ the other is
one which requires a compensatory energy-transform-
ation in order that it may happen. In the first
reaction energy is dissipated ; in the second one it
is accumulated.
^ It is no use saying that apart from the electric spark the combination
would not take place, for we do not know that the O and H of the mixture
do not combine very slowly, molecule by molecule, so to speak. At all events
there is no functionality between the infinitesimal quantity of energy supplied
by the spark, and the energy which becomes kinetic in the explosion.
88 THE PHILOSOPHY OF BIOLOGY
We are thus led to the consideration of the second
principle of energetics and its limitations, but before
entering upon this discussion we must consider the
nature of the activities of the organism.
By the term " metabolism " we understand the
totality of the physico-chemical changes which occur
in the living substance of the organism. In physio-
logical writings we usually find that two categories
of metabolic changes are described : (i) anabolic
processes, in the course of which simple chemical
compounds possessing relatively little energy are built
up into much more complex substances, containing
a relatively large quantity of available energy, and
therefore capable of doing work. The transformations
constituting an anabolic change must be accompanied
by corresponding compensatory energy-transform-
ations, to account for the energy which becomes
potential in the substances formed. The formation
of starch from carbon dioxide and water, by the green
plant, is such an anabolic change, and the compensatory
energy-transformation is ttie absorption of radiation
from the ether by the cells of the plant. A further
anabolic change in the plant organism is the formation
of amido-substances from the ammonia or nitrate
absorbed from the soil, and from the soluble carbo-
hydrates formed from the starch manufactured in the
green cells.
The typical activities of the chlorophyll-containing
organism are of this nature ; they are anabolic. The
organism may be a green land-plant ; a marine green,
red, or brown alga ; a yellow-green diatomx, a yellow,
green, red, or brown peridinian or other holophytic
protozoan ; an ascidian, mollusc, echinoderm, polyzoan,
worm, or coral containing " symbiotic algae " (that
is the chlorophyll - containing cells of some plant
THE ACTIVITIES OF THE ORGANISM 89
organism which have become associated with the
animal and incorporated in its tissues). In all these
cases the presence of this chlorophyllian substance
confers on the organism the power of effecting the
compensatory energy-transformation, by the aid of
which carbon dioxide and water are iDuilt up into
starch. What this transformation is, and what are
the steps by which the carbon dioxide and water be-
come carbohydrate we do not exactly know. Solar
radiation impinging upon an inorganic substance is
partly reflected and partly absorbed. The absorbed
fraction may become transformed in such a way as to
render the substance phosphorescent, or it may trans-
form into chemical energy, as when light impinges on
a photographic plate, but as a general rule it is trans-
formed into heat. In the green plant, however, the
transformation of radiation into heat does not occur —
at least the heating is very small — and it passes directly
or indirectly into the potential chemical energy of the
starch which is synthesised. We must regard this
power of absorbing radiation and utilising it in com-
pensatory transformations as a general character of
protoplasm. It is true that it is now specialised in
the cells containing the chlorophyll bodies, but there
are indications that it may be present in the tissues
of the animal devoid of chlorophyll.
Other anabolic transformations occur in the animal.
The food-stuffs which are absorbed from the intestine
are substances which have undergone dissociations,
the nature of which is such as to render them capable
of absorption and of reconstruction. These anabolic
changes in the higher animal are exceptional, and their
usefulness lies in the fact that by their means substances
become capable of being transported by the tissue
fluids of the body.
90 THE PHILOSOPHY OF BIOLOGY
(2) Kataboiic changes in the animal body corre-
spond in their frequency of occurrence to the anabohc
changes of the plant organism. In them complex
chemical substances undergo transformation into
relatively simple substances, and the contained energy
at the same time undergoes a parallel transformation,
passing into the form of heat and mechanical energy,
while a fraction becomes dissipated. Food-stuffs taken
into the alimentary canal break down in this way, but
to a very limited extent. Proteids undergo dissoc-
iation or decomposition into amido-substances, while
fats are dissociated into fatty acids and glycerine.
Doubtless energy is dissipated in these processes,
serving no other purpose but to heat the contents of
the ahmentary canal, but this energy -transformation
has not been v/orked out very completely and it is a
question whether, given a healthy animal and perfect
food-stuffs, any energy would necessarily be lost
during the digestive processes. The reactions involved
in the latter do not belong to the category of chemical
changes proceeding from the complex to the simple,
with a liberation of energy ; but appear to involve
rather a rearrangement of the constituents of a com-
plex molecule, a process in which the contained energy
need not undergo change in quantity. These processes
involve the action of enzymes.
Enzymes play a great part in modern physiological
theory and we must consider them in detail. Let us
attach a concrete meaning to the general notion of
enzyme-activity by considering the phenomena known
as catalysis. The metal platinum can be brought
into a very fine stage of division when it is known as
platinum black. In this condition it brings about
reactions in chemical mixtures or substances which
would not otherwise occur : a mixture of oxygen and
THE ACTIVITIES OF THE ORGANISM 91
hydrogen explodes when brought in contact with
platinum black, and a mixture of coal gas and air
inflames, a reaction which is made use of in the little
gas-lighting apparatus which most people have seen.
If, again, a powerful electric current be passed between
platinum wires which are a little distance apart, and
are immersed in water, the metal becomes torn away
from the points of the wire in the form of an impalpable
powder, colloidal platinum. The liquid containing
this colloid then has the power of setting up chemical
changes in other substances, changes which would
not otherwise occur, or, at least, would occur very
slowly.
In general such catalysts, platinum black or
colloidal platinum for instance, have the following
characters : (i) a small quantity is sufficient to cause
change in a large (theoretically an infinite) quantity
of the substance acted upon ; (2) the nature and
quantity of the catalyst remain at the end the same,
as at the beginning of the reaction ; (3) a catalyst does
not start a reaction in any other substance or sub-
stances, it can only influence the rate at which this
reaction may occur : apparently it does, in some
cases, start a reaction, but in such cases we suppose
that the latter proceeds so slowly as to be imper-
ceptible ; (4) the final state of the reaction is not
affected by the catalyst ; it depends only on the nature
of the interacting substance or substances ; (5) the
final state is not affected either by the nature or
quantity of the catalyst : it is the same if we employ/
different catalysts, or a large or small quantity of the
same catalyst. Finally, it appears that the phenomena
of catalysis are universal : " There is probably no kind
of chemical reaction," says Ostwald, " which cannot
be influenced catalytically, and there is no substance,
92 THE PHILOSOPHY OF BIOLOGY
element, or compound which cannot act as a
catalyser." ^
Enzymes, then, are agents which are produced by
the organism, and which act by influencing (accelerat-
ing or retarding) chemical reactions. An enzyme, as
such, need not exist in a tissue ; it is there as a zymogen,
a substance which may become an enzyme when
required. An enzyme need not be active : it may be
necessary that it should be " activated " by a kinase,
another substance produced at the same time. Asso-
ciated with many enzymes are anti-enzymes, substances
which undo what their corresponding enzymes have
done. Finally some, perhaps most, enzymes are re-
versible, that is, if they produce a change in a certain
substance they can also produce the opposite kind of
change : the meaning of this will become clearer a
little later on. We have spoken of enzymes as
" agents " or " substances," but it is not at all certain
that they are definite chemical compounds. In the
preparation of an enzyme what the bio-chemist obtains
is a liquid, a glycerine or other extract which possesses
catalytic properties. An actual catalytic substance,
like platinum black, cannot be obtained from this
liquid. A white powder may be obtained, but this
usually proves to be proteid in composition ; it is not
the actual enzyme itself but is the impurity associated
with the latter. Now the very great number of
enzymes " isolated " by the physiologists has rather
destroyed the original simplicity of the idea of enzyme
activity and suggests a parallel statement to that made
by Ostwald about catalysts : any tissue substance
may influence the reactions that may possibly occur in
^ A statement of interest in view of the enormous number of " ferments "
or enzymes discovered by physiologists. It would appear that any tissue in
any organism is capable of yielding an enzyme to modern investigation.
THE ACTIVITIES OF THE ORGANISM 93
other tissue substances. But while pure chemistry
has to deal with definitely known chemical compounds
in the phenomena of catalysis, this cannot be said to
be the case wdth physiology in dealing with enzymes.
Reasoning by analogy, we may say that it is probable
that enzymes are definite proteids, or chemical sub-
stances allied to these, but this has not been clearly
demonstrated, and it is possible that the phenomena
of enzyme activity may belong to some other category
of energy-transformations.
However this may be, the conception is a useful
one in describing the reactions of the organism, and
it may be illustrated by considering the digestion and
absorption of fat in the mammalian intestine, a process
which appears to be better known than that of proteid
digestion. A neutral fat consists of an acid radicle,
oleic, palmitic or stearic acids, for instance, united
with glycerine. The action of the pancreatic or
intestinal enzymes is to dissociate this fatty salt. Let
us write the formula of the latter as G F, G being the
glycerine base, and F the fatty acid ; then
G F ^ G + F
which means that the enzyme can cause the neutral
fat to dissociate into glycerine and fatty acid. This
action will go on until a state of equilibrium is attained,
in which there is a certain quantity of each of the
radicles, and a certain quantity of unchanged neutral
fat, the ratio of all these to each other depending on
various things. When this state of equilibrium is
attained the enzyme does indeed go on splitting up
more neutral fat, but it is a reversible enzyme, and it
also causes the glycerine and fatty acid already split
up to recombine, forming neutral fat. A condition is^
94 THE PHILOSOPHY OF BIOLOGY
therefore, reached in which the composition of the
mixture remains constant.
Now there is dissociated fat in the intestine after a
meal, but there is only neutral fat in the wall of the
intestine. The fat itself cannot pass through the cells
forming the intestinal wall, but the glycerine and fatty
acid into which it is dissociated can so pass, since they
are soluble in the liquids of the intestine. We suppose
that the cells of the wall of the intestine also contain
the fat-splitting ferment ; this ferment in the cells
acts on the glycerine and fatty acid immediately they
enter and recombines these radicles again into neutral
fat, the above equation now reading from right to left.
But after a time this reaction in the cells will also
begin to reverse, for the enzyme will begin to split up
the synthesised neutral fat when the state of chemical
equilibrium in the new conditions is attained. Fatty
acid and glycerine will then diffuse out from the cells
into the adjacent lymph stream or blood stream —
perhaps neutral fat will also pass from the cells into
these liquids, we are not sure. At all events the lymph
and blood after a meal containing much fat are crowded
with minute fat globules. But why are there no fatty
acids or glycerine in the blood, for the latter also con-
tains lipase (the fat-splitting enzj^me)? The explan-
ation is, apparently, that either an anti-enzyme is pro-
duced, or that the enzyme passes into a zymoid con-
dition. Why also does fat accumulate in the tissues ?
Here, again, the activity of the enzyme, which from
other considerations we may regard as being universally
present almost everywhere in the body, must be
supposed to be arrested by some means.
The conception of a catalytic agent, such as we can
study in pure chemistry, thus carries us a long way
in our description of the processes of digestion, absorp-
THE ACTIVITIES OF THE ORGANISM 95
tion, and assimilation. We have applied it to the case
of fat-digestion, but very much the same general
scheme might also apply to many other processes in
the body. Obviously it enables us to describe these
processes in terms of physico-chemical reactions, but
we cannot fail to see that ultimately we are compelled
to assume the existence of reactions which were not
included in the original conception — the activation
of the enzyme at the proper moment by the kinase,
the operation of the anti-enzyme, and the passage of
the enzyme into the zymoid. Just why these things
happen as they do we do not know, yet the whole
problem becomes shifted on to these reactions.
In the same way we appl}^ the purely physical
processes of the osmosis and diffusion of liquids to the
circulation of substances in the animal body. The
nature of these processes will probably be familiar
to the reader, nevertheless it may be useful to remind
him that by diffusion we understand the passage of a
liquid, containing some substance in solution, through
a membrane ; and by osmosis the passage of a solvent
(but not of the substance dissolved in it) through a
" semi-permeable membrane." The molecules of the
solvent (water, for instance) pass through the membrane
(the wall of a capillary, or lymphatic vessel), but the
molecules of the substance (salt, for instance) dis-
solved in the solvent do not pass. Let us suppose that
a strong solution of common salt in water is injected
into the blood stream : what happens is that osmosis
takes place, the water in the surrounding lymph spaces
passing into the blood stream because the concen-
tration of salt there is greater than it is in the lymph.
While this is happening, the capillary walls are acting
as semi-permeable membranes, allowing the molecules
of water to pass through but not the molecules of salt.
96
THE PHILOSOPHY OF BIOLOGY
Very soon, however, the process of osmosis becomes
succeeded by one of diffusion, and the salt molecules
pass through the capillary wall into the lymph and
are excreted.
Undoubtedly the purely physical processes of
diffusion and osmosis occur all over the animal body
and are the means whereby food-materials, secretory,
and excretory substances are transported from blood
to lymph, or vice versa, from lymph to cell substance
or to glandular cavities, and so on. But it is also the
case that in very many processes the activity of the cells
NervelS.
(jland
Fig 9.
themselves plays an important part. It may even be
the case that a particular process, after all physical
agencies are taken into account, reduces down to this
action of the cells. To understand this we must con-
sider the mode of working of some well-knowTi organ,
and the best possible example of such an organ, con-
sidered as a mechanism, is that of the sub-maxillary
salivary gland of the mammal.
What, then, is this mechanism and how does it act ?
The gland is a compound tubular one, its internal
cavity being prolonged into the duct which opens into
the mouth. The saliva prepared in the gland issues
from this duct. Blood is carried to the gland by twigs
of the facial artery, and, after circulating through it.
THE ACTIVITIES OF THE ORGANISM 97
is carried away by factors of the jugular vein. Two
nerves supply the gland : one is the chorda tympani,
a branch of a cranial nerve, and the other is a sym-
pathetic nerve. Lymph also leaves the gland by a
little vessel.
Now suppose we have laid bare all this mechanism
in a living animal and make experiments upon it.
If we stimulate the chorda tj^mpani there is a copious
flow of thin watery saliva, but if we stimulate the
sympathetic there is a less copious flow of thick viscid
saliva. Why is this ? We find on closer analysis
that the chorda contains fibres which dilate the small
arteries so that there is an increased flow of blood
through the gland ; but that, on the other hand, the
sympathetic contains fibres which constrict the
arteries, thus leading to a reduced flow of blood. This
accounts for the fact that " chorda-saliva " is abundant
and thin, while " sympathetic-saliva " is scarce and
thick. It was thought at one time that the chorda
contained fibres which stimulated the gland to produce
watery saliva, while the sympathetic contained fibres
which stimulated it to produce mucid saliva. This,
however, is not the case. Both nerves contain the
same kind of secretory fibres : their other fibres differ
mainly in that they act differently on the arteries.
It might be the case — indeed it was at one time
thought that it was the case — that secretion of saliva
was simply a matter of blood-flow : an abundant
arterial circulation gave rise to abundant saliva, a
sparse flow to a sparse saliva. Undoubtedl}^ the
secretion depends on blood supply, but not solely.
If it did, then the whole process might be conceived to
be a very simple mechanical one — filtration or diffusion
of the saliva from the blood stream through the thin
walls of the blood vessels, and the walls of the tubules
98 THE PHILOSOPHY OF BIOLOGY
into the cavity of the gland. If this were the case,
then the Uquid in the gland would be the same in com-
position and concentration as the liquid part of the
blood — the plasma. But it is really different in com-
position and it is not so concentrated. Now osmotic
pressure — on the action of which so much is based —
cannot help us, for the liquid in the gland is less con-
centrated than that in the blood vessels, so that water
ought to pass from gland to blood instead of from blood
into gland. Again, if we tie the duct, so that the saliva
cannot escape, secretion still goes on, though the hydro-
static pressure of saliva in the cavity of the gland may
be considerably greater than that of the liquid in the
blood vessels. Yet again, if we stop the blood flow by
tying the artery, secretion of saliva may still go on
for a time.
Therefore the only physical agencies we can think
of do not explain the secretion. The latter is actually
the work of the individual cells, stimulated by the
nerves. If the volume of the gland be measured just
while it is being stimulated to secrete, it will be found
that the organ becomes smaller, yet while it is being
stimulated the blood-vessels are being dilated so that
the volume of the whole structure ought to become
greater. Obviously part of the substance of the gland
is being emptied out through its duct as the secretion.
If we examine the cells of the gland in various
states we see clearly that granules of some material,
different in nature from the substance of the proto-
plasm itself, are being formed within them. Evidently
these granules swell up during secretion and discharge
their contents into the ducts. Further changes in the
characters of the cell-substance, and in the nucleus,
can be observed, and all these indicate that the proto-
plasm of the cells, as the result of stimulation, elaborates
THE ACTIVITIES OF THE ORGANISM 99
certain substances ; that these substances are then
washed out, so to speak, into the duct by the withdrawal
of water from the cell ; and that thereafter the cell
absorbs fresh nutritive material from the lymph which
exudes from the blood vessels, along with water.
The distinctive part of the whole train of processes is,
then, this elaboration of material by the cells them-
selves ; while the concomitant changes in the calibre
of the blood vessels and in the flow of blood and lymph
are subsidiary ones. In the process of secretion of
saliva energy is absorbed from the chemical substances
of the blood to bring about the passage of water from
a region of high to a region of low osmotic pressure ;
oxygen and nitrogen, with other elements of course,
are withdrawn from the arterial blood stream for the
purpose of the secretion, and carbon dioxide and other
substances are given off to the venous blood and
lymph.
The problem thus is pushed back from the mechani-
cal events occurring in the nervous and circulatory pro-
cesses, to the physico-chemical ones occurring in the
cells of the gland tubules ; and it thus becomes much
more obscure. It is true that we can formulate a
hypothesis which describes, in a kind of way, these
intra-cellular metabolic changes, in terms of physico-
chemical reactions, and, without doubt, reactions of
this kind must occur within the cell. But if we could
test any such hypothesis as easily as the mechanical
ones suggested, should we find it any more self-
sufficient ? 1
^ We have not referred to " psychical secretion." If we smell some very-
savoury substance our " mouth waters," that is, secretion of saliva occurs.
If we even see some such substance the same secretion occurs. All this is
clear and can be " explained " mechanistically : the stimulation of the
olfactory or visual organs begins a kind of reflex process. But if we even
think about some very savoury morsel saliva may be secreted. We must
100 THE PHILOSOPHY OF BIOLOGY
Irritability and contractility are general pro-
perties of the organism. These properties are illus-
trated by the irritability of an Amceba or Paramoecium
to stimuli of many kinds ; by the movements of the
pseudopodia of the former animal, or of the cilia of
the latter ; by the nervous irritability of the higher
animal, and the contraction of its muscles when they
are stimulated. They are among the fundamental
properties or functions of living protoplasm, and their
study is of paramount interest, and carries us to the
very centre of the problem of the activities of the
organism. Naturally physiologists have never ceased
to attempt to describe irritability and contractility in
terms of physics, but though we ma^^ be quite certain
that the things that do occur in these phenomena are
controlled physico-chemical reactions, it must be re-
membered that what we positively know about their
precise nature is exceedingly little.
What is the nature of a nervous impulse ? When
a receptor organ is stimulated, as, for instance, when
light impinges on the cone cells of the retina, or when
the nerve-endings in a " heat-spot " in the skin are
warmed, or when the wires conveying an electric
current are laid on a naked nerve, an impulse is set
up in the nerve proceeding from the place stimulated,,
and we must suppose that approximately the same
amount of energy moves along the nerve as was com-
municated to the receptor or the nerve itself bj^ a
stimulus of minimal strength. How does it so move ?
suppose now that our consciousness, something which has nothing to do, it
must be noted, with energy — changes in the body, can react on the body. If
we show a dog an attractive bone it will secrete saliva; if we show it again
and again, the same thing occurs. But after certain such trials the dog will
realise that he is being played with, and the exhibition of the bone no longer
evokes a flow of secretion. Why is this ? The whole process has now become
more mysterious than ever.
THE ACTIVITIES OF THE ORGANISM 101
Several facts of capital importance result from the
experimental work, (i) The impulse travels with a
velocity variable within certain limits, say from 8
to 30 metres per second ; (2) it travels faster if the
temperature is raised (up to a certain limit) ; (3) it is
difficult to demonstrate that the passage of this impulse
is accompanied by definite chemical changes in the nerve
substance : it is stated that carbon dioxide is produced,
but this is not certainly proved ; (4) an electric
current is produced in the nerve as the result of stimula-
tion ; (5) no heat is produced, or at least the rise of
temperature, if it occurs, is less than 0.0002° C.
Thus it is quite certain that physical changes
accompany the propagation of the nerve-impulse, for
the latter has a certain velocity, which depends on the
temperature, and an electric change also occurs in the
substance of the nerve. Is this electric change the
actual nerve impulse ? It is hardly likely, since the
velocity of the impulse is very much less than that
of the propagation of an electric change through a
conductor ; besides, the passage of the impulse is not
accompanied by a measurable heat evolution, although
the flow of electricity along a poor conductor must
generate heat and dissipate energy. Is it a chemical
change ? Then we should be able to observe meta-
bolism in the nerve substance — that is if the energy-
change is a thermodynamic one — w^hile it is not at all
certain that metabolic changes do occur. Nevertheless
it seems probable that a physico-chemical change is
actually propagated when we consider the chemical
specialisation of the substance of the axis-cylinder of
the nerve. Now the velocity of propagation of the
nervous impulse is of the same order of magnitude
as that of an explosive change in chemical substances
{using the term " explosion " to connote chemical
102 THE PHILOSOPHY OF BIOLOGY
disintegrations rather than combustions). If we
imagine a long rod of dynamite, or picric acid, or a long
strand of loosely-packed gun-cotton to be exploded by
percussion at one end, then a transmission of the
chemical disintegration of any of these substances will
pass along the rod, etc., with a velocity which will
certainly vary with the physical condition of the
material. It would be a high velocity in a rod of
dynamite, or fused picric acid, but a lower velocity
in a loosely aggregated strand of gun-cotton, or a
trail of picric acid powder. Is this what happens in
the nerve when an impulse travels along it ? Ob-
viously not, since the substance of the nerve is not
altered appreciably, while that of the explosive sub-
stance passes into other chemical phases. We might
imagine, then, such a change in the nerve fibrils as that
of a reversible transformation of some chemical con-
stituent : —
(2)
(I)
: a+b : a+b
: c + d : c + d
a + b
H
c + d
a + b
c + d
a + b:
: H :
c + d :
Let us imagine the substance of the fibril to be composed
of, or at least to contain, the substances a+b which
dissociate reversibly into the substances c+d. At any
moment, and in any particular physical state, as much
of a and b pass into c and d diS c and d pass into a and
b. There will be equilibrium. But now let a stimulus
alter the physical conditions : prior to the stimulus
the phase was a„, + ^» = Cp + d, — the suffixes m, n, p, r,
denoting the concentrations of a, b, c, and d — but after
the stimulus the phase may be rt„,i + 6„i=Cpi + ^,.i. Now
the element of the nerve substance (i) forms a system
THE ACTIVITIES OF THE ORGANISM 103
with the element (2). The condition in (2) is fl,„ + &^ =
Cp + d,, and that of (i) a„^v + h„i^Cpi + d,x, but these
two together now fall into a new state of equilibrium
and this is transmitted along the whole nerve-fibril
with a velocity which belongs to the order of magni-
tude of that of chemical changes. If the stimulus
remains constant (a constant electric current for in-
stance), the new condition of equilibrium will be
established throughout the whole length of the fibril
and the nervous impulse will be a momentary one
(as it is in this case). But if the stimulus is an inter-
mittent one (an interrupted electric current, light-
vibration, sound- vibrations), then in the intervals the
former condition of equilibrium will become re-estab-
lished and the nervous impulse will be intermittent
(as it is). There would be no work done on the whole
in the changes, except that done by the transmission
of the changed state of equilibrium to the substance
of the effector organ in which the nerve-fibril terminates
— the substance of a muscle fibre, or the cell of a
secretory gland, for instances. There would, prob-
ably, be a certain dissipation of energy as in the case
of the propagation of an electric impulse through a
poor conductor, but all our knowledge of the chemistry
of the nerve fibre points to this amount of dissipation
as tending to vanish.
Something analogous to this may be expected to
take place in a muscle fibre when it contracts ; except
that, of course, energy is transformed in this case.
What precisely does happen we do not know and at
the present time no physico-chemical hypothesis of
the nature of muscular contraction exactly describes
all that can be observed to take place. Certain
positive results have, of course, been obtained by
chemical and physical investigation of the contracting
104 THE PHILOSOPHY OF BIOLOGY
muscle : carbon dioxide is given off to the lymph
and blood stream, and the amount of this is increased
when an increased amount of work is done by the
muscle ; heat is produced and this too increases with
the work performed ; glycogen is used up, and lactic
acid is produced ; finally oxygen is required, and more
oxygen is required by an actively contracting muscle
than by a quiescent one. Now the obvious hypothesis
correlating all these facts is that the muscle substance
is oxidised, and that the heat so produced is trans-
formed into mechanical energy. " We must assume,"
says a recent book on physiology, " that there is some
mechanism in the muscle by means of which the energy
liberated during the mechanical change is utilised in
causing movement, somewhat in the same way as the
heat energy developed in a gas-engine is converted
by a mechanism into mechanical movement."
Now, must we assume anything of the kind ? To
begin wdth, life goes on, and mechanical energy is pro-
duced in many organisms living in a medium which
contains no oxygen. Anaerobic organisms are fairly
well known, and we cannot suppose that in them
energy is generated by the combustion of tissue sub-
stance in the inspired oxygen. A muscle removed
from a cold-blooded anim.al will continue to contract
in an atmosphere containing no oxygen, and it will
continue to produce carbon dioxide. It is true that
the contractions soon cease, even after continued stimu-
lation under conditions excluding the fatigue of the
muscle, but do the contractions cease because the
oxygen supply is cut off, or because the muscle dies
in these conditions ? We know that some complex
chemical substance is disintegrated during contraction
and that mechanical energy and heat are produced and
that carbon dioxide is also produced. We know that
THE ACTIVITIES OF THE ORGANISM 105
the carbon contained in the latter gas corresponds
roughly with the carbon contained in the muscle sub-
stance which undergoes disintegration, but does all
this justify us in saying that this substance is oxidised
in order that its potential chemical energy may be
transformed into mechanical energy ? Obviously
not, since we might equally well suppose that the
complex metabolic substance of the muscle splits
down into simpler substances and that in this trans-
formation energy is generated. Suppose that these
simpler substances are poisonous and that they must
be removed as rapidly as formed. The role of the
oxygen may be to oxidise them, thus transforming
them into carbon dioxide, an innocuous substance
which can be carried away quickly in the blood stream.
This line of thought, according to which the role of
oxygen is an anti-poisonous one, is held at the present
day by some physiologists, and many considerations
appear to support it ; the existence of " oxidases,"
for instance, enzymes which produce oxidations which
would not otherwise occur in their absence. Such
enzymes exist in very many tissues, and they may,
apparently, be present in an inactive form, requiring
the agency of a " kinase " before they are able to act.
The usual view among physiologists is that the
muscle fibre is a thermodynamic apparatus transform-
ing the heat generated during metabolism into
mechanical energy. How is this transformation
effected ? It cannot be said that we have any one
hypothesis more convincing than another. It has
been suggested that alterations of surface tension play
a part, or that the heat produced by oxidation causes
the fibre to imbibe water and shorten. Engelmann
has devised an artificial muscle consisting of a catgut
string and an electrical current passing through a coil
106 THE PHILOSOPHY OF BIOLOGY
of wire, and by means of this he has reproduced the
phenomena of simple contraction and tetanus. But it
remains for future investigation to verify any one of
these hypotheses.
When Huxley published his Physical Basis of Life,
probably few physiologists had any doubt that proto-
plasm was a definite chemical substance, differing from
other organic substances only by its much greater
complexity. But in 1880 Reinke and Rodewald
published the results of an analysis of the substance of
a plant protoplasm and these appear to have demon-
strated that the substance was really a mixture of a
number of true chemical compounds and was not
a single definite one. Now all of these substances
might exist apart from protoplasm, and in the lifeless
form, and a simple mixture of them could hardly bring
forth vital reactions. These results were followed by
the morphological study of the cell — the discovery of
the architecture of the nucleus, and so on, and so
opinion began to turn to the hypothesis that the
vital manifestations of protoplasm were the result of
its structure. Microscopical examination of the cell
appeared to disclose a definite arrangement, the " foam "
or " froth " of Butschli, for instance. But, again, it
was easity shown that the foam, or alveolar structure
of protoplasm was merely the expression of physical
differences in the substances composing the cell-
stuff — they reduced to phenomena of surface tension
and the like. Artificial protoplasm and artificial
AmoehcB were made — at least mixtures of olive oil and
various other substances were made which simulated
many of the phenomena of protoplasm in much the
same way as crystalline products may be made which
simulate the growth of a plant stem with its branches.
For instance, one has only to shake up a little soapy
THE ACTIVITIES OF THE ORGANISM 107
water in a flask to see what resembles surprisingly
the arrangement of certain kinds of connective tissues
in the organism. Obviously these artificial phenomena
have nothing to do with living substance.
Yet if we grind up a living muscle with some sand
in a mortar we do destroy something. The muscle
could be made to contract, but after disintegration this
power is lost. We have certainly destroyed a structure,
or mechanism, of some kind. But, again, the paste of
muscle substance and sand still possesses some kind
of vital activity, for with certain precautions it can be
made to exhibit many of the phenomena of enzyme
activity displayed by the intact muscle fibres, or even
the entire organism. Mechanical disintegration, there-
fore, abolishes some of the activities of the organism,
but not all of them. If, however, we heat the muscle
paste above a certain temperature, the residue of vital
phenomena exhibited by it are irreversibly removed,
so that heating destroys the mechanism. This we can
hardly imagine to be the case (within ordinary limits
of temperature at least) \vith a physical mechanism,
but again a mechanism which is partly chemical might
be so destroyed. We see, then, that protoplasm
possesses a mechanical structure, but that all of its
vital activities do not necessarily depend on this
structure. The full manifestation of these activities
depends on the protoplasmic substance possessing a
certain volume or mass, and also on a certain chemical
structure.
If living protoplasm has a structure, and is not
simply a mixture of chemical compounds, what is it
then ? Two or three physico-chemical concepts are
at the present time very much in evidence in this
connection. When the substances known as colloids
were fully investigated by the chemists, much attention
108 THE PHILOSOPHY OF BIOLOGY
was paid to them by the physiologists, so that Hfe was
called " the chemistry of the colloids," just as after the
investigation of the enzymes it was called the
" chemistr}^ of the enzymes," and when the discovery
of the relative abundance of phosphorus in cell-nuclei
and in the brain was discovered, it was called the
" chemistry of phosphorus." Colloids (e.g. glue) are
substances that do not readily diffuse through certain
membranes, in opposition to crystalloids {e.g. solution
of common salt) which do readily so diffuse. They
form solutions which easily gelatinise reversibly, that
is, can become liquid again (glue) ; or coagulate
irreversibly, that is, cannot become liquid again
(albumen) ; which have no definite saturation point ;
which have a low osmotic pressure (and derived pro-
perties), etc. ; and the molecules of which are com-
pound ones consisting of combinations of the molecules
of the substance with the molecules of the solvent,
or with each other, that is, they are molecular aggre-
gates.
Colloids pass insensibly into crystalloids on the one
hand and into coarse suspensions (water shaken up
with fine mud, for instance) on the other. We may
replace the concept of a colloid by those of " sus-
pensoids " and " emulsoids." A suspensoid is a liquid
containing particles in a fine state of division — if the
division is that into the separate molecules we have a
solution, if into large aggregates of molecules we have
a suspension. If the substance in the liquid is itself
liquid, the whole is called an emulsoid. On the one
hand this approaches to a mixture of oil in soap and
water — an emulsion — and on the other hand to such
a mixture as chloroform shaken up with water, when
the drops of chloroform readily join together so that
two layers of liquid (chloroform and water) form.
THE ACTIVITIES OF THE ORGANISM 109
What we see, then, in protoplasm is a viscid substance
possessing a structure of some kind, and containing
specialised protoplasmic bodies in its mass (nuclei,
nucleoli, granules of various kinds, chlorophyll, and
other plastids, etc.). It may contain or exhibit
suspensoid or emulsoid parts or substances, or it may
contain truly crystalloid solutions. These phases of
its constituents are not fixed, but pass into each other
during its activity. Nothing that we know about it
justifies us in speaking about a " living chemical sub-
stance." On analysis we find that it is a mixture
of true chemical substances rather than a substance.
It is no use saying that in order to analyse it we must
kill it, for what we can observe in it without destroying
its structure or activities indicates that it is chemically
heterogeneous.
This is not a textbook of general physiology, and
the examples of physico-chemical reactions in the
organism which we have selected have been quoted
in order to show to what extent the chemical and
physical methods applied by the physiologists have
succeeded in resolving the activities of the organism.
The question for our consideration is this : do these
results of physico-chemical analysis fully describe
organic functioning ? Dogmatic mechanism says
" yes " without equivocation.
Now it is clear, from even the few typical examples
that we have quoted, that physiological analysis shows,
indeed, a resolution of the activities of the organism
into chemical and physical reactions. How could it
do otherwise ? How could chemical and physical
methods of investigation yield anything else than
chemical and physical results ? The fact that these
methods can be applied to the study of the organism
with consistent results shows that their application
110 THE PHILOSOPHY OF BIOLOGY
is valid ; that we are justified in seeing physico-chemical
activities in life. But are these results all that we have
reason to expect ?
We turn now to Bergson's fertile comparison of
the physiological analysis of the organism with the
action of a cinematograph. If we take a series of
photographic snapshots of, e.g., a trotting horse and
then superpose these pictures upon each other, we
produce all the semblance of the co-ordinated motions
of the limbs of the animal. Yet all that is contained
in the simulated motion is immobility. From a suc-
cession of static conditions we appear to produce a
flux. Yet if we could contract our duration of, e.g.,
a week, into that corresponding to five minutes — if
we could speed up our perceptual activity — should
we not see the cinematographic pictures as they really
are — a series of immovable postures and nothing more :
truly an illusion ? If, again, we reverse the direction
of motion of the film, we integrate our snapshots
into something which is absolutely different from the
reality which they at first represented ; and by such
devices the illusions and paradoxical effects of the
picture-house farces are made possible. Well, then,
in the physiological analysis of the activity of the
organism do we not do something very analogous to
this ? The complexity of even the simplest function
of the animal is such that we can only attend to one
or two aspects of it at once, arbitrarily neglecting all
the rest. We find that the hydrostatic pressure of
blood, and lymph, and secretion, the osmotic pressure,
the diffusibility, vaso-motor actions, and other things
must be investigated when considering the question
of how the submaxillary gland secretes saliva. One,
or as many as possible, of these reactions are in-
vestigated at one time, and then the results are pieced
THE ACTIVITIES OF THE ORGANISM
111
together — integrated — in order to reproduce the full
activity of the whole indivisible process. But in doing
this do we not introduce something new — a direction
or order of happening — into the elements of the dis-
sociated activity of the organism ? Each elemental
process must occur at just the right time.
What right have we to say that the activity of the
organism is made up of physico-chemical elements ?
Just as much as we have in saying that a curve is
made up of infini-
tesimal straight ^'
lines. Let us
adopt Bergson's
illustration, with
a non - essential
modification.
The curve i-8
is a line which
we draw freehand
with a single in-
divisible motion
of the hand and fjg. lo.
arm and eye. It
is something unique and individualised, in that no
other curve ever drawn, in a similar manner, exactly
resembles it. Let us investigate it mathematically.
We can select very small portions of it — elements
we may call them — and each of these elements, if it
is small enough does not differ sensibly from a straight
line. Let us produce each of these straight lines in
both directions, it is then a tangent to the curve, and
it does actually coincide wdth the curve at one mathe-
matical point — the points i-8 in the figure. The
tangent then has something in common with the curve,
but would a series of infinitesimally small tangents
112 THE PHILOSOPHY OF BIOLOGY
reproduce the curve ? Obviously not, for the equa-
tions of the tangents would have the form ax + hy
while that of the curve itself would be quite different,
containing x as powers of x, or as transcendental
functions of x. In this investigation what we succeed
in obtaining are the derivatives of the curve, and
to reproduce the latter from its elements we have to
integrate the derivatives ; that is, another operation
differing in kind from our analytical one must be per-
formed. Now in this illustration we have doubtless
something more than an analogy with our physico-
chemical analysis of life. The activities of the organsim
do reduce to bio-chemical ones (the elemental straight
lines on the curve), and each of these reactions has
something in common with life (it is tangent to life,
touching it at one point). But if we attempt to
reconstitute life from its physico-chemical derivatives
we must integrate the latter, and in doing so we over-
pass the bounds of physics, just as integrating a mathe-
matical function we necessarily introduce the concept
of the " infinitely small."
The physico-chemical reactions into which we
dissociate any vital function of the organism have^
then, each of them, something in common with the
vital function. But their mere sum is not the function.
To reproduce the latter we have to effect a co-ordination
and give directions to these reactions. In all physio-
logical investigations we proceed a certain length with
perfect success ; thus the elements, so to speak, of
the function of the secretion of saliva are (i) the blood-
pressure, (2) the hydrostatic pressure of the secretion
in the lumina of the gland tubules, (3) the diffus-
bility of the substances dissolved in the blood and
lymph through the walls of these vessels, (4) the
osmotic pressure of the same substances, and (5) the
THE ACTIVITIES OF THE ORGANISM 113
stimulation of the gland cells by " secretory nerve
fires." Now the investigations carried out — and no
part of the physiology of the mammal has been so
patiently studied as the salivary gland — fail, so far,
completely to describe the function in terms of these
elements. In the end we have to refer the secretion
to intra-cellular processes, and then we begin to invoke
again processes of osmotic pressure, diffusibility, and
so on with reference to the formation of the drops of
secretion which we can see formed in the gland cells.
We are forced to the formulation of a logical hypo-
thesis as to the nature of these intra-cellular processes,
and since much that goes on in the cell substance
is, so far, beyond physico-chemical investigation, our
hypothesis will be as difficult to disprove as to verify.
Let us return now to Huxley's comparison of the
activity of the green plant with the chemical reaction
which occurs when an electric spark is passed through
a mixture of oxygen and hydrogen. The lecture on
the '' Physical Basis of Life " was published in i86g ;
in 1852 William Thomson published his paper " On
a Universal Tendency of Nature to Dissipation of
Energy," and a year or two before that Clausius had
applied Camot's law to the kinetic theory of heat :
the second principle of energetics had therefore even
then been exactly formulated, but its significance for
biological speculation had not been recognised by
Huxley, any more than it has generally been recog-
nised by most biologists since 1869. What, then, does
the comparison of Huxley show ? Clearly that the
physical changes which occur in the explosion of a
mixture of oxygen and hydrogen trend in a different
direction from those which occur in the photo-synthesis
114 THE PHILOSOPHY OF BIOLOGY
of starch by a green plant. Generally speaking,
chemical activity, that is, the possibility of occurrence
of chemical reactions, is a case of the second law of
energetics. Energy passes from a state of high to
a state of low potential. A chemical reaction will
occur if this change of potential is possible.
In all such changes energy is dissipated. What
exactly does this mean ? It means that, generally
speaking, the potential energy of chemical compounds
tends to transform into kinetic energy ; while differ-
ences in the intensity factor of the kinetic energy of
the bodies forming a system tend to become minimal.
In a mixture of oxygen and hydrogen there is energy
of two kinds, (i) potential energy due to the position
of the molecules (O and H molecules are separated) ;
and (2) kinetic energy of the molecules (which are
moving about in the masses of gas) . After. the explosion
the potential energy acquired in the separation of the
molecules of O and H has disappeared (the molecules
having combined to form water), but the kinetic
energy has greatly increased, since the explosion
results in the formation of steam at high temperature.
But now this steam radiates off heat to adjacent
bodies, or becomes cooled by direct contact with the
envelope which contains it. The energy of the explo-
sion is therefore distributed to the adjoining bodies,
and the temperature of the latter becomes raised.
But these again radiate and conduct heat to other
bodies, and in this way the heat generated becomes
indefinitely diffused.
The general effect of all physico-chemical changes
is therefore the generation of heat, and then this heat
tends to distribute itself throughout the whole system
of bodies in which the physico-chemical changes occur.
The energy passes into the state of kinetic energy,
THE ACTIVITIES OF THE ORGANISM 115
that is, the motion of the molecules of the bodies to
which the heat is communicated. This molecular
motion is least in solids, greater in liquids, and greatest
in gases. If solids, liquids, and gases are in contact,
forming complex systems, the kinetic energy of their
molecules becomes distributed in definite ways, depend-
ing on the constants of the systems. After this re-
distribution the kinetic energy of these molecules is
unavailable for further energy transformations, so that
phenomena or change in the system ceases. There is
no longer effective physical diversity among the parts
of the system.
We find that this conception of dissipation of
energy cannot be applied to the organism, at least not
with the generality in which it applies to physical
systems. Why ? Not because the conception is un-
sound, or because the physico-chemical reactions that
occur in material of the organism are of a different
order from those that occur in inorganic systems — they
are of the same order. The second law of energetics
is subject to limitations, and it is because it is applied
to organic happenings without regard to these limn-
tations that it does not describe the activities of the
organism as well as it describes those of inorganic
nature.
What, then, are these limitations ? We note in
the first place that the laws of thermodynamics apply
to bodies of a certain range of size ; or at least the
possibility of mathematical investigation (on which,
of course, all depends) is limited to " differential ele-
ments " of mass, energy, and time. We cannot apply
mathematical analysis to bodies, or time-intervals of
" finite size," since the methods of the differential
and integral calculus would not strictly be applicable.
But molecules are so small (i cubic centimetre of a gas
116
THE PHILOSOPHY OF BIOLOGY
WMMM^^^M
i
»AK-JPM»
may contain about 5.4 xio^^ of them) that even such
a minute part of a body, or Hquid, or gas as approxi-
mates to the infinitesimally small dimensions required
by the calculus, contains an enormous number of
molecules.
Obviously we cannot investigate the individual
molecules. Even if experimental methods could be
so applied, such concepts as density, pressure, volume,
or temperature would have no meaning. Physics,
then, is based on collections of molecules, and the pro-
perties of a body are not those of a molecule of the same
body. Such concepts as temperature and pressure
are statistical ones, and
are applied to the mean
properties of a large
number of molecules.
We can best illus-
trate this by consider-
ing Maxwell's famous
Fig. II. fiction of the " sorting
demons." Let us im-
agine a mass of gas contained in a vessel the walls
of which do not conduct heat. Let there be a par-
tition in this vessel also of non-conducting material,
and let there be an aperture in this partition greater
in area than a molecule, but smaller than the mean
free path of a molecule. Now this mass of gas
has a certain temperature which is proportional
to the mean velocity of movement of the molecules.
The second law says that heat cannot pass from a
cold region in a system to a hot region without
work being done on the system from outside, nor can
an inequality of temperature be produced in a mass
of gas or liquid except under a similar condition. But
*' conceive a being," says Maxwell, " whose faculties
W0'4/m^^/^^^^' ■i-->^'' ■■■■-
J^^^**
I
THE ACTIVITIES OF THE ORGANISM 117
are so sharpened that he can follow every molecule in
its course ; such a being, whose attributes are still as
essentially finite as our own, would be able to do what
is at present impossible to us." ^ For the temperature
of the gas depends on the velocities of the molecules,
and in any part of the gas these velocities are very
different. Suppose that the demon saw a molecule
approach which was moving at a much greater velocity
than the mean : he would then open the door in the
aperture and let it pass through from - to +. On
the other hand, should a molecule moving at a velocity
much less than the mean approach he would let it
pass from + to - . In this way he would sort out
molecules of high from those of low velocity. But
the collisions between the molecules in either division
of the vessel would continually produce diversity of
individual velocity, and in this way the difference of
temperature between + and - would continually be
increased. Heat would thus flow from a region of
low to a region of high temperature without an equi-
valent amount of work being expended.
Now we must not introduce demonology into
science, so, lest this fiction of Maxwell's should savour
of mysticism, or something equally repugnant, we
shall state the idea involved in it in quite unexception-
able terms. The conclusions of physics are founded
on the assumption that we cannot control the motions
of individual molecules. In a mass of gas, or liquid,
or in a solid, the molecules are free to move and do
move. Their individual velocities and free paths vary
considerably from each other. These motions and
paths are un-co-ordinated — " helter-skelter " — if we
^ Impossible, in the sense that while we are unable to " abrogate " a
physical law. Maxwell's finite demon could, although his faculties were similar
in nature to ours.
118 THE PHILOSOPHY OF BIOLOGY
like so to term them. Physics considers only the
statistical mean velocities and free paths. The irre-
versibility of physical phenomena, the fact that energy
tends to dissipate itself, the second law of thermo-
dynamics, depend on the assumption that Maxwell's
demons exist onl}'^ in imagination. We must appeal
to experience now. There is no a priori reason why
the phenomena of physics should be directed one way
and not the other, for it is possible to conceive a con-
dition of our Universe in which, for instance, solid
iron would fuse when exposed to the atmosphere. In
such conditions organisms would grow backwards from
old age to birth, with conscious knowledge of the future
but no recollections of the past. Experience shov>rs,
however, that phenomena do tend in one way — hut this
experience is that of experimental physics, so that for
the latter science Maxwell's demons do not exist. Now
physiology has borrowed from physics, not only the
experimental methods, but also the fundamental con-
cepts of thermodynamics. The organism, therefore (so
physiology must conclude) , cannot control the motions
of individual molecules, and so vital processes are
irreversible. But we have seen that the processes
of terrestrial life as a whole are reversible, or tend to
reversibility. We must therefore seek for evidence
that the organism can control the, otherwise, un-co-
ordinated motions of the individual molecules.
The Brownian movement of very small particles
of matter is so familiar to the biologist that we need
not describe it. It is doubtless due to the impact of
the molecules of the liquid in which the particles are
suspended. Groups of molecules travelling at velocities
above the mean hit the particle now on one side, and
again on the other, and so produce the peculiar
trembling which Brown thought was life. Now the
THE ACTIVITIES OF THE ORGANISM 119
particle must be below a certain size in order to
be so affected. Are there organisms of this size?
Undoubtedly there are, for many baciUi show Brown-
ian movements, while we have reasons for believing
that ultra-microscopic organisms exist. Also, on the
mechanistic hypothesis there are " biophors," the size
of which is of the same order as that of the molecules
of the more complex organic compounds. All these
must be affected by the molecular impacts of the
liquid in which they are suspended. Can they dis-
tinguish between the impacts of high- velocity molecules
and those of mean-velocity ones, and can they utilise
the surplus energy of the former ? This has been sug-
gested by the physicists. In Brownian movement,
says Poincare, "we can almost see Maxwell's demons
at work."
The suggestion is not merely a speculative one, for
it is well within the region of expeiiment. To prove
it experimentally we should only have to show that
the temperature of a heat-insulated culture of proto-
trophic bacteria falls while the organisms multiply.
Is it not strange that the biologists, to whom the
Brownian movement is so familiar, should have failed
to see its possibly enormous significance ? Is it not
strange that the biologists, to whom the distinction
between the statistical and individual methods of
investigation is so familiar, should have failed to
appreciate this distinction when it was made by the
physicists ? Is it not strange that while we see that
most of our human effort is that of directing natural
agencies and energies into paths which they would not
otherwise take, we should yet have failed to think of
primitive organisms, or even of the tissue elements in
the bodies of the higher organisms, as possessing also
this power of directing physico-chemical processes ?
CHAPTER IV
THE VITAL IMPETUS
Two main conclusions emerge from the discussions of
the last three chapters : (i) that physiology encourages
no notions as to a " vital principle " or force, or form
of energy peculiar to the organism ; and (2) that
although physiological analysis resolves the meta-
bolism of the plant and animal body into physico-
chemical reactions, yet the direction taken by these
is not that taken by corresponding reactions occurring
in inorganic materials. From these two main con-
clusions we have, therefore, to construct a conception
of the organism which shall be other than that of a
physico-chemical mechanism.
The ordinary person, unacquainted with the results
of physiological analysis, and knowing only the general
modes of functioning of the human organism, has,
probably, no doubt at all that it is " animated " by a
principle or agency which has no counterpart in the
inorganic world. This is the " natural " conclusion,
and the other one, that life is only an affair of physics
and chemistry, must appear altogether fanciful to any-
one who knows no more than that the heart propels the
blood, that the latter is " purified " in the lungs, that
the stomach and liver secrete substances which digest
the food, and so on. It is difhcult for the modern
student of biology, saturated with notions of bio-
chemical activities, gels and sols and colloids and
120
THE VITAL IMPETUS 121
reversible enzymes and kinases and the like, to realise
that the belief in a vital agency is an intuitive one,
and that the mechanistic conception of life is only
the result of the extension to biology of methods of
investigation, and not a legitimate conclusion from
their results.
To the anatomist, the embryologist, and the natu-
ralist, as well as to the physicist unacquainted with
the details of physiology, no less than to the ordinary
person this is perhaps by far the most general attitude
of mind. It would probably be impossible for anyone
to study only organic form and habits and come to
any other conclusion than that there was something
immanent in the organism entirely different from the
agencies which, for instance, shape continents, or
deltas, or river valleys. And this conclusion would
probably come with still greater force to the embryo-
logist, even though he still possessed a general know-
ledge of physiological science.
The mechanistic conception of life has, without
doubt, been the result of the success of a method of
analysis. One sees clearly that just in proportion as
physical and chemical sciences have been most prolific
of discovery, so physiology, leaning upon them and
borrowing their methods, has been most progressive
and mechanistic.
Mechanistic hypotheses of the organism may all
be traced back to Descartes, who built upon the work
of Galileo and Harvey. The anatomy of Vesalius and
his successors would have led to no such notions, had
not the discoveries of Copernicus, Tycho, and Kepler
shown men an universe actuated by mechanical law.
To a thinker like Descartes, at once the very type
of philosopher and man of science, Harvey's discovery
of the circulation of the blood must have suggested
122 THE PHILOSOPHY OF BIOLOGY
irresistibly the extension of mechanical law to the
functioning of the human organism, and it is significant
that he made this extension without including a single
chemical idea, and yet produced a logical hypothesis
of life as satisfactory and complete in its day as, for
instance, the Weisrnannian hypothesis of heredity has
been in ours.
His hypothesis of the organism was purely mech-
anical. It has been said that his organism was an
automaton, like the mechanical Diana of the palace
gardens which hid among the rose-bushes when the
foot of a prying stranger pressed upon the springs
hidden in the ground. Its functions were matters of
hydraulics : of heat, and fluids, and valves. His physi-
ology was Galenic, apart from Harvey's discovery of
the motion of the blood in a circuit, for he did not
accept the notion of the heart as a propulsive apparatus.
The food of the intestine was absorbed as chyle by the
blood and carried to the liver, where it became endued
with the " natural spirits," and then passing to the
heart it became charged with the " vital spirits " by
virtue of the flame, or innate heat, of the heart, and
the action of the lungs. This flame of the heart, fed
by the natural spirits, expanded and rarefied the blood,
and the expansion of the fluid produced a motion,
which, directed by the valves of the heart and great
vessels, became the circulation. The more rarefied
parts of the blood ascended to the brain, and there, in
the ventricles, became the " animal spirits."
Subtle and rarefied though they were, these animal
spirits were a fluid, amenable to all the laws of hydro-
dynamics. This was contained in the cerebral ven-
tricles, and its flow was regulated just like the water
in the pipes and fountains of the garden mechanisms.
From the brain it flowed through the nerves, which
THE VITAL IMPETUS 123
were delicate tubes in communication with the
ventricles, and which were provided with valves ; and
this outward flow corresponds to our modem efferent
nervous impulse. The afferent impulse was represented
by the action of the axial threads contained in the
nerve tubuli. When a sensory surface was stimulated,
these threads became pulled, and the pull, acting on
the wall of the cerebral ventricle, caused a valve to
open and allowed animal spirits to flow along the
nerve to all the parts of the body supplied by the
latter. In the effector organs, muscles or glands, this
influx of animal spirits produced motion or other
effects. This, in brief, was the physiology of Descartes.
He spoiled it, says Huxley, by his conception of
the "rational soul." Fearing the fate of Galileo, he
introduced the soul into his philosophy of the organism
as a sop to the Cerberus of the Church. It was un-
worthy : a sacrifice of the truth which he saw clearly.
Is it likely that Descartes deliberately made part of
his philosophy antagonistic to the rest with the object
of averting the censure of the Church ? He was not
a man likely to rush upon disaster, but the conviction
that what he wTote had in it something great and
lasting must have made it hardly possible that he
should traffic with what he held to be the truth.
The rational soul was something superadded to
the bodily mechanism. It was not a part of the body
though it was placed in the pineal gland ; a part of
the brain, which by its sequestered situation and rich
blood supply suggested itself as the seat of some
important and mysterious function. Its existence
was bound up v/ith the integrity of the body, and on
the death of the latter the soul departed. But the body
did not die because the soul quitted it, it had rather
become an unfit habitation for the soul. Without
124 THE PHILOSOPHY OF BIOLOGY
the latter the functions of the healthy body might
still proceed automatically, and if the soul influenced
action it actuated an existing mechanism, and without
that mechanism it could not act, though the mechanism
might act without the soul. Thought, understanding,
feeling, will, imagination, memory, these were the
prerogatives of the soul, and not those of the automatic
body. But the movements of the latter, even volun-
tary movements, depended on a proper disposition
of organs, and without this they were wanting or
imperfect.
Thus to a thoroughgoing mechanism Descartes
joined a spiritualistic and immortal entity ; and this,
to the materialism of the middle of the nineteenth
century, was the blemish on his philosophy. Now of
all men who have ever lived he is probably the one
who has most profoundly influenced modern thought
and investigation : to us what he wrote seems strangely
modern, and this apparently arbitrary association of
spiritualistic and materialistic elements in life seems
almost the most modern thing in his writings. Being,
he said, was indeed thought, but how could he derive
thought from his clockwork body, with its valves and
conduits and wires ? No more can we derive con-
sciousness from the wave of molecular disturbance
passing through afferent nerve and cerebral tracts.
We must account for all the energy of this disturbance,
from its origin in the receptor organ to its transforma-
tion into the wave of chemical reaction in the muscle,
and we must regard its transmission as a conserva-
tive process. But how does the state of consciousness
accompanying the passage through the cortex of this
molecular disturbance come into existence ? None of
the energy of the nerve disturbance has been trans-
formed into consciousness : the latter is not energy
THE VITAL IMPETUS 125
nor anything physical. It is something concomitant
with the physico-chemical events involved in a nervous
process, an " epiphenomenon." We have to imagine
a " parallelism " between the mechanistic body and
the mind. But if we admit that consciousness may be
an effective agency in our behaviour, what is the differ-
ence between modern theories of physico-psychic
parallelism and the Cartesian theory of a rational soul
in association with an automatic body ? Descartes
denied the existence in animals other than man of the
rational soul ; the latter was not necessary. But he,
like us, must have been familiar with reflex actions and
must have seen that consciousness was not invariably
associated, even in himself, with bodily activity. And
he must have recognised the great distinction between
the intelligent acting of man and the instinctive
behaviour of the lower animals. There was something
in man that was not in the brute.
Thus the first physiology, borrowing its ideas and
methods from the first physics, was, like the latter, a
mechanical science. After Galileo and Torricelli came
Borelli mth his purely mechanical conceptions of
animal movement, and of the blood circulation, intro-
ducing even then mathematics into biology. There
was no chemistry in these speculations, though Basil
Valentine and Paracelsus and Van Helmont had
preceded Descartes and Borelli. This chemistry was
mystical, and though chemical reactions had been
studied in the organism, they were supposed to be
controlled by spiritual agencies, the " archei " of the
first bio-chemists. But that notion was to disappear,
and with Sylvius the conception of the animal body
as a chemical mechanism arose. All that was valuable
in Van Helmont's chemistry was taken up by Sylvius,
but in his mind the fermentations of the older chemists
126 THE PHILOSOPHY OF BIOLOGY
were sufficient in themselves without the mystical
" sensitive soul " and " archei." With Sylvius and
Mayow physiology became based upon chemical dis-
covery and again became mechanistic, and remained
so until the time of Stahl, when chemical discovery
attained for the time its greatest development.
The seventeenth century ended with the work of
Stahl. It is well known to students of science how
the views of this great chemist sterilised chemical
investigation almost until the time of Lavoisier. The
notion of phlogiston as an active constituent of material
bodies entering and leaving them in their reactions with
each other was a clear and simple one, and it served as
a working hypothesis for the chemists who immediately
followed Stahl. It was, of course, a false hypothesis,
and retarded discovery to the extent that the greater
part of the eighteenth century is a blank for chemistry,
when compared with the seventeenth and nineteenth
centuries. Deprived therefore of the stimulus afforded
by new physico-chemical methods of investigation,
physiology ceased to maintain the progress it had
made during the previous century, and the only great
name of this period is that of von Haller. Comparative
anatomy, and zoological exploration, on the other
hand, made enormous advances, and for these branches
of biology the eighteenth century was the great
period. It was the period of the historic vitalistic
views — vital principles, and vital and formative forces.
Stahl's teaching dominated physiology just as it did
chemistry. Chemical and physical reactions occurred
in the living body just as they did in non-living matter,
but they were controlled and modified by the soul, or
vital principle. It has been said that Stahl's vitalistic
teaching retarded the progress of physiology, but it
does not seem clear that this was the case. What did
THE VITAL IMPETUS 127
retard physiological discovery was the lack of progress
made by chemistry and physics, and this may have
been the result of the Stahlian phlogistic hypothesis.
However this may be, it seems clear that it was
the discoveries of the great chemists of the close of the
eighteenth century that again introduced mechanistic
views into physiology. With the discoveries of
Lavoisier and his successors the latter science ac-
quired new methods of research and the older working
hypotheses were re-introduced. There has been no
recession from this position during the nineteenth
century. Mechanistic biology culminated in the
writings of Huxley and Max Verwom and received a
new accession of strength almost in our own day in
the modern discoveries of physical chemistry ; and
when ph^^siology became truly a comparative science,
and embraced the lower invertebrates, it became
perhaps most mechanistic — witness the writings of
Jacques Loeb.
Of far greater philosophical importance than the
physico-chemical investigation of the functioning ot
individual organisms has been the essentially modern
experimental study of embryological processes. The
former deals essentially with the means of growth,
reproduction, and so on. We can no longer doubt
that the changes which we can observe taking place
in the organism, either the developing embryo or the
fully formed animal, are, in the long run, physico-
chemical changes ; and in ultimate analysis we cannot
expect to find anything else than processes of this
nature.
But physiological investigation has failed to
provide anything more than this analysis. If we
watch the development of the egg of an animal into a
larval form, and continue to trace the metamorphosis
128 THE PHILOSOPHY OF BIOLOGY
of the larva into the perfect animal, we cannot fail to
conclude that, beside the individual physico-chemical
reactions which proceed, there is also organisation.
The elementary processes must be integrated. There
must be a due order and succession in them. In
studying developmental processes, in considering the
developing organism as a whole, we are impressed
above all else with the notion that not only do physico-
chemical reactions occur, but that these are marshalled
into place, so to speak. When we attempt to make a
description of this integration of those ultimate pro-
cesses which we can describe in terms of physical
chemistry, physiology fails us. " At present," says
Morgan, " we cannot see how any known principles of
chemistry or of physics can explain the development
of a definite form by the organism or by a piece of the
organism." It is true that we can attempt to imagine
a physico-chemical mechanism which is the organisation
of the developing embryo ; but this must be a logically
constructed mechanism, not only incapable of expe-
rimental verification, but which can also be demon-
strated, purely by physical arguments, to be false.
This conclusion may, without exaggeration, be said to
be that of modern experimental embryology.
There have always been (in modern times) two
views as to the nature of the embryological process :
(i) that the egg contained the fully formed organism
in a kind of roUed-up condition, and that the process
of development consisted merely in the unfolding (evolu-
tion) of this embryonic organism, and in the increase
in volume of its parts. This was the hypothesis of
preformation held in the beginning of embryological
science. It involved various consequences : the hmi-
tation, for instance, of the duration of a species, since
each generation of female organisms contained in their
THE VITAL IMPETUS
129
o'vum.
2- bloistbrr.ere
St a. as.
^■Uastbrnere
Sfa.a,e.
5
ovaries all the future generations ; with other conse-
quences which the preformationists did not hesitate
to accept. (2) The other view was the later one
of epigenesis : the ^%g was truly homogeneous and
the embryo grew from it. Obviously the acceptance
of this hypothesis led to vitalism, and we find that it
was abandoned just as soon as the embryologists recog-
nised that physics provided a corpuscular theory of
matter, when a return was made to the preformation
views of earlier times ; views which lent themselves to
the construction of a
mechanistic hypothesis
of development.
We may state very
briefly the main facts of
the development of a
typical animal ovum,
such as that of the sea-
urchin.
The fertilised ovum
divides into two (2) , and
then each of these blastomeres divides again in a plane
perpendicular to the first division plane (3). The third
division plane is at right angles to the first two, and it
cuts off a tier of smaller blastomeres from the tops of the
first four. There are now (4) two tiers of blastomeres,
a lower tier of large blastomeres and an upper tier
of smaller ones. This is the 8-cell stage. Next,
each of these blastomeres divides in two simultaneously
so that the embryo now consists of sixteen cells. After
this the divisions proceed with less regularity, but
after about ten divisions the embryo consists of about
1000 cells (2^°), and these are arranged to form a
hollow sphere consisting of a single layer of cells. The
latter are furnished with cilia, and the whole embryo,
Fig. 12.
130
THE PHILOSOPHY OF BIOLOGY
now known as the blastula, can swim about by the
movements of these cilia. Further development results
in another larval form — the gastrula, and yet another,
the pluteus larva. After this the transformation into
the fully formed sea-urchin occurs.
With various modifications this scheme represents
the early development of a very large number of animals
belonging to most groups.
If we study the process of cell-division we shall
find it very complicated. The ovum, immediately
after fertilisation, consists of two main parts, the
nucleus and the cytoplasm.
Within the nucleus is
a substance distinguishable
from the rest ; it is distri-
buted in granules and is called
the chromatin (i). When the
cell is about to divide this
chromatin becomes arranged
in a long coiled thread (2), and
then (3) this chromatic thread
breaks into short rods called chromosomes. Two little
granules now appear, one at each end of the nucleus, and
very delicate threads, the asters, appear to pass from each
of these bodies towards the chromosomes (4). Each
of the latter then splits lengthways into two, and a
half chromosome appears to be drawn by the asters
towards the poles of the nucleus. The latter then
divides (5) and then the whole cell divides. What
thus, in essence, happens in nuclear divisions is that
the chromatin of the nucleus is more or less accurately
halved. Apparently this substance consists of very
minute granules and the whole process is directed
towards the splitting of each of these granules into two.
A half-granule then goes to each of the daughter nuclei.
Fig. 13.
THE VITAL IMPETUS 131
Every time the embryo divides this process is repeated
Thus each of the (theoretically) 1028 cells of the
blastula contains xoWth of the substance of each
chromatic granule in the fertilised ovum.
Pfiuger and Roux (in 1883 and 1888 respectively)
were the pioneers in the experimental study of the
development of the ovum, and the results of their
work and that of their successors has, more than any-
thing else in biology, modified and shaped our notions
of the activities of the organism. Roux found or
thought so at least, that the first division of the frog's
egg marked out the right and left halves of the body,
the one blastomere giving rise to the right half the
other to the left half. The next division, which
separates each of these blastomeres, marked out the
anterior and posterior parts of the embryo. Thus :—
Anteriorf--^ ,^^ Anferior
I^rt [^ -^l Rlahf
Foster: oi\. yPosferior
Fig. 14.— The frog's egg in the 4-blastomere
stage seen from the top.
Now in an experiment which has become classical
Roux succeeded in killing one of the blastomeres in
the 2-cell stage, while the other remained aUve.
The uninjured blastomere then continued to develop,
hut it gave rise to a half-embryo only.
Upon these experiments the Roux-Weismann
hypothesis of development— the " Mosaik-Theorie "—
was developed. The lay reader will see how obviously
the facts of nuclear division and the experimental
results indicated above lend themselves to a mechanistic
132 THE PHILOSOPHY OF BIOLOGY
hypothesis. Notice that but for the physical concep-
tion of matter as made up of molecules and atoms the
mosaic-theory would hardly have shaped itself in the
minds of biologists. But this notion of matter con-
sisting of corpuscles must have suggested that the
essential "' living material " of the organism consisted
also of corpuscles, as soon as a microscope powerful
enough to see the chromatic granules was turned on a
dividing cell prepared so as to render these bodies
visible. Obviously the primordial ovum contained ail
the elements of the organisms into which it was going
to develop. But then in the process of division of the
ovum all these chromatic granules are shared out among
the cells, and a really very pretty mechanism comes
into existence for this purpose of distribution.
Weismann built up his hypothesis of the germ-plasm
upon the observations we have outlined. The chro-
matic matter of the nucleus consists of elements called
determinants, the determinants themselves being com-
posed of ultimate bodies called biophors. Each de-
terminant possesses all the mechanism, or factors,
necessary for the development of a part of the body :
there are determinants for muscles, nerves, connective
tissues, for the retina of the eye, for hairs of each colour,
for the nails, and so on. All these determinants are
contained in the chromatin of the nucleus of the egg,
and in the divisions of the latter they are gradually
separated so that ultimately each cell of the larva
contains the determinants for one individual part, or
organ, or organ-system of the adult body. The right
blastomere, for instance, contains all the determinants
for the right side of the frog's body, those for the left
side being contained in the left half. The process of
cell-division involved in the segmentation of the egg
consists then in the orderly disintegration of this
THE VITAL IMPETUS 133
complex of determinants, and in the marshalling into
place of the isolated elements. The cell body — the
cytoplasm — carried out a very subordinate role, mainly
that of nourishing the essential chromatic substance.
Such was the Roux-Weismann Mosaic-theory of
development in its pristine form.
It is clearly a preformation hypothesis. It is true
that the actual organism is not contained in the germ,
but all the parts of the latter, even the colours of the
eyes or hair, are present in it in the form of the de-
terminants. Obviously it involves a mechanism of
almost incredible complexity. But if we regard it as
a working hypothesis of development this complexity
of detail does not matter ; its truth would be indicated
by the fact that all analysis of the processes involved
would tend to simplify it and to smooth out the com-
plexity. But this is exactly what has not happened,
for all subsequent investigation has necessitated sub-
sidiary hypothesis after hypothesis. As a theory of
development it has failed entirely.
If, after one of the blastomeres in the frog's egg at
the 2-cell stage be killed, the egg is then turned upside
down, the results of the experiment become totally
different ; the uninjured blastomere develops into a
whole embryo, differing from the normal one chiefly in
that it is smaller. If the uninjured egg in the 2-cell
stage be turned upside down two whole embryos, con-
nected together in various ways, develop. In the
frog's egg the two first blastomeres cannot be separated
from each other without rupturing them, but in the
egg of the salamander they can be separated. After
this separation two perfect, but small, embr3^os develop.
In the egg of the newt a fine thread can be tied round
the furrow formed by the first division. If this ligature
be tied loosely it does not affect development, and then
134 THE PHILOSOPHY OF BIOLOGY
it can be seen that the median longitudinal plane of
the embryo does not correspond, except by chance^
with the first division plane. If the ligature be tied
tightly, then each of the blastomeres gives rise to an
entire embryo. If it is tied in various places monsters
of various types are produced. Therefore there is no
segregation of the determinants in the first two blasto-
meres. These results, moreover, are not exceptional,
for similar ones have been obtained with other animal
embryos, in fishes, Amphioxus, ascidians, medusae, and
hydrozoa, and in some cases even each of the first four
blastomeres develops into an entire embryo when it is
separated from the rest. In the sea-urchin embryo
the blastomeres can be shaken apart ; or by removing
the calcium which is contained in sea water the blasto-
meres can easily be separated from each other. It
was then found by Driesch that each of the blasto-
meres in the i6-cell stage could develop into an entire
embryo. It is plain, then, that up to this stage at
least there has been no segregation of the determinants.
Upon the results of these experiments Driesch
based his first proof of vitalism. Let us suppose that
there is a mechanism in the developing egg. Now the
embryo which results from the latter sooner or later
acquires a three-dimensional arrangement of parts :
head-end differs from tail-end, dorsal surface difters
from ventral surface, and the parts differ on either side
of the median plane. The mechanism must, therefore^
be one which acts in three dimensions, anterior and
posterior, laterally, and dorso-ventrally. We may
represent it by a diagram of three co-ordinate axes,
X, y, z ; X and y being in the plane of the paper, and z
at right angles to the plane of the paper. Now in the
2-cell stage the same mechanism must be present, for
this stage develops normally into one entire embryo.
THE VITAL IMPETUS
135
Fig. 15
But since either of the blastomeres may develop into
an entire embryo, the mechanism must also be present
in each of them, and
since in the i6-cell ^
stage each blastomere
may develop an entire
embryo, it must be
present in each of the
sixteen blastomeres.
A three - dimensional
mechanism is there-
fore capable of division
down to certain limits.
Suppose now that
we allow the sea-urchin egg to develop normally up
to the blastula stage. In this stage it is a hollow
sphere, the wall of which is a single layer of cells.
It is similar all round, that is, we cannot distinguish
between top and bottom, right and left, anterior and
posterior regions ; but since it develops into a larva
in which all these distinctions become apparent very
soon, it must possess the three-dimensional mechanism,
since the ^^activity of the developmental process is
going to produce different structures in each direction.
Now the blastula, by very careful
manipulation can be divided, cut
into parts with a sharp knife. Since
it is similar all round the direction
of the cut is purely a matter of
chance. It can be cut through along
the planes i 2, 3 4, 5 6, 7 8, for in-
stance ; really there are an infinite
number of planes along which the
blastula can be cut into two separate parts, and
the direction of the plane is not a matter of choice.
^^-.
Fig. 1 6.
136
THE PHILOSOPHY OF BIOLOGY
but purely a matter of chance. Nevertheless, each of
the parts into which the larva is cut becomes an entire
embryo. For a time the partial blastula — approxi-
mately a hollow hemisphere in form — goes on develop-
ing as if it were going to become a partial embryo, but
soon the opening closes up and development becomes
normal. It does not matter even if the two parts into
which it is divided are not alike in size ; provided that
a part is not too small, it will follow the ordinary course
of development.
Suppose the blastula opened out on the flat, like
the Mercator pro-
j"
M
r
J
.H
o
Fig. 17.
-JT
jection of a globe on
a flat map. Suppose
that a is a small ele-
ment of it. Suppose
- that the rectangles
hcdCy FGHe, I JcL,
MNoe, and as many
more as we care to
make, represent the
pieces of the blastular wall separated by our operation
— they all contain the element a, but this is in a
different position in each case. There are really an
infinite number of such parts of the blastula and a
occupies an infinitely variable position in each of
them.
This demonstration is very important, so let us
make it as clear as possible : Driesch's logical proof of
vitalism may be stated as follows : —
The different parts of the blastula are going to
become different parts of an embryo.
The part a, occupying a definite position in the
entire blastula, is going to become a definite part,
having a definite position, in the embryo ;
THE VITAL IMPETUS 137
But each partial blastula becomes an entire
embryo and the same part a occupies a different
position in each.
Therefore any part of the blastula may become
any part of the embryo.
Now if a mechanism is involved, it must, according
to our ideas of mechanism, be one which is different
in its parts, for each part of it produces a different
result from the others ;
But since any part of the mechanism may produce
any of the different results contained in the embryo,
every one of its parts must be similar to every
other one.
That is, all the parts of the mechanism are the
same, though the hypothesis requires that they
should be different.
We conclude, then, that a mechanism such as we
understand a mechanism to be in the physical sciences
cannot be present in the developing ovum.
Nevertheless, an organisation, using this term as an
ill-defined one for the present, must exist in the ovum,
or the system of undifferentiated cells into which the
ovum divides, during the first stages of segmentation.
In certain animals, Ctenophores (Chun, Driesch, and
Morgan), and MoUusca (Crampton), for instance,
separation of the blastomeres in the first stages of
segmentation produces different results from those
mentioned above. In these cases the isolated blasto-
meres develop as partial embryos, that is, the latter are
incomplete in certain respects, and this incompleteness
corresponds, in a general way, to the incompleteness
of the part of the ovum undergoing development. We
have thus the apparently contradictory results : (i)
each of the first few blastomeres resulting from the first
divisions of the ovum, is similar to the entire ovum.
138 THE PHILOSOPHY OF BIOLOGY
and develops like it ; and (2) each of the first few
blastomeres is different from the others, and from the
entire ovum, and develops differently from the others,
and from the entire ovum.
Let us try to construct a notion of what this organi-
sation in the developing ovum must be. In the
i6-blastomere stage of the sea-urchin egg we have a
" system " of parts. In the case of normal develop-
ment each of these parts has a certain actual fate —
it will form a part of the larva into which the embryo
is going to develop : It has, as Driesch says, a pro-
spective value. But let the normal process be inter-
fered with, and then each of these parts does something
else. In the extreme case of interference, when the
blastomeres are separated from each other, each
blastomere, instead of forming only a part of a larva,
forms a whole larva. The prospective potency of the
part, that is its possible fate, is greater than its pro-
spective value. Normally it has a limited, definite
function in development, but if necessary it may greatly
exceed this function.
What any one blastomere in the system will become
depends upon its position with regard to the other
blastomeres. When the egg of the frog is floating
freely in water it lies in a certain position with the
lighter part uppermost, and then development is
normal, each of the two first blastomeres giving rise
to a particular part of the body of the larva ; that is,
each of them is affected by the contact of the other
and develops into whatever part of the normal embryo
the other does not. But let the egg in the 2-cell stage
be turned over and held so that the heavy part is
uppermost : the protoplasm then begins to rotate so
as to bring the lighter part uppermost; but the two
blastomeres do not, as a rule, adjust themselves to the
THE VITAL IMPETUS 139
same extent, and at the same rate, and corresponding
parts may fail to come into contact with each other.
Lacking, then, the normal stimulus of the other part,
each blastomere begins to develop by itself, and a
double embryo is produced. It is clear, then, both
from this case and the last one, that the actual fate
of any one part of the system of blastorneres is a
junction of its position. What it will become depends
precisely on where it is situated with respect to the
other parts.
Driesch, then, calls the system of parts in such cases
as the 2-cell frog embryo, or the i6-cell sea-urchin
embryo, an equipotential system, since each part is
potentially able to do what any other part may do,
and what the whole system may do. But in normal
development each part has a definite fate and its
activity is co-ordinated with that of all the other parts.
It is, therefore, an harmonious equipotential system, each
part acting in harmony, and towards a definite result,
with all the others ; although if necessary it can take
the place of any or all of the others.
Such an harmonious equipotential system exists
only at the beginning of the development of the egg.
It is represented by the 8-cell stage of Echinus but
not by the i6-cell stage, since, though the T5^-blasto-
meres produce gastrulae (the first larval stage) , they do
not produce plutei (the second stage). It is repre-
sented by the 4-cell stage of Amphioxus but not by
the 8-cell stage. It is not exhibited even by the
2-cell stage of the Ctenophore egg. What does this
mean ? It means that the further development pro-
ceeds, the less complete does the " organisation "
inherent in any one part of the system become. " The
ontogeny assumes more and more the character of a
mosaic work as it proceeds " (Wilson).
140 THE PHILOSOPHY OF BIOLOGY
Or perhaps it means, and this is the better way of
putting it, that the " organisation," whatever it may
be, depends on size. "We see this very clearly in the
experiment of cutting in two the blastula of the sea-
urchin. If the pieces are of approximately equal size
each will form an entire Pluteus larva, but if one of
them is below a certain limit of size it will not continue
to develop. The " organisation," therefore, has a
certain volume, and this volume is much greater than
that of any one of the cells of which the fragment
exhibiting it is composed. It is enormously greater
than the volume of any group of determinants which
we can imagine to represent the different kinds of cells
composing the body of the Pluteus larva, and still
more enormously greater than the volume of a " mole-
cule " of protoplasm. Now^ this association of
" organisation " and size is of immense philosophical
importance, for it does away, once and for all, with the
idea that the " organisation " is solely a series of
chemical reactions. If it were, one cell of the blastula
would contain it, for on the mechanistic hypothesis
one cell, the egg-cell, contains it, and this cell can be
divided innumerable times and still contain it. The
egg is a complex equipotential system (Driesch). which
divides again and again throughout innumerable
generations, and still contains the " organisation."
It is in vain that we attempt the misleading analogy
of the " mass action " of physical chemistry, to show
that volume may influence chemical action. In such
a mass action what we have is this : —
the letters A , B and C standing for chemical substances
present, and the letters a and h, etc., representing the
THE VITAL IMPETUS 141
active masses of these substances. But variations in
this active mass affect only the velocity of the reaction.
What we have to account for in our blastula experi-
ments is the nature of the reaction, and how can
velocity or even nature of reaction affect form ? If we
could show that the form of the crystals deposited
from a solution in some reaction depended on the
volume of the solution, the analogy would be closer,
though even then the difficulties in pressing it would
be so enormous as to render it futile to attempt to
entertain it.
A chemical mechanism cannot, then, be imagined,
much less described, and the only other mechanism so
far suggested is the Roux-Weismann one, involving
the disintegration of the determinants supposed to be
present in the egg nucleus. Let us suppose (in spite
of the incredible difficulty in so doing) that there is
such a mechanism. It must usher the nuclei contain-
ing the determinants of the embryonic structure into
their places : those for the formation of the nerve-
centre go forward ; those for the mouth, gut, and anus
go backwards and downwards ; those for the arms go
forwards, ventrally, and posteriorly, in a very definite
way ; and those for the complicated skeleton are
distributed in a variety of directions which defy
description. These nuclei are, in short, moved up
and down, right and left, backwards and forwards,
and become built up into a complicated archi-
tecture. Suppose we prevent this. Suppose we com-
press the segmenting egg between glass plates so that
the nuclei are compelled to distribute themselves
in one plane only : to form a flattened disc in which
the only directions are right and left and anterior
and posterior. This has been done by Driesch and
others. On the Roux-Weismann original hypothesis
142 THE PHILOSOPHY OF BIOLOGY
a monstrous larva ought to result, for the first nuclei
separated from each other have been forced into
positions altogether different from those which they
should have occupied had they developed normally.
Yet on releasing the pressure readjustment takes
place. New divisions occur so as to restore the normal
form of larva. The Roux-Weismann subsidiary
hypothesis is that the stimulus of the pressure has
compelled the nuclei to divide at first in such a way
as to compensate for the disturbance.
Let us remove some of the blastomeres. On the
original hypothesis the determinants for the structures
which the nuclei of these blastomeres contained have
been lost. These structures should, therefore, be missing
in the embryo. But nothing of the sort is the result.
Other nuclei divide and replace the lost ones, and the
embryo develops as in the normal mode. The reply
is that in addition to the determinants which were
necessary for their own peculiar function, these nuclei
contained a reserve of all others. On disturbance
these determinants, " latent " in all other conditions,
became active and restituted the lost parts.
Let us remove some organ from an adult organism.
The most remarkable experiment of this kind is the
removal of the crystalline lens from the eye of the
salamander. Now the lens of the eye develops from
the primitive integument (ectoderm) of the head, but
the iris of the eye develops mainly from a part of the
primitive brain. After the operation a new lens is
formed from the iris and not from the cornea. There-
fore the highly specialised iris contains also deter-
minants of other kinds. Does it contain those for
itself and lens only, or others ? If it contains many
kinds, then we conclude that even the definite adult
structures contain determinants of many other kinds
THE VITAL IMPETUS 143
than their own, that is, reserve determinants are
handed down in all cells capable of restitutive pro-
cesses, practically all the cells of the body. Or does it
contain only its own and those of the lens ? Then
this highly artificial operation was anticipated, an
absurd hypothesis which need not be considered.
This particular mechanistic process (and no other
one is nearly so plausible) crumbles away before
attempts at verification, and it survives only by the
addition of subsidiary hypothesis after hypothesis.
In itself this demonstrates that it is an explanation
incompetent to describe the facts.
What, then, is the "organisation"? It is some-
thing elemental, and we may just as well ask what
is gravity, or chemical energy, or electric energy. It
cannot be said to be any of these things or any com-
bination of them. " At present," says a skilful and
distinguished experimxcnter, T. H. Morgan, " we cannot
see how any known principle of chemistry or of physics
can explain the development of a definite form by the
organism or a piece of the organism." " Probably we
shall never be able," concludes Morgan, who is anything
but a vitalist. But does not this mean just that in
biology we observe the working of factors which are
not physico-chemical ones ?
We have seen that the physiologist studies some-
thing very different from that which the embryologist
or naturalist studies. The former investigates a part
of the animal, arbitrarily detached from the whole
because the complexity of the functions of the simplest
organism is such that all of them cannot be examined
at once. He adopts the methods of physical chemistry
in his investigation and whatever results he obtains are
necessarily of the same order. Inevitably, from the
mere nature of his method, he can see, in the organism.
144 THE PHILOSOPHY OF BIOLOGY
only physico-chemical phenomena. The embryologist,
on the other hand, studies the organism as a whole and
seeks to determine how definite forms are produced,
and how a change in the external conditions affects
the assumption of these forms. We have seen with
what little success the attempts to relate embryological
processes with physico-chemical ones alone have met.
In all studies of organic form mechanism has failed.
It is useless to attempt to press the analogies of
crystalline form, and the forms assumed in nature by
dynamical geological agencies. If the reader examines
these analogies critically he will see that they are
superficial only.
We seem, however, to see in those actions of the
organism which are called " tropistic " or " tactic,"
reactions of a purely physico-chemical nature, and
starting with these as a basis a plausible theory of
organic movements on a strictly mechanistic basis
might be built up.^ A " tropism " is the movement of
a fixed organism with respect to a definitely directed
external stimulus. This movement may be that pro-
duced by growth of its parts, or by the differential
contraction or expansion of its parts. A " taxis " we
may call the motion of a freely-moving organism in
response to the same directed stimuli. The move-
ments whereby a green plant turns towards the light
are called heliotropic, and those of its roots in the
perpendicular direction are called geotropic. The
motion of the freely-moving larva of a barnacle, for
instance, in swimming towards a source of light are
called " phototactic."
In all these cases we have to think of the stimulus
as a " field of energy " in the sense in which physicists
speak of electric, or magnetic, or electromagnetic, or
^ Many of Jacques Loeb's remarkable investigations point in this direction.
THE VITAL IMPETUS
145
thermal, or gravity fields. In all these cases the
factors affecting the movements of the organism are
directed ones.
An electric field, for instance, (i), is produced by-
placing the electrodes of a galvanic cell at opposite
extremities of a water-trough : we imagine the electrons
moving from one side of the trough to the other in
parallel lines, and in a certain direction. A light
field (2) would be produced by the radiation of light
travelling in straight lines through the water.
The movements of the organism displaying a
-^■
(1)
(S)
Fig. 18.
tropism or a taxis are not caused by the stimuli of the
field, but are only directed by it. In the absence of
these stimuli it would swim at random. In a field,
however, it will orientate itself in some direction with
reference to the lines of force. A " positively photo-
tactic " animal swims towards the focus from which
the light radiation emanates, and a " negatively
phot ot actio " one swims in the other direction. On
the theory of tropistic and tactic movements this
orientation is produced by the differential stimulation
of the opposite sides of the organism. Let us take as
a concrete example the case of a caterpillar which
creeps up the stem of a plant to feed on the tender
shoots near the apex. The animal possesses an
E
146 THE PHILOSOPHY OF BIOLOGY
elongated body, with muscles beneath the integument,
and sensory nerve-endings in the latter. Its muscles
are in a state of " tone," that is, they are normally
always slightly tense. The incident rays of light
affect the dermal sense-organs, stimulating ganglionic
centres and setting up efferent impulses which descend
to the muscles. Let us suppose the animal is moving
so that the longitudinal axis of its body is at an angle,
say of 45°, to the direction of the incident light : one
side of the body is therefore stimulated and the other
is not. The stimulation of the lighted side sets up
efferent nerve impulses which descend to the muscles
of this side and increase their tone (or else the lack of
stimulation of the other side produces impulses which
inhibit the muscular tone, or impulses which would
otherwise preserve the tone cease in the absence of
light stimulation). In any case the muscles of the
lighted side contract, and the body of the caterpillar
moves so that it sets itself parallel to the direction of
the radiation. Both sides of the body are then equally
stimulated and the animal moves towards the light.
The animal feeds and it then creeps back down the
plant. Why does it do this ? Because, says Loeb,
the act of feeding has reserved the " sign " of the taxis.
Before, when it was hungry, it was positively photo-
tactic, but the act of feeding (all at once, it would
appear, before digestion and assimilation of the food
itself) has produced chemical substances in the muscles
which cause the latter to relax in response to an impulse
which previously produced contraction.
The nervous link is not, of course, a necessary one.
The stimulation by the energy of the field may affect
the muscle substance directly, or it may, as in the case
of a protozoan animal, affect the general body proto-
plasm in the same way. In the majority of cases.
I
THE VITAL IMPETUS 147
however, the orientation would be affected through the
chain of sense-organ, afferent nerve, nerve centre,
efferent nerve, and effector organ. This is the chain
of events which on this hypothesis causes a moth to
fly into a flame, or a sea-bird to dash itself against the
lantern of a lighthouse.
A taxis is, then, an inevitable response by move-
ment in a definite direction, to a directed stimulus.
Including also tropisms it may be admitted that the
movement is a purposeful, or at least, a useful one in
some cases, as for instance the heliotropism and
geotropism of the green plant. If we admit that Loeb's
description of the feeding of the caterpillar, as a tactic
act, is true, we may also call this a useful act. But in
the majority of cases tropisms and tactes are acts which
appear to be of no use to the organism. The invasion
of a part of the body which is irritated by a poison (as
in inflammation) by leucocytes, is useful to the body
itself, but we must regard the leucocytes as organisms,
and their tactic motion leads to their destruction, and
so also with other analogous acts. Just because of
this we find difficulty in accounting for their origin in
terms of natural selection.
This does not matter so much, since it can hardly
be maintained now that the tropistic or tactic act has
any reality except in a very few cases — the motions
of plants, galvano-taxis, the chemico-taxic movements
of bacteria and leucocytes, and some other analogous
cases, perhaps, are these exceptions. It can hardly
be doubted that the extension of the concept to cover
the motions of many invertebrates, and even some
vertebrate actions, by Loeb and his school is a straining
after generality which has not been justified. The
hypothesis, as Loeb has stated it, is evidently almost
certainly a logical one and was obviously elaborated
148 THE PHILOSOPHY OF BIOLOGY
as a protest against the anthropomorphism which saw
in the flying of a moth into a flame the expression of
an emotion ; or in the movements of a caterpillar on a
green shrub the expression of hunger and satiety and
of the inherited experience of the animal ; or in the
avoidance by a Paramcecium of a drop of acid the
emotion of dislike of the feeling of pain. Well, let it
be granted that this is so, and that the protest was a
useful one, for it is obviously impossible that these
notions as to the causes of the movements can be
verified : does it improve matters to take refuge in
an hypothesis which is just as purely physico-chemical
dogmatism as the other is anthropomorphism ? But
the former hypothesis is at all events one which is
susceptible of experimental verification and in this lies
its usefulness, inasmuch as it has stimulated investiga-
tion. It is evident, however, that this verification
has not yet been made. The differential afferent
impulses set up by the energy-field ; the increases or
inhibition of muscular tone ; the presence of photo-
sensitive substances in the tissues of tactically acting
lower animals ; the change of velocity of chemical
reaction, in these cases, which ought to follow stimula-
tion— all these things could be verified if they possess
reality. Yet it is only indirect proofs, capable perhaps
of other interpretations, and not direct experimental
ones, which have so far been adduced in favour of a
general theory of tropisms.
Moreover, the close analj^sis of the actions of some
of the lower organisms by Jennings has shown that
the tactic hypothesis is probably false in the majority
of cases. This observer studied the acting of the
organisms themselves and not the beginning and end
of the series, and he shows that the behaviour of the
organisms is far more obviously described by saying
THE VITAL IMPETUS
149
that it adopts a method of " trial and error." Let us
suppose a number of infusoria (Paramcecium) in a
film of water, at one part of which is a drop of acetic
acid slowly diffusing out into the surrounding medium.
There is a zone of changing concentrations round the
drop : if we draw imaginary contours through the
points where the concentration is approximately the
same (the concentric rings in the diagram), and then
draw straight lines normal to these rings (the radial
lines) we can construct a " field " analogous to an
electric or magnetic field. The
animal on approaching the field
ought to orientate itself and
take the direction of the " lines
of force." It does not, how-
ever, behave in this way, but
only enters the field at random.
Having entered, it remains
within a part where the con-
centration is within certain
limits. If it approaches the
m^argin of this limited field it
stops, swims backwards, revolves round its own axis,
and then turns to the aboral side ; and it repeats this
series of movements whenever it approaches (by
random) a region where the concentration is too
high, or one where it is too low. In this, and other
organisms we see then what Jennings has called a
typical " avoiding reaction," the precise nature of
which depends on the " motor-system " of the
animal. Its general movements are random ones,
but having found a region of " optimum conditions "
(conditions which are most suitable in its particular
physiological state), it remains there.
Suppose (what indeed repeatedly happens) that an
Fig. 19.
150 THE PHILOSOPHY OF BIOLOGY
extensive " bed " of young mussels forms on a part of
the sea bottom. In a short time the bed becomes
populated by a shoal of small plaice feeding greedily
on the little shellfish. In their peregrinations the
fishes must repeatedly pass out beyond the borders
of this feeding-ground. Usually, however, they will
return, for failing to find the food they like they swim
about in variable directions and so re-enter the shell-
fish bed.
Suppose (this was really a fine experiment made
by Yerkes) a crab is confined in a box from which
two paths lead out but only one of which leads to the
water. The animal nins about at random, finds the
wrong path, retraces it, tries again and again, and
then finds the right path and gets back to the water.
If the experiment is repeated the animal finds the
right path again with rather less trouble, and after
many trials it ends by finding it at once on every
repetition of the experiment.
^^ All this discussion of concrete cases leads up to
our consideration of the modes of acting in the higher
organisms. On the strictly mechanistic manner of
thinking the actions of the organism in general are
based on reactions of the tactic kind — inevitable re-
actions the nature of which is determined, and which
follow a stimulus with a certainty often fatal to the
organism displaying them. Accepting these tactic
reactions as, in general, truly descriptive of the be-
haviour of the organism, we can build up a theory
of instincts. In their simplest form instincts are
reflexes — tactic movements. In their more complex
forms they are concatenated reflexes, or tactes. A
complicated instinctive action is one consisting of
many individual actions, each of which is the stimulus
for the next one ; or, of course, it may also be complex
THE VITAL IMPETUS 151
in the sense that several simple reactions proceed
simultaneously, upon simultaneous stimulation of
different receptors. Now the extension of all this to
movements of a " higher " grade is obvious.
Let us note in the first place, that the stimuli so
far considered in all the examples quoted are simple
elemental ones. There are, of course, relatively few
such stimuli : gravity, conducted heat (the kinetic
energy of material bodies), radiated heat (the energy
of the ether), electric energy, chemical energy, and
mechanical contact or pressure (including atmospheric
vibrations). In all these cases we have a definite,
measurable, physical quantity, with which we must
relate a definite response in the form of a definite
measurable, physico-chemical reaction. There should
be a functionality between the stimulus and response, a
definite, quantitative energy-transformation. To take
a concrete example, a certain quantity of light energy
falling upon the receptor organs of Loeb's caterpillar
ought to transform into another quantity of " nervous
energy," and this travelling in an analogous way to a
" wave of explosion " ought to transform into an
energy quantity of some kind, which initiates another
" wave of explosion " in the muscle substance. All
these transformations must be quantitative ones, and
the energy of the individual light must be traced from
the receptor organ to the points in the muscle where
it disturbs a condition of false equilibrium in the sub-
stance of the latter. Nothing less than this is required
to demonstrate the purely physical nature of a reaction,
on the part of the organism, to an external stimulus.
It may safely be said that physiological investigation
has not yielded anything even approximating to such
an experimental demonstration.
What are the stimuli to the actions of a higher
152 THE PHILOSOPHY OF BIOLOGY
organism ? It is true that their elements are energies
such as we have indicated, but these energies are
integrated to form individualised stimuli (Driesch).
The stimulus in an experimentally studied taxis is,
perhaps, a field of parallel pencils of light rays of
definite wave length ; but in the action of a man, or
a dog say, the stimulus is an immensely complicated
disturbance of the ether, producing an image upon
the retina of the animal. A sound stimulus employed
in an investigation may be the relatively simple
atmospheric disturbance produced by the sustained
note of a syren or violin-string ; but the stimulus in
listening to an orchestra may consist of dozens of
notes, with all their harmonies, sounding simultaneously
at the rate perhaps of some hundred or two in the
minute. All these are integrated by the trained listener,
and one or two false ones among the multitude may
entirely spoil the effect of the execution. Surely there
is here something more than a mere difference in
degree.
More important still is the strict functionality
between stimulus and action that the theory of tactic
responses imposes on itself. Putting this very precisely
(but no more precisely than the theory demands), we
say that lA=^f{x, y, z), that is, the series of actions
"^A (the dependent variable) is a mathematical
function of the independent variables x, y, z. Now is
there anything like this functionality between the
acting of the higher animal and the stimulus ? Evi-
dently there is not. We recognise someone whom we
know very well by any one of a hundred different
characters, mannerisms of walk, speech, dress, etc.
He or she is the same person, whether seen close at
hand, or afar off, or sideways, or in any one of almost
infinitely different attitudes, and we respond to each
THE VITAL IMPETUS 153
of these verj^ different physical stimuU by the same
reaction of recognition : pleasure, dislike, avoidance,
greeting, or whatever it may be. To a sportsman
shooting wild game the stimulus may be some almost
imperceptible tint or shading in cover of some kind,
differing so little from its environment as hardly at all
to be seen, yet, to his experience, upon this almost
infinitesimxal variation of stimulus depends his action
with all its consequences. In Driesch's example two
polyglot friends met and one says to the other, " My
brother is seriously ill," or " Mon frere est severement
malade," or " mein Bruder ist ernstlich erkrankt."
Here the physical stimulus is fundamentally different
in each case, but the reaction — the expressions of
sympathy and concern, the discussions of mutual
arrangements, etc., are absolutely the same. Or let the
one friend say to the other, " My mother is seriously
ill," and in spite of the very insignificant difference
between the consonantal sound br in this sentence and
the corresponding sound m in the other English sentence,
the reaction, that is, the subsequent conversation, and
the arrangements between the two friends may be
entirely different.
Putting this argument in abstract form we may
say, generally, that two stimuli, which are, in the
physical sense, entirely different from each other, may
produce absolutely the same series of reactions ; and
conversely two stimuli differing from each other in
quite an insignificant degree may produce entirely
different reactions. It is also easy to see, by analysis
of the antecedents to the actions of the intelligent
animal, that these stimuli are, in the majority of cases,
not elemental physical agencies, but individualised
and integrated groupings of these agencies ; and that
the animal reacts, not to their mathematical sum, as
154 THE PHILOSOPHY OF BIOLOGY
it should do on a purely mechanistic hypothesis of
action, but to the typical wholes which are expressed
in these groupings.^
It is no answer to this argument to say that it is
not the actual atmospheric vibrations (in the case of
the conversation), nor the optical image (in the case
of the recognition of a friend), which are the true
stimuli, but rather the mental conditions, or states of
consciousness, aroused by these physical agencies. If
we are to adopt a strictly mechanistic method of ex-
plaining actions, such a method as that indicated by
Loeb's hypothesis of the purely tactic behaviour of
his caterpillars, then these atmospheric vibrations
and optical images are most undoubtedly the true
stimuli, and the reactions must be functions of them
in the mathematical sense. But since this strict
functionality does not exist in any behaviour-reaction
closely analysed, we must grant at once that it is,
indeed, not the physical series of events that deter-
mines the actual response, but truly the conscious
state immediately succeeding to these physical sense-
impressions. Now let us see to what conclusions this
admission leads us.
Between the external stimulus (the atmospheric
undulations impinging on the auditory membranes,
or the light radiations impinging on the retinae) and
the behaviour-reaction something intervenes. This is
the individual history of the organism, the " associa-
tive memory " of Jacques Loeb, the " physiological
state " of Jennings, the " historical basis of reacting "
(historische Reaktionsbasis) of Driesch, or the " dura-
tion " of Bergson. The last concept is the most subtle
^ Thus to the ordinary woman the sight of a cow in the middle of a country
road produces a certain definite feeUng of apprehension, which is always the
same although the optical image of the animal differs remarkably in different
adventures.
THE VITAL IMPETUS 155
and adequate one and we shall adopt it. The physical
stimulus, then, leads to a state of consciousness, a
perception, and this is succeeded by the action. What
is the perception ? There may be no perception in a
reflex action ; there is none in a taxis.^ These kinds of
reaction follow inevitably from the nature of the
stimulus — depend upon the latter, in fact ; but we
cannot fail to observe that the intelligent behaviour
of the higher animal involves choice between alternative
kinds of action. The perception, then, is this choice,
or it is intimately associated with it. But it is some-
thing more than the choice of one among many kinds
of response. The whole past experience of the animal
enters into the perception, or at least all that part of
the past experience which illuminates, in anj^ way,
the present situation. What the intelligent animal
does in response to a stimulus depends not only on
the stimulus but on all the stimuH that it has received
in its past, and on all the effects of all those stimuli.
Into the perception that intervenes between the external
stimulus, then, and the action by which the animal
responds what we usually call its memory enters. Its
duration is really the something which is changed by
the stimulus, and which then leads to the behaviour-
reaction.
Duration, then, is memory, but it is more than
memory as we usually think of this quality. The past
endures in us in the form of " motor habits," and when
we recall it we maj^ act over again those motor events.
Careful introspection will readily convince the reader
that in recalling a conversation he is really speaking
inaudibly, setting in motion the nerves and muscles
1 We do not find this explicitly stated in this way in mechanistic biological
writings. None the less it is implied, and is the legitimate conclusion from
the arguments used.
156 THE PHILOSOPHY OF BIOLOGY
of his vocal mechanisms. Actions that have been
learned endure ; in some way cerebral and spinal
tracts and connections become established and persist :
undoubtedly when a cerebral lesion destroys or
impairs memory it is these physical nerve tracts and
cells that become affected. But in addition to this
we have pure memory (Bergson's " souvenir pur ").
What, for instance, is the visual image of some thing
seen in the past, which most people can form, but pure
recollection ? ^
All the past experience of the organism — all its
perceptions, and all the actions it has performed —
endures, either as motor habits or mechanisms, or as
pure memories. All this need not be present in its
consciousness ; the motor habits would not, of course,
and only so much of the past would be recalled as
would be relevant to the choice which the organism
was about to make of the many kinds of responses
possible to its motor organisations. Out of this past
it would select all that was connected in any way with
the actions which were possible to it in the present.
It would recall all actions previously performed which
resembled the one provisionally decided upon ; but
recalling also the other circumstances associated with
those past actions, it would discover something which
would lead it to modify that provisional action. Now
in describing the whole behaviour of the acting organism
in this way are we doing any more than simply ex-
pressing in more precise terms the " commonsense "
notions of the ordinary person ? The latter would sum
up all this discussion by saying that what he would
do in any set of circumstance depended not only on
the circumstances themselves but upon his experience.
^ A visual image may, of course, be something that has never been actually
seen. But then its elements have had actual perceptual existence in the past.
THE VITAL IMPETUS 157
Physiology shows us as clearly as possible that in the
stimulation of a receptor organ, the propagation of a
nervous impulse along an afferent nerve, the trans-
mission of this impulse through the cord or brain," or
both — in the propagation again of the impulse through
an efferent nerve and the transformation of this
impulse into a releasing agency, setting free the energy
potential in the muscle substance — that in all this
there can be nothing more than physico-chemical
energy-transformations. All this is clear and certain.
But why should the same afferent stimuli, entering
the central nervous system at different times by the
same avenues, and in the same manner, traverse
different tracts, and issue along different efferent
nerves, producing different results ? Or why should
different stimuli entering the central nervous system
take the same intra-cerebral paths and then affect the
same efferent nerves and effector organs ? It is
because these stimuli lead to perceptions which fuse
with, and become part of the duration of, the organism.
And the response then becomes a response not to
the physical stimulus, but to the duration modified in
this way.
Can we conceive of any physical mechanism in
which the duration of the organism accumulates ?
Can we think of any way in which memories are
stored in the central nervous system ? When we say
" stored," it is our ingrained habit of thinking in terms
of space and number that makes us regard memories
as laid by somewhere, in the way we file papers in a
cabinet, or store specimens in a museum. Supposing
perceptions are stored in this way, we think of them
as stored or recorded in the same way as a conversa-
tion is recorded and stored in a phonograph. The
phonograph can reproduce the conversation just as
158 THE PHILOSOPHY OF BIOLOGY
it was received, but what we make use of when we
utilise our experience is obviously the elements of that
experience, selected and re-integrated as we require
them. There must, then, be something like an analysis
of our perceptions, a dissociation of these into simple
constituents, and a means of restoring and recording
these constituents in such a way that they can be re-
combined in any order, and again made to enter into
our consciousness.
It is quite possible to imagine such a mechanism.
Let us suppose that an efferent impulse enters the
cerebral cortex via any one axon : there is a perfect
labyrinth of paths along which the impulse may travel.
Everywhere in the central nervous system we come
upon interruptions of nervous paths formed by inter-
digitating arborescent formations. The twigs of these
arborescences do not, apparently, come into actual
contact with each other and the impulse leaps across
the gap between them. This gap is, of course, ex-
ceedingly narrow, and one can almost speak of it as a
membrane, since it must be occupied by some organised
substance. It has been called the synaptic membrane.
Let us suppose that a stimulus of a certain nature
passes through the synapse, modifying it physico-
chemically as it passes. Thereafter a stimulus of
similar nature will tend to pass across this particular
synapse, the resistance of the latter having been
decreased. It will thus tend to travel by a definite
tract through the central nervous system. Now the
latter we may regard in a kind of way as a very com-
plicated switchboard, the function of which is to place
any one stimulus (or series of stimuli) out of many in
connection with any one motor ^ mechanism (or series
^ Or more generally effector mechanism. This enables us to include
reactions, such as secretory ones, which are not motor.
THE VITAL IMPETUS 159
of mechanisms) out of many. A motor habit, or path,
is then estabhshed and will persist.
Such a conception is clear and reasonable in principle,
and all work on nervous physiology tends to show that
it is a good working hypothesis. We cannot read
modern books without feeling that immense advances
\vill be made by its aid. But the complexity of the
brain of the higher vertebrate is so incredibly great,
and the difficulties of imagining the nature of the
necessary physico-chemical reactions in the synapses,
and elsewhere, are so immense that experimental
verification may be impossible. And all that we have
said applies to a single elemental stimulus, yet in any
common action the stimulus is a synthesis of almost
innumerable simple ones, while the response is also a
synthesis. The optical image of almost any object
contains a very great number of tints and colours
differing almost imperceptibly : there must at least
be as many simple stimuli as there are rod or cone
elements in the part of the retina covered by the
image. The motor responses consist of a multitude of
delicately adjusted and co-ordinated muscular con-
tractions and relaxations. If we are to accept a
mechanistic hypothesis of action, of this kind, and
which includes only such processes as are suggested
above, it is not enough that a logical description, con-
sistent in itself, and consistent with physico-chemical
knowledge, should be formulated. The mere state-
ment of such an hypothesis does not carry us far. If
it is, in essence, mechanistic, it must be capable of
experimental verification in detail.
Even if it were verified experimentally it would
still leave untouched the problem of consciousness.
All that we have considered are series of physico-
chemical energy-transformations. How, then, does
160 THE PHILOSOPHY OF BIOLOGY
consciousness arise ? We cannot even imagine its
association in a functional sense with, the train of
events forming an afferent impulse. In some form or
other mechanism must assume a dualism — a parallelism
of physical and psychical processes. Physical events
in the central nervous system are associated with
psychical ones — when the former occur so do the latter
— yet the former are not "causes " in any physical sense
of the latter. Consciousness follows cerebral energy-
transformations as a parallel " epiphenomenon." At
once we leave the province of mechanism, and how can
we remain content with such a limitation of our descrip-
tions ? And if we conclude, as we seem obliged to do,
that consciousness is an affective agency in modifying
our responses to external stimuli, does not this in itself
show that our concept of behaviour as a purely physico-
chemical process is insufficient in its exclusiveness ?
We return to a consideration of the main results
of experimental embryology in a later chapter, but let
us notice here what is the direction in which these
results, and those of the analysis of instinctive and
intelligent action, carry us. It is towards the con-
clusion that physico-chemical processes in the organism
are only the means whereby the latter develops, and
grows, and functions, and acts. In the analysis of
these processes we see nothing but the reactions studied
in physical chemistry ; but whenever we consider the
organism as a whole we seem to see a co-ordination,
or a control or a direction of these physico-chemical
processes. Nageli has said that in the development
of the embryo every cell acts as it if knew what every
other cell were doing. There is a kind of autonomy
in the developing embryo, or regenerating organism,
such that the normal, typical form and structure comes
into existence even when unforeseen interference with
THE VITAL IMPETUS 161
the usual course of development has been attempted :
in this case the physico-chemical reactions which
proceed in the normal train of events proceed in some
other way, and the new direction is imposed on the
developing embryo by the organisation which we have
to regard as inherent in it. This same direction and
autonomy must be recognised in the behaviour of the
adult organism as a whole. What is it ? We attempt
to think of it as an impetus which is conferred upon the
physico-chemical reactions which are the manifesta-
tions of the life of the organism. It is the dan vital
of Bergson, or the entelechy of Driesch. What is
included in these concepts we consider in the last
chapter of this book ; and before so doing it will be
necessary to consider the organism from another point
of view, that of its mutability when it is regarded as
one member of a series of generations.
CHAPTER V
THE INDIVIDUAL AND THE SPECIES
What is an individual organism ? A Protozoan,
such as an Amceha or a Paramcecium, is a single cell :
it is an aggregate of phj^sical and chemical parts,
nucleus, cytoplasm, etc., and no one of these parts
can be removed if the organism is to continue to live.
The cell can be mutilated to some extent, but, in
general, its life depends on the integrity of its essential
structures, and it cannot be divided without ceasing
to be what it was. It contains the minimum number
of parts which are necessary for continued organic
existence.
Such an organism as a Hydra consists of an aggre-
gate of cells which are not all of the same kind. The
outer layer, or ectoderm, is sensory and protective,
and contains organs of aggression ; while the inner
layer consists of cells which subserve the functions of
digestion and assimilation. All these parts are, in
general, necessary for the life of the Hydra. They can
be mutilated ; the animal can be cut into two parts,
and each of these parts may regenerate, by growth,
the part that was removed. Yet the existence of
ectoderm and endoderm, in a certain minimum of
mass, is necessary for this regeneration. The higher
animal, or Metazoon, is therefore an aggregate of
cells, each of which is equivalent to the individual
Protozoon ; but these cells are not all alike — that is,
162
THE INDIVIDUAL AND THE SPECIES 163
there is differentiation of tissues in the multicellular
organism.
Again, the Coelenterates provide examples of
animals which are aggregates of parts, each of which
is the morphological equivalent of a single Hydra.
Such an animal as a Siphonophore, for instance,
consists of zooids, and each of these units has the
essential structure of a Hydra. But the zooids are
not all alike : some of them subserve the function of
locomotion, others of aggression, others of digestion
and assimilation, and so on. Here, again, the whole
organism may be mutilated ; parts may be removed
and regeneration may occur ; but, as a Siphonophore,
all of the different zooids must be present if the char-
acteristic functioning of the animal is to continue.
The Protozoon is, therefore, an individual of the
first order, the Hydra an individual of the second
order, and the Siphonophore an individual of the
third order. Some such conception of degrees of
individuality will probably be regarded as satisfactory
by most zoologists, yet consideration will show that
it is very inadequate. Many unicellular plants and
animals may consist of a number of cells, which are
all alike. The Diatoms and Peridinians reproduce by
the division of their cell bodies and nuclei, and the
parts thus formed may remain in connection with each
other. A Diatom may consist of one cell, or it may
consist of a variable number of such connected together
by filaments, or in other ways ; and the dissociation
of such a series may occur without interfering in any
way with the functioning of the parts separated. A
Tapeworm consists of a " head " or scolex, containing
a central nervous mass and organs of fixation ; and
organically continuous with this is a series of segments
or proglottides. These proglottides are formed con-
164 THE PHILOSOPHY OF BIOLOGY
tinuously from the posterior part of the scolex, and
they may remain in connection with each other, and
with the central nervous system and some other
organs which are concentrated in the scolex. Never-
theless, each proglottis contains a complete set of
reproductive organs ; it has locomotory organs so that
it can move about, and can hx itself to any surface
into which it comes in contact. It can lead, for a
considerable time, at least, an independent existence
apart from that of the scolex and the other proglottides
with which it was originally in continuity. In the
majority of Polyzoa, the common Sea-Mat, for instance,
the organism consists of a very large number of polypes
or zooids, each of which secretes an investment of
some kind round itself, but all of which may be con-
nected together by a common flesh. In many Zoo-
phytes there is essentially the same structure. In
Corals there are very numerous zooids, each of which
Hves in a calcareous calyx secreted by itself. Polyzoa,
Zoophytes, and Corals are individuals of the third
order, and we might regard the tapeworm strobila—
the scolex with its chain of proglottides— as belonging
also to the same category. Nevertheless, a part of a
Polyzoan or Hydrozoan colony, or a proglottis from a
tapeworm, may become detached, when it will continue
to Hve and reproduce and exhibit all the character-
istic functioning of the species to which it belonged.
Such an animal as a Hydra, or a Planarian or Chse-
topod worm, or a starfish, may be cut into several
pieces, and provided that each of these pieces exceeds
a certain minimum of mass, it will regenerate the whole
structure of the organism of which it formed a part.
In the developing embryo of the Sea-urchin the eight-
cell stage may be treated so that the blastomeres may
come apart from each other : each of them will then
THE INDIVIDUAL AND THE SPECIES 165
begin to segment again and will reproduce the typical
larval Sea-urchin. The parasitic flat-worm, known
as the liver-fluke, produces larvae which develop to
form other larvae called rediae. Each redia normally
develops into another larval form, called a cercaria,
which Anally develops into the adult worm. But in
certain circumstances each redia may divide and
reproduce a number of daughter- rediae, and there may
even be several generations of these larvae. In many
lower animals buds may be formed from almost any
part of the body, and each of these buds may reproduce
the entire organism. In plants the entire organism
may be grown from a very restricted part or cutting.
Thus the individual, whether of the first, second, or
third order, may be divided without necessarily
ceasing to be what it was.
Regeneration of fragments detached from the
fully developed adult body so as to form complete
organisms does not, in general, occur among the higher
animals, nor, as a general rule, does reproduction by
bud-formation occur. When such animals reproduce,
an ovum develops to form a large mass of cells, which
later on become differentiated to form the tissues and
organs of the adult body. But a relatively small
number of the undifferentiated cells persists in the
ovaries of the females, or in the testes of the males,
and each of these cells may again develop and reproduce
the organism. There is apparently no limit to this
process : any animal ovum may become divided
successively so that an infinite geometrical series is
produced, and in every term of this series all the
potentialities of the first one are contained.
The physical concept of individuality — that which
cannot be divided, or which may not be divided with-
out ceasing to be what it was — such individuality as
166 THE PHILOSOPHY OF BIOLOGY
the chemical molecule possesses cannot be applied
to the organism. Any definition that involves the
idea of materiality fails. Obviously the notion of the
individual most commonly met with in zoological
writings — that it is the product of the development
of a single ovum — fails, for, logically applied, it would
regard the entire progeny of the ovum, that is, all the
organismiS belonging to the species, as the individual.
It is clear that the difficulties of the concept arise
from our attempt to identify the life of the organism
with the material constellation in which this life is
manifested. In the course of generation after genera-
tion the ovum becomes divided and grows and is
again divided, and so on without apparent limit.
But if we assume that the " organisation " or " en-
telechy " is material and is capable of this infinite
divisibility without impairment of its attributes, do
we not extend to matter a property which belongs
only to the concepts dealt with by mathematics ?
The discussion of individuality with regard to the
organism, considered as a morphological entity, is,
indeed, rather a formal one, and it is valuable only
in so far as it has for its object the establishment of
the most convenient terminology. Nevertheless, the
notion of organic individuality is clear to us though
it is a notion felt intuitively and incapable of analysis.
We see in nature animals like ourselves, and we do
not doubt that each of them is an entity isolated from
the rest of the universe, and to which the rest of
the universe is relative. We ourselves are primarily
centres of action. Motion, or change of position
with respect to some object apart from ourselves in
nature, is only relative, and there is no standard or
point in the universe which is motionless and to which
we can refer the motion of a body apart from our
THE INDIVIDUAL AND THE SPECIES 167
own. But the motion of our own body is something
felt or experienced intuitively, something absolute.
As we move, the universe, our universe rather — that
is, all that we act upon, actually or in our contemplation
— contracts in one direction and expands in another.
We feel ourselves to be apart from it although we may,
to some extent, control it. We have no doubt that
the higher animals have this feeling of isolation from,
and relation to, an universe which is something apart
from themselves ; though, of course, the attempt to
demonstrate this leads to all the kinds of difficulties
suggested in our attempt to discuss individuality.
It is a conviction so strongly felt that we have no
doubt about it. The organic individual we may then
describe as an isolated, autonomic constellation of
physico-chemical parts capable of indefinite growth
or reproduction .1
What is reproduction ? It is organic growth by
dissociation accompanied in the higher organisms by
differentiation and reintegration. To make this state-
ment clear, we must now consider the phenomena of
reproduction in the lower and higher organisms.
We know purely physical growth. If a small
crystal of some suitable substance be suspended in an
indefinitely large quantity of a solution of the same
chemical substance it will begin to grow, and there is
no apparent limit to the mass which it may attain.
Such giant crystals may be grown in the laboratory
or they may be found in rock masses. Growth
here is a process of accretion in which a particular
form is maintained. Form in inorganic nature may
be essential or accidental. Accidental forms are such
^ The description is, of course, only a convenient one. The notion of
individuaUty, as it is expressed in the earlier part of this paragraph, is an
intuitively felt, or subjective, one. It is best called personality.
168 THE PHILOSOPHY OF BIOLOGY
as are partially the result of a very great number of
small and unco-ordinated causes : the form of an
island or a mountain suffering erosion, or the shape
of a river valley or delta, or the arrangement of the
stones forming a moraine at the side of a glacier.
Essential forms are such as are assumed as the result
of the operation of one or a few co-ordinated causes,
and such are the forms of crystals. They are invari-
able, or they vary within very small limits about an
invariable mean form.
The form of a crystal depends on the structure of
the molecules of the chemical substance from which
it is produced. We cannot, of course, speak of the
shape of a molecule, but we know that the atoms of
which it is composed have certain positions in space
relative to each other — positions which are con-
ceptualised in the structural formulae of the chemists.
In the solution, or mother-liquor, these molecules
move freely among each other, but in the crystal they
become locked together and their motions are re-
stricted. The shape of the crystal depends on the
way in which the molecules are locked together, or on
the way in which they are arranged. A cube may
be built up by the arrangement of a number of very
small cubes : obviously we could not make a cube from
a number of very small hexagonal prisms if the latter
were to be packed together in such a way as to occupy
the minimum of space. An infinitely great number
of cubes might also be formed by adding single layers
of very small cubes to the faces of an already existing
one — that is, by the accretion of elements of essentially
similar form. In every cube (or crystal) of this infinite
number the geometrical form would be the same,
and if we were to measure any one side of any cube
of this series we should find that the total surface
THE INDIVIDUAL AND THE SPECIES 169
would always be a definite function of the length of
this side. The mass of a cube would also be a function
of such a measurement : it would be al^, a being a
constant depending on the unit of mass and on the
specific ^veight of the substance of which the crystal
was composed. If we take a series of crystals of
increasing size, this relation holds for every one of
them : M=al\ M being the mass, a the constant
referred to above, and /, the independent variable,
being any one length of a side of the crystal.
If the organism grows by accretion in the same way
as does a crystal, this relation ought also to hold in all
the exciusiveness with which we expect it to hold in
the growth of a crystal. But it does not so grow. Its
growth is something essentially different, and none
of the superficial analogies so prevalent nowadays
ought to obscure this difference. The organism may
grow by accretion, thus layers of calcareous matter
may be added to the outside of a membrane bone from
the investing periosteum, or it may grow by the
deposition of matter within the actual cell bodies,
(the process of growth by intussusception of the plant
physiologists). But the extent of growth by accretion
is strictly limited in all organisms : for each there is
a maximal mass determined by the nature of the
animal or plant, and this mass is that of the uni-
cellular organism itself, or that of the cells of which
the multi-cellular organism is composed. There may
also be growth by accretion in the case of the formation
of skeletal structures, which are laid down by the
agency of the cells of the organism ; but if we confine
our attention to the growth of the actual living sub-
stance we shall see that accretion ceases when the
mass characteristic of the cells has been attained,
when growth by dissociation begins. The cell then
170
THE PHILOSOPHY OF BIOLOGY
divides, and each of the parts into which it has divided
grows to the limiting size, and division again occurs.
This is what happens in the case of the growth of the
Sea-urchin egg to form the larva, or blastula. The
ovum segments into two blast omeres, each of which
then grows to a certain extent, and again segments
into two blast omeres. After the completion of ten
divisions there are about looo cells which are arranged
so as to form a hollow ball — the blastula.
Differentiation is now set up. In the blastula
stage all the cells are alike, actually and potentially.
But soon one part of the
hollow ball of cells be-
comes pushed inwards,
and the cells of this
inturned layer become
different from those of
the external layer, while
cells of a third kind
appear in the space be-
tween the external and
internal layers. This is the process of differentiation
leading to the development of the various tissues —
protective, sensory, digestive, skeletal, etc. The cells
still continue to divide and grow to their maximal
size, but when the process of differentiation begins,
the cells which are formed are not quite the same
as those from which they originated. Finally, how-
ever, when the rudiments of all the tissues of the
adult body have been laid down, the cells begin to
produce daughter-cells of only one kind. Growth of
the embryo consists, therefore, of the dissociation or
division of the substance of the ovum and blastomeres,
followed by a gradually increasing differentiation of
the cells so produced.
— Ectoderm
Mesodermal
cells
-£ndocLerm
Fig. 20. — The Sea-urchin Gastrula
larva in section.
THE INDIVroUAL AND THE SPECIES 171
Reintegration proceeds all the time. Blastula
and gastrula larvae are really organisms capable of
leading an independent existence— that is, they are
autonomous entities or individuals. The activities
of the parts of which they are composed — ectodermal
locomotory cells, ectodermal sensory cells, endodermal
assimilatory cells, and so on, must be co-ordinated.
The cells are in organic material continuity with
each other, and events which occur in any one of them
affect all the rest. Impressions made upon the
sensory cells are transmitted to the locomotory cells,
and food-material assimilated by the assimilatory
cells is distributed to all the others. At all stages the
growing embryo is an organic unity. The more fully
it is developed, the greater the morphological com-
plexity of the organism, and the more numerous its
activities, the greater is the differentiation ; but the
greater also is the co-ordination of the organs and
tissues. In the higher animals this co-ordination and
integration of activities is effected (mainly) by the
central and peripheral nervous systems, but specially
differentiated nervous cells are not necessary for this
purpose. Differentiation during growth is therefore
necessarily accompanied by reintegration of the parts
dissociated and different iated.^
In the process of organic growth the relation
between mass and form no longer holds in all the
^ Societies and civilisations, the associations of bees and ants, or the
Modern State, obviously exhibit this differentiation. It is morphological
and functional in the case of the Arthropods, since individuals performing
difierent duties are modified in form. It is functional only in the case of human
societies. Integration of the activities of the individuals in both kinds of
societies is effected by inter-communication : articulate symbols in the case
of the lower animals, language in the case of man. If the concept of " orders
of individuahty " were anything more than a convenient, though artificial,
analysis of naturally integral entities, we might speak of the ideal state or the
insect society as a " fourth order of individuality."
172 THE PHILOSOPHY OF BIOLOGY
exactness with which it apphes to the growth of the
crystal. We might spend a Hfetime growing tablets
of cane-sugar, but in all cases we should find that the
mass of any crystal was proportional to the cube of a
length of a diameter : there would be a strict relation
between mass and geometrical form. But this strict
relation does not hold in the case of a series of organ-
isms belonging to the same species but differing in
size. If we m^easure, for instance, the lengths of a
great number of fishes of the same species, we should
find that we must describe the law of growth, not by
the simple equation M=al^, but by an empirically
evaluated expression of the form M==^a-\-hl-\-cl^+dP^
. . . and that the constants in this equation would
vary with the species studied and with the conditions
in which it is living — that is, the organism changes in
form as it increases in size. This is inconceivable in
the case of purely physical growth by the accretion
of molecules, and we find again that the characters
of the organism depend not only on what it is but also
upon what it has been — that is, upon its duration.
Growth, then, in plants and animals implies variability
in form, in general cumulative variability, leading to
an indefinite departure from the typical form.
The organism, therefore, does not grow simply by
the accretion of material, but, having attained a
certain limit of size, it divides or reproduces. In the
lowest plants and animals this process of division is
simple : either the organism (unicellular or multi-
cellular) divides itself into two approximately equal
parts or it divides into a number of such parts. The
first process is represented by the reproduction of a
bacterium or an Amceba, or by the division of a
Planarian worm ; the second is represented by the
division (in many Protozoa, for instance) of the whole
THE INDIVIDUAL AND THE SPECIES 173
organism into a number of spores. Fundamentally
the two processes are alike : the simple, binary division
of the Bacterium is followed at once by growth by
accretion, while in brood-formation (the cases of
multiple division) the parent cell divides, and then
each of the daughter-cells divide, and so on for
several generations. After the completion of these
divisions the brood-cells grow by accretion to their
normal size. It is meaningless, in the light of our
previous discussion, to say that the individuality of the
mother-cell " is merged in that of the daughter-cells."
But we may believe that a Paramoecium possesses
some degree of consciousness. Does it possess person-
ality— that is, the feeling of isolation from the rest of
the universe, and the feeling of oneness with its own
past-memory or conscious duration ? If so, its person-
ality, when it divides, becomes one with that of its
daughter-cells. Or is its personality and conscious
past that also of its sister-cells, and also that of the no
longer existent mother-cell, and the cell of which this
in its turn was a part ? We must remember that such
an organism as a Paramcecium shows in its behaviour
most of the signs of intelligence ; that the parts into
which it divides when it reproduces are equally de-
veloped ; and that the process of division may not
interrupt the conscious duration of either part. Is
there a common personality, or oneness of conscious-
ness, of all the organisms of this kind which are
descended from the same individual ?
Reproduction by division, simple or multiple,
does not proceed indefinitely in the case of the uni-
cellular organisms. Sooner or later there is a limit,
and the cell is then no longer able to continue divid-
ing. Conjugation then occurs in one of many modes.
Essentially two organisms come into contact and
174 THE PHILOSOPHY OF BIOLOGY
their nuclei fuse, or rather some of the material of one
nucleus is transferred to the other. The cells then
separate and reproduction by division begins again.
This is not necessarily sexual reproduction : it is
the conjugation of essentially similar morphological
entities. If two conjugating Paramcecia possessed
distinct personalities we might imagine a merging or
addition of two conscious durations or memories.
Sexuality, however, includes less than this. In this
mode of reproduction the conjugating bodies are not
organisms in the usual sense, but rather modified
organisms or highly modified parts of organisms. In
some lower plants the conjugating cells may be modi-
fied with respect to the cells characteristic of the
organism, but they may be approximately equal in
size. But in the multicellular plant and animal, in
general, the conjugates are cells detached from the
parental body, and differing chiefly from the cells of
the latter in that they show a lack of differentiation.
One of these cells, that detached from the paternal
body, is the spermatozoon (in the case of the animal),
or the pollen cell (in the case of the plant). It is
much smaller than the sexual cell detached from the
maternal body : this is the ovum in the case of the
animal, or the oosphere in the case of the plant. In
general the ovum is a relatively large cell, since it
contains abundant cytoplasm, which may also be
loaded with yolk or other reserve food material.
The spermatozoon is very much smaller and consists
of a nucleus with a minimal mass of c3rtoplasm. The
ovum is, in general, immobile ; the spermatozoon is
generally highly mobile.
The essential process in the sexual reproduction
of the unicellular organisms is therefore the con-
jugation of the organisms themselves. In multi-
THE INDIVIDUAL AND THE SPECIES 175
cellular organisms, modified cells — the germ-cells —
become detached from the bodies of the parents, and
these cells conjugate. In many lower plants and
animals phases of sexual and asexual reproduction
alternate, thus Paramcechmi reproduces by simple
division, but at intervals conjugation occurs. In
plants sporophytic and gametophytic generations
alternate, the sporophyte reproducing by multiple
division — that is, by the formation of spores, and the
gametophyte reproducing by the formation of germ-
cells. There are few organisms — possibly none — in
which continued asexual reproduction by simple or
multiple division, spore-formation, bud-formation, etc.,
can proceed without limit. In the great majority of
cases investigated asexual reproduction becomes
feeble after a time and then ceases, and it has been
held that the stimulus of conjugation of the cells, or
that of sexual reproduction, is necessary for its
renewal. In such cases the organism is said to have
become " senescent," and " rejuvenescence " by some
means becomes necessary. As a general rule rejuven-
escence is effected by the interchange of nuclear matter
between two conjugating organisms, but it may be
effected by rest, or by a change of environment, or
by the supply of some unusual food-material to the
liquid in which the dividing organism is contained.
Thus, if various materials be added to the water in-
habited by a dividing Paramcecium, the Protozoon
may continue to reproduce by simple division for at
least two thousand generations. We must remember,
however, that " senescence " and " rejuvenescence "
are only words ; what is the essential nature of the
changes denoted by them we do not know.
In sexual reproduction, as it occurs in the great
majority of plants and animals, the ovum, or female
176 THE PHILOSOPHY OF BIOLOGY
germ-cell, is fertilised or " activated " by the male
germ-cell. But this activation by the spermatozoon
is not necessary, for the ovum itself is capable of
division and development to form a complete organism.
This occurs in the cases of natural parthenogenesis
among insects and some other animals, where the
ovum proceeds, without fertilisation, to segmentation
and development. In some lower plants, where the
size of the male and female germ-cells is nearly equal,
either of them may undergo parthenogenetic develop-
ment : in such cases we cannot, of course, properly
speak of sexual differentiation. In the cases cf
organisms normally reproducing sexually, the stimulus
to development is afforded by the entrance into the
ovum of the spermatozoon — that is, by the mixture
of the male and female germ-plasms ; but in some
animals this stimulus may be replaced by the addition
to the water in which they are living of certain chemical
substances. This is the process of artificial partheno-
genesis first studied by Loeb in the case of the eggs
of the Sea-urchin ; and its anatysis suggests that the
spermatozoon conveys some substance into the egg,
and that this substance initiates segmentation by
setting up a train of chemical reactions. What these
reactions are exactly, and what is the process of
" formative stimulation " by the spermatozoon, we
do not know. It is quite certain, however, that much
more than this process of formative stimulation is
involved in the fertilisation of the egg by the sperma-
tozoon. The mixture of the male and female germ-
plasms resulting from conjugation confers upon the
embryo the characters of both the parents and of
their ancestries.
In an unicellular organism the " body " consists
of a single cell containing a nucleus. The extra-
THE INDIVIDUAL AND THE SPECIES 177
nuclear part of the cell — the cytoplasm — ^is modified
in various ways : thus it may possess flagella, or
cilia, so that it may be actively locomotory. It is at
once a receptor apparatus, susceptible to changes in
the medium in which it lives, and it is also an effector
apparatus, capable of transforming stimuli received into
motor impulses. It may be able to accumulate avail-
able energy by making use of the energy of radiation
in the synthesis of carbohydrate and proteid from the
inorganic substances in solution in the water in which
it Uves ; and it is also able to expend this energy in
controlled movements. All the characteristics of life,
in fact, are exhibited by the unicellular organism,
the dift'erentiation of the cytoplasm corresponding
functionally to the differentiation of the tissues of the
multicellular animal or plant.
In the latter the organs, organ-systems, and tissues
are composed of differentiated cells. Development
consists essentially of a process of cell-formation by
simple division, and at the end of this process of
segmentation various rudiments (Anlagen) are estab-
lished. The older embryologists sought to recognise
the formation of three " germ-layers " in most groups
of animals : these were the outer layer or ectoderm,
the middle layer or mesoderm, and the internal layer
or endoderm. The ectoderm, it was held, gave rise
to the integument, the central and peripheral nervous
systems, and the sensory organs. The mesoderm gave
rise to the musculature and skeleton, the excretory
organs, and some other tissues. The endoderm gave
rise mainly to the alimentary canal and its glands.
The " Gastrea-Theory " of Haeckel sought to recognise
a similar larval form, or " Gastrea," in the develop-
ment of most multicellular animals, and much
ingenuity of argument was required for the estab-
M
178 THE PHILOSOPHY OF BIOLOGY
lishment of this homology. The newer embryology
recognises the difficulties implied in the application,
in all its exclusiveness, of the Gastrea-theory to the
higher phyla of multicellular animals ; so that nowa-
days it has been necessary to abandon the notion of
the metazoan animal as being built up from these three
primary germ-layers. At the conclusion of segmenta-
tion, then, the embryo consists of a mass of cells
similar to each other in structure, but differing in fate
and in potency. Some of these cells are destined to
give rise to the integument, the nervous system, and
the sense-organs ; others become the skeleton and
musculature ; and others again the organs of digestion,
assimilation, and excretion. A primary arrangement
of these groups of cells into three layers is indeed set
up in many cases of development, but it is plain that
this arrangement is far from being an universal one.
Modern embryology shows in the clearest possible
manner that at the end of segmentation the embryo
consists of a group of cells each of which has normally
a different fate in subsequent development. What
precisely each cell will become depends on its position
with regard to the others. But each cell is capable
of becoming more than it normally becomes : its
potency is greater than its actual fate. If the normal
course of development is interrupted, a cell, which
would usually have given rise to a part of the skeleton,
may give rise to a part of the alimentary canal. The
cells of the developing embryo are autonomous.
In the normal course of development most of the
cells existing at the end of segmentation give rise to
the " body " of the organism, undergoing differentia-
tion as they so develop. But a few embryonic cells
persist without stmctural modification throughout the
development of the animal. They divide and grow
THE INDIVIDUAL AND THE SPECIES 179
and become greater in number, but remain unchanged
in other respects. These cells become the essential
reproductive organs, or gonads, of the adult animal—
that is, the ovaries of the female and the testes of the
male. In the females of the higher animals (the
mammals, and perhaps some of the Arthropods)
these cells only divide and grow during the early
stages of development, and long before the beginning
of adult life the number of ova in the gonads has
become fixed. In all males, and in the females of
most animals, however, the reproductive cells appear
to be capable of unlimited multiplication.
The essential cells of the gonads, the ovarian
mother-cells or the sperm mother-cells, constitute the
germ-plasm. In modern, speculative, biological litera-
ture the term germ-plasm is, however, restricted
to the chromatic material in the nuclei of the repro-
ductive cells, the cytoplasm being regarded as non-
essential for the transmission of the hereditary qualities
of the organism. It seems clear, however, that this
distinction between the cytoplasm and the chromatic
matter of the nucleus is not always a valid one, so
that it is best to speak of the whole cell as constituting
the germ-plasm. The embryonic cells, therefore, have
different fates : some of them become transformed
during development into the body or soma, and others
remain unmodified throughout life as the germ. The
soma enters into intimate relationships with the
environment ; it is affected by the vicissitudes of
the latter; and it may actively respond to them.
The germ-cells may possibly migrate through the body,
perhaps, it has been suggested, developing fatally and
irresponsibly into the mysterious, malignant tumours
of adult life. Normally, however, they remain segre-
gated in the reproductive glands, secluded from the
180 THE PHILOSOPHY OF BIOLOGY
outer environment. Their activities are inherent in
themselves, are rhjrthmic, and become functional
only on the assumption by the soma of the phase of
sexual maturity. From the point of the species the
soma is only the envelope of the germ-cells. It is
affected by every change of the environment, and
being usually cumulatively affected by the latter it
becomes at length an unfit envelope. Somatic death
then follows as a natural consummation, but the germ-
cells are, in a sense, immortal in that they remain
capable of indefinite growth by division.
In the sexual reproduction of the higher organism
a part of the germ-plasm becomes detached, under-
goes growth, and develops into an organism exhibiting
the parental organisation. But in the development
of the offspring, part of the germ-plasm received from
the parent persists unchanged, is transmitted to
another generation, and so on without apparent limit.
Something is transmitted from parent to offspring.
This something we regard as a cell exhibiting a definite
chemical and physical structure ; but while the germ-
cell differs in certain respects from an ordinary somatic
cell, these structural and chemical differences are
insignificant when they are compared with the differ-
ences in the potentialities of the cells. The somatic
cells are, in general, capable of reproducing only the
general character of the tissues of which they form
part. Some of them, the cells of the grey matter of
the central nervous system, for instance, appear to be
incapable of division and growth. But again the
facts of regeneration appear to point to the possession
by the somatic cells of more than this restricted power
of reproducing the tissues of which they form part :
to this extent the regeneration experiments tend to
remove the essential distinction between the somatic
THE INDIVIDUAL AND THE SPECIES 181
and germinal cells. Neglecting these results in the
meantime, we see that the germ-cells contain within
themselves the potentiality of reproducing the entire
organism in all its specificity. That which is trans-
mitted from the parent to the offspring is the parental
organisation in all its specificity ; and to say that this
organisation is a material thing is, of course, to state
a hypothesis, not a fact of observation.
This transmission of a specific form and mode of
behaviour from generation to generation is what a
hypothesis of heredity attempts to explain — that is, to
describe in the simplest possible terms, making use
of the concepts of physical science. " Twelve years
ago," says Jacques Loeb, " the field of heredity was
the stamping ground for the rhetorician and meta-
physician ; it is to-day perhaps the most exact and
rationalistic part of biology, where facts cannot only
be predicted qualitatively, but also quantitatively."
Let the reader examine for himself the meagre array
of facts on which this apotheosis of mechanistic biology
is based.
Two modern hypotheses of heredity demand atten-
tion— Weismann's hypothesis of the continuity of the
germ-plasm, and Semon's " Mnemic " hypothesis. In
the latter it is assumed that the basis of heredity is
the unconscious memory of the organism : modes of
functioning are " remembered " by the germ-plasm
and are transmitted. This notion presents many points
of similarity to that which we consider later on, so
that it need only be mentioned here. Weismann's
hypothesis — like Darwin's hypothesis of Pangenesis —
is a corpuscular one, and has obviously been sug-
gested by the modern development of the concepts of
molecules and atoms in the physical sciences. It
supposes that that which is handed down is a material
182 THE PHILOSOPHY OF BIOLOGY
substance of a definite chemical and physical structure.
This is not the germ-cell, nor even the nucleus of the
latter, but a certain material contained in the nucleus.
The latter contains protein substances containing a
greater proportion of phosphoric acid than does the
cytoplasm of the cells in general ; these proteins are
known as nucleo-proteins, though our knowledge of
their chemical structure is, so far, not very exact.
It is not, however, these that are the germ-plasm, but
a substance in the nucleus which becomes visible when
the cell is killed in certain ways, and which becomes
stained by certain basic dyes. It is distinguished by
this character alone and on that account is loosely
called " chromatin." This substance Weismann
identifies as " the material basis of inheritance."
When a cell divides, a very complex train of events
usually occurs. This process of " Mitosis " exhibits
many variations of detail, and without actual demon-
stration it is rather difficult to explain clearly. But
its essential feature is evidently the exact halving of
all the structures in the cell which is about to divide.
In the ordinary cell which is not going to divide immedi-
ately, the chromatin is diffused throughout the nucleus
as very numerous fine granules, recognised only by their
staining reactions. They may be concentrated at
some part of the nucleus, so that a division through
a plane of geometrical symmetry of the cell would
not, in general, exactly halve the chromatin. Prior
to division, therefore, this substance becomes aggre-
gated as granules lying along a convoluted filament
of a substance called " linin," which is characterised
principally by the fact that it does not stain with the
dyes that stain the chromatin. The filament breaks up
into short rods, called Chromosomes, and these rods
become arranged in the equator of the nucleus. The
THE INDIVIDUAL AND THE SPECIES 183
rods then split longitudinally, and one-half of each
moves towards one pole of the nucleus, the other half
moving towards the other pole. Various other modi-
fications of the cell and nucleus occur concomitantly
with these changes, but the essential thing that happens
seems to be the halving of all the structures of the cell,
and this is the simplest explanation of the phenomena
of mitotic cell division. Two daughter-cells are then
formed by the division of the mother-cell, and each of
these daughter-cells receives one-half of each of the
chromatin granules that were contained in the mother-
cell.
The chromosomes, or " Idants," are seen to consist
of discrete granules, and these are (generally) the
bodies known as the " Ids." The id cannot be resolved
by the microscope into any smaller structures : it lies
on the Hmits of aided vision ; but the hypothesis
assumes that it is composed of parts called " Deter-
minants," and the determinants are further supposed
to consist of " Biophors." The biophors are the
ultimate organic units or elements, and they are of
the same order of magnitude as chemical molecules.
We must suppose them to be raore complex than a
protein molecule, and the latter contains many
hundreds (at least) of chemical atoms. Now it is
possible to calculate the number of atoms contained
in a particle of the same size as the id : such a calcula-
tion may be made by different methods, all of them
yielding concordant results. This calculated number
of atoms may be less than that which we must
suppose to be present in the biophors, of which the
hypothetical id is composed ! ^
1 " But," says Weismann, referring to an objection of this nature, " it
should rather be asked whether the size of the atoms and molecules is a
fact, and not rather the very questionable result of an uncertain method of
investigation."
184 THE PHILOSOPHY OF BIOLOGY
The id is supposed to contain all the potentialities
of the completely developed organism. It is com-
posed of a definite number of determinants, each of
the latter being a " factor " for some definite, material
constituent of the adult body. There would be a
determinant for each kind of cell in the retina of the
eye, one for the lens, one for the cornea (or rather for
each kind of tissue in the latter), one for each kind of
pigment in the choroid and iris, and so on ; every
particular kind of tissue in the body would be repre-
sented by a determinant. Thus packed away in a
particle which lies just on the limits of microscopic
vision are representatives of all those parts of the
body which are chemically and physically individual-
ised, each of these hypothetical " factors " being a
very complex assemblage of chemical atoms. In
development the determinants become separated from
each other, so that whatever parts of the body are
formed by the first two blastomeres are represented
by determinants which are contained in those cells,
and which are sifted out from each other and segre-
gated. As development proceeds this process of
sifting becomes finer and finer, until when the rudi-
ments of each kind of tissue have been laid down a
cell contains only one kind of determinant. This con-
sists of biophors of a special kind, and the latter then
migrate out from the chromatin into the cytoplasm
of the cells in which they are contained, and proceed
to build up the particular kind of tissue required.
The nucleus of the germ-cell is thus a mixture of
incredible complexity, but in addition to this material
mixture there must exist in it the means for the
arrangement of the determinants in the positions
relative to each other occupied by the adult organs
and tissues. A mechanism of unimaginable complexity
THE INDIVIDUAL AND THE SPECIES 185
would be required for this purpose, and it must be
a mechanism involving only known chemical and
physical factors. It is safe to say that absolutely no
hint as to the nature of this mechanism is contained
in the hypothesis.
The determinants must be able to grow by repro-
duction, or by the accretion of new biophors, since in
each generation new germ-cells are formed. If we
say that they grow by reproduction in the sense that
an organism grows by reproduction, we beg the question
of their means of formation. Do they grow by the
addition of similar substances in the way that a crystal
grows ? If so, the molecules of which they are com-
posed must exist in the lymph stream bathing the
germ-cells — that is, the biophors themselves must
already exist in this liquid, for if we suppose that the
biophors are able to divide and grow by making use
of the protein substances which we know are present
in the lymph stream, then we confer upon these bodies
all the properties of the fully developed organism.
If they are present in the blood, then the composition
of the latter must be one of inconceivable complexity,
since it must contain as many substances as there
are distinct tissues in the animal body. We know, of
course, that this is not the case. How, then, are the
biophors reproduced ?
We must leave this field of unbridled speculation
(which cannot surely be " the most exact and rational-
istic part of biology.") What the study of the repro-
duction of the organism does show is that something
— -which we call the specific organisation — is handed
do^vn from parent to offspring, and that this some-
thing may possess a high degree of stability. No
apparent change of significance can be observed in
the very numerous generation of organisms (the 2000
186 THE PHILOSOPHY OF BIOLOGY
generations of Paramcecium, for instance, which were
bred by Woodruff) which can be produced by ex-
perimental breeding. Some species of animals — the
Brachiopod Lingitla, for instance — have persisted
unchanged since Palaeozoic times. Throughout the
incredibly numerous generations represented by this
animal series, the specific organisation must have been
transmitted in an almost absolutely unchanged con-
dition. The germ-plasm is therefore continuous from
generation to generation, and it possesses an exceed-
ingly great degree of constancy of character. This
conception of the continuity and stability of the specific
organisation is the feature of value in Weismannism,
and all that we know of the phenomena of heredity
confirms it. But it is pure speculation to regard
the organisation as an aggregate of chemically dis-
tinct substances, or if we say that this speculation
is rather a working hypothesis, then it must justify
itself by leading us back again to the results of
experience.
It is, however, not quite accurate to say that the
organisation persists unchanged from generation to
generation. The offspring is similar to the parent —
that is, the organisation has been transmitted un-
changed. But the offspring also differs just a little
from the parent — that is to say, the organisation is
modified by each transmission. In these two state-
ments we formulate in the simplest manner the law
of organic variability. Organisms may obviously be
arranged in categories in such a way that the
individuals in any one category resemble each other
more closely than they resemble the individuals belong-
ing to another category. We may, by experimental
breeding, produce an assemblage of organisms ail of
which have had a common ancestor, or a pair of
THE INDIVIDUAL AND THE SPECIES isr
ancestors. Now the individuals composing such an
assemblage would exhibit a close resemblance to
each other, such a resemblance as our categories of
naturally occurring organisms are seen to exhibit.
We should also find that the individuals of our natur-
ally occurring assemblage would be able to interbreed
among themselves, just as in the case of the experi-
mentally produced population. It may be concluded,
then, that the naturally occurring population is also
the product of a pair of ancestors. This inter-fertility,
as well as the close moi-phological resemblance of the
individuals, are the facts on which the hypothesis of
the common origin and unity of the assemblage, or
species, is formed.
The morphological resemblance between the
individuals, either in the natural or the artificial
populations, is not absolute. If we take any single
character capable of measurement we shall find that
it is variable from organism to organism. This
important concept of organic variability may be
made more clear by a concrete example. Exam-
ination of a large number of cockle shells taken
from the same restricted part of the sea-shore,
and therefore belonging presumably to the same
race, will show that the number of the radiating
ridges on the shell varies from 19 to 27, and that
the ratio of the length to the depth of the shell
also varies from 1:0.59 to 1:0.85. In the former
case the most common number of ridges is 23, and
in the latter case the most common ratio of length
to depth is 1:0.71. These are the characteristic
or modal values of the morphological characters in
question, and the other or less commonly occurring
values are distributed symmetrically on either side
of the mean or modal value, forming " frequency
188 THE PHILOSOPHY OF BIOLOGY
distributions." ^ The 'Value of the first character
changes b}^ unity in any distribution : obviously there
cannot be a fraction of a ridge ; and this kind of
variation is called " discontinuous." The value of
the second character may change imperceptibly, and
it is therefore called " continuous," a term which is
not strictly accurate, since in applying it we assume
that the numerical difference between two variates
may be less than any finite number, however smalL
In this assumption we postulate for biology the dis-
tinctive mathematical concept of infinite divisibility.
The difference from the mode, or mean, with
respect to a definite character in a fully grown organism
may be due to the direct action of the environment, in
the sense in which we have regarded the environment
as influencing the organism ; or it may be due to the
changes in the organism resulting from the increased
or decreased use of some of its parts. The conditions
with regard to nutrition, for instance, will not be the
same for all the individuals composing a cluster of
mussels growing on the sea-bottom. Those in the
interior of the cluster do not receive so abundant a
supply of sea-water as those on the outside of the
cluster ; and since the amount of food received by
any individual depends on the quantity of water
streaming over it in unit time, we shall find that the
internally situated individuals will be stunted or
dwarfed, while those on the outside will be well grown.
Such variations are acquired ones, but even when we
allow for them, even if we take care that all the
organisms studied live under conditions which are as
nearly uniform as possible, there will still be some
degree of variability. We cannot be sure that this
absolute uniformity ever exists ; and the notion of
1 See Appendix, p. 350.
THE INDIVIDUAL AND THE SPECIES
189
the environment of an organism may be extended
so as to include the medium in which embryonic
development took place, and even the parental body
which formed the environment for the germ-cells
from which embryonic development began. But it
is probably the case that even with an uniform en-
vironment, or with one in which the differences
were insignificant, variability would still exist. The
variations that might be observed in such a case
would belong to two kinds — " fluctuating variations,"
and " mutations."
4
>--
-.--[-.
"Kjr -.—
i
1
—
pa'pulf ^ can we attempt its analysis).
/\^\ \ /'y^^\ As 3, rule this process results
/ ^^ ' /X \ in a fluctuation, but if its
^f /TTv^ ]/ extent, or degree of opera-
V /7v\ / '^^^^' exceeds a certain " cri-
\ y^/ ' \^\ / ^^c^- value " a mutation is
\<(^^/ \ \^ v^ produced. We may, follow-
^"^i^^^^ < ^^,^^ ing the example of the phys-
8 icists, illustrate this by a
^^^•^3. "model."
This model is a modifica-
tion of Galton's illustration of the degrees of stability
of a species. It is a disc of wood rolling on its
periphery. We divide it into sectors, and the arcs
db, cd, ef, and gh have all the same radius, lo, 20,
30, and 40. Then we flatten the sectors be, de, fg,
and ha, so that their radii are greater than are those
of the other arcs. Now let us cause the disc to roll
about the point 8 as a centre. It will oscillate back-
wards and forwards about a mean position 8. Let us
think of these oscillations as fluctuations.
Suppose, however, that we cause the disc to roll
^ See Appendix, p. 351.
THE INDIVIDUAL AND THE SPECIES 193
a little more violently, so that it oscillates until either
of the points 3 or 4 are perpendicularly beneath the
centre 0. In either of these positions the disc is in a
condition of " unstable equilibrium," and an infini-
tesimal increase in the extent of an oscillation will
cause it to roll beyond the points 3 or 4. But if it
does pass either of these critical points it will begin
to oscillate about either of the new centres 5 or 7, thus
rolling on one of the arcs, ha or de. This assumption
of a new condition of stability we may compare with
the formation of a mutation.
All this is merely a conceptual physical model of
a process about which we know nothing at all. It is
meant to illustrate the view that the organisation of
a plant or animal is not something absolutely fixed
and invariable. The organism in respect of each
recognisable and measurable character oscillates
about a point of stability, that is to say exhibits
fluctuating variations about the mean value of this
character. If the stability of the organisation is
upset, so that it oscillates, or fluctuates about a
new centre, that is, if the variations deviate in either
direction from a new " type " or mean, a mutation
has been established. A mutation is not, therefore,
necessarily a large departure from " normality," It
is not necessarily a " discontinuous variation," nor a
" sport " nor a " freak." It is essentially a shifting
of the mean position about which the variations
exhibited by the organism fluctuate.
Such a mutation will, in general, involve the
creation of an " elementary species." We have con-
sidered only one character, say stature, in the above
discussion, but it generally happens that the assump-
tion of a new centre of stability involves all the char-
acters of the mutating organism. An elementary
N
194 THE PHILOSOPHY OF BIOLOGY
species therefore differs a little in respect of all its
characters from the species from which it arose, or
from the other elementary species near which it is
situated. This is what we do usually find in the
cases of the " races," or " local varieties," of any one
common species of plant or animal. That we do not re-
cognise that most, or perhaps all, of the species known
to systematic biology are really composed of such local
races is merely because such results involve an amount
of close investigation such as has not generally been
possible except in the few cases studied with the object
of proving such variability ; or in the case of those
species which are studied with great attention to detail
because of their economic importance. Thus the
herrings of North European seas can be divided into
such races, and it is possible for a person possessing great
familiarity with these fishes to identify the various
races or elementary species — that is, to name the
locality from which the fish were taken — by considering
the characteristics in respect of which the herrings of
one part of the sea differ from those of other parts.
The term " variety " has rather a different con-
notation in systematic biology from that which is
included by the term " elementary species." The
meaning of the latter is simple and clear. Two or
more elementary species are assemxblages of organisms,
in each of which assemblages the mean positions
about which the various characters fluctuate is diff-
erent. The term " variety " cannot so easily be defined.
The progeny of two different species (in the sense of
the term as it is usually applied by systematists)
may be called a hybrid variety of one or other of the
parent species. In the case of the ordinary species
of zoology such a hybrid would, in general, be infertile,
or if it did produce offspring these would be infertile.
THE INDIVIDUAL AND THE SPECIES 195
In the case of ordinarily bred offspring from parents
of the same species a large deviation from the parental
characters might be a malformation, or the result of
some irregularity of development. An " atavistic "
variation we may regard as the reappearance of some
character present in a more or less remote ancestor.
Thus dogfishes and skates are no doubt descended
from some elasmobranch fish which possessed an
anterior dorsal fin. This fin persists in the dog-fishes,
but has been lost in the skates and rays. Yet it may
appear in the latter fishes as an atavistic variation.
In a variety (following de Vries' analysis) a char-
acter which disappears is not really lost : it is only
suppressed, and it still exists in a latent form. Some
flowers are coloured, for instance, but there may be
varieties in the species to which they belong in which
the flowers are colourless. It may not be quite correct,
in the physical sense, to say that the colour has been
lost, but we may put it in this way. These flowers
are then coloured and colourless varieties of the same
species. Colour or lack of colour is not, however,
fixed in the variety, for the individual plant bearing
colourless flowers also bears in its organisation the
potentiality of producing coloured flowers. The petals
of a flower may be smooth or covered with hairs, and
in the same stock both of these varieties may occur.
But we must not speak of the presence or absence of
hairs as constituting a difference of kind : the smooth-
petalled flowers might be regarded as containing the
epidermal rudiments of hairs. So also coloured and
colourless flowers may be regarded as containing the
same kinds of pigment, but these pigments are mixed
in different proportions. Such a view enables us to
look upon these contrasting characters in the same
way as we look upon fluctuating variations, that is,
196 THE PHILOSOPHY OF BIOLOGY
as quantitative differences in the value of the same
character.
Such a suppression of a character is not really a
loss. An organism belonging to an elementary species
in which, say, monochromatic flowers are usually
produced may produce flowers which are striped.
The progeny of the plant may still produce mono-
chromatic flowers, but we must think of it as also
possessing the potentiality of producing striped flowers.
In the terminology of Mendelism the characters are
dominant and recessive ones.
In discussing Mendelian varieties we consider the
manner in which two contrasting characters — one
present in the male parent and one in the female —
are transmitted to the offspring. The characters in
question may be the tallness of the male parent and
the contrasting shortness of the female ; or the brown
eyes of the male and the blue eyes of the female ; or
the brown skin of the female parent and the white
skin of the male one. These characters may be
inherited in two ways : either they may be blended
or they may remain distinct in the offspring. The
children of the brown mother and the white father
are usually coloured in some tint intermediate between
those of the parents. The mulatto hybrid is fertile
with either of the parent races, and again the off-
spring may take a tint intermediate between those of
the parents, and so on through a number of generations.
But somewhere in this series the concealed or recessive
brown colour may appear in all its completeness,
showing that it has been present in the organisations
of all the intervening generations. The progeny of a
tall male parent and a short female parent are not,
in general, intermediate in stature between the parents ;
some of them may be tall and others short. The
THE INDIVIDUAL AND THE SPECIES 197
children of a brown-eyed mother and a blue-eyed
father do not usually have eyes in which the colours
of the parental eyes are blended : they are blue-eyed
or brown- eyed. The contrasting characters are spoken
of as dominant and recessive : if tallness is trans-
mitted to offspring, which may nevertheless produce
dwarf offspring, the latter character is said to be
recessive to tallness. The contrasting characters of
the parents therefore remain distinct in the progeny,
some of the latter exhibiting the one character and
some the other ; while it may happen that the one
character or the other may be segregated, so that it
only appears in, and is transmitted by, the offspring.
There are numerical relationships between the numbers
of the offspring in which the contrasting characters
appear.
Obviously, tallness and dwarf ness are not charac-
ters which differ in quality : they are different degrees
of the same thing. Brown eyes and blue eyes are not
necessarily different in quality, for we may think of
the same kinds of pigment as being present in the iris
but mixed in different proportions. But the term-
inology of this branch of biology appears to sug-
gest that the contrasting characters are, each of them,
something quite different from the other : there
are "factors" for "tallness," " dwarf ness," for blue
eyes and brown eyes, and so on. These qualities are
called " unit-characters," and they are supposed to
possess much the same individuality in the germ-
plasm as the " radicles " of the chemist possess in a
compound. Sodium chloride, for instance, is not a
blend of sodium and chlorine : the two kinds of atoms
do not fuse together but are held together merely.
The analogy is, however, very imperfect, for in the
chemical molecule the characters are not those of either
198 THE PHILOSOPHY OF BIOLOGY
of the constituents but something quite different,
whereas in the Mendehan cross the characters remain
distinct, but one of them is patent while the other is
latent. In the molecule, however, the atoms are
regarded by the chemist as lying beside each other
in certain positions, and the Mendelian factors are
also spoken of as if they lay side by side in the germ-
plasm. This terminology is useful, perhaps necessary,
in the work of investigation, but we must not forget
that it symbolises, rather than describes, the results
of experiment. If the factors are identified with
certain morphological structures in the nuclei of the
germ-cells, obviously all the objections that may be
urged against the Weismannian hypothesis as an
hypothesis of development apply also to the Mendelian
hypotheses as descriptions of a physical process of
the transmission of morphological characters.
It should clearly be understood what is implied
in the construction of such a hypothesis. Certain
processes are observed to take place when a somatic
cell divides : these processes we have regarded as
having for their object the exact division of all the
parts of the cell into two halves. This process of
somatic cell division is modified when a germ cell
divides prior to maturation (the process fitting it to
become fertilised). Then the cell nucleus divides into
four daughter-nuclei. One of these remains in the
cell substance which is to become the ovum, and the
other three, each of them invested in a minimal
quantity of cytoplasm, are eliminated as the " polar
bodies." Also the number of chromosomes in the
mother-cell becomes halved, so that the mature ovum,
or spermatozoon, possesses only one-half of the number
of chromosomes which are present in the ordinary
somatic cell. Now let the reader puzzle out for
THE INDIVIDUAL AND THE SPECIES 199
himself what may be meant by this behaviour of the
germ cells, and he will certainly see that several inter-
pretations are possible. But suppose that the chro-
matin consists of an incredibly large number of bodies
differing in chemical structure from each other, and
occupying definite positions with regard to each
other ; and suppose that there is a mechanism of
unimaginable complexity in the cell capable of rejecting
some of these chemically indi\'id.ualised parts, and
of " assembling " or arranging the others in much the
same way as an engineer assembles the parts of a
dynamo when he completes the machine. Then we
may regard the hypothetical discrete bodies which
form the hypothetical nuclear architecture as the
material carriers of Mendelian characters. It is
strange that the correspondence of such a logically
constructed mechanism with the effects which it would
produce if it existed should be regarded as a proof
that it does exist, yet biological speculation has
actually made use of such an argument. " It seems
exceedingl}^ unlikely that a mechanism so exactly
adapted to bring it " (the separation from each other
of the Mendelian material " factors " of inheritance)
" about should be found in every developing germ
cell if it had no connection with the segregation of
characters that is observed in experimental breeding."
Put quite plainly this argument is as follows : there
is a certain segregation to be seen in experimental
breeding, and certain processes may be observed to
occur in the developing germ cell. Add to these
processes many others logically conceivable, and add
to the observed material structure of the cell another
structure also logically conceivable. Then the assumed
mechanism and structure is " exactly adapted "
to (produce the effects which are to be explained.
200 THE PHILOSOPHY OF BIOLOGY
Therefore the mechanism and structure do actually
exist !
That which renders the son similar to the father —
the specific organisation — is undoubtedly very stable,
and it may persist in the face of a variable environment.
But now and then the son differs from the father.
The differences may be " accidental " and may not
be transmitted further — then we have to deal with an
unstable fluctuation ; or the differences may be
permanent — then we have to deal with a stable muta-
tion. What " produces " a mutation ? A change of
the environment, it may be said : if so, the mutation
is an active change or adaptation of the organism
to a change in its surroundings, and this adaptation
is a permanent one and is transmitted. Or the muta-
tion may be a spontaneous change of functioning.
If this disturbance of the stability of the organisation
is general, if it affects all the characters of the organism,
we have to deal with the establishment of a new
elementary species. But if the disturbance affects
only one, or a few characters, then we need not recognise
that a new elementary species has come into existence.
Men and women remain men and women (in their
morphology), although some time or other among the
brown eyes characteristic of a race blue eyes may have
appeared. The result of the disturbance, in this case,
has been to cause one, or a few, of the characters
that fluctuate to surpass their limits of stability.
The idea of the elementary species is a clear and
simple one. It is a group of organisms connected by
ties of blood relationship : all have descended from
one pair of ancestors. The individuals exhibit certain
characters, all of which are variable. This variability
is not cumulative ; in generation after generation
the individuals of the species display variations which
THE INDIVIDUAL AND THE SPECIES 201
fluctuate round the same mean values. Two or more
elementary species may have had the same origin —
a common ancestor or ancestors — but the organisms
in one species exhibit characters vv^hich, although
similar in nature to those of the other species, yet
fluctuate about different mean values.
This is not the " species " of the systematic biologist.
The Linnean or systematic species is a concept which
is much more difficult to define : it is a concept indeed
which has not any clear and definite meaning, in
actual practice.
We often forget how very young the science of
systematic biology is, and how intimately its progress
has been dependent on that of human invention and
industrial enterprise. Physics and mathematics might
be studied in a monastic cell, but the study of systematic
biology can only be carried on when we have ships
and other means of travelling — the means, in short,
of collecting the animals and plants inhabiting all
the parts of the earth's surface. Until a comparatively
few years ago the fauna and flora of great tracts of
land and sea were almost unknown : even now our
knowledge of the life of many parts of the earth is
scanty and inaccurate. Systematic biology has there-
fore had to collect and describe the organisms of the
earth, and in so doing it has set up the Linnean species
of plants and animals. These we may describe as,
in the main, categories of morphological struc-
tures. The older and more familiar species are clearly
defined in this respect : such are cats and dogs,
rabbits, tigers, herrings, lobsters, oysters, and so on :
the individuals in each of these categories are clearly
marked out with respect to their morphology, and the
limits of the categories are clearly defined. In all of
them the specific organisation has attained a high
202 THE PHILOSOPHY OF BIOLOGY
degree of stability so that the individuals " breed
true to type " ; and it has also attained a high degree
of specialisation, so that it does not fuse with other
organisations.
Yet, in the marjoity of the systematic species of
biology, this criterion of specific individuality — this
recognition of the isolation of the species from other
species — cannot be applied. Very many species have
been described from a few specimens only, many from
only one. How does a systematist recognise that an
organism with which he is dealing has not already been
classified ? It differs from, all other organisms most
like it, that is, he cannot identify it with any known
specific description. But the differences may be very-
small, and if he had a number of specimens of the
species most nearly resembling it he might find that
these differences were less than the limits of variation
in this most closely allied species, and he would then
relegate it to this category. But if he has to compare
his specimen with the " type " one, that is, the only
existing specimen on which the species of comparison
was founded, the test would be unavailable. The
question to be answered is this : are the difference
or differences to be regarded as fluctuations, or are
they of " specific rank " ? Now certainly many
systematists of great experience possess this power
of judgment, though they might be embarrassed by
having to state clearly what were the grounds on which
their judgment was based. But on the other hand
hosts of species have been made by workers who
did not possess this quality of judgment ; and even
with the great systematists of biology confusion has
originated. Slowly, very slowly, the organic world
is becoming better known, and this confusion is
disappearing.
THE INDIVIDUAL AND THE SPECIES 203
The species, then, whether it is the systematic
group of the biological systems, or the elementary
species based on the study of variability and inherit-
ance, is an intellectual construction : an artifice
designed to facilitate our description of nature. This
is clearly the case with the higher orders of groups
in classifications : genera, famihes, orders, classes, and
phyla express logical relationships, or describe in a
hypothetical form our notions of an evolutionary
process. But species, it may be said, have an actual
reality : there are no genera in nature, only species.
These categories of organisms really exist ; they have
individuality, a certain kind of organic unity, inas-
much as the individuals composing them have de-
scended from a common ancestor. Yet just as much
may be said of genera, families, and the other groupings.
One species originates from another by a process of
transmutation : a genus is a group of species which
have all had a common origin ; a family is a similarly
related group of genera, and so on. The higher
categories of biological science are intended to intro-
duce order and simplification into the confusion and
richness of nature as we observe it, but obviously
the concept of the species has the same practical
object. Must we then say that there are no species
in nature, only individuals ? If so, we are at once
embarrassed by the difficulty of forming a clear notion
of what is meant by organic individuality. Does it
not indicate that life on the earth is really integral,
and that our analysis of its forms — species, genera,
families, and so on — are only convenient ways of
dealing actively with all its richness ?
Systematic biology is a very matter-of-fact occupa-
tion, and one is surprised to find upon reflection how
he, in his handling of the concepts of the science,
204 THE PHILOSOPHY OF BIOLOGY
follows the methods of ancient philosophy. In
classical metaphysical systems mutability was an
illusion. Behind the confusion and change given to
sensation there is something that is immutable and
eternal. If there is change there is something that
changes ; or, at least there ought to be something that
changes when it is perceived through the mists of
sensation, just as the image of a well-known object
on the horizon wavers and is distorted by refraction.
This immutable reality is the Form or Essence of the
Platonic Idea : that which is in some way degraded
by its projection into materiality, so that we become
aware of it only through our imperfect organs of
sense. We do not see the Form itself, but its quality
rather, the Form with something added or something
taken away from it.
The Form itself is only a phase in a process of
transmutation. Everything that exists in time flows
or passes into something else. But it is not a momen-
tary or instantaneous view of the flux that we see,
but rather a certain aspect of the reality that flows, that
in some way expresses the nature of the transmutation
from one Form into another. The sculptor represents
the motion of a man running by symbolising in one
attitude all the actions of body and limbs ; so that
from our actual, sensible experience or intuition of
the movement of the runner we see in the rigid marble
all the plasticity of life. The instantaneous photo-
graph shows us a momentary fixed attitude of the
runner — an attitude which is strange and unfamiliar.
The Idea does not, then, represent a moment of
becoming like the photograph, but rather a typical
or essential phase of the process of transmutation,
just as the sculptor represents in immobile form the
characteristic leap forward of the runner. Just as
THE INDIVIDUAL AND THE SPECIES 205
our intuitive knowledge of the actions of our own
bodies enables us to read into the characteristic atti-
tude represented in the marble all the other attitudes
of the series of movements, so our experience enables
us to expand the formal moment of becoming into the
action which it symbolises.
This action has a purpose, an intention or design
which was contemplated before it began. There is
therefore the threefold meaning in the Platonic Idea :
(i) an immutable and essential Form of which we per-
ceive only the quality ; (2) the characteristic phase in
the transmutation of this Form into some other one ; and
(3) the design or intention of the transmutation.
This was, as Bergson says, the natural metaphysics
of the intellect. It was, in reality, the " practical "
way of introducing order and simplification into the
confusion of the sensible world — all that is presented
to us by our intuitions. And in the effort to reduce
to order the welter of the organic world biology has
followed the same method, so that it represents the
species with the threefold significance of the Platonic
Idea. That which is expressed in the term species
is an assemblage of organisms each of which is defined
by an essential form and an essential mode of behaviour
— the characters indicated in the specific diagnosis.
But organisms are variable, their specific characters
fluctuate round a mean, and in saying this we sug-
gest that there is something which varies — there ought
to be an essential form from which the observed
forms of the individuals deviate, something invariable
which nevertheless varies accidentally. This is (i) the
quality of the specific idea. So also we never do
actually observe the essential individual ; what we
do see is the embryo, or the young and sexually im-
mature organism, or the sexually mature one, or the
206 THE PHILOSOPHY OF BIOLOGY
senescent one : there is continual change from the
time of birth to that of senile decay. This confusion
is unmanageable, and for it we substitute the char-
acteristic form and functioning, and that phase in
the life-history of the organism which suggests all
that the previous phases have led up to, and all that
subsequent phases take away. Thus there is con-
tained in our idea of the species (2) the notion
of a typical moment in an individual transforma-
tion. It is not a " snap-shot " of some moment
in the life-history that we make : in identifying
a larval form as some species of animal we are
identifying it with all the other phases of the life-
history.
Since we accept the doctrine of transformism, the
specific idea also includes that of an evolutionary
process. For the organic world is a flux of becoming,
and species are only moments in this becoming. It
does not help us to reflect that if the hypothesis of
evolution by mutations is true the process is a dis-
continuous one : mutability is the result of periods
of immutability during which the change was germi-
nating, so to speak. In this flux of becoming we seize
moments at which the specific form flashes out — not
as instantaneous views of the flux, but as aspects
of it which suggest the steps, the morphological pro-
cesses, by which the transmutation of the species
has been effected. Thus our specific idea represents
not only a phase of becoming in an individual life-
history, but also a phase of becoming in an evolutionary
history.
Whether we consider this evolutionary movement
as the working out of a Creative Thought, or as the
development of elements assembled together by design,
or as the results of the action of a mechanism working
THE INDIVIDUAL AND THE SPECIES 207
by itself, we must suppose that underlying it there is
design, or purpose, or determinism. All is given,
therefore, and our comparison between the meta-
physical Platonic Idea and the modern concept of
the species becomes complete.
CHAPTER VI
TRANSFORMISM
The species is therefore a group of organisms all of
which exhibit the same morphological characters.
This sameness is not absolute, for the individuals
composing the species may vary from each other
with respect to any one character. But the range of
these variations is limited. They fluctuate about an
imaginary mean value which remains constant in the
case of a species which is not undergoing selection,
and is therefore nearly the same throughout a series
of generations. The formal characters which we
regard as diagnostic of the species are these imaginary
mean ones.
It is possible to breed from stock a very great
number of animals, all of which are connected by a tie
of blood-relationship, that is, all have descended from
the same ancestor or ancestors. Such an assemblage
of animals would resemble those assemblages living
in the wild which we call species, in that a certain
morphological similarity would be exhibited by all the
individuals. If the breeding were conducted so as to
avoid selection, the range of variability would be very
much the same as that observed in the wild race. The
two groups of animals — that bred artificially, and that
observed in natural conditions — would be very much
alike, and it is impossible to resist the conclusion that
the natural race, hke the artificial one, is a family in
208
TRANSFORMISM 209
the human sense, that is, all the individuals compos-
ing it are connected together by a tie of common
descent.
Let us extend this reasoning to categories of organ-
isms of higher orders than species. We can associate
together groups of species in the same way that we
associate together the individuals of the same species.
There are certain morphological characters which are
common to all the species in the category, but there
are also differences between specific group and specific
group, and these differences may be regarded as
variations from the generic morphological type. All
the Cats, for instance, have certain characters in
common : fully retractile claws, a certain kind of
dentition, certain cranial characters, and so on. We
postulate a feline type of structure, and we then
regard the characters displayed by the cat, lion, tiger,
leopard, etc., as deviations from this feline m'oi-pho-
logical type. Thus we establish the Family Felidae.
But again we find that the Felidce together with the
Canidae, and many other species of animals, also display
common characters, dental and osteological chiefly,
and we express this resemblance by assembling all
these families in one Order, the Carnivora. The
Carnivores, however, are only one large group of
Quadrupeds : there are many others, such as the
Rodents, Ungulates, Cetacea, etc., and all of these
possess common characters. In all of tliem the
integument is provided with hairs, or other similarly
developed structures ; all breathe by means of a dia-
phragm; in all, the young are nourished by suckling
the mammae of the mother; and all develop on a
placenta. We therefore group them all in the Class
Mammaha. Now the Mammals possess an internal
skeleton of which the most fundamental part is an
11
210 THE PHILOSOPHY OF BIOLOGY
axial rod — the notochord — developing to form a
vertebral column ; and this notochordal skeleton is
also possessed by the Birds, Reptiles, Amphibia, and
Fishes. There are also some smaller groups in which
the notochord is present but does not develop to form
segmented vertebrae. Including these, we are able
to form a large category of animals — the Chordata —
and this phylum is sharply distinguished from all
other cognate groups.
All animals and plants may be classified in a similar
way. Insects, Spiders, and Crustacea, for instance,
are all animals in which the body is jointed, each joint
or segment being typically provided with a pair of
jointed appendages or limbs. Because of this simi-
larity of fundamental structure we include all these
animals, with some others, in one phylum, the Arthro-
poda. So also with the rest of the animal kingdom,
and similar methods may be extended to the Iclassi-
iication of the plants. A few small groups in each of
the kingdoms are difficult to classify, but it has
been possible to arrange m.ost living organisms in a
small number of sub-kingdoms or phyla, and even to
attempt to trace relationships between these various
categories.
The mere systematic description of the organic
world would have resulted in such a reasoned classifi-
cation apart altogether from any notions of an evolu-
tionary process. But the classification, originally a
conventional way of making a list of organisms, would
at once suggest morphological similarities. It would
suggest that all the Cats were Carnivores, that all the
Carnivores were Mammals, and that all the Mammals
were Chordates. It would suggest that all Wasps
were Hymenoptera, that all Hymenoptera were Insects,
and that all Insects were Arthropods. It would
TRANSFORMISM 211
establish a host of logical relations between animals
of all kinds.
It would show us a number of groups of animals
separated from each other by morphological dissimi-
larities. But let us also consider all those animals which
lived m the past of the earth, and the remains of which
are found m the rocks as fossils. Including all the forms
of hte known to Paleontology, we should find that the
dissimilarities between the various groups would tend
to disappear. The gaps between existing Birds and
Reptiles, for instance, would become partially bridged.
Palaeontology would also supplement morphology in
another way. The study of the structure of animals
leads us to describe them as " higher " and " lower "—
higher in the sense of a greater complexity of structure.
Thus the body of a Carnivore is more complex than
that of a Fish, inasmuch as it possesses the homologues
of the truly piscine gills, but it also possesses a four-
chambered heart instead of a two-chambered one ;
and it possesses the mammalian lungs, diaphragm, and
placenta, structures which are not present in the Fish.
Now, so far as its imperfect materials go, palaeontology
shows us that the higher forms of life appeared on the
earth at a later date than did the lower forms. The
remains of Mammals, for instance, are first found in
rocks which are younger than (that is, they are super-
posed upon) those rocks in which Reptiles first appear ;
and so also Reptiles appear later in the rock series
than do Fishes. Palaeontology thus adds to the logical
order suggested by morphology a chronological order
of this nature : higher, or more complex forms of life
appeared at a later date in the history of the earth
than did lower or less complex ones.
A parallel chronological sequence would also be
suggested by the results of embryology. This branch
212 THE PHILOSOPHY OF BIOLOGY
of biology shows us that all animals pass through a
series of stages in their individual development, or
ontogeny. The earlier stages represent a simple type
of structure, usually a hollow ball of cells, but as
development proceeds, the structure of the embryo
becomes more and more complex. The process of
development is continuous in many animals, but in
others (perhaps in most) larval stages appear, that is,
development is interrupted, and the animal may lead
for a time an independent existence similar to that of
the fully developed form. Often these larval stages
suggest types of structure lower than that of the
fully developed animal into which they transform.
Even if larval stages may not appear in the ontogeny,
it is very often the case that the developing embiyo
exhibits traces, or at least reminiscences, of the types
of morphology characteristic of the animals which
are lower or less complex than itself ; thus the piscine
gills appear during the development of the tailed
Amphibian, and even in that of the Mammal, and then
vanish, or are converted into organs of another kind.
The individual thus passes through a series of develop-
mental stages of increasing complexity : it repeats,
in its ontogeny, the palseontological sequence in a
distorted and abbreviated form.
It is true that the evidence afforded by palaeontology
is very meagre. The preservation of the remains of
organisms in the stratified rocks is a very haphazard
process, and it depends for its success on a series of
conditions that are not always present. As the
surface of the earth becomes better knovv'^n, our know-
ledge of the life of the past will become fuller, but there
can be little doubt that whole series of organisms
must have existed in the past, and that no recognisable
traces of these are known to us. There is also no
TRANSFORMISM 213
doubt that the sequences indicated by palceontology
are very incomplete : they are obscured and shortened
by many conditions. The earUer embr3^ologists enter-
tained hopes that the study of embryology would
reveal the direction of the evolutionary process in
many groups of animals : if the organism repeats in
its ontogeny the series of stages through which it
passed in its phylogenetic development, then a close
study of the embryological process ought to disclose
these stages. Although these hopes have not been
realised, there is yet sufficient truth in the doctrine of
recapitulation to enable us to state that there is a
rough parallelism between the palseontological and
embryological sequences.
We therefore state a plausible hypothesis when we
assert that different species may be related to each
other in the same way that the individuals of the same
species are related, that is, by a tie of blood-relation-
ship ; and that different genera, families, orders, and so
on are also so related. Morphological studies enable
us to arrange numbers of species in such a way
that series, in each of which there is an increasing
specialisation of structure, are formed. Both palae-
ontology and embryology show, to some extent at least,
that these stages of ever-increasing specialisation of
structure occurred one after the other. Now, stated
briefly and baldly as we have put it, this argument
may not appear to the general reader to possess much
force, but it is almost impossible to over-state the
strength of the appeal which it makes to the student
of biology. To such a one a belief in a process of
transformism will appear to be inseparable from a
reasoned description of the facts of the science.
But it would be no more than a belief, not even
a hypothesis, if we did not attempt to verify it experi-
214 THE PHILOSOPHY OF BIOLOGY
mentally. It is merely logical relationships that we
establish, and the chronological succession of forms
of life, higher forms succeeding lower ones, does not
itself do more than suggest an evolutionary process.
All that we have said is compatible with a belief in a
process of special creation. But if we cling to such a
belief, if we suppose that the organisms inhabiting
the earth, now and in the past, are the manifestations
of a Creative Thought, we must still accept the notion
of logical and chronological relationships between all
these forms of life. If we permit ourselves to speculate
on the working of the Creative Thought, we seem to
recognise that the ideas of the different species must
have generated each other, and that the genesis of
living things must have occurred in some such order
as is indicated by a scientific hypothesis of transform-
ism. An evolutionary process must have occurred
somewhere, but the kinships so established between
organisms would be logical and not material ones.
Science must not, of course, describe the mode of
origin of species in this way. So long as it investigates
living things by the same methods which it uses in
the investigation of inorganic things, it must hold that
the concepts of physical science are also adequate
for the description of organic nature. It must assume
that matter and energy and natural law are given ;
and that, even in the conditions of our world, life must
have originated from lifeless matter ; must have
shaped itself, and undergone the transformations that
are suggested by the results of biology. It must
assume, in spite of the formidable difficulties that the
assumption encounters, that cosmic physical processes
are reversible and cyclical ; and that worlds and solar
systems are born, evolve, and decay again. Every
stage in such a cosmic process, as well as every stage
TRANSFORMISM 215
in the evolution of living things, must have been
inevitably determined by the stages preceding it.
Such a mechanistic explanation must assume that a
superhuman intellect, but still a finite intellect like
our own, such a calculator as that imagined by Laplace
or Du Bois-Reymond, would be able to deduce any
state of the world, or universal system, from any other
state, by means of an immense system of differential
equations. It would be able, as Huxley says, to
calculate the fauna of Great Britain from a knowledge
of the properties of the primitive nebulosity with as
much certainty as we can say what will be the fate
of a man's breath on a frosty day. Such a fine
notion as that of an universal mathematics must ever
remain as the ideal towards which science strives to
approximate.
Or we may suppose that a plan or design has been
superposed on nature, is immanent in matter and
energy, and works itself out, so to speak. Such a
teleological explanation of inorganic and organic evolu-
tion inevitably forces itself upon us if we reject the
notion of radical mechanism. We think of an uni-
versal system of matter and energies as consisting of
elements which, when assembled together, interact
in a certain way, and with results which are definite
and calculable. The assembling together of the
elements of the system would be the result of the
previous phases of the system. That is radical
mechanism. But let us think of the elements of the
system as being differently assembled — thus involving
the idea of an agency, external to the system, which
rearranges them — then the same energies inherent
in this system, as in that previously imagined, will
also work out by themselves. But the result will
be different, and will depend on the manner in which
216 THE PHILOSOPHY OF BIOLOGY
the elements were originally arranged. That would be
radical finalism.
Science must reject this notion as it rejects that of
special creation, since it introduces indeterminism
into the evolutionary process. It must regard the
organism and its environment as a physico-chemical
system studied from without. It must avoid all
attempts to acquire an intuitive knowledge of the
actions of the organism, for the latter, and the things
which environ it, are only bodies moving in nature.
In the systems studied by it time must be the inde-
pendent variable, and there must be a strict function-
ality between the parts of the organism and the parts
of the reacting environment, so that any change in
the one must necessarily be dependent on a change
in the other. Such a S3^stem and series of interactions
is that which is described in a mechanistic hypothesis
of transformism.
All this is indeed suggested to ordinary and aided
methods of observation. The plant or animal acts
upon, and is acted on by, the environment, though it
is usually the modification of the organism to which
we attend. A man's face becomes reddened by wind
and sun and rain ; manual labour roughens his hands
and develops callosities ; in the summer he sweats
and loses heat ; in the winter the blood-vessels of his
skin contract and heat is economised. In the winter
months the fur of many animals becomes more luxu-
riant and may change in colour. Fishes which inhabit
lightly coloured sand are lightly pigmented, but their
skins become dark when they move on to darkly
coloured sea-bottoms ; prawns which are brown when
they live on brown weed, become green when they
are placed on green weed. Birds migrate into warmer
countries, and vice versa, when the seasons change.
TRANSFORMISM 217
Such are instances of the adaptations of the morpho-
logy and functioning of organisms consequent on
changes of environment.
What is an adaptation ? The term plays a great
part in biological speculation, but it is often used in a
loose and inaccurate manner, and not always in the
same sense. It suggests that the organism is contained
by the environment, and that its form becomes
adapted to that of the latter, just as the metal which
the ironfounder pours into the mould takes the form
of the cavity in the sand. "' We see once more how
plastic is the organism in the grasp of its environ-
ment " — such a quotation from morphological litera-
ture is perhaps a typical one. Over and over again
this passive change in the organism as the result of
the action of something rigid which presses upon it
is what is understood by an adaptation. No doubt
the organism may be so affected, and of ten the change
w^hich it experiences is of the same order as the en-
vironmental change. In the winter many animals
become sluggish and may hibernate ; their heart-beats
slow down ; their respiratory movements become less
frequent, and generally the rate of metabolism, that
is the rapidity with which chemical reactions proceed
in their tissues, becomes lessened. All these changes
become reversed in sign when the temperature again
rises. The time of year at which a fish spawns de-
pends on the nature of the previous season. The rate
of development of the egg of a cold-blooded animal
varies with the temperature. The quantity of starch
formed in a green leaf depends on certain variables
— the intensity of light, the temperature, and the
quantity of carbonic acid contained in the medium
in which it is placed. In all these cases the rate at
which certain metabolic processes go on in the body
218 THE PHILOSOPHY OF BIOLOGY
of an organism varies according to the conditions of
the environment. In general they are cases of van't
Hoff' s law, that is, the rapidity at which a chemical
reaction proceeds varies according to the temperature.
They are changes of functioning passively experi-
enced by the organism as the result of environmental
changes, and we must clearly distinguish between them
and such changes as are the result of some activity
or effort on the part of the organism. A flounder
which lives in a river migrates out to sea when the
first of the winter snows melt and flood the estuary
with ice-cold water. Brown or striped prawns living
on brown or striped weeds become green when they
are placed on green weed, changing their pigmentation
to match that of the alga. A kitten brought up in a
cold-storage warehouse develops a sleeker and more
luxuriant coat than does its sister reared in a well-
warmed house. An animal which recovers from
diphtheria forms an antitoxin which enables it to
resist, for a time at least, repeated infection. A man
who goes exploring in polar seas puts on warmer
clothing than he wears in the tropics.
It is not necessary that an environmental change
should occur in order that an adaptation should be
evoked, for the organism may react actively and
purposefully to a change in itself. The athlete acquires
by running or rowing a more powerful heart ; the
blacksmith develops more muscular shoulders and
arms ; and the professional pianist more supple wrists
and fingers. If one kidney is removed by operation,
or if one lung becomes diseased, the organ on the other
side of the body becomes hypertrophied. Aphasia,
which is due to a lesion in the unilateral speech-centre,
may pass away if the previously unused centre on the
other side of the brain should become functionally
TRANSFORMISM 219
active. In general, the continued use of an organ
leads to its increase in size and efficiency, and con-
versely disuse leads to a decrease of size and even
to atrophy.
The essence of an adaptation is that it is an active,
purposeful change of behaviour, or functioning, or
morphology, by which the organism responds to some
change in its physical environment, or to some other
change in its own behaviour, or functioning, or mor-
phology. It is also a change which remains as a
permanent character in the organisation of the animal
exhibiting it. It does not matter even if the change
of behaviour is one which is willed in response to
some change of environment actually experienced, or
whether it anticipates some change that is foreseen.
A changed mode of behaviour adapted intelligently
leaves, at the least, a memory which becomes a per-
manent part of the consciousness of the animal, and
may influence its future actions ; or if it is evoked by
a process of education it must involve the establish-
ment of a " motor habit." The education of a singer
sets up, in the cortex and lower centres of the brain,
a nervous mechanism which controls and co-ordinates
the muscles of the chest and larynx, and which did not
exist prior to the process of education. Adaptations
are therefore acquired changes of some kind or other
by means of which the organism is able to exert a
greater degree of mastery over its environment, in-
cluding in the latter both the inert matter of inorganic
nature and the other organisms with which the animal
competes.
They are acquirements because of which the organ-
ism deviates from the morphological structure char-
acteristic of the species to which it belongs. Do they
affect the entire organisation of the animal exhibiting
220 THE PHILOSOPHY OF BIOLOGY
them, that is, may an acquired change of structure
be so fundamental that it affects not only the body
of the animal in which it occurs but also the progeny
of this animal ? Let us suppose that this is the
case ; let us suppose that quite a large proportion
of all the individuals of a species inhabiting a re-
stricted part of the earth's surface acquire the same
change of character simultaneously ; and that they
transmit this deviation of structure to their progeny.
Then we should have an adequate means whereby
the specific type becomes modified — a means of
transformism.
This is the hypothesis which is associated with the
name of Lamarck, and its essential postulate is that
characters which are acquired by an organism during
its own lifetime are transmitted to its offspring. It
seems reasonable to suppose that this transmission
of acquired characters should occur — how reasonable
we should note when we see that de Vries tacitly
assumes that fluctuating variations due to the action
of the environment may be inherited by the offspring
of organisms which exhibit them. That transmutation
of species might occur in this way was a popular and
widespread belief in England and Germany through-
out the greater part of the nineteenth century ; and
it was a belief entertained by Darwin himself, and
confidently, and even dogmatically affirmed at one
time by the majority of biologists in both countries.
How was it, then, that a very general change of
opinion with regard to this question occurred both in
England and Germany during the last two decades
of the last century ? Certainly many botanists and
zoologists continued to adhere to the older hypothesis,
and most physiologists still do not appear to make
any clear distinction between morphological characters
TRANSFORMISM 221
which are inherited and those which are acquired ;
but the majority of biologists did not hesitate to con-
clude that not only was the transmission of acquired
characters an unproved conjecture, but that it was
even theoretically inconceivable. At the beginning
of the nineteenth century this belief had alm.ost become
a doctrine dogmatically asserted, and one cannot fail
to notice a tone of irritation and impatience on the
part of the spokesmen of zoology when the contrary
opinions are expressed. " Nature," says Sir E. Ray
Lankester, " (and there's an end of it) does not use
acquired characters in the making and sustaining of
species for the very simple reason that she cannot
do so."
There can be little doubt that the interrogation
of nature with regard to this question was not a very
thorough process. The dogmatic denial of the trans-
mission of acquired characters was not the result of
exhaustive experiment and observation, but was due
rather to the very general acceptance in England and
Germany of Darwin's hypothesis of the transmutation
of species by means of natural selection, and of Weis-
mann's hypothesis of the continuity of the germ-plasm.
The newer hypothesis of transmutation was one
which seemed adequate to account for the diversity
of forms of life, so that it was unnecessary to invoke
the older one ; though Darwin himself admitted that
the individual acquirement of structural modifications
might be a factor in the evolutionary process ; and
for more than twenty 3^ears after the publication of
the " Origin of Species " Lamarck's hypothesis was
not strenuously denied by naturalists. Early in the
'eighties, however, Weismann published his book on
the germ-plasm, and the brilliancy and constructive
ability of the speculations contained in this remarkable
222 THE PHILOSOPHY OF BIOLOGY
work, as well as the analogies which they suggested
between organic and inorganic phenomena, compelled
the attention of biologists. The essential parts of
Weismann's hypothesis, as it was first presented to
the world, are as follows : very early in the evolution
of living from non-living matter many kinds of life-
substance came into existence. These were chemical
compounds of great complexity, able to accumulate
and expend energy, and capable of indefinite growth
and reproduction. They were able to exist in an
environment which was hostile to them and which
tended always to their dissolution, and which was
able to modify their nature and their manner of
reacting, though it could not destroy them. These
elementary life-substances were very different from
those which we know in the world of to-day. They
were naked protoplasmic aggregates, undifferentiated
into cellular or nuclear plasmata, much less into
somatic and germinal tissues. All of their parts were
similar, or rather their substance was homogeneous.
But even with the evolution of the unicellular organism
a profound change was initiated, for henceforth one
part of the living entity, the nucleus, became charged
with the function of reproduction, although it still
continued to exercise general control over the func-
tions of the extra-nuclear part of the cell. When the
multi-cellular plant and animal became evolved, the
heterogeneity of the parts of the organism became
greater still. All the cells of the metazoan animal
do indeed contain nuclei, but these structures are
only the functional centres of the cells : some of the
latter are sensory, others motor, others assimilatory,
others excretory, and so on. Only in the nuclei which
form the essential parts of the reproductive organs does
the reproductive function persist in all its entire
TRANSFORMISM 223
potentiality : there only does the protoplasm retain
all the properties which were possessed by the primitive
life-substance before it became heterogeneous, that is,
before nucleus and cytoplasm evolved. When part
of the primitive life-substance became secluded in a
nuclear envelope, it became, to that extent, shielded
from the action of the physical environment, and when
the organism became composed of multicellular tissues
this seclusion became more complete. Clothed in
the garments of the ilesh, it was henceforth protected
from the shocks of the environment, and it became
the immutable germ-plasm. But for a very long
time before this evolution of tissues the naked life-
substance had been exposed to the action of external
physical agencies, and it had been modified by these
into very numerous forms of protoplasmic matter.
When multicellular plants and animals had been
evolved there were, therefore, not one, but many kinds
of life-substance in existence, and these have persisted
until to-day as the unchanging germ-plasmata of the
existing organisms.
The Weismannian hypothesis of to-day, supported
and amplified, as it is, by subsidiary hypotheses, does
not make the same appeal to the student as did the
pristine and altogether attractive speculation of thirty
years ago. The analogy which it then presented
with the matured chemical theory of matter must
have been almost irresistible. Just as the indefinitely
numerous compounds of chemistry are only the per-
mutations and combinations of some of eighty-odd
different kinds of matter, so all the forms of life are
combinations and permutations of some of the many
different kinds of life-substance which came into
existence before the evolution of the multicellular
organism. And just as the chemical elements were
224 THE PHILOSOPHY OF BIOLOGY
regarded (in 1883) as immutable things, preserving
their individuahty even when they were associated
together as compounds, so Weismann and his followers
looked upon the different kinds of life-substance con-
tained in the chromatic matter of the nucleus as
immutable and immortal living entities. Associated
together in indeiinitely numerous ways by sexual
conjugation, the}^ may build up indefinitely variable
living structures, but they remain individualised and
lying side by side in the germ-plasmata of organisms,
just as the atoms were supposed to lie side by side
in the chemical molecule of the inorganic compound.
If these speculations were true, a change of mor-
phology or functioning, acquired by the body, or
somatoplasm, could not possibly be transmitted to
the progeny of the organism, for by hypothesis the
germ-plasm cannot be affected by external changes,
and it is only the germ-plasm contained in the
spermatozoon of the male parent, or in the ovum of
the female, that shapes and builds the body of the off-
spring. As if this were not enough, Weismann and
his followers argued that the transmissibility of a
somatic change to the germ was inconceivable. Why ?
Because the germ-cells are apparently simple : they
are only semi-fluid protoplasmic cell bodies and
nuclei, not differing appreciably from the cell bodies
and nuclei of the somatoplasm (by hypothesis, it should
be noted, the difference is profound). There are no
structural connections — no nerves, for instance —
which join together the cells of the bodil}^ tissues
with the parts of the germ and transmit changes in
the former to the latter. How, then, could a somatic
change affect the germ so that when the latter developed
into an organism this particular change became repro-
1 We know now that this statement is not quite accurate.
TRANSFORMISM 225
duced ? Now this may have seemed a conclusive
argument in 1883, but is it so conclusive to-day ? We
know that the cells and tissues are not isolated particles,
but that all are connected together by protoplasmic
filaments. We know that specialised nervous tissues
are not necessary for the transmission of an impulse
from a sensory to a motor surface, but that such an
impulse may be transmitted by undifferentiated proto-
plasm. We know that nerve-cells and nerve-fibres
are not structurally continuous with each other but
that the impulse leaps across gaps, so to speak. We
know that events that occur in one part of the body
of the mammal may affect other parts by means of
the liberation of a chemical substance, or hormone,
into the blood stream. It would be strange indeed
if a logical hypothesis capable of accounting for the
transmission of a particular change from the soma to
the germ could not be elaborated.
But acquired characters were not really transmitted
after all. So those who clung to Weismannism argued
— an unnecessary task surely if this transmissibility
were inconceivable. We cannot discuss the evidence
here, and it is unnecessary that we should do so, since
it is all considered in the popular books on heredity.
There is an apparent consensus of opinion in these
books which should not influence the reader un-
familiar with zoological literature, nor obscure the
fact that many zoologists and botanists accept the
opposite conclusion. The discussion is all very tire-
some, but we may glean some results of positive value
from it. It is unquestionable that very few con-
clusive and adequate investigations have been made :
one cannot help noticing that the literature contains
an amount of controversy out of all proportion to the
amount of sound experimental and observational
226 THE PHILOSOPHY OF BIOLOGY
work actually carried out. Most of the experiments
deal with the consideration of traumatic lesions or
mutilations, and it seems to be proved that such
defects are not transmitted, or at least are very
rarely transmitted. The tails of kittens have been
cut off ; the ears of terrier-dogs have been lopped ;
and the feet and waists of Chinese and European
ladies have been compressed, and all throughout
very numerous generations, yet these defects are not
transmitted from parent to offspring. This kind of
evidence forms the bulk of that which orthodox
zoological opinion has adduced in favour of the belief
in the non-inheritabiiity of acquired characters, but
does it all really matter ? What might be transmitted
is a useful, purposeful modification of morphology,
or functioning, or behaviour, induced by the environ-
ment throughout a number of generations — an adapta-
tion rather than a harmful lesion. There is little
conclusive evidence that such adaptations are inherited,
though anyone who carefully studies the evidence in
existence will not be likely to say that they are
certainly not transmitted. Does, for instance, the
blacksmith transmit his muscular shoulders and arms
to his sons, or the pianiste her supple wrists and
fingers to her daughters ? There are no observations
and experiments in the literature worthy of the
importance attaching to the question at issue.
It should be noted also that the germ-plasm is
certainly not the immutable substance that the hypo-
thesis originally postulated. Changes in the outer
physical environment may certainly affect it ; thus
the larvae bred from animals which live in abnormal
physical conditions (temperature, moisture, etc.) may
differ morphologically from the larvae bred from animals
belonging to the same species but living in a normal
TRANSFORMISM 227
environment. The latter must therefore react on the
germ-plasm, but the environment formed by the
bodily tissues which surround the germ-cells may also
so react : thus the germ-cells may be affected by such
bodily changes as differences in the supply of nutritive
matter, for instance. The offspring may deviate from
the parental structure as the result of structural modi-
fications acquired by the parent during its own lifetime,
and, even if the filial deviation were not of the same
nature as the parental modification, its inheritance would
be an adequate cause of some degree of transmutation.
It is, however, certainly difficult to prove that
organisms transm.it to their progeny the same kinds of
deviation from the specific structure that they them-
selves acquire as the result of the action of the envi-
ronment. Even if they did transmit such acquired
deviations, it does not seem clear that this kind of
inheritance alone would be a sufficient cause of the
diversity of forms of life that we do actually observe
in nature. Change of morphology would indeed occur,
but we should expect to find insensible gradations of
form and not individualised species. Let us suppose
that Lamarckian inheritance acts for a considerable
time on two or three originally distinct species in-
habiting an isolated tract of land, and let us suppose
that we investigate the variations occurring among all
the organisms which are accessible to our observation
with respect to some one variable character.
The diagram A represents what would seem to be
the result of this process of transmutation. The
numbers along the horizontal line are proportional
to their distance from o, the origin, and represent the
magnitude of the variation considered ; and the
height of the vertical lines represents the number of
organisms exhibiting each degree of variation. We
228
THE PHILOSOPHY OF BIOLOGY
should expect to find that all the variations were
equally frequent in their occurrence, but this is not
what a study of variability in such a case as we have
supposed — that of the animals inhabiting an isolated
part of land — does actually indicate. What we should
find would be the conditions represented by the diagram
B. There would be two or more modes, that is, values
of the variable character which are represented by a
greater number of individuals than any other value
of the variation. The environmental conditions favour
the individuals displaying this variation to a greater
extent than they favour the rest.
5" 4- 3 £
3^
A
4^3 8 / Q I B i ■^ 3 Z ' a I S 'i '^
Fig. 24.
That is to say, the environment selects some kinds
of variations among the many that are exhibited, and
this is, of course, the essential feature of the hypothesis
of the transmutation of species by means of natural
selection of variable characters. Organisms enter the
world differently endowed with the power of acting on
the medium in which they live, or on the environ-
ment consisting of their fellow-organisms. Those that
are most favourably endowed live longest and have
a more numerous progeny than those that are less
favourably endowed, and they transmit this favour-
able endowment to their offspring. Among the progeny
of the progeny there may be some in which the favour-
able variation is still more favourable than it v/as when
it first appeared. Thus the variations which are
TRANSFORMISM 229
selected increase in amount. Elimination of the
weakest occurs. The idea is eminently clear and
simple, and possesses a great degree of generality :
it is self-evident, says Driesch, meaning that it cannot
be refuted, for it was certainly not clearly obvious
to the naturalists before Darwin and Wallace. But,
unless we choose to be dogmatic, we can hardly claim
that it is an all-sufficient cause for the evolutionary
process, and it is useless to attempt to minimise the
difficulties of the hypothesis. It is not easy to make
it account for the origin of instincts or tropisms, or
for restitutions and regenerations of lost parts, or for
the appearance of the first non-functional rudiments
of organs which later become functional and useful.
It is, indeed, possible to devise plausible hypotheses
accounting for all these things in terms of natural
selection, but each such subsidiary hypothesis loads
the original one and weakens it to that extent.
Natural selection does not, of course, induce or
evoke variations ; these are given to its activity, and
they are the material on which it operates. What, then,
is the nature of the deviations from the specific types
of morphology that are selected or eliminated ? Not
those induced by the environment, and transmitted in
their nature and direction to the progeny of the
organisms first displaying them. It is not unproved
that such variations do occur, and it is even probable
that they do occur. But we may conclude that the
frequency of their occurrence is not great enough to
afford sufficient material for natural selection. It is
also clear that the ordinarily occurring variations that
we observe in any large group of organisms collected
at random are not alone the material for selection ;
for we have seen that experimental breeding from such
variations does not lead to the establishment of a
230 THE PHILOSOPHY OF BIOLOGY
stable race or " variety." Nevertheless some effect
is produced, and this may be accounted for by suppos-
ing that the observed variations are really of two
kinds — fluctuating variations, which are not inherited,
and mutations, which are inherited. The small ob-
served effect is due to the selection of the mutations
alone : it is a real effect of selection, an undoubted
transmutation of the specific form, but experimental
and statistical investigations seem to show that selec-
tion from the variations that we usually observe is
too slow a process to account for the existing forms
of life.
Natural selection acts, therefore, on mutations.
Now it seems that we are forced to recognise the exist-
ence of two categories of mutations, (i) those stable
modifications of an " unit-character " which we term
" Mendelian characters," and (2) those groups of stable
modifications to which de Vries applied the term
mutations. It seems at first difhcult to see how per-
manent modifications of the specific form can be
brought about by the transmission of Mendelian char-
acters, for these characters are always transmitted in
pairs. Let us take a concrete case — that of a man
who has six fingers on his right hand, and let us
suppose that this was a real, spontaneously appearing
character or mentation which had not previously
occurred in the ancestry of the man. Two contrasting
characters would then be transmitted, (i) the normal
five-fingered hand, and (2) the six-fingered hand.
Both of these characters are supposed to be present at
the same time in the organisation of the men and women
of the family originating in this individual, but one
of them is always latent or recessive. There would,
however, be individuals in which only one of the char-
acters would be present — either the normal or abnormal
TRANSFORMISM 281
number of digits, but intermarriage with individuals
belonging to the other pure strain would immediately
lead again to the transmission of the contrasting
characters, or allelomorphs, although marriage with an
individual belonging to the same pure strain would
carry on the normal or abnormal unmixed character
into another generation. But if the possession of six
fingers conveyed an undoubted advantage, and if
natural selection did really act in civilised man as
regards the transmission of morphological characters,
then a stable variety {Homo sapiens hexadactylus , let
us say) might be produced by its agency. The muta-
tions which we consider in the investigation of the
inheritance of alternating characters are therefore just
as much the material for natural selections as the
mutations which occur among the ordinary variations
displayed by organisms in general : but since only one
or two characters appear to be subject to this mode of
transmission, the process would be so slow as to be
inadmissible as an exclusive cause of evolution.
If we assume that de Vries' mutations are the
material on which selection works, this difficulty is
immediately removed, for we now have to deal with
groups of stable deviations : not one or two, but all
the characters of the organism appear to share in the
mutability. But another difficulty now arises. A
species of plant or animal may have got along very
well with its ordinary structural endowment, and then
a number of individuals begin to mutate. Some of the
deviations from the specific type may be of real advan-
tage, but others may not : we can, indeed, imagine an
in-co-ordination between the mutating parts or organs
which would be fatal to the animal ; on the other hand,
there might be complete co-ordination, with the result
that great advantage might be conferred upon the
232 THE PHILOSOPHY OF BIOLOGY
individual. It is easy to see how co-ordination of
mutating parts is absolutely essential. An animal
which preserves its existence by successful avoidance
of its enemies would not be greatly benefited by a
more transparent crystalline lens if the vitreous humour
of its eye were slightly opaque ; and even if all the
parts of the eye were perfectly co-ordinated, increased
acuity of vision would not greatly help it if its limbs
were not able to respond all the more quickly to the
more acute sensation. Un-co-ordinated mutations
would therefore tend to become eliminated, while
co-ordinated ones would become selected and would
become the characters of new species.
We must now ask why some groups of variations
are co-ordinated while others are not, and it is here
that we encounter the most formidable of the difficulties
of any hypothesis of transformism which depends on
the concept of natural selection. If we assume that
the environment induces the appearance of variations,
it seems to follow that these variations are likely to be
co-ordinated, but we then invoke the principle of the
acquirement of characters and their transmission by
heredity. If, on the other hand, we assume that varia-
tions appear spontaneously, and quite irresponsibly,
so to speak, in the germ-plasm of the organism, the
selection, or elimination, by the environment will not
occur until the co-ordinated or un-co-ordinated varia-
tions appear. It is far more likely that a large number
of simultaneously appearing variations will be un-co-
ordinated than that they will be co-ordinated. Merely
as a matter of probability the progressive modification
of a species will take place slowly — too slowly to account
for what we see.
Two examples wall make it easier to appreciate this
difiiculty. Evolution has undoubtedly proceeded in
TRANSFORMISM 233
definite directions. There are two dominant groups
of fishes, the Teleosts and the Elasmobranchs, and
both must have originated from a common stock. All
the characters in each kind of fish must have been
useful (since they were selected) , and all must have been
modifications of the characters of the common stock.
The latter became modified along two main lines, or
directions, which are indicated by the characters of
the existing Teleosts and Elasmobranchs. The whole
skeleton, the gills, the circulatory system, and the brain
differ in certain respects in these groups. Therefore a
modification of the brain in the primitive Elasmo-
branchs was associated with a modification of the
cranium, and therefore with the jaw-apparatus, and
so with the branchial skeleton and the gills, and there-
fore also with the heart, and so on. Suppose that
the evolutionary process included ten useful and co-
ordinated variations — not an unlikely hypothesis — and
suppose that each of these ten useful variations was
associated with nineteen useless ones. The chance
that any one of them did occur was therefore one in
twenty ; and if they all occurred independently, that
is, if the occurrence of any one of them was compatible
with the occurrence of any other one. or of all the others,
then the chance that all the ten variations occurred
simultaneously was 20"'°, that is, one in the number
20 followed by 10 cyphers, a rather great improbability.
Most biological students are familiar with the
similarity of the so-called eye of the mollusc Pecten
and that of the vertebrate. The resemblance is one of
general structure : in each of these organs there is a
camera obscura, a transparent cornea, and behind that
a crystalline lens. On the posterior wall of the camera
there is a receptor organ, or retina, and this is composed
of several layers of nervous elements. The actual
234 THE PHILOSOPHY OF BIOLOGY
nerve-endings are on the surface of the retina, which is
turned away from the hght, that is, the optic nerve
runs towards the anterior surface of the retina, and
then its fibres turn backwards. This " inversion of
the retinal layers " occurs in all vertebrate animals, but
it is exceptional in the invertebrates. The above
general description applies equally well to the eye of
the vertebrate and to that of Pecten.
Let us admit that these mantle organs in Pecten
are eyes, for there is no conclusive experimental evi-
dence that they really are visual organs, and plausible
reasoning suggests that they may subserve other
functions. Let us assume that the minute structure
of the Pecten eye is similar to that of the vertebrate,
and that its development is also similar : as a matter
of fact both histology and embryology are different.
Then we have to explain, on the principles of natural
selection, the parallel evolution of similar structures
along independent lines of descent ; for mollusc and
vertebrate have certainly been evolved from some very
remote common ancestor in which the eye could not
have been more than a simple pigment spot with a
special nerve termination behind it. In each case the
organ was formed by a very great number of serially
occurring variations, yet these two sets of variations
must have been the same at each stage in two in-
dependently occurring processes. On any reasonable
assumption as to the number of co-ordinated variations
required, and their chances of occurrence, the mathe-
matical improbability that these two series of varia-
tions did occur is so great as to amount to impossibility
so far as our theory of transformism is concerned.
Natural selection could not, therefore, have produced
these two organs.
This argument of Bergson's fails, of course, in the
TRANSFORMISM 235
particular instance chosen by him, but this is because
the case is an unfortunate one. Probably a morpho-
logist could find a very much better case of convergent
evolution — the parallelism between the teeth of some
Marsupials and some Rodents, for instance. If detailed
histological and embryological investigation should
show a similarity of structure and development, in
such compared organs Bergson's argument would re-
tain all its force. We should then have to assume
that there was a directing agency, or tendency in the
organism, co-ordinating, or perhaps actually producing,
variations.
Mechanistic biology can suggest no means whereby
simultaneously occurring variations are co-ordinated :
let us therefore think of these variations as occurring
independently of each other, and let us ignore the
difficulty of the infrequency of occurrence of suitably
co-ordinated variations. Variations are exhibited by
the evolving organism, and the selection of co-ordi-
nated series is the work of the environment. But the
environment is merely a passive agency, and it has to
confer direction on the innumerable variations pre-
sented to it by the organism, rejecting most but
selecting some. Let us think of the environment, says a
critic of Bergson, as a blank wall against which nume-
rous jets of sand are being projected. The jets scatter
as they approach the wall : each of them represents
the variations displayed by some organ or organ-
system of an animal. Let us think of a pattern drawn
on the wall in some kind of adhesive substance : where
the wall is blank the sand would strike, but would fall
off again, but it would adhere to the parts covered by
the adhesive paint. The sand grains: strike the wall from
all sides, that is, their directions are un-co-ordinated.
The wall is passive, yet a pattern is imprinted upon it.
236 THE PHILOSOPHY OF BIOLOGY
From passivity and un-co-ordination come symmetry
and order.
This argument withstands superficial examination,
but to accept it is truly to be " fooled by a metaphor."
For what is the pattern on the wall ? It is the environ-
ment, says the critic. But what is the environment ?
Inevitably we think of it as something that makes or
moulds the organism, a way of regarding it that drags
after it all the confusion of thought implied in the
above analogy. Clearly the environment is made by
the organism. Its form, that is, space, is only the mode
of motion possible to the organism ; it is clear that
whether the space perceived by an organism is one-,
two-, or three-dimensional, space depends upon its mode
of motion. Its universe is whatever it can act upon,
actually or in contemplation. Atoms and molecules,
planets and suns are its environment because it can in
some measure act upon these bodies, or at least they
can be made useful to it. Chloroform or saccharine,
or methyl-blue and all the dye-stuffs prepared from
coal-tar by the chemists, are part of our environ-
ment because we have made them. They existed only
in potentiality prior to the development of organic
chemistry. They were possible, but man had to
assemble their elements before they became actual.
In making them, he conferred direction on inorganic
reactions.
Surely the organism itself selects the variations of
structure and functioning that are exhibited by itself.
If we hesitate to say that these modifications are crea-
tions, let us say that they are permutations of elements
of structure, and that they were potential in the
organisation of the creature exhibiting them. They
occur in the latter if we must not say that they are
produced. If they are detrimental, the organism is the
TRANSFORMISM 23T
less able to live and reproduce, and if it does reproduce,
its progeny are subject to the same disability. If, as
is usual, they simply do not matter, they may or may
not affect the direction of evolution. If they are of
advantage, that is, if they confer increased mastery-
over the environment, over the inert things with which
the organism comes into contact, the latter enlarges its
universe or environment, lives longer, and transmits
to its progeny its increased powers of action. Indefinite
increase of power over inert matter is potential in
living things, and variation converts this potentiality
into actuality.
This discussion is all very formal, but two conclusions
emerge from it : (i) the insufficiency of the mechanistic
hypotheses of transformism to account for all the
diversity of life that has appeared on the earth during
the limited period of time which physics allows for the
evolutionary process. There does not appear to be
any possibility of meeting this objection if we continue
to adhere to the hypothesis of transformism already
discussed : it faces us at every turn in our discussion.
How great a part is played, for instance, by " pure
chance " in the elimination of individual organisms
during the struggle for existence ! Let us think of a
shoal of sprats on which sea-birds are feeding : it is
chance which determines whether the birds prey on
one part of the shoal rather than another. Or let us
think of the millions of young fishes that are left
stranded on the sea-shore by the receding tide : it is
chance that determines whether an individual fish will be
left stranded in a shallow sandpool which dries up under
the sun's rays, rather than in a deeper one that retains
its water until the tide next flows over it. It is no
use to urge that there is no such thing as " pure chance,"
and that what we so speak of is only the summation
238 THE PHILOSOPHY OF BIOLOGY
of a multitude of small independent causes. Let us
grant tliis, and it still follows that the alternative of life
or death to multitudes of organisms depends not upon
their adaptability but upon minute un-co-ordinated
causes which have nothing to do with their morphology
or behaviour. These are instances among many others
which will occur to the field naturalist : they shorten
still further the time available for natural selection in
the shaping of species, for they reduce the material on
which this factor operates.
The other result of our discussion is to indicate
that the problem of transformism of species is in
reality the problem of organic variability. Let us
assume that all the hypotheses of evolution are true :
that the environment may induce changes of mor-
phology and functioning in animals and plants, and
that these changes themselves — the actual acquire-
ments themselves, that is — are transmissible by
heredity. Let us assume that the germ-cells may be
affected by the environment, either the outer physical
environment, or the inner somatic environment, and
that mutations may thus arise. Let us assume that
mutations may be selected in some way, so that
specific discontinuities of structure — " individualised "
categories of organisms, or species — may thus come into
existence. Even then transformism is still as great a
problem as ever, for the question of the mode of origin
of these variations or modifications still presses for
solution.
The simplest possible cases that we can think of
present the most formidable difficulties. The muscles
of the shoulders and arms of the blacksmith become
bigger and stronger as the result of his activity. Why ?
We say that the increased katabolism of the tissues
causes a greater output of carbonic acid and other
TRANSFORMISM 239
excretory substances, and that these stimulate certain
cerebral centres, which in turn accelerate the rate of
action of the heart and respiratory organs. An in-
creased flow of nutritive matter and oxygen then
traverses the blood-vessels in the muscles of the
shoulders and arms, and the latter grow. Probably
processes of this kind do occur, but to say that they
do is not to give any real explanation of the hyper-
trophy of the musculature of the man's body, for what
essentially occurs is the division of the nuclei and the
formation of new muscle fibres. How precisely does
an increased supply of nutritive matter cause these
nuclei to divide and grow ? This is a relatively simple
example of the adaptability of a single tissue-system
to a change in the general bodily activity, that is to
say it is a variation of structure induced by an environ-
mental change.
In most cases, however, the variations of structure
that form the starting-points of transmutation processes
cannot clearly be related to environmental changes.
Some fishes produce very great numbers of ova in
single broods — a female ling, for instance, is said to
spawn annually some eighteen millions of eggs. If we
examine these ova we shall find that there is consider-
able variation in the diameter and in other measureable
characters. We may attempt to correlate these devia-
tions from the mean characters with environmental
differences. All the eggs " mature," that is, they
absorb water and swell, while various parts, such as
the yolk, undergo chemical changes, during the month
or so before the fish spawns. This process of matura-
tion takes place in the closed ovarian sac ; and the
eggs lie practically free in this sac, and are bathed in a
fluid which exudes from the blood-vessels in its walls.
It may indeed be the case that there are variations in
240 THE PHILOSOPHY OF BIOLOGY
the composition of this fluid in the dififerent parts of
the sac ; but these variations cannot be great ; the
fluid is not really a nutritive one ; and the process of
maturation is not hurried. We can hardly believe that
the differences in morphology are due to these minute
environmental differences. We may indeed say that
we do not really study the germ cells when we measure
the diameter of the egg or investigate any other measur-
able character, for the real germ-plasm is the chromatic
matter of the nucleus. But this obviously begs the
whole question : all the parts of the egg that are
accessible to observation do vary, and ought we to
conclude that the parts which are not accessible do not
vary ? They must vary : the germ-plasm of each egg
must be different from that of all the others, for the
organisms which develop from these germs show in-
heritable differences. Further, can we contend that
such minute environmental differences as we have
indicated affect the germ-plasm ? Is it so susceptible
to external changes ? A high degree of stability of
the germ-plasm is postulated in the mechanistic
hypothesis that we have considered, and indeed every-
thing indicates that the specific organisation is very
stable. Can it then be upset by such minute differences
in the somatic environment ?
But the germ-plasm is not really simple, says
Weismann ; it is a complex mixture of ancestral
germ-plasms. The individual fish that we were con-
sidering arose from an aggregate of determinants, and
half of these determinants were received from the male
parent and half from the female one. But each of
these parents also arose from a similar aggregate of
determinants, which again were received from both
parents, and so on throughout the ancestry of the fish.
It is true that the germ-plasms contributed by the
TRANSFORMISM 241
ancestors were not quite different, but they differed to
some extent. Then there must have been as many
permutations of determinants in the ovum from which
the fish developed as there were permutations of char-
acters in the eighteen milHons of ova produced by it.
Does not the hypothesis collapse by its own weight ?
It could only have been such difficulties as are here
suggested that led Weismann to formulate his hytho-
thesis of germinal selection. All those eighteen millions
of eggs arose from the division of relatively few germ
cells. Each of these original cells contained the
specific assemblage of determinants, and the elements
of the latter are of course the biophors. The biophors,
it will be remembered, are either very complex chemical
molecules, or aggregates of such. When the germ
cells of the germinal epithelium divide to form those
cells which are going to become the ova, the biophors
must divide and grow to their former size, and again
divide— it is really a chemical hypothesis that we are
stating, though we have to employ language which
seems to do violence to all sound chemical notions !
Now while the biophors were dividing and growing
they were " competing " for the food matter which was
in the liquid bathing them, and some got less, while
others got more than the average quantity. In this
way their characters became different, so that the eggs,
on the attainment of maturity, became different from
each other. Now, apart altogether from the impossi-
bility of applying any test as to the objective reality
of this hypothesis, it must be rejected, for it confers on
bodies which belong to the order of molecules properties
which are really those of aggregates of molecules.
The typical properties of a gas, for instance, are not
the properties of the molecules of which the gas is
composed, but are statistical properties exhibited bv
Q
242 THE PHILOSOPHY OF BIOLOGY
aggregates of molecules. On the hypothesis of germinal
selection the properties of the animals which develop
from the biophors are extended to the biophors them-
selves. It was surely a desperate plight which evoked
this notion ! It is, as WilHam James said about Mr
Bradley's intellectualism, mechanism in extremis !
We seem forced to the conclusion — and this is
the result to which all this discussion is intended to
approximate — that variations, heritable variations at
least, arise spontaneously. That is, there are organic
differences which have no causes, a conclusion against
which all our habits of reasoning rebel. Yet it may be
possible to argue that the problem of the causes of
variations is really a pseudo-problem after all, and
that there is no logical reason why we should be com-
pelled to postulate such causes. When we think of
organic variability, do we not think, surreptitiously it
may be, of something that varies, that is, something
that ought to be immutable but which is compelled to
deviate ? But what is given to our observation is
simply the variations among organisms.
Let us think of the crude minting machines of
Tudor times which produced coins which were not very
similar in weight and design. From that time onward
minting machines have continually been improved,
each successive engine turning out coins more and
more alike in every respect, so that we now possess
machines which stamp out sovereigns as nearly as
possible identical with each other. Yet they are not
quite alike, and this is because the action of the engine,
in all its operations, is not invariably the same. In
imagination, however, we make a minting machine
which does work perfectly, and turns out coins abso-
lutely alike, but this ideal engine is only the conceptual
limit to a series of machines each of which is more nearly
TRANSFORMISM 243
perfect than was the last one. It is unlikely that
matter possesses the rigidity and homogeneity which
would enable us to obtain this perfect identity of
result ; nevertheless this identity has a very obvious
utility, and we strive after it, so that the result of our
activity is the conception of a perfect mechanism,
and of products which are identical. We assume that
the reasons why our early and cruder machines were
imperfect are also the reasons why our later and more
perfect ones do not produce the results that we desire.
We are artisans first of all, and then philosophers,
and so we extend this ingrained mechanism of the
intellect into our speculations. To the biologist the
organism is a mechanism which, in reproduction, ought
to turn out perfect replicas of itself. It does not do so.
Now, if biology shows us anything, it shows us that
living matter is essentially " labile," that is, something
fluent, while lifeless matter is essentially rigid, or
nearly so. Yet, ignoring this difference, we expect
from the organism that identity of result and operation
that we conceptualise, but do not actually obtain from
the artificial machine. We regard the organism, not
only as a mechanism like the minting machine, but as
the conceptual limit to a series of mechanisms. The
reproductive apparatus of our fish does not turn out
ova which are identical, but which differ from each
other. Some of this variation, we say, is due to the
action of the environment ; and some of it is due to
the condition that each ovum receives a slightly
different legacy of characters from the multitude of
ancestors. The rest we conceive as due to the im-
perfect working of the reproductive machinery.
It is useful that science should so regard the working
of the organism, for in the search for the causes of varia-
tion our analysis of the phenomena of life becomes
244 THE PHILOSOPHY OF BIOLOGY
more penetrating. But does any result of investigation
or reasoning justify us in assuming, as a matter of pure
speculation, that deviations from the specific type of
structure are physically determined in all their extent ?
Have we not just as much justification for the belief
that these deviations are truly spontaneous, and that
they arise de novo ? So we approach, from the point of
view of experimental biology, Bergson's idea of Creative
Evolution.
CHAPTER VII
THE MEANING OF EVOLUTION
Apart from experimental investigation, the results of
comparative anatomy, even if they are amplified by
those of comparative embryology, and even if they
include fossil as well as living organisms, do no more
than suggest the occurrence of an evolutionary process.
It is in vain that we attempt a demonstration of trans-
mutation oi forms of life by showing that a similarity
of structure is to be observed in all animals belonging
to the same group. We may show successfully that
the skeleton of the limbs and limb-girdles of vertebrate
animals is anatomically the same series of parts, whether
it be the arms and legs of man, or the wings and legs
of birds, or the pectoral and pelvic fins of fishes : such
homologies as these were indeed suggested by the
mediaeval comparative anatomists apart altogether
from any notions as to an evolutionary process. We
may show that the simplicity of the skeleton of the
head of man is apparent only, and that in it are to be
traced most of the anatomical elements that enter into
the skull and visceral arches of the fish ; and that
fusions and losses and translocations of parts have
occurred and can be made to account for the observed
differences of form. All this might just as easily be
explained by assuming a process of special creation,
or the gradual development of a plan or design. Just
as God made Eve from a superfluous rib taken from
245
246 THE PHILOSOPHY OF BIOLOGY
the body of her husband, so He may have formed the
auditory ossicles of the higher vertebrate from those
parts of the visceral arches of the lower forms which
had become superfluous in the construction of the
more highly organised creature. However much the
language of evolution may force itself on biology, it
does no more than symbolise the results of anatomy
and embryolog}^ and provide a convenient framework
on which these may be arranged.
But if, as all modern experimental work shows, the
form of the organism is, in the long run, the result of
its interaction with the environment ; if, as indeed we
see, this form is not an immutable one, but a stage in
a flux ; and if deviations from it may occur with all
the appearance of spontaneity, then it would appear
that the observed facts of comparative anatomy and
embryology are capable of only one explanation.
They represent the results of an evolutionary process,
and the relationships that morphological studies in-
dicate are no longer merely logical, but really material
ones. We can now endeavour to utilise these results
in the attempt to trace the directions taken by the
process of evolution.
In so doing we set up the schemes of phylogeny.
We divide all organisms into plants and animals, and
then we subdivide each of these kingdoms of life intO'
a small number of sub-kingdoms, in each of which we
set up classes, orders, families, genera, and species.
But our classification is no longer merely a formal
arrangement whereby we introduce order into the
confusion of naturally occurring things. It is now a
" family tree," and from it we attempt to deduce the
descent of any one of the members represented in it.
The sub-kingdoms, or phyla, of organisms are the
primary groups in this evolutionary classification. We
THE MEANING OF EVOLUTION 247
divide all animals into about nine of these phyla — the
Protozoa or unicellular organisms ; the Porifera or
sponges ; the Coelenterates, a group which includes all
such organisms as Zoophytes, Corals, Sea-Anemones,
and " Jelly-fishes ; the Platyhelminth worms, that is
the Tapeworms, Trematodes, and some other struc-
turally similar animals which live freely in nature ;
the Annelids, a rather heterogeneous assemblage of
creatures which includes all those animals commonly
called worms ; the Echinoderms, which are the Star-
fishes, Sea-Urchins, and Feather-Stars found in the sea ;
the Molluscs, that is the animals of which the Oyster,
the Periwinkle, the Garden-Slug and the Octopus are
good examples ; the Arthropods, which include the
Crustacea, the Insects, and the Spiders ; and lastly
the Vertebrates. Any such classification we naturally
endeavour to make as complete a one as possible, but
round the bases of the larger groups there cling small
groups of organisms the precise relationships of which
are doubtful. Yet, on the whole, these sub-kingdoms
of organisms represent clearly the main directions along
which the present complexity of animal structure has
been evolved.
There is an essential structure which we endeavour
to assign to all the animals of each phylum, and which
is different from the structure of the animals belonging
to all other phyla. The Protozoa, which for the present
we regard as animals, are organisms the bodies of which
consist of single cells. These cells may become aggre-
gated into colonies, but they may as well exist apart
from each other. They may be enclosed in limy,
siliceous, or cellulose skeletons or shells, or they may
possess limy or siliceous spicules in their tissues — these
parts are non-essential, and the schematic Protozoan
is a cell containing a single nucleus, and capable of
248 THE PHILOSOPHY OF BIOLOGY
independent existence. The Porifera, and all the other
phyla, include organisms the bodies of which are made
up of aggregates of cells. In the Porifera the cells,
which are specially modified in structure, are arranged
to form the internal walls of a "sponge-work" the
cavities of which open to the outside by series of pores
through which water is circulated. The bodies of the
Coelenterates are typically sacs formed by a double
wall of cells — endoderm and ectoderm. This sac opens
to the exterior by a single opening, or mouth, sur-
rounded by a circlet of tentacles, and its cavity is
the only one contained in the body of the animal. The
Platyhelminth worms are animals the bodies of which
are also composed of ectodermal and endodermal tissues,
between which is intercalated another mesodermal
tissue. They have a single digestive sac or alimentary
canal opening to the exterior by means of a mouth
only ; and they all possess a complex, hermaphrodite,
reproductive apparatus. In all the other phyla there
are also three principal layers or kinds of tissue, but in
addition to the cavity of the alimentary canal there is
also a body cavity, or coelom, which is contained in the
mesodermal tissues. The Echinoderms are such coelom-
ate animals, but the alimentary canal now opens to
the exterior by means of both mouth and anus ; there
are separate systems of vessels through which water
and blood circulate ; the blood-vascular system of
vessels is closed to the exterior, the water-vascular
system being open ; and the integument is armed by
means of calcareous spines or plates. The Annelids
are animals with cylindrically shaped bodies, segmented
so as to form numerous joints. Each segment bears
spines or hairs or appendages of some sort, and also
contains a separate nerve-centre. The alimentary
canal opens externally by a mouth and anus, and there is
THE MEANING OF EVOLUTION 249
a spacious body cavity. The Molluscs are unsegmented
animals. The dorsal part of their bodies contains the
viscera, and is protected by a shell ; while the ventral
part is modified for the purpose of locomotion. A fold
of integument hangs down all round the body and
encloses a cavity in which the gills are contained. The
Arthropods are segmented animals. The body is
armed by a calcareous carapace or shell which forms
the exo-skeleton. Each bodily segment bears a pair
of jointed appendages, and also contains a separate
nerve-centre. The whole series of ganglia are connected
together by means of a nerve-cord, and the nervous
system lies ventral to the alimentary canal. The
Vertebrata are also segmented animals, but the seg-
mentation is not apparent externally. The skeleton is
an internal one, and is built up round an axial rod or
notochord. The nervous system is situated dorsally
to the alimentary canal. There are two pairs of limbs.
Thus we set up an essential or schematic structure
characteristic of each phylum. These schemata have
no real existence : they are morphological types from
which the actual bodily structure of the animals in
each phylum may be deduced. They represent the
minimum of parts which must be present in order that
an animal may be placed in the phylum to which we
assume that it may belong. But these anatomical parts
need not actually be present in the fully developed organ-
ism : thus there are Crustacea in which the body is not
segmented, and in which neither calcareous exo-skeleton
nor jointed appendages are present ; and there are Verte-
brata in which the limbs may be absent. But in such
cases we require evidence that the essential anatomical
characters which are absent in the fully developed
animal have appeared at some stage in its ontogeny,
and this evidence is usually available. Or if embryo-
250 THE PHILOSOPHY OF BIOLOGY
logical evidence cannot be obtained, we require proof
that the animal can be traced backwards in time, by-
means of other characters, to some form in v/hich the
missing structures reappear. The schemata are thus
the generalised or conceptual morphology of the phyla.
They are not the morphology of an individual organism,
but they include the morphology of the race.
They are, Bergson says, themes on which innu-
merable variations have been constructed. Structural
elements may be suppressed, as when the notochord
disappears in the development of the individual
Tunicate, though it is present in the larva. Or elements
may disappear and become replaced by other structures,
as when the true molluscan gills are lost in the Nudi-
branchs and are replaced by the respiratory plumes.
They may be reduced to vestiges, as in the case of the
" pen " of the Squids, or the ' cuttlebone " of the cuttle-
fish, remnants of the domed shell of the primitive
mollusc ; or in the appendix vermif ormis of the human
being, a remnant of the voluminous caecum of the
herbivorous animal. Structures which were originally
distinct may coalesce, as when the greater number of
the primitively distinct segments of the thorax of the
crustacean fuse to form the " body " of the crab ; or
when the segmental ganglia of the same animal fuse
together to form the great thoracic nerve-centre. The
form and situation of a structure may vary within
wide limits : thus the digestive cavity of some Coelenter-
ates may be a simple sac, as in the Hydra, but it may
be partially subdivided by numerous mesenteries as in
the zooid of the Corals ; or the simple tubular alimen-
tary canal in some Platyhelminth worms may be
bifurcated in others, triple-branched in others again,
or even provided with numerous lateral branches, as
in the more specialised species in the group. Organs
THE MEANING OF EVOLUTION 251
originally simple may undergo progressive modifica-
tion : thus the eye of a mollusc may be a simple
integumentary cavity in the floor of which there are
some simple nerve-endings, and some black pigment ;
or this cavity may close up so as to form a sac, and the
anterior part of the sac may become transparent so as
to form a cornea. Behind the cornea a lens may be
formed, and the simple terminal twigs of the nerve-
endings may become a many-layered retina of great
complexity of structure. In the lowest Chordates the
central part of the blood-vascular system is a simple
contractile vessel, but this becomes the two-chambered
heart of the fish, the three-chambered heart of the
reptile, or the powerful four-chambered heart of the
warm-blooded animal. Anatomical elements may
change in function ; thus parts of the visceral skeleton
in the fish may become the ossicles of the middle ear
in the Reptiles and Mammals ; while its swim-bladder
may possibly be represented in the higher vertebrates
by the lungs.
Thus there may be suppression of parts leading to
entire disappearance or to mere vestiges of the original
morphology. A structure degenerating through disuse
may become removed from its typical relations with
other structures and may acquire altogether new ones.
Or its increasing importance may lead to its hyper-
trophy and to increased complexity of structure, and
perhaps to the inclusion of new anatomical elements,
or to the incorporation of other parts, the function of
which may originally have been quite different. In all
sorts of ways organs and organ-systems may become
anatomically different as the result of adaptive modi-
fications, or indirectly as non-adaptive modifications
induced by the adaptive modifications of adjacent
parts. It is the task of comparative anatomy to
252 THE PHILOSOPHY OF BIOLOGY
trace these changes of morphology, aided by the study
of embryology and by the comparison of the structure
of the parts of fossil animals. Regarding the process
of transf ormism as proved by experiments and observa-
tions in breeding and heredity, the naturaUst endeavours
to trace the lines along which evolution has proceeded
from the results of morphological investigations.
Such results cannot have more than a very limited
value, and it is often the case that several interpreta-
tions of morphological results are equally probable.
We may conclude that the existing Teleost and Elas-
mobranch fishes are descended from a common stock
which no longer exists; we may similarly conclude
that the Birds and Reptiles are closely allied, more so
than either group is to the Mammals ; and we may
conclude that the Primates — the group of Mammals to
which Man belongs — is descended from some group
allied to the existing Ungulates or Insectivores, while
the Mammals themselves may have come down from
some group of vertebrates related to both the Amphibia
and the Reptiles. But as to the nature of the animals
which combined the characters of the Birds and Reptiles,
or of the Reptiles and Amphibia, we know nothing.
Palaeontology, if its results were more numerous than
they are, would afford us the material for the discovery
of these " missing links," and there can be no doubt
that as the world becomes better known our knowledge
of palseontological stages in the history of existing
groups will become more complete, so that we may, in
time, possess an actual historical record of the phylo-
geny of the main groups of animals. But it is remark-
able that while the results of comparative anatomy
and embryology, aided by those of palaeontology,
enable us to trace back short series of stages in the
evolutionary process, they still show us gaps at all the
THE MEANING OF EVOLUTION
25a
xfoto - for m
places where lines of descent ought to converge. They
show us, for instance, that the oldest Birds known
were decidedly reptilian in their morphology, but they
do not show us an animal which was neither Bird nor
Reptile, but from which both groups of Vertebrata
have descended ; and this is almost always the case in
our hypothetical schemes of phylogeny. Morphology
has continually to postulate the existence of " an-
nectant " forms, " Archi-Mollusc," " Protosaurian,"
" Protochordate," etc. : hypothetical animals which
combine the characters of
those which lie near the
bases of diverging lines of
descent. There is nothing
to guide us in the con-
struction of these annectant
forms except the progres-
sive simplicity of structure
indicated in the morpho-
logical and palaeontological
series. The earlier Birds
had teeth, for instance, and
so have the Reptiles, there-
fore the annectant form had teeth, and it was an
animal combining the schematic morphology of both
Birds and Reptiles. But just according to the value
which we attach to one morphological character
rather than another, so will the structure of the
annectant form differ. Is, for instance, the alimentary
canal of the Vertebrate the most fundamental and
conservative part of its morphology : that is, is it the
structure which has been most resistant to change in
the course of the evolutionary process ? Then we may
regard the Vertebrates as having descended from some
animal which was closely related to the Annelid worms.
Archi- Form
Fig. 25.
254 THE PHILOSOPHY OF BIOLOGY
Or is the nervous system the most conservative part
of the Vertebrate anatomy ? If so, we may trace back
the main Chordate stem to animals which included
among their characters those of the most primitive
Arthropods. In the one case the annectant form
joins together the Vertebrate and Annelid stems, but in
the other case it would join together the Vertebrate
and Arthropod stems, a conclusion which a rigid appli-
cation of the results of morphology would seem to
make the more probable one.
But, however this m.ay be, we must not fail to notice
that annectant forms — " Archi-Mollusc " " Proto-
saurian," " Protochordate/' and the like, are only
fictions which we base on the precise importance that
we attach to one part of the essential morphology of
a group of animals rather than another. These hypo-
thetical animals, and the genealogical schemes or
phylogenies of which they form the roots, are conven-
tional summaries of the results of comparative anatomy,
this term being used to include the anatomy of the de-
veloping animal and that of extinct forms. So long as
we do not possess a representative series of the fossil
remains of the animals which have existed in the past,
all schemes of descent founded on the comparison of
the parts or the organs of living animals, or on the
comparison of stages of development, must possess
doubtful value when they profess to indicate the direc-
tion taken by evolution. Their true value lies rather
in the way they epitomise our knowledge of morphology,
and in the incentive which they give to sustained and
minute investigation of the structure of animals.
Why did Haeckel's " Gastrea-Theorie " gain the
acceptance that it did during the latter part of the
nineteenth century ? It correlated a great number of
facts, in that it postulated a general uniformity of
THE MEANING OF EVOLUTION
255
A
C
■ Coelenleton
, CoelerTtercn
Lllllilflj
/
structure in the early developmental stages of very
many animals belonging to widely separated groups.
In all of these the ovum segments into a mass of cells,
which then become arranged as a hollow ball [A). One
side of this ball becomes pushed in so that the inner
part of the hollow sphere becomes opposed to the inner
wall of the upper part. Thus a little sac, consisting
of two layers of cells, ectoderm
and endoderm, and opening to
the outside by an aperture, the
blastopore, is formed {B) . This
is essentially the anatomy of
the schematic Coelenterate ^
animal — Hydra, for instance,
strongly suggests it. Suppose
now that the lips of the blas-
topore fuse together at one
place so that there are two
openings into the cavity of
the gastrula instead of one ;
and suppose that the spherical D
organism elongates so as to
form a cylinder, the elongation
involving the fused part of
the blast oporic region. Then
we obviously have a worm-like animal with an alimen-
tary canal, a mouth and an anus (C). Suppose further
that an additional layer of cells becomes formed between
the endoderm and ectoderm by proliferation from one
of these tissues, and suppose that this becomes double
and that a cavity appears between the two sheets
of cells forming this middle layer : this cavity be-
comes the body cavity or coelom (Z)). Now such blas-
tula and gastrula stages appear in the ontogeny of
animals belonging to widely different groups, and
.Moijrh JAous
Echder/n
I'iesocierrn
esodeffr,
256 THE PHILOSOPHY OF BIOLOGY
such a formation of the middle layer, or mesoblast, and
of the mesobiastic or coelomic cavities also actually
occurs. Let us assume therefore that all multicellular
animals have descended from a primitive Gastrea-form
essentially similar in morphology to the gastrula larva ;
and let us assume that all coelomate animals have
descended from a form in which a third layer of cells,
or mesoblast, became intercalated between the other
two. These two assumptions are the bases of the
classic phylogenies of the last century ; all Coelenterate
animals have descended from a Gastrea-form, and all
animals higher than the C(Klenterates have been evolved
from a three-layered form. Implied in this hypothesis
is also a third one, that the Gastrea-stage of evolution
possesses such a degree of stability that it has persisted,
though in an obscure condition it may be, in the
development of nearly all multicellular animals. The
triple germinal layers, endoderm, ectoderm, and meso-
derm, which first became distinct from each other in
the primitive coelomate animal, also acquired a high
degree of stability, and they have been transmitted by
heredity to all animals higher than Coelenterates. The
Gastrea and the three germinal layers are therefore to
be sought for in the developmental stages of all the
higher animals, and they have usually been found.
Let it be admitted that they may make a transient
appearance — that they may be obscured in many ways,
still they ought to be there.
The Gastrea-Theorie ceased to be useful, as a means
of description, or a working hypothesis of investigation,
after the rise of experimental embryology. It could
not be proved that the process of development by
gastrulation and the cleavage of a mesodermal layer
are so very conservative that they have persisted
throughout the greater part of the evolution of the
THE MEANING OF EVOLUTION 257
animal world, yet ^vithout this proof it could not be
contended that the veiled gastrula of the developing
frog's egg, for instance, is related genetically to the
gastrula of the Echinoderm larva. What experimental
embryology does indicate is that the formation of
gastrula and (in most groups) the three germinal
layers are only the means of morphogenesis. In the
division of the ovum, and the arrangement of the cells
to form the organ-rudiments, the formation of the
gastrula and the mesoderm are in general the line of
least resistance in the process of development. If they
do not appear, or are difficult to recognise in the
ontogeny of a group of animals, it is not a sound method
to assume their presence in an abbreviated or distorted
form, postulating that they ottght to be present, having
been transmitted by heredity. Physical conditions
undoubtedly influence developmental processes and
there is no reason for assuming that all ontogenetic
processes were originally the same.
If we do not strain the facts of our descriptions of
organic nature, and if we do not build on unprovable
conjectures, all that morphology certainly shows us is
that the evolutionary process has led to the establish-
ment of some dozen or so great groups of organisms,
each with appended smaller groups more or less closely
related to them. Whether these greater lines of
descent are to be represented, as they usually are, as
branches springing from a single stem, or whether they
are truly collateral, each evolved independently of all
the others, is a question which is not to be solved merely
by the methods of comparative anatomy or embryology.
The widely different, and equally probable, phylogenies
of the past indicate that data for the solution of such a
problem do not exist, not just yet at all events. What
we may discuss with greater advantage is the question
R
258 THE PHILOSOPHY OF BIOLOGY
as to which of the great subdivisions of life repre-
sents the main results of the evolution of complex
organic entities from the simple living substances in
which we suppose life first became materialised on
our earth. What activities and structural forms
represent the main manifestations of the evolution-
ary process ?
That is to say, what great groups of organisms are
the dominant ones on the earth ? Greater or less
degrees of dominance are indicated by the extent to
which a group of organisms is distributed on the earth,
by its abundance, and by the period of time during
which it can be recognised in the fossil condition.
Ubiquitous distribution implies a high degree of adapta-
bility : a group of organisms inhabiting land and sea
and atmosphere is obviously one in which the morpho-
logical structure has been elastic enough to admit of
the development of various modes of locomotion ;
and the limbs may be either the appendages of a
terrestrial animal, or the fins, or other swimming organs,
of an aquatic creature, or the wings of one adapted
for flight. Dominance in this respect implies mobility
and activity, and a relatively highly developed nervous
system ; it impHes the development of organs special-
ised for prehension, that is, for the capture of food ;
and it also imphes a high degree of adaptability to
widely different physical conditions, to temperature
changes, for instance. Dominance in geological time
means also this great adaptability to changes in climatic
conditions, and the development of means of distribu-
tion sufficient to overcome extensive physical changes
on the surface of the earth. A terrestrial species might
become isolated by the formation of a mountain range,
or the submergence of the land adjacent to that which
it inhabited, and some widely distributed species of
THE MEANING OF EVOLUTION 259
plants and insects must have been able to traverse
oceanic areas. The abundance of a group obviously
implies great powers of reproduction, the ability to
withstand physical changes, and the ability to resist
competition with other predatory creatures. Domin-
ance, in short, means that the organism possesses in
high degree the inherent powers of reproduction ; and
also those activities which enable it to respond by
adaptations of morphology, functioning, and behaviour,
to environmental changes. These environmental
changes are those which must have been experienced
during lengthy geological periods, and also those ex-
perienced by the organism in its attempt continually
to enlarge its area of distribution.
If we make a broad survey of the animal world we
shall find that dominance in these respects has been
acquired by three great groups of organisms, (i) the
Bacteria, (2) the chlorophyllian organisms- (3) the
Arthropods, and (4) the Vertebrates. In each case the
threefold condition of wide distribution over all the
earth, both in fresh and marine water areas, on the
land and in the atmosphere ; of existence throughout
the greater part of geological time ; and of ability to
withstand environmental change, are satisfied. The
bacteria are known to have existed in the carboniferous
period. At the present time their distribution on the
earth is universal : no part of the land surface, and no
water masses, either marine or lacustrine — no matter
how unsuitable they may be for the life of more highly
organised creatures — are untenanted by bacteria.
They are able to withstand extremes of temperature,
or of salinity, which would be fatal to the multicellular
plant or animal. Parasitism is a mode of life which
they exhibit in a more manifold degree than do any
other organsims. The upper regions of the atmosphere
260 THE PHILOSOPHY OF BIOLOGY
are the only parts of the earth and its envelopes which
they do not inhabit.
The chlorophyllian organisms include those uni-
cellular plants and animals — the distinction becomes
obscure with regard to these organisms — which are
pigmented blue, green, brown, or red owing to the
existence in the cells of chlorophyll, or of some substance
allied to this compound, and they include, of course^
the green plants. Like the Bacteria their distribution
is world-wide, extending over land and sea and fresh-
water areas ; and it is restricted mainly by the distribu-
tion of sunlight, and by a lower limit of temperature.
The Marine Algae, the Diatoms, the Peridinians, and
other chlorophyll-containing organisms appear to in-
habit all parts of the world ocean, certainly within a
depth of about twenty to fifty fathoms from the surface
of the sea. Green plants inhabit the land everywhere
except within polar areas, the tops of high mountains,
and over areas desert by reason of lack of water, or
by the presence of mineral substances.
These conditions — temperature, light, soil, etc. — do
not appear to limit the distribution of the Arthropods
and Vertebrates. We find both kinds of animals in
the deepest oceanic abysses (deep-sea fishes and Crus-
tacea), in polar land and sea regions (Man, some
Insects, Crustacea, and Birds), as well as in desert areas
and on the summits of the loftiest mountains. The
Ants share the subsoil with the Bacteria. Birds and
Insects conquer the atmosphere by their activity and
not, like the Bacteria, merely by being blown about.
Crustaceans such as the Copepoda have much the same
distribution in the sea as the Insects have in the atmo-
sphere, while Isopods and Amphipods are a parallel,
so far as the sea bottom is concerned, to the Spiders,
Millipedes, and Ants on the land. Fishes are distributed
THE IVIEANING OF EVOLUTION 261
throughout all depths, and in almost all physical con-
ditions in the sea. Some species of marine Mammalia
and Birds are quite cosmopolitan except that they are
restricted to the upper layers of the ocean. Land
Mammals are subject to the same restrictions as are
the green plants, being unable to survive in desert and
polar areas. The only parts of the sea which are not
inhabited by Arthropods and Vertebrates are those
limited deep strata of water (as in the case of the deeper
layers of the Black Sea) where there are accumulations
of poisonous chemical substances in solution. But the
Bacteria inhabit even these regions.
Green plants, Arthropods, and Vertebrates appear
as fossils in almost every part of the stratified rocks.
The Trilobites represent the end of a long evolutionary
process, and the same is to be said of the first fishes
found in Silurian rocks, so that these groups of animals
must have existed in the geological periods represented
by those remains of rocks which are older than the
earliest fossiliferous ones. Plant remains are present
in Silurian rocks, but there can be no doubt that Ferns
and other chlorophyllian organisms must have been in
existence long before this time. We can hardly suppose
that the Bacteria found in the Carboniferous rocks
first appeared at this time in the earth's history : like
the other great groups of life they probably had a pro-
longed history prior to that date of the geological
formations in which they are first to be recognised.
Our dominant groups of organisms may therefore be
traced back almost to the very beginnings of life on
the earth.
Dominance, such as we have defined it, cannot be
said to have been attained by any other of the sub-
kingdoms of life. Coelenterates and sponges appear to
have existed throughout the whole period during which
262 THE PHILOSOPHY OF BIOLOGY
the remains of organisms are to be traced in the rocks,
but they have always been exclusively aquatic animals
and they are very sparsely distributed in fresh water
regions. Echinoderms are also a very old group, but
they were more abundant in the past than they are
now, and they appear to have been an exclusively
marine group of animals. Molluscs have existed since
the beginnings of stratified deposits and they are both
aquatic and terrestrial animals, but they belong pre-
dominantly to the sea. They have always been
relatively sluggish and inactive animals, with the ex-
ceptions of the great Squids and Cuttlefishes, but
fortunately for the other inhabitants of the sea these
formidable creatures appear to possess restricted
powers of reproduction, and they have never been very
abundant. All the smaller groups of animals are
restricted in their distribution : the flat-worms occur
sparingly both on the land and in the sea, and they
attain their highest development as parasites in the
bodies of other animals. Annelid worms, Gephyrea,
Nemertine worms, Polyzoa, Rotifers, etc., are all
groups of animals occurring mainly in fresh and sea
water and none of them is abundant. Related to most
of the great phyla are smaller groups : the extinct
Trilobites, Eurypterids, etc., in relation to the Arthro-
poda ; the group represented now by Peripatus in
relation to the Arthropods and Annelids ; the Entero-
pneusta and some other creatures which appear to
possess affinities with the Echinoderms and Chordates ;
and the extinct Ostracoderms, which appear to have
been related to either the Arthropods or Vertebrates, or
to both. All these smaller groups of animals we must
regard as representing sidepaths taken by the evolu-
tionary process — paths which have either ended blindly,
as in the case of those groups which have become extinct »
THE MEANING OF EVOLUTION 263
or which we can still trace in the existing remnants of
groups which were formerly more abundant than they
are now.
Only among the existing Bacteria, chlorophyllian
organisms, Arthropods, and Vertebrates has the vital
impetus found its most complete manifestation, and
we may even narrow down the main path that evolution
has taken to certain groups in each of these phyla.
Some of the Bacteria — those which are exclusively
parasitic in the bodies of the warm-blooded animals —
have adopted a most specialised mode of life, and may
even be said to exist only ^\ith difficulty, since the
healthy animal is able to destroy them. Only those
Bacteria living in the open or upon the dead tissues of
plants and animals have attained to real dominance.
Some green plants, like the Ferns, are far less abundant
now than they were in the past ; while the Fungi and
some other saprophytic and parasitic plants have
specialised in much the same way as have the parasitic
worms, and are restricted in their distribution. Marine
Algae are confined to a relatively narrow selvedge of
sea round the land margin. The great trees, the
grasses, and the microscopic green plants such as the
Diatoms and Peridinians, represent the truly dominant
organisms in the vegetable kingdom. On the side of
the Arthropods and Vertebrates there have been many
unsuccessful lines of evolution : the Trilobites, for
instance, in the former group ; and the armoured
Ganoid fishes, the armed Reptiles, the volant Reptiles,
and the giant Saurians and Mammals among the Verte-
brates. Among the existing Arthropods and Verte-
brates there are some smaller groups which persist, so
to speak, only with difficulty. Such are the Spiders,
Mites, and Scorpions among the Arthropods ; and the
Tunicates, the Dipnoan fishes, the tailed Amphibians,
264 THE PHILOSOPHY OF BIOLOGY
many Reptiles, and the volant Mammals among the
Chor dates : such are, of course, only instances of the
less successful lines of evolution in these phyla. The
dominant Arthropods and Vertebrates are the Crustacea,
the Hymenopterous Insects, the Teleost and Elasmo-
branch fishes, and the terrestrial Mammals. The earth
belongs to Man, to the social and solitary Ants, Wasps
and Bees, the marine Crustacea, the Teleost fishes,
the Trees, Grasses, and unicellular Diatoms and Peri-
dinians, and to the putrefactive and prototrophic
Bacteria. These are the organisms in which life has
attained its fullest manifestations, and has been most
successful in its master}^ over inert matter.
In what kinds of activity and morphology, then,
has the vital impetus found most complete expression ?
We see at once that in relation to energetic processes
life has followed two divergent lines — animal and
vegetable. There is no absolute distinction between
the energy-transformations which proceed in the living
plant and animal — we return to this point later on —
but we may trace an unmistakable difference in
tendency, that is, in the direction taken by evolution.
This difference we have already considered in an earlier
chapter, but we may illustrate it by considering a
lifeless earth, and also one tenanted only by plants,
or animals, or by both.
In a lifeless earth all energetic processes would tend
continually toward a condition of stability. The crust
of the earth, that is, the part known to us by direct
observation, is made up of rocks and the remains of
rocks ; materials consisting of compounds of oxygen,
silicon, iron, aluminium, sodium, potassium, calcium,
and so on. They are substances which would be stable
but for the eroding action of water, the gases of the
atmosphere, and volcanic activity. But as volcanic
THE MEANING OF EVOLUTION 265
activity tends always toward cessation, the oxygen of
the atmosphere would gradually disappear, first by
its combination with oxidisable substances, and second
by its combination with the nitrogen of the atmosphere
under the influence of electric discharges. Carbon
dioxide would either combine with materials in the
rocks, or would remain in the atmosphere along with
nitrogen and other inert gases in a stable condition.
Water, moved by the tides and winds, would gradually
plane down the surface of the land, unless along with
other gases it would gradually become dissipated into
outer space. We see, then, that the materials of the
earth tend to fall into stable combinations, and that
they approximate toward conditions in which potential
chemical energy becomes reduced to a minimum, the
whole energy possessed by matter being that of the
motions of the molecules, that is, kinetic energy un-
available for transformations of any kind. It would
be an earth devoid of phenomena.
Vegetable life alone would be possible only for a
time on an earth such as we know it at present. The
green plant depends for its existence on the presence in
the soil of mineral substances such as salts of nitric
acid and of ammonia, and on the presence of water and
carbon dioxide in the atmosphere. The chlorophyllian
apparatus is essentially a mechanism whereby these
substances become built up into carbohydrates, like
starch and sugar ; hydrocarbons, like resins and oils ;
and proteids. The energy necessary for these syntheses
is obtained from solar radiation through the agency of
the chlorophyll plastids. The green plant would
depend for its supply of nitrate or ammonia on the
combination of the nitrogen of the atmosphere with
oxygen, or on the exhalations from volcanoes, and
these are irreversible processes which tend continually
266 THE PHILOSOPHY OF BIOLOGY
toward cessation. The plant requires also carbon
dioxide and the amount of this substance in the atmo-
sphere is very Hmited, while the only inorganic source
from which it can be renewed seems to be volcanic
activity : this substance also would tend to disappear.
A time would therefore come when plant life on the
earth would cease to be possible because of the disap-
pearance of the materials on which it depends ; but
while it did exist its result would be the accumulation
of chemical compounds of high potential energy. The
result of the metabolism of the plant is the formation
of such compounds as cellulose from woody tissues and
shed leaves, of other plant carbohydrates, of oils and
resins, and of proteids. In the absence of bacteria such
substances would persist unchanged : even in an earth
tenanted by bacteria such products as oils, lignite,
peat, coal, etc., have been able to accumulate through-
out geological time. The tendency of plant life is
therefore toward the accumulation of compounds of
high potential energy, and this process also is irre-
versible.
Bacterial activity would, of itself, make continued
plant life possible on the earth. The essential characters
of these organisms are their ability to bring about the
most varied energy-transformations. From our present
point of view bacteria may be divided into paratrophic,
metatrophic, and prototrophic forms. Paratrophic
bacteria are those which live as parasites within the
living tissues of plants and animals : this mode of life
is obligatory, and these organisms are unable to live in
the open. The result of their activity is the breaking
down of protoplasmic substance. Metatrophic bacteria
are those that produce putrefaction and fermentation
of organic compounds. They may be parasitic in
their mode of life, but most of them live in soil, in water.
THE MEANING OF EVOLUTION 267
and in the cavities of the animal body — the mouth,
ahmentary canal, nose, and vagina. Proteids are
decomposed by them into simple chemical compounds
such as amido-acids, and then these substances, along
with carbohydrates, are fermented so as ultimately to
form water, carbonic acid, and salts of nitric acid.
These bacteria obtain their energy from the conversion
of chemical compounds of high potential energy into
compounds of low potential energy. Prototrophic bac-
teria are never parasites, nor do they live in the cavities
of the bodies of animals : they always live in the open.
They carry on still further the action of the putrefactive
bacteria by converting ammonia into nitrous acid, and
nitrous acid into nitric acid. Others reverse this series
of changes by reducing nitric acid to nitrous acid,
nitrous acid to ammonia, and ammonia to free nitrogen.
Others again oxidise sulphuretted hydrogen to sulphuric
acid, others ferrous hj^drate to ferric hydrate, while it
has recently been shown that some bacteria are ap-
parently able to oxidise the carbon of coal to carbonic
acid. Some are able to oxidise the free nitrogen of the
atmosphere into nitrous and nitric acids. How pre-
cisely the energy necessary for these transformations is
obtained is not at all clearly understood, and it may be
possible that some of the prototrophic bacteria obtain
their energy by making use of the un-co-ordinated kinetic
energy of the medium in which they live. From our
point of view the net result of the activity of the pre-
dominant species of bacteria which inhabit the earth
is that they reverse the processes which are the mani-
festations of the metabolism of plants and animals.
The result of the metabolism of plants is the accumula-
tion of stores of high potential compounds such as
carbohydrates, and the depletion of the terrestrial
stores of carbon dioxide and other materials necessary
268 THE PHILOSOPHY OF BIOLOGY
for the continued existence of the plants themselves.
The result of the metabolism of the bacteria is the
break-down of this accumulation of such compounds
as carbohydrates, and the replenishing of the stores
of carbon dioxide and nitrogenous mineral substance
on which the plant depends. If bacteria are present,
the life process becomes a reversible one.
Plant life and bacterial life are thus complementary
to each other, for, on the whole, the energetic processes
of the green plant proceed in the opposite direction to
those of the bacteria. An organic world consisting of
green plants and bacteria would therefore be one
capable of permanent existence. Now, so far, we need
only consider these various kinds of organisms as living
protoplasmic substances in which energy-transforma-
tions of different types proceed. The bacterium is
simply a cell containing a nucleus, and the green plant
need only be a nucleated cell containing a chlorophyll
plastid : this is, indeed, all that it is in the case of a
Diatom or a Peridinian. The morphology of the green
plant is only accessory to the c?ilorophyllian apparatus.
Neglecting the reproductive apparatus, the higher green
plant consists essentially of the chlorophyllian cells in
the parenchyma of the leaf, for roots and stomata are
only organs for the absorption of water and mineral
salts from the soil and carbon dioxide from the atmo-
sphere ; while the tissues of the trunk, stems, and
branches are, in the main, apparatus for the conduction
of these raw materials through the body of the plant,
and, of course, the nutritive substances into which they
are elaborated. All the innumerable variations of
form in the plant (apart from the structure of the
flower or other reproductive organ) are adaptations
which provide for the absorption and distribution of
these substances ; or for the mechanical support of
THE MEANING OF EVOLUTION 26&
the plant body ; or are non-adaptive variations, pure
luxuries, so to speak.
More than this is represented by the structure of
the animal body, but we must first of all consider the
points of difference between plant and animal re-
garded merely as apparatus in which energ^^-trans-
formations occur. In the green plant energy is accumu-
lated in the form of high potential chemical compounds,
but in the animal energy is expended. Inorganic
mineral substances are built up by the plant into
carbohydrate, proteid, and fat or oil, but in the
animal body carbohydrate, proteid, and fat are
dissociated into water, carbonic acid, and urea (or
some other nitrogenous excretory substance) ; and
the urea or other analogous substance is broken down
by bacteria into nitrate, water, and carbon dioxide.
The metabolic activities of the animal are said to be
" analytic " or destructive, while those of the plant
are said to be " synthetic " or constructive, but
these contrasting terms hardly describe accurately the
essential nature of the activities of the two kinds of
organisms. What further constitutes " animality " ?
It is purposeful mobility, and the energy-transforma-
tions that occur are the means whereby this mobility
is attained. The plant is essentially immobile, for such
movements as the turning of leaves toward the light,
the down-growth of roots, the up-growth of stems, the
twining of tendrils round supporting objects, and the
opening and closing of flowers are only the movements
of parts of the plant organism. They are constant,
directed responses to external stimuli — real tropisms —
and the extension of this kind of response so as to
describe in general the movements of animals is only
an instance of the insufficient analysis of facts. The
movements of the typical green plant are therefore
270 THE PHILOSOPHY OF BIOLOGY
movements of its parts, they are few in number, they
belong to a few simple types, and they are evoked by
simple external physical changes in the medium. The
movements of the typical animal are movements of
the organism as a whole ; they are iniinitely varied in
their nature ; they are evoked by individualised stimuli
and they are continually being modified by the experi-
ence of the organism.
The bodily structure of the animal is the means
whereby this purposeful mobility is attained and the
energy-transformations directed ; and the greater and
more varied the movements of the animal, the more
complex is its structure. In respect of the manner in
which the energy-transformations are effected, that is,
in respect of the material means whereby energy falls
from a state of high potential to a state of low potential,
the morphology of the animal is similar to that of the
plant, that is, the energy-transformations are the
functions of nucleated cells. But in the plant the
kinetic energy of solar radiation passes into the potential
energy of chemical compounds which become stored
in the body of the plant ; while in the animal the
potential energy of ingested chemical compounds
passes into the kinetic energy of the movements of the
animal itself. How exactly it moves, how this kinetic
energy is employed is determined by the sensori-
motor system.
It is the existence of the sensori-motor system that
makes the animal an animal. What, then, is the
sensori-motor system ? It is the skeleton and muscles,
that is, the organs of locomotion, aggression, prehension,
and mastication ; the peripheral sensory and motor
nerves ; and the central nervous system or brain.
The skeleton of an animal, whether it be the carapace
or exoskeleton of a crustacean, or the vertebral column,
THE MEANING OF EVOLUTION 271
limb-girdles, and limb-bones of a vertebrate, is a rigid
and fixed series of supports to which the muscles are
attached. Organs of locomotion are, for instance, the
appendages of a crustacean, the wings of a bird or
insect, the tail and fins of a fish, or the limbs of a
vertebrate. Organs of aggression are t?ie mandibles
of a spider or blood-sucking fly, the chelate claws of a
crab or lobster, the jaws of a fish, or the claws and
teeth of a terrestrial vertebrate. Organs of prehension
and mastication are in the main also those of aggression.
All these parts consist of modified skeletal structures,
teeth, claws, etc., attached to muscles which originate
in the rigid parts of the skeleton. When we speak
of the movements of an animal we speak of the
motions of such parts as we have mentioned ; other
parts do indeed move — the heart pulsates, the
lungs dilate and contract, and the blood and other
fluids circulate through closed vessels ; but these are
movements of the parts of the animal, and are
comparable rather with those movements of the
plant organism that we have considered. They are
not to be regarded as examples of the mobility of
the animal in the sense of the exercise of its
sensori-motor system.
A central and peripheral nervous system is, of course,
bound up with a motor system. Receptor organs,
eyes, olfactory, auditory, tactile organs of sense, and
so on, are the means whereby the animal is affected by
changes in its environmant — it need not be cognisant
of, or become aware of, or perceive these impressions
on its receptor organs. These stimuli are transmitted
along the sensory, or afferent, nerves to the central
nervous system : this is the way in. The effector
nervous organs are the motor plates, that is, the nervous
structures in the muscles in which the nerves terminate.
272 THE PHILOSOPHY OF BIOLOGY
The motor nerves are the efferent paths, the way out
from the central nervous system.
The central nervous system is essentially the organ
for the integration of the activities of the whole body.
It is the " seat of multitudinous synapses," a description
which better than any other applies to the morphology
of the brain of the vertebrate animal. We have already
considered what is meant by the term " reflex action,'*
it is the series of processes which occur when a " reflex
arc " becomes functionally active. A reflex arc consists
of (i) a receptor organ, say a tactile corpuscle in the
skin ; (2) an afferent nerve fibre ; (3) a nerve cell in
the brain or spinal cord ; (4) an efferent nerve fibre ;
and (5) an effector nerve organ, say a motor plate in a
muscle fibre. The series of processes involved in a reflex
action consist of the stimulation of the receptor organ,,
the passage of the afferent impulse into the brain or cord,
the passage of the impulse through a series of cells in
the nerve centre forming a synapse, the transmission
of the impulse through the efferent nerve fibre into the
effector organ in the muscle and the stimulation of the
latter to an act of contraction. This is a purely
schematic description of the structures and processes
forming a reflex action and arc : in reality the path
both into and out from the central nervous system is
interrupted again and again, and at each place of
interruption there are alternative paths. The interrup-
tions occur at the synapses. At a synapse the nervous
impulse passes through an arborescence of fine nervous
twigs, into which the fibre breaks up, into a similar
arborescence, and these two arborescences are not in
actual physical contact : the impulse leaps over a gap.
At numerous places in both brain and cord there are
alternative synapses and at these places the impulse
may travel in more than one direction.
THE MEANING OF EVOLUTION 273
The brain and cord are a switch-board of unimagin-
able complexity, so that an efferent impulse entering
it from, say, the eye, can be shunted on to one nerve
path after another, so that it may affect any muscle
in the whole body. This is no fiction : it may actually
be the case. In normal respiration a centre in the
hind-brain is stimulated to rhythmical activity by the
presence of carbon dioxide in the blood, and from it
efferent impulses originate which stimulate the muscles
of the chest wall and diaphragm. But in the distress
of asphyxia every muscle of the body may be stimulated
to activity in the effort to accelerate the oxygenation
of the blood, and these are not spasmodic movements
of the muscles of limbs, etc., but purposeful contractions
having for their object the increased intake of air into
the lungs. The central nervous system is, therefore,
a switch-board — so mechanistic physiology teaches,
neglecting any idea of an operator. But the whole
trend of modem investigation is to show that every
increase of specialisation in the evolution of the higher
animal adds to the complexity of this nervous apparatus
by increasing the number of alternative paths that an
impulse originating anywhere in the body may take
before it issues from the brain or spinal cord. Yet
with all this increase of complexity it is nevertheless
the case that in the higher animal the various parts of
the central and peripheral nervous system are more
and more integrated, so that in the actions of the
animal it becomes more and more the organism as a
whole that acts.
All other organs in the animal body — excepting
always the reproductive apparatus — are accessory to
the sensori-motor system. The alimentary canal and
its glands dissolve the food-stuffs ingested ; the meta-
bolic organs, that is, the cells of the wall of the intestine,
s
274 THE PHILOSOPHY OF BIOLOGY
the liver, etc., transform these ingested proteids, fats,
and carbohydrates of the food into the proteids, fats,
and carbohydrates of the animal itself ; the heart,
blood, and lymph vessels carry this food material to
the muscles and nervous organs ; the respiratory
organs absorb oxygen which is distributed throughout
the body in the blood stream ; the execretory organs,
that is, the lungs, skin, and kidneys, remove noxious
materials like carbonic acid and urea, or its precursors ;
and purposeful changes of functioning of all these
organs are brought about by changes in motor activity.
Round the sensori-motor system all the rest of the
structure of the animal body is built up.
What we see clearly in the evolution of the animal
body is the progressive increase of activity of the
sensori-motor system. The animal becomes more and
more mobile. It is in this way that dominance has
been attained and all the directions of structural
evolution in the past that have not tended in this
direction have been unsuccessful, irreversible, evolu-
tionary processes. Great size has not succeeded in the
animal kingdom, and so the gigantic reptiles and
mammals of the secondary and tertiary periods have
become extinct. Defence against enemies by the de-
velopment of dermal armour has not succeeded, and so
the Dinosaurs, and other armed animals of the Tertiary
Age have also become extinct. The transformation of
the fore limbs of the reptile into wings, or the legs of the
mammal into flappers, did not succeed, because all
the rest of the structure of these animals had become
adapted to locomotion on dry land, and the change of
structure had become too profound to be modified :
so the Pterodactyls passed away, as the whales of
our own period are also passing. Only in the lightly
boned, feathered bird, with the possibility of the
THE MEANING OF EVOLUTION 275
development of powerful pectoral muscles, did in-
definite possibilities of flight reside ; and only in the
fish, with the concomitant evolution of gills, the re-
duction of a minimum of the mass of the alimentary
canal and its glands, and the conversion of most of
the muscles of the body into organs actuating the tail
fin, was the completeness of adaptation to aquatic
life realised. Mobility, a bodily structure capable of
indefinitely varied movements, and a nervous system
by the aid of which any part of the body might become
linked to any other part — these were the structural
adaptations that have been successful alike in
Arthropod and Vertebrate.
There were apparently two main types of structure
by means of which this mobility and elasticity could
be attained, the Arthropod type and the Vertebrate
type. There seems little to choose between them if
we had to select one of them* in order to obtain a highly
mobile organic mechanism. Arthropod and Vertebrate
seem to be equally complex if we take account of
difference in size and the additional bodily mechanism
that great size must involve. Certainly the muscula-
ture of the Vertebrate is more complex than in the
Arthropod. But greater weight must require larger
and more powerful muscles if the same degree of
mobility relative to the size of the animal is to be
attained, and this more complex musculature must
carry with it a more complex brain. It must also be
concomitant with a more massive skeleton, for rigid
supports for the muscles must be present in the mechan-
ism. Why are there no great insects or crustaceans ?
Mr Wells has suggested in one of his novels the for-
midability of a wasp two feet long ! Such a creature
would indeed be more dreadful than any predatory
bird that we know if its activity were also that of the
276 THE PHILOSOPHY OF BIOLOGY
wasps that we know, just as a Copepod as large as a
shark would be a more formidable animal than the
fish. It seems possible that the reason for the smaller
size of the Vertebrate is to be found in the nature of the
skeleton. Powerful muscles would require a very-
strong and thick carapace, and this would attain a mass
in a very large insect or crustacean which would require
too much energy for its rapid transport. A rigid
exoskeleton like that of an Arthropod also means that
growth must take place by a process of ecdysis, that is,
the animal grows only during the periods when it casts
its shell ; and the necessity of this process of ecdysis
must be a formidable disadvantage in the case of a
very large animal, if indeed it would be possible at all.
Thus the Arthropod developing an exoskeleton must
remain small, and this smallness, fortunately for the
Vertebrate, has made it the less formidable animal.
It was an accident of evolution that the Arthropods
developed an exoskeleton instead of an endoskeleton.
Undoubtedly the internal skeleton of the Verte-
brates, with its light, hollow, cancellated bones, was
mechanically the best means for the attachment of
muscles. It made possible a greater degree of freedom
of movement of the parts of the body, greater variety
and plasticity of action, and it removed, to some extent,
the limit of size and the embarrassing discontinuity of
growth by ecdysis, with all the dangers that this
involves. Above all, it led to the increased complexity
of the central nervous system, since this became bound
up with the increasing variety of bodily movement.
In the evolution of the dominant groups of organ-
isms we see, then, the development of several tendencies.
First, that tendency which seems to offer the greatest
contrast to the universal tendency displayed in in-
organic processes, the dissipation of energy. The
THE MEANING OF EVOLUTION 277
plant organism is essentially a system in which energy
is accumulated in the potential form. Then, in the
animal kingdom we see that the main tendency of
evolution has been the development of systems in
which energy becomes expended in infinitely varied
movements. It may seem, on superficial examination,
that in the animal mode of metabolism energy is dis-
sipated as it is in inorganic processes ; and this is the
conclusion that we should reach if we considered the
actions, and the results of the actions, of the lower
animals only, that is, animals lower than man. We
return to this point later on, but in the meantime it is
to be noted that the fundamental division of organisms
is that founded upon their activities as energy-trans-
formers, that is, into plants and animals. Within each
of these kingdoms of organisms structural evolution
has occurred : the unicellular green plant has evolved
along very numerous lines, each of them characterised
by a different type of morphological structure. The
unicellular animal has also evolved in a similar w^ay
with the result that the present phyla have become
established. Looking at these great groups of animals,
we see that two of them have attained dominance by
the development along different lines of a sensori-
motor system. Here w^e see another fundamental
difference between the plant and animal organism, but
one which is a consequence of the difference that exists
between the two kingdoms in respect of the energy-
transformations carried out by them. The plant is
characterised by immobility, the animal by mobility.
Immobility implies unconsciousness, mobility con-
sciousness, and this physical difference is the third one
which we can establish between the plant and the
animal. Now few physiologists are likely to accept
this distinction as one which has any real objective
278 THE PHILOSOPHY OF BIOLOGY
meaning. Consciousness is not a concept to be dealt
with in any process of reasoning, it is not even some-
thing felt in the way in which we speak of the feelings
of pain, or light, or hunger : these are all states of our
consciousness. The difference in ourselves, says Ladd,
when we are sunk in sound dreamless sleep, and v/hen
we are in full waking activity, that is consciousness.
If we reason about organisms and their activities as
we do about inorganic things we have no right to speak
about consciousness, for outside our own Ego it has
no existence. The acting animal is only a body, or a
system of bodies, moving in nature, and all its activities
are to be described by a system of generalised force and
position co-ordinates with reference to some arbitrarily
chosen point of space. " This animal machine," says
a zoologist, writing about instinct, " which I call my
wife, exhibits certain facial contortions and emits
certain articulate sounds which correspond with those
emitted by myself when I have a headache, but I have
no right to say that she has a headache." This kind of
argument does not appear to be capable of refutation
except, perhaps, by the domestic conflicts which it
would usually evoke if applied in such cases as that
quoted. In a description of nature by the methods
and symbolism of science we see only systems of mole-
cules in motion, and in those systems which we describe
as organisms the motions are only more complex than
they are in inorganic systems. Such is the method of
science, as irrefutable in the study of the organism as
we know that it is false. Valid in pure speculation
according to the methods of the intellect it would never-
theless be absurd in the everyday affairs of common
civilised life ; and the scientific man who applies it in
his writing would nevertheless hesitate to apply it in
the affairs of his own household.
THE MEANING OF EVOLUTION 279
We must recognise that our knowledge that other
beings hke ourselves, as well as animals lower in organi-
sation than ourselves, are consciously acting organisms
is intuitive knowledge, attainable because of community
of organisation : our intuitive knowledge of the be-
haviour and feelings of our own brothers and sisters
is greater than our knowledge of other men and women ;
and we can, by intuition, place ourselves within the
consciousness of an intelligent dog to a greater extent
than in the case of other animals. This knowledge of
the consciousness of other animals is not scientific
knowledge and it is unattainable and unprovable by
reasoning or methods of scientific observation. It is
a conviction in itself incapable of analysis or proof,
but yet a conviction on which we confidently base
most of our dealings with our fellow-creatures, and
which is justified by our experience.
It is nevertheless a scientific hypothesis of much
the same validity as many other scientific hypotheses.
We cannot bring ourselves to doubt that other men
and women are consciously acting organisms, however
impossible it may be to adduce scientific reason for the
faith that is in us. We cannot doubt that a compass
needle which " responds " by turning one or other of
its poles towards us according as we push forwards one
or other of the poles of a magnet is an unconscious piece
of metal, though we find it impossible to say why this
belief possesses such conviction. From this to the
movements of the typical green plant is only a step.
The turning of a green leaf towards the source of light,
or the downward movement of a root into the soil, are
responses to external stimuli which exhibit most of the
inevitability of response of the magnet. They are
" tropisms " : the plant leaf is obliged to turn towards
the light so that the latter strikes against its surface
280 THE PHILOSOPHY OF BIOLOGY
perpendicularly, and the root must grow downwards
because gravity acts along vertical lines. But suppose
that reflex actions are tropistic : suppose, for instance,
that the moth is bound to fly into the candle flame
because the light stimulates both sides of its body
equally and this orientates it and guides it towards the
direction from which the stimulus proceeds. Complex
actions, in the higher animal, on this view are chains
of reflexes, and the acting must be unconscious and
inevitable, just as the turning of the magnet or green
leaf are unconscious movements. Therefore the actions
of our fellow-creatures are unconscious and automatic,
a conclusion toward which the whole tendency of
mechanistic physiology forces us. Yet we know that
the conclusion cannot be true.
Between the obUgatory reaction of the compass
needle to the magnet, or the analogous heliotropism
and geotropism of the plant organism, and the infinitely
variable responses of the higher animal toward changes
in its en\4ronment, consciousness must come into exist-
ence. It is absent in the inorganic system and the
typical green plant ; it is dim in the sedentary sea-
anemone or mollusc ; it becomes brighter in the freely
mo\'ing Arthropod or fish ; and it is most intense in
man. This, it must be admitted, is only a belief, but
accepting it as such we may attempt to support it by
showing a parallelism of stages of structural complexity
and actions. The sensori-motor system is absent in
the green plant ; it is simple in the extreme in the sea-
anemone ; and it is rudimentary or vestigial in the
sedentarv^ moUusc. It becomes more complex in the
Arthropod or fish, and it is developed to the greatest
degree in ourselves. If we now examine our own
mental states, with their corresponding conditions of
bodily acti\dty, we see as clearly as possible that our
THE MEANING OF EVOLUTION 281
consciousness waxes and wanes with our activities.
It is absent in normal sleep, when bodily activity in
the real sense ceases almost absolutely, when the
cerebral cortex becomes inactive, and when the only
movements performed are those truly automatic ones
of parts of the body which are analogous to the move-
ments of the plant organism. Such movements are the
rhythmic ones of the heart and lungs, the movements of
the blood, and so on, in general the movements leading
to constructive metabolism. Consciousness is most
intense in difficult unfamiliar actions : the lad learning
to row ; the child learning scales on the piano, or the
fingering of the violin ; the engineer assembling to-
gether the parts of a nevv^ machine ; or the artist
engaged on a picture. In each of these cases the worker
is acutely conscious, in a deliberative manner, of his
own bodily actions. But with the habitual exercise
of these movements, and with the ease and facility
with which they are performed, consciousness that they
are being performed fades towards nothingness.
What does this mean but that degrees of conscious-
ness are parallel to degrees of complexity of deliberated
and purposeful bodily movements or actions ? Or
degrees of consciousness are also parallel to the attempt
of the organism to perform these actions. What is
pain, the most acutely felt of all our mental states ?
It is, Bergson says, the consciousness of the persistent
and unsuccessful effort of the tissues to respond purpose-
fully to a persistently renewed stimulus. But complex
actions require for their performance systems of
skeletal and muscular parts capable of moving in the
m^ost varied ways, and a system of afferent and efferent
nerves with all their connections in the central nervous
system : that is, a sensori-motor system. Therefore
just as the sensori-motor system is more or less
282 THE PHILOSOPHY OF BIOLOGY
complex so, in general, is consciousness more or less
acute.
Yet in the same organism consciousness is the more
or less acute as the actions which it performs are more
or less familiar. The pianist who plays scales as a
matter of exercise carries out most complex movements
of hands and wrists unconsciously and without effort,
but to play an unfamiliar composition for the first time
without error involves attention of the highest degree.
A girl who counts the sheets of paper coming from a
machine seizes a handful in one hand, and drops a
separate sheet between every two fingers of the other
hand, repeating this most difficult operation with great
rapidity, and counting the handfuls of sheets accurately
while thinking and talking deliberately about some
other matter. At the beginning of her work these
actions were clumsily performed and facility was only
attained by sustained attention to the movements of
the hands, yet with experience they become uncon-
sciously performed. Complex movements of the body
and limbs and digits, involving the co-ordinated activity
of numerous muscles, nerves, and nerve centres, are
performed at first only after a high degree of conscious
effort, but with each repetition of the series of move-
ments the animal ceases to be aware of them, or at
least of their difficulty. In the higher animals there
are, therefore, two categories of actions, (i) those un-
familiar actions which are difficult, and in the perform-
ance of which the animal becomes conscious of complex
muscular activities ; and (2) those habitual actions
which have become easy by dint of repetition, and the
performance of which is unattended by conscious effort.
Analysis of our own activities reveals these two cate-
gories of actions, and we have no doubt whatever that
the higher animals have the same feelings of difficulty
THE MEANING OF EVOLUTION 28S
and effort in the one case, and of lack of conscious effort
in the other.
The difference is one of those which separate
instinctive from intelligent activities. Now we hesitate
to attempt the discussion of this much-controverted
question of the distinction between instinct and intelli-
gence : after reading much that has been said as to
the nature of this difference, one rises with the uncom-
fortable impression that the time is not yet ripe for its
discussion, and that the problem is still one far more
for the naturalist than for the psychologist. Reliable
data are still urgently required. Yet it is a question
which we cannot fail to consider. The typical plant
differs from the typical animal in that a sensori-motor
system has been evolved in the one but not in the
other ; and among the animals in which this system
is developed to a high degree the activities which involve
its exercise differ in their form. Actions of a stereo-
typed pattern characterise the behaviour of the higher
Invertebrate, while in the higher Vertebrate all that we
see indicates that the behaviour is the result of delibera-
tion, and that the actions performed are not stereotyped
but differ infinitely in their patterns. Just as clearly
as differences in morphology differentiate Arthropod
from Vertebrate, so also do differences in the mode of
activity of the sensori-motor system mark divergent
lines of evolution culminating in the Hymenopterous
Insect on the one hand and in Man on the other.
What is the essential difference between an action
performed instinctively and one performed intelli-
gently ? It is not that the animal is unaware of its
activity in the first case and not in the second ; how-
ever much we tend to " explain " organic activity in
terms of inorganic reactions, we do not really believe
that the instinctively acting wasp is a pure automaton,
284 THE PHILOSOPHY OF BIOLOGY
while admitting that the schoolgirl is acutely conscious
of her own naultifarious activities. It is not that the
instinctive action displays a " finish," or perfection of
technique, that the deliberative action lacks : the comb
built by the wasp is not more perfect in its way than is
the doorway constructed by a skilled mason, or the
" buttonholes " stitched by a seamstress. It is not
that instinctive actions are so absolutely stereotyped,
as is sometimes assumed, while intelligent actions grow
more perfect in their result by repetition : the work of
the insect or bird is often faulty and it is improved
by practice. The most obvious difference is that the
instinctive action is effective the very first time it is
performed, while the intelligent action only becomes
effective after it has been attempted several times, or
very many times, according to its difficulty. The flight
of the young swallow is effective inasmuch as it sustains
the bird in the air, but it is also an exceedingly difficult
series of muscular efforts which is at first clumsily
performed and which becomes more perfect by repeti-
tion. But the flight of an aeroplane, even now after
years of experiment, is not always effective, and ex-
hibits at its best all the imperfections of the flight of
the young swallow. Yet can we doubt that in time it
will exhibit all the ease and certainty and finish of the
flight of the bird ?
The typical intelligently performed action is the
action of a tool, or of a part of the body which is used
for some other purpose than that which is indicated
by its immediate evolutionary history, or by its previous
use. The typical instinctively performed action is
always the action of a bodily organ, the structure and
immediate evolutionary history of which indicates
that it originated as an adaptation for the performance
of these particular actions, or category of actions.
THE MEANING OF EVOLUTION 285
Here it seems to us that we find the distinction between
the two kinds of bodily activity ; and the distinction
is one which depends for its vaUdity on our notions as
to what a tool is. An implement made by man is a
piece of inert matter fashioned in order that it may
be used for a definite preconceived purpose. It has an
existence as a definite specific object apart from its
use ; and its exercise by the man who made it and its
existence in nature are two different things. Its use
must be learned, and the results obtained by its employ-
ment become more perfect with every repetition of its
use. But the mandibles of an insect are implements
purposefully adapted for some action or series of
actions, just as the pincers of the blacksmith are so
adapted. They are, however, implements which are
part of the organisation of the animal using them —
organised tools — and it does not seem as if we ought
to think of them, and of their shape and nature, as
something apart from their exercise. Must we think
of an animal as having to learn how to use any part of
its body ? If so, then the problem of instinct remains
with us in all its historic obscurity. But if we think
of the existence of a bodily tool as something insepar-
able from the functioning of the tool, the problem be-
comes less obscure, or at least it can be stated in terms
of some other problems which we have already con-
considered.
We do actually think of bodily parts or organs as
material structures quite apart from the consideration
of their functions : it is the distinction between mor-
phology and physiology — an altogether artificial one.
An animal, for the morphologist , is a complex of
skeleton, muscles, nerves, glands, and so on ; and it
does not matter whether it is contained in a jar of
methylated spirit or is running about in a cage. For
286 THE PHILOSOPHY OF BIOLOGY
the physiologist it is " something happening " ; but is
it not really both things, and are not the structure and
the functioning only two convenient, but arbitrary,
aspects from which we consider the organism ? We
ought not to think of diaphragm and lungs apart from
the movements of these organs, and we do not say that
the first breath drawn by the newly-born mammal is
an instinctive action, involving the use of inborn
bodily tools — the diaphragm, lungs, etc. We ought
not to think of the lips and mouth and pharynx of the
young baby apart from the actions of suckling the
mammae of its mother, but usually we say that this
action is an instinctive one. Where does the ordinary
functioning of an organ end and its instinctive function-
ing begin ? Are the muscular actions of the lobster
when it frees its body and appendages from the carapace
during the act of ecdysis instinctive ones ? Most
zoologists would say that they are not, any more than
the movements of the maxillipedes in respiration are
instinctive ones, yet they probably would not hesitate
to say that the action of the " soft " lobster in creeping
into a rock crevice is instinctive. Does a young child
really " learn " to walk ? It is more likely that the
actions of walking are potential in its limbs and that
they become actual when all the connections of nerve
tracts and centres in its brain and spinal cord become
established. What is the difference between the
acquirement of the ability to walk and to write ?
The latter series of actions are unfamiliar combina-
tions of nervous and muscular activities which are no
part of the organisation of the young child ; while
the former are simply the result of the complete
functional development of certain nervous and
muscular apparatus.
It seems difficult, then, to express clearly what is
THE MEANING OF EVOLUTION 287
the essential difference between instinctive and in-
telligent behaviour ; and it is doubtless the case that
reasoned experiments and observations are still too
few to enable us to make sound deductions. But it
certainly seems as if we ought to think of instinctive
actions as having evolved concomitantly with the
structure of the organs which effect them : they are
those inheritable adaptations of behaviour which are
bound up with — are indeed the same things as — inherit-
able adaptations of structure. In performing them the
instinctively acting animal is doubtless aware of its
own activity, but we must think of this awareness as
being of much the same nature as our consciousness
of the automatic activities of our own bodies — the
rhythmic activities of the heart and respiratory organs,
or the actions of our arms and legs in walking, for
instance. It is knowledge of the inborn ability of the
organisms to use an inborn bodily tool.
In the intelligent action we certainly see something
different from this. The organ or organ-system which
carries out such an action functions in a manner which
is different from that for which it was evolved : the
action is the conscious adaptation of the organ for
some form of activity new to it, and this acquirement
of activity seems to be non-inheritable — at least it is
non-inheritable in the sense in which we speak of
acquired characters being non-inherited. It is accom-
panied, while it is being acquired, by a consciousness
which is deliberative, and is different from that aware-
ness of its own activity which accompanies the acting
of the instinctive animal — the knowledge that it is
acting in an effective manner. It does not seem as if
the animal in so acting is aware of the relation of the
bodily tool to the object on which it is acting. But
intelligence seems to imply more than this : it implies
288 THE PHILOSOPHY OF BIOLOGY
the knowledge of the organism that some parts of its
body bear certain relations to the parts of the environ-
ment on which they are acting, and that these relations
are variable ones and may be the objects of conscious
choice.
CHAPTER VIII
THE ORGANIC AND THE INORGANIC
It is convenient that we should express the results of
biological investigation in schemes of classification, for
only in this way can we reduce the apparent chaos
of naturally occurring organic things to order, and
state our knowledge in such a way that it can easily
be communicated to others. But we must always
remember that the classifications of systematic bio-
logy are conceptual arrangements, depending for their
precise nature on the point of view taken by their
authors. The clear-cut distinctions that apparently
separate phylum from phylum, class from class, order
from order, and so on, do not really exist. There are
no such categories of organisms in nature as genera,
families, and the higher groupings. All that we can
say exist naturally are the species, since all the organ-
isms composing each of these groups are related to-
gether by ties of blood-relationship, and all are isolated
from the organisms composing other species by physio-
logical dissimilarities which render the plants or animals
of one species infertile with those of any other. Such
would doubtless have been the opinion of most botanists
and zoologists prior to the work of de Vries, but we
must now recognise that the systematic, or Linnean,
species of the nineteenth century was just as artificial
a category as were the genera and families. Our
arrangements of plants and animals into systematic
II
290 THE PHILOSOPHY OF BIOLOGY
species and the higher groupings are therefore conve-
nient ways of symboHsing the results of morphological
and physiological investigations, although they also
indicate the main directions taken by the evolutionary
process, but the manner in which they are stated in
taxonomic schemes is always a more or less formal one.
There are no absolute distinctions between group
and group, even between the animals and the plants.
There is nothing, for instance, in the morphology of a
Diatom to indicate that it belongs to the vegetable
kingdom, or in that of a Radiolarian, to indicate that
it is an animal. Peridinians are either plants or animals
according to the general argument, or the point of
view of the author who writes about them. Even a
study of the energy-transformations that are effected
in the living substance of these lower organisms does
not afford an absolute distinction : synthetic metabolic
processes in which energy passes into the potential
condition may be carried out in animals, while many
plants — the saprophytic fungi, or the insectivorous
plants, for instances — may effect analytic energy-
transformations of essentially the same nature as those
exhibited in the typical mode of animal metabolism.
Motility and the possession of a sensori-motor system
do not afford the means of making a sharply drawn
line of division between plants and animals. Potential
energy passes into the condition of kinetic energy in
the typical animal, and this kinetic energy is directed
by the sensori-motor system. But some lower uni-
cellular plants are motile, and they possess the rudi-
ments of a sensori-motor system in the flagelia by which
their movements are effected. On the other hand, the
sensori-motor system has become vestigial in many
animal parasites — in the Crustacean Sacculina, for in-
stance, which is parasitic on some Crabs. The possession
THE ORGANIC AND THE INORGANIC 291
of consciousness, in so far as we can say that other
animals than ourselves possess it, is no distinction
between the two kingdoms of life. Consciousness,
judged by the degree of development of motility, must
be supposed to be absent or very dim in the extreme
cases of parasitism attained by some animals ; on the
other hand, we may assume that it is present, to some
extent at least, in the highly motile zoospores of the
Algae. Thus som.e lower organisms, the Peridinians
and the algal spores, exhibit all the characters which
we utilise in separating animals from plants — the
chlorophyllian apparatus, by means of which the
kinetic energy of solar radiation becomes transformed
into the potential energy of organic chemical com-
pounds ; the apparatus of receptor and motile organs, by
means of which the potential energy of stored chemical
compounds passes into the kinetic energy of bodily
movements ; and the existence (so far as we can say
that it exists in organisms other than ourselves) of
some degree of consciousness.
Neither do those morphological schemata which we
construct as diagnostic of phyla, or classes, or orders,
etc., separate these groups from each other so clearly
and unequivocally as our classifications suggest. It
might seem for instance that the presence or absence
of a notochord would sharply distinguish between the
vertebrate and invertebrate, but structures which
suggest in their development the true notochordal
skeleton of the typical vertebrate animal are to be
traced in animals which exhibit few or none of the
characters which we regard as diagnostic of the Verte-
brate. Typical Arthropods and typical Vertebrates
seem to be distinct from each other, but the extinct
Ostracoderms of Silurian times may have been animals
which possessed an internal axial skeleton, and which
292 THE PHILOSOPHY OF BIOLOGY
were also armed by a heavy dermal exo-skeleton. It is
a hypothesis of considerable plausibility that they
really were Arthropods, on the other hand they are
usually regarded as Vertebrates. So also with most
other phyla : the morphological characters which
absolutely distinguish between one group and others
are very few indeed, and the small appended groups
that lie about the bases of these larger groups may
present one or other of the characters of several phyla.
Looking at the morphology of the animal kingdom in
a general kind of way, one does indeed see that a certain
structural plan is characteristic of the organisms be-
longing to each of the great phyla, while more detailed
structural plans may be said to be characteristic of the
sub-groups. But minute morphological and embryo-
logical investigation reduces almost to nothing the
characters which are absolutely diagnostic of these
various groups.
No more than the nature of the energy-transforma-
tions, and the essential morphology, does the behaviour
of animals afford us the means of setting up absolute
distinctions between group and group. Really tropistic
behaviour is exhibited by the movements of the stems,
roots, and leaves of green plants, or in the movements
of Bacteria, and perhaps some unicellular animals.
Typically instinctive behaviour is exhibited by the
individuals of societies of Insects and by many solitary-
living animals belonging to this class ; and typically
intelligent behaviour is exhibited by the acting of the
higher Mammalia. Yet there is undoubtedly much
that is truly instinctive in the behaviour of Man, and
something of the same nature as his intelligence seems
to inhere in the instinctively- acting mammal or insect :
how else could an instinctive action become capable of
improvement ? We cannot doubt that intelligence is
THE ORGANIC AND THE INORGANIC 293
manifested by a dog or by much that we see in the
behaviour of ants. No rigid distinctions between
tropisms, such as we have mentioned above, and the
reflexes that may be taken to constitute instinctive
behaviour, can be estabhshed. Minute analysis, such
as that carried out by Jennings on the swimming
movements of the Protozoa, leaves us quite in doubt
as to how these modes of behaviour are most properly
to be described ; and all the controversy as to the
nature of tropisms, reflexes, instinct, and intelligence
surely indicates that these modes of behaviour have
something that is common to ail of them, and that no
clear and certain distinction can be said to separate
one from the other. Even those psychic processes
which we call intellectual do not seem to be different
in kind from some that we attribute to the lower
animals : the Protozoan Paramcecium studied by
Jennings, or the crabs, crayfishes, and starfishes studied
by Yerkes and others really learn to perform actions,
but this learning is said to be the result of a process
of " trial and error." The animal tries one series of
movements and finds that it fails, tries another and
another with a similar result, and in the end finds one
that is effective. This is remembered, and when the
same problem again confronts the animal it is solved
after fewer trials, and finally, after experience, the
end-result is attained at once without previous trials.
Now many of what we call truly intellectual pro-
cesses are certainly processes of precisely this nature.
Hypothesis after hypothesis occurs to the scientific
man (or to the detective, or to the engineer confronted
with some exceptional difficulty) , and one after another
is tested by actual trial, or by a process of reasoning
(which is really the rapid and formal resuming of
previous experience), until a hypothesis verifiable, or
294 THE PHILOSOPHY OF BIOLOGY
a priori verifiable, is found. What, for instance, are
our mathematical methods of integrating a function,
or working a long division sum, but methods of scien-
tific " guessing," and verification of the hjrpotheses
so made ? They are truly instances of the method of
trial and error practised by the lower animals.
All the above amounts to saying that there is a
community of energetic processes, of morphology, and
of behaviour in animals and plants. " Protoplasm "
is the same, or much the same chemical aggregate,
whether it is contained in the cells of animals or plants.
The cell, with its nucleus, chromatic architecture, cell-
inclusions, and cell-wall, is essentially the same structure
in all organisms. The complex and specialised process
of nuclear division in tissue growth, or the series of
events which constitute the acts of fertilisation of the
ovum or its plant correlative, are the same all through
the organic world. The sensori-motor system. — receptor
organ, nerve-fibre and cell, and effector-motor organ —
is the same all through the animal kingdom. Ali-
mentary canal and glands, enzymes, excretory tubules,
contractile blood-vascular apparatus — all these are
structures which are functionally the same, which are
built on essentially the same morphological plan.
Life, whether it is the life of plant or animal, makes use
of the same material means of perpetuating itself on
the earth and avoiding the descent of matter towards
complete inertia.
Absolute dissimilarities, dissimilarities such as those
between atoms of hydrogen and oxygen, or between a
point and a straight line, or between rest and motion,
do not exist between the different categories of entities
that make up the organic world. Yet differences do
exist, and must we conclude that because these differ-
ences are not absolute ones, because the}^ are differences
THE ORGANIC AND THE INORGANIC 295
of degree, and not of kind, they are not essential,
are not differences at all ? Must we say, for instance,
that although an animal is a much more efficient
machine than a gas-engine (in the sense of efficiency
as understood by the engineer), there is really no
difference between them, that they are both thermo-
dynamic mechanisms, since in both energy is dissipated ?
Ought we to say that, because the last steps in the
formation of urea in the animal body are synthetic
ones, there is really no difference between the nature of
the energy-transformations that occur in the animal
and the plant modes of metabolism ? Ought we to say
that, because a dog may sometimes act intelligently
and a man instinctively, psychically they are similarly-
behaving organisms ? Surely this amounts to saying
that, because things are not absolutely different, they
are the same ; and surely the mode of reasoning is a
vicious one !
What we clearly see in the different kinds of organ-
isms— in the metabolically constructive plant and the
metabolically destructive animal ; or in the instinc-
tively-acting Arthropod and the intelligently-acting
Mammal — is the progressive development of different
tendencies. If the green plant is, in its essence, the
same kind of physico-chemical constellation as is the
animal, yet the tendency of its evolution has been that
more and more it has acquired the habit, or the power,
of using solar radiation to combine together carbon
dioxide, water, and nitrogenous inorganic salts to form
proteid and carbohydrate substances. On the other
hand, the tendency of the animal has been more and
more to absorb into its own tissues the proteid and
carbohydrates synthesised by the green plant, and
then to break these substances do%vn into carbon
dioxide and water, and less and less to effect such
296 THE PHILOSOPHY OF BIOLOGY
syntheses as are effected by the plant. Even if the
Annehd worm, the Arthropod, and the Vertebrate were,
at the origin of their ancestries, animals which were
very like each other in the morphological sense ; even
if there are some Arthropods which are very like
Annelids, and some Annelids which might very easily
be imagined to become transformed into Vertebrates,
and some extinct Arthropods which may after all have
been Vertebrates, yet it is the case that the tendencies
of the evolution of each of these groups have been very
different. All the while the Vertebrate tended more
and more to develop a rigid axial rod or notochord,
becoming later a jointed vertebral column, and a soft,
pliable, exo-skeleton ; while the Arthropod tended more
and more to develop a rigid exo-skeleton, and to remain
soft in its axial parts. Even if these two tendencies
may not have been fully realised, is it not the case that
they are really different things ? The evolutionary
process has therefore been, in its essence, the develop-
ment, or unfolding, of tendencies originally one.
What is the evolutionary process ? It is usually
regarded as a progress from organic simplicity towards
organic complexity. Yet if we think about it as a
physical process we cannot say that any one stage is
any more simple or complex than any other stage.
Let us compare organic evolution with the process of
inorganic evolution, as, of course, we are compelled to
do if we regard the former process as a physico-chemical
one. Assume, then, that the nebular hypothesis of
Kant and Laplace is true — it will make no difference
to our argument even if this hypothesis is not true,
and it is more easily understood than any other hypo-
thesis of planetary evolution. Originally all the
materials composing our solar system existed in the
form of a gaseous nebula possessing a slow rotatory
THE ORGANIC AND THE INORGANIC 297
motion of its own. It does not matter that the silicates,
carbonates, oxides, and all other mineral substances
that v/e now know existed then in the form of chemical
elements, or the precursors of chemical elements : all
the material bodies now present in the solar system
were present in the original nebula. The energy of this
nebula consisted of the potential energy represented by
the separation of atoms which later on became com-
bined together, and of the kinetic energy of motion of
these atoms ; and this material and energy, together
with the other cosmic bodies radiating energy to it
and those bodies receiving the energy which it lost by
its own radiation, constituted a system, in the sense of
the term as it is employed by the physicists. Now, in
the process of cosmic evolution this system became
transformed, because it was continually losing energy
by radiation. As it cooled, the mean free paths of its
atoms and molecules became less and less, and finally
condensation to the liquid and then to the solid con-
dition occurred. The parts of the nebula continually
gravitated together, so that it became smaller and
smaller while its rotatory motion became greater.
Finally, mechanical strains became set up in its mass
as the consequence of the increased velocity of rotation,
and disruption occurred with the formation of the sun,
the planets, and the satellites. There was no increase of
complexity of the system. At any moment of time its
elements, that is, the chemical atoms composing it
and the energy of these atoms, was the same as at any
other moment of time. Heat-energy may have been
radiated from one part of the system — the heated
nebula — to some other part of the system — the other
cosmic bodies absorbing this radiation, but the total
energy of the system remained the same. The chemical
atoms may have combined together to form molecules
298 THE PHILOSOPHY OF BIOLOGY
and compounds, and their energy of position may have
become the energy of motion, but the ultimate materials
were still the same. What happened during the cooling
and contraction of the nebula was a rearrangement of
the elements of the system, that is, of the atoms and
their energies. At any moment of time the condition
of the system was an inevitable consequence of the
condition at the moment immediately preceding this,
and a strict functionality, in the mathematical sense,
existed between the two conditions. It was not more
complex in the later stage than in the earlier one — it
was merely different. Stages of evolution were really
phases in a transforming system of matter and energies.
If we choose to regard organic evolution as a
similar process of physico-chemical transformation, we
must also regard the totality of life on our earth, with
all the inorganic materials which interact with organic
things, and with all the energies, cosmic and terrestrial,
which also so interact, as a system in the physical
sense. We are now compelled to think about this
system in the same way as we thought about the cosmic
one, that is, we must postulate that a rigid mathematical
functionality existed between any two conditions of it,
and that the latter condition was inevitably determined
by the former one. We must think of the system as
at all times composed of the same elements. In its
later condition life may have been manifested in a
greater mass of material substance than in its earlier
conditions, but this increase of mass was only the
increase of one part of the system at the expense of
another part. At all times, then, the constitution of the
system was the same, and different stages of the evolu-
tionary process have only been different phases, or
arrangements, of the same elements. At no time was
the organic world any more or less complex than at any
THE ORGANIC AND THE INORGANIC 299
other time. In its " primitive " condition all was
given.
Mechanistic biology does not, of course, hesitate to
accept this view of the evolutionary process. The
" Laplacian mind " must have been able to calculate
what would be the condition of the system at any
phase, knowing the positions of all the atoms or mole-
cules in the original nebula, and the velocities and
directions of motions of all these atoms or molecules.
Just as (in Huxley's illustration) a physicist is able to
calculate v/hat will be the fate of a man's breath on a
frosty day, so the Laplacian mind must have been able
to predict the fauna and flora of the world in the year
1913 from a complete knowledge of the material nature
and energetic properties of the nebula from which it
arose.
We cannot fail to see, on reflection, to what this
view of the nature of the evolutionary process leads us.
The primitive world-nebula was a system of parts
which had extension in space. Materially it consisted
of atoms isolated from each other by space, and energeti-
cally it consisted of the movements of these atoms, and
of the energy of their positions with regard to each
other. No two atoms could occupy the same space —
they mutually excluded each other : this is what we
mean by saying that the original — and every other —
state of the system was a state of material things or
elements spatially extended. Therefore, if the physical
analogy is consistently to be retained, the organic
system undergoing evolution was a system of elements
which at any moment whatever were spatially extended.
It was really a system of atoms or molecules possessing
kinetic energy of motion, or potential energy of position
— molecules which lay outside each other, and energies
which were really the movements or positions of these
300 THE PHILOSOPHY OF BIOLOGY
molecules, and which therefore lay outside each other
in the same sense.
The evolution of the individual organism must be
a process of the same kind. Like cosmic and phylo-
genetic evolution, it is apparently a progress from the
simple to the complex. A minute fragment of proto-
plasmic matter, homogeneous in composition, or ap-
parently so, grows and differentiates, becoming the
complex structure of the adult organism. Here the
system in the physical sense is the fertilised ovum, the
oxygen and nutritive matter which have become in-
corporated with it, and the physical environment with
which these things interact. All these elements existed
in that phase of the system which contained among its
parts the fertilised ovum, as well as in that phase which
contained the fully developed organism. Complex by
comparison with the fertilised ovum and its environ-
ment as the adult animal and its environment may
seem to be, it is only a different phase of the same
system. Further, all the parts that form the tissues
of the adult, and all their motions, are spatially ex-
tended, and are only rearrangements of the molecules
and of the motions of the molecules that were actually
present in the system in its initial phase. Speculation
along these lines has led to all the results of Weismann-
ism. All the parts of the adult organism are really
present in the fertilised ovum and the nutritive matter
which is to build up the fully developed animal, not in
potentiality it must be noted, but actually present in
the spatially extended condition. It is true that the
hypothesis only requires that the determinants of the
adult organs and tissues, and of the adult qualities,
should be present in the ovum ; but since the energies
necessary for the separation of these determinants, and
for their arrangement and growth in mass, must also be
THE ORGANIC AND THE INORGANIC 301
present in the initial phase of the system, it is evident
that the hypothesis impHes that all the material
structure of the animal is present in the spatially ex-
tended form in the initial phase of the system. Just
as the adult animal is a manifoldness of material parts
and energies that possess extension, so also is the un-
differentiated embryo and its material environment an
extensive manifoldness. We cannot otherwise conceive
it if we are to retain the mechanistic view of the develop-
ment of the individual organism.
Let us think of the process of organic evolution in
another way by comparing it with the mathematical
process by which we form the permutations and com-
binations of a number of different things. Individual
development is termed the assumption of a mosaic
structure, that is, all the parts of the adult are assumed
to be present in the embryo, but in a sort of " jumbled-
up " condition. As development proceeds, these parts
become sorted out and arranged in a pattern which
continually becomes more and more distinct. Much
the same process of arrangement and segregation must
be assumed to have occurred during the process of
racial evolution : the parts of the " primitive " life-
substance, with all the parts of the physical environ-
ment which become incorporated with it during its
evolution, must have become segregated and arranged
so as to form the existing species of plants and animals.
A permutation, then, of the separate things a, h, c —
X, y, z, is an arrangement of all these things : obviously
there are a very great number of ways in which the
letters of the alphabet may be arranged, \^ in all. But
we may take some of the letters and arrange them in
different ways : the selections a, h, c, d, can be arranged
in \± ways ; b, c, d, e, also in \± ways, and so on. Thus
by a process of dissociation and arrangement of a certain
302 THE PHILOSOPHY OF BIOLOGY
number of elements, a very great number of different
things — things which consist of elements spatially
extended — can be obtained.
The group of things, a, b, c, d — x, y, z, was an extensive
manifoldness, since it was formed by juxtaposing in
space the separate units of which it is composed. Yet
it is an unitary thing, for it is a different thing from the
group, h, c, a — x, y, z. It is also a multiplicity, for it can
be transformed into every one of the |^ permutations,
and broken up into the selections of some of the separate
things of which it is composed, and of the permutations
of the things taken in each of these selections. In a
way these arrangements exist in the group a, b, c—
X, y, z, and yet the group itself possesses no other actual
extended existence than the group of things that it is.
It is an intensive multiplicity or manifoldness in that the
potentiality of all the arrangements exists in it but not
in the spatially extended condition. It is a multi-
plicity only when we associate with it the mental opera-
tions by which we conceive of its dissociation and
rearrangement. By reason of these mental operations
the intensive multiplicity of the group becomes the
extensive multiplicity of its arrangements.
This appears to be the only really philosophical way
in which we can attempt to picture to ourselves the
processes of individual and racial evolution. The
" primitive " life-substance, or the undifferentiated
ovum, each of them with its environment, was an
intensive manifoldness, a multiplicity of distinct things
or qualities which co-existed, and which were not
separate each from other in that they occupied different
compartments of space, but which interpenetrated
each other. This notion of distinct things co-existing
in time, yet occupying the same space, is not at all a
difficult one. Our consciousness is such a multiplicity
THE ORGANIC AND THE INORGANIC 303
of states or qualities all in one. The idea of a group of
figures has a very real existence for the sculptor, and
he may visualise it with almost all the appearance of
reality that the actual, material piece of statuary
possesses. In his mind it is a real manifold existence,
which nevertheless does not occupy the three-dimen-
sional space which the marble fills. The musical notes
C, F, A, C, heard in arpeggio, are things which possess
real existence, but which are extended in time, and
when we think of these separate sounds we lay them
alongside each other in our mind in an empty, homo-
geneous medium which seems to be all that we think
of as space. Yet the same notes heard simultaneously
as a chord are not extended. They interpenetrate
each other, but 3^et they are distinct things, since on
hearing the chord we can recognise the notes compos-
ing it. As an arpeggio the notes are an extensive
manifoldness, but as a chord they are an intensive
manifoldness.
The mechanistic biology of the latter part of the
nineteenth century based itself on the methods and
concepts of physics, and it was therefore compelled to
assume that the manifoldness of the " primitive " life-
substance — the " Biophoridae " of Weismann and his
followers — or that of the fertilised ovum, was a mani-
foldness that had spatial extension. All the systems
studied by physics were aggregates of elements, or
parts, that had such extension : the sun, with its
attendant planets and satellites, was a system of bodies
isolated from each other in space. Even the atmos-
phere, or the sea, media which to our unaided senses
appear to be homogeneous, are really media consisting
of discrete bodies, or molecules, which are not actually
in contact with each other, but which are separated
from each other by empty space. Chemical compounds
304 THE PHILOSOPHY OF BIOLOGY
were assemblages of molecules, molecules were assem-
blages of atoms, and the atoms themselves were either
simple or were composed of corpuscles, or still smaller
bodies. This mode of analysis was forced upon the
human mind by formal logic and geometry, and it was
apparently" the only method of acquiring mastery over
nature. Yet there were difficulties, appreciated no less
by the philosophical physicists than by the writers on
formal philosophy. How could bodies, or molecules,
or atoms that were separated from each other act upon
each other ? The molecule A could only act upon the
molecule B if there were some particles between them
which could convey the impulse or attraction, but then
we must suppose that there were other particles between
these intermediate ones, and so on ad infinitum, other-
wise how could a body act, that is, really exist, where it
was not ? In other words, how could there be action
at a distance ? How, for instance, could the atoms
of the earth attract those of the moon with a force
sufficient to break a steel rope of 400 miles in diameter ?
Physics had therefore to invent the ether of space, not
only to account for interstellar or interplanetary gravi-
tation and other modes of radiant energy, but also to
account for the interaction of the atoms or molecules
which make up chemical compounds. In our own day
atoms have ceased to be the limits to the subdivision of
things : they are composed of electrons, but the elect-
rons are entities separated from each other by empty
space. They are not, however, the ultimate limits of
subdivision of matter, as the atoms were supposed to
be by the chemistry of the early part of the last century,
but are regarded as " singularities " in an universal
continuous medium or ether. It is of no moment
that we are unable to describe the ether in terms of
our former concepts of matter and energy, or at least
THE ORGANIC AND THE INORGANIC 305
that we can only so describe it in such a way that it is
represented by negative quaHties : we are compelled
to postulate its existence in order to avoid philosophical
confusion. The universe is therefore a continuum, and
an atom or any other body exists wherever it can act.
The atoms of a fixed star, so far away that we can only
represent its distance in billions of miles, are neverthe-
less on our earth as well as at the point of space which
we regard as their astronomical position, for the light
emitted by them acts on our retinas. The universe is
an unitary thing in that it is a continuous medium or
substance in the philosophic sense, but it is also a
multiplicity in that singularities or conditions of this
medium pervade each other throughout space. Such
seem to be the conclusions towards which the later
physics forces us, and it is interesting to reflect how
different biological speculation might have been had it
been formulated now instead of half a century ago !
Why has a process of evolution occurred at all ?
Why is it that tendencies that might have co-existed,
that indeed do co-exist to some extent, have become
separate from each other ? It is possible to conceive
of an organism which contains chlorophyll, and which
might therefore S3mthesise carbohydrate and proteid
from inorganic substances, but which might also contain
a sensori-motor system, and which might therefore
expend the energy so obtained in regulated movements.
To a certain extent such organisms combining the plant
and animal modes of metabolism do exist among the
Protista. Yet, the effect of the evolutionary process
has been more and more to dissociate the plant and
animal modes of metabolism until the typical animal
is quite unable to make use of carbon dioxide and
water as materials to be synthesised, while the typical
plant has lost all power of motion except the tropistic
306 THE PHILOSOPHY OF BIOLOGY
movements of its roots, leaves, and stems. Instinctive
and intelligent behaviour coexist in many animals,
yet the tendency of man, most highly intelligent of
all, is more and more to act intellectually ; while the
opposing tendency, that is, to act instinctively, has been
evolved in the Hymenoptera. It seems as if such con-
trasting methods of transforming energy, or of acting,
were incompatible with each other, and yet it is clear
that they are not really incompatible, for they may
co-exist. But it does seem clear that each of these
contrasting tendencies cannot be manifested to the
fullest extent if it is accompanied by the other. That
is to say, life is limited in its power over inert matter.
Manifested in the same material constellation, it
cannot both use solar radiation to build up substances
of high potential energy and then break down these
substances so as to obtain kinetic energy of movement.
Now we see clearly that life on our earth is indeed
limited to a very restricted range of physical conditions.
When we think of the mass of the earth we are surprised
to find what an insignificant fraction of all this matter
displays vital phenomena. The surface of the land
is clothed with a layer of vegetation, luxuriant and
abundant as we see it when we walk through a tropical
forest, but which is really a film of inconceivable tenuity
when we compare its thickness with the diameter of
the globe. Even the whole surface of the land is not
so clothed with vegetation, for polar regions and the
tops of high mountains are almost lifeless, while desert
tracts may be absolutely so. The lower strata of the
atmosphere are inhabited by birds, insects, and bac-
teria, but the total mass of these is infinitesimal when
compared with the total mass of the gases of which the
atmosphere is composed. Even the sea, which we regard
as rich in life, is not really so : estimates of the luxuri-
THE ORGANIC AND THE INORGANIC 307
ance of planktonic life are really misleading, for although
a single drop of water may contain some hundreds of
organisms, the mass of these is exceedingly small and
is usually expressed as one or two parts per million.
All this means that life has difficulty in manifesting
itself in material forms. Whether it be simply a mode
of interaction of some complex chemical substances
with a relatively simple physico-chemical environment
—the mechanistic view— or whether it be an impetus
or agency which is neither physical nor chemical, but
which acts through physical and chemical elements—
the vitalistic view,— life is capable of acting on terrestrial
materials to a very limited extent. Acting through all
the tendencies which we see to exist in it, life may be,
so to speak, diluted ; but by being concentrated in one
or a few of them it becomes more effective. The dis-
sociation of this bundle of tendencies which we call life
is therefore the meaning of the evolutionary process.
Ontogenetic development, says Roux, is the pro-
duction of a visible manifoldness. It cannot be said
that this cautious description of the developmental
process has been apprehended by those who expound
the dogmas of mechanistic biology. Development is
indeed the production of a diversity, but this diversity
is only a phase of a preceding diversity, a rearrangement
of spatially extended pre-existing elements. How else
could the developing embryo and its material environ-
ment be regarded as a system of physico-chemical
elements, capable of study by the methods of experi-
mental and mathematical physics, except by regarding
It as a system passing through phases each of which is
a necessary consequence of the preceding one, and each
of which contained the same elements separated from
each other in space ? Let us think of water occupying
a vessel at a high temperature and continually cooling.
N
308 THE PHILOSOPHY OF BIOLOGY
The states of this system are (i) the gaseous state in
which the molecules of the water are moving at
a high velocity and are a relatively considerable dis-
tance apart, and in which they are incessantly colliding
with each other and with the walls of the vessel ;
(2) the state of the system consisting of the separate
phases, liquid water and gaseous steam in contact
with it ; and (3) the solid phase, in which the
molecular motions almost, or quite, cease. Here the
progress of the system through its phases leads to
physical diversity and then again to physical homo-
geneity. But the diversity of the different phases is
in a sense an apparent one only : any single phase, or
at least those which involve the passage of the system
from the gaseous to the liquid phases, and vice versa,
can be represented by van der Waal's general equation,
RT = (p + -^) ("^-b). Does anything in modern biological
investigation, except, of course, the speculations of
non-physical physiologists, suggest that an ontogenetic
process can be represented in such a m.anner ?
Are the arbitrary " stages " of the embryologists —
the ovum, blastula, gastrula, etc., phases in a system in
the above sense, the only sense in which the process can
be regarded as capable of physico-chemical analysis ?
What precisely is the embryo at the close of the process
of segmentation ? It is an harmonious equipotential
system, that is to say, an assemblage of discrete organic
parts or cells, each of which has all the potentialities
that every one of the others has. Any cell in the
blastula may become a cell, or a series of such, in any
part of the gastrula or pluteus larva. This is what the
parts are in potentiality, but actually their individual
fates are different. The system is an harmonious one,
and each of its parts, although able to do whatever
THE ORGANIC AND THE INORGANIC 309
any other part can do, yet does one thing only : it
becomes an endoderrn cell, or an ectodermal cell, or a
part of the skeleton, and so on ; what it does depends
on its position with regard to the other cells. An
extensive manifoldness or diversity is produced, but
this was not the consequence of a preceding extensive
manifoldness, for in the preceding stage all the parts of
the system were the same. The manifoldness of the ovum
or blastula — that potential manifoldness which became
actual in development — must be an intensive manifold-
ness, and admitting this we must abandon the comparison
of the ontogenetic (and, of course, phylogenetic) pro-
cesses with the phases of a physico-chemical system in
process of transformation. Evolution is the transforma-
tion of an intensive into an extensive manifoldness.
More than this — much more than this — must be
the difference between the transforming systems of
physics and the evolving systems of biology. There is
a quality, or sense, or direction in all naturally occurring
inorganic processes which is not like that of organic
evolutionary processes. We return now to the con-
sideration of the second law of thermodynamics, for
only in this way can we approach the notion of the
vital impetus. If an energy-transformation occurs in
inorganic nature, that is to say, if anything happens,
the transformation occurs or the thing happens because
there were diversities in the system in which it occurred.
The condition for inorganic happening is that there
must have been differences of energy in the different
parts of the system : in the most general sense there
must have been diversity of the elements. But with
the transformation this diversity disappears, or tends
to disappear, and it cannot be restored — that is, differ-
ences of energy cannot again be established unless by
a compensatory energy-transformation ; that is, energy
310 THE PHILOSOPHY OF BIOLOGY
must be expended on the system from without by some
external agency. Whatever else physics shows us it
shows us an unitary universe, that is, an universe in
which anything that happens affects, to some extent,
all the other parts. Therefore the diminution of
diversities, or energy-differences, is something that
cannot be undone, or compensated, for there is nothing
without the universe.^ Everything that happens in
our universe reduces the possibility of further happen-
ing. We desire, at the risk of reiteration, that this
principle of energetics should be perfectly clear : in-
organic happening, of whatever kind it may be, is a
case or consequence of the second law of energetics — is
the second law itself in a sense. All energy-transform-
ations occur because energy-differences are being
diminished, because diversities are being abolished.
This is the sense, or quality, or direction of inorganic
phenomena.
It is not the direction of organic evolution. In the
development of the individual organism what we most
clearly see is the progressive increase of diversity of the
parts. In phylogenetic evolution one, or a few, simple
morphological forms of life have become, and are
becoming, indefinitely numerous morphological forms.
Diversity is continually increasing. If we cling to the
mechanistic view of life, we must suppose that the
diversity of the fully developed organism, or that of the
organic world with all its species, was also the diversity
of the fertilised ovum or that of the primitive life-sub-
stance in another phase. Then we commit ourselves
to all the crudities of modern speculations on heredity.
With this increasing diversity of form there is a
^ It is assumed that the universe is a finite one. If it were infinite the
whole discussion becomes meaningless, and we must give up this and other
problems.
THE ORGANIC AND THE INORGANIC 311
concomitant segregation of energy. We see as clearly
as possible that the tendency of all inorganic happening
is the transformation of potential into kinetic energy,
and the equal distribution of this kinetic energy through-
out all the parts of the system in which the happening
occurred. On the other hand, the tendency of organic
happening is the transformation of kinetic energy into
potential energy, (i) in the stores of chemical com-
pounds which result from the metabolism of the green
plants, and which are capable of yielding energy again ;
and (2) in the results of the instinctive or intelligent
activities of the animal's organism. The first result of
organic evolution is clearly to be traced and needs no
further explanation, the second is apparent on reflection,
but is perhaps not clearly apprehended in all its signifi-
cance by the student of biology and physics.
Organic evolution is the process which has had,
or is having, for its tendency the development of the
putrefactive and fermentation bacteria, the chlorophyl-
lian organisms, the Arthropods, and man and other
mammals. All that we have said has been futile if
this teleological description of the evolutionary pro-
cess has not been clearly suggested. The indefinitely
numerous forms of life that have appeared on the
earth in the past, and are now appearing, seem to be
experiments most of which have been unsuccessful.
Only in the organisms mentioned, organisms which are
complementary in their metabolic activities, has life
been successful in manifesting itself in activities which
are compensatory to those of inorganic nature. The
energy which is dissipated in the radiation of the
cooling sun is again made potential in the form of the
carbohydrates, synthesised from water and carbon
dioxide by the agency of the chlorophyllian organisms,
and this energy accumulates. It is employed by the
312 THE PHILOSOPHY OF BIOLOGY
instinctive and intelligent animal, in that it is used as
food and converted into bodily energ}^, which can then be
utilised for any purpose that is contemplated. These
plant substances taken in by the animal as sources of
energy are broken down into excretory substances, which
are further broken down by the metabolic activity of
the fermentation and putrefaction bacteria, and be-
come the substances used as foods by the chlorophyllian
organisms.
If the activities of man were only those of un-
directed or misapplied muscular movements (as indeed
most of his activities have so far been), then cosmic
energy would truly be dissipated after it had become
the energy of organisms. But does not all the history
of man point to his ever-increasing activity in the
conquest over nature, that is, the effort to hoard and
employ natural sources of energy, and to arrest its
tendency towards dissipation ?
It must be admitted that the past history of human
civilisation has been almost entirely that of the irre-
sponsible exploitation of natural resources — for it has
been founded on the thoughtless and wasteful utilisa-
tion of energy which was made potential by the plant
and animal organisms of the past. Man, the hunter,
maintained himself and multiplied by the destruction
of other animals or plants, or by the mere collection
and utilisation of naturally occurring fruits and other
plant-substances. During historic times the bison and
other animals have almost become extinct owing to his
i-uthless activity, just as in our own days the whale,
sole, and turbot are disappearing before the activity
of the machine-aided fisherman. Industrial man has
been successful with his factories and railroads and
steamships, and his electrical power and transport,
only because he has been able to utilise the stores of
THE ORGANIC AND THE INORGANIC 313
energy contained in the coal and oil accumulated in the
rocks of the earth. The progress of civilisation has been
a progress rendered possible by discovery and invention,
and by the application of the knowledge so obtained
to the practical things of human life, but in this specu-
lation and its application two different things are
indicated. For the scientific man and the philosopher
the reduction of the apparent chaos of nature to law
and regularity is the beginning and end of his mental
activity; but the object of the "entrepreneur" or
" organiser " or the " captain of industry " has been
to employ these results of thought to the irresponsible
exploitation and the selfish depletion of natural sources
of energy. Just as the bison and other animals have
disappeared or are disappearing before the hunter and
fisherman, so the stores of coal and oil are disappearing
before the activities of commerce. It has been said that
the triumphs of industrialism are only the triumphs
of the scientific childhood of our race. Human effort
has so far only contributed to the general dissipation
of natural energy.
Yet just as man, the hunter, has been succeeded by
man, the agriculturalist, so this irresponsible depletion
of natural wealth must be succeeded by the endeavour
to retard, and not to accelerate, the degradation of
energy. Plants and animals which were simply killed
by primitive man are now sown and harvested, or
cultivated and bred ; so that the energy of solar radia-
tion, which formerly ran to waste, so to speak, is now
being fixed by the metabolic activity of the green plants
of our crops and harvests. Rainfall and winds, tides
and rivers, all represent energy primarily derived from
solar radiation and from the orbital and rotatory
motions of the earth and moon. This energy even now
is almost entirely dissipated as waste, irrecoverable,
314 THE PHILOSOPHY OF BIOLOGY
low-temperature heat ; but more and more as our stores
of coal and oil are being depleted, the attention of men
is being directed to these sources of kinetic energy.
Waterwheels and windmills, and the more effective
mechanisms that must be evolved from these primitive
motors, will capture this waste energy and convert it
into the kinetic energy of machines serviceable to man,
or into the potential energy of chemical compounds
capable of storage and future utilisation. The study
of radio-activity has made us acquainted with the
enormous stores of potential energy locked up in the
atoms, and if it ever should become possible to utilise
this by the disintegration of these particles, the down-
ward trend of natural energetic processes will further
be retarded.
Life, when we regard it from the point of view of
energetics, appears therefore as a tendency which is
opposed to that which we see to be characteristic of
inorganic processes. The direction of the latter is
towards the conversion of potential into kinetic energy,
and the equal distribution of the latter throughout all
the parts of the universe. The direction of the tendency
which we call life is towards the conversion of kinetic
into potential energy, or towards the establishment
and maintenance of differences of kinetic energy, where-
by the latter remains available for the performance of
work. In general terms, the effect of the movement
which we call inorganic is towards the abolition of
diversities, while that which we call life is towards the
maintenance of diversities. They are movements
which are opposite in their direction.
What is cosmic evolution ? In all the hypotheses
which astronomical physics has imagined we see the
transformation of a system — a part of the universe
arbitrarily detached from all the rest — through a series
THE ORGANIC AND THE INORGANIC 315
of stages, each phase of the series being marked by a
progressive decrease of diversity, that is, by some
degradation of energy. Two main series of hypotheses
accounting for the present condition of the universe
seem to have been the result of physical investigation :
(i) the origin of discrete solar and planetary bodies
by a process of condensation of a gaseous nebular sub-
stance ; and (2) the origin of the same systems by
aggregations of meteoric dust. Plausible as is the
nebular hypothesis on first consideration, it fails when
it is subjected to minute analysis. What is a gaseous
nebula ? It is a mass of heated vapour contracting
by the mutual gravity of its parts as its molecules lose
their heat by radiation — so the hypothesis states.
But it has been pointed out that we cannot be certain
that the gaseous nebulae known to astronomy are hot,
or even that they gravitate. The great nebula in Orion,
it is stated, is at an enormous distance from us, and
making a minimal estimate of this distance the volume
of the nebula must still be incredibly great. There are
good reasons for believing that the mass of the visible
universe cannot be greater than that of a thousand
million of suns such as our own. Assuming that all this
matter is contained in the great nebula in Orion (and
obviously only a small portion of it can be so contained) ,
we find on calculation that the " gas " so formed would
be much less dense than even the trace of gas contained
in a high vacuum artificially produced."^ How, then, can
we speak of such a body as this nebula as an extended
mass of hot gas, cooling and gravitating as it loses heat ?
Even on the other hypotheses, those of the forma-
tion of discrete suns and planets by the aggregation of
meteoric dust, and the compensatory dispersal of such
* Its density would be -^ ^th that of our atmosphere.
316 THE PHILOSOPHY OF BIOLOGY
dust by radiation pressure, apparently insurmount-
able difficulties arise. All such hypotheses as we have
indicated assume material substance and modes of
energy-transformation similar to those that we study
in laboratory processes, and all such hypotheses involve
the notion of the degradation of energy. So long as
we suppose that all cosmic processes are transforma-
tions of extended systems of material substances we
must assume that energy is dissipated at every stage
of the transformation, and whenever we assume this
we admit that the processes are irreversible ones, and
that the material universe as a whole tends towards a
condition of inertia. Yet this, we see, cannot be true,
for the universe teems with diversity. Is the progress
towards the ultimate state of inertia an asymptotic
one, as Ward suggests ? This does not help us, since all
that the suggestion does is to misapply a mathematical
device of service only in the treatment of the problems
for v/hich it was developed. Somewhere or other, it
has been said, the second law of thermodynamics must
be evaded in our universe.
How can it be evaded ? That movement or pro-
gress which we call inorganic is a movement of energy-
transformations in one direction — towards their cessa-
tion. It is a movement which we can easily reverse
in imagination. A cigarette consumed by a smoker
represents the downfall of energy : the cellulose and
oils of the tobacco burn with the liberation of heat,
and the formation of water, carbon dioxide, and some
soot ; and this is what happens when potential energy
contained in an organised substance becomes converted
into kinetic energy. Now, the opposite process can
clearly be conceived — it can even be pictured. If we
make a kinematographic record of the smoking of the
cigarette and then reverse the direction of motion of the
THE ORGANIC AND THE INORGANIC 317
film, we shall see the particles of soot recombinmg to
form the substance of the cigarette, and we can imagine
the concomitant combination of the water, carbon
dioxide, and other substances formed during the combus-
tion with the absorption of kinetic energy. This is not
a mere analogy, for the same reversal of ordinary chemi-
cal happening occurs whenever a green plant builds up
starch from the water and carbon dioxide of the atmos-
phere ; and it also occurs whenever a chemical syn-
thesis of an " organic " compound, like that of urea by
Wohler, or that of the sugars by Fischer, is brought
about in the laboratory. In all such syntheses the
experimenter reverses the direction of inorganic chemical
happening. He may cause endothermic chemical re-
actions, reactions accompanied by the absorption of
available energy, to take place, and in these kinetic
energy becomes transformed into potential energy.
All the syntheses of organic compounds so complacently
instanced by mechanistic biologists and chemists as
indicative of the lack of distinction between the organic
and the inorganic point to no such conclusion. Sugar
is built up in the cells of the green plant from the in-
organic compounds, water, and carbon dioxide, and is
therefore a compound prepared by life — that of the
plant organism. But sugar may also be built up in
the laboratory from inorganic compounds, which may
further have been synthesised by the chemist from their
elements. Does this destroy the distinction between
compounds formed by the agency of the organism and
those formed by inorganic agencies ? Obviously it
does not, for in the green plant the sugar was formed
as the result of the vital agency of the living chloro-
phyllian cell, while in the laboratory it was built up
because of the intelligence of the experimenter. Apart
from this intelligence or vital agency, the series of
318 THE PHILOSOPHY OF BIOLOGY
chemical transformations beginning with the elements
carbon, oxygen, and hydrogen, and ending with the
substance sugar, would not have occurred. We have
no right to say, therefore, that such syntheses destroy
the distinction between the organic and the inorganic.
What they do indicate is the distinction between the
tendency expressed by the second law of thermo-
dynamics (inorganic processes), and those that occur
as the result of direction conferred upon processes
taken as a whole, either by the vital agency of the livmg
cell, or by the intelligence of man (vital processes).
The direction, therefore, that may be conferred on
a series of physico-chemical processes is what we must
understand by the " vital impetus " of Bergson, or the
*' entelechy " of Driesch.
It must be admitted that it is difficult to describe
more precisely than we have done above what is meant
by these terms. It is with very much the same em-
barrassment that is experienced by the physicist
when he has to apply the concepts of mass and inertia,
in their eighteenth-century meaning, to his description
of an universe in terms of electro-magnetic theory, that
we seek to describe the modern concept of entelechy.
Yet the physicist has had to make this step forward,
and the same adventure awaits the biologist if the
speculative side of his science is to make further pro-
gress, and if he is disinclined to make his science an
appendage of physics and chemistry. Entelechy does
not correspond to the eighteenth-century notion of a
" vital force," or to the " soul " of Descartes, as the
writer of a book on evolutionary biology seems to
suggest. It is a concept which is forced upon us
mainly because of the failure of mechanistic hypotheses
of the organism. If our physical analysis of the
behaviour of the developing embryo, or the evolving
THE ORGANIC AND THE INORGANIC 319
race or stock, or the activities of the organism in the
midst of an ever-changing environment, or even the
reactions of the functioning gland, fail, then we seem to
be forced to postulate an elemental agency in nature
manifesting itself in the phenomena of the organism,
but not in those of inorganic nature. This argument per
ignorantium possesses little force to many minds : it
makes little appeal to the thinker, or the critic, or the
general reader, but it is almost impossible to over-
estimate the appeal which it makes to the investigator,
as his experience of the phenomena of the organism
increases, and as he feels more and more the difficulty
of describing in terms of the concepts of physics the
activities of the living animal.
We may, however, attempt to illustrate mainly by
analogy what is meant by Driesch's entelechia, a more
precise concept than is Bergson's elan vital. We return
to the consideration of the behaviour of the embryo at
the close of the process of segmentation. The organ-
ism at this stage consists of a num.ber of cells organically
in continuity with each other, either by actual proto-
plasmic filaments or by the apposition of parts of their
surfaces, thus constituting " semi-permeable " mem-
branes. These cells are all similar to each other, both
structurally and functionally. It does not matter that
modern speculations on heredity describe them as
unlike in that each contains a different part of the
original germ-plasm which had been disintegrated
in the process of the division of the ovum and the first
few blastomeres ; and it does not matter that these
hypotheses are compelled to assume that a part of the
original germ-plasm remains intact, being destined to
form the gonads of the adult animal. These are hypo-
theses invented to account for the differentiation of
the embryo in terms of eighteenth-century physics and
320 THE PHILOSOPHY OF BIOLOGY
chemistry, and they have yet to be supported by
experiment before we can accept them as a description
of what is to be observed in the processes of nuclear
division and segmentation. Further, it is certainly
the case that any one cell of the early embryo can give
rise to any part of the larva. The segmented embryo
is therefore a system of parts, all of which are potentially
similar to each other. But actually each of these parts
has a different fate in the process of the development
of the larva, and this fate depends on what is the fate
of the adjacent cells. There is also a plan or design
in the development of the embryo — that is, a very
definite structure results from this process — and each
of the cells shares in the evolution of this design. The
system of cells is therefore an harmonious equipotential
system. The cells themselves are not the ultimate
parts of this system, for each of them is an aggregate of
a very great number of substances which are physico-
chemically characterised — at least our methods of
analysis seem to show that each cell is a mixture of a
number of chemical compounds, but we must never
forget that it is the dead cell which we thus subject to
analysis, and not a living organism. Let us call these
supposed chemical constituents of the living cells the
elements of the system ; then at the beginning of the
process of development the latter is composed of
elements which are not definitely arranged but which
are distributed in an " homogeneous " manner very
like the distribution which is effected on shuffling a
pack of cards. But as differentiation proceeds, the
elements of this system become unequally distributed,
and the diversity becomes greater and greater, attain-
ing its maximum when the definitive tissues and organs
of the adult become established, just as at the close of
a game of bridge the cards acquire a particular arrange-
THE ORGANIC AND THE INORGANIC 321
ment indicative of a very definite plan which was
present in the minds of the players shortly after the
game began.
Mechanistic biology would seek to explain this
transformation of a homogeneous system of elements
into a heterogeneous and specific arrangement by the
interaction of the elements with each other, and by
the reaction of the environment. But, given a homo-
geneous arrangement of elements capable of interacting
with each other, then only one final phase can be
supposed to be produced. A mixture of sulphur,
carbon dust, copper and iron filings raised suddenly to
a high temperature will only interact in one way, and
the final phase of the system will depend on the com-
position of the mixture, on the temperature, and on
the conduction of heat into the mixture in the initial
stage of heating. A mixture of chloroform and water
shaken up in a bottle is at first a " homogeneous "
mixture of the particles of the two substances, but
under the influence of gravity the liquids separate
from each other and form two distinct layers, each of
which will contain in solution some of the other liquid.
A homogeneous mixture of different substances there-
fore becomes a heterogeneous arrangement in the in-
organic system, as in the organic one, but while we can
predict the former one we cannot predict the latter.
We can express the result of the combination of the
elements of the inorganic mixture as something that
depends on chemical and physical potentials, but this
is quite impossible in the case of the development of
the embryonic system. It is not only that our know-
ledge of the developmental process is imperfect : the
distinction between the two processes of differentiation
is a fundamental one. A change in the conditions
under which the inorganic system differentiates leads
X
322 THE PHILOSOPHY OF BIOLOGY
of necessity to a different final phase, but a change in
the conditions under which the embryo develops need
have no such effect. If some unforeseen occurrence
takes place — some artificial interference with the
process of segmentation, which could never have been
experienced in the racial history of the organism — a
regulation by the parts of the embryo occurs, and the
final phase of development may be the same as if no
interference had been experienced. That which is
operating in the development of the embryo is some-
thing that is permitting, or suspending, or arranging
physico-chemical reactions.
Let us think of the developing embryo merely as an
aggregation of substances contained in an inorganic
medium : the segmented frog's egg floating on the
water at the surface of a pond is an example. As an
inorganic system its fate is determined. Autolysis of
the substances in the cells will occur and the proteids
will break down with the formation of amido-bodies,
while other chemical changes, strictly predictable if
our knowledge of organic chemistry were more complete
than it is, would also occur. Putrefactive and fermen-
tative bacteria will attack the proteids, fats, and carbo-
hydrates, and in the end our aggregation of chemical
substances will become an aggregation of much simpler
compounds — water, carbon dioxide, marsh gas, sulphur-
etted hydrogen, phosphoretted hydrogen, ammonia,
nitrates, etc., all of which will dissolve in the water of
the pond, or will diffuse into the adjacent atmosphere.
But in the living embryo this is not what occurs : an
entirely different, and much more complex, arrange-
ment of the chemical substances originally present in
the segmented egg, or at least a physical and chemical
re-arrangement, is brought about. The entelechy of
the developing embryo prevents some reactions from
1
THE ORGANIC AND THE INORGANIC 323
occurring and directs the energy which is potential in
the system towards the performance of other reactions.
Two analogies, suggested by Driesch, will perhaps
make the role of entelechy more clear. A workman,
a heap of bricks, some mortar, some food, and some
oxygen constitute a system in the physico-chemical
sense. From his heap of bricks and mortar the work-
man may build one of several different kinds of small
house, or he may perhaps construct several walls with-
out any definite arrangement, or he may merely con-
vert one " disorderly " heap of bricks and mortar into
another " disorderly " heap. In the same way a man,
a case of movable types, some food, and some oxygen
constitute another system. The initial phase of this
system consists of the compositor, his food, and some
fifty-odd boxes of types, each of which contains a large
number of similar elements. A final phase of the
system may be the arrangement of the types to form
an epic poem, or a series of dramatic criticisms, or a
meaningless jumble of correctly spelt words. In all
these cases the same amount of energy was expended :
the bricklayer used up the same quantity of food and
oxygen and excreted the same quantities of water,
carbon dioxide, and urea, whether he made a house, or
a small chimney, or a heap of bricks without archi-
tectural arrangement. The system of bricks and
mortar acquired during the process of differentiation a
gradually increasing complexity ; while in the case of
the type-setting the diversity of arrangement acquired
in the final phases may be of a very high order. Yet
the intelligent mind of the worker remained in either
case unchanged.
Let us consider further a man walking along the
ties, or sleepers, of a railway track. The ties are at
variable distances apart, so that the steps of the walker
324 THE PHILOSOPHY OF BIOLOGY
must vary in length, being sometimes closer together,
sometimes further apart. The ?nean step has a definite
length and requires the expenditure of a certain amount
of energy, and the condition that the man takes some-
times a long step and sometimes a short one does not
require that the energy expended on the steps should
be more than if every one of them were of the mean
length, for the additional energy that is required for
the long steps is saved from the short ones. That
which operates here is the power of regulation exercised
by the walker regarded as a mechanism. There is no
purely inorganic process precisely similar to this. It
might be thought that the governor of a steam engine
did very much the same thing, admitting more steam
into the cylinder when the load on the engine increases,
and vice versa. But the governor is a mechanism
designed to compensate for variations that are given in
advance. In the case of the man walking on the rail-
way track, entelechy operates by suspending energetic
happening (the muscular contractions of the short
steps) when necessary, and allowing it to proceed when
necessary. Entelechy itself, whatever it may be, need
not be affected by these regulations.
The organism is therefore an aggregation of chemi-
cal substances arranged in a typical manner. These
substances possess energy in the potential form, capable
of undergoing transformation so that they may give
rise to other chemical substances — secretions, for
instance — or to energy in the kinetic form, that is, the
movements of muscles. In the resting organism these
transformations do not take place : the energy remains
potential, so that chemical happening is suspended. In
the unfertilised ovum, for instance, nothing happens
although all the potentialities of segmentation are
contained in the cell. If reactions did occur in con-
THE ORGANIC AND THE INORGANIC 325
sequence of the chemical potentials contained in the
substances of the cells, the progress of these would be
such as to lead to the formation of substances in which
potential energy was minimal, and in which the original
energy of the cell would be represented by the un-
co-ordinated kinetic energy of the molecules resulting
from the breakdown of the substances undergoing the
chemical changes. This is not what happens in the
differentiation of the ovum : the developing cell forms
new substances from those of its inorganic medium
similar to the substances of which it is already com-
posed, and then these substances become arranged to
produce the specific form of the organism into which
the ovum is about to develop.
All hypotheses which attempt to describe the
functioning of the differentiating ovum, or the function-
ing organism, in terms of the physical concepts of
matter and energy alone, fail on being subjected to
close analysis. The manifestations of the life of the
organism are, it is said, particular " energy-forms," of
the same order as light, heat, chemical and electrical
energy, etc. All these energy-forms are "concaten-
ated," that is, each can be converted into any of the
others. A particular frequency of the vibration of
the ether can be converted into a movement of the
molecules of a material body, and so become heat, while
chemical energy may become converted into electrical
energy, or vice versa, and so on. It is said that life may
be merely a transformation of some "energy-form"
known to us : the potential energy of food may be
converted into " biotic energy," and this may then
manifest itself in the characteristic behaviour of the
organism. This is the method of physical science.
Energy continually disappears from our knowledge :
the mechanical energy which was employed to carry a
326 THE PHILOSOPHY OF BIOLOGY
weight to the top of a hill, or that which raises a
pendulum to the highest point of its swing, apparently
disappears. If we pass a current of electricity through
water, energy disappears, for it requires more current
to pass through water than through a piece of metal
of the same section. In these and similar cases physics
invents potential energies in order to preserve the
validity of the law of conservation. The kinetic energy
of the weight, or that of the swinging pendulum, be-
comes the potential energy of the weight resting at
the top of the hill, or that of the bob of the pendulum
at its highest point, while the electrical energy that
has apparently been lost becomes the potential energy
of the changed positions of the molecules of oxygen
and hydrogen. This assumption that the visible
kinetic energy of motion becomes converted into the
invisible potential energy of position is justified by our
experience, for (neglecting dissipation) we can recover
this lost energy, in its original quantity, from the con-
dition of the bodies which became changed physically
when the kinetic energy disappeared. Apply the same
method to the phenomena of the organism and suppose
that the chemical potential energy of the food con-
sumed becomes converted into the kinetic energy of
motion of the parts of the body : we are justified in this
assumption by the results of physiology. But then
some of this chemical energy undergoes a transforma-
tion of quite another kind and becomes the " biotic
energy," which is apparently that which is in us which
enables us to perform regulations, or establishes that
condition which we call consciousness. We cannot say
exactly what this " biotic energy " is, or what are t'^-e
steps by which the energy of food becomes converted
into it ; but no more can we say what is electrical
energy, nor what are the steps by which chemical energy
THE ORGANIC AND THE INORGANIC 327
becomes converted into it. Thus our ignorance of the
precise nature of the energy-transformations of in-
organic things — an ignorance which is all the while
disappearing — becomes the excuse for a comparison of
these with vital transformations, and for the assump-
tion that there is a fundamental similarity in the two
kinds of happening.
Less is assumed in the assumption of an entelechian
agency than in assuming that the manifestations of
life are the consequences of a vital " energy-form,"
different from inorganic forms, though belonging to
the same order, inasmuch as it may be concatenated
with these inorganic energy-forms. We need not sup-
pose that a particular kind of transformation occurs
only in the sphere of the organic : all that we need
assume is that, by some agency inherent in the activities
of the organism, chemical reactions that would occur if
the constellation of parts were an inorganic one are
suspended. Nothing unfamiliar to physical science is
involved in this assumption. Hydrogen and chlorine,
gases that combine together when mixed with the
production of heat and hght, may be mixed under
conditions such that the combination may be delayed
for an indefinite time. Iron which dissolves in nitric
acid may nevertheless be brought into the " passive "
form when it remains in contact with the re-agent but
is not dissolved by it. Enzymes which are in contact
with the walls of the alimentary canal do not dissolve
these membranes so long as the tissues are alive, and
they do not dissolve the food stuff until they have been
" activated." Oxygen which is contained in the
tissues does not oxidise the tissue substances until an
enzyme or a catalase has exerted its influence. More
and more, as physiology has become more searching in
its study of the functions of the animal, has it sought
328 THE PHILOSOPHY OF BIOLOGY
to explain the metabolic processes by assuming the
intervention of enzymes, until the number of these
substances has become legion, and much of the original
simplicity of the notion of ferment-activity has been
lost. But why do not these enzymes, if they are always
present in the tissues, always act ? They must be
activated, says modern physiology ; that is, the enzyme
really exists in the tissues as a " zymogen '* or a sub-
stance which is not, but which may become, an enzyme ;
or they exist as " zymoids," that is, substances which
appear to be chemically enzymes, but which must
be activated by " kinases " before they can become
functional.
Undoubtedly it is along these lines that physiology
is making advances, has increased our knowledge of
the activities of the animal, and is conferring on the
physician greater power of combating disease ; but the
hypotheses of the activity of the enzymes is obviously
one which has been based on the results of the
physico-chemical investigation of inorganic reactions,
and it has taken the precise form it has because of the
attempted analogy of many metabolic processes with
catalytic processes. Why do the inert zymoids become
activated by the kinases just when they are required
by the general economy of the whole organism ? We
do know that kinases are produced by the entrance
of digested food into certain parts of the alimentary
canal, and that these kinases are carried in the blood
stream to other parts where they activate the zymoids
already there. But of the nature of the machinery
by means of which all this is effected physiology gives
us no hint, and it is an assumption that the mechanism
involved is a purely physico-chemical one. Suppose we
say that the entelechy of the organism possesses the
power of suspending the activation of the enzyme,
THE ORGANIC AND THE INORGANIC 329
that is to say, of arresting the drop of chemical potential
involved in the process of the hydrolysis of (say) a
proteid. When this process of hydrolysis is necessary
in the interest of the organism entelechy can then
institute the reaction which it has itself suspended :
all this is in accord with the law of conservation.
Entelechy does not cause chemical reactions to occur
which are " impossible " : it could not, for instance,
cause sulphuric acid and an alkaline phosphate to
react with the formation of hydrochloric acid. But
chemical reactions which are possible may be sus-
pended, and suspended reactions may then become
actual when this is necessary in the interest of the
organism.
Entelechy is therefore not energy, nor any parti-
cular form of energy-transformation, and in its opera-
tions energy is neither used nor dissipated. In all
that it does the law of conservation holds with all the
rigidity with which we imagine it to hold in purely in-
organic happening — at least we need not assume that
it does not hold — and this is the essential difference
between the entelechian manifestations and the mani-
festations of the " vital " or " biotic " forces or energies
of the historic sj^stems of vitalism. It is essentially
arrangement, or order of happening, and it is therefore
a non-energetic agency. The workman who may build
half-a-dozen zigzag walls, or an archway, or a small
house, from the same materials and with the ex-
penditure of the same quantity of energy, is indeed an
energetical agent, but he is more than that. He is a
physico-chemical system in which any one phase is
not determined by the preceding phase. Different
results may arise from the same initial arrangement of
materials and energies, and this is because the system
contains more than the material and energetical
330 THE PHILOSOPHY OF BIOLOGY
elements. It contains the intelligence or entelechy of
the workman.
What is this entelechy ? Sooner oi later in all our
speculation on organic happening we must cross the
arbitrary line which divides the space of our concepts
from the non-spatial — the intensive from the extensive.
Just as the physicists have left materiality behind them
in their speculations and treatment of the phenomena
of radiation, so biolog}/ must attempt to trace back
the materiality of the organism to something which is
immaterial. Just as physics has now abandoned the
idea of matter as something which consists of discrete
particles, or atoms, having extension in space, and
which therefore exclude each other, so biology must
seek the origin of living things, not in the hypo-
thetical " biophoridae," or other ultimate living material
particles, but in the intensive manifoldness of entelechy.
There is a manifoldness in the potentiality which the
simple and homogeneous ovum possesses of becoming
the heterogeneous adult organism. This manifoldness,
says the mechanistic biologist, consists of a manifold-
ness of extended material units, the determinants of
Weismann, and the organisation that arranges these
units — what is this organisation ? It cannot be a
three-dimensional machinery, as all close analysis of
the facts of development and regulation shows. It is
then something that is intensive, something which is
not in space, but which acts into space, and the result
of which is manifested in spatial material arrange-
ments and activities. Vague and incomprehensible as
is this concept of the activities of the organisms, it is
only vague and incomprehensible because we have been
accustomed to express all chemical and physical
happening in terms of the fundamental concepts of
matter and energy, and the science of the last two
THE ORGANIC AND THE INORGANIC 331
centuries has left us with a terminology which applies
strictly to operations in which only these concepts are
involved. But if, as all minute analysis of vital
phenomena shows, the search for the antecedents of
some energetic, material, extended system of elements
in a preceding energetical, material, extended system
of elements only leads to confusion and contradictions,
then this concept of an agency which is neither energetic,
nor material, nor spatial must be formulated. En-
telechy, then, is not energy, but rather the arrangement
and co-ordination of energetic processes. It is not
something that is extended in space, but something
which acts into space. It is not material, but it mani-
fests itself in material changes. It is a manifoldness, or
organisation, but the manifoldness is an intensive one.
Compare this definition with the notion of the ether of
space now accepted by the mathematical physicists,
and it will be seen that our speculations are similar to
those of the physicists, and, like them, the test of their
reality and usefulness is to be justified pragmatically.
We may now attempt a formal description of the
organism based on the discussions of the previous
chapters. 1
The organism is a typical constellation of physico-
chemical parts or elements.
That is to say, it is an object in nature possessing
a definite form, which is the result of the arrangement
of its tissues. Each tissue is again an arrangement of
cells, and each cell is a complex of chemical substances.
The organism therefore resembles, so far as our defini-
tion goes, an inorganic crystal. But it is the typical
1 This description is largely an expansion of Driesch's " Analytical definition
of the individual living organism." The reader should note also that it includes
the Bergsonian idea of duration, and that of the organism as a typical phase
in an evolutionary flux, as parts of the description.
332 THE PHILOSOPHY OF BIOLOGY
organism that we are considering, and this is a pure
conception, for our typical organism does not occur in
nature. The organisms that are accessible to our
observation are constellations of physico-chemical parts,
but these constellations tend continually to deviate
from the conceptual arrangement. Progressive varia-
tion from the type is something that distinguishes the
organic constellation from the inorganic one.
The organism is an entity in which energy-trans-
fovmations of a particular nature are effected. These
transformations raise energy from a state of low, to a state
of high potential.
This is the general tendency of terrestrial life, and
it is expressed most fully in the metabolism of the green
plant. The energy -transformations that are effected
here are those in which the kinetic energy of radiation
is employed to build up chemical compounds of high
potential, from inorganic substances incapable in them-
selves of undergoing further transformations. The
general tendency of all inorganic transformations is
towards inertia. In them energy is not destroyed, but
it is dissipated : it becomes uniformly distributed
throughout material bodies as the un-co-ordinated
motions of the molecules of which those bodies are
composed, and it ceases to be available for further
transformations. The green plant reverses this trans-
formation, and accumulates energy in the form of
chemical compounds of high potential. Inorganic
processes are those in which available energy becomes
unavailable, and this unavailable energy can only
become available again if a compensatory energy-
transformation is effected. Life is that which effects
these compensatory energy-transformations.
The organism is a constellation capable of indefinite
growth hy dissociation.
THE ORGANIC AND THE INORGANIC 333
That is to say, it is a constellation which reproduces
itself in all its specificity. Gro\\i;h consists in the
separation from the organism of a part, or reproductive
cell, which divides (or dissociates) repeatedly, each
dissociated part growing again in mass by the addition
of substances similar to its own, but which are taken
from a medium dissimilar in composition to itself.
The aggregate of parts so formed then differentiates
so that the constellation is reproduced in all its
specificity. There is nothing precisely similar to
this in inorganic happening. The growth of a crystal
consists simply of the accretion of elements similar in
nature to those of the growing body, and there is no
differentiation.
The organism exhibits autonomy.
It is a constellation which persists in the midst of
an ever-changing environment, and the typical organic
form remains the same, although the material of which
it is composed undergoes continual change. There are
inorganic entities which resemble the organism in this
respect : the form of a cyclone or atmospheric dis-
turbance, for instance, remains the same even though
the air of which it is composed is continually changed.
But the form of the organism does not vary strictly
with the changes in the environment in which it is
placed, for it may respond to an environmental change
by a regulation, or compensatory change in form or
functioning, the effect of which is to maintain the con-
stellation in all its specificity. The regulation is not
a complete or perfect one, for environmental changes
do, to some extent, produce changes in the organic
constellation, but there is no functionality between the
environmental change and the organic response. In
inorganic happening a change in one part of a trans-
forming system necessarily determines the nature and
834 THE PHILOSOPHY OF BIOLOGY
extent of the changes that occur in the other parts of
the system.
The organism is a centre of continuous action.
It is first of all a part of nature in which energy-
transformations continually take place — a description
which applies equally well to plants and animals. It
is only when we attempt to seek an inorganic system
to which this definition would apply that we find how
well it differentiates the organic from the inorganic.
An inorganic system which transforms energy is either
one which tends continually towards stability, or it is
a machine made by man for a definite purpose, and it
is therefore a system involving a teleological idea. An
organic centre of action is one in which energy-trans-
formations proceed without cessation.
In the plant organism the energy-transformations re-
present, with the exception of the reproductive processes,
the whole activity of the organism. In the animal organ-
ism they are accessory to regulated and purposeful motile
activity, that is, muscular action. The object of this mus-
cular activity varies with the stage of evolution attained
by the animal. Its sole object in the lower animal is
that of individual or racial preservation. Living in an
organic and inorganic environment which is always
hostile and tends continually towards its destruction,
the whole activity of the organism is directed to the
attempt to master this environment : it struggles for
its individual existence, and that of its offspring. The
activities of man are also these, but they are more than
these, for, knowing that physical processes tend con-
tinually towards inertia, he seeks to control these
processes, and to preserve the instability of nature on
which the possibility of further becoming depends.
The activity of the organism, whether it be the
energy-transformations of the plant or the motile
THE ORGANIC AND THE INORGANIC 335
activities of the animal, are directed and regulated
activities. The activity of the organism is not a
functional activity in the sense that the activity of a
djTiamo is a function of the nature of the machine,
and of the nature and quantity of the energy supplied
to it. The nature of the activity of the organism is
regulated autonomously by purposes which it " wills "
to carry out.
J^he organism is a phase in an evolutionary /lux.
Categories of organisms — varieties, species, genera,
etc. — are fictions. They are arbitrary definitions de-
signed to facilitate our description of nature. They
are types or ideas. In constructing them we follow
the method of the intellect, and we represent by im-
mobility that which is essentially mobile and flows.
Between the fertilised egg and the senile organism
there is absolute continuity. Our description of the
individual organism is a description of it at a typical
moment of its life-history, and this description includes
all that has led up to, as well as all that will fall away
from, the morphology at this particular t3rpical moment.
Even then the arbitrarily defined organism is only
a phase. In defining it we arrest, not only the
individual, but also the racial, evolutionary fiux. The
specific morphology is that of a typical moment in a
racial flux. Leading up to it at this moment are all
the variations that have joined it with its ancestry,
and leading away from it will be all the variations that
will convert it into its descendants.
The individual and racial developments are true
evolutions. They are the unfolding of an organisation
which was not expressed in a system of material
particles or elements interacting with each other, and
with the elements of the environment, but which we
must seek in an intensive, non-spatial manifoldness.
336 THE PHILOSOPHY OF BIOLOGY
In the evolutionary flux the changes are non-
functional ones, that is to say, any phase, whether it
be one in an individual or a racial development, is not
merely a rearrangement of the elements of the preceding
phases, as in the case of a transforming system of
material particles and energies. There is inherent,
spontaneous variability.
The organism endures.
That is, all its activities persist and become part of
its organisation. It does not matter whether or not
we decide that characters which are acquired are
transmitted, nor does it matter whether or not we
conclude that the environment is the cause of these
acquirements. Some time or other in the individual
or racial history new characters arise by the activity
of the organism itself, and these characters either
persist in an individual or in a race. They endure.
All its activities, even its thoughts, persist and form
the experience of the animal — an experience which
continually modifies its conduct. In man those true
acquirements, the results of education and of investiga-
tion, persist as written language, or as tradition, even
if they are not inherited.
Duration is not time. The mathematician does
not employ, in his investigations, intervals of duration.
When he relates something which is happening now to
something which happened some time ago he employs
the differential co-efficient dyjdx, so that the interval
between the two occurrences becomes an " infini-
tesimal " one. When the astronomer predicts events
that will happen some years hence, or describes those
that happened some years ago, he is really describing
things that are all there at once, so to speak, things
which are given. If we unfold a fan, stick by stick,
we see the separate members in succession, but they
THE ORGANIC AND THE INORGANIC 337
are all there, and we can, if we like, see them all
at once.
The more we reflect on it the more we see that
mathematical time is only a way in which we see things
apart from each other. Things become extended in
time as they become extended in space. Whether
occurrences capable of analysis by the methods of
physics are what we call past or future occurrences, they
are all given, in that each of them is only a phase of
the others.
Duration belongs to the organism. The past is
known because all that has occurred to the organism
still persists in its organisation. The future is unknown
because it has still to be made. Duration is therefore
a vector — something having direction, and the organism
progresses out of the past into the future. It grows
older but not younger.
Such appears to be the nature of life. Can we
discuss the problem of its origin ?
Did life originate on our earth ? We must first
consider what we mean when we speak of an origin.
The organic world of the present moment, with all its
environment — that is to say, the totality of organisms
on the earth, with all the materials which they can
utilise in any way, the energy of radiation from which
they ultimately derive their energy, and all the parts
of the cosmos which interact with them — constitute a
system in the physical sense. The present condition
of the organic world, that is, the kinds and numbers of
organisms, and their distribution, and the distribution
of the materials which they can utilise, and the quantity
and nature of the energy which is available to them,
are the present phase of this system. All the conditions
of life in the past, that is to say, the kinds, and numbers,
338 THE PHILOSOPHY OF BIOLOGY
and distribution of organisms, and the quantity and
nature of their environment at any time, together
formed phases of this system. If there was a time when
life, as we know it, did not exist, then the materials
and the energies, which were antecedent to life when
it did appear, were also a phase of the system. On a
strictly mechanistic hypothesis there could be no
origin : there could only be a transformation of a
system which was already in existence. All that
exists to-day was given then. When, therefore, we
speak of the origin of life from non-living materials
we mean simply a transformation of those materials
and energies.
There was a time, it is said, when life could not
exist on the earth. For the organism is essentially
that aggregate of chemical compounds which we call
protoplasm, and this cannot exist at temperatures
higher than loo' C, and it cannot function at tempera-
tures lower than o° C. It requires carbon dioxide, and
ammonia or nitrate, as the materials for its constructive
metabolism, and there was a time when these com-
pounds could not exist, for they must have been dis-
sociated by the heat of the gaseous nebula from which
our earth originated. The organism requires energy
in the form of solar radiation of a particular frequency
of vibration, and there was a time when the sun's
radiation was different from what it is now. Therefore
life did not exist then. Even if we believe that life came
to the earth as germs, which existed previously in outer
cosmic space, this belief does not solve the problem,
which simply becomes transferred from, our earth to
some other cosmic body.
But life, as we know it, makes use of the materials
and the energies which are available to it in the con-
ditions in which it exists. The plant organism obtains
THE ORGANIC AND THE INORGANIC 339
its energy from solar radiation because this is the most
abundant source of terrestrial energy. The human eye
is most susceptible to light of a particular frequency
of wave-length, but this is the radiation that is most
abundant in the light of the sun. Does this not mean
that the organism has merely adapted itself to the
material and energetic conditions in which it exists ?
Does it necessarily mean that because the conditions
were very different life could not exist ? Protoplasm
could not exist at a temperature of several thousand
degrees Centigrade, but does that mean that life,
which on any hypothesis of mechanism must be
described in terras of energy, could not exist in these
conditions ?
It must have had an origin, says Weismann,
because it has an end. Organic things are destroyed,
inasmuch as they disintegrate into inorganic things.
Organisms die. Thus the organic process comes to an
end, and because it comes to an end it must have a
beginning. Spontaneous generation of life is thus, for
Weismann, a " logical necessity."
Need this logical necessity exist ? The argument
clearly implies that life is a reversible process. Organic
things become inorganic, and therefore inorganic things
must become organic things. The first statement is
a fact of our experience, but the second one would only
be logically true if we were to postulate that the process
of life, whatever it may be, is a reversible process.
But we must not postulate this if we are to hold to a
physico-chemical mechanism, for it is a fundamental
result of physical investigation that all inorganic pro-
cesses are irreversible : reversible inorganic processes
are only the limits to irreversible ones. Physical pro-
cesses go only in one way, and that organic substance is
destroyed to the extent that it becomes inorganic is a
340 THE PHILOSOPHY OF BIOLOGY
particular case of this irreversible physical tendency.
Now the mechanism of Weismann 'must base itself on
the concepts of physics and chemistry, and it must
postulate the origin of life from non-living substances.
Why ? Because life is a reversible process, that is, it
exhibits a tendency which does not exist in inorganic
processes. Clearly the logic is faulty ! And must we
conclude that life has an end ? Weismann himself
suggests that nothing in the results of biology indicates
that physical death is a necessity : it is rather an
adaptation. The soma, or body, is the envelope of
the germ-plasm, and exposed as it is to the vicissitudes
of an environment which is always hostile, it becomes
at length an unfit envelope. But with the reproductive
act the germ-plasm acquires a new soma, and it is no
longer necessary that the former one should continue
to exist as an unfit envelope. Physical death therefore
occurs as an adaptation serving for the best inter-
ests of the race. The organism need not die, for the
germ-plasm may be a physical continuum throughout
innumerable generations. Somatic death is only a
destructive metabolism : it is a catastrophic meta-
bolism, if we like.
We may legitimately discuss such problems as the
origin of the protoplasm of the prototrophic organism,
or that of the chlorophyll-containing cell, or that of
the nerve-cell. On the mechanistic view each of these
conditions is a phase of a transforming physico-chemical
system, and it is within the scope of the methods of
physical science to investigate the nature of these
transformations. But if the argument of this book is
sound, then the problem of the origin of life, as it is
usually stated, is only a pseudo-problem ; we may as
usefully discuss the origin of the second law of thermo-
dynamics ! If life is not only energy but also the
THE ORGANIC AND THE INORGANIC 341
direction and co-ordination of energies ; if it is a
tendency of the same order, but of a different direc-
tion, from the tendency of inorganic processes, all that
biology can usefully do is to inquire into the manner
in which this tendency is manifested in material things
and energy-transformations. But the tendency itself
is something elemental.
APPENDIX
MATHEMATICAL AND PHYSICAL NOTIONS'
INFINITY
What is really meant when the mathematician uses
the concept of infinity in his operations ? Suppose that
we take a line of finite length and divide it into halves,
and then divide each half into halves, and so on ad
infinitwn. We make cuts in the line, and these cuts
have no magnitude, so that the sum of the lengths into
which we divide the line is equal to the length of the
undivided line. We can divide the line into as many
parts as we choose, that is, into an " infinite " number
of parts.
Suppose that we are making a thing which is to
match another thing, and suppose that we can make
the thing as great as we choose. If, then, no matter
how great we make the thing, it is still too small, the
thing that we are trying to match is infinitely great.
Substitute " small " for " great," and this is also
a definition of the infinitely small.
Clearly the idea of infinity does not reside in the
results of an operation, but in its tendency. It inheres
in our intuition of striving towards something, but not
in the results of our striving.
1 It must be understood that some of the things dealt with in these appen-
dices are very hard to understand by the reader acquainted only with the
results of biological science. We urge, however, that they are all relevant if
biological results are to be employed speculatively.
342
APPENDIX
343
FUNCTIONALITY
If we pour some mercury into a U-tube closed at
one end, the air in this end will be contained in a closed
vessel under pressure. We can increase the pressure
by pouring more mercury into the open end of the tube.
We can measure the volume of the air by measuring
the length of the tube which it occupies. We can
measure the pressure on this air by measuring the
difference of length of the mercury in the two limbs
of the tube. By taking
all necessary precau-
tions we shall find that
for each value which
the pressure attains
there is a correspond-
ing value of the volume
of the air.
We thus find the
pressure values, p^, pi,
pa, p4, pb, etc., and the
corresponding volumes,
Vu V2, V3, Vi, v„ etc.,
and we may then plot these values so as to make a
graph.
In this figure the values represented along the
horizontal axis are pressure-values, and those repre-
sented along the vertical axis are volume- values. We
have so made the experiment that we can make the
pressure- values whatever we choose — let us call them
the values of the independent variable or argument.
For each value of the pressure, or argument, there is
a corresponding value of the volume, which depends
on the pressure — let us call these values of the volume
values of the dependent variable or function.
Fig. 27.
344 THE PHILOSOPHY OF BIOLOGY
We can make arbitrary values of the pressure, but
whenever we do this the corresponding values of the
volume are fixed. We say, then, that the volume is a
function of the pressure. In general, when we choose
one value of an independent variable, or argument,
there can be only one, or a small number, of values of
the dependent variable, or function. If there are two
or more values of the function for one value of the
argument each of these is necessarily determined by
the value which we choose to assign to the argument.
There is a strict functionality between the two series
of variables. In the experiment we have chosen this
functionality is expressed by the equation pv=k(/+ai),
where p is the pressure, v the volume, k and a constants,
and t is the temperature at which the experiment is
carried out. In a number of experiments like that
which we have mentioned, k, a, and t are the same
throughout, and this is why we call them constants.
We give p any value we like, and then v can be calculated
from the equation.
RATE OF VARIATION
If we know the equation pv=k{/+ at) , we can find how
much the volume changes when the pressure changes,
that is, the rate of variation of v with respect to p.
But even if we don't know that this equation applies,
we can still find the rate of variation from our experi-
ments. We see from the graph that, when the pressure
increases from pi to p^, the volume decreases from v, to
V2, but that if the pressure is again increased to p^, that
is, by a similar amount to the increase of pressure from
pi to pi, the volume decreases from v^ to V3. Now we
find, by measurements made on the graph, that the
decrease v^ to v^ is greater than the decrease r, to v^,
APPENDIX
345
and the latter decrease is greater again than the
decrease from fg to v^. Evidently the rate of variation
of volume is not like the rate of variation of pressure,
that is, the same throughout, and when we look at the
graph we see that the rate of variation is greatest where
the slope of the curve is steepest. The latter is steepest
near the point a, less steep near the point b, and still
less steep near the point c. Now any small part of
the curve is indistinguishable from a straight line. Let
us draw a straight line
eei, which appears to
coincide with a small
part of the curve near
a, and similar straight
lines^i ,and ggi , which
also appear to coin-
cide with small parts
of the curve near b
and c. Then the
steepness of the curve
will be proportional
to the angles which
these straight lines
make with the axis op, and these angles are measured
by their tangents, that is, by the ratio
makes with op,
Fig. 28.
e^e
—' which
oe
the ratio
is the tangent that
^, and the ratio -^\
The point a on the curve corresponds with a
pressure a^ and a volume Un. The point b corre-
sponds with a pressure b^ and a volume bn, and
c with a pressure Ci and a volume Cn- The average
rate of variation of the volume of the gas, as
the pressure changes from a to c, is therefore
346 THE PHILOSOPHY OF BIOLOGY
and
og'
proportional to the sum of the tangents — and — ,
oe og
divided by 2.
THE NOTION OF THE LIMIT
Suppose that we wish to find the rate of variation
of volume for a pressure change in the immediate
vicinity of the value bi, that is, the rate of variation as
the pressure changes from a little less than ^i to a little
more than bi. If we find the point b on the curve
corresponding to b}, and if we then draw a line ^,,
touching the curve at the point b, we shall obtain the
angle 0^1. It might appear now that the tangent of
this angle, that is, the ratio -^, would give us a measure
of the rate of variation of volume.
But the reasoning would be faulty. The line ^i
only touches the curve, it does not coincide with an
element of the curve. Also at the point bi the pressure
has a certain definite value, and there is no change. At
the corresponding point b^ the volume also has a
certain definite value, and there is no change. There
can therefore be no rate of variation. The value of
the tangent does not give us a measure of the rate of
variation : it gives us the limit to the rate of varia-
tion, when the pressure is changing in the immediate
vicinity of bi.
We must stick to the notion of a pressure change
in the immediate vicinity of b^. What do we mean by
" immediate vicinity " ? We mean that we are think-
ing of a range of pressure- values in which the particular
pressure-value b^ is contained, but not as an end-point.
We mean also that we choose a definite standard of
approximation to the value b^, so that any pressure-
value within our interval differs from b^ by less than this
APPENDIX 347
standard of approximation. It means further that, no
matter how small is the number representing this
standard of approximation, any pressure- value within
the interval will differ from hi by less than this number.
This is what we really mean when we say that the
interval we are thinking about is an " infinitely small
one."
Now corresponding to this interval of pressure-
values in the immediate vicinity of h^, there will be an
interval of volume-values in the immediate vicinity of
6n, and, as before, any one of these volume- values will
differ from h^ by less than any number representing
a standard of approximation to b^. We then find the
point on the curve corresponding to both h^ and 6,1,
that is h, and v/e draw the line^i, and find the tangent
of the angle which this line makes with op. The value
of this tangent is the limit of the rate of variation of
the volume of the gas when the pressure undergoes a
change in the immediate vicinity of h-^.
" Rate of variation " is a function of the argument
" pressure." This function has the limit I for a value
of its argument b^, when, as the argument varies in the
immediate vicinity of b^, the value of the function
approximates to / within any standard whatever of
approximation.^
We should not, of course, find the rate of variation
of volume of the gas by this means. We should calcu-
late the value of the differential co-efficient ^- from
dp
the equation pv=k{i-\-at) : this would be - ^ ^ f' .
P
But the reasoning involved in the methods of the
calculus are those which we have attempted to outline.
^ If the reader does not understand this, he should read Whitehead's
" Introduction to Mathematics." He should read this book in any case.
348 THE PHILOSOPHY OF BIOLOGY
We try to avoid the terms " infinitely small," " infi-
nitely near/' "infinitely small quantities," and so on,
by the device of standards of approximation. It may
appear to the non-mathematical reader that all this is
rather to be regarded as " quibbling," but the success
of the methods of mathematical physics should convince
him that such is not the case. He should also reflect
that clear and definite ideas on the fundamental
concepts of the science are just as necessary in specu-
lative biology as they are in mathematics.
(Another example.)
Let us consider the case of a stone falling from a
state of rest. Observations will show that when the
stone has fallen for one second it has traversed a space
of 1 6 feet ; at the end of two seconds it has fallen
through 64 feet ; and at the end of three seconds the
space traversed is 144 feet. From these and similar
data we can deduce the velocity of motion of the stone
as it passes any point in its path.
The velocity is the space traversed in a certain time
-. If we take any easily observable space (say five
feet) on either side of the point chosen, and then deter-
mine the times when the stone was at the extremities
of this interval, and divide the interval of space by the
interval of time, we shall obtain the average velocity
of motion of the stone over this fraction of the whole
path chosen. But the velocity did not vary in a
constant manner during this interval (as we see by
considering the spaces traversed during the first three
seconds of the fall). Therefore our average velocity
does not accurately represent the velocity of the stone
as it passes the point at the middle of the path chosen.
We therefore reduce the length of the path more and
more so as to make the average velocity approximate
APPENDIX 34&
closer and closer to the velocity near the middle portion
of the path. In this way we find the^ ratio ^, where
8s is a very small interval of path containing the point
chosen, but not as an end-point, and St is a very small
interval of time. Perhaps this average velocity may
be near enough for our purposes, but perhaps it may
not. The interval of path Ss is still a finite interval,
and St is still a finite time, and so long as these values
are finite ones the velocity deduced from them remains
a mean one. All that we can say is that it approxi-
mates to the velocity, as the arbitrary point was passed,
within a certain standard of approximation.
Obviously the smaller the interval Ss, the closer will
be this approximation . Suppose , then , that we diminish
8s till it " becomes zero." It might appear now that
when Ss coincides with the point chosen we shall
obtain the velocity of the stone at this point. But if
there is no interval of path, and no interval of time,
there can be no velocity, which is an interval of path
divided by an interval of time ; and if the stone is " at
the point," it does not move at all. We must stick to
the idea of intervals of space and time, and yet we must
think of these intervals as being so small that no error
whatever is involved in regarding the mean velocity
deduced from them as the " true velocity." We there-
fore think of the point as being placed in an interval
of path, but not at an end-point of this interval. We
think of the velocity as a mean one, but we must have
a standard of approximation, so that we may be able
to say that the mean velocity approximates to the
" actual " or limiting velocity of the stone as it passes
the point, within this standard of approximation.
The smaller we make the interval, the closer will the
mean velocity approximate to the limiting velocity.
350 THE PHILOSOPHY OF BIOLOGY
We therefore think of the stone as moving in the
immediate vicinity of the point in the sense already
discussed. We say that the " immediate vicinity " is
an interval such that any point in it, pi, approximates
to the arbitrary point -p which we are considering within
any standard of approximation : that is, no point in
the interval is further away from p than a certain
number expressing the standard of approximation, and
this can be any number, however small. We say the
same thing about the interval of time. That is to say,
we make the intervals as small as we like : they can be
smaller than any interval Vv^hich will cause an error in
our deduced velocity, no matter how small this error
may be.
The limit of the velocity of a stone falling past a
point in its path is, therefore, that velocity towards
which the mean velocities approximate within any
standard of approximation, when we regard the
interval of space as being the immediate vicinity of
the point, and the interval of time as being the time in
the immediate vicinity of the mom.ent when the stone
passes the point. The limit of the velocity is not ^
ds
but J- dt and ds being, not finite intervals of time and
space, but "differentials." We determine this limit
by the methods of the differential calculus.
FREQUENCY DISTRIBUTIONS AND PROBABILITY
Let the reader keep a note of the number of
trumps held by himself and partner in a large
number of games of whist (the cards being cut for
trump). In 200 hands he may get such results as
the following :
APPENDIX 351
No. 0/ trumps in his own and partner's hands — 0, i,
2, 3. 4. 5> 6, 7, 8, 9, 10, II, 12, 13.
No. of times this hand was held — o, o, o, i, 9, 29,
53. 52, 35. 14. 6, I, o, o.
He should note also the number of times that
trumps were spades, clubs, diamonds, and hearts : he
will get some such results as the following : spades, 46 ;
clubs, 53 ; diamonds, 51 ; hearts, 50.
The numbers in the lower line of the first series
form a " frequency distribution," for they tell us the
frequency of occurrence of the hands indicated in the
numbers above them. "No. of trumps " is the in-
dependent variable, and "no. of times these nos. of
trumps were held " is the dependent variable.
A frequency distribution represents the way in
which the results of a series of experiments differ from
the mean result. A particular result is expected from
the operation of one, or a few, main causes. But a
number of other relatively unimportant causes lead to
the deviation of a number of results from this mean or
characteristic one. Yet since one, or a few, main
causes are predominant, the majority of the results of
the experiment will approximate closely to the mean ;
and a relatively small proportion will deviate to vari-
able distances on either side of the mean. If a pack of
cards were shuffled so that all the suits were thoroughly
mixed among each other, then Vv^e should expect the
trumps to be as equally divided as possible between
the four players. But a number of causes lead to
irregularities in this desired uniform distribution, and
so the results of a large number of deals deviate from
the mean result. It is possible, by an application of
the theory of probability, to calculate ideal, or theoreti-
cal frequency distributions, basing our reasoning on the
considerations suggested above. We then find that the
352 THE PHILOSOPHY OF BIOLOGY
observed and calculated frequency distributions may
be very much alike.
In biological investigation, far more than in physi-
cal investigation, we deal with mean results. It is,
however, just as important that the mean should be
considered as the individual divergences from the mean.
We want to know the mean results, and the way and
the extent in which the individual results diverge
from the mean.
There is a mean or " ideal " result, but we must
think of a great number of small independent causes
which cause the actually obtained results to diverge
from this mean. If these small un-co-ordinated causes
are just as likely to cause the results to be less than the
mean, as greater than the mean, we shall obtain a fre-
quency distribution resembling the one given above,
in that the variations from the mean are equal on both
sides of the mean. But if the general tendency of the
small un-co-ordinated causes is to cause the results, on
the whole, to tend to be greater than the mean, then the
frequency distribution will be "one-sided," that is, if
we represent it by a curve the latter will be an asym-
metrical one. Curves which are asymmetrical are those
most frequently obtained in biological, statistical
investigations.
MATTER
Our generalised notion of matter is that it is the
physical substance underlying phenomena. Immedi-
ately, or intuitively, we attain the notion of matter
because of our perceptions of touch, and our perception
of muscular exertion. The distance sense-receptors,
visual, auditory, and olfactory, would not give us this
intuition of matter.
APPENDIX 353
Material things are extended, that is, they have
form, and they exclude each other, so that they cannot
occupy the same place. They appear to us to be
aggregates of different nature : they may be solid and
homogeneous, like a piece of metal ; or solid and porous,
like a piece of pumice-stone ; or loose and granular,
like sand ; or viscous or liquid, like pitch or water.
They may have colour. They are opaque, or transparent
in various degrees. They may have odour. Material
things, as they are perceived by the distance sense-
receptors, appear to have qualities.
Material things are aggregates of molecules. The
aggregates may possess essential form, like that of a
crystal, or an organism. The form of the aggregate
may be essential and homogeneous, so that it consists
of molecules, all of which are of the same kind, like a
crystal. It may be heterogeneous and essential, like
the body of the organism, when it consists of molecules
which are not all of the same kind. The aggregates
may have accidental form, like that of a river valle}'-,
or a delta, or a mountain, and the form in these, and
similar cases, is not a part of the essential nature of the
aggregate.
The molecules are selections (in the mathematical
sense) of some of about eighty different kinds of atoms.
A molecule is a small number of atoms arranged to-
gether in a definite way, and its nature depends, not only
on the kinds of atoms of which it is composed, but also
on the arrangement of these atoms. Two or more
different arrangements of the same atoms are, in
general, different molecules.
MASS
When matter is perceived by the tactile and
muscular sense organs, we have the intuition of mass.
z
354 THE PHILOSOPHY OF BIOLOGY
It is heavy, and the degree of heaviness is proportional
to the quantity of matter in the body which we feel,
that is, to its mass. Heaviness is s3monymous with
weight, but weight does not depend alone on the quantity
of matter in the body. If the latter were removed to an
infinite distance from the earth or other cosmic bodies,
its weight would disappear, but its mass would remain.
We could still touch and move it, and we should still
find that different degrees of muscular exertion would
be necessary when bodies of different masses had to
be moved.
INERTIA
If the body were in motion, we should find that
muscular exertion is necessary in order that it might be
brought to rest ; and if it were at rest, we should find that
muscular exertion was necessary in order that it might
be moved. The body, matter in general, possesses
inertia, and this is its most fundamental attribute.
Mass we can only conceive in terms of inertia. If
two bodies were at rest, and if the same degree of
muscular exertion conferred on each the same initial
velocity of motion, their masses would be equal. If
the same degree of muscular exertion conferred diffe-
rent velocities on different bodies, their masses would
be different, and would vary directly with the initial
velocities conferred.
FORCE
The feeling which we experience when we move a
body from a state of rest, or stop a body which is
moving, is what we call force. If on climbing a stair in
the dark we think there is one step more than there is,
and so have the queer, familiar, feeling of treading on
APPENDIX 355
nothing, we have the intuition of energy ; but when
we tread on the steps, and so raise our body, we have the
intuition of force. Force is that which accelerates the
velocity of a mass. If the latter is at rest, we consider
it to have zero velocity. If it is moving, and we stop
it, there is still acceleration, but this is negative.
Matter, that is, the substantia physica, is clearly to
be conceived only in terms of energy. It is, to our
direct intuitions, resistance, or inertia, that which re-
quires energy in order that it may be made to undergo
change. Our static idea of physical solidity, or
massiveness, disappears on ultimate analysis. Mole-
cules are made up of atoms, and the atoms are assumed
to have all the characters of matter : we could not see
them, of course, even if we possessed all the magnifying
power that we wished, for they would be too small to
reflect light. Modern physical theory is compelled to
regard atoms as complex, and imagines them as being
composed of moving electrons. The electron is im-
material— it is the unit-charge of electricity. It is
said to possess mass, but mass is now understood to
mean inertia. So long as the electron is moving, it sets
up a field of energy round it, and this field — the electro-
magnetic one — extends in all directions. Periodic dis-
turbances in it constitute radiation, and this radiation
travels with the velocity of light. It is because of the
existence of this field that we are obliged to postulate
the existence of an ether of space. Unfamiliar to us
until the discovery of Hertzian waves and " wireless "
telegraphy, this electro-magnetic radiation in space is
now accessible to our direct intuitions. We can initiate
it by setting electrons in motion, that is, by expending
energy (producing the sparking in the transmitters of
the wireless telegraphy apparatus) ; and we can stop
it, if it is in existence, by absorbing the energy (in the
356 THE PHILOSOPHY OF BIOLOGY
receivers of the wireless telegraphy apparatus). This
is essentially what we understand by the inertia of
gross matter. We set a body in motion by expending
energy on it (the explosion of the powder in a cartridge,
which converts potential chemical energy into the
kinetic energy of the moving projectile) ; and we can
stop a body which is in motion by absorbing this energy
of motion (by causing the projectile to strike against a
target, when the kinetic energy of its motion becomes
the kinetic energy of the heat of the arrested body) .
Inertia is therefore the same thing whether it be
the inertia of visible, material bodies, or the inertia
of invisible, material molecules, or the inertia of the
immaterial, non-tangible ether. It is the condition
that energy-changes must occur if anything accessible
to our observation is to change its state of rest or
motion.
ENERGY
Energy is therefore indefinable. It is an elemental
aspect of our experience.
Nature to us is an aggregate of particles in motion.
We have to speak of massive particles, whether we call
these visible material bodies, or molecules, or atoms,
or electrons, in order that we may describe nature. We
must employ the fiction of a substantia physica. We
only know the substance or matter in terms of energy ;
it is really the latter that is known to us. It is the
poverty of our language, or rather it is the legacy of a
materialistic age, that compels us to speak of par-
ticles that move, rather than of motions as entities in
themselves.
Considering, then, the idea of particles in motion as
a fiction necessary for clear description, we can study
I
APPENDIX 357
energy. There is only one kind, or form, of energy
which presents itself to our aided or unaided intuitions,
that is kinetic energy. Bodies that move possess this
energy represented by their motion : they can be made
to do work, that is, their energy can be transformed into
other forms of energy. All things are in motion. A
gas consists of molecules incessantly moving with high
velocity, and colliding and rebounding from each other.
The energy of a gas is the sum of one-half of the masses
of all the molecules, multiplied by the squares of the
velocities of all the molecules, that is, t^mv^. This is
also the kinetic energy of a projectile, or of a planet
revolving round the sun. Kinetic energy is that of the
uniform, unchanging motion of some entity possessing
mass, but we must extend our notion of mass so as
to include immaterial, imponderable entities such as
electrons.
This energy cannot be destroyed or created — the
law of conservation of energy. This is a principle or
mode of our thought. We are unable scientifically or
philosophically to think of an entity ceasing to be.
Dreams and phantoms show us entities which are real
while they last, but which cease to exist. If we do
attempt to think of entities that appear from, or dis-
appear into, nothing, we surrender the notion of reality.-
The more we think of it the more clearly we shall see
that the things which we call real are the things which
are conserved.
Yet energy, to our immediate intuitions, seems to
disappear. A flying bullet strikes against a target and
becomes flattened out into a motionless piece of lead.
A red-hot piece of iron cools down to the temperature
of its surroundings. A golf -ball driven up the side of
a hill comes to rest in the grass. A current of electricity
passing through water is used up, that is, electricity
358 THE PHILOSOPHY OF BIOLOGY
of a higher potential is required to force the current
through water than to force it through thick copper'wire.
In all these cases we might think that energy is lost, but
we cannot believe this. The kinetic energy of the flying
bullet becomes transformed into the increase of the
kinetic energy of the molecules of the metal of which
the bullet was composed ; for the latter becomes greatly
heated when its flight is arrested ; and this increased
heat ought to be equal to the kinetic energy of the
bullet in flight. The red-hot piece of iron cools, and
the kinetic energy of its molecules becomes less and less,
but this does not cease to exist, for the energy is simply
transferred by radiation and conduction to the sur-
rounding bodies, the temperature of which it raises.
The golf-ball driven up the hill comes to rest and loses
its kinetic energy. Some of this has been transferred
to the air through which it passes, the latter being
heated very slightly ; some of it is expended by friction
with the grass over which the ball rolls before coming to
rest, and this energy is traceable in heat-effects, or in
mechanical eft'ects, but the rest of it apparently ceases
to exist. But this would be contradictory to the
principle of conservation, and so we say that the lost
kinetic energy has become potential. The current of
electricity may heat the water through which it passes,
and some of the energy which seems to disappear is so
to be traced, but the greater fraction is apparently lost.
A quantity of free hydrogen and oxygen is, however,
generated, and we say that the kinetic energy of the
moving electrons has become transformed into the
potential chemical energy of the gaseous mixture.
POTENTIAL ENERGY
Therefore, if energy disappears or appears, we do
not say that it is destroyed or is created : we invent
APPENDIX 359
potential energies, into which we suppose that the
energies in question have become transformed, in order
that we may still think of them as being subject to an
a priori principle of conservation. Although a particle
of radium continually generates heat, we do not there-
fore think of the first principle of energetics as being
invalidated, for we suppose that the energy which thus
appears was really potential in the atoms of radium.
But it was contrary to all our former experience of atoms
that they should contain any other energy than that of
their own motion, and so the further assumption was
made that the atom, at least the atom of the radio-
active substance, is really complex, and not simple, as
chemical theory demands. It is made up of smaller
particles, and possesses a definite structure. In certain
circumstances the atom may disintegrate, and the
energy which held together its particles, whether these
were simpler corpuscles or electrons, is given off as the
heat which the radio-active substance apparently
generates. The potential energy of the chemical atom
is therefore a hjrpothesis which has been devised in
order to preserve the validity of the law of conservation,
and the reality of this hypothesis is being tested by
investigation. If we accept it as true, are the deduc-
tions made from it justified in our experience ? That
is the test which must be satisfied in all the hypotheses
where potential energies are invented, and the potentials
are only real if the test is satisfactory. The golf ball
at rest at the top of the hill is a different entity from
the golf ball at rest at the bottom of the hill : it is
capable of developing energy, for a touch may cause it
to roll down the hill, when most of the energy which
was expended in order to drive it to the top of the hill
will reappear in the form of the kinetic energy of motion
of the ball. The atoms of hydrogen and oxygen which
360 THE PHILOSOPHY OF BIOLOGY
were dissociated by the energy of the electric current
are different things from the atoms of hydrogen and
oxygen which are combined together to form the mole-
cules of water. Their state when the gases are in the
elementary condition, or are " free," is that of mole-
cules moving rapidly and incessantly, rebounding from
each other after colliding with each other : they possess
energy of position — potential energy — because they are
separate from each other. If they " combine," as when
a minute electric spark explodes the mixture of gases,
they tractate together, and remain in proximity to each
other, becoming molecules of water. The energy which
became potential in the gaseous mixture, when the
electric energy of the current seemed to disappear, now
appears as the heat generated by the combustion, that
is, as the greatly increased kinetic energy of the mole-
cules of the gas (steam) which takes the place of the
mixture of hydrogen and oxygen. Previous to the
explosion this gas was a mixture of molecules of
hydrogen and oxygen (2H2+2O) at the ordinary
temperature, but after the explosion it consists of a
smaller number of molecules at a very much higher
temperature.
What is " energy of position " ? The golf ball at
the bottom of the hill was at a distance of R feet from
the centre of the earth, but at the top of the hill it is at
a distance of R+100 feet from the centre of the earth.
In the first case it was free to fall R feet, but in the
second case it is free to fall 2? +100 feet. The atoms
of the constituent molecules of water occupy the
position H - O - H, the bonds ( - ) indicating that
the atoms are very close together ; but when the
water is decomposed by an electric current, the
atoms occupy the positions O - 0-f H - H+H - H,
the (-I-) indicating that the atoms are relatively
APPENDIX 361
far apart from each other. Now the golf ball and
the earth; or the atoms of hydrogen and oxygen,
are physically the same material entities, whether
they are close together or far apart, yet when
the earth and the ball, or the atoms of oxygen and
hydrogen, are separated from each other, their " pro-
perties " are different from what they are when they are
close together. What is it that makes the difference ?
It is that which is between them. Is it, in the last case,
" the potential energy of chemical affinity " ? This
dreadful phrase is actually used in a recent book on
biology : "In the elements carbon and oxygen, so
long as they remain separate, a certain amount of
energy remains latent. When the carbon and oxygen
atoms are allowed to come together and unite, this
potential energy of chemical affinity is liberated as
kinetic energy/." What is changed by the tract at ion
and pellation (the terms suggested by Soddy in place
of the anthropomorphic ones, "attraction" and " re-
pulsion ") ? It is the ether which has become changed
in some way. Potential energy resides therefore in
the ether of space.
ISOTHERMAL AND ADIABATIC CHANGES
Let us consider the changes which occur in a gas
under the influence of changes in temperature and
pressure, premising that the remarks which we have
to make can be applied to bodies in the liquid and
solid conditions, with some necessary modifications.
A gas, then, consists of a very great number of particles,
or molecules, in motion. These molecules move in
straight lines at very high velocities, and if the envelope
in which the gas is contained is a restricted one, the
molecules collide with each other, and with the walls
362
THE PHILOSOPHY OF BIOLOGY
of the envelope ; and, being assumed perfectly elastic,
they rebound from each other, and from the walls of
the vessel, with the same velocity which they had when
they collided. The pressure of the gas (say that of
steam at a temperature of iio° C, and a pressure of
120 lbs. to the square inch in a steam boiler) is the sum
of the impacts of the molecules on the walls of the
containing vessel. When the temperature is high
the molecules are moving at a higher mean velocity
than when the temperature is lower, and their mean
free path tends to become
greater. The volume of a
certain mass of gas, that is,
the volume occupied by a
certain very great number
of molecules, is greater the
higher is the temperature,
provided the envelope is
one capable of yielding. If
,p we reduce the capacity of
the envelope in which the
gas is contained, the pressure
will rise, for the intrinsic
energy of the gas is still the same ; but we have done
work on it, and by the law of conservation this work,
or at least the energy represented by it, must still
exist. It is represented by the decreased length of
free path of the molecules, and this means that the
impacts on the walls of the vessel will be greater than
they were. There is, therefore, a certain relation
between the volume of a gas and its pressure, and this
relation can be represented by an equation involving
the temperature, the pressure, and the volume.
The diagram represents the pressure and the volume
of a gas when these things change. There are two
Fig. 29.
APPENDIX 363
conditions, (i) when the heat developed by the com-
pression is allowed to escape through the walls of the
vessel to the outside, or when the heat lost in the ex-
pansion of the gas is compensated by the conduction
of heat through the walls of the vessel from outside ;
and (2) when the heat developed is retained in the gas,
as when the latter is contained in a vessel the walls of
which do not conduct heat. The pressure of the gas is
measured along the horizontal axis, and the volume is
measured along the vertical axis, and a curve is drawn
so that for any value of the pressure there is a cor-
responding value of the volume. Thus the values of
the pressures p and pi in the diagram correspond to the
value of the volume v. The curve relating the change
of pressure with a corresponding change of volume is,
in general, that called a rectangular hyperbola. But
there are two kinds of such curves : (i) that which we
obtain by plotting the corresponding ^^alues of pressure
and volume, when the temperature of the gas remains
constant throughout the series of changes, that is,
when the rise of temperature which would occur
when the gas is compressed is compensated by the
conduction of this heat to the outside of the vessel
containing the gas. Such a series of changes of pres-
sure and volume is called an isothermal one. (2) When
the heat developed by the compression of the gas is
retained in the gas, as when the walls of the vessel in
which these changes are effected are such as do not
conduct heat : such a series of changes is called an
adiabatic one. Adiabatic curves are steeper than are
isothermal ones.
THE CARNOT ENGINE
This is an imaginary mechanism which performs a
certain cycle of operations. It does not really exist.
364 THE PHILOSOPHY OF BIOLOGY
but the conception of its operation is of the
greatest value in the consideration of energy-trans-
formations, and it is for this reason that we discuss
it here.
Consider a gas, or some other substance capable
of expanding or contracting. It contains intrinsic
energy, and it is capable of doing work. Thus, since
a gas can expand indefinitely it can be made to do
mechanical work. A mass of gas at a pressure pu and
having a volume Vi, and at a temperature T°, can do
work by expanding till its pressure is reduced to
„o ^o p, and its volume
\ \ increased to v. If
\ \N it expands adia-
""" V^ batically its tem-
i\^^ perature will fall
: ^^^^?^=^^/o^ pose that t° is the
; .JT^""*=^z"' temperature of
1 1 i> the surrounding
pjj, 30 ' medium : the gas
cannot therefore
cool further, and we can obtain no more work from it.
If the gas is the substance which v/e wish to employ
as the working substance in the Carnot engine, we
must therefore bring it back to the condition repre-
sented by A . That is, we must raise its temperature
to T°, we must reduce its volume to Vi, and we must
increase its pressure to pi.
Thus the steam of an engine is (say) at a temperature
of 110° C, and a pressure of 120 lbs. to the square inch.
When it has passed through the cylinder and condenser
it is water at a temperature of, say, 15° C, and it is at
atmospheric pressure. We must, therefore, bring it
back to its former condition by heating this water in
APPENDIX
365
the boiler till it is steam under the former conditions
of temperature and pressure.
Therefore we must, in order to obtain a self-acting
engine, cause the working substance, and the mechanism
of the engine, to perform a series of cyclical operations.
The Camot engine is a cylinder containing a gas
called the working substance S, and this gas can
be brought into thermal contact with a source
of heat, or a refrigerator, that is, the gas can be
heated or cooled by a mechanism
outside itself. The walls of the
cylinder are made of some substance
which is a perfect non-conductor of
heat, but the bottom of the cylinder
is made of a substance which con-
ducts heat perfectly. There is a
piston in the cylinder which fits it
closely, but which moves up and down
without friction. At the bottom of
the latter is a valve which can be
turned so as to place the bottom of
the cylinder, and therefore the gas,
in thermal contact with a reservoir
of heat (4-), or a refrigerator (-).
But when the valve is turned so that the non-con-
ducting part 0 fills the bottom, the gas is perfectly
insulated, and heat can neither enter nor leave it.
Such an engine is, of course, an imaginary one, since
there can be no mechanism in which there is not a
certain amount of friction between moving parts, and
there are no substances which conduct or insulate
heat perfectly. The engine is, in fact, the limit to a
series of engines each of which is supposed to be more
perfect than the last one. It is a fiction which is of
considerable use in theoretical work.
Fig. 31.
366
THE PHILOSOPHY OF BIOLOGY
THE CARNOT POSITIVE CYCLE
We have therefore a substance which can be heated
by contact with a hot body, and which can then
expand, doing mechanical work by raising a piston,
and perhaps turning a flywheel, and on which work
is then done so that it returns to its original condition.
This is a cycle of operations. If we consider only the
changes which occur in the working substance we can
represent these changes by a diagram.
.c
«
V <5a uni'h of
N^ / heoit enter
Q, un'/Ts ^
of heat lecLi^e
—* IncreoLS i n^ uolume ^
Fig. 32.
First operation, (i->2). We suppose that the valve
is turned so that the non-conducting plug closes the
cylinder. The piston is in the position II (Fig. 31).
Heat cannot then enter or leave the gas. But the
latter already contains heat : it is at a temperature
of Tj^, so that it can expand doing work. Let it
expand, forcing up the piston. During this operation
the pressure of the gas will fall from a point on the
vertical axis opposite i to a point opposite 2, and its
volume will increase from a point on the horizontal
axis beneath i to a point beneath 2. It will cool
because it has expanded, and no heat is allowed to
APPENDIX 367
enter it during this act of expansion. The expansion
is therefore adiabatic ; the temperature falls from
Ta^ to Ti° ; and work is done hy the gas.
Second operation, (2^3). The piston is now at the
position I, that is, at the upper end of its stroke, and
we must bring it back again to the lower end of the
cylinder. The valve is turned so that the bottom of
the cylinder is placed in thermal communication with
the refrigerator ( - ), and the piston is pushed in to the
position II. The gas is therefore compressed until its
volume decreases from a point beneath 2 to a point
beneath 3. As it is being compressed, heat is generated
and its temperature would rise, but as this heat is
generated it flows into the refrigerator, so that the
temperature of the gas remains the same during the
operation. The contraction is therefore an isothermal
one ; the temperature remains at T,° \ and work is
done on the gas from outside.
Third operation, (3->4). But the piston is not
at the lower end of its stroke yet. We turn the valve
so that the bottom of the cylinder is closed by the
non-conducting plug 0, and then push in the piston
until it reaches the position III. The gas is still
further compressed, and this compression generates
heat. But the heat cannot escape, so that the tempera-
ture of the gas rises until it reaches T°. The con-
traction is therefore an adiabatic one. Work is done
on the gas.
Fourth operation, (4^1). The piston is now at the
lower end of its stroke. We turn the valve so that the
bottom of the cylinder is placed in communication
with the source of heat (+). The gas expands from
the point beneath 4 to the point beneath i, raising
the piston to the position 11. This expansion of the
gas would lower its temperature, but it is in com-
368 THE PHILOSOPHY OF BIOLOGY
munication with the source of heat, and so it does not
cool, but draws heat from the source and remains at
a constant temperature, 7*2° • The expansion is there-
fore an isothermal one. Work is done by the gas.
This completes the cycle. But the gas is heated,
and when the piston is at position II, the valve is
turned so as to close the cylinder by the non-conduct-
ing plug 0. The heat already contained in the gas
continues to expand, the latter doing more work, but
this expansion causes the temperature to fall from
7^2° to T°. This is the operation with which the
cycle commenced.
Summarising the positive Carnot cycle, we see that
the engine takes heat from a source (+) and gives up
part of this to a refrigerator ( - ), (in an actual steam-
engine heat is taken from the boiler and given up to
the condenser water). If we measure the quantity of
heat taken from the boiler in the steam which enters
the cylinders we shall find that this quantity of heat is
greater than the quantity which is given up to the
condenser water. What becomes of the balance ? It
is converted into the mechanical work of the engine.
The Carnot engine therefore takes a quantity of heat,
Q^, from the source and gives up another quantity of
heat, Qi, to the refrigerator. We find that Q.2 is
greater than Qu and the balance, Q^ - Q^ is represented
by the work done by the engine. Heat-energy falls
from a state of high, to a state of low potential, and is
partly transformed into mechanical work.
THE CARNOT NEGATIVE CYCLE
This is simply the positive cycle reversed. The
reader should puzzle it out for himself if he is not
already familiar with it. It consists of an adiabatic
APPENDIX 369
contraction 2-^1, an isothermal contraction i->-4, an
adiabatic expansion 4-^3, and an isothermal expansion
3^2. A quantity of heat, Q^, is taken from the refrig-
erator at a temperature Ti°, and another quantity, Q^,
is given up to the source at a temperature 7^2°. But
Q-i is greater than Qi, and the engine therefore gives up
more heat than it receives, while, further, heat flows
from a body at a low temperature to another body at
a higher temperature. Where does the engine get
this energy from ? It gets it because work is done
upon it by means of an outside agency, and all of
this work is converted into heat.
REVERSIBILITY
The Carnot engine and cycle are therefore perfectly
reversible. Not only can the engine turn heat into
work, but it can turn work into heat. This perfect,
quantitative reversibility is, however, a property of the
imaginary mechanismx only, and it does not exist in
any actual engine.
ENTROPY
Let us consider the cycle more closely. In the
operation 4^1, which is an isothermal expansion, there
is a flow of heat-energy from the source and a trans-
formation of energy into work. The gas in the con-
dition represented by the point 4 had a certain pressure
and a certain volume. In the condition represented by
the point i, its pressure has decreased, its volume has
increased, and its temperature is the same. Its physical
condition has been changed, and to bring it back into its
former condition something must be done to it. Let,
then, the gas continue to expand without receiving
any more heat, or parting with any : that is, let it
2 a
370 THE PHILOSOPHY OF BIOLOGY
undergo the adiabatic expansion i->2 until its tem-
perature falls to that of the refrigerator, T^"". We now
compress the gas while keeping it at this temperature,
that is, we cause it to undergo the isothermal con-
traction 2->3, during which operation it is giving up
heat to the refrigerator, so that there is again a flow
of heat-energy. We then compress it still further
without allowing heat to escape from it, that is, we
cause it to undergo the adiabatic contraction 3^4.
During this operation the gas rises in temperature to
T2°- It is now in the condition that it was when the
cycle commenced.
In this cycle of operations heat first entered, and
then left the gas, and with this entrance or rejection
of heat, the condition of the gas with respect to its
power of doing work changed. We investigate this
flow of heat, and the concomitant change of properties
of the substance, with regard to which the flow took
place, by forming the concept called entropy. We
make the convention that when heat enters a substance
the entropy of the latter increases, and when heat
leaves it its entropy decreases. We call the quantity
of heat entering or leaving a substance Q, and the
temperature of the substance T. Then ^ is pro-
portional to the change of entropy of the substance
when the quantity of heat, Q, enters or leaves it.
Now it is a fact of our experience that heat can
only flow, of itself, from a hotter to a colder body.
Consider two such bodies forming an isolated system,
the temperature of the hotter one being T^ , and that
of the colder one Ti'. Let Q units of heat flow from
the body at T/ to that at Ty no work being done.
Then the loss of entropy of the hotter body is ^o, and
1 1
APPENDIX 371
the gain of entropy of the colder body is ^^. The
-t 1
nett change of entropy of the system is ^ - ^.
Since T^"" is greater than Ti", ^^ is less than ^, . There-
fore the expression ^^ - ^^ is positive, that is, the
entropy of the system, as a whole, has increased.
When heat flows from a hotter to a colder body
the nett entropy of the two bodies, therefore, in-
creases.
But we can also cause heat to flow from a colder to
a hotter body by effecting a compensatory energy-trans-
formation. Such a compensation would not occur by
itself in any system capable of effecting an energy-
transformation, if it is to be effected some external
agency must act on the transforming system. We
can suppose it to happen m a perfectly reversible
imaginary mechanism.. Suppose a Camot engine works
in the positive direction, taking heat from a reservoir
at temperature 7*2°, and giving up part of this heat to
a refrigerator at Ti\ and doing a certain amount of
work W. Suppose that this work is stored up, so to
speak, say by raising a heavy weight, which can then
fall and actuate the same Camot engine in the opposite
(negative) direction. The engine then exactly reverses
its former series of operations. The work it did is
reconverted into heat, and as much of this heat flows
from the refrigerator into the source, that is, from a
colder to a hotter body, in the negative operations, as
flowed from the source to the refrigerator in the
positive operations. In this primary energy- transfor-
mation, combined with a compensatory energy-trans-
formation, there is no change of entropy. The
372 THE PHILOSOPHY OF BIOLOGY
mechanism is an ideal one — the limit to an irreversible
mechanism.
But— and now we appeal to experience and cease to
work with ideal mechanisms — the actual engine which
we can design and work is one in w^hich there will be
friction, in which some parts will conduct heat im-
perfectly, and other parts will insulate heat imperfectly.
Let the friction generate q units of heat, and let the
quantity of heat which is " wasted " by imperfect
conduction and insulation be q^^. This heat will flow
into the refrigerator, or will be radiated or conducted
to the surrounding medium, which we suppose to
be at the same temperature as the refrigerator. If,
then, we divide this total quantity of heat by the
temperature T°, we get -^j^=Si as the quantity
of entropy which is generated as the result of
the imperfections of the engine, in addition to the
quantity of entropy, S, which would be generated
if the engine were a perfect one. Both S and S.
are positive.
Also in the working of the engine in the negative
direction a certain quantity of entropy. Si, is generated
for reasons similar to those mentioned above.
The entropy generated when the engine works in
the positive direction is therefore S+5i, and when it
works negatively the quantity generated is also Si.
The entropy destroyed when the engine works negatively
is S. The total change of entropy is therefore 2S1+S
- S, that is, 2S1. In an actual energy-transformation
combined with a compensatory energy-transformation
there is therefore an increase of entropy.
We can generalise these statements so that they
will apply not only to a heat-engine but to all mechan-
isms which effect energy-transformations. In all such
APPENDIX 373
transformations entropy is generated. Therefore the
Entropy of the Universe tends to a maximum.
AVAILABLE AND UNAVAILABLE ENERGY
Consider the Carnot engine as a perfect mechanism.
It takes heat-energy from a source at a temperature
Ta", and it gives up heat to a refrigerator at a tempera-
ture T°, Ti° being greater than T^". In the adiabatic
expansion 1^2 the gas continues to expand until its
temperature becomes equal to that of the refrigerator.
It cannot, then, expand and do work any longer, and
thus the proportion of the heat, Q.2, received from the
source, which can be converted into work, depends on
the difference of temperature 2^2° - T^°. The greater
is this difference the greater will be the proportion of
the heat-energy received which can be converted into
work. If the engine were a perfect one, and if the gas
were also a perfect one (that is a gas which would
continue to expand according to the equation for the
adiabatic expansion of gases), and if the refrigerator
were absolutely cold, then all the heat energy received
from the source could be converted into work.
We cannot produce a refrigerator of absolute tem-
perature 0°, and therefore only a certain proportion
of the heat which is received by the engine can be
transformed into mechanical work. But this work
can be used to reverse the action of the engine, and
thus the same fraction of the total heat-energy which
was given to the refrigerator can be taken from it and
given back to the source. The perfect engine is there-
fore reversible without loss of available energy.
Now consider still the engine as a mechanism which
takes heat from a source and gives it to a refrigerator,
but let it be an actual engine. Instead of giving up
374 THE PHILOSOPHY OF BIOLOGY
a certain fraction of the heat received to the refriger-
ator — a fraction equal to Qi ^jh, it gives up rather
more, because it is not a perfect mechanism, that is, it
generates friction, etc. Some of the heat received
thus ceases to be available for the performance of
work; and passes into the refrigerator. The fraction
of the heat-energy which passes into the refrigerator
in the perfectly reversible engine was unavailable
energy in the conditions in which the mechanism
worked, or was imagined to work, but in the actual
engine this fraction is increased. If we divide the
increase of unavailable energy by the temperature of
the refrigerator, the product is the increase of entropy
generated in the actual engine over that generated
in the ideal engine. Because of this reduction of
available energy the actual engine is an irreversible
mechanism.
This is the connection between unavailable energy
and entropy. In all transformations some fraction
of the transforming energy becomes heat, and this
heat flows by conduction and radiation into the sur-
rounding bodies. In general this heat simply raises
the temperature of the medium into which it flows,
and becomes unavailable for further transformations.
With every transformation that occurs some part of
the energy involved becomes unavailable. Therefore
although the sum of the available and unavailable
energy of the Universe remains constant, the fraction of
unavailable energy tends continually to a maximum.
INERT MATTER
We can see now what is indicated by Bergson's
*' inert matter." It is not matter deprived of energy
APPENDIX 875
— such an expression has no meaning — it is energy
which is unavailable for further transformations.
The matter in which we choose to say that this
energy is inherent has become inert. Let us substitute
for the Camot engine the actual steam-engine of a
ship, the condenser of which is cooled by the sea water
which is taken in, and which is then heated and flows
out again into the sea. The heat derived from the
source, that is, from the furnace of the boiler where
coal is burned to raise steam, thus passes out into the
sea. Now the heat capacity of the sea is so great
that the temperature of the water is not appreciably
raised by this heat, which drains into it from the
engine : even if it were appreciably raised, the heat
would be conducted into the earth, or would be radiated
out into space, and would then raise the temperature
of the material bodies of the universe. But let all
this heat remain in the sea. It then simply raises the
temperature of the water by an exceedingly small
amount, and the motions of the molecules become in-
finitesimally increased. But the heat becomes equally
distributed by conduction and convection throughout
the mass of the water in the sea, and as there are no
differences in adjacent parts there are no means where-
by the energy which thus passes into the sea can be
again transformed.
A new order of things is the result of the processes
we have indicated. The segregated, available heat-
energy of material bodies has become transferred to
the un-co-ordinated, diffuse, unavailable energies of
the molecules which compose these bodies. The
transformations which we can effect depend on the
condition that the energy which we utilise is that of
aggregates of molecules which are in a different physical
condition, as regards this energy, from adjacent aggre-
376 THE PHILOSOPHY OF BIOLOGY
gates. But when this energy becomes equally dis-
tributed among the molecules of all the aggregates,
the matter in which it inheres becomes inert. If we
could, by a sorting process like that of Maxwell's
hypothetical demons, a process which does not expend
the energy with which it deals, separate the molecules
which were moving slowly from those which were
moving more quickly, we could make this energy
again available. But it must clearly be understood
that our physics is the physics not of individual mole-
cules, but of aggregates of molecules.
INDEX
Absolute, Driesch's theory of, 47.
Acceleration (in physics), 355.
Acquired characters
induced by the environment, 216 ; a means of transformism, 220
evidence of transmission scanty, 225 ; transmission not inconceivable,
226,
Actions, categories of, and consciousness, 282 ; deliberative, 283 ; mechanistic
hypothesis of, 157 ; stereotyped, 283 ; at a distance, 304.
Activation of the ovum, 176.
Adaptability, indicative of dominance, 258.
Adaptation, 217 ;
and acquired characters, 219 ; and changes of morphology and function,
219 ; not inherited, 220; causes of, 239.
Adaptive response, 219.
Adiabatic changes, 361,
Aggregates, molecular, 353.
Algae, distribution of, 260.
Allelomorphs, Mendelian, 231.
Alternation of generations, 175.
Amido-substances, 88
Anabolism, 88.
Anatomical parts, homologies of, 251.
Animal action, considered objectively, 278.
Animal and plant contrasted, 269
Animality, 269.
Annectant forms of life, 253.
Annelids, morphology of, 248.
Anthropomorphism in theories of action, 148.
Anti -enzymes, 94.
Antitoxins, 36.
Ants, a dominant group, 260.
Appendix vermiformis, 250.
Approximation, standards of, 347.
Armoured animals, 263.
Arthropods, morphology of, 249 ;
a dominant group, 259 ; distribution, 260 ; musculature of, 275 ; adapta-
tions for mobility, 275 ; limits to size of, 275.
Assimilation, 67.
Atoms, constitution of, 355 ;
arrangements of, 353.
3-7
378 THE PHILOSOPHY OF BIOLOGY
Automatism of animals deduced from mechanistic theories, 280,
Autonomy in development, 322.
Available energy, 62 ;
and entropy, 374.
Bacteria, a dominant group, 259 ;
distribution, 259 ; geological history, 259, 261 ; morphology, 268 ;
metabolism, 266; specialisation, 263; parasitism, 259; nitrogen, 73;
prototrophic, 119, 266; paratrophic, 266 ; putrefactive, 266; fermenta-
tion, 266 ; and Brownian movements, 119; compensatory to plants, 267.
Bergson, 28 ; .- ^ f H l//'
creative evolution, 244 ; duration, 154 ; animals and plants, 78 ; eye of
Pecten, 234 ; inert matter, 375 ; infinitesimal analysis of the organism,
in; kinematographic analysis, no; theory of intellectualism, 51;
memory, 156 ; morphological themes, 250 ; theory of pain, 281 ; theory
of perception, 7, 10 ; the vital impetus, 318. ;
Biology, systematic, 201, 203.
Biophors, 132 ;
size of, 183 ; growth of, 185.
Biotic energy, 325.
Borelli and animal mechanism, 125.
Brownian movement, 118 ;
significance of, 119.
Bryan and thermodynamics, 62.
Bud-formation, 165.
Calculus, infinitesimal, 25, 115, 350.
Calorimetric experiments, 65, 68.
Capacity-energy factors, 61.
Carnot's cycle, 69, 78, 113 ;
negative, 368 ; description of, 363, 366 ; compared with plant meta-
bolism, 75 ; compared with the organism, 72>-
Catalysis, 90 ;
universality of, 91.
Catalysts, characters of, 91.
Categories of organisms, 209.
Central nervous system, specialisation of, 273 ;
a switchboard, 273 ; evolution of, parallel with evolution of muscular
system, 281.
Chance in evolution, 237.
Chemical affinity, 361.
Chemical energy, degradation of, 75.
Chemical reactions, direction of, 78 ;
exothermic, 86 ; explosive, 86 ; similar in organic and inorganic
systems, 78.
Chemical synthesis, involve vital activity, 318.
Chemistry, medieval, 125.
INDEX 379
Chlorophyll, 69.
Chlorophyllian organisms, 88 ;
metabolism of, 265 ; a dominant group, 259 ; essential morphology ot,
268 ; distribution of, 260.
Chromatin of the nucleus, 130 ;
the material basis of inheritance, 182.
Chromosomes, 130, 182, 183.
Classification of organisms, 209.
Classificatory systems, are artificial arrangements, 289 ;
suggest evolutionary process, 210.
Clausius, 54 ;
and Camot's Law, 113.
Coelenterates, morphology of, 248.
Ccelomate animals, 256.
Colloidal platinum, 91.
Colloids, 107.
Colonial organisms, 164.
Comparative anatomy, task of, 251.
Compensatory energy-transformations eftected by life, 309.
Conjugation, 173 ;
and heredity, 176 ; a stimulus to growth, 175.
Consciousness
involves analysis of the environment, 1 1 ; analysis of, is an arbitrary
process, 12 ; a feeling of normality, 6 ; a part of crude sensation,
40 ; simplified by reasoning, 41 ; an intensive multiplicity, 303 ;
degree of, is parallel to development of sensori-motor system,
280 ; not existent outside ourselves, 278 ; not a function of chemico-
physical mechanism, 160 ; intense in difficultly performed operations^
281 : and activity of cerebral cortex, 281 ; absent in parasites,
291.
Conservation a test of reality, 357.
Conservation of energy, 52 ;
in organisms, 83.
Conservation of structure, 253, 256.
Constants, mathematical, 344.
Continuity of cells in embryo, 171.
Contractility, 100 ;
muscular, 103.
Co-ordinates, systems of, 23.
Corals, 164.
Cosmic evolution, 314 ;
is a tendency towards degradation of energy, 316.
Creation, special, 214.
Curvature, 27.
Curves, isothermal and adiabatic, 362.
Cuttle-fishes, 250.
Cytoplasm, 130.
380 THE PHILOSOPHY OF BIOLOGY
Darwin, and natural selection, 221 ;
acquired characters are inherited, 220 ; hypothesis of pangenesis, 181.
Death, is catastrophic katabohsm, 340.
Degradation of energy, 81.
Deliberation and consciousness, 281.
Demons, Maxwell's, 116.
Descartes and mechanism, 121 ;
the rational soul, 123, 318 ; his physiology, 122 ; his spiritualism, 124 ;
and animal automatism, 125.
Descent, collateral, 257.
Determinants in embryology, 132, 183 ;
arrangement of, 184 ; latent in regenerative processes, 142.
Development, organisation in, 128 ;
parthenogenetic, 176 ; reverses inorganic tendencies, 324 ; impossibility
of chemical hypotheses, 141 ; is the assumption of a mosaic structure,
301 ; blastula stage in, 129 ; gastrula stage in, 130; pluteus stage in,
140 ; individual, 300.
Developmental systems
prospective value of, 138 ; prospective potency of, 138.
Diatoms, 163 ;
distribution of, 260.
Dififerential elements, 115.
Differentiation in development, 170.
Diffusion in the animal body, 95.
Digestion, 67 ;
chemistry of, 72.
Dinosaurs, an unsuccessful line of evolution, 275.
Dissipation of energy, 114 ;
in physical mechanisms, 59 ; by the organism, 68, 79.
Distribution of organisms, 262 ;
limits to, 259 ; indicative of dominance, 258,
Diversity, physical, 54.
effective and ineffective, 115.
Dominance
in geological time, 258; implies long geological history, 261 ;
Mendelian, 196.
Dominant organisms, 258, 259, 264.
Driesch
natural selection, 229 ; analytical definition of the organism, 331 ;
entelechy, 318; experimental embryology, 134; historical basis of re-
acting, 154; logical proof of vitalism, 136; proof of vitalism from
behaviour, 153 ; theory of the absolute, 47.
Duration, 28 ;
duration and time illustrated, 30 : illustrated by immunity, 35 ; more
than memory, 155 ; a factor in responding, 155.
Ecdysis, 276.
INDEX 381
Echinoderms, morphology of, 248.
Ectoderm, 177.
Effector organs, 158, 271.
Elan vital, 161.
Electromagnetism, 355.
Electrons, 304, 355.
Elimination, natural, 229.
Embryological stages compared with physical phases, 308.
Embryology, 127 ;
hypotheses of, 128; physical hypotheses fail, 128 ; experimental, 128;
suggests phylogenetic history, 213.
Emulsoids, 108.
Endoskeleton, 177, 276.
Energetics, first law of, 51 ;
second law of, 113.
Energy, 356 ;
available and unavailable, 55 ; biotic, 325 ; chemical, 61 ; and causation,
54 ; degradation of, 63 ; dissipation of, 53 ; electrical, 61 ; forms of,
325 ; kinetic, 52, 357 ; mechanical, 60, 61 ; potential, 53, 358 ; of posi-
tion, 360.
Energy-transformations, 54, 371 ;
anabolic, 89 ; in the animal, 70 ; compensatory, 88 ; compensatory
organic, 268; irreversible, 59 ; in physical mechanisms, 58 ; in the plant, 71.
Engelmann, and the artificial muscle, 105.
Entelechy, 161, 318 ;
not energy, 329 ; is power of direction, 329 ; not spatial but acts into
space. 330 ; an intensive manifoldness, 330 ; is arrangement, 323 ;
involves regulations, 323 ; arrests inorganic happening, 327 ; initiates
chemical happening, 327 ; compared with enzyme action, 327 ; illustrated
by analogy, 322.
Entropy, 54 ;
augmentation of, 75 ; and Carnot engine, 369.
Environment, does not select variations, 235 ;
made by the organism, 236.
Enzymes, 90 ;
nature of, 92 ; pancreatic, 93 ; reversible, 93 ; activation of, 92.
Enzyme activity, 93.
Epigenesis in development, 129.
Equilibrium, chemical, 102.
false, 86, 151.
Ether of space, 46, 304, 361 ;
potential energy resides in, 361.
Evolution
tendencies of, 252, 264, 276, 295 ; separation of tendencies, 296 ; a trans-
formation of intensive into extensive manifoldness, 309 ; a dissociation
of tendencies originally coalescent, 305 ; increases diversity, 310 ;
segregates energy, 311 ; compared with permutations and combinations,
382 THE PHILOSOPHY OF BIOLOGY
301 ; a series of phases in a transforming system, 298 ; a logical hypo-
thesis, 214 ; parallel processes in, 234 ; geological time inadequate for
237 ; side paths in, 262 ; mechanistic hypotheses inadequate, 237 ;
cosmic, 214, 297, 314 ; of the crust of the earth, 264.
Excretory products, 269.
Exoskeleton, 276.
Exothermic reactions, 86.
Experience and duration, 156.
Experimental biology proves evolution, 246.
Explosive reactions, loi.
Extension in space, 18.
Extinct groups, 263.
Fats, digestion of, 93.
Fecundity of animals, 179, 239.
Ferments, 92.
Fertilisation (in reproduction), 176.
Finalism, 216.
Fishes, distribution of, 261.
Fluctuating variations, 200.
Food-stuffs, absorption of, 89.
Force, 354.
Form, accidental and essential, 167, 353 ;
geological, 168 ; crystalline, 168.
Frequency distributions, 22, 187, 350.
Frog, development of egg of, 131.
Functionality, 343 ;
in physical systems, 307.
Galvanotropism, 145.
Gases, compression of, 362 ;
kinetic theory of, 117, 361.
Gastrea-theory, 177;
illustrated, 255 ; limitations of, 256.
Genera, stability of, 186.
Geometry, Cartesian, 25 ;
Euclidean, 19, 25 ; perceptual and conceptual limits, 21.
Geotropism, 144.
Germ-cells, 175 ;
and soma, 179.
Germinal selection, 241.
Germ-layers, 177 ;
theory of, 256.
Germ-plasm, a mixture, 240 ;
stability of, 240.
Givenness, 47.
Gonads, 179
INDEX 383
Growth
law of, in the organism, 172; by accretion, 169; by ecdysis, 276;
geometrical, 169 ; physical, 167 ; of crystals, 167 ; and differentiation,
170; variability of, 172.
Haeckel, the Gastrea-Theorie, 177, 254.
Harmonic analysis, 11.
Harvey, and the circulation of the blood.
Heat, flow of, 117 ;
production of, in physical changes, 114.
Heliotropism, 144.
Heredity, 181.
Hertzian waves, 355.
Homoiothermic animals, 67.
Hormones, 225.
Human activity, tends to arrest dissipation of energy, 312.
Huxley, 84 ;
and mechanistic biology, 127 ; and the physical basis of life, 113; and
mechanism, 106 ; and universal mathematics, 215.
Hybrids, Mendelian, 196 ;
infertility of, 195 ; between Linnean species, 194,
Hydra, regeneration of, 162.
Idants, 183.
Idealism founded on pure reasoning, 45 ;
of Berkeley, 45.
Ids, 183.
Immunity, 35.
Individual, 162 ;
definition of, 167.
Individuality, orders of, 163 ;
physical concept of, 165 ; morphologically an artificial concept, 166 ;
in societies, 171.
Inertia, 354.
Infinity, a definition of, 342.
Inorganic happening abolishes diversity, 310.
Instinct, a problem for naturalists, 283 ;
an inheritable adaptation of behaviour, 287.
Instinct and intelligence, 283 ;
distinction not absolute, 294 ; may coexist, 306.
Instinct and functioning, 286.
Instinctive actions not necessarily unconscious, 283 ;
not learned, 286 ; not necessarily perfect, 284 ; effective from the first,
285 ; capable of improvement, 285.
Intelhgent actions, non-inheritable adaptations of behaviour, 287 ;
involve deliberation, 50, 287 ; involve conscious relations with the
environment, 288 ; involve use of tools, 284.
384 THE PHILOSOPHY OF BIOLOGY
Intensity-factors, 6i.
Intensive multiplicity, 303.
Irreversibility, 62.
Irritability, 100.
Isothermal changes, 361.
James, William (and academic philosophies), 80.
Jennings, and physiological states, 154 ;
behaviour of Protozoa, 293 ; animal movements, 149 ; the avoiding"
reaction, 149.
Katabolism, 90.
Kinases, 92.
Kinematographic analysis, 316.
Lamarck, hypotheses of evolution, 220.
Lamarckian inheritance, an inadequate cause of transformism, 227.
Lankester, acquired characters not inherited, 221.
Laplace, and universal mathematics, 215.
Laplacian mind, 299.
Larval stages, 170.
Latency (of characters), 195.
Lavoisier, and chemistry of the organism, 127.
Life
and adaptation to physical conditions, 338 ; and reversibility, 339 ; a
direction of energies, 341 ; defined energetically, 337 ; cosmic origin of,
338 ; physical conditions for, 338 ; limited in power, 306 ; sparsity of,
on the earth, 306 ; tends to arrest dissipation of energy, 314 ; its origin
a pseudo-problem, 337.
Life-substance, the primitive, 301.
Locomotion, 258.
Loeb and the associative memory, 155 ;
and artificial parthenogenesis, 176; mechanism and life, 127; stereo-
tropism, 19 ; theory of tropisms, 144 ; tropistic movements, 146 ;
theories of heredity, 181.
Limit, the mathematical, 346.
Limits to perceptual activity, 23.
Links, missmg, 252.
Linnean species, 201.
Manifoldness, intensive, 302.
Mass, 353.
Mass action, 140.
Materialism., 85.
Mathematics, evades consideration of time, 35.
Matter, 353 ;
inert, 375 ; notion of is an intuitive one, 352.
Maxwell, and sorting demons, 116, 377.
INDEX 385
Mayow, and chemical physiology, 126.
Mechanical work, done by the animal, 67 ; not done by the plant, 71
Mechanism, organic and inorganic, 78; i- ' /
the thermodynamic, 66 ; radical, 215 ; in life, 121
Membranes, semi-permeable, 95.
Memor>', 39 ;
a possible cerebral mechanism of, 158; mechanistic hypotheses
impossible, 157.
Mendelism, 196 :
a logical hypothesis, 199 ; terminology is a symbolism, 198 ; analo-y of
unit characters with chemical radicles, 197 j transmission of characters
01, 230.
Mesoderm, 177 ;
origin of, 255.
Metabolism, ^7, 88, 209 ;
analytic, 269; of animals, 65,675 constructive, 269; destructive, 269 ;
direction of, 69 ; m green plant, 70, 7S ; intra-cellular, 99; integration
of Its activities, in; role of oxygen in, 105; specialisation of durin the dominant, 258; a function of the environment, 216;
a mechanism, 51 ; the primitive, 222; a physico-chemical system, 65 ;
a thermodynamic mechanism, 104.
Organic chemical syntheses, 317.
Organisation in development, 137.
Organ-rudiments, 257.
Osmosis, 95, 99.
Ostracoderms, 291.
Ostwald on catalysis, 91.
Ovum, development of, 129 ;
maturation of, 198, 239 ; an intensive manifoldness, 302
Oxidases, 105.
Oxygen in metabolism, 69.
Pain, Bergson on, 281.
Palaeontology, 210 ;
relates groups of organisms, 211.
INDEX 387
Pangenesis, i8i.
ParamcEcium, division of, 173, 175 ;
responses of, 4.
Parasitism, 259 ;
tends to immobility, 290.
Parthenogenesis, 176 ;
artificial, 176.
Particles, 356.
Pecten, eye of, 233.
Perception
not merely physical stimulation, 7 ; involves effector activity, 7 ;
involves deliberative action, 9 ; arises from acting, 50 ; and choice of
response, 155; is unfamiliar cerebral activity, 8 ; skeletonises conscious-
ness, 40.
Peridinians, ']'], 163 ;
distribution of, 260.
Personal equation, 45.
Personality, 167 ;
an intuition, 167 ; division of, 173 ; is absolute, 48.
Pfliiger, and experimental embryology, 131.
Phases in physical systems and organic systems, 321 ;
in transforming systems, 308.
Phenomenalism, 46.
Photosynthesis, 70, 76, 86.
Phototaxis, 144.
Phyla
animal, 247 ; morphology of, 247 ; relations between, 252 ; ancestries
of, 252.
Phylogenies, 253 ;
are summaries of morphological results, 254 ; indicative of directions
of evolution, 254 ; criteria of, 253.
Phylogeny, 246.
Phylum, 210.
Physical basis of life, 84.
Physico-chemical reactions, 80 ;
are directed, 118; the means of development and behaviour in the
organism, 160.
Physico-psychical parallelism, 160.
Physics, a statistical science, 116, yn.
Physiology
Galenic, 122 ; an analysis of organic activity, 120, 328.
Plants, geological history of, 261 ;
characterised by immobility, 277 ; contrasted with animals, 277.
Platonic ideas, 204.
Platyhelminths, morphology of, 248.
Poikilothermic animals, 68.
Poincar6, and Brownian movement, 119.
388 THE PHILOSOPHY OF BIOLOGY
Polar bodies, 198.
Polyzoa, 164.
Porifera, 248.
Potential, 61.
Potential energy, 58, 114. •
Preformation an embryological hypothesis, 128.
Probability, 350.
Proteids, digestion of, 90,
Proto-forms, 254.
Protoplasm, nature of, 106 ;
artificial, 106 ; disintegration of, 107 ; activities of, 107 ; similar in
plant and animal, 294.
Protozoa, 247 ;
behaviour of, 293.
Pterodactyls, 274.
Races (in specific groups), 194.
Radiation, 355 ;
of sun, 51 ; transformation of energy of, 57.
Radio-activity, 56, 359.
Reality, objective, 43.
Reception, 3 ;
organs of, 271 ; by specialised sense-organs, 11.
Recessiveness, Mendelian, 196.
Reflex action, 4, 272 ;
concatenated, 150; a complex series of actions, 6; not necessarily
accompanied by perception, 155; the basis of instincts, 150; a
schematic description, 5 ; in decapitated frog, 6 ; frictionless cerebral
activity, 8 ; involves a limited part of the environment, 50.
Reflex arcs, 272.
Regeneration, 142 ;
in Hydra, 164 ; in sea-urchin embryo, 164 ; in Planaria, 164.
Regression, 189.
Reinke, and structure of protoplasm, 106.
Reintegration in development, 171.
Rejuvenescence, 175.
Releasing agencies, 157.
Reproduction, 167;
asexual, 175 ; by brood-formation, 173 ; by conjugation, 173 ; sexual,
174; by division, 172; compared with minting machine, 242; of the
tissues, 180.
Responses of organisms, 217 ;
directed, 269 ; of magnet, 279 ; of green plant, 279.
Reversibility, physical, 369.
Rodewald, chemical nature of protoplasm, 106.
Roux, experimental embryology, 131 ;
development the production of a visible manifoldness, 307.
INDEX 389
Saliva, secretion of, g6.
Salivary glands, metabolism of, 96.
Salivary secretion, not a purely mechanistic process, 112.
Sea, not really rich in life, 306.
Sea-urchin gastrula, 170.
Secretion described mechanistically, 98.
Secretion, psychical, 99.
Segmentation of the ovum, 129.
Selection, natural, 228 ;
from fluctuating variations, 189 ; from mutations, 190.
Semon, mnemic hypothesis of heredity. 181.
Senescence, 175.
Sensation, 2 ; •
analysis of, 13.
Sense-receptors and the idea of matter, 352.
Sensori-motor system, 270 ;
dominant in animals, 271, 273 ; specialisation of, 271, 273 ; essentially
the same in all animals, 294 ; absent in plants, 269 ; vestigial in some
parasites.
Sexuality, 174.
Siphonophores, regeneration in, 163.
Size of animals, 274.
Skeleton of vertebrates, 276 ;
of arthropods, 276 ;
and mobility, 276.
Soddy, and chemical energy, 361.
Soma, 179 ;
evolution of, 223.
Space, form of, 18 ;
3-dimensional, 18; 3-dimensional space an intuition, 19; 2-dimensional,
19 ; the form of, depends on modes of activity, 21, 25.
Species, are categories of structure, 201 ;
comparison with Platonic ideas, 204 ; criteria of, 202 ; elementary, 193;
are intellectual constructions, 203 ; individuality of, 203 ; Linnean, 201,
289 ; are phases in an evolutionary flux, 206 ; are families in the human
sense, 208 ; systematic, 201.
Specific organisation, stability of, 186.
Stahl, and the phlogistic hypothesis, 126 ;
and vitalism, 126.
Stimuli, elemental, 151 ;
physico-chemical, 151 ; formative, 176; complex auditory, 152 ; integra-
tion of, 152; individualised, 152, 270; contractile, 103.
Stimulus and response, functionality of, 152.
Substantia physica, 46, 355,
Surface tension, 105, 106.
Suspensoids, 108.
Sylvius, the organism a chemical mechanism, 125.
390 THE PHILOSOPHY OF BIOLOGY
Symbiosis, ']'].
Symbiotic organisms, 88.
Synapses, in central nerv'ous system, 158, 272.
Synthetic chemistry, 236, 317.
System, isolated, 63.
Systems in development
equipotential, 139; harmonious equipotential, 139; complex equi-
potential, 140.
Taxis, 144 ;
no perception in, 155
Telegraphy, wireless, 355.
Temperature of sun, 56 ;
of space, 57,
Thermodynamics, 51 ;
1st law of, 51 ; 2nd law of, 54, 63, 309, 316; and Maxwell's demons,
118 ; laws of subject to limitations, 115.
Thermodynamical mechanism, the organism not a, 69.
Thomson, W., dissipation of energy, 113.
Time a series of standard events, 28 ;
astronomical, 34 ; time differentials, 34.
Tissues, evolution of, 223.
Tools, nature of, 285 ;
use of must be learned, 285 ; bodily, 285.
Toxins, 36.
Transformism, 213.
Trematodes, larval stages of, 165.
Trial and error, 293 ;
in reasoning, 293 ; a hypothesis of animal movem.ents, 1 50.
Trigger reactions, 87.
Trilobites, an ancient group, 261.
Tropisms, 144 ;
in plants, 269, 279; in moths, 280; and natural selection, 147; and
movements of caterpillars, 146; an inadequate basis for a theory of
animal movements, 147.
Tunicates, suppressed notochord of, 250.
Unavailable energy and entropy, 375 ;
tendency to increase of, 375.
Unicellular organisms, energy-transformations in, 177.
Unit-characters, 230.
Van't Hoff's law, 218.
Variability, 172, 186 ;
continuous, 188; discontinuous, 188; examples of, 187; and the en-
vironment, 189; independent of the environment, 239; and growth,
188 ; tendencies of, 235.
INDEX 391
Variation, rate of (mathematical), 344 ;
in biology, 186 ;
atavistic, 195 ; direction of, 233; fluctuating, 189; must be co-ordinated,
231 ; mathematical probability of co-ordination of, 233 ; the material
for selection, 229 ; origin of, 230 ; selected by the organism, 237 ; cause
of, a pseudo-problem, 242 ; arise de novo, 244.
Variables (mathematical), 343.
Varieties, specific, 194.
Vegetable life, 265.
Vertebrates, 249 ;
adaptations securing mobility, 275 ; ancestry of, 253 ; morphology of,
249 ; a dominant group, 259 ; distribution of, 260.
Vervvorn, and mechanism in life, 127.
Vesalius, anatomical school of, 121.
Vital activities, integration of, 128 ; co-ordination of, 171
de Vries and mutations, 191 ;
fluctuating variations inherited, 220.
Vital force, 318.
Van der Waal's equation, 308.
Weber's law, 16 ;
a quasi-mathematical relation, 17.
Weismann, hypothesis of heredity, 182 ;
hypothesis of germinal selection, 241 ; hypothesis of development, 132 ;
mosaic-theory, 131 ; preformation hypothesis, 133 ; hypothesis of the
germ.-plasm, continuity of the germ-plasm, 181; germinal changes in-
conceivable, 224 ; size of biophors, 183 ; origin of life, 339 ; spontaneous
generation a logical necessity, 339.
Weismannism, a series of logical hypotheses, 320 ; physico-chemical
analogies, and subsidiary hypotheses, 223.
Whales, an unsuccessful line of evolution, 274.
Whitehead, and mathematical reasoning, 347.
Wilson, mosaic-theory of development, 1 39.
Yerkes, and behaviour of Crustacea, 293,
Zymogens, 92.
Zymoids, 94
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