I endeavored in my Generelle Morphologie(1866) to draw the attention of biologists to these simplest and lowest organisms which have no visible organization or composition from different organs. I therefore proposed to give them the general title of monera. The more I have studied these structureless beings—cells without nuclei!—since that time, the more I have felt their importance in solving the greatest questions of biology—the problem of the origin of life, the nature of life, and so on. Unfortunately, these primitive little beings are ignored or neglected by most biologists to-day. O. Hertwig devotes one page of his three-hundred-page book on cells and tissues to them; he doubts the existence of cells without nuclei. Reinke, who has himself shown the existence of unnucleated cells among the bacteria (beggiatoa), does not say a word about their general significance. Bütschli, who shares my monistic conception of life, and has given it considerable support by his own thorough study of plasma-structures and the artificial production of them in oil and soap-suds, believes, like many other writers, that the "composition of even the simplest elementary organism from cell-nucleus and protoplasm" (the primitive organs of the cell) is indispensable. These and other writers suppose that the nucleus has been overlooked in the protoplasm of the monera I have described. This may be true for one section of them; but they say nothing about the other section, in which the nucleus is certainly lacking. To this class belong the remarkable chromacea (phycochromacea or cyanophycea), and especially the simplest forms of these, the chroococcacea (chroococcus, aphanocapsa, glœocapsa, etc.). These plasmodomous (plasma-forming) monera, which live at the very frontier of the organic and inorganic worlds, are by no means uncommon or particularly difficult to find; on the contrary, they are found everywhere, and are easy to observe. Yet they are generally ignored because they do not square with the prevailing dogma of the cell.
I ascribe this special significance to the chromacea among all the monera I have instanced because I take them to be the oldest phyletically, and the most primitive of all living organisms known to us. In particular their very simple forms correspond exactly to all the theoretic claims which monistic biology can make as to the transition from the inorganic to the organic. Of the chroococcacea, the chroococcus, glœocapsa, etc., are found throughout the world; they form thin, usually bluish-green coats or jelly-like deposits on damp rocks, stones, bark of trees, etc. When a small piece of this jelly is examined carefully under a powerful microscope, nothing is seen but thousands of tiny blue-green globules of plasma, distributed irregularly in the common structureless mass. In some species we can detect a thin structureless membrane enclosing the homogeneous particle of plasm; its origin can be explained on purely physical principles by "superficial energy"—like the firmer surface-layer of a drop of rain, or of a globule of oil swimming in water. Other species secrete homogeneous jelly-like envelopes—a purely chemical process. In some of the chromacea the blue-green coloring matter (phyocyan) is stored in the surface-layer of the particle of plasm, while the inner part is colorless—a sort of "central body." However, the latter is by no means a real, chemically and morphologically distinct, nucleus. Such a thing is completely lacking. The whole life of these simple, motionless globules of plasm is confined to their metabolism (or plasmodomism, chapter x.) and the resulting growth. When the latter passes a certain stage, the homogeneous globule splits into two halves (like a drop of quicksilver when it falls). This simplest form of reproduction is shared by the chromacea (and the cognate bacteria) with the chromatella or chromatophora, the green particles of chlorophyll inside ordinary plant-cells; but these are only parts of a cell. Hence no unprejudiced observer can compare these unnucleated and independent granules of plasm with real (nucleated) cells, but must conceive them rather as cytodes. These anatomic and physiological facts may easily be observed in the chromacea, which are found everywhere. The organism of the simplest chromacea is really nothing more than a structureless globular particle of plasm; we cannot discover in them any composition of different organs (or organella) for definite vital functions. Such a composition or organization would have no meaning in this case, since the sole vital purpose of these plasma-particles is self-maintenance. This is attained in the simplest fashion for the individual by metabolism; for the species it is effected by self-cleavage, the simplest conceivable form of reproduction.
Modern histologists have discovered a very intricate and delicate structure in many of the higher unicellular protists and in many of the tissue-cells of the higher animals and plants (such as the nerve-cells). They wrongly conclude that this is universal. In my opinion, this complication of the structure of the elementary organism is always a secondary phenomenon, the slow and gradual result of countless phylogenetic processes of differentiation, initiated by adaptation and transmitted to posterity by heredity. The earliest ancestors of all these elaborate nucleated cells were at first simple, unnucleated cytodes, such as we find to-day in the ubiquitous monera. We shall see more about them in the ninth and fifteenth chapters.
Naturally, this lack of a visible histological structure in the plasma-globule of the monera does not exclude the possession of an invisible molecular structure. On the contrary, we are bound to assume that there is such a structure, as in all albuminoid compounds, and especially all plasmic bodies. But we also find this elaborate chemical structure in many lifeless bodies; some of these, in fact, show a metabolism similar to that of the simplest organisms. We will return subsequently to this subject of catalysis. Briefly, the only difference between the simplest chromacea and inorganic bodies that have catalysis is in the special form of their metabolism, which we call plasmodomism (formation of plasm), or "carbon-assimilation." The mere fact that the chromacea assume a globular form is no sign whatever of a morphological vital process; drops of quicksilver and other inorganic fluids take the same shape when the individual body is formed under certain conditions. When a drop of oil falls into a fluid of the same specific gravity with which it cannot mix (such as a mixture of water and spirits of wine), it immediately assumes a globular shape. Inorganic solids usually take the form of crystals instead. Hence the distinctive feature of the simplest organism, the plasma-particles of the monera, is neither anatomic structure nor a certain shape, but solely the physiological function of plasmodomism—a process of chemical synthesis.
The difference between the monera I have described and any higher organism is, I think, greater in every respect than the difference between the organic monera and the inorganic crystals. Nay, even the difference between the unnucleated monera (as cytodes) and the real nucleated cells may fairly be regarded as greater still. Even in the simplest real cell we find the distinction between two different organella, or "cell-organs," the internal nucleus and the outer cell-body. The caryoplasm of the nucleus discharges the functions of reproduction and heredity; the cytoplasm of the cell-body accomplishes the metabolism, nutrition, and adaptation. Here we have, therefore, the first, oldest, and most important process of division of labor in the elementary organism. In the unicellular protists the organization rises in proportion to the differentiation of the various parts of the cell; in the tissue-forming histona it rises again in proportion to the distribution of work (or ergonomy) among the various organs. Darwin has given us in his theory of selection a mechanical explanation of the apparent design and purposiveness in this.
In order to have a correct monistic conception of organization, it is important to distinguish the individuality of the organism in its various stages of composition. We shall treat this important question, about which there is a good deal of obscurity and contradiction, in a special chapter (vii.). It suffices for the moment to point out that the unicellular beings (protists) are simple organisms both in regard to morphology and physiology. On the other hand, this is only true in the physiological sense of the histona, the tissue-forming animals and plants. From the morphological point of view they are made up of innumerable cells, which form the various tissues. These histonal individuals are called sprouts in the plant world and persons in the animal world. At a still higher stage of organization we have the trunk or stem (cormus), which is made up of a number of sprouts or persons, like the tree or the coral-stem. In the fixed animal stems the associated individuals have a direct bodily connection, and take their food in common; but in the social aggregations of the higher animals it is the ideal link of common interest that unites the individuals, as in swarms of bees, colonies of ants, herds of mammals, etc. These communities are sometimes called "animal-states." Like human polities, they are organisms of a higher type.
However, in order to avoid misunderstanding, we must take the word "organism" in the sense in which most biologists use it—namely, to designate an individual living thing, the material substratum of which is plasm or "living substance"—a nitrogenous carbon-compound in a semi-fluid condition. It leads to a good deal of misunderstanding when separate functions are called organisms, as is done sometimes in speaking of the soul or of speech. It would be just as correct to call seeing or running an organism. It is advisable also in scientific treatises to refrain from calling inorganic compounds as such "organisms," as, for instance, the sea or the whole earth. Such names, having a purely symbolical value, may very well be used in poetry. The rhythmic wave-movement of the ocean may be regarded as its respiration, the surge as its voice, and so on. Many scientists (like Fechner) conceive the whole earth with all its organic and inorganic contents as a gigantic organism, whose countless organs have been arranged in an orderly whole by the world-reason (God). In the same way the physiologist, Preyer, regards the glowing heavenly bodies as "gigantic organisms, whose breath is, perhaps, the glowing vapor of iron, whose blood is liquid metal, and whose food may be meteorites." The danger of this poetic application of the metaphorical sense of organism is very well seen in this instance, as Preyer builds on it a quite untenable hypothesis of the origin of life (see chapter xv.).
In the wider sense the word "organic" has long been used in chemistry as an antithesis to inorganic. By organic chemistry is generally understood the chemistry of the compounds of carbon, that element being distinguished from all the others (some seventy-eight in number) by very important properties. It has, in the first place, the property of entering into an immense variety of combinations with other elements, and especially of uniting with oxygen, hydrogen, nitrogen, and sulphur to form the most complicated albuminoids (see the Riddle, chapter xiv.). Carbon is a biogenetic element of the first importance, as I explained in my carbon-theory in 1866. It might even be called "the creator of the organic world." At first these organogenetic compounds do not appear in the organism in organized form—that is to say, they are not yet distributed into organs with definite purposes. Such organization is a result, not the cause, of the life-process.
I have already shown in the fourteenth chapter of the Riddle(and at greater length in the fifteenth chapter of my History of Creation) that the belief in the essential unity of nature, or the monism of the cosmos, is of the greatest importance for our whole system. I gave a very thorough justification of this cosmic monism in 1866. In the fifth chapter of the Generelle Morphologie I considered the relation of the organic to the inorganic in every respect, pointing out the differences between them on the one hand, and their points of agreement in matter, form, and force on the other. Nägeli some time afterwards declared similarly for the unity of nature in his able Mechanisch-physiologische Begründung der Abstammungslehre(1884). Wilhelm Ostwald has recently done the same, from the monistic point of view of his system of energy, in his Naturphilosophie, especially in the sixteenth chapter. Without being acquainted with my earlier work, he has impartially compared the physico-chemical processes in the organic and inorganic worlds, partly adducing the same illustrations from the instructive field of crystallization. He came to the same monistic conclusions that I reached thirty-six years ago. As most biologists continue to ignore them, and as, especially, modern vitalism thrusts these inconvenient facts out of sight, I will give a brief summary once more of the chief points as regards the matter, form, and forces of bodies.
Chemical analysis shows that there are no elements present in organisms that are not found in inorganic bodies. The number of elements that cannot be further analyzed is now put at seventy-eight; but of these only the five organogenetic elements already mentioned which combine to form plasm—carbon, oxygen, hydrogen, nitrogen, and sulphur—are found invariably in living things. With these are generally (but not always) associated five other elements—phosphor, potassium, calcium, magnesium, and iron. Other elements may also be found in organisms; but there is not a single biological element that is not also found in the inorganic world. Hence the distinctive features which separate the one from the other can be sought only in some special form of combination of the elements. And it is carbon especially, the chief organic element, that by its peculiar affinity enters into the most diverse and complicated combinations with other elements, and produces the most important of all substances, the albuminoids, at the head of which is the living plasm (cf. chapter vi.).