The Mechanism of Life Part 15

We are often told "not to force the a.n.a.logy." But error is equally produced by the exaggeration of unimportant differences. We have already seen that nutrition, absorption, transformation, and excitation are not the characteristics of living organisms alone; nor is reaction to external impressions the appanage only of animate beings. To insist on the resemblance between an osmotic production and a living being is not to force an a.n.a.logy but to demonstrate a fact.

Let us briefly recapitulate. An osmotic growth has an evolutionary existence; it is nourished by osmosis and intussusception; it exercises a selective choice on the substances offered to it; it changes the chemical const.i.tution of its nutriment before a.s.similating it. Like a living thing it ejects into its environment the waste products of its function.

Moreover, it grows and develops structures like those of living organisms, and it is sensitive to many exterior changes, which influence its form and development. But these very phenomena--nutrition, a.s.similation, sensibility, growth, and organization--are generally a.s.serted to be the sole characteristics of life.

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CHAPTER XIII

EVOLUTION AND SPONTANEOUS GENERATION

By many biologists, even at the present day, the origin and evolution of living beings is considered to be outside the domain of natural phenomena, and hence beyond the reach of experimental research. The change in our views on this subject is due to a Frenchman, Jean Lamarck, who was the true originator of the scientific doctrine of evolution. At a time when the miraculous origin of every living being was regarded as an unchangeable verity, and was defended like a sacred dogma, Lamarck boldly formulated his theory of evolution, with all its attendent consequences, from spontaneous generation to the genealogy of man.

In his _Philosophie Zoologique_, which appeared in 1809, Lamarck put forth his claim to regard all the phenomena of life, of living beings, and of man himself as pertaining to the domain of natural phenomena. According to him, all bodies which are met with in nature, organic and inorganic alike, are subject to the same laws. Life is a physical phenomenon, and all the processes of life are due to mechanical causes, either physical or chemical. He writes: "a leur source le physique et le moral ne sont sans doute qu'une seule et meme chose. Il faut rechercher dans la consideration de l'organisation les causes memes de la vie."

In the intellectual evolution of the human mind perhaps no advance has been more important than that of Lamarck--the conquest of the domain of life by human intelligence. In conformity with the true scientific method, he founds his doctrine on the facts and phenomena of nature. "I confine myself," he says, "within the bounds of a simple contemplation {161} of nature." It was this observation of the gradual perfecting of living organisms from the simplest to the most complicated that inspired Lamarck with the idea of evolution and transformation. "How," he says, "can we help searching for the cause of such wonderful results? Are we not compelled to admit that nature has produced successively bodies endowed with life, proceeding from the simplest to the most complex?"

The various products of nature have been divided into cla.s.ses, genera, and species, simply to facilitate their study. Modern research tends to show that there is no definite line of demarcation even between the animal, vegetable, and mineral kingdoms. All our cla.s.sification is artificial, and the pa.s.sage from one division to another is gradual and insensible. Lamarck expresses this idea very clearly: "We must remember that cla.s.ses, orders, and families, and all such nomenclature, are methods of our own invention.

In nature there are no such things as cla.s.ses or orders or families, but only individuals. As we become better acquainted with the productions of nature, and as the number of specimens in our collections increases, we see the intervals between the cla.s.ses gradually fill up, and the lines of separation become effaced."

Lamarck also raises his voice against the supposed immutability of species.

"Species have only a relative constancy, depending on the circ.u.mstances of the individuals. The individuals of a given species perpetuate themselves without variation only so long as there is no variation in the circ.u.mstances which influence their existence. Numberless facts prove that when an individual of a given species changes its locality, it is subjected to a number of influences which little by little alter, not only the consistency and proportions of its parts, but also its form, its faculty, and even its organization; so that in time every part will partic.i.p.ate in the mutations which it has undergone."

Lamarck also clearly affirms the fact of spontaneous generation. "I hope to prove," he says, "that nature possesses means and faculties for the production of all the forms which we so much admire. Rudimentary animals and plants have {162} been formed, and are still being formed to-day, by spontaneous generation."

Lamarck himself gives a resume of his doctrine in the following six propositions:--

1. "All the organized bodies of our globe are veritable productions of Nature, which she has successively formed during the lapse of ages.

2. "Nature began, and still recommences day by day, with the production of the simplest organic forms. These so-called spontaneous generations are her direct work, the first sketches as it were of organization.

3. "The first sketches of an animal or a vegetable growth being begun under favourable conditions, the faculties of commencing life and of organic movement thus established have gradually developed little by little the various parts and organs, which in process of time have become diversified.

4. "The faculty of growth is inherent in every part of an organized body; it is the primary effect of life. This faculty of growth has given rise to the various modes of multiplication and regeneration of the individual, and by its means any progress which may have been acquired in the composition and forms of the organism has been preserved.

5. "All living things which exist at the present day have been successively formed by this means, aided by a long lapse of time, by favourable conditions, and by the changes on the surface of the globe--in a word, by the power which new situations and new habits have of modifying the organs of a body which is endowed with life.

6. "Since all living things have undergone more or less change in their organization, the species which have been thus insensibly and successively produced can have but a relative constancy, and can be of no very great antiquity."

The admirable work of Lamarck was absolutely neglected in France, where it was treated as unworthy even of consideration. This neglect profoundly afflicted Lamarck, who gradually sank a victim to the opposition of his contemporaries. He left, however, one disciple, Etienne Jeoffroy St. {163} Hilaire, but he too was soon reduced to silence under the weight of authority of his adversaries.

[Ill.u.s.tration: FIG. 62.--Osmotic vegetation.]

Before the doctrine of evolution could live and take its proper place, it had to be reborn in England--the country of liberty. This resuscitation was due to Darwin, who added to it his illuminating doctrine of natural selection. But apart from this and a perfecting of its various details, Lamarck had already formulated the doctrine of evolution with perfect precision. Lamarck's work was still-born, whereas that of Darwin lived and grew to its full development. This was due, not to any imperfection or insufficiency in Lamarck's work, but {164} to the milieu into which it was born. It was the environment that stifled the offspring of Lamarck.

In 1868, Ernest Haeckel speaks of the genius of Lamarck in these words: "The chief of the natural philosophers of France is Jean Lamarck, who takes his place beside Goethe and Darwin in the history of evolution. To him belongs the imperishable glory of being the first to formulate the theory of descent, and of founding the philosophy of nature on the solid basis of biology," and adds, "There is no country in Europe where Darwin's doctrine has had so little influence as in France." Haeckel has but done tardy justice in his discovery of and testimony to the genius of Lamarck.

The spirit of opposition does not seem to have much changed in France since Lamarck's time. In 1907 the Academie des Sciences de Paris excluded from its _Comptes Rendus_ the report of my researches on diffusion and osmosis, because it raised the question of spontaneous generation.

The majority of scientists seem to consider that the question of spontaneous generation was definitely settled once for all when Pasteur's experiments showed that a sterilized liquid, kept in a closed tube, remained sterile.

Without the idea of spontaneous generation and a physical theory of life, the doctrine of evolution is a mutilated hypothesis without unity or cohesion. On this point Lamarck speaks most clearly: "Although it is customary when one speaks of the members of the animal or vegetable kingdom to call them products of nature, it appears that no definite conception is attached to the expression. Our preconceived notions hinder us from recognising the fact that Nature herself possesses all the faculties and all the means of producing living beings in any variety. She is able to vary, very slowly but without cessation, all the different races and all the different forms of life, and to maintain the general order which we see in all her works."

The doctrine of Lamarck is frequently misinterpreted. We often hear it expressed as "Function makes the organ," or even "Function creates the organ." This is equivalent to saying, "Life makes the living being," which is incomprehensible, {165} making of function a sort of immaterial and independent ent.i.ty which constructs a material organ in order to lodge within it. No such idea is to be found in all the works of Lamarck. He formulates his law in the following terms: "In every animal which is still undergoing development, the frequent and sustained use of any one organ increases its size and power, whereas the constant neglect of the use of such organ weakens and deteriorates it, so that it finally disappears."

In his expression of this law Lamarck insists on the fact that organization precedes function. He affirms only that function, _i.e._ action and reaction, modifies the organ; or, in other words, that organisms are modelled by the action of exterior forces acting upon them. It is in this sense only that function may be said to make an organ, but this mode of expression should be avoided, as it is apt to be misunderstood.

Astronomy teaches us that our globe was detached from the sun in an incandescent state, and geology a.s.serts that this earth has pa.s.sed through a period of long ages when its temperature was incompatible with the existence of life. It was only with the cooling of the earth crust that it was possible for living beings to make their appearance. Hence they must of necessity have been produced spontaneously from terrestrial material under the influences of chemical and physical forces. This opinion imposes itself on all who reflect and judge freely. In the same way the doctrine of evolution necessitates as a corollary the doctrine of spontaneous generation. The doctrine of evolution should reconst.i.tute every link in the chain of beings from the simplest to the most complicated; it cannot afford to leave out the most important of all, viz. the missing link between the inorganic and the organic kingdoms. If there is a chain, it must be continuous in all its parts, there can be no solution of continuity.

Evolutionists like Lamarck and Haeckel admit spontaneous generation, not as the most probable, but as the only possible explanation of the phenomenon of life.

Lamarck shows us the apparition of living things at a certain epoch of the earth's evolution, and the gradual {166} development of more complicated forms as the conditions changed on the surface of the globe. Darwin shows how heredity and natural selection tend to accentuate the variations which are favourable to existence. Haeckel demonstrates the parallelism between ontogenesis and philogenesis--between the successive forms in the evolution of the embryo and the successive forms of the individual in the evolution of a race. These are great and admirable conquests of the human intelligence, they have demonstrated the first appearance and the progressive evolution of living beings; it now only remains for us to explain them.

[Ill.u.s.tration: FIG. 63.--Marine forms of osmotic growth.]

The doctrine of evolution, while enforcing the fact of spontaneous generation and progressive evolution, gives us no hint as to the physical mechanism of such generation. It does not tell us by what forces, or according to what laws, the simpler forms of life have been produced, or in what manner differences of environment have acted in order to modify them.

The doctrine a.s.serts the simultaneous variations in organic forms and in the physical influences which produce them, but says {167} nothing as to their mode of action. The Darwinian theory shows how acquired variations are transmitted and accentuated by natural selection, but it says nothing as to how these variations may be acquired. In the same way we are in entire ignorance as to the physical mechanism of ontogenetic development, the evolution of the embryo.

The morphogenic action of diffusion produces osmotic growths of extreme variety. Most of these forms recall those of living things--sh.e.l.ls, fungi, corals, and algae. The a.n.a.logy of function is quite as close as the resemblance of form. The study of osmosis, however, is as yet in its infancy, and osmotic productions vary with the physical conditions of chemical const.i.tution, temperature, concentration, and the like. The study of the organizing action of osmosis on organic material has as yet been hardly attempted.

Osmosis produces growths of great complexity, much more complicated indeed than the more simple forms of living organisms. This marvellous complexity of an osmotic growth may be compared with another fact, the ontogenetic development of the ovum, a single cell which under favourable conditions of environment may evolve into a most complicated organism. These considerations lead to the belief that the beginning of life has not been the production of a simple primitive form from which all others are descended, but that a number of such primitive forms may have been produced, forms which by a rapid physical development attained a high degree of complexity. Osmotic morphogenesis shows us that the ordinary physical forces have in fact a power of organization infinitely greater than has been hitherto supposed by the boldest imagination.

When we consider the ignorance in which we still remain as to the phenomena which pa.s.s before our very eyes, how can we expect to understand those which occurred in past ages, when the physical and chemical conditions were so immensely different from those which obtain in our own time? What do we know even now of the physical and chemical phenomena which take place in the unfathomed depths of the ocean, where for aught we know even at the present time the same {168} process may be going on--the genesis of life, and the emergence of living beings out of the inanimate mineral world?

"Even now," says Albert Gaudry, "polyps and oceanic animalculae are building up vast coral reefs and rocks. The oxygen and hydrogen which existed once was water, the oxygen and nitrogen which once made air, the carbon, the phosphorus, the silica and the lime which once were solid rock, now form the substance of living beings. The silica is deposited in the skeleton of a sponge or a radiolaria, the sh.e.l.l of a foraminifera or the carapace of a crustacean, or unites with phosphorus to form the bones of a vertebrate. A very tumult of life has succeeded to the primitive silence of inert matter.

Life has invaded the earth, and we see on all sides the inanimate mineral kingdom being changed into a living world."

The admission that life may have appeared on the earth under the influence of natural forces and according to physical laws and conditions different from those of the present era throws a vivid light on the study of biogenesis, spontaneous generation, and evolution. The means of research are now indicated, and we have only to study the doc.u.ments already in our possession in order to know the conditions which obtained when life first appeared on the globe. We must endeavour to reproduce these conditions and to study their effects.

Since all living beings are formed of the same elements as those of the mineral world, the term "organic" as applied to combinations can only be used in order to emphasize the complexity of their const.i.tution. It was formerly believed that these organic combinations were the result of life, and could not be reproduced except by living organisms. To-day many of these organic substances are produced in the laboratory from inorganic materials. In the past history of the globe it is easy to imagine conditions which would facilitate the synthesis of organic substances without the interposition of life. At the temperature of the electric furnace, which was that of the earth at an early period of its evolution, chemical combinations are possible quite other than those obtaining under the present conditions of temperature and pressure. At the higher temperature of the early {169} geological era, silicides, carbides, phosphides, and nitrides were formed in stable combinations instead of the oxides, silicates, carbonates, phosphates, and nitrates of the present time. These combinations existed on the earth at a time when the conditions of temperature precluded the existence of water in a liquid state. As the temperature cooled, and the water vapour became condensed, it entered into chemical combination with the various rocks, producing organic compounds like acetylene, which results from the action of water on calcium carbide.

H. Lenicque has developed a theory as to the formation of various rocks under these conditions, which he communicated in 1903 to the French Society of Civil Engineers.

The chemical evolution of the globe has undergone great changes as the temperature gradually fell and the const.i.tution of its crust altered. As long as the temperature was higher than that at which water can exist, all chemical reactions must have taken place between anhydric substances, elements and salts in a state of fusion. These conditions are very different from those of the present-day chemistry, which is the chemistry of aqueous solutions. We may hope to be able to reproduce the earlier conditions by the experimental study of anhydric substances in a state of fusion.

At a later period, that of the primary and secondary rocks, there was a uniform and constant temperature of about 40 C. The atmosphere was charged with water vapour, and all the conditions were present for the production of storms and tempests. The atmosphere during long ages must have been the seat of formidable and incessant electric discharges; these discharges are the most powerful of all physical agents of chemical synthesis, and will cause nitrogen to combine directly to form various compounds--nitrates, cyanides, and ammonia. Carbonic acid would also be present in abundance and would enter into combination with these nitrogenous compounds. In this way we may imagine that compounds were formed which by some process of physical synthesis subsequently gave rise to vast quant.i.ties of alb.u.minoid matter.

At that time the seas and oceans contained all those substances which have {170} since been fixed by the metamorphism of the primitive rocks, or deposited in the sedimentary strata. Most of the elements in our minerals were formerly in a state of solution in these primeval seas, which contained carbonates, silicates, and soluble phosphates in great abundance.

As the crust gradually cooled, the terrestrial atmosphere of necessity altered in composition, and the slow evolution of the atmosphere no doubt also exercised an influence on the development of living beings.

Palaeontology teaches us that the earliest living organism appeared in the sea. The most ancient of living things, those of the primary ages, which were of greater duration than all other ages put together, were all aquatic. We find moreover that every living organism consists of liquids, solutions of crystalloids and colloids separated by osmotic membranes; and it is significant that the ocean, that vast laboratory of life, is also a solution of crystalloids and colloids. It is evident, then, that we must look to the study of solutions if we would hope to discover the nature and origin of life.

Life is an ensemble of functions and of energy-transformations, an ensemble which is conditioned by the form, the structure, and the composition of the living being. Life, therefore, may be said to be conditioned by form, _i.e._ the external, internal, and molecular forms of the living being.

All living things consist of closed cavities, which are limited by osmotic membranes, and filled with solutions of crystalloids and colloids. The study of synthetic biology is therefore the study of the physical forces and conditions which can produce cavities surrounded by osmotic membranes, which can a.s.sociate and group such cavities, and differentiate and specialize their functions. Such forces are precisely those which produce osmotic growths, having the forms and exhibiting many of the functions of living beings. Of all the theories as to the origin of life, that which attributes it to osmosis and looks on the earliest living beings as products of osmotic growths is the most probable and the most satisfying to the reason.

[Ill.u.s.tration: FIG. 64.--Osmotic sh.e.l.ls and corals.]

We have already seen that the seas of the primary and {171} secondary ages presented in a high degree the particular conditions favourable for the production of osmotic growths. During these long ages an exuberant growth of osmotic vegetation must have been produced in these primeval seas. All the substances which were capable of producing osmotic membranes by mutual contact sprang into growth,--the soluble salts of calcium, carbonates, phosphates, silicates, alb.u.minoid matter, became organized as osmotic productions,--were born, developed, evolved, dissociated, and died.

Millions of ephemeral forms must have succeeded one another in the natural evolution of that age, when the living world was represented by matter thus organized by osmosis.