The History of Biological Theories

A similar fate overtook another hypothetical ancestor of the animal kingdom the so-called Eozoon. The oldest Canadian gneiss contains a certain marble in which are scattered granules, strands and bands of serpentine and other silicates. The serpentine lamellae are often wavy as if formed of cells, and the spaces around them in the marble are also penetrated by this serpentine. Some thought this the remains of an extremely primitive organ- ism the shell represented by the marble, the cast of its body by the serpentine. The belief in its organic origin was gradually dissipated, and now no one holds this view.

There were other factors at work which caused the belief in the monera to be gradually abandoned. When Haeckel propounded his theory the cell-nucleus was be- lieved to be nothing but a mass of denser protoplasm. Towards the end of the century, however, histologists began to study the minute structure of the nucleus and its very striking living processes, and the protoplasm came to be regarded more and more as an undifferen- tiated covering to the nucleus. The monera then became an anachronism; and though it was referred to in the text-books until a few years ago, this was merely due to inertia on the part of writers.

Haeckel's idea of a middle kingdom, the Protista, inter- mediate between plants and animals, was also gradually discarded. It went the way of earlier theories of a similar kind. In the eighteenth century, and indeed back to Aristotle, the belief had been very generally held that beings exist which are half-plants, half-animals. These were called Zoophytes (plant animals). Lamarck's pupil, Bory de St. Vincent, was a strong supporter of this idea. Many other theories streamed from Haeckel's fertile brain of spontaneous generation, of the origin of speech and of Man, and so on. Here we will add a short note on Monism the theory which Haeckel put forward in oppo- sition to the teaching of the Church. He added nothing to what Strauss had already said, and he continually quotes the work of Strauss. There is no duality of soul and body, living and non-living matter. The only thing that exists is matter, and this is composed of atoms. There is no personal immortality, although matter and force are both indestructible. The God of Christianity is merely a personification of human attributes. Haeckel is full of hope that 'ancient superstitions' will be swept away by science, and that their place will be taken by the theory of evolution and its servant monism. For monism teaches that the world was gradually evolved out of some primeval substance (Kant and Laplace), that life arose from the non-living according to mechanical laws, and that everything that exists, even atoms, have souls. Man is merely the most perfect animal. He owes his dominant position to the fact that, in his body is a combination of characters which elsewhere only occur singly (e.g. a larynx, brain, limbs, and the upright position). Traces

of religious feeling, of a moral sense, of powers of judge- ment are exhibited by certain animals. Haeckel's popularity led his followers to regard the Church with complete indifference, and this led, in its turn, to passionate opposition. His attack on the Church is now out of date, as is also the Church's criticism of his teaching. Those interested in this controversy will find many more original thinkers taking part in it than Haeckel. Haeckel wrote the first history of the theory of evolu- tion. Many have followed him in this as in all his other activities. A writer who was anxious to show how great was the influence of Aristotle once said that all those who went before were his 'forerunners', while all those who came after were his imitators. Haeckel's opinion of Darwin was equally high. Hence, one of the chief occupations of those who essayed to write histories of biology became the discovering of Darwin's forerunners.

Haeckel exerted a very great influence on his contem- poraries. Neither Darwin nor Huxley alone would have succeeded in making the evolutionary theory the world- power that it became ; for Darwin was no controversialist, while Huxley was not sufficiently dogmatic to influence the masses. Haeckel possessed both these qualities in a very high degree. First it was necessary to break the power of the specialists for these, like any other conservative group, believed themselves to be the beati possidentes of all truth. They did not try to understand new and strange theories. Only when he had won the approbation of the masses by his popular writings did they admit, under protest, that Haeckel was a leader of biological thought.

His influence in informed circles was partly due to his own absolute conviction, but even more to the fact that he did not demand from biologists any complete change of view. Under his leadership a morphologist could remain a morphologist, an embryologist be still an embryologist, the systematist could still continue to weave his systems. None of these branches of science was condemned by the new philosophy; none was dislodged. The only demand made by Haeckel was that the word 'evolu- tionary' should be affixed to each of them. The religious difficulties of the Radicals were settled by all sorts of com- promises, and so their path was smoothed.

For nearly forty years Haeckel was the leading figure in biological science, the acknowledged or unacknow- ledged head, always ready to fight for his convictions. It is hardly possible to count the number of those who, when his fame was at its height, hitched themselves to his triumphal wagon. He had philosophers among his followers, especially in Germany (A. Lang, G. Fechner, E. Hartmann), as well as sociologists, students of ethics and of language, and above all, biologists. From 1870 on- wards morphology has dealt solely with the questions that Haeckel propounded, and the embryologists have been completely under the spell of his fundamental law of biogenesis. Darwin, Huxley, Gegenbaur, Ray Lankester,

F. M. Balfour, Wiedersheim, Forel, &c., were all his faithful followers. Until recently HaeckePs pupils were the leaders of German science Oscar Hertwig in Berlin ; W. Roux, who founded evolutionary mechanics, and who admitted that his theories were evolved from those of Haeckel and it is obvious that they are merely an adaptation of these ; Verworn, the Jena physiologist, who not many years ago won a great reputation by applying these theories to physiology.

To-day Haeckel's influence has waned, and he is declared to be unscientific. How often do we hear Haeckel disparaged while Darwin is praised for his care and caution? Who could guess, without delving into forgotten records, that Darwin accepted all Haeckel's theories indeed, did more than this. When Haeckel's most important book, Naturliche Schbpfungsgeschicbte^ was published, Darwin said: 'If this work had appeared before my essay had been written I should probably never have completed it. Almost all the con-

elusions at which I have arrived I find confirmed by this naturalist, whose knowledge on many points is much fuller than mine* (Descent of Man). When Darwin is praised for his modesty, in opposition to Haeckel's bombast, how many remember the explanation he gave of the process of menstruation, for example ? He said that it dates from the time when the ancestors of the human race lived in the sea, where they were at the mercy of the waves, which depend in their turn on the tides, and so on the 'moon'. And did not Darwin also publish a genealogical tree for man? Haeckel is condemned because he wrote about religion and philosophy without real knowledge. How much did Darwin understand of the views of the theologians and philosophers ?

PHILOSOPHERS of the early Christian era delighted in contrasting God's omnipotence with man's impo- tence. 'We are mere flesh, a mere breath, and we depart never to return,' said St. Augustine, echoing the goth Psalm. Such, too, is the teaching of modern science. Man is only a grain of dust, a moment, a nothing-at-all in a boundless universe. Nevertheless, medieval ideas were not at all akin to those of our own times. In those days, though Man was believed to be as nothing when compared with the creative idea, with an all-powerful God, he was regarded as the lord of the material world, the ruler of the earth and of all that is therein. Animals and plants were created solely on his behalf. In our times we strive to 'explain' material pheno- mena, and have lost the overwhelming conviction of an Almighty God. We make our estimates of the age of the earth ; we are thrilled with its antiquity ; we are rendered dizzy by the billions of miles in which we measure the extent of the universe. We recognize the immensity of space, and it is in this way that we become conscious of our own insignificance.

The whole trend of modern science leads us to the realization of our weakness. Copernicus, Galileo, and Kepler robbed our earth of its proud dominion, and made it a mere hanger-on of the infinitely greater sun. Later she sank still further, becoming a mere grain of sand among a myriad stars a grain scarcely noticeable from those vast spaces which are about the stars. Geology has disclosed that Man's time on the earth is merely a short episode in the countless eons of the world's history. Every new discovery extends the boun- daries of the knowable universe and decreases the signifi- cance of Man and that minor activity we call Life.

There are illimitable events and phenomena quite outside every form of life. Only the thin crust of the earth is habitable, and its tremendous interior is not available to any living thing. Only by a stretch of imagination do we dare to dream that any of the planets are inhabited, and there is certainly no life in the glowing bodies of the sun and the fixed stars. Life is only possible between extremely narrow physical and chemical limits, and the slightest disturbance can destroy it completely.

Belief in spontaneous generation, in the origin of life from non-living matter, is as old as is conscious thought about Nature. We read it in the myths that man arose from stone, gods from sea-foam. Aristotle believed and taught that frogs may arise from slime. The alchemists were always hoping to be able to create man from the mixtures in their phials. The idea once held that fossils merely represent Nature's unsuccessful attempts to pro- duce Hfe is an aspect of this belief. All these ideas expressed the conviction that life is everywhere, and that if the right means be used this life may be awakened.

A belief in spontaneous generation was still current even in the early nineteenth century. Johannes Miiller, in his Physiology (1837), mentions several writers who believed in it and quotes various arguments in its favour. He re- jects the idea on the balance of evidence, but without any overwhelming conviction ; in particular he finds it difficult to imagine how life can otherwise have first appeared. The literature of those times is full of references to 'Priestley's matter' the thin film of microscopic green algae which is liable to form on water. Some believed that this material arose out of the water itself, and that from it the higher plants and animals were derived. Thus in 1821 a writer describes how he saw minute Crustacea (Cypris and Dapbnia) arise from algae ; and how from their dead bodies algae arose once more, to give rise in their turn to similar Crustacea. Purkinje believed in spontaneous generation, and said he had observed it in the fungi and elsewhere.

Not every investigator believed in the origin of life from non-living matter, but even the sceptics had very few facts to argue from -their appeal was chiefly to general considerations. Ehrenberg led the unbelievers ; using a poor microscope, he observed the living forms in a drop of water ; he noted that the wheel Rotifers have various internal organs. He failed to distinguish these from Infusoria, and noted that the latter also showed some internal organization (nucleus and vacuoles), though these he could only dimly see. He therefore concluded that the Infusoria have a stomach, sexual organs, &c., and from this he inferred that even the lowliest organisms are so complicated in structure that it is impossible to believe they have crystallized out from non-living matter. In those days the method of propagation of many lowly forms of life was unknown, and it was thus easier to believe in sponta- neous generation. Ehrenberg, however, saw the Infusoria reproduce by division, and this increased his mistrust.

The question continued to be discussed, though without conclusive result. But at last in 1862, driven to it by the definite assertions of Pouchet, the French Academy offered a prize for a new experimental solution of the whole question. Pouchet had asserted that the eggs of various forms of life arise spontaneously in turbid water, and develop there as well as in the natural body if air, warmth, and electricity are given to the decaying mass (1859). Pasteur received the prize.

Pasteur first examined the air itself. He drove air through a filter of cotton-wool. This caught all the float- ing solid matter. In this filtrate he found microscopically many of the lower forms of life and their spores. Further, he submitted a mixture of sugar solution and yeast to prolonged boiling, and let it cool in air which had been strongly heated. The sugar-containing vessel was then sealed. In the fluid nothing living developed, even when he passed through it more heated air. If ordinary un- heated air, on the other hand, had access to the solution, living organisms developed in it at once.

So Pasteur solved the problem at least in the form propounded by Pouchet j but the question continued to be discussed by the Academy. Pouchet's supporters brought it to the notice of the newspapers, who took Pouchet's side! Interest was, however, subsiding, when it was reawakened by the English physician Bastian who, using Pouchet's methods, arrived at similar conclusions (1872). He introduced a theory of infectious disease which was based on these observations. Bacteria do not infect the body from the outside they develop within it. These views were challenged by J. J. Lister, afterwards Lord Lister, who originated antiseptic methods in surgery. Bastian, however, continued his work, and in 1903 he published a large book in support of his earlier views. The book passed almost unnoticed. From time to time rumours again arise that this, that, or the other experi- mentor has succeeded in producing bacteria, or other simple forms of life, from dead matter. Such rumours are always received with mistrust. The mistrust is justified, for such experiments do not attempt to throw any new and independent light on the problem of the nature and origin of life. They always begin with the assumption that, somehow or the other, life must have arisen out of the non-living.

The problem has been attacked more recently from another point of view. Life, it has been assumed, consists in some peculiar activation of matter, and so the attempt has been made to imitate some, at least, of the activities generally associated with living matter. Quincke, a physicist, suggested that an amoeba moves through water because the molecular tensions between the surface of its body and the water particles are altered at certain points ; the change leads to a movement in the direction of the smallest tension. The trend of this argu- ment becomes clear if we remember the streaming move- ments that occur in water when alcohol is poured into it. The movements that occur between the amoeba and the water were supposed to be of this order. By choosing the

right combination of fluids Quincke succeeded in imitat- ing amoeboid movement. Interest in these experiments became more general when Biitschli propounded the theory (1892) that living matter consists essentially of two substances which, when mixed with one another, form a 'foam'. Biitschli attempted to demonstrate this structure in various living cells and to show how the living activities of the cell may result from it; he also tried to make artificial foams which should behave to some extent like living matter. He prepared a substance by soaking benzol (or xylol) in a soap solution. He asserted that this was very much like the protoplasm of certain cells. Others improved upon this method of making 'artificial protoplasm'. It was found that a drop of a mixture of very finely powdered sugar or common salt with inspissated olive oil, exhibits a structure much like that of protoplasm, and even moves almost like an amoeba.

In recent years investigators have turned their attention from such experiments to the finding of analogies between the behaviour of certain lifeless objects and certain living processes. Rhumbler endeavoured to construct mechani- cal models which would imitate the behaviour of the liv- ing cell during division. Lehmann, the crystallographer, described a new group of crystals, and he pointed out certain analogies between the movements of such crystals and the simpler movements of living matter. Some workers would have us believe that there is a striking analogy between the phenomena of regeneration, exhibited by certain organisms, and the power which some crystals have of regaining their perfect form, if a small fragment is immersed in a supersaturated solution.

More recently still, it has been suggested that radium, that 'philosopher's stone' of modern experimental science may have been able to bring about the spontane- ous production of life. A few biologists abandoned the attempt to discover the origin of life, and attacked the problem from the opposite pole. Life, they suggested, must always have existed, and lifeless matter have been produced by it. This led W. Preyer (1877) anc ^ certain other thinkers to very fanciful lengths.

There were others who thought that life had been transferred to our planet from other worlds, carried thither by meteors ; that it is the Wandering Jew of the Universe, journeying from one planet to another, to re- main for a time, to develop, and then, as the planet cools, to disappear once more, only to develop again on a new planet. Scientists have not been wanting who thought that they had discovered known forms of life sponges, corals, crinoids, and the rest existing as fossils in meteorites!

who still believed that Man, fashioned in clay, had come direct from the hands of his Maker. The conviction had spread that there was more than one Adam. Philoso- phical and political discussions concerning the equality of man had exerted an influence on science. The question of the freeing of the American negro slaves led not only to the war of North versus South it also divided anthropologists into two camps, the one believing in the equality of white and black races, the other stoutly deny- ing it. In America, in particular, the view that the negro is as far removed from the Caucasian race as he is from the chimpanzee was a very popular one. He is descended from a different Adam. This was the view of Agassiz. Other writers suggested that there must have been at least 1 80 Adams, as many progenitors as there are sub- divisions of the human race !

These ideas and the theories of Darwin were poles asunder. Agassiz suggested that there had been many more and more perfect Adams from the ancestor of the modern chimpanzee to the founder of the whole white race of mankind. He nevertheless believed that each of these suggested ancestors was an independent creation; each represented a separate thought in the Mind of the Creator. The chimpanzee ancestor embodied an animal design, the white Adam the idea of an intelligent being.

Darwin held that the chimpanzee and Man are funda- mentally alike, but Man has become more highly evolved, has a larger brain, and commands a wider experience. Moreover, Darwin did not believe in the existence of any Adam, in any beginning; only in a history which had lasted for millions of years, which had not yet reached its climax, but which was going forward to a higher future a future as yet all unknown. The path had been pre- pared for this view in many ways.

Cuvier believed that Man has only existed during the most modern geological epoch, and that he has always inhabited the parts of the world which he inhabits to- day. He brought much learning to prove that Man is not older than is claimed by the Bible. He defended the assertion that there were no fossil men in the face of those cases where fossil human remains were said to have been found. After his death such finds increased in number both in France and in other countries. For this a large share of credit must be given to the French investigator, Boucher de Perthes. From 1839 onwards ^ e was a diligent seeker for traces of prehistoric man. For long his work was ignored, but at length he received from anthropologists the recognition that was his due.

Similar investigations were pursued in Sweden. In 1863 Charles Lyell, in his Geological Evidences of the Antiquity of Man, gave a summary of these scattered references to prehistoric man, and so was led for the second time into opposition to Cuvier. The book was not very well received in England; it was said to be a mere compilation. LyelPs personal prestige was, however, great, and the book made itself felt in Germany, where investigators turned their attention to the most recent rocks. Lyell held that there had never been a Flood a general catastrophe which had engulfed the whole world. He pointed out that, in the fables of most peoples, in- habiting widely separated portions of the globe, there is a story of a flood. We find it among the Chinese, the South American Indians, the Egyptians, &c. ; anywhere, where there are great rivers and seas subject to those local floods which were the foundation of such tales. The geological idea of the Diluvium was now given, for the first time, a definite form ; it is the consequence of the erosive action

of wind, water, and glacier such erosion going on for thousands of years. Lyell had arrived at the knowledge that Europe had experienced great extremes of cold at an early date. Later geologists proved that there had been several such epochs in our latitudes, between three and six at least, during the period in question. During the so-called tertiary period, the climate had been so mild that sub-tropical plants and animals flourished in France, while in Greenland, where to-day only the hardiest of plants can maintain a miserable existence, palms once grew abundantly. Then followed many centuries of extreme cold, when glaciers stretched southwards into the plains of France and of Bavaria, when practically the whole of England, the whole of North Germany from the mouth of the Rhine to the northern boundaries of Bohemia, and the greater part of Russia, lay under a covering of ice. Warmer times followed ; the glaciers receded until all that was left were the ice-caps on the tops of high mountains. Then they began to creep down into the valleys once more. As the second ice age spread southwards, animals and plants that needed warmth either moved southwards too or died out and were replaced by new forms from the north. On the cold plains which bordered on the glaciers lived rein- deer, mammoths, and rhinoceros, all clothed with a thick coating of hair, together with bears, hyenas, lions, and deer. These did not belong to the species which exist to-day.