When we carefully consider the intelligent experiments that have been made in regard to archigony in the light of these facts, it is clear that their negative result does not in the slightest degree affect our question. The much-admired experiments of Pasteur and his colleagues prove merely that in certain artificial conditions infusoria are not formed in decomposing organic compounds (or the dead tissues of highly organized histona); they cannot possibly prove that saprobioses of this kind do not take place under other conditions. They tell us nothing whatever about the possibility or reality of archigony; in the form in which I put the scientific hypothesis in 1866 it is completely untouched by all these experiments. It remains intact as the first attempt to give a provisional reply—if only in the form of a temporary hypothesis—on the basis of modern science to one of the chief questions of natural philosophy.
In my General Morphology (1866), and afterwards in my Biological Studies on the Monera and other Protists, and the first volume of my Systematic Phylogeny (1894), I attempted to sketch in detail the stages of the process to which I give the name of archigony. I distinguished two principal stages—autogony (the formation of the first living matter from inorganic nitrogenous carbon-compounds) and plasmogony (the formation of the first individualized plasm; the earliest organic individuals in the form of monera). In more recent efforts I have made use of the important results reached by Nägeli (1884) in his investigations of the same subject. In regard to some important points relating to the chemico-physical part of the question, Nägeli has, in his Mechanico-physiological Theory of Evolution (chapter ii.), gone more into the details of the process of archigony. To the earliest living things, which were formed by "unicellular organization" of the plasm out of simple inorganic compounds, he gives the name of probia or probionta, and thinks that these had an even simpler structure than my monera. This view seems to rest on a misunderstanding. Nägeli does not strictly follow my definition, "organisms without organs" (that is to say, structureless living particles of plasm without morphological differentiation), but he has in mind the individual rhizopod-like organisms which I had at first described as monera—protamœba, protogenes, protomyxa, etc. In my present view the chromacea, or plasmodomous phytomonera, are much more important than these plasmophagous zoomonera. It is curious that Nägeli does not make thorough use of their primitive organization for the establishment of his theory, although he has had the great merit of describing these most primitive of all living organisms as unicellular algæ (1842). As a matter of fact, the simplest chromacea (chroococcus and related forms) approach so closely to his hypothetical probia or probionta that the only things we can regard as the rudiments of organization in the chroococcacea are the secretion of a protective membrane about the homogeneous plasma-globule and the separation of the blueish-green cortical zone from the colorless central granule. The more important of the further conclusions of Nägeli are those which relate to the mode of the primitive abiogenesis and the frequent repetition of this physical process.
Recently Max Kassowitz, in the second volume of his General Biology (1899), has gone fully into the various stages of the process of archigony, as a sequel to his metabolic theory of the building up and decay of plasm, from the point of view of physiological chemistry. He says very truly that the development of living from lifeless matter must not be conceived as a sudden leap; the very complicated chemical unities which now form the basis of life have been slowly and gradually evolved during an incalculably long period by the way of substitution for simpler compounds. We may join these views—which generally accord with my earlier deductions—with Pflüger's cyanogen theory, and so draw up the following theses:
1. A preliminary stage to archigony is the formation of certain nitrogenous carbon-compounds which may be classed in the cyanic group (cyanic acid, etc.). 2. When the crust of the earth stiffened, water was formed in the fluid condition; under its influence, and in consequence of the great changes in the carbonic-acid laden atmosphere, a series of complicated nitrogenous carbon-compounds were formed from these simple cyanic compounds, and these first produced albumin (or protein). 3. The molecules of albumin arranged themselves in a certain way, according to their unstable chemical attractions, in larger groups of molecules (pleona or micella). 4. The albumin-micella combined to form larger aggregations, and produced homogeneous plasma-granules (plassonella). 5. As they grew the plassonella divided, and formed larger plasma-granules of a homogeneous character: monera (= probionta). 6. In consequence of surface-strain or of chemical differentiation, there took place a separation of the firmer cortical layer (membrane) from the softer marrow layer (central granule), as in many of the chromacea. 7. Afterwards the simplest (nucleated) cells were formed from these unnucleated cytodes, the hereditary mass of the plasm gathering within the monera and condensing into a firm nucleus.
It is an interesting, but at present unanswered, question whether the process of archigony only occurred once in the course of time or was frequently repeated. Reasons can be given for both views. Pflüger says: "In the plant the living albumin only continues to do what it has done ever since its origin—constantly to regenerate itself or to grow; hence I believe that all the albumin in the world comes from that source. On that account I doubt if spontaneous generation takes place in our time. Moreover, comparative biology directly shows that all life has come from one single root." However, this view does not exclude the possibility of the chemical process of spontaneous plasmodomism having been frequently repeated—under like conditions—in the same form in primordial times.
On the other side, Nägeli especially has pointed out that there is no reason to prevent us from thinking that archigony was repeated several times, even down to our own day. Whenever the physical conditions for the chemical process of plasmodomism were given, it might be repeated anywhere at any time. As to locality, the sea-shore probably affords the most favorable conditions; as, for instance, on the surface of fine moist sand the molecular forces of matter in all its conditions—gaseous, fluid, viscous, and solid—find the best conditions for acting on each other. It is a fact that to-day all the various evolutionary forms of living matter—from the simplest moneron (chroococcus) to the plain nucleated cell, from this to the highly organized cell of the radiolaria and infusoria, from the simple ovum to the most elaborate tissue-structure in the higher plants and animals, from the amphioxus to man—come in an order of succession. There are only two ways of explaining this fact: either the simplest living organisms, the chromacea and bacteria, the palmella and amœbæ, have remained unchanged or made very little advance in organization since the beginning of life—more than a hundred million years; or else the phylogenetic process of their transformation has been frequently repeated in the course of this period, and is being repeated to-day. Even if the latter were the case, we should hardly be in a position to learn it by direct observation.
Assuming that the simplest organisms are still formed by abiogenesis, the direct observation of the process would probably be impossible, or at least extremely difficult, for the following reasons: 1. The earliest and simplest organisms are most probably globular particles of plasm, without any visible structure, like the simplest living chromacea (chroococcus). 2. These plasmodomous monera cannot be distinguished from the chromoplasts (chlorophyll-granules), which live inside plant-cells, and may continue after the death of the cells to multiply independently by cleavage. 3. We must admit with Nägeli that the original size of these probionta (in spite of the relatively colossal size of their molecules) is very small—much too small to come within the range of the best microscope. 4. In the same way the primitive metabolism and the slow, simple growth of these monera would not come within direct observation. 5. As a matter of fact, we do often find in stagnant water, and in the sea, tiny granules which consist, or seem to consist, of plasm. We usually regard them as detached portions of dead animals or plants; little isolated chlorophyll-granules that may be found everywhere are looked upon as rejected products of vegetal cells. But who could refute the assumption that they are really plassonella or young monera, which grow slowly and unite with similar particles to form larger plasmic bodies?
It is often objected to our naturalistic and monistic conception of archigony that we have not yet succeeded in forming albuminous bodies, and especially plasm, in our chemical laboratories by artificial synthesis; from this the perverse dualistic conclusion is drawn that it is only supernatural vital forces that can do this. It is forgotten that we do not yet know the complicated structure of albuminous bodies, and that we do not yet know what really happens inside the green chlorophyll-granules which in every plant-cell convert the radiant energy of sunlight into the virtual energy of the new-formed plasm. How can we be expected to reproduce synthetically, with the imperfect and crude methods of present chemistry, an elaborate chemical process the nature of which is not analytically known to us? However, the worthlessness of this sceptical objection is obvious: we can never claim that a natural process is supernatural because we cannot artificially reproduce it.