THEORY OF THE DEVELOPMENT OF THE UNIVERSE AND OF THE EARTH. SPONTANEOUS
GENERATION. THE CARBON THEORY. THE PLASTID THEORY.
History of the Development of the Earth.—Kant’s Theory
of the Development of the Universe, or the Cosmological
Gas Theory.—Development of Suns, Planets, and
Moons.—First Origin of Water.—Comparison of Organisms
and Anorgana.—Organic and Inorganic Substances.—Degrees
of Density, or Conditions of Aggregation.—Albuminous
Combinations of Carbon.—Organic and Inorganic
Forms.—Crystals and Formless Organisms without
Organs.—Stereometrical Fundamental Forms of Crystals and
of Organisms.—Organic and Inorganic Forces.—Vital
Force.—Growth and Adaptation in Crystals and in
Organisms.—Formative Tendencies of Crystals.—Unity of
Organic and Inorganic Nature.—Spontaneous Generation, or
Archigony.—Autogony and Plasmogony.—Origin of Monera by
Spontaneous Generation.—Origin of Cells from
Monera.—The Cell Theory.—The Plastid Theory.—Plastids,
or Structural Units.—Cytods and Cells.—Four Different
Kinds of Plastids.
In our considerations hitherto we have endeavoured to answer the
question, “By what causes have new species of animals and plants arisen
out of existing species?” We have answered this question according to
Darwin’s theory, that natural selection in the struggle for
existence—that is, the interaction of the laws of Inheritance and
Adaptation—is completely sufficient for producing mechanically the
endless variety of the different animals and plants, which have the
appearance of being organized according to a plan for a definite
purpose. Meanwhile the question must have already repeatedly presented
itself to the reader, how did the first organisms, or that one original
and primæval organism arise, from which we derive all the others?
This question Lamarck(2) answered by the hypothesis of _spontaneous
generation_, or _archigony_. But Darwin passes over and avoids this
subject, as he expressly remarks that he has “nothing to do with the
origin of the soul, nor with that of life itself.” At the conclusion of
his work he expresses himself more distinctly in the following
words:—“I imagine that probably all organic beings which ever lived on
this earth descended from some primitive form, which was first called
into life by the Creator.” Moreover, Darwin, for the consolation of
those who see in the Theory of Descent the destruction of the whole
“moral order of the universe,” appeals to the celebrated author and
divine who wrote to him, that “he has gradually learnt to see that it is
just as noble a conception of the Deity to believe that he created a few
original forms capable of self-development into other and needful forms,
as to believe that he required a fresh act of creation to supply the
voids caused by the action of his laws.”
Those to whom the belief in a supernatural creation is an emotional
necessity may rest satisfied with this conception. They may reconcile
that belief with the Theory of Descent; for in the creation of a single
original organism possessing the capability to develop all others out of
itself by inheritance and adaptation, they can really find much more
cause for admiring the power and wisdom of the Creator than in the
independent creation of different species.
If, taking this point of view, we were to explain the origin of the
first terrestrial organisms, from which all the others are descended, as
due to the action of a personal Creator acting according to a definite
plan, we should of course have to renounce all scientific knowledge of
the process, and pass from the domain of true science to the completely
distinct domain of poetical faith. By assuming a supernatural act of
creation we should be taking a leap into the inconceivable. Before we
decide upon this latter step, and thereby renounce all pretension to a
scientific knowledge of the process, we are at all events in duty bound
to endeavour to examine it in the light of a mechanical hypothesis. We
must at least examine whether this process is really so wonderful, and
whether we cannot form a tenable conception of a completely
non-miraculous origin of the first primary organism. We might then be
able entirely to reject miracle in creation.
It will be necessary for this purpose, first of all, to go back further
into the past, and to examine the history of the creation of the earth.
Going back still further, we shall find it necessary to consider the
history of the creation of the whole universe in its most general
outlines. All my readers undoubtedly know that from the structure of the
earth, as it is at present known to us, the notion has been derived, and
as yet has not been refuted, that its interior is in a fiery fluid
condition, and that the firm crust, composed of different strata, on the
surface of which organisms are living, forms only a very thin pellicle
or shell round the fiery fluid centre. We have arrived at this idea by
different confirmatory experiments and reasonings. In the first place,
the observation that the temperature of the earth’s crust continually
increases towards the centre is in favour of this supposition. The
deeper we descend, the greater the warmth of the ground, and in such
proportion, that with every 100 feet the temperature increases about one
degree. At a depth of six miles, therefore, a heat of 1500° would be
attained, sufficient to keep most of the firm substances of our earth’s
crust in a molten, fiery, fluid state. This depth, however, is only the
286th part of the whole diameter of the earth (1717 miles). We further
know that springs which rise out of a considerable depth possess a very
high temperature, and sometimes even throw water up to the surface in a
boiling state. Lastly, very important proofs are furnished by volcanic
phenomena, the eruption of fiery fluid masses of stone bursting through
certain parts of the earth’s crust. All these phenomena lead us with
great certainty to the important assumption that the firm crust of the
earth forms only quite a small fraction, not nearly the one-thousandth
part of the whole diameter of the terrestrial globe, and that the rest
is still for the most part in a molten or fiery fluid state.
Now if, starting with this assumption, we reflect on the ancient history
of the development of the globe, we are logically carried back a step
further, namely, to the assumption that at an earlier date the whole
earth was a fiery fluid body, and that the formation of a thin,
stiffened crust on the surface was only a later process. Only gradually,
by radiating its intrinsic heat into the cold space of the universe, has
the surface of the glowing ball become condensed into a thin crust.
That the temperature of the earth in remote times was much higher than
it is now, is proved by many phenomena. Among other things, this is
rendered probable by the equal distribution of organisms in remote times
of the earth’s history. While at present, as is well known, the
different populations of animals and plants correspond to the different
zones of the earth and their appropriate temperature, in earlier times
this was distinctly not the case.
We see from the distribution of fossils in the remoter ages, that it was
only at a very late date, in fact, at a comparatively recent period of
the organic history of the earth (at the beginning of the so-called
cænolithic or tertiary period), that a separation of zones and of the
corresponding organic populations occurred. During the immensely long
primary and secondary periods, tropical plants, which require a very
high degree of temperature, lived not only in the present torrid zone,
under the equator, but also in the present temperate and frigid zones.
Many other phenomena also demonstrate a gradual decrease of the
temperature of the globe as a whole, and especially a late and gradual
cooling of the earth’s crust about the poles. Bronn, in his excellent
“Investigations of the Laws of Development of the Organic World,” has
collected numerous geological and palæontological proofs of this fact.
These phenomena and the mathematico-astronomical knowledge of the
structure of the universe justify the theory that, inconceivable ages
ago, long before the first existence of organisms, the whole earth was a
fiery fluid globe. Now, this theory corresponds with the grand theory of
the origin of the universe, and especially of our planetary system,
which, on the ground of mathematical and astronomical facts, was put
forward in 1755 by our critical philosopher Kant,(22) and was later more
thoroughly established by the celebrated mathematicians, Laplace and
Herschel. This cosmogeny, or theory of the development of the universe,
is now almost universally acknowledged; it has not been replaced by a
better one, and mathematicians, astronomers, and geologists have
continually, by various arguments, strengthened its position.
Kant’s cosmogeny maintains that _the whole universe, inconceivable ages
ago, consisted of a gaseous chaos_. All the substances which are found
at present separated on the earth, and other bodies of the universe, in
different conditions of density—in the solid, semi-fluid, liquid, and
elastic fluid or gaseous states of aggregation—originally constituted
together one single homogeneous mass, equally filling up the space of
the universe, which, in consequence of an extremely high degree of
temperature, was in an exceedingly thin gaseous or nebulous state. The
millions of bodies in the universe which at present form the different
solar systems did not then exist. They originated only in consequence of
a universal rotatory movement, or rotation, during which a number of
masses acquired greater density than the remaining gaseous mass, and
then acted upon the latter as central points of attraction. Thus arose a
separation of the chaotic primary nebula, or gaseous universe, into a
number of rotating nebulous spheres, which became more and more
condensed. Our solar system was such a gigantic gaseous or nebulous
ball, all the particles of which revolved round a common central point,
the solar nucleus. The nebulous ball itself, like all the rest, in
consequence of its rotatory movement, assumed a spheroidal or a
flattened globular form.
While the centripetal force attracted the rotating particles nearer and
nearer to the firm central point of the nebulous ball, and thus
condensed the latter more and more, the centrifugal force, on the other
hand, always tended to separate the peripheral particles further and
further from it, and to hurl them off. On the equatorial sides of the
ball, which was flattened at both poles, this centrifugal force was
strongest, and as soon as, by increase of density, it attained
predominance over the centripetal force, a circular nebulous ring
separated itself from the rotating ball. This nebulous ring marked the
course of future planets. The nebulous mass of the ring gradually
condensed, and became a planet, which revolved round its own axis, and
at the same time rotated round the central body. In precisely the same
manner, from the equator of the planetary mass, as soon as the
centrifugal force gained predominance over the centripetal force, new
nebulous rings were ejected, which moved round the planets as the latter
moved round the sun. These nebulous rings, too, became condensed into
rotating balls. Thus arose the moons, only one of which moves round our
earth, whilst four move round Jupiter, and six round Uranus. The ring of
Saturn still shows us a moon in its early stage of development. As by
increasing refrigeration these simple processes of condensation and
expulsion repeated themselves over and over again, there arose the
different solar systems, the planets rotating round their central suns,
and the satellites or moons moving round their planets.
The original gaseous condition of the rotating bodies of the universe
gradually changed, by increasing refrigeration and condensation, into
the fiery fluid or molten state of aggregation. By the process of
condensation, a great quantity of heat was emitted, and the rotating
suns, planets, and moons, soon changed into glowing balls of fire, like
gigantic drops of melted metal, which emitted light and heat. By loss of
heat, the melted mass on the surface of the fiery fluid ball became
further condensed, and thus arose a thin, firm crust, which enclosed a
fiery fluid nucleus. In all essential respects our mother earth probably
did not differ from the other bodies of the universe.
In view of the object of these pages, it will not be of especial
interest to follow in detail the _history of the natural creation of the
universe_, with its different solar and planetary systems, and to
establish it mathematically by the different astronomical and geological
proofs. The outlines of it, which I have just mentioned, must be
sufficient here, and for further details I refer to Kant’s[5] “General
History of Nature and Theory of the Heavens.”(22) I will only add that
this wonderful theory, which might be called _the cosmological gas
theory_, harmonizes with all the general series of phenomena at present
known to us, and stands in no irreconcilable contradiction to any one of
them. Moreover, it is purely mechanical or monistic, makes use
exclusively of the inherent forces of eternal matter, and entirely
excludes every supernatural process, every prearranged and conscious
action of a personal Creator. Kant’s Cosmological Gas Theory
consequently occupies a similar supreme position in _Anorganology_,
especially in _Geology_, and forms the crown of our knowledge in that
department, in the same way as Lamarck’s Theory of Descent does in
_Biology_, and especially in _Anthropology_. Both rest exclusively upon
mechanical or unconscious causes (causæ efficientes), in no case upon
prearranged or conscious causes (causæ finales). (Compare above, p.
100-106.) Both therefore fulfil all the demands of a scientific theory,
and consequently will remain generally acknowledged until they are
replaced by better ones.
I will, however, not deny that Kant’s grand cosmogeny has some weak
points, which prevent our placing the same unconditional confidence in
it as in Lamarck’s Theory of Descent. The notion of an original gaseous
chaos filling the whole universe presents great difficulties of various
kinds. A great and unsolved difficulty lies in the fact that the
Cosmological Gas Theory furnishes no starting-point at all in
explanation of the first impulse which caused the rotary motion in the
gas-filled universe. In seeking for such an impulse, we are
involuntarily led to the mistaken questioning about a “first beginning.”
We can as little imagine a _first beginning_ of the eternal phenomena of
the motion of the universe as of its final end.
The universe is unlimited and immeasurable in both space and time. It is
eternal, and it is infinite. Nor can we imagine a beginning or end to
the uninterrupted and eternal motion in which all particles of the
universe are always engaged. The great laws of the _conservation of
force_(38) and the _conservation of matter_, the foundations of our
whole conception of nature, admit of no other supposition. The universe,
as far as it is cognisable to human capability, appears as a connected
chain of material phenomena of motion, necessitating a continual change
of forms. Every form, as the temporary result of a multiplicity of
phenomena of motion, is as such perishable, and of limited duration.
But, in the continual change of forms, matter and the motion inseparable
from it remain eternal and indestructible.
Now, although Kant’s Cosmological Gas Theory is not able to explain the
development of motion in the whole universe in a satisfactory manner,
beyond that gaseous state of chaos, and although many other weighty
considerations may be brought forward against it, especially by
chemistry and geology, yet we must on the whole acknowledge its great
merit, inasmuch as it explains in an excellent manner, by due
consideration of development, the whole structure of all that is
accessible to our observation, that is, the anatomy of the solar
systems, and especially of our planetary system. It may be that this
development was altogether different from what Kant supposes, and our
earth may have arisen by the aggregation of numberless small meteorides,
scattered in space, or in any other manner, but hitherto no one has as
yet been able to establish any other theory of development, or to offer
one in the place of Kant’s cosmogeny.
After this general glance at the monistic cosmogeny, or the
non-miraculous history of the development of the universe, let us now
return to a minute fraction of it, to our mother earth, which we left as
a ball flattened at both poles and in a fiery fluid state, its surface
having condensed by becoming cooled into a very thin firm crust. The
crust, on first cooling, must have covered the whole surface of the
terrestrial sphere as a continuous smooth and thin shell. But soon it
must have become uneven and hummocky; for, since during the continued
cooling, the fiery fluid nucleus became more and more condensed and
contracted, and consequently the diameter of the earth diminished, the
thin cold crust, which could not closely follow the softer nuclear mass,
must have fallen in, in many places. An empty space would have arisen
between the two, had not the pressure of the outer atmosphere forced
down the fragile crust towards the interior, breaking it in so doing.
Other unevennesses probably arose from the fact that, in different
parts, the cooled crust during the process of refrigeration contracted
also itself, and thus became fissured with cracks and rents. The fiery
fluid nucleus flowed up to the external surface through these cracks,
and again became cooled and stiff. Thus, even at an early period there
arose many elevations and depressions, which were the first foundations
of mountains and valleys.
After the temperature of the cooled terrestrial ball had fallen to a
certain degree, a very important new process was effected, namely, the
_first origin of water_. Water had until then existed only in the form
of steam in the atmosphere surrounding the globe. The water could
evidently not condense into a state of fluid drops until the temperature
of the atmosphere had considerably decreased. Now, then, there began a
further transformation of the earth’s crust by the force of water. It
continually fell in the form of rain, and in that form washed down the
elevations of the earth’s crust, filling the depressions with the mud
carried along, and, by depositing it in layers, it caused the extremely
important neptunic transformations of the earth’s crust, which have
continued since then uninterruptedly, and which in our next chapter we
shall examine a little more closely.
It was not till the earth’s crust had so far cooled that the water had
condensed into a fluid form, it was not till the hitherto dry crust of
the earth had for the first time become covered with liquid water, that
the origin of the first organisms could take place. For all animals and
all plants—in fact, all organisms—consist in great measure of fluid
water, which combines in a peculiar manner with other substances, and
brings them into a semi-fluid state of aggregation. We can therefore,
from these general outlines of the inorganic history of the earth’s
crust, deduce the important fact, that at a certain definite time life
had its beginning on earth, and that terrestrial organisms did not exist
from eternity, but at a certain period came into existence for the first
time.
Now, how are we to conceive of this origin of the first organisms? This
is the point at which most naturalists, even at the present day, are
inclined to give up the attempt at natural explanation, and take refuge
in the miracle of an inconceivable creation. In doing so, as has already
been remarked, they quit the domain of scientific knowledge, and
renounce all further insight into the eternal laws which have determined
nature’s history. But before despondingly taking such a step, and before
we despair of the possibility of any knowledge of this important
process, we may at least make an attempt to understand it. Let us see if
in reality the origin of a first organism out of inorganic matter, the
origin of a living body out of lifeless matter, is so utterly
inconceivable and beyond all experience. In one word, let us examine the
question of _spontaneous generation, or archigony_. In so doing, it is
above all things necessary to form a clear idea of the principal
properties of the two chief groups of natural bodies, the so-called
inanimate or inorganic, and the animate or organic bodies, and then
establish what is common to, and what are the differences between, the
two groups. It is desirable to go somewhat carefully into the
_comparison of organisms and anorgana_, since it is commonly very much
neglected, although it is necessary for a right understanding of nature
from the monistic point of view. It will be most advantageous here to
look separately at the three fundamental properties of every natural
body; these are matter, form, and force. Let us begin with _matter_.
(Gen. Morph. iii.)
By chemistry we have succeeded in analysing all bodies known to us into
a small number of elements or simple substances, which cannot be further
divided, for example, carbon, oxygen, nitrogen, sulphur, and the
different metals: potassium, sodium, iron, gold, etc. At present we know
about seventy such elements or simple substances. The majority of them
are unimportant and rare; the minority only are widely distributed, and
compose not only most of the anorgana, but also all organisms. If we
compare those elements which constitute the body of organisms with those
which are met with in anorgana, we have first to note the highly
important fact that in animal and vegetable bodies no element occurs but
what can be found outside of them in inanimate nature. There are no
special organic elements or simple organic substances.
The chemical and physical differences existing between organisms and
anorgana, consequently, do not lie in their material foundation; they do
not arise from the different nature of the _elements_ composing them,
but from the different manner in which the latter are united by
chemical _combination_. This different manner of combination gives rise
to certain physical peculiarities, especially in density of substance,
which at first sight seems to constitute a deep chasm between the two
groups of bodies. Inorganic or inanimate natural bodies, such as
crystals and the amorphous rocks, are in a state of density which we
call the firm or solid state, and which we oppose to the liquid state of
water and to the gaseous state of air. It is familiar to every one that
these three different degrees of density, or states of aggregation of
anorgana, are by no means peculiar to the different elements, but are
the results of a certain degree of temperature. Every inorganic solid
body, by increase of temperature, can be reduced to the liquid or melted
state, and, by further heat, to the gaseous or elastic state. In the
same way most gaseous bodies, by a proper decrease of temperature can
first be converted into a liquid state, and further, into a solid state
of density.
In opposition to these three states of density of anorgana, the living
body of all organisms—animals as well as plants—is in an altogether
peculiar fourth state of aggregation. It is neither solid like stone,
nor liquid like water, but presents rather a medium between these two
states, which may therefore be designated as the firm-fluid or swollen
state of aggregation (viscid). In all living bodies, without exception,
there is a certain quantity of water combined in a peculiar way with
solid matter, and owing to this characteristic combination of water with
solid matter we have that soft state of aggregation, neither solid nor
liquid, which is of great importance in the mechanical explanation of
the phenomena of life. Its cause lies essentially in the physical and
chemical properties of a simple, indivisible, elementary substance,
namely, _carbon_ (Gen. Morph. i. 122-130).
Of all elements, carbon is to us by far the most important and
interesting, because this simple substance plays the largest part in all
animal and vegetable bodies known to us. It is that element which, by
its peculiar tendency to form complicated combinations with the other
elements, produces the greatest variety of chemical compounds, and among
them the forms and living substance of animal and vegetable bodies.
Carbon is especially distinguished by the fact that it can unite with
the other elements in infinitely manifold relations of number and
weight. By the combination of carbon with three other elements, with
oxygen, hydrogen, and nitrogen (to which generally sulphur, and
frequently, also, phosphorus is added), there arise those exceedingly
important compounds which we have become acquainted with as the first
and most indispensable substratum of all vital phenomena, the albuminous
combinations, or albuminous bodies (protean matter).
We have before this (p. 185) become acquainted with the simplest of all
species of organisms in the Monera, whose entire bodies when completely
developed consist of nothing but a semi-fluid albuminous lump; they are
organisms which are of the utmost importance for the theory of the first
origin of life. But most other organisms, also, at a certain period of
their existence—at least, in the first period of their life—in the
shape of egg-cells or germ-cells, are essentially nothing but simple
little lumps of such albuminous formative matter, known as plasma, or
protoplasma. They then differ from the Monera only by the fact that in
the interior of the albuminous corpuscle the cell-kernel, or nucleus,
has separated itself from the surrounding cell-substance (protoplasma).
As we have already pointed out, the cells, with their simple attributes,
are so many citizens, who by co-operation and differentiation build up
the body of even the most perfect organism; this being, as it were, a
cell republic (p. 301). The fully developed form and the vital phenomena
of such an organism are determined solely by the activities of these
small albuminous corpuscles.
It may be considered as one of the greatest triumphs of recent biology,
especially of the theory of tissues, that we are now able to trace the
wonder of the phenomena of life to these substances, and that we can
demonstrate the _infinitely manifold and complicated physical and
chemical properties of the albuminous bodies to be the real cause of
organic or vital phenomena_. All the different forms of organisms are
simply and directly the result of the combination of the different forms
of cells. The infinitely manifold varieties of form, size, and
combination of the cells have arisen only gradually by the division of
labour, and by the gradual adaptation of the simple homogeneous lumps of
plasma, which originally were the only constituents of the cell-mass.
From this it follows of necessity that the fundamental phenomena of
life—nutrition and generation—in their highest manifestations, as well
as in their simplest expressions, must also be traced to the material
nature of that albuminous formative substance. The other vital
activities are gradually evolved from these two. Thus, then, the general
explanation of life is now no more difficult to us than the explanation
of the physical properties of inorganic bodies. All vital phenomena and
formative processes of organisms are as directly dependent upon the
chemical composition and the physical forces of organic matter as the
vital phenomena of inorganic crystals—that is, the process of _their_
growth and _their_ specific formation—are the direct results of their
chemical composition and of their physical condition. The _ultimate
causes_, it is true, remain in _both_ cases concealed from us. When gold
and copper crystallize in a cubical, bismuth and antimony in a
hexagonal, iodine and sulphur in a rhombic form of crystal, the
occurrence is in reality neither more nor less mysterious to us than is
every elementary process of organic formation, every self-formation of
the organic cell. In this respect we can no longer draw a fundamental
distinction between organisms and anorgana, a distinction of which,
formerly, naturalists were generally convinced.
Let us secondly examine the agreements and differences which are
presented to us in the _formation_ of organic and inorganic natural
bodies (Gen. Morph. i. 130). Formerly the simple structure of the latter
and the composite structure of the former were looked upon as the
principal distinction. The body of all organisms was supposed to consist
of dissimilar or heterogeneous parts, of instruments or organs which
worked together for the purposes of life. On the other hand, the most
perfect anorgana, that is to say, crystals, were supposed to consist
entirely of continuous or homogeneous matter. This distinction appears
very essential. But it loses all importance through the fact that in
late years we have become acquainted with the exceedingly remarkable and
important Monera.(15) (Compare above, p. 185.) The whole body of these
most simple of all organisms—a semi-fluid, formless, and simple lump of
albumen—consists, in fact, of only a single chemical combination, and
is as perfectly simple in its structure as any crystal, which consists
of a single inorganic combination, for example, of a metallic salt or of
a silicate of the earths and alkalies.
As naturalists believed in differences in the inner structure or
composition, so they supposed themselves able to find complete
differences in the external forms of organisms and anorgana, especially
in the mathematically determinable crystalline forms of the latter.
Certainly crystallization is pre-eminently a quality of the so-called
anorgana. Crystals are limited by plane surfaces, which meet in straight
lines and at certain measurable angles. Animal and vegetable forms, on
the contrary, seem at first sight to admit of no such geometrical
determination. They are for the most part limited by curved surfaces and
crooked lines, which meet at variable angles. But in recent times we
have become acquainted, among Radiolaria(23) and among many other
Protista, with a large number of lower organisms, whose body, in the
same way as crystals, may be traced to a mathematically determinable
fundamental form, and whose form in its whole, as well as in its parts,
is bounded by definite geometrically determinable planes and angles. In
my general doctrine of _Fundamental Forms, or Promorphology_, I have
given detailed proofs of this, and at the same time established a
general system of forms, the ideal stereometrical type-forms, which
explain the real forms of inorganic crystals, as well as of organic
individuals (Gen. Morph. i. 375-574). Moreover, there are also perfectly
amorphous organisms, like the Monera, Amœba, etc., which change their
forms every moment, and in which we are as little able to point out a
definite fundamental form as in the case of the shapeless or amorphous
anorgana, such as non-crystallized stones, deposits, etc. We are
consequently unable to find any essential difference in the external
forms or the inner structure of anorgana and organisms.
Thirdly, let us turn to the _forces_ or the _phenomena of motion_ of
these two different groups of bodies (Gen. Morph. i. 140). Here we meet
with the greatest difficulties. The vital phenomena, known as a rule
only in the highly developed organisms, in the more perfect animals and
plants, seem there so mysterious, so wonderful, so peculiar, that most
persons are decidedly of opinion that in inorganic nature there occurs
nothing at all similar, or in the least degree comparable to them.
Organisms are for this very reason called animate, and the anorgana,
inanimate natural bodies. Hence, even so late as the commencement of the
present century, the science which investigates the phenomena of life,
namely physiology, retained the erroneous idea that the physical and
chemical properties of matter were not sufficient for explaining these
phenomena. In our own day, especially during the last ten years, this
idea may be regarded as having been completely refuted. In physiology,
at least, it has now no place. It now never occurs to a physiologist to
consider any of the vital phenomena as the result of a mysterious _vital
force_, of an active power working for a definite purpose, standing
outside of matter, and, so to speak, taking only the physico-chemical
forces into its service. Modern physiology has arrived at the strictly
monistic conviction that all of the vital phenomena, and, above all, the
two fundamental phenomena of nutrition and propagation are purely
physico-chemical processes, and directly dependent on the material
nature of the organism, just as all the physical and chemical qualities
of every crystal are determined solely by its material composition. Now,
as the elementary substance which determines the peculiar material
composition of organisms is carbon, we must ultimately reduce all vital
phenomena, and, above all, the two fundamental phenomena of nutrition
and propagation to the properties of the carbon. _The
peculiar-chemico-physical properties, and especially the semi-fluid
state of aggregation, and the easy decomposibility of the exceedingly
composite albuminous combinations of carbon, are the mechanical causes
of those peculiar phenomena of motion which distinguish organisms from
anorgana, and which in a narrow sense are usually called “life.”_
In order to understand this “_carbon theory_,” which I have established
in detail in the second book of my General Morphology, it is necessary,
above all things, closely to examine those phenomena of motion which are
common to both groups of natural bodies. First among them is the
_process of growth_. If we cause any inorganic solution of salt slowly
to evaporate, crystals are formed in it, which slowly increase in size
during the continued evaporation of the water. This process of growth
arises from the fact that new particles continually pass over from the
fluid state of aggregation into the solid, and, according to certain
laws, deposit themselves upon the firm kernel of the crystal already
formed. From such an apposition of particles arise the mathematically
definite crystalline shapes. In like manner the growth of organisms
takes place by the accession of new particles. The only difference is
that in the growth of organisms, in consequence of their semi-fluid
state of aggregation, the newly-added particles penetrate into the
interior of the organism (inter-susception), whereas anorgana receive
homogeneous matter from without only by apposition or an addition of new
particles to the surface. This important difference of growth by
inter-susception and by apposition is obviously only the necessary and
direct result of the different conditions of density or state of
aggregation in organisms and anorgana.
Unfortunately I cannot here follow in detail the various exceedingly
interesting parallels and analogies which occur between the formation of
the most perfect anorgana, the crystals, and the formation of the
simplest organisms, the Monera and their next kindred forms. For this I
must refer to a minute comparison of organisms and anorgana, which I
have carried out in the fifth chapter of my General Morphology (Gen.
Morph. i. 111-160). I have there shown in detail that there exist no
complete differences between organic and inorganic natural bodies,
neither in respect to form and structure, nor in respect to matter and
force; and that the actually existing differences are dependent upon the
peculiar nature of the _carbon_; and that there exists no insurmountable
chasm between organic and inorganic nature. We can perceive this most
important fact very clearly if we examine and compare the origin of the
forms in crystals and in the simplest organic individuals. In the
formation of crystal individuals, two different counteracting formative
tendencies come into operation. The _inner constructive force_, or the
inner formative tendency, which corresponds to the Heredity of
organisms, in the case of the crystal is the direct result of its
material constitution or of its chemical composition. The form of the
crystal, so far as it is determined by this inner original formative
tendency, is the result of the specific and definite way in which the
smallest particles of the crystallizing matter unite together in
different directions according to law. That independent inner formative
force, which is directly inherent in the matter itself, is directly
counteracted by a second formative force. The _external constructive
force_, or the external formative tendency, may be called Adaptation in
crystals as well as in organisms. Every crystal individual during its
formation, like every organic individual, must submit and adapt itself
to the surrounding influences and conditions of existence of the outer
world. In fact, the form and size of every crystal is dependent upon its
whole surroundings, for example, upon the vessel in which the
crystallization takes place, upon the temperature and the pressure of
the air under which the crystal is formed, upon the presence or absence
of heterogeneous bodies, etc. Consequently, the form of every single
crystal, like the form of every single organism, is the result of the
interaction of two opposing factors—the _inner_ formative tendency,
which is determined by the chemical constitution of the _matter itself_,
and of the _external_ formative tendency, which is dependent upon the
influence of _surrounding_ matter. Both these constructive forces
interact similarly also in the organism, and, just as in the crystal,
are of a purely mechanical nature and directly inherent in the substance
of the body. If we designate the growth and the formation of organisms
as a process of life, we may with equal reason apply the same term to
the developing crystal. The teleological conception of nature, which
looks upon organisms as machines of creation arranged for a definite
purpose, must logically acknowledge the same also in regard to the
forms of crystals. The differences which exist between the simplest
organic individuals and inorganic crystals are determined by the _solid_
state of aggregation of the latter, and by the _semi-fluid_ state of the
former. Beyond that the causes producing form are exactly the same in
both. This conviction forces itself upon us most clearly, if we compare
the exceedingly remarkable phenomena of growth, adaptation, and the
“correlation of parts” of developing crystals with the corresponding
phenomena of the origin of the simplest organic individuals (Monera and
cells). The analogy between the two is so great that, in reality, no
accurate boundary can be drawn. In my General Morphology I have quoted
in support of this a number of striking facts (Gen. Morph. i. 146, 156,
158.)
If we vividly picture to ourselves this “_unity of organic and inorganic
nature_” this essential agreement of organisms and anorgana in matter,
form, and force, and if we bear in mind that we are not able to
establish any one fundamental distinction between these two groups of
bodies (as was formerly generally assumed), then the question of
spontaneous generation will lose a great deal of the difficulty which at
first seems to surround it. Then the development of the first organism
out of inorganic matter will appear a much more easily conceivable and
intelligible process than has hitherto been the case, whilst an
artificial absolute barrier between organic or animate, and inorganic or
inanimate nature was maintained.
In the question of _spontaneous generation, or archigony_, which we can
now answer more definitely, it must be borne in mind that by this
conception we understand generally the _non-parental generation of an
organic individual_, the origin of an organism independent of a
parental or producing organism. It is in this sense that on a former
occasion (p. 183) I mentioned spontaneous generation (archigony) as
opposed to parental generation or propagation (tocogony). In the latter
case the organic individual arises by a greater or less portion of an
already existing organism separating itself and growing independently.
(Gen. Morph. ii. 32.)
In spontaneous generation, which is often also called original
generation (generatio spontanea, æquivoca, primaria etc.), we must first
distinguish two essentially different kinds, namely, _autogeny_ and
_plasmogeny_. By _autogeny_ we understand the origin of a most simple
organic individual in an _inorganic formative fluid_, that is, in a
fluid which contains the fundamental substances for the composition of
the organism dissolved in simple and loose combinations (for example,
carbonic acid, ammonia, binary salts, etc.). On the other hand, we call
spontaneous generation _plasmogeny_ when the organism arises in an
_organic formative fluid_, that is, in a fluid which contains those
requisite fundamental substances dissolved in the form of complicated
and fluid combinations of carbon (for example, albumen, fat, hydrate of
carbon, etc.). (Gen. Morph. i. 174, ii. 33.)
Neither the process of autogeny, nor that of plasmogeny, has yet been
directly observed with perfect certainty. In early, and also in more
recent times, numerous and interesting experiments have been made as to
the possibility or reality of spontaneous generation. Almost all these
experiments refer not to autogeny, but to plasmogeny, to the origin of
an organism out of already formed organic matter. It is evident,
however, that this latter process is only of subordinate interest for
our history of creation. It is much more important for us to solve the
question, “Is there such a thing as autogeny? Is it possible that an
organism can arise, not out of pre-existing organic, but out of purely
inorganic, matter?” Hence we can quietly lay aside all the numerous
experiments which refer only to plasmogeny, which have been carried on
very zealously during the last ten years, and which for the most part
have had a negative result. For even supposing that the reality of
plasmogeny were strictly proved, still autogeny would not be explained
by it.
The experiments on autogeny have likewise as yet furnished no certain
and positive result. Yet we must at the outset most distinctly protest
against the notion that these experiments have proved the impossibility
of spontaneous generation in general. Most naturalists who have
endeavoured to decide this question experimentally, and who, after
having employed all possible precautionary measures, under
well-ascertained conditions, have seen no organisms come into being,
have straightway made the assertion, on the ground of these negative
results: “That it is altogether impossible for organisms to come into
existence by themselves without parental generation.” This hasty and
inconsiderate assertion they have supported by the negative results of
their experiments, which, after all, could prove nothing except that,
under these or those highly artificial circumstances created by the
experimenters themselves, no organism was developed. From these
experiments, which have been for the most part made under the most
unnatural conditions, and in a highly artificial manner, we can by no
means draw the conclusion that spontaneous generation in general is
impossible. The impossibility of such a process can, in fact, never be
proved. For how can we know that in remote primæval times there did not
exist conditions quite different from those at present obtaining, and
which may have rendered spontaneous generation possible? Indeed, we can
even positively and with full assurance maintain that the general
conditions of life in primæval times must have been entirely different
from those of the present time. Think only of the fact that the enormous
masses of carbon which we now find deposited in the primary coal
mountains were first reduced to a solid form by the action of vegetable
life, and are the compressed and condensed remains of innumerable
vegetable substances, which have accumulated in the course of many
millions of years. But at the time when, after the origin of water in a
liquid state on the cooled crust of the earth, organisms were first
formed by spontaneous generation, those immeasurable quantities of
carbon existed in a totally different form, probably for the most part
dispersed in the atmosphere in the shape of carbonic acid. The whole
composition of the atmosphere was therefore extremely different from the
present. Further, as may be inferred upon chemical, physical, and
geological grounds, the density and the electrical conditions of the
atmosphere were quite different. In like manner the chemical and
physical nature of the primæval ocean, which then continuously covered
the whole surface of the earth as an uninterrupted watery sheet, was
quite peculiar. The temperature, the density, the amount of salt, etc.,
must have been very different from those of the present ocean. In any
case, therefore, even if we do not know anything more about it, there
remains to us the supposition, which can at least not be disputed, that
at that time, under conditions quite different from those of to-day, a
spontaneous generation, which now is perhaps no longer possible, may
have taken place.
But it is necessary to add here that, by the recent progress of
chemistry and physiology, the mysterious and miraculous character which
at first seems to belong to this much disputed and yet inevitable
process of spontaneous generation, has been to a great extent, or almost
entirely, destroyed. Not fifty years ago, all chemists maintained that
we were unable to produce artificially in our laboratories any
complicated combination of carbon, or so-called “organic combination.”
The mystic “vital force” alone was supposed to be able to produce these
combinations. When, therefore, in 1828, Wöhler, in Göttingen, for the
first time refuted this dogma, and exhibited pure “organic” urea,
obtained in an artificial manner from a purely inorganic body (cyanate
of ammonium), it caused the greatest surprise and astonishment. In more
recent times, by the progress of synthetic chemistry, we have succeeded
in producing in our laboratories a great variety of similar “organic”
combinations of carbon, by purely artificial means—for example alcohol,
acetic acid, formic acid. Indeed, many exceedingly complicated
combinations of carbon are now artificially produced, so that there is
every likelihood, sooner or later, of our producing artificially the
most complicated, and at the same time the most important of all,
namely, the albuminous combinations, or plasma-bodies. By the
consideration of this probability, the deep chasm which was formerly
and generally believed to exist between organic and inorganic bodies is
almost or entirely removed, and the way is paved for the conception of
spontaneous generation.
Of still greater, nay, the very greatest importance to the hypothesis of
spontaneous generation are, finally, the exceedingly remarkable
_Monera_, those creatures which we have already so frequently mentioned,
and which are not only the simplest of all observed organisms, but even
the simplest of all imaginable organisms. I have already described these
wonderful “_organisms without organs_,” when examining the simplest
phenomena of propagation and inheritance. We already know seven
different genera of these Monera, some of which live in fresh water,
others in the sea (compare above, p. 184; also Plate I. and its
explanation in the Appendix). In a perfectly developed and freely motile
state, they one and all present us with nothing but a simple little lump
of an albuminous combination of carbon. The individual genera and
species differ only a little in the manner of propagation and
development, and in the way of taking nourishment. Through the discovery
of these organisms, which are of the utmost importance, the supposition
of a spontaneous generation loses most of its difficulties. For as all
trace of organization—all distinction of heterogeneous parts—is still
wanting in them, and as all the vital phenomena are performed by one and
the same homogeneous and formless matter, we can easily imagine their
origin by spontaneous generation. If this happens through _plasmogeny_,
and if plasma capable of life already exists, it then only needs to
individualize itself in the same way as the mother liquor of crystals
individualizes itself in crystallization. If, on the other hand, the
spontaneous generation of the Monera takes place by true _autogeny_,
then it is further requisite that that plasma capable of life, that
primæval mucus, should be formed out of simpler combinations of carbon.
As we are now able artificially to produce, in our laboratories,
combinations of carbon similar to this in the complexity of their
constitution, there is absolutely no reason for supposing that there are
not conditions in free nature also, in which such combinations could
take place. Formerly, when the doctrine of spontaneous generation was
advocated, it failed at once to obtain adherents on account of the
composite structure of the simplest organisms then known. It is only
since we have discovered the exceedingly important Monera, only since we
have become acquainted in them with organisms not in any way built up of
distinct organs, but which consist solely of a single chemical
combination, and yet grow, nourish, and propagate themselves, that this
great difficulty has been removed, and the hypothesis of spontaneous
generation has gained a degree of probability which entitles it to fill
up the gap existing between Kant’s cosmogony and Lamarck’s Theory of
Descent. Even among the Monera at present known there is a species which
probably, even now, always comes into existence by spontaneous
generation. This is the wonderful _Bathybius Hæckelii_, discovered and
described by Huxley. As I have already mentioned (p. 184), this Moneron
is found in the greatest depths of the sea, at a depth of between 12,000
and 24,000 feet, where it covers the ground partly as retiform threads
and plaits of plasma, partly in the form of larger or smaller irregular
lumps of the same material.[6]
Only such homogeneous organisms as are yet not differentiated, and are
similar to inorganic crystals in being homogeneously composed of one
single substance, could arise by spontaneous generation, and could
become the primæval parents of all other organisms. In their further
development we have pointed out that the most important process is the
formation of a _kernel_ or _nucleus_ in the simple little lump of
albumen. We can conceive this to take place in a purely physical manner,
by the condensation of the innermost central part of the albumen. The
more solid central mass, which at first gradually shaded off into the
peripheral plasma, becomes sharply separated from it, and thus forms an
independent, round, albuminous corpuscle, the kernel; and by this
process the Moneron becomes a _cell_. Now, it must have become evident
from our previous chapters, that the further development of all other
organisms out of such a cell presents no difficulty, for every animal
and every plant, in the beginning of its individual life, is a simple
cell. Man, as well as every other animal, is at first nothing but a
simple egg-cell, a single lump of mucus, containing a kernel (p. 297,
Fig. 5).
In the same way as the kernel of the organic cell arose in the interior
or central mass of the originally homogeneous lump of plasma, by
separation, so, too, the first _cell-membrane_ was formed on its
surface. This simple, but most important process, as has already been
remarked, can likewise be explained in a purely physical manner, either
as a chemical deposit, or as a physical condensation in the uppermost
stratum of the mass, or as a secretion. One of the first processes of
adaptation effected by the Moneron originating by spontaneous generation
must have been the condensation of an external crust, which as a
protecting covering shut in the softer interior from the hostile
influences of the outer world. As soon as, by condensation of the
homogeneous Moneron, a cell-kernel arose in the interior and a membrane
arose on the surface, all the fundamental parts of the unit were
furnished, out of which, by infinitely manifold repetition and
combination, as attested by actual observation, the body of higher
organisms is constructed.
As has already been mentioned, our whole understanding of an organism
rests upon the cell theory established thirty years ago by Schleiden and
Schwann. According to it, every organism is either a simple cell or a
cell-community, a republic of closely connected cells. All the forms and
vital phenomena of every organism are the collective result of the forms
and vital phenomena of all the single cells of which it is composed. By
the recent progress of the cell theory it has become necessary to give
the elementary organisms, that is, the “organic” individuals of the
first order, which are usually designated as _cells_, the more general
and more suitable name of _form-units_, or _plastids_. Among these
form-units we distinguish two main groups, namely, the cytods and the
genuine cells. The _cytods_ are, like the Monera, pieces of plasma
without a kernel (p. 186, Fig. 1). _Cells_, on the other hand, are
pieces of plasma containing a kernel or nucleus (p. 188, Fig. 2). Each
of these two main groups of plastids is again divided into two
subordinate groups, according as they possess or do not possess an
external covering (skin, shell, or membrane). We may accordingly
distinguish the following four grades or species of plastids, namely: 1.
_Simple cytods_ (p. 186, Fig. 1 _A_); 2. _Encased cytods_; 3. _Simple
cells_ (p. 188, Fig. 2 _B_); 4. _Encased cells_ (p. 188, Fig. 2 _A_).
(Gen. Morph. i. 269-289.)
Concerning the relation of these four forms of plastids to spontaneous
generation, the following is the most probable:—1. The _simple cytods_
(Gymnocytoda), naked particles of plasma without kernel, like the still
living Monera, are the only plastids which directly come into existence
by spontaneous generation. 2. The _enclosed cytods_ (Lepocytoda),
particles of plasma without kernel, which are surrounded by a covering
(membrane or shell), arose out of the simple cytods either by the
condensation of the outer layers of plasma or by the secretion of a
covering. 3. The _simple cells_ (Gymnocyta), or naked cells, particles
of plasma with kernel, but without covering, arose out of the simple
cytods by the condensation of the innermost particles of plasma into a
kernel, or nucleus, by differentiation of a central kernel and
peripheral cell-substance. 4. The _enclosed cells_ (Lepocyta), or
testaceous cells, particles of plasma with kernel and an outer covering
(membrane or shell), arose either out of the enclosed cytods by the
formation of a kernel, or out of the simple cells by the formation of a
membrane. All the other forms of form-units, or plastids, met with,
besides these, have only subsequently arisen out of these four
fundamental forms by natural selection, by descent with adaptation, by
differentiation and transformation.
By this _theory of plastids_, by deducing all the different forms of
plastids, and hence, also, all organisms composed of them, from the
Monera, we obtain a simple and natural connection in the whole series of
the development of nature. The origin of the first Monera by spontaneous
generation appears to us as a simple and necessary event in the process
of the development of the earth. We admit that this process, as long as
it is not directly observed or repeated by experiment, remains a pure
hypothesis. But I must again say that this hypothesis is indispensable
for the consistent completion of the non-miraculous history of creation,
that it has absolutely nothing forced or miraculous about it, and that
certainly it can never be positively refuted. It must be taken into
consideration that the process of spontaneous generation, even if it
still took place daily and hourly, would in any case be exceedingly
difficult to observe and establish with absolute certainty as such. With
regard to the Monera, we find ourselves placed before the following
alternative: _either_ they are actually directly derived from
pre-existing, or “created,” most ancient Monera, and in this case they
would have had to propagate themselves unchanged for many millions of
years, and to have maintained their original form of simple particles of
plasma; _or_, the _present_ Monera have originated much later in the
course of the organic history of the earth, by repeated acts of
spontaneous generation, and in this case spontaneous generation may take
place now as well as then. The latter supposition has evidently much
more probability on its side than the former.
If we do not accept the hypothesis of spontaneous generation, then at
this one point of the history of development we must have recourse to
the miracle of a _supernatural creation_. The Creator must have created
the first organism, or a few first organisms, from which all others are
derived, and as such he must have created the simplest Monera, or
primæval cytods, and given them the capability of developing further in
a mechanical way. I leave it to each one of my readers to choose between
this idea and the hypothesis of spontaneous generation. To me the idea
that the Creator should have in this one point arbitrarily interfered
with the regular process of development of matter, which in all other
cases proceeds entirely without his interposition, seems to be just as
unsatisfactory to a believing mind as to a scientific intellect. If, on
the other hand, we assume the hypothesis of spontaneous generation for
the origin of the first organisms, which in consequence of reasons
mentioned above, and especially in consequence of the discovery of the
Monera, has lost its former difficulty, then we arrive at the
establishment of an uninterrupted natural connection between the
development of the earth and the organisms produced on it, and, in this
last remaining lurking-place of obscurity, we can proclaim the _unity of
all Nature, and the unity of her laws of Development_ (Gen. Morph. i.
164).