DEGENERATION
"I went by the field of the slothful, and
by the vineyard of the man void of understanding; and lo, it was all grown over
with thorns, and nettles had covered the face thereof, and the stone wall
thereof was broken down. Then I saw and considered it well; I looked upon it
and received instruction.-- SOLOMON.
"How shall we escape if we neglect so great
salvation?" --Hebrews.
"We have as possibilities either Balance,
or Elaboration, or Degeneration."--E. Ray Lankester.
IN one of his best known books, Mr. Darwin
brings out a fact which may be illustrated in some such way as this: Suppose a
bird fancier collects a flock of tame pigeons distinguished by all the infinite
ornamentations of their race. They are of all kinds, of every shade of colour,
and adorned with every variety of marking. He takes them to an uninhabited
island and allows them to fly off wild into the woods. They found a colony
there, and after the lapse of many years the owner returns to the spot. He will
find that a remarkable change has taken place in the interval. The birds, or
their descendants rather, have all become changed into the same colour. The
black, the white and the dun, the striped, the spotted, and the ringed, are all
metamorphosed into one--a dark slaty blue. Two plain black bands monotonously
repeat themselves upon the wings of each, and the loins beneath are white; but
all the variety, all the beautiful colours, all the old graces of form it may
be, have disappeared. These improvements were the result of care and nurture,
of domestication, of civilization; and now that these influences are removed,
the birds themselves undo the past and lose what they had gained. The attempt
to elevate the race has been mysteriously thwarted. It is as if the original
bird, the far remote ancestor of all doves, had been blue, and these had been
compelled by some strange law to discard the badges of their civilization and
conform to the ruder image of the first. The natural law by which such a change
occurs is called The Principle of Reversion to Type.
It is a proof of the universality of this
law that the same thing will happen with a plant. A garden is planted, let us
say, with strawberries and roses, and for a number of years is left alone. In
process of time it will run to waste. But this does not mean that the plants
will really waste away, but that they will change into something else, and, as
it invariably appears, into something worse; in the one case, namely, into the
small, wild strawberry of the woods, and in the other into the primitive
dog-rose of the hedges.
If we neglect a garden plant, then, a natural
principle of deterioration comes in, and changes it into a worse plant. And if
we neglect a bird, by the same imperious law it will be gradually changed into
an uglier bird. Or if we neglect almost any of the domestic animals, they will
rapidly revert to wild and worthless forms again.
Now the same thing exactly would happen in the
case of you or me. Why should Man be an exception to any of the laws of Nature?
Nature knows him simply as an animal--Sub-kingdom Vertebrata, Class
Mammalia, Order Bimana. And the law of Reversion to Type runs
through all creation. If a man neglect himself for a few years he will change
into a worse man and a lower man. If it is his body that he neglects, he will
deteriorate into a wild and bestial savage--like the de-humanized men who are
discovered sometimes upon desert islands. If it is his mind, it will degenerate
into imbecility and madness--solitary confinement has the power to unmake men's
minds and leave them idiots. If he neglect his conscience, it will run off into
lawlessness and vice. Or, lastly, if it is his soul, it must inevitably
atrophy, drop off in ruin and decay.
We have here, then, a thoroughly natural basis
for the question before us. If we neglect, with this universal principle
staring us in the face, how shall we escape? If we neglect the ordinary means
of keeping a garden in order, how shall it escape running to weeds and waste?
Or, if we neglect the opportunities for cultivating the mind, how shall it
escape ignorance and feebleness? So, if we neglect the soul, how shall it
escape the natural retrograde movement, the inevitable relapse into barrenness
and death?
It is not necessary, surely, to pause for proof
that there is such a retrograde principle in the being of every man. It is
demonstrated by facts, and by the analogy of all Nature. Three possibilities of
life, according to Science, are open to all living organisms--Balance,
Evolution, and Degeneration. The first denotes the precarious persistence of a
life along what looks like a level path, a character which seems to hold its
own alike against the attacks of evil and the appeals of good. It implies a set
of circumstances so balanced by choice or fortune that they neither influence
for better nor for worse. But except in theory this state of equilibrium,
normal in the inorganic kingdom, is really foreign to the world of life; and
what seems inertia may be a true Evolution unnoticed from its slowness, or
likelier still a movement of Degeneration subtly obliterating as it falls the
very traces of its former height. From this state of apparent Balance,
Evolution is the escape in the upward direction, Degeneration in the lower. But
Degeneration, rather than Balance or Elaboration, is the possibility of life
embraced by the majority of mankind. And the choice is determined by man's own
nature. The life of Balance is difficult. It lies on the verge of continual
temptation, its perpetual adjustments become fatiguing, its measured virtue is
monotonous and uninspiring. More difficult still, apparently, is the life of
ever upward growth. Most men attempt it for a time, but growth is slow; and
despair overtakes them while the goal is far away. Yet none of these reasons
fully explains the fact that the alternative which remains is adopted by the
majority of men. That Degeneration is easy only half accounts for it. Why is it
easy? Why but that already in each man's very nature this principle is supreme?
He feels within his soul a silent drifting motion impelling him downward with
irresistible force. Instead of aspiring to Conversion to a higher Type he
submits by a law of his nature to Reversion to a lower. This is
Degeneration--that principle by which the organism, failing to develop itself,
failing even to keep what it has got, deteriorates, and becomes more and more
adapted to a degraded form of life.
All men who know themselves are conscious that
this tendency, deep-rooted and active, exists within their nature.
Theologically it is described as a gravitation, a bias toward evil. The Bible
view is that man is conceived in sin and shapen in iniquity. And experience
tells him that he will shape himself into further sin and ever deepening
iniquity without the smallest effort, without in the least intending it, and in
the most natural way in the world if he simply let his life run. It is on this
principle that, completing the conception, the wicked are said further in the
Bible to be lost. They are not really lost as yet, but they are on the sure way
to it. The bias of their lives is in full action. There is no drag on anywhere.
The natural tendencies are having it all their own way; and although the
victims may be quite unconscious that all this is going on, it is patent to
every one who considers even the natural bearings of the case that "the end of
these things is Death." When we see a man fall from the top of a five-storey
house, we say the man is lost. We say that before he has fallen a foot; for the
same principle that made him fall the one foot will undoubtedly make him
complete the descent by falling other eighty or ninety feet. So that he is a
dead man, or a lost man from the very first. The gravitation of sin in a human
soul acts precisely in the same way. Gradually, with gathering momentum it
sinks a man further and further from God and righteousness, and lands him, by
the sheer action of a natural law, in the hell of a neglected life.
But the lesson is not less clear from analogy.
Apart even from the law of Degeneration, apart from Reversion to Type, there is
in every living organism a law of Death. We are wont to imagine that Nature is
full of Life. In reality it is full of Death. One cannot say it is natural for
a plant to live. Examine its nature fully, and you have to admit that its
natural tendency is to die. It is kept from dying by a mere temporary
endowment, which gives it an ephemeral dominion over the elements--gives it
power to utilize for a brief span the rain, the sunshine, and the air. Withdraw
this temporary endowment for a moment and its true nature is revealed. Instead
of overcoming Nature it is overcome. The very things which appeared to minister
to its growth and beauty now turn against it and make it decay and die. The sun
which warmed it, withers it; the air and rain which nourished it, rot it. It is
the very forces which we associate with life which, when their true nature
appears, are discovered to be really the ministers of death.
This law, which is true for the whole
plant-world, is also valid for the animal and for man. Air is not life, but
corruption--so literally corruption that the only way to keep out corruption,
when life has ebbed, is to keep out air. Life is merely a temporary suspension
of these destructive powers; and this is truly one of the most accurate
definitions of life we have yet received--"the sum total of the functions which
resist death."
Spiritual life, in like manner, is the sum total
of the functions which resist sin. The soul's atmosphere is the daily trial,
circumstance, and temptation of the world. And as it is life alone which gives
the plant power to utilize the elements, and as, without it, they utilize it,
so it is the spiritual life alone which gives the soul power to utilize
temptation and trial; and without it they destroy the soul. How shall we escape
if we refuse to exercise these functions--in other words, if we neglect?
This destroying process, observe, goes on quite
independently of God's judgment on sin. God's judgment on sin is another and a
more awful fact of which this may be a part .But it is a distinct fact by
itself, which we can hold and examine separately, that on purely natural
principles the soul that is left to itself unwatched, uncultivated, unredeemed,
must fall away into death by its own nature. The soul that sinneth "it shall
die." It shall die, not necessarily because God passes sentence of death upon
it, but because it cannot help dying. It has neglected "the functions which
resist death," and has always been dying. The punishment is in its very nature,
and the sentence is being gradually carried out all along the path of life by
ordinary processes which enforce the verdict with the appalling faithfulness of
law.
There is an affectation that religious truths lie
beyond the sphere of the comprehension which serves men in ordinary things.
This question at least must be an exception. It lies as near the natural as the
spiritual. If it makes no impression on a man to know that God will visit his
iniquities upon him, he cannot blind himself to the fact that Nature will. Do
we not all know what it is to be punished by Nature for disobeying her? We have
looked round the wards of a hospital, a prison, or a madhouse, and seen there
Nature at work squaring her accounts with sin. And we knew as we looked that if
no Judge sat on the throne of heaven at all there was a Judgment there, where
an inexorable Nature was crying aloud for justice, and carrying out her heavy
sentences for violated laws.
When God gave Nature the law into her own hands
in this way, He seems to have given her two rules upon which her sentences were
to be based. The one is formally enunciated in this sentence, "WHATSOEVER A MAN
SOWETH THAT SHALL HE ALSO REAP." The other is informally expressed in this, "IF
WE NEGLECT HOW SHALL WE ESCAPE?"
The first is the positive law, and deals with
sins of commission. The other, which we are now discussing, is the negative,
and deals with sins of omission. It does not say anything about sowing, but
about not sowing. It takes up the case of souls which are lying fallow. It does
not say, if we sow corruption we shall reap corruption. Perhaps we would not be
so unwise, so regardless of ourselves, of public opinion, as to sow corruption.
It does not say, if we sow tares we shall reap tares. We might never do
anything so foolish as sow tares. But if we sow nothing, it says, we shall reap
nothing. If we put nothing into the field, we shall take nothing out. If we
neglect to cultivate in summer, now shall we escape starving in winter?
Now the Bible raises this question, but does not
answer it--because it is too obvious to need answering. How shall we escape if
we neglect? The answer is, we cannot. In the nature of things we cannot. We
cannot escape any more than a man can escape drowning who falls into the sea
and has neglected to learn to swim. In the nature of things he cannot
escape--nor can he escape who has neglected the great salvation.
Now why should such fatal consequences follow a
simple process like neglect? The popular impression is that a man, to be what
is called lost, must be an open and notorious sinner. He must be one who has
abandoned all that is good and pure in life, and sown to the flesh with all his
might and main. But this principle goes further. It says simply, "If we
neglect." Any one may see the reason why a notoriously wicked person should not
escape; but why should not all the rest of us escape? What is to hinder people
who are not notoriously wicked escaping--people who never sowed anything in
particular? Why is it such a sin to sow nothing in particular?
There must be some hidden and vital relation
between these three words, Salvation, Neglect, and Escape--some reasonable,
essential, and indissoluble connection. Why are these words so linked together
as to weight this clause with all the authority and solemnity of a sentence of
death?
The explanation has partly been given already. It
lies still further, however, in the meaning of the word Salvation. And this, of
course, is not at all Salvation in the ordinary sense of forgiveness of sin.
This is one great meaning of Salvation, the first and the greatest. But this is
spoken to people who are supposed to have had this. It is the broader word,
therefore, and includes not only forgiveness of sin but salvation or
deliverance from the downward bias of the soul. It takes in that whole process
of rescue from the power of sin and selfishness that should be going on from
day to day in every human life We have seen that there is a natural principle
in man lowering him, deadening him, pulling him down by inches to the mere
animal plane, blinding reason, searing conscience, paralysing will. This is the
active destroying principle, or Sin. Now to counteract this, God has discovered
to us another principle which will stop this drifting process in the soul,
steer it round, and make it drift the other way. This is the active saving
principle, or Salvation. If a man find the first of these powers furiously at
work within him, dragging his whole life downward to destruction, there is only
one way to escape his fate--to take resolute hold of the upward power, and be
borne by it to the opposite goal. And as this second power is the only one in
the universe which has the slightest real effect upon the first, how shall a
man escape if he neglect it? To neglect it is to cut off the only possible
chance of escape. In declining this he is simply abandoning himself with his
eyes open to that other and terrible energy which is already there, and which,
in the natural course of things, is bearing him every moment further and
further from escape.
From the very nature of Salvation, therefore, it
is plain that the only thing necessary to make it of no effect is neglect.
Hence the Bible could not fail to lay strong emphasis on a word so vital. It
was not necessary for it to say, how shall we escape if we trample upon the
great salvation, or doubt, or despise, or reject it. A man who has been
poisoned only need neglect the antidote and he will die. It makes no difference
whether he dashes it on the ground, or pours it out of the window, or sets it
down by his bedside, and stares at it all the time he is dying. He will die
just the same, whether he destroys it in a passion, or coolly refuses to have
anything to do with it. And as a matter of fact probably most deaths,
spiritually, are gradual dissolutions of the last class rather than rash
suicides of the first.
This, then, is the effect of neglecting salvation
from the side of salvation itself; and the conclusion is that from the very
nature of salvation escape is out of the question. Salvation is a definite
process. If a man refuse to submit himself to that process, clearly he cannot
have the benefits of it. As many as received Him to them he gave power
to become the sons of God. He does not avail himself of this power. It
may be mere carelessness or apathy. Nevertheless the neglect is fatal. He
cannot escape because he will not.
Turn now to another aspect of the case--to the
effect upon the soul itself. Neglect does more for the soul than make it miss
salvation. It despoils it of its capacity for salvation. Degeneration in the
spiritual sphere involves primarily the impairing of the faculties of salvation
and ultimately the loss of them. It really means that the very soul itself
becomes piecemeal destroyed until the very capacity for God and righteousness
is gone.
The soul, in its highest sense, is a vast
capacity for God. It is like a curious chamber added on to being, and somehow
involving being, a chamber with elastic and contractile walls, which can be
expanded, with God as its guest, illimitably, but which without God shrinks and
shrivels until every vestige of the Divine is gone, and God's image is left
without God's Spirit. One cannot call what is left a soul; it is a
shrunken, useless organ, a capacity sentenced to death by disease, which droops
as a withered hand by the side, and cumbers nature like a rotted branch. Nature
has her revenge upon neglect as well as upon extravagance. Misuse, with her, is
as mortal a sin as abuse.
There are certain burrowing animals--the mole for
instance--which have taken to spending their lives beneath the surface of the
ground. And Nature has taken her revenge upon them in a thoroughly natural
way--she has closed up their eyes. If they mean to live in darkness, she
argues, eyes are obviously a superfluous function. By neglecting them these
animals made it clear they do not want them. And as one of Nature's fixed
principles is that nothing shall exist in vain, the eyes are presently taken
away, or reduced to a rudimentary state. There are fishes also which have had
to pay the same terrible forfeit for having made their abode in dark caverns
where eyes can never be required. And in exactly the same way the spiritual eye
must die and lose its power by purely natural law if the soul choose to walk in
darkness rather than in light.
This is the meaning of the favourite paradox of
Christ, "From him that hath not shall be taken away even that which he hath;"
"take therefore the talent from him." The religious faculty is a talent, the
most splendid and sacred talent we possess. Yet it is subject to the natural
conditions and laws. If any man take his talent and hide it in a napkin,
although it is doing him neither harm nor good apparently, God will not allow
him to have it. Although it is lying there rolled up in the darkness, not
conspicuously affecting any one, still God will not allow him to keep it. He
will not allow him to keep it any more than Nature would allow the fish to keep
their eyes. Therefore, He says, "take the talent from him." And Nature does
it.
This man's crime was simply neglect--"thou wicked
and slothful servant." It was a wasted life-- a life which failed in the
holy stewardship of itself. Such a life is a peril to all who cross its path.
Degeneration compasses Degeneration. It is only a character which is itself
developing that can aid the Evolution of the world and so fulfil the end of
life. For this high usury each of our lives, however small may seem our
capital, was given us by God. And it is just the men whose capital seems small
who need to choose the best investments. It is significant that it was the man
who had only one talent who was guilty of neglecting it. Men with ten talents,
men of large gifts and burning energies, either direct their powers nobly and
usefully, or misdirect them irretrievably. It is those who belong to the rank
and file of life who need this warning most. Others have an abundant store and
sow to the spirit or the flesh with a lavish hand. But we, with our small gift,
what boots our sowing? Our temptation as ordinary men is to neglect to sow at
all. The interest on our talent would be so small that we excuse ourselves with
the reflection that it is not worth while.
It is no objection to all this to say that we are
unconscious of this neglect or misdirection of our powers. That is the darkest
feature in the case. If there were uneasiness there might be hope. If there
were, somewhere about our soul, a something which was not gone to sleep like
all the rest; if there were a contending force anywhere; if we would let even
that work instead of neglecting it, it would gain strength from hour to hour,
and waken up one at a time each torpid and dishonoured faculty till our whole
nature became alive with strivings against self, and every avenue was open wide
for God. But the apathy, the numbness of the soul, what can be said of such a
symptom but that it means the creeping on of death? There are accidents in
which the victims feel no pain. They are well and strong they think. But they
are dying. And if you ask the surgeon by their side what makes him give this
verdict, he will say it is this numbness over the frame which tells how some of
the parts have lost already the very capacity for life.
Nor is it the least tragic accompaniment of this
process that its effects may even be concealed from others. The soul undergoing
Degeneration, surely by some arrangement with Temptation planned in the
uttermost hell, possesses the power of absolute secrecy. When all within is
festering decay and rottenness, a Judas, without anomaly, may kiss his Lord.
This invisible consumption, like its fell analogue in the natural world, may
even keep its victim beautiful while slowly slaying it. When one examines the
little Crustacea which have inhabited for centuries the lakes of the
Mammoth Cave of Kentucky, one is at first astonished to find these animals
apparently endowed with perfect eyes. The pallor of the head is broken by two
black pigment specks, conspicuous indeed as the only bits of colour on the
whole blanched body; and these, even to the casual observer, certainly
represent well-defined organs of vision. But what do they with eyes in these
Stygian waters? There reigns an everlasting night. Is the law for once at
fault? A swift incision with the scalpel, a glance with a lens, and their
secret is betrayed. The eyes are a mockery. Externally they are organs of
vision--the front of the eye is perfect; behind, there is nothing but a mass of
ruins. The optic nerve is a shrunken, atrophied and insensate thread. These
animals have organs of vision, and yet they have no vision. They have eyes, but
they see not.
Exactly what Christ said of men: They had eyes,
but no vision. And the reason is the same. It is the simplest problem of
natural history. The Crustacea of the Mammoth Cave have chosen to abide
in darkness. Therefore they have become fitted for it. By refusing to see they
have waived the right to see. And Nature has grimly humoured them. Nature had
to do it by her very constitution. It is her defence against waste that decay
of faculty should immediately follow disuse of function. He that hath ears to
hear, he whose ears have not degenerated, let him hear.
Men tell us sometimes there is no such thing as
an atheist. There must be. There are some men to whom it is true that there is
no God. They cannot see God because they have no eye. They have only an
abortive organ, atrophied by neglect.
All this, it is commonplace again to insist, is
not the effect of neglect when we die, but while we live. The process is in
full career and operation now. It is useless projecting consequences into the
future when the effects may be measured now. We are always practising these
little deceptions upon ourselves, postponing the consequences of our misdeeds
as if they were to culminate some other day about the time of death. It makes
us sin with a lighter hand to run an account with retribution, as it were, and
delay the reckoning time with God. But every day is a reckoning day. Every soul
is a Book of Judgment, and Nature, as a recording angel, marks there every sin.
As all will be judged by the great Judge some day, all are judged by Nature
now. The sin of yesterday, as part of its penalty, has the sin of to-day. All
follow us in silent retribution on our past, and go with us to the grave. We
cannot cheat Nature. No sleight-of-heart can rob religion of a
present, the immortal nature of a now. The poet sings--
"I looked behind to
find my past,
And lo, it had gone before."
But no, not
all. The unforgiven sins are not away in keeping somewhere to be let loose upon
us when we die; they are here, within us, now. To-day brings the resurrection
of their past, to-morrow of to-day. And the powers of sin, to the exact
strength that we have developed them, nearing their dreadful culmination with
every breath we draw, are here, within us, now. The souls of some men are
already honey-combed through and through with the eternal consequences of
neglect, so that taking the natural and rational view of their case just
now, it is simply inconceivable that there is any escape just
now. What a fearful thing it is to fall into the hands of the living
God! A fearful thing even if, as the philosopher tells us, "the hands of the
Living God are the Laws of Nature."
Whatever hopes of a "heaven" a neglected soul may
have, can be shown to be an ignorant and delusive dream. How is the soul to
escape to heaven if it has neglected for a lifetime the means of escape from
the world and self? And where is the capacity for heaven to come from if it be
not developed on earth? Where, indeed, is even the smallest spiritual
appreciation of God and heaven to come from when so little of spirituality has
ever been known or manifested here? If every Godward aspiration of the soul has
been allowed to become extinct, and every inlet that was open to heaven to be
choked, and every talent for religious love and trust to have been persistently
neglected and ignored, where are the faculties to come from that would even
find the faintest relish in such things as God and heaven give?
These three words, Salvation, Escape, and
Neglect, then, are not casually, but organically and necessarily connected.
Their doctrine is scientific, not arbitrary. Escape means nothing more than the
gradual emergence of the higher being from the lower, and nothing less. It
means the gradual putting off of all that cannot enter the higher state, or
heaven, and simultaneously the putting on of Christ. It involves the slow
completing of the soul and the development of the capacity for God.
Should any one object that from this scientific
standpoint the opposite of salvation is annihilation, the answer is at hand.
From this standpoint there is no such word.
If, then, escape is to be open to us, it is not
to come to us somehow, vaguely. We are not to hope for anything startling or
mysterious. It is a definite opening along certain lines which are definitely
marked by God, which begin at the Cross of Christ and lead direct to Him. Each
man in the silence of his own soul must work out this salvation for himself
with fear and trembling--with fear, realizing the momentous issues of his task;
with trembling, lest before the tardy work be done the voice of Death should
summon him to stop.
What these lines are may, in closing, be
indicated in a word. The true problem of the spiritual life may be said to be,
do the opposite of Neglect. Whatever this is, do it, and you shall escape. It
will just mean that you are so to cultivate the soul that all its powers will
open out to God, and in beholding God be drawn away from sin. The idea really
is to develop among the ruins of the old a new "creature"--a new creature
which, while the old is suffering Degeneration from Neglect, is gradually to
unfold, to escape away and develop on spiritual lines to spiritual beauty and
strength. And as our conception of spiritual being must be taken simply from
natural being, our ideas of the lines along which the new religious nature is
to run must be borrowed from the known lines of the old.
There is, for example, a Sense of Sight in the
religious nature. Neglect this, leave it undeveloped, and you never miss it.
You simply see nothing. But develop it and you see God. And the line along
which to develop it is known to us. Become pure in heart. The pure in heart
shall see God. Here, then, is one opening for soul-culture--the avenue through
purity of heart to the spiritual seeing of God.
Then there is a Sense of Sound. Neglect this,
leave it undeveloped, and you never miss it. You simply hear nothing. Develop
it, and you hear God. And the line along which to develop it is known to us.
Obey Christ. Become one of Christ's flock. "The sheep hear His voice, and He
calleth them by name." Here, then, is another opportunity for the culture of
the soul--a gateway through the Shepherd's fold to hear the Shepherd's
voice.
And there is a Sense of Touch to be acquired--
such a sense as the woman had who touched the hem of Christ's garment, that
wonderful electric touch called faith, which moves the very heart of God.
And there is a Sense of Taste--a spiritual hunger
after God; a something within which tastes and sees that He is good. And there
is the Talent for Inspiration. Neglect that, and all the scenery of the
spiritual world is flat and frozen. But cultivate it, and it penetrates the
whole soul with sacred fire, and illuminates creation with God. And last of all
there is the great capacity for Love, even for the love of God--the expanding
capacity for feeling more and more its height and depth, its length and
breadth. Till that is felt no man can really understand that word, "so great
salvation," for what is its measure but that other "so" of Christ--God so loved
the world that He gave His only begotten Son? Verily, how shall we escape if we
neglect that?[52]
[52] For the scientific basis of thls
spiritual law the following works may be consulted:--
"The Origin of Species." By Charles Darwin, F.R.S. London: John Murray. 1872.
"Degeneration." By E. Ray Lankester, F.R.S. London: Macmillan. 1880.
"Der Ursprung der Wirbelthiere und das Princip des Functions-Wechsels." Dr. A.
Dorhn. Leipzig: 1875.
"Lessons from Nature." By St. George Mivart, F.R.S. London: John Murray.
1876.
"The Natural Conditions of Existence as they Affect Animal Life." Karl Semper
London: C. Kegan Paul & Co. 1881