PARALLEL PATHS All Rights Reserved PARALLEL PATHS A STUDY IN BIOLOGY, ETHICS, AND ART BY T. W. ROLLESTON " II faudrait, en un mot, suivre la grande route si profondement creusee . . . mais il serait necessaire aussi de tracer en 1'air un chemin parallele, une autre route, d'atteindre les en de9a et les apres, de faire, en un mot, un naturalisme spiritualiste ; ce serait autrement fier, autrement complet, autrement fort." J. K. 'HUYSMANS. LONDON DUCKWORTH & CO. HENRIETTA STREET, COVENT GARDEN 1908 PREFACE IN a recent work by an eminent man of science, Dr. J. Reinke, Professor of Botany at the Uni- versity of Kiel, there occurs a passage which I cannot do better than place in the forefront of this book as an indication of its aim. " Physiology," writes Professor Reinke, " has become the study of the movements which, taken together, make up life. There is no manner of doubt that nourishment, metabolism, 1 reproduction, development, and sensation rest on processes of movement which depend on material systems of peculiar molecular conformation. For the bodies of plants and of animals are material systems whose conformation is of a most intricate character. " So far as physiology has at present advanced in the analysis of these phenomena of movement, their problems have fallen naturally into two groups. The first of these groups of phenomena is comparatively transparent, and stands in agreement with the general processes of the material world ; it can be investigated by observation and experiment. We may, therefore, hope to decipher it com- pletely, and to reduce it, in the end, to chemico-physical processes. Of this kind are the phenomena of nutrition, taking that word in its widest sense. But behind these 1 Metabolism : see p. 27. vi PREFACE processes there stand the facts of development and of reproduction, and here, in all investigations, and in spite of every attempt to demonstrate a basis of physical energy, research finds itself confronted by an X, a factor which mocks every effort to explain it by physics or chemistry. And this X which lurks in all the phenomena of develop- ment takes a part in the nutritive processes also; so essential a factor does it appear in all the processes of life that chemical and physical forces alone would not suffice to keep alive even the most rudimentary of organisms, not to mention creating such an organism out of non-living chemical constituents." 1 If this X force exists and can be established, it will give us the clue, I believe, to much more than the operations of physical nature. The following pages are an attempt to establish it, to define its character, and to indicate the lines on which this un- known factor in evolution seems to bring into a rational unity the phenomena of the physical world and the moral and aesthetic faculties of man. The time appears to have come for such an attempt. The fermentation of mind produced by Darwin's massive and victorious promulgation of the evolution theory is beginning to subside ; it is now possible in some measure to take stock of what has been destroyed, of what has been left intact, by the immense tidal wave 1 J. Reinke. DIE WELT ALS TAT, p. 173. The term 'de- velopment ' (Entwitklung) includes both what we commonly under- stand by that term (as, the transformation of an embryo into a complete animal) and also what we call Evolution, the development of one species into another. PREFACE vii of new thought which then swept over the world. Some conceptions which were thought to have been submerged for ever are reappearing in more or less altered shapes, and science is called on to recon- struct a universe less one-sided, less aridly simple, than that which Darwinism, as at first understood, appeared to have left us. The result, so far as it is successful, will be the establishment of a spiritual view of the universe on a natural basis. It is an attempt which is at present occupying many minds, and which will doubtless have to occupy many more before complete success is attained. I propose, in the following pages, to take the reader over the most material and significant part of the ground by which I have myself travelled towards certain conclusions. Much of this ground lies in the region of biological science. No doubt to readers acquainted with that science I shall often seem to delay too long in well-trodden and familiar paths. But I have had to consider the fact that English education is still very much specialized. It is either literary or it is scientific. In the great majority of cases it is literary. And though scientific problems and theories are understood by every educated man and woman to be of deep importance and interest, and though questions like those discussed in the present work are questions on which all such persons are well entitled, and many feel themselves bound, to have an opinion, very few, comparatively, have even viii PREFACE the elementary knowledge of science and its termin- ology necessary to enable them to take up the discussion at an advanced point. When it is an- nounced from time to time that some chemist has again succeeded in forming an organic compound out of inorganic chemical constituents in his laboratory, 1 how many readers are there out of the small circle of trained chemists who would not be far more im- pressed if they heard that he had made a diamond ? It is for these persons the layman and the lay- woman in point of science that I mainly write, and my own training having been philosophical and literary rather than scientific I think I understand most of their difficulties. I have, therefore, tried to ' begin at the beginning ' ; and I hope that this book, besides whatever value its conclusions may have, will prove useful to some readers by putting them in a position to appreciate the extraordinarily interesting and fruitful discoveries of biology in recent years. " The lotus of physics," as Schopenhauer says, " is rooted in the soil of metaphysics," and if these studies pretended to offer a complete explanation of the riddle of existence, the metaphysical basis for the speculations contained in them would have to be elaborated at considerable length. But, after all, the conclusions reached would only be those which most people are willing to accept as a necessary assump- tion, if all thought on the constitution of the universe . 1 See p. 24. PREFACE ix is not to be a pure futility. Suffice it to say Man is here regarded as an organic part of Nature, and his consciousness as Nature's way of mirroring herself to herself. Since, like other natural things, the soul is not a complete and unalterable entity, but is part of the eternal Becoming, it never can be claimed that its reflection of the world is absolutely pure and complete, yet some reality, some significance this reflection must surely have. The fact that man is not something different from the world, observing it from outside, but is vitally related to it, would alone entitle us to believe that, however much his observations may need to be purified and corrected, and however false may be the argumentative deductions sometimes drawn from them, he is still capable of a real and fruitful apprehension of the phenomena by which he is surrounded, and of their relations to each other and to himself. All sincere thought must therefore tend to brighten a little the mirror of the human soul. If this book should do so in any degree, were it merely by provoking other minds to more successful labours, the writer will thankfully say, like Apollo's temple- sweeper in the play of Euripides, Fair is the service of Light. T. W. ROLLESTON. GLENEALY, Co. WICKLOW. / have to thank The Macmillan Co. for permission to re- produce two illustrations (Figs. I and 2) from Wilson's THE CELL IN DEVELOPMENT AND INHERITANCE, and Mr. Edward Arnold for a similar favour in regard to Fig. 3 from Weismanrfs THE EVOLUTION THEORY. CONTENTS PART I. BIOLOGY CHAPTER I THE ARGUMENT FROM DESIGN PAGE Paley and the Watch . . . I The Analogy Inapplicable . . Y . 4 Paley 's Conception of Design . . . . 8 The Evolutionary Conception . . . . . 1 1 Conquest of Nature by the Evolution Theory . . .16 The Philosophic Basis of Nature-study . . . . 17 CHAPTER II THE WHEEL OF LIFE Continuity of Animal, Vegetable, and Mineral Life . .21 Characters of Organic Life . . . . 23 Living Matter: Its Functions . . > . . .24 Its Substance * . . . ; . 27 Its Structure . 28 CHAPTER III DE MINIMIS Growth and Development . . * . .32 Development a Cell-problem . . . . .33 The Mechanical Conception of Life . J . .34 The Cell and its Structure . '. . . .38 xi xii CONTENTS PAGE Cell-division and Heredity . . 4 Reproductive Cells and Body-cells . . 45 The Origin of Conjugation . . . . 46 The Mechanism of Conjugation . . 5 1 Significance of Elementary Vital Processes . . 59 Adaptability, a Fundamental Character of Life . . 63 CHAPTER IV THE MECHANICAL THEORY OF EVOLUTION : THE DARWIN-LAMARCK EXPLANATION The Fixity of Species, how Maintained . 66 The Mutability of Species . . ... 67 Lamarck's Explanation of the Origin of Species . . 68 Natural Selection of Innate Variations . . 7 2 Difficulties of Lamarckism . . ... 77 Need of a deeper Explanation . . . . 89 CHAPTER V THE MECHANICAL THEORY OF EVOLUTION : THE DARWIN- WEISMANN EXPLANATION Lamarck, or 'Metaphysics'? . . . . . 91 Weismann's Escape . . . 93 The Struggle among the Determinants . . 95 Chance-Variations and Co-adaptation . . 97 Other Difficulties of the Chance-Variation Theory . . 99 Natural Selection . . . ... 103 Impossible before Competition Existed . . . . 104 Co-operation and Competition . ... 104 Protective Mimicry, Inexplicable by Chance -Variations and Natural Selection . . . 106 Innate Capacities of Life . . . . 109 Outline of Preceding Arguments . . .in CONTENTS xiii CHAPTER VI THE DIRECTIVE THEORY OF EVOLUTION PAGE Nature's Power of Response . . . . 115 Reinke's Theory of Dominants . ... 120 Cases of their Action in Evolution . . . 123 Law and Directivity . . . . . 128 Intelligence and Directivity . . . . . 130 The Analogy of Social Evolution . . . . 131 The Analogy of Language . . . . . 133 Synthetic Movement of the Cosmic Reason . . .137 Objections from Imperfect Adaptations and Regressive Forms Stated . . . ... 143 Mechanical and Psychic Agencies, how Distinguished . . 146 Science versus 'Mysticism' . . . . . 150 Reply to Objection from Imperfect Adaptations, etc. . .152 Man, the Growing-point of Earthly Life .. . . 154 Immanence or Transcendence of the Cosmic Reason? . 155 Man's Relations to the Whole .,' . .' . . 157 PART II. ETHICS CHAPTER VII LAW, FREE WILL, PERSONALITY Free Will and Determinism . ,. . ...161 The Determinist Position . . . . . ..163 The Free Will Position . . ... 164 Conditions necessary for Free Will . ' . . .168 Has the Will an Ethical Bias? . . . . 169 Limitations of Free Will ... . . . .172 Evolution of the Will . . . . . 174 Free Will and Monism ., . . . . .176 Free Will and Brain-structure . . . . . . .177 Relations of Mind and Matter . . . .186 Immortality . . r .189 xiv CONTENTS CHAPTER VIII THE ETHICAL CRITERION PAGE The Visible and the Invisible Worlds . . . . 194 Dualism and Monism . . . . 195 Monism and the Moral Law . . . . . 198 The Hedonistic Basis of Morals . ... 200 The Natural Basis of Morals . . ... 203 CHAPTER IX THE ETHICAL SANCTION The Individual and the Whole . . . 208 A Scale of Motives . . . . . . 210 Conscience and its Commands, how respectively Derived . 211 Results of Duty and of Self-indulgence Compared . .212 The False and the True Asceticism . . . .214 Ethics for Life : Implications of this Doctrine . . . 220 Is Life Dependent on Matter? . . . 222 The Cosmic Life gives Immortality to the Individual . . 225 And Demands his Allegiance . . ... 226 Ethics Originates in the Visible Order, but does not end there 228 Hence, Ethics is for Death as well as Life . . . 229 The Martyrdoms of Socrates and of Christ . . . 230 Outline of the Conclusions arrived at . . . 233 PART III. ART CHAPTER X ART AND LIFE Tolstoy's Account of the Nature of Art ... 236 Of the Standard of Art . . ... 241 Of the Purpose of Art . . . . . 241 Criticism of his Conclusions . . ... 245 CONTENTS xv PAGE Art, Man's expression of Life . ... 246 Art and Beauty . . . . . . 251 Order and Change as Principles of Life and Art . .253 Classification of the Arts . . ... 254 Examples of the Presentative Arts (a) Architecture . . 256 (6) Ornament . . . ... 259 (c) Music . . . ... 261 The Representative Arts (a) The Plastic Arts . . . 265 (b) Dancing . . . ... 270 The Evocative Art : Literature . . . 271 The Union of Music and Poetry . ... 272 Conclusion . . . ... 273 APPENDIX A Sum ergo Cogito . . . ... 275 APPENDIX B Co-operation and Competition . ... 279 APPENDIX C Is Life worth Living? . . ... 282 APPENDIX D St. Francis the Poet . . ... 285 APPENDIX E Isabella and Claudio . 288 INDEX , . , . ... 295 PARALLEL PATHS PART I: BIOLOGY CHAPTER I THE ARGUMENT FROM DESIGN " The wisdom of the divine rule is apparent not in the perfection but in the improvement of the world." LORD ACTON. PALEY'S NATURAL THEOLOGY though not by any means an epoch-making may perhaps be called an epoch-marking book. It was the crown of the endeavour of eighteenth-century religious phil- osophy to found a theology on the evidences of external nature. According to such exact knowledge of Nature's operations as was then generally avail- able, Paley's attempt might well be thought to have succeeded. He opens his argument with a striking and effective illustration. He imagines a wayfarer crossing a heath who strikes his foot against a stone, and who asks himself how it came into being. Paley thinks he might be content with vaguely supposing that it was there 'always.' But suppose that what he had found at his foot was not a stone but a watch and that he now saw such an instrument 2 PARALLEL PATHS for the first time. He would then certainly have not been so easily contented with an answer to the riddle of its existence. He would, if he examined it minutely, have observed that it was a structure intended for a certain purpose, and having all its parts arranged for that object, and mutually inter- dependent. The different substances of which it was composed would be discovered to have each its special appropriateness for the fulfilling of some particular function in the economy of the whole. Though unacquainted with watches he would, if he was a man of sense and cultivation, infallibly conclude that he had before him an instrument intelligently con- structed with a certain object in view the object of measuring the flight of time. He would feel assured of this, even though he should find that the object of the mechanism were not attained with absolute accuracy, and even though there were some parts of it whose functions were not clear to him. The watch would be rightly regarded as a work of design ; and the observer would be justified in arguing from it to the existence of a designer, endowed with the facul- ties of intelligence and conscious purpose, by whom the watch must have been put together. The rest of Paley's NATURAL THEOLOGY is an application of this analogy to the question of the origin of the universe. Ranging over the whole field of animate and inanimate nature he points to instance after instance of what appears to be the THE ARGUMENT FROM DESIGN 3 minute and thoughtful adaptation of means to ends, the co-ordination of part with part in the interest of the whole, and he has no difficulty, from this point of view, in showing the world of nature to be a piece of mechanism far more wonderfully and ingeniously constructed than any watch, and bearing prima facie evidence of the most convincing kind of its con- struction by a Being possessed of intelligence, purpose and foresight precisely resembling those attributes as displayed by man, but vastly heightened and enlarged. As the watch must have been made by man, so a manlike being, endowed with the neces- sary powers and faculties, must be postulated as the maker of the material universe. And thus the exist- ence of a God made in the image of man appeared to have been demonstrated to the satisfaction of eighteenth-century theology. But minds of real philosophic depth have always shrunk from pressing home deductions of this sort. They have felt that the matter is probably not quite so simple as it might appear on the surface, and they have recognised that if one is allowed to argue from the phenomena of nature to the qualities of the author of nature one cannot draw an arbitrary line including only those facts which testify to wisdom, power and goodness, and excluding from view all those which reveal imperfection of design and execu- tion, or which would convict a man, if he were their author, of inhumanity and injustice. If the universe 4 PARALLEL PATHS is really analogous to a watch one is entitled to examine it throughout as one would examine a watch. All watches testify to intelligence and design, but besides good watches there are bad ones, there are those which are made of cheap materials, rudely put together, with showy exteriors and unreliable works. Every watch, if examined by experts in mechanism, in art, and so forth, would reveal the characteristics of its designer and maker, and these characteristics would not always be admirable. They would rarely, in fact, be altogether admirable. If we apply these methods of inquiry to a universe which contains malarial mosquitoes, slave-making ants, snakes, earth- quakes, and all the pests which blight and deform life without calling forth any strong or noble quali- ties to carry on the contest with them, we shall go where Paley certainly never intended to lead us, but we shall go there by Paley's road. The fact is that these methods are altogether fantastic and inapplic- able. The universe is not made like a watch. When we observe a human being or one of the higher animals we say, ' He has such and such qualities ; he is faithful, false, brave, cowardly, diligent, indolent, strong, weak, beautiful or ugly/ but we do not think of referring his qualities back to certain attributes of an unknown maker of his physical and mental organism. A philosophy worthy of the name has always tended to regard the world as in some sense a vital organism, and has asked 'What is it?' rather THE ARGUMENT FROM DESIGN 5 than 'What does it prove about some other being?' " How green must be the maker of all grass " was quite a legitimate satire on all such attempts to de- duce the qualities of a hypothetical creator from the phenomena of the universe. Thus the mistake of Paley and his school was fundamental. It was the mistake of seeking God in fragmentary phenomena the same mistake, essentially, as that rebuked by Christ, by which every calamity or material blessing is regarded as a 'judgment' or a reward. His method, if applied with thorough-going consistency, destroys its own basis, for the One and the Many, the Whole and the Parts, cannot be apprehended at one and the same time by one and the same faculty of any human mind. Looking at phenomena alone, and thinking in that sphere, we cannot say that God made the world but rather that the world is becom- ing divine. Philosophically and religiously, God is all in all historically, He is not the beginning, He is rather the end, the end in which the whole history is resumed. Paley's elaborate argument was felt by the ortho- dox of his time to be called for, even though at this period his way of thinking was popular. The con- ception of the world as a vital organism was as yet, indeed, very vague, and unsupported by any detailed, scientific scrutiny of the facts of nature, but it was in the air it had always been in the air ; it always held 6 PARALLEL PATHS the minds of cautious students back from a complete surrender to the facile but illusory way of thinking typified by Paley's famous analogy of the universe and the watch. Bacon knew that species could be transformed by the action of a new environment. 1 Goethe had a clear conception of the evolution theory, based on a study of organic structure. Erasmus Darwin, in 1794, had uttered the great and final word : " The world has been generated rather than created." 2 Lamarck's PHILOSOPHIE ZOOLOGIQUE was not published till 1809, nine years after Paley's NATURAL THEOLOGY, but his conception of the de- velopment of special characteristics by habitual exer- cise and their transmission by inheritance had been freely mooted in Paley's day, for Paley frequently takes occasion to combat it. Even the conception of natural selection as an agency in the formation of types of being may be traced in a fantastic form as far back as to Empedocles, 3 while Plato, or whoever composed a striking couplet attributed to him in the Greek Anthology, had divined the plasticity of natural forms. " Time," he wrote, " sways the whole 1 SYLVA SYLVARUM, Century VI. 2 ZOONOMIA, Vol. II, p. 247, third edition, 1801. Darwin is here adopting David Hume's conjecture, which is worked out in some de- tail in the ZOONOMIA, the conclusion being that probably "one and the same kind of living filaments is and has been the cause of all organic life" (p. 244). He attributed evolution to internal forces im- pressed on living matter by the Creator. 3 He taught that nature had produced a multitude of disconnected parts which afterwards combined and recombined at random until the appropriate parts had come together and remained stable. THE ARGUMENT FROM DESIGN 7 world ; time has power in its prolonged lapse to change the names and shapes, the nature and the destiny of things." 1 Fifty years after the appearance of Paley's work, the grandson of Erasmus Darwin wrote ' No thorough- fare' on the entrance to Paley's line of speculation, and closed it to mankind for ever. He did this in two ways first by marshalling from his studies of comparative anatomy and of embryology an extra- ordinary volume of convincing evidence for the fact of the mutability of natural forms, and secondly by his attempt to establish a plausible method by which the change and development of organs and types might actually have taken place. The method, summed up in the phrases 'natural selection' and ' survival of the fittest/ was what really caught the attention of the world, and gave his doctrine the wings which carried it into almost every sphere of human thought. However we take it, it was cer- tainly an immense contribution to the organization of knowledge, but whether it is really what it first seemed to be, the basic fact at the bottom of all the phenomena of evolution, is coming to look more and more doubtful in the light of later researches. 2 1 Aiwc irdv Jac. Anth., II, 20. "It has lately become the fashion, at least among the younger school of biologists, to attach small value to natural selection, if not, indeed, to regard it as a superseded formula." (A. Weismann, THE EVOLUTION THEORY, Engl. trans., II, 391.) 8 PARALLEL PATHS This question will have to be considered later on in the course of this study, and in relation to its main inquiry, which is this : What precisely was the change in philosophic and religious outlook brought about by the full and final establishment of the doctrine of evolution ? Where has evolution left the argument from design ? Must we study nature as a mass of unrelated phenomena, or can we dis- cern, through these, any fundamental unity to which they stand in organic relation ; and if we can, what is the nature of this unity ? It will be useful in the first place to have before us a typical specimen of Paley's method. I shall choose as an example the case which he con- sidered so striking that he deemed it almost suffi- cient in itself to bear the whole weight of his argu- ment. In his ninth chapter, 'On the Muscles,' he writes : "The next circumstance which I shall mention under this head of muscular arrangement is so decisive a mark of intention, that it always appeared to me to supersede, in some measure, the necessity of seeking for any other obser- vation upon the subject; and that circumstance is, the tendons which pass from the leg to the foot being bound down by a ligament to the ankle. The foot is placed at a considerable angle with the leg. It is manifest, therefore, that flexible strings, passing along the interior of the angle, if left to themselves, would, when stretched, start from it. THE ARGUMENT FROM DESIGN 9 The obvious preventive is to tie them down. And this is done, in fact. Across the instep, or rather just above it, the anatomist finds a strong ligament, under which the tendons pass to the foot. The effect of the ligament as a bandage can be made evident to the senses ; for if it be cut, the tendons start up. The simplicity, yet the clearness of this contrivance, its exact resemblance to established resources of art, place it amongst the most indubitable manifestations of design with which we are acquainted. " There is also a further use to be made of the present example, and that is, as it precisely contradicts the opinion that the parts of animals may have been formed by what is called appetency^ i.e, endeavour perpetuated and imper- ceptibly working its effect through an incalculable series of generations. We have here no endeavour but the reverse of it a constant renitency and reluctance. The endeavour is all the other way. The pressure of the ligament constrains the tendons ; the tendons react upon the pressure of the ligament. It is impossible that the ligament should ever have been generated by the exercise of the tendon, or in the course of that exercise, forasmuch as the force of the tendon perpendicularly resists the fibre, which confines it, and is constantly endeavouring not to form, but to rupture and displace, the threads of which the ligament is com- posed." Paley's account of the function of the annular ligament at the ankle is correct, and strikingly put. A similar ligament occurs at the wrist, and navvies who have hard muscular work to do in digging and shovelling are wont to reinforce this ligament and to keep it from rupture by a leather strap round the io PARALLEL PATHS wrist. The strap performs exactly the same function as the ligament, and from Paley's point of view one is as artificial, as much a ' contrivance,' as the other. But his point of view is wrong. He conceives the Creator as having at his disposal fully formed ele- ments or materials sinews, bones, ligaments, and the like and assembling them into a working mechan- ism. In fact, however, none of these things is now what it was originally time, as Plato says, has changed its "name and shape." The annular liga- ments are recognized by modern anatomists as having originated in special thickenings of the fascial sheaths of the adjoining muscles of the wrist and ankle. They had a function which was not originally connected with keeping down the long tendons that run along the interior angle of the leg and foot. Contractility, as biologists tell us, is a fundamental property of living proto- plasm ; and it is easy to imagine that, at the very beginning of the formation of muscular structure and bone articulation, two lines of contractile force might cross each other and thus permit the gradual evolution of the present arrangement, nature con- tinually visiting with disability and extinction those individuals in whom the resisting power of the muscles which were eventually to form the annular ligament was unduly feeble, and giving a better chance of life, and of the propagation of their kind, to those in whom it was strong. The instance, in THE ARGUMENT FROM DESIGN n fact, is one of those in which the explanation of development by natural selection is most obvious and plausible. In his second paragraph Paley touches on the theory of " appetency," the supposed tendency of natural structure to alter and adapt itself on the lines indicated by the actual exercise of function, and in consequence of that exercise. This is prac- tically the theory since identified with the name of Lamarck. Paley scarcely does it justice, for no Lamarckian would suggest that a muscle could, in the course of its exercise, develop the ligament whose function is to restrain it. The ligament would be developed by its own exercise. But as Lamarckism will be discussed later on, the issue as between these rival theories need not be debated here. Let us set beside Paley's argument on the annular ligament of the ankle a passage from a modern scientific work, Strasburger's TEXT BOOK OF BOTANY. It will introduce us, from the side of the strictest scientific observation and of the fullest acceptance of the evolution theory, to the same kind of prob- lems as those discussed in Paley's NATURAL THEOLOGY, and it will raise in a very distinct and unevadable fashion the question, what we are to think of the power manifested in the operations of Nature. In the introduction to his work, in which Dr. Stras- burger had associated with him three other eminent 12 PARALLEL PATHS German botanists, we find the following remarkable passage dealing with circumstances observed to exist in the ' phylogenetic ' or tribal (as opposed to the 'ontogenetic' or individual) history of plant species: "Although the great importance of natural selection in the development of the organic world has been fully recognised by most naturalists, the objection has been raised that it alone is not a sufficient explanation of all the different processes in the phylogeny of an organism. Attention has been called to such organs as would be incapable of exercising their function until in an advanced stage of development, and so could not originally have been of any advantage in a struggle for existence. How could natural selection tend to develop an organ which would be useless so long as it was still in a rudimentary condition ? This objection has led to the supposition of an internal force residing in the substance of the organisms themselves and controlling their development in certain definite directions. Many naturalists indeed have gone so far as to affirm that only the less advan- tageous qualities have been affected by the struggle for existence, while the more advantageous have been unin- fluenced by it" l One can easily imagine what a modern Paley bent on reconciling orthodoxy and evolution would say to this. He would cry, Design, forethought, intelligence 1 TEXT BOOK OF BOTANY, p. 3. English translation by Dr. H. C. Porter, 1898. In the fifth German edition, which served as the basis of a revised English translation (1903), another passage (taking note of De Vries' Mutations Theory) is substituted for the above quoted, but the essential meaning is the same. THE ARGUMENT FROM DESIGN 13 here is the clearest evidence of it ! And indeed there are many modern biologists who do not shrink from the admission that the processes of nature must ultimately be interpreted in terms of will or inten- tion, not in terms of chance or blind mechanism. Thus, to the Darwinian argument that organs can be and are, demonstrably, formed by gradual adapta- tion to surrounding conditions without assuming the necessity of purposeful design, it is often replied that the very fact of adaptability is itself one of the strongest evidences if not of design at least of pur- pose. And J. v. Uexkiill, who describes life as con- sisting essentially in the fact that it proceeds according to design (J>lanmassig\ has the following remarkable passage in his EXPERIMENTAL BIOLOGY* : " When we look backwards, every phase in the process of development seems to us to have proceeded in a strictly causal manner from physico-chemical processes. But when we turn to look forward, it is certain that the physico- chemical processes if left to their own causality must immediately bring about the destruction of the organism. In fact, the clearest definition we can give of dying is to say of an organism that its processes now go on no longer Ideologically (zweckmassig) but only causally." 2 1 LKITFADEN IN DAS STUDIUM DKR EXPERIMENTELLEN Bio- LOGIE DER WASSERTIERE, p. 67. The subject is ably treated by Keyserling, DAS GEFUGE DER WELT, p. 190. 2 For instance, the development of an embryo in the womb takes place in strict accordance with physico-chemical laws. But withdraw the element which we call life and how different a set of processes would at once supervene! Yet the physical energies in the embryo would remain in amount exactly what they were before. 14 PARALLEL PATHS Yet the modern Paley would be rash in arguing from facts like these (supposing them fully estab- lished) to the conscious, intelligent contrivance of a single foreseeing Mind. For very few things in this universe appear to be done as a presiding, conscious intelligence would do them. Conscious intelligence would not have evolved the giant arma- dillo only that the whole species might be destroyed by the sabre-toothed tiger, and would not have armed the sabre-toothed tiger for the attack on the armadillo in such a way that when he had ex- terminated the victim - species the formation of his teeth rendered it impossible for him to prey on any other animal. 1 Conscious intelligence would not have allowed the relic of a disused organ, in the shape of the vermiform appendix, to be a con- stant source of danger and suffering to countless generations of men danger against which no exer- cise of prudence or energy can secure them. Let us examine a couple of other crucial cases. The embryo of every mammalian animal is pre- pared in the womb for the life it is to live under wholly different conditions. Lungs are formed when there is no air for them to breathe, eyes when there is no light, a digestive system when nourishment is derived as yet direct from the mother's blood. This capacity for anticipatory development during a period of gestation or incubation becomes absolutely neces- 1 See Weismann, THE EVOLUTION THEORY, II, 358. THE ARGUMENT FROM DESIGN 15 sary for the maintenance of life as soon as animals, ceasing to multiply by merely dividing in two, become more highly organized and have to devote special germ-cells to reproductive purposes. Here is cer- tainly purpose, or, as I should prefer to call it, direc- tivity here we recognize what Reinke calls the ^"-factor in nature. But conscious, intelligent con- trivance ? We must recollect how many of these embryos are destined to perish at birth or before attaining any appreciable degree of independent life. Would not intelligence foresee that, and bring to birth only what was destined to endure ? Again, there are certain species of butterflies which have put on a coloration and a form the effect of which is to aid them in evading the attacks of birds. They were not created so; they have become so; and the precise manner of the becoming will be fully discussed in a later chapter. Let us assume for the moment that this adaptation did not occur by a series of lucky accidents or by any merely mechani- cal process. Are we, then, bound to attribute it to intelligent contrivance? The question will be best answered by simply putting a case which admits of no doubt. Suppose there were an island in which there were no birds, except such as prey on fishes or on each other, but never on insects. The butterflies on this island, if there were any, would certainly show no trace of protective form or colora- tion. But at some time or other insect-eating birds 16 PARALLEL PATHS might be introduced to the island, as the English sparrow has been introduced in Australia. Then, if the extermination of the butterflies did not pro- ceed too rapidly, we might expect, in the course of generations, to see protective adaptations assumed. But could we expect to see them assumed in anticipa- tion of the advent of the destroyers ? We could not. Naturalists, however much they may differ, as they do differ, upon the question as to how protective adaptations actually take place, would all agree that they could not possibly take place in anticipation of needs not yet present. If they did, we should have a miracle, and where miracle comes in knowledge goes out. The cases where conscious, intelligent con- trivance would be unmistakably recognizable are just the cases which never occur. The signal service rendered by the champions of the evolution theory, Quos nee fama Deum, nee fulmina, nee minitanti Murmure compressit Coelum, is that they conquered the realm of organic nature for true knowledge, and gave the drama of its de- velopment a new and profound interest, by showing with an uncompromising courage only equalled by the extraordinarily minute and patient research which justified it, that the apparent instances of divine contrivance with which nature teems must be ex- plained by the responsiveness, the adaptability, of living protoplasm. Needless to say, this demonstration THE ARGUMENT FROM DESIGN 17 does not in the least disprove the existence of God as a supreme, conscious, personal Intelligence. 1 But it does forbid us to deduce the existence of such a Being from the observation of natural phenomena. A living, developing universe has been set in the place of a Divine Mechanician operating on dead matter. The question, what conception we are to form of the forces of evolution, will be more fully discussed in the succeeding chapters on Biology, as a founda- tion for views which will afterwards be put forward in relation to Ethics and to Art. But first we must clear the ground a little by con- sidering what it really is that we are to study, and if it be possible to study it at all. Nature-study if it is to be possible must begin, and if it is to be fruit- ful must end, in something which is not strictly the study of nature, but which we call Philosophy. One of the most brilliant examples of that union of philosophic speculation with nature-study which is so marked a feature of the German thought of our day is H. von Keyserling's work, THE STRUCTURE OF THE WORLD. 2 Keyserling begins by laying it down as a postulate of thinking that " The Universe is a rounded, inwardly coherent Whole." 1 For my own part, I may say I have a difficulty in conceiving the Divine under the human and limited category of intelligent personality. 2 DAS GEFUGE DER WELT, Hermann Graf v. Keyserling, 1906. c i8 PARALLEL PATHS A postulate of thinking this is indeed, and more than that it is a postulate of living. If under all the variety and apparent discontinuity of the universe there does not lie One all-pervading and unifying Power, then meditation and action are alike vain, for none can tell the hour when some incursion of the unknown may not shatter our cosmos into chaos, or leave us in a new universe with the edifice of our past experience, the familiar home of the spirit, lying in ruins around us. Every one assumes, consciously or unconsciously, that there is such a Power, that the universe is One, that however mysterious, however little known or understood it may be, it is not essen- tially deceptive or incalculable. The savage and the philosopher alike assume this, and act upon the assumption. It is perhaps possible not merely to assume but to prove it. For let us try to imagine what would be the case if it were not true. If the Principle, the ultimate Reality of the universe, be not one it must be at least dual. There must be not less than two principles. Now there are only three ways in which these two principles and what we say will hold good for any greater number can be related to each other. They must either (i) be identical, or (2) they must be complementary, each possessing something which the other is lacking in, or (3) they must negate each other and be mutually contra- dictory and exclusive. But two absolutely identical principles, if we can conceive such a thing, are in- THE ARGUMENT FROM DESIGN 19 distinguishable from one. Two or more complemen- tary principles, again, make up, when taken together, but a single whole, as in the Christian Trinity. There- fore if the universe be really dual, its two principles must negate and contradict each other. Now these two hostile principles must either be equal in force or one must be more powerful than the other. In the latter event, seeing that they divide between them the sum total of existence and thus stand in naked and essential antagonism, with no place for evasion, and no auxiliary or modifying forces to call in, it follows of necessity that if one surpassed the other by even the smallest conceivable excess, it must, in eternity, master it and reduce it to impotence. So by this road we come back to unity again. If, however, we suppose our two forces to be co-equal and co- eternal, we have to ask ourselves what we mean by supposing them to be antagonistic. Antagonism can only arise when there is action. But two equal forces acting in direct contradiction to each other must mutually cancel each other, and the result is zero. On such an hypothesis the universe could never have come into being. It may also be pointed out that the hypothesis itself seems to be irrational. For action means the production of a change of some kind, change in the nature or situation of objects. But if one of our forces is producing changes of a certain kind and the other producing changes of another kind, then they are not contradictory but comple- 20 PARALLEL PATHS mentary. The only real antagonism between two ultimate principles must consist in one of them being identified with action, change, life, the other with immobility and death. But a principle of im- mobility and death, if there could be such a thing, could not also be a principle of action, not even of destructive action, for to act at all would be a con- tradiction of its own nature. It would begin and end in total maction, and the field would be clear for the other Power, just as if nothing else existed. It follows that, in the living and moving universe around us, there cannot be any such thing as an active principle of destruction and death. We are obliged to perceive Being under the guise of Becoming and Becoming under the guise of Change and Progression. This is a process taking place in the visible and temporal order of things and capable, under certain conditions, of partial arrest or retrogression. But the Whole, regarded as a whole, can be and can contain nothing but life, and must under all its diversity (which is an aspect of life) be One. It is this unity which alone can make intelligible and rational the diversity of which every study of life must treat. It is my endeavour in the present work to bring into clear light some important aspects of this unity, as revealed in the interrelations of the parts of which, to our eyes, it seems to be composed. 1 1 See Appendix A. CHAPTER II THE WHEEL OF LIFE I heard them in their sadness say The earth rebukes the thought of God ; We are but embers wrapped in clay, A little nobler than the sod. But I have touched the lips of clay ; Mother, thy rudest sod to me Is thrilled with fire of hidden day, And haunted by all mystery. A.E. IT has long been known that no definite line of demarcation can be drawn between the animal and the vegetable worlds. There are lowly organ- isms which cannot be decisively referred either to the one or to the other. It has been more recently shown that the apparently more strongly marked line between the living and the non-living also grows wavering and indistinct in places. Metals are known to respond to stimuli and to show 'fatigue' in a manner commonly attributed only to the nervous system of animals, 1 while some of the phenomena of 1 See Jagadis Chunder Bose, RESPONSE IN THE LIVING AND THE NON-LIVING, /a.m#2. The following passage sums up the results of many delicate experiments in the response to electrical stimulus. " We have seen," writes the Indian physicist, " that the criterion by which 21 22 PARALLEL PATHS crystallization strongly resemble those of vitality. 1 Le Dantec has uttered the latest word of physics on this subject, where he insists on the " absence of all essential difference and all absolute discontinuity be- tween living and non-living matter." 2 Indeed, one vital response is differentiated is its abolition by the action of certain reagents the so-called poisons. We find, however, that ' poisons ' also abolish the response in plants and metals. Just as animal tissues pass from a state of responsiveness while living to a state of irre- sponsiveness when killed by poisons, so also we find metals transformed from a responsive to an irresponsive condition by the action of similar poisonous reagents " (p. 1 88). 1 At a meeting of the British Association in 1905, Professor H. A. Miers, in a lecture on ' The Growth of a Crystal,' is reported to have said, The most wonderful feature of crystals was the manner in which they grew, just as though they were living things. Two features deserved special attention. The first was the remarkable power crystals possessed of healing themselves when mutilated. If a grow- ing crystal were removed from a solution, broken at one of its corners, and re-immersed in the solution, it would continue to grow, and as it grew would restore the missing part, and become once more a com- pletely symmetrical figure. This 'power of continuing to grow was possessed by a crystal even after countless ages, so soon as it was immersed into the appropriate solution. In this sense the crystal was immortal, for it never lost its vitality, or power of growing. The other remarkable feature was the growth of crystals in over-saturated solu- tions. In solutions only slightly over-saturated, no spontaneous generation of crystals was possible. It was true that a solution only slightly over-saturated would often begin to crystallize, apparently spontaneously, when exposed to the air, but this was because there were minute crystal fragments of the dissolved substance floating about in the air which got into the solution with the dust and so inoculated the solution with crystal germs, just as the human body might be inoculated with disease by a disease germ. If these germs were kept out, the solution would not crystallize until it was very strongly over-saturated, and then, at a certain strength, it would suddenly begin to crystallize spontaneously and with great rapidity. Times, August 5, 1907. 2 THE NATURE AND ORIGIN OF LIFE (Eng. trans.), p. 250. THE WHEEL OF LIFE 23 may say of nature-study in general, that if, as Plato said, the beginning of knowledge is in definitions and classification, the end of it lies in getting rid of them. There is probably no such thing as a universally ap- plicable definition of any group of natural phenomena. There is certainly no condition of matter of which we are entitled to say that Life is impossible without it. Still, natural groups have well-marked central features, even if at their margins they melt into something else. Now the things which in the ordinary sense of the word we call Living are marked by these characters : Their chemical constituents are always compounds of carbon. These compounds are what is called ' unstable ' they ' consume ' or disintegrate by combining with oxygen in air or water. In this process organisms obtain the energy necessary for assimilation and growth. The above characters (carbon-compounds, chemical instability, and faculty of assimilation) apply to plants and animals alike. But we find, in general, that plants are able, from inorganic mineral constituents such as carbonic acid, water, nitrates, sulphates, etc., 1 to build up the organic compounds like proteid, albumin, the carbohydrates, alcohol, fat; while animals use for their nourishment not the inorganic substances but 1 It is not to be assumed, however, that these substances are merely passive objects in the process. The life which is in them has doubt- less as much to do with the result as the life which is in the plant. This is a side of the question which calls for further investigation. 24 PARALLEL PATHS only organic compounds already formed by plants or by other animals. A well-developed vegetable world must therefore, it would seem, have preceded the appearance of animal life on the globe. 1 It was long believed that these organic compounds of carbon could only be formed by the vital action of living vegetation. One of the epochs in the history of modern chemistry has been the demonstration (first by Wohler, in 1828,) that many of them can be produced in the laboratory from inorganic chemical constituents. But this is only effected by circuitous and difficult ways, and a circumstance often overlooked it only resembles what is ac- complished in nature if we include under nature the directive agency represented by the chemist himself, as well as the materials with which he deals. The characteristic colour of living vegetation is green. This is also the rarest of colours among the higher animals. 2 It is due in vegetables to the presence in their cells of grains of the substance known as chlorophyll, which very few animals 1 It is however suggested by Professor E. Ray Lankester, in his article, ' Protozoa,' in the ENCYCLOPAEDIA BRITANNICA, that the most primitive forms of organic life did not possess chlorophyll but fed on albuminoids, etc., which constituted the earliest steps in their own evolution. 2 In Beddard's ANIMAL COLORATION note is taken of the green fur of the sloth as a most uncommon if not unique phenomenon. It has been ascertained that the sloth has grooved or fluted hairs, which form the habitat of a minute green fungus to which the colour is due. THE WHEEL OF LIFE 25 possess or have need of. It is developed normally under the action of sunlight, and plays a most important part in the economy of the plant The usual method by which any organism obtains the energy necessary for its vital functions is through the oxidization, i.e. the slow burning, of its substance, by combination with the oxygen of the air. The process is to all intents the same as the more rapid oxidiz- ation, under great heat, of coal in a steam-engine. If a plant can obtain sugar, which oxidizes easily in contact with atmospheric oxygen, it has thus a fund of energy to draw on for all the processes of its life. Now sugar is composed of carbon and water. Carbon exists in the air, in combination with oxygen, in the form known as carbonic acid. Chlorophyll, in some way as yet unexplained, enables plants, when acted upon by light, to take in carbonic acid from the air and to disintegrate it into its constituents, carbon and oxygen. The oxygen disappears again in the air, and the released carbon combines with water in the plant to form sugar, 1 thus giving the plant its needed store of potential energy. All it does with this energy is to live, grow, and reproduce its kind ; till at length a time comes when the assimilative energy weakens relatively to the forces of decay, and the plant dies ; it is again resolved into the chemical constituents from which it was built 1 Or starch, which easily decomposes into sugar, and which is composed of the same elements. 26 PARALLEL PATHS up ; but not without having passed on the flame of life to burn afresh in its descendants. Plants which have no chlorophyll, like certain bacteria and moulds, and which, therefore, cannot de- compose the carbonic acid in the air for their nourish- ment, offer an interesting example of the manner in which Nature contrives to get her way, if not by the normal instruments, then by the utilization of others. They acquire their first store of energy sometimes like animals, from other organic compounds, or they take carbon from acetates and tartrates. The nitro- bacteria appear to depend on ammonia derived from decaying animal matter, and the moulds draw their energy from sugar, which (as in our jams, etc.) they find already formed. There are other plants, such as the fly-eating Drosera, which feed upon organic substances with the aid of digestive juices, exactly as animals do ; and there are animals, such as Hydra and others, of very primitive form, 1 which produce chlorophyll and are thereby enabled, like plants, to feed upon carbonic acid. The distinction therefore which has been drawn between the two kingdoms as regards their modes of nourishment must, like other de- finitions of natural groups, be taken to apply to central and typical forms and not to constitute a distinct boundary line. Allowing for these excep- tional cases, we may say broadly that the wheel of 1 Ray Lankester, op. cit. THE WHEEL OF LIFE 27 life makes its full circle in passing from inorganic matter through plants to animals and thence back to gases and minerals again. The process of taking in fresh matter, transforming it chemically into living tissue, and thus repairing the waste occasioned by the decomposition of the carbon-compounds of that tissue, is technically known as Metabolism. This is the typical and characteristic function of organic life. Now this function of living matter, or Protoplasm, depends upon two elements : first, its Substance ; secondly, its Structure. As regards the former, we are in this serious difficulty, that living matter can never be chemically investigated by any means at present known, for it dies immediately in presence of any of the reagents which are used to ascertain its chemical composition. It is known that there are no elementary substances in living matter which are not also found in the world of inorganic matter, but it is also known that their synthetic combination in living is different from that which obtains in dead tissue, 1 and it is precisely through this factor that of the grouping or synthesis of elements that the most remarkable forms of energy are developed. 1 Verworn, GENERAL PHYSIOLOGY, pp. 102, 478: "Physiological chemistry has shown that between the two kinds of substance very essential chemical differences exist, which prove that living substance experiences in dying pronounced chemical changes. A widespread difference between the two consists in their reaction. The reaction of living substance is almost without exception alkaline or neutral, and 28 PARALLEL PATHS The secret of life, therefore, cannot be stated in terms of chemistry, because we cannot surprise the secret of its chemical synthesis. Even if we could do this we should still be unable to say why certain syntheses should appear in living matter and resolve themselves into others at death. We find, however, in the investigation of organic tissue (plant or animal) by such means as are avail- able, that one substance is common to all the organic and is never found (as such) in the inorganic world. This is called Proteid. It is composed of five ele- ments Carbon, Hydrogen, Sulphur, Nitrogen, and Oxygen, which are combined in proportions not at present ascertained. Subject to the limitations just set forth we may say that proteid is the essential stuff of organic tissue. The two other usual (though not, like proteid, universal) constituents of this tissue the Carbohydrates (sugar, starch, etc.) and the Fats are, it is believed, formed partly from the pro- ducts of the metabolism of proteid. When we come to deal with the essential Structure of life we are in much the same difficulty as that in which we found ourselves in investigating its chemical Substance. We can observe living cells under the microscope, but the most powerful micro- with death changes usually to acid. . . . Physiological chemistry has shown similar changes in death in great number. All these facts prove that in the death of living cell-substance certain chemical com- pounds undergo transformations ; hence substances exist in it which are not to be found in dead cell-substance." THE WHEEL OF LIFE 39 scope has never reached the limits beyond which we can say that there is no structure. There is another limitation too. The microscope has revealed the fact that all living tissue is made up of cells, but the internal structure of the cell, beyond the fact that it is composed of a fluid substance within which a darker coloured nucleus is usually embedded, could not be ascertained until the recent device of staining the object with aniline dyes had been thought of. Different substances in the cell are found to take these dyes differently, and thus a world of structure of the most singular kind has been revealed in what formerly seemed a simple, semi-transparent fluid. Some parts of this structure hover, as it were, upon the very edge of perceptibility, the most suit- able dyes for bringing them under observation not having been as yet discovered. There may be others which no dye can reveal, but which are yet active and necessary parts of the organism. More- over, here too the cell is killed by the means taken to observe it, and the processes in which its structure is engaged can only as a rule be deduced from the observation of a great number of cells in which their internal movements are arrested at different stages of completion. It has been practically demonstrated that all organic life must be at least duplex if not multiplex in its constituent elements. In its simplest known form it consists of Protoplasm and Nucleus. We 30 PARALLEL PATHS know that the carrying-on of all vital functions depends on peculiar relations existing between these two elements, but what these relations exactly are is still quite obscure. Both protoplasm and nucleus are compounds of proteid with other chemical sub- stances not yet fully determined. Protoplasm is a fluid, and has been shown by the epoch-making observations of Butschli 1 to have a structure re- sembling that of an exceedingly minute foam. The nucleus usually exists in the form of a single definite body, but it may be scattered through the protoplasm of the organism in little granules. In the lowliest of organisms, the Amcebcz, we have simply a speck of protoplasm containing a nucleus, but with no surrounding wall of the harder substance which protoplasm builds up for itself in the cells belonging to higher forms of life. Such amoeboid forms are the white corpuscles in the human blood, whose slow changes of form we can observe under the microscope, and which play so important a part in our economy by feeding on the noxious bacteria which produce the various forms of blood-poisoning and zymotic disease. A more detailed account of the functions and structure of the cell must be reserved for the next 1 In 1892. An English translation of Butschli's work on Micro- scopic Foams and Protoplasm, by E. A. Minchin, appeared in 1894. The nucleus is really a form of protoplasm, chiefly differentiated from the ' cytoplasm,' or protoplasm of the cell, by containing a large amount of phosphorus. THE WHEEL OF LIFE 31 chapter. In considering these and all other pheno- mena of vitality let me again recall the warning expressed in the taunt of Mephistopheles to the young student : the lines are as true to-day as they were when Goethe wrote them over a hundred years ago: " If some living thing you would learn about, You begin by driving its Spirit out ; There lie the parts of it, one by one, But the binding Spirit, alas, is gone ! " CHAPTER III DE MINIMIS Immense have been the preparations for me, Faithful and friendly the arms that have help'd me. Before I was born out of my mother generations guided me, My embryo has never been torpid, nothing could overlay it.'* WALT WHITMAN. THERE are two functions of organic life which are often confused together, but which it is well to keep distinct in our thought. These are Growth and Development. The mark of growth Is that an organism, by assimilation from the outside world, becomes larger than it was. But in development it becomes different from what it was. The history of an embryo in the womb presents a succession of phe- nomena which, when one comes to realize them, al- most stagger thought ; for, while remaining the same thing o\\ through, it is continually becoming a different class of thing first two cells, then one cell, then a fish, a quadruped, ultimately a human being. This is Development. Once born, it is laid hold of by the principle of Growth which lasts until maturity. Now in the groups called Species, as well as in individuals, we observe exactly the same distinction. 32 DE MINIMIS 33 The members of a species multiply and increase their numbers. This is Growth. But under certain conditions, which we have now to investigate, they vary in type and ultimately give rise to new species differing widely from that from which they sprang. This we call Development or, in the more popu- lar term for the process when applied to species, Evolution. The investigation of this process in all its details has been the master-impulse of biology ever since the fact of the process was established by the re- searches of Darwin. In Darwin's time the study of evolution was mainly an affair of what is called Natural History But it has now been realized that fully to comprehend the processes involved so far as they can ever be comprehended it is necessary to find out of what kind of material living beings are composed, and how their fundamental processes take place. " The ultimate problems of sex, fertilization, inheritance, and development," says Wilson, have been now "shown to be cell-problems"^ Before going further, therefore, we must give some account of the leading facts connected with the structure and vital action of the cell. Since the publication of the ORIGIN OF SPECIES, probably the most important contribution to bio- 1 THE CELL IN DEVELOPMENT AND INHERITANCE, 2nd edition, p. 9. D 34 PARALLEL PATHS logical theory is to be found in the researches of Dr. A. Weismann, and particularly in his large work, THE EVOLUTION THEORY, of which a masterly English translation has recently appeared. 1 Weismann, on one side, represents an heroic attempt to bring back to the strictly mechanical principles of Darwinism the tide of biological speculation, which has been flowing more and more in the direction of recog- nizing an essential and not a merely fortuitous con- nexion between the goal of the evolution of natural forms and the means taken by nature to attain it. On another side he has brought the physiology of the cell into true relation with the natural history of the organism and of the species, and has become the author, or at least the first great expounder and sys- tematizer, of a theory of heredity the now famous Germ-Plasm theory much of which seems a solid, permanent, and deeply important contribution to knowledge. But this theory seems to lead straight to a non-mechanical or psychic conception of the driving-force of evolution, and Weismann has there- fore supplied the other part which, in the view of the present writer and of many others better qualified to judge, seems to be of the nature of a baseless and improbable hypothesis, devised to find a means of avoiding recourse to any non-mechanical conception of the ultimate nature of evolutionary processes. As we shall be much concerned with Weismann's 1 By J. A. and M. R. Thomson, 1904. DE MINIMIS 35 views, let us place at the head of our study of them a couple of passages in which his general attitude towards the phenomena of vital processes is ex- pressed. "In our time," he writes, "the great riddle has been solved the riddle of the origin of what is best suited to its purpose without the co-operation of purposive forces." l " We must certainly assume," he declares, " that the mechanical theory of life is correct." 2 A longer passage shows us what he understands by ' mechanical ' : "The living machine differs essentially from other machines in the fact that it constructs itself; it arises by development from a cell, by going through numerous stages of development, but none of these stages is a dead thing, each in itself is a living organism whose chief func- tion is to give rise to the next stage. Thus each stage of the development may be compared to a machine whose function consists in producing a similar but more complex machine. Each stage is thus composed, just like the complete organism, of a number of such ' constellations ' of elementary substances and elementary forces, whose number in the beginnings is relatively small, but increases rapidly with each new stage." 3 It would have been simpler, but it would not have suited Weismann's conception of nature, to say that the "living machine" differs essentially from other machines in not being a machine at all, or anything 1 THE EVOLUTION THEORY, II, p. 391. 3 Ibid., I, p. 368. * Ibid., I, p. 404. 36 PARALLEL PATHS in the least like one. No machine constructs itself. No machine can do anything but repeat a certain series of movements, each series exactly similar to the last. What Weismann has described is not a machine, just because it is a living organism. It is surely as true in biology as it is in mechanics that in any purely physical chain of sequences you cannot by any possibility get more out at the end than you put in at the beginning, unless you take it in upon the way. " Development," writes Weismann, " is an expres- sion of life." l But " life," again, is merely "a chemico- physical phenomenon." 2 To say that development is an expression of a chemico-physical phenomenon does not seem a very illuminating or helpful generalization. The fact is that the statement that life is a chemico- physical phenomenon does not take us further towards an understanding of the subject than when we say, what is equally true, that chemical and physical phenomena are a manifestation of life. Life is everywhere. We use it as a convenient term for the energies associated with 'living' protoplasm, because we observe that when it is present proto- plasmic structures act and react (as in the phenomena of nutrition, for instance) in certain chemico-physical ways, while, if it be absent, the same protoplasm acts in other ways, also chemico-physical, but quite dif- ferent from the former, and analogous to the ways of 1 THE EVOLUTION THEORY, I, p. 353. 2 Ibid., II, p. 52. DE MINIMIS 37 minerals and of gases into which dead protoplasm finally resolves itself. The chemico-physical actions and reactions appear in a living plant or animal to be under the direction of a force devoted to the preservation of that particular organism. The smallest atom of organic life includes not only a chemical compound but a chemist. In the mineral world we may say broadly that there is no in- dividuality of parts. 1 With protoplasmic structure, therefore, a stage is reached in the evolution of life which we may rightfully call ' life ' par excellence, but there has been no breach of continuity, and it is highly probable, as Weismann himself suggests, that far below the limits of microscopic observation the transforma- tion of ' dead ' into ' living ' matter is continually going forward. When, therefore, we speak of the action of living protoplasm the distinction is rather between this action and that of a piece of mechanism than between protoplasm and minerals or gases. The phenomena of cell-growth, reproduction, and heredity are those which lie at the basis of all organized protoplasmic life, and in all the forms of that life, vegetable as well as animal, they are extraordinarily similar ; there is, in fact, nothing which all the species of living things have so much in common. One of the most wonderful and fas- cinating chapters in the whole range of science is 1 But note the transition stage exemplified in the natural history of crystals (vide p. 22). 3 8 PARALLEL PATHS that which contains the account of these processes, and it is only within the last few years that it has been possible to write it. Weismann, in a certain section of his EVOLUTION THEORY, has brought the facts together in a manner which, for its lucidity and mastery of the subject-matter, deserves to be called a classic example of scientific exposition. 1 To under- stand the basis of the higher manifestations of life, these processes, as we have said, must first be understood, and an account of them, based on Weismann, and accepting his germ-plasm theory so far as it seems to accord with established facts, will be given, of course only in the broadest outlines. 2 At the same time it will be attempted, here and there, to throw some light on the rationale of the processes described. All animal and vegetable structure arises from cellular tissue, and in fact is either cellular tissue or, as in the case of bones, scales, etc., the mineral deposit formed by the action of cells. The simplest living forms are composed of single cells, and the most complex and huge of them were each once nothing more than a single cell, possessed of the powers of development and growth. In multi- 1 "It has been Weismann's great service to place the keystone between the work of the evolutionists and that of the cytologists, and thus to bring the cell-theory and the evolution-theory into organic connexion" (E. B. Wilson, THE CELL, p. 13). 2 Prof. Wilson's work on the cell (see note on p. 33) may be referred to for a comprehensive and detailed statement of all that is known at present on this subject. DE MINIMIS 39 cellular organisms, this single originating cell is usually formed by the fusion of two imperfect cells by what is indifferently called conjugation, sexual reproduction, or ' amphimixis.' All cells, whether they are the product of conjugation or not, grow, when they do grow, fundamentally in the same way, and this way must now be described. The contents of the typical cell are broadly differentiated into (i) a more or less hardened en- velope containing (2) a subtance called cytoplasm (Gk. KUTO?, a cell), and (3) a small, rounded, dark-coloured body called the nucleus. Until recently nothing more than this was known of the structure of the cell, and nothing at all of the functions of the nucleus. Now, keener microscopic research and better instru- ments have thrown a flood of light on cell-organiza- tion, and the nucleus is revealed as a powerful factor in the vital processes of the cell and the bearer of its hereditary substance 1 that which makes it a cell of some particular organism, plant or animal, and of no other. This hereditary substance, divined by the botanist Nageli, and since observed by Weismann and others, is called ' chromatin ' (from the fact that it is observed by means of the stain it takes from the addition of an aniline dye), or 'idioplasm' (Nageli's appellation), which might be rendered the 'selfhood substance ' of the cell. 1 According to Wilson (op. cit.) this was guessed by Haeckel in 1866, and confirmed in 1884-5 by the almost simultaneous discoveries of O. Hertwig, Strasburger, Kolliker, and Weismann. 40 PARALLEL PATHS Cellular structure begins, as has long been known, by the division of a cell into two, each of the parts then proceeding to grow by the assimilative power of protoplasm and in due time to divide in its turn. A mass of these cells is called ' cellular tissue.' The so-called 'budding' of a small cell from the side of the parent is, of course, simply a form of division. The process of division and redivision goes on, ac- companied by a differentiation in the shape and function of the different cells or groups of cells which are formed, until the structure of the plant or animal is completed. In these operations the nucleus plays the principal part. The division of the cell is essentially the division of the nucleus. A detached portion of a cell which contains nothing of the nucleus can reproduce itself no more ; it perishes. When a cell is about to divide, an organ of recent discovery, termed the 'centrosome,' comes into play. This appears as the core of a sort of rayed or star-like figure, and it takes up its position beside the nucleus. When the cell is resting, the chromatin is dispersed through the nucleus in a mass of broken lines, forming a kind of network. When division begins, this broken- up substance forms itself into a series of small threads, sometimes straight, sometimes looped or curved. These are called 'chromosomes.' There are always a definite and invariable number of chromosomes for every species of plant or animal the cell of a man f felll .,:, : ^& ma /'_ ' .-' ^ '?** ' M' FIG. i. This illustration, which (by permission of The Macmillan Co. ) I take from Wilson's work, THE CELL, is one of remarkable interest, for in it the microscope has caught, in a piece of actual tissue from the skin of the salamander, Amblystoma, three nuclei in different stages of mitotic division. Most of the nuclei, which are seen as large, roundish objects in their respective cells, show the chromatin in its ' resting' con- dition interspersed through the nucleus. The nucleus under a shows the chromatin gathered into chromosomes. At b the centrosomes with their astral figures (which can barely be detected) have been formed, the chromosomes have carried out their longitudinal division, and are being attracted half towards one centrosome and half towards the other. A little above this the process has been carried further, and the sides of the cell are beginning to contract, preparatory to forming two new ones. In Fig. 2 will be found a clear representation of the astral figures. To face p. 40. DE MINIMIS 41 has so many, 1 of a grasshopper so many, of a lily so many. The chromosomes range themselves in a belt across the centre of the nucleus, and the centre- Centrosphcrt con- taining the cen- trosome Spindle. Chromosomes forming the equatorial plate. FlG. 2. The above illustration from Wilson's THE CELL shows in more or less diagrammatic form the stage of nuclear division in which the chromosomes, as yet undivided, have arranged themselves in the centre of the nucleus. The centrosomes with their astral figures have been formed, and have taken their places near each pole of the nucleus. The next stage is represented at b in Fig. i. some breaks into two parts, which take up a posi- tion one at each end of the nucleus. Regarding the nucleus as a tiny globe, we may say that the chromo- 1 Sixteen have been counted in the human cell. A grasshopper has twelve, a lily twenty-four. The number is almost always an even one, but as with everything in Nature there are exceptions to the rule. 42 PARALLEL PATHS somes lie in the equatorial plane, while the two parts of the centrosome move towards the North and South Poles respectively. The centrosomes, at the two poles of the nucleus, are surrounded each with a halo of ray-like processes (the centrosphere), and on the sides next each other these rays penetrate the nucleus and join, forming a spindle- shaped figure with a centrosphere at each end. This spindle figure appears to be the organ by which the division is accomplished, for each of the chromo- somes now splits itself in two longitudinally, as one cleaves a log of wood, and one half passes over to each centrosphere, thus making an exact division of the whole chromatin or hereditary substance. An indentation now appears in the outer wall of the cell and also in the nucleus it deepens and deepens, and finally two cells appear instead of one, each with a nucleus, a centrosome, and a supply of chromatin, the latter now breaking up into its original condition of diffusion through the nucleus. In multicellular organisms the two new cells, of course, do not separate, but a wall is formed between them. Some plant-cells contain several nuclei; in this case division of the nucleus is not necessarily followed by that of the cell. 1 1 The process briefly described above is that of ' mitotic ' division (Gk. nirot, a thread, from the appearance of the chromosomes). Amitotic division, in which the cell and nucleus simply divide in two without the formation of chromosomes, also occurs under certain con- ditions, but is usually an abnormal or degenerative process (cf. Wilson, THE CELL, pp. 116-119). DE MINIMIS 43 Throughout the processes of cell division it is ap- parent that the utmost care is taken to ensure an exact partition of the chromatin between the two new cells. This partition has to be qualitative as well as quanti- tative ; for one chromosome may, and no doubt does, differ in function and influence from another, and has various elements within itself. The longitudinal divi- sion of each chromosome, in which the elements are arranged like beads on a rosary, ensures that the different elements of the whole hereditary substance shall appear in each new cell in exactly the same relative proportion as in the parent cell ; just as if two persons had to divide between them a dozen apples of different varieties, and secured perfect equality, not by taking six apples each, but by divid- ing every apple in two. This is the fundamental cause of the fixity of species, which means the production of offspring having the same specific characteristics as their parents. How, under these conditions, the mutability of species is brought about must be dis- cussed later. It is first of all necessary to inquire more closely into the composition of the chromatin, and to study the special phenomena of cell-growth in connexion with conjugation, where new and extra- ordinary features come to light. A chromosome is not, or is not usually, a simple body. In all but the very lowest organisms it is composed, as we have said, of a number of elements. 44 PARALLEL PATHS Each of these elements is styled a ' determinant,' and it controls the form, colour, and function of some definite part of the future plant or animal. Weismann believes the determinants to be grouped into com- plex bodies called 'ids/ each id containing all the determinants necessary for a whole being, and each chromosome being composed of a number of ids. These ids are microscopically visible ; they form the beads on the rosary already referred to ; but their exact composition and potency are largely conjectural at present. How far the subdivision of determinants may go, it is, of course, impossible to as- certain. We cannot say, for instance, whether there is a determinant for every hair of the head, or one for the hirsute covering in general, or one for each of the different sections of the scalp. But the division is very minute. Each of the ids may be a very com- plex body, as we see by the manner in which, in some families, small physical signs like a patch of hair differing from the colour of the rest, or a tiny pit or mole on the skin of a certain part of the body, may be handed down, in that precise position, for generations. There may be, and, in fact, in the higher plants and animals there must be, a number of determinants for each part of the structure, and the final characteristics of that part must be the re- sultant of a blend of all these determinants, the more powerful predominating in proportion to their vitality and force. The whole body of the chromo- DE MINIMIS 45 somes may therefore be said to represent one or more complete beings in diagrammatic form, each part of the complete animal or plant being repre- sented by some part of a chromosome, though of course not physically resembling it. And we thus strike on the very curious and startling fact that, as far as we can see, every cell in every organism throughout the world of life contains all the ele- ments of the whole being to which it belongs, and is, potentially, that being. 1 All the higher organisms possess two kinds of cells reproductive cells which have the faculty of fusing together to reproduce their kind, and ' somatic ' or body cells, which, although they all originate in a reproductive cell, multiply only by division, and have the function of forming the various parts of the bodily structure. Of the nucleus of a germ cell "we cannot say that it differs in any essential or definite way from the nucleus of any other cell." 2 All possess the chro- matin or hereditary substance of the organism, though, according to Boveri, the germ cells alone receive all the chromatin of the parent cell, the derived somatic cells having to part with some of it. 3 There may be some distinction, though on what 1 ' ' Every animal appears as a sum of vital entities, each of which bears within itself the complete character of life" (Virchow, CELLULAR- PATHOLOGIE, p. 12, 1858). 2 Weismann, THE EVOLUTION THEORY, I, 251. 8 It is cast out into the cytoplasm the substance surrounding the nucleus where it degenerates (see Wilson, THE CELL, p. 147). 46 PARALLEL PATHS it may be based it is at present impossible to say, between cells that are capable of developing into a complete organized creature and those that are not. Every somatic cell is doomed to perish, but every reproductive cell now upon the globe is united, not metaphorically, not by a chain of successive origina- tions or impulses, but by actual identity of substance, with the first beginnings of protoplasmic life in the abyss of time ; and it has before it a potential im- mortality commensurate with life itself. It is not, as used to be thought, a physiological product of the organism in which it dwells ; it is a part of the original reproductive cell from which that organism sprang. To understand these conceptions we must now study the phenomena of reproduction in the light of recent discoveries. The lowest form of the reproductive process is, of course, by simple division and redivision. This is characteristic of many of those organisms which consist only of a single cell, and it may co-exist, even in these, with a considerable degree of structural complexity, as in the 'trumpet animalcule,' Stentor raselii. But among the lowest of these unicellular organisms a curious process is sometimes observed to take place, in which we may doubtless recognize the origin of sexual reproduction. Two, three, or DE MINIMIS 47 more Amcebce 1 approach each other, partially coalesce, and remain united for some time. They then separ- ate again. No new creatures are formed by this contact ; there are no visible results at all. But that something which is for the advantage of the organisms takes place during this period of union is certain, and in the light of what is known of processes in other organ- isms we can make a very good guess at what this some- thing is. Each Amoeba parts with some of its chro- matin to some other and receives an equivalent in exchange. The creature is thus reconstituted. The element of change, which always provides so marked a stimulus to vital processes, has been obtained. The process has actually been observed in a certain In- fusorian, Noctiluca. Two Noctilucas coalesce, and then proceed to divide at right angles to the plane of contact. This necessarily has the effect of giving to each of the two new Noctilucas which result from the division half the nucleus and chromatin of one parent and half of the other. There is, however, no actual new birth or multiplication of beings ; there are only two Noctilucas as before. We can now imagine that if a certain class of unicellular organisms are in the habit of approaching each other for the purpose of this interchange of portions of their chromatin, they might occasionally, under the influence of the approaching conjugation, expel those portions of chromatin before another cell 1 Amoeba. See p. 30. 48 PARALLEL PATHS was in a position to receive it. What would happen if two cells, each of which had thus got rid of half its chromatin, were to come into contact? Plainly, they would fuse together; they would not separate again ; they would become a new organism. Each would have supplied just what the other lacked. This process, forming the bridge from mere cell division to sexual reproduction, is a hypothetical one ; it has not, I believe, been actually observed in uni- cellular organisms, but it is exactly what we find to be taking place when we reach the stage of sexual reproduction among multicellulars. Multicellular organisms of more or less elaborate structure plainly cannot, without breaking up, fuse together like single cells. How, then, are they, as a species, to gain the advantages of the temporary union and inter- change of elements which we have observed in the low unicellular organisms? Only in one way by producing special cells for this purpose. These cells must \ represent the whole parent, they must be capable of shedding half their chromatin, and, when they have fused, must be capable of growing into a complete organism like the parent. When these specialized cells have been formed, the others, the somatic cells, will at the same time have been special- ized for other functions, and will thus naturally lose the original capacity for interchanging chromatin with other cells,z>. for conjugation. We see the significance, then, of Weismann's remark, " germ cells made their DE MINIMIS 49 appearance along with the multicellularbody." l They are an instance of that differentiation of structure and function which takes place in all highly organ- ized life. We must note also that the benefits of conjugation which are realized individually by the lowest unicellular forms are only realized as a species by the multicellulars. A species must, then, be regarded as in some sense an organic whole, and not as a mere aggregate of individuals. In some very curious cases which stand on the borderland between sexual and non-sexual reproduc- tion, the same organism is capable of employing both methods. Thus, among the lower seaweeds (Alg