chapter vi. of the _Riddle_. Romanes suffered a good deal from illness

and grief at the loss of friends in his last years. In this condition of extreme depression and melancholy he fell under mystic influences which promised him rest and hope by belief in the supernatural. It is hardly necessary to point out to impartial readers that such a conversion as this does not shake his earlier monistic views. As in similar cases where deep emotional disturbance, painful experiences, and exuberant hope have clouded the judgment, we must still hold that it is the place of the latter, and not of the emotions or of any supernatural revelation, to attain a knowledge of the truth. But for such attainment it is necessary for the organ of mind, the phronema, to be in a normal condition.[3]

Of all the wonders of life, consciousness may be said to be the greatest and most astounding. It is true that to-day most physiologists are agreed that man's consciousness, like all his other mental powers, is a function of the brain, and may be reduced to physical and chemical processes in the cells of the cortex. Nevertheless, some biologists still cling to the metaphysical view that this "central mystery of psychology" is an insoluble enigma, and not a natural phenomenon. In face of this, I must refer the reader to the monistic theory of consciousness which I have given in chapter x. of the _Riddle_, and must insist that in this case again embryology is the best guide to a comprehension of the subject. Sight is next to consciousness, in many respects, as one of the wonders of life. The well-known embryology of the eye teaches us how sight--the perception of images from the external world--has been gradually evolved from the simple sensitiveness to light of the lower animals, by the development of a transparent lens. In the same way the conscious soul, the internal mirror of the mind's own action, has been produced as a new wonder of life out of the unconscious associations in the phronema of our earlier vertebrate ancestors.

From this thorough and unprejudiced appreciation of the biology of the phronema it follows that the knowledge of truth, the aim of all science, is a natural physiological process, and that it must have its organs like all other psychic functions. These organs have been revealed to us so fully in the advance of biology during the last half-century that we may be said to have a generally satisfactory idea of the natural character of their organization and action, though we are still far from enjoying a complete anatomical and physiological insight into their details. The most important acquisition we have made is the conviction that all knowledge was originally acquired _a posteriori_ and from experience, and that its first sources are the impressions made on our organs of sense. Both these--the peripheral sense-organs--and the phronema, or central psychic organ, are subject to the law of substance; and the action of the phronema is just as reducible to chemical and physical processes as the action of the organs of sense.

In diametrical opposition to our monistic and empirical theory of knowledge, the prevailing dualistic metaphysics assumes that our knowledge is only partly empirical and _a posteriori_, and is partly quite independent of experience and _a priori_, or due to the original constitution of our "immaterial" mind. The powerful authority of Kant has lent enormous prestige to this mystic and supernatural view, and the academic philosophers of our time are endeavoring to maintain it. A "return to Kant" is held to be the only means of salvation for philosophy; in my opinion it should be a return to nature. As a fact, the return to Kant and his famous theory of knowledge is an unfortunate "crab-walk" on the part of philosophy. Our modern metaphysicians regard the brain, as Kant did one hundred and twenty years ago, as a mysterious, whitish-gray, pulpy mass, the significance of which as an instrument of the mind is very enigmatic and obscure. But for modern biology the brain is the most wonderful structure in nature, a compound of innumerable soul-cells or neurona. These have a most elaborate finer structure, are combined in a vast psychic apparatus by thousands of interlacing nerve-fibrils, and are thus fitted to accomplish the highest mental functions.

FIRST TABLE

ANTITHESIS OF THE TWO WAYS OF ATTAINING THE TRUTH

MONISTIC THEORY OF KNOWLEDGE │ DUALISTIC THEORY OF KNOWLEDGE │ 1. Knowledge is a natural process,│ 1. Knowledge is a supernatural not a miracle. │ process, a miracle. │ 2. Knowledge, as a natural │ 2. Knowledge, as a transcendental process, is subject to the │ process, is not subject general law of substance. │ to the law of substance. │ 3. Knowledge is a physiological │ 3. Knowledge is not a physiological, process, with the brain for │ but a purely spiritual, its anatomic organ. │ process. │ 4. The part of the human brain │ 4. The part of the human brain in which knowledge is │ which seems to act as exclusively engendered │ organ of knowledge is is a definite and limited │ really only the instrument part of the cortex, the │ that allows the spiritual phronema. │ process to appear. │ 5. The organ of knowledge, or │ 5. The organ of knowledge, or the phronema, consists of │ the phronema (the sum of the association-centres, │ the association-centres), and differs by its special │ is merely a part of the histological structure from │ instrument of mind, like the neighboring sensory │ the neighboring and correlated and motor centres in the │ sensory and motor-centres. cortex, and it is in close │ relation with these. │ │ 6. The innumerable cells which │ 6. The innumerable phronetal make up the phronema--the │ cells, as the microscopic phronetal cells--are │ elementary parts of the the elementary organs of │ phronema, are, it is true, the cognitive process: the │ indispensable instruments possibility of knowledge │ of the cognitive process, depends on their normal │ but not its real factors--merely physical texture and chemical │ finer parts of its composition. │ instrument. │ 7. The physical process of │ 7. The metaphysical process of knowledge consists in the │ knowledge consists in the combination or association │ combination or association of presentations, the │ of presentations, which are first sources of which are │ only partly traceable to the impressions transmitted │ sense-impressions, and are to the sense-centres. │ partly supersensual, transcendental │ processes. │ 8. Hence all knowledge originally │ 8. Hence knowledge is of two comes from experience, │ kinds: empirical and _a by means of the │ posteriori_ knowledge, obtained organs of sense; partly │ by experience, and directly (direct experience, │ transcendental _a priori_ observation, and experiment │ knowledge, independent of of the present), │ experience. Mathematics partly indirectly (historical │ especially belongs to the and indirectly transmitted │ latter class, its axioms past experiences). │ differing from empirical All knowledge (even mathematical) │ truths by their absolute is of empirical │ certainty. origin and _a posteriori_. │

II

LIFE

Definition of life--Comparison with a flame--Organism and organization--Machine theory of life--Organisms without organs: monera--Organization and life of the chromacea--Stages of organization--Complex organisms--Symbolic organisms--Organic compounds--Organisms and inorganic bodies compared in regard to matter, form, and function--Crystalloid and colloid substances--Life of crystals--Growth of crystals--Waves of growth--Metabolism--Catalysis--Fermentation--Biogenesis--Vital force--Old and new vitalism--Palavitalism--Antivitalism--Neovitalism.

As the object of this work is the critical study of the wonders of life, and a knowledge of the truth concerning them, we must first of all form a clear idea of the meaning of "life" and "wonder," or miracle. For thousands of years men have appreciated the difference between life and death, between living and lifeless bodies; the former are called organisms, and the latter known as inorganic bodies. Biology--in the widest sense--is the name of the science which treats of organisms; we might call the science which deals with the inorganic "abiology," abiotik, or anorgik. The chief difference between the two provinces is that organisms accomplish peculiar, periodically repeated, and apparently spontaneous movements, which we do not find in inorganic matter. Hence life may be conceived as a special process of movement. Recent study has shown that this is always connected with a particular chemical substance, _plasm_, and consists essentially in a circulation of matter, or _metabolism_. At the same time modern science has shown that the sharp distinction formerly drawn between the organic and the inorganic cannot be sustained, but that the two kingdoms are profoundly and inseparably united.

Of all the phenomena of inorganic nature with which the life-process may be compared, none is so much like it externally and internally as the flame. This important comparison was made two thousand four hundred years ago by one of the greatest philosophers of the Ionic school, Heraclitus of Ephesus--the same thinker who first broached the idea of evolution in the two words, _Panta rei_--all things are in a state of flux. Heraclitus shrewdly conceived life as a fire, a real process of combustion, and so compared the organism to a torch.

Max Verworn has lately employed this metaphor with great effect in his admirable work on general physiology, and has especially dealt with the comparison of the individual life-form with the familiar butterfly shape of the gas-flame. He says:

The comparison of life to a flame is particularly suitable for helping us to realize the relation between form and metabolism. The butterfly-shape of a gas-flame has a very characteristic outline. At the base, immediately above the burner, there is still complete darkness; over this is a blue and faintly luminous zone; and over this again the bright flame expands on either side like the wings of a butterfly. This peculiar form of the flame, with its characteristic features, which are permanent, as long as we do not interfere with the gas or the environment, is solely due to the fact that the grouping of the molecules of the gas and the oxygen at various parts of the flame is constant, though the molecules themselves change every moment. At the base of the flame the molecules of the gas are so thickly pressed that the oxygen necessary for their combustion cannot penetrate; hence the darkness we find here. In the bluish zone a few molecules of oxygen have combined with the molecules of the gas: we have a faint light as the result. But in the body of the flame the molecules of the gas are so freely combined with the oxygen of the atmosphere that we have a lively combustion. However, the exchange of matter (metabolism) between the outpouring gas and the surrounding air is so regulated that we always find the same molecules in the same quantity at the same spot. Thus we get the permanent flame, with all its characteristics. But if we alter the circulation by lessening the stream of gas, the shape of the flame changes, because now the disposition of the molecules on both sides is different. Thus the study of the gas-jet gives us, even in detail, the features we find in the structure of the cell.

The scientific soundness of this metaphor is all the more notable as the phrase, "the flame of life," has long been familiar both in poetry and popular parlance.

In the sense in which science usually employs the word "organism," and in which we employ it here, it is equivalent to "living thing" or "living body." The opposite to it, in the broad sense, is the anorganic or inorganic body. Hence the word "organism" belongs to physiology, and connotes essentially the visible life-activity of the body, its metabolism, nutrition, and reproduction.

However, in most organisms we find, when we examine their structure closely, that this consists of various parts, and that these parts are put together for the evident purpose of accomplishing the vital functions. We call them _organs_, and the manner in which they are combined, apparently on a definite plan, is their _organization_. In this respect, we compare the organism to a machine in which some one has similarly combined a number of (lifeless) parts for a definite purpose, but according to a preconceived and rationally initiated design.

The familiar comparison of an organism to a machine has given rise to very serious errors in regard to the former, and has, of late, been made the base of false dualistic principles. The modern "machine-theory of life" which is raised thereon demands an intelligent design and a deliberate constructing engineer for the origin of the organism, just as we find in the case of the machine. The organism is then very freely compared to a watch or a locomotive. In order to secure the regular working of such a complicated mechanism, it is necessary to arrange for a perfect co-operation of all its parts, and the slightest accident to a single wheel suffices to throw it out of gear. This figure was particularly employed by Louis Agassiz (1858), who saw "an incarnate thought of the Creator" in every species of animal and plant. Of late years it has been much used by Reinke in the support of his theosophic dualism. He described God, or "the world-soul," as the "cosmic intelligence," but ascribes to this mystic immaterial being the same attributes that the catechism and the preacher give to the Creator of heaven and earth. He compares the human intelligence which the watch-maker has put into the elaborate structure of the watch with the "cosmic intelligence" which the Creator has put in the organism, and insists that it is impossible to deduce its purposive organization from its material constituents. In this he entirely overlooks the immense difference between the "raw material" in the two cases. The "organs" of the watch are metallic parts, which fulfil their purpose in virtue only of their physical properties (hardness, elasticity, etc.). The organs of the living organism, on the other hand, perform their functions chiefly in virtue of their chemical composition. Their soft plasma-body is a chemical laboratory, the highly elaborate molecular structure of which is the historical product of countless complicated processes of heredity and adaptation. This invisible and hypothetical molecular structure must not (as is often done) be confused with the real and microscopically discoverable structure of the plasm, which is of great importance in the question of organization. If one is disposed to assume for this molecular structure a simple chemical substance, a deliberate design, and an "intelligent natural force" for cause, one is bound to do the same for powder, and say that the molecules of charcoal, sulphur, and saltpetre have been purposively combined to produce an explosion. It is well known that powder was not made according to a theory, but accidentally discovered in the course of experiment. The whole of this favorite machine-theory of life, and the far-reaching dualistic conclusions drawn from it, tumble to pieces when we study the simplest organisms known to us, the monera; for these are really organisms without organs--and without organization!

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_,