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.