wea 6 9878E800 | | a viii OLNOHOL JO ALISHAAINN RH eee 1 ee 8 SEES SEECUL SESE RE PLR CRSEL ESCHER PR ir ttag Digitized by the Internet Archive in 2008 with funding from Microsoft Corporation http://www.archive.org/details/footnotestoevolu00jorduoft ps Wises : os ii te fag! Asin ote Fe ree 4 * Sige > J Seas a> hd vine qu, q ea J . ve 7) ins > Waa "a G Pe lesrnitaie Monw Co. Hownsendiy oly mays Yrundeorime Co. & Mlawios Mirror Santa Clara CG —S ee Gutowwos semnur Drckuasou Co Some chipmunks of California, showing distinct species produced through isolation. From nature, by William Sacketon Atkinson. FOOT-NOTES TO EVOLUTION A SERIES OF POPULAR ADDRESSES ON THE EVOLUTION OF LIFE BY DAVID STARR JORDAN, Pu. D. PRESIDENT OF LELAND STANFORD JUNIOR UNIVERSITY WITH SUPPLEMENTARY ESSAYS BY EDWIN GRANT CONKLIN, Pu. D. PROFESSOR OF COMPARATIVE EMBRYOLOGY IN THE UNIVERSITY OF PENNSYLVANIA FRANK MACE McFARLAND, Pu. D. ASSOCIATE PROFESSOR OF HISTOLOGY IN LELAND STANFORD JUNIOR UNIVERSITY JAMES PERRIN SMITH, Pu. D. PROFESSOR OF PALEONTOLOGY IN LELAND STANFORD JUNIOR UNIVERSITY NEW YORK D. APPLETON AND COMPANY eee CopyRIGHT, 1898, By DAVID STARR JORDAN. TO TIMOTHY HOPKINS, OF MENLO PARK, CALIFORNIA, FOUNDER OF THE SEASIDE LABORATORY OF BIOLOGY ON MONTEREY BAY, IN RECOGNITION OF HIS FRIENDLY AID TO SCIENTIFIC INVESTIGATION. PREFATORY NOTE, THE present volume is made up of popular essays or addresses on the general subject of Organic Evolution. These were originally given as oral lectures before University Extension societies in California, having been condensed and written out in their present form after delivery. Three of these papers have already appeared in Appletons’ Popular Science Monthly, and three in The Arena. To the editors of these periodicals I am indebted for the privilege of reprinting them. Besides the twelve essays of my own, it is my good fortune to enhance the value of the volume by the in- sertion of three papers of special importance, setting forth the present state of knowledge concerning the method of evolution and the method of heredity. The first of these, on the Factors of Organic Evolution as displayed in the Process of Development, is by Professor Edwin Grant Conklin, of the University of Pennsyl- vania; the second, on the Physical Basis of Heredity, is by Professor Frank Mace McFarland, of Leland Stan- ford Jr. University ; the third, on the Testimony from Paleontology, is by Professor James Perrin Smith, of vii Viil FOOT-NOTES TO EVOLUTION. Leland Stanford Jr. University. The essay of Professor Conklin was read before the American Philosophical So- ciety. The others are here presented for the first time. I may add that the present volume is not intended as a text-book in Evolution, although most phases of organic development are in one way or another touched upon, some of them, however, most briefly. The treat- ment of different topics is necessarily unequal. The time is long past when any one man can master what is known in any science, least of all the universal science of life. In the supplementary essays I have asked my scientific friends to do for this volume certain work which I could not do except by the unsatisfactory method of compilation. DavipD STARR JORDAN. PALo ALTO, CALIFORNIA, January 19, 1898. ANALYSIS OF CONTENTS. PAGE I.—THE KINSHIP OF LIFE. ¢ _ 3 3 : . I What is the cause of variety in life? Whatisaspecies? The number of species. The unity of type. Unity in variety. The meaning of homology. The origin of va- riety and the origin of homology. The origin of life un- known. The answer of Linneus. The answer of Cuvier. The answer of Lamarck. The answer of Agassiz. What is special creation? All life from life. Uncertain bound- aries of species. The species of fishes of North Amer- ica. The species of the Galapagos. Do species change with space? The species of South American edentates. Do species change with time? Darwin’s answer. Dar- win’s method. The origin of species. The Darwinian theory. Artificial selection. Natural selection. The struggle for existence. Relation of bees to clover. Re- lation of cats to England’s greatness. The equilibrium of Nature. More organisms born than can mature. How the hare becomes white. How selection becomes adaptation. Acceleration of development. How bisex- ual parentage brings variety. ‘‘ Vom Vater hab’ ich die Statur.”” The value of death. The saving of time. Al- truism and its struggle for existence. Every fact has a meaning. Geographical distribution. Survival of the existing. Geological distribution. Epoch-making events. Change not progress. Vestigial organs. The pineal eye. Origin of complex structures. The individual repeats the history of the race. Embryology and evolution (John Sterling Kingsley). Similarity of early stages in embry- onic life. The egg of the mammal. Embryonic struc- ix x FOOT-NOTES TO EVOLUTION. PAGE tures in man. Gill slits in man. Objections to the the- ory of descent. Relation of present heredity to past environment. Darwin’s hope. The species of eel. The reality of species. The old idea of species has passed away. The acceptance of the theory of descent. The philosophy of evolution. Influence of theory of de- scent. Origin of man. Meaning of homology. Decay- ing scientific beliefs. Darwin’s words. The conception of God. Darwin’s home. Boyesen on evolution. II.—EVOLUTION: WHAT IT IS AND WHAT IT IS NOT .. 54 What evolutionis. The science of organic evolution or bionomics. Meaning of law. Soundness and solvency of Nature. The indifference of Nature. Evolution asa theory of organic development. Each fact has a mean- ing. Evolution as a method of study. Evolution as a system of cosmic philosophy. Decay of formule. What evolution is not. Man not a developed monkey. Not progress, but adaptation. Humanity not the goal of evo- lution. Change by slow divergence. No innate tend- ency toward progression. Spontaneous generation. Evolution not a creed. Evolution not a religion. Sci- ence its own witness. III.—THE ELEMENTS OF ORGANIC EVOLUTION . 4 WS Heredity. Irritability. Individuality. Natural selec- tion. Concessions of life. Self-activity. Altruism. Iso- lation. Nutritionin transmission. Survival of the exist- ing. Inheritance of acquired characters. The unknown factors. I[V.—THE FACTORS OF EVOLUTION FROM THE STAND- POINT OF EMBRYOLOGY. By Professor Edwin Grant Conklin . : A ; : : ‘ . 100 Embryology shows the method of evolution. Statement of propositions. Causes of development. Intrinsic causes dependent on nature of protoplasm. Inherited charac- ters predetermined in structure of germ cell. Germinal ANALYSIS OF CONTENTS. xi PAGE protoplasm relatively but not absolutely stable. Do ex- trinsic factors affect germinal protoplasm? Diminished nutrition. Changes in environment. Use and disuse. Mechanical conditions. Results of impact. Value of direct experiment. Return to the position of Darwin. The final word still far distant. V.—THE HEREDITY OF RICHARD ROE . ; 5 eS Formation of character. Hereditary tendencies. I[n- heritance of humanity. Inheritance of race characters. Individual characters. The germ cell. Protoplasm. Chromatin. Inequality of Nature’s divisions. Atavism. The mid-parent. The thoroughbred. Changes through experience. Inheritance of acquired characters. Nature of acquired characters. Prenatal influences. Transmis- sion of impaired vitality. Ibsen’s ghosts. Potentialities not character. The higher heredity. The unity of the ego. The ego a co-operation. Fame not greatness. Counting one’s ancestors. Lineage of a little girl. All Englishmen of noble birth. Effect of primogeniture. Origin of the English character. Race types and the survival of the existing. VI—THE PHYSICAL BASIS OF HEREDITY. By Professor Frank Mace McFarland . F : : : tA 7, Thecell theory. The meaning of theterm ‘‘cell.” Uni- cellular and multicellular organisms. The essential parts of the cell. The protoplasm. The nucleus. Ka- ryokinesis. The chromosomes. Division of the centro- some. The spindle. Division of the chromosomes. Phases of cell division by karyokinesis. Direct division. Somatic and reproductive tissues. Differentiation of so- matic and reproductive tissues in Ascaris. Reproduction in Protozoa. Conjugation. Gradual differentiation of reproductive cells. Reproduction in Eudorina. Repro- duction in Metazoa. Fundamental identity of the germ cells. The egg cell. Maturation. The sperm cell. Fertilization. Cleavage. The reduction of the chromo- somes. Theories as to structure and significance of the xil Vil VIII.—LATITUDE AND VERTEBRAE .—THE DISTRIBUTION OF SPECIES FOOT-NOTES TO EVOLUTION. chromosome. The ultimate vital units.” Significance of reduction. Reduction in Ascaris. Reduction in Crusta- cea. The chromatin as the bearer of hereditary influence. Indirect evidence. Direct experimental evidence. Illustrations not arguments. Cumulative evidence. The fauna of the Galapagos. Island life. Effects of mi- gration on species. Effects of isolation. Barriers to diffu- sion. Holarctic realm. Neotropical realm. Ethiopian realm. Indianrealm. Australian realm. Anomalies in distribution. Adaptation of animals to environment. Invasion of the Australian realm. Trout in Yellowstone Park. Two-Ocean Pass. Laws of distribution of ani- mals. Barriers of land, sea, and climate. Interdepend- ence of species. The arctic birch. Crossing the bar- riers. The flying fish. Subspecies or geographical variations. Doubtful species. Darwin’s experience. The shore larks. Work of Dr. J. A. Allen. Species de- fined by missing links. Analogy between variations of species and of words. A fauna like a language. The survival of the existing. How species change with time. Physiological isolation. Northern fishes have most vertebre. Fewest vertebre in shore fishes of the tropics. Fewer vertebre indicates greater specialization. Analogy of tropical waters to cities of men. Origin of eels. Coral reefs the centre of fish competition. Cephalization through competition. IX.—EVOLUTION OF FOSSIL CEPHALOPODA. By Pro- fessor James Perrin Smith Introduction: General evidence of paleontology; in- completeness of the record. Law of acceleration of de- velopment. Nomenclature of stages of growth. Paleon- togeny: General statement; Brachiopoda; Crustacea; Mollusca; Pelecypoda; Cephalopoda; Method of work- PAGE . 19! - 22X . 229 ANALYSIS OF CONTENTS. ing. Development of Glyphioceras. Development of Schlenbachia. ; X.—THE EVOLUTION OF THE MIND 5 : : 5 Mind the sum total of psychic changes. Mind not con- sciousness. Function precedes structure. Irritability the basis of mind. The brain adequate for the mind. The marvel of life. Activities of Protozoa. Sensation related to action. Mind of the plant. Locomotion de- mands sensation. Reflex action. The higher heredity. Realities and illusions. Selections of sensations. Ro- bust men make history. Relation of the child to the environment. The sensorium. Nature of instinct. In- stinct of the fur seal. Nature of the intellect. Effect of adversity on the intellect. Intellect of the monkey peo- ple. Intellect the choice of responses. Intellect of the furseal. The ‘‘Clavier” theory of mind. Colonial con- sciousness. ‘‘ Cogito, ergo sum.” Development of the ego. The building of the self. Sensation without action. Impulse and action. Degeneration. Power of attention. Defects in mental operation. Phenomena of hysteria. Effect of drugs. The mind of nations. XI.—DEGENERATION . : ; 2 x : ; * Decline in range of activities. Quiescent animals. Tunicates. Parasiticanimals. Sacculina. Animal pau- perism homologous with human pauperism. Law of compensation. Degeneration of senility. Race de- generation. Lineage of degeneracy short. Withered branches. Degeneration through charity. The cretins of Aosta. Degeneration in isolation. The Jukes. The poor whites. Degeneration in slavery. Degeneration in the slums. Degeneration in the tropics. Degenera- tion in luxury. Mental dyspepsia. The higher foolish- ness. Nordau on degeneration. The mattoid. The normal man. Disease of the nerves not genius. De- cadence for mercantile purposes. Causes of decadence. The despondency of Europe. The wholesome world. Degeneration under institutions. Mental pauperism. Spiritual pauperism. xill PAGE 256 277 xiv FOOT-NOTES TO EVOLUTION. XIIL.—HEREDITARY INEFFICIENCY . ‘ s ° The art of living. Mutual help preserves the incapa- ble. The easy world. Poverty not pauperism. Degen- eration of the inactive. The tribe of Ishmael. Paupers as parasites. Pauperism a factor in government. Cor- ruption fund of public charity. Foreign immigration. Taking away the ‘‘ freedom which is thraldom to sin.” XIII.—THE WOMAN OF EVOLUTION AND THE WOMAN XIV.—THE STABILITY OF TRUTH OF PESSIMISM Primary meaning of sex. Primal equality of sexes. Specialization of germ cells. Specialization of the em- bryo. Maternity and companionship. Woman not un- developed man. The altruism of parenthood. The philosophy of pessimism. The philosophy of evolution. Schopenhauer’s essay on woman. Woman a modified man. Inefficiency of woman. Beauty of young girls. Beauty as a weapon. Triviality of women. Early ma- turity of woman. Kindness of woman. Deceit of woman. Woman lives for the species. Trade jealousy among women. The unesthetic sex. No mastery of art. Philistinism of woman. The sexes unequal. Woman in European society. The lady-nuisance. The laws of marriage. Dependence of woman. The lord- nuisance. Blindness of pessimism. Woman from man’s standpoint. Unnatural competition. Evolution of the home. Freedom of man. For each defect a historic cause. Force breeds deceit. The equal marriage. Being a woman. Release from work not idleness. Assaults on the integrity of science. The secret of power. Human experience the basis of knowledge. Knowledge and belief. Views of the Marquis of Salis- bury. Views of Arthur J. Balfour. Human experience not objective. Ineffectiveness of reason. The nature of self. The terms of human experience. The measure of aman. Nature of sanity. The infinite understanding. The test of truth. The matter philosophy deals with. . 312 » 334 XV. INDEX . - A ‘ : A A ‘ S j ANALYSIS OF CONTENTS. Protyl. Religion and belief. Haeckel’s Confession of Faith. Monism. Unity of organic and inorganic Na- ture. Unity of chemical elements. Monism not science. Spontaneous generation not science. Reincarnation. Haeckel’s definition of belief. The inheritance of ac- quired characters. The courage of patience. Revision of science by philosophy. Science stops where facts stop. Primal motive of science. Message of science. Philo- sophic doubt and common sense. Each organism a link in the chain of life. Life dealsin realities. Convention- ality. Authority. Instinct springs from past conditions. Intellect points forward. Practicality of sensations. The sober mind. The recrudescence of superstition. Life based on dreams and illusions. Sensation truthful in the degree that action is possible. Hyperesthesia of sci- ence. Trust in reality makes life safe. Meaning of pain. Value of ideals. The course of life. The world as it is. Subordination of impulses. The search for truth. —THE STRUGGLE FOR REALITIES The price of truth. The mystic sanction. The strug- gle against tradition. The struggle against learning. The struggle in the human mind. Nature of the mind. Practicality of the senses. Suggestion and convention- ality. The forces outside ourselves. Fear and worship of the unseen powers. The science of our childhood. The world as it is. The conflict between science and re- ligion. The struggle between science and dogmatic the- ology. The essence of conservatism. The effort to limit thought. The effort to control action. The passing of institutions. XV PAGE . 366 - 379 FIG. . Pineal eye of lizard (Hatteria) (after Spencer) . 3 2 py34: . Pineal eye of lizard, in section (after Spencer) ; 5 By . Head of horned toad (PArynosoma) (after nature, by LIST OF ILLUSTRATIONS. W.S. Atkinson) . : ‘ : : aoe 3S . Conjugation of Infusoria (after feuckart) : c : 2 . Karyokinesis of cell (after Driiner) . : 2 kS5 Reduction of chromatin in egg-cleavage (atten: Boveri. 160 . Development of Pandorina (after Pringsheim) ‘ Los . Colony of Zudorina with antherozooids (after Goebel) . 167 . Diagram of development of spermatozoa (after Boveri) . 172 . Fertilization of egg (after Boveri) . 174 . Reduction of chromosomes in developing. egg Gites Brauer). ; 5 5 Loo) . Maturation of egg of Gielors (after Riickert) : ‘ werS2 . Larva of Achinus (after Boveri) : 187 . Hybrid larva of chinus and Spher shina (arte Baveri) 189 . The arctic birch (after nature, by Anne L. Brown). 5 | Hole’ . Skeleton of greenling (Hexagrammos) (after nature, by W.S. Atkinson) . : 224 . Skeleton of scarlet rock-fish ES haces) eben nature, by W.S. Atkinson) . 224 . Skeleton of angel fish (Anzclichshys} Gitar: nature, By W.S. Atkinson) . . : 5 eG . Sacculina after leaving the egg after Late) : - 5 GIG) . Sacculina attaching itself (after Lang) . ‘: : . 280 . Sacculina, an early stage (after Lang) ¢ ‘ . 280 . Sacculina after absorption of limbs (after Lang). 5 Bsio) . Adult Sacculina attached to crab (after Lang). F ne eRe 2 xvii XVll FOOT-NOTES TO EVOLUTION. FIG. PAGE 24. Section of mature Sacculina (after Lang). : : 28r 25. Sacculina attached (after Lang) p a 5 - = 252 26. Sacculina with limbs absorbed (after Lang) . 282 27. Cretin of Aosta (after a photograph by Dr. J. W. jeakS) 285 28. Cretin of Aosta (after Edward Whymper) : : . 286 FULL-PAGE PLATES. FACING PLATE PAGE Some chipmunks of California, showing distinct spe- cies produced through isolation (after nature, by William Sacketon Atkinson) . . Lrontispiece I.—Cephalopoda; development of Glyphioceras (after na- ture, by Mrs. Frances Rand Smith). : ‘ 7240 II.—Development of Glyphioceras (after nature, by Frances Rand Smith) . é : 2 bee 42 III.—Development of Schloenbachia (iter nature, by Fran ces Rand Smith) : : 246 IV.—Development of septa in Reese: Ges nature, Frances Rand Smith) : : : 248 V.—Forms of Ammonites (after nature, by Pradees Rand Smith) ‘ . : 2 3 a x = e252 FOOT_-NOTES TO, EVOLUTION. 1¢ THE KINSHIP OF LIFE. No one with good eyes and brains behind them has ever looked forth on the varied life of the world, on forest or meadow or brook or sea, with- ee 2 eee, out at least once asking himself the ques- ns ed tion, ‘“ What is the cause of Nature’s end- less variety ?” We see many kinds of birds and trees and insects and fishes and flowers and blades of grass, and yet when we look closely we find not one blade of grass in the meadow quite like another blade. The green cloak which covers the brown earth is the shield under which millions of organisms, brown or green, carry on their life work; yet not one organism in the world in body or mind is the exact measure of its neighbour. But with all this the real variety in life is far greater than that which appears. Each kind of animal or plant, that is, each set of forms which in the vicissitudes of the ages has become segregated and set off from its neigh- bours, is called in biology a species. The number of these species is great beyond any ordinary conception. I have an old book in my library, the tenth edition of the Systema Nature, I What is a species? 2 FOOT-NOTES TO EVOLUTION. published by Linnzus in 1758. This book treats of all the species of animals known a century and a half ago. In its eight hundred and twenty-three pages some four thousand different kinds of animals are named and described. But for every one of these enumerated by Linnzus, more than two hundred kinds are known to the modern natu- ralist, and the number of species still unknown doubt- less exceeds that of those already recorded. Every year since 1864 there has been published in London a plump octavo volume known as the Zodlogical Record. Each of these volumes, larger than the whole Systema Nature, contains the names of animals new to science added to our list during the year of which it treats. And in the record of each year we find the names of about three times as many animals as are mentioned in the Systema Nature. Yet the field shows no signs of exhaustion. As these volumes stand on the shelf together it is easy to see that the later volumes are the thickest, and that the record for the present year is the largest of all. Moreover, what is true of the increase of knowledge in systematic zodlogy is even more marked in the case of botany. Such, then, is the variety of life on the globe —a variety of which Linnzus and his successors had never dared to dream. And yet, great as this variety is, there are, after all, only a few types of structure among all animals and plants, some three or four or eight or ten general modes of development, and all the rest are modifications from these few types. It is, moreover, true that all living forms are but series of modifications and extensions of one single plan of structure. All have the same frame- work of cells, and in each cell we find the same ultimate substance—the mysterious semi-fluid network of proto- The number of species. The unity of type. THE KINSHIP OF LIFE. 3 plasm, which is, so far as we know, the physical basis of all life; and the equally mysterious nuclear substance or chromatin which in some fashion presides over all the movements of the protoplasm and is the physical basis of the phenomena of heredity. The same laws of heredity, variability, and of response to outside stimulus hold in all parts of the organic world. All organisms have the same need of reproduction. All are forced to make concession after concession to their surroundings, and in these concessions all progress in life consists. And at last each organism or each alliance of organisms must come to the greatest concession of all, which we call death. The unity in life is then not less a fact than is life’s great diversity. Whatever the emphasis we may lay upon the diversity of life, the essential unity of all organisms must not be for- gotten. This fundamental likeness among widely varied forms stands as the basis of all classification. It is this only which makes classification possible or conceivable. These bonds of union, which are real as distinguished from resemblances which are merely superficial or ap- parent, are known to the naturalist as homology. The existence of homologies is the fundamental fact in bio- logical science. It has been regarded as a mystery of mysteries, but this mystery assumes the form of natural law in the light of the plain fact that identity of structure is the simple result of identity of parentage. Homology in any form is simply the stamp of heredity. In other words, homology means blood-relationship. The sim- plest explanation is the truest and would long ago have been recognized had it not been for prejudices of va- rious sorts—theological prejudices that saw the image of God in man only, and scientific prejudices which arose from the surface study of surfaces. For it is the Unity in variety. 4 FOOT-NOTES TO EVOLUTION. inside of an animal which tells the real history of its ancestry; its outside tells us only where its ancestors have been. It is perfectly certain that homology represents some real law of Nature, something other than the results of mere chance. When I compare my arm with that of my neighbour, I find differ- ences in size and proportions. But these are superficial, and there is the underlying correspond- ence of each bone and muscle, each nerve fibre, artery, and vein. When I compare my arm with the fore leg of a dog I find more striking differences, for the dog’s station in life is quite unlike my own, and he uses his arm for different purposes. When I compare my arm with the wing of a bird or the pectoral fin of a fish, the results are still similar. Though the differences in each succeeding case become more and more striking, and the resemblance less easy to trace, yet the same re- semblances exist, and a closer study shows that these resemblances far outweigh the differences. We say, then, that homology is real, and whatever power or cause has acted on fishes to provide them with pectoral fins has given to birds wings, to the dog fore legs, and to me and my neighbour arms. The arms are appendages more specialized—that is, more highly fin- ished and suited to more purposes than the others—but all are formed of the same pieces, arranged in the same way. When I compare my arm, however, with the claw of a lobster, the limb of a tree, or the arm of a star- fish, all resemblances in gross structure disappear, and we have only the analogies connected with similar- ity of function. The ultimate homology of cell for cell, however, remains even here with all that this may signify. Now the problem before us is this; What is the The meaning of homology. THE KINSHIP OF LIFE. 5 origin of variety in life, and how does it come that this variety is based on essential unity? Or,in other words, what is the origin of species, and what is the origin of homology? Obviously, neither of these questions can be an- swered without considering the other, and obviously both presuppose the existence of life. As to the origin of life, we have as yet no basis for speculation. We can only say as a matter of fact that life exists on the earth, which was once lifeless. How the first organism came to be we can not even guess. By what clashing of elements the vital spark came forth, and whether like causes can or do still produce like effects, no one can say. Thespontaneous generation of organ- isms has never been seen, nor with our dull senses and clumsy instruments could it ever be seen; for an organism without a history, untouched by heredity, un- selected by struggle, unaffected by environment, a coin fresh from the mint of creation, would be a fragment of pristine simplicity as far beyond our grasp as the mole- cules of the chemist. It is likely that it is indeed a molecule, and a molecule in size compares with a drop of water much as an orange compares with the sun. If spontaneous generation exists, such creatures as bacilli and infusoria, small though they are, are not the prod- ucts of it; for these little creatures have their life his- tory, their habits, and their heredity as firmly fixed as those of the dog or the oak. A life history presupposes a long ancestry, and it is absurd to expect such battle- scarred organisms as the least we know to spring full developed from the combination of any of the compo- nent atoms. The origin of life is as yet beyond the reach of spec- ulation. We can not even bring it under investigation, The origin of va- riety and the ori- gin of homology. The origin of life unknown. 6 FOOT-NOTES TO EVOLUTION. for we know too little of it to ask of Nature even an intelligent question which shall bear upon it. But sci- ence does not shrink from unanswered problems. What- ever exists may some time be found out, and some day the law of creation may become as mucha part of our biological knowledge as the law of heredity bids fair soon to become. Having stated our problem of the origin of species, let us see what answers have been made to it by some of the great minds of the past. The past in biology is not far distant, for it is barely a century since biological problems were first treated as living questions. A cen- tury ago, as I have already said, comparatively few species, either of animals or plants, were known to the naturalist, as but few are now known to those who are not engaged in Nature study. Most of these were not known well. The question as to their origin could not be asked, for the very idea of origins was an unfamiliar one. The fact of the enormous succession of ages that makes up geological time, the thought that “time is as long as space is wide,” had scarcely entered the minds even of the boldest thinkers of that day. In this condition of knowledge the answer to our question was easy. Linnzeus said a century and a half ago: “There are as many different spe- cies now as there were different forms created in the beginning by the Infinite Being.” But Linnzus, with his few boxes of dried plants and his little cabinet of stuffed birds and dried fish skins, had scant conception of the range of variety in Nature, while of the underlying unity he had only occasional glimpses. That the animals and plants in his catalogue were the last in a long succession of life in which species after species had appeared and dropped out, dying or undergoing such changes as to seem to us The answer of Linneus. THE KINSHIP OF LIFE. 7 like new creations, was wholly unknown to him. And surely these considerations, these discoveries of a cen- tury of scientific activity, can not be ignored in forming our answer to the question of the origin of species. Some half a century after Linnzus, another natural- ist, still greater than he, gave himself to the study of homologies, and formed a classification of all animals on the basis of the resem- blances seen in their plans of organi- zation. It was known to him that there had been many changes in the history of life, and that the forms now living are but a tithe of the total number of those which have existed. So the answer of Cuvier was substantially this: There have been many creations and destructions of life in the history of the earth. So far as we can see, it appears that there are as many species now as there were different forms created by the Infinite Being at the beginning of the present geological era. But it was not easy to show just when the present era began, and the reasons for believing in the repeated total extinctions and creations became less and less strong the more closely the evidence was examined. Nor was it clear why the new creations should be as it were merely modified duplicates of the creatures which had preceded them. Why should the Creator, for in- stance, in covering the earth with a new creation, carry it right on in the same lines as the old one? Why should he give us not merely birds, reptiles, insects, shells, and ferns as before, but birds, reptiles, insects, shelis, and ferns only to be distinguished from their pre- decessors by the most careful study of men who have given their lives to such discriminations ? And then there were some men in Cuvier’s time who were not satisfied with the answer of Cuvier. Such men The answer of Cuvier. 8 FOOT-NOTES TO EVOLUTION, were Lamarck and Saint-Hilaire, and: with them was he who has been called “the sanest of men ’”—Geethe. There had been, they thought, in reality no new era and no new creation—only a gradual change from old to new, from old life under old conditions to new life with new envi- ronment. The natural tendency toward progress in life, the influence of the creatures’ own desires and needs, the attempt of creatures to. fit themselves to new sur- roundings were, they thought, in some way the causes of the changes in forms which Cuvier ascribed to new creations. But there were some facts not easy to explain on these suppositions, and the causes of change suggested by Lamarck seemed to most thinkers of his time entirely disproportionate to the changes themselves. Again, the weight of the great names of Linnzus and Cuvier rested on the other side, and authority has its weight in science as elsewhere when we come to estimate the relative probability of different conclusions. Besides, not enough of fact was in anybody’s possession to take these dis- cussions out of the region of speculation. There is rea- son to believe that Cuvier himself doubted his own dic- tum as to the special creation, unchanging permanence, and ultimate extinction of species. But Cuvier saw no way to any better view, and he believed that the advance- ment of science would come through the gathering and sorting of facts rather than from any hypotheses, how- ever ingenious, as to the origin of present conditions. But the permanence and persistence of type which Cuvier had demonstrated came to be a necessary ele- ment in the answer to the still vexed question of the origin of species. And this fact of unity formed the corner- stone in the answer given by Agassiz. The species rep- The answer of Lamarck. The answer of Agassiz. THE KINSHIP OF LIFE. 9 resent the divine thoughts embodied in the act of crea- tion. The unity exists in the mind of the Creator. He made them all, and so all bear the stamp of his workmanship. He is infinite, and so they exist in in- finite variety. That “material form is the cover of spirit’’ was to Agassiz “a truth at once fundamental and self-evident.’’ Each species is, then, the material form which clothes a divine idea. Homologies arise not from diverging lines of descent, but from the asso- ciations of divine ideas. They are the stamp of uni- formity which must accompany all works of a single mind, even though that mind be infinite. To trace this out in Nature is for us to think again the thoughts of God. This was Agassiz’s answer, and it has the charm of poetry, besides breathing the spirit of deep reverence which characterized this great naturalist, to whom the laboratory was not less holy than the church, and “a physical fact not less sacred than a moral principle.” It is a beautiful conception, but one which can not be exactly measured or verified. All science at the bot- tom is quantitative, and whatever is true to us can be reduced to measurement. We may, moreover, say if we choose that the “ thought of God ”’ is not “ the unchang- ing species,” but the law under which species are modi- fied and changed. Nature is made up of changing beings produced and acted upon by unchanging laws. It is the mighty unseen force itself rather than the visible and transitory object of its action which, in the language of poetry, we may call the “ thought of God.” The progress of knowledge comes not from the growth of beautiful conceptions, but from the subjec- tion of all conceptions and theories to the crucial test of fact. A thought which can not be put to the test of human experience forms no part of science. 10 FOOT-NOTES TO EVOLUTION. And so, without affirming or denying these views of Agassiz, scientific men have not been satisfied to rest with them. Admitting that each species has been created, the question of method is still pertinent. What is creation ? How is it performed? What do we mean, for example, by “special crea- tion’ in opposition to the production of species through variations due to natural causes? What knowledge have we of the origin of species as distin- guished from the birth point of one of the individuals of this species? If each of the million species of ani- mals and plants which now live, and each of the mil- lions of kinds which have become extinct, has been the object of a “ special creation,” then “special creation ” is but a name to cover our ignorance of the law by which species are produced. What has been done so many times must be done in some uniform way. All our experience in the universe tells us that everything is done in its way and in no other. We no longer pic- ture the Creator as forming dogs and horses and men out of clay and then breathing into them the breath of life. We no longer, with Milton, “imagine” the new created lion as pawing the earth “to free his hinder parts.” That is not the way we find lions made. The lion develops from the unborn lion kitten, and this un- born kitten, through heredity typifies its cat-like ances- tors. They were cat-like before they became lion-like. “All life comes from life,” is a maxim of the early naturalists. We understand in some measure the method of birth, the method by which individuals are created. Why should we think that the creation of species, special series of individuals, has come about in any way other than this, when we know of no other ? What is special creation ? All life from life. ee THE KINSHIP OF LIFE. II Then again, if species be the subject of special in- tervention such as some have imagined, how is it that after years of study we are still uncer- “eit op tain_as to their characters and bounda- ries? We have found that no two indi- viduals of any species are ever quite alike. We know that these variations group themselves together so as to form subordinate races or varieties— species within species. We know that again and again these minor forms or subspecies have been mistaken for real species. We know that in thousands of cases to- day the good and the true species of one writer will be only varieties with another. We know that every year intermediate forms are found which break down the walls between species, so that the better any group is known the smaller becomes its list of species and the greater the range of variations. There is absolutely no test by which we can separate species from races or varieties. Our actual test is the test of ignorance. When we do not know any intervening forms we regard two given species as distinct. When we find intergrada- tions we unite these species. All naturalists have been forced to admit that species seem to be but varieties “of a larger growth,” while varieties seem to be incipient species. These facts had been noticed and had been admitted long before most naturalists were willing to believe that such appearances were anything but most deceitful. Professor Cope tells us of a concholo- gist who kept his species of shells from varying by crushing under his heel all specimens which in any way tended to depart from the proper type. It is only by such methods as this that different species can be kept distinct from each other. Let us take an illustration out of many that come to hand. Continued explorations bring to light from year species. 12 FOOT-NOTES TO EVOLUTION. to year new species of fishes in North American rivers; but the number of new forms now discovered each year is usually less than the number of old spe- cies which are yearly proved intenable. Four complete lists of the fresh-water fishes of the United States have been published by the present writer and his associates. That of 1876 enumerated 670 species; that of 1878 contained 665; the third, in 1885, only 587 species, although up- ward of 75 new species were detected in the nine years which elapsed between the first and the third list. The list of 1896, with 50 more additions, contains 599 spe- cies. Additional specimens from intervening localities are found to form connecting links among the nominal species, and thus several supposed species become in time merged in one, while not unfrequently the sup- posed minor variations are the marks of what we must finally regard as real species. Their reality consists simply in the extinction of the intervening forms. We have briefly reviewed the condition of this prob- lem and its answers before 1836, when Charles Darwin returned to England after the voyage of the Beagle. While in South America he had been greatly impressed by two phases of the question which came to his notice during his explorations there. The first of these was the fauna of the Galapagos Islands, a rocky cluster lying well out to sea some five hundred miles off the coast of Peru and Ecuador. The sea birds of these islands are essentially the same as those of the shores of Peru. So with most of the fishes. We can see how this might well be, for both sea birds and fishes can readily pass from the one region to the other. But the land birds, as well as the reptiles, insects, and plants, are mostly peculiar to the islands. The same species are found nowhere else; but The species of fishes of North America. The species of the Galapagos. THE KINSHIP OF LIFE. 13 other species, very much like them in all respects, are found, and these live along the coast of Peru. In the Galapagos Islands, according to Darwin’s notes, “ there are twenty-six land birds. Of these, twenty-one, or perhaps twenty-three, are ranked as distinct species and _ would commonly have been assumed to have been here created, yet the close affinity of most of these birds to American species is manifest in every character, in their habits, gestures, and tones of voice. So it is with the other animals and with a large proportion of the plants. _... The naturalist, looking at the inhabitants of these volcanic islands in the Pacific, feels that he is standing on American land.” The question, then, is this: If these species have been created as we find them on the Galapagos Islands, why is it that they should all be very similar in type to other animals living under wholly different conditions but on a coast not so very far away? And, again, why are the animals and plants of another cluster of volcanic islands—the Cape Verde Islands—similarly related to those of the neighbouring coast of Africa and wholly un- like those of the Galapagos? If the animals were cre- ated to match their conditions of life, then those of the Galapagos should be like those of Cape Verde, the two archipelagos being extremely alike in respect to soil, climate, and physical surroundings. If the species on the islands are products of separate acts of creation, what is there in the nearness of the coasts of Africa or Peru to influence the act of creation so as to cause the island species to be, as it were, echoes of those on . shore ? If, on the other hand, we should adopt the obvious conclusion that both of these clusters of islands have been at one time or another colonized by emigrants from the mainland, by the waifs of wind and storm, the fact of 14 FOOT-NOTES TO EVOLUTION. uniformity of type is accounted for. But what of the difference of species? If change of conditions may on the islands cause great and permanent changes in a spe- cies so as to transform it into a different Pear species, may not the same change take change with 1 h ; : i space? place elsewhere? May it not happen on the mainland as well as on the islands? And if on the mainland, what guarantee have we of the permanence of species anywhere? May they not be con- stantly changing ? May not what we consider as a distinct species be only the present phase in the changing history of the series of forms which constitutes the species ? The other phase of the problem which was presented to Darwin was that of the succession of fossil and re- cent mammalia, especially the edentates (ant-eaters, armadillos), etc., in South America. We find in the extinct species the same peculiarities of structure that we see in the forms still living. These peculiarities are not shown by animals either recent or fossil in other parts of the globe. If each of these species has been an independent creation, by what law should the re- cent forms duplicate the peculiarities of the extinct forms? Is the process of creation in some way influ- enced by the peculiarities of forms which have pre- ceded these in the same region and not by forms which live in other regions? The explanation is not to be found in the adjustment of species to their conditions of life, for under similar conditions in other regions, as in Australia, are found forms wholly IESEPEEIES different. But as edentate has suc- change with : - pets ceeded edentate in South America, so marsupial has succeeded marsupial in Australia. Is the explanation in both cases to be found in the supposition that the recent forms in both of these The species of South American edentates. Pe ee eer THE KINSHIP OF LIFE. 15 continents are modified descendants of extinct forms? But if this be so, what certainty have we that other creatures have not been similarly modified ? And may they not be still undergoing modification? Then why may not the origin of species be due to descent with modifications? ‘The difference in species would then be the result of the influences which make for change, and the unity would be due simply to the action of the law of the heredity. And this is the theory which Darwin finally reached. The unity would be accounted for easily enough, for by this view homology is the simple index of common he- redity. The fact of variation could be shown, but what could be the cause of variations so universal and on such a grand scale as we find them in Nature? If this law could be worked out, then the innumerable facts of homology and variation would have a meaning in- stead of being as before so many isolated curiosities of Nature. To the working out of this law he gave twenty-five years of his life, gathering information from every source accessible to man. To the famous botanist, Joseph D. Hooker, Darwin wrote in 1844: “ Besides a general interest about the southern lands, I have been now ever since my return engaged in a very pre- sumptuous work, and I know no one individual who would not say a very foolish one. I was so struck with the distribution of the Galapagos organ- isms and with the character of the American fossil mam- mifers that I determined to collect blindly every sort of fact which could bear in any way on what are species. I have read heaps of agricultural and horticultural books and have never ceased collecting facts. At last gleams of light have come, and I am almost convinced (quite contrary to the opinion I started with) that species are 3 Darwin’s answer. 16 FOOT-NOTES TO EVOLUTION. not (it is like confessing a murder) immutable. Heaven forfend me from Lamarck nonsense of a tendency to ‘progression,’ ‘adaptations from the slow willing of animals,’ etc. But the conclusions I am led to are not widely different from his, though the means of change are wholly so. I think I have found out (here’s pre- sumption!) the simple way by which species beccme exquisitely adapted to various ends.” In the preface to the Origin of Species, published in 1859, he outlined his plan of work in the following words: “When on board H. M. S. Beagle as naturalist, I was much struck with certain facts in the distribution of the organic beings inhabiting South America, and in the geological relations of the present to the past inhabitants of the continent. These facts seem to throw some light on the origin of species, that mystery of mysteries, as it has been called by one of our greatest philosophers. On my return home it occurred to me (in 1837) that something might perhaps be made out on this question by patiently accumulating and reflecting on all sorts of facts which could possibly have any bearing on it. After five years I allowed myself to speculate on the subject, and drew up some short notes. These I en- \arged in 1844 into a sketch of the conclusions which then seemed to me to be probable. From that period to the present day I have steadily pursued the same object. I hope that I may be excused for entering upon these personal details, as I give them to show that I have not been hasty in coming to a conclusion.” “Mother Nature,” says Huxley, “is singularly ob- durate to honeyed words. Only those who understand the ways of things, and can silently and effectively use them, get much good out of her.” Darwin’s method. THE KINSHIP OF LIFE. 17 Let me speak of certain traits of this work, the Ori- gin of Species, which give it a position almost alone among books of science. There is in it no statement of fact of any import- ance which, during the nearly forty years since it was first published, has been shown to be false. In its theoretical part there is no argument which has been shown to be unfair or fallacious. In these forty years no serious objection has been raised to any important conclusion of his which was not at the time fully anticipated and frankly met by him. Indeed, there are but few of these objections which with our present knowledge are not much less weighty than Dar- win then admitted. The progress of science has bridged over many chasms in the evidence. There is in this work nowhere a suggestion of special pleading or of overstatement. The writer is a judge and not an advocate, and from his decisions there has been no successful appeal. There is in this or any other of Darwin’s works scarcely a line of controversial writ- ing. He has been the faithful mirror of Nature. The relations of Nature to metaphysics he has left to others. The tornados which have blown about the Origin of Species are not his work. He felt, perhaps, that most systems of philosophy are like air plants which thrive equally well in any soil; with just facts enough for their roots to cling to, they may grow and bloom perennially, without other food than the air. The “Darwinian theory,” as resulting from these many years of gathering of facts, may be briefly stated as follows: The various species of ani- mals and plants now on the earth are the descendants of pre-existing forms which have in various ways undergone modification. The homologies existing among them are the result of The Origin of Species. The Darwinian theory. 18 FOOT-NOTES TO EVOLUTION. inheritance from their common ancestry. The differ- ences have come about through various natural influ- ences, chief among which is the competition in the struggle for existence between individuals and between species, whereby those best adapted to their surroundings live and reproduce their kind. Any advantage of the individual, no matter how small, must be a help in its life struggle. This advantage inherited becomes the gain of thespecies. The various influences connected with this struggle were summed up in the comprehensive term of “natural selection,” or, as Mr. Herbert Spencer has termed it, “the survival of the fittest.” The latter term is, however, only half as large as the former, because “ the survival of the existing” is in many regards a factor as potent as the actual survival of the fittest. To be onthe ground is a factor not less important in determining sur- vival than to have a special fitness for the conditions of life. The epithet “natural” in natural selection is also of vital importance as distinguished on the one hand from “ artificial,” or produced by human agency, and on the other hand from “supernatural,” or produced by un- knowable agencies. ‘“ Fitness” in this sense of course means simply the power to win in the particular kind of contest that may be in question, no moral element and no element of general progress being necessarily in- volved. The term “natural selection” originated from the use of the word “selection” by breeders of animals to indicate the process of “‘ weeding out”’ by which they improve their herds. For the method by which in Nature a new species is brought into existence seems to be precisely parallel to that by which we may arti- ficially produce a new breed of cows or of dogs, a new race of pigeons, or a new variety of roses. The record of man’s work in the creation of species covers some of the most glorious of human achievements, none the less won- ee THE KINSHIP OF LIFE. 19 derful because they have taken place before our very eyes. To know the laws of heredity and to select domes- tic animals and plants so to reach our ends in accord- ance with these laws is indeed a creation. Artificial selection, says Youatt, is the “‘ magician’s wand” by which the breeder can sum- mon up whatever animal form he will. One might, according to Somerville, chalk out on the wall the form of sheep he most desired, and then de- velop it by attention to selection of parentage. The processes of heredity would bring this about by laws as unvarying as that by which a stream is forced to turna mill. Professor Goodale tells us that were all our fruit trees destroyed and the species exterminated, they could all be won back again by the selective culture of wild pomes and berries. “Natural selection” is, however, an affirmative phrase for what is largely a negative process. ‘ Natural extinction,” or the destruction of the unfittest, would some- times express the same idea better. No more striking statement of the universality of the struggle for existence and of its power to compel some form of selection—natural, of course—has ever been made than that given by Darwin in the Origin of Species. From this I quote: “T use this term, struggle for existence, in a large and metaphorical sense, including dependence of one being on another, and including (which is more important) not only the life of the individual, but success in leaving progeny. Two canine animals, in atime of dearth, may be truly said to struggle with each other which shall get food and live. Buta plant on the edge of a desert is said to struggle for life against the drouth, though more Artificial selection. Natural selection. The struggle for existence. 20 FOOT-NOTES TO EVOLUTION. properly it should be said to be dependent upon the moisture. A plant which annually produces a thousand seeds, of which only one on an average comes to matur- ity, may be more truly said to struggle with the plants of the same and other kinds which already clothe the ground. The mistletoe is dependent on the apple and a few other trees, but it can only in a far-fetched sense be said to struggle with these trees for if too many of these parasites grow on the same tree it languishes and dies. But several seedling mistletoes growing close together on the same branch may more truly be said to struggle with each other. As the mistletoe is dissemi- nated by birds, its existence depends upon them; and it may metaphorically be said to struggle with other fruit- bearing plants in tempting the birds to devour and thus disseminate its seeds. In these several senses, which pass into each other, I use for convenience’ sake the general term of ‘ struggle for existence.’ ” Darwin says that there is nothing which people are more willing to concede than the struggle for existence, and yet nothing can be more inadequate than the ordi- nary conception of it. He further says: “A struggle for existence inevitably follows from the high rate at which all organic beings tend to increase. Every being, which during its natural lifetime produces several eggs or seeds, must suffer destruction during some period of its life, and during some season or occa- sional year; otherwise, on the principle of geometric increase, the numbers would quickly become so inordi- nately great that no country could support the product.” It is one of the axioms of mathematics that any geo- metrical progression will in time outrun any arithmetical one. Multiplication outruns addition. ““Hence . .. there must in every case be a struggle for existence, either one individual with another of the THE KINSHIP OF LIFE. 21 _ same species, or with the 11 dividuals of distinct species, or with the physical conditions of life. It is the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms; for in this case there can be no artificial increase of food, and no pru- dential restraint from marriage. Although some species may be now increasing, more or less rapidly, in numbers, all can not do so, for the world would not hold them. There is no exception to the rule that every organic being naturally increases at so high a rate that if not destroyed the earth would soon be covered with the progeny of asingle pair. Even slow-breeding man has doubled in twenty-five years, and, at this rate, in less than a thousand years there would literally not be stand- ing room for his progeny. . . . The elephant is reckoned the slowest breeder of all known animals, and I have taken some pains to estimate its probable minimum rate of increase; it will be safest to assume that it begins breeding when thirty years old, and goes on breeding until ninety years old, bringing forth six young in the interval, and surviving till one hundred years old; if this be so, after a period of from seven hundred and forty to eight hundred and forty years there would be nearly nineteen million elephants alive, descended from the first pair.” Darwin continues: “I have found that the visits of bees are necessary for the fertilization of some kinds of clover; for instance, twenty heads of white clover (Zvifoltum repens) yielded two thousand two hundred and ninety seeds, but twenty other heads protected from bees pro- duced not one. Again, one hundred heads of red clover (Trifolium pratense) produced two thousand seven hun- dred seeds, but the same number of protected heads pro- duced not a single seed. Humble-bees alone visit red clo- Relation of bees to clover. 22 FOOT-NOTES TO EVOLUTION. ver, as other bees can not reach the nectar. .. . Hence we may infer as highly probable that, if the whole genus of humble-bees became extinct or very rare in England, the heartease and red clover would become very rare or wholly disappear. The number of humble-bees in any district depends in a great measure on the number of field mice, which destroy their combs and nests; and Col. Newman, who has long attended to the habits of humble-bees, believes that more than two thirds of them are thus destroyed all over England. Now the number of mice is largely dependent, as every one knows, on the number of cats; and Col. Newman says, ‘ Near villages and small towns I have found the nests of humble-bees more numerous than elsewhere, which I attribute to the num- ber of cats that destroy the mice.’ Hence it is quite credible that the presence of feline animals in large numbers in a district might determine, through the in- tervention first of mice and then of bees, the frequency of certain flowers in that district.” Huxley carries this calculation still further by show- ing that the number of cats is dependent on the number of unmarried women. On the other hand, clover produces beef, and beef strength. Thus in a degree the prowess of England is related to the number of spinsters in its rural districts. This statement would be true in all seriousness were it not that so many other ele- ments come into the calculation. -But whether true or not, it illustrates the way in which causes and effects in biology become intertangled. The calculation has been lately made by Prof. Rufus L. Green that at the normal rate of increase from a pair of English sparrows, if none were to die except of old age, it would take but twenty years to give one sparrow to every square inch in the State of Indiana. But such Relation of cats to England’s greatness. THE KINSHIP OF LIFE: 23 increase is actually impossible; for more than a hundred other species of similar birds are disputing the same ter- ritory, and there can not be place or food for all. With such conditions, the struggle for exist- ence between sparrow and sparrow, and between sparrows and other birds, grows yearly more severe. Each year now the sparrow gains a little and other birds lose correspondingly, but sooner or later with each species a point will be reached when the loss exactly balances the increase. This produces a condition of apparent equiliibrum—the equilibrium of Nature; a sort of armed neutrality which a superficial observer mistakes for real peace and permanence. But this equilibrium is broken as soon as any individual or group of individuals appears that can do something more than merely hold its own ina struggle for existence. It is thus evident that throughout all Nature the number of organisms born into life is far in excess of the number of those which can come to maturity. In every species the majority never reach their full growth, and this is because, for one reason or another, they can not do so. All live who can. Nature asks each organism, Why should you live? And those who can not give an answer pass away. “So careful of the type she seems; so careless of the single life.” It is also evident, to use the language of Professor Bergen,. that “the killing will not be indiscriminate, but it will first and mainly comprise those individuals which are least able to resist the attack.” It is this “ weeding- out” process in Nature, this “natural selection,” which in Darwin’s view constitutes the essential cause of change and progress. Of the many possible illustra- tions of the action of “natural selection,” one may serve our purpose at present. The equilibrium of Nature. More organisms born than can mature. 24 FOOT-NOTES TO EVOLUTION. In the eastern United States there are two native species of hare or wild rabbit. These are the gray rabbit or “cotton-tail” (Zepus sylvaticus) of the region south of Pennsylvania, and the white rabbit (Zepus americanus) of the woodlands of the North. The southern hare is smaller than the other; it is much less shy, and its winter dress is not very different from its summer dress, the fur which comes in after the autumn shedding being of the same grayish colour. The northern hare is in summer not very different in colour from the other, but when it renews its fur in the fall its winter coat is pure snow- white. There are some other distinctions between the two species, but we need notice simply the difference in colour as showing the principle of “natural selection.” We may presume the two species to have had one com- mon origin, probably in a form not very different from the gray rabbit as we know it. In every dozen rabbits which we may examine we shall find a considerable variation in shade of colour. Some will be darker than the average, some grayer, some browner, and others evidently paler. We shall find also differences in size and proportions, besides other differences, but for the present we need only consider the matter of colour. In the South, where the ground is mostly free from snow, even in winter, whiteness would be of no sort of advantage to a rabbit. The nearer the animal is in colour to the dead grass and dried leaves about him, the better are its chances of escaping detection, the greater the likelihood that it may elude its enemies and live out its days, leaving descendauts to inherit its peculiarities. Not so with the northern species. The nearer it is in winter to the colour of the snow, the less likely it is to fall a prey to carnivorous animals or birds. And so for ages in the northern winter the action of competition in How the hare becomes white. THE KINSHIP OF LIFE. 25 Nature, of “natural selection,’ has saved the whiter rabbits and condemned the darker ones to destruction. In the summer these conditions are changed; those in- dividuals who retain the ancestral gray are then the ones best fitted to live. And so after many centuries, as we may conceive, there has come about a gradual change in the fur of our hares, until now in the northern species the fur is white in winter, while all are alike gray or brown in the summer. Precisely similar is the change in the plumage of the arctic partridge, or ptarmigan, as well as in the various other northern birds. But this is not all. A change in colour such as enables the hare or the ptarmigan to evade its pursuers would also aid these pursuers to steal un- aware on their prey. Nature has no preferences, and helps alike victim and victor. And so it comes about that predatory weasels and owls in winter assume a snow-white garb, and that this is laid aside in the sum- mer. It is doubtless true that other influences co-oper- ate in producing these changes in colour. White fur is warmest in cold weather, for it radiates less heat. We may say that all these animals are dressed in white in winter to keep them warm. But this again would be sim- ply a phase of “natural selection.” If the animals suffer from cold, the dark: ones will be chilled first. Thus in more ways than one the white animal has the advantage of the other in the winter. This advantage enables it to outlive the other. It causes its descendants to outlive and eventually to displace those of its darker rival. To such causés as these we must ascribe the nice adjustment of each species to its surroundings. Ifa species or a group of individuals can not adapt them- selves to their environment, they will be crowded out by others who can do so. The former will disappear en- tirely from the earth, or else they will be limited to 26 FOOT-NOTES TO EVOLUTION. surroundings in which they come into perfect adjust- ment. A partial adjustment must with time become a complete one, for the individuals not adapted will be exterminated in the struggle for life. Everywhere in Nature there is the closest adap- tation of life to its conditions. But this adaptation must come about through the survival of those organisms fittest to live under these conditions, while the unfit die out and leave no progeny. Thus, in the words of Professor Bergen, “ with much the same result as that which the farmer obtains by selecting his seed corn, the gardener by thinning out his beds, or the cattle-raiser by selling off his roughest calves for veal, Nature is at work on an inconceivably great scale, thin- ning out the least perfect individuals of each species.” But the thinning-out process is not the whole of “natural selection.” Other influences work in connec- tion with this. In the higher animals changes may be wrought by conscious or unconscious effort on the part of the creatures themselves, and the power to put forth such effort may be perpetuated by “natural selection.” Cer- tain organisms may carry their growth farther than their ancestors have done, so that the completed structures of their ancestors would be with them only a stage of development. And, as Professor Cope has shown, devel- opment may be hastened by the abridgment or omis- sion of useless stages. Thus the ultimate maturity of the animal may be carried to a degree of specialization beyond that of its ancestry. If this “accelerated de- velopment” be for the gain of the species, “ natural selection ’’ will cause it to be retained. We may prop- erly include under “ natural selection” all those changes which come from the special use or disuse of any part How selection becomes adap- tation. Acceleration of development. ———s THE KINSHIP OF LIFE. 27 of the structure. For “natural selection” must, in a way, be operative among the organs of the body. “Die Kampf der Theile,” as it has been called by a German writer (“the battle of the parts’’), is a real struggle in which fitness determines survival. It is not merely the simple structures and the com- mon instincts which may be developed and fixed by natural selection. The differentiation of the sexes is a result of the demand for greater variation. It is the fact of bisexual parentage that makes of each individual not simply an “elongation or continu- ance of the parent,” but a new life which shall be the resultant of the lives and experiences of its ancestors, a mosaic of the char- acters of its parents and its parents’ parentage. By the fact of sex no individual can be the mere slavish copy of any other. Through the operation of sex the law of heredity which is to promote sameness is made sub- servient to the equal need of the promotion of variety. This idea of the formation of the mosaic of per- sonal character is the motive of Goethe’s “Vom Vaterhab’ famous poem, Vom Vater hab’ ich die ich die Statur.” Beatar © How bisexual parentage brings variety. * “Vom Vater hab’ ich die Statur, Des Lebens ernstes Fuhren ; Vom Mutterchen die Frohnatur Und Lust zu fabuliren. Urahnherr war der schonsten Hold, Das spukt so hin und wieder. Urahnfrau liebte Schmuck und Gold, Das zuckt wohl durch die Glieder. Sind nun die Elemente nicht An dem Complex zu trennen ; Was ist denn an dem ganzen Wicht Original zu nennen?”—GOETHE, Zahme Xenien, vi, 28 FOOT-NOTES TO EVOLUTION. Again, the fact of death has been shown by Weis- mann to be a simple necessity of the law of natural se- lection. Creatures of one cell are in a sense biological units; they may be killed but they do not die a natural death. They are wholly alive or else wholly dead: never dying. They multiply by self-division, and this process is supposably eternal, for natural death is known only among many-celled or colonial organisms. It is a ne- cessity arising from complexity of organization. Com- plication and specialization of structure as we know it in man and the other many-celled creatures is bought at the cost of mortality. These cells grouped in tis- sues and organs in one part or another must suffer in the struggle for existence. Every compound animal is in some part dead or dying. The old and mutilated organisms cumber the way of the young and fresh ones, and by the law of selection it comes about that for these to die of old age is useful to the species. Those spe- cies in which old age brings decay and in which the in- dividuals perish naturally when they cease to be self-de- pendent are then preserved in the struggle for existence. It is common in these days to speak of altruism as a means of doing away with the struggle for existence among men. But altruism itself is only a higher or more advanced result of the same struggle. Those who band to- gether win, be they wolves or men, and natural selection favours those qualities which make for mutual advantage. To band together against enemies or for protection from the elements is a most effective way in which the struggle for existence may be carried on. The law of love is not an abrogation of the law of struggle. It represents a better way to fight. The con- quests of science are simply the first results of co-opera- The value of death. Altruism and the struggle for existence. —-- a a THE KINSHIP OF LIFE. 29 tion. If we “put our heads together” we may know or do everything. If we stand apart we can do nothing, and in the struggle for existence those who can stand shoulder to shoulder loyally have the promise of the future. Those who can not hold together find every man’s hand raised against them. This principle holds good whether applied to the directors of a hospital or to a band of wolves. Whatever form the struggle for existence may take, it is a permanent factor in all operations of life. Each creature must take part in a threefold struggle—with like forms of life, with unlike forms of life or creatures unlike itself, and with the conditions of life themselves. Each man must, whether he will or not, compete with his neighbours, must compete with other creatures, and must be judged by the conditions of food, climate, and environment under which life exists. Sometimes one element will determine, sometimes another. In the city one competes with his neighbours, in the jungle with the beasts, and in the arctic with the elements of cold and storm. Ina similar way each animal has to justify its existence. Co-operation may modify and dignify the struggle for existence among men, but it can not set it aside. It may change its point of incidence, but it can not reduce its stress. Were it not for this struggle, which calls out from each generation its best and strongest for life purposes, there could be no progress in life. With- out competition there could be no adaptation, without selection there would not be a creature on earth to-day higher than a toadstool! It was a favourite saying of Agassiz that “ Facts are stupid things until brought into connection with some general law.” The law of descent, with change through “natural selection,” brings into organic connection a host of facts hitherto isolated. Each one considered by 30 FOOT-NOTES TO EVOLUTION. itself would be without meaning or explanation. The essential argument in favour of ‘“ Darwinism” is that it brings all biological facts into unison from whatever field of investigation these facts may be derived. How- ever much evolutionists have at times seemed to drift away from Darwin’s con- clusions, it is always the most accurate research and the sanest thought which come nearest the opinions set forth in the Origin of Species. The body of facts has grown enormously year by year, but the conclusions we must accept are substantially those laid down by Darwin himself. The facts of “ geographical distribution,” for exam- ple, have a meaning to us when we view them as the results of centuries of the restlessness of individuals. Each species of animal or plant has been subjected to the vari- ous influences implied in the term “natural selection,” and under varying conditions its representatives have undergone many different modifications. Each species may be conceived as making each year inroads on terri- tory occupied by other species. If these colonies are able to hold their own in the struggle for possession they will multiply in the new conditions and the range of the species becomes widened. If the surroundings are different, new species or varieties may be formed with time, and these new forms may again invade the territory of the parent species. Again, colony after colony of species after species may be destroyed by other species or by uncongenial surroundings. Only in the most general way can the history of any species be traced; but, could we know it all, it would be as long and eventful a story as the history of the colonization and settlement of North America by immi- grants from Europe. Each region where animals or Every fact has a meaning. Geographical distribution. THE KINSHIP OF LIFE. 31 plants can live has been thousands of times discovered, its colonization a thousand times attempted. In these efforts there is no co-operation. Every individual is for himself, every struggle a struggle for life and death. To each species each member of every other species is an alien and a savage. The study of geographical distribution shows the re- lations of creative processes to space. The forms in- habiting one district arethe children of the earlier inhabitants. The survival of these forms is due to. that which I have elsewhere called the “survival of the existing,” for it is certain that in any part of the world a totally dif- ferent grouping of animals or plants would have been equally fitted to the environment. The laws of geo- graphical distribution may be summed up thus: The reason why any given species of animal or plant is not found in a given district is (2) because it could not get there from its own habitat, or (4), being there, it could not maintain itself either in competition with others or from the stress of environment, or else (c) it has in maintaining itself become altered into a distinct species. In like manner the facts of geological distribution have a meaning when we view them in the light of the theory of descent. The birth, increase, decline, and final change or disappear- ance of species or types in geological history are necessary parts of the Darwinian theory. They would be inexplicable on any other hypothesis. These changes represent the survival of the fittest as related to time. With the lapse of time come changes in environment, and these changes produce correspond- ing changes in animal or plant life. But these changes on the earth and in its life are for the most part gradual 4 Survival of the existing. Geological dis- tribution. 32 FOOT-NOTES TO EVOLUTION. ones. The evolution of the earth and its life has rarely been subject to great leaps and catastrophes. Yet epoch-making events have taken place on the earth. Such changes in life, as the acquisition of lungs, of wings, of speech, are marked by the increased rapidity of the pro- cesses of evolution. Professor Bergen says: “ Until an evolutionary rise of species had been assigned as an explanation of the succession of higher and higher animals and plants throughout the geological ages, what adequate reason for this progress of life could be given? Strike out from our present conception of the organic world, class after class, all notion of actual relationship by descent, and what have we left but a mighty host of extinct creatures whose rise, progress, and disappearance are far more unaccountable than that of the genii in the Arabian Nights?” But not all change has been progress. The idea of some of the earlier evolutionists that the advance of life has been the simple result of an in- nate “uniform tendency toward pro- gression’’ can not be maintained. For progress, while general, is by no means uniform or uni- versal. Progress ceases when its direct cause ceases. In every group there are some members characterized by degeneration and loss of specialization. This is in- volved in the theory of “natural selection.” If prog- ress comes through competition, lack of competition would imply retrogression. When animals or plants are withdrawn from the stress of life to some protected con- dition, the character of the type is lowered. ‘There is less need for specialization when the range of wants is narrowed. Hence it is that all parasitic animals or plants—lice, leeches, dodders, mistletoe, Indian pipe—are Epoch making events. Change not progress. THE KINSHIP OF LIFE. 36 degenerate forms. So it is with cave animals, as well as with most organisms of the deep sea or the far North. All forms which are withdrawn from open competition to a solitary and secluded life lose one by one the ad- vantages which competition has gained for them, and are known as degenerate types. What is true of the lower animals is likewise true of man. The highest type of manhood, of human powers and human virtues, will come from victory in the struggle for existence and not from withdrawal from the struggle. Easy living always brings degeneration. The sheltered life is the source of weakness. The desire to get something for nothing is the bane of human society. Parallel with the case of general degeneration of type is that of the degeneration of individual parts of the organism. An organ well developed in one group of animals or plants may in some other be reduced to an imperfect organ or rudi- ment so small or incomplete as not to perform its nor- mal function, or, indeed, to serve any purpose whatever. Such rudimentary or functionless structures may be found in the body of any of the higher animals and in most or all of the higher plants. The appendix vermi- formis and the unused muscles of the ears in man are examples. Such are also the atrophied lung, pelvis, and limbs of the snake, the “thumb” of the bird, the splint bone of the horse, and the like, without mentioning less familiar internal organs. By the theory of descent we may understand how much structures may be retained by the action of the law of heredity, while their reduc- tion may be the result of long-continued disuse, or the growth and selection of other organs at the expense of these which are no longer needed. Among a multitude of examples I need refer espe- cially to but one—a recent discovery in homology. Vestigial organs. 34 FOOT-NOTES TO EVOLUTION. Within the brain of man, resting on the optic lobes, is a little roundish structure scarcely larger than a pea, known as the pineal “ gland” or “ conari- The pineal eye. 0 : um. It has no evident purpose or function, and a_ philosopher p once suggested that it might be the seat of the soul. It is larger in the embryo, and Sea still larger in the brains of yo, 1—Pineal body in the liz- some of the lower vertebrates. | ard_ (Hatteria) developed as Recent investigations have dg aye eet) as shown that it is especially de- veloped in certain lizards, and that in them it ends ina more or less perfect eye, which is placed between the others in the centre of the forehead. These lizards have in fact three eyes, and the pi- neal body is the optic nerveofthethird. In the common horned toad the pearl - like scale above the pineal eye can be readily rec- ognised. The shrunk- SASS SS SS ig ik f en rudiment found in SX k SS « man is therefore what is left of an ancestral third eye, probably once characteristic of vertebrates, but now displaced and de- stroyed by the increased development and greater per- fection of the outer pair. By the theory of descent the presence of the pineal body in man is a simple result Fic. 2.—Pineal eye of the lizard (Hatteria). After Spencer. Le THE KINSHIP OF LIFE. 35 of heredity. If, however, man possessed no “ blood re- lationship ” to three-eyed vertebrates, the existence of Fic. 3.—Head of the lizard, or ‘“‘horned toad” (Phrynosoma blain- dillei), showing the translucent pearly scale covering the pineal eye. From Nature, by W. S. Atkinson. the pineal body in the human brain would be wholly inexplicable. It has been difficult to explain, on the theory of de- scent, how complex organs like the eyes and ears of the higher animals could develop from small beginnings. To embryology we must look for explanation. Embryology tells us that these organs do not in the individual reach per- fection “all at once.’’ In every case the embryonic his- tory of a highly specialized organ shows a succession of Origin of com- plex structures. 36 FOOT-NOTES TO EVOLUTION. stages of incompleteness before the organ is finished. Each of these stages finds a more or less perfect repre- sentation in the adult condition of some animal of less complexity. The long-continued “ survival of the fittest ” brings these organs to a greater and greater perfection. But by the side of these creatures with the most complex organs will be found those in which the development of some particular part may be less and less complete. An organ highly developed in one animal may be quite rudimentary and imperfect in some other animal whose superior fitness may be in some other direction. Thus fitness for underground life relieves the mole from the need of good eyes. Skill to live by his wits relieves man from the need of the monkey’s power to climb trees. Somewhere in the animal kingdom we may find each degree of each organ’s development. These or- gans in their varying degrees of complexity corre- spond more or less perfectly to the several stages of development of the same organ in the individual of the highest type. The record of the devel- opment of the individual is in a way the recapitulation of the past history of its species. ‘“ The physical life of the individual is an epitome of the history of the group to which it belongs.”” Thus the embryonic life of man ‘corresponds, so far as we can trace it, to the history of that branch of the group of vertebrates which has cul- minated in man. Each individual lives over again the life of the race. ‘Under each grave lies a world his- tory,” * says a German proverb. This fact is, however, no mysterious or meaningless law. It is simply a natural result of the processes of heredity. Heredity repeats that which has been, and natural selection suppresses The individual repeats the his- tory of the race. * ““Unter jedem Grab liegt eine Weltgeschichte,” , K : THE KINSHIP OF LIFE. 27 that which is injurious. The process of development of any individual is that of its ancestors with the harm- ful stages abbreviated or suppressed. The young frog has the ancestral gill of the fish and so has the human child in embryo. ‘This stage is useful to the frog; it is not harmful to the unborn child. It is thus retained by heredity, but its retention is always governed by its pos- sible harmfulness. It is not an easy task to put in a few words and popu- lar language even a hint of the wealth of evidence which embryology brings to the support of the theory of evolution. This evidence was in Mr. Darwin’s mind the most convinc- ing of all evidence, its force being even stronger than that derived from his own studies in geographical and geological distribution. In this connection the follow- ing paragraphs have been contributed by Dr. John Ster- ling Kingsley : “To appreciate the weight and extent of embryo- logical evidence, one needs the special training of the biological laboratory, for it is only by watching the won- derful changes which every egg goes through in its de- velopment that one can begin to realize the importance of the facts. The training of the metaphysician is here of no value, for it is not of the slightest avail in weigh- ing the evidence. “ To state this evidence briefly, we may state that the history of every developing egg and embryo is utterly incapable of explanation from any other standpoint than that of evolution. Why should the young verte- brate have kidneys like those of worms? Why does man have muscles to move the ears? Why do young spiders develop legs which will utterly disappear in the adult? Why does the nervous system communicate with the alimentary canal in the young frog or bird? Embryology and evolution. 38 .FOOT-NOTES TO EVOLUTION. All of these questions, and thousands more which will suggest themselves at once to every student of embry- ology, are problems which receive no adequate explana- tion on the supposition of special creations. With the theory of evolution as a basis, the answers are easy. They are inheritances from ancestral conditions. In the terms of evolution they remain because the history of the individual is a more or less detailed recapitula- tion of the history of the race. “The truth of this assumption is easily tested. The conclusions of embryology must be in full accord with those of geology, or one or the other must be wrong. In the rocks we have an indisputable record of the suc- cession of the forms of life, and the conclusions of em- bryology must point to a similar succession. “While neither our limits nor the character of the present article will allow anything like a discussion of the embryological evidence in support of evolution, a few examples will serve to indicate its character. “In the development of all eggs the earlier stages are essentially alike, or easily reducible to a common type. It is only in the later stages that the variations occur that are to convert one egg into a fish, another into a chicken, There ‘are;.i1t-is) true.minos differences from the start, but these are largely to be explained on mechanical grounds. An egg differs from the other cells in the tissues of the parent chiefly in its Capacity to reproduce the species. It divides again and again, and the resulting cells build anew the parent form, but in the character of this division or ‘ segmenta- tion’ many variations are recognised. In some the eggs are small and composed entirely of protoplasm, and here the segmentation is regular, but other eggs are larger, and this increase in size is due to the addition of Similarity of early stages in embryonic life. THE KINSHIP OF LIFE. 39 a larger amount of ‘food yolk’ stored up to supply the wants of the growing embryo till the time comes when it shall be able to shift for itself. Protoplasm is active, ‘food yolk’ passive, and the relative amounts of these two and the positions which they occupy in the egg affect, in a purely mechanical manner, the segmentation, and interfere with or destroy its typical regularity. In the egg of the common hen this ‘food yolk’ forms almost the whole of the yolk, the really important pro- toplasm occurring only in the lighter yellow spot, which is always uppermost in the egg. Taking it for granted that this amount of food yolk influences the character of the early stages of development (a point easily proved by the embryologists), let us consider a special case in which conclusions drawn from development have re- ceived later confirmation from other sources. “In the mammals the eggs are very small and con- sist of pure protoplasm, food yolk being entirely absent. Indeed, nourished by the mother, as the young of most of these forms are, no store of food yolk is necessary. Hence, on a priori grounds, one would say that the segmenta- tion of the mammalian egg would be regular in its char- acter. When, however, naturalists came to study the development of the mammalian egg, it was found that in its early stages it presented (in eggs without food yolk) some astonishing peculiarities. How to explain these peculiarities was a problem. If, however, it were assumed that the mammals have descended from forms with larger eggs, and that in the course of evolution they have lost the yolk but had retained the tendencies of development, the explanation were easy. This ex- planation, however, seemed very improbable, for it had been held, on grounds of structure, that the mammals must have descended from the batrachia, a group con- The egg of the mammal. 40 FOOT-NOTES TO EVOLUTION. taining the frogs and salamanders, in which the eggs are not large enough to serve the conditions of the problem. So the matter was allowed to rest until new evidence should be found. It came in 1864. In that year Pro- fessor Cope found the remains of certain reptiles in the rocks of Texas which he, not being aware of the em- bryological problem, stated must be regarded as the ancestors of both birds and mammals. His evidence was solely derived from the bony structure. As all reptiles have eggs in which there is a large amount of food yolk, this discovery answered all the requirements of the problem. Both embryology and geology were in full accord. But the end was not yet. In the same year, and a few weeks later, Caldwell and Haacke dis- covered that two of the species of monotremes, those wonderful bird-like mammals for which Australia is noted—the duckbill and the spiny ant-eater—do not nourish their embryos like other mammals, but that they, like birds, lay eggs. It was found, further, that these eggs are large; they contain a large amount of food yolk, and they develop at first in the same way as the eggs of reptiles. Here was additional confirmation of the embryological conclusions. ‘There are many other features in the development of the mammals which are equally wonderful and con- clusive of the truth of the theory of evolution. According to the geological record, man must be descended from mammals with tails. We find that in the early stages of the embryo of man there is a time when there exists a regular tail supported by eight dis- tinct bones, like the tail bones of any other mammal. With growth, however, these bones unite and all disap- pear except three, which, joined in one, persist in the adult, On the theory of evolution this tail is easily ex- Embryonic structures in man. THE. KINSHIP OF LIFE. 4! plained; special creation can not account for it. Going still further back in the history of the development of the mammals, the record shows that both these and the reptiles must have arisen from fish-like forms which breathed water by means of gills. To this embryology offers ample support. In the embryos of reptiles, birds, and mammals, soon after the heart is formed, there appear on the sides of the neck openings which in both origin and structure re- semble the gill arches of fishes, and through these gills the blood flows exactly as it does in the fish. Later the gill arches close up, the blood takes other courses, and of all the complicated apparatus which persists through- out life in the fish there remain only a few obscure traces in the adult reptile, bird, or mammal.” This fact must show that the higher mammals have had a water-breathing, fish-like ancestry. Only the force of heredity can explain the existence and retention of these structures. On any other supposition an explana- tion is inconceivable. Dr. Kingsley further says: “ These examples are but a tithe of the evidence; thousands of pages might be written detailing similar facts not only in connection with the embryology of the vertebrates but of all groups of animals and plants. Every case would lead us to the same conclusions, but except for the special student of biology they would have but little interest. Each in- stance would be inexplicable except upon an evolu- tionary basis, but, if one adopt the hypothesis that the history of the individual is an epitome of that of the race, all is at once as clear as day. Special creation is utterly inadequate to explain embryological problems ; evolution leaves no room for doubt or question.” The difficulties and objections to the theory of de- scent will be found in the Origin of Species, stated by Gill slits in man. 42 FOOT-NOTES TO EVOLUTION. Darwin himself with a fullness, fairness, and clearness which none of his opponents has been able to reach. Increasing knowledge has steadily di- minished the apparent value of these objections. None of them can now be regarded as of any serious importance. Our chief questions as to the origin of species relate to the relative importance of the various elements which enter into “natural selection,” to a better definition of the laws of variation, and especially to the existence of a possible unknown factor in evolution which causes the transmission of the results of the efforts and experiences of the individual. Just now evolutionists are nearly equally divided on this great question, on which even their conventional beliefs have been lately rudely shaken. Relation of pres- Are acquired characters ever inherited, ent heredity to and, if so, under what conditions and past environ- ee We: , aan limitations? Is the experience of the parent part of the heritage of the child? Does the environment of the father enter into the hered- ity of the son? Are the reactions which follow the various external conditions restricted to the individual alone, and is the next generation untouched by its par- ents’ successes or failures, as though it were a new creation ? To ask these questions is not to answer them, and and the final solution of the relation of present heredity to past environment will be the work of the student of the twentieth century. Darwin’s work was addressed at first only to natural- ists, with no expectation that the public would pay any attention to it. He had confidence that the younger and more observant of his fellow workers would find in their own work confirma- Objections to the theory of descent. Darwin’s hope. THE KINSHIP OF LIFE. 43 tion of his conclusions. The times were riper than he had realized. He has outlived nearly all his scientific opponents, the greatest and perhaps the last of whom was Agassiz. To-day there is not one whose scien- tific studies have been such as to give him a right to speak, whose views are not in substantial accord with those of the Origin of Species. Darwin’s work has destroyed forever the closet-formed idea of a “spe- cies” in biology as something fundamentally different from a variety or a race. Let me take an illustration. Camille Dareste, writing of the hundred or more alleged species of the true eel (Anguilla), says: “There are at least four distinct types, resulting from the combination of a certain number of characters ; but the study of a very large number of specimens be- longing to these four specific types has convinced me that each of these characters may vary independently, and that, consequently, certain individuals exhibit a com- bination of characters belonging to two distinct types. It is therefore possible to establish clearly defined bar- riers separating these two types. The genus Anguilla exhibits, then, a phenomenon which is found in many other genera, and even in the genus Homo itself, and which can be explained in only two ways: Either these four forms have had a common origin and are races merely, and not species; or else they are distinct in origin and are true species, but have been more or less commingled, and have produced by their mingling inter- mediate forms, which co-exist with those which are primitive. Science is not in the position to decide be- tween these two alternatives.” It is on idle problems like this as to the reality of species that the strength of the naturalists of the past The species of eel. 44 FOOT-NOTES TO EVOLUTION. century has been largely wasted. Which of the forms we study are species, and therefore represent separate acts of the Creator, and which are mere varieties, chance products of varying surroundings, and therefore to be despised and ignored? Scarcely ever did two earnest students of any group reach an agreement as to this question, for agreement is only possible when material is lacking. A single additional specimen often unsettles every conclu- sion, and the contents of all the museums are but the slightest fragment of the life of the globe. “We can only predicate and define species at all,” says Dr. Coues, ‘from the mere circumstance of missing links. Our species are twigs of a tree separated from the parent stem. We name and arrange them arbitrarily in default of means of reconstructing the whole tree in accordance with Nature’s ramifications.” Among Dareste’s eels we may have one species, or four, or forty, as our collection may be deficient in connecting forms, or as we may choose to magnify or disregard slight differences. There are just as many kinds of eels as there are races of men or of dogs. Future naturalists will again describe those eels; but they will know them for what they are—the varying descendants of some one degenerated type of fishes, crawling in the weeds and ooze of many seas and rivers, and thus variously modified by their sur- roundings. Meanwhile the old notion of a species has passed away forever. We can no more return to it than as- tronomers can return to the Ptolemaic notion of the solar system. The same lesson comes up from every hand. It is the common experience of all students of species. I do not know of a single naturalist in the world who has made a thoughtful study of the relations The reality of species. The old idea of species has passed away. SE Se THE KINSHIP OF LIFE. 45 of species in any group who entertains the old notion as to their distinct origin. There is not one who could hold this view and look an animal in the face! And for this change we have to thank Darwin, “It is easy to plough where the field is cleared,” and what he first of all saw clearly we can not fail to see now. The fact is that every student of species and of the facts of geographical distribution has reached, willingly or unwillingly, the conclusion that species are not im- mutable; that those differences by which he tried to discriminate the groups of organisms which he calls spe- cies were not differences originating in the act of crea- tion, but produced in some way by outside influences or by the organism’s reaction in adjustment to these in- fluences. One might safely pledge himself to convert to some phase of the development theory any honest and intelligent man who would spend a month in a care- ful study of a large collection of specimens in any group in which the existing species are found over wide areas on the surface of the earth. The study of squirrels, eels, catfishes, pine trees, asters, butterflies, clams, snails, horses, or men—any of these will serve to accomplish this purpose. The general acceptance of the Darwinian theory by naturalists is not due exclusively to the Origin of Spe- cies or to any of the numerous com- mentaries and expositions which have come from other hands. It arises from the results of the studies themselves. No authority has compelled it, for Darwin’s influence was not, like that of Cuvier or of Agassiz, the force of an overmastering personality. He was rather the voice of Nature. His word was the impersonal word of Nature herself. To see truthfully is to see with Darwin’s eyes. The idea of development gives the only clew by which The acceptance of the theory of descent. 46 FOOT-NOTES TO EVOLUTION. the naturalist can be guided in his work. If the affini- . ties of species are not related to the law of heredity they are unintelligible. If the variation of species is really immutability in disguise we can not trust our senses. It is said, I know not on what authority, that the distinguished ichthyologist, Albert Giinther, was converted to Darwinism by the study of the British sal- mon. Whether this is true or not, such a study could have no other effect. I was brought to the same be- liefs through a study of the minnows and darters of the Mississippi Valley. In the study of species one must choose between some form of development theory on the one hand and a hopeless, unscientific, impossible ignorance on the other; and in all forms of biological investigation, comparative anatomy, morphology, em- bryology, histology, we reach the same choice of alter- natives. The theory of descent by “natural selection” has become in the hands of Herbert Spencer a part of a general philosophy of evolution, a con- ception much older in time than the theory of Darwinism. Manifestly we could not imagine a homogeneous universe or a homo- geneous earth which could perpetually retain a homo- geneous condition. A cooling earth must lose its per- fect rotundity, its surface must become diversified, and its relation to the sun must cause its equatorial portion to become different from its poles. A single homogene- ous form of life could not remain single and uniform, because life must respond to the conditions of its envi- ronment. Any organism under a tropical sun is not what it would be, exposed to arctic cold. Diversity once begun, and a rate of increase more rapid than a limited earth could permit unchecked, the natural competition in the struggle for existence accounts for the rest. The philosophy of evolution. THE KINSHIP OF LIFE. 47 The theory of evolution, in brief, is this: There ex- ists in all things a tendency to become specialized and differentiated. In accordance with this tendency nebu- lous masses have been concentrated into planets and the generalized creatures of early time have been special- ized into distinct forms. The formula of the process of evolution as stated by Mr. Spencer resolves itself into this: “Evolution is a change from an indefinite, inco- herent homogeneity to a definite, coherent heterogeneity through successive differentiations and integrations.” That this is true in the world of life is beyond ques- tion, and we have reason to believe that something of the sort is true in the world outside of life, whether the laws and forces in question be in essential respects com- parable or not. The influence of the theory of descent on all forms of modern mental activity has been great beyond com- parison. The thoughts of every student have been more or less modified by it. In philosophy as in science the publica- tion of the Origin of Species has been the great event of the nineteenth century. Not only have all the strictly biological sciences undergone a complete transformation since the year 1859, but such allied sciences as psychology, philology, sociology, and ethics have felt the same impulse and have fallen under the same influences. Even the organization of charities in every well-ordered community is avowedly based on the principles of Darwinism. The various attacks on the theory of descent have been nearly all based on the question of the origin of man. For the human race is likewise a species of animals, and from its physical side it must be discussed with other species. If we sup- pose that the various forms of the lower animals and 5 Influence of theory of descent. Origin of man. 48 FOOT-NOTES TO EVOLUTION. plants had their origin in pre-existing forms more or less different, we may presume this to have been true of man also. That it is true of man in fact we know, for not many thousands of years ago our ancestors in Europe were barbarians, cave dwellers, lake dwellers, and dwellers in hollow trees, using only the rude imple- ments they shaped from metal and flint. The origin of civilized man from barbarous man gives the clew to the origin of barbarous man from forms still less specialized. The question of the origin of man, though perhaps the most interesting problem in science, offers to the stu- dent of Nature peculiar difficulties. Materials for exact knowledge are few and prejudices are strong, and all tendencies favour an immediate decision on doubtful points, though the evidence be far from sufficient. Of not one man, nor monkey, nor bird, nor beast in half a million does a trace remain after a thousand years—not a bone, nora relic, nor a thought. Living on the sur- face, we crumble into dust; and the current phases of human life, a few centuries out of hundreds, are all of man’s history we surely know. Many links are missing still, and most of these we can never find. Our early ancestry we can best infer from our knowledge of the embryonic history and mental development of the man of to-day. But if anything in science is certain, it is that homol- ogy is a fact, and that it has a meaning. Among us backboned animals, all structures, all functions, and all mental operations show distinct homologies. The essence of the development theory is this: Homology is the stamp of heredity. Homology means blood relation- ship. No other meaning of homology has ever been shown, nor is there the slightest evidence that any other interpretation is possible. Blood relationship implies a Meaning of homology. THE KINSHIP OF LIFE. 49 common action of heredity, and a common heredity is the only source yet known for the likenesses we call homology. I resemble my neighbour so closely that people say we look like brothers. My little boy shows similar ex- actness of homology to me, and people say that he is the very image of his father. My neighbour on the left shows wider divergencies, but then he too is evidently an Anglo-Saxon. Angle or Saxon, we were all of one blood not many centuries ago. Still farther away the whole Aryan race becomes one, and we are willing in Adam to’recognise our homology even with our poor relations—the Bushman and the Hottentot. But still poorer relations we have, and they too carry on their faces the unmistakable evidences of kinship by blood. In every bone and muscle my dog shows his likeness to me, and even in every function of his feeble little brain the resemblance is apparent. We have no explanation of such homologies other than that of kinship by blood. For this reason we know that the various races of men and the various species of monkeys have some time had a common ancestry. For this reason we believe that at a period of time far back in the geological record all vertebrate animals sprang from a common stock. We have substantially the same evidence, differing only slightly in degree, for believing that my dog and my- self are related by blood in some form of distant cousin- ship, as there is to show a similar relationship between myself and any one of my neighbours. In neither case can we secure proof by appeal to history. Our records go back for a few generations only, and the great past is lost. In either case our acknowledged kinship is only an inference based on known facts of heredity and homology. No two groups can show homologies with each other 50 FOOT-NOTES TO EVOLUTION. more clearly than the members of the highest order of mammals. Either these homologies are real and thus show the existence of a real bond of union, or else they are mere mockeries like the face in the pansy flower. If homologies are mockeries, then indeed our science has made no progress, for this was the belief of the middle ages. So much for what we know. Our objections to rec- ognising our kinship with the lower forms—if we have any such objections—rest on considerations outside the domain of knowledge. They do not rest on religious grounds. Those who think so deceive themselves. ‘“Secondary causes,’ as the phrase is used, belong to the province of science. They are outside the domain of religion. “Theology and science,” says Darwin ‘should each run its own course. .. . Iam not respon sible if their meeting point should still be far off.” This is not a question of preference one way o another. Personal preference has no place in science Man was not present at the foundation of the world. It is not a question to be decided one way or another by a majority vote. Truth cares nothing for majorities, and the majority of one age may be the wonder or the shame of the next. The only question is this: Is it true? And if it be the truth, nothing in the universe can be truer. “ Ex- tinguished theologians,” Huxley tells us, “lie about the cradle of every science as the strangled snakes beside that of the infant Hercules.’ Looking along the history of human thought, we see the attempt to fasten to Chris- tianity each decaying belief in science. Every failing scientific notion has claimed orthodoxy for itself. That the carth is round, that it moves about the sun, that it is old, that granite ever‘was melted—all these beliefs, now Decaying scientific beliefs. THE KINSHIP OF LIFE. 51 part of our common knowledge, have been declared con- trary to religion, and Christian men who knew these things to be true have suffered all manner of evil for their sake. We see the hand of the Almighty in Nature everywhere; but everywhere he works with law and order. We have found that even comets have orbits; that valleys were dug out by water, and hills worn down by ice; and all that we have ever known to be done on earth has been done in accordance with law. Darwin says: “To my mind it accords better with what we know of the laws impressed on matter by the Creator, that the production and ex- tinction of the past and present inhab- itants of the world should have been due to secondary causes, like those determining the birth and death of an ‘ndividual. When I view all beings, not as special crea- ions, but as lineal descendants of some few beings who lived before the first bed of the Silurian was deposited, they seem to me to become ennobled. “There is a grandeur in this view of life, with its several powers having been originally breathed by the Creator into a few forms or into one, and that while this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning, endless forms most beautiful and most wonderful have been and are being evolved.” With the growth of the race has steadily grown our conception of the omnipotence of God. Our ancestors felt, as many races of men still feel, that they were forsaken unless each house- hold had a god of its own, for, numer- ous as the greater gods were, they were busy with priests and kings. The people could hardly believe that the God of their tribe could be the God of the Gentiles also. That he could dwell in temples not made Darwin’s words. The conception of God. 52 FOOT-NOTES TO EVOLUTION. with hands, removed him from human sight. That) there could be two continents was deemed impossible, for one God could not watch them both. That the| earth was the central and sole inhabited planet rested on the same limited conception of God. That the be-| ginning of all things was a little while ago is another | phase of the same idea, as is the idea of special creation’ for every form of animal and plant. | A Chinese sage, whose words remain while his name is lost in the ages between him and us, has said: “ He can not be concealed; he will appear without showing himself, effect renovation without moving, and create perfection without acting. It is the law of heaven an earth, whose way is solid, substantial, vast, and un changing.” Not long ago I walked across the Kentish fields to Down, a pilgrim to the shrine of Darwin. I saw th stately mansion in which he lived— great stone house surrounded by tree and shut in by an ivy-covered wall. I talked with the vil lagers of Down, the landlord of the George Inn, and the working people who had been his neighbours all their lives, and to whom Charles Darwin was not the world- | renowned investigator, but the kindly friend. His love for his wife and family, his love for flowers and birds and trees, his love for all things true and beautiful—all this forms the fair background before which rises the noblest work in science. i Forty years ago obloquy and derision were heaped t upon the name of Darwin from all sides, sometimes éven | from his scientific associates. He outlived it all, and | when he died his mother country paid him the highest | tribute in her power. He lies in Westminster Abbey, by | the side of Isaac Newton, one of the noblest of the long | line of men of science whose lives have made his own — Darwin’s home. THE KINSHIP OF ETRE: 53 life possible. For every truth that is won for humanity takes the life of a man. Among all who have written or spoken of Darwin since he died, by none has an unkind word been said. His was a gentle, patient, and reverent spirit, and by his life has not only science but our conception of Chris- tianity been advanced and ennobled. “A sacred kinship I would not forego Binds me to all that breathes ; through endless strife The calm and deathless dignity of life © Unites each bleeding victim to its foe. “‘T am the child of earth and air and sea. My lullaby by hoarse Silurian storms Was chanted, and through endless changing forms Of tree and bird and beast unceasingly The toiling ages wrought to fashion me. ““Lo! these large ancestors have left a breath Of their great souls in mine, defying death And change. I grow and blossom as the tree, And ever feel deep-delving earthy roots Binding me daily to the common clay ; Yet with its airy impulse upward shoots My soul into the realms of light and day. And thou, O sea, stern mother of my soul, Thy tempests ring in me, thy billows roll!” HJALMAR HjortuH BoyEsEn. II. EVOLUTION: WHAT IT IS AND WHAT IT IS NOT. Tuis is the age of evolution. The word is used by many men in many senses, and still oftener perhaps in no sense at all. By some it is spoken with a haunting dread, as though it were another name for the downfall of religion and of social stability. Still others speak it glibly and joyously, as though progress and freedom were secured by the mere use of the name. ‘“ The word evolution (Zxtwickelung),” says a German writer, “fills the vocal cords more perfectly than any other word.” It explains everything and “ puts the key to the universe into one’s vest pocket.” So various has been the use of the word, so rarely is this use associated with any definite idea, that one hesi- tates to call himself an evolutionist. ‘ Evolution” and “evolutionist” are almost ready to be cast into that “limbo of spoiled phraseology ” which Matthew Arnold has found necessary for so many words in which other generations delighted and which they soiled or spoiled by careless usage. But as the word evolution is not yet put away, as it is the bugbear of many good people and the “religion” of as many more equally good, it may be worth while to consider what it still means and what it does not mean, for if we that use the word can agree on a definition half our quarrel is over. 54 What evolution is. WEAT IT IS-AND WHAT IT IS NOT. 55 It seems to me that the word evolution is now legiti- mately used in four different senses. It is the name of a branch of science; it is a theory of organic existence; it is a method of investigation; and it is the basis of a system of philosophy. As a science, evolution is the study of changing be- ings acted upon by unchanging laws. It is a matter of common observation that organisms change from day to day, and that day by day some alteration in their envi- ronment is produced. It is a conclusion from scientific investigation that these changes are greater than they appear. They affect not only the in- dividual animal or plant, but they affect all groups of living things, classes or races or species. No character is permanent, no trait of life without change; and as the living organism and groups of organisms are under- going alteration, so does change take place in the ob- jects of the physical world about them. “Nothing endures,” says Huxley, “save the flow of energy and the rational order that pervades it.” The structures and objects change their forms and relations, and to forms and relations once abandoned they never return; but the methods of change are, so far as we can see, im- mutable. The laws of life, the laws of death, and the laws of matter never change. If the invisible forces which rule all visible things are themselves subject to modification and evolution we have not detected it. If these vary, their aberrations are so fine as to defy human observation and computation. In the control of the uni- verse we find no trace of “ variableness nor shadow of turning.” “It is the law of heaven and earth, whose way is solid, substantial, vast, and unchanging.” But the things we know do not endure. Only the Shortness of human life allows us to speak of species or The science of organic evolution. 56 FOOT-NOTES TO EVOLUTION. even of individuals as permanent entities. The mountain chain is no more nearly eternal than the drift of sand. It endures beyond the period of human observation; it antedates and outlasts human history. So does the species of animal or plant outlast and antedate the life- time of one man. Its changes are slight even in the lifetime of the race. ‘Thus the species, through the per- sistence of its type among its changing individuals, comes to be regarded as something which is beyond modification, unchanging so long as it exists. “T believe,” said the rose to the lily in the parable, “T believe that our gardener is immortal. I have watched him from day to day since I bloomed, and I see nochangein him. The tulip who died yesterday told me the same thing.” As a flash of lightning in the duration of the night, so is the life of man in the duration of Nature. When one looks out on a storm at night he sees for an instant the landscape illumined by the lightning flash. All seems at rest. The branches in the wind, the flying clouds, the falling rain, are all motionless in this instantaneous view. The record on the retina takes no account of change, and to the eye the change does not exist. Brief as the lightning flash in the storm is the life of man compared with the great time record of life upon earth. To the untrained man who has not learned to read these records, species and types in life are endur- ing. From this illusion arose the theory of special crea- tion and permanence of type, a theory which could not persist when the fact of change and the forces causing it came to be studied in detail. But when man came to investigate the facts of indi- vidual variation and to think of their significance, the current of life no longer seemed at rest. Like the flow of a mighty river, ever sweeping steadily on, never re- WHA Gh aSVANDSWitAT if IS NOT: 57 turning, is the movement of all life. The changes in human history are only typical of the changes that take place in all living creatures. In fact, human history is only a part of one great life current, the movement of which is everywhere governed by the same laws, depends on the same forces, and brings about like results. The facts and generalizations of change constitute the subject matter of evolution ; and as the fact of life is a fundamental one and in some degree modifies all phenomena which it concerns, we have as the central axis of the science in question the study of organic evo- lution. In fact, while inorganic evolution or orderly change in environment also exists, we do not know to what degree the laws and forces of organic evolution can be reduced to the same terms of expression. The theory of the essential and necessary unity of life and non-life, of mind and matter, is still a matter of phil- osophical speculation only. We can neither prove the truth of Monism nor understand it; nor is the contrary hypothesis either comprehensible or credible. The fundamental unity of organic evolution and inorganic evolution is likewise yet to be proved, while the laws which govern living matter are certainly in part peculiar to life. For this reason the evolution of astronomy, of dynamic geology, of geography, as well as the purely hypothetical evolution of chemistry, must be separated from life evolution. Cosmic evolution and organic evo- lution show or seem to show some divergence from each other. To regard them as identical is to introduce con- fusion and not order into our conception of evolution. There are some elements which are not held in com- mon, or which at least are not identical when measured in human terms. It is not evident that any force in the evolution of life is homologous with any which has brought about the evolution of stars and planets, This 58 FOOT-NOTES TO EVOLUTION. unity of forces may be a philosophical necessity ; it is not a fact. For the science which treats of organic evolution we are in great need of a distinctive term. This need was met by Prof. Patrick Geddes, who sug- gested the term bionomics. Bionomics (Bios, life; vouos, law or custom) is the science which treats of the changes in life forms and of the laws and forces on which these changes depend. Even as thus restricted, organic evolution, or bio- nomics, is the greatest of the sciences, including in its sub- ject matter not only all natural history, not only pro- cesses like cell division and nutrition, not only the laws of heredity, variation, natural selection,,and mutual help, but all matters of human history, and the most complicated relations of civics, economics, and ethics. In this enormous science no fact can be without a mean- ing, and no fact or its underlying forces can be sepa- rated from the great forces whose interaction from mo- ment to moment writes the great story of life. And as the basis to the science of bionomics, as to all other science, must be taken the conception that nothing is due to chance or whim. Whatever occurs comes as the resultant of moving forces. Could we know and estimate these forces, we should have, so far as our estimate is accurate and our logic perfect, the gift of prophecy. Knowing the law, and knowing the facts, we should foretell the results. To be able in some degree to do this is the art of life. It is the ulti- mate end of science, which finds its final purpose in hu- man conduct. “A law,” according to Darwin, “is the ascertained sequence of events.” The necessary sequence of events it is, in fact, but man knows nothing of what is neces- sary, only of what has been ascertained to occur. Be- Bionomics. WHAT Er 1S:4AND; WHAT IT IS NOT. 59 cause human observation and logic can be only partial, no law of life can be fully stated. Because the processes of the human mind are human, with organic limitations, the study of the mind itself becomes a part of the science of bionomics. For it is itself an instrument or a combination of instruments by which we acquire such knowledge of the world out- side of ourselves as may be needed in the art of liv- ing, in the degree in which we are able to practise that art. The necessary sequence of events exists, whether we are able to comprehend it or not. The fall of a leaf follows fixed laws as surely as the motion of a planet. It falls by chance because its short movement gives us no time for observation and calculation. It falls by chance because, its results being unimportant to us, we give no heed to the details of its motion. But as the hairs of our head are all numbered, so are numbered all the gyrations and undulations of every chance au- tumn leaf. All processes in the universe are alike nat- ural. The creation of man or the growth of a state is as natural as the formation of an apple or the growth of a snow bank. All are alike supernatural, for they all rest on the huge unseen solidity of the uni- verse, the imperishability of matter and the immanence of law. We sometimes classify sciences as exact and inexact, in accordance with our ability exactly to weigh forces and results. The exact sciences deal with simple data accessible and capable of measurement. The results of their interactions can be reduced to mathematics. Be- cause of their essential simplicity, the mathematical sci- ences have been carried to great comparative perfection. It is easier to weigh an invisible planet than to measure the force of heredity in a grain of corn. The sciences of life Meaning of law. 60 FOOT-NOTES TO EVOLUTION. are inexact because the human mind can never grasp all their data. The combined effort of all men, the flower of the altruism of the ages, which we call science has made only a beginning in such study. But, however in- complete our realization of the laws of life, we may be sure that they are never broken. Each law is the ex- pression of the best possible way in which causes and results can be linked. It is the necessary sequence of events, therefore the dest sequence, if we may imagine for a moment that the human words “ good” and “ bad” are applicable to world processes. The laws of Nature are not executors of human justice. Each one has its own operation and no other. Each represents its own tendency toward cosmic order. A law in this sense can not be “ broken.” “If God should wink at a single act of injustice,” says the Arab proverb, “the whole uni- verse would shrivel up like a cast-off snake skin.” If God should wink at any violated law the universe would vanish. Not long ago, in an examination in a theological seminary, the question was asked of the candidates for the ministry, “Is it right to pray for a change of sea- son?” ‘The candidates thought that it was not, for the relations which produce winter and summer are fixed in the structure of the solar system and can not be altered for man’s pleasure or man’s need. “Is it right to pray for rain?’’ The candidates generally thought that it was, because the conditions of rain are so unstable that a little change in one way or another would bring rain or fair weather. It is proper to ask for such a change, as it does not concern the economy of the universe. The third question was: “ When the signal service of the United States is well established, so that weather conditions are perfectly known, will it then be right to WHAT IT 1S AND WHAT IT IS NOT. 61 pray * for rain?” And the candidates for the ministry could not tell, for they began to see that even simple changes of weather may have the strength of the whole universe behind them. It has never yet rained when by any possibility it could do otherwise. It has never failed to rain when rain was possible. We hear good men say sometimes that the crying need of this sceptical age is that it may see some law of Nature definitely broken, that it may rain when rain is impossible, or that some burning bush may, uncon- suming, proclaim that the force which is behind all law is also above it and can break or repeal all its own laws at will. Emerson somewhere speaks of the purpose in life— “to be sound and solvent.” As his life was in all ways “sound and solvent,” perhaps such rule of conduct was his own. But one may say, This is only a human resolu- tion. The man himself should be above all rules and requirements of his own making. Let Mr. Emerson show that his life is above his principles. Let him break these rules to show his power. Let him be “unsound and insolvent” for a time. Then only will his real greatness appear. But the soundness and sol- vency were the expression of Emerson’s life. Without these he would not be Emerson. The laws of Nature are the expression of the infinite soundness and solvency of the universe. They will not be broken, nor through their unsoundness and insol- Soundness and solvency of Nature. * “ The essence of prayer is to bring two things into unison— the will of God and the will of man. Superstition imagined, no doubt, that prayer would change the will of God, but the more Spiritually minded have always understood that the will which must be modified in prayer was the will of man.”—Sernard Bosanquet. 62 FOOT-NOTES TO EVOLUTION. vency will the “ heavens roll away as a scroll,’ nor “the universe shrivel up as a cast-off snake skin.” In the growing recognition of law has lain the prog- ress of science. From the casting aside of human no- tions of chance and whim the “ warfare of science’”’ has had its rise. For every fact carried over into the realm of law some man has given his life. Many a time in the growth of humanity it has been necessary that the wisest, clearest, most humane should die on the stake or the gibbet or the cross, that men should come to realize the power of an idea; that they should know the mean- ing of truth. Many men have been distressed over the insensibil- ity of Nature. She goes on with her own affairs. If the ship leaks, she drowns a prophet as she would a rat. The stones in the street should have cried out at the mur- der of Cesar. But they did not. It was only men who cried. Once, when a fugitive slave was seized in Massa- chusetts, there were those who felt outraged that Nature did not rebel against it. It was a surprise to Thoreau that the squirrels went on with their hoard and the wind rustled in the trees, as though nothing had happened. But what should Nature do? She attends only to her own affairs... She is only a figure of speech by which we personify her affairs. Her “just keeping on the same, calmer than clockwork and not caring,” is the expression of the solidity of the universe. She is as indifferent as the multiplication table is, for the multiplication table is only another expression of unchanging law. A law of Nature is “no respecter of persons.” A varying mul- tiplication table would be the destruction of mathe- matics. A varying law of Nature would be the destruc- tion of the universe. The laws of evolution have in themselves no neces- The indifference of Nature. WHAT IT IS AND WHAT IT IS NOT. 63 sary principle of progress. Their functions each and all may be defined as cosmic order. The law of gravita- tion brings order in rest or motion. The laws of chemi- cal affinity bring about molecular stability. Heredity repeats strength or weakness, good or ill, with like in- difference. The past will not let go of us; we can not let go of the past. The law of mutual help brings the perpetuation of weakness as well as the strength of co- operation. Even the law of pity is pitiless, and the law of mercy merciless. ‘The nerves carry sensations of pleasure or pain, themselves as indifferent as the tele- graph wire which is man’s invention to serve similar pur- poses. Some men who call themselves pessimists because they can not read good into the operations of Nature forget that they can not read evil. For both good and evil belong to man’s reaction from the influences of environment. It is the growth of love and wisdom through struggle and storm that makes this world the abode of righteousness. It is the effort of man that deifies Nature. It is this that raises the process of evolution above the level of the multiplica- tion table. It is this that makes the whole of Nature greater than the sum of all her parts. In a different sense the word evolution is applied to the theory of the origin of organs and of species by divergence and development. This the- ory teaches that all forms of life now existing or that have existed on the earth have sprung from a common stock, which has undergone change in a multitude of ways and under varied conditions, the forces and influences pro- ducing such change being known as the “factors of organic evolution.” All characters and attributes of species and groups have developed with changing con- ditions of life. The homologies among animals are the 6 Evolution as a theory of organic development. 64 FOOT-NOTES TO EVOLUTION. result of common descent. The differences are due to various influences, chief among these being competition in the struggle for existence between individuals and between species, whereby those best adapted to their surroundings live and reproduce their kind. This theory is now the central axis of all biological investigation in all its branches, from ethics to histology, from anthropology to bacteriology. In the light of this — theory every peculiarity of structure, every character or quality of individual or species, has a meaning and a cause. It is the work of the investigator to find this meaning as well as to record the fact. “One of the noblest lessons left to the world” by Darwin, Frank Cramer says, “is this, which to him amounted to a pro- | found, almost religious, conviction, that — every fact in Nature, no matter how in- significant, every stripe of colour, every tint of flowers, the length of an orchid’s nectary, un- usual height in a plant, all the infinite variety of appar-— ently insignificant things, is full of significance. For him it was an historical record, the revelation of a cause, the lurking place of a principle.” According to the theory of evolution every structure of to-day finds its meaning in some condition of the past. The inside of an animal tells what it really is, for it bears the record of heredity. The outside of an ani- mal tells where its ancestors have been, for it bears record of concessions to environment. Similarity in essential structure is known as homology. By the theory of evolution homology, wherever it is found, is proof of blood relationship. The theory of organic evolution through natural law was first placed on a stable footing by the observa- tions and inductions of Darwin. It has therefore been | long known as Darwinism, although that term has been | Each fact has a meaning. WHAT IT IS AND WHAT IT IS NOT. 65 usually associated with the recognition of natural selec- tion as the great motive power in organic change. Darwinism was at first regarded as a “ working hypoth- esis.” It is now an integral part of biological science, because all opposing hypotheses have long since ceased to work. It is as well attested as the theory of gravita- tion, and its elements are open to less doubt. All in- vestigations in biology must assume it, as without it most such investigations would be impossible. Natural- ists could no more go back to the old notion of special creation for each species and its organs than astrono- mers could go back to the old notion of guiding angels as directors of planetary motion. Without the theory of organic development through natural selection the biological science of to-day would be impossible. In a third sense the word evolution is applied to a method of investigation. It is the study of present con- ditions in the light of the past. The preliminary work of science is the de- scriptive part. This involves accuracy of observation and precision of statement, but makes no great demands on the powers of logical analysis and synthesis. The easy work of science is largely already done. Those who would continue investigation must - study not only facts and structures, but the laws that govern them. In the words of John Fiske, “ Whether planets or mountains or molluscs or subjunctive modes or tribal confederacies be the things studied, the scholars who have studied them most fruitfully were those who have studied them as phases of development. Their work has directed the current of thought.” The most difficult problems in life are susceptible of more or less perfect solution if approached by the methed of evolu- tion. They can not be even stated as problems in any Other terms. In every science worthy of the name the Evolution as a method of study. 66 FOOT-NOTES TO EVOLUTION. history of origins and the study of developing forces must take a leading part. In a fourth sense the word evolution has been ap- plied to the philosophical conceptions to which the theory of evolution gives rise. Phi- Evolution as losophy is not truth. When it is so it glean becomes science. At the best it points philosophy. the way to truth. The broader the in- ductive basis of any system of philoso- phy, the greater its value as an intellectual help. The system of Herbert Spencer, the greatest exponent of the philosophy of evolution, is based wholly on the re- sults of scientific investigation. It consists of a series of more or less broad and more or less probable de- ductions from the facts and laws already known. Sys- tems like these which rest on scientific knowledge do not rise high above it. They can therefore be revised or rewritten as knowledge increases. They provide the means for their own correction. Systems resting on aphorisms or assumptions or definitions must disappear ~ as knowledge increases. Philosophy is never wholly identical with truth. The partial truth which it may contain becomes wholly error with the advance of science. The growth of exact knowledge transforms the truth in philosophy into science, leaving the absolute falsehood as the final re- siduum, From this necessary fact comes the ultimate decay of all creeds or philosophic formule. Throughout the ages science and philosophy have been in conflict. Science is the same to all minds capable of grasping its conclu- ‘ sions. Philosophy changes with the point of view. It is the evanescent perspective in which the facts and phenomena of the universe are seen. This can never Decay of formule. WHAT IT IS AND WHAT IT IS NOT. 67 be the same under changing times and conditions. With the larger knowledge of to-morrow there will be large modifications in the accepted philosophy of evolution. Each succeeding generation will give to the applications of the laws of organic life a different philosophical ex- pression. In these four senses the word evolution is used with some degree of accuracy; but in the current literature of the day the word has many other meanings, some of them very far from any just basis. Some things which evo- lution is not we may here notice briefly. Evolution is not a theory that “man is a developed monkey.” The question of the immediate origin of man is not the central or overshadowing What evolution is not. Man not a question of evolution. This question developed ff ial difficulti in th onkey. offers no special difficulties 1 eory, although the materials for exact knowl- edge are in many directions incomplete. Homologies more perfect than those connecting man with the great group of monkeys could not exist. These imply the blood relationship of the human race with the great host of apes and monkeys. As to this there can be no shadow of a doubt, and, as similar homologies connect man with all members of the group of mammals, similar blood relationship must exist; and homologies less close but equally unmistakable connect all backboned ani- mals one with another, and the lowest backboned types are Closely joined to wormlike forms not usually classed as vertebrates. It is perfectly true that in the higher or anthro- poid apes the relations with man are extremely inti- mate; but man is not simply “a developed ape.” Apes and men have diverged from the same primitive stock— apelike, manlike, but not exactly the one nor the other. 68 FOOT-NOTES TO EVOLUTION. No apes nor monkeys now extant could apparently have been ancestors of primitive man. None can ever “ de- velop” into man. As man changes and diverges, race from race, so do they. The influence of effort, the in- fluence of surroundings, the influence of the sifting process of natural selection, each acts upon them as it acts upon man. The process of evolution is not progress, but better adaptation to conditions of life. As man becomes fitted for social and civic life, so does the ape become fitted for life in the tree tops. The movement of monkeys is toward “simianity,” not humanity. The movement of cat life is toward felinity, that of the dog races toward caninity. Each step in evolution upward or downward, whatever it may be, carries each species or type farther from the primitive stock. ‘These steps are never retraced. For an ape to become a man he must go back to the simple characters of the simple common type from which both have sprung. These characters are shown in the ape baby and in the human embryo in its corresponding stages, for ancestral traits lost in the adult are evident in the young. This persistence comes through the op- eration of the great force of cell memory which we call heredity. The evidence of biology points to the descent of all mammals, of all vertebrates, of all animals, of all or- ganic beings, from a common stock. Of all the races of animals the anthropoid apes are nearest man. Their divergence from the same stock must be comparatively recent. Man is the nomadic, the apes are the arboreal, branch of the same great family. Evolution does not teach that all or any living forms are tending toward humanity. It does not teach, as in Bishop Wilberforce’s burlesque, ‘‘that every favourable Not progress, but adaptation. WHAT IT IS AND WHAT IT IS NOT. 69 variety of the turnip is tending to become man.”’ It is not true that evolutionists expect to find, as Dr. Seelye has affirmed, “the growth of the highest alga into a zodphyte, a phenomenon for which sharp eyes have sought, and which is not only natural but inevitable on the Darwinian hypothesis, and whose discovery would make the fame of any obsérver.” It is no wonder that a clear thinker should have re- jected “‘ the Darwinian hypothesis’ when stated in such terms as this. The line of junction in evolution is al- ways at the bottom. It is the lowest mammals which approach the lowest reptiles; it is the lower types of plants which approach the lower types of animals; it would be the lowest alga, to use Dr. Seelye’s illustration, which would be transmutable into the lowest zodphyte ; it is the unspecialized, undifferentiated type from which branches diverge in different ways. Humanity is not the “ goal of evolution,” not even that of human evolu- tion. There will be no second “creation of man” ex- cept from man’s own loins. There will not be a second Anglo-Saxon race unless it has the old Anglo-Saxon blood in its veins. Adaptation by divergence—for the most part by slow stages—is the movement of evolution. While occasional leaps or sudden changes occur in the process, they are by no means the rule. In most cases of “saltatory evolution ”’ the suddenness is in appearance only. It comes from our inability to trace the intermediate stages. When an epoch-making character is acquired, as the wings of a bird or the brain of man, the process of readjustment of other characters goes on with greatly increased rapidity. But this rapidity of evolution is along the same lines as the slower processes. Radical changes Humanity not the goal of evolution. Change by slow divergence. 70 FOOT-NOTES TO EVOLUTION. from generation to generation never occur. We do not expect to find birds arising from a “ flying-fish in the air, whose scales are disparting into feathers.” A flying- fish is no more of the nature of a bird than any other fish is. A cow will never give birth to a horse, nor a horse to acow. The slow operation of existing causes is the central fact of organic evolution, as it is of the evolu- tion of mountains and valleys. Seasons change as the relations which produce them change. But midsummer never gives way to midwinter in an instant. Nor does the child in an instant become a man, though in some periods of growth epoch-marking causes may make de- velopment more rapid. Life is conservative. The law of heredity is the expression of its conservatism. Life changes slowly, but it must constantly change, and all change is by necessity divergence. There is in Nature no single “law of progress,” nor is progress in any group a necessity regardless of con- ditions. That which we call progress No innate tend- rests simply on the survival of the better ency toward p : : arene eine. adapted, their survival being accom- panied. by their reproduction. Those that live repeat themselves. The “innate tendency toward progression” of the early evolutionists is a philosophic myth. Progress and degeneration are alike the resultants of the various forces at work from gen- eration to generation on and within a race or species. The same forces which bring progress to a group under one set of conditions will bring degradation under another. In their essence the factors of evolution are no more laws of progress than the attraction of gravita- tion is. Cosmic order comes from gravitation. Or- ganic order comes from the factors of evolution. Evo- lution is simply orderly change. Nor is evolution identical with the notion of sponta- WHAT IT IS AND WHAT IT IS NOT. 71 neous generation. There is no necessary connection between the one theory and the other. Spontaneous generation, or birth without parentage, on the part of small or useless creatures was accepted in early times without question. As men began to observe these animals more carefully, the fact of their spontaneous generation was doubted. A great step was made when it was found that to screen meat from flies would protect it from maggots. A greater step came in our own time when it was proved that to screen infusions from air dust is to protect them from putrefaction or fermentation. Fer- mentation is “life without air.” It is the decomposition of sugar by minute creatures who disintegrate it in their life processes. Putrefaction and decay are also the same in nature. There is literal truth in Carlyle’s state- ment that there is still force in a fallen leaf, “else how could it rot?” It is the force of the minute organisms hidden in the leaf, and whose life is the leaf’s decay. The decay and death of men from contagious diseases are known to be due to life processes of minute organ- isms, as is the gangrene which follows unskilful sur- gery. The study of the “fauna and flora” within living organisms has now become a science of itself, demand- ing the greatest care in observation and the most com- plete of appliances. ‘“ Omne vivum ex vivo,” “all life from life,” was an aphorism of the naturalists of a century or two ago. It was to them a new and broad generali- zation. It has not yet been set aside. The classic ex- periments of Tyndall show that this law applies to all creatures we have yet recognised or classified. As far as science can tell, spontaneous generation is still a myth, having no basis in observation, no warrant in ex- periment. It remains as a pure deduction from the phi- losophical conception of Monism. It is incapable of Spontaneous generation. 72 FOOT-NOTES TO EVOLUTION. proof, insusceptible of refutation. The argument for it is chiefly this: Life exists on a globe once lifeless. How did life begin? If not through spontaneous generation, how did it come? Must it not have been by the opera- tion of those laws and forces which through all time change lifeless into living matter? Very likely, but we do not know. We know nothing whatever of such laws and forces, and we gain nothing by veiling our ignorance under a philosophical necessity. Moreover, if spontaneous generation occurs as a re- sultant of any forces, like forces would produce it again. We have never known it to occur. Should it occur, the organisms thus produced would have no bonds of blood relationship with those already in existence. With these they should show no homology, as they could have no inheritance in common. But all known organisms have common homologies. The factors of organic evolu- tion are essentially the same for all. The unity of life amid all its diversity seems to point to origin froma common stock. If not from one stock, the lines of division between one and another are hidden from us. The study of embryology breaks down the time-honoured branch lines of vertebrates, articulates, molluscs, and radiates. The groups of animals are more numerous, more complex, and more intertangled than Cuvier and Agassiz thought. The number of primary branches of animals or plants is uncertain, their boundaries unde- fined. If spontaneous generation exists, it is a factor in evolution. If it is a factor, our explanation of the meaning and nature of homology must be fundamentally changed. But it may be that it should be changed. We can not show that spontaneous generation does not exist. All we know is that we have no means of recog- nising it. If there is now spontaneous generation of WHAT IT IS AND WHAT IT IS NOT. 73 protoplasm, it can not take the form of any creature we know. An organism fresh from the mint of creation would be too small for us to see with any microscope. It would be too simple for us to trace by any instru- mentality now in our possession. It could contain but a few molecules, and a molecule in a drop of water is as small as an orange beside the sun. Such a race of crea- tures, spontaneously generated, without concessions to environment, would grow hoary with the centuries be- fore it came to our notice. Its descendants would have belonged for ages to the unnumbered hosts of microbes before we should be aware of its creation. Evolution is not a creed or a body of doctrine to be believed on authority. There is no saving grace in being an evolutionist. ‘There are many who take this name and have no interest in finding out what it means or in mak- ing any application of its principles to the affairs of life. For one who cares not to master its ideas there is no power in the word. Evolution is not a panacea or a medicine to be applied to social or personal ills. It is simply an expression of the teaching of enlightened common sense as to the order of changes in life. If its principles are mastered a knowledge of evolution is an aid in the conduct of life, as knowledge of gravitation is essential in the building of machinery. Ther2 is nothing “occult ’’ in the science of evolu- tion. It is not the product of philosophic meditation or of speculative philosophy. It is based on hard facts, and with hard facts it must deal. It seems to me that it is not true that ‘“ Evolution is a new religion, the religion of the future.” There are many definitions of religion, but evolution does not fit any of them. It is no more a religion than gravitation is. One may imagine that some enthusiastic follower of Evolution not a creed. 74 FOOT-NOTES TO EVOLUTION. Newton may, for the first time, have seen the majestic order of the solar system, may have felt how futile was the old notion of guiding angels, one for each planet to hold it up in space. He may have re- ceived his first clear vision of the simple relations of the planets, each forever falling toward the sun and toward one another, each one by the same force forever preserved from collision. Such a man might have exclaimed, ‘“ Great is gravita- tion; it is the new religion, the religion of the future!” In such manner, men trained in dead traditions, once brought to a clear insight of the noble simplicity and adequacy of the theory of evolution, may have exclaimed, “Great is evolution; it is the new religion, the religion of the future!” But evolution is religion in the same sense that every truth of the physical universe must be religion. That which is true is the truest thing in the world, and the recognition of the infinite soundness at the heart of the universe is an inseparable part of any worthy religion. But, whether religion or not, the truths of evolution must be their own witness. They can be neither strengthened nor controverted by any authority which may speak in the name of philosophy or of theology or of re- ligion or of reason. “ Roma locuta est; causa finita est”’ is not a dictum which science can regard. Her causes are never finished. No power on earth can give before- hand the answer to her questions. Her only court of appeal is the experience of man. Evolution not a religion. Science its own witness. rit: THE ELEMENTS OF ORGANIC EVOLUTION. ALL the laws of life, whatever their nature, are valid throughout the organic world. They control the life processes of man, those of the lower animals, and those of “our brother organisms, the plants.” They extend to each in its degree. The fact that the laws of hered- ity, for example, extend unchanged in essence from one extreme of organic life to another is most vital to our understanding of the nature of life. For such homology as this, for any fact of homology whatsoever, we have found but one cause, the influence of common descent. There are many elements or factors which enter into the processes of organic evolution, and they stand in varied relations to one another. It is not possible to make a classification of them in which there shall not be inequality and overlapping of elements. For the purpose of our present discussion we may group these forces and factors under eight principal heads. I. Heredity —This is the “law of persistence in a se- ries of organisms.”” Throughout Nature each creature tends to reproduce its own qualities and those of its an- cestors. “Like begets like.” Creatures resemble their ancestors. The germ cell specialized for purposes of reproduction is capable in its development “ of repeat- ing the whole with the precision of a work of art.” Heredity is the great conservative force of evolution. 75 76 FOOT-NOTES TO EVOLUTION. Its influence is shown in the persistence of type, in the existence of broad homologies among living forms, in | the possibility of natural systems of classification in any group, in the retention of vestigial organs, in the early development and subsequent obliteration of out- worn structures once useful to the race or type. The physical basis of heredity has been in recent | years the subject of many elaborate investigations. The complete homology of the germ cell with the one-celled | animals, or protozoa, is now generally recognised, and there is large reason to believe that in the bands and | loops of the nucleus of the germ cell is found the visible | vehicle by which hereditary tendencies are transmitted. Il. /rritability—All living beings are affected by their environment. Living matter must always respond in some degree to every external stimulus. All living beings are moved by or react from every phase of their surroundings. The nervous system and its associated sense organs are directly related to the conditions of life. They are concessions made to the environment. The power of motion, whatever it may be, requires the guidance obtained from the impressions made by ex- ternal things. In all animals this knowledge, whatever its degree of completeness, tends to work itself out in action. In plants the same thing is in some degree true. The essential difference is that, having no power of locomotion, the plant is without a general sensorium. The parts that move—growing rootlets, tips of branches, and the like—have sensibility and power of motion in the same series of cells. The animal, a colony of cells which move as a whole, has a specialized nervous sys- tem which guides the whole. Asa rule, the environment does not act directly on the individual. Its influence is felt chiefly in modifying its action, in increasing, diminishing, or changing its THE ELEMENTS OF ORGANIC EVOLUTION. Vd. efforts. The effects of environment are practically rec- ognised in processes of education, of agriculture, the care and nurture of men and of horses and trees and wheat. Evil surroundings produce evil effects. Easy surroundings, reducing the stimulus to effort, tend to produce organic degeneration. In larger ways response to environment produces a long series of “ concessions.” A character or condition in itself of the nature of a re- sponse to outside stimulus may be called a concession. Among such concessions are the skin, the eyes, the brain, the sense of pain, in fact, in the ultimate analysis, every organ and every function of the body. For with- out environment all these would be unnecessary. Their existence would be inconceivable. The fitness by which organisms have been perpetu- ated is simply obedience or adaptation. Those which survive are fitted to the conditions of life. In other words, they are obedient to these conditions. Hence we may define the process as one of the survival of the obedient. The force which commands obedience is that of the environment, and the obedience demanded is that of such a reaction or relation to this environment as will not obstruct the processes of life. Every form or phase of obedience shows itself as adaptation. Every adaptation is a concession to the actual environment on the one hand, to the laws of lifeon the other. The func- tion of the eye, for example, is to give information as to the nature of objects more or less re- mote from the organism. The purpose of giving this knowledge is to enable the organism to act upon it. To be able to act demands that the action must be safe. If the creature could not act, it would have no need for such knowledge. If its acts were not in accord with knowledge, the knowledge would be useless. If there Concessions of life. 78 FOOT-NOTES TO EVOLUTION. were no break in the uniformity of the environment, there would be no need of such knowledge. If there were no variation in lights and shadows, the eye would be powerless to bring information. The senses deal with changes or breaks in reality rather than with reali- ties themselves. Because, in action, the organism must be obedient to the demands of its environment, it is the function of the eye to make known these demands. The existence of the eye is therefore a concession to the environment. A concession of like nature is the brain itself, of which the eye and the sense organs in general may be considered as prolongations. These appendages of the brain carry to it truth of varying kind or degree. This truth as to external nature furnishes the basis of that obedience which in the animal expresses itself in action. The respiratory apparatus is an adaptation for the purpose of purifying the blood from the waste produced in the processes of life. It is a concession on the one hand to the demands of life in cell and tissue, and on the other hand to the nature of the surrounding medium. A change in the atmosphere would demand a correspond- ing change in the organs of breathing. If such a con- cession were impossible, the species in question would become extinct, as its individuals would perish. If the concessions necessary to continued existence should in- volve changes in other organs, the process of the sur- vival of the obedient would in time produce these changes. If there were no surrounding medium there would be no organ of respiration. If there were no light there would be no organ of vision. If there were no sound there would be no ear. If there were no motion there would be no need for knowledge, and therefore no sen- sation. If there were no power of locomotion there THE ELEMENTS OF ORGANIC EVOLUTION. 79 would be no sensorium. If there were no environment there would be no concessions to it. Without conces- sion there would be no specialization of functions or organs. Without variation in environment there could be no choice in action. The concessions to the environ- ment constitute, therefore, practically the whole structure of any animal and the whole of the functions of its life. It is in the response to environment, the concession, the adaptation, the specialization, that the progress of life consists. It is in characters thus produced that man and the higher animals differ from the protozoa. Even the protozoan has its concessions. ‘The phenomenon of growth causes the substance of the one-celled animal to increase faster than its absorptive power. The waste of the body varies as the substance—that is, as the cube of the diameter of the creature. The absorptive power of its surface must increase as the square of the diameter —that is, as the surface. Hence, a one-celled animal passing a given small size must either starve to death or else make some concession to its surroundings. This concession is reproduction—the one-celled crea- ture must split into two animals. This increases the digestive power, with no increase of substance. Even the presence of skin on a protozoan is a concession to its surroundings. That a given protozoan is developed with an outside covering shows that natural selection has been long at work on its ancestry in preparing such a concession to external demands. A creature which had known no environment and which had inherited no concession would be formless and structureless. It could be little if anything more than an organic molecule, or at the most a nebulous mist of organic molecules without parts or form or function. We know no such nebulous life as this. All the ani- mals and plants on the records of science show traces of 7 80 FOOT-NOTES TO EVOLUTION, a long ancestral history. Their bodies are full of con- cessions to environment, and their functions are all in the line of obedience to those conditions in life in which their ancestors have been thrown. We recognise that man is the highest in structure among living beings. This fact implies that in his phys- ical structure are the greatest concessions to environ- ment. In his functions the most perfect obedience is made possible. His power of choice among competing lines of action but emphasizes the need of choosing the best action. The best action is the safe action—safe for the individual, safe for the species, for only those races survive who care for their young as they care for themselves. The greatness of the human intellect depends on the progressive concessions to environment by which the human brain through the ages has been gradually built up. Ill. /ndividuality—No two organisms are exactly alike. There is in each individual of whatever species “a divine initiative ’’ which prevents it from being the slavish copy of any which have gone before. The “sur- vival of the fittest’ rests on the existence of different _ degrees and kinds of fitness. This it is the part of the laws of variation to produce. Every step in divergence or specialization gives room for more life. The abun- dance of life is dependent upon its variety. Thus the world is never full, for there is always room for organ- isms better or differently adapted to each set of its varied conditions. The arrangement of double parent- age tends to promote variety in life. Each new indi- vidual has all the ancestors of its father as well as all | those of its mother, and with each one these are brought | into new combinations. The process of amphimixis, the mingling of the hereditary characters of the two germ | THE ELEMENTS OF ORGANIC EVOLUTION. 87 cells, male and female, to form a new fertilized cell, has as its essential function the promotion of variation. The processes of karyokinesis, the subdivision of the nuclear material in the formation of a new cell, tend in the same direction. By the result of the subdivisions incident in forming the sperm cell or the ovum, no one of these is left exactly like any other. From this point of view we say that variation is, as Professor Osborn has pointed out, “in reality a phase of heredity.’”’ The same structures that provide for the continuance of the species prevent the actual repetition of the individual. Besides these sources of germinal variation there are the forces or laws which produce acceleration or retar- dation in growth. Much of the advance in power or specialization among organisms comes from the saving of time in the process of development. As growth goes on, the forms we call lower pass slowly through the various stages of life. Their development is finished before any high degree of specialization is reached. The embryo of the higher form passes through the same course, but with a rapidity in some degree proportioned to its future possibility. Less time is spent on non- essentials, and we may say that by the saving of time and force it is enabled to push on to higher devel- opment. The gill structures of the fish by which its blood is purified by contact with air dissolved in water last its whole lifetime. The fish never outgrows this structure and never acquires the function of breathing atmospheric air. The frog is fish-like for a period in its life, but the development is accelerated, organs for breathing atmos- pheric air are produced, and the gills become atrophied and disappear from view. Their traces remain, for by the law of heredity no creature can ever wholly let go of its past. That its ancestors once breathed in water 82 FOOT-NOTES TO EVOLUTION. can never be forgotten. With bird or mammal the ac- celeration is still more marked, and the gill structure has passed into atrophy before the egg is hatched or the animal born. The force of acceleration hurries the em- bryo along through these temporary stages, and with this shortening of useless steps comes the possibility of higher development. Conversely retarded development brings about de- generation, while variations in any direction with species or organs has the larger purpose of increasing variety, of promoting individuality. Similar results are brought about by variations in use or in effort. The organ which is used thrives, while the unused organ disappears with its function. These changes affect the individual vitally and directly. Whether they are transmitted from generation to gen- eration in any degree is still unknown. Characters re- -sulting from the use, effort, or experience of the indi- vidual are known as acquired characters. Such acquired characters are the strong arm of the blacksmith, the skilled hand of the artist, the trained ear of the musi- cian. These characters are not subject to inheritance by the laws of heredity in the same way or in the same degree that inborn characters are. Nevertheless, it is claimed by a large number of evolutionists, the so-called Neo-Lamarckian school, that there is a law of the trans- mission of acquired characters. Such a law was formu- lated by Lamarck as his fourth law of evolution in these words: “All that has been acquired, begun, or changed in the structure of individuals in their lifetime is pre- served in reproduction and transmitted to the new in- dividuals which spring from those who have inherited the change.” In the words of Herbert Spencer, the leader of the THE ELEMENTS OF ORGANIC EVOLUTION. 83 Neo-Lamarckians, “‘ Change of function produces changes of structure; it is a tenable hypothesis that changes of structure so produced are inheritable.” The transmission of acquired characters is still one of the hypothetical factors of evolution, but we may here give it only this passing reference. Among the remaining factors which promote variety in life must be reckoned variation in environment. No two organisms can have exactly the same surroundings, and the sur- roundings modify development. With this goes the destruction of the unadapted, the various phases of the great sifting process known collectively as natural selection. The “survival of the fittest’ must rest on the existence of the fittest. The “origin of the fittest” involves a series of difficult problems, some of them still unsolved. IV. Natural Selection The great motive power of organic evolution is the force or process of natural selec- tion. Inthe conditions of life those organisms last long- est which are best fitted to these conditions. The term “natural selection” originated from the use of the word “selection”? by breeders of animals to indicate the process of “ weeding out” by which they improve their breeds. For the method by which in Nature a new spe- cies is brought into existence seems to be precisely par- allel to that by which we may artificially produce a new breed of cows or of dogs, a new race of pigeons, or a new variety of roses. Throughout all Nature the number of organisms brought into life is far in excess of the number of those which can come to maturity. All live that can live, and in general those that can not live are those whose individual variations are least favourable. Only a small minority of the whole reach their full growth. The destruction of the others, to use Bergen’s words, is 84 FOOT-NOTES TO EVOLUTION. “not indiscriminate, but it will first and mainly com- prise those individuals least able to resist attack.” This is the essential fact upon which rests Herbert Spencer’s law of “the survival of the fittest.” At the same time the survival of the fittest does not tell the whole story of natural selection. But a small part of the actual characters of animals and plants can be traced directly and solely to the principle of utility. The survival of the existing likewise is a large element in the great process of natural selection. Thus, a water bird has webbed feet. The webbing is useful in swim- ming. Its presence is due to its utility. The survival of the fittest in water birds may mean the survival of the best swimmer, and the best swimmer is the one with the most useful webbing. But a character quite as per- sistent may be a perfectly useless one, as a special ar- rangement of the plates on the tarsus, or the flattening of a single claw. This may have in itself no utility at all. Its presence may not be due to the survival of the fittest. It persists because such a character was pos- sessed by some ancestor. It has been retained through heredity. The nails must have some form, the plates some arrangement, the wing coverts some colour. This ancestral form or colour is as good as some other would be. Hence comes its persistence, which is simply a sur- vival of the existing, no question of relative fitness being involved. : From the “survival of the existing’’ arises the per- sistence of those forms which actually inhabit a given district whether they be ideally the fittest or not. By such means the faunz of isolated regions are perpetu- ated, the barriers of land or sea or climate excluding them from competition with the “ fitter’ organisms that may inhabit other regions. ‘ Possession is nine points of the law”’ of organic survival, as it is said to be else- THE ELEMENTS OF ORGANIC EVOLUTION. 85 where. Possession and not abstract fitness has deter- mined the nature of the island faunz, lake faune, and isolated faunz and flore generally. ‘This is shown by the rapidity by which the species composing these be- come extinct when brought into competition with the more persistent forms which the continent has developed. But as all this represents a natural adjustment pro- duced by natural relations as distinguished from artifi- cial selection produced by the act of man, we may still include it under the head of natural selection. What- ever result is brought about in the struggle for exist- ence by the action of natural forces without human aid is natural selection in the sense in which Darwin used the term. The term “fitness’’ as used in these discussions means, of course, only the power to win in the peculiar kind of contest that may be in question, no moral ele- ment and no element of general progress being necessa- rily involved. In the question of fitness or unfitness the question of goodness or badness is only incidentally concerned. To be fit, in the biological sense, is not necessarily to be good, except as in the long run altruism promotes individual power and strength. The struggle for existence appears under a three- fold form: the struggle of creatures with like creatures, the struggle with unlike forms, and the struggle with the conditions of environment. In general, when the environment is most favourable, the competition of in- dividual with individual will be most severe. Where this environment is alike favourable for many different forms or species, the struggle between species and spe- cies becomes intensified. Where conditions are adverse, the number of forms able to maintain themselves will be smaller, but those which acquire adaptation, not , 86 FOOT-NOTES TO EVOLUTION. being crowded by competing forms, often exist in count- less numbers. The distribution of fishes may illustrate this. The most favourable condition for fish life is found about coral reefs, in the clear, equable waters of the tropics. Here many forms find favourable conditions, but the competition among their individuals is severe. In arctic waters but few species appear; the most are ex- cluded by the temperature itself. But these few forms are represented each by myriads of individuals. Only a few kinds can enter into competition. The struggle is not that of species against species; it is the survival of those that can react from the environment, that can maintain themselves against the hard conditions of life. But these conditions are not hard to these individuals who survive. The arctic life is the life they are fitted for. The struggle for existence is not felt as a stress or strain by the adapted. Hence comes the fact noticed by Darwin, that, while all intelligent men admit the struggle for existence, very few realize it. Men in general are fitted to the struggle endured by their ancestors, as they are fitted to the pressure of the air. They do not realize the pressure itself, but only its fluctuations. Hence it comes that many writers have supposed that the struggle for exist- ence belonged only to animals and that man is or should be exempt from it. Competition has been identified with injustice, fraud, or trickery, and it has been supposed that some act of legislation would put an end to it for- ever. But competition is inseparable from life. The struggle for existence may be hidden in social conven- tions, but it can never be extinguished. Nor should it be, for it is the essential force in the progress of life. Malthus’s law of population, often quoted, is in sub- stance this: Man tends to increase by a geometrical THE ELEMENTS OF ORGANIC EVOLUTION. 87 ratio—that is, by multiplication. The increase of food supply is by arithmetical ratio—that is, by addition; hence, whatever may be the ratio of increase, a geo- metrical progression will sooner or later outrun an arith- metical one. Hence, sooner or later the world must be overstocked, did not vice, misery, or prudence come in as checks, reducing the ratio of multiplication. This law has been criticised as a partial truth, so far as man is concerned. This means simply that there are factors also in evolution other than those recognised by Mal- thus. Nevertheless, Malthus’s law is a sound statement of one great factor. And this law is simply the ex- pression of the struggle for existence as it appears among men. In a world limited in extent and in possibilities, any rate of increase among organisms must bring about a struggle for existence. The ratio of increase is a mat- ter of minor importance, for each species would fill up the whole world at last. It is the ratio of actual net increase above loss which determines the fate of a spe- cies. Those increase and maintain themselves in which the death rate does not exceed the rate of increase. Those who live “beyond their means” must sooner or later perish. Thus it comes about through natural selection that there is everywhere seemingly perfect adaptation, the “fitting of the dough to the pan,” of the river to its bed. But this fitting is never wholly perfect, for still more complete adaptation may come; and as conditions change adaptations must changealso. Progress follows organic dissatisfaction. Where there is no reason for change there is no progress; degeneration may set in, and de- generation of one sort or another follows withdrawal from the current of the struggle for existence. ‘ What- ever is desirable,” says Weismann, “ becomes necessary 88 FOOT-NOTES TO EVOLUTION. as soon as it is possible.” Whatever is not needed tends to decline and disappear. In our discussion of social evolution we need some- times to remember that the very perfection of society must always appear as imperfection; for a highly devel- oped society is dynamic. It is moving on. A static society, no matter how perfect it may seem, whether a Utopia, Icaria, or City of the Sun, is in a condition of ar- rested development. Its growth has ceased, and its per- fection is that of death. The most highly advanced social conditions are the most unstable. The individual man counts for most under those conditions; for the growth of the individual man is the only justification for the institutions of which he forms part. The most highly developed organism shows the greatest imperfec- tions. The most perfect adaptation to conditions needs readaptation, as conditions themselves speedily change. The dream of a static millennium, when struggle and change shall be over, when all shall be secure and happy, finds no warrant in our knowledge of man and the world. Self-realization in life is only possible when self-per- dition is also possible. When cruelty and hate are excluded by force, charity and helpfulness will go with them. Strength and virtue have their roots within man, not without. They may be checked but they can not be greatly stimulated by institutions and statutes. In this connection we have also to remember that the struggle for existence in human society does not mean brutality. It is not necessarily a war to the knife, nor a struggle with fists nor with balances of trade. The elements of ultimate success in the struggle are not teeth, nor claws, nor brute strength, nor trickery. Through all the ages love has been stronger than force; and those creatures who could help each other have been stronger than those who could only fight. THE ELEMENTS OF ORGANIC EVOLUTION. 89 By good or right in human development we mean simply the opportunity for more life or higher life. That is good which makes me strong and gives strength tomy neighbours. Might does not make right, but what- ever is right will justify itself in persistence, and per- sistence is strength. That which is weak dies. We only know God’s purposes by what he permits. That which persists and grows must be in line with such pur- poses. A law is only an observed generalization of what is. There is no law which reads, ‘ This and this ought to be, but is not.” V. Self-activity—Another factor in evolution is fur- nished by the functional activity of the individual. Nature is a thrifty investor. She withdraws all unused capital. The old parable of the talents, wherein the owner of the unused talent lost all that he had, describes the workings of Nature. The unused organ loses its power and dwindles away. What comes out of a man de- termines his character. What he has done in the past furnishes the law of his future. The essence of indi- vidual character building, with the lower animals as with man, lies in action. Whatever he is he must make of himself. Heredity only furnishes the tools, and the en- vironment is the leverage. Nor is this great law con- fined to animals alone. Even with plants the function must justify the organ. The branch which does not carry sap withers and dies. The fruit which does not Tipen is cast to the ground. In a sense, too, the func- tion must precede the organ. Where something is to be done, there will arise a special method of doing it, and the organ which supplies this better method will survive in natural selection. Among the higher animals functional activity is the basis of individual happiness. There is no permanent feeling of joy except through functional activity. Dis- 90 FOOT-NOTES TO EVOLUTION. sipation, Stimulation, tricks on the nervous system of any sort whatever give only a counterfeit happiness. Subjective joys are followed by subjective misery. There is “no pleasure in them.” “The very fiends weave ropes of sand rather than taste pure hell in idle- ness.” There is a wild joy in “ Nature red in tooth and claw ” that is not found in static life. And while higher development brings higher pleasures, these bear the same relation to self-activity. The pressure of envi- ronment gives only pain in itself. Ennui is chronic pain, Nature’s warning against the dry rot of functional inactivity. To enjoy life, man or animal must be doing, working, thinking, fighting, loving, helping—something positive. And no thought or feeling of the mind is com- plete till it has somehow wrought itself into action. VI. Altruism.—Another of the great forces in or- ganic development is mutual help, or altruism. Where organisms come into any sort of relation one with an- other, there must be some conditions more favourable than others. The law of altruism is the expression of the best relation of one organism to another of its own kind or type. The words good, better, are expressive of human affairs. They are subjective terms, referring to the welfare of the individual. In the general sense, that is good which makes more or higher life possible. That is good in Nature which “ gives life more abun- dantly.” It is good to “make two blades of grass grow where only one grew before.”’ It is good also to make possible the growth of a specialized and highly adapted form, where only creatures of a lowly organization had existed before. Altruism is the expression of the per- manence of mutual respect and mutual forbearance. The rule we call golden is the expression of strength as well as of right. It is not true that “might is right” THE ELEMENTS OF ORGANIC EVOLUTION. gI in the narrow sense in which that phase is commonly used ; but it is true that what is right will justify itself sooner or later by becoming might. Cruelty, vice, and selfishness are wrong as the expression of weakness, of low vitality, of conditions which make abundance of life impossible. Altruism is in no sense confined to man. There is no part of the animal kingdom in which it is unknown, no part of the vegetable kingdom without its traces. Favourable interrelations are possible wherever life is. The expression of such relations is altruism. It can be shown that social virtues are powerful aids to survival in the struggle for existence. The race is not “to the swift” nor “the battle to the strong,” but “to them who can keep together.” The care of the young isa far more effective agency in the survival of the species than iron muscles or huge jaws. The will- ingness to die for the young is a guarantee that the young may live. “More ancient than competition,” says Oscar Mc- Culloch, “is combination. The little, feeble, fluttering folk of God, like the spinning insects, the little mice in the meadow, the rat in the cellar, the crane on the marshes, or the booming bittern—all these have learned that God’s greatest word is together and not alone. He who is striving to make God’s blessing and bounty possible to most is stepping into line with Nature. The selfish man is the isolated man.” Altruism is a robust sentiment set deep in the breast of organic life, and not in danger of extinction. It is as old as selfishness and as hard to eradicate. It no more needs coddling than hunger does. It depends on no external sanction, for the creatures without altruism pass away, leaving no descendants. There is a bounty on their heads, whether they be wolves or hawks or men. g2 FOOT-NOTES TO EVOLUTION. Altruism expresses itself in all that make the human life sane, joyous, effective. Science is herself a con- summate result of the altruism of the ages, whereby no man’s experiences belong to himself alone, but become part of the heritage of those who follow him. Human institutions have grown out of the social instinct. They are the fossils of past altruism. All forms of art, litera- ture, music, religion, arise and are developed through mutual help. And while the relations of altruism tend to limit the freedom of the individual, it is only through such limitations that the individual can develop in security or in realfreedom. In the very beginnings of life appear the beginnings of altruism. Among the one-celled animals or pro- tozoa is seen the rela- tion of mutual help. In the conjugation of cells among these crea- tures appear the begin- nings of the gigantic fact of sex. By this pro- cess two minute one- celled creatures come together, and part of the hereditary substance of the one is exchanged for that of the other. After this exchange neither the one nor the other is exactly what it was before. The results of this change are propagated in the descendants of each. The ultimate purpose of the exchange is to produce and promote variety in life, That is the ultimate purpose of the whole sex relation. From the beginning to the end it is essentially altruistic, Fic. 4.—Conjugation of infusoria. THE ELEMENTS OF ORGANIC EVOLUTION. 93 It never becomes selfish except in its perversion. Its perversion is its destruction. And from the simple altru- istic beginnings of the conjugation of cells in those simple organisms arise with evolution all the complex possibilities of love, conjugal, filial, and parental. In another way the altruistic tendencies are shown in the aggregation of cells. Among animals of one cell the ordinary processes of division give rise to a new organism for each division. But if the new cells formed by such subdivision still remain attached to each other, a complex organism is built up. It is thus that the single germ cell in the higher animals grows into the embryo, and the embryo through the stages of infancy and youth into the adult organism. The co-operation of the members of the colony of cells of which the compound animal is composed makes possible all the various forms of organic differentiation. A single cell is a unit, complete in itself and inde- pendent. All the functions possible to it are united in a single structure. With a complex organism the dif- ferent cells are gathered into groups to form tissues. Out of these tissues different organs are built up, and each different organ performs a distinct function. In the compound structure of man a multitude of cells are joined to perform the work of assimilation, and a host of others purify the blood; to another multitude is as- signed the task of locomotion. Still others, of finer tex- ture, receive impressions of external things and trans- mit these impressions into the phenomena of motion. Specialization, differentiation, organization, and the ex- quisite functions of nerve tissue, are all resultants of the altruistic co-operation of cells. As individual men under altruistic impulses unite together to form societies and states, so are individual cells gathered together to form the human body. The conjugation of cells is a method 94 FOOT-NOTES TO EVOLUTION. by which life is continued and renewed in an endless chain which death has never broken. The aggregation of cells gives rise to all that makes life effective. But the division of labour and specialization of parts brings death to the individual. Sooner or later the correlation of parts must be broken and the outworn individual must give place to one freshly formed. The gains through altruism as a factor in evolution can not be overstated. Love and kindness, specializa- tion and adaptation, instinct and intelligence—all these belong to its biological results. In human society mutual help has given science, which is the garnered wisdom of society. It has given art, education, religion. All these are in one way or another related to the good or pleasure of others. From altruism institutions arise, and institutions bring security and effectiveness. To all this there is, of necessity, another side. All the gifts of the gods have some drawback connected with them. This is the so-called law of compensation. Mutual help leads to mutual dependence. Combination destroys absolute freedom in making freedom worth having. Alliances degrade as well as help, for the needs and functions of the individual are lost in those of the alliance. The single cell is self-sufficient, independent, and, until altruisic relations come in, immortal. As Weismann has shown, the subdivision of the single cell, by which it divides into two similar cells, is not homol- ogous with death. Death is a necessary attribute of compound animals only. It is the price paid for special- ization. If it be true, as is claimed, that the cells pre- vented from conjugation ultimately die a natural death, still this death is a price paid for altruism. It did not exist before combination became possible. In like fashion the growth of society has abridged the freedom of the individual man in making that free- THE ELEMENTS OF ORGANIC EVOLUTION. 95 dom worth having. Mutual help in society has brought about mutual dependence. It has at the same time brought a security and strength which must be forever impossible under purely individualistic conditions. The tendency for organisms to join together for mutual aid is therefore one of the primal tendencies of life. It is involved in the very definition of life itself. It can never become outworn or exhausted. It must in greater and greater degree rule the hearts of men, as men be- come wiser, purer, stronger in the progress of evolution. “In the very nature of things God has made this law of mutual aid so strong that he has impressed and stamped it on the life of everything that breathes.” As the cell is related to the tissue, so is the individual man connected with society. The essential difference is the obvious one that the individual man moves, lives, and dies as an individual, while the individual cell is confined to its place by physical limitations. In recognising the fact that the parallelism exists, it is not necessary to push it too far. From the aggre- gation of cells results specialization of parts, division of labour among organs, progress, and adaptation; and ultimately from the same source springs the necessity for organic death. Being bound together by physical bonds, the wearing out of one organ means the decay of the whole. In like manner, from the altruism of the individual results the strength of the state, the division of labour among men, and the consequent increase of effectiveness, the progress of knowledge, and the ameni- ties of life. Wedo not need to say that a society or a nation must die for like reasons, for its units are bound not by physical bonds, but by invisible forces, and the wearing out of one organ could not necessarily destroy the whole. But the complex animal and the complex society are alike manifestations of the law of altruism, 8 96 FOOT-NOTES TO EVOLUTION. And, as Dr. Amos Griswold Warner has wisely observed, no species and “no race ever became extinct through an excess of brotherly love.” VII. /solation.—A great factor in the production of variant forms is the isolation of groups of individuals from the mass of their species. The barriers of the earth, separating one group of individuals from other individuals of the same kind, cause them to be exposed to different influences. The reaction from environment is different in one case from another. Asa result, the presence of barriers shows itself in specific variation. Each species of animal or plant tends to extend and to cover the world. That a given species has not occu- pied any certain area is due to one of three causes: either (a) the species has never entered the district; or (4), having entered it, it could not maintain itself; or (c), having maintained itself the changed conditions have made of it another species. Thus we may say that the reason why the civet cat is not found in New England is because it has never been able to reach that district in its movements. The skylark, which has been brought there, has not main- tained itself because, in the individual cases at least, it could not; while the European rabbit, introduced years ago into Porto Santo in the Madeiras, does not exist because its descendants are so much altered that we can not recognise them as the same species. With one of these three general propositions, self- evident, no doubt, all the facts of geographical distribu- tion may be ccnnected. Each species extends its range wherever it can, maintains itself if itcan, and undergoes change wherever its members are brought into new conditions or separated by barriers from the mass of their kind. The characters to be attributed directly to isolation THE ELEMENTS OF ORGANIC EVOLUTION. 97 are for the most part those of minor importance, the superficial traits of the species rather than the deep- seated qualities of the group. But these are none the less real, and to this series of influences much of the variety of the life of the globe must be attributed. The survival of the existing, which is the basis of most of the distinctions between one species and another, is not less real than the survival of the fittest. In making up the fauna or flora of any region, those creatures actually present must leave their qualities as an inheritance. If they can not maintain themselves, their type passes away as unfit. If they maintain themselves in isolation, their characters become persistent as those of the new species. Still other factors in organic evolution may be more or less clearly defined, either in connection with those above mentioned or as fundamentally distinct. One of these is the following: The transmission of characters of the parent as distinct from proper hered- ity. A starved hill of corn means ill- nourished grains. The plants produced from ill-nourished seeds may be stunted by lack of vitality or lack of starch without any change or deficiency in the germ itself. In like manner feeble children may owe their traits to the temporary illnesses of a strong mother. A sound mind demands a sound body, and a sound body is necessary to well-nourished offspring. With the characters of the germ cell these conditions have nothing to do, and their homologue is found in such defects as insufficiency of milk. VILL. Lnheritance of Acquired Characters—The in- heritance of acquired characters mentioned above, a process of transmission possibly different from germ heredity, has been lately the subject of much discussion. Survival of the existing. ; Nutrition in transmission. 98 FOOT-NOTES TO EVOLUTION. To this the present writer does not care to add. Ac- cording to some writers, as Herbert Spencer, this inheri- tance is a prominent factor in evolution itself. Accord- ing to August Weismann, it is simply a myth invented to explain phenomena the causes of which are unknown. Most of the arguments on both sides, thus far, have been theoretical only, based on no inductive evidence, and in science arguments of this sort are without value. Both suppositions rest, as Prof. Henry Fairfield Os- born has said, less “in fact than the logical improbabili- ties of other theories.” “Certainly,” Professor Osborn goes on to say, “we shall not assist research with any evolution factor grounded upon logic rather than upon inductive demonstration. A retrograde chapter in the history of science would open if we should do so, and should accept, as established, laws which rest so largely upon negative reasoning. Darwin’s survival of the fit- test we may alone regard as absolutely demonstated as a real factor without committing ourselves as to the ori- gin of fitness. The (next) step is to recognise that there may be an unknown factor or factors which will cause quite as great a surprise as Darwin's. The feeling that there is such first came to the writer in 18go, in considering the want of an explanation for the definite and appar- ently purposeful character of certain variations. Since then a similar feeling has been voiced by Romanes and others, and quite lately by Scott, but the most extreme expression of it has recently come from Dr. Driesch in the implication that there is a factor not unknown but jf unknowable! . . . We are far from finally testing or dis- | missing these old factors, but the reaction from specula- © tion upon them is itself a silent admission that we must | reach out for some unknown quantity. If such does | exist there is little hope that we shall discover it except | The unknown factors. THE ELEMENTS OF ORGANIC EVOLUTION. 99 by the most laborious reseatch; and while we may pre- dict that conclusive evidence of its existence will be found in morphology, it is safe to add that the fortunate discoverer will be a physiologist. “Chief among the unknown factors are the relations between the various stages of development and the en- vironment.” Professor Osborn concludes this discussion with the belief that “ progressive inheritance is rather a process of substitution of certain characters and potentialities than the actual elimination implied by Weismann. ‘“ My last word is,” he says, ‘‘ that we are entering the thresh- old of the evolution problem instead of standing within the portals. The harder tasks lie before us, not behind us, and their solution will carry us well into the twenti- eth century.” IV, THE FACTORS OF ORGANIC EVOLUTION FROM THE STANDPOINT OF EMBRYOLOGY. By PRoF. EDWIN GRANT CONKLIN. Our knowledge of the mechanics of evolution must always depend in large part upon the study of indi- vidual development. More than any other science, embryology holds the | keys to the method of evolution. If on- | togeny (life history of the individual) is | not a true recapitulation it is at least a true type of evo- | lution, and the study of the causes of development will go far to determine the factors of phylogeny or race | development. | The causes and methods of evolution are intimately | bound up with those general phenomena of life, such as | assimilation, growth, differentiation, metabolism, inher- | itance, and variation; and the evolution problem can | never be solved except through a study of these general | phenomena of life itself. Our great need at present is | not to know more of the course of evolution, but to dis- | cover, if possible, the causes of growth, differentiation, | repetition, and variation. All these general phenomena | are most beautifully illustrated in the development of | individual organisms, and because they are fundamental | to any theory of evolution I shall dwell upon them | 100 Embryology shows the meth- od of evolution. THE FACTORS OF ORGANIC EVOLUTION. jor rather than upon the evidences for the Lamarckian or the Darwinian factors. I call attention very briefly to the following propo- sitions: 1. Development, and consequently evolution, is the result of the interaction of extrin- sic and intrinsic causes. 2. Intrinsic causes are dependent upon protoplas- mic structure. 3. Inherited characters must be prede- termined in the structure of the germinal protoplasm. 4. Germinal, as compared with somatic,* protoplasm is relatively stable and continuous, but not absolutely so, as maintained by Weismann; therefore, extrinsic causes ‘may modify both germinal and somatic protoplasm. 5. It is extremely difficult to determine whether or not extrinsic factors have modified the structure of the germinal protoplasm. This is illustrated by some of the evidences advanced for the inherited effects of diminished nutrition, changes in environment, use and disuse. 6. Experiment alone can furnish the crucial tests of these Lamarckian factors. 1. The causes of development in general are usually recognised as twofold—extrinsic and intrinsic. As ex- amples of extrinsic causes may be men- tioned gravity, surface tension, light, heat, moisture, and chemism in general ; examples of intrinsic causes are the non-exosmosis of salts from living bodies in water, the pouring of a glan- dular secretion or the sap of plants into a cavity under high pressure, the active changes in shape and position on the part of cells, assimilation, growth, division, etc. There is not, however, a uniformly sharp and distinct line of demarcation between these two factors of develop- Statement of propositions. Causes of de- velopment. * Somatic cells are those composing the tissues of the body as distinguished from germ cells—those destined to form the new organism. 102 FOOT-NOTES TO EVOLUTION. ment. Phenomena once supposed to be due entirely to intrinsic Causes are now known to be the result of ex- trinsic ones, and it is practically certain that this will be found true of still other phenomena. But although it is not possible to draw any hard and fast line between these two classes of causes, one can, in general, recog- nise a very marked difference between them. Extrinsic causes may, in large part, supply the stimulus and the energy for development, and may more or less modify its course; the intrinsic causes are of a much more com- plex character than the extrinsic ones, they are inher- ent in the living matter and in large part predetermine the course of development. In one form or another the distinction between these two classes of causes is recog- nised by all naturalists. Professor His calls the intrinsic causes “ the law of growth,” the extrinsic ones the con- ditions under which that law operates. These designa- tions correspond, at least in part, to Professor Cope’s anagenesis and katagenesis, and to Roux’s “ simple and complex components ” of developmental processes. While it is necessary to emphasize the differences between these two classes of causes, it is not intended thereby to dogmatically assert their total difference in kind. It may well be that these extrinsic and intrinsic causes are totally different in kind, but in our present state of ignorance it would be unjustifiable to affirm it. On the other hand, it would be just as unwarrantable to dogmatically affirm that there is no difference in kind between these two classes of causes, and that, therefore, — all vital phenomena are only the manifestations of heat, light, electricity, attraction, repulsion, chemism, and the like. It may be that this is true, but there is as yet no sufficient evidence for it, and to attempt, as certain dynamical and mechanical hypotheses do, to refer all vital phenomena directly to such simple components as THE FACTORS OF ORGANIC EVOLUTION. 103 those named above is practically to make impossible at present any explanation of vital phenomena. “If we would advance without interruption,” says Roux,* “ we must be content, for many years to come, with an analy- sis into complex components.” 2. We need not now further concern ourselves with an explanation of extrinsic causes or simple components, since this subject properly belongs to chemistry and physics. If, however, we examine more closely some of the 7”- trinsic Causes or complex components, we will find that they are always associated with more or less complex structures ; in fact, they are dependent upon structure. The smallest and simplest mass of protoplasm that can manifest all the fundamental phenomena of life, such as assimilation, growth, division, and metabolism, is an entire cell, nucleus and cytoplasm, and probably centrosome. The cell is composed, as microscopic study plainly reveals, of many dissimilar but perfectly co- adapted parts, each performing its specific function, and it may therefore properly be called an organism. Some phenomena of cell life may be directly referred to the various visible constituents of the cell, but many of them are evidently connected with structures which we can not see, structures which may perhaps never be seen, and yet which must be vastly more complex than the most complex molecules known to chemistry, and yet much more simple than the microsomes, centro- somes, and chromosomes which are visible in the cell. With these ultra-microscopical particles many of the most fundamental phenomena of life are associated— Viz., assimilation, growth, metabolism, and probably Intrinsic causes arise from nature of protoplasm. * Wilhelm Roux. Einleitung: Archiv fiir Entwickelungsmecha- nik der Organism, 104. > FOOT-NOTES TO EVOLUTION. differentiation, repetition, and variation. These func- tions are so co-ordinated that there can be no question that the ultra-microscopical structure is an organization, with part coadapted to part. The organization of the cell, therefore, does not stop with what the microscope reveals, but must be supposed to extend to the small- est ultimate particles of living matter which manifest specific functions. These are the vital units so gener- ally postulated, the “smallest parts” of living matter, as they were called by Briicke, who first demonstrated that they must exist; the ‘“ physiological units” of Spencer, the “gemmules” of Darwin, the “ micella groups” of Nageli, the “ pangenes” of De Vries, the “plasomes” of Wiesner, the “idioblasts” of Hertwig, the ‘“biophores” of Weismann. Such ultimate units have been found absolutely necessary to explain those most fundamental of all vital phenomena, assimilation and growth, while many other phenomena, especially particulate inheritance, the independent variability of parts, and the hereditary transmission of /atent and patent char- acters, can at present only be explained by referring them to ultra-microscopical units of structure. To deny that there are such units does not simplify the problem, as some seem to suppose, but renders it impossible of ap- proach. A corpuscular hypothesis of life, like that of light, may be only a temporary makeshift, but it is better than nothing. Whitman * well says: “ Briicke’s great merit consists in this, that he taught us the necessity of assuming structure as the basis of vital phenomena, in spite of the negative testimony of our imperfect microscopes. That function presupposes structure is now an accepted axiom, and we need only extend Briicke’s method of *C.O. Whitman. The Inadequacy of the Cell Theory of De- velopment. Biological Lectures, 1893. THE FACTORS OF ORGANIC EVOLUTION. 105 reasoning from the tissue cell to the egg cell in order to see that there is no escape from the conclusion that the whole course of developmental phenomena must be referred to organization of some sort. Development, no less than other vital phenomena, is a function of organization.” 3. A study of the phenomena of development, as well as the principle of causality, make it certain that all the characters of the species are pre- Inherited charac- determined within the protoplasm of the ters predeter- fertilized egg cell. From a frog’s egg mined in struc- s : Mire oh ecum cell. only a frog will develop, from an echino- derm egg only an echinoderm, and the course of the development is, under normal circum- stances, definitely marked out in each case, even down to the minutest details. All the results of experiment, as well as observation and induction, only serve to render this conclusion the more certain. It should be observed that to affirm that characters are predetermined is a very different thing from saying they are preformed. The one merely asserts that the cause of the transforma- tions which lead from one step to another in the devel- opment is determined by the initial conditions of the fertilized egg cell; the other affirms that those trans- formations have already taken place. The absolute determinism of development depends primarily upon the constant structure of the egg cell, but also to a certain extent upon a definite relation to extrinsic factors. Since, however, these extrinsic fac- tors may be exactly the same in two cases, and yet the result of development be very different (e. g., the egg of the starfish and that of the sea urchin), we can only conclude that while ontogenetic differences may be caused by a disturbance of the extrinsic factors, imhertted characters are always the result of a definite structure of 100 FOOT-NOTES TO EVOLUTION. the germinal protoplasm, and that, therefore, develop- ment is, in the words of Professor Whitman, “a function of organization.” Inheritance and variation are general terms which include a great many different kinds of phenomena, many of which seem to be due to entirely different fac- tors. A great many phenomena of inheritance seem to be due entirely to extrinsic forces, but a more careful inquiry always reveals the fact that they are invariably due to the reaction of certain extrinsic causes on a per- fectly definite living structure. As examples may be mentioned the following: (z) The tiger-like striping of the egg of Fundulus, which is very characteristic and would certainly be re- garded as an inherited character, has been shown by Loeb* to be due entirely to the position of the blood vessels of the blastoderm. The pigment cells are at first uniformly distributed, but when the blood vessels are formed they gather around them, probably through chemotropic action, and thus the characteristic banded appearance is produced. Graf} has since shown that the colour patterns of leeches are produced in the same way. It is not necessary, therefore, to assume that the colour patterns in these cases are specifically represented in the germinal protoplasm; it may even be that the position of the blood vessels is not so represented, but there must be some ultimate cause back in the germinal plasm itself which determines the series of causes which finally produces the colour patterns. In short, this fea- ture, like most others, was predetermined from the be- ginning. * Jacques Loeb. Some Facts and Principles of Physiological Morphology. Biological Lectures, 1893. + Arnold Graf. Ueber den Ursprung des Pigments und. der Zeichnung bei den Hirudineen. Zool. Anzeiger, No, 468, 1895. THE FACTORS OF ORGANIC EVOLUTION. 107 (2) Herbst * has shown in a series of interesting ex- periments that by the use of various chemical substances the development of echinoderms may be profoundly modified. For example, in sea water deficient in cal- cium chloride, or in which there is an excess of potas- sium chloride, the Pluteus larva, instead of developing calcareous spicules and the long ciliated arms which give the normal larva an angular, easel-shaped appear- ance, remains rounded in shape much like the larva of Balanoglossus, in which no spicular skeleton is developed. The withdrawal, therefore, of certain normally present substances from the environment may profoundly modi- fy the final result. But in this case, as in the other, it is absolutely certain that the calcareous spicules were pre- determined in the egg cell, although in the absence of calcareous matter from the water those spicules could not be built—the plan was there, but the building ma- terial was lacking. Such modifications resulting from unusual conditions of pressure, temperature, density, nutrition—in fact, any alteration of the chemical or physical environment—may appear in any stage of development from the unseg- mented egg to the adult condition, but it must not be supposed that the entire development can be reduced to such factors. Loeb argues that we do not inherit our body heat from our parents because it depends upon certain chemical processes; but is it not absolutely cer- tain that we inherit a certain protoplasmic structure which determines those chemical processes, and hence the body temperature? To assume that extrinsic causes determine whether there shall hatch from an egg a chicken or an eagle is the sheerest nonsense. The’ study of extrinsic factors in relation to inheritance will * Zeit. wiss. Zool., Bd. lv. 108 FOOT-NOTES TO EVOLUTION. serve to simplify some of the intricate problems to be explained, but surely no one believes that development can ever be referred entirely to such factors. The fact is that determinism, which is the most fundamental characteristic of inheritance, is manifested at every step of development, and there is certainly no escape from the conclusion that this determinism depends upon pro- toplasmic structure, and that this structure it is which is transmitted from generation to generation, and which forms the physical basis of inheritance. All really inherited characters must, therefore, be represented in the structure of the germinal protoplasm, and must consequently be present from the beginning of development. ‘We must consider it as a law derivable from the causality principle,” says Hatschek,* “that in the phylogenetic alterations of an animal form the end stages are not alone altered, but the entire series from the egg cell to the end stage. Every alteration of an end stage or addition of a new one must be caused by an alteration of the egg cell itself.” Nagelit has ex- pressed a similar view in the following famous sentence: “ Egg cells must contain all the essential characteristics of the species as perfectly as do adult organisms, and hence they must differ from one another no less as egg cells than in the fully developed state. The species is contained in the egg of the hen as completely as in the hen, and the hen’s egg differs as much from the frog’s egg as the hen from the frog.” 4. The remarkable tenacity of inheritance, as shown especially in reversions and the preservation of useless and embryonic characters through many hundreds or * Berthold Hatschek. Ueber die Entwickelungsgeschichte von Toredo. Arb. Zool. Inst., Wien, 1880. + Nageli. Mechanisch-physiologische Theorie der Abstam- mungslehre, 1884. THE FACTORS OF ORGANIC EVOLUTION. 109 thousands of generations, and amid the most diverse circumstances, bears strong testimony to the great sta- bility of that living structure which is the basis of in- heritance. On the other hand, all experience goes to prove that the living substance of the body cells in gen- eral is readily modified, and that in a surprisingly short time. The fact of this great difference can not fail to be recognised ; its cause is at present merely a matter of conjecture. Weismann at one time supposed the cause of this to be an absolutely stable, absolutely separate, and per- petually continuous germ plasm. How- Germinal proto- eyer, there is the most convincing and plasm relatively abundant evidence that although the but not abso- : 5 Bicly stable. germ plasm is relatively very stable and continuous, it does not possess those divinely perfect characters ascribed to it. More re- cently Weismann has practically abandoned each and all of these characters,* and now, like a good Lamarck- ian, finds “the cause of hereditary variation in the direct effects of external influences on the biophores and determinants.” The outcome of the whole matter, then, is that we find ourselves much in the same position as we were be- fore Weismann denied the possibility of the inheritance of acquired characters. Al hereditary variations are caused by the action of extrinsic forces on the germinal pro- toplasm, producing changes in its ‘structure. Strangely enough, this proposition was admitted as a logical neces- sity by one who undertook by rigorous logic to prove the reverse. Since almost the only objection to this position was the one raised by Weismann, it may now be considered as definitely settled, and the only ques- * See Romanes’s Examination of Weismannism, 1893. 110 FOOT-NOTES TO EVOLUTION. tion before us, then, is: How can extrinsic causes modify the structure of the germinal protoplasm ? Since by his own admissions, as Romanes has shown, the most characteristic features of Weismann’s system, both as to inheritance and evolution, have been virtually abandoned, it seems to some that his theories have been of no real value, and that, like an zgnis fatuus, they have only served to lead biologists astray far from the path of science into the dangerous quagmires of speculation. I do not share any such opinion. Apart from his splen- did observations and the great stimulus to investigation which Weismann’s theories have furnished, there remain many elements of permanent value in his work. Osborn* thinks that Weismann’s most “ permanent service to biology is his demand for direct evidence of the Lamarckian principle.” It seems to me that his greatest service consists in the emphasis which he has laid upon the intrinsic factors of development and evo- lution as opposed to the extrinsic factors, a thing which he has indeed overemphasized but which has sadly needed a strong defender in these later years. Largely as an outcome of his work we now recognise the possi- bilities and the limitations of the selection theory as never before, and we also recognise that many of the evidences which were adduced in support of the La- marckian factors are not conclusive, while the method of securing conclusive evidence is clearly marked out. Whatever we may think of his theories, this certainly is no slight service. 5. It is by no means an easy task to determine whether the influence of extrinsic forces has really reached the germinal protoplasm and modified its struc- ture; much more difficult is it to determine how that * Osborn. The Unknown Factors of Evolution. Biological Lectures, 1894. THE FACTORS OF ORGANIC EVOLUTION. f11II modification takes place. I believe it is safe to say that a majority of the cases which are supposed to prove the inheritance of acquired characters prove only that char- acters are acquired, not that they are Do external inherited. There is great need of cau- Bee tion against supposing that any charac- Bee issn’ ter is inherited unless it repeats itself under many and different conditions. Apart altogether from inheritance, similar conditions may produce similar results, and consequently this source of error must be eliminated if we would be cer- tain that the structure of the germinal protoplasm has really been modified. Many of the alleged cases of the inheritance of mutilations, of the direct influence of the environment, and of use and disuse, fall away under this precaution. The general evidence for the inheritance of mutila- ‘tions is so notoriously bad that I pass it by altogether and select for consideration a few cases, chosen from a ‘recent work on the subject,* which have by various writers been alleged as showing the direct influence of ‘environment in modifying species and also the inherited effects of use and disuse. . | (a2) It is well known that certain gasteropods if reared in small vessels are smaller than when grown in large ones, and this case has been cited meoened as showing the influence of environment oo in modifying species. There is good evidence, however, that this modification does not affect the germinal protoplasm, for these same gasteropods will grow larger if placed in larger vessels. It seems very probable that the diminished size of these animals is due to deficient food supply, but this has so little | *E. D. Cope. The Primary Factors of Organic Evolution, 1896, | | g 112 FOOT-NOTES TO EVOLUTION. modified the somatic protoplasm that, although they may be fully developed as shown by sexual maturity, they at once increase in size as soon as more abundant food is provided, and this takes place by the active growth and division of all the cells of the body. In higher animals, once maturity has been reached, there ig little chance for growth, apparently because many of the cells are so highly differentiated that they can no longer divide; consequently the growth is limited, and hence the size of the adult may depend in part upon the amount of nutriment furnished to the embryo. This limitation of growth is due to the high degree of dif- ferentiation of the somatic cells. But as the germ cells are not highly differentiated and are capable of di- vision, it follows that they would not be permanently modified by starving. It may be, as Professor Brewer argues, that long-continued starving and consequent dwarfing of animals may leave its mark on the germinal plasm; but, as he also remarks, this influence must be very slight as compared with the cumulative effects of selection in breeding, and it is safe to assert that there is no such wholesale and immediate modification of the germinal plasm due to the influence of nutrition as some people seem to suppose. (4) The interesting experiments of Schmankewitsch in transforming one species of Artemia into another by gradually increasing the salinity of the | water, or in transforming Artemia into another genus, Branchinecta, by decreas- — ing the salinity of the water, are well known and are | often cited as illustrations of the fact that specific and | even generic differences may suddenly be produced under the influence of the environment. The very fact, | however, that these changes are suddenly produced, and | that they can at will be quickly modified in one direction Changes in environment. THE FACTORS OF ORGANIC EVOLUTION. ie te) or the other, is evidence that they are not represented in the structure of the germinal plasm; and the fact that definite extrinsic causes, such as salt or fresh water, act- ing upon this plasm, produce results which are con- stantly the same is the best evidence that the internal mechanism—i. e., the structure of the germinal plasm— is constantly the same. The same can be said of many artificially produced modifications, such as the exogas- trulas and potassium larve of Herbst, all of which pro- found changes are due entirely to extrinsic and not to intrinsic Causes, as is shown by the fact that they disap- pear as soon as the immediate extrinsic cause is with- drawn. The same thing is shown in Poulton’s experi- ments on the colours of lepidopterous larve, and in this case also it is known that the changes are not inherited, at least during the limited period through which the experiments were conducted ; and it should be observed that to assume that this would take place at the end of an indefinite number of generations is simply to beg the question. Very many other cases of a similar character might be instanced under this head, but I hasten on to another class of evidence. (c) Under the subject of the inherited effects of use and disuse the following cases may be mentioned as showing how inconclusive much of the evidence is: (x) In the first place, this whole line of argument starts with the assumption that the individual habits of an animal are inherited, and that these habits ultimately determine the structure, an assumption which really begs the whole question; for, after all, the substratum of any habit must be some physical structure, and if modified habits are inherited it must be because some modified structure is inherited. I take an example Use and disuse. 114 FOOT-NOTES TO EVOLUTION. which will serve as an illustration of a whole class: Jackson * says that the elongated siphon of Mya, the long-necked clam, is due to its habit of burrowing in the mud, or to quote his words: “It seems very evi- dent that the long siphon of this genus was brought about by the effort to reach the surface, induced by the habit of deep burial.” It certainly would be pertinent to inquire where it got this habit, and how it happened to be transmitted. It is surely as difficult to explain the acquisition and inheritance of habits, the basis of which we do not know, as it is to explain the acquisition and inheritance of structures which are tangible and visible. Such a method of procedure, in addition to begging the whole question, commits the further sin of reasoning from the relatively unknown to the relatively known. This case is but a fair sample of a whole class, among which may be mentioned the following: The derivation of the long hind legs of jumping animals, the. long fore legs of climbing animals, and the elongation of all the legs of running animals through the influence of an inherited habit. All such cases are open to the very serious objection mentioned above. (y) Another whole class of arguments may be re- duced to this proposition: Because necessary mechan- ical conditions are never violated by organisms, therefore modifications due to such conditions show the inheritance of acquired characters. Plainly, the alternative propo- sition is this: If acquired characters are not inherited, organisms ought to do impossible things. (z) Many of the arguments advanced to prove the inheritance of characters acquired through use or dis- use seem to me to prove entirely too much. For ex- Mechanical conditions. { * R, T. Jackson. Memoirs Boston Soc, Nat. Hist., 18go. I} | } THE FACTORS OF ORGANIC EVOLUTION. 115 ample, Professor Cope argues very ably that bones are lengthened by both stretch and impact, and that modifi- cations thus produced are inherited. Even granting that this is true, how would it be possible for this pro- cess of lengthening to cease, since in active animals the stretch and impact must be continual? Professor Cope answers that the growth ceases when “ equilibrium ”’ is reached. I confess I can not understand this explana- tion, since the assumed stimulus to growth must be con- tinual. But, granting again that growth may stop when an animal’s legs become long enough to “satisfy its needs,” how on this principle are we to account for the shortening of legs, as, for example, in the turnspit dog and the ancon sheep and numberless cases occurring in Nature? If any one species was able, by taking thought of mechanical stresses and strains, to add one cubit unto its stature, how could the same stresses and strains be invoked to decrease its stature ? These evidences are, I know, not the strongest ones which can be adduced in support of the Lamarckian factors. There are at present a relatively small num- ber of such arguments which seem to be valid and the great force of which I fully admit. But the cases which I have cited are, I believe, fair samples of the majority of the evidences so far presented, and in the face of such “evidence” it is not surprising that one who is himself a profound student of the subject and a con- vinced Lamarckian prays that the Lamarckian theory may be delivered from its friends.* 6. Another line of evidence, and by far the most promising, is that of direct experiment. So far, most of the experiments which have been carried on to deter- mine this question have been carried only halfway toa *H. F. Osborn. Evolution and Heredity. Biological Lec- tures, 1890. 116 FOOT-NOTES TO EVOLUTION. conclusion—they have shown that characters are ac- quired, they have usually failed to show that they are transmitted to descendants. Among animals one of the best-known cases is the inheritance of epilepsy and other disorders in guinea- pigs, due to certain nervous lesions of the parents. But Romanes,* who spent much time in trying to corroborate these results, concludes as fol- lows: “On the whole, then, as regards Brown-Séquard’s experiments, it will be seen that I have not been able to furnish any approach to a full corroboration.” Among plants, on the other hand, there is more and better experimental evidence, but it is not by any means as full or satisfactory as could be wished. Of one thing we may be certain—a satisfactory solution of the prob- lem can be reached only by experiment. The mere observations and inductions of the morphologist, while affording valuable collateral evidence, can never furnish the crucial test. As long as we deal merely with proba- bilities of a low order there will be profound differences of opinion—e. g., Cope believes in all the Lamarckian factors ; Romanes rejects use and disuse, but believes in the others; Weismann rejects all of them. Why? Is it because each does not know the facts upon which the others build? Certainly not. Those so-called facts are merely probabilities of a higher or lower order, and to one man they seem more important than to another. No conviction based even upon a high degree of proba- bility can ever be reached in this way. There is here a deadlock of opinion, each challenging the other to produce indubitable proof. This can never be furnished by observation alone. Possibly even experiment may fail in it, but at least it is the only hope. Value of direct experiment. *G. J. Romanes. Post-Darwinian Questions, 1895. THE FACTORS OF ORGANIC EVOLUTION. 117 On the whole, then, I believe the facts which are at present at our disposal justify a return to the position of Darwin. Neither Weismannism nor Lamarckism alone can explain the causes of evolution. But Darwinism can ex- plain those causes. Darwin endeavoured to show that variations, perhaps even adaptations, were the result of extrinsic factors acting upon the organism, and that these variations or adaptations were increased and improved by natural selection. This is, I believe, the only ground which is at present tenable, and it is but another testimony to the greatness of that man of men that, after exploring for a score of years all the ins and outs of pure selection and pure adaptation, men are now coming back to the position outlined and un- swervingly maintained by him. Finally, we ought not to suppose that we have al- ready reached a satisfactory solution of the evolution problem, or are, indeed, near such a solution. “We must not conceal from ourselves the fact,’ says Roux, “that the causal investigation of organism is one of the most difficult, if not the most difficult, problem which the human intellect has attempted to solve, and that this investigation, like every causal science, can never reach completeness, since every new cause ascertained only gives rise to fresh questions concerning the cause of this cause.”’ Return to the position of Darwin. The final word still far distant. Ve THE HEREDITY OF RICHARD ROE. ‘“Vom Vater hab’ ich die Statur.” *—GoETHE. WHEN Richard Roe was born, “the gate of gifts was closed”’ to him. Henceforth he must expect nothing new and must devote himself to the development of the heritage he had received from his father and mother. He must bring its discordant elements into some sort of harmony. He must form his Ego by the union of these elements. He must soften down their contradictions. He must train his elements of strength to be helpful to some one in some way, that others may be helpful Formation of character. * “ Stature from father and the mood Stern views of life compelling ; From mother, I take the joyous heart And the love of story-telling. ‘* Great-grandsire’s passion was the fair, What if I still reveal it? Great-granddam’s, pomp and gold and show, And in my bones I feel it. ** Of all the various elements That make up this complexity, What is there left when all is done, To call originality ?” GOETHE: Zahme Xenien, vi; Bayard Taylor’s translation in part, 118 THE HEREDITY OF RICHARD ROE. 119 to him. He must give his weak powers exercise, so that their weakness shall not bring him disaster in the competition of life. For it is likely that some- where, somehow, it will be proved that no chain is stronger than its weakest link. Other powers not too weak, nor over strong, Richard Roe must perforce neglect, because in the hurry of life there is not time for every desirable thing. In these ways the character of Richard Roe’s inheritance is steadily changing under his hands. As he grows older, one after another of the careers that might have been his, the men he might have been, vanish from his path forever. On the other hand, by steady usage a slender thread of capacity has so grown as to become like strong cordage. Thus Richard Roe learns anew the old parable of the talents. The power he hid in a napkin is taken away altogether, while that which is placed at usury is returned a hundredfold. Now, for the purpose of this discussion, you, gentle reader, “who are an achievement of importance,” or I, ungentle writer, concerning whom the less said the bet- ter, may be Richard Roe. So might any of your friends Or acquaintances. So far as methods and principles are concerned, Richard Roe may be your lapdog or your favourite horse—or even your Jéte notre, if you cherish beasts of that character. Any beast will do. With Al- gernon Fitzclarence de Courcy or Clara Vere de Vere the case would be just the same. Let Richard Roe stand at present for the lay figure of heredity—or, if it seems best to you to humanize this discussion, let him be a man. The man Richard Roe enters life with a series of qualities and tendencies granted him by heredity. Let us examine this series. Let us ana- lyze the contents of this pack which he is to carry through life to the gates of the Golden City. Hereditary tendencies. 120 FOOT-NOTES TO EVOLUTION. First, from his parents, Richard Roe has inherited humanity, the parts and organs and feelings of a man. “ Hath he not eyes? Hath he not hands, organs, dimensions, senses, affections, passions? fed with the same food, hurt with the same weapons, subject to the same diseases, healed by the same means, warmed and cooled by the same winter and summer” as you or I or any other king or beggar we know of? “If you prick us, do we not bleed? if you tickle us, do we not laugh? if you poison us, do we not die? if you wrong us, shall we not revenge?” All this, the common heritage of Jew or Gentile, goes to the making of Richard Roe. His an- cestors on both sides have been human, and that for many and many generations, so that “the knowledge of man runneth not to thecontrary.” Even the prehuman ancestry, dimly seen by the faith of science, had in it the potentialities of manhood. Descended for countless ages from man and woman, man born of woman Richard Roe surely is. We may go farther with certainty. Richard Roe will follow the race type of his parentage. If he is Anglo- Saxon, as his name seems to denote, all Anglo-Saxon by blood, he will be all Anglo-Saxon in quality. To his charac- ters of common humanity we may add those common to the race. He will not be negro nor Mongolian, and he will have at least some traits and tendencies not found in the Latin races of southern Europe. But his friends will know Richard Roe best not by the great mass of his human traits nor by his race characteristics. These may be predomi- nant and ineradicable, but they are not distinctive. He must be known by his peculiarities, by his specialties and his deficiencies. Inheritance of humanity. Inheritance of race characters. Individual characters. THE HEREDITY OF RICHARD ROE, I2I Within the narrowest type there is room for an almost infinite play in the minor variations. For almost any possible one of these, Richard Roe could find warrant in his ancestry. His combination of them must be his own. That is his individuality. Colour of the eyes and hair, length of nose, hue of skin, form of ears, size of hands, character of thumb prints, in all these and ten thousand other particulars some allotment must fall to Richard Roe. He must have some combination of his own, for Nature has “broken the die” in moulding each of his ancestors, and will tolerate no servile copy of any of her works. By the law of sex, Richard Roe has twice as many ancestors as his father or mother had. There- fore these could give him anything they had severally received from their own parents. The hereditary gifts must be divided in some way, else Richard Roe would be speedily overborne by them. Furthermore, any system of division Nature may adopt could only be on the average an equal division. Richard Roe’s father might supply half his endowment of inborn characters, his mother furnishing the other half. Nature tries to arrange for some partition like this. But she can never divide evenly, and some qualities will not bear division. Richard Roe’s share forms a sort of mosaic, made partly of unchanged characters standing side by side in new combinations, partly a mixture of characters, and part of characters in perfect blending. The physical reason for all this the physiologists are just beginning to trace. The machinery of division and integration they find in the germ cell itself—the egg and its male cognate. At the same time they find that Nature’s love of varia- tion is operative even here. She has never yet made two eggs or two sperm cells exactly alike. The germ cell. 122 FOOT-NOTES TO EVOLUTION. The germ cell, male or female—and the two are alike in all characters essential to this discussion—is one of the vital units or body cells set apart for a special pur- pose. It is not essentially different from other cells, either in structure or in origin. But in its growth it is capable of repeating the whole organism from which it came, ‘“‘ with the precision of a work of art.” The germ cell is made up of protoplasm, a jelly-like substance, less simple than it appears, not a “ sub- stance”’ at all, in fact, but a structure as complex as any in Nature. In con- nection with this structure all known phenomena of life are shown. Inside the germ cell, or in any other cell, is a smaller cellule called the nucleus. In connection with the nucleus appear most of the phenomena of hereditary transmission. Its structure in the higher animals is a complicated arrangement of loops and bands, the material of which these are made being called chromatin. This name, chromatin, is given be- cause its substance takes a deeper stain or colour (chroma in Greek) than ordinary protoplasm or other cell materials. In the chromatin are the determinants of heredity, and these preside in some way over all movements and all changes of the protoplasm. In the fertilized egg, the mixed chromatin * of the two cells which have been fused into one may be said to contain the architect’s plan by which the coming animal is to be built up. In the mixed chromatin of the cell which is to grow and to divide, to separate and integrate, till it forms Richard Roe, the potentialities of Richard Roe all lie in some way hidden. How this is we can not tell. We know that the struc- ture of a single cell is a highly complex matter, more Protoplasm. Chromatin. * For a discussion of this and other views more or less hy- pothetical, see the essay on the Physical Basis of Heredity. THE HEREDITY OF RICHARD ROE. 123 complex than the Constitution of the United States, with a far more perfect system of checks and balances. When we can understand all that takes place in a single cell we shall “know what God is and what man is.” It is not, like the Constitution of our nation, a simple written document with definite powers and definite limi- tations. It may rather be compared to the unwritten constitution of civilization, and a single cell may hold in potentiality even all that this supposed constitution may embrace. It is not easy, for example, to understand how Richard’s tone of voice, or the colour of his hair, or his ear for music, or other hereditary qualities can be thus hidden. But so they seem to be, and if Science should stop whenever she came to a problem we cannot think out, the growth of knowledge would be hemmed in more closely than it is now. When Nature is getting the germ cells ready, the hereditary material or chromatin is increased in each one and then again divided and subdivided, till in the ripened cell but half the usual amount is present.* The cell is then ready to unite with its fellow to form a per- fect cell, from which, under favourable circumstances, the great alliance of cells which constitute the body of Richard Roe can be built up. Nature makes her divisions evenly enough, but never quite equally. She is satisfied with an approximate equality, better satisfied than if she could make a perfect division. She knows no straight lines, she never made a perfect sphere, and she takes the cor- ner away from every angle. It satisfies her desire for likeness to have her children almost alike. Exact sym- metry would exclude variation, for which she cares Inequality of Nature’s divisions. * This explanation is probable but not certain. 124 FOOT-NOTES TO EVOLUTION. still more than for likeness, and for good reason. If her creatures are left unlike, it is so much the easier for her to find places for them in the crowded world of life. Moreover, unlikeness gives play for selection. She can save her favourites and discard her failures. So in the chromatin of his two parents Richard Roe finds his potentialities, his capacities, and his limita- tions. But latent in these are other capacities and other limitations handed down from other generations before them. Each grand- father and grandmother has some claim on Richard Roe, and behind these dead hands from older graves are still beckoning in his direction. The past will not let go, but with each generation the dust or the crust grows deeper over it. Moreover, these old claims grow less and less with time, because with each new genera- tion there are twice as many competitors. Besides this, as we shall see beyond, these past generations can make no claim on him except through the agency of his own parents.* Atavism. * We may sum up Richard Roe’s inheritance by making use of the formule of algebra, a science which deals with unknown characters that bear definite relations to each other. Let A be the aggregate of species and race characters inherited from the father. Let A’ be the species and race characters inher- , as , as A = A’, will amount to 2+ 2 A again. A forms the greater part of Richard Roe in numerical aggregate, but in the Anglo-Saxon race it is an invariable quan- tity, and therefore not of importance in making up the character by which we know him from his fellows. Let B be the recognisable peculiarities of the father, and B’ - the recognisable peculiarities of the mother. How shall these be / Brae should be expected, 2+ 2 fora body can not be made up of peculiarities. We may infer from Galton’s studies that these figures are in excess of the ited from the mother. Then divided? Obviously not more than THE HEREDITY OF RICHARD ROE. 125 Out of these elements Mr. Galton frames the idea of a “ mid-parent,” a sort of centre of gravity of heredity, which in language, not algebra, would represent the same set of ideas. But, as Dr. Brooks has observed, ‘It may be well to ask what evidence there is that the child does inherit from any ancestor except its parents, for descent from a long line of ancestors is not necessarily equivalent to inheritance from them, and it is quite possible that the conception of a ‘mid-parent’ may be nothing but a logical abstrac- tion.” * The parents of Richard Roe were his father and The mid-parent. fact. In each process of generation, half these qualities, al- ready once divided, are lost or rendered unrecognisable by indi- vidual variations or by contradictory blendings. To each parent Galton assigns about twenty-five per cent of these personal / : : B qualities. Accepting this as approximate, a ate mau be nearer the actual fact, and we may so take it. But the latent influence of the grandparents must come in, these represented by C, C’, C”, and C’” respectively. In this case the divisor may apparently be 16, which corresponds to Galton’s estimate of 6% per cent. Should we wish to go farther back, the influence of the great- grandparents, D, D’ D”, etc., eight of them, could be added, each with 64 as its divisor. It is evident that these divisors are all proximate only, and varying at each cleavage of the germinal chromatin. The un- known and fluctuating element in this division we may designate would represent the direct heritage of his : Bi C Ct father to Richard Roe. ThenA a A ae Be et ar c” Ci’? 8 Dieter. 16 E etc. gers p coe! mse x at 64 cae +356 + aA cars 4 etc., will be our first rough draft of the hereditary framework of Richard Roe. * In that case the formula given in the above note would be modified to this extent. The value of C, D, E, etc., would be limited to the hereditary characters latent but undeveloped in B, etc. Their value would be less than B, for some part of B would B astm. Hence 4x” 126 FOOT-NOTES TO EVOLUTION. mother, not his grandfather or grandmother, nor yet the whole human race, in one of the chains of which he forms a single link. When a son inherits his maternal grandfather’s beard it is really his mother’s beard which he acquires. It is the beard which his mother would have had had she been a man. Dr. Brooks says: “ When. the son of a beardless boy grows up and acquires a beard, we may be permitted to _ say that he has inherited his grandfather’s beard; but this is only a figure of speech, and he actually inherits the beard his father might have acquired had he lived; nor would the case of a child descended from a series of ten or a hundred beardless boys be any different.” * The species and race characters being the same for father and mother, must be the same for the son. They have to be subtracted from each of them. For it is evident that the inheritance from the grandparents and from far-off ancestors came through the parents. If not active in them, these qualities must have been latent, and in either case they came from them to Richard Roe. In strictness the inheritance of C, D, E, etc., is included in B, as are also the race qualities and the qualities of the species. * Setting aside these considerations, it isevident that, as A + B, A+B’ ,A+C,A+D’, etc., represent each a distinct personality, Richard Roe from the first will differ notably from A + B, as- sumed as the original formula of his father. To what extent this difference goes depends on the value of A as compared with B, B’, etc. ; in other words, on the uniformity of the pedigree. If B, C, D and the rest were very closely alike, as is the case with ‘‘thoroughbreds,” the differential elements will be small, and the complete Richard Roe will be very like the rest of them. If B, C, D are small quantities, and A + B essentially similar to A+ D, the addition of will count for but little in the ag- c 16+n gregate. To be thoroughbred is to be bred so as to exclude indi- vidual variation. It tends to prevent failures or deficiencies, and at the same time it tends to limit advance. THE HEREDITY OF RICHARD ROE. 127 are added together and divided by two. Half comes from each side in the process of inheritance, but the two halves are alike. But the personal peculiarities recognisable in the father are different from those seen in the mother. The son can not inherit all from both sources. Certainly not more than half could come from either source, for the new generation could not be built of peculiarities alone. The old large, common heritage must always have precedence. Galton has made a cal- culation (referred to in the note above), based on wide observations, that on the average 25 per cent of the individual peculiarities are directly inherited from each parent. On the average, each parent exerts the same force of heredity. Half the characters come from each, but in each half it would appear that about one half is lost or rendered unrecognisable by other variation or by contradictory blendings. The first division of qualities in half is necessary and natural, for there are two parents. The second division in half is an arbitrary assumption which seems to find its warrant in Galton’s studies. We might assume without theoretical difficulty a third or a fifth as being preserved intact among possible variations and combinations. One half, however, seems nearer the fact, and to find the fact is the only purpose of theory. To the characters received from the parents we must add the latent influence of grandparents, great-grand- parents, and the long array of dead hands which, how- ever impotent, can never wholly let go. As the small- est wave must go on, in theory at least, till it crosses _ the ocean, so the influence of every ancestor must go on ) to the end of the generation. Each of us must feel in a degree the strength or weakness of each one of them. | To each grandparent Galton assigns 63 per cent. There | are four grandparents and two stages of generation sepa- Tate them from Richard Roe. Half the force of each, 10 ) 128 FOOT-NOTES TO EVOLUTION. twice lost, seems to give to each grandparent one fourth the potency in heredity the father or mother has. In the same way to the great grandparent we must assign the relation of 14% per cent (one sixty-fourth), and so on. The “bluer” the blood—that is, the more closely alike these ancestors are—the greater will be the com- mon factor, the less the amount derived from the individual. In perfect thor- oughbreedings the individual should have no peculiarities at all. This condition is never reached, but it may sometimes be approximated. Insuch . case the addition of an ancestral sixteenth or sixty fourth could make no visible change. This may be true among the very bad as well as among the very good. Weak- ness or badness are more often thoroughbred than strength or virtue. The bluest of blood may run in the veins of the pauper as well as in the aristocrat who W boasts that -—————————. in his formula stands for 21474736487 + William the Norman. And for Richard Roe’s own sake let us hope that he is not too thoroughbred, and that he has no record of W and W’’, nor even of E. Too nar- row a line of descent tends to intensify weaknesses. Vigour and originality come from the mingling of vari- ant elements. Nature does not favour “in-and-in breed- ing.” There is no loss to the individual if decided and different qualities come from father or mother. Con- tradictory or even incongruous peculiarities are better than none at all. Ancestry, too, like wine, becomes stale if it remains too long in the sunshine. An ancestry which is readily traced has lived too long in easy places.